Električna vodljivost, Hallov koeficijent i termoelektrična snaga ikosaedarskih i-Al 62Cu25.5Fe12.5 i i-Al63Cu25Fe12 kvazikristala

The electrical conductivity, Hall coefficient and thermoelectric power of icosahedral i-Al62Cu25.5Fe12.5 quasicrystal samples in the temperature range 2 K - 340 K are measured, and comparison with icosahedral i-Al63Cu25Fe12 quasicrystal samples is made. We have analysed the temperature dependence of the conductivity below 70 K and the results of this analysis are consistent with the predictions of the weak-localisation and the electron-electron interaction theories. The temperature dependence of the electrical conductivity, Hall coefficient and thermoelectric power above 40 K are consistently explained by a two-band model. Although the overlapping of the valence and conduction bands at Fermi level is responsible for the coexistence of both types of carriers, and it enables us to describe quasicrystals as semi-metals, the temperature variation of the electrical conductivity is determined by that of carrier density which makes the situation essentially the same as that in normal semiconductors.Mjerili smo električnu vodljivost, Hallov koeficijent i termoelektričnu snagu uzorka ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5 u području temperature 2 K – 340 K i usporedili s uzorkom ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5. Analizirali smo temperaturnu ovisnost električne vodljivosti ispod 70 K i ustanovili da su rezultati u skladu s predviđanjima teorija slabe lokalizacije i međudjelovanja elektronelektron. Ovisnost električne vodljivosti, Hallovog koeficijenta i termoelektrične snage o temperaturi iznad 40 K uspješno se objašnjava modelom dviju vrpci. Iako je predodžba o preklapanju valentne i vodljive vrpce na Fermijevoj razini odgovorna za istovremeno postojanje dviju vrsta nositelja i za opis kvazikristala kao polumetala, temperaturna ovisnost električne vodljivosti je, kao i kod normalnih poluvodiča, određena promjenom gustoće nositelja

Električna vodljivost, Hallov koeficijent i termoelektrična snaga ikosaedarskih i-Al 62Cu25.5Fe12.5 i i-Al63Cu25Fe12 kvazikristala

The electrical conductivity, Hall coefficient and thermoelectric power of icosahedral i-Al62Cu25.5Fe12.5 quasicrystal samples in the temperature range 2 K - 340 K are measured, and comparison with icosahedral i-Al63Cu25Fe12 quasicrystal samples is made. We have analysed the temperature dependence of the conductivity below 70 K and the results of this analysis are consistent with the predictions of the weak-localisation and the electron-electron interaction theories. The temperature dependence of the electrical conductivity, Hall coefficient and thermoelectric power above 40 K are consistently explained by a two-band model. Although the overlapping of the valence and conduction bands at Fermi level is responsible for the coexistence of both types of carriers, and it enables us to describe quasicrystals as semi-metals, the temperature variation of the electrical conductivity is determined by that of carrier density which makes the situation essentially the same as that in normal semiconductors.Mjerili smo električnu vodljivost, Hallov koeficijent i termoelektričnu snagu uzorka ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5 u području temperature 2 K – 340 K i usporedili s uzorkom ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5. Analizirali smo temperaturnu ovisnost električne vodljivosti ispod 70 K i ustanovili da su rezultati u skladu s predviđanjima teorija slabe lokalizacije i međudjelovanja elektronelektron. Ovisnost električne vodljivosti, Hallovog koeficijenta i termoelektrične snage o temperaturi iznad 40 K uspješno se objašnjava modelom dviju vrpci. Iako je predodžba o preklapanju valentne i vodljive vrpce na Fermijevoj razini odgovorna za istovremeno postojanje dviju vrsta nositelja i za opis kvazikristala kao polumetala, temperaturna ovisnost električne vodljivosti je, kao i kod normalnih poluvodiča, određena promjenom gustoće nositelja

Transparenz und Evaluierbarkeit des erziehungswissenschaftlichen Publikationsaufkommens. Eine anwendungsorientierte Studie

Der Beitrag stellt Ziele und erste Ergebnisse des DFG-Projekts "Innovative bibliometrische Verfahren zur kontinuierlichen Beobachtung der sozialwissenschaftlichen Forschungsproduktion" vor. Eine Analyse des Publikationsverhaltens von Erziehungswissenschaftlern zeigt die große Bedeutung des Publikationstyps Sammelwerksbeitrag und der Publikationssprache Deutsch, aber auch eine ausgeprägte Heterogenität in der Publikationspraxis von erziehungswissenschaftlichen Institutionen. Skizziert wird schließlich der Vorschlag für einen neuen, dieser Publikationspraxis angemessenen, bibliometrischen Indikator. (DIPF/Autor

Dynamics of viscous amphiphilic films supported by elastic solid substrates

The dynamics of amphiphilic films deposited on a solid surface is analyzed for the case when shear oscillations of the solid surface are excited. The two cases of surface- and bulk shear waves are studied with film exposed to gas or to a liquid. By solving the corresponding dispersion equation and the wave equation while maintaining the energy balance we are able to connect the surface density and the shear viscocity of a fluid amphiphilic overlayer with experimentally accessible damping coefficients, phase velocity, dissipation factor and resonant frequency shifts of shear waves.Comment: 19 pages, latex, 3 figures in eps-forma

The role of dipole interactions in hyperthermia heating colloidal clusters of densely-packed superparamagnetic nanoparticles

This work aims to investigate the influence of inter-particle dipole interactions on hyperthermia heating colloidal clusters of densely-packed Fe3O4 nanoparticles at low field intensity. Emulsion droplet solvent evaporation method was used to assemble oleic acid modified Fe3O4 particles into compact clusters which were stabilized by surfactant in water. Both experimental and simulation works were conducted to study their heating performance at different cluster’s sizes. The dipole interactions improve the heating only when the clusters are small enough to bring an enhancement in clusters’ shape anisotropy. The shape anisotropy is reduced at greater clusters’ sizes, since the shapes of the clusters become more and more spherical. Consequently, the dipole interactions change to impair the heating efficiency at larger sizes. When the clusters are totally isotropic in shape, the heating efficiency is lower than that of non-interacting particles despite the cluster’s size, although the efficiency increases by a little bit at a particular size most likely due to the dipole couplings. In these situations, one has to use particles with higher magnetic anisotropy and/or saturation magnetization to improve the heating

Endocrinologic, neurologic, and visual morbidity after treatment for craniopharyngioma

Craniopharyngiomas are locally aggressive tumors which typically are focused in the sellar and suprasellar region near a number of critical neural and vascular structures mediating endocrinologic, behavioral, and visual functions. The present study aims to summarize and compare the published literature regarding morbidity resulting from treatment of craniopharyngioma. We performed a comprehensive search of the published English language literature to identify studies publishing outcome data of patients undergoing surgery for craniopharyngioma. Comparisons of the rates of endocrine, vascular, neurological, and visual complications were performed using Pearson’s chi-squared test, and covariates of interest were fitted into a multivariate logistic regression model. In our data set, 540 patients underwent surgical resection of their tumor. 138 patients received biopsy alone followed by some form of radiotherapy. Mean overall follow-up for all patients in these studies was 54 ± 1.8 months. The overall rate of new endocrinopathy for all patients undergoing surgical resection of their mass was 37% (95% CI = 33–41). Patients receiving GTR had over 2.5 times the rate of developing at least one endocrinopathy compared to patients receiving STR alone or STR + XRT (52 vs. 19 vs. 20%, χ2P < 0.00001). On multivariate analysis, GTR conferred a significant increase in the risk of endocrinopathy compared to STR + XRT (OR = 3.45, 95% CI = 2.05–5.81, P < 0.00001), after controlling for study size and the presence of significant hypothalamic involvement. There was a statistical trend towards worse visual outcomes in patients receiving XRT after STR compared to GTR or STR alone (GTR = 3.5% vs. STR 2.1% vs. STR + XRT 6.4%, P = 0.11). Given the difficulty in obtaining class 1 data regarding the treatment of this tumor, this study can serve as an estimate of expected outcomes for these patients, and guide decision making until these data are available

TEMPERATURE DEPENDENCE OF THE EXTRAORDINARY HALL EFFECT IN AMORPHOUS ( FeCoNi)78B12Si10 ALLOYS

Temperature dependence of the extraordinary Hall coeficient Rs and resistivity ?, yield Rs~?2 (arising from the side-jump mechanism) for the majority of investigated FeCoNi-based alloys. The deviation from ?2 variation in Co-rich alloys is probably due to the temperature dependence of the magnetic anisotropy in these alloys