2,873 research outputs found

    AN ECONOMIC EVALUATION OF THE COLORADO RIVER BASIN SALINITY CONTROL PROGRAM

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    Dissolved salts (salinity) adversely affect numerous urban and agricultural users of Colorado River water in California and Arizona. Congress in 1974 authorized a major salinity control program. Studies of general economic benefits from salinity abatement and the cost per unit of salinity reduction expected from specific proposed projects have been developed by the responsible federal agencies, but no project-by-project evaluation has been published. We find a conceptual basis for a substantial downward revision of prospective economic benefits of salinity abatement. Revised benefits are compared with estimated costs, and only for five of the nineteen projects do economic benefits appear to exceed costs.Resource /Energy Economics and Policy,

    Normal Bias in the Direction of Fetal Rotation Depends on Blastomere Composition during Early Cleavage in the Mouse

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    Interest in establishing the basis of left/right asymmetry during embryogenesis has burgeoned in recent years. Relevant studies in mammals, focused largely on the mouse, have revealed involvement of a variety of genes that are common to the process in other animals. In the mouse, lateral differences in gene expression are first evident late in gastrulation when directional rotation of nodal cilia has been implicated in effecting the normally very strong bias in handedness. Reconstructing cleavage stages with correspondingly positioned blastomeres from appropriate numbers of conceptuses with similar division planes provides a way of testing whether they differ in potency without the confounding effects of reduced cell number. In a study using this strategy, 4-cell stage conceptuses reconstructed from blastomeres produced by equatorial as opposed to meridional second cleavage were found to be compromised in their ability to support normal development. Here, in more refined reconstructions undertaken at both the 4- and 8-cell stage, no significant impairment of development to the 9th or 12th day of gestation was found for products of equatorial second cleavage or their 8-cell stage progeny. Most surprisingly, however, a significant increase in reversal of the direction of axial rotation was found specifically among fetuses developing from conceptuses reconstructed from 8-cell stage progeny of products of equatorial second cleavage. Hence, manipulations during early cleavage some 6 days before fetal asymmetries are first evident can perturb the normally very strong bias in specification of a facet of left-right asymmetry

    Does the butcher-on-the-bus phenomenon require a dual-process explanation? A signal detection analysis

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    The butcher-on-the-bus is a rhetorical device or hypothetical phenomenon that is often used to illustrate how recognition decisions can be based on different memory processes (Mandler, 1980). The phenomenon describes a scenario in which a person is recognized but the recognition is accompanied by a sense of familiarity or knowing characterized by an absence of contextual details such as the person’s identity. We report two recognition memory experiments that use signal detection analyses to determine whether this phenomenon is evidence for a recollection plus familiarity model of recognition or is better explained by a univariate signal detection model. We conclude that there is an interaction between confidence estimates and remember-know judgments which is not explained fully by either single-process signal detection or traditional dual-process models

    Effect of Green Tea on Streptococcus mutans Metabolic Activity, Planktonic Growth, and Biofilm Activity in the Presence of Nicotine

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    poster abstractStreptococcus mutans is the main bacterial cause of dental caries, and it has been proven by previous research that its growth is affected by various concentrations of nicotine and other agents. The amount of S. mutans in the mouth is directly proportional to the number of dental cavities. Studies have shown that smokers have an increased amount of caries, much of which is due to the low concentrations of nicotine the mouth is exposed to. It is known that S. mutans thrives in low-moderate concentrations of nicotine, and that nicotine is a promoting agent for S. mutans. S. mutans has also been proven as a contributor to atherosclerosis, resulting from dental plaque entering the bloodstream. Green Tea is a commonly consumed beverage, which has been known to reduce the number of dental cavities. Previous research has concluded that green tea contains polyphenols, which have antimicrobial effects, including an inhibitory effect on S. mutans. The objective of this research is to observe how green tea affects S. mutans metabolic activity, as well as biofilm and planktonic growth, in the presence of nicotine. The experiments compared S. mutans treated with nicotine concentrations (0-8 mg/ml), and S. mutans treated with a 2.5 g/200 mL concentration of Sencha Jade Reserve Japanese green tea in conjunction with the various nicotine concentrations. The assays were performed in a microtiter plate; the XTT and biofilm assays measured absorbance, and the planktonic assay measured kinetic growth. The experiments conclude that green tea has an inhibitory effect on nicotine-treated S. mutans metabolic activity and planktonic growth, with higher concentrations of green tea inhibiting more effectively. It was also concluded that green tea increases biofilm formation. These conclusions provide evidence of the inhibitory effect green tea has on nicotine-treated S. mutans, and may indicate a way to reduce the incidence of caries and atherosclerosis

    Effects of alternative electricity rates and rate structures on electricity and water use on the Colorado High Plains

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    October 1984.Contract report for Colorado Commission on Higher Education.Bibliography: pages 60-62

    Does the Butcher-on-the-Bus Phenomenon Require a Dual-Process Explanation? A Signal Detection Analysis

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    The butcher-on-the-bus is a rhetorical device or hypothetical phenomenon that is often used to illustrate how recognition decisions can be based on different memory processes (Mandler, 1980). The phenomenon describes a scenario in which a person is recognized but the recognition is accompanied by a sense of familiarity or knowing characterized by an absence of contextual details such as the person’s identity. We report two recognition memory experiments that use signal detection analyses to determine whether this phenomenon is evidence for a recollection plus familiarity model of recognition or is better explained by a univariate signal detection model. We conclude that there is an interaction between confidence estimates and remember-know judgments which is not explained fully by either single-process signal detection or traditional dual-process models

    PARASITES FROM HUMAN COPROLITES FROM MEXICO ZOONOTIC AND HUMAN PARASITES OF INHABITANTS OF CUEVA DE LOS MUERTOS CHIQUITOS, RIO ZAPE VALLEY, DURANGO, MEXICO.

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    We present the first reconstruction of the parasitoses among the people of the Loma San Gabriel culture, as represented by 36 coprolites excavated from the Cueva de los Muertos Chiquitos in Durango, Mexico. The coprolites date to approximately 1,400-yr-ago. Species identified based on eggs recovered include the trematode Echinostoma sp., the tapeworms Hymenolepis sp. and Dipylidium caninum, and the nematodes Ancylostoma duodenale, Enterobius vermicularis, and Trichuris trichiura. After rehydration and screening, 2 methods were used to recover eggs from these samples including spontaneous sedimentation and flotation. Samples were analyzed by 3 different laboratories for independent verification and comparison of methods. Spontaneous sedimentation resulted in the discovery of hymenolepidid eggs that were not found with flotation. Sedimentation was a more-sensitive indicator of prevalence as well. The modified method of flotation permitted estimation of egg concentration and resulted in the detection of a few specimens not found by sedimentation. The results of both methods showed that 19 (of 36) coprolites contained helminth eggs. Our results detected the presence of pathogenic helminths including hookworms and whipworms. The cestodes found do not cause severe pathology in humans. The early dates of hookworm and whipworm, relative to other findings in the southwest United States, indicate that these parasites arrived relatively late in prehistory in Arizona and New Mexico, probably moving into the area with travelers from Mesoamerica
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