bluuebunny/crossref_metadata_2025 huggingface dataset:
Extending the treatment of backbone energetics in protein force fields: Limitations of gas‐phase quantum mechanics in reproducing protein conformational distributions in molecular dynamics simulations
Authors: Mackerell Alexander D. , Feig Michael , Brooks Charles L.
Published: June 2004

Computational studies of proteins based on empirical force fields represent a powerful tool to obtain structure–function relationships at an atomic level, and are central in current efforts to solve the protein folding problem. The results from studies applying these tools are, however, dependent on the quality of the force fields used. In particular, accurate treatment of the peptide backbone is crucial to achieve representative conformational distributions in simulation studies. To improve the treatment of the peptide backbone, quantum mechanical (QM) and molecular mechanical (MM) calculations were undertaken on the alanine, glycine, and proline dipeptides, and the results from these calculations were combined with molecular dynamics (MD) simulations of proteins in crystal and aqueous environments. QM potential energy maps of the alanine and glycine dipeptides at the LMP2/cc‐pVxZ//MP2/6‐31G* levels, where x = D, T, and Q, were determined, and are compared to available QM studies on these molecules. The LMP2/cc‐pVQZ//MP2/6‐31G* energy surfaces for all three dipeptides were then used to improve the MM treatment of the dipeptides. These improvements included additional parameter optimization via Monte Carlo simulated annealing and extension of the potential energy function to contain peptide backbone ϕ, ψ dihedral crossterms or a ϕ, ψ grid‐based energy correction term. Simultaneously, MD simulations of up to seven proteins in their crystalline environments were used to validate the force field enhancements. Comparison with QM and crystallographic data showed that an additional optimization of the ϕ, ψ dihedral parameters along with the grid‐based energy correction were required to yield significant improvements over the CHARMM22 force field. However, systematic deviations in the treatment of ϕ and ψ in the helical and sheet regions were evident. Accordingly, empirical adjustments were made to the grid‐based energy correction for alanine and glycine to account for these systematic differences. These adjustments lead to greater deviations from QM data for the two dipeptides but also yielded improved agreement with experimental crystallographic data. These improvements enhance the quality of the CHARMM force field in treating proteins. This extension of the potential energy function is anticipated to facilitate improved treatment of biological macromolecules via MM approaches in general. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1400–1415, 2004
Geldanamycin induces mitotic catastrophe and subsequent apoptosis in human glioma cells
Authors: Nomura Motohiro , Nomura Naoko , Newcomb Elizabeth W. , Lukyanov Yevgeniy , Tamasdan Cristina , Zagzag David
Published: June 2004

Geldanamycin (GA) binds to heat shock protein 90 (Hsp90) and interferes with its function which is to protect various cellular proteins involved in signaling, growth control, and survival from ubiquitination and subsequent degradation by the proteasome. Recently, we demonstrated that GA inhibited migration of glioma cells in vitro associated with downregulation of hypoxia‐inducible factor (HIF‐1α) and phosphorylation of focal adhesion kinase (FAK) (Zagzag et al., 2003, J Cell Physiol 196:394–402). Here, we have investigated the mechanisms through which GA treatment of the T98G glioma cell line induces apoptosis. We found that GA treatment induced cell death in a caspase‐dependent manner through activation of caspase‐3 and PARP cleavage together with release of cytochrome c and apoptosis inducing factor (AIF) from the mitochondria. Use of synchronized T98G cells showed that GA treatment of glioma cells during S‐phase enhanced cytotoxicity followed by M‐phase arrest, resulting in mitotic catastrophe. In addition, apoptosis was associated with the downregulation of the survival protein, phosphorylated Akt (pAkt), an important signaling protein in the PI3K pathway, that is overexpressed in many cancers including gliomas. Given that many glioma tumors show deregulation of the PI3K signaling pathway, either through loss of the tumor suppressor protein PTEN or overexpression of the growth factor EGFR, the ability to identify different subsets of patients using simple immunohistochemistry for the presence of absence of pAkt could enable selection of the appropriate kinase inhibitor, such as GA, for drug therapy. Based on our data presented here, GA or its analogs may have potential in the treatment of glioma. © 2004 Wiley‐Liss, Inc.
Progression elevated gene‐3 (PEG‐3) induces pleiotropic effects on tumor progression: Modulation of genomic stability and invasion
Authors: Emdad Luni , Sarkar Devanand , Su Zao‐Zhong , Boukerche Habib , Bar‐Eli Menashe , Fisher Paul B.
Published: June 2004

Progression elevated gene‐3 (PEG‐3) is a novel rodent gene, identified and cloned by subtraction hybridization, that associates with transformation progression in virus‐ and oncogene‐transformed rat embryo (RE) cells. Previous reports document that ectopic expression of PEG‐3 in rodent or human tumor cells produces an aggressive transformed/tumorigenic phenotype. Moreover, PEG‐3 expression in rodent tumor cells correlates directly with genomic instability, as indicated by chromosomal alterations and gene amplification, and it promotes angiogenesis. The present studies were designed to further elucidate the functional significance and role of PEG‐3 in cancer progression with a specific focus on genomic instability and cancer invasion. Genomic instability was assessed by micronucleus assays and staining of centrosomes to define centrosomal amplification. Immunocytochemical observations revealed that overexpression of PEG‐3 in transformed rodent cells induced a loss of chromosomes as established by the appearance of micronuclei and staining of the centrosomes with γ‐tubulin antibody, thereby confirming centrosome amplification. Overexpression of PEG‐3 modulated the expression of several genes involved in centrosomal duplication, such as p21CIP1/WAF1/MDA‐6, nucleophosmin (NPM), and aurora‐A kinase. In vitro invasion of transformed rodent cells was augmented by PEG‐3, which correlated with an increase in the transcription and activity of matrix metalloproteinase‐2 and ‐9 (MMP‐2 and MMP‐9), which play important roles in local invasion during cancer progression. These findings demonstrate that PEG‐3 plays a central role in augmenting tumor progression by modulating several critical parameters of the carcinogenic process, such as genomic stability and local tumor cell invasion. © 2005 Wiley‐Liss, Inc.
Sea‐surface temperature and salinity changes in the northwest Pacific since the Last Glacial Maximum
Authors: Oba Tadamichi , Murayama Masafumi
Published: June 2004

The oxygen isotope records of both benthic and planktonic Foraminifera in five piston cores, collected from the region between the Oyashio and Kuroshio Currents near Japan, clearly show the marked latitudinal shifts of these two currents during the past 25 kyr. Under the present hydrographic condition, a clear relationship between the sea‐surface temperature (SST) and oxygen isotope differences from benthic to planktonic Foraminifera is observed in this region. Using this relationship, we find decreased SSTs of 12–13°C (maximum 15°C) in the southernmost core site at the Last Glacial Maximum (LGM), indicating the Oyashio Current shifted southward. The SSTs at the southern two core sites abruptly increased more than 10°C at 10–11 ka, suggesting the Kuroshio Current shifted northward over these sites at 10–11 ka. In contrast, the northern two core sites have remained under the influence of the cold Oyashio Current for the past 25 kyr. With the reasonable estimate of bottom‐water temperature decrease of 2.5°C at the LGM, the SSTs estimated by this new method give exactly the same SST values calculated from Mg/Ca ratio of planktonic Foraminifera, allowing palaeosea‐surface salinities to be reconstructed. The result suggests that the ice volume effect was 1.0 ± 0.1‰ at the LGM. Copyright © 2004 John Wiley & Sons, Ltd.
Late Neogene–Quaternary evolution of the intermontane Clusone Basin (Southern Alps, Italy): integration of seismic and geological data
Authors: de Franco R. , Berra F. , Biella G. , Boniolo G. , Caielli G. , Corsi A. , Forcella F. , Lazzati F. , Lozej A. , Morrone A. , Tondi R.
Published: June 2004

In the Clusone Basin (a large intermontane basin filled by thick late Neogene–Quaternary sediments in the Middle Val Seriana, Southern Alps), two high‐resolution seismic profiles have been acquired in order to reconstruct the geometries of the sediments that fill the depression, with a maximum thickness of more than 200 m as documented by available well data, and to define their relationships with the bedrock, consisting of Late Triassic carbonates. In addition to standard seismic reflection processing, a seismic refraction inversion technique has been applied. The integration of geological (both surface and well data) and seismic data indicates a complex history of the drainage patterns of the Clusone Basin, documenting a shift of the Serio River from a palaeodrainage toward the southeast (Val Borlezza) to the present situation, toward the south (Val Seriana): between the older and the present‐day drainages an important depositional stage occurred, as documented by the thick sediments that fill the Clusone Basin, controlling the capture of the Serio River along the Val Seriana. Copyright © 2004 John Wiley & Sons, Ltd.
Practices of managing knowledge sharing: towards a second wave of knowledge management
Authors: Huysman Marleen , de Wit Dirk
Published: June 2004

This paper presents case study findings on practices of knowledge sharing in 10 large companies, each with more than 1000 employees. All initiatives belong to the so‐called ‘first wave of knowledge management’, where the focus is on knowledge acquisition, exchange and creation by individual employees, supported by information and communications technologies and introduced by management. We found various biases and traps that seem to be general within the ‘first wave’ of managing knowledge. Based on this research, we discuss conditions of the ‘second wave of knowledge management’ that might overcome the various problems that we encountered. Copyright © 2004 John Wiley & Sons, Ltd.
Knowledge management implementation frameworks: a review
Authors: Wong Kuan Yew , Aspinwall Elaine
Published: June 2004

One reason why many organizations are still struggling with knowledge management (KM) and failing in their endeavours to realize its full potential is that they lack the support of a strong theoretical foundation to guide them in its implementation. A sound KM implementation framework helps to fulfil this need by providing important guiding principles and directions. However, developing such a framework can be a challenging task for managers and practitioners as they may lack the knowledge of what characteristics, elements and constructs should be included in it. Implementation frameworks that do not have the necessary elements in place can paint an incomplete picture of KM and its implementation process, thus providing a suboptimal guidance for conducting KM. This paper reviews the existing KM implementation frameworks presented in the literature in order to determine and propose a set of guidelines for constructing them. By utilizing these guidelines to develop a KM implementation framework, it is hoped that a stronger theoretical foundation can be constructed, thus facilitating the accomplishment of KM. Copyright © 2004 John Wiley & Sons, Ltd.
Imidazoline binding sites and their ligands: An overview of the different chemical structures
Authors: Dardonville Christophe , Rozas Isabel
Published: June 2004

Since Bousquet et al. discovered the imidazoline binding sites (IBS) two decades ago, when they realized that the antihypertensive drug clonidine interacts not only with the α2‐adrenenoceptors (α2‐AR) but also with a distinct imidazoline preferring binding site, these receptors have been paid a great deal of attention. At least two subtypes, I1 and I2, have been characterised based on their binding affinity for different radioligands, but their structures still remain unknown. The pharmacological profile of these IBSs has been the objective of several and very thorough reviews. However, a medicinal chemistry overview of the different IBS ligands prepared to date has never been attempted. In this study, we attempt to compile all the different chemical structures reported to date as IBS ligands and classify them in function of their chemical structure and binding affinity for the different IBS subtypes. Thus, we comment on the different endogenous IBS ligands known as well as the drugs described to interact with the I1‐IBS which have found application as antihypertensive drugs. Then, we review those compounds described in the literature to interact with the I2‐IBS, classifying them by their chemical families (imidazolines, guanidines, 2‐aminoimidazolines, β‐carbolines). Finally, some conclusions are drawn. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 5, 639–661, 2004
The design and performance of a new miniature mixer for specialty polymer blends and nanocomposites
Authors: Breuer Orna , Sundararaj Uttandaraman , Toogood Roger W.
Published: June 2004

A novel miniature mixer called the “Alberta Polymer Asymmetric Minimixer” (APAM) was designed, built and tested. In this study, polymer blends and nanofiber composites were compounded using a total of approximately 2 grams per sample. This mixer has a unique, asymmetric design consisting of a varying clearance between the rotor blade tips and the cup wall, enabling the material to be squeezed, stretched and kneaded in high shear and converging zones. Unlike the few other miniature mixing devices that are commercially available, the APAM has a combination of good mixing capability and complex flow modes required for dispersive flow, and requires minimal sample mass. In this work, the final morphology of non‐reactive blends created in the APAM was similar to that obtained in an internal mixer and in a twin‐screw extruder, and was much finer than that obtained in a MiniMAX™ mixer. The final morphology in reactive blends was comparable for all the mixers. The dispersion of nanofibers is uniform for the nanocomposites blended in the APAM and comparable to the dispersion obtained in the internal batch mixer, whereas for the MiniMAX™, the nanofibers remained in bundles and were not wetted by the matrix polymer. Polym. Eng. Sci. 44:868–879, 2004. © 2004 Society of Plastics Engineers.
Ejection force in tubular injection moldings. Part I: Effect of processing conditions
Authors: Pontes A. J. , Pouzada A. S.
Published: June 2004

The development and manufacture of injection molds for high quality technical parts are complex tasks involving the knowledge of the injection molding process and the material changes induced by processing. In the case of some specific shapes (boxes, tubular fittings), the shrinkage is partially restricted by the mold. The molding shrinks against the core, inserts or pins. Thus, upon ejection, it will be necessary to overcome the frictional forces resulting from the shrinkage. The knowledge of the ejection force is a useful contribution to optimizing the design of molds with these features, and to guaranteeing the structural integrity of the moldings. A study on the effect of conditions on the ejection force required for deep tubular moldings is described for the cases of three common thermoplastic polymers. The studies were based on tubular moldings (60 mm diameter, 146 mm length, and 2 mm thickness). The injection unit cell consisted of a 1 MN clamp force injection molding machine, thermal regulator, and material dryer. During processing, pressure, temperature and ejection force evolutions were recorded. The results show that the processing conditions noticeably influence the ejection force. Polym. Eng. Sci. 44:891–897, 2004. © 2004 Society of Plastics Engineers.
Semi‐interpenetrating polymer networks based on polyurethane and poly(vinyl pyrrolidone) obtained by photopolymerization: Structure‐property relationships and bacterial adhesion
Authors: Karabanova L. V. , Mikhalovska S. V. , Sergeeva L. M. , Meikle S. T. , Helias M. , Lloyd W.
Published: June 2004

A range of semi‐interpenetrating polymer networks (semi‐IPNs) based on polyurethane (PU) and poly(vinyl pyrrolidone) (PVP) have been synthesized and characterized with respect to their thermodynamic characteristics, morphology, mechanical properties, surface properties, water sorption and bacterial adhesion. The free energies of mixing of PU and PVP in semi‐IPNs have been determined by the vapor sorption method and were shown to be positive for all compositions. The surface properties of semi‐IPNs were investigated using the dynamic contact angle analysis. It was shown that the advancing contact angle changes from 83.1° to 65.3° with increasing PVP from 7.05% to 57.38%. Scanning electron microscopy demonstrated that the semi‐IPNs are two‐phase systems with incomplete phase separation. The mechanical properties reflect the changes in structure of semi‐IPNs with increasing of amounts of PVP in the system. Incorporation of PVP into the semi‐IPN with PU restricts the ability of PVP to sorb water. As infection is likely to be caused by bacterial adherence to biomedical implants, the bacterial adhesion data suggests that the semi‐IPNs with PVP content below 22.52% may be useful for biomedical material applications. Polym. Eng. Sci. 44:940–947, 2004. © 2004 Society of Plastics Engineers.
Effect of shrinkage and process parameters on the monitoring of bulk and surface stream temperatures in injection molding via the infrared waveguide method
Authors: Bendada A. , Simard Y. , Lamontagne M.
Published: June 2004

This paper analyzes for the first time the application of the infrared hollow waveguide method for the remote sensing of the temperature decay of polymer streams during injection molding. The key feature of the infrared procedure employed is its low transmission loss of the thermal energy in the mid and far infrared spectral regions. This particular advantage allows the hollow waveguide device to measure not only the bulk temperature within the polymer, as commercially available full‐core optical fiber instruments do, but also the temperature at the polymer surface. Moreover, the hollow waveguide device is able to measure quite low temperatures, which conventional thermometers cannot do either. Experimental trials have been run on a Husky injection molding press in order to investigate the effect of some process parameters and shrinkage on the bulk and surface temperature decay signals. The results showed a drastic deviation between the kinetic behaviors of the surface and bulk temperature traces throughout the injection cycle. Particularly, it was noticed that the cooling rate of the surface temperature was more affected by part shrinkage than the cooling rate of the bulk temperature. The experimental results showed also that temperatures below 60°C could be reliably measured with reasonable signal‐over‐noise ratio. Polym. Eng. Sci. 44:955–964, 2004.
The effect of long chain branching on the processability of polypropylene in thermoforming
Authors: Gotsis A. D. , Zeevenhoven B. L. F. , Hogt A. H.
Published: June 2004

Linear polypropylene was modified by reaction with peroxydicarbonates in a twin screw extruder to obtain varied degrees of long chain branching. The melt strength and the elasticity of the modified polymers were found to increase with the modification. The processability in foaming and thermoforming processes improved with branching and showed an optimum, beyond which higher degrees of long chain branching appeared not to help any further. The branched PP samples showed distinct strain hardening in the elongational viscosity, which was absent from the original linear melts. Melt strength, elasticity and strain hardening increased with the increase of the number of long chain branches on the main chain. The effect of molecular weight and molecular weight distribution of the precursor on the improvement of the processability of the polymer was examined. Polym. Eng. Sci. 44:973–982, 2004. © 2004 Society of Plastics Engineers.
Assessing factors for reliable quantitative proteomics based on two‐dimensional gel electrophoresis
Authors: Fiévet Julie , Dillmann Christine , Lagniel Gilles , Davanture Marlène , Negroni Luc , Labarre Jean , de Vienne Dominique
Published: June 2004

We statistically analysed various factors to get accurate estimates of protein quantities from two‐dimensional gels. Yeast proteins were labelled with 35S or stained with Coomassie Brilliant Blue G‐250, and spots were automatically quantified with software packages Kepler, ImageQuaNT, Melanie 3.0 and Progenesis. The different software packages proved to have very similar performances. With 35S‐labelled actin spot as a reference, we studied the staining efficiency of colloidal Coomassie blue as a function of amino acid composition of the protein, and derived an equation to estimate the number of molecules per cell from blue‐stained proteins. Absolute quantification of most glycolytic enzymes was carried out in two yeast strains.
Comparative proteome analysis of Hansenula polymorpha DL1 and A16
Authors: Kim Yang‐Hoon , Han Kyung Yeon , Lee Kibeom , Heo Joo‐Hyung , Kang Hyun Ah , Lee Jeewon
Published: June 2004

Proteomic responses of methylotrophic yeasts (Hansenula polymorpha DL1 and A16) to growth medium tuning by carbon source shift (glycerol→methanol) were monitored and analyzed by two‐dimensional gel electrophoresis. Through comparative analyses of two‐dimensional gels, intracellular yeast proteins with complex expression patterns were systematically sorted into: (1) proteins that are commonly expressed with comparable high abundance in both strains; (2) strain‐specific proteins that are expressed at high level only in a particular strain; (3) strain‐specific and methanol‐induced proteins that are expressed only in the presence of methanol; and (4) strain‐specific and constitutively‐expressed proteins that are expressed consistently irrespective of carbon source shift without extreme change in expression level. Among the DL1‐specific proteins belonging to group four, the four proteins showing the highest expression levels in the course of the fermentation process were identified as: glucose‐6‐phosphate dehydrogenase, isocitrate lyase, succinyl‐CoA synthetase, and glycerol‐3‐phosphate dehydrogenase. From these results, it is suggested that DL1 has distinct metabolic characteristics including enhanced metabolic activities both in glycerol uptake and the glyoxylate bypass cycle, as compared to A16. This is likely to explain why the DL1 strain shows a significantly higher rate of glycerol and methanol consumption during the fermentation process. Our systematic approach to the analysis of proteomic responses and the detailed analysis results reported here will be useful to better understand the global physiology of H. polymorpha, as proteome databases for various methylotrophic yeasts are established.
Focal‐point anchoring: Large proton relaxivity observed for gadolinium‐cored dendrimer complexes in water
Authors: Kawa Manabu , Takahagi Takayuki
Published: June 2004

Water‐soluble Gd3+‐cored poly(ether amide) dendrimer complexes, bearing a diethylenetriaminepentaacetic acid Gd3+ complex (GdDTPA) core, were synthesized. The longitudinal proton relaxivity (R1), governed mainly by the rotation correlation time of the paramagnetic Gd3+ center, was measured in water (37 °C, 20 MHz). An anchor effect at the focal point of the hydrophilic dendrimer was experimentally evaluated for the first time, through a comparison of the R1 values with the ones reported for various Gd3+ complexes, including linear copolymers of GdDTPA linked by various lengths of aliphatic chains via amide bonds. Unusually large R1 values for the first‐ and second‐generation Gd3+‐cored dendrimer complexes (6.1 and 9.3 mM−1 s−1, respectively), even with relatively low molecular weights (1355 and 3877, respectively), suggested a remarkable increase in the local rigidity around the GdDTPA core. The internal rigidity of the dendrimer was supposed to take advantage of the increased nominal molecular weight in water via multihydration to the dendron to increase the rotation correlation time, and this resulted in the observed R1 gain. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2680–2689, 2004
Small molecule matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry using a polymer matrix
Authors: Soltzberg Leonard J. , Patel Pina
Published: June 2004

We have employed a light‐absorbing electrically conductive polymer as a matrix to determine the molecular mass of small organic molecules using matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. This method, which is in contrast to the usual MALDI strategy for matrix selection in which a small molecule matrix is used with a high molecular mass analyte, addresses the problem of matrix interference which limits the usefulness of MALDI‐TOF for small molecule analysis. Use of negative ion mode offers advantages for this application. Using this approach, we have obtained clean molecular ion mass spectra of small organic molecules in the mass range 100–300 Da. Copyright © 2004 John Wiley & Sons, Ltd.
Water formation from O2 and H2 on Rh tips: studies by field ion microscopy and pulsed field desorption mass spectrometry
Authors: Visart de Bocarmé Thierry , Beketov Gennadiy , Kruse Norbert
Published: June 2004

The catalytic oxidation of hydrogen on Rh tips was investigated using field ion microscopy and pulsed field desorption mass spectrometry (PFDMS). The reaction was carried out in the 10−3 Pa range at 400–600 K. In a first series of experiments, emphasis was laid on revealing tip morphologies during the ongoing water formation. At a reaction temperature of 500 K, remarkable similarities with the previously studied pure oxygen case were found. Accordingly, a polyhedral tip shape with missing‐row‐type reconstruction on {011} and {113} planes was formed. In a second series of experiments, the gas mixture was varied to demonstrate the occurrence of local structural changes as well as multistability in the surface reaction at temperatures between 400 and 500 K and viewing fields of 10 V nm−1. A phase diagram was established within this temperature range. At 550 K and 9 V nm−1, self‐sustained kinetic oscillations with cycles of ∼40 s were observed in a continuous flow of O2H2 (pO2 = 1.0 × 10−3 Pa and pH2 = 1.3 × 10−3 Pa). Using PFDMS, ∼400 atomic sites close to the central (001) pole of the Rh tip were probed with varying pulse heights. During imaging in a wide range of H2O2 gas mixtures it was found that water ionization causes formation of the field ion image, leading to the conclusion that brightness analysis is suitable for measuring the local catalytic activity. On the oxygen side of the phase diagram, water molecules were formed on an oxidized surface so that RhO2+, RhO+ and Rh2O+ appeared in the mass spectra. On the other hand, by increasing the H2 pressure, the surface oxide was reacted off within ∼0.1 s, thereby leaving a relatively dark surface (H‐side of the diagram). Chemical probing in the latter case demonstrated fast water formation leaving few oxygens on the surface, i.e. negligible RhxOn+ amounts appeared in the mass spectra. Copyright © 2004 John Wiley & Sons, Ltd.
Nanostructural evolution of Al3Sc precipitates in an AlScMg alloy by three‐dimensional atom probe microscopy
Authors: Marquis Emmanuelle A. , Seidman David N.
Published: June 2004

The effects of Mg alloying on the precipitation of Al3Sc precipitates were investigated, focusing on nanostructural evolution during isothermal aging at 300°C. Three‐dimensional atom probe microscopy was performed on samples both in the as‐quenched state and after aging for various times. Magnesium tends to segregate at the coherent Al/Al3Sc interface, with a measured value of 1.9 ± 0.5 atom nm−2 for the relative Gibbsian excess of Mg with respect to Al and Sc. This value is constant for all heat treatments, thereby demonstrating that the system is in global thermodynamic equilibrium. This study provides direct experimental evidence for first‐principles calculations, which explain morphological changes of Al3Sc precipitates in the presence of Mg observed by high‐resolution electron microscopy. Evidence for the presence of Mg atoms in the center of the precipitates is also found, and is discussed in terms of heterogeneous nucleation of the precipitates on MgSc atomic clusters. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical analysis of liquid metal flow in the presence of an electric field: application to liquid metal ion source
Authors: Suvorov Vasily G.
Published: June 2004

Two‐dimensional axisymmetric flow of a viscous, incompressible liquid metal with a free boundary subject to the action of an electric field is investigated in the context of liquid metal ion source operation. It is established that an almost flat surface evolves with time into a cone‐like shape, with the cone angle equal to Taylor's static value of 98.6°. The growth time of the Taylor cone and the time‐dependent behaviour of basic physical quantities (electric field strength, fluid velocity and surface curvature) near the cone apex are studied. A possible physical explanation of the effect of globule formation on the supporting needle of the liquid metal ion source has been put forward. The simulation is based on the method of adaptive numerical grid generation. Copyright © 2004 John Wiley & Sons, Ltd.
Characterization of precipitates in an aged 7xxx series Al alloy
Authors: Sha Gang , Cerezo Alfred
Published: June 2004

Precipitates in a 7050 Al alloy under two‐step ageing treatments were characterized using an energy‐compensated optical position‐sensitive atom probe and transmission electron microscopy. Selected‐area diffraction analyses indicated that the early‐stage precipitates present after a stabilization ageing treatment at 121°C for 4 h have a crystallographic structure similar to η′, but probably rich with defects. After T6 treatment ageing at 121°C for 24 h followed by 12 h at 154°C, η′ and η coexist within the Al matrix. Energy‐compensated optical position‐sensitive atom probe analysis was used to measure the partitioning of Zn, Mg and Cu to the precipitates. Early‐stage precipitates in the alloy after stabilization treatment have a Zn/Mg ratio of ∼1.3 and a (Zn + Cu)/Mg ratio of 1.4. The T6‐aged alloy contained η precipitates with an Zn/Mg ratio of ∼1.2 and a (Zn + Cu)/Mg ratio of 1.3 coexisting with η′ precipitates with a Zn/Mg ratio of ∼0.7 and a (Zn + Cu)/Mg ratio of ∼1. Copyright © 2004 John Wiley & Sons, Ltd.
Nanoscale studies of segregation at coherent heterophase interfaces in α‐Fe based systems
Authors: Isheim Dieter , Seidman David N.
Published: June 2004

Heterophase interfaces are characterized with respect to atomic‐scale local compositions in two α‐Fe‐based alloy systems by three‐dimensional atom probe microscopy. The proximity histogram method is utilized for determining the compositions of the precipitates, the matrix phase and the Gibbsian interfacial excess of solute. Suitable methods to measure segregation in multicomponent systems at heterophase interfaces independent of the position of the dividing interface are discussed. Very little Sb segregates to the heterophase interface between coherent plate‐shaped moybdenum nitride precipitates, which are <1 nm thick, and the α‐Fe matrix: the relative interfacial excess of Sb is only 0.12 ± 0.1 nm−2. This is in sharp contrast to the interfacial excess of 7 ± 3 nm−2 for molybdenum nitride plates that have grown to 2–10 nm thick (or 20–30 nm in diameter for spheroidal precipitates) with a semicoherent interface with misfit dislocations, as reported earlier. Small coherent Cu‐rich precipitates with a metastable bcc structure in an α‐Fe matrix exhibit interfacial segregation of Ni and Mn at their interfaces with excesses of 1.47 ± 0.43 and 0.95 ± 0.31 nm−2, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Precipitation of niobium carbides in Fe–C–Nb steel
Authors: Bémont E. , Cadel E. , Maugis P. , Blavette D.
Published: June 2004

The precipitation of carbides in Fe–C–Nb alloy has been investigated using field ion microscopy and atom probe tomography. Analyses show that niobium carbide precipitates already exist in the state quenched from 1240°C. Detailed structural analysis of the states aged at 750°C reveals the existence of two types of niobium carbide precipitates with different concentrations of carbon. In addition, the direction of the habit plane for the matrix/niobium carbide interface has been determined. Copyright © 2004 John Wiley & Sons, Ltd.
Dependence of interfacial excess on the threshold value of the isoconcentration surface
Authors: Yoon Kevin E. , Noebe Ronald D. , Hellman Olof C. , Seidman David N.
Published: June 2004

The proximity histogram (or proxigram for short) is used for analyzing data collected by a three‐dimensional atom probe microscope. The interfacial excess of Re (2.41 ± 0.68 atoms nm−2) is calculated by employing a proxigram in a completely geometrically independent way for γ/γ′ interfaces in René N6, a third‐generation single‐crystal Ni‐based superalloy. A possible dependence of interfacial excess on the variation of the threshold value of an isoconcentration surface is investigated using the data collected for René N6 alloy. It is demonstrated that the dependence of the interfacial excess value on the threshold value of the isoconcentration surface is weak. Copyright © 2004 John Wiley & Sons, Ltd.
Application of nanocarbon cold cathodes in lighting elements
Authors: Obraztsov A. N. , Volkov A. P. , Petrushenko Yu. V. , Satanovskaya O. P.
Published: June 2004

We have manufactured cathodoluminescent lamps equipped with field emitters composed of carbon nanotubes and nanosized graphite crystallites. The nanocarbon film material was obtained by chemical vapour deposition onto Si and Ni substrates and was used as grown in the vacuum light‐emitting devices. Various light‐emitting arrangements were realized, showing wide possibilities for different applications, including flat panel displays, indicators and light signs. A record power efficiency of >30% was achieved for the cylindrical diode lamps with nanocarbon cold cathodes. This shows their suitability as lighting elements. Copyright © 2004 John Wiley & Sons, Ltd.
Influence of electron irradiation on the microstructure of ferritic model alloys
Authors: Radiguet B. , Pareige P. , Barbu A.
Published: June 2004

Understanding the mechanisms at the origin of radiation embrittlement is of great interest for predicting the evolution of reactor vessel steel during nuclear power plant running. To examine the behaviour of different solutes under irradiation, electron irradiation has been performed with a Van de Graff accelerator on two model alloys (Fe–0.1%Cu and Fe–1.5%Mn–0.8%Ni–0.12%Cu–0.01%P) and a commercial steel. The nanostructure of these materials has been characterized by atom probe techniques before and after irradiation. The results show the influence of the copper content of the material on the formation of copper‐rich clusters and also the behaviour of phosphorus under irradiation. Comparison between these results and results on ion irradiation determines the influence of the way in which point defects are created (isolated Frenkel pairs or displacement cascades) on the ability of copper atoms to gather. Copyright © 2004 John Wiley & Sons, Ltd.
Plasma CVD characterization of nanocarbon film growth
Authors: Obraztsov A. N. , Zolotukhin A. A. , Ustinov A. O. , Volkov A. P.
Published: June 2004

We report on the characterization of d.c. discharge plasma‐enhanced chemical vapour deposition of nanocarbon film materials in a hydrogen–methane gas mixture. The effects of the gas composition and pressure on the current–voltage characteristics and optical emission spectra of the discharge plasma are studied. By varying the parameters we obtain various carbon thin‐film materials, the structure and composition of which are characterized qualitatively by Raman spectroscopy and electron microscopy. The data obtained by optical emission spectroscopy show the presence of H, H2, CH and C2 activated species in the discharge plasma. We assume that C2 dimers play a decisive role in nanostructured graphite‐like carbon film formation and carbon condensation in the gas phase. Copyright © 2004 John Wiley & Sons, Ltd.
Acid treatment of carbon nanofibres with encapsulated catalytic iron nanoparticles
Authors: Wu P. , Deng S. Z. , Chen Jun , She J. C. , Xu N. S.
Published: June 2004

Acid treatment was used to remove the Fe nanoparticles encapsulated in the carbon nanofibres grown by thermal chemical vapour deposition. Transmission electron microscopy was used to determine the structure of the carbon nanofibres. Field emission scanning electron microscopy and x‐ray energy‐dispersive spectroscopy were employed to analyse the effect of the treatment. It was found that treatment with HCl can partially remove the Fe nanoparticles on tips. Treatment using a mixture of HNO3 and H2SO4 is an effective way to remove the Fe nanoparticles on tips. Also, the tips of carbon nanofibres having Fe nanoparticles seem to be more stable against O2 plasma etching than the bodies of the carbon nanofibres. Copyright © 2004 John Wiley & Sons, Ltd.
Radikalidentifizierung auf Polymeren nach Plasmabehandlung. Radical Identification on Polymers after Plasma Treatment
Authors: Meyer‐Plath Asmus
Published: June 2004

Radikale bilden den Ausgangspunkt für Reaktionen chemisch inerter Polymere. So kann der Einbau funktioneller chemischer Gruppen in eine Polymeroberfläche über Reaktionen mit funktionsgruppentragenden Partnern erfolgen, wenn die Oberfläche, die Reaktionspartner oder beide über Radikalcharakter verfügen. Dabei bestimmt die Reaktivität und Dichte der Radikale auf der Polymeroberfläche die Effizienz des Funktionalisierungsprozesses entscheidend mit. Nach dessen Abschluß erlangen nicht‐abgesättigte Radikale, d. h. solche, die nicht an der Kopplungsreaktion teilgenommen haben, besondere Bedeutung. Sie können noch mit Luftsauerstoff zu Peroxiden reagieren und anschließend zu einer (unbeabsichtigten) Sekundärfunktionalisierung der Oberfläche mit allen denkbaren Arten sauerstoffhaltiger Gruppen führen. Aus diesen Gründen gewinnt der Nachweis von Radikalen auf Polymeroberflächen für derzeit in der Entwicklung befindliche Ansätze der hocheffizienten und/oder hoch einheitlichen Oberflächenfunktionalisierung zunehmend an Bedeutung. Es werden daher wichtige Verfahren zur Quantifizierung von Oberflächenradikalen vorgestellt. Ferner wird ein neuer Ansatz zur Ausrüstung von Polymeroberflächen mit Radikalen vorgestellt, die dann ihrerseits Ausgangspunkt von Funktionalisierungsreaktionen sein können.
Sol‐Gel Technik zur Realisierung von funktionellen Beschichtungen. Sol‐gel technique for preparation of functional coatings
Authors: Mahltig Boris
Published: June 2004

Die Sol‐Gel Technik ermöglicht die einfache Herstellung transparenter und gut haftender Metalloxidfilme (z. B. Siliciumoxid) auf einer Vielzahl von Materialien. Als Beschichtungsmittel dienen flüssige Nanosole, welche nach Trocknung und Temperung dünne transparente Gelfilme ausbilden. Durch chemische oder physikalische Modifizierung der Nanosole ist eine nahezu unbegrenzte Vielfalt an Materialvariationen und somit an Möglichkeiten zur Funktionalisierung der Schichteigenschaften gegeben. Potentielle Möglichkeiten und beispielhafte Ergebnisse zur Funktionalisierung von Oberflächen werden vorgestellt.
Endoscopic Management of Early Postoperative Biliary Ascariasis in Patients with Biliary Tract Surgery
Authors: Zargar Showkat Ali , Khan Bashir Ahmad , Javid Gul , Yattoo Ghulam Nabi , Shah Altaf Hussain , Gulzar Ghulam Mohammad , Singh Jaswinder , Khan Mushtaq Ahmad , Shah Nisar Ahmad
Published: June 2004

Bile leak and residual stones are well known complications of biliary tract surgery. In endemic areas of ascariasis, invasion of the biliary tract by roundworms during the early postoperative period is an infrequent but serious complication. The present study describes the endoscopic management of postoperative biliary ascariasis in 19 consecutive patients. There were 5 men and 14 women with a mean age of 33.3 ± 6.3 years. All patients had undergone cholecystectomy, with choledocholithotomy and placement of a T‐tube in 13 (68.4%) patients. Eight (42.1%) patients including two with T‐tubes were acutely sick at referral. Altogether, 16 (84.2%) patients had widened papillae due to previous endoscopic sphincterotomy (3 patients) or recent dilatation of the sphincter of Oddi by Bake’s dilators (13 patients). All patients with a T‐tube in situ had undergone unsuccessful attempts to remove the worms by flushing saline through the T‐tube. Endoscopic retrograde cholangiopancreatography was performed 4 to 16 days after biliary tract surgery and revealed roundworms in the common bile duct in 10 patients, in the hepatic ducts in 2, or in both ducts in 7. Three patients had coexisting biliary leakage: from the cystic duct stump in two and from a T‐tube track in one. Endoscopic treatment consisted of extracting the worms from the biliary tree and placing stents in those with coexisting leakage. Endoscopic success was defined as complete worm extraction and resolution of biliary leakage and was achieved in all patients. Complications occurred in one (5.3%) patient. We concluded that endoscopic management is an effective, safe approach for extracting ascarids from the biliary tree during the early postoperative period. It reduces the hospital stay, avoids T‐tube‐related complications, and permits a postoperative complication to be treated using a nonsurgical method.
Microscopic Liver Metastasis: Prognostic Factor for Patients with pT2 Gallbladder Carcinoma
Authors: Endo Itaru , Shimada Hiroshi , Takimoto Atsushi , Fujii Yoshiro , Miura Yasuhiko , Sugita Mitsutaka , Morioka Daisuke , Masunari Hideki , Tanaka Kuniya , Sekido Hitoshi , Togo Shinji
Published: June 2004

Hepatic metastasis is the most frequent mode of recurrence of advanced gallbladder cancer after radical resection. The aims of this study were to clarify the clinical significance of microscopic liver metastasis from pT2 gallbladder cancer and to clarify whether partial hepatectomy can prevent hepatic recurrence in patients with microscopic liver metastasis. The subjects included 20 patients with pT2 tumors who underwent radical surgery and partial hepatectomy with lymph node dissection. Microscopic liver metastasis was defined as a distant metastatic nodule including cancer cell nests in the lumen of the portal vein and discrete nodular lesions in the liver, all less than 5 mm in diameter. Cox’s proportional hazard regression was used to analyze factors that contributed to outcomes. Microscopic metastases were detected in the resected livers from 5 of 20 patients. There were more metastatic lesions within 1 cm of the gallbladder bed than were located 1 to 2 cm away from it. Microscopic liver metastases showed a strong correlation with the extent of blood vessel invasion around the primary tumor and were frequently detected in patients with a primary tumor localized on the hepatic side and with more than 3 cm of subserosal invasion. In four of five patients with microscopic liver metastases, recurrence was found in the remnant liver, which led to death within 15 months after the initial operation. Microscopic liver metastasis, operative curability, and lymph node metastasis were assessed as independent prognostic factors. A large proportion of patients with microscopic liver metastasis suffered from hepatic recurrence. Our results suggest that partial hepatectomy alone cannot prevent hepatic recurrence in patients with microscopic liver metastasis.
Changes in Liver Enzymes after Surgery in Anti‐Hepatitis C Virus‐positive Patients
Authors: Murakami Saburo , Okubo Katsuhiko , Tsuji Yoshitaka , Sakata Hideto , Takahashi Takehiro , Kikuchi Masataka , Hirayama Renzo
Published: June 2004

The aim of this study was to assess the influence of surgical intervention on changes in liver enzymes in patients with antibodies to hepatitis C virus (HCV). Of 623 patients who underwent laparotomy in our department during the 2 years between January 2000 and December 2001, a group of 39 (6.3%) who were positive for the HCV antibody were enrolled in this study. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and cholinesterase (ChE) were the standard liver tests performed. The antibody to HCV was measured in serum using an ELISA kit that can detect antibodies against the combined epitopes. The postoperative elevated values of AST and ALP in the anti‐HCV‐positive group were significantly higher than those in the anti‐HCV‐negative group (p < 0.05). The postoperative decreased values of ChE in the anti‐HCV‐positive group were significantly greater than those in the anti‐HCV‐negative group (p < 0.02). The postoperatively decreased ratios of ChE in the anti‐HCV positive group were significantly greater than those in the anti‐HCV negative group (p < 0.0001). Using multivariate logistic regression modeling, testing positive for the antibody to HCV was independently and significantly associated with abnormal levels of ALT and ALP (p = 0.035 and 0.018, respectively). Monitoring liver enzymes such as ChE, ALT, and ALP might be effective for evaluating liver function after surgery in anti‐HCV‐positive patients.
Acid phosphatase activity in gerbil prostate: comparative study in male and female during postnatal development
Authors: Custódio Maria Galvan Ana , Góes Maira Rejane , Taboga Roberto Sebastião
Published: May 2004

The prostate is present in both male and female mammals. It is composed of secretory epithelium, connective stroma, smooth muscle and neuroendocrine cells, which are under hormonal regulation. Acid phosphatases catalyze the hydrolysis of orthophosphate monoesters. We have compared the expression of acid phosphatases in gerbil (Meriones unguiculatus) prostate glands in both sexes using young, adult and old animals. Eighteen prostates were isolated, frozen, sectioned, fixed, incubated with sodium β‐glycerophosphate sodium, washed with acetate buffer solution, treated with ammonium sulfide and counterstained with Methyl‐Green aqueous solution. Ultracytochemical analyses were also conducted. This substrate revealed total acid phosphatase activity. The expression of the enzyme was heterogeneous, occurring in all ages during postnatal development. The data revealed that the female prostate matured before the male prostate. In addition, acid phosphatase activity in both sexes was regulated by androgen variation concomitant with development.