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1.
The swelling properties of different chitosan–poly(vinyl alcohol) (PVA) hydrogels were investigated as functions of the medium pH and salt concentration. The maximum swelling ability of the hydrogels was at a buffer pH of approximately 3, regardless of the PVA content in the hydrogels. The maximum mass of the swollen hydrogels was about 13 times that of their contracted counterparts. The cyclical swelling and contraction between pH 3 and pH 7 buffers and pH 3 and pH 3 buffers with salt confirmed the Donnan swelling mechanism of these hydrogels. The swelling mechanism was considered the transfer of water molecules driven by a concentration gradient. This was represented by a simplified mass‐balance model, which neglected the effect of the ionization reaction, for the initial swelling period. The effective mass‐transfer coefficient of water molecules during swelling, estimated with this model, gradually decreased with increasing PVA content in the hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4665–4671, 2006 相似文献
2.
The effect of ozone on Aspergillus niger causing black rot disease in onion was studied in culture. Ozone induced the spore germination in all treatments and few spores showed rapid swelling, resulting in the production of 2-3 germ tubes per spore compared to control. Although all the ozone treated spores germinated, all of them did not produce uniform colony morphology. Some colonies which developed from ozone treated spores failed to produce spores and such colonies appeared as grey patches of mycelia without spores amidst surrounding black sporulating colonies. Further work is in progress to study the mechanism involved in formation of sterile mycelia by ozone. 相似文献
3.
An analysis of the nature and distribution of disallowed Ramachandran conformations of amino acid residues observed in high resolution protein crystal structures has been carried out. A data set consisting of 110 high resolution, non-homologous, protein crystal structures from the Brookhaven Protein Data Bank was examined. The data set consisted of a total of 18,708 non-Gly residues, which were characterized on the basis of their backbone dihedral angles (phi, psi). Residues falling outside the defined "broad allowed limits" on the Ramachandran map were chosen and the reported B-factor value of the alpha-carbon atom was used to further select well defined disallowed conformations. The conformations of the selected 66 disallowed residues clustered in distinct regions of the Ramachandran map indicating that specific phi, psi angle distortions are preferred under compulsions imposed by local constraints. The distribution of various amino acid residues in the disallowed residue data set showed a predominance of small polar/charged residues, with bulky hydrophobic residues being infrequent. As a further check, for all the 66 cases non-hydrogen van der Waals short contacts in the protein structures were evaluated and compared with the ideal "Ala-dipeptide" constructed using disallowed dihedral angle (phi, psi) values. The analysis reveals that short contacts are eliminated in most cases by local distortions of bond angles. An analysis of the conformation of the identified disallowed residues in related protein structures reveals instances of conservation of unusual stereochemistry. 相似文献
4.
A rapid and simple approach for visible determination of mercury ions (Hg2+) in aqueous solutions was developed based on surface plasmon resonance phenomenon using L‐arginine‐functionalized gold nanorods (AuNRs). At pH greater than 9, the deprotonated amine group of L‐arginine on the AuNRs bound with Hg2+ leading to the side‐by‐side assembly of AuNRs, which was verified by transmission electron microscopy images. Thus, when Hg2+ was present in the test solution, a blue shift of the typical longitudinal plasmon band of the AuNRs was observed in the ultra violet‐visible‐near infrared (UV‐Vis‐NIR) spectra, along with a change in the color of the solution, which occurred within 5 min. After carefully optimizing the potential factors affecting the performance, the L‐arginine/AuNRs sensing system was found to be highly sensitive to Hg2+, with the limit of detection of 5 nM (S/N = 3); it is also very selective and free of interference from 10 other metal ions (Ba2+, Ca2+, Cd2+, Co2+, Cs+, Cu2+, K+, Li+, Ni2+, Pb2+). The result suggests that the L‐arginine‐functionalized AuNRs can potentially serve as a rapid, sensitive, and easy‐to‐use colorimetric biosensor useful for determining Hg2+ in food and environmental samples. 相似文献
5.
An investigation of the electrical transport properties of graphene-oxide thin films 总被引:3,自引:0,他引:3
Gunasekaran Venugopal Karthikeyan KrishnamoorthyRajneesh Mohan Sang-Jae Kim 《Materials Chemistry and Physics》2012,132(1):29-33
The electrical transport properties of graphene-oxide (GO) thin films were investigated. The GO was synthesized by a modified Hummers method and was characterized by X-ray diffraction and UV-visible spectroscopy. The thin film of GO was made on a Si/SiO2 substrate by drop-casting. The surface morphology of the GO film was analyzed by using scanning electron microscopy and atomic force microscopy techniques. Temperature dependent resistance and current-voltage measurements were studied using four-terminal method at various temperatures (120, 150, 175, 200, 250 and 300 K) and their charge transport followed the 3D variable range hopping mechanism which was well supported by Raman spectra analysis. The presence of various functional groups in GO were identified by using high resolution X-ray photo electron (XPS) and Fourier transform infra red (FT-IR) spectroscopic techniques. Graphene-oxide thin film field effect transistor devices show p-type semiconducting behavior with a hole mobility of 0.25 cm2 V−1 s−1 and 0.59 cm2 V−1 s−1 when measured in air and vacuum respectively. 相似文献
6.
Performance of gas chlorination in decolourization of textile dyeing wastewater: a pilot study 总被引:1,自引:0,他引:1
This study presents performance of gas chlorination in decolourization/degradation of textile dyeing wastewater, optimisation of operating parameters and process kinetics of gas chlorination since it eliminates the generation of hazardous sludge and economical treatment method. The pH, contact time and chlorine dosage were found optimised at 9, 30 min and 300 ppm, respectively. Colour (m?1) of raw effluent was found in the range of 17–85, 14–52 and 15–24 and after the treatment, it was 3–7, 2–4 and 1–3 complying with the International colour standards at 436, 525 and 620 nm wavelengths, respectively. The percentage of colour removal and COD degradation were in the range of 89–95 and 28–45, respectively. Rate of reaction on colour removal and COD degradation were behaved in first order with kinetic rate constant ranged from 0.274 to 0.373 (min?1) and 0.046 to 0.103 (min?1), respectively. Performance of colour removal was achieved better than COD degradation. 相似文献
7.
D. Thirumoolan Vikas A. Katkar G. Gunasekaran Tapan Kanai K. Anver Basha 《Progress in Organic Coatings》2014
Hyperbranched poly(cyanurateamine) (POCYAM) was tested as a novel corrosion inhibitor for mild steel in 0.5–3 M HCl using chemical and electrochemical techniques at 25–70 °C. The results show that this compound has good corrosion inhibiting properties for mild steel in HCl at very low concentrations. Corrosion inhibition efficiency rises with POCYAM concentration. The adsorption of the POCYAM onto the mild steel surface obeys Langmuir adsorption isotherm model. The inhibition mechanism was further corroborated by the values of thermodynamic parameters obtained from the experimental data. 相似文献
8.
Mathan K. Kumar Priyan Malarvizhi Panchatcharam Parthasarathy Manogaran Gunasekaran Varadharajan R. 《Design Automation for Embedded Systems》2022,26(2):125-125
Design Automation for Embedded Systems - 相似文献
9.
The properties of concrete using coconut shell as coarse aggregate were investigated in an experimental study. Compressive, flexural, splitting tensile strengths, impact resistance and bond strength were measured and compared with the theoretical values as recommended by the standards. For the selected mix, two different water–cement ratios have been considered to study the effect on the flexural and splitting tensile strengths and impact resistance of coconut shell concrete. The bond properties were determined through pull-out test. Coconut shell concrete can be classified under structural lightweight concrete. The results showed that the experimental bond strength of coconut shell concrete is much higher than the bond strength as estimated by BS 8110 and IS 456:2000 for the mix selected. 相似文献
10.
Generally, inventory control policies for deteriorating items are very sensitive to different marketing policies especially in chemical, food and pharmaceutical industries. Realizing the importance of such inventory policies in practice, an integrated production-inventory-marketing model is developed for determining the economic production quantity (EPQ) and economic order quantity (EOQ) for raw materials in a multi-stage production system. This model considers the effect of different marketing policies such as the price per unit product and the advertisement frequency on the demand of a perishable item. A search method is employed to determine the values of EPQ and EOQ which would result in the maximum total net profit. 相似文献