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981.
982.
In this study, a two-state Markov switching count-data model is proposed as an alternative to zero-inflated models to account for the preponderance of zeros sometimes observed in transportation count data, such as the number of accidents occurring on a roadway segment over some period of time. For this accident-frequency case, zero-inflated models assume the existence of two states: one of the states is a zero-accident count state, which has accident probabilities that are so low that they cannot be statistically distinguished from zero, and the other state is a normal-count state, in which counts can be non-negative integers that are generated by some counting process, for example, a Poisson or negative binomial. While zero-inflated models have come under some criticism with regard to accident-frequency applications - one fact is undeniable - in many applications they provide a statistically superior fit to the data. The Markov switching approach we propose seeks to overcome some of the criticism associated with the zero-accident state of the zero-inflated model by allowing individual roadway segments to switch between zero and normal-count states over time. An important advantage of this Markov switching approach is that it allows for the direct statistical estimation of the specific roadway-segment state (i.e., zero-accident or normal-count state) whereas traditional zero-inflated models do not. To demonstrate the applicability of this approach, a two-state Markov switching negative binomial model (estimated with Bayesian inference) and standard zero-inflated negative binomial models are estimated using five-year accident frequencies on Indiana interstate highway segments. It is shown that the Markov switching model is a viable alternative and results in a superior statistical fit relative to the zero-inflated models. 相似文献
983.
• | This paper discusses international market and operation strategies of service MNEs from small and open economies (SMOPECs). The focus in the analysis will be on the special challenges that these type of companies face in their internationalisation process. |
• | A conceptual framework and propositions are developed based on earlier research of internationalisation of manufacturing companies and companies in different service sectors. A multicase study of four service MNEs, which are telecommunications operators (telcos), is used to illustrate and test the propositions. |
• | International processes of the case companies deviate in many areas from those suggested by traditional theories, especially their market strategies. Several industry specific characteristics played an important part in this, as they further enhanced many challenges common to internationalising companies from smaller countries. |
相似文献
984.
Saturation currents and chemiluminescence, especially at the CH∗ and wavelengths, are measured for a range of small, laminar methane flames during progressive addition of air, with the principal objective of distinguishing between pure diffusion flames, premixed flames of compositions falling between the upper and lower flammability limits, and the broad range of aerated flames lying in between these regimes. Flame areas defined by the loci of maximum luminosity and by schlieren contours were recorded, so that saturation current densities, CH∗ and emission per unit flame area, as well as burning velocities could be deduced. For admixtures of less than 70 vol.%, air appears to act, surprisingly, as an inert diluent as regards saturation currents, so that saturation currents are essentially proportional to fuel flow alone. Much the same applies to chemiluminescence. However, schlieren contours, which were recorded both to provide a basis for burning velocity measurements and to explore density changes in the reactants, indicated the presence of a burner - stabilised propagating reaction zone ahead of the luminous flame surface starting at around 50 vol.% and possibly even at lower air admixtures. This evidence of a steep change in refractive index is indicative of a premixed reaction zone involving the added oxygen, which however generates no chemi-ionization and emits no light. Even photographing the flame by radiation emitted at the CH∗ and wavelengths shows no sign of its existence. Its burning velocity is about 10 cm/s, when stabilized by the surrounding diffusion flame. The most plausible rationale for these observations is the formation of syngas by the partial oxidation of methane. The subsequent burning of CO and H2 is known to occur without chemi-ionization or appreciable light emission. 相似文献
985.
Guido Sala Ton van Vliet Martien A. Cohen Stuart George A. van Aken Fred van de Velde 《Food Hydrocolloids》2009
The large deformation properties of gelatine, κ-carrageenan and whey protein isolate (WPI) gels filled with bound and unbound oil droplets were studied as a function of compression speed. The rheological properties of the gel matrices controlled the compression speed-dependency of the gels containing oil droplets. Polymer gels (gelatine and κ-carrageenan gels) showed a predominantly elastic behaviour. Their Young's modulus was not affected by the compression speed. The increase of fracture stress and strain observed with increasing compression speed was related to friction between the structural elements of the gels and, for gelatine, to the unzipping of physical bonds. Particle gels (WPI gels) showed a more viscoelastic behavior. Their Young's modulus and fracture stress increased with compression speed. This was attributed to the viscous flow of the matrix and friction phenomena between structural elements of the gel. The effect of an increase in the oil volume fraction (φ) on the Young's modulus was for all gels according to the Van der Poel theory. In addition, oil droplets embedded in the gel matrix acted as stress concentration nuclei and increased friction. The relative impact of these two effects was related to the viscoelastic properties of the gels and to droplet–matrix interaction. For polymer gels and gels with bound droplets, stress concentration phenomena played a relatively larger role. For particle gels and gels with unbound droplets, friction phenomena were relatively more important, increasing the viscoelastic character of the gels. As a result, an increase in φ resulted in a decrease of both fracture stress and fracture strain for polymer gels and in an increase of the fracture stress and a decrease of fracture strain for particle gels. 相似文献
986.
Kirsten Hülsktter Fred Lühder Alexander Flügel Vanessa Herder Wolfgang Baumgrtner 《International journal of molecular sciences》2021,22(16)
Tamoxifen is frequently used in murine knockout systems with CreER/LoxP. Besides possible neuroprotective effects, tamoxifen is described as having a negative impact on adult neurogenesis. The present study investigated the effect of a high-dose tamoxifen application on Theiler’s murine encephalomyelitis virus (TMEV)-induced hippocampal damage. Two weeks after TMEV infection, 42% of the untreated TMEV-infected mice were affected by marked inflammation with neuronal loss, whereas 58% exhibited minor inflammation without neuronal loss. Irrespective of the presence of neuronal loss, untreated mice lacked TMEV antigen expression within the hippocampus at 14 days post-infection (dpi). Interestingly, tamoxifen application 0, 2 and 4, or 5, 7 and 9 dpi decelerated virus elimination and markedly increased neuronal loss to 94%, associated with increased reactive astrogliosis at 14 dpi. T cell infiltration, microgliosis and expression of water channels were similar within the inflammatory lesions, regardless of tamoxifen application. Applied at 0, 2 and 4 dpi, tamoxifen had a negative impact on the number of doublecortin (DCX)-positive cells within the dentate gyrus (DG) at 14 dpi, without a long-lasting effect on neuronal loss at 147 dpi. Thus, tamoxifen application during a TMEV infection is associated with transiently increased neuronal loss in the hippocampus, increased reactive astrogliosis and decreased neurogenesis in the DG. 相似文献
987.
Elien Lemmens Alice V. Moroni Jennifer Pagand Pieter Heirbaut Anneli Ritala Yann Karlen Kim‐Anne Lê Hetty C. Van den Broeck Fred J.P.H. Brouns Niels De Brier Jan A. Delcour 《Comprehensive Reviews in Food Science and Food Safety》2019,18(1):305-328
Sprouting induces activation and de novo synthesis of hydrolytic enzymes that make nutrients available for plant growth and development. Consumption of sprouted grains is suggested to be beneficial for human health. Positive consumer perceptions about sprouted cereals have resulted in new food and beverage product launches. However, because there is no generally accepted definition of “sprouting,” it is unclear when grains are to be called sprouted. Moreover, guidelines about how much sprouted grain material food products should contain to exert health benefits are currently lacking. Accordingly, there is no regulatory base to develop appropriate food labeling for “sprouted foods.” This review describes the nutritional and technological properties of sprouted grains in relation to processing conditions and provides guidelines to optimize sprouting practices in order to maximize nutritive value. Relatively long sprouting times (3 to 5 days) and/or high processing temperatures (25 to 35 °C) are needed to maximize the de novo synthesis and/or release of plant bioactive compounds. Nutrient compositional changes resulting from sprouting are often associated with health benefits. However, supportive data from clinical studies are very scarce, and at present it is impossible to draw any conclusion on health benefits of sprouted cereals. Finally, grains sprouted under the above‐mentioned conditions are generally unfit for use in traditional food processing and it is challenging to use sprouted grains as ingredients without compromising their nutrient content. The present review provides a basis for better defining what “sprouting” is, and to help further research and development efforts in this field as well as future food regulations development. 相似文献
988.
Felmingham Kim; Williams Leanne M.; Kemp Andrew H.; Liddell Belinda; Falconer Erin; Peduto Anthony; Bryant Richard 《Canadian Metallurgical Quarterly》2010,119(1):241
Although women have a greater propensity than men to develop posttraumatic stress disorder (PTSD) following trauma, sex differences in neural activations to threat have received little investigation. This study tested the prediction that trauma would heighten activity in automatic fear-processing networks to a greater extent in women than in men. Functional magnetic resonance imaging (fMRI) data were recorded in 23 participants with PTSD (13 women, 10 men), 21 trauma-exposed controls (9 women, 12 men), and 42 non-trauma-exposed controls (22 women, 20 men) while they viewed masked facial expressions of fear. Exposure to trauma was associated with enhanced brainstem activity to fear in women, regardless of the presence of PTSD, but in men, it was associated only with the development of PTSD. Men with PTSD displayed greater hippocampal activity to fear than did women. Both men and women with PTSD showed enhanced amygdala activity to fear relative to controls. The authors conclude that greater brainstem activation to threat stimuli may contribute to the greater prevalence of PTSD in women, and greater hippocampal activation in men may subserve an enhanced capacity for contextualizing fear-related stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
989.
Crosnoe Robert; Morrison Fred; Burchinal Margaret; Pianta Robert; Keating Daniel; Friedman Sarah L.; Clarke-Stewart K. Alison 《Canadian Metallurgical Quarterly》2010,102(2):407
Children enter elementary school with widely different skill levels in core subjects. Whether because of differences in aptitude or in preparedness, these initial skill differences often translate into systematic disparities in achievement over time. How can teachers reduce these disparities? Three possibilities are to offer basic skills training, to expose students to higher order instruction, or to provide socioemotional support. Repeated measures analyses of longitudinal data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Study of Early Child Care and Youth Development revealed that children with low, average, or high math skills prior to elementary school followed different but parallel trajectories of math achievement up through fifth grade. When enrolled in classes with inference-based instruction, however, the initially least skilled children narrowed the achievement gap as long as they did not have conflictual relations with their teachers. They did not make this kind of progress if they were in classes focused exclusively on basic skills instruction or if they were in inference-focused classes but had conflictual relations with teachers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
990.
The set of citations received by a set of publications consists of citations received by articles in the h-core and citations received by articles in the h-tail. Denoting the cardinalities of these fours sets as C, P, C
H and C
T we introduce the tail-core ratio (C
T/C
H) and show that in practical cases this ratio tends to increase. Introducing further the k-index, defined as k = (C/P)/(C
T/C
H), we show that this index decreases in most practical cases. A power law model is in accordance with these practical observations. 相似文献