bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra‐Low‐Loss Acrylate Polymers for Planar Light Circuits
Authors: Shacklette L.W. , Blomquist R. , Deng J.M. , Ferm P.M. , Maxfield M. , Mato J. , Zou H.
Published: June 2003

We have developed a materials system composed of liquid multifunctional fluorinated acrylate monomers that achieves very low absorption losses within both datacom and telecom wavelength ranges. Identified structure–property relationships have guided the design of polymers that are optimized with respect to their inherent materials properties and their ability to be processed into low‐loss optical waveguides. Together these co‐developed materials and processes combine to produce waveguides that have propagation losses equivalent to planar glass guides, and significantly reduced polarization dependence and improved thermal response needed for the performance of thermo‐optic devices. Extensive environmental studies have demonstrated robustness well beyond that required for normal operating conditions.
Sulfur Composite Cathode Materials for Rechargeable Lithium Batteries
Authors: Wang J. , Yang J. , Wan C. , Du K. , Xie J. , Xu N.
Published: June 2003

Conductive polymer/sulfur composite materials were prepared by heating the mixture of polyacrylonitrile (PAN) and sublimed sulfur. During the heating process, PAN was dehydrogenated by sulfur, forming a conductive main chain similar to polyacetylene. At the same time, the high‐polarity functional group –CN cyclized at the melt state, forming a thermally stable heterocyclic compound in which sulfur was embedded. The nanodispersed composites showed excellent electrochemical properties. Tested as cathode material in a non‐aqueous lithium cell based on poly(vinylidene fluoride) (PVDF) gel electrolyte at room temperature, the composite exhibited a specific capacity up to 850 mA h g–1 in the initial cycle. Its specific capacity remained above 600 mA h g–1 after 50 cycles, about five times that of LiCoO2, and recovered partly after replacement of the anode with a fresh lithium sheet. The utilization of the electrochemically active sulfur was about 90 % assuming a complete reaction to the product, Li2S.
Layer‐Structured Photoconducting Polymers: A New Class of Photorefractive Materials
Authors: Kwon O‐P. , Lee S.‐H. , Montemezzani G. , Günter P.
Published: June 2003

We study the photorefractive (PR) properties of a new kind of low glass‐transition temperature (Tg) polymer composite based on layered photoconductive polymers, poly(p‐phenylene terephthalate) carbazoles (PPT‐CZs). These photoconductors consist of the rigid backbone of PPT with pendant oxyalkyl CZ groups. The compounds are doped with the photosensitizer C60 and nonlinear optical chromophores diethylaminodicyanostyrene (DDCST), and no plasticizers are added. When the host polymers are mixed with various PR ingredients, the layers are preserved and their layer distance increases, indicating that all the guest molecules are confined to the nanoscale interlayer space. These composites showed very low Tg values (< ϕ °C). Despite the absence of a plasticizer and the lower concentration of the carbazole photoconductive moieties as compared to poly(N‐vinylcarbazole) systems, these materials show excellent PR properties, i.e., a PR gain of Γ = 250 cm–1 under an external electric field of 60 V μm–1, and diffraction efficiency and PR sensitivity of 93 % and 24 ± 7 cm2 kJ–1 at E = 100 V μm–1, respectively.
Metastable Hexagonal In2O3 Nanofibers Templated from InOOH Nanofibers under Ambient Pressure
Authors: Yu D. , Yu S.‐H. , Zhang S. , Zuo J. , Wang D. , Qian Y.T.
Published: June 2003

Single‐crystal, metastable, hexagonal In2O3 (H‐In2O3) nanofibers with an average diameter of 80 nm and length of up to several micrometers were synthesized on a large scale, for the first time under ambient pressure, by annealing InOOH nanofibers at 490 °C. The InOOH nanofibers were prepared by a controlled hydrolysis solvothermal reaction, using InCl3·4H2O as the starting material and ether as the solvent, in the temperature range of 190–240 °C. The solvent has significant effects on the formation of the metastable phase and the morphology of the In2O3 nanocrystals during the synthesis of the precursor InOOH. Room‐temperature optical absorption spectra of the hexagonal In2O3 nanofibers showed strong absorption peak located at 325 nm (3.83 eV) with a slight blue‐shift compared with that of bulk In2O3 (3.75 eV). The H‐In2O3 nanofibers photoluminesce at room temperature with emission peaks at 378 nm, 398 nm, and 420 nm. The successful production of metastable hexagonal In2O3 nanofibers in large scale under mild conditions could be of interest both for applications and fundamental studies.
High‐Tg Carbazole Derivatives as Blue‐Emitting Hole‐Transporting Materials for Electroluminescent Devices
Authors: Kundu P. , Justin Thomas K.R. , Lin J.T. , Tao Y.‐T. , Chien C.‐H.
Published: June 2003

A series of dicarbazolyl derivatives bridged by various aromatic spacers and decorated with peripheral diarylamines were synthesized using Ullmann and Pd‐catalyzed C–N coupling procedures. These derivatives emit blue light in solution. In general, they possess high glass‐transition temperatures (Tg > 125 °C) which vary with the bridging segment and methyl substitution on the peripheral amine. Double‐layer organic light‐emitting devices were successfully fabricated using these molecules as hole‐transporting and emitting materials. Devices of the configuration ITO/HTL/TPBI/Mg:Ag (ITO: indium tin oxide; HTL: hole‐transporting layer; TPBI: 1,3,5‐tris(N‐phenylbenzimidazol‐2‐yl)benzene) display blue emission from the HTL layer. The EL spectra of these devices appear slightly distorted due to the exciplex formation at the interfaces. However, for the devices of the configuration ITO/HTL/Alq3/Mg:Ag (Alq3 = tris(8‐hydroxyquinoline)aluminum) a bright green light from the Alq3 layer was observed. This clearly demonstrates the facile hole‐transporting property of the materials described here.
Electroactivity of Polyaniline Multilayer Films in Neutral Solution and Their Electrocatalyzed Oxidation of β‐Nicotinamide Adenine Dinucleotide
Authors: Tian S. , Baba A. , Liu J. , Wang Z. , Knoll W. , Park M.‐K. , Advincula R.
Published: June 2003

In this paper, we report an alternative simple method to shift the electroactivity of polyaniline (PANI) films to neutral pH conditions by forming multilayer assemblies with poly(anions) using the layer‐by‐layer (LBL) deposition method. A series of self‐assembled PANI multilayer films with poly(anions), such as sulfonated polyaniline (SPANI), poly(acrylic acid) (PAA), poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS), were prepared by the LBL method. Their electrochemical behavior and catalytic ability for the oxidation of β‐nicotinamide adenine dinucleotide (NADH) in neutral solution were investigated by electrochemistry (EC) combined with surface plasmon spectroscopy (SPS) and the quartz crystal microbalance (QCM) technique. Results indicated that all the films showed very good stability, reversibility, and electroactivity in neutral solution. All the multilayer films can electrocatalyze the oxidation of NADH, with the catalytic ability of PANI/SPANI being higher than that of the other assemblies under the same conditions. The catalytic abilities of the films with the same thickness prepared by the copolymerization method and the LBL method were also compared.
Laser‐Ablation Growth and Optical Properties of Wide and Long Single‐Crystal SnO2 Ribbons
Authors: Hu J.Q. , Bando Y. , Liu Q.L. , Golberg D.
Published: June 2003

Wide and long ribbons of single‐crystalline SnO2 have been achieved via laser ablation of a SnO2 target. Transmission electron microscopy (TEM) shows the as‐grown SnO2 ribbons are structurally perfect and uniform, with widths of 300–500 nm, thicknesses of 30–50 nm (width‐to‐thickness ratio of ∼ 10), and lengths ranging from several hundreds of micrometers to the order of millimeters. X‐ray diffraction (XRD) pattern and energy‐dispersive X‐ray spectroscopy (EDS) spectral analysis indicate that the ribbons have the phase structure and chemical composition of the rutile form of SnO2. Selected‐area electron diffraction (SAED) patterns and high‐resolution TEM images reveal that the ribbons are single crystals and grow along the [100] crystal direction. Photoluminescence measurements show that the synthesized SnO2 ribbons have one strong emission band at ∼ 605 nm and a red‐shift of ∼ 30 nm, as compared to standard SnO2 powder, which may be attributed to crystal defects and residual strains accommodated during the growth of the ribbons.
Electrophosphorescence from a Polymer Guest–Host System with an Iridium Complex as Guest: Förster Energy Transfer and Charge Trapping
Authors: Gong X. , Ostrowski J.C. , Moses D. , Bazan G.C. , Heeger A.J.
Published: June 2003

We report high‐efficiency green electrophosphorescent light‐emitting diodes obtained by using tris[9,9‐dihexyl‐2‐(phenyl‐4′‐(‐pyridin‐2″‐yl))fluorene]iridium(III) (Ir(DPPF)3) as the guest, and a blend of poly(vinylcarbazole) (PVK) with 2‐tert‐butylphenyl‐5‐biphenyl‐1,3,4‐oxadiazol (PBD) as the host. The electrophosphorescent emission is characteristic of Ir(DPPF)3, with its maximum at 550 nm. An external quantum efficiency of 8 % photons per electron and luminous efficiency of 29 cd A–1, with maximum brightness of 3500 cd m–2, were achieved at 1 wt.‐% concentration of Ir(DPPF)3. The devices exhibited no emission from PVK or PBD, even at the lowest concentration of Ir(DPPF)3 (0.1 wt.‐%). The results indicate that Förster energy transfer plays a minor role in achieving high efficiencies in these devices. Direct charge trapping appears to be the main operating mechanism.
From Hybrid Microgels to Photonic Crystals
Authors: Xu S. , Zhang J. , Paquet C. , Lin Y. , Kumacheva E.
Published: June 2003

We have synthesized semiconductor and metal nanoparticles (NPs) in the constrained geometry of polymer microgels. We used electrostatically driven attraction between the ionic groups of the microgels and the precursor cations in the bulk liquid medium to introduce the cations in the interior of the microgel. In the second step, the cations in the microgel interior reacted with the anion (to obtain semiconductor NPs) or they were treated with a reducing agent (to obtain metal NPs). Good control over the size and the concentration of the NPs in the microgel particles was achieved by changing the composition of the corresponding microgel. The doped microgel spheres were heated at pH 4 above the volume‐transition temperature of the polymer to expel the water from the microsphere interior; then the polymer was encapsulated with a hydrophobic polymeric shell. Hybrid core–shell particles were used as the building blocks of the nanostructured material with properties of a photonic crystal.
Size‐Specific Interactions Between Single‐ and Double‐Stranded Oligonucleotides and Cationic Water‐Soluble Oligofluorenes
Authors: Wang S. , Liu B. , Gaylord B.S. , Bazan G.C.
Published: June 2003

An improved synthetic approach was developed for the synthesis of 1,4‐bis[9′,9′‐bis(6″‐(N,N,N‐trimethylammonium)‐hexyl)‐fluoren‐2′‐yl]benzene tetrabromide (1a), 1,4‐bis[9′,9′;9″,9″‐tetra(6″′‐(N,N,N‐trimethylammonium)‐hexyl)‐7′,2″‐bisfluoren‐2′‐yl] benzene octabromide (1b) and 1,4‐bis[9′,9′;9″,9″;9″′,9″′‐hexakis(6″″‐(N,N,N‐trimethylammonium)‐hexyl)‐7′,2″,7″,2″′‐trifluoren‐2′‐yl] benzene dodecabromide (1c). These molecules provide a size‐specific series of water‐soluble oligofluorene molecules with increasing numbers of repeat units to model the interactions between cationic conjugated polymers and DNA. Fluorescence quenching and energy‐transfer measurements were performed with 1a–c and single‐stranded (ss) DNA and double‐stranded (ds) DNA, with and without fluorescein (Fl). These studies show that, on a per‐negative‐charge basis, ssDNA quenches the emission of 1a–c more effectively than dsDNA. Furthermore, we show that the energy‐transfer ratios dsDNA–Fl/ssDNA–Fl are dependent on the number of repeat units in 1a–c.
Glycosyltransferase Microarray Displayed on the Glycolipid LB Membrane
Authors: Nagahori Noriko , Niikura Kenichi , Sadamoto Reiko , Taniguchi Masahiro , Yamagishi Akihiko , Monde Kenji , Nishimura Shin‐Ichiro
Published: June 2003

β(1→4) Galactosyltransferase expressed as a fusion protein with maltose binding protein (MBP‐GalT) was displayed specifically on a Langmuir–Blodgett (LB) membrane prepared by photopolymerization of maltotriose‐carrying glycolipid (1) with 1,2‐bis(10,12‐tricosadiynoyl)‐sn‐glycero‐3‐phosphocholine (2). The catalytic activity of MBP‐GalT on the LB film was directly monitored by the surface plasmon resonance (SPR) method using a GlcNAc‐carrying water‐soluble polymer (3) as an acceptor substrate. Highly sensitive sigmoidal‐type signals were obtained upon the addition of the acceptor substrate in the presence of the donor substrate, UDP‐galactose (UDP‐Gal), while the binding of 3 was not detected in the absence of UDP‐Gal. The intensities of the signals were dependent on the amount of immobilized MBP‐GalT on the LB film, which was estimated from the images obtained by atomic force microscope (AFM).
Glutaryl Acylases: One‐Reaction Enzymes or Versatile Enantioselective Biocatalysts?
Authors: Raimondi Stefano , Monti Daniela , Pagnoni Ugo Maria , Riva Sergio
Published: June 2003

A significant broad substrate specificity, that crosses over the usual β‐lactam derivatives, has been observed with an industrial glutaryl‐7‐aminocephalosporanic acid acylase (GA). This enzyme possesses significant enantioselective amidase and even esterase activity, with a stereopreference for the S‐enantiomer. The easy separation of products from unreacted reagents, possessing different physical‐chemical properties, is achieved by solvent extraction, avoiding chromatography or distillation during reaction work‐up.
Baeyer–Villiger Monooxygenases, an Emerging Family of Flavin‐Dependent Biocatalysts
Authors: Kamerbeek Nanne M. , Janssen Dick B. , van Berkel Willem J. H. , Fraaije Marco W.
Published: June 2003

Baeyer–Villiger monooxygenases (BVMOs) are flavoenzymes that catalyze a remarkably wide variety of oxidative reactions such as regio‐ and enantioselective Baeyer–Villiger oxidations and sulfoxidations. Several of these conversions are difficult to achieve using chemical approaches. Due to their selectivity and catalytic efficiency, BVMOs are highly valuable biocatalysts for the synthesis of a broad range of fine chemicals. For a long time, only one member of this class of flavin‐containing biocatalysts had been cloned and overexpressed which has limited their application for synthetic processes. Recently a number of new genes that encode BVMOs have been sequenced and overexpressed. In this paper the biocatalytic properties of recently cloned BVMOs are reviewed. Furthermore, the potential for obtaining novel BVMOs from sequenced genomes will be discussed.
Chemo‐ and Enantioselective Acyl Transfers by Lipases and Acylase I: Preparative Applications in Hydroxymethylpiperidine Chemistry
Authors: Lundell Katri , Lehtinen Petka , Kanerva Liisa T.
Published: June 2003

The lipase‐ and acylase I‐catalysed acylation of bifunctional 2‐ and 3‐hydroxymethylpiperidines (1 and 2) and the alcoholysis of the corresponding diacylated counterparts 7 and 8 have been studied. Lipase AK from Pseudomonas fluorescens allowed the preparative‐scale resolution of 7 in neat butanol at 50% conversion whereas the 3‐regioisomer 8 reacted with negligible enantioselectivity (E=7). The lipase‐ and acylase I‐catalysed acylations of 1 and 2 in organic solvents proceeded with low enantioselectivity. On the other hand, more than 90% of 1 and 2 were transformed to amino esters 3 and 4, respectively, in a highly chemoselective O‐acylation with 2,2,2‐trifluoroethyl butanoate in the presence of Candida antarctica lipase A in TBME. The O‐protected product 3 in the reaction mixture was readily available to another transformation at the piperidine nitrogen although 3 was not separated due to intramolecular O→N acyl migration. The tendency for acyl migration was much less significant in the case of 4.
High Throughput Discovery of Alcohol Dehydrogenases for Industrial Biocatalysis
Authors: Ravot Gilles , Wahler Denis , Favre‐Bulle Olivier , Cilia Valérie , Lefevre Fabrice
Published: June 2003

To speed up the discovery of novel biocatalysts for industrial synthesis, an efficient screening approach has been set up. The huge potential of natural biodiversity has been taken advantage of in a discovery protocol using bioinformatics analysis, polymerase chain reaction (PCR) techniques and direct in vitro expression of enzymes. This approach led to the direct characterization of 19 novel thermoactive alcohol dehydrogenases with a broad substrate range, that set up a useful enzymatic “toolbox” for fine chemistry synthesis.
Immobilisation of P450 BM‐3 and an NADP+ Cofactor Recycling System: Towards a Technical Application of Heme‐Containing Monooxygenases in Fine Chemical Synthesis
Authors: Maurer Steffen C. , Schulze Holger , Schmid Rolf D. , Urlacher Vlada
Published: June 2003

Abstract: Cytochrome P450 monooxygenases are potentially a very useful class of hydroxylation catalysts; they are able to introduce oxygen at activated and non‐activated carbon‐hydrogen bonds and thus lead to regio‐ and/or stereochemically pure compounds. However, this potential is lowered by their intrinsic low activity and inherent instability. P450‐catalysed biotransformations require a constant supply of NAD(P)H, making the process an expensive one. To render these catalysts more suitable for industrial biocatalysis, the immobilisation of P450 BM‐3 (CYP 102A1) from Bacillus megaterium in a sol‐gel matrix was combined with a cofactor recycling system based on NADP+‐dependent formate dehydrogenase (EC 1.2.1.2) from Pseudomonas sp. 101 and tested for practical applicability. This approach was used for the conversion of β‐ionone, octane and naphthalene to the respective hydroxy compounds with DMSO as cosolvent using sol‐gel immobilised P450 BM‐3 mutants.
Enantioselective Enzymatic Cleavage of N‐Benzyloxycarbonyl Groups
Authors: Patel Ramesh N. , Nanduri Venkata , Brzozowski David , McNamee Clyde , Banerjee Amit
Published: June 2003

A new enzymatic process for the enantioselective cleavage of N‐benzyloxycarbonyl (Cbz) groups from protected amino acids and related compounds has been developed. The Cbz‐deprotecting enzyme was isolated from cell extracts of Sphingomonas paucimobilis SC 16113 and purified to homogeneity. The purified protein has a molecular weight of 155,000 daltons and a subunit size of 44,000 daltons.
Cofactor Regeneration of both NAD+ from NADH and NADP+ from NADPH:NADH Oxidase from Lactobacillus sanfranciscensis
Authors: Riebel Bettina R. , Gibbs Phillip R. , Wellborn William B. , Bommarius Andreas S.
Published: June 2003

A possible solution for the regeneration of NAD+ from NADH is the oxidation of NADH with concomitant reduction of oxygen catalyzed by NADH oxidase (E. C. 1.6.‐.‐). We employ NADH oxidase from Lactobacillus sanfranciscensis, which reduces O2 to innocuous H2O, and (R)‐alcohol dehydrogenase [(R)‐ADH] from Lactobacillus brevis to perform enantioselective oxidation of racemic phenylethanol to acetophenone and (S)‐phenylethanol with regeneration of either NADH or NADPH to their respective oxidized precursors. NADH oxidase from L. sanfranciscensis accepts both NADH and NADPH; in contrast, the wild‐type (R)‐ADH only accepts NADP(+)(H) whereas its G37D mutant strongly prefers NAD(+)(H). Highly purified. NADH oxidase (221 U/mg, two‐step protocol) was coupled with wild‐type ADH from L. brevis on NADP(H) and mutant ADH from L. brevis on NAD(H) to achieve 50% conversion of racemic phenylethanol to (S)‐phenylethanol and acetophenone. Depending on the relative concentration of alcohol to cofactor, up to more than 100 turnovers were observed. We believe that this is the first demonstration of a regeneration scheme for both NAD+ from NADH and NADP+ from NADPH with the same enzyme.
Modulation von Protein‐Protein‐Wechselwirkungen mit niedermolekularen organischen Molekülen
Authors: Berg Thorsten
Published: June 2003

Viele Proteine üben ihre biologische Funktion als Bestandteile von Komplexen aus, und die Funktionen von Proteinen werden oft durch die spezifischen Wechselwirkungen mit anderen Proteinen bestimmt. Wegen der zentralen Bedeutung von Protein‐Protein‐Wechselwirkungen für zelluläre Prozesse kann die Modulation dieser Wechselwirkungen Funktionen bestimmter Proteine innerhalb der Zelle wirksam beeinflussen. Zellpermeable organische Modulatoren von Protein‐Protein‐Wechselwirkungen sind daher interessante Verbindungen sowohl für die Untersuchung physiologischer zellulärer Prozesse als auch für die Behandlung zahlreicher Krankheiten. Hier werden einige Protein‐Protein‐Wechselwirkungen vorgestellt, die weithin als pharmazeutische Angriffspunkte gelten, und der Leser wird mit erfolgreichen Strategien zur Identifizierung niedermolekularer Modulatoren dieser Wechselwirkungen vertraut gemacht. Diese Beispiele lassen erwarten, dass die interdisziplinäre Forschung in der funktionellen Proteomik, der Assay‐Entwicklung und der organischen Synthese neuartige Wege und Möglichkeiten für die zukünftige Behandlung von Humankrankheiten eröffnen wird.
Modulation of Protein–Protein Interactions with Small Organic Molecules
Authors: Berg Thorsten
Published: June 2003

Many proteins exert their biological roles as components of complexes, and the functions of proteins are often determined by their specific interactions with other proteins. Because of the central importance of protein–protein interactions for cellular processes, the ability to interfere with specific protein–protein interactions provides a powerful means of influencing the function of selected proteins within the cell. Cell‐permeable small organic modulators of protein–protein interactions are thus highly desirable tools both for the study of physiological cellular processes and for the treatment of numerous diseased states. Herein a number of protein–protein interactions that are considered to be pharmaceutical targets are presented, which will familiarize the reader with the strategies that have been employed for the successful identification of small molecule modulators of these protein–protein interactions. These encouraging examples suggest that combined research efforts in the areas of functional proteomics, assay development, and organic synthesis will open up novel possibilities for the treatment of human diseases in the future.
Reductive Electron Transfer and Transport of Excess Electrons in DNA
Authors: Wagenknecht Hans‐Achim
Published: June 2003

In principle, DNA‐mediated charge transfer processes can be categorized as either oxidative hole transfer or reductive electron transfer. In research on DNA damage, major efforts have focused on the investigation of oxidative hole transfer or transport, resulting in insights on the mechanisms. On the other hand, the transport or transfer of excess electrons has a large potential for biomedical applications, mainly for DNA chip technology. Yet the mechanistic details of this type of charge transfer chemistry were unclear. In the last two years this mechanism has been addressed in γ‐pulse radiolysis studies with randomly DNA‐bound electron acceptors or traps. The major disadvantage of this experimental setup is that the electron injection and trapping is not site‐selective. More recently, new photochemical assays for the chemical and spectroscopic investigation of reductive electron transfer and electron migration in DNA have been published which give new insights into these processes. Based on these results, an electron‐hopping mechanism is proposed which involves pyrimidine radical anions as intermediate electron carriers.
Small Sample Correction for the Variance of GEE Estimators
Authors: Morel J.G. , Bokossa M.C. , Neerchal N.K.
Published: June 2003

When clustered multinomial responses are fit using the generalized logistic link, Morel (1989) introduced a small sample correction in the Taylor series based estimator of the covariance matrix of the parameter estimates. The correction reduces the bias of the Type I error rates in small samples and guarantees positive definiteness of the estimated variance‐covariance matrix. It is well known that small sample bias in the use of the Delta method persists in any application of the Generalized Estimating Equations (GEE) methodology. In this article, we extend the correction originally suggested for the generalized logistic link, to other link functions and distributions, when parameters are estimated by GEE. In a Monte Carlo study with correlated data generated under different sampling schemes, the small sample correction has been shown to be effective in reducing the Type I error rates when the number of clusters is relatively small.
Zero‐Inflated Negative Binomial Mixed Regression Modeling of Over‐Dispersed Count Data with Extra Zeros
Authors: Yau Kelvin K. W. , Wang Kui , Lee Andy H.
Published: June 2003

In many biometrical applications, the count data encountered often contain extra zeros relative to the Poisson distribution. Zero‐inflated Poisson regression models are useful for analyzing such data, but parameter estimates may be seriously biased if the nonzero observations are over‐dispersed and simultaneously correlated due to the sampling design or the data collection procedure. In this paper, a zero‐inflated negative binomial mixed regression model is presented to analyze a set of pancreas disorder length of stay (LOS) data that comprised mainly same‐day separations. Random effects are introduced to account for inter‐hospital variations and the dependency of clustered LOS observations. Parameter estimation is achieved by maximizing an appropriate log‐likelihood function using an EM algorithm. Alternative modeling strategies, namely the finite mixture of Poisson distributions and the non‐parametric maximum likelihood approach, are also considered. The determination of pertinent covariates would assist hospital administrators and clinicians to manage LOS and expenditures efficiently.
Optimal Representation of Supplementary Variables in Biplots from Principal Component Analysis and Correspondence Analysis
Authors: Graffelman Jan , Aluja‐Banet Tomàs
Published: June 2003

This paper treats the topic of representing supplementary variables in biplots obtained by principal component analysis (PCA) and correspondence analysis (CA). We follow a geometrical approach where we minimize errors that are obtained when the scores of the PCA or CA solution are projected onto a vector that represents a supplementary variable. This paper shows that optimal directions for supplementary variables can be found by solving a regression problem, and justifies that earlier formulae from Gabriel are optimal in the least squares sense. We derive new results regarding the geometrical properties, goodness of fit statistics and the interpretation of supplementary variables. It is shown that supplementary variables can be represented by plotting their correlation coefficients with the axes of the biplot only when the proper type of scaling is used. We discuss supplementary variables in an ecological context and give illustrations with data from an environmental monitoring survey.
Novel type of in situ extraction: Use of solvent containing microcapsules for the bioconversion of 2‐phenylethanol from L‐phenylalanine by Saccharomyces cerevisiae
Authors: Stark D. , Kornmann H. , Münch T. , Sonnleitner B. , Marison I. W. , von Stockar U.
Published: June 2003

A novel in situ product removal (ISPR) method that uses microcapsules to extract inhibitory products from the reaction suspension is introduced into fermentation technology. More specifically, L‐phenylalanine (L‐Phe) was transformed by Saccharomyces cerevisiae to 2‐phenylethanol (PEA), which is inhibitory toward the yeast. In order to continuously remove PEA from the vicinity of the cells, the reaction suspension was brought into contact with capsules of 2.2‐mm diameter that had a hydrophobic core of dibutyl sebacate and an alginate‐based wall. This novel process combines the advantages of a normal in situ extraction process (fast mass transfer and simple process set‐up) with the benefits of a membrane‐based process (reduction of the solvent toxicity and avoidance of stable emulsions). In particular, the microbial cells are shielded from the phase toxicity of the organic solvent by a hydrogel layer surrounding the organic core. By placing the microcapsules into the fermenter, the final overall concentration of PEA in a fed‐batch culture was increased from 3.8 to 5.6 g/L because a part of the inhibitory product dissolved in the dibutyl sebacate core. In another fermentation experiment, the capsules were placed in a fluidized bed that was connected via a loop to the fermenter. In addition, the fluidized bed was connected via a second loop to a back‐extractor to regenerate the capsules. By alternating the extraction and back‐extraction cycles, it was possible to limit the PEA concentration of the fed‐batch culture in the fermenter to 2.4 g/L while producing important quantities of PEA that accumulated in an external reservoir. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 376–385, 2003.
Micro‐assembly of functionalized particulate monolayer on C18‐derivatized SiO2 surfaces
Authors: Huang Tom T. , Geng Tao , Akin Demir , Chang Woo‐Jin , Sturgis Jennifer , Bashir Rashid , Bhunia Arun K. , Robinson J. Paul , Ladisch Michael R.
Published: June 2003

This work describes a simple approach to immobilize functionalized colloidal microstructures onto a C18‐coated SiO2 substrate via specific or non‐specific bio‐mediated interactions. Biotinylated bovine serum albumin pre‐adsorbed onto a C18 surface was used to mediate the surface assembly of streptavidin‐coated microbeads (2.8 μm), while a bare C18 surface was used to immobilize anti‐Listeria antibody‐coated microbeads (2.8 μm) through hydrophobic interactions. For a C18 surface pre‐adsorbed with bovine serum albumin, hydrophobic polystyrene microbeads (0.8 μm) and positively charged dimethylamino microbeads (0.8 μm) were allowed to self‐assemble onto the surface. A monolayer with high surface coverage was observed for both polystyrene and dimethylamino microbeads. The adsorption characteristics of Escherichia coli and Listeria monocytogenes on these microbead‐based surfaces were studied using fluorescence microscopy. Both streptavidin microbeads pre‐adsorbed with biotinylated anti‐Listeria antibody and anti‐Listeria antibody‐coated microbeads showed specific capture of L. monocytogenes, while polystyrene and dimethylamino microbeads captured both E. coli and L. monocytogenes non‐specifically. The preparation of microbead‐based surfaces for the construction of microfluidic devices for separation, detection, or analysis of specific biological species is discussed. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 416–427, 2003.
Combined sequence and structure analysis of the fungal laccase family
Authors: Kumar S. V. Suresh , Phale Prashant S. , Durani S. , Wangikar Pramod P.
Published: June 2003

Plant and fungal laccases belong to the family of multi‐copper oxidases and show much broader substrate specificity than other members of the family. Laccases have consequently been of interest for potential industrial applications. We have analyzed the essential sequence features of fungal laccases based on multiple sequence alignments of more than 100 laccases. This has resulted in identification of a set of four ungapped sequence regions, L1–L4, as the overall signature sequences that can be used to identify the laccases, distinguishing them within the broader class of multi‐copper oxidases. The 12 amino acid residues in the enzymes serving as the copper ligands are housed within these four identified conserved regions, of which L2 and L4 conform to the earlier reported copper signature sequences of multi‐copper oxidases while L1 and L3 are distinctive to the laccases. The mapping of regions L1–L4 on to the three‐dimensional structure of the Coprinus cinerius laccase indicates that many of the non‐copper‐ligating residues of the conserved regions could be critical in maintaining a specific, more or less C‐2 symmetric, protein conformational motif characterizing the active site apparatus of the enzymes. The observed intraprotein homologies between L1 and L3 and between L2 and L4 at both the structure and the sequence levels suggest that the quasi C‐2 symmetric active site conformational motif may have arisen from a structural duplication event that neither the sequence homology analysis nor the structure homology analysis alone would have unraveled. Although the sequence and structure homology is not detectable in the rest of the protein, the relative orientation of region L1 with L2 is similar to that of L3 with L4. The structure duplication of first‐shell and second‐shell residues has become cryptic because the intraprotein sequence homology noticeable for a given laccase becomes significant only after comparing the conservation pattern in several fungal laccases. The identified motifs, L1–L4, can be useful in searching the newly sequenced genomes for putative laccase enzymes. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 386–394, 2003.
Optimal covalent immobilization of glucose oxidase‐containing liposomes for highly stable biocatalyst in bioreactor
Authors: Wang Shaoqing , Yoshimoto Makoto , Fukunaga Kimitoshi , Nakao Katsumi
Published: June 2003

The glucose oxidase‐containing liposomes (GOL) were prepared by entrapping glucose oxidase (GO) in the liposomes composed of phosphatidylcholine (PC), dimyristoyl L‐α‐phosphatidylethanolamine (DMPE), and cholesterol (Chol) and then covalently immobilized in the glutaraldehyde‐activated chitosan gel beads. The immobilized GOL gel beads (IGOL) were characterized to obtain a highly stable biocatalyst applicable to bioreactor. At first, the glutaraldehyde concentration used in the gel beads activation as well as the immobilizing temperature and time were optimized to enhance the immobilization yield of the GOL to the highest extent. The liposome membrane composition and liposome size were then optimized to obtain the greatest possible immobilization yield of the GOL, the highest possible activity efficiency of the IGOL, and the lowest possible leakage of the entrapped GO during the GOL immobilization. As a result, the optimal immobilization conditions were found to be as follows: the liposome composition, PC/DMPE/Chol = 65/5/30 (molar percentage); the liposome size, 100 nm; the glutaraldehyde concentration, 2% (w/v); the immobilizing temperature, 4°C; and the immobilizing time, 10 h. Furthermore, the optimal IGOL prepared were characterized by its rapidly increasing effective GO activity to the externally added substrate (glucose) with increasing temperature from 20 to 40°C, and also by its high stability at 40°C against not only the thermal denaturation in a long‐term (7 days) incubation but also the bubbling stress in a bubble column. Finally, compared to the conventionally immobilized glucose oxidase (IGO), the higher operational stability of the optimal IGOL was verified by using it either repeatedly (4 times) or for a long time (7 days) to catalyze the glucose oxidation in a small‐scale airlift bioreactor. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 444–453, 2003.
Growth dynamics of Artemisia annua hairy roots in three culture systems
Authors: Kim Yoo Jeong , Weathers Pamela J. , Wyslouzil Barbara E.
Published: June 2003

The transient growth of Artemisia annua hairy roots was compared for cultures grown in shake flasks and in bubble column and mist reactors. Instantaneous growth rates were obtained by numerically differentiating the transient biomass measurements. Specific sugar consumption rates showed good agreement with literature values. From the growth rate and sugar consumption rate, the specific yield and maintenance coefficient for sugar were determined for all three culture systems. These values were statistically indistinguishable for roots grown in shake flasks and bubble columns. In contrast, the values for roots grown in bubble columns and mist reactors were statistically different, suggesting that sugar utilization by roots grown in these two systems may be different. By measuring respiration rates in the bubble column reactor we also determined the actual biomass yield and maintenance coefficient for O2 and CO2. Together with an elemental analysis of the roots, this allowed us to obtain a reasonable carbon balance. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 428–443, 2003.
Effect of heat on phycoerythrin fluorescence: Influence of thermal exposure on the fluorescence emission of R‐phycoerythrin
Authors: Vaidya S. , Orta‐Ramirez A. , Smith D. M. , Ofoli R. Y.
Published: June 2003

The goal of this work was to measure and model the effect of thermal exposure on the fluorescence emission of R‐phycoerythrin (R‐PE). The long‐term objective of our work is to assess the feasibility of encapsulating R‐PE for use as the critical component of a time‐temperature integrator (TTI) for ascertaining the degree of inactivation of food pathogens such as Salmonella. In this article we present a study to measure and model the thermally induced fluorescence emission decay of R‐PE in several isothermal experiments. We used the isothermal data to determine the kinetic parameters, based on a general nth order reaction, and evaluated the utility of the resulting model by using it to predict R‐PE fluorescence emission decay for several nonisothermal experiments based on published USDA safe harbor guidelines for cooked beef products. The transient experiments were conducted over the same temperature range used in the isothermal study. Very good agreement was obtained between theory and experiment at temperatures of 62.8°C and above, although the model slightly underpredicted the extent of fluorescence emission decay at 60°C. Our results indicate that R‐PE fluorescence emission decay kinetics is well behaved and that the protein is a strong candidate for use as a time‐temperature integrator. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 465–473, 2003.
Scale‐down of continuous filtration for rapid bioprocess design: Recovery and dewatering of protein precipitate suspensions
Authors: Reynolds T. , Boychyn M. , Sanderson T. , Bulmer M. , More J. , Hoare M.
Published: June 2003

The early specification of bioprocesses often has to be achieved with small (tens of millilitres) quantities of process material. If extensive process discovery is to be avoided at pilot or industrial scale, it is necessary that scale‐down methods be created that not only examine the conditions of process stages but also allows production of realistic output streams (i.e., streams truly representative of the large scale). These output streams can then be used in the development of subsequent purification operations. The traditional approach to predicting filtration operations is via a bench‐scale pressure filter using constant pressure tests to examine the effect of pressure on the filtrate flux rate and filter cake dewatering. Interpretation of the results into cake resistance at unit applied pressure (α) and compressibility (n) is used to predict the pressure profile required to maintain the filtrate flux rate at a constant predetermined value. This article reports on the operation of a continuous mode laboratory filter in such a way as to prepare filter cakes and filtrate similar to what may be achieved at the industrial scale. Analysis of the filtration rate profile indicated the filter cake to have changing properties (compressibility) with time. Using the insight gained from the new scale‐down methodology gave predictions of the flux profile in a pilot‐scale candle filter superior to those obtained from the traditional batch filter used for laboratory development. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 454–464, 2003.
Enzymatic catalysis via liquid–liquid interfaces
Authors: Straathof Adrie J.J.
Published: June 2003

Enzymes acting in a biphasic liquid of water and organic solvent may show catalytic activity dependent on the amount of phase interface available. Such an effect may be caused by several mechanisms. For example, for hydroxynitrile lyase from Prunus amygdalus, substrate mass transfer limitation has been advocated, but also adsorption of the enzyme on the interface. In this commentary it is shown that often these two mechanisms will have qualitatively similar consequences. The reaction rate will be influenced by the organic substrate concentration, by the initial enzyme concentration, and by the volume‐specific interfacial area, and these influences will be linear at low values but reach a saturation level at high values. To rule out any of the models, their quantitative mathematical descriptions should be compared, taking into account that both models may be valid simultaneously. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83:371–375, 2003.
Biofiltration of a mixture of volatile organic compounds on granular activated carbon
Authors: Aizpuru A. , Malhautier L. , Roux J. C. , Fanlo J. L.
Published: June 2003

The performance of a biofilter packed with Active Carbon (AC) was evaluated. The effluent (alcohol, ketones, esters, aromatic and chlorinated compounds) treated was a representative mixture of most common industrial emissions. To achieve a better knowledge of multicomponent adsorption mechanisms, and to underline the interest of inoculating AC, a control abiotic humidified filter had been operated in the same conditions as the biofilter. For a load of 110 g VOC m−3 AC h−1, after 55 days of operation, the removal efficiency was higher in the biotic than in the abiotic filter (85% vs 55%, respectively). Moreover, in the biofilter, at steady state, the elimination of all compounds was almost complete except for chlorinated compounds and p‐xylene (removal efficiency of 25% and 64%, respectively). The microbial colonization of AC involved a decrease of the adsorption sites accessibility and enhanced the treatment of VOCs (volatile organic compounds) having a lower affinity for activated carbon. Moreover, while aromatic compounds and MIBK were eliminated along the overall height of the biofilter, pollutants with reduced affinity for AC, such as methanol, acetone, and halogenated compounds were only treated on the second half of the reactor. Thus, the affinity for activated carbon was an important parameter controling the biodegradation process. Nevertheless, the use of AC as packing material in biofilters treating complex mixtures of VOCs is limited. Actually, similar removal efficiency could be reached, in the same conditions, for a biofilter packed with granular peat. Furthermore, for the biofilter packed with AC, the column height necessary to remove biodegradable compounds, with reduced affinity for the support, was important. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 479–488, 2003.
Vascular changes in duodenal mucosa in shigellosis and cholera
Authors: Koshi Rachel , Chandy George , Mathan Minnie , Mathan V.I.
Published: June 2003

Vascular endothelial cells are highly specialized cells with numerous sensory and modulator functions. Our previous studies show extensive microvascular changes in rectal mucosal vasculature of patients with acute infective diarrhea (Mathan and Mathan 1985a, Gut 26:710–717).We looked for changes in the duodenal mucosal vasculature in two naturally occurring diarrheal infections: shigellosis and cholera. Duodenal mucosal biopsies from 14 patients with shigellosis, 12 patients with cholera, and 10 healthy volunteers were examined under the electron microscope. There were extensive microvascular changes in the duodenum in shigellosis and cholera. Congestion and dilatation of capillaries and venules, stagnation of blood, thinning of the endothelial lining, and platelet clumping were commonly seen in both conditions. Endothelial damage was also common to both conditions but was mild to moderate in cholera and severe in shigellosis with frank hemorrhage, frequent formation of stress fibers, widening of intercellular spaces, cytoplasmic blebbing, cell fragmentation, and intravascular thrombosis. Erythrocyte aggregates, platelet aggregates, and leucocyte plugging lead to capillary obstruction. The arterioles were severely constricted. These changes in the endothelial lining of the microvasculature could contribute to the pathogenesis of the disease resulting in peripheral vascular insufficiency, inadequate oxygen delivery to intestine, and organ dysfunction. The factors influencing these changes, their implications, and possible therapeutic interventions are discussed. Clin. Anat. 16:317–327, 2003. © 2003 Wiley‐Liss, Inc.
Plastination and computerized 3D reconstruction of the temporal bone
Authors: Qiu Ming‐Guo , Zhang Shao‐Xiang , Liu Zheng‐Jin , Tan Li‐Wen , Wang Yu‐Su , Deng Jun‐Hui , Tang Ze‐Sheng
Published: June 2003

The purpose of this study was to generate a computerized 3D reconstruction of the temporal bone and intratemporal structures. A plastination technique was used to obtain equidistant serial thin sections of 1.2 mm thickness and, on an SGI workstation, a Contour‐Marching Cubes algorithm was selected to reconstruct the temporal bone and intratemporal structures in three dimensions. All reconstructed structures can be represented individually or jointly and rotated in any plane. Any diameter and angle of a structure can be conveniently measured. The capability of reconstructing individual and combined images of intratemporal structures, viewing them from all surgical angles, and accurately measuring their spatial relationships gives skull base and otologic surgeons important guidance. The reconstructed model can also be used for resident education, rehearsal of an unfamiliar surgery, and for developing a new surgical approach. Clin. Anat. 16:300–303, 2003. © 2003 Wiley‐Liss, Inc.
Calcaneal angle in Ugandans
Authors: Igbigbi P.S. , Mutesasira A.N.
Published: June 2003

We investigated the calcaneal angle from 206 unilateral radiographs of the lateral aspect of the foot in Ugandans, comprising 114 males and 92 females, aged 20–40 years. The mean angle in males was 35.1° with a standard deviation (SD) of 7.5° and, in females, 37.6° with SD 5.6°. The range of the angle for both sexes together was 20–50° with females having a significantly higher mean value than males (P < 0.01). There was also a significant difference in the angle between Ugandan and Nigerian men (P < 0.01) and between Ugandan and Nigerian women (P < 0.001). Our reported range was the widest so far documented in Africans. Our study reinforces the need to establish the normal range of the angle in a given population and also highlights the clinical importance of the angle to orthopedic surgeons managing calcaneal fractures in this part of the world. Clin. Anat. 16:328–330, 2003. © 2003 Wiley‐Liss, Inc.
Anatomical variations and clinical implications of the artery to the lingual nerve
Authors: Harn Stanton D. , Durham Timothy M.
Published: June 2003

The pterygomandibular space is a critical anatomic area for the delivery of local anesthesia in the practice of dentistry. The neurovascular contents of this area are subject to trauma and its resultant local and systemic complications. This study of 202 cadaveric specimens reaffirms the literature as to the percent distributions of the superficial and deep routes of the maxillary artery and details for the first time the anatomic variations of the artery to the lingual nerve. This artery courses through the pterygomandibular space placing it at risk for injection trauma along with the other neurovascular contents. It has been uncommonly identified and referred to in the literature, yet it may be the first artery encountered when entering the space with a needle or during surgical intervention in the area. Clin. Anat. 16:294–299, 2003. © 2003 Wiley‐Liss, Inc.