Nanostructured TTT(TCNQ)2 organic crystals as promising thermoelectric n-type materials: 3D modeling

Thermoelectric properties of quasi-one-dimensional TTT(TCNQ)2 organic crystals are investigated in order to appreciate the prospect of using this compound as n–type thermoelectric material. A more complete three-dimensional (3D) physical model is elaborated. It takes into account two the most important interactions of conduction electrons with longitudinal acoustic phonons, the electrons’ scattering on neighbor molecular chains, as well as the scattering by impurities and defects. The electrical conductivity, thermopower, the power factor, electronic thermal conductivity and the thermoelectric figure of merit in the direction along conductive molecular chains are calculated numerically for different degrees of crystal purity. It is shown that in stoichiometric compounds the thermoelectric figure of merit ZT remains small even after the increase of crystal perfection degree. The thermoelectric properties may be significantly enhanced by simultaneous increase of crystal perfection and of electron concentration. The latter can be achieved by additional doping with donors. For less pure crystals, the interaction with impurities predominates over the weak interchain interaction and the simpler one-dimensional (1D) physical model is applicable. When the impurity scattering is reduced, the interchain interaction begins to limit the carrier mobility and the application of the 3D physical model is required. The optimal parameters permitting to predict ZT~ 1 are determined

Thermoelectric properties of tetrathiotetracene iodide crystals: modeling and experiment

A more complete physical model for nanostructured crystals of tetrathiotetracene-iodide that takes into account the interaction of carriers with the neighboring one-dimensional (1D) conductive chains and also the scattering on impurities and defects is presented. For simplicity, the 2D approximation is applied. It is shown that this model describes very well the temperature dependencies of electrical conductivity in the temperature interval between 180 and 300 K, and of the Seebeck coefficient between 50 and 300 K, the highest temperature for which the measurements were reported. For lower temperatures, it is necessary to also consider the fluctuations of dielectric phase that appear before the metal–dielectric transition. It is found that the predictions made in the 1D approximation are valid only if the crystal purity is not very high, and the electrical conductivity is limited up to ∼3.5×106Ω−1m−1 and the thermoelectric figure of merit up to ZT∼4

Cancerul endometrial. Particularităţi clinice, ultrasonografice şi histologice

Actualmente, cancerul endometrial reprezintă una din problemele stringente abordate în ginecologia oncologică. Ocupând poziţia a 4-a în structura maladiilor genitale feminine, această patologie solicită un interes deosebit reţelei medico- sanitare şi necesită efectuarea unor studii suplimentare în acest domeniu. Investigaţiile clinice au inclus 232 de paciente afectate de cancer endometrial şi 54 de paciente cu patologii benigne ale uterului. Vârsta medie a fost de 53,0±8,2 ani. Concluzii: prezentul studiu a demonstrat întâietatea tipului endometrioid al cancerului endometrial în structura reprezentării histologice a cancerului endometrial (73,3%); tumorile neendometrioide cu pronostic nefavorabil au alcătuit 26,7%