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551.
A general methodology “malonic ester amide synthesis” has been demonstrated, which uses α-substituted/unsubstituted diethyl malonates for the decarboxylative acylation of various aromatic/heteroaromatic primary/secondary amines to form one-carbon homologated amides, thus providing easy access to amides with odd/even chain lengths and an array of substituents on the alkyl/aryl part while avoiding use of acyl chlorides or peptide coupling reagents. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
552.
Kumar P Ma X Liu X Jia J Bucong H Xue Y Li ZR Yang SY Wei YQ Chen YZ 《Journal of computer-aided molecular design》2011,25(5):455-467
Various in vitro and in-silico methods have been used for drug genotoxicity tests, which show limited genotoxicity (GT+) and
non-genotoxicity (GT−) identification rates. New methods and combinatorial approaches have been explored for enhanced collective
identification capability. The rates of in-silco methods may be further improved by significantly diversified training data
enriched by the large number of recently reported GT+ and GT− compounds, but a major concern is the increased noise levels
arising from high false-positive rates of in vitro data. In this work, we evaluated the effect of training data size and noise
level on the performance of support vector machines (SVM) method known to tolerate high noise levels in training data. Two
SVMs of different diversity/noise levels were developed and tested. H-SVM trained by higher diversity higher noise data (GT+
in any in vivo or in vitro test) outperforms L-SVM trained by lower noise lower diversity data (GT+ in in vivo or Ames test
only). H-SVM trained by 4,763 GT+ compounds reported before 2008 and 8,232 GT− compounds excluding clinical trial drugs correctly
identified 81.6% of the 38 GT+ compounds reported since 2008, predicted 83.1% of the 2,008 clinical trial drugs as GT−, and
23.96% of 168 K MDDR and 27.23% of 17.86M PubChem compounds as GT+. These are comparable to the 43.1–51.9% GT+ and 75–93%
GT− rates of existing in-silico methods, 58.8% GT+ and 79% GT− rates of Ames method, and the estimated percentages of 23%
in vivo and 31–33% in vitro GT+ compounds in the “universe of chemicals”. There is a substantial level of agreement between
H-SVM and L-SVM predicted GT+ and GT− MDDR compounds and the prediction from TOPKAT. SVM showed good potential in identifying
GT+ compounds from large compound libraries based on higher diversity and higher noise training data. 相似文献
553.
Pankaj Soni Santosh K. Sar Anand Kamavisdar Rajmani Patel 《Journal of Analytical Chemistry》2011,66(6):596-599
A new simple procedure for the spectrophotometric determination of tricyclic antidepressant drug imipramine is proposed. The
method is based on the enhancement of the colour intensity of the Fe(III)-SCN− complex due to the addition of the drug imipramine. The value of molar absorptivity of the Fe(III)-SCN− imipramine complex in terms of the drug lies in the range of (2.77–3.16) × 103 L/mol cm at the absorption maximum 460 nm. The detection limit of the method was 250 μg/L. The slope, intercept, and correlation
co-efficient for the present method were found to be 0.008, 0.005, and 0.998, respectively. The effect of analytical variables
on the determination of the drug and the composition of the complex are discussed. The method is applicable to the determination
of imipramine in the drug samples. 相似文献
554.
Pankaj Chaturvedi Vinay Malvimat Gautam Sengupta 《The European Physical Journal C - Particles and Fields》2018,78(9):776
We propose a covariant holographic conjecture for the entanglement negativity of bipartite mixed states in \((1+1)\)-dimensional conformal field theories dual to bulk non static \(AdS_{3}\) configurations. Application of our conjecture to \((1+1)\)-dimensional conformal field theories dual to bulk non extremal and extremal rotating BTZ black holes exactly reproduce the corresponding entanglement negativity obtained through the replica technique, in the large central charge limit. We briefly discuss the issue of the generalization of our conjecture to higher dimensions. 相似文献
555.
We study the bifurcation characteristics of a lumped-parameter model of rotary drilling with 1:1 internal resonance between the axial and the torsional modes which leads to the largest stability thresholds. For this special case, the two-degree-of-freedom model for the drill-string reduces to an effectively single-degree-of-freedom system facilitating further analysis. The regenerative effect of the cutting action due to the axial vibrations is incorporated through a delayed term in the cutting force with the delay depending on the torsional oscillations. This state dependency of the delay introduces nonlinearity in the current model. Steady drilling loses stability via a Hopf bifurcation, and the nature of the bifurcation is determined by an analytical study using the method of multiple scales. We find that both subcritical and supercritical Hopf bifurcations are present in this system depending on the choice of operating parameters. Hence, the nonlinearity due to the state-dependent delay term could both be stabilizing or destabilizing in nature, and the self-interruption nonlinearity is essential to capture the global behavior. Numerical bifurcation analysis of a global axial–torsional model of rotary drilling further confirms the analytical results from the method of multiple scales. Further exploration of the rotary drilling dynamics unravels more complex phenomena including grazing bifurcations and possibly chaotic solutions. 相似文献
556.
The far-infrared spectra of Ge10Se90−xTex where x = 0, 10, 20, 30, 40, 50 glassy alloys were measured in the wavenumber region 50-650 cm−1 at room temperature. The results were explained in terms of the vibrations of the isolated molecular units. The addition of Te in Ge10Se90 has shown the appearance of GeTe2 and GeTe4 molecular units and vibrations of Se-Te bond as Se8−xTex mixed rings. The assignment of various absorption bands has been made on the basis of absorption spectra of pure Se, binary Ge-Se, Ge-Te, Se-Te and ternary Ge-Se-Te glassy alloys. The far-infrared transmission spectrum has been found to shift a little towards lower wavenumber side with the addition of Te content to Ge10Se90. The addition of Te to Ge-Se system replacing Se has found to reduce the Se-Se bonds and Ge-Se bonds and leads to the formation of Se-Te, Ge-Te and Te-Te bonds. 相似文献
557.
558.
Kulbir Sandip Das Tarali Devi Mrigaraj Goswami Mahesh Yenuganti Prabhakar Bhardwaj Somnath Ghosh Subash Chandra Sahoo Pankaj Kumar 《Chemical science》2021,12(31):10605
Nitrate reductases (NRs) are molybdoenzymes that reduce nitrate (NO3−) to nitrite (NO2−) in both mammals and plants. In mammals, the salival microbes take part in the generation of the NO2− from NO3−, which further produces nitric oxide (NO) either in acid-induced NO2− reduction or in the presence of nitrite reductases (NiRs). Here, we report a new approach of VCl3 (V3+ ion source) induced step-wise reduction of NO3− in a CoII-nitrato complex, [(12-TMC)CoII(NO3−)]+ (2,{CoII–NO3−}), to a CoIII–nitrosyl complex, [(12-TMC)CoIII(NO)]2+ (4,{CoNO}8), bearing an N-tetramethylated cyclam (TMC) ligand. The VCl3 inspired reduction of NO3− to NO is believed to occur in two consecutive oxygen atom transfer (OAT) reactions, i.e., OAT-1 = NO3− → NO2− (r1) and OAT-2 = NO2− → NO (r2). In these OAT reactions, VCl3 functions as an O-atom abstracting species, and the reaction of 2 with VCl3 produces a CoIII-nitrosyl ({CoNO}8) with VV-Oxo ({VV O}3+) species, via a proposed CoII-nitrito (3, {CoII–NO2−}) intermediate species. Further, in a separate experiment, we explored the reaction of isolated complex 3 with VCl3, which showed the generation of 4 with VV-Oxo, validating our proposed reaction sequences of OAT reactions. We ensured and characterized 3 using VCl3 as a limiting reagent, as the second-order rate constant of OAT-2 (k2/) is found to be ∼1420 times faster than that of the OAT-1 (k2) reaction. Binding constant (Kb) calculations also support our proposition of NO3− to NO transformation in two successive OAT reactions, as Kb(CoII–NO2−) is higher than Kb(CoII–NO3−), hence the reaction moves in the forward direction (OAT-1). However, Kb(CoII–NO2−) is comparable to Kb{CoNO}8, and therefore sequenced the second OAT reaction (OAT-2). Mechanistic investigations of these reactions using 15N-labeled-15NO3− and 15NO2− revealed that the N-atom in the {CoNO}8 is derived from NO3− ligand. This work highlights the first-ever report of VCl3 induced step-wise NO3− reduction (NRs activity) followed by the OAT induced NO2− reduction and then the generation of Co-nitrosyl species {CoNO}8.Single metal-induced reduction of NO3− → {NO2−} → NO via oxygen atom transfer reaction. 相似文献
559.
Dr. Pankaj Sharma Dr. Monika Sharma Dr. Malcolm Dearg Dr. Martin Wilding Dr. Thomas J. A. Slater Prof. C. Richard A. Catlow 《Angewandte Chemie (International ed. in English)》2023,62(20):e202301239
Despite extensive efforts to develop high-performance H2 evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H2 production (154.7 mmol g−1 h−1), removing the need for a pre-synthesized photocatalyst. In addition, we also report simultaneous in situ synthesis of Pt single-atoms anchored CdS nanoparticles (PtSA-CdSIS) during photoirradiation. The highly dispersed in situ incorporation of extensive Pt single atoms on CdSIS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar-to-hydrogen conversion efficiency of ≈1 % and an apparent quantum yield of over 91 % (365 nm) for H2 production. Our work not only provides a promising strategy for maximising H2 production efficiency but also provides a green process for H2 production and the synthesis of highly photoactive PtSA-CdSIS nanoparticles. 相似文献
560.
Michael B. Hicks Keith Mattern Jonathan Fine Shane Grosser Daya Patel Lauren Weisel Pankaj Aggarwal 《Journal of separation science》2023,46(21):2300300
Pharmaceutical development currently relies on quality separation methods from early discovery through to line-of-site manufacturing. There have been significant advancements made regarding the column particle packing, internal diameter, length connectivity, the understanding of the impact key parameters like void volume, flow rate, and temperature all that affects the resultant separation quality, that is, resolution, peak shape, peak width, run time, and signal-to-noise ratio. There is however a strong need to establish better alternatives to large bulky high-performance liquid chromatography racks either for process analytical reaction monitoring or mass spectrometry analysis in establishing product quality. Compact, portable high-pressure liquid chromatography can be a more efficient alternative to traditional ultra-high pressure liquid chromatography and traditional liquid chromatography. The compact versatile instrument evaluated here allows good separation control with either the on-board column with fixed ultra-violet wavelength cartridge or for use with a high-resolution mass spectrometry. Significant space reduction results in greener lab spaces with improved energy efficiency for smaller labs with lower energy demands. In addition, this compact liquid chromatography was used as a portable reaction monitoring solution to compare forced degradation kinetics and assess portable liquid chromatography-mass spectrometry capability for the analyses required for pharmaceutical drug product testing. 相似文献