bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of reaction kinetics of epoxy and a nickel(II) complex using dynamic DSC technique
Authors: Ghaemy M. , Omrani A. , Rostami A. A. 
Published: April 2005

AbstractThe curing reaction kinetics of an epoxy based on the diglycidyl ether of bisphenol A (DGEBA) with an inorganic complex based on nickel(II) chelate with ethylenediamine (en) as a ligand were studied using DSC in dynamic mode. The complex curing agent was synthesized and characterized by the elemental analysis, FT‐IR, and ICP‐Plasma techniques. Thermal dissociation behavior of curing agent was also studied using thermogravimetric (TG) analysis in isolated form. Three kinetic models, Kissinger, Ozawa‐Flynn‐Wall, and Expanded Freeman‐Carrole, were used to determine the kinetic parameters. The effect of hardener concentration on the kinetic parameters and the shape of DSC thermograms of the DGEBA/Ni(en)3Br2 system were investigated. Finally, the previous proposed mechanism by another researcher was used to explain the DSC data in detail. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 265–271, 2005
Cationic photopolymerization of oxetane‐functionalized hyperbranched polymers
Authors: Sangermano M. , Di Gianni A. , Malucelli G. , Roncuzzi C. , Priola A. , Voit B. 
Published: April 2005

AbstractAn aliphatic–aromatic pehenolic hyperbranched starting material (HBP‐OH) with phenolic end groups was 85% functionalized by a Mitsunobu reaction with oxetane groups (OXT‐HBP). This new hyperbranched polyester was used, at a concentration of 5–20 wt %, as an additive for the cationic photopolymerization of a commercial oxetane‐based resin, 4,4′‐bis[(3‐ethyl‐3‐ethyl‐3‐oxetanyl) methoxymethyl]biphenyl (OXBP). HBP‐OXT acted as a multifunctional crosslinker, copolymerizing with the oxetane ring of the OXBP resin, reacting through chain transfer with the remaining phenolic OH groups, or doing both. The result was an increase in the glass‐transition temperature due to the increase in the crosslinking density. An increase in the weight residue at a high temperature was found in the presence of HBP‐OXT and was attributed to the presence of phenolic groups, which are commonly used as antioxidant additives. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 293–299, 2005
Morphology and properties of thermoplastic polyurethane composites incorporating hydrophobic layered silicates
Authors: Finnigan Bradley , Martin Darren , Halley Peter , Truss Rowan , Campbell Kayleen 
Published: April 2005

AbstractPolyurethane (PU) composites incorporating Cloisite 15A (15A) were prepared via melt compounding and solvent casting. The melt‐compounded composites had better dispersion and a smaller silicate stack size as a result of the higher shear forces associated with twin‐screw extrusion. The PU microphase separation and hard domain order were greater in the melt‐processed materials. At the concentrations of 15A employed in this study (≤7 wt %), the filler did not have an observable effect on the microphase texture of either the solvent‐ or melt‐processed PU. The tensile properties of the melt‐compounded materials were lower than those of their solvent‐cast counterparts because of thermal degradation. The solvent‐cast composite containing a 3 wt % loading of 15A displayed improved tensile strength and elongation, primarily because of plasticization by the silicate organic treatment. The addition of layered silicates with high aspect ratios increased the hysteresis and permanent set of this PU elastomer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 300–309, 2005
Comparative study of cellulose isolated by totally chlorine‐free method from wood and cereal straw
Authors: Sun J. X. , Xu F. , Geng Z. C. , Sun X. F. , Sun R. C. 
Published: April 2005

AbstractHighly purified cellulose preparations were obtained by pretreatment of dewaxed barley straw, oil palm frond fiber, poplar wood, maize stems, wheat straw, rice straw, and rye straw with 2.0% H2O2 at 45°C and pH 11.6 for 16 h, and sequential purification with 80% acetic acid–70% nitric acid (10/1, v/v) at 120°C for 15 min. The purified cellulose obtained was relatively free of bound hemicelluloses (2.3–3.2%) and lignin (0.4–0.6%) and had a yield of 35.5% from barley straw, 39.6% from oil palm frond fiber, 40.8% from poplar wood, 36.0% from maize stems, 34.1% from wheat straw, 23.4% from rice straw, and 35.8% from rye straw. The weight‐average molecular weights of the purified cellulose ranged from 39,030 to 48,380 g/mol. The thermal stability of the purified cellulose was higher than that of the corresponding crude cellulose. In comparison, the isolated crude and purified cellulose samples were also studied by Fourier transform IR and cross‐polarization/magic‐angle spinning 13C‐NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 322–335, 2005
Functional copolymers of p‐cumyl phenyl methacrylate and glycidyl methacrylate: Synthesis, characterization, and reactivity ratios
Authors: Ratnaprabha Khisti , Daliya P. K. 
Published: April 2005

AbstractFree‐radical polymerization of p‐cumyl phenyl methacrylate (CPMA) was performed in benzene using bezoyl peroxide as an initiator at 80°C. The effect of time on the molecular weight was studied. Functional copolymers of CPMA and glycidyl methacrylate (GMA) with different feed ratios were synthesized by free‐radical polymerization in methyl ethyl ketone at 70°C, and they were characterized by FTIR and 1H‐NMR spectroscopy. The molecular weights and polydispersity indexes of the polymers and copolymers were determined by gel permeation chromatography. The copolymer composition was determined by 1H‐NMR. The glass‐transition temperature of the polymer and the copolymers was determined by differential scanning calorimetry. The reactivity ratios of the monomers were determined by the Fineman–Ross and Kelen–Tudos methods. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 336–347, 2005
Morphological studies of polypropylene–nanoclay composites
Authors: Mani Gopinath , Fan Qinguo , Ugbolue Samuel C. , Yang Yiqi 
Published: April 2005

AbstractPolypropylene–clay nanocomposites were prepared by a solution technique and a subsequent melt‐mixing process. A titanate coupling agent was used to improve the compatibility of the nanoclay particles with the polypropylene. The dispersion of the nanoclay particles in polypropylene was studied with X‐ray diffraction (XRD) and transmission electron microscopy (TEM). An increased d‐spacing value of the clay particles in the nanocomposites was observed, and it was compared with the values of as‐mined (pristine) and as‐received (organophilic) clay particles. The number of intercalated layers in a single clay crystallite was determined to be 4, and the number was confirmed with XRD data and TEM images. On the basis of the Daumas–Herold model (which is widely used for graphite intercalation compounds), the stage 2 and stage 3 structures of montmorillonite particles in polypropylene were recommended. A study on the stage structure suggested a way of determining the presence of polymer molecules in the clay galleries. The results confirmed the existence of single‐layered platelets with improved dispersion in polypropylene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 218–226, 2005
Effect of hypochlorite concentration on properties of posttreated outer‐skin ultrafiltration membranes spun from cellulose acetate/poly(vinyl pyrrolidone) blends
Authors: Qin Jian‐Jun , Cao Yi‐Ming , Li Ying 
Published: April 2005

AbstractAn outer‐skin hollow‐fiber ultrafiltration (UF) membrane was spun from a new dope solution containing cellulose acetate (CA)/poly(vinyl pyrrolidone) (PVP 360K)/N‐methyl‐2‐pyrrolidone (NMP)/water using a wet‐spinning technique. The as‐spun fibers were posttreated with a hypochlorite solution over a range of concentrations for a fixed period of 24 h. The experimental results showed that the pure water flux of the treated membrane increased with increasing hypochlorite concentration. The treated membrane experienced an increased fouling tendency with increasing hypochlorite concentration because the hydrophilicity of the treated membrane decreased as a result of the removal of PVP contents in the membrane matrix after hypochlorite treatment. SEM images revealed that the membrane had an outer dense skin, a porous inner surface, and a spongelike structure, which confirmed that addition of PVP favored the suppression of macrovoids in the membrane. The membrane pore size could be significantly increased when the hypochlorite concentration reached 200 mg/L. It was concluded that hypochlorite treatment provided an additional option to easily alter the pore size of UF membranes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 227–231, 2005
Curing of low level melamine‐modified urea‐formaldehyde particleboard binder resins studied with dynamic mechanical analysis (DMA)
Authors: Young No B. , Kim Moon G. 
Published: April 2005

AbstractEffects of resin formulation, catalyst, and curing temperature were studied for particleboard binder‐type urea‐formaldehyde (UF) and 6 ∼ 12% melamine‐modified urea‐melamine‐formaldehyde (UMF) resins using the dynamic mechanical analysis method at 125 ∼ 160°C. In general, the UF and UMF resins gelled and, after a relatively long low modulus period, rapidly vitrified. The gel times shortened as the catalyst level and resin mix time increased. The cure slope of the vitrification stage decreased as the catalyst mix time increased, perhaps because of the deleterious effects of polymer advancements incurred before curing. For UMF resins, the higher extent of polymerization effected for UF base resin in resin synthesis increased the cure slope of vitrification. The cure times taken to reach the vitrification were longer for UMF resins than UF resins and increased with increased melamine levels. The thermal stability and rigidity of cured UMF resins were higher than those of UF resins and also higher for resins with higher melamine levels, to indicate the possibility of bonding particleboard with improved bond strength and lower formaldehyde emission. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 377–389, 2005
Studies on the intermolecular structural heterogeneity of a propylene‐ethylene random copolymer using preparative temperature rising elution fractionation
Authors: Liu Yonggang , Bo Shuqin , Zhu Yejuan , Zhang Wenhe 
Published: April 2005

AbstractThe intermolecular structural heterogeneity of a propylene‐ethylene random copolymer was studied by preparative temperature rising elution fractionation combined with GPC, 13C‐NMR, differential scanning calorimetry, and wide‐angle X‐ray diffraction analysis of the obtained fractions. The isotacticity of fractions increased with increasing elution temperature, and the ethylene content decreased monotonously. Fitting of the obtained comonomer triad sequences by Bernoullian and first‐order Markovian statistical models indicated that lower isospecific active sites are more active toward ethylene. The isolated ethylene unit disrupted the crystallizable isotactic sequence and lowered the crystallizability of the polypropylene chain. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 232–239, 2005
Propagation through conical crossings: An asymptotic semigroup
Authors: Lasser Caroline , Teufel Stefan 
Published: April 2005

AbstractWe consider the standard model problem for a conical intersection of electronic surfaces in molecular dynamics. Our main result is the construction of a semi‐group in order to approximate the Wigner function associated with the solution of the Schrödinger equation at leading order in the semiclassical parameter. The semigroup stems from an underlying Markov process that combines deterministic transport along classical trajectories within the electronic surfaces and random jumps between the surfaces near the crossing. Our semigroup can be viewed as a rigorous mathematical counterpart of so‐called trajectory surface hopping algorithms, which are of major importance in molecular simulations in chemical physics. The key point of our analysis, the incorporation of the nonadiabatic transitions, is based on the Landau‐Zener type formula of Fermanian‐Kammerer and Gérard10 for the propagation of two‐scale Wigner measures through conical crossings. © 2005 Wiley Periodicals, Inc.
On the modelling of publish/subscribe communication systems
Authors: Baldoni R. , Beraldi R. , Tucci Piergiovanni S. , Virgillito A. 
Published: April 2005

AbstractThis paper presents a formal framework of a distributed computation based on a publish/subscribe system. The framework abstracts the system through two delays, namely the subscription/unsubscription delay and the diffusion delay. This abstraction allows one to model concurrent execution of publication and subscription operations without waiting for the stability of the system state and to define a Liveness property which gives the conditions for the presence of a notification event in the global history of the system. This formal framework allows us to analytically define a measure of the effectiveness of a publish/subscribe system, which reflects the percentage of notifications guaranteed by the system to subscribers. A simulation study confirms the validity of the analytical measurements. Copyright © 2005 John Wiley & Sons, Ltd.
Benchmarking message‐oriented middleware: TIB/RV versus SonicMQ
Authors: Maheshwari Piyush , Pang Michael 
Published: April 2005

AbstractMessage‐oriented middleware (MOM) has become a vital part of the complex application integration projects. MOM is used to pass data and workflow in the form of messages between different enterprise applications. The performance of integrated applications greatly depends on how effectively the MOM performs. This paper presents a benchmark comparison between two industry well‐known MOMs—TIBCO Rendezvous (TIB/RV) and SonicMQ. Although the two MOMs are very similar in certain respects, their native implementation and architecture are very different. We provide an unbiased benchmark reference to the middleware selection process. The primary objective of our work is to evaluate and compare the MOMs by testing their effectiveness in the delivery of messages in publish/subscribe and point‐to‐point message domains, their program stability and the system resource utilization. Copyright © 2005 John Wiley & Sons, Ltd.
MEAD: support for Real‐Time Fault‐Tolerant CORBA
Authors: Narasimhan P. , Dumitraş T. A. , Paulos A. M. , Pertet S. M. , Reverte C. F. , Slember J. G. , Srivastava D. 
Published: April 2005

AbstractThe OMG's Real‐Time CORBA (RT‐CORBA) and Fault‐Tolerant CORBA (FT‐CORBA) specifications make it possible for today's CORBA implementations to exhibit either real‐time or fault tolerance in isolation. While real‐time requiresa prioriknowledge of the system's temporal operation, fault tolerance necessarily deals with faults that occur unexpectedly, and with possibly unpredictable fault recovery times. The MEAD (Middleware for Embedded Adaptive Dependability) system attempts to identify and to reconcile the conflicts between real‐time and fault tolerance, in a resource‐aware manner, for distributed CORBA applications. MEAD supports transparent yet tunable fault tolerance in real‐time, proactive dependability, resource‐aware system adaptation to crash, communication and timing faults with bounded fault detection and fault recovery. Copyright © 2005 John Wiley & Sons, Ltd.
The First Picoseconds in Bacterial Photosynthesis—Ultrafast Electron Transfer for the Efficient Conversion of Light Energy
Authors: Zinth Wolfgang , Wachtveitl Josef 
Published: April 2005

AbstractIn this Minireview, we describe the function of the bacterial reaction centre (RC) as the central photosynthetic energy‐conversion unit by ultrafast spectroscopy combined with structural analysis, site‐directed mutagenesis, pigment exchange and theoretical modelling. We show that primary energy conversion is a stepwise process in which an electron is transferred via neighbouring chromophores of the RC. A well‐defined chromophore arrangement in a rigid protein matrix, combined with optimised energetics of the different electron carriers, allows a highly efficient charge‐separation process. The individual molecular reactions at room temperature are well described by conventional electron‐transfer theory.
Molecular Photobleaching Kinetics of Rhodamine 6G by One‐ and Two‐Photon Induced Confocal Fluorescence Microscopy
Authors: Eggeling Christian , Volkmer Andreas , Seidel Claus A. M. 
Published: April 2005

AbstractUnder high‐excitation irradiance conditions in one‐ and two‐photon induced fluorescence microscopy, the photostability of fluorescent dyes is of crucial importance for the detection sensitivity of single molecules and for the contrast in fluorescence imaging. Herein, we report on the dependence of photobleaching on the excitation conditions, using the dye Rhodamine 6G as a typical example. The different excitation modes investigated include 1) one‐photon excitation into the first‐excited singlet state in the range of 500 to 528 nm by continuous wave and picosecond‐pulsed lasers and 2) two‐ and one‐photon excitation to higher‐excited singlet states at 800 and 350 nm, respectively, by femtosecond pulses. Experimental strategies are presented, which allow resolving the photophysics. From single‐molecule trajectories and fluorescence correlation spectroscopy, as well as with a simple theoretical model based on steady‐state solutions of molecular rate equation analysis, we determined the underlying photobleaching mechanisms and quantified the photokinetic parameters describing the dependence of the fluorescence signal on the excitation irradiance. The comparison with experimental data and an exact theoretical model show that only minor deviations between the different theoretical approaches can be observed for high‐pulsed excitation irradiances. It is shown that fluorescence excitation is in all cases limited by photolysis from higher‐excited electronic states. In contrast to picosecond‐pulsed excitation, this is extremely severe for both one‐ and two‐photon excitation with femtosecond pulses. Furthermore, the photostability of the higher‐excited electronic states is strongly influenced by environmental conditions, such as polarity and temperature.
High‐Resolution Colocalization of Single Molecules within the Resolution Gap of Far‐Field Microscopy
Authors: Heinlein Thomas , Biebricher Andreas , Schlüter Pia , Roth Christian Michael , Herten Dirk‐Peter , Wolfrum Jürgen , Heilemann Mike , Müller Christian , Tinnefeld Philip , Sauer Markus 
Published: April 2005

AbstractTo obtain detailed information about the three‐dimensional (3D) organization of small biomolecular assemblies with a size of less than 100 nanometers, advanced techniques are required that enable the determination of absolute 3D positions and distances between individual fluorophores well below the resolution limit of conventional light microscopy. We show how spectrally resolved fluorescence lifetime imaging microscopy (SFLIM) can provide significant contributions and allow us to determine distances between conventional individual fluorophores (Bodipy 630/650 and Cy5.5) that are less than 20 nm apart. We take advantage of fluorescent dyes (here Cy5.5 and Bodipy 630/650) that can be efficiently excited by a single pulsed diode laser emitting at 635 nm but differ in their fluorescence lifetime and emission maxima. The potential of the method for ultrahigh colocalization studies is demonstrated by measuring the end‐to‐end distance between single fluorophores separated by double‐stranded DNA of various lengths. Combining SFLIM with polarization‐modulated excitation allows us to obtain, simultaneously, information about the relative orientation of fluorophores. Furthermore, we show that the environment‐dependent photophysics of conventional fluorophores, that is, photostability, blinking pattern, and the tendency to enter irreversible nonfluorescent states, sets certain limitations to their in vitro and in vivo applications.
Green and Red Fluorescent Proteins: Photo‐ and Thermally Induced Dynamics Probed by Site‐Selective Spectroscopy and Hole Burning
Authors: Bonsma S. , Purchase R. , Jezowski S. , Gallus J. , Könz F. , Völker S. 
Published: April 2005

AbstractThe cloning and expression of autofluorescent proteins in living matter, combined with modern imaging techniques, have thoroughly changed the world of bioscience. In particular, such proteins are widely used as genetically encoded labels to track the movement of proteins as reporters of cellular signals and to study protein–protein interactions by fluorescence resonance energy transfer (FRET). Their optical properties, however, are complex and it is important to understand these for the correct interpretation of imaging data and for the design of new fluorescent mutants. In this Minireview we start with a short survey of the field and then focus on the photo‐ and thermally induced dynamics of green and red fluorescent proteins. In particular, we show how fluorescence line narrowing and high‐resolution spectral hole burning at low temperatures can be used to unravel the photophysics and photochemistry and shed light on the intricate electronic structure of these proteins.
Alkaline hemolysis fragility is dependent on cell shape: Results from a morphology tracker
Authors: Ionescu‐Zanetti Cristian , Wang Lee‐Ping , Di Carlo Dino , Hung Paul , Di Blas Andrea , Hughey Richard , Lee Luke P. 
Published: April 2005

AbstractBackgroundThe morphometric analysis of red blood cells (RBCs) is an important area of study and has been performed previously for fixed samples. We present a novel method for the analysis of morphologic changes of live erythrocytes as a function of time. We use this method to extract information on alkaline hemolysis fragility. Many other toxins lyse cells by membrane poration, which has been studied by averaging over cell populations. However, no quantitative data are available for changes in the morphology of individual cells during membrane poration‐driven hemolysis or for the relation between cell shape and fragility.MethodsHydroxide, a porating agent, was generated in a microfluidic enclosure containing RBCs in suspension. Automatic cell recognition, tracking, and morphometric measurements were done by using a custom image analysis program. Cell area and circular shape factor (CSF) were measured over time for individual cells. Implementations were developed in MATLAB and on Kestrel, a parallel computer that affords higher speed that approaches real‐time processing.ResultsThe average CSF went through a first period of fast increase, corresponding to the conversion of discocytes to spherocytes under internal osmotic pressure, followed by another period of slow increase until the fast lysis event. For individual cells, the initial CSF was shown to be inversely correlated to cell lifetime (linear regression factor R = 0.44), with discocytes surviving longer than spherocytes. The inflated cell surface area to volume ratio was also inversely correlated to lifetime (R = 0.43) but not correlated to the CSF. Lifetime correlated best to the ratio of cell inflation volume (Vfinal − Vinitial) to surface area (R = 0.65).ConclusionsRBCs inflate at a rate proportional to their surface area, in agreement with a constant flux model, and lyse after attaining a spherical morphology. Spherical RBCs display increased alkaline hemolysis fragility (shorter lifetimes), providing an explanation for the increased osmotic fragility of RBCs from patients who have spherocytosis. © 2005 Wiley‐Liss, Inc.