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31.
Giant Hysteretic Sorption of CO2: In Situ Crystallographic Visualization of Guest Binding within a Breathing Framework at 298 K 下载免费PDF全文
Dr. Prem Lama Dr. Himanshu Aggarwal Charl X. Bezuidenhout Prof. Leonard J. Barbour 《Angewandte Chemie (International ed. in English)》2016,55(42):13271-13275
A dynamic ZnII‐MOF has been shown to exhibit extreme breathing behavior under gas pressure. The very narrow pore form of the activated framework opens up in the presence of carbon dioxide, thus making it a suitable material for CO2 capture. Sorption of CO2 at 298 K and relatively high pressure clearly shows a two‐step isotherm with giant hysteresis for the second step. In‐situ single‐crystal diffraction analysis was carried out under CO2 gas pressure at 298 K using an environmental gas cell in order to visualize the interaction between CO2 and the host framework. The results are well supported by pressure‐gradient differential scanning calorimetry (P‐DSC) and variable‐pressure powder X‐ray analysis. Theoretical calculations have been carried out in order to further back up the crystallographic data. 相似文献
32.
Ren D Pipes GD Hambly DM Bondarenko PV Treuheit MJ Brems DN Gadgil HS 《Journal of chromatography. A》2007,1175(1):63-68
A diphenyl column was able to resolve two closely related monoclonal IgG2 molecules, while a C8 column failed to separate these IgGs under identical chromatographic conditions. The diphenyl column also showed a better separation of a mixture of two light and two heavy chains than the C8 column. The influence of amino acid side chains from protein sequences in binding to the diphenyl and C8 stationary phases was studied by using a set of synthetic peptides with the sequence GXXLLLKK, where X represents substitution with all of the 20 amino acids. Peptides containing aromatic amino acids showed a greater binding on the diphenyl column than on the C8 column. This increase in retention was attributed to pi-pi interactions between the aromatic amino acid side chains and the diphenyl ligand. Based on the retention of peptides on the diphenyl column, new retention coefficients were assigned for the separation of proteins. A good correlation was observed between the sum of retention coefficients (SigmaRc) for IgGs and their retention time on the diphenyl column. On-column hydrogen-deuterium exchange showed that the diphenyl column had a larger surface of interaction with protein than the C8 column. pi-pi interactions and the large contact surface resulted in improved resolution of IgGs and their fragments on the diphenyl column. 相似文献
33.
Ahmad Shameem Raushan M. A. Gupta Himanshu Kattayat Sandhya Kumar Shalendra Dalela Saurabh Alvi P. A. Siddiqui M. J. 《Optical and Quantum Electronics》2019,51(7):1-13
Optical and Quantum Electronics - Arithmetic logic unit (ALU) is the core of any digital processing systems. For creating an all optical ALU one needs basic logic gates such as optical NOT, OR and... 相似文献
34.
A strictly nonlinear state feedback control law is designed for an aeroelastic system to eliminate subcritical limit cycle oscillations. Numerical continuation techniques and harmonic balance methods are employed to generate analytical estimates of limit cycle oscillation commencement velocity and its sensitivity with respect to the introduced control parameters. The obtained estimates are used in a multiobjective optimization framework to generate optimal control parameters which maximize the limit cycle oscillation commencement velocity while minimizing the control cost. Numerical simulations are used to show that the assumed nonlinear state feedback law with the optimal control parameters successfully eliminates any existing subcritical limit cycle oscillations by converting it to supercritical limit cycle oscillations, thereby guaranteeing safe operation of the system in its flight envelope. 相似文献
35.
Kumar Brajesh A.K. Himanshu Himanshu Sharma Kiran KumariRajeev Ranjan S.K. BandhopadhyayT.P. Sinha 《Physica B: Condensed Matter》2012,407(4):635-641
Pyrochlore phase free [Pb0.94Sr0.06] [(Mn1/3Sb2/3)0.05(Zr0.53Ti0.47)0.95] O3 ceramics has been synthesized with pure Perovskite phase by semi-wet route using the columbite precursor method. The field dependences of the dielectric response and the conductivity have been measured in a frequency range from 50 Hz to 1 MHz and in a temperature range from 303 K to 773 K. An analysis of the real and imaginary parts of the dielectric permittivity with frequency has been performed, assuming a distribution of relaxation times. The scaling behavior of the dielectric loss spectra suggests that the distribution of the relaxation times is temperature independent. The SEM photographs of the sintered specimens present the homogenous structures and well-grown grains with a sharp grain boundary. The material exhibits tetragonal structure. When measured at frequency (100 Hz), the polarization shows a strong field dependence. Different piezoelectric figures of merit (kp, d33 and Qm) of the material have also been measured obtaining their values as 0.53, 271 pC/N and 1115, respectively, which are even higher than those of pure PZT with morphotropic phase boundary (MPB) composition. Thus the present ceramics have the optimal overall performance and are promising candidates for the various high power piezoelectric applications. 相似文献
36.
Dr. Arundhati Roy Dr. Himanshu Joshi Ruijuan Ye Dr. Jie Shen Dr. Feng Chen Prof. Dr. Aleksei Aksimentiev Dr. Huaqiang Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4836-4843
Reported herein is a series of pore-containing polymeric nanotubes based on a hydrogen-bonded hydrazide backbone. Nanotubes of suitable lengths, possessing a hollow cavity of about a 6.5 Å diameter, mediate highly efficient transport of diverse types of anions, rather than cations, across lipid membranes. The reported polymer channel, having an average molecular weight of 18.2 kDa and 3.6 nm in helical height, exhibits the highest anion-transport activities for iodide (EC50=0.042 μm or 0.028 mol % relative to lipid), whcih is transported 10 times more efficiently than chlorides (EC50=0.47 μm ). Notably, even in cholesterol-rich environment, iodide transport activity remains high with an EC50 of 0.37 μm . Molecular dynamics simulation studies confirm that the channel is highly selective for anions and that such anion selectivity arises from a positive electrostatic potential of the central lumen rendered by the interior-pointing methyl groups. 相似文献
37.
Debapriya Gupta Ankit Kumar Gaur Pravesh Kumar Himanshu Kumar Anjali Mahadevan Dr. Sudha Devi Dr. Saonli Roy Dr. Sugumar Venkataramani 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3463-3472
Light-responsive molecular systems with multiple photoswitches in C3-symmetric designs have enormous application potential. The design part of such molecular systems is critical due to its influence in several properties associated with the photoswitches. In order to tune, and in the evaluation of the design–property relationship, we synthesized 18 tripodal systems with variations in the core, linkers, connectivity, and azo(hetero)arene photoswitches. Through extensive spectroscopic and computational studies, we envisaged the factors controlling near-quantitative photoisomerization in both the directions (bistability) and the thermal stability of the metastable states. Furthermore, we also evaluated the impact of designs in obtaining reversible photo-responsive sol-gel phase transitions, solvatochromism, photo- and thermochromism. 相似文献
38.
Three phytochemicals, curcumin 1, demethoxycurcumin 2 and β-sitosterol-3-O-β-d-glucopyranoside 3 have been isolated from the ethyl acetate extract of rhizomes of Curcuma aromatica. Chemical structures of all the three isolates were determined using spectroscopic and chemical analyses. β-Sitosterol-3-O-β-d-glucopyranoside has been isolated for the first time from this plant. 相似文献
39.
This paper examines geometric scaling models for field flow fractionation systems to understand how channel dimensions affect resolution and retention. Specifically, the changing contribution of the instrumental plate height during miniaturization of field flow fractionation (FFF) systems is reported. The work is directed towards determining the optimal geometrical parameters for miniaturization of field flow fractionation systems. The experimental relationship between channel height in FFF systems and instrumental plate heights is reported. FFF scaling models are modified to: (i) better clarify the dependence of plate height and resolution on channel height in FFF and (ii) include a more complete geometrical scaling analysis and model comparison in the low retention regime. Electrical field flow fractionation has been shown to benefit from miniaturization, so this paper focuses on that subtype, but surprisingly, the results also indicate the possibility of improvement in performance with miniaturization of other field flow fractionation systems including general FFF subtypes in which the applied field does not vary with channel height. This paper also discusses the potential role of more powerful microscale field flow fractionation systems as a new class of sample preparation units for micro-total-analysis systems (mu-TAS). 相似文献
40.
Kovalskiy A Jain H Miller AC Golovchak RY Shpotyuk OI 《The journal of physical chemistry. B》2006,110(45):22930-22934
The structural origin of reversible gamma-induced effects in vitreous Ge(23.5)Sb(11.8)S(64.7) has been investigated by high-resolution X-ray photoelectron spectroscopy (XPS). The changes in valence band spectrum from gamma-irradiation suggest a decrease of sulfur lone pair electron concentration accompanied by changes in bonding states of S and Ge. The appearance of additional doublets in the core-level XPS spectra of Ge, Sb, and S atoms for gamma-irradiated sample is described by the formation of over- and under-coordinated charged defect pairs (Ge(3)(-)-S(3)(+)) as a result of radiation treatment. The results verify the switching of Ge-S covalent bonds into S-S bonds as the main microstructural mechanism for gamma-induced optical effects in this glass. 相似文献