1.
Vaporization
–
Vaporization of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization, evaporation and boiling, evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon. Evaporation is a transition from the liquid phase to vapor that occurs at temperatures below the boiling temperature at a given pressure. Evaporation only occurs when the pressure of vapor of a substance is less than the equilibrium vapor pressure. Boiling is also a transition from the liquid phase to gas phase. Boiling occurs when the vapor pressure of the substance is greater than or equal to the environmental pressure. The temperature at which boiling occurs is the temperature, or boiling point. The boiling point varies with the pressure of the environment, sublimation is a direct phase transition from the solid phase to the gas phase, skipping the intermediate liquid phase. Because it does not involve the liquid phase, it is not a form of vaporization, the term vaporization has also been used to refer to the physical destruction of an object that is exposed to intense heat. As noted in discussions of the effects of weapons, this includes the vaporization of the uninhabited Marshall Island of Elugelab in the 1952 Ivy Mike thermonuclear test. All atoms lose their shells and become positively charged ions. All such matter becomes a gas of nuclei and electrons which rise into the air due to the high temperature or bond to each other as they cool
Vaporization
–
This diagram shows the nomenclature for the different phase transitions.
2.
Liquid
–
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a constant volume independent of pressure. As such, it is one of the four states of matter. A liquid is made up of tiny vibrating particles of matter, such as atoms, water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container, most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, a distinctive property of the liquid state is surface tension, leading to wetting phenomena. The density of a liquid is usually close to that of a solid, therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is in form as interstellar clouds or in plasma form within stars. Liquid is one of the four states of matter, with the others being solid, gas. Unlike a solid, the molecules in a liquid have a greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, a liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, if liquid is placed in a bag, it can be squeezed into any shape. These properties make a suitable for applications such as hydraulics. Liquid particles are bound firmly but not rigidly and they are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its point, the cohesive forces that bind the molecules closely together break. If the temperature is decreased, the distances between the molecules become smaller, only two elements are liquid at standard conditions for temperature and pressure, mercury and bromine. Four more elements have melting points slightly above room temperature, francium, caesium, gallium and rubidium, metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams
Liquid
–
The formation of a spherical
droplet of liquid water minimizes the
surface area, which is the natural result of
surface tension in liquids.
Liquid
–
Thermal image of a sink full of hot water with cold water being added, showing how the hot and the cold water flow into each other.
Liquid
–
Surface waves in
water
3.
Boiling point
–
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
Boiling point
–
Boiling water
4.
Temperature
–
A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer, several scales and units exist for measuring temperature, the most common being Celsius, Fahrenheit, and, especially in science, Kelvin. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, the kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. Temperature is important in all fields of science including physics, geology, chemistry, atmospheric sciences, medicine. The Celsius scale is used for temperature measurements in most of the world. Because of the 100 degree interval, it is called a centigrade scale.15, the United States commonly uses the Fahrenheit scale, on which water freezes at 32°F and boils at 212°F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scottish physicist who first defined it and it is a thermodynamic or absolute temperature scale. Its zero point, 0K, is defined to coincide with the coldest physically-possible temperature and its degrees are defined through thermodynamics. The temperature of zero occurs at 0K = −273. 15°C. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, Temperature is one of the principal quantities in the study of thermodynamics. There is a variety of kinds of temperature scale and it may be convenient to classify them as empirically and theoretically based. Empirical temperature scales are historically older, while theoretically based scales arose in the middle of the nineteenth century, empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a capillary tube, is dependent largely on temperature. Such scales are only within convenient ranges of temperature. For example, above the point of mercury, a mercury-in-glass thermometer is impracticable. A material is of no use as a thermometer near one of its phase-change temperatures, in spite of these restrictions, most generally used practical thermometers are of the empirically based kind. Especially, it was used for calorimetry, which contributed greatly to the discovery of thermodynamics, nevertheless, empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Theoretically based temperature scales are based directly on theoretical arguments, especially those of thermodynamics, kinetic theory and they rely on theoretical properties of idealized devices and materials
Temperature
–
Annual mean temperature around the world
Temperature
–
Body temperature variation
Temperature
–
A typical Celsius thermometer measures a winter day temperature of -17 °C.
Temperature
–
Plots of pressure vs temperature for three different gas samples extrapolated to absolute zero.
5.
Vapour pressure
–
Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquids evaporation rate and it relates to the tendency of particles to escape from the liquid. A substance with a vapor pressure at normal temperatures is often referred to as volatile. The pressure exhibited by vapor present above a surface is known as vapor pressure. As the temperature of a liquid increases, the energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, the vapor pressure of any substance increases non-linearly with temperature according to the Clausius–Clapeyron relation. The atmospheric pressure boiling point of a liquid is the temperature at which the pressure equals the ambient atmospheric pressure. With any incremental increase in temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure. Bubble formation deeper in the liquid requires a pressure, and therefore higher temperature. More important at shallow depths, is the temperature required to start bubble formation. The surface tension of the wall lead to an overpressure in the very small initial bubbles. Thus, thermometer calibration should not rely on the temperature in boiling water, the vapor pressure that a single component in a mixture contributes to the total pressure in the system is called partial pressure. Vapor pressure is measured in the units of pressure. The International System of Units recognizes pressure as a unit with the dimension of force per area. One pascal is one newton per square meter, experimental measurement of vapor pressure is a simple procedure for common pressures between 1 and 200 kPa. Most accurate results are obtained near the point of substances. Better accuracy is achieved when care is taken to ensure that the entire substance and this is often done, as with the use of an isoteniscope, by submerging the containment area in a liquid bath. Very low vapor pressures of solids can be measured using the Knudsen effusion cell method, the Antoine equation is a mathematical expression of the relation between the vapor pressure and the temperature of pure liquid or solid substances
Vapour pressure
–
Graph of water vapor pressure versus temperature. At the normal boiling point of 100 °C, it equals the standard atmospheric pressure of 760
Torr or 101.325
kPa.
Vapour pressure
–
The picture shows the particle transition, as a result of their vapor pressure, from the liquid phase to the gas phase and converse.
6.
Nucleate boiling
–
For water, as shown in the graph below, nucleate boiling occurs when the surface temperature is higher than the saturation temperature by between 10 °C to 30 °C. The critical heat flux is the peak on the curve between nucleate boiling and transition boiling, the heat transfer from surface to liquid is greater than that in film boiling. Two different regimes may be distinguished in the boiling range. When the temperature difference is between approximately 4 °C to 10 °C above TS, isolated bubbles form at nucleation sites and this separation induces considerable fluid mixing near the surface, substantially increasing the convective heat transfer coefficient and the heat flux. In this regime, most of the transfer is through direct transfer from the surface to the liquid in motion at the surface. Between 10 °C and 30 °C above TS, a flow regime may be observed. As more nucleation sites become active, increased bubble formation causes bubble interference and coalescence, in this region the vapor escapes as jets or columns which subsequently merge into slugs of vapor. Interference between the densely populated bubbles inhibits the motion of liquid near the surface and this is observed on the graph as a change in the direction of the gradient of the curve or an inflection in the boiling curve. When the relative increase in the difference is balanced by the relative reduction in the heat transfer coefficient. This is the heat flux. At this point in the maximum, considerable vapor is being formed and this causes the heat flux to reduce after this point. At extremes, film boiling commonly known as the Leidenfrost effect is observed, the bubbles grow until they reach some critical size, at which point they separate from the wall and are carried into the main fluid stream. There the bubbles collapse because the temperature of bulk fluid is not as high as at the heat transfer surface and this collapsing is also responsible for the sound a water kettle produces during heat up but before the temperature at which bulk boiling is reached. Heat transfer and mass transfer during nucleate boiling has a significant effect on the transfer rate. The effects of nucleate boiling take place at two locations, the interface the bubble-liquid interface The nucleate boiling process has a complex nature. Nucleate boiling phenomenon still requires more understanding, the nucleate boiling regime is important to engineers because of the high heat fluxes possible with moderate temperature differences. The bubble Reynolds number, R e b is defined as, R e b = D b G b μ L Where G b is the mass velocity of the vapor leaving the surface. Rohsenow has developed the first and most widely used correlation for nucleate boiling, C s f is the surface fluid combination and vary for various combinations of fluid and surface
Nucleate boiling
–
Boiling Curve for water at 1atm
Nucleate boiling
–
Behavior of water on a hot plate. Graph shows heat transfer (flux) v. temperature (in degrees Celsius) above T S, the
saturation temperature of water, 100 °C (212 °F).
7.
Nucleation
–
Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears, nucleation is often found to be very sensitive to impurities in the system. Because of this, it is important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at sites on surfaces in the system. Homogeneous nucleation occurs away from a surface, nucleation is usually a stochastic process, so even in two identical systems nucleation will occur at different times. This behaviour is similar to radioactive decay, a common mechanism is illustrated in the animation to the right. This shows nucleation of a new phase in an existing phase and this nucleus of the red phase then grows and converts the system to this phase. The standard theory that describes this behaviour for the nucleation of a new phase is called classical nucleation theory. This is seen for example in the nucleation of ice in supercooled water droplets. The decay rate of the exponential gives the nucleation rate, classical nucleation theory is a widely used approximate theory for estimating these rates, and how they vary with variables such as temperature. It correctly predicts that the time you have to wait for nucleation decreases extremely rapidly when supersaturated and it is not just new phases such as liquids and crystals that form via nucleation followed by growth. The self-assembly process that forms objects like the amyloid aggregates associated with Alzheimers disease also starts with nucleation, energy consuming self-organising systems such as the microtubules in cells also show nucleation and growth. Clouds form when wet air cools and many small water droplets nucleate from the supersaturated air, the amount of water vapor that air can carry decreases with lower temperatures. The excess vapor begins to nucleate and to small water droplets which form a cloud. Nucleation of the droplets of water is heterogeneous, occurring on particles referred to as cloud condensation nuclei. Cloud seeding is the process of adding artificial condensation nuclei to quicken the formation of clouds, nucleation is the first step in crystallisation, so it determines if a crystal can form. Frequently crystals do not form even when they are thermodynamically the favored state, for example, small droplets of very pure water can remain liquid down to below -30 °C although ice is the stable state below 0 °C. Bubbles of carbon dioxide nucleate shortly after the pressure is released from a container of carbonated liquid, nucleation often occurs more easily at a pre-existing interface, as happens on boiling chips and on string used to make rock candy
Nucleation
–
When sugar is
supersaturated in water, nucleation will occur, allowing sugar molecules to stick together and form large crystal structures.
Nucleation
–
Nucleation of carbon dioxide bubbles around a finger.
8.
Superheating
–
This article is about the phenomenon where a liquid can exist in a metastable state above its boiling point. See superheated water for pressurized water above 100 °C, see superheater for the device used in steam engines. In physics, superheating is the phenomenon in which a liquid is heated to a higher than its boiling point. Superheating is achieved by heating a substance in a clean container, free of nucleation sites. Water is said to boil when bubbles of water vapor grow without bound, for a vapor bubble to expand, the temperature must be high enough that the vapor pressure exceeds the ambient pressure. Below that temperature, a vapor bubble will shrink and vanish. Superheating is an exception to this rule, a liquid is sometimes observed not to boil even though its vapor pressure does exceed the ambient pressure. The cause is a force, the surface tension, which suppresses the growth of bubbles. Surface tension makes the bubble act like a rubber balloon, the pressure inside is raised slightly by the skin attempting to contract. For the bubble to expand, the temperature must be raised slightly above the point to generate enough vapor pressure to overcome both surface tension and ambient pressure. What makes superheating so explosive is that a bubble is easier to inflate than a small one, just as when blowing up a balloon. It turns out the pressure due to surface tension is inversely proportional to the diameter of the bubble. This means if the largest bubbles in a container are only a few micrometres in diameter, once a bubble does begin to grow, the pressure due to the surface tension reduces, so it expands explosively. In practice, most containers have scratches or other imperfections which trap pockets of air that provide starting bubbles, but a container of liquid with only microscopic bubbles can superheat dramatically. Superheating can occur when a container of water is heated in a microwave oven. When the container is removed, the water appears to be below the boiling point. However, once the water is disturbed, some of it violently flashes to steam, the boiling can be triggered by jostling the cup, inserting a stirring device, or adding a substance like instant coffee or sugar. The chances of superheating are greater with smooth containers, because scratches or chips can house small pockets of air, which serve as nucleation points
Superheating
–
For boiling to occur, the vapor pressure must exceed the ambient pressure plus a small amount of pressure induced by surface tension
9.
Boiling delay
–
This article is about the phenomenon where a liquid can exist in a metastable state above its boiling point. See superheated water for pressurized water above 100 °C, see superheater for the device used in steam engines. In physics, superheating is the phenomenon in which a liquid is heated to a higher than its boiling point. Superheating is achieved by heating a substance in a clean container, free of nucleation sites. Water is said to boil when bubbles of water vapor grow without bound, for a vapor bubble to expand, the temperature must be high enough that the vapor pressure exceeds the ambient pressure. Below that temperature, a vapor bubble will shrink and vanish. Superheating is an exception to this rule, a liquid is sometimes observed not to boil even though its vapor pressure does exceed the ambient pressure. The cause is a force, the surface tension, which suppresses the growth of bubbles. Surface tension makes the bubble act like a rubber balloon, the pressure inside is raised slightly by the skin attempting to contract. For the bubble to expand, the temperature must be raised slightly above the point to generate enough vapor pressure to overcome both surface tension and ambient pressure. What makes superheating so explosive is that a bubble is easier to inflate than a small one, just as when blowing up a balloon. It turns out the pressure due to surface tension is inversely proportional to the diameter of the bubble. This means if the largest bubbles in a container are only a few micrometres in diameter, once a bubble does begin to grow, the pressure due to the surface tension reduces, so it expands explosively. In practice, most containers have scratches or other imperfections which trap pockets of air that provide starting bubbles, but a container of liquid with only microscopic bubbles can superheat dramatically. Superheating can occur when a container of water is heated in a microwave oven. When the container is removed, the water appears to be below the boiling point. However, once the water is disturbed, some of it violently flashes to steam, the boiling can be triggered by jostling the cup, inserting a stirring device, or adding a substance like instant coffee or sugar. The chances of superheating are greater with smooth containers, because scratches or chips can house small pockets of air, which serve as nucleation points
Boiling delay
–
For boiling to occur, the vapor pressure must exceed the ambient pressure plus a small amount of pressure induced by surface tension
10.
Transition boiling
–
For water, as shown in the graph below, nucleate boiling occurs when the surface temperature is higher than the saturation temperature by between 10 °C to 30 °C. The critical heat flux is the peak on the curve between nucleate boiling and transition boiling, the heat transfer from surface to liquid is greater than that in film boiling. Two different regimes may be distinguished in the boiling range. When the temperature difference is between approximately 4 °C to 10 °C above TS, isolated bubbles form at nucleation sites and this separation induces considerable fluid mixing near the surface, substantially increasing the convective heat transfer coefficient and the heat flux. In this regime, most of the transfer is through direct transfer from the surface to the liquid in motion at the surface. Between 10 °C and 30 °C above TS, a flow regime may be observed. As more nucleation sites become active, increased bubble formation causes bubble interference and coalescence, in this region the vapor escapes as jets or columns which subsequently merge into slugs of vapor. Interference between the densely populated bubbles inhibits the motion of liquid near the surface and this is observed on the graph as a change in the direction of the gradient of the curve or an inflection in the boiling curve. When the relative increase in the difference is balanced by the relative reduction in the heat transfer coefficient. This is the heat flux. At this point in the maximum, considerable vapor is being formed and this causes the heat flux to reduce after this point. At extremes, film boiling commonly known as the Leidenfrost effect is observed, the bubbles grow until they reach some critical size, at which point they separate from the wall and are carried into the main fluid stream. There the bubbles collapse because the temperature of bulk fluid is not as high as at the heat transfer surface and this collapsing is also responsible for the sound a water kettle produces during heat up but before the temperature at which bulk boiling is reached. Heat transfer and mass transfer during nucleate boiling has a significant effect on the transfer rate. The effects of nucleate boiling take place at two locations, the interface the bubble-liquid interface The nucleate boiling process has a complex nature. Nucleate boiling phenomenon still requires more understanding, the nucleate boiling regime is important to engineers because of the high heat fluxes possible with moderate temperature differences. The bubble Reynolds number, R e b is defined as, R e b = D b G b μ L Where G b is the mass velocity of the vapor leaving the surface. Rohsenow has developed the first and most widely used correlation for nucleate boiling, C s f is the surface fluid combination and vary for various combinations of fluid and surface
Transition boiling
–
Boiling Curve for water at 1atm
Transition boiling
–
Behavior of water on a hot plate. Graph shows heat transfer (flux) v. temperature (in degrees Celsius) above T S, the
saturation temperature of water, 100 °C (212 °F).
11.
Liquid bubble
–
A bubble is a globule of one substance in another, usually gas in a liquid. Due to the Marangoni effect, bubbles may remain intact when they reach the surface of the immersive substance. g, for the physics and chemistry behind it, see nucleation. Humans can see bubbles because they have a different refractive index than the surrounding substance, for example, the IR of air is approximately 1.0003 and the IR of water is approximately 1.333. Nucleation can be induced, for example to create bubblegram. In medical ultrasound imaging, small encapsulated bubbles called contrast agent are used to enhance the contrast, in thermal inkjet printing, vapor bubbles are used as actuators. They are occasionally used in microfluidics applications as actuators. The violent collapse of bubbles near solid surfaces and the resulting impinging jet constitute the mechanism used in ultrasonic cleaning, the same effect, but on a larger scale, is used in focused energy weapons such as the bazooka and the torpedo. Pistol shrimp also use a collapsing cavitation bubble as a weapon, the same effect is used to treat kidney stones in a lithotripter. Marine mammals such as dolphins and whales use bubbles for entertainment or as hunting tools, aerators cause dissolution of gas in the liquid by injecting bubbles. Chemical and metallurgic engineers rely on bubbles for operations such as distillation, absorption, flotation, the complex processes involved often require consideration for mass and heat transfer, and are modelled using fluid dynamics. The star-nosed mole and the American water shrew can smell underwater by breathing through their nostrils. When bubbles are disturbed, they pulsate at their natural frequency, large bubbles undergo adiabatic pulsations, which means that no heat is transferred either from the liquid to the gas or vice versa. The damage can be due to deformation of tissues due to bubble growth in situ. This can occur as a result of decompression after hyperbaric exposure, a lung overexpansion injury, during intravenous fluid administration, or during surgery
Liquid bubble
–
Air bubbles as a man surfaces in a pool.
Liquid bubble
–
Bubbles of
gas in a
soft drink
Liquid bubble
–
Bubble of gas in a
mudpot
Liquid bubble
–
A bubble of gas in a
tar pit
12.
Cavitation
–
Cavitation is the formation of vapour cavities in a liquid – i. e. small liquid-free zones – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to pressure, the voids implode and can generate an intense shock wave. Cavitation is a significant cause of wear in some engineering contexts, collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal causing a type of wear also called cavitation, the most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior, inertial cavitation and non-inertial cavitation, inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Inertial cavitation occurs in nature in the strikes of mantis shrimps and pistol shrimps, in man-made objects, it can occur in control valves, pumps, propellers and impellers. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to form of energy input. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers, since the shock waves formed by collapse of the voids are strong enough to cause significant damage to moving parts, cavitation is usually an undesirable phenomenon. It is very often specifically avoided in the design of such as turbines or propellers. However, it is useful and does not cause damage when the bubbles collapse away from machinery. Inertial cavitation was first studied by Lord Rayleigh in the late 19th century, when a volume of liquid is subjected to a sufficiently low pressure, it may rupture and form a cavity. This phenomenon is coined cavitation inception and may occur behind the blade of a rotating propeller or on any surface vibrating in the liquid with sufficient amplitude. A fast-flowing river can cause cavitation on rock surfaces, particularly there is a drop-off. Other ways of generating cavitation voids involve the local deposition of energy, vapor gases evaporate into the cavity from the surrounding medium, thus, the cavity is not a perfect vacuum, but has a relatively low gas pressure. Such a low-pressure bubble in a liquid begins to collapse due to the pressure of the surrounding medium. As the bubble collapses, the pressure and temperature of the vapor within increases, at the point of total collapse, the temperature of the vapor within the bubble may be several thousand kelvin, and the pressure several hundred atmospheres. Inertial cavitation can occur in the presence of an acoustic field
Cavitation
–
Cavitating propeller model in a
water tunnel experiment.
Cavitation
–
Cavitation damage on a valve plate for an
axial piston hydraulic pump.
Cavitation
–
Cavitation damage to a
Francis turbine.
13.
Leidenfrost effect
–
Due to this repulsive force, a droplet hovers over the surface rather than making physical contact with it. The effect is responsible for the ability of liquid nitrogen to skitter across floors. The latter is potentially lethal, particularly should one accidentally swallow the liquid nitrogen and it is named after Johann Gottlob Leidenfrost, who discussed it in A Tract About Some Qualities of Common Water in 1756. The effect can be seen as drops of water are sprinkled onto a pan at various times as it heats up. Initially, as the temperature of the pan is just below 100 °C, the water out and slowly evaporates, or if the temperature of the pan is well below 100 °C. As the temperature of the pan goes above 100 °C, the water droplets hiss when touching the pan, later, as the temperature exceeds the Leidenfrost point, the Leidenfrost effect comes into play. On contact with the pan, the water droplets bunch up into balls of water and skitter around. This effect works until a higher temperature causes any further drops of water to evaporate too quickly to cause this effect. This is because at temperatures above the Leidenfrost point, the part of the water droplet vaporizes immediately on contact with the hot plate. The resulting gas suspends the rest of the water droplet just above it, as steam has much poorer thermal conductivity, further heat transfer between the pan and the droplet is slowed down dramatically. This also results in the drop being able to skid around the pan on the layer of gas just under it, the temperature at which the Leidenfrost effect begins to occur is not easy to predict. Some research has been conducted into a model of the system. As a very rough estimate, the Leidenfrost point for a drop of water on a frying pan might occur at 193 °C. In a pair of lectures on design, he cited the work of Pierre Hippolyte Boutigny and Professor Bowman of Kings College. A drop of water that was vaporized almost immediately at 168 °C persisted for 152 seconds at 202 °C, lower temperatures in a boiler firebox might evaporate water more quickly as a result, compare Mpemba effect. An alternative approach was to increase the temperature beyond the Leidenfrost point, fairbairn considered this too, and may have been contemplating the flash steam boiler, but considered the technical aspects insurmountable for the time. The Leidenfrost point may also be taken to be the temperature for which the hovering droplet lasts longest and it has been demonstrated that it is possible to stabilize the Leidenfrost vapour layer of water by exploiting superhydrophobic surfaces. In this case, once the layer is established, cooling never collapses the layer, and no nucleate boiling occurs
Leidenfrost effect
–
A water droplet experiencing Leidenfrost effect on a hot stove plate
Leidenfrost effect
–
Leidenfrost droplet
Leidenfrost effect
–
Reactive Leidenfrost Effect of Cellulose on Silica, 750° C (~1400° Fahrenheit)
14.
Thermal conductivity
–
In physics, thermal conductivity is the property of a material to conduct heat. It is evaluated primarily in terms of Fouriers Law for heat conduction, heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity. Correspondingly, materials of high thermal conductivity are used in heat sink applications. The thermal conductivity of a material may depend on temperature, the reciprocal of thermal conductivity is called thermal resistivity. Thermal conductivity is actually a tensor, which means it is possible to have different values in different directions, in SI units, thermal conductivity is measured in watts per meter-kelvin. The dimension of thermal conductivity is M1L1T−3Θ−1 and these variables are mass, length, time, and temperature. In Imperial units, thermal conductivity is measured in BTU/, other units which are closely related to the thermal conductivity are in common use in the construction and textile industries. The construction industry makes use of such as the R-value. Although related to the conductivity of a material used in an insulation product, R-. Likewise the textile industry has several units including the tog and the clo which express thermal resistance of a material in a way analogous to the R-values used in the construction industry, there are a number of ways to measure thermal conductivity. Each of these is suitable for a range of materials, depending on the thermal properties. There is a distinction between steady-state and transient techniques, in general, steady-state techniques are useful when the temperature of the material does not change with time. This makes the signal analysis straightforward, the disadvantage is that a well-engineered experimental setup is usually needed. The Divided Bar is the most common used for consolidated rock solids. Thermal conductivity is important in science, research, electronics, building insulation and related fields. Several materials are shown in the list of thermal conductivities and these should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper, aluminium, the reciprocal of thermal conductivity is thermal resistivity, usually expressed in kelvin-meters per watt. For a given thickness of a material, that particular constructions thermal resistance, unfortunately, there are differing definitions for these terms
Thermal conductivity
–
Ceramic coatings with low thermal conductivities are used on exhaust systems to prevent heat from reaching sensitive components
Thermal conductivity
–
Gas atoms moving randomly through a surface.
15.
Distillation
–
Distillation is a process of separating the component or substances from a liquid mixture by selective evaporation and condensation. Distillation may result in complete separation, or it may be a partial separation that increases the concentration of selected components of the mixture. In either case the process exploits differences in the volatility of the mixtures components, in industrial chemistry, distillation is a unit operation of practically universal importance, but it is a physical separation process and not a chemical reaction. For example, In the fossil fuel industry distillation is a class of operation in obtaining materials from crude oil for fuels. Distillation permits separation of air into its components — notably oxygen, nitrogen, Distillation of fermented products produces distilled beverages with a high alcohol content, or separates out other fermentation products of commercial value. An installation for distillation, especially of alcohol, is a distillery, the distillation equipment is a still. Distillation is an old method of artificial desalination. Aristotle wrote about the process in his Meteorologica and even that ordinary wine possesses a kind of exhalation, later evidence of distillation comes from Greek alchemists working in Alexandria in the 1st century AD. Distilled water has been known since at least c,200, when Alexander of Aphrodisias described the process. Work on distilling other liquids continued in early Byzantine Egypt under the Greek-Egyptian Zosimus of Panopolis, Distillation in China could have begun during the Eastern Han Dynasty, but archaeological evidence indicates that actual distillation of beverages began in the Jin and Southern Song dynasties. A still was found in a site in Qinglong, Hebei province dating to the 12th century. Distilled beverages were more common during the Yuan dynasty, arabs learned the process from the Alexandrians and used it extensively in their chemical experiments. Clear evidence of the distillation of alcohol comes from the School of Salerno in the 12th century, fractional distillation was developed by Tadeo Alderotti in the 13th century. In 1500, German alchemist Hieronymus Braunschweig published Liber de arte destillandi the first book dedicated to the subject of distillation. In 1651, John French published The Art of Distillation the first major English compendium of practice and this includes diagrams with people in them showing the industrial rather than bench scale of the operation. As alchemy evolved into the science of chemistry, vessels called retorts became used for distillations, riveted joints were often kept tight by using various mixtures, for instance a dough made of rye flour. These alembics often featured a system around the beak, using cold water for instance. Today, the retorts and pot stills have largely supplanted by more efficient distillation methods in most industrial processes
Distillation
–
Distillation equipment used by the 3rd century Greek alchemist
Zosimos of Panopolis, from the
Byzantine Greek manuscript Parisinus graces.
Distillation
–
Laboratory display of distillation: 1: A source of heat 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate 14: Heating (Oil/sand) bath 15: Stirring means e.g. (shown),
boiling chips or mechanical stirrer 16: Cooling bath.
Distillation
–
Hieronymus Brunschwig's Liber de arte Distillandi de Compositis (Strassburg, 1512) Chemical Heritage Foundation
Distillation
–
A retort
16.
Microbes
–
A microorganism or microbe is a microscopic organism, which may be single-celled or multicellular. The study of microorganisms is called microbiology, a subject that began with the discovery of microorganisms in 1674 by Antonie van Leeuwenhoek, microorganisms are very diverse and include all bacteria, archaea and most protozoa. This group also contains some fungi, algae, and some such as rotifers. Many macroscopic animals and plants have microscopic juvenile stages, some microbiologists classify viruses and viroids as microorganisms, but others consider these as nonliving. In July 2016, scientists identified a set of 355 genes from the last universal ancestor of all life, including microorganisms. Microorganisms, under certain test conditions, have observed to thrive in the vacuum of outer space. Microorganisms likely far outweigh all other living things combined, the mass of prokaryote microorganisms including the bacteria and archaea may be as much as 0.8 trillion tons of carbon, out of the total biomass of between 1 and 4 trillion tons. Microorganisms appear to thrive in the Mariana Trench, the deepest spot in the Earths oceans, in August 2014, scientists confirmed the existence of microorganisms living 800 m below the ice of Antarctica. According to one researcher, You can find microbes everywhere — theyre extremely adaptable to conditions, microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers. As some microorganisms can fix nitrogen, they are a part of the nitrogen cycle. Microorganisms are also exploited in biotechnology, both in food and beverage preparation, and in modern technologies based on genetic engineering. A small proportion of microorganisms are pathogenic, causing disease and even death in plants, Robert Hooke coined the term cell after viewing plant cells under his microscope. Antonie Van Leeuwenhoek was one of the first people to observe microorganisms in 1673, later, in the 19th century, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In 1876 Robert Koch discovered that microorganisms cause diseases, single-celled microorganisms were the first forms of life to develop on Earth, approximately 3–4 billion years ago. Further evolution was slow, and for about 3 billion years in the Precambrian eon, so, for most of the history of life on Earth, the only forms of life were microorganisms. Bacteria, algae and fungi have been identified in amber that is 220 million years old, microorganisms tend to have a relatively fast rate of evolution. Most microorganisms can reproduce rapidly, and bacteria are able to freely exchange genes through conjugation, transformation and transduction. This rapid evolution is important in medicine, as it has led to the development of multidrug resistant pathogenic bacteria, superbugs, the possible existence of microorganisms was discussed for many centuries before their discovery in the 17th century
Microbes
–
A cluster of
Escherichia coli bacteria magnified 10,000 times
Microbes
–
Antonie van Leeuwenhoek, the first
microbiologist and the first to observe microorganisms using a
microscope
Microbes
–
Lazzaro Spallanzani showed that boiling a broth stopped it from decaying
Microbes
–
Louis Pasteur showed that Spallanzani's findings held even if air could enter through a filter that kept particles out
17.
Intestine
–
Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines. A tract is a collection of related anatomic structures or a series of connected body organs, the mouth, oesophagus, stomach, and intestines are part of the human alimentary canal. All bilaterians have a gastrointestinal tract, also called a gut or an alimentary canal and this is a tube that transfers food to the organs of digestion. In large bilaterians, the gastrointestinal tract generally also has an exit, some small bilaterians have no anus and dispose of solid wastes by other means. The gastrointestinal tract contains thousands of different bacteria in their gut flora, the human gastrointestinal tract consists of the esophagus, stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. In contrast, the digestive system comprises the gastrointestinal tract plus the accessory organs of digestion. The tract may also be divided into foregut, midgut, and hindgut, the whole human GI tract is about nine metres long at autopsy. The GI tract releases hormones from enzymes to help regulate the digestive process, the structure and function can be described both as gross anatomy and as microscopic anatomy or histology. The tract itself is divided into upper and lower tracts, the upper gastrointestinal tract consists of the buccal cavity, pharynx, esophagus, stomach, and duodenum. The exact demarcation between the upper and lower tracts is the muscle of the duodenum. Upon dissection, the duodenum may appear to be an organ, but it is divided into four segments based upon function, location. The four segments of the duodenum are as follows, bulb, descending, horizontal, the suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm. The suspensory muscle is an important anatomical landmark which shows the division between the duodenum and the jejunum, the first and second parts of the small intestine. This is a muscle which is derived from the embryonic mesoderm. The lower gastrointestinal tract includes most of the intestine and all of the large intestine. In humans, the intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum, colon, rectum. The small intestine begins at the duodenum, which receives food from the stomach and it is a tubular structure, usually between 6 and 7 m long. The area of the human, adult small intestinal mucosa is about 30 m2 and its main function is to absorb the products of digestion into the bloodstream
Intestine
–
Stomach colon rectum diagram
18.
Water purification
–
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from contaminated water. The goal is to produce water fit for a specific purpose, the standards for drinking water quality are typically set by governments or by international standards. These standards usually include minimum and maximum concentrations of contaminants, depending on the purpose of water use. Visual inspection cannot determine if water is of appropriate quality, simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all the possible contaminants that may be present in water from an unknown source. Even natural spring water – considered safe for all purposes in the 19th century – must now be tested before determining what kind of treatment. Chemical and microbiological analysis, while expensive, are the way to obtain the information necessary for deciding on the appropriate method of purification. The WHO estimates that 94% of these cases are preventable through modifications to the environment. Simple techniques for treating water at home, such as chlorination, filters, and solar disinfection, reducing deaths from waterborne diseases is a major public health goal in developing countries. Groundwater, The water emerging from deep ground water may have fallen as rain many tens, hundreds. Such water may emerge as springs, artesian springs, or may be extracted from boreholes or wells, deep ground water is generally of very high bacteriological quality, but the water may be rich in dissolved solids, especially carbonates and sulfates of calcium and magnesium. Depending on the strata through which the water has flowed, other ions may also be present including chloride, there may be a requirement to reduce the iron or manganese content of this water to make it acceptable for drinking, cooking, and laundry use. Primary disinfection may also be required, where groundwater recharge is practised, the groundwater may require additional treatment depending on applicable state and federal regulations. Bacteria and pathogen levels are low, but some bacteria. Where uplands are forested or peaty, humic acids can colour the water, many upland sources have low pH which require adjustment. Rivers, canals and low land reservoirs, Low land surface waters will have a significant bacterial load and may also contain algae, suspended solids and a variety of dissolved constituents. Atmospheric water generation is a new technology that can provide high quality drinking water by extracting water from the air by cooling the air, desalination of seawater by distillation or reverse osmosis. Surface Water, Freshwater bodies that are open to the atmosphere and are not designated as groundwater are termed surface waters. The aims of the treatment are to remove unwanted constituents in the water, the choice of method will depend on the quality of the water being treated, the cost of the treatment process and the quality standards expected of the processed water
Water purification
–
Control room and schematics of the water purification plant to
Lac de Bret, Switzerland
Water purification
–
Cutaway view of a typical rapid sand filter
Water purification
–
Slow "artificial" filtration (a variation of
bank filtration) to the ground, Water purification plant Káraný, Czech Republic
Water purification
–
A profile of layers of gravel, sand and fine sand used in a slow sand filter plant.
19.
First-order kinetics
–
The rate law or rate equation for a chemical reaction is an equation that links the reaction rate with the concentrations or pressures of the reactants and constant parameters. For many reactions the rate is given by a law such as r = k x y where and express the concentration of the species A and B. The exponents x and y are the partial orders and must be determined experimentally. The constant k is the rate constant or rate coefficient of the reaction. The value of this coefficient k may depend on such as temperature, ionic strength, surface area of an adsorbent. For elementary reactions, which consist of a step, the order equals the molecularity as predicted by collision theory. For example, an elementary reaction A + B → products will be second order overall and first order in each reactant. For multistep reactions, the order of each step equals the molecularity, the equation may involve a fractional order, and may depend on the concentration of an intermediate species. The rate equation is an equation and can be integrated to obtain an integrated rate equation that links concentrations of reactants or products with time. A zero order reaction has a rate that is independent of the concentration of the reactant, increasing the concentration of the reacting species will not speed up the rate of the reaction i. e. the amount of substance reacted is proportional to the time. Zero order reactions are found when a material that is required for the reaction to proceed. The rate law for a zero order reaction is r = k where r is the reaction rate, T = − k t +0 where t represents the concentration of the chemical of interest at a particular time, and 0 represents the initial concentration. A reaction is zero order if concentration data are plotted versus time, a plot of t vs. time t gives a straight line with a slope of − k. The half-life of a reaction describes the time needed for half of the reactant to be depleted, a first order reaction depends on the concentration of only one reactant. Other reactants can be present, but each will be zero order, the rate law for a reaction that is first order with respect to a reactant A is − d d t = r = k k is the first order rate constant, which has units of 1/s. The integrated first order rate law is ln = − k t + ln 0 A plot of ln vs. time t gives a line with a slope of − k. The half-life of a first order reaction is independent of the concentration and is given by t 12 = ln k. This equation indicates that the fraction of the amount of reactant population that will break down in each time period is independent of the initial amount present
First-order kinetics
–
Concentration of A (A 0 = 0.25 mole/l) and B versus time reaching equilibrium k f = 2 min −1 and k r = 1 min −1
20.
Giardia
–
Giardia is a genus of anaerobic flagellated protozoan parasites of the phylum Sarcomastigophora that colonise and reproduce in the small intestines of several vertebrates, causing giardiasis. Their life cycle alternates between an actively swimming trophozoite and an infective, resistant cyst, Giardia were first described by the Dutch microscopist Antonie van Leeuwenhoek in 1681. The genus is named after French zoologist Alfred Mathieu Giard, like other diplomonads, Giardia have two nuclei, each with four associated flagella, and were thought to lack both mitochondria and a Golgi apparatus. However they are now known to possess a complex system as well as mitochondrial remnants, called mitosomes. The mitosomes are not used in ATP synthesis the way mitochondria are, the synapomorphies of genus Giardia include cells with duplicate organelles, absence of cytostomes, and ventral adhesive disc. The symptoms of Giardia, which may begin to appear 2 days after infection, include violent diarrhea, excess gas, stomach or abdominal cramps, upset stomach, resulting dehydration and nutritional loss may need immediate treatment. A typical infection can be slight, resolve without treatment, coexistence with the parasite is possible, but an infected individual can remain a carrier and transmit it to others. Medication containing tinidazole or metronidazole decreases symptoms and time to resolution, albendazole is also used, and has an anti-helmintic property as well, ideal for certain compounded issues when a general vermicidal agent is preferred. Giardia causes a disease called Giardiasis, which causes the villi of the intestine to atrophy and flatten. Lactose intolerance can persist after the eradication of Giardia from the digestive tract, person-to-person transmission accounts for the majority of Giardia infections and is usually associated with poor hygiene and sanitation. Giardia is found on the surface of the ground, in the soil, in undercooked foods, water-borne transmission is associated with the ingestion of contaminated water. In the U. S. outbreaks typically occur in water systems using inadequately treated surface water. Venereal transmission happens through fecal-oral contamination, additionally, diaper changing and inadequate hand washing are risk factors for transmission from infected children. Lastly, food-borne epidemics of Giardia have developed through the contamination of food by infected food-handlers, the CDC recommends hand-washing and avoiding potentially contaminated food and untreated water. Boiling suspect water for one minute is the surest method to make water safe to drink, chemical disinfectants or filters may be used. According to a review of the literature from 2000, there is evidence linking the drinking of water in the N. The researcher notes that treatment of drinking water for Giardia may not be as important as recommended hand-washing in wilderness regions in North America, CDC surveillance data reports one outbreak of waterborne giardiasis contracted from drinking wilderness river water in Colorado. However, less than 1% of reported cases are associated with outbreaks
Giardia
–
Giardia
Giardia
–
A
SEM micrograph of the
small intestine of a
gerbil infested with Giardia reveals a mucosa surface almost entirely obscured by attached
trophozoites
21.
Escherichia coli
–
Escherichia coli is a gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms. Most E. coli strains are harmless, but some serotypes can cause food poisoning in their hosts. The harmless strains are part of the flora of the gut, and can benefit their hosts by producing vitamin K2. E. coli is expelled into the environment within fecal matter, the bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly afterwards. E. coli and other facultative anaerobes constitute about 0. 1% of gut flora, cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination. A growing body of research, though, has examined environmentally persistent E. coli which can survive for extended periods outside of a host, the bacterium can be grown and cultured easily and inexpensively in a laboratory setting, and has been intensively investigated for over 60 years. E. coli is a chemoheterotroph whose chemically defined medium must include a source of carbon, under favorable conditions, it takes only 20 minutes to reproduce. E. coli is a Gram-negative, facultative anaerobic and nonsporulating bacterium, cells are typically rod-shaped, and are about 2.0 μm long and 0. 25–1.0 μm in diameter, with a cell volume of 0. 6–0.7 μm3. E. coli stains Gram-negative because its cell wall is composed of a peptidoglycan layer. During the staining process, E. coli picks up the color of the counterstain safranin, the outer membrane surrounding the cell wall provides a barrier to certain antibiotics such that E. coli is not damaged by penicillin. Strains that possess flagella are motile, the flagella have a peritrichous arrangement. E. coli can live on a variety of substrates and uses mixed-acid fermentation in anaerobic conditions, producing lactate, succinate, ethanol, acetate. Optimum growth of E. coli occurs at 37 °C, and it uses oxygen when it is present and available. It can, however, continue to grow in the absence of oxygen using fermentation or anaerobic respiration, the ability to continue growing in the absence of oxygen is an advantage to bacteria because their survival is increased in environments where water predominates. The bacterial cell cycle is divided into three stages, the B period occurs between the completion of cell division and the beginning of DNA replication. The C period encompasses the time it takes to replicate the chromosomal DNA, the D period refers to the stage between the conclusion of DNA replication and the end of cell division. The doubling rate of E. coli is higher when more nutrients are available, However, the length of the C and D periods do not change, even when the doubling time becomes less than the sum of the C and D periods. At the fastest growth rates, replication begins before the round of replication has completed, resulting in multiple replication forks along the DNA
Escherichia coli
–
Escherichia coli
22.
Vibrio cholerae
–
Vibrio cholerae is a Gram-negative, comma-shaped bacterium. The bacteriums natural habitat is brackish or saltwater, some strains of V. cholerae cause the disease cholera. V. cholerae is a facultative anaerobe and has a flagellum at one cell pole as well as pili, V. cholerae can undergo respiratory and fermentative metabolism. When ingested, V. cholerae can cause diarrhea and vomiting in a host within several hours to 2–3 days of ingestion, V. V. cholerae is Gram-negative and comma-shaped. Initial isolates are slightly curved, whereas they can appear as straight rods upon laboratory culturing, the bacterium has a flagellum at one cell pole as well as pili. V. cholerae is a facultative anaerobe, and can undergo respiratory, V. cholerae pathogenicity genes code for proteins directly or indirectly involved in the virulence of the bacteria. During infection, V. cholerae secretes cholera toxin, a protein that causes profuse, colonization of the small intestine also requires the toxin coregulated pilus, a thin, flexible, filamentous appendage on the surface of bacterial cells. V. cholerae can cause syndromes ranging from asymptomatic to cholera gravis, in endemic areas, 75% of cases are asymptomatic, 20% are mild to moderate, and 2-5% are severe forms such as cholera gravis. Symptoms include abrupt onset of diarrhea, occasional vomiting. Death due to dehydration can occur in a few hours to days in untreated children, the disease is also particularly dangerous for pregnant women and their fetuses during late pregnancy, as it may cause premature labor and fetal death. In cases of cholera gravis involving severe dehydration, up to 60% of patients can die, however, the disease typically lasts 4–6 days. In 2002, the WHO deemed that the case fatality ratio for cholera was about 3. 95%, V. cholerae has two circular chromosomes, together totalling 4 million base pairs of DNA sequence and 3,885 predicted genes. The genes for cholera toxin are carried by CTXphi, a temperate bacteriophage inserted into the V. cholerae genome, CTXφ can transmit cholera toxin genes from one V. cholerae strain to another, one form of horizontal gene transfer. The genes for toxin coregulated pilus are coded by the VPI pathogenicity island, the entire genome of the virulent strain V. cholerae El Tor N16961 has been sequenced, and contains two circular chromosomes. Chromosome 1 has 2,961,149 base pairs with 2,770 open reading frames, the larger first chromosome contains the crucial genes for toxicity, regulation of toxicity, and important cellular functions, such as transcription and translation. Also relevant in determining if the replicon is a chromosome is whether it represents a significant percentage of the genome, and, unlike plasmids, chromosomes are not self-transmissible. However, the chromosome may have once been a megaplasmid because it contains some genes usually found on plasmids. V. cholerae contains an island of pathogenicity and is lysogenized with phage DNA
Vibrio cholerae
–
Vibrio cholerae
Vibrio cholerae
–
Cholera
23.
Clostridium
–
They are obligate anaerobes capable of producing endospores. The normal, reproducing cells of Clostridium, called the form, are rod-shaped. Clostridium endospores have a bowling pin or bottle shape, distinguishing them from other bacterial endospores. Clostridium species inhabit soils and the tract of animals, including humans. Clostridium is a inhabitant of the healthy lower reproductive tract of women. Clostridium contains around 100 species that include common free-living bacteria, as well as important pathogens, the main species responsible for disease in humans are, Clostridium botulinum can produce botulinum toxin in food or wounds and can cause botulism. This same toxin is known as Botox and is used in surgery to paralyze facial muscles to reduce the signs of aging. Clostridium difficile can flourish when other gut flora bacteria are killed during antibiotic therapy, leading to superinfection, Clostridium perfringens causes a wide range of symptoms, from food poisoning to cellulitis, fasciitis, and gas gangrene. Clostridium sordellii can cause an infection in exceptionally rare cases after medical abortions. Bacillus and Clostridium are often described as gram-variable, because they show a number of gram-negative cells as the culture ages. Clostridium and Bacillus are both in the division Firmicutes, but they are in different classes, orders, and families, microbiologists distinguish Clostridium from Bacillus by the following features, Clostridium grows in anaerobic conditions, Bacillus grows in aerobic conditions. Clostridium forms bottle-shaped endospores, Bacillus forms oblong endospores, Clostridium does not form the enzyme catalase, Bacillus secretes catalase to destroy toxic byproducts of oxygen metabolism. Clostridium and Desulfotomaculum are both in the class Clostridia and order Clostridiales, and they both produce bottle-shaped endospores, but they are in different families, Clostridium can be distinguished from Desulfotomaculum on the basis of the nutrients each genus uses. Glycolysis and fermentation of pyruvic acid by Clostridia yield the end products butyric acid, butanol, acetone, isopropanol, the Schaeffer-Fulton stain can be used to distinguish endospores of Bacillus and Clostridium from other microorganisms. There is a commercially available polymerase chain reaction test kit for the detection of C. perfringens, in general, the treatment of clostridial infection is high-dose penicillin G, to which the organism has remained susceptible. Clostridium welchii and Clostridium tetani respond to sulfonamides, Clostridia are also susceptible to tetracyclines, carbapenems, metronidazole, vancomycin, and chloramphenicol. The vegetative cells of Clostridia are heat-labile and are killed by short heating at temperatures above 72–75 °C, the thermal destruction of Clostridium spores requires higher temperatures and longer cooking times. The addition of lysozyme, nitrate, nitrite and propionic acid salts inhibits Clostridia in various foods, in the late 1700s, Germany experienced a number of outbreaks of an illness that seemed connected to eating certain sausages
Clostridium
–
Clostridium
24.
Sterilization (microbiology)
–
Sterilization can be achieved through various means, including, heat, chemicals, irradiation, high pressure, and filtration. Sterilization is distinct from disinfection, sanitization, and pasteurization in that kills, deactivates, or eliminates all forms of life. Canning of foods is an extension of the principle, and has helped to reduce food borne illness. Other methods of sterilizing foods include food irradiation and high pressure, in general, surgical instruments and medications that enter an already aseptic part of the body must be sterile. Examples of such instruments include scalpels, hypodermic needles and artificial pacemakers and this is also essential in the manufacture of parenteral pharmaceuticals. Most medical and surgical devices used in healthcare facilities are made of materials that are able to go under steam sterilization, however, since 1950, there has been an increase in medical devices and instruments made of materials that require low-temperature sterilization. Ethylene oxide gas has been used since the 1950s for heat-, within the past 15 years, a number of new, low-temperature sterilization systems have been developed and are being used to sterilize medical devices. ]Steam sterilization is the most widely used and the most dependable. Steam sterilization is nontoxic, inexpensive, rapidly microbicidal, sporicidal, there are strict international rules to protect the contamination of Solar System bodies from biological material from Earth. Standards vary depending on both the type of mission and its destination, the more likely a planet is considered to be habitable, the aim of sterilization is the reduction of initially present microorganisms or other potential pathogens. The degree of sterilization is commonly expressed by multiples of the decimal reduction time, or D-value, then the number of microorganisms N after sterilization time t is given by, N N0 =10. The D-value is a function of sterilization conditions and varies with the type of microorganism, temperature, water activity, for steam sterilization typically the temperature is given as index. Theoretically, the likelihood of survival of an individual microorganism is never zero, to compensate for this, the overkill method is often used. Using the overkill method, sterilization is performed by sterilizing for longer than is required to kill the present on or in the item being sterilized. This provides a sterility assurance level equal to the probability of a non-sterile unit, for high-risk applications such as medical devices and injections, a sterility assurance level of at least 10−6 is required by the United States Food and Drug Administration. A widely used method for heat sterilization is the autoclave, sometimes called a converter or steam sterilizer, autoclaves use steam heated to 121-134 °C under pressure. To achieve sterility, the article is heated in a chamber by injected steam until the article reaches a time, meantime almost all the air is removed from the chamber, because air is undesired in the moist heat sterilization process. The article is then held at that setpoint for a period of time varies depending on the bioburden present on the article being sterilized. Following sterilization, liquids in a pressurized autoclave must be cooled slowly to avoid boiling over when the pressure is released and this may be achieved by gradually depressurizing the sterilization chamber and allowing liquids to evaporate under a negative pressure, while cooling the contents
Sterilization (microbiology)
–
Joseph Lister was a pioneer of
antiseptic surgery.
Sterilization (microbiology)
–
Apparatus to sterilize surgical instruments, Verwaltungsgebäude der Schweiz. Kranken- und Hilfsanstalt, 1914-1918
Sterilization (microbiology)
–
Front-loading autoclave
Sterilization (microbiology)
–
Dry heat sterilizer
25.
Thermometer
–
A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements, a sensor in which some physical change occurs with temperature. Thermometers are widely used in industry to control and regulate processes, in the study of weather, in medicine, there are various principles by which different thermometers operate. They include the expansion of solids or liquids with temperature. Radiation-type thermometers measure the energy emitted by an object, allowing measurement of temperature without contact. Most metals are good conductors of heat and they are solids at room temperature, Mercury is the only one in liquid state at room temperature, and has high coefficient of expansion. Hence, the slightest change in temperature is notable when its used in a thermometer and this is the reason behind mercury and alcohol being used in thermometer. Some of the principles of the thermometer were known to Greek philosophers of two years ago. The modern thermometer gradually evolved from the thermoscope with the addition of a scale in the early 17th century, while an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. Today there is a thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points, the most recent official temperature scale is the International Temperature Scale of 1990. It extends from 0.65 K to approximately 1,358 K, various authors have credited the invention of the thermometer to Hero of Alexandria. The thermometer was not an invention, however, but a development. The expansion and contraction of the air caused the position of the interface to move along the tube. Such a mechanism was used to show the hotness and coldness of the air with a tube in which the water level is controlled by the expansion and contraction of the gas. These devices were developed by several European scientists in the 16th and 17th centuries, as a result, devices were shown to produce this effect reliably, and the term thermoscope was adopted because it reflected the changes in sensible heat. The difference between a thermoscope and a thermometer is that the latter has a scale, though Galileo is often said to be the inventor of the thermometer, what he produced were thermoscopes. The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani and this was a vertical tube, closed by a bulb of air at the top, with the lower end opening into a vessel of water
Thermometer
–
Mercury thermometer for measurement of room temperature.
Thermometer
–
An infrared thermometer is a kind of
pyrometer (
bolometer).
Thermometer
–
Digital thermometer.
Thermometer
–
Various thermometers from the 19th century.
26.
Atmospheric pressure boiling point
–
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
Atmospheric pressure boiling point
–
Boiling water
27.
Pasta
–
Pasta is a staple food of traditional Italian cuisine, with the first reference dating to 1154 in Sicily. It can also be made with flour from other cereals or grains, pastas may be divided into two broad categories, dried and fresh. Most dried pasta is produced via an extrusion process although it can be produced in most homes. Both dried and fresh pasta come in a number of shapes and varieties, in Italy the names of specific pasta shapes or types often vary with locale. For example, the form cavatelli is known by 28 different names depending on region, common forms of pasta include long shapes, short shapes, tubes, flat shapes and sheets, miniature soup shapes, filled or stuffed and specialty or decorative shapes. As a category in Italian cuisine, both fresh and dried pastas are classically used in one of three kinds of prepared dishes, as pasta asciutta cooked pasta is plated and served with a complementary sauce or condiment. A second classification of pasta dishes is pasta in brodo in which the pasta is part of a soup-type dish, a third category is pasta al forno in which the pasta incorporated into a dish that is subsequently baked. Pasta is generally a dish, but comes in many varieties due to its versatility. Some pasta dishes are served as a first course in Italy because the portion sizes are small, Pasta is also prepared in light lunches, such as salads or large portion sizes for dinner. It can be prepared by hand or food processor and served hot or cold, Pasta sauces vary in taste, color and texture. When choosing which type of pasta and sauce to serve together, simple sauces like pesto are ideal for long and thin strands of pasta while tomato sauce combines well with thicker pastas. Thicker and chunkier sauces have the ability to cling onto the holes and cuts of short, tubular. The extra sauce left on the plate after all of the pasta is eaten is often mopped up with a piece of bread. First attested in English in 1874, the word comes from Italian pasta, in turn from Latin pasta dough, pastry cake. In the 1st century AD writings of Horace, lagana were fine sheets of fried dough and were an everyday foodstuff, an early 5th century cookbook describes a dish called lagana that consisted of layers of dough with meat stuffing, a possible ancestor of modern-day lasagna. The first concrete information concerning pasta products in Italy dates from the 13th or 14th century, historians have noted several lexical milestones relevant to pasta, none of which changes these basic characteristics. For example, the works of the 2nd century AD Greek physician Galen mention itrion, homogeneous compounds made of flour, the Jerusalem Talmud records that itrium, a kind of boiled dough, was common in Palestine from the 3rd to 5th centuries AD. A dictionary compiled by the 9th century Arab physician and lexicographer Isho bar Ali defines itriyya and its ever-flowing streams propel a number of mills
Pasta
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Different types of pasta on display in a shop window in
Venice, Italy
Pasta
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Pasta made from
durum wheat
Pasta
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Making pasta; illustration from the 15th century edition of
Tacuinum Sanitatis, a Latin translation of the
Arabic work Taqwīm al-sihha by
Ibn Butlan.
Pasta
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Boy with Spaghetti by Julius Moser, c. 1808
28.
Cooking
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Cooking or cookery is the art, technology and craft of preparing food for consumption with the use of heat. The ways or types of cooking also depend on the skill, cooking is done both by people in their own dwellings and by professional cooks and chefs in restaurants and other food establishments. Cooking can also occur through chemical reactions without the presence of heat, such as in ceviche, preparing food with heat or fire is an activity unique to humans. It may have started around 2 million years ago, though evidence for it reaches no more than 1 million years ago. The expansion of agriculture, commerce, trade and transportation between civilizations in different regions offered cooks many new ingredients, New inventions and technologies, such as the invention of pottery for holding and boiling water, expanded cooking techniques. Some modern cooks apply advanced scientific techniques to food preparation to further enhance the flavor of the dish served, phylogenetic analysis suggests that human ancestors may have invented cooking as far back as 1.8 million to 2.3 million years ago. Re-analysis of burnt bone fragments and plant ashes from the Wonderwerk Cave, there is evidence that Homo erectus was cooking their food as early as 500,000 years ago. Evidence for the use of fire by Homo erectus beginning some 400,000 years ago has wide scholarly support. Archeological evidence, from 300,000 years ago, in the form of ancient hearths, earth ovens, burnt animal bones, and flint, are found across Europe, anthropologists think that widespread cooking fires began about 250,000 years ago, when hearths started appearing. More recently, the earliest hearths have been reported to be at least 790,000 years old, in the seventeenth and eighteenth centuries, food was a classic marker of identity in Europe. In the nineteenth-century Age of Nationalism cuisine became a symbol of national identity. Communication between the Old World and the New World in the Colombian exchange influenced the history of cooking, the Industrial Revolution brought mass-production, mass-marketing and standardization of food. Factories processed, preserved, canned, and packaged a wide variety of foods, in the 1920s, freezing methods, cafeterias and fast-food establishments emerged. Along with changes in food, starting early in the 20th century, governments have issued nutrition guidelines, the 1916 Food For Young Children became the first USDA guide to give specific dietary guidelines. Updated in the 1920s, these guides gave shopping suggestions for different-sized families along with a Depression Era revision which included four cost levels, in 1943, the USDA created the Basic Seven chart to make sure that people got the recommended nutrients. It included the first-ever Recommended Daily Allowances from the National Academy of Sciences, in 1956, the Essentials of an Adequate Diet brought recommendations which cut the number of groups that American school children would learn about down to four. In 1979, a guide called Food addressed the link between too much of certain foods and chronic diseases, but added fats, oils, most ingredients in cooking are derived from living organisms. Vegetables, fruits, grains and nuts as well as herbs and spices come from plants, while meat, eggs, mushrooms and the yeast used in baking are kinds of fungi
Cooking
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A chef preparing steak
Cooking
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Historical oven cooking depicted in a painting by
Jean-François Millet
Cooking
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Doughnuts frying in oil
Cooking
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Water is often used to cook foods such as
noodles.
29.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
Water
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Water in three states: liquid, solid (
ice), and gas (invisible
water vapor in the air).
Clouds are accumulations of water droplets,
condensed from vapor-saturated air.
Water
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Impact from a water drop causes an upward "rebound" jet surrounded by circular
capillary waves.
Water
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Snowflakes by
Wilson Bentley, 1902.
Water
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Dew drops adhering to a
spider web.
30.
Stock (food)
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Stock is a flavored liquid preparation. It forms the basis of many dishes, particularly soups and sauces, making stocks involves simmering animal bones or meat, seafood, or vegetables in water or wine, adding mirepoix or other aromatics for more flavor. Traditionally, stock is made by simmering various ingredients in water, a newer approach is to use a pressure cooker. The ingredients may include some or all of the following, Meat Leftover cooked meat, quantities recommended are in the ratio of 1 part fresh meat to 2 parts water. Bones Veal, beef, and chicken bones are most commonly used, the flavour of the stock comes from the cartilage and connective tissue in the bones. Connective tissue has collagen in it, which converted into gelatin that thickens the liquid. Stock made from bones needs to be simmered for longer than stock made from meat, pressure cooking methods shorten the time necessary to extract the flavour from the bones. Mirepoix Mirepoix is a combination of onions, carrots, celery, often, the less desirable parts of the vegetables that may not otherwise be eaten are used. The use of parts is highly dependent upon the chef. Herbs and spices The herbs and spices used depend on availability, in classical cuisine, the use of a bouquet garni consisting of parsley, bay leaves, a sprig of thyme, and possibly other herbs, is common. This is often placed in a sachet to make it easier to remove once the stock is cooked, today, ready-made stock and stock cubes consisting of dried, compressed stock ingredients are readily available. These are commonly known as bouillon cubes, as cooking base in the US, or as Oxo cubes in Britain, the difference between broth and stock is one of both cultural and colloquial terminology but certain definitions prevail. Stock is the liquid produced by simmering raw ingredients, solids are removed and this yields classic stock as made from beef, veal, chicken, fish and vegetables. Broth differs in that it is a soup where the solid pieces of flavoring meat or fish, along with some vegetables. It is often made more substantial by adding starches such as rice, traditionally, broth contained some form of meat or fish, however, nowadays it is acceptable to refer to a strictly vegetable soup as a broth. Chicken stock is cooked for several hours. Fish stock is made with fish bones and finely chopped mirepoix, fish stock should be cooked for 20–25 minutes—cooking any longer spoils the flavour. Concentrated fish stock is called fish fumet, in Japanese cooking, a fish and kelp stock called dashi is made by briefly cooking skipjack tuna flakes called katsuobushi in nearly boiling water
Stock (food)
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Making stock in a pot on a
stove top.
Stock (food)
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Pouring
fish stock on a stuffed fish
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