bluuebunny/crossref_metadata_2025 huggingface dataset:
Two‐Step Smectic CA Phase Formation from Isotropic Liquid upon Supercooling in Main‐Chain Liquid‐Crystalline BB‐5(1‐Me) Polyester
Authors: Ishige Ryohei , Tokita Masatoshi , Funaoka Shin‐ichiro , Kang Sungmin , Watanabe Junji
Published: November 2010

The mesophase formation process of a main‐chain BB‐5(1‐Me) polyester in the supercooled isotropic‐liquid state has been studied using DSC, WAXD, and optical microscopy. The supercooled isotropic liquid follows two different SmCA formation processes. Above 85 °C, it forms the expected SmCA phase. Below, it yields a metastable SmA phase that displays a layer spacing almost twice the one of the SmCA phase. The SmA phase develops from a homogeneous nucleation followed by 3D growth and thereafter transforms to the SmCA phase. This two‐step SmCA formation involves a change in polymer chain configuration: first, the chains are folded in each two units to form the SmA phase and then they stretch to achieve the characteristic zigzag arrangement of the mesogens in the SmCA phase.

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An Intriguing Morphology Evolution of Polyoxometalate‐Polystyrene Hybrid Amphiphiles from Vesicles to Tubular Aggregates
Authors: Han Yao‐Kun , Zhang Zi‐Jian , Wang Yong‐Liang , Xia Nan , Liu Bo , Xiao Yu , Jin Liu‐Xin , Zheng Ping , Wang Wei
Published: November 2010

The originally synthesized hydrophobic hybrid polymer Bu4N+‐POM‐PS is tuned into a giant amphiphile composed of a hydrophilic H+‐POM head and a hydrophobic PS tail through protonation. Immediately, the hybrid amphiphiles self‐assemble into vesicles. A further annealing treatment induces an evolution from vesicles to tubular aggregates containing H+‐POM nanotubes wrapped with PS coronas. After this transformation, the tubular aggregates grow further and then arrange in a parallel manner to form domains. This interesting morphology evolution provides us an opportunity to understand the intriguing aggregation behavior of the hybrid amphiphiles and, meanwhile, to generate POM nanotubes which might be utilized to create nanomaterials for potential applications.

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Facile One‐Pot Approach for Preparing Functionalized Polymeric Nanoparticles via ROMP
Authors: Liu Jingwei , Liao Yang , He Xiaohua , Yu Jiahui , Ding Liang , Xie Meiran
Published: November 2010

A facile approach to the preparation of functionalized polymeric nanoparticles with UV‐crosslinkable core and bromine‐bearing shell has been developed from the polymerization‐induced self‐assembly of the block copolymers PBNBE‐b‐PCONBI and PBNBE‐b‐PCONBI‐b‐PONBDM. The block copolymers were characterized by means of 1H NMR and GPC. The polymeric nanoparticles with a fixed shell length and varied core lengths were obtained through the control of the molar ratio of monomers in the feed. The micelles were crosslinked using UV‐irradiation, and the characteristics of the polymeric nanoparticles in toluene, THF, or CHCl3 before and after UV irradiation were investigated by means of DLS, UV‐Vis, GPC, AFM, and TEM.

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Assembly Properties of an Alanine‐Rich, Lysine‐Containing Peptide and the Formation of Peptide/Polymer Hybrid Hydrogels
Authors: Grieshaber Sarah E. , Nie Ting , Yan Congqi , Zhong Sheng , Teller Sean S. , Clifton Rodney J. , Pochan Darrin J. , Kiick Kristi L. , Jia Xinqiao
Published: November 2010

An alanine‐based peptide doped with charged lysines with a sequence of (AKA3KA)2 (AK2) was selected from the crosslinking regions of the natural elastin as a starting point for the fabrication of chemically diverse and structurally complex peptide/polymer hybrid hydrogels. At low peptide concentration, Pluronic F127 (F127) micelles are capable of increasing the peptide helicity and stabilizing it against thermal denaturation. At higher peptide concentration in basic media, the AK2 peptide developed a substantial amount of β‐sheet structure. The self‐assembled nanoscale structures were covalently interlocked. The crosslinked hybrid hydrogels were viscoelastic, exhibiting an elastic modulus of approximately 17 kPa and a loss tangent of 0.2.

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Solid‐State Dye‐Sensitized Solar Cells with Conjugated Polymers as Hole‐Transporting Materials
Authors: Zhang Wei , Cheng Yueming , Yin Xiong , Liu Bin
Published: November 2010

DSCs are a promising alternative to conventional silicon‐based solar cells owing to their low cost and relatively high efficiency. However, the utilization of a liquid electrolyte containing the iodine/iodide redox couple in traditional DSCs brings practical problems for their long‐term application, which leads to rapid development of SDSCs based on inorganic p‐type semiconductors or organic HTMs. In this review, we summarize the current research on SDSCs using conjugated polymer as HTM. Special attention is paid to understand the effects of polymer HTM structure and deposition process on SDSC performance. The limiting factors for SDSC energy conversion efficiency are discussed and strategies to improve device performance are proposed.

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Rheological Behavior and Morphologies of Reactively Compatibilized PVDF/TPU Blends
Authors: Ma Haiying , Xiong Zhengrong , Lv Fengxian , Li Chan , Yang Yuming
Published: November 2010

Using the comb copolymer PVDF‐g‐AAc as a compatibilizer, five reactively compatibilized PVDF/TPU blends with different compositions were prepared. During melt blending, the carboxylic acid groups of PVDF‐g‐AAc react with the urethane linkages of TPU to generate the graft copolymers PVDF‐g‐AAc‐g‐TPU, which lead to compatibilization of the PVDF/TPU blends. The rheological behavior of the compatibilized PVDF/TPU blends can be described by a generalized Zener model. PVDF/TPU 50/50 and PVDF/TPU 30/70 blends show a particle network structure, indicating elastic interactions between the grafted shells of compatibilized PVDF domains. SEM shows that almost all compatibilized PVDF/TPU blends exhibit a dispersion‐type morphology.

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Click‐Chemistry: An Alternative Way to Functionalize Poly(2‐methyl‐2‐oxazoline)
Authors: Volet Gisèle , Lav Thanh‐Xuan , Babinot Julien , Amiel Catherine
Published: November 2010

CROP has been used to synthesize well‐defined POXZ with a monofunctional (iodomethane) or a bifunctional (1,3‐diiodopropane) initiator. POXZ has been functionalized with an azido group at one (α‐azido‐POXZ, $\overline {M} _{{\rm n}} $ = 3.58 × 103 g · mol−1) or both ends (α,ω‐azido‐POXZ, $\overline {M} _{{\rm n}} $ = 6.21 × 103 g · mol−1) of the macromolecular chain. The Huisgen 1,3‐dipolar cycloaddition has been investigated between azido‐POXZ and a terminal alkyne on a small or larger molecule (PEG). In each case, the click reaction has been successful and quantitative. In this way, different telechelic polymers (polymers bearing different functions such as acrylate, epoxide, or carboxylic acid) and block copolymers of POXZ and PEG have been prepared. The polymers have been characterized by means of FTIR, 1H NMR, and SEC.

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Controlled Synthesis of Well Defined Poly(3‐hydroxyalkanoate)s‐based Amphiphilic Diblock Copolymers Using Click Chemistry
Authors: Babinot Julien , Renard Estelle , Langlois Valérie
Published: November 2010

A modular synthesis of short chain length and medium chain length poly(3‐hydroxyalkanoate)s‐b‐poly(ethylene glycol) (PHAs‐b‐PEG) diblock copolymers is described. First, length‐controlled oligomers of hydrophobic poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBHV), poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHHx), and poly(3‐hydroxyoctanoate‐co‐hydroxyhexanoate) (PHOHHx) containing a carboxylic acid end group were obtained by thermal treatment, with molar masses ranging from 3 800 to 15 000 g · mol−1. After quantitative functionalization with propargylamine, ligation with azide‐terminated poly(ethylene glycol) of 5 000 g · mol−1 was accomplished using the copper (I) catalyzed azide alkyne cycloaddition (CuAAC). Well‐defined diblock copolymers were obtained up to 93% yield, with molar masses ranging from 9 900 to 23 100 g · mol−1. All products were fully characterized using 1H NMR, COSY, SEC, TGA, and DSC.

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Nanostructured Polymer Blends: From Core/Shell Nanoobjects to Continuous Three‐Phase Morphologies
Authors: Lei Liangcai , Detrembleur Christophe , Jeusette Mélanie , Leclère Philippe , Lazzaroni Roberto , Jérôme Robert
Published: November 2010

A PS‐b‐PIP‐b‐PMMA copolymer has been melt‐blended with homo‐PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.‐% mixture, the components form 3D bicontinuous lamellae. Upon annealing at 190 °C, a more regular network is observed, which consists of PMMA and 55 nm‐thick bilayered lamellae of triblock copolymer, both being continuous. This co‐continuity persists even when$\overline {M} _{{\rm n}} $of the homo‐PMMA is twice that of the PMMA block in the copolymer. For 30:70 and 20:80 wt.‐% copolymer/homopolymer pair, the copolymer forms cylindrical and spherical phases, respectively. Blends have also been prepared by solvent casting. Large domains of copolymer interconnected by few lamellae are observed in the 50:50 blend that reorganize into a bicontinuous network upon annealing.

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Plasma Polymerization Surface Modification of Carbon Black and its Effect in Elastomers
Authors: Mathew Tony , Datta Rabin N. , Dierkes Wilma K. , Talma Auke G. , van Ooij Wim J. , Noordermeer Jacques W. M.
Published: November 2010

Surface modification of carbon black by plasma polymerization was aimed to reduce its surface energy in order to compatibilize the filler with various elastomers. A fullerenic carbon black was used for the modification process. Thermogravimetric analysis, wetting behavior with liquids of known surface tension, TEM and TOF‐SIMS were used to characterize the carbon black before and after modification. The state of plasma‐coated carbon black in rubber was studied by means of conductivity measurements. The behavior of the modified filler in rubber was studied using the Payne effect and stress/strain properties. The study shows that plasma‐coated carbon black results in a better dispersion in different rubber systems than the uncoated version.

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Dramatic Effects of Scalable SNN‐Assisted Melt Dispersion on Thermal Conductivity and Coefficient of Thermal Expansion of Nanocomposites
Authors: Kumar Sandeep , Lively Brooks , Liu Tian , Sun Lili , Tangpong Annie , Zhong Wei‐Hong
Published: November 2010

It is demonstrated that SNN‐assisted melt dispersion can lead to a significant improvement of the thermal conductivity of PC/MWCNT composites accompanied by a dramatic reduction in their linear CTE. The thermal conductivity of the SNN‐containing composites after the 2‐step process was about 95% higher than that of neat PC and 25% higher than that from 1‐step processing at same loading. The CTE below the glass‐transition temperature of composites with a 1.0 wt.‐% MWCNT loading is substantially reduced compared to the neat polymer. A reduction in the CTE of up to 60.8% is observed for composites from the 2‐step process. Simultaneous achievement of high thermal conductivity and low CTE is required for electronic packaging in microelectronics for device protection.

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Design of Nanostructured Waterborne Adhesives with Improved Shear Resistance
Authors: Bellamine Amel , Degrandi Elise , Gerst Matthias , Stark Rüdiger , Beyers Cornelis , Creton Costantino
Published: November 2010

The mechanical and adhesive properties of a series of model nanostructured waterborne PSA films have been characterized. The base polymer composition of the latex has been kept constant but systematic modifications have been carried out: the introduction of nanoparticles localized at the interfaces between particles, and the incorporation of a crosslinking agent. The mechanical properties have been characterized and show that the most effective modifications result in an increase in the low‐frequency modulus in the small‐strain regime and in a more pronounced softening and strain‐rate‐dependent behavior in the large‐strain regime. In industrial standard tests, this combination gives a dramatically increased resistance to shear while maintaining a high value of peel resistance.

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Preparation and Characterization of High‐Performance Poly(trimethylene terephthalate) Nanocomposites Reinforced with Exfoliated Graphite
Authors: Li Meilu , Jeong Young Gyu
Published: November 2010

To improve the physical properties of poly(trimethylene terephthalate) (PTT), a series of nanocomposites based on PTT and exfoliated graphite (EG) are prepared via melt compounding and their structures, thermal stabilities, mechanical, and electrical properties are studied. XRD and SEM show that graphene nanosheets are well dispersed in the PTT matrix without forming crystalline aggregates even at high EG content. Thermal stability and dynamic mechanical moduli of the nanocomposites are substantially improved by EG addition, and a pronounced increase in electrical volume resistivity from an insulator to almost a semiconductor is observed with increasing EG content. The electrical percolation threshold of the nanocomposites is found to be formed at the EG concentration between 3.0 and 5.0 wt.‐%.

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A Comparison of Triazole‐forming Bioconjugation Techniques for Constructing Comb‐Shaped Peptide–Polymer Bioconjugates
Authors: Canalle Luiz A. , van der Knaap Matthijs , Overhand Mark , van Hest Jan C. M.
Published: November 2010

The grafting‐to of a peptide to a side chain functional polymer was investigated using “click” chemistry. Two click reactions were compared: the copper‐free strain‐promoted azide‐alkyne 1,3‐cycloaddition (SPAAC) and the traditional copper‐catalyzed azide‐alkyne 1,3‐cycloaddition (CuAAC). For the resulting comb‐shaped products, it was found that the steric bulk of the conjugation moiety used in SPAAC limits the degree of grafting for these highly dense systems, whereas CuAAC gives (near) quantitative functionalization.

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Periodic Incorporation of Pendant Hydroxyl Groups in Repeating Sequence PLGA Copolymers
Authors: Stayshich Ryan M. , Weiss Ryan M. , Li Jian , Meyer Tara Y.
Published: November 2010

A series of repeating sequence poly(lactic‐co‐glycolic acid) copolymers (RSC PLGAs) has been prepared with the precise incorporation of a pendant benzyl‐ether substituted monomer derived from serine. Copolymers were synthesized from the assembly of sequence‐specific, stereopure dimeric, and trimeric segmers of lactic, glycolic, and (S)‐3‐benzyloxy‐2‐hydroxypropionic acids with controlled and varied tacticities. Deprotection of the hydroxyl groups was accomplished by catalytic hydrogenolysis to yield highly functionialized, hydrophilic polyesters. The 1H and 13C NMR spectra for all of the copolymers were consistent with sequence and stereochemical retention and lacked the signal broadening that is inherent with more random copolymers.

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Silent saliva aspiration in Parkinson's disease
Authors: Rodrigues Bernardo , Nóbrega Ana Caline , Sampaio Marília , Argolo Natalie , Melo Ailton
Published: November 2010

Background: Silent laryngeal penetration and silent aspiration (SLP/SA) are common manifestations in Parkinson's disease (PD) patients and are frequently associated with dysphagia. However, little is known about saliva aspiration in this population. Objective: We investigated the frequency and characteristics of saliva SLP/SA in PD patients with daily drooling (Group A) and in individuals without PD or daily drooling (Group B). Method: Both groups were evaluated by fiberoptic endoscopic evaluation of swallowing (FEES) after dyeing the oral cavity with blue dye. The oropharynx was assessed for the presence of the stasis of saliva, and sensitivity was tested by direct tactile stimuli. Results: PD patients (n = 28) and controls (n = 18) were evaluated. We observed silent aspiration of saliva in 10.7% and silent laryngeal penetration of saliva near the vocal folds in 28.6% of Group A; however, none of these events was observed in Group B. Sensitivity in the epiglottis and posterior wall of the hypopharynx was decreased in 89.2% of Group A and in 33.3% of Group B, whereas in the aryepiglottic folds and interarytenoid area, a decrease in sensitivity was observed in 92.8% and in 44.4% of Groups A and B, respectively. Conclusion: Silent aspiration and laryngeal penetration of saliva are common features in PD patients with daily drooling. The presence of hypoesthesia of the laryngeal structures and the lack of protective reflexes in such patients may play a major role in the mechanisms of SLP/SA. © 2010 Movement Disorder Society.
Rantes secreted from macrophages disturbs skeletal muscle regeneration after cardiotoxin injection in Cbl‐b‐deficient mice
Authors: Kohno Shohei , Ueji Tatsuya , Abe Tomoki , Nakao Reiko , Hirasaka Katsuya , Oarada Motoko , Harada‐Sukeno Akiko , Ohno Ayako , Higashibata Akira , Mukai Rie , Terao Junji , Okumura Yuushi , Nikawa Takeshi
Published: November 2010

Deficiency of the Cbl‐b ubiquitin ligase gene activates macrophages in mice. This study aimed to elucidate the pathophysiological roles of macrophages in muscle degeneration/regeneration in Cbl‐b‐deficient mice. We examined immune cell infiltration and cytokine expression in cardiotoxin‐injected tibialis anterior muscle of Cbl‐b‐deficient mice. Ablation of the Cbl‐b gene expression delayed regeneration of cardiotoxin‐induced skeletal muscle damage compared with wild‐type mice. CD8‐positive T cells were still present in the damaged muscle on day 14 after cardiotoxin injection in Cbl‐b‐deficient mice, but there was dispersal of the same cells over that time‐frame in wild‐type mice. Infiltrating macrophages in Cbl‐b‐deficient mice showed strong expression of RANTES (regulated‐on‐activation, normal T cell expressed and secreted), a chemokine for CD8‐positive T cells. In turn, a neutralizing antibody against RANTES significantly suppressed the infiltration of CD8‐positive T cells into the muscle, resulting in restoration of the disturbed muscle regeneration. Cbl‐b is an important regulatory factor for cytotoxic T‐cell infiltration via RANTES production in macrophages. Muscle Nerve, 2011
Thermal Residual Stresses and Triaxiality Measures
Authors: Wippler Johannes , Böhlke Thomas
Published: November 2010

High performance ceramics have found their way into many highly challenging engineering tasks. For example silicon nitride is one of the best choices, if a material for demanding applications like metal forming and cutting is required. Due to the brittle nature of these hard and strong materials it is useful to know about thermal residual stresses, which can arise during the sintering process. In order to gain insight into the material behaviour, a single grain inclusion is exposed to thermal loads. Due to thermal mismatch, it undergoes a residual stress and strain field. The geometry of the model and the material data are motivated by the properties of silicon nitride. The stress fields are analyzed by three different measures for stress triaxiality. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical problems of the theory of elasticity for solids with double porosity
Authors: Svanadze Merab
Published: November 2010

In this paper the dynamical theory of elasticity for solids with double porosity is presented. The single‐layer and double‐layer potentials are constructed and basic properties are established. The uniqueness theorems of the internal and external boundary value problems (BVPs) of steady vibrations are proved. The existence theorems of classical solution of the external BVPs by means of the boundary integral method and the theory of multidimensional singular integral equations are proved. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Aerodynamic Optimization of Wind Farm Layout
Authors: Rašuo Boško , Bengin Aleksandar , Veg Aleksandar
Published: November 2010

This paper presents a method for determination of optimum positions of single wind turbines within the wind farms installed on arbitrary configured terrains, in order to achieve their maximum production effectiveness. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of mixed Lie derivatives in nonlinear control
Authors: Röbenack Klaus
Published: November 2010

Several algorithms in nonlinear control require Lie derivatives. The symbolic computation using computer algebra software is straightforward. However, the applicability of symbolic computation in nonlinear control is limited due to a considerable increase of the sizes of higher order derivatives. This problem can be circumvented using an alternative computation technique for derivatives called algorithmic differentiation. We extend existing approaches to calculate mixed Lie derivaties. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Malignant germ cell tumors associated with Swyer syndrome
Authors: Stachowicz‐Stencel Teresa , Synakiewicz Anna , Iżycka‐Świeszewska Ewa , Kobierska‐Gulida Grażyna , Balcerska Anna
Published: November 2010

Swyer syndrome is characterized by a higher risk of developing genital malignancies. In this disorder, the most common is gonadoblastoma and dysgerminoma but also, in rare cases, choriocarcinoma. The prognosis in choriocarcinoma is poor. The early diagnosis of dysgenetic gonads is necessary in view of the risk of malignancies. It can be difficult due to its different clinical masks. When the neoplasm precedes the diagnosis of gonadal dysgenesis, adequate oncological treatment should be introduced with parallel gonadectomy. We present a case of 14‐year‐old female with 46, XY karyotype with choriocarcinoma in one gonad and dysgerminoma in the second one. Pediatr Blood Cancer 2011;56:482–483. © 2010 Wiley‐Liss, Inc.
Risks of congenital malformations and perinatal events among infants exposed to calcium channel and beta‐blockers during pregnancy
Authors: Davis Robert L. , Eastman David , McPhillips Heather , Raebel Marsha A. , Andrade Susan E , Smith David , Yood Marianne Ulcickas , Dublin Sascha , Platt Richard
Published: November 2010

Purpose

Calcium channel blockers and beta‐blockers (BBs) are widely used during pregnancy, but data on their safety for the developing infant are scarce. We used population‐based data from 5 HMOs to study risks for perinatal complications and congenital defects among infants exposed in‐utero.

Methods

We studied women older than 15 years delivering an infant between 1/1/96 and 12/31/00, who had been continuously enrolled with prescription drug coverage for ≥1 year prior to delivery. Information on prescription drug dispensings, inpatient, and outpatient diagnoses and procedures was obtained from automated databases at each HMO.

Results

There were 584 full‐term infants exposed during pregnancy to BBs and 804 full‐term infants exposed to calcium‐channel blockers, and over 75 000 unexposed mother–infant pairs with ≥30 days follow‐up. Infants exposed to BBs in the third trimester of pregnancy had over threefold increased risk for hypoglycemia (RR 3.1; 95% CI 2.2, 4.2) and an approximately twofold increased risk for feeding problems (RR 1.8; 95% CI 1.3, 2.5). Infants exposed to calcium‐channel blockers in the third trimester had an increased risk for seizures (RR 3.6 95% CI 1.3, 10.4). Chart review confirmed the majority of the exposed seizure and hypoglycemia cases. There were no increased risks for congenital anomalies among either group of infants, except for the category of upper alimentary tract anomalies; this increased risk was based on only two exposed cases.

Conclusions

Infants whose mothers receive BBs are at increased risk for neonatal hypoglycemia, while those whose mothers take calcium‐channel blockers are at increased risk for neonatal seizures. Copyright © 2010 John Wiley & Sons, Ltd.
The curing retardation and mechanism of high temperature vulcanizing silicone rubber filled with superconductive carbon blacks
Authors: Zhang Yuanyuan , Pang Minglei , Xu Qiang , Lu Haifeng , Zhang Jie , Feng Shengyu
Published: November 2010

The curing retardation and mechanism of high‐temperature vulcanizing silicone rubber (HTV SR) filled with superconductive carbon black (CB) BP2000 have been studied experimentally and theoretically. The results show that both rubber matrix and CBs have influences on the peroxide curing of rubber/CBs composites. The retardation does not appear as prominent in nature rubber (NR)/BP2000 composites as in HTV SR/BP2000 composites. Quantum chemistry calculations reveal that the curing retardation of HTV SR/BP2000 composite should not be attributed to the curing reaction dynamics of HTV SR molecules. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) analyses of CBs show that the effect of radical scavenging of phenol‐OH groups existing on BP2000 surface is the main reason for the retardation in the peroxide curing reaction. The effect is found to be more effective in HTV SR/BP2000 composite and thus retards its curing. The curing retardation does not appear in silicone rubber (SR)/BP2000 composites vulcanized by condensation reaction, and the resulting vulcanizates have excellent physical properties. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.
Dielectric spectroscopy of poly(butylene succinate‐co‐butylene adipate) films
Authors: Tai Horng‐Jer
Published: November 2010

The results of dielectric studies in semicrystalline poly (butylene succinate‐co‐butylene adipate) (PBSA) by means of dielectric relaxation spectroscopy from 163 to 353 K and in the frequency range of 0.056–17,800 Hz are reported. The subglass β process is found to follow an Arrhenius temperature dependence, whereas the segmental α process follows a Vogel–Fulcher–Tammann temperature dependence. The higher temperature Maxwell–Wagner–Sillars (MWS) process was studied by applying the Bruggeman‐Hanai equation, which helped to understand the underlying relaxation dynamics. The MWS process originates from the charge accumulation at the interface between the low‐conductivity continuous medium and the high‐conductivity dispersed particles. A three‐phase model in which the medium comprises the crystalline and rigid amorphous phases (RAPs) and the particle comprises solely the mobile amorphous phases (MAPs) is required to explain the particle fraction variation with temperature. With increasing temperature, the MAP fraction increases at the expense of the RAP fraction within the continuous medium. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.
Biobased cyanate ester composites with epoxidized soybean oil and in situ generated nano‐silica
Authors: Zhan Guozhu , Tang Xiaolin , Yu Yingfeng , Li Shanjun
Published: November 2010

Biobased cyanate ester (CE) nanocomposites have been prepared from renewable resource, epoxidized soybean oil (ESO) and in situ generated nano‐silica via sol–gel process. The isothermal curing process was investigated by differential scanning calorimetry (DSC) and rheometry. The results indicate that the incorporation of silica accelerates the reaction at the beginning stage of curing process but descends the final isothermal curing conversion. The morphological study of nanocomposites by scanning electron microscope and transmission electron microscope suggests that the silica exists in the forms of both nanoparticles and silica networks, while the diameter of ESO‐rich phase diminished with the increase of silica loading. In addition, the thermal–physical and mechanical properties were evaluated by dynamic mechanical analysis, thermogravimetric analysis, and tensile mechanical test. The biobased CE nanocomposites show effectively improved properties compared to the systems without nano‐silica. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.
Crosslinking of poly(N‐vinyl‐2‐pyrrolidone) in the coating of cotton yarn
Authors: Immich Ana Paula Serafini , de Araújo Pedro Henrique Hermes , Catalani Luiz Henrique , de Souza Antônio Augusto Ulson , Souza Selene M.A. Guelli U.
Published: November 2010

Coating of cotton yarn is employed in the textile industry to increase the mechanical resistance of the yarns and resistance to vibration, friction, impact, and elongation, which are some of the forces to which the yarn is subjected during the weaving process. The main objective of this study is to investigate the usage of a synthetic hydrophilic polymer, poly(N‐vinyl‐2‐pyrrolidone) (PVP), to coat 100% cotton textile yarn, aiming to give the yarn a temporary mechanical resistance. For the improvement of the mechanical resistance of the yarn, the following crosslinking processes of PVP were investigated: UV‐C (ultraviolet) radiation, the Fenton and photo‐Fenton reactions, and sensitized UV‐C radiation. The influence of each crosslinking process was determined through tensile testing of the coated yarns. The results indicated that the best crosslinking process employed was UV‐C radiation; increasing the mechanical resistance of the yarn up to 44% if compared with the pure cotton yarn, that is, without polymeric coating and crosslinking. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.
In situ binary sol–gel reaction of various trifunctional alkoxysilane in the silane‐grafted polyolefin matrix and its effect upon the mechanical properties
Authors: Adachi Kenta , Honda Kensuke , Yamazaki Suzuko , Hirano Tomoyuki , Kurokawa Hiroshi , Wakabayashi Akinobu , Kasai Paul H. , Nakamae Katsuhiko , Iwabuki Hitoshi , Murakami Koji
Published: November 2010

The vinyltrimethoxysilane‐grafted ethylene‐propylene copolymer/trifunctional methoxysilane (EPR‐g‐VTMS/RTMS) composites were prepared via in situ silica sol–gel reactions. Five trifunctional methoxysilane compounds (n‐hexyltrimethoxysilane, n‐decyltrimethoxysilane, n‐tetradecyltrimethoxysilane, n‐octadecyltrimethoxysilane, and phenyltrimethoxysilane) have been selected for this study. The water‐cross‐linked EPR‐g‐VTMS/RTMS composites were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy, gel content, solid‐state 29Si CP/MAS NMR, wide‐angle x‐ray scattering, tensile strength, and field emission scanning electron microscopy measurements. The type of RTMS additive has a substantial influence on the nature of siloxane band networks and eventually the mechanical tensile properties. This finding suggests that the interaction and/or entanglement between the EPR‐g‐VTMS matrix and the substituent of the RTMS additives are crucial for the modifying mechanical properties. Moreover, for the water‐cross‐linked EPR‐g‐VTMS/CnTMS (n = 6, 10, 14, and 18) composites, the joint evidence provided by attenuated total reflectance‐Fourier transform infrared spectroscopy, 29Si CP/MAS NMR, and wide‐angle x‐ray scattering results suggested the formation of ladder‐type poly(n‐alkyl silsesquioxane)s and the presence of the highly ordered structure with a thickness equal to the length of two n‐alkyl groups in all‐trans conformation. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.
Comments Regarding ‘An Essay on Contact Angle Measurements’
Authors: Di Mundo Rosa , Palumbo Fabio
Published: November 2010

In this commentary we discuss the assay by M. Strobel and C. S. Lyons on contact angle measurements, critical and popular topic in surface/plasma science community. We agree with stressing the importance of dynamic contact angle measurements (i.e. the evaluation of both advancing and receding). However, we make some remarks about the meaning of angle hysteresis with particular regard to the concepts of roughness and chemical heterogeneity, on the basis of our experience in hydrophobic and super‐hydrophobic surfaces. Further, we describe our different point of view in the dispute between Wilhelmy balance and sessile drop methods.
The structure of the ends of α‐helices in globular proteins: Effect of additional hydrogen bonds and implications for helix formation
Authors: Leader David P. , Milner‐White E. James
Published: November 2010

We prepared a set of about 2000 α‐helices from a relational database of high‐resolution three‐dimensional structures of globular proteins, and identified additional main chain i ← i+3 hydrogen bonds at the ends of the helices (i.e., where the hydrogen bonding potential is not fulfilled by canonical i ← i+4 hydrogen bonds). About one‐third of α‐helices have such additional hydrogen bonds at the N‐terminus, and more than half do so at the C‐terminus. Although many of these additional hydrogen bonds at the C‐terminus are associated with Schellman loops, the majority are not. We compared the dihedral angles at the termini of α‐helices having or lacking the additional hydrogen bonds. Significant differences were found, especially at the C‐terminus, where the dihedral angles at positions C2 and C1 in the absence of additional hydrogen bonds deviate substantially from those occurring within the α‐helix. Using a novel approach we show how the structure of the C‐terminus of the α‐helix can emerge from that of constituent overlapping α‐turns and β‐turns, which individually show a variation in dihedral angles at different positions. We have also considered the direction of propagation of the α‐helix using this approach. If one assumes that helices start as a single α‐turn and grow by successive addition of further α‐turns, the paths for growth in the N → C and C → N directions differ in a way that suggests that extension in the C → N direction is favored. Proteins 2011. © 2010 Wiley‐Liss, Inc.
Impurities in graphene
Authors: Zhang Yan‐Yang , Hu Jiangping , Bernevig B. A. , Wang X. R. , Xie X. C. , Liu W. M.
Published: November 2010

We report the transport properties of graphene in the presence of topological and (non‐topological) long‐range impurities, in the framework of a tight‐binding model. We first investigate the electronic transport properties of a zigzag edge graphene nanoribbon with several kinds topological defects: a pentagon, a heptagon, and a pentagon–heptagon pair at the center. On the aspect of non‐topological impurities, we perform systematic calculations to investigate the effect of the impurity potential range and its density on the conductance of graphene nanoribbon. Moreover, we demonstrate that the nonlinear dependence in the recent experiment can also be explained when scattering due to the low density and long‐range impurities are accounted. We also calculate the scaling properties of disordered graphene with long‐range impurities in the framework of finite‐size scaling. On the marginal metallic side, we find that the conductance is independent of the system size, which is a characteristic of the Kosterlitz–Thouless type transition in conventional 2D systems with random magnetic field. We explicitly probe the K–T transition nature of the MIT by identifying the bounding and unbounding vortex‐anti‐vortex local currents in the system.
InxGa1−xAs quantum wire network‐like and ordered checker board‐like nanostructures on GaAs (311) by low In composition multi‐layer stacking
Authors: Lee Jihoon , Wang Zhiming , Yazdanpanah V. , Kim Eun‐Soo , Koo Sang‐Mo , Salamo Gregory J.
Published: November 2010

Unique quantum wire (QWR) network‐like nanostructures (QWRNNs) and ordered checker board‐like nanostructures (OCBNs) were demonstrated on GaAs (311) A and B by applying a low In composition multiple‐layer stacking technique. More specifically, the combination of low In composition and multilayer systems, [In0.18Ga0.82As/GaAs]m where m = 1, 4, 8, 10, 12, and 16 periods, have been investigated on GaAs (311) A and B by molecular beam epitaxy (MBE). Under a same growth condition, QWRNNs were demonstrated on GaAs (311)A while OCBNs were fabricated on GaAs (311)B as a result of the strain accumulation and transfer through the multiple layers stacked. An appropriate control of the number of layers stacked and spacer thickness can result in an improved ordering and uniformity of QWRNNs and OCBNs.
Analyses of the As doping of SiO2/Si/SiO2 nanostructures
Authors: Ruffino Francesco , Tomasello Mario Vincenzo , Miritello Maria , De Bastiani Riccardo , Nicotra Giuseppe , Spinella Corrado , Grimaldi Maria Grazia
Published: November 2010

We illustrate the behaviour of As when it is confined, by the implantation technique, in a SiO2(70nm)/Si(30nm)/SiO2(70nm) multilayer and its spatial redistribution when annealing processes are performed. By Rutherford backscattering spectrometry and Z‐contrast transmission electron microscopy we found an As accumulation at the Si/SiO2 interfaces and at the Si grain boundaries with no segregation of the As in the Si layer.

Such an effect is in agreement with a model that assumes a traps distribution in the Si in the first 2–3 nm above the SiO2/Si interfaces and along the Si grain boundaries. The traps concentration at the Si/SiO2 interfaces was estimated in 1014 traps/cm2. The outlined results can open perspectives on the doping properties of As in Si nanocrystals, whose applications in nanoelectronics and optoelectronics are widely investigated (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical characterisation of Si‐SiO2 structures
Authors: Capan Ivana , Pivac Branko , Slunjski Robert
Published: November 2010

The possibility of studying the Si‐SiO2 structures by means of deep level transient spectroscopy (DLTS) has been presented. Contrary to the standard application of this technique, the temperature interval has to be reduced. In order to minimize the influence, and possible errors due to the capacitance base line shift and the Fermi level pinning, C‐V characterization at different temperatures is crucial prior the DLTS measurement. The interface traps related to the Pb centers, distributed around 0.35 eV below the conduction band, have been observed (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation of breather and soliton in a substituted polythiophene with a degenerate ground state
Authors: Kobayashi Takayoshi , Du Juan , Feng Wei , Yoshino Katsumi , Tretiak Sergei , Saxena Avadh , Bishop Alan R.
Published: November 2010

The ultrafast dynamics of a unique polythiophene derivative that has a degenerate ground state due to a quantum mechanical resonance was investigated using a sub‐5‐fs pulse laser. The method allowed us to study the electronic relaxation and vibrational dynamics in completely same conditions at the same time. The dynamics of a breather composed of a dynamic bound state of solitons generated immediately after photoexcitation was time‐resolved to reveal coupling between the vibrational modes and the solitons. The C‐C and C=C stretching modes were found to be modulated by the breather, whose lifetime was determined to be 30‐50 fs. The results of quantum‐chemical excited‐state molecular dynamics simulation are consistent with experimental results. Our modeling results allow to identify related vibrational normal modes strongly coupled to the electronic degrees of freedom. Moreover, analysis of calculated trajectories of excited state shows appearance of short‐lived breather excitation decaying due to intramolecular vibrational energy equilibration on a timescale of hundreds of femtoseconds, which also agrees well with the experimental results. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and magnetic properties of diluted magnetic semiconductor GaGdN nanorods
Authors: Tambo H. , Hasegawa S. , Higashi K. , Kakimi R. , Tawil S. N. M. , Zhou Y. K. , Emura S. , Asahi H.
Published: November 2010

Diluted magnetic semiconductor GaGdN nanorods were grown on Si (001) substrates with native silicon oxides by molecular‐beam epitaxy with radio frequency nitrogen plasma. The Gd cell temperature dependences of their structural and magnetic properties were systematically studied. It was found that higher Gd fluxes suppress the growth of nanorods along the c‐direction and form GdN secondary phase. Magnetic measurement also revealed that nanorods of high content Gd showed small magnetization, indicating that GdN come to form and therefore the amount of Gd atoms substituted for Ga sites in GaGdN decreases. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface analysis of n‐GaN crystal damaged by RF‐plasma‐etching with Ar, Kr, and Xe gases
Authors: Niibe Masahito , Maeda Yoshie , Kawakami Retsuo , Inaoka Takeshi , Tominaga Kikuo , Mukai Takashi
Published: November 2010

To understand the etching phenomenon or preferential etching in the GaN crystal that consisted of two elemental atoms, dry etchings were carried out using rare gases with a simple structure. n‐type GaN crystals were RF‐plasma‐etched with Ar, Kr, and Xe gases at various gas pressures and etching times. The etched surfaces were analysed with the XPS method. The surface composition (N/Ga ratio) of the samples etched at Ar pressure of 10 mTorr and 200 mTorr almost agreed with the calculation values of the plasma particle model (PIS). N/Ga ratio of Ar etched sample at the pressure of 50 – 100 mTorr was approximately one and did not agree with the PIS calculation. This discrepancy seems to be related to the pit‐like defect formation at the pressure range. The values of the N/Ga ratio of the samples etched with Kr and Xe gases were approximately one and did not agree with the theoretical PIS calculation, which predicts N/Ga > 1. This discrepancy may have occurred by N2 molecule formation with excess N atoms, and which may have been desorbed from the surface. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic characterization of thin aluminum nitride microstructures
Authors: Knöbber F. , Bludau O. , Röhlig C.‐C. , Sah R. E. , Williams O. A. , Kirste L. , Leopold S. , Pätz D. , Cimalla V. , Ambacher O. , Lebedev V.
Published: November 2010

In this work we report on the mechanical and material properties of membranes made of AlN and nanodiamond for the use in tunable micro‐optics. AlN membranes with and without metal contacts have been studied in dynamic mode by laser Doppler vibrometry. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The optimization of TiO2 compact layer in dye‐sensitized solar cell by the analysis of performance and internal impedance
Authors: Kim Jin‐Kyoung , Seo Hyunwoong , Son Min‐Kyu , Shin Inyoung , Choi Jin‐Ho , Choi Seok‐Won , Kim Hee‐Je
Published: November 2010

The working electrode of a Dye–sensitized Solar Cell (DSC) is a fluorine‐doped tin oxide (FTO) glass substrate pasted with nano‐porous TiO2. Under the illumination, dye molecules are excited and electrons are emitted. The electrons pass through two interfaces of dye/TiO2 and TiO2/FTO. Therefore, electron of the TiO2 conduction band combines with I3‐ ion of the electrolyte. A compact layer between the FTO and nano‐porous TiO2 layer makes adherence of TiO2 to FTO surface improved, and the electron recombination reduced because it blocks the direct contact between the redox electrolyte and the FTO surface. Although some researches have studied the insertion of compact layer so far, only materials and the coating methods were studied. To the best of our knowledge, there was no study of a correlation between thickness and efficiency. Therefore, in this study, we investigated on the change in the output characteristics of DSCs according to thickness of TiO2 compact layer fabricated by coating in TiCl4 aqueous solution. The thickness of compact layer was controlled by repetitive coatings and measured by field emission scanning electron microscopy. The effects in terms of the I‐V characteristics and the electrochemical impedance spectroscopy (EIS) were examined for the analysis of the change in the thickness of TiO2 compact layer. As a result, the optimum thickness which has the highest output in the I‐V characteristics and the smallest area of EIS semi‐circle was derived. And the photovoltaic performance of DSC with an optimum compact layer was maximized (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interaction between conduction‐band edge and nitrogen‐related localized levels in nitrogen δ ‐doped GaAs
Authors: Harada Yukihiro , Kojima Osamu , Kita Takashi , Wada Osamu
Published: November 2010

We have studied sharp emission lines created by interacting between the GaAs host‐matrix conduction‐band edge and nitrogen‐related localized levels in nitrogen δ ‐doped GaAs by using magneto‐photoluminescence spectroscopy. According to the decreased diamagnetic coefficient of 75 μeV/T2 at the 1.515‐eV line, the interaction between the conduction‐band edge and localized levels has been confirmed. Furthermore, we have observed a linear polarization anisotropy for these emission lines. This polarization splitting demonstrates that the electronic states of the nitrogen pair couple with the GaAs conduction‐band edge. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
1/f noise models and low‐frequency noise characteristics of InAlAs/InGaAs devices
Authors: Pavelka Jan , Tacano Munecazu , Tanuma Nobuhisa , Šikula Josef
Published: November 2010

Transport and low frequency noise characteristics of In0.52Al0.48As/InxGa1‐xAs heterostructures were measured in wide temperature range (15 K to 450 K) and experimental results compared with intrinsic 1/f noise models, estimating mobility fluctuations due to various scattering processes. The 1/f phonon energy partition fluctuation model predicts the value of Hooge parameter given as the ratio of the lattice constant and mean free path and several p‐type and n‐type samples reveal corresponding values of αH ≅ 0.5 and αH ≅ 4×10‐3, respectively. Most of the lattice‐matched n‐type samples however give much lower αH of about 10‐5 for temperature below 200 K, which is closer to the quantum 1/f noise theory limit. At elevated temperatures g‐r noise was observed with trap activation energy 0.63 eV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Broadband light sources using InAs quantum dots with InGaAs strain‐reducing layers
Authors: Tsuda Megumi , Inoue Tomoya , Kita Takashi , Wada Osamu
Published: November 2010

We fabricated broadband superluminescent diodes (SLDs) for optical coherence tomography (OCT). We used three kinds of quantum dot (QD) layers with different emission peak wavelengths in the active region of SLD. The emission wavelength was controlled by reducing the strain in QDs; by using the In0.1Ga0.9 As strain‐reducing layer, the peak wavelength shifted toward the longer‐wavelength side, and the photoluminescence peak intensity becomes strong in contrast to QDs on GaAs.

By stacking these strain‐controlled QD layers, the SLD device shows a broad electroluminescence spectrum with the center wavelength of 1130 nm and the spectral linewidth of approximately 240 nm at the injection of 1A caused by the increased emission intensity from the excited states. This corresponds to an resolution of 2.3 μm in OCT. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature‐insensitive photoluminescence emission wavelength in GaAs1–xBix/GaAs multiquantum wells
Authors: Tominaga Yoriko , Oe Kunishige , Yoshimoto Masahiro
Published: November 2010

GaAs1–xBix/GaAs multiquantum wells (MQWs) were grown on GaAs substrate by molecular beam epitaxy at a growth temperature of 350 ºC. The MQWs showed clear satellite peaks and interference fringes between the satellite peaks in their high‐resolution x‐ray diffraction patterns. It was confirmed that photoluminescence (PL) emission wavelengths in GaAs1–xBix/GaAs MQWs have temperature insensitivity. The temperature coefficient of the PL peak energy in GaAs1–xBix/GaAs MQWs decreased with increasing GaBi molar fraction. For GaAs0.946Bi0.054/GaAs MQWs, the temperature coefficient of the PL peak energy was confirmed to be –0.19 meV/K (180–300 K) that is 40% of the value for the band gap of GaAs. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)