Nucleation and Growth of the Zn-Fe Alloy from a Chloride Electrolyte

In this study, the kinetics of Zn-Fe codeposition was investigated in chloride acidic solution using cyclic voltammetry. Anomalous codeposition is detected and this mechanism depends on the Zn(II) / Fe(II) concentration ratio in the electrolytic bath. The study of early stages of electrodeposition showed that Zn- Fe follows a theoretical response to instantaneous nucleation evolves into a progressive nucleation according to the model of Scharifker and Hills. The morphology and structure of the coatings is discussed using characterization techniques. Dense, uniform, and singlephased Zn-Fe coatings could be obtained with a Zn-Fe ratio of 1/3. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3531

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

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

Changes in the growth mode of electrodeposited silver layers : Surface rearrangements induced by the presence of lead adatoms

The surface characteristics of Ag electrodeposits prepared on polyfaceted Pt(sc) electrodes have been followed through complete Pb upd/stripping voltammetry. The growth mode of Ag overlayers at constant temperature depends on both the cathodic electrodeposition overvoltage and the silver ion concentration in solution. Ag surface rearrangements can be induced by either holding the potential or Pb upd/stripping cycling in the potential range where the degree of surface coverage by Pb adatoms is between 0 and 1. The voltammograms of Ag overlayers at the monolayer level show considerable changes compared with those obtained for thicker Ag overlayers. The present results allow us to establish a correlation between the development of rough electrodeposits and the surface diffusion properties of metal atoms.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electrochemical kinetics and growth modes of silver deposits on polyfaceted platinum spherical electrodes

The Ag electrodeposition on Pt spherical substrates was investigated over a wide range of experimental conditions to establish a correlation between the kinetics of the process and the different growth modes of the Ag overlayer. At Ed ≊ Erev, the electrodeposition of the first Ag layer obeys a combined adsorption-desorption and nucleation and 2-D growth process under diffusion control. At Ed ≊ Erev, the formation of the 2-D Ag layer proceeds through an adsorption mechanism, whereas the formation of the 3-D Ag layer fits a progressive nucleation and 3-D growth mechanism under diffusion control. Finally, when Ed rev, a potential threshold related to Ag dendritic growth, the kinetics of the reaction apparently obeys a progressive nucleation and 1-D growth. This process is triggered at edges and corners of large Ag crystals. Dendritic growth takes place outside the diffusion layer defined around the Pt substrate sphere. In this case migration plays a substantial role in the process.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Preparation of 100−160-nm-sized branched palladium islands with enhanced electrocatalytic properties on HOPG

A method for the preparation of stable 100-160-nm-sized quasi-2D branched palladium islands on highly oriented pyrolitic graphite (HOPG) is described. This type of island is electrodeposited from an aqueous acidic palladium chloride solution containing an excess of sodium perchlorate at potentials just a few millivolts above the threshold potential of the hydrogen evolution reaction. Each branched palladium island consists of a central 3D core and large quasi-2D branches that form a dense radial pattern. In contrast to massive palladium, branched islands exhibit enhanced electrocatalytic properties for the hydrogen atom electroadsorption/electrodesorption reaction and the electrooxidation reaction of hydrazine. This enhancement is mainly related to the fractal characteristics of branched palladium islands on HOPG.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Transcriptomic Events Involved in Melon Mature-Fruit Abscission Comprise the Sequential Induction of Cell-Wall Degrading Genes Coupled to a Stimulation of Endo and Exocytosis

Background: Mature-fruit abscission (MFA) in fleshy-fruit is a genetically controlled process with mechanisms that, contrary to immature-fruit abscission, has not been fully characterized. Here, we use pyrosequencing to characterize the transcriptomes of melon abscission zone (AZ) at three stages during AZ-cell separation in order to understand MFA control at an early stage of AZ-activation. Principal Findings: The results show that by early induction of MFA, the melon AZ exhibits major gene induction, while by late induction of MFA, melon AZ shows major gene repression. Although some genes displayed similar regulation in both early and late induction of abscission, such as EXT1-EXT4, EGase1, IAA2, ERF1, AP2D15, FLC, MADS2, ERAF17, SAP5 and SCL13 genes, the majority had different expression patterns. This implies that time-specific events occur during MFA, and emphasizes the value of characterizing multiple time-specific abscission transcriptomes. Analysis of gene-expression from these AZs reveal that a sequential induction of cell-wall-degrading genes is associated with the upregulation of genes involved in endo and exocytosis, and a shift in plant-hormone metabolism and signaling genes during MFA. This is accompanied by transcriptional activity of small-GTPases and synthaxins together with tubulins, dynamins, V-type ATPases and kinesin-like proteins potentially involved in MFA signaling. Early events are potentially controlled by down-regulation of MADS-box, AP2/ERF and Aux/IAA transcription-factors, and up-regulation of homeobox, zinc finger, bZIP, and WRKY transcription-factors, while late events may be controlled by up-regulation of MYB transcription-factors. Significance: Overall, the data provide a comprehensive view on MFA in fleshy-fruit, identifying candidate genes and pathways associated with early induction of MFA. Our comprehensive gene-expression profile will be very useful for elucidating gene regulatory networks of the MFA in fleshy-fruit

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