Effect of hypokinesia on blood microcirculation

Blood microcirculation in the region of the scleral bulbar conjunctiva and the nail folds on the fingers and toes was studied in 18 practically healthy men during 182 day antiorthostatic hypokinesia and 30 day rehabilitation period. Marked changes in microcirculation in the sclera and feet and less evident changes on the hands was revealed. A complex of special prophylactic physical exercises had a distinctly favorable effect on circulation in the hands

Breakdown of the Migdal-Eliashberg theory in the strong-coupling adiabatic regime

In view of some recent works on the role of vertex corrections in the electron-phonon system we readress an important question of the validity of the Migdal-Eliashberg theory. Based on the solution of the Holstein model and inverse coupling constant expansion, we argue that the standard Feynman-Dyson perturbation theory by Migdal and Eliashberg with or without vertex corrections cannot be applied if the electron-phonon coupling constant $\lambda$ is larger than 1 for any ratio of the phonon and Fermi energies. In the extreme adiabatic limit of the Holstein model electrons collapse into self-trapped small polarons or bipolarons due to spontaneous translational-symmetry breaking when $\lambda$ is between 0.5 and 1.3 (depending on the lattice dimensionality). With the increasing phonon frequency the region of the applicability of the theory shrinks to lower values of the coupling constant.Comment: 4 pages, 1 figur

Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities

Differential cross sections for Compton scattering from the deuteron were measured at MAX-lab for incident photon energies of 55 MeV and 66 MeV at nominal laboratory angles of $45^\circ$, $125^\circ$, and $135^\circ$. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and difference of the isospin-averaged nucleon polarizabilities, $\alpha_N + \beta_N = 17.4 \pm 3.7$ and $\alpha_N - \beta_N = 6.4 \pm 2.4$ (in units of $10^{-4}$ fm$^3$), have been determined. By combining the latter with the global-averaged value for $\alpha_p - \beta_p$ and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of $\alpha_n= 8.8 \pm 2.4$(total) $\pm 3.0$(model) and $\beta_n = 6.5 \mp 2.4$(total) $\mp 3.0$(model), respectively.Comment: 4 pages, 2 figures, revtex. The text is substantially revised. The cross sections are slightly different due to improvements in the analysi

Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures

Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2 . We also test reasonable parameter changes of the photo-ionization model. We find that photo- ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in nitrogen with high purity, but not in air.Comment: 12 figure

Synthesis of multi-loop automatic control systems by the nonlinear programming method

The article deals with the problem of calculation of the multi-loop control systems optimal tuning parameters by numerical methods and nonlinear programming methods. For this purpose, in the paper the Optimization Toolbox of Matlab is used

About the connection between vacuum birefringence and the light-light scattering amplitude

Birefringence phenomena stemming from vacuum polarization are revisited in the framework of coherent scattering. Based on photon-photon scattering, our analysis brings out the direct connection between this process and vacuum birefringence. We show how this procedure can be extended to the Kerr and the Cotton-Mouton birefringences in vacuum, thus providing a unified treatment of various polarization schemes, including those involving static fields

The Restoration of the Function of the Thumb using Sequential Arthroplasty of the Trapeziometacarpal and Metacarpophalangeal Joints

Background. The opposition function of the thumb is extremely important and is provided mainly due to the biomechanical features of the trapeziometacarpal and metacarpophalangeal joints. Surgical treatment of complex deformities of these joints is often described in isolated studies, and there are practically no descriptions of the results of their combined treatment. The authors of the article did not find a single report on total arthroplasty of the adjacent joints of the thumb.Aim of the study. To analyze the clinical observation of two patients in the early period after performing sequential non-simultaneous total arthroplasty of the trapeziometacarpal and metacarpophalangeal joints of the thumb using ceramic endoprostheses. Both endoprostheses were presented in pairs with two unconnected components, installed using the press-fit method. When the head and cup interact, there are no shear forces in them that impede multiaxial movements.Materials and methods. The study included two patients: a 67-year-old man and a 77-year-old woman. Patients had stage 3 osteoarthritis of the trapeziometacarpal and metacarpophalangeal joints of the thumb and underwent staged surgical treatment (about 2–3 years between the stages). In 1 month and 1 year after the treatment we assessed the results using clinical and instrumental research methods.Conclusion. No complications were observed during the follow-up. There were no indications for revision surgery. The design features of ceramic endoprostheses, due to their short stems, make it possible to combine components in the adjacent joints of the thumb. In our opinion, joint arthroplasty is an effective and promising method of functional restoration. It remains the patient’s last hope for maintaining painless, stable mobility of the thumb

Speciation of rhenium in chloride melts: Spectroscopic and electrochemical study

Speciation of rhenium in high-temperature alkali chloride-based melts was studied using electronic absorption and IR spectroscopy of molten salts and diffuse reflectance spectroscopy of quenched melts. Rhenium was added to the melts by anodic dissolution of the metal (at anodic current densities of 0.005-0.05 A/cm2), by reacting Re and ReO2 with Cl 2 and HCl, and by dissolving K2[ReCl6]. The melts included 3LiCl-2KCl and NaCl-2CsCl eutectics, an NaCl-KCl equimolar mixture, and pure NaCl, KCl and CsCl between 450 and 850 °C. Rhenium was present in the melts as Re(IV) hexachloro-ions, [ReCl6]2-; no evidence of species containing rhenium in oxidation states below four was obtained. The kinetics of [ReCl6]2- disproportionation in molten alkali chlorides were investigated, and the IR spectra of [ReO 4]- ions in molten CsCl-CsI and CsI were measured for the first time. © 2008 Verlag der Zeitschrift für Naturforschung, Tübingen

Prospects for SIMPLE 2000: A large-mass, low-background Superheated Droplet Detector for WIMP searches

SIMPLE 2000 (Superheated Instrument for Massive ParticLE searches) will consist of an array of eight to sixteen large active mass ($\sim15$ g) Superheated Droplet Detectors(SDDs) to be installed in the new underground laboratory of Rustrel-Pays d'Apt. Several factors make of SDDs an attractive approach for the detection of Weakly Interacting Massive Particles (WIMPs), namely their intrinsic insensitivity to minimum ionizing particles, high fluorine content, low cost and operation near ambient pressure and temperature. We comment here on the fabrication, calibration and already-competitive first limits from SIMPLE prototype SDDs, as well as on the expected immediate increase in sensitivity of the program, which aims at an exposure of $>$25 kg-day during the year 2000. The ability of modest-mass fluorine-rich detectors to explore regions of neutralino parameter space beyond the reach of the most ambitious cryogenic projects is pointed out.Comment: 19 pages, 10 figures included. New Journal of Physics, in pres

χ (2) -Lens Mode-Locking of a High Average Power Nd:YVO 4 Laser

Abstract: We report over 20 W, 6 ps, 170 MHz, passive mode-locking of a Nd:YVO 4 laser using χ Among laser materials, neodymium-doped vanadate Nd:YVO 4 has been the most extensively studied and widely used in diode-pumped high average power continuous-wave (CW) and mode-locked lasers for the past two decades. Nd:YVO 4 has large emission cross-section and polarized emission attributed to its natural birefringence as well as capacity for being pumped efficiently by laser diodes. The major drawback which limits the output power of Nd:YVO 4 lasers is the poorer thermo-mechanical properties of the crystal in comparison with that of Nd:YAG. Typically, multi-Watt operation of picosecond Nd:YVO 4 lasers has been demonstrated mainly using a modelocking technique based on semiconductor saturable absorber mirrors (SESAMs) In this work we report χ (2) -lens mode-locking of a Nd:YVO 4 laser using a LBO SHG crystal. The laser generates 6 ps transform-limited pulses at 170 MHz with output power of 20.1 W. To our knowledge, it is the maximum output power achieved by a χ (2) -lens mode-locked laser. The design of the mode-locked laser is based on a 810 mm long linear cavity