bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature optimization for improved determination of phosphatidylserine species by micro liquid chromatography with electrospray tandem mass spectrometric detection
Authors: Larsen Åsmund , Molander Paal 
Published: March 2004

AbstractA sensitive method for determination of disaturated phosphatidylserine species in the presence of their monounsaturated analogs has been developed, using micro liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The hydrophobic nature of the phosphatidylserine species required a combination of low‐eluting sample solvents and sub‐ambient temperatures in order to focus large sample volumes up to 20 μL. The samples were dissolved in 2‐propanol : hexane : water (20 : 10 : 4, v/v/v) prior to 1 : 9 dilution with ammonium formate buffer : 2‐propanol : tetrahydrofuran (30 : 55 : 15, v/v/v) and final 1 : 4 dilution with ammonium formate buffer (10 mM) : 2‐propanol : tetrahydrofuran (55 : 37.5 : 7.5, v/v/v). The analytical column was a 0.5×150 mm stainless steel column packed with 5 μm C30 particles, while the mobile phase contained ammonium formate buffer (10 mM) : 2‐propanol : tetrahydrofuran (30 : 55 : 15, v/v/v). A temperature program from 5°C (hold for 3 minutes) to 75°C at 8 K/min provided separation of the disaturated phosphatidylserine species from their monounsaturated analogs, making available a sensitive determination of the isobaric species. The mass limit of detection for dipalmitoyl phosphatidylserine was 100 pg, corresponding to a concentration limit of detection of 5 pg/μL when using an injection volume of 20 μL. This is an improvement by a factor of 20 as compared to previously reported numbers obtained with conventional LC columns. The within‐assay precision of dipalmitoyl phosphatidylserine was 11.9% RSD (n = 3), while the retention time precision was 4.1% RSD (n = 6).
Recognition of hepatotoxic homologues of Microcystin using a combination of selective adsorption media
Authors: Kubo Takuya , Hosoya Ken , Watabe Yoshiyuki , Tanaka Nobuo , Sano Tomoharu , Kaya Kunimitsu 
Published: March 2004

AbstractMicrocystin, a hepatotoxin produced by cyanobacteria, was chromatographically discriminated with newly prepared selective adsorption media. Since the name Microcystin refers to up to 70 different homologues, we have developed a novel technique to prepare selective recognition sites, based on the “Fragment Imprinting Effect”. The homologues of Microcystin can be individually discriminated from each other by antigen‐antibody assay as well as by C18‐based HPLC. This is mainly due to differences in the three dimensional structure of Microcystin homologues; however, differences in toxicity are relatively small among the homologues. Therefore we have to measure the total amount of Microcystin homologues present to determine contamination by Microcystins. We have demonstrated the first group recognition for Microcystin homologues through combination of two different selective adsorption media prepared by a fragment imprinting technique.
Artificial Opals as Effect Pigments in Clear‐Coatings
Authors: Egen Marc , Braun Lydia , Zentel Rudolf , Tännert Klaus , Frese Peter , Reis Oliver , Wulf Martin 
Published: March 2004

AbstractSummary: In this paper, we describe the use of artificial opals from polymer beads as effect pigments in transparent industrial and automotive coatings. For this purpose, we synthesized monodisperse colloids from fluorinated methacrylates by surfactant‐free emulsion polymerization. The fluorinated monomers, in combination with crosslinking, lead to a refractive index contrast, thermal stability, and solvent resistivity necessary for use as effect pigments. After crystallization of the monodisperse polymer beads, crystal flakes with iridescent colors can be obtained. The crystal flakes can act as effect pigments in various transparent industrial and automotive coatings. Due to photonic crystal behavior of effect pigments, color flops up to 100 nm are observed.Crystal flakes of CS‐7 as effect pigments in a transparent coating. The diameter of the tube is 5 mm.magnified imageCrystal flakes of CS‐7 as effect pigments in a transparent coating. The diameter of the tube is 5 mm.
Fire Retardance in Poly(butylene terephthalate). The Effects of Red Phosphorus and Radiation‐Induced Cross‐Links
Authors: Balabanovich Aliaksandr I. , Zevaco Thomas A. , Schnabel Wolfram 
Published: March 2004

AbstractSummary: The combustion performance of poly(butylene terephthalate) (PBT) can be improved by the addition of red phosphorus provided it is intermolecularly cross‐linked upon irradiation with 60Co γ‐rays in the presence of triallyl cyanurate (TAC). At a content of 3 or 4 wt.‐% the latter significantly promotes cross‐linking in the presence of air. From combustion tests with samples containing red phosphorus (Pred) and having been γ‐irradiated in the presence of TAC it turned out that an improved fire resistance of PBT is achieved if the red phosphorus content is at least 12.5 wt.‐%. In this case test samples were self‐extinguishing and the UL 94 rating corresponded to V‐1. Product analysis and thermal gravimetric analysis revealed that Pred stimulates aromatization and charring. These processes involve the reaction of Pred with the polymer. 31P NMR spectroscopy revealed that the residue contained chemically bonded phosphorus.Decomposition of anhydride groups resulting in phenyl radicals.magnified imageDecomposition of anhydride groups resulting in phenyl radicals.
Investigation Into Poly(propylene)/Montmorillonite/Calcium Carbonate Nanocomposites
Authors: Tang Yong , Hu Yuan , Zhang Rui , Wang Zhengzhou , Gui Zhou , Chen Zuyao , Fan Weicheng 
Published: March 2004

AbstractSummary: A novel method was used to prepare poly(propylene)/montmorillonite/calcium carbonate nanocomposites by melt‐mixing, using pristine montmorillonite (MMT), hexadecyltrimethylammonium bromide (C16), calcium carbonate (CaCO3) and a matrix in a twin‐screw extruder. Two different sizes of calcium carbonate were used (nanosized CaCO3 and micron‐sized CaCO3, the average sizes being 60 nm and 12 μm respectively). The nanocomposite structure was evidenced using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electronic microscopy (HREM). Tensile tests and Izod notch impact tests suggested that the incorporation of nanosized CaCO3 into PP/montmorillonite nanocomposites increased the mechanical properties of the composites, but the improvement in the micro‐sized CaCO3‐filled PP/montmorillonite nanocomposites was found to be minimal. The thermal stability and flammability properties were characterized by thermogravimetric analysis (TGA) and a cone calorimeter respectively.
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Effect of Short Chain Branching of LDPE on its Miscibility with Linear HDPE
Authors: Hameed Tayyab , Hussein Ibnelwaleed A. 
Published: March 2004

AbstractSummary: The influences of short chain branching (SBC) on the melt miscibility of low‐density polyethylene (LDPE) with linear high‐density polyethylene (HDPE) were investigated by rheological methods. Two LDPE resins with different branch contents were blended with the same linear HDPE. Dynamic and steady shear measurements were carried out using a Rheometrics ARES rheometer at 190 °C. The rheology of the low‐SCB LDPE (9 CH3/1 000 C) blends with HDPE can be predicted by the linear additivity rule. Hence, blends were suggested to be completely miscible at all compositions. However, blends of the high branch content LDPE (SCB = 19 CH3/1 000 C) were completely immiscible. Also, the different viscous and elastic properties of all the immiscible blends were much higher than the corresponding values for the more viscous and elastic blend component. The ratio of interfacial tension to droplet radius was estimated from Scholz et al. model as ≈1 500 N · m−2. The level of SCB in LDPE was found to have a strong influence on its miscibility with linear HDPE.Cole‐Cole plot for blends of LDPE1 with HDPE.magnified imageCole‐Cole plot for blends of LDPE1 with HDPE.
Nanoporous Low Dielectric Cyclosiloxane Bearing Polysilsesquioxane Thin Films Templated by Poly(ε‐caprolactone)
Authors: Hyeon‐Lee Jingyu , Lyu Yi Yeol , Lee Mong Sup , Hahn Jun‐Hee , Rhee Ji Hoon , Mah Sang Kook , Yim Jin‐Heong , Kim Sang Youl 
Published: March 2004

AbstractSummary: Dielectric cyclosiloxane bearing polysilsesquioxanes (CS‐PSSQs) were prepared by acid catalyzed polymerization using 2,4,6,8‐tetramethyl‐2,4,6,8‐tetra(trimethoxysilylethyl)cyclotetrasiloxane. The molecular weight, and content of the functional end‐groups of the CS‐PSSQs were found to be dependent on the process parameters, such as the molar ratio of water and catalyst to the OCH3 group of the silane monomer, the amount of solvent, and the poly(ε‐caprolactone) (PCL) content, etc. Based on these CS‐PSSQ prepolymers, nanoporous organic/inorganic hybrid thin films were fabricated by spin‐coating mixtures of these prepolymers with star‐shaped PCL on the silicon substrate, and subsequently heating them at 150 and 250 °C for 1 minute each and then at 420 °C for 1 hour. A dielectric constant as low as 2.28 was achieved for the nanoporous PCL/CS‐PSSQ (3:7 v/v) film, along with low moisture absorption in ambient and water conditions, primarily due to the presence of hydrophobic moieties such as ethylene and methyl groups of the polymer and nano‐sized hydrophobic pores inside the matrix, resulting in the film having stable dielectric properties. Moreover, the PCL/CS‐PSSQ (3:7 v/v) nanohybrid film revealed a nanoporous structure containing ca. 1.52 nm of average‐sized mesopores, as measured by the N2 adsorption method. The CS‐PSSQ‐only film showed high mechanical strengths having an elastic modulus and hardness of 6.64 and 0.88 GPa, respectively, for the 7 500 Å thick film and 2.41 and 0.38 GPa, respectively, for the PCL/CS‐PSSQ (3:7 v/v) film. In addition, the crack velocity of the CS‐PSSQ‐only film was found to be ca. 10−11 m · s−1 in ambient conditions and an aqueous environment, probably due to the enhanced hydrophobicity and mechanical toughness of the incorporated methyl group, siloxane unit and ethylene moieties in the polymer matrix.
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Synergistic Effect of the Charring Agent on the Thermal and Flame Retardant Properties of Polyethylene
Authors: Hu Xiao‐Ping , Li Ya‐Lan , Wang Yu‐Zhong 
Published: March 2004

AbstractSummary: A new charring agent (CA), a derivative of triazines, was synthesized. The flame retardancy and thermal behavior of a new intumescent flame‐retardant (IFR) system for PE (PE‐IFR) were investigated by limited oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and FTIR spectroscopy. The TG curves shows that the amount of residue of IFR‐PE system are largely increased compared to those of PE at temperatures ranging from 350 to 700 °C. The new PE‐IFR system can apparently reduce the amount of decomposing products at higher temperatures and promotes the formation of carbonaceous charred layers. It showed a distinct synergistic flame retardant effect (SE) between nitrogen and phosphorus. The flame retardant PE composition was optimized to achieve a LOI value of 31.2 and UL‐94 V‐0 performance with the synthesized charring agent, ammonium polyphosphate (APP).TG curves of PE, APP, CA, and different PE/CA/APP systems.magnified imageTG curves of PE, APP, CA, and different PE/CA/APP systems.
Copper Removal in Atom Transfer Radical Polymerization through Electrodeposition
Authors: Nasser‐Eddine Mohamad , Delaite Christelle , Dumas Philippe , Vataj Rame , Louati Alain 
Published: March 2004

AbstractSummary: We describe the removal of copper from atom transfer radical polymerization (ATRP) through electrochemistry. tert‐Butyl methacrylate ATRP initiated by a PEO macroinitiator was run with CuBr complexed by N‐alkyl‐2‐pyridylmethanimine (Schiff base) or 2,2′‐bipyridyl (bpy) as catalyst. Voltammetry experiments using a CuBr/(Schiff base N‐morpholine‐2‐pyridylmethanimine)2 complex on a Pt electrode shows an oxidation peak of the ligand at 1.2 V permitting the oxidative destruction of the complex and so the elimination of copper. Using a Hg electrode, it is possible to directly reduce these complexes (at −2.1 V for the morpholine‐2‐pyridylmethanimine, −2.19 V for the butyl‐2‐pyridylmethanimine, and −2.25 V for the bpy). This complex reduction, followed by the formation of a copper amalgam, leads to the quantitative removal of copper and proceeds without polymer degradation.The electrochemical removal of copper from the ATRP reaction.magnified imageThe electrochemical removal of copper from the ATRP reaction.
Phase Behavior of Poly(butyl acrylate) Networks in Nematic Liquid Crystal Solvents
Authors: Vendamme Richard , Bouchaour Tewfik , Pakula Tadeusz , Coqueret Xavier , Benmouna Mustapha , Maschke Ulrich 
Published: March 2004

AbstractSummary: This paper reports the phase behavior of photochemically crosslinked poly(butyl acrylate) networks in nematic liquid crystal (LC) solvents. The swelling properties are studied as a function of temperature for two low molecular weight nematic LCs, 4‐cyano‐4′‐pentylbiphenyl (5CB) and the eutectic mixture of cyanoparaphenylenes (E7). Chemically crosslinked polymer networks were formed by the UV radiation of initial solutions of the reactive monomer, butyl acrylate, a crosslinker (hexanediol diacrylate), and a photoinitiator. To obtain different network densities, the ratio of butyl acrylate to hexanediol diacrylate was varied prior to polymerization/crosslinking reactions. Immersion in an excess of the LC solvent allowed for the measurement of size increase by polarized optical microscopy in terms of temperature. Length, width, and diagonal ratios were calculated considering swollen to dry network states of the samples. In general, swelling leads to an increase in the network size by increasing the temperature with a significant dependence on the degree of crosslinking. A large shift in the swelling ratio was found in the vicinity of the nematic to isotropic transition temperatures of the LCs.
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Relationships Between the Crystal Structures and the Multiple Melting Behaviors of Poly(ethylene 2,6‐naphthalate)
Authors: Gao Xia , Hou Weimin , Zhou Jianjun , Li Lin , Zhao Liqun 
Published: March 2004

AbstractSummary: Poly(ethylene 2,6‐naphthalate) (PEN) can crystallize either from the glassy state or from the melt state. When crystallized from the glassy state, the sample was quenched from the melt in liquid nitrogen and then annealed at certain crystallization temperatures. When crystallized from the melt state, the sample was cooled to a preset temperature from the melt and then annealed for a certain time. The crystal modifications, morphologies and melting behaviors of PEN were investigated by means of wide‐angle X‐ray diffraction (WAXD), polarized optical microscopy (POM), small‐angle light scattering (SALS) and differential scanning calorimetry (DSC). The results show that an α crystal modification of PEN was obtained when PEN crystallized from the glassy state, whilst a β crystal modification was obtained when PEN crystallized from the melt state at a higher temperature. An hedritic morphology of PEN crystal was obtained with only one melting peak observed in DSC curves when PEN was crystallized at a higher temperature from either the glassy state or the melt state. The α crystal modification could also be obtained when PEN was crystallized at a lower temperature from the melt. Spherulitic or banded spherulitic morphologies of PEN crystals, exhibiting multiple melting peaks in DSC curves, were observed when PEN was crystallized at a lower temperature. The multiple melting behaviors of PEN crystals may be associated with spherulitic structures composed of lamellae of varying thickness.WAXD patterns of PEN isothermally crystallized from different states.magnified imageWAXD patterns of PEN isothermally crystallized from different states.
Cover Picture: Macromol. Mater. Eng. 2/2004
Authors: Egen Marc , Braun Lydia , Zentel Rudolf , Tännert Klaus , Frese Peter , Reis Oliver , Wulf Martin 
Published: March 2004

Cover: The picture on the cover shows “artificial polymer opals”, which can be used as effect pigments in clear coatings. Shown is an EM picture, a dispersion of the opaline flakes and coated steel plates.Further details can be found in the Full Paper by M. Egen, L. Braun, R. Zentel,* K. Tännert, P. Frese, O. Reis, and M. Wulf on page 158.
Estimates for norms of resolvents and an application to the perturbation of spectra
Authors: Bandtlow Oscar F. 
Published: March 2004

AbstractLet A belong to the Schatten‐von Neumann ideal Sp for 0 < p < ∞. We give an upper bound for the operator norm of the resolvent (zI – A)–1 of A in terms of the departure from normality of A and the distance of z to the spectrum of A. As an application we provide an upper bound for the Hausdorff distance of the spectra of two operators belonging to Sp. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solutions with boundary‐layers and spike‐layers to singularly perturbed quasilinear Dirichlet problems
Authors: Guo Zongming 
Published: March 2004

AbstractThe structure of nontrivial nonnegative solutions to singularly perturbed quasilinear Dirichlet problems of the form –ϵΔpu = f(u) in Ω, u = 0 on ∂Ω, Ω ⊂ RN a bounded smooth domain, is studied as ϵ → 0+, for a class of nonlinearities f(u) satisfying f(0) = f(z1) = f(z2) = 0 with 0 < z1 < z2, f < 0 in (0, z1), f > 0 in (z1, z2) and $ \underline {\lim} _{u \to 0_{+}} $f(u)/up–1 = –∞. It is shown that there are many nontrivial nonnegative solutions with spike‐layers. Moreover, the measure of each spike‐layer is estimated as ϵ → 0+. These results are applied to the study of the structure of positive solutions of the same problems with f changing sign many times in (0,∞). Uniqueness of a solution with a boundary‐layer and many positive intermediate solutions with spike‐layers are obtained for ϵ sufficiently small. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tilings, packings, coverings, and the approximation of functions
Authors: Hinrichs Aicke , Richter Christian 
Published: March 2004

AbstractA packing (resp. covering) ℱ of a normed space X consisting of unit balls is called completely saturated (resp. completely reduced) if no finite set of its members can be replaced by a more numerous (resp. less numerous) set of unit balls of X without losing the packing property (resp. covering property) of ℱ. We show that a normed space X admits completely saturated packings with disjoint closed unit balls as well as completely reduced coverings with open unit balls, provided that there exists a tiling of X with unit balls.Completely reduced coverings by open balls are of interest in the context of an approximation theory for continuous real‐valued functions that rests on so‐called controllable coverings of compact metric spaces. The close relation between controllable coverings and completely reduced coverings allows an extension of the approximation theory to non‐compact spaces. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Estimates of difference norms for functions in anisotropic Sobolev spaces
Authors: Kolyada V. I. , Pérez F. J. 
Published: March 2004

AbstractWe investigate the spaces of functions on ℝn for which the generalized partial derivatives Dkf exist and belong to different Lorentz spaces L . For the functions in these spaces, the sharp estimates of the Besov type norms are found. The methods used in the paper are based on estimates of non‐increasing rearrangements. These methods enable us to cover also the case when some of the pk's are equal to 1. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized random recursive constructions and geometric properties of random fractals
Authors: Liu Yan‐Yan , Wen Zhi‐Ying , Wu Jun 
Published: March 2004

AbstractWe study random recursive constructions in which the contracting vectors have different distributions at different stages. With such constructions, the one parameter family of martingales are introduced and the probabilistic behaviours of the limit random objects (not identically distributed) are discussed. We prove that the random fractal associated with such construction has a constant Hausdorff dimension almost surely and give an explicit formula to determine it. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the central limit theorem for the stationary Poisson process of compact sets
Authors: Pawlas Zbyněk , Beneš Viktor 
Published: March 2004

AbstractStochastic geometry models based on a stationary Poisson point process of compact subsets of the Euclidean space are examined. Random measures on ℝd, derived from these processes using Hausdorff and projection measures are studied. The central limit theorem is formulated in a way which enables comparison of the various estimators of the intensity of the produced random measures. Approximate confidence intervals for the intensity are constructed. Their use is demonstrated in an example of length intensity estimation for the segment processes. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic analysis of nonselfadjoint operators generated by coupled Euler‐Bernoulli and Timoshenko beam model
Authors: Shubov Marianna A. , Peterson Cheryl A. 
Published: March 2004

AbstractIn the current paper, we present a series of results on the asymptotic and spectral analysis of coupled Euler‐Bernoulli and Timoshenko beam model. The model is well‐known in the different branches of the engineering sciences, such as in mechanical and civil engineering (in modelling of responses of the suspended bridges to a strong wind), in aeronautical engineering (in predicting and suppressing flutter in aircraft wings, tails, and control surfaces), in engineering and practical aspects of the computer science (in suppressing bending‐torsional flutter of a new generation of hard disk drives, which is expected to pack high track densities (20,000+TPI) and rotate at very high speeds (25,000+RPM)), in medical science (in bio mechanical modelling of bloodcarrying vessels in the body, which are elastic and collapsible). The aforementioned mathematical model is governed by a system of two coupled differential equations and a two parameter family of boundary conditions representing the action of the self‐straining actuators. This linear hyperbolic system is equivalent to a single operator evolution equation in the energy space. That equation defines a semigroup of bounded operators and a dynamics generator of the semigroup is our main object of interest. We formulate and proof the following results: (a) the dynamics generator is a nonselfadjoint operator with compact resolvent from the class 𝔖p with p > 1; (b) precise spectral asymptotics for the two‐branch discrete spectrum; (c) a nonselfadjoint operator, which is the inverse of the dynamics generator, is a finite‐rank perturbation of a selfadjoint operator. The latter fact is crucial for the proof that the root vectors of the dynamics generator form a complete and minimal set. In our forthcoming paper, we will use the spectral results to prove that the dynamics generator is Riesz spectral, which will allow us to solve several boundary and distributed controllability problems via the spectral decomposition method. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Amphiphilic Comb‐Like Poly(oxyethylene) and Its Complexes with LiClO4: Synthesis and Mesomorphic Behavior
Authors: Kim Jong‐Uk , Cha Sang‐Ho , Lee Jong‐Chan 
Published: March 2004

AbstractSummary: We prepared an amphiphilic, comb‐like poly(oxyethylene) containing decyl‐tri(oxyethylene) amphiphiles in the side chain using a polymer analogous reaction to obtain a novel nonionic amphiphilic polymeric system with high molecular weight. The amphiphilic comb‐like poly(oxyethylene) itself only showed a side‐chain crystalline phase below its melting temperature of −31 °C. When the polymer was mixed with lithium perchlorate, a smectic liquid‐crystalline phase appeared. The ordered phases of the polymer and the polymer mixture were studied by differential scanning calorimetry, polarized optical microscopy, and X‐ray diffraction.POM image (200 X) of D3OTP1 at room temperature.imagePOM image (200 X) of D3OTP1 at room temperature.