Study of nuclear recoils in liquid argon with monoenergetic neutrons

For the development of liquid argon dark matter detectors we assembled a setup in the laboratory to scatter neutrons on a small liquid argon target. The neutrons are produced mono-energetically (E_kin=2.45 MeV) by nuclear fusion in a deuterium plasma and are collimated onto a 3" liquid argon cell operating in single-phase mode (zero electric field). Organic liquid scintillators are used to tag scattered neutrons and to provide a time-of-flight measurement. The setup is designed to study light pulse shapes and scintillation yields from nuclear and electronic recoils as well as from {\alpha}-particles at working points relevant to dark matter searches. Liquid argon offers the possibility to scrutinise scintillation yields in noble liquids with respect to the populations of the two fundamental excimer states. Here we present experimental methods and first results from recent data towards such studies.Comment: 9 pages, 8 figures, proceedings of TAUP 2011, to be published in Journal of Physics: Conference Series (JCPS

Interplay of Surface Diffusion and Surface Tension in the Evolution of Solid/Liquid Interfaces : Dealloying of β-Brass in Aqueous Sodium Chloride

The dealloying of β-brass in 0.5 M aqueous NaCl was studied by electrochemical techniques at different temperatures in the range 278 K ≤ T ≤ 318 K, complemented with in situ scanning tunneling microscopy (STM) imaging. In the potential region where the electrodissolution of zinc and the formation of vacancies and copper islands take place, two different roughness regimes were distinguished. When dealloying involves only a few monolayers (ML) the process approaches a quasiuniform alloy electrodissolution, whereas after electrodissolution of more than 20 ML, void formation takes place. In both regimes the interface evolution was analyzed by applying the dynamic scaling method to in situ STM imaging data. The first roughness regime exhibits a stable interface consisting of copper-rich islands that coarsen with time according to a surface diffusion controlled process. The second roughness regime exhibits an unstable interface due to a curvature dependent corrosion rate enhancing zinc electrodissolution at cavities. The overall interface evolution is well-described by a differential stochastic equation containing an electrodissolution term and surface rearrangement terms related to surface diffusion and negative surface tension effect.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Evaluation of nitrous oxide emission by soybean inoculated with Bradyrhizobium strains commonly used as inoculants in South America

Aims: The purpose of this work was to analyze the agronomic and environmental performance of soybean plants inoculated with the Bradyrhizobium strains widely used as soybean biofertilizers in South America and to determine if these strains possess any functional or taxonomic trait associated with the NO emission. Methods: Bradyrhizobium japonicum E109 and CPAC 15, B. diazoefficiens USDA 110 and CPAC 7, and B. elkanii SEMIA 5019 and SEMIA 587 were used to inoculate soybean seeds. The field experiment was carried out in a soil without history of soybean cultivation in the Argentinian Humid Pampa. The natural N abundance method was applied to estimate N-fixation, and NO production was evaluated using gas chromatography. Among other physiological parameters, shoot dry weight, shoot N content, and crop yield were estimated after harvest. Results: B. japonicum inoculation produced the greatest increases in soybean growth and crop yield but also led to higher NO emissions compared to all other inoculated treatments. Plants inoculated with B. diazoefficiens released the lowest amount of NO, and their growth and yield were the least affected. Inoculation with B. elkanii resulted in intermediate NO emission fluxes and crop yield compared with B. japonicum and B. diazoefficiens. Conclusions: We found that soybean inoculation with strains of B. japonicum and B. elkanii that lack the nosZ gene led to the highest NO emissions under field conditions, but also to the highest crop yield, while inoculation with strains that carry out complete denitrification, nosZ-containing B. diazoefficiens, showed lower NO emission and lower crop yield.To the Instituto de Investigaciones Agrobiotecnológicas (INIAB); Universidad Nacional de Río Cuarto (UNRC); Consejo Nacional de Investigaciones Científcas y Tecnológicas (CONICET), Fondo Nacional de Ciencia y Tecnología (FONCyT); Instituto Nacional de Tecnología Agropecuaria (INTA). FC is Researcher of CONICET at the UNRC. DT and FD are Postdoc and PhD students at the UNRC granted by CONICET. MOC is a former PhD student at the UNRC granted by CONICET. To Mariano Cicchino from INTA Chascomús, who was in charge of sowing and yield estimation at R8. To Juan Pedro Ezquiaga from INTA Castelar, for their contribution to N2O measurements

The ArDM experiment

The aim of the ArDM project is the development and operation of a one ton double-phase liquid argon detector for direct Dark Matter searches. The detector measures both the scintillation light and the ionization charge from ionizing radiation using two independent readout systems. This paper briefly describes the detector concept and presents preliminary results from the ArDM R&D program, including a 3 l prototype developed to test the charge readout system.Comment: Proceedings of the Epiphany 2010 Conference, to be published in Acta Physica Polonica

Interplay of Surface Diffusion and Surface Tension in the Evolution of Solid/Liquid Interfaces : Dealloying of β-Brass in Aqueous Sodium Chloride

The dealloying of β-brass in 0.5 M aqueous NaCl was studied by electrochemical techniques at different temperatures in the range 278 K ≤ T ≤ 318 K, complemented with in situ scanning tunneling microscopy (STM) imaging. In the potential region where the electrodissolution of zinc and the formation of vacancies and copper islands take place, two different roughness regimes were distinguished. When dealloying involves only a few monolayers (ML) the process approaches a quasiuniform alloy electrodissolution, whereas after electrodissolution of more than 20 ML, void formation takes place. In both regimes the interface evolution was analyzed by applying the dynamic scaling method to in situ STM imaging data. The first roughness regime exhibits a stable interface consisting of copper-rich islands that coarsen with time according to a surface diffusion controlled process. The second roughness regime exhibits an unstable interface due to a curvature dependent corrosion rate enhancing zinc electrodissolution at cavities. The overall interface evolution is well-described by a differential stochastic equation containing an electrodissolution term and surface rearrangement terms related to surface diffusion and negative surface tension effect.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Sister chromatid exchanges and micronuclei in peripheral lymphocytes of shoe factory workers exposed to solvents.

We examined sister chromatid exchanges (SCEs) and micronuclei (MN; cytokinesis-block method) in cultured peripheral lymphocytes from 52 female workers of two shoe factories and from 36 unexposed age- and sex-matched referents. The factory workers showed an elevated level of urinary hippuric acid, a biomarker of toluene exposure, and workplace air contained high concentrations of various organic solvents such as toluene, gasoline, acetone, and (in one of the plants only) ethylacetate and methylenediphenyl diisocyanate. The shoe factory workers showed a statistically significant higher frequency of micronucleated binucleate lymphocytes in comparison with the referents. This finding agreed with three preliminary MN determinations (each comprising 27-32 shoe workers and 16-20 controls) performed in one of the plants 2-5 years earlier. The shoe factory workers also had a lower average level of blood hemoglobin than the referents. In contrast, no difference was found between the groups in SCE analysis. Smokers showed significantly higher mean frequencies of SCEs per cell and high frequency cells (HFC) than nonsmokers. Aging was associated with increased MN rates and reduced cell proliferation. Polymorphism of the glutathione S-transferase M1 gene (GSTM1) did not affect the individual level of SCEs; but in smoking shoe workers an effect of the occupational exposure on the frequency of micronucleated cells could be seen only in GSTM1 null subjects. The low prevalence of the glutathione S-transferase T1 (GSTT1) null genotype precluded the evaluation of the influence of GSTT1 polymorphism. Our results show that the shoe factory workers have experienced genotoxic exposure, which is manifest as an increase in the frequency of MN, but not of SCEs, in peripheral lymphocytes. The exposures responsible for the MN induction could not be identified with certainty, but exposure to benzene in gasoline and methylenediphenyl diisocyanate may explain some of the findings

First results on light readout from the 1-ton ArDM liquid argon detector for dark matter searches

ArDM-1t is the prototype for a next generation WIMP detector measuring both the scintillation light and the ionization charge from nuclear recoils in a 1-ton liquid argon target. The goal is to reach a minimum recoil energy of 30\,keVr to detect recoiling nuclei. In this paper we describe the experimental concept and present results on the light detection system, tested for the first time in ArDM on the surface at CERN. With a preliminary and incomplete set of PMTs, the light yield at zero electric field is found to be between 0.3-0.5 phe/keVee depending on the position within the detector volume, confirming our expectations based on smaller detector setups.Comment: 14 pages, 10 figures, v2 accepted for publication in JINS

Characterization of mixed lymphocyte reaction blocking antibodies (MLR-Bf) in human pregnancy

BACKGROUND: It is known that during normal pregnancy and after immunotherapy blocking antibodies are developed, these antibodies inhibit mixed lymphocyte reaction and are also anti-mitogenic in nature. Mixed lymphocyte reaction blocking antibodies are specific to the husband's lymphocytes. In the present study an attempt has been made to characterize the mixed lymphocyte reaction blocking antibodies in normal pregnancy and in women with recurrent spontaneous abortion after immunotherapy. METHODS: Serum was obtained from women of different gestational windows of pregnancy (Ist, IInd, IIIrd trimesters and post delivery period of normal pregnancy), recurrent spontaneous aborters from pre and post immunization. Healthy (male and females) controls were screened for the presence of mixed lymphocyte reaction blocking antibodies. The standard mixed lymphocyte reaction technique was used to evaluate the inhibitory effect of serum in the mixed lymphocyte reaction. Each serum was tested for cytotoxic antibodies. Immunoglobulin G and its isotypes were isolated according to the standard protocol. RESULTS: In the present study we have observed that there was significant inhibition of proliferation response when immunoglobulin G from different trimesters of pregnancy were added to one way mixed lymphocyte reaction or to phytohemagglutinin activated lymphocyte proliferation assay. Similar pattern was seen when immunoglobulin G isolated from adequately immunized women with recurrent spontaneous abortion was used. It was further confirmed that amongst all the isotypes of immunoglobulin G, only immunoglobulin G-3 was found to be positive for the inhibitory effect. CONCLUSIONS: Present study indicates that mixed lymphocyte reaction blocking antibodies are immunoglobulin G-3 in nature. It is developed during pregnancy and also after immunotherapy in women with recurrent spontaneous abortion who subsequently have the successful pregnancy

Autocracy-Sustaining Versus Democratic Federalism:Explaining the Divergent Trajectories of Territorial Politics in Russia and Western Europe

This article provides a comparative assessment of territorial politics in Russia and Western Europe. The consolidation or deepening of regional autonomy in Western Europe contrasts with the transformation of Russia from a segmented and highly centrifugal state into a centralized authoritarian state in the course of just two decades. The consolidation of territorial politics in Western Europe is linked to the presence of endogenous safeguards that are built into their territorial constitutional designs and most importantly to the dynamics that emanate from multi-level party competition in the context of a liberal and multi-level democracy. In contrast, in Russia, neither endogenous safeguards nor multi-level party democracy play an important role in explaining the dynamics of Russian federalism, but who controls key state resources instead. We argue that under Putin power dependencies between the Russian center and the regions are strongest where regional democracy is at its weakest, thus producing ‘autocracy-sustaining’ instead of a democratic federation. By studying the relationship between federalism and democracy in cases where both concepts are mutually reinforcing (as in Western Europe) with the critical case of Russia where they are not, we question the widely held view that democracy is a necessary pre-condition for federalism.Peer reviewe