排序方式: 共有25条查询结果,搜索用时 31 毫秒
11.
12.
Experimental results on the nuclear spin-lattice and nuclear spin-spin relaxation times in the ferromagnetic EuB6 at temperatures below 4·2 K are presented using the external magnetic field,H
ext, in the range of 0 ⩽H
ext ⩽ 10 kG. Nuclear spin-spin relaxation time computed on the basis of the Suhl-Nakamura process turns out to be 3·2μs, which compares well with the experimental value 11·1μs obtained with the 10 kG magnetic field at 1·7 K. It is found that in the ferromagnetic EuB6,T
1 is approximately 5 × 103 times larger thanT
2 at 1·7 K with the 10 kG magnetic field. Thus the effect ofT
1 onT
2 can be neglected. From the experimental value ofT
2, the value of the homogeneous line broadening is found to be 14 kHz. The corresponding value obtained from the cw method
is 175 kHz. This evidently shows the presence of the inhomogeneous line broadening in the cw NMR. 相似文献
13.
We consider the time-dependent shear flow of an Oldroyd-B fluid with slip along the fixed wall. Slip is allowed by means
of a generic slip equation predicting that the shear stress is a non-monotonic function of the velocity at the wall. The complete
one-dimensional stability analysis to one-dimensional disturbances is carried out and the corresponding neutral stability
diagrams are constructed. Asymptotic results for large values of the elasticity number and finite element calculations are
also presented. The instability regimes are within or coincide with the negative-slope regime of the slip equation. The numerical
calculations agree with the linear stability results when the size of the initial perturbation is small. Large perturbations
may destabilize a linearly stable steady state, leading to a periodic solution. The period and the amplitude of the periodic
solutions increase with elasticity.
Received: 19 June 1997 Accepted: 22 September 1997 相似文献
14.
Sans résumé 相似文献
15.
16.
MM. D. Letouz J. Duflos G. Queguiner P. Pastour 《Journal of heterocyclic chemistry》1973,10(6):1075-1076
This communication describes the synthesis of 7-one (7H) cyclohepta[b]pyridine and some derivatives (6,8-dimethyl; 8-methyl; 8-ethyl….). These compounds have been obtained by condensation of ketones with 2,3-diformylpyridine. 相似文献
17.
The three-dimensional problem of advection-dispersion associated with an elliptical non-aqueous-phase liquid (NAPL) pool is addressed using the boundary element method. The boundary condition on the plane of the pool is such that over the pool the concentration is equal to the saturation concentration while a no flux boundary condition is imposed in the region not covered by the pool. The numerical results are verified by asymptotic analytical solutions obtained in the limits of diffusion-dominated and convection-dominated mass transport. For cases of practical interest an empirical expression is obtained for the Sherwood number that matches the numerical results over a wide range of the relevant parameters. Comparison with experimental results suggests that the corresponding numerical results predict a higher overall mass transfer coefficient. 相似文献
18.
The objective of this study was to determine if topical anesthesia to the larynx and pharynx affects vocal fold motion during dynamic voice evaluation with transnasal flexible endoscopy. Transnasal dynamic laryngeal examinations of 10 patients with no voice complaints were evaluated by five blinded fellowship-trained laryngologists. Each patient was examined before and after application of topical anesthetic. Reviewers rated briskness of right and left vocal fold movement and longitudinal tension on a visual analogue scale. Statistical comparisons were made between individual subject scores before and after anesthetic application. Inter-rater reliability was also assessed. No statistical difference was observed between subject scores before and after anesthetic application. Average intraclass correlation coefficients were 0.643 and 0.591 for pre- and postanesthesia scores, respectively. Application of topical anesthesia to the larynx and pharynx does not affect vocal fold motion. 相似文献
19.
Constantinos V. Chrysikopoulos Evangelos A. Voudrias Marios M. Fyrillas 《Transport in Porous Media》1994,16(2):125-145
A mathematical model for transient contaminant transport resulting from the dissolution of a single component nonaqueous phase liquid (NAPL) pool in two-dimensional, saturated, homogeneous porous media was developed. An analytical solution was derived for a semi-infinite medium under local equilibrium conditions accounting for solvent decay. The solution was obtained by taking Laplace transforms to the equations with respect to time and Fourier transforms with respect to the longitudinal spatial coordinate. The analytical solution is given in terms of a single integral which is easily determined by numerical integration techniques. The model is applicable to both denser and lighter than water NAPL pools. The model successfully simulated responses of a 1,1,2-trichloroethane (TCA) pool at the bottom of a two-dimensional porous medium under controlled laboratory conditions.Notation
a,a
1
defined in (45a) and (45b), respectively
-
b
defined in (45c)
-
b
vector of true model parameters (n×1)
-
vector of estimated model parameters (n×1)
-
c
liquid phase solute concentration (solute mass/liquid volume), M/L3
-
c
s
aqueous saturation concentration (solubility), M/L3
-
C
dimensionless liquid phase solute concentration, equal toc/c
s
-
molecular diffusion coefficient, L2/t
-
e
effective molecular diffusion coefficient, equal to
/
*, L2/t
-
D
x
longitudinal hydrodynamic dispersion coefficient, L2/t
-
D
z
hydrodynamic dispersion coefficient in the vertical direction, L2/t
-
e
random vector with zero mean (m×1)
- erf[x]
error function, equal to (2/
1/2)
-
f
vector of fitting errors or residuals (m×1)
-
Fourier operator
-
-1
Fourier inverse operator
-
g
vector of model simulated data (m×1)
-
k
mass transfer coefficient, L/t
-
average mass transfer coefficient, L/t
-
K
d
partition or distribution coefficient (liquid volume/solids mass), L3/M
-
pool length, L
-
o
distance between the pool and the origin of the specified Cartesian coordinate system, L
-
Laplace operator
-
-1
Laplace inverse operator
-
m
number of observations
-
M
Laplace/Fourier function defined in (38)
-
n
number of model parameters
-
N
Laplace/Fourier function defined in (39)
-
p
defined in (46)
- Pe
x
Péclet number, equal toU
x
/D
x
- Pe
z
Péclet number, equal toU
x
/D
z
-
q
defined in (47)
-
R
retardation factor
-
s
Laplace transform variable
-
S
objective function
- Sh
local Sherwood number, equal tok/
e
- Sh
o
overall Sherwood number, equal to
l/
e
-
t
time,t
-
T
dimensionless time, equal toU
x
t/
-
u
dummy integration variable
-
u
vector of independent variables
-
U
x
average interstitial velocity, L/t
-
x
spatial coordinate in the longitudinal direction, L
-
X
dimensionless longitudinal length, equal to (x–)/
-
y
vector of observed data (m×1)
-
z
spatial coordinate in the vertical direction, L
-
Z
dimensionless vertical length, equal toz/
-
Fourier transform variable
-
defined in (37)
-
defined in (50)
-
porosity (liquid volume/aquifer volume), L3/L3
-
defined in (52a) and (52b), respectively
-
decay coefficient, t–1
-
dimensionless decay coefficient, equal to /U
x
-
bulk density of the solid matrix (solids mass/aquifer volume), M/L3
-
dummy integration variable
-
*
tortuosity 相似文献
20.
Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Although a subject of intense research, the etiology of PD remains poorly understood. Recently, several lines of evidence have implicated an intimate link between aberrations in the ubiquitin proteasome system (UPS) and PD pathogenesis. Derangements of the UPS, which normally functions as a type of protein degradation machinery, lead to alterations in protein homeostasis that could conceivably promote the toxic accumulation of proteins detrimental to neuronal survival. Not surprisingly, various cellular and animal models of PD that are based on direct disruption of UPS function reproduce the most prominent features of PD. Although persuasive, new developments in the past few years have in fact raised serious questions about the link between the UPS and PD. Here I review current thoughts and controversies about their relationship and discuss whether strategies aimed at mitigating UPS dysfunction could represent rational ways to intervene in the disease. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com). 相似文献