Lambda and Lambda-bar Polarization in Lepton Induced Processes

The study of the longitudinal polarization of Lambda and Lambda-bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in Z0 decays allows to access the spin dynamics of the quark fragmentation process. Different phenomenological spin transfer mechanisms are considered and predictions for the Lambda and Lambda-bar longitudinal polarization in various processes using unpolarized and polarized targets are made. Current and future semi-inclusive deep inelastic scattering experiments will provide soon accurate enough data to study these phenomena and distinguish between various models for the spin transfer mechanisms.Comment: 17 pages, LaTex with epsfig.sty, including 10 figures One reference adde

Gluon Polarization from Correlated High-p_T Hadron Pairs in Polarized l - N Scattering

We propose to access the gluon polarization $\Delta G$ by measuring the cross section spin-asymmetry in semi-inclusive polarized lepton -- nucleon scattering. The photon-gluon fusion sub-process will be tagged by detecting high-$p_T$ correlated hadron pairs in the forward hemisphere. Selecting oppositely charged kaon pairs will allow to suppress the background coming from gluon radiation.Comment: 6 pages, 3 eps figures, aipproc.cls and aipproc.sty include

The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries Does the observational evidence support their existence?

Context. Period variations have been detected in a number of eclipsing close compact binary subdwarf B stars (sdBs) and these have often been interpreted as caused by circumbinary massive planets or brown dwarfs. Various evolutionary scenarios have been proposed for these stars, but a definite mechanism remains to be established. Equally puzzling is the formation of these putative circumbinary objects which must have formed either from the remaining post common envelope circumbinary disk or survived its evolution. Aims. In this paper we review the eclipse time variations (ETVs) exhibited by seven such systems and explore if there is conclusive evidence that the ETVs observed over the last two decades can reliably predict the presence of circumbinary bodies. Methods. We report 246 new observations of the seven sdB systems made between 2013 September and 2017 July using a worldwide network of telescopes. We combined our new data with previously published measurements to analyse the ETVs of these systems. Results. Our data shows that period variations cannot be modelled simply on the basis of circumbinary objects. This implies that more complex processes may be taking place in these systems. From eclipse time variations, it has historically been suggested that five of the seven binary systems reported herein had circumbinary objects. Based on our recent observations and analysis only three systems remain serious contenders. We find agreement with other observers that at least a decade of observations is required to establish reliable ephemeris. With longer observational baselines it is quite conceivable that the data will support the circumbinary object hypothesis of these binary systems. Also we generally agree with other observers that larger values of (O-C) residuals are found with secondary companions of spectral type M5/6 or earlier as a result of an Applegate type mechanismComment: 15 pages, 13 figures, 4 tables. 3 tables archived on CD

Gluon polarization from correlated high-pT hadron pairs in polarized electro-production

We propose to measure the gluon distribution function Delta G(eta) at eta < 0.2 via pseudo jet production in polarized fixed target lepton nucleon scattering at typical lepton beam energies of 200 GeV. The measurement of the spin-asymmetry for the production of correlated charge conjugated hadrons of opposite transverse momentum can be directly related to Delta G(eta) through the photo-gluon fusion process. Wa also present a numerical analysis of the accuracy which can be obtained for different flavors and kinematics of the observed hadron pair.Comment: 18 pages, 6 eps figure

Research Paper Polyclonal antibodies production against Staphylococcus aureus protein A: ELISA technique optimization for milk quality control

The main aim of this project is to produce polyclonal antibodies directed against the Staphylococcus aureus protein A and their use to appreciate bacteriological analysis of milk quality. In this context, an immunization produce was set up to test and detect in a batch of animals the convenient responder to the injected antigen. Furthermore, to optimize all parameters of retained ELISA test, a cross-table was conceived by using various concentrations of different reagents and has allowed selecting the optimaldilutions as follows: 1) 1/1000 for anti-Staphylococcus aureus protein A mouse antibodies and 1/2000 for anti-Staphylococcus aureus protein A rabbit antibodies. 2) 1/4000 for anti-Staphylococcus aureus treated by heat mouse antibodies and 1/500 for anti-Staphylococcus aureus protein A rabbit antibodies. 3) 1/2000 for anti-Staphylococcus aureus treated by NaClO mouse antibodies and 1/500 for anti-Staphylococcus aureus protein A rabbit antibodies. The application of optimized ELISA test to searchand detect Staphylococcus aureus germs in different samples of milk has shown very satisfying results when compared to those obtained by bacteriological method. Indeed, the sensitiveness and the reproducibility, as well as the possibility to analyze a great number of samples in the same time at a reduced manner make the immunochemical method a best choice of test able to replace recent bacteriological methods

Noise and conversion properties of Y-Ba-Cu-O Josephson mixers at operating temperatures above 20 K

We have measured the noise performance and conversion efficiency of Y-Ba-Cu-O bicrystal Josephson mixers at operating temperatures between 20 and 60 K and at operating frequencies around 90 GHz. A double-sideband mixer noise temperature of about 1600 K and a conversion efficiency of -10 dB at 20 K operating temperature has been measured using the Y-factor method. The absorbed local oscillator power was in the range of 10 nW. The dependence of the mixer performance on the normalized frequency Omega and the fluctuation parameter Gamma has been studied. In accordance with the resistively shunted junction model, the experimental data show the presence of excess noise. The temperature dependence of the mixer noise temperature can be explained by the variation of the linewidth of the Josephson oscillations with the operating temperature. (C) 2000 American Institute of Physics. [S0003-6951(00)00113-3]

The mutualistic fungus Piriformospora indica protects barley roots from a loss of antioxidant capacity caused by the necrotrophic pathogen Fusarium culmorum

Fusarium culmorum causes root rot in barley (Hordeum vulgare), resulting in severely reduced plant growth and yield. Pretreatment of roots with chlamydospores of the mutualistic root-colonizing basidiomycete Piriformospora indica (Agaricomycotina) prevented necrotization of root tissues and plant growth retardation commonly associated with Fusarium root rot. Quantification of Fusarium infections with a real-time PCR assay revealed a correlation between root rot symptoms and the relative amount of fungal DNA. Fusarium-infected roots showed reduced levels of ascorbate and glutathione (GSH), along with reduced activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR). Consistent with this, Fusarium-infected roots showed elevated levels of lipid hydroperoxides and decreased ratios of reduced to oxidized forms of ascorbate and glutathione. In clear contrast, roots treated with P. indica prior to inoculation with F. culmorum showed levels of ascorbate and GSH that were similar to controls. Likewise, lipid peroxidation and the overall reduction in antioxidant enzyme activities were largely attenuated by P. indica in roots challenged by F. culmorum. These results suggest that P. indica protects roots from necrotrophic pathogens at least partly, through activating the plant’s antioxidant capacity

Realtime calibration of the A4 electromagnetic lead fluoride calorimeter

Sufficient energy resolution is the key issue for the calorimetry in particle and nuclear physics. The calorimeter of the A4 parity violation experiment at MAMI is a segmented calorimeter where the energy of an event is determined by summing the signals of neighbouring channels. In this case the precise matching of the individual modules is crucial to obtain a good energy resolution. We have developped a calibration procedure for our total absorbing electromagnetic calorimeter which consists of 1022 lead fluoride (PbF_2) crystals. This procedure reconstructs the the single-module contributions to the events by solving a linear system of equations, involving the inversion of a 1022 x 1022-matrix. The system has shown its functionality at beam energies between 300 and 1500 MeV and represents a new and fast method to keep the calorimeter permanently in a well-calibrated state