bluuebunny/crossref_metadata_2025 huggingface dataset:
Modified micellar electrokinetic chromatography in the analysis of catechins and xanthines in chocolate
Authors: Gotti Roberto , Fiori Jessica , Mancini Francesca , Cavrini Vanni
Published: October 2004

Modified micellar electrokinetic chromatography (MEKC) analysis of monomeric flavanols (catechin and epicatechin) and methylxanthines (caffeine and theobromine) in chocolate and cocoa was performed by using sodium dodecyl sulfate (SDS) as a principal component of the running buffer. Because of the reported poor stability of catechins in alkaline solutions, acidic conditions (pH 2.5) were chosen and consequently the electroosmotic flow (EOF) was significantly suppressed; this resulted in a fast anodic migration of the analytes partitioned into the SDS micelles. Under these conditions, variations of either pH value in acidic range or SDS concentration, showed to be not suitable to modulate the selectivity. To overcome this limit, use of additives to the SDS‐based running buffer was successfully applied and three different systems were optimized for the separation of (+)‐catechin, (−)‐epicatechin, caffeine, and theobromine in chocolate and cocoa powder samples. In particular, two mixed micelle systems were applied; the first consisted of a mixture of SDS and 3‐[(3‐cholamidopropyl)dimethylammonio]‐1‐propansulfonate (CHAPS) with a composition of 90 mM and 10 mM, respectively; the second was SDS and taurodeoxycholic acid sodium salt (TDC) with a composition of 70 mM and 30 mM, respectively. A further MEKC approach was developed by addition of 10 mM hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) to the SDS solution (90 mM); it provided a useful cyclodextrin(CD)‐modified MEKC. By applying the optimized conditions, different separation profiles of the flavanols and methylxanthines were obtained showing interesting potential of these combined systems; their integrated application showed to be useful for the identification of the low level of (+)‐catechin in certain real samples. The CD‐MEKC approach was validated and applied to the determination of catechins and methylxanthines in aqueous extracts from four different commercial chocolate types (black and milk) and two cocoa powders.
Pyrimidine 5'‐nucleotidase activities detected in real samples by means of micellar electrokinetic chromatography
Authors: Zanone Chiara , Chiarelli Laurent R. , Valentini Giovanna , Perani Eleonora , Annovazzi Laura , Viglio Simona , Iadarola Paolo
Published: October 2004

A micellar electrokinetic chromatographic method that allows simultaneous determination of both nucleotidase and transferase activities of cytosolic 5'‐nucleotidase III is presented. This electrophoretic approach was successfully applied to human erythrocyte lysates to monitor the enzyme activities indicated above, using either physiological substrate or the nucleoside analogue 3'‐azido‐3'‐deoxythymidine as the phosphate acceptor.
Capillary electrophoresis studies on the aggregation process of β‐amyloid 1‐42 and 1‐40 peptides
Authors: Sabella Stefania , Quaglia Milena , Lanni Cristina , Racchi Marco , Govoni Stefano , Caccialanza Gabriele , Calligaro Alberto , Bellotti Vittorio , De Lorenzi Ersilia
Published: October 2004

The possibility to monitor, in solution, the steps of β‐amyloid (Aβ) nucleation and therefore to describe this dynamic process by using capillary electrophoresis and under optimized experimental conditions is described. Striking differences in the electrophoretic patterns of Aβ 1‐42 and Aβ 1‐40 over time are here shown, and different aggregation states are elucidated, which reflect the very diverse oligomerization behavior of two very similar peptides. The isolation of one aggregated species of high molecular weight by ultracentrifugation allowed us to assess its role as toxic oligomer. The perturbation of the existing equilibrium among the identified species by the addition of small molecules can in principle interfere with the aggregation process of the peptides and ultimately prevent the plaque formation in vitro.
Obituary: Professor Csaba Horváth (1930–2004)
Authors: Guttman András
Published: October 2004

No abstracts.
Microscale fractionation facilitates detection of differentially expressed proteins in Alzheimer's disease brain samples (vol. 25, Issue 15, pp. 2557‐2563)
Authors: Lopez Mary F. , Mikulskis Alvydas , Golenko Eva , Melov Simon , Bennett David , Cherkasskiy Alex , Kuzdzal Scott , Kramer Susan , Sissors Dan
Published: October 2004

See original http://dx.doi.org/10.1002/elps.200406011
Reduction of Nitrates by Means of Immobilized Microorganisms
Authors: Rathjen A. , Hasch M.
Published: October 2004

Continuous denitrification of a model solution was carried out in a honeycombed gel bioreactor using immobilized Paracoccus pantotrophus DSM 65 over a period of seven weeks. Supply of nitrate was varied during operation to determine the nitrate degradation rate as a function of nitrate concentration. The experiments have shown that by entrapping living microorganisms into a monolithic block of κ‐Carrageen gel a delicate biological system can gently be transformed into a rugged apparatus.
Synthesis of Optically Active Diols by Escherichia coli Transformant Cells that Express the Glycerol Dehydrogenase Gene of Hansenula polymorphaDL‐1
Authors: Yamada‐Onodera K. , Kawahara N. , Tani Y. , Yamamoto H.
Published: October 2004

Chiral alcohols are useful as intermediates for the synthesis of drugs. In the production of chiral alcohols, microbial enzymes are promising since high optical purity is required. Under these conditions, the reaction by resting cells is more convenient and inexpensive than by an enzyme reaction. Chiral 1,2‐propanediol and 2,3‐butanediol were obtained using cells expressing the enzyme which demonstrated high stereospecificity. By means of recombinant cells expressing the glycerol dehydrogenase of Hansenula polymorpha DL‐1, the medium was enriched with (S)‐1,2‐propanediol (98 % enantiometric excess, e.e.) during a 24‐h incubation, whereas the (R)‐form was removed from 100 mM of the racemate (R:S = 1:1). For an asymmetric reduction, a recombinant was constructed which also expressed the glucose dehydrogenase gene of Bacillus subtilis origin as an NADH reproducer. In the resting cell reaction, the pH control at 7.5 promoted the conversion from ketone to alcohol. (2R,3R)‐2,3‐butanediol (e.e. > 99.9 %; 308 mM) was produced from 800 mM acetoin (R:S = 3:4); (R)‐1,2‐propanediol (e.e. > 99.9 %; 550 mM) from 800 mM acetol in a 33‐h incubation by the addition of glucose and ketone with pH control. In this reaction, (S)‐forms of both 2,3‐butanediol and 1,2‐propanediol were not produced. The pH control and feeding of the substrates were uncomplicated. The production process of the chiral alcohol by the recombinants which expresses glycerol dehydrogenase proved convenient.
Development of Bifidobacterium lactis Bb 12 on β‐(2,6)‐Linked Fructan‐Containing Substrate
Authors: Semjonovs S.P. , Marauska M. , Linde R. , Grube M. , Zikmanis P. , Bekers M.
Published: October 2004

β‐(2,1)‐linked fructan of plant origin (inulin) and the related oligosaccharides (FOS) as non‐digestible carbohydrates, i.e., potent prebiotics, can stimulate the growth of various probiotic lactic acid bacteria, including a number of bifidobacteria strains. The related β‐(2,6)‐linked fructans of microbial origin (levan and FOS), however, have scarcely been investigated in this respect. Therefore, the bifidogenic properties of various fructans, i.e., inulin, levan, fructooligosaccharides (FOS) and fructan syrup (FS), were tested as glucose substitutes in MRS media and were compared concerning their effect on the commercial strain Bifidobacterium lactis Bb 12. Although glucose was the preferred substrate for growth and biomass formation, FS exhibited a comparable cell growth (8.4 × 107 counts/mL and 1.0 × 107 counts/mL, respectively) and acidification power (84 °T and 74 °T, respectively) during 48 h of fermentation, as well as an increase in lactic acid and decrease in acetic acid formation. Bifidobacterium lactis Bb 12 did not utilize inulin as a sole carbon source as judged from the 60 % decrease in cell count and the insignificant (0.1 pH unit) acidification of the growth medium, whereas levan provided a noticeable increase in cell count and acidification (0.4 pH units) during 48 h of fermentation. FOS preparation appeared to be a satisfactory carbon source for this strain, but lower acidification power (56 °T) and cell counts were observed as compared to glucose‐ or FOS‐containing media (2.6 % and 22 %, respectively). The products obtained under conditions of mild lactic acid hydrolysis of levan (37 °C, pH 3.3, 24 h) enhanced the cell count (7–10 %) and acidification power (by a factor of 2.7) of Bifidobacterium lactis Bb 12.
Gene Cloning of Dihydroxyacetone Reductase from a Methylotrophic Yeast, Hansenula ofunaensis, and its Expression in Escherichia coli HB101 for Production of Optically Active 2‐Pentanol
Authors: Yamada‐Onodera K. , Nariai H. , Tani Y. , Yamamoto H.
Published: October 2004

Optically active alcohols are important building blocks as versatile chiral synthons for asymmetric syntheses of pharmaceuticals and agrochemicals. The aim of this paper is to efficiently prepare chiral 2‐pentanol by means of microorganisms. The gene of dihydroxyacetone reductase (EC 1.1.1.6) from a methylotrophic yeast, Hansenula ofunaensis, was cloned and chiral 2‐pentanol was produced by the recombinant Escherichia coli harboring the gene. The gene encoding the enzyme was cloned from an H. ofunaensis genomic library. In the deduced amino acid sequence of 364 residues, the NAD(H) binding motif and the cysteine residues that correspond to the cysteine ligands in the zinc atom were conserved, as they are in alcohol dehydrogenases from other origins. Dihydroxyacetone reductase was similar to alcohol dehydrogenases of prokaryotes. For the production of chiral compounds, an E. coli HB101 strain was transformed. The H. ofunaensis gene product, dihydroxyacetone reductase, catalyzed the NAD+‐dependent oxidation of 2‐pentanol to 2‐pentanone as well as the corresponding reverse reactions, showing specificity towards the secondary alcohol in (R)‐configuration. From 100 mM 2‐pentanone, (R)‐2‐pentanol (98 mM, > 99.9 % enantiometric excess, e.e.) was obtained in a 30‐min reaction with resting cells of the E. coli HB101 strain harboring the expression plasmid, pSG‐HOD1, which possesses the genes of both dihydroxyacetone reductase and glucose dehydrogenase as an NADH reproducing system. The stereospecificity changed during the reduction, depending on the pH. E. coli HB101 was also transformed by the expression plasmid, pSE‐HOD4, in which the gene of glucose dehydrogenase was removed from pSG‐HOD1, and designated as E. coli HB101 (pSE‐HOD4). E. coli HB101 (pSE‐HOD4) oxidized only (R)‐2‐pentanol in 100 mM of the racemate (R:S = 52:48), and the reaction medium was enriched with (S)‐2‐pentanol (48 mM, 98 % e.e.) after 30 min of incubation. The reaction was sufficiently promoted without the other additives. E. coli transformants expressing the gene of this enzyme could be particularly advantageous to the production of optically active 2‐pentanol.
Selection of Callus Cultures of Taxus baccata L. as a Potential Source of Paclitaxel Production
Authors: Bruňáková K. , Babincová Z. , Čellárová E.
Published: October 2004

The discovery of paclitaxel, a diterpene pseudalkaloid with antineoplastic properties has started a new medicinal use of yew. Although the ability of plant cell cultures to produce paclitaxel is well established, the manipulation of nutritional and environmental conditions, as well as the selection and cloning of new cell lines with appropriate genetic, biochemical and physiological properties is a crucial point for the future biotechnological production of taxanes.
Analysis of streptonigrin‐induced incomplete chromosome elements and interstitial fragments in Chinese hamster cells using a telomeric PNA probe
Authors: Bolzán Alejandro D. , Bianchi Martha S.
Published: October 2004

We investigated the induction of incomplete chromosome elements (ICEs; i.e., elements with a telomeric signal at only one terminal end) and interstitial fragments induced by the antibiotic streptonigrin (SN) in a Chinese hamster embryo (CHE) cell line using FISH with a telomeric peptide nucleic acid probe. CHE cells were treated with 0–250 ng/ml SN and chromosomal aberrations were analyzed in the first mitosis after treatment using the telomeric probe. Exposure of CHE cells to SN resulted in a linear concentration‐related increase in all of the aberration types analyzed (P < 0.05) except ring chromosomes. Depending on the SN concentration employed, 33–68% of the metaphases contained one or more pairs of ICEs (an incomplete chromosome accompanied by a terminal fragment or two incomplete chromosomes accompanied by a compound fragment). Pooled data from all SN concentrations revealed that 77.8% of the acentric fragments were terminal fragments, 18.8% interstitial fragments, and 3.4% compound fragments. Furthermore, it was estimated that about 80% of excess acentric fragments induced by SN originated from incomplete exchanges or terminal deletions and 20% from complete exchanges (interstitial deletions). These results show that incomplete chromosomes and terminal fragments are the most frequent asymmetrical chromosomal aberrations induced by SN and indicate that true incompleteness is a very common event following exposure to SN. Environ. Mol. Mutagen. 44:277–282, 2004. © 2004 Wiley‐Liss, Inc.
The MMA1 gene family of cancer‐testis antigens has multiple alternative splice variants: Characterization of their expression profile, the genomic organization, and transcript properties
Authors: de Wit Nicole J. W. , Cornelissen Ine M. H. A. , Diepstra J. Heleen S. , Weidle Ulrich H. , Ruiter Dirk J. , van Muijen Goos N. P.
Published: October 2004

Previously, we reported the identification of MMA1A by screening for differential gene expression in two human melanoma cell lines displaying diverse metastatic behavior after subcutaneous inoculation into nude mice. Splice variant MMA1B, which also was identified through database homology searches, showed a high degree of similarity with the MMA1A for exons 1, 2, and 4, but was missing exon 3. Through extensive expression profiling among normal and tumor samples, both MMA1A and ‐1B were found to belong to the family of cancer‐testis antigens. In this study, we identified four additional alternatively spliced MMA1 variants, named MMA1C, MMA1D, MMA1E, and MMA1F. Generally, these novel MMA1 transcripts differ from MMA1A in that exon 2 or exon 3 is enlarged because of the use of alternative splice sites in intron 2 of the MMA1 gene. Moreover, MMA1E also lacks exon 3, as was previously seen in MMA1B. In screening for expression of the novel MMA1 transcripts in normal and tumor tissues, we demonstrated that MMA1C, ‐1D, and ‐1E also are members of the cancer‐testis antigen family. MMA1F was found in only one melanoma metastasis sample and therefore is believed to have been expressed incidentally. Furthermore, we comprehensively elucidated the genomic structure of the MMA1 gene and the characteristic features of the alternatively spliced MMA1 transcripts. © 2004 Wiley‐Liss, Inc.
Number of oligodendrocyte progenitors recruited to the lesioned spinal cord is modulated by the levels of the cell cycle regulatory protein p27Kip‐1
Authors: Crockett David P. , Burshteyn Mark , Garcia Corina , Muggironi Michela , Casaccia‐Bonnefil Patrizia
Published: October 2004

Remyelination is a critical step for recovery of function after demyelination and defines the ability to generate new myelin. This repair process is dependent on the presence of resident oligodendrocyte progenitors (OLPs) that have been shown to remyelinate axons after demyelination. We have previously shown that the levels of the cell cycle inhibitor p27Kip‐1 modulate the number of neonatal cortical OLPs. We now asked whether this cell cycle molecule plays also a role in regulating the number of adult OLP in the spinal cord after demyelination induced by lysolecithin injection. The proliferative response of OLP in the spinal cord of injected wild‐type (wt) and p27Kip‐1 null mice was evaluated 3 days after lesion. In vivo labeling with bromodeoxyuridine (BrdU) was used to identify cells in S phase. Double immunofluorescence for the OLP marker NG2, and for BrdU was used to count the number of proliferating progenitors. Consistent with a role of p27Kip‐1 in regulating the number of adult OLP in the injured spinal cord, a larger number of proliferating OLPs was observed in p27Kip‐1null mice compared with wild‐type controls. These cells were able to differentiate as assessed by the presence of MBP+ cells in the spinal cord 14 days after injury. We conclude that the cellular levels of the cell cycle inhibitor p27Kip‐1 modulate the repair response of OLPs to injury in the adult spinal cord. © 2004 Wiley‐Liss, Inc.
High‐voltage‐activated calcium channels in Müller cells acutely isolated from tiger salamander retina
Authors: Welch Nicole C. , Wood Stephanie , Jollimore Christine , Stevens Kelly , Kelly Melanie E.M. , Barnes Steven
Published: October 2004

Müller cells mediate retinal function by stabilizing the ionic environment and signal glial network activity via calcium waves. Using whole‐cell patch clamp recording, we describe a high‐voltage‐activated, slowly inactivating Ca channel current in isolated salamander Müller cells that has unusual pharmacological properties. The Ca channel current has an activation midpoint of ∼−8 mV and an inactivation midpoint of ∼−26 mV in 10 mM Ba2+. The time constant for inactivation is ∼380 ms at potentials positive to zero. The current is blocked by Cd2+ with an EC50 of <100 nM. nisoldipine (10 μM) blocks ∼50%, while nifedipine (1 μM), diltiazem (20 μM), and verapamil (50 μM) each block one‐third of the current. In contrast to its typical actions, BayK 8644 blocks the current by ∼ 25%. Blockers of other Ca channel subtypes were also tested: ω‐agatoxin IVA (200 nM) blocked only 13% of the Ca channel current, while ω‐conotoxin GVIA (1 μM) blocked 84% of the current. Immnohistochemistry supported the presence of α1A, α1B, α1C, and α1D Ca channel subunits. Mapping of dihydropyridine‐binding sites with DM‐BODIPY revealed a distribution of channels over the entire membrane of the Müller cell with a higher density at the apical region. Overall, these observations suggest either the presence of a mix of L‐ and N‐type Ca channels or a single, unconventional HVA Ca channel subtype sharing L‐ and N‐type Ca channel characteristics. © 2004 Wiley‐Liss, Inc.
Boiling heat transfer in a narrow space controlled by punched interference plate
Authors: Shimada Ryohachi , Izumi Masaaki , Kumagai Satoshi , Adachi Takeshi
Published: October 2004

An experiment on pool boiling in methanol was performed for a case in which the boiling space was controlled by an interference plate with many holes. The narrow space, 0.12 mm in thickness, between the heat transfer surface and the interference plate was hermetically sealed at the perimeter. Therefore, the vapor and liquid were only exchanged through the holes in the interference plate. The degree of superheat at the onset of boiling was 0.7 K without overshoot at 10‐mm plate thickness, 1‐mm hole diameter, and 3.85‐mm hole pitch. The critical heat flux obtained was the same value without the interference plate mentioned above. The interference plate disturbed free convection and a superheat layer was provided under small heat flux on the heat transfer surface. The critical bubble diameter for the onset of boiling was decreased as the temperature of the superheat layer was increased. Thus, the degree of superheat at the onset of boiling was decreased. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(7): 462–471, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20028
A simplified model of gas–liquid two‐phase flow pattern transition
Authors: Ito Koji , Inoue Mitsuru , Ozawa Mamoru , Shoji Masahiro
Published: October 2004

An experiment of upward gas–liquid two‐phase flow was conducted in an air–water isothermal system under atmospheric pressure. The differential pressure was measured at the fully developed section by using a variable reluctance type transducer to classify the flow patterns and their transitions. The flow behavior was observed with a high‐speed video camera. The probability density function (PDF) of the differential pressure signal was employed to identify the flow pattern. A simplified one‐dimensional flow model was proposed to clarify dominant factors affecting the formation and transitions of flow patterns. The model dealt with the gas‐component advection based on the spatiotemporal void fraction behaviors by considering the gas compressibility, the wake, and the liquid phase redistribution mechanism. The simulation results of the model indicated four kinds of the void wave patterns (ripple‐like, rectangular, distorted rectangular, and uniform wave patterns) depending on gas and liquid volumetric fluxes. These void wave patterns corresponded well to the experimentally observed flow patterns. The transitions among void wave patterns agree well with the Mishima–Ishii flow pattern map. The friction loss estimated by the present model coincides fairly well with Chisholm's empirical formula. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(7): 445–461, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20029
The heat transfer and pressure drop characteristics of finned tube banks in forced convection (comparison of the pressure drop characteristics of spiral fins and serrated fins)
Authors: Kawaguchi Kiyoshi , Okui Kenichi , Kashi Takaharu
Published: October 2004

In recent years there has been a growing need for reduction of energy consumption in an effort to solve problems of global warming and the shortage of petroleum resources. For example, in the power generation field, thermal power generation now occupies 60% of the power generation demand, and the need for improved thermal efficiency is thus considerable. In this paper, the pressure drop characteristics of the finned tube banks used for the heat exchanger in thermal power generation were clarified by testing the serrated finned tube banks for improvement of higher heat transfer and the conventional spiral finned tube banks under the same test conditions, and equations for predicting the pressure drop coefficient which is necessary to design the heat exchanger were proposed. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(7): 431–444, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20030
Cytokine secretion from mononuclear cells cultured in vitro with starch‐based polymers and poly‐L‐lactide
Authors: Marques Alexandra P. , Reis Rui L. , Hunt John A.
Published: October 2004

The cytokine network is one of the major controlling systems of the inflammatory process, driving the magnitude and duration of the host response against invading microorganisms, foreign materials, or altered internal stimuli. Pro‐ and antiinflammatory cytokines were quantified after in vitro culture of a mixed population of monocytes/macrophages and lymphocytes with biodegradable polymers. Different blends of starch‐based polymers and their composites filled with hydroxyapatite were studied and compared with poly‐L‐lactide. Interleukin (IL)‐1β, IL‐6, and tumour necrosis factor‐α were investigated as the markers of immunological reactivity because they are known to act at the early stages of injury/invasion. Interferon‐γ, recognized as a proinflammatory cytokine, although not present during early responses was also investigated. Contrarily, IL‐4 derived from T lymphocytes, was investigated because it is an immunoregulator that counteracts some aspects of inflammation. T lymphocyte activation was also determined by quantifying IL‐2. The results support the hypothesis that different biodegradable polymers can affect mononuclear cell activation and the production of several cytokines associated with the inflammatory process. No IL‐2 or interferon‐γ was found in the culture supernatants after 3, 7, and 14 days in the presence of any of the materials. IL‐6 was detected in the highest amounts, for all the conditions, followed by tumour necrosis factor‐α. IL‐1β was produced in very low amounts, being undetectable with some of the starch‐based materials. IL‐4 was the only cytokine that did not demonstrate any significant difference within this group of materials. Starch‐based polymers and composites induced lower production of proinflammatory cytokines in comparison to poly‐L‐lactide. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 419–429, 2004
Scalable fine‐grained parallelization of plane‐wave–based ab initio molecular dynamics for large supercomputers
Authors: Vadali Ramkumar V. , Shi Yan , Kumar Sameer , Kale Laxmikant V. , Tuckerman Mark E. , Martyna Glenn J.
Published: October 2004

Many systems of great importance in material science, chemistry, solid‐state physics, and biophysics require forces generated from an electronic structure calculation, as opposed to an empirically derived force law to describe their properties adequately. The use of such forces as input to Newton's equations of motion forms the basis of the ab initio molecular dynamics method, which is able to treat the dynamics of chemical bond‐breaking and ‐forming events. However, a very large number of electronic structure calculations must be performed to compute an ab initio molecular dynamics trajectory, making the efficiency as well as the accuracy of the electronic structure representation critical issues. One efficient and accurate electronic structure method is the generalized gradient approximation to the Kohn–Sham density functional theory implemented using a plane‐wave basis set and atomic pseudopotentials. The marriage of the gradient‐corrected density functional approach with molecular dynamics, as pioneered by Car and Parrinello (R. Car and M. Parrinello, Phys Rev Lett 1985, 55, 2471), has been demonstrated to be capable of elucidating the atomic scale structure and dynamics underlying many complex systems at finite temperature. However, despite the relative efficiency of this approach, it has not been possible to obtain parallel scaling of the technique beyond several hundred processors on moderately sized systems using standard approaches. Consequently, the time scales that can be accessed and the degree of phase space sampling are severely limited. To take advantage of next generation computer platforms with thousands of processors such as IBM's BlueGene, a novel scalable parallelization strategy for Car–Parrinello molecular dynamics is developed using the concept of processor virtualization as embodied by the Charm++ parallel programming system. Charm++ allows the diverse elements of a Car–Parrinello molecular dynamics calculation to be interleaved with low latency such that unprecedented scaling is achieved. As a benchmark, a system of 32 water molecules, a common system size employed in the study of the aqueous solvation and chemistry of small molecules, is shown to scale on more than 1500 processors, which is impossible to achieve using standard approaches. This degree of parallel scaling is expected to open new opportunities for scientific inquiry. © 2004 Wiley Periodicals, Inc. J Comput Chem 16: 2006–2022, 2004
Efficiency of the algorithms for the calculation of Slater molecular integrals in polyatomic molecules
Authors: Fernández Rico J. , López R. , Ema I. , Ramírez G.
Published: October 2004

The performances of the algorithms employed in a previously reported program for the calculation of integrals with Slater‐type orbitals are examined. The integrals are classified in types and the efficiency (in terms of the ratio accuracy/cost) of the algorithm selected for each type is analyzed. These algorithms yield all the one‐ and two‐center integrals (both one‐ and two‐electron) with an accuracy of at least 12 decimal places and an average computational time of very few microseconds per integral. The algorithms for three‐ and four‐center electron repulsion integrals, based on the discrete Gauss transform, have a computational cost that depends on the local symmetry of the molecule and the accuracy of the integrals, standard efficiency being in the range of eight decimal places in hundreds of microseconds. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1987–1994, 2004
Differentiation of sulfate and phosphate by H/D exchange mass spectrometry: application to isoflavone
Authors: Kanakubo Akira , Isobe Minoru
Published: October 2004

Often phosphorylation or sulfation is an important step which occurs in the signal transduction and cascade of metabolic pathways. Some natural products and metabolites contain one or more sulfate or phosphate groups. Isoflavone sulfate has been identified from high‐resolution mass spectrometry (HRMS) and enzymatic digestion by sulfatase. We previously reported the new water‐soluble isoflavone analogs, daidzein 7‐O‐phosphate and genistein 7‐O‐phosphate, which were surprisingly hydrolyzed by sulfatase. In this previous study, we could not determine the phosphate from the results of HRMS and enzymatic digestion, that is, HRMS and enzymatic digestion did not provide clear evidence. In this case, we drew conclusions from NMR analysis. HRMS has been ineffective with a regular fast atom bombardment (FAB) mass spectrometer to distinguish between phosphate and sulfate since the mass difference is only 0.009 mass units. There was, however, no conventional method of microanalysis to distinguish phosphate from sulfate owing to the same nominal mass. It is still very difficult to determine by negative FABMS [OP(O)(OH)2] = 80 and [OS(O)2OH] = 80. In this paper, we report a method to distinguish between these groups by using a popular low‐resolution mass instrument; thus, phosphate and sulfate were measured by H/D exchange mass spectrometry at the picomole level to differentiate [OP(O)(OD)2] = 82 and [OS(O)2OD] = 81, respectively. This method is applicable not only to the isoflavone, but also to other phospho and sulfo compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Using collision‐induced dissociation with corrections for the ion number of degrees of freedom for quick comparisons of relative bonding strength
Authors: Vinokur Natalia , Ryzhov Victor
Published: October 2004

The number of degrees of freedom‐dependent stability of ions and ion–neutral non‐covalent complexes under collision‐induced dissociation (CID) conditions was studied in a quadrupole ion trap mass spectrometer. It was found that the stability of ions as probed by energy‐variable CID has a linear dependence on the total number of degrees of freedom for the ions (or ion–neutral complexes) with the same (or nearly the same) bonding energy. The slope of such a stability vs number of degrees of freedom dependence correlates with the binding energy. Proton‐bound amine dimers display the lowest slope as they have weak bonds. Breaking covalent bonds will result in much greater slopes. In addition to the binding energy, the vibrational frequencies of the ion also affect the stability vs number of degrees of freedom behavior. Studying such a dependence of the CID stability in a system paves the way for direct relative binding energy comparisons. The application of this approach is demonstrated by testing the relative heme affinities of anti‐malaria drugs and related compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Fragmentation patterns of selected ergot alkaloids by electrospray ionization tandem quadrupole mass spectrometry
Authors: Lehner Andreas F. , Craig Morrie , Fannin Neil , Bush Lowell , Tobin Thomas
Published: October 2004

Tall fescue toxicosis and other maladies in livestock result from the ingestion of vasoconstrictive ergot alkaloids produced by fungal endophytes associated symbiotically with the grass. In order to facilitate future analyses of grass extracts considered responsible for outbreak of related livestock diseases, we examined the electrospray ionization mass spectra of specific ergot alkaloids under conditions that permit protonation. Our purposes were both to record the spectra with interpretation of mechanisms of fragmentation and to derive commonalities that would allow the prediction of mass spectra of related compounds for which standards were not readily available. With [M + H]+values in parentheses, water‐insoluble lysergic acid peptide ergot derivatives ergovaline (m/z534), ergotamine (m/z582), ergocornine (m/z562), ergocryptine (m/z576) and ergocrystine (m/z610) exhibited a consistent loss of water (−18 u) from the C‐12′ α‐hydroxy functionality. Of this group, ergovaline and ergotamine generated anm/z320 fragment deriving from cleavage of ring E amide and ether functions with retention of the peptide ring system methyl group. Ergocornine, ergocryptine and ergocrystine similarly formed anm/z348 fragment with retention of isopropyl. These assignments were supported by the lack of similar fragments from the water‐soluble ergot ergonovine, which lacks a peptide ring system. Clavine‐type ergot alkaloids lysergic acid and lysergol lack any substituents beyond simple ones directly on the C‐8 position and, similarly to ergonovine, lack significant fragments atm/z268, 251 and 225 shared by the peptide ergot alkaloids. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of arginine and asymmetric dimethylarginine (ADMA) in human plasma by liquid chromatography/mass spectrometry with the isotope dilution technique
Authors: Martens‐Lobenhoffer Jens , Krug Olga , Bode‐Böger Stefanie M.
Published: October 2004

Arginine (ARG) is a substrate for endogenous nitric oxide (NO) production whereas its metabolite, asymmetric dimethylarginine (ADMA), acts as an inhibitor. Sufficient NO production is essential for cardiovascular key functions, thus elevated concentration levels of ADMA are related to a range of cardiovascular diseases. Owing to the lack of reliable methods for the measurement of ARG and ADMA in human plasma, concentration values determined with these methods can differ considerably. We present here a simple and very robust liquid chromatographic/mass spectrometric method for the determination of ARG and ADMA utilizing isotope‐labeled internal standards. Sample preparation requires only protein precipitation; the analytes were derivatized with o‐phthalaldehyde–mercaptoethanol and separated on a reversed‐phase C18 column with gradient elution. The analytes were detected with an electrospray ionization ion trap instrument working in the full‐scan single mass spectrometry mode. Concentration values obtained with this method for healthy controls were ARG = 63.9 ± 23.9 µM and ADMA = 0.355 ± 0.066 µM, with a normal range for ADMA from 0.225 to 0.485 µM. The corresponding values for end‐stage chronic renal failure patients are ARG = 48.1 ± 18.5 µM, p < 0.01 and ADMA = 0.673 ± 0.134 M, p < 0.001. Copyright © 2004 John Wiley & Sons, Ltd.
Investigation into factors affecting precision in ion trap mass spectrometry using different scan directions and axial modulation potential amplitudes
Authors: Dobson G. , Murrell J. , Despeyroux D. , Wind F. , Tabet J.‐C.
Published: October 2004

Electrospray ionization mass spectra obtained from different scan directions are observed to be dependent on the axial modulation potential amplitudes used for resonant ejection and on the positive deviation caused by higher even‐multipole fields present in most commercial ion traps. The axial modulation voltage influences the dissociation of ions during resonant ejection and the observed mass shifts. The higher even‐multipole fields in commercial ion traps are known to influence resonant ejection from the ion trap and can cause a loss in mass resolution for peaks in reverse scan mass spectra compared with that obtained by the forward scan. However, along with the dissociation of ions during resonant ejection causing a loss in resolution, the possibility of resolving an isotopic distribution is also shown to be influenced by the mass shifts caused by the space charge. These mass shifts differ depending on the scan direction employed. A significant loss in resolution can also result from resonant ejection using non‐optimal axial modulation voltages. We also present results showing the ejection of ions at $\beta_{z} = {1 \over 2}$ using the reverse scan mode without the axial modulation voltage. Ion ejection at $\beta_{z} = {1 \over 2}$ is uncommon in commercial (stretched ion traps) with the conventional analytical scan without the use of a frequency of the axial modulation voltage corresponding to this non‐linear resonance. Copyright © 2004 John Wiley & Sons, Ltd.
Changes in spring–summer cirrus cloud amount over Estonia, 1958–2003
Authors: Eerme Kalju
Published: October 2004

The data of hourly cloud detection during daytime at the Tartu–Tõravere meteorological station for the period 1958–2003 have been treated to find the monthly mean amounts of cirrus clouds (in tenths) for March–September and to study their variance. The highest mean value (4.1 tenths) was found in April and the lowest (three tenths) in July. The results of previous cloud‐type notation frequency‐based studies using no quantitative measure for cirrus cloud amount exhibit a maximum in June. The smoothed March–September cirrus cloud amount for 1958–2003 manifests alternation of relatively high and relatively low amounts with a period of approximately 20 years. The relative contribution of clear skies (cirrus amounts less than one tenth) has decreased, the lowest being during 1991–96. The cirrus cloud amount was weakly correlated with local characteristics of atmospheric moisture, such as precipitation, total cloud amount and low cloud amount. Low average cirrus amounts, however, were often recorded when the spring was dry. High cirrus amounts were observed when spring and most months were wet. Copyright © 2004 Royal Meteorological Society
The influence of atmospheric circulation on plant phenological phases in central and eastern Europe
Authors: Aasa Anto , Jaagus Jaak , Ahas Rein , Sepp Mait
Published: October 2004

The objective of this study is to analyse relationships between the start dates of spring phenological phases and large‐scale atmospheric circulation patterns. The timing of phenological phases in temperate zones is driven by temperature, and temperature regime is generally determined by atmospheric circulation. The database analysed consists of the first dates of flowering of coltsfoot (Tussilago farfara L.), of birch (Betula pendula Roth.) leaf unfolding and of flowering of lilac (Syringa vulgaris L.); the North Atlantic oscillation (NAO) and the Arctic oscillation (AO) indices, frequencies of the circulation forms classified by Vangengeim and Girs, and of the groups of Grosswetterlagen presented by Hess and Brezowsky. The study area covers central and eastern Europe, and the period considered is 1951–98.

The results show that the influence of the westerly airflow is more pronounced in the winter half‐year, and weakens and even disappears as spring advances. Phases have the highest correlation with NAO and AO indices during winter (December–March) and the first three months of the year (January–March), which have correlations stronger than −0.5 in the Baltic Sea region. Among the phenological phases, flowering of coltsfoot is the most strongly correlated with the NAO and AO indices, followed by leafing of birch and flowering of lilac. Airflow from the north and from the east has a greater influence in springtime, particularly in the northernmost and southernmost regions of the study area. Copyright © 2004 Royal Meteorological Society
Australian dust storms: temporal trends and relationships with synoptic pressure distributions (1960–99)
Authors: Ekström Marie , McTainsh Grant H. , Chappell Adrian
Published: October 2004

Mean‐sea‐level‐pressure patterns of the main atmospheric circulation for Australia were created using principal component analysis and non‐hierarchical cluster analysis. The patterns are related to dust storm occurrence from 95 meteorological stations across Australia during the period 1960–99. Dust storm stations were separated into two groups with distinct dust storm seasons: the spring–summer (September–February) dust storm group and the summer–autumn (December–May) dust storm group. Spring–summer dust storms are most likely controlled by the timing of non‐precipitation cold fronts over southern and central Australia and limited by summer precipitation. The summer–autumn dust storms are most likely controlled by the length of the driest period of the year. The stations of the first group are located mainly in the interior of the continent, and those of the second group are located mainly near the coastal regions of southern and western Australia. The location of the subtropical Indian Ocean high is shown here to influence dust storm occurrence during both seasons. A more westward displacement of this pressure centre in the Great Australian Bight allows cold fronts to enter the continent and increase the potential for dust storm activity. Copyright © 2004 Royal Meteorological Society
Hydro‐meteorological variability in the greater Ganges–Brahmaputra–Meghna basins
Authors: Chowdhury MD. Rashed , Ward Neil
Published: October 2004

The flows of the Ganges, Brahmaputra and Meghna (GBM) are highly seasonal, and heavily influenced by monsoon rainfall. As a result, these rivers swell to their banks and often overflow during the monsoon months. This is most pronounced in the downstream regions, particularly in Bangladesh, which is the lowest riparian country. The objective of this paper is to study this hydro‐meteorological variability in the greater GBM regions, including the headwater regions in India and their role in streamflows in Bangladesh, and explore the large‐scale oceanic factors affecting this hydro‐meteorological variability. Global precipitation data, Bangladesh rainfall and streamflow records have been analysed and related to large‐scale climate patterns, including upstream rainfall, regional atmospheric circulation and patterns of sea‐surface temperature.

The findings have quantified how the streamflows of these rivers in Bangladesh are highly correlated with the rainfall in the upper catchments with typically a lag of about 1 month. Therefore, streamflows in Bangladesh could be reasonably estimated for 1 to 3 months in advance (especially for the Ganges and Brahmaputra rivers) by employing simple correlation, if rainfall data from countries further up are available on a real‐time and continuous basis. In the absence of rainfall data, streamflow forecasts are still possible from unusually warm or cold sea‐surface temperatures in the tropics. The study concludes that hydro‐meteorological information flow between Bangladesh and other neighbouring countries is essential for developing a knowledge base for evaluating the potential implications of seasonal streamflow forecast in the GBM basins in Bangladesh. Copyright © 2004 Royal Meteorological Society
Variability and trends in the duration and depth of snow cover in Poland in the 20th century
Authors: Falarz Małgorzata
Published: October 2004

This study investigates the changes and variability of the number of days with snow cover of ≥1 cm depth and the seasonal maximum snow cover depth at 66 meteorological stations throughout Poland, spanning a period of 50 (1948–49 to 1997–98) to 108 (1895–96 to 2002–03) winter seasons. A slight decreasing trend was observed with snow cover characteristics in most of Poland during the second half of the 20th century, but no change was distinguished for the longer periods. The snow cover changes are related to circulation changes, and particularly to the increased frequency of western advection over Poland. However, the scale of the snow cover change is not proportional to the air temperature changes, which have been found in many previous studies to display an increasing statistically significant trend in winter. An increasing trend of snow cover in the last 50 winter seasons is observed in areas with abundant snow cover only, i.e. in northeastern Poland (snow cover depth) and in the mountains (snow cover duration). In lowland areas of Poland the snow cover duration indicates an 8 year periodicity. The year‐to‐year variability of snow cover has been increasing, particularly during the second half of the 20th century. Copyright © 2004 Royal Meteorological Society
Investigation of ischemia damaging action on blood serum by Raman spectroscopy method
Authors: Baranov A N , Vlasova I M , Saletsky A M
Published: October 2004

Raman spectroscopy method is applied for analysis of ischemia damaging action on serum. The registered changes of low-density lipoprotein (LDL) after brain ischemia (size increasing, density reducing) are explained in frameworks of free radical theory of oxidative stress. We confirmed by Raman spectroscopy method our hypothesis, according to which the increase in LDL size and decrease of LDL density after an ischemia, in contrast to LDL of healthy animals, is caused by loosing of LDL phospholipid monolayer under damaging action of free radicals. The obtained results show the possibility of using of Raman spectroscopy method for an estimation of ischemic damages.
Femtosecond photon echo in dye-doped polymer film at liquid nitrogen temperature
Authors: Konturov S V , Lobkov V S , Salikhov K M , Samartsev V V , Safiullin G M , Zuikov V A
Published: October 2004

The first observation is reported of the primary
femtosecond photon echo at a liquid nitrogen temperature in a
dye-doped polymer film at a wavelength of 780 nm. Echo signals
were generated by pulses with the duration of 130 fs. The echo
signal decay can not be described by a simple exponential
function. There is a fast decay region below 250-300 fs and a slow
decay region at longer time intervals. There were also detected
signals of the self-diffraction of exciting pulses on a
nonequilibrium population difference grating, induced in resonant
medium by these pulses.
Super‐resolution image reconstruction using multisensors
Authors: Ching Wai‐Ki , Ng Michael K. , Sze Kenton N. , Yau Andy C.
Published: October 2004

Super‐resolution image reconstruction refers to obtaining an image at a resolution higher than that of a camera (sensor) used in recording the image. In this paper, we present a new joint minimization model in which an objective function is set up consisting of three terms: the data fitting term, the regularization terms for the reconstructed image and the observed low‐resolution images. An alternating minimization iterative algorithm is proposed and developed to reconstruct the image. We give a convergence analysis of the alternating minimization iterative algorithm and show that it converges forH1‐norm regularization functional. Numerical examples are given to illustrate the effectiveness of the joint minimization model and the efficiency of the algorithm. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical behaviour of multigrid methods for symmetric Sinc–Galerkin systems
Authors: Ng Michael K. , Serra‐Capizzano Stefano , Tablino‐Possio Cristina
Published: October 2004

The symmetric Sinc–Galerkin method developed by Lund (Math. Comput. 1986; 47:571–588), when applied to second‐order self‐adjoint boundary value problems on d dimensional rectangular domains, gives rise to an N × N positive definite coefficient matrix which can be viewed as the sum of d Kronecker products among d − 1 real diagonal matrices and one symmetric Toeplitz‐plus‐diagonal matrix. Thus, the resulting coefficient matrix has a strong structure so that it can be advantageously used in solving the discrete system. The main contribution of this paper is to present and analyse a multigrid method for these Sinc–Galerkin systems. In particular, we show by numerical examples that the solution of a discrete symmetric Sinc–Galerkin system can be obtained in an optimal way only using O(N log N) arithmetic operations. Numerical examples concerning one‐ and two‐dimensional problems show that the multigrid method is practical and efficient for solving the above symmetric Sinc–Galerkin linear system. Copyright © 2004 John Wiley & Sons, Ltd.