bluuebunny/crossref_metadata_2025 huggingface dataset:
Foreign gene expression (β‐galactosidase) during the cell cycle phases in recombinant CHO cells
Authors: Gu Man Bock , Todd Paul , Kompala Dhinakar S.
Published: December 2004

Recombinant mammalian cultures for heterologous gene expression typically involve cells traversing the cell cycle. Studies were conducted to characterize rates of accumulation of intracellular foreign protein in single cells during the cell cycle of Chinese hamster ovary (CHO) cells transfected with an expression vector containing the gene for dihydrofolate reductase (dhfr) and the lacZ gene for bacterial β‐galactosidase (a nonsecreated protein). The lacZ gene was under the control of the constitutive cytomegalovirus promoter. These normally attachment‐grown cells were adapted to suspension culture in 10−7 M methotrexate, and a dual‐laser flow cytometer was used to simultaneously determine the DNA and foreign protein (β‐galactosidase) content of single living cells. Expression of β‐galactosidase as a function of cell cycle phase was evaluated for cells in the exponential growth phase, early plateau phase, and inhibited traverse of the cell cycle during exponential growth. The results showed that the β‐galactosidase production rate is higher in the S phase than that in the G1 or G2/M phases. Also, when cell cycle progression was stopped at the S phase by addition of aphidicolin, β‐galactosidase content in single cells was higher than that in exponential phase or plateau phase cells and increased with increasing culture time. Although the cells did not continue to divide after aphidicolin addition, the production of β‐galactosidase per unit volume of culture was very similar to that in normal exponential growth. © 1993 John Wiley & Sons, Inc.
Rapid renaturation of denatured and aggregated proteins using liquid paraffin as a pseudolipid bilayer membrane
Authors: Yoshii Hidefumi , Kojima Tsugio , Furuta Takeshi , Yasunishi Akira
Published: December 2004

A means of rapidly renaturing denatured protein was devised and evaluated. Three liquids were laminarly layered in a centrifuge tube, in which two solutions sandwiched liquid paraffin so as to form a pseudolipid bilayer. Denatured and aggregted protein placed on the upper surface of liquid paraffin was renatured as it passed through liquid‐paraffin layer into the renaturation buffer during the centrifugation. The aggregated and denatured protein selectively passed through the liquid‐paraffin layer, whereas other solutions, such as chaotropic agents or organic solvent, could not. This means that a rapid dilution condition favorable for protein renaturation was realized in a small scale. Aggregated and denatured BSA and ribonuclease A were renatured and resolubilized as they passed through the liquid‐paraffin layer into an appropriate renaturation buffer solution. This method was also applied to the rapid heme reconstitution of myoglobin from Feprotoporphyrin IX to Zn‐protoporphyrin IX. © 1994 John Wiley & Sons, Inc.
Increased thermostability of Asn182 → Ala mutant Aspergillus awamori glucoamylase
Authors: Reilly Peter J. , Chen Hsiu‐Mei , Bakir Ufuk , Ford Clark
Published: December 2004

Asn182 → Ala Aspergillus awamori glucoamylase expressed in Saccharomyces cerevisiae had a first‐order thermodeactivation coefficient 40% that of wild‐type glucoamylase at pH 4.5 between 60° and 65°C, caused by the elimination of an Asn—Gly sequence subject to deamidation and eventual chain breakage. Above 70°C, and at pHs 3.5 and 5.5, thermodeactivation coefficients of wild‐type and mutant enzymes were roughly equal, because the fastest deactivation mechanism was no longer deamidation. The mutation had little effect on the enzyme's optimal pH for activity and subsite map, or on the glucose yield from starch dextrin hydrolysis. During enzyme production by yeast fermentation, highest cell densities and activities of wild‐type and mutant glucoamylases were attained after a period of glucose starvation, followed by a second addition of glucose. © 1994 John Wiley & Sons, Inc.
Kinetics of chondrocyte growth in cell‐polymer implants
Authors: Freed L. E. , Marquis J. C. , Langer R. , Vunjak‐Novakovic G.
Published: December 2004

In vitro cultivation of cartilage cells (chondrocytes) on biodegradable polyglycolic acid (PGA) scaffolds resulted in implants which could potentially be used to repair damaged joint cartilage or for reconstructive surgery. Cell growth kinetics were studied to define conditions under which the cellularity of implants made from isolated calf chondrocytes reached that of the parent calf cartilage. In static cultures, condrocyte growth rates decreased as either implant thickness or implant cell density increased. Over 4 weeks of cultivation, implant permeability to glucose decreased to 3% that of the plain polymer scaffold; this effect was attributed to the decrease in effective implant porosity associated with cartilage tissue regeneration.

In a well‐mixed culture, implants 1 cm in diameter by 0.3 cm thick maintained high cell growth rates over 7 weeks and hard normal cell densities. Regenerated cartilage with these dimensions is large enough to resurface small joints such as the trapezium bone at the base of the human thumb. Such implants could not be grown statically, since cell growth stopped at 3–4 weeks and cell densities remained below normal. Optimization of the tissue culture environment is thus essential in order to cultivate clinically useful cartilage implants in vitro. © 1994 John Wiley & Sons, Inc.
Oxygen is a factor determining in vitro tissue assembly: Effects on attachment and spreading of hepatocytes
Authors: Rotem Avi , Toner Mehmet , Bhatia Sangeeta , Foy Brent D. , Tompkins Ronald G. , Yarmush Martin L.
Published: December 2004

Many recent studies related to the development of bioartificial liver devices have utilized hepatocytes cultured within devices of various geometries. Because hepatocytes are anchorage‐dependent cells, they need to attach and spread onto the extracellular matrix to be able to function, a process that requires energy. Thus, it is important to deliver enough oxygen to hepatocytes contained within bioartificial liver devices during the early phase of cellular organization while the cells interact with the extracellular matrix. In this study, we investigated the effect of oxygen on the attachment and spreading of hepatocytes. Increasing the gas phase oxygen from 0 to 160 mmHg resulted in an increase in the percentage of cells attaching from 43.0 ± 5.8% to 103.6 ± 29%, 1 h after seeding. In a similar manner, increasing the gas phase oxygen from 0 to 160 mmHg resulted in an increase of the projected surface area from 310 ± 35 to 827 ± 127 μm2, 24 h after seeding. Furthermore, the partial pressure of oxygen at the cell level was estimated using a diffusion‐reaction model. The model indicated that a cell surface oxygen partial pressure of 0.064 mmHg was required for the half‐maximal (K) attachment of hepatocytes to collagen‐based substrate. On the other hand, the K value of the spreading process was predicted to be 0.13 mmHg. The results of this study demonstrate the importance of oxygen during the initial stages of attachment and spreading of hepatocytes, and it has important implications in the design of hepatocyte‐based bioartificial liver devices. © 1994 John Wiley & Sons, Inc.
Facilitated transport of lactic acid in a stirred transfer cell
Authors: Lazarova Z. , Peeva L.
Published: December 2004

The application of liquid membrane extraction to the recovery of lactic acid from model systems and fermentation media was investigated. An experimental study of the facilitated transport of lactic acid using ALIQUAT 336 as a mobile carrier in a stirred transfer cell is reported. The effect of stirring speed, initial lactic acid concentration, carrier concentration, and NaCl as a reagent in the acceptor phase are considered. © 1994 John Wiley & Sons, Inc.
Biodegradation of pesticides in nonionic water‐in‐oil microemulsions of tween 85: Relationship between micelle structure and activity
Authors: Komives Claire F. , Lilley Erin , Russell Alan J.
Published: December 2004

Water‐in‐oil microemulsion systems have been studied in recent years for a number of applications in protein separation and enzymology. Although it is well established that reversed micelle systems provide an excellent medium for nonaqueous biocatalytic studies, there is still much speculation as to the interaction of the enzyme with the surfactant interface. Polyoxyethylene sorbitan trioleate (Tween 85) is a nonionic surfactant which has some interesting properties for microemulsion formation and protein solubilization. In conjunction with a separate article describing the structural features of Tween 85 reversed micelles in hexane with isopropanol as a cosurfactant, this work describes the activity of an enzyme, organophosphorus hydrolase, for degrading organophosphorus pesticides in this microemulsion system. Ternary phase diagrams were constructed to outline the phase boundaries at different temperatures and isopropanol concentrations, which elucidate the role of the cosurfactant alcohol, as well as some features of micelle structure. Kinetic and stability studies with organophosphorus hydrolase show the effect of enzyme partitioning between the micelle surfactant layer and aqueous core. © 1994 John Wiley & Sons, Inc.
Effect of solution pH and ionic strength on the separation of albumin from immunoglobulins (IgG) by selective filtration
Authors: Saksena Skand , Zydney Andrew L.
Published: December 2004

Although protein fractionation by selective membrane filtration has numerous potential applications in both the downstream processing of fermentation broths and the purification of plasma proteins, the selectivity for proteins with only moderately different molecular weights has generally been quite poor. We have obtained experimental data for the transport of bovine serum albumin (BSA) and immunoglobulins (IgG) through 100,000 and 300,000 molecular weight cutoff polyethersulfone membranes in a stirred ultrafiltration device at different solution pH and ionic strength. The selectivity was a complex function of the flux due to the simultaneous convective and diffusive solute transport through the membrane and the bulk mass transfer limitations in the stirred cell. Under phsioligical conditions (pH 7.0 and 0.15MNaCI) the maximum selectivity for the BSA‐IgG separation was only about 2.0 due primarily to the effects of protein adsorption. In contrast, BSA‐IgG selectivities as high as 50 were obtained with the same membranes when the protein solution was at pH 4.8 and 0.0015MNaCl. This enhanced selectivity was a direct result of the electrosatatic contributions to both bulk and membrane transport. The membrane selectivity could actually be reversed, with higher passage of the larger IgG molecules, by using a 300,000 molecular weight cutoff membrane at pH 7.4 and an ionic strength of 0.0015MNaCl. These results clearly demonstrate that the effectiveness of selective protein filtration can be dramatically altered by appropriately controlling electrostatic interactions through changes in pH and/or ionic strength. © 1994 John Wiley & Sons, Inc.
Pervaporative butanol fermentation by Clostridium acetobutylicum B18
Authors: Geng Qinghuang , Park Chang‐Ho
Published: December 2004

Extractive acetone‐butanol–ethanol (ABE) fermentation was carried out successfully using pervaporation and a low‐acid‐producing Clostridium acetobutylicum B18. A pervaporation module with 0.17 m2 of surface area was made of silicone membrane of 240 μm thickness. Pervaporation experiments using make‐up solutions showed that butanol and acetone fluxes increased linearly with their concentrations in the aqueous phase. Fickian diffusion coefficients were constants for fixed air flow rates, and increased at higher sweep air flow rates. During batch and fed‐batch fermentations, pervaporation at an air flow rate of 8 L/min removed butanol and acetone efficiently. Butanol concentration was maintained below 4.5 g/L even though Clostridium acetobutylicum B18 produced butanol steadily. Pervaporation could not remove organic acids efficiently, but organic acids did not accumulate because strain B18 produced little organic acid and recycled added organic acids efficiently. With pervaporation, glucose consumption rate increased compared to without pervaporation, and up to 160 g/L of glucose was consumed during 80 h. Cell growth was not inhibited by possible salt accumulation or oxygen diffusion through the silicone tubing. The culture volume was maintained relatively constant during fed‐batch operation because of an offsetting effect of water and product removal by pervaporation and addition of nutrient supplements. © 1994 John Wiley & Sons, Inc.
Photolithotrophic cultivation of Laminaria saccharina gametophyte cells in a stirred‐tank bioreactor
Authors: Qi Hans , Rorrer Gregory L.
Published: December 2004

Filamentous cell cultures derived from female gametophytes of the temperate brown macroalga Laminaria saccharina were photolithotrophically cultivated in artificial seawater medium within an illuminated 1.3‐L stirred‐tank bioreactor at 13°C using CO2 in air as the carbon source. A Monod model adequately described light‐saturated growth. The apparent half‐saturation constant (Ko) was 23 μE/m2‐s, and maximum specific growth rate was 0.15 day−1. At a constant inoculation cell density of 50 mg DCW/L, biomass productivity after 26 days of cultivation increased from 630 mg DCW/L at 18 μE/m2‐s to 890 mg DCW/L at 228 μE/m2‐s. At 98 μE/m2‐s, 1.1 vvm aeration rate, and 250 rpm impeller speed, the CO2 transfer rates (CO2 TRs) and CO2 consumption rates (r) were determined over the cultivation period. At peak CO2 demand, the maximum CO2 TR was 0.19 mmol CO2/L‐h, but r was only 0.15 mmol CO2/L‐h, implying that the culture was not CO2 transport limited. This is the first reported bioreactor cultivation study of cell cultures derived from a macrophytic marine alga. © 1995 John Wiley & Sons, Inc.
Kinetics of nitrate inhibition of carbon tetrachloride transformation by a denitrifying consortia
Authors: Skeen Rodney S. , Valentine Nancy B. , Hooker Brian S. , Petersen James N.
Published: December 2004

The kinetics of nitrate inhibition of carbon tetrachloride (CT) transformation were examined using a denitrifying consortium. Comparison of data from fed‐batch experiments to the model reported by Hooker et al. indicate that the inhibition constant ranges between 3.2 and 21 mg/L, with an average of 8.8 mg/L. This range is much lower than the previously reported value of 169 mg/L. Simulations using the corrected parameter accurately reflect this new data and the data reported by Hooker et al. In contrast, the earlier reported coefficient value does not reflect the data reported in this work. © 1995 John Wiley & Sons, Inc.
Microbial production of (+)‐trans‐isochorismic acid
Authors: Schmidt Karsten , Leistner Eckhard
Published: December 2004

Two methods are described for the preparation of enantiomerically pure (+)‐trans‐isochorismic acid, an important metabolite of the postchorismate pathway. Both methods can be employed to prepare isotopically labeled isochorismic acid. One of the two methods is suitable to prepare bulk quantities of isochorismic acid using a recombinant strain of Klebsiella pneumoniae 62‐1. © 1995 John Wiley & Sons, Inc.
Intracellular flux analysis in hybridomas using mass balances and in vitro 13C nmr
Authors: Zupke Craig , Stephanopoulos Gregory
Published: December 2004

Intracellular fluxes are important in defining cellular physiology and its changes in response to environmental variations. Stoichiometric balances combined with extra cellular metabolite measurements were applied to the estimation of intracellular fluxes and the study of energy metabolism in the hybridoma cell line ATCC CRL 1606. Redundant measurements allowed the evaluation of the consistency of the stoichiometry, measurements, and pseudo‐steady‐state assumption leading to refinement of the assumed biochemistry and identification of measurement errors. To validate the flux estimates, two batch experiments were performed with glucose labeled in the 1 position with 13C. The distribution of 13C in secreted lactate was measured via nuclear magnetic resonance spectroscopy (NMR) and compared to that predicted from the estimated intracellular fluxes. There was good agreement between the measured and estimated isotope distributions, demonstrating the validity of the flux estimates obtained from stoichiometric balances. © 1995 John Wiley & Sons, Inc.
Removal of phenols and aromatic amines from wastewater by a combination treatment with tyrosinase and a coagulant
Authors: Wada Shinji , Ichikawa Hiroyasu , Tastsumi Kenji
Published: December 2004

Removal of phenols and aromatic amines from industrial wastewater by tyrosinase was investigated. A color change from colorless to darkbrown was observed, but no precipitate was formed. Colored products were found to be easily removed by a combination treatment with tyrosinase and a cationic polymer coagulant containing amino group, such as hexamethylenediamine‐epichlorohidrin polycondensate, polyethleneimine, or chitosan. The first two coagulants, synthetic polymers, were more effective than chitosan, a polymer produced in crustacean shells. Phenols and aromatic amines are not precipitated by any kind of coagulants, but their enzymatic reaction products are easily precipitated by a cationic polymer coagulant. These results indicate that the combination of tyrosinase and a cationic polymer coagulant is effective in removing carcinogenic phenols and aromatic amines from an aqueous solution. Immobilization of tyrosinase on magnetite gave a good retention of activity (80%) and storage stability i.e., only 5% loss after 15 days of storage at ambient temperature. In the treatment of immobilized tyrosinase, colored enzymatic reaction products were removed by less coagulant compared with soluble tyrosinase. © 1995 John Wiley & Sons, Inc.
Esterification reactions catalyzed by Chromobacterium viscosum lipase in CTAB‐based microemulsion systems
Authors: Rees Gareth D. , Robinson Brian H.
Published: December 2004

Chromobacterium viscosum (CV) lipase solubilized in water‐in‐oil (w/o) microemulsions based on the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) have been used for multigram‐scale ester synthesis, including the kinetic resolution of a secondary alcohol. The stability of CV lipase in all the CTAB microemulsions studied was excellent and was superior to that observed in aqueous buffer at the same pH and temperature. Kinetic studies were performed using the synthesis of ethylhexadecanoate as a model reaction. Under pseudo‐first‐order conditions, the synthesis rates were linearlydependent on the enzyme and fatty acid concentrations and the R dependence shows the characteristic bell‐shaped curve (where R = [H2O]/[surfactant]). The dependence of enzyme activity toward octyldecanoate synthesis on the pH of the dispersed buffer phase is in marked contrast to that observed for the pH dependence of CV lipase toward p‐nitrophenylbutyrate hydrolysis. In the former case, the pH‐activity profile is approximately sigmoidal, which may reflect the ionization state of the fatty acid substrate. In the latter case, the pH dependence is minimal at both R = 10 and R = 50, suggesting the enzyme does not experience a changed pH environment. Inclusion of a pH‐sensitive probe molecule into those incubations containing fatty acid clearly demonstrates that the probe molecule experiences a changed environment consistent with that expected for the selected buffer. An in situ Fourier transform nuclear magnetic resonance (FT‐NMR) assay has been developed which allows continuous monitoring of the esterification reactions, thereby providing an additional means of determining initial rates. The method may be of general value for lipase assays in microemulsions since it may provide, at the same time, information regarding enzyme regioselectivity. © 1995 John Wiley & Sons, Inc.
Kinetics of ethanol production by recombinant Escherichia coli KO11
Authors: Olsson L. , Hahn‐Hägerdal B. , Zacchi G.
Published: December 2004

The fermentation kinetics for separate as well as simultaneous glucose and xylose fermentation with recombinant ethanologenic Escherichia coli KO11 are presented. Glucose and xylose were consumed simultaneously and exhibited mutual inhibition. The glucose exhibited 15 times stronger inhibition in xyclose fermentation than vice versa. The fermentation of condensate from steampretreated willow (Salix) was investigated. The kinetics were studied in detoxified as well as in nondetoxified condensate. The fermentation of the condensate followed two phases: First the glucose and some of the pentoses (xylose in addition to small amounts of arabinose) were fermented simultaneously, and then the remaining part of the pentoses were fermented. The rate of the first phase was independent of the detoxification method used, whereas the rate of the second phase was found to be strongly dependent. When the condensate was detoxified with overliming in combination with sulfite, which was the best detoxification method investigated, the sugars in the condensate, 9 g/L, were fermented in 11 h. The same fermentation took 150 h in nondetoxified condensate. The experimental data were used to develop an empirical model, describing the batch fermentation of recombinant E. coli KO11 in the condensate. The model is based on Monod kinetics including substrate and product inhibition and the sum of the inhibition exerted by the rest of the inhibitors, lumped together. © 1995 John Wiley & Sons, Inc.
Structured modeling and state estimation in a fermentation process: Lipase production by Candida rugosa
Authors: Montesinos J. L. , Lafuente J. , Gordillo M. A. , Valero F. , Solà C. , Charbonnier S. , Cheruy A.
Published: December 2004

A simple structured mathematical model coupled with a methodology of state and parameter estimation is developed for lipase production by Candida rugosa in batch fermentation. The model describes the system according to the following qualitative observations and hypothesis: Lipase production is induced by extracellular oleic acid present in the medium. The acid is transported into the cell where it is consumed, transformed, and stored. Lipase is excreted to the medium where it is distributed between the available oil‐water interphase and aqueous phase. Cell growth is modulated by the intracellular substrate concentration. Model parameters have been determined and the whole model validated against experiments not used in their determination. The estimation problem consists in the estimation of three state variables (biomass, intra‐ and extracellular substrate) and two kinetic parameters by using only the on‐line measurement provided by exhaust gas analysis. The presented estimation strategy divides the complex problem into three subproblems that can be solved by stable algorithms. The estimation of biomass (X) and the specific growth rate (μ), is achieved by a recursive prediction error algorithm using the on‐line measurement of the carbon dioxide evolution rate. μ is then used to perform an estimation of intracellular substrate and the other kinetic parameter related to substrate transport (A) by an adaptive observer. Extracellular substrate is then evaluated by means of the estimated values of intracellular substrate and biomass through the material balance of the reactor. Simulation and experimental tests showed good performance of the developed estimator, which appears suitable to be used for process control and monitoring. © 1995 John Wiley & Sons, Inc.
Fatty acid esterification using nylon‐immobilized lipase
Authors: Zaidi Ahmed , Gainer John L. , Carta Giorgio
Published: December 2004

The esterification of a long‐chain fatty acid was conducted using a nylon‐immobilized lipase from Candida cylindracea in a nearly anhydrous, nonpolar organic medium, hexane. Butyl laurate was produced from lauric acid and n‐butanol at a maximum initial reaction rate of 37 mmol/h. g immobilized enzyme when the substrates were present in equimolar amounts at an initial concentration of 0.5 mol/L. Lower rates were obtained using nonstoichiometric amounts of the substrates. The rate of reaction increased with temperature, reaching a maximum between 35 and 45°C and decreasing sharply at higher temperatures. © 1995 John Wiley & Sons, Inc.
Modeling simultaneous hexavalent chromium reduction and phenol degradation by a defined coculture of bacteria
Authors: Shen Hai , Wang Yi‐Tin
Published: December 2004

Based on the kinetics of Cr(VI) reduction by Escherichia coli ATCC 33456 and phenol degradation by Pseudomonas putida DMP‐1, a mathematical model is developed to describe simultaneous Cr(VI) reduction and phenol degradation in the coculture of the two species. The developed model incorporates the toxicity effects of Cr(VI) and phenol on phenol degradation and Cr(VI) reduction in the coculture. The model illustrates the inhibitory effects of phenol on Cr(VI) reduction and Cr(VI) toxicity toward phenol degradation. The model also reveals the recoveries of the activities of the repressed bacterial cells with continuous Cr(VI) reduction and phenol degradation in the coculture. The model is capable of predicting simultaneous Cr(VI) reduction and phenol degradation within a broad range of Cr(VI) and phenol concentrations and under an appropriate composition of populations. However, the model simulates lower concentrations of phenol than experimental observations once Cr(VI) is reduced to a low level (<7 mg/L). The model simulation for Cr(VI) also deviates from experimental data when P. putida is outnumbered by E. coli by a ratio of 1:5. © 1995 John Wiley & Sons, Inc.
Thermodynamic approach to explain cell adhesion to air–medium interfaces
Authors: Chattopadhyay Devamita , Rathman James F. , Chalmers Jeffrey J.
Published: December 2004

Cell damage has been observed in suspension cell cultures with air sparging, especially in the absence of any protective additives. This damage is associated with cells adhering to bubbles, and it has been shown that if this adhesion is prevented, cell damage is prevented. This article presents a thermodynamic approach for predicting cell adhesion at the air–medium interface. With this relationship it can be shown that cell–gas adhesion can be prevented by lowering the surface tension of the liquid growth medium through the addition of surface–active protective additives. The thermodynamic relationship describes the change in free energy as a function of the interfacial tensions between the (i) gas and liquid phases, (ii) gas and cell phases, and (iii) liquid and cell phases. Experimental data, along with theoretical and empirical equations, are used to quantify the changes in free energy that predict the process of cell–gas adhesion. The thermodynamic model is nonspecific in nature and, consequently, results are equally valid for all types of cells. © 1995 John Wiley & Sons, Inc.
Kinetics of chlorinated ethylene dehalogenation under methanogenic conditions
Authors: Skeen Rodney S. , Gao Jianwei , Hooker Brian S.
Published: December 2004

Kinetics were determined for methanogenic activity and chlorinated ethylene dehalogenation by a methanol‐enriched, anaerobic sediment consortium. The culture reductively dechlorinated perchloroethylene (PCE) to trichloroethylene (TCE), 1,1‐dichloroethylene (1,1‐DCE), vinylchloride (VC), and ethylene and ethane. The absence : of methanol or the addition of 2‐bromoethanesulfonic. acid in the presence of methanol suppressed both methanogenic activity and dechlorination. In contrast, acetate production continued in the presence of 2‐bromoethanesulfonic acid. These results suggest that dechlorination was strongly linked to methane formation and not to acetate production. A kinetic model, developed to describe both methanogenesis and dechlorination, successfully predicted experimentally measured concentrations of biomass, methane, substrate, and chlorinated ethylenes. The average maximum specific dehalogenation rates for PCE, TCE, 1,1‐DCE, and VC were 0.9 ± 0.6, 0.4 ± 0.1, 12 ± 0.1, and 2.5 ± 1.7 μmol contaminant/ g. DW/day, respectively. This pattern for dechlorination rates is distinctly different than that reported for transition metal cofactors, where rates drop by approximately one order of magnitude as each successive chlorine is removed. The experimental results and kinetic analysis suggest that it will be impractical to targeting methanol consuming methanogenic organisms for in situ ground‐water restoration. © 1995 John Wiley & Sons, Inc.
Analysis of Noncovalent Complexes between Human Telomeric DNA and Polyamides Containing N‐Methylpyrrole and N‐Methylimidazole by Using Electrospray Ionization Mass Spectrometry
Authors: Zhou Jiang , Yuan Gu
Published: December 2004

Electrospray ionization mass spectrometry (ESI‐MS) was used to investigate noncovalent complexes formed between four novel polyamides containing N‐methylpyrrole (Py) and N‐methylimidazole (Im), and human telomeric DNA. Of the four polyamides investigated, PyPyPyγImImImβDp (3) had the highest binding affinity towards the duplex d(TTAGGGTTAGGG/CCCTAACCCTAA) (D1). Results of competition analysis showed that the polyamides had binding affinities with D1 in the order PyPyPyγImImImβDp (3)>PyPyPyPyγPyImImPyβDp (4)>PyPyPyβImImImβDp (2)≫ImImImβDp (1). MS/MS spectra confirmed that binding between D1 and the hairpin polyamides is more stable than that with the three‐ring polyamides. By contrast, in the case of single‐stranded d(TTAGGGTTAGGG)(D2), the binding order changes to ImImImβDp (1)>PyPyPyγImImImβDp (3)>PyPyPyβImImImβDp (2).
Helical Arrays of Pendant Fullerenes on Optically Active Poly(phenylacetylene)s
Authors: Nishimura Tatsuya , Maeda Katsuhiro , Ohsawa Sousuke , Yashima Eiji
Published: December 2004

Novel, optically active, stereoregular poly(phenylacetylene)s bearing the bulky fullerene as the pendant were synthesized by copolymerization of an achiral phenylacetylene bearing a [60]fullerene unit with optically active phenylacetylene components in the presence of a rhodium catalyst. The C60‐bound phenylacetylene was prepared by treatment of C60 with N‐(4‐ethynylbenzyl)glycine in a Prato reaction. The obtained copolymers exhibited induced circular dichroism (ICD) in solution both in the main‐chain region and in the achiral fullerene chromophoric region, although their ICD intensities were highly dependent on the structures of the optically active phenylacetylenes and the solution temperature. These results indicate that the optically active copolymers form one‐handed helical structures and that the pendant achiral fullerene groups are arranged in helical arrays with a predominant screw sense along the polymer backbone. The structures and morphology of the copolymers on solid substrates were also investigated by atomic force microscopy.
Insight into the Mechanism of Oxidative Kinetic Resolution of Racemic Secondary Alcohols by Using Manganese(III)(Salen) Complexes as Catalysts
Authors: Li Zhen , Tang Zhong H. , Hu Xiao X. , Xia Chun G.
Published: December 2004

The oxidative kinetic resolution of various racemic secondary alcohols with PhI(OAc)2 catalyzed by chiral [MnIII(salen)] complexes in the presence of KBr was studied in a water/organic solvent mixture. The dramatic, synergetic effect of additives, organic solvent, and the substituents of chiral salen ligands on the enantioselectivities of the reactions is reported. Results from UV/Vis spectroscopy and ESI‐MS studies provide evidence that these reactions are induced by the formation of a high‐valent manganese intermediate.
Erhöhung des Wirkungsgrades von Katalysatoren für Gasreaktionen
Authors: Reitlinger O.
Published: December 2004

Es wird ein Verfahren beschrieben, die wirksame Oberfläche eines Katalysators ohne Behinderung des Gastransportes zu erhöhen durch Aufbringen des katalysierenden Stoffes in Pulverform auf impräginerte Körner ohne Beimischung eines Bindemittels und ohne mechanischen Druck. Die Katalysatoren sind schüttfest. Sechs Beispiele mit vergleichenden Versuchen an großtechnisch wichtigen Prozessen zeigen eine um ein Vielfaches erhöhte Ausbeute.
Betriebssicherheit neuzeitlicher Lösungsmittel‐Wiedergewinnungsanlagen
Authors: Knop W.
Published: December 2004

Im Hinblick auf die zunehmende Bedeutung der Verfahren zur Wiedergewinnung von Lösungsmitteln sind die Fragen der Betriebssicherheit derartiger Anlagen von großem technischen Interesse. Es zeigt sich, daß das Adsorptionsverfahren mit Aktivkohle gegenüber dem Verfahren mit Silicarbon bezüglich der Sicherheit keine Nachteile hat, da die Entzündungstemperaturen beider Adsorbentien praktisch gleich hoch liegen. Beide Adsorbentien sind bei den üblichen Verfahrenstemperaturen praktisch nicht entzündbar. Bei Einhaltung der Bedienungsvorschriften ist eine gute Betriebssicherheit gewährleistet.
Temperaturverlauf und Wärmeverluste beim Anheizen und Abkühlen dickwandiger, kugelförmiger Behälter. Teil I: Anheizen flüssigkeitsgefüllter Behälter
Authors: Baehr H. D.
Published: December 2004

Die Berechnung des Temperaturverlaufs und der Wärmeströme beim Anheizen oder Abkühlen dickwandiger Behälter stellt ein verwickeltes Problem der nichtstationären Wärmeleitung dar. Man kann nämlich in diesem Fall, etwa bei isolierten oder ausgemauerten Behältern, die Wärmespeicherung in den Behälterwänden nicht vernachlässigen. Im folgenden wird das Anheizen von flüssigkeitsgefüllten, kugelförmigen Behältern behandelt, bei denen die Wärme im Innern des Behälters zugeführt wird. Die Heizleistung ist variabel, wird jedoch als abschnittsweise konstant angesehen. Von der üblichen Lösung der Wärmeleitungs‐Differentialgleichung, die als eine unendliche Reihe erscheint, wird nur das erste Glied beibehalten. Da diese Vereinfachung für den Beginn des Anheizens zu Fehlern führt, werden mit Hilfe der Laplace‐Transformation andere Lösungen entwickelt, die bei Beginn des Anheizens brauchbar sind. Mehrere Diagramme erleichtern die Anwendung der Gleichungen, die an einem Beispiel gezeigt wird. Im zweiten Fall der Untersuchung wird der Abkühlungsvorgang behandelt und die bisher gewonnenen Ergebnisse werden auf gasgefüllte Behälter ausgedehnt.
CVD of CeO2‐Doped Y2O3‐Stabilized Zirconia onto Dense and Porous Substrates
Authors: Siadati Mohammad H. , Ward Timothy L. , Martus Jeffrey , Atanasova Paolina , Xia Changfeng , Schwartz Robert W.
Published: December 2004

Fabrication of dense films of mixed‐conducting oxides on porous surfaces is of interest for membrane, sensor, fuel cell, and battery applications. In this work, atmospheric‐pressure metal‐organic CHEMICAL VAPOR DEPOSITION was used to fabricate CeO2‐doped Y2O3‐stabilized ZrO2 films on dense silicon and porous alumina substrates. Aerosol‐assisted delivery of a toluene solution of the precursors Zr(tfac)4, Y(hfac)3, and Ce(tmhd)4 was used to deposit films with thicknesses around 1 μm. The effects of carrier gas O2 content (0–5 mol‐%), H2O vapor (0–3.4 mol‐%), deposition temperature (300–600°C), and the type of substrate on film morphology, composition, and purity were investigated. The porous substrate had a marked effect on the film morphology, producing a columnar film structure with column diameters that roughly approximated the particle diameter of the substrate (∼0.5 μm). Lower temperatures (300°C) provided a more uniform film with better connectivity between columnar structures than deposition at 400 and 600°C, and higher precursor concentrations produced very non‐uniform films with exaggerated growth features.
Characterization of Frzb‐Cre transgenic mouse
Authors: Tylzanowski Przemko , Bossuyt Wouter , Thomas J. Terrig , Luyten Frank P.
Published: December 2004

The Wnt family of glycoproteins is involved in numerous developmental and disease processes in higher eukaryotes, exerting their action by binding to cell‐surface receptors. In the extracellular space, Wnts are negatively regulated by secreted antagonists that either bind to the receptors directly (Dkk1) or to Wnt molecules themselves (Sfrp‐FRZB family), preventing its subsequent binding to the receptor. Here we report on a transgenic mouse expressing Cre under the control of the mouse Frzb promoter element. Analysis of the Cre expression was carried out at 10.5 and 14.5 dpc using the ROSA26R mouse line. Expression of the transgenic construct was detected in the limbs, the heart, the nasal epithelium, bone, whiskers, and around the orbita of the eye. The mouse could be used for conditional gene modification in those tissues. genesis 40:200–204, 2004. © 2004 Wiley‐Liss, Inc.
Workshop on characterization of calcium phosphate materials
Authors: Koeneman James , Lemons Jack , Ducheyne Paul , Lacefield William , Magee Frank , Calahan Thomas , Kay John
Published: December 2004

Calcium phosphate materials are being extensively investigated for orthopaedic and dental applications. Bone grafts and bone substitutes are being developed using many forms of these materials. Numerous medical devices are being coated with them. Because of the many forms that calcium phosphate materials take, characterization of the material under investigation is essential. Aworkshop sponsored by the Society For Biomaterials on characterization of calcium phosphate materials was held on June 14 and 15, 1989. Sessions discussing the historical development, in vitro characterization, in vitro coating characterization, in vivo coating characterization, the FDA perspective, and the manufacturers perspective were held. A summary of the workshop with references is presented.
Pyrolytic carbon prosthetic heart valve occluder wear: In Vivo vs. In Vitro results for the Bjork‐Shiley prosthesis
Authors: More Robert B. , Silver Malcolm D.
Published: December 2004

Pyrolytic carbon (Pyrolite® carbon) valve occluders from 18 clinical Bjork‐Shiley prostheses recovered at necropsy were examined for wear. In situ durations extended to 12 years. Results were combined with data from 17 recovered valves in the literature to produce a data base of 35 Bjork‐Shiley valves. Cumulative in vivo results were compared to in vitro, Shiley type, accelerated life‐cycle tester results for Bjork‐Shiley prostheses. Comparative results were then interpreted using Hertzian impact wear theory. The theory provided a rational basis for the difference in wear observed in terms of applied dynamic load levels. Furthermore, Hertzian impact wear theory yielded an estimate of in vivo total dynamic loads on the order of 1 to 22 Newtons (0.2–5 lbf.) acting on the occluder of the heart valve prosthesis.
Anodic polarization measurements of orthopaedic implant alloys in bovine serum albumin
Authors: Nakayama Yuichiro , Yamamuro Takao , Kumar Praveen , Shimizu Kouichiro , Kotoura Yoshihiko , Oka Masanori , Kawafuku Junji , Takashima Takahiro
Published: December 2004

Anodic polarization measurements of several orthopaedic implant alloys—AISI 316L stainless steel, CoCrMo alloy (ASTM F‐75), nickel‐titanium (NiTi) alloy, commercial pure titanium, and Ti6Al4V—were carried out in Ringer's solution containing 1% bovine serum albumin (BSA) and in simple Ringer's solution. Constituent metals in the medium were analyzed by inductively coupled plasma emission spectrophotometry after measurements. Pitting potentials and total anodic current of former two alloys were constant in the two mediums and not affected by the addition of bovine serum albumin. However, the amount of dissolved metals from pure nickel and AISI 316L stainless steel were increased by the addition of BSA; dissolved metals from CoCrMo alloy were decreased by it.
Applied biomaterials standards report
Authors: Daniels A. U. “Dan”
Published: December 2004

The purpose of my column is to provide readers with current information on biomaterialsrelated standards produced by both private groups and government agencies, and standards‐related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.

Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This inviation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.

And last, a caveat‐since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in September 1990.
Emailliertes Aluminium
Authors: Vielhaber Louis
Published: December 2004

In den USA und in England ist man dazu übergegangen, Aluminium zu emaillieren. Hierfür mußten neuartige Emails entwickelt werden, deren Wärmeausdehnung der des Aluminiums angepaßt ist und die bei 660°C eingebrannt werden können. Um diesen niedrigen Erweichungspunkt zu erreichen, wurden zuerst stark bleihaltige Emails entwickelt, später gelang es auch durch Verwendung eutektischer Mischungen bleifreie Emails herzustellen. Die englischen „Aluglas”︁ ‐Emails können ohne besondere Vorbehandlung des Al aufgeschmolzen werden. Im Übrigen wird eine vorherige Verkupferung oder Erzeugung einer Chrom‐Aluminium‐Oxydschicht empfohlen. Emailliertes Aluminium soll nicht das emaillierte Eisen ersetzen, sondern bisherige Veredelungsverfahren für Aluminium. Für Eß‐,Koch‐ und Trinkgefäße ist emailliertes Aluminium nicht geeignet. Vorgeschlagen für das Emaillieren werden Platten zur Wandbekleidung, Fensterrahmen, Schilder, Schutzverkleidungen usw. Die Anforderungen an diese Emaillierungen sind mannigfaltig und die Prüfung der Emaillierung muß sich daher auch auf die verschiedensten Eigenschaften erstrecken. Infolge des geringen Kieselsäuregehaltes der Al‐Emails ist nicht mit einer großen Säurebeständigkeit zu rechnen. Emaillierungen von Aluminium sind aber auf alle Fälle dauerhafter als z. B. Anstriche aus Alkyd‐Amin.
Theorie und Praxis des Flammstrahlens
Authors: Sippell Karl W.
Published: December 2004

Bei der Anwendung des Flammstrahlens ist die Einhaltung bestimmter Verfahrensregeln besonders zu beachten. Es wird daher ein Überblick gegeben über den Einfluß der Flammentemperatur auf die Eigenschaften von Baustählen und über den Einfluß verschiedener Brenngase auf die Wirksamkeit des Verfahrens. Weiterhin stimmen die Ergebnisse einer Anzahl von Untersuchungen zur Ermittlung der günstigsten Flammstrahlbedingungen mit den in der Praxis gefundenen Werten in fast allen Fällen überein. Infolgedessen ist es nun möglich, endgültige Verfahrensregeln mitzuteilen.

Eine ausführliche Beschreibung der praktischen Durchführung des Verfahrens soll jeden Zweifel an der richtigen Handhabung der Geräte und der zweckmäßigen Einrichtung der Arbeitsstelle ausschließen.

Die Einwirkungen verschiedener bisher üblicher Säuberungsmethoden und des Flammstrahlens auf die Beschaffenheit der behandelten Stahloberflächen lassen neben anderen Vorzügen die Überlegenheit des Verfahrens erkennen. Die Wirksamkeit und Wirtschaftlichkeit des Flammstrahlens wird durch eine Anzahl Beispiele dargestellt, wobei die neuesten Erkenntnisse über das Beseitigen der Walzhaut an Blechen ihrer Bedeutung entsprechend einen breiten Raum einnehmen.

Abschließend ist auf eine noch in der Entwicklung befindliche Methode der zusätzlichen Passivierung von gesäuberten Stahloberflächen hingewiesen.
Stand der amerikanischen Arbeiten über die Beurteilung galvanischer Überzüge auf Grund von Schnellkorrosionsversuchen
Authors: Kutzelnigg A.
Published: December 2004

Es wird an Hand von Tabellen über das Forschungsvorhaben Nr. 15 der American Electroplaters' Society Berichtet, das sich eingehend mit der Beurteilung galvanischer Überzüge auf Grund von Kurzbeanspruchungsverfahren befaßt.
Polyvinylchlorid‐Plastikrohre. Lieferarten, Dimensionen, Eigenschaften, Prüfung, Bearbeitung, Verbindung und Verlegung
Authors: Köhler W.
Published: December 2004

Rohre aus Polyvinylchlorid (Supradur) finden infolge ihrer guten allgemeinen und spezifischen Eigenschaften, insbesondere ihres ausgezeichneten Korrosionschemischen Verhaltens, zunehmende Verwendung in Anlagen zur Förderung aggressiver Flüssigkeiten und Gase. Im Hinblick darauf gibt der vorliegende Fortschrittsbericht einen zusammenfassenden und zeitgemäßen Überblick über Lieferarten und Dimensionierung, über das physikalische und korrosionschemische Verhalten sowie über die Verlegung und Verbindung von Polyvinylchlorid‐Plastikrohren.
Elektrochemische Vorgänge bei der Spannungskorrosion
Authors: Gerischer H.
Published: December 2004

Elektrochemische Untersuchungen an einem einfachen Modellsystem haben ergeben, daß die bei verschiedenen Metall‐Legierungen auftretende Spannungskorrosion vor allem auf das Zusammenwirken zweier Effekte zurückgeführt werden kan. Die enge Lokalisierung des Korrosionsvorganges wird hervorgerufen durch den Mechanismus plastischer Verformungsvorgänge. Die Atome an Durchstoßungslinien der Gleitebenen oder abgleitenden Korngrenzen mti der Oberfläche werden bei plastischer Verformung aktiviert und gehen sehr bevorzugt in Lösung. Bei allen spannungskorrosionsempfindlichen Legierungen entstehen durch die Korrosion auf der Oberfläche korrosinshemmende Deckschichten. (Anreicherung eines edleren Legierungsbestandteils oder Passivierung). Das Aufreißen solcher Deckschichten bei der plastischen Verformung verstärkt die Lokalisierung des Korrosionsvorganges außerordentlich und führt zu dem Phänomen der Spannungs‐Korrosion.

In der Arbeit wird gezeigt, wie sich solche Vorgänge im anodischen Korrosionsstrom nachweisen lassen.
Synthetische Kautschuk‐Arten als Korrosionsschutz
Authors: Reiner St.
Published: December 2004

In der chemischen und den verwandten Industrieen werden Reaktionsgefäße, Rohrleitungen und dgl. vorzugsweise mit natürlichen oder synthetischen Hochpolymeren belegt. Die Verfahren, die beute als Korrosionsschutz angewendet werden, sind sehr mannigfaltig. Solche Schutzbeläge werden hergestellt:

Aus Buna, Perbunan, Neoprene, Butylkautschuk, Siliconkautschuk, Hypalon, Hycar.

Diese Beläge sind vulkanisierbar und beständig gegen:

Schwefelsäure, Salzsäure, Flußsäure, Essigsäure, Kalilauge, Chlor usw.

Die Verbindung zwischen Metall und Schutzbelag muß vollständig homogen sein, da sonst im Betrieb erhebliche Störungen auftreten können. Die synthetischen Hochpolymere müssen nach ganz bestimmten Vorschriften der Verarbeitung eingesetzt werden. Die Technik der Mischungen, die Verarbeitung und schließlich die Vulkanisation sind für die Güte der Beläge ausschlaggebend.

Man kennt das Messingverfahren, das Dartex‐Verfahren, das Desmodur‐Verfahren, die Siliconbeläge und die Hypalon‐Bindungen.

Die fertigen Beläge werden nach der Vulkanisation mit einem Induktionsapparat auf Dichtigkeit geprüfl. Die Prüfung erfolgt bei 2000 V‐Spannung, die etwa einer Funkenstrecke von 20 min entspricht.