Fast ion conductor
In materials science, fast ion conductors are solids with mobile ions. These materials are important in the area of solid-state ionics, are known as solid electrolytes and superionic conductors; these materials are useful in various sensors. Fast ion conductors are used in solid oxide fuel cells; as solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure. Fast ion conductors are intermediate in nature between crystalline solids which possess a regular structure with immobile ions, liquid electrolytes which have no regular structure and mobile ions. Solid electrolytes find use in all solid-state supercapacitors and fuel cells, in various kinds of chemical sensors. In solid electrolytes, the ionic conductivity Ωi can be any value, but it should be much larger than the electronic one. Solids where Ωi is on the order of 0.0001 to 0.1 Ohm−1 cm−1 are called superionic conductors.
Proton conductors are a special class of solid electrolytes, where hydrogen ions act as charge carriers. Unlike conventional solid electrolytes and superionic conductors. Superionic conductors where Ωi is more than 0.1 Ohm−1 cm−1 and the activation energy for ion transport Ei is small, are called advanced superionic conductors. The most famous example of advanced superionic conductor-solid electrolyte is RbAg4I5 where Ωi > 0.25 Ohm−1 cm−1 and Ωe ~10−9 Ohm−1 cm−1 at 300 K. The Hall ionic mobility in RbAg4I5 is about 2×10−4 cm2/ at room temperatures; the Ωe – Ωi systematic diagram distinguishing the different types of solid-state ionic conductors is given in the figure. No clear examples have been described as yet, of fast ion conductors in the hypothetical advanced superionic conductors class. However, in crystal structure of several superionic conductors, e.g. in the minerals of the pearceite-polybasite group, the large structural fragments with activation energy of ion transport Ei < kBT had been discovered in 2006.
A common solid electrolyte is yttria-stabilized zirconia, YSZ. This material is prepared by doping Y2O3 into ZrO2. Oxide ions migrate only in solid Y2O3 and in ZrO2, but in YSZ, the conductivity of oxide increases dramatically; these materials are used to allow oxygen to move through the solid in certain kinds of fuel cells. Zirconium dioxide can be doped with calcium oxide to give an oxide conductor, used in oxygen sensors in automobile controls. Upon doping only a few percent, the diffusion constant of oxide increases by a factor of ~1000. Other conductive ceramics function as ion conductors. One example is NASICON, a sodium super-ionic conductor Another example of a popular fast ion conductor is beta-alumina solid electrolyte. Unlike the usual forms of alumina, this modification has a layered structure with open galleries separated by pillars. Sodium ions migrate through this material since the oxide framework provides an ionophilic, non-reducible medium; this material is considered as the sodium ion conductor for the sodium–sulfur battery.
Lanthanum trifluoride is conductive for F− ions, used in some ion selective electrodes. Beta-lead fluoride exhibits a continuous growth of conductivity on heating; this property was first discovered by Michael Faraday. A textbook example of a fast ion conductor is silver iodide. Upon heating the solid to 146 °C, this material adopts the alpha-polymorph. In this form, the iodide ions form a rigid cubic framework, the Ag+ centers are molten; the electrical conductivity of the solid increases by 4000x. Similar behavior is observed for copper iodide, rubidium silver iodide, Ag2HgI4. Silver sulfide, conductive for Ag+ ions, used in some ion selective electrodes Lead chloride, conductive at higher temperatures Some perovskite ceramics – strontium titanate, strontium stannate – conductive for O2− ions Zr 2 ⋅ n H 2 O – conductive for H+ ions UO 2 HPO 4 ⋅ 4 H 2 O – conductive for H+ ions Cerium oxide – conductive for O2− ions Many gels, such polyacrylamides, etc. are fast ion conductors A salt dissolved in a polymer – e.g. lithium perchlorate in polyethylene oxide Polyelectrolytes and Ionomers – e.g. Nafion, a H+ conductor The important case of fast ionic conduction is one in a surface space-charge layer of ionic crystals.
Such conduction was first predicted by Kurt Lehovec. As a space-charge layer has nanometer thickness, the effect is directly related to nanoionics. Lehovec's effect is used as a basis for developing nanomaterials for portable lithium batteries and fuel cells. Mixed conductor
A rain gutter, eavestrough or surface water collection channel is a component of water discharge system for a building. Water from a pitched roof flows down into a parapet gutter or an eaves gutter. An eaves gutter is known as an eavestrough, eaves channel, guttering, rainspouting or as a gutter; the word gutter derives from Latin gutta, meaning "a drop, spot or mark". Guttering in its earliest form consisted of lined wooden or stone troughs. Lead is still used in pitched valley gutters. Many materials have been used to make guttering: cast iron, asbestos cement, UPVC, cast and extruded aluminium, galvanized steel, copper and bamboo. Gutters prevent water ingress into the fabric of the building by channelling the rainwater away from the exterior of the walls and their foundations. Water running down the walls causes dampness in the affected rooms and provides a favourable environment for growth of mould, wet rot in timber. A rain gutter may be a: Roof integral trough along the lower edge of the roof slope, fashioned from the roof covering and flashing materials.
Discrete trough of metal, or other material, suspended beyond the roof edge and below the projected slope of the roof. Wall integral structure beneath the roof edge, traditionally constructed of masonry, fashioned as the crowning element of a wall. A roof must be designed with a suitable fall to allow the rainwater to discharge; the water drains into a gutter, fed into a downpipe. A flat roof will have a watertight surface with a fall of 1 in the case of lead, they can drain internally or to an eaves gutter, which has a minimum 1 in 360 fall towards the downpipe. The pitch of a pitched roof is determined by the construction material of the covering. For slate this will be at 25%, for machine made tiles it will be 35%. Water falls towards a valley gutter or an eaves gutter; when two pitched roofs meet at an angle, they form a pitched valley gutter: the join is sealed with valley flashing. Parapet gutters and valley gutters discharge into internal rainwater pipes or directly into external down pipes at the end of the run.
The capacity of the gutter is a significant design consideration. The area of the roof is calculated and this is multiplied by rainfall, assumed to be 0.0208. This gives a required discharge outfall capacity.. Rainfall intensity, the amount of water to generated in a two-minute rainstorm is more important that average rainfall, the British Standards Institute notes that an indicative storm in Essex, delivers 0.022 l/s/m²- while one in Cumbria delivers 0.014 l/s/m². Eaves gutters can be made from a variety of materials such as cast iron, zinc, galvanised steel, painted steel, painted aluminium, PVC and from concrete and wood. Water collected by a rain gutter is fed via a downpipe, from the roof edge to the base of the building where it is either discharged or collected; the down pipe can terminate in a shoe and discharge directly onto the surface, but using modern construction techniques would be connected through an inspection chamber to a drain that led to a surface water drain or soakaway.
Alternatively it would connect via a gulley with 50mm water seal to a combined drain. Water from rain gutters may be harvested in a cistern. Rain gutters can be equipped with gutter screens, micro mesh screens, louvers or solid hoods to allow water from the roof to flow through, while reducing passage of roof debris into the gutter. Clogged gutters can cause water ingress into the building as the water backs up. Clogged gutters can lead to stagnant water build up which in some climates allows mosquitoes to breed; the Romans brought rainwater systems to Britain. The technology was re-introduced by the Normans; the White Tower, at the Tower of London had external gutters. In March 1240 the Keeper of the Works at the Tower of London was ordered by King Henry "to have the Great Tower whitened both inside and out"; this was according to the fashion at the time. That year the king wrote to the Keeper, commanding that the White Tower's lead guttering should be extended with the effect that "the wall of the tower... newly whitened, may be in no danger of perishing or falling outwards through the trickling of the rain".
In Saxon times, the thanes erected buildings with large overhanging roofs to throw the water clear of the walls in the same way that occurs in thatched cottages. The cathedral builder used lead parapet gutters, with elaborate gargoyles for the same purpose. With the dissolution of the monasteries- those buildings were recycled and there was plenty of lead that could be used for secular building; the yeoman would lead lined wooden gutters. When The Crystal Palace was designed in 1851 by Joseph Paxton with its innovative ridge-and-furrow roof, the rafters that spanned the space between the roof girders of the glass roof served as the gutters; the wooden Paxton gutters had a deep semi-circular channel to remove the rainwater and grooves at the side to handle the condensation. They were under trussed with an iron plate and had preformed notches for the glazing bars: they drained into a wooden box gutter that drained into and through structural cast iron columns; the industrial revolution introduced new methods of casting-iron and the railways brought a method of distributing the heavy cast-iron items to building sites.
The relocation into the cities created a demand for housing. Dryer houses
The Underground Railroad was a network of secret routes and safe houses established in the United States during the early to mid-19th century, used by African-American slaves to escape into free states and Nova Scotia with the aid of abolitionists and allies who were sympathetic to their cause. The term is applied to the abolitionists, both black and white and enslaved, who aided the fugitives. Various other routes led to Mexico or overseas. An earlier escape route running south toward Florida a Spanish possession, existed from the late 17th century until Florida became a United States territory in 1821. However, the network now known as the Underground Railroad was formed in the late 1700s, it ran north to the free states and Canada, reached its height between 1850 and 1860. One estimate suggests that by 1850, 100,000 slaves had escaped via the "Railroad". British North America, where slavery was prohibited, was a popular destination, as its long border gave many points of access. Most former slaves settled in Ontario.
More than 30,000 people were said to have escaped there via the network during its 20-year peak period, although U. S. Census figures account for only 6,000. Numerous fugitives' stories are documented in the 1872 book The Underground Railroad Records by William Still, an abolitionist who headed the Philadelphia Vigilance Committee. At its peak, nearly 1,000 slaves per year escaped from slave-holding states using the Underground Railroad – more than 5,000 court cases for escaped slaves were recorded – many fewer than the natural increase of the enslaved population; the resulting economic impact was minuscule, but the psychological influence on slave holders was immense. Under the original Fugitive Slave Act of 1793, officials from free states were required to assist slaveholders or their agents who recaptured runaway slaves, but and governments of many free states ignored the law, the Underground Railroad thrived. With heavy lobbying by southern politicians, the Compromise of 1850 was passed by Congress after the Mexican–American War.
It stipulated a more stringent Fugitive Slave Law. Because the law required sparse documentation to claim a person was a fugitive, slave catchers kidnapped free blacks children, sold them into slavery. Southern politicians exaggerated the number of escaped slaves and blamed these escapes on Northerners interfering with Southern property rights; the law deprived suspected slaves of the right to defend themselves in court, making it difficult to prove free status. In a de facto bribe, judges were paid a higher fee for a decision that confirmed a suspect as a slave than for one ruling that the suspect was free. Many Northerners who might have ignored slave issues in the South were confronted by local challenges that bound them to support slavery; this was a primary grievance cited by the Union during the American Civil War, the perception that Northern States ignored the fugitive slave law was a major justification for secession. The escape network was not underground nor a railroad, it was figuratively "underground" in the sense of being an underground resistance.
It was known as a "railroad" by way of the use of rail terminology in the code. The Underground Railroad consisted of meeting points, secret routes and safe houses, personal assistance provided by abolitionist sympathizers. Participants organized in small, independent groups. Escaped slaves would move north along the route from one way station to the next. "Conductors" on the railroad came from various backgrounds and included free-born blacks, white abolitionists, former slaves, Native Americans. Church clergy and congregations played a role the Religious Society of Friends, Congregationalists and Reformed Presbyterians, as well as certain sects of mainstream denominations such as branches of the Methodist church and American Baptists. Without the presence and support of free black residents, there would have been no chance for fugitive slaves to pass into freedom unmolested. To reduce the risk of infiltration, many people associated with the Underground Railroad knew only their part of the operation and not of the whole scheme.
"Conductors" transported the fugitives from station to station. A conductor sometimes pretended to be a slave. Once a part of a plantation, the conductor would direct the runaways to the North. Slaves traveled at about 10 -- 20 miles to each station, they rested, a message was sent to the next station to let the station master know the runaways were on their way. They would stop at the so-called "stations" or "depots" during the rest; the stations were located in barns, under church floors, or in hiding places in caves and hollowed-out riverbanks. The resting spots where the runaways could sleep and eat were given the code names "stations" and "depots", which were held by "station masters". "Stockholders" gave money or supplies for assistance. Using biblical references, fugitives referred to Canada as the "Promised Land" or "Heaven" and the Ohio River as the "River Jordan", which marked the boundary between slave states and free states. Although the fugitives sometimes traveled on boat or train, they traveled
Electrical conduction system of the heart
The electrical conduction system of the heart transmits signals generated by the sinoatrial node to cause contraction of the heart muscle. The pacemaking signal generated in the sinoatrial node travels through the right atrium to the atrioventricular node, along the Bundle of His and through bundle branches to cause contraction of the heart muscle; this signal stimulates contraction first of the right and left atrium, the right and left ventricles. This process allows blood to be pumped throughout the body; the conduction system consists of specialised heart muscle cells, is situated within the myocardium. There is a skeleton of fibrous tissue that surrounds the conduction system which can be seen on an ECG. Dysfunction of the conduction system can slow heart rhythms. Electrical signals arising in the SA node stimulate the atria to contract; the signals travel to the atrioventricular node, located in the interatrial septum. After a delay, the electrical signal diverges and is conducted through the left and right bundle of His to the respective Purkinje fibers for each side of the heart, as well as to the endocardium at the apex of the heart finally to the ventricular epicardium.
These signals are generated rhythmically, which in turn results in the coordinated rhythmic contraction and relaxation of the heart. On the microscopic level, the wave of depolarization propagates to adjacent cells via gap junctions located on the intercalated disc; the heart is a functional syncytium. In a functional syncytium, electrical impulses propagate between cells in every direction, so that the myocardium functions as a single contractile unit; this property allows synchronous depolarization of the myocardium. While advantageous under normal circumstances, this property can be detrimental, as it has potential to allow the propagation of incorrect electrical signals; these gap junctions can close to isolate damaged or dying tissue, as in a myocardial infarction. Embryologic evidence of generation of the cardiac conduction system illuminates the respective roles of this specialized set of cells. Innervation of the heart begins with a brain only centered parasympathetic cholinergic first order.
It is followed by rapid growth of a second order sympathetic adrenergic system arising from the formation of the thoracic spinal ganglia. The third order of electrical influence of the heart is derived from the vagus nerve as the other peripheral organs form. Cardiac muscle has some similarities to neurons and skeletal muscle, as well as important unique properties. Like a neuron, a given myocardial cell has a negative membrane potential when at rest. Stimulation above a threshold value induces the opening of voltage-gated ion channels and a flood of cations into the cell; the positively charged ions entering the cell cause the depolarization characteristic of an action potential. Like skeletal muscle, depolarization causes the opening of voltage-gated calcium channels and release of Ca2+ from the t-tubules; this influx of calcium causes calcium-induced calcium release from the sarcoplasmic reticulum, free Ca2+ causes muscle contraction. After a delay, potassium channels reopen, the resulting flow of K+ out of the cell causes repolarization to the resting state.
There are important physiological differences between nodal cells and ventricular cells. In order to maximize efficiency of contractions and cardiac output, the conduction system of the heart has: Substantial atrial to ventricular delay; this will allow the atria to empty their contents into the ventricles. The atria are electrically isolated from the ventricles, connected only via the AV node which delays the signal. Coordinated contraction of ventricular cells; the ventricles must maximize systolic pressure to force blood through the circulation, so all the ventricular cells must work together. Ventricular contraction begins at the apex of the heart, progressing upwards to eject blood into the great arteries. Contraction that squeezes blood towards the exit is more efficient than a simple squeeze from all directions. Although the ventricular stimulus originates from the AV node in the wall separating the atria and ventricles, the Bundle of His conducts the signal to the apex. Depolarization propagates through cardiac muscle rapidly.
Cells of the ventricles contract nearly simultaneously. The action potentials of cardiac muscle are unusually sustained; this prevents premature relaxation, maintaining initial contraction until the entire myocardium has had time to depolarize and contract. Absence of tetany. After contracting, the heart must relax to fill up again. Sustained contraction of the heart without relaxation would be fatal, this is prevented by a temporary inactivation of certain ion channels. An electrocardiogram is a recording of the electrical activity of the heart. Under normal conditions, electrical activity is spontaneously generated by the SA node, the cardiac pacemaker; this electrical impulse is propagated throughout the right atrium, through Bachmann's bundle to the left atrium, stimulating the myocardium of the atria to contract. The conduction of the electrical impulses throughout the atria is seen on the ECG as the P wave; as the electrical activity is spreading throughout the atria, it travels via specialized pa
Shining Time Station
Shining Time Station is an American children's television series jointly created by British television producer Britt Allcroft and American television producer Rick Siggelkow. The series was produced by The Britt Allcroft Company and Quality Family Entertainment in New York City for New York City's PBS station WNET, was taped in New York City during its first season and in Toronto during the rest of its run, it incorporated sequences from the British television show Thomas & Friends, in turn based on a series of books, written by the Reverend Wilbert Awdry. The series aired on PBS from January 29, 1989 until June 11, 1993, continued on the network in reruns until June 11, 1998, it aired on Fox Family from 1998 to 1999. It aired on Nick Jr. in 2000 and on Canadian television networks such as APTN and SCN. Elements from the show were incorporated into the Thomas and Friends film Thomas and the Magic Railroad. After the success of Thomas & Friends in the United Kingdom, Britt Allcroft and her production company teamed up with PBS station WNET in New York City to produce and distribute the sitcom-esque Shining Time Station, every episode of which would include a couple of episodes of Thomas & Friends.
The series starred Ringo Starr, George Carlin, Didi Conn, Brian O'Connor, The Flexitoon Puppets. Ringo Starr, providing the voice of the storyteller for the British series, agreed to extend the role to include the on-screen character called Mr. Conductor in Shining Time Station, he left the show and was replaced by George Carlin. Shining Time Station received critical acclaim. In a review for Entertainment Weekly, Ken Tucker states that, compared to the faster paced Where in the World Is Carmen Sandiego?, "'Shining Time Station' wants to slow things down. It's an old-fashioned show that creates a gentle, lulling atmosphere to convince children that life is fun and that trains are the way to travel." It was a ratings success as well. In its first season, the show averaged a 0.9 Nielsen rating, translating to about 1.2 million viewers on average. At the peak of its popularity, the show brought in up to 7.5 million viewers per week. The Shining Time Station is a train station on the Indian Valley Railroad in an unknown part of the United States of America.
It is managed by Stacy Jones. Its workshop is run in the first season by Harry Cupper, thereafter by Billy Twofeathers. A local named Horace Schemer referred to as Schemer, runs the station's arcade and serves as the series's comic relief; the narrative is driven by incidental visitors to the station. Mr. Conductor is a tiny man who lives in a signal house inside the station's mural and tells the stories taken from Thomas & Friends to the kids, he introduces songs to the kids in The Anything Tunnel. Sometimes, he may present a magic bubble to the kids that has the song inside as a way of introducing it. On occasion, the kids may look through a film viewer to see the film. Didi Conn – Stacy Jones Brian O'Connor – Horace Schemer Ringo Starr – Mr. Conductor Leonard Jackson – Henry "Harry" Cupper Jason Woliner – Matthew "Matt" Jones Nicole Leach – Tanya Cupper Ringo Starr – Mr. Conductor Didi Conn – Stacy Jones Brian O'Connor – Horace Schemer Jason Woliner – Matthew "Matt" Jones Nicole Leach – Tanya Cupper Ardon Bess – Tucker Cooper Lloyd Bridges – Mr. Nicholas Judy Marshak – Claire Rachel Miner – Vickie George Carlin – Mr. Conductor Erica Luttrell – Kara Cupper Ari Magder – Daniel "Dan" Jones Danielle Marcot – Becky Tom Jackson – Billy Twofeathers Jerome Dempsey - Mayor Osgood Bob Flopdinger Mart Hulswit - Mr. J.
B. King, Esq. Bobo Lewis - Midge Smoot Jason Woliner – Matthew "Matt" Jones Nicole Leach – Tanya Cupper Jonathan Shapiro – Schemee Gerard Parkes – Barton Winslow Barbara Hamilton – Ginny Johnson Aurelio Padrón – Felix Perez George Carlin – Mr. Conductor's Evil Twin George Carlin – Mr. Conductor Didi Conn – Stacy Jones Tom Jackson – Billy Twofeathers Erica Luttrell – Kara Cupper Danielle Marcot – Becky Brian Edward O'Connor – Horace Schemer Barbara Hamilton – Ginny Johnson Bobo Lewis – Midge Smoot Jerome Dempsey – Mayor Osgood Bob Flopdinger Mart Hulswit – Mr. J. B. King, Esq. Bucky Hill – Kit Twofeathers Ari Magder – Daniel "Dan" Jones Jonathan Shapiro – Schemee Aurelio Pardón – Felix Perez Leonard Jackson – Henry "Harry" Cupper Teri Garr – Sister Conductor Jeannette Charles – The Queen Jonathan Freeman – Tito Swing The Piano Man Olga Marin – Didi The Drummer Wayne White – Tex The Guitarist Alan Semok – Tex The Guitarist Craig Marin – Rex The Guitarist Peter Baird/Alan Semok/Vaneese Thomas – Grace The Bass Player Peter Baird/Kenny Miele – Grace The Bass Player Their songs were produced and arranged by Steve Horelick and co-arranged by Larry Wolf.
The intro to each episode consists of the main theme song of the show, played to various footage of Union Pacific 844 and beginning credits of the recurring characters. Only the first verse is sung for the beginning theme; the closing credits contain more shots of the 844 and the credits, in addition to the full Shining Time Station theme song. Flexitoons Puppets & Marionettes - The Jukebox Band - the show's station band that performs a song inside the jukebox, they consist of pianist Tito Swing, drummer Didi, guitarists Tex and Rex, bass guitarist Grace Bass. JJ Silvers is the manager of The Jukebox Band. Thomas the Tank Engine & Friends - Storytellers, Ringo Starr and George Carlin The Anything Tu
The thermal conductivity of a material is a measure of its ability to conduct heat. It is denoted by k, λ, or κ. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals have high thermal conductivity and are efficient at conducting heat, while the opposite is true for insulating materials like Styrofoam. Correspondingly, materials of high thermal conductivity are used in heat sink applications and materials of low thermal conductivity are used as thermal insulation; the reciprocal of thermal conductivity is called thermal resistivity. The defining equation for thermal conductivity is q = − k ∇ T, where q is the heat flux, k is the thermal conductivity, ∇ T is the temperature gradient; this is known as Fourier's Law for heat conduction. Although expressed as a scalar, the most general form of thermal conductivity is a second-rank tensor. However, the tensorial description only becomes necessary in materials.
Consider a solid material placed between two environments of different temperatures. Let T 1 be the temperature at x = 0 and T 2 be the temperature at x = L, suppose T 2 > T 1. A possible realization of this scenario is a building on a cold winter day: the solid material in this case would be the building wall, separating the cold outdoor environment from the warm indoor environment. According to the second law of thermodynamics, heat will flow from the hot environment to the cold one in an attempt to equalize the temperature difference; this is quantified in terms of a heat flux q, which gives the rate, per unit area, at which heat flows in a given direction. In many materials, q is observed to be directly proportional to the temperature difference and inversely proportional to the separation: q = − k ⋅ T 2 − T 1 L; the constant of proportionality k is the thermal conductivity. In the present scenario, since T 2 > T 1 heat flows in the minus x-direction and q is negative, which in turn means that k > 0.
In general, k is always defined to be positive. The same definition of k can be extended to gases and liquids, provided other modes of energy transport, such as convection and radiation, are eliminated. For simplicity, we have assumed here that the k does not vary as temperature is varied from T 1 to T 2. Cases in which the temperature variation of k is non-negligible must be addressed using the more general definition of k discussed below. Thermal conduction is defined as the transport of energy due to random molecular motion across a temperature gradient, it is distinguished from energy transport by convection and molecular work in that it does not involve macroscopic flows or work-performing internal stresses. Energy flow due to thermal conduction is classified as heat and is quantified by the vector q, which gives the heat flux at position r and time t. According to the second law of thermodynamics, heat flows from high to low temperature. Hence, it reasonable to postulate that q is proportional to the gradient of the temperature field T, i.e. q = − k ∇ T, where the constant of proportionality, k > 0, is the thermal conductivity.
This is called Fourier's law of heat conduction. In actuality, it is not a law but a definition of thermal conductivity in terms of the independent physical quantities q and T; as such, its usefulness depends on the ability to determine k for a given material under given conditions. Note that k