SEARCH · PubMed Health

Results for “Resolution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,189 records · Page 66Linked to original sources

PubMed1998

Genetic algorithm-based wavelength selection for the near-infrared determination of glucose in biological matrixes: initialization strategies and effects of spectral resolution.

An improved genetic algorithm (GA)-based wavelength selection procedure is developed to optimize both the near-infrared wavelengths used and the number of latent variables employed in building partial least-squares (PLS) calibration models. This GA-based wavelength selection algorithm is applied to the determination of glucose in two different biological matrixes. With random selection of a small number of initial wavelengths, a dramatic reduction in the number of wavelengths required for building the PLS calibration models is observed. The fitness function used to guide the GA, the method of recombination used, and the effect of spectral resolution on the wavelength selection are also studied. In the resolution study, the original data with a point spacing of 2 cm-1 are deresolved to 4-, 8-, and 16-cm-1 point spacings by truncating the collected interferograms before applying the Fourier processing step. The use of lower resolution spectra is found to reduce further the number of final wavelengths selected by the GA, and the performance of the optimal calibration models obtained with the original spectra is maintained with the lower resolution spectra of both 4- and 8-cm-1 point spacing. Degradation in performance is observed with the spectra computed with a point spacing of 16 cm-1, however.

Algorithms↗

PubMed1999

Trace analyses of arsenic in drinking water by inductively coupled plasma mass spectrometry: high resolution versus hydride generation.

A magnetic sector inductively coupled plasma mass spectrometer (ICPMS) was applied to the determination of arsenic in drinking water samples using standard liquid sample introduction in the high-resolution mode (M/delta M = 7800) and hydride generation in the low-resolution mode (M/delta M = 300). Although high mass resolution ICPMS allowed the spectral separation of the argon chloride interference, the accompanying reduction in sensitivity at high resolution compromised detection and determination limits to 0.3 and 0.7 microgram/L, respectively. Therefore, a hydride generation sample introduction method, utilizing a new membrane gas-liquid separator design, was developed to overcome the chloride interference. Due to the high transport efficiency and the 50-100 times higher sensitivity at M/delta M = 300, the HG-ICPMS method resulted in an over 2000-fold increase in relative sensitivity. The routine detection and quantification limits were 0.3 and 0.5 ng/L, respectively. The results for both methods applied to the analysis of over 400 drinking water samples showed very good agreement at concentrations above 1 microgram/L. For concentrations between 0.01 and 1 microgram/L, only HG-ICPMS provided accurate quantitative results. Membrane desolvation, mixed-gas plasmas, and the addition of organic solvents for the reduction of the ArCl+ interference were also investigated and evaluated for trace As determination.

Arsenic↗

PubMed2001

Structural elucidation of microporous and mesoporous catalysts and molecular sieves by high-resolution electron microscopy.

Twenty years ago, one of us embarked (Bursill, L. A.; Lodge, E. A.; Thomas, J. M. Zeolitic structures as revealed by high-resolution electron microscopy. Nature 1980, 286, 111-113) on the study of zeolites (renowned for their electron-beam sensitivity) by high-resolution transmission electron microscopy (HRTEM). In the ensuing years, high-resolution imaging aided by optical diffractometry has yielded details of the open framework structures of a number of new aluminosilicate and aluminophosphate molecular sieves and catalysts. The nature of intergrowth and recurrently twinned structures, as well as new types of structural imperfection in hitherto uncharacterized materials, has also been elucidated. With continued improvements in instrumental development, encompassing higher accelerating voltages, better objective lenses and vacua, computational advances, and the arrival of slow-scan CCD detectors, electron crystallographic methods and HRTEM imaging now enable the ab initio three-dimensional structures of micro- and mesoporous solids, with their occluded structure-directing organic species, to be determined. High-resolution scanning transmission electron microscopy using subnanometric probes provides supplementary structural and ultramicro analytical information and electron spectroscopic imaging (at the attogram level). In its high-angle annular dark-field mode, it is capable of locating and determining the composition of individual nanoparticle catalysts (consisting of just a few atoms) supported on porous hosts.

Journal Article↗

PubMed1977

Structure of bovine trypsinogen at 1.9 A resolution.

The three-dimensional crystal structure of bovine trypsinogen at approximately pH 7.5 was initially solved at 2.6 A resolution using the multiple isomorphous replacement method. Preliminary refinement cycles of the atomic coordinates trypsinogen have been carried out first to a resolution of 2.1 A, and later to 1.9 A, using constrained difference Fourier refinement; During the process, structure factors Fc and phi c were calculated from the trypsinogen structure and final interpretation was based on an electron-density map computed with terms (2 Fo - Fc) and phases phic at a resolution of 1.9 A. Crystals of trypsinogen grown from ethanol-water mixtures are trigonal with space group P3121, and cell dimension a = 55.17 A and c = 109.25 A. The structure is compared with the bovine diisopropylphosphoryltrypsin structure at approximately pH 7.2, oirginally determined from orthohombic crystals by Stroud et al. (Stroud, R.M., Kay L.M., and Dickerson, R.E. (1971), Cold Spring Harbor Symp. Quant. Biol. 36, 125-140; Stroud, R.M., Kay, L.M., and Dickerson, R.E. (1974), J. Mol. Biol. 83, 185-208), and later refined at 1.5 A resolution by Chambers and Stroud (Chambers, J.L., and Stroud, R.M. (1976), Acta Crystallogr. (in press)). At lower pH, 4.0-5.5 diogen, with cell dimensions a = 55.05 A and c = 109.45 A. This finding was used in the solution of the six trypsinogen heavy-atom derivatives prior to isomorphous phase analysis, and as a further basis of comparison between trypsinogen and the low pH trypsin structure. There are small differences between the two diisopropylphosphoryltrypsin structures. Bovine trypsinogen has a large and accessible cavity at the site where the native enzyme binds specific side chains of a substrate. The conformation and stability of the binding site differ from that found in trypsin at approximately pH 7.5, and from that in the low pH form of diisopropylphosphoryltrypsin. The catalytic site containing Asp-102, His-57, and Ser-195 is similar to that found in trypsin and contains a similar hydrogen-bounded network. The carboxyl group of Asp-194, which is salt bridged to the amino terminal of Ile-16 in native trypsin or other serine proteases, is apparently hydrogen bonded to internal solvent molecules in a loosely organized part of the zymogen structure. The unusually charged N-terminal hexapeptide of trypsinogen, whose removal leads to activation of the zymogen, lies on the outside surface of the molecule. There are significant structural changes which accompany activation in neighboring regions, which include residues 142-152, 215-550, 188A-195. The NH group of Gly-193, normally involved in stabilization of reaction intermediates (Steitz, T.A., Henderson, R., and Blow, D.M. (1969), J. Mol. Biol. 46, 337-348; Henderson, R. (1970), J. Mol. Biol. 54, 341-354; robertus, J.D., Kraut, J., Alden, R.A., and Birkoft, J.J. (1972), Biochemistry 11, 4293-4303) in the enzyme, is moved 1.9 A away from its position in trypsin...

Animals↗

PubMed2004

Impact of finer grid resolution on the spatial distribution of vehicle emissions inventories.

The ability to model air quality dispersion at increasingly smaller resolutions requires a concomitant improvement in the resolution of the gridded mobile source emissions used as input to these models. Two methods are currently used to allocate mobile emissions to grids; because of the limitations associated with these methods, their application is usually restricted to coarser grid resolutions. This paper uses a new mobile emissions inventory model (UCDrive) to explore the spatial distribution of mobile source emissions using finer grid cell resolutions. Our results indicate that the new model improves the precision of the spatial allocation of mobile source emissions, which in turn improves our ability to identify and implement pollutant control strategies.

Air Pollutants↗

PubMed2003

What should be impossible: resolution of the mononuclear gallium coordination complex, Tris(benzohydroxamato)gallium(III).

Complexes of Ga3+, a d10 metal ion which lacks ligand-field-stabilization energy, are considered labile. In fact, hexaaquagallium(III) has a ligand exchange rate of 403 s-1, 2.5 times that of the analagous Fe3+ complex (Hugi-Cleary, D.; Helm, L.; Merbach, A. E. J. Am. Chem. Soc. 1987, 109, 4444-4450). Given this lability, resolution of Ga3+ complexes should be impossible. Despite this, we report the resolution of the Lambda and Delta isomers of tris(benzohydroxamate)gallium (III) (1), the first resolution of a mononuclear gallium complex. Not only is resolution possible, but these resolved complexes show remarkable resistance to racemization in aprotic solvents. The unprecedented stability of Lambda- and Delta-1 is a surprise, and as such, alters our understanding of classical coordination chemistry.

Circular Dichroism↗

PubMed2005

High-resolution four-dimensional 1H-13C NOE spectroscopy using methyl-TROSY, sparse data acquisition, and multidimensional decomposition.

An approach for recording four-dimensional (4D) methyl (1)H-(13)C-(13)C-(1)H NOESY spectra with high resolution and sensitivity is presented and applied to Malate Synthase G (723 residues, 82 kDa). Sensitivity and resolution have been optimized using a highly deuterated, methyl-protonated sample in concert with methyl-TROSY, sparse data sampling in the three indirect dimensions, and 4D spectral reconstruction using multidimensional decomposition (MDD). A sparse data acquisition protocol is introduced that ensures that sufficiently long indirect acquisition times can be employed to exploit the decreased relaxation rates associated with methyl-TROSY, without increasing the duration of the 4D experiment beyond acceptable measurement times. In this manner, only a fraction ( approximately 30%) of the experimental data that would normally be needed to achieve a spectrum of high resolution is acquired. The reconstructed 4D spectrum is of similar resolution and sensitivity to three-dimensional (3D) (13)C-edited NOE spectra, is straightforward to analyze, and resolves ambiguities that emerge when 3D data sets only are considered.

Carbon Isotopes↗

PubMed2001

Kinetic resolution of acyclic secondary allylic silyl ethers catalyzed by chiral ketones.

Kinetic resolution of acyclic secondary allylic silyl ethers by chiral dioxiranes generated in situ from chiral ketones (R)-1 and (R)-2 and Oxone was investigated. An efficient and catalytic method has been developed for kinetic resolution of those substrates with a CCl(3), tert-butyl, or CF(3) group at the alpha-position. In particular, high selectivities (S up to 100) were observed for kinetic resolutions of racemic alpha-trichloromethyl allylic silyl ethers 7 and 9-15 catalyzed by ketones (R)-2. Both the recovered substrates and the resulting epoxides were obtained in high enantiomeric excess. On the basis of steric and electrostatic interactions between the chiral dioxiranes and the racemic substrates, a model was proposed to rationalize the enantioselectivities and diastereoselectivities in the chiral ketone-catalyzed kinetic resolution process.

Journal Article↗

PubMed2002

Practical enantioselective synthesis of endothelin antagonist S-1255 by dynamic resolution of 4-methoxychromene-3-carboxylic acid intermediate.

A practical multikilogram-scale synthesis of enantiomerically pure S-1255 (1), a potent and orally active ET(A) receptor antagonist, is described. Utilizing readily available starting materials and reagents, the entire sequence of reactions starting from 2,5-dihydroxyacetophenone 8 proceeded under mild conditions to give 1 in an excellent chemical yield (8 steps, 41% overall yield) and in a high enantiopurity (98% ee). The crucial step of the synthesis is a dynamic resolution of key intermediate 16. (R)-Methoxy acid (R)-16 having 97-99% ee was obtained in 83-84% yield from racemic 16 as a crystalline (1S,2R)-(+)-norephedrine or (+)-cinchonine salt by the dynamic resolution comprising concurrent crystallization and in situ racemization. A mechanism of the dynamic resolution through a ring-opened zwitterionic intermediate is discussed. In the final synthetic step, an effective carbon-carbon bond formation between the C4 carbon and the p-anisyl group was accomplished by a conjugate addition-elimination reaction of Grignard reagent 3 to (R)-16 to give 1 having 98% ee. Owing to high efficiencies of functional group transformations, carbon-carbon bond formations, and the dynamic resolution, the synthesis required no chromatographic purification and was amenable to a multikilogram-scale preparation. Several kilograms of 1 for clinical trials were successfully prepared by this process.

Benzopyrans↗

PubMed2006

Chirped coherent anti-stokes Raman scattering for high spectral resolution spectroscopy and chemically selective imaging.

We describe a simple multiplex vibrational spectroscopic imaging technique based on employing chirped femtosecond pulses in a coherent anti-Stokes Raman scattering (CARS) scheme. Overlap of a femtosecond Stokes pulse with chirped pump/probe pulses introduces a temporal gate that defines the spectral resolution of the technique, allowing single-shot acquisition of high spectral resolution CARS spectra over a several hundred wavenumber bandwidth. Simulated chirped (c-) CARS spectra match the experimental results, quantifying the dependence of the high spectral resolution on the properties of the chirped pulse. c-CARS spectromicroscopy offers promise as a simple and generally applicable high spatial resolution, chemically specific imaging technique for studying complex biological and materials samples.

Journal Article↗

PubMed2006

Proteome resolution by two-dimensional gel electrophoresis varies with the commercial source of IPG strips.

By facilitating reproducible first dimension separations, commercial immobilized pH gradient (IPG) strips enable high throughput and high-resolution proteomic analyses using two-dimensional gel electrophoresis (2DE). Amersham, Biorad, Invitrogen, and Sigma all market linear pH 3-10 IPG strips. We have applied optimized 2DE protocols with both membrane and soluble brain protein extracts to critically evaluate all four products. Resolved protein spots were quantitatively evaluated after carrying out these protocols using IPG strips from the four companies. Biorad and Amersham IPG strips resolved a high number of membrane and soluble proteins, respectively. Furthermore, Amersham IPG strips eluted the largest amount of protein into the second dimension gels and had the most protein remaining in the strip after 2DE. Biorad and Amersham IPG strips maintained a consistent linear pH 3-10 gradient, whereas those from Invitrogen appeared nonlinear or "compressed" within the central pH region. The gradient range within Sigma IPG strips appeared to be slightly less than pH 3-10, due to one extended pH unit within the gradient. Overall, all four commercially available IPG strips have the ability to resolve both membrane and soluble brain proteomes. The difference is that Amersham and Biorad do so more consistently and with better spot resolution. It appears that the physical/chemical nature of commercially available IPG strips can vary considerably, leading to marked differences in subsequent protein resolution in 2DE. These differences likely reflect variations in the uptake of proteins into the strips, and differences in the focusing and elution of proteins from the first to the second dimension. These differences would appear, in part, to underlie some inter-lab variations in the effective resolution of proteomes.

Animals↗

PubMed2001

Noninvasive transthoracic low frequency ultrasound augments thrombolysis in a canine model of acute myocardial infarction--evaluation of the extent of ST-segment resolution.

BACKGROUND: Recently it has been demonstrated that transcutaneous delivery of ultrasound combined with tissue plasminogen activator (tPA) is more effective than tPA alone in recanalizing acutely thrombosed canine coronary arteries. In the present study, we investigated the incidence of partial (> or =50%) and complete (> or =70%) ST-segment elevation resolution in the precordial leads of dogs with experimental acute myocardial infarction that were treated with tissue plasminogen activator (tPA) alone or in combination with noninvasive transcutaneous delivery of high-intensity low frequency (27[emsp3 ]kHz) ultrasound. METHODS: Thrombotic coronary occlusions were induced in the midportion of left anterior descending (LAD) coronary artery by electrical injury in 24 dogs. All dogs were given intravenous heparin and tPA. Dogs were randomized to tPA alone (n=12) or combined tPA and adjunctive transcutaneous ultrasound (US) delivery (n=12). Electrocardiograms were recorded at 1) baseline, 2) after coronary occlusion just before initiation of therapy, 3) when coronary angiography showed recanalization of the coronary artery (or at 90 minutes after initiation of therapy if reperfusion did not occur before then) and 4) 90 minutes later. ST amplitude was measured in all 6 precordial leads. RESULTS: ST-segment amplitude at baseline was comparable between the tPA and the US group. Before initiation of therapy, sum of ST-segment elevation tended to be higher in the US group. At reperfusion and 90 minutes thereafter, sum of ST-segment amplitude tended to be smaller for the US group than in the tPA group (p<0.001 for the time effect; p=0.118 for the time x group interaction). Up to 90 minutes after initiation of therapy >/=50% resolution of the sum of precordial ST elevation was detected in 7 out of 11 dogs (63.6%) in the tPA group versus 10 out of 11 dogs (90.9%) in the US group. Ninety minutes thereafter, 3 out of 7 dogs in the tPA group (42.9%) versus 9 of 11 dogs in the US group (81.8%) had >/=50% resolution of the sum of precordial ST elevation. CONCLUSIONS: The combination of tPA with noninvasive transcutaneous delivery of low frequency high-intensity ultrasound resulted in greater resolution of ST-segment elevation when reperfusion occurs and 90 minutes thereafter, as well as a higher rate of epicardial coronary artery reperfusion.

Animals↗

PubMed2002

Resolution of fluorescence in-situ hybridization mapping on rice mitotic prometaphase chromosomes, meiotic pachytene chromosomes and extended DNA fibers.

Fluorescence in-situ hybridization (FISH) is a quick and affordable approach to map DNA sequences to specific chromosomal regions. Although FISH is one of the most important physical mapping techniques, research on the resolution of FISH on different cytological targets is scarce in plants. In this study, we report the resolution of FISH mapping on mitotic prometaphase chromosomes, meiotic pachytene chromosomes and extended DNA fibers in rice. A majority of the FISH signals derived from bacterial artificial chromosome (BAC) clones separated by approximately 1 Mb of DNA cannot be resolved on mitotic prometaphase chromosomes. In contrast, the relative positions of closely linked or even partially overlapping BAC clones can be resolved on a euchromatic region of rice chromosome 10 at the early pachytene stage. The resolution of pachytene FISH is dependent on early or late pachytene stages and also on the location of the DNA probes in the euchromatic or heterochromatic regions. We calibrated the fiber-FISH technique in rice using seven sequenced BAC clones. The average DNA extension was 3.21 kb/microm among the seven BAC clones. Fiber-FISH results derived from a BAC contig that spanned 1 Mb DNA matched remarkably to the sequencing data, demonstrating the high resolution of this technique in cytological mapping.

Chromosomes, Bacterial↗

PubMed2002

HLA polymorphism in Bulgarians defined by high-resolution typing methods in comparison with other populations.

In the present study we analyzed for the first time HLA class I and class II polymorphisms defined by high-resolution typing methods in the Bulgarian population. Comparisons with other populations of common historical background were performed. Most HLA-A, -B, -DRB alleles and haplotypes observed in the Bulgarian population are also common in Europe. Alleles and haplotypes considered as Mediterranean are relatively frequent in the Bulgarian population. Observation of Oriental alleles confirms the contribution of Asians to the genetic diversity of Bulgarians. The use of high-resolution typing methods allowed to identify allele variants rare for Europeans that were correlated to specific population groups. Phylogenetic and correspondence analyses showed that Bulgarians are more closely related to Macedonians, Greeks, and Romanians than to other European populations and Middle Eastern people living near the Mediterranean. The HLA-A,-B,-DRB1 allele and haplotype diversity defined by high-resolution DNA methods confirm that the Bulgarian population is characterized by features of southern European anthropological type with some influence of additional ethnic groups. Implementation of high-resolution typing methods allows a significantly wider spectrum of HLA variation to be detected, including rare alleles and haplotypes, and further clarifies the origin of Bulgarians.

Bulgaria↗

PubMed1996

The resolution of ruptures in the therapeutic alliance.

This article outlines some of the main features of a research program on ruptures in the therapeutic alliance and reports some of the major findings to date. A rupture in the therapeutic alliance is a deterioration in the quality of the relationship between patient and therapist; it is an interpersonal marker that indicates a critical opportunity for exploring and understanding the processes that maintain a maladaptive interpersonal schema. Following the task-analytic research paradigin, a preliminary model of the resolution process was developed and then tested and revised with 2 different data sets. A series of lag 1 sequential analyses were used to confirm the hypothesized sequences of events within resolution sessions and to demonstrate a difference between resolution and nonresolution sessions. This article describes the evolution of a model of rupture resolution and then discusses its implications for treatment development and evaluation.

Adaptation, Psychological↗

PubMed1999

Sequential priming in hierarchically organized figures: effects of target level and target resolution.

Three experiments are reported in which participants identified target letters that appeared at either the global or local level of hierarchically organized stimuli. It has been previously reported that response time is facilitated when targets on successive trials appear at the same level (L. M. Ward, 1982; L. C. Robertson, 1996). Experiments 1 and 2 showed that this sequential priming effect can be mediated by target-level information alone, independent of the resolution, or actual physical size, of targets. Target level and resolution were unconfounded by manipulating total stimulus size, such that global elements of the smaller stimuli subtended the same amount of visual angle as local elements of the larger stimuli. Experiment 3, however, showed that when level information is less useful than resolution in parsing targets from distractors, resolution does become critical in intertrial priming. These data are discussed as they relate to the role of attention in local vs. global (part vs. whole) processing.

Attention↗

PubMed1990

Age differences in the enjoyment of incongruity-resolution and nonsense humor during adulthood.

This study tested a model of the development of incongruity-resolution and nonsense humor during adulthood. Subjects were 4,292 14- to 66-year-old Germans. Twenty jokes and cartoons representing structure-based humor categories of incongruity resolution and nonsense were rated for funniness and aversiveness. Humor structure preferences were also assessed with a direct comparison task. The results generally confirmed the hypotheses. Incongruity-resolution humor increased in funniness and nonsense humor decreased in funniness among progressively older subjects after the late teens. Aversiveness of both forms of humor generally decreased over the ages sampled. Age differences in humor appreciation were strongly correlated with age differences in conservatism. An especially strong parallel was found between age differences in appreciation of incongruity-resolution humor and age differences in conservatism.

Adolescent↗

PubMed1994

The lexical nature of syntactic ambiguity resolution [corrected].

Ambiguity resolution is a central problem in language comprehension. Lexical and syntactic ambiguities are standardly assumed to involve different types of knowledge representations and be resolved by different mechanisms. An alternative account is provided in which both types of ambiguity derive from aspects of lexical representation and are resolved by the same processing mechanisms. Reinterpreting syntactic ambiguity resolution as a form of lexical ambiguity resolution obviates the need for special parsing principles to account for syntactic interpretation preferences, reconciles a number of apparently conflicting results concerning the roles of lexical and contextual information in sentence processing, explains differences among ambiguities in terms of ease of resolution, and provides a more unified account of language comprehension than was previously available.

Cognition↗