bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increase of the yields of eicosapentaenoic and docosahexaenoic acids by the microalga Pavlova lutheri following random mutagenesis
Authors: Meireles Luís A. , Guedes A. Catarina , Malcata F. Xavier 
Published: November 2002

AbstractThe high commercial values of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids have driven a strain‐improvement program, aimed at increasing the content of those fatty acids in the microalga Pavlova lutheri (SMBA 60) as parent strain. After a round of mutation using UV‐light as mutagenic agent, an isolate strain (tentatively called II#2) was obtained, the EPA and DHA contents of which (in % dry biomass) were 32.8% and 32.9% higher than those of the control, native strain. The final EPA yields, when the cultures were maintained under appropriate conditions, were 17.4 and 23.1 mg · g−1 dry biomass, for the wild‐type and the II#2 strain, respectively, whereas the final DHA yields were 8.0 and 10.6 mg · g−1 dry biomass, respectively. These results suggest that random mutagenesis can successfully be applied to increase the yield of n‐3 fatty acids by microalgae. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 50–55, 2003.
Metabolic flux analysis of cultured hepatocytes exposed to plasma
Authors: Chan Christina , Berthiaume François , Lee Kyongbum , Yarmush Martin L. 
Published: November 2002

AbstractHepatic metabolism can be investigated using metabolic flux analysis (MFA), which provides a comprehensive overview of the intracellular metabolic flux distribution. The characterization of intermediary metabolism in hepatocytes is important for all biotechnological applications involving liver cells, including the development of bioartificial liver (BAL) devices. During BAL operation, hepatocytes are exposed to plasma or blood from the patient, at which time they are prone to accumulate intracellular lipids and exhibit poor liver‐specific functions. In a prior study, we found that preconditioning the primary rat hepatocytes in culture medium containing physiological levels of insulin, as opposed to the typical supraphysiological levels found in standard hepatocyte culture media, reduced lipid accumulation during subsequent plasma exposure. Furthermore, supplementing the plasma with amino acids restored hepatospecific functions. In the current study, we used MFA to quantify the changes in intracellular pathway fluxes of primary rat hepatocytes in response to low‐insulin preconditioning and amino acid supplementation. We found that culturing hepatocytes in medium containing lower physiological levels of insulin decreased the clearance of glucose and glycerol with a concomitant decrease in glycolysis. These findings are consistent with the general notion that low insulin, especially in the presence of high glucagon levels, downregulates glycolysis in favor of gluconeogenesis in hepatocytes. The MFA model shows that, during subsequent plasma exposure, low‐insulin preconditioning upregulated gluconeogenesis, with lactate as the primary precursor in unsupplemented plasma, with a greater contribution from deaminated amino acids in amino acid‐supplemented plasma. Concomitantly, low‐insulin preconditioning increased fatty acid oxidation, an effect that was further enhanced by amino acid supplementation to the plasma. The increase in fatty acid oxidation reduced intracellular triglyceride accumulation. Overall, these findings are consistent with the notion that the insulin level in medium culture presets the metabolic machinery of hepatocytes such that it directly impacts on their metabolic behavior during subsequent plasma culture. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 33–49, 2003.
Metabolic model for glycogen‐accumulating organisms in anaerobic/aerobic activated sludge systems
Authors: Zeng Raymond J. , van Loosdrecht Mark C. M. , Yuan Zhiguo , Keller Jürg 
Published: November 2002

AbstractGlycogen‐accumulating organisms (GAO) have the potential to directly compete with polyphosphate‐accumulating organisms (PAO) in EBPR systems as both are able to take up VFA anaerobically and grow on the intracellular storage products aerobically. Under anaerobic conditions GAO hydrolyse glycogen to gain energy and reducing equivalents to take up VFA and to synthesise polyhydroxyalkanoate (PHA). In the subsequent aerobic stage, PHA is being oxidised to gain energy for glycogen replenishment (from PHA) and for cell growth. This article describes a complete anaerobic and aerobic model for GAO based on the understanding of their metabolic pathways. The anaerobic model has been developed and reported previously, while the aerobic metabolic model was developed in this study. It is based on the assumption that acetyl‐CoA and propionyl‐CoA go through the catabolic and anabolic processes independently. Experimental validation shows that the integrated model can predict the anaerobic and aerobic results very well. It was found in this study that at pH 7 the maximum acetate uptake rate of GAO was slower than that reported for PAO in the anaerobic stage. On the other hand, the net biomass production per C‐mol acetate added is about 9% higher for GAO than for PAO. This would indicate that PAO and GAO each have certain competitive advantages during different parts of the anaerobic/aerobic process cycle. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 92–105, 2003.
A mutant of the green alga Dunaliella salina constitutively accumulates zeaxanthin under all growth conditions
Authors: Jin EonSeon , Feth Brian , Melis Anastasios 
Published: November 2002

AbstractA novel mutant (zea1) of the halotolerant unicellular green alga Dunaliella salina is impaired in the zeaxanthin epoxidation reaction, thereby lacking a number of the β‐branch xanthophylls. HPLC analysis revealed that the zea1 mutant lacks neoxanthin (N), violaxanthin (V) and antheraxanthin (A) but constitutively accumulates zeaxanthin (Z). Under low‐light physiological growth conditions, the zea1 (6 mg Z per g dry weight or 8 × 10−16 mol Z/cell) had a substantially higher Z content than the wild type (0.2 mg Z per g dry weight or 0.5 × 10−16 mol Z/cell). Lack of N, V, and A did not affect photosynthesis or growth of the zea1 strain. Biochemical analyses suggested that Z constitutively and quantitatively substitutes for N, V, and A in the zea1 strain. This mutant is discussed in terms of its commercial value and potential utilization by the algal biotechnology industry for the production of zeaxanthin, a high‐value bioproduct. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 115–124, 2003.
The response of virally infected insect cells to dissolved oxygen concentration: Recombinant protein production and oxidative damage
Authors: Saarinen Mark A. , Murhammer David W. 
Published: November 2002

AbstractThe effects of dissolved oxygen (DO) concentration on virally infected insect cells were investigated in 3‐L bioreactor culture. Specifically, cultures of Spodoptera frugiperda Sf‐9 (Sf‐9) and Trichoplusia ni BTI‐Tn‐5B1‐4 (Tn‐5B1‐4) were infected with Autographa californica multiple nucleopolyhedrovirus expressing secreted alkaline phosphatase (SEAP). Following infection at a DO concentration of 50% air saturation, the DO concentration was adjusted to a final value of either 190%, 50%, or 10% air saturation. Recombinant SEAP production, cell viability, protein carbonyl content, and thiobarbituric acid reactive substances (TBARS) content were monitored. The increases in protein carbonyl and TBARS contents are taken to be indicators of protein oxidation and lipid oxidation, respectively. DO concentration was found to have no noticeable effect on SEAP production or cell viability decline in the Sf‐9 cell line. In the Tn‐5B1‐4 cell line, cells displayed an increased peak SEAP production rate for 190% air saturation and displayed an increased rate of viability decline at increased DO concentration. Protein carbonyl content showed no significant increase in the Sf‐9 cell line by 72 h postinfection (pi) at any DO concentration but showed a twofold increase at 10% and 50% DO concentration and a threefold increase at 190% DO concentration by 72 h pi in Tn‐5B1‐4 cells. TBARS content was found to increase by ≈ 50% in Sf‐9 cells and by ≈ twofold in Tn‐5B1‐4 cells by 72 h pi with no clear relationship to DO concentration. It is hypothesized that oxygen uptake changes due to the viral infection process may bear a relation to the observed increases in protein and lipid oxidation and that lipid oxidation may play an important role in the death of virally infected insect cells. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 106–114, 2003.
Novel CNBP‐ and La‐based translation control systems for mammalian cells
Authors: Schlatter Stefan , Fussenegger Martin 
Published: November 2002

AbstractThroughout the development of Xenopus, production of ribosomal proteins (rp) is regulated at the translational level. Translation control is mediated by a terminal oligopyrimidine element (TOP) present in the 5′ untranslated region (UTR) of rp‐encoding mRNAs. TOP elements adopt a specific secondary structure that prevents ribosome‐binding and translation‐initiation of rp‐encoding mRNAs. However, binding of CNBP (cellular nucleic acid binding protein) or La proteins to the TOP hairpin structure abolishes the TOP‐mediated transcription block and induces rp production. Based on the specific CNBP‐TOP/La‐TOP interactions we have designed a translation control system (TCS) for conditional as well as adjustable translation of desired transgene mRNAs in mammalian cells. The generic TCS configuration consists of a plasmid encoding CNBP or La under control of the tetracycline‐responsive expression system (TETOFF) and a target expression vector containing a TOP module between a constitutive PSV40 promoter and the human model product gene SEAP (human secreted alkaline phosphatase) (PSV40‐TOP‐SEAP‐pA). The TCS technology showed excellent SEAP regulation profiles in transgenic Chinese hamster ovary (CHO) cells. Alternatively to CNBP and La, TOP‐mediated translation control can also be adjusted by artificial phosphorothioate anti‐TOP oligodeoxynucleotides. Confocal laser‐scanning microscopy demonstrated cellular uptake of FITC‐labeled oligodeoxynucleotides and their localization in perinuclear organelles within 24 hours. Besides their TOP‐based translation‐controlling capacity, CNBP and La were also shown to increase cap‐independent translation from polioviral internal ribosomal entry sites (IRES) and La alone to boost cap‐dependent translation initiation. CNBP and La exemplify for the first time the potential of RNA‐binding proteins to exert translation control of desired transgenes and to increase heterologous protein production in mammalian cells. We expect both of these assets to advance current gene therapy and biopharmaceutical manufacturing strategies. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 1–12, 2003.
Expression of a plant‐derived peptide harboring water‐cleaning and antimicrobial activities
Authors: Suarez M. , Entenza J. M. , Doerries C. , Meyer E. , Bourquin L. , Sutherland J. , Marison I. , Moreillon P. , Mermod N. 
Published: November 2002

AbstractDrinking water is currently a scarce world resource, the preparation of which requires complex treatments that include clarification of suspended particles and disinfection. Seed extracts of Moringa oleifera Lam., a tropical tree, have been proposed as an environment‐friendly alternative, due to their traditional use for the clarification of drinking water. However, the precise nature of the active components of the extract and whether they may be produced in recombinant form are unknown. Here we show that recombinant or synthetic forms of a cationic seed polypeptide mediate efficient sedimentation of suspended mineral particles and bacteria. Unexpectedly, the polypeptide was also found to possesses a bactericidal activity capable of disinfecting heavily contaminated water. Furthermore, the polypeptide has been shown to efficiently kill several pathogenic bacteria, including antibiotic‐resistant isolates of Staphylococcus, Streptococcus, and Legionella species. Thus, this polypeptide displays the unprecedented feature of combining water purification and disinfectant properties. Identification of an active principle derived from the seed extracts points to a range of potential for drinking water treatment or skin and mucosal disinfection in clinical settings. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 13–20, 2003.
The segment projection method for interface tracking
Authors: Tornberg Anna‐Karin , Engquist Björn 
Published: November 2002

AbstractThere has recently been important progress in the development of front tracking and level set methods for the numerical simulation of moving interfaces. The segment projection method is a new technique for computational geometry. It can be seen as a compromise between front tracking and level set methods. It is based on the regular mathematical representation of a manifold as an atlas of charts. Each chart or segment is evolved independently by a partial differential equation that is discretized on an Eulerian grid. The connectivity of the segments is handled by an appropriate data structure and by numerical interpolation. The method is presented and its properties are analyzed. Applications to multiphase flow, epitaxial growth, and high‐frequency wave propagation are given. © 2002 Wiley Periodicals, Inc.
Multiscale homogenization with bounded ratios and anomalous slow diffusion
Authors: Ben Arous Gérard , Owhadi Houman 
Published: November 2002

AbstractWe show that the effective diffusivity matrix D(Vn) for the heat operator ∂t − (Δ/2 − ∇Vn∇) in a periodic potential Vn = ΣUk(x/Rk) obtained as a superposition of Hölder‐continuous periodic potentials Uk (of period 𝕋d := ℝd/ℤd, d ∈ ℕ*, Uk(0) = 0) decays exponentially fast with the number of scales when the scale ratios Rk+1/Rk are bounded above and below. From this we deduce the anomalous slow behavior for a Brownian motion in a potential obtained as a superposition of an infinite number of scales, dyt = dωt − ∇V∞(yt)dt. © 2002 Wiley Periodicals, Inc.
On Schrödinger maps
Authors: Nahmod Andrea , Stefanov Atanas , Uhlenbeck Karen 
Published: November 2002

AbstractWe study the question of well‐posedness of the Cauchy problem for Schrödinger maps from ℝ × ℝ2 to the sphere 𝕊2 or to ℍ2, the hyperbolic space. The idea is to choose an appropriate gauge change so that the derivatives of the map will satisfy a certain nonlinear Schrödinger system of equations and then study this modified Schrödinger map system (MSM). We then prove local well‐posedness of the Cauchy problem for the MSM with minimal regularity assumptions on the data and outline a method to derive well‐posedness of the Schrödinger map itself from it. In proving well‐posedness of the MSM, the heart of the matter is resolved by considering truly quatrilinear forms of weighted L2‐functions. © 2002 Wiley Periodicals, Inc.
Extracting macroscopic stochastic dynamics: Model problems
Authors: Huisinga Wilhelm , Schütte Christof , Stuart Andrew M. 
Published: December 2002

AbstractThe purpose of this work is to shed light on an algorithm designed to extract effective macroscopic models from detailed microscopic simulations. The particular algorithm we study is a recently developed transfer operator approach due to Schütte et al. [20]. The investigations involve the formulation, and subsequent numerical study, of a class of model problems. The model problems are ordinary differential equations constructed to have the property that, when projected onto a low‐dimensional subspace, the dynamics is approximately that of a stochastic differential equation exhibiting a finite‐state‐space Markov chain structure. The numerical studies show that the transfer operator approach can accurately extract finite‐state Markov chain behavior embedded within high‐dimensional ordinary differential equations. In so doing the studies lend considerable weight to existing applications of the algorithm to the complex systems arising in applications such as molecular dynamics. The algorithm is predicated on the assumption of Markovian input data; further numerical studies probe the role of memory effects. Although preliminary, these studies of memory indicate interesting avenues for further development of the transfer operator methodology. © 2002 Wiley Periodicals, Inc.
Parenting style and obsessive‐compulsive symptoms and personality traits in a student sample
Authors: Aycicegi Ayse , Harris Catherine L. , Dinn Wayne M. 
Published: December 2002

AbstractThere is widespread acceptance of the idea that aspects of parenting such as overprotectiveness and perfectionism contribute to the pathogenesis of obsessive‐compulsive disorder (OCD). Less resolved is whether the important dimensions of parenting are overprotectiveness, lack of acceptance, authoritarian style, discouragement of risk‐taking, and/or induction of guilt. It is also unclear whether different parenting characteristics are associated with the development of symptoms of OCD, compared to the traits of obsessive‐compulsive personality disorder (OCPD). OCD symptoms and OC personality traits were measured in a non‐clinical, student sample and correlated with students' report of parents' acceptance, disciplinary firmness, and psychological control (a construct which included psychological manipulation and guilt‐induction). Following the literature on both clinical and subclinical OCD and OCPD, we predicted that all three scales would correlate with OCD symptoms and OCPD traits. Stepwise regression analysis revealed that psychological control was the unique predictor, controlling for depressive symptoms. Unexpectedly, a controlling parenting style was not selectively associated with classical OC symptoms or OC personality traits. Rather, psychological control was associated with a broad‐spectrum of anxiety and depressive symptoms which cut across diagnostic boundaries. Findings are generally compatible with a single underlying vulnerability to both OCD and OCPD, as well as generalized/social anxiety and depressive symptoms, which can be shaped by cultural and familial factors to a specific clinical presentation. Copyright © 2002 John Wiley & Sons, Ltd.
Homogeneous and heterogeneous distributed cluster processing for two‐ and three‐dimensional viscoelastic flows
Authors: Baloch A. , Grant P. W. , Webster M. F. 
Published: November 2002

AbstractA finite‐element study of two‐ and three‐dimensional incompressible viscoelastic flows in a planar lid‐driven cavity and concentric rotating cylinders is presented. The hardware platforms consist of both homogeneous and heterogeneous clusters of workstations. A semi‐implicit time‐stepping Taylor–Galerkin scheme is employed using the message passing mechanism provided by the Parallel Virtual Machine libraries. DEC‐alpha, Intel Solaris and AMD‐K7(Athlon) Linux clusters are utilized. Parallel results are compared against single processor (sequentially) solutions, using the parallelism paradigm of domain decomposition. Communication is effectively masked and practically ideal, linear speed‐up with the number of processors is realized. Copyright © 2002 John Wiley & Sons, Ltd.
Computation of unsteady viscous incompressible flows in generalized non‐inertial co‐ordinate system using Godunov‐projection method and overlapping meshes
Authors: Pan H. , Damodaran M. 
Published: November 2002

AbstractTime‐dependent incompressible Navier–Stokes equations are formulated in generalized non‐inertial co‐ordinate system and numerically solved by using a modified second‐order Godunov‐projection method on a system of overlapped body‐fitted structured grids. The projection method uses a second‐order fractional step scheme in which the momentum equation is solved to obtain the intermediate velocity field which is then projected on to the space of divergence‐free vector fields. The second‐order Godunov method is applied for numerically approximating the non‐linear convection terms in order to provide a robust discretization for simulating flows at high Reynolds number. In order to obtain the pressure field, the pressure Poisson equation is solved. Overlapping grids are used to discretize the flow domain so that the moving‐boundary problem can be solved economically. Numerical results are then presented to demonstrate the performance of this projection method for a variety of unsteady two‐ and three‐dimensional flow problems formulated in the non‐inertial co‐ordinate systems. Copyright © 2002 John Wiley & Sons, Ltd.
Performance of finite volume solutions to the shallow water equations with shock‐capturing schemes
Authors: Erduran K. S. , Kutija V. , Hewett C. J. M. 
Published: November 2002

AbstractNumerical methods have become well established as tools for solving problems in hydraulic engineering. In recent years the finite volume method (FVM) with shock capturing capabilities has come to the fore because of its suitability for modelling a variety of types of flow; subcritical and supercritical; steady and unsteady; continuous and discontinuous and its ability to handle complex topography easily.This paper is an assessment and comparison of the performance of finite volume solutions to the shallow water equations with the Riemann solvers; the Osher, HLL, HLLC, flux difference splitting (Roe) and flux vector splitting. In this paper implementation of the FVM including the Riemann solvers, slope limiters and methods used for achieving second order accuracy are described explicitly step by step. The performance of the numerical methods has been investigated by applying them to a number of examples from the literature, providing both comparison of the schemes with each other and with published results. The assessment of each method is based on five criteria; ease of implementation, accuracy, applicability, numerical stability and simulation time. Finally, results, discussion, conclusions and recommendations for further work are presented. Copyright © 2002 John Wiley & Sons, Ltd.
Energy dynamics in a turbulent channel flow using the Karhunen‐Loéve approach
Authors: Webber G. A. , Handler R. A. , Sirovich L. 
Published: November 2002

AbstractThe dynamical equations for the energy in a turbulent channel flow have been developed by using the Karhunen‐Loéve modes to represent the velocity field. The energy balance equations show that all the energy in the flow originates from the applied pressure gradient acting on the mean flow. Energy redistribution occurs through triad interactions, which is basic to understanding the dynamics. Each triad interaction determines the rate of energy transport between source and sink modes via a catalyst mode. The importance of the proposed method stems from the fact that it can be used to determine both the rate of energy transport between modes as well as the direction of energy flow. The effectiveness of the method in determining the mechanisms by which the turbulence sustains itself is demonstrated by performing a detailed analysis of triad interactions occurring during a turbulent burst in a minimal channel flow. The impact on flow modification is discussed. Copyright © 2002 John Wiley & Sons, Ltd.