127 research outputs found

    Ultraviolet asymptotics for quasiperiodic AdS_4 perturbations

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    Spherically symmetric perturbations in AdS-scalar field systems of small amplitude epsilon approximately periodic on time scales of order 1/epsilon^2 (in the sense that no significant transfer of energy between the AdS normal modes occurs) have played an important role in considerations of AdS stability. They are seen as anchors of stability islands where collapse of small perturbations to black holes does not occur. (This collapse, if it happens, typically develops on time scales of the order 1/epsilon^2.) We construct an analytic treatment of the frequency spectra of such quasiperiodic perturbations, paying special attention to the large frequency asymptotics. For the case of a self-interacting phi^4 scalar field in a non-dynamical AdS background, we arrive at a fairly complete analytic picture involving quasiperiodic spectra with an exponential suppression modulated by a power law at large mode numbers. For the case of dynamical gravity, the structure of the large frequency asymptotics is more complicated. We give analytic explanations for the general qualitative features of quasiperiodic solutions localized around a single mode, in close parallel to our discussion of the probe scalar field, and find numerical evidence for logarithmic modulations in the gravitational quasiperiodic spectra existing on top of the formulas previously reported in the literature.Comment: 18 pages; v3: minor improvements, published versio

    A study of a flapper-nozzle amplifier

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    Call number: LD2668 .R4 1965 J2

    Cruise passengers’ perception of key quality attributes of cruise lines in North America

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    This study identified cruise passengers’ perceived importance and performance of quality attributes for cruise lines in North America by utilizing an importance–performance analysis tool. The results concluded that: (a) room temperature, behavior of other passengers, food and beverages, and accommodation require immediate attention from cruise line operators; (b) the cruise lines are succeeding in providing excellent services for their customers, as well as maintaining a high level of overall shipboard cleanliness; and (c) cruise marketing efforts should promote the attractiveness of onboard activities and facilities, including entertainment, recreation and sports facilities, fitness and health facilities, supplementary facilities, and facilities for children. Overall, the results of this study help cruise lines identify which onboard attributes need more attention and determine the areas that may be consuming too many resources

    Strong fisheries management and governance positively impact ecosystem status

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    Fisheries have had major negative impacts on marine ecosystems, and effective fisheries management and governance are needed to achieve sustainable fisheries, biodiversity conservation goals and thus good ecosystem status. To date, the IndiSeas programme (Indicators for the Seas) has focussed on assessing the ecological impacts of fishing at the ecosystem scale using ecological indicators. Here, we explore fisheries Management Effectiveness' and Governance Quality' and relate this to ecosystem health and status. We developed a dedicated expert survey, focused at the ecosystem level, with a series of questions addressing aspects of management and governance, from an ecosystem-based perspective, using objective and evidence-based criteria. The survey was completed by ecosystem experts (managers and scientists) and results analysed using ranking and multivariate methods. Results were further examined for selected ecosystems, using expert knowledge, to explore the overall findings in greater depth. Higher scores for Management Effectiveness' and Governance Quality' were significantly and positively related to ecosystems with better ecological status. Key factors that point to success in delivering fisheries and conservation objectives were as follows: the use of reference points for management, frequent review of stock assessments, whether Illegal, Unreported and Unregulated (IUU) catches were being accounted for and addressed, and the inclusion of stakeholders. Additionally, we found that the implementation of a long-term management plan, including economic and social dimensions of fisheries in exploited ecosystems, was a key factor in successful, sustainable fisheries management. Our results support the thesis that good ecosystem-based management and governance, sustainable fisheries and healthy ecosystems go together.IOC-UNESCO; EuroMarine; European FP7 MEECE research project; European Network of Excellence Eur-Oceans; FRB EMIBIOS project [212085]info:eu-repo/semantics/publishedVersio

    Bowel Preparation for Capsule Endoscopy: A Prospective Randomized Multicenter Study

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    Background/Aims: The ability to visualize the small bowel mucosa by capsule endoscopy is limited. Moreover, studies involving small-bowel preparation with purgative drugs have failed to establish which preparations produce better images and higher diagnostic yields. The aim of this study was to evaluate the efficacies and diagnostic yields of different bowel preparations. Methods: A cohort of 134 patients with suspected small bowel disease was randomly assigned to 3 groups. Patients in group A (n=44) fasted for 12 h before being administered an M2A capsule (Given Imaging, Yoqneam, Israel). Patients in group B (n=45) were asked to drink two doses of 45 mL of sodium phosphate (NaP) with water during the afternoon and evening on the day before the procedure and to drink at least 2 L of water thereafter. Patients in group C (n=45) drank 2 L of a polyethylene glycol (PEG) lavage solution the evening before the procedure. Results: Overall cleansing of the small bowel was adequate in 43% of patients in group A, 77% of those in group B, and 56% of those in group C (group A vs; group B, p=0.001). Diagnoses for obscure gastrointestinal bleeding were established in 9 patients (39%) in group A, 16 patients (69%) in group B, and 14 patients (50%) in group C. No significant difference in diagnostic yield was observed between groups. Conclusions: Bowel preparation with NaP for capsule endoscopy improved small-bowel mucosal visualization when compared to 12-h overnight fasting. (Gut and Liver 2009;3:180-185)Wei W, 2008, AM J GASTROENTEROL, V103, P77, DOI 10.1111/j.1572-0241.2007.01633.xCheon JH, 2007, GUT LIVER, V1, P118van Tuyl SAC, 2007, ENDOSCOPY, V39, P1037, DOI 10.1055/s-2007-966988Ben-Soussan E, 2005, J CLIN GASTROENTEROL, V39, P381FIREMAN Z, 2005, WORLD J GASTROENTERO, V11, P5863DAI N, 2005, GASTROINTEST ENDOSC, V61, P28Viazis N, 2004, GASTROINTEST ENDOSC, V60, P534Niv Y, 2004, SCAND J GASTROENTERO, V39, P1005, DOI 10.1080/00365520410003209Fireman Z, 2004, ISRAEL MED ASSOC J, V6, P521Albert J, 2004, GASTROINTEST ENDOSC, V59, P487Pennazio M, 2004, GASTROENTEROLOGY, V126, P643, DOI 10.1053/j.gastro.2003.11.057Mylonaki M, 2003, GUT, V52, P1122Costamagna G, 2002, GASTROENTEROLOGY, V123, P999, DOI 10.1053/gast.2002.35988Lewis BS, 2002, GASTROINTEST ENDOSC, V56, P349, DOI 10.1067/mge.2002.126906Kastenberg D, 2001, GASTROINTEST ENDOSC, V54, P705Aronchick CA, 2000, GASTROINTEST ENDOSC, V52, P346

    NASA's Soil Moisture Active and Passive (SMAP) Mission

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    The Soil Moisture Active-Passive (SMAP) Mission is one of the first Earth observation satellites being formulated by NASA in response to the 2007 National Research Council s Decadal Survey. SMAP will make global measurements of soil moisture at the Earth's land surface and its freeze-thaw state. These measurements will allow significantly improved estimates of water, energy and carbon transfers between the land and atmosphere. Soil moisture measurements are also of great importance in assessing flooding and monitoring drought. Knowledge gained from SMAP observations can help mitigate these natural hazards, resulting in potentially great economic and social benefits. SMAP observations of soil moisture and freeze/thaw timing over the boreal latitudes will also reduce a major uncertainty in quantifying the global carbon balance and help to resolve an apparent missing carbon sink over land. The SMAP mission concept will utilize an L-band radar and radiometer sharing a rotating 6-meter mesh reflector antenna flying in a 680 km polar orbit with an 8-day exact ground track repeat aboard a 3-axis stabilized spacecraft to provide high-resolution and high-accuracy global maps of soil moisture and freeze/thaw state every two to three days. In addition, the SMAP project will use these surface observations with advanced modeling and data assimilation to provide estimates of deeper root-zone soil moisture and net ecosystem exchange of carbon. SMAP recently completed its Phase A Mission Concept Study Phase for NASA and transitioned into Phase B (Formulation and Detailed Design). A number of significant accomplishments occurred during this initial phase of mission development. The SMAP project held several open meetings to solicit community feedback on possible science algorithms, prepared preliminary draft Algorithm Theoretical Basis Documents (ATBDs) for each mission science product, and established a prototype algorithm testbed to enable testing and evaluation of the performance of candidate algorithms. SMAP conducted an Applications Workshop in September 2009 to coordinate with potential application users interested in the mission data. A draft Applications Plan describing the Project s planned outreach to potential applications users has been prepared and will be updated during Phase B. SMAP made a significant evaluation of the potential terrestrial radio frequency interference (RFI) source environment and established radiometer and radar flight hardware and ground processing mitigation approaches. SMAP finalized its science orbit and orbit injection approach to optimize launch mass and prepared launch and commissioning scenarios and timeline. A science data communications approach was developed to maximize available science data volume to improve science margins while maintaining moderately short data product latencies to support many potential applications using existing ground assets and with minimum impact to the flight system. SMAP developed rigid multi-body and flexible body dynamics and control models and system designs for the 6-meter rotating instrument reflector-boom assembly (RBA) and flight system to confirm pointing and control performance, and devised strategies to efficiently implement on-orbit balancing if needed. Industry partners were selected for the spin mechanism assembly (SMA) and RBA. Preliminary designs for the radar and radiometer were initiated, including constructing breadboards of key assemblies

    Mapping development and health effects of cooking with solid fuels in low-income and middle-income countries, 2000-18 : a geospatial modelling study

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    Background More than 3 billion people do not have access to clean energy and primarily use solid fuels to cook. Use of solid fuels generates household air pollution, which was associated with more than 2 million deaths in 2019. Although local patterns in cooking vary systematically, subnational trends in use of solid fuels have yet to be comprehensively analysed. We estimated the prevalence of solid-fuel use with high spatial resolution to explore subnational inequalities, assess local progress, and assess the effects on health in low-income and middle-income countries (LMICs) without universal access to clean fuels.Methods We did a geospatial modelling study to map the prevalence of solid-fuel use for cooking at a 5 km x 5 km resolution in 98 LMICs based on 2.1 million household observations of the primary cooking fuel used from 663 population-based household surveys over the years 2000 to 2018. We use observed temporal patterns to forecast household air pollution in 2030 and to assess the probability of attaining the Sustainable Development Goal (SDG) target indicator for clean cooking. We aligned our estimates of household air pollution to geospatial estimates of ambient air pollution to establish the risk transition occurring in LMICs. Finally, we quantified the effect of residual primary solid-fuel use for cooking on child health by doing a counterfactual risk assessment to estimate the proportion of deaths from lower respiratory tract infections in children younger than 5 years that could be associated with household air pollution.Findings Although primary reliance on solid-fuel use for cooking has declined globally, it remains widespread. 593 million people live in districts where the prevalence of solid-fuel use for cooking exceeds 95%. 66% of people in LMICs live in districts that are not on track to meet the SDG target for universal access to clean energy by 2030. Household air pollution continues to be a major contributor to particulate exposure in LMICs, and rising ambient air pollution is undermining potential gains from reductions in the prevalence of solid-fuel use for cooking in many countries. We estimated that, in 2018, 205000 (95% uncertainty interval 147000-257000) children younger than 5 years died from lower respiratory tract infections that could be attributed to household air pollution.Interpretation Efforts to accelerate the adoption of clean cooking fuels need to be substantially increased and recalibrated to account for subnational inequalities, because there are substantial opportunities to improve air quality and avert child mortality associated with household air pollution. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd.Peer reviewe
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