ABSTRACT We present extensive optical (UBV RI, , and open CCD) and near-infrared (ZY JH) photometry for the very nearby Type IIP SN 2013ej extending from +1 to +461 days after shock breakout, ...estimated to be MJD 56496.9 0.3. Substantial time series ultraviolet and optical spectroscopy obtained from +8 to +135 days are also presented. Considering well-observed SNe IIP from the literature, we derive UBV RIJHK bolometric calibrations from UBV RI and unfiltered measurements that potentially reach 2% precision with a B − V color-dependent correction. We observe moderately strong Si ii as early as +8 days. The photospheric velocity ( ) is determined by modeling the spectra in the vicinity of Fe ii whenever observed, and interpolating at photometric epochs based on a semianalytic method. This gives km s−1 at +50 days. We also observe spectral homogeneity of ultraviolet spectra at +10-12 days for SNe IIP, while variations are evident a week after explosion. Using the expanding photosphere method, from combined analysis of SN 2013ej and SN 2002ap, we estimate the distance to the host galaxy to be Mpc, consistent with distance estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimated to be 94 7 days long, yields an explosion energy of erg, a final pre-explosion progenitor mass of 15.2 4.2 and a radius of 250 70 . We observe a broken exponential profile beyond +120 days, with a break point at +183 16 days. Measurements beyond this break time yield a 56Ni mass of 0.013 0.001 M .
Abstract We present cosmological analysis of 12 nearby ( z < 0.06) Type IIP supernovae (SNe IIP) observed with the ROTSE-IIIb telescope. To achieve precise photometry, we present a new ...image-differencing technique that is implemented for the first time on the ROTSE SN photometry pipeline. With this method, we find up to a 20% increase in the detection efficiency and significant reduction in residual rms scatter of the SN lightcurves when compared to the previous pipeline performance. We use the published optical spectra and broadband photometry of well-studied SNe IIP to establish temporal models for ejecta velocity and photospheric temperature evolution for our SNe IIP population. This study yields measurements that are competitive with other methods even when the data are limited to a single epoch during the photospheric phase of SNe IIP. Using the fully reduced ROTSE photometry and optical spectra, we apply these models to the respective photometric epochs for each SN in the ROTSE IIP sample. This facilitates the use of the Expanding Photosphere Method (EPM) to obtain distance estimates to their respective host galaxies. We then perform cosmological parameter fitting using these EPM distances, from which we measure the Hubble constant to be 72.9 − 4.3 + 5.7 km s − 1 Mpc − 1 , which is consistent with the standard ΛCDM model values derived using other independent techniques.
Recent research provides evidence that, contrary to implicit assumptions in much of the strategic human resource management (SHRM) literature, human resource (HR) systems and practices are in fact ...enacted with substantial variation across units even within organizations, with such variation largely a function of the line managers involved in implementing HR practices in the units under their supervision. While instrumental in demonstrating the critical role that line managers play in facilitating the causal chain linking organizations' HR practices with intended employee and organizational outcomes, we contend that the focus of this research on HR practice implementation as a singular and unidimensional characterization of line managers' involvement in human resource management (HRM) represents an oversimplification on several counts. Broadly, we propose that this focus fails to account for the varied nature of line managers' downward influences in the context of HRM. Thus, we integrate insights from research on HR practice implementation, workforce differentiation, and autonomous strategic behavior to develop a more complete understanding of line managers' downward involvement in HRM. Based on our synthesis of relevant insights from these literatures, we propose a research agenda focusing on questions spanning four broad areas with the aim of fostering and guiding future SHRM scholarship to further our understanding of the antecedents, processes, and consequences associated with line managers' influences on HR system content and process in organizations.
Although strategic human resource (HR) management research has established a significant relationship between high-performance HR practices and firm-level financial and market outcomes, few studies ...have considered the important role of employees’ perceptions of HR practice use or examined the more proximal outcomes of high-performance HR practices that may play mediating roles in the HR practice–performance relationship. To address recent calls in the literature for an investigation of this nature, this study examined the relationships between employees’ perceptions of high-performance HR practice use in their job groups and employee absenteeism, intent to remain with the organization, and organizational citizenship behavior, dedicating a focus to the possible mediating role of affective organizational commitment in these relationships. Data in this study were collected from surveys of employees at a large multiunit food service organization. The model was tested with CWC(M) mediation analysis (i.e., centered within context with reintroduction of the subtracted means at Level 2), which accounted for the multilevel structure of the data. Results indicate that employees’ perceptions of high-performance HR practice use at the job group level positively related to all dependent variables and that affective organizational commitment partially mediated the relationship between HR practice perceptions and organizational citizenship behavior and fully mediated the relationship between HR practice perceptions and intent to remain with the organization. The discussion reviews the implications of these results and suggests future directions for research in this vein.
We provide a pipeline for data preprocessing, biomarker selection, and classification of liquid chromatography-mass spectrometry (LCMS) serum samples to generate a prospective diagnostic test for ...Lyme disease. We utilize tools of machine learning (ML), e.g., sparse support vector machines (SSVM), iterative feature removal (IFR), and k-fold feature ranking to select several biomarkers and build a discriminant model for Lyme disease. We report a 98.13% test balanced success rate (BSR) of our model based on a sequestered test set of LCMS serum samples. The methodology employed is general and can be readily adapted to other LCMS, or metabolomics, data sets.
Do star employees enhance or constrain the innovative performance of an organization? Using data from 456 biotechnology firms between 1973 and 2003, we highlight the duality of the effects that stars ...have on firm performance. We show that while stars positively affect firms' productivity, their presence constrains the emergence of other innovative leaders in an organization. We find that firm productivity and innovative leadership among non-stars in a firm are greatest when a star has broad expertise and collaborates frequently. We offer cross-disciplinary insights into the role of human capital as a source of competitive advantage, suggesting that the value of human capital in a firm is contingent on the mutual dependence inherent in high-status employees' relationships with other individuals in a firm.
The theoretical soundness and practical relevance of strategic human resource management (SHRM) scholarship has recently come under scrutiny. The goal of this symposium is to offer a starting point ...for SHRM scholars to rethink our approach to understanding the achievement of competitive advantage through HR, guided by a reconsideration of what it means to achieve horizontal fit and vertical fit in HRM. Collectively, the three papers in this symposium contribute to this effort through a reconsideration of the content of the HR systems we study, an expansion of the strategic bases against which we consider the vertical fit of HR systems, and a more explicit incorporation of complexity and change into our understanding of both the horizontal and vertical fit of the HR "ecosystems" in organizations. In this paper, I introduce the key issues and questions with which the papers in the symposium interface and highlight potential avenues that future SHRM scholarship could pursue to address them.
We address calls for contextualization in the study of slack resources by examining the pursuit of strategic change as a contingency that shapes the effects of human resource (HR) slack and financial ...slack on firm performance. Using data on U.S. commercial banks from 2002 to 2014, we demonstrate that HR slack is more positively related to firm performance in firms pursuing strategic change, and that this relationship is stronger in the presence of greater financial slack. Moreover, we find that the moderating effect of financial slack on HR slack in the strategic change context operates through changes in organizations' human capital investment, offering a unique examination of a key mechanism through which slack resources create value and through which complementarities between different types of slack come to fruition. Our paper advances the contingency perspective within the slack literature and brings important insights from the resource management perspective to the conversation on slack and performance.
How do the specific characteristics of a departing star influence the effects of the star’s turnover on a firm’s innovation processes? Proposing a contingency model of key employee turnover, we argue ...and demonstrate that the individual characteristics of a star scientist who exits a firm determine the effects of the star’s turnover for the organization. Based on a longitudinal study of star scientist turnover in the biotechnology industry (1972-2003), we show that while star turnover disrupts existing innovation routines and thus decreases exploitation, this “shock” creates opportunities for the firm to search beyond existing knowledge boundaries, thereby increasing exploration. However, these effects are moderated by the departing star’s innovative and collaborative involvement within the firm. Specifically, the results indicate that a departing star’s innovative involvement strengthens the negative effects and weakens the positive effects of the star’s turnover on exploitation and exploration in the firm, respectively. On the other hand, a departing star’s collaborative involvement within a firm strengthens the negative effect of the star’s exit on exploitation but increases the positive effect of star turnover on exploration, thereby fostering opportunities for technological renewal. We suggest therefore that the prognosis for firms losing stars may vary, and may not always be dire. Our findings indicate that the short-term and long-term value of human capital is contingent on the social mechanisms surrounding its utilization. Thus, we offer a redirection for research and extend the resource-based view and human capital theory by introducing a resource dependence perspective into this theoretical context.
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