131,200 research outputs found
Two new species of the Drosophila serido sibling set (Diptera, Drosophilidae)
No full textDrosophila antonietae sp. nov. and D. gouveai sp. nov. are members of the D. buzzatii cluster of the D. repleta species group of the genus Drosophila. They can be distinguished from their cryptic species, D. borborema Vilela & Sene, 1977, D. koepferae Fontdevila & Wasserman, 1988, D. serido Vilela & Sene, 1977, and D. seriema Tidon-Sklorz & Sene, 1995 by morphological, genetic and ecological criteria.Em processament
Phenotypic variation of the Aedeagus of Drosophila serido Vilela & Sene (Diptera: Drosophilidae)
No full textDrosophila serido Vilela & Sene is a polytypic and cactophilic species with broad geographic distribution in Brazil. The morphology of the aedeagi of eight natural populations of D. serido was analyzed. Based on features of their aedeagi, populations of D. serido were discriminated with an efficiency of nearly 75%. The analysis using the Mantel test suggests that the morphological divergence of D. serido is correlated with the geographic distance among populations. There is no single cause to explain the observed pattern; therefore, the results were discussed considering the three main hypotheses to explain the aedeagus evolution: lock and key, pleiotropy and sexual selection. Alternatively, the aedeagus variability of D. serido might be related to environmental causes, such as temperature and/or host cacti.Fil:Soto, I.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Phenotypic variation of the Aedeagus of Drosophila serido Vilela & Sene (Diptera: Drosophilidae)
No full textDrosophila serido Vilela & Sene is a polytypic and cactophilic species with broad geographic distribution in Brazil. The morphology of the aedeagi of eight natural populations of D. serido was analyzed. Based on features of their aedeagi, populations of D. serido were discriminated with an efficiency of nearly 75%. The analysis using the Mantel test suggests that the morphological divergence of D. serido is correlated with the geographic distance among populations. There is no single cause to explain the observed pattern; therefore, the results were discussed considering the three main hypotheses to explain the aedeagus evolution: lock and key, pleiotropy and sexual selection. Alternatively, the aedeagus variability of D. serido might be related to environmental causes, such as temperature and/or host cacti.Fil:Soto, I.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
The Effect of Tibiofemoral Bony Morphological Risk Factors for ACL Injury on Knee Mechanics
No full textAnterior cruciate ligament (ACL) tears have a high rate of occurrence, debilitating symptoms, arduous recovery process, and economic impact that necessitate improved injury prevention programs and clinical treatment. Patient-specific care has improved clinical outcomes and additional individualized measures are needed. Tibiofemoral bony morphology impacts knee mechanics by influencing knee motion through bone-to-bone articulation. Therefore, determining tibiofemoral bony morphological risk factors for ACL injuries and their influence on knee mechanics would provide clinicians with parameters to individualize injury prevention and treatment. The objective of this dissertation is to provide a better understanding of tibiofemoral bony morphological risk factors for ACL injury and their effect on knee mechanics before and after injury and treatment.
Using statistical shape modeling, a smaller anterior-posterior length of the tibial plateau, a greater angle between the femoral long axis and femoral condylar axis, and a more lateral mechanical axis of the distal femur were determined to associate with ACL injuries compared to uninjured subjects. No differences were determined between the ACL injured knee and the contralateral knee of the ACL injured subject demonstrating their knees are at equal risk for injury. A computational model of the knee used this data to predict that smaller anterior posterior length of the tibial plateau and more lateral mechanical axis resulted in greater force in the ACL in response to an anterior drawer at 30° and 60° of flexion. Functional bracing was also found to provide additional rotatory stability to the knee and decreased the force in the ACL in response to a simulated pivot shift at lower flexion angles using a cadaveric model. These findings demonstrate that functional braces can reduce ACL injury risk. Tibiofemoral bony morphological features were also correlated with knee kinematics and kinetics before and after application of a brace and lateral extraarticular tenodesis demonstrating that certain morphological features influence the impact of each treatment option. Overall, tibiofemoral bony morphological features are risk factors for ACL injury, influence knee mechanics differently after injury and treatment, and impact biomechanical behavior of the knee. Implementing individualized programs that account for these morphological features may result in better clinical outcomes
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Factors Affecting Loan Repayment Performance Among Yam Farmers in the Sene District, Ghana
No full textThe study analyzed the factors that are critical in improving loan repayment by yam farmers in the Sene district of Ghana. Random sampling technique was used to select 100 respondents in the district and structured questionnaire was administered to collect data. Descriptive statistics and the probit model were employed. The results show that 42% of yam farmers in Sene district are illiterates. More males (93%) are involved in yam farming than females (7%) and most of the farmers are married (91%). Also most of the yam farmers in the district have a family size of 6-10 households (66%) and 54% of them have 1-10 years of yam farming experience. Also, the results show that education, experience, profit, age, supervision and off-farm income have positive effects on loan repayment performance. Conversely, gender and marriage have negative effects on loan repayment while the effect of household size was found to be ambiguous
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