Cómo hombres y mujeres aprenden movimientos de manera autodirigida : diferencias de género en la utilización de las estrategias de aprendizaje

Learning strategies, defined as specific and situational learning activities, have been a topic of psychological research for many years, mostly in academic context. The findings indicate gender differences in the use of learning strategies. This paper presents a study in which male and female subjects (N = 30) autonomously learned how to juggle balls. The learning strategies were measured by a questionnaire. The results reveal numerous gender differences in the use of single learning strategies rather than in the use of types of learning strategie

Investigation of the contact resistance as a function of the temperature for connectors and wire terminals

The hardness of coating materials such as tin or gold is temperature-dependent, so the contact area and thus the contact resistance change depending on the temperature. Contact resistance measurements are carried out on hard gold- and tin-coated connector contacts at elevated temperatures. It is shown that the contact resistance decreases significantly with increasing temperature. Tests are also being carried out with solid and stranded copper wires. In addition to the hardness, foreign layers on the copper conductors have a further influence on the contact resistance

Anodic dissolution of aluminum and anodic passivation in [EMIm]Cl-based ionic liquids

The anodic dissolution of aluminum in Lewis acidic ionic liquids consisting of AlCl3 and 1-ethyl-3-methylimidazolium chloride was studied using linear sweep and cyclic voltammetry, an electrochemical quartz crystal microbalance (EQCM) and chronopotentiometry at ambient temperature. Anodic passivation of the working electrode was observed in a 2:1 electrolyte while no passivation was found in a 1.5:1 electrolyte. Chronopotentiometry proves the passivation to be caused by local solidification of the electrolyte due to an increase in the aluminum concentration near the anode. EQCM data support these results

Low-frequency pulse plating for tailoring the optical appearance of chromium layers for decorative applications

The optical appearance of electroplated chromium layers is a crucial factor for decorative applications. Currently in the decorative chromium plating industry the so far used hexavalent electrolytes are being replaced progressively by solutions of trivalent chromium. However, chromium deposited from trivalent baths tends to have a yellowish color hue at thicknesses beyond 100 nm, which is undesired for most applications. The shift in color is related to a change in surface morphology due to the globular growth of the chromium nuclei. By utilizing pulsed current with on-times in the range of seconds, the grain growth is suppressed and the formation of fresh nuclei is favored. As a result, the average grain size of the layer can be decreased significantly. Compact chromium layers with small grains and improved color values are formed. A blueish appearance and high brightness were maintained up to thicknesses of more than 200 nm. Based on the results a combination of constant and pulsed current is suggested, yielding similar visual appearance as in the case of pulsed current only, but reaching the targeted film thickness much faster

Analysis of motor performance of children and adolescents in Germany

The development of motor abilities plays an important role in the general development of children and adolescents. In recent years, several studies have shown that the motor abilities of today’s German children and adolescents are worse than 20 or 30 years ago. In this review, studies dealing with this topic are presented and discussed critically. The literature review then focuses on studies realized in Germany. Results show that a decrease of motor performance is only observed in the late childhood and in the adolescence (older than 10 years). A possible reason might be the more frequently use of media and the change in the leisure time behavior of today’s children and adolescents

Electrochemical preparation of Cobalt-Samarium nanoparticles in an aprotic ionic liquid

Electrochemical preparation of Co-Sm nanoparticles was conducted in an aprotic room temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Co(TFSA)2 and Sm(TFSA)3. The cyclic voltammetry on a glassy carbon (GC) electrode indicated the electrochemically generated Sm(II) reacted with Co(II) at 25 °C. Potentiostatic cathodic reduction on a GC electrode in BMPTFSA containing 30 mM Co(TFSA)2 and 5 mM Sm(TFSA)3 at 25 °C gave the deposits, which were found to be composed of Co and Sm by energy dispersive X-ray spectroscopy (EDX). The deposits were found to be the aggregates of SmCo7 nanoparticles by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The formation of SmCo7 nanoparticles dispersed in the ionic liquid was also confirmed by TEM. SmCo7 nanoparticles were considered to form by the disproportionation reaction of Sm(II) in the presence of elementary Co, which was formed by the reduction of Co(II) by Sm(II)

Electrocatalysis of Lithium (Poly-) Sulfides in Organic Ether-Based Electrolytes

This work aims at identifying an effective electrocatalyst for polysulfide reactions to improve the electrode kinetics of the sulfur half-cell in liquid organic electrolytes for alkali-sulfur cells. To increase the charge and discharge rates and energy efficiency of the cell, functionalized electrocatalytic coatings have been prepared and their electrode kinetics have been measured. To the best of our knowledge, there is no extensive screening of electrocatalysts for the sulfur electrode in dimethoxyethane:1,3-dioxolane (DME:DOL) electrolytes. In order to identify a suitable electrocatalyst, apparent exchange current densities at various materials (Al, Co, Cr, Cu, Fe, Steel, glassy carbon, ITO, Ni, Pt, Ti, TiN, Zn) are evaluated in a polysulfide electrolyte using potentiodynamic measurements with a Butler-Volmer fit. The chemical stability and surface morphology changes after electrochemical measurements are assessed with X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The results show that cobalt is a promising candidate with appropriate electrocatalytic properties for polysulfide reactions while being stable in the electrochemical environment, followed by chromium in terms of catalytic activity and stability. Sputtered TiN was found to be a very stable material with very low catalytic activity, a possible current collector for the cell

Structure and formation of trivalent chromium conversion coatings containing cobalt on zinc plated steel

The present study intends to elucidate the effect of treatment solution composition on the formation and structure of Trivalent Chromium-based Conversion (TCC) coatings containing cobalt on zinc substrates. Model solutions with two different complexing agents, viz. fluoride and oxalate, with and without cobalt were applied to zinc plated steel. The scanning electron microscopy and atomic force microscopy images revealed a morphology with microstructural defects that can be improved to a more uniform and adherent structure by adding cobalt to the passivating bath. The elemental composition of the layer was investigated by auger electron spectroscopy (AES). Furthermore, the amounts of Cr and Co in the coatings were also measured with the aid of inductively coupled plasma optical emission spectroscopy (ICP-OES). In good agreement with AES, cobalt was also detected in the layers via ICP-OES measurement. The results of accelerated corrosion tests suggested that the formation of a densely packed layer is crucial for a good corrosion resistance of the coating

Electrochemical supercapacitors based on a novel graphene/conjugated polymer composite system

An efficient method for the preparation of a highly conducting hybrid material from graphene oxide nanosheets (GNS) and a novel conjugated polymer, poly(3,4-propylenedioxythiophene), is demonstrated. A functionalized monomer based on 3,4-propylenedioxythiophene, namely ProDOT-OH, was covalently functionalized with GNS, followed by oxidative polymerization to prepare GNS-f-PProDOT composites. The covalent functionalization process of GNS with the monomer ProDOT-OH was activated through the simple esterification reaction between the acyl chloride derivative on the nanosheets and the pendant hydroxyl group present in the monomer. Furthermore, the monomer functionalized GNS were co-polymerized with thiophene resulting in hybrid graphene nanostructures coated with highly conducting co-polymers with a room temperature electrical conductivity as high as 22.5 S cm(-1). The resulting hybrid materials were characterized using a range of analytical techniques. The specific capacitance value of the composite and the co-polymer hybrids at a scan rate of 10 mV s(-1) has been determined to be 158 and 201 F g(-1) respectively and hence particularly promising for supercapacitors.close232