排序方式: 共有16条查询结果,搜索用时 31 毫秒
1.
An environmentally benign, three-component, one-pot integrated chemical process has been developed for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzoxanthene-11-one by nucleophilic addition reaction between aldehyde and β-naphthol followed by Michael addition of dimedone, catalyzed by thiamine hydrochloride in aqueous micellar medium with excellent yield. Simple reaction conditions, no requirement of chromatographic separation, short reaction time, ease of isolation, use of inexpensive, easily recoverable and reusable catalyst makes this protocol very interesting from an economic and environmental perspective. 相似文献
2.
In many classification applications and face recognition tasks, there exist unlabelled data available for training along with
labelled samples. The use of unlabelled data can improve the performance of a classifier. In this paper, a semi-supervised
growing neural gas is proposed for learning with such partly labelled datasets in face recognition applications. The classifier
is first trained on the labelled data and then gradually unlabelled data is classified and added to the training data. The
classifier is retrained; and so on. The proposed iterative algorithm conforms to the EM framework and is demonstrated, on
both artificial and real datasets, to significantly boost the classification rate with the use of unlabelled data. The improvement
is particularly great when the labelled dataset is small. Comparison with support vector machine classifiers is also given.
The algorithm is computationally efficient and easy to implement. 相似文献
3.
Basic Ionic Liquid Promoted Domino Knoevenagel–Thia‐Michael Reaction: An Efficient and Multicomponent Strategy for Synthesis of 1,3‐Thiazines
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I. R. Siddiqui Rahila Shayna Shamim Pragati Rai Shireen Malik A. Waseem Arjita Srivastava Anjali Srivastava 《Journal of heterocyclic chemistry》2016,53(4):1284-1291
An efficient, three‐component strategy for synthesis of 1,3‐thiazines with high atom economy in one‐pot mediated by room temperature basic ionic liquid is described here. The strategy involves basic ionic liquid, [bmim]OH‐catalyzed Knoevenagel condensation between ethyl cyanoacetate and aromatic aldehyde and subsequent thia‐Michael addition with substituted thioureas. The reaction sequence is smooth and quantitative under ambient temperature. [bmim]OH was recovered and reused four times without any appreciable decrease in its reactivity and product yield. 相似文献
4.
Simon Doherty Julian G. Knight Adam L. Bell Shireen El-Menabawey Christopher M. Vogels Andreas Decken Stephen A. Westcott 《Tetrahedron: Asymmetry》2009,20(12):1437-1444
Rhodium complexes of (R)-Me-CATPHOS and (R)-(S)-JOSIPHOS form a complementary pair of catalysts for the highly efficient asymmetric hydrogenation of a selection of (E)- and (Z)-β-aryl-β-(enamido)phosphonates, respectively, in the majority of cases giving excellent yields and ee’s in excess of 99%; the highest to be reported for this class of substrate. 相似文献
5.
An Efficient One‐Pot Regioselective Approach Towards the Synthesis of Thiopyrano[2,3‐d]thiazole‐2‐thiones Catalyzed by Basic Ionic Liquid under Microwave Irradiation
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I. R. Siddiqui Arjita Srivastava Shayna Shamim Anjali Srivastava Shireen Malik A. Waseem 《Journal of heterocyclic chemistry》2016,53(3):849-858
A green, regioselective protocol for the synthesis of thiopyrano[2,3‐d]thiazole‐2‐thiones catalyzed by basic ionic liquid [bmIm]OH has been developed. The reaction proceeds smoothly under microwave irradiation, and high yields of the products are obtained in very short reaction times (5–11 min). The ionic liquid plays a dual solvent‐catalyst role. 相似文献
6.
Gajendra P. Singh Shireen Goh Michelangelo Canzoneri Rajeev J. Ram 《Journal of Raman spectroscopy : JRS》2015,46(6):545-550
We demonstrate the detection of glucose and lactate concentrations with high accuracy in the supernatants of Chinese hamster ovary (CHO) cell culture, grown in shake flasks in batch fermentation mode, using Raman spectroscopy and explicit model‐based classical least squares (CLS) algorithm. A deterministic Raman spectral library of pure components was created by acquiring Raman spectra from credible nutrient media constituents and CHO cell culture metabolites. Only analytes present with concentration above the instrument detection limit were included in this library. Residuals obtained after CLS analyses were used to identify missing components and to generate a revised library. An algorithmic sieve was thus construed to obtain an appropriate Raman spectral library from a complex chemical mixture that is well‐defined but an industrial secret. High performance liquid chromatography (HPLC) was used to provide reference glucose and lactate concentrations. [Correction added on 30 April 2015, after first online publication: the last three sentences of the abstract (previously stated in the abstract) have been deleted]. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
Goenaga-Infante H Kassam S Stokes E Hopley C Joel SP 《Analytical and bioanalytical chemistry》2011,399(5):1789-1797
The formation of intracellular dimethylselenide (DMSe) as a product of exposure of non-malignant (PBMCs) and lymphoma (RL
and DHL-4) cell lines to methylseleninic acid (MSA) at clinical levels is suggested here for the first time. This was achieved
by analysis of cell lysates by HPLC coupled to ICP-MS via APEX-Q nebulisation, enabling limits of detection for target methyl-Se
species which are up to 12-fold lower than those obtained with conventional nebulisation. Methyl-Se-glutathione (CH3Se-SG), although detected in lysates of cells exposed to MSA, was found to be a reaction product of MSA with glutathione.
This was confirmed by HPLC-ESI MS (MS) analysis of lysates of control cells (unexposed to Se) spiked with MSA. The MS/MS data
obtained by collision-induced dissociation fragmentation of the ion m/z 402 (for [M+H]+
80Se) were consistent with the presence of CH3Se-SG. Formation of DMSe was not detected by HPLC-ICP-MS in these spiked lysates, and it was found to require live cells in
cell media containing MSA. Interestingly, the ratio of DMSe to CH3Se-SG was significantly higher in lymphoma cells exposed to MSA in comparison to non-malignant cells. Moreover, maximum Se
uptake levels in lymphoma cell lines seemed to be reached much earlier (after 10 min of MSA exposure) than in non-malignant
cells. Finally, the GC-TOF-MS speciation data obtained for cell headspace suggested that the major Se species (dimethyldiselenide)
appeared to be present in lymphoma cell headspace at significantly higher concentrations than in non-malignant cell headspace
after only 10 min of exposure to MSA. Evidence for the presence of dimethylselenidesulfide in lymphoma cell headspace is also
provided for the first time. 相似文献
8.
Marshall SR Incarvito CD Shum WW Rheingold AL Miller JS 《Chemical communications (Cambridge, England)》2002,(24):3006-3007
CoII[N(CN)2]2(H2BiIm)2, 1, and [CoII[N(CN)2](H2BiIm)2]Cl, 2 (H2BiIm = 2,2'-biimidazole) have been structurally, spectroscopically, and magnetically characterized with both containing dicyanamides bound in unprecedented manners; namely, solely via the amide nitrogen for 1, and via an imide N forming 1-D helical chains for 2. 相似文献
9.
Keryn G. Woodman Chantal A. Coles Shireen R. Lamand Jason D. White 《Molecules (Basel, Switzerland)》2021,26(4)
Duchenne muscular dystrophy (DMD) is a progressive fatal neuromuscular disorder with no cure. Therapies to restore dystrophin deficiency have been approved in some jurisdictions but long-term effectiveness is yet to be established. There is a need to develop alternative strategies to treat DMD. Resveratrol is a nutraceutical with anti-inflammatory properties. Previous studies have shown high doses (100–400 mg/kg bodyweight/day) benefit mdx mice. We treated 4-week-old mdx and wildtype mice with a lower dose of resveratrol (5 mg/kg bodyweight/day) for 15 weeks. Voluntary exercise was used to test if a lower dosage than previously tested could reduce exercise-induced damage where a greater inflammatory infiltrate is present. We found resveratrol promoted skeletal muscle hypertrophy in wildtype mice. In dystrophic muscle, resveratrol reduced exercise-induced muscle necrosis. Gene expression of immune cell markers, CD86 and CD163 were reduced; however, signalling targets associated with resveratrol’s mechanism of action including Sirt1 and NF-κB were unchanged. In conclusion, a lower dose of resveratrol compared to the dosage used by other studies reduced necrosis and gene expression of inflammatory cell markers in dystrophic muscle suggesting it as a therapeutic candidate for treating DMD. 相似文献
10.