147 research outputs found

    Superheated water extraction of essential oils of Origanum micranthum

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    Superheated water extraction is used to extract essential oil of leaves of Origanum micranthum. The effect of different temperatures on the essential oil profile and rate of extraction as a function of time is investigated. The components of essential oil of Origanum micranthum are removed from the aqueous extract by C18 solid-phase extraction. The identification of components is carried out using comprehensive gas chromatography-time of flight-mass spectrometry. The number of extracted components is almost the same; however, the concentrations change with changing temperature. The highest yield (0.64%) is found at a temperature of 150°C, 2 mL/min and 60 bar for 30 min. The increasing temperature from 100°C to 175°C increased the rate of extraction of six selected components of essential oil of Origanum micranthum. cis-Sabinenehydrate exhibits the fastest rate of extraction at all temperatures studied. Some degradation products are observed at a temperature of 175°C

    The influence of early efficacy beliefs on teams' reactions to failing to reach performance goals

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    Cataloged from PDF version of article.Although a considerable amount of theoretical and empirical attention has been devoted to understanding individuals' responses to goal–performance discrepancies (GPDs), little attention has been devoted to examining how teams respond to GPDs. The present research sought to examine how teams responded to negative GPDs. We predicted that failing to reach higher goals would be perceived as less negative than failing to reach lower goals, and we examined the moderating influence of setting higher versus lower goals on how teams responded to performance that fell short of those goals. We also examined the role that efficacy beliefs that were formed early in those teams played in further explaining these effects. Results from 94 teams who all failed to reach self-set goals revealed that teams that failed to reach higher goals downwardly revised their goals less than teams that failed to reach lower goals. Early efficacy beliefs further explained these effects. High efficacy beliefs lessened the negative effects of failing to reach lower goals on subsequent goals. High efficacy beliefs also lessened the negative effects of failing to reach higher goals while low efficacy beliefs strengthened the negative effects of failing to reach higher goals. The implications of these findings for theory, research, and practice are discussed

    When does teamwork translate into improved team performance? a resource allocation perspective

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    Drawing on resource allocation theory, the authors examined boundary conditions for the positive effects of two aspects of teamwork (backing up behavior and performance monitoring) on team performance. Participants were 276 undergraduate business students who were organized into 69 teams and who worked on a computer simulation across multiple performance episodes. Approximately half the teams experienced a workload distribution problem. Results indicated that performance monitoring had positive effects on team performance when teams experienced a workload distribution problem. Backing up behavior had positive effects only when teams had both a workload distribution problem and during early performance episodes. The findings of this study suggest that resource allocation theory can provide insights regarding when members should devote and coordinate their own individual resources to assist others in teams. The implications of these findings for future theory and practice regarding teamwork are discussed. © The Author(s) 2010

    Does backing up behavior explain the efficacy-performance relationship in teams?

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    Although the relationship between collective efficacy beliefs and team performance has been well-documented, few studies have explored the causal mechanisms that might explain these effects. In the current study, the authors explore the role of backing up behavior, a specific form of teamwork behavior, in explaining why high efficacy beliefs lead to high levels of team performance. Participants were 416 undergraduate business students who were organized into 104 four-person teams. The teams worked on an interdependent, computerized, decision-making task. Results of the study revealed that collective efficacy beliefs were positively related to team performance and that backing up behaviors largely mediated these effects. The theoretical and practical implications of these findings are discussed. © The Author(s) 2011

    John Schuster, Descartes-agonistes: Physico-mathematics, method and corpuscular-mechanism, 1618–1633

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    We report on a 10 ks simultaneous Chandra/HETG-NuSTAR observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 years of quiescence. The source is detected up to 60 keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains constant. The 0.5-70 keV spectra of the persistent and dip emission are the same within errors, and well described by a blackbody (BB), a power-law with an exponential rolloff, a 10 keV feature, and a 6.7 keV emission feature, all modified by neutral absorption. Assuming that the BB emission originates in an accretion disc, we estimate its inner (magnetospheric) radius to be about 4x10^7 cm, which translates to a surface dipole field B~9x10^10 G. The Chandra/HETG spectrum resolves the 6.7 keV feature into (quasi-)neutral and highly ionized Fe XXV and Fe XXVI emission lines. XSTAR modeling shows these lines to also emanate from a truncated accretion disk. The burst spectra, with a peak flux more than an order of magnitude higher than Eddington, are well fit with a power-law with an exponential rolloff and a 10~keV feature, with similar fit values compared to the persistent and dip spectra. The burst spectra lack a thermal component and any Fe features. Anisotropic (beamed) burst emission would explain both the lack of the BB and any Fe components.Comment: 15 pages, 11 figures, Accepted in Ap

    Chandra Observations of the Anomalous X-ray Pulsar 1E 2259+58.6

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    We present X-ray imaging, timing, and phase resolved spectroscopy of the anomalous X-ray pulsar 1E 2259+58.6 using the Chandra X-ray Observatory. The spectrum is well described by a power law plus blackbody model with power law index = 3.6(1), kT_BB = 0.412(6) keV, and N_H=0.93(3) x 10^{22} cm^{-2}; we find no evidence for spectral features (0.5-7.0 keV). We derive a new, precise X-ray position for the source and determine its spin period, P=6.978977(24) s. Time resolved X-ray spectra show no significant variation as a function of pulse phase. We have detected excess emission beyond 4 arcsec from the central source extending to beyond 100 arcsec, due to the supernova remnant and possibly dust scattering from the interstellar medium

    Status of the ROTSE-III telescope network

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    ROTSE-III is a homogeneous worldwide array of 4 robotic telescopes. They were designed to provide optical observations of γ-ray burst (GRB) afterglows as close as possible to the start of γ-ray emission. ROTSE-III is fulfilling its potential for GRB science, and provides optical observations for a variety of astrophysical sources in the interim between GRB events

    Prompt Optical Detection of GRB 050401 with ROTSE-IIIa

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    The ROTSE-IIIa telescope at Siding Spring Observatory, Australia, detected prompt optical emission from Swift GRB 050401. In this letter, we present observations of the early optical afterglow, first detected by the ROTSE-IIIa telescope 33 s after the start of gamma-ray emission, contemporaneous with the brightest peak of this emission. This GRB was neither exceptionally long nor bright. This is the first prompt optical detection of a GRB of typical duration and luminosity. We find that the early afterglow decay does not deviate significantly from the power-law decay observable at later times, and is uncorrelated with the prompt gamma-ray emission. We compare this detection with the other two GRBs with prompt observations, GRB 990123 and GRB 041219a. All three bursts exhibit quite different behavior at early times.Comment: 4 pages, 3 figures. Accepted for publication in ApJ Letter
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