Analysis Of Bulk Samples Research Articles

Application of x-ray diffraction to analytical problems of occupational health.

A review of the application of x-ray diffraction to the analytical problems encountered in an industrial hygiene laboratory is presented. Among these problems are the analysis of bulk, rafter, airborne dust, and biological samples for the presence of minerals which have been implicated as causative agents in silicosis, pneumoconiosis, and other related occupational lung diseases. Automatic scanning x-ray diffraction techniques for both qualitative and quantitative analyses of samples mentioned above are discussed. X-ray diffraction is presented as an analytical tool for crystalline substances which are hazards in an occupational environment.

Nucleation in undercooled Bi-Te alloys

Thermal analysis of bulk samples of Bi-Te alloys as a function of compositional change from hypo-eutectic to hyper-eutectic composition has proved that the intermediate phase Bi7Te3 with a rhombohedral crystal structure is a very efficient nucleant for bismuth. This technique is a modification of an earlier one applied by the authors as a critical experiment to test Jackson’s objection to Sundquist and Mondolfo’s droplet technique for determination of nucleation catalysis. The modified method described in this paper is unique and eliminates another possible source of error in the determination of nucleation capacity in eutectic systems.

Changes in valency state of ions in CuMn2O4 at high temperatures

Thin films of copper manganite with three different molar ratios of Cu∶Mn viz 1∶1, 1∶2 and 1∶3 have been deposited on quartz plates. The electrical conductivity of these thin films has been studied as a function of temperature. The energy of activation for electrical conduction in these compounds is found to increase from 0.20 eV to about 0.62 eV above 600° K. Differential thermal analysis of bulk sample of copper manganite also shows a small endothermic change at 600° K, while thermogravimetric analysis does not show any change in weight. It has been concluded from these results that the stable form of the ionic configuration of copper manganite at low temperatures, i.e. Cu1+[Mn3+Mn4+]O4 changes at high temperatures to Cu2+[Mn23+]O4

An evaluation of the U234/U238method as a tool for dating pelagic sediments

The possibility of using the 15% excess U234 activity in oceanic uranium for dating pelagic sediments in the age range 100,000 years to more than 1 m.y. has been explored. Results from a series of analyses of bulk samples, mechanical separates, and acid leach fractions indicate that separation of authigenic uranium from detrital uranium by either mechanical or chemical means is impractical. Measurements on totally dissolved samples reveal that the sediments do not form a closed system; post-depositional migration of U234 in the sedimentary column takes place. Based on the experimental data obtained from three red-clay cores with sedimentation rates ranging from 2 to 6 mm/1000 yr, a model depicting diffusion of the U234 generated within the sediments is proposed. The diffusion equation includes three parameters: sedimentation rate, diffusion coefficient for U234, and fraction of the internally produced U234 subject to mobility. If the amount of U234 lost from these cores is typical, a sizeable part of the U234 excess in the sea must be from this source.

Radiocarbon dating of California Basin sediments : Emery K. O. and E. E. Bray 1962. Bull. Amer. Ass. Petrol. Geol., 46(10): 1839–1856.

Eleven radiocarbon age determinations clearly show that a lens of Holocene fluvial organic debris on the Alaskan Arctic Coastal Plain contains mostly pre-Holocene organic material. Radio-carbon ages of identified plant macrofossils indicate the material was deposited about 9000 to 9500 yr B.P. Radiocarbon analyses of bulk samples from this deposit, however, range from 13,300 to 30,300 yr B.P. Most of the old organic matter seems to be in the smaller size fractions in the deposit, particularly in the fraction between 0.25 and 0.5 mm, but all size fractions are contaminated. Particular caution must be exercised in submitting bulk samples for radiocarbon dating from areas where conditions favor redeposition of isotopically “dead” carbon.

Reflection profiling in and around the Puerto Rico Trench : Ewing J. and M. Ewing 1962. J. Geophys. Res., 67(12): 4729–4740.

Eleven radiocarbon age determinations clearly show that a lens of Holocene fluvial organic debris on the Alaskan Arctic Coastal Plain contains mostly pre-Holocene organic material. Radio-carbon ages of identified plant macrofossils indicate the material was deposited about 9000 to 9500 yr B.P. Radiocarbon analyses of bulk samples from this deposit, however, range from 13,300 to 30,300 yr B.P. Most of the old organic matter seems to be in the smaller size fractions in the deposit, particularly in the fraction between 0.25 and 0.5 mm, but all size fractions are contaminated. Particular caution must be exercised in submitting bulk samples for radiocarbon dating from areas where conditions favor redeposition of isotopically “dead” carbon.

Use of Indicator Methods in Range Digestion Trials. A Review

The nutrition of range livestock is necessarily an important consideration not only of the individual rancher but also the technical range manager. Of the environmental factors which affect animal productivity, probably the most important is that of nutrition. An increased productivity per animal generally means a better ranch income to the operator and is definitely concerned with stabilizing the livestock industry which is one of the goals of range management. As range livestock operations are generally quite extensive in nature and as low productive ranges are commonly utilized, t.he nutrition of range livestock is often found to be marginal or submarginal. In contrast with farm livestock production, economics do not allow for range livestock to be kept continually on a high plane of nutrition, but an opt.imum does exist below which an animal’s productivity is apt to be curtailed. During the past 35 years considerable work has been done on the chemical analysis of bulk samples of the more common range plants. Although this is an index to the value of different species, it is not entirely satisfactory. Cook and Harris (1951) reported that nutritive value as measured by chemical content alone is not a reliable index to the availability of the various nutrients contained in the forage unless accompanied by digestibility determinations or balance trials. This necessitates the more extensive use of digestion and metabolization trials. Kennedy and Dinsmore (1909) in their early work in Nevada showed farsightedness in expressing concern that reseeded plants must not only seed themselves but must be valuable from the standpoint of nutrition. Also, the decreased livestock weight gains and percent calf crop which accompany overgrazing are due primarily to a lowered plane of nutrition of the grazing animals.

Measuring Consumption and Digestibility of Winter Range Plants by Sheep

EXTENSIVE areas of desert range in the intermountain area are the sole ;source of forage for sheep during the winter grazing season. The diversity in soil, climate, and topography provides a variety of native forage for grazing animals, and the nutritive content of the diet varies widely depending upon environmental conditions, and animal selectivity for various species and parts of plants. Thus, a knowledge of the nutritive qualities of native forage plants is of extreme importance for a better understand-ing and appraisal of the animal's diet under range conditions. Most studies of the nutrients supplied by range forage have dealt with chemical analyses of bulk samples of herbage collected from the range. However, chemical content is not a reliable index to availability of the various nutrients and is of limited value unless accompanied by digestibility determinations or balance trials. For this reason a method for determining digestibility of native forage under range conditions was developed and used in obtaining the data presented in this paper.

Measuring the Nutritive Content of a Foraging Sheep's Diet under Range Conditions

Need for an understanding of the nutrition problems on the western range is of paramount importance. Despite the importance of this problem, little is known as to the actual composition of the grazing animal's diet. The reasons for this lack of knowledge are many fold, including (a) difficulty of collecting representative samples of vegetation because of soil, site, and seasonal variations, (b) difficulty of finding what species and portions of plants actually are consumed, and (c) difficulty in interpreting the nutritive content of the ingested forage. The method here presented for determining the nutritive content of the sheep's diet under range conditions is an entirely new approach to this problem and is based upon chemical analyses of the vegetation before being grazed as compared to chemical analyses after being grazed. Briefly, the method consists of collecting a predetermined number of plant units before grazing and a similar number after grazing. Each plant species is sampled both before and after grazing and each sample is weighed and chemically analyzed. The difference in weight and chemical composition between the before-grazing sample and the after-grazing sample serves as a measure of the nutrient content of the ingested forage. It was found from this study that sheep are highly selective in their diet and consume largely leaves and tender stems, rejecting the more fibrous parts of the plant. Consequently, a much better quality of forage actually makes up the diet than chemical analyses of bulk samples would indicate.