bluuebunny/crossref_metadata_2025 huggingface dataset:
ANG II‐stimulated DNA synthesis is mediated by ANG II receptor‐dependent Ca2+/PKC as well as EGF receptor‐dependent PI3K/Akt/mTOR/p70S6K1 signal pathways in mouse embryonic stem cells
Authors: Han Ho Jae , Han Ji Yeon , Heo Jung Sun , Lee Sang Hun , Lee Min Young , Kim Yun Hee
Published: January 2007

Effect of angiotensin II (ANG II) on mouse embryonic stem (ES) cell proliferation was examined. ANG II increased [3H] thymidine incorporation in a time‐ (>4 h) and dose‐ (>10−9 M) dependent manner. The ANG II‐induced increase in [3H] thymidine incorporation was blocked by inhibition of ANG II type 1 (AT1) receptor but not by ANG II type 2 (AT2) receptor, and AT1 receptor was expressed. ANG II increased inositol phosphates formation and [Ca2+]i, and translocated PKC α, δ, and ζ to the membrane fraction. Consequently, the inhibition of PLC/PKC suppressed ANG II‐induced increase in [3H] thymidine incorporation. The inhibition of EGF receptor kinase or tyrosine kinase prevented ANG II‐induced increase in [3H] thymidine incorporation. ANG II phosphorylated EGF receptor and increased Akt, mTOR, and p70S6K1 phosphorylation blocked by AG 1478 (EGF receptor kinase blocker). ANG II‐induced increase in [3H] thymidine incorporation was blocked by the inhibition of p44/42 MAPKs but not by p38 MAPK inhibition. Indeed, ANG II phosphorylated p44/42 MAPKs, which was prevented by the inhibition of the PKC and AT1 receptor. ANG II increased c‐fos, c‐jun, and c‐myc levels. ANG II also increased the protein levels of cyclin D1, cyclin E, cyclin‐dependent kinase (CDK) 2, and CDK4 but decreased the p21cip1/waf1 and p27kip1, CDK inhibitory proteins. These proteins were blocked by the inhibition of AT1 receptor, PLC/PKC, p44/42 MAPKs, EGF receptor, or tyrosine kinase. In conclusion, ANG II‐stimulated DNA synthesis is mediated by ANG II receptor‐dependent Ca2+/PKC and EGF receptor‐dependent PI3K/Akt/mTOR/p70S6K1 signal pathways in mouse ES cells. J. Cell. Physiol. 211: 618–629, 2007. © 2007 Wiley‐Liss, Inc.
Backbone colorings for graphs: Tree and path backbones
Authors: Broersma Hajo , Fomin Fedor V. , Golovach Petr A. , Woeginger Gerhard J.
Published: January 2007

We introduce and study backbone colorings, a variation on classical vertex colorings: Given a graph G = (V,E) and a spanning subgraph H of G (the backbone of G), a backbone coloring for G and H is a proper vertex coloring V → {1,2,…} of G in which the colors assigned to adjacent vertices in H differ by at least two. We study the cases where the backbone is either a spanning tree or a spanning path. We show that for tree backbones of G the number of colors needed for a backbone coloring of G can roughly differ by a multiplicative factor of at most 2 from the chromatic number χ(G); for path backbones this factor is roughly ${{3}\over{2}}$. We show that the computational complexity of the problem “Given a graph G, a spanning tree T of G, and an integer ℓ, is there a backbone coloring for G and T with at most ℓ colors?” jumps from polynomial to NP‐complete between ℓ = 4 (easy for all spanning trees) and ℓ = 5 (difficult even for spanning paths). We finish the paper by discussing some open problems. © 2007 Wiley Periodicals, Inc. J Graph Theory 55: 137–152, 2007
The influence of dietary hazelnut kernel oil on the performance and fatty acid composition of broilers
Authors: Erener Guray , Ocak Nuh , Garipoglu Ali Vaiz
Published: January 2007

A total of 360 one‐day‐old broilers (Ross 308) were allocated to three treatment groups with four replicates each of 30 chicks to evaluate the effects of the dietary hazelnut kernel oil (HKO) inclusion on the performance and the composition of fatty acid of meat in broilers. Treatments were diets with (1) soybean oil (SO), (2) HKO, or (3) HKO + SO (in equal amount, HKSO) added to the basal diets. There were no significant differences in weight gain, feed per gain, dressing percentage, abdominal fat weight, and mortality among the different dietary oil sources. Dietary HKO decreased (P < 0.01) linoleic and linolenic acids contents and the ratio of SFA:MUFA (saturated fatty acids:unsaturated fatty acids) of breast meats in broiler, and increased oleic acid content compared to SO. The result indicates that meat from broiler chickens fed diets containing HKO, singly or combined with SO could be an important source of oleic acid for human diets. Copyright © 2007 Society of Chemical Industry
Comparison of fresh and predegenerated muscle‐vein‐combined guides for the repair of rat median nerve
Authors: Tos P. , Battiston B. , Nicolino S. , Raimondo S. , Fornaro M. , Lee J.M. , Chirila L. , Geuna S. , Perroteau I.
Published: January 2007

Over the last 10 years, we have investigated a particular type of bioengineered nerve guide, the muscle‐vein‐combined tube, which is made by filling a vein with skeletal muscle. In our previous studies we have always used fresh skeletal muscle to fill vein conduits. In the present study we compared the use of fresh and predegenerated (freeze‐thawed) skeletal muscle for muscle‐vein‐combined nerve guides. In this study, a 10‐mm‐long rat median nerve defect was repaired using either type of nerve guide. The samples were analyzed 5 and 30 days after surgery by light and electron microscopy. In addition, reverse transcription polymerase chain reaction (RT‐PCR) was carried out to investigate the expression of mRNAs coding for glial markers, as well as glial growth factor (NRG1) and its receptors (erbB2 and erbB3). Results showed differences between the two types of nerve guides at postoperative day 5; however, no difference was detected at day 30 suggesting that both types of tissue‐engineered conduit are effective for repairing peripheral nerve defects in this experimental model. © 2007 Wiley‐Liss, Inc. Microsurgery, 2007.
Improved cine displacement‐encoded MRI using balanced steady‐state free precession and time‐adaptive sensitivity encoding parallel imaging at 3 T
Authors: Kim Daniel , Kellman Peter
Published: January 2007

Cine displacement‐encoded MRI is a promising modality for quantifying regional myocardial function. However, it has two major limitations: low signal‐to‐noise ratio (SNR) and data acquisition efficiency. The purpose of this study was to incrementally improve the SNR and the data acquisition efficiency of cine displacement‐encoded MRI through the combined use of balanced steady‐state free precession (b‐SSFP) imaging, 3T imaging, echo‐combination image reconstruction, and time‐adaptive sensitivity encoding (TSENSE) parallel imaging. Phantom experiments were performed to empirically determine the optimal excitation angle (α) and to estimate the measurement errors in the presence of 130 Hz peak‐to‐peak static magnetic field (B0) variation. The optimal α was determined to be 20°. The intrinsic phase correction in the echo‐combination effectively reduced the phase error, which produced small displacement errors (0.11 versus 0.11 mm) and negligible strain errors (−0.001 versus −0.002). Six healthy volunteers were imaged in three short‐axis levels of the heart to evaluate the SNR and the relative accuracy of strain calculations. Compared with the 24‐heartbeat cine echo‐planar imaging acquisition, the 24‐heartbeat non‐accelerated b‐SSFP acquisition yielded approximately 65% higher SNR, and the 12‐heartbeat twofold accelerated b‐SSFP acquisition yielded approximately 28% higher SNR. The 12‐heartbeat twofold accelerated b‐SSFP acquisition yielded functional maps with spatial resolution of 3.6 × 3.6 mm, temporal resolution of 35 ms, and relatively high SNR (31.2 ± 5.4 at end diastole; 19.9 ± 3.6 at end systole; 10.3 ± 1.1 at late diastole; mean ± SD). The left ventricular strain values between the non‐accelerated and twofold accelerated b‐SSFP acquisitions correlated strongly (slope = 0.99; bias = 0.00; R2 = 0.91) and were in excellent agreement. The combined implementation of b‐SSFP imaging, 3T imaging, echo‐combination image reconstruction, and TSENSE parallel imaging can be used to incrementally improve the cine displacement‐encoded MRI pulse sequence. Copyright © 2007 John Wiley & Sons, Ltd.
A new finite element based on the theory of a Cosserat point—extension to initially distorted elements for 2D plane strain
Authors: Boerner E. F. I. , Loehnert S. , Wriggers P.
Published: January 2007

This paper describes an improvement of the Cosserat point element formulation for initially distorted, non‐rectangular shaped elements in 2D. The original finite element formulation for 3D large deformations shows excellent behaviour for sensitive geometries, large deformations, coarse meshes, bending dominated and stability problems without showing undesired effects such as locking or hourglassing, as long as the initial element shape resembles that of a rectangular parallelepiped. In the following, an extension of this element formulation for 2D plane strain is presented which has the same good properties also for the case of non‐rectangular initial element shapes. Results of numerical tests are presented, that clearly show the advantages of the improved Cosserat point element compared to the standard displacement elements and the original version of the Cosserat point element. Copyright © 2007 John Wiley & Sons, Ltd.
Quartic B‐spline collocation algorithms for numerical solution of the RLW equation
Authors: Saka Bülent , Dağ İdris
Published: January 2007

The collocation method based on quartic B‐spline interpolation is studied for numerical solution of the regularized long wave (RLW) equation. The time‐split RLW equation is also solved with the quartic B‐spline collocation method. Numerical accuracy is tested by obtaining the single solitary wave solution. Then, interaction, undulation and evolution of solitary waves are studied. Solutions are compared with available results. Conservation quantities are computed for all test experiments. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007
Extrapolation of the bilinear element approximation for the Poisson equation on anisotropic meshes
Authors: Lin Qun , Lin Jia‐fu
Published: January 2007

The bilinear finite element approximation for the Poisson equation has an asymptotic error expansion on the anisotropic rectangular meshes. Extrapolation can be obtained based on this expansion and the postprocessing interpolation. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007
An iterative method for the reconstruction of a stationary flow
Authors: Johansson Tomas , Lesnic Daniel
Published: January 2007

In this article, an iterative algorithm based on the Landweber‐Fridman method in combination with the boundary element method is developed for solving a Cauchy problem in linear hydrostatics Stokes flow of a slow viscous fluid. This is an iteration scheme where mixed well‐posed problems for the stationary generalized Stokes system and its adjoint are solved in an alternating way. A convergence proof of this procedure is included and an efficient stopping criterion is employed. The numerical results confirm that the iterative method produces a convergent and stable numerical solution. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007
Multiresolution schemes for strongly degenerate parabolic equations in one space dimension
Authors: Bürger Raimund , Kozakevicius Alice , Sepúlveda Mauricio
Published: January 2007

An adaptive finite volume method for one‐dimensional strongly degenerate parabolic equations is presented. Using an explicit conservative numerical scheme with a third‐order Runge‐Kutta method for the time discretization, a third‐order ENO interpolation for the convective term, and adding a conservative discretization for the diffusive term, we apply the multiresolution method combining two fundamental concepts: the switch between central interpolation or exact computing of numerical flux and a thresholded wavelet transform applied to cell averages of the solution to control the switch. Applications to mathematical models of sedimentation‐consolidation processes and traffic flow with driver reaction, which involve different types of boundary conditions, illustrate the computational efficiency of the new method. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007
Consumer attitudes towards self‐referral with early signs of cancer: implications for symptom awareness campaigns
Authors: Eadie Douglas , MacAskill Susan
Published: January 2007

Traditionally, secondary prevention programmes have employed mass screening approaches to assess for asymptomatic signs of cancer. It has been suggested that early detection strategies, involving public education and self‐referral may prove more cost‐effective, with low‐risk populations for cancers with symptomatic presentation. The success of public education approaches is dependent on careful consideration of the psycho‐social factors of self‐examination and referral. This paper presents the findings from an exploratory study, using qualitative methods with an at‐risk population of older people living in deprived communities in west‐central Scotland. The study examines consumer perceptions of the early detection of cancer and the cultural barriers to self‐referral, as well as response to aspects of communication strategy. The implications for design of symptom awareness campaigns, including use of message appeals, specification of target symptoms, identification of target audience and selection of communication channels, are discussed.

Copyright © 2007 John Wiley & Sons, Ltd.
Biopolymers as fillers for rubber blends
Authors: Kramárová Z. , Alexy P. , Chodák I. , Špirk E. , Hudec I. , Košíková B. , Gregorová A. , Šúri P. , Feranc J. , Bugaj P. , Ďuračka M.
Published: January 2007

Polymeric materials from renewable resources have been tested as additives for rubber blends and vulcanisates. Their influence on the vulcanisation process, tensile strength properties and dynamical‐mechanical properties has been studied and compared with silica. The corn starch, collagen hydrolysate, corn protein and various types of lignin have been added to natural and styrene butadiene rubber in order to find convenient fillers for rubber blends which are able to modify the properties of rubber products. Correlation between Wolf activity coefficient and mechanical properties of vulcanisates is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Synthetic, layered nanoparticles for polymeric nanocomposites (PNCs)
Authors: Utracki L. A. , Sepehr M. , Boccaleri E.
Published: January 2007

This review discusses preparation and use of the synthetic layered nanoparticles in polymer matrices, i.e., in the polymeric nanocomposites (PNCs). Several types of synthetic or semi‐synthetic layered materials are considered, namely the phyllosilicates (clays), silicic acid (magadiite), layered double hydroxides (LDHs), zirconium phosphates (ZrPs), and di‐chalcogenides. The main advantage of synthetic clays is their chemical purity (e.g. absence of amorphous and gritty contaminants, as well as arsenic, iron, and other heavy metals), white to transparent color that assures reproducibly of brightly colored products, as well as a wide range of aspect ratios, p = 20 to ≤6000. Several large scale production facilities have been established. The synthetic clay and LDH industries are oriented toward big volume markets: catalysis, foodstuff, cosmetics, pharmaceuticals, toiletry, etc. The use of these materials in PNCs is limited to synthetic clays and LDHs, mainly for reinforcement, permeability control, reduction of flammability, and stabilization, e.g. during dehydrohalogenation of chlorinated macromolecules. The use of lamellar ZrPs and di‐chalcogenides is at the laboratory stage of functional polymeric systems development, e.g. for electrically conductive materials, catalysts or support for catalysts, in photochemistry, molecular and chiral recognition, or in fuel cell technologies, etc. Copyright © 2007 John Wiley & Sons, Ltd.
Changes in albumin precursor and heat shock protein 70 expression and their potential role in response to corneal epithelial wound repair
Authors: Mushtaq Shamim , Naqvi Zulfiqar A. , Siddiqui Anwar A. , Palmberg Carina , Shafqat Jawed , Ahmed Nikhat
Published: January 2007

Many proteins displayed differential expression (either up‐ or down‐regulation) when proteome of migrating and non‐migrating epithelium was assessed using 2‐DE and ESI‐Q‐TOF MS/MS. From the up‐regulated set, we have identified for the first time a 69‐kDa albumin precursor protein with four peptides sequences and 70‐kDa heat shock protein (hsp70) with one peptide in the active phase of cell migration (48 h) during the healing process. Western blot analysis was used to further characterize these proteins at different phases (24, 48 and 72 h) of healing. An increase in the mRNA expression (measured using RT‐PCR) in the active migration phase (48 h) for albumin precursor and hsp70 was also observed. Furthermore, co‐immunoprecipitation studies with anti‐albumin precursor and anti‐hsp70 antibodies, followed by immunoblotting with anti‐fibronectin antibody demonstrated a novel and biologically relevant interaction between albumin precursor protein and fibronectin in corneal epithelial wound healing but not with hsp70. The increased gene and protein expression of albumin and hsp70 during the active phase of cell migration (48 h) in the corneal epithelium suggests their possible role in corneal wound healing. These findings may have broader implications for developing therapeutic strategies for treating wound healing disorders.
Proteome analysis of human macrophages reveals the upregulation of manganese‐containing superoxide dismutase after toll‐like receptor activation
Authors: Rakkola Riitta , Matikainen Sampsa , Nyman Tuula A.
Published: January 2007

Macrophages are essential for the development of innate immune responses against a variety of infectious factors. They detect invading pathogens via their pattern recognition receptors such as toll‐like receptors (TLRs). TLR7/8 recognizes ssRNA from various viruses. In the present study, we have used 2‐DE gel‐based proteomics to find novel TLR7/8 target proteins in human monocyte‐derived macrophages in order to improve our understanding of the virus recognition by this TLR. A total of 27 protein spots were found to be reproducibly differentially expressed between control and TLR7/8 activated 2‐DE gel pairs, 18 spots being more than two‐fold upregulated and nine spots being at least two‐fold downregulated. Several proteins involved in defense against toxic superoxide (O2−) and other reactive oxygen species, such as manganese‐containing superoxide dismutase (SOD2), glutathione peroxidase, and peroxiredoxins 1 and 6 were highly upregulated after TLR7/8 activation. Western blot analysis showed that activation of macrophages with TLR2, TLR3, TLR4, and TLR7/8 ligands also strongly upregulated SOD2 protein expression. In conclusion, our results show that the activation of pattern recognition receptors of the innate immune system results in strong upregulation of SOD2 gene expression suggesting that SOD2 protects macrophages from oxidative stress during microbial infection.
Translational and transcriptional analysis of Sulfolobus solfataricus P2 to provide insights into alcohol and ketone utilisation
Authors: Chong Poh Kuan , Burja Adam M. , Radianingtyas Helia , Fazeli Alireza , Wright Phillip C.
Published: January 2007

The potential of Sulfolobus solfataricus P2 for alcohol or ketone bioconversion was explored in this study. S. solfataricus was grown in different concentrations (0.1–0.8% w/v) of alcohols or ketones (ethanol, iso‐propanol, n‐propanol, acetone, phenol and hexanol) in the presence of 0.4% w/v glucose. Consequently, the addition of these alcohols or ketones into the growth media had an inhibitory effect on biomass production, whereby lag times increased and specific growth rates decreased when compared to a glucose control. Complete glucose utilisation was observed in all cultures, although slower rates of glucose consumption were observed in experimental cultures (average of 14.9 mg/L/h compared to 18.9 mg/L/h in the control). On the other hand, incomplete solvent utilisation was observed, with the highest solvent consumption being approximately 51% of the initial concentration in acetone cultures. Translational responses of S. solfataricus towards these alcohols or ketones were then investigated using the isobaric tags for relative and absolute quantitation (iTRAQ) technique. The majority (>80%) of proteins identified and quantified showed no discernable changes in regulation compared to the control. These results, along with those obtained from transcriptional analysis of key genes involved within this catabolic process using quantitative RT‐PCR and metabolite analysis, demonstrate successful alcohol or ketone conversion in S. solfataricus.
A combined dataset of human cerebrospinal fluid proteins identified by multi‐dimensional chromatography and tandem mass spectrometry
Authors: Pan Sheng , Zhu David , Quinn Joseph F. , Peskind Elaine R. , Montine Thomas J. , Lin Biaoyang , Goodlett David R. , Taylor Greg , Eng Jimmy , Zhang Jing
Published: January 2007

Human cerebrospinal fluid (CSF) is an important source for studying protein biomarkers of age‐related neurodegenerative diseases. Before characterizing biomarkers unique to each disease, it is necessary to categorize CSF proteins systematically and extensively. However, the enormous complexity, great dynamic range of protein concentrations, and tremendous protein heterogeneity due to post‐translational modification of CSF create significant challenges to the existing proteomics technologies for an in‐depth, nonbiased profiling of the human CSF proteome. To circumvent these difficulties, in the last few years, we have utilized several different separation methodologies and mass spectrometric platforms that greatly enhanced the identification coverage and the depth of protein profiling of CSF to characterize CSF proteome. In total, 2594 proteins were identified in well‐characterized pooled human CSF samples using stringent proteomics criteria. This report summarizes our efforts to comprehensively characterize the human CSF proteome to date.
Simple proteomic checks for detecting noncoding RNA
Authors: Cruveiller Stéphane , Clay Oliver , Jabbari Kamel , Bernardi Giorgio
Published: January 2007

Proper validation can accelerate sequence‐based discovery of proteins and protein‐coding genes. Databases currently contain a backlog of experimentally unverified gene models and tentative assignments of observed transcripts to coding or noncoding RNA. We present and apply a general principle, founded on base composition and the genetic code and validated here by bulk 2‐D gels, that can improve the reliability of such classifications and of the algorithms or pipelines that lead to them.
Preparation and characterization of poly(2‐methacryloyloxyethyl phosphorylcholine)‐block‐poly(D,L‐lactide) polymer nanoparticles
Authors: Hsiue Ging‐Ho , Lo Chun‐Liang , Cheng Ching‐Hao , Lin Che‐Ping , Huang Chun‐Kai , Chen Hung‐Hao
Published: January 2007

A poly(D,L‐lactide)–bromine macroinitiator was synthesized for use in the preparation of a novel biocompatible polymer. This amphiphilic diblock copolymer consisted of biodegradable poly(D,L‐lactide) and 2‐methacryloyloxyethyl phosphorylcholine and was formed by atom transfer radical polymerization. Polymeric nanoparticles were prepared by a dialysis process in a select solvent. The shape and structure of the polymeric nanoparticles were determined by 1H NMR, atomic force microscopy, and ζ‐potential measurements. The results of cytotoxicity tests showed the good cytocompatibility of the lipid‐like diblock copolymer poly(2‐methacryloyloxyethyl phosphorylcholine)‐block‐poly(D,L‐lactide). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 688–698, 2007
Synthesis and characterization of stimuli‐sensitive micro‐ and nanohydrogels based on photocrosslinkable poly(dimethylaminoethyl methacrylate)
Authors: Gupta Smrati , Kuckling Dirk , Kretschmer Katja , Choudhary Veena , Adler Hans‐Jürgen
Published: January 2007

The aim of this work was the development of a versatile route for the preparation of temperature‐ and pH‐responsive hydrogels with small dimensions. The copolymerization of N,N‐dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2′‐azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro‐ and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature‐ and pH‐responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669–679, 2007
Synthesis of macrocycles by the ring‐crossover reaction of a cyclic dithioester
Authors: Kudo Hiroto , Makino Shinya , Nishikubo Tadatomi
Published: January 2007

The ring‐crossover polymerization of cyclic dithioester 1 was performed in the presence of quaternary onium salts as catalysts at 70–150 °C for 24 h in NMP. It was found that predictable cyclic polymers with the same repeating structures as 1 were obtained with Mns in the range between 700 and 3,500, quantitatively. It was observed that intermolecular and intramolecular thioester‐exchange reactions proceeded between cyclic monomer 1 and resulting cyclic polymers under thermodynamic control to give a lower‐molecular‐weight cyclic polymer with a lower polydispersity ratio (Mn = 2,400, Mw/Mn = 1.70). © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 680–687, 2007
Novel epoxy nanocomposite of low Dk introduced fluorine‐containing POSS structure
Authors: Wang Yen‐Zen , Chen Wen‐Yi , Yang Chao‐Chen , Lin Chen‐Lung , Chang Feng‐Chih
Published: January 2007

A nanoporous additives, polyhedral oilgomeric silisesquioxane containing eight functional hexafluorine groups, octakis(dimethylsiloxyhexafluoropropyl ether)silsesquioxane (OF) has been synthesized and blended with the UV‐cured epoxy resin. The OF containing (10%) epoxy has significantly lower dielectric constant (2.65) than the plain epoxy (3.71). The incorporation of fluorine containing additives is well‐known to reduce dielectric constant due to lower its polarizability. In addition, the presence of the bulky POSS structure is able to create additional free space or pores and further reduces the dielectric constant of the epoxy matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 502–510, 2007
Effect of SSL and HSC on morphology and properties of PHA based SMPU synthesized by bulk polymerization method
Authors: Chen Shaojun , Hu Jinlian , Liu Yeqiu , Liem Haiming , Zhu Yong , Liu Yijun
Published: January 2007

Searching new shape memory polymer and the associating synthesis technology are critical on the development of smart materials. In this paper, a comprehensive study on Poly(hexylene adipate) PHA being the soft segment of shape memory polyurethane (SMPU) was presented. Bulk polymerization method was employed to synthesize the SMPU with different soft segment length (SSL) and hard segment content (HSC). The influences of SSL and HSC on its morphology and thermomechanical property using DSC, DMA, POM, and shape memory behavior were presented here. The results indicate that the thermal properties, dynamic mechanic properties, and crystal morphology of SMPU are influenced significantly by SSL and HSC. And it is found that the shape fixity increases with SSL but decreases with HSC. On the other hand, the shape recovery decreases with both SSL and HSC, and the associated recovery temperature increases either with the increasing SSL or with decreasing HSC. Lastly, it is concluded that in the PHA‐based‐SMPU, the lower limiting value of SSL for polyurethane having shape memory effect is 2000; their response temperature varied with SSL and HSC, changing from 41.0 to 51.9 °C. Stable hard segment crystal are formed at above 30% HSC sample in bulk polymerization, but shape memory behavior can also be observed when its physical crosslink point are formed in the lower HSC PHA‐based‐SMPU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 444–454, 2007
Reversible melting and crystallization of high‐molar‐mass poly(oxyethylene)
Authors: Qiu W. , Pyda M. , Nowak‐Pyda E. , Habenschuss A. , Wunderlich B.
Published: January 2007

The heat capacity of poly(oxyethylene) (POE) with a molar mass of 900,000 Da has been analyzed with differential scanning calorimetry and quasi‐isothermal, temperature‐modulated differential scanning calorimetry. The crystal structure, lattice parameters, and coherently scattering domain sizes have been measured with wide‐angle X‐ray diffraction as a function of temperature. The high‐molar‐mass POE crystals are in a folded‐chain macroconformation and show some locally reversible melting starting already at about 250 K. At 335 K, the thermodynamic heat capacity reaches the level of the melt. The reversible crystallinity depends on the modulation amplitude and has been varied in the melting range from ±0.2 to ±3.0 K. Before melting, there is neither a change in the crystal structure nor a change in the domain size, but the expansivity of the crystals increases at about 320 K. These observations support the interpretation that the monoclinic POE crystals possess a glass transition temperature with a midpoint at about 324 K, whereas the maximum melting temperature is 341 K. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 475–489, 2007
Weight distribution in standing and sitting positions, and weight transfer during reaching tasks, in seated stroke subjects and healthy subjects
Authors: Tessem Siri , Hagstrøm Nora , Fallang Bjørg
Published: January 2007

Background and Purpose. The recovery of sitting balance after a stroke is assumed to be essential to obtain independence in other vital functions. The purpose of the present study was to investigate weight distribution while sitting and standing still, and weight transfer during seated reaching tasks performed by stroke subjects and healthy subjects. Method. The study was cross‐sectional. Twenty‐one stroke subjects and 21 healthy subjects, matched by age and gender, participated. Main measures were weight distribution while standing and sitting still, and displacements of centre of pressure (COP) during seated reaching tasks. Data were collected using a balance performance monitor (BPM), including software. Results. Stroke subjects had less symmetrical weight distribution in standing than that of healthy subjects (p < 0.001). No significant differences between the groups were found while sitting still, and no associations between asymmetries in standing still and sitting positions within individual stroke subjects were found. Neither did the degree of weight distribution in sitting correspond to COP displacements in seated reaching tasks. However, COP displacement patterns in reaching tasks in the seated position were different in stroke subjects from those of healthy subjects. Stroke subjects showed more lateral displacement when reaching forwards (p < 0.001), and less lateral displacement when reaching sideways to the unaffected side (p = 0.01). Conclusion. COP displacement patterns in stroke subjects deviate more than those of healthy subjects in seated reaching tasks. The deviating COP displacement patterns are discussed as a possible dysfunction in the ability to make postural adjustments and learn an efficient movement pattern. Copyright © 2007 John Wiley & Sons, Ltd.
String theory: exact solutions, marginal deformations and hyperbolic spaces
Authors: Orlando D.
Published: January 2007

This thesis is almost entirely devoted to studying string theory backgrounds characterized by simple geometrical and integrability properties. The archetype of this type of system is given by Wess‐Zumino‐Witten models, describing string propagation in a group manifold or, equivalently, a class of conformal field theories with current algebras. We study the moduli space of such models by using truly marginal deformations. Particular emphasis is placed on asymmetric deformations that, together with the CFT description, enjoy a very nice spacetime interpretation in terms of the underlying Lie algebra. Then we take a slight detour so to deal with off‐shell systems. Using a renormalization‐group approach we describe the relaxation towards the symmetrical equilibrium situation. In he final chapter we consider backgrounds with Ramond‐Ramond field and in particular we analyze direct products of constant‐curvature spaces and find solutions with hyperbolic spaces.
Protein–RNA contacts at crystal packing surfaces
Authors: Phipps Kathleen R. , Li Hong
Published: January 2007

The crystal packing surfaces comprising protein–RNA interactions were analyzed for 50 RNA‐protein crystal structures in the Protein Data Bank database. Protein–RNA crystal contacts, which represent nonspecific protein–RNA interfaces, were investigated for their amino acid propensities, hydrogen bond patterns, and backbone and side chain interactions. When compared to biologically relevant interactions, the protein–RNA crystal contacts exhibit similarities as well as differences with respect to the principles of protein–RNA interactions. Similar to what was observed at cognate protein–RNA interfaces, positively charged amino acids have high propensities at noncognate protein–RNA interfaces and preferentially form hydrogen bonds with RNA phosphate groups. In contrast, nonpolar residues are less frequently associated with noncognate interactions. These results highlight the important roles of both electrostatic and hydrogen bonding interactions, facilitated by positively charged amino acids, in mediating both specific and nonspecific protein–RNA interactions. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Current spreading and thermal effects in blue LED dice
Authors: Bulashevich K. A. , Evstratov I. Yu. , Mymrin V. F. , Karpov S. Yu.
Published: January 2007

We have applied simulations to study current the spreading and heat transfer in blue III‐nitride light‐emitting diodes (LEDs) with the focus on self‐heating and its effect on the device characteristics. A conventional planar design of an LED die is considered for the heat sink through a sapphire substrate. The computations predict a great current crowding at the contact electrode edges, resulting in a non‐uniform temperature distribution over the die. The thermal effect on the current‐voltage characteristic, output optical power, and series resistance of the diode is analyzed and the theoretical predictions are compared with available observations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic constants of aluminum nitride
Authors: Kazan M. , Moussaed E. , Nader R. , Masri P.
Published: January 2007

We report on the application of Brillouin spectroscopy as an approach to non‐destructive optical characterization of the elastic constants of semiconductors with the wurtzite symmetry. Three different configurations were used to achieve a complete determination of the elastic stiffness constants of bulk AlN substrates grown by the Physical Vapor Transport (PVT) method. The scattering diagrams of these three configurations are presented showing the geometrical arrangements necessary to observe all the elastic stiffness constants for the partially nontransparent wurtzite type of the crystal structure. Because aluminum nitride (AlN) is a suitable material for the fabrication of light emitting devices, the characterization of its elastic constants was carried out very precisely to provide a reliable data which can be used for the determination of residual stress arising during the growth of AlN thin films or wide band gap semiconductor thin films on substrates of AlN. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of AlGaN, Te‐doped GaN and Mg‐doped GaN grown by hydride vapor phase epitaxy
Authors: Jang K. S. , Kim K. H. , Hwang S. L. , Jeon H. S. , Ahn H. S. , Yang M. , Choi W. J. , Kim S. W. , Honda Y. , Yamaguchi M. , Sawaki N. , Yoo J. , Lee S. M. , Koike M.
Published: January 2007

The AlxGa1–xN, Te‐doped GaN and Mg‐doped GaN layers on GaN/Al2O3 substrates are grown by mixed‐source hydride vapor phase epitaxy (HVPE) method. The metallic Ga mixed with Al is used as group III source material to get the AlxGa1–xN layers. The values of the compositions x of the AlxGa1–xN layers characterized by X‐ray diffraction (XRD) measurements are 0.6% ∼ 80% at the various temperatures of the source zone. The metallic Ga mixed with Te (or Mg) is used as source material for n‐type (or p‐type) doping. The electron concentrations of the Te‐doped GaN layers are varied from 1.8 × 1017 to 8.3 × 1018/cm3. The hole concentrations of the Mg‐doped GaN layers are varied from 1.5 × 1016 to 3.2 × 1016/cm3. We find that the mixed‐source HVPE method is suitable to get a thick AlGaN layer with an arbitrary composition, a Te‐doped GaN layer with a high n‐type concentration and a Mg‐doped GaN layer with p‐type concentration. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of InGaN layer on GaN templated Al2O3 (0001) and Si (111) substrates by mixed‐source HVPE
Authors: Hwang S. L. , Jang K. S. , Kim K. H. , Jeon H. S. , Ahn H. S. , Yang M. , Kim S. W. , Honda Y. , Yamaguchi M. , Sawaki N. , Yoo J. , Lee S. M. , Koike M.
Published: January 2007

The InGaN layers on GaN templated sapphire (0001) and Si (111) substrates are grown by mixed‐source hydride vapor phase epitaxy (HVPE) method. As a new attempt in obtaining an InGaN layers, the growth of the thick InGaN layer is performed by putting small amount of Ga into the In source. The InGaN layer is compounded from chemical reaction between a NH3 and an Indium‐gallium chloride formed by HCl flown over metallic In mixed with Ga. The InGaN layer is analyzed by X‐ray photoelectron spectroscopy (XPS) to characterize the InGaN ternary crystal alloy. The optical property of the selective area growth (SAG) of the InGaN layer is investigated by the photoluminescence (PL) spectrum and the cathodoluminescence (CL) images. Indium compositions are estimated to be in the range 3‐10%. In order to obtain the GaN layer on GaN templated Si (111) substrates, an InGaN layer is used as an intermediate layer. The PL and CL of the InGaN intermediate layer are measured at 300K. We find that the InGaN intermediate layer is possible to be one of the growth methods of thick GaN layer on Si substrates by HVPE method. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnO films fabricated by spin coating and their application to UV electroluminescent devices
Authors: Yoshioka K. , Egawa S. , Kobayashi T. , Baba T. , Sugimoto K. , Arai M. , Nomura H. , Sato M. , Honda T.
Published: January 2007

ZnO films were fabricated by spin coating. The photoluminescence (PL) spectra of the films, which included a near‐band‐edge emission, were observed at RT. The estimated external quantum efficiency of their PL is approximately 1.2%. Electroluminescent devices (ELDs) using the ZnO films were also fabricated. The violet light emission was observed from the devices. The results indicate that the spin‐coated ZnO films have high potential for application to UV light‐emitting devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN‐based Schottky‐type UV light‐emitting diodes and their integration for flat‐panel displays
Authors: Kobayashi Toshiaki , Egawa Shinichi , Sawada Masaru , Honda Tohru
Published: January 2007

Schottky‐type light‐emitting diodes (ST‐LEDs) were fabricated using GaN epilayers grown on (0001) sapphire substrates by metal‐organic vapor phase epitaxy. The UV light emission (374 nm) was observed from the integrated ST‐LEDs under reverse bias conditions. The integrated ST‐LEDs are good candidates for the UV excitation sources of flat‐panel display systems combined with red, green and blue phosphors. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High brightness GaN vertical light emitting diodes on metal alloyed substrate for general lighting application
Authors: Chu Chen‐Fu , Cheng Chao‐Chen , Liu Wen‐Huan , Chu Jiunn‐Yi , Cheng Hao‐Chun , Fan Feng‐Hsu , Yen Jui‐Kang , Tran Chuong Anh , Doan Trung
Published: January 2007

The characteristics of the GaN based Vertical Light Emitting Diodes on Metal alloyed Substrate (VLEDMS) were investigated. The VLEDMS exhibits very good current‐voltage behaviour with low average dynamic resistance of 0.7 Ω and low operated voltage of 3.2 V at 350 mA. High current operation up to 2000 mA in continuous mode was demonstrated without any performance deterioration. The high thermal conductivity of metal alloyed substrate demonstrated excellent heat dissipation capability. Chip scaling without efficiency loss shows a unique property of VLEDMS and enabled to enlarge up to 2 mm × 2 mm chip size. A light output efficiency of 70 lm/W or better was achieved in single chip or multiple chips package. Coupled with mass production ability, VLEDMS is very suitable for general lighting application. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Negative characteristic temperature of InGaN blue multiple‐quantum‐well laser diodes
Authors: Ryu H. Y. , Ha K. H. , Lee S. N. , Jang T. , Kim H. K. , Son J. K. , Chae J. H. , Kim K. S. , Choi K. K. , Paek H. S. , Sung Y. J. , Sakong T. , Nam O. H. , Park Y. J.
Published: January 2007

We report anomalous temperature characteristics of InGaN laser diodes (LDs) emitting around 450 nm. Our blue LD shows negative characteristic temperature in the usual operation temperature range from 20 °C to 80 °C. This peculiar temperature characteristic is attributed to originate from unique carrier transport properties of InGaN quantum wells with high In composition, as deduced from the simulation of carrier density and optical gain. In addition, it is found that wall plug efficiency of the blue LD is even improved as temperature increases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface modifications and optical properties of blue InGaN single quantum well by in‐situ thermal treatments
Authors: Lee Sung‐Nam , Paek H. S. , Son J. K. , Sakong T. , Kwon Y. N. , Nam O. H. , Park Y.
Published: January 2007

We investigated the surface modifications and optical properties of blue InGaN single quantum well (SQW) using the in‐situ annealing process with different two temperatures. The surface of blue InGaN SQW was significantly modified from spiral surface to step‐like surface structure as well as the degradation of InGaN PL emission efficiency after in‐situ annealing process at a 1030 °C for 3 min in the metalorganic chemical vapor deposition (MOCVD) system. However, the surface of InGaN SQW was modified from spiral surface to spinodal pattern surface structure after in‐situ annealing process at the InGaN growth temperature of 750 °C. These results implied that the surface atoms of InGaN could significantly rearranged by the thermal treatments at the high temperatures just after the InGaN growth. This surface reconstruction process can be caused by the desorption, the evaporation, and the surface migration of surface adatoms to reduce the thermodynamical instability. Moreover, it is possible to be happened the spinodal related phase separation of InGaN SQW under the in‐situ annealing process with the InGaN growth temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of internal field effect and blue‐shift in InGaN‐based blue laser diodes by time‐resolved optical technique
Authors: Son J. K. , Sakong T. , Hwang J. S. , Lee S. N. , Paek H. S. , Ryu H. Y. , Ha K. H. , Cho Y. H. , Nam O. , Park Y.
Published: January 2007

Power dependent time‐resolved photoluminescence measurements were performed on AlInGaN‐based blue laser diode structures with different well widths. Emission peak shifts were monitored in evolving time at different power of excitation laser. We observed two types of shift. One is power dependent and the other is a constant shift with respect to excitation power density. In particular, the power dependent shift was explained by internal electric field effect but the constant one was not. The reduction of a peak shift was achieved by narrowing the quantum well thickness, mostly attributing to the reduction of the internal field effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN property evolution at all stages of MOVPE Si/N treatment growth
Authors: Halidou I. , Benzarti Z. , Fitouri H. , Fathallah W. , Jani B. El
Published: January 2007

An investigation of MOVPE GaN growth on sapphire (0001) using Si/N treatment is reported. The growth was monitored in situ He‐Ne laser reflectometry. By fitting the reflectivity signal, we derived expressions for the refractive index variation of both sapphire substrate and GaN as a function of the temperature. The morphological and optical property evolutions of the layer at all the growth stages were studied by atomic force microscopy (AFM) and transmittance measurements. A good agreement between AFM images and laser reflectometry signal is obtained. During the island growth and coalescence as clearly revealed by AFM images of the GaN layers, the transmittance signal evolves from featureless characteristic to a signal with regular oscillations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the use of the thermal step method as a tool for study of space charge in semiconductor gallium nitride: GaN
Authors: Bergaoui M. S. , Matoussi A. , Chaabane N. , Guermazi S. , Toureille A. , El Jani B.
Published: January 2007

Thermal step method (TSM) is a non destructive technique which measures the distribution of electric field and the space charge density across a solid insulators. In this paper, we report the experimental results obtained by the Thermal step method (TSM) and The capacitive voltage (C‐V) characterisations of the gallium nitride films grown by the Metal Organic Vapour Phase Epitaxy on silicon substrate. The C‐V curves shows a MOS structure behaviours, this was attributed to the existence of an SiO2 insulator between silicon and GaN. Experimental results were in good accordance with TSM measurements. These where performed under different applied bias voltage, remnant saturation current indicate a sign inversion above ‐75 mV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blue light emitting diodes on Si(001) grown by MOVPE
Authors: Schulze F. , Dadgar A. , Bertram F. , Bläsing J. , Diez A. , Veit P. , Clos R. , Christen J. , Krost A.
Published: January 2007

We report on the growth of GaN‐based light emission diodes on Si(001) substrates. The optically active region of the samples consists of a fivefold InGaN/GaN multiple quantum well grown on a 2.5 µm thick AlGaN/GaN buffer layer structure. By growing on 4° off‐oriented substrates and inserting four thin low‐temperature AlN interlayers, a flat, smooth, and crack‐free surface was obtained. The presented samples show an electrically stimulated emission of bright blue light at 455 and 490 nm, respectively. The crystallographic properties were analyzed by X‐ray diffraction measurements and transmission electron microscopy, and the optical properties by photo‐, electro‐, and spatially resolved cathodoluminescence. The local peak‐wavelength distribution amounts to 14.8 meV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)