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1.
Physical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to
both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface.
As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended
to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants
no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface
under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential
difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions
of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental
results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting
relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic
solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium
and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of
glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient
analitycal sensing device for quantitative determination in the field. 相似文献
2.
Wei Q Liu F Xia L Crozier S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,172(2):222-230
This paper presents a finite-difference time-domain (FDTD) simulator for electromagnetic analysis and design applications in MRI. It is intended to be a complete FDTD model of an MRI system including all RF and low-frequency field generating units and electrical models of the patient. The program has been constructed in an object-oriented framework. The design procedure is detailed and the numerical solver has been verified against analytical solutions for simple cases and also applied to various field calculation problems. In particular, the simulator is demonstrated for inverse RF coil design, optimized source profile generation, and parallel imaging in high-frequency situations. The examples show new developments enabled by the simulator and demonstrate that the proposed FDTD framework can be used to analyze large-scale computational electromagnetic problems in modern MRI engineering. 相似文献
3.
The electrical and thermal resistivities of liquid gallium are calculated over a range of temperatures above the melting point
using the solutions of the Boltzmann equation. The experimental x-ray structure factor of Waseda and the form factor derived
using the Heine-Abarenkov model potential are used in these calculations. The ratio of the electrical and thermal conductivities
is calculated and compared to experimental values and to the theoretical Lorenz number. 相似文献
4.
Thin films of mixed of Copper Phthalocyanine (CuPc) and Nickel Phthalocyanine (NiPc) are deposited onto a pure glass substrate
by a simultaneous thermal evaporation technique at room temperature. The material D.C. electrical conductivity of films at
room temperature and also films annealed at 523 K has been investigated. The optical absorption and band gaps of the films
are also measured. The results show that the electrical resistance is lower for the mixed films compared with the pure samples
and also the optical band gap decreases for the mixed samples compared to the pure samples. 相似文献
5.
From the independence of the contour of spectral density of the rotational (orientation) correlation function of a rigid molecular
top of arbitrary symmetry on temperature in the frequency scale based on the reduced time of rotational orientation relaxation
and from the near independence of the rotational contour of vibrational and vibronic absorption bands of dipole transitions
in the same coordinates in a model of “regular diffusion” of the transition oscillator with a classically rotating rigid molecular
top, it is suggested that it is possible to use the halfwidth of the contour for estimation of temperatures. Data are presented
on the halfwidth of 48 contours of bands of A, B, and C types at this frequency for 12 compounds for a temperature range of
from units to 500 degrees of absolute temperature measured experimentally and (for low temperatures) calculated by the quantum
theory.
Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 312–317, May–June, 1997. 相似文献
6.
Young-Woo Ok Min-Gu Kang Donghwan Kim Jeong Chul Lee Kyung Hoon Yoon 《Current Applied Physics》2009,9(6):1186-1190
We fabricated point-contacted a-Si:H(p)/c-Si(n) heterojunction solar cells using patterned SiO2 and investigated their electrical properties using the light current–voltage (I–V) curve and Suns-Voc measurements. The light I–V curves showed bias-dependent changes according to the applied voltage in the point-contacted cells, especially in the samples with a long distance between the point-contacted junctions. The Suns-Voc measurements showed that the bias-dependence of the light I–V curves did not originate from the recombination in the SiO2/Si or a-Si:H(p)/c-Si(n) interface, but from the series resistances. It is possible to explain the bias-dependent light I–V curve in terms of the conductivity of a-Si:H(p) and difference in the electrical contact properties between a-Si:H(p), ZnO and c-Si(n). These results mean that the electrical properties of the a-Si:H(p) layer and the contact properties with this layer are also critical to obtain a high Jsc and fill factor in n-type based Si heterojunction solar cells. 相似文献
7.
Conclusion The specialized measuring setup described in the paper makes it possible to measure correctly and with reasonably high accuracy
the luminescence decay kinetics of dyes within the time range from 40 psec to 5 nsec upon excitation in the visible range
and at 1.064 μm.
The system is highly flexible, having at the same time reasonably large data storage memory, and is completely automated.
Such a system, undoubtedly, will be helpful for researchers working in the field of physics of laser media and dyes—passive
modulators for femtosecond laser systems.
The authors are grateful to M. V. Bondar for fruitful discussions and for help with the experiments.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 1, pp. 128–134, January–February, 1995. 相似文献
8.
以单质硼和高纯石墨的混合粉末压制成型的靶材作为靶源,采用过滤阴极真空电弧技术制备不同硼含量的掺硼四面体非晶碳膜.分别采用四探针法、阻抗分析仪和电化学界面对薄膜的变温电导率、I-V特性和C-V特性进行了测试和研究.实验结果表明,当B含量由0增加至6.04 at%时,薄膜的室温电导率先逐渐增大而后逐渐减小,相应薄膜的电导激活能先逐渐减小而后逐渐增大,并在2.13 at%时分别出现最大和最小值1.42×10-7S/cm和0.1eV.此外,掺硼四面体非晶碳/n型硅异质结的I-V曲线表现出典型的整流特性,表明p-n结二极管已经形成,且结两端的掺杂能级在空间上连续统一.
关键词:
四面体非晶碳
电导率
I-V曲线')" href="#">I-V曲线
C-V曲线')" href="#">C-V曲线 相似文献
9.
The resonant and non-resonant dynamies of a Gaussian quantum wave packet travelling through a double barrier system is studied
as a function of the initial characteristics of the spectrum and of the parameters of the potential. The behaviour of the
tunnelling time shows that there are situations where the Hartman effect occurs, while, when the resonances are dominant,
and in particular for b>π/Δk (b being the inter-barrier distance and Δk the spectrum width), the tunnelling time becomes very large and the Hartman effect
does not take place. 相似文献
10.
The dynamics of formation of optical radiation in spectral lines in a longitudinal nanosecond helium discharge under conditions
of wave breakdown is investigated. A discharge tube with a diameter of 0.4 cm and a length of 50 cm was placed in a metallic
shield 1 cm in diameter. The gas pressure was varied within 1–60 torr for an amplitude of the voltage pulses of up to 50 kV.
Asymmetry of spontaneous radiation recorded from different ends of the discharge tube is detected. This is shown to be a consequence
of nonuniform distribution of the functions of the primary brightness of the flux and the absorption coefficient along the
tube length.
Dagestan State University, 43a, M. Gadzhiev Str., Makhachkala, 367025, Russia. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 66, No. 3, pp. 415–420, May–June, 1999. 相似文献
11.
Terry Morris 《Applied Physics A: Materials Science & Processing》2009,95(4):941-944
Photonic interconnections provide a viable means to overcome the fundamental limitations imposed upon computer system topologies
by electrical signaling. Direct board-to-board (or assembly-to-assembly) signaling, without need of a backplane, provides
multiple points of connectivity between adjacent electronic complexes while obviating the need to route all board-level signals
to and through a central connector choke point. Optical busses can permit full-speed signaling between multiple chips, memory
units, or processing units without requiring an active control plane. One-to-many and all-to-all photonic broadcasts greatly
simplify multi-processor and multi-core system design. 相似文献
12.
K. P. Kureichik S. N. Pupkevich V. S. Granos I. S. Kharamchenkov 《Journal of Applied Spectroscopy》1999,66(5):851-854
We describe a modified GELIOS System intended to automate the atomic-absorption spectrometers AAS, S115, SATURN, and Perkin-Elmer
503. Software is prepared in the visual environment of programming DELFI-3 and functions under the control of Windows 95.
A distinguishing feature of the GELIOS System is simultaneous search for the peak and area of the absorption signal, correction
of the errors of measurements, automatic digital filtration of data, control of the time of operation of hollow-cathode lamps,
measurement of spectra and the statistical resource of the service life of hollow-cathode lamps, use of different methods
to construct a calibrating graph, the possibility of memorizing the data of the analysis in an archived file, and a formation
of the report for printing. The system contains an electrovic data directory on atomicabsorption analysis in five volumes
for 67 elements of the Mendeleev system.
To whom correspondence should be addressed.
“University” Science and Production Center, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi
Spektroskopii, Vol. 66, No. 5, pp. 734–737, September–October, 1999. 相似文献
13.
This work addresses the difficulties in the measurements of the nonlinear medium parameter B/A and presents a modification of the finite amplitude method (FAM), one of the accepted procedures to determine this parameter. The modification is based on iterative, hybrid approach and entails the use of the versatile and comprehensive model to predict distortion of the pressure–time waveform and its subsequent comparison with the one experimentally determined. The measured p–t waveform contained at least 18 harmonics generated by 2.25 MHz, 29 mm effective diameter, single element, focused PZT source (f-number 3.5) and was recorded by Sonora membrane hydrophone calibrated in the frequency range 1–40 MHz. The hydrophone was positioned coaxially at the distal end of the specially designed, two-section assembly comprising of one, fixed length (60 mm), water-filled cylindrical container and the second, variable length (60–120 mm) container that was filled with unknown medium. The details of the measurement chamber are described and the reasons for this specific design are analyzed. The data were collected with the variable length chamber filled with 1.3-butanediol, which was used as a close approximation of tissue mimicking phantom. The results obtained provide evidence that a novel combination of the FAM with the semi-empirical nonlinear propagation model based on the hyperbolic operator is capable of reducing the overall uncertainty of the B/A measurements as compared to those reported in the literature. The overall uncertainty of the method reported here was determined to be ±2%, which enhances the confidence in the numerical values of B/A measured for different, clinically relevant media. Optimization of the approach is also discussed and it is shown that it involves an iterative procedure that entails a careful selection of the acoustic source and its geometry and the axial distance over which the measurements need to be performed. The optimization also depends critically on the experimental determination of the source surface pressure amplitude. 相似文献
14.
In this paper we present an axiomatic, geometric, formulation of electromagnetism with only one axiom: the field equation for the Faraday bivector field F. This formulation with F field is a self-contained, complete and consistent formulation that dispenses with either electric and magnetic fields or the electromagnetic potentials. All physical quantities are defined without reference frames, the absolute quantities, i.e., they are geometric four-dimensional (4D) quantities or, when some basis is introduced, every quantity is represented as a 4D coordinate-based geometric quantity comprising both components and a basis. The new observer-independent expressions for the stress-energy vector T(n) (1-vector), the energy density U (scalar), the Poynting vector S and the momentum density g (1-vectors), the angular momentum density M (bivector) and the Lorentz force K ((1-vector) are directly derived from the field equation for F. The local conservation laws are also directly derived from that field equation. The 1-vector Lagrangian with the F field as a 4D absolute quantity is presented; the interaction term is written in terms of F and not, as usual, in terms of A. It is shown that this geometric formulation is in a full agreement with the Trouton-Noble experiment. 相似文献
15.
A simple method to determine the thermal focal length of LD end-pumped solid-state laser with stable resonator is presented. The M2 factor describing the quality of the beam can be obtained by scanning a slit through the multi-mode Gaussian beam field. The waist width of the beam and the corresponding TEM00 under the same parameters of laser are then deduced through the law of multi-mode Gaussian beam propagation. Based on the standard matrix theory of stable resonator, the thermal focal length of the gain medium can be easily achieved. To show the application of this approach, the thermal focal length of an LD pumped Nd:YVO4 laser is measured and the experimental results are in agreement with the theoretical prediction. 相似文献
16.
We study the phenomenon of stochastic resonance on
small-world networks consisting of bistable genetic regulatory units,
whereby the external subthreshold periodic forcing is introduced as a
pacemaker trying to impose its rhythm on the whole network through the
single unit to which it is introduced. Without the addition of additive
spatiotemporal noise, however, the whole network remains forever trapped in
one of the two stable steady states of the local dynamics. We show that the
correlation between the frequency of subthreshold pacemaker activity and the
response of the network is resonantly dependent on the intensity of additive
noise. The reported pacemaker driven stochastic resonance depends
significantly on the asymmetry of the two potential wells characterizing the
bistable dynamics, which can be tuned via a single system parameter. In
particular, we show that the ratio between the clustering coefficient and
the characteristic path length is a suitable quantity defining the ability
of a small-world network to facilitate the outreach of the pacemaker-emitted
subthreshold rhythm, but only if the asymmetry between the potentials is
practically negligible. In case of substantially asymmetric potentials the
impact of the small-world topology is less profound and cannot warrant an
enhancement of stochastic resonance by units that are located far from the
pacemaker. 相似文献
17.
Thermodynamic stability conditions for nanoparticles (resulting from non-negativity of the second variation of the free energy)
have been analyzed for two cases: (i) a nonvolatile nanosized particle with the size-dependent surface tension; (ii) the limiting
case of larger objects when the surface tension takes its macroscopic value. It has been shown that the mechanical stability
of a nanoparticle, i.e. its stability relative to the volume fluctuations, is defined by an interplay between the excess (“surface”)
free energy and the volumetric elastic energy. According to the results obtained, noble gas clusters and metal nanoparticles
satisfy the mechanical stability condition. At the same time, water nanodrops, as well as nanoparticles presented by nonpolar
organic molecules, correspond to the stability limit. Among the investigated systems, the stability condition is not carried
out for n-Pentane clusters. 相似文献
18.
采用脉冲激光沉积技术,在Si(111)衬底上成功制备出不同含量Na,Co共掺的ZnO薄膜.利用X射线衍射仪、原子力显微镜、荧光光谱仪以及四探针电阻率测试台对薄膜的结构、表面形貌和光电性质进行了表征.重点讨论了不同掺杂浓度对薄膜光电性质的影响.结果表明:Na,Co共掺没有改变ZnO的六角纤锌矿结构且掺杂导致薄膜仅有的的紫外发光峰出现红移.当Na,Co掺杂浓度分别为10%时,峰值最强且红移最明显,发光峰波长为397 nm,薄膜的电阻率最低,达到了8.34×10-1 Ω ·cm.深入讨论了
关键词:
脉冲激光沉积
1-x-yNaxCoyO薄膜')" href="#">Zn1-x-yNaxCoyO薄膜
光电性质
红移 相似文献
19.
Olavi Kärner 《Central European Journal of Physics》2005,3(2):190-208
Temporal variability of daily time series for total solar irradiance at the top of the atmosphere, the Microwave Sounding
Unit (MSU) based global, hemispherical and zonal average temperature for the lower troposphere and stratosphere together with
5 surface air temperature data, measured at various meteorological stations have been studied by means of the structure function.
From the growth rate of the structure function in the time interval between 32 and 4096 days it follows that the variability
of the series represents an anti-persistent (AP) behavior. This property in turn shows a domination of negative feedback in
the physical system generating the lower tropospheric temperature variability. Distribution of the increments over various
ranges and correlations between them are calculated in order to determine the quantitative characteristics describing temporal
variability. 相似文献