1.
Cardiology
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Cardiology is a branch of medicine dealing with disorders of the heart as well as parts of the circulatory system. The field includes medical diagnosis and treatment of heart defects, coronary artery disease, heart failure, valvular heart disease. Physicians who specialize in this field of medicine are called cardiologists, pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in surgery are called cardiothoracic surgeons or cardiac surgeons. Although the cardiovascular system is linked to blood, cardiology is relatively unconcerned with hematology. Some obvious exceptions that affect the function of the heart would be blood tests, decreased oxygen carrying capacity, all cardiologists study the disorders of the heart, but the study of adult and child heart disorders are through different training pathways. Therefore, an adult cardiologist is inadequately trained to care of adults. The surgical aspects are not included in cardiology and are in the domain of cardiothoracic surgery, for example, coronary artery bypass surgery and cardiopulmonary bypass are both surgical procedures performed by surgeons, not cardiologists. However the insertion of stents, pacemakers and valves are performed by cardiologists, Cardiology is a specialty of internal medicine. To be a cardiologist in the United States, a residency in internal medicine is followed by a three-year fellowship in cardiology. It is possible to further in a sub-specialty. Recognized sub-specialties in the United States by the ACGME are cardiac electrophysiology, echocardiography, interventional cardiology, recognized subspecialties in the United States by the American Osteopathic Association Bureau of Osteopathic Specialists include clinical cardiac electrophysiology and interventional cardiology. Per doximity, adult cardiologists make an average of $436,849 in the United States, Cardiac electrophysiology is the science of elucidating, diagnosing, and treating the electrical activities of the heart. The term is used to describe studies of such phenomena by invasive catheter recording of spontaneous activity as well as of cardiac responses to programmed electrical stimulation. These studies are performed to assess complex arrhythmias, elucidate symptoms, evaluate abnormal electrocardiograms, assess risk of developing arrhythmias in the future and these procedures increasingly include therapeutic methods in addition to diagnostic and prognostic procedures. Other therapeutic modalities employed in this field include antiarrhythmic drug therapy and implantation of pacemakers, such studies may also be conducted in the presence of a newly implanted or newly replaced cardiac pacemaker or AICD. Clinical cardiac electrophysiology is a branch of the specialty of cardiology and is concerned with the study. Cardiologists with expertise in this area are referred to as electrophysiologists
2.
Inflammation
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The classical signs of inflammation are heat, pain, redness, swelling, and loss of function. Inflammation is a response, and therefore it is considered as a mechanism of innate immunity, as compared to adaptive immunity. Too little inflammation could lead to tissue destruction by the harmful stimulus. In contrast, chronic inflammation may lead to a host of diseases, such as hay fever, periodontitis, atherosclerosis, rheumatoid arthritis, Inflammation is therefore normally closely regulated by the body. Inflammation can be classified as acute or chronic. Acute inflammation is the response of the body to harmful stimuli and is achieved by the increased movement of plasma. A series of biochemical events propagates and matures the inflammatory response, involving the vascular system, the immune system. Inflammation is not a synonym for infection, Inflammation on the other hand describes purely the bodys immunovascular response, whatever the cause may be. But because of how often the two are correlated, words ending in the suffix -itis are sometimes described as referring to infection. There are also situations where microbial invasion does not result in classic inflammatory response—for example, parasitosis. Acute inflammation is a process, usually appearing within a few minutes or hours. It involves a coordinated and systemic mobilisation response locally of various immune, endocrine, in a normal healthy response, it becomes activated, clears the pathogen and begins a repair process and then ceases. It is characterized by five signs, An acronym that may be used to remember the key symptoms is PRISH, for pain, redness, immobility, swelling. Loss of function has multiple causes, Acute inflammation of the lung does not cause pain unless the inflammation involves the parietal pleura, which does have pain-sensitive nerve endings. PAMPs are compounds that are associated with pathogens, but which are distinguishable from host molecules. DAMPs are compounds that are associated with host-related injury and cell damage, at the onset of an infection, burn, or other injuries, these cells undergo activation and release inflammatory mediators responsible for the clinical signs of inflammation. Vasodilation and its resulting increased blood flow causes the redness and increased heat, increased permeability of the blood vessels results in an exudation of plasma proteins and fluid into the tissue, which manifests itself as swelling. Some of the released mediators such as increase the sensitivity to pain
3.
Endocardium
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The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the cells that line blood vessels. The endocardium also provides protection to the valves and heart chambers, the endocardium underlies the much more voluminous myocardium, the muscular tissue responsible for the contraction of the heart. The outer layer of the heart is termed epicardium and the heart is surrounded by an amount of fluid enclosed by a fibrous sac called the pericardium. The endocardium, which is made up of endothelial cells, controls myocardial function. This modulating role is separate from the homeometric and heterometric regulatory mechanisms that control myocardial contractility, moreover, the endothelium of the myocardial capillaries, which is also closely appositioned to the cardiomyocytes, is involved in this modulatory role. Thus, the cardiac endothelium controls the development of the heart in the embryo as well as in the adult, additionally, the contractility and electrophysiological environment of the cardiomyocyte are regulated by the cardiac endothelium. The endocardial endothelium may also act as a kind of blood–heart barrier, in myocardial infarction, ischemia of the myocardium can extend to the endocardium, disrupting the inner lining of the heart. Less extensive infarctions are often subendocardial and do not affect the epicardium, in the acute setting, subendocardial infarctions are more dangerous than transmural infarctions because they create an area of dead tissue surrounded by a boundary region of damaged myocytes. This damaged region will conduct impulses more slowly, resulting in irregular rhythms, the damaged region may enlarge or extend and become more life-threatening. During depolarization the impulse is carried from endocardium to epicardium, in infective endocarditis, the endocardium is affected by bacteria
4.
Heart valve
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A heart valve normally allows blood to flow in only one direction through the heart. The four valves commonly represented in a mammalian heart determine the pathway of blood flow through the heart, a heart valve opens or closes incumbent on differential blood pressure on each side. The four main valves in the heart are, The two atrioventricular valves, the valve, and the tricuspid valve, which are between the upper chambers and the lower chambers. The two semilunar valves, the valve and the pulmonary valve, which are in the arteries leaving the heart. The mitral valve and the valve are in the left heart, the tricuspid valve. There are also the coronary sinus and the inferior vena cava valves, the heart valves and the chambers are lined with endocardium. Heart valves separate the atria from the ventricles, or the ventricles from a blood vessel, heart valves are situated around the fibrous rings of the cardiac skeleton. The valves incorporate leaflets or cusps, which are pushed open to allow blood flow, the mitral valve has two cusps, whereas the others have three. There are nodules at the tips of the cusps that make the seal tighter, the pulmonary valve has left, right, and anterior cusps. The aortic valve has left, right, and posterior cusps, the tricuspid valve has anterior, posterior, and septal cusps, and the mitral valve has just anterior and posterior cusps. These are the mitral and tricuspid valves, which are situated between the atria and the ventricles and prevent backflow from the ventricles into the atria during systole and they are anchored to the walls of the ventricles by chordae tendineae, which prevent the valves from inverting. The chordae tendineae are attached to muscles that cause tension to better hold the valve. Together, the muscles and the chordae tendineae are known as the subvalvular apparatus. The function of the apparatus is to keep the valves from prolapsing into the atria when they close. The subvalvular apparatus has no effect on the opening and closure of the valves, however, the peculiar insertion of chords on the leaflet free margin, however, provides systolic stress sharing between chords according to their different thickness. The closure of the AV valves is heard as lub, the first heart sound, the closure of the SL valves is heard as dub, the second heart sound. The mitral valve is called the bicuspid valve because it contains two leaflets or cusps. The mitral valve gets its name from the resemblance to a bishops mitre and it is on the left side of the heart and allows the blood to flow from the left atrium into the left ventricle
5.
Platelet
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Platelets, also called thrombocytes, are a component of blood whose function is to stop bleeding by clumping and clotting blood vessel injuries. Platelets have no nucleus, they are fragments of cytoplasm that are derived from the megakaryocytes of the bone marrow. These unactivated platelets are biconvex discoid structures, 2–3 µm in greatest diameter, platelets are found only in mammals, whereas in other animals thrombocytes circulate as intact mononuclear cells. On a stained blood smear, platelets appear as purple spots. The smear is used to examine platelets for size, shape, qualitative number, the ratio of platelets to red blood cells in a healthy adult is 1,10 to 1,20. The main function of platelets is to contribute to hemostasis, the process of stopping bleeding at the site of interrupted endothelium and they gather at the site and unless the interruption is physically too large, they plug the hole. First, platelets attach to substances outside the interrupted endothelium, adhesion, second, they change shape, turn on receptors and secrete chemical messengers, activation. Third, they connect to each other through receptor bridges, aggregation, formation of this platelet plug is associated with activation of the coagulation cascade with resultant fibrin deposition and linking. These processes may overlap, the spectrum is from a predominantly platelet plug, or white clot to a predominantly fibrin clot, the final result is the clot. Some would add the subsequent clot retraction and platelet inhibition as fourth and fifth steps to the completion of the process, low platelet concentration is thrombocytopenia and is due to either decreased production or increased destruction. Elevated platelet concentration is thrombocytosis and is either congenital, reactive, or due to unregulated production, a disorder of platelet function is a thrombocytopathy. An arterial thrombus may partially obstruct blood flow, causing downstream ischemia, or may completely obstruct it, george Gulliver in 1841 drew pictures of platelets using the twin lens microscope invented in 1830 by Joseph Jackson Lister. This microscope improved resolution sufficiently to make it possible to see platelets for the first time, william Addison in 1842 drew pictures of a platelet-fibrin clot. Lionel Beale in 1864 was the first to publish a drawing showing platelets, max Schultze in 1865 described what he called spherules, which he noted were much smaller than red blood cells, occasionally clumped, and were sometimes found in collections of fibrin material. Queens College, Birmingham physician Dr Richard Hill Norris was the first to describe the action of platelets in 1880, giulio Bizzozero in 1882 studied the blood of amphibians microscopically in vivo. He named Schultzs spherules piastrine, little plates, william Osler observed them and, in published lectures in 1886, called them a third corpuscle and a blood plaque and described them as a colorless protoplasmic disc. Thrombocytes are cells found in the blood of non-mammalian vertebrates and they are the functional equivalents of platelets, but circulate as intact mononuclear cells, and are not simply cytoplasmic fragments of bone marrow megakaryocytes. In some contexts, the thrombus is used interchangeably with the word clot
6.
Fibrin
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Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen which causes it to polymerize, the polymerized fibrin together with platelets forms a hemostatic plug or clot over a wound site. When the lining of a vessel is broken, platelets are attracted forming a platelet plug. These platelets have thrombin receptors on their surfaces that bind serum thrombin molecules which in turn convert soluble fibrinogen in the serum into fibrin at the wound site, Fibrin forms long strands of tough insoluble protein that are bound to the platelets. Factor XIII completes the cross-linking of fibrin so that it hardens, the cross-linked fibrin forms a mesh atop the platelet plug that completes the clot. Ineffective generation or premature lysis of fibrin increases the likelihood of a hemorrhage, dysfunction or disease of the liver can lead to a decrease in the production of fibrins inactive precursor, fibrinogen, or to the production of abnormal fibrinogen molecules with reduced activity. Hereditary abnormalities of fibrinogen are both quantitative and qualitative in nature and include afibrinogenaemia, hypofibrinogenaemia, dysfibrinogenaemia, and hypodysfibrinogenaemia, reduced, absent, or dysfunctional fibrin is likely to render patients as hemophiliacs. Fibrin from different animal sources is generally glycosylated with complex type biantennary asparagine linked glycans, variety is found in the degree of core fucosylation and in the type of sialic acid and galactose linkage. The image at the left is a structure of the double-d fragment from human fibrin with two bound ligands. The experimental method used to obtain the image was X-ray diffraction, the structure is mainly made up of single alpha helices shown in red and beta sheets shown in yellow. The two blue structures are the bound ligands, the chemical structures of the ligands are Ca2+ ion, alpha-D-mannose, and D-glucosamine. D-dimer Fibrin glue Fibrin scaffold Fibrinolysis TGW1916. net, Defibrinated blood harvested from sheep Fibrin, Molecule of the Month, by David Goodsell, RCSB Protein Data Bank
7.
Microorganism
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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
8.
Hemodialysis
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Hemodialysis, also spelled haemodialysis, commonly called kidney dialysis or simply dialysis, is a process of purifying the blood of a person whose kidneys are not working normally. This type of dialysis achieves the extracorporeal removal of waste such as creatinine and urea. Hemodialysis is one of three renal replacement therapies, an alternative method for extracorporeal separation of blood components such as plasma or cells is apheresis. Hemodialysis can be an outpatient or inpatient therapy, routine hemodialysis is conducted in a dialysis outpatient facility, either a purpose built room in a hospital or a dedicated, stand-alone clinic. Less frequently hemodialysis is done at home, Hemodialysis is the choice of renal replacement therapy for patient who need dialysis acutely, and for many patients as maintenance therapy. It provides excellent, rapid clearance of solutes, a nephrologist decides when hemodialysis is needed and the various parameters for a dialysis treatment. These include frequency, length of treatment, and the blood and dialysis solution flow rates. The composition of the solution is also sometimes adjusted in terms of its sodium and potassium. In general, the larger the size of an individual. In North America and the UK, 3-4 hour treatments given 3 times a week are typical, twice-a-week sessions are limited to patients who have a substantial residual kidney function. Four sessions per week are often prescribed for patients, as well as patients who have trouble with fluid overload. Finally, there is growing interest in short daily home hemodialysis, there is also interest in nocturnal dialysis, which involves dialyzing a patient, usually at home, for 8–10 hours per night, 3-6 nights per week. Nocturnal in-center dialysis, 3-4 times per week, is offered at a handful of dialysis units in the United States. Side effects caused by removing too much fluid and/or removing fluid too rapidly include low blood pressure, fatigue, chest pains, leg-cramps, nausea and headaches. These symptoms can occur during the treatment and can persist post treatment, the severity of these symptoms is usually proportionate to the amount and speed of fluid removal. However, the impact of an amount or rate of fluid removal can vary greatly from person to person. The risk of infection varies depending on the type of access used, bleeding may also occur, again the risk varies depending on the type of access used. Infections can be minimized by strictly adhering to infection control best practices, heparin is the most commonly used anticoagulant in hemodialysis, as it is generally well tolerated and can be quickly reversed with protamine sulfate
9.
Drug injection
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Drug injection is a method of introducing a drug into the bloodstream via a hollow hypodermic needle and a syringe, which is pierced through the skin into the body. It often applies to substance dependence and recreational drug use and this act is often colloquially referred to as slamming, shooting, banging, pinning, or jacking-up, often depending on the specific drug subculture in which the term is used. Although there are methods of taking drugs, injection is favoured by some users as the full effects of the drug are experienced very quickly, typically in five to ten seconds. This shorter, more intense high can lead to a dependency—both physical, as of 2004, there were 13.2 million people worldwide who used injection drugs, of which 22% are from developed countries. This means that the drug will have a strong and rapid onset. With some drugs, this can produce sensations not found with other routes of administration, more efficient usage — A smaller amount is enough as injection means that more of the drug will reach the brain than with other methods. This is because the defenses and detoxifying mechanisms are bypassed. This means that it requires less drug to achieve the same effect, abscessed infections of injection sites are caused by lack of hygiene and a lack of aseptic technique. Increased chance of overdose — Because IV injection delivers a dose of drug straight into the bloodstream, in addition, because of the rapid onset of intravenous drugs, overdose can occur very quickly, requiring immediate action. Scarring of the peripheral veins — This arises from the use of blunt injecting equipment and this is particularly common with users who have been injecting while in jail and re-use disposable syringes sometimes hundreds of times. IV drug use for an extended period may result in collapsed veins, though rotating sites and allowing time to heal before reuse may decrease the likelihood of this occurring, collapse of peripheral veins may still occur with prolonged IV drug use. IV drug users are among the most difficult patient populations to obtain blood-specimens from because of peripheral venous scarring, the darkening of the veins due to scarring and toxin buildup produce tracks along the length of the veins and are known as track marks. Arterial damage — Arterial pseudoaneurysms may form at sites, which can rupture, potentially resulting in hemorrhage, distal ischemia. Inadvertent intra-arterial injection can also result in endarteritis and thrombosis, with similar consequences. Increased chance of addiction — The heightened effect of administering drugs intravenously can make the chances of more likely. Social stigma — In many societies, there is a stigma attached to IV drug use, in addition to the more general stigma around illegal drug use. The drug—usually in a powder or crystal form—is dissolved in water, normally in a spoon, tin, bottle cap, cylindrical metal containers—sometimes called cookers—are provided by needle exchange programs. Users draw the required amount of water into a syringe and squirt this over the drugs, the solution is then mixed and heated from below if necessary
10.
Streptococcus
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Streptococcus is a genus of coccus Gram-positive bacteria belonging to the phylum Firmicutes and the order Lactobacillales. Cell division in this genus occurs along an axis in these bacteria, thus they grow in chains or pairs, hence the name—from Greek στρεπτός streptos, meaning easily bent or twisted. Most are oxidase-negative and catalase-negative, and many are facultative anaerobes, in 1984, many bacteria formerly considered Streptococcus were separated out into the genera Enterococcus and Lactococcus. Currently, over 50 species are recognised in this genus, however, many streptococcal species are not pathogenic, and form part of the commensal human microbiota of the mouth, skin, intestine, and upper respiratory tract. Furthermore, streptococci are an ingredient in producing Emmentaler cheese. Species of Streptococcus are classified based on their hemolytic properties, alpha-hemolytic species cause oxidization of iron in hemoglobin molecules within red blood cells, giving it a greenish color on blood agar. Beta-hemolytic species cause complete rupture of red blood cells, on blood agar, this appears as wide areas clear of blood cells surrounding bacterial colonies. Beta-hemolytic streptococci are further classified by Lancefield grouping, a serotype classification, the 20 described serotypes are named Lancefield groups A to V. In the medical setting, the most important groups are the alpha-hemolytic streptococci S. pneumoniae and Streptococcus viridans group, table, Medically relevant streptococci When alpha hemolysis is present, the agar under the colony is dark and greenish. Streptococcus pneumoniae and a group of oral streptococci display alpha hemolysis and this is sometimes called green hemolysis because of the color change in the agar. Other synonymous terms are incomplete hemolysis and partial hemolysis, alpha hemolysis is caused by hydrogen peroxide produced by the bacterium, oxidizing hemoglobin to green methemoglobin. S. pneumoniae, is a cause of bacterial pneumonia and occasional etiology of otitis media, sinusitis, meningitis. Inflammation is thought to be the cause of how pneumococci cause disease. The viridans streptococci are a group of commensal bacteria, that are either α-hemolytic, producing a green coloration on blood agar plates. Beta hemolysis, sometimes called complete hemolysis, is a complete lysis of red cells in the media around and under the colonies, streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells. SLS affects immune cells, including polymorphonuclear leukocytes and lymphocytes, and is thought to prevent the host immune system from clearing infection, Streptococcus pyogenes, or group A Streptococcus, displays beta hemolysis. Some weakly beta-hemolytic species cause intense beta hemolysis when grown together with a strain of Staphylococcus and this is called the CAMP test. Clostridium perfringens can be identified presumptively with this test, Listeria monocytogenes is also positive on sheeps blood agar
11.
Staphylococcus
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Staphylococcus is a genus of Gram-positive bacteria. Under the microscope, they appear round, and form in grape-like clusters, the Staphylococcus genus includes at least 40 species. Of these, nine have two subspecies, one has three subspecies, and one has four subspecies, most are harmless and reside normally on the skin and mucous membranes of humans and other organisms. Found worldwide, they are a component of soil microbial flora. Succinus As with all names in binomial nomenclature, Staphylococcus is capitalized when used alone or with a specific species. Also, the abbreviations Staph and S. when used with a species are correctly italicized and capitalized, however, Staphylococcus is not capitalized or italicized when used in adjectival forms, as in a staphylococcal infection, or as the informal plural. The S. saprophyticus and S. sciuri groups are generally novobiocin-resistant, members of the S. sciuri group are oxidase-positive due to their possession of the enzyme cytochrome c oxidase. This group is the only clade within the staphylococci to possess this gene, the S. sciuri group appears to be the closest relations to the genus Macrococcus. S. pulvereri has been shown to be a synonym of S. vitulinus. Within these clades, the S. haemolyticus and S. simulans groups appear to be related, as do the S. aureus, S. lugdunensis appears to be related to the S. haemolyticus group. S. petrasii may be related to S. haemolyticus, the taxonomic position of S. lyticans, S. pettenkoferi, S. petrasii, and S. pseudolugdunensis has yet to be clarified. The published descriptions of species do not appear to have been validly published. Staphylococcus species can be differentiated from other aerobic and facultative anaerobic, all species grow in the presence of bile salts. All species were thought to be coagulase-positive, but this has since been disproven. Growth can also occur in a 6. 5% NaCl solution, on Baird Parker medium, Staphylococcus species grow fermentatively, except for S. saprophyticus, which grows oxidatively. Staphylococcus species are resistant to bacitracin and susceptible to furazolidone, further biochemical testing is needed to identify to the species level. When these bacteria divide, they do so along two axes, so form clumps of bacteria and this is as opposed to streptococci, which divide along one axis, so form chains. One of the most important phenotypical features used in the classification of staphylococci is their ability to produce coagulase, six species are currently recognised as being coagulase-positive, S. aureus, S. delphini, S. hyicus, S. intermedius, S. lutrae, S
12.
Ultrasound
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Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from normal sound in its physical properties and this limit varies from person to person and is approximately 20 kilohertz in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz, Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances, Ultrasound imaging or sonography is often used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws, industrially, ultrasound is used for cleaning, mixing, and to accelerate chemical processes. Animals such as bats and porpoises use ultrasound for locating prey, scientist are also studying ultrasound using graphene diaphragms as a method of communication. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. The first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917, the piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. Ultrasound is defined by the American National Standards Institute as sound at frequencies greater than 20 kHz, in air at atmospheric pressure ultrasonic waves have wavelengths of 1.9 cm or less. The upper frequency limit in humans is due to limitations of the middle ear, auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear. Children can hear some high-pitched sounds that older adults cannot hear, the Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people. Bats use a variety of ultrasonic ranging techniques to detect their prey and they can detect frequencies beyond 100 kHz, possibly up to 200 kHz. Many insects have good hearing and most of these are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids, upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger an action in the noctuid moth that cause it to drop slightly in its flight to evade attack. Tiger moths also emit clicks which may disturb bats echolocation, dogs and cats hearing range extends into the ultrasound, the top end of a dogs hearing range is about 45 kHz, while a cats is 64 kHz. The wild ancestors of cats and dogs evolved this higher hearing range to hear sounds made by their preferred prey. A dog whistle is a whistle that emits ultrasound, used for training and calling dogs, porpoises have the highest known upper hearing limit, at around 160 kHz
13.
Antibiotics
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Antibiotics, also called antibacterials, are a type of antimicrobial drug used in the treatment and prevention of bacterial infections. They may either kill or inhibit the growth of bacteria, a limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the cold or influenza. Drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics, sometimes the term antibiotic is used to refer to any substance used against microbes, synonymous with antimicrobial. Some sources distinguish between antibacterial and antibiotic, antibacterials are used in soaps and disinfectants, while antibiotics are used as medicine, Antibiotics revolutionized medicine in the 20th century, and have together with vaccination led to the near eradication of diseases such as tuberculosis in the developed world. However, their effectiveness and easy access led to overuse, especially in raising, prompting bacteria to develop resistance. All classes of antibiotics in use today were first discovered prior to the mid 1980s, substances with antibiotic properties had been used for various purposes since ancient times. Before the early 20th century, treatments for infections were based primarily on medicinal folklore, mixtures with antimicrobial properties that were used in treatments of infections were described over 2000 years ago. Many ancient cultures, including the ancient Egyptians and ancient Greeks, used specially selected mold and plant materials, more recent observations made in the laboratory of antibiosis between microorganisms led to the discovery of natural antibacterials produced by microorganisms. Louis Pasteur observed, if we could intervene in the antagonism observed between some bacteria, it would offer perhaps the greatest hopes for therapeutics. In 1874, physician Sir William Roberts noted that cultures of the mold Penicillium glaucum that is used in the making of types of blue cheese did not display bacterial contamination. In 1876, physicist John Tyndall also contributed to this field, Louis Pasteur conducted research showing that Bacillus anthracis would not grow in the presence of the related mold Penicillium notatum. In his thesis, Duchesne proposed that bacteria and molds engage in a battle for survival. Duchesne observed that E. coli was eliminated by the fungus Penicillium glaucum when they were grown in the same culture. He also observed that when he inoculated animals with lethal doses of typhoid bacilli together with Penicillium glaucum. Unfortunately Duchesnes army service after getting his degree prevented him from doing any further research, Duchesne died of tuberculosis, a disease now treated by antibiotics. In 1928, Sir Alexander Fleming identified penicillin, a molecule produced by molds that kills or stops the growth of certain kinds of bacteria. Fleming was working on a culture of disease-causing bacteria when he noticed the spores of a mold, Penicillium chrysogenum
