Laboratory techniques, field

This technique relies on the formation of ions by various means in a high-vaeuum ehamber, their aeeeleration by an eleetrieal field and subsequent separation by mass/eharge ratio in a magnetie field and the deteetion of eaeh speeies. It ean be used for both inorganic and organic substances, be very sensitive, and be of value in examining mixtures of compounds especially if linked to glc. Usually this is a laboratory technique but portable or transportable models are now available. ... 

Another major change was the shift from extensive use of field laboratory exploration techniques to the laboratory techniques hke ICP-AES and INAA. These produce a higher quality data than had resulted from the dc arc and other field techniques, with respect to both repeatability of measurement and improved detection limits. The metrology laboratory certifications for As and Hg in soils and sediments as key environmental toxins provided strong support to mineral exploration programs. 

Conway, M.U. and Harris, L.E. "A Laboratory and Field Evaluation of a Technique for Hydraulic Fracturing Stimulation of Deep Wells," SPE paper 10964, 1982 SPE Annual Technical Conference and Exhibition of AIME, New Orleans, September 26 29. 

The use of in situ techniques such as FTIR in both laboratory and field studies has also permitted measurement of a variety of compounds associated with biomass burning that are difficult to analyze by traditional methods. For example, as seen in Fig. 6.41, Yokelson et al. (1996, 1997) have identified formic and... 

Sirju, A.-P., and P. B. Shepson, Laboratory and Field Investigation of the DNPH Cartridge Technique for the Measurement of Atmospheric Carbonyl Compounds, Environ. Sci. Technol., 29, 384-392 (f 995). 

S.J. Odierno, "Information Pertaining to Fuzes , Vol VII (1966), "Fuze Design Testing Techniques , Picatinny Arsenal, Dover, NJ, 07801. [Listings and reviews of laboratory and field tests, described more fully in MIL-STD-331 (which is superseding MIL-STD-330-and some other earlier MIL-STD s) and in some other sources]... 

According to Aristotle, it was theoretically possible to transform any substance to another substance simply by altering the relative proportions of the four basic qualities. This meant that, under the proper conditions, a metal like lead could be transformed to gold. This concept laid the foundation of alchemy, a field of study concerned primarily with finding potions that would produce gold or confer immortality. Alchemists from the time of Aristotle to as late as the 1600s tried in vain to convert various metals to gold. Despite the futility of their efforts, the alchemists learned much about the behavior of many chemicals, and many useful laboratory techniques were developed. 

In recent years, Raman spectroscopy has undergone a major transformation from a specialist laboratory technique to a practical analytical tool. This change was driven on several parallel fronts by dramatic advances in laser instrumentation, detectors, spectrometers, and optical filter technology. This resulted in the advent of a new generation of compact and robust Raman instruments with improved sensitivity and flexibility. These devices could be operated for the first time by non-specialists outside the laboratory environment. Indeed, Raman spectroscopy is now found in the chemical and pharmaceutical industries for process control and has very recently been introduced into hospitals. Handheld instruments are used in forensic and other security applications and battery-operated versions for field use are found in environmental and geological studies. 

Diffusion coefficients of nucleic acids in solutions and gels have been accurately measured with the development of advanced laboratory techniques, such as pulsed field-gradient NMR and FRAP (Lapham et al., 1997 Pluen et al., 1999 Politz et al., 1998). These data may provide some semi-quantitative information applicable to interstitial transport of nucleic acids in tumor tissues. 

Specifically we wished to measure the rate of reaction of OH with MSA to enable modelling calculations of the stability of MSA in aerosol droplets. The one reported measurement of this rate (2), using pulse radiolysis techniques, 3.2 x 109 M 1 s 1, is fast enough to suggest that this reaction pathway could be an important sink for MSA. This is of interest in explaining an apparent discrepancy that exists between laboratory and field studies of tne oxidation of dimethyl sulfide. Although a number of laboratory studies (6-9 ) show that MSA is the major stable product, and SO2 a minor one, field observation suggest MSA is only a minor (10%) fraction (2) of total non-sea-salt sulfur in marine aerosols. Two possible rationalizations of this are that i) MSA is subject to further reaction in marine aerosols and ii) other reaction pathways of dimethyl sulfide, or perhaps other non-methylated sulfur compounds should be considered. 

Gas phase molecular aggregates that contain acid molecules have been produced with free jet expansion techniques and detected by using electron impact ionization mass spectrometry. The clusters of aqueous nitric acid paralleled many properties of the condensed phase. Multiple nitric acid molecules were found in the clusters that were sufficiently dilute. The acid molecule was absent in the ionized clusters involving HC1 and only water was evident. Experiments also demonstrated the reactivity of ammonia with aqueous nitric acid and sulfur dioxide clusters and of sulfur trioxide with water clusters. The natural occurrence of acid cluster negative ions offers a means to probe the gas phase acid loading of the atmosphere through laboratory and field studies of the ion chemistry. 

By the end of the twentieth century, industrial applications of biotechnology started gaining momentum and proven laboratory techniques started to move into potentially huge markets. The field of industrial biotech-... 

Early experiments in our laboratory were concerned with methods for sampling and analysis of TDAL from formulations (6), insects (7) and from the forest atmosphere (8). This work was largely founded upon concepts developed previously by Beroza e t al. (9, 10, 11). Since then, several other groups have applied these concepts to the measurement of a number of different insect pheromone release rates (12, 13). On the basis of our early findings, we were convinced that the existing laboratory techniques for release rate determination from formulations were inadequate. Laboratory tested formulations did not experience the extremes of climatic variation which are the norm in the field and consequently the release rate results were not transferable to field performance. 

Unlike the reactions of GEM in solution, experimental data on the gas-phase reactions of elemental mercury with some atmospheric oxidants are limited due to challenges including complexity of reactions, the low concentrations of species at atmospheric conditions, the low volatility of products, sensitivity to temperature and pressure, and the strong effects of water vapour and surface on kinetics. The possible effects and distribution of mercury isotope fractionation have not been analysed in any of the studies. The isotopes dilute the signal and mean that with current mass spectrometry techniques, ambient RGM compounds can not be identified. The possibility of theoretically predicting the thermochemistry of mercury-containing species of atmospheric interest is important and is complementary to laboratory and field studies. 

The accuracy of exposure assessment is determined by systematic and random errors in the assessment. For quantitative exposure assessments, important sources of error include measurement errors (i.e. from laboratory and field monitoring techniques), as well as variations in exposure over time and space. For qualitative exposure proxies (e.g. self-reported past exposures, occupational histories or expert evaluations), the most important sources of error are recall bias (systematic differences in exposure recall between cases and controls) and random error, expressed in terms of intra- and inter-rater agreement. Although systematic errors can result in serious misinterpretations of the data, especially due to scaling problems, random errors have received more attention in epidemiology because this type of error is pervasive, and its effect is usually to diminish estimates of association between exposure and disease. The magnitude of random errors can be considerable in epidemiological field studies. 

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