Simulations for the Development of Thermoelectric Measurements

In thermoelectricity, continuum theoretical equations are usually used for the calculation of the characteristics and performance of thermoelectric elements, modules or devices as a function of external parameters (material, geometry, temperatures, current, flow, load, etc.). An increasing number of commercial software packages aimed at applications, such as COMSOL and ANSYS, contain vkernels using direct thermoelectric coupling. Application of these numerical tools also allows analysis of physical measurement conditions and can lead to specifically adapted methods for developing special test equipment required for the determination of TE material and module properties. System-theoretical and simulation-based considerations of favorable geometries are taken into account to create draft sketches in the development of such measurement systems. Particular consideration is given to the development of transient measurement methods, which have great advantages compared with the conventional static methods in terms of the measurement duration required. In this paper the benefits of using numerical tools in designing measurement facilities are shown using two examples. The first is the determination of geometric correction factors in four-point probe measurement of electrical conductivity, whereas the second example is focused on the so-called combined thermoelectric measurement (CTEM) system, where all thermoelectric material properties (Seebeck coefficient, electrical and thermal conductivity, and Harman measurement of zT) are measured in a combined way. Here, we want to highlight especially the measurement of thermal conductivity in a transient mode. Factors influencing the measurement results such as coupling to the environment due to radiation, heat losses via the mounting of the probe head, as well as contact resistance between the sample and sample holder are illustrated, analyzed, and discussed. By employing the results of the simulations, we have developed an improved sample head that allows for measurements over a larger temperature interval with enhanced accuracy.     

Use of adipose stem cells and polylactide discs for tissue engineering of the temporomandibular joint disc

There is currently no suitable replacement for damaged temporomandibular joint (TMJ) discs after discectomy. In the present study, we fabricated bilayer biodegradable polylactide (PLA) discs comprising a non-woven mat of poly(L/D)lactide (P(L/D)LA) 96/4 and a P(L/DL)LA 70/30 membrane plate. The PLA disc was examined in combination with adipose stem cells (ASCs) for tissue engineering of the fibrocartilaginous TMJ disc in vitro. ASCs were cultured in parallel in control and chondrogenic medium for a maximum of six weeks. Relative expression of the genes, aggrecan, type I collagen and type II collagen present in the TMJ disc extracellular matrix increased in the ASC-seeded PLA discs in the chondrogenic medium. The hypertrophic marker, type X collagen, was moderately induced. Alcian blue staining showed accumulation of sulphated glycosaminoglycans. ASC differentiation in the PLA discs was close to that observed in pellet cultures. Comparison of the mRNA levels revealed that the degree of ASC differentiation was lower than that in TMJ disc-derived cells and tissue. The pellet format supported the phenotype of the TMJ disc-derived cells under chondrogenic conditions and also enhanced their hyalinization potential, which is considered part of the TMJ disc degeneration process. Accordingly, the combination of ASCs and PLA discs has potential for the development of a tissue-engineered TMJ disc replacement.     

Test-taking behaviors in a neurocognitive assessment: Associations with school-age outcomes in a Finnish longitudinal follow-up.

Test-taking behaviors (i.e., task focus, maintenance of attention, and cooperation) affect children's cognitive test performance, and, thus, it is critical to take test-taking behavior into account when drawing conclusions and making recommendations. Prior studies have evaluated test-taking behaviors at the end of the assessment; the present study focused on the fluctuation of cooperation and attention during a neuropsychological assessment. We examined the attention and cooperation of 5-year-old children in a test-taking situation; the associations between these aspects of their test-taking behavior and the children's concurrent neurocognitive test performance, IQ, and parent-rated behavior; and the associations with their IQ, behavioral outcomes, and academic achievement at 8 years of age. The data (for 76 boys and 63 girls) were drawn from the Jyv?skyl? Longitudinal Study of Dyslexia (Lyytinen et al., 2001, 2004). All the children were Caucasian and spoke Finnish as their native language. As a whole, the 5-year-old children showed high cooperation and attention, but a slight decrement in test-taking behavior toward the end of the session was rather common. Three subgroups of children with different levels of cooperation and attention were identified. Children in the subgroup with nonoptimal attention and cooperation showed decreasing neurocognitive test performance toward the end of the assessment session. They also showed more inattentive behavior 3 years later. The findings imply that the examiner's observations of waning attention and cooperation during the assessment session are highly relevant, as these provide stable and clinically meaningful information about the child's behavioral tendencies. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Experimental studies for verification of thermal effects in cutting

Investigations on metal-cutting machining processes that were conducted since the second half of the twentieth century have considerably contributed to disclosing the principles underlying the cutting process. Although numerous studies have been carried out on this subject, a generally valid model of the cutting process and the interactions in the separating processes does not exist yet. Such a model could guarantee the disclosure of the principles of thermodynamic interactions between the cutting process and the involved machine structure. This contribution is twofold and presents an experimental setup used to determine cutting forces and temperatures in orthogonal cutting processes. The results are then used as a reference for simulations made with the Discrete Element Method (DEM). The DEM is due to its meshless nature well suited to capture large deformations and rupture of material which is included very naturally. It is examined to which extent the measured results can be captured with the DEM model.     

Simultaneous heat exchanger network synthesis for direct and indirect heat transfer inside and between processes

Process plants are typically divided into different process parts having specific processing tasks with possibly different ownership. Heat integration between these processes can increase the energy- and economic efficiency for both the overall plant and the individual processes. In this paper we present a heat exchanger network synthesis MINLP-model that allows simultaneous heat integration directly between streams in the same process and both directly and indirectly between streams in different processes. The indirect heat transfer is accomplished by using intermediate streams. Two examples, one small explanatory one and one from the literature, are optimized. The results verify that the model works logically.     

Role of microbes in controlling the speciation of arsenic and production of arsines in contaminated soils

The influence of microbes on the speciation of arsenic and production of arsines in contaminated soils was investigated under laboratory conditions. Microbes were able to carry out reactions that resulted in changes in the speciation of arsenic in soil. The transformation of soil dominating species, arsenate [As(V)], under both aerobic and anaerobic conditions to arsenite [As(III)], monomethylarsonic acid [MMAA], dimethylarsinic acid [DMAA] and to volatile trimethylarsine [TMA] was, however, less than 0.5%, of which the production of TMA represented 0.02-0.3%. The volatilization process was also verified in the field, in the soil of a dumping area. The 'life-time' of arsines in air was, however, short and they were rapidly converted back to water soluble species, As(V) and trimethyl arsine oxide (TMAO).     

Strength retention of drawn self-reinforced polyglycolide rods and fixation properties of the distal femoral osteotomies with these rods. An experimental study on rats

Drawn self-reinforced polyglycolide (SR-PGA) rods, Ø 2 mm and 26 mm long, were implanted in the dorsal subcutaneus tissue of 16 rats. Osteotomies of the distal femur were fixed with SR-PGA rods (2 mm by 15 mm) in another 38 rats. The follow-up times varied from one week to one year. After sacrifice, three-point bending and shear tests were performed for subcutaneously placed rods. Radiological, histological, histomorphometrical, microradiographic, and oxytetracycline-fluorescence studies of osteotomized and intact control femora were also performed. At three weeks the flexural strength of the rods was 50% of the initial value, and the flexural modulus was 46% of the initial value. Five osteotomy specimens had to be excluded due to dislocation or non-union. One of the 33 evaluated osteotomy specimens showed signs of postoperative infection. Thirty-two osteotomies healed uneventfully. No gross signs of inflammatory or foreign-body reaction were observed. The amount of osteoid surface and active osteoid formation surface reached their highest value in the histomorphometrical analysis at 24 weeks. The present investigation demonstrated that the mechanical strength and fixation properties of the drawn SR-PGA rods are suitable for fixation of cancellous bone osteotomies in rats. The present article is the first report on the successful application of drawn SR-PGA rods for fixation of cancellous bone osteotomies.     

Protein identification by MALDI-TOF-MS peptide mapping: a new strategy

A new strategy for identifying proteins by MALDI-TOF-MS peptide mapping is reported. In contrast to current approaches, the strategy does not rely on a good relative or absolute mass accuracy as the criterion that discriminates false positive results. The protein sequence database is first searched for all proteins that match a minimum five of the submitted masses within the maximum expected relative errors when the default or externally determined calibration constants are used, for instance, +/-500 ppm. Typically, this search retrieves many thousand candidate sequences. Assuming initially that each of these is the correct protein, the relative errors of the matching peptide masses are calculated for each candidate sequence. Linear regression analysis is then performed of the calculated relative errors as a function of m/z for each candidate sequence, and the standard deviation to the regression is used to distinguish the correct sequence among the candidates. We show that this parameter is independent of whether the mass spectrometric data were internally or externally calibrated. The result is a search engine that renders internal spectrum calibration unnecessary and adapts to the quality of the raw data without user interference. This is made possible by a dynamic scoring algorithm, which takes into account the number of matching peptide masses, the percentage of the protein's sequence covered by these peptides and, as new parameter, the determined standard deviation. The lower the standard deviation, the less cleavage peptides are required for identification and vice versa. Performance of the new strategy is demonstrated and discussed. All necessary computing has been implemented in a computer program, free access to which is provided in the Internet.     

Interpersonal violations,speeding violations and their relation to accident involvement in Finland

The aim of the present study was to replicate the distinction between errors, lapses and violations, and to identify aggressive violations from normal or highway code violations. Furthermore, the relationship of these behaviours with road traffic accidents was examined. A total number of 1126 Finnish drivers completed a questionnaire containing the Driver Behaviour Questionnaire (DBQ) with extended violations scale, and questions regarding background information, such as age, gender and mileage. Also, questions about previous accidents and fines were asked. Factor analysis showed that a four-factor structure seemed more appropriate than the earlier established three-factor structure. The four factors were errors, lapses, speeding violations and interpersonal violations. The two types of violations result from different motives, and seem to be associated with different kinds of affect. Both interpersonal and speeding violations were reported most by young males, which was consistent with earlier findings. Logistic regression analyses indicated that errors predicted active accident involvement after partialling out the effects of demographic variables, whereas interpersonal violations were positively related to involvement in passive accidents. This was presumably due to different reporting tendencies of respondents. Speeding tickets were predicted by speeding and interpersonal violations and lapses and penalties for speeding by both kinds of violations and errors. Penalties for speeding, parking and other offences were predicted by interpersonal violations. The implications of these results are discussed.