bluuebunny/crossref_metadata_2025 huggingface dataset:
Etching Characteristics of Polycrystalline 3C-SiC Films Using Enhanced RIE
Authors: Chung Gwiy Sang , Ohn Chang Min
Published: March 2009

This paper describes magnetron reactive ion etching (RIE) characteristics of polycrystalline
(poly) 3C-SiC thin films grown on thermally oxidized Si substrates by atmospheric
pressure chemical vapor deposition (APCVD). The best vertical structures were obtained by the
addition of 40 % O2, 16 % Ar, and 44 % CHF3 reactive gas at 40 mTorr of chamber pressure. Stable
etching was achieved at 70 W and the poly 3C-SiC was undamaged. These results show that in a
magnetron RIE system, it is possible to etch SiC with lower power than that of the commercial RIE
system. Therefore, poly 3C-SiC etched by magnetron RIE has the potential to be applied to
micro/nano electro mechanical systems (M/NEMS).
SiC JFET: Currently the Best Solution for an Unipolar SiC High Power Switch
Authors: Rueschenschmidt Kathrin , Treu Michael , Rupp Roland , Friedrichs Peter , Elpelt Rudolf , Peters Dethard , Blaschitz Peter
Published: March 2009

Today a main focus in high efficiency power electronics based on silicon carbide (SiC)
lies on the development of an unipolar SiC switch. This paper comments on the advantages of SiC
switching devices in comparison to silicon (Si) switches, the decision for the SiC JFET against the
SiC MOSFET, and will show new experimental results on SiC JFETs with focus on the production
related topics like process window and parameter homogeneity which can be achieved with the
presented device concept.
Due to material properties unipolar SiC switches have, other than their Si high voltage counterparts,
very low gate charge, good body diode performance, and reduced switching losses because of the
potential of lower in- and output capacitances. The most common unipolar switch is the MOSFET.
However, the big challenge in the case of a SiC MOSFET is the gate oxide. A gate oxide on SiC
that provides adequate performance and reliability is missing until now. An alternative unipolar
switching device is a normally-on JFET. The normally-on behavior is a benefit for current driven
applications. If a normally-off behavior is necessary the JFET can be used together with a low
voltage Si MOSFET in a cascode arrangement. Recently manufactured SiC JFETs show results in
very good accordance to device simulation and demonstrate the possibility to fabricate a SiC JFET
within a mass production. A growing market opportunity for such a SiC switch becomes visible.
Advances in Multi- and Single-Wafer SiC Epitaxy for the Production and Development of Power Diodes
Authors: Hecht Christian , Thomas Bernd , Stein René A. , Friedrichs Peter
Published: March 2009

In this paper, we present results of epitaxial layer deposition for production needs using our hot-wall CVD multi-wafer system VP2000HW from Epigress with a capability of processing 7×3” or 6×100mm wafers per run in a new 100mm setup. Intra-wafer and wafer-to-wafer homogeneities of doping and thickness for full-loaded 6×100mm and 7×3” runs will be shown. Results on Schottky Barrier Diodes (SBD) processed in the multi-wafer system will be given. Furthermore, we show results for n- and p-type SiC homoepitaxial growth on 3”, 4° off-oriented substrates using a single-wafer hot-wall reactor VP508GFR from Epigress for the development of PiN-diodes with blocking voltages above 6.5 kV. Characteristics of n- and p-type epilayers and doping memory effects are discussed. 6.5 kV PiN-diodes were fabricated and electrically characterized. Results on reverse blocking behaviour, forward characteristics and drift stability will be presented.
10 kV Silicon Carbide Junction Barrier Schottky Rectifier
Authors: McNutt Ty , Van Campen Stephen , Walker Andy , Ha Kathy , Kirby Chris , Sherwin Marc , Singh Ranbir , Hearne Harold
Published: March 2009

The development of 10 kV silicon carbide (SiC) MOSFETs and Junction Barrier Schottky
(JBS) diodes for application to a 13.8kV 2.7 MVA Solid State Power Substation (SSPS) is shown.
The design of half-bridge power modules has extensively used simulation, from electron level device
simulations to the system level trade studies, to develop the most efficient module for use in the SSPS.
In the work presented within, numerical simulations and experimental results are shown to
demonstrate the design and operation of 10 kV JBS diodes. It is shown that JBS diodes at 10 kV can
reduce 31% of the switching losses at 20 kHz than the fastest SiC PiN diodes.
Structure Analysis of In-Grown Stacking Faults and Investigation of the Cause for High Reverse Current of 4H-SiC Schottky Barrier Diode
Authors: Harada Shin , Namikawa Yasuo , Sugie Ryuichi
Published: March 2009

Two types of structures related to in-grown SF having a different influence on reverse
currents of 4H-SiC SBDs were investigated. One type contained only a single SF formed by 1c of 8H
poly-type and showed low reverse currents. The other type was accompanied with short SFs which
consisted of 3C poly-type in addition to two SFs formed by 1c of 8H poly-type and showed high
reverse currents. SF formed by 1c of 8H poly-type was not the cause of the high reverse current, and
we speculate that the barrier height lowering at the short SF attributed to the high reverse currents of
SBDs.
Impact of High-k Dielectrics on Breakdown Performances of SiC and Diamond Schottky Diodes
Authors: Brezeanu Gheorghe , Brezeanu M. , Boianceanu C. , Udrea F. , Amaratunga G.A.J. , Godignon Philippe
Published: March 2009

This paper presents a comparison between SiC and diamond Schottky barrier diodes using
the oxide ramp termination. The influences of the dielectric thickness and relative permittivity on the
diode’s electrical performance are investigated. Typical commercial drift layer parameters are used for
this study. The extension of the space charge area throughout the drift region and the current distribution
at breakdown are shown. The efficiency of the termination is also evaluated for both SiC and diamond
diodes.
Bevel Mesa Combined with Implanted Junction Termination Structure for 10 kV SiC PiN Diodes
Authors: Hiyoshi Toru , Hori Tsutomu , Suda Jun , Kimoto Tsunenobu
Published: March 2009

A 10 kV 4H-SiC PiN diode with an improved junction termination structure has been
fabricated. An improved bevel mesa structure, nearly vertical side-wall at the edge of pn junction
and rounded corner at mesa bottom, has been formed by reactive ion etching (RIE). The junction
termination extension (JTE) region has been optimized by device simulation, and simulated
breakdown voltage has been compared with experimental results. The locations of electric field
crowding and diode breakdown have been discussed.
Seam Welds in Hollow Profile Extrusion: Process Mechanics and Product Properties
Authors: Donati Lorenzo , Tomesani Luca
Published: March 2009

In this paper a review of several papers published on seam weld formation also by the authors is presented and discussed: the process mechanics is deeply investigated and several experimental results are related to process parameters by means of FEM simulations. The relation between die design and local welding parameters, such as contact pressure, temperature, time of contact, strain and strain rate paths is analyzed. In particular, by testing profiles extruded in different conditions, it was found that it is possible to find optimum processing conditions for a welded profile to behave like a not welded one. The possibility to adopt criteria for assessing the welding quality is finally discussed, together with its implementation directly inside process FEM codes.
Bulk Metallic Glasses
Authors: Baricco Marcello , Başer Tanya A. , Fiore Gianluca , Piccin Rafael , Satta Marta , Castellero Alberto , Rizzi Paola , Battezzati Livio
Published: March 2009

Rapid quenching techniques have been successfully applied since long time for the preparation of metallic glasses in ribbon form. Only in the recent years, the research activity addressed towards the synthesis of bulk metallic glasses (BMG), in form of ingots with a few millimetres in thickness. These materials can be obtained by casting techniques only for selected alloy compositions, characterised by a particularly high glass-forming tendency. Bulk amorphous alloys are characterised by a low modulus of elasticity and high yielding stress. The usual idea is that amorphous alloys undergo work softening and that deformation is concentrated in shear bands, which might be subjected to geometrical constraints, resulting in a substantial increase in hardness and wear resistance. The mechanical properties can be further improved by crystallisation. In fact, shear bands movement can be contrasted by incorporating a second phase in the material, which may be produced directly by controlled crystallisation. Soft magnetic properties have been obtained in Fe-based systems and they are strongly related to small variations in the microstructure, ranging from a fully amorphous phase to nanocrystalline phases with different crystal size. The high thermal stability of bulk metallic glasses makes possible the compression and shaping processes in the temperature range between glass transition and crystallisation. Aim of this paper is to present recent results on glass formation and properties of bulk metallic glasses with various compositions. Examples will be reported on Zr, Fe, Mg and Pd-based materials, focussing on mechanical and magnetic properties.
Superplastic Deformation of Twin Roll Cast AZ31 Magnesium Alloy
Authors: Ceschini Lorella , El Mehtedi Mohamad , Morri Alessandro , Sambogna Giuliano , Spigarelli Stefano
Published: March 2009

The aim of the present work was to evaluate the potential for superplastic deformation of the AZ31 magnesium alloy produced by Twin Roll Casting (TRC), a continuous casting technology able to convert molten metals directly into a coiled strip. In order to develop a superplastic microstructure, the TRC sheets were heated at 400 °C for 2 h, then rolled by multiple passes with re-heating between them, with a total thickness reduction of about 60%. The superplastic behaviour of the alloy was studied by tensile tests, carried out at in the temperature range from 400 °C to 500 °C and with initial strain rates of 1•10-3 s-1 and 5•10-4 s-1. The microstructural and fractographic characterization of the alloy was carried out by means of optical (OM) and scanning electron microscopy (SEM). The tensile tests evidenced a superplastic behaviour of the processed AZ31 Mg alloy, with a maximum elongation to failure of about 500% at 460 °C, with a strain rate of 5•10-4 s-1. The microstructure of the alloy after superplastic deformation showed fine and equiaxed grains, with a large fraction of high angle boundaries. Analyses of the fracture surfaces evidenced flow localization around the grains, suggesting that grain boundary sliding (GBS) was the main deformation mechanism. Failure occurred by cavitation, mainly at the higher testing temperature, due to the prevailing effect of grain growth.
Study of Hot Formability of High Nitrogen Martensitic Stainless Steel
Authors: El Mehtedi Mohamad
Published: March 2009

Alloying high-chromium steels with Nitrogen leads to increase in strength, fatigue life and corrosion resistance, but reduce ductility and could induce cracks formation during forging. In order to address these problems, the hot working response of a high Nitrogen martensitic stainless steel (Fe-16.2%Cr-1.1%Mo-0.33%N-0.34%C) has been investigated by means of hot torsion tests up to rupture, in the temperature and strain rate ranges of 900-1200°C and 0.005-5 s-1 respectively. The peak stresses of the flow curves were related to strain rate (e&) and temperature (T) by the well known sinh equation. The ductility and the safe working conditions were presented in terms of processing map. The microstructure of the steel in the quenched state after deformation was analyzed by means of optical microscopy; the differences in term of morphology and distribution of the various constituents were discussed.
Fabrication and Characterisation of Nanostructured Coatings by Magnetron Sputtering for Wear Resistant Applications
Authors: Vallauri D. , Grassini S. , DeBenedetti Bruno , Alexandre R.
Published: March 2009

Magnetron sputtering is a powerful process for the production of thin films and coatings employed for the surface modification of tools and engineering components in various industrial sectors. Nanostructured coatings for multifunctional applications were deposited by means of magnetron sputtering by adjusting the experimental parameters in order to tailor the chemistry, the microstructure and the morphology of the coatings. Among the several systems that were investigated, TiC–TiB2 for wear applications were successfully tested. TiC–TiB2 coatings were deposited on a hardmetal WC–Co substrate in an unbalanced DC magnetron sputtering system starting from composite targets fabricated by the Self-propagating High-temperature Synthesis (SHS) consolidation method, involving the material synthesis and densification in one step. The results, showing the achievement of nanostructured films with thickness ranging between 1 and 2 µm, are here presented. The properties evaluated on the developed films (hardness, adhesion, friction coefficient and volumetric wear) are promising for the improvement of wear-resistant applications.
Creep Response and Microstructural Changes during Intermittent Heating of Advanced Tempered Martensitic 9-12%Cr Steels
Authors: Sklenička Václav , Kuchařová Květa , Svoboda Milan , Saxl Ivan
Published: March 2009

Significant developments have been made in recent years in the description of microstructure evolution and its effects on the creep behaviour in advanced 9-12%Cr steels. However, data available for assessing the predictability of the creep behaviour are somewhat scarce since creep testing has generally been for constant temperature and load conditions. The present investigation was conducted on three advanced 9-12%Cr martensitic/ferritic steels (P91, P92 and E911) in an effort to obtain more complete description and understanding of the role of degradation processes in high temperature creep during intermittent heating. A comparison between the creep characteristics of non-steady and monotonously loaded creep specimens has revealed no significant deterioration of the creep strength and fracture resistance of the steels P91, P92 and E911 under non-steady loading in power-law (dislocation) creep. The final part of this paper deals with detailed experimental microstructural and fractographic investigations of crept specimens to explain the observed creep behaviour. Special attention is paid to the thermodynamic calculations using the software package Thermo-Calc, that have been used to predict precipitation reactions during intermittent heating of 9-12% chromium steels. The results of the thermodynamic calculations are in a good agreement with experimental data.
Warm Formability of AZ31 Magnesium Alloy Sheets under Different Process Conditions
Authors: Bruni Carlo , Forcellese Archimede , Gabrielli Filippo , Simoncini M.
Published: March 2009

The effect of the process parameters on the sheet formability of AZ31 magnesium alloy has been investigated by means of uniaxial tensile and hemispherical punch tests at different temperatures and strain rates. The results of the uniaxial tensile tests were analysed in terms of flow curves, ductility and microstructural evolution; the constitutive parameters were evaluated and related to the forming limit curves obtained by the hemispherical punch tests carried out at different temperatures and punch speeds.
Ti – ZrO2 Interactions during Manufacturing of High Porous Ti/Ti-Based MMC of Regulated Structure
Authors: Orlova Yuliya , Maekawa K. , Rack Henry J.
Published: March 2009

The present paper reports a microstructure inspection of powder fabrication of regulated structure Ti/Ti-based metal matrix composites (MMC) utilizing sacrificial NaCl particles. Blending, compaction and sintering of Ti and YSZ reinforced Ti compacts containing NaCl resulted in regulated foam structures with porosities between 45 and 70 pct. SEM observations indicated that three pore sizes and morphologies were formed while XRD analysis suggested that the yttria stabilized zirconia (YSZ) reinforcements are unstable at the high temperature sintering conditions considered in this study.
Constitutive Equations for Mg Alloy Hot Work Modeling
Authors: McQueen H.J. , Leo Paola , Cerri Emanuela
Published: March 2009

Constitutive equations for hot working are of great importance in optimizing forming processes to balance reductions in preheating and force, to avoid defects and to improve properties. Flow curve shapes and. constitutive parameters are affected by variations in composition, in homogenization, in grain morphology and significantly in texture. Confidence in published analyses is enhanced by existence of many data for the same or similar alloys. In this paper, constitutive equations have been collected for commercial Mg alloys from torsion, compression and tension tests in the range from 10-3 to 10 s-1 and 180 – 500°C. Some data were determined by the authors’ but more came from published reports; in some cases they have been re-calculated in a common manner. The deformation and restoration mechanisms that control the flow curve shape and the material parameters are summarized. Microstructure investigations of strained samples are illustrated. Applications to extrusion or rolling are discussed; comparisons to Al are made as appropriate.
Microstructural Modeling of Ferroelectric Materials: State of the Art, Challenges and Opportunities
Authors: Leach Sarah , Garcia R. Edwin
Published: March 2009

In the last ten years of ongoing research in the modeling of polycrystalline ferroelectric ceramics a myriad of analytical and numerical implementations have emerged to predict and support the engineering of ferroelectrics in both its single-crystal and polycrystalline forms. Traditional atomistic approaches capture the intrinsic behaviors, and have led to great improvements in the chemistries of these systems. Similarly, macroscopic engineering approaches have focused on the development of phenomenological descriptions that capture the empirical static and time-independent behavior. At the interface of these two apparently divorced approaches, thermodynamic-based microstructural evolution descriptions inspired in phase field models have risen as the necessary link between the atomic and macroscopic levels. This new and emerging methodology starts from the predicted behaviors given by their atomic counter-parts, and resolves the effects of grain boundaries, and de-convolves the grain-grain mesoscopic interactions. Much of the future of ferroelectrics lies in the delivery of improved chemistries and microstructures, and on bridging the understanding currently existing atomistic and continuum descriptions. Overall, it is expected that current and emerging technological challenges will be the driving force to minimize ferroelectric fatigue and realize lead-free materials with performances close to currently existing (lead containing) ones. Moreover, it is expected that while an accurate understanding of the intrinsic properties of materials are key to define improved ferroelectric solids, it will be the detailed understanding of the extrinsic response of ferroelectric materials, in both bulk and thin film form, that will take these materials to reach the highest performances possible.
Processing, Microstructure and Properties of Nanograin Barium Titanate Ceramics by Spark Plasma Sintering
Authors: Wang Xiao Hui , Deng Xiang Yun , Li Long Tu
Published: March 2009

Bulk dense nanocrystalline BaTiO3 ceramics ranging from 15 nm to 100 nm have been successfully prepared by the spark plasma sintering method. Raman spectra and X-ray diffraction were used in combination with electron microscopy to study the evolution of lattice structure and phase transformation behavior with grain growth from nanoscale to micrometre scale for BaTiO3 ceramics. Scanning nonlinear dielectric microscopy measurements revealed temperature-dependent variations in contrast, which were attributed to domain rearrangements in BaTiO3 ceramics below 100 nm. Furthermore the piezoresponse hysteresis loops showed that the nanocrystalline BaTiO3 ceramics were switchable and ferroelectricity was retained at the high temperature of 290 oC, demonstrating the existence of nano ferroelectric domains and the ferroelectric phase still retained above Curie temperature, which confirmed the diffused phase transition character in nanograin BaTiO3 ceramics. The dielectric data also show a ferroelectric to paraelectric phase transition in nanograin BaTiO3 ceramics.
Advanced Nano-Scale Metrology for the Characterization of Ceramic Materials in the Scanning Electron Microscope
Authors: Pezzotti Giuseppe , Matsutani Atsuo , Munisso Maria Chiara , Zhu Wen Liang
Published: March 2009

With the proliferation of several types and classes of high performance ceramic materials, the screening, evaluation and integration of new materials into structures and devices require a new and more effective approach. Evaluation on the nano-scale of the mechanical characteristics of new ceramic materials requires multiple complementary metrology tools. We report here about an advanced metrology tool, cathodoluminescence (CL) spectroscopy, which has a potential to rapidly screen and evaluate residual stress characteristics in advanced ceramic materials and structures. Nano-scale stress measurements are made in situ into an integrated metrology vacuum chamber in a field-emission gun scanning electron microscope (FEG-SEM). Complementing this tool, we also describe a new image analysis based on CL emission for fast screening and ranking of domain structures in ferroelastic ceramics. The end result of this paper is to show how crystallographic and mechanical characteristics of ceramics can be quantitatively characterized in a hybrid device combining electro-stimulated imaging and spectroscopic outputs.
Silicon Based Heterostructures: Advances in Channel Materials
Authors: Kasper Erich
Published: March 2009

Heterostructure device concepts promise several advantages in micro- and optoelectronics. From the material point of view, the main obstacle to be overcome is the large lattice mismatch of silicon based heterostructures. One of the best of them, silicon germanium (SiGe) is lattice mismatched to silicon by up to 4% depending on its Ge content. Basic investigations on strained layer growth, interface properties, and deviation from equilibrium are done with SiGe / Si heterostructures. Early results are discussed in context with our recent understanding. The application focus of this review is devoted to micro- and optoelectronic devices which could be fabricated after solving or understanding the basic interface problems. This includes devices already in production, and those in emerging fields for inclusion in the next generation of integrated circuits, as well as a selection of future device concepts with high merits to be proven in experiment.
Thallium Based Superconducting Thin Films Synthesized by RF-Sputtering and Ex Situ Thallination
Authors: Guerfi Tarek , Beauquis S. , Galez P. , Mosbah M.F.
Published: March 2009

Thallium based superconducting thin films of TlBa2CaCu2O7 (Tl-1212), Tl2Ba2CaCu2O8 (Tl-2212) and Tl2Ba2Ca2Cu3O10 (Tl-2223) of about 100-125 nm in thickness have been prepared on (001) LaAlO3 single crystal substrate using rf-sputtering deposition of Ba2Ca2Cu3O7 precursor films and ex-situ thallination in sealed quartz tube under different atmospheres (oxygen, argon and nitrogen). We have studied phases formation as function of partial pressure of Tl2O which may be adjusted by varying thallium source content TlxBa2Ca2Cu3Oz (x = 1.5, 1.6, 1.7, 1.8, 1.9, 2.0) and atmosphere pressure at ambient temperature (300, 500 mbar). The influence of the temperature and time of thallination (60 min to 1400 min) is also presented. The synthesized films were characterised by optical microscopy, atomic force microscopy AFM, AC susceptibility and XRD measurements. The XRD measurement shows that the obtained films contain several superconducting phases and are strongly c-axis oriented. The properties of the resulting films are critically dependant on the microstructures developed during thallination process. Thallium source content as well as the time of thallination and partial atmosphere pressure at room temperature play an important role in the obtained film’s quality and phase’s purity.
Elaboration of Porous Silicon Multilayer Using Resistive p-Type Si
Authors: Fellahi O. , Hadjersi T. , Guerbous L.
Published: March 2009

Porous silicon is largely studied in the field of photonics because of its interesting optical properties. In this work we present an experimental study about the elaboration of a multilayer structure by photoelectrochemical etching. p-Si(100) with resistivity of 100 Ωcm is used in this work. Two different current densities were used namely 150 mA/cm2 and 10 mA/cm2. We found that the anodization time is a crucial parameter for the formation of multilayer structures. The times of 2 and 5 seconds appears as optimal times for the elaboration of multilayer structures with 16 layers. Finally, we have determined that these structures exhibit strong luminescence at 600 nm.
A FET Gas Sensor Device Based on Porous Silicon
Authors: Zouadi N. , Gabouze N. , Bradai D. , Dahmane D.
Published: March 2009

The hydrogen-sensing property of new type field-effect gas sensor device was studied. The device had an FET structure based on porous silicon. Adsorption of molecules into the porous silicon strongly changes the electrical properties of the transistor structure. Interestingly, the current variation induced by Hydrogen gas vapour that is the sensitivity of the sensor can be electrically tuned by changing polarization voltage. It has been shown that the device exhibited excellent hydrogen-sensing characteristic at room temperature. The results show that current-voltage characteristics are modified by the gas reactivity on the PS surface.
In conclusion, the FET gas sensor based on porous silicon shows a rapid response to low concentration of the hydrogen gas at room temperature.
Photoluminescence of Passivated a-Si:H
Authors: Brunner Róbert , Kobayashi Hikaru , Kučera M. , Takahashi Masao , Rusnák Jaroslav , Pinčík Emil
Published: March 2009

. Experimental results relating to evolution of the a-Si:H photoluminescence spectra are presented. The investigated samples were prepared by deposition of thin a-Si:H layer on glass substrate. In the a-Si:H surface region very thin oxide layer was prepared by wet chemical oxidation in 40% nitric acid solution. The defect states of amorphous silicon layer and its interface with oxide were passivated in HCN aqueous solutions. The attention was focused on decomposition procedure of photoluminescence spectra observed at 6 K. The results confirm the existence of several structurally different phases inside of the a-Si:H amorphous matrix.
PACS: 78.55.-m, 78.55.Qr, 81.05.Gc
Effects of Hydrogen Partial Pressure on Boron-Doped Hydrogenated Amorphous Silicon (a-Si:H(B)) Properties
Authors: Khelifati N. , Cherfi R. , Keffous A. , Rahal A. , Kechouane M.
Published: March 2009

Boron-doped hydrogenated amorphous silicon (a-Si:H(B)) thin films have been prepared by DC magnetron sputtering technique under argon and hydrogen mixture. The films were deposited at various hydrogen pressures between 0 and 9 10-5 mbar. The boron concentration estimated from Secondary Ion Mass Spectrometry (SIMS) analysis was found to be around 1.5 1021 cm-3 for all samples. Their physico-chemical, optical and electrical properties are investigated. The physico-chemical properties were studied by infrared absorption measurements. The bonded hydrogen content in the films is then determined using the absorption band of stretching mode. The optical transmission measurements show an increase of the static refractive index and a decrease of optical gap value when hydrogen pressure increases. The dark-conductivity and the photo-conductivity measurements according to the temperature are also reported. We have observed the decreasing of dark-conductivity when hydrogen pressure increases. A slight sensitivity of light was observed for the film deposited at the highest hydrogen pressure. The dark-conductivity was affected by annealing temperature for the whole of the films through its increase in the annealing temperature region 200-350°C.
The Effects of Different Hydroxyapatite/TiO2 Composite Coatings on Protein Expression of Osteoblast
Authors: Han Jian Ye , Yu Zhen Tao , Zhou Lian
Published: March 2009

Hydroxyapatite/TiO2 composite material was coated onto Ti25Nb3Mo2Sn3Zr (TLM) alloy substrate. To study the effects of hydroxyapatite/TiO2 composite coatings on bone-related protein expression, the osteoblast were cultured with composite coatings for different times. The phase transformation and compound formation of the HA/TiO2 coatings were investigated using XRD (X-ray diffraction). The mRNA expression of Type I collagen, alkaline phosphatase (ALP) and osteocalcin were studied by RT-PCR (reverse transcriptional polymerase chain reaction). The titania delayed the crystallization of HA. The mRNA expressions of Type I collagen are decreased as the increasing of TiO2 percentage. The mRNA expressions of osteocalcin are approached. The ALP expression on H4 coating (HA/TiO2 mol ration is 5) after the osteoblast cultured with composite coating for 6 days is the highest. The increasing of TiO2 amount decreases the bioactivity of the composite coatings.
Biocompatibility of Chitosan/Heparin Multilayer Coating on NiTi Alloy
Authors: Dong Ping , Yuan Ling Wei , Hao Wei Chang , Xia Ya Yi , Da Guo Zu , Wang Tian Min
Published: March 2009

Nickel Titanium alloy has been used widely in clinical iatrology for years because of its unique shape memory capability, proper elasticity and considerable biocompatibility. But as an implanted material, its possible release of Ni ions which might cause toxic effect and its improvable biocompatibility draw attentions of researchers. In this study, chitosan/heparin multilayer is coated on NiTi shape memory alloy by electrostatic self-assemble method. Field emission scanning electron microscopy (FE-SEM), contact angle test is used to show its surface character; hemolysis test, dynamic clotting time experiment and platelet binding test are utilized to investigate the blood compatibility of the materials. The results reveal that the hydrophilic character of the coated one is better than the substrate, and blood compatibility of NiTi is improved by coating treatment.
Analysis on Process and Forming Defects of Large-Scale Complex Integral Component Isothermal Local Loading
Authors: Sun Zhi Chao , Yang He
Published: March 2009

Isothermal local loading forming is an advanced technology for large-scale complex integral component forming, but the process is with coupling effects of multi-fields and multi-factors due to the local loading mode and high temperature condition, thus makes deformation mechanism extremely complicated and some forming defects may occur. Based on DEFORM3D software, relative FE models for the isothermal local loading forming of large-scale complex integral components of TA15 titanium alloy have been established, and key technologies for modeling have been dealt with properly. Then taking a representative large-scale complex integral component as object the froming process, the typical deformation behavior and metal flow were investigated. And typical forming defects which may occur during the process and causes for them are discussed.
Effects of Downstream Rolling on Microstructure and Mechanical Properties of Twin Roll Casting AZ31B Strip
Authors: Zhao Hong Yang , Hu Xiao Dong , Ju Dong Ying
Published: March 2009

Experimental study on downstream rolling process for twin roll casting magnesium alloy strip was carried out. The microstructure of the casting and rolling strip were observed by OM, SEM, and TEM. The effects of homogenizing process, the parameters of rolling process and annealing after rolled on secondary rolling of AZ31B casting strip were analyzed. The results show that the twin roll casting strip are suitable for rolling at 380-420 °C after homogenizing at 400 oC for two hours, the reduction rate of each pass should be controlled lower than 18%. Mg alloy sheets with thickness from 0.3-1 mm can be produced in once annealing period in this way. By controlling the pass reduction and rolling temperature, the fabricated AZ31B Mg alloy sheets can achieve both high strength and good plasticity by grain refining below 10μm. The mechanical properties of rolled strip after annealing at 400 oC for 0.5h-1h could get tensile strength 220MPa and meantime elongation rate 20%.
Formation of Protrusive Micro/Nano Patterns atop Shape Memory Polymers
Authors: Huang W.M. , Liu N. , Lan X. , Lin J.Q. , Pan J.H. , Leng Jin Song , Phee S.J. , Fan H. , Liu Y.J. , Tong T.H.
Published: March 2009

The surface morphology of materials is of fundamental importance to many applications (e.g., surface wetting, friction, surface roughness, reflection, drag, adhesion, etc). Various approaches for micro/nano patterning atop polymer surfaces have been proposed in recent years. However, a cost effective technique is still highly in demand. In this paper, we demonstrate a few novel but rather simple and generic approaches for surface micro/nano patterning using shape memory polymers (SMPs). Reversible micro vertical chains, crown shaped protrusion arrays and strip/labyrinth wrinkles atop SMPs are presented.
Porous Ti/HA Biocomposites for Biomaterial Applications
Authors: Liu Zhi Guang , Zhang Yu Mei , Shi Huan , Xu Li Juan , Chen Yu Yong , Woo Kee Do
Published: March 2009

In the present study, we tried to make Ti matrix/hydroxyapatite biocomposites using powder metallurgy and chemical treatments. Three composites were produced: Ti-30vol%HA, Ti15Mo-30vol%HA and Ti13Nb13Zr-44vol%HA. After mechanical milling and spark plasma sintering, Ti/HA composite compacts were produced. Microstructure observations and mechanical property tests showed that composites with two components (Ti-HA) have high hardness, moderate compress strength and lower density. The produced Ti/HA bulk composites were subjected to chemical treatment of immersion into phosphoric acid solution and porous structure was obtained. The obtained porous structure was characterized.
Key to the Paraplatyptilia species of eastern Canada with description of a new species (Lepidoptera: Pterophoridae)
Authors: Landry Bernard , Gielis Cees
Published: March 2009

Paraplatyptilia atlanticasp. nov. is described as new from northwestern Newfoundland and the Gaspé Peninsula, Quebec, Canada. A key to the four species of Paraplatyptilia Bigot and Picard known to occur in eastern Canada (east of Manitoba) is provided.
Serendipity with chewing lice (Phthiraptera: Menoponidae, Philopteridae) infesting rock pigeons and mourning doves (Aves: Columbiformes: Columbidae) in Manitoba, with new records for North America and Canada
Authors: Galloway Terry D. , Palma Ricardo L.
Published: March 2009

An extensive survey of chewing lice from rock pigeon,Columba liviaGmelin, and mourning dove,Zenaida macroura(L.), carried out from 1994 to 2000 and from 2003 to 2006 in Manitoba, Canada, produced the following new records:ColocerastovornikaeTendeiro for North America;Columbicola macrourae(Wilson),Hohorstiellalata(Piaget),H.paladinellaHill and Tuff, andPhysconelloides zenaidurae(McGregor) for Canada; andBonomiella columbaeEmerson,Campanulotes compar(Burmeister),Columbicola baculoides(Paine), andC. columbae(L.) for Manitoba. We collected 25 418 lice of four species (C. compar,C. columbae,H.lata, andC.tovornikae) from 322 rock pigeons. The overall prevalence of infestation was 78.9%, 52.5%, and 23.3% forC.compar,C.columbae, andH.lata, respectively.Coloceras tovornikaewas not discovered until 2003, after which its prevalence was 39.9% on 114 pigeons. We collected 1116 lice of five species (P.zenaidurae,C.baculoides,C. macrourae,H.paladinella, andB.columbae) from 117 mourning doves.Physconelloides zenaiduraewas encountered most often (prevalence was 36.7%), while the prevalence of the other four species was 26.3%, 18.4%, 3.5%, and 2.6%, respectively.
Review of the Nearctic Lonchopteridae (Diptera), including descriptions of three new species
Authors: Klymko John , Marshall S.A.
Published: March 2009

The Nearctic species of Lonchoptera Meigen are reviewed, including three new species: L. barberi Klymko sp. nov. from Manitoba, Newfoundland, Ontario, Quebec, Iowa, Michigan, Minnesota, and New Hampshire, L. megaloba Klymko sp. nov. from British Columbia and California, and L. longiphallus Klymko sp. nov. from British Columbia and the Northwest Territories. Lonchoptera borealis Curran is proposed as a new junior synonym of L. impicta Zetterstedt, and L. occidentalis Curran is proposed as a new junior synonym of L. uniseta Curran. Lonchoptera nigrociliata Duda, formerly known only from the Palaearctic Region, is recorded from the Yukon and Alaska. Descriptions, a key, and Nearctic distribution maps are presented. Phylogenetic relationships are briefly discussed and two sister species pairs are documented.
Biology of Caloptilia fraxinella (Lepidoptera: Gracillariidae) on ornamental green ash, Fraxinus pennsylvanica (Oleaceae)
Authors: Evenden M.L.
Published: March 2009

The ash leaf cone roller, Caloptilia fraxinella (Ely), is a leaf-mining moth that has recently become a significant pest of horticultural ash, Fraxinus L., species in communities throughout the western prairie provinces of Canada. The study examines the spatial and temporal within-host distribution of immature stages of C. fraxinella on green ash, Fraxinus pennsylvanica Marsh. Female C. fraxinella showed a preference for oviposition sites in the lower canopy and on the south side of the tree at the beginning and middle of the 3-week oviposition period, respectively, but no preference at the end of the period. Oviposition was constrained temporally and occurred mainly just after green ash bud flush. Immature stages were sampled throughout the growing season, and measured widths of larval head capsules showed five instars. Fourth-instar larvae disperse from the mined leaflet to a new leaflet, roll it into a cone, and pupate. Neither canopy height nor ordinal direction affected the position of larvae in the canopy, but numbers of immature stages varied by tree within a site. Female and male moths eclose from rolled leaf cones synchronously throughout the emergence period. The study provides some of the basic biological information required to design an integrated pest management program to target this emerging pest of horticultural ash trees.
Tenebrionidae (Coleoptera) of the Maritime Provinces of Canada
Authors: Majka Christopher G. , Bouchard Patrice , Bousquet Yves
Published: March 2009

The Tenebrionidae of the Maritime Provinces of Canada are surveyed. Forty-eight species have been reported from the region. Eleven of these species (ten Palearctic and one Nearctic) have been introduced to the region, five of which are apparently now extirpated. Dates of first detection of these species are provided for each province and North America. Thirteen species are newly recorded in New Brunswick, 25 in Nova Scotia, and 15 on Prince Edward Island, for a total of 53 new provincial records. Of these, 18 species including Bolitophagus corticola Say, Neatus tenebrioides (Palisot de Beauvois), Helops gracilis Bland, Blapstinus substriatus Champion, Hymenorus obesus Casey, Hymenorus picipennis Casey, Hymenorus pilosus (Melsheimer), Mycetochara bicolor (Couper), Mycetochara binotata (Say), Mycetochara fraterna (Say), Platydema excavatum (Say), Platydema teleops Triplehorn, Corticeus praetermissus (Fall), Alobates pennsylvanicus (DeGeer), Haplandrus fulvipes (Herbst), Xylopinus saperdioides (Olivier), an undescribed species of Paratenetus Spinola, and an undescribed species of Neatus LeConte are newly recorded for the Maritime Provinces as a whole. One of these, Helops gracilis, is recorded for the first time in Canada. The fauna is discussed from the perspective of the patterns of distribution of species in the region and their possible underlying causes. Island faunas are discussed, as is the saproxylic component of the fauna, with a brief consideration of the importance of this trophic group in the dynamics of forest ecosystems in the region.
New Chemical Systems and Placement Methods to Stabilize and Seal Deepwater Shallow-Water Flow Zones
Authors: Eoff Larry , Sweatman Ron , Faul Ronnie
Published: March 2009

This paper describes two matrix-permeability treating fluids that can helpconsolidate and impair the permeability of unconsolidated shallow-waterflow(SWF) sands. These treatments offer unique solutions to many problems presentedby shallow-water flow zones.

Overpressured, unconsolidated formations will begin flowing water and sandupon penetration. Uncontrolled water and sand flow can increase hole size and destabilize the wellbore and the adjacent formation. In these areas, formationpore pressures are often close to fracturing pressures, presentinglost-circulation problems during drilling and cementing operations. The systemsdescribed in this paper can penetrate SWF formations and gel downhole, providing adequate mechanical strength and reducing formation permeability. Byimproving hole conditions, these systems can help (1) expand thefracture-gradient/pore-pressure window, (2) stabilize the hole for lower mudweights, (3) prevent washouts, (4) allow hole section extensions withoutrequiring operators to set pipe, and (5) improve long-term well integrity. Thispaper presents laboratory data for the two chemical systems, describesplacement techniques, provides case histories, and describes software systemsthat can aid treatment fluid volume design and placement.

Introduction

SWF sands are encountered at depths less than 2,000 ft below the mudline in30 to 40% of the drilling operations in the Gulf of Mexico. These zones areformed from sand and silt eroding from the continental shelf and settling overolder deepwater formations. Over time, many layers were formed as graded-sediment beds, with the heaviest particles settling to the bottom. The formation of successive layers undercompacted and overpressured the sediments. During the drilling process, penetration can cause flow through layers. Thisflow can result in significant problems during drilling, cementing, andproduction. In addition, these overpressured zones exhibit low fracturegradients that further complicate drilling and cementing operations. Theresulting concerns include possible casing collapse, buckling, or wear. Wellbore stability throughout the life of the well is absolutely critical. If SWF zones compromise the stability, the entire well could be lost.
Citrus
Authors: Peña Leandro , Cervera Magdalena , Fagoaga Carmen , Romero Juan , Ballester Alida , Soler Nuria , Pons Elsa , Rodríguez Ana , Peris Josep , Juárez José , Navarro Luis
Published: March 2009

Citrus is the most important fruit tree crop in the world, with a production of more than 100 million tons annually. The area of origin of Citrus is believed to be southeastern Asia, where its domestication started. It has become clear that only citron, mandarin, and pummelo are true species within genus Citrus, being other important Citrus types, as sweet orange, sour orange, lemon, lime, grapefruit and other mandarins originated from hybridization between these ancestral species. In spite of the many efforts put in classical breeding programs in the last 100 years, current citrus industry relies on various groups of varieties that are grafted onto rootstocks adapted to different abiotic and biotic stresses. Most of these genotypes have been generated by chance, mostly as budsports but also as natural hybrids or seedlings selected by men in the wild or in orchards. Citrus breeding is complicated due to its complex reproductive biology. In this context, genetic transformation offers an important alternative for the genetic improvement of citrus. Moreover, it is probably the most efficient approach to make reverse genetics in citrus to investigate gene function and thus to gain better understanding in metabolic processes and plant‐pathogen‐environment interactions.
Computer aided design for sustainable industrial processes: Specific tools and applications
Authors: Fermeglia Maurizio , Longo Gennaro , Toma Letitia
Published: March 2009

Chemical Process Sustainability can be estimated using different sustainability indicators. The quantitative estimation of those indicators is necessary (i) for evaluating the environmental impact of a chemical process and (ii) for choosing the best design among different available alternatives. To accomplish these goals, the computerized calculation of sustainability indicators requires the use of at least three computer tools: (i) process simulation, (ii) molecular modeling and a (iii) sustainability indicators software code. In this work, a complete software platform, Process Sustainability Prediction Framework, integrated with process simulation programs, which support the CAPE‐OPEN interfaces, is presented and discussed. The article contains also description and application of molecular modeling techniques to estimate different toxicological data, which are used in the calculation of sustainability indicators. A representative example of one chemical process and thermo‐physical properties used in the toxicological data calculation, are reported to demonstrate the applicability of the software to real cases. © 2009 American Institute of Chemical Engineers AIChE J, 2009
A new high‐resolution computed tomography (CT) segmentation method for trabecular bone architectural analysis
Authors: Scherf Heike , Tilgner Rico
Published: March 2009

In the last decade, high‐resolution computed tomography (CT) and microcomputed tomography (micro‐CT) have been increasingly used in anthropological studies and as a complement to traditional histological techniques. This is due in large part to the ability of CT techniques to nondestructively extract three‐dimensional representations of bone structures. Despite prior studies employing CT techniques, no completely reliable method of bone segmentation has been established. Accurate preprocessing of digital data is crucial for measurement accuracy, especially when subtle structures such as trabecular bone are investigated. The research presented here is a new, reproducible, accurate, and fully automated computerized segmentation method for high‐resolution CT datasets of fossil and recent cancellous bone: the Ray Casting Algorithm (RCA). We compare this technique with commonly used methods of image thresholding (i.e., the half‐maximum height protocol and the automatic, adaptive iterative thresholding procedure). While the quality of the input images is crucial for conventional image segmentation, the RCA method is robust regarding the signal to noise ratio, beam hardening, ring artifacts, and blurriness. Tests with data of extant and fossil material demonstrate the superior quality of RCA compared with conventional thresholding procedures, and emphasize the need for careful consideration of optimal CT scanning parameters. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.