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排序方式: 共有103条查询结果,搜索用时 15 毫秒
1.
This study examined the mediating role of health behaviors in the relationship between neuroticism and depressive symptoms among spouse caregivers. Path analysis was used to test a model of the caregiver stress process among 233 caregivers of people with dementia. Results indicate that neuroticism has a significant direct effect on depressive symptoms and also indirectly influences depressive symptoms through health behaviors and perceived stress. When individual health behaviors were examined in the path model, only physical activity served a significant mediating role. These findings suggest that neuroticism may lead to depressive symptoms among caregivers partly through declines in physical activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Improved wetland remote sensing in Yellowstone National Park using classification trees to combine TM imagery and ancillary environmental data 总被引:6,自引:0,他引:6
The U.S. Fish and Wildlife Service uses the term palustrine wetland to describe vegetated wetlands traditionally identified as marsh, bog, fen, swamp, or wet meadow. Landsat TM imagery was combined with image texture and ancillary environmental data to model probabilities of palustrine wetland occurrence in Yellowstone National Park using classification trees. Model training and test locations were identified from National Wetlands Inventory maps, and classification trees were built for seven years spanning a range of annual precipitation. At a coarse level, palustrine wetland was separated from upland. At a finer level, five palustrine wetland types were discriminated: aquatic bed (PAB), emergent (PEM), forested (PFO), scrub-shrub (PSS), and unconsolidated shore (PUS). TM-derived variables alone were relatively accurate at separating wetland from upland, but model error rates dropped incrementally as image texture, DEM-derived terrain variables, and other ancillary GIS layers were added. For classification trees making use of all available predictors, average overall test error rates were 7.8% for palustrine wetland/upland models and 17.0% for palustrine wetland type models, with consistent accuracies across years. However, models were prone to wetland over-prediction. While the predominant PEM class was classified with omission and commission error rates less than 14%, we had difficulty identifying the PAB and PSS classes. Ancillary vegetation information greatly improved PSS classification and moderately improved PFO discrimination. Association with geothermal areas distinguished PUS wetlands. Wetland over-prediction was exacerbated by class imbalance in likely combination with spatial and spectral limitations of the TM sensor. Wetland probability surfaces may be more informative than hard classification, and appear to respond to climate-driven wetland variability. The developed method is portable, relatively easy to implement, and should be applicable in other settings and over larger extents. 相似文献
3.
We previously have found that monocytes from patients with allergic rhinitis and/or asthma produce less PGE2 than cells from normal subjects in response to a histamine-induced lymphokine. In order to investigate this observation further,
we measured the fatty acid content in the total phospholipids derived from the plasma, red cells, buffy coat cells, neutrophils,
monocytes and lymphocytes of 27 allergic patients and 21 normal controls. There were no substantial differences between atopics
and normals in the fatty acid analyses carried out for plasma and red cells. However, linoleic acid (18∶2n−6) levels were
elevated significantly in the buffy coat fraction, while arachidonic acid (20∶4n−6) levels were reduced. Measurement of fatty
acid levels after fractionation of the buffy coat population into neutrophils and monocytes yielded similar elevations in
18∶2n−6 and reduced 20∶4n−6. In contrast, lymphocytes appeared to have the reverse pattern, i.e., significantly reduced 18∶2n−6
and elevated 20∶4n−6 levels. These data suggest that atopic leukocytes may have altered essential fatty acid metabolism. 相似文献
4.
The impact of misregistration on SRTM and DEM image differences 总被引:2,自引:0,他引:2
Thomas G. Van Niel Tim R. McVicar LingTao Li John C. Gallant QinKe Yang 《Remote sensing of environment》2008,112(5):2430-2442
Image differences between Shuttle Radar Topography Mission (SRTM) data and other Digital Elevation Models (DEMs) are often performed for either accuracy assessment or for estimating vegetation height across the landscape. It has been widely assumed that the effect of sub-pixel misregistration between the two models on resultant image differences is negligible, yet this has not previously been tested in detail. The aim of this study was to determine the impact that various levels of misregistration have on image differences between SRTM and DEMs. First, very accurate image co-registration was performed at two study sites between higher resolution DEMs and SRTM data, and then image differences (SRTM–DEM) were performed after various levels of misregistration were systematically introduced into the SRTM data. It was found that: (1) misregistration caused an erroneous and dominant correlation between elevation difference and aspect across the landscape; (2) the direction of the misregistration defined the direction of this erroneous and systematic elevation difference; (3) for sub-pixel misregistration the error due solely to misregistration was greater than, or equal to the true difference between the two models for substantial proportions of the landscape (e.g., greater than 33% of the area for a half-pixel misregistration); and (4) the strength of the erroneous relationship with aspect was enhanced by steeper terrain. Spatial comparisons of DEMs were found to be sensitive to even sub-pixel misregistration between the two models, which resulted in a strong erroneous correlation with aspect. This misregistration induced correlation with aspect is not likely specific to SRTM data only; we expect it to be a generic relationship present in any DEM image difference analysis. 相似文献
5.
Properties and Printability of Inkjet and Screen-Printed Silver Patterns for RFID Antennas 总被引:2,自引:0,他引:2
José F. Salmerón Francisco Molina-Lopez Danick Briand Jason J. Ruan Almudena Rivadeneyra Miguel A. Carvajal L. F. Capitán-Vallvey Nico F. de Rooij Alberto J. Palma 《Journal of Electronic Materials》2014,43(2):604-617
We report the modeling, and geometrical and electrical characterization, of inkjet and screen-printed patterns on different polymeric substrates for use as antennas in radio-frequency identification (RFID) applications. We compared the physical and electrical characteristics of two silver nanoparticle-based commercial inkjet-printable inks and one screen-printable silver paste, when deposited on polyimide (PI), polyethylene terephthalate (PET), and polyetherimide (PEI) substrates. First, the thickness of the inkjet-printed patterns was predicted by use of an analytical model based on printing conditions and ink composition. The predicted thickness was confirmed experimentally, and geometrical characterization of the lines was completed by measuring the root-mean-square roughness of the patterns. Second, direct-current electrical characterization was performed to identify the printing conditions yielding the lowest resistivity and sheet resistance. The minimum resistivity for the inkjet-printing method was 8.6 ± 0.8 μΩ cm, obtained by printing four stacked layers of one of the commercial inks on PEI, whereas minimum resistivity of 44 ± 7 μΩ cm and 39 ± 4 μΩ cm were obtained for a single layer of screen-printed ink on polyimide (PI) with 140 threads/cm mesh and 90 threads/cm mesh, respectively. In every case, these minimum values of resistivity were obtained for the largest tested thickness. Coplanar waveguide transmission lines were then designed and characterized to analyze the radio-frequency (RF) performance of the printed patterns; minimum transmission losses of 0.0022 ± 0.0012 dB/mm and 0.0016 ± 0.0012 dB/mm measured at 13.56 MHz, in the high-frequency (HF) band, were achieved by inkjet printing on PEI and screen printing on PI, respectively. At 868 MHz, in the ultra-high-frequency band, the minimum values of transmission loss were 0.0130 ± 0.0014 dB/mm for inkjet printing on PEI and 0.0100 ± 0.0014 dB/mm for screen printing on PI. Although the resistivity achieved is lower for inkjet printing than for screen printing, RF losses for inkjetted patterns were larger than for screen-printed patterns, because thicker layers were obtained by screen printing. Finally, several coil inductors for the HF band were also fabricated by use of both printing techniques, and were used as antennas for semi-passive smart RFID tags on plastic foil capable of measuring temperature and humidity. 相似文献
6.
Linda M. Gallant Cynthia Irizarry Gloria M. Boone Brenna Ruiz‐Gordon 《Journal of Computer-Mediated Communication》2010,15(4):552-574
This study explores the nature and extent of Spanish language translation of hospital websites. A quantitative content analysis of 121 U.S. hospital websites located in Hispanic communities was conducted. Results indicate that a significant number of U.S. hospitals fail on their websites to offer equal content for Spanish language users. The study also examines several factors potentially associated with the incidence of website translation. First, organizational factors such as hospital size, ownership type and formal statements of diversity commitment are investigated. Second, demographic factors such as county population size and Hispanic population size are also considered. Hispanics' use of the Internet, the digital divide, culture's impact on Internet use, and eHealth provide a background for discussion of the findings. 相似文献
7.
Crosslinking effect on polydimethylsiloxane elastic modulus measured by custom‐built compression instrument
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A macroscopic compression test utilizing a simple custom‐built instrument was employed to measure polydimethylsiloxane (PDMS) elastic modulus. PDMS samples with varying crosslinking density were prepared with the elastomer base to the curing agent ratio ranging from 5 : 1 to 33 : 1. The PDMS network elastic modulus varied linearly with the amount of crosslinker, ranging from 0.57 MPa to 3.7 MPa for the samples tested. PDMS elastic modulus in MPa can be expressed as 20 MPa/PDMS base to curing agent ratio. This article describes a simple method for measuring elastic properties of soft polymeric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41050. 相似文献
8.
M. L. Becker J. A. Fagan N. D. Gallant B. J. Bauer V. Bajpai E. K. Hobbie S. H. Lacerda K. B. Migler J. P. Jakupciak 《Advanced materials (Deerfield Beach, Fla.)》2007,19(7)
Well‐defined length fractions of DNA‐wrapped single‐walled carbon nanotubes (SWNTs) of below 200 nm are taken up preferentially by IMR‐90 human lung fibroblasts, while longer DNA wrapped SWNTs are excluded from the cell interior (inset), report Matt Becker and coworkers on p. 939. The cover image construct includes overlaid images of the labeled cell membrane, the nuclei (blue), and the fluorescently labeled DNA wrapped SWNTs (red) that have gained access to the cell interior. 相似文献
9.
Perceptron-based learning algorithms 总被引:1,自引:0,他引:1
A key task for connectionist research is the development and analysis of learning algorithms. An examination is made of several supervised learning algorithms for single-cell and network models. The heart of these algorithms is the pocket algorithm, a modification of perceptron learning that makes perceptron learning well-behaved with nonseparable training data, even if the data are noisy and contradictory. Features of these algorithms include speed algorithms fast enough to handle large sets of training data; network scaling properties, i.e. network methods scale up almost as well as single-cell models when the number of inputs is increased; analytic tractability, i.e. upper bounds on classification error are derivable; online learning, i.e. some variants can learn continually, without referring to previous data; and winner-take-all groups or choice groups, i.e. algorithms can be adapted to select one out of a number of possible classifications. These learning algorithms are suitable for applications in machine learning, pattern recognition, and connectionist expert systems. 相似文献
10.
A gender-specific psychiatric diagnosis, named after an aspect of normal menstrual cycle physiology ("Late Luteal Phase" Dysphoric Disorder, or LLPD), is currently being considered for full diagnostic status in the upcoming catalog of psychiatric disorders, the DSM-IV. Psychologists have had surprisingly little voice in the ongoing debate about LLPD, despite the severe methodological difficulties involved in establishing reliability and validity for the proposed diagnosis. To stimulate research contributions by psychologists, we discuss the risks for over- and underdiagnosis, identify gaps in knowledge, and highlight specific empirical questions that require attention if the debate is to be informed by assessments with demonstrated and acceptable levels of reliability and validity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献