bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Axial Ligation or π–π‐Type Interactions on Photochemical Charge Stabilization in “Two‐Point” Bound Supramolecular Porphyrin–Fullerene Conjugates
Authors: D'Souza Francis , Chitta Raghu , Gadde Suresh , Zandler Melvin E. , McCarty Amy L. , Sandanayaka Atula S. D. , Araki Yasuyaki , Ito Osamu 
Published: May 2005

AbstractTwo types of structurally well‐defined, self‐assembled zinc porphyrin–fullerene conjugates were formed by “two‐point” binding strategies to probe the effect of axial ligation or π–π‐type interactions on the photochemical charge stabilization in the supramolecular dyads. To achieve this, meso‐tetraphenylporphyrin was functionalized to possess one or four [18]crown‐6 moieties at different locations on the porphyrin macrocycle while fullerene was functionalized to possess an alkyl ammonium cation, and a pyridine or phenyl entities. As a result of the crown ether–ammonium cation complexation, and zinc–pyridine coordination or π–π‐type interactions, stable zinc porphyrin–fullerene conjugates with defined distance and orientation were formed. Evidence for the zinc–pyridine complexation or π–π‐type interactions was obtained from the spectral and computational studies. Steady‐state and time‐resolved emission studies revealed efficient quenching of the zinc–porphyrin singlet excited state in these dyads, and the measured rates of charge separation, kCS were found to be slightly better in the case of the dyads held by axial coordination and crown ether–cation complexation. Nanosecond transient absorption studies provided evidence for the electron transfer reactions, and these studies also revealed charge stabilization in these dyads. The lifetimes of the radical ion pairs were found to depend upon the type of porphyrins utilized to form the dyads, that is, porphyrin possessing the crown ether moiety at the ortho position of one of the phenyl rings yielded prolonged charge stabilized states. Addition of pyridine to the supramolecular dyads eliminated the zinc–pyridine coordination or π–π‐type interactions of the “two‐point” bound systems due to the formation of a new zinc–pyridine axial bond thus giving a unique opportunity to probe the effect of axial coordination or π–π interactions on kCS and kCR. Under these conditions, the measured electron transfer rates revealed faster kCS and slower kCR as compared to those obtained in the absence of added pyridine. The evaluated lifetimes of the radical ion‐pairs were found to be hundreds of nanoseconds and were longer in the presence of pyridine.
Analysis of force generation during flagellar assembly through optical trapping of free‐swimming Chlamydomonas reinhardtii
Authors: McCord Rachel Patton , Yukich John N. , Bernd Karen K. 
Published: May 2005

AbstractMany studies have used velocity measurements, waveform analyses, and theoretical flagella models to investigate the establishment, maintenance, and function of flagella of the biflagellate green algae Chlamydomonas reinhardtii. We report the first direct measurement of Chlamydomonas flagellar swimming force. Using an optical trap (“optical tweezers”) we detect a 75% decrease in swimming force between wild type (CC124) cells and mutants lacking outer flagellar dynein arms (oda1). This difference is consistent with previous estimates and validates the force measurement approach. To examine mechanisms underlying flagella organization and function, we deflagellated cells and examined force generation during flagellar regeneration. As expected, fully regenerated flagella are functionally equivalent to flagella of untreated wild type cells. However, analysis of swimming force vs. flagella length and the increase in force over regeneration time reveals intriguing patterns where increases in force do not always correspond with increases in length. These investigations of flagellar force, therefore, contribute to the understanding of Chlamydomonas motility, describe phenomena surrounding flagella regeneration, and demonstrate the advantages of the optical trapping technique in studies of cell motility. Cell Motil. Cytoskeleton 61:137–144, 2005. © 2005 Wiley‐Liss, Inc.
Similar long‐term results of breast‐conservation treatment for Stage I and II invasive lobular carcinoma compared with invasive ductal carcinoma of the breast
Authors: Santiago Roberto J. , Harris Eleanor E. R. , Qin Li , Hwang Wei‐Ting , Solin Lawrence J. 
Published: May 2005

AbstractBACKGROUNDThe objective of the current study was to determine the long‐term results of breast‐conservation treatment in women with early‐stage, invasive lobular carcinoma of the breast.METHODSBetween 1977 and 1995, 1093 women with Stage I and II invasive ductal carcinoma of the breast and 55 women with invasive lobular carcinoma of the breast underwent lumpectomy, axillary lymph node dissection, and radiation treatment. Overall, 49% of the women received adjuvant systemic therapy (chemotherapy and/or hormones).RESULTSThe median age was 52 years for patients in the invasive ductal group and 54 years for patients in the invasive lobular group. The median follow‐up was 8.7 years and 10.2 years for patients in the invasive ductal and invasive lobular groups, respectively. A comparison of patients who had invasive lobular carcinoma with patients who had invasive ductal carcinoma showed no difference in the 10‐year actuarial rates of overall survival (85% vs. 79%, respectively; P = 0.73), cause‐specific survival (93% vs. 84%, respectively; P = 0.85), or freedom from distant metastases (81% vs. 80%, respectively; P = 0.76). The 10‐year rates of local failure were 18% for patients with invasive lobular carcinoma and 12% for patients with invasive ductal carcinoma (P = 0.24), and the 10‐year rates of contralateral breast carcinoma development for the 2 groups were 12% and 8%, respectively (P = 0.40).CONCLUSIONSBreast‐conservation treatment yielded similar long‐term results for women with early‐stage, invasive lobular carcinoma and women with the more prevalent invasive ductal carcinoma. Cancer 2005. © 2005 American Cancer Society.
Interobserver reliability of computed tomography‐derived primary tumor volume measurement in patients with supraglottic carcinoma
Authors: Mukherji Suresh K. , Toledano Alicia Y. , Beldon Clifford , Schmalfuss Ilona M. , Cooper Jay S. , Sicks JoRean D. , Amdur Robert , Sailer Scott , Loevner Laurie A. , Kousouboris Phil , Ang Kian 
Published: May 2005

AbstractBACKGROUNDPrior studies have determined that macroscopic (“gross”) tumor volume (GTV), as calculated from pretreatment computer tomography (CT), was capable of predicting local control in squamous cell carcinoma arising in different subsites in the head and neck in patients who were treated with nonsurgical organ‐preservation therapy. The majority of these studies were single‐institution, retrospective investigations. Consequently, there has been concern that GTV measurements may not be reproducible by different readers at different institutions. The objective of the current study was to measure the interobserver reliability for GTV measurements for squamous cell carcinoma of the supraglottic larynx (SGSCCA) performed by different readers at different institutions.METHODSEight experienced readers (4 neuroradiologists and 4 radiation oncologists) from different institutions independently measured the pretreatment GTV of 20 patients with SGSCCA. The CT scans were obtained from patients entered into the definitive radiation therapy arm of Radiation Therapy Oncology Group protocol 91‐11, who had supraglottic carcinoma and underwent pretreatment CT scans of the neck. Statistical analysis focused on interobserver reliability as measured by the intraclass correlation coefficient.RESULTSThe intraclass correlation coefficient was 0.81 (95% lower confidence bound, 0.71). This value was interpreted as “excellent.”CONCLUSIONSGTV measurements were reliable and reproducible when performed by neuroradiologists and radiation oncologists who were experienced in the interpretation of CT scans of the extracranial head and neck in patients with SGSCCA. The result implied that the correlation between GTV and local control should be reproducible across institutions. Cancer 2005. © 2005 American Cancer Society.
Energy‐adjustable mechanism of the combined hybrid finite element method and improvement of Zienkiewicz's plate‐element
Authors: Xie Xiao‐ping , Hu Jian‐cheng 
Published: May 2005

AbstractThe combined hybrid finite element method for plate bending problems allows arbitrary combinations of deflection interpolation and bending moment approximations. A novel expression of the approach discloses the energy‐adjustable mechanism of the hybrid variational principle to enhance accuracy and stability of displacement‐based finite element models. For a given displacement approximation, appropriate choices of the bending moment mode and the combination parameter α ∈ (0,1) can lead to accurate energy approximation which generally yields numerically high accuracy of the displacement and bending moment approximations. By virtue of this mechanism, improvement of Zienkiewicz's triangular plate‐element is discussed. The deflection is approximated by Zienkiewicz incomplete cubic interpolation. And three kinds of bending moments approximations are considered: a 3‐parameter constant mode, a 5‐parameter incomplete linear mode, and a 9‐parameter linear mode. Since the parameters of the assumed bending moments modes can be eliminated at an element level, the computational cost of the combined hybrid counterparts of Zienkiewicz's triangle are as same as that of Zienkiewicz's triangle. Numerical experiments show that the combined hybrid versions can attain high accuracy at coarse meshes. Copyright © 2005 John Wiley & Sons, Ltd.
Analysis of multiscale methods for stochastic differential equations
Authors: Weinan E , Liu Di , Vanden‐Eijnden Eric 
Published: May 2005

AbstractWe analyze a class of numerical schemes proposed [26] for stochastic differential equations with multiple time scales. Both advective and diffusive time scales are considered. Weak as well as strong convergence theorems are proven. Most of our results are optimal. They in turn allow us to provide a thorough discussion on the efficiency as well as optimal strategy for the method. © 2005 Wiley Periodicals, Inc.
The Influence of Solid‐State Molecular Organization on the Reaction Paths of Thiyl Radicals
Authors: Faucitano Antonio , Buttafava Armando , Mariani Mario , Chatgilialoglu Chryssostomos 
Published: May 2005

AbstractElectron paramagnetic resonance (EPR) spectroscopy has been employed to investigate the effect of solid‐state molecular organization on the reaction of thiyl radicals with thiols. In an irradiated C18H37SH/thiourea clathrate, the conversion of thiyl to perthiyl radicals is substantial, due to the head‐to‐head arrangement of the reactants within the channels and the suppression of other possible competing reactions due to hindrance by the clathrate walls. The perthiyl radical was identified using EPR analysis of its molecular dynamics within the clathrate channels. Irradiated polyethylene film containing 30 % C18H37SH afforded a negligible conversion of thiyl to perthiyl radicals because of the random distribution of reactants. These results suggest that in the absence of favorable structure‐control effects, the reaction between RS. and RSH is unimportant with respect to other competing reactions. Perthiyl radicals are also the major product in the vacuum solid‐state radiolysis of lysozyme. A proposal of the mechanism involved in all cases is based on the equilibrium RS.+RSH⇌RSS.(H)R, followed by the irreversible conversion of the sulfuranyl radical to the perthiyl radical. As the equilibrium is strongly shifted to the left, the intermediate sulfuranyl radicals were not detected, but the lack of other competing reactions for the thiyl radicals caused the formation of perthiyl radicals to become the major path in the clathrate and in solid lysozyme radiolysis.
Probing Binding‐Mode Diversity in Guanidinium–Oxoanion Host–Guest Systems
Authors: Haj‐Zaroubi Manal , Schmidtchen Franz P. 
Published: May 2005

AbstractAn attempt to experimentally estimate the role of binding‐mode diversity (structural fuzziness) on the molecular recognition seen in the prominent guanidinium–oxoanion host–guest pair is described. The global heat response as measured by isothermal titration calorimetry in acetonitrile, which was obtained from the interaction of five different but structurally closely related guanidinium hosts with three rigid phosphinate guests of decreasing accessibility of their binding sites, is correlated to provide a trend analysis. All host–guest associations of 1:1 stoichiometry in this series are strongly enthalpy‐driven. The change in complexation entropy can be related to the tightness of the mutual fit of the host–guest partners, which approaches a minimum limit and is interpreted as the unique lock‐and‐key binding mode. The ordinary host–guest complexation in this ensemble features substantial positive entropy changes that correlate inversely with the binding interface area. This finding excludes desolvation effects as the major cause of entropy production, and provides evidence for the existence of a broad variety of complex configurations rather than a single binding mode to represent the associated host–guest pair. This result bears on the molecular design of systems that vitally depend on structural fidelity, such as nanoassemblies or homogeneous catalysis.
A Computational Study of Thiolate and Selenolate Oxidation by Hydrogen Peroxide
Authors: Cardey Bruno , Enescu Mironel 
Published: May 2005

AbstractAb initio molecular orbital calculations have been used to study the effects of the molecular environment on the oxidation of thiolate and selenolate by hydrogen peroxide. The reaction was first examined in vacuo at the QCISD(T)/6‐311+G(2df,2pd)//MP2/6‐311+G(d,p) level of theory. It was found for both thiolate and selenolate that a reactant aggregate is formed, which has a dissociation rate constant comparable to the activation rate constant (about 10−3 s−1 for thiolate and 10−1 s−1 for selenolate). Using the polarizable continuum model (PCM) it was then found that the dissociation barrier energy decreases dramatically in water giving a dissociation rate constant of the order of 109 s−1. In this case, the predicted overall rate constant of the thiolate reaction was about 10.2 mol−1 dm3 s−1, which is in good agreement with the experimental rate constant of cysteine oxidation in aqueous solution. The calculated rate constant for the selenolate reaction was somewhat higher (about 35.4 mol−1 dm3 s−1). However, this value is several orders of magnitude smaller than the experimental value reported for the oxidation of selenocysteine in glutathione peroxidase. By considering the effect of the PCM dielectric constant on the reaction rate constant it was concluded that the high reactivity of the selenocysteine in glutathione peroxidase, as compared with cysteine, could be mainly due to the molecular environment of the selenocysteine residue.
Mesoscopic Structures of Maghemite Nanocrystals: Fabrication, Magnetic Properties, and Uses
Authors: Pileni Marie‐Paule , Ngo Anh‐Tu 
Published: May 2005

AbstractMesoscopic structures made of maghemite (γ‐Fe2O3) nanocrystals with different coatings and shapes are described. They are controlled by a combination of van der Waals and magnetic dipolar interactions and their shapes are responsible for the collective magnetic response of the nanocrystals. It is shown that spherical γ‐Fe2O3 nanocrystals can be used as a mask to reproduce the mesoscopic structure on a silicon wafer.
Switching Mechanism in Polar Columnar Mesophases Made of Bent‐Core Molecules
Authors: Gorecka Ewa , Vaupotič Nataša , Pociecha Damian , Čepič Mojca , Mieczkowski Jozef 
Published: May 2005

AbstractThe behaviour of polar, broken‐layer‐type columnar phases made of bent molecules (B1Rev and B1RevTilted) was studied under an applied electric field. There are two competing mechanisms of ferroelectric switching in the polar B1RevTilted columnar phase: collective rotation around the long molecular axis and collective rotation around the tilt cone. The proposed model shows that the main factor discriminating the type of switching is the width of the column cross‐section.
Particle Distribution in a Microporous Material: Experiments with Zeolite A
Authors: Meyer Marc , Leiggener Claudia , Calzaferri Gion 
Published: May 2005

AbstractThe theory on particle distribution and exchange equilibria in a microporous material is applied to experimental ion‐exchange data involving zeolite Na‐A and zeolite K‐A, with silver ions as the exchanging species. The presented method enables direct evaluation of the measured data and consideration of nonequivalent particle sites. The isotherms of the K+ versus Ag+ exchange in zeolite K‐A rise much more steeply, at low exchange degrees, than those of the Na+ versus Ag+ exchange in zeolite Na‐A. This result implies a different course of the ion‐exchange reactions. Spectroscopic measurements on dehydrated, partly silver‐exchanged zeolites Na‐A and K‐A do indeed show that in zeolite Na‐A, the Na+ ions occupying four‐ring positions are exchanged faster for Ag+ than the Na+ ions occupying eight‐ and six‐ring positions, while in zeolite K‐A the exchange does not start with the four‐ring ion but with six‐ring ions, followed by the four‐ring ion. These findings are consistent with the results obtained from evaluation of the ion‐exchange data. The resulting thermodynamic quantities significantly differ from published reference values, which we suggest should be revised.
RBMX gene is essential for brain development in zebrafish
Authors: Tsend‐Ayush Enkhjargal , O'Sullivan Lynda A. , Grützner Frank S. , Onnebo Sara M.N. , Lewis Rowena S. , Delbridge Margaret L. , Marshall Graves Jennifer A. , Ward Alister C. 
Published: May 2005

AbstractThe human RBMX gene was discovered recently through its homology to the spermatogenesis candidate gene RBMY. Its position on the human X chromosome suggests that it may be involved in X‐linked mental retardation syndromes. However, to date there is scant information on the in vivo role of RBMX. To address this issue, we have isolated a zebrafish rbmx orthologue and characterized its embryonic expression pattern. Zebrafish rbmx is maternally expressed and then widely expressed in the embryo up to 24 hr postfertilization. In later stages of embryonic development, rbmx transcripts are localized predominantly in the brain, branchial arches, and liver primordium. The function of rbmx during embryonic development was examined by the use of an antisense morpholino targeting rbmx. The rbmx‐morphants displayed an underdeveloped head and eyes, reduced body size, defective somite patterning, and absence of jaws. Furthermore, in the absence of functional rbmx, expression of specific markers for the fore‐ and hindbrain (otx2, krox20) was severely reduced. These studies demonstrate for the first time that rbmx is required for normal embryonic development, in particular of the brain, consistent with a role in X‐linked mental retardation. Developmental Dynamics 234:682–688, 2005. © 2005 Wiley‐Liss, Inc.
Fabricating of Acetylcholine Biosensor by a Layer‐by‐layer Deposition Technique for Determining Trichlorfon
Authors: Shi Haibin , Zhao Zixia , Song Zhao , Huang Jiadong , Yang Yu , Anzai Jun‐ichi , Osa Tetsuo , Chen Qiang 
Published: May 2005

AbstractAn acetylcholine (ACh) biosensor has been fabricated with bienzymes/poly(diallyldimethylammonium chloride) (PDDA) multilayer film‐modified platinum (Pt) electrodes by a layer‐by‐layer technique (LBL). The ACh biosensor was optimized and the properties are described. This ACh biosensor was used for the detection of organophosphate pesticide trichlorfon. The detection limits (found 0.001 μg/mL for trichlorfon) make it possible to detect the pollutants. This simple protocol of biosensor preparation, high sensitivity and stability are very promising for the determination of environmental pollutants in field conditions.
Polycrystalline Gold Electrodes: A Comparative Study of Pretreatment Procedures Used for Cleaning and Thiol Self‐Assembly Monolayer Formation
Authors: Carvalhal Rafaela Fernanda , Sanches Freire Renato , Kubota Lauro Tatsuo 
Published: May 2005

AbstractThe influence of different surface pretreatment procedures on the electrochemical response of a polycrystalline gold electrode was evaluated. Mechanical polishing with slurry alumina (M), chemical oxidation with H2SO4/H2O2 (C), electrochemical polishing (potential cycling between −0.1 V and 1.2 V vs. SCE) (E), chemical reduction with ethanol, and combinations among these treatments were employed to change the surface electrode characteristics. The efficiency of the proposed pretreatments was evaluated by electrochemical responses towards the redox couple ferri(II/III)‐ammonium sulfate and by the formation of a self‐assembly monolayer of 3‐mercaptopropionic acid (3 MPA SAM) on gold electrodes. The procedure (C) allowed important gold surfaces activation. Using procedures (C) and (E) the roughness of polycrystalline gold surfaces was significantly minimized and more reproducible surfaces could be obtained. From the profile of reductive desorption of 3 MPA SAM it was possible to verify that reduced gold surfaces generated better packed monolayers than oxidized ones and a comparative study using CV and DPV techniques showed that between the two desorption peaks, the one localized at more negative potential values corresponds to the cleavage of Au‐S bond from the chemisorbed thiol. In general, the improvement in the studied electrochemical responses could not only be attributed to an increase in the real surface area of the electrode, but to the chemical surface states set off by the pretreatment procedure.
Sensitivity and Selectivity of Polypyrrole Based AC‐Amperometric Sensors for Electroinactive Ions – Frequency and Applied Potential Influence
Authors: Walkiewicz Sebastian , Michalska Agata , Maksymiuk Krzysztof 
Published: May 2005

AbstractOxidation/reduction of polypyrrole films coupled with ion exchange on the polymer/solution interface can be utilized for amperometric sensing of electroinactive ions. Anion or cation exchanging films (polypyrrole doped by chloride or poly(4‐styrenesulfonate) ions, respectively) can be used to determine common anions (as Cl−, NO$\rm{ {_{3}^{-}}}$, SO$\rm{ {_{4}^{2-}}}$ etc) or cations (K+, Na+, Li+, Ca2+, Mg2+) under conditions of alternating current (AC) amperometry in the range 10−4–1 M. A sensitivity can be tuned by choosing appropriate electrode potential, corresponding to polypyrrole oxidation (anion‐exchanging films) or reduction (cation‐exchangers). Electrochemical impedance spectroscopy and AC‐voltammetry studies have shown that applied frequency and potential could also affect the observed dependence of the signal (admittance or AC‐current) on ion concentration. For high frequency the sensitivity is higher but selectivity lower, due to influence of solution conductivity on the response. For low frequencies the sensitivity is lower; however, a selectivity increase was observed due to diverse mobility of ions in the polymer film. Selectivity of AC‐amperometric responses was studied both in separate and mixed solutions.