Cell biology, SevERing mitochondria

The endoplasmic reticulum is an active participant in the division of another organelle, the mitochondrion

Mechanisms of mitochondria and autophagy crosstalk

Autophagy is a cellular survival pathway that recycles intracellular components to compensate for nutrient depletion and ensures the appropriate degradation of organelles. Mitochondrial number and health are regulated by mitophagy, a process by which excessive or damaged mitochondria are subjected to autophagic degradation. Autophagy is thus a key determinant for mitochondrial health and proper cell function. Mitophagic malfunction has been recently proposed to contribute to progressive neuronal loss in Parkinson's disease. In addition to autophagy's significance in mitochondrial integrity, several lines of evidence suggest that mitochondria can also substantially influence the autophagic process. The mitochondria's ability to influence and be influenced by autophagy places both elements (mitochondria and autophagy) in a unique position where defects in one or the other system could increase the risk to various metabolic and autophagic related diseases

Farm poultry houses

Good growth of poultry and heavy egg production depend to a large extent upon the proper housing of the stock. This bulletin sets forth the essentials of a good house for Iowa in brief form and then offers working plans of three houses that embody these essentials. The first consideration in building a poultry house is its location. It is of greatest importance to select a site having well-drained soil as will be explained later. It is next important to have a convenient location. The poultry house may be nearer the residence than the live stock barns and as women have a large share in the management of the flock on the average farm, it should be so located. It is undesirable to build the poultry house near granaries, cribs, or barns which may furnish a harbor for rats and other vermin which prey on poultry. A sunny location well sheltered from the north winds is highly desirable whenever it is possible to obtain it without sacrificing good ground drainage

Calibration of liquid argon and neon detectors with 83Krm^{83}Kr^m

We report results from tests of $^{83}$Kr$^{\mathrm{m}}$, as a calibration source in liquid argon and liquid neon. $^{83}$Kr$^{\mathrm{m}}$ atoms are produced in the decay of $^{83}$Rb, and a clear $^{83}$Kr$^{\mathrm{m}}$ scintillation peak at 41.5 keV appears in both liquids when filling our detector through a piece of zeolite coated with $^{83}$Rb. Based on this scintillation peak, we observe 6.0 photoelectrons/keV in liquid argon with a resolution of 6% ($\sigma$/E) and 3.0 photoelectrons/keV in liquid neon with a resolution of 19% ($\sigma$/E). The observed peak intensity subsequently decays with the $^{83}$Kr$^{\mathrm{m}}$ half-life after stopping the fill, and we find evidence that the spatial location of $^{83}$Kr$^{\mathrm{m}}$ atoms in the chamber can be resolved. $^{83}$Kr$^{\mathrm{m}}$ will be a useful calibration source for liquid argon and neon dark matter and solar neutrino detectors.Comment: 7 pages, 12 figure

Measurement of charge and light yields for Xe 127 L -shell electron captures in liquid xenon

Dark matter searches using dual-phase xenon time-projection chambers (LXe-TPCs) rely on their ability to reject background electron recoils (ERs) while searching for signal-like nuclear recoils (NRs). ER response is typically calibrated using β-decay sources, such as tritium, but these calibrations do not characterize events accompanied by an atomic vacancy, as in solar neutrino scatters off inner-shell electrons. Such events lead to emission of x rays and Auger electrons, resulting in higher electron-ion recombination and thus a more NR-like response than inferred from β-decay calibration. We present a cross-calibration of tritium β-decays and Xe127 electron-capture decays (which produce inner-shell vacancies) in a small-scale LXe-TPC and give the most precise measurements to date of light and charge yields for the Xe127 L-shell electron-capture in liquid xenon. We observe a 6.9σ (9.2σ) discrepancy in the L-shell capture response relative to tritium β decays, measured at a drift field of 363±14 V/cm (258±13 V/cm), when compared to simulations tuned to reproduce the correct β-decay response. In dark matter searches, use of a background model that neglects this effect leads to overcoverage (higher limits) for background-only multi-kiloton-year exposures, but at a level much less than the 1-σ experiment-to-experiment variation of the 90% C.L. upper limit on the interaction rate of a 50 GeV/c2 dark matter particle

Direct WIMP identification: Physics performance of a segmented noble-liquid target immersed in a Gd-doped water veto

We evaluate background rejection capabilities and physics performance of a detector composed of two diverse elements: a sensitive target (filled with one or two species of liquefied noble gasses) and an active veto (made of Gd-doped ultra-pure water). A GEANT4 simulation shows that for a direct WIMP search, this device can reduce the neutron background to O(1) event per year per tonne of material. Our calculation shows that an exposure of one tonne $\times$ year will suffice to exclude spin-independent WIMP-nucleon cross sections ranging from $10^{-9}$ pb to $10^{-10}$ pb.Comment: 17 pages, 5 figures. Version accepted for publication in JCA

Hybrid simulations of lateral diffusion in fluctuating membranes

In this paper we introduce a novel method to simulate lateral diffusion of inclusions in a fluctuating membrane. The regarded systems are governed by two dynamic processes: the height fluctuations of the membrane and the diffusion of the inclusion along the membrane. While membrane fluctuations can be expressed in terms of a dynamic equation which follows from the Helfrich Hamiltonian, the dynamics of the diffusing particle is described by a Langevin or Smoluchowski equation. In the latter equations, the curvature of the surface needs to be accounted for, which makes particle diffusion a function of membrane fluctuations. In our scheme these coupled dynamic equations, the membrane equation and the Langevin equation for the particle, are numerically integrated to simulate diffusion in a membrane. The simulations are used to study the ratio of the diffusion coefficient projected on a flat plane and the intramembrane diffusion coefficient for the case of free diffusion. We compare our results with recent analytical results that employ a preaveraging approximation and analyze the validity of this approximation. A detailed simulation study of the relevant correlation functions reveals a surprisingly large range where the approximation is applicable.Comment: 12 pages, 9 figures, accepted for publication in Phys. Rev.