bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetization transfer ratio and myelin in postmortem multiple sclerosis brain
Authors: Schmierer Klaus , Scaravilli Francesco , Altmann Daniel R. , Barker Gareth J. , Miller David H. 
Published: July 2004

AbstractSeveral quantitative magnetic resonance (MR) measures are used to investigate multiple sclerosis (MS) in vivo. Precise quantitative investigation of the histopathological correlates of such measures has, to date, been limited. This study investigates the relationship of quantitative measures of myelin content, axonal density, and gliosis with quantitative MR measures in postmortem (PM) MS tissue. MR imaging (MRI) was performed on a 1.5T scanner and T1‐relaxation time (T1‐RT) and magnetization transfer ratio (MTR) maps were acquired in fresh PM brain of 20 MS subjects. Myelin content, axonal counts, and the extent of gliosis all were quantified using morphometric and digital imaging techniques. MRI and pathological data were in most cases coregistered using stereotactic navigation. Using multiple regression analysis, we detected significant correlations between myelin content (Trmyelin) and MTR (r = −0.84, p < 0.001) and myelin content and axonal count (−0.80, p < 0.001); MTR correlated with T1‐RT (r = −0.79, p < 0.001). No association was detected between the extent of gliosis and either MR measure. MTR was significantly higher in remyelinated than demyelinated lesions (means: 30.0 [standard deviation, 2.9] vs 23.8 [standard deviation, 4.3], p = 0.008). In conclusion, MTR is affected by myelin content in MS white matter. Ann Neurol 2004
The effect of temperature on the viscoelastic response of semicrystalline polymers
Authors: Drozdov A. D. , Agarwal S. , Gupta R. K. 
Published: July 2004

AbstractThree series of isothermal torsion relaxation tests were performed at various temperatures ranging from room temperature to T = 120°C on isotactic polypropylene, low‐density polyethylene, and linear low‐density polyethylene. Constitutive equations are derived for the viscoelastic behavior of a semicrystalline polymer at small strains. A polymer is treated as an equivalent network of strands bridged by temporary junctions (entanglements, physical crosslinks on the surfaces of crystallites, and lamellar blocks). The network is thought of as an ensemble of mesoregions with various activation energies for detachment of active strands from their junctions. The time‐dependent response of the ensemble reflects thermally induced rearrangement of strands (separation of active strands from temporary junctions and merging of dangling strands with the network). Stress–strain relations are developed by using the laws of thermodynamics. The governing equations involve five adjustable parameters that are found by fitting the experimental data. This study focuses on the influence of temperature and crystalline morphology of polyolefins on the material parameters in the constitutive relations. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 9–23, 2004
pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers
Authors: Fevola Michael J. , Bridges J. Kasey , Kellum Matthew G. , Hester Roger D. , McCormick Charles L. 
Published: July 2004

AbstractA comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via 13C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na+ and Cl−. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 106 g/mol, corresponding to DPs of 1.6–1.9 × 104 repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (Rg–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The Rg–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004
Anticoagulation activity of crosslinked N‐sulfofurfuryl chitosan membranes
Authors: Liu Wenguang , Zhang Jianrong , Cheng Nan , Cao Zhiqiang , Yao Kangde 
Published: July 2004

AbstractN‐Sulfofurfuryl chitosan (SuCS) was prepared through the coupling of 5‐formyl‐2‐furansulfonic acid (FFSA) with chitosan via Schiff's base reaction in an aqueous solution of acetic acid. Fourier transform infrared spectra confirmed the formation of SuCS, and elemental analysis indicated that the concentration of the sulfonic acid groups in modified chitosan increased as the feeding ratio of FFSA increased. A protein adsorption experiment revealed that at higher concentrations of the sulfonic acid groups, glucose aldehyde crosslinked SuCS membranes were inclined to adsorb bovine serum albumin, but the adsorption of fibrinogen was hindered to some extent. Circular dichroism demonstrated that SuCS significantly altered the conformation of thrombin, whereas no obvious variation in the conformation of thrombin was observed with the addition of chitosan. The anticoagulation activity of glucose aldehyde crosslinked SuCS and chitosan membranes was evaluated through assays of the prothrombin time (PT), thrombin time (TT), and activated partial thromboplastin time (APTT). APTT of an SuCS membrane was prolonged in comparison with that of its chitosan counterpart and showed a rising trend with an increasing concentration of the sulfonic acid moieties. However, PT and TT were not markedly affected. The anticoagulant mechanism of the SuCS membranes supposedly originated from an intrinsic pathway to the inhibition of coagulation enzymes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 53–56, 2004
Effect of the intercalation agent content of montmorillonite on the swelling behavior and drug release behavior of nanocomposite hydrogels
Authors: Lee Wen‐Fu , Jou Leng‐Long 
Published: July 2004

AbstractA series of novel dual functional nanocomposite hydrogels were prepared from N‐isopropylacrylamide (NIPAAm), acrylic acid (AA) that is neutralized 50 mol % by sodium hydroxide (SA50), and montmorillonite (MMT). MMT was intercalated with three different contents of intercalation agent of (3‐acrylamidopropyl) trimethyl ammonium chloride (TMAACl). Investigation of the effect of intercalated MMT with three contents of intercalation agent (TMAACl) in the present nanocomposite hydrogels on the swelling and drug release behaviors is the main purpose in this study. The microstructure was identified by X‐ray diffraction (XRD). Results showed that the swelling ratio for the present nanocomposite hydrogels decreased with an increase in the content of the intercalation agent. The gel strength of the present gels did not change obviously with an increase in the content of intercalation agent. XRD results indicated that exfoliation of MMT was achieved in the dry and swollen gel state. Finally, the drug release behaviors for these gels were accessed also. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 74–82, 2004
The emitting species formed by the oxidation of hydrazides with hypohalites or N‐halosuccinimides
Authors: Francis Paul S. 
Published: July 2004

AbstractThe chemiluminescence accompanying the oxidation of salicylic hydrazide (2‐hydroxybenzoic acid hydrazide) with hypochlorite, hypobromite, N‐chlorosuccinimide, N‐bromosuccinimide or hydrogen peroxide with cobalt(II) matched the photoluminescence emission of salicylic acid. In a related reaction, the oxidation of a mixture of isoniazid and ammonia, a synergistic effect was observed. The chemiluminescence spectrum for this reaction matches that accompanying the oxidation of the hydrazide, rather than the oxidation of ammonia. These results were used to assess mechanisms proposed by previous authors. Copyright © 2004 John Wiley & Sons, Ltd.
A rapid screening method for the detection of viable spores in powder using bioluminescence
Authors: Lee JiYoung , Deininger Rolf A. 
Published: July 2004

AbstractA rapid diagnosis of a biological threat in a powder sample is important for ﬁrst responders who have to make decisions on‐site. The present culture‐based method does not provide timely results, which is a critical barrier for a quick response when a suspicious powder sample is found. The ATP bioluminescence method, combined with a heat shock, was investigated to determine the presence of spores in powder. The results show that only spore‐containing powder samples provided a dramatic increase in the bioluminescence signal after the heat shock, which induces germination of the spores. Various conditions were tested to ﬁnd the most effective and rapid germination procedure. Elevated temperatures (37°C and 50°C) were more effective in germination than room temperature. At 50°C, a double‐strength germinant was more effective in germination than the regular strength. The 37°C/15 min procedure induced the germination of spores most effectively, while a 50°C/2 min procedure provided reasonably high signals, so it could make the entire procedure even faster (< 5 min). The detection limit of the bioluminescence method is < 100 spores. Copyright © 2004 John Wiley & Sons, Ltd.
Multi‐channel electrochemiluminescence of luminol at a copper electrode
Authors: Yu Hong‐Xiao , Cui Hua , Guo Ji‐Zhao 
Published: July 2004

AbstractMulti‐channel electrochemiluminescence (ECL) of luminol at a copper electrode has been studied under conventional cyclic voltammetric (CV) conditions. Compared with the ECL of luminol at other electrodes, three ECL peaks were observed at 0.30, −0.24 and −0.65 V (vs. SCE), respectively, which was also imaged by a CCD camera. The effects of potential scan direction, anodic reverse potential, the presence of N2 and O2 of the solution, the pH of the solution, the NaNO3 concentration and the potential scan rate were examined. The effect of n‐alkanethiol self‐assembled monolayers on copper electrodes and 20 l‐amino acids, dopamine, adrenaline and noradrenaline on the ECL of luminol were also investigated. The emission spectra of various ECL peaks at different potentials demonstrated that all ECL peaks were related to the luminol reaction. The results show that the oxygen dissolved in solution and copper oxide covered on the surface of the electrode play an important role in the luminol ECL process at a copper electrode. It has been proposed that three ECL channels of luminol at a copper electrode resulted from the reactions of luminol or luminol radical electrooxidized by luminol with various electrogenerated oxygen‐containing species, such as O2, OOH− and copper oxides at different potentials. Copyright © 2004 John Wiley & Sons, Ltd.
Low molecular weight heparin for the prevention of venous thromboembolism after abdominal surgery
Authors: Bergqvist D 
Published: July 2004

Abstract

Background
Abdominal surgery carries a significant risk of venous thrombosis, a risk further increased in patients with cancer.

Methods
Embase and Pubmed searches between 1980 and 2003, using the key words ‘heparin,’ ‘surgery,’ ‘abdominal or rectal or colorectal or rectum or colon’ and ‘clinical trial’, were conducted to identify studies of thromboprophylaxis in patients having abdominal surgery.

Results
A total of 16 comparative studies were identified. These show that low molecular weight heparin (LMWH) is as effective as unfractionated heparin (UFH) in reducing venous thromboembolism after abdominal surgery and, at appropriate doses, can reduce bleeding complications. In very high-risk patients, a higher dose of LMWH may offer increased efficacy without increasing bleeding risk. Extending the standard 7–10-day period of prophylaxis may benefit certain high-risk groups; recent data show a significant benefit of 4-week enoxaparin thromboprophylaxis compared with a standard regimen, at no cost to safety.

Conclusion
Patients undergoing abdominal surgery should be stratified according to thromboembolism risk and managed accordingly. LMWH is a recommended alternative to UFH in moderate- or high-risk patients. In patients with cancer, high doses of LMWH may offer increased efficacy without increasing the bleeding risk and an extended 4-week period of prophylaxis appears beneficial.
Reactions under Autogenic Pressure at Elevated Temperature (RAPET) of Various Alkoxides: Formation of Metals/Metal Oxides‐Carbon Core‐Shell Structures
Authors: Pol Swati V. , Pol Vilas G. , Gedanken Aharon 
Published: July 2004

AbstractThe RAPET reaction at 700 °C, of different alkoxides (Ti, V, and Si) led to three different nanocomposites. Carbon is the element common to all three structures. Carbon was found as the core in the decomposition of TEOS, as the shell in the decomposition of VO(OEt)3 and embedded in, or mixed completely with, TiO2 in the decomposition of Ti(OiPr)4. This novel method using only metallic alkoxide precursor, in the absence of catalyst, leads in a one‐step process to core‐shell structures.
Intramolecular Carbohydrate–Aromatic Interactions and Intermolecular van der Waals Interactions Enhance the Molecular Recognition Ability of GM1 Glycomimetics for Cholera Toxin
Authors: Bernardi Anna , Arosio Daniela , Potenza Donatella , Sánchez‐Medina Inmaculada , Mari Silvia , Cañada F. Javier , Jiménez‐Barbero Jesús 
Published: July 2004

AbstractThe design and synthesis of two GM1 glycomimetics, 6 and 7, and analysis of their conformation in the free state and when complexed to cholera toxin is described. These compounds, which include an (R)‐cyclohexyllactic acid and an (R)‐phenyllactic acid fragment, respectively, display significant affinity for cholera toxin. A detailed NMR spectroscopy study of the toxin/glycomimetic complexes, assisted by molecular modeling techniques, has allowed their interactions with the toxin to be explained at the atomic level. It is shown that intramolecular van der Waals and CH–π carbohydrate–aromatic interactions define the conformational properties of 7, which adopts a three‐dimensional structure significantly preorganized for proper interaction with the toxin. The exploitation of this kind of sugar–aromatic interaction, which is very well described in the context of carbohydrate/protein complexes, may open new avenues for the rational design of sugar mimics.
New Iridacyclohexadienes and Iridabenzenes by [2+2+1] Cyclotrimerization of Alkynes and Facile Interconversion between Iridacyclohexadienes and Iridabenzenes
Authors: Chin Chong Shik , Lee Hyungeui 
Published: July 2004

AbstractIridabenzenes [Ir{CHCHCHCHC(CH2R)}(CH3CN)2(PPh3)2]2+ (R=Ph 4 a, R=p‐C6H4CH3 4 b) are obtained from the reactions of H+ with iridacyclohexadienes [Ir{‐‐CHCHCHCHC(CH‐p‐C6H4R′)}(CO)(PPh3)2]+ (R′=H 3 a, R′=CH3 3 b), which are prepared from [2+2+1] cyclotrimerization of alkynes in the reactions of [Ir(CH3CN)(CO)(PPh3)2]+ with HCCH and HCCR. Iridabenzenes 4 react with CO and CH3CN in the presence of NEt3 to give iridacyclohexadienes [Ir{‐‐CHCHCHCHC(CHR)}(CO)2(PPh3)2]+ (6) and [Ir{‐‐CHCHCHCHC(CHR)}(CH3CN)2(PPh3)2]+ (7), respectively. Iridacyclohexadienes 6 and 7 also convert to iridabenzenes 4 by the reactions with H+ in the presence of CH3CN. Alkynyl iridacyclohexadienes [Ir{‐‐CHCHCHCHC(CH‐p‐C6H4R′)}(CCH)(PPh3)2] (8) undergo a cleavage of CC bond by H+/H2O to produce [Ir{‐‐CHCHCHCHC(CH‐p‐C6H4R′)}(CH3)(CO)(PPh3)2] (10) via facile inter‐conversion between iridacyclohexadienes and iridabenzenes.
Structural Isomerism in Crystals of Redox‐Active Secondary ortho‐Diamides: The Role of Competing Intra‐ and Intermolecular Hydrogen Bonds in Directing Crystalline Topologies
Authors: Baudron Stéphane A. , Avarvari Narcis , Canadell Enric , Auban‐Senzier Pascale , Batail Patrick 
Published: July 2004

AbstractThe solid‐state chemistry of a series of seven ortho‐bis(alkylamido)ethylenedithiotetrathiafulvalene derivatives EDT‐TTF‐(CONHR)2 (R=Me, 1; Et, 2; Pr, 3; Bu, 4; Pent, 5; Hex, 6; and Bz, 7), in their neutral and one‐electron‐oxidized, radical cation states, was investigated with an eye on the topology of intra‐ and intermolecular hydrogen‐bond motifs. In the case of neutral, monomolecular solids, an intramolecular NH⋅⋅⋅O hydrogen bond seals a constrained seven‐membered ring for 1, 2, 3, and 7, which is disrupted in butyl derivative 4 in favor of an antiparallel ladder at the expense of any intramolecular hydrogen bond. In the solid‐state, the competition between intra‐ and intermolecular hydrogen bonding observed in solution depends on the packing of the molecules. Electrocrystallization of methyl derivative 1 with ReO4− or ClO4−, two anions of different volumes but otherwise identical charge and symmetry, revealed a fine sensitivity of the constrained seven‐membered ring to the internal chemical pressure exerted by the anion. [1]2.+ReO4 (σRT=8.5 S cm−1, activation energy Δ=600 K at high temperature) and β′′‐[1]2.+ClO4 (σRT=0.03 S cm−1, Δ=1600 K; under pressure at room temperature, the conductivity increases by three orders of magnitude up to 17 kbar with a linear variation of the activation energy with pressure, Δ=aP with a=0.202 106 K kbar−1) have vastly different architectures, dimensionalities, electronic structures, and collective properties, a consequence of the presence of the closed or open structural isomers in one or the other. This exemplifies the flexibility of functionalized TTF derivatives, even when the functional group is directly attached to the electro‐active core. This allows an analogy to be drawn with tetrafunctionalized metallocenes, in which such flexibility has already been observed. The experimental data are supported by theoretical calculations of the energy profile of a model molecule on rotation of the amido groups.
Electronic Structures of Zinc and Palladium Tetraazaporphyrin Derivatives Controlled by Fused Benzo Rings
Authors: Miwa Hideya , Ishii Kazuyuki , Kobayashi Nagao 
Published: July 2004

AbstractZinc and palladium tetracyclic aromatic complexes lying structurally between tetraazaporphyrin (TAP) and phthalocyanine (Pc), that is, monobenzo‐, adjacently dibenzo‐, oppositely dibenzo‐, and tribenzo‐fused TAPs, have been prepared, and their electronic structures investigated by electronic absorption, magnetic circular dichroism (MCD), fluorescence, phosphorescence, and time‐resolved electron paramagnetic resonance (TREPR) spectroscopy, as well as cyclic voltammetry. The last‐named indicated that the first oxidation potentials shift to more negative values with increasing number of the fused benzo rings, but also suggested that the first reduction potential apparently has no correlation with the size and symmetry of the π‐conjugated systems. However, this latter behavior is reasonably interpreted by the finding that the effect of the fused benzo rings on destabilization of the LUMO depends on the orbital to which they are fused (i.e., whether it is an egx or egy orbital), since the LUMOs of TAP complexes are degenerate with D4h symmetry. The energy splitting of the LUMOs, that is, ΔLUMO, was evaluated experimentally for the first time by analyzing the relationship between the first reduction potential and the size and shape of the π‐conjugated system. Electronic absorption and MCD measurements indicate that the lowest excited singlet states are split in the case of the low‐symmetry TAP derivatives, although these excited states are degenerate for Pc and TAP with D4h symmetry. These energy splittings ΔESS correlate well with the ΔLUMO values. To investigate the electronic structures in the lowest excited triplet state, zero‐field splitting (zfs) was analyzed by time‐resolved EPR (TREPR) spectroscopy. The energy splitting in the lowest excited triplet state, ΔETT was quantitatively evaluated from the temperature dependence of the zfs or spin–orbit coupling of the Pd complexes. Consequently, it is demonstrated that ΔLUMO, ΔESS, and ΔETT values exhibiting a mutually good relationship can be determined experimentally.
New chiral selectors: Design and synthesis of 6‐TBDMS‐2,3‐methyl β‐cyclodextrin 2‐2′ thioureido dimer and 6‐TBDMS‐2,3‐methyl (or 2‐methyl‐3‐acetyl) β‐cyclodextrin bearing an (R) mosher acid moiety
Authors: Cravotto Giancarlo , Bicchi Carlo , Tagliapietra Silvia , Costa Luisa , Di Carlo Stefano , Nervi Carlo 
Published: July 2004

AbstractCyclodextrin (CD) derivatives are important selectors for analytical chiral recognition. Their enantioselectivities and chemical properties depend on ring size and on nature, number and location of substituents. This paper describes the synthesis of 6‐O‐TBDMS‐2,3‐O‐methyl β‐cyclodextrins bearing in position 2 either a single (R)‐Mosher acid moiety or a second CD unit, in view of their possible application as chiral selectors. Most synthetic steps were successfully carried out under high‐intensity ultrasound using a new sonochemical reactor developed in the authors' laboratory. 6‐O‐TBDMS‐2‐O‐methyl‐3‐[(S)‐2‐methylbutyl]‐β‐CD was also synthesized and tested with gas chromatography; the enantiorecognition power of the other CD derivatives is also being tested. A computational study of model structures to design these CD derivatives. Chirality 16:526–533, 2004. © 2004 Wiley‐Liss, Inc.