Landscape science: a Russian geographical tradition

The Russian geographical tradition of landscape science (landshaftovedenie) is analyzed with particular reference to its initiator, Lev Semenovich Berg (1876-1950). The differences between prevailing Russian and Western concepts of landscape in geography are discussed, and their common origins in German geographical thought in the late nineteenth and early twentieth centuries are delineated. It is argued that the principal differences are accounted for by a number of factors, of which Russia's own distinctive tradition in environmental science deriving from the work of V. V. Dokuchaev (1846-1903), the activities of certain key individuals (such as Berg and C. O. Sauer), and the very different social and political circumstances in different parts of the world appear to be the most significant. At the same time it is noted that neither in Russia nor in the West have geographers succeeded in specifying an agreed and unproblematic understanding of landscape, or more broadly in promoting a common geographical conception of human-environment relationships. In light of such uncertainties, the latter part of the article argues for closer international links between the variant landscape traditions in geography as an important contribution to the quest for sustainability

THERMOELECTRIC PROPERTIES OF HOT-PRESSED p-TYPE Mg2Si0.3Sn0.7 SOLID SOLUTION

It is shown that thermoelectric energy conversion which gives the possibility for utilizing a low potential heat is one of the ways for adoption of energy-saving technologies; and semiconductor materials with p-type and n-type conductivities having high thermoelectric figure of merit are necessary for operation of thermoelectric generators. The paper deals with possibility of usage of the p-Mg2Si0.3Sn0.7 solid solution (with a nanostructured modification) as a couple for the well studied thermoelectric material based on n-Mg2Si-Mg2Sn. A technological scheme for fabrication of heavily doped Mg2Si0.3Sn0.7 solid solution of p-type by hot pressing from nanopowder is developed. The given technology has made it possible to reduce duration of a homogeneous material fabrication and has improved its physical and chemical properties. The samples were made by three ways: direct fusion for polycrystals fabrication; hot pressing from microparticles; nanostructuring, i.e. hot pressing from nanoparticles. By X-ray diffraction it is shown that sizes of structural elements in the fabricated samples are about 40 nm. The probe technique is used for measurement of electric conductivity and Seebeck coefficient. The stationary absolute method is used for measurement of thermal conductivity. Thermoelectric figure of merit is defined by measured values of kinetic coefficients in the temperatures range of 77 – 800 K. It was demonstrated, that electric conductivity, Seebeck coefficient and the power factor do not depend practically on a way of solid solution preparation. Thermal conductivity of samples pressed from nanoparticles has appeared to be higher, than of samples, obtained by direct fusion; i.e. in this case nanostructuring has not led to increase of thermoelectric figure of merit. The conclusion is drawn, that polycrystalline semiconductor Mg2Si0.3Sn0.7 can be used as a p-branch for a thermoelectric generator though nanostructuring has not led to the figure of merit growth. The assumption is made, that thermoelectric figure of merit improvement can be expected at the further reduction of the nanograins size

Cryopreservation of human ovarian tissue by direct plunging into liquid nitrogen: Negative effect of disaccharides in vitrification solution

Given that it has been possible to successfully cryopreserve human ovarian tissue by direct plunging into liquid nitrogen, this study was designed to establish the future direction to be taken in this line of research. Bovine oviductal epithelial fragments (as a tissue model) and large biopsy fragments (~2.0 mm3) of human ovarian tissue were used for cryopreservation. Two protocols were tested: with permeable cryoprotectants (dimethyl sulphoxide, propylene glycol, glycerol) + egg yolk + sucrose or trehalose + a synthetic blocker of ice nucleation, Supercool® X-1000; and using only permeable cryoprotectants (glycerol and ethylene glycol) + egg yolk + Supercool® X-1000. The cryopreserved tissue specimens were subsequently thawed and the cryoprotectants removed by dilution in graded sucrose solutions. Both the dynamic growth and hormonal activity of the ovarian tissue pieces, vitrified using only permeable cryoprotectants, were greater than after vitrification in a mixture of permeable cryoprotectants and sucrose. Unlike the case for other reproductive tissue (spermatozoa, oocytes, embryos), these findings suggest that the cryopreservation of ovarian tissue by direct plunging into liquid nitrogen must be achieved by vitrification using only permeable cryoprotectants and agents that prevention ice formation

Double vitrification of rat embryos at different developmental stages using an identical protocol

The aim of the present investigation was to test the effectiveness of a method of vitrifying rat embryos at different stages of development (from early morula to expanding blastocyst) in a double vitrification procedure. Wistar rat embryos were vitrified and warmed in super-fine open-pulled straws (SOPS). Before being plunged into liquid nitrogen, the embryos were exposed to 40% ethylene glycol + 0.75 M sucrose in TCM-199 + 20% fetal calf serum (FCS) for 20 s at 38°C. Subsequent warming and direct rehydration of the embryos was conducted in culture medium (TCM-199 + 20% FCS) at 38°C. Early morula stage (7-10 blastomeres) embryos (n = 358) were vitrified, warmed and cultured in vitro (EM group). Batches of these embryos were then cryopreserved again (revitrified) at the early blastocyst (EB group, n = 87), blastocyst (B group, n = 93) or expanding blastocyst stage (ExpB group, n = 73). After the first (EM group) and repeated (EB, B, and ExpB groups) vitrification procedures, developmental rates of 81, 83, 34 and 76%, respectively were achieved (for EM-EB-ExpB P > 0.1; for EM, EB, ExpB-B P < 0.005). Our data demonstrate the possibility of using the described identical protocol for the SOPS vitrification of rat early morulae, early blastocysts and expanding blastocysts. The low survival rate of blastocysts subjected to double vitrification requires further investigation

The Influence of Weak Tin Doping on the Thermoelectric Properties of Zinc Antimonide

ZnSb would be a good thermoelectric material with carrier concentration above 10^(19)/cm^3, but unfortunately this has been shown to be difficult to achieve, particularly with Sn as a dopant. Two series ZnSb samples doped with Sn and ZnSn were prepared using hot-pressing technics, and their thermoelectric properties were investigated in the temperature range from 300 K to 700 K. The tin content of the samples was in the range from 0.1 to 0.5 at.%. Surprisingly, samples with lower tin content achieved higher carrier concentration, which is beneficial for thermoelectric performance. Samples doped with 0.1 at.% Sn achieved Hall carrier concentration above 1 × 10^(19)/cm^3, reaching ZT of 0.9, while for samples doped with 0.5 at.% Sn, the Hall carrier concentration was close to the hole concentration of pure ZnSb. Also, by analyzing hysteresis present in the heating–cooling cycles, we conclude that the role of intrinsic defects in ZnSb is important and that these defects clearly determine the ability of ZnSb to achieve ZT near 1