Formaldehyde is a occurring organic compound with the formula CH2O. It is the simplest of the aldehydes; the common name of this substance comes from its relation to formic acid. Formaldehyde is an important precursor to chemical compounds. In 1996, the installed capacity for the production of formaldehyde was estimated at 8.7 million tons per year. It is used in the production of industrial resins, e.g. for particle board and coatings. In view of its widespread use and volatility, formaldehyde poses a significant danger to human health. In 2011, the US National Toxicology Program described formaldehyde as "known to be a human carcinogen". Formaldehyde is more complicated than many simple carbon compounds in that it adopts several different forms; as a gas, formaldehyde has a characteristic pungent, irritating odor. Upon condensation, the gas converts to various other forms of formaldehyde that are of more practical value. One derivative is the cyclic trimer metaformaldehyde with the formula 3. There is a linear polymer called paraformaldehyde.
These compounds have similar chemical properties and are used interchangeably. When dissolved in water, formaldehyde forms a hydrate, with the formula H2C2; this compound exists in equilibrium with various oligomers, depending on the concentration and temperature. A saturated water solution, of about 40% formaldehyde by volume or 37% by mass, is called "100% formalin". A small amount of stabilizer, such as methanol, is added to suppress oxidation and polymerization. A typical commercial grade formalin may contain 10–12% methanol in addition to various metallic impurities. "Formaldehyde" was first used as a generic trademark in 1893 following a previous trade name, "formalin". Processes in the upper atmosphere contribute up to 90% of the total formaldehyde in the environment. Formaldehyde is an intermediate in the oxidation of methane, as well as of other carbon compounds, e.g. in forest fires, automobile exhaust, tobacco smoke. When produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons, it becomes part of smog.
Formaldehyde has been detected in outer space. Formaldehyde and its adducts are ubiquitous in living organisms, it is formed in the metabolism of endogenous amino acids and is found in the bloodstream of humans and other primates at concentrations of 0.1 millimolar. Experiments in which animals are exposed to an atmosphere containing isotopically labeled formaldehyde have demonstrated that in deliberately exposed animals, the majority of formaldehyde-DNA adducts found in non-respiratory tissues are derived from endogenously produced formaldehyde. Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde converting it to formic acid, so it does not accumulate in the body. Formaldehyde appears to be a useful probe in astrochemistry due to prominence of the 110←111 and 211←212 K-doublet transitions, it was the first polyatomic organic molecule detected in the interstellar medium.
Since its initial detection in 1969, it has been observed in many regions of the galaxy. Because of the widespread interest in interstellar formaldehyde, it has been extensively studied, yielding new extragalactic sources. A proposed mechanism for the formation is the hydrogenation of CO ice: H + CO → HCO HCO + H → CH2OHCN, HNC, H2CO, dust have been observed inside the comae of comets C/2012 F6 and C/2012 S1. Formaldehyde was first reported in 1859 by the Russian chemist Aleksandr Butlerov and was conclusively identified in 1869 by August Wilhelm von Hofmann. Formaldehyde is produced industrially by the catalytic oxidation of methanol; the most common catalysts are silver metal or a mixture of an iron and molybdenum or vanadium oxides. In the used formox process and oxygen react at ca. 250–400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation: 2 CH3OH + O2 → 2 CH2O + 2 H2OThe silver-based catalyst operates at a higher temperature, about 650 °C.
Two chemical reactions on it produce formaldehyde: that shown above and the dehydrogenation reaction: CH3OH → CH2O + H2In principle, formaldehyde could be generated by oxidation of methane, but this route is not industrially viable because the methanol is more oxidized than methane. Formaldehyde is a building block in the synthesis of many other compounds of specialised and industrial significance, it is more reactive. Formaldehyde, unlike most aldehydes, oligomerizes spontaneously; the trimer is 1,3,5-trioxane, the polymer is called paraformaldehyde. Many cyclic oligomers have been isolated. Formaldehyde hydrates to give the geminal diol methanediol, which condenses further to form oligomers HOnH. Monomeric CH2O is encountered, it is oxidized by atmospheric oxygen into formic acid. For this reason, commercial formaldehyde is contaminated with formic acid. Formaldehyde is a good electrophile. With good nucleophiles such as thiols and amides, no acid catalyst is required; the resulting hydroxymethyl derivatives react further.
Thus amines give hexahydro-1,3,5-triazines. When combined with hydrogen sulfide, it forms trithiane. 3CH2O + 3H2S → 3 + 3H2OIn the presence of acids, it participates in electrophilic aromatic substitu
Nikolai Arkadievich Dudin, known as the "Grim Maniac", is a Soviet-Russian serial killer who killed 13 people in the town of Furmanov between 1987 and 2002. Nikolai Dudin was born on December 1973 in the village of Mikhalkovo, Ivanovo Oblast. Dudin suffered because of his father's beatings in his childhood, as well as specific skills that his father instilled in him, such as teaching him hunting at a young age and cutting up the warm carcasses of dead animals. In the end, all of this led to Nikolai shooting his father with a sawed-off shotgun on December 3, 1987. Arkady Dudin's body was well hidden, but after a year Nikolai was arrested for rape, confessed to his father's murder; the court considered that at the time of the murder, Nikolai was still under 14 years of age, did not execute him, instead imprisoning him for 7 years. Subsequently, he was penalized for defiance of the administration, trying to organize a riot and escape, attempting to kill a prisoner from a neighboring cell, as a result of which he was again convicted and released in 2000, 12 years after the conviction.
The next murder Dudin committed was on February 15, 2002. His victim was an employee of the Furmanov telecommunications company. In a state of intoxication, he struck her with a hard blunt object on the head, breaking the base of the skull, as a result of which the victim died. Dudin subsequently claimed. On the same day, he committed a double murder, this time the victims being two employees of a local sewing shop; as it turned out, the drunk Dudin had decided to get acquainted with the girls, but they rejected his advances, prompting him to stab them with a knife, causing a total of 28 wounds on the first woman, 32 on the second. The killer committed the following murders during the May holidays: on the night between May 1st and 2nd, 2002, a resident of the city disappeared without a trace, her body being discovered only after Dudin was arrested. On May 8, he committed a triple murder. In a state of intoxication, he leaned on the face of a house on Kremlyovskaya Street, bringing it down; the owner of the house, Andrei Polozov, was present, Dudin pulled out his sawn-off and opened fire.
He shot the wife and killed their 11-year-old daughter with a knife. On May 10, Dudin committed another triple murder under similar circumstances; the situation in the city was heated, panic ensued, as Dudin committed a double murder shortly after. On July 17, 2002, the killer was captured red-handed with a new murder attempt. On August 6, 2002, he wrote a confession, explaining his motive was that he killed people who humiliated his dignity. In December 2003, Dudin was sentenced to life imprisonment in a special regime colony by the Ivanono District Court; the Supreme Court of Russia upheld the verdict without change. He is serving his sentence in the White Swan prison. Elena Aristarkhova; the grim maniac. Rossiyskaya Gazeta
Optical coherence elastography is an emerging imaging technique used in biomedical imaging to form pictures of biological tissue in micron and submicron level and maps the biomechanical property of tissue. Elastography was first used in 1979 and subsequent progress in the ﬁeld has been extensive, based on ultrasound, magnetic resonance imaging. Optical techniques have been proposed for elastography to probe mechanical properties of tissues dates back to at least the 1950s. In 1998, Schmitt ﬁrst proposed optical coherence elastography, in employing optical coherence tomography detect depth-resolved sample deformation induced by quasi-static compression, but the term optical coherence elastography was first coined in a 2004 paper with Brett Bouma. Requiring no injections, OCE is an non-invasive imaging method can gives more details than ultrasound or MRI. Using light source to image biological tissue, OCE is considered safe compared to CT scan and other radiographic imaging modalities which involve with ionizing radiation.
And it is more affordable and time efficient compared to MRI. However, OCE can cause tissue damage in some handling. For example, surface acoustic wave OCE can cause to a tissue is concentrated on temperature effects. In the focus point, the temperature of the tissue will rise locally. Therefore, it is necessary to take this into account in certain circumstances. OCE is characterized by its niche in intermediate spatial resolution and degree of depth penetration and, by exploiting optical interferometry, its high sensitivity to small mechanical changes—at the microstrain level. However, it’s still in the early stage of development and needs more clinical practice before enters into the market, but the term optical coherence elastography was first coined in a 2004 paper with Brett Bouma. Although optical coherence tomography provide crucial information for the diagnosis, they are insufficient for early diagnosis, before structural changes occur. Elastography, the display of the elastic properties of soft tissues, may be performed using ultrasound, magnetic resonance imaging or OCT.
Elastography has been proven feasible for characterization of ocular tissues. Tissue exhibits varying degrees of viscoelasticity and anisotropy, as well as a nonlinear relationship between elasticity and the applied load; as a starting point in establishing the link between elasticity and displacement, a number of simplifying assumptions are made about tissue behavior and structure. Most tissue is approximated as a linear elastic solid with isotropic mechanical properties; the assumption of linearity is valid for the level of strain applied in elastography. Optical coherence elastography holds great promise for detecting and monitoring the altered mechanical properties that accompany many clinical conditions and pathologies in cancer, cardiovascular disease and eye disease. In ophthalmology, OCE could be utilized to characterize the mechanical properties of cornea in order to diagnose related ocular disease: to diagnose and assess the properties of keratoconus, which provides necessary information to establish adaptive biomechanical models of the cornea for the optimization of individual laser ablation procedure.
It helps improve the management of collagen cross-linking therapy. The methods utilizing OCE to study these properties are still under investigation and some particular ones listed below seem promising to be developed into clinical use. Methods could be divided into two main categories based on required interactions which are in-contact and non-contact detections. In contact detection using a standard clinical gonioscopy. Direct contact with the cornea using gonioscopy creates static compression and resultant displacement amplitude inside the cornea responding to the compression indicates the heterogeneous mechanical properties of the cornea. Non-contact detection methods including creating mechanical contrasts by pulsed laser and focused air puff stimulation. Non-contact OCE detection methods are more to be developed into clinical usages since they are more comfortable and applicable for patients. Pulsed laser is used to generate surface acoustic waves on the cornea and quantitative Young’s modulus measurements of the cornea could be obtained.
The focused air puff, described as short duration and low pressure is capable to measure the cornea stiffness in a safe and easy-to-control stimulus. The elasticity of skin could indicate related pathologies such as cancer. Developing OCE technology could detect differences in stiffness of human skin layers in vivo. Besides, with dynamic mechanical loading coupled to skin surface, OCE is capable of making Young’s modulus measurements from the quantification of the surface wave velocity based on phase shift of the displacement profile, thus showing the hydration and dehydration effect of the in vivo human skin. Imaging ex vivo excised tissues to perform two-dimensional mapping of elastic modulus. By either applying static or dynamic compression loading, different sample regions with different stiffness could be highlighted with the mapping of displacement amplitude in a 2D depth-resolved elastogram. Experiments have shown that such method could be utilized to detect tumor region in ex vivo rat mammary tissues.
Assisting intraoperative assessment by detecting exact tumor margin. The needle OCE technique is applied whereas integrates OCE with a needle probe; the needle tip works as the compression loading when inserted into tissue, the resultant displacement amplitude of tissue is plotted over depth. I