Optimal prediction for moment models: Crescendo diffusion and reordered equations

A direct numerical solution of the radiative transfer equation or any kinetic equation is typically expensive, since the radiative intensity depends on time, space and direction. An expansion in the direction variables yields an equivalent system of infinitely many moments. A fundamental problem is how to truncate the system. Various closures have been presented in the literature. We want to study moment closure generally within the framework of optimal prediction, a strategy to approximate the mean solution of a large system by a smaller system, for radiation moment systems. We apply this strategy to radiative transfer and show that several closures can be re-derived within this framework, e.g. $P_N$, diffusion, and diffusion correction closures. In addition, the formalism gives rise to new parabolic systems, the reordered $P_N$ equations, that are similar to the simplified $P_N$ equations. Furthermore, we propose a modification to existing closures. Although simple and with no extra cost, this newly derived crescendo diffusion yields better approximations in numerical tests.Comment: Revised version: 17 pages, 6 figures, presented at Workshop on Moment Methods in Kinetic Gas Theory, ETH Zurich, 2008 2 figures added, minor correction

Entrepreneurial Intentions of Teams: Sub-Dimensions of Machiavellianism Interact With Team Resilience

Machiavellians are often seen as manipulative people who contribute negatively to teams and ventures. However, recent work has shown that Machiavellians can also cooperate and act in pro-social ways in a team context. Thus, some aspects of Machiavellianism might be conducive for teams and team members’ intentions to start a business venture. Most studies in this area have failed to (a) assess the effect of Machiavellianism at the team level, (b) take into account the dimensional nature of Machiavellianism, and (c) assess moderators of these effects. We propose that the combination of Machiavellianism and resilience in teams predict team entrepreneurial intentions (EI). Moreover, we propose that different team level dimensions of Machiavellianism (amoral manipulation, desire for status, desire for control, distrust of others) are differentially related to EI. More specifically, we expect at the team level that amoral manipulation and desire for status are positively related to changes in EI (as teams high on these dimensions feel that they can use unethical practices that give them an advantage in being successful), whereas desire for control and distrust of others should be negatively related to changes in EI (as entrepreneurial teams usually work in less structured situations and need to closely work together). Furthermore, all sub-dimensions of Machiavellianism should interact positively with team resilience as resilience acts as a buffer that protects teams from potential negative effects of Machiavellianism. In a multi-wave study among newly formed teams engaged in entrepreneurship projects, controlling for psychopathy and narcissism, we found partial support for our hypotheses. Results supported our expectations for the “amoral manipulation” and “desire for control” sub-dimensions, but not for the “desire for status” and the “distrust of others” sub-dimensions of Machiavellianism, with distrust of others showing unexpectedly opposite effects. This study contributes to the literature by looking at the dimensions of Machiavellianism at the level of entrepreneurial teams in conjunction with the more positive team characteristic, resilience. Our results indicate that the relationship between Machiavellianism and EI is more complex than previously hypothesized, as the sub-dimensions are s

Inhibin in immature rat Sertoli cell conditioned medium: a 32 kDa αβ-B dimer

Abstract Conditioned medium of cultured Sertoli cells from 21-day-old rats was used as starting material for the isolation of inhibin. Inhibin activity was monitored by the dose dependent suppression of the folliclestimulating hormone release of cultured rat pituitary cells. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of the highly purified inhibin preparation revealed a 32 kDa protein after silver staining, which could be separated in subunits of 18 kDa and 12 kDa after reduction. Western blot analysis with an antibody recognizing the 22 N-terminal amino acids of the α-subunit of 32 kDa bovine inhibin confirmed the presence of a 32 kDa inhibin molecule under non-reducing conditions, whereas an 18 kDa a-subunit was found after reduction. An antibody recognizing the β-A subunit of inhibin did not yield a signal after Western blotting. N-terminal amino acid sequence analysis of two highly purified preparations of inhibin obtained using different methods yielded the sequence predicted for a 32 kDa αβ-B dimer on basis of cDNA nucleotide sequence. This result is in agreement with the large excess of β-B over β-A mRNA in the rat testis

Climate distress, climate-sensitive risk factors, and mental health among Tanzanian youth:a cross-sectional study

Background: Climate change threatens youth mental health through multiple mechanisms, yet empirical studies typically focus on single pathways. We explored feelings of distress over climate change among Tanzanian youth, considering associations with climate change awareness and climate-sensitive risk factors, and assessed how these factors relate to mental health. Methods: Tanzanian youth (aged 18–23 years) from a cluster randomised controlled trial in Mbeya and Iringa regions of Tanzania were interviewed between Jan 25, and March 3, 2021, and included in this cross-sectional study. A threshold of at least 10 on the ten-item Centre for Epidemiological Studies Depression Scale was used to classify symptom severity indicative of depression. Regardless of climate change awareness, respondents were asked about their feelings of distress on climate change using inclusive language (changing weather patterns or changing seasons). We estimated rate differences in climate change distress (slight or moderate or extreme vs none) by youth characteristics, extent of climate awareness, and climate-sensitive livelihoods (eg, agriculture, tending livestock) and climate-sensitive living conditions (eg, food or water insecurity), using generalised linear models. We compared depression prevalence by extent of climate change distress and climate-sensitive living conditions.Findings: Among 2053 youth (1123 [55%] were male and 930 [45%] were female) included in this analysis, 946 (46%) had reported any distress about climate change. Distress was higher among female, more educated, more religious, older youth, and those working in extreme temperatures. Adjusting for climate awareness—a factor strongly associated with climate distress—helped to explain some of these associations. Depression was 23 percentage points (95% CI 17–28) higher among youth who had severe water insecurity than those who did not. Similarly, youth who had severe food insecurity had 23 percentage points higher depression (95% CI 17–28) compared with those who did not. Those reporting climate change distress also had worse mental health—extremely distressed youth had 18 percentage points (95% CI 6–30) higher depression than those reporting none. Interpretation: Living in conditions worsened by climate change and feeling distressed over climate change have mental health implications among young people from low-resource settings, indicating that climate change can impact youth mental health through multiple pathways. </p

Algebraic geometric comparison of probability distributions

We propose a novel algebraic framework for treating probability distributions represented by their cumulants such as the mean and covariance matrix. As an example, we consider the unsupervised learning problem of finding the subspace on which several probability distributions agree. Instead of minimizing an objective function involving the estimated cumulants, we show that by treating the cumulants as elements of the polynomial ring we can directly solve the problem, at a lower computational cost and with higher accuracy. Moreover, the algebraic viewpoint on probability distributions allows us to invoke the theory of Algebraic Geometry, which we demonstrate in a compact proof for an identifiability criterion

Experimental and computational assessment of the temperature dependency of the stacking fault energy in face-centered cubic high-entropy alloys

The activation of deformation mechanisms in face-centered cubic materials is considered closely related with the stacking fault energy. Experimentally determined stacking fault energy (SFE) values are exclusively positive. However, results obtained by first principle methods predict that the intrinsic SFE of metastable face-centered cubic metals and alloys is negative. It was previously shown that SFE values from the first principle methods and experiments can be reconciled by accounting for the resolved shear stress for Shockley partial dislocations. Determining this resolved shear stress for Shockley partial dislocations is experimentally challenging, making the reconciliation of experimental and first-principles SFE values a laborious exercise. In the present contribution, we demonstrate that the critical resolved shear stress for Shockley partial dislocations and SFE values can be determined from a single in-situ neutron diffraction experiment, thus enabling more confident and efficient reconciliation of experimental and theoretical SFE values

Precision Measurements and Fermion Geography in the Randall-Sundrum Model Revisited

We re-examine the implications of allowing fermion fields to propagate in the five-dimensional bulk of the Randall-Sundrum (RS) localized gravity model. We find that mixing between the Standard Model top quark and its Kaluza Klein excitations generates large contributions to the rho parameter and consequently restricts the fundamental RS scale to lie above 100 TeV. To circumvent this bound we propose a `mixed' scenario which localizes the third generation fermions on the TeV brane and allows the lighter generations to propagate in the full five-dimensional bulk. We show that this construction naturally reproduces the observed m_c / m_t and m_s / m_b hierarchies. We explore the signatures of this scenario in precision measurements and future high energy collider experiments. We find that the region of parameter space that addresses the hierarchies of fermion Yukawa couplings permits a Higgs boson with a mass of 500 GeV and remains otherwise invisible at the LHC. However, the entire parameter region consistent with electroweak precision data is testable at future linear colliders. We briefly discuss possible constraints on this scenario arising from flavor changing neutral currents.Comment: 44 pages, 20 ps files; VII, typos fixed and refs adde

Inhibin reduces spermatogonial numbers in testes of adult mice and chinese hamsters

Bovine follicular fluid (bFF) injected ip in mice during 2 days (65,000 U inhibin/day, 1 U inhibin the activity in 1 /μg bFF protein) caused a significant decrease in the numbers of A4, intermediate (In), and B spermatogonia to 91%,74%, and 67% of the control values, respectively. The numbers of undifferentiated spermatogonia remained unchanged. These injections suppressed peripheral FSH levels to 6% of the control values, suggesting that FSH might be the modulator of the effects on spermatogenesis. However, in the Chinese hamster, intratesticular injections of bFF during 4 days (6500 U inhibin/day into one testis) also caused a significant decrease in the numbers of A3, In, B1, and B2 spermatogonia to 86%, 61%, 55%, and 94% of the control values, respectively. Similarly, treatment with a partially purified inhibin preparation from rat Sertoli cell-conditioned medium (rSCCM) during 4 days (Mono Q fraction; 1512 U inhibin/day; 37.8 μg protein) caused a significant decrease in the numbers of A3, In, B1, and B2 spermatogonia to 90%, 87%, 66%, and 93% of the control values, respectively. Treatment with a highly purified inhibin preparation from rSCCM during 4 days (30K inhibin; 750 U inhibin/day; 100 ng protein) significantly decreased the numbers of In and B1 spermatogonia to, respectively, 87% and 91% of the control values. These effects were limited to the testis into which the material was injected; the contralateral testis or testes injected with control fluid always showed normal numbers of spermatogonia. This implies that the effects on the seminiferous epithelium are not FSH mediated. Intratesticular injections of bFF or pure inhibin did not affect the number of undifferentiated spermatogonia. However, the Mono Q fraction caused a significant increase in the numbers of undifferentiated spermatogonia in stages IV-VII of the cycle, suggesting the presence of a mitogenic factor for undifferentiated spermatogonia in rSCCM which is not present or is counteracted in bFF. The results suggest that inhibin may have a role in the regulation of spermatogonial development in the adult animal

Childhood obesity's influence on socioeconomic disparities in young adolescents’ mental health

Purpose: We investigated whether socioeconomic inequalities in young adolescents’ mental health are partially due to the unequal distribution of childhood obesity across socioeconomic positions (SEP), i.e. differential exposure, or due to the effect of obesity on mental health being more detrimental among certain SEPs, i.e. differential impact. Methods: We studied 4660 participants of the Generation R study, a population-based study in the Netherlands. SEP was estimated by mother's education and household income at age five of the child. We estimated the contribution of the mediating and moderating effects of high body fat percentage to the disparity in mental health. This was done through a four-way decomposition using marginal structural models with inverse probability of treatment weighting. Results: Comparing children with the least to most educated mothers and the lowest to highest household income, the total disparity in emotional problems was 0.98 points (95%CI:0.35–1.63) and 1.68 points (95%CI:1.13–2.19), respectively. Of these total disparities in emotional problems, 0.50 points (95%CI:0.15–0.85) and 0.24 points (95%CI:0.09–0.46) were due to the differential exposure to obesity. Obesity did not contribute to disparities in behavioural problems. Conclusion: Addressing the heightened obesity prevalence among children in low SEP families may reduce inequalities in emotional problems in early adolescence.</p