40 research outputs found
A fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight binding approximation and path integral theory
We present calculations of free energy barriers and diffusivities as
functions of temperature for the diffusion of hydrogen in bcc-Fe. This is a
fully quantum mechanical approach since the total energy landscape is computed
using a new self consistent, transferable tight binding model for interstitial
impurities in magnetic iron. Also the hydrogen nucleus is treated quantum
mechanically and we compare here two approaches in the literature both based in
the Feynman path integral formulation of statistical mechanics. We find that
the quantum transition state theory which admits greater freedom for the proton
to explore phase space gives result in better agreement with experiment than
the alternative which is based on fixed centroid calculations of the free
energy barrier. We also find results in better agreement compared to recent
centroid molecular dynamics (CMD) calculations of the diffusivity which
employed a classical interatomic potential rather than our quantum mechanical
tight binding theory. In particular we find first that quantum effects persist
to higher temperatures than previously thought, and conversely that the low
temperature diffusivity is smaller than predicted in CMD calculations and
larger than predicted by classical transition state theory. This will have
impact on future modeling and simulation of hydrogen trapping and diffusion
COMBINED HORMONOTHERAPY WITH GNRG ANALOGUE AND INTRAUTERINE LEVONORGESTREL-RELEASING SYSTEM OF ATYPICAL ENDOMETRIAL HYPERPLASIA AND WELL-DIFFERENTIATED ENDOMETRIAL CARCINOMA: PROSPECTIV PILOT RESEARCH
The article presents the results of organ-preserving treatment protocol of atypical endometrial hyperplasia and well-differentiated endometrial carcinoma in young women. This protocol was applied in 24 patients. The period of patients observation was 3—6 years. During 6—9 months the patients were given GnRG analogue with add-back therapy. Intrauterine levonorgestrel-releasing system was inserted with therapeutic purpose for the period of not less than 6 months in atypical endometrial hyperplasia and for 1 year for well differentiated endometrial carcinoma. Combined using of GnRG analogue and intrauterine levonorgestrel-releasing system is effective method for treatment of atypicalendometrial hyperplasia and endometrial carcinoma stage I А in young women, especially in cases of unrealized fertility and can be considered as an alternative way to hysterectomy
HIGH RESOLUTION LIF SPECTROSCOPY OF KCs MOLECULE
Author Institution: University of Latvia, Department of Physics, 19 Rainis blvd., LV-1586, Riga, Latvia; Sofia University, Department of Physics, 5 J Bourchier blvd, 1164 Sofia, Bulgaria; Leibniz Universitat Hannover, Inst.f. Quantenoptik, Welfengarten 1, 30167 Hannover, Germany\maketitle Among intensively studied heteronuclear alkali dimers theKCs molecule remains the one which is almost unstudied by experimentalists. Most information on the KCs electronic structure comes from recent \emph{ab initio} calculations} \underline{\textbf{78}}, 977 (2000); M. Korek et al., \textit{J. Chem. Phys}. \underline{\textbf{124}}, 094309 (2006).}. We present here the first high resolution analysis of laser induced fluorescence (LIF) of this molecule with the goal to obtain the potential of the X ground state in a possibly wide range of internuclear distances accessible by conventional spectroscopy. KCs molecules were produced by heating a mixture of K (10 g) and Cs (7 g) in a heat-pipe oven at a temperature of about 270 C under ca. 3 mbar of Ar buffer gas pressure. KCs molecular fluorescence was induced by different laser sources: the 454.5, 457.9, 465.8, and 472.7 nm lines of an Ar laser; a dye laser with Rh6G dye (excitation frequency around 16870 cm); or 850 nm and 980 nm diode lasers (11500 - 11900 cm and 10200 - 10450 cm tuning range respectively). The fluorescence to the ground state was recorded using a Bruker IFS-125HR Fourier transform spectrometer with 0.03 cm spectral resolution. Particularly, applying the 850 nm diode laser allowed us to observe LIF progressions to very high vibrational levels of the ground state close to dissociation limit. The present data field contains term values \emph{v, J} for the X ground state which cover a range from \emph{v}^{\prime\prime} = 0 to 96 with \emph{J}^{\prime\prime} varying from \emph{J} = 14 to 185. More than 4000 fluorescence lines were used to fit the ground state potential energy curve via the Inverted Perturbation Approach procedure. The present empirical potential extends up to ca. 11 {\AA} and covers more than 95 of the well depth describing most of the spectral lines with the precision of 0.005 cm. Future plans on KCs excited states studies will be discussed. The Riga team acknowledges support by NATO SfP 978029 Optical Field Mapping grant and by Latvian Science Council grant No. 04.1308. The Hannover team acknowledges support through SFB407 by DFG