983 research outputs found

    Wireless recording of the calls of Rousettus aegyptiacus and their reproduction using electrostatic transducers

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    Bats are capable of imaging their surroundings in great detail using echolocation. To apply similar methods to human engineering systems requires the capability to measure and recreate the signals used, and to understand the processing applied to returning echoes. In this work, the emitted and reflected echolocation signals of Rousettus aegyptiacus are recorded while the bat is in flight, using a wireless sensor mounted on the bat. The sensor is designed to replicate the acoustic gain control which bats are known to use, applying a gain to returning echoes that is dependent on the incurred time delay. Employing this technique allows emitted and reflected echolocation calls, which have a wide dynamic range, to be recorded. The recorded echoes demonstrate the complexity of environment reconstruction using echolocation. The sensor is also used to make accurate recordings of the emitted calls, and these calls are recreated in the laboratory using custom-built wideband electrostatic transducers, allied with a spectral equalization technique. This technique is further demonstrated by recreating multi-harmonic bioinspired FM chirps. The ability to record and accurately synthesize echolocation calls enables the exploitation of biological signals in human engineering systems for sonar, materials characterization and imaging

    Generalized Totalizer Encoding for Pseudo-Boolean Constraints

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    Pseudo-Boolean constraints, also known as 0-1 Integer Linear Constraints, are used to model many real-world problems. A common approach to solve these constraints is to encode them into a SAT formula. The runtime of the SAT solver on such formula is sensitive to the manner in which the given pseudo-Boolean constraints are encoded. In this paper, we propose generalized Totalizer encoding (GTE), which is an arc-consistency preserving extension of the Totalizer encoding to pseudo-Boolean constraints. Unlike some other encodings, the number of auxiliary variables required for GTE does not depend on the magnitudes of the coefficients. Instead, it depends on the number of distinct combinations of these coefficients. We show the superiority of GTE with respect to other encodings when large pseudo-Boolean constraints have low number of distinct coefficients. Our experimental results also show that GTE remains competitive even when the pseudo-Boolean constraints do not have this characteristic.Comment: 10 pages, 2 figures, 2 tables. To be published in 21st International Conference on Principles and Practice of Constraint Programming 201

    Multiple sequence alignment based on set covers

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    We introduce a new heuristic for the multiple alignment of a set of sequences. The heuristic is based on a set cover of the residue alphabet of the sequences, and also on the determination of a significant set of blocks comprising subsequences of the sequences to be aligned. These blocks are obtained with the aid of a new data structure, called a suffix-set tree, which is constructed from the input sequences with the guidance of the residue-alphabet set cover and generalizes the well-known suffix tree of the sequence set. We provide performance results on selected BAliBASE amino-acid sequences and compare them with those yielded by some prominent approaches

    People with Alcohol Use Disorders in Specialized Care in Eight Different European Countries

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    Aim: To provide a description of patients receiving alcohol treatment in eight different European countries, including the level of comorbidities and functional limitations. Methods: Drinking behaviours, DSM-IV alcohol use disorder (AUD), mental and somatic comorbidities, disability and health services utilization of 1767 patients from various specialized treatment settings were assessed as representative for regions of eight European countries. Severity of alcohol dependence (AD) in terms of drinking level was compared with a large representative US sample. Results: Patients in specialized care for AUDs showed high levels of consumption [average level of daily ethanol intake: 141.1 g, standard deviation (SD): 116.0 g], comorbidity [e.g. liver problems: 19.6%, 95% confidence interval (CI): 17.5-21.6%; depression: 43.2%, 95% CI: 40.7-45.8%; anxiety: 50.3%, 95% CI: 47.8-52.9%], disability and health services utilization (average number of nights spent in hospital(s) during the last 6 months: 8.8, SD: 19.5 nights). Severity of AD was similar to the US sample, but European men consumed on average more alcohol daily. Conclusions: High levels of consumption, somatic and mental comorbidities, disability and functional losses were found in this representative treatment sample, indicating that treatment was initiated only at severe stages of AUDs. Earlier initiation of treatment could help avoid some of the health and social burde

    Electronic properties of LaOFFeAs in the normal state probed by NMR/NQR

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    We report 139La, 57Fe and 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements on powders of the new LaO1-xFxFeAs superconductor for x = 0 and x = 0.1 at temperatures up to 480 K, and compare our measured NQR spectra with local density approximation (LDA) calculations. For all three nuclei in the x = 0.1 material, it is found that the local Knight shift increases monotonically with an increase in temperature, and scales with the macroscopic susceptibility, suggesting a single magnetic degree of freedom. Surprisingly, the spin lattice relaxation rates for all nuclei also scale with one another, despite the fact that the form factors for each site sample different regions of q-space. This result suggests a lack of any q-space structure in the dynamical spin susceptibility that might be expected in the presence of antiferromagnetic correlations. Rather, our results are more compatible with simple quasi-particle scattering. Furthermore, we find that the increase in the electric field gradient at the As cannot be accounted for by LDA calculations, suggesting that structural changes, in particular the position of the As in the unit cell, dominate the NQR response.Comment: 17 pages, 6 figure

    Premotor cortex in observing erroneous action: An fMRI study

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    The lateral premotor cortex (PMC) is involved during action observation in monkeys and humans, reflecting a matching process between observed actions and their corresponding motor schemata. In the present study, functional magnetic resonance imaging (fMRI) was used to investigate if paying attention to the two observable action components, objects and movements, modulates premotor activation during the observation of actions. Participants were asked to classify presented movies as showing correct actions, erroneous actions, or senseless movements. Erroneous actions were incorrect either with regard to employed objects, or to performed movements. The experiment yielded two major results: (1) The ventrolateral premotor cortex (vPMC) and the anterior part of the intraparietal sulcus (aIPS) are strongly activated during the observation of actions in humans. Premotor activation was dominantly located within Brodmann Area (BA) 6, and sometimes extended into BA 44. (2) The presentation of object errors and movements errors allowed to disentangle brain activations corresponding to the analysis of movements and objects in observed actions. Left premotor areas were more involved in the analysis of objects, whereas right premotor areas were dominant in the analysis of movements. It is suggested that the analysis of categorical information, like objects, and that of coordinate information, like movements, are pronounced in different hemispheres

    Evolutionary biology of birds and their associated microbiota in the Madrean Archipelago sky islands

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    Sky islands are disjunct patches of montane forested habitat in a matrix of desert, grasslands, and scrub. I investigated intraspecific evolutionary biology of two bird species—the White­‐breasted Nuthatch (Sitta carolinensis) and the Brown Creeper (Certhia americana)—in the Madrean Archipelago sky islands (Arizona, USA), a biodiversity and evolution hotspot. In addition, I explored patterns of codiversification of these two birds and their associated gut microbial communities. The two bird studies revealed different patterns of diversification within the sky islands. The White­‐breasted Nuthatch exhibits a pattern of isolation by environment, where genetic differences among populations are related to environmental differences of those localities. In contrast, the Brown Creeper has a strong genetic break between northern and southern populations, with no evidence of gene flow between lineages. When I investigated codiversification of birds and their microbial communities, I found no relationship between host genetic diversity and microbial community alpha diversity, while genetic differentiation between birds was significantly related with beta diversity between microbial communities. This dissertation provides a first step in comparative evolutionary biology of Madrean Archipelago avian taxa, and adds to the knowledge of the factors shaping microbial community diversity in wild animals

    Economic burden associated with alcohol dependence in a German primary care sample : a bottom-up study

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    BACKGROUND: A considerable economic burden has been repeatedly associated with alcohol dependence (AD) - mostly calculated using aggregate data and alcohol-attributable fractions (top-down approach). However, this approach is limited by a number of assumptions, which are hard to test. Thus, cost estimates should ideally be validated with studies using individual data to estimate the same costs (bottom-up approach). However, bottom-up studies on the economic burden associated with AD are lacking. Our study aimed to fill this gap using the bottom-up approach to examine costs for AD, and also stratified the results by the following subgroups: sex, age, diagnostic approach and severity of AD, as relevant variations could be expected by these factors. METHODS: SAMPLE: 1356 primary health care patients, representative for two German regions. AD was diagnosed by a standardized instrument and treating physicians. Individual costs were calculated by combining resource use and productivity data representing a period of six months prior to the time of interview, with unit costs derived from the literature or official statistics. The economic burden associated with AD was determined via excess costs by comparing utilization of various health care resources and impaired productivity between people with and without AD, controlling for relevant confounders. Additional analyses for several AD characteristics were performed. RESULTS: Mean costs among alcohol dependent patients were 50 % higher compared to the remaining patients, resulting in 1836 € excess costs per alcohol dependent patient in 6 months. More than half of these excess costs incurred through increased productivity loss among alcohol dependent patients. Treatment for alcohol problems represents only 6 % of these costs. The economic burden associated with AD incurred mainly among males and among 30 to 49 year old patients. Both diagnostic approaches were significantly related to the economic burden, while costs increased with alcohol use disorder severity but not with other AD severity indicators. CONCLUSIONS: Our study confirms previous studies using top-down approaches to estimate the economic burden associated with AD. Further, we highlight the need for efforts aimed at preventing adverse outcomes for health and occupational situation associated with alcohol dependence based on factors associated with particularly high economic burden

    Gaze following is modulated by expectations regarding others’ action goals

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    Humans attend to social cues in order to understand and predict others' behavior. Facial expressions and gaze direction provide valuable information to infer others' mental states and intentions. The present study examined the mechanism of gaze following in the context of participants' expectations about successive action steps of an observed actor. We embedded a gaze-cueing manipulation within an action scenario consisting of a sequence of naturalistic photographs. Gaze-induced orienting of attention (gaze following) was analyzed with respect to whether the gaze behavior of the observed actor was in line or not with the action-related expectations of participants (i.e., whether the actor gazed at an object that was congruent or incongruent with an overarching action goal). In Experiment 1, participants followed the gaze of the observed agent, though the gaze-cueing effect was larger when the actor looked at an action-congruent object relative to an incongruent object. Experiment 2 examined whether the pattern of effects observed in Experiment 1 was due to covert, rather than overt, attentional orienting, by requiring participants to maintain eye fixation throughout the sequence of critical photographs (corroborated by monitoring eye movements). The essential pattern of results of Experiment 1 was replicated, with the gaze-cueing effect being completely eliminated when the observed agent gazed at an action-incongruent object. Thus, our findings show that covert gaze following can be modulated by expectations that humans hold regarding successive steps of the action performed by an observed agent

    Characteristics and drivers of forest cover change in the post-socialist era in Croatia: evidence from a mixed-methods approach

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    © 2016, Springer-Verlag Berlin Heidelberg.Extensive forests in Croatia represent an important biological and economic resource in Europe. They are characterised by heterogeneity in forest management practices dating back to the socialist planned economy of the pre-1991 era. In this study we investigated the difference in rates of deforestation and reforestation in private- and state-owned forests during the post-socialist period and the causal drivers of change. The selected region of Northern Croatia is characterised by a high percentage of privately owned forests with minimal national monitoring and control. We used a mixed-methods approach which combines remote sensing, statistical modelling and a household-based questionnaire survey to assess the rates of forest cover change and factors influencing those changes. The results show that predominantly privately owned forests in Northern Croatia have recorded a net forest loss of 1.8 % during the 1991–2011 period, while Croatia overall is characterised by a 10 % forest cover increase in predominantly state-owned forests. Main factors influencing forest cover changes in private forests are slope, altitude, education structure, population age and population density. The results also show that the deforestation in private forests is weakening overall, mostly due to the continuation of the de-agrarisation and de-ruralisation processes which began during socialism
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