bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of MRI‐induced heating of an implanted medical lead wire with an electric field transfer function
Authors: Park Sung‐Min , Kamondetdacha Rungkiet , Nyenhuis John A.
Published: October 2007

Purpose

To develop and demonstrate a method to calculate the temperature rise that is induced by the radio frequency (RF) field in MRI at the electrode of an implanted medical lead.

Materials and Methods

The electric field near the electrode is calculated by integrating the product of the tangential electric field and a transfer function along the length of the lead. The transfer function is numerically calculated with the method of moments. Transfer functions were calculated at 64 MHz for different lengths of model implants in the form of bare wires and insulated wires with 1 cm of wire exposed at one or both ends.

Results

Heating at the electrode depends on the magnitude and the phase distribution of the transfer function and the incident electric field along the length of the lead. For a uniform electric field, the electrode heating is maximized for a lead length of approximately one‐half a wavelength when the lead is terminated open. The heating can be greater for a worst‐case phase distribution of the incident field.

Conclusion

The transfer function is proposed as an efficient method to calculate MRI‐induced heating at an electrode of a medical lead. Measured temperature rises of a model implant in a phantom were in good agreement with the rises predicted by the transfer function. The transfer function could be numerically or experimentally determined. J. Magn. Reson. Imaging 2007;26:1278–1285. © 2007 Wiley‐Liss, Inc.
Measuring local RF heating in MRI: Simulating perfusion in a perfusionless phantom
Authors: Akca Imran B. , Ferhanoglu Onur , Yeung Christopher J. , Guney Sevin , Tasci T. Onur , Atalar Ergin
Published: October 2007

Purpose

To overcome conflicting methods of local RF heating measurements by proposing a simple technique for predicting in vivo temperature rise by using a gel phantom experiment.

Materials and Methods

In vivo temperature measurements are difficult to conduct reproducibly; fluid phantoms introduce convection, and gel phantom lacks perfusion. In the proposed method the local temperature rise is measured in a gel phantom at a timepoint that the phantom temperature would be equal to the perfused body steady‐state temperature value. The idea comes from the fact that the steady‐state temperature rise in a perfused body is smaller than the steady‐state temperature increase in a perfusionless phantom. Therefore, when measuring the temperature on a phantom there will be the timepoint that corresponds to the perfusion time constant of the body part.

Results

The proposed method was tested with several phantom and in vivo experiments. Instead, an overall average of 30.8% error can be given as the amount of underestimation with the proposed method. This error is within the variability of in vivo experiments (45%).

Conclusion

With the aid of this reliable temperature rise prediction the amount of power delivered by the scanner can be controlled, enabling safe MRI examinations of patients with implants. J. Magn. Reson. Imaging 2007;26:1228–1235. © 2007 Wiley‐Liss, Inc.
Full‐wave‐based transmission‐line model for lossy‐substrate multiconductor interconnects
Authors: Kordi Behzad , Bridges Greg E. , LoVetri Joe , Nordstrom John E.
Published: October 2007

A full‐wave‐based modal analysis is used for simulating a multiconductor coplanar waveguide (CPW) over a selectively etched lossy silicon substrate. Propagating modes, which are similar to the classic ‘common’ and ‘differential’ modes, are extracted, and circuit theory energy relationships are used for the determination of transmission‐line model parameters. A time‐frequency domain technique is employed for implementing the transmission‐line model within a circuit simulator. The model is used to study the effect of etching the dielectric and the substrate for a two‐conductor CPW line. The simulation results show that etching both the dielectric and the lossy substrate improves the loss and dispersion characteristics of the CPW line. Copyright © 2007 John Wiley & Sons, Ltd.
Cx29 and Cx32, two connexins expressed by myelinating glia, do not interact and are functionally distinct
Authors: Ahn Meejin , Lee Jonathan , Gustafsson Andreas , Enriquez Alan , Lancaster Eric , Sul Jai‐Yoon , Haydon Philip G. , Paul David L. , Huang Yan , Abrams Charles K. , Scherer Steven S.
Published: October 2007

In rodents, oligodendrocytes and myelinating Schwann cells express connexin32 (Cx32) and Cx29, which have different localizations in the two cell types. We show here that, in contrast to Cx32, Cx29 does not form gap junction plaques or functional gap junctions in transfected cells. Furthermore, when expressed together, Cx29 and Cx32 are not colocalized and do not coimmunoprecipitate. To determine the structural basis of their divergent behavior, we generated a series of chimeric Cx32‐Cx29 proteins by exchanging their intracellular loops and/or their C‐terminal cytoplasmic tails. Although some chimerae reach the cell membrane, others appear to be largely localized intracellularly; none form gap junction plaques or functional gap junctions. Substituting the C‐terminus or the intracellular loop and the C‐terminus of Cx32 with those of Cx29 does not disrupt their colocalization or coimmunoprecipitation with Cx32. Substituting the C‐terminus of Cx29 with that of Cx32 does not disrupt the coimmunoprecipitation or the colocalization with Cx29, whereas substituting both the intracellular loop and the C‐terminus of Cx32 with those of Cx29 diminishes the coimmunoprecipitation with Cx29. Conversely, the Cx32 chimera that contains the intracellular loop of Cx29 coimmunoprecipitates with Cx29, indicating that the intracellular loop participates in Cx29‐Cx29 interactions. These data indicate that homomeric interactions of Cx29 and especially Cx32 largely require other domains: the N‐terminus, transmembrane domains, and extracellular loops. Substituting the intracellular loop and/or tail of Cx32 with those of Cx29 appears to prevent Cx32 from forming functional gap junctions. © 2007 Wiley‐Liss, Inc.
Virtual 3D planning of acetabular fracture reduction
Authors: Citak Musa , Gardner Michael J. , Kendoff Daniel , Tarte Ségolène , Krettek Christian , Nolte Lutz‐Peter , Hüfner Tobias
Published: October 2007

Displaced acetabular fractures are best treated with open reduction to achieve anatomic reduction and maximize the chance of a good functional outcome. Because of the anatomic complexity and often limited visualization, fracture reduction can be difficult. Virtual planning software can allow the surgeon to understand the fracture morphology and to rehearse reduction maneuvers. The purpose of this study was to determine the effect of a novel virtual fracture reduction module on time and accuracy of reduction. Four acetabular fracture patterns were created in synthetic pelves, which were implanted with fiducial markers and were registered with CT scan. Ten surgeons used virtual fracture reduction software or conventional 2D planning methods and immediately reduced the fractures blindly in a viscous gel medium. 3D imaging was again performed and the accuracy of reduction was assessed. The average malreduction was significantly improved following planning with the virtual software compared to the standard technique. The time taken for reduction was also significantly less for two of the four fracture patterns. Virtual software may be useful for visualizing and planning treatment of fractures of the acetabulum, potentially leading to more accurate and efficient reductions, and may also be an effective educational tool. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:547–552, 2008
Effect of altered mechanical load conditions on the structure and function of cultured tendon fascicles
Authors: Abreu Eduardo L. , Leigh Diane , Derwin Kathleen A.
Published: October 2007

We have developed an in vitro model system to investigate the relationships between mechanical unloading and tendon matrix remodeling. Remodeling was characterized by changes in the functional and structural characteristics of rat tail tendon fascicles (RTTF) subjected to no load conditions for 1 week in vitro. We hypothesized that the absence of load will: (I) maintain cross‐sectional area (CSA), with decreased elastic modulus and increased stress‐relaxation; (II) cause an increase in denatured collagen and a decrease in water and total glycosaminoglycan (GAG) content. Fascicles cultured under a nominal static stress were used as control for culture conditions effects. Unloading resulted in a decrease of approximately 23% in the elastic modulus of cultured fascicles, consistent with previous stress‐deprivation studies. Contrary to our hypothesis, a nominal static stress caused an increase in elastic modulus (∼30%) and a significant decrease in stress‐relaxation when compared to fresh fascicles at 1% strain. Mechanical changes were associated with changes in the GAG content of the fascicles, but not their CSA, water, or collagen content. Furthermore, we did not find evidence of measurable denatured collagen in the cultured fascicles. Together these results suggest a role for GAG but not collagen or water in the elastic and viscoelastic changes measured in tendon fascicles cultured for 1 week under altered load conditions. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:364–373, 2008
The changing orientation of marketing: an emerging post‐modern perspective
Authors: Dekel Ofer , Prince Christopher , Beaver Graham
Published: October 2007

This paper argues that British society, together with the other parts of the post‐industrial world, is undergoing extraordinary change. Moreover, this change seems to be affecting all people and institutions. This paper argues that this transformation presents a number of challenges to current marketing orthodoxy and explores how marketing might need to evolve to operate in the emerging mass customization, post‐modern, post‐industrial environment.

The paper presents the argument that the new role of marketing in this post‐modern world will be to help individuals in consumer culture to increase their ability to choose identities and negotiate their position in society by the creative use of their lifestyles and consumption. While presenting real challenges, the new marketing landscape offers real business opportunities to those who are willing to engage with this new emerging reality.

Copyright © 2007 John Wiley & Sons, Ltd.
The evolution of business knowledge in SMEs: conceptualizing strategic space
Authors: Jones Oswald , Macpherson Allan , Thorpe Richard , Ghecham Adnan
Published: October 2007

This paper develops a conceptualization of the way in which owner‐managers in SMEs create strategic space. The term is defined as the time, resources, motivation and capabilities needed for owner‐managers to reflect on and review existing practices leading to learning, transformation and higher organizational performance.

The empirical data is based on a longitudinal study of 90 SMEs operating in six broad sectors. The analysis uses two statistical tests to examine links between 20 activities within these SMEs and their performance.

The results identify strong links between two groups of factors and positive performance claims by owner‐managers. Social attributes include work atmosphere, meetings and socializing. Structural attributes include training, knowledge structure, certification, systems and procedures.

Copyright © 2007 John Wiley & Sons, Ltd.
Online preconcentration using monoliths in electrochromatography capillary format and microchips
Authors: Augustin Violaine , Proczek Gaëlle , Dugay José , Descroix Stéphanie , Hennion Marie‐Claire
Published: October 2007

Online preconcentration and separation of analytes using an in situ photopolymerized hexyl acrylate‐based monolith stationary phase was evaluated using electrochromatography in capillary format and microchip. The band broadening occurring during the preconcentration process by frontal electrochromatography and during the desorption process by elution electrochromatography was studied. The hexyl acrylate‐based monolith provides high retention for neutral analytes allowing the handling of large sample volumes and its structure allows rapid mass transfer, thus reducing the band broadening. For moderately polar analytes such as mono‐chlorophenols that are slightly retained in water, it was shown that enrichment factors up to 3500 can be obtained by a hydrodynamic injection of several bed volumes for 120 min under 0.8 MPa with a decrease in efficiency of 50% and a decrease of 30% for the resolution between 2‐ and 3‐chlorophenol. An 8 min preconcentration time allows enrichment factors above 100 for polyaromatic hydrocarbons. The interest of these monoliths when synthesized in microchip is also demonstrated. A 200‐fold enrichment was easily obtained for PAHs with only 1 min as preconcentration time, without decrease in efficiency.
Kinetic modeling of aqueous phenol degradation by UV/H2O2 process
Authors: Edalatmanesh Maryam , Dhib Ramdhane , Mehrvar Mehrab
Published: October 2007

A dynamic kinetic model for the oxidation of phenol in water by an UV/H2O2 process is developed. The model is based on the elementary chemical and photochemical reactions, initiated by the photolysis of hydrogen peroxide into hydroxyl radicals. The model is validated by using experimental data obtained from the open literature for an actual UV/H2O2 process. Using those data and the developed kinetic model, kinetic rate constants for phenol intermediates, catechol and hydroquinone, are estimated. Moreover, the optimum initial hydrogen peroxide concentration is estimated by means of the validated model. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 40: 34–43, 2008
Orthodontic brackets removal under shear and tensile bond strength resistance tests – a comparative test between light sources
Authors: Silva P C G , Porto-Neto S T , Lizarelli R F Z , Bagnato V S
Published: October 2007

We have investigated if a new LEDs system has enough efficient energy to promote efficient shear and tensile bonding strength resistance under standardized tests. LEDs 470 ± 10 nm can be used to photocure composite during bracket fixation. Advantages considering resistance to tensile and shear bonding strength when these systems were used are necessary to justify their clinical use. Forty eight human extracted premolars teeth and two light sources were selected, one halogen lamp and a LEDs system. Brackets for premolar were bonded through composite resin. Samples were submitted to standardized tests. A comparison between used sources under shear bonding strength test, obtained similar results; however, tensile bonding test showed distinct results: a statistical difference at a level of 1% between exposure times (40 and 60 seconds) and even to an interaction between light source and exposure time. The best result was obtained with halogen lamp use by 60 seconds, even during re-bonding; however LEDs system can be used for bonding and re-bonding brackets if power density could be increased.
Photoresponsive New Polysiloxanes with 4‐Substituted Azobenzene Side‐Groups. Synthesis, Characterization and Kinetics of the Reversible Trans‐Cis‐Trans Isomerization
Authors: Hurduc Nicolae , Adès Dominique , Belleney Joël , Siove Alain , Sauvet Georges
Published: October 2007

New polydimethylsiloxanes with p‐substituted azobenzene side‐groups were synthesized. Thin films and solutions exhibit a photochemical trans‐cis isomerization of the azobenzene groups, followed by their cis‐trans thermal relaxation in the dark. In films, relaxation rates were found to be 100–1 000 times slower than the rates of photoisomerization, the former being very sensitive to the electron‐acceptor character of the substituents. in solution, the rates of cis‐trans relaxation are lower than those obtained for the solid state. This is ascribed to the dipolar intramolecular interactions between cis chromophores, which are favored in solution.

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Molecularly Imprinted Polymers for Cholecystokinin C‐Terminal Pentapeptide Recognition
Authors: Papaioannou Emmanuel H. , Liakopoulou‐Kyriakides Maria , Papi Rigini M. , Kyriakidis Dimitrios A.
Published: October 2007

Molecularly imprinted polymers (MIPs) have been prepared from methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as the functional monomer and crosslinker, respectively, for cholecystokinin C terminal pentapeptide (CCK‐5), and screened for their rebinding characteristics. They were produced with alterations in the molar ratio of template/monomer/crosslinker and the percentage of net rebinding and the imprinting factor (IF) were used for the evaluation of their imprinting efficacy. The dissociation constant values determined in the case of the polymers with better characteristics, further confirmed the results above. Scanning electron microscopy (SEM) images of MIPs were also obtained in an attempt to correlate their characteristics with polymer's morphology. Rebinding experiments with CCK‐5 and CCK‐8 peptides in the case of the polymer that presented higher performance, with net rebinding values 11.9 and 9%, respectively, indicated that this polymer may be a good candidate for the analysis of CCK‐related peptides.

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Silver Nanoparticles Stabilized by Thermoresponsive Microgel Particles: Synthesis and Evidence of an Electron Donor‐Acceptor Effect
Authors: Dong Yang , Ma Ying , Zhai Tianyou , Shen Fugang , Zeng Yi , Fu Hongbing , Yao Jiannian
Published: October 2007

Well‐dispersed silver nanoparticles were successfully fabricated within poly[(N‐isopropylacrylamide)‐co‐(acrylic acid)] [P(NIPAM‐co‐AA)] microgel particles which were synthesized with different cross‐linking densities. Their structures were studied by field‐emission scanning electron microscopy, transmission electron microscopy, UV‐vis spectroscopy, X‐ray diffraction and FT‐IR spectroscopy. The interactions between the microgel particles and the incorporated silver nanoparticles were investigated by X‐ray photoelectron spectroscopy. The results revealed that there was charge transfer from the carbonyl groups of the microgel particles to the silver nanoparticles. Moreover, as the diameter of the AgNPs decreases, the charge‐transfer efficiency increases accordingly. The P(NIPAM‐co‐AA)/AgNPs hybrid microgel particles were thermoresponsive and their behavior completely reversible with several heating/cooling cycles.

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Hierarchical Nanoporous Structures by Self‐Assembled Hybrid Materials Based on Block Copolymers
Authors: Fahmi Amir , Pietsch Torsten , Gindy Nabil
Published: October 2007

Hierarchical nanoporous structures are fabricated by adsorption of micelles of diblock copolymer‐templated Au‐nanoparticles onto a hydrophilic solid substrate. Gold nanoparticles are prepared using micelles (19 nm) of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) as nanoreactors. Deposition of thin films of the micellar solution, modified with a non‐selective solvent (THF), on hydrophilic surfaces leads to the formation of hierarchical nanoporous morphologies. The thin films exhibit two different pore diameters and a total pore density of 15 × 108 holes per cm2. The structure was analyzed in terms of topography and chemical composition using AFM, TEM and XPS measurements. The PS‐b‐P4VP template was subsequently removed by oxygen plasma etching, to leave behind metallic nanopores that mimic the original thin film morphology.

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A Template‐Free Route to Polypyrrole Nanofibers
Authors: Tran Henry D. , Shin Koo , Hong Won G. , D'Arcy Julio M. , Kojima Robert W. , Weiller Bruce H. , Kaner Richard B.
Published: October 2007

A template‐free method for the production of polypyrrole nanofibers is presented. By adding a small amount of bipyrrole into the oxidative polymerization of pyrrole, a drastic change in the morphology of the observed material is observed from large, granular particles to nanofibrils with an average diameter of 20 nm. This simple procedure allows for the production of polypyrrole nanofibers without the presence of surfactants or other structural directing agents. The polypyrrole nanofibers can form stable water dispersions which can be cast into films of sufficient quality to function as chemical sensors for analytes such as ammonia.

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Overlapping Schwarz waveform relaxation method for the solution of the convection–diffusion equation
Authors: Daoud Daoud S.
Published: October 2007

In this article we study the convergence of the overlapping Schwarz wave form relaxation method for solving the convection–diffusion equation over multi‐overlapped subdomains. It is shown that the method converges linearly and superlinearly over long and short time intervals, and the convergence depends on the size of the overlap. Numerical results are presented from solving specific types of model problems to demonstrate the convergence and the role of the size of the overlap. Copyright © 2007 John Wiley & Sons, Ltd.
Infinite boundary elements for electromagnetics
Authors: Chadwick Edmund
Published: October 2007

Consider a two‐dimensional plane wave transverse magnetic mode scattering from a perfectly electric conducting ground plane. Let the ground plane be of infinite extent and comprise two regions, a near field and a far field. In the far field, let the ground plane be flat and let us choose the co‐ordinates (x, y) such that it lies on the axis y=0. Over the interior region, let the profile of the ground plane change such that it can lie partially above and also partially below the axis y=0. Finally, let us assume that the source of the excitation lies above the ground plane.

To model this general class of problems, a method of moments electric field integral equation formulation is proposed which uses infinite boundary elements to model the far field and boundary elements to model the near field. In the far field, the field variable is approximated by the highest order terms in the far‐field asymptotic expansion. The integrals over the infinite boundary elements are infinite in extent and contain oscillatory terms and hence require special integration rules.

The formulation is tested for the specific problem of a semi‐circular cylindrical protrusion of radius a lying above an infinite flat ground plane, such that ka=1 where k is the wave number. This problem is chosen because it has an analytic solution in the form of a Bessel function expansion; hence, the accuracy of the formulation can be tested. In particular, the radar cross section results for various angles of incidence of the plane wave source are calculated and compared with analytic results. Copyright © 2007 John Wiley & Sons, Ltd.
Superconvergence and stability for boundary penalty techniques of finite difference methods
Authors: Li Zi‐Cai , Huang Hung‐Tsai , Huang Jin
Published: October 2007

The finite difference method (FDM) is used for Dirichlet problems of Poisson's equation, and the Dirichlet boundary condition is dealt with by boundary penalty techniques. Two penalty techniques, penalty‐integrals and penalty‐collocations (i.e., fixing), are proposed in this paper. The error bounds in the discrete H1 norm and the infinite norms are derived. The stability analysis is based on the new effective condition number (Cond_eff) but not on the traditional condition number (Cond). The bounds of Cond_eff are explored to display that both the penalty‐integral and the penalty‐collocation techniques have good stability; the huge Cond is misleading. Since the penalty‐collocation technique (i.e., the fixing technique) is simpler, it has been applied in engineering problem for a long time. It is worthy to point out that this paper is the first time to provide a theoretical justification for such a popular penalty‐collocation (fixing) technique. Hence the penalty‐collocation is recommended for dealing with the complicated constraint conditions such as the clamped and the simply support boundary conditions of biharmonic equations. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
Pronounced bilateral asymmetry of the complete upper extremity: a case from the early Neolithic Baikal, Siberia
Authors: Lieverse A. R. , Metcalf M. A. , Bazaliiskii V. I. , Weber A. W.
Published: October 2007

An adult male skeleton from the early Neolithic cemetery of Shamanka II on the south coast of Lake Baikal (Siberia, Russia) presents one of most striking examples of upper limb bilateral asymmetry documented without obvious indicators of skeletal pathology or trauma to the afflicted arm. The condition is noteworthy not only for its severity, with asymmetry values as high as 89.5%, but also for its involvement of the whole upper extremity, from clavicle to manual phalanges. The lack of any demonstrable hypertrophy on the unaffected left arm, and the clear evidence of extensive hypotrophy/atrophy on the right, leave little doubt that this asymmetry has a pathological or traumatic basis rather than a functional (activity‐induced) one. It most likely reflects paralysis or paresis of the entire right arm resulting from complete brachial palsy incurred prior to the attainment of skeletal maturity in that limb. Copyright © 2007 John Wiley & Sons, Ltd.
p53 and Mdm2: not all cells are equal
Authors: Coates PJ
Published: October 2007

The human TP53 gene is well known as a tumour suppressor. Less well appreciated are the potential roles of p53 in regulating postnatal development and the cell‐type specific effects of p53. In this issue of the Journal of Pathology, Lozano and colleagues show that p53 has the ability to block progenitor cell expansion in haematopoiesis and spermatogenesis but not in specific epithelial tissues. These data challenge the view that p53 acts equally in all cell types and have important implications for the applicability of p53 therapeutics in the treatment of human cancers. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Neurotrophin receptor expression in human primary retinoblastomas and retinoblastoma cell lines
Authors: Stephan Harald , Zakrzewski Johannes L. , Bölöni Réka , Grasemann Corinna , Lohmann Dietmar R. , Eggert Angelika
Published: October 2007

Background

Neurotrophin receptor signaling regulates proliferation, differentiation and death of neuronal cells. Expression of Trk receptors has been implicated in the pathogenesis and prognosis of embryonal tumors, including neuroblastoma, nephroblastoma, and medulloblastoma.

Procedure

We analyzed TrkA, TrkB, TrkC, and p75 expression using semi‐quantitative RT‐PCR in 23 retinoblastomas and 8 retinoblastoma cell lines. Comparison of mRNA expression with clinical variables as well as the proliferation (PI) and apoptotic index (AI) of the tumor, was performed by Pearson correlation analysis and two‐sample t‐test.

Results

Almost all tumor samples and cell lines demonstrated high expression of all Trk receptors. Expression of TrkB and its ligand, BDNF, was most pronounced, suggesting TrkB to be the major Trk receptor involved in retinoblastoma biology. In contrast, p75 expression was substantially reduced in a subset of tumors and cell lines, in particular compared to its expression in normal retina. Tumors with infiltrative growth demonstrated significantly lower relative levels of TrkC expression than localized tumors (P = 0.004). High expression of TrkA was associated with a higher AI (P = 0.04), and high expression of TrkC was associated with a younger age of the patients (P = 0.03). Inhibition of Trk signaling by K252a resulted in marked growth inhibition of retinoblastoma cells in vitro.

Conclusions

Our findings suggest a role for neurotrophin signaling in the biology of retinoblastoma. General Trk inhibitors are effective in decreasing growth rates of retinoblastoma cells in vitro, and should be evaluated in in vivo studies. Pediatr Blood Cancer 2008;50:218–222. © 2007 Wiley‐Liss, Inc.
Role of total skin electron beam therapy for leukemia cutis in pediatric patients
Authors: Pepek Joseph M. , Paulino Arnold C. , Briones Michael A. , Marcus Robert B. , Esiashvili Natia
Published: October 2007

The role of radiation therapy for those with leukemia cutis, particularly pediatric patients, remains unclear. This report describes the first two cases of disseminated leukemia cutis in adolescents treated with total skin electron beam therapy. Both patients had resolution of their skin disease and significant palliation of symptoms. Total skin electron irradiation is an option for adolescents suffering from significant extramedullary leukemia involving the skin. While it is uncertain if this treatment has any improvement in disease‐free survival, the benefits of total skin electron therapy for symptom palliation should be considered. Pediatr Blood Cancer 2008;50:1054–1055. © 2007 Wiley‐Liss, Inc.
Effect of the 1BL.1RS translocation on the wheat endosperm, as revealed by proteomic analysis
Authors: Gobaa Samy , Bancel Emmanuelle , Kleijer Geert , Stamp Peter , Branlard Gérard
Published: October 2007

The introduction of the 1RS chromosome of rye into wheat made wheat more resistant to several pathogens. Today, this resistance has been overcome but the 1BL.1RS translocation remains interesting because of the improved yield and despite the lower rheological properties it produces. Nothing has been reported yet on the impact of rye chromatin introgression on the grain proteome of wheat. The comparison of the 2‐DE profiles of 16 doubled haploid lines, with or without the 1BL.1RS translocation, revealed quantitative and qualitative proteic variations in prolamins and other endosperm proteins. Eight spots were found specifically in lines having the 1BL.1RS translocation; 16 other spots disappeared from the same lines. Twelve spots, present in both genotypes, met the criteria for up‐ or down‐regulated spots. In translocated genotypes, a highly overexpressed spot, identified as a γ‐gliadin with nine cysteine residues, suggests that the lack of LMW‐GS induced by 1BL.1RS is counterbalanced by an overexpression of a relatively similar prolamin. Moreover, a spot that was absent from 1BL.1RS genotypes was identified as a dimeric alpha‐amylase inhibitor. It was considered to be a valuable candidate to explain the sticky dough associated with translocated cultivars.
“Living”/controlled free radical polymerization of MMA in the presence of cobalt(II) 2‐ethylhexanoate: A switch from RAFT to ATRP mechanism
Authors: Zhang Zhengbiao , Zhang Wei , Zhu Xiulin , Cheng Zhenping , Zhu Jian
Published: October 2007

A metal complex, cobalt(II) 2‐ethylhexanoate (CEH), was added to the system of thermal‐initiated reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent at 115 °C. The polymerization rate was remarkably enhanced in the presence of CEH in comparison with that in the absence of CEH, and the increase of the CPDN concentration also accelerated the rate of polymerization. The polymerization in the concurrence of CPDN and CEH demonstrated the characters of “living”/controlled free radical polymerization: the number‐average molecular weights (Mn) increasing linearly with monomer conversion, narrow molecular weight distributions (Mw/Mn) and obtained PMMA end‐capped with the CPDN moieties. Meanwhile, CEH can also accelerate the rate of RAFT polymerization of MMA using the PMMA as macro‐RAFT agent instead of CPDN. Similar polymerization profiles were obtained when copper (I) bromide (CuBr)/N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine was used instead of CEH. Extensive experiments in the presence of butyl methacrylate, bis(cyclopentadienyl) cobalt(II) and cumyl dithionaphthalenoate were also conducted; similar results as those of MMA/CPDN/CEH system were obtained. A transition of the polymerization mechanism, from RAFT process without CEH addition to atom transfer radical polymerization in the presence of CEH, was possibly responsible for polymerization profiles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5722–5730, 2007
Synthesis of poly(4‐vinylpyridine) by reverse atom transfer radical polymerization
Authors: Lewis Gregory T. , Nguyen Van , Cohen Yoram
Published: October 2007

Controlled radical polymerization of 4‐vinylpyridine (4VP) was achieved in a 50 vol % 1‐methyl‐2‐pyrrolidone/water solvent mixture using a 2,2′‐azobis(2,4‐dimethylpentanitrile) initiator and a CuCl2/2,2′‐bipyridine catalyst–ligand complex, for an initial monomer concentration of [M]0 = 2.32–3.24 M and a temperature range of 70–80 °C. Radical polymerization control was achieved at catalyst to initiator molar ratios in the range of 1.3:1 to 1.6:1. First‐order kinetics of the rate of polymerization (with respect to the monomer), linear increase of the number–average degree of polymerization with monomer conversion, and a polydispersity index in the range of 1.29–1.35 were indicative of controlled radical polymerization. The highest number–average degree of polymerization of 247 (number–average molecular weight = 26,000 g/mol) was achieved at a temperature of 70 °C, [M]0 = 3.24 M and a catalyst to initiator molar ratio of 1.6:1. Over the temperature range studied (70–80 °C), the initiator efficiency increased from 50 to 64% whereas the apparent polymerization rate constant increased by about 60%. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5748–5758, 2007
Synthesis of PS and PDMAEMA mixed polymer brushes on the surface of layered silicate and their application in pickering suspension polymerization
Authors: Yang Yongfang , Zhang Jian , Liu Li , Li Chenxi , Zhao Hanying
Published: October 2007

An ammonium free radical initiator was ion exchanged onto the surface of clay layers. Polystyrene (PS) and poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) mixed polymer brushes on the surface of clay layers were prepared by in situ free radical polymerization. PS colloid particles armored by clay layers with mixed polymer brushes were prepared by Pickering suspension polymerization. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the colloid particles. Clay layers on the surface of PS colloid particles can be observed. Because of the cationic nature of the PDMAEMA brushes the colloid particles have positive zeta potentials at low pH values. X‐ray photoelectron spectroscopy (XPS) was used to analyze the surface of the colloid particles. N1s binding energy of PDMAEMA chains on the surface of clay layers was detected by XPS. The two peaks of the N1s binding energy indicate two different nitrogen environments on the surface of clay layers. The peak with a lower binding energy is characteristic of neutral nitrogen on PDMAEMA chains, and the peak with a higher binding energy is attributed to protonated nitrogen on PDMAEMA chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5759–5769, 2007
Fluorinated bio‐acceptable polymers via an ATRP macroinitiator approach
Authors: Hansen Natanya M. L. , Haddleton David M. , Hvilsted Søren
Published: October 2007

Polymers derived from bio‐acceptable poly(methyl methacrylate) (PMMA), poly(2‐methoxyethyl acrylate) (PMEA), and poly(oligo(ethylene glycol) methyl ether methacrylate) (PPEGMA) have been prepared via atom transfer radical polymerization (ATRP) utilizing an initiator prepared from a fluoroalkoxy‐terminated oligoethylene glycol. Polymerizations are controlled as seen by both linear first‐order kinetics and molecular weight evolution coupled with low polydispersities (<1.25) with respect to conversion. A range of ligands have been used depending upon the nature of the monomer: N‐(n‐propyl)‐2‐pyridyl‐methanimine with the methacrylates MMA and PEGMA and 1,1,4,7,10,10‐hexamethyltriethylene tetramine (HMTETA) with MEA. In all cases the use of the fluorinated initiator results in a lower apparent rate of propagation (kpapp) as compared with the more conventional and nonfluorinated initiator, ethyl 2‐bromoisobutyrate. The initiator generally also serves as an internal plasticizer lowering the glass transition temperature from the parent polymers. The surface characteristics of the fluoroinitiator containing polymers are altered compared with the nonfluorinated analogues. This is reflected in a significant increase in the advancing water contact angles of all fluoro‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5770–5780, 2007
Nanopore microspheres prepared by a cationic surfmer in the miniemulsion polymerization of styrene
Authors: Cao Nana , Wang Xinbo , Song Lingyong , Zhang Zhi Cheng
Published: October 2007

A polymerizable cationic quaternary ammonium surfactant (CQAS) based on 2‐(dimethylamino)ethyl methacrylate (DMAEMA) was successfully synthesized via quaternization reaction. The product was characterized by FTIR and 1H NMR spectroscopy, and its critical micelle concentration (CMC) was obtained by surface tension measurement. The surfmer acted well as comonomer and surfactant to stabilize monomer droplets during miniemulsion polymerization. To identify whether this system undergoes miniemulsion nucleation mechanism, surface tension, particle size, and Ndroplet/Nparticle of the system were also measured. The effect of concentration and counter‐ion of the surfmer, and pH value of the system were systematically investigated by kinetic analysis and dynamic light scattering (DLS). The resulting nanopore microspheres were observed by transmission electron micrograph (TEM) and field emission scanning electron micrograph (FESEM) and showed the nanopore morphology with reasonable stability. Another cationic surfactant cetyltrimethylammonium bromide (CTAB) was used for comparative studies. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5800–5810, 2007
Science and technology of perfluorocyclobutyl aryl ether polymers
Authors: Iacono Scott T. , Budy Stephen M. , Jin Jianyong , Smith, Dennis W.
Published: October 2007

This article highlights the preparation of perfluorocyclobutyl (PFCB) aryl ether polymers for a multitude of commercial technologies that are of academic and commercial global interest. In this account, the synthesis of various aryl trifluorovinyl ether (TFVE) monomers tailored for specific applications is discussed. The preparation of PFCB aryl ether polymers and their properties is then presented. Topics of PFCB aryl ether polymers and their applications include photonics, polymer light emitting diodes (PLEDs), proton exchange membranes (PEMs) for fuel cells, atomic oxygen (AO) resistant coatings, and hybrid composites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5705–5721, 2007
Polymer nanocomposites
Authors: Krishnamoorti Ramanan , Vaia Richard A.
Published: October 2007

Polymer nanocomposites are distinguished by the convergence of length scales corresponding to the radius of gyration of the polymer chains, a dimension of the nanoparticle and the mean distance between the nanoparticles. The consequences of this convergence on the physics of the polymer chains are considered, and some of the outstanding issues and their potential consequences on structure—property relations for polymer nanocomposites are highlighted. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3252–3256, 2007
Effects of structural imperfections on the dynamic mechanical response of main‐chain smectic elastomers
Authors: Patil Harshad P. , Hedden Ronald C.
Published: October 2007

We examine the influence of structural imperfections on mechanical damping in polydomain smectic main‐chain liquid crystalline elastomers (MCLCE) subjected to small strain oscillatory shear. The mechanical loss factor tan δ = G″(ω)/G′(ω) exhibits a strong maximum (tan δ ≈ 1.0) near the smectic‐isotropic (clearing) transition. “Optimal” elastomers that exhibit minimal equilibrium swelling in a good solvent are compared with highly swelling “imperfect elastomers” that contain higher concentrations of structural imperfections such as pendant chains. For the imperfect elastomers, tan δ is markedly enhanced in the isotropic state because of relaxation of pendant chains and other imperfections. However, within the smectic state, the magnitude of tan δ and its temperature dependence are similar for optimal and imperfect elastomers at ω = 1 Hz. The prominent loss peak near the clearing transition arises from segment‐level relaxations that are insensitive to the details of chain connectivity. Smectic MCLCE can be tailored for applications as vibration‐damping materials by manipulating the clearing transition temperature through the backbone structure or by deliberate introduction of structural imperfections such as pendant chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3267–3276, 2007
Looking inside the entanglement “tube” using molecular dynamics simulations
Authors: Larson Ronald G.
Published: October 2007

For 30 years, the dynamics of entangled polymers have been explained using the phenomenological “tube” model, where the “tube” represents the confining effects of surrounding chains, but the tube properties, such as its length and diameter, could only be inferred indirectly by fitting the tube model to rheological data. Now, however, molecular simulations are allowing these properties to be directly computed. The computational advances in molecular dynamics and related methods that have made this possible are here reviewed. In addition, it is discussed how new findings, such as an apparent time dependence of the tube diameter and direct observation of “hopping” of branch points along the tube, are helping to refine the tube model. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3240–3248, 2007
Modeling the accessible conformations of the intrinsically unstructured transactivation domain of p53
Authors: Lowry David F. , Stancik Amber , Shrestha Ranjay Mann , Daughdrill Gary W.
Published: October 2007

Internuclear distances derived from paramagnetic relaxation enhancement (PRE) data were used to restrain molecular dynamics simulations of the intrinsically unstructured transactivation domain of the tumor suppressor protein, p53. About 1000 structures were simulated using ensemble averaging of replicate molecules to compensate for the inherent bias in the PRE‐derived distances. Gyration radii measurements on these structures show that the p53 transactivation domain (p53TAD) is statistically predominantly in a partially collapsed state that is unlike the open structure that is found for p53TAD bound to either the E3 ubiquitin ligase, MDM2, or the 70 kDa subunit of replication protein A, RPA70. Contact regions that potentially mediate the collapse were identified and found to consist of mostly hydrophobic residues. The identified contact regions preferentially place the MDM2 and RPA70 binding regions in close proximity. We show that our simulations thoroughly sample the available range of conformations and that a fraction of the molecules are in an open state that would be competent for binding either MDM2 or RPA70. We also show that the Stokes radius estimated from the average gyration radius of the ensemble is in good agreement with the value determined using size exclusion chromatography. Finally, the presence of a persistent loop localized to a PXP motif was identified. Serine residues flanking the PXP motif become phosphorylated in response to DNA damage, and we postulate that this will perturb the equilibrium population to more open conformations. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Identification of GATC‐ and CCGG‐recognizing Type II REases and their putative specificity‐determining positions using Scan2S—A novel motif scan algorithm with optional secondary structure constraints
Authors: Niv Masha Y. , Skrabanek Lucy , Roberts Richard J. , Scheraga Harold A. , Weinstein Harel
Published: October 2007

Restriction endonucleases (REases) are DNA‐cleaving enzymes that have become indispensable tools in molecular biology. Type II REases are highly divergent in sequence despite their common structural core, function and, in some cases, common specificities towards DNA sequences. This makes it difficult to identify and classify them functionally based on sequence, and has hampered the efforts of specificity‐engineering. Here, we define novel REase sequence motifs, which extend beyond the PD‐(D/E)XK hallmark, and incorporate secondary structure information. The automated search using these motifs is carried out with a newly developed fast regular expression matching algorithm that accommodates long patterns with optional secondary structure constraints. Using this new tool, named Scan2S, motifs derived from REases with specificity towards GATC‐ and CGGG‐containing DNA sequences successfully identify REases of the same specificity. Notably, some of these sequences are not identified by standard sequence detection tools. The new motifs highlight potential specificity‐determining positions that do not fully overlap for the GATC‐ and the CCGG‐recognizing REases and are candidates for specificity re‐engineering. Proteins 2008. © 2007 Wiley‐Liss, Inc.
High‐throughput allelic discrimination of B and Q biotypes of the whitefly, Bemisia tabaci, using TaqMan allele‐selective PCR
Authors: Jones Christopher M , Gorman Kevin , Denholm Ian , Williamson Martin S
Published: October 2007

BACKGROUND: B and Q biotypes of the whitefly, Bemisia tabaci (Gennadius), are generally regarded as the most significant given their global distribution and strong resistance to insecticides. Since these biotypes can coexist and differ markedly in their insecticide resistance profiles, a rapid but reliable means of discriminating between them would be a valuable complement to resistance monitoring and management programmes. Recently, PCR‐based methods have been developed to determine the biotype status of B. tabaci populations. However, these require post‐amplification procedures, which increase time and labour.

RESULTS: The authors have developed an allelic discrimination real‐time PCR assay using fluorescent dye‐labelled probes to distinguish the B and Q biotypes. The assay targets a single nucleotide polymorphism (SNP) in the mitochondrial cytochrome oxidase I (mtCOI) gene. To evaluate the assay, DNA was extracted from individual whiteflies of six known biotype strains, and all scored correctly as either a B or Q biotype. As further validation, 72 individuals from field samples collected in different parts of the world were also tested by the assay. No failed reactions were observed, with all 72 samples scoring clearly as either the B or Q biotype.

CONCLUSION: The development of this rapid and high‐throughput assay has important potential for routine monitoring of B and Q biotypes on ornamental plants and for the screening of B. tabaci populations in countries where these biotypes are not yet established. Copyright © 2007 Society of Chemical Industry