bluuebunny/crossref_metadata_2025 huggingface dataset:
SWI/SNF: The crossroads where extracellular signaling pathways meet chromatin
Authors: Simone Cristiano
Published: September 2005

The coordinated expression of the genome in response to extracellular cues is ensured by enzymatic cascades signaling to the nucleus. These pathways generate chromatin modifications at specific loci controlling the transcription of signal‐dependent and tissue‐specific genes. The SWI/SNF chromatin remodeling complex offers the ideal surface for integrating these signals in the execution of diverse or even opposite biological programs. J. Cell. Physiol. 207: 309–314, 2006. © 2005 Wiley‐Liss, Inc.
Gene therapy for cartilage defects
Authors: Cucchiarini Magali , Madry Henning
Published: September 2005

Focal defects of articular cartilage are an unsolved problem in clinical orthopaedics. These lesions do not heal spontaneously and no treatment leads to complete and durable cartilage regeneration. Although the concept of gene therapy for cartilage damage appears elegant and straightforward, current research indicates that an adaptation of gene transfer techniques to the problem of a circumscribed cartilage defect is required in order to successfully implement this approach. In particular, the localised delivery into the defect of therapeutic gene constructs is desirable. Current strategies aim at inducing chondrogenic pathways in the repair tissue that fills such defects. These include the stimulation of chondrocyte proliferation, maturation, and matrix synthesis via direct or cell transplantation‐mediated approaches. Among the most studied candidates, polypeptide growth factors have shown promise to enhance the structural quality of the repair tissue. A better understanding of the basic scientific aspects of cartilage defect repair, together with the identification of additional molecular targets and the development of improved gene‐delivery techniques, may allow a clinical translation of gene therapy for cartilage defects. The first experimental steps provide reason for cautious optimism. Copyright © 2005 John Wiley & Sons, Ltd.
Analysis of pesticide residues by on‐line reversed‐phase liquid chromatography–gas chromatography in the oil from olives grown in an experimental plot
Authors: Sanchez Raquel , Vazquez Ana , Villén‐Altamirano José , Villén Jesús
Published: September 2005

This paper describes the use of a fully automated on‐line reversed‐phase liquid chromatography–gas chromatography (RPLC‐GC) method for the determination of four organophosphorus pesticides (dimethoate, methidathion, chlorpyriphos and fenitrothion) in olive oil. These pesticides are among those more extensively used to control pests and disease in olive trees. Various treatments with these pesticides, at various doses and stages of olive ripening, were carried out in an olive grove. The olives were harvested in mid‐December and immediately processed into oil in the laboratory. Fully automated analyses by on‐line RPLC‐GC using the through oven transfer adsorption desorption (TOTAD) interface was carried out without any kind of sample pretreatment other than a simple filtration step. A statistical analysis was performed. No dimethoate remained in the oil owing to the high solubility of dimethoate in water. Differences between the other three pesticide residues were significant. Chlorpyriphos provided the lowest residues, followed by fenitrothion and methidathion. Treatments carried out in June did not leave residues in the oil, but all the treatments carried out in October and December led to pesticide residues that were higher than the limits of detection. Copyright © 2005 Society of Chemical Industry
The isolation and properties of a concentrated red‐purple betacyanin food colourant from Opuntia stricta fruits
Authors: Castellar MR , Obón JM , Fernández‐López JA
Published: September 2005

A red‐purple food colourant from Opuntia stricta fruits was obtained and studied. Four steps were involved in its isolation: washing, extraction, centrifugation and concentration. Ethanol:water 60:40 (v/v) was selected as the optimum extraction solvent to reduce the viscosity caused by the presence of mucilage and pectins. The resulting 40‐fold concentrated extract had a high colour strength (3.9, OD 535 nm, 1% v/v sol), a high betanin concentration (4.7 g L−1) and low viscosity (59.0 cP). It also showed high stability (t1/2 = 236.6 d, 4 °C) mainly due to its low pH (3.4) and low water content (571 g kg−1). These characteristics were in the same range as shown by three commercially available liquid concentrated colourants studied (red beet, red carrot and red grape skin). The colour parameters of this concentrated extract of Opuntia stricta were compared with those of commercial red colourants (red beet, red carrot, red grape skin, cochineal, elderberry, hibiscus and red cabbage). CIELAB values of Opuntia stricta (1.5 mL L−1) were L* = 69.8, a* = 59.7 and b* = −23.5. Opuntia stricta presented a vivid red‐purple colour which was distinguishable from the colours shown by the other natural red food colourants. Copyright © 2005 Society of Chemical Industry
Mechanical stress distributions in cross‐sections of cucumber cultivars during the fracture process
Authors: Dan Haruka , Okuhara Kazutake , Kohyama Kaoru
Published: September 2005

The fracture process of six cucumber cultivars was examined to explore the mechanical properties that determine cultivar‐specific crispy and crunchy textures. The postfailure portion of the load–strain curves was targeted in cucumber compression tests. The series of fractures after the initial fracture were examined at the tissue level by expressing the two‐dimensional stress intensity as a map. The stress map for the difference between the fracture point and 0.01 s after the fracture point indicated that the stress distribution changed in a broad area for two cultivars (D and F), while it changed locally and in a small area for two other cultivars (A and E). Several load drops were observed on the load–strain curve for the cucumbers. The peak number between the fracture and the local minimal points was quite small for cultivars D and F, whereas it was substantial for cultivars A and E. A global fracture event occurred over the entire cross‐sectional area at the initial fracture for cultivars D and F. The initial fracture occurred locally for cultivars A and E, and there were repeated sequential small local fractures as sample compression progressed. Two other cultivars (B and C), typical of those normally eaten raw, showed intermediate values for most parameters. This measurement provided the first demonstration of structural fracture during a series of load drops. How these postfailure properties will be associated with the texture characteristics of cucumber cultivars is discussed. Copyright © 2005 Society of Chemical Industry
Fatty acid composition in some selected marine fish species living in Turkish waters
Authors: Bayır Abdulkadir , Haliloǧlu H İbrahim , Sirkecioǧlu A Necdet , Aras N Mevlüt
Published: September 2005

The muscle fatty acid (FA) composition of 12 selected marine fish species living in Turkish waters was determined. FA profiles of muscle were compared in terms of total and individual saturated (SFAs) and unsaturated fatty acids. Total SFA, monounsaturated fatty acid (MUFA), n‐3 polyunsaturated fatty acid (n‐3 PUFA) and n‐6 polyunsaturated fatty acid (n‐6 PUFA) contents as well as n‐3/n‐6 FA and eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) ratios differed (P < 0.01) in all fish species. Palmitic acid (16:0) among total SFAs, oleic acid (18:1n‐9) among MUFAs, DHA (22:6n‐3) among n‐3 PUFAs and 18:2n‐6 and 20:4n‐6 among n‐6 PUFAs were the most abundant FAs. The ratio of n‐3/n‐6 PUFA contents, indicating the availability of n‐3 PUFAs that are beneficial for human health, ranged from 2.67 to 12.61. The EPA/DHA ratio was between 0.17 and 0.83 in the marine fish species studied. Copyright © 2005 Society of Chemical Industry
Optimization of extraction process for phenolic acids from black cohosh (Cimicifuga racemosa) by pressurized liquid extraction
Authors: Mukhopadhyay Sudarsan , Luthria Devanand L , Robbins Rebecca J
Published: September 2005

An investigation to optimize the extraction of phenolic acids from black cohosh using a pressurized liquid extractor system was studied with the aim of developing a generalized approach for sample preparation of phenolic compounds from plant matrices. Operating parameters such as solvent composition, solid‐to‐solvent ratio, temperature, particle size distribution, and number of extraction cycles were identified as main variables that influence extraction efficiency. A mixture of methanol and water (60:40 v/v) was found to be the best solvent for total phenolics (TP) and individual phenolic acids. The four phenolic acids extracted from black cohosh were identified by HPLC and LC‐MS as caffeic acid, ferulic acid, sinapic acid and isoferulic acid. Over 96% of the measured phenolics were extracted in first two cycles. The extraction efficiency for black cohosh with MeOH:H2O (60:40 v/v) was found to be maximum at a solid‐to‐solvent ratio of 80 mg ml−1. TP content of the extract was found to increase with temperature up to 90 °C. Particle size was found to have a large impact on extraction efficiency of TP. Samples with particle size between 0.25 mm and 0.425 mm provided optimum extraction of phenolics from black cohosh. Published in 2005 for SCI by John Wiley & Sons, Ltd.
Determination of interferon‐gamma in Chinese hamster ovary cell culture supernatant by coupled‐column liquid chromatography
Authors: Goh Lin‐Tang , Yap Miranda Gek Sim
Published: September 2005

A robust tandem HPLC method coupling size‐exclusion (Shodex Asahipak GS‐320HQ) and reversed phase (Vydac 218TP54) columns with ultraviolet detection was developed for quantitative determination of interferon‐γ (IFN‐γ) in Chinese hamster ovary cell culture supernatant. The 2D‐HPLC system was linked up by a 6‐port 2‐position low hold‐up volume switch valve. Compared to a commercial ELISA kit for IFN‐γ, the coupled column LC approach was able to detect and quantify soluble IFN‐γ, regardless of the glycoprotein's molecular/conformational variability and sample background. Each LC‐LC analysis took 90 minutes inclusive of column regeneration. The relative standard deviation of measurements (n = 5) was less than 3%. The limit of detection (LOD) was determined to be 0.35 μg IFN‐γ.
Peptide and peptidomimetic chiral selectors in liquid chromatography
Authors: Li Tingyu
Published: September 2005

The application of peptide and peptidomimetic chiral selectors in LC is reviewed in this article. In particular, methods for finding these types of selectors using combinatorial library approaches are discussed, as well as recent advances in the use of peptides and peptidomimetics as general chiral selectors for LC. In terms of the library approaches, batch screening and reciprocal screening are discussed. As for general chiral selectors, one example involves the application of chiral diamide phases. Another example shows the versatility of oligoproline chiral stationary phases, which exhibit resolution for a number of racemic analytes, comparable to other well‐established chiral stationary phases.
The coupling of the electrostatic potential with the transport and adsorption mechanisms in ion‐exchange chromatography systems: Theory and experiments
Authors: Liapis Athanasios I. , Grimes Brian A.
Published: September 2005

The coupling of the constitutive expression for the electrostatic potential as specified through Poisson's equation together with the constitutive equations for the mechanisms of convection, diffusion, electrophoretic migration, and adsorption provides the necessary set of constitutive expressions to be employed in the material balance equations of ion‐exchange chromatography systems to construct macroscopic continuum models that could be used to design and simulate the dynamic behavior of systems involving a single charged adsorbate or multiple charged adsorbates. A physically relevant and consistent macroscopic continuum model that can predict, as has been observed experimentally by UV confocal microscopy (UVCM), the presence or absence of the concentration overshoot phenomenon, based on the pH and ionic strength of the liquid solution, is discussed and expanded to describe the behavior of IEC systems involving competitive adsorption of two or more charged adsorbates. Furthermore, UVCM and confocal scanning laser microscopy (CSLM) experiments and the macroscopic continuum models that could be used to analyze their data are indicated. Results are also presented that have been obtained from molecular dynamics (MD) modeling and simulation studies (microscopic modeling and analysis) employing realistic atomistic models derived from fundamental physics, and indicate the physical mechanisms that are relevant and actively involved in the transport and adsorption of charged adsorbates in IEC systems, as well as their relative importance. The results obtained from the MD simulations show that when a charged macromolecule is adsorbed it is restrained by a strong dominant Coulombic interaction and is trapped by a hydration layer adjacent to the surface and these lead to zero lateral displacement of the adsorbed macromolecule. This finding indicates that surface diffusion could be a physically implausible mechanism in IEC systems involving charged adsorbate macromolecules. Also, the results obtained from the MD simulation studies show that the transport coefficients that characterize the mass transfer of a charged adsorbate in the liquid solution by diffusion and electrophoretic migration have magnitudes along the lateral direction that are different from those along the direction that is normal to the charged surface.
Effects of Moisture on Glass Transition and Microstructure of Glycerol‐Plasticized Soy Protein
Authors: Chen Pu , Zhang Lina , Cao Feifei
Published: September 2005

Summary: The glass transition behavior of the glycerol‐plasticized soy protein sheets (SL series) at various relative humidity (RH) was investigated by using differential scanning calorimetry with the aluminum pan and O‐ring‐sealed stainless steel capsule, and the microstructure of these sheets was detected on small‐angle X‐ray scattering. The results revealed that there were three glass transitions (Tg1, Tg2 and Tg3), corresponding to glycerol‐rich, protein‐rich and protein‐water domains, in the protein‐glycerol‐water ternary system. The Tg1 values of the SL‐series sheets at 75% RH decreased from −49.3 to −83.8 °C with an increase of glycerol content from 10 to 50 wt.‐%, whereas Tg2 and Tg3 were almost invariable at about 60 °C and 3 °C, respectively. In addition, the Tg1, Tg2 and Tg3 values of the SL‐25 containing 25 wt.‐% glycerol at 0%, 35%, 58%, 75% and 98% RH were in the range of −12.7–−83.2 °C, 65.8–53.1 °C and 3.5–1.9 °C, respectively. The result from small‐angle X‐ray scattering indicated that the radii of gyration (Rg) of protein‐rich domain were in the range of 60–63 nm; this suggested the existence of protein macromolecules as aggregates in the stable protein‐rich and protein‐water domains. With an increase of RH, the tensile strength and Tg values of the SL‐series sheets decreased, but the elongation at break increased. In view of the results above, the moisture in ambient environment significantly influenced the Tg values and microstructures of the glycerol‐plasticized soy protein sheets, leading to the changes of the mechanical and thermal properties.

Three glass transitions corresponding to glycerol‐rich, protein‐water and protein‐rich domains in glycerol‐plasticized soy protein sheets at a relative humidity of 75%.

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Three glass transitions corresponding to glycerol‐rich, protein‐water and protein‐rich domains in glycerol‐plasticized soy protein sheets at a relative humidity of 75%.
Effects of Ethyl and Benzyl Groups on the Miscibility and Properties of Castor Oil‐Based Polyurethane/Starch Derivative Semi‐Interpenetrating Polymer Networks
Authors: Cao Xiaodong , Wang Yixiang , Zhang Lina
Published: September 2005

Summary: Cornstarch derivative (ES), prepared using diethyl sulfate as an etherifying reagent, was blended with castor oil‐based polyurethane (PU) prepolymer to obtain a series of semi‐interpenetrating polymer network (semi‐IPN) materials, named as UES films. Simultaneously, other kinds of semi‐IPN (UBS2) were prepared from PU and benzyl starch (BS2) to compare the effects of the substitute groups. The differences in the miscibility and properties of the two series of materials were investigated using attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, dynamic mechanical thermal analysis, ultraviolet‐visible spectroscopy, water‐sensitivity and tensile testing. The experimental results revealed that UBS2 films exhibit stronger interfacial attraction and better phase mixing than the UES films, as a result of specific interactions between the PU hard segments and BS2 phenyl groups. The optical transmittance, water‐resistivity, tensile strength, and elongation at break of the UBS2 films were clearly higher than those of the UES films containing the same concentration of PU. In particular, the miscibility and properties of the UES film with 40 wt.‐% ES, were very poor, whereas the semi‐IPN films containing 70 wt.‐% benzyl starch still had a certain miscibility and good properties.1 Therefore, the phenyl groups play an important role in the improvement of the miscibility and properties of the semi‐IPN materials.

Tensile strength and elongation at break of the PU/ES and PU/BS2 films with concentration of the two starch derivatives, ES and BS2.

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Tensile strength and elongation at break of the PU/ES and PU/BS2 films with concentration of the two starch derivatives, ES and BS2.
Monomers for Adhesive Polymers, 5
Authors: Pavlinec Juraj , Zeuner Frank , Angermann Jörg , Moszner Norbert
Published: September 2005

Summary: 2,4,6‐Trimethylphenyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate (1) was synthesized by silylation of 2,4,6‐trimethylphenyl 2‐[4‐(dimethoxyphosphoryl)‐2‐oxa‐butyl]acrylate with trimethylsilyl bromide (TMSBr) and the hydrolysis of the silyl ester resulted in the formation of polymerizable phosphonic acid 1. The structure of this new monomer was characterized by IR, 1H, 13C and 31P NMR spectroscopy. The monomer dissolves well in ethyl acetate, ethanol or water and shows a high hydrolytic stability. 1 was homopolymerized with 2,2′‐azobisisobutyronitrile (AIBN), 2,2′‐azobis‐(2‐methylpropionamidine) dihydrochloride (AMPAHC) or dibenzoyl peroxide (DBPO) as the initiators. In a tetrahydrofuran (THF) solution, the deviations from the standard reaction kinetics were comparable with those of polymerizations of the other water soluble acrylate monomers. The unusual polymerization rate‐monomer concentration dependence with monomer intensity exponent less than 1 (m = 0.5) observed in THF solutions was even more declined from 1 in the polar medium EtOH‐H2O. The DBPO was a more effective polymerization initiator than AIBN. However, the overall activation energy of 81 kJ · mol−1 showed a usual temperature‐rate dependence observed in methacrylate ester polymerizations. In addition, monomer 1 was copolymerized with methyl methacrylate (MMA), ethyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate (2), and N,N′‐diethyl‐1,3‐bis(acrylamido)propane (3), respectively, using THF as the solvent and AIBN as the initiator. The copolymerization curves revealed only slight deviations from the ideal copolymer‐feed composition. The estimated copolymerization parameters indicate a ready incorporation of comonomer units into polymer chains, preferably by alteration rather than at random.

2,4,6‐Trimethylphenyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate.

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2,4,6‐Trimethylphenyl 2‐[4‐(dihydroxyphosphoryl)‐2‐oxa‐butyl]acrylate.
Preparation of Silica‐Coated Polystyrene Hybrid Spherical Colloids
Authors: Chen Min , Zhou Shuxue , Wu Limin , Xie Songhai , Chen Ying
Published: September 2005

Summary: A novel preparation method for stable PS/SiO2 core‐shell hybrid colloid was proposed. In this process, a positively charged PS colloid was first synthesized via surfactant‐free emulsion polymerization of styrene by using a cationic initiator, and the hydrolysis and condensation of tetraethoxysilane (TEOS) was then carried out in acidic aqueous ethanol medium in the presence of PS colloids. Silica layer was deposited onto the surface of PS particle via electrostatic interaction between positively charged PS colloids and negatively charged silica. No surface treatment and centrifugation/redispersion cycle process were needed. TEM, SEM, and zeta potential measurements indicated that silica layer was successfully coated onto the surfaces of PS colloids.

PS/SiO2 hybrid core‐shell colloids with PS as core and silica layer as shell.

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PS/SiO2 hybrid core‐shell colloids with PS as core and silica layer as shell.
Synthesis, Characterization and Behavior in Aqueous Solution of Star‐Shaped Poly(acrylic acid)
Authors: Plamper Felix A. , Becker Harald , Lanzendörfer Michael , Patel Mushtaq , Wittemann Alexander , Ballauff Matthias , Müller Axel H. E.
Published: September 2005

Summary: We report the synthesis of star‐shaped poly(acrylic acid) (PAA), with 5, 8, and 21 arms, by atom transfer radical polymerization of tert‐butyl acrylate. We employ the core‐first approach using glucose‐, saccharose‐ and cyclodextrin‐based initiators. Subsequent acidic treatment of poly(tert‐butyl acrylate) (PtBA) leads to star‐shaped poly(acrylic acid) (PAA). Alkaline cleavage of the arms enabled us to determine the initiation site efficiency. The PAA stars and arms were esterified to poly(methyl acrylate) (PMA). Molecular weight determination by means of GPC/viscosity, MALDI‐TOF MS and NMR end‐group determination showed that the initiation site efficiency is close to unity. Results from potentiometric titration of PAA arms and stars show that the apparent pKa values increase with increasing arm number, which is a direct result of increasing segment density. Osmometry measurements of aqueous solutions of the PAA stars result in osmotic coefficients between 0.05 and 0.38, indicating that most of the counterions are confined within the star. The confinement increases with arm number.

Potentiometric titration curves for stars (PAA100)21, (PAA100)8, (PAA100)5, and linear PAA100.

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Potentiometric titration curves for stars (PAA100)21, (PAA100)8, (PAA100)5, and linear PAA100.
Propylene Polymerization Behavior of Fluorinated Bis(phenoxy‐imine) Ti Complexes with an MgCl2‐Based Compound (MgCl2‐Supported Ti‐Based Catalysts)
Authors: Nakayama Yasushi , Saito Junji , Bando Hideki , Fujita Terunori
Published: September 2005

Summary: Fluorinated bis(phenoxy‐imine)Ti complexes 1–3 combined with MgCl2/i‐BunAl(OR)3−n (MgCl2‐supported catalysts) were able to polymerize propylene in a living fashion at room temperature to provide slightly to highly syndiotactic poly(propylenes) (PPs) with extremely narrow distributions of molecular weight. These represent the first examples of MAO‐ and borate‐free group 4 metal‐based living catalysts. The supported complexes 2 and 3 formed PPs with higher syndiotacticity and Tm's than the corresponding homogeneous MAO‐activation systems (e.g., 3: rr 97%, Tm 155 °C; MAO activation: rr 93%, Tm 152 °C). The measured Tm of 155 °C represents the highest known Tm for syndiotactic PPs synthesized at room temperature.

Polymerization of propylene to poly(propylene) with supported Ti‐based catalysts.

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Polymerization of propylene to poly(propylene) with supported Ti‐based catalysts.
Characterization of Glycidyl Methacrylate Based Copolymers by Inverse Gas Chromatography under Finite Surface Coverage
Authors: Nastasović Aleksandra B. , Onjia Antonije E. , Milonjić Slobodan K. , Vuković Zorica M. , Jovanović Slobodan M.
Published: September 2005

Summary: Inverse gas chromatography under finite surface coverage conditions (IGC‐FC) was used for the investigation of sorption of hexane, benzene, chloroform and tetrahydrofuran on macroporous crosslinked poly[(glycidyl methacrylate)‐co‐(ethylene glycol dimethacrylate)], poly(GMA‐co‐EGDMA), and copolymer modified with ethylene diamine, EDA, poly(GMA‐co‐EGDMA)‐en, in the temperature range 333–363 K. Two poly(GMA‐co‐EGDMA) samples with different porosity parameters were synthesized by suspension copolymerization and modified using a ring‐opening reaction of the pendant epoxy groups with EDA. The specific surface areas of the initial and modified copolymer samples were determined by the BET method from low temperature nitrogen adsorption isotherms (77 K). The adsorption isotherms determined from chromatographic peaks of adsorbates were analyzed using the BET theoretical model and used for estimation of the surface area, isosteric heat of adsorption and the adsorption energy distribution on the surface of the initial and modified copolymer samples. It was observed that the adsorbate nature and the properties of the solid surface of the initial and modified copolymer governed the uptake of adsorbate by the copolymer. The deviations observed for the Sa values obtained by the BET method from the low temperature nitrogen adsorption isotherms and hexane was attributed not only to the difference in molecule size, but also to the specific polymer‐adsorbate interactions. The isosteric heat of adsorption approached a constant value with increasing adsorbate loading. A large variation in the shapes of the qst‐α curves resulted from strong acid‐base interactions, as well as dissolution phenomena. Of the four studied adsorbates, chloroform was shown to have the greatest affinity towards the surface of the investigated polymer samples.

Adsorption isotherms of hexane on sample 1 and 1a.

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Adsorption isotherms of hexane on sample 1 and 1a.
Cover Picture: Macromol. Mater. Eng. 9/2005
Authors: Nastasović Aleksandra B. , Onjia Antonije E. , Milonjić Slobodan K. , Vuković Zorica M. , Jovanović Slobodan M.
Published: September 2005

Cover: The picture on the cover shows (A) adsorption isotherms, (B) isosteric heat of adsorption and (C) adsorption energy distribution for macroporous poly(GMA‐co‐EGDMA). These parameters, estimated from IGC data using BET adsorption model, were used to study the surface characteristics of the polymer. Further details can be found in the article by A. B. Nastasović,* A. E. Onjia, S. K. Milonjić, Z. M. Vuković, and S. M. Jovanović on page 884.
Amphiphilic Block Copolymer Micelles: New Dispersant for Single Wall Carbon Nanotubes
Authors: Shin Hye‐in , Min Byung Gil , Jeong Wonyong , Park Cheolmin
Published: September 2005

Summary: This manuscript describes a new simple method to disperse single wall carbon nanotubes (SWNTs) in various organic solvents. The method is based on using amphiphilic block copolymer micelles as a dispersant. We have found that the stabilization of SWNTs by block copolymer micelles adhering to the surface of nanotubes is much superior to that by either surfactants or high‐molecular‐weight polymers currently used. Our nondestructive method is beneficial because the amphiphilic property of the block copolymer micelles enables us to stabilize SWNTs in either polar solvents or nonpolar ones at the same time. We also demonstrate that silver nanoparticles are selectively synthesized in polar cores of micelles adsorbed on the surface of SWNTs and the subsequent heat treatment modifies the surface of SWNTs.

Dispersion of silver nanoparticles on the surface of SWNTs.

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Dispersion of silver nanoparticles on the surface of SWNTs.
Dielectric Properties of Polyimide‐Mica Hybrid Films
Authors: Zhang Yi‐He , Dang Zhi‐Min , Xin John H. , Daoud Walid A. , Ji Jun‐Hui , Liu Yuyang , Fei Bin , Li Yuanqing , Wu Juntao , Yang Shiyong , Li Lai‐Feng
Published: September 2005

Summary: Polyimide‐mica hybrid films were prepared via ultrasonic dispersion and in situ polymerization process from a solution of a polyimide precursor and mica in N,N‐dimethylacetamide, and their structure was characterized by FTIR and XRD techniques. The dependence of dielectric properties, such as dielectric constant and electrical breakdown strength, of the hybrid films on the content of mica was studied at room and cryogenic temperatures. The results show that the dielectric constant of PI‐mica hybrid films decreases with the increase of the mica content at temperatures from −150 to 150 °C and at frequency range from 1 kHz to 1 MHz. It was found that the cryogenic electrical breakdown strength of the PI‐mica hybrid films could meet the requirements of cryogenic insulating materials.

Effect of frequency on the dielectric constant of PI‐mica hybrid films at 140 °C at the frequency from 1 kHz to 1 MHz.

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Effect of frequency on the dielectric constant of PI‐mica hybrid films at 140 °C at the frequency from 1 kHz to 1 MHz.
Observations of Gelation and Vitrification of a Thermosetting Resin during the Evolution of Polymerization Shrinkage
Authors: Yu Hong , Mhaisalkar Subodh G. , Wong Ee Hua
Published: September 2005

Summary: We report a new methodology to determine the gelation and vitrification of a thermosetting material during the polymerization process by detecting the evolution of cure shrinkage through a thermomechanical analyzer (TMA) and a differential scanning calorimeter (DSC). The gelation and vitrification determined by the evolution of cure shrinkage correspond favorably with that measured by conventional rheological techniques. The isoconversional phenomenon at gelation point was further confirmed by monitoring cure shrinkage at temperatures ranging from 90 to 110 °C. Whereas, vitrification was observed to occur at higher degrees of cure with increasing cure temperatures. Inhibited cure shrinkage was also observed in the vitrification region where the reaction transitioned from chemical to diffusion controlled.

Combination of dimension change detected by DMA and heat flow detected by DSC for determining the relationship of cure shrinkage and degree of cure.

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Combination of dimension change detected by DMA and heat flow detected by DSC for determining the relationship of cure shrinkage and degree of cure.
Living Polymerization of N,N‐Diphenylacrylamide with Triisobutylaluminum
Authors: Kim Yeon Cu , Jeon Manseong , Kim Sang Youl
Published: September 2005

Summary: N,N‐Diphenylacrylamide was polymerized in a living fashion with triisobutylaluminum in THF at 0 °C. The polymerization results showed an increase of molecular weight proportional to the amount of monomer consumed and a first‐order kinetics at −78 °C. The intermediates obtained with excess initiator at −78 °C revealed that the polymerization was initiated through 1,4‐addition of hydride from a triisobutyl group in the triisobutylaluminum and then proceeded through aluminum‐oxygen bond interchange.

N,N‐Diphenylacrylamide was polymerized in a living fashion with triisobutylaluminum in THF at 0 °C.

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N,N‐Diphenylacrylamide was polymerized in a living fashion with triisobutylaluminum in THF at 0 °C.
A Convenient A2 + B3 Approach to Hyperbranched Poly(arylene oxindole)s
Authors: Smet Mario , Fu Yu , Zhang Xi , Schacht Etienne H. , Dehaen Wim
Published: September 2005

Summary: We developed a facile approach to hyperbranched polymers by applying a superelectrophilic reaction within an A2 + B3 strategy. A significant reactivity difference between the intermediate and the starting material was utilized to avoid gelation in the A2 + B3 polymerization. A number of hyperbranched poly(arylene oxindole)s were achieved in a one‐step polymerization and characterized by NMR spectroscopy and gel permeation chromatography. Moreover, further modifications at the interior and exterior of the resulting polymers were explored as well.

Structure of the hyperbranched polymers produced using the A2 + B3 approach.

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Structure of the hyperbranched polymers produced using the A2 + B3 approach.
Enhancement of Biomolecular Recognition of DTIC Based on Functional Monodisperse Polystyrene Spheres
Authors: Zhang Renyun , Chen Haihua , Wu Chunhui , Wang Xuemei , Gu Zhongze
Published: September 2005

Summary: Monodisperse carboxy polystyrene (PS) spheres were synthesized and utilized as an interface to increase the detection sensitivity of some biomolecules. The binding behavior of dacarbazine (DTIC), an anticancer drug, with DNA bases in the absence and presence of the PS spheres was investigated. The results indicated a remarkable effect of PS on the binding behavior of DTIC to DNA bases and significantly enhanced detection sensitivity for the relative biomolecular recognition.

Electrochemical detection of DTIC on a GCE surface in the absence and presence of polystyrene spheres.

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Electrochemical detection of DTIC on a GCE surface in the absence and presence of polystyrene spheres.
NMR spectroscopic characterization of the membrane affinity of polyols
Authors: Fischer Daniela , Geyer Armin
Published: September 2005

Residual dipolar couplings (RDCs) are applied here for the analysis of weak, transient binding events between phosphatidylcholine bilayers and polyols. Large signal responses are observed even for low percentages of ‘ligand‐receptor complexes,’ making RDCs a sensitive tool for the analysis of molecular recognition events. The different degree of alignment in solution can be compared as a result of the calculation of the alignment tensor elements. By varying polarity and/or charge of the molecules under investigation, nonspecific hydrophobic effects can be excluded. Copyright © 2005 John Wiley & Sons, Ltd.
In vivo 3T spiral imaging based multi‐slice T1ρ mapping of knee cartilage in osteoarthritis
Authors: Li Xiaojuan , Han Eric T. , Ma C. Benjamin , Link Thomas M. , Newitt David C. , Majumdar Sharmila
Published: September 2005

T1ρ describes the spin‐lattice relaxation in the rotating frame and has been proposed for detecting damage to the cartilage collagen‐proteoglycan matrix in osteoarthritis. In this study, a multi‐slice T1ρ imaging method for knee cartilage was developed using spin‐lock techniques and a spiral imaging sequence. The adverse effect of T1 regrowth during the multi‐slice acquisition was eliminated by RF cycling. Agarose phantoms with different concentrations, 10 healthy volunteers, and 9 osteoarthritis patients were scanned at 3T. T1ρ values decreased as agarose concentration increased. T1ρ values obtained with imaging methods were compared with those obtained with spectroscopic methods. T1ρ values obtained during multi‐slice acquisition were validated with those obtained in a single slice acquisition. Reproducibility was assessed using the average coefficient of variation of median T1ρ, which was 0.68% in phantoms and 4.8% in healthy volunteers. There was a significant difference (P = 0.002) in the average T1ρ within patellar and femoral cartilage between controls (45.04 ± 2.59 ms) and osteoarthritis patients (53.06 ± 4.60 ms). A significant correlation was found between T1ρ and T2; however, the difference of T2 was not significant between controls and osteoarthritis patients. The results suggest that T1ρ relaxation times may be a promising clinical tool for osteoarthritis detection and treatment monitoring. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Quantification of perfusion fMRI using a numerical model of arterial spin labeling that accounts for dynamic transit time effects
Authors: Hernandez‐Garcia Luis , Lee Gregory R. , Vazquez Alberto L. , Yip Chun‐Yu , Noll Douglas C.
Published: September 2005

A new approach to modeling the signal observed in arterial spin labeling (ASL) experiments during changing perfusion conditions is presented in this article. The new model uses numerical methods to extend first‐order kinetic principles to include the changes in arrival time of the arterial tag that occur during neuronal activation. Estimation of the perfusion function from the ASL signal using this model is also demonstrated. The estimation algorithm uses a roughness penalty as well as prior information. The approach is demonstrated in numerical simulations and human experiments. The approach presented here is particularly suitable for fast ASL acquisition schemes, such as turbo continuous ASL (Turbo‐CASL), which allows subtraction pairs to be acquired in less than 3 s but is sensitive to arrival time changes. This modeling approach can also be extended to other acquisition schemes. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Paramagnetic viral nanoparticles as potential high‐relaxivity magnetic resonance contrast agents
Authors: Allen Mark , Bulte Jeff W. M. , Liepold Lars , Basu Gautam , Zywicke Holly A. , Frank Joseph A. , Young Mark , Douglas Trevor
Published: September 2005

In order to compensate for the inherent high threshold of detectability of MR contrast agents, there has been an active interest in the development of paramagnetic nanoparticles incorporating high payloads of Gd3+ with high molecular relaxivities. Toward this end, the protein cage of Cowpea chlorotic mottle virus (CCMV), having 180 metal binding sites, is being explored. In vivo CCMV binds Ca2+ at specific metal binding sites; however, Gd3+ can also bind at these sites. Using fluorescence resonance energy transfer we have characterized the binding affinity of Gd3+ to the metal binding sites by competition experiments with Tb3+. The measured dissociation constant (Kd) for Gd3+ bound to the virus is 31 μM. The T1 and T2 relaxivities of solvent water protons in the presence of Gd3+‐bound CCMV were 202 and 376 mM−1 s−1, respectively, at 61 MHz Larmor frequency. The unusually high relaxivity values of the Gd3+–CCMV are largely a result of the nanoparticle virus size and the large number of Gd3+ ions bound to the virus. These preliminary results should encourage further investigations into the use of viral protein cages as a new platform for MR contrast agents. Magn Reson Med, 2005. Published 2005 Wiley‐Liss, Inc.
S5FP: Spectrally selective suppression with steady state free precession†
Authors: Derbyshire J. A. , Herzka D. A. , McVeigh E. R.
Published: September 2005

A method is presented that employs the inherent spectral selectivity of the Steady‐State Free Precession (SSFP) pulse sequence to provide a spectral band of suppression. At TE = TR/2, SSFP partitions the magnetization into two phase‐opposed spectral components. Z‐storing one of these components simultaneously further excites the other, which is then suppressed by gradient crushing and RF spoiling. The Spectrally Selective Suppression with SSFP (S5FP) method is shown to provide significant attenuation of fat signals, while the water signals are essentially unaffected and provide the normal SSFP contrast. Fat suppression is achieved with relatively little temporal overhead (less than 10% reduction in temporal resolution). S5FP was validated using simulations, phantoms, and human studies. Magn Reson Med, 2005. Published 2005 Wiley‐Liss, Inc.
Two‐dimensional, J‐resolved spectroscopic imaging of GABA at 4 Tesla in the human brain
Authors: Jensen J. Eric , Frederick Blaise deB. , Wang Liqun , Brown John , Renshaw Perry F.
Published: September 2005

A method for measuring brain gamma‐amino butyric acid (GABA) levels is presented that combines 2D J‐resolved magnetic resonance spectroscopy (J‐MRS) techniques with chemical‐shift imaging (2D‐JMRSI) at 4 Tesla (T). The results of phantom and in vivo experiments agree well in demonstrating that the 2CH2 GABA resonance situated at 2.97 ppm can be resolved from the neighboring creatine (Cr) resonance at 3.03 ppm and quantified. Single‐voxel, J‐resolved standard and metabolite‐nulled in vivo experiments on six healthy subjects reveal a broad component from the underlying macromolecules (MM) that resonates at and around 3.00 ppm, which is estimated to contribute approximately 15% to the J‐resolved GABA resonance in this large voxel at a repetition time (TR) of 4.5 s. With our 2D‐JMSRI at 1.25 s TR, the macromolecule resonance contribution to our GABA measurements is approximated to be 12%. Six healthy human subjects underwent scanning at 4T with this sequence, yielding a global brain GABA concentration of 0.76 ± 0.20 mM after correction for 12% macromolecule contribution. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Biological correlates of diffusivity in brain abscess
Authors: Mishra Asht M. , Gupta Rakesh K. , Saksena Sona , Prasad Kashi N. , Pandey Chandra M. , Rathore Divya , Purwar Ankur , Rathore Ram K.S. , Husain Nuzhat , Jha Deepak K. , Jaggi Ramandeep S. , Husain Mazhar
Published: September 2005

Restricted diffusion in brain abscess is assumed to be due to a combination of inflammatory cells, necrotic debris, viscosity, and macromolecules present in the pus. We performed diffusion‐weighted imaging (DWI) on 41 patients with proven brain abscesses (36 pyogenic and five tuberculous), and correlated the apparent diffusion coefficient (ADC) from the abscess cavity with viable cell density, viscosity, and extracellular‐protein content quantified from the pus. On the basis of the correlation between cell density and ADC in animal tumor models and human tumors in the literature, we assumed that the restricted ADC represents the cellular portion in the abscess cavity. We calculated restricted and unrestricted lesion volumes, and modeled cell density over the restricted area with viable cell density per mm3 obtained from the pus. The mean restricted ADC in the cavity (0.65 ± 0.01 × 10–3 mm2/s) correlated inversely with restricted cell density in both the pyogenic (r = −0.90, P = <0.05) and tuberculous (0.60 ± 0.04 × 10–3 mm2/s, r = −0.94, P = <0.05) abscesses. We conclude that viable cell density is the main biological parameter responsible for restricted diffusion in brain abscess, and it is not influenced by the etiological agents responsible for its causation. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
How to investigate oxygen supply, uptake, and utilization simultaneously by interleaved NMR imaging and spectroscopy of the skeletal muscle
Authors: Carlier P. G , Brillault‐Salvat C. , Giacomini E. , Wary C. , Bloch G.
Published: September 2005

Human skeletal muscle perfusion, oxygenation, and high‐energy phosphate distribution were measured simultaneously by interleaved 1H and 31P NMR spectroscopy and 1H NMR imaging in vivo. From these parameters, arterial oxygen supply (DO2), muscle reoxygenation rate, mitochondrial ATP production, and O2 consumption (VO2) were deduced at the recovery phase of a short ischemic exercise bout. In addition, by using a reformulation of the mass conservation law, muscle maximum O2 extraction was calculated from these parameters. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
New insights into the mechanisms of signal formation in RF‐spoiled gradient echo sequences
Authors: Denolin Vincent , Azizieh Céline , Metens Thierry
Published: September 2005

RF spoiling is a well established method to produce T1‐weighted images with short repetition‐time gradient‐echo sequences, by eliminating coherent transverse magnetization with appropriate RF phase modulation. This paper presents 2 novel approaches to describe signal formation in such sequences. Both methods rely on the formulation of RF spoiling as a linear increase of the precession angle between RF pulses, which is an alternative to the commonly used quadratic pulse phase scheme. The first technique demonstrates that a steady state signal can be obtained by integrating over all precession angles within the voxel, in spite of the lack of a genuine steady‐state for separate isochromats. This clear mathematical framework allows a straightforward incorporation of off‐resonance effects and detector phase settings. Moreover, it naturally introduces the need for a large net gradient area per repetition interval. In the second step, a modified partition method including RF spoiling is developed to obtain explicit expressions for all signal components. This provides a physical interpretation of the deviations from ideal spoiling behavior in FLASH and echo‐shifted sequences. The results of the partition method in the small flip angle regime are compared with numerical simulations based on a Fourier decomposition of magnetization states. Measurements performed with in vitro solutions were in good agreement with numerical simulations at short relaxation times (T1/TR = 32 and T2/TR = 4); larger deviations occurred at long relaxation times (T1/TR = 114 and T2/TR = 82). Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Immediate early gene activity in song control nuclei and brain areas regulating motivation relates positively to singing behavior during, but not outside of, a breeding context
Authors: Heimovics Sarah A. , Riters Lauren V.
Published: September 2005

In some species, such as songbirds, much is known about how the brain regulates vocal learning, production, and perception. What remains a mystery is what regulates the motivation to communicate. European starlings (Sturnus vulgaris)sing throughout most of the year, but the social and environmental factors that motivate singing behavior differ seasonally. Male song is highly sexually motivated during, but not outside of, the breeding season. Brain areas outside the song control system, such as the medial preoptic nucleus (POM) and ventral tegmental area (VTA), have been implicated in regulating sexually motivated behaviors in birds, including song. The present study was designed to explore whether these regions, as well as three song control nuclei [area X, the high vocal center (HVC), and the robust nucleus of the arcopallium (RA)], might be involved differentially in song produced within compared to outside of a breeding context. We recorded the behavioral responses of breeding and nonbreeding condition male starlings to the introduction of a female conspecific. Males did not show context‐dependent differences in the overall amount of song sung. However, immunocytochemistry for the protein product of the immediate early gene cFOS revealed a positive linear relationship between the total amount of songs sung and number of cFOS‐labeled cells in POM, VTA, HVC, and RA for birds singing during, but not outside of, a breeding context. These results suggest that these regions differentially regulate male song production depending on reproductive context. Overall the data support the hypothesis that the POM and VTA interact with the song control system, specifically HVC and RA, to regulate sexually motivated vocal communication in songbirds. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005