bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation in the continuous time mover‐stayer model with an application to bond ratings migration
Authors: Frydman Halina , Kadam Ashay
Published: May 2004

The usual tool for modelling bond ratings migration is a discrete, time‐homogeneous Markov chain. Such model assumes that all bonds are homogeneous with respect to their movement behaviour among rating categories and that the movement behaviour does not change over time. However, among recognized sources of heterogeneity in ratings migration is age of a bond (time elapsed since issuance). It has been observed that young bonds have a lower propensity to change ratings, and thus to default, than more seasoned bonds.

The aim of this paper is to introduce a continuous, time‐non‐homogeneous model for bond ratings migration, which also incorporates a simple form of population heterogeneity. The specific form of heterogeneity postulated by the proposed model appears to be suitable for modelling the effect of age of a bond on its propensity to change ratings. This model, called a mover–stayer model, is an extension of a Markov chain.

This paper derives the maximum likelihood estimators for the parameters of a continuous time mover–stayer model based on a sample of independent continuously monitored histories of the process, and develops the likelihood ratio statistic for discriminating between the Markov chain and the mover–stayer model. The methods are illustrated using a sample of rating histories of young corporate issuers. For these issuers the default probabilities predicted by the Markov chain and mover–stayer models are different. In particular for 1–4 years old bonds the mover–stayer model estimates substantially lower default probabilities from rating C than a Markov chain. Copyright © 2004 John Wiley & Sons, Ltd.
DM27, an enaminone, modifies the in vitro transport of antiviral therapeutic agents
Authors: Salama Noha N. , Scott Kenneth R. , Eddington Natalie D.
Published: May 2004

Objective—For most antiviral drugs, low or variable bioavailability is attributed to poor absorption, susceptibility to efflux, or first pass metabolism. Enaminones are beta dicarbonyl compounds, which display P‐glycoprotein (P‐gp) substrate properties with high efflux ratios. This study investigates the influence of DM27, an enaminone, on the in vitro transport of antiviral agents and the possibility of using DM27 as a P‐gp inhibitor to prevent the efflux of certain antiretroviral agents.

Methods—The transport of [3H]amprenavir, [3H]saquinavir, [3H]ritonavir, [14C]zidovudine (AZT) and [3H]acyclovir was evaluated across Caco‐2 cells with DM27 (10−10–10−4 M). In addition, the effect of DM27 (10−6 M) on the transport of transcellular and paracellular markers was tested to evaluate its influence on these transport pathways. The apparent permeability coefficient (Papp) for each drug or marker was calculated with/without DM27 and toxicity evaluation for DM27 was performed using the MTS assay.

Results—The mean Papp for the investigated antiviral agents significantly increased by 22%–51% after DM27 incubation without any toxicity to the Caco‐2 cells. In addition, DM27 did not influence the transcellular or paracellular transport of propranolol and mannitol, respectively.

Conclusions—DM27, an enaminone, increased the transport of antiretroviral drugs and acyclovir in a nontoxic manner without affecting the paracellular or transcellular transport of these drugs. This study suggests that DM27 may be used as a P‐gp efflux inhibitor to enhance the oral bioavailability of antiviral drugs and that drug–drug interactions will most probably be encountered upon co‐administration of P‐gp substrate drugs with enaminones. Copyright © 2004 John Wiley & Sons, Ltd.
β2‐amino acids—syntheses, occurrence in natural products, and components of β‐peptides1,2
Authors: Lelais Gérald , Seebach Dieter
Published: May 2004

Although they are less abundant than their α‐analogues, β‐amino acids occur in nature both in free form and bound to peptides. Oligomers composed exclusively of β‐amino acids (so‐called β‐peptides) might be the most thoroughly investigated peptidomimetics. Beside the facts that they are stable to metabolism, exhibit slow microbial degradation, and are inherently stable to proteases and peptidases, they fold into well‐ordered secondary structures consisting of helices, turns, and sheets. In this respect, the most intriguing effects have been observed when β2‐amino acids are present in the β‐peptide backbone. This review gives an overview of the occurrence and importance of β2‐amino acids in nature, placing emphasis on the metabolic pathways of β‐aminoisobutyric acid (β‐Aib) and the appearance of β2‐amino acids as secondary metabolites or as components of more complex natural products, such as peptides, depsipeptides, lactones, and alkaloids. In addition, a compilation of the syntheses of both achiral and chiral β2‐amino acids is presented. While there are numerous routes to achiral β2‐amino acids, their EPC synthesis is currently the subject of many investigations. These include the diastereoselective alkylation and Mannich‐type reactions of cyclic‐ or acyclic β‐homoglycine derivatives containing chiral auxiliaries, the Curtius degradation, the employment of transition‐metal catalyzed reactions such as enantioselective hydrogenations, reductions, C–H insertions, and Michael‐type additions, and the resolution of rac. β2‐amino acids, as well as several miscellaneous methods. In the last part of the review, the importance of β2‐amino acids in the formation of β‐peptide secondary structures is discussed. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 2004
Double Ring‐Closing Metathesis Reaction of Nitrogen‐Containing Tetraenes: Efficient Construction of Bicyclic Alkaloid Skeletons and Synthetic Application to Four Stereoisomers of Lupinine and Their Derivatives
Authors: Ma Shengming , Ni Bukuo
Published: May 2004

The double ring‐closing metathesis reaction of nitrogen‐containing tetraenes was studied. The selectivity of the fused/dumbbell‐type products can be controlled by the electronic/steric effects of the substituents attached to the CC bonds and the s‐cis/s‐trans conformational ratios of the substrates. This methodology has also been successfully applied to the enantioselective synthesis of four stereoisomers of lupinine and their derivatives.
How Does the Exchange of One Oxygen Atom with Sulfur Affect the Catalytic Cycle of Carbonic Anhydrase?
Authors: Schenk Stephan , Kesselmeier Jürgen , Anders Ernst
Published: May 2004

We have extended our investigations of the carbonic anhydrase (CA) cycle with the model system [(H3N)3ZnOH]+ and CO2 by studying further heterocumulenes and catalysts. We investigated the hydration of COS, an atmospheric trace gas. This reaction plays an important role in the global COS cycle since biological consumption, that is, uptake by higher plants, algae, lichens, and soil, represents the dominant terrestrial sink for this gas. In this context, CA has been identified by a member of our group as the key enzyme for the consumption of COS by conversion into CO2 and H2S. We investigated the hydration mechanism of COS by using density functional theory to elucidate the details of the catalytic cycle. Calculations were first performed for the uncatalyzed gas phase reaction. The rate‐determinig step for direct reaction of COS with H2O has an energy barrier of ΔG=53.2 kcal mol−1. We then employed the CA model system [(H3N)3ZnOH]+ (1) and studied the effect on the catalytic hydration mechanism of replacing an oxygen atom with sulfur. When COS enters the carbonic anhydrase cycle, the sulfur atom is incorporated into the catalyst to yield [(H3N)3ZnSH]+ (27) and CO2. The activation energy of the nucleophilic attack on COS, which is the rate‐determining step, is somewhat higher (20.1 kcal mol−1 in the gas phase) than that previously reported for CO2. The sulfur‐containing model 27 is also capable of catalyzing the reaction of CO2 to produce thiocarbonic acid. A larger barrier has to be overcome for the reaction of 27 with CO2 compared to that for the reaction of 1 with CO2. At a well‐defined stage of this cycle, a different reaction path can emerge: a water molecule helps to regenerate the original catalyst 1 from 27, a process accompanied by the formation of thiocarbonic acid. We finally demonstrate that nature selected a surprisingly elegant and efficient group of reactants, the [L3ZnOH]+/CO2/H2O system, that helps to overcome any deactivation of the ubiquitous enzyme CA in nature.
A Caged Lanthanide Complex as a Paramagnetic Shift Agent for Protein NMR
Authors: Prudêncio Miguel , Rohovec Jan , Peters Joop A. , Tocheva Elitza , Boulanger Martin J. , Murphy Michael E. P. , Hupkes Hermen‐Jan , Kosters Walter , Impagliazzo Antonietta , Ubbink Marcellus
Published: May 2004

A lanthanide complex, named CLaNP (caged lanthanide NMR probe) has been developed for the characterisation of proteins by paramagnetic NMR spectroscopy. The probe consists of a lanthanide chelated by a derivative of DTPA (diethylenetriaminepentaacetic acid) with two thiol reactive functional groups. The CLaNP molecule is attached to a protein by two engineered, surface‐exposed, Cys residues in a bidentate manner. This drastically limits the dynamics of the metal relative to the protein and enables measurements of pseudocontact shifts. NMR spectroscopy experiments on a diamagnetic control and the crystal structure of the probe‐protein complex demonstrate that the protein structure is not affected by probe attachment. The probe is able to induce pseudocontact shifts to at least 40 Å from the metal and causes residual dipolar couplings due to alignment at a high magnetic field. The molecule exists in several isomeric forms with different paramagnetic tensors; this provides a fast way to obtain long‐range distance restraints.
Synthesis of Furano‐Epothilone D
Authors: Schinzer Dieter , Bourguet Erika , Ducki Sylvie
Published: May 2004

The total synthesis of furano‐epothilone D by a convergent route is reported. The key fragments are available on a large scale to provide sufficient material for biological evaluation. The approach involves a palladium‐catalyzed coupling that generates a highly functionalized aldehyde which is connected in a stereoselective aldol reaction to yield the framework of furano‐epothilone D. Finally, a macrolactonization provides furano‐epothilone D.
Correlation between Host–Guest Binding and Host Amplification in Simulated Dynamic Combinatorial Libraries
Authors: Corbett Peter T. , Otto Sijbren , Sanders Jeremy K. M.
Published: May 2004

We present a versatile computer model of diverse dynamic combinatorial libraries, and examine how molecular recognition between library members and a template can be used to amplify the best binders. The correlation between host–guest binding and amplification was examined for a set of 50 libraries with >300 components each over a wide range of template and building block concentrations. Depending on these concentrations correlations vary from poor (when using a large excess of template) to good (for very dilute libraries and/or substoichiometric template concentrations), highlighting the need to choose the experimental conditions for dynamic combinatorial libraries thoughtfully.
Long‐term efficacy and safety of zoledronic acid in the treatment of skeletal metastases in patients with nonsmall cell lung carcinoma and other solid tumors
Authors: Rosen Lee S. , Gordon David , Tchekmedyian N. Simon , Yanagihara Ronald , Hirsh Vera , Krzakowski Maciej , Pawlicki Marek , de Souza Paul , Zheng Ming , Urbanowitz Gladys , Reitsma Dirk , Seaman John ,   On behalf of the Zoledronic Acid Lung Cancer and Other Solid Tumors Study Group
Published: May 2004

BACKGROUND

The authors previously reported the efficacy of a dose of 4 mg of zoledronic acid in reducing skeletal complications in patients with bone metastases secondary to lung carcinoma and other solid tumors (except carcinomas of the breast and prostate). In the current study, they update these results and report the long‐term efficacy and safety of 21 months of treatment with zoledronic acid in a randomized, placebo‐controlled trial.

METHODS

A total of 773 patients were randomized to receive zoledronic acid (4 mg or 8 mg) or placebo via a 15‐minute infusion every 3 weeks for 21 months. The 8‐mg dose later was reduced to 4 mg (8/4‐mg group). The primary efficacy endpoint was the percentage of patients at 21 months with ≥ 1 skeletal‐related event (SRE) (pathologic fracture, spinal cord compression, radiation therapy to bone, or surgery to bone). Secondary analyses (time to first SRE, annual incidence of SREs, and multiple‐event analysis) included hypercalcemia of malignancy.

RESULTS

Fewer patients treated with zoledronic acid developed at least 1 SRE at 21 months compared with patients treated with placebo (39% of those treated at the 4‐mg dose [P =0.127] and 36% of those treated at the 8/4‐mg dose [P = 0.023], compared with 46% of those treated with placebo). Furthermore, 4 mg of zoledronic acid significantly delayed the median time to first SRE (236 days with 4 mg vs. 155 days with placebo; P = 0.009) and significantly reduced the annual incidence of SREs (1.74 per year with the 4‐mg dose vs. 2.71 per year with placebo; P = 0.012). Moreover, the 4‐mg dose of zoledronic acid was found to reduce the risk of developing a skeletal event by 31% (hazard ratio of 0.693; P = 0.003). Zoledronic acid was found to be well tolerated with long‐term use; the most commonly reported adverse events in all treatment groups included bone pain and the transient, acute‐phase reactions of nausea, anemia, and emesis.

CONCLUSIONS

To the authors' knowledge, zoledronic acid is the first bisphosphonate to demonstrate long‐term safety and efficacy in this patient population. Cancer 2004. © 2004 American Cancer Society.
Interface Synthesis, Characterization and Catalytic Properties of Dialkyldichlorotin and Tetraalkyl Distannoxane Functionalities Grafted to Insoluble Polystyrene Beads by a Hexamethylene Spacer
Authors: Biesemans Monique , Mercier Frédéric A. G. , Van Poeck Manu , Martins José C. , Dumartin Gilles , Willem Rudolph
Published: May 2004

Insoluble polystyrene‐grafted compounds of the type [(P−H)(1−t){P−(CH2)6SnBuCl2}t] and [(P−H)(1−t)({P−(CH2)6SnBuX}2O)t/2], where (P−H) represents a cross‐linked polystyrene, X is Cl, OH or OOCCH3, and t is the degree of functionalization, were synthesized from Amberlite XE‐305, a polystyrene cross‐linked with divinylbenzene. The compounds were characterized by elemental analysis, IR and Raman spectroscopy, solid‐state 13C and 117Sn NMR spectroscopy and, where appropriate, by 119Sn hr‐MAS NMR spectroscopy. The influence of the variable t and tin functionality on the catalytic activity of these compounds was assessed in the transesterification reaction of ethyl acetate with octanol. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Fluorescence Assay and Screening of Epoxide Opening by Nucleophiles
Authors: Badalassi Fabrizio , Klein Gérard , Crotti Paolo , Reymond Jean‐Louis
Published: May 2004

Terminal epoxides such as 1 react with nucleophiles (H2O, Cl−, Br−, N3−, and CN−) at the primary oxirane carbon atom to give mostly anti‐Markovnikov‐type regioisomers 5a−d. The opening products of epoxide (R)‐1 with chloride (5a), bromide (5b) and azide (5c) are oxidized by horse liver alcohol dehydrogenase and NAD+ to give the corresponding ketones 7a−c and, subsequently, umbelliferone 4 by β‐elimination, leading to a fluorescence increase at λem = 460 ± 20 nm (λex = 360 ± 20 nm). The epoxide hydrolysis products give no signal. We used this enantio‐ and chemo‐selective fluorogenic assay for epoxide opening to search for catalytic antibodies for nucleophilic epoxide opening that were raised against 1,2‐azidoammonium hapten 8, as a mimic for epoxide opening by azide, and against chloromethyl phosphonate hapten 9, as a mimic for the transition state of chlorohydrin formation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Impact of collagen structure on matrix trafficking by human fibroblasts
Authors: Abraham Leah C. , Vorrasi John , Kaplan David L.
Published: May 2004

Biodegradation of collagen biomaterial matrices and the deposition of new collagen extracellular matrix (ECM) are critical to the integration of in vitro bioengineered materials and tissues in vivo. In previous studies, we observed significant impact of collagen matrix structure on primary lung fibroblast behavior in vitro. In the present work, to begin to understand the mechanistic basis for our previous observation, the response of human fibroblasts (IMR‐90) to the structural state of collagen matrices was studied with respect to cell proliferation, cell morphology, β‐galactosidase level, and transcript content for collagen (Col‐1), matrix metalloproteinases (MMP‐1, MMP‐2), tissue inhibitors of matrix metalloproteinase (TIMP‐1 and TIMP‐2). Collagen digestion was assessed quantitatively by uptake of collagen‐coated fluorescent beads incorporated in the preformed collagen matrix. Transcript levels related to the deposition of new ECM proteins varied as a function of the structure of the collagen matrix presented to the cells. Col‐1 expression was 2‐fold higher and expression for MMP‐1, MMP‐2, TIMP‐1, and TIMP‐2 increased for cells when grown on 156 μg/cm2 denatured collagen compared with cells grown on tissue culture (TC) plastic. On 156 μg/cm2 nondenatured (native) collagen, Col‐1 expression was decreased by half and MMP‐2 was increased by 2.5‐fold compared with cells grown on TC plastic. On 78 μg/cm2 denatured collagen, Col‐1 expression was 80% whereas the MMPs and TIMPs were increased by 1.25‐ to 2‐fold compared with cells grown on TC plastic. On 78 μg/cm2 nondenatured collagen expression of all 5 transcripts was reduced 60‐90% of the levels determined for the cells grown on TC plastic. Cell viability, based on cell morphology and β‐galactosidase activity, was improved on the denatured collagen. A higher level of collagen matrix incorporation was observed for cells grown on denatured collagen than on nondenatured collagen or TC plastic. These data suggest that tissue engineering matrices incorporating denatured collagen may promote more active remodeling toward new ECM in comparison to cells grown on nondenatured collagen or cells grown on TC plastic. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 39–48, 2004
A new austenitic stainless steel with a negligible amount of nickel: An in vitro study in view of its clinical application in osteoporotic bone
Authors: Fini M. , Giavaresi G. , Giardino R. , Lenger H. , Bernauer J. , Rimondini L. , Torricelli P. , Borsari V. , Chiusoli L. , Chiesa R. , Cigada A.
Published: May 2004

A biomaterial named P558 is a new austenitic stainless steel (SS) with a negligible amount of Ni (<0.20%). In previous in vitro and in vivo studies it was compared with conventional SS and Ti6Al4V and shown to be a promising material in orthopedics. Because osteoporosis is a type of pathology very often encountered in implanted patients and can be studied with in vitro models, the purpose of the present study was to evaluate P558 in vitro through comparison of normal (nOB) with osteopenic (oOB) bone‐derived primary rat osteoblasts. Osteoblasts were cultured directly on P558 and polystyrene as controls for 72 h. Osteoblast proliferation, adhesion, and activity (ALP, OC, TGF‐β1, and IL‐6) were evaluated at 24 and 72 h. Results demonstrated that the growth of nOB and oOB cultured on P558 was not affected negatively when compared to control. Cells on P558 did not show any alteration in terms of adhesion, proliferation, and metabolic marker production in nOB and oOB cultures, and a significant increase in ALP, OC, and TGF‐β1 production was observed. SEM images revealed no alteration in cell morphology. The current findings demonstrate that P558 promotes osteoblast proliferation, activation, and differentiation not only in normal bone, but also in osteopenic bone‐derived osteoblasts. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 30–37, 2004
Novel clusters of receptors for sphingosine‐1‐phosphate, sphingosylphosphorylcholine, and (lyso)‐phosphatidic acid: New receptors for “Old” ligands
Authors: Kostenis Evi
Published: May 2004

The (lyso)phospholipid mediators sphingosine‐1‐phosphate (S1P), lysophosphatidic acid (LPA), sphingosylphosphorylcholine (SPC), and phosphatidic acid (PA) regulate diverse cellular responses such as proliferation, survival and death, cytoskeletal rearrangements, cell motility, and differentiation among many others. Signaling is complex and many signaling events are mediated through the activation of cell surface seven transmembrane (7TM) G protein coupled receptors. Five high affinity receptors for S1P have been identified so far and named S1P1, 2 ,3 ,4 ,5 (formerly referred to as endothelial differentiation gene (edg)1, 5, 3, 6, 8). Recently, the orphan receptor GPR63 was identified a low affinity S1P receptor structurally distant from the S1P1–5 family. The orphan GPR3, 6, 12 cluster, phylogenetically related to the edg and melanocortin receptors appears to be subject to modulation by S1P and SPC although all three receptors are strong constitutive stimulators of the Gαs‐adenylyl cyclase (AC) pathway and would not require additional ligand stimulation but rather inverse agonism to control activity. Ovarian cancer G protein coupled receptor 1 (OGR1) and GPR4, two structurally closely related receptors were assigned in functional and binding studies as high affinity molecular targets for SPC. Very recently, however, both OGR1 and GPR4 were described as receptors endowed with the ability to signal cells in response to protons. LPA exerts its biological effects through the activation of G protein coupled LPA1–3 receptors (formerly referred to as edg2, 4, 7). A fourth high affinity LPA receptor has been identified: P2Y9 (GPR23) structurally related to nucleotide receptors and phylogenetically quite distant from the high affinity LPA1–3 cluster. This review attempts to give an overview about the existing families of lysophosholipid receptors and the spectrum of lipid agonists they use as high or low affinity ligands to relay extracellular signals into intracellular responses. Recently deorphaned lipid receptors, within and outside the known lipid receptor clusters will receive particular attention. © 2004 Wiley‐Liss, Inc.
G protein mediated signaling pathways in lysophospholipid induced cell proliferation and survival
Authors: Radeff‐Huang Julie , Seasholtz Tammy M. , Matteo Rosalia G. , Brown Joan Heller
Published: May 2004

Agonist activation of a subset of G protein coupled receptors (GPCRs) stimulates cell proliferation, mimicking the better known effects of tyrosine kinase growth factors. Cell survival or apoptosis is also regulated via pathways initiated by stimulation of these same GPCRs. This review focuses on aspects of signaling by the lysophospholipid mediators, lysophosphatidic acid (LPA), and sphingosine 1 phosphate (S1P), which make these agonists uniquely capable of modulating cell growth and survival. The general features of GPCR coupling to specific G proteins, downstream effectors and signaling cascades are first reviewed. GPCR coupling to Gi and Ras/MAPK or to Gq and phospholipase generated second messengers are insufficient to regulate cell proliferation while G12/13/Rho engagement provides additional complementary signals required for cell proliferation. Survival is best predicted by coupling to Gi pathways that regulate PI3K and Akt, but other signals generated through different G protein pathways are also implicated. The unique ability of LPA and S1P to concomitantly stimulate Gi, Gq, and G12/13 pathways, given the proper complement of expressed LPA or S1P receptors, allows these receptors to support cell survival and proliferation. In pathophysiological situations, e.g., vascular disease, cancer, brain injury, and inflammation, components of the signaling cascade downstream of lysophospholipid receptors, in particular those involving Ras or Rho, may be altered. In addition, up or downregulation of LPA or S1P receptor subtypes, altering their ratio, and increased availability of the lysophospholipid ligands at sites of injury or inflammation, likely contribute to disease and may be important targets for therapeutic intervention. © 2004 Wiley‐Liss, Inc.
Vitamin D regulated keratinocyte differentiation
Authors: Bikle Daniel D.
Published: May 2004

The epidermis is the largest organ in the body. It is comprised primarily of keratinocytes which are arranged in layers that recapitulates their programmed life cycle. Proliferating keratinocytes are on the bottom—the stratum basale. As keratinocytes leave the stratum basale they begin to differentiate, culminating in the enucleated stratum corneum which has the major role of permeability barrier. Calcium and the active metabolite of vitamin D, 1,25(OH)2D3, play important roles in this differentiation process. The epidermis has a gardient of calcium with lowest concentrations in the stratum basale, and highest concentrations in the stratum granulosum where proteins critical for barrier function are produced. Vitamin D is made in different layers of the epidermis, but 1,25(OH)2D3 is made primarily in the stratum basale. Together calcium and 1,25(OH)2D3 regulate the ordered differentiation process by the sequential turning on and off the genes producing the elements required for differentiation as well as activating those enzymes involved in differentiation. Animal models in which the sensing mechanism for calcium, the receptor for 1,25(OH)2D3, or the enzyme producing 1,25(OH)2D3 have been rendered inoperative demonstrate the importance of these mechanisms for the differentiation process, although each animal model has its own phenotype. This review will examine the mechanisms by which calcium and 1,25(OH)2D3 interact to control epidermal differentiation. © 2004 Wiley‐Liss, Inc.
A group extensions approach to relative difference sets
Authors: Galati John C.
Published: May 2004

A new approach to (normal) relative difference sets (RDSs) is presented and applied to give a new method for recursively constructing infinite families of semiregular RDSs. Our main result (Theorem 7.1) shows that any metabelian semiregular RDS gives rise to an infinite family of metabelian semiregular RDSs. The new method is applied to identify several new infinite families of non‐abelian semiregular RDSs, and new methods for constructing generalized Hadamard matrices are given. The techniques employed are derived from the general theory of group extensions. © 2004 Wiley Periodicals, Inc. J Combin Designs 12: 279–298, 2004.
Control of H2S waste gas emissions with a biological activated carbon filter
Authors: Chung Ying‐Chien , Lin Yu‐Yen , Tseng Ching‐Ping
Published: May 2004

The removal of high concentrations of H2S from waste gases containing mixtures of H2S and NH3 was studied using the pilot‐scale biofilter. Granular activated carbon (GAC), selected as support material in this study, demonstrated its high adsorption capacity for H2S and good gas distribution. Extensive tests to determine removal characteristics, removal efficiency, and removal capacity of high H2S levels and coexisting NH3 in the system were performed. In seeking the appropriate operating conditions, the response surface methodology (RSM) was employed. H2S removal capacities were evaluated by the inoculated bacteria (biological conversion) and BDST (Bed Depth Service Time) methods (physical adsorption). An average 98% removal efficiency for 0.083–0.167 mg dm−3 of H2S and 0.004–0.021 mg dm−3 of NH3 gases was achieved during the operational period because of rapid physical adsorption by GAC and subsequently an effective biological regeneration of GAC by inoculated Pseudomonas putida CH11 and Arthrobacter oxydans CH8. The results showed that H2S removal efficiency for the system was not affected by inlet NH3 concentrations. In addition, no acidification was observed in the BAC biofilter. High buffer capacity and low moisture demand were also advantages of this system. The maximal inlet loading and critical loading for the system were 18.9 and 7.7 g‐H2S m−3 h−1, respectively. The results of this study could be used as a guide for the further design and operation of industrial‐scale systems. Copyright © 2004 Society of Chemical Industry
Electrolytic recovery of zinc from zinc ash using a catalytic anode
Authors: Ramachandran P , Nandakumar V , Sathaiyan N
Published: May 2004

The process of galvanisation of steel generates zinc ash as the waste product, thus creating pollution problems. The recovery of zinc metal from zinc ash, with a zinc content of about 76% by leaching and electrowinning has been studied. The presence of chloride has been identified as the major problem area. A catalytic anode based on iridium dioxide (IrO2) was used as the anode material to overcome this problem. Catalyst loading was kept at an economically acceptable level. The catalyst's stability, energy consumption and efficiency of zinc recovery are discussed. The service life of the IrO2 active coating has been established by an accelerated polarisation test. The zinc deposit recovered from the zinc ash has been examined by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Copyright © 2004 Society of Chemical Industry
Influence of acid treatment on the surface activity and mass transfer inhibition of a splittable surfactant
Authors: Lee Yuh‐Lang , Lin Shi‐Yow
Published: May 2004

A splittable surfactant, Triton SP‐190, was used to evaluate the effects of acid treatment on the mass transfer rate of an extraction process and on the interfacial tension‐lowering activity of a system containing this surfactant. Equilibrium and dynamic interfacial tensions at the interface of CCl4 and the aqueous phase containing surfactant were measured by using pendent drop tensiometry enhanced by video digitization. A single‐drop extraction apparatus was used to obtain the extraction percentage of acetic acid from the dispersed CCl4 droplets to the aqueous phase. The results indicate that the inorganic acid treatment can inhibit the dynamic and equilibrium interfacial tension‐lowering activity of Triton SP‐190. The mass transfer resistance induced by the addition of Triton SP‐190 can also be reduced by the pre‐treatment of acid. The effectiveness of acid treatment on both properties was greater at low pH values, lower surfactant concentrations, and longer treatment times. With HCl treatment, the equilibrium interfacial tension was not able to increase to the value of a surfactant‐free system, but approached a maximum value which was independent of the pH value, but dependent on surfactant concentration. On the contrary, the extraction percentage, which has decreased due to the presence of surfactant, can be recovered completely to that of a surfactant‐free system by acid treatment. The acid‐treatment time required to achieve a significant recovery of mass transfer rate was much longer than that required to recover the interfacial tension. The present results also demonstrate that the constituents contained in an acid‐treatment system had different effectiveness in affecting the interfacial tension and mass transfer rate due to the different mechanisms involved. Copyright © 2004 Society of Chemical Industry
Effect of pH and activated charcoal adsorption on hemicellulosic hydrolysate detoxification for xylitol production
Authors: Mussatto Solange I , Santos Júlio C , Roberto Inês C
Published: May 2004

Biotechnological conversion of xylose into xylitol using hydrolysates obtained from the hemicellulosic fraction of lignocellulosic materials is compromised by the presence of compounds released or formed during the hydrolysis process, some of them being toxic to microorganisms. In order to improve the bioconversion of these hydrolysates it is necessary to find methods to reduce their toxicity. In the present work, rice straw hemicellulosic hydrolysate was treated by six different procedures (all of them involving pH adjustment, with or without activated charcoal adsorption), before being used as a fermentation medium for xylitol production. The most effective method of treatment was to increase the initial pH (0.4) to 2.0 using solid NaOH, followed by the addition of activated charcoal (25 g kg−1) and increase in the pH to 6.5 using solid NaOH. Lignin degradation products were the most inhibitory compounds present in the hydrolysate; their removal was selective and strongly dependent on the pH employed in the treatment. The highest yield of xylitol was 0.72 g g−1 xylose, with a productivity of 0.55 g dm−3 h−1. Copyright © 2004 Society of Chemical Industry
Transformation of 2,4‐dichlorophenoxy‐ethanoic acid (2,4‐D) by a photoassisted ferrous oxalate/H2O2 system
Authors: Kwan CY , Chu W
Published: May 2004

The kinetics of the dependence of pH, oxalate, and hydrogen peroxide concentrations on the degradation performance of the herbicide 2,4‐dichlorophenoxyethanoic acid (2,4‐D) was studied in a novel ferrous oxalate/H2O2/UV system. The formation and destruction of the primary intermediate, 2,4‐dichlorophenol (2,4‐DCP), was also monitored in the study. A rate enhancement of about 2.9 times was found when 1.2 mM of oxalate was added to the conventional Fe2+/H2O2/UV process. However, excess oxalate suppressed the reaction due to the scavenging and light attenuation effects. The 2,4‐D transformation at a lower initial pH was faster than that at a higher pH, and the different reaction mechanisms were investigated. In addition to the decay rates, the yield of the intermediate 2,4‐DCP was also affected by the initial solution pH. The increment of hydrogen peroxide concentration did not increase the initial decay rates of 2,4‐D, yet it improved the overall removal of 2,4‐D and elevated the formation of the corresponding intermediate (2,4‐DCP). Copyright © 2004 Society of Chemical Industry
Crises, setbacks and chronic problems—the determinants of economic stress events among poor households in India
Authors: Noponen Helzi , Kantor Paula
Published: May 2004

This study analyses the incidence, frequency, costs and subsequent coping strategies of economic stress events which disrupt the household economy among poor self‐employed women organized by SEWA, a grassroots development NGO. An analysis of the determinants of stress levels reveals that women who were members in SEWA for longer periods, who held savings accounts in SEWA Bank and who provided greater earnings share to total family income had fewer stresses. The analysis underscores the positive effect of programs in financial service, social security, co‐operative and trade union activities. The findings lend support to arguments in favour of the efficacy of credit‐plus rather than minimalist creict programmes for poor women. Copyright © 2004 John Wiley & Sons, Ltd.
Political and economic determinants of private investment
Authors: Le Quan V.
Published: May 2004

This paper presents empirical evidence that links private investment to rate of return differential, risk aversion, and several types of political and economic risk. Estimating private investment equation for a panel of 25 developing countries over 21 years yields the following results: (i) socio‐political instability characterized by nonviolent protests promotes private investment while violent uprisings hinder private investment; (ii) regime change instability characterized by constitutional government change promotes private investment while unconstitutional government change hinders private investment; and (iii) policy uncertainty characterized by variability of contract enforcement rights promotes private investment while variability of government political capacity hinders private investment. Copyright © 2004 John Wiley & Sons, Ltd.
Aggregate agricultural supply response in Ethiopia: a farm‐level analysis
Authors: Abrar Suleiman , Morrissey Oliver , Rayner Tony
Published: May 2004

This study examines the responsiveness of peasant farmers in Ethiopia to price and non‐price factors. Quadratic production and restricted profit functions are estimated using farm‐level survey data from Ethiopia in 1994. The results indicate that farmers respond only modestly to price incentives. The own‐price output supply elasticity is very low and output supply is not responsive to fertilizer prices or the wage rate. Non‐price factors are far more important in affecting production and resource use than price incentives. The results are robust to whether the primal or dual approach is used to estimate elasticities. The results underscore the need to strengthen market incentives through effective policies that will improve farmers' access to fertilizer, land and credit, public investment in roads and irrigation. Copyright © 2004 John Wiley & Sons, Ltd.
Growth, poverty and the IMF
Authors: Bird Graham
Published: May 2004

Although the IMF presents itself as a monetary institution, it plays an important role in providing support to poor countries via its Poverty Reduction and Growth Facility. It is difficult to imagine more central development issues than poverty and growth. However, while there is a broad consensus surrounding the stabilization issues with which IMF programmes conventionally deal, there is much less agreement about the causes of economic growth and poverty. This carries lessons for the design of the PRGF. While most reviews of it focus on ‘process’, this paper offers a more fundamental analysis of the Fund's involvement in growth and poverty reduction. It suggests that the design of conditionality needs to distinguish between elements according to the degree of scientific consensus. It also suggests that the success of the Fund's attempts to facilitate growth and poverty reduction will be severely constrained unless the necessary external, financial support is provided. Copyright © 2004 John Wiley & Sons, Ltd.
Ghost of the financing gap: an overlooked aspect of the aid debate
Authors: Ranaweera Thilak
Published: May 2004

In the decades‐old intense debate on foreign aid, a great deal has been said about qualitative aspects of aid and aid‐effectiveness (i.e. fungibility, among other things). The latest landmark in the debate was the World Bank publication Assessing Aid: What Works, What Doesn't, and Why, which generated a new wave of controversy about foreign aid and policy conditionality. Much of the recent debate has focused on the qualitative aspects of the aid‐growth relationship and the role of ‘good’ policies. However, little attention had been paid so far to some important quantitative aspects. The present study draws attention to this often overlooked aspect of the aid debate to demonstrate that the level of aid requirements of a country is an equally important and integral part of aid and aid‐effectiveness. Estimation of the magnitude of external assistance requirements of countries used by international financial institutions is compared with an alternative model, the so‐called ‘Balance of Payments Constrained Growth Model’ (based on the Harrod trade multiplier). It is revealed that the latter is not a real alternative as it is an incomplete model. More importantly, it is shown that international financial institutions use these quantitative frameworks in a very flexible and pragmatic way to carry on a meaningful policy dialogue with both donors and recipient countries, which has an important bearing on overall aid and aid‐effectiveness. Copyright © 2004 John Wiley & Sons, Ltd.
Expression of brain‐derived neurotrophic factor immunoreactivity and mRNA in the hippocampal CA1 and cortical areas after chronic ischemia in rats
Authors: Lee Tsong‐Hai , Yang Jen‐Tsung , Kato Hiroyuki , Wu June Hsieh , Chen Sien‐Tsong
Published: May 2004

We studied the expression of brain‐derived neurotrophic factor (BDNF) immunoreactivity and mRNA in the ischemia‐vulnerable cerebral hippocampal CA1 and cortical areas after permanent occlusion of bilateral internal carotid arteries. Four groups of rats were studied, including 1) young normotensive Wistar‐Kyoto (WKY) rats, 2) aged normotensive WKY rats, 3) young spontaneous hypertensive rats (SHR), and 4) aged SHR. Each group contained rats from sham operation and 1 week, 4 weeks, and 8 weeks after cerebral ischemia (n = 3–5 at each time point). Hematoxylin and eosin staining and in situ apoptosis detection showed no neuronal damage from 1 week to 8 weeks in all the ischemic rats. Immunohistochemistry and Western blot showed that BDNF immunoreactivity increased only at 1 week in the CA1 area of young WKY rats (P < .001) and SHR (P = .002) and decreased only at 8 weeks in the cortical area of aged WKY rats (P = .02). In situ hybridization and TaqMan real‐time RT‐PCR showed that BDNF mRNA decreased consistently from 1 week to 8 weeks in both CA1 and cortical areas in young SHR (P < .05 and P < .01, respectively) and in aged WKY rats (P < .01 and P < .05, respectively) but was not changed in young WKY rats or aged SHR (P > .05) compared with the sham‐operated rats. Our study demonstrates an expression disparity of BDNF immunoreactivity and mRNA in the hippocampal CA1 and cortical areas, especially in the young SHR and aged WKY rats after mild cerebral ischemia. Our study suggests that, under permanent occlusion of bilateral internal carotid arteries, aging and the level of blood pressure may have influence on the expression of BDNF. © 2004 Wiley‐Liss, Inc.
Developmental, regional, and cellular expression of SFT/UbcH5A and DMT1 mRNA in brain
Authors: Knutson Mitchell , Menzies Sharon , Connor James , Wessling‐Resnick Marianne
Published: May 2004

Brain iron has marked developmental, regional, and cellular distribution patterns. To characterize better the potential mechanisms for iron transport into and within the brain, we have analyzed expression patterns of two factors: divalent metal transporter 1 (DMT1) and stimulator of Fe transport (SFT). DMT1 is known to participate in brain iron uptake although functional information is lacking. Even less clear is the possible role of SFT, which is related to a member of the ubiquitin‐conjugating E2 family UbcH5A, but previous studies have found SFT/Ubc5Ha mRNA expressed abundantly in mouse brain. Like DMT1, SFT function has been implicated in transferrin and nontransferrin‐bound iron uptake. Comparative Northern analysis indicates that SFT/UbcH5A mRNA levels are threefold higher in 3‐day‐old mice than at later ages, whereas levels of DMT1 mRNA do not change. In situ analysis of neonatal mouse brain reveals prominent SFT/UbcH5A mRNA expression in epithelial and ependymal cells in the choroid plexus and neurons of the olfactory bulb, hippocampus, and cortex. Adult mouse brain expresses SFT/UbcH5A mRNA mainly in white matter of the cerebellum and pons. Using a multiple tissue expression (MTE) array containing 20 different human brain regions, the highest levels of both SFT/UbcH5A and DMT1 mRNA are detected in the corpus callosum and cerebellum. The significantly elevated levels of SFT/UbcH5A mRNA in the neonatal mouse and its localization to choroid plexus, a major site of brain iron acquisition, suggest that this factor may contribute to the rapid rate of brain iron uptake that occurs in the early postnatal period. © 2004 Wiley‐Liss, Inc.
Symbol calculus and Fredholmness for a Banach algebra of convolution type operators with slowly oscillating and piecewise continuous data
Authors: Bastos Maria Amélia , Bravo António , Karlovich Yuri
Published: May 2004

A symbol calculus for the smallest Banach subalgebra 𝒜[SO,PC] of the Banach algebra ℬ︁(Lnp(ℝ)) of all bounded linear operators on the Lebesgue spaces Lnp(ℝ) (1 < p < ∞, n ≥ 1) which contains all the convolution type operators Wa,b = aℱ−1bℱ with a ∈ [SO, PC]n×n and b ∈ [SOp, PCp]n×n is constructed. Here [SO, PC]n×n means the C*‐algebra generated by all slowly oscillating (SO) and all piecewise continuous (PC) n × n matrix functions, and [SOp, PCp]n×n is a Fourier multiplier analogue of [SO, PC]n×n on Lp(ℝ). As a result, a Fredholm criterion for the operators A ∈ 𝒜[SO,PC] is established. The study is based on the compactness of the commutators AWa,b − Wa,bA where A ∈ 𝒜[SO,PC], a ∈ SO, and b ∈ SOp, on the Allan‐Douglas local principle, and on the two projections theorem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wave diffraction by a strip grating: the two‐straight line approach
Authors: Bastos M. A. , Moura Santos A. , dos Santos A. F.
Published: May 2004

Boundary‐value problems of wave diffraction by a periodic strip grating are associated with a Toeplitz operator acting on a space of functions defined on a two‐straight line contour. Simple formulas are given for the left inverse of the operator associated with the Neumann boundary‐value problem and for the right inverse of the operator associated with the Dirichlet boundary‐value problem when the period of the grating is equal to double the width of the strips. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A direct approach to convolution type operators with symmetry
Authors: Castro L. P. , Speck F.‐O. , Teixeira F. S.
Published: May 2004

We consider convolution type operators that carry a certain symmetry in their structure. The study is motivated by several applications in mathematical physics where this kind of operators appears. They can be regarded as a class of Wiener‐Hopf plus Hankel operators acting in spaces of Bessel potentials. But the common approach of reduction to systems of Wiener‐Hopf equations is avoided by a more direct factorization scheme. The main results are: Fredholm criteria, analytical representation of generalized inverses, and the constructive solution of normalization problems. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The essential spectrum of a model problem in 2‐dimensional magnetohydrodynamics: a proof of a conjecture by J. Descloux and G. Geymonat
Authors: Faierman M. , Mennicken R. , Möller M.
Published: May 2004

Descloux and Geymonat considered a model problem for plasma in a toroidal configuration and conjectured that the essential spectrum has an explicitly given band structure. Here we prove this conjecture by employing an operator matrix representation of the problem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reynolds type equation for a thin flow under intensive transverse percolation
Authors: Nazarov Sergueï , Videman Juha H.
Published: May 2004

A two‐dimensional Reynolds type equation is derived and justified for a three‐dimensional viscous incompressible flow, taking place between two smooth fixed adjacent curved walls, under intensive percolation. Resulting from the dimension reduction, the model is proved to admit fluxes of order 1 = h0 with respect to the relative thickness h, a small parameter. Thus, velocities are allowed to be of order h−1, which is just the case where linear and nonlinear terms have the same asymptotic powers O(h−3). Boundary layers are also taken into account and estimates obtained for the remainder terms in the asymptotic representation formulae. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The boundary value problems of the Stokes resolvent equations in n dimensions
Authors: Varnhorn Werner
Published: May 2004

We construct a solution for the boundary value problems of the Stokes resolvent system in bounded and exterior domains of ℝn (n ≥ 2) with prescribed Dirichlet‐ and Neumann boundary data. The construction is based on the explicit form of the corresponding fundamental and double layer tensor and uses hydrodynamical potential theory and the method of integral equations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)