bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Study of the Alkaline Hydrolysis of Tricyclic Carbapenem
Authors: Fasoli Hector J. , Frau Juan 
Published: April 2005

AbstractAlkaline hydrolysis is a good test to evaluate the properties of β‐lactam compounds and derivatives. In this work, a RHF/6‐31+G*//RHF/6‐31+G* theoretical study of the mechanism controlling the alkaline hydrolysis of sanfetrinem was conducted. The geometric properties of this compound are consistent with an intrinsic reactivity similar to that of other β‐lactams including penicillins and cephalosporins. Also, similarly to cephalosporins, the MeO group provides an alternative route for the hydrolysis mechanism.
Formation and Dissociation of Tetrahedral Nickel(II) and Cobalt(II) Complexes of ‘Dithioimidodiphosphato’ Ligands, Measurement of Kinetically Determined Stability Constants, and Kinetic Investigations of the Rapid Formation of Tetrahedral Bis(ligand)copper(II) Complexes and Their Rates of Reduction to Trinuclear Copper(I) Species
Authors: Moore Peter , Errington William , Sangha Satindra P. 
Published: April 2005

AbstractThe stopped‐flow technique was used to measure the rates of formation and dissociation of tetrahedral [ML2] complexes (M2+=Ni2+or Co2+) of four bidentate S2‐donor ‘dithioimidodiphosphato’ ligands L−(HL=[R1R2P(S)]NH[P(S)R3R4], R1to R4=alkyl) at 25.0° in MeOH/H2O 95 : 5 (v/v) solution and in the presence of either MOPS (=3‐(morpholin‐4‐yl)propane‐1‐sulfonic acid) or 2,6‐lutidine (=2,6‐dimethylpyridine) buffers. The kinetically determined equilibrium formation constants for [ML]+ions (M=Ni or Co) are 10−5 K=0.50±0.01 or 1.64±0.07 l mol−1for L=L3(R1=R2=Me(CH2)2CH(Me), R3=R4=Me2CH), 1.27±0.02 or 7.93±0.09 l mol−1for L=L7(R1to R4=Me2CHCH2), 0.88±0.04 or 3.84±0.13 l mol−1for L=L8(R1to R4=Me2CH), and in case of Ni2+1.88±0.04 l mol−1for L=L6(R1=R3=Bu, R2=R4=tBu) (seeTable 3; for L3and L6–L8, seeTable 1). Whereas the tetrahedral Ni2+complexes dissociate more slowly than the analogous Co2+species, in all cases, the Co2+complexes are more stable than those of Ni2+due to their larger formation rate constants (Table 3). Reactions of Cu2+with eight ligands HL (R1to R4=alkyl, alkoxy, aryl, and aryloxy) show that formation of intensely colored tetrahedral [CuIIL2] species is too fast be measured with the available stopped‐flow apparatus (t1/2<2 ms), but the subsequent rates of reduction of [CuIIL2] to give trinuclear products [CuI3L3] are measurable. An X‐ray analysis establishes the structure of one of the [Cu3L3] complexes, where R1=R2=Me2CHO and R3=R4=2‐(tert‐butyl)phenyl (L=L5), and a multiwavelength stopped‐flow kinetic experiment establishes the spectrum of a tetrahedral [CuIIL2] species prior to the reduction reactions. The redox reactions proceed at 25.0° with first‐order rate constants in the range 0.285 s−1(R1to R4=PhO; L=L11) to 2.58⋅10−4 s−1(R1to R4=Me2CHCH2; L=L7) (Table 4).
Functionalization of the 6,14‐Bridge of the Orvinols
Authors: Chen Weibin , Parrish Damon A. , Deschamps Jeffrey R. , Coop Andrew 
Published: April 2005

AbstractThe anion 5 of thebaine (1) reacts with small electrophiles exclusively at the 5‐position (Scheme 1). Reaction of thebaine anion with a range of alkylarylsilyl chlorides showed that reaction at the 7‐position was favored with increasing steric bulk, with triphenylsilyl chloride yielding only the 7‐substituted product 7e (Scheme 1). Reaction of 7‐(triphenylsilyl)thebaine (7e) with benzoquinone gave rise to the expected Diels–Alder adduct 8 (Scheme 2), an analog of thevinone (2) with a silyl substituent at the 6,14‐etheno bridge. The presence of this substituent gives a handle for potentially functionalizing the bridge of this important class of compounds.
A comparison of MODIS and NOHRSC snow‐cover products for simulating streamflow using the Snowmelt Runoff Model
Authors: Lee Songweon , Klein Andrew G. , Over Thomas M. 
Published: April 2005

AbstractRemote sensing is an important source of snow‐cover extent for input into the Snowmelt Runoff Model (SRM) and other snowmelt models. Since February 2000, daily global snow‐cover maps have been produced from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS). The usefulness of this snow‐cover product for streamflow prediction is assessed by comparing SRM simulated streamflow using the MODIS snow‐cover product with streamflow simulated using snow maps from the National Operational Hydrologic Remote Sensing Center (NOHRSC). Simulations were conducted for two tributary watersheds of the Upper Rio Grande basin during the 2001 snowmelt season using representative SRM parameter values. Snow depletion curves developed from MODIS and NOHRSC snow maps were generally comparable in both watersheds: satisfactory streamflow simulations were obtained using both snow‐cover products in larger watershed (volume difference: MODIS, 2·6%; NOHRSC, 14·0%) and less satisfactory streamflow simulations in smaller watershed (volume difference: MODIS, −33·1%; NOHRSC, −18·6%). The snow water equivalent (SWE) on 1 April in the third zone of each basin was computed using the modified depletion curve produced by the SRM and was compared within situSWE measured at Snowpack Telemetry sites located in the third zone of each basin. The SRM‐calculated SWEs using both snow products agree with the measured SWEs in both watersheds. Based on these results, the MODIS snow‐cover product appears to be of sufficient quality for streamflow prediction using the SRM in the snowmelt‐dominated basins. Copyright © 2005 John Wiley & Sons, Ltd.
Hydration process as an activation of trans‐ and cisplatin complexes in anticancer treatment. DFT and ab initio computational study of thermodynamic and kinetic parameters
Authors: Burda Jaroslav V. , Zeizinger Michal , Leszczynski Jerzy 
Published: April 2005

AbstractThe thermodynamic and kinetic aspects of hydration reactions of cis‐/transplatin were explored. The polarizable continuum model was used for estimation of solvent effects. Using the B3LYP/6‐31+G(d) method, the structures were optimized and vibrational frequencies estimated. Interaction energies and activation barriers were determined at the CCSD(T)/6‐31++G(d,p) level within the COSMO approach. An associative mechanism was assumed with a trigonal‐bipyramidal structure of the transition state. Within the applied model, all the hydration reactions are slightly endothermic. The Gibbs energies of cisplatin hydration amount to 7.0 and 14.2 kcal/mol for the chloride and ammonium replacement, respectively. Analogous values for the transplatin reactions are 6.8 and 11.9 kcal/mol. The determined rate constants are by several (three to four) orders of magnitude larger for the dechlorination process than for deammination. The cisplatin dechlorination rate constant was established as 1.3 · 10−4 s−1 in excellent accord with the experiment. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 907–914, 2005
Capillary electrochromatographic chiral separations with potential for pharmaceutical analysis
Authors: Mangelings Debby , Maftouh Mohamed , Vander Heyden Yvan 
Published: April 2005

AbstractThe use of capillary electrochromatography as a chiral separation technique for pharmaceutical applications is reviewed. Publications of the past 10 years that provide a potential practical application in pharmaceutical analysis are considered. Method development or validation, separation strategies, and potential routine analysis by the methods/applications cited are the main subjects on which we focused our attention. The indirect chiral separation method was only used once in CEC mode. In the direct chiral separations, the use of chiral stationary phases was obviously preferred over the use of chiral mobile phases with non‐chiral stationary phases. Amongst the chiral stationary phases, those based on macrocyclic antibiotics and polysaccharide selectors were the most frequently used. Monolithic stationary phases also have several applications, but not so extended as those with packed capillary electrochromatography. The considered papers not only describe the applicability of the technique for relatively large sets of chiral analytes, they also showed that various types of stationary phases can be produced in‐house in a simple manner. However, to survive as a mature separation technique, considerable time and effort are still needed to solve some disadvantages currently characterizing capillary electrochromatography.
Capillary electrochromatography using polyelectrolyte multilayer coatings
Authors: Kamande Mary W. , Fletcher Kristin A. , Lowry Mark , Warner Isiah M. 
Published: April 2005

AbstractThis review covers recent progress in polyelectrolyte multilayer (PEM) coatings applied to analytical separations using open‐tubular capillary electrochromatography (OT‐CEC). The simple preparation procedure involved in the PEM approach has provided some attractive features over other modes of capillary electrophoresis‐based separations including packed column capillary electrochromatography (PC‐CEC) and micellar electrokinetic chromatography (MEKC). PEM coatings have been used to alleviate the adsorption of basic analytes, to improve separations, and to improve the stability of the electroosmotic flow. Fundamental aspects of PEM coatings on surfaces and analytical separation platforms are briefly outlined in this review. In addition, applications of PEM coatings to fused‐silica capillaries or microchip separation devices for the separation of small achiral or chiral analytes, as well as large biomolecules, are discussed.
Study on the Gelation of a No‐Flow Underfill Through Monte Carlo Simulation
Authors: Zhang Zhuqing , Yamashita Tsuyoshi , Wong Ching P. 
Published: April 2005

AbstractSummary: The gelation behavior of an epoxy/anhydride system was studied using the differential scanning calorimeter (DSC) and a stress rheometer. It was found that the gelation was dependent on the curing temperature. At a higher curing temperature, the resin tended to gel at lower degree of cure (DOC). Monte Carlo (MC) simulation was performed, to investigate the effect of curing kinetics on the network formation and the gelation. Both the effects of the propagation rate and the catalyst concentration was studied. The temperature dependent gelation was related to the change of propagation/initiation ratio with temperature according to the simulation results.Reaction mechanism of the epoxy/anhydride curing.magnified imageReaction mechanism of the epoxy/anhydride curing.
Acrylic‐Based Polyurethane/Silica Hybrids Prepared by Acid‐Catalyzed Sol–Gel Process: Structure and Mechanical Properties
Authors: Chen Guodong , Zhou Shuxue , Gu Guangxin , Wu Limin 
Published: April 2005

AbstractSummary: Silica sols were first prepared based on different ratios of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) by an acid‐catalyzed sol–gel process, and then incorporated into acrylic‐based polyurethanes. The structures and morphologies of silicone‐oxo clusters were studied by 29Si NMR, SAXS, and scanning electron microscopy (SEM), whereas the mechanical properties of polyurethane/silica hybrids were characterized by DMA and tensile tests. The silicone‐oxo clusters in both silica sol and polyurethane hybrids became denser and larger at a higher molar ratio of TEOS/MTES and higher silica content, and the silica‐oxo clusters of polyurethane/silica hybrids even became more compact and larger than those of silica sols, increasing the elastic modulus and tensile strength of polyurethane/silica hybrids.Typical structure of silica sol prepared from the hydrolysis and condensation of TEOS and MTES with acid as the catalyst.magnified imageTypical structure of silica sol prepared from the hydrolysis and condensation of TEOS and MTES with acid as the catalyst.
Influence of Addition of Organoclays on Morphologies in Nylon 6/LLDPE Blends
Authors: Yoo Youngjae , Park Changhyun , Lee Sung‐Goo , Choi Kil‐Yeong , Kim Dae Su , Lee Jae Heung 
Published: April 2005

AbstractSummary: Polymer blend nanocomposites containing linear low density polyethylene (LLDPE), nylon 6 and organoclays were prepared by melt mixing, and their morphologies and structures were examined with a field emission scanning electron microscope (FE‐SEM) and an X‐ray diffractometer (XRD). The size of phase‐separated domains decreased considerably with increasing content of organoclay. The d‐spacing of organoclay in the nanocomposites was increased from about 18.6 to over 28 Å. This effect was highly dependent on nylon 6 contents because nylon 6 is more polar and shows higher affinity to the organoclays compared to LLDPE.
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Quantitative Analysis of Compositional Distribution in Biodegradable Poly(ethylene oxide)/Poly(3‐hydroxybutyrate) Blend Film with Compositional Gradient by FT‐IR Microspectroscopy
Authors: Zhao Li , He Yong , Inoue Yoshio 
Published: April 2005

AbstractSummary: FT‐IR microspectroscopy was used to map the compositional distribution along the cross‐section on the gradient films of fully biodegradable poly(ethylene oxide) (PEO)/poly(3‐hydroxybutyrate) (PHB) blend system. First, a linear fitting line for a calibration, related the absorbance ratio of two peaks to the fraction of PEO in the blend, was established. During linear fitting, a new equation was deduced and the influence of the different crystallinities on the absorption peaks at the wavenumber 962 and 1 342 cm−1 for PEO, 980 and 1 380 cm−1 for PHB, have been taken into account. For the PEO/PHB blend system, it was found that the crystallinity has little effect on the absorbance ratios of A962/A1 380 and A1 342/A1 380. Based on the results from the linear fitting, which comes from the relation of the absorbance ratios of A962/A1 380 or A1 342/A1 380 and the combination of the weight fraction of PEO (WPEO/(1 − WPEO)), the compositional distributions on the cross‐section of three kinds of compositional gradient films of the PEO/PHB blend prepared by different technologies have been successfully estimated. Furthermore, the better method for preparing the PEO/PHB blend film with compositional gradient was found based on the result of the quantitative analysis of the compositional distribution.The compositional distribution along the cross‐section of the gradient films based on PEO/PHB binary system for the Type I gradient film.magnified imageThe compositional distribution along the cross‐section of the gradient films based on PEO/PHB binary system for the Type I gradient film.
Reliability of spatiotemporal gait outcome measures in Huntington's disease
Authors: Rao Ashwini K. , Quinn Lori , Marder Karen S. 
Published: April 2005

AbstractGait impairments are very important in Huntington's disease (HD), because loss of independence in gait is an important predictor of nursing home placement. Given this importance, it is imperative to test reliable and sensitive outcome measures that can be tested easily in various clinical environments. Here, we examined the test–retest reliability of gait outcome measures using the GAITRite instrumented carpet. We tested 12 subjects with HD and 12 age‐matched controls in two separate sessions. At each session, subjects walked across the GAITRite carpet at a comfortable speed. We used the intraclass correlation coefficient (ICC) and coefficient of variation (CoV) to measure test–retest reliability. Reliability was very high for all outcome measures (velocity, cycle time, stride length, cadence, and base of support), as seen by high ICC scores (0.86 to 0.95) and low CoV scores (0.042–0.102). In addition, the performance across the two subject groups was very different, indicating that the GAITRite is sensitive enough to distinguish between populations. Given that the GAITRite is a relatively inexpensive and portable piece of equipment, it can be used in a wide variety of clinical settings and clinical trials. Our data on high test–retest reliability and sensitivity extends the utility of the GAITRite to the HD population. © 2005 Movement Disorder Society
Effects of dietary fiber on inflammatory bowel disease
Authors: Galvez Julio , Rodríguez‐Cabezas M. Elena , Zarzuelo Antonio 
Published: April 2005

AbstractThe chronic idiopathic inflammatory bowel diseases (IBDs), namely Crohn's disease and ulcerative colitis, appear to be derived from an inappropriate reaction towards a luminal agent, most probably driven by the intestinal microflora, which upregulates the synthesis and release of different pro‐inflammatory mediators, thus contributing to tissue damage that characterizes these intestinal conditions. Several studies have reported that IBD is associated with impairment in short‐chain fatty acid (SCFA) production, mainly acetate, propionate, and butyrate. They are produced in the large bowel by anaerobic bacterial fermentation of undigested dietary carbohydrates and fiber polysaccharides, with butyrate being considered as the major fuel source for colonocytes. These SCFAs have been proposed to play a key role in the maintenance of colonic homeostasis. Therefore, it is reasonable to consider therapeutic approaches that increase colonic SCFA production, as it can be achieved by administration of dietary fiber to IBD patients. Unfortunately, there is quite limited documentation of efficacy of dietary fiber in properly designed trials. This review discusses the rationale, available evidence for the use of dietary fiber and its mechanisms of action in the treatment and prevention of IBDs.
Complex tauto‐ and rotamerism of 2‐(R‐phenyl)‐1,2,3,4‐tetrahydroquinazolines
Authors: Gawinecki Ryszard , Kolehmainen Erkki , Kuczek Agnieszka , Pihlaja Kalevi , Ośmiałowski Borys 
Published: April 2005

AbstractDetailed NMR spectral analysis of CDCl3 solutions of 2‐(R‐phenyl)‐1,2,3,4‐tetrahydroquinazolines reveals three or four tautomeric forms. Apart from 2‐[(benzylideneamino)methyl]aniline, the other chain tautomeric forms are present only in minor quantities. In general, electron‐donating substituents increase the contribution of all chain forms. Lowering the temperature of the CDCl3 solution of 2‐(R‐phenyl)‐1,2,3,4‐tetrahydroquinazolines decreases the content of the 2‐[(benzylideneamino)methyl]aniline form. At the same time, the amount of the ring form increases. Opening of the tetrahydropyrimidine ring in 2‐(R‐phenyl)‐1,2,3,4‐tetrahydroquinazolines was found to be an endothermic process especially for less electron‐donating substituents. Copyright © 2005 John Wiley & Sons, Ltd.
Kinetics and mechanism of oxime formation from methyl benzoylformate
Authors: Malpica A. , Calzadilla M. 
Published: April 2005

AbstractRate and equilibrium constants for methyl benzoylformate oxime formation were determined as a function of pH over the range from about 0 to 6. The reaction occurs with rate‐determining carbinolamine dehydration over the entire range of pH investigated. Specific acid catalysis is dominant at pH < 4. Above that value, a pH‐independent reaction becomes apparent. This early appearance of an uncatalyzed reaction is interpreted as intramolecular assistance of the ester moiety in carbinolamine dehydration. Copyright © 2005 John Wiley & Sons, Ltd.
Kinetic study of the amination of Grignard reagents and cuprates with O‐methylhydroxylamine
Authors: Erdik Ender , Eroğlu Fatma , Kâhya Didem 
Published: April 2005

AbstractSubstituent effects on the rate of electrophilic amination of phenylmagnesium bromides, magnesium diphenylcuprates and catalytic phenylzinc cyanocuprates with O‐methyhydroxylamine in THF were investigated in a competitive kinetic study. Rate data and Hammett substituent constants are discussed on the basis of proposed mechanisms for the substitution reactions of these organometallics with an electrophilic amino transfer reagent. Copyright © 2005 John Wiley & Sons, Ltd.
Influence of the loading rate on liquid‐crystalline epoxy resin systems
Authors: Harada Miyuki , Aoyama Kentaro , Ochi Mitsukazu 
Published: April 2005

AbstractThe fracture toughness of liquid‐crystalline epoxy systems, which had a nematic polydomain structure (domain size about 40 μm), with an increasing loading rate was evaluated. In this system, the fracture toughness dramatically decreased from 1.96 to 0.22 MN/m3/2 with an increasing loading rate (0.1–5 mm/min). The network orientation near the fracture surface of different loading rate systems was investigated with polarized optical microscopy and polarized infrared spectroscopy. As a result, a large oriented region of mesogenic groups was observed near the fracture surface in the relatively low loading rate (0.1 and 0.5 mm/min) systems, but such a phenomenon was not observed in the high loading rate (2 and 5 mm/min) systems. These results showed that the high fracture toughness of the system at the low loading rate was due to the magnitude and region of the reorientation of the mesogenic groups in the fracture process and that high toughness could not be achieved at a high loading rate because the loading rate was too fast to allow orientation of the networks containing the mesogenic groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1296–1302, 2005
Direct determination of the ethanol metabolites ethyl glucuronide and ethyl sulfate in urine by liquid chromatography/electrospray tandem mass spectrometry
Authors: Politi Lucia , Morini Luca , Groppi Angelo , Poloni Vala , Pozzi Fulvia , Polettini Aldo 
Published: April 2005

AbstractA liquid chromatography/electrospray tandem mass spectrometry (LC/ESI‐MS/MS) method for the determination in urine samples of two ethanol metabolites, ethyl glucuronide (EtG) and ethyl sulfate (EtS), was developed and validated. Pentadeuterated EtG was used as internal standard for both EtG and EtS. In addition to the surviving ions, two MS/MS reactions were monitored for each analyte, with the deprotonated molecule as precursor ion: m/z 221 → 75, m/z 221 → 85 (EtG), and m/z 125 → 97, m/z 125 → 80 (EtS). Sample pretreatment, though very simple and rapid (1:50 water dilution and centrifugation of 50 μL of urine), was found to contain the occurrence of matrix effects. The method was accurate and precise over the linear dynamic range (0.05–10 mg/L). The analytes were stable in frozen urine for at least 1 month. The assay was applied to several authentic urine samples from social drinkers and to alcoholic beverages. Copyright © 2005 John Wiley & Sons, Ltd.
Laser desorption/ionization time‐of‐flight mass spectrometry of triacylglycerols in oils
Authors: Calvano Cosima D. , Palmisano Francesco , Zambonin Carlo G. 
Published: April 2005

AbstractSelected triacylglycerols (TAGs) were directly analyzed on a standard stainless steel target plate by laser desorption/ionization time‐of‐flight mass spectrometry (LDI‐TOFMS). Sodium and potassium ion adducts of TAGs were produced, and the thermal desorption/ionization mechanism was invoked to rationalize the experimental observations. The method permits a simple and fast qualitative analysis of TAGs. Advantages of this approach relative to matrix‐assisted laser desorption/ionization (MALDI) are simpler sample preparation, lack of need to use a matrix with consequent absence of matrix interference peaks in the spectra, and potential improvements in shot‐to‐shot reproducibility due to the absence of the crystallization step resulting in a more homogenously deposited sample. The procedure was successfully applied to the determination of TAGs in whole oils, yielding very fast TAG fingerprints. Copyright © 2005 John Wiley & Sons, Ltd.