bluuebunny/crossref_metadata_2025 huggingface dataset:
Abrasive-Free Planarization of 3-Inch 4H-SiC Substrate Using Catalyst-Referred Etching
Authors: Okamoto Takeshi , Sano Yasuhisa , Tachibana Kazuma , Arima Kenta , Hattori Azusa N. , Yagi Keita , Murata Junji , Sadakuni Shun , Yamauchi Kazuto
Published: March 2011

Catalyst-referred etching (CARE) is an abrasive-free planarization method. We used 3-inch and 2-inch 4H-SiC (0001) 4° off-axis substrates to investigate the processing characteristics that are affected by the substrate diameter. The surface roughness of the 3-inch substrate was extremely smooth over the whole substrate. The surface roughness and removal rate of the 3-inch substrate were approximately the same as those of the 2-inch substrate.
Oxidation Process by RTP for 4H-SiC MOSFET Gate Fabrication
Authors: Constant Aurore , Camara Nicolas , Montserrat Josep , Pausas Esther , Camassel Jean , Godignon Philippe
Published: March 2011

Rapid Thermal Processing (RTP) has been evaluated as an alternative to the conventional furnace process for the gate oxide formation of SiC lateral MOSFETs. We show that this innovative oxidation method has not only the advantage to significantly reduce the thermal budget compared to classical oxidation, but also produces a significant improvement of MOSFET performance when using N2O as oxidizing gas. Studying different surface preparation before gate oxidation, we demonstrate that in-situ surface preparation by H2 annealing increases considerably the channel mobility and also the electrical stability with respect to constant bias stress at low-field.
Growth of SiC Microwires through Si Microwires Carburization
Authors: Ollivier Maelig , Mantoux Arnaud , Bano Edwige , Rogdakis Konstantinos , Zekentes Konstantinos , Baron Thierry , Latu-Romain Laurence
Published: March 2011

Silicon microwires (MWs) previously synthesized using the VLS method with gold catalyst are being carburized at 1100°C under methane aiming to their conversion to SiC. SEM, TEM as well as XPS and Raman spectroscopy were used for structural and morphological characterization. After carburization achievement, SiC is found to be polycrystalline with a high density of stacking faults associated to an increase of surface roughness. Directions for the carburization process optimization are given.
Fabrication of n-Type Nanocrystalline Diamond/3C-SiC/p-Si(001) Junctions
Authors: Goto Masaki , Koga Akira , Yamada Kazuhiro , Kato Yoshimine , Teii Kungen
Published: March 2011

Nanocrystalline diamond (NCD)/3C-SiC layered films are deposited on Si substrates by using a moderate-pressure microwave plasma apparatus. The epitaxial 3C-SiC thin layer is grown on p-type Si(001) above 1200°C in 2%CH4/98%H2 by plasma-assisted carbonization and the n-type NCD overlayer is subsequently grown at 830°C in 1%CH4/30%N2/69%Ar by plasma-enhanced chemical vapor deposition (CVD). According to cross sectional TEM observations, the initial thickness of the 3C-SiC layer (~20 nm) is reduced to 10 nm or less in the beginning of the NCD growth due most likely to etching. A rectifying current-voltage characteristic is obtained for an n-type NCD/epitaxial 3C-SiC/p-type Si(001) junction in a diode configuration.
SiC Zener Diode for Gate Protection of 4.5 kV SiCGT
Authors: Nakayama Koji , Ishii Ryosuke , Asano Katsunori , Miyazawa Tetsuya , Tsuchida Hidekazu
Published: March 2011

Zener voltages of the fabricated SiC Zener diodes with various nitrogen concentrations in the range from 7×1017 to 5×1019 cm-3 are 17 to 87 V, and decreased with an increase in the nitrogen concentration. Furthermore, in a chopper circuit using SiC Zener diodes for SiCGT gate protection, the commutated current decreases slowly even though cathode current falls rapidly, and the SiCGT gate is protected from surge voltage by SiC Zener diode. Moreover, the value of Zener voltage after the operation was the same as that before half bridge operation at 47 V.
Thermally-Assisted Tunneling Model for 3C-SiC p+-n Diodes
Authors: Zippelius Bernd , Krieger M. , Weber Heiko B. , Pensl Gerhard , Nagasawa Hiroyuki , Kawahara Takamitsu , Hatta Naoki , Yagi Kuniaki , Uchida Hidetsugu , Kobayashi Motoki
Published: March 2011

The dependence of the reverse current of 3C-SiC p+-n diodes on the temperature and on the reverse bias is measured and a model based on thermally-assisted tunneling is proposed to explain the dominating mechanism responsible for the leakage current. Taking into account an additional ohmic shunt resistance, the experimental reverse characteristics and thermal barrier heights B can sufficiently be reproduced.
Low Earth Orbit Space Environment Testing of Extreme Temperature 6H-SiC JFETs on the International Space Station
Authors: Neudeck Philip G. , Prokop Norman F. , Greer III Lawrence C. , Chen Liang Yu , Krasowski Michael J.
Published: March 2011

This paper reports long-term electrical results from two 6H-SiC junction field effect transistors (JFETs) presently being tested in Low Earth Orbit (LEO) space environment on the outside of the International Space Station (ISS). The JFETs have demonstrated excellent functionality and stability through 4600 hours of LEO space deployment. Observed changes in measured device characteristics tracked changes in measured temperature, consistent with well-known JFET temperature-dependent device physics.
600-V Symmetrical Bi-Directional Power Switching Using SiC Vertical-Channel JFETs with Reliable Edge Termination
Authors: Veliadis Victor , Urciuoli Damian , Ha H.C. , Hearne Harold , Scozzie Charles
Published: March 2011

Numerous high-voltage applications require symmetrical bi-directional power flow control and protection circuitry. While mechanical contactors and circuit breakers provide bi-directional fault protection, they have slow actuation and suffer severe degradation during repeated fault isolation. The normally-on (N-ON) SiC vertical-channel Junction-Field-Effect-Transistor (VJFET) is an efficient solution for bi-directional circuit-breaker applications due to its low conduction/switching losses, +500°C operational capability, ON-state match of the no-fault operating mode of the system, efficient gate-drive operation under unipolar biasing, and majority carrier device scalability. Efficient 600-V/10-A symmetrical bi-directional power flow was demonstrated using 0.1-cm2 1200-V rated N-ON VJFETs with a gate driver applying 0-V and -34 V gate biases during the ON and OFF states, respectively. A self-aligned trenched guard-ring structure provides reliable edge termination.
1700V, 20A 4H-SiC DMOSFETs Optimized for High Temperature Operation
Authors: Hull Brett A. , Ryu Sei Hyung , Zhang Q. Jon , Jonas Charlotte , O'Loughlin Michael  J. , Callanan Robert , Palmour John W.
Published: March 2011

DMOSFETs fabricated in 4H-SiC with capabilities for blocking in excess of 1700V and conducting 20A continuous current in the on-state are presented. These SiC DMOSFETs remain functional to temperatures in excess of 225°C, with leakage current at 1700V at 225°C of less than 5 A with VGS = 0V. The DMOSFETs show excellent switching characteristics, with total switching energy of 1.8 to 1.95 mJ over the entire temperature range of testing (25°C to 200°C), when switched from the blocking state at 1200V to conducting at 20A in a clamped inductive load switching circuit. The electrical characteristics are compared to commercially available Si IGBTs rated to 1700V with similar current ratings as the SiC DMOSFET described herein.
Fabrication of P-Channel MOSFETs on 4H-SiC C-Face
Authors: Okamoto Mitsuo , Iijima Miwako , Yatsuo Tsutomu , Nagano Takahiro , Fukuda Kenji , Okumura Hajime
Published: March 2011

We investigated the 4H-SiC C-face MOS interface properties around valence-band, and fabricated 4H-SiC C-face p-channel MOSFETs for the first time. For C-face p-channel MOSFETs, relatively low-temperature wet-gate-oxidation was preferable. Post-deposition-annealing for contact metal was found to degrade the C-face MOS interface around valence-band. Low-temperature (800°C) PDA in hydrogen including ambient was effective to some extent in order to suppress the degradation owing annealing. We obtained C-face p-channel MOSFET with normal FET operation by utilizing 900°C wet-gate-oxidation and 800°C PDA in He-H2 forming gas ambient.
Use of Vacuum as a Gate Dielectric: The SiC VacFET
Authors: Speer Kevin M. , Neudeck Philip G. , Mehregany Mehran
Published: March 2011

We introduce the vacuum field-effect transistor (VacFET), the first SiC FET to use a vacuum-sealed cavity in place of the traditional, solid gate dielectric. This device architecture eliminates the need to thermally oxidize the SiC surface, a practice which has been widely reported to inhibit the performance and reliability of SiC MOSFETs. Using a combination of batch-compatible electronics and micromachining processing techniques, a polycrystalline SiC bridge is suspended above a 4H-SiC substrate, and the underlying cavity is sealed under vacuum. The fundamental studies made possible by such a device could shed much-needed light on the basic electronic properties of an inverted SiC surface. In this introductory report, we detail the analytical design and fabrication necessary to manufacture the VacFET, and we also demonstrate proof of the concept using turn-on and output characteristics of the first functional SiC device.
980 V, 33A Normally-Off 4H-SiC Buried Gate Static Induction Transistors
Authors: Takatsuka Akio , Tanaka Yasunori , Yano Koji , Yatsuo Tsutomu , Arai Kazuo
Published: March 2011

In this work, we succeeded in developing high performance normally-off SiC buried gate static induction transistors (SiC-BGSITs). To achieve the normally-off characteristics, design parameters around the channel region were optimized and process conditions were improved to realize these parameters. The off-state characteristic of the SiC-BGSIT showed an avalanche breakdown voltage of VBR=980 V at a gate voltage of VG=0 V. Furthermore, the leakage current at VD=950 V is lower than 0.5 μA. These results indicate that the BGSIT has a good normally-off characteristic. At VG=2.5 V, an on-resistance of 28.0 mΩ corresponding to the specific on-resistance of 1.89 mΩ•cm2 was obtained and the current rating was calculated as 33 A at a power density of 200 W/cm2 in the on-state characteristic.
Reducing Stacking Faults in Highly Doped N-Type 4H-SiC Crystal
Authors: Kojima Kazutoshi , Kato Tomohisa , Ito Sachiko , Kojima Jun , Hirose Fusao , Kito Yasuo , Yamauchi Shoichi , Nishikawa Koichi , Adachi Ayumu
Published: March 2011

We investigated a way of reducing the stacking fault (SF) density on a highly nitrogen (N) doped 4H-SiC crystal. SFs were generated at highly N doped crystal exceeding 4 x 1019 cm-3 and the density was increased with increasing N concentration. We found that Al co-doping had the potential to suppress this SF generation and was effective up to an N concentration of about 1 x 1021cm-3. This effect depended strongly on the Al concentration. We discussed the reason for the SF suppression effect of Al co-doping.
InGaN/GaN Multiple Quantum Well Blue LEDs on 3C-SiC/Si Substrate
Authors: Han Ji Sheng , Dimitrjiev Sima , Wang Li , Iacopi Alan , Shuang Qu , Xu Xian Gang
Published: March 2011

Gallium nitrides are primarily used for their excellent light emission properties. GaN LEDs are mostly grown on foreign substrates, essentially sapphire and SiC, but more recently, also on Si substrates. In this paper, we will demonstrate that the high structural quality of InGaN/GaN multiple quantum wells can be deposited on 3C-SiC/Si (111) substrate using MOCVD. This demonstrates that 3C-SiC/Si is a promising template for the epitaxial growth of InGaN/GaN multiple quantum wells for LEDs.
Electrical Characterization of Metastable Defects Introduced in GaN by Eu-Ion Implantation
Authors: Auret F. Danie , Meyer Walter E. , Diale M. , Janse Van Rensburg P.J. , Song S.F. , Temst Kristiaan , Vantomme André
Published: March 2011

Gallium nitride (GaN), grown by HVPE, was implanted with 300 keV Eu ions and then annealed at 1000 oC . Deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) were used to characterise the ion implantation induced defects in GaN. Two of the implantation induced defects, E1 and E2, with DLTS peaks in the 100 – 200 K temperature range, had DLTS signals that could be studied with L-DLTS. We show that these two defects, with energy levels of 0.18 eV and 0.27 eV below the conduction band, respectively, are two configurations of a metastable defect. These two defect states can be reproducibly removed and re-introduced by changing the pulse, bias and temperature conditions, and the transformation processes follow first order kinetics.
Atomistic Simulation of SiC Growth at the SiC(0001)/Si1-XCx Interface by the Monte Carlo Method
Authors: Itoh Makoto , Uda Tsuyoshi , Nara Jun , Ohno Takahisa
Published: March 2011

We developed the computer simulation method to study growth of SiC at the SiC(0001)/Si1-xCx interface based on the Monte Carlo method. Energy is calculated by using the Tersoff potential and the lattice spacing is sub-divided to enable the structural relaxation in a dicrete manner. Before making an attempt for the atomic difusion via the species exchange process in the Metropolis alogrithm, local relaxation is carried out to locate atoms at the local minima of the potential surface. Then, parallel computation is carried out to thermally equilibrate a system.
Determination of Residual Stresses in Thermal and Cold Sprayed Coatings by the Hole-Drilling Method
Authors: Ryabchikov Alexander , Lille Harri , Toropov Stanislav , Kõo Jakub , Pihl Toomas , Veinthal Renno
Published: March 2011

Residual stresses in most coatings have a significant influence on adhesion, on mechanical properties and on tribological performance. Residual stress can not be measured directly, rather strain is measured and stress is calculated. In this study residual stresses were investigated in thick thermal Ni95Al5 and cold sprayed Ni, Cu, NiZn, AlZn powder coatings using the semi-destructive hole-drilling and layer growing curvature methods. Residual stresses obtained for the thermal spray coating were compressive and with a relatively large deviation of the results indicating the nonuniformity of residual stress. Cold sprayed coatings have more uniform structure than thermal sprayed coatings. Residual stresses were compressive, and results obtained by hole-drilling and curvature method were comparable.
Determination of Residual Stresses in Welded Structural Steels with Help of Micromagnetic Measurements
Authors: Nitschke-Pagel Thomas , Dilger Klaus , Eslami-Chalandar Hamdollah
Published: March 2011

The micromagnetic measurement method is a fast and easy to handle alternative for the determination of residual stresses in steel welds. The accuracy is lower in comparison to diffraction techniques but it can be applied faster and under rough conditions however connected with a lower accuracy. Experimental results of investigations with different steel welds show that the method requires an external calibration and the consideration of particular boundary conditions as well as certain limitations must be accepted. Then the method is a good alternative or more a complementary measurement methods which helps to reduce the effort for the analysis of residual stresses in welded components.
External Reference Samples for Residual Stress Analysis by X-Ray Diffraction
Authors: Lefebvre Fabien , Francois M. , Cacot J. , Hemery C. , Le-Bec P. , Baumhauer E. , Bouscaud Denis , Bergey T. , Blaize D. , Gloaguen D. , Lebrun Jean Lu , Cosson A. , Kubler Regis , Cheynet Y. , Daniel E. , Michaud H. , Monvoisin J.C. , Blanchet P. , Allain P. , Mrini Y , Sprauel Jean Michel , Goudeau Philippe , Barbarin P. , Charles C. , Le Roux J.M. , Seiler Wilfrid , Fischer C. , Desmas L. , Ouakka A. , Moya M.J. , Bordiec Y.
Published: March 2011

The GFAC (French Association for residual stress analysis) decided in 2007 to work on external reference samples for residual stress analysis by X-ray diffraction as defined in the XPA 09-285 and EN 15305-2009 standards. Seven materials are studied: ferritic steel, martensitic steel, aluminium alloy, titanium alloy, 2 types of Nickel-Chromium alloy and tungsten thin layers deposited on silicon wafers. The purpose of this external round robin campaign is threefold: (i) to give possibilities for each laboratory involved in the campaign test to obtain external reference samples for each material tested, (ii) to validate a common procedure for qualification of external samples and (iii) to commercialise validated external reference samples through the GFAC association. A common approach of X-Ray diffraction parameters, samples geometry and standard procedure has been chosen and adopted by each laboratory involved in these tests. No indication in terms of residual stress calculation method is given; the choice of the method (centroid, middle point, maximum of peak, fitting…) is the choice of the laboratory according to their X-ray diffraction set-ups, softwares and experience. Once all samples are analysed, values given by each laboratory are compared and analysed.
Residual Stresses in Austenitic Stainless Steel due to High Strain Rate
Authors: Suzuki Kenji , Shobu Takahisa
Published: March 2011

Austenitic stainless steel (SUS316L) was used as specimen material, and the plate specimens were deformed plastically with a wide range of strain rates (6.67×10-5~ 6.70×102/s). The residual micro-stress for each lattice plane was measured with hard synchrotron X-rays. The residual macro-stress due to tensile deformation depended on strain rate. The residual micro-stresses varied from tension to compression, depending on the diffraction elastic constant. The soft lattice plane had tensile residual stress, and the hard lattice plane had compressive residual stress. The higher the strain rate, the smaller the difference in residual micro-stresses. The residual micro-stresses of the surfaces peened with the laser-peening or water-jet-peening were examined. Both surfaces had exhibited large compressive residual stress. The residual micro-stress on the peened surfaces showed a tendency opposite to residual micro-stress due to tensile deformation.
Thermal Fatigue Study of Hardfaced Hot Forging Tool Using Numerical Analysis and Residual Stress Evaluation
Authors: Fekih Ahmed Walid , Bonnefoy Herve , Levesque Alexandra , Crequy Samuel , Lodini Alain
Published: March 2011

Hot forging tools are exposed to severe thermo-mechanical load which cause their failure. The main failure mechanisms are mechanical fatigue, thermal fatigue, plastic deformation and abrasive wear. The use of hardfacing is an effective solution to increase tool life and consequently reducing the cost of forged part. In this work the use of a cobalt-base hard-facing obtained by Plasma Transferred Arc process is studied. The hardfacing is used for tool failed by thermal cracking. The high rate of temperature variation and high temperature gradient at the tool surface induce material softening and surface plastic deformation. These plastic deformations are accumulated during each cycle and eventually cause cracks in the most exposed zones and then tool failure after a few thousand cycles. Microstructure characterization and mechanical behavior analyses are required to prove the quality of coating. Finite element method is used to calculate stress distribution in tool resulting from external loading in order to optimize the thickness and the choice of coating used. Evaluation of residual stresses by ultrasonic technique is used to validate the finite element results and analyze the stress state by non destructive method.
Quantifying the Drilling Effect during the Application of Incremental Hole-Drilling Technique in Laminate Composites
Authors: Nobre Joao P. , Stiffel J. H. , Paepegem W. Van , Nau Andreas , Batista António Castanhola , Marques Maria José , Scholtes Berthold
Published: March 2011

In this work, a methodology to quantify the effect of the drilling operation, during the application of the incremental hole-drilling technique (IHD) for measuring residual stresses in laminate composites, in particular, the polymer matrix composites (PMC), is presented. This technique will allow the optimization of the drilling procedures and its parameters, enabling the quantification of the drilling effect. This quantification is obtained by using an experimental calibration procedure followed by a numerical simulation of the whole process. The direct comparison of the experimental and numerical results will allow quantifying the effect of the drilling operation. As example, the methodology was applied to the case of carbon/epoxy cross-ply laminate [0°/90°]5s. The holes have been made by using two different drilling procedures, but the same tool geometry. High speed milling powered by air compression, a process usually employed in the case of the application of hole-drilling technique to metal alloys and a conventional computer numerically controlled (CNC) milling machine, were used. The results seem to show that incremental hole-drilling could be a reliable technique to determine residual stresses in fibre-reinforced polymers.
Investigation of Residual Stress Distribution of Wheel Rims Using Neutron Diffraction
Authors: Alessandroni Marco , Paradowska Anna Maria , Cippo Enrico Perelli , Senesi Roberto , Andreani Carla , Gorini G. , Montedoro P. , Chiti Fernando , Sala D. , Spinelli D.
Published: March 2011

Damage accumulation due to fatigue significantly reduces the safety of railway vehicles. Shattered wheel rim failures are the result of large fatigue cracks that propagate roughly parallel to the wheel tread surface. The large stress, most likely due to wheel/rail impact or material discontinuity, is responsible for the initiation of shattered rims. The voids and inclusions of sufficient size in a stress field will also lead to failure of wheels. Significant improvements have been made in recent years to prevent the shattered rim failure. The ‘new’ wheels have a better resistance to the shattered rim failure, due to the fact that the circumferential residual stress on tread of a new wheel must be compressive to comply with requirements of international standard EN 13262. However, this may not necessarily apply for millions of ‘old’ wheels that are still currently in use. At the moment the residual stress measurements are carried out using destructive methods (such as slitting or hole drilling), or using quantitatively ultrasound method obtaining the average stress across the whole section. The main objective of this research was to apply non-destructive neutron diffraction method to quantitatively measure residual stress distribution of the wheel rim in as manufactured condition.
Determining Ti-17 β-Phase Single-Crystal Elasticity Constants through X-Ray Diffraction and Inverse Scale Transition Model
Authors: Fréour Sylvain , Lacoste Emmanuel , François Manuel , Guillén Ronald
Published: March 2011

The scope of this work is the determination of single-crystals elastic constants (SEC) from X-ray diffraction lattice strains measurements performed on multi-phase polycrystals submitted to mechanical load through a bending device. An explicit three scales inverse self-consistent model is developed in order to express the SEC of a cubic phase, embedded in a multi-phase polycrystal, as a function of its X-ray Elasticity Constants. Finally, it is applied to a two-phases (α+β) titanium based alloy (Ti-17), in order to estimate Ti-17 β-phase unknown SEC. The purpose of the present work is to account the proper microstructure of the material. In particular, the morphologic texture of Ti-17 a-phase, i.e. the relative disorientation of the needle-shaped grains constituting this phase, is considered owing to the so-called Generalized Self-Consistent model.
Microstructure and Mechanical Properties of a 1.6C (pct) Ultra-Fine Grained Ultra-High Carbon Steel
Authors: Fan Ya Jun , Cao Ji Min , Wang Wei Min , Liu Yong Ning
Published: March 2011

With massive trials, spheroidized by austeniting at 810°C and cooling by 1°C/min, a 1.6C (pct) Ultra-high Carbon Steel shows a microstructure of uniformly distributed fine carbides in the ultra-fine ferrite matrix. The grain size of ferrite matrix and spheroidized carbides are about 5um and 0.1～2um, respectively. Further investigation by TEM shows that much dislocation together with twins is obtained for the UHCS, and generally finer grains have higher dislocation density. The spheroidized steel exhibits high tensile strength of 910 MPa and high yielding strength of 653 MPa at room temperature, together with excellent elongation of 18.3%, which shows the UHCS can entirely satisfy certain grades of engineering materials and means the steel may substitute present engineering steel considering lower cost. Furthermore, the steel owns good high-temperature superplasticity, the elongation of 216% obtained at 800°C under a strain rate of 2.5×10-4. Initial analysis suggests that the superplastic deformation mechanics of the steel is grain boundary sliding and grain rotating (GBSR), coordinated by migration of dislocation.
A Comparison of Temperature-Dependent Compressive Deformation Features of Ultrafine-Grained Ti and Cu Produced by ECAP
Authors: Jiang Qing Wei , Xiao Lin , Li Xiao Wu
Published: March 2011

The temperature-dependent deformation and damage behaviors of ultrafine-grained (UFG) Cu and Ti produced by equal channel angular pressing (ECAP) were investigated and compared. It was found that ECAPed materials with different crystalline structures, e.g. the present fcc Cu and hcp Ti, exhibited significantly distinctive high-temperature deformation and damage characteristics. As the testing temperature is below recrystallization, small- and large-scale cracks or voids formed along the shear bands (SBs) on the surface of UFG Cu, whereas only a few fine shear lines and some non-propagation voids appeared on the surface of UFG Ti. As the temperature is above recrystallization, some small cracks (or voids) formed along grain boundaries and slip deformation took place in many coarsened grains, while only extrusions and intrusions instead of obvious cracks or voids are observable for UFG Ti. The corresponding microstructual changes after compressive deformation, e.g. grain coarsening, were also examined and confirmed by TEM observations.
Heterologous T Cells Can Help Restore Function in Dysfunctional Hepatitis C Virus Nonstructural 3/4A-Specific T Cells during Therapeutic Vaccination
Authors: Chen Antony , Ahlén Gustaf , Brenndörfer Erwin D. , Brass Anette , Holmström Fredrik , Chen Margaret , Söderholm Jonas , Milich David R. , Frelin Lars , Sällberg Matti
Published: March 2011

The hepatitis C virus (HCV)-specific T cell response in patients with chronic HCV is dysfunctional. In this study, we aimed at restoring immunological function through therapeutic vaccination in a transgenic mouse model with impaired HCV-specific T cell responses due to a persistent presence of hepatic HCV nonstructural (NS)3/4A Ags. The HCV-specific T cells have an actively maintained dysfunction reflected in reduced frequency, impaired cytokine production, and impaired effector function in vivo, which can be partially restored by blocking regulatory T cells or programmed cell death ligand 1. We hypothesized that the impairment could be corrected by including sequences that created a normal priming environment by recruiting “healthy” heterologous T cells and by activating innate signaling. Endogenously expressed hepatitis B core Ag (HBcAg) can recruit heterologous T cells and activate TLR (TLR7) signaling. Hence, by combining HCV NS3/4A with different forms of HBcAg we found that heterologous sequences somewhat improved activation and expansion of NS3/4A-specific T cells in a wild-type host. Importantly, the signals provided by HBcAg effectively restored the activation of HCV-specific T cells in a tolerant NS3/4A-transgenic mouse model. The adjuvant effect could also be transferred to the priming of dysfunctional HLA-A2–restricted NS3-specific T cells in vivo. Thus, recruiting healthy heterologous T cells to the site of priming may also help restore HCV-specific responses present in a chronically infected host.
The Reproduction in Women Affected by Cooley Disease
Authors: Pafumi Carlo , Leanza Vito , Coco Luana , Vizzini Stefania , Ciotta Lilliana , Messina Alessandra , Leanza Gianluca , Zarbo Giuseppe , D'Agati Alfio , Palumbo Marco Antonio , Iemmola Alessandra , Gulino Ferdinando Antonio , Teodoro Maria Cristina , Attard Matthew , Plesca Alina Cristina , Soares Catarina , Kouloubis Nina , Chammas Mayada
Published: March 2011

The health background management and outcomes of 5 pregnancies in 4 women affected by Cooley Disease, from Paediatric Institute of Catania University, are described, considering the preconceptual guidances and cares for such patients. These patients were selected among a group of 100 thalassemic women divided into three subgroups, according to their first and successive menstruation characteristics: (i) patients with primitive amenorrhoea, (ii) patients with secondary amenorrhoea and (iii) patients with normal menstruation. Only one woman, affected by primitive amenorrhoea, needed the induction of ovulation. A precise and detailed pre-pregnancy assessment was effected before each conception. This was constituted by a series of essays, including checks for diabetes and hypothyroidism, for B and C hepatitis and for blood group antibodies. Moreover were evaluated: cardiac function, rubella immunity and transaminases. Other pregnancy monitoring, and cares during labour and delivery were effected according to usual obstetrics practice. All the women were in labour when she were 38 week pregnant, and the outcome were five healthy babies born at term, weighting between 2600 and 3200 gs. The only complication was the Caesarean section. The improvements of current treatments, especially in the management of iron deposits, the prolongation of survival rate, will result in a continuous increase of pregnancies in thalassemic women. Pregnancy is now a real possibility for women affected by such disease. We are furthermore studying the possibility to collect the fetus' umbilical cord blood, after the delivery, to attempt eterologus transplantation to his mother trying to get a complete marrow reconstitution.
The Combined Influence of Oral Contraceptives and Human Papillomavirus Virus on Cutaneous Squamous Cell Carcinoma
Authors: Efird Jimmy T. , Toland Amanda E. , Lea C. Suzanne , Phillips Christopher J.
Published: March 2011

The vast majority of cutaneous squamous cell carcinoma (CSCC) will occur in those with fair complexion, tendency to burn, and high ultraviolet radiation (UVR) exposure. Organ transplant recipients also are an important population at great risk for CSCC. An association has been reported between oral contraceptive (OC) use, human papillomavirus virus (HPV) and cervical cancer, and there could be a similar association for CSCC. The cutaneous HPV β-E6 protein, a close cousin of the transformative E6 protein underlying anogenital cancers, has been shown to inhibit apoptosis in response to UVR damage and stimulate morphologic transformation in rodent fibroblast cell lines. Furthermore, OC use has been shown to enhance HPV transcription and may contribute to CSCC risk through this pathway.
A Preliminary Study of the Effectiveness of Chinese Therapeutic Food on Regulating Female Reproductive Hormones
Authors: Fu Lulu , Xu Hong
Published: March 2011

This study investigated the effectiveness of Chinese therapeutic food on female reproductive hormones in a double –blind, placebo –controlled clinical trial. Chinese kiwi fruit extract (Hong En No. 1) was provided for Australian peri-menopausal women for one month. Chinese medical assessment and urinary 2-hydroxyestrone (2-OHE) and 16alpha-hydroxyestrone (16alpha-OHE) tests were conducted. Twenty-six urinary samples (pre and post-trial) which met the requirement of testing were analysed, the ratio 2-OHE:16alpha-OHE of pre-trial (1.18 ± 0.34) and post-trial (0.97 ± 0.29) in the control group (n = 6) decreased but showed no significant change, this ratio of pre-trial (1.44 ± 0.16) and post-trial (1.65 ± 0.21) in the treatment group (n = 7) indicated an improvement ( P = 0.066), which results in beneficial hormone regulation. The Chinese medicine assessment indicated that the patterns of disharmony mainly include Liver Qi stagnation and Liver-Kidney Yin deficiency patterns. No significant change observed in the control group, significant score reduction of the patterns of disharmony was achieved at post-trial in the treatment group, which indicates an improvement of general health condition.
Rigorous derivation of the Kuramoto–Sivashinsky equation from a 2D weakly nonlinear Stefan problem
Authors: Brauner Claude-Michel , Hulshof Josephus , Lorenzi Luca
Published: March 2011

We are interested in a rigorous derivation of the Kuramoto–Sivashinsky (K-S) equation from a free boundary problem. As a paradigm, we consider a two-dimensional Stefan problem in a strip, a simplified version of a solid-liquid interface model. Near the instability threshold, we introduce a small parameter ε and define rescaled variables accordingly. At fixed ε, our method is based on: definition of a suitable linear 1D operator, projection with respect to the longitudinal coordinate only, and the Lyapunov–Schmidt method. As a solvability condition, we derive a self-consistent parabolic equation for the front. We prove that, starting from the same configuration, the latter remains close to the solution of K-S on a fixed time interval, uniformly in ε sufficiently small.
On the evolution of subcritical regions for the Perona–Malik equation
Authors: Ghisi Marina , Gobbino Massimo
Published: March 2011

The Perona–Malik equation is a celebrated example of forward-backward parabolic equation. The forward behavior takes place in the so-called subcritical region, in which the gradient of the solution is smaller than a fixed threshold. In this paper we show that this subcritical region evolves in a different way in the following three cases: dimension one, radial solutions in dimension greater than one, general solutions in dimension greater than one.In the first case subcritical regions do not shrink, that is, that they expand with a nonnegative rate. In the second case they expand with a positive rate and
always spread over the whole domain
after a finite time, depending only on the (outer) radius of the domain. As a by-product, we obtain a nonexistence result for global-in-time classical radial solutions with large enough gradient. In the third case we show an example where subcritical regions do
not
expand.Our proofs exploit comparison principles for suitable degenerate and nonsmooth free boundary problems.
A toroidal tube solution to a problem involving mean curvature and Newtonian potential
Authors: Ren Xiaofeng , Wei Juncheng
Published: March 2011

The Ohta–Kawasaki theory for block copolymer morphology and the Gierer–Meinhardt theory for morphogenesis in cell development both give rise to a nonlocal geometric problem. One seeks a set in

ℝ^3

which satisfies an equation that links the mean curvature of the boundary of the set to the Newtonian potential of the set. An axisymmetric, torus shaped, tube like solution exists in

ℝ^3

if the lone parameter of the problem is sufficiently large. A cross section of the torus is small and the distance from the center of the cross section to the axis of symmetry is large. The solution is stable in the class of axisymmetric sets in a particular sense. This work is motivated by the recent discovery of a toroidal morphological phase in a triblock copolymer.
Long-term analysis of carbon dioxide and methane column-averaged mole fractions retrieved from SCIAMACHY
Authors: Schneising O. , Buchwitz M. , Reuter M. , Heymann J. , Bovensmann H. , Burrows J. P.
Published: March 2011

Abstract. Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases contributing to global climate change. SCIAMACHY onboard ENVISAT (launch 2002) was the first and is now with TANSO onboard GOSAT (launch 2009) one of only two satellite instruments currently in space whose measurements are sensitive to CO2 and CH4 concentration changes in the lowest atmospheric layers where the variability due to sources and sinks is largest. We present long-term SCIAMACHY retrievals (2003–2009) of column-averaged dry air mole fractions of both gases (denoted XCO2 and XCH4) derived from absorption bands in the near-infrared/shortwave-infrared (NIR/SWIR) spectral region focusing on large-scale features. The results are obtained using an upgraded version (v2) of the retrieval algorithm WFM-DOAS including several improvements, while simultaneously maintaining its high processing speed. The retrieved mole fractions are compared to global model simulations (CarbonTracker XCO2 and TM5 XCH4) being optimised by assimilating highly accurate surface measurements from the NOAA/ESRL network and taking the SCIAMACHY averaging kernels into account. The comparisons address seasonal variations and long-term characteristics. The steady increase of atmospheric carbon dioxide primarily caused by the burning of fossil fuels can be clearly observed with SCIAMACHY globally. The retrieved global annual mean XCO2 increase agrees with CarbonTracker within the error bars (1.80±0.13 ppm yr−1 compared to 1.81±0.09 ppm yr−1). The amplitude of the XCO2 seasonal cycle as retrieved by SCIAMACHY, which is 4.3±0.2 ppm for the Northern Hemisphere and 1.4±0.2 ppm for the Southern Hemisphere, is on average about 1 ppm larger than for CarbonTracker. An investigation of the boreal forest carbon uptake during the growing season via the analysis of longitudinal gradients shows good agreement between SCIAMACHY and CarbonTracker concerning the overall magnitude of the gradients and their annual variations. The analysis includes a discussion of the relative uptake strengths of the Russian and North American boreal forest regions. The retrieved XCH4 results show that after years of stability, atmospheric methane has started to rise again in recent years which is consistent with surface measurements. The largest increase is observed for the tropics and northern mid- and high-latitudes amounting to about 7.5±1.5 ppb yr−1 since 2007. Due care has been exercised to minimise the influence of detector degradation on the quantitative estimate of this anomaly.
Distribution and air-sea exchange of mercury (Hg) in the Yellow Sea
Authors: Ci Z. J. , Zhang X. S. , Wang Z. W. , Niu Z. C. , Diao X. Y. , Wang S. W.
Published: March 2011

Abstract. The Yellow Sea, surrounded by East China and the Korea Peninsula, is a potentially important receptor for anthropogenic mercury (Hg) emissions from East Asia. However, there is little documentation about the distribution and cycle of Hg in this marine system. During the cruise covering the Yellow Sea in July 2010, gaseous elemental mercury (GEM or Hg(0)) in the atmosphere, total Hg (THg), reactive Hg (RHg) and dissolved gaseous mercury (DGM, largely Hg(0)) in the waters were measured aboard the R/V Kexue III. The mean (±SD) concentration of GEM over the entire cruise was 2.61 ± 0.50 ng m−3 (range: 1.68 to 4.34 ng m−3), which were generally higher than other open oceans. The spatial distribution of GEM generally reflected a clear gradient with high levels near the coast of East China and low levels in open waters, suggesting the significant atmospheric Hg outflow from East China. The mean concentration of THg in the surface waters was 1.69 ± 0.35 ng l−1 and the RHg accounted for a considerable fraction of THg (RHg: 1.08 ± 0.28 ng l−1, %RHg/THg = 63.9%). The mean concentration of DGM in the surface waters was 63.9 ± 13.7 pg l−1 and always suggested the supersaturation of Hg(0) in the surface waters with respect to Hg(0) in the atmosphere (the degree of saturation: 7.8 ± 2.3 with a range of 3.6–14.0). The mean Hg(0) flux at the air-sea interface was estimated to be 18.3 ± 11.8 ng m−2 h−1 based on a two-layer exchange model. The high wind speed and DGM levels induced the extremely high Hg(0) emission rates. Measurements at three stations showed no clear vertical patterns of DGM, RHg and THg in the water column. Overall, the elevated Hg levels in the Yellow Sea compared with other open oceans suggested that the human activity has influenced the oceanic Hg cycle downwind of East Asia.
The H2O–O2 water vapour complex in the Earth's atmosphere
Authors: Kasai Y. , Dupuy E. , Saito R. , Hashimoto K. , Sabu A. , Kondo S. , Sumiyoshi Y. , Endo Y.
Published: March 2011

Abstract. Until recently, abundance estimates for bound molecular complexes have been affected by uncertainties of a factor 10–100. This is due to the difficulty of accurately obtaining the equilibrium constant, either from laboratory experiments or by statistical thermodynamic calculations. In this paper, we firstly present laboratory experiments that we performed in order to determine the molecular structure of H2O-O2. We also derive global abundance estimates for H2O-O2 in the Earth's atmosphere. The equilibrium constant Kp evaluated using the "anharmonic oscillator approach" (AHOA) (Sabu et al., 2005) was employed: the AHOA explains well the structure of the complex obtained by the present experiment. The Kp calculated by this method shows a realistic temperature dependence. We used this Kp to derive global abundance estimates for H2O-O2 in the Earth's atmosphere. The distribution of H2O-O2 follows that of water vapour in the troposphere and seems inversely proportional to temperature in the lower stratosphere. Preliminary estimates at the surface show amount of H2O-O2 is comparable to CO or N2O, ranking water vapour complexes among the ten most abundant species in the boundary layer.
Elucidating determinants of aerosol composition through particle-type-based receptor modeling
Authors: McGuire M. L. , Jeong C.-H. , Slowik J. G. , Chang R. Y.-W. , Corbin J. C. , Lu G. , Mihele C. , Rehbein P. J. G. , Sills D. M. L. , Abbatt J. P. D. , Brook J. R. , Evans G. J.
Published: March 2011

Abstract. An aerosol time-of-flight mass spectrometer (ATOFMS) was deployed at a semi-rural site in Southern Ontario to characterize the size and chemical composition of individual particles. Particle-type-based receptor modelling of these data was used to investigate the determinants of aerosol chemical composition in this region. Individual particles were classified into particle-types and positive matrix factorization (PMF) was applied to their temporal trends to separate and cross-apportion particle-types to factors. The extent of chemical processing for each factor was assessed by evaluating the internal and external mixing state of the characteristic particle-types. The nine factors identified helped to elucidate the coupled interactions of these determinants. Nitrate-laden dust was found to be the dominant type of locally emitted particles measured by ATOFMS. Several factors associated with aerosol transported to the site from intermediate local-to-regional distances were identified: the Organic factor was associated with a combustion source to the north-west; the ECOC Day factor was characterized by nearby local-to-regional carbonaceous emissions transported from the south-west during the daytime; and the Fireworks factor consisted of pyrotechnic particles from the Detroit region following holiday fireworks displays. Regional aerosol from farther emissions sources were reflected through three factors: two biomass burning factors and a highly chemically processed long range transport factor. The biomass burning factors were separated by PMF due to differences in chemical processing which were caused in part by the passage of two thunderstorm gust fronts with different air mass histories. The remaining two factors, ECOC Night and Nitrate Background, represented the night-time partitioning of nitrate to pre-existing particles of different origins. The distinct meteorological conditions observed during this month-long study in the summer of 2007 provided a unique range of temporal variability, enabling the elucidation of the determinants of aerosol chemical composition, including source emissions, chemical processing, and transport, at the Canada-US border. This paper presents the first study to characterize the coupled influences of these determinants on temporal variability in aerosol chemical composition using single particle-type-based receptor modelling.
Detailed comparisons of airborne formaldehyde measurements with box models during the 2006 INTEX-B campaign: potential evidence for unmeasured and multi-generation volatile organic carbon oxidation processing
Authors: Fried A. , Cantrell C. , Olson J. , Crawford J. H. , Weibring P. , Walega J. , Richter D. , Junkermann W. , Volkamer R. , Sinreich R. , Heikes B. G. , O'Sullivan D. , Blake D. R. , Blake N. , Meinardi S. , Apel E. , Weinheimer A. , Knapp D. , Perring A. , Cohen R. C. , Fuelberg H. , Shetter R. E. , Hall S. R. , Ullmann K. , Brune W. H. , Mao J. , Ren X. , Huey L. G. , Singh H. B. , W Hair J. , Riemer D.
Published: March 2011

Abstract. Detailed comparisons of airborne CH2O measurements acquired by tunable diode laser absorption spectroscopy with steady state box model calculations were carried out using data from the 2006 INTEX-B campaign in order to improve our understanding of hydrocarbon oxidation processing. Select previous comparisons in other campaigns have highlighted some locations in the boundary layer where steady state box models have tended to underpredict CH2O, suggesting that standard steady state modeling assumptions might be unsuitable under these conditions, and pointing to a possible role for unmeasured hydrocarbons and/or additional primary emission sources of CH2O. Employing an improved instrument, more detailed measurement-model comparisons with better temporal overlap, up to date measurement and model precision estimates, up to date rate constants, and additional modeling tools based on both Lagrangian and Master Chemical Mechanism (MCM) runs, we have explained much of the disagreement between observed and predicted CH2O as resulting from non-steady-state atmospheric conditions in the vicinity of large pollution sources, and have quantified the disagreement as a function of plume lifetime (processing time). We show that in the near-field (within ~4 to 6 h of the source), steady-state models can either over-or-underestimate observations, depending on the predominant non-steady-state influence. In addition, we show that even far field processes (10–40 h) can be influenced by non-steady-state conditions which can be responsible for CH2O model underestimations by as much as a factor of 2. At the longer processing times in the 10 to 40 h range during Mexico City outflow events, MCM model calculations, using assumptions about emissions of high-order NMHCs, further indicate the potential importance of CH2O produced from unmeasured and multi-generation hydrocarbon oxidation processing, particularly methylglyoxal and 3-hyroxypropanal.
A laboratory experiment of intact polar lipid degradation in sandy sediments
Authors: Logemann J. , Graue J. , Köster J. , Engelen B. , Rullkötter J. , Cypionka H.
Published: March 2011

Abstract. Intact polar lipids (IPLs) are considered biomarkers for living biomass. Their degradation in marine sediments, however, is poorly understood and complicates interpretation of their occurrence in geological samples. To investigate the turnover of IPLs, a degradation experiment with anoxic sandy sediments from the North Sea was conducted. Intact cells of two organisms that do not naturally occur in North Sea sediments were chosen as IPL sources: (i) Saccharomyces cerevisiae, representative for ester-bound acyl lipids that also occur in Bacteria, and (ii) the archaeon Haloferax volcanii, representative for ether-bound isoprenoid lipids. Surprisingly, IPLs with phosphoester-bound head groups showed approximately the same degradation rate as IPLs with glycosidic head groups. Furthermore, the results indicate a relatively fast degradation of S. cerevisiae IPLs with ester-bound moieties (analogs of bacterial membrane lipids) and no significant degradation of archaeal IPLs with ether-bound moieties. Pore water and 16S rRNA-based DGGE analysis showed only a minor influence of the IPL source on microbial metabolism and community profiles. Due to our results, the IPL-based quantification of Archaea and Bacteria should be interpreted with caution.