Quantum Effects in the Thermoelectric Power Factor of Low-Dimensional Semiconductors.

We theoretically investigate the interplay between the confinement length L and the thermal de Broglie wavelength Λ to optimize the thermoelectric power factor of semiconducting materials. An analytical formula for the power factor is derived based on the one-band model assuming nondegenerate semiconductors to describe quantum effects on the power factor of the low-dimensional semiconductors. The power factor is enhanced for one- and two-dimensional semiconductors when L is smaller than Λ of the semiconductors. In this case, the low-dimensional semiconductors having L smaller than their Λ will give a better thermoelectric performance compared to their bulk counterpart. On the other hand, when L is larger than Λ, bulk semiconductors may give a higher power factor compared to the lower dimensional ones.

Multicentre prospective study on dengue classification in four South-east Asian and three Latin American countries.

OBJECTIVE: To evaluate the existing WHO dengue classification across all age groups and a wide geographical range and to develop a revised evidence-based classification that would better reflect clinical severity. METHODS: We followed suspected dengue cases daily in seven countries across South-east Asia and Latin America and then categorised them into one of three intervention groups describing disease severity according to the overall level of medical and nursing support required. Using a pre-defined analysis plan, we explored the clinical and laboratory profiles characteristic of these intervention categories and presented the most promising options for a revised classification scheme to an independent group of WHO dengue experts for consideration. Potential warning signs were also evaluated by comparing contemporaneous data of patients who progressed to severe disease with the data of those who did not. RESULTS: A total of 2259 patients were recruited during 2006-2007 and 230 (13%) of the 1734 laboratory-confirmed patients required major intervention. Applying the existing WHO system, 47/210 (22%) of patients with shock did not fulfil all the criteria for dengue haemorrhagic fever. However, no three-tier revision adequately described the different severity groups either. Inclusion of readily discernible complications (shock/severe vascular leakage and/or severe bleeding and/or severe organ dysfunction) was necessary to devise a system that identified patients requiring major intervention with sufficient sensitivity and specificity to be practically useful. Only a small number of subjects (5%) progressed to severe disease while under observation; several warning signs were identified, but much larger studies are necessary to fully characterize features associated with disease progression. CONCLUSIONS: Based on these results, a revised classification system comprised of two entities, 'Dengue' and 'Severe Dengue', was proposed and has now been incorporated into the new WHO guidelines.

Comprehensive analyses and characterization of haemophagocytic lymphohistiocytosis in Vietnamese children.

Haemophagocytic lymphohistiocytosis (HLH) is a fatal haematological disorder with diverse aetiology. This prospective study was undertaken to characterize HLH cases in Vietnamese children. Clinical and laboratory data, genetic analyses and outcome of the HLH patients were analysed. A total of 33 patients were enrolled from March 2007 to December 2008, with a median age of 3 years. Mutations of the SH2D1A (SAP) and PRF1 genes were detected in one patient, respectively. The virus association was high, up to 63.6% (21/33), including Epstein-Barr virus (19/33), cytomegalovirus (2/33) and dengue virus (2/33). Five patients had malignant lymphoma and two had autoimmune diseases. Twenty-eight patients were treated according to the HLH-2004 protocol. The first response rate was 64.3% (18/28), with an early death rate of 35.7% (10/28). High levels of interferon-gamma, interleukin-10, MIG and interferon-inducible protein-10 (IP-10) were associated with early mortality (P < 0.05). Reactivation among the responders was high (9/18) and the uneventful resolution was low (3/18) after a median follow-up of 35 weeks. In conclusion, the majority of HLH cases are associated with virus infections in Vietnamese children. Familial HLH is rare. The frequent reactivation and high mortality demands a more appropriate therapeutic regimen in tropical areas like Vietnam.