1,721,588 research outputs found
Nematode migration and nutrient diffusion between vetch and barley material in soil
No full textThis paper deals with migration of nematodes along nutrient gradients in soil. Portions of barley straw and green vetch leaves were mixed with soil and buried at 6, 12, 18, and 50mm distance from each other in soil. During the following 12 weeks respiration activity, microbial (SIR) biomass, nitrogen limitation of respiration activity in soil slurries all indicated that nitrogen was transferred in the soil from the nutrient rich vetch to the nutrient poor barley at least during the first 3 weeks of the experiment. Twelve out of 39 taxonomic groups of nematodes showed different growth in the two plant material-soil mixtures. Only one of these taxonomic groups (long rhabditid larvae) suggested that migration could have contributed to population development; for three other groups (short rhabditid larvae, Aphelenchoides, and Bursilla) nutrient transport through the soil was the likely mechanism for a distance-dependant population development. We suggest that for most microbivorous nematodes, except larvae of fast growing bacterivores, migration over distances exceeding one centimetre does not contribute markedly to population development even when cues such as nutrient gradients to stimulate the activity exis
A phosphate kinetics model in hemodialysis therapy
No full text<p><strong>Kinetic model</strong></p><p>The model builds on a three-compartment model previously presented as model variation numbers 8 and 10 (fitted to four- and eight-hour HD, respectively) as described by Laursen et al. in the paper <i>Distribution Volume Assessment Compartment Modelling: Theoretic Phosphate Kinetics in Steady State Hemodialys Patients</i> (2015). In this present version of the model, modifications have been made to the volumes of distribution in the three compartments (V1, V2, and V3), dialyzer phosphate clearance (kd) and two mass transfer coefficients (k1 and k2). The components V1, V2, V3, and kd were calculated and remained fixed for each patient, whereas k1 and k2 were estimated. The calculation and estimation of the components are available in the subsections below.</p><p> </p><p><i>Determination of volumes of distribution</i></p><p>The volume of distribution in compartment 1 (V1) was assumed to be equal to the fluid in plasma. The volume of distribution in compartment 2 (V2) was assumed to be the remaining fluid in the extracellular fluid (ECF) from the expection that V2 = ECF - V1. The volume of distribution in compartment 3 (V3) was assumed to be the intracellular fluid and thus equal to total body water (TBW) minus ECF. </p><p>The formulas suggested by P.E. Watson in the paper <i>Total body water volumes for adult males and females estimated from simple anthropometric measurements</i> (1980) were used to calculate TBW for each male and female patient. Ultrafiltration (UF) was ignored in the calculation of body weight. The individual predialytic body weight was entered into the equations.</p><p>The TBW was set to be equal to V1+V2+V3 for each male or female patient based on knowledge about the distribution of physiological molecules in general.</p><p>Based on knowledge about fluid distribution in the body, ECF was set to 1/3 of TBW, and plasma was set to ¼ of ECF. This led to: V1 = TBW * 1/3 * ¼; V2= TBW*1/3 * ¾; V3 = TBW * 2/3.</p><p> </p><p><i>Determination of mass transfer coefficients and phosphate clearance </i></p><p>The dialyzer phosphate clearance (kd) was set to be equal to the mean dialyzer clearance value for each patient—i.e., the value was calculated based on the dialysate phosphate samples from each patient, mean dialysate flow rate, and plasma phosphate concentrations at the time points where dialysate was measured in HD1. The following equation illustrates the calculation.</p><p> kd</p>
<p> </p><p>The np and nd components are the number of plasma samples and dialysate samples, respectively. The two mass transfer coefficients (k1 and k2)<i> </i>were determined for each patient using the <i>Solver</i> function in Excel. The <i>Solver</i> function was used to obtain the optimum solutions for k1 and k2 and included minimization of the root mean square error (RMSE) using the measured plasma phosphate concentrations from HD1 and the corresponding modeled plasma phosphate concentrations.</p><p> </p><p><strong>Data analysis and validation</strong></p><p>The goodness of fit to the patient data was calculated for the model simulation showing the lowest RMSE value in each patient for HD1 and HD2, respectively. As described in the previous subsection, the lowest RMSE value was found using the <i>Solver</i> function in Excel in each treatment case. To assess the goodness of fit to the patient data, the coefficient of determination (R2) was determined using the Excel RSQ function that returns the square of the Pearson product-moment correlation coefficient, R.</p><p> </p><p> </p>
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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