bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance comparison of three types of GPU‐accelerated indirect boundary element method for voxel model analysis
Authors: Hamada Shoji
Published: February 2013

An indirect boundary element method that is geared to electrostatic field analysis in voxel models is accelerated by graphics processing units (GPUs). The method considers square walls on cubic voxels as boundary surface elements and uses the fast multipole method (FMM) to analyze large‐scale models. On the basis of two conventional CPU codes, three GPU codes are programmed in search of higher computing performance. These GPU codes are designed as follows: In GPU code 1, direct and far fields in the FMM are simultaneously calculated on the GPU and the CPU, respectively; in GPU code 2, both fields are calculated on the GPU with a rotation‐coaxial translation–rotation decomposition algorithm; and in GPU code 3, both fields are calculated on the GPU with a diagonal translation scheme. The electric fields in human models are generated by applying a 50‐Hz magnetic field or by injecting direct‐current (DC) current through two electrodes and they were calculated successfully using a personal computer with three GPUs and six CPU cores. An analysis with 3.9 million surface elements took 89.4 s to solve its governing linear system with double‐precision floating‐point arithmetic. GPU codes 1, 2, and 3 demonstrated the least memory usage, the greatest speed‐up ratio, and the fastest calculation time, respectively. These results show an example of the trade‐off relationships of computation performances on a heterogeneous CPU–GPU system. Copyright © 2013 John Wiley & Sons, Ltd.
Patterns of prophylactic gastrostomy tube placement in head and neck cancer patients: A consideration of the significance of social support and practice variation
Authors: Locher Julie L. , Bonner James A. , Carroll William R. , Caudell Jimmy J. , Allison Jeroan J. , Kilgore Meredith L. , Ritchie Christine S. , Tajeu Gabriel S. , Yuan Ya , Roth David L.
Published: February 2013

Objectives/Hypothesis

The purpose of this study was to examine factors associated with prophylactic placement of feeding tubes in head and neck cancer patients receiving radiation therapy as a part of treatment using multilevel models that account for patient‐, physician‐, and institution‐level sources of variation.

Study Design

A retrospective analysis using binary logistic regression and hierarchical linear models was run to evaluate independent predictors of prophylactic feeding tube placement.

Methods

Surveillance, Epidemiology, and End Results–Medicare data were used. Head and neck cancer patients diagnosed with locoregionally advanced stage disease from 2000 to 2005 were included in this study (N = 8,306).

Results

Across all models, prophylactic gastrostomy tube placement was found to be more likely in patients who had cancer of the larynx or oropharynx compared with those with cancer of the nasopharynx or oral cavity; who had regional instead of local cancer; who did not receive surgery as a part of treatment, but did receive chemotherapy; and who were divorced, separated, or widowed. Additionally, although practice variation was observed to occur, its overall contribution in predicting prophylactic gastrostomy tube placement was minimal.

Conclusions

As health care enters an era of patient‐centered care, further investigation of the potential role of social support (or lack of social support) in influencing treatment decisions of head and neck cancer patients and providers is warranted.

Level of Evidence

2b Laryngoscope, 123:1918–1925, 2013
Facile One‐Pot Synthesis of a Polyvinylpyrrolidone‐Based Self‐Crosslinked Fluorescent Film
Authors: Yin Meizhen , Ye Yong , Sun Mengmeng , Kang Naiwen , Yang Wantai
Published: February 2013

A polyvinylpyrrolidone (PVP)‐based fluorescent film with stable optical properties is successfully prepared in one pot without any additive. The reaction mechanism of ring‐opening and self‐crosslinking of linear PVP is proposed and demonstrated. The morphologies and the nanostructures of the fluorescent film as well as the unmodified film are investigated. The dye is incorporated into the film networks via covalent linkages, thus leading to the highly stable optical properties. The facile and effective synthesis approach opens a new way for the design of other multi‐functional composite materials based on linear PVP.

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Formation of Integral Asymmetric Membranes of AB Diblock and ABC Triblock Copolymers by Phase Inversion
Authors: Jung Adina , Filiz Volkan , Rangou Sofia , Buhr Kristian , Merten Petra , Hahn Janina , Clodt Juliana , Abetz Clarissa , Abetz Volker
Published: February 2013

The formation of integral asymmetric membranes from ABC triblock terpolymers by non‐solvent‐induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐b‐P2VP‐b‐PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post‐functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements.

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Obstacles to the Development of a Neuroprotective Therapy for Parkinson's Disease
Authors: Stocchi Fabrizio , Olanow C. Warren
Published: February 2013

A neuroprotective or disease‐modifying therapy that can slow or stop disease progression and prevent the development of intolerable disability is the major unmet medical need in the treatment of Parkinson's disease (PD). Many putative neuroprotective agents have been identified in the laboratory, but none has been unequivocally demonstrated to provide disease‐modifying effects in PD patients, even when clinical trials are positive. Obstacles to defining a neuroprotective therapy in PD include: (1) uncertainty about the cause of PD and precisely what to target, (2) a reliable animal model in which to test putative neuroprotective agents that accurately predicts results in PD patients, (3) insight about which dose to employ in clinical trials and which patient group to study, (4) a clinical trial design that reliably differentiates disease‐modifying and symptomatic effects and that is acceptable to regulatory authorities, and (5) the cost and time of the development program. Advances have been made in each of these areas, thereby increasing the prospects of developing a neuroprotective or disease‐modifying therapy in the not‐too‐distant future. These issues are reviewed in the present article. © 2013 Movement Disorder Society
Trophic Factor Gene Therapy for Parkinson's Disease
Authors: Kordower Jeffrey H. , Bjorklund Anders
Published: February 2013

Parkinson's disease (PD) is a chronic and progressive neurodegenerative movement disorder for which there is presently no cure. Pharmacological remedies targeting the dopaminergic network are relatively effective at ameliorating motor deficits, especially in the early stages of the disease, but none of these therapies are curative and many generate their own problems. Recent advances in PD research have demonstrated that gene delivery of trophic factors, glial cell line–derived neurotrophic factor (GDNF) and neurturin, in particular, can provide structural and functional recovery in rodent and nonhuman primate models of PD. Similar success has been gleaned in open‐label clinical trials, although this has yet to be realized in double‐blinded analyses. This work reviews the field of trophic factor gene delivery for PD. © 2013 Movement Disorder Society
Parkinson's Disease and Alpha Synuclein: Is Parkinson's Disease a Prion‐Like Disorder?
Authors: Olanow C. Warren , Brundin Patrik
Published: February 2013

Altered protein handling is thought to play a key role in the etiopathogenesis of Parkinson's disease (PD), as the disorder is characterized neuropathologically by the accumulation of intraneuronal protein aggregates (Lewy bodies and Lewy neurites). Attention has particularly focused on the α‐synuclein protein, as it is the principal component of Lewy pathology. Moreover, point mutations in the α‐synuclein gene cause rare familial forms of PD. Importantly, duplication/triplication of the wild type α‐synuclein gene also cause a form of PD, indicating that increased levels of the normal α‐synuclein protein is sufficient to cause the disease. Further, single nucleotide polymorphisms in the α‐synuclein gene are associated with an increased risk of developing sporadic PD. Recent evidence now suggests the possibility that α‐synuclein is a prion‐like protein and that PD is a prion‐like disease. Within cells, α‐synuclein normally adopts an α‐helical conformation. However, under certain circumstances, the protein can undergo a profound conformational transition to a β‐sheet–rich structure that polymerizes to form toxic oligomers and amyloid plaques. Recent autopsy studies of patients with advanced PD who received transplantation of fetal nigral mesencephalic cells more than a decade earlier demonstrated that typical Lewy pathology had developed within grafted neurons. This suggests that α‐synuclein in an aberrantly folded, β‐sheet–rich form had migrated from affected to unaffected neurons. Laboratory studies confirm that α‐synuclein can transfer from affected to unaffected nerve cells, where it appears that the misfolded protein can act as a template to promote misfolding of host α‐synuclein. This leads to the formation of larger aggregates, neuronal dysfunction, and neurodegeneration. Indeed, recent reports demonstrate that a single intracerebral inoculation of misfolded α‐synuclein can induce Lewy‐like pathology in cells that can spread from affected to unaffected regions and can induce neurodegeneration with motor disturbances in both transgenic and normal mice. Further, inoculates derived from the brains of elderly α‐synuclein–overexpressing transgenic mice have now been shown to accelerate the disease process when injected into the brains of young transgenic animals. Collectively, these findings support the hypothesis that α‐synuclein is a prion‐like protein that can adopt a self‐propagating conformation that causes neurodegeneration. We propose that this mechanism plays an important role in the development of PD and provides novel targets for candidate neuroprotective therapies. © 2013 Movement Disorder Society
Efficient bloch‐siegert B1+ mapping using spiral and echo‐planar readouts
Authors: Saranathan Manojkumar , Khalighi Mohammad Mehdi , Glover Gary H. , Pandit Prachi , Rutt Brian K.
Published: February 2013

The Bloch‐Siegert (B‐S) B1+ mapping technique is a fast, phase‐based method that is highly SAR limited especially at 7T, necessitating the use of long repetition times. Spiral and echo‐planar readouts were incorporated in a gradient‐echo based B‐S sequence to reduce specific absoprtion rate (SAR) and improve its scan efficiency. A novel, numerically optimized 4 ms B‐S off‐resonant pulse at + 1960 Hz was used to increase sensitivity and further reduce SAR compared with the conventional 6 ms Fermi B‐S pulse. Using echo‐planar and spiral readouts, scan time reductions of 8–16 were achieved. By reducing the B‐S pulse width by a factor of 1.5, SAR was reduced by a factor of 1.5 and overall sensitivity was increased by a factor of 1.33 due to the nearly halved resonance offset of the new B‐S pulse. This was validated on phantoms and volunteers at 7 T. Magn Reson Med 70:1669–1673, 2013. © 2013 Wiley Periodicals, Inc.
Induced clustered nanoconfinement of superparamagnetic iron oxide in biodegradable nanoparticles enhances transverse relaxivity for targeted theranostics
Authors: Ragheb Ragy R. T. , Kim Dongin , Bandyopadhyay Arunima , Chahboune Halima , Bulutoglu Beyza , Ezaldein Harib , Criscione Jason M. , Fahmy Tarek M.
Published: February 2013

Purpose

Combined therapeutic and diagnostic agents, “theranostics” are emerging valuable tools for noninvasive imaging and drug delivery. Here, we report on a solid biodegradable multifunctional nanoparticle that combines both features.

Methods

Poly(lactide‐co‐glycolide) nanoparticles were engineered to confine superparamagnetic iron oxide contrast for magnetic resonance imaging while enabling controlled drug delivery and targeting to specific cells. To achieve this dual modality, fatty acids were used as anchors for surface ligands and for encapsulated iron oxide in the polymer matrix.

Results

We demonstrate that fatty acid modified iron oxide prolonged retention of the contrast agent in the polymer matrix during degradative release of drug. Antibody‐fatty acid surface modification facilitated cellular targeting and subsequent internalization in cells while inducing clustering of encapsulated fatty‐acid modified superparamagnetic iron oxide during particle formulation. This induced clustered confinement led to an aggregation within the nanoparticle and, hence, higher transverse relaxivity, r2, (294 mM−1 s−1) compared with nanoparticles without fatty‐acid ligands (160 mM−1 s−1) and higher than commercially available superparamagnetic iron oxide nanoparticles (89 mM−1 s−1).

Conclusion

Clustering of superparamagnetic iron oxide in poly(lactide‐co‐glycolide) did not affect the controlled release of encapsulated drugs such as methotrexate or clodronate and their subsequent pharmacological activity, thus highlighting the full theranostic capability of our system. Magn Reson Med 70:1748–1760, 2013. © 2013 Wiley Periodicals, Inc.
Water/fat‐resolved whole‐heart Dixon coronary MRA: An initial comparison
Authors: Börnert Peter , Koken Peter , Nehrke Kay , Eggers Holger , Ostendorf Peter
Published: February 2013

Purpose

To improve coronary vessel visualization in whole‐heart coronary magnetic resonance angiography (CMRA), fat suppression is typically applied. However, recent studies have shown that cardiac fat can also have diagnostic value. To enhance CMRA image quality by improved fat suppression and to provide additionally fat‐only information highly resolved, dual‐echo Dixon CMRA approaches have been developed.

Methods

In this pilot study, approved by the institutional review board, 30 patients were investigated comparing whole‐heart T1‐weighted dual‐echo Dixon CMRA to conventional whole‐heart fat‐suppressed balanced fast field echo CMRA, integrated into a routine clinical protocol that includes the administration of gadolinium for perfusion and late enhancement measurements. Signal‐to‐noise‐ratio, contrast‐to‐noise‐ratio, and image quality were analyzed.

Results

Dual‐echo Dixon significantly (P<0.000001) improved image quality compared with conventional fat‐suppressed balanced fast field echo CMRA. Signal‐to‐noise‐ratio and contrast‐to‐noise‐ratio were found to be comparable when balanced fast field echo was performed before gadolinium and dual‐echo Dixon fast field echo after gadolinium administration.

Conclusion

Dual‐echo Dixon can help to improve whole‐heart CMRA image quality significantly. The additional whole‐heart fat information delivered by this approach can support a number of new clinical studies addressing the diagnostic and the predictive value of intramyocardial and extramyocardial fatty deposits. Magn Reson Med 71:156–163, 2014. © 2013 Wiley Periodicals, Inc.
Inspection games with local and global allocation bounds
Authors: Deutsch Yael , Golany Boaz , Goldberg Noam , Rothblum Uriel G.
Published: February 2013

This article discusses a two‐player noncooperative nonzero‐sum inspection game. There are multiple sites that are subject to potential inspection by the first player (an inspector). The second player (potentially a violator) has to choose a vector of violation probabilities over the sites, so that the sum of these probabilities do not exceed one. An efficient method is introduced to compute all Nash equilibria parametrically in the amount of resource that is available to the inspector. Sensitivity analysis reveals nonmonotonicity of the equilibrium utility of the inspector, considered as a function of the amount of resource that is available to it; a phenomenon which is a variant of the well‐known Braess paradox. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013
miR‐29a inhibition normalizes HuR over‐expression and aberrant AU‐rich mRNA stability in invasive cancer
Authors: Al‐Ahmadi Wijdan , Al‐Ghamdi Maha , Al‐Souhibani Norah , Khabar Khalid SA
Published: February 2013

The activities of RNA‐binding proteins are perturbed in several pathological conditions, including cancer. These proteins include tristetraprolin (TTP, ZFP36) and HuR (ELAVL1), which respectively promote the decay or stability of adenylate‐uridylate‐rich (AU‐rich) mRNAs. Here, we demonstrated that increased stabilization and subsequent over‐expression of HuR mRNA were coupled to TTP deficiency. These findings were observed in breast cancer cell lines with an invasive phenotype and were further confirmed in ZFP36‐knockout mouse fibroblasts. We show that TTP–HuR imbalance correlated with increased expression of AU‐rich element (ARE) mRNAs that code for cancer invasion genes. The microRNA miR‐29a was abundant in invasive breast cancer cells when compared to non‐tumourigenic cell types. When normal breast cells were treated with miR‐29a, HuR mRNA and protein expression were up‐regulated. MiR‐29a recognized a seed target in the TTP 3′ UTR and a cell‐permeable miR‐29a inhibitor increased TTP activity towards HuR 3′ UTR. This led to HuR mRNA destabilization and restoration of the aberrant TTP–HuR axis. Subsequently, the cancer invasion factors uPA, MMP‐1 and MMP‐13, and cell invasiveness, were decreased. The TTP:HuR mRNA ratios were also perturbed in samples from invasive breast cancer patients when compared with normal tissues, and were associated with invasion gene expression. This study demonstrates that an aberrant ARE‐mediated pathway in invasive cancer can be normalized by targeting the aberrant and functionally coupled TTP–HuR axis, indicating a potential therapeutic approach. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
An elaboration on the shear characterization of dry woven fabrics using trellising tests
Authors: Komeili M. , Milani A.S.
Published: February 2013

Material characterization of woven fabric composites in dry form is one of the most crucial steps prior to the design and optimization of composite manufacturing processes. High stiffness of yarns under axial tension and low stiffness under in‐plane shear makes the latter the dominant deformation mode during draping of woven fabrics. Bias‐extension (BE) and shear frame (SF) tests are two widely used experimental setups for the characterization of woven fabrics under the shear (also called trellising) mode. This article outlines two general approaches for the characterization and normalization of data collected from the above standard tests. The first approach is based on the total energy absorbed by the fabric specimen along with the total work induced by the external force on the moving head of the tensile test machine. The second approach uses a variational formulation along with the principle of virtual work. Using both approaches, it is shown how, in the BE test, an auxiliary specimen with a different aspect ratio can be used to cope with the problem of nonuniform deformation (formation of three different shear regions) in the specimens. To illustrate the application of both methods, they are applied to predict in‐plane shear stiffness of a glass/PP plain weave under SF and BE tests. It is suggested that the shear stress can be used as a normalized parameter to compare data from different trellising tests. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Effect of plasma modification on the mechanical properties of carbon fiber/phenolphthalein polyaryletherketone composites
Authors: Li Wei , Yao Shu Yong , Ma Ke Ming , Chen Ping
Published: February 2013

A study was carried out to investigate the effect of plasma modification on the mechanical properties of carbon fiber/phenolphthalein polyaryletherketone composites. The influence of oxygen plasma treatment on the surface properties of carbon fibers was investigated by X‐ray photoelectron spectroscopy and atomic force microscopy. The results indicated that oxygen plasma treatment was capable of increasing the concentrations of the oxygen‐containing groups of the carbon fiber surface as well as enhancing surface roughness. Both the chemical bonding and mechanical interlocking gave rise to an increase of the interlaminar shear strength of composite. Scanning electron microscope photographs showed that the destruction mode of composites was changed after the carbon fibers were treated by oxygen plasma. The results also indicated that the flexural properties of plasma‐treated carbon fiber composites were improved. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Investigation of the effect of different silane coupling agents on mechanical performance of basalt fiber composite laminates with biobased epoxy matrices
Authors: España J.M. , Samper M.D. , Fages E. , Sánchez‐Nácher L. , Balart R.
Published: February 2013

In recent years, it has been detected an increased interest in the development of materials from renewable resources. This trend has been intensified in the industrial sector where significant efforts have been made in this field in order to adapt these natural fibers to conventional industrial processes and applications. As a result, research has been done into developing new thermoplastic matrices which are compatible with this type of reinforcing fibers. This study evaluates the influence of different coupling agents based on silanes, on the mechanical properties of composite laminates made from a biobased epoxy resin matrix and basalt fabric by using vacuum assisted resin transfer moulding. The curing behavior of the biobased epoxy resin was evaluated by differential scanning calorimetry (DSC), gel point determination, and ionic conductivity. The evaluation of mechanical properties was done by tensile, flexural, impact, and hardness tests. Compatibility between basalt fibers and epoxy resin generally has managed to increase through the addition of silanes, after the addition of these, their mechanical properties are substantially improved compared to the sample without silane treatment, obtaining this way an easily processable material, with good properties and capable of competing with materials with petroleum‐based epoxy resins. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Orientated CNT‐polypropylene nanocomposite films made from extruded monofilaments
Authors: Tanami Golan A. , Wachtel Ellen , Marom Gad
Published: February 2013

In this study, a method for making an orientated polymer nanocomposite film was developed. Melt‐drawn nanocomposite monofilaments of isotactic polypropylene and acicular nanofillers, i.e. carbon nanotubes (CNT) or vapor grown carbon nanofibers (VGCF), were prepared and characterized from the aspect of polymer chain orientation, mechanical properties, and overall morphology. A marked improvement in mechanical properties was observed as a function of the addition of CNT, increasing draw down ratio (DDR) and annealing. Nanocomposite films were prepared from drawn monofilaments by hot‐pressing under low pressure in order to maintain the orientation of the monofilaments. Wide angle X‐ray diffraction showed a high degree of residual orientation in the films. Electron microscopy (high‐resolution scanning electron microscopy, transmission electron microscopy) unexpectedly revealed that the CNT‐matrix interface is amorphous. However, differential scanning calorimetry found no measurable influence of the CNT on the overall crystallinity as determined by the enthalpy of melting of the matrix. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Simulation of polymer flow using smoothed particle hydrodynamics method
Authors: Riviere S. , Khelladi S. , Farzaneh S. , Bakir F. , Tcharkhtchi A.
Published: February 2013

Reactive rotational molding (RRM) is a process to manufacture hollow plastic articles. Comparing to rotational molding of thermoplastics, it decreases the process cycle time due to the reactivity of the system. However, the number of influent parameters is relatively high and optimization of the process is complex. During RRM, the viscosity is one of the key parameters and varies according to the polymer molecular weight due to chemical reactions. Simulation is a way to optimize this process. Prediction of the reactive flow is of great interest to optimize process conditions and wall thickness distribution of the molded part. We developed a solver based on smoothed particle hydrodynamics method. This Lagrangian meshfree method is well adapted to simulate free surface flows like those occurring in RRM. First, we validated the code comparing the simulation results to analytical Couette flow solution and experimental measurements of dam break problem. Then, we performed two‐dimensional (2D) and 3D simulations to observe the influence of the change of viscosity on the flow, due to the chemical reactions. Adhesion of the polymer on the mold surface is modeled by new boundary conditions. POLYM. ENG. SCI., 53:2509–2518, 2013. © 2013 Society of Plastics Engineers
EVOLUTION, NOT REVOLUTION: SCHOOL PSYCHOLOGISTS’ CHANGING PRACTICES IN DETERMINING SPECIFIC LEARNING DISABILITIES
Authors: Unruh Susan , Mckellar Nancy A.
Published: February 2013

The profession of school psychology has been impacted by the response to intervention (RTI) model in various ways. RTI data are being used to make decisions regarding academic and behavioral interventions and to make eligibility determinations in comprehensive evaluations conducted by multidisciplinary teams. A survey of almost 400 school psychologist practitioners reveals a changing landscape in terms of school psychologists’ methods of determining eligibility for specific learning disabilities (SLD) in RTI site and non‐RTI site schools. The survey also brings to light differences between numbers of initial evaluations and levels of challenge and job satisfaction. Implications of these changes and future directions for research are discussed.
Synthesis, thermal, and photocrosslinking studies of thermotropic liquid crystalline poly(benzylidene‐ether)esters containing α,β‐unsaturated ketone moiety in the main chain
Authors: Muthusamy Athianna , Balaji Krishnasamy , Murugavel Salem Chandrasekaran
Published: February 2013

A series of poly(benzylidene‐ether)esters containing a photoreactive benzylidene chromophore in the main chain were synthesized from 2,6‐bis(4‐hydroxy‐3‐methoxybenzylidene)cyclohexanone (BHMBCH) with various aliphatic and aromatic diacid chlorides by an interfacial polycondensation technique. The intrinsic viscosity of the synthesized homo and copolymers determined by Ubbelohde viscometer was found to be 0.12 to 0.17 dL/g. The molecular structure of the monomer and polymers was confirmed by FT‐IR, 1H NMR, and 13C NMR spectral analyses. These polymers were studied for their thermal stability and photochemical properties. Thermal properties were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that the polymers were stable up to 280 °C and start degrading thereafter. Increase in acid methylene spacer length decreased the thermal stability. The self‐extinguishing property of the synthesized polymers was studied by calculating the limiting oxygen index (LOI) value using a Van Krevelen's equation. The influence of the length of methylene spacer on phase transition was investigated using DSC and odd‐even effect has been observed. Hot‐stage optical polarizing microscopic (HOPM) study showed that most of the polymers exhibited birefringence and opalescence properties. The photolysis of liquid crystalline poly(benzylidene‐ether)esters revealed that α,β‐unsaturated ketone moiety in the main chain dimerises through 2π + 2π cycloaddition reaction to form a cyclobutane derivative and leads to crosslinking. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Ion transport in sulfonated polymers
Authors: Park Moon Jeong , Kim Sung Yeon
Published: February 2013

As the focus on proton exchange fuel cells continues to escalate in the era of alternative energy systems, the rational design of sulfonated polymers has emerged as a key technique for enhancing device efficiency. Although the synthesis and characterization of a wide variety of sulfonated polymers have been extensively reported over the last decade, quantitative understanding of the factors governing the ion transport properties of these materials is in its infancy. In this article, we describe the current understanding of the thermodynamics and ion transport in sulfonated polymers. Various strategies for accessing improved transport properties of sulfonated polymers are presented by focusing on their structure‐property relationship. The major accomplishment of obtaining well‐defined morphologies for these sulfonated polymers is highlighted as a novel means of controlling the transport properties. Recent studies on the thermodynamics, morphologies, and anhydrous transport properties of sulfonated block copolymers comprising ionic liquids, geared towards high temperature polymer electrolyte membranes as a prospective technology, are also expounded. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
Design and fabrication of thermally stable nanoparticles for well‐defined nanocomposites
Authors: Yoo Misang , Kim Seyong , Bang Joona
Published: February 2013

The nanocomposites consisted of polymer and nanoparticles (NPs) have been regarded as one of core materials in the nanotechnology. From the practical viewpoint, the heat treatment is often required in many nanocomposite fabrication processes. However, some NPs such as gold NPs exhibit the low thermal stability due to the dissociation of ligands from the nanoparticle surface at elevated temperature, limiting their use in many applications. Herein, we provide an overview of the recent efforts in strategies for the design and fabrication of inorganic NPs which have enhanced thermal stability. The recent investigation on the phase behavior of thermally stable NPs within the polymer matrices (polymer blends and block copolymer), morphologies of nanocomposites induced by NPs, and examples of their applications are also discussed. These approaches may provide useful strategy to employ the NPs for the fabrication of nanocomposites in diverse applications especially where heat treatment are required. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
The Formation of Pd Nanocrystals from Pd2(dba)3 Microcrystals
Authors: Chung Sungwook , Leonard Donovan N. , Altoe Virginia , Aloni Shaul , De Yoreo James J. , Franzen Stefan
Published: February 2013

As‐grown platelets formed from tris‐(dibenzylideneacetone) dipalladium(0) [Pd2(dba)3] precursor in the presence of Pd17 RNA are investigated before and after thermal annealing. Results show that as‐grown platelets are disordered crystals of Pd2(dba)3 containing 1−2 nm Pd clusters and platelets grown in the absence of RNA are morphologically and structurally similar to those formed with RNA. The initially formed crystals are so sensitive to environmental variables that the degree of crystallinity can not be determined accurately by electron diffraction. X‐ray crystallography on as‐grown platelets gives a crystal structure consistent with Pd2(dba)3, but reveals a composition of ≈Pd1.07(dba)3, indicating one Pd atom in Pd2(dba)3 is lost from the structure. Both electron beam and thermally induced decomposition of as‐grown Pd2(dba)3 platelets having a hexagonal habit on the micrometer scale produces elemental Pd platelets having a hexagonal habit on the nanometer scale. These hexagonal platelets are composed of a partially sparse form of Pd2(dba)3 that is initially crystalline but rapidly degrades due to the loss of Pd atoms from organic ligand cages. Once released, Pd atoms aggregate to form Pd clusters, which grow and transform into well‐formed Pd nanocrystals under electron‐beam irradiation or through thermal annealing.
Mechanism for retardation of amyloid fibril formation by sugars in Vλ6 protein
Authors: Abe Masahiro , Abe Yoshito , Ohkuri Takatoshi , Mishima Tomonori , Monji Akira , Kanba Shigenobu , Ueda Tadashi
Published: February 2013

Sugars, which function as osmolytes within cells, retard the amyloid fibril formation of the amyloidosis peptides and proteins. To examine the mechanism of this retardation in detail, we analyzed the effect of sugars (trehalose, sucrose, and glucose) on the polypeptide chains in 3Hmut Wil, which is formed by the mutation of three His residues in Wil mutant as a cause of amyloid light‐chain (AL) amyloidosis, at pH 2, a pH condition under which 3Hmut Wil was almost denatured. Sugars caused the folding of 3Hmut Wil so that its polypeptide chains adopted a native‐like rather than a denatured conformation, as suggested by tryptophan fluorescence, CD spectroscopy, and heteronuclear NMR. Furthermore, these sugars promoted the folding to a native‐like conformation according to the effect of preferential hydration rather than direct interaction. However, the type of sugar had no effect on the elongation of amyloid fibrils. Therefore, it was concluded that sugar affected the thermodynamic stability of 3Hmut Wil but not the elongation of amyloid fibrils.
Protein–protein interactions: General trends in the relationship between binding affinity and interfacial buried surface area
Authors: Chen Jieming , Sawyer Nicholas , Regan Lynne
Published: February 2013

Protein–protein interactions play key roles in many cellular processes and their affinities and specificities are finely tuned to the functions they perform. Here, we present a study on the relationship between binding affinity and the size and chemical nature of protein–protein interfaces. Our analysis focuses on heterodimers and includes curated structural and thermodynamic data for 113 complexes. We observe a direct correlation between binding affinity and the amount of surface area buried at the interface. For a given amount of surface area buried, the binding affinity spans four orders of magnitude in terms of the dissociation constant (Kd). Across the entire dataset, we observe no obvious relationship between binding affinity and the chemical composition of the interface. We also calculate the free energy per unit surface area buried, or “surface energy density,” of each heterodimer. For interfacial surface areas between 500 and 2000 Å2, the surface energy density decreases as the buried surface area increases. As the buried surface area increases beyond about 2000 Å2, the surface energy density levels off to a constant value. We believe that these analyses and data will be useful for researchers with an interest in understanding, designing or inhibiting protein–protein interfaces.
Fmoc‐based peptide thioester synthesis with self‐purifying effect: heading to native chemical ligation in parallel formats
Authors: Thomas Franziska
Published: February 2013

The chemical synthesis of proteins has facilitated functional studies of proteins due to the site‐specific incorporation of post‐translational modifications, labels, and non‐proteinogenic amino acids. Moreover, native chemical ligation provides facile access to proteins by chemical means. However, the application of the native chemical ligation reaction in the synthesis of parallel formats such as protein arrays has been complicated because of the often cumbersome and time‐consuming synthesis of the required peptide thioesters. An Fmoc‐based peptide thioester synthesis with self‐purification on the sulfonamide ‘safety‐catch’ linker widens this bottleneck because HPLC purification can be avoided. The method is based on an on‐resin cyclization–thiolysis reaction sequence. A macrocyclization via the N‐terminus of the full‐length peptide followed by a thiolytic C‐terminal ring opening allows selective detachment of the truncation products and the full‐length peptide. A brief overview of the chemical aspects of this method is provided including the optimization steps and the automation process. Furthermore, the application of the cyclization–thiolysis approach combined with the native chemical ligation reaction in the parallel synthesis of a library of 16 SH3‐domain variants of SHO1 in yeast is described, demonstrating the value of this new technique for the chemical synthesis of protein arrays. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.
AlGaN/AlN quantum dots for UV light emitters
Authors: Himwas C. , Hertog M. den , Donatini F. , Dang Le Si , Rapenne L. , Sarigiannidou E. , Songmuang R. , Monroy E.
Published: February 2013

We report on the growth and properties of two types of AlGaN/AlN nanostructures: Stranski‐Krastanow quantum dots (SK‐QDs) and nanodisks (NDs) created by nanowire heterostructuring. In both cases, the emission wavelength can be tuned in the range of 240‐350 nm at room temperature by varying the flux ratio and the nominal amount of AlGaN in the nanostructures. The efficient carrier confinement in these nanostructures leads to an internal quantum efficiency around 0.5. However, the emission spectra of AlGaN/AlN NDs show broader linewidth than those of SK‐QDs, which is attributed to inhomogeneities in height and in chemical composition. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray multiple diffraction as a new approach to structural characterization of III‐nitride layers
Authors: Kyutt R. N. , Scheglov M. P.
Published: February 2013

X‐ray multiple diffraction in epitaxial films of III‐nitrides has been studied. A series of single layers of GaN, AlN, AlGaN and superlattices AlGaN/GaN of different thickness and structural perfection grown on c‐sapphire are under study. Renninger scans for a primary forbidden 0001 reflection was used. The three beam diffraction peaks were measured in both φ‐scans and θ‐scans and their FWHM was analyzed. In the Renninger pattern all the possible 10 multiple peaks in an angular range (0–30)° are observed. It is shown that the FWHM of the φ‐peaks reflects a crystalline perfection level but does not depend markedly on the multiple combination type. The angular width of the θ‐scan peaks also increases with increasing of dislocation density and strongly depends on the type of three‐wave reflection. The combinations with pure Laue secondary reflection (1–100)/(–1101), (3–1–20)/(–3121) and (3–2–10)/(–3211) are most sensi‐tive to the dislocations. Most narrow peaks for the samples with the large dislocation density take place for the multiple combination (01–13)/(0–11–2) with the largest Bragg component of the diffraction vector. For the superlattices, θ–2θ‐scan curve measured in the multiple position on the φ‐scale contains satellites with angular distance corresponding to the forbidden 0001 reflection. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Regression modeling of the cumulative incidence function with missing causes of failure using pseudo‐values
Authors: Moreno‐Betancur Margarita , Latouche Aurélien
Published: February 2013

Competing risks arise when patients may fail from several causes. Strategies for modeling event‐specific quantities often assume that the cause of failure is known for all patients, but this is seldom the case. Several authors have addressed the problem of modeling the cause‐specific hazard rates with missing causes of failure. In contrast, direct modeling of the cumulative incidence function has received little attention. We provide a general framework for regression modeling of this function in the missing cause setting, encompassing key models such as the Fine and Gray and additive models, by considering two extensions of the Andersen–Klein pseudo‐value approach. The first extension is a novel inverse probability weighting method, whereas the second extension is based on a previously proposed multiple imputation procedure. We evaluated the gain in using these approaches with small samples in an extensive simulation study. We analyzed the data from an Eastern Cooperative Oncology Group breast cancer treatment clinical trial to illustrate the practical value and ease of implementation of the proposed methods. Copyright © 2013 John Wiley & Sons, Ltd.
Asymmetric rivalry within and between strategic groups
Authors: Mas‐Ruiz Francisco J. , Ruiz‐Moreno Felipe , Ladrón de Guevara Martínez Antonio
Published: February 2013

Our study examines asymmetric rivalry within and between strategic groups defined according to the size of their members. We hypothesize that, owing to several forms of group‐level effects, including switching costs and efficiency, strategic groups comprising large firms expect to experience a large amount of retaliation from firms within their group and accommodation from the group comprising smaller firms. Small firms, on the other hand, expect to experience a small amount of retaliation from the group comprising large firms and no reaction from the other firms in their group. We estimate the effect of group‐level strategic interactions on firm performance. Our analysis reveals that the rivalry behavior within and between groups is asymmetric, which supports the dominant‐fringe relation between firms, as described in our hypothesis. Copyright © 2013 John Wiley & Sons, Ltd.
Targeting the Cytosolic Innate Immune Receptors RIG-I and MDA5 Effectively Counteracts Cancer Cell Heterogeneity in Glioblastoma
Authors: Glas Martin , Coch Christoph , Trageser Daniel , Daßler Juliane , Simon Matthias , Koch Philipp , Mertens Jerome , Quandel Tamara , Gorris Raphaela , Reinartz Roman , Wieland Anja , Von Lehe Marec , Pusch Annette , Roy Kristin , Schlee Martin , Neumann Harald , Fimmers Rolf , Herrlinger Ulrich , Brüstle Oliver , Hartmann Gunther , Besch Robert , Scheffler Björn
Published: February 2013

Cellular heterogeneity, for example, the intratumoral coexistence of cancer cells with and without stem cell characteristics, represents a potential root of therapeutic resistance and a significant challenge for modern drug development in glioblastoma (GBM). We propose here that activation of the innate immune system by stimulation of innate immune receptors involved in antiviral and antitumor responses can similarly target different malignant populations of glioma cells. We used short-term expanded patient-specific primary human GBM cells to study the stimulation of the cytosolic nucleic acid receptors melanoma differentiation-associated gene 5 (MDA5) and retinoic acid-inducible gene I (RIG-I). Specifically, we analyzed cells from the tumor core versus “residual GBM cells” derived from the tumor resection margin as well as stem cell-enriched primary cultures versus specimens without stem cell properties. A portfolio of human, nontumor neural cells was used as a control for these studies. The expression of RIG-I and MDA5 could be induced in all of these cells. Receptor stimulation with their respective ligands, p(I:C) and 3pRNA, led to in vitro evidence for an effective activation of the innate immune system. Most intriguingly, all investigated cancer cell populations additionally responded with a pronounced induction of apoptotic signaling cascades revealing a second, direct mechanism of antitumor activity. By contrast, p(I:C) and 3pRNA induced only little toxicity in human nonmalignant neural cells. Granted that the challenge of effective central nervous system (CNS) delivery can be overcome, targeting of RIG-I and MDA5 could thus become a quintessential strategy to encounter heterogeneous cancers in the sophisticated environments of the brain.
Glycogen synthase kinase‐3β (GSK3β) expression in a mouse model of Alzheimer's disease: A light and electron microscopy study
Authors: Gandy Johanna C. , Melendez‐Ferro Miguel , Bijur Gautam N. , Van Leuven Fred , Roche Joy K. , Lechat Benoit , Devijver Herman , Demedts David , Perez‐Costas Emma , Roberts Rosalinda C.
Published: February 2013

Glycogen synthase kinase‐3β (GSK3β) activity has been previously linked to Alzheimer's disease (AD) by its phosphorylation of tau and activation by amyloid. GSK3β intracellular distribution is important in regulating its activity by restricting access to compartment‐specific substrates. This study investigated regional and intracellular distribution of GSK3β in a mouse model of AD, a bigenic mouse with combined amyloid and tau pathology (BiAT), and controls (FVB). At two different ages, the entire rostrocaudal extent of each brain was examined. Young (6‐months‐old) FVB and BiAT mice did not differ in GSK3β expression and localization. In old (13‐month‐old) BiAT mice, neurons showed increased GSK3β expression only in AD‐relevant brain regions as compared with modest staining in region‐ and age‐matched controls. Two regions with the most robust changes between FVB and BiAT mice, the amygdala and piriform cortex, were quantified at the light microscopic level. In both regions, the density of darkly labeled neurons was significantly greater in the old BiAT mice vs. the old FVB mice. Electron microscopy of the piriform cortex showed neuronal GSK3β labeling in the rough endoplasmic reticulum, on ribosomes, and on microtubules in dendrites in both strains of mice. In old BiAT mice, GSK3β labeling was qualitatively more robust compared to age‐matched controls, and GSK3β also appeared in neurofibrillary tangles. In conclusion, GSK3β expression was increased in specific intracellular locations and was found in tangles in old BiAT mice, suggesting that GSK3β overexpression in specific brain areas may be intrinsic to AD pathology. Synapse, 2013. © 2013 Wiley Periodicals, Inc.
Photo‐curable highly water‐repellent nanocomposite coatings
Authors: Mülazim Yusuf , Çakmakçı Emrah , Kahraman Memet Vezir
Published: February 2013

Modification and use of natural products have gained a lot of interest in recent years due to their environmental friendliness and their availability from different sources. In this study, (castor oil)‐based photo‐curable highly hydrophobic coatings were prepared and characterized. Castor oil was first modified with 3‐isocyanatopropyltriethoxysilane and then hydrolyzed prior to the coating preparation. The resulting precursor was mixed with norbornyl acrylate and hexanediol diacrylate, and highly roughened hydrophobic coatings were prepared with the aid of fluorinated/nonfluorinated alkoxysilane coupling agents and hydrophobic fumed nanosilica particles. The coatings were applied on borofloat glass. The addition of fluorine and nanosilica showed a significant impact on the properties of the coatings. As the fluorine and nanosilica contents were increased in the formulations, flame retardancy and the contact angle values of the coatings increased. The surface roughness of the coatings increased with the addition of hydrophobic fumed nanosilica particles. Also, the relation between the surface energy and the contact angle values of the coatings was investigated. J. VINYL ADDIT. TECHNOL., 19:31–38, 2013. © 2013 Society of Plastics Engineers