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
Urea known as carbamide, is an organic compound with chemical formula CO2. This amide has two –NH2 groups joined by a carbonyl functional group. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals, it is a colorless, odorless solid soluble in water, non-toxic. Dissolved in water, it is neither alkaline; the body uses it in most notably nitrogen excretion. The liver forms it by combining two ammonia molecules with a carbon dioxide molecule in the urea cycle. Urea is used in fertilizers as a source of nitrogen and is an important raw material for the chemical industry. Friedrich Wöhler's discovery in 1828 that urea can be produced from inorganic starting materials was an important conceptual milestone in chemistry, it showed for the first time that a substance known only as a byproduct of life could be synthesized in the laboratory without biological starting materials thereby contradicting the held doctrine of vitalism.
More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has the lowest transportation costs per unit of nitrogen nutrient. Many soil bacteria possess the enzyme urease, which catalyzes conversion of urea to ammonia or ammonium ion and bicarbonate ion, thus urea fertilizers transform to the ammonium form in soils. Among the soil bacteria known to carry urease, some ammonia-oxidizing bacteria, such as species of Nitrosomonas, can assimilate the carbon dioxide the reaction releases to make biomass via the Calvin cycle, harvest energy by oxidizing ammonia to nitrite, a process termed nitrification. Nitrite-oxidizing bacteria Nitrobacter, oxidize nitrite to nitrate, mobile in soils because of its negative charge and is a major cause of water pollution from agriculture. Ammonium and nitrate are absorbed by plants, are the dominant sources of nitrogen for plant growth.
Urea is used in many multi-component solid fertilizer formulations. Urea is soluble in water and is therefore very suitable for use in fertilizer solutions, e.g. in'foliar feed' fertilizers. For fertilizer use, granules are preferred over prills because of their narrower particle size distribution, an advantage for mechanical application; the most common impurity of synthetic urea is biuret. Urea is spread at rates of between 40 and 300 kg/ha but rates vary. Smaller applications incur lower losses due to leaching. During summer, urea is spread just before or during rain to minimize losses from volatilization; because of the high nitrogen concentration in urea, it is important to achieve an spread. The application equipment must be calibrated and properly used. Drilling must not occur on contact with or close to seed, due to the risk of germination damage. Urea dissolves in water for application through irrigation systems. In grain and cotton crops, urea is applied at the time of the last cultivation before planting.
In high rainfall areas and on sandy soils and where good in-season rainfall is expected, urea can be side- or top-dressed during the growing season. Top-dressing is popular on pasture and forage crops. In cultivating sugarcane, urea is side-dressed after planting, applied to each ratoon crop. In irrigated crops, urea can be applied dry to the soil, or dissolved and applied through the irrigation water. Urea dissolves in its own weight in water, but becomes difficult to dissolve as the concentration increases. Dissolving urea in water is endothermic—the solution temperature falls when urea dissolves; as a practical guide, when preparing urea solutions for fertigation, dissolve no more than 3 g urea per 1 L water. In foliar sprays, urea concentrations of between 0.5% and 2.0% are used in horticultural crops. Low-biuret grades of urea are indicated. Urea absorbs moisture from the atmosphere and therefore is stored either in closed or sealed bags on pallets or, if stored in bulk, under cover with a tarpaulin.
As with most solid fertilizers, storage in a cool, well-ventilated area is recommended. Overdose or placing urea near seed is harmful. Urea is a raw material for the manufacture of two main classes of materials: urea-formaldehyde resins and urea-melamine-formaldehyde used in marine plywood. Urea can be used to make urea nitrate, a high explosive, used industrially and as part of some improvised explosive devices, it is a stabilizer in nitrocellulose explosives. Urea is used in SNCR and SCR reactions to reduce the NOx pollutants in exhaust gases from combustion from Diesel, dual fuel, lean-burn natural gas engines; the BlueTec system, for example, injects a water-based urea solution into the exhaust system. The ammonia produced by the hydrolysis of the urea reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter. Trucks and cars using these catalytic converters need to carry a supply of diesel exhaust fluid, a solution of urea in water. Urea in concentrations up to 10 M is a powerful protein denaturant as it disrupts the noncovalent bonds in the proteins.
This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as
The Paris Observatory, a research institution of PSL Research University, is the foremost astronomical observatory of France, one of the largest astronomical centres in the world. Its historic building is to be found on the Left Bank of the Seine in central Paris, but most of the staff work on a satellite campus in Meudon, a suburb southwest of Paris. Administratively, it is a grand établissement of the French Ministry of National Education, with a status close to that of a public university, its missions astrophysics. It maintains a radio astronomy observatory at Nançay, it was the home to the International Time Bureau until its dissolution in 1987. The Paris Observatory Library, founded in 1785, provides the researchers with documentation and preserves the ancient books and heritage collections of the institution. Many collections are available on the Paris Observatory digital library, its foundation lies in the ambitions of Jean-Baptiste Colbert to extend France's maritime power and international trade in the 17th century.
Louis XIV promoted its construction, started in 1667 and completed in 1671. It thus predates by a few years the Royal Greenwich Observatory in England, founded in 1675; the architect of the Paris Observatory was Claude Perrault whose brother, was secretary to Colbert and superintendent of public works. Optical instruments were supplied by Giuseppe Campani; the buildings were extended in 1730, 1810, 1834, 1850, 1951. The last extension incorporates the spectacular Meridian Room designed by Jean Prouvé; the world's first national almanac, the Connaissance des temps, was published by the observatory in 1679, using eclipses in Jupiter's satellites to aid sea-farers in establishing longitude. In 1863, the observatory published the first modern weather maps. In 1882, a 33 cm astrographic lens was constructed, an instrument that catalysed what proved to be the over-ambitious international Carte du Ciel project. In November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless signals with the United States Naval Observatory to determine the exact difference of longitude between the two institutions.
The Paris Observatory library preserves a great number of original works and letters of the Observatory and well known astronomers. The entire collection - archives, iconography - has been inventoried on Alidade; some of the work is now digitized on the digital library such as Hevelius, Lalande or Delisle letters. Among other, are to be found: Administrativ documents Scientific observations Scientifc work of Giovanni Domenico Cassini Scientific work of Jacques Cassini Scientific work of Charles Messier Annual reports from 1878 to 1940 Numerous images of instruments and persons The Meudon great refractor was a 83 cm aperture refractor, which with September 20, 1909 observations by E. M. Antoniadi helped disprove the Mars canals theory, it was a double telescope completed in 1891, with secondary having 62 cm aperture lens for photography. It was one of the largest active telescopes in Europe; the title of Director of the Observatory was given for the first time to César-François Cassini de Thury by a Royal brevet dated November 12, 1771.
However, the important role played by his grandfather and father in this institution during its first century gives them somewhat the role of director. Solar Observatory Tower Meudon Chateau de Meudon LESIA space and astrophysics instrumentation research laboratory Nançay radio telescope Also known as the Observatoire du Pic de Château Renard, the Observatoire de Saint-Véran was built in 1974 on top of the Pic de Château Renard, on the commune of Saint-Véran in the Haut Queyras. A coronograph was in operation there for ten years. Nowadays, the AstroQueyras amateur astronomy association operates the facility, using a 60 cm telescope on loan from the Observatoire de Haute Provence. Numerous asteroids have been discovered there. "Paris Observatory", Encyclopædia Britannica, Deluxe CDROM edition Aubin, D.. "The fading star of the Paris Observatory in the nineteenth century: astronomers' urban culture of circulation and observation". Osiris. 18: 79–100. Doi:10.1086/649378. Guinot, B.. "History of the Bureau International de l'Heure".
Polar Motion: Historical and Scientific problems. Pp. 175–184. Bibcode:2000ASPC..208..175G. Paris Observatory Location in Paris Inventory of astronomy heritage Digital library for astronomy archives Publications of the Observatoire de Paris in Gallica, the digital library of the BnF
The Jmol applet, among other abilities, offers an alternative to the Chime plug-in, no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, the Sculpt mode. Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS 9. Jmol operates on a wide variety of platforms. For example, Jmol is functional in Mozilla Firefox, Internet Explorer, Google Chrome, Safari. Chemistry Development Kit Comparison of software for molecular mechanics modeling Jmol extension for MediaWiki List of molecular graphics systems Molecular graphics Molecule editor Proteopedia PyMOL SAMSON Official website Wiki with listings of websites and moodles Willighagen, Egon. "Fast and Scriptable Molecular Graphics in Web Browsers without Java3D". Doi:10.1038/npre.2007.50.1
Mineral dust is atmospheric aerosols originated from the suspension of minerals constituting the soil. It is composed of various carbonates. Human activities lead to 30% of the dust load in the atmosphere; the Sahara Desert is the major source of mineral dust, which subsequently spreads across the Mediterranean and Caribbean seas into northern South America, Central America, North America, Europe. Additionally, it plays a significant role in the nutrient inflow to the Amazon rainforest; the Gobi Desert is another source of dust in the atmosphere, which affects eastern Asia and western North America. Mineral dust is constituted of the oxides and carbonates that constitute the Earth's crust. Global mineral dust emissions are estimated at 1000-5000 millions of tons per year, of which the largest part is attributed to deserts. Although this aerosol class is considered of natural origin, it is estimated that about a quarter of mineral dust emissions could be ascribed to human activities through desertification and land use changes.
Large dust concentrations may cause problems to people having respiratory problems. Another effect of dust clouds is more colorful sunsets; the Sahara is the major source on Earth of mineral dust. Saharan dust can be lifted by convection over hot desert areas, can thus reach high altitudes; the dust combined with the hot, dry air of the Sahara Desert forms an atmospheric layer called the Saharan Air Layer which has significant effects on tropical weather as it interferes with the development of hurricanes. There is a large variability in the dust transport across the Atlantic into the Caribbean and Florida from year to year. Due to the trade winds large concentrations of mineral dust can be found in the tropical Atlantic, reaching the Caribbean. Saharan plumes can form iberulites when these plumes travel through North Africa and the eastern North Atlantic Ocean, reach the circum-Mediterranean areas of Western Europe. In the Mediterranean region, Saharan dust is important as it represents the major source of nutrients for phytoplankton and other aquatic organisms.
Saharan dust carries the fungus Aspergillus others. Aspergillus borne by Saharan dust falls into the Caribbean Sea and infects coral reefs with Sea Fan disease, it has been linked to increased incidence of pediatric asthma attacks in the Caribbean. Since 1970, dust outbreaks have worsened due to periods of drought in Africa. Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida since the 1970s. According to a NASA article, NASA satellites have shown that "the chilling effect of dust was responsible for one-third of the drop in North Atlantic sea surface temperatures between June 2005 and 2006 contributing to the difference in hurricane activity between the two seasons." There were only 5 hurricanes in 2006 compared with 15 in 2005. It is known that one of the major factors that create hurricanes is warm water temperatures on the surface of the ocean. Evidence shows that dust from the Sahara desert caused surface temperatures to be cooler in 2006 than in 2005.
In Eastern Asia, mineral dust events that originate in the Gobi Desert during springtime give rise to the phenomenon called Asian dust. The aerosols are carried eastward by prevailing winds, pass over China and Japan. Sometimes, significant concentrations of dust can be carried as far as the Western United States. Areas affected by Asian dust experience decreased visibility and health problems, such as sore throat and respiratory difficulties; the effects of Asian dust, are not negative, as it is thought that its deposition enriches the soil with important trace minerals. An American study analyzing the composition of Asian dust events reaching Colorado associates them to the presence of carbon monoxide incorporated in the air mass as it passes over industrialized regions in Asia. Although dust storms in the Gobi desert have occurred from time to time throughout history, they became a pronounced problem in the second half of the 20th century due to intensified agricultural pressure and desertification.
Azores High Canary Current Dust storm Dust bowl Dust devil Iberulites Iron fertilization Sahel Western Hemisphere Warm Pool Kubilay and Saydam, "Trace elements in atmospheric particulates over the Eastern Mediterranean: concentration and temporal variability", Atmospheric Environment 29, 2289-2300. Morales, "The airborne transport of Saharan dust: a review", Climate Change 9, 219-241. Loyë-Pilot et al. "Influence of Saharan dust on the rain acidity and atmospheric input to the Mediterranean", Nature 321, 427-428. Sokolik and Toon, "Direct radiative forcing by anthropogenic airborne mineral aerosols", Nature 381, 681-683. Tegen and Fung, "Contribution to the atmospheric mineral aerosol load from land surface modification", Journal of Geophysical Research 100, 18707-18726. Yücekutlu, N. Terzioğlu, S. Saydam, C. and Bildacı, I. Organic Farming By Using Saharan Soil: Could It Be An Alternative To Fertilizers? Hacettepe J. Biol. and Chem. 39, 29–37, 2011. The Dust Hypothesis for Caribbean Coral Bleaching as reported by the United States Geological Survey Saharan dust in America The Bibliography of Aeolian Research High quality video of dust from Sahara to Am
Cosmic dust called extraterrestrial dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles are between a few molecules to 0.1 µm in size. Cosmic dust can be further distinguished by its astronomical location: intergalactic dust, interstellar dust, interplanetary dust and circumplanetary dust. In the Solar System, interplanetary dust causes the zodiacal light. Solar System dust includes comet dust, asteroidal dust, dust from the Kuiper belt, interstellar dust passing through the Solar System. Thousands of tons of cosmic dust are estimated to reach the Earth's surface every year, with each grain having a mass between 10−16 kg and 10−4 kg; the density of the dust cloud through which the Earth is traveling is 10−6/m3. Cosmic dust contains some complex organic compounds that could be created and by stars. A smaller fraction of dust in space is "stardust" consisting of larger refractory minerals that condensed as matter left by stars. Interstellar dust particles were collected by the Stardust spacecraft and samples were returned to Earth in 2006.
Cosmic dust was once an annoyance to astronomers, as it obscures objects they wish to observe. When infrared astronomy began, the dust particles were observed to be significant and vital components of astrophysical processes, their analysis can reveal information about phenomena like the formation of the Solar System. For example, cosmic dust can drive the mass loss when a star is nearing the end of its life, play a part in the early stages of star formation, form planets. In the Solar System, dust plays a major role in the zodiacal light, Saturn's B Ring spokes, the outer diffuse planetary rings at Jupiter, Saturn and Neptune, comets; the interdisciplinary study of dust brings together different scientific fields: physics, fractal mathematics, surface chemistry on dust grains) meteoritics, as well as every branch of astronomy and astrophysics. These disparate research areas can be linked by the following theme: the cosmic dust particles evolve cyclically; the evolution of dust traces out paths in which the Universe recycles material, in processes analogous to the daily recycling steps with which many people are familiar: production, processing, collection and discarding.
Observations and measurements of cosmic dust in different regions provide an important insight into the Universe's recycling processes. The astronomers accumulate observational ‘snapshots’ of dust at different stages of its life and, over time, form a more complete movie of the Universe's complicated recycling steps. Parameters such as the particle's initial motion, material properties, intervening plasma and magnetic field determined the dust particle's arrival at the dust detector. Changing any of these parameters can give different dust dynamical behavior. Therefore, one can learn about where that object came from, what is the intervening medium. Cosmic dust can be detected by indirect methods that utilize the radiative properties of the cosmic dust particles. Cosmic dust can be detected directly using a variety of collection methods and from a variety of collection locations. Estimates of the daily influx of extraterrestrial material entering the Earth's atmosphere range between 5 and 300 tonnes.
NASA collects samples of star dust particles in the Earth's atmosphere using plate collectors under the wings of stratospheric-flying airplanes. Dust samples are collected from surface deposits on the large Earth ice-masses and in deep-sea sediments. Don Brownlee at the University of Washington in Seattle first reliably identified the extraterrestrial nature of collected dust particles in the latter 1970s. Another source is the meteorites. Stardust grains are solid refractory pieces of individual presolar stars, they are recognized by their extreme isotopic compositions, which can only be isotopic compositions within evolved stars, prior to any mixing with the interstellar medium. These grains condensed from the stellar matter. In interplanetary space, dust detectors on planetary spacecraft have been built and flown, some are presently flying, more are presently being built to fly; the large orbital velocities of dust particles in interplanetary space make intact particle capture problematic. Instead, in-situ dust detectors are devised to measure parameters associated with the high-velocity impact of dust particles on the instrument, derive physical properties of the particles through laboratory calibration.
Over the years dust detectors have measured, among others, the impact light flash, acoustic signal and impact ionisation. The dust instrument on Stardust captured particles intact in low-density aerogel. Dust detectors in the past flew on the HEOS-2, Pioneer 10, Pioneer 11, Giotto and Cassini space missions, on the Earth-orbiting LDEF, EURECA, Gorid satellites, some scientists have utilized the Voyager 1 and 2 spacecraft as giant Langmuir probes to
A protostar is a young star, still gathering mass from its parent molecular cloud. The protostellar phase is the earliest one in the process of stellar evolution. For a low mass star, it lasts about 500,000 years The phase begins when a molecular cloud fragment first collapses under the force of self-gravity and an opaque, pressure supported core forms inside the collapsing fragment, it ends when the infalling gas is depleted, leaving a pre-main-sequence star, which contracts to become a main sequence star at the onset of Hydrogen fusion. The modern picture of protostars, summarized above, was first suggested by Chushiro Hayashi in 1966. In the first models, the size of protostars was overestimated. Subsequent numerical calculations clarified the issue, showed that protostars are only modestly larger than main-sequence stars of the same mass; this basic theoretical result has been confirmed by observations, which find that the largest pre-main-sequence stars are of modest size. Star formation begins in small molecular clouds called dense cores.
Each dense core is in balance between self-gravity, which tends to compress the object, both gas pressure and magnetic pressure, which tend to inflate it. As the dense core accrues mass from its larger, surrounding cloud, self-gravity begins to overwhelm pressure, collapse begins. Theoretical modeling of an idealized spherical cloud supported only by gas pressure indicates that the collapse process spreads from the inside toward the outside. Spectroscopic observations of dense cores that do not yet contain stars indicate that contraction indeed occurs. So far, the predicted outward spread of the collapse region has not been observed; the gas that collapses toward the center of the dense core first builds up a low-mass protostar, a protoplanetary disk orbiting the object. As the collapse continues, an increasing amount of gas impacts the disk rather than the star, a consequence of angular momentum conservation. How material in the disk spirals inward onto the protostar is not yet understood, despite a great deal of theoretical effort.
This problem is illustrative of the larger issue of accretion disk theory, which plays a role in much of astrophysics. Regardless of the details, the outer surface of a protostar consists at least of shocked gas that has fallen from the inner edge of the disk; the surface is thus different from the quiescent photosphere of a pre-main sequence or main-sequence star. Within its deep interior, the protostar has lower temperature than an ordinary star. At its center, hydrogen-1 is not yet fusing with itself. Theory predicts, that the hydrogen isotope deuterium fuses with hydrogen-1, creating helium-3; the heat from this fusion reaction tends to inflate the protostar, thereby helps determine the size of the youngest observed pre-main-sequence stars. The energy generated from ordinary stars comes from the nuclear fusion occurring at their centers. Protostars generate energy, but it comes from the radiation liberated at the shocks on its surface and on the surface of its surrounding disk; the radiation thus created must traverse the interstellar dust in the surrounding dense core.
The dust reradiates them at longer wavelengths. A protostar is not detectable at optical wavelengths, cannot be placed in the Hertzsprung-Russell diagram, unlike the more evolved pre-main-sequence stars; the actual radiation emanating from a protostar is predicted to be in the infrared and millimeter regimes. Point-like sources of such long-wavelength radiation are seen in regions that are obscured by molecular clouds, it is believed that those conventionally labeled as Class 0 or Class I sources are protostars. However, there is still no definitive evidence for this identification. Stellar Birthline Pre-main-sequence star Protoplanetary disk Star Formation Stellar Evolution Planet-Forming Disks Might Put Brakes On Stars Jul 25, 2006 Planets could put the brakes on young stars Lucy Sherriff Thursday 27 July 2006 13:02 GMT Why Fast-Spinning Young Stars Don't Fly Apart 24 July 2006 03:10 pm ET