Measuring Matter

In 1987, health- and welfare-based standards for particulate matter (measured as PM , particles 10 micrometers in diameter or smaller) were established. A 10 micrometer (micron) particle is quite small about 100 PM,o particles will fit across the one millimeter diameter of a typical ballpoint pen. For PM particles, an annual standard was set at 50 micrograms per cubic meter (50 jJlg/m ) and a 24-hour standard was set at 150 M-g/ni . 

Refuse tips invariably result in the production of methane from the decay of organic matter. Measures are necessary to avoid trapping the methane in or beneath the building. This can be achieved by a system of methane vent pipes in the fill together with an impermeable membrane at sub-ground-floor level. Alternatively, a vented cavity can be constmcted sub-ground floor. 

Air pollution control agencies in the Los Angeles area have accumulated 22 years of consecutive hourly samples of "particulate matter measured in Km units." It was shown that the historical Km data should be proportional to elemental carbon concentrations present, and the Km samplers were calibrated to read elemental... 

Density is defined as the concentration of matter, measured by the mass per unit volume [1]. The molar volume, Vm, is defined as the volume occupied by 1 mol of a substance. The molar volume of an ideal gas is 22.4140dm3mol-1 (22.4140liter mol-1) at 1 atm pressure and 0°C. Vapor densities pv are derived through rearrangement of the ideal gas law equation as... 

Because radiation has the ability to penetrate matter, measurements can be made without direct physical contact of the sensor with the material being measured. 

Salat DH, Tuch DS, Hevelone ND, Fischl B, Gorkin S, Rosas HD, Dale AM (2005) Age-related changes in prefrontal white matter measured by diffusion tensor imaging. Ann N Y Acad Sci 1064 37 9. 

Evaluation of the validity of immunoassay measurements requires that the performance at various regions of the immunoassay curve be known. Ideally, this type of evaluation would involve measurement of sufficient replicate samples at each standard point on the curve. This would provide an assessment of the variability at each point. As a practical matter, measurement at the level of detection, 20% displacement, mid-range and the 80% displacement level of the standard curve would provide a reasonable assessment of performance. 

The high-volume sampler has become the most widely used tool for monitoring particulate matter air pollution. It is a low-cost, portable, easily maintained, and reasonably precise sampling device. Improvements in sampler performance have resulted from incorporation of automatic timers, flowrate recorders, and size separation devices into the basic system. Although hi-vols are the accepted standard in particulate matter monitoring, they inherently lack the ability to provide realtime particulate matter measurements. 

Ingebrethsen, B.J., D.L. Heavner, A.L. Angel, J.M. Conner, T.J. Steichen, and C.R. Green A comparative study of environmental tobacco smoke particulate matter measurements in an environmental chamber J. Air Pollut. Cont. Assoc. 38 (1988) 413 17. 

Estimated production of organic matter measured in tonnes of carbon at different trophic levels in the food chain, if the annually synthesized amount of phytoplankton in the oceans is 1.9 X 10 ° t of C (the calculations were based on ecological efficiencies of 10, 15 and 20% Schaefer, 1965)... 

Total dry extract (or total dry matter), measured under carefully controlled conditions by spreading the wine on a spiral of blotting paper until it is completely absorbed and evaporating it in an oven at 70°C, under a partial pressure of 20-25 mm of mercury. This corresponds to a dry air current of 40 1/h. Total dry extract is expressed in g/1, and results must be determined to within 0.5 g/1. Red wines generally contain approximately 25-30 g/1 dry extract. Dry white wines contain less than 25 g/1. In sweet wines, this value depends on the sugar content. 

DOC is involved primarily in the absorption of the UV component of solar radiation in seawater [119]. As a result, it seems hkely that UV radiation is responsible for most of the photochemical transformations of this carbon [120]. The depth to which UV can penetrate in seawater is about 20 m in the case of UV-B (280-320 nm) radiation and about 60 m in the case of UV-A (320-400 nm) radiation [121]. As a result, the photochemical effects of UV are restricted to the upper regions of a photic zone extending to a depth of about 100 m in the open ocean. Photochemical transformations of the organic matter measured as DOC can be caused by the direct absorption of hght or indirectly by the production of peroxides and free radicals [122]. The major identifiable photoproduct of DOC is CO2 [122,123], but a number of low molecular weight organic products are also produced [100,101,120,122]. 

Evidence has grown over the last decade, that urban airborne particles at ambient concentration levels common in many cities in Europe, America and Asia exert adverse effects on human health. Short- or long-term exposure to particulate matter (measured as PMio or PM2.5) is associated with an increase risk of cardiovascular and respiratory morbidity and mortality. Collectively the toxicological and epidemiological studies provide sufficient evidence that a causal relationship is likely to exist between exposure to ambient concentrations of PMjo or PM2.5 and specific human morbidity (exacerbation of chronic bronchitis, asthma or coronary heart disease) and premature deaths. 

Suspended particulate matter Measured in terms of the number of particles per unit volume of air, their surface area, or their volume. When the density of the particles is known, volume can be converted to mass, and vice versa (see Fig. 1 and Table IV). Chemical and physical processes in the atmosphere cause fine particles to grow by condensation and coagulation mechanisms to become coarse particles, which leave the atmosphere by sedimentation, rainout, and washout. 

That which changes the state of rest or motion in matter, measured by the rate of change of momentum. 

The following data give the recovery of bromide from spiked samples of vegetable matter, measured by using a gas-liquid chromatographic method. The same amount of bromide was added to each specimen. 

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