Unconventional trapping of ultracold neutrons

In unconventional storage experiments we filled ultracold neutrons (UCN) into a Fomblin-grease coated trap and then immediately removed the UCN from the storage volume by an absorber, until their residual density in the trap was measured to be negligible. When subsequently the absorber was withdrawn a significant number of UCN of higher energies emerged from the trap. Their appearance cannot be attributed to heating or cooling of residual UCN. Further experiments were performed to investigate the origin of these UCN which we call `late UCN'. We noticed that application of a magnetic field gradient at the trap wall as well as a replacement of Fomblin grease on the surface by Fomblin oil gave rise to small but measurable alterations of storage behavior. These phenomena are consistent with the hypothesis of temporary adhesion of a few UCN to a rough wall.     

具有负系数的单叶函数的推广

Let R_A,B(α,β,q) denote the class of functions f(z) = z(?) which are analytic and nnivalent in < 1, and satisfy the condition. Also let R_A,B(α,β,q,t) denote the class of functions (1 - t)z + tf(z), where f(z) ∈R_A,B(α,β, q) and t ∈(0, 1].Sharp results concerning representation, distortion theorems and radius of convexityfor the class R_A,B(α,β, q, t) are determined. It is shown that the class R_A,B(α,β,q, t)is closed under linear combinations. Furthermore extreme points and support points forthe class R_A,B(α,β,q, t) are also determined.     

Analysis of the fusariotoxins zearalenone and vomitoxin (deoxynivalenol) in human foods and animal feeds by high-performance liquid chromatography (HPLC)

Summary HPLC procedures for analyses of the fusariotoxins zearalenone and vomitoxin in individual food- and feedstuffs as well as in mixed feed are described. Zearalenone is separated on a column with polar stationary phase (25 cm × 4.6 mm i.d., particle size 7 m), eluted with a chloroform-isooctane (75/25, v/v)+1.5% methanol mixture and detected fluorometrically. The quantitative determination was possible in all analyzed samples with a detection limit of 2g/kg with 70–80% recovery. Vomitoxin is fractionated by HPLC (C ₁₈ ¹ column, 25 cm×4 mm i.d., 5 m particle size) with water-methanol (60/40, v/v) mobile phase and determined by combining GLC or TLC with UV detection. The detection limit in mixed feed with interfering substances was 25 g/kg (recovery 25–35%). The separation by HPLC makes preparation of pure vomitoxin possible. The described methods are fast, simple and low cost and are suitable for routine analyses.     

A Third‐Generation Hydrogen Peroxide Biosensor Based on Horseradish Peroxidase Covalently Immobilized on Electrografted Organic Film on Screen‐Printed Carbon Electrode

A new convenient strategy to fabricate a third‐generation hydrogen peroxide biosensor was described. The screen‐printed carbon electrode (SPCE) was first modified with a layer of 4‐nitrophenyl assembled from the 4‐nitroaniline diazonium salt synthesized in situ in acidic aqueous solution. Next, the nitro groups were converted to amines followed by crosslinking to the horseradish peroxidase (HRP) by glutaraldehyde. The redox chemistry of the active center of the HRP was observed and the HRP‐modified electrode displayed electrocatalytic activity towards the reduction of hydrogen peroxide (H₂O₂) without any mediators. H₂O₂ was determined in a linear range from 5.0 μM to 50.0 μM, with a detection limit of 1.0 μM. Furthermore, the biosensor exhibited fast amperometric response, good reproducibility and long‐term stability.     

Activity concentrations of 238U and 232Th in some soil and fertilizer samples using passive and active techniques

Uranium and thorium concentrations in some soil and fertilizer samples were determined using passive technique with CR-39 and LR-115 polymeric nuclear track detectors, whereas the fertilizer samples were measured using active technique with passive technique. The two different techniques have been used in order to ensure and compare between the obtained results. The main purpose of the present investigation is to assess the activity concentration of ²³⁸U and ²³²Th in soil of particular regions and measure the pollution due to the production plant of complex fertilizers. From the obtained data we can conclude that there is no radioactive healthy hazard for human and living beings in the selected area.     

Aluminum corrosion prevention in 1.0 M HCl solution by cystosiera myrica extract: An experimental and biological study

Potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS), tests, mass loss (ML) and Hydrogen evolutions (HE) methods were used to examine the effects of the newly plant extracted compound (Cystosiera myrica). All these quantities exhibited that the effectiveness of inhibition increase with a rise in inhibitor concentration and with a rise in temperature. Polarization curves displayed that the inhibitor studied was an inhibitor of a mixed kind. Langmuir isotherm was attained for the adsorption of the inhibitor on the Aluminum surface. Thermodynamic parameters were determine and deduced such as activation enthalpy (ΔH*), activation entropy (ΔS*), adsorption equilibrium constant (K_ads) and free adsorption energy (G^o_ads) have been measured. UV/visible spectral, Attenuated Total Reflection Infra-Red (ATR-IR) and Atomic Force Microscopy (AFM) tested have observed the effect of this inhibitor on Al surface morphology. All other data approaches were compatible and in line with each other.     

Effective models for reactive flow under a dominant Péclet number and order one Damköhler number: Numerical simulations

The paper is devoted to the longitudinal dispersion of a soluble substance released in a steady laminar flow through a slit channel with heterogeneous reaction at the outer wall. The reactive transport happens in the presence of a dominant Péclet number and order one Damköhler number. In particular, these Péclet numbers correspond to Taylor’s dispersion regime. An effective model for the enhanced diffusion in this context was derived recently. It contains memory effects and contributions to the effective diffusion and effective advection velocity, due to the flow and chemistry reaction regime. In the present paper, we show through numerical simulations the efficiency of this new model. In particular, using Taylor’s ‘historical’ parameters, we illustrate that our derived contributions are important and that using them is necessary in order to simulate correctly the reactive flows. We emphasize three main points. First, we show how the effective diffusion is enhanced by chemical effects at dispersive times. Second, our model captures an intermediate regime where the diffusion is anomalous and the distribution is asymmetric. Third, we show how the chemical effects also slow down the average speed of the front.