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排序方式: 共有60条查询结果,搜索用时 15 毫秒
1.
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
2.
The newly derived dynamic-crack-branching criterion with its modifications is verified by the dynamicphotoelastic results of dynamic crack branchings in thinpolycarbonate, single-edged crack-tension specimens. Successful crack branching was observed in four specimens and unsuccessful branching in another. Crack branching consistently occurred when the necessary conditions ofK I =K I b =3.3 MPa \(\sqrt m\) and the sufficiency condition ofr o =r c =0.75 mm were satisfied simultaneously. In the unsuccessful branching test, the necessary condition was not satisfied sinceK I was always less thanK I b . 相似文献
3.
AR Engel 《Contemporary Physics》2013,54(6):523-526
This article reviews some of the applications of physics to the solution of archaeological problems. The use of magnetic, resistivity and electromagnetic surveying techniques for the location of buried features is described. Various methods of age determination are outlined while the problems associated with radiocarbon dating of organic material and thermoluminescent dating of pottery are discussed in detail. The techniques, including petrological examination, chemical analysis and isotopic analysis, employed in the physical examination of archaeological artefacts are described. Examples of the application of these techniques in establishing the source of the raw materials used in pottery, metal and stone implements and in elucidating the techniques of manufacture of pottery and metal objects are also given. 相似文献
4.
5.
M. Ramulu 《Experimental Mechanics》1988,28(2):214-220
The purpose of the investigation reported here was to examine experimentally the transition behavior of a short crack in detail
using surface-crack measurements with a traveling microscope and micromeasurements obtained by scanning-electron microscopy
(SEM). The cyclic growth and transition of initial part-through cracks into through the thickness flaws are documented through
experiments by using compact-type specimens fabricated from 7075-T6 aluminum, 2024-T3 aluminum, and mild-steel material, with
a keyhole notch.
Paper was presented at the 1986 SEM Fall Conference on Experimental Mechanics held in Keystone, CO on November 2–5. 相似文献
6.
Numerical modeling via finite element analyses (FEA) and experimental measurements via moiré interferometry were applied to the investigation of abrasive waterjet (AWJ) drilling. Polycarbonate and alumina blocks with dimensions of 25.4 mm×19.5 mm×6.25 mm were subjected to concentrated static loads experimentally and numerically. The assumptions of the FEA model are verified by comparing the experimental results with the numerical solution. A closed-form solution confirmed the correlation between the two. It was concluded that the assumption of the FEA model (e.g. mesh, boundary conditions, pressure loading, etc.) represented the static conditions. This conclusion allowed the application of a hybrid numerical/experimental technique to understand the complex interaction of the target material and the AWJ slurry column during drilling. 相似文献
7.
In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•+), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•+, DPPH•, and FRAP activities (IC50: 0.05 ± 0.0001 mg/mL, IC50: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC50: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source. 相似文献
8.
The low velocity and low energy impact response of two common sheet mold compound (SMC) material systems—SMC-R27, and SMC-R37—were
investigated. In addition to characterizing the low velocity impact response and failure progression of the material systems,
the edge effects of diamond saw cutting, waterjet cutting and abrasive waterjet cutting were investigated using optical microscopy
and contact surface profilometry. Impact force–time and displacement–time responses were measured and used to characterize
energy absorption capabilities and potential correlation to post processing operation and fiber volume fraction. Pre and post-impact
edge surface micrographs were examined to relate the failure behavior on the machined surfaces. Experiments and measurements
all show that the failure zone size and growth behavior are clearly dependent on the edge finishing process. 相似文献
9.
Investigation of displacement fields in an abrasive waterjet drilling process: Part 1. Experimental measurements 总被引:1,自引:0,他引:1
The transient state of displacement fields in the machining zone of a target material during abrasive waterjet impinging and drilling was investigated. A moiré interferometry experimental setup for recording displacement fields and a dynamometer for measuring the reaction force were developed. Whole fields of surface displacement fields and the reaction force of the ceramic and polycarbonate target materials were successfully recorded when the specimen was being pierced by high-pressure abrasive waterjet (AWJ). This paper demonstrates that bothu andv displacement fields of a workpiece during AWJ drilling can be recorded in real time and simultaneously by the moiré interferometry experimentation. The measured surface displacement distributions and the machining forces will be used to drive a finite element model in the second part of this investigation, in which the authors study the stress and strain state for the target material associated with the jet-materials interaction during the jet penetration process. 相似文献
10.
ÜMMÜHAN OCAK HALIT KANTEKIN YAŞAR GÖK H. BASIR ŞENTÜRK 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):87-91
The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N2O2S2-macrobicycle. Metal picrates such as Pb2+, Co2+, Zn2+, Ni2+,Cu2+ and Cd2+ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb2+ only among the other metals. The extraction constant (log K
ex) was determined to be 13.8 for Pb2+ complex. 相似文献