bluuebunny/crossref_metadata_2025_split huggingface dataset:
The scatter of documents over databases in different subject domains: How many databases are needed?
Authors: Hood William W. , Wilson Concepción S. 
Published: August 2002

AbstractThe distribution of bibliographic records in on‐line bibliographic databases is examined using 14 different search topics. These topics were searched using the DIALOG database host, and using as many suitable databases as possible. The presence of duplicate records in the searches was taken into consideration in the analysis, and the problem with lexical ambiguity in at least one search topic is discussed. The study answers questions such as how many databases are needed in a multifile search for particular topics, and what coverage will be achieved using a certain number of databases. The distribution of the percentages of records retrieved over a number of databases for 13 of the 14 search topics roughly fell into three groups: (1) high concentration of records in one database with about 80% coverage in five to eight databases; (2) moderate concentration in one database with about 80% coverage in seven to 10 databases; and (3) low concentration in one database with about 80% coverage in 16 to 19 databases. The study does conform with earlier results, but shows that the number of databases needed for searches with varying complexities of search strategies, is much more topic dependent than previous studies would indicate.
Maximum likelihood estimation of a latent variable time‐series model
Authors: Bartolucci Francesco , De Luca Giovanni 
Published: August 2002

AbstractRecently, Fridman and Harris proposed a method which allows one to approximate the likelihood of the basic stochastic volatility model. They also propose to estimate the parameters of such a model maximising the approximate likelihood by an algorithm which makes use of numerical derivatives. In this paper we propose an extension of their method which enables the computation of the first and second analytical derivatives of the approximate likelihood. As will be shown, these derivatives may be used to maximize the approximate likelihood through the Newton–Raphson algorithm, with a saving in the computational time. Moreover, these derivatives approximate the corresponding derivatives of the exact likelihood. In particular, the second derivative may be used to compute the standard error of the estimator and confidence intervals for the parameters. The paper presents also the results of a simulation study which allows one to compare our approach with other existing approaches. Copyright © 2001 John Wiley & Sons, Ltd.
Statistical challenges in credit card issuing
Authors: Lucas Alan 
Published: August 2002

AbstractThe credit card industry is awakening to the fact that the vast amounts of data it has on its customers should be treated as a valuable asset and that extracting knowledge from this data is crucial if one wants to optimize ones credit book. The company I work for—Barclaycard has over 7 million customers and over 9 million credit cards in circulation and deals with over 300 million credit card transactions per annum—a tremen dous amount of data. This paper is intended to provide a flavour of some of the statistical work that is required to take advantage of this asset. The suggestions are only the tip of the iceberg. Credit cards are a complex business. A factor that makes up this complexity is that credit card customers use their cards for a number of non‐credit reasons, namely: payment convenience, smoothing of finances, paying regular bills, emergencies and spontaneous spending. Moreover, managing customers implies balancing revenue, churn and bad debt issues, and the explosion of competetion in recent years is making it more difficult to attract and retain profitable, low‐risk customers. In the paper I will examine the traditional statistical methodology behind the issue of credit, along with some of the problems that have been solved and some that are still outstanding. The paper then provides an overview of the new Customer Value Management paradigm, also known as Customer Relationship Management (CRM), highlighting the new challenges that have emanated from this and the implications for statisticians. Copyright © 2001 John Wiley & Sons, Ltd.
Increased mouse survival, tumor growth inhibition and decreased immunoreactive p53 after exposure to magnetic fields
Authors: Tofani Santi , Cintorino Marcella , Barone Domenico , Berardelli Michele , De Santi Maria Margherita , Ferrara Adriana , Orlassino Renzo , Ossola Piero , Rolfo Katia , Ronchetto Flavio , Tripodi Sergio Antonio , Tosi Piero 
Published: August 2002

AbstractThe possibility that magnetic fields (MF) cause antitumor activity in vivo has been investigated. Two different experiments have been carried out on nude mice bearing a subcutaneous human colon adenocarcinoma (WiDr). In the first experiment, significant increase in survival time (31%) was obtained in mice exposed daily to 70 min modulated MF (static with a superimposition of 50 Hz) having a time average total intensity of 5.5 mT. In the second independent experiment, when mice bearing tumors were exposed to the same treatment for four consecutive weeks, significant inhibition of tumor growth (40%) was reported, together with a decrement in tumor cell mitotic index and proliferative activity. A significant increase in apoptosis was found in tumors of treated animals, together with a reduction in immunoreactive p53 expression. Gross pathology at necroscopy, hematoclinical/hematological and histological examination did not show any adverse or abnormal effects. Since pharmacological rescue of mutant p53 conformation has been recently demonstrated, the authors suggest that MF exposure may obtain a similar effect by acting on redox chemistry connected to metal ions which control p53 folding and its DNA‐binding activity. These findings support further investigation aimed at the potential use of magnetic fields as anti‐cancer agents. Bioelectromagnetics 23:230–238, 2002. © 2002 Wiley‐Liss, Inc.
Genotoxicity of radiofrequency signals. I. Investigation of DNA damage and micronuclei induction in cultured human blood cells
Authors: Tice Raymond R. , Hook Graham G. , Donner Maria , McRee Donald I. , Guy Arthur W. 
Published: August 2002

AbstractAs part of a comprehensive investigation of the potential genotoxicity of radiofrequency (RF) signals emitted by cellular telephones, in vitro studies evaluated the induction of DNA and chromosomal damage in human blood leukocytes and lymphocytes, respectively. The signals were voice modulated 837 MHz produced by an analog signal generator or by a time division multiple access (TDMA) cellular telephone, 837 MHz generated by a code division multiple access (CDMA) cellular telephone (not voice modulated), and voice modulated 1909.8 MHz generated by a global system of mobile communication (GSM)‐type personal communication systems (PCS) cellular telephone. DNA damage (strand breaks/alkali labile sites) was assessed in leukocytes using the alkaline (pH>13) single cell gel electrophoresis (SCG) assay. Chromosomal damage was evaluated in lymphocytes mitogenically stimulated to divide postexposure using the cytochalasin B‐binucleate cell micronucleus assay. Cells were exposed at 37±1°C, for 3 or 24 h at average specific absorption rates (SARs) of 1.0–10.0 W/kg. Exposure for either 3 or 24 h did not induce a significant increase in DNA damage in leukocytes, nor did exposure for 3 h induce a significant increase in micronucleated cells among lymphocytes. However, exposure to each of the four RF signal technologies for 24 h at an average SAR of 5.0 or 10.0 W/kg resulted in a significant and reproducible increase in the frequency of micronucleated lymphocytes. The magnitude of the response (approximately four fold) was independent of the technology, the presence or absence of voice modulation, and the frequency (837 vs. 1909.8 MHz). This research demonstrates that, under extended exposure conditions, RF signals at an average SAR of at least 5.0 W/kg are capable of inducing chromosomal damage in human lymphocytes. Bioelectromagnetics 23:113–126, 2002. © 2002 Wiley‐Liss, Inc.
The intestinal epithelial stem cell
Authors: Marshman Emma , Booth Catherine , Potten Christopher S. 
Published: August 2002

AbstractThis article considers the role of the adult epithelial stem cell, with particular reference to the intestinal epithelial stem cell. Although the potential of adult stem cells has been revealed in a number of recent publications, the organization and control of the stem cell hierarchy in epithelial tissues is still not fully understood. The intestinal epithelium is an excellent model in which to study such hierarchies, having a distinctive polarity and high rate of cell proliferation and migration. Studies on the small intestinal crypt provide insight into the characteristics of the stem cells in normal and regenerating circumstances and demonstrate why a thorough understanding of these cells is an essential pre‐requisite for stem cell based therapeutic approaches. BioEssays 24:91–98, 2002. © 2002 John Wiley & Sons, Inc.
Synaptic modification in neural circuits: A timely action
Authors: Berninger Benedikt , Bi Guo‐Qiang 
Published: August 2002

AbstractLong‐term modification of synaptic strength is thought to be the basic mechanism underlying the activity‐dependent refinement of neural circuits and the formation of memories engrammed on them. Studies ranging from cell culture preparations to humans subjects indicate that the decision of whether a synapse will undergo strengthening or weakening critically depends on the temporal order of presynaptic and postsynaptic activity. At many synapses, potentiation will be induced only when the presynaptic neuron fires an action potential within milliseconds before the postsynaptic neuron fires, whereas weakening will occur when it is the postsynaptic neuron that fires first. Such processes might be important for the remodeling of neural circuits by activity during development and for network functions such as sequence learning and prediction. Ultimately, this synaptic property might also be fundamental for the cognitive process by which we structure our experience through cause and effect relations. BioEssays 24:212–222, 2002. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/bies.10060
Putting its fingers on stressful situations: the heavy metal‐regulatory transcription factor MTF‐1
Authors: Lichtlen P. , Schaffner W. 
Published: August 2002

AbstractIt has been suggested that metallothioneins, discovered about 45 years ago, play a central role in heavy metal metabolism and detoxification, and in the management of various forms of stress. The metal‐regulatory transcription factor‐1 (MTF‐1) was shown to be essential for basal and heavy metal‐induced transcription of the stress‐responsive metallothionein‐I and metallothionein‐II. Recently it has become obvious that MTF‐1 has further roles in the transcriptional regulation of genes induced by various stressors and might even contribute to some aspects of malignant cell growth. Furthermore, MTF‐1 is an essential gene, as mice null‐mutant for MTF‐1 die in utero due to liver degeneration. We describe here the state of knowledge on the complex activation of MTF‐1, and propose a model with MTF‐1 as an interconnected cellular stress‐sensor protein involved in heavy metal metabolism, hepatocyte differentiation and detoxification of toxic agents. BioEssays 23:1010–1017, 2001. © 2001 John Wiley & Sons, Inc.
Conformational changes of enzymes adsorbed at liquid– solid interface: Relevance to enzymatic activity
Authors: Noinville S. , Revault M. , Baron M.‐H. 
Published: August 2002

AbstractFTIR with attenuated total reflectance spectroscopy was used to study in situ adsorption of enzymes at water–solid interfaces to better understand how conformational changes may monitor enzymatic activity. Because the adsorption process depends on hydrophobic and electrostatic interactions, conformational changes were studied as a function of the nature of the adsorbing substrates, which are hydrophobic or hydrophilic in character. The adsorption kinetics of two examples of serine enzymes, α‐chymotrypsin (α‐chym) and Humicola lanuginosa lipase (HLL), were studied. The secondary structure and solvation of the adsorbed enzymes were both compared to the dissolved enzymes. The positively charged α‐ chym was adsorbed on a negatively charged hydrophilic support with minor structural changes, but the negatively charged lipase had no affinity for a similar support. Both enzymes were strongly retained on the hydrophobic support. The secondary and tertiary structures of the α‐chym adsorbed on the hydrophobic support were strongly altered, which correlates to the inhibition of enzymatic hydrolysis. The specific solvation obtained for the adsorbed HLL is consistent with the existence of the open conformer in relation to the enhanced enzymatic activity at the water–hydrophobic interface. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 323–326, 2002
Analysis of biological wastewater treatment processes using multicomponent gas phase mass balancing
Authors: Gapes Daniel , Keller Jurg 
Published: August 2002

AbstractA reactor system using off‐gas analysis was developed for analyzing wastewater treatment process reactions. Using a mass spectrometer for the gas analysis provides the ability to simultaneously measure several gas components (such as oxygen, nitrogen, carbon dioxide, and argon). One of the benefits of the reactor design was the precise control of the dissolved oxygen concentration, uncoupled from the system turbulence, which was controlled via a gas recycle loop. This feature allowed control of the turbulence within the reactor without any need for mechanical stirring. Using oxygen as the test gas, the reactor was shown to perform well in the measurement of oxygen uptake rate of nitrifying activated sludge. The oxygen uptake rate calculations were made using a simple calibration method developed for the reactor system. The reactor was able to provide precise and accurate results for this test case. Furthermore, the system was capable of measuring under dynamic process conditions, as well as when the process rates were constant (steady state). © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 361–375, 2001.
Optimization of L‐phenylalanine production of Corynebacterium glutamicum under product feedback inhibition by elevated oxygen transfer rate
Authors: Shu Chin‐Hang , Liao Chii‐Cherng 
Published: August 2002

AbstractProduction feedback inhibition both on cell growth and on product formation of phenylalanine fermentation might be alleviated by elevated oxygen supply. Batch fermentations by a high phenylalanine producing strain Corynebacterium glutamicum CCRC 18335 at various initial phenylalanine concentrations (P0) ranging from 0 to 20 g/L and different oxygen transfer rate coefficients (KLa) ranging from 23 to 76 h−1 were studied. The fermentation parameters with respect to P0 were strongly dependent on KLa. Cell yield favored higher KLa and lower P0. Product yield with respect to varying phenylalanine concentration was evaluated by the relative oxygen availability (ROA). The optimal ROA for phenylalanine formation was strongly dependent on the product concentration. While P0 was low, the product inhibition was less significant and the maximum product yield occurred while ROA was at 0.5–0.6. While P0 was high, the product inhibition was significant and the maximum product yield occurred while ROA was at 0.8–0.9. These results suggest that the product feedback inhibition of phenylalanine fermentation processes can be alleviated by a gradual increase in oxygen supply rate while the increasing product concentration is taken into account. The strategy is demonstrated in a fed‐batch culture with elevated oxygen supply. The final phenylalanine concentration was 23.2 g/L, which was 45% better than that of the fed‐batch fermentation without elevated oxygen supply. Likewise, the maximum productivity was improved by 42% at 0.37 g/(L · h). © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 131–141, 2002.
Use of isolated cyclohexanone monooxygenase from recombinant Escherichia coli as a biocatalyst for Baeyer–Villiger and sulfide oxidations
Authors: Zambianchi F. , Pasta P. , Carrea G. , Colonna S. , Gaggero N. , Woodley J. M. 
Published: August 2002

AbstractThe performance, in Baeyer–Villiger and heteroatom oxidations, of a partially purified preparation of cyclohexanone monooxygenase obtained from an Escherichia coli strain in which the gene of the enzyme was cloned and overexpressed was investigated. As model reactions, the oxidations of racemic bicyclo[3.2.0]hept‐2‐en‐6‐one into two regioisomeric lactones and of methyl phenyl sulphide into the corresponding (R)‐sulphoxide were used. Enzyme stability and reuse, substrate and product inhibition, product removal, and cofactor recycling were evaluated. Of the various NADPH regeneration systems tested, 2‐propanol/alcohol dehydrogenase from Thermoanerobium brockii appeared the most suitable because of the low cost of the second substrate and the high regeneration rate. Concerning enzyme stability, kosmotropic salts were the only additives able to improve it (e.g., half‐life from 1 day in diluted buffer to 1 week in 1 M sodium sulphate) but only under storage conditions. Instead, significant stabilization under working conditions was obtained by immobilization on Eupergit C (half‐life approximately 2.5 days), a procedure that made it possible to reuse the catalyst up to 16 times with complete substrate (5 g·L−1) conversion at each cycle. Reuse of free enzyme was also achieved in a membrane reactor but with lower efficiency. Water‐organic solvent biphasic systems, which would overcome substrate inhibition and remove from the aqueous phase, where reaction takes place, the formed product, were unsuccessful because of their destabilizing effect on cyclohexanone monooxygenase. More satisfactory was continuous substrate feeding, which shortened reaction times and, very importantly, yielded in the case of bicyclo[3.2.0]hept‐2‐en‐6‐one (10 g·L−1) both lactone products with high optical purity (enantiomeric excess ≥96%), which was not the case when all of the substrate was added in a single batch. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 489–496, 2002.
Effect of oxygen transfer on glycerol biosynthesis by an osmophilic yeast Candida magnoliae I2B
Authors: Sahoo Debendra K. , Agarwal Gopal P. 
Published: August 2002

AbstractThe influence of oxygen on glycerol production by an osmophilic yeast, Candida magnoliae I2B, was studied in a bioreactor. Oxygen transfer rates (OTRs) and volumetric oxygen transfer coefficients (kLa) were determined at different aeration and agitation rates. Cell growth as well as glycerol production was strongly affected by oxygen supply. Improvement in OTRs resulted in increased cell growth and glycerol yield. However, at high OTRs, there was a reduction in glucose uptake rate, indicating Pasteur Effect, and glycerol accumulation was also reduced at kLa of 253 h−1. The availability of oxygen per unit of cell mass was found to be the most important factor that controlled cell growth, glucose uptake, and glycerol yield. The overall productivity and yield of glycerol could be related with kLa. The biosynthesis of glycerol was found to both growth‐ and non‐growth‐associated, although glycerol was mainly produced in post‐exponential phase. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 545–555, 2002.
Stability of crystalline proteins
Authors: Shenoy Bhami , Wang Yi , Shan Weizhong , Margolin Alexey L. 
Published: August 2002

AbstractBy using two model proteins, glucose oxidase and lipase, we demonstrate that dry crystalline formulations are significantly more stable than their amorphous counterparts. The results of Fourier‐transform infrared spectroscopy indicate that crystalline proteins better maintain their native conformation in accelerated stability studies. The lower tendency of crystalline proteins to aggregate is confirmed by size‐exclusion chromatography. The data suggest that protein crystallization may significantly improve some aspects of protein handling, and change the way biopharmaceuticals are produced, formulated, and delivered. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 358–369, 2001.
Effects of oxygenation and flow on the viability and function of rat hepatocytes cocultured in a microchannel flat‐plate bioreactor
Authors: Tilles Arno W. , Baskaran Harihara , Roy Partha , Yarmush Martin L. , Toner Mehmet 
Published: August 2002

AbstractThe goal of this study was to investigate the viability and synthetic function of rat hepatocytes cocultured with 3T3‐J2 fibroblasts in a small‐scale microchannel flat‐plate bioreactor with and without an internal membrane oxygenator under flow. Bioreactor channel heights ranged between 85 and 500 μm and medium flow rates ranged between 0.06 and 4.18 mL/min. The results showed that the bioreactor without the oxygenator resulted in significantly decreased viability and function of hepatocytes, whereas hepatocytes in the bioreactor with internal membrane oxygenator were able to maintain their viability and function. The shear stress calculations showed that, at lower wall shear stresses (0.01 to 0.33 dyn/cm2), hepatocyte functions, measured as albumin and urea synthesis rates, were as much as 2.6‐ and 1.9‐fold greater, respectively, than those at higher wall shear stresses (5 to 21 dyn/cm2). Stable albumin and urea synthesis rates for 10 days of perfusion were also demonstrated in the bioreactor with internal membrane oxygenator. These results are relevant in the design of hepatocyte bioreactors and the eventual scaling‐up to clinical devices. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 379–389, 2001.
Intra‐particle oxygen diffusion limitation in solid‐state fermentation
Authors: Oostra J. , le Comte E. P. , van den Heuvel J. C. , Tramper J. , Rinzema A. 
Published: August 2002

AbstractOxygen limitation in solid‐state fermentation (SSF) has been the topic of modeling studies, but thus far, there has been no experimental elucidation on oxygen‐transfer limitation at the particle level. Therefore, intra‐particle oxygen transfer was experimentally studied in cultures of Rhizopus oligosporus grown on the surface of solid, nutritionally defined, glucose and starch media. The fungal mat consisted of two layers—an upper layer with sparse aerial hyphae and gas‐filled interstitial pores, and a dense bottom layer with liquid‐filled pores. During the course of cultivation ethanol was detected in the medium indicating that oxygen was depleted in part of the fungal mat. Direct measurement of the oxygen concentrations in the fungal mat during cultivation, using oxygen microelectrodes, showed no oxygen depletion in the upper aerial layer, but revealed development of steep oxygen concentration gradients in the wet bottom layer. Initially, the fungal mat was fully oxygenated, but after 36.5 hours oxygen was undetectable at 100 μm below the gas–liquid interface. This was consistent with the calculated oxygen penetration depth using a reaction‐diffusion model. Comparison of the overall oxygen consumption rate from the gas phase to the oxygen flux at the gas‐liquid interface showed that oxygen consumption of the microorganisms occurred mainly in the wet part of the fungal mat. The contribution of the aerial hyphae to overall oxygen consumption was negligible. It can be concluded that optimal oxygen transfer in SSF depends on the available interfacial gas–liquid surface area and the thickness of the wet fungal layer. It is suggested that the moisture content of the matrix affects both parameters and, therefore, plays an important role in optimizing oxygen transfer in SSF cultures. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 13–24, 2001.