Maximum occupation number for composite boson states

One of the major differences between fermions and bosons is that fermionic states have a maximum occupation number of one, whereas the occupation number for bosonic states is in principle unlimited. For bosons that are made up of fermions, one could ask the question to what extent the Pauli principle for the constituent fermions would limit the boson occupation number. Intuitively one can expect the maximum occupation number to be proportional to the available volume for the bosons divided by the volume occupied by the fermions inside one boson, though a rigorous derivation of this result has not been given before. In this letter we show how the maximum occupation number can be calculated from the ground-state energy of a fermionic generalized pairing problem. A very accurate analytical estimate of this eigenvalue is derived. From that a general expression is obtained for the maximum occupation number of a composite boson state, based solely on the intrinsic fermionic structure of the bosons. The consequences for Bose-Einstein condensates of excitons in semiconductors and ultra cold trapped atoms are discussed.Comment: 4 pages, Revte

Peer victimization and substance use: Understanding the indirect effect of depressive symptomatology across gender

OBJECTIVE: Peer victimization in school is common, with emerging literature suggesting that it may also increase risk for substance abuse. Yet, little is known about the underlying mechanisms within this risk pathway. The objective of this study is to use a prospective 3-wave design to examine the mediating role of depressive symptomatology on the relationship between peer victimization and substance use, as well as examine if the pathway varies based on gender. METHOD: 801 youth between 6th and 12th grade completed surveys across three years, which included measures on school peer victimization, depression symptomatology and substance use. Models tested the mediational pathway between victimization, depressive symptoms, and substance use. Models were stratified by gender. RESULTS: Controlling for grade and the effect of each variable across waves, a significant indirect effect of peer victimization on substance use through depressive symptoms was found for females, with a non-significant indirect effect for males. CONCLUSION: Results suggest that female youth who are victimized by peers engage in substance use behaviors, at least in part, due to increases in depressive symptoms. Given its effect on depression, female victims may therefore benefit from coping skills training that targets emotion regulation and distress tolerance skills in order to combat increased risk for substance use behaviors as a coping response to their victimization. Further research is warranted to better understand the risk pathway for male youth who also experience peer victimization

Perspectives of family medicine physicians on the importance of adolescent preventive care: a multivariate analysis

BACKGROUND: The study objective was to identify commonalities amongst family medicine physicians who endorse annual adolescent visits. METHODS: A nationally weighted representative on-line survey was used to explore pediatrician (N = 204) and family medicine physicians (N = 221) beliefs and behaviors surrounding adolescent wellness. Our primary outcome was endorsement that adolescents should receive annual preventive care visits. RESULTS: Pediatricians were significantly more likely (p < .01) to endorse annual well visits. Among family medicine physicians, bivariate comparisons were conducted between those who endorsed an annual visit (N = 164) compared to those who did not (N = 57) with significant predictors combined into two multivariate logistic regression models. Model 1 controlled for: patient race, proportion of 13-17 year olds in provider's practice, discussion beliefs scale and discussion behaviors with parents scale. Model 2 controlled for the same first three variables as well as discussion behaviors with adolescents scale. Model 1 showed for each discussion beliefs scale topic selected, family medicine physicians had 1.14 increased odds of endorsing annual visits (p < .001) and had 1.11 greater odds of endorsing annual visits with each one-point increase in discussion behaviors with parents scale (p = .51). Model 2 showed for each discussion beliefs scale topic selected, family medicine physicians had 1.15 increased odds of also endorsing the importance of annual visits (p < .001). CONCLUSIONS: Family medicine physicians that endorse annual visits are significantly more likely to affirm they hold strong beliefs about topics that should be discussed during the annual exam. They also act on these beliefs by talking to parents of teens about these topics. This group appears to focus on quality of care in thought and deed

Deterministic Partial Differential Equation Model for Dose Calculation in Electron Radiotherapy

Treatment with high energy ionizing radiation is one of the main methods in modern cancer therapy that is in clinical use. During the last decades, two main approaches to dose calculation were used, Monte Carlo simulations and semi-empirical models based on Fermi-Eyges theory. A third way to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. Starting from these, we derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free-streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on [BerCharDub], that exactly preserves key properties of the analytical solution on the discrete level. Several numerical results for test cases from the medical physics literature are presented.Comment: 20 pages, 7 figure

Examining the Protective Effect of Ethnic Identity on Drug Attitudes and Use Among a Diverse Youth Population

Ethnic identity is an important buffer against drug use among minority youth. However, limited work has examined pathways through which ethnic identity mitigates risk. School-aged youth (N = 34,708; 52 % female) of diverse backgrounds (i.e., African American (n = 5333), Asian (n = 392), Hispanic (n = 662), Multiracial (n = 2129), Native American (n = 474), and White (n = 25718) in grades 4–12 provided data on ethnic identity, drug attitudes, and drug use. After controlling for gender and grade, higher ethnic identity was associated with lower past month drug use for African American, Hispanic, and Multiracial youth. Conversely, high ethnic identity was associated with increased risk for White youth. An indirect pathway between ethnic identity, drug attitudes, and drug use was also found for African American, Hispanic, and Asian youth. Among White youth the path model was also significant, but in the opposite direction. These findings confirm the importance of ethnic identity for most minority youth. Further research is needed to better understand the association between ethnic identity and drug use for Multiracial and Hispanic youth, best ways to facilitate healthy ethnic identity development for minority youth, and how to moderate the risk of identity development for White youth

Peer Victimization, Mood Symptoms, and Alcohol Use: Examining Effects Among Diverse High School Youth

Peer victimization is associated with alcohol use among adolescents. However, few studies have examined the mediating role of depression and anxiety, or differences by race. The current study examined the prospective relationship of peer victimization, depressive and anxiety symptoms, and alcohol use across two timeframes: 9th to 11th grade and 10th to 12th grade among African American and White youth. 2,202 high school youth (57.6% female) who identified as either African American (n=342, 15.2%) or White (n=1860, 82.6%) provided data on study variables. Path analysis among the overall sample indicated that anxiety symptoms was a significant mediator for both timeframes, with depressive symptoms mediating the pathway during the 10th to 12th grade timeframe. The findings were most consistent among White youth, with no significant indirect effects observed for African American youth. Thus, addressing depressive and anxiety symptoms may be effective targets to decrease alcohol use risk as a result of peer victimization among White youth. However, further research is needed to better understand risk models for peer victimization exposure on substance use outcomes among racial/ethnic minority youth

Hydrodynamic object recognition using pressure sensing

Hydrodynamic sensing is instrumental to fish and some amphibians. It also represents, for underwater vehicles, an alternative way of sensing the fluid environment when visual and acoustic sensing are limited. To assess the effectiveness of hydrodynamic sensing and gain insight into its capabilities and limitations, we investigated the forward and inverse problem of detection and identification, using the hydrodynamic pressure in the neighbourhood, of a stationary obstacle described using a general shape representation. Based on conformal mapping and a general normalization procedure, our obstacle representation accounts for all specific features of progressive perceptual hydrodynamic imaging reported experimentally. Size, location and shape are encoded separately. The shape representation rests upon an asymptotic series which embodies the progressive character of hydrodynamic imaging through pressure sensing. A dynamic filtering method is used to invert noisy nonlinear pressure signals for the shape parameters. The results highlight the dependence of the sensitivity of hydrodynamic sensing not only on the relative distance to the disturbance but also its bearing

Excitonic condensate and quasiparticle transport in electron-hole bilayer systems

Bilayer electron-hole systems undergo excitonic condensation when the distance d between the layers is smaller than the typical distance between particles within a layer. All excitons in this condensate have a fixed dipole moment which points perpendicular to the layers, and therefore this condensate of dipoles couples to external electromagnetic fields. We study the transport properties of this dipolar condensate system based on a phenomenological model which takes into account contributions from the condensate and quasiparticles. We discuss, in particular, the drag and counterflow transport, in-plane Josephson effect, and noise in the in-plane currents in the condensate state which provides a direct measure of the superfluid collective-mode velocity.Comment: 7 pages, 3 figure