Quantifying Bar Strength: Morphology Meets Methodology

A set of objective bar-classification methods have been applied to the Ohio State Bright Spiral Galaxy Survey (Eskridge et al. 2002). Bivariate comparisons between methods show that all methods agree in a statistical sense. Thus the distribution of bar strengths in a sample of galaxies can be robustly determined. There are very substantial outliers in all bivariate comparisons. Examination of the outliers reveals that the scatter in the bivariate comparisons correlates with galaxy morphology. Thus multiple measures of bar strength provide a means of studying the range of physical properties of galaxy bars in an objective statistical sense.Comment: LaTeX with Kluwer style file, 5 pages with 3 embedded figures. edited by Block, D.L., Freeman, K.C., Puerari, I., & Groess,

A universal model for mobility and migration patterns

Introduced in its contemporary form by George Kingsley Zipf in 1946, but with roots that go back to the work of Gaspard Monge in the 18th century, the gravity law is the prevailing framework to predict population movement, cargo shipping volume, inter-city phone calls, as well as bilateral trade flows between nations. Despite its widespread use, it relies on adjustable parameters that vary from region to region and suffers from known analytic inconsistencies. Here we introduce a stochastic process capturing local mobility decisions that helps us analytically derive commuting and mobility fluxes that require as input only information on the population distribution. The resulting radiation model predicts mobility patterns in good agreement with mobility and transport patterns observed in a wide range of phenomena, from long-term migration patterns to communication volume between different regions. Given its parameter-free nature, the model can be applied in areas where we lack previous mobility measurements, significantly improving the predictive accuracy of most of phenomena affected by mobility and transport processes.Comment: Main text and supplementary informatio

Assortment optimisation under a general discrete choice model: A tight analysis of revenue-ordered assortments

The assortment problem in revenue management is the problem of deciding which subset of products to offer to consumers in order to maximise revenue. A simple and natural strategy is to select the best assortment out of all those that are constructed by fixing a threshold revenue $\pi$ and then choosing all products with revenue at least $\pi$. This is known as the revenue-ordered assortments strategy. In this paper we study the approximation guarantees provided by revenue-ordered assortments when customers are rational in the following sense: the probability of selecting a specific product from the set being offered cannot increase if the set is enlarged. This rationality assumption, known as regularity, is satisfied by almost all discrete choice models considered in the revenue management and choice theory literature, and in particular by random utility models. The bounds we obtain are tight and improve on recent results in that direction, such as for the Mixed Multinomial Logit model by Rusmevichientong et al. (2014). An appealing feature of our analysis is its simplicity, as it relies only on the regularity condition. We also draw a connection between assortment optimisation and two pricing problems called unit demand envy-free pricing and Stackelberg minimum spanning tree: These problems can be restated as assortment problems under discrete choice models satisfying the regularity condition, and moreover revenue-ordered assortments correspond then to the well-studied uniform pricing heuristic. When specialised to that setting, the general bounds we establish for revenue-ordered assortments match and unify the best known results on uniform pricing.Comment: Minor changes following referees' comment

Evaluation of a Previously Suggested Plasma Biomarker Panel to Identify Alzheimer's Disease

There is an urgent need for biomarkers in plasma to identify Alzheimer's disease (AD). It has previously been shown that a signature of 18 plasma proteins can identify AD during pre-dementia and dementia stages (Ray et al, Nature Medicine, 2007). We quantified the same 18 proteins in plasma from 174 controls, 142 patients with AD, and 88 patients with other dementias. Only three of these proteins (EGF, PDG-BB and MIP-1δ) differed significantly in plasma between controls and AD. The 18 proteins could classify patients with AD from controls with low diagnostic precision (area under the ROC curve was 63%). Moreover, they could not distinguish AD from other dementias. In conclusion, independent validation of results is important in explorative biomarker studies

Social capital of venture capitalists and start-up funding

How does the social capital of venture capitalists (VCs) affect the funding of start-ups? By building on the rich social capital literature, we hypothesize a positive effect of VCs' social capital, derived from past syndication, on the amount of money that start-ups receive. Specifically, we argue that both structural and relational aspects of VCs' social networks provide VCs with superior access to information about current investment objects and opportunities to leverage them in the future, increasing their willingness to invest in these firms. Our empirical results, derived from a novel dataset containing more than 1,500 first funding rounds in the Internet and IT sector, strongly confirm our hypotheses. We discuss the implications of our findings for theories of venture capital and entrepreneurship, showing that the role and effect of VCs' social capital on start-up firms may be more complex than previously argued in the literature

Carotid endarterectomy and carotid artery stenting utilization trends over time

<p>Abstract</p> <p>Background</p> <p>Carotid endarterectomy (CEA) has been the standard in atherosclerotic stroke prevention for over 2 decades. More recently, carotid artery stenting (CAS) has emerged as a less invasive alternative for revascularization. The purpose of this study was to investigate whether an increase in stenting parallels a decrease in endarterectomy, if there are specific patient factors that influence one intervention over the other, and how these factors may have changed over time.</p> <p>Methods</p> <p>Using a nationally representative sample of US hospital discharge records, data on CEA and CAS procedures performed from 1998 to 2008 were obtained. In total, 253,651 cases of CEA and CAS were investigated for trends in utilization over time. The specific data elements of age, gender, payer source, and race were analyzed for change over the study period, and their association with type of intervention was examined by multiple logistic regression analysis.</p> <p>Results</p> <p>Rates of intervention decreased from 1998 to 2008 (P < 0.0001). Throughout the study period, endarterectomy was the much more widely employed procedure. Its use displayed a significant downward trend (P < 0.0001), with the lowest rates of intervention occurring in 2007. In contrast, carotid artery stenting displayed a significant increase in use over the study period (P < 0.0001), with the highest intervention rates occurring in 2006. Among the specific patient factors analyzed that may have altered utilization of CEA and CAS over time, the proportion of white patients who received intervention decreased significantly (P < 0.0001). In multivariate modeling, increased age, male gender, white race, and earlier in the study period were significant positive predictors of CEA use.</p> <p>Conclusions</p> <p>Rates of carotid revascularization have decreased over time, although this has been the result of a reduction in CEA despite an overall increase in CAS. Among the specific patient factors analyzed, age, gender, race, and time were significantly associated with the utilization of these two interventions.</p

Improving biomass production and saccharification in Brachypodium distachyon through overexpression of a sucrose-phosphate synthase from sugarcane

The substitution of fossil by renewable energy sources is a major strategy in reducing CO2 emission and mitigating climate change. In the transport sector, which is still mainly dependent on liquid fuels, the production of second generation ethanol from lignocellulosic feedstock is a promising strategy to substitute fossil fuels. The main prerequisites on designated crops for increased biomass production are high biomass yield and optimized saccharification for subsequent use in fermentation processes. We tried to address these traits by the overexpression of a sucrose-phosphate synthase gene (SoSPS) from sugarcane (Saccharum officinarum) in the model grass Brachypodium distachyon. The resulting transgenic B. distachyon lines not only revealed increased plant height at early growth stages but also higher biomass yield from fully senesced plants, which was increased up to 52 % compared to wild-type. Additionally, we determined higher sucrose content in senesced leaf biomass from the transgenic lines, which correlated with improved biomass saccharification after conventional thermo-chemical pretreatment and enzymatic hydrolysis. Combining increased biomass production and saccharification efficiency in the generated B. distachyon SoSPS overexpression lines, we obtained a maximum of 74 % increase in glucose release per plant compared to wild-type. Therefore, we consider SoSPS overexpression as a promising approach in molecular breeding of energy crops for optimizing yields of biomass and its utilization in second generation biofuel production

A histomorphometric meta-analysis of sinus elevation with various grafting materials

Several grafting materials have been used in sinus augmentation procedures including autogenous bone, demineralized freeze-dried bone (DFDBA), hydroxyapatite, β-tricalcium phosphate (β-TCP), anorganic deproteinized bovine bone and combination of these and others. Up to now a subject of controversy in maxillofacial surgery and dentistry is, what is the most appropriate graft material for sinus floor augmentation

Use of electronic personal health record systems to encourage HIV screening: an exploratory study of patient and provider perspectives

<p>Abstract</p> <p>Background</p> <p>When detected, HIV can be effectively treated with antiretroviral therapy. Nevertheless in the U.S. approximately 25% of those who are HIV-infected do not know it. Much remains unknown about how to increase HIV testing rates. New Internet outreach methods have the potential to increase disease awareness and screening among patients, especially as electronic personal health records (PHRs) become more widely available. In the US Department of Veterans' Affairs medical care system, 900,000 veterans have indicated an interest in receiving electronic health-related communications through the PHR. Therefore we sought to evaluate the optimal circumstances and conditions for outreach about HIV screening. In an exploratory, qualitative research study we examined patient and provider perceptions of Internet-based outreach to increase HIV screening among veterans who use the Veterans Health Administration (VHA) health care system.</p> <p>Findings</p> <p>We conducted two rounds of focus groups with veterans and healthcare providers at VHA medical centers. The study's first phase elicited general perceptions of an electronic outreach program to increase screening for HIV, diabetes, and high cholesterol. Using phase 1 results, outreach message texts were drafted and then presented to participants in the second phase. Analysis followed modified grounded theory.</p> <p>Patients and providers indicated that electronic outreach through a PHR would provide useful information and would motivate patients to be screened for HIV. Patients believed that electronic information would be more convenient and understandable than information provided verbally. Patients saw little difference between messages about HIV versus about diabetes and cholesterol. Providers, however, felt patients would disapprove of HIV-related messages due to stigma. Providers expected increased workload from the electronic outreach, and thus suggested adding primary care resources and devising methods to smooth the flow of patients getting screened. When provided a choice between unsecured emails versus PHRs as the delivery mechanism for disease screening messages, both patients and providers preferred PHRs.</p> <p>Conclusions</p> <p>There is considerable potential to use PHR systems for electronic outreach and social marketing to communicate to patients about, and increase rates of, disease screening, including for HIV. Planning for direct-to-patient communications through PHRs should include providers and address provider reservations, especially about workload increases.</p