Radiative Correction to the Transferred Polarization in Elastic Electron-Proton Scattering

Model independent radiative correction to the recoil proton polarization for the elastic electron-proton scattering is calculated within method of electron structure functions. The explicit expressions for the recoil proton polarization are represented as a contraction of the electron structure and the hard part of the polarization dependent contribution into cross-section. The calculation of the hard part with first order radiative correction is performed. The obtained representation includes the leading radiative corrections in all orders of perturbation theory and the main part of the second order next-to-leading ones. Numerical calculations illustrate our analytical results.Comment: 14 pages, 4 figure

A xylem sap retrieval pathway in rice leaf blades: evidence of a role for endocytosis?

The structure and transport properties of pit membranes at the interface between the metaxylem and xylem parenchyma cells and the possible role of these pit membranes in solute transfer to the phloem were investigated. Electron microscopy revealed a fibrillar, almost tubular matrix within the pit membrane structure between the xylem vessels and xylem parenchyma of leaf blade bundles in rice (Oryza sativa). These pits are involved primarily with regulating water flux to the surrounding xylem parenchyma cells. Vascular parenchyma cells contain large mitochondrial populations, numerous dictyosomes, endomembrane complexes, and vesicles in close proximity to the pit membrane. Taken collectively, this suggests that endocytosis may occur at this interface. A weak solution of 5,6-carboxyfluorescein diacetate (5,6-CFDA) was applied to cut ends of leaves and, after a minimum of 30 min, the distribution of the fluorescent cleavage product, 5,6-carboxyfluorescein (5,6-CF), was observed using confocal microscopy. Cleavage of 5,6-CFDA occurred within the xylem parenchyma cells, and the non-polar 5,6-CF was then symplasmically transported to other parenchyma elements and ultimately, via numerous pore plasmodesmata, to adjacent thick-walled sieve tubes. Application of Lucifer Yellow, and, separately, Texas Red-labelled dextran (10 kDa) to the transpiration stream, confirmed that these membrane-impermeant probes could only have been offloaded from the xylem via the xylem vessel–xylem parenchyma pit membranes, suggesting endocytotic transmembrane transfer of these membrane-impermeant fluorophores. Accumulation within the thick-walled sieve tubes, but not in thin-walled sieve tubes, confirms the presence of a symplasmic phloem loading pathway, via pore plasmodesmata between xylem parenchyma and thick-walled sieve tubes, but not thin-walled sieve tubes

Universal conductance fluctuations in three dimensional metallic single crystals of Si

In this paper we report the measurement of conductance fluctuations in single crystals of Si made metallic by heavy doping (n \approx 2-2.5n_c, n_c being critical composition at Metal-Insulator transition). Since all dimensions (L) of the samples are much larger than the electron phase coherent length L_\phi (L/L_\phi \sim 10^3), our system is truly three dimensional. Temperature and magnetic field dependence of noise strongly indicate the universal conductance fluctuations (UCF) as predominant source of the observed magnitude of noise. Conductance fluctuations within a single phase coherent region of L_\phi^3 was found to be saturated at \approx (e^2/h)^2. An accurate knowledge of the level of disorder, enables us to calculate the change in conductance \delta G_1 due to movement of a single scatterer as \delta G_1 \sim e^2/h, which is \sim 2 orders of magnitude higher than its theoretically expected value in 3D systems.Comment: Text revised version. 4 eps figs unchange

Liquidity and the drivers of search, due diligence and transaction times for UK commercial real estate investments

Trading commercial real estate involves a process of exchange that is costly and which occurs over an extended and uncertain period of time. This has consequences for the performance and risk of real estate investments. Most research on transaction times has occurred for residential rather than commercial real estate. We study the time taken to transact commercial real estate assets in the UK using a sample of 578 transactions over the period 2004 to 2013. We measure average time to transact from a buyer and seller perspective, distinguishing the search and due diligence phases of the process, and we conduct econometric analysis to explain variation in due diligence times between assets. The median time for purchase of real estate from introduction to completion was 104 days and the median time for sale from marketing to completion was 135 days. There is considerable variation around these times and results suggest that some of this variation is related to market state, type and quality of asset, and type of participants involved in the transaction. Our findings shed light on the drivers of liquidity at an individual asset level and can inform models that quantify the impact of uncertain time on market on real estate investment risk

Noise Probe of the Dynamic Phase Separation in La2/3Ca1/3MnO3

Giant Random Telegraph Noise (RTN) in the resistance fluctuation of a macroscopic film of perovskite-type manganese oxide La2/3Ca1/3MnO3 has been observed at various temperatures ranging from 4K to 170K, well below the Curie temperature (TC = 210K). The amplitudes of the two-level-fluctuations (TLF) vary from 0.01% to 0.2%. We use a statistical analysis of the life-times of the TLF to gain insight into the microscopic electronic and magnetic state of this manganite. At low temperature (below 30K) The TLF is well described by a thermally activated two-level model. An estimate of the energy difference between the two states is inferred. At higher temperature (between 60K and 170K) we observed critical effects of the temperature on the life-times of the TLF. We discuss this peculiar temperature dependence in terms of a sharp change in the free energy functional of the fluctuators. We attribute the origin of the RTN to be a dynamic mixed-phase percolative conduction process, where manganese clusters switch back and forth between two phases that differ in their conductivity and magnetization.Comment: 15 pages, PDF only, Phys. Rev. Lett. (in press

Ashwagandha Leaf Derived Withanone Protects Normal Human Cells Against the Toxicity of Methoxyacetic Acid, a Major Industrial Metabolite

The present day lifestyle heavily depends on industrial chemicals in the form of agriculture, cosmetics, textiles and medical products. Since the toxicity of the industrial chemicals has been a concern to human health, the need for alternative non-toxic natural products or adjuvants that serve as antidotes are in high demand. We have investigated the effects of Ayurvedic herb Ashwagandha (Withania somnifera) leaf extract on methoxyacetic acid (MAA) induced toxicity. MAA is a major metabolite of ester phthalates that are commonly used in industry as gelling, viscosity and stabilizer reagents. We report that the MAA cause premature senescence of normal human cells by mechanisms that involve ROS generation, DNA and mitochondrial damage. Withanone protects cells from MAA-induced toxicity by suppressing the ROS levels, DNA and mitochondrial damage, and induction of cell defense signaling pathways including Nrf2 and proteasomal degradation. These findings warrant further basic and clinical studies that may promote the use of withanone as a health adjuvant in a variety of consumer products where the toxicity has been a concern because of the use of ester phthalates

Quantum Size Effect transition in percolating nanocomposite films

We report on unique electronic properties in Fe-SiO2 nanocomposite thin films in the vicinity of the percolation threshold. The electronic transport is dominated by quantum corrections to the metallic conduction of the Infinite Cluster (IC). At low temperature, mesoscopic effects revealed on the conductivity, Hall effect experiments and low frequency electrical noise (random telegraph noise and 1/f noise) strongly support the existence of a temperature-induced Quantum Size Effect (QSE) transition in the metallic conduction path. Below a critical temperature related to the geometrical constriction sizes of the IC, the electronic conductivity is mainly governed by active tunnel conductance across barriers in the metallic network. The high 1/f noise level and the random telegraph noise are consistently explained by random potential modulation of the barriers transmittance due to local Coulomb charges. Our results provide evidence that a lowering of the temperature is somehow equivalent to a decrease of the metal fraction in the vicinity of the percolation limit.Comment: 21 pages, 8 figure

Electron Glass in Ultrathin Granular Al Films at Low Temperatures

Quench-condensed granular Al films, with normal-state sheet resistance close to 10 k$\Omega/\Box$, display strong hysteresis and ultraslow, non-exponential relaxation in the resistance when temperature is varied below 300 mK. The hysteresis is nonlinear and can be suppressed by a dc bias voltage. The relaxation time does not obey the Arrhenius form, indicating the existence of a broad distribution of low energy barriers. Furthermore, large resistance fluctuations, having a 1/f-type power spectrum with a low-frequency cut-off, are observed at low temperatures. With decreasing temperature, the amplitude of the fluctuation increases and the cut-off frequency decreases. These observations combine to provide a coherent picture that there exists a new glassy electron state in ultrathin granular Al films, with a growing correlation length at low temperatures.Comment: RevTeX 3.1, 4 pages, 4 figures (EPS files) (Minor Additions