bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of organo‐phosphorus and nano‐clay materials on the thermal and fire performance of epoxy resins
Authors: Hussain M. , Varley R. J. , Mathys Z. , Cheng Y. B. , Simon G. P.
Published: November 2003

The results of flame retardance and thermal stability of a reactively modified organo‐phosphorus diglycidylether of bisphenol‐A and an organo‐phosphorus tetraglycidyl diaminodiphenylmethane are reported here. The organo‐phosphorus epoxy resins were synthesized by the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and diglycidyl ether of bisphenol‐A and tetraglycidyl diaminodiphenylmethane, respectively, and then cured with a mixture of 3,5‐diethyltoluene‐2,4‐diamine and 3,5‐diethyltoluene‐2,6‐diamine. In addition to this, between 5 and 7.5% of organically modified polymeric layered silicate nano‐clay was also added to neat epoxy resin or to the phosphorus‐modified epoxy resin to investigate any synergies, or otherwise, a combination of clay and phosphorus on the flame, degradation, and thermal properties are also reported. The reaction kinetics of phosphorus‐modified and epoxy cure were studied by FTIR, 1H‐NMR, and DSC. Thermal properties and morphology of the final product were analyzed by thermogravimetric analysis, dynamic mechanical thermal analysis, X‐ray diffraction, and cone calorimetry. Improvement in flame retardance by cone calorimetry was demonstrated by the addition of only 3% phosphorus or 7.5% clay into the epoxy compared with unmodified epoxy resins, whereas no evidence of synergy for a phosphorus and clay combination was found. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1233–1253, 2004
Application of chitosan‐entrapped β‐galactosidase in a packed‐bed reactor system
Authors: Wentworth Danielle S. , Skonberg Denise , Donahue Darrell W. , Ghanem Amyl
Published: November 2003

The model enzyme β‐galactosidase was entrapped in chitosan gel beads and tested for hydrolytic activity and its potential for application in a packed‐bed reactor. The chitosan beads had an enzyme entrapment efficiency of 59% and retained 56% of the enzyme activity of the free enzyme. The Michaelis constant (Km) was 0.0086 and 0.011 μmol/mL for the free and immobilized enzymes, respectively. The maximum velocity of the reaction (Vmax) was 285.7 and 55.25 μmol mL−1min−1for the free and immobilized enzymes, respectively. In pH stability tests, the immobilized enzyme exhibited a greater range of pH stability and shifted to include a more acidic pH optimum, compared to that of the free enzyme. A 2.54 × 16.51‐cm tubular reactor was constructed to hold 300 mL of chitosan‐immobilized enzyme. A full‐factorial test design was implemented to test the effect of substrate flow (20 and 100 mL/min), concentration (0.0015 and 0.003M), and repeated use of the test bed on efficiency of the system. Parameters were analyzed using repeated‐measures analysis of variance. Flow (p< 0.05) and concentration (p< 0.05) significantly affected substrate conversion, as did the interaction progressing from Run 1 to Run 2 on a bed (p< 0.05). Reactor stability tests indicated that the packed‐bed reactor continued to convert substrate for more than 12 h with a minimal reduction in conversion efficiency. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1294–1299, 2004
Resistivity‐temperature behavior of carbon fiber filled semicrystalline composites
Authors: Di Weihua , Zhang Guo
Published: November 2003

Carbon fiber (CF) filled low‐density polyethylene (LDPE) composites were prepared by the conventional melt‐mixing method. The distribution of CF in the composite was studied by wide‐angle X‐ray diffraction (WAXD) and scanning electron microscope (SEM) observations. A phenomenological model was proposed to illustrate the resistivity‐temperature behavior of CF‐filled semicrystalline composites. The effects of the content and aspect ratio of CF on the positive temperature coefficient (PTC) and the room temperature resistivity were elucidated. A balance between the PTC intensity and the room‐temperature resistivity can be achieved by using a mixture of CFs with low and high aspect ratios. The negative temperature coefficient (NTC) phenomenon can be effectively eliminated by crosslinking under γ‐ray radiation, and the crosslinked composite exhibits a higher PTC intensity and PTC transition temperature than the noncrosslinked counterpart. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1222–1228, 2004
Composition and long‐term stability of polyglycidol prepared by cationic ring‐opening polymerization
Authors: Timothy Royappa A. , Vogt Michael L. , Sharma Venkatanarayanan
Published: November 2003

Polyglycidol synthesized by cationic ring‐opening polymerization of glycidol (boron trifluoride initiation in dichloromethane) was purified of low molecular weight contaminants by centrifugal filtration. The high and low molecular weight fractions were characterized by NMR, GPC, osmometry, viscometry, DSC, and FTIR. The 13C‐NMR spectrum of this polymer was completely annotated by proposing a new step in the reaction mechanism. The four thermal dimers of glycidol were also isolated and identified as 2,5‐bis(hydroxymethyl)‐1,4‐dioxane and 2,6‐bis(hydroxymethyl)‐1,4‐dioxane, each of which can exist in cis and trans configurations. Polyglycidol was found to be hygroscopic, picking up about 5% by weight of atmospheric moisture. It was also found that, over time (ca. 1–2 years), polyglycidol crosslinks into a rubbery, insoluble mass. It is therefore recommended that this polymer be stored dry and used within a few months of synthesis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1344–1351, 2004
Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials
Authors: Wang Hong‐Wen , Chang Kung‐Chin , Yeh Jui‐Ming , Liou Shir‐Joe
Published: November 2003

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na+‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004
Binding and reversible denaturation of double‐stranded DNA by Ff gene 5 protein
Authors: Mou Tung‐Chung , Shen Michelle C. , Terwilliger Thomas C. , Gray Donald M.
Published: November 2003

The gene 5 protein (g5p) from Ff filamentous virus is a model single‐stranded DNA (ssDNA) binding protein that has an oligonucleotide/oligosaccharide binding (OB)‐fold structure and binding properties in common with other ssDNA‐binding proteins. In the present work, we use circular dichroism (CD) spectroscopy to analyze the effects of amino acid substitutions on the binding of g5p to double‐stranded DNA (dsDNA) compared to its binding to ssDNA. CD titrations of poly[d(A) · d(T)] with mutants of each of the five tyrosines of the g5p showed that the 229‐nm CD band of Tyr34, a tyrosine at the interface of adjacent protein dimers, is reversed in sign upon binding to the dsDNA, poly[d(A) · d(T)]. This effect is like that previously found for g5p binding to ssDNAs, suggesting there are similarities in the protein–protein interactions when g5p binds to dsDNA and ssDNA. However, there are differences, and the possible perturbation of a second tyrosine, Tyr41, in the complex with dsDNA. Three mutant proteins (Y26F, Y34F, and Y41H) reduced the melting temperature of poly[d(A) · d(T)] by 67°C, but the wild‐type g5p only reduced it by 2°C. This enhanced ability of the mutants to denature dsDNA suggests that their binding affinities to dsDNA are reduced more than are their binding affinities to ssDNA. Finally, we present evidence that when poly[d(A) · d(T)] is melted in the presence of the wild‐type, Y26F, or Y34F proteins, the poly[d(A)] and poly[d(T)] strands are separately sequestered such that renaturation of the duplex is facilitated in 2 mM Na+. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 637–648, 2003
Tryptophanyl substitutions in apomyoglobin affect conformation and dynamic properties of AGH subdomain
Authors: Sirangelo Ivana , Iannuzzi Clara , Malmo Clorinda , Irace Gaetano
Published: November 2003

The solvent accessibilities to the tryptophanyl microenvironments of wild type sperm whale apomyoglobin (apoMb) and two mutants (W7F and W14F) containing a single tryptophan are measured by fluorescence quenching studies. The results are compared to those relative to horse apoMb. In the wild type sperm whale protein, no difference is noticed in the solvent accessibility of the two indole residues, as documented by the values of the Stern–Volmer constants. By contrast, the two tryptophan residues of horse apoMb are exposed to the solvent in a different way, thus indicating that some local conformational differences exist between the two homologous proteins in solution. The single W → F substitution at either position 7 or 14 determines local conformational changes that increase the accessibility of the remaining indole residue but do not affect the overall architecture of the protein molecule. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70:649–654, 2003
Effects of metallic silver island films on resonance energy transfer between N,N′‐(dipropyl)‐tetramethyl‐ indocarbocyanine (Cy3)‐ and N,N′‐(dipropyl)‐tetramethyl‐ indodicarbocyanine (Cy5)‐labeled DNA
Authors: Malicka Joanna , Gryczynski Ignacy , Kusba Jozef , Lakowicz Joseph R.
Published: November 2003

Resonance energy transfer (RET) is typically limited to distances below 60 Å, which can be too short for some biomedical assays. We examined a new method for increasing the RET distances by placing donor‐ and acceptor‐labeled DNA oligomers between two slides coated with metallic silver particles. A N,N′‐(dipropyl)‐tetramethylindocarbocyanine donor and a N,N′‐(dipropyl)‐tetramethylindodicarbocyanine acceptor were covalently bound to opposite 5′ ends of complementary 23 base pair DNA oligomers. The transfer efficiency was 25% in the absence of silver particles or if only one slide was silvered, and it increased to an average value near 64% between two silvered slides. The average value of the Forster distance increased from 58 to 77 Å. The energy transfer data were analyzed with a model assuming two populations of donor–acceptor pairs: unaffected and affected by silver island films. In an affected fraction of about 28%, the apparent energy transfer efficiency is near 87% and the Forster distance increases to 119 Å. These results suggest the use of metallic silver particles to increase the distances over which RET occurs in biomedical and biotechnology assays. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 595–603, 2003
Effects of aluminum sorption on calcium‐polygalacturonate network used as soil–root interface model
Authors: Mimmo T. , Marzadori C. , Francioso O. , Deiana S. , Gessa C. E.
Published: November 2003

The objective of this study is to determine the influence of aluminum sorption on a calcium–polygalacturonate (Ca‐PG) network used as a soil–root interface model. The Ca‐PG network is exposed to aluminum solutions at different concentrations (25–800 μM) at pH 3.50. High concentrations lead to a release of calcium (80%) and aluminum becomes the predominant reticulating cation of the polygalacturonic chains. The FTIR spectra show how aluminum sorption induces shifts of the characteristic bands of carbohydrates in the spectral regions of 1700–1400 and 1200–800 cm−1, which are enhanced by decreasing intensities. This might be induced by a weakening of the metal–PG complex through conformational variations of the structure. Scanning electron micrographs also show a collapse of the fibrillar structure of Ca‐PG that is due to aluminum sorption. This structural rearrangement suggests that the soil–root interface could modify its functionality, affecting the transport of metal ions (nutrients) across the interface and consequently through the cell membranes. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 655–661, 2003
Cervical cancer control, priorities and new directions
Authors: Monsonego Joseph , Bosch F. Xavier , Coursaget Pierre , Cox John Thomas , Franco Eduardo , Frazer Ian , Sankaranarayanan Rengaswamy , Schiller John , Singer Albert , Wright Tom , Kinney Walter , Meijer Chris , Linder James
Published: November 2003

Cervical cancer is caused by infection with a range of high risk “oncogenic” human papillomavirus (HPV) types, and it is now accepted that >99% of cervical cancer is initiated by HPV infection. The estimated lifetime risk of cervical cancer is nevertheless relatively low (less than 1 in 20 for most community based studies). Although sensitivity and specificity of the available diagnostic techniques are suboptimal, screening for persistent HPV infection is effective in reducing the incidence of cervical cancer. Infection can be detected by molecular techniques or by cytological examination of exfoliated cervical cells. Persistent infection is the single best predictor of risk of cervical cancer.1

The latest findings of HPV and cervical cancer research need to be widely disseminated to the scientific and medical societies that are updating screening and management protocols, public health professionals, and to women and clinicians. This report reviews current evidence, clinical implications and directions for further research in the prevention, control and management of cervical cancer. We report the conclusions of the Experts' Meeting at the EUROGIN 2003 conference. © 2003 Wiley‐Liss, Inc.
Identification of candidate antigens for serologic detection of Helicobacter pylori‐infected patients with gastric carcinoma
Authors: Krah Alexander , Miehlke Stephan , Pleissner Klaus‐Peter , Zimny‐Arndt Ursula , Kirsch Christian , Lehn Norbert , Meyer Thomas F. , Jungblut Peter R. , Aebischer Toni
Published: November 2003

Helicobacter pylori colonizes the stomach of almost half the world population and is a causative agent of gastric carcinomas and duodenal ulcers. Only a small fraction of infected people will develop these severe illnesses and a predictive test to identify people at high risk would greatly benefit disease management. Our study aimed to identify conserved bacterial antigens that may be useful for the development of such a diagnostic test. High‐resolution immunoproteomics by 2‐dimensional electrophoresis of H. pylori 26695 proteins was carried out with sera from infected patients with either duodenal ulcer (n=30) or gastric carcinoma (n=30), 2 clinically divergent conditions. According to their antigen recognition patterns clear groups of patients were identified. Although this classification did not correspond to the clinical status, it may be correlated to other bacterial or host factors that influence the outcome of infection. In general antigen recognition patterns were found to be highly variable, however by utilizing powerful image analysis and statistical tests the recognition of 14 antigenic protein species was found to differ significantly (p<0.01) between both diseases. Particular protein species of GroEL, HyuA, GroES and AtpA appear to be useful surrogate markers for gastric carcinoma detection and consequently should be considered for further prospective studies to assess their predictive value. For one protein species of AtpA, evidence was found that different post‐translational modifications may confer different immunogenicities. © 2003 Wiley‐Liss, Inc.
PGE2‐mediated upregulation of iNOS in murine breast cancer cells through the activation of EP4 receptors
Authors: Timoshenko Alexander V. , Lala Peeyush K. , Chakraborty Chandan
Published: November 2003

We report here that endogenous prostaglandin E2 (PGE2) resulting from cyclooxygenase (COX)‐2 expression in a highly metastatic murine breast cancer cell line C3L5 upregulates IFN‐γ + LPS‐induced nitric oxide (NO) synthase (iNOS) expression and NO production. This action of PGE2 is mediated through the EP4 receptor in a cAMP‐dependent manner. Both nonselective and selective COX‐2 inhibitors suppressed IFN‐γ + LPS‐induced NO production, which was largely restored by exogenous PGE2 or EP4 receptor agonist PGE1 alcohol. EP4 antagonist AH‐23848B inhibited NO production with a concomitant downregulation of iNOS mRNA in IFN‐γ + LPS‐stimulated cells. cAMP dependence of NO production by cells under inducible conditions was demonstrated by the use of known modulators of intracellular cAMP. Since both COX‐2 and iNOS are implicated in breast cancer progression, our findings of EP4 receptor‐mediated upregulation of iNOS in COX‐2‐expressing breast cancer cells suggest that blocking COX‐2 and/or EP4 may provide a simple therapeutic modality in this tumor model. © 2003 Wiley‐Liss, Inc.
Density functional investigation of reaction of borohydride cation BH with propylene
Authors: Qu Zheng‐Wang , Zhu Hui , Li Ze‐Sheng , Zhang Xing‐Kang , Zhang Qi‐Yuan
Published: November 2003

The reactions of BH with propylene (CH2CHCH3) to form both the adducts BC3H and the H2‐elimination products BC3H + H2 have been investigated at the density functional B3LYP/6‐311G(d,p) level of theory. It is shown that the electrophilic attacks of BH towards two olefinic carbons of H2CCHCH3 and two subsequent 1,3‐H‐shifts may form four low‐lying BC3H isomers (with the relative energies in parentheses in kcal/mol): 1 BH · CH2CHCH3 (0.0), 1′ BH · CH3CHCH2 (6.3), 3 BHCH2CH2CH (4.3), and 4 BHCH(CH3) (5.0), respectively. On the other hand, further H2‐eliminations may also occur easily between BC bonds of isomers 1 and 1′ and between CC bonds of isomers 3 and 4 to form two dissociation products (P1) HBCHCHCH + H2 and (P2) HBC(CH3)CH + H2, with H2‐elimination from isomer 1 to be energetically most favorable. According to our calculated mechanism, the collisional stabilization processes of low‐lying isomers 1, 1′, 3, and 4 may compete extensively with their H2‐eliminations processes for the title reaction, leading mainly to some linear carborane cations. This study may be helpful for understanding the stereochemical aspects of borohydride cations towards alkylenes. © 2003 Wiley Periodicals, Inc. J Comput Chem 25: 258–264, 2004
Reorganization of the structures, morphologies, and conformations of polymers by coalescence from their crystalline inclusion compounds formed with cyclodextrins
Authors: Tonelli Alan E.
Published: November 2003

We and several other research groups have recently reported the ability of cyclodextrins (CDs) to act as hosts in the formation of inclusion compounds (ICs) with guest polymers. Polymer‐CD‐ICs are crystalline materials formed by the close packing of host CD stacks, which results in a continuous channel of ∼5‐10Å in diameter running down the interior of the CD stacks. The guest polymers are confined to the narrow, continuous CD channels, and so are necessarily highly extended and segregated from neighboring polymer chains by the walls of the CD stacks. We have shown that coalescence of guest polymers from their CD‐IC crystals can result in a significant reorganization of the structures, morphologies, and even conformations that are normally observed in their bulk samples. For example, when poly(ethylene terephthalate) (PET) is coalesced from its γ‐CD‐IC, we find that in the non‐crystalline regions of the sample the PET chains are adopting highly extended kink conformations, which result in their facile recrystallization from the melt and prevent quenching of the coalesced PET to achieve an amorphous sample during rapid cooling from above Tm. We have also created well‐mixed blends of normally incompatible polymers by coalescing them from CD‐ICs containing both polymers, where they are necessarily spatially proximal. Finally we have found the unique morphologies created by the coalescence of homopolymers, block copolymers, and homopolymer pairs from their CD‐ICs are generally stable to heat treatment for substantial periods above their Tm's and/or Tg's, and so may be thermoplastically processed without loss of the unique morphologies achieved through coalescence from their CD‐IC crystals.
Free energy and dimensions of macromolecules under confinement in layered assemblies
Authors: Cifra Peter , Bleha Tomáš , Škrinárová Zuzana
Published: November 2003

The changes in the free energy ΔA accompanying penetration of polymer solutions from bulk into slit‐like cavities were determined by lattice simulations. In dilute solutions the thermodynamics of penetration is controlled mainly by the parameter ϵw specifying interaction between polymer and walls of repulsive or adsorptive cavities. However, the magnitude of |ΔA| is substantially reduced by increasing concentration ∅︁ in bulk solution. Furthermore, compression of chains by concentration in good solvents and adsorptive cavities was found to be larger in the slit then in the bulk. At intermediate confinement, a region of a minimum coil size was observed at all concentrations and attraction strengths, where molecules are squeezed along all three axes.
Properties of poly(vinyl alcohol)‐graft‐polyacrylamide copolymers depending on the graft length. 1. Redistribution of hydrogen bonds and its influence on the copolymer behavior in aqueous solution
Authors: Zheltonozhskaya Tatyana , Demchenko Olga , Rakovich Irina , Guenet Jean‐Michel , Syromyatnikov Vladimir
Published: November 2003

A series of poly(vinyl alcohol)‐graft‐polyacrylamide copolymers (PVA‐g‐PAA) with a constant number N but various molecular weights (lengths) of graft chains, which are intramolecular polymer‐polymer complexes (intraPC), were investigated. The changes in the system of intramolecular hydrogen bonds and state of macromolecules in a solution are considered. The effect of partial detachment of PAA grafts from the main chain caused by the increase in molecular weight of grafts to a more than some critical value (M̄ vPAAcrit≈4.3·105 at N=9) has been revealed. When the length of grafts increases, the thermodynamic quality of water with respect to copolymers improves. The values of z‐average radius of inertia, characteristic viscosity and the number of macromolecules in associate go through a minimum at M̄ vPAA=4.3·105 and then sharply grow with increasing length of grafts.
Dye‐ligand immobilized IPNs membrane for removal heavy metal ions
Authors: Bayramoğlu Gülay , Yalçın Emine , Genç Ömer , Arıca M. Yakup
Published: November 2003

We have developed a novel approach to obtain high metal sorption capacity utilizing a membrane containing chitosan and an immobilized reactive dye (i.e. Reactive Yellow‐2). The composite membrane was characterized by SEM, FT‐IR, swelling test, and elemental analysis. The membrane has uniform small pores distribution and the pore dimensions are between 5 and 10 μm, and the HEMA:chitosan ratio was 50:1. The reactive dye immobilized composite membrane was used in the removal of heavy metal ions [i.e., Pb(II), Hg(II) and Cd(II)] from aqueous medium containing different amounts of these ions (5‐600 mg l−1) and at different pH values (2.0‐7.0). The maximum adsorption capacities of heavy metal ions onto the composite membrane under non‐competitive conditions were 64.3 mmol m−2 for Pb(II), 52.7 mmol m−2 for Hg(II), 39.6 mmol m−2 for Cd(II) and the affinity order was Pb(II) > Hg(II)>Cd(II).
Formation of poly(ethylene glycol) inclusion complexes in aqueous solutions of mixed cyclodextrins
Authors: Horský Jiří , Walterová Zuzana
Published: November 2003

Even though the addition of modified cyclodextrins (modified CDs) accelerates the precipitation in aqueous solutions of poly(ethylene glycol) (PEG) and α‐cyclodextrin (α‐CD) the final amount of formed solid complex remains unchanged, with no significant presence of modified CDs detected by MALDI‐TOF mass spectrometry. Thus unsuitability of kinetic turbidity measurements for determination of binding parameters was confirmed. On the other hand, theoretical calculations based on a model of a chain of freely accessible binding sites demonstrated that the results do not necessarily contradict the finding that individual modified CD molecules can thread onto PEG chains with the efficiency comparable to that of natural (unmodified) α‐CD.
Combined‐modality therapy for gastric cancer
Authors: Yao James C. , Mansfield Paul F. , Pisters Peter W.T. , Feig Barry W. , Janjan Nora A. , Crane Christopher , Ajani Jaffer A.
Published: November 2003

Gastric cancer has a poor prognosis. It is often diagnosed at an advanced stage, and potentially curative treatments often can not be exercised. Even when a curative surgical resection is possible, only a minority of patients survive beyond 5 years, and locoregional failures are frequent among patients undergoing curative resections. Recently, the use of postoperative adjuvant chemoradiotherapy has yielded some notable benefits. Earlier studies have shown survival benefits in patients undergoing chemoradiotherapy for locally advanced unresectable gastric cancer. The recently reported Intergroup 0116 trial compared surgery alone with surgery plus postoperative chemotherapy plus chemoradiotherapy. Superior overall and disease‐free survival rates among patients given combined‐modality postoperative therapy were observed. These results established a new standard of care for patients following resection of gastric carcinoma. Preoperative combined‐modality chemoradiotherapy may improve resectability, and is under investigation at the University of Texas M. D. Anderson Cancer Center. The development of novel radioenhancers and the selection of therapy on the basis of molecular determinants of response may result in much‐needed advances in this field. Semin. Surg. Oncol. 21:223–227, 2003. © 2003 Wiley‐Liss, Inc.
An experimental and numerical approach to investigate the dynamic response of a four‐flue chimney of a thermo‐electrical plant
Authors: Cavacece Massimo , Valentini Pier Paolo
Published: November 2003

This paper describes an experimental procedure and a numerical model for the study of the dynamic behaviour of a chimney of a thermo‐electrical plant. The experimental part is based on the measurement of the structure's dynamic response by means of several accelerometers. Different signals from forced time‐periodic excitations, spanning a range of frequencies, have been collected and compared with those from a finite elements model. In particular, the first four modal shapes and their frequencies are computed. Following this validation, the finite element model has also been applied to investigate the response of the chimney subjected to a generic wind periodic excitation (vortex shedding). The numerical results show good agreement with the experimentally collected data. Copyright © 2003 John Wiley & Sons, Ltd.
A new procedure for the analysis of construction loads in multistory reinforced concrete structures
Authors: de Almeida Prado José Fernão Miranda , Corrêa Márcio Roberto Silva , Ramalho Marcio Antonio
Published: November 2003

Construction loads in a multistory reinforced concrete building are largely influenced by the construction schedule. These loads may exceed the designed strength of the building's structure or produce early cracking of the floor, with adverse consequences to its service conditions, because of amplifications of time‐dependent deflections. Fresh floors are supported by previously cast floors, using a formwork system with shores and reshores. The definition of floor loads, considering the construction sequence, provides an outlook of the load history on the structural elements from the beginning to the end of the construction work. Models for evaluating that phenomenon are very important and, as far as possible, should be simple and suitable for quick analysis. The present work proposes a new method to analyze the distribution of construction loads. This method is based on the experience of the authors in using finite elements in sequential structural analyses of multistory reinforced concrete buildings. Using the concept of primary structures, the new method offers a viable way of distributing construction loads between the formwork and the interconnected floors. Copyright © 2003 John Wiley & Sons, Ltd.
Occurrence distributions of the auroral kilometric radiation ordinary and extraordinary wave modes
Authors: Hanasz J. , Panchenko M. , de Feraudy H. , Schreiber R. , Mogilevsky M. M.
Published: November 2003

Occurrence distributions of the auroral kilometric radiation (AKR) and its right‐hand extraordinary (R‐X) and left‐hand ordinary (L‐O) wave modes are determined from polarization measurements on Interball‐2 (Auroral). The AKR is much less frequent on the dayside (20% of the observing time) than on the nightside (70%). A bulk of its occurrence extends from invariant latitude of 80 at afternoon hours of MLT to 60 at night hours. Like the nightside AKR, the dayside one is generated through the electron‐cyclotron maser instability. This is concluded from domination of the R‐X mode on the dayside similarly to the nightside. On the dayside the L‐O mode of AKR is roughly three times more frequent (30% of the AKR time) than that on the nightside (10%). At afternoon hours the L‐O occurs more frequently at lower invariant latitudes. This is explained by propagation of the L‐O mode from nightside sources far beyond the “horizon” of the R‐X mode. We find two classes of the circular polarization spectra: “regular,” with the dominating R‐X mode observed in the upper part of the AKR frequency spectrum and the weak L‐O mode in its lower part, and patchy “irregular,” with different polarizations interwoven randomly over the whole frequency range of AKR. For “regular” spectra the L‐O/R‐X power ratios are between 0.2 and 0.002. For the “irregular” ones they are between 1 and 0.01. The “irregular” spectra, reported for the first time, are interpreted as due to irregular refraction of the R‐X rays on the plasma density fluctuations near the nightside sources. We show also evidence of another component of the AKR observed on the dayside, which arrives from directions of possible dayside sources likely related to the cusp or the low‐latitude boundary layers.
Mesoscale variability of phytoplankton and of new production: Impact of the large‐scale nutrient distribution
Authors: Lévy Marina
Published: November 2003

Concomitance at the mesoscale between doming isopycnals and phytoplankton maxima is often observed. A different situation is sometimes revealed by satellite images, where chlorophyll varies at the submesoscale. These two situations are rationalized using numerical simulations of interactive oceanic eddies, in the standard situation where they result from baroclinic instability. The driving parameter is found to be the nutrient distribution in the region where the eddies are formed. It is shown that the existence of a large‐scale horizontal gradient is a sufficient condition for observing phytoplankton maxima within the eddies. The proposed mechanism is based on the direct horizontal cascade and involves horizontal transport. This mechanism is different from eddy pumping, which involves vertical transport, but leads to similar distributions of nutrients, phytoplankton, and density at the eddy scale. When vertical gradients are dominant, the regime is that of small‐scale nutrient injection. In this regime, eddy‐induced upwelling and associated nutrient transport occur on a scale one order of magnitude below the eddy scale. In both regimes, new production resembles vorticity and displays energetic small‐scale features. On the contrary, phytoplankton distribution shows different characteristics depending on the regime. In the absence of horizontal gradients, submesoscale upwelling and subsequent stirring lead to enhanced phytoplankton in vorticity filaments. Otherwise, when horizontal gradients prevail, phytoplankton is primarily driven by the horizontal cascade and resembles the mesoscale temperature field. Another important result is that small‐scale subduction can contribute to the export and decrease new production.
Changes in soil temperature and active layer thickness during the twentieth century in a region in western Canada
Authors: Chen Wenjun , Zhang Yu , Cihlar Josef , Smith Sharon L. , Riseborough Daniel W.
Published: November 2003

Increases in active layer thickness and permafrost degradation induced by climate warming may have profound socio‐economic and eco‐environmental consequences. Using a process‐based model of Northern Ecosystem Soil Temperature (NEST) and data from climate records, remote sensing vegetation parameters, and soil features, we simulated soil temperature and active layer thickness (ALT) for a region in western Canada during the twentieth century. The results showed that the region‐averaged annual mean soil temperatures at different depths responded to air temperature forcing consistently during the twentieth century, but with reduced magnitudes in both long‐term trend and interannual variation. From the 1900s to 1986–1995, ALT increased 124 cm (or 79%) in the isolated and sporadic discontinuous permafrost zones, 59 cm (or 37%) in the extensive discontinuous permafrost zone, and 20 cm (or 21%) in the continuous permafrost zone on the basis of the current permafrost distribution map. The simulated results also indicated the disappearance of 17% of the permafrost in the discontinuous permafrost zone from the 1900s to the 1940s, and another 22% from the 1940s to 1986–1995. General agreement was found when comparing the simulated results with soil temperature records at climate stations, ALT at survey sites, and rates of permafrost degradation interpreted from aerial photographs. Owing to differences in spatial scales, spatial coverage, and time periods, many of the comparisons were not strict 1‐to‐1 comparisons and should instead be viewed as indirect supporting evidence.
Large‐scale and evaporation‐wind feedbacks in a box model of the tropical climate
Authors: Bellon G. , Le Treut H. , Ghil M.
Published: November 2003

A four‐box model of the tropical climate is used to assess its sensitivity to changes in the relative area of the moist and dry regions and to radiative perturbations. The feedbacks modulating this sensitivity are analyzed, particularly the dynamical feedbacks associated with the surface fluxes. The link between the large‐scale circulation and these fluxes is found to play a crucial role in the tropics' sensitivity to radiative perturbations.
Sn attenuation in the Anatolian and Iranian plateau and surrounding regions
Authors: Gök Rengin , Sandvol Eric , Türkelli Niyazi , Seber Dogan , Barazangi Muawia
Published: November 2003

The propagation characteristics of the regional Sn shear waves have been mapped to provide insight into the lithospheric structure of the Anatolian and Iranian plateau and the surrounding regions. Thousands of regional earthquakes within the distance range of 2–15 degrees were recorded by broadband and short period stations located in Turkey and nearby regions, especially new data recorded by 29 broadband stations in the Eastern Turkey Seismic Experiment network. The propagation efficiencies of Sn were determined visually using their amplitude and frequency content. Attenuation maps were then tomographically constructed using the observed propagation efficiencies. Our results confirm that Sn propagates efficiently in the uppermost mantle beneath the Mediterranean Sea, the Black Sea, and the Caspian Sea and along the Zagros fold and thrust belt. Sn is not observed in eastern Turkey, northwestern Iran, or central Anatolia. In contrast to previous available studies, this study considerably improved the mapped location of the boundaries between the zones of efficient and attenuated Sn. Our results are best explained by an absence of lithospheric mantle, or the presence of thin and hot lithospheric mantle beneath most of the Anatolian and Iranian plateau.
Simulation of frontal eddies on the East Florida Shelf
Authors: Fiechter Jerome , Mooers Christopher N. K.
Published: November 2003

Frontal eddies are typical features on the cyclonic side of the Florida Current (FC) along the East Florida Shelf (EFS), producing characteristic “shingle” patterns in sea surface temperature. Intensive observations and idealized numerical analyses have described such eddies over the past three decades. Here, simulations from a high‐resolution (2 to 10 km), curvilinear coastal ocean circulation model demonstrate their structure and evolution with realistic bottom topography and FC over an extended domain including the Straits of Florida and the entire EFS. Simulations agree with observations in estimating translation speed, recurrence period, strength, characteristic length‐scales, and overall circulation patterns. In addition, the simulations demonstrate the interactions between the frontal eddies and the meander crests and bottom topography as they translate along the EFS. Overall, a first level of model validation has been established that will facilitate consideration of the forecast problem for frontal eddies associated with the FC on the EFS.
Linear stability analysis of Richter rolls
Authors: Korenaga Jun , Jordan Thomas H.
Published: November 2003

The planform of sublithospheric convection is studied by a 3‐D linear stability analysis of longitudinal rolls in the presence of vertical shear. Rayleigh numbers up to 106 are considered. The transition Rayleigh number over which longitudinal rolls are unstable is derived as a function of surface velocity. Effects of nonlinear vertical shear are shown to be insignificant unless nonlinearity becomes extreme. Our results are in good agreement with previous studies, except at high Rayleigh numbers where the meaning of roll stability becomes ambiguous owning to inherently time‐dependent convection. When applied to small‐scale convection in the upper mantle, our results suggest that the roll stability is very sensitive to plate velocity if the upper mantle viscosity is relatively high (∼1020 Pa s); Richter rolls may be expected only beneath fast‐moving plates such as the Pacific plate.
An ice core indicator of Antarctic sea ice production?
Authors: Wolff Eric W. , Rankin Andrew M. , Röthlisberger Regine
Published: November 2003

The sea ice surface, not open water, is the dominant source of sea salt to aerosol and ice cores in coastal Antarctica. Here, we show that it may also form the dominant source for central Antarctica. We can then explain higher concentrations in the winter and last glacial maximum (LGM) as being due to increased sea ice production. This suggests that ice core sea salt can indicate at least the timing of changes in Antarctic sea ice production. The pattern of sea salt in ice cores is consistent with marine evidence about sea ice changes in the Holocene and LGM. Sea salt shows no change at the initial CO2 increase out of the last glacial, making it unlikely this was primarily due to changing sea ice cover. The sea salt record should not be treated as an indicator of meridional transport.
Modeling the propagation of solar energetic particles in corotating compression regions of solar wind
Authors: Kocharov L. , Kovaltsov G.A. , Torsti J. , Anttila A. , Sahla T.
Published: November 2003

We present the first modeling of solar energetic particle (SEP) events inside corotating compression regions. We consider gradual compressions in the interplanetary magnetic field brought on by interaction of the solar wind streams of different speed. The compression model is similar to that previously suggested for the acceleration of low‐energy particles associated with corotating interaction regions (CIRs). In the framework of focused transport, we perform Monte Carlo simulations of the SEP propagation, adiabatic deceleration and reacceleration. A trap‐like structure of the interplanetary magnetic field modifies the SEP intensity‐time profiles, energy spectra, and anisotropy. Particle diffusion and adiabatic deceleration are typically reduced. For this reason, at a corotating vantage point the SEP event development after the intensity maximum is slower than would be expected based on the modeling in the standard, Archimedean spiral field. At the noncorotating spacecraft the magnetic tube convection past the observer becomes more important. The numerical model forms a basis on which to interpret SEP observations made by present and future spacecrafts at the longitude‐dependent speed of solar wind. In particular, the modeling results are similar to the patterns observed with the ERNE particle telescope on board SOHO in August 1996. In the proton anisotropy data, we find a signature of the magnetic mirror associated with the CIR. A relation is established between the spectra observed at 1 AU and the SEP injection spectrum near the Sun.
Time and scale size of planetary wave signatures in the ionospheric F region: Role of the geomagnetic activity and mesosphere/lower thermosphere winds
Authors: Altadill D. , Apostolov E. M.
Published: November 2003

The time and scale size of planetary wave signatures (PWS) in the mid latitude F region ionosphere of the Northern Hemisphere and the main pattern of their possible sources of origin are presented. The PWS involved in this study have periods of about 2–3, 5–6, 10, 13.5, and 16 days. The PWS in the ionosphere are large scale phenomena. PWS with periods of about 2–3 and 5–6 days have a typical longitudinal size of 80°, they are coherent some 6000 km apart, and they occur about 12% and 14% of the entire observational record respectively. The typical longitudinal size of PWS with periods of about 10 and 13 days is 100°, they are coherent some 7500 km apart, and they occur about 24% and 22% of the entire observational record respectively. PWS with periods of about 16 days seem to be global scale phenomena, and they occur about 30% of the entire observational record. The results estimate that geomagnetic activity variations play the most important role for driving PWS in the ionosphere. The geomagnetic activity variations can drive at least 20–30% of the PWS with periods of about 2–3, 5–6, 10 and 16 days, but even up to 65–70% for the PWS with periods of about 10 and 16 days, and they practically drive 100% of the PWS with periods of about 13.5 days. The planetary wave activity in the mesosphere/lower thermosphere (MLT) winds can drive about 20–30% of the PWS with periods of about 2–3, 5–6, 10 and 16 days. There is a significant percentage of existence of PWS in the F region apparently ‘independent’ from the geomagnetic activity variations and of the MLT winds. The latter is better expressed for PWS with shorter period. PWS with periods of about 13.5 days are an exception to that. A candidate mechanism for the ‘independent’ events may be the non linear interaction or the amplitude modulation between different PWS.
Geology of the MER 2003 “Elysium” candidate landing site in southeastern Utopia Planitia, Mars
Authors: Tanaka Kenneth L. , Carr Michael H. , Skinner James A. , Gilmore Martha S. , Hare Trent M.
Published: November 2003

The NASA Mars Exploration Rover (MER) Project has been considering a landing‐site ellipse designated EP78B2 in southeastern Utopia Planitia, southwest of Elysium Mons. The site appears to be relatively safe for a MER landing site because of its predicted low wind velocities in mesoscale atmospheric circulation models and its low surface roughness at various scales as indicated by topographic and imaging data sets. Previously, the site's surface rocks have been interpreted to be marine sediments or lava flows. In addition, we suggest that Late Noachian to Early Hesperian collapse and mass wasting of Noachian highland rocks contributed to the deposition of detritus in the area of the ellipse. Furthermore, we document partial Late Hesperian to Early Amazonian resurfacing of the ellipse by flows and vents that may be of mud or silicate volcanic origin. A rover investigation of the Utopia landing site using the MER Athena instrument package might address some fundamental aspects of Martian geologic evolution, such as climate change, hydrologic evolution, and magmatic and tectonic history.
Groundwater and microbial processes of Alabama coastal plain aquifers
Authors: Penny Elizabeth , Lee Ming‐Kuo , Morton Cynthia
Published: November 2003

We integrate groundwater geochemistry, microbiology, and numerical modeling techniques to study the origin of elevated salinity and chemical evolution of groundwaters in the coastal plain aquifers of Alabama. Our field data indicate that chemical composition of groundwater evolves by various geochemical and microbial processes as it moves deeper into the subsurface. Sequential peaks of Ca2+, Mg2+, K+, and Na+ along flow paths indicate that separation of ions may be driven by cation exchange. Microbial‐mediated reactions are important for the formation of several discrete hydrochemical zones containing Fe2+, Mn2+, Sr2+, and SO42− rich groundwaters. Elevated Fe2+, Mn2+, and Sr2+ concentrations may be derived from bacterial iron and manganese reduction. High sulfate concentrations observed a short distance from the recharge may be partly explained by microbial sulfur oxidation and nitrate reduction (denitrification). The presence of denitrifying and sulfur‐oxidizing bacteria in water further supports these reactions. Major ion compositions and δD and δ18O values are used to determine the source of salinity and the nature of mixing of different groundwaters. Three water types were identified; these include carbonate groundwater, brines associated with evaporites, and groundwater of meteoric origin. Groundwater age differences and flow velocities were calculated using the 36Cl/Cl ratios. Calculated groundwater flow velocities within the Eutaw and Tuscaloosa aquifers are about 0.20 m/yr and 0.15 m/yr, respectively. We modeled basin‐scale hydrologic and solute transport processes in a cross section extending from the aquifer outcrops to the Gulf Coast. The modeling result shows that the buried Jurassic Louann Salt can significantly increase groundwater salinity in the overlying coastal plain aquifers by density‐driven advection and hydrodynamic dispersion. The modeling results are consistent with Cl/Br ratios and O/H isotope signatures, which indicate that salinity of the groundwater could be derived from seawater that has been evaporated beyond halite saturation. The predicted groundwater flow pattern reveals the mixing of meteoric water, carbonate groundwater (from the Ordovician Knox Group), and saline brines associated with the Louann Salt. The hydrologic model is consistent with the hydrochemical facies distribution in the Alabama coastal plain.