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摘要:Polymer blends have been obtained in the form of dimensionally stable and free standing films and their properties were characterized by different techniques. FTIR analysis and Raman spectroscopic analysis cleared the hydrogen bonding intermolecular interaction between –CONH2 groups in Poly Acrylamide (PAM) and C-O-C and –CH2OH group in Poly Ethylene Oxide (PEO). From Differential Scanning Calorimeter (DSC) the study shows that crystallinity is increasing with PEO wt%. From polymer interaction parameter we also show that the polymer blend is miscible. Thermal stability of films is investigated by Thermo Gravimetric Analysis (TGA) and derivative Thermo Gravimetric Analysis (DrTG). From UV-Vis absorption spectra, absorption band edge, direct/ indirect band gap and optical activation energy have been calculated....
[期刊论文] Wing-Fu Lai
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2015年 01期
摘要:
Polymers have a wide diversity of applications, ranging from therapeutics delivery to tissue engineering. While advances in polymer chemistry have facilitated synthesis and development of new polymers, increasing efforts have also been directed to engineer properties of existing polymers. One of the common approaches to modify polymer properties is cold drawing, which can align polymer chains and orient the chains in a crystalline manner. Regarding the industrial significance of cold drawing in polymer engineering, this study used semi-crystalline high density polyethylene (HDPE) as a model to examine the effect of cold drawing on the anisotropic mechanical properties of polymers. During cold drawing, the yield strength of the polymer was shown to be in a positive relationship with the strain rate, and the hardness of the cold-drawn region was demonstrated to be significantly enhanced. Our results confirmed the feasibility of engineering the properties of polymers by applying tension for plastic deformation, and highlighted the importance of precise control of the strain rate in the treatment.
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[期刊论文] H. H. Hardy
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2015年 03期
摘要:Linear algebra provides insights into the description of elasticity without stress or strain. Classical descriptions of elasticity usually begin with defining stress and strain and the constitutive equations of the material that relate these to each other. Elasticity without stress or strain begins with the positions of the points and the energy of deformation. The energy of deformation as a function of the positions of the points within the material provides the material properties for the model. A discrete or continuous model of the deformation can be constructed by minimizing the total energy of deformation. As presented, this approach is limited to hyper-elastic materials, but is appropriate for infinitesimal and finite deformations, isotropic and anisotropic materials, as well as quasi-static and dynamic responses....
[期刊论文] Alla V. Nushtaeva
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2014年 01期
摘要:

The results of studies of thinning free water-in-oil emulsion films stabilized by solid particles by the Applied Pressure Drop Technique (APDT) are reported. The quasi-equilibrium film thickness achieved by slow increasing the pressure drop was smaller than the rupture thickness obtained by sharp increasing the pressure. It is shown that non-equilibrium films ruptured with thicknesses corresponding to adjustment of the packing of solid particles in the films. It is supposed that the restructuring package is the cause of the earlier breakthrough of the film.

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摘要:

The properties of mixtures of poly (ethylene oxide) (PEO) and mixed micelles formed from sodium cholate (NaC) and sodium dodecyl sulfate (SDS) in tris/HCl buffered solutions at pH 9.00 were investigated by measuring the mean surface tension. The variation in the superficial tension as a function of the time after formation of solutions containing PEO and NaC was characterized by monitoring the time required for the system to reach equilibrium between the micellar and aqueous phases. These results could serve as a reference for the minimum aging time required for solutions before any surface tension measurements can be performed.

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摘要:

Egypt faces a high population growth rate nowadays, which demands for an increase in agricultural production efficiency. Consequently, agricultural field residues will increase. Rice straw is one of the main agriculture residues in Egypt. So this study was performed on rice straw as a resource for production of bioethanol. Eight microbial isolates, five yeasts and three fungi were isolated from rice straw. Yeast isolates were selected for their ability to utilize different sugars and cellulose. Chipped and grinded rice straw was subjected to different pretreatment methods physically through steam treatment by autoclaving and different doses of gamma γ irradiation (50 and 70 Mrad). Autoclaved pretreated rice straw was further enzymatically treated throughout solid state fermentation process by different fungal isolates; F68, F94 and F98 producing maximum total reducing sugars of 12.62, 13.58, 17.00 g/L, respectively. Bioethanol production by separate microbial hydrolysis and fermentation (SHF) process of rice straw hydrolysate was performed by the two selected fungal isolates; Trichoderma viride F94 and Aspergillus terreus F98 and two yeast isolates (Y26 and Y39). The two yeast isolates have been identified by 18S, RNA as Candida tropicalis Y26 and Saccharomyces cerevisiae Y39. SHF processes by F94 and Y26 produced 45 gallon/ton rice straw while that of F98 and Y39 produced 50 gallon/ton rice straw.

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[期刊论文] Stig E. Friberg
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2013年 01期
摘要:The separation of phases after the stability composition at a plait point is exceeded has significant effect on the reactions during spontaneous emulsification, but experimental efforts to obtain accurate information are extremely difficult, because even the smallest scattering of the numbers has a large effect on the result. In the present contribution a model system was applied that closely mirrored experimental values and the mass ratio of the two phases could be calculated with high accuracy. Extrapolation of the ratio between phase masses towards the critical composition showed the two phase masses each close to 0.5, while a composition with a miniscule difference from this composition extrapolated to 1.0. The results showed spontaneous emulsification between solutions at the plait point and water to consist of two processes; an initial extremely fast reaction and a slower process between the aqueous phase formed in the primary emulsification and water....
[期刊论文] Anderson Ho Cheung SHUM
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2013年 02期
摘要:Editorial: Soft...
摘要:

In nature, tyrosol (TY) and hydroxytyrosol (HT) are found in olive leaves which are for medical aims, with immune stimulant and antibiotic properties as well as the ability to be used for the treatment of neurodegenerative diseases such as Alzheimer. This ability of phytochemical TY and HT compounds are mainly believed to be of higher radical scavenging potential with effective antioxidant properties. In order to establish the possible structure-antioxidant activity relationship of tyrosol, hydroxytyrosol, hydroxytyrosol acetate and two designed hydroxytyrosol derivatives were studied by the help of quantum chemical calculations. The molecular electronic properties such as heat formation of the neutral, radical and orbitals energies were calculated as descriptors to predict the H atom donating abilities of compounds. Considering the results from the calculated descriptors, the derivatives having OH group substitutions in position number four of the aromatic ring can be classified highly active and better antioxidant compound. Therefore, the designed hydroxytyrosol derivatives showed most active feasible H atom donation. This work can be useful to design novel antioxidants.

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摘要:

The thermo- and pH-responsive hydrogels were synthesized via copolymerization of N-isopropylacrylamide and al-lylamine hydrochloride monomers. The equilibrium swelling of the hydrogels was studied as a function of temperature and pH in aqueous solutions. It was shown that controlled alteration of the hydrogel phase transition temperature can be achieved by changing their composition and pH of the environment. Increase in content of hydrophilic allylamine from 10 to 60 wt% in monomer mixture causes a shift of the phase transition temperature from 35oC to 47oC. Hydrogels with N-isopropylacrylamide/allylamine hydrochloride mass ratio of 3:2 show the highest pH-response. Values of average molecular weight between polymer cross-links, , and Flory parameter, χ, were calculated using temperature dependences of the equilibrium swelling of the synthesized hydrogel.

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摘要:Study of interfacial processes between incorporated biomolecules and hydrogel matrix is of primary importance for the application of synthetic hydrogels as biomaterials, sensors, etc. Their hydrophilic nature, however, hampers fat-soluble biomolecule incorporation. We synthesized N-isopropylacrylamide (NIPAAm)- and Acrylamide (AA)-based hydrogels with hydrophilic-lipophilic balance that under specific conditions permit homogeneous incorporation of provitamins D3(7-dehydrocholesterol) and D2(ergosterol) dissolved in ethanol. Similarity of provitamins D photoisomerization in such hydrogel matrices with the photoreaction in ethanol shows great potential of the novel material for personal dosimetry of biologically active ‘antirachitic' UV radiation.

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[期刊论文] Rong-Cong Luo Chia-Hung Chen
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2012年 01期
摘要:Droplet based microfluidic is an effective, versatile and scalable approach which can be used to produce structured microgels with desirable features. The high degree of control endowed with microfluidics enables the formation of various functional microgels such as multicompartment encapsulations, Janus shaped particles and non spherical microgels. These microgels have aroused great interest in biological engineering aspect, since they outperform their counterparts produced from other techniques and have been applied in drug delivery, 3 Dimensional cell culture, micro tissues, single cell assay, tissue engineering and bioimaging. In this review, we will summarize the fabrication processes, technology comparisons and the usages in biomedical applications....
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