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排序方式: 共有139条查询结果,搜索用时 568 毫秒
81.
Danick Reynard Dr. Sunny Maye Dr. Pekka Peljo Vimanshu Chanda Prof. Hubert H. Girault Dr. Solène Gentil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(32):7250-7257
The MnIII/MnII redox couple with a standard potential of +1.51 V versus the standard hydrogen electrode (SHE) has attracted interest for the design of V/Mn redox flow batteries (RFBs). However, MnIII disproportionation leads to a loss of capacity, an increase in pressure drop, and electrode passivation caused by the formation of MnO2 particles during battery cycling. In this work, the influence of TiIV or/and VV on MnIII stability in acidic conditions is studied by formulating four different electrolytes in equimolar ratios (Mn, Mn/Ti, Mn/V, Mn/V/Ti). Voltammetry studies have revealed an ECi process for MnII oxidation responsible for the electrode passivation. SEM and XPS analysis demonstrate that the nature and morphology of the passivating oxides layer depend strongly on the electrolyte composition. Spectroelectrochemistry highlights the stabilization effect of TiIV and VV on MnIII. At a comparable pH, the amount of MnIII loss through disproportionation is decreased by a factor of 2.5 in the presence of TiIV or/and VV. Therefore, VV is an efficient substitute for TiIV to stabilize the MnIII electrolyte for RFB applications. 相似文献
82.
Kestutis Juodkazis Jurga Juodkazytė Putinas Kalinauskas Titas Gertus Edgaras Jelmakas Hiroaki Misawa Saulius Juodkazis 《Journal of Solid State Electrochemistry》2010,14(5):797-802
Influence of direct laser writing with femtosecond pulses on electrochemical etching of n-type low conductivity (>1,000 Ωcm)
silicon is demonstrated. It has been shown that thermal 1-μm-thick SiO2 layer on silicon surface can be used as a protective layer in the electrochemical etching process. It has been found that
laser ablation changes not only the surface morphology and structure of silicon samples but also the character of their anodic
etching in aqueous solution of hydrofluoric acid. Formation of microvoids and caverns of irregular shape has been observed
at the laser-ablated sites. It is proposed that the change of silicon conductivity from n- to p-type takes place at the laser
fabricated regions. Processes of Si anodic oxidation and electrochemical etching are discussed. 相似文献
83.
Mei‐Yi Zhang Ying Gao Joan Btesh Natasha Kagan Edward Kerns Tarek A. Samad Pranab K. Chanda 《Journal of mass spectrometry : JMS》2010,45(2):167-177
Endocannabinoids (ECs), such as anandamide (AEA) and 2‐arachidonoylglycerol (2‐AG), modulate a number of physiological processes, including pain, appetite and emotional state. Levels of ECs are tightly controlled by enzymatic biosynthesis and degradation in vivo. However, there is limited knowledge about the enzymes that terminate signaling of the major brain EC, 2‐AG. Identification and quantification of 2‐AG, 1‐AG and arachidonic acid (AA) is important for studying the enzymatic hydrolysis of 2‐AG. We have developed a sensitive and specific quantification method for simultaneous determination of 2‐AG, 1‐AG and AA from mouse brain and adipose tissues by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using a simple brain sample preparation method. The separations were carried out based on reversed phase chromatography. Optimization of electrospray ionization conditions established the limits of detection (S/N = 3) at 50, 25 and 65 fmol for 2‐AG, 1‐AG and AA, respectively. The methods were selective, precise (%R.S.D. < 10%) and sensitive over a range of 0.02–20, 0.01–10 and 0.05–50 ng/mg tissue for 2‐AG, 1‐AG and AA, respectively. The quantification method was validated with consideration of the matrix effects and the mass spectrometry (MS) responses of the analytes and the deuterium labeled internal standard (IS). The developed methods were applied to study the hydrolysis of 2‐AG from mouse brain extracts containing membrane bound monoacylglycerol lipase (MAGL), and to measure the basal levels of 2‐AG, 1‐AG and AA in mouse brain and adipose tissues. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
84.
The light distribution in the disks of many galaxies is ‘lopsided’ with a spatial extent much larger along one half of a galaxy than the other, as seen in M101. Recent observations show that the stellar disk in a typical spiral galaxy is significantly lopsided, indicating asymmetry in the disk mass distribution. The mean amplitude of lopsidedness is 0.1, measured as the Fourier amplitude of the m=1 component normalized to the average value. Thus, lopsidedness is common, and hence it is important to understand its origin and dynamics. This is a new and exciting area in galactic structure and dynamics, in contrast to the topic of bars and two-armed spirals (m=2) which has been extensively studied in the literature. Lopsidedness is ubiquitous and occurs in a variety of settings and tracers. It is seen in both stars and gas, in the outer disk and the central region, in the field and the group galaxies. The lopsided amplitude is higher by a factor of two for galaxies in a group. 相似文献
85.
Yu Pu Joseph P. Medendorp Chanda R. Yonzon 《Journal of Raman spectroscopy : JRS》2011,42(11):1994-1999
In a typical aqueous nasal suspension manufacturing process, the homogeneity of the active pharmaceutical ingredient (API) dispersion in a premix vessel is determined merely by visual observation. In this study, to better demonstrate in‐process control, Raman spectroscopy was developed as a process analytical tool (PAT) to monitor the real‐time API dispersion homogeneity in the active premix process. The end‐point variations of the API dispersion as a function of the surfactant type, surfactant concentration, and agitation speed were evaluated by dispersive Raman spectroscopy in combination with multivariate analysis for both lab‐scale and pilot‐scale batches. The optimal surfactant concentration and type were determined to be 0.2% surfactant A for the active dispersion based on a quantitative end‐point comparison. In addition, a chemometric model was developed successfully for the real‐time prediction of API concentration in the active premix, with a root mean squared error of prediction (RMSEP) of 5.4%. In conclusion, Raman spectroscopy has proven to be a viable PAT tool to qualitatively and quantitatively assess the active premix homogeneity in an aqueous nasal suspension manufacturing process. In the future, this method can potentially be used in the commercial manufacturing process for in‐process control of the dispersion homogeneity of the suspension. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
86.
The enolization temperature overrides all other aspects, including the sterics of the alkyl group of the boron reagent and the alkoxy group of the ester during the enolboration–aldolization of phenylacetates. This study has led to the first n-Bu2BOTf-mediated anti-selective aldol reaction of an ester. 相似文献
87.
Sourav Dey Titas Mukherjee Sandipan Sarkar Helen Stoeckli Evans Pabitra Chattopadhyay 《Transition Metal Chemistry》2011,36(6):631-636
The hexa-coordinated copper(II) complex [Cu(L)(DMF)2(ClO4)2], where L = 5-nitro-1,10-phenanthroline, was synthesized and characterized. The X-ray crystal structure shows that the copper
is coordinated by the two N-atoms of the 1,10-phenanthroline ligand plus four O-atoms, two from DMF ligands and two from the
perchlorate anions. Thermal analysis showed that the complex was stable up to 285 °C. The interaction of the complex with
calf thymus DNA was investigated using absorption and emission spectroscopic studies, and the binding constant (K
b) and linear Stern–Volmer quenching constant (K
sv) have been determined. Electrochemical characterization of the complex in acetonitrile showed a quasi-reversible one-electron
exchange voltammogram for the Cu2+/Cu+ redox couple at ca. E
1/2 = −1.00 V (versus SCE) with ΔE = 200 mV and i
pc/i
pa ≈ 1. 相似文献
88.
Fluorescence Properties of Donor Acceptor Chromophores on Newly Synthesized Pyridine-3-Carbonitriles 总被引:1,自引:1,他引:0
Raghunath B. Toche Muddassar A. Kazi Bhausaheb K. Ghotekar Sandeep M. Bagul Chanda D. Tantak Madhukar N. Jachak 《Journal of fluorescence》2009,19(6):1119-1124
A convenient route was successfully developed for the synthesis of novel heterocycles such as pyridine-3-carbonitriles 4 from
chalcone 3 in good yields. The pyridine-3-carbonitrile derivatives synthesized were further studied for their photophysical
properties and observed that absorption and emission was changed, due to the chromospheres at C4-position in phenyl ring and C2-position in pyridine-3-carbonitrile derivatives. 相似文献
89.
R. Vyas B. M. Chanda A. A. Belhekar D. R. Patel R. N. Ram A. V. Bedekar 《Journal of molecular catalysis. A, Chemical》2000,160(2):70-241
Chloromethylated styrene-divinyl benzene of 8% cross-link was functionalized using o-phenylene diamine and finally it was treated with Mn(II) for the formation of metal complex on the surface. The metal content was estimated using atomic absorption spectroscopy. The thermal stability of the catalyst was seen by the use of DTA-TG analyses and the catalyst was found to be stable up to ˜125°C. The modern spectroscopic methods such as FT-IR, ESR were used in order to confirm the probable structure of the catalyst. The catalytic activity of this supported Mn(II)-complex was investigated for aziridination of olefins with bromamine-T as the source of nitrogen. The catalyst was found to be effective in this reaction and could be reused with no substantial loss of activity for up to three cycles. 相似文献
90.