4,528 research outputs found

    Aerodynamic force measurements with a strain-gage balance in a cryogenic wind tunnel

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    Aerodynamic force measurements on a generalized 75 deg delta wing model with sharp leading edges were made with a three component internal strain gage balance in a cryogenic wind tunnel at stagnation temperatures of 300 K, 200 K, and 110 K. The feasibility of using a strain gage balance without thermal control in a cryogenic environment as well as the use of electrical resistance heaters, an insulator between the model and the balance, and a convection shield on the balance was investigated. Force and moment data on the delta wing model as measured by the balance are compared at the different temperatures while holding constant either the Reynolds number or the tunnel stagnation pressure. Tests were made at Mach numbers of 0.3 and 0.5 and at angles of attack up to 29 deg. The results indicate that it is feasible to acquire accurate force and moment data while operating at steady state thermal conditions in a cryogenic wind tunnel, either with or without electrical heaters on the balance. Within the limits of the balance accuracy, there were no apparent Reynolds number effects on the aerodynamic results for the delta wind model

    Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European long‐term field experiments

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    Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and life‐history groups are used for calculating food web indices, i.e., maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used high‐throughput amplicon sequencing to investigate the effects of tillage (conventional vs. reduced) and organic matter addition (low vs. high) on nematode communities and food web indices in 10 European long‐term field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality

    Personal Initiative and Job Performance Evaluations: Role of Political Skill in Opportunity Recognition and Capitalization

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    This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this recordIn recent years, personal initiative has been found to predict job performance. However, implicit in this direct initiative–performance relationship are more complex process dynamics that can be better understood when contextual antecedents, moderators, and mediators are considered. Drawing from perspectives of proactive behavior as a goal-directed process, a research model of personal initiative was tested in a three-study investigation intended to build upon and advance prior work. Specifically, the model indicates that climate for initiative interacts with the social astuteness dimension of political skill (i.e., opportunity recognition) to influence the demonstration of personal initiative, and this first part of the model is tested and supported in Study 1. Then, personal initiative is hypothesized to interact with the interpersonal influence dimension of political skill (i.e., opportunity capitalization) to predict supervisor assessments of job performance, and this part of the model is tested and supported in Study 2. Study 3 provided a test of the entire model and demonstrated support for moderated mediation, thus adding increased confidence in the validity of the theory and findings through constructive replication

    Further specification of the leader political skill–leadership effectiveness relationships: transformational and transactional leader behavior as mediators

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    This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordThe present investigation was a three-source test of the intermediate linkages in the leader political skill–leader effectiveness and follower satisfaction relationships, which examined transformational and transactional (i.e., contingent reward behavior) leader behavior as mediators. Data from 408 leaders (headmasters) and 1429 followers (teachers) of state schools in the western part of Germany participated in this research. The results of mediation analyses, based on bias-corrected bootstrapping confidence intervals, provided support for the hypotheses that political skill predicts both transformational and transactional leader behavior, beyond other established predictors, and that transformational and transactional leader behavior mediate the relationships between leader political skill and leadership effectiveness. The contributions to theory and research, strengths and limitations, directions for future research, and practical implications are discussed

    Impact of slurry application method on phosphorus loss in runoff from grassland soils during periods of high soil moisture content

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    Abstract Previous studies have reported that the trailing shoe application technique reduces phosphorus (P) in the runoff postslurry application when compared to the traditional splash-plate application technique. However, the effectiveness of the trailing-shoe technique as a means of reducing P losses has not been evaluated when slurry is applied during periods of high soil moisture levels and lower herbage covers. To address this issue, three treatments were examined in a 3 × 4 factorial design split-plot experiment, with treatments comprising three slurry treatments: control (no slurry), splashplate and trailing-shoe, and four slurry application dates: 7 December, 18 January, 1 March and 10 April. Dairy cow slurry was applied at a rate of 20 m3/ha, while simulated runoff was generated 2, 9 and 16 days later and analysed for a range of P fractions. Dissolved reactive P concentrations in runoff at day two was 41% lower when slurry was applied using the trailing-shoe technique, compared to the splash-plate technique (P &lt; 0.05). In addition, P concentrations in runoff were higher (P &lt; 0.05) from slurry applied in December and March compared to slurry applied in January or April, coinciding with periods of higher soil moisture contents. While the latter highlights that ‘calendar’-based non-spreading periods might not always achieve the desired consequences, the study demonstrated that further field-scale investigations into the trailing shoe as a mitigation measure to reduced P loss from agricultural soils is warranted.</jats:p
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