806 research outputs found

    Bowhead Whale (Balaena mysticetus) Migration and Calling Behaviour in the Alaskan Beaufort Sea, Autumn 2001–04: An Acoustic Localization Study

    Get PDF
    The westward migration of bowhead whales (Bering Sea stock) was studied during autumn 2001–04 as part of an oil industry monitoring program. An array of Directional Autonomous Seafloor Acoustic Recorders (DASARs) was deployed northeast of the Northstar oil production island near Prudhoe Bay, Alaska. Underwater sounds were recorded continuously for 24–35 days per year, mainly in September. More than 130 000 bowhead calls were detected, and the directional capability of DASARs allowed triangulation of whale position for ~93 500 calls. The migration pathway was closer to shore in 2003–04 than in 2001–02. Calls were clumped in space and time, and there was significantly more calling at night than by day. From 65% to 82% of calls were simple frequency-modulated calls, and the percentage of complex calls was positively related to the daily number of calls. No songs were detected, but in 2004 there were numerous call sequences consisting of repeated identical calls in series and generally lasting up to a few minutes. The DASAR methodology provides detailed information on the temporal and spatial distribution of calling whales and on their acoustic repertoire.La migration Ă  l’ouest de la baleine borĂ©ale (population de la mer de BĂ©ring) a Ă©tĂ© Ă©tudiĂ©e durant quatre automnes (2001-2004) dans le cadre d’un programme d’étude de l’industrie pĂ©troliĂšre. Un rĂ©seau d’enregistreurs sous-marins autonomes et directionnels (DASAR) a Ă©tĂ© dĂ©ployĂ© au nord-est de Northstar, une Ăźle artificielle d’exploitation pĂ©troliĂšre prĂšs de Prudhoe Bay en Alaska. Des enregistrements sous-marins continus ont Ă©tĂ© rĂ©coltĂ©s pendant 24 Ă  35 jours chaque annĂ©e, principalement pendant le mois de septembre. Plus de 130 000 appels de baleines ont Ă©tĂ© enregistrĂ©s et la capacitĂ© directionnelle des DASAR a permis de dĂ©terminer par triangulation la position des baleines pour ~ 93 500 de ces appels. Le corridor de migration s’est avĂ©rĂ© plus proche de la cĂŽte en 2003-2004 qu’en 2001-2002. Les appels des baleines Ă©taient groupĂ©s dans le temps et l’espace et il y avait significativement plus d’appels la nuit que le jour. Soixante-cinq Ă  82 % des appels appartenaient au type dit « simple », et le pourcentage d’appels du type « complexe » Ă©tait positivement corrĂ©lĂ© au nombre journalier d’appels. Aucun chant n’a Ă©tĂ© dĂ©tectĂ©, mais les enregistrements de 2004 contenaient de nombreuses sĂ©quences d’appels composĂ©es de sĂ©ries d’appels identiques rĂ©pĂ©tĂ©s pendant 30 minutes et plus. L’utilisation des DASAR a permis d’obtenir des renseignements dĂ©taillĂ©s sur la distribution spatiale et temporelle de baleines borĂ©ales vocalisant ainsi que sur leur rĂ©pertoire acoustique

    Group testing with Random Pools: Phase Transitions and Optimal Strategy

    Full text link
    The problem of Group Testing is to identify defective items out of a set of objects by means of pool queries of the form "Does the pool contain at least a defective?". The aim is of course to perform detection with the fewest possible queries, a problem which has relevant practical applications in different fields including molecular biology and computer science. Here we study GT in the probabilistic setting focusing on the regime of small defective probability and large number of objects, p→0p \to 0 and N→∞N \to \infty. We construct and analyze one-stage algorithms for which we establish the occurrence of a non-detection/detection phase transition resulting in a sharp threshold, Mˉ\bar M, for the number of tests. By optimizing the pool design we construct algorithms whose detection threshold follows the optimal scaling Mˉ∝Np∣log⁡p∣\bar M\propto Np|\log p|. Then we consider two-stages algorithms and analyze their performance for different choices of the first stage pools. In particular, via a proper random choice of the pools, we construct algorithms which attain the optimal value (previously determined in Ref. [16]) for the mean number of tests required for complete detection. We finally discuss the optimal pool design in the case of finite pp

    Informal entrepreneurship in developing economies: the impacts of starting-up unregistered on firm performance

    Get PDF
    To advance understanding of the entrepreneurship process in developing economies, this paper evaluates whether registered enterprises that initially avoid the cost of registration, and focus their resources on overcoming other liabilities of newness, lay a stronger foundation for subsequent growth. Analyzing World Bank Enterprise Survey data across 127 countries, and controlling for other firm performance determinants, registered enterprises that started-up unregistered and spent longer operating unregistered are revealed to have significantly higher subsequent annual sales, employment and productivity growth rates compared with those that registered from the outset. The theoretical and policy implications are then discussed

    Tidal Evolution of Close Binary Asteroid Systems

    Get PDF
    We provide a generalized discussion of tidal evolution to arbitrary order in the expansion of the gravitational potential between two spherical bodies of any mass ratio. To accurately reproduce the tidal evolution of a system at separations less than five times the radius of the larger primary component, the tidal potential due to the presence of a smaller secondary component is expanded in terms of Legendre polynomials to arbitrary order rather than truncated at leading order as is typically done in studies of well-separated system like the Earth and Moon. The equations of tidal evolution including tidal torques, the changes in spin rates of the components, and the change in semimajor axis (orbital separation) are then derived for binary asteroid systems with circular and equatorial mutual orbits. Accounting for higher-order terms in the tidal potential serves to speed up the tidal evolution of the system leading to underestimates in the time rates of change of the spin rates, semimajor axis, and mean motion in the mutual orbit if such corrections are ignored. Special attention is given to the effect of close orbits on the calculation of material properties of the components, in terms of the rigidity and tidal dissipation function, based on the tidal evolution of the system. It is found that accurate determinations of the physical parameters of the system, e.g., densities, sizes, and current separation, are typically more important than accounting for higher-order terms in the potential when calculating material properties. In the scope of the long-term tidal evolution of the semimajor axis and the component spin rates, correcting for close orbits is a small effect, but for an instantaneous rate of change in spin rate, semimajor axis, or mean motion, the close-orbit correction can be on the order of tens of percent.Comment: 40 pages, 2 tables, 8 figure

    One-fits-all pretreatment protocol facilitating Fluorescence in Situ Hybridization on formalin-fixed paraffin-embedded, fresh frozen and cytological slides

    Get PDF
    Background: The Fluorescence In Situ Hybridization (FISH) technique is a very useful tool for diagnostic and prognostic purposes in molecular pathology. However, clinical testing on patient tissue is challenging due to variables of tissue processing that can influence the quality of the results. This emphasizes the necessity of a standardized FISH protocol with a high hybridization efficiency. We present a pretreatment protocol that is easy, reproducible, cost-effective, and facilitates FISH on all types of patient material simultaneously with good quality results. During validation, FISH analysis was performed simultaneously on formalin-fixed paraffin-embedded, fresh frozen and cytological patient material in combination with commercial probes using our optimized one-fits-all pretreatment protocol. An optimally processed sample is characterized by strong specific signals, intact nuclear membranes, non-disturbing autofluorescence and a homogeneous DAPI staining. Results: In our retrospective cohort of 3881 patient samples, overall 93% of the FISH samples displayed good quality results leading to a patient diagnosis. All FISH were assessed on quality aspects such as adequacy and consistency of signal strength (brightness), lack of background and / or cross-hybridization signals, and additionally the presence of appropriate control signals were evaluated to assure probe accuracy. In our analysis 38 different FISH probes from 3 commercial manufacturers were used (Cytocell, Vysis and ZytoLight). The majority of the patients in this cohort displayed good signal quality and barely non-specific background fluorescence on all tissue types independent of which commercial probe was used. Conclusion: The optimized one-fits-all FISH method is robust, reliable and reproducible to deliver an accurate result for patient diagnostics in a lean workflow and cost-effective manner. This protocol can be used for widespread application in cancer and non-cancer diagnostics and research

    A global horizon scan of issues impacting marine and coastal biodiversity conservation

    Get PDF
    The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5–10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems

    Updated precision measurement of the average lifetime of B hadrons

    Get PDF
    The measurement of the average lifetime of B hadrons using inclusively reconstructed secondary vertices has been updated using both an improved processing of previous data and additional statistics from new data. This has reduced the statistical and systematic uncertainties and gives \tau_{\mathrm{B}} = 1.582 \pm 0.011\ \mathrm{(stat.)} \pm 0.027\ \mathrm{(syst.)}\ \mathrm{ps.} Combining this result with the previous result based on charged particle impact parameter distributions yields \tau_{\mathrm{B}} = 1.575 \pm 0.010\ \mathrm{(stat.)} \pm 0.026\ \mathrm{(syst.)}\ \mathrm{ps.
    • 

    corecore