bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Modifications of nc-Si/SiO2 Superlattices by Localized Photo-induced Heating
Authors: Kamenev B. V. , Grebel H. , Tsybeskov L. , Timoshenko V. Yu. 
Published: April 2011

ABSTRACTStructural modifications in nanocrystalline silicon-silicon dioxide (nc-Si/SiO2) superlattices (SL) under high intensity laser irradiation have been studied experimentally and theoretically. The melting threshold in nc-Si/SiO2 SLs was found in the range of 5–8 kW/cm2 for cw excitation by 514 nm line of Ar+ laser and ∼11–15 mJ/cm2 for pulsed irradiation by 248 nm, π∼20 ns KrF laser. The irradiation of the samples above the melting threshold induces the irreversible modification of nc-Si layers, which is controlled by the thickness of the separating SiO2 layers, and increases the PL intensity increases by more than 300%.
Enhancing the Sound Pressure of Thermally Induced Ultrasonic Emitter Based on Nanocrystalline Porous Silicon
Authors: Tsubaki Kenji , Komoda Takuya , Koshida Nobuyoshi 
Published: April 2011

ABSTRACTIt is shown that the acoustic pulse output of nanocrystalline porous silicon (nc-PS) ultrasonic emitter can be enhanced by appropriate control of both the driving mode and the nc-PS structure. The device is composed of a patterned heater electrode, an nc-PS layer, and a single-crystalline silicon (c-Si) substrate. As the sound pressure is proportional to input power in principle, the nc-PS device can generate a high acoustic power under the mode of temporal burst electrical input. The most important limiting factor for maximum electrical input power is a mechanical stress at the electrode/nc-PS interface induced by a rapid interfacial temperature raise rather than a simple electro-migration inside the thin metal film. In fact the maximum sound pressure is enhanced with increasing the hardness and Young's modulus of the nc-PS layer. The present result provides useful information for further progress of the nc-PS acoustic device.
Size Control and Phonon Confinement of Silicon Nanowires Synthesized by Laser Ablation
Authors: Fukata N. , Oshima T. , Tsurui T. , Ito S. , Murakami K. 
Published: April 2011

ABSTRACTSize control of silicon nanowires (SiNWs) synthesized by laser ablation of a Si target with nickel (Ni) as catalysts were investigated. The diameter of SiNWs decreased with decreasing synthesis temperature and content of Ni catalyst. Gradual down shift and asymmetric broadening of Si optical phonon peak depending on the diameter of SiNWs were observed for continuously, thermally oxidized SiNWs and SiNWs with smaller diameters formed at lower temperature. This can be interpreted by the phonon confinement effect. On the other hand, further thermal oxidation produced an upshift of the optical phonon peak. This is considered to be due to compressive stress since this stress was relieved by removing the surface oxide layers formed around the SiNW cores, resulting in a downshift of the optical phonon peak.
Synthesis and Characterization of Nanocrystalline Diamond and Its Biomedical Application
Authors: Xu Zhenqing , Kumar Arun , Kumar Ashok , Sikder Arun 
Published: April 2011

ABSTRACTDiamond is known as the material that has excellent mechanical, electrical and chemical properties. Diamond is also an ideal interface that is compatible with microelectronics process and biological environments to work as a biosensor platform with excellent selectivity and stability. In our study, nanocrystalline diamond (NCD) films were grown on Si substrates by the microwave plasma enhanced chemical vapor deposition (MPECVD) method. Parameters such as gas composition, temperature and pressure are investigated to get the best film quality. Scanning electron microscopy (SEM) and Raman spectroscopy were used to characterize the NCD films. Then the NCD films were treated by hydrogen plasma in the CVD chamber to obtain the hydrogen terminated surface. This hydrogenated NCD film is ready for bio-modification and can work as the platform of the biosensors. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) were employed to confirm the surface hydrogenation.
Adhesion Improvement of CVD Diamond Coatings on WC-Co Substrates for Machining Applications
Authors: Xu Zhenqing , Kumar Ashok , Lev Leonid , Lukitsch Michael , Sikder Arun 
Published: April 2011

ABSTRACTIn order to improve the performance of WC-Co cutting tools, high quality microcrystalline diamond coatings were produced using microwave plasma enhanced chemical vapor deposition (MPECVD) method. The adhesion of the diamond film deposited on the substrate has been considered to play an important role in the performance of the cutting tools in machining applications. A thin layer of Cr was coated on the WC-Co substrate before the diamond deposition; 75 μm diamond powders were sandblasted on the surface at 40 Psi to increase the nucleation density. Diamond film has been successfully deposited on the substrate at temperature around 750°C with 1.5 % CH4 in Hydrogen plasma. Scanning electron microscopy (SEM) has been used to study the surface morphology and Raman spectroscopy has been performed to characterize the quality of the diamond films and measure the residual stress. The adhesion of the diamond film has been evaluated by Rockwell indentation test. The results indicated that film grown on the Cr interlayer with diamond powder sandblasting has much better adhesion strength.
200. mm Silicon Wafer-to-Wafer Bonding with Thin Ti Layer under BEOL-Compatible Process Conditions
Authors: Yu J. , McMahon J. J. , Lu J.-Q. , Gutmann R. J. 
Published: April 2011

ABSTRACTWafer level monolithic three-dimensional (3D) integration is an emerging technology to realize enhanced performance and functionality with reduced form-factor and manufacturing cost. The cornerstone for this 3D processing technology is full-wafer bonding under back-end-of-the-line (BEOL) compatible process conditions. For the first time to our knowledge, we demonstrate nearly void-free 200 mm wafer-to-wafer bonding with an ultra-thin Ti adhesive coating, annealed at BEOL-compatible temperature (400 °C) in vacuum with external pressure applied. Mechanical integrity test showed that bonded wafer pair survived after a stringent three-step thinning process (grinding/polishing/wet-etching) with complete removal of top Si wafer, while allowing optical inspection of bonding interface. Mechanisms contributing to the strong bonding at Ti/Si interface are briefly discussed.
Development of Biodegradable Polyphosphazene- Nanohydroxyapatite Composite Nanofibers Via Electrospinning
Authors: Bhattacharyya Subhabrata , Nair Lakshmi S. , Singh Anurima , Krogman Nick R. , Bender Jared , Greish Yaser E. , Brown Paul W. , Allcock Harry R. , Laurencin Cato T. 
Published: April 2011

ABSTRACTBiodegradable polymeric nanofibers are of great interest as scaffolds for tissue engineering and drug delivery due to their extremely high surface area, high aspect ratio and similarity in structure to the extracellular matrix (ECM). Polyphosphazenes due to their synthetic flexibility, wide range of physico-chemical properties, non-toxic and neutral degradation products and excellent biocompatibility are suitable candidates for biomedical applications. The objective of the present study was to develop and evaluate composite nanofibers of a biodegradable polyphosphazene, poly[bis(ethyl alanato)phosphazene] (PNEA) and nanocrystals of hydroxyapatite (nHAp) via electrospinning. A suspension of nHAp in dimethyl formamide (DMF) sonicated with PNEA solution in tetrahydrofuran (THF) was used to develop composite nanofiber matrices via electrospinning at ambient conditions. In the present study the theoretical loading of nHAp was varied from 50%-90% (w/w) to PNEA. The nHAp content (actual loading of nHAp) of the composite nanofibers was determined by gravimetric estimation. The composite nanofibers were characterized by transmission electron microscopy (TEM), gravimetry and energy dispersive X-ray mapping. This study demonstrated the feasibility of developing novel composite nanofibers of biodegradable polyphosphazenes with more than 50% (w/w) loading of nHAp on and within the nanofibers.
Floating Zone Growth of Bulk Single Crystals of Complex Oxides
Authors: Guptasarma Prasenjit , Williamsen Mark S. , Ray Shishir K. 
Published: April 2011

ABSTRACTIn this MRS Proceedings paper, we present a review of the floating zone growth process, and describe growth techniques as relevant to four selected families of current or continued interest in the area of condensed matter physics of highly correlated electron systems: Cuprate oxides (Bi2Sr2CaCu2Oy), Ruthenate oxides (Sr2RuO4), Manganite oxides (La1-xSrxMnO3, La2–2xSr1+2xMn2O7, (RE) MnO3 (RE=Rare Earth)) and Ferrite oxides (BiFeO3). We also discuss our experiences with factors that tend to contribute to poor crystal growth, as relevant to experiments to probe correlated-electron physics in such crystals.
Fabrication of Anatase TiO2 Thin Film Using Pulsed DC Magnetron Sputtering
Authors: Al-Homoudi Ibrahim A. , Zhang Linfeng , McCullen Erik F. , Huang Changhe , Rimai L. , Baird R.J. , Simon Ng K.Y. , Naik R. , Auner G.W. , Newaz G. 
Published: April 2011

ABSTRACTTiO2 thin films (500 – 1000 nm in thickness) were deposited using pulsed DC magnetron reactive sputtering, on glass substrates. The depositions used a Ti source in an Ar+O2 gas mixture with different parameters of power (350 - 500W), substrate temperature (no additional heat - 400°C), growth pressure (3.0 - 5.0 mTorr) and oxygen gas flow rate (6.0 - 8.0 sccm). The x-ray diffractions (XRD) show amorphous and/or anatase phases depending on the deposition conditions. The films were found to be amorphous at lower substrate temperature and at lower powers. The sample with 4 mTorr, 400W of power, a substrate temperature of 250 C with 7.0 sccm of oxygen flow has the best crystalline quality. The temperature dependent electrical conductivity measurement in air for the above films shows an exponential increase in conductivity with temperature.
Crystallochemistry of Thortveitite-Like and Thortveitite-Type Compounds
Authors: Juarez-Arellano E. A. , Campa-Molina J. , Ulloa-Godínez S. , Bucio L. , Orozco E. 
Published: April 2011

ABSTRACTIn this article we present the main features and structural relationships between thortveitite-type and thortveitite-like germanates compounds. We describe in detail the crystal structures, how they are built and the difference between them. Bond-valence and polyhedra distortion analysis are made and crystal structure stability ranges are given.
Effect of Mn Doping on the Structural and Ferroelectric properties of SrBi2Ta2O9
Authors: Sookawee T. , Pdungsap L. , Winotai P. , Suryanarayanan R. , Naik V.M. , Naik R. 
Published: April 2011

ABSTRACTSrBi2Ta2O9 (SBT) samples have been prepared by sol-gel technique with varying amount of excess Bi added to the starting composition. The excess Bi profoundly affects the dielectric and ferroelectric properties. The dielectric constant (ε) and remnant polarization increases from 80 and 1.4 μ C/cm2 for SBT with 1 mole % of excess Bi to 120 and 6.5 μ C/cm2 for SBT with 20 mole % of excess Bi. The Raman spectra, scanning electron microscopy images and the x-ray diffraction analysis show an improvement in structural quality of the samples with addition of excess Bi to the starting composition. The effect of Mn doping has also been studied by preparing SrBi2Ta2-x Mnx O9 (SBT-Mn) with x = 0 – 0.1. In the case of SBT-Mn samples, the XRD spectra revealed an unknown phase when x > 0.025. However, Raman spectra reveal the retention of Bi layer structure for all Mn compositions, with possibly small distortions. With Mn addition, ε increased to ∼ 140 for x < 0.005, but decreased to ≤ 120 when x > 0.015. The value of ε is independent of frequency from 60 to 85 kHz for all compositions of Mn. The effect of Mn addition resulted in a strong decrease in the area of the hysteresis loops.
The Contribution To Bond Valences By Lone Electron Pairs
Authors: Wang Xiqu , Liebau Friedrich 
Published: April 2011

ABSTRACTBond valence sums (BVS) calculated for lone-pair cations are found increasingly higher than their formal valences as the retraction of the lone electron pair (LEP) from the nucleus is more pronounced. The increase in BVS is interpreted as a continuous increase of an effective valence of an atom that is a measure of its actual ability to bind other atoms without changing its formal valence. How the LEP of a lone-pair cation affects the effective valence of other atoms in a structure is studied by bond valence calculations for specific structures. For structures rich in alkali cations, it is found that the high effective valence of the lone-pair cations tends to be balanced by low effective valence of alkali cations. The LEP transfers bonding power or effective valence from the alkali cations to the lone-pair cations by joining the coordination sphere of the alkali cations.
Study of the percolative nature of thermoelectric power and resistivity in Pr0.66R0.04Sr0.3MnO3 (R = Tb, Y, Ho and Er) manganites.
Authors: Rama N. , Sankaranarayanan V. , Rao M.S.R. 
Published: April 2011

ABSTRACTWe have studied the resistivity and thermoelectric power of Pr0.66R0.04Sr0.3MnO3 where R = Tb, Y, Ho and Er and have analyzed it within a percolative framework. Both resistivity and thermoelectric power quantities were found to show a strong dependence on the disorder (<σ>2) with the high temperature activation energy in both increasing as <σ>2 is increased, implying that as the disorder increases, carriers get more localized. The percolative nature of the thermopower was analyzed assuming that the lattice has coexisting metallic (Smet) and insulating (Sins) components above and below the Curie temperature (TC) which are independent of each other. Hence total S(T) = pSmet(T) + (1-p)Sins with the volume metallic fraction p=1/(1+exp(-Uo(1-T/TC)/kBT) [1]. A similar analysis was done using the resistivity data. It was seen that the TC from both thermopower and resistivity fits were nearly the same indicating that they have a common origin. This analysis clearly proves that the metal insulator transition in manganites is percolative in nature and that the transport properties show a strong percolation tendency.
Phase Change Mechanisms in Pulsed Laser-Matter Interaction
Authors: Xu Xianfan 
Published: April 2011

ABSTRACTLaser micro-machining is finding many applications in materials processing and manufacturing. Various laser techniques are being used to fabricate micro-electronics, optics, and medical components. This paper will mainly deal with the fundamental issues involved in laser-matter interaction. Our studies are focused on laser induced thermal and thermomechanical phenomena and phase change mechanisms that determine the materials removal process during laser micro-machining. It is shown that during nanosecond laser machining, explosive phase change could occur, during which the liquid is superheated to close to the thermodynamic critical point, followed by an explosive, homogeneous phase transformation. On the other hand, it is observed in the experiment that the time needed for nucleation during laser induced phase explosion is on the order of one nanosecond. Thus, when a laser with a pulsewidth of the order of picosecond or less is used, it is likely that the material can be heated above the critical point, and another type of phase change, spinodal decomposition is possible. Molecular dynamics studies showed that with the use of a femtosecond laser pulse, it is possible to superheat the material to above the critical point, and spinodal decomposition is the dominant mechanism for materials removal.
Processing and Characterization of Short Glass Fiber/ABS/Polyamide-6 Composites
Authors: Ozkoc Guralp , Bayram Goknur , Bayramli Erdal 
Published: April 2011

ABSTRACTThe main objective of this study is to determine the effects of short glass fiber (SGF) content and extrusion conditions such as screw speed and barrel temperature, on the mechanical properties and morphologies of structural composites produced by compounding SGFs with poly (acrylonitrile-butadiene-styrene) (ABS). It was also aimed to determine the effects of adhesion at the fiber/matrix interface, which was promoted by incorporation of polyamide-6 (PA6) to the ABS/SGF composite. Results showed that increasing screw speed during extrusion decreased the average fiber length; therefore mechanical properties of the composites affected negatively. The increasing extrusion temperature decreased the fiber length degradation and higher tensile strength and modulus values were obtained. The use of PA6 in composites increased the interfacial adhesion, which was supported by SEM microphotographs; therefore, improved mechanical properties were obtained.
Porphyromonas Gingivalis is Associated With Protease‐Activated Receptor‐2 Upregulation in Chronic Periodontitis
Authors: Fagundes José Américo G. , Monoo Letícia D. , Euzébio Alves Vanessa Tubero , Pannuti Cláudio Mendes , Cortelli Sheila Cavalca , Cortelli José Roberto , Holzhausen Marinella 
Published: April 2011

Background: We previously reported a higher expression of protease‐activated receptor‐2 (PAR2) together with higher interleukin (IL)‐1α, IL‐6, IL‐8, and tumor necrosis factor‐α levels, total proteolytic activity, Porphyromonas gingivalis (Pg) prevalence, and neutrophil‐protease 3 messenger RNA (mRNA) expression in patients with chronic periodontitis compared to healthy control patients. The aim of the present study is to expand this observation by considering the site level according to the presence of Pg.Methods: Microbiologic and gingival crevicular fluid samples were collected from patients with chronic periodontitis. Pg presence was evaluated by polymerase chain reaction and PAR2 mRNA expression was evaluated by reverse‐transcription polymerase chain reaction. Total proteolytic activity in the crevicular fluid was analyzed by using a specific substrate benzoylarginine nitroanilide, and the proinflammatory mediators IL‐1α, IL‐6, IL‐8, and tumor necrosis factor‐α were analyzed by enzyme‐linked immunosorbent assay.Results: In Pg–positive periodontal sites, the mean probing depth and clinical attachment level, the prevalence of bleeding on probing sites, and crevicular fluid volume were higher (P <0.05) compared to Pg–negative sites. In addition, with the exception of IL‐8, all other inflammatory mediators were positively (P <0.05) associated with Pg presence. Pg presence was also positively associated with a higher proteolytic activity (P = 0.0037) and higher PAR2 mRNA expression (P = 0.0271).Conclusions: We conclude that in chronic periodontitis, periodontal pockets presenting Pg show an upregulation of PAR2 gene expression, and higher proinflammatory profile associated with advanced clinical destruction, therefore suggesting that Pg plays a pivotal role on PAR2‐mediated periodontal inflammation in humans.
Public Perceptions of Urban Air Pollution Risks
Authors: Saksena Sumeet 
Published: April 2011

AbstractUnderstanding public perception and attitudes toward air quality and regulation is critical for successful citizen involvement as shifts toward new technologies and management alternatives take place. While urban air pollution continues to be a major risk in most parts of the world, very few studies and surveys have been conducted to systematically study public perceptions related to air pollution. Even fewer studies have focused on developing countries. This gap is critical because of the complex interaction between poverty, livelihoods and sustainable development in developing countries. A Pressure‐State‐Response framework is used to review studies of public perceptions of air pollution and knowledge gaps are identified. The paper highlights unique characteristics of urban areas in developing countries in the context of air pollution related perceptions.
Like a phoenix from the ashes
Authors: Zaniewicz Grzegorz , Busse Przemysław 
Published: April 2011

Like a phoenix from the ashes
From 1967 until 1990, populations of five Sylvia species migrating through the southwestern coast of the Baltic Sea were considerably low and significantly decreasing in the Blackcap (Sylvia atricapilla), Garden Warbler (S. borin) and Barred Warbler (S. nisoria). While after that period a rapid increase in the populations of these migratory species was noted. Similar changes that had started about 1991 were shown by all five Sylvia species. Such coincidence could indicate some common factors acting upon the studied group of migrants at the same time. Apart from a clear increase in the long-term dynamics of the species observed at Bukowo-Kopań station, the Pearson correlation coefficients of these dynamics calculated for every pair of the analysed Sylvia species in 1967-2006 were high and statistically significant.
Based on the distribution of recoveries of the Lesser Whitethroat (S. curruca) we assumed that the main fraction of birds passing the south-western coast of the Baltic Sea originated from the Scandinavian Peninsula. Recent climate changes observed in this area were consistent with the time when the increase in the number of caught birds was noted. Consequently, we suspect that the analysed Sylvia species passing this part of the coast share vast breeding grounds located mainly on the Fennoscandian Peninsula, where their populations are affected by the same common factors.
Timing, age classes and water-crossing behaviour of Black Kites (Milvus migrans) during spring migration across the Central Mediterranean
Authors: Panuccio Michele , Agostini Nicolantonio 
Published: April 2011

Timing, age classes and water-crossing behaviour of Black Kites (Milvus migrans) during spring migration across the Central Mediterranean
The main migratory passage of Black Kites across the Mediterranean Sea occurs at the Strait of Gibraltar, where the migration peak is observed in early March. Conversely, in the Central Mediterranean the migration of this species is scarce during the supposed peak period, while hundreds of individuals are observed migrating later in the season, mostly in April and May. In the present study we investigate the spring migration of Black Kites at two sites of the Central Mediterranean, the island of Ustica and the Strait of Messina. Timing, age classes and water-crossing behaviour of this species suggest that large numbers of non-breeders use this route during spring. However, a peculiar migration timing of breeding pairs belonging to the Italian population cannot be excluded.
The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)
Authors: Ahadnejad Vahid , Hirt Ann , Valizadeh Mohammad-Vali , Bokani Saeed 
Published: April 2011

The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)The ammonium (NH4+) contents of the Malayer area (Western Iran) have been determined by using the colorimetric method on 26 samples from igneous and metamorphic rocks. This is the first analysis of the ammonium contents of Iranian metamorphic and igneous rocks. The average ammonium content of metamorphic rocks decreases from low-grade to high-grade metamorphic rocks (in ppm): slate 580, phyllite 515, andalusite schist 242. In the case of igneous rocks, it decreases from felsic to mafic igneous types (in ppm): granites 39, monzonite 20, diorite 17, gabbro 10. Altered granitic rocks show enrichment in NH4+(mean 61 ppm). The high concentration of ammonium in Malayer granites may indicate metasedimentary rocks as protoliths rather than meta-igneous rocks. These granitic rocks (S-types) have high K-bearing rock-forming minerals such as biotite, muscovite and K-feldspar which their potassium could substitute with ammonium. In addition, the high ammonium content of metasediments is probably due to inheritance of nitrogen from organic matter in the original sediments. The hydrothermally altered samples of granitic rocks show highly enrichment of ammonium suggesting external sources which intruded additional content by either interaction with metasedimentary country rocks or meteoritic solutions.