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排序方式: 共有465条查询结果,搜索用时 29 毫秒
101.
Eylem Turan Serkan Demirci Tuncer Caykara 《Journal of Polymer Science.Polymer Physics》2008,46(16):1713-1724
Dual temperature‐ and pH‐sensitive hydrogels composed of N‐isopropylacrylamide (NIPAM) and 2‐acrylamido‐2‐methyl‐propanosulfonic acid (AMPS) were prepared by free‐radical crosslinking copolymerization in aqueous solution at 22 °C. The mole percent of AMPS in the comonomer feed was varied between 0.0 and 7.5, while the crosslinker ratio was fixed at 5.0/100. The effect of AMPS content on thermo‐ and pH‐ induced phase transitions as well as equilibrium swelling/deswelling, interior morphology and network structure was investigated. The volume phase transition temperature (VPT‐T) was determined by both swelling/deswelling measurements and differential scanning calorimetry (DSC) technique. In addition, the volume phase transition pH (VPT‐pH) was detected from the derivative of the curves of the swelling ratio (dQv/dpH) versus pH. The polymer‐solvent interaction parameter (χ) and the average molecular mass between crosslinks ( ) of hydrogels were calculated from swelling ratios in buffer solutions at various pHs. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter of hydrogels were also determined by using the modified Flory–Rehner equation. The negative values for ΔH and ΔS indicated that the hydrogels had a negative temperature‐sensitive property in water, that is, swelling at a lower temperature and shrinking at a higher temperature. It was observed that the experimental swelling data of hydrogels at different temperature agreed with the modified Flory‐Rehner approach based on the affine network model. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1713–1724, 2008 相似文献
102.
Journal of Fluorescence - A novel quinoline-functionalized calix [4] arene derivative (Quin-Calix) has been successfully synthesized at partial cone conformation and duly characterized by using... 相似文献
103.
The lag-entrainment method, which is a well-established integral method for predicting the development of turbulent boundary layers, is used in this study to predict two-dimensional turbulent separated flow. The method is used in an inverse mode, in which the displacement thickness is specified together with other integral parameters of the boundary layer. It is concluded that the prediction of two-dimensional separated flow by an integral method is feasible, but there is a need for accurate data for both equilibrium and general separated flows for making a comparison. 相似文献
104.
M. Yavuz Corapcioglu 《Transport in Porous Media》1991,6(4):435-444
Electrokinetic techniques have been used for various purposes including consolidation of soils, dewatering of sludges, and hazardous waste remediation among others. Estimating the feasibility of employing electro-osmosis in a particular operation depends on the ability to predict the outcome under a variety of conditions. Predictions of this type are frequently facilitated by the use of a mathematical model designed to represent the physical system under consideration in a rigorous fashion. First, a review of fundamental aspects of electro-chemico-osmotic flow in soils is presented. Following a brief outline of previous studies, identification and quantification of the significant processes, and the construction of mathematical representations are given. This is achieved using an approach based on the macroscopic conservation of mass equations and the principle of a continuum, in contrast to an approach based on the irreversible thermodynamics of coupled flows. Special emphasis is given to coupling effects on transport processes. A complete model and associated boundary conditions are then obtained for electrokinetic processes in a compressible porous medium. The proposed model takes into consideration the migration of a contaminant plume in a flow field generated by an applied electric potential.Symbols
a
v
soil compressibility
-
A
an entity
-
C
w
mass fraction of water component in the water phase
-
C
s
mass fraction of chemical component in the water phase
-
C
*
capacitance of the porous medium per unit volume of porous volume
-
D
mechanical dispersion coefficient
-
D
fw
ps
hydrodynamic diffusion tensor for the chemical component in the water phase
-
D
fw
pw
hydrodynamic dispersion coefficient for the water component in the water phase
-
D
f( )/Dt
material derivative with respect to an observer moving at the water phase velocity V
f
-
D
s( )/Dt
material derivative with respect to moving solids
-
e
void ratio
-
f
a function
-
F = 0
equation of a moving boundary
-
g
gravitational acceleration
-
k
permeability tensor of the porous medium
-
k
e
coefficient of electro-osmotic permeability
-
k
ec
coefficient of migration potential
-
k
hc
chemico-osmotic coupling coefficient
-
m
i
number of moles of the ith component
-
m
i0
number of moles of the ith component at a reference level
-
n
porosity
-
p
pore pressure
-
p
oi
pore pressure at a reverence level
-
q
specific discharge of water phase
-
q
e
current density
-
q
fe
p0
constant current density applied at a boundary
-
q
0
constant flow rate
-
q
r
specific discharge of the water phase relative to the moving solid matrix
-
R
net mass transfer rate of the chemical component in the water phase
-
t
time
-
u
velocity of a moving surface
- i
partial molar density of ith component
-
V
f
velocity of the water phase
-
V
s
velocity of the solid (rate of deformation)
-
x
vertical coordinate
-
coefficient of matrix compressibility
-
p
compressibility of water phase in motion
-
total (overburden) stress tensor
-
effective stress tensor
-
h
streaming current conductivity
-
e
electrical conductivity
-
electrical potential
-
f
viscosity of the water phase
-
hf
density of the water phase 相似文献
105.
More Than 12 % Polarization and 20 Minute Lifetime of 15N in a Choline Derivative Utilizing Parahydrogen and a Rhodium Nanocatalyst in Water 下载免费PDF全文
Jeffrey McCormick Dr. Sergey Korchak Dr. Salvatore Mamone Dr. Yavuz N. Ertas Zhiyu Liu Luke Verlinsky Dr. Shawn Wagner Dr. Stefan Glöggler Prof. Louis‐S. Bouchard 《Angewandte Chemie (International ed. in English)》2018,57(33):10692-10696
Hyperpolarization techniques are key to extending the capabilities of MRI for the investigation of structural, functional and metabolic processes in vivo. Recent heterogeneous catalyst development has produced high polarization in water using parahydrogen with biologically relevant contrast agents. A heterogeneous ligand‐stabilized Rh catalyst is introduced that is capable of achieving 15N polarization of 12.2±2.7 % by hydrogenation of neurine into a choline derivative. This is the highest 15N polarization of any parahydrogen method in water to date. Notably, this was performed using a deuterated quaternary amine with an exceptionally long spin‐lattice relaxation time (T1) of 21.0±0.4 min. These results open the door to the possibility of 15N in vivo imaging using nontoxic similar model systems because of the biocompatibility of the production media and the stability of the heterogeneous catalyst using parahydrogen‐induced polarization (PHIP) as the hyperpolarization method. 相似文献
106.
New adducts of ethylenediamine (en), N,N-dimethylethylenediamine (ndmen) and N,N′-dimethylethylenediamine (dmen) with squarate as counter-ions were synthesized and characterized by physico-chemical methods
(IR and UV/vis spectroscopy, magnetic susceptibility and thermoanalytical measurements). The crystal structure of tris(ethylenediamine)cobalt(III)
1.5 squarate hexahydrate, [Co(en)3](sq)1.5 · 6H2O, was determined by single crystal X-ray diffraction. Co(III), Ni(II) and Cu(II) ions in the monomeric octahedral tris(ethylenediamine)cobalt(III)
1.5 squarate hexahydrate (1), tris(ethylenediamine)nickel(II) squarate 0.5 hydrate (2) and diaquabis(ethylenediamine)copper(II) squarate dihydrate (3) are chelated by ethylenediamines through two amine nitrogen atoms. Cu(II) atoms in the diaquabis(ndmen)copper(II) squarate
(4) and diaquabis(dmen)copper(II) squarate (5) monomeric octahedral complexes are coordinated by ndmen and dmen molecules through two amine nitrogen atoms in a bidentate
chelating manner. Water molecules complete the octahedral coordination. The orange (1), violet (4) and violet (5) complexes upon heating transform to claret, green and green species on dehydration, respectively, which revert immediately
after cooling in the open atmosphere. The violet (3) complex upon heating loses water molecules yielding a deep blue dehydrated species, which on further heating undergoes an
exothermic phase transition accompanied by thermochromism, deep blue to brown in the solid state. The decomposition mechanism
and thermal stability of the solid complexes are interpreted in terms of their structures. The final decomposition products
– the respective metal oxides – were identified by IR spectroscopy. 相似文献
107.
AbstractMolecularly imprinted cryogels for protein recognition have received much attention in recent years with the development of supermacroporous polymer systems. Molecularly imprinted cryogels, which offer great advantages for the selective and effective purification and separation of biomacromolecules from their sources, have become an important candidate for affinity matrix. Cryogels with their macroporous structure give rise to use them in different applications, such as tissue engineering, protein recognition and separation fields and environmental issues. This review highlights the principles of molecular imprinting technology, the preparation and properties of cryogels, the recent developments and applications of molecularly imprinted cryogels especially in protein chromatography. 相似文献
108.
Yavuz Abdulcabbar Kaplan Kaan Bedir Metin 《Journal of Solid State Electrochemistry》2022,26(6):1333-1347
Journal of Solid State Electrochemistry - The motivation of this study is to understand the usability of annealed stainless steel mesh obtained by a straightforward method for energy storage... 相似文献
109.
In this paper, we first consider a generalization of Kim’s -adic -integral on including parameters and . By using this integral, we introduce the -Daehee polynomials and numbers with weight . Then, we obtain some interesting relationships and identities for these numbers and polynomials. We also derive some correlations among -Daehee polynomials with weight , -Bernoulli polynomials with weight and Stirling numbers of second kind. 相似文献
110.
B. Harihara Venkatraman Piyali D. Chaudhuri Serkan Yurt D. Venkataraman 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):983-985
In this paper, we show a common strategy to synthesize tetraalkenylmethanes, a cross-linker series for building three-dimensional hydrocarbon networks. To demonstrate the feasibility of this method, we have synthesized tetrapentenylmethane. Attempts to synthesize this cross-linker from pentaerythrityl tetrabromide using substitution reactions resulted in the formation of a spiro compound due to intramolecular cyclization. We also show that the difficulty in reactions at the neopentyl carbon site is due to the neopentyl carbanion stability, not the sterics. 相似文献