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151.
The hydrogen-bonding ability of five-membered heteroaromatic molecules containing one chalcogen and two heteroatoms with nitrogen
in addition to chalcogen, respectively, have been analyzed using density functional and molecular orbital methods through
adduct formation with water. The stabilization energies for all the adducts are established at B3LYP/6-31+G* and MP2/6-31+G*
levels after correcting for the basis set superposition error by using the counterpoise method and also corrected for zero-point
vibrational energies. A natural bond orbital analysis at B3LYP/6-31+G* level and natural energy decomposition analysis at
HF/6-31+G* using MP2/6-31+G* geometries have been carried out to understand the nature of hydrogen-bonding interaction in
monohydrated heterocyclic adducts. Nucleus-independent chemical shift have been evaluated to understand the correlation between
hydrogen bond formation and aromaticity. 相似文献
152.
153.
Bondar A Garmash A Mizuk R Santel D Kinoshita K Adachi I Aihara H Arinstein K Asner DM Aushev T Aziz T Bakich AM Barberio E Belous K Bhardwaj V Bischofberger M Bozek A Bračko M Browder TE Chang MC Chang P Chen A Cheon BG Chilikin K Chistov R Cho IS Cho K Choi SK Choi Y Dalseno J Danilov M Doležal Z Drutskoy A Eidelman S Epifanov D Fast JE Gaur V Gabyshev N Goh YM Golob B Haba J Hara T Hayasaka K Hoshi Y Hyun HJ Iijima T Inami K Ishikawa A Iwabuchi M Iwasaki Y Iwashita T Julius T Kang JH 《Physical review letters》2012,108(12):122001
We report the observation of two narrow structures in the mass spectra of the π(±)Υ(nS) (n=1, 2, 3) and π(±)h(b)(mP) (m=1, 2) pairs that are produced in association with a single charged pion in Υ(5S) decays. The measured masses and widths of the two structures averaged over the five final states are M(1)=(10,607.2±2.0) MeV/c2, Γ(1)=(18.4±2.4) MeV, and M(2)=(10,652.2±1.5) MeV/c2, Γ(2)=(11.5±2.2) MeV. The results are obtained with a 121.4 fb(-1) data sample collected with the Belle detector in the vicinity of the Υ(5S) resonance at the KEKB asymmetric-energy e+ e- collider. 相似文献
154.
Bhupendra Singh Rathore Mulayam Singh Gaur Kripa Shanker Singh 《Journal of Thermal Analysis and Calorimetry》2012,107(2):675-680
The thermally stimulated charge relaxation properties of polycarbonate (PC) filled with SiO2 nanofiller were studied by means of thermally stimulated discharge current (TSDC). The nanocomposite samples were further
characterized by UV–vis spectroscopy, scanning electron microscopy, energy dispersive X-ray spectra, and differential scanning
calorimetry (DSC) techniques to investigate the dispersion of nanofillers in polymer matrix and glass transition temperature.
All pristine and nanocomposites samples of thickness about 25 μm were prepared using solution mixing method. The suitable
weight percentage of SiO2 nanofillers has been chosen to prevent the nonuniform dispersion. TSDC measurement of PC (Pristine) and PC+ (7% SiO2) shows the single peak, while TSDC characteristic of other nanocomposites are showing two peaks. The higher temperature TSDC
peak of pristine and nanocomposites samples is originated due to the charge relaxation from shallower and deeper trapping
sites, however, low temperature peak is caused by dipolar relaxation of charge carriers. Since the position of higher temperature
TSDC peak is generally an analysis of glass transition temperature of polymer/polymer nanocomposites. The authors have observed
that the temperature of this peak is almost same as the T
g measured by DSC with 0 to ±5% variation. This article presents the deeper understanding of charge relaxation mechanism caused
by SiO2 nanofillers in polycarbonate. 相似文献
155.
The steady state fluorescence measurements have been performed on Pluronic F127 and P103 with dimethylene-bis-(dodecyldimethylammonium bromide) (12-2-12) mixtures at 21-40 degrees C. From the pyrene fluorescence, the critical micelle concentration (cmc), micelle mole fraction (x), micropolarity, and aggregation number have been computed for both mixtures over the whole mixing range at different temperatures. These micelle parameters indicate that the mixed micelle formation between the unlike components of both mixtures takes place due to the synergistic interactions and which increase with an increase in temperature. 相似文献
156.
Doping of individual single-walled carbon nanotubes via noncovalent adsorption of polyethylenimine which converts p-type semiconducting nanotubes into n-type is examined by micro-Raman studies. Distinctively different responses are observed in metallic and in semiconducting nanotubes. Very little or no changes in the radial breathing and the disorder modes are observed upon polymer adsorption on semiconducting carbon nanotubes indicating noncovalent nature of this process. Tangential G-band spectral downshift of up to approximately 10 cm(-)(1) without line broadening is observed for semiconducting tubes suggesting similar magnitude of electron transfer as commonly observed in electrochemical doping with alkali metals. Strong diameter dependence is also observed and can be explained by thermal ionization of charge carriers with activation barrier that scales as the energy gap of the semiconducting nanotubes. In contrast, metallic nanotubes exhibit very different behavior with significant line broadening of the G-band and concurrent enhancement of the disorder mode. In certain cases, initially symmetric Lorentzian line shapes of the G-band features with narrow line widths similar to semiconducting tubes are converted to a broad, asymmetric Breit-Wigner-Fano line shape. Implications on the effects of electron injection and the local chemical environment on the intrinsic line shape of isolated carbon nanotubes are discussed. 相似文献
157.
Poly(vinyl alcohol)/cellulose nanocrystal barrier membranes 总被引:4,自引:0,他引:4
In this study, barrier membranes were prepared from poly(vinyl alcohol) (PVOH) with different amounts of cellulose nanocrystals (CNXLs) as filler. Poly(acrylic acid) (PAA) was used as a crosslinking agent to provide water resistance to PVOH. The membranes were heat treated at various temperatures to optimize the crosslinking density. Heat treatment at 170 °C for 45 min resulted in membranes with improved water resistance without polymer degradation. Infrared spectroscopy indicated ester bond formation with heat treatment. Mechanical tests showed that membranes with 10% CNXLs/10% PAA/80% PVOH were synergistic and had the highest tensile strength, tensile modulus and toughness of all the membranes studied. Polarized optical microscopy showed agglomeration of CNXLs at filler loadings greater than 10%. Differential thermogravimetric analysis (DTGA) showed a highly synergistic effect with 10% CNXL/10% PAA/80% PVOH and supported the tensile test results.Transport properties were studied, including water vapor transport rate and the transport of trichloroethylene, a representative industrial toxic material. Water vapor transmission indicated that all the membranes allowed moisture to pass. However, moisture transport was reduced by the presence of both CNXLs and PAA crosslinking agent. A standard time lag diffusion test utilizing permeation cups was used to study the chemical barrier properties. The membranes containing ≥10% CNXLs or PAA showed significantly reduced flux compared to the control. The CNXLs were then modified by surface carboxylation in order to better understand the mechanism of transport reduction. While barrier performance improvements were minimal, the chemical modification improved the dispersion of the modified CNXLs which led to improved performance. Of special note was an increase in the initial degradation temperatures of both modified and unmodified systems, with the modified system showing an initial degradation temperature >100 °C higher than the cellulose alone. This may reflect more extensive crosslinking in the modified composite. 相似文献
158.
Enzyme‐Mediated Site‐Specific Bioconjugation of Metal Complexes to Proteins: Sortase‐Mediated Coupling of Copper‐64 to a Single‐Chain Antibody 下载免费PDF全文
Dr. Brett M. Paterson Dr. Karen Alt Charmaine M. Jeffery Prof. Roger I. Price Shweta Jagdale Dr. Sheena Rigby Dr. Charlotte C. Williams Prof. Karlheinz Peter Prof. Christoph E. Hagemeyer Assoc. Prof. Paul S. Donnelly 《Angewandte Chemie (International ed. in English)》2014,53(24):6115-6119
The enzyme‐mediated site‐specific bioconjugation of a radioactive metal complex to a single‐chain antibody using the transpeptidase sortase A is reported. Cage amine sarcophagine ligands that were designed to function as substrates for the sortase A mediated bioconjugation to antibodies were synthesized and enzymatically conjugated to a single‐chain variable fragment. The antibody fragment scFvanti‐LIBS targets ligand‐induced binding sites (LIBS) on the glycoprotein receptor GPIIb/IIIa, which is present on activated platelets. The immunoconjugates were radiolabeled with the positron‐emitting isotope 64Cu. The new radiolabeled conjugates were shown to bind selectively to activated platelets. The diagnostic potential of the most promising conjugate was demonstrated in an in vivo model of carotid artery thrombosis using positron emission tomography. This approach gives homogeneous products through site‐specific enzyme‐mediated conjugation and should be broadly applicable to other metal complexes and proteins. 相似文献
159.
We have investigated the thermodynamic properties of electron-doped perovskite manganite CaMnO3 by incorporating the effect of lattice distortions. In this paper the functional relation between the MnO6 distortions, charge and size mismatch and the thermal properties is determined. In the insulating state, distortions of the Mn-O environment are linear with calcium concentration. In the low-temperature spin-ordered ferromagnetic/anti-ferromagnetic state, at least 50% of the distortion is removed. The lattice contributions to the specific heat at constant volume (Cv(lattice)) of Ca1−xRExMnO3 (x=0.05, 0.1, 0.15, 0.20) with rare earth cation doping at the A-site has been studied as a function of temperature (10 K≤T≤500 K) by means of a Modified Rigid Ion Model (MRIM). In addition, the results on the bulk modulus (B), cohesive energy (φ), molecular force constant (f), Reststrahlen frequency (ν0) and Gruneisen parameter (γ) are also presented. Findings indicate an anomalous behavior of some highly Jahn-Teller (JT) distorted Ca1−xRExMnO3. 相似文献
160.
Dr. Chenikkayala Siva Sankara Dr. Shweta Bhagat Dr. Ajeet Chandra Prof. Dr. Irishi N. N. Namboothiri 《European journal of organic chemistry》2023,26(15):e202300069
An enantioselective desymmetrization of curcumins with 3-olefinic oxindoles involving a cascade double-Michael addition strategy provides direct access to spirocyclohexanone-oxindoles with complete regio- and diastereoselectivities and excellent enantioselectivities, besides good to excellent yields. The products possess three contiguous chiral centers and multiple reactive functionalities. The observed selectivities were rationalized by transitions state energy calculations at B3LYP//6-31g(d) level of DFT. 相似文献