326 research outputs found
Examining Strategic Antecedents of the Appointment of Women to Top Management Teams
Purpose – The purpose of this study is to examine the organizational and environmental antecedents to the appointment of a woman to a non-CEO top management team (TMT) position.
Design/methodology/approach – This study uses a conditional fixed effects logistic regression model to analyze non-CEO TMT appointment data collected from the S&P 500 between 2008 and 2016.
Findings – Women were more likely to be appointed to non-CEO TMT positions when a firm was undergoing strategic change, had slack resources, and was in a less munificent environment.
Originality/value – This article contributes to the literature concerning the antecedents of the selection of women to executive leadership (e.g. the glass cliff) roles by examining organizational and environmental contexts at the non-CEO TMT unit of analysis
Distributive Effects of Forest Service Attempts to Maintain Community Stability
Community stability is an objective of USDA Forest Service timber sales. This paper examines that objective, and the success the Forest Service can have in attaining it, through its intended maintenance of a constant volume timber harvest schedule. We apply a three-factor, two-sector modified general equilibrium model with empirical evidence from the timber-based counties of western Montana. Departure from a market responsive timber policy can have positive impacts on the wood products sector, but the net effects on the local community are very small. The costs to the public treasury of pursuing such a policy dwarf these small community benefits
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¹⁸F-FDG PET for the early diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI).
BACKGROUND: ¹⁸F-FDFG uptake by brain tissue as measured by positron emission tomography (PET) is a well-established method for assessment of brain function in people with dementia. Certain findings on brain PET scans can potentially predict the decline of mild cognitive Impairment (MCI) to Alzheimer's disease dementia or other dementias. OBJECTIVES: To determine the diagnostic accuracy of the ¹⁸F-FDG PET index test for detecting people with MCI at baseline who would clinically convert to Alzheimer's disease dementia or other forms of dementia at follow-up. SEARCH METHODS: We searched the Cochrane Register of Diagnostic Test Accuracy Studies, MEDLINE, EMBASE, Science Citation Index, PsycINFO, BIOSIS previews, LILACS, MEDION, (Meta-analyses van Diagnostisch Onderzoek), DARE (Database of Abstracts of Reviews of Effects), HTA (Health Technology Assessment Database), ARIF (Aggressive Research Intelligence Facility) and C-EBLM (International Federation of Clinical Chemistry and Laboratory Medicine Committee for Evidence-based Laboratory Medicine) databases to January 2013. We checked the reference lists of any relevant studies and systematic reviews for additional studies. SELECTION CRITERIA: We included studies that evaluated the diagnostic accuracy of ¹⁸F-FDG PET to determine the conversion from MCI to Alzheimer's disease dementia or to other forms of dementia, i.e. any or all of vascular dementia, dementia with Lewy bodies, and fronto-temporal dementia. These studies necessarily employ delayed verification of conversion to dementia and are sometimes labelled as 'delayed verification cross-sectional studies'. DATA COLLECTION AND ANALYSIS: Two blinded review authors independently extracted data, resolving disagreement by discussion, with the option to involve a third review author as arbiter if necessary. We extracted and summarised graphically the data for two-by-two tables. We conducted exploratory analyses by plotting estimates of sensitivity and specificity from each study on forest plots and in receiver operating characteristic (ROC) space. When studies had mixed thresholds, we derived estimates of sensitivity and likelihood ratios at fixed values (lower quartile, median and upper quartile) of specificity from the hierarchical summary ROC (HSROC) models. MAIN RESULTS: We included 14 studies (421 participants) in the analysis. The sensitivities for conversion from MCI to Alzheimer's disease dementia were between 25% and 100% while the specificities were between 15% and 100%. From the summary ROC curve we fitted we estimated that the sensitivity was 76% (95% confidence interval (CI): 53.8 to 89.7) at the included study median specificity of 82%. This equates to a positive likelihood ratio of 4.03 (95% CI: 2.97 to 5.47), and a negative likelihood ratio of 0.34 (95% CI: 0.15 to 0.75). Three studies recruited participants from the same Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort but only the largest ADNI study (Herholz 2011) is included in the meta-analysis. In order to demonstrate whether the choice of ADNI study or discriminating brain region (Chételat 2003) or reader assessment (Pardo 2010) make a difference to the pooled estimate, we performed five additional analyses. At the median specificity of 82%, the estimated sensitivity was between 74% and 76%. There was no impact on our findings. In addition to evaluating Alzheimer's disease dementia, five studies evaluated the accuracy of ¹⁸F-FDG PET for all types of dementia. The sensitivities were between 46% and 95% while the specificities were between 29% and 100%; however, we did not conduct a meta-analysis because of too few studies, and those studies which we had found recruited small numbers of participants. Our findings are based on studies with poor reporting, and the majority of included studies had an unclear risk of bias, mainly for the reference standard and participant selection domains. According to the assessment of Index test domain, more than 50% of studies were of poor methodological quality. AUTHORS' CONCLUSIONS: It is difficult to determine to what extent the findings from the meta-analysis can be applied to clinical practice. Given the considerable variability of specificity values and lack of defined thresholds for determination of test positivity in the included studies, the current evidence does not support the routine use of ¹⁸F-FDG PET scans in clinical practice in people with MCI. The ¹⁸F-FDG PET scan is a high-cost investigation, and it is therefore important to clearly demonstrate its accuracy and to standardise the process of ¹⁸F-FDG PET diagnostic modality prior to its being widely used. Future studies with more uniform approaches to thresholds, analysis and study conduct may provide a more homogeneous estimate than the one available from the included studies we have identified
Physical Optics Solution for the Scattering of a Partially-coherent Wave from a Statistically Rough Material Surface
The scattering of a partially-coherent wave from a statistically rough material surface is investigated via derivation of the scattered field cross-spectral density function. Two forms of the cross-spectral density are derived using the physical optics approximation. The first is applicable to smooth-to-moderately rough surfaces and is a complicated expression of source and surface parameters. Physical insight is gleaned from its analytical form and presented in this work. The second form of the cross-spectral density function is applicable to very rough surfaces and is remarkably physical. Its form is discussed at length and closed-form expressions are derived for the angular spectral degree of coherence and spectral density radii. Furthermore, it is found that, under certain circumstances, the cross-spectral density function maintains a Gaussian Schell-model form. This is consistent with published results applicable only in the paraxial regime. Lastly, the closed-form cross-spectral density functions derived here are rigorously validated with scatterometer measurements and full-wave electromagnetic and physical optics simulations. Good agreement is noted between the analytical predictions and the measured and simulated results. © 2013 Optical Society of Americ
Examining the Validity of Using a Gaussian Schell-Model Source To Model the Scattering of A Fully Coherent Gaussian Beam From A Rough Impedance Surface
Military applications that use adaptive optics (AO) often require a point source beacon at the target to measure and correct for wavefront aberrations introduced by atmospheric turbulence. However, turbulence prevents the formation of such a point beacon. The extended beacons that are created instead have finite spatial extents and exhibit varying degrees of spatial coherence. Modeling these extended beacons using a Gaussian Schell-model (GSM) form for the autocorrelation function would be a convenient approach due to the analytical tractability of Gaussian functions. We examine the validity of using such a model by evaluating the field scattered from a rough impedance surface using a full-wave computational technique called the method of moments (MoM). The MoM improves the fidelity of the analysis since it captures all the physics of the laser-target interaction, such as masking, shadowing, multiple reflections, etc. Two rough-surface targets with different roughness statistics are analyzed. The simulation results are verified with experimental bidirectional reflectance distribution function measurements. It is seen that for rough surfaces, in general, the scattered-field autocorrelation function is not of a GSM form. However, under certain conditions, modeling an extended beacon as a GSM source is legitimate. This analysis will aid in understanding the behavior of extended beacons and how they affect the overall performance of an AO system
Sustained Economic Value of a Wellness and Disease Prevention Program: An 8-Year Longitudinal Evaluation
The objective of this study was to determine the sustained economic impact of a health promotion/disease prevention program delivered through a large regional health plan. This was a retrospective analysis of health risk, health claims, and cost using a mixed model factorial design for the years 2002?2009 that compared program participants to nonparticipants. All analyses were adjusted for age, sex, morbidity, and baseline health care costs as appropriate. The findings presented herein indicate a positive return on investment (ROI) for each program year with ratios ranging from a low of 1.16:1 to a high of 2.83:1. The average ROI collapsed across all 8 years was 2.02:1. The 2009 ROI approximated over $6 million in total savings. This study demonstrates the sustained economic value of a comprehensive health promotion program. (Population Health Management 2014;17:90?99)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140181/1/pop.2013.0042.pd
Synergistic effect of low dose Cyclosporine A and human interleukin 10 overexpression on acute rejection in rat lung allotransplantation
Objective: Electroporation mediated transfer of plasmid DNA into peripheral muscle results in high transfection efficiency. The aim of this study was to investigate the effect of gene transfer of human IL-10 (hIL-10) into the tibialis anterior muscle (MTA) in combination with low dose Cyclosporine A (CsA) on acute rejection of lung allografts in the rat. Methods: Lung allotransplantation was performed from male BN donor to male Fisher F344 rats. Gene transfer was achieved by intramuscular injection into the MTA of the recipient followed by electroporation (4×20ms impulses at 200V/cm) 24h prior to the transplantation. Group A (n=5) received CsA (2.5mg/kg bw ip) for 5 days post-transplant and group B (n=5) 2.5μg of PCIK hIL-10 (plasmid expression vector containing human CMV immediate early gene promoter and enhancer) and a low dose CsA (2.5mg/kg bw i.p.). Graft function was assessed by blood gas at day 5 after exclusion of the native lung. Animals were sacrificed and blood was drawn to measure serum hIL-10 levels (ELISA) and tissue was sampled for histological grading of rejection. Results: Local expression of hIL-10 was confirmed at the mRNA level by in situ hybridization. All group A control animals showed severe signs of rejection. At day 5 all grafts in group B showed good gas exchange mean PaO2 233±123mmHg, vs 44±8mmHg in group A. Histological examination revealed moderate to severe rejection in all animals in group A (IIIB, ISHLT) in contrast to low moderate rejection in group B (II-IIIA). hIL-10 serum levels on day 5 were 14±7pg/ml in group B vs. 0 in group A. Conclusions: Electroporation mediated hIL-10 overexpression in a peripheral muscle of the recipient in combination with low dose CsA reduces acute rejection in this model of rat lung allotransplantatio
Synergistic effect of low dose Cyclosporine A and human interleukin 10 overexpression on acute rejection in rat lung allotransplantation
Objective: Electroporation mediated transfer of plasmid DNA into peripheral muscle results in high transfection efficiency. The aim of this study was to investigate the effect of gene transfer of human IL-10 (hIL-10) into the tibialis anterior muscle (MTA) in combination with low dose Cyclosporine A (CsA) on acute rejection of lung allografts in the rat. Methods: Lung allotransplantation was performed from male BN donor to male Fisher F344 rats. Gene transfer was achieved by intramuscular injection into the MTA of the recipient followed by electroporation (4×20ms impulses at 200V/cm) 24h prior to the transplantation. Group A (n=5) received CsA (2.5mg/kg bw ip) for 5 days post-transplant and group B (n=5) 2.5μg of PCIK hIL-10 (plasmid expression vector containing human CMV immediate early gene promoter and enhancer) and a low dose CsA (2.5mg/kg bw i.p.). Graft function was assessed by blood gas at day 5 after exclusion of the native lung. Animals were sacrificed and blood was drawn to measure serum hIL-10 levels (ELISA) and tissue was sampled for histological grading of rejection. Results: Local expression of hIL-10 was confirmed at the mRNA level by in situ hybridization. All group A control animals showed severe signs of rejection. At day 5 all grafts in group B showed good gas exchange mean PaO2 233±123mmHg, vs 44±8mmHg in group A. Histological examination revealed moderate to severe rejection in all animals in group A (IIIB, ISHLT) in contrast to low moderate rejection in group B (II–IIIA). hIL-10 serum levels on day 5 were 14±7pg/ml in group B vs. 0 in group A. Conclusions: Electroporation mediated hIL-10 overexpression in a peripheral muscle of the recipient in combination with low dose CsA reduces acute rejection in this model of rat lung allotransplantation
Models of Intragroup Conflict in Management: A Literature Review
The study of intragroup dynamics in management studies views conflict as a contingency process that can benefit or harm a group based of characteristics of the group and context. We review five models of intragroup conflict in management studies. These models include diversity-conflict and behavioral negotiation models that focus primarily on conflict within a group of people; social exchange and transaction cost economics models that focus primarily on conflict within a group of firms; and social dilemma models that focus on conflict in collectives of people, organizations, communities, and generations. The review is constituted by summarizing the insights of each model, foundational papers to each model; the most recent uses and developments of the models in the last decade; the complementarity of these models; and the future research directions
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