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31.
Alex Yong Sheng Eng Adriano Ambrosi Chun Kiang Chua Filip Šaněk Prof. Zdeněk Sofer Prof. Martin Pumera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12673-12683
Graphene and graphene oxides are materials of significant interest in electrochemical devices such as supercapacitors, batteries, fuel cells, and sensors. Graphene oxides and reduced graphenes are typically prepared by oxidizing graphite in strong mineral acid mixtures with chlorate (Staudenmaier, Hofmann) or permanganate (Hummers, Tour) oxidants. Herein, we reveal that graphene oxides pose inherent electrochemistry, that is, they can be oxidized or reduced at relatively mild potentials (within the range ±1 V) that are lower than typical battery potentials. This inherent electrochemistry of graphene differs dramatically from that of the used oxidants. Graphene oxides prepared using chlorate exhibit chemically irreversible reductions, whereas graphene oxides prepared through permanganate‐based methods exhibit very unusual inherent chemically reversible electrochemistry of oxygen‐containing groups. Insight into the electrochemical behaviour was obtained through cyclic voltammetry, chronoamperometry, and X‐ray photoelectron spectroscopy experiments. Our findings are of extreme importance for the electrochemistry community as they reveal that electrode materials undergo cyclic changes in charge/discharge cycles, which has strong implications for energy‐storage and sensing devices. 相似文献
32.
Peter Kunstadt P. Eng Colyn Steeves Daniel Beaulieu P. Eng 《Radiation Physics and Chemistry》1993,42(1-3)
The number of products being radiation processed worldwide is constantly increasing and today includes such diverse items as medical disposables, fruits and vegetables, spices, meats, seafoods and waste products. This range of products to be processed has resulted in a wide range of irradiator designs and capital and operating cost requirements.This paper discusses the economics of low dose food irradiation applications and the effects of various parameters on unit processing costs. It provides a model for calculating specific unit processing costs by correlating known capital costs with annual operating costs and annual throughputs. It is intended to provide the reader with a general knowledge of how unit processing costs are derived. 相似文献
33.
Theoretical ab initio calculations using the HF and B3LYP methods have been carried out to investigate the conformational differences of three cyclic rings, dibenzo-p-dioxin (DPD), thianthrene (THT), and selenanthrene (SET). The physical origin for the conformational preference of each molecule has been studied using the natural bond orbital (NBO) analysis. The NBO results indicate that DPD exists in a planar form due to strong electron delocalization caused by the specific orbital interaction, around the X atom. On the other hand, THT and SET exist as puckered forms with high inversion barriers due to less effective electron delocalization. The NBO analysis also shows that the conformational stabilization in DPD is caused by a more effective overlap of the orbitals, compared with the overlap of the orbitals in THT. 相似文献
34.
Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC. 相似文献
35.
A novel indole alkaloid, viz., macrodasine A, incorporating fused spirocyclic tetrahydrofuran rings onto a macroline-like moiety, was obtained from a Malayan Alstonia species. The structure, which is also notable for the presence of an unprecedented spiroacetal moiety in an indole alkaloid, was established by spectroscopic analysis. 相似文献
36.
Eng William Palumbo Anthony V. Sriharan Shobha Strandberg G. W. 《Applied biochemistry and biotechnology》1991,(1):887-899
The effect of methanol on trichloroethylene (TCE) degradation by mixed and pure methylotrophic cultures was examined in batch
culture experiments. Methanol was found to relieve growth inhibition ofMethylosinus trichosporium (OB3b) at high (14 mg/L) TCE concentrations. Degradation of TCE was determined by both radiolabeling and gas chromatography
techniques. When cultures were grown on methanol over 10 to 14 d with 0.3 mg/L TCE, OB3b degraded 16.89 ±0.82% (mean± SD)
of the TCE, and a mixed culture (DT type II) degraded 4.55±0.11%. Mixed culture (JS type I) degraded 4.34±0.06% of the TCE.
When grown on methane with 0.3 mg/L TCE, 32.93±2.01% of the TCE was degraded by OB3b, whereas the JS culture degraded 24.3
±1.38% of the TCE, and the DT culture degraded 34.3 ±2.97% of the TCE. The addition of methanol to cultures grown on methane
reduced TCE degradation to 16.21 ±1.17% for OB3b and to 5.08±0.56% for JS. Although methanol reduces the toxicity of TCE to
the cultures, biodegradation of TCE cannot be sustained in methanol-grown cultures. Since high TCE concentrations appear to
inhibit methane uptake and growth, we suggest the primary toxicity of TCE is directed towards the methane monooxygenase. 相似文献
37.
Electrodeposited Amorphous Tungsten‐doped Cobalt Oxide as an Efficient Catalyst for the Oxygen Evolution Reaction 下载免费PDF全文
Linh N. Nguyen Dr. Ung Thi Dieu Thuy Dr. Quang Duc Truong Prof. Itaru Honma Prof. Quang Liem Nguyen Dr. Phong D. Tran 《化学:亚洲杂志》2018,13(12):1530-1534
Thin film of amorphous tungsten‐doped cobalt oxide (W:CoO) was successfully grown on a conducting electrode via an electrochemical oxidation process employing a [Co(WS4)2]2? deposition bath. The W:CoO catalyst displays an attractive performance for the oxygen evolution reaction in an alkaline solution. In an NaOH solution of pH 13, W:CoO operates with a moderate onset overpotential of 230 mV and requires 320 mV overpotential to generate a catalytic current density of 10 mA cm?2. A low Tafel slope of 45 mV decade?1 was determined, indicating a rapid O2‐evolving kinetics. The as‐prepared W:CoO belongs to the best cobalt oxide‐based catalysts ever reported for the oxygen evolution (OER) reaction. 相似文献
38.
Differential stable isotope labeling of peptides for quantitation and de novo sequence derivation. 总被引:7,自引:0,他引:7
D R Goodlett A Keller J D Watts R Newitt E C Yi S Purvine J K Eng P von Haller R Aebersold E Kolker 《Rapid communications in mass spectrometry : RCM》2001,15(14):1214-1221
We have demonstrated the use of per-methyl esterification of peptides for relative quantification of proteins between two mixtures of proteins and automated de novo sequence derivation on the same dataset. Protein mixtures for comparison were digested to peptides and resultant peptides methylated using either d0- or d3-methanol. Methyl esterification of peptides converted carboxylic acids, such as are present on the side chains of aspartic and glutamic acid as well as the carboxyl terminus, to their corresponding methyl esters. The separate d0- and d3-methylated peptide mixtures were combined and the mixture subjected to microcapillary high performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). Parent proteins of methylated peptides were identified by correlative database searching of peptide tandem mass spectra. Ratios of proteins in the two original mixtures could be calculated by normalization of the area under the curve for identical charge states of d0- to d3-methylated peptides. An algorithm was developed that derived, without intervention, peptide sequence de novo by comparison of tandem mass spectra of d0- and d3-peptide methyl esters. 相似文献
39.
The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M+‐29], [M+‐55], and [M+‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed. 相似文献
40.