共查询到20条相似文献,搜索用时 31 毫秒
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Elizabeth R. Hawkins Lara Pogson-Manning Christian Jaehnichen Justin J. Meager 《Marine Mammal Science》2020,36(2):500-521
Understanding the social organization of coastal dolphins, particularly those that reside adjacent to major cities and urbanized regions, is important for understanding the vulnerability of populations to human impacts. We investigated the sexual segregation and social dynamics in a population of Australian humpback dolphins (Sousa sahulensis) inhabiting the near-urban embayment of Moreton Bay, Queensland. Over 160 vessel-based surveys, 148 adults were photographically identified. This included 116 assumed females and 32 assumed males. The population was sexually segregated (SSAS = 0.52, p < .001) and individuals preferred to associate with others of the same sex occupying the same spatial area (p < .025). Association indices between paired males were almost double those of females ( , SD = 0.04 and , SD = 0.02, respectively). However, females were more gregarious than males and maintained a larger network of associates based on preferred companionships. The social network was also modular with five clusters identified, and a limited number of individuals had a disproportionate influence on connectivity between clusters. This highly fragmented social network implies that the population may be vulnerable to social disruptions from human impacts. 相似文献
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Cluster randomized trials (CRTs) are widely used in different areas of medicine and public health. Recently, with increasing complexity of medical therapies and technological advances in monitoring multiple outcomes, many clinical trials attempt to evaluate multiple co-primary endpoints. In this study, we present a power analysis method for CRTs with binary co-primary endpoints. It is developed based on the GEE (generalized estimating equation) approach, and three types of correlations are considered: inter-subject correlation within each endpoint, intra-subject correlation across endpoints, and inter-subject correlation across endpoints. A closed-form joint distribution of the K test statistics is derived, which facilitates the evaluation of power and type I error for arbitrarily constructed hypotheses. We further present a theorem that characterizes the relationship between various correlations and testing power. We assess the performance of the proposed power analysis method based on extensive simulation studies. An application example to a real clinical trial is presented. 相似文献
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Henry T. Reich 《Biometrics》2020,76(3):1017-1027
We present general theoretical limits on the possible accuracy (mean squared error or MSE) of occupancy estimates for a large range of occupancy study designs with imperfect detection and confirm our theoretical results via a simulation study. In particular, we show that for a given total survey effort, the best possible MSE is driven by two design-related factors: the fraction of visits made at occupied sites (regardless of whether that occupancy status is known or not) and the number of visits made to each site with unknown occupancy status (ie, sites with no detections). The limits reveal that there is very little room for improvement over optimal implementations of the three existing occupancy design paradigms: standard design (visit S sites K times each), removal design (visit S sites up to K times each, halting visits to each site following a positive detection), and conditional design (visit S sites once, then resurvey sites with a positive detection an additional times). For the small portion of the occupancy-detection parameter space where improvement can be achieved, we introduce a new hybrid survey design with accuracy closer to the theoretical limit, which we illustrate by reanalyzing an existing coyote (Canis latrans) camera trap dataset. Our results provide new clarity and intuition regarding key factors of occupancy study design. 相似文献
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Tadej Tomanic Luka Rogelj Jost Stergar Bostjan Markelc Tim Bozic Simona Kranjc Brezar Gregor Sersa Matija Milanic 《Journal of biophotonics》2023,16(1):e202200181
Understanding tumors and their microenvironment are essential for successful and accurate disease diagnosis. Tissue physiology and morphology are altered in tumors compared to healthy tissues, and there is a need to monitor tumors and their surrounding tissues, including blood vessels, non-invasively. This preliminary study utilizes a multimodal optical imaging system combining hyperspectral imaging (HSI) and three-dimensional (3D) optical profilometry (OP) to capture hyperspectral images and surface shapes of subcutaneously grown murine tumor models. Hyperspectral images are corrected with 3D OP data and analyzed using the inverse-adding doubling (IAD) method to extract tissue properties such as melanin volume fraction and oxygenation. Blood vessels are segmented using the B-COSFIRE algorithm from oxygenation maps. From 3D OP data, tumor volumes are calculated and compared to manual measurements using a vernier caliper. Results show that tumors can be distinguished from healthy tissue based on most extracted tissue parameters ( ). Furthermore, blood oxygenation is 50% higher within the blood vessels than in the surrounding tissue, and tumor volumes calculated using 3D OP agree within 26% with manual measurements using a vernier caliper. Results suggest that combining HSI and OP could provide relevant quantitative information about tumors and improve the disease diagnosis. 相似文献
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Dejeanne Doublet David H. Johnson Fitsum Abadi Martha J. Desmond 《The Journal of wildlife management》2023,87(1):e22339
Development activities associated with urbanization can directly displace animals, causing high mortality and dispersal rates. Wildlife managers have attempted to mitigate the impacts of development on burrowing owls (Athene cunicularia), a species susceptible to ground-disturbing activities, by translocating them away from areas slated for development. In this study, we evaluated the effects of translocation on burrowing owl reproduction by comparing nest survival and productivity of owls involved in an ongoing translocation program in Arizona, USA, with that of resident owls. We used nest survival models to evaluate differences in nest survival and generalized linear models with Poisson error to assess differences in productivity. In 2017, cumulative nest survival (CNS) was lower among current-year translocated owls (i.e., owls translocated within the last year; CNS = 0.34, 95% CI = 0.18, 0.51) compared to non-translocated resident owls (0.83, 95% CI = 0.71, 0.94), but CNS was similar between previously translocated owls (i.e., those translocated >1 yr ago, CNS = 0.81, 95% CI = 0.64, 0.98) and residents. Likewise, in 2018, CNS was lower for current-year translocated owls (CNS = 0.12, 95% CI = 0.00, 0.24) compared to residents (CNS = 0.68, 95% CI = 0.50, 0.87) and previously translocated owls (CNS = 0.65, 95% CI = 0.40, 0.90). Productivity was significantly lower for current-year translocated owls ( = 0.5 fledglings/nest) compared to residents ( = 2.4 fledglings/nest) and previously translocated owls ( = 1.5 fledglings/nest) across sites and years. With the current methods of translocation, owls had poor reproductive success in the first year after release, but if they survived 2 years after release, they had similar nest survival and productivity compared to residents. Our results demonstrate that the current practice of releasing translocated burrowing owls in the Phoenix, Arizona area during the breeding season depresses reproduction and should be substantially changed. Nest survival was low and this was mainly attributed to nest establishment of translocated owls within release tents (acclimation structures used in translocations that involve soft release) where 85% of nests failed following tent removal. Translocation approaches that reflect a closer fit to the timing and behavior of the species should be tested to determine whether they result in better success. In particular, future studies should examine the translocation results of releasing owls as male-female pairs or single birds during the nonbreeding period. 相似文献
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Anjali Thomas Souradip Paul Mayanglambam Suheshkumar Singh 《Journal of biophotonics》2023,16(2):e202200157
We report an adaptive energy-compensated synthetic aperture focusing technique (eC-SAFT) for improving the imaging performance of photoacoustic microscopy (PAM) in terms of depth of field (DOF), spatial resolution (both axial and lateral), and SNR. In addition to coherency and time-delay (in conventional SAFT), our beamforming-based reconstruction algorithm takes into account acoustic energy loss—a primary physical parameter in acoustic wave propagation—following Beer-Lambert's law. Experimental validation studies were performed in tissue-mimicking (Agar) phantoms, complex leaf veins, and chicken breast tissues. Results demonstrate that our proposed eC-SAFT+CF outperforms conventional SAFT+CF to improve axial resolution (up to ), lateral resolution (up to ), SNR (up to ) and CR (up to ). 相似文献
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David Cheng Abhishek Chakrabortty Ashwin N. Ananthakrishnan Tianxi Cai 《Biometrics》2020,76(3):767-777
We consider estimating average treatment effects (ATE) of a binary treatment in observational data when data-driven variable selection is needed to select relevant covariates from a moderately large number of available covariates . To leverage covariates among predictive of the outcome for efficiency gain while using regularization to fit a parametric propensity score (PS) model, we consider a dimension reduction of based on fitting both working PS and outcome models using adaptive LASSO. A novel PS estimator, the Double-index Propensity Score (DiPS), is proposed, in which the treatment status is smoothed over the linear predictors for from both the initial working models. The ATE is estimated by using the DiPS in a normalized inverse probability weighting estimator, which is found to maintain double robustness and also local semiparametric efficiency with a fixed number of covariates p. Under misspecification of working models, the smoothing step leads to gains in efficiency and robustness over traditional doubly robust estimators. These results are extended to the case where p diverges with sample size and working models are sparse. Simulations show the benefits of the approach in finite samples. We illustrate the method by estimating the ATE of statins on colorectal cancer risk in an electronic medical record study and the effect of smoking on C-reactive protein in the Framingham Offspring Study. 相似文献
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In identifying subgroups of a heterogeneous disease or condition, it is often desirable to identify both the observations and the features which differ between subgroups. For instance, it may be that there is a subgroup of individuals with a certain disease who differ from the rest of the population based on the expression profile for only a subset of genes. Identifying the subgroup of patients and subset of genes could lead to better-targeted therapy. We can represent the subgroup of individuals and genes as a bicluster, a submatrix, , of a larger data matrix, , such that the features and observations in differ from those not contained in . We present a novel two-step method, SC-Biclust, for identifying . In the first step, the observations in the bicluster are identified to maximize the sum of the weighted between-cluster feature differences. In the second step, features in the bicluster are identified based on their contribution to the clustering of the observations. This versatile method can be used to identify biclusters that differ on the basis of feature means, feature variances, or more general differences. The bicluster identification accuracy of SC-Biclust is illustrated through several simulated studies. Application of SC-Biclust to pain research illustrates its ability to identify biologically meaningful subgroups. 相似文献
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Eric C. Lofroth Richard D. Weir Larry R. Davis Ingebjorg Jean Hansen 《The Journal of wildlife management》2023,87(1):e22315
Fishers (Pekania pennanti) are a forest-dependent carnivore of conservation concern in British Columbia, Canada. Ecological, spatial, and genetic evidence suggests that there are 2 distinct populations (Boreal and Columbian) that occur in forests at low to moderate elevations in the boreal and central interior regions of the province. In British Columbia, fishers occur at low densities relative to other parts of their range in North America, are trapped for their fur, and are sensitive to habitat change. Despite these factors, little demographic information exists to assist with management decisions for these populations. We collated and analyzed survival and reproductive data from 100 radio-tagged fishers from 5 independent studies conducted between 1990 and 2012 in British Columbia: 2 in the Boreal population, and 3 in the Columbian population. We also collated litter size data from 1 den box study and a translocation project of fishers from the Columbian population. Annual survival rates were not significantly different between the populations or between males and females; however, adult survival rates were higher than subadults (0.79 and 0.63, respectively). Subadult females had significantly lower survival rates than other sex or age classes. Reproductive rates were significantly different between the 2 populations (denning rate = 0.54 [Columbian], 0.82 [Boreal]; litter size = 1.7 [Columbian], 2.6 [Boreal]). These differences resulted in net reproductive rates in the Columbian population that were less than half of those in the Boreal population (0.92 kits/reproductive season compared to 2.13, respectively). Population growth rates suggest that the Columbian population may have been declining during the studies, whereas the Boreal population may have been increasing (0.96 compared to 1.20). Consequently, we suggest that focused and intensive habitat and population management for fishers are needed in British Columbia to ensure population sustainability, particularly for the Columbian population. 相似文献
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Tayler N. LaSharr Samantha P. H. Dwinnell Brittany L. Wagler Hall Sawyer Rhiannon P. Jakopak Anna C. Ortega Luke R. Wilde Matthew J. Kauffman Katey S. Huggler Patrick W. Burke Miguel Valdez Patrick Lionberger Douglas G. Brimeyer Brandon Scurlock Jill Randall Rusty C. Kaiser Mark Thonhoff Gary L. Fralick Kevin L. Monteith 《The Journal of wildlife management》2023,87(1):e22333
Capture and handling techniques for individual-based, long-term research that tracks the life history of animals by recapturing the same individuals for several years has vastly improved study inferences and our understanding of animal ecology. Yet there are corresponding risks to study animals associated with physical trauma or capture myopathy that can occur during or following capture events. Rarely has empirical evidence existed to guide decisions associated with understanding the magnitude of capture-related risks, how to reduce these risks when possible, and implications for mortality censoring and survival estimates. We used data collected from 2,399 capture events of mule deer (Odocoileus hemionus) via helicopter net-gunning to compare daily survival probabilities within a 10-week period centered on a capture event and evaluated how animal age, nutritional condition (body fat), and various handling methods influenced survival before, during, and following a capture event. Direct mortality resulting from capture efforts was 1.59%. Mean daily survival was 0.9993 ± 0.0001 (SE) during the 5-week pre-capture window, was depressed the day of capture at 0.9841 ± 0.0004, and rebounded to 0.9990 ± 0.0008 during the 5-week post-capture window. Neither capture nor handling had a detectable effect on post-capture survival, including handling time ( = 13.30 ± 1.87 min), capture time of year (i.e., Dec or Mar), tooth extraction, and the number of times an animal had been recaptured (2–17 times). Although mortality rate was slightly elevated during capture (resulting from physical trauma associated with capture), age and nutritional condition did not influence the probability of mortality during a capture event. Following a capture event, nutritional condition influenced survival; however, that relationship was consistent with expected effects of nutritional condition on winter survival and independent of capture and handling. Overall survival rates 5 weeks before capture and 5 weeks after capture were not different. A specified window of time with depressed survival following capture and handling was not evident, which contradicts the implementation of a predetermined window often used by researchers and managers for censoring mortalities that occur after capture. Previous notions that censorship of all mortality data in the 2 weeks following capture is unwarranted and risks removal of meaningful data. With previous evidence guiding our protocols for capture (e.g., reduced chase time) and handling (e.g., temperature mitigation), low direct mortality and almost undetectable indirect mortality post capture reinforces the efficacy of helicopter net-gunning for capture and recapture of mule deer in long-term, individual-based studies. 相似文献
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Accounting for time-varying confounding when assessing the causal effects of time-varying exposures on survival time is challenging. Standard survival methods that incorporate time-varying confounders as covariates generally yield biased effect estimates. Estimators using weighting by inverse probability of exposure can be unstable when confounders are highly predictive of exposure or the exposure is continuous. Structural nested accelerated failure time models (AFTMs) require artificial recensoring, which can cause estimation difficulties. Here, we introduce the structural nested cumulative survival time model (SNCSTM). This model assumes that intervening to set exposure at time to zero has an additive effect on the subsequent conditional hazard given exposure and confounder histories when all subsequent exposures have already been set to zero. We show how to fit it using standard software for generalized linear models and describe two more efficient, double robust, closed-form estimators. All three estimators avoid the artificial recensoring of AFTMs and the instability of estimators that use weighting by the inverse probability of exposure. We examine the performance of our estimators using a simulation study and illustrate their use on data from the UK Cystic Fibrosis Registry. The SNCSTM is compared with a recently proposed structural nested cumulative failure time model, and several advantages of the former are identified. 相似文献
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Dejeanne D. Doublet Fitsum Abadi David H. Johnson Martha J. Desmond 《The Journal of wildlife management》2023,87(1):e22283
Given the rapid pace of urbanization, mitigation translocations are increasingly being used to reduce human-wildlife conflicts, especially to move animals out of the path of land development. Burrowing owls (Athene cunicularia) are commonly subjected to translocations because of their association with flat, open lands that are attractive to development. But outcomes of burrowing owl translocations and the effects they have on their demographic parameters are seldom documented. From 2017–2019, we tracked the fates of 42 resident (non-translocated) burrowing owls and 43 translocated owls using very high frequency radio-telemetry across 4 release sites in southcentral Arizona, USA. Translocations were conducted by Wild At Heart (WAH), a non-profit raptor rehabilitation program, and owls were moved from areas with planned development activities to release sites that contained artificial burrows. Each year, WAH held translocated owls in groups of 6–10 owls with varying male to female ratios in aviaries prior to taking the owls to release sites where the owls stayed in soft-release tents for an acclimation period of 30 days before release. Resident owls were located at or near the 4 release sites. We used the joint live encounter and dead recovery model to evaluate differences in survival and fidelity probabilities between resident (non-translocated) and translocated burrowing owls and to assess factors that influenced these probabilities including sex, year, site, captivity duration, and the number of males in release cohorts for translocated owls. Annual survival was consistently lower for translocated owls (0.35, 95% CI = 0.10, 0.61 and 0.01, 95% CI = 0.00, 0.03 for 2017 and 2018, respectively) compared to resident owls (0.68, 95% CI = 0.45, 0.92 and 0.69, 95% CI = 0.47, 0.90 for 2017 and 2018, respectively). Annual fidelity was lower for translocated owls (0.05, 95% CI = 0.00, 0.15) compared to resident owls (0.79, 95% CI = 0.57, 1.00) in 2018, but fidelity did not differ significantly between translocated (0.54, 95% CI = 0.19, 0.89) and resident owls (0.62, 95% CI = 0.37, 0.87) in 2017. For translocated owls, the number of males in release cohorts negatively affected survival ( = −0.74, 95% CI = −1.07, −0.40) and fidelity ( = −0.73, 95% CI = −1.17, −0.29). Our results indicate the need for substantial changes to the current translocation methodology for burrowing owls in Arizona. Breeding season releases that included owl groups and multiple males within cohorts resulted in agonistic interactions, high mortality, and low fidelity. Translocations of this territorial species should be restricted to male-female pairs or single individuals. Earlier releases may allow owls time to become established on release sites prior to the breeding season, which could promote fidelity. We recommend these changes be implemented and evaluated along with an examination of other release methods. 相似文献
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The total free energy of a hydrated biomolecule and its corresponding decomposition of energy and entropy provides detailed information about regions of thermodynamic stability or instability. The free energies of four hydrated globular proteins with different net charges are calculated from a molecular dynamics simulation, with the energy coming from the system Hamiltonian and entropy using multiscale cell correlation. Water is found to be most stable around anionic residues, intermediate around cationic and polar residues, and least stable near hydrophobic residues, especially when more buried, with stability displaying moderate entropy-enthalpy compensation. Conversely, anionic residues in the proteins are energetically destabilized relative to singly solvated amino acids, while trends for other residues are less clear-cut. Almost all residues lose intraresidue entropy when in the protein, enthalpy changes are negative on average but may be positive or negative, and the resulting overall stability is moderate for some proteins and negligible for others. The free energy of water around single amino acids is found to closely match existing hydrophobicity scales. Regarding the effect of secondary structure, water is slightly more stable around loops, of intermediate stability around strands and turns, and least stable around helices. An interesting asymmetry observed is that cationic residues stabilize a residue when bonded to its N-terminal side but destabilize it when on the C-terminal side, with a weaker reversed trend for anionic residues. 相似文献
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The spectral-based photochemical reflectance index (PRI) and leaf surface temperature (Tleaf) derived from thermal imaging are two indicative metrics of plant functioning. The relationship of PRI with radiation-use efficiency (RUE) and Tleaf with leaf transpiration could be leveraged to monitor crop photosynthesis and water use from space. Yet, it is unclear how such relationships will change under future high carbon dioxide concentrations ([CO2]) and drought. Here we established an [CO2] enrichment experiment in which three wheat genotypes were grown at ambient (400 ppm) and elevated (550 ppm) [CO2] and exposed to well-watered and drought conditions in two glasshouse rooms in two replicates. Leaf transpiration (Tr) and latent heat flux (LE) were derived to assess evaporative cooling, and RUE was calculated from assimilation and radiation measurements on several dates along the season. Simultaneous hyperspectral and thermal images were taken at 1.5 m from the plants to derive PRI and the temperature difference between the leaf and its surrounding air ( Tleaf−air). We found significant PRI and RUE and Tleaf−air and Tr correlations, with no significant differences among the genotypes. A PRI–RUE decoupling was observed under drought at ambient [CO2] but not at elevated [CO2], likely due to changes in photorespiration. For a LE range of 350 W m–2, the ΔTleaf−air range was 10°C at ambient [CO2] and only 4°C at elevated [CO2]. Thicker leaves in plants grown at elevated [CO2] suggest higher leaf water content and consequently more efficient thermoregulation at high [CO2] conditions. In general, Tleaf was maintained closer to the ambient temperature at elevated [CO2], even under drought. PRI, RUE, ΔTleaf−air, and Tr decreased linearly with canopy depth, displaying a single PRI-RUE and ΔTleaf−air Tr model through the canopy layers. Our study shows the utility of these sensing metrics in detecting wheat responses to future environmental changes. 相似文献