Chlorine-35 Nuclear Quadrupole Resonance Studies in 2,3- and 3,5-Dichloroanisoles

The temperature variation of the 3’Cl n.q.r. frequencies in 3,5- and 2,3- dichloroanisoles has been reported here. Both compounds show two lines each, and these have been assigned to the two chlorines in the same molecule with the help of the additive model for the substituent effect. The temperature dependence has been analysed in terms of Bayer-Kushida-Brown model.The torsional frequencies and their temperature dependence have been calculated numerically under a two-mode approximation. 0.n comparing the results in 3,5-dichloroanisole with those in 3,5-dichlorophenol it can be seen that they show similar behaviour owing to the absence of hydrogen bonding in both.

Nuclear Magnetic-Resonance Spectra Of Oriented Biologically Important Molecules - The Structure Of And The Internal-Rotation In N,N-Dimethyluracil

From the proton NMR spectra of Nfl-dimethyluracil oriented in two different nematic solvents, the internal rotation of the methyl groups about the N-C bonds is studied. It has been observed that the preferred conformation of the methyl group having one carbonyl in the vicinity is the one where a C-H bond is in the ring plane pointing toward the carbonyl group. The results are not sensitive to the mode of rotation of the other methyl group. These data are interpreted in terms of the bond polarizations.

1H and 13C nuclear magnetic resonance studies on X-537A (lasalocid-A)-calcium complexes: observation of a sandwich complex

Studies on the conformational and binding characteristics of the ionophoric antibiotic X-537A (lasalocid-A)�calcium ion complexes have been carried out in deuteriated acetonitrile (CD3 CN) using proton and carbon-13 nuclear magnetic resonance (1 H and 13C n.m.r.) spectroscopy. Detailed analysis of the salt-induced chemical shifts at various X-537A to calcium concentration ratios indicated that X-537A forms charged complexes with calcium with 2 : 1 and 1 : 1 stoicheiometries. The conformational model for the complex based on the n.m.r. data showed that the calcium ion is preferentially bound to one end of the molecule, which is binding to three oxygen atoms, the other end (the salicylic acid part) being relatively free. In the 2 : 1 (sandwich) complex, the calcium ion is sandwiched between two X-537A molecules with three oxygen atoms binding to it from each molecule.

Unterprima (eleventh grade) boys school class portrait Portraits Groups Men

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Unterprima (eleventh grade) boys school class portrait Portraits Groups Men

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Mechanisms of transmembrane cation transport studied by nuclear magnetic resonance spectroscopy

Several molecules like ionophores, vitamins, ion-binding cyclic peptides, acidic phospholipids, surfactants are known to expose the inner side of vesicles, to the externally added cations. Whereas ionophores and certain other systems bring about these changes by a selective transport (influx) of the cation by specialized mechanisms known as the carrier and channel mechanism, other systems cause lysis and vesicle fusion. These systems have been successfully studied using1H,31 P and13C nuclear magnetic resonance spectroscopy after the demonstration, fifteen years ago, of the ability of paramagnetic lanthanide ions to distinguish the inside of the vesicle from the outside. The results of these ’nuclear magnetic resonance kinetics’ experiments are reviewed.

Pressure dependence of 35Cl nuclear quadrupole resonance in 2,5-, 2,6- and 3,5-dichlorophenols

Pressure dependence of the 35Cl Nuclear Quadrupole Resonances (N.Q.R.) in 2,5-, 2,6- and 3,5-dichlorophenols (DCP) has been studied up to a pressure of about 6·5 kbar at room temperature. While the pressure dependence of the two resonance lines in 2,6-DCP is essentially similar, the lower frequency line in 2,5-DCP is almost pressure independent and the higher frequency line shows a linear variation with pressure upto about 3·5 kbar but shows a negative pressure coefficient beyond this pressure. The two lines in 3,5-DCP have a non-linear pressure dependence with the curvature changing smoothly with pressure. The pressure coefficient for both lines becomes negative beyond a pressure of 5 kbar. The pressure dependence of the N.Q.R. frequencies is discussed in relation to intra- and inter-molecular contacts. Also, a thermodynamic analysis of the data is carried out to determine the constant volume temperature derivative of the N.Q.R. frequency.

Peritoneal washing cytology

Peritoneal washing cytology (PWC) is a useful indicator of ovarian surface involvement and peritoneal dissemination by ovarian tumours. It may identify subclinical peritoneal spread and thus provide valuable staging and prognostic information, particularly for non-serous ovarian tumours. The role of PWC as a prognostic indicator for endometrial carcinoma is less clear, due in part to the questionable significance of identifying endometrial tumour cells in the peritoneum. Detection of metastatic carcinoma in PWC is based on recognition of non-mesothelial cell characteristics, however a number of conditions such as reactive mesothelial cells, endometriosis and endosalpingiosis may mimic this appearance. Cells from these conditions may have a similar presentation in PWC to that of serous borderline tumours and low grade serous carcinoma. The presence of cilia, lack of single atypical cells, prominent cytoplasmic vacuolation, marked nuclear atypia or two distinct cell populations are features favouring a benign process. Attention to these features along with close correlation with clinical history and the results of surgical pathology should help avoid errors. Additional assistance may be provided by the use of cell blocks and special stains.

Zeeman effect of nuclear quadrupole resonance in 1-chloro-2,4-dinitrobenzene

The Zeeman effect of NQR was studied in 1-chloro-2,4-dinitrobenzene. A low value of the asymmetry parameter (0.10) was obtained. Four physically inequivalent field gradients were located and their orientations in the crystallographic abc system were determined using symmetry considerations. From these data the orientations of the molecules in the unit cell were determined. The results agree well with the two-dimensional x-ray structural data. The bond characters of the C[Single Bond]Cl bond were calculated, and the values compare well with those generally obtained for C[Single Bond]Cl bonds in chlorine derivatives of benzene. ©1973 The American Institute of Physics.

Activated carbon + HFC 134a based two stage thermal compression adsorption refrigeration using low grade thermal energy sources

A thermodynamic analysis is presented for the two stage thermal compression process for an adsorption refrigeration cycle with HFC-134a as the working fluid and activated carbon as the adsorbent. Three specimens of varying achievable packing densities were evaluated. The influence of evaporating, condensing/adsorption and desorption temperatures was assessed through three performance indicators, namely,the uptake efficiency, the coefficient of performance and the exergetic efficiency. Conditions under which a two stage thermal compression process performs better than the single stage unit are identified. It is concluded that two stage thermal compression will be a viable proposition when the heat source temperature is low or when adsorption characteristics are weak or when adequate packing densities are difficult to realize. (C) 2008 Elsevier Ltd. All rights reserved.

Aspects and Applications of Pulse Sequence Design for Solution-State Nuclear Magnetic Resonance Spectroscopy

NMR spectroscopy enables the study of biomolecules from peptides and carbohydrates to proteins at atomic resolution. The technique uniquely allows for structure determination of molecules in solution-state. It also gives insights into dynamics and intermolecular interactions important for determining biological function. Detailed molecular information is entangled in the nuclear spin states. The information can be extracted by pulse sequences designed to measure the desired molecular parameters. Advancement of pulse sequence methodology therefore plays a key role in the development of biomolecular NMR spectroscopy. A range of novel pulse sequences for solution-state NMR spectroscopy are presented in this thesis. The pulse sequences are described in relation to the molecular information they provide. The pulse sequence experiments represent several advances in NMR spectroscopy with particular emphasis on applications for proteins. Some of the novel methods are focusing on methyl-containing amino acids which are pivotal for structure determination. Methyl-specific assignment schemes are introduced for increasing the size range of 13C,15N labeled proteins amenable to structure determination without resolving to more elaborate labeling schemes. Furthermore, cost-effective means are presented for monitoring amide and methyl correlations simultaneously. Residual dipolar couplings can be applied for structure refinement as well as for studying dynamics. Accurate methods for measuring residual dipolar couplings in small proteins are devised along with special techniques applicable when proteins require high pH or high temperature solvent conditions. Finally, a new technique is demonstrated to diminish strong-coupling induced artifacts in HMBC, a routine experiment for establishing long-range correlations in unlabeled molecules. The presented experiments facilitate structural studies of biomolecules by NMR spectroscopy.