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991.
The interaction of sulfonated tetraphenylporphins H2 TPPS4(HCl)2 and in CuTPPS4 with poly-N-vinylpyrrolidone (PVP) is studied using small-angle neutron scattering, dynamic light scattering, visible spectrophotometry, and viscometry. It is shown that porphyrin molecules form complexes with PVP, thus charging the polymeric chain. 相似文献
992.
993.
T. Zemčík 《Hyperfine Interactions》1990,55(1-4):1099-1102
A systematic increase of the average hyperfine magnetic induction at57Fe measured at room temperature during interrupted isothermal annealing was found to be inherent to the irreversible relaxation
processes in the Fe−B based soft magnetic alloys at moderately elevated temperatures. Assuming superimposed asymptotic exponential
field vs. time dependences. several processes can be distinguished, their relaxation times determined and from the Arrhenius-like
log τ vs. 1/T plots average activation enthalpies estimated. Results on the Fe70Co10B20 and Fe85−x
Co
x
B15 (x=17, 19 and 21 at. % Co) amorphous ribbons between 100 and 200°C are compared and discussed in terms of possible stress relief,
free volume annihilation and short range ordering mechanisms. 相似文献
994.
For a class of materials for which the principal strain directions always coincide with the principal stress directions one can determine the stress field in an inhomogeneously deformed body from given boundary conditions and a known strain field without knowing the constitutive equations. Each point of the inhomogeneously deformed body contains information such as that derived from an individual homogeneous identification test. The practically important two-dimensional case leads to a problem of solving a linear hyperbolic system where two differential equations describe the principal stress components. The problem can be reduced to that of integration along characteristics.Under a certain globality condition the existence, uniqueness, and correctness of the solution are guaranteed in the whole test piece. It is shown that the globality condition is closely related to whether or not the test piece is isotropic and elastic. The influence of experimental error on the correctness of problem formulation is discussed.
Abstrakte Für die Klasse der Materialen, für welche die Grundspannungsrichtungen und die Grundverformungsrichtungen gleich sind, kann man das Spannungsfeld in einem inhomogen deformierten Körper für gegebene Randbedingungen und einem bekannten Verformungsfeld ohne Kenntnis der detailierten Form der Dehnungs-Spannungsgleichung bestimmen. Jeder Punkt des inhomogen deformierten Körpers liefert dieselbe Information wie ein individueller homogener Test. Der praktisch wichtige zweidimensionale Fall führt zu einem Problem der Lösung eines linear hyperbolischen Systems von zwei Differentialgleichungen für die Grundspannungskomponenten. Das Problem kann auf die Integration entlang der Charakteristik des Systems reduziert werden.Unter einer Bedingung der Globalität das die Existent, Eindeutigkeit und Richtigkeit der Lösung in der ganzen Testprobe gewährleistet sind. Es wird gezeigt, dass diese Globalitätsbedingung damit zusammenhängt eng, ob die Testprobe isotrop und elastisch ist. Der Einfluss der experimentellen Fehler auf die Richtigkeit der Formulation des Problems wird auch analysiert.相似文献
995.
The present investigation was concerned with the rheological behaviour of dilute suspensions of solid particles in a gas in a vertical cocurrent flow moving upwards. Starting from the experimentally determined dependence of the pressure drop on the concentration of solid particles and the Reynolds number of the carrier medium in the steady flow region, the rheological parameters were estimated using pseudo-shear diagrams. Air was the carrier medium and the dispersed phase was one of six fractions of polypropylene powder and five fractions of glass ballotini. The results show that the investigated two-phase systems have pseudoplastic character which becomes more pronounced with increases in concentration, equivalent diameter and density of solid particles in the flowing suspension.
C
d
coefficient of particle resistance
-
d
e
equivalent diameter of particles
-
D
column diameter
-
Fr
Froude number
-
g
gravitational acceleration
-
K
rheological parameter
-
L
length
-
n
rheological parameter
-
p
t
pressure drop due to friction
-
p
m
total pressure drop
-
p
ag
pressure drop due to acceleration of the gas phase
-
p
as
pressure drop due to acceleration of the solid phase
-
p
g
hydrostatic pressure of the gas phase
-
p
s
specific effective weight of the dispersed phase
-
r
radius
-
Re
Reynolds number
-
Re
p
Reynolds number of a particle
-
Re
G
generalized Reynolds number
-
Re
G1
generalized Reynolds number relating to the end of the laminar flow region
-
Re
G2
generalized Reynolds number relating to the beginning of the turbulent flow region
-
w
z
axial component of velocity
-
u
t
steady free-fall velocity of a single particle
-
w
average velocity
-
w
g
average velocity of the gas phase
-
w
s
average velocity of the dispersed phase of solid particles
-
relative mass fraction of solid particles
-
x
s
volume fraction of solid particles
-
g
coefficient of pressure drop due to friction
-
µ
dynamic viscosity
-
g
density of the gas phase
-
m
density of the suspension
-
s
density of solid particles
-
ds
density of the dispersed phase
-
w
shear stress at the wall 相似文献
996.
Vapor generation-inductively coupled plasma-optical emission spectrometry was used for the determination of sulfide in water samples preserved by the addition of a zinc acetate and sodium hydroxide solution. Hydrogen sulfide and acid-volatile sulfides were transformed, by acidification, to a gaseous phase in a vapor generator and subsequently detected by inductively coupled plasma optical emission spectrometry. Compounds interfering with iodometric titration and spectrophotometric determination were examined as potential chemical interferents. The proposed method provides results comparable to iodometric titration in the tested concentration range 0.06-22.0 mg L−1. Limit of detection for the determination of hydrogen sulfide by this method is 0.03 mg L−1. 相似文献
997.
Two trisaccharides as new sulfonic acid mimetics of the sialyl Lewis A tetrasaccharide were synthesized. The natural sialic acid residue is replaced by a C-sulfonic acid moiety attached to position C-3′ of the lactosamine unit of the mimetics. The l-fucose unit was also replaced by a d-arabinose ring in one of the analogues. Formation of the sulfonic acid moiety on the trisaccharide level could be successfully achieved by means of introduction of an acetylthio moiety into the galactose skeleton and subsequent oxidation. The equatorial arrangement of the acetylthio group linked to C-3 of the galactose ring could be achieved by double nucleophilic substitution; efficient formation of the gulo-triflate derivatives required low-power microwave activation. Oxidation of the acetylthio group was carried out using Oxone in acetic acid. 相似文献
998.
András Székács Éva Lauber Eszter Takács Béla Darvas 《Analytical and bioanalytical chemistry》2010,396(6):2203-2211
The distribution of Cry1Ab toxin was detected in the leaves of genetically modified maize of genetic event MON 810 by enzyme-linked immunosorbent assay. Cry1Ab toxin contents in the leaves at reproductive (milk, R3) phenological stage were
measured to be between 3,878 and 11,148 ng Cry1Ab toxin/g fresh weight. Toxin content was significantly lesser (significant
difference (SD) = 1,823 ng Cry1Ab toxin/g fresh leaf weight, p < 0.01) in leaves at the lowest leaf level, than at higher leaf levels, probably due to partial leaf necrotisation. A substantial
(up to 22%) plant-to-plant variation in Cry1Ab contents in leaves was observed. When studying toxin distribution within the
cross and longitudinal sections of single leaves, lesser variability was detected diagonally, with approximately 20% higher
toxin concentrations at or near the leaf vein. More significant variability (SD = 2,220 ng Cry1Ab toxin/g fresh leaf weight,
p < 0.01) was seen lengthwise along the leaf, starting at 1,892 ng Cry1Ab toxin/g fresh weight at the sheath and rising to
maximum concentration at the middle of the lamella. Cry1Ab toxin content may suffer significant (SD = 2,230 ng Cry1Ab toxin/g
fresh leaf weight, p < 0.01) decreases in the leaf due to necrotisation. The results indicate that the longitudinal dimension of the leaf has
more significance for sampling purposes than the diagonal position. 相似文献
999.
Jakub Plášil Elena Buixaderas Jiří Čejka Jiří Sejkora Jan Jehlička Milan Novák 《Analytical and bioanalytical chemistry》2010,397(7):2703-2715
The uranyl sulphate mineral zippeite was studied by Raman spectroscopy. The phase purity of the sample was initially checked
by X-ray powder diffraction and its chemical composition was defined by electron microprobe (wavelength dispersive spectroscopy,
WDS) analysis. The Raman spectroscopy research focused on the low wavenumber and uranyl stretching vibration regions. Vibration
bands down to 50 cm–1 were tentatively assigned. The U–O bond lengths were calculated based on empirical relations. Inferred values are consistent
with those obtained from the crystal structure analysis of synthetic zippeite. Number of bands was interpreted on the basis
of factor group analysis. 相似文献
1000.
V. T. Lebedev D. N. Orlova V. M. Lebedev Gy. Török A. B. Mel’nikov L. V. Vinogradova 《Russian Journal of Applied Chemistry》2010,83(5):864-868
Association of short-chain sulfopolystyrene ionomers containing 5.2 mol % ionic SO3Li groups in carbon tetrachloride was studied by cold neutron scattering. 相似文献