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排序方式: 共有156条查询结果,搜索用时 15 毫秒
1.
Sung Hwan Koo Dong Jun Li Taeyeong Yun Dong Sung Choi Kyung Eun Lee Gil Yong Lee Youngtak Oh Joonwon Lim Suchithra Padmajan Sasikala Ho Jin Lee In Ho Kim Hong Ju Jung Rishabh Jain Sang Ouk Kim 《Particle & Particle Systems Characterization》2019,36(7)
Efficient water electrolysis catalyst is highly demanded for the production of hydrogen as a sustainable energy fuel. It is reported that cobalt derived nanoparticle (CoS2, CoP, CoS|P) decorated reduced graphene oxide (rGO) composite aerogel catalysts for highly active and reliable hydrogen evolution reaction electrocatalysts. 7 nm level cobalt derived nanoparticles are synthesized over graphene aerogel surfaces with excellent surface coverage and maximal expose of active sites. CoS|P/rGO hybrid aerogel composites show an excellent catalytic activity with overpotential of ≈169 mV at a current density of ≈10 mA cm?2. Accordingly, efficient charge transfer is attained with Tafel slope of ≈52 mV dec?1 and a charge transfer resistance (Rct) of ≈12 Ω. This work suggests a viable route toward ultrasmall, uniform nanoparticles decorated graphene surfaces with well‐controlled chemical compositions, which can be generally useful for various applications commonly requiring large exposure of active surface area as well as robust interparticle charger transfer. 相似文献
2.
K. Madhavan B. S. R. Reddy 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2980-2989
A series of poly(dimethylsiloxane‐urethane) elastomers based on hexamethylenediisocyanate, toluenediisocyanate, or 4,4′‐methylenediphenyldiisocyanate hard segment and polydimethylsiloxane (PDMS) soft segment were synthesized. In this study, a new type of soft‐segmented PDMS crosslinker was synthesized by hydrosilylation reaction of 2‐allyloxyethanol with polyhydromethylsiloxane, using Karstedt's catalyst. The synthesized soft‐segmented crosslinker was characterized by FT‐IR, 1H, and 13C NMR spectroscopic techniques. The mechanical and thermal properties of elastomers were characterized using tensile testing, thermogravimetric analysis, differential scanning calorimetry (DSC), and dynamical mechanical analysis measurements. The molecular structure of poly(dimethylsiloxane‐urethane) membranes was characterized by ATR‐FTIR spectroscopic techniques. Infrared spectra indicated the formation of urethane/urea aggregates and hydrogen bonding between the hard and soft domains. Better mechanical and thermal properties of the elastomers were observed. The restriction of chain mobility has been shown by the formation of hydrogen bonding in the soft and hard segment domains, resulting in the increase in the glass‐transition temperature of soft segments. DSC analysis indicates the phase separation of the hard and soft domains. The storage modulus (E′) of the elastomers was increasing with increase in the number of urethane connections between the hard and soft segments. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2980–2989, 2006 相似文献
3.
K. Ramulu B. M. Rao P. Madhavan M. Lalitha Devi M. K. Srinivasu K. B. Chandrasekhar 《Chromatographia》2007,65(3-4):249-252
A simple and new isocratic normal phase chiral HPLC method has been developed for the determination of enantiomeric purity
of pemetrexed disodium (l-enantiomer) in bulk drugs with a short run time of about 20 min. Chromatographic separation of l and d-enantiomers of pemetrexed disodium was achieved on an amylose based chiral stationary phase using a mobile phase consists
of hexane, ethanol and trifluoro acetic acid. The resolution between the enantiomers was found to be more than 2.0. The system
precision and method precision were found to be within 5% RSD for the distomer (d-enantiomer) at its specification level (i.e. not more than 1.0% w/w). The limit of detection and limit of quantification of distomer were 1.6 and 5 μg mL−1, respectively for 10 μL injection volume. The percentage recovery of distomer was ranged from 90.6 to 105.7 in bulk drug
samples. The test solution was found to be stable in the diluent for 48 h. The method was found to be specific for the enantiomers
of pemetrexed disodium and can be conveniently used for the quantification of undesired d-enantiomer present in the bulk drug samples of pemetrexed disodium. 相似文献
4.
P. Madhavan Bandlamudi Mallikarjuna Rao B. Pravin S. Abhishek P. R. Kumar M. Sreenivasulu K. B. Chandrasekhar 《Chromatographia》2007,66(3-4):243-246
A chiral liquid chromatographic method for enantiomeric resolution of β-amino-β-(3-methoxyphenyl) propionic acid was developed
and validated. The “hybrid” π-electron donor–acceptor based stationary phase (R,R) Whelk-01 was found to be enantiomerically
selective for (R) and (S) enantiomers of β-amino-β-(3-methoxyphenyl) propionic acid with a resolution greater than 2.0. The effects of isopropyl alcohol
and ethanol on enantioselectivity and resolution of enantiomers were evaluated. Calibration curves were linear over the range
of 0.10–1.00, with a regression coefficient (r) of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were 300 and 1,000 ng mL−1 respectively for 10 μL injection volume. The percentage RSD of the peak area of six replicate injections of (S) enantiomer at LOQ concentration was 2.8. The percentage recovery of (S) enantiomer from (R) enantiomer samples ranged from 92 to 102. The test solution was observed to be stable up to 24 h after the preparation.
The developed normal phase chiral LC method can be used for the enantiomeric purity evaluation of R-β-amino-β-(3-methoxyphenyl) propionic acid. 相似文献
5.
6.
Gayatri Mohanto S. R. Abhilash D. Kabiraj N. Madhavan R. K. Bhowmik 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1129-1131
Targets of isotopically enriched 170Er (erbium) were prepared on 45 μg/cm2 carbon backing using the method of vacuum evaporation. Another layer of carbon with thickness 23 μg/cm2 was deposited on it as a protective cap with the help of an electron gun. Carbon backing, Er and the capping carbon layer were deposited using resistive heating and electron gun deposition without disturbing the vacuum. The thickness of 170Er was measured by X-ray fluorescence analysis as well as with Rutherford backscattering spectrometry and it was found to be 150 μg/cm2. Successful preparation of sandwiched targets was very sensitive to substrate temperature, deposition rate, duration of in situ annealing, cooling rate etc. 相似文献
7.
Harinash Rao Sulin Choo Sri Raja Rajeswari Mahalingam Diajeng Sekar Adisuri Priya Madhavan Abdah Md. Akim Pei Pei Chong 《Molecules (Basel, Switzerland)》2021,26(7)
Biofilms play an essential role in chronic and healthcare-associated infections and are more resistant to antimicrobials compared to their planktonic counterparts due to their (1) physiological state, (2) cell density, (3) quorum sensing abilities, (4) presence of extracellular matrix, (5) upregulation of drug efflux pumps, (6) point mutation and overexpression of resistance genes, and (7) presence of persister cells. The genes involved and their implications in antimicrobial resistance are well defined for bacterial biofilms but are understudied in fungal biofilms. Potential therapeutics for biofilm mitigation that have been reported include (1) antimicrobial photodynamic therapy, (2) antimicrobial lock therapy, (3) antimicrobial peptides, (4) electrical methods, and (5) antimicrobial coatings. These approaches exhibit promising characteristics for addressing the impending crisis of antimicrobial resistance (AMR). Recently, advances in the micro- and nanotechnology field have propelled the development of novel biomaterials and approaches to combat biofilms either independently, in combination or as antimicrobial delivery systems. In this review, we will summarize the general principles of clinically important microbial biofilm formation with a focus on fungal biofilms. We will delve into the details of some novel micro- and nanotechnology approaches that have been developed to combat biofilms and the possibility of utilizing them in a clinical setting. 相似文献
8.
Lakshminarayana B. N. Sreenatha N. R. Jeevan Chakravarthy A. S. Suchithra B. Hariprasad S. 《Crystallography Reports》2022,67(2):201-208
Crystallography Reports - The molecular structure of 2-chloro-3-(1'-napthyl)-5,5-dimethyl-2- cyclohexenone was determined by single crystal X-ray diffraction. The compound crystallized in a... 相似文献
9.
The kinetics of reaction between benzyl chloride and phenol (or substituted phenols) in the presence of sodium hydroxide have
been investigated. A differential application of the effect of substituents on the reaction rate to distinguish between a
rate-limiting oxygen or carbon attack has been attempted. Considerable scatter in the Hammett plot for the latter attack points
to an essentially O-alkylation. The rate constants correlate well with pKa values of the different phenols. The influence of salt and solvent on the reaction rate suggests this reaction to be an ion-dipole
one. 相似文献
10.
Madhavan Narayanan Vijay R. Singh Goutham Kodali Katarina Moravcevic Robert J. Stanley 《Photochemistry and photobiology》2017,93(1):343-354
Reduced anionic flavin adenine dinucleotide (FADH?) is the critical cofactor in DNA photolyase (PL) for the repair of cyclobutane pyrimidine dimers (CPD) in UV‐damaged DNA. The initial step involves photoinduced electron transfer from *FADH? to the CPD. The adenine (Ade) moiety is nearly stacked with the flavin ring, an unusual conformation compared to other FAD‐dependent proteins. The role of this proximity has not been unequivocally elucidated. Some studies suggest that Ade is a radical intermediate, but others conclude that Ade modulates the electron transfer rate constant (kET) through superexchange. No study has succeeded in removing or modifying this Ade to test these hypotheses. Here, FAD analogs containing either an ethano‐ or etheno‐bridged Ade between the AN1 and AN6 atoms (e‐FAD and ε‐FAD, respectively) were used to reconstitute apo‐PL, giving e‐PL and ε‐PL respectively. The reconstitution yield of e‐PL was very poor, suggesting that the hydrophobicity of the ethano group prevented its uptake, while ε‐PL showed 50% reconstitution yield. The substrate binding constants for ε‐PL and rPL were identical. ε‐PL showed a 15% higher steady‐state repair yield compared to FAD‐reconstituted photolyase (rPL). The acceleration of repair in ε‐PL is discussed in terms of an ε‐Ade radical intermediate vs superexchange mechanism. 相似文献