289 research outputs found

    A hierarchy of models related to nanoflows and surface diffusion

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    In last years a great interest was brought to molecular transport problems at nanoscales, such as surface diffusion or molecular flows in nano or sub-nano-channels. In a series of papers V. D. Borman, S. Y. Krylov, A. V. Prosyanov and J. J. M. Beenakker proposed to use kinetic theory in order to analyze the mechanisms that determine mobility of molecules in nanoscale channels. This approach proved to be remarkably useful to give new insight on these issues, such as density dependence of the diffusion coefficient. In this paper we revisit these works to derive the kinetic and diffusion models introduced by V. D. Borman, S. Y. Krylov, A. V. Prosyanov and J. J. M. Beenakker by using classical tools of kinetic theory such as scaling and systematic asymptotic analysis. Some results are extended to less restrictive hypothesis

    Malnutrition as a factor aggravating the heart failure course in the elderly and senile age

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    Cardiovascular diseases are the main death causes in the modern world. Heart failure (HF) is the terminal stage of most cardiovascular diseases. The prevalence of HF is increasing in patients of older age groups. At the same time, the number of geriatric syndromes increases with age, one of which is malnutrition. Recent studies demonstrate the mutually aggravating effect of heart failure and malnutrition, and that the correction of malnutrition can improve the heart failure course. The introduction of screening and timely correction of malnutrition will reduce the hospitalization and mortality rates in geriatric patients with HF

    All-fibre source of amplitude-squeezed light pulses

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    An all-fibre source of amplitude squeezed solitons utilizing the self-phase modulation in an asymmetric Sagnac interferometer is experimentally demonstrated. The asymmetry of the interferometer is passively controlled by an integrated fibre coupler, allowing for the optimisation of the noise reduction. We have carefully studied the dependence of the amplitude noise on the asymmetry and the power launched into the Sagnac interferometer. Qualitatively, we find good agreement between the experimental results, a semi-classical theory and earlier numerical calculations [Schmitt etl.al., PRL Vol. 81, p.2446, (1998)]. The stability and flexibility of this all-fibre source makes it particularly well suited to applications in quantum information science

    Generalized probabilities taking values in non-Archimedean fields and topological groups

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    We develop an analogue of probability theory for probabilities taking values in topological groups. We generalize Kolmogorov's method of axiomatization of probability theory: main distinguishing features of frequency probabilities are taken as axioms in the measure-theoretic approach. We also present a review of non-Kolmogorovian probabilistic models including models with negative, complex, and pp-adic valued probabilities. The latter model is discussed in details. The introduction of pp-adic (as well as more general non-Archimedean) probabilities is one of the main motivations for consideration of generalized probabilities taking values in topological groups which are distinct from the field of real numbers. We discuss applications of non-Kolmogorovian models in physics and cognitive sciences. An important part of this paper is devoted to statistical interpretation of probabilities taking values in topological groups (and in particular in non-Archimedean fields)

    Diffusion in multiscale spacetimes

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    We study diffusion processes in anomalous spacetimes regarded as models of quantum geometry. Several types of diffusion equation and their solutions are presented and the associated stochastic processes are identified. These results are partly based on the literature in probability and percolation theory but their physical interpretation here is different since they apply to quantum spacetime itself. The case of multiscale (in particular, multifractal) spacetimes is then considered through a number of examples and the most general spectral-dimension profile of multifractional spaces is constructed.Comment: 23 pages, 5 figures. v2: discussion improved, typos corrected, references adde

    Influence of nodular and severe forms of diffuse adenomyosis on reproductive function: a review of reproductive outcomes of surgical interventions and IVF

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    This review includes an analysis of clinical studies evaluating the effect of adenomyosis on reproductive function, as well as a review of studies on the relationship between surgical treat-ment options for adenomyosis and reproductive outcomes. Different studies of women populations after in vitro fertilization and/or intracytoplasmic sperm injection (IVF/ICSI) and after surgical treatment of  deep adenomyosis have shown that adenomyosis in both cases has a negative effect on the reproductive outcome, although there are significant differences in these populations. In the literature, there are relatively few data on the degree of influence of the depth of the lesion on the realization of the reproductive function, however, a significant correlation was revealed between them. The positive effect of treatment with gonadotropin-releasing hormone agonists, followed by surgical treatment of adenomyosis, has also been described in several literary sources, but there have been no controlled studies on this topic. Many studies do not meet the validity criteria due to the lack of clear criteria for inclusion and exclusion from the study.The choice of the optimal treatment options for adenomyosis based on the actual data is difficult due to the lack of reliable evidence of the relationship between fertility and the degree of adenomyosis. However, it is known that adenomyosis can reduce the likelihood of successful implantation so  ramatically that surgical or other treatment options are reasonably recom-mended. At the same time, it is necessary to assess the possible positive effect of the treatment options available in the doctor’s arsenal. Thus, timely referral to specialized treatment of ade-nomyosis may be crucial for the successful implementation of reproductive function in patients with suspicion or with an established diagnosis of adenomyosis in combination with recurrent miscarriage, who refuse to use assisted reproductive technologies, medical institutions. This review will analyze the relationship between infertility and adenomyosis, as well as review studies of reproductive outcomes in different options for surgical treatment of adenomyosis in infertile patients

    The Fermi-Pasta-Ulam problem: 50 years of progress

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    A brief review of the Fermi-Pasta-Ulam (FPU) paradox is given, together with its suggested resolutions and its relation to other physical problems. We focus on the ideas and concepts that have become the core of modern nonlinear mechanics, in their historical perspective. Starting from the first numerical results of FPU, both theoretical and numerical findings are discussed in close connection with the problems of ergodicity, integrability, chaos and stability of motion. New directions related to the Bose-Einstein condensation and quantum systems of interacting Bose-particles are also considered.Comment: 48 pages, no figures, corrected and accepted for publicatio

    Soliton Squeezing in a Mach-Zehnder Fiber Interferometer

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    A new scheme for generating amplitude squeezed light by means of soliton self-phase modulation is experimentally demonstrated. By injecting 180-fs pulses into an equivalent Mach-Zehnder fiber interferometer, a maximum noise reduction of 4.4±0.34.4 \pm 0.3 dB is obtained (6.3±0.66.3 \pm 0.6 dB when corrected for losses). The dependence of noise reduction on the interferometer splitting ratio and fiber length is studied in detail.Comment: 5 pages, 4 figure

    Exploration of structural, thermal, vibrational and spectroscopic properties of new noncentrosymmetric double borate Rb3NdB6O12

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    New noncentrosymmetric rare earth borate Rb3NdB6O12 is found in the ternary system Rb2O–Nd2O3–B2O3. The Rb3NdB6O12 powder was fabricated by solid state synthesis at 1050 K for 72 h and the crystal structure was obtained by the Rietveld method. Rb3NdB6O12 crystallized in space group R32 with unit cell parameters a = 13.5236(4), c = 31.162(1) Å, Z = 3. From DSC measurements, the reversible phase transition (I type) in Rb3NdB6O12 is observed at 852–936 K. The 200 μm thick tablet is transparent over the spectral range of 0.3–6.5 μm and the band gap is found as Eg ∼ 6.29 eV. Nonlinear optical response of Rb3NdB6O12 tested via SHG is estimated to be higher than that of K3YB6O12. Blue shift of Nd luminescent lines is found in comparison with other borates. The vibrational parameters of Rb3NdB6O12 are evaluated by experimental methods
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