The Hertz Corporation

About: The Hertz Corporation is a based out in . It is known for research contribution in the topics: Population & Soil water. The organization has 9562 authors who have published 11044 publications receiving 447929 citations. The organization is also known as: Hertz Rental Car & Hertz Rent-a-Car.

Distribution of pyrophosphate-extractable iron and organic carbon in soils of various groups

Abstract: Summary Potassium pyrophosphate (0.1m) removes very little Fe from crystalline Fe oxides at pH 10, but peptizes finely divided hydrous amorphous oxides and organic matter in soils. Fe and C contents of extracts from each horizon of twenty-six British soil profiles show distinctive patterns, independent of the residual dithionite-soluble Fe. Thus extracts of humus Fe podzols have maximum Fe and C in the B horizon, peaty gley podzol has maximum Fe in the B horizon but maximum C in the surface. These groups are differentiated from non-podzols which have maximum pyrophosphate extractable Fe and C in the surface horizon, decreasing with depth. Intermediate patterns help to quantify differences in soils of classes having properties of more than one soil group.

The effects of increasing CO2 on crop photosynthesis and productivity: a review of field studies

Abstract: . Only a small proportion of elevated CO2 studies on crops have taken place in the field. They generally confirm results obtained in controlled environments: CO2 increases photosynthesis, dry matter production and yield, substantially in C3 species, but less in C4, it decreases stomatal conductance and transpiration in C3 and C4 species and greatly improves water-use efficiency in all plants. The increased productivity of crops with CO2 enrichment is also related to the greater leaf area produced. Stimulation of yield is due more to an increase in the number of yield-forming structures than in their size. There is little evidence of a consistent effect of CO2 on partitioning of dry matter between organs or on their chemical composition, except for tubers. Work has concentrated on a few crops (largely soybean) and more is needed on crops for which there are few data (e.g. rice). Field studies on the effects of elevated CO2 in combination with temperature, water and nutrition are essential; they should be related to the development and improvement of mechanistic crop models, and designed to test their predictions.

Design and accuracy of calipers for measuring subcutaneous tissue thickness.

Abstract: A considerable proportion of the body fat lies in the subcutaneous tissue which, in many parts of the body, is only loosely attached to the underlying tissue and can be pulled up between the thumb and forefinger into a fold (Pl. I). The thickness of this fold of skin and subcutaneous tissues can be measured by applying some form of caliper to either side of it, and this technique has been widely used to give an estimate of body fat by those concerned with nutrition (Sinclair, 1948; Keys & Broiek, 1953), with fat distribution (Edwards, 1950), with child growth (Franzen, 1929; Reynolds, 1950; Tanner, 1953) and with anthropometric surveys (Berry, Cowin & Magee, 1951 ; Hammond, 1953). However, the observed thickness depends on how the skinfold is picked up and on the design of the caliper with which it is measured; if, for example, the jaws of the caliper are approximated by a spring the reading will depend on the strength of the spring, since the tissue is compressible. Despite these facts, there has been little information published on the best design of skinfold calipers, and no general standardization either of instrument or of technique. Hence the comparison of the results of different observers is usually impossible, and much work in the field is vitiated. The purpose of the present investigation was (a) to test various designs of caliper and to recommend principles that all calipers should follow, and (b) to introduce, and test the accuracy of, a new skinfold caliper which we believe to be the most satisfactory yet produced. The paper is divided into two parts : Part I describes two experiments on caliper design and ends with a set of general recommendations; Part z describes the new caliper and gives the results of three experiments made to assess its accuracy in practical use. * This investigation was carried out at the request of the Medical Research Council's Committee

Cadmium accumulation in populations of Thlaspi caerulescens and Thlaspi goesingense

Abstract: The capacity to accumulate cadmium (Cd) and zinc (Zn) was compared in Thlaspi goesingense and four populations of Thlaspi caerulescens. Two populations of T. caerulescens were grown in hydroponics at five concentrations of Cd. In addition, plants were grown in pots containing compost in which three different concentrations of Cd and two concentrations of Zn were added. A field trial was conducted to compare Zn and Cd uptake by three populations of T. caerulescens on nine selected plots of the Woburn Market Garden Experiment (UK) which had been contaminated to different degrees with heavy metals owing to past applications of sewage sludge. Results show that the four populations of T. caerulescens had the same ability to hyperaccumulate Zn but were significantly different in terms of Cd accumulation. Two populations of T. caerulescens from Southern France accumulated much more Cd than the populations from Prayon (Belgium) and Whitesike (UK). Generally, uptake of Cd was not decreased by increased concentrations of Zn in the substrate. These results indicate that the mechanisms of Cd and Zn hyperaccumulation are not identical in this species. This is the first report of hyperaccumulation of Cd by T. goesingense, but the growth of this species was markedly reduced by the large concentrations of Zn in the substrate. Future work should focus on the differences between Cd and Zn uptake in hyperaccumulator plants at the species and population level.

Tactics for managing pesticide resistance in arthropods: theory and practice

Abstract: The evolution of resistance to insecticides and acaricides by arthropod pests can be viewed and studied from two contrasting perspectives. At a fun­ damental level, resistance provides an almost ideal model of adaptation to withstand severe environmental stress. Work on the genetic (127, 128), biochemical (30, 82), and more recently, the molecular basis of resistance mechanisms (32) has cast light on the nature of this adaptation in several insect species, leading in some cases to diagnostic assays for specific genes or gene products (3, 22, 45). Similarly, population geneticists have exploited opportunities to analyze the selection of resistance in laboratory and field experiments (94, 95), and to predict, using theoretical models, how fast resistance genes are likely to evolve under different pesticide exposure re­ gimes ( l lS, 120). Unlike most evolutionary phenomena, however, resistance is also of great practical and economic significance. Not only have resistant species increased greatly in number (56), but the severity and extent of some resistance prob­ lems has increased alarmingly. For example, in some populations of the diamondback moth, Plutella xylostella (6), and Colorado potato beetle, Lepti­ notarsa decemlineata (50), resistance to virtually all available insecticides has