Preparation of Ring-Shaped Thermoelectric Legs from PbTe Powders for Tubular Thermoelectric Modules

Waste heat recovery—for example, in automotive applications—is a major field for thermoelectric research and future application. Commercially available thermoelectric modules are based on planar structures, whereas tubular modules may have advantages for integration and performance in the field of automotive waste heat recovery. One major drawback of tubular generator designs is the necessity for ring-shaped legs made from thermoelectric material. Cutting these geometries from sintered tablets leads to considerable loss of thermoelectric material and therefore high cost. Direct sintering of ring-shaped legs or tubes of thermoelectric material is a solution to this problem. However, sintering such rings with high homogeneity and density faces some difficulties related to the mechanical properties of typical thermoelectric materials such as lead telluride (PbTe)—particularly brittleness and high coefficient of thermal expansion. This work shows a process for production of thermoelectric rings made of p- and n-doped PbTe. Long tubes of PbTe have been sintered in a current-assisted sintering process with specially designed sintering molds, coated with a diffusion barrier, and finally cut into ring-shaped slices. To demonstrate the technology, a tubular thermoelectric module has been assembled using these PbTe rings.     

The social bookmark and publication management system bibsonomy

Social resource sharing systems are central elements of the Web 2.0 and use the same kind of lightweight knowledge representation, called folksonomy. Their large user communities and ever-growing networks of user-generated content have made them an attractive object of investigation for researchers from different disciplines like Social Network Analysis, Data Mining, Information Retrieval or Knowledge Discovery. In this paper, we summarize and extend our work on different aspects of this branch of Web 2.0 research, demonstrated and evaluated within our own social bookmark and publication sharing system BibSonomy, which is currently among the three most popular systems of its kind. We structure this presentation along the different interaction phases of a user with our system, coupling the relevant research questions of each phase with the corresponding implementation issues. This approach reveals in a systematic fashion important aspects and results of the broad bandwidth of folksonomy research like capturing of emergent semantics, spam detection, ranking algorithms, analogies to search engine log data, personalized tag recommendations and information extraction techniques. We conclude that when integrating a real-life application like BibSonomy into research, certain constraints have to be considered; but in general, the tight interplay between our scientific work and the running system has made BibSonomy a valuable platform for demonstrating and evaluating Web 2.0 research.     

Medication take-home doses and contingency management.

Two studies examined contingent take-home medication doses during treatment of opiate or cocaine dependence. In the first study, methadone maintenance patients were randomly assigned to one of two 8-week baseline take-home (TH) conditions differing in frequency of clinic visits per week. This was followed by a 12-week contingency management (CM) procedure in which frequent THs resulted from drug-free urines. Participants receiving more frequent THs during baseline had lower illicit drug use during the first 6 weeks of CM. In the second study, fluoxetine (0-, 20-, 40-mg) TH doses were similarly contingent in treatment of cocaine dependence. The 40-mg group used less cocaine during contingency than did other groups. The combination of fluoxetine and environmental contingencies may produce benefit where neither alone is sufficient. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural analysis of the GAP-related domain from neurofibromin and its implications

Neurofibromin is the product of the NF1 gene, whose alteration is responsible for the pathogenesis of neurofibromatosis type 1 (NF1), one of the most frequent genetic disorders in man. It acts as a GTPase activating protein (GAP) on Ras; based on homology to p120GAP, a segment spanning 250-400 aa and termed GAP-related domain (NF1GRD; 25-40 kDa) has been shown to be responsible for GAP activity and represents the only functionally defined segment of neurofibromin. Missense mutations found in NF1 patients map to NF1GRD, underscoring its importance for pathogenesis. X-ray crystallographic analysis of a proteolytically treated catalytic fragment of NF1GRD comprising residues 1198-1530 (NF1-333) of human neurofibromin reveals NF1GRD as a helical protein that resembles the corresponding fragment derived from p120GAP (GAP-334). A central domain (NF1c) containing all residues conserved among RasGAPs is coupled to an extra domain (NF1ex), which despite very limited sequence homology is surprisingly similar to the corresponding part of GAP-334. Numerous point mutations found in NF1 patients or derived from genetic screening protocols can be analysed on the basis of the three-dimensional structural model, which also allows identification of the site where structural changes in a differentially spliced isoform are to be expected. Based on the structure of the complex between Ras and GAP-334 described earlier, a model of the NF1GRD-Ras complex is proposed which is used to discuss the strikingly different properties of the Ras-p120GAP and Ras-neurofibromin interactions.     

Platelet morphology in patients with mechanical circulatory support

OBJECTIVE: Mechanical circulatory support is a therapy for patients with end stage cardiac insufficiency. The thromboembolic events are feared complications during support, due to the surface thrombogenicity of the implanted device. Activated blood platelets play a major role in this context. Consequently the platelet morphology of patients was investigated. METHODS: Platelets of eight patients were observed by means of scanning electron microscopy during the period of support with the Novacor left ventricular assist system N100. Blood was collected preoperatively and daily during the first week as well as weekly during the first 3 months. Samples were fixed with cacodylic-acid buffered glutaraldehyde. Platelet alterations were classified as non-activated, activated and aggregated, based on the so-called 'shape change' morphology. In addition, blood coagulation parameters were evaluated (e.g. activated partial thromboplastin time, prothrombin time, antithrombin III). RESULTS: Preoperatively, 15.0 +/- 4.6% (overall mean values) of activated platelets were found. Within the first postoperative week, the mean level of activated platelets increased to 32.8 +/- 8.0% (P < 0.05). Comparing short- (< 30 days; n = 4) vs. long-period (> 30 days; n = 4) support, a significant difference of activated platelets was evaluated (24.3 +/- 3.3% vs. 34.8 +/- 3.4%, P = 0.004). A correlation was found between the values of activated clotting time and activated platelets. Specific platelet deformations and damages appeared during support, which could not be found preoperatively. CONCLUSIONS: The platelet morphology showed alterations in all patients probably most strongly induced by the surface activation of the implanted device. These observations should be taken into consideration in management of postoperative anticoagulation therapy.     

Resonant measurements of surface resistance of high-Tc superconducting films: How good or bad are they?

Errors in measurements of surface resistanceR _s of HTS materials are due to discrepancy between a mathematical model describing physical phenomena and a real measurement environment, finite accuracy of measurements of theQ-factor, and finite accuracy of constants used for calculation ofR _s . In this paper we analyze errors inR _s due to uncertainties in theQ-factor, geometrical coefficients, loss tangent,R _scu, and other factors when a cylindrical copper cavity with an HTS end plate, a stripline resonator, and sapphire rod resonators are used for HTS characterization.     

The V3-directed immune response in natural human immunodeficiency virus type 1 infection is predominantly directed against a variable, discontinuous epitope presented by the gp120 V3 domain

The specific binding of antibodies to the V3 loop in sera from human immunodeficiency type 1 (HIV-1)-infected individuals was investigated. Different V3 structures were analyzed as full-length loops or by pepscan. Our data show that on full-length V3 loops, both variable regions on either side of the tip of the loop (GPGRAF) contribute to a common epitope for type-specific antibodies. Type-specific antibodies bound strongly and at high titers to native V3 loops but negligibly once the loop was denatured. In contrast to the type-specific, discontinuous epitope, the linear, conserved epitopes presented by the full-length V3 loop, the tip, the amino-terminal base, and the carboxy-terminal base were not accessible to serum antibody. When the V3 sequences were analyzed with linear peptides, antibodies bound preferentially to peptides containing the conserved GPGRAF sequence. Thus, two different specificities of V3-directed antibodies were detected in patient sera. Unlike group-specific antibodies directed against GPGRAF peptides, lack of type-specific antibodies directed against the discontinuous epitope was correlated with viral escape from autologous neutralization. Our data suggest that the full-length conformation of the V3 loop is accessible predominantly to highly type-specific antibodies present in sera from HIV-1-infected individuals. These antibodies are directed against discontinuous V3 epitopes, not against conserved linear V3 targets. The implications of these findings for viral escape and blockade of infection with V3-based vaccines are discussed.