FE calculations on a three stage metal forming process of Sandvik Nanoflex

Sandvik NanoflexTM combines good corrosion resistance with high strength. This steel has good deformability in\ud austenitic conditions. It belongs to the group of metastable austenites, which means that during deformation a strain-induced\ud transformation into martensite takes place. After deformation, transformation continues as a result of internal stresses. Both\ud transformations are stress-state and temperature dependent. A constitutive model for this steel has been formulated, based\ud on the macroscopic material behaviour measured by inductive measurements. Both the stress-assisted and the strain-induced\ud transformation into martensite have been incorporated in this model. Path-dependent work hardening has also been taken\ud into account. This article describes how the model is implemented in an internal Philips FE code called CRYSTAL, which is\ud a dedicated robust and accurate finite element solver. The implementation is based on lookup tables in combination with\ud feed-forward neural networks. The radial return method is used to determine the material state during and after plastic\ud flow, however, it has been extended to cope with the stiff character of the partial differential equation that describes the\ud transformation behaviour

Patch depletion, niche structuring and the evolution of co-operative foraging

<p>Abstract</p> <p>Background</p> <p>Many animals live in groups. One proposed reason is that grouping allows cooperative food finding. Group foraging models suggest that grouping could increase food finding rates, but that such group processes could be evolutionarily unstable. These models assume discrete food patches which are fully detectable. However, often animals may only be able to perceive local parts of larger-scale environmental patterns. We therefore use a spatial individual-based model where food patches are aggregates of food items beyond the scale of individual perception. We then study the evolution of foraging and grouping behavior in environments with different resource distributions.</p> <p>Results</p> <p>Our results show that grouping can evolve to increase food intake rates. Two kinds of grouping evolve: traveling pairs and opportunistic grouping, where individuals only aggregate when feeding. Grouping evolves because it allows individuals to better sense and deplete patches. Such enhanced patch depletion is particularly apparent on fragmented and partially depleted patches, which are especially difficult for solitary foragers to deplete. Solitary foragers often leave a patch prematurely because a whole patch cannot be observed directly. In groups, individuals that are still eating allow other individuals that inadvertently leave the patch, to return and continue feeding. For this information sharing a grouping tendency is sufficient and observing whether a neighbor is eating is not necessary. Grouping therefore leads to a release from individual sensing constraints and a shift in niche specialization, allowing individuals to better exploit partially depleted patches.</p> <p>Conclusions</p> <p>The evolved group foraging can be seen as cooperative in the sense that it leads to a mutually-beneficial synergy: together individuals can achieve more than on their own. This cooperation exists as a group-level process generated by the interaction between grouping and the environment. Thus we reveal how such a synergy can originate in evolution as a side-effect of grouping via multi-level selection. Here there is no cooperative dilemma as individuals cannot avoid producing information for their neighbors. This scenario may be a useful starting point for studying the evolution of further social and cooperative complexity.</p

Biomarkers in early phase development of central nervous system drugs: a conceptual framework

The main objective of this thesis is to provide a conceptual framework for the use of Central Nervous System (CNS) biomarkers in early phase clinical drug development. In the Introduction the current use of biomarkers in early CNS drug development is discussed. A conceptual framework for the classification of biomarkers is suggested, based on general questions that these markers should provide information on. The body of this thesis (Chapters 1-7) exemplifies the use of these markers within this conceptual framework. In the Conclusions and Discussion a critical evaluation of the presented conceptual biomarker framework is give and directions for future biomarker research are offered.LEI Universiteit LeidenCentre for Human Drug ResearchPathophysiologie van aanvalsgewijs en chronisch progressief verlopende aandoeningen van het centrale perifere zenuwstelse

Skill learning and the evolution of social learning mechanisms

This research was supported by a grant from The John Templeton Foundation.Background. Social learning is potentially advantageous, but evolutionary theory predicts that (i) its benefits may be self-limiting because social learning can lead to information parasitism, and (ii) these limitations can be mitigated via forms of selective copying. However, these findings arise from a functional approach in which learning mechanisms are not specified, and which assumes that social learning avoids the costs of asocial learning but does not produce information about the environment. Whether these findings generalize to all kinds of social learning remains to be established. Using a detailed multi-scale evolutionary model, we investigate the payoffs and information production processes of specific social learning mechanisms (including local enhancement, stimulus enhancement and observational learning) and their evolutionary consequences in the context of skill learning in foraging groups. Results. We find that local enhancement does not benefit foraging success, but could evolve as a side-effect of grouping. In contrast, stimulus enhancement and observational learning can be beneficial across a wide range of environmental conditions because they generate opportunities for new learning outcomes. Conclusions. In contrast to much existing theory, we find that the functional outcomes of social learning are mechanism specific. Social learning nearly always produces information about the environment, and does not always avoid the costs of asocial learning or support information parasitism. Our study supports work emphasizing the value of incorporating mechanistic detail in functional analyses.Publisher PDFPeer reviewe

Quantum chaos in 2D gravity

We present a quantitative and fully non-perturbative description of the ergodic phase of quantum chaos in the setting of two-dimensional gravity. To this end we describe the doubly non-perturbative completion of semiclassical 2D gravity in terms of its associated universe field theory. The guiding principle of our analysis is a flavor-matrix theory (fMT) description of the ergodic phase of holographic gravity, which exhibits U(n|n) causal symmetry breaking and restoration. JT gravity and its 2D-gravity cousins alone do not realize an action principle with causal symmetry, however we demonstrate that their universe field theory, the Kodaira-Spencer (KS) theory of gravity, does. After directly deriving the fMT from brane-antibrane correlators in KS theory, we show that causal symmetry breaking and restoration can be understood geometrically in terms of different (topological) D-brane vacua. We interpret our results in terms of an open-closed string duality between holomorphic Chern-Simons theory and its closed-string equivalent, the KS theory of gravity. Emphasis will be put on relating these geometric principles to the characteristic spectral correlations of the quantum ergodic phase

Risk factors associated with challenging behaviour in people with profound intellectual and multiple disabilities

BACKGROUND: Several factors that correlate with the onset or continuation of challenging behaviour are mentioned in research. These are factors related to persons with ID, but also to direct support professionals and the context. Although many of these factors seem to affect the onset or continuation of challenging behaviour in people with ID in general, results are often inconclusive and have little focus on people with profound intellectual and multiple disabilities (PIMD). The present study aimed to assess the extent to which known factors related to challenging behaviour are also applicable to a group of 198 people with PIMD. METHOD: To determine which factors were associated with challenging behaviour, univariate analyses on associations between known risk factors and challenging behaviour were conducted. The associated factors were then subject to a regression analysis to determine the extent to which they explain the prevalence of challenging behaviour and can thus be seen as factors associated with challenging behaviour. RESULTS: The results show that, in particular, factors concerning the personal characteristics of people with PIMD, such as sleeping problems and auditory problems, were related to the variance in mean frequency of challenging behaviour. Only one factor related to the direct support professionals was found: when these professionals had been offered training on the subject of challenging behaviour in people with intellectual disabilities in general, they identified significantly more withdrawn behaviour. We found no contextual factors related to challenging behaviour. CONCLUSION: These findings are generally consistent with findings reported in other studies, especially concerning the personal characteristics of people with PIMD. Further research should focus on the effects of providing safe auditory environments and appropriate sleep schedules for people with PIMD on the occurrence of challenging behaviour

Активность лептина и интерлейкина­-6 в сыворотке крови у больных полиэндокринопатией

Установлена взаимосвязь лептина с метаболическими и некоторыми иммунологическими показателями у больных сахарным диабетом 2−го типа в сочетании с аутоиммунным тиреоидитом. Выявлены наличие иммуносупрессии и повышение уровней интерлейкина−6 и лептина при сопутствующем ожирении и дислипидемии.Встановлено взаємозв’язок лептину з метаболічними і деякими імунологічними показниками у хворих на цукровий діабет 2−го типу у поєднанні з аутоімунним тиреоідитом. Виявлено наявність імуносупресії та підвищення рівнів інтерлейкіну−6 і лептину при супутньому ожирінні та дисліпідемії.Association between leptin and some immunological parameters in patients with type 2 diabetes mellitus accompanied by autoimmune thyroiditis was established. The presence of immune suppression and increased levels of interleukin−6 and leptin was revealed at accompanying obesity and dyslipidemias

Labour and Neonatal Outcome in Small for Gestational Age Babies Delivered Beyond 36+0 Weeks: A Retrospective Cohort Study

Objective. Small for gestational age (SGA) is associated with increased neonatal morbidity and mortality. At present, evidence on whether these pregnancies should be managed expectantly or by induction is lacking. To get insight in current policy we analysed data of the National Dutch Perinatal Registry (PRN). Methods. We used data of all nulliparae between 2000 and 2005 with a singleton in cephalic presentation beyond 36+0 weeks, with a birth weight below the 10th percentile. We analysed two groups of pregnancies: (I) with isolated SGA and (II) with both SGA and hypertensive disorders. Onset of labour was related to route of delivery and neonatal outcome. Results. Induction was associated with a higher risk of emergency caesarean section (CS), without improvement in neonatal outcome. For women with isolated SGA the relative risk of emergency CS after induction was 2.3 (95% Confidence Interval [CI] 2.1 to 2.5) and for women with both SGA and hypertensive disorders the relative risk was 2.7 (95% CI 2.3 to 3.1). Conclusion. Induction in pregnancies complicated by SGA at term is associated with a higher risk of instrumental deliveries without improvement of neonatal outcome. Prospective studies are needed to determine the best strategy in suspected IUGR at term