bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of photoinitiator on photopolymerization of inorganic–organic hybrid polymers (ORMOCER®)
Authors: Kim Woo‐Soo , Houbertz Ruth , Lee Tae‐Ho , Bae Byeong‐Soo 
Published: April 2004

AbstractInorganic–organic hybrid polymers have been developed and tested for evaluation in optical and electrical applications. Although hybrid inorganic–organic polymers can be synthesized by sol–gel chemistry at first, the physical properties of hybrid inorganic–organic polymers are changed during thin film‐making processes, that is, photocuring and thermal curing. To investigate the effect of photoinitiator on the material properties during processing, a model system containing methacrylic groups as organically polymerizable units was selected. The conversion of CC double bond of methacrylic groups depending on some kinds of photoinitiator quantities was characterized by Fourier transform infrared spectroscopy. It was confirmed to correlate the degree of CC double bond conversion with the refractive indices. Thermodynamically, the enthalpy of the photopolymerization of hybrid polymer was investigated by UV–DSC. UV–DSC spectra showed the exothermic nature of photopolymerization of ORMOCER® to be in dependence of photoinitiator quantities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1979–1986, 2004
Electron spin resonance investigation of molecular motions in oil‐extended styrene–butadiene–styrene block copolymers. I. The temperature dependence of resonance spectra: Glass, narrowing, and inflection temperatures
Authors: Chipara M. , Rowlands C. C. , Galatanu A. N. 
Published: April 2004

AbstractSpin‐probe research into nanometer‐scale molecular motions occurring in oil‐extended styrene–butadiene–styrene diblock copolymers within the glass‐transition range is reported. Complex resonance spectra are deconvoluted, and their intricate temperature dependence, resulting from the convolution of individual spectra due to nitroxide molecules located in different phases of the block copolymers, is analyzed. It is proved that a Boltzmann sigmoid accurately describes the temperature dependence of outer line separation. The characteristic inflection point of each sigmoid is used to assign an inflection temperature to each phase of the block copolymers. The inflection temperature coincides with the narrowing temperatures, within the experimental error. It is concluded that the inflection temperature is estimated with a higher accuracy than the narrowing temperature and that it allows a more profound analysis of molecular motions. The anomalous dependence of the glass, narrowing, and inflection temperatures for spin probes immobilized within the hard phase on the oil content has been assigned to morphological modifications, on the nanometer scale, induced by oil molecules added to the block copolymers. The experimental data demonstrate the sensitivity of spin‐probe data to modifications of the nanometer‐size architecture of block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1960–1971, 2004
Antibody recognition of chiral surfaces. Structural models of antibody complexes with leucine–leucine–tyrosine crystal surfaces
Authors: Geva Merav , Eisenstein Miriam , Addadi Lia 
Published: April 2004

AbstractMolecular models are built of the recognition domains of two antibodies, which are raised and selected against crystals of (L)leucine‐(L)leucine‐(L)tyrosine. The model of one antibody, which is stereo‐ and enantioselective, reveals astounding chemical and structural complementarity to the recognized crystal surface. The enantioselective binding of this antibody is explained by the significantly fewer chemical interactions arising in the complex, after docking of the antibody to the (D)Leu‐(D)Leu‐(D)Tyr crystal face, relative to its enantiomer, the (L)Leu‐(L)Leu‐(L)Tyr crystal face. The modeling and docking of the second antibody, which is poorly stereoselective and is not enantioselective, indicates that binding is based on electrostatic interactions. The docking models of the antibody–crystal complexes provide a rationale for the experimental results while demonstrating the power of modeling techniques to meet the challenge of describing antibody–antigen interactions in detail. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Magnetically quantized continuum distorted‐wave theory in atomic and molecular collisions
Authors: O'Rourke S. F. C. , McSherry D. M. , Crothers D. S. F. 
Published: April 2004

AbstractThe continuum distorted‐wave eikonal initial‐state (CDW‐EIS) theory of Crothers and McCann (J Phys B 1983, 16, 3229) used to describe ionization in ion–atom collisions is generalized (G) to GCDW‐EIS to incorporate the azimuthal angle dependence of each CDW in the final‐state wave function. This is accomplished by the analytic continuation of hydrogenic‐like wave functions from below to above threshold, using parabolic coordinates and quantum numbers including magnetic quantum numbers, thus providing a more complete set of states. At impact energies lower than 25 keVu−1, the total ionization cross‐section falls off, with decreasing energy, too quickly in comparison with experimental data. The idea behind and motivation for the GCDW‐EIS model is to improve the theory with respect to experiment by including contributions from nonzero magnetic quantum numbers. We also therefore incidentally provide a new derivation of the theory of continuum distorted waves for zero magnetic quantum numbers while simultaneously generalizing it. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Fragmentation patterns of novel dispirocyclopiperazinium dibromides with strong analgesic activity under electrospray ionization tandem mass spectrometry conditions
Authors: Wang Xin , Sha Yaowu , Li Runtao 
Published: April 2004

AbstractThe fragmentation patterns of a series of dispirocyclopiperazinium dibromides with strong analgesic activity are analyzed by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry (ESI‐MSn). Instead of the parent molecular ions, the fragment ions [MBr]+ are detected as characteristic double peaks and usually the base peaks. Meanwhile, the fragment ions [M2Br]2+ are unique for this series of diquaternary ammonium dibromides and show high intensity. Besides the common fragmentation patterns around the carbonyl group, elimination of hydrogen bromide from [MBr]+ ions is another important pathway. Following the elimination, an interesting rearrangement takes place in the unsaturated spirocyclopiperazine and transforms it into a dihydropyrrole structure, whose fragmentations are similar to its precursor ion in the succeeding steps. Copyright © 2004 John Wiley & Sons, Ltd.
Polymer‐assisted laser desorption/ionization analysis of small molecular weight compounds
Authors: Woldegiorgis Andreas , Kieseritzky Fredrik von , Dahlstedt Emma , Hellberg Jonas , Brinck Tore , Roeraade Johan 
Published: April 2004

AbstractThe use of non‐polar, small polymers as matrices for the analysis of low molecular weight compounds in polymer‐assisted laser desorption/ionization mass spectrometry (PALDI‐MS) is demonstrated. The matrices evaluated were either based on an oligothiophene or a benzodioxin backbone. Metallocenes, polycyclic hydrocarbons, a fluorosurfactant, and a subset of small organic compounds with various functionalities, served as model analytes. The mechanism of ionization charge transfer is discussed and ionization potentials for the matrices in the study have been estimated using density functional theory (DFT) calculations. Some of the results are possibly contradictory to the generally accepted limiting conditions for gas‐phase charge‐transfer reactions. These results are interpreted in the light of energy pooling. Also a new mass calibration procedure for the low‐mass region in positive ion mode is presented, and some aspects of the ionization/desorption process leading to radical cations are studied. Copyright © 2004 John Wiley & Sons, Ltd.
Structure of Lipid A from Pseudomonas corrugata by electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry
Authors: Corsaro M. M. , Piaz F. Dal , Lanzetta R. , Naldi T. , Parrilli M. 
Published: April 2004

AbstractThe use of the electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (ESI‐QTOFMS) technique for the structural determination of Lipid A from Pseudomonas corrugata is described. This technique appears to be more sensitive with respect to other commonly used tandem mass spectrometric approaches, and was very valuable in the structural determination of the highly heterogeneous Lipid A fractions. The Lipid A fraction consists mainly of a pentaacyl component in which 3‐hydroxydecanoyl [10:0(3‐OH)] and 3‐hydroxydodecanoyl [12:0(3‐OH)] are linked as primary acyl substituents to the classical bisphosphorylated β‐(1′ → 6)‐linked D‐glucosamine disaccharide. Secondary substitution of N‐acyl fatty acids with dodecanoyl residues [12:0] and/or its 2‐OH derivatives was also observed. Copyright © 2004 John Wiley & Sons, Ltd.
A high‐throughput monoamine oxidase inhibition assay using liquid chromatography with tandem mass spectrometry
Authors: Yan Zhengyin , Caldwell Gary W. , Zhao Boyu , Reitz Allen B. 
Published: April 2004

AbstractA highly efficient method utilizing liquid chromatography with tandem mass spectrometry (LC/MS/MS) was developed and employed for high‐throughput screening of compounds for monoamine oxidase (MAO) inhibition. The method used kynuramine as a common substrate for both MAO‐A and MAO‐B in incubations, and the 4‐hydroxyquinoline (4‐HQ) resulting from deamination of kynuramine followed by intramolecular condensation was analyzed using LC/MS/MS; formation of 4‐HQ was used as the marker of MAO activity to evaluate the effects of test compounds. Isocratic liquid chromatography was applied to reduce the run time to 2 min. Because of the high specificity and sensitivity of detection of 4‐HQ by LC/MS/MS, this method was able to use MAO enzymes at very low concentrations and to perform short incubations; as a result, consumable cost was minimized, and sample preparations were completely avoided. The inhibition data are highly reproducible, and the IC50 values determined by the method are in good agreement with literature values. The results suggest that this method is very robust and can be used as a generic approach to screen for MAO inhibitors in drug discovery. Copyright © 2004 John Wiley & Sons, Ltd.
Mass spectral fragmentation of 2a,4‐disubstituted 2,2a,3,4‐tetrahydro‐2‐phenoxy‐1H‐azeto[2,1‐d][1,5]benzothiazepin‐1‐ones under electron impact ionization conditions
Authors: Xu Jiaxi , Huang Xu 
Published: April 2004

AbstractThe mass spectrometric fragmentation of 2a,4‐disubstituted 2,2a,3,4‐tetrahydro‐2‐phenoxy‐1H‐azeto[2,1‐d][1,5]benzothiazepin‐1‐ones has been investigated using the aid of mass‐analyzed ion kinetic energy spectrometry. All compounds tend to eliminate a phenoxy, phenol, and phenoxyketene, respectively, from molecular ions. [M+PhO] ions could also form [M+PhOH] ions, which could further lose alkenes. [M+PhOCHCO] ions could further yield 2‐arylbenzothiazole ions and other fragment ions. Copyright © 2004 John Wiley & Sons, Ltd.
Handling drop‐out in longitudinal studies
Authors: Hogan Joseph W. , Roy Jason , Korkontzelou Christina 
Published: April 2004

AbstractDrop‐out is a prevalent complication in the analysis of data from longitudinal studies, and remains an active area of research for statisticians and other quantitative methodologists. This tutorial is designed to synthesize and illustrate the broad array of techniques that are used to address outcome‐related drop‐out, with emphasis on regression‐based methods. We begin with a review of important assumptions underlying likelihood‐based and semi‐parametric models, followed by an overview of models and methods used to draw inferences from incomplete longitudinal data. The majority of the tutorial is devoted to detailed analysis of two studies with substantial rates of drop‐out, designed to illustrate the use of effective methods that are relatively easy to apply: in the first example, we use both semi‐parametric and fully parametric models to analyse repeated binary responses from a clinical trial of smoking cessation interventions; in the second, pattern mixture models are used to analyse longitudinal CD4 counts from an observational cohort study of HIV‐infected women. In each example, we describe exploratory analyses, model formulation, estimation methodology and interpretation of results. Analyses of incomplete data requires making unverifiable assumptions, and these are discussed in detail within the context of each application. Relevant SAS code is provided. Copyright © 2004 John Wiley & Sons, Ltd.
GEE approaches to marginal regression models for medical diagnostic tests
Authors: Martus Peter , Stroux Andrea , Jünemann Anselm M. , Korth Matthias , Jonas Jost B. , Horn Folkert K. , Ziegler Andreas 
Published: April 2004

AbstractThe evaluation of a new medical diagnostic test may focus on two different scientific questions: (1) The new test may replace an existing one because of lower cost or higher validity. A related question would be the selection of the ‘best’ test(s) from a bundle of new or established measurements. (2) The new test may be used supplementary to other new or established procedures. In a recent publication, Leisenring and co‐workers (Stat Med 1997; 16:1263–1281) developed a general marginal regression model for comparisons of diagnostic tests focussing on question (1), i.e. on the selection of the ‘best’ procedure. They applied the GEE approach of Liang and Zeger (Biometrika 1987; 73:13–22) to adjust for the correlation of data as a nuisance parameter. Using the general framework provided by Leisenring et al., we extend their approach and apply the GEE methodology to question (2), i.e. to the investigation of which of several diagnostic tests should be used supplementary to each other. We analyse data from a longitudinal study concerning pathogenesis, diagnosis and long‐term course of the eye disease glaucoma. We find a dependence of the correlation structure of several diagnostic measurements on the severity of the disease. This result may be useful in clinical applications as regards the selection of subsets of diagnostic measurements in individual diagnostic processes but also in investigations concerning the relationship of the pathogenic process and the rationales of the different diagnostic procedures. Copyright © 2004 John Wiley & Sons, Ltd.
What to add to nothing? Use and avoidance of continuity corrections in meta‐analysis of sparse data
Authors: J. Sweeting Michael , J. Sutton Alexander , C. Lambert Paul 
Published: April 2004

AbstractObjectives: To compare the performance of different meta‐analysis methods for pooling odds ratios when applied to sparse event data with emphasis on the use of continuity corrections.Background: Meta‐analysis of side effects from RCTs or risk factors for rare diseases in epidemiological studies frequently requires the synthesis of data with sparse event rates. Combining such data can be problematic when zero events exist in one or both arms of a study as continuity corrections are often needed, but, these can influence results and conclusions.Methods: A simulation study was undertaken comparing several meta‐analysis methods for combining odds ratios (using various classical and Bayesian methods of estimation) on sparse event data. Where required, the routine use of a constant and two alternative continuity corrections; one based on a function of the reciprocal of the opposite group arm size; and the other an empirical estimate of the pooled effect size from the remaining studies in the meta‐analysis, were also compared. A number of meta‐analysis scenarios were simulated and replicated 1000 times, varying the ratio of the study arm sizes.Results: Mantel–Haenszel summary estimates using the alternative continuity correction factors gave the least biased results for all group size imbalances. Logistic regression was virtually unbiased for all scenarios and gave good coverage properties. The Peto method provided unbiased results for balanced treatment groups but bias increased with the ratio of the study arm sizes. The Bayesian fixed effect model provided good coverage for all group size imbalances. The two alternative continuity corrections outperformed the constant correction factor in nearly all situations. The inverse variance method performed consistently badly, irrespective of the continuity correction used.Conclusions: Many routinely used summary methods provide widely ranging estimates when applied to sparse data with high imbalance between the size of the studies' arms. A sensitivity analysis using several methods and continuity correction factors is advocated for routine practice. Copyright 2004 John Wiley & Sons, Ltd.
Immediate skin reactivity to histamine and to allergens in cohorts of 9‐year‐old schoolchildren studied 16 years apart
Authors: Ronchetti R. , Villa M. P. , Pagani J. , Martella S. , Guglielmi F. , Paggi B. , Bohmerova Z. , Falasca C. , Barreto M. 
Published: April 2004

SummaryBackground
Differing or increasing prevalence of positive allergen skin‐prick tests observed in Europe could at least in part be explained by population changes in histamine skin reactivity. These changes would also alter the relationship between positive allergen skin‐prick tests and serum IgE.Objective
To assess changes in histamine reactivity, allergen skin‐prick tests and serum IgE in our geographical setting.Methods
We compared the outcome of two epidemiological surveys conducted 16 years apart in unselected 9‐year‐old schoolchildren (170 in 1983 and 176 in 1999) from a semi‐rural region in central Italy. Outcome measures were skin‐prick tests with two histamine concentrations (10 and 1 mg/mL) and 11 locally relevant allergens; serum total and specific IgE for positive allergens.Results
The two histamine concentrations induced significantly larger mean weal diameters in 1999 than in 1983 (10 mg/mL: 5.28±0.82 mm vs. 3.25±0.97 mm; P<0.001). Whereas the prevalence of subjects with at least one positive allergen‐induced weal reaction (≥3 mm) increased over the 16 years (from 15.3% in 1983 to 25.6% in 1999), the prevalence of positive skin‐prick tests, expressed as the allergen/ histamine weal ratio, remained almost unchanged. A given allergen weal diameter yielded less total (P<0.05 by Student's t‐test for cumulative weals <8 mm) and specific (P<0.01 by Student's t‐test for weals <3 mm, P<0.05 by Kruskal–Wallis test) serum IgE in 1999 than in 1983.Conclusions
Although the causes and mechanisms remain unclear, the increased histamine skin reactivity over time is associated with an increase in positive allergen skin‐prick tests. In the presence of increased tissue and organ susceptibility to histamine, minute amounts of specific IgE could have important biological consequences.
Role of mitogen‐activated protein kinases in influenza virus induction of prostaglandin E2 from arachidonic acid in bronchial epithelial cells
Authors: Mizumura K. , Hashimoto S. , Maruoka S. , Gon Y. , Kitamura N. , Matsumoto K. , Hayashi S. , Shimizu K. , Horie T. 
Published: April 2004

SummaryBackground
Influenza virus (IV) infection causes airway inflammation; however, it has not been determined whether IV infection could catabolize arachidonic acid cascade in airway epithelial cells. In addition, the responsible intracellular signalling molecules that catabolize arachidonic acid cascade have not been determined.Objective
In the present study, to clarify these issues, we examined the cyclooxygenase (COX) expression, cytosolic phospholipase A2 (cPLA2) phosphorylation and prostaglandin E2 (PGE2) release in human bronchial epithelial cells (BEC) upon IV infection, and the role of mitogen‐activated protein kinase (MAPK) including extracellular signal‐regulated kinase (ERK), p38 MAPK and c‐Jun‐NH2‐terminal kinase (JNK) in catabolizing arachidonic acid cascade in BEC.Methods
COX‐2 expression, phosphorylation of cPLA2 and phosphorylation of ERK, JNK and p38 MAPK were determined by Western blot. The concentrations of PGE2 were determined by ELISA. PD 98059 as a specific inhibitor of MAPK kinase‐1 (MEK‐1), an up‐stream kinase of ERK, SB 203580 as a specific inhibitor of p38 MAPK and CEP‐11004 as a specific inhibitor of JNK cascade were used to investigate the role of ERK, p38 MAPK and JNK in catabolizing arachidonic acid cascade in BEC.Results
The results showed that (1) IV infection increases COX‐2 expression, cPLA2 phosphorylation and PGE2 release, (2) ERK, p38 MAPK and JNK were phosphorylated, (3) CEP‐11004 and PD 98059 predominantly attenuated COX‐2 expression and cPLA2 phosphorylation, respectively, (4) SB 203580 did not remarkably affect COX‐2 expression and cPLA2 phosphorylation, and (5) each inhibitor dose‐dependently attenuated PGE2 release by various extents.Conclusion
These results indicate that IV infection activates three distinct MAPKs, ERK, p38 MAPK and JNK, to participate to various extents in the induction of PGE2 synthesis from arachidonic acid in BEC.
Endotoxin contamination contributes to the pulmonary inflammatory and functional response toAspergillus fumigatusextract inhalation in heaves horses
Authors: Pirie R. S. , Dixon P. M. , McGorum B. C. 
Published: April 2004

SummaryBackgroundMould extract inhalation challenges have been used extensively in the investigation of heaves. Such challenges have induced pulmonary neutrophilic inflammation and dysfunction, consistent with, but less severe than the natural disease. However, the method of mould extract production is likely to result in endotoxin contamination.ObjectiveTo investigate whether insufficient dose delivery was responsible for the shortfall in response to inhaled extract compared with natural disease, and whether endotoxin contamination of mould extract contributed to the pulmonary inflammation and dysfunction.MethodsWe measured the response of six heaves horses following inhalation of saline (placebo) and three doses ofAspergillus fumigatusextract. We then compared the response of six heaves horses toA. fumigatusextract inhalation before and after lipopolysaccharide (LPS) depletion.ResultsInhalation challenge with 0.5, 1.6 and 5 mg ofA. fumigatusextract resulted in a significant increase in bronchoalveolar lavage fluid (BALF) neutrophil ratio when compared with saline inhalation. Only 1.6 and 5 mg extract inhalation resulted in significant lung dysfunction compared with saline. There was no significant difference between 1.6 and 5 mg extract inhalation with respect to airway neutrophil numbers or lung function, suggesting a plateau in both measured responses. LPS depletion of 1.6 mgA. fumigatusextract resulted in a significant reduction in airway neutrophil numbers and increase in arterial oxygen tension. There was no significant difference between saline and the LPS‐depletedA. fumigatusextract challenges with respect to neutrophil count and lung function. The reduction in airway neutrophil numbers was greater than would be predicted by extrapolation from previously reported soluble LPS dose–response inhalation experiments.ConclusionThis study supports a role for other inhalants, in addition to soluble components ofA. fumigatus, in the aetiopathogenesis of heaves. Also the amplification in response to LPS when inhaled withA. fumigatusextract, suggests that the role of inhaled endotoxin in the pulmonary inflammation and dysfunction in naturally occurring heaves may currently be underestimated.