Gallium arsenide (GaAs) is a compound of the elements gallium and arsenic. It is a III/V semiconductor, and is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells and optical windows.
The global market for GaAs devices was $4.9 billion in 2010, up 32 percent on 2009, according to market research firm Strategy Analytics. The adoption of smartphones and data-centric networks will also drive growth in the GaAs market in 2011 and 2012 and on to reach nearly $6.1 billion in 2014.
Purity for the raw materials used to produce gallium arsenide must be at least 99.9999% pure for optoelectronic devices (light-emitting diodes (LEDs), laser diodes, photodetectors, solar cells), 99.99999% is required for integrated circuits. These purity levels are referred to by several names: 99.9999%-pure gallium is often called 6-nines, 6N or ptoelectronic grade while 99.99999%-pure gallium is called 7-nines, 7N, semi-insulating (SI) or integrated circuit (IC) grade.
The GaAs placed on the market built into the above mentioned devices, are cristalline form substances, characterised by low bioavailability and solubility. The crystal is stable enough that ingested pieces may be passed with negligible absorption by the body, residential time is also short.
When ground into very fine particles, such as in wafer-polishing processes, the high surface area enables more reaction with water releasing some arsine and/or dissolved arsenic, beacuse the cristal surface maybe partially damaged.
Particles in the form of dust may get into the lung by inhalation (during production and workplace uses) and cause carcer. Other exposure pathways are not proven to be carcinogenic. Originating from the lung no systemic concentrations were measured and no systemic carcinogeneity has been arised in testanimals. The residential time of GaAs particles in the lung is much higher, that in case of ingestion, increasing the risk of absorption by the tissue.
Read more: http://monographs.iarc.fr/ENG/Monographs/vol86/mono86-8A.pdf
gallon is a measure of volume approximately equal to four litres. There are three definitions in current use. In United States customary units there are the liquid (≈ 3.78 liters) and the lesser used dry (≈ 4.4 liters) gallons. There is also the imperial gallon (≈ 4.5 liters) which is in unofficial use within the United Kingdom and Ireland and is in semi-official use within Canada.
|gallons, liquid (US)||cubic feet||0.133 680 6|
|gallons, liquid (US)||cubic inches||231|
|gallons, liquid (US)||cubic meters||0.003 785 411 784|
|gallons, liquid (US)||cubic yards||0.004 951 13|
|gallons, liquid (US)||gills (US)||32|
|gallons, liquid (US)||liquid gallons (British)||0.832 67|
|gallons, liquid (US)||liquid ounces||128|
|gallons, liquid (US)||liquid pints||8|
|gallons, liquid (US)||liquid quarts||4|
|gallons, liquid (US)||liters||3.785 411 784|
|gallons, liquid (US)||milliliters||3,785.411 784|
|gallons, liquid (US)||minims||61,440|
an achromatic lesion smaller than the width of one chromatid, and with minimum misalignment of the chromatids.
garbage, trush, rubbish all are worthless, mixed or diffusely dispersed, not reused, not utilised materaials, products or objects.
gas chromatography is an analytical technique employing a gaseous mobile phase that separates mixtures into their individual components. The stationary phase can be solid or immobilized liquid. The separation is based on dynamic sorption-desorption processes. Compounds volatilized without decomposition can be separated. The technique is not suitable for the separation of ionic compounds and of large molecules like proteins, peptides, polysacharides, etc. (Source: Balla J.: Analytical applications of gas chromatography. Budapest, 1987)
In environmental analysis gas chromatography is applied for the measurement of volatile and semivolatile organic compounds (VOC and SVOC, resp.) in air, in surface and subsurface water, as well as in potable water, in soil, of residual content of a chemical in food, in animal and plant samples. It is applied for identification of the source of the contamination, the transport of contaminants, bioaccumulation, assessment of contaminated sites, technology monitoring, etc.
gasoil is an intermediate distillate product from petroleum, used for diesel fuel, heating fuel and sometimes as feedstock for other industries, e.g. plastic industry.
refined petroleum distillate, normally boiling within the limits of 30-210°C, which, combined with certain additives, earlier with organic tin compounds, such as tintetraethyl, nowadays with e.g. methyl-terc.-butyl-ether (MTBE), is used as fuel for spark-ignition engines. By extension, the term is also applied to other products that boil within this range. The soil at the fuel stations gets often contaminated with gasoline. The low boiling components are evaporating while those of higher boiling temperature remain in the soil till biodegraded by the microflora.
GCP = Good Clinical Practice
GDP = Gross Domestic Product is the statistical measure of the total economic value of all the goods and services produced by an economy in a given year. The size and rate of growth of GDP are often taken as indicators of the level of development acheived by a society. GDP also contains many items such as spending to clean up environmental damage, treat drug addicts, keep criminals in jail, etc., that reflects social difficulties rather than social well-being. GDP excludes important items such as the unpaid costs of the environmental damage and the lost value of depleted natural resources.
gelatin is substance in gel form obtained by denaturing animal skin and bone collagen subjected to the prolonged action of boiling water.
Gelatin has a wide range of applications in the food, the pharmaceutical and the photographic industries. It is also used in cosmetics, in the refining of metals, in the polymerisation of plastics and the sizing of paper.
gene transfer may be carried out by the following mediators:
- Gene transfer by liposomes
- DNA transfer in the form of a calciumphosphate complex
- Transfection: the introduction of foreign DNA into a host cell by viral or bacterial infection.
- Gene transfer by virus: incorporation of new DNA into and organism's cells, usually by a vector such as a modified virus.
a gene gun or a biolistic particle delivery system, originally designed for plant transformation, is a device for injecting cells with genetic information. The payload is an elemental particle of a heavy metal coated with plasmid DNA. This technique is often simply referred to as bioballistics or biolistics.
This device is able to transform almost any type of cell, including plants, and is not limited to genetic material of the nucleus: it can also transform organelles, including plastids.
The gene gun was originally a Crosman air pistol modified to fire dense tungsten particles. The earliest custom manufactured gene guns used a 22 caliber nail gun cartridge to propel an extruded polyethylene cylinder (bullet) down a 22 cal. Douglas barrel.
A droplet of the tungsten powder and genetic material was placed on the bullet and shot down the barrel at a lexan "stopping" disk with a petri dish below. The bullet welded to the disk and the genetic information blasted into the sample in the dish with a doughnut effect (devastation in the middle, a ring of good transformation and little around the edge). The gun was connected to a vacuum pump and was under vacuum while firing.
The early design was put into limited production later the design was refined by removing the "surge tank" and changing to nonexplosive propellants. DuPont added a plastic extrusion to the exterior to visually improve the machine for mass production to the scientific community.
Biorad contracted with Dupont to manufacture and distribute the device. Improvements include the use of helium propellant and a multi-disk-collision delivery mechanism. Other heavy metals such as gold and silver are also used. Gold may be favored because it has better uniformity than tungsten and tungsten can be toxic to cells, but its use may be limited due to availability and cost.
transformation is a process by which the genetic material carried by an individual cell is altered by incorporation of exogenous DNA into its genome.
genomic library is a collection of clones made from a set of randomly generated overlapping DNA fragments that represent the entire genome of an organism.
The genomic library is normally made by lambda-phage vectors, instead of plasmid vectors. The reason for that is, that the entire human genome is about 3 x 109 bp long while a plasmid or lambda-phage vector may carry up to 20 kb fragment. This would require 1.5 x 105 recombinant plasmids or phages. When plating E. coli colonies on a normal petri dish, the maximum number to allow isolation of individual colonies is about 200 colonies per dish. Thus, at least 700 petri dishes are required to construct a human genomic library. By contrast, as many as 5 x 104 lambda phage plagues can be screened on a typical petri dish. This requires only 30 petri dishes to construct a human genomic library. Another advantage of l phage vector is that its transformation efficiency is about 1000 times higher than the plasmid vector.
the first of the -omics technologies to be developed, genomics has resulted in massive amounts of DNA sequence data requiring great amounts of computer capacity. Genomics has progressed beyond sequencing of organisms (structural genomics) to identifying the function of the encoded genes (functional genomics).
geobiology is a science that combines geology and biology to study the interactions of organisms with their environment: the interactions of the biosphere with the lithosphere, or with the athmosphere.
geochemistry is the combination of earth and chemical sciences. It deals with the properties and origin of minerals and rocks focusing on the chemical composition of the Earth and of other planets, chemical processes and reactions occurring in rocks and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosphere. At present the distribution of chemical elements in the Earth is changing as a result of human activity. To monitor these changes modern geological and chemical measurement techniques are used.
an alternative or green energy-source. Steam and hot water from below the Earth’s surface have been used historically to provide heat for buildings, industrial processes, and domestic water and to generate electricity in geothermal power plants. In power plants, two boreholes are drilled – one for steam alone or liquid water plus steam to flow up, and the second for condensed water to return after it passes through the plant. In some plants, steam drives a turbine; in others, hot water heats another fluid that evaporates and drives the turbine.
GHG = greenhouse gas, a term for a gases such as carbon dioxide or methane that increases global temperatures by trapping solar elecromagnetic radiation. This phenomenon is called greenhouse effect.
The Globally Harmonised System of Classification and Labelling of Chemicals (GHS) has been the subject of more than a decade of work; its aim is to provide a framework to bring together the various national and regional hazard communication systems which control the supply of hazardous chemicals in much the same way that the ‘Orange Book’ offers a global framework for the transport of dangerous goods. The purpose of GHS is to provide a single, globally harmonized system to address classification of chemicals, labels, and safety data sheets. The first edition of GHS was published in July 2003 as the ‘Purple Book’, it is revised evey December of even numbered years (and usually published in the following summer). Further details about the publication status, its ‘adoption’ throughout the world, and often access to electronic versions (when these are eventually made available), can be found on the UNECE website:
More information can also be obtained on the HSE GHS website at a special section for GHS related issues http://www.hse.gov.uk/ghs/index.htm. Note however that updating of the HSE website pages sometimes lags behind developments by several months. HSE is the lead on the development of the GHS and consults on GHS issues through its Standing Committee on Hazard Information and Packaging (SCHIP). Those do not get SCHIP communications via their Trade Association, and who wish to be sent such communications when issued should contact Desmond Waight (email Desmond@dangoods.co.uk) who is an ‘independent’ associate member of SCHIP asking to be placed on his “Emerging Classification” circulation. There is no charge.
The EU have passed legislation (the Regulation (EC) No 1272/2008 (CLP)) that will over time harmonise the EU supply provisions with the GHS. See the section of this website for further information.
Transport implementation is via the UN Recommendations and Model Regulations (Orange Book) and by subsequent adoption in the various international modal provisions (ADR, RID, ADN, IMDG Code, ICAO TIs / IATA DGRs).
a geographic information system (GIS), captures, stores, analyzes, manages, and presents data that refers to or is linked to location. An information system that integrates, stores, edits, analyzes, shares, and displays geographic information. In a more generic sense, GIS applications are tools that allow users to create interactive queries (user created searches), analyze spatial information, edit data, maps, and present the results of all these operations.
In the United States 12 soil orders are defined. In 1975, Soil Taxonomy was published by the United States Department of Agriculture's Soil Survey Staff. This system for classifying soils has undergone numerous changes since that time, and the 2nd edition was published in 1999. Soil Taxonomy remains one of the most widely used soil classification systems in the world.
At the highest level, Soil Taxonomy places soils in one of 12 categories known as orders: the 12 soil orders are listed below in the sequence in which they key out in Soil Taxonomy:
- Gelisols - soils with permafrost within 2 m of the surface
- Histosols - organic soils
- Spodosols - acid forest soils with a subsurface accumulation of metal-humus complexes
- Andisols - soils formed in volcanic ash
- Oxisols - intensely weathered soils of tropical and subtropical environments
- Vertisols - clayey soils with high shrink/swell capacity
- Aridisols - CaCO3-containing soils of arid environments with subsurface horizon development
- Ultisols - strongly leached soils with a subsurface zone of clay accumulation and <35% base saturation
- Mollisols - grassland soils with high base status
- Alfisols - moderately leached soils with a subsurface zone of clay accumulation and >35% base saturation
- Inceptisols - soils with weakly developed subsurface horizons
- Entisols - soils with little or no morphological development.
The World Reference Base (WRB) ensures the uniform classification of soils all around the world.
WRB was originally an initiative of FAO and UNESCO, supported by UNEP and the International Society of Soil Science which dates back to 1980. The intention of the project was to work towards the establishment of a framework through which ongoing soil classification could be harmonized. The final objective was to reach international agreement on the major soil groups to be recognized at a global scale as well as on the criteria and methodology to be applied for defining and separating them.
Such an agreement was meant to facilitate the exchange of information and experience, to provide a common scientific language, to strengthen the applications of soil science and to enhance the communication with other disciplines. Several meetings of the ISSS subgroup were held starting in 1982 in New Delhi. In 1992, in Montpellier, France, it was decided that there was no justification to develop a completely new classification system very different from the Revised Legend published by FAO in 1988. Therefore the FAO Revised Legend was to be adopted as the Framework for WRB’s future work and that it would be the task of the working group to further develop its definitions and linkages to the existing FAO units, in order to give them more depth and validity.
Source of description:
the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century is called global warming. A continuation is projected.
According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th century. Most of the observed temperature increase since the middle of the 20th century was caused by increasing concentrations of greenhouse gases, which results from human activity such as the burning of fossil fuel and deforestation. Global dimming, a result of increasing concentrations of atmospheric aerosols that block sunlight from reaching the surface, has partially countered the effects of greenhouse gas induced warming.
glycogen is the molecule that functions as the secondary long-term energy storage in animal and fungal cells. It is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach. Glycogen is the analogue of starch, and is commonly referred to as animal starch, having a similar structure to amylopectin. Glycogen is found in the form of granules in the cytosol in many cell types, and plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be quickly mobilized to meet a sudden need for glucose.
the goal of LCA is to compare the full range of environmental effects assignable to products and services in order to improve processes, support policy and provide a sound basis for informed decisions.
The term life cycle refers to the notion that a fair, holistic assessment requires the assessment of raw-material production, manufacture, distribution, use and disposal including all intervening transportation steps necessary or caused by the product's existence.
There are two main types of LCA. Attributional LCAs seek to establish the burdens associated with the production and use of a product, or with a specific service or process, at a point in time (typically the recent past). Consequential LCAs seek to identify the environmental consequences of a decision or a proposed change in a system under study (oriented to the future), which means that market and economic implications of a decision may have to be taken into account. Social LCA is under development as a different approach to life cycle thinking intended to assess social implications or potential impacts. Social LCA should be considered as an approach that is complementary to environmental LCA.
The procedures of life cycle assessment (LCA) are part of the ISO 14000 environmental management standards: in ISO 14040:2006 and 14044:2006. (ISO 14044 replaced earlier versions of ISO 14041 to ISO 14043.)
 Four main phases
Illustration of LCA phases.
According to the ISO 14040 and 14044 standards, a Life Cycle Assessment is carried out in four distinct phases as illustrated in the figure shown to the right.The phases are often interdependent in that the results of one phase will inform how other phases are completed.
An LCA starts with an explicit statement of the goal and scope of the study, which sets out the context of the study and explains how and to whom the results are to be communicated. This is a key step and the ISO standards require that the goal and scope of an LCA be clearly defined and consistent with the intended application. The goal and scope document therefore includes technical details that guide subsequent work:
* the functional unit, which defines what precisely is being studied and quantifies the service delivered by the product system, providing a reference to which the inputs and outputs can be related;
* the system boundaries;
* any assumptions and limitations;
* the allocation methods used to partition the environmental load of a process when several products or functions share the same process; and
* the impact categories chosen.
the status achieved by a surface water body when both its ecological status and its chemical status are at least "good".
Good Laboratory Practice (GLP) is a quality system concerned with the organisational process and the conditions under which non-clinical health and environmental safety studies are planned, performed, monitored, recorded, archived and reported. (Source: REACH Glossary)
OECD Guidelines on Good Laboratory Practice part 1, available at: http://www.oecd.org/findDocument/0,2350,en_26...
GLP = Good Laboratory Practices
According to 2004/10/EC, Good Laboratory Practice (GLP) is defined as a quality system concerned with the organizational process and the conditions under which non-clinical health and environmental safety studies are planned, performed, monitored, recorded, archived and reported. The main objective of GLP is to ensure test data produced by different laboratories can be mutually recognized so as to avoid repeat testing. GLP provides an assurance to regulatory authorities that the data submitted are a true reflection of the results obtained during the study and can therefore be relied upon when making risk/safety assessments.
Member States of the European Union have to take measures to comply with the principle of GLP when evaluating chemicals safety according to 67/548/EEC. SGS has a worldwide network of laboratories that are GLP compliant contractual laboratories for physico-chemical, toxicological and ecotoxicological tests.
Source: REACH, Glossary