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51.
Deen GR Alsted T Richtering W Pedersen JS 《Physical chemistry chemical physics : PCCP》2011,13(8):3108-3114
Thermo-responsive crosslinked nanogels of N-isopropylacrylamide (NIPAM) were synthesized by emulsion polymerization and the size was varied using different concentrations of surfactant (sodium dodecyl sulfate, SDS) in the polymerization process. The collapse behavior of the nanogels at the lower critical solution temperature at around 32 °C was investigated by dynamic light scattering, and by combined static light scattering (SLS) and small-angle X-ray scattering (SAXS). The combined data from SLS and SAXS were analyzed by a model for the nanogels which at intermediate temperatures included a central core and a more diffuse outer layer describing pending polymer chains with a low degree of cross linking. In the expanded state, the particles were modeled with a single component with a broad graded surface. In the collapsed state the nanogels were modeled as homogeneous and relatively compact particles. The amount of surfactant used had a profound effect on the final size of the nanogels owing to the phenomenon of colloidal stabilization of the emulsion droplets during polymerization. The combination of SLS and SAXS as applied to the nanogels is an attractive method for particle characterization as it spans a very large range of scattering vector from q = 0.0004 to 0.22 ?(-1). 相似文献
52.
Abbas Azimi Roshan Manouchehr Mamaghani Nosrat Ollah Mahmoodi Farhad Shirini 《中国化学快报》2012,23(4):399-402
An efficient ultrasound-assisted preparation of a series of novel 4-aryl-3-methyl-4,5-dihydro-l//-pyrazolo[34-b]pyridin-6(7H)ones via the reaction of 5-amino-3-methyl-1H-pyrazole,Meldrum’s acid and various arylaldehydes using one-pot three-component approach is described.This rapid method produced the products in short reaction times(3-4 min) and excellent yields(87-95%). 相似文献
53.
Analysis of Pore Pressure Distribution in Shale Formations under Hydraulic,Chemical, Thermal and Electrical Interactions 总被引:1,自引:0,他引:1
Change in pore pressure in chemically active rocks such as shale is caused by several mechanisms and numerous studies have
been carried out to investigate these mechanisms. However, some important coupling terms or driving forces have been neglected
in these studies due to simplifying assumptions. In this study, a hydro-chemo-thermo-electrical model based on finite element
method is presented to investigate the change in pore pressure in shale formations resulted from thermal, hydraulic, chemical
and electric potential gradients. The change in pore pressure is induced by hydraulic conduction, chemical, electrical and
thermal osmotic flow. In order to solve the problem of ion transfer under the influence of an electrical field, the Nernst–Planck
equation is used. In addition, ion advection is considered to investigate its possible effect on ion transfer for the range
of shale permeability. All equations are derived based on the thermodynamics of irreversible processes in a discontinuous
system. The numerical results are compared against existing and derived uncoupled analytical solutions and good agreement
is observed. The numerical results showed that the ion transfer and pore pressure are considerably affected by the electric
field in the vicinity of the wellbore. It was also found that advection can play a remarkable role in ion transfer in shale
formations. It was further shown that the change in pore pressure in shale formation is characterized by the combined effect
of hydraulic, chemical, thermal and electro osmotic flow. 相似文献
54.
55.
G. Roshan Deen Vivien Chua Usman Ilyas 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3363-3372
Poly(N‐acryloyl‐N′‐ethyl piperazine‐co‐N‐isopropylacrylamide) hydrogels were prepared by thermal free‐radical copolymerization of N‐acryloyl‐N′‐ethyl piperazine (AcrNEP) and N‐isopropylacrylamide (NIPAM) in solution using N, N′‐methylene bisacrylamide as the crosslinking agent. The gels were responsive to changes in external stimuli such as pH and temperature. The pH and temperature responsive character of the gels was greatly dependent on the monomer content, namely AcrNEP and NIPAM, respectively. The gels swelled in acidic (pH 2) and de‐swelled in basic (pH 10) solutions with a response time of 60 min. With increase in temperature from 23 to 80 °C the swelling of the gels decreased continuously and this effect was different in acidic and basic solutions. The temperature dependence of equilibrium water content of the gels was evaluated by the Gibbs–Helmholtz equation. Detailed analysis of the swelling properties of these new gels in relation to molecular heterogeneity in acidic (pH 2) and basic (pH 10) solutions were performed. Water transport property of the gels was studied gravimetrically. In acidic solution, the diffusion process was non‐Fickian (anomalous) while in basic solution, the diffusion was quasi‐Fickian. The effect was more evident in solution of pH 2 than in pH 10. Various structural parameters of the gels such as number‐average molar mass between crosslink (Mc), the crosslink density (ρc), and the mesh size (ξ) were evaluated. The mesh sizes of the hydrogels were between 64 and 783 Å in the swollen state in acidic solution and 20 and 195 Å in the collapsed state in basic solution. The mesh size increased between three to four times during the pH‐dependent swelling process. The amount of unbound water (free water) and bound water of the gels was also evaluated using differential scanning calorimetry. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
56.
57.
Acoustic non-linearity parameter B/A is calculated for five binary liquid mixtures using Tong and Dong equation along with
the Flory’s statistical theory. Similar to other excess thermodynamical quantities an excess non-linearity parameter (B/A)E is defined for binary liquid mixtures. The interactions in the liquid mixtures are explained on the basis of the excess non-linearity
parameter. 相似文献
58.
Antony Godwin Ji-Won Choi Elisa Pedone Sibu Balan Roshan Jumnah Sunil Shaunak Steve Brocchini Mire Zloh 《Theoretical chemistry accounts》2007,117(2):259-265
Proteins that are used as therapeutic drugs act in the extracellular microenvironment. They usually have a small number of
intramolecular disulfide bonds to help maintain their tertiary structure in the vascular circulation. In general, most cysteine
residues are part of a disulfide bond with free sulfhydrals being uncommon. We have studied whether the site-specific chemical
reduction of disulfides and the incorporation of a 3-carbon methylene bridge between the cysteines in interferon-α 2a would
change the structure of this protein. Bridging of both of the disulfide bonds of interferon-α 2a was studied using two different
molecular simulation protocols: (1) molecular dynamics, and (2) stochastic dynamics. We have shown that the disulfide bonds
in interferon-α 2a can be reduced and chemically modified without significantly altering the tertiary structure of the protein.
This offers the novel possibility of chemically modifying therapeutically important proteins without affecting their biological
properties. 相似文献
59.
Roshan R. Kulkarni Ketaki Shurpali Vijay M. Khedkar Vedavati G. Puranik Dhiman Sarkar 《Natural product research》2016,30(6):675-681
Phytochemical investigation of the acetone extract of the aerial parts of Anisochilus verticillatus afforded a new 8,9-secopimarane diterpene (1), two new isopimarane diterpenes (2, 3) and the known ursolic acid (4), α-amyrin (5), β-amyrin (6), stigmast-5-en-3-one (7) and hydroxychavicol (8). Structures of the new compounds were elucidated with the help of 1D and 2D nuclear magnetic resonance spectroscopic data, and single crystal X-ray crystallography of compound 3. Compounds 2 and 8 inhibited Mycobacterium tuberculosis H37Ra with an IC50 of 11.3 (IC90 of 20.0 μg/mL) and 12.5 μg/mL, respectively. Correspondingly, molecular docking studies with Extra Precision Glide revealed a correlation between score and biological activity for these compounds to describe the molecular basis for the most significant SAR results. 相似文献
60.
We prove some common fixed point results for four mappings satisfying generalized weak contractive condition in partially ordered complete b-metric spaces. Our results extend and improve several comparable results in the existing literature 相似文献