bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and characterization of poly(butylene terephthalate)/silica nanocomposites
Authors: Yao Xiayin , Tian Xingyou , Zhang Xian , Zheng Kang , Zheng Jin , Wang Ruoxi , Kang Shenghong , Cui Ping 
Published: February 2009

AbstractIn this study, we presented a convenient, in situ polymerization route for the preparation of Poly (butylene terephthalate) (PBT)/silica nanocomposites, in which silica was not premodified. The nanocomposites were synthesized by in situ polymerization of terephthalic acid (TPA), 1,4‐butanediol (BD) and silica. The structure of these nanocomposites were investigated by Fourier transform infrared (FTIR) and thermogravimetric analyses (TGA). The results show that PBT chains were successfully grafted onto the surface of silica. Transmission electron microscope (TEM) micrographs revealed that silica were homogeneously dispersed in PBT matrix at a size level of 10–20 nm. The isothermal crystallization kinetics of pure PBT and PBT/silica nanocomposites were investigated by differential scanning calorimeter (DSC) and simulated by Avrami model. The existence of silica could lead to an acceleration of crystallization and enhance the thermal stability of PBT. According to dynamic mechanical analysis (DMA), the storage modulus of PBT/silica nanocomposites were markedly improved compared with pure PBT. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Nylon 66/clay nanocomposite structure development in a twin screw extruder
Authors: Lin Bin , Thümen Anne , Heim Hans‐Peter , Scheel Gerhard , Sundararaj Uttandaraman 
Published: February 2009

AbstractNylon 66/clay nanocomposites were prepared in a Berstorff ZE25A UTX Ultra‐glide corotating twin screw extruder at 270°C. Two types of extruder configurations with different mixing sections were used. One comprised two kneading block sections in the screws (KB only) and the other had a combination of a multi‐process‐element (MPE) section and a kneading block section. Samples at eight different locations along the extruder screw were obtained and analyzed using scanning electron microscope and transmission electron microscope to examine the morphology development of clay inside nylon down the length of the extruder. It is found that the clay aggregates are quickly broken into smaller tactoids (micron size) and then even much smaller clay bundles (nanometer size) and single clay platelets in the first mixing section. The structure changes in the second mixing section are much less significant. X‐ray diffraction (XRD) analysis of the nanocomposite products showed small, or disappearance of, characteristic XRD (001) peaks, which indicates partial exfoliation, or complete exfoliation, respectively, of clay inside nylon matrix. Differential scanning calorimetry nonisothermal study shows that the crystallization temperature of the nanocomposites has increased around 17°C when compared with neat nylon 66. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Comparative proteomic analysis of differentially expressed proteins in an in vitro cellular carcinogenesis model of oral squamous cell carcinoma
Authors: Zhong Lai‐ping , Zhang Lei , Yang Xiao , Pan Hong‐ya , Zhou Xiao‐jian , Wei Kui‐jie , Ye Dong‐xia , Jiang Qian , Chen Wan‐tao , Zhang Zhi‐yuan 
Published: February 2009

AbstractIn vitro cellular model is an important tool to be used to investigate the cellular events related to pathophysiological conditions in humans. We have developed an in vitro cellular carcinogenesis model of oral squamous cell carcinoma (OSCC). In this study, we performed comparative proteomic analysis using 2‐DE and LC‐tandem mass chromatography to separate and identify differentially expressed proteins. Forty‐five proteins were identified, including 24 proteins with decreased expression and 19 proteins with increased expression during carcinogenesis from immortalized oral epithelial cells to squamous cancerous cells. The identified known proteins were classified into three ontologies of cellular component, molecular function, and biological process. Further validation of five identified proteins (ANXA1, ANXA2, CTSB, KRT17, and S100A6) in the cellular carcinogenesis model and cancerous tissues from OSCC patients confirmed the comparative proteomic results. Moreover, Annexin A1 and A2 expression levels correlated with the pathological differentiation grade of cancerous tissues. Thus, this work provides a dynamic protein file of differentially expressed proteins in oral squamous carcinoma cells, which could provide clues to study the mechanisms of OSCC carcinogenesis and possibly be developed as potential biomarkers for clinical diagnosis or prognostic monitoring.
Structure of a mutant human purine nucleoside phosphorylase with the prodrug, 2‐fluoro‐2′‐deoxyadenosine and the cytotoxic drug, 2‐fluoroadenine
Authors: Afshar Sepideh , Sawaya Michael R. , Morrison Sherie L. 
Published: February 2009

AbstractA double mutant of human purine nucleoside phosphorylase (hDM) with the amino acid mutations Glu201Gln:Asn243Asp cleaves adenosine‐based prodrugs to their corresponding cytotoxic drugs. When fused to an anti‐tumor targeting component, hDM is targeted to tumor cells, where it effectively catalyzes phosphorolysis of the prodrug, 2‐fluoro‐2′‐deoxyadenosine (F‐dAdo) to the cytotoxic drug, 2‐fluoroadenine (F‐Ade). This cytotoxicity should be restricted only to the tumor microenvironment, because the endogenously expressed wild type enzyme cannot use adenosine‐based prodrugs as substrates. To gain insight into the interaction of hDM with F‐dAdo, we have determined the crystal structures of hDM with F‐dAdo and F‐Ade. The structures reveal that despite the two mutations, the overall fold of hDM is nearly identical to the wild type enzyme. Importantly, the residues Gln201 and Asp243 introduced by the mutation form hydrogen bond contacts with F‐dAdo that result in its binding and catalysis. Comparison of substrate and product complexes suggest that the side chains of Gln201 and Asp243 as well as the purine base rotate during catalysis possibly facilitating cleavage of the glycosidic bond. The two structures suggest why hDM, unlike the wild‐type enzyme, can utilize F‐dAdo as substrate. More importantly, they provide a critical foundation for further optimization of cleavage of adenosine‐based prodrugs, such as F‐dAdo by mutants of human purine nucleoside phosphorylase.
What is new in nitride laser diodes reliability studies
Authors: Marona L. , Wiśniewski P. , Leszczyński M. , Prystawko P. , Grzegory I. , Suski T. , Porowski S. , Czernecki R. , Czerwinski A. , Pluska M. , Ratajczak J. , Perlin P. 
Published: February 2009

AbstractIn the present paper we discuss possible degradation mechanisms of InGaN violet laser diodes, grown on bulk GaN substrates. Lifetime tests include electrical and optical parameters monitoring, temperature and microstructural studies. Our results point out at very strong, the exponential dependence of the degradation rate on the operation current of the device. The square root‐like behavior of the degradation as a function of time is also reconfirmed. Our microstructural analysis indicates also that the appearance of strain driven defects (dislocation loops formed around AlGaN/GaN interface) may have an influence on the laser diode degradation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gap bowing in Inx Ga1–xN and Inx Al1–xN under pressure
Authors: Gorczyca I. , Suski T. , Christensen N. E. , Svane A. 
Published: February 2009

AbstractThe electronic band structures of InxGa1–xN and InxAl1–xN alloys are calculated by ab‐initio methods in a supercell geometry, and the effects of varying the composition and applying external pressure examined. Indium segregation is also simulated, and it is shown that it strongly influences the band gap and its pressure derivative. Both the band gaps and their pressure coefficients are considerably lower when In atoms are clustered, than when they are uniformly distributed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlInN optical confinement layers for edge emitting group III‐nitride laser structures
Authors: Schenk H. P. D. , Nemoz M. , Korytov M. , Vennéguès P. , Demolon P. , Dräger A. D. , Hangleiter A. , Charash R. , Maaskant P. P. , Corbett B. , Duboz J. Y. 
Published: February 2009

AbstractAl1–xInxN ternary alloys with solid phase indium compositions between x = 0.15 and 0.28 have been grown by metalorganic chemical vapor deposition under indium rich conditions. Within the growth temperature range of 750‐810 °C the indium incorporation into the solid is increasingly reduced by a competing process with thermal activation energy of 1.07 eV. Using this growth scheme, smooth epitaxial layers with root mean‐squares surfaces roughness of 0.3‐0.8 nm are obtained. Extrinsic origin is suggested for the low temperature photoluminescence peak associated with these layers. (Al,In)N films lattice‐matched to GaN have been introduced into laser diode structures for optical confinement. Optical gain is observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Realization of 270 nm band AlGaN based UV‐LEDs on large area AlN templates with high crystalline quality
Authors: Takano Takayoshi , Hirayama Hideki , Fujikawa Sachie , Tsubaki Kenji 
Published: February 2009

AbstractSemiconductor light‐emitting diodes (LEDs) with emission wavelengths in the range 250‐350nm have a wide range of potential applications. So far, high power AlGaN‐ and InAlGaN‐based LEDs in the ultraviolet (UV) region have been fabricated. However, for the realization of commercially‐available low‐cost UV‐LEDs, the fabrication of structures on large‐sized or multiple wafers is desirable. We have now demonstrated the growth of AlN templates using an ammonia (NH3) pulsed‐flow multilayer (ML) growth technique and AlGaN based UV‐LEDs on (0001) sapphire substrates by low‐pressure metalorganic chemical vapour deposition (MOCVD) in a 2″ × 3 reactor system. In the case of the (10‐12) X‐ray rocking curve (XRC), the full‐width‐at‐half‐maximum (FWHM) increased from 510 arcsec to 580 arcsec when scanning from the center to the edge of the wafer. On the other hand, the FWHM of the (0002) XRC was slightly increased from 170 arcsec to 190 arcsec. Furthermore, Emission peaks for UV‐LEDs were clearly observed in the range from 268 nm to 284 nm. The output power at 100 mA and maximum output power were 0.2 mW and 0.3 mW, respectively. These results indicate that sub‐milliwatt operation in the deep‐UV range was successfully achieved. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of total pressure and precursors flow rates on the growth of aluminium nitride by high temperature chemical vapor deposition (HTCVD)
Authors: Claudel Arnaud , Blanquet Elisabeth , Chaussende Didier , Pique Didier , Pons Michel 
Published: February 2009

AbstractIn order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750 °C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influence of total pressure, Cl2 flow rate and NH3 flow rate on AlN growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 μm.h–1 have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As‐grown AlN layers were characterized by SEM and X‐ray Diffraction. Surface morphology was studied by SEM and FEG‐SEM and crystallographic orientations were obtained by X‐ray diffraction on θ/2θ. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly luminescent InxGa1–xN thin films grown over the entire composition range by energetic neutral atom beam lithography & epitaxy (ENABLE)
Authors: Williamson T. L. , Hoffbauer M. A. , Yu K. M. , Reichertz L. A. , Hawkridge M. E. , Jones R. E. , Miller N. , Ager J. W. , Liliental‐Weber Z. , Walukiewicz W. 
Published: February 2009

AbstractIn‐rich alloys of InxGa1–xN are becoming highly sought after because of the significant role they may play in a number of technologies including photovoltaics, solid‐state lighting, and high frequency electronics. Unfortunately, these alloys are difficult to produce with high quality by conventional growth technologies. We describe our efforts to create high‐quality In‐rich InxGa1–xN alloys by a new growth technology called energetic neutral atom beam lithography & epitaxy (ENABLE). ENABLE uses a collimated beam of neutral N atoms (kinetic energies of ∼2.0 eV) as the reactive group V species in InxGa1–xN growth, allowing for a substantial reduction in substrate growth temperatures (typically 450 °C to 750 °C). Directly providing a significant portion of the required reaction energy by the N atoms rather than by high substrate temperatures improves InxGa1–xN film quality across the full stoichiometric range. ENABLE‐grown InN on sapphire is shown to be highly crystalline by XRD and RBS. The observed photoluminescence (PL) peak energy is 0.74 eV, and the electron concentrations are between 7x1018 and 7x1019 cm–3 with the highest mobility exceeding 1200 cm2/Vs. ENABLE has been used to produce highly luminescent InxGa1–xN with PL peak energies in the 1.5 to 2.5 eV range, spanning the visible range. ENABLE grown InxGa1–xN films are shown by XRD to be highly crystalline consisting of a uniform single phase. These results establish ENABLE as a new technique uniquely capable of low temperature growth of high‐quality InxGa1–xN films over widely varying compositions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of time‐resolved photoluminescence from InGaN single quantum wells grown on nonpolar and semipolar bulk GaN substrates
Authors: Garrett Gregory A. , Shen Hongen , Wraback Michael , Tyagi Anurag , Schmidt Mathew C. , Speck James S. , DenBaars Steven P. , Nakamaura Shuji 
Published: February 2009

AbstractSingle quantum wells of low InN concentration InGaN grown on high quality nonpolar and semipolar substrates cut from bulk GaN boules are studied by time‐resolved photoluminescence techniques. Data is presented for different well widths at varying pump fluence and sample temperature to study nonlinear non‐radiative recombination, radiative lifetimes, and carrier localization or separation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnO quantum dots embedded in a SiO2 nanoparticle layer grown by atomic layer deposition
Authors: Wu M. K. , Shih Y. T. , Chen M. J. , Yang J. R. , Shiojiri M. 
Published: February 2009

AbstractWe have fabricated ZnO quantum dots embedded in an amorphous silicon oxide layer by atomic layer deposition (ALD). SiO2 nanoparticles with diameters of approximately 10 nm dispersed in isopropyl alcohol solution were spin‐on coated on the Si substrate and dried in an oven. Subsequently, ALD of ZnO was performed using two precursors, Zn(C2H5)2 and H2O, which can infiltrate into the small voids between SiO2 nanoparticles. It is revealed that the deposited ZnO was uniformly embedded in the SiO2 layer as crystalline ZnO quantum dots with diameters in the range of about 3–8 nm after a high‐temperature post‐deposition annealing treatment. The quantum confinement effect of the ZnO dots is well manifested by a significant blue‐shift of about 80 meV in the photoluminescence spectrum at room temperature. This technique is applicable to a new fabrication route of optoelectronic devices, such as UV light emitting diodes and lasers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
QSAR Models for Prediction of PPARδ Agonistic Activity of Indanylacetic Acid Derivatives
Authors: Lather Viney , Fernandes Miguel X. 
Published: February 2009

AbstractPeroxisome Proliferator Activated Receptor β/δ (PPAR β/δ), one of three PPAR isoforms is a member of nuclear receptor superfamily and ubiquitously expressed in several metabolically active tissues such as liver, muscle, and fat. Tissue specific expression and knock‐out studies suggest a role of PPARδ in obesity and metabolic syndrome. Specific and selective PPARδ ligands may play an important role in the treatment of metabolic disorders. Indanylacetic acid derivatives reported as potent and specific ligands against PPARδ have been studied for the Quantitative Structure–Activity Relationships (QSAR). Molecules were represented by chemical descriptors that encode constitutional, topological, geometrical, and electronic structure features. Four different approaches, i.e., random selection, hierarchical clustering, k‐means clustering, and sphere exclusion method were used to classify the dataset into training and test subsets. Forward stepwise Multiple Linear Regression (MLR) approach was used to linearly select the subset of descriptors and establish the linear relationship with PPARδ agonistic activity of the molecules. The models were validated internally by Leave One Out (LOO) and externally for the prediction of test sets. The best subset of descriptors was then fed to the Artificial Neural Networks (ANN) to develop non‐linear models. Statistically significant MLR models; with R2 varying from 0.80 to 0.87 were generated based on the different training and test set selection methods. Training of ANNs with different architectures for the different training and test selection methods resulted in models with R2 values varying from 0.83 to 0.94, which indicates the high predictive ability of the models.
Exploring 2D and 3D QSARs of 2,4‐Diphenyl‐1,3‐oxazolines for Ovicidal Activity Against Tetranychus urticae
Authors: Roy Kunal , Paul Somnath 
Published: February 2009

AbstractQuantitative Structure–Activity Relationship (QSAR) studies have been carried out for ovicidal activity of 2,4‐diphenyl‐1,3‐oxazoline analogues against two‐spotted spider mite Tetranychus urticae, which causes serious damage to agricultural products. The studies have been performed with 2D (physicochemical, structural, and topological) and 3D (shape, spatial, electronic, and molecular field) descriptors. The chemometrics tools used for the analyses are Genetic Function Approximation (GFA) and Genetic Partial Least Squares (G/PLS). The whole dataset (n=90) was divided into a training set (75% of the dataset) and a test set (remaining 25%) on the basis of K‐means clustering technique of standardized topological and structural descriptor matrix. Models developed from the training set were used to predict the activity of the test set compounds. All the models have been validated internally, externally, and by Y‐randomization technique. However, different models emerged as the best ones according to different validation criteria. We have tried a consensus model, which is based on the results obtained by all predictive models and this may provide the most stable solution. Models obtained by using 2D parameters revealed that the chain length of the substituent at para position of the 4‐phenyl ring is a critical factor. Lipophilicity of the molecule also reflects a dominant role for the ovicidal activity. Models generated from 3D descriptors suggest that the shape of the substituents should be optimum and the lipophilic substituents having electronegative atoms with distributed positive charge over a surface may enhance the ovicidal activity. The model obtained from Molecular Field Analysis (MFA) suggests that bulky substituents with optimally distributed charge may increase the ovicidal activity.
A special reactor coupled with a high‐temperature mass spectrometer for the investigation of the vaporization and cracking of organometallic compounds
Authors: Violet Perrine , Nuta Ioana , Artaud Laurent , Collas Hervé , Blanquet Elisabeth , Chatillon Christian 
Published: February 2009

AbstractA special reactor coupled to a high‐temperature mass spectrometer was specifically designed for the study of vaporization and thermal cracking of organometallic precursors. This reactor has two kinds of settings. One is a single Knudsen effusion cell which enables the analysis of the composition of saturated vapors and the determination of the partial pressure of each gaseous molecule in equilibrium with its condensed phase. This cell is an evaporation/sublimation cell (operating from 243 to 473 K), which can be tightly closed – like a vacuum chamber – in order to protect organometallic compounds against moisture and atmospheric components. This cell can be independently weighed usefully to evaluate the equilibrium vapor pressures of the sample using the mass‐loss method. During experiments, the effusion aperture is externally opened for direct mass spectrometric measurements. The other setting dedicated to the study of thermal decomposition of gaseous molecules consists of a set of tandem cells: the previously described Knudsen cell and a cracking cell (operating from 293 to 973 K). Copyright © 2009 John Wiley & Sons, Ltd.
Corn plant sensing using real‐time stereo vision
Authors: Jin Jian , Tang Lie 
Published: February 2009

AbstractThough some two‐dimensional (2D) machine vision–based systems for early‐growth‐stage corn plant sensing exist, some of their shortcomings are difficult to overcome. The greatest challenge comes from separating individual corn plants with overlapped plant canopies. With 2D machine vision, variation in outdoor lighting conditions and weeds in the background also pose difficulties in corn plant identification. Adding the depth dimension has the potential to improve the performance of such a sensing system. A new corn plant sensing system using a real‐time stereo vision system was investigated in this research. Top‐view depth images of corn plant canopy were acquired. By processing the depth images, the algorithm effectively updated the plant skeleton structures and finally recognized individual corn plants and detected their center positions. The stereo vision system was tested over corn plants of V2–V3 growth stages in both laboratory and field conditions. Experimental results showed that the stereo vision system was capable of detecting both separated and overlapped corn plants. During the field test, 96.7% of the corn plants were correctly detected, and plant center positions were estimated with maximum distance errors of 5 and 1 cm for 74.6% and 62.3% of detections, respectively. © 2009 Wiley Periodicals, Inc.