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排序方式: 共有537条查询结果,搜索用时 15 毫秒
1.
The effects of retinoic acid (RA) on osteoblastic differentiation and activity were studied in fetal rat calvaria cells cultured for up to 24 days. Fetal bovine serum used for the experiments was treated with an anion-exchange resin to remove endogenous RA. The depletion of RA in the treated serum was confirmed by high-performance liquid chromatography and tritiated RA tracing. Under the culture conditions employed, the continuous presence of RA for 14 days at 10(-9) mol/l or higher decreased both alkaline phosphatase (ALP) activity on day 12 and the number of bone nodules on day 14 in a dose-dependent manner. Short-term (24 h) exposure to RA at 10(-8) mol/l, which is a physiological concentration, decreased and increased the levels of ALP and osteopontin mRNA on day 6, respectively. Retinoic acid at 10(-8) mol/l also increased the level of osteocalcin mRNA on day 12. However, these effects were not obvious at later stages (days 18 and 24). At a high concentration (10(-6) mol/l), RA increased the level of osteopontin mRNA on day 6 and decreased the levels of ALP and osteocalcin mRNA irrespective of culture period. These results suggest that, at physiological concentrations, RA suppresses the differentiation of osteoprogenitor cells and regulates osteoblastic functions. 相似文献
2.
This study examines the links between antecedents and consequences of Gabonese teachers' (N= 152) work motivation. The theoretical underpinnings are based on the Motivational Model of Job Burnout (MMJB) which is grounded in Self-Determination Theory (SDT) and states that the more supervisors satisfy an employee's need for self-determination, competence, and relatedness, the more self-determined is the latter's work motivation. The level of self-determined motivation has an impact on job satisfaction, which in turn determines life satisfaction. Higher levels of self-determined motivation also buffer emotional exhaustion and psychological distress. The model was confirmed via structural equation modeling and provides support for the validity and generalizability of the MMJB and SDT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
The appraisal process consists of the subjective evaluation that occurs during an individual's encounter with significant events in the environment, determining the nature of the emotional reaction and experience. Placed in the context of appraisal theories of emotion-elicitation and differentiation, the aim of the present research was to test empirically the hypothesis that the intrinsic pleasantness evaluation occurs before the goal conduciveness evaluation. In two studies, intrinsically pleasant and unpleasant images were used to manipulate pleasantness, and a specific event in a Pacman-type videogame was used to manipulate goal conduciveness. Facial EMG was used to measure facial reactions to each evaluation. As predicted, facial reactions to the intrinsic pleasantness manipulation were faster than facial reactions to the goal conduciveness manipulation. These results provide good empirical support for the sequential nature of the appraisal process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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The semantic definition of action refinement on labelled configuration structures is compared with the notion ofsyntactic substitution, which can be used as another notion of action refinement in a process algebraic setting. The comparison is done by studying a process algebra equipped with sequential composition, parallel composition with an explicit synchronisation set, and an operator for action refinement. On the one hand, the language (including the refinement operator) is given a configuration structure semantics. On the other hand, a reduction procedure transforms a process termPinto aflatterm (i.e., with the refinement operator not occurring in it)red(P) by means of syntactic substitution, defined in a structural inductive way. The main aim of the paper is to investigate general conditions under which the termsPandred(P) have the same semantics. The results we present are essentially dependent on the question whether the refined action can be synchronised or not. In the latter case,Pandred(P) give rise to isomorphic configuration structures under mild assumptions. The former case is considerably more difficult, since then refinement cannot be expected to distribute over parallel composition. We give necessary and sufficientsemanticconditions under which distribution still holds up to semantic equivalence. Subsequently, we also give sufficient (but not necessary)syntacticconditions for reducible terms. Finally, we generalise these results to a language with recursion. 相似文献
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Walter Lang Frank Jakobs Elena Tolstosheeva Hannes Sturm Azat Ibragimov Antonia Kesel Dirk Lehmhus Ursula DickeAuthor vitae 《Sensors and actuators. A, Physical》2011,171(1):3-11
Ubiquitous computing is about to become part of our everyday lives by integrating hundreds of “invisible” to us computing devices in our environment, so that they can unobtrusively and constantly assist us. This will imply more and smaller “invisible” sensors, homogeneously distributed and at the same time densely packed in host materials, responding to various stimuli and immediately delivering information. In order to reach this aim, the embedded sensors should be integrated within the host material, heading towards sensorial materials. The first step is to omit all parts that are not needed for the sensorial task and to find new solutions for a gentle integration. This is what we call function scale integration. The paper discusses sensor embedding in the human hand as an example of integration in nature, new technological applications and main challenges associated with this approach. 相似文献
9.
In this paper we give an overview over a series of experiments to visualize and measure flow fields in the human vascular
system with respect to their diagnostic capabilities. The experiments utilize a selection of GPU-based sparse and dense flow
visualization algorithms to show the diagnostic opportunities for volumetric cardiovascular phase contrast magnetic resonance
imaging data sets. Besides classical hardware accelerated particle and line-based approaches, an extensible tublet-based visualization,
a four-dimensional volumetric line integral convolution and a new two-dimensional cutting plane tool for three-dimensional
velocity data sets have been implemented. To evaluate the results, several hearts of human subjects have been investigated
and a flow phantom was built to artificially simulate distinctive flow features. Our results demonstrate that we are able
to provide an interactive tool for cardiovascular diagnostics with complementary hardware accelerated visualizations.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.
相似文献
Dieter SchmalstiegEmail: |
10.
Anjana Ramkumar Pieter Jan Stappers Wiro J. Niessen Sonja Adebahr Tanja Schimek-Jasch Ursula Nestle 《International journal of human-computer interaction》2017,33(2):123-134
HCI plays an important role in interactive medical image segmentation. The Goals, Operators, Methods, and Selection rules (GOMS) model and the National Aeronautics and Space Administration Task Load Index (NASA-TLX) questionnaire are different methods that are often used to evaluate the HCI process. In this article, we aim at improving the HCI process of interactive segmentation using both the GOMS model and the NASA-TLX questionnaire to: 1) identify the relations between these two methods and 2) propose HCI design suggestions based on the synthesis of the evaluation results using both methods. For this, we conducted an experiment where three physicians used two interactive segmentation approaches to segment different types of organs at risk for radiotherapy planning. Using the GOMS model, we identified 16 operators and 10 methods. Further analysis discovered strong relations between the use of GOMS operators and the results of the NASA-TLX questionnaire. Finally, HCI design issues were identified, and suggestions were proposed based on the evaluation results and the identified relations. 相似文献