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41.
P G van der Varst P L Lemmens M C Peters A J Plasschaert 《Journal of biomechanics》1991,24(5):341-347
To assess the clinical performance of restorative materials with respect to mechanical failure, the shape of the restoration, the strength and fatigue properties and the loading history are important. This study deals with the feasibility of a method to estimate the mechanical lifetime of dental restorations. The method takes into account that the mechanical lifetime is a stochastic quantity determined by shape, strength and fatigue properties and by the cyclic nature of the mastication forces. The general outline of the method is described and the necessary experimental data are discussed. Preliminary estimates of the lifetime of a composite and an amalgam restoration are made. The method is found to be feasible and the estimated lifetimes of the restoration are of the same order of magnitude as found clinically. 相似文献
42.
AHNAK controls 53BP1-mediated p53 response by restraining 53BP1 oligomerization and phase separation
Indrajeet Ghodke Michaela Remisova Audrey Furst Sinan Kilic Bernardo Reina-San-Martin Anna R. Poetsch Matthias Altmeyer Evi Soutoglou 《Molecular cell》2021,81(12):2596-2610.e7
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43.
44.
A conflict of interest occurs in a situation in which professional judgement regarding a primary interest, such as research, education or patient care, may be unduly influenced by a secondary interest, such as financial gain or personal prestige. Conflicts of interest exist in every walk of life, including medicine and science. There is nothing inherently unethical in finding oneself in a conflict of interest. Rather, the key questions are whether one recognizes the conflict and how one deals with it. Strategies include disclosing the conflict, establishing a system of review and authorization, and prohibiting the activities that lead to the conflict. 相似文献
45.
The dose-response of an individual organism can be described by a step functions if the organism survives when the dose is
below a certain lethal level and dies when this level is exceeded. If, in a population of organism, the lethal dose for an
individual has a unimodal distribution, the latter's properties will determine the shape of the population's response in the
following manner. If the distribution is symmetric the dose-response curve has a symmetric sigmoid shape when plotted on linear
coordinates. The location of the inflection point and the curve's slope around it are determined by the distribution's mode
and variance. When the distribution is skewed, the dose-response curve has an asymmetric sigmoid shape which becomes reminiscent
of an exponential decay when the distribution is strongly skewed to the right. The population's dose-response curve can be
constructed by integration of the step changes over the distribution range. The step function representing the dose-response
of an individual organism can be approximate by a Fermi function, and the distribution of an lethal doses can be represented
by the Weibull distribution function. When the two functions are combined, the resulting dose-response of the populationS(X)), which is the fraction of survivors after exposure to a doseX, is given by:S(X)=∫
0
1
[1/{+exp{(X-X
c
(φ))/a
i
]}]dω whereX
c
(ω)={(1/b)[-ln(1-ω)]}(1/n),n andb being the constants of the Weibull distribution anda
i
an arbitrarily small number, i.e.a
i
≪[X−X
c
(ϕ)], whose actual magnitude is of little significance. This model can be used to determine the underlying distributions of
experimental dose-response relationship. It was applied to published survival data of microorganisms exposed to pulsed electric
field, X-ray radiation and ozone to show that the different observed shapes of the dose-response curve, and shifts between
them, can be expressed in terms of the correponding distribution parameters, namely the mode, variance and skewness. 相似文献
46.
Birgit Gielen Hans J. De Boeck Catherine M. H. M. Lemmens Roland Valcke Ivan Nijs Reinhart Ceulemans 《Physiologia plantarum》2005,125(1):52-63
Model ecosystems were grown in 12 sunlit, climate-controlled chambers to gain insight into the effects of elevated (+3°C) air temperature (Tair ) on temperate grasslands. In this study, the hypothesis of delayed senescence in response to elevated Tair was tested for Rumex acetosa L. and Plantago lanceolata L. During the autumn of the first treatment year, frequent measurements were made of leaf chlorophyll a (Chl a ) fluorescence transients. Chl fluorescence images of individual leaves as well as digital colour images of these ecosystems were captured. Chl fluorescence variables, such as the maximum quantum yield of primary photochemistry (Fv /Fm ), indicated a decreasing efficiency with time. Despite no treatment effect on Fv /Fm , other variables derived from the Chl fluorescence transients showed a strong trend towards a positive effect of a 3°C temperature increase on the photosynthetic performance of R. acetosa and P. lanceolata in the first year. After mid-September, the initial positive treatment effect disappeared for R. acetosa , strongly suggesting that leaf lifespan of this species was shortened by higher Tair . One possible explanation is more intense drought stress in the elevated compared to the ambient temperature treatments. Second-year measurements were possibly too limited in time to confirm this trend. These results show that temperate grassland species may take advantage of a future increase in Tair during autumn. This will ultimately depend on the species' degree of acclimation to a temperature change and on the resistance to drought stress. 相似文献
47.
Katharina Simon Stephanie Hennen Nicole Merten Stefanie Bl?ttermann Michel Gillard Evi Kostenis Jesus Gomeza 《The Journal of biological chemistry》2016,291(2):705-718
Recent studies have recognized G protein-coupled receptors as important regulators of oligodendrocyte development. GPR17, in particular, is an orphan G protein-coupled receptor that has been identified as oligodendroglial maturation inhibitor because its stimulation arrests primary mouse oligodendrocytes at a less differentiated stage. However, the intracellular signaling effectors transducing its activation remain poorly understood. Here, we use Oli-neu cells, an immortalized cell line derived from primary murine oligodendrocytes, and primary rat oligodendrocyte cultures as model systems to identify molecular targets that link cell surface GPR17 to oligodendrocyte maturation blockade. We demonstrate that stimulation of GPR17 by the small molecule agonist MDL29,951 (2-carboxy-4,6-dichloro-1H-indole-3-propionic acid) decreases myelin basic protein expression levels mainly by triggering the Gαi/o signaling pathway, which in turn leads to reduced activity of the downstream cascade adenylyl cyclase-cAMP-PKA-cAMP response element-binding protein (CREB). In addition, we show that GPR17 activation also diminishes myelin basic protein abundance by lessening stimulation of the exchange protein directly activated by cAMP (EPAC), thus uncovering a previously unrecognized role for EPAC to regulate oligodendrocyte differentiation. Together, our data establish PKA and EPAC as key downstream effectors of GPR17 that inhibit oligodendrocyte maturation. We envisage that treatments augmenting PKA and/or EPAC activity represent a beneficial approach for therapeutic enhancement of remyelination in those demyelinating diseases where GPR17 is highly expressed, such as multiple sclerosis. 相似文献
48.
H. Buerstmayr M. Lemmens G. Fedak P. Ruckenbauer Communicated B. S. Gill 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(1):76-85
Fusarium head blight (FHB or scab) caused by Fusarium spp. is a widespread disease of cereals causing yield and quality losses and contaminating cereal products with mycotoxins. The
breeding of resistant varieties is the method of choice for controlling the disease. Unfortunately, the genetic basis of scab
resistance is still poorly understood. We present the results of a back-cross reciprocal monosomic analysis of FHB resistance
using the highly resistant Hungarian winter wheat line ‘U-136.1’ and the highly susceptible cultivar ‘Hobbit-sib’. Resistance
testing was performed in a field trial artificially inoculated with a Fusarium culmorum conidial suspension. Five hemizygous families containing ‘U-136.1’ chromosomes 6B, 5A, 6D, 1B, and 4B had a visually reduced
spread of infection compared to lines having the ‘Hobbit-sib’ chromosome. Chromosome 2B from ‘U-136.1’ had an increased spread
of infection. The critical chromosomes controlling seed weight were 6D, 3B, 5A, and 6B while those controlling deoxynivalenol
(DON) content were homoeologous groups 2 and 6, although the latter effects were not significant due to a high coefficient
of variation. Results from this and other studies show that chromosomes 6D, 6B, 5A, 4D, and 7A have frequently been associated
with scab resistance in a number of wheat cultivars. Research groups now attempting to map scab resistance in wheat using
markers should pay special attention to the above-mentioned chromosomes.
Received: 31 March 1998 / Accepted: 14 July 1998 相似文献
49.
Research ethics recommendations for whole-genome research: consensus statement 总被引:1,自引:1,他引:0
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50.
Rutters F Nieuwenhuizen AG Lemmens SG Born JM Westerterp-Plantenga MS 《Obesity (Silver Spring, Md.)》2009,17(1):72-77
Obesity results from chronic deregulation of energy balance, which may in part be caused by stress. Our objective was to investigate the effect of acute and psychological stress on food intake, using the eating in the absence of hunger paradigm, in normal and overweight men and women (while taking dietary restraint and disinhibition into account). In 129 subjects (BMI = 24.5 +/- 3.4 kg/m(2) and age = 27.6 +/- 8.8 years), scores were determined on the Three Factor Eating Questionnaire (dietary restraint = 7.2 +/- 4.4; disinhibition = 4.5 +/- 2.6; feeling of hunger = 3.9 +/- 2.6) and State-Trait Anxiety Inventory (trait score = 31.7 +/- 24.2). In a randomized crossover design, the "eating in absence of hunger" protocol was measured as a function of acute stress vs. a control task and of state anxiety scores. Energy intake from sweet foods (708.1 kJ vs. 599.4 kJ, P < 0.03) and total energy intake (965.2 kJ vs. 793.8 kJ, P < 0.01) were significantly higher in the stress condition compared to the control condition. Differences in energy intake between the stress and control condition were a function of increase in state anxiety scores during the stress task (Delta state anxiety scores) (R(2) = 0.05, P < 0.01). This positive relationship was stronger in subjects with high disinhibition scores (R(2) = 0.12, P < 0.05). Differences in state anxiety scores were a function of trait anxiety scores (R(2) = 0.07, P < 0.05). We conclude that acute psychological stress is associated with eating in the absence of hunger, especially in vulnerable individuals characterized by disinhibited eating behavior and sensitivity to chronic stress. 相似文献