Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography, projectional radiography, fluoroscopy. Radiocontrast agents are iodine, barium-sulphate or gadolinium based compounds, they absorb external X-rays. This is different from radiopharmaceuticals used in nuclear medicine. Magnetic resonance imaging functions through different principles and thus utilizes different contrast agents; these compounds work by altering the magnetic properties of nearby hydrogen nuclei. Radiocontrast agents used in X-ray examinations can be grouped based on its use. Iodinated contrast contains iodine, it is the main type of radiocontrast used for intravenous administration. Its uses include: Contrast CTs Angiography Venography VCUG HSG IVU Organic iodine molecules used for contrast include iohexol and ioversol. Barium sulfate is used in the imaging of the digestive system; the substance exists as a water-insoluble white powder, made into a slurry with water and administered directly into the gastrointestinal tract.
Barium enema and DCBE Barium swallow Barium meal and double contrast barium meal Barium follow through CT pneumocolon / virtual colonoscopyBarium sulfate, an insoluble white powder is used for enhancing contrast in the GI tract. Depending on how it is to be administered the compound is mixed with water, thickeners, de-clumping agents, flavourings to make the contrast agent; as the barium sulfate doesn't dissolve, this type of contrast agent is an opaque white mixture. It is only used in the digestive tract. After the examination, it leaves the body with the feces; as in the picture on the right where both air and barium are used together air can be used as a contrast material because it is less radio-opaque than the tissues it is defining. In the picture it highlights the interior of the colon. An example of a technique using purely air for the contrast medium is an air arthrogram where the injection of air into a joint cavity allows the cartilage covering the ends of the bones to be visualized.
Before the advent of modern neuroimaging techniques, air or other gases were used as contrast agents employed to displace the cerebrospinal fluid in the brain while performing a pneumoencephalography. Sometimes called an "air study", this once common yet highly-unpleasant procedure was used to enhance the outline of structures in the brain, looking for shape distortions caused by the presence of lesions. Carbon dioxide has a role in angiography, it is low-risk. However, it can be used only below the diaphragm as there is a risk of embolism in neurovascular procedures, it must be used to avoid contamination with room air when injected. It is a negative contrast agent. Thorotrast was a contrast agent based on thorium dioxide, radioactive, it was first introduced in 1929. While it provided good image enhancement, its use was abandoned in the late 1950s since it turned out to be carcinogenic. Given that the substance remained in the bodies of those to whom it was administered, it gave a continuous radiation exposure and was associated with a risk of cancers of the liver, bile ducts and bones, as well as higher rates of hematological malignancy.
Thorotrast may have been administered to millions of patients prior to being disused. In the past, some non water-soluble contrast agents were used. One such substance was iofendylate, an iodinated oil-based substance, used in myelography. Due to it being oil-based, it was recommended that the physician remove it from the patient at the end of the procedure; this was a painful and difficult step and because complete removal could not always be achieved, iofendylate's persistence in the body might sometimes lead to arachnoiditis, a painful and debilitating lifelong disorder of the spine. Iofendylate's use ceased. With the advent of MRI, myelography became much less-commonly performed. Modern iodinated contrast agents - non-ionic compounds - are well tolerated; the adverse effects of radiocontrast can be subdivided into type A reactions, type B reactions. Patients receiving contrast via IV experience a hot feeling around the throat, this hot sensation moves down to the pelvic area. Iodinated contrast may be toxic to the kidneys when given via the arteries prior to studies such as catheter coronary angiography.
Non-ionic contrast agents, which are exclusively used in computed tomography studies, have not been shown to cause CIN when given intravenously at doses needed for CT studies. Iodinated radiocontrast can induce underactivity of the thyroid gland; the risk of either condition developing after a single examination is 2-3 times that of those who have not undergone a scan with iodinated contrast. Thyroid underactivity is mediated by a phenomenon called the Wolff–Chaikoff effect, where iodine su
A health system sometimes referred to as health care system or as healthcare system, is the organization of people and resources that deliver health care services to meet the health needs of target populations. There is a wide variety of health systems around the world, with as many histories and organizational structures as there are nations. Implicitly, nations must design and develop health systems in accordance with their needs and resources, although common elements in all health systems are primary healthcare and public health measures. In some countries, health system planning is distributed among market participants. In others, there is a concerted effort among governments, trade unions, religious organizations, or other co-ordinated bodies to deliver planned health care services targeted to the populations they serve. However, health care planning has been described as evolutionary rather than revolutionary; the World Health Organization, the directing and coordinating authority for health within the United Nations system, is promoting a goal of universal health care: to ensure that all people obtain the health services they need without suffering financial hardship when paying for them.
According to WHO, healthcare systems' goals are good health for the citizens, responsiveness to the expectations of the population, fair means of funding operations. Progress towards them depends on how systems carry out four vital functions: provision of health care services, resource generation and stewardship. Other dimensions for the evaluation of health systems include quality, efficiency and equity, they have been described in the United States as "the five C's": Cost, Consistency and Chronic Illness. Continuity of health care is a major goal. Health system has been defined with a reductionist perspective, for example reducing it to healthcare system. In many publications, for example, both expressions are used interchangeably; some authors have developed arguments to expand the concept of health systems, indicating additional dimensions that should be considered: Health systems should not be expressed in terms of their components only, but of their interrelationships. The World Health Organization defines health systems as follows: A health system consists of all organizations and actions whose primary intent is to promote, restore or maintain health.
This includes efforts to influence determinants of health as well as more direct health-improving activities. A health system is therefore more than the pyramid of publicly owned facilities that deliver personal health services, it includes, for example, a mother caring for a sick child at home. It includes inter-sectoral action by health staff, for example, encouraging the ministry of education to promote female education, a well known determinant of better health. Healthcare providers are individuals providing healthcare services. Individuals including health professionals and allied health professions can be self-employed or working as an employee in a hospital, clinic, or other health care institution, whether government operated, private for-profit, or private not-for-profit, they may work outside of direct patient care such as in a government health department or other agency, medical laboratory, or health training institution. Examples of health workers are doctors, midwives, paramedics, medical laboratory technologists, psychologists, chiropractors, community health workers, traditional medicine practitioners, others.
There are five primary methods of funding health systems: general taxation to the state, county or municipality national health insurance voluntary or private health insurance out-of-pocket payments donations to charitiesMost countries' systems feature a mix of all five models. One study based on data from the OECD concluded that all types of health care finance "are compatible with" an efficient health system; the study found no relationship between financing and cost control. The term health insurance is used to describe a form of insurance that pays for medical expenses, it is sometimes used more broadly to include insurance covering disability or long-term nursing or custodial care needs. It may be provided from private insurance companies, it may be purchased by individual consumers. In each case premiums or taxes protect the insured from unexpected health care expenses. By estimating the overall cost of health care expenses, a routine finance structure can be developed, ensuring that money is available to pay for the health care benefits specified in the insurance agreement.
The benefit is administered by a government agency, a non-profit health fund or a
Nasogastric intubation is a medical process involving the insertion of a plastic tube through the nose, past the throat, down into the stomach. Orogastric intubation is a similar process involving the insertion of a plastic tube through the mouth. A nasogastric tube is used for feeding and administering drugs and other oral agents such as activated charcoal. For drugs and for minimal quantities of liquid, a syringe is used for injection into the tube. For continuous feeding, a gravity based system is employed, with the solution placed higher than the patient's stomach. If accrued supervision is required for the feeding, the tube is connected to an electronic pump which can control and measure the patient's intake and signal any interruption in the feeding. Nasogastric tubes may be used as an aid in the treatment of life threatening eating disorders if the patient is not compliant with eating. Nasogastric aspiration is the process of draining the stomach's contents via the tube. Nasogastric aspiration is used to remove gastrointestinal secretions and swallowed air in patients with gastrointestinal obstructions.
Nasogastric aspiration can be used in poisoning situations when a toxic liquid has been ingested, for preparation before surgery under anaesthesia, to extract samples of gastric liquid for analysis. If the tube is to be used for continuous drainage, it is appended to a collector bag placed below the level of the patient's stomach, it can be appended to a suction system, however this method is restricted to emergency situations, as the constant suction can damage the stomach's lining. In non-emergency situations, intermittent suction is applied giving the benefits of suction without the untoward effects of damage to the stomach lining. Suction drainage is used for patients who have undergone a pneumonectomy in order to prevent anesthesia-related vomiting and possible aspiration of any stomach contents; such aspiration would represent a serious risk of complications to patients recovering from this surgery. Types of nasogastric tubes include: Levin catheter, a single lumen, small bore NG tube.
It is more appropriate for administration of nutrition. Salem Sump catheter, a large bore NG tube with double lumen; this avails for aspiration in one lumen, venting in the other to reduce negative pressure and prevent gastric mucosa from being drawn into the catheter. Dobhoff tube, a small bore NG tube with a weight at the end intended to pull it by gravity during insertion. Before an NG tube is inserted, it must be measured from the tip of the patient's nose, loop around their ear and down to 5 cm below the xiphoid process; the tube is marked at this level to ensure that the tube has been inserted far enough into the patient's stomach. Many commercially available stomach and duodenal tubes have several standard depth markings, for example 18", 22", 26" and 30" from distal end; the end of a plastic tube is inserted into one of the patient's anterior nares. Treatment with 2.0 mg of IV midazolam reduces patient stress. The tube should be directed straight towards the back of the patient as it moves through the nasal cavity and down into the throat.
When the tube enters the oropharynx and glides down the posterior pharyngeal wall, the patient may gag. Once the tube is past the pharynx and enters the esophagus, it is inserted down into the stomach; the tube must be secured in place to prevent it from moving. Great care must be taken to ensure that the tube has not passed through the larynx into the trachea and down into the bronchi; the reliable method is to aspirate some fluid from the tube with a syringe. This fluid is tested with pH paper to determine the acidity of the fluid. If the pH is 4 or below the tube is in the correct position. If this is not possible correct verification of tube position is obtained with an X-ray of the chest/abdomen; this is the most reliable means of ensuring proper placement of an NG tube. The use of a chest x-ray to confirm position is the expected standard in the UK, with Dr/ physician review and confirmation. Future techniques may include measuring the concentration of enzymes such as trypsin and bilirubin to confirm the correct placement of the NG tube.
As enzyme testing becomes more practical, allowing measurements to be taken and cheaply at the bedside, this technique may be used in combination with pH testing as an effective, less harmful replacement of X-ray confirmation. If the tube is to remain in place a tube position check is recommended before each feed and at least once per day. Only smaller diameter nasogastric tubes are appropriate for long-term feeding, so as to avoid irritation and erosion of the nasal mucosa; these tubes have guidewires to facilitate insertion. If feeding is required for a longer period of time, other options, such as placement of a PEG tube, should be considered. Function of an NG tube properly placed and used for suction is maintained by flushing; this may be done by flushing small amounts of saline and air using a syringe or by flushing larger amounts of saline or water, air, assessing for the air to circulate
X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and longer than those of gamma rays. In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen who discovered these on November 8, 1895, credited as its discoverer, who named it X-radiation to signify an unknown type of radiation. Spelling of X-ray in the English language includes the variants x-ray, X ray. Before their discovery in 1895 X-rays were just a type of unidentified radiation emanating from experimental discharge tubes, they were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. Many of the early Crookes tubes undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below.
Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube; the earliest experimenter thought to have produced. In 1785 he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a evacuated glass tube, producing a glow created by X-rays; this work was further explored by his assistant Michael Faraday. When Stanford University physics professor Fernando Sanford created his "electric photography" he unknowingly generated and detected X-rays. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as studied by Heinrich Hertz and Philipp Lenard.
His letter of January 6, 1893 to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner. Starting in 1888, Philipp Lenard, a student of Heinrich Hertz, conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air, he built a Crookes tube with a "window" in the end made of thin aluminum, facing the cathode so the cathode rays would strike it. He found that something came through, that would cause fluorescence, he measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were X-rays. In 1889 Ukrainian-born Ivan Pulyui, a lecturer in experimental physics at the Prague Polytechnic who since 1877 had been constructing various designs of gas-filled tubes to investigate their properties, published a paper on how sealed photographic plates became dark when exposed to the emanations from the tubes.
Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his announcement, it was formed on the basis of the electromagnetic theory of light. However, he did not work with actual X-rays. In 1894 Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this radiant energy of "invisible" kinds. After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design, as well as Crookes tubes. On November 8, 1895, German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard tubes and Crookes tubes and began studying them, he wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to Würzburg's Physical-Medical Society journal. This was the first paper written on X-rays. Röntgen referred to the radiation as "X"; the name stuck.
They are still referred to as such in many languages, including German, Danish, Swedish, Estonian, Japanese, Georgian and Norwegian. Röntgen received the first Nobel Prize in Physics for his discovery. There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a reconstruction by his biographers: Röntgen was investigating cathode rays from a Crookes tube which he had wrapped in black cardboard so that the visible light from the tube would not interfere, using a fluorescent screen painted with barium platinocyanide, he noticed a faint green glow from the screen, about 1 meter away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow, he found they could pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper. Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays.
The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death."The discovery of X-rays stimul
European Chemicals Agency
The European Chemicals Agency is an agency of the European Union which manages the technical and administrative aspects of the implementation of the European Union regulation called Registration, Evaluation and Restriction of Chemicals. ECHA is the driving force among regulatory authorities in implementing the EU's chemicals legislation. ECHA helps companies to comply with the legislation, advances the safe use of chemicals, provides information on chemicals and addresses chemicals of concern, it is located in Finland. The agency headed by Executive Director Bjorn Hansen, started working on 1 June 2007; the REACH Regulation requires companies to provide information on the hazards and safe use of chemical substances that they manufacture or import. Companies register this information with ECHA and it is freely available on their website. So far, thousands of the most hazardous and the most used substances have been registered; the information is technical but gives detail on the impact of each chemical on people and the environment.
This gives European consumers the right to ask retailers whether the goods they buy contain dangerous substances. The Classification and Packaging Regulation introduces a globally harmonised system for classifying and labelling chemicals into the EU; this worldwide system makes it easier for workers and consumers to know the effects of chemicals and how to use products safely because the labels on products are now the same throughout the world. Companies need to notify ECHA of the labelling of their chemicals. So far, ECHA has received over 5 million notifications for more than 100 000 substances; the information is available on their website. Consumers can check chemicals in the products. Biocidal products include, for example, insect disinfectants used in hospitals; the Biocidal Products Regulation ensures that there is enough information about these products so that consumers can use them safely. ECHA is responsible for implementing the regulation; the law on Prior Informed Consent sets guidelines for the import of hazardous chemicals.
Through this mechanism, countries due to receive hazardous chemicals are informed in advance and have the possibility of rejecting their import. Substances that may have serious effects on human health and the environment are identified as Substances of Very High Concern 1; these are substances which cause cancer, mutation or are toxic to reproduction as well as substances which persist in the body or the environment and do not break down. Other substances considered. Companies manufacturing or importing articles containing these substances in a concentration above 0,1% weight of the article, have legal obligations, they are required to inform users about the presence of the substance and therefore how to use it safely. Consumers have the right to ask the retailer whether these substances are present in the products they buy. Once a substance has been identified in the EU as being of high concern, it will be added to a list; this list is available on ECHA's website and shows consumers and industry which chemicals are identified as SVHCs.
Substances placed on the Candidate List can move to another list. This means that, after a given date, companies will not be allowed to place the substance on the market or to use it, unless they have been given prior authorisation to do so by ECHA. One of the main aims of this listing process is to phase out SVHCs where possible. In its 2018 substance evaluation progress report, ECHA said chemical companies failed to provide “important safety information” in nearly three quarters of cases checked that year. "The numbers show a similar picture to previous years" the report said. The agency noted that member states need to develop risk management measures to control unsafe commercial use of chemicals in 71% of the substances checked. Executive Director Bjorn Hansen called non-compliance with REACH a "worry". Industry group CEFIC acknowledged the problem; the European Environmental Bureau called for faster enforcement to minimise chemical exposure. European Chemicals Bureau Official website
Rectal administration uses the rectum as a route of administration for medication and other fluids, which are absorbed by the rectum's blood vessels, flow into the body's circulatory system, which distributes the drug to the body's organs and bodily systems. A drug, administered rectally will in general have a faster onset, higher bioavailability, shorter peak, shorter duration than the oral route. Another advantage of administering a drug rectally, is that it tends to produce less nausea compared to the oral route and prevents any amount of the drug from being lost due to emesis. In addition, the rectal route bypasses around two thirds of the first-pass metabolism as the rectum's venous drainage is two thirds systemic and one third hepatic portal system; this means the drug will reach the circulatory system with less alteration and in greater concentrations. Rectal administration can allow patients to remain in the home setting when the oral route is compromised. Unlike intravenous lines, which need to be placed in an inpatient environment and require special formulation of sterile medications, a specialized rectal catheter can be placed by a clinician, such as a hospice nurse or home health nurse, in the home.
Many oral forms of medications can be crushed and suspended in water to be given via a rectal catheter. The rectal route of administration is useful for patients with any digestive tract motility problem, such as dysphagia, ileus, or bowel obstruction, that would interfere with the progression of the medication through the tract; this includes patients near the end of life. Because using the rectal route enables a rapid and lower cost alternative to administration of medications, it may facilitate the care of patients in long-term care or palliative care, or as an alternative to intravenous or subcutaneous medication delivery in other instances. Rectal administration of medication may be performed with any of the following: A suppository, a drug delivery system inserted into the rectum. An enema, the act of introducing a liquid-drug solution into the rectum and sometimes the colon. A specialized catheter designed for rectal administration of medications and liquids, that can be placed safely and remain comfortably in the rectum for repeated use.
A bulb syringe. Rectal discharge Routes of administration