Non-Rigid Band Structure in Mg2Ge for Improved Thermoelectric Performance

Magnesium silicide and its solid solutions are among the most attractive materials for thermoelectric generators in the temperature range of 500-800 K. However, while n-type Mg2(Si,Ge,Sn) materials show excellent thermoelectric performance, the corresponding p-type solid solutions are still inferior, mainly due to less favorable properties of the valence bands compared to the conduction bands. Here, Li doped Mg2Ge with a thermoelectric figure of merit zT of 0.5 at 700 K is reported, which is four times higher than that of p-type Mg2Si and double than that of p-type Mg2Sn. The reason for the excellent properties is an unusual temperature dependence of Seebeck coefficient and electrical conductivity compared to a standard highly doped semiconductor. The properties cannot be captured assuming a rigid band structure but well reproduced assuming two parabolic valence bands with a strong temperature dependent interband separation. According to the analysis, the difference in energy between the two bands decrease with temperature, leading to a band convergence at around 650 K and finally to an inversion of the band positions. The finding of a combination of a light and a heavy band that are non-rigid with temperature can pave the way for further optimization of p-type Mg2(Si,Ge,Sn).

Preliminary study on the effect of a herbal formulation "Deepaniyavati" in hyperlipidemia

To examine the effect of "DeepaniyaVati", a herbal formulation in the management of hyperlipidemia, a randomized group pre-test post-test study trial was carried out on fifty male (30 to 70 yrs) hyperlipidemic volunteers who were asked to follow their normal routine diet and activity pattern throughout the investigation period. The formulation, prepared by mixing nine plant products in equal proportion, when given in a daily dose of 2g, twice a day for a period of one month, brought about an observable improvement in all the lipid parameters by significantly reducing total cholesterol (10%), low density lipoprotein cholesterol (12.76%), very low density lipoprotein cholesterol (27.4%), triglycerides (34.7%) and bringing these values much nearer to the normal levels. In control group, no such effect was noticed. A concomitant significant increase in the HDL-C levels suggests the possible utility of "Deepaniya Vati" in the management of hyperlipidemia and the need for further detailed study.

Influence of growth regulators on somatic embryogenesis, plantlet regeneration, and post-transplant survival of Echinochloa frumentacea

After placement on Murashige and Skoog's basal medium supplemented with 3-5 mg/l 2,4-D, immature inflorescence expiants of Echinochloa frumentacea gave rise to three distinct types of callus: a) loosely arranged and soft; b) compact and translucent; c) compact, sticky and mucilaginous. Somatic embryo formation occurred in type 'b' callus in about 18-24 d. Callus types 'a' and 'c' did not produce somatic embryos. The highest percentage of cultures exhibiting somatic embryogenesis occurred on the medium containing 5 mg/l 2,4-D and 0.5 mg/l kinetin. Somatic embryos also formed directly on the inflorescence (without intervening callus formation) in about 15% of the expiants placed on this medium. The addition of paclobutrazol or uniconazole (0.25 or 1 mg/l) to the medium had no influence on the percentage of cultures exhibiting direct somatic embryogenesis, but paclobutrazol slightly increased the mean number of somatic embryos per culture. Many of the callus-derived somatic embryos germinated when subcultured on basal MS medium supplemented with kinetin. Addition of paclobutrazol or uniconazole to the culture medium at 0.25 or 1 mg/l decreased somatic embryo germination and shoot elongation but increased root length and leaf width. Both paclobutrazol and uniconazole increased survival of the plantlets following transplanting to soil. Increased post-transplant survival was accompanied by reduced water loss from plantlets produced on culture media containing triazoles.