排序方式: 共有33条查询结果,搜索用时 15 毫秒
1.
Z. Damijan 《The European physical journal. Special topics》2008,154(1):45-49
Body vibrations training has become popular in sports
training, fitness activity, it is still a rare form of physical
rehabilitation.. Vibrations are transmitted onto the whole body or some body
parts of an exercising person via a vibration platform subjected to
mechanical vertical vibrations. During the training session a participant
has to maintain his body position or do exercises that engage specific
muscles whilst vibrations of the platform are transmitted onto the person's
body. This paper is the continuation of the earlier study covering the
effects of low-frequency vibrations on selected physiological parameters of
the human body. The experiments were conducted to find the answer to the
question if vibration exposure (total duration of training sessions 6 hours
20 min) should produce any changes in hepatic profile of blood. Therefore a
research program was undertaken at the University of Science and Technology
AGH – UST to investigate the effects of low-frequency vibration on selected
parameters of hepatic profile of human blood. Cyclic fluctuations of bone
loading were induced by the applied harmonic vibration 3.5 Hz and amplitude
0.004 m. The experiments utilizing two vibrating platforms were performed in
the Laboratory of Structural Acoustics and Biomedical Engineering AGH-UST.
The applied vibrations were harmless and not annoying, in accordance with
the standard PN-EN ISO 130901-1, 1998. 23 women volunteers had 19 sessions
on subsequent working days, at the same time of day. during the tests the
participants remained in the standing position, passive. The main hypothesis
has it that short-term low-frequency vibration exposure might bring about
the changes of the hepatic profile of blood, including: bilirubin
(BILIRUBIN), alkaline phosphatase (Alp), alanine aminotransferase (ALT),
aspartate aminotransferase (AST) and albumin (ALBUMIN) levels. Research data
indicate the low-frequency vibrations exposure produces statistically
significant decrease of bilirubin level [umol/l] in blood serum from 14.05
to 9.70 for 82% of participants, the probability level being p = 0.000041. 相似文献
2.
M.?Miklav?i?Email author C. Y.?Wang 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,55(2):235-246
Von Kármáns problem of a rotating disk in an
infinite viscous fluid is extended to
the case where the disk surface admits partial slip. The nonlinear similarity equations
are integrated accurately for the full range of slip coefficients.
The effects of slip are discussed. An existence proof is also
given. 相似文献
3.
It is shown that a perturbation argument that guarantees persistence of inertial (invariant and exponentially attracting) manifolds for linear perturbations of linear evolution equations applies also when the perturbation is nonlinear. This gives a simple but sharp condition for existence of inertial manifolds for semi-linear parabolic as well as for some nonlinear hyperbolic equations. Fourier transform of the explicitly given equation for the tracking solution together with the Plancherel's theorem for Banach valued functions are used. 相似文献
4.
A new ferromagnetic hysteresis model for soft magnetic composite materials based on their specific properties is presented. The model relies on definition of new anhysteretic magnetization based on the Cauchy-Lorentz distribution describing the maximum energy state of magnetic moments in material. Specific properties of soft magnetic composite materials (SMC) such as the presence of the bonding material, different sizes and shapes of the Fe particles, level of homogeneity of the Fe particles at the end of the SMC product treatment, and achieved overall material density during compression, are incorporated in both the anhysteretic differential magnetization susceptibility and the irreversible differential magnetization susceptibility. Together they form the total differential magnetization susceptibility that defines the new ferromagnetic hysteresis model. Genetic algorithms are used to determine the optimal values of the proposed model parameters. The simulated results show good agreement with the measured results. 相似文献
5.
Miklav? Mastinšek 《Journal of Mathematical Analysis and Applications》2002,269(2):770-783
A functional differential equation in Hilbert space with initial data on [−h,0] is considered. An unbounded operator A and a square integrable weight function are acting in the distributed delay term. For a not necessarily continuous weight function the norm continuity of the associated solution semigroup is established at every t>h. In the case that the spectrum of A is real and negative, the asymptotic stability of the solution is obtained. 相似文献
6.
7.
Cukjati D Batiuskaite D André F Miklavcic D Mir LM 《Bioelectrochemistry (Amsterdam, Netherlands)》2007,70(2):501-507
In vivo cell electroporation is the basis of DNA electrotransfer, an efficient method for non-viral gene therapy using naked DNA. The electric pulses have two roles, to permeabilize the target cell plasma membrane and to transport the DNA towards or across the permeabilized membrane by electrophoresis. For efficient electrotransfer, reversible undamaging target cell permeabilization is mandatory. We report the possibility to monitor in vivo cell electroporation during pulse delivery, and to adjust the electric field strength on real time, within a few microseconds after the beginning of the pulse, to ensure efficacy and safety of the procedure. A control algorithm was elaborated, implemented in a prototype device and tested in luciferase gene electrotransfer to mice muscles. Controlled pulses resulted in protection of the tissue and high levels of luciferase in gene transfer experiments where uncorrected excessive applied voltages lead to intense muscle damage and consecutive loss of luciferase gene expression. 相似文献
8.
Electroporation (EP) is one of the successful physical methods for intracellular drug delivery, which temporarily permeabilizes plasma membrane by exposing cells to electric pulses. Orientation of cells in electric field is important for electroporation and, consequently, for transport of molecules through permeabilized plasma membrane. Uptake of molecules after electroporation are the greatest at poles of cells facing electrodes and is often asymmetrical. However, asymmetry reported was inconsistent and inconclusive—in different reports it was either preferentially anodal or cathodal. We investigated the asymmetry of polar uptake of calcium ions after electroporation with electric pulses of different durations, as the orientation of elongated cells affects electroporation to a different extent when using electric pulses of different durations in the range of 100 ns to 100 µs. The results show that with 1, 10, and 100 µs pulses, the uptake of calcium ions is greater at the pole closer to the cathode than at the pole closer to the anode. With shorter 100 ns pulses, the asymmetry is not observed. A different extent of electroporation at different parts of elongated cells, such as muscle or cardiac cells, may have an impact on electroporation-based treatments such as drug delivery, pulse-field ablation, and gene electrotransfection. 相似文献
9.
Flow driven by an externally imposed pressure gradient in a vertical porous channel is analysed. The combined effects of viscous dissipation and thermal buoyancy are taken into account. These effects yield a basic mixed convection regime given by dual flow branches. Duality of flow emerges for a given vertical pressure gradient. In the case of downward pressure gradient, i.e. upward mean flow, dual solutions coincide when the intensity of the downward pressure gradient attains a maximum. Above this maximum no stationary and parallel flow solution exists. A nonlinear stability analysis of the dual solution branches is carried out limited to parallel flow perturbations. This analysis is sufficient to prove that one of the dual solution branches is unstable. The evolution in time of a solution in the unstable branch is also studied by a direct numerical solution of the governing equation. 相似文献
10.
Archive for Rational Mechanics and Analysis - 相似文献