235 research outputs found

    Constraining Managers without Owners: Governance of the Not-for-Profit Enterprise

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    In the absence of owners, how effective are the constraints imposed by the state in promoting effective firm governance? This paper develops state-level indices of the legal and reporting rules facing not-for-profits and examines the effects of these rules on not-for-profit behavior. Stronger non-distribution constraints are associated with greater charitable expenditures and foundation payouts while more stringent reporting requirements are associated with lower insider compensation. The paper also examines how governance influences an alternative metric of not-for-profit performance -- the provision of social insurance. Stronger governance measures are associated with intertemporal smoothing of resources and greater activity in response to negative economic shocks.

    Early Systolic Dysfunction and Impact of Gene Mutation Severity in Marfan Syndrome

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    Background Marfan syndrome is caused by a mutation in the fibrillin-1 gene that manifests with a variety of features including aortic root dilation. Recent research has identified a primary cardiomyopathy in patients with Marfan syndrome, hypothesized to be due to the presence of abnormal fibrillin-1 in the myocardium. Controversy over the nature and significance of this cardiomyopathy remains. Echocardiographic measurement of the first-phase of ejection (defined as the beginning of systole to peak aortic valve flow) may be more sensitive to systolic dysfunction and provide useful clinical information. The purpose of this study is to: Assess systolic dysfunction in patients with Marfan syndrome Describe first-phase fractional area change (FAC1) in patients with Marfan syndrome and determine how it varies between Marfan syndrome patients and a control group Verify there is a difference in propensity for cardiomyopathy in mild vs severe gene mutation Marfan syndrome patients not secondary to increased aortic stiffness Methods Patients were identified from a pre-existing list of patients with Marfan syndrome maintained by the Children\u27s Hospital and Medical Center and University of Nebraska Medical Center. All relevant medical records were reviewed. Echocardiographic parameters will include left ventricular (LV) ejection fraction, LV FAC1, LV end-diastolic volume, global longitudinal strain, aortic root diameter, and aortic stiffness. Patients were excluded if they have more than mild aortic insufficiency or mitral valve regurgitation. Neonatal Marfan syndrome patients and patients with other significant congenital heart disease will also be excluded. Statistical analysis of the data will be performed including basic statistical tests, univariate regression, and multivariate regression to compare data from each group. P values will be calculated and a p value \u3c 0.05 will be considered statistically significant. Results At the time of writing, 126 patients with Marfan syndrome have been identified. 44 were excluded based on significant mitral or aortic valve disease, prior cardiovascular surgery, or poor echocardiographic image quality. Of the 82 patients not excluded, genetic testing results are available for 59 and are being categorized to allow for statistical analysis. Echocardiographic measurements are underway.https://digitalcommons.unmc.edu/chri_forum/1002/thumbnail.jp

    Measurement of the shear strength of a charge-density wave

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    We have explored the shear plasticity of charge density waves (CDWs) in niobium triselenide samples with cross-sections having a single micro-fabricated thickness step. Shear stresses along the step result from thickness-dependent CDW pinning. For small thickness differences the CDW depins elastically at the volume average depinning field. For large thickness differences the thicker, more weakly pinned side depins first via plastic shear. A simple model describes the qualitative features of our data, and yields a value for the CDW's shear strength of approximately 9.5*10^3 N/m^2 and a lower bound for the elastic shear modulus of 2.1*10^4 N/m^2. These values are orders of magnitude smaller than the CDW's longitudinal modulus but are much larger than corresponding values for flux-line lattices, and may explain the relative coherence of the CDW response.Comment: 10 pages, 4 figures, submitted to Physical Review Letter

    Necrotic gangrenous intrathoracic appendix in a marfanoid adult patient: a case report

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    BACKGROUND: A diaphragmatic hernia is defined as a defect in part of the diaphragm through which abdominal contents can protrude into the thorax. It may be congenital or acquired. In this case report, we aim to demonstrate a congenital diaphragmatic hernia in an adult marfanoid patient which required emergency treatment CASE PRESENTATION: A 43 year old woman was admitted with classical appendicitis requiring surgery. She incidentally had Marfan's clinical features with a positive family history for the syndrome. At operation she had grossly abnormal abdominal anatomy. Radiological investigations demonstrated a large right congenital diaphragmatic hernia with an intrathoracic hernial sac containing a perforated gangrenous appendix. The hernial sac was opened surgically and the appendix excised. The patient made a full recovery. CONCLUSION: Diaphragmatic hernias are usually congenital in nature often requiring early corrective surgery for future survival. We have demonstrated the presence of an unusually large diaphragmatic defect, almost a hemidiaphragmatic defect, of unknown direct etiology, but of some possible association with Marfan's syndrome in an adult patient presenting with an acute perforated gangrenous appendix requiring emergency life-saving surgery

    Crossover from 2-dimensional to 1-dimensional collective pinning in NbSe3

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    We have fabricated NbSe3_3 structures with widths comparable to the Fukuyama-Lee-Rice phase-coherence length. For samples already in the 2-dimensional pinning limit, we observe a crossover from 2-dimensional to 1-dimensional collective pinning when the crystal width is less than 1.6 μ\mum, corresponding to the phase-coherence length in this direction. Our results show that surface pinning is negligible in our samples, and provide a means to probe the dynamics of single domains giving access to a new regime in charge-density wave physics.Comment: 4 pages, 2 figures, and 1 table. Accepted for publication in Physical Review

    NbSe3: Effect of Uniaxial Stress on the Threshold Field and Fermiology

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    We have measured the effect of uniaxial stress on the threshold field ET for the motion of the upper CDW in NbSe3. ET exhibits a critical behavior, ET ~ (1 - e/ec)^g, wher e is the strain, and ec is about 2.6% and g ~ 1.2. This ecpression remains valid over more than two decades of ET, up to the highest fields of about 1.5keV/m. Neither g nor ec is very sensitive to the impurity concentraction. The CDW transition temperature Tp decreases linearly with e at a rate dTp/de = -10K/%, and it does not show any anomaly near ec. Shubnikov de-Haas measurements show that the extremal area of the Fermi surface decreases with increasing strain. The results suggest that there is an intimate relationship between pinning of the upper CDW and the Fermiology of NbSe3.Comment: 4 pages, 5 figure

    Assessment of Immune Status, Latent Viral Reactivation and Stress during Long Duration Bed Rest as an Analog for Spaceflight

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    As logistical access for in-flight space research becomes more limited, the use of ground based spaceflight analogs for life science studies will increase. These studies are particularly important as NASA progresses towards the Lunar and eventually Mars missions outlined in the 2005 Vision for Space Exploration. Countermeasures must be developed to mitigate the clinical risks associated with exploration class space missions. In an effort to coordinate studies across multiple disciplines, NASA has selected 90-day bed rest as the analog of choice, and initiated the Flight Analogs Project to implement research studies with or without the evaluation of countermeasures. Although bed rest is not the analog of choice to evaluate spaceflight-associated immune dysfunction, a standard Immune Assessment was developed for subjects participating in the 90-day bed best studies. The Immune Assessment consists of: leukocyte subset distribution, T cell functional responses, intracellular cytokine production profiles, latent viral reactivation, virus specific T cell levels, virus specific T cell function, stress hormone levels and a behavioral assessment using stress questionnaires. The purpose of the assessment during the initial studies (without countermeasure) is to establish control data against which future studies (with countermeasure) will be evaluated. It is believed that some of the countermeasures planned to be evaluated in future studies, such as exercise, pharmacologic intervention or nutritional supplementation, have the ability to impact immune function. Therefore immunity will likely be monitored during those studies. The data generated during the first three control studies showed that the subjects in general did not display altered peripheral leukocyte subsets, constitutive immune activation, significant latent viral reactivation (EBV, VZV) or altered T cell function. Interestingly, for some subjects the level of constitutively activated T cells (CD8+/CD69+) and virus-specific T cells (CMV and EBV) both decreased during the studies. This likely reflects the isolation of the subjects (from an immunological perspective) and absence of everyday subclinical challenges to the immune system. Cortisol levels (plasma and saliva) did not vary significantly during the studies. This probably reflects a lack of physiological stress during the study and the stress of readaptation to the 1xG environment at R+1. These data demonstrate the absence of significant immune alteration during 90-day bed rest, and establish control data against which future studies (including countermeasures) may be compared

    Contributions of spontaneous phase slippage to linear and non-linear conduction near the Peierls transition in thin samples of o-TaS_3

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    In the Peierls state very thin samples of TaS_3 (cross-section area \sim 10^{-3} mkm^2) are found to demonstrate smearing of the I-V curves near the threshold field. With approaching the Peierls transition temperature, T_P, the smearing evolves into smooth growth of conductance from zero voltage interpreted by us as the contribution of fluctuations to the non--linear conductance. We identify independently the fluctuation contribution to the linear conductance near T_P. Both linear and non-linear contributions depend on temperature with close activation energies \sim (2 - 4) x 10^3 K and apparently reveal the same process. We reject creep of the {\it continuous} charge-density waves (CDWs) as the origin of this effect and show that it is spontaneous phase slippage that results in creep of the CDW. A model is proposed accounting for both the linear and non-linear parts of the fluctuation conduction up to T_P.Comment: 6 pages, 5 Postscript figure, RevTeX, accepted for publication in PR

    A simulated ‘sandbox’ for exploring the modifiable areal unit problem in aggregation and disaggregation

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    We present a spatial testbed of simulated boundary data based on a set of very high-resolution census-based areal units surrounding Guadalajara, Mexico. From these input areal units, we simulated 10 levels of spatial resolutions, ranging from levels with 5,515–52,388 units and 100 simulated zonal configurations for each level – totalling 1,000 simulated sets of areal units. These data facilitate interrogating various realizations of the data and the effects of the spatial coarseness and zonal configurations, the Modifiable Areal Unit Problem (MAUP), on applications such as model training, model prediction, disaggregation, and aggregation processes. Further, these data can facilitate the production of spatially explicit, non-parametric estimates of confidence intervals via bootstrapping. We provide a pre-processed version of these 1,000 simulated sets of areal units, meta- and summary data to assist in their use, and a code notebook with the means to alter and/or reproduce these data

    Atenolol versus losartan in children and young adults with Marfan's syndrome

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    BACKGROUND : Aortic-root dissection is the leading cause of death in Marfan's syndrome. Studies suggest that with regard to slowing aortic-root enlargement, losartan may be more effective than beta-blockers, the current standard therapy in most centers. METHODS : We conducted a randomized trial comparing losartan with atenolol in children and young adults with Marfan's syndrome. The primary outcome was the rate of aortic-root enlargement, expressed as the change in the maximum aortic-root-diameter z score indexed to body-surface area (hereafter, aortic-root z score) over a 3-year period. Secondary outcomes included the rate of change in the absolute diameter of the aortic root; the rate of change in aortic regurgitation; the time to aortic dissection, aortic-root surgery, or death; somatic growth; and the incidence of adverse events. RESULTS : From January 2007 through February 2011, a total of 21 clinical centers enrolled 608 participants, 6 months to 25 years of age (mean [+/- SD] age, 11.5 +/- 6.5 years in the atenolol group and 11.0 +/- 6.2 years in the losartan group), who had an aorticroot z score greater than 3.0. The baseline-adjusted rate of change (+/- SE) in the aortic-root z score did not differ significantly between the atenolol group and the losartan group (-0.139 +/- 0.013 and -0.107 +/- 0.013 standard-deviation units per year, respectively; P = 0.08). Both slopes were significantly less than zero, indicating a decrease in the degree of aortic-root dilatation relative to body-surface area with either treatment. The 3-year rates of aortic-root surgery, aortic dissection, death, and a composite of these events did not differ significantly between the two treatment groups. CONCLUSIONS : Among children and young adults with Marfan's syndrome who were randomly assigned to losartan or atenolol, we found no significant difference in the rate of aorticroot dilatation between the two treatment groups over a 3-year period
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