Social Aspects of CSCL Environments: A Research Framework

Although there are research findings supporting the positive effects of computer-supported col- laborative learning (CSCL), problems have been reported regarding the learning process itself, group formation, and group dynamics. These problems can be traced back to impeded social interaction between group members. Social interaction is necessary (a) for group members to learn from each other in a CSCL environment and (b) for socioemotional processes to help cre- ate a social space where trust, sense of community, and strong interpersonal relationships exist. This article introduces a theoretical framework consisting of three core elements: sociability, social space, and social presence, along with their relationships with group members’ mental models, social affordances and learning outcomes. It postulates that the three core elements influence the social interaction needed for both learning and the emergence of a social space. This framework serves as a basis for a research agenda for systematic social CSCL research

Reversible amorphous-crystalline phase changes in a wide range of Se1-xTex alloys studied using ultrafast differential scanning calorimetry

The reversible amorphous-crystalline phase change in a chalcogenide material, specifically the Se1-xTex alloy, has been investigated for the first time using ultrafast differential scanning calorimetry. Heating rates and cooling rates up to 5000 K/s were used. Repeated reversible amorphous-crystalline phase switching was achieved by consecutively melting, melt-quenching, and recrystallizing upon heating. Using a well-conditioned method, the composition of a single sample was allowed to shift slowly from 15 at. % Te to 60 at. % Te, eliminating sample-to-sample variability from the measurements. Using Energy Dispersive X-ray Spectroscopy composition analysis, the onset of melting for different Te-concentrations was confirmed to coincide with the literature solidus line, validating the use of the onset of melting T-m as a composition indicator. The glass transition T-g and crystallization temperature T-c could be determined accurately, allowing the construction of extended phase diagrams. It was found that T-m and T-g increase (but T-g/T-m decrease slightly) with increasing Te-concentration. Contrarily, the T-c decreases substantially, indicating that the amorphous phase becomes progressively unfavorable. This coincides well with the observation that the critical quench rate to prevent crystallization increases about three orders of magnitude with increasing Te concentration. Due to the employment of a large range of heating rates, non-Arrhenius behavior was detected, indicating that the undercooled liquid SeTe is a fragile liquid. The activation energy of crystallization was found to increase 0.5-0.6 eV when the Te concentration increases from 15 to 30 at. % Te, but it ceases to increase when approaching 50 at. % Te. (C) 2014 AIP Publishing LLC

Expression of hypoxia-induced proteins in ductal carcinoma in situ and invasive cancer of the male breast

AIMS: The aim of this study was to determine the role of hypoxia in male breast carcinogenesis by evaluating the expression of the hypoxia-related proteins, hypoxia-inducible factor-1α (HIF-1α), carbonic anhydrase IX (CAIX) and glucose transporter-1 (Glut-1), in ductal carcinoma in situ (DCIS) of the male breast in relation to invasive cancer (IC). METHODS: Tumour tissue blocks of 18 cases of pure DCIS, 58 DCIS cases adjacent to IC (DCIS-AIC) and the 58 IC cases were stained by immunohistochemistry for HIF-1α, CAIX and Glut-1, and expression frequencies and patterns (diffuse and/or perinecrotic) were noted. RESULTS: HIF-1α overexpression was observed in 61.1% (11/18) of pure DCIS, in 37.9% (22/58) of DCIS-AIC and in 36.2% (21/58) of IC cases (not significant (n.s.)). CAIX overexpression was observed in 16.7% (3/18) of pure DCIS, in 37.9% (22/58) of DCIS-AIC and in 24.1% (14/58) of IC cases (n.s.). Glut-1 overexpression was observed in 61.1% (11/18) of pure DCIS, in 75.9% (44/58) of DCIS-AIC and in 62.1% (36/58) of IC cases (n.s.). Expression of hypoxia-related proteins was seen around necrosis in a little over one-third of DCIS cases, and often coincided with expression in adjacent IC when present. All these observations indicate that the hypoxia response is already at its maximum in the preinvasive DCIS stage. CONCLUSIONS: In conclusion, male DCIS frequently shows activated hypoxia response, comparable to male IC. This indicates that the activated hypoxia response previously seen in male IC is not a late bystander but likely a genuine carcinogenetic event

Strain Relaxation in "2D/2D and 2D/3D Systems":Highly Textured Mica/Bi2Te3, Sb2Te3/Bi2Te3, and Bi2Te3/GeTe Heterostructures

Strain engineering as a method to control functional properties has seen in the last decades a surge of interest. Heterostructures comprising 2D-materials and containing van der Waals(-like) gaps were considered unsuitable for strain engineering. However, recent work on heterostructures based on Bi2Te3, Sb2Te3, and GeTe showed the potential of a different type of strain engineering due to long-range mutual straining. Still, a comprehensive understanding of the strain relaxation mechanism in these telluride heterostructures is lacking due to limitations of the earlier analyses performed. Here, we present a detailed study of strain in two-dimensional (2D/2D) and mixed dimensional (2D/3D) systems derived from mica/Bi2Te3, Sb2Te3/Bi2Te3, and Bi2Te3/GeTe heterostructures, respectively. We first clearly show the fast relaxation process in the mica/Bi2Te3 system where the strain was generally transferred and confined up to the second or third van der Waals block and then abruptly relaxed. Then we show, using three independent techniques, that the long-range exponentially decaying strain in GeTe and Sb2Te3 grown on the relaxed Bi2Te3 and Bi2Te3 on relaxed Sb2Te3 as directly observed at the growth surface is still present within these three different top layers a long time after growth. The observed behavior points at immediate strain relaxation by plastic deformation without any later relaxation and rules out an elastic (energy minimization) model as was proposed recently. Our work advances the understanding of strain tuning in textured heterostructures or superlattices governed by anisotropic bonding

Enteral Glutamine Administration in Critically Ill Nonseptic Patients Does Not Trigger Arginine Synthesis

Glutamine supplementation in specific groups of critically ill patients results in favourable clinical outcome. Enhancement of citrulline and arginine synthesis by glutamine could serve as a potential mechanism. However, while receiving optimal enteral nutrition, uptake and enteral metabolism of glutamine in critically ill patients remain unknown. Therefore we investigated the effect of a therapeutically relevant dose of L-glutamine on synthesis of L-citrulline and subsequent L-arginine in this group. Ten versus ten critically ill patients receiving full enteral nutrition, or isocaloric isonitrogenous enteral nutrition including 0.5 g/kg L-alanyl-L-glutamine, were studied using stable isotopes. A cross-over design using intravenous and enteral tracers enabled splanchnic extraction (SE) calculations. Endogenous rate of appearance and SE of glutamine citrulline and arginine was not different (SE controls versus alanyl-glutamine: glutamine 48 and 48%, citrulline 33 versus 45%, and arginine 45 versus 42%). Turnover from glutamine to citrulline and arginine was not higher in glutamine-administered patients. In critically ill nonseptic patients receiving adequate nutrition and a relevant dose of glutamine there was no extra citrulline or arginine synthesis and glutamine SE was not increased. This suggests that for arginine synthesis enhancement there is no need for an additional dose of glutamine when this population is adequately fed. This trial is registered with NTR228

Patient-reported health outcomes in long-term lung transplantation survivors

During the last three decades lung transplantation (LTx) has become a proven modality for increasing both survival and health-related quality of life (HRQoL) in patients with various end-stage lung diseases. Most previous studies have reported improved HRQoL shortly after LTx. With regard to long-term effects on HRQoL, however, the evidence is less solid. This prospective cohort study was started with 828 patients who were on the waiting list for LTx. Then, in a longitudinal follow-up, 370 post-LTx patients were evaluated annually for up to 15 years. For all wait-listed and follow-up patients, the following four HRQoL instruments were administered: State-Trait Anxiety Inventory, Zung Self-rating Depression Scale, Nottingham Health Profile, and a visual analogue scale. Cross-sectional and generalized estimating equation (GEE) analysis for repeated measures were performed to assess changes in HRQoL during follow-up. After LTx, patients showed improvement in all HRQoL domains except pain, which remained steady throughout the long-term follow-up. The level of anxiety and depressive symptoms decreased significantly and remained constant. In conclusion, this study showed that HRQoL improves after LTx and tends to remain relatively constant for the entire life span