Learners' questions and comprehension in a tutoring setting.

Three experiments, presented within the framework of Activity Theory, deal with the relationship between adult learners' questions and subsequent comprehension in a tutorial learning setting. Students were first given verbal instructions (acquisition) to a novel card game and then asked to play one hand with the teacher (implementation). In Experiment 1, there was no correlation between number of questions asked during acquisition and comprehension, but questions during implementation were negatively correlated with comprehension. In Experiment 2, learners whose questions were answered during acquisition scored higher than those whose questions were not answered. In Experiment 3, learners whose questions were answered during implementation showed greater gains in comprehension than those whose questions were answered during acquisition. Individual differences in question-asking during implementation but not acquisition were significantly related to comprehension. The results confirm the view that questions answered during knowledge implementation more effectively aid comprehension than those answered during acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms for the formation of low temperature,non-alloyed Au-Ge ohmic contacts to n-GaAs

Low temperature, non-alloyed Au-Ge contact formation ton-GaAs is a multi-step pro-cess. During the first 5 min of annealing at 320° C the Au and Ge segregate into regions a few microns in size and extend over the entire thickness of the metal layer and sig-nificant in-diffusion of the Au and Ge and out-diffusion of the Ga and As occurs. This intermixing reduces the barrier height from 0.75 to 0.40 eV. The contact does not show ohmic behavior until it has been annealed for 3 hr. During this time Ge continues to in-diffuse but at a slower rate than it did initially. The rate of Ge in-diffusion is en-hanced by the presence of Au since samples containing less Au require longer anneals to show ohmic behavior and have higher specific contact resistances. The presence of excess As, which is prevented from evaporating by a Si₃N₄ cap has the opposite effect since capped layers have higher specific contact resistances. Au-Ge phases appear after approximately 3 hr of annealing, therefore, Au-Ge phases cannot be responsible for the reduction in barrier height. The interface morphology is smooth, differing from that of pure Au and alloyed contacts that often contain spiking of the metals into the semi-conductor. The orientation relationship for the Au grains differs from that of pure Au. Work performedat U.S. Army ETDL, Fort Monmouth, NJ 07703. Work performed at U.S.Army ETDL, Fort Monmouth, NJ 07703.     

An extended shear angle model derived from in situ strain measurements during orthogonal cutting

There are numerous cutting models which describe the chip formation process. However, they are based on a number of simplifying assumptions. In order to verify these assumptions and to get a better understanding of the cutting process, the different stress states in the chip formation zone were determined by means of diffraction experiments with monochromatic high-energy synchrotron X-radiation during orthogonal, quasistatic cutting of the material C45E. The results from the experiments are compared with simulated stresses. The experimental data indicate that the assumption of a free chip flow according to the shear angle model of Opitz and Hucks is not valid. The model was therefore extended considering the normal stresses in direction of the chip flow.     

Die Bestimmung von St?rke in Pektin- und Apfels?ften auf sedimentrischem Wege

Ohne Zusammenfassung     

Structure of adrenodoxin and function in mitochondrial steroid hydroxylation

The three-dimensional structure of a truncated mutant of bovine adrenodoxin has been resolved at 1.85 A resolution by MAD. The protein consists of a large core region and a more flexible hairpin loop bearing residues which have been previously described as being involved in redox partner recognition. To study the role of distinct protein domains and amino acids of adrenodoxin in interaction with adrenodoxin reductase (AdR), CYP11A1 and CYP11B1, as well as in electron transfer, mutants of adrenodoxin have been prepared by site-directed mutagenesis and produced in Escherichia coli, and their structural and functional properties have been characterized in detail. It could be demonstrated that Tyr82 is located at the edge of the flexible interaction loop of adrenodoxin participating in interactions with AdR and P450s. His56, being close to Tyr82, forms a bridge between the core region of adrenodoxin and the interaction loop. Its role in transmitting changes of the cluster region to the interaction site has also been supported by functional studies. Pro108 of adrenodoxin, the only proline residue contained in the protein and being conserved in this position among several other vertebrate-type ferredoxins, has been demonstrated to be of importance for the correct folding of this protein.     

Characterization of Mo/Au Transition-Edge Sensors with Different Geometric Configurations

Mo/Au transition-edge sensors exhibit weak-link behavior in the measured temperature, \(T\) and field, \(B\) dependence of the critical current \(I_\mathrm{{C}}(T,B)\) . This is a consequence of the longitudinal proximitization between the Nb electrical bias contacts and the bilayer. Understanding how weak-link superconductivity impacts the resistive transition and the detector energy resolution is of great interest. In this contribution we present studies of \(I_\mathrm{{C}}(T,B)\) for three devices that have different geometries of metallic depositions on top of the sensor used for noise mitigation and X-ray absorption. Results show that these features change the measured \(I_\mathrm{{C}}(T,B)\) compared to the previously seen measurements on devices without additional deposition layers. Measurements of the small signal transition parameters \(\alpha \) and \(\beta \) also reveal differences between designs that impact the measured response to X-rays and energy resolution.     

High Count-Rate Studies of Small-Pitch Transition-Edge Sensor X-ray Microcalorimeters

We are developing kilo-pixel arrays of small-pitch transition-edge sensors for high spectral-resolving, high count-rate applications in astrophysics and solar physics measurements. We have fabricated and tested pixels that are \(65\,\upmu \) m in size on a silicon substrate with an X-ray flux of \({\sim }100\) counts per second (cps) per pixel. The X-ray pulses were recorded and analyzed in various ways to obtain high throughput with good energy resolution. We have demonstrated 2.3 eV FWHM resolution with 99.6 % throughput for a 6-keV X-ray flux of 100 cps.     

A potent cell death activity associated with transient high level expression of BCL-2

The BCL-2 proto-oncogene contains unusually long untranslated 5' and 3' sequences. Deletion of the sequences flanking the BCL-2 open reading frame dramatically increases the level of protein expression. Transient high level BCL-2 protein expression mediated by plasmid transfection or by infection with recombinant adenovirus results in potent apoptosis of several cell lines. Detailed mutational (deletion and add-back) analysis reveals that both 5'- and 3'-flanking sequences contribute to the negative modulation of protein expression from the BCL-2 open reading frame. It appears that these sequences exert the negative regulatory effect in an orientation-dependent manner. Analysis of BCL-2 RNA levels indicate that elevated levels of mRNA may be the primary cause of elevated levels of protein expression. Apoptosis induced by adenovirus vectors expressing elevated levels of BCL-2 can be readily inhibited by the caspase inhibitor z-VAD-fmk, suggesting that high levels of BCL-2 expression induce apoptosis via the caspase cascade. Mutational analysis of BCL-2 indicates that its pro-apoptotic activity is separable from its anti-apoptosis activity. Our results raise the possibility that oncogenic conversion of BCL-2 may require somatic mutations in the pro-apoptotic activity, in addition to other activating mutations that result in enhanced expression. Consistent with this hypothesis, a somatic mutation of BCL-2 observed in multiple human tumors results in reduced apoptosis activity.     

Design of conical and toriconical shells under internal pressure based on finite-elements-analyses

Existing design codes propose different methods for the analysis for the junction region of conical and toriconical shells (limit analysis, shake down analysis, Kellog design approach, area replacement method) submitted to internal pressure load. However, now it is possible to develop generally valid an very precise guidelines based on linear and nonlinear Finite Elements-Analyses. A clear difference is made between design with respect to fatigue strength and design according to load carrying capacity criteria. A. Major advantage of the Finite-Elements-Method(FEM) is the opportunity of its adaptation to given design criteria such as a strain limit or a plastification limit. It shown how design curves can be directly derived from the FE-analysis with respect to fatigue strength (stress concentration factors) and load carrying capacity (design factors for the calculation of a required wall thickness). The materials behavior in the plastic region is considered with an without strain hardening. Large deformation effects as geometric nonlinearities can be involved in the analysis. The method can easily be applied for the analysis of other pressure vessel components.