On the Electrochemical Reduction Mechanism of CaWO4 to W Powder

The reduction mechanism of CaWO4 to W in molten eutectic CaCl2-NaCl electrolyte has been studied. Cyclic voltammetry and constant potential electrolysis tests were performed to determine the reversible cell potential. Analyses of the experimental results revealed that at least 2.2 V was required to compensate the potentials for the accompanying cell reaction and the electrode polarizations. A cell reaction was proposed by associating the experimental results and the Gibbs energy changes of the possible reactions

On the Preparation of Mg2Ni by Combining Electrodeoxidation and Electrolysis Techniques

Mg2Ni is a well-known hydrogen storage alloy. Most of the preparative methods for this alloy require high temperature processing of pure magnesium and nickel. The proposed method, studied in this work, involves the production of Mg2Ni alloy directly from NiO and MgCl2 in an electrochemical cell. This method can eliminate the difficulties that may arise, during handling due to the reactive nature of metallic components, especially Mg. XRD patterns of reduced samples indicated the partial formation of Mg2Ni. Experimental results also showed that sintering of NiO, which resulted in the decrease of porosities, adversely affects the formation of Mg-Ni intermetallic compounds. Such an observation was thought to be the result of higher molar volume of Mg2Ni as compared to that of NiO

Electrochemical decomposition of SiO2 pellets to form silicon in molten salts

Direct electrochemical reduction of porous SiO2 pellets in molten CaCl2 salt and CaCl2-NaCl salt mixture was investigated by applying 2.8 V potential. The study focused on the effects of temperature, particle size of SiO2 powder starting material and the behavior of cathode contacting materials during electrochemical reduction process. The starting materials and the electrolysis products were characterized by X-ray diffraction analysis and scanning electron microscopy mainly. The studies showed that smaller particle sizes and higher temperatures had slightly positive effects in increasing the reduction rate within the ranges covered in this study. The results were interpreted from variations of current and accumulative electrical charge that passed through the cell as a function of duration of electrochemical reduction under different conditions. Microstructures and compositions of the reduced pellets were used to infer that electrochemical reduction of SiO2 in molten salts may become a method to produce silicon that could be used in solar energy utilization. Furthermore, X-ray diffraction analysis results indicated that the silicon produced at the cathode reacts with contacting materials; nickel, and iron in stainless steel to form Ni-Si and Fe-Si compounds due to very reactive nature of silicon especially at high temperatures

Effects of fabrication method on initial powder characteristics and liquid phase sintering behaviour of tungsten

Direct electrochemical production of tungsten involves removal of oxygen in solid state from an important tungsten compound, calcium tungstate, in molten salts. A detailed experimental study was performed to characterize the liquid phase sintering behaviour of the tungsten powder (WE), which was produced by the direct electrochemical reduction technique. All of the tungsten heavy alloy (WHA) compositions covered in this study, contained four parts nickel, one part cobalt and over 90 wt% tungsten. The pellets were sintered at 1500 and 1550 degrees C under continuous flow of an equimolar hydrogen-argon gas mixture. A commercially available tungsten powder (W-C) was also used to prepare the same tungsten heavy alloy compositions as those prepared by the electrochemically produced tungsten powder to act as a control group. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and hardness measurements were employed for characterization. The analyses provided that; the tungsten powder as obtained from the direct electrochemical reduction process contained some unreduced CaWO4 particles and they limited the grain growth and mass transport in the liquid phase. Although calculated relative densities were a bit lower than desired, the tungsten heavy alloys produced by the electrochemical reduction technique was promising for use when average grain size, dissolved tungsten contents and general/matrix hardness values are considered

Combined sensory integration therapy plus neurodevelopmental therapy (NT) versus NT alone for motor and attention in children with Down syndrome: a randomized controlled trial

Article; Early AccessIn this study, we aimed to analyze the incremental effects of sensory integration therapy (SIT) plus neurodevelopmental therapy (NT) versus NT alone on the attention and motor skills in children with Down syndrome (DS). We randomly assigned into experimental (i.e. SIT + NT; n = 21) and control (i.e. NT alone; n = 21) groups. While NT was applied to both groups for six weeks, SIT was applied simultaneously to the experimental group for six weeks. Participants' motor functions (Bruininks-Oseretsky Test of Motor Proficiency-Short form (BOT-2 SF)) and attention skills (Stroop TBAG (Turkish Scientific and Technological Research Association) Form) were evaluated before and after treatment (6 weeks later). Stroop TBAG and BOT-2 SF scores of the groups were similar at the baseline (p > 0.05). Significant improvement from baseline was observed in both BOT-2 SF, and Stroop TBAG results in both groups (p 0.05). In addition, the improvement in both BOT-2 SF and Stroop TBAG results was found to be greater in the experimental group compared to the control group (p 0.01). There were clear advantages to adding SIT to NT alone when seeking to improve motor and attention skills in children with DS

Characterization of dual-phase steels using magnetic barkhausen noise technique

The aim of this work is to nondestructively characterize the dual phase steels using the Magnetic Barkhausen Noise (MBN) method. By quenching of AISI 8620 steel specimens having two different starting microstructures, from various intercritical annealing temperatures (ICAT) in the ferrite-austenite region, the microstructures consisting of different volume fractions of martensite with morphological variations have been obtained. The microstructures were first conventionally characterized by metallographical investigations and hardness tests. Then, the MBN measurements were performed using a mu SCAN commercial system. Good correlations between the martensite volume fraction, hardness and MBN emission have been obtained. MBN signal height clearly decreased as the ICAT, therefore the volume fraction of martensite increased. The effect of the initial microstructure prior to intercritical annealing has also been differentiated by the MBN measurements. It has been concluded that MBN method can be used as a useful tool for nondestructive characterization of dual phase steels

QT and QTc prolongation and decreased heart rate after IV administration of levamisole hydrochloride in conscious rabbits

Intravenous doses of 2.5 mg/kg and 5.0 mg/kg of levamisole on RR, QT, QTc (corrected QT), and heart rate in conscious rabbits were evaluated. The study was performed on 14 New Zealand rabbits, 1 year old, weighing between 2.5-3 kg. The animals were assigned to 2 equal groups. Rabbits of groups I and II received via the auricular vein 2.5 mg/kg and 5 mg/kg of levamisole HCl, respectively. Alligator clips were attached to four limbs. ECG records were taken by direct writing electrocardiograph before the study and after 2, 4, 6, 8, 10, 15, and 20 min of the experiment. The QT interval was manually calculated from the beginning of Q wave to the end of T wave. The same leads (II and aVR) were selected for all QT interval measurement. The animals were not given any sedatives or anaesthetics before and during ECG recording. In group I, two rabbits had the second degree atrial block at the 2(nd) and 4(th) min after the injection, which disappeared later. Heart rates were 216-230 beats/min at min 0 and dropped to 193-210 beats/min at the 2(nd) min after the injection in both groups, and remained low throughout the study. Heart rates of both groups taken at 2, 4, 6, 8, 10, 15, and 20 min after the injection were significantly lower than the values taken at 0 min except for the values of the 15(th) min in group II. QT and QTc prolongation was noticed in both groups when compared to 0 min values. Although we have no solid data to explain the mechanism involved in bradycardia and atrial block provoked by levamisole, its use resulted in bradycardia, second-degree atrial block, and acute prolongation of QT and QTc in conscious rabbits

QT interval prolongation and decreased heart rates after intravenous bolus oxytocin injection in male and female conscious rabbits

The aim of this study was to evaluate changes in heart rate (HR), QT and RR intervals and corrected QT (QTc) values in conscious male and female New Zealand rabbits which intravenously received oxytocin (OXT) at different dosages. Animals were divided into 6 equal groups: group I (n = 6 male, received 0.75 U OXT per animal); group 11 (n = 6 male, received 1.5 U OXT per animal); group III (n = 6 male, received 3 U OXT per animal); group TV (n = 6 female, received 0.75 U OXT per animal); group V (n = 6 female, received 1.5 U OXT per animal); group VI (n = 6 female, received 3 U OXT per animal). ECG recording were taken from all animals before injection and then at 2, 4, 6, 8, 10, 15 and 20 min of OXT administration. QT and RR intervals obtained at 2 min of OXT administration were significantly prolonged in all groups (p < 0.05) with one exception that is the 1.5 U OXT injected female group where only QT interval did not change. The prolongation of QT and RR intervals persisted for 20 min in 1.5 U OXT injected male group while only QT interval prolongation was obvious for 20 min in 3 U OXT injected female group as for the other groups the prolonged interval were observed for 8-10 min and then returned to baseline values. Generally, a significant prolongation of QTc was noticed in both male and female rabbits at the 2 and 4 min in all groups and bradycardia was noticed at 2 min of OXT administration in all groups. Heart beats returned to normal values in all groups after 8 min of OXT administration. The change of HR, RR, QT and QTc was gender- but not dose-dependent (p < 0.001). The male rabbits were more sensitive to OXT effect then female rabbits. In conclusion, OXT used in therapeutic dosages decreased heart rate and prolonged QT and QTc intervals. Although cardiovascular effect of OXT are of short duration, its use in patient with risk factors for malignant arrhythmias requires more attention