The coding and effector transfer of movement sequences.

Three experiments utilizing a 14-element arm movement sequence were designed to determine if reinstating the visual–spatial coordinates, which require movements to the same spatial locations utilized during acquisition, results in better effector transfer than reinstating the motor coordinates, which require the same pattern of homologous muscle activation. Results demonstrated better transfer when visual–spatial coordinates were reinstated than when motor coordinates where reinstated regardless of the amount of practice (1, 4, or 12 days; Experiments 1–3, respectively). Transfer (left to right and right to left) was symmetric when visual–spatial coordinates were reinstated but not when motor coordinates were reinstated. When motor coordinates were reinstated after 12 days of practice and vision occluded, transfer was better from right limb to left than vice versa. The data are also consistent with the notion that multiple codes (visual, spatial, and motor) are developed over practice, with each contributing to transfer performance when the respective coordinates are reinstated. Further, the results indicate a disruption of the linkage (concatenation) between subsequences when one or more coordinates are changed on the transfer test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Berechnung von dreidimensionalen elektromagnetischen Feldern bei der induktiven Erwärmung

Übersicht Es wird ein numerisches 3D-Berechnungsverfahren vorgestellt, mit dem die elektromagnetischen (EM-) Felder bei induktiver Hochfrequenz-(HF-) oder Banderwärmung, also im Fall dünner stromführender Schichten, simuliert werden. Darüber hinaus lassen sich Leistungs- und Kraftverteilungen sowie integrale Größen, wie z. B. Impedanz, Spannung und Wirkleistung, ermitteln. Für das Berechnungsprogramm werden die prozeßrelevanten Teile der betrachteten Anlagen entsprechend ihrer elektromagnetischen Eigenschaften bestimmten Gruppen zugeordnet. Für jede Gruppe gelten spezifische Randbedingungen an der Oberfläche bezüglich der EM-Felder. Das Berechnungsprogramm basiert auf der Boundary-Element-Methode (BEM) und berücksichtigt die anlagenspezifischen Symmetrien, so daß Rechner genutzt werden können, die in Forschung und Entwicklung heute allgemein zugänglich sind (PC, Workstation). Am Beispiel zweier Anwendungsfälle wird die Leistungsfähigkeit des entwickelten Programmpaketes aufgezeigt.

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Calculation of threedimensional electromagnetic fields during induction heating

Contents A numerical 3D-calculation method for the simulation of the electromagnetic field during high frequency induction heating or induction strip heating, i.e. in case of thin current-carrying layers, is presented. In addition, the described programme allows to calculate the distributions of power and force as well as integral quantities, for example the impedance, the voltage and the active power. The parts of the setup to be considered are assigned to certain groups according to their electromagnetic properties. Each group has its specific boundary conditions at the surface describing the electromagnetic field. The calculation program uses the boundary element method and takes into account the set-up specific symmetries. Therefore the program runs on computers (PC, Workstations), which are widely available for research and development purposes nowadays. Finally, two examples basing on industrial applications show the efficiency of the developed program.

     

Frequency of food intake and natural dietary components are potent modulators of bone resorption and bone mass in rats

Prevention of low bone mass is important to reduce the incidence of osteoporotic fractures. In this report evidence is provided that feeding habits per se, that is, increased frequency of food intake as well as a diet containing soy and other raw components, decrease bone resorption and increase bone mass in growing rats. Interim results after 6 weeks indicate that food fractionation and natural dietary components are both capable of inhibiting trabecular bone loss in aged rats. These interim results indicate that the effect of both dietary interventions are additive and together are capable of nearly completely blunting the age-dependent loss of trabecular bone mineral density. These dietary manipulations are, however, only partially effective in inhibiting the strongly increased loss of trabecular bone mineral density induced by estrogen deprivation. The fact that the natural dietary components are not more effective in ovariectomized rats as compared to intact females confirms our contention that these components may not operate by mimicking the effect of estradiol. Whether bone mass in humans is also under the control of dietary habits is not known. If so, an increased frequency of meals of appropriate composition may be used to prevent osteoporosis.     

Berechnung des dreidimensionalen Hochfrequenzfeldes beim Zonenschmelzen von Silizium

Übersicht Beim tiegelfreien Zonenschmelzen von Halbleiter-Silizium werden spezielle Induktoren verwendet, deren axiale Symmetrie gestÖört ist. Dadruch entsteht ein dreidimensionales (3D) elektromagnetisches Feldproblem. Da der Induktor mit hochfrequenten Strömen im Megahertzbereich gespeist wird, läßt sich die Stromverteilung und die umgesetzte spezifische Leistung im System vorteilhaft mit der Boundary-Element-Methode (BEM) numerisch berechnen. Für die Aufstellung der zu lösenden Integralgleichung werden Vektorpotentiale, der magnetischen Induktion und des Stromes eingeführt. Die Aufteilung der Oberflächen des Systems, bestehend aus Induktor und Einsatz (Silizium), in einzelne Oberflächenstromelemente überführt diese Gleichung in ein lineares algebraisches Gleichungssystem für die skalare Stromfunktion, des Oberflächenstromes. Die Lösung erfolgt mit Hilfe der Gaußschen Elimination. Numerische Ergebnisse für eine stark vereinfachte Modellanordnung stimmen mit den erhaltenen Meßergebnissen gut überein. Das entwickelte Pascal-Programm wird für die bei der optimalen Auslegung, des Induktors notwendigen, Parameterstudien eingesetzt.

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Calculation of the three-dimensional RF-field during the float zone-growth of silicon

Contents Special induction coils., of which the axial symmetry is essentially disturbed, are used in float zone melting of silicon, crystals. This gives rise to three-dimensional (3D) electromagnetic field problem. Since the induction coil is supplied with high-frequency current in the megacycle region, the numerical calculation of the current distribution and of the converted specific power in the system can be efficiently performed with the aid of the Boundary Element Method (BEM). Vector potentials of the magnetic induction and of the current are introduced in order to set up the integral equation that is to be solved. The splitting up of the surfaces of the system, consisting of induction coil and ingot (silicon), into individual surface current elements transforms this equation into a linear algebraic system of equations for the scalar stream function of the surface current. The solution is achieved with the aid of Gaussian elimination. Numerical results for a greatly simplified model set up show good agreement with the results obtained by measurements. The Pascal programme that has been developed is used for the necessary parameter studies required for the optimum design of the induction coil.

     

Carbon in silicon: Properties and impact on devices

The properties, origin and analysis of carbon in silicon and its influence on the electrical characteristics of devices are investigated and reviewed. The typical carbon concentrations in electronic-grade silicon are still some 10¹⁶ cm^?3. The small distribution coefficient (k₀ = 0.058) causes an inhomogeneous incorporation of carbon along the crystal axis and across the crystal diameter during crystal growth. Carbon concentrations exceeding about 5 × 10¹⁶ cm^?3 in float-zoned silicon can lead to the formation of process-induced defects in the fabrication of power rectifiers and thyristors. These defects which are frequently arranged in a swirl-like pattern strongly deteriorate the electrical characteristics of these devices. It is shown that carbon is involved primarily in the generation of the defect nuclei whereas the defects finally observed form via precipitation of oxygen and agglomeration of silicon interstitials. Reasons for the benign behavior of high carbon concentrations in the processing of integrated circuits are discussed. In powder device processing the formation of carbon-induced defects is safely avoided by application of silicon containing carbon less than 5 × 10¹⁶ cm^?3.     

Sex-specific analysis of cartilage volume in the knee joint--a quantitative MRI-based study

Thrombospondin-1 (TSP-1), an adhesive glycoprotein, plays an important role in platelet adhesion, inflammation, cell-to-cell interaction, and angiogenesis. TSP-1 is expressed by endothelial cells, fibroblasts, and macrophages. TSP-1's unique cysteine-serine-valine-threonine-cysteine-glycine (CSVTCG) specific receptor plays an important role in the binding and modulation of cellular adhesion and invasion. This article histologically and quantitatively evaluates TSP-1 and its CSVTCG receptor in adult burn wounds over time. Tissue was obtained from burn wounds on several days and samples that were 5 microns thick were placed on slides. Expression of TSP-1 and its CSVTCG receptor were evaluated immunohistochemically and quantitated by computer image analysis in units of absorbance. Immunoglobin G (IgG) (negative) controls were performed and subtracted from the TSP-1 sample to eliminate background absorbance readings. Serum (negative) control was used for the CSVTCG receptor. Platelet concentrates were used as the positive control. A quantitative examination of the results yielded the following information, expressed as absorbance +/- standard error of the mean: TSP-1: day 1, 62.0 +/- 10.13; day 3, 76.2 +/- 6.90; day 5, 36.0 +/- 3.96; day 7, 60.4 +/- 5.67; and day 9, 29.5 +/- 2.91. TSP-1 displays an early peak, followed by a steep decrease over the time period studied. The readings for the CSVTCG receptor are as follows: day 1, 33.8 +/- 1.87; day 3, 34.5 +/- 5.39; day 7, 39.1 +/- 1.93; day 21, 39.1 +/- 1.93; day 28, 34.8 +/- 3.67. In contrast, the CVSTCG receptor continues to be present in the wound over time. Histologic findings are reported, and photographs and a histopathologic analysis are included. The information presented in this article leads to the conclusion that temporal and histologic differences exist in the localization and expression of TSP-1 and its CSVTCG receptor. TSP-1 is up-regulated in injured tissues immediately after the injury; it is rapidly down-regulated as the tissue heals. In contrast, the levels of the CSVTCG receptor remain relatively constant during the healing process. These data are consistent with TSP-1's known role in cell-to-cell interaction, including the modulation of the growth factor and protease activity.     

Effects of ions on adenosine binding and enzyme activity of purified S-adenosylhomocysteine hydrolase from bovine kidney

The present investigation was undertaken to determine the effect of various ions on the characteristics of S-adenosylhomocysteine (SAH) hydrolase from bovine kidney. The binding sites of [3H]-adenosine to purified SAH hydrolase were not influenced by phosphate, magnesium, potassium, sodium, chloride or calcium ions at physiological cytosolic concentrations. To test whether NAD+ in the SAH hydrolase is essential for adenosine binding, we prepared the apoenzyme by removing NAD+ with ammonium sulfate. The resulting apoenzyme did not exhibit any [3H]-adenosine binding. Since the apoenzyme was enzymatically inactive, it is suggested that adenosine binds to the active site and not to an allosteric site of the intact enzyme. The kinetics of the hydrolysis and the synthesis of SAH catalyzed by the enzyme SAH hydrolase were measured in the presence and absence of phosphate and magnesium. Phosphate increased the Vmax for both synthesis and hydrolysis. However, only the affinity of adenosine for SAH synthesis was significantly enhanced from 10.1+/-1.3 microM to 5.4+/-0.5 microM by phosphate. This effect was already maximal at a phosphate concentration of 1 mM. All other tested ions were without effect on the enzyme activity. Our results show that phosphate at physiological concentrations shifts the thermodynamic equilibrium of SAH hydrolase in the direction of SAH synthesis. These findings imply that SAH-sensitive transmethylation reactions are inhibited during renal hypoxia when intracellular levels of phosphate, adenosine, and SAH are elevated.     

Extension of the k-ε model for the numerical simulation of the melt flow in induction crucible furnaces

Checking the calculations of turbulent melt flow in induction crucible furnaces that were carried out with various modifications of the two-dimensional (2-D)k-ε model using experimental findings has shown basic differences in the distributions of the specific generation of the turbulent energy and the kinetic energy of the turbulence. The discrepancies are explained by the distinctive three-dimensional (3-D) character of the pulsations and the low-frequency fluctuations of the macroscopic toroidal eddy; these are not taken into account in the numerical methods mentioned. With the aid of this 3-D model, the additional component of turbulent kinetic energy involved is estimated, and an approximation formula for the low-frequency component of the specific generation of turbulence is given. This results in an extension of the 2-Dk-ε model for a recirculated flow with several toroidal eddies, leading to good qualitative agreement of the characteristics of turbulent flow with the experimental findings. Since the numerical simulation—in agreement with industrial practice and the experiments carried out—demonstrates good effective mixing of the entire flow region, there is thus a possibility for the simulation of aterial transport in the melt of induction crucible furnaces as part of the widespread 2-D computation methods.