bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ettringit‐ und Thaumasittreiben in Betonwerkstoffen: Analytische Betrachtung und Ursachenermittlung mittels Röntgendiffraktometrie und Rasterelektronenmikroskopie
Authors: Göske Jürgen , Pöllmann Herbert , Wenda Richard 
Published: April 2007

AbstractSeit einigen Jahren werden vermehrt Bauschäden an Betonbauwerken beobachtet, die auf Treiberscheinungen infolge von Ettringit‐ und Thaumasit‐ Kristallisation rückzuführen sind. Die Ursachen hierfür sind meistens mineralische Treiberscheinungen. Als Maßnahme gegen derartige Angriffe werden sulfatbeständige Zemente eingesetzt, die sich durch besonders niedrigen C3A‐Gehalt auszeichnen (d. h. entsprechend wenig Aluminat für die Ettringit‐Bildung enthalten). Trotzdem kam es in letzter Zeit zu Langzeitschäden an Betonbauwerken durch Sulfatangriff, die auf Thaumasit‐Bildung zurückgeführt werden. Mit Hilfe von Röntgendiffraktometrie, Rasterelektronenmikroskopie und energiedispersiver Röntgenspektroskopie konnten an prädestinierten Schadensfällen die hierfür ursächlichen mineralischen Phasen zweifelsfrei analysiert, identifiziert und in den Betonwerkstücken lokalisiert werden.
Elucidation of the mechanism and end products of glutaraldehyde crosslinking reaction by X‐ray structure analysis
Authors: Wine Yariv , Cohen‐Hadar Noa , Freeman Amihay , Frolow Felix 
Published: April 2007

AbstractGlutaraldehyde has been used for several decades as an effective crosslinking agent for many applications including sample fixation for microscopy, enzyme and cell immobilization, and stabilization of protein crystals. Despite of its common use as a crosslinking agent, the mechanism and chemistry involved in glutaraldehyde crosslinking reaction is not yet fully understood. Here we describe feasibility study and results obtained from a new approach to investigate the process of protein crystals stabilization by glutaraldehyde crosslinking. It involves exposure of a model protein crystal (Lysozyme) to glutaraldehyde in alkaline or acidic pH for different incubation periods and reaction arrest by medium exchange with crystallization medium to remove unbound glutaraldehyde. The crystals were subsequently incubated in diluted buffer affecting dissolution of un‐crosslinked crystals. Samples from the resulting solution were subjected to protein composition analysis by gel electrophoresis and mass spectroscopy while crosslinked, dissolution resistant crystals were subjected to high resolution X‐ray structural analysis. Data from gel electrophoresis indicated that the crosslinking process starts at specific preferable crosslinking site by lysozyme dimer formation, for both acidic and alkaline pH values. These dimer formations were followed by trimer and tetramer formations leading eventually to dissolution resistant crystals. The crosslinking initiation site and the end products obtained from glutaraldehyde crosslinking in both pH ranges resulted from reactions between lysine residues of neighboring protein molecules and the polymeric form of glutaraldehyde. Reaction rate was much faster at alkaline pH. Different reaction end products, indicating different reaction mechanisms, were identified for crosslinking taking place under alkaline or acidic conditions. Biotechnol. Bioeng. 2007;98:711–718. © 2007 Wiley Periodicals, Inc.
Proteome analysis of antibody‐producing CHO cell lines with different metabolic profiles
Authors: Pascoe Deborah E. , Arnott David , Papoutsakis Eleftherios T. , Miller William M. , Andersen Dana C. 
Published: April 2007

AbstractTwo‐dimensional gel electrophoresis and tandem mass spectrometry were used to identify proteins associated with a metabolic shift during fed‐batch cultures of two recombinant antibody‐producing CHO cell lines. The first cell line underwent a marked change in lactate metabolism during culture, initially producing lactate and then consuming it, while the second cell line produced lactate for a similar duration but did not later consume it. The first cell line displayed a declining specific antibody productivity during culture, correlating to the 2‐D gel results and the intracellular antibody concentration determined by HPLC. Several statistical analysis methods were compared during this work, including a fixed fold‐change criterion and t‐tests using standard deviations determined in several ways from the raw data and mathematically transformed data. Application of a variance‐stabilizing transformation enabled the use of a global empirical standard deviation in the t‐tests. Most of the protein spots changing in each cell line did not change significantly in the other cell line. A substantial fraction of the changing proteins were glycolytic enzymes; others included proteins related to antibody production, protein processing, and cell structure. Enolase, pyruvate kinase, BiP/GRP78, and protein disulfide isomerase were found in spots that changed over time in both cell lines, and some protein changes differed from previous reports. These data provide a foundation for future investigation of metabolism in industrially relevant mammalian cell culture processes, and suggest that along with differences between cell types, the proteins expressed in cultures with low lactate concentrations may depend on how those conditions were generated. Biotechnol. Bioeng. 2007;98: 391–410. © 2007 Wiley Periodicals, Inc.
A genetic time‐delay circuitry in mammalian cells
Authors: Weber Wilfried , Kramer Beat P. , Fussenegger Martin 
Published: April 2007

AbstractGene expression circuitries with time‐delayed expression profiles regulate key events, such as oscillating systems, noise elimination, and coordinated multi‐step processes, in all organisms from bacteria to mammalian cells. We present the rational synthesis of a genetic circuit displaying time‐delayed expression in silico and in mammalian cells. The network is based on a time‐delay circuit, where the tetracycline‐responsive transactivator (tTA) induces expression of the pristinamycin‐responsive repressor PIP‐KRAB, which silences expression of the terminal human placental secreted alkaline phosphatase (SEAP). While the addition of pristinamycin I inactivates PIP‐KRAB and results in the immediate resumption of SEAP expression, addition of tetracycline abolishes PIP‐KRAB synthesis. Consequently, SEAP production remains repressed until the PIP‐KRAB buffer in the cell is eliminated. We characterized in silico and in vivo the time‐delayed expression properties and analyzed the impact of the size and stability of the PIP‐KRAB buffer on fine‐tuning of the response kinetics. This tunable time‐delay circuitry represents a biologic building block for emulating a fundamental circuit topology in integrated artificial synthetic gene networks for the design of tailor‐made cell types and organisms. Biotechnol. Bioeng. 2007;98: 894–902. © 2007 Wiley Periodicals, Inc.
Effect of moderate electric field on the metabolic activity and growth kinetics of Lactobacillus acidophilus
Authors: Loghavi L. , Sastry S.K. , Yousef A.E. 
Published: April 2007

AbstractModerate electric fields (MEF), applied across microbial growth media may potentially affect the permeability of cell membranes. We investigated the effects of MEF on bacteriocin (lacidin A) production during fermentation and on microbial growth kinetics of Lactobacillus acidophilus OSU 133. We comparatively investigated the following treatments: conventional, MEF (1 V/cm, 60 Hz, for 40 h), combinations of MEF (1 V/cm, 60 Hz, for the first 5 h) and conventional fermentation (for 35 h), and discrete MEF (1 V/cm, 2 min on and off, for 40 h). In all treatments, except as noted below, temperature was set at 30°C. The two exceptions were control (conventional) and discrete MEF treatment, which were conducted both at 30 and 37°C. MEF treatments at the early stage of fermentation at 30°C showed the maximum bacteriocin activity. Minimum bacteriocin production was observed under conventional fermentation at 37°C. A mathematical model based on Monod growth kinetics was used to predict bacteriocin production and showed results consistent with conventional treatment data. MEF did not have a significant effect on the lag time, maximum specific growth rate, biomass production and pH change under the different experimental conditions at each specific temperature. Based on the observations, bacteriocin activity under the presence of MEF at the early stage of fermentation increased without significant change in the final biomass. Biotechnol. Bioeng. 2007; 98: 872–881. © 2007 Wiley Periodicals, Inc.
Size comparison between proteins PEGylated with branched and linear poly(ethylene glycol) molecules
Authors: Fee Conan J. 
Published: April 2007

AbstractTherapeutic proteins conjugated with branched poly(ethylene glycol) (PEG) have extended in vivo circulation half‐lives compared to linear PEG‐proteins, thought to be due partly to a greater hydrodynamic volume of branched PEG‐proteins, which reduces the glomerular sieving coefficient. In this paper, viscosity radii of PEGylated α‐lactalbumin (Mr = 14.2 kDa) and bovine serum albumin (Mr = 67 kDa) prepared with linear and branched PEGs (with nominal molecular weights 5, 10, 20 and 40 kDa) were compared experimentally using size exclusion chromatography (SEC). PEG adduct:protein molecular weight ratios of the PEGylated proteins covered the range 1:12 to 6:1. Direct comparisons of experimentally measured viscosity radii were found to be misleading due to differences between actual and nominal molecular weights of the PEG reagents used. Comparison with predicted viscosity radii shows that there is no significant difference between the viscosity radii of branched and linear PEG‐proteins having the same total molecular weight of PEG adducts. Therefore, longer in vivo circulation half‐lives of branched PEG‐proteins compared to linear PEG‐proteins are not explained by size difference. It is also calculated that the molecular size cut‐off for glomerular filtration, 60 Å for a 30 kDa PEG, matches the 30–50 Å size range for the pores of the glomerular basement membrane. Finally, it is confirmed that prediction of PEG‐protein viscosity radii should be based upon conservation of the total PEG adduct surface area to volume ratio for both linear and branched PEG‐proteins regardless of PEGylation extent. Biotechnol. Bioeng. 2007;98: 725–731. © 2007 Wiley Periodicals, Inc.
A novel solid–liquid two‐phase partitioning bioreactor for the enhanced bioproduction of 3‐methylcatechol
Authors: Prpich George P. , Daugulis Andrew J. 
Published: April 2007

AbstractThe bioproduction of 3‐methylcatechol from toluene via Pseudomonas putida MC2 was performed in a solid–liquid two‐phase partitioning bioreactor with the intent of increasing yield and productivity over a single‐phase system. The solid phase consisted of HYTREL™, a thermoplastic polymer that was shown to possess superior affinity for the inhibitory 3‐methylcatechol compared to other candidate polymers as well as a number of immiscible organic solvents. Operation of a solid–liquid biotransformation utilizing a 10% (w/w) solid (polymer beads) to liquid phase ratio resulted in the bioproduction of 3‐methylcatechol at a rate of 350 mg/L‐h, which compares favorably to the single phase productivity of 128 mg/L‐h. . HYTREL™ polymer beads were also reconstituted into polymer sheets, which were placed around the interior circumference of the bioreactor and successfully removed 3‐methylcatechol from solution resulting in a rate of 3‐methylcatechol production of 343 mg/L‐h. Finally, a continuous biotransformation was performed in which culture medium was circulated upwards through an external extraction column containing HYTREL™ beads. The design maintained sub lethal concentrations of 3‐methylcatechol within the bioreactor by absorbing produced 3‐methylcatechol into the polymer beads. As 3‐methylcatechol concentrations in the aqueous phase approached 500 mg/L the extraction column was replaced (twice) with a fresh column and the process was continued representing a simple and effective approach for the continuous bioproduction of 3‐methylcatechol. Recovery of 3‐methylcatechol from HYTREL™ was also achieved by bead desorption into methanol. Biotechnol. Bioeng. 2007; 98: 1008–1016. © 2007 Wiley Periodicals, Inc.
Peptide Derivatized Lamellar Aggregates as Target‐Specific MRI Contrast Agents
Authors: Tesauro Diego , Accardo Antonella , Gianolio Eliana , Paduano Luigi , Teixeira José , Schillén Karin , Aime Silvio , Morelli Giancarlo 
Published: April 2007

AbstractThe relaxivity behaviour and the structural characterization of new supramolecular aggregates (bilayer structures and micelles) obtained by combining two different amphiphilic monomers are reported. One monomer, (C18)2DTPAGlu‐Gd, contains a very stable gadolinium complex, and the other, DSPE‐PEG2000‐CCK8, contains the bioactive CCK8 peptide. Samples that contained only DSPE‐PEG2000‐CCK8, or up to 50 % (C18)2DTPAGlu‐Gd, aggregated as double‐layer structures (lamellar aggregates) with a thickness of∼80–100 Å, as evaluated by SANS measurement and Cryo‐TEM imaging. A transition to micelle formation was observed when the amount of (C18)2DTPAGlu‐Gd in the aggregate was increased. These were rod‐like micelles ∼40 Å in radius and >200 Å in length. The proton relaxivities for both lamellar aggregates and rod‐like micelles were the same (17.2 mM−1 s−1), although the values were the results of different combinations of local and global contributions. The in vitro target selectivity of aggregates that contained the CCK‐8 peptide was demonstrated by using nuclear medicine techniques.
Der Ölmarkt in Turbulenzen
Authors: Proidl H. 
Published: April 2007

AbstractDas Jahr 2006 bestimmte aus energiewirtschaftlicher Sicht nachhaltig der hohe Ölpreis. Kein Superlativ wurde ausgelassen, um den Rohölpreis und seine Auswirkungen auf die Preise für Endenergieträger zu beschreiben. Zwar hat es in den vergangenen Wochen eine leichte Entspannung am internationalen Markt gegeben, doch der anstehende Winter und Förderkürzungen der OPEC ließen den Rohölpreis zuletzt wieder steigen. Der folgende Beitrag fasst einige zentrale Entwicklungen am Ölmarkt in der Vergangenheit zusammen, beleuchtet die Preise und wirft einen Blick in die Zukunft.
Transition‐State Energy and Position along the Reaction Coordinate in an Extended Activation Strain Model
Authors: de Jong G. Theodoor , Bickelhaupt F. Matthias 
Published: April 2007

AbstractWe investigate palladium‐induced activation of the CH, CC, CF, and CCl bonds in methane, ethane, cyclopropane, fluoromethane, and chloromethane, using relativistic density functional theory (DFT) at ZORA‐BLYP/TZ2P. Our purpose is to arrive at a qualitative understanding, based on accurate calculations, of the trends in activation barriers and transition state (TS) geometries (e.g. early or late along the reaction coordinate) in terms of the reactants’ properties. To this end, we extend the activation strain model (in which the activation energy ΔE≠ is decomposed into the activation strain ΔE≠strain of the reactants and the stabilizing TS interaction ΔE≠int between the reactants) from a single‐point analysis of the TS to an analysis along the reaction coordinate ζ, that is, ΔE(ζ)=ΔEstrain(ζ)+ΔEint(ζ). This extension enables us to understand qualitatively, trends in the position of the TS along ζ and, therefore, the values of the activation strain ΔE≠strain=ΔEstrain(ζTS) and TS interaction ΔE≠int=ΔEint(ζTS) and trends therein. An interesting insight that emerges is that the much higher barrier of metal‐mediated CC versus CH activation originates from steric shielding of the CC bond in ethane by CH bonds. Thus, before a favorable stabilizing interaction with the CC bond can occur, the CH bonds must be bent away, which causes the metal–substrate interaction ΔEint(ζ) in CC activation to lag behind. Such steric shielding is not present in the metal‐mediated activation of the CH bond, which is always accessible from the hydrogen side. Other phenomena that are addressed are anion assistance, competition between direct oxidative insertion (OxIn) versus the alternative SN2 pathway, and the effect of ring strain.
Joint packet scheduling and dynamic base station assignment for CDMA data networks
Authors: Makaya Christian , Aïssa Sonia 
Published: April 2007

AbstractIn current code division multiple access (CDMA) based wireless systems, a base station (BS) schedules packets independently of its neighbours, which may lead to resource wastage and the degradation of the system's performance. In wireless networks, in order to achieve an efficient packet scheduling, there are two conflicting performance metrics that have to be optimized: throughput and fairness. Their maximization is a key goal, particularly in next‐generation wireless networks. This paper proposes joint packet scheduling and BS assignment schemes for a cluster of interdependent neighbouring BSs in CDMA‐based wireless networks, in order to enhance the system performance through dynamic load balancing. The proposed schemes are based on sector subdivision in terms of average required resource per mobile station and utility function approach. The fairness is achieved by minimizing the variance of the delay for the remaining head‐of‐queue packets. Inter‐cell and intra‐cell interferences from scheduled packets are also minimized in order to increase the system capacity and performance. The simulation results show that our proposed schemes perform better than existing schemes available in the open literature. Copyright © 2007 John Wiley & Sons, Ltd.
Prognostic value of serum liver enzymes levels in type 2 diabetic patients
Authors: Monami Matteo , Balzi Daniela , Lamanna Caterina , Melani Cecilia , Cocca Carmen , Lotti Elena , Fedeli Angela , Masotti Giulio , Marchionni Niccolò , Mannucci Edoardo 
Published: April 2007

AbstractBackgroundElevated liver enzymes are associated with cardiovascular disease, while their relationship with cancer‐related mortality has not been assessed so far in diabetic patients.MethodsAn observational cohort study was performed on a consecutive series of 1952 type 2 diabetic patients. The association of liver enzymes with all‐cause and cause‐specific mortality was assessed. Information on all‐cause mortality was obtained by the City of Florence Registry Office.ResultsThe average duration of follow‐up was 6.4 ± 2.7 years. Over that period, 362 deaths were recorded (26.9%), with a yearly mortality rate of 4.2%. Age‐ and sex‐adjusted HR of all‐cause mortality for gamma glutamyl‐transpeptidase (γ‐GT) γ‐GT > 40 U/l was 1.610 [1.245–2.082]. An increased cardiovascular mortality rate was observed in patients with elevation of γ‐GT, and γ‐GT and/or alanine aminotransferase (ALT), when compared with the rest of the sample (15.3 vs 10.8%, p < 0.05; and 15.2 vs 10.7%, p < 0.05, respectively). Similar results were observed when considering cancer‐related mortality.The association of higher γ‐GT levels with all‐cause, cardiovascular, and cancer‐related mortality was confirmed at a multivariate analysis after adjustment for potential confounders.ConclusionsThe present study shows that, in type 2 diabetic patients, higher γ‐GT, but not ALT, is associated with increased mortality for cardiovascular disease and malignancies. Copyright © 2007 John Wiley & Sons, Ltd.
Carbon Ceramic Electrodes Modified with Laccase from Trametes hirsuta: Fabrication, Characterization and Their Use for Phenolic Compounds Detection
Authors: Haghighi Behzad , Rahmati‐Panah Amir , Shleev Sergey , Gorton Lo 
Published: April 2007

AbstractFungal laccase (Lc) from the basidiomycete Trametes hirsuta was immobilized on top of a carbon ceramic electrode using physical absorption. Direct, unmediated heterogeneous electron transfer between Lc and the carbon ceramic electrode (CCE) under aerobic conditions was shown. The bioelectrocatalytic reduction of oxygen on Lc‐CCE started at about 430 mV vs. Ag|AgCl|KClsat at pH 3.5 and moved with about 57 mV in the cathodic region per pH unit. The Lc‐modified CCE was then used as a biosensing detection element in a single line flow injection system for the amperometric determination of a variety of phenolic substrates of the enzyme. The experimental conditions were studied and optimized for catechol serving as a model compound. Statistical aspects were applied and the sensor characteristics and Michaelis‐Menten constants of the investigated phenolic compounds were calculated and compared with those obtained for solid graphite electrodes modified with Trametes hirsuta laccase. The results showed that the CCE based biosensor in comparison with the solid graphite based biosensor offers a lower detection limit, a wider linear dynamic range, and excellent operational stability with no sensor passivation, indicating that the sol–gel lattice improves the electrochemical behavior of the biosensor.
Electrochemical Determination of Oxalate at Pyrolytic Graphite Electrodes
Authors: Šljukić Biljana , Baron Ronan , Compton Richard G. 
Published: April 2007

AbstractThe electrocatalytic oxidation of oxalate at several carbon based electrodes including basal plane (BPPG) and edge plane (EPPG) pyrolytic graphite and glassy carbon (GC) electrode, was studied. The electrodes were examined for the sensing of oxalate ions in aqueous solutions and all three electrodes showed a response to oxalate additions. The peak of oxalate oxidation at BPPG electrode appeared at lower potential, +1.13 V vs. SCE, than at EPPG (+1.20 V vs. SCE) and GC electrode (+1.44 V vs. SCE). Oxalate oxidation at BPPG electrode was studied in more details for response characteristics (potential and current), effects of pH, temporal characteristics of response potential and current. The results indicated that oxalate oxidation proceeds as two‐electron process at the BPPG electrode with a transfer coefficient β and a diffusion coefficient D evaluated to be 0.45 and 1.03 (±0.04)×10−5 cm2 s−1 respectively. The BPPG electrode was found to be suitable for oxalate determination in aqueous media showing linear response to oxalate concentration with a sensitivity of 0.039 AM−1 and a limit of detection of 0.7 μM.
Simultaneous chiral separation of ephedrine alkaloids by MEKC‐ESI‐MS using polymeric surfactant II: Application in dietary supplements
Authors: Hou Jingguo , Zheng Jie , Shamsi Shahab A. 
Published: April 2007

AbstractChiral MEKC‐MS method was utilized for separation, identification, and quantitation of ten enantiomers of ephedrine and related compounds. Enantioselective separations of all ephedrine alkaloids were accomplished through a combination of polysodium N‐undecenoxycarbonyl‐L‐leucinate (poly‐L‐SUCL) with 30% v/v ACN. Interestingly, the more hydrophilic stereoisomers were eluted later than the hydrophobic ones indicating that hydrogen bonding interactions are much stronger than hydrophobic interactions in the presence of ACN in chiral MEKC. The method was validated in terms of linearity, LOD, LOQ, precision and robustness. The method was finally used in the analysis of three standard reference materials (SRMs). Results of (–)‐ephedrine ranged from 12.49 to 0.24 mg/g, for (+)‐pseudoephedrine from 4.04 to 0.019 mg/g, for (–)‐norephedrine from 0.36 to 0.0031 mg/g, for (+)‐norpseudoephedrine from 0.68 to 0.0052 mg/g, for (–)‐methylephedrine from 1.18 to 0.0092 mg/g and for (+)‐methylpseudoephedrine from 0.086 to 0.00037 mg/g in the SRMs.