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排序方式: 共有465条查询结果,搜索用时 15 毫秒
51.
在医院集中式DICOM医用打印系统中,一台高速DICOM打印机往往连接着多台DICOM主机。由于各主机对输出图像的质量要求不同,如何在打印机端适应主机的要求,控制打印图像质量,是得到令人满意的胶片输出的医用图像的关键。本文以AGFADrystar5500干式相机为例探讨该DICOM医用打印机的图像控制原理和方法,以及在临床上的实际应用。 相似文献
52.
Among the plant traits that affect performance, vitality and herbivore resistance in rangeland vegetation, biomass partitioning ranks top, commonly outweighing processes at single leaves (e.g., photosynthesis, respiration). We explored the allometry of a broad sample of herbaceous species from two high elevation sites in the Andes in order to explain biomass partitioning under harsh climatic conditions and risk of biomass losses under strong camelid grazing pressure. We combined data from NW-Argentina and W-Bolivia from elevations between 4200 and 4250 m in a landscape dominated by tall Festuca orthophylla tussocks and a drought driven seasonality (rainfall only between November and March). Across 10–20 taxa per region we found less investment in leaves with a mean leaf mass fraction of only 11% and instead a massive storage in below-ground compartments (rhizomes, tap roots), particularly at the colder Argentinean site. Though grazing pressure was much greater in Bolivia, the foliage mass fraction was there larger than in Argentina. The inter-tussock space in these open, dry plains (‘pajonal’) was dominated by rosette forming species with a below-ground shoot apex and massive tap roots (70% of all species), rendering these species less sensitive to grazing and trampling. The storage organs of these species represented more than 50% of total biomass. Llamas, which represented the main vertebrate herbivore in these open plains at the Bolivian site, preferred non tap-root herbs and species with low leaf nitrogen concentration. Palatable forbs for llamas (22% of all species at the Bolivian site) only survived when nested (facilitated) in the rigid, tall Festuca orthophylla tussocks or thorny shrubs. In conclusion, these extremely high elevation rangeland herbs invest preferentially in structures for persistence (K-strategy) rather than maximizing carbon gain. 相似文献
53.
Enno Merivee Anne Must Anne Luik Ingrid Williams 《Journal of insect physiology》2010,56(11):1671-1678
This study gives the first electrophysiological evidence of hygroreceptors in carabids. Extracellular recordings from the antennal dome-shaped sensilla of the carabid beetle Pterostichus oblolongopunctatus (Coleoptera, Carabidae) clearly show the presence of moist and dry neuron antagonistically responding to humidity changes. The cold neuron of the same sensillum did not respond to changes in humidity. For the first time, we demonstrate that the binary system of two antagonistic hygroreceptor neurons discriminates differences between steady-state humidity levels more sensitively than either neuron separately. Another advantage of the binary system is that it guarantees immediate and strong phasic-tonic response to rapid humidity changes in either direction. In the hygrosensing system of carabids, this would allow detection of subtle step-changes in humidity with greater sensitivity than differences in steady-state values of humidity. Thus, construction of the hygrosensing system with opposing receptor neurons may allow insects to detect environmental humidity differences critical for their habitat and microhabitat selection, and survival with great precision. 相似文献
54.
During the last few years, geographical information systems (GIS) have spread as powerful tools for landscape analysis. The main purpose of this work was to use GIS to display an ecological network made up of core areas, key areas and ecological corridors. As an example of the application of this method we refer to the population of deer (Cervus elaphus) and roe deer (Capreolus capreolus) in an alpine area in northwestern Italy. The method provided an overall view of the ecological network of the area, highlighting how linear infrastructures can affect animal populations and consequently, their survival probability. 相似文献
55.
An identification key for 20 common strand-forming indoor wood decay fungi is given. The key is based on observations of material from affected buildings and on wood samples that have been incubated in the laboratory. The key is with macro- and microscopic photographs. 相似文献
56.
Tear proteomic studies revealed distinct similarities between contact lens wearers and dry eye patients. AMO Complete® multipurpose contact lens cleaning solutions containing taurine seem to have a beneficial effect regarding contact lens induced dry eye. To illuminate the effect of taurine on the tear proteome of contact lens wearers and sicca patients we developed a gel-based RP-RP capillary HPLC–MALDI TOF/TOF MS strategy. Two contact lens wearer groups, one using eye drops containing 0.05% taurine; the other for control physiological NaCl solution were monitored. Also, a third group of sicca patients using taurine solution was studied (N = 4 individuals/group). Tear pools of each group at six time points over 5 weeks were analyzed. In summary 267 tear proteins were identified. We found a protein subset showing a linear taurine response with R2 values ≥ 0.5. Taurine effects were detected predominantly in the contact lens group demonstrated by distinct level decreases. Most protein candidates were related to inflammation. Since levels of these proteins differentiate from those of a healthy non-contact lens wearer reference they are supposed to be involved in contact lens induced dry eye and should be focused on in further studies. 相似文献
57.
山东省冬小麦干热风灾害预警模型研究 总被引:2,自引:0,他引:2
以30年的气象和产量数据为研究对象,对冬小麦成熟收获前16天的23个温度指标、23个空气相对湿度指标和16个风速指标与相对气象产量进行统计分析.通过相关分析确定不同生态区的干热风灾害风险因子,对不同生态区的风险因子和相对气象产量进行回归分析,构建冬小麦干热风灾害风险预警模型.结果表明:同类气象因子在不同生态区中的作用表现不同,模型因素构成以因子的互作为主,单因子的直接影响作用不突出.鲁西北和鲁中是干热风灾害的高危险区,鲁西南干热风灾害的危险最小. 相似文献
58.
59.
Seasonal tropical forests exhibit a great diversity of leaf exchange patterns. Within these forests variation in the timing
and intensity of leaf exchange may occur within and among individual trees and species, as well as from year to year. Understanding
what generates this diversity of phenological behaviour requires a mechanistic model that incorporates rate-limiting physiological
conditions, environmental cues, and their interactions. In this study we examined long-term patterns of leaf flushing for
a large proportion of the hundreds of tree species that co-occur in a seasonal tropical forest community in western Thailand.
We used the data to examine community-wide variation in deciduousness and tested competing hypotheses regarding the timing
and triggers of leaf flushing in seasonal tropical forests. We developed metrics to quantify the nature of deciduousness (its
magnitude, timing and duration) and its variability among survey years and across a range of taxonomic levels. Tree species
varied widely in the magnitude, duration, and variability of leaf loss within species and across years. The magnitude of deciduousness
ranged from complete crown loss to no crown loss. Among species that lost most of their crown, the duration of deciduousness
ranged from 2 to 21 weeks. The duration of deciduousness in the majority of species was considerably shorter than in neotropical
forests with similar rainfall periodicity. While the timing of leaf flushing varied among species, most (∼70%) flushed during
the dry season. Leaf flushing was associated with changes in photoperiod in some species and the timing of rainfall in other
species. However, more than a third of species showed no clear association with either photoperiod or rainfall, despite the
considerable length and depth of the dataset. Further progress in resolving the underlying internal and external mechanisms
controlling leaf exchange will require targeting these species for detailed physiological and microclimatic studies. 相似文献
60.
Jones MB Fulford GR Please CP McElwain DL Collins MJ 《Bulletin of mathematical biology》2008,70(2):323-343
This paper presents an elastohydrodynamic model of the human eyelid wiper. Standard lubrication theory is applied to the fluid
layer between the eyelid wiper and ocular surface. The role of the lubrication film is to reduce the shear stresses by preventing
solid to solid contact between the eyelid wiper and ocular surface. For the lubrication film to be effective, it is required
that the orientation of the eyelid wiper changes between the opening and closing phases of a blink. In order to model this,
the hydrodynamic model is coupled with an elastic mattress model for the soft tissue of the eyelid wiper and ocular surface.
This leads to a one-dimensional non-linear partial differential equation governing the fluid pressure in the lubrication film.
In order to solve the differential equation, a loading condition or constraint equation must be specified. The resulting system
is then solved numerically. The model allows predictions of the tear film flux from under the upper eyelid, as well as normal
and shear stresses acting on the ocular surface. These factors are important in relation to dry eye syndrome, deformation
of the cornea and contact lens design. It is found that the pressure and shear stress under the eyelid act across a length
of approximately 0.1 mm which is consistent with clinical observations. It order to achieve a flow of tears from under the
upper eyelid during a blink, the model requires that the normal force the eyelid applies to the ocular surface during the
closing phase of the blink is significantly higher than during the opening phase of the blink.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献