bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Kinetics and Quantum Dynamics of Intramolecular Rearrangements in Highly Symmetrical Complexes: The Berry Pseudorotation
Authors: Merx Hendrik , Brickmann Jürgen 
Published: February 2004

Abstract
It is known that the intramolecular rearrangement of the ligands in trigonal-bipyramidal (TBP) molecules (e.g. PF5) follows a scheme first proposed by Berry and termed the Berry pseudorotation (BPR). There are 20 isomers, which are interconnected by 30 BPR reaction paths. In this paper, the time evolution of a given initial state is treated based on a set of first-order kinetic equations as well as on the basis of state-to-state tunneling processes. The dynamic equations are solved analytically using the eigenvalues and eigenvectors of the reaction-path connectivity matrix. It is shown that in the kinetic case the populations of all isomers approach an equilibrium value pi
(∞) = 1/20 while in the quantum case the individual isomers are never equivalent neither in time nor as time average. This fact is related to the strong regularity of the eigenvalue spectrum of the connectivity matrix for the reaction graph network. Consequently, pure quantum effects cannot be the basis for the occurrence of five equivalent ligands in PF5 (as was found experimentally).
Nanomaterials as Flow Regulators in Dry Powders
Authors: Zimmermann Ingfried , Eber M. , Meyer K. 
Published: February 2004

Abstract
From a physical point of view powders represent an intermediary state between solids and fluids. This holds especially with respect to their flow properties. Gravitational forces as well as interparticle forces are acting on particles in bulk powders. As long as the gravitational forces are prevailing the powder is able to flow. However as soon as the interparticle forces dominate the powder becomes cohesive. It does not flow any longer. Based on empirical observations highly dispersed Silicone dioxide is added to powders to improve their flowability. In the present paper we will present some findings obtained from studies on binary mixtures consisting of 0.2(m/m) of a nanoscaled material and corn starch. They give some insight into the mechanism of action of flow regulators. In addition they allow to classify flow regulators with respect to their efficiency as well as to their effectiveness. Furthermore the findings give hints on how to optimize existing flow regulators or to develop new improved ones.
Steady‐state pharmacokinetics of fluvastatin in healthy subjects following a new extended release fluvastatin tablet, Lescol® XL
Authors: Barilla Denise , Prasad Pratapa , Hubert Martine , Gumbhir‐Shah Kavita 
Published: February 2004

AbstractThis was an open‐label, randomized, three‐period, three‐treatment, multiple dose, crossover study in 12 healthy male and female subjects. This study evaluated single dose and steady‐state pharmacokinetics of fluvastatin following single and multiple dose administrations of a new extended release fluvastatin 8 h matrix tablet, Lescol® XL 80 mg and 160 mg doses once a day. The study also included a twice a day administration of an immediate release (IR) form of fluvastatin capsule, Lescol®, for comparative purposes. All doses were administered for 7 days. The safety and tolerability were also assessed. The pharmacokinetics of fluvastatin were evaluated on days 1 and 7 following each treatment. Fluvastatin systemic exposure was 50% less when administered as Lescol® XL 80 mg qd compared with Lescol® IR 40 mg bid. Conversely, fluvastatin systemic exposure was 22% higher when administered as Lescol® XL 160 mg qd compared with Lescol® IR 40 mg bid. Single doses of Lescol® XL 80 mg and 160 mg were dose proportional but, deviation (30%) from dose proportionality was observed for the Lescol® XL 160 mg at steady‐state. There appeared to be moderate (20%–40%) accumulation of serum fluvastatin maximal concentrations and exposure after multiple doses of Lescol® XL tablets. Both Lescol® XL 80 mg and 160 mg showed delayed absorption and longer apparent elimination half‐life compared with fluvastatin IR capsule. Single and multiple doses of fluvastatin were generally well tolerated in this healthy volunteer population. Adverse event profiles were consistent with the published safety profile of the marketed formulations. Aside from one incidence of creatine phosphokinase (CPK) elevation (following Lescol® XL 160 mg qd treatment), there were no safety concerns with any of the treatments when administered acutely (7 days). Copyright © 2004 John Wiley & Sons, Ltd.
Simple method for the assay of linezolid in Brain Heart Infusion broth by high‐performance liquid chromatography
Authors: Li Jian , Rayner Craig R. , Dixson Shirley , Nation Roger L. 
Published: February 2004

AbstractA simple HPLC method was developed and validated for quantiﬁcation of linezolid in Brain Heart Infusion (BHI) broth. Eperezolid was employed as internal standard and the sample pre‐treatment procedure was simple. Calibration standards ranged from 0.05 to 16 mg/L. Accuracy was within 7.8% and reproducibility (RSD) was less than 8.3%. Recovery was approximately 100% at all concentrations examined. Linezolid was stable in the autosampler insert for at least 24 h at ambient temperature and in BHI for 72 h at 37°C. This assay is rapid and ideal for analysis of a large number of samples. Copyright © 2003 John Wiley & Sons, Ltd.
High performance liquid chromatographic analysis of dehydroepiandrosterone and its pharmaceutical tablet formulation
Authors: Aboul‐Enein Hassan Y. 
Published: February 2004

AbstractA rapid, sensitive and stability indicating high performance liquid chromatographic method was developed and validated for the analysis of dehydroepiandrosterone (DHEA) in pharmaceutical tablet formulation. The analysis was done on a Supelcosil C18 column (25 cm × 4.6 mm i.d., 5 µm). The mobile phase consisted of methanol:sodium acetate buffer solution (5 g/L):acetic acid (500 mL/L), 57:42:1, v/v/v, adjusted to pH 5 at a ﬂow rate of 1 mL/min. Detection was carried out at a wavelength of 258 nm. The polynomial regression data for the calibration curve showed good linear relationship in the concentration range of 0.2–1 mg/mL with r = 0.9996. The method was validated for precision, accuracy and recovery. The limit of detection was found to be 50 ng/µL. The method was applied for the analysis of DHEA in its pharmaceutical tablet formulation. The effects of different buffers and alcohols on the retention of DHEA were studied and the role of acetic acid as an organic phase modiﬁer was also investigated. Copyright © 2003 John Wiley & Sons, Ltd.
Separation and determination of gentiopicroside and swertiamarin in Tibetan medicines by micellar electrokinetic electrophoresis
Authors: Zhao Shengguo , Liu Qing , Chen Xingguo , Hu Zhide 
Published: February 2004

AbstractMicellar electrokinetic electrophoresis was employed to determine two active components, gentiopicroside (GE) and swertiamarin (SW) in one Tibetan preparation medicine named shiweilongdankeli, two Tibetan herbal medicines named Gentiana rhodantha and Gentiana kitag and three other Chinese Gentiana medicines named Gentiana scabra, Gentiana rigescens and Gentiana macrophylla. The dissociation constants of gentiopicroside and swertiamarin determined by MEKC were 7.71 and 6.25. The optimum buffer system was 70 mm borate–10 mm sodium dodecylsulfate (SDS) –6% (v/v) ispropanol (pH 9.0). The voltage was 15 kV and detection was at 254 nm. The lower limits of detection (deﬁned as a signal‐to‐noise ratio of about 3) were approximately 3.86 mg L−1 for GE and 5.88 mg L−1 for SW. The relative standard deviation of the migration time and peak area of the GE and SW were 2.33, 2.47 and 1.27, 2.19%, respectively and the recoveries of the two compounds were 96–104% for GE and 92–102% for SW. Copyright © 2003 John Wiley & Sons, Ltd.
Liquid chromatographic assay for the cyclic depsipeptide aplidine, a new marine antitumor drug, in whole blood using derivatization with trans‐4′‐hydrazino‐2‐stilbazole
Authors: Sparidans Rolf W. , Schellens Jan H. M. , López‐Lázaro Luis , Jimeno José M. , Beijnen Jos H. 
Published: February 2004

AbstractA sensitive bio‐analytical assay for the depsipeptide aplidine in plasma has been modiﬁed and tested for human whole blood samples. The adapted method is based on reversed‐phase liquid chromatography and ﬂuorescence detection of the trans‐4′‐hydrazino‐2‐stilbazole derivative of the analyte. Aplidine is isolated from the matrix by solid‐phase extraction on an octadecyl modiﬁed silica stationary phase. After evaporation of the acetone eluate, the derivatization with the hydrazino reagent is performed in a water–acetonitrile mixture at pH = 4. The reaction mixture is injected directly into the chromatograph and the analyte is quantiﬁed by ﬂuorescence detection at 410 and 560 nm for excitation and emission, respectively. The method has been validated in the 2–100 ng/mL range, with 2 ng/mL being the lower limit of quantiﬁcation. Precision and accuracy both meet the current requirements for a bioanalytical assay. The stability of aplidine in whole blood at ambient temperature and at 37°C is limited; recoveries in the range 60–85% were observed after 7 h. Further, adequate stability of aplidine in plasma at −80 and −20°C for 35 months could now be demonstrated. Copyright © 2003 John Wiley & Sons, Ltd.
Toxicokinetic assessment of methylphenidate (Ritalin®) in a 13‐week oral toxicity study in dogs
Authors: Bakhtiar Ray , Ramos Luis , Tse Francis L. S. 
Published: February 2004

AbstractRitalin® or methylphenidate (MPH) is often prescribed for the treatment of attention deﬁcit hyperactivity disorder (ADHD) and narcolepsy. The therapeutic activity of MPH is principally due to d‐threo‐[2R,2′R]‐MPH. Hence, in order to establish a kinetic relationship between doses and exposure levels in a non‐rodent species, a 13‐week oral (capsule) toxicity study of d‐threo‐[2R,2′R]‐MPH was performed in beagle dogs. A previously reported chiral liquid chromatography tandem mass spectrometry (LC‐MS/MS) with a limit of quantiﬁcation (LLOQ) of 1.09 ng/ml was utilized. The results of this study indicated that MPH appeared to be rapidly absorbed in dogs following oral administration. The peak concentration was reached within 1–2 h. Based on the area under the curve (AUC) values, the plasma exposure of d‐MPH was over‐proportional to the dose. With the exception of two groups of animals (male/female, 7.5 mg/kg/day on day 1 and male/female, 3.0 mg/kg/day on week 7), the data showed no difference in MPH concentrations between the male and female dogs. Taking the statistical variations into account, concentrations of d‐MPH that were observed after 7.5 mg/kg/day doses of d‐MPH and 15 mg/kg/day doses of the racemate were similar. Following the racemate doses, the concentrations of l‐MPH were consistently higher than those of the d‐isomer. No accumulation of MPH was observed after 13 weeks of repeated daily administration. Copyright © 2003 John Wiley & Sons, Ltd.
Quantitative determination of p‐aminosalicylic acid and its degradation product m‐aminophenol in pellets by ion‐pair high‐performance liquid chromatography applying the monolithic Chromolith Speedrod RP‐18e column
Authors: Vasbinder E. , Van der Weken G. , Vander Heyden Y. , Baeyens W. R. G. , Debunne A. , Remon J. P. , García‐Campaña A. M. 
Published: February 2004

AbstractAn ion‐pair high performance liquid chromatographic method was developed for the simultaneous determination of p‐aminosalicylic acid (PAS) and its degradation product m‐aminophenol (MAP) in a newly developed multiparticular drug delivery system. Owing to the concencentration differences of PAS and MAP, acetanilide and sulfanilic acid were used as internal standards, respectively. The separation was performed on a Chromolith SpeedROD RP‐18e column, a new packing material consisting of monolithic rods of highly porous silica. The mobile phase composition was of 20 mm phosphate buffer, 20 mm tetrabutylammonium hydrogen sulphate and 16% (v/v) methanol adjusted to pH 6.8, at a ﬂow‐rate of 1.0 mL/min, resulting in a run‐time of about 6 min. Detection was by UV at 233 nm. The method was validated and proved to be useful for stability testing of the new dosage form. Separation efﬁciency was compared between the new packing material Chromolith SpeedROD RP‐18e and the conventional reversed‐phase cartridge LiChroCART 125‐4 (5 µm). A robustness test was carried out on both columns and different separation parameters (retention, resolution, run time, temperature) were determined. Copyright © 2004 John Wiley & Sons, Ltd.
Development of a fully coupled control‐volume finite element method for the incompressible Navier–Stokes equations
Authors: Ammara Idriss , Masson Christian 
Published: February 2004

AbstractThis paper proposes and investigates fully coupled control‐volume finite element method (CVFEM) for solving the two‐dimensional incompressible Navier–Stokes equations. The proposed method borrows many of its features from the segregated CVFEM described by Baliga et al. Thus finite‐volume discretization is employed on a colocated grid using either the MAW or the FLO schemes and an element‐by‐element assembling procedure is applied for the construction of the discretizations equations. In this paper, and unlike the case for most fully coupled formulations available in the literature, the Poisson pressure equation has been retained from the segregated approach. The use of a pressure equation leads to an unfavourable size increase of the fully coupled linear system, but significantly improves the system's conditioning. The fully coupled system obtained is solved using an ILUT preconditioned GMRES algorithm. The other important element in this paper is the proposal of a Newton linearization of the convection terms in lieu of the common Picard iteration procedure. A systematic comparison between two segregated and four fully coupled fomulations has been presented which has allowed for an evaluation of the individual benefits and strengths of the coupling and linearization procedure by studying lid‐driven cavity problems and flows past a circular cylinder. All coupled formulations have proven to be significantly superior both in robustness and efficiency, as compared with the segregated formulation. In some circumstances, the coupled methods yield a converged solution of the system of discretized equations constructed using the FLO scheme, while the segregated formulations diverge. Compared to Picard's linearization, Newton's linearization is more efficient at reducing the number of iterations needed to converge, but requires more computational effort per iteration from the linear equation solver. Furthermore, the Jacobian matrix should include contributions from the nonlinearity appearing at both the governing‐equation level and the interpolation‐scheme level to ensure Newton's method convergence. The key element in guaranteeing successful, fully coupled solutions lies in the use of an efficient linear equation solver and preconditioner. Copyright © 2004 John Wiley & Sons, Ltd.
A Lagrangian Discontinuous Galerkin‐type method on unstructured meshes to solve hydrodynamics problems
Authors: Loubère R. , Ovadia J. , Abgrall R. 
Published: February 2004

AbstractThis paper concerns a new Lagrangian Discontinuous Galerkin‐type method to solve 2D fluid flows on unstructured meshes. By using a basis of Bernstein polynomials of degree m in each triangle, we define a diffusion process which ensures positivity and stability of the scheme. The discontinuities of the physical variables at the interfaces between cells are solved with an acoustic Riemann solver. A remeshing/remapping process is performed with a particle method: the remapping is locally conservative and its accuracy can be adapted to the accuracy of the numerical method. Copyright © 2004 John Wiley & Sons, Ltd.
Analytical formulas for the velocity field induced by an infinitely thin vortex ring
Authors: Yoon Sam S. , Heister Stephen D. 
Published: February 2004

AbstractThree different analytical solutions are presented for a potential vortex ring using three different streamfunctions. Verification studies confirm that all three approaches are valid. It is found that the solution obtained using the Biot–Savart law is the most efficient method due to its simplicity. It is shown that all analytical results are accurate to within machine accuracy and sample calculations are included. Copyright © 2004 John Wiley & Sons, Ltd.
Tryptophan reduces creatine kinase activity in the brain cortex of rats
Authors: Cornelio Andrea Renata , Rodrigues Valnês , de Souza Wyse Angela Terezinha , Dutra‐Filho Carlos Severo , Wajner Moacir , Wannmacher Clovis Milton Duval 
Published: February 2004

AbstractHypertryptophanemia is a rare inherited metabolic disorder probably caused by a blockage in the conversion of tryptophan to kynurenine, resulting in the accumulation of tryptophan and some of its metabolites in plasma and tissues of affected patients. The patients present mild‐to‐moderate mental retardation with exaggerated affective responses, periodic mood swings, and apparent hypersexual behavior. Creatine kinase plays a key role in energy metabolism of tissues with intermittently high and fluctuating energy requirements, such as nervous tissue. The main objective of the present study was to investigate the effect of acute administration of tryptophan on creatine kinase activity in brain cortex of Wistar rats. We also studied the in vitro effect of this amino acid on creatine kinase activity in the brain cortex of non‐treated rats. The results indicated that tryptophan inhibits creatine kinase in vitro and in vivo. We also observed that the in vitro inhibition was fully prevented but not reversed by pre‐incubation with reduced glutathione, suggesting that the inhibitory effect of tryptophan on CK activity is possibly mediated by oxidation of essential thiol groups of the enzyme and/or long‐lasting adduct formation. Considering the importance of creatine kinase for the maintenance of energy homeostasis in the brain, it is conceivable that an inhibition of this enzyme activity in the brain may be one of the mechanisms by which tryptophan might be neurotoxic.
Role of maternal adrenal glands on the developing serotoninergic and aminoacidergic systems of the postnatal rat brain
Authors: Leret M.L. , Peinado V. , Suárez L.M. , Tecedor L. , Gamallo A. , González J.C. 
Published: February 2004

AbstractSerotonin, γ‐aminobutyric acid and glutamate, which are regulated by glucocorticoids in the central nervous system, are involved in neuroendocrine functions and the development of the brain. The present study investigates the effect of maternal adrenalectomy on the developing serotoninergic, GABAergic and glutamatergic systems. Neurotransmitter levels were measured in four brain areas of both male and female offspring on postnatal days 1, 8, 12 and 22. At postnatal day 1 and 8, the pups of adrenalectomized dams showed higher concentrations of serotonin than controls in all the brain areas studied. Serotonin levels decreased significantly in males at postnatal day 22 in the hippocampus and cortex. During the first 2 weeks of postnatal life, the lack of maternal corticosterone produced an increase in glutamate and a reduction in γ‐aminobutyric acid concentrations, mainly in males. Further, on postnatal day 1, increased serotonin and glutamate levels and lower levels of γ‐aminobutyric were observed in the hypothalamus of male pups born to adrenalectomized dams. The absence of maternal corticosterone affects the pattern of development of the serotoninergic system, especially in the hippocampus and cortex, and particularly in males. A delay in the maturation of the aminoacidergic systems, mainly of the GABAergic system and in males, was also seen. A sexually dimorphic response to the removal of maternal glucocorticoids was seen in terms of neurotransmitter levels, mainly in the hippocampus and hypothalamus.
Effects of histidine and imidazolelactic acid on various parameters of the oxidative stress in cerebral cortex of young rats
Authors: Tansini C.M. , Durigon K. , Testa C.G. , Belló‐Klein A. , Wajner M. , Wannmacher C.M.D. , Wyse A.T.S. , Dutra‐Filho C.S. 
Published: February 2004

AbstractHistidinemia is an inherited metabolic disorder caused by deficiency of histidase activity, which leads to tissue accumulation of histidine and its derivatives. Affected patients usually present with speech delay and mental retardation, although asymptomatic patients have been reported. Considering that the pathophysiology of the neurological dysfunction of histidinemia is not yet understood and since histidine has been considered a pro‐oxidant agent, in the present study we investigated the effect of histidine and one of its derivatives, l‐β‐imidazolelactic acid, at concentrations ranging from 0.1 to 10 mM, on various parameters of oxidative stress in cerebral cortex of 30‐day‐old Wistar rats. Chemiluminescence, total radical‐trapping antioxidant potential (TRAP), thiobarbituric acid reactive substances (TBA‐RS), and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐Px) were measured in tissue homogenates in the presence of l‐histidine or l‐β‐imidazolelactic acid. We observed that l‐histidine provoked an increase of chemiluminescence and a reduction of TRAP at concentrations of 2.5 mM and higher, while TBA‐RS measurement, GSH‐Px, CAT and SOD activities were not affected. Furthermore, l‐β‐imidazolelactic acid provoked antioxidant effects at high concentrations (5–10 mM) as observed by the reduction of chemiluminescence, although this compound enhanced chemiluminescence at low concentrations (0.5–1 mM). These results suggest that in vitro oxidative stress is elicited by histidine but only at supraphysiological concentrations.
Fetal origin of single nucleated erythroblasts and free DNA in the peripheral blood of pregnant women
Authors: Chen H.P. , Wang T.R. , Xu J.P. , Xu X.Y. , Dangol S.D. , He G.F. 
Published: February 2004

AbstractObjectives: To investigate the feasibility of using single fetal nucleated erythroblasts (FNRBCs) and free DNA in maternal blood for non‐invasive prenatal diagnosis. Methods: Single FNRBCs were isolated from 51 of 116 samples of maternal blood analyzed by micromanipulation after density gradient centrifugation. Furthermore, the nested polymerase chain reaction (PCR) method was used to amplify the SRY gene of single FNRBCs. Primer extension pre‐amplification and nested PCR were used to amplify the SRY gene of the plasma DNA extracted from 65 samples of maternal blood. Results: The detection rate of single FNRBCs was 90.20% (46/51). The concordance rates between real fetal sex and sex determined by amplification of the SRY gene from single cells and from free DNA analysis were 82.61% (38/46) and 90.77% (59/65), respectively. Conclusions: Single nucleated erythroblasts and free DNA in maternal blood are of fetal origin and can be valuable fetal material sources for non‐invasive prenatal diagnosis.