92 research outputs found
Π ΠΠΠΠ ΠΠΠΠΠ§ΠΠ‘Π’ΠΠ’ΠΠΠ ΠΠΠΠΠ ΠΠ¦ΠΠ Π ΠΠΠ’ΠΠΠΠΠΠ’Π ΠΠΠΠΠ ΠΠΠΠΠ ΠΠ’ΠΠ Π Π‘ΠΠ§ ΠΠ ΠΠΠΠΠ―Π₯ ΠΠΠΠΠ ΠΠΠ Π‘ ΠΠΠ’ΠΠ§ΠΠ‘ΠΠΠ Π£Π‘ΠΠΠΠΠΠΠ
The theoretical investigation of the single-frequency oscillation in all-optical gain optoelectronic oscillator based on fiberoptic delay lines is performed. It is shown that there is no need in microwave phase shifters within the optoelectronic oscillator loop in order to provide low phase noise and spurious level oscillations. Threshold of the dynamical instabilities in the all-optical gain optoelectronic oscillator is calculated. It is shown that the reproducibility of the oscillation frequency is provided by means of the continuous tuning of the loop gain during the switching-on.Β Π Π΄Π°Π½Π½ΠΎΠΉ ΡΠ°Π±ΠΎΡΠ΅ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ΠΎ ΡΠ΅ΠΎΡΠ΅ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ ΠΊΠ²Π°Π·ΠΈΠ³Π°ΡΠΌΠΎΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ Π² ΠΎΠΏΡΠΎΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΌ Π³Π΅Π½Π΅ΡΠ°ΡΠΎΡΠ΅ Π½Π° Π»ΠΈΠ½ΠΈΡΡ
Π·Π°Π΄Π΅ΡΠΆΠΊΠΈ Ρ ΠΎΠΏΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΡΠΈΠ»Π΅Π½ΠΈΠ΅ΠΌ. Π Π°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°ΡΡΡΡ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ Π‘ΠΠ§-ΡΠ°Π·ΠΎΠ²ΡΠ°ΡΠ°ΡΠ΅Π»Π΅ΠΉ Π΄Π»Ρ ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠ΅Π½ΠΈΡ ΠΊΠ²Π°Π·ΠΈΠ³Π°ΡΠΌΠΎΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ Ρ Π½ΠΈΠ·ΠΊΠΈΠΌ ΡΠ°Π·ΠΎΠ²ΡΠΌ ΡΡΠΌΠΎΠΌ ΠΈ ΡΡΠΎΠ²Π½Π΅ΠΌ Π΄ΠΈΡΠΊΡΠ΅ΡΠ½ΡΡ
ΡΠΎΡΡΠ°Π²Π»ΡΡΡΠΈΡ
Π² ΡΠΏΠ΅ΠΊΡΡΠ΅ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ, Π° ΡΠ°ΠΊΠΆΠ΅ ΡΠ°ΡΡΡΠΈΡΠ°Π½ΠΎ ΠΏΠΎΡΠΎΠ³ΠΎΠ²ΠΎΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΠ΅ ΠΊΠΎΡΡΡΠΈΡΠΈΠ΅Π½ΡΠ° ΡΡΠΈΠ»Π΅Π½ΠΈΡ ΠΊΠΎΠ½ΡΡΡΠ° ΠΎΠ±ΡΠ°ΡΠ½ΠΎΠΉ ΡΠ²ΡΠ·ΠΈ, ΠΏΡΠΈ ΠΊΠΎΡΠΎΡΠΎΠΌ Π² ΠΎΠΏΡΠΎΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΌ Π³Π΅Π½Π΅ΡΠ°ΡΠΎΡΠ΅ Π½Π° Π»ΠΈΠ½ΠΈΡΡ
Π·Π°Π΄Π΅ΡΠΆΠΊΠΈ Ρ ΠΎΠΏΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΡΠΈΠ»Π΅Π½ΠΈΠ΅ΠΌ Π½Π°ΡΡΡΠΏΠ°Π΅Ρ ΡΠ΅ΠΆΠΈΠΌ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
Π½Π΅ΡΡΠ°Π±ΠΈΠ»ΡΠ½ΠΎΡΡΠ΅ΠΉ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ ΠΌΠ΅ΡΠΎΠ΄ ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠ΅Π½ΠΈΡ ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΡ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ Π² ΠΎΠΏΡΠΎΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΌ Π³Π΅Π½Π΅ΡΠ°ΡΠΎΡΠ΅ Π½Π° ΡΠ°ΡΡΠΎΡΠ΅ ΠΌΠ°ΠΊΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΡΡΠΈΠ»Π΅Π½ΠΈΡ.
Validation, reproducibility and safety of trans dermal electrical stimulation in chronic pain patients and healthy volunteers
<p>Abstract</p> <p>Background</p> <p>Surrogate pain models have been extensively tested in Normal Human Volunteers (NHV). There are few studies that examined pain models in chronic pain patients. Patients are likely to have altered pain mechanisms. It is of interest to test patient pain responses to selective pain stimuli under controlled laboratory conditions.</p> <p>Methods</p> <p>The Institutional Ethic Committee approved the study. 16 patients with chronic neuropathic radiculopathy and 16 healthy volunteers were enrolled to the study after obtaining informed consent. During electrical stimulation (150 minutes for volunteers and 75 minutes for patients) the following parameters were measured every 10 minutes:</p> <p>Ongoing pain: Visual Analogue Scale (VAS) and Numeric Rate Scale (NRS)</p> <p>Allodynia (soft foam brush)</p> <p>Hyperalgesia (von Frey monofilament 20 g)</p> <p>Flare</p> <p>For each endpoint, the area under the curve (AUC) was estimated from the start of stimulation to the end of stimulation by the trapezoidal rule. The individual AUC values for both periods were plotted to show the inter- and intra-subject variability. For each endpoint a mixed effect model was fitted with random effect subject and fixed effect visit. The estimate of intra-subject variance and the mean value were then used to estimate the sample size of a crossover study required to have a probability of 0.80 to detect a 25% change in the mean value. Analysis was done using GenStat 8<sup>th </sup>edition.</p> <p>Results</p> <p>Each endpoint achieved very good reproducibility for patients and NHV. Comparison between groups revealed trends towards:</p> <p>Faster habituation to painful stimuli in patients</p> <p>Bigger areas of hyperalgesia in patients</p> <p>Similar area of allodynia and flare (no statistical significance)</p> <p>Conclusion</p> <p>The differences demonstrated between patients and NHVs suggest that the electrical stimulation device used here may stimulate pathways that are affected in the pathological state.</p
Π’Π΅ΠΏΠ»ΠΎΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠ²ΠΎΠΉΡΡΠ²Π° ΠΈ ΡΡΡΡΠΊΡΡΡΠ° ΠΎΡΠ»ΠΎΠΆΠ΅Π½ΠΈΠΉ Π½Π° ΠΏΠΎΠ²Π΅ΡΡ Π½ΠΎΡΡΡΡ Π½Π°Π³ΡΠ΅Π²Π° ΡΠ½Π΅ΡΠ³Π΅ΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΠ±ΠΎΡΡΠ΄ΠΎΠ²Π°Π½ΠΈΡ
The paper shows influence of heating surface material, design peculiarities, operational conditions of heat exchangers and water-chemical regime on chemical and structural composition of deposits, their heat conduction and porosity.ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π° ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ Π½Π°Π³ΡΠ΅Π²Π°, ΠΊΠΎΠ½ΡΡΡΡΠΊΡΠΈΠ²Π½ΡΡ
ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠ΅ΠΉ, ΡΡΠ»ΠΎΠ²ΠΈΠΉ ΡΠΊΡΠΏΠ»ΡΠ°ΡΠ°ΡΠΈΠΈ ΡΠ΅ΠΏΠ»ΠΎΠΎΠ±ΠΌΠ΅Π½Π½ΡΡ
ΡΡΡΡΠΎΠΉΡΡΠ² ΠΈ Π²ΠΎΠ΄Π½ΠΎ-Ρ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ΅ΠΆΠΈΠΌΠ° Π½Π° Ρ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΈ ΡΡΡΡΠΊΡΡΡΠ½ΡΠΉ ΡΠΎΡΡΠ°Π² ΠΎΡΠ»ΠΎΠΆΠ΅Π½ΠΈΠΉ, ΠΈΡ
ΡΠ΅ΠΏΠ»ΠΎΠΏΡΠΎΠ²ΠΎΠ΄Π½ΠΎΡΡΡ ΠΈ ΠΏΠΎΡΠΈΡΡΠΎΡΡΡ
The Role of Interdiffusion and Spatial Confinement in the Formation of Resonant Raman Spectra of Ge/Si(100) Heterostructures with Quantum-Dot Arrays
The phonon modes of self-assembled Ge/Si quantum dots grown by molecular-beam
epitaxy in an apparatus integrated with a chamber of the scanning tunneling
microscope into a single high-vacuum system are investigated using Raman
spectroscopy. It is revealed that the Ge-Ge and Si-Ge vibrational modes are
considerably enhanced upon excitation of excitons between the valence band
and the conduction band (the E1 and E1 +
transitions). This makes it possible to observe the Raman spectrum of very
small amounts of germanium, such as one layer of quantum dots with a germanium
layer thickness of 10 \r{A}. The enhancement of these modes suggests a strong
electron-phonon interaction of the vibrational modes with the E1 and E1 +
excitons in the quantum dot. It is demonstrated that the frequency
of the Ge-Ge mode decreases by 10 cm^-1 with a decrease in the thickness of the
Ge layer from 10 to 6 \r{A} due to the spatial-confinement effect. The optimum
thickness of the Ge layer, for which the size dispersion of quantum dots is
minimum, is determined.Comment: 14 pages, 9 figure
Absorption of Terahertz Radiation in Ge/Si(001) Heterostructures with Quantum Dots
The terahertz spectra of the dynamic conductivity and radiation absorption
coefficient in germanium-silicon heterostructures with arrays of Ge hut
clusters (quantum dots) have been measured for the first time in the frequency
range of 0.3-1.2 THz at room temperature. It has been found that the effective
dynamic conductivity and effective radiation absorption coefficient in the
heterostructure due to the presence of germanium quantum dots in it are much
larger than the respective quantities of both the bulk Ge single crystal and
Ge/Si(001) without arrays of quantum dots. The possible microscopic mechanisms
of the detected increase in the absorption in arrays of quantum dots have been
discussed.Comment: 9 pages, 4 figures; typos correcte
Kinetics of ATP release following compression injury of a peripheral nerve trunk
Compression and/or contusion of a peripheral nerve trunk can result in painful sensations. It is possible that release of ATP into the extracellular space may contribute to this symptom. In the present study, we used real-time measurements of ATP-induced bioluminescence together with electrophysiological recordings of compound action potentials to follow changes in the extracellular ATP concentration of isolated rat spinal roots exposed to mechanical stimuli. Nerve compression for about 8Β s resulted in an immediate release of ATP into the extracellular space and in a decrease in the amplitude of compound action potentials. On average, a rise in ATP to 60Β nM was observed when nerve compression blocked 50% of the myelinated axons. After the compression, the extracellular concentration of ATP returned to the resting level within a few minutes. The importance of ecto-nucleotidases for the recovery period was determined by exposure of isolated spinal roots to high concentrations of ATP and by use of inhibitors of ecto-nucleotidases. It was observed that spinal roots have a high capacity for ATP hydrolysis which is only partially blocked by Ξ²Ξ³-methylene ATP and ARL 67156. In conclusion, acute nerve compression produces an increase in the extracellular concentration of ATP and of its metabolites which may be sufficient for activation of purinergic P2 and/or P1 receptors on axons of nociceptive afferent neurons
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