bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental investigations of multiple steady states in aerobic continuous cultivations of Saccharomyces cerevisiae
Authors: Lei Frede , Olsson Lisbeth , Jørgensen Sten Bay 
Published: April 2003

AbstractThe steady‐state behavior of a glucose‐limited, aerobic, continuous cultivation of Saccharomyces cerevisiae CEN.PK113‐7D was investigated around the critical dilution rate. Oxido‐reductive steady states were obtained at dilution rates up to 0.09 h−1 lower than the critical dilution rate by operating the bioreactor as a productostat, where the dilution rate was controlled on the basis of an ethanol measurement. Thus, the experimental investigations revealed that multiple steady states exist in a region of dilution rates below the critical dilution rate. The existence of multiple steady states was attributed to two distinct physiological effects occurring when growth changed from oxidative to oxido‐reductive: (i) a decrease in the efficiency of ATP production and utilization (at ethanol concentrations below 3 g/L) and (ii) repression of the oxidative metabolism (at higher ethanol concentrations). The first effect was best observed at low ethanol concentrations, where multiple steady states were observed even when no repression of the oxidative metabolism was evident, i.e., the oxidative capacity was constant. However, at higher ethanol concentrations repression of the oxidative metabolism was observed (the oxidative capacity decreased), and this resulted in a broader range of dilution rates where multiple steady states could be found. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 766–777, 2003.
Dynamics of the anaerobic process: Effects of volatile fatty acids
Authors: Pind Peter F. , Angelidaki Irini , Ahring Birgitte K. 
Published: April 2003

AbstractA complex and fast dynamic response of the anaerobic biogas system was observed when the system was subjected to pulses of volatile fatty acids (VFAs). It was shown that a pulse of specific VFAs into a well‐functioning continuous stirred tank reactor (CSTR) system operating on cow manure affected both CH4 yield, pH, and gas production and that a unique reaction pattern was seen for the higher VFAs as a result of these pulses. In this study, two thermophilic laboratory reactors were equipped with a novel VFA‐sensor for monitoring specific VFAs online. Pulses of VFAs were shown to have a positive effect on process yield and the levels of all VFA were shown to stabilize at a lower level after the biomass had been subjected to several pulses. The response to pulses of propionate or acetate was different from the response to butyrate, iso‐butyrate, valerate, or iso‐valerate. High concentrations of propionate affected the degradation of all VFAs, while a pulse of acetate affected primarily the degradation of iso‐valerate or 2‐methylbutyrate. Pulses of n‐butyrate, iso‐butyrate, and iso‐valerate yielded only acetate, while degradation of n‐valerate gave both propionate and acetate. Product sensitivity or inhibition was shown for the degradation of all VFAs tested. Based on the results, it was concluded that measurements of all specific VFAs are important for control purposes and increase and decrease in a specific VFA should always be evaluated in close relationship to the conversion of other VFAs and the history of the reactor process. It should be pointed out that the observed dynamics of VFA responses were based on hourly measurements, meaning that the response duration was much lower than the hydraulic retention time, which exceeds several days in anaerobic CSTR systems. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 791–801, 2003.
Potential of cell retention techniques for large‐scale high‐density perfusion culture of suspended mammalian cells
Authors: Voisard D. , Meuwly F. , Ruffieux P.‐A. , Baer G. , Kadouri A. 
Published: April 2003

AbstractThis review focuses on cultivation of mammalian cells in a suspended perfusion mode. The major technological limitation in the scaling‐up of these systems is the need for robust retention devices to enable perfusion of medium as needed. For this, cell retention techniques available to date are presented, namely, cross‐flow filters, hollow fibers, controlled‐shear filters, vortex‐flow filters, spin‐filters, gravity settlers, centrifuges, acoustic settlers, and hydrocyclones. These retention techniques are compared and evaluated for their respective advantages and potential for large‐scale utilization in the context of industrial manufacturing processes. This analysis shows certain techniques have a limited range of perfusion rate where they can be implemented (most microfiltration techniques). On the other hand, techniques were identified that have shown high perfusion capacity (centrifuges and spin‐filters), or have a good potential for scale‐up (acoustic settlers and inclined settlers). The literature clearly shows that reasonable solutions exist to develop large‐scale perfusion processes. © 2003 Wiley Periodicals, Inc. Biotechol Bioeng 82: 751–765, 2003.
Effect of salts on lysozyme stability at the water–oil interface and upon encapsulation in poly(lactic‐co‐glycolic) acid microspheres
Authors: Pérez Caroline , Griebenow Kai 
Published: April 2003

AbstractEncapsulation of proteins in poly(lactic‐co‐glycolic) acid (PLGA) microspheres by the water‐in‐oil‐in‐water (w/o/w) technique is very challenging because of the inherent physical instability of proteins. In particular, exposure of proteins to the first water‐in‐oil emulsion causes unwanted interface‐induced protein inactivation and aggregation. We tested whether salts could afford stabilization of a model protein, hen egg‐white lysozyme, against the detrimental events occurring at the w/o interface and subsequently upon w/o/w encapsulation. First, we investigated the effect of salts on the specific enzyme activity and generation of soluble precipitates and insoluble aggregates upon emulsification of an aqueous lysozyme solution with methylene chloride. It was found that lysozyme precipitation occurred upon emulsification. The amount of precipitate formed at salt concentrations between 10–100 mM was related to the position of the anion in the electroselectivity series (SO42− > SCN− > Cl− > H2PO4−) while high salt concentrations (1M) led to > 80% of lysozyme precipitation regardless of the salt. The precipitates consisted of buffer‐soluble protein precipitates and water‐insoluble noncovalent aggregates. Lysozyme precipitation, aggregation, and inactivation upon emulsification were largely prevented in the presence of 50 mM KH2PO4 while KSCN caused an increase in these detrimental events. Second, it was tested whether the improved structural integrity of lysozyme at the w/o interface would improve its stability upon w/o/w encapsulation in PLGA microspheres. Some conditions indeed led to improved stability, particularly codissolving lysozyme with 50 mM KH2PO4 reduced loss in the specific activity and aggregation. In conclusion, the type and concentration of salts is a critical parameter when encapsulating protein in PLGA microspheres. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 825–832, 2003.
Development of apoptosis‐resistant dihydrofolate reductase‐deficient Chinese hamster ovary cell line
Authors: Lee Suk Kyoo , Lee Gyun Min 
Published: April 2003

AbstractApoptosis‐resistant dihydrofolate reductase‐deficient CHO cell line (dhfr− CHO‐bcl2) was developed by introduction of the bcl‐2 gene into the dhfr− CHO cell line (DUKX‐B11, ATCC CRL‐9096) and subsequent selection of clones stably overexpressing Bcl‐2 in the absence of selection pressure. When the dhfr− CHO‐bcl2 cell line was used as a host cell line for development of a recombinant CHO (rCHO) cell line expressing a humanized antibody, it displayed stable expression of the bcl‐2 gene during rCHO cell line development and no detrimental effect of Bcl‐2 overexpression on specific antibody productivity. Taken together, the results obtained demonstrate that the use of an apoptosis‐resistant dhfr− CHO cell line as the host cell line saves the effort of establishing an apoptosis‐resistant rCHO cell line and expedites the development process of apoptosis‐resistant rCHO cells producing therapeutic proteins. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 872–876, 2003.
Flocculation behavior of Sphingobium chlorophenolicum in degrading pentachlorophenol at different life stages
Authors: Chang You‐Im , Su Chia‐Ying 
Published: April 2003

AbstractThe cell flocculation behavior of degrading pentachlorophenol (PCP) by using Sphingobium chlorophenolicum (Flavobacterium sp., ATCC 39723) is investigated in the present paper. It is found that these Sphingobium cells can efficiently degrade PCP when the concentration of this toxic compound is below 150 ppm. These degradation rates of PCP can be facilitated with the additions of three supplementary carbons: glutamate (4.0 g/L), glucose (3.2 g/L), and cellobiose (3.05 g/L), among which the highest specific growth rate of cells is obtained when glucose is added. More importantly, in these biodegradation experiments described herein, in order to investigate the cell flocculation behavior, the temporal variations of cell size, zeta potential, and stability ratio of the cell suspension are also measured. It is found that, no matter what kind of supplementary carbon source is added, the highest stability ratio of the cell suspension can be always obtained at the end of the exponential growth phase, which can be well explained by using the results of cell size and zeta potential measurements according to the DLVO theory. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 843–850, 2003.
High level of expression of recombinant human granulocyte‐macrophage colony stimulating factor in transgenic rice cell suspension culture
Authors: Shin Yun‐Ji , Hong Shin‐Young , Kwon Tae‐Ho , Jang Yong‐Suk , Yang Moon‐Sik 
Published: April 2003

AbstractRecombinant human granulocyte‐macrophage colony stimulating factor (hGM‐CSF) has been previously produced in tobacco cell suspension cultures. However, the amount of hGM‐CSF accumulated in the culture medium dropped quickly from its maximum of 150 μg/L at 5 d after incubation. To overcome this problem, we sought an expression system in which heterologous gene expression could be induced at high levels. We selected a rice amylase expression system in which the promoter Ramy3D is induced to express recombinant protein by sucrose starvation. This induction system was found to give good yield of recombinant hGM‐CSF in transgenic rice cell suspension culture and protease activity of this culture medium was low compared to that of tobacco culture system. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 778–783, 2003.
Chemical biotechnology for the specific oxyfunctionalization of hydrocarbons on a technical scale
Authors: Bühler Bruno , Bollhalder Irene , Hauer Bernhard , Witholt Bernard , Schmid Andreas 
Published: April 2003

AbstractOxygenases catalyze, among other interesting reactions, highly selective hydrocarbon oxyfunctionalizations, which are important in industrial organic synthesis but difficult to achieve by chemical means. Many enzymatic oxygenations have been described, but few of these have been scaled up to industrial scales, due to the complexity of oxygenase based biocatalysts and demanding process implementation. We have combined recombinant whole‐cell catalysis in a two‐liquid phase system with fed‐batch cultivation in an optimized medium and developed an industrially feasible process for the kinetically controlled and complex multistep oxidation of pseudocumene to 3,4‐dimethylbenzaldehyde using the xylene monooxygenase of Pseudomonas putida mt‐2 in Escherichia coli. Successful scale up to 30 L working volume using downscaled industrial equipment allowed a productivity of 31 g L−1 d−1 and a product concentration of 37 g L−1. These performance characteristics meet present industry requirements. Product purification resulted in the recovery of 469 g of 3,4‐dimethyl‐ benzaldehyde at a purity of 97% and an overall yield of 65%. This process illustrates the general feasibility of industrial biocatalytic oxyfunctionalization. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 833–842, 2003.
A novel pathway to enzyme deactivation: The cutinase model
Authors: Baptista R. P. , Chen L. Y. , Paixão A. , Cabral J. M. S. , Melo E. P. 
Published: April 2003

AbstractCutinase in aqueous solution at pH 4.5 deactivates following a parallel pathway. At 53°C, 88% of the cutinase molecules are in the unfolded conformation, which can aggregate with a reaction order of 3 if the protein concentration is high (≥12 μM). The aggregates show a sixfold increase in size as determined by dynamic light scattering. This aggregation process is the first phase observed during a deactivation experiment; however, after significant cutinase depletion and maturation of the aggregates, a first‐order step starts to dominate and a second phase independent of the protein concentration is observed. Kinetic partitioning between aggregation and first‐order irreversible changes of the unfolded conformation can occur during enzyme deactivation when the equilibrium between the native and the unfolded conformation is shifted and kept toward the unfolded conformation. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 851–857, 2003.
Accrediting Standards Affecting Mid‐Level Teacher Education Preparation in the Community College
Authors: Imig David G. , Harrill‐McClellan Mary 
Published: April 2003

AbstractThis chapter reviews the accrediting standards of the National Council for the Accreditation of Teacher Education and the Teacher Education Accreditation Council, assessess the ease or difficulty with which community colleges could meet the required standards, and suggests accreditation models appropriate for community colleges.
Multi‐wavelength image space: another Grid‐enabled science
Authors: Williams Roy , Berriman Bruce , Deelman Ewa , Good John , Jacob Joseph , Kesselman Carl , Lonsdale Carol , Oliver Seb , Prince Thomas A. 
Published: April 2003

AbstractWe describe how the Grid enables new research possibilities in astronomy through multi‐wavelength images. To see sky images in the same pixel space, they must be projected to that space, a computer‐intensive process. There is thus a virtual data space induced that is defined by an image and the applied projection. This virtual data can be created and replicated with Planners and Replica catalog technology developed under the GriPhyN project. We plan to deploy our system (MONTAGE) on the U.S. Teragrid. Grid computing is also needed for ingesting data—computing background correction on each image—which forms a separate virtual data space. Multi‐wavelength images can be used for pushing source detection and statistics by an order of magnitude from current techniques; for optimization of multi‐wavelength image registration for detection and characterization of extended sources; and for detection of new classes of essentially multi‐wavelength astronomical phenomena. The paper discusses both the Grid architecture and the scientific goals. Copyright © 2003 John Wiley & Sons, Ltd.
An adaptive parallel genetic algorithm system for i‐Computing environment
Authors: Wong Yuk‐Yin , Lee Kin‐Hong , Leung Kwong‐Sak 
Published: April 2003

AbstractMany real‐world optimization problems in the scientific and engineering fields can be solved by genetic algorithms (GAs) but it still requires a long execution time for complex problems. At the same time, there are many under‐utilized workstations on the Internet. In this paper, we present a self‐adaptive parallel GA system named APGAIN, which utilizes the spare power of the heterogeneous workstations on the Internet to solve complex optimization problems. In order to maintain a balance between exploitation and exploration, we have devised a novel probabilistic rule‐driven adaptive model (PRDAM) to adapt the GA parameters automatically. APGAIN is implemented on an Internet Computing system called DJM. In the implementation, we discover that DJM's original load balancing strategy is insufficient. Hence the strategy is extended with the job migration capability. The performance of the system is evaluated by solving the traveling salesman problem with data from a public database. Copyright © 2003 John Wiley & Sons, Ltd.
A scalable HPF implementation of a finite‐volume computational electromagnetics application on a CRAY T3E parallel system
Authors: Pan Yi , Shang Joseph J. S. , Guo Minyi 
Published: April 2003

AbstractThe time‐dependent Maxwell equations are one of the most important approaches to describing dynamic or wide‐band frequency electromagnetic phenomena. A sequential finite‐volume, characteristic‐based procedure for solving the time‐dependent, three‐dimensional Maxwell equations has been successfully implemented in Fortran before. Due to its need for a large memory space and high demand on CPU time, it is impossible to test the code for a large array. Hence, it is essential to implement the code on a parallel computing system. In this paper, we discuss an efficient and scalable parallelization of the sequential Fortran time‐dependent Maxwell equations solver using High Performance Fortran (HPF). The background to the project, the theory behind the efficiency being achieved, the parallelization methodologies employed and the experimental results obtained on the Cray T3E massively parallel computing system will be described in detail. Experimental runs show that the execution time is reduced drastically through parallel computing. The code is scalable up to 98 processors on the Cray T3E and has a performance similar to that of an MPI implementation. Based on the experimentation carried out in this research, we believe that a high‐level parallel programming language such as HPF is a fast, viable and economical approach to parallelizing many existing sequential codes which exhibit a lot of parallelism. Copyright © 2003 John Wiley & Sons, Ltd.
Design and implementation of a user‐level Sockets layer over Virtual Interface Architecture
Authors: Kim Jin‐Soo , Kim Kangho , Jung Sung‐In , Ha Soonhoi 
Published: April 2003

AbstractThe Virtual Interface Architecture (VIA) is an industry standard user‐level communication architecture for system area networks. The VIA provides a protected, directly‐accessible interface to a network hardware, removing the operating system from the critical communication path. In this paper, we design and implement a user‐level Sockets layer over VIA, named SOVIA (Sockets Over VIA). Our objective is to use the SOVIA layer to accelerate the existing Sockets‐based applications with a reasonable effort and to provide a portable and high‐performance communication library based on VIA to application developers.SOVIA realizes comparable performance to native VIA, showing a minimum one‐way latency of 10.5 $\mu$s and a peak bandwidth of 814 Mbps on Giganet's cLAN. We have shown the functional compatibility with the existing Sockets API by porting File Transfer Protocol (FTP) and Remote Procedure Call (RPC) applications over the SOVIA layer. Compared to the Giganet's LAN Emulation (LANE) driver which emulates TCP/IP inside the kernel, SOVIA easily doubles the file transfer bandwidth in FTP and reduces the latency of calling an empty remote procedure by 77% in RPC applications. Copyright © 2003 John Wiley & Sons, Ltd.
NPACI Rocks: tools and techniques for easily deploying manageable Linux clusters
Authors: Papadopoulos Philip M. , Katz Mason J. , Bruno Greg 
Published: April 2003

AbstractHigh‐performance computing clusters (commodity hardware with low‐latency, high‐bandwidth interconnects) based on Linux are rapidly becoming the dominant computing platform for a wide range of scientific disciplines. Yet, straightforward software installation, maintenance, and health monitoring for large‐scale clusters has been a consistent and nagging problem for non‐cluster experts. The NPACI Rocks distribution takes a fresh perspective on management and installation of clusters to dramatically simplify software version tracking and cluster integration.NPACI Rocks incorporates the latest Red Hat distribution (including security patches) with additional cluster‐specific software. Using the identical software tools used to create the base distribution, users can customize and localize Rocks for their site. Strong adherence to widely‐used (de facto) tools allows Rocks to move with the rapid pace of Linux development. Version 2.2.1 of the toolkit is available for download and installation. Over 100 Rocks clusters have been built by non‐cluster experts at multiple institutions (residing in various countries) providing a peak aggregate of 2 TFLOPS of clustered computing. Copyright © 2003 John Wiley & Sons, Ltd.
p‐Jigsaw: a cluster‐based Web server with cooperative caching support
Authors: Chen Ge , Wang Cho‐Li , Lau Francis C. M. 
Published: April 2003

AbstractClustering provides a viable approach to building scalable Web systems with increased computing power and abundant storage space for data and contents. In this paper, we present a pure‐Java‐based parallel Web server system, p‐Jigsaw, which operates on a cluster and uses the technique of cooperative caching to achieve high performance. We introduce the design of an in‐memory cache layer, called Global Object Space (GOS), for dynamic caching of frequently requested Web objects. The GOS provides a unified view of cluster‐wide memory resources for achieving location‐transparent Web object accesses. The GOS relies on cooperative caching to minimize disk accesses. A requested Web object can be fetched from a server node's local cache or a peer node's local cache, with the disk serving only as the last resort. A prototype system based on the W3C Jigsaw server has been implemented on a 16‐node PC cluster. Three cluster‐aware cache replacement algorithms were tested and evaluated. The benchmark results show good speedups with a real‐life access log, proving that cooperative caching can have significant positive impacts on the performance of cluster‐based parallel Web servers. Copyright © 2003 John Wiley & Sons, Ltd.
Clusterfile: a flexible physical layout parallel file system
Authors: Isaila Florin , Tichy Walter F. 
Published: April 2003

AbstractThis paper presents Clusterfile, a parallel file system that provides parallel file access on a cluster of computers. We introduce a file partitioning model that has been used in the design of Clusterfile. The model uses a data representation that is optimized for multidimensional array partitioning while allowing arbitrary partitions. The paper shows how the file model can be employed for file partitioning into both physical subfiles and logical views. We also present how the conversion between two partitions of the same file is implemented using a general memory redistribution algorithm. We show how we use the algorithm to optimize non‐contiguous read and write operations. The experimental results include performance comparisons with the Parallel Virtual File System (PVFS) and an MPI‐IO implementation for PVFS. Copyright © 2003 John Wiley & Sons, Ltd.