bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzymatische Eliminierung von Ammoniak aus Histidin und Phenylalanin: der Friedel‐Crafts‐ähnliche Mechanismus
Authors: Poppe László , Rétey János 
Published: May 2005

AbstractDie erstaunlich hohe katalytische Aktivität und Selektivität von Enzymen manifestiert sich einerseits in einer Beschleunigung der Zielreaktion und andererseits in der Unterdrückung alternativer Reaktionswege, die ohne das betreffende Enzym kinetisch kompetitiv oder sogar dominant wären. Histidin‐ und Phenylalanin‐Ammoniak‐Lyasen (HALs und PALs) z. B. bewirken eine Abspaltung des nicht‐aciden β‐Protons dieser Aminosäuren, ohne das weitaus acidere Ammonium‐Proton anzutasten. Beide Ammoniak‐Lyasen enthalten eine katalytisch wichtige elektrophile Gruppe, die während dreißig Jahren für Dehydroalanin gehalten wurde. Die Röntgenkristallstruktur von HAL ließ jedoch eine andere elektrophile Gruppe erkennen, nämlich 5‐Methylen‐3,5‐dihydroimidazol‐4‐on (MIO), die UV‐spektroskopisch auch in PAL nachgewiesen wurde. Kürzlich ermittelte Röntgenkristallstrukturen von PAL aus Rhodosporidium toruloides und Petrosilenum crispum bestätigten das Vorliegen der MIO‐Gruppe. Experimente legen nahe, dass die Reaktion durch einen elektrophilen Angriff von MIO auf den aromatischen Ring des Substrates gestartet wird. Diese Friedel‐Crafts‐ähnliche Reaktion aktiviert das β‐Proton und führt zu seiner stereospezifischen Abspaltung mit nachfolgender Eliminierung von Ammoniak und Regenerierung der MIO‐Gruppe. Die Plausibilität eines solchen Mechanismus wird durch ein synthetisches Modell gestützt. Diskutiert wird außerdem die Anwendung der PAL‐Reaktion in der biokatalytischen Synthese von enantiomerenreinen α‐Amino‐β‐arylpropionaten aus Arylacrylaten.
Friedel–Crafts‐Type Mechanism for the Enzymatic Elimination of Ammonia from Histidine and Phenylalanine
Authors: Poppe László , Rétey János 
Published: May 2005

AbstractThe surprisingly high catalytic activity and selectivity of enzymes stem from their ability to both accelerate the target reaction and suppress competitive reaction pathways that may even be dominant in the absence of enzymes. For example, histidine and phenylalanine ammonia‐lyases (HAL and PAL) trigger the abstraction of the nonacidic β protons of these amino acids while leaving the much more acidic ammonium hydrogen atoms untouched. Both ammonia‐lyases have a catalytically important electrophilic group, which was believed to be dehydroalanine for 30 years but has now been revealed by X‐ray crystallography and UV spectroscopy to be a highly electrophilic 5‐methylene‐3,5‐dihydroimidazol‐4‐one (MIO) group. Experiments suggest that the reaction is initiated by the electrophilic attack of MIO on the aromatic ring of the substrate. This incomplete Friedel–Crafts‐type reaction leads to the activation of a β proton and its stereospecific abstraction, followed by the elimination of ammonia and regeneration of the MIO group. The plausibility of such a mechanism is supported by a synthetic model. The application of the PAL reaction in the biocatalytic synthesis of enantiomerically pure α‐amino β‐aryl propionates from aryl acrylates is also discussed.
Degradation profiles of polyester–urethane (hydroxylated polyester/diphenylmethane diisocyanate) and polyester–melamine (hydroxylated polyester/hexamethoxymethylmelamine) coatings: An accelerated weathering study
Authors: Narayan Ramanuj , Chattopadhyay D. K. , Sreedhar B. , Raju K. V. S. N. , Mallikarjuna N. N. , Aminabhavi T. M. 
Published: May 2005

AbstractThe successful material performance of coatings depends on the environmental conditions to which they are exposed. The effects of the diol structure and acetoacetylation on the weathering degradation of hydroxylated polyester (HP)/hexamethoxymethylmelamine and HP/diphenylmethane diisocyanate clear coatings were studied. The acetoacetylation of HPs led to better performance for higher application solids than the acetoacetylation of their base counterparts. Weathering degradation profiles were investigated with dynamic mechanical thermal analysis, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The structural variations of the building blocks and acetoacetylation were found to be important for enhancing the stability of coatings at higher application solids. Polyester–urethane coatings were more stable toward weathering than polyester–melamine coatings. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1069–1081, 2005
Preparation of crosslinked composite nanoparticles
Authors: Liu Wen‐Fang , Guo Zhao‐Xia , Yu Jian 
Published: May 2005

AbstractCrosslinked composite nanoparticles were prepared by adding a trifunctional monomer (trimethyol propane trimethacrylate) or a difunctional monomer (divinyl benzene) as a crosslinker into the emulsion polymerization system of styrene in the presence of inorganic nanosilica. A coupling agent, 3‐methacryloxypropyltrimethoxysilane (MPS), was added along with the monomer, crosslinker, and silica to improve the interfacial interaction between silica and polymer and thus to obtain high binding efficiency. The role of MPS was examined. The effects of crosslinkers on the kinetics of emulsion polymerization, monomer conversion, and yield were investigated. The morphology of the composite particles was observed by TEM. The particle size and size distribution of composite latex particles were measured by the dynamic light scattering method. The binding efficiency and swelling ratio were determined by reluxing the sample in xylene using a Soxhlet extraction apparatus. FTIR spectra and TGA verified the participation of crosslinker and silica. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1538–1544, 2005
An automated approach to the analysis of the arrangement of post‐pits at Stanton Drew
Authors: Linford P. K. 
Published: May 2005

AbstractAfter the surprising discovery of concentric arrangements of post‐pits within the megalithic stone circles at Stanton Drew in Somerset, it was decided to map their geometry using an automated approach. The algorithm developed relies on the use of correlation registration to allow the locations of pit anomalies to be identified automatically. Concentric circular arrangements of pits are then classified using a modified Hough transform, adapted to detect circular rather than linear patterns. Finally the co‐ordinates of the centres of all pits identified as lying on the same circle are extracted and fed to an algorithm that determines the parameters of the circle of best fit by the method of least squares. The result is an objective determination of the parameters of the nine concentric circles of pits within the Great stone circle and three circles within the south‐southwest stone circle, which it is hoped will help inform the interpretation of the monument. Although the computational procedures described represent a solution to the analysis of a possibly unique data set, it is hoped that elements of the method might provide ideas for techniques that can be generalized for other applications. Copyright © 2005 John Wiley & Sons, Ltd.
The use of ASTER satellite imagery in archaeological contexts
Authors: Altaweel Mark 
Published: May 2005

AbstractMultispectral ASTER satellite imagery has recently become available for scholarly research. The overall bandwidth and spatial resolution of the system give it an advantage over older Landsat satellites. In northern Mesopotamia, modern day north Iraq, hollow ways, sites and canals have all been located using the ASTER system. This system has proven to be useful in both verifying results found in CORONA satellite data and locating potential archaeological features that cannot be easily distinguished on CORONA imagery. Spectral signatures and visual manipulation can both be used to assist in the identification of distinct feature types. Reflectance information obtained from imagery can also be checked with ASTER's spectral library. With proper analytical methods applied, significant benefits for landscape archaeology can be achieved. Copyright © 2005 John Wiley & Sons, Ltd.
Complementary integrated geophysical investigation around Al‐Zayyan temple, Kharga oasis, Al‐Wadi Al‐Jadeed (New Valley), Egypt
Authors: Atya M. A. , Kamei H. , Abbas A. M. , Shaaban F. A. , Hassaneen A. Gh. , Alla M. A. Abd , Soliman M. N. , Marukawa Y. , Ako T. , Kobayashi Y. 
Published: May 2005

AbstractQasr Al‐Zayyan or Al‐Zayyan temple in Al‐Kharga oasis is documented as a node in the fortress chain that was built by the Romans to secure Darb Al‐Arbain; the slaver's trade caravan route between Asyuit and Sudan. The historical and archaeological background of the temple is very scarce; it has been ascribed to Amenebis and was restored during the reign of Emperor Antoninus AD 138–161. In March 2001, an integrated ground‐penetrating radar (GPR) and magnetic survey to the west of the temple showed the possibility of an existing structural complex intersecting the present temple at about 45°. It was interpreted as a multigate structure or a tomb complex. In March 2002, the relative topographic elevations were measured and the surface archaeological features were marked on a map. Also a complementary integrated geophysical survey including electromagnetic, geomagnetic and GPR was conducted along northern and western extensions of, and partially covering, the formerly prospected structure in the survey of 2001. It was designed to verify the structure, to define its extent on both the northern and western sides, and to decide about a possible excavation.The results verified the formerly prospected structure of 2001; some of its particular features have been detected. The structure therefore has been mapped over the surveyed area at the northern and western parts of the 2001 structure and it might extend wider than the surveyed area. The former proposition of a multigate structure becomes stronger because of its general appearance, and the idea of a tomb complex still exists owing to the presence of some depressions thought to be graves. Copyright © 2005 John Wiley & Sons, Ltd.
Airborne multi‐spectral prospection for buried archaeology in mobile sand dominated systems
Authors: Winterbottom S. J. , Dawson T. 
Published: May 2005

AbstractMuch of the UK's potential archaeological resource is under threat from coastal erosion. Undiscovered sites are often lost or damaged by erosion before rescue excavation can take place. This project tested the use of multispectral remote sensing for detecting archaeological features in mobile sand‐dominated systems, which are common on the western and northern coasts and islands around the UK. Airborne multispectral data were collected for a number of coastal areas on the Islands of Coll and Tiree. A range of data processing techniques were used to enhance the data for visual interpretation, which highlighted potential features for further inspection in the field. Features that were successfully detected by the methods used included enclosures, cairns, relict field boundaries and cultivation/soil marks, buried walls and buried structures. Multispectral remote sensing provides an extremely useful tool which can be used to significantly enhance the archaeological record, although further work is required to test the techniques under a range of conditions. Copyright © 2005 John Wiley & Sons, Ltd.
Exploring a prehistoric site for remains of human structures by three‐dimensional seismic tomography
Authors: Polymenakos L. , Papamarinopoulos S. P. 
Published: May 2005

AbstractSeismic tomography is applied in the exploration of the subsurface of a prehistoric site for remains of human structures. Prehistoric sites are important for accessing information on human history in times of limited written evidence. Knowledge of the subsurface character and pattern of possible structural remains can be of great help in excavation design and assessment. A case history of the application of seismic tomography at Palamari prehistoric site, Skyros Island, Aegean Sea, Greece, is presented. Energy sources and recorders are placed on the ground surface. Travel time data are analysed and processed with three‐dimensional tomographic inversion software. Seismic velocity images of the subsurface are constructed. Modelling of the subsurface is used to improve the interpretation and assist in the evaluation of the significance and reliability of the results. Velocity variations are known to correlate well with the lithological character of the earth materials, thus providing important structural and lithological information of the subsurface. The results show a good correlation, in terms of location, geometry and dimensions, with expected and excavated real dimensions and pattern of the foundation and near‐surface structure. Copyright © 2005 John Wiley & Sons, Ltd.
Automated identification of technologically similar organizations
Authors: Breitzman Anthony 
Published: May 2005

AbstractThis article introduces and validates a method for identifying technologically similar organizations, industries, or regions by applying the techniques from information science for term similarity to international patent classifications. Several applications of the method are explored, including identifying hidden competitive threats, finding potential acquisition targets, locating university expertise within a technology, identifying competitor strategy shifts, and more. One advantage of the method is that it is size invariant, meaning, for example, that it is possible for a huge corporation to identify smaller firms in its space before they become significant competitors. Another advantage is that technologically similar organizations can be identified on a large scale without any particular knowledge of the technology or business of either source organizations or target organizations.
Comparative knowledge management: A pilot study of Chinese and American universities
Authors: Geng Qian , Townley Charles , Huang Kun , Zhang Jing 
Published: May 2005

AbstractComparative study of knowledge management (KM) promises to lead to more effective knowledge use in all cultural environments. This pilot study compares KM priorities, needs, tools, and administrative structure components in large Chinese and American universities. General KM theory and literature related to KM in higher education are analyzed to develop the four components of the study. Comparative differences in KM practice at large Chinese and American universities are analyzed for each component. A correlation matrix reveals statistically significant co‐variation among all but one of the study components. Four conclusions related to comparative KM and suggestions for future research are presented.
Comparative pharmacokinetics of two tablet formulations of Losartan: bioequivalence assessment
Authors: Tamimi J.J.I. , Salem I.I. , Mahmood Alam S. , Zaman Q. , Dham Ruwayda 
Published: May 2005

AbstractThe pharmacokinetic profiles of two brands of losartan 50 mg tablets were compared in 24 healthy adult volunteers after a single oral dose in a randomized cross‐over study. The study was conducted at the ACDIMA Center for Bioequivalence & Pharmaceutical Studies, Amman, Jordan. The reference (Cozaar, MSD, The Netherlands) and test (Blosart, Julphar, UAE) products were administered to fasting volunteers. Blood samples were collected at specified time intervals, and the plasma separated and analysed for losartan and its active metabolite (losartan carboxylic acid) using a validated HPLC method with fluorescence detection. Pharmacokinetic parameters AUC0−t, AUC0−α, Cmax, Tmax, T1/2, elimination rate constant, MRT, Cl/F and Vss/F were determined from plasma concentration‐time profiles of both formulations and found to be in good agreement with reported values. Three parameters (AUC0−t, AUC0−α, and Cmax) were compared statistically to evaluate the bioequivalence between the two brands, using statistical modules recommended by the FDA. Analysis of variance (ANOVA) did not show any significant difference between the two formulations and 90% confidence intervals fell within the acceptable range (80%–125%) for bioequivalence. Based on these statistical inferences it was concluded that the two formulations exhibited comparable pharmacokinetic profiles and that Julphar's Blosart is bioequivalent to Cozaar of MSD, The Netherlands. Copyright © 2005 John Wiley & Sons, Ltd.
Variable omeprazole kinetics in healthy Jordanian adults
Authors: Albsoul‐Younes Abla , Tayyem Rabab , Najib Naji 
Published: May 2005

AbstractObjectives. The objective of this study was to examine the pharmacokinetics of orally administered omeprazole in healthy adult Jordanian men.Method. Plasma concentrations of omeprazole were measured over a 12 h period after administration of a single oral dose of 40 mg omeprazole (Losec®, AstraZeneca, UK). Subjects were healthy adult Jordanian men age 18–38 (24±4, mean±SD). The pharmacokinetic parameters were derived from the plasma concentration‐time profiles for AUC0‐t, AUC0‐inf, Cmax, tmax, t1/2e and Ke.Results. The pharmacokinetic of omeprazole were scattered over a wide range. The median AUC0‐inf was 784.86±1182.88 (ng·h/ml), and the median Cmax was 521±354 (ng/ml) (median±SD). In general, most subjects showed normal distribution (∼90%). Some subjects (10%) did show very high AUC and Cmax compared with the reported AUC and Cmax levels. These subjects had higher half‐lives and lower rates of elimination.Conclusion. Significant difference in the pharmacokinetics of omeprazole after a single dose administration was noted. Approximately 10% of the study group showed very high omeprazole plasma levels and AUCs. Differences in the pharmacokinetics might be due to differences in the genetic make‐up of subjects. Copyright © 2005 John Wiley & Sons, Ltd.
The influence of weight with assay error on gentamicin pharmacokinetics using the Bayesian and nonlinear least square regression analysis in appendicitis patients
Authors: Burm Jin Pil 
Published: May 2005

AbstractThe purpose of this study was to determine the influence of weight with gentamicin assay error on the Bayesian and nonlinear least squares regression analysis in 12 Korean appendicitis patients. Gentamicin was administered intravenously over 0.5 h every 8 h. Three specimens were collected 48 h after the first dose from all patients at the following times, just before the regularly scheduled infusion, at 0.5 h and 2 h after the end of the 0.5 h infusion. Serum gentamicin levels were analysed by fluorescence polarization immunoassay technique with TDxFLx. The standard deviation (SD) of the assay over its working range had been determined at the serum gentamicin concentrations of 0, 2, 4, 8, 12 and 16 µg/ml in quadruplicate. The polynominal equation of gentamicin assay error was found to be SD (µg/ml)=0.0246−(0.0495C)+(0.00203C2). There were differences in the influence of weight with gentamicin assay error on pharmacokinetic parameters of gentamicin using the nonlinear least squares regression analysis but there were no differences on the Bayesian analysis. This polynominal equation can be used to improve the precision of fitting of pharmacokinetic models to optimize the process of model simulation both for population and for individualized pharmacokinetic models. The result would be improved dosage regimens and the better, safer care of patients receiving gentamicin. Copyright © 2005 John Wiley & Sons, Ltd.
Novel reactive perstraction system applied to the hydrolysis of penicillin G
Authors: Wyss A. , Seitert H. , von Stockar U. , Marison I.W. 
Published: May 2005

AbstractThe activity of penicillin acylase has been studied in aqueous and organic solvents, as free enzyme as well as immobilized within the membrane of liquid‐core capsules. The activity of the enzyme is inhibited by the accumulation of the products of the hydrolysis reaction, namely phenyl acetic acid (PAA). In order to overcome this inhibition a range of organic solvents were tested for use in in situ product recovery. Of these solvents dibutyl sebacate (DBS) was chosen due to the rapid extraction rate, the high logP and to facilitate capsule production. The extraction efficiency at pH 3.5 for PAA was >80% for phase ratios of >50% free solvent with partition coefficients of 8 and 0.7 for PAA and penicillin G (PenG), respectively, thereby showing that PAA could be selectively extracted at pH 3.5 and 25°C. Liquid‐core capsules containing DBS were shown to efficiently remove PAA selectively and the PAA could be effectively back‐extracted and the capsules re‐used in a three‐stage process resulting in high product separation. Immobilization of penicillin acylase onto the capsule membranes resulted in increased operational stability of the enzyme and a very high enzyme activity. Over 53.3% of the PAA formed could be recovered in the capsule core with a concentration over sevenfold higher than in the aqueous phase. Higher extraction efficiencies could be obtained by varying the substrate concentration and number of capsules. The enzyme immobilized on capsules could be stored for over 4 months at pH 8 and 4°C with no loss of activity. Over 80% of the initial activity could be recovered over five repeated batch cycles of the bioconversion process. The importance of capsular perstraction and reactive capsular perstraction has been clearly demonstrated. © 2005 Wiley Periodicals, Inc.
Determination of clozapine and its metabolites in serum and urine by reversed phase HPLC
Authors: Zeren Wang , Minglian Lu , Peipei Xu , Yanlin Zeng , Yanlin Zeng 
Published: May 2005

AbstractA rapid, specific and sensitive method using reversed phase HPLC for the simultaneous determination of clozapine and its two metabolites in serum and urine has been developed. The mobile phase was a mixture of 67% (v/v) methanol in water containing 0.4% tetramethylethylenediamine and 0.32% acetic acid (pH 5.5). The influence of methanol content, the pH of the mobile phase and the effect of adding alkylammonium ions as peak tailing reducer in the mobile phase have been investigated. The solvent for extracting clozapine from serum and urine was ether. 50 μ1 of 0.25 M H2SO4 solution was used to redissolve the dry residue to eliminate the endogenous compounds which could otherwise be eluted together with clozapine from the HPLC column. The analysis of a single sample was accomplished within half an hour. The identities of the chromatographic peaks of clozapine and its N‐demethyl metabolite collected from the patient urine sample were confirmed by mass spectrometry. The method is sufficiently sensitive (5 ng/ml) and reproducible (CV 2.9%–6.7%) for clinical and pharmacokinetic studies, and preliminary results in these respects are presented.