bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quadrupole effects in solid‐state NMR spectra of spin‐½ Nuclei: A perturbation approach
Authors: Grondona Patricia , Olivieri Alejandro C. 
Published: March 2007

AbstractIn solution, the effect of quadrupolar nuclei on the resonances of spin‐% nuclei are confined to relaxation processes and, in favorable cases, to J‐coupling interactions. In the solid state, however, an interesting phenomenon takes place: the appearance of unexpected field‐dependent multiplicities. The application of a perturbation approach to the understanding of these multiplicities is discussed; particular attention is given to the 13C, l4N spin pair.
Magnetization transfer via isotropic mixing: An introduction to the HOHAHA experiment
Authors: Hicks Rickey P. , Young John K. , Moskau Detlef 
Published: March 2007

AbstractThe theory of the cross‐polarization two‐dimensional homonuclear Hartmann‐Hahn experiment is introduced. The product operator formalism is used to develop expressions to explain the transfer of magnetization under the influence of the isotropic Hamiltonian. The various modifications of the HOHAHA/TOCSY experiment are presented. The MLEV‐17 pulse cycle for generation of the spin‐lock pulse is discussed in detail. The intensity of magnetization transfer is shown both mathematically and graphically to be dependent on the relationship mixing time 1/(2JAX). The HOHAHA experiment is also discussed in relation to the other spin‐lock experiments, ROESY and CAMELSPIN.
Superconducting NMR magnet design
Authors: Laukien Dirk D. , Tschopp Werner H. 
Published: March 2007

AbstractGeneral information is given about solenoidal superconducting magnets and an overview is given of the design principles and theories for superconducting magnets. Issues relevant to NMR are reviewed in detail. Advantages and disadvantages of different superconducting wire, construction methods, and mathematical concepts necessary for the main components of a superconducting magnet applicable to high‐resolution NMR are surveyed. Major components such as joints, dump resistors, heat shields, and magnet dewars are illustrated and described.
Product operators, coherence pathways, and phase cycling part i: product operators, spin‐spin coupling, and coherence pathways
Authors: Kingsley Peter B. 
Published: March 2007

AbstractThe vector model is compared with product operator descriptions of NMR pulse sequences. For coupled spins, the relationship between the counter‐rotating vectors of the vector model and antiphase product operators is explained. Coherence pathways for an uncoupled spin I = ½ are explained in vector terms. The compact Cartesian coordinate product operator (C3PO) formalism is shown to provide complete coherence pathway information with vector pictures.
A pictorial representation for multispin evolutions
Authors: Wei Guowei , Snider R. F. 
Published: March 2007

AbstractModern NMR techniques involve keeping track of the evolutions of two or more coupled spins. A new multivector representation adequate for visualizing such evolutions is presented. This representation can be put in one‐one correspondence with product operators, and has the advantage that it retains all possible orientations of each spin in the product operator. Thus, as the spins evolve, faithful pictures can be drawn both to indicate the directional change of the spins magnetizations and to deduce the detailed signals that arise from their evolution. The results are in full agreement with density matrix calculations. In particular, one can visualize multiple‐quantum coherence transfer. Evolutions due to chemical shift, J coupling, and the effect of radio frequency (rf) pulses are pictured. A simple heteronuclear chemical shift correlation pulse sequence is used to illustrate how the multivector representation can follow through a combination of spin evolutions and how the signals can be correctly deduced entirely from pictures without the need to refer to density matrix or operator algebra calculations.
Product operators, coherence pathways, and phase cycling. Part III: phase cycling
Authors: Kingsley Peter B. 
Published: March 2007

AbstractThe coherence pathway approach allows the systematic design of phase cycles to eliminate unwanted coherence pathway signals in multipulse NMR sequences. Some quadrature receiver imperfections are shown to be equivalent to detection of magnetization in coherence level p = + 1 in addition to the normally observable p = −1. Other receiver artifacts do not correspond to p = +1 but also can be removed by phase cycling. Selection of signals in one‐, two‐, and three‐pulse sequences is described for uncoupled and coupled spins.
New method to quantify erythrophagocytosis by autologous monocytes
Authors: Fendel Rolf , Mordmüller Benjamin , Kreidenweiss Andrea , Rudat Annika , Steur Claudia , Ambrosch Christian , Kirstein Max , Berdel Wolfgang E. , Kremsner Peter G. , Brandts Christian 
Published: March 2007

AbstractBackground:Anemia is the net result of decreased red blood cell (RBC) production and increased removal of RBCs. Replication and maturation of erythroid precursors and RBC lysis can be measured by standardized in vitro methods and surrogate markers, respectively. In contrast, erythrophagocytosis by autologous phagocytes is more difficult to quantify.Methods:We developed a method to assess erythrophagocytosis by autologous monocytes from 5 ml of whole blood. RBCs were labeled with carboxyfluorescein‐diacetate‐succinimidyl ester (CFDA‐SE) and subsequently coincubated with autologous CD14+ monocytes. Phagocytosis was quantified using flow cytometry. After standardization, the assay was validated in patients with severe malarial anemia (SMA), a condition that is associated with increased erythrophagocytosis.Results:After labeling, CFDA‐SE was stably incorporated into RBCs and no significant leakage leading to contamination of nonlabeled cells was observed. Monocytes ingested opsonized, labeled RBCs seven times more than nonopsonized controls. Erythrophagocytosis was significantly higher in SMA than in healthy controls.Conclusions:The established assay showed enhanced autoerythrophagocytosis associated with SMA and hence was able to detect clinically relevant erythrophagocytosis. This novel assay is well suited for rapid quantification of in vitro erythrophagocytosis by autologous monocytes. © 2007 International Society for Analytical Cytology.
Androgenic, but not estrogenic, protection of motoneurons from somal and dendritic atrophy induced by the death of neighboring motoneurons
Authors: Fargo Keith N. , Sengelaub Dale R. 
Published: March 2007

AbstractMotoneuron loss is a significant medical problem, capable of causing severe movement disorders or even death. We have been investigating the effects of motoneuron loss on surviving motoneurons in a lumbar motor nucleus, the spinal nucleus of the bulbocavernosus (SNB). SNB motoneurons undergo marked dendritic and somal atrophy following the experimentally induced death of other nearby SNB motoneurons. However, treatment with testosterone at the time of lesioning attenuates this atrophy. Because testosterone can be metabolized into the estrogen estradiol (as well as other physiologically active steroid hormones), it was unknown whether the protective effect of testosterone was an androgen effect, an estrogen effect, or both. In the present experiment, we used a retrogradely transported neurotoxin to kill the majority of SNB motoneurons on one side of the spinal cord only in adult male rats. Some animals were also treated with either testosterone, the androgen dihydrotestosterone (which cannot be converted into estradiol), or the estrogen estradiol. As seen previously, partial motoneuron loss led to reductions in soma area and in dendritic length and extent in surviving motoneurons. Testosterone and dihydrotestosterone attenuated these reductions, but estradiol had no protective effect. These results indicate that the neuroprotective effect of testosterone on the morphology of SNB motoneurons following partial motoneuron depletion is an androgen effect rather than an estrogen effect. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Zinc, Cadmium and Mercury Dithiocarboxylates: Synthesis, Characterization, Structure and Their Transformation to Metal Sulfide Nanoparticles
Authors: Kedarnath Gotluru , Jain Vimal K. , Ghoshal Shamik , Dey Gautam K. , Ellis Carol A. , Tiekink Edward R. T. 
Published: March 2007

AbstractReactions of M(OAc)2·nH2O and M(OAc)2(tmeda) with dithiocarboxylic acids gave [M(S2CTol)2]n (1) (M = Zn or Cd; Tol = C6H4Me‐4) and [M(S2CAr)2(tmeda)] (3) (M = Zn, Cd, Hg; Ar = Ph or Tol), respectively, in high yields as deep‐colored crystalline solids. The former are soluble in pyridine to give pyridine adducts [M(S2CTol)2(py)] (2). These complexes were characterized by elemental analysis, UV/Vis and NMR (1H, 13C) spectroscopy. The absorptions in the electronic spectra have been assigned to ligand‐to‐ligand charge‐transfer transitions. The crystal and molecular structures of the monomeric species [Zn(S2CTol)2(py)] (2), [Zn(S2CPh)2(tmeda)] (3a), [Zn(S2CTol)2(tmeda)] (3b) and [Cd(S2CTol)2(tmeda)] (3d) have been established by X‐ray crystallography. In [Zn(S2CTol)2(py)], chelating dithiocarboxylate ligands and pyridine define a coordination geometry intermediate between square pyramidal and trigonal bipyramidal. In each of 3a and 3b, tetrahedral N2S2 coordination geometries are found as the dithiocarboxylate ligands are effectively monodentate; evidence for the greater coordination potential is found for –S2CTol over –S2CPh. Chelating dithiocarboxylate ligands in [Cd(S2CTol)2(tmeda)] (3d) lead to an octahedral geometry. Thermal behavior has been studied by thermogravimetric analysis. The [M(S2CAr)2(tmeda)] complexes underwent a three‐step decomposition. Pyrolysis in the temperature range 300–500 °C and solvothermal decomposition in ethylenediamine and hexadecylamine (HDA) gave metal sulfide nanoparticles. The MS (M = Zn, Cd, Hg) nanoparticles were characterized by XRD, EDAX, absorption/emission spectroscopy and electron microscopy (TEM). Solvothermal decomposition gave hexagonal phases of nanoparticles whereas heating in a furnace gave cubic ZnS and HgS, and hexagonal CdS. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Multi‐scale modelling approach for the pushover analysis of existing RC shear walls—Part II: Experimental verification
Authors: Mulas Maria Gabriella , Coronelli Dario , Martinelli Luca 
Published: March 2007

AbstractIn a companion paper two different modelling approaches have been described, operating at the meso‐scale of the fibre elements and at the micro‐scale of the finite element (FE) method. The aim of this paper is to explore the efficiency of these models in the pushover analysis for the seismic assessment of existing reinforced concrete (RC) structures. To this purpose a prototype reference structure, one of the RC shear walls designed according to the multi‐fuse concept and tested on shaking table for the CAMUS Project, is modelled at different levels of refinement. At the micro‐scale the reinforcement and anchorage details are described with increasing accuracy in separate models, whereas at the meso‐scale one single model is used, where each element represents a large part of the structure. Static incremental non‐linear analyses are performed with both models to derive a capacity curve enveloping the experimental results and to reproduce the damage pattern at the displacement level where failure is reached. The comparison between experimental and numerical results points out the strong and weak points of the different models inside the procedure adopted, and the utility of an integration of results from both approaches. This study confirms, even for the rather difficult case at study, the capability of the pushover in reproducing the non‐linear dynamic response, both at a global and a local level, and opens the way to the use of the models within a displacement‐based design and assessment procedure. Copyright © 2007 John Wiley & Sons, Ltd.
Treatment strategy and risk of functional decline and mortality after nursing‐home acquired lower respiratory tract infection: two prospective studies in residents with dementia
Authors: van der Steen Jenny T. , Mehr David R. , Kruse Robin L. , Ribbe Miel W. , van der Wal Gerrit 
Published: March 2007

AbstractBackgroundAlthough lower respiratory tract infections (LRI) cause considerable morbidity and mortality among nursing home residents with dementia, the effects of care and treatment are largely unknown. Few large prospective studies have been conducted.MethodsWe pooled data from two large prospective cohort studies in 61 Dutch nursing homes and 36 nursing homes in the state of Missouri, United States. We included 551 US residents and 381 Dutch residents with dementia and LRI. Main outcome measures were 3‐month mortality and decline in activities of daily living (ADL) function after 3 months compared with pre‐illness status. Using multivariable multinomial logistic regression to control for confounding, we assessed associations of restraint use and antibiotic type (oral compared with parenteral), with outcomes of lower respiratory tract infection (LRI). Survival without ADL decline was the reference category.ResultsAfter multivariable adjustment, restraint use was associated with ADL decline (OR 1.9, 95% CI 1.1–3.3). Oral antibiotics were not associated with 3‐month mortality (OR 0.83; 95% CI 0.56–1.2). Severe dementia was the strongest independent predictor of decline; mortality was most strongly associated with male gender.ConclusionsAmong Dutch and US nursing home residents with dementia and LRI, restrained residents suffered more decline. Parenteral antibiotic treatment was not associated with better outcome in residents at low to moderate risk of mortality. Aggressive treatment strategies may provide little benefit for the majority of nursing home residents with dementia and LRI. Copyright © 2007 John Wiley & Sons, Ltd.
Hybrid molecular dynamics‐quantum mechanics simulations of solute spectral properties in the condensed phase: Evaluation of simulation parameters
Authors: Zwier Matthew C. , Shorb Justin M. , Krueger Brent P. 
Published: March 2007

AbstractWe have explored the impact of a number of basic simulation parameters on the results of a recently developed hybrid molecular dynamics‐quantum mechanics (MD‐QM) method (Mercer et al., J Phys Chem B 1999, 103, 7720). The method utilizes MD simulations to explore the ground‐state configuration space of the system and QM evaluation of those structures to yield the time‐dependent electronic transition energy, which is transformed into the optical line‐broadening function using the second‐order cumulant expansion. Both linear and nonlinear optical spectra can then be generated for comparison to experiment. The dependence of the resulting spectra on the length of the MD trajectory, the QM sampling rate, and the QM model chemistry have all been examined. In particular, for the system of oxazine‐4 in methanol studied here, at least 20 ps of MD trajectory are needed for qualitative convergence of linear spectral properties, and > 100 ps is needed for quantitative convergence. Surprisingly, little difference is found between the 3‐21G and 6‐31G(d) basis sets, and the CIS and TD‐B3LYP methods yield remarkably similar spectra. The semiempirical INDO/s method yields the most accurate results, reproducing the experimental Stokes shift to within 5% and the FWHM to within 20%. Nonlinear 3‐pulse photon echo peak shift (3PEPS) decays have also been simulated. Decays are generally poorly reproduced, though the initial peak shift which depends on the overall coupling of motions to the solute transition energy is within 15% of experiment for all model chemistries other than those using the STO‐3G basis. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Molecular structures of the two most stable conformers of free glycine
Authors: Kasalová Veronika , Allen Wesley D. , Schaefer Henry F. , Czinki Eszter , Császár Attila G. 
Published: March 2007

AbstractThe equilibrium molecular structures of the two lowest‐energy conformers of glycine, Gly‐Ip and Gly‐IIn, have been characterized by high‐level ab initio electronic structure computations, including all‐electron cc‐pVTZ CCSD(T) geometry optimizations and 6‐31G* MP2 quartic force fields, the latter to account for anharmonic zero‐point vibrational effects to isotopologic rotational constants. Based on experimentally measured vibrationally averaged effective rotational constant sets of several isotopologues and our ab initio data for structural constraints and zero‐point vibrational shifts, least‐squares structural refinements were performed to determine improved Born‐Oppenheimer equilibrium (re) structures of Gly‐Ip and Gly‐IIn. Without the ab initio constraints even the extensive set of empirical rotational constants available for 5 and 10 isotopologues of Gly‐Ip and Gly‐IIn, respectively, cannot satisfactorily fix their molecular structure. Excellent agreement between theory and experiment is found for the rotational constants of both conformers, the rms residual of the final fits being 7.8 and 51.6 kHz for Gly‐Ip and Gly‐IIn, respectively. High‐level ab initio computations with focal point extrapolations determine the barrier to planarity separating Gly‐IIp and Gly‐IIn to be 20.5 ± 5.0 cm−1. The equilibrium torsion angle τ(NCCO) of Gly‐IIn, characterizing the deviation of its heavy‐atom framework from planarity, is (11 ± 2)°. Nevertheless, in the ground vibrational state the effective structure of Gly‐IIn has a plane of symmetry. © 2007 Wiley Periodicals, Inc. J Comput Chem 2007
Molecular dynamics simulation in the grand canonical ensemble
Authors: Eslami Hossein , Müller‐Plathe Florian 
Published: March 2007

AbstractAn extended system Hamiltonian is proposed to perform molecular dynamics (MD) simulation in the grand canonical ensemble. The Hamiltonian is similar to the one proposed by Lynch and Pettitt (Lynch and Pettitt, J Chem Phys 1997, 107, 8594), which consists of the kinetic and potential energies for real and fractional particles as well as the kinetic and potential energy terms for material and heat reservoirs interacting with the system. We perform a nonlinear scaling of the potential energy parameters of the fractional particle, as well as its mass to vary the number of particles dynamically. On the basis of the equations of motion derived from this Hamiltonian, an algorithm has been proposed for MD simulation at constant chemical potential. The algorithm has been tested for the ideal gas, for the Lennard–Jones fluid over a wide range of temperatures and densities, and for water. The results for the low‐density Lennard–Jones fluid are compared with the predictions from a truncated virial equation of state. In the case of the dense Lennard–Jones fluid and water our predicted results are compared with the results reported using other available methods for the calculation of the chemical potential. The method is also applied to the case of vapor‐liquid coexistence point predictions. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
MR imaging of the central nervous system in divers
Authors: Rinck Peter A. , Svihus Rasmus , de Francisco Patricia 
Published: March 2007

AbstractA group of 70 professional divers and 47 healthy control subjects who had never dived were examined with magnetic resonance (MR) imaging to determine the prevalence of focal white matter changes in the brain. Spots of high signal intensity in white matter on proton density‐and/or T2‐weighted spin‐echo images were detected in 42% of the control subjects and in 34% of the divers. In the control subjects, the prevalence of more than three changes was related to smoking, use of alcohol, head trauma, age of more than 35 years, and a combination of several cerebrovas‐cular risk factors. This relationship was not present in the divers. The prevalence of changes in divers was inversely related to diving depth, amount of diving, participation in “unsafe diving,” and decompression sickness. The reasons for these results could not be ascertained. The results are compared with those of MR imaging studies of white matter changes recently presented by other research groups.
MR imaging shoulder injuries in professional baseball players
Authors: Burk D. Lawrence , Torres Jorge L. , Marone Phillip J. , Mitchell Donald G. , Rifkin Matthew D. , Karasick David 
Published: March 2007

AbstractMagnetic resonance (MR) imaging was used to evaluate the shoulders of 10 symptomatic professional baseball players and one asymptomatic player, with surgical correlation in six cases and arthrographic correlation in two cases. Seven small rotator cuff tears measuring 0.5–1 cm were identified on MR images, with arthrographic and surgical confirmation of these findings in two patients and surgical confirmation only in three patients. Cortical irregularity and/or subchondral cyst formation at the posterior aspect of the greater tuberosity near the insertion site of the infraspinatus tendon was found in five of the seven players with rotator cuff tears. Similar findings were noted in the asymptomatic volunteer and in one of the three players without cuff tear, who also had irregular thickening of the posterior capsule. These findings are believed to represent chronic avulsive changes resulting from the deceleration stresses of the follow‐through motion.
Phase‐contrast MR angiography with reduced acquisition time: New concepts in sequence design
Authors: Hausmann Richard , Lewin Jonathan S. , Laub Gerhard 
Published: March 2007

AbstractA new acquisition scheme for three‐dimensional (3D) phase‐contrast MR angiography reduces by 33% the measurement time for a data set sensitive to flow in all three orthogonal directions. Background suppression is achieved by acquiring a flow‐compensated data set and three data sets flow encoded in the three orthogonal directions, with subsequent complex subtraction. The data are acquired in an interleaved fashion, eliminating misregistration artifacts due to patient motion between measurements sensitive to different flow directions. A standard maximum‐intensity‐projection algorithm is applied to the combined 3D data set to obtain angiographic projections sensitive to all three orthogonal flow directions. The theory and implementation of the method are described and examples of its application to the intracranial and abdominal circulation are provided.
Polymeric gastrointestinal MR contrast agents
Authors: Tilcock Colin , Unger Evan C. , Ahkong Quet Fah , Fritz Tom , Koenig Seymour H. , Brown Rodney D. 
Published: March 2007

AbstractCombining either paramagnetic (gadolinium chelatea) or superparamagnetic (ferrite) contrast agents with polymers such as polyethylene glycol or cellulose, or with simple sugars such as dextrose, results in mixtures that exhibit improved T1 and/or T2 relaxivity compared with that of the contrast agent alone. It is suggested that the addition of such inexpensive and nontoxic polymers or saccharides may improve the effectiveness and decrease the cost of enteric contrast agents.
Atypical appearance of lipomatous tumors on MR images: High signal intensity with fat‐suppression STIR sequences
Authors: Murphy William D. , Hurst Gregory C. , Duerk Jeffrey L. , Feiglin David H. , Christopher Mark , Bellon Errol M. 
Published: March 2007

AbstractLipomatous tumors generally have signal characteristics that allow them to be diagnosed with great accuracy by means of magnetic resonance imaging. These tumors usually have signal intensities similar to those of subcutaneous fat on both T1‐ and T2‐weighted spin‐echo images. Previous reports have not, to the authors' knowledge, described the appearance of lipomatous tumors on images obtained with a short‐inversion‐time inversion‐recovery (STIR) sequence, which can be used to suppress signal from fat. Three lipomatous tumors (two liposarcomas and one lipoma) with signal characteristics unlike those of normal subcutaneous fat at all pulse sequences are presented.