292 research outputs found

    Energy conditions allow eternal inflation

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    Eternal inflation requires upward fluctuations of the energy in a Hubble volume, which appear to violate the energy conditions. In particular, a scalar field in an inflating spacetime should obey the averaged null energy condition, which seems to rule out eternal inflation. Here we show how eternal inflation is possible when energy conditions (even the null energy condition) are obeyed. The critical point is that energy conditions restrict the evolution of any single quantum state, while the process of eternal inflation involves repeatedly selecting a subsector of the previous state, so there is no single state where the conditions are violated. </p

    The double smeared null energy condition

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    The null energy condition (NEC), an important assumption of the Penrose singularity theorem, is violated by quantum fields. The natural generalization of the NEC in quantum field theory, the renormalized null energy averaged over a finite null segment, is known to be unbounded from below. Here, we propose an alternative, the double smeared null energy condition (DSNEC), stating that the null energy smeared over two null directions has a finite lower bound. We rigorously derive DSNEC from general worldvolume bounds for free quantum fields in Minkowski spacetime. Our method allows for future systematic inclusion of curvature corrections. As a further application of the techniques we develop, we prove additional lower bounds on the expectation values of various operators such as conserved higher spin currents. DSNEC provides a natural starting point for proving singularity theorems in semi-classical gravity

    Multiple outcome meta-analysis of gene-expression data in inflammatory bowel disease

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    We performed a multivariate meta-analysis of microarray data in Crohn's disease (CD) and Ulcerative colitis (UC), which are the main forms of inflammatory bowel disease (IBD). They share similar symptoms but differ in the location and extent of inflammation and in complications. We identified 249 differentially expressed genes (DEGs) in CD and 38 in UC at a false discovery rate of 1%. 20 of the DEGs were common to both diseases. A multivariate test identified 260 DEGs associated with IBD, 53 of which were not found in any of the disorders. We identified important molecular pathways implicated in the pathogenesis of IBD, such as the JAK/STAT and interferon-gamma signaling pathways, genes involved in cell adhesion, apoptosis and carcinogenesis. Among others, BCAT1 and GZMB are interesting novel DEGs that deserve further investigation in experimental models. The method could also be useful to other cases of meta-analysis of gene expression data

    Perceived barriers to commuter and exercise bicycling in U.S. adults: The 2017 National Household Travel Survey

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    Introduction: Bicycling is a type of physical activity associated with positive health outcomes, but many barriers exist to regular bicycling for recreation and transportation. The objective of this study was to describe self-reported barriers to bicycling overall, and by bicycling domain, among a national sample of persons aged 16 and above that reported bicycling outside in the past week. Methods: This analysis, conducted in 2019, utilized data from the United States (US) Department of Transportation's 2017 National Household Travel Survey (NHTS). Weighted point estimates and 95% confidence intervals were calculated for reported barriers to bicycling by category of bicyclist: exercise-exclusive, multi-use, and commuter. Results: The final analytic sample was 18,189, representing approximately 7% of the US population (N = 20,911,680). Barriers that prevented bicycling more was reported by 37.9% of the US population of adult bicyclists (95% CI 37.2, 38.6). Barriers related to safety were more commonly reported (31.9% of total bicyclists), compared to barriers related to infrastructure (22.1% of total bicyclists). Safety-related barriers were more commonly reported among multi-use bicyclist (33.7% vs. 30.9% of exercise-exclusive). Commuter bicyclists reported infrastructure barriers the least (13.9% vs. 22.7% of exercise-exclusive). The most commonly reported single barrier to bicycling more, regardless of bicycling category, was heavy traffic (10.3% of total bicyclists), followed by no nearby paths or trails (7.6% of total bicyclists). Overall, distribution of individual barriers was similar across categories of bicyclists: exercise-exclusive, multi-use, and commuter. Conclusions: Heavy traffic and lack of separated paths or trails were the most frequently identified barriers to bicycling more. Communities wishing to promote bicycling for transportation, recreation, or both should consider how traffic reduction strategies and changes in the built environment could make bicycling safer and more accessible

    First identification of Bartonella coopersplainsensis in wild rodents (Rattus norvegicus) in Greece

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    Η μελέτη αυτή ήταν μια πρώτη προσπάθεια για ανίχνευση της Bartonella sp. σε ιστούς (ήπαρ και καρδιά) πουπάρθηκαν από άγρια τρωκτικά {Rattus norvegicus) στην κεντρική Ελλάδα. Εξετάστηκαν δεκαοκτώ (18) δείγματα ήπατος και δεκαοκτώ (18) δείγματα καρδιάς, τα οποία προέρχονταν από είκοσι τρία (23) ζώα. Δυο (2) δείγματα ήπατος βρέθηκαν θετικάενώ όλα τα δείγματα καρδιάς ήταν αρνητικά για το γονίδιο 16S-23S intergenic spacer rDNA της Bartonella sp. Η αλληλουχίατων βάσεων του DNA των θετικών δειγμάτων και η σύγκριση με τα διαθέσιμα δεδομένα της GenBank με τη χρησιμοποίησητου προγράμματος BLAST, αποκάλυψε το ίδιο είδος Bartonella και στα δύο θετικά δείγματα με 100% ομοιότητα με τηναλληλουχία των βάσεων της Bartonella coopersplainsensis. This study was a preliminary attempt to detect Bartonella sp. in tissues (liver and heart) obtained from wild rodents {Rattus norvegicus) in central Greece. Eighteen (18) liver and eighteen (18) heart samples were examined, which were obtained from twenty three (23) animals. Two (2) liver samples were found positive, while the heart samples examined were found negative for Bartonella sp. 16S-23S intergenic spacer rDNA gene by PCR. Sequencing of the positive PCR products and comparison with those available in GenBank using the BLAST program revealed the same species of Bartonella in both positive samples with 100% sequence homology to Bartonella coopersplainsensis

    A scoping review of psychoeducational interventions for people after transient ischemic attack and minor stroke

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    Background: Psychoeducation can provide information and support to cope with the physical and emotional effects of a health condition. This scoping review aimed to identify the evidence regarding psychoeducational interventions for people after a Transient Ischaemic Attack (TIA) and minor stroke. Methods: This review was conducted in accordance with the PRISMA Extension for Scoping Reviews. Three electronic databases (MEDLINE, Embase, PsycINFO) were searched for articles on interventions related to psychoeducational support post TIA and minor/mild stroke. Search retrieved 3722 articles. Three reviewers independently screened titles, abstracts, full-texts, and then extracted data for included studies. Study quality was assessed using the JADAD scale. TIDieR checklist was used to describe interventions. Results: Fifteen RCTs were included. Twelve studies were of high quality (JADAD score ≥2), two were low quality. A total of 1500 participants were recruited across the studies. Definition of TIA and minor stroke were unclear, leading to the exclusion of several studies. Various interventions were included, including education/psychoeducation (n=4); exercise and lifestyle advice (n=3); telephone-based education/counselling (n=3); secondary prevention education (n=1); motivational interviewing (n=2); self-management (n=2). Interventions were inconsistently described, with information missing about who delivered it and tailoring. Conclusions: Definitions of stroke severity are not adequately reported. There are variety of interventions including education about a range of stroke-specific topics. Many interventions are not adequately defined, thus making it difficult to determine if the aim was to provide information or support to promote self-management and wellbeing post TIA/minor stroke. There is a need for a more in-depth systematic review to develop a clear definition of psychoeducation

    Battery capacity design for electric vehicles considering the diversity of daily vehicles miles traveled

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    In this paper, we study battery capacity design for battery electric vehicles (BEVs). The core of such design problems is to find a good tradeoff between minimizing the capacity to reduce financial costs of drivers and increasing the capacity to satisfy daily travel demands. The major difficulty of such design problems lies in modeling the diversity of daily travel demands. Based on massive trip records of taxi drivers in Beijing, we find that the daily vehicle miles traveled (DVMT) of a driver (e.g., a taxi driver) may change significantly in different days. This investigation triggers us to propose a mixture distribution model to describe the diversity in DVMT for various driver in different days, rather than the widely employed single distribution model. To demonstrate the merit of this new model, we consider value-at-risk and mean-variance battery capacity design problems for BEV, with respect to conventional single and new mixture distribution models of DVMT. Testing results indicate that the mixture distribution model better leads to better solutions to satisfy various drivers
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