共查询到20条相似文献,搜索用时 15 毫秒
1.
F. G. Baksht S. V. Gavrish V. B. Kaplan V. F. Lapshin A. M. Martsinovsky 《Plasma Physics Reports》2010,36(13):1199-1202
Results of theoretical and experimental studies of the optical spectrum of a pulse-periodic high-pressure cesium discharge
are presented. The results of calculations are in good agreement with experimental data. The possibility of creating an efficient
light source based on recombination emission from the discharge plasma is demonstrated. The formation mechanisms of the continuous
spectrum of discharge radiation are considered. 相似文献
2.
O. N. Gilev V. I. Afonin V. I. Ostashev V. Yu. Politov A. M. Gafarov A. L. Zapysov A. V. Andriyash É. P. Magda L. N. Shamraev A. A. Safronov A. V. Komissarov N. A. Khavronin N. A. Pkhaĭko L. V. Antonova L. N. Shushlebin 《Plasma Physics Reports》2006,32(2):138-143
Results are presented from experiments on the laser generation of X-ray radiation at the wavelength λ=469 ? (ε=26.4 eV) on
the 3p(J=0)−3s(J=1) transition of Ne-like Ar ions. Experiments were carried out on the SIGNAL electrophysical facility with a 3.1-mm-diameter
157-mm-long Al2O3 ceramic capillary filled with argon at a pressure of 0.2–1.0 Torr. The discharge current amplitude was I ∼ 25–40 kA, the current rise rate being dI/dt ∼ 1012 A/s. By a vacuum X-ray diode tuned to detect X-ray photons with energies in the range 10–40 eV, laser pulses with a duration
of t
1 ∼ 1 ns and maximum energy of E
1,max ∼ 1 μJ were recorded. The pulses were generated 35 ns after the discharge current was switched on. The line spectra in the
wavelength range of 150–500 ? showed the bright λ=469 ? line. The angular divergence of the generated X-ray laser beam was
estimated to be Δϑ ∼ 2 mrad.
Original Russian Text ? O.N. Gilev, V.I. Afonin, V.I. Ostashev, V.Yu. Politov, A.M. Gafarov, A.L. Zapysov, A.V. Andriyash,
é.P. Magda, L.N. Shamraev, A.A. Safronov, A.V. Komissarov, N.A. Khavronin, N.A. Pkhaĭko, L.V. Antonova, L.N. Shushlebin, 2006,
published in Fizika Plazmy, 2006, Vol. 32, No. 2, pp. 160–165. 相似文献
3.
N. L. Aleksandrov M. N. Vasil’ev S. L. Lysenko A. Kh. Makhir 《Plasma Physics Reports》2005,31(5):425-435
An argon plasma produced by a quasi-steady high-energy electron beam was studied experimentally. The plasma density was measured using an open barrel-shaped microwave cavity. The gas temperature was shown to be a few times higher than room temperature. Electron beam propagation, as well as heat-transfer and kinetic processes in plasma, is modeled self-consistently for the actual experimental conditions. It is shown that the plasma density is largely governed by the conversion rate of the atomic ions into molecular ones. The calculated results are compared to the experimental data. 相似文献
4.
V. A. Gurashvili I. D. Dzhigailo N. A. Dyatko E. M. Zanozina I. V. Kochetov D. I. Spitsyn D. Yu. Tkachenko 《Plasma Physics Reports》2012,38(1):46-51
The spatial distribution of the current density of fast electrons and the ionization rate in a gap filled with atmospheric-pressure
air under the conditions of a non-self-sustained discharge controlled by a fast electron beam were investigated. The experiments
were carried out in a gas-discharge chamber with a grid electrode arranged in parallel to the exit window of the ionization
source. Spatial variations in the current density of fast electrons resulting from the grid were measured. The propagation
of the electron beam through the discharge system was simulated numerically by the Monte Carlo method in the so-called “effective
collision” approximation. The calculated results agree well with the experimental data. 相似文献
5.
A. V. Kozyrev N. S. Sochugov K. V. Oskomov A. N. Zakharov A. N. Odivanova 《Plasma Physics Reports》2011,37(7):621-627
Results are presented for experimental studies of the plasma glow in a high-current pulsed magnetron discharge by using a
high-speed optical frame camera. It is found that the discharge plasma is inhomogeneous in the azimuthal direction. The plasma
bunches rotate with a linear velocity of ∼1 cm/μs in the direction of electron Hall drift, and their number is proportional
to the discharge current. Plasma inhomogeneities in the form of plasma jets propagate in the form of plasma jets from the
cathode region toward the anode. It is shown analytically that the formation of inhomogeneities is caused by the necessity
to transfer high-density electron current across the magnetic field. 相似文献
6.
The parameters of a repetitive volume discharge in CF2Cl2 (CFC-12) and its mixtures with argon at pressures of P(CF2Cl2)≤0.4 kPa and P(Ar)≤1.2 kPa are studied. The discharge was ignited in an electrode system consisting of a spherical anode and a plane cathode by applying a dc voltage Uch≤1 kV to the anode. The electrical and optical characteristics of a volume discharge (such as the current-voltage characteristics; the plasma emission spectra; and the waveforms of the discharge voltage, the discharge current, and the total intensity of plasma emission) are investigated. It is found that, by shunting the discharge gap with a pulsed capacitor with a capacitance of C0≤3.5 nF, it is possible to control the amplitude and duration of the discharge current pulses, as well as the characteristics of the pulsed plasma emission. The increase in the capacitance C0 from 20 to 3500 pF leads to a significant increase in the amplitude and duration of the discharge current pulses, whereas the pulse repetition rate decreases from 70 to 3 kHz. The glow discharge exists in the form of a domain with a height of up to 3 cm and diameter of 0.5–3.0 cm. The results obtained can be used to design an untriggered repetitive germicidal lamp emitting in the Cl2(257/200 nm) and ArCl (175 nm) molecular bands and to develop plasmachemical methods for depositing amorphous fluorocarbon and chlorocarbon films. 相似文献
7.
A. V. Meshchanov Yu. Z. Ionikh A. I. Shishpanov S. A. Kalinin 《Plasma Physics Reports》2016,42(10):978-989
Results are presented from experimental studies of the breakdown stage of a low-pressure discharge (1 and 5 Torr) in a glass tube the length of which (75 cm) is much larger than its diameter (2.8 cm). Breakdowns occurred under the action of positive voltage pulses with an amplitude of up to 9.4 kV and a characteristic rise time of 2–50 μs. The discharge current in the steady-state mode was 10–120 mA. The electrode voltage, discharge current, and radiation from the discharge gap were detected simultaneously. The dynamic breakdown voltage was measured, the prebreakdown ionization wave was recorded, and its velocity was determined. The dependence of the discharge parameters on the time interval between voltage pulses (the socalled “memory effect”) was analyzed. The memory effect manifests itself in a decrease or an increase in the breakdown voltage and a substantial decrease in its statistical scatter. The time interval between pulses in this case can reach 0.5 s. The effect of illumination of the discharge tube with a light source on the breakdown was studied. It is found that the irradiation of the anode region of the tube by radiation with wavelengths of ≤500 nm substantially reduces the dynamic breakdown voltage. Qualitative explanations of the obtained results are offered. 相似文献
8.
Microdialysis sampling was performed to monitor localized metabolism in vivo and in vitro. A mathematical model that accounts for analyte mass transport during microdialysis sampling was used to predict metabolite concentrations in the microdialysis probe during localized metabolism experiments. The model predicts that metabolite concentrations obtained in the microdialysis probe are a function of different experimental parameters including membrane length, perfusion fluid flow rate, and sample diffusive and kinetic properties. Different microdialysis experimental parameters including membrane length and perfusion fluid flow rate were varied to affect substrate extraction efficiency (E(d)), or loss to the sample matrix, in vivo and in vitro. Local hepatic metabolism was studied in vivo in male Sprague-Dawley rats by infusing acetaminophen through the microdialysis probe. Acetaminophen sulfate concentrations increased linearly with respect to acetaminophen E(d) in contrast to modeling predictions. Xanthine oxidase was used as an in vitro model of localized metabolism. In vitro experimental results partially matched modeling predictions for 10-mm probes. These results suggest that monitoring local metabolism using microdialysis sampling is feasible. It is important to consider system parameters such as dialysis flow rate, membrane length, and sample properties because these factors will affect analyte concentrations obtained during local metabolism experiments. 相似文献
9.
The anisotropy of the yield and energy of neutrons generated in a small-size plasma focus chamber with a total neutron yield of about 4 × 109 DD neutrons per shot was investigated experimentally. The neutrons were recorded using scintillation detectors on a 3-m-long flight base. The measurements were performed at the angles 0° and 90° with respect to the chamber axis. The maximum neutron energy measured by the time-of-flight method at the angles 0° and 90° was found to be 2.8 and 2.5 MeV, respectively. The measured anisotropy of the neutron yield was in the range 1.15–1.88. The integral DD neutron yield of the source was measured using the activation method (by activating silver isotopes). It is found that the neutron yield and the yield anisotropy depend linearly on the discharge current jump ΔI at the instant of neutron generation. 相似文献
10.
The characteristics of a dc discharge excited between a metal anode and a water cathode in argon were studied experimentally. The dimensions of the positive column and the electric field in it were measured, and the vibrational temperature in the positive column was determined from the N2 C 3Πu → B 3Πg (0–2) emission band. It is shown that the power deposited in the positive column is almost entirely spent on gas heating. The obtained dependence of the reduced electric field on the gas pressure and the ionization frequencies calculated by solving the Boltzmann equation indicate that electrons are lost diffusively, whereas ionization proceeds in a stepwise manner via the lower metastable states of argon atoms. 相似文献
11.
The structural properties of the xTeO2·(1-x)B2O3 glasses (x = 0.6; 0.7) were investigated by FT-IR spectroscopy. From the analysis of the FTIR spectra, it is reasonable to
assume that by the increasing of boron ions content, the tetrahedral [BO4] units are gradually replaced by the trigonal [BO3] units. The increase in the number of non-bridging oxygen atoms would decrease the connectivity of the glass network and
will yield the depolymerization of the borate chains. The molecular structure and vibrational frequencies of the proposed
structural models have been studied by exploring the density functional theory (DFT) calculations. The FTIR spectra of the
xTeO2·(1-x)B2O3 vitreous systems were compared with the calculated spectrum. This procedure allowed us to assign most of the observed IR
bands. 相似文献
12.
It has been recently suggested that compensatory changes in Photosystem II (PS II) electron turnover rates can protect photosynthesis from photoinhibition [Behrenfeld et al. (1998) Photosynth Res 58: 259–268]. We have further explored this feature of PS II using a rate electrode for simultaneous measurements of the steady-state rate of oxygen evolution and the oxygen flash yield depending on the background irradiance in both control and photoinhibited algal cells of Chlorella Böhm. Theoretical simulations based on the two-electron gate model agree qualitatively with experimental data if we assume an increase of the electron turnover rate in the remaining functional PS II centers of the photoinhibited sample. Our results confirm the hypothesis that the compensatory effect enables cells to maintain the maximal rates of photosynthesis even in the presence of moderate photoinhibition (decrease of up to 50% in the number of functional centers) and that the effect originates from the inner capacity of electron transport through PS II. The origin of the compensatory effect is briefly discussed. 相似文献
13.
Antonio R. da Cunha Evandro L. Duarte Hubert Stassen M. Teresa Lamy Kaline Coutinho 《Biophysical reviews》2017,9(5):729-745
Emodin is one of the most abundant anthraquinone derivatives found in nature. It is the active principle of some traditional herbal medicines with known biological activities. In this work, we combined experimental and theoretical studies to reveal information about location, orientation, interaction and perturbing effects of Emodin on lipid bilayers, where we have taken into account the neutral form of the Emodin (EMH) and its anionic/deprotonated form (EM?). Using both UV/Visible spectrophotometric techniques and molecular dynamics (MD) simulations, we showed that both EMH and EM? are located in a lipid membrane. Additionally, using MD simulations, we revealed that both forms of Emodin are very close to glycerol groups of the lipid molecules, with the EMH inserted more deeply into the bilayer and more disoriented relative to the normal of the membrane when compared with the EM?, which is more exposed to interfacial water. Analysis of several structural properties of acyl chains of the lipids in a hydrated pure DMPC bilayer and in the presence of Emodin revealed that both EMH and EM? affect the lipid bilayer, resulting in a remarkable disorder of the bilayer in the vicinity of the Emodin. However, the disorder caused by EMH is weaker than that caused by EM?. Our results suggest that these disorders caused by Emodin might lead to distinct effects on lipid bilayers including its disruption which are reported in the literature. 相似文献
14.
The possibility of separating charges in an ordinary electric discharge was demonstrated. The luminous object formed after the end of the discharge was found to exist over a few hundred milliseconds, or six orders of magnitude longer than the lifetime of an ideal plasma of the same volume. It is shown that the luminous object has a negative electric charge and has no free charged particles of opposite sign. 相似文献
15.
High-density (n > 1012 cm?3) argon-mercury plasma produced by a short (t ~ 20 μs) high-power pulsed discharge in argon with an admixture of mercury vapor at a discharge current of ~50 A, an argon pressure of ~4 mm Hg, and a mercury vapor pressure of ~10?3 mm Hg was studied using optical spectroscopy and radio physics methods. It is found that the lifetime of this plasma after the end of the discharge pulse is up to 10?2 s. It is shown that such an abnormally long lifetime of such an afterglow plasma, as compared to the plasma of an argon discharge without an admixture of mercury vapor, is related to the long residence time of atoms and ions of both argon and mercury in highly excited states due to chemi-ionization processes involving long-lived metastable argon ions. It is suggested that dissociative recombination of highly excited molecular ions of argon play an important role in the transfer of excitation to argon atoms and ions that are close to autoionization states. 相似文献
16.
Experimental and theoretical studies of the three-dimensional structure of human interleukin-4 总被引:2,自引:0,他引:2
B M Curtis S R Presnell S Srinivasan H Sassenfeld R Klinke E Jeffery D Cosman C J March F E Cohen 《Proteins》1991,11(2):111-119
The structure of human interleukin 4 (IL-4) was predicted utilizing a series of experimental and theoretical techniques. Circular Dichroism (CD) spectroscopy indicated that IL-4 belonged to the all alpha-helix class of protein structures. Secondary structure prediction, site-directed mutagenesis, and CD spectroscopy suggested a predominantly alpha-helical structure, consistent with a four-helix bundle structural motif. A human/mouse IL-4 chimera was constructed to qualitatively evaluate alternative secondary structure predictions. The four predicted helices were assembled into tertiary structures using established algorithms. The mapping of three disulfide bridges in IL-4 provided additional constraints on possible tertiary structures. Using accessible surface contact area as a criterion, the most suitable structures were right handed all antiparallel four-helix bundles with two overhand loop connections. Successful loop closure and incorporation of the three disulfide constraints were possible while maintaining the expected shape, solvent accessibility, and steric interactions between loops and helices. Lastly, energy minimization was used to regularize the chain. 相似文献
17.
18.
Mechanical properties of proteins are important for a wide range of biological processes including cell adhesion, muscle contraction, and protein translocation across biological membranes. It is necessary to reveal how proteins achieve their required mechanical stability under natural conditions in order to understand the biological processes and also to use the knowledge for constructing new biomaterials for medical and industrial purposes. In this connection, it is important to know how a protein will behave in response to various impacts. Theoretical and experimental works on mechanical unfolding of globular proteins will be considered in detail in this review. 相似文献
19.
Yu. V. Kovtun A. I. Skibenko E. I. Skibenko Yu. V. Larin A. N. Shapoval E. D. Volkov V. B. Yuferov 《Plasma Physics Reports》2010,36(12):1065-1071
The parameters of a dense (1013–1014 cm−3) plasma produced by ionization of a H2 + Ti mixture in a moderate-power (W ≤ 10 MW) pulsed reflective discharge are investigated. The dynamics of the plasma density, the elemental composition of the
generated plasma, the radial distribution of the electron density, the rotation velocity and frequency of the plasma layer
with n
p
≥ n
cr, the radial electric field, the coefficient of plasma particle separation, and the coefficient of plasma recombination in
the stage of plasma decay are determined. 相似文献