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UN orgnisations for the environment
unabsorbed dose

represents that washed from the skin surface after exposure and any present on the nonocclusive cover, including any dose shown to volatilise from the skin during exposure.


United Nations Convention to Combat Desertification

The objective of the Convention is to combat desertification and mitigate the effects of drought in countries experiencing serious drought and/or desertification, particularly in Africa, through effective action at all levels, supported by international cooperation and partnership arrangements, in the framework of an integrated approach which is consistent with Agenda 21, with a view to contributing to the achievement of sustainable development in affected areas.

Achieving this objective will involve long-term integrated strategies that focus simultaneously, in affected areas, on improved productivity of land, and the rehabilitation, conservation and sustainable management of land and water resources, leading to improved living conditions, in particular at the community level.

Sorce: http://www.unccd.int/convention/text/convention.php

uncertainty factor

mathematical adjustments for reasons of safety when knowledge is incomplete.

For example, factors used in the calculation of doses that are not harmful (adverse) to people. These factors are applied to the lowest-observed-adverse-effect-level (LOAEL) or the no-observed-adverse-effect-level (NOAEL) to derive a minimal risk level (MRL). Uncertainty factors are used to account for variations in people's sensitivity, for differences between animals and humans, and for differences between a LOAEL and a NOAEL. Scientists use uncertainty factors when they have some, but not all, the information from animal or human studies to decide whether an exposure will cause harm to people.

For the estimation of ecosystem PNEC, the uncertainty factors are determined according to the precisity of the applied tests. The mathematical method which uses these factors between measured and extrapolated data is called factorial extrapolation.

It is also called safety factor.

See also Predicted No Effects Concentration (PNEC)

under audible sound

United Nations Environment Programme (UNEP).

See also: http://www.unep.org/

unit converter

on the internet you can find several unit converters, which are able to convert physical unites of measure from ones system to an other one, e.g. to the metric system.

On the web-address of http://www.digitaldutch.com/unitconverter/density.htm you can find a converter able to convert area, density, energy, force, length, mass, power, pressure, speed, temperature and volume, bits and bytes.

unit process, LCA
unprotected groundwater extraction plant
unresolved complex mixture
the thousands of compounds that can not be fully resolved into peaks in gas chromatography, abbreviated as UCM. The extracts of soils contaminated by hydrocarbons (diesel, transformer, black oil) result in such chromatograms.
unsaturated soil zone
upper explosion border concentration
Environmental Protection Agency, USA
USA environmental Protection Agency

Universal Serial Bus

use category (UC), REACH
means an exposure scenario covering a wide range of processes or uses, where the processes or uses are communicated, as a minimum, in terms of the brief general description of use, (Source: REACH Glossary)
use category of chemical substances
use conditions of chemical substances
use of chemical substances, REACH

use means any processing, formulation, consumption, storage, keeping, treatment, filling into containers, transfer from one container to another, mixing, production of an article or any other utilisation.
Conditions of use refer to the Operational Conditions and Risk Management Measures (RMM) as described in an Expousre Scenarios.
(Source: REACH Glossary)

use of chemicals
utilisation limit value
utilised source water system
UV detector in liquid chromatography
detection system in liquid chromatography based on absorption of ultraviolet light. Based on their absorbance spectra certain compounds such as PAHs can be identified. The absorbance is proportional to the quantity (concentration) of the analyte.
UV radiation

ultraviolet light can be detected by suitable photodiodes and photocathodes which can be tailored to be sensitive in different parts of the UV spectrum. Sensitive ultraviolet photomultipliers are also available. These detectors make possible the detection of any levels and changes in levels of UV-light. As such, they can be applied as detectors of many analytical methods as part of spectrometers or coupled with liquid-chromatographs.

UVCB materilas

substances of Unknown or Variable composition, Complex reaction products or Biological materials. A type of chemical substances within REACH regulation.