Exponential torsion growth for random 3-manifolds

We show that a random 3-manifold with positive first Betti number admits a tower of cyclic covers with exponential torsion growth

Investigation of dynamic quality changes and optimization of drying parameters of carrots (Daucus carota var. laguna)

The effect of air temperature and sample thickness on the color changes and total carotenoids content of carrot slices was investigated. Temperature, exposure time, and moisture levels significantly affected the dynamic changes of total carotenoids and color. A slow and linear decrease in total carotenoids was observed at higher moisture content until reaching an inflection point at around 0.45 gw/gdm for all temperatures studied. Thereafter, the retention in total carotenoids decreased rapidly. The highest retention for a final product was 66.2% when drying at 60°C while retention was between 42.2 and 51.1% when drying at 50 and 70°C. These changes occurred alongside a noticeable change in color at moisture contents below the inflection point of 0.45 gw/gdm for all drying temperatures. Design of experiment based optimization of the drying process resulted in an ideal temperature of 59.8°C and 3.5 mm slice thickness with the predicted values for La*b*; ΔE of 62.18 ± 5.12, 22.46 ± 1.98, 40.35 ± 6.64, 6.31 ± 4.74; rehydration ratio of 0.48 ± 0.07; and total carotenoids of 163.83 ± 17.38 μg/g or 67.38%, respectively, all at a 95% prediction interval

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

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

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

First steps towards smart drying of beef slices seasoned with different pre-treatments

In this study, beef slices seasoned with salt (S) and salt and vinegar (S+V) were dried at 60 °C in a convective drier and the development of moisture ratio (MR) and colour change (ΔE) was compared to blind samples (B). Hyperspectral imaging (HSI) was applied to create prediction models for moisture content and L, a* and b* values. Regression coefficients of >0.9 could be achieved related to each pre-treatment, but also for combined data of all the pre-treatments

Progress of the Felsenkeller shallow-underground accelerator for nuclear astrophysics

Low-background experiments with stable ion beams are an important tool for putting the model of stellar hydrogen, helium, and carbon burning on a solid experimental foundation. The pioneering work in this regard has been done by the LUNA collaboration at Gran Sasso, using a 0.4 MV accelerator. In the present contribution, the status of the project for a higher-energy underground accelerator is reviewed. Two tunnels of the Felsenkeller underground site in Dresden, Germany, are currently being refurbished for the installation of a 5 MV high-current Pelletron accelerator. Construction work is on schedule and expected to complete in August 2017. The accelerator will provide intense, 50 uA, beams of 1H+, 4He+, and 12C+ ions, enabling research on astrophysically relevant nuclear reactions with unprecedented sensitivity.Comment: Submitted to the Proceedings of Nuclei in the Cosmos XIV, 19-24 June 2016, Niigata/Japa

Missing 2k_F Response for Composite Fermions in Phonon Drag

The response of composite Fermions to large wavevector scattering has been studied through phonon drag measurements. While the response retains qualitative features of the electron system at zero magnetic field, notable discrepancies develop as the system is varied from a half-filled Landau level by changing density or field. These deviations, which appear to be inconsistent with the current picture of composite Fermions, are absent if half-filling is maintained while changing density. There remains, however, a clear deviation from the temperature dependence anticipated for 2k_F scattering.Comment: 4 pages, 3 figures. Submitted to Phys. Rev. Let

Excitonic condensation in a symmetric electron-hole bilayer

Using Diffusion Monte Carlo simulations we have investigated the ground state of a symmetric electron-hole bilayer and determined its phase diagram at T=0. We find clear evidence of an excitonic condensate, whose stability however is affected by in-layer electronic correlation. This stabilizes the electron-hole plasma at large values of the density or inter-layer distance, and the Wigner crystal at low density and large distance. We have also estimated pair correlation functions and low order density matrices, to give a microscopic characterization of correlations, as well as to try and estimate the condensate fraction.Comment: 4 pages, 3 figures, 2 table