Salter Science was a brand of science kits sold by Thomas Salter Ltd. a Scotland-based company which manufactured toys and science activity kits for children. Kits included activities with electricity, microscopy and crystal gardens, but the company is best known for their chemistry sets; the company produced other toys related to TV series such as'KOJAK' ACTION SET and produced Crafts Plaster Moulding Set's Frog & Owl. Thomas Salter Ltd. was founded in London in 1913, moved to Glenrothes and closed in 1992. Chemistry sets from Salter Science included a various number of chemicals, which were numbered, so that the numbers were the same across the sets; some of the chemicals included were: Copper Sulfate Sodium Carbonate Calcium Oxychloride Iron Filings Calcium Hydroxide Sodium Hydrogen Sulfate Tartaric Acid Methyl Orange Ferrous Sulfate Ammonium Carbonate Magnesium Ribbon Copper Wire Ammonium Chloride Sodium Thiosulfate Sodium Perborate Cobalt Chloride Also included were small glass test tubes, a spatula, a funnel, corks, a small bottle brush and a test tube rack.
Larger sets included a methylated spirit burner for heating
The lymphatic vessels are thin-walled vessels structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessels are lined by endothelial cells, have a thin layer of smooth muscle, adventitia that bind the lymph vessels to the surrounding tissue. Lymph vessels are devoted to the propulsion of the lymph from the lymph capillaries, which are concerned with absorption of interstitial fluid from the tissues. Lymph capillaries are larger than their counterpart capillaries of the vascular system. Lymph vessels that carry lymph to a lymph node are called afferent lymph vessels, those that carry it from a lymph node are called efferent lymph vessels, from where the lymph may travel to another lymph node, may be returned to a vein, or may travel to a larger lymph duct. Lymph ducts drain the lymph into one of the subclavian veins and thus return it to general circulation. Lymph flows away from the tissues to lymph nodes and to either the right lymphatic duct or the largest lymph vessel in the body, the thoracic duct.
These vessels left subclavian veins respectively. The general structure of lymphatics is based on that of blood vessels. There is an inner lining of single flattened epithelial cells composed of a type of epithelium, called endothelium, the cells are called endothelial cells; this layer functions to mechanically transport fluid and since the basement membrane on which it rests is discontinuous. The next layer is that of smooth muscles that are arranged in a circular fashion around the endothelium, which by shortening or relaxing alter the diameter of the lumen; the outermost layer is the adventitia. The general structure described here is seen only in larger lymphatics; the smallest vessels lack both the outer adventitia. As they proceed forward and in their course are joined by other capillaries, they grow larger and first take on an adventitia, smooth muscles; the lymphatic conducting system broadly consists of two types of channels—the initial lymphatics, the prelymphatics or lymph capillaries that specialize in collection of the lymph from the ISF, the larger lymph vessels that propel the lymph forward.
Unlike the cardiovascular system, the lymphatic system has no central pump. Lymph movement occurs despite low pressure due to peristalsis and compression during contraction of adjacent skeletal muscle and arterial pulsation; the lymphatic circulation begins with blind ending permeable superficial lymph capillaries, formed by endothelial cells with button-like junctions between them that allow fluid to pass through them when the interstitial pressure is sufficiently high. These button-like junctions consist of protein filaments like platelet endothelial cell adhesion molecule-1, or PECAM-1. A valve system in place here prevents the absorbed lymph from leaking back into the ISF. There is another system of semilunar valves that prevents back-flow of lymph along the lumen of the vessel. Lymph capillaries have many interconnections between them and form a fine network. Rhythmic contraction of the vessel walls through movements may help draw fluid into the smallest lymphatic vessels, capillaries. If tissue fluid builds up the tissue will swell.
As the circular path through the body's system continues, the fluid is transported to progressively larger lymphatic vessels culminating in the right lymphatic duct and the thoracic duct. The system collaborates with white blood cells in lymph nodes to protect the body from being infected by cancer cells, viruses or bacteria; this is known as a secondary circulatory system. The lymph capillaries drain the lymph to larger contractile lymphatics, which have valves as well as smooth muscle walls; these are called the collecting lymphatics. As the collecting lymph vessel accumulates lymph from more and more lymph capillaries in its course, it becomes larger and is called the afferent lymph vessel as it enters a lymph node. Here the lymph is removed by the efferent lymph vessel. An efferent lymph vessel may directly drain into one of the lymph ducts, or may empty into another lymph node as its afferent lymph vessel. Both the lymph ducts return the lymph to the blood stream by emptying into the subclavian veins The functional unit of a lymph vessel is known as a lymphangion, the segment between two valves.
Since it is contractile, depending upon the ratio of its length to its radius, it can act either like a contractile chamber propelling the fluid ahead, or as a resistance vessel tending to stop the lymph in its place. Lymph vessels act as reservoirs for plasma and other substances including cells that have leaked from the vascular system and transport lymph fluid back from the tissues to the circulatory system. Without functioning lymph vessels, lymph cannot be drained and edema results; the afferent lymph vessels enter at all parts of the periphery of the lymph node, after branching and forming a dense plexus in the substance of the capsule, open into the lymph sinuses of the cortical part. It carries unfiltered lymph into the node. In doing this th
Dental plaque is a biofilm or mass of bacteria that grows on surfaces within the mouth. It is a sticky colorless deposit at first, but when it forms tartar, it is brown or pale yellow, it is found between the teeth, on the front of teeth, behind teeth, on chewing surfaces, along the gumline, or below the gumline cervical margins. Dental plaque is known as microbial plaque, oral biofilm, dental biofilm, dental plaque biofilm or bacterial plaque biofilm. Bacterial plaque is one of the major causes for dental gum disease. Progression and build-up of dental plaque can give rise to tooth decay – the localised destruction of the tissues of the tooth by acid produced from the bacterial degradation of fermentable sugar – and periodontal problems such as gingivitis and periodontitis. Plaque control and removal can be achieved with correct daily or twice-daily tooth brushing and use of interdental aids such as dental floss and interdental brushes. Oral hygiene is important as dental biofilms may become acidic causing demineralization of the teeth or harden into dental calculus.
Calculus cannot be removed through tooth brushing or with interdental aids, but only through professional cleaning. Dental plaque is a biofilm that attaches to tooth surfaces and prosthetic appliances if left undisturbed. Understanding the formation and characteristics of plaque helps in its control. An acquired pellicle is a layer of saliva, composed of glycoproteins and forms shortly after cleaning of the teeth or exposure of new teeth. Bacteria attach to the pellicle layer, form micro-colonies, mature on the tooth, which can result in oral diseases; the following table provides a more detailed explanation of biofilm formation: Different types of bacteria are present in the mouth. These bacteria, as well as leukocytes, neutrophils and lymphocytes, are part of the normal oral cavity and contribute to the individual's health. 80–90% of the weight of plaque is water. While 70% of the dry weight is bacteria, the remaining 30% consists of polysaccharides and glycoproteins; the bulk of the microorganisms that form the biofilm are Streptococcus mutans and other anaerobes, though the precise composition varies by location in the mouth.
Examples of such anaerobes include actinobacteria. S. mutans and other anaerobes are the initial colonisers of the tooth surface, play a major role in the establishment of the early biofilm community. These microorganisms all occur present in the oral cavity and are harmless. However, failure to remove plaque by regular tooth-brushing allows them to proliferate unchecked and thereby build up in a thick layer, which can by virtue of their ordinary metabolism cause any of various dental diseases for the host; those microorganisms nearest the tooth surface obtain energy by fermenting dietary sucrose. The bacterial equilibrium position varies at different stages of formation. Below is a summary of the bacteria that may be present during the phases of plaque maturation: Early biofilm: Gram-positive cocci Older biofilm: increased numbers of filaments and fusiforms 4–9 days undisturbed: more complex flora with rods, filamentous forms 7–14 days: Vibrio species, more Gram-negative organisms Dental plaque is considered a biofilm adhered to the tooth surface.
It is a meticulously formed microbial community, organised to a particular structure and function. Plaque is rich in species, given the fact that about 1000 different bacterial species have been recognised using modern techniques. A clean tooth surface would be colonised by salivary pellicles, which acts as an adhesive; this allows the first bacteria to attach to the tooth colonise and grow. After some growth of early colonisers, the biofilm becomes more compliant to other species of bacteria, known as late colonisers. Streptococcus species Eikenella spp. Haemophilus spp. Prevotella spp. Priopionibacterium spp. Capnocytophaga spp. Veil- lonella spp. A. actino- mycetemcomitans Prevotella intermedia Eubacterium spp. Treponema spp. Porphyromonas gingivalis. Fusobacterium nucleatum is found between the late colonisers, linking them together; some salivary components are crucial for plaques ecosystem, such as salivary alpha-amylase which plays a role in binding and adhesion. Proline-rich rich proteins and statherins are involved in the formation of plaque.
Supragingival biofilm is dental plaque that forms above the gums, is the first kind of plaque to form after the brushing of the teeth. It forms in between the teeth, in the pits and grooves of the teeth and along the gums, it is made up of aerobic bacteria, meaning these bacteria need oxygen to survive. If plaque remains on the tooth for a longer period of time, anaerobic bacteria begin to grow in this plaque. Subgingival biofilm is plaque, located under the gums, it occurs after the formation of the supragingival biofilm by a downward growth of the bacteria from above the gums to below. This plaque is made up of anaerobic bacteria, meaning that these bacteria will only survive if there is no oxygen; as this plaque attaches in a pocket under the gums, they are not exposed to oxygen in the mouth and will therefore thrive if not removed. The extracellular matrix contains long-chain polysaccharides and lipids; the most common reasons for ecosystem disruption are the ecological factors discussed in the environment section.
The bacteria that exhibit the most fit plasticity for the cha
Ullmann's Encyclopedia of Industrial Chemistry
Ullmann's Encyclopedia of Industrial Chemistry is a reference work related to industrial chemistry published in English and German. As of 2016 it is in its 7th edition; the first edition was published in German by Fritz Ullmann in 1914. The 4th Edition, published 1972 to 1984 contained 25 volumes; the fifth edition, published 1985 to 1996, was the first version available in English. In 1997, the first online version was available, updated at least every other month; as of 2016, Ullmann's Encyclopedia is in 40 volumes including one index volume. While PDF versions of individual chapters used to be available for purchase from the Wiley Online Library, as of at least 9/2018, it appears that Wiley has restricted access to the online version only to institutional users. Therefore, it is no longer possible to purchase individual chapters through the Wiley Online Library. For individuals or small companies, the only option is to purchase the entire hardcopy 40-volume set for $11,150. Industrial chemistry is the study of chemistry with a higher mathematics and physics education for critical processes engineering and maintenance.
The industrial chemist strengthens the association of new materials investigation and manufacturing development, amid research chemistry and chemical engineering, through innovative intelligence and quality management. Subject areas include "inorganic and organic chemicals, pharmaceuticals and plastics, metals and alloys and biotechnological products, food chemistry, process engineering and unit operations, analytical methods, environmental protection and others"; as of 2016, Barbara Elvers is Editor-in-Chief and the editorial board consists of 17 editors, all but 3 of them from Germany
Sentinel lymph node
The sentinel lymph node is the hypothetical first lymph node or group of nodes draining a cancer. In case of established cancerous dissemination it is postulated that the sentinel lymph node/s is/are the target organs reached by metastasizing cancer cells from the tumor; the sentinel node procedure is the identification and analysis of the sentinel lymph nodes of a particular tumour. The spread of some forms of cancer follows an orderly progression, spreading first to regional lymph nodes the next echelon of lymph nodes, so on, since the flow of lymph is directional, meaning that some cancers spread in a predictable fashion from where the cancer started. In these cases, if the cancer spreads it will spread first to lymph nodes close to the tumor before it spreads to other parts of the body; the concept of sentinel lymph node surgery is to determine if the cancer has spread to the first draining lymph node or not. If the sentinel lymph node does not contain cancer there is a high likelihood that the cancer has not spread to any other area of the body.
The concept of the sentinel lymph node is important because of the advent of the sentinel lymph node biopsy technique known as a sentinel node procedure. This technique is used in the staging of certain types of cancer to see if they have spread to any lymph nodes, since lymph node metastasis is one of the most important prognostic signs, it can guide the surgeon to the appropriate therapy. There are various procedures entailing the sentinel node detection: Preoperative planar lymphoscintigraphy Preoperative planar lymphoscintigraphy in conjunction with SPECT/CT Intraoperative visual blue dye detection Intraoperative fluorescence detection Intraoperative gamma probe/Geiger meter-detection Preoperative or intraoperative super paramagnetic iron oxide nanoparticles injection, detection by using Sentimag® instrument Postoperative scintigraphy of main specimen with planar acquisitionIn everyday clinical activity, entailing sentinel node detection and sentinel lymph node biopsy, it is not required to include all different techniques listed above.
In skilled hands and in a center with sound routines, two or three of the listed methods can be considered sufficient. To perform a sentinel lymph node biopsy, the physician performs a lymphoscintigraphy, wherein a low-activity radioactive substance is injected near the tumor; the injected substance, filtered sulfur colloid, is tagged with the radionuclide technetium-99m. The injection protocols differ by doctor but the most common is a 500 μCi dose divided among 5 tuberculin syringes with 1/2 inch, 24 gauge needles. In the UK 20 megabecquerels of nanocolloid is recommended; the sulphur colloid is acidic and causes minor stinging. A gentle massage of the injection sites spreads the sulphur colloid, relieving the pain and speeding up the lymph uptake. Scintigraphic imaging is started within 5 minutes of injection and the node appears from 5 min to 1 hour; this is done several hours before the actual biopsy. About 15 minutes before the biopsy the physician injects a blue dye in the same manner. During the biopsy, the physician visually inspects the lymph nodes for staining and uses a gamma probe or a Geiger counter to assess which lymph nodes have taken up the radionuclide.
One or several nodes may take up the dye and radioactive tracer, these nodes are designated the sentinel lymph nodes. The surgeon removes these lymph nodes and sends them to a pathologist for rapid examination under a microscope to look for the presence of cancer. A frozen section procedure is employed, so if neoplasia is detected in the lymph node a further lymph node dissection may be performed. With malignant melanoma, many pathologists eschew frozen sections for more accurate "permanent" specimen preparation due to the increased instances of false-negative with melanocytic staining. There are various advantages to the sentinel node procedure. First and foremost, it decreases lymph node dissections where unnecessary, thereby reducing the risk of lymphedema, a common complication of this procedure. Increased attention on the node identified to most contain metastasis is more to detect micro-metastasis and result in staging and treatment changes, its main uses are in breast cancer and malignant melanoma surgery, although it has been used in other tumor types with a degree of success.
Other cancers which have been investigated with this technique are penile cancer, urinary bladder cancer, prostate cancer, testicular cancer and renal cell cancer. As a bridge to translational medicine, various aspects of cancer dissemination can be studied using sentinel node detection and ensuing sentinel node biopsy. Tumor biology pertaining to metastatic capacity, mechanisms of dissemination, the EMT-MET-process and cancer immunology are some subjects which can be more distinctly investigated. However, the technique is not without drawbacks when used for melanoma patients; this technique only has therapeutic value in patients with positive nodes. Failure to detect cancer cells in the sentinel node can lead to a false negative result—there may still be cancerous cells in the lymph node basin. In addition, there is no compelling evidence that patients who have a full lymph node dissection as a result of a positive sentinel lymph node result have improved survival compared to those who do not have a full dissection until in their disease, when the lymph nodes can be felt by a physician.
Such patients may be having an unnecessary full dissection, with the attendant risk of lym
A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH of the solution can be determined visually. Hence, a pH indicator is a chemical detector for hydronium ions or hydrogen ions in the Arrhenius model; the indicator causes the color of the solution to change depending on the pH. Indicators can show change in other physical properties; the pH value of a neutral solution is 7.0 at 25°C. Solutions with a pH value below 7.0 are considered acidic and solutions with pH value above 7.0 are basic. As most occurring organic compounds are weak protolytes, carboxylic acids and amines, pH indicators find many applications in biology and analytical chemistry. Moreover, pH indicators form one of the three main types of indicator compounds used in chemical analysis. For the quantitative analysis of metal cations, the use of complexometric indicators is preferred, whereas the third compound class, the redox indicators, are used in titrations involving a redox reaction as the basis of the analysis.
In and of themselves, pH indicators are weak acids or weak bases. The general reaction scheme of a pH indicator can be formulated as: HInd + H2O ⇌ H3O+ + Ind−Here, HInd stands for the acid form and Ind− for the conjugate base of the indicator; the ratio of these connects the color to the pH value. PH indicators that are weak protolytes, the Henderson–Hasselbalch equation for them can be written as: pH = pKa + log10 / The equation, derived from the acidity constant, states that when pH equals the pKa value of the indicator, both species are present in a 1:1 ratio. If pH is above the pKa value, the concentration of the conjugate base is greater than the concentration of the acid, the color associated with the conjugate base dominates. If pH is below the pKa value, the converse is true; the color change is not instantaneous at the pKa value, but a pH range exists where a mixture of colors is present. This pH range varies between indicators, but as a rule of thumb, it falls between the pKa value plus or minus one.
This assumes that solutions retain their color as long as at least 10% of the other species persists. For example, if the concentration of the conjugate base is 10 times greater than the concentration of the acid, their ratio is 10:1, the pH is pKa + 1. Conversely, if a 10-fold excess of the acid occurs with respect to the base, the ratio is 1:10 and the pH is pKa − 1. For optimal accuracy, the color difference between the two species should be as clear as possible, the narrower the pH range of the color change the better. In some indicators, such as phenolphthalein, one of the species is colorless, whereas in other indicators, such as methyl red, both species confer a color. While pH indicators work efficiently at their designated pH range, they are destroyed at the extreme ends of the pH scale due to undesired side reactions. PH indicators are employed in titrations in analytical chemistry and biology to determine the extent of a chemical reaction; because of the subjective choice of color, pH indicators are susceptible to imprecise readings.
For applications requiring precise measurement of pH, a pH meter is used. Sometimes, a blend of different indicators is used to achieve several smooth color changes over a wide range of pH values; these commercial indicators are used. Tabulated below are several common laboratory pH indicators. Indicators exhibit intermediate colors at pH values inside the listed transition range. For example, phenol red exhibits an orange color between pH 6.8 and pH 8.4. The transition range may shift depending on the concentration of the indicator in the solution and on the temperature at which it is used; the figure on the right shows indicators with color changes. An indicator may be used to obtain quite precise measurements of pH by measuring absorbance quantitatively at two or more wavelengths; the principle can be illustrated by taking the indicator to be a simple acid, HA, which dissociates into H+ and A−. HA ⇌ H + + A − The value of pKa, must be known; the molar absorbances, εHA and εA− of the two species HA and A− at wavelengths λx and λy must have been determined by previous experiment.
Assuming Beer's law to be obeyed, the measured absorbances Ax and Ay at the two wavelengths are the sum of the absorbances due to each species. A x = ε HA x + ε A − x A y = ε HA y + ε A − y. Once solved, the pH is obtained as p H = p
Disclosing tablets are chewable tablets used to make dental plaque visible. The tablets, sold over the counter in many countries, contain a dye that stains plaque a bright color. After brushing, one rinses. Colored stains on the teeth indicate areas where plaque remains after brushing, providing feedback to improve brushing technique. For self-examination, a dental mirror may be needed. More sophisticated varieties contain several dyes. With the most common variety, immature plaque stains red, mature purple, pathological acidic plaque blue; this is owing to the blue dye washing off immature plaque, acid degrading the red dye. An example of a dye with a patented use as a "Dental Plaque Disclosing Agent" is Erythrosine