bluuebunny/crossref_metadata_2025 huggingface dataset:
Collision-Free Tool Path Generation for Five-Axis High Speed Machining
Authors: Zhang Li Qiang , Yue Min
Published: April 2011

Collision detection is a critical problem in five-axis high speed machining. Using a combination of process simulation and collision detection based on image analysis, a rapid detection approach is developed. The geometric model provides the cut geometry for the collision detection and records a dynamic geometric information for in-process workpiece. For the precise collision detection, a strategy of image analysis method is developed in order to make the approach efficient and maintian a high detection precision. An example of five-axis machining propeller is studied to demonstrate the proposed approach. It has shown that the collision detection task can be achieved with a near real-time performance.
Ultrasound In Situ Testing of early Hydration Process of Supplementary Cementitious Pastes
Authors: Liu Zhi Yong , Zhang Yun Sheng , Sun Guo Wen , Jiang Qian , Zhu Wei Wei
Published: April 2011

The early hydration process was investigated using ultrasonic monitoring apparatus for pastes made with various mineral admixtures: silica fume (4%, 13%), slag (10%, 30%, 50%, 70%), and fly ash (10%, 30%, 50%). The influence of water to binder ratio (0.23, 0.35 and 0.53) was also studied. The results show that the hydration rate of cementitious material is obviously accelerated with decreasing in water to cement ratio and Silica fume addition, while the reverse phenomenon is observed when fly ash and slag are incorporated.
Mechanical Properties and Permeability of Recycled Aggregate Concrete at Low Water/Binder Ratio
Authors: Peng Gai Fei , Liu Qi Bin , Guo Zhu Bo , Hou Qiao Xing , Cao Si Qi , Zhang Jiu Feng
Published: April 2011

This paper presents an experimental research on mechanical properties and permeability of recycled aggregate concrete (RAC). Concretes at a water/binder ratio of 0.255 were broken into recycled aggregates (RA). A type of thermal treatment was employed to remove mortar in RA. Tests were conducted on aggregate to measure water absorption and crushed values, and on RAC and natural aggregate concrete (NAC) to measure compressive strength, tensile splitting strength, and fracture energy. The results revealed that both gravel damage and mortar attached can significantly influence the water absorption and crushed value of RA. The mechanical properties RAC were obviously lower than those of NAC at an identical mix proportion. Moreover the removal of mortar caused a decrease in mechanical properties. The behavior of the chloride ion penetration of RAC under compressive loading is different that of NAC, which may be related to the flaws of RA. Further experimental research is needed to identify its mechanism.
Experimental Study on Statistical Parameters of Concrete Strength Based on Weibull Probability Distribution
Authors: He Xi Xi , Xie Zhi Hui
Published: April 2011

Along with deterministic size effect theory statement, Weibull distributed size effect has been neglected generally. The author believes that, deterministic size effect is not established to the basic strength index of plain concrete without notches. Definite size effect has an application limitation on the large-size zone. The most recent development of size effect is the fracture size effect theory based on probability in modern times. As a result of stress concentration caused by the notches, failure mechanism is bond to be affected. Therefore, the existing fracture theory needs to be tested. Meanwhile, the weakest chain link theory of material unit is still used in the existing statistics energy size effect model, which still needs to fix Weibull parameter m. Through more than 1000 dates of 24 groups of various kinds of concrete cube compressive strength and splitting tensile strength statistical tests in the recent years by our project group, the article has analyzed the statistical characteristics of basic strength of concrete and its influencing factors. Regression statistical analysis on shape and scale parameters of Weibull distribution has been studied.
Effects of Powdery Mill Tailings from Magnetite on Workability and Strength of Concretes
Authors: Cai Ji Wei , Wu Ji Xu , Lü Zheng Hang , Gao Guang Liang
Published: April 2011

The discarded mill tailings behind the dam will cause disasters at any time. A solution to this problem may be to utilize those wastes, e.g. mill tailings from magnetite, as the Manufactured Fine Aggregates (MFA) for preparation of concretes. The mill tailings from magnetite can be considered as new resources of sand. However, in production of MFA from mill tailings, the particles smaller than 75 μm were strictly eliminated. The degranulation results in not only lower utilization of the resources but also worse micro grading of MFA. The micro fines, i.e. powdery mill tailings from magnetite, supplements powder content in concrete systems in w/c>0.40 to modify the ratio of water to total powder (w/p). The perfect micro grading for good workability can be reached in the case of optimal w/p ratio. The filling effect owing to perfect micro grading of powdery mill tailings makes concretes more compact and the pozzolanic constituents in micro particles of the tailings contribute to the strength of concretes.
The Effect of Activators on the Fly Ash-Based Geopolymers
Authors: Hou Yun Fen , Wang Dong Min
Published: April 2011

This paper studies the influences of concentration and modulus of sodium silicate solution (Na activator) and sodium potassium silicate solution (Na-K activator) on the phase composition, microstructure and strength development in the geopolymers prepared using Class F fly ash. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and MAS NMR were utilized. It shows that the compressive strength increases while Na activator solution modulus increases, but when modulus exceeds 1.4, the compressive strength decreases, and it decreases markedly while modulus is greater than 2.0. The compressive strength improves with increase of sodium silicate solution concentration, and when concentration is 32%, compressive strength reaches the maximum, and then it reduces with concentration increment. It shows that the compressive strength increases while Na-K activator solution modulus increases, but when modulus exceeds 1.7, the compressive strength decreases, and it decreases markedly while modulus is greater than 2.0. The compressive strength improves with increase of Na-K activator solution concentration, and when concentration is 36%, compressive strength reaches the maximum. The main product of reaction in the geopolymeric material is amorphous alkali aluminosilicate gel.
A Probabilistic Approach to the Simulation of Non-Linear Stress-Strain Relationships for Oriented Strandboard Subject to In-Plane Tension
Authors: McTigue Antony T. , Harte Annette M.
Published: April 2011

This paper presents the results from an experimental test program conducted on commercially available oriented strandboard (OSB) panels and statistical analyses of the results. Standardised testing was used to determine the short-term behaviour of OSB/3 panels subjected to tension loading. A variety of thicknesses sourced from three different producers were used. Analysis of the results indicate that a quadratic expression in the form of  = a2 + b provides the best description of the relationship between stress (and strain ( up to the point of failure. It has also been shown that the coefficients a and b of the quadratic regression equations are negatively correlated to each other. Anderson-Darling goodness-of-fit tests were conducted on the results for tension strength and modulus of elasticity (MOE). The results indicate that the tension strength and MOE come from populations that follow either normal or lognormal probability distributions.
The Formation and Occurrence of Non-Metallic Inclusions of Si-Doped Steel during Continuous Casting
Authors: Lin Dong Yih , Yang Sheng Min
Published: April 2011

Inclusion in steel material plays a decisive role on the purity of steels that becomes more important in the energy critical age. This study was focused on the number and morphology of inclusions with different cooling rate in the continuous casting process. A low carbon steel with 3.36 wt% silicon content was used as test material, which was soaked at 1100°C, 1250°C and 1400°C for 2 hours. The analyzed results of microstructure and chemical compositions showed the inclusions were not dissolved into matrix but formed as compounds like oxide, sulfide, and nitride after reheating at 1100°C. However, the inclusion size and average number possessed increasable trend, compared to as-cast sample. Manganese sulfide began to be dissolved into matrix by reheating at 1250°C. Some evidences showed the dissolution of aluminum nitride under the reheating at 1400°C. The inclusion size varied from 8 μm to 3 μm, and average number decreased with increasing soaking temperature.
Amorphization Behavior of Ni57Zr20Ti22Ge1 Powders by Mechanical Alloying
Authors: Kuo Kai Chen , Lee Pee Yew , Yen Jai Yush
Published: April 2011

In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Ge1 powder was examined in details. The conventional X-ray diffraction results confirm that the fully amorphous powders formed after 5 hours of milling. The thermal stability of the Ni57Zr20Ti22Ge1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 761 K and 839 K, respectively. The supercooled liquid region ΔT is 78 K. The appearance of wide supercooled liquid region may be mainly due to the Ge additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Ge1 powders.
Band Structure Calculations for EuCo2X2 (X = Ge, Si) and EuM5 (M = Cu, Ni)
Authors: Goraus Jerzy , Maślankiewicz Paweł , Szade Jacek
Published: April 2011

Band structure calculations for EuCo2X2 (X = Si, Ge) and EuM5¬ (M = Ni, Cu) were performed using FP-LAPW and FPLO DFT codes. Correlations were taken into account within Around Mean Field (AMF) and Fully Localized Limit (FLL) approaches. Antiferromagnetic supercell was constructed for EuCo2X2. Several exchange-correlation potentials were used for EuM5. Equilibrium lattice parameters were calculated for EuM5 and used to study the magnetic properties. Calculated europium valence is between 2.3 and 2.5 and slightly higher for EuNi5 and EuCo2Si2 than for EuCu5 and EuCo2Ge2. LSDA+U calculations within the AMF double-counting scheme are in better agreement with photoemission data than calculations using the FLL approach.
Thermally Induced High-Spin Low-Spin Transition in Co[Cr0.5Ga1.5]S4 Spinel
Authors: Krok-Kowalski J. , Maciążek Ewa , Groń Tadeusz , Pacyna Andrzej W. , Mydlarz Tadeusz , Władarz G.
Published: April 2011

A high spin (HS) – low spin (LS) transition has been discovered in the Co[Cr0.5Ga1.5]S4 spinel, where the Co ions occupy tetrahedral sites and the Cr and Ga ions octahedral ones. The latter are diluted by the non-magnetic Ga-ions. Application of magnetic fields revealed ferrimagnetic order with a Curie temperature TC = 126 K, a strong suppression of the magnetic susceptibility () and a slight shift of TC to lower temperatures. A cusp at 15.6 K on the ac (T) curve suggests a spin frustration of the re-entrant type. Characteristic for the HS-LS transition is an inflection point at 150 K on the 1/(T) curve, a lack of the Curie-Weiss region above TC and a small value of the magnetization, 4.76 emu/g at 4.4 K and at a magnetic field of 57.5 kOe.
Siderophore mediated metal uptake by Pseudomonas fluorescens and its comparison to Iron (III) chelation
Authors: Bhattacharya Aditi
Published: April 2011

Siderophores are iron chelating substances that are also known to bind metals such as Molybdenum and Lead. The pigment produced by P. fluorescens is a siderophore whose ability to bind to different metal ions was investigated in this study. Pigment production was increased in the presence of Sodium, Potassium, Lead, Molybdenum and Cadmium. Siderophores were detected using CAS assay and catechol - siderophores by Arnow assay. Peak changes and changes in extinction coefficient values are indicators of complex formation. Maximum difference was observed in siderophore free Iron and Iron-siderophore complexes. Some changes were also noted for siderophore- metal complexes for all metals included in this study. Thus siderophore of P. fluorescens shows a tendency to form complexes with almost all metals tested. Key words: pigment; CAS assay; metal ions; complex formation; peak changes; molar extinction coefficient. DOI: 10.4038/cjsbs.v39i2.3001 Cey. J. Sci. (Bio. Sci.) 39 (2): 147-155, 2010
IL-23 Receptor Regulation by Let-7f in Human CD4+ Memory T Cells
Authors: Li Zhaoxia , Wu Feng , Brant Steven R. , Kwon John H.
Published: April 2011

CD4+ memory T cells include the Th17 cell population, which has been shown to be implicated in autoimmune and inflammatory diseases. These memory T cells express higher IL-23R and produce more IL-17 compared with their naive counterparts. However, the molecular mechanisms that regulate IL-23R expression in human T cells are not completely understood. MicroRNAs play important roles in a wide range of biological events through posttranscriptional suppression of target mRNAs. In this article, we provide evidence that a specific microRNA, Let-7f, inhibits IL-23R expression in human CD4+ memory T cells. Endogenous expression of Let-7f in memory T cells is significantly lower when compared with naive T cells, and Let-7f blocks IL-23R expression through its complementary target sequence within 3′ untranslated region of target gene. Furthermore, exogenous transfection of a Let-7f mimic into memory T cells results in downregulation of IL-23R and its downstream cytokine, IL-17. Our findings reveal a novel mechanism in regulating the IL-23/IL-23R pathway and subsequent downstream IL-17 production, which may provide novel therapeutics for human inflammatory and autoimmune diseases.
Serum Amyloid A Activates the NLRP3 Inflammasome via P2X7 Receptor and a Cathepsin B-Sensitive Pathway
Authors: Niemi Katri , Teirilä Laura , Lappalainen Jani , Rajamäki Kristiina , Baumann Marc H. , Öörni Katariina , Wolff Henrik , Kovanen Petri T. , Matikainen Sampsa , Eklund Kari K.
Published: April 2011

Serum amyloid A (SAA) is an acute-phase protein, the serum levels of which can increase up to 1000-fold during inflammation. SAA has a pathogenic role in amyloid A-type amyloidosis, and increased serum levels of SAA correlate with the risk for cardiovascular diseases. IL-1β is a key proinflammatory cytokine, and its secretion is strictly controlled by the inflammasomes. We studied the role of SAA in the regulation of IL-1β production and activation of the inflammasome cascade in human and mouse macrophages, as well as in THP-1 cells. SAA could provide a signal for the induction of pro–IL-1β expression and for inflammasome activation, resulting in secretion of mature IL-1β. Blocking TLR2 and TLR4 attenuated SAA-induced expression of IL1B, whereas inhibition of caspase-1 and the ATP receptor P2X7 abrogated the release of mature IL-1β. NLRP3 inflammasome consists of the NLRP3 receptor and the adaptor protein apoptosis-associated speck-like protein containing CARD (a caspase-recruitment domain) (ASC). SAA-mediated IL-1β secretion was markedly reduced in ASC−/− macrophages, and silencing NLRP3 decreased IL-1β secretion, confirming NLRP3 as the SAA-responsive inflammasome. Inflammasome activation was dependent on cathepsin B activity, but it was not associated with lysosomal destabilization. SAA also induced secretion of cathepsin B and ASC. In conclusion, SAA can induce the expression of pro–IL-1β and activation of the NLRP3 inflammasome via P2X7 receptor and a cathepsin B-sensitive pathway. Thus, during systemic inflammation, SAA may promote the production of IL-1β in tissues. Furthermore, the SAA-induced secretion of active cathepsin B may lead to extracellular processing of SAA and, thus, potentially to the development of amyloid A amyloidosis.
Dual Protective Mechanisms of Matrix Metalloproteinases 2 and 9 in Immune Defense against Streptococcus pneumoniae
Authors: Hong Jeong-Soo , Greenlee Kendra J. , Pitchumani Ramanan , Lee Seung-Hyo , Song Li-zhen , Shan Ming , Chang Seon Hee , Park Pyong Woo , Dong Chen , Werb Zena , Bidani Akhil , Corry David B. , Kheradmand Farrah
Published: April 2011

A localized and effective innate immune response to pathogenic bacterial invasion is central to host survival. Identification of the critical local innate mediators of lung defense against such pathogens is essential for a complete understanding of the mechanism(s) underlying effective host defense. In an acute model of Streptococcus pneumoniae lung infection, deficiency in matrix metalloproteinase (MMP)2 and MMP9 (Mmp2/9−/−) conferred a survival disadvantage relative to wild-type mice treated under the same conditions. S. pneumoniae-infected Mmp2/9−/− mice recruited more polymorphonuclear leukocytes to the lung but had higher bacterial burdens. Mmp2/9−/− mice showed significantly higher levels of IL-17A, IP-10, and RANTES in the lung. Although MMP2-dependent cleavage partially inactivated IL-17A, MMP9 was critical for effective bacterial phagocytosis and reactive oxygen species generation in polymorphonuclear neutrophils. These data demonstrate critical nonredundant and protective roles for MMP2 and MMP9 in the early host immune response against S. pneumoniae infection.
Pannexin-1 Is Required for ATP Release during Apoptosis but Not for Inflammasome Activation
Authors: Qu Yan , Misaghi Shahram , Newton Kim , Gilmour Laurie L. , Louie Salina , Cupp James E. , Dubyak George R. , Hackos David , Dixit Vishva M.
Published: April 2011

Apoptotic cell death is important for embryonic development, immune cell homeostasis, and pathogen elimination. Innate immune cells also undergo a very rapid form of cell death termed pyroptosis after activating the protease caspase-1. The hemichannel pannexin-1 has been implicated in both processes. In this study, we describe the characterization of pannexin-1–deficient mice. LPS-primed bone marrow-derived macrophages lacking pannexin-1 activated caspase-1 and secreted its substrates IL-1β and IL-18 normally after stimulation with ATP, nigericin, alum, silica, flagellin, or cytoplasmic DNA, indicating that pannexin-1 is dispensable for assembly of caspase-1–activating inflammasome complexes. Instead, thymocytes lacking pannexin-1, but not the P2X7R purinergic receptor, were defective in their uptake of the nucleic acid dye YO-PRO-1 during early apoptosis. Cell death was not delayed but, unlike their wild-type counterparts, Panx1−/− thymocytes failed to recruit wild-type peritoneal macrophages in a Transwell migration assay. These data are consistent with pannexin-1 liberating ATP and other yet to be defined “find me” signals necessary for macrophage recruitment to apoptotic cells.
Multi-Scale Ballistic Impact Simulation of Dry Woven Fabric with Elastic Crimped Fibers
Authors: Tabiei Ala , Nilakantan Gaurav
Published: April 2011

A material model has been developed to realistically simulate the behavior of loose woven fabrics with elastic crimped fibers subject to varying loading conditions such as in-plane and transverse loading. It is based upon a multi-scale micromechanical approach that includes the architecture of the fabric and the phenomenon of fiber reorientation, with fiber simplified as one dimensional elastic members with a single failure criterion. The material model is implemented as a user-defined subroutine in the explicit, non-linear dynamic finite element code LSDYNA. Results of fabric test simulations run in LSDYNA using this material model agree well with experimental results, demonstrating the material model s capability to accurately simulate ballistic impact of woven fabrics.
Conselho de administração das empresas de governança corporativa listadas na BM&FBovespa: análise à luz da entropia da informação da atuação independente
Authors: Moura Geovanne Dias de , Beuren Ilse Maria
Published: April 2011

A propriedade acionária concentrada de empresas pode resultar em ambiente de conflitos na relação entre acionistas minoritários e majoritários. A governança corporativa busca minimizar esse conflito, tendo o conselho de administração como principal órgão de atuação. Porém, a atuação dependerá do seu nível de independência, que está associado com a maior ou menor influência dos acionistas controladores. O estudo objetiva verificar se o conselho de administração das empresas listadas no nível 1, nível 2 e novo mercado da BM&Fbovespa atua de maneira independente em relação aos acionistas controladores sob a ótica da entropia da informação. Pesquisa descritiva, com abordagem quantitativa, foi realizada por meio de pesquisa documental. A população da pesquisa compreende as companhias abertas da BM&Fbovespa e a amostra compõe-se das 156 participantes dos níveis de governança corporativa. Nas Informações Anuais (IAN) das empresas foram coletados os dados referentes ao exercício findo em 31/12/2009. Os dados foram organizados em tabelas, evidenciando-se aspectos do conselho de administração, o total de cada item e suas respectivas médias. Como a análise pela média pode resultar em viés, para testar se o conselho de administração das empresas possui as configurações obtidas pelas médias, foi calculada a entropia da informação. Os resultados indicaram um ambiente com possibilidade de conflitos, pois existe concentração de capital principalmente entre as empresas do novo mercado. Conclui-se que em virtude da forte influência dos controladores no conselho de administração, seus membros não atuam de maneira independente e podem ter suas atuações de redução de conflito de agência prejudicadas.
Comparison between Anti-Vascular Endothelial Growth Factor Therapy and Photodynamic Therapy for Myopic Choroidal Neovascularization
Authors: Matsuo Misa , Honda Shigeru , Matsumiya Wataru , Kusuhara Sentaro , Tsukahara Yasutomo , Negi Akira
Published: April 2011

Purpose

To compare the efficacy of anti–vascular endothelial growth factor (VEGF) therapy versus photodynamic therapy (PDT) for myopic choroidal neovascularization (mCNV).

Methods

This study is a retrospective interventional study. Forty-two eyes from 42 patients with mCNV (36 subfoveal, 4 juxtafoveal, and 2 extrafoveal) treated and followed up for more than 6 months were included. Twenty eyes from 20 patients were treated by PDT (PDT group) at 1.5±0.9 months after the symptoms and 22 eyes from 22 patients were treated by anti-VEGF therapy (anti-VEGF group) at 0.9±0.8 months after the symptoms. Photodynamic therapy was performed, followed up, and retreated by standard procedures. Anti-VEGF therapy was repeated as needed. Gender, age, best-corrected visual acuity (BCVA), greatest linear dimension (GLD), central retinal thickness (CRT), and outer nuclear layer (ONL) thickness at the fovea were then compared between the anti-VEGF and PDT groups.

Results

No differences were detected in baseline parameters between the anti-VEGF and PDT groups. The mean BCVA (logMAR) at month 3 and 6 after the initial treatment was improved (–0.30 and −0.29) from baseline in the anti-VEGF group, which was statistically significant (p=0.0048 and 0.021, respectively). In the PDT group, modest improvements were observed in the mean BCVA at the same time periods (–0.05 and −0.10) with no statistical significance (p=0.79 and 0.90, respectively). The mean CRT was significantly reduced from baseline to month 6 in the anti-VEGF and PDT groups. The ONL thickness was significantly reduced in both groups, although the magnitude was significantly greater in the PDT group than the anti-VEGF group.

Conclusions

Treatment with anti-VEGF therapy had significantly better visual outcomes than PDT for mCNV.
Towards Integrated Molecular Electronic Devices: Characterization of Molecular Layer Integrity During Fabrication Processes
Authors: Mahmoud Amr M. , Bergren Adam Johan , Pekas Nikola , McCreery Richard L.
Published: April 2011

Reproducible carbon/molecule/Cu molecular junctions are made with high yield using diazonium reduction of aromatic molecules on carbon with direct evaporation of Cu as a top contact. This report investigates the stability of these devices in response to fabrication steps. Raman spectroscopy through a transparent support shows that direct deposition of Au or Cu causes little change in molecular layer structure, while Ti and Pt deposition cause significant damage to the molecules. AFM, Raman, and XPS examination of Au, Cu, and Ti devices after removal of deposited metal confirm that Cu and Au have minimal effects on molecular structure. However, the molecular layer is rougher after Au deposition, probably due to partial penetration of Au atoms into the molecular layer. Completed carbon/molecule/Cu devices can be heated to 250 °C without significant changes in electronic behaviour while nitroazobenzene molecular layers on carbon were unaffected by photolithography or by 5 min at 400 °C in vacuum. Completed devices could be sealed with parylene‐N, stabilizing them to aqueous etching solution. The stability of carbon/molecule/Cu junctions is due, in part, to the strong carbon–carbon bonding and aggressive nature of diazonium surface modification. The results significantly expand the range of processing variables compatible with molecular electronic junctions.
Strain‐Based Temperature Memory Effect for Nafion and Its Molecular Origins
Authors: Xie Tao , Page Kirt A. , Eastman Scott A.
Published: April 2011

A shape memory polymer traditionally refers to a polymer that can memorize one temporary shape and recover to its permanent shape upon exposure to an external stimulus. Although this basic concept has been known for at least half a century, recent advances have led to the discoveriy of previously uncovered memory properties that challenge the traditional concept of shape memory polymers. In particular, a temperature memory effect refers to the capability of a polymer to memorize temperatures instead of shapes. Thus far, the reported temperature memory effect has been established under iso‐strain stress recovery conditions, in which the maximum recovery stress appears at a temperature roughly identical to the deformation temperature. This effect can be called recovery stress based temperature memory effect. In this work, experiments were designed in an attempt to establish a temperature memory effect based on the stress free strain recovery behaviors of Nafion. The results show that, under carefully selected conditions, the temperature at which a maximum strain recovery rate is observed can indeed be quantitatively related to the deformation temperature. In addition, indications that the polymer is capable of memorizing more than one deformation temperature (i.e., multi‐temperature memory effect) are shown. The molecular origin of Nafion’s temperature memory effect is elucidated through small angle neutron scattering study.
Modification of Exciton Lifetime by the Metal Cathode in Phosphorescent OLEDs, and Implications on Device Efficiency and Efficiency Roll‐off Behavior
Authors: Song Dandan , Zhao Suling , Aziz Hany
Published: April 2011

Time resolved photoluminescence and electroluminescence measurements are used to study changes in the emission characteristics of materials typically used in phosphorescent organic light emitting devices (PhOLEDs). Studies on archetypical PhOLEDs with phosphorescent material, fac‐tris(2‐phenylpyridine) iridium (Ir(ppy)3), show that the lifetime of triplet exciton is modified when in close proximity to a metal layer. Interactions with a metal layer ∼30–100 nm away, as is typically the case in PhOLEDs, result in an increase in the spontaneous emission decay rate of triplet excitons, and causes the exciton lifetime to become shorter as the distance between the phosphorescent material and the metal becomes smaller. The phenomenon, possibly the result of the confined radiation field by the metal, affects device efficiency and efficiency roll‐off behavior. The results shed the light on phenomena affecting the efficiency behavior of PhOLEDs, and provide new insights for device design that can help enhance efficiency performance.
“Brick‐and‐Mortar” Self‐Assembly Approach to Graphitic Mesoporous Carbon Nanocomposites
Authors: Fulvio Pasquale F. , Mayes Richard T. , Wang Xiqing , Mahurin Shannon M. , Bauer John C. , Presser Volker , McDonough John , Gogotsi Yury , Dai Sheng
Published: April 2011

Mesoporous carbon materials do not have sufficient ordering at the atomic scale to exhibit good electronic conductivity. To date, mesoporous carbons having uniform mesopores and high surface areas have been prepared from partially‐graphitizable precursors in the presence of templates. High temperature thermal treatments above 2000 °C, which are usually required to increase conductivity, result in a partial or total collapse of the mesoporous structures and reduced surface areas induced by growth of graphitic domains, limiting their applications in electric double layer capacitors and lithium‐ion batteries. In this work, we successfully implemented a “brick‐and‐mortar” approach to obtain ordered graphitic mesoporous carbon nanocomposites with tunable mesopore sizes below 850 °C without using graphitization catalysts or high temperature thermal treatments. Phenolic resin‐based mesoporous carbons act as mortar to highly conductive carbon blacks and carbon onions (bricks). The capacitance and resistivity of final materials can be tailored by changing the mortar to brick ratios.
Asymmetric Supercapacitors Based on Graphene/MnO2 and Activated Carbon Nanofiber Electrodes with High Power and Energy Density
Authors: Fan Zhuangjun , Yan Jun , Wei Tong , Zhi Linjie , Ning Guoqing , Li Tianyou , Wei Fei
Published: April 2011

Asymmetric supercapacitor with high energy density has been developed successfully using graphene/MnO2 composite as positive electrode and activated carbon nanofibers (ACN) as negative electrode in a neutral aqueous Na2SO4 electrolyte. Due to the high capacitances and excellent rate performances of graphene/MnO2 and ACN, as well as the synergistic effects of the two electrodes, such asymmetric cell exhibits superior electrochemical performances. An optimized asymmetric supercapacitor can be cycled reversibly in the voltage range of 0–1.8 V, and exhibits maximum energy density of 51.1 Wh kg−1, which is much higher than that of MnO2//DWNT cell (29.1 Wh kg−1). Additionally, graphene/MnO2//ACN asymmetric supercapacitor exhibits excellent cycling durability, with 97% specific capacitance retained even after 1000 cycles. These encouraging results show great potential in developing energy storage devices with high energy and power densities for practical applications.
Functionalization and Patterning of Protein‐Based Materials Using Active Ultrabithorax Chimeras
Authors: Huang Zhao , Salim Taha , Brawley Autumn , Patterson Jan , Matthews Kathleen S. , Bondos Sarah E.
Published: April 2011

A key advantage of protein‐based materials is the potential to directly incorporate novel functions via gene fusion to produce a single chimeric polypeptide capable of both self‐assembly and the desired activity. However, facile production of functionalized protein materials is frequently hampered by the need to trigger materials assembly using conditions that will not irreversibly damage the functional protein. In contrast, the recombinant Drosophila melanogaster transcription factor Ultrabithorax (Ubx) rapidly self‐assembles under mild, aqueous conditions to form highly extensible materials with a variety of morphologies. Here, it is demonstrated that materials composed of Ubx chimeras with Enhanced Green Fluorescent Protein (EGFP), mCherry, luciferase, or myoglobin display the functions of the appended proteins, indicating that these activities are neither impaired by the assembly process nor by confinement within the materials. Finally, methods are established that combine EGFP‐Ubx and mCherry‐Ubx monomers to self‐assemble materials patterned on the microscale to macroscale. The self‐adhesive properties of Ubx materials also permit manual construction and patterning of more complex forms. The ability to easily functionalize and pattern protein‐based materials greatly expands their potential utility in a wide variety of applications.
Direct Writing of Metal Nanoparticles by Localized Plasma Electrochemical Reduction of Metal Cations in Polymer Films
Authors: Lee Seung Whan , Liang Dong , Gao Xuan P. A. , Sankaran R. Mohan
Published: April 2011

A non‐lithographic, dry approach to patterning metal nanoparticles is presented. Solutions of metal salt and polymer are spin‐coated onto a substrate, dried, and exposed to a rastered microscale plasma operated at atmospheric pressure and room temperature. Interaction of the electrons in the plasma with the film results in electrochemical reduction of the metal cations to crystalline metal nanoparticles. The process is highly localized, making it possible to obtain microscale patterns of metal nanoparticles with line widths as small as ∼30 μm. We have applied this technique to a wide range of metals such as Ag, Au, Pt, Ir, and Ru, in various polymeric systems such as polyvinyl alcohol (PVA) and poly(methyl methacrylate) (PMMA). Overall, the approach allows the fabrication of transparent, flexible, patterned films of metal nanoparticles at low cost and high throughput for applications ranging from plasmonics to catalysis.
Engineering of Ultra‐Hydrophobic Functional Coatings Using Controlled Aggregation of Bicomponent Core/Shell Janus Particles
Authors: Berger Sebastian , Ionov Leonid , Synytska Alla
Published: April 2011

The morphology and wetting properties of coatings prepared using fully‐ covered, mono‐ and bicomponent polymeric Janus particles are investigated and compared. The particles are adsorbed on silica wafers, which were preliminarily coated by thin layers of chemically grafted polymer. The fully‐covered particles form hexagonally packed layers with very hydrophobic wetting properties. In contrast, the Janus particles tend to form aggregates. This is possible due to their ability to self‐assemble and form hierarchical structured aggregates in dispersions. The deposition of these agglomerates on the substrate leads to the formation of hierarchical rough layers which possess a certain level of fractality. The obtained layers are either very hydrophobic or ultra‐hydrophobic, depending on the chemical structure of the polymers grafted to the Janus particles, on the nature of supported substrate, and on the level of aggregation of Janus particles into hierarchical structures. The obtained findings could be very important for design of novel materials with advanced properties.
Controlling Interface Intermixing and Properties of SrTiO3‐Based Superlattices
Authors: Mizoguchi Teruyasu , Ohta Hiromichi , Lee Hak‐Sung , Takahashi Nobuaki , Ikuhara Yuichi
Published: April 2011

By combining state‐of‐the‐art microscopy, spectrosccopy, and first‐principles calculations, atomic‐scale intermixing behavior at heterointerfaces in SrTiO3‐based superlattices is investigated. It is found that Nb is confined to a unit‐cell thickness without intermixing, whereas Ba diffuses only to the adjoining Nb‐doped SrTiO3 layer. It is revealed that the intermixing behaviors at the heterointerfaces are determined by not only the migration energy, but also by the vacancy‐formation energy and the Fermi energy of each layer. Based on these results, we find a method to control the atomic‐scale intermixing at the nonpolar heterointerfaces and clearly demonstrate the property improvements obtained by constructing an abrupt heterointerface.
Bifunctional cobalt Salen complex: a highly selective catalyst for the coupling of CO2 and epoxides under mild conditions
Authors: Li Hongchun , Niu Yongsheng
Published: April 2011

A bifunctional cobalt Salen complex containing a Lewis acid metal center and two covalent bonded Lewis bases on the ligand was designed and used for the coupling of CO2 and epoxides under mild conditions. The complex exhibited excellent activity (turnover frequency = 673/h) and selectivity (no less than 97%) for polymer formation in the copolymerization of propylene oxide (PO) and CO2 at an appropriate combination of all variables. High molecular weight of 110 200 and yield 99% were achieved at a higher [PO]/[complex] ratio of 6000:1. The complex also worked satisfactorily for the terpolymerization of CO2, PO and cyclohexene oxide (CHO), without formation of cyclic carbonate or ether linkages to give the polycarbonate. High cyclohexene carbonate unit content in the CO2/PO/CHO terpolymers resulted in enhanced thermal stability. Copyright © 2011 John Wiley & Sons, Ltd.
Synthesis and antimicrobial studies of bis(O,O′‐dialkyl and alkylene dithiophosphoric acid) adducts of diphenyl diselenide
Authors: Khaldy A. A. S. El , Abushanab A. M. , Alkhair Emad Abu
Published: April 2011

Dialkyl and alkylene dithiophoshoric acids react with diphenyl diselenide in a 1:2 molar ratio in refluxing benzene to yield Ph2Se2·2HS2P(OR)2 (R = Et, Pr‐n, Pr‐i, Bu‐i and Ph) and , where G = ‐CH2CMe2CH2‐, ‐CH2CEt2CH2‐ and ‐CMe2CMe2‐. The complexes are yellow solids (in the cyclic chain) and yellow sticky solids (in the open chain), are soluble in common organic solvents and are monomeric in nature. They were characterized on the basis of elemental analyses, molecular weight determinations, IR and NMR (1H, 13C and 31P). The spectral data revealed addition of dithiophosphate moieties to the diselenide. Studies were conducted to assess the growth‐inhibiting potential of some of the synthesized complexes against various bacterial strains. Copyright © 2011 John Wiley & Sons, Ltd.
Process design methodology for high‐energy saving HIDiC based on self‐heat recuperation
Authors: Kansha Yasuki , Kishimoto Akira , Tsutsumi Atsushi
Published: April 2011

In this article, a novel design methodology based on self‐heat recuperation for a heat integrated distillation column (HIDiC) is proposed. HIDiC is a well‐known energy saving distillation process, in which the condensation heat of the rectification section is recovered and exchanged with the vaporization heat of the stripping section. By following self‐heat recuperation technology, the energy input/output of the HIDiC can be analyzed and the whole process heat can be recirculated by pressure change in the process, leading to further reduction of energy consumption. The simulation results demonstrate that the energy consumption for the HIDiC based on the proposed design methodology using self‐heat recuperation is drastically decreased compared with benchmark processes which use external heat sources. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Experimental and numerical study of pulverized bituminous coal ignition characteristics in O2/N2 and O2/CO2 atmospheres
Authors: Wu Le , Qiao Yu , Yao Hong
Published: April 2011

An unsteady‐state model of a pulverized coal cloud including the submodels of radiation and convection was used to study the ignition characteristics of a Datong bituminous coal under the conditions of O2/N2 and O2/CO2 atmospheres. An increase in the ignition temperature was calculated for the bituminous coal when air (21% O2 + 79% N2) was replaced with a mixture of 21% O2 + 79% CO2. With the increase of coal concentration, the ignition temperature reduced under O2/CO2 atmosphere. The ignition temperature of a Datong bituminous coal was investigated using thermogravimetric analysis (TGA) and a small furnace; experiment results showed a similar trend with the calculated results. Pulverized coal in ignition mode also appears very differently when the atmosphere changes. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Synthesis of SiO2/PS composite particles via emulsion polymerization
Authors: Han Zhaorang , Wang Li , Zhu Jianmin , Zhang Shufen , Zhou Wei
Published: April 2011

SiO2 particles prepared by Stöber method were modified using 1,3,5,7‐tetravinyl‐1,3,5,7‐tetramethylcyclotetrasiloxane (Vi‐D4), and SiO2/polystyrene (PS) composite particles with core‐shell structure were synthesized adopting mulsion polymerization of PS in a water–ethanol medium. The products were characterized by infrared spectra, X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Zetasizer analyzer. The average diameter of SiO2 particles prepared by Stöber method was about 80 nm, the SiO2 particles were modified using the molar ratio of Vi‐D4 and SiO2 particles 1 : 10 (the dosage of Vi‐D4 benever too much), and the size of modified silica particles was about 90 nm. The infrared spectra indicated that the Vi‐D4 had bonded to the silanol groups on surface of SiO2 particles, and XPS indicated the grafting efficiency of Vi‐D4 on surface of SiO2 particles had reached 90%. The infrared spectra indicated the PS had been incorporated with SiO2 particles, and TEM indicated the composite particles have obvious core‐shell structure. The suitable size of SiO2 particles should be lower than 200 nm, and the optimum volume ratio of ethanol and water should be 1 : 9 or 1 : 4. A kind of monodisperse SiO2/PS composite particles having function of self‐assembling was successfully and effectively synthesized. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Modification of linear low‐density polyethylene film using oxygen scavengers for its application in storage of bun and bread
Authors: Matche Rajeshwar S. , Sreekumar R. K. , Raj Baldev
Published: April 2011

Linear low‐density polyethylene (LLDPE) film was modified by blending with zinc, iron, or ascorbic acid as oxygen scavenger. The modified films were characterized for their physicomechanical properties and their application for oxygen scavenging. There was no significant change in the physicomechanical properties. The oxygen scavenging property of the films was studied by shelf‐life studies of bun and bread. The shelf life studies were conducted using the modified films and LLDPE film as a control. The sensory analysis showed good taste and texture of bun and bread till the fifth day. The control sample was not acceptable even on second day. This was supported by instrumental texture analysis. There was no significant change in force required to compress the sample in case of packed scavenging film while the control sample showed significant change. The moisture analysis also showed similar results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Crystallization and melting behavior of biodegradable poly(ethylene succinate‐co‐6 mol % butylene succinate)
Authors: Yang Yan , Qiu Zhaobin
Published: April 2011

The crystallization, melting behavior, and spherulitic growth kinetics of biodegradable poly(ethylene succinate‐co‐6 mol % butylene succinate) [P(ES‐co‐6 mol % BS)] were investigated and compared with those of the homopolymer poly(ethylene succinate) (PES) in this work. The crystal structure of P(ES‐co‐6 mol % BS) was the same as that of neat PES, but the crystallinity decreased slightly because of the incorporation of the butylene succinate content. The glass‐transition temperature decreased slightly for P(ES‐co‐6 mol % BS) compared to that for neat PES. The melting point of P(ES‐co‐6 mol % BS) decreased apparently; moreover, the equilibrium melting point was also reduced. Two melting endotherms were found for P(ES‐co‐6 mol % BS) after isothermal crystallization; this was ascribed to the melting, recrystallization, and remelting mechanism. The spherulitic growth rate of P(ES‐co‐6 mol % BS) was slower than that of neat PES at a given crystallization temperature. Both neat PES and P(ES‐co‐6 mol % BS) exhibited a crystallization regime II to III transition; moreover, the crystallization regime transition temperature of P(ES‐co‐6 mol % BS) shifted to a low temperature compared with that of neat PES. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and thermal response behavior of poly(N‐isopropylacrylamide‐co‐a crylic acid) microgels via soap‐free emulsion polymerization based on AIBN initiator
Authors: Chen Shufan , Jiang Long , Dan Yi
Published: April 2011

Poly(N‐isopropylacrylamide‐co‐acrylic acid) (poly(NIPAM‐co‐AA)) microgels with different copolymer compositions were prepared through soap‐free emulsion polymerization at 80°C, and 2, 2′‐azobisisobutyronitrile (AIBN) was used as initiator. Scanning electron microscope (SEM) characterization shows that the prepared microgels are regular and smooth and not easy to distort. Result of 1H‐NMR characterization shows that with increasing of the initial concentration of AA (AA in feed), the AA content in polymer chains increases. The thermal response of microgels latex was investigated by UV‐3010 spectrophometer through detecting the transmittance of the latex at different temperature in the range of 190–900 nm. The thermal response of the poly(NIPAM‐co‐AA) microgels was tested by dynamic light scattering (DLS). The results show that with the increase of AA content in polymer chains, the low critical solution temperature (LCST) of microgels latex first decreases and then increases. Still, with increasing of AA in poly(NIPAM‐co‐AA) microgels, the LCST of microgels first increases and then decreases. The basic reasons causing the changes of LCST of microgels latex and microgels are interpreted clearly in this article from the perspective of hydrogen bonding interaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Synthesis and characterization of tetrakis‐ derivatives of bisphenol‐A with 4‐phenylazoaniline and 5‐(4‐aminophenylazo)‐25,26,27‐tribenzoyloxy‐ 28‐hydroxycalix[4]arene
Authors: Karakuş Özlem Özen , Deligöz Hasalettin
Published: April 2011

The synthesis of tetrakis‐ derivatives of bisphenol‐A containing azo groups at their 2,2′,6,6′‐positions is reported. Novel examples of bisphenol‐A, coupled with diazonium salts and derived from 4‐phenylazoaniline and 5‐(4‐aminophenylazo)‐25,26,27‐tribenzoyloxy‐28‐hydroxycalix [4]arene, have been synthesized. It has been observed that the coupling reaction of diazonium salt obtained from 4‐phenylazoaniline with bisphenol‐A gives tetrakis‐ while those derived from 5‐(4‐aminophenylazo)‐25,26,27‐tribenzoyloxy‐28‐hydroxycalix [4]arene give partially substituted bisphenol‐A analogues. The newly prepared tetrakis‐azo substituted bisphenol‐A compounds (1 and 2) are characterized by using UV‐vis, FT‐IR, 1H‐NMR spectroscopic methods as well as elemental analysis techniques. These azo compounds give rise to bathochromic shifts in the absorption spectra, which can even be detected by “naked eye.” © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Use of rosin‐based nonionic surfactants as petroleum crude oil sludge dispersants
Authors: Atta Ayman M. , Elsaeed Ashraf M.
Published: April 2011

The present work provides better knowledge for composition analyses of the sludge and evaluates the best effective and economical treatment of petroleum sludge. In this respect, nonionic polymeric surfactants based on rosin were prepared by esterification of rosin with different molecular weights of polyethylene glycol (PEG 400, 600, 1000, 2000) to produce rosin ester surfactants. The esterified rosin was reacted with maleic anhydride followed by reaction with diaminobutane or triethylene tetramine to produce rosin‐imide. The products were etherified with PEG 600 and PEG 2000 to produce rosin‐imide ERID‐1, ERID‐2, ERIT‐1 and ERIT‐2, which were characterized by FT‐IR and 1H‐NMR analyses. The surfactants were tested as sludge dispersants from viscosity measurements of sludge crude oil mixtures at different times. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011