bluuebunny/crossref_metadata_2025 huggingface dataset:
Trade-Off Relationship between Si Recess and Defect Density Formed by Plasma-Induced Damage in Planar Metal–Oxide–Semiconductor Field-Effect Transistors and the Optimization Methodology
Authors: Eriguchi Koji , Nakakubo Yoshinori , Matsuda Asahiko , Kamei Masayuki , Takao Yoshinori , Ono Kouichi
Published: August 2011

Physical damage induced by high-energy ion bombardment during plasma processing is characterized from the viewpoint of the relationship between surface-damaged layer (silicon loss) and defect site underneath the surface. Parameters for plasma-induced damage (PID), Si recess depth (dR) and residual (areal) defect density after wet-etch treatment (Ndam), are calculated on the basis of a modified range theory, and the trade-off relationship betweendRandNdamis presented. We also model their effects on device parameters such as off-state leakage (Ioff) and drain saturation current (Ion) of n-channel metal–oxide–semiconductor field effect transistors (MOSFETs). Based on the models, we clarify the relationship among plasma process parameters (ion energy and ion flux),dR,Ndam,Ioff, andIon. Then we propose a methodology optimizing ion energy and ion flux under the constraints defined by device specificationsIoffandIon, viadRandNdam. This procedure is regarded as so-called optimization problems. The proposed methodology is applicable to optimizing plasma parameters that minimize degradation of MOSFET performance by PID.
Comparative Study of Plasma-Charging Damage in High-k Dielectric and p–n Junction and Their Effects on Off-State Leakage Current of Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Kamei Masayuki , Takao Yoshinori , Eriguchi Koji , Ono Kouichi
Published: August 2011

Plasma-induced charging damage (PCD) to a metal–oxide–semiconductor field-effect transistor (MOSFET) with a high-kdielectric was studied in detail using a capacitively coupled plasma reactor for various exposure times. From the drain current versus gate voltage characteristics, we observed the threshold voltage shift (ΔVth) and the increase in reverse-leakage current (Ij) at the n+/p junction in plasma-exposed n-channel MOSFETs. The observed ΔVthin the negative direction was due to positive trap-site creation in the high-kdielectric. The combined effect by PCD increased off-state leakage current (Ioff) in n-channel MOSFETs, however, theIjincrease was found to be dominant in theIoffincrease. By employing a capacitance-measurement technique, we clarified that theIjconsiderably was increased at the junction by PCD, whereas the maximum capacitance at the junction in accumulation decreased. We also identified that the generated defect site density (nd) at the junction induces the observedIjincrease as a trap-assist tunneling site.
Effect of Low Growth Rate in Chemical Beam Epitaxy on Carrier Mobility and Lifetime of p-GaAsN Films
Authors: Honda Takahiko , Ikeda Kazuma , Inagaki Makoto , Suzuki Hidetoshi , Kojima Nobuaki , Ohshita Yoshio , Yamaguchi Masafumi
Published: August 2011

Decreasing the growth rate in chemical beam epitaxy (CBE) is effective to improve the hole mobility and minority-carrier lifetime in p-GaAsN films. The hole mobility increased from 120 to 150 cm2 V-1 s-1 for the N composition of 0.6%. The minority-carrier lifetime improved from 3.2×10-1 ([N] = 0.6%) to 9.0×10-1 ns ([N] = 0.8%) despite the higher N composition. N-related scattering centers are indicated to be the dominant scattering centers at approximately room temperature. Controlling the growth rate is considered to be effective to reduce the amount of N-related scattering centers and nonradiative recombination centers.
Preparation of SiO2 Passivation Thin Film for Improved the Organic Light-Emitting Device Life Time
Authors: Hong Jeong Soo , Kim Sang Mo , Kim Kyung-Hwan
Published: August 2011

To improve the organic light-emitting diode (OLED) lifetime, we prepared a SiO2 thin film for OLED passivation using a facing target sputtering (FTS) system as a function of oxygen gas flow rate and working pressure. The properties of the SiO2 thin film were examined by Fourier transform infrared (FT-IR), photoluminescence (PL) intensity measurement, field emission scanning electron microscopy (FE-SEM), and ultraviolet–visible (UV–vis) spectrometry that As a result, we found that a SiO2 thin film is formed at a 2 sccm oxygen gas flow rate and results the minimum damage to the organic layer is observed at a 1 mTorr working pressure. Also, from the water vapor transmission rate (WVTR), we observed that all of the as-deposited SiO2 thin films showed the ability of blocking moisture. After the properties were evaluated, an optimized SiO2 thin film was applied to OLED passivation. As a result, the property of the OLED fabricated by SiO2 passivation is similar to the OLED fabricated by glass passivation. However, the performance of OLED was degraded by enhancing of SiO2 passivation. This is the organic layer of the device is exposed to plasma for a prolonged period. Therefore, a method of minimizing damage to the organic layer and optimum conditions for what are important.
Enhancement in Electron Field Emission of Microcrystalline Diamond Films upon Iron Coating and Annealing Processes
Authors: Huang Pin-Chang , Shih Wen-Ching , Chen Huang-Chin , Lin I-Nan
Published: August 2011

The electron field emission (EFE) properties of diamond films were markedly improved by Fe-coating and postannealing processes. Transmission electron microscopy examination indicated that the possible mechanism of enhancing the EFE behavior is the reaction of the Fe layer with diamond and the reprecipitation of the dissolved carbon species to form nanographite. Scanning electron micrographs showed that the Fe coating first formed Fe particles at 700 °C and then reacted with diamond, forming iron carbide (Fe3C) at 800 °C. The dissolution and reprecipitation processes occurred simultaneously during the postannealing process at higher temperatures (800–950 °C), which leads to the formation of amorphous carbon when the postannealing temperature is low (800–850 °C) and to that of nanographite when the postannealing temperature is high (900–950 °C). The 900 °C-postannealed diamond films exhibit the best EFE properties, which can be turned on at a field of E
0=2.8 V/µm, and attain an EFE current density of J
e=21.4 µA/cm2 at 8 V/µm.
Magnetron Sputtering Deposition of Conductive Diamond-Like Carbon Films with Embedded Nanoparticles
Authors: Sasaki Koichi , Tsutsumi Takahiko , Takada Noriharu
Published: August 2011

We developed a process technology for synthesizing conductive diamond-like carbon (DLC) films, in which nanoparticles embedded in the DLC films played the role of the paths of electric current. The synthesis process consisted of three steps. The first step was the deposition of nanoparticles, which was realized by operating a magnetron sputtering source with pure argon at a pressure of 500 mTorr. The second step was the deposition of a DLC film, which was realized by operating the same magnetron sputtering source with the mixture of argon and hydrogen at a pressure of 5 mTorr. The third step was the removal of the residual DLC film on nanoparticles. This step was realized using a plasma with the mixture of argon and oxygen, which was produced by applying an rf power to the substrate holder of the same magnetron sputtering source. The conductivity of a DLC film with embedded copper nanoparticles was nearly high enough to be the surface coating of separators in polymer electrolyte fuel cells.
Formation of High-Density Pt Nanodots on SiO2 Induced by Millisecond Rapid Thermal Annealing Using Thermal Plasma Jet for Floating Gate Memory
Authors: Makihara Katsunori , Matsumoto Kazuya , Yamane Masato , Okada Tatsuya , Morisawa Naoya , Ikeda Mitsuhisa , Higashi Seiichiro , Miyazaki Seiichi
Published: August 2011

We formed nanometer-scale Pt dots on SiO2 by thermal plasma jet (TPJ) irradiation and demonstrated the feasibility of TPJ millisecond annealing for controlling the areal density of the dots. 2–10-nm-thick Pt/quartz was exposed to an Ar plasma jet at peak temperatures of 455–695 °C for a duration of 1–2 ms. When the Pt/quartz was annealed by TPJ irradiation without any extra heating, the Pt nanodot density was controlled in the range of 7.8 ×1010 to 2.0 ×1011 cm-2 by changing the annealing temperature and the number of irradiations. These results imply that ultra-rapid annealing using a TPJ plays an important role in enhancing the surface migration of Pt atoms in order to reduce the interface energy of Pt/quartz.
Atomic Force Microscopy to Study Mechanics of Living Mitotic Mammalian Cells
Authors: Toyoda Yusuke , Stewart Martin P. , Hyman Anthony A. , Müller Daniel J.
Published: August 2011

While biochemical pathways within mitotic cells have been intensively studied, the mechanics of dividing cells is only poorly understood. In our recent report, an experimental system combining fluorescence and atomic force microscopy was set up to study dynamics of mitotic rounding of mammalian cells. We show that cells have a rounding pressure that increases upon mitotic entry. Using specific inhibitors or perturbations, we revealed biological processes required for force generation that underpin the cell rounding shape change during mitosis. The significance of the finding and an outlook are discussed.
Transformations of Molecular Frameworks by Host–Guest Response: Novel Routes toward Two-Dimensional Self-Assembly at the Solid–Liquid Interface
Authors: Cardenas Luis , Lipton-Duffin Josh , Rosei Federico
Published: August 2011

We review recent new avenues for controlling two-dimensional (2D) self-assembly stabilized by non-covalent interactions. The use of host–guest architectures has opened new pathways for supramolecular self-assembly in two dimensions by immobilizing molecules of interest in 2D nano-porous networks. We also describe how a judicious choice of guest molecule can induce effective changes in host templates. These transformations could enable full control of 2D self-assembly with nanoscale precision, by tuning parameters such as stoichiometry, geometry and non-covalent interactions. This approach is of paramount importance for understanding changes of dimensionality and subsequently the formation of 2D and 3D supramolecular networks and ordered films that can be used as active materials for applications (e.g., electronic devices).
Electric Field Control of Fe Nano Magnets: Towards Metallic Nonvolatile Data Storage Devices
Authors: Yamada Toyo Kazu , Gerhard Lukas , Balashov Timofey , Takács Albert F. , Wesselink Rien J. H. , Wulfhekel Wulf
Published: August 2011

Magnetoelectric coupling at metal surfaces opens up a new possibility for metallic nonvolatile magnetic data-storage devices, in which the magnetic bits are controlled by an electric field. We studied the atomic and magnetic order in bilayer Fe nano-islands grown on a Cu(111) substrate with a scanning tunneling microscopy setup in ultra high vacuum at 4.5 K. Electric field pulses (108–109 V/m) were found to be able to cause a displacement of the Fe atoms, switching simultaneously the crystalline and the magnetic order, which is the prove of magnetoelectric coupling at the metallic Fe surface. We also succeeded in controlling the direction of the switching by the polarity of the electric field.
Mechanics of Intracellular Stress Fibers: A Short Review
Authors: Ikai Atsushi , Watanabe-Nakayama Takahiro , Machida Shinichi , Saito Masakazu , Afrin Rehana
Published: August 2011

The mechanical response of living cells against external stimuli depends largely on the physical and biochemical properties of an intracellular structure called cytoskeleton. Three main kinds of filamentous protein structures, namely, microtubules, intermediate filaments, and actin thin filaments comprise the cytoskeleton. In the case of cells cultured on an adhesive substrate, the development of actin-based cytoskeleton, especially linearly bundled actin filaments called stress fibers (SFs), is well established. SFs are formed close to the cell membrane with one or both of their ends associated with the transmembrane structure called the focal adhesion (FA). In this article, we review some fundamental facts about SFs in live cells starting from the early description of the bundled filaments as observed under optical and electron microscopies. The morphology, chemical components, and biological functions of SFs, and recent work on the mechanical nature of SFs are reviewed.
Spin-Polarized Tunneling between Optically Pumped GaAs(110) Surface and Spin-Polarized Tip
Authors: Ishida Nobuyuki , Sueoka Kazuhisa
Published: August 2011

We performed spin-polarized scanning tunneling spectroscopy (SP-STS) on the optically pumped GaAs(110) surface with the Fe-coated W tip to investigate the spin-polarized tunneling effect between them. The optical effects that could be superimposed on the spin-dependent signal were carefully investigated with the nonmagnetic W tip. In the SP-STS experiment, the intensity and circular-polarization of the light were simultaneously modulated, and the modulation signals of the tunneling current were compared in order to distinguish the spin dependent component. We demonstrated that the spin-dependent tunneling effect could be detected when we carefully choose the energy range to avoid the parasitic optical effect.
Study of Initial Growth Layer of GaSb on Si(111) by Scanning Tunneling Microscopy
Authors: Hara Shinsuke , Fuse Kazuhiro , Machida Ryuto , Yagishita Kazuki , Irokawa Katsumi , Miki Hirofumi , Kawazu Akira , Fujishiro Hiroki I.
Published: August 2011

The initial growth layer of GaSb on a Si(111) surface has been studied by scanning tunneling microscopy. After the simultaneous deposition of Ga and Sb atoms at 0.85 and 1.45 monolayers, respectively, Sb/Si(111)-2×1 and -√3×√3-R30° structures were formed on a large area of the Si(111) surface. In addition, the protrusions of the cross-hatch pattern, which was higher than that of the Sb/Si(111) structures by a bilayer height, were observed. The pattern area is suggested to correspond to the initial growth layer of GaSb. Three types of layer domains were observed. These domains are formed because of the strain caused by the lattice mismatch between GaSb and Si. Based on both cases of group-III and -V polar surface structures, the atomic structural models of these domains are proposed: one domain is a layer with strain relaxation, formed by the reconstruction of on-top atoms; the second is a layer formed on the reconstructed Si surface; and the third is a layer with uniaxial strain relaxation. Three-dimensional hut-shaped islands were observed to form infrequently on the local surface area. A cross-hatch pattern similar to the initial growth layer was observed on the facets of these islands. It is suggested that the islands are composed of GaSb crystals. An initial growth layer of GaSb was observed around some of the islands. From these results, we speculate that the GaSb dot crystals grow epitaxially on the initial layer.
Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO2(111) with Changing Annealing Condition
Authors: Shahed Syed Mohammad Fakruddin , Sainoo Yasuyuki , Komeda Tadahiro
Published: August 2011

The surface morphology variation of CeO2(111) with changing annealing condition was examined by scanning tunneling microscopy (STM). Hexagonal islands and pits containing two types of step edge have been found as characteristic features in a short-time-annealed surface. We observed that the triangular pits having only one type of step edge increase in number with annealing time, while the hexagonal pits and islands decrease and the deviated hexagonal pits increase. Step edges of the hexagonal pits that have higher coordinative saturation get preferential thermodynamic stability to form triangular pits, the most stable surface structures on the CeO2(111) surface in the equilibrium stage of annealing. These results have important implications for controlling catalytic activity on ceria.
Photoabsorption Properties in InAs Wire Structures Investigated by Dual Light Illumination Method in Scanning Tunneling Microscopy
Authors: Katsui Shuichi , Takahashi Takuji
Published: August 2011

The photoabsorption properties of InAs wire structures have been investigated through photoinduced current (PIC) measurements by a dual light illumination method in scanning tunneling microscopy. On InAs wires with a width of around 50 nm, the dependences of the PIC signal on incident photon energy and on a light polarization were examined. A steplike shape in the photoabsorption spectrum, obtained from the photon energy dependence, as well as weak polarization dependence indicate that this wire structure behaved like a quantum well because of a weak lateral confinement effect. On the other hand, apparent polarization dependence was observed on the InAs wires with a width of around 25 nm, which is attributable to an enhancement of structural anisotropy in the thinner wire.
Structural Dependence of Grain Boundary Resistivity in Copper Nanowires
Authors: Kim Tae-Hwan , Nicholson Don M. , Zhang X.-G. , Evans Boyd M. , Kulkarni Nagraj S. , Kenik Edward A. , Meyer Harry M. , Radhakrishnan Balasubramaniam , Li An-Ping
Published: August 2011

We report the direct measurement of individual grain boundary (GB) resistances and the critical role of GB structure in the increased resistivity in copper nanowires. By measuring both intra- and inter-grain resistance with a four-probe scanning tunneling microscope, large resistance jumps are revealed owing to successive scattering across high-angle random GBs, while the resistance changes at twin and other coincidence boundaries are negligibly small. The impurity distributions in the nanowires are characterized in correlating to the microstructures. The resistance of high symmetry coincidence GBs and the impurity contributions are then calculated using a first-principle method which confirms that the coincidence GBs have orders of magnitude smaller resistance than the high-angle random GBs.
Single-Electron Charging in Phosphorus Donors in Silicon Observed by Low-Temperature Kelvin Probe Force Microscope
Authors: Anwar Miftahul , Kawai Yuya , Moraru Daniel , Nowak Roland , Jablonski Ryszard , Mizuno Takeshi , Tabe Michiharu
Published: August 2011

Kelvin probe force microscopy (KFM) working at low temperatures (13 K) is used to study local electronic potential fluctuations induced by individual phosphorus donors. Electronic potential maps were measured at the surface of thin phosphorus-doped channel of silicon-on-insulator field-effect transistors for different values of backgate voltage. We observed local changes of the potential profile with increasing backgate voltage, indicating electron injection in the channel. Single-step changes in the depth of the fine potential wells, observed by changing backgate voltage, are ascribed to single-electron charging in individual donors. For clusters of donors, with overlapped potential wells, electron charging occurs gradually, without single-step behavior, as the backgate voltage becomes more positive.
Structural Analysis of Si-Based Nanodot Arrays Self-Organized by Selective Etching of SiGe/Si Films
Authors: Takahashi Masahiko , Nakamura Yoshiaki , Kikkawa Jun , Nakatsuka Osamu , Zaima Shigeaki , Sakai Akira
Published: August 2011

Atomic force microscopy (AFM) revealed the surface structures of nanodot arrays fabricated by selective etching of SiGe/Si films that have pure-edge dislocation networks at the SiGe–Si interface. By varying the etching time, it is possible to control the composition of the nanodot arrays, allowing either SiGe or Si nanodot arrays to be fabricated. The surface roughness of the nanodot arrays does not originate from the nanodots themselves, but from the spatial variation in the depth of dislocations in the SiGe/Si films prior to etching. Individual nanodots in SiGe nanodot arrays have smoother profiles than those in Si nanodots although the nanodots in SiGe and Si nanodot arrays have similar heights and diameters. The rougher surface of individual Si nanodots is due to the lower etching selectivity, which results from the smaller dislocation influence on the etching reaction in Si substrates far from the interface. Transmission electron microscopy images reveal the formation of arrays of epitaxial SiGe nanodots with smooth surfaces, which is consistent with the AFM results.
Fabrication of Quartz Cantilevers for Small-Amplitude Dynamic Force Microscopy Using an Optical Deflection Sensor
Authors: Morita Ken-ichi , Sasagawa Yuuki , Murai Yuusuke , Sugimoto Yoshiaki , Abe Masayuki , Morita Seizo
Published: August 2011

We studied about a method of fabricating quartz cantilevers with a conductive tip. The quartz cantilever is a key part for small-amplitude dynamic force microscopy combined with an optical deflection sensor. The stiffness of cantilevers enables us a stable small-amplitude operation, because a sufficiently high oscillation energy, which is based on a high spring constant value prevents the cantilever from contacting the sample. We performed topographic imaging with atomic resolution and site-specific force distance curve measurement using a quartz cantilever at room temperature.
Separate Detection of Sodium and Potassium Ions with Sub-micropipette Probe
Authors: Takami Tomohide , Son Jong Wan , Lee Joo-Kyung , Park Bae Ho , Kawai Tomoji
Published: August 2011

A novel method of detecting sodium and potassium ions separately with a sub-micropipette probe of approximately 100 nm inner diameter has been demonstrated. A poly(vinyl chloride) film containing crown ether ligands in sub-micropipettes filtered the ions. Sodium ions were trapped with bis(12-crown-4), whereas potassium ions were trapped with bis(benzo-15-crown-5). Alternate and direct bias voltages were applied to the counter electrode in the sub-micropipette so that the local ion concentrations could be observed as current signals after conversion to milivolt output signals with our low-current detection system prepared for this study.
Rheological Properties of Growth-Arrested Fibroblast Cells under Serum Starvation Measured by Atomic Force Microscopy
Authors: Miyaoka Atsushi , Mizutani Yusuke , Tsuchiya Masahiro , Kawahara Koichi , Okajima Takaharu
Published: August 2011

The rheological properties of growth-arrested and quiescent (G0 phase) mouse fibroblast cells under serum starvation were investigated by atomic force microscopy (AFM) with a microarray technique. The number distribution of complex shear modulus,G*, of quiescent cells at the serum concentration,CS=0.1%, followed a log-normal distribution, and the frequency dependence ofG*exhibited a power law behavior, which were similar to those under a control condition atCS=10%. On the other hand, we found that the Newtonian viscosity coefficient of the quiescent cells significantly increased, and the distribution broadened, as compared with the control cells, whereas the power-law exponent was unchanged. The result indicated that the rheological properties of quiescent fibroblast cells were not identical to those in the G1 phase during cell cycle. This finding suggests that the Newtonian viscosity of cells is one of the useful indicators for evaluating growth-arrested cells under serum starvation.
Interference Phenomena Observed on an Atomic Force Microscope Cantilever by Laser Confocal Microscopy
Authors: Yanagiya Shin-ichiro , Goto Nobuo
Published: August 2011

We investigated interference phenomena that were observed on a cantilever bar of an atomic force microscope by using a laser confocal microscope (LCM). First, we established a simple model and calculated the fringe interval. Interference fringe patterns were observed under the following conditions: (1) changing the focus and confocal aperture of the LCM, (2) increasing the reflectance by sputtering TiO2 on the cantilever bar and glass plate, and (3) changing the medium from air to water in the space between the glass plate and the cantilever. The purpose of a previous experiment was to measure the refractive index of water. It was theoretically determined that the fringe interval depended not on the height of the cantilever from the surface but on the wavelength, refractive index, and tilt angle of the cantilever. We obtained the following experimental results: (1) the fringe interval was independent of the confocal plane when using a monochromatic laser, (2) a sharpened interference fringe was observed when we used a TiO2-coated cantilever and glass plate, and (3) the refractive index of a small quantity of water could be measured.
Development of Novel System Combining Scanning Tunneling Microscope-Based Cathodoluminescence and Electroluminescence Nanospectroscopies
Authors: Watanabe Kentaro , Nakamura Yoshiaki , Kuboya Shigeyuki , Katayama Ryuji , Onabe Kentaro , Ichikawa Masakazu
Published: August 2011

Novel system equipped with conductive optical fiber probe scanning tunneling microscope (STM) and bipolar sample holder is a powerful tool to characterize light-emitting devices by several STM-based techniques at the same sample position, which can realize photoluminescence (PL), cathodoluminescence (CL), electroluminescence (EL), and electron beam induced current (EBIC) measurements with higher spatial resolutions than conventional techniques. In this study, we developed a STM-CL/EL system which combines STM-CL technique for high CL excitation power and high spatial resolution and STM-EL technique for local EL collection. We demonstrated spatially resolved STM-CL/EL spectroscopy of GaAs/AlGaAs heterostructure (110) cross-sections.
Fill and spill in Lethe Vallis: a recent flood-routing system in Elysium Planitia, Mars
Authors: Balme M. R. , Gallagher C. J. , Gupta S. , Murray J. B.
Published: August 2011

Lethe Vallis is an approximately 230 km-long and 1.5 km-wide channel connecting several shallow basins in the Elysium Planitia region of Mars. It sits within a distinctive morphological unit defined by a platy-ridged-polygonized texture. We have documented the geomorphology of the system, and constructed topographical long profiles of the channel thalweg and the contacts of the platy-ridged-polygonized material.

The Lethe thalweg is shallow (with a slope of about 0.0001) but contains steeper sections that match the locations of observed cataract systems. The contact profiles suggest that the small basins linked by Lethe progressively ponded and over-spilled as the system developed, the cataracts being associated with this over-spill. Other landforms observed in the system include streamlined islands, anastomosing distributary systems, fluvial hanging channels and terraces on the channel margins. There are also possible dunes and/or antidunes within the channel. These all point to catastrophic fluvial flooding. Estimates of formative discharge are of the order of 1×10
4
–5×10
4
m
3
s
−1
, similar to the discharge of the Mississippi River.

We infer that Lethe Vallis formed as a fluvial ‘fill and spill’ catastrophic flood system. This demonstrates that the main Western Elysium Basin, the upstream source of Lethe Vallis, contained a substantial transient lake.
Geologically recent water flow inferred in channel systems in the NE Sulci Gordii region, Mars
Authors: Towner M. C. , Eakin C. , Conway S. J. , Harrison S.
Published: August 2011

A series of fluid-carved channels in the Sulci Gordii region of Mars were investigated. Numerous channel networks exist in Sulci Gordii, part of the Olympus Mons aureole, and this area comprises some of the youngest volcanic terrain on Mars. The channels ranged in length from 43 to 155 km, with widths of 128–288 m. The morphology of the channels was analysed assuming both lava and water as possible agents. For three of the four channels studied, water appears to be the likely agent, while one channel is probably lava-formed. For the water-formed channels, discharge rates were estimated at 8000–36 000 m
3
s
−1
. The lava channel was probably formed from short-lived episodic activity by a low-viscosity lava. The age of the channels and surrounding area was estimated using crater counting to be 100 Ma. Water has appeared to have flowed for almost 150 km under the climatic conditions at this time. There is some evidence for later tectonic activity, possibly as recent as 10 Ma, but crater-dating accuracy was limited by the lack of high-resolution images of some areas. Sulci Gordii is therefore a dynamic site with evidence of hydrological and volcanic activity extending into the recent geological past.
Layering and degradation of the Rupes Tenuis unit, Mars – a structural analysis south of Chasma Boreale
Authors: Kneissl T. , Van Gasselt S. , Wendt L. , Gross C. , Neukum G.
Published: August 2011

The circum north-polar Rupes Tenuis unit forms the polar-proximal basal stratigraphical and morphological units that delineate the north polar cap between 180° and 300°E. In the region of the mouth of the Chasma Boreale re-entrant, the Rupes Tenuis unit is likely to extend further southwards into the northern plains. This is suggested by the occurrence of isolated remnants that have been interpreted as basaltic shield volcanoes, maar craters or mud volcanoes in the past.

As key elements of this study, we assessed the quantitative characteristics of this unit using layer attitudes derived from high-resolution images and terrain-model data, and by performing cross-correlations of prominent layers whose outcrops are observed at eight cone-like remnants. The identification and unambiguous correlation of characteristic layers across the study area provided a reasonable basis for introducing at least three additional stratigraphical subunits of the Rupes Tenuis unit. Extrapolation of altitude data indicates a gentle southward dip of remnant layers, suggesting that the unit had a much larger areal extent in Martian history. The palaeo-layer contact between two subunits of the Rupes Tenuis unit correlates well with elevation values of the Hyperborea Lingula surface. Both results disagree with an interpretation of a volcanic origin for isolated mesas but underpin that they are erosional relicts of the Rupes Tenuis unit. Average erosion rates of 2.5×10
−4
±4×10
−5
mm year
−1
are relatively high when compared to Amazonian rates but are not exceptional for areas undergoing deflation. They also corroborate the idea of aeolian denudation of the Rupes Tenuis unit.
A comparative study of interior layered deposits on Mars
Authors: Sowe Mariam , Jaumann Ralf , Neukum Gerhard
Published: August 2011

Interior layered deposits (ILDs) of the eastern Valles Marineris and adjacent chaos regions were analysed using high-resolution imagery, topography and spectral data in order to detect possible correlations. We find that ILDs are susceptible to erosion and weathering, as proven by their shapes (mesa, buttes), surface structures (pitted, fluted, yardangs), stair-stepped morphologies at different scales, and metre-sized boulders and talus. ILDs bear hydrated sulphates; consequently, we conclude that aqueous conditions dominated during their formation. Subhorizontal layering and parallel bedding of the ILDs could then indicate that deposition took place under low-energy aquatic conditions. Their superposition on chaotic terrain suggests that they are younger than chaotic terrain and, hence, younger than Late Hesperian. For the hydrated ILDs, which show polyhydrated on top of monohydrated sulphates, we think that formation within an evaporative body is not conceivable and we assume instead that a conversion of sulphates by post-formational humidity changes took place. As hydrated ILDs correlate well with rock fragmentation, we suppose that volume changes due to water content are responsible for rock fragmentation. Despite the different ILD settings, the basic conditions during sedimentation and erosion of ILDs could not have varied greatly because comparable mineralogies and morphologies are found among ILDs.
A background to Mars exploration and research
Authors: Bargery Alistair S. , Balme Matthew R. , Warner Nicholas , Gallagher Colman J. , Gupta Sanjeev
Published: August 2011

Mars is the fourth planet in our Solar System and orbits roughly 230×10
6
km from the Sun. It has an orbital period of 687 Earth days and a solar day that is approximately 40 min longer than an Earth day. Mars is less dense and has half the radius of the Earth, and so has about one-tenth the mass; hence, the surface gravity of Mars is about four-tenths that of the Earth. Mars has no oceans and its surface area is therefore almost as large as that of Earth's continents. In this chapter, we present a summary of the Martian environment, global geography and geology, and provide some background on the missions and instruments that have played a role in developing our current understanding. Our aim is to provide a broad overview for those unfamiliar with Mars, rather than providing an exhaustive summary of every aspect of the planet's evolution.
Morphological and geographical evidence for the origin of Phobos' grooves from HRSC
Mars Express
images
Authors: Murray John B. , Iliffe Jonathan C.
Published: August 2011

The surface of Phobos, the 27×22×18 km inner moon of Mars, is dominated by several families of parallel grooves. At least seven different groups of hypotheses have been advanced to explain their origin, but studies have always been limited by the fact that, until recently, much of Phobos was imaged at a resolution too low to show grooves. Now, however, the High Resolution Stereo Camera (HRSC) on board the European
Mars Express
mission has made 134 imaging fly-bys past Phobos. The pictures of the previously poorly imaged regions and much of the rest of the satellite have been returned with resolutions down to a few metres, facilitating the construction of a more complete map of the grooves. Each of the seven hypotheses was tested against the new data on groove morphology, positions and orientations, and it was found that six of the previous hypotheses could be discarded. The only hypothesis to pass all tests was that they are chains of secondary impact craters from primary impacts on Mars. An implication of these results is that previous estimates of an unusually thick Phobos regolith of 100–200 m depth are no longer necessary, and our conclusions place no constraints on the interior of Phobos, so recent evidence that Phobos is a ‘rubble pile’ is consistent with our work. The preferred hypothesis also sheds light on the origin of crater chains on Eros, and on impact processes in the early stages of crater excavation.
Periglacial geomorphology and landscape evolution of the Tempe Terra region, Mars
Authors: Van Gasselt S. , Hauber E. , Rossi A.-P. , Dumke A. , Orosei R. , Neukum G.
Published: August 2011

A systematic survey was undertaken and an investigation carried out into the geomorphological characteristics of lobate debris aprons in the Tempe Terra region of Mars. Based on the most recent high-resolution (sub 15 m per pixel) imagery and on new topography data, this study endeavoured to raise and discuss questions regarding their formation (emplacement) and modification (deformation sequence), as well as the role of a mantling deposit found at mid-latitude locations on Mars. Furthermore, a model for the formation of debris aprons in the Tempe Terra–Mareotis Fossae settings is proposed. Image survey, in combination with basic morphometric observations within a geomorphological context, provided additional insights into the source, emplacement and modification of hillslope debris material. Our results imply that lobate debris aprons are not mainly relicts of remnant degradation but are substantially composed of mantling material probably deposited episodically in the course of planetary obliquity changes and over a long timespan, as derived erosion rates suggest. Crater-size frequency statistics and the derivation of absolute ages show ages of sub-recent modification and document earlier resurfacing events.
Evolution of periglacial landforms in the ancient mountain range of the Thaumasia Highlands, Mars
Authors: Rossi Angelo Pio , Van Gasselt Stephan , Pondrelli Monica , Dohm James , Hauber Ernst , Dumke Alexander , Zegers Tanja , Neukum Gerhard
Published: August 2011

Possible periglacial and relict glacial landforms in the ancient mountain range of the Thaumasia Highlands, Mars, are described. The landforms include large-scale mantling, lineated crater and valley-fill materials, debris aprons, protalus lobes and ramparts. The most pristine ice-related landforms appear to be small-scale protalus lobes and ramparts with no visible distinct impact craters at both medium (High Resolution Stereo Camera (HRSC)) and high (Mars Orbiter Camera (MOC) narrow angle (NA), Context Camera (CTX)) spatial resolution. These small landforms are possibly active at present and post-date more extensive features such as crater fills, possibly formed during high obliquity climatic periods.

In contrast to the rock glacier-like landforms with distribution preferentially occurring on south-facing slopes, possibly controlled by enhanced exposure to the Sun, older, less pristine lineated fill materials show a less systematic distribution of flow directions, suggesting a more generalized periglacial and possibly glacial environment in the Thaumasia Highlands.
Landforms indicative of ground-ice thaw in the northern high latitudes of Mars
Authors: Gallagher C. J. , Balme M. R.
Published: August 2011

The confirmation of near-surface ground ice and perchlorates at the
Phoenix
landing site suggest that high-latitude ground-ice thaw may be more easily achieved than previously envisaged, providing the potential to drive significant, distinctive morphogenesis. We describe the results of a survey of 23 High Resolution Imaging Science Experiment (HiRISE) images covering 337° of longitude between latitudes 59°N and 79°N in which such morphogenesis is apparent, confirming that thaw has been a regionally important morphological agent. Some of the strongest geomorphological indicators of cyclical ground-ice thaw described are assemblages of sorted landforms, including clastic patterned ground resulting from cryoturbation of ice-rich regolith and lobate forms reflecting solifluction. Also described are braided gully-fan systems sourced at thermokarst pits and channels that have evolved from enlarged thermal contraction cracks. Not only are these landforms indicative of thaw and flowing liquid but the incision of solifluction lobes by thermokarst gullies demonstrates that thaw has been responsible for polycyclic morphogenesis. The presence of these landforms across the high northern latitudes of Mars indicates that the regional importance of thaw has been underestimated. This in turn has important implications for the development of better climate models and the search for life on Mars.
Water ice sublimation-related landforms on Mars
Authors: Mangold N.
Published: August 2011

Sublimation-related landforms are ubiquitous on Mars, especially at mid to high latitudes. This paper reviews the main landforms interpreted to form due to sublimation of subsurface ice on Mars. Pits, knobs and dissected terrains are classical landforms thought to form due to subsurface ice sublimation as observed with high-resolution imagery. Sublimation-related processes on Mars are strongly latitude dependent, with sublimation being increasingly important from high (>60°) to low latitudes (down to 25°) due to correspondingly higher mean annual temperatures. Equatorial regions (within 25° latitude) are mainly devoid of any sublimation-related landforms, reflecting an ice-free shallow subsurface. Mean temperatures and water vapour pressure strongly control the sublimation rate, but diffusion and water adsorption are fundamental and vary depending on the regolith porosity and composition, leading to variations in the theoretical depth at which water ice becomes stable. From a geomorphological point of view, this review highlights the importance of subsurface structure (fractures, layering) in the shaping of landforms and in the control of sublimation rates, in addition to usual physicochemical parameters.
Identifying Martian gully evolution
Authors: Aston A. H. , Conway S. J. , Balme M. R.
Published: August 2011

Martian gullies are small-scale, geologically recent features characterized by the alcove-channel-apron morphology associated with flows with a component of liquid water. Theories advanced to explain Martian gully formation include groundwater processes and melting of near-surface ice due to climate variation. Gullies are often associated with ‘mantling terrain’ that drapes topography at mid to high latitudes and which has been proposed to be ice-rich.

We have morphologically classified Martian gullies into four groupings according to whether they form solely within the mantle (Type A), erode into ‘bedrock’ (Type B), and by how well developed they appear (1 or 2). Orientation, length, geological setting and latitude were also recorded, as well as whether more than one generation of gullies formed on a given slope (labelled ‘reactivated’).

About 25% of gullies form solely within the mantle; these are generally shorter than gullies that erode bedrock and the morphologically simplest gullies (A1) are the shortest. We present latitude and orientation trends for the most recent episode of gully formation. We suggest that this recent activity is probably controlled by either deposition of ice-rich material or degradation of pre-existing ice-rich material.
Linked opening angle and histological and mechanical aspects of the proximal pulmonary arteries of healthy and pulmonary hypertensive rats and calves
Authors: Tian Lian , Lammers Steven R. , Kao Philip H. , Reusser Mark , Stenmark Kurt R. , Hunter Kendall S. , Qi H. Jerry , Shandas Robin
Published: August 2011

Understanding how arterial remodeling changes the mechanical behavior of pulmonary arteries (PAs) is important to the evaluation of pulmonary vascular function. Early and current efforts have focused on the arteries' histological changes, their mechanical properties under in vitro mechanical testing, and their zero-stress and no-load states. However, the linkage between the histology and mechanical behavior is still not well understood. To explore this linkage, we investigated the geometry, residual stretch, and histology of proximal PAs in both adult rat and neonatal calf hypoxic models of pulmonary hypertension (PH), compared their changes due to chronic hypoxia across species, and proposed a two-layer mechanical model of artery to relate the opening angle to the stiffness ratio of the PA outer to inner layer. We found that the proximal PA remodeling in calves was quite different from that in rats. In rats, the arterial wall thickness, inner diameter, and outer layer thickness fraction all increased dramatically in PH and the opening angle decreased significantly, whereas in calves, only the arterial wall thickness increased in PH. The proposed model predicted that the stiffness ratio of the calf proximal PAs changed very little from control to hypertensive group, while the decrease of opening angle in rat proximal PAs in response to chronic hypoxia was approximately linear to the increase of the stiffness ratio. We conclude that the arterial remodeling in rat and calf proximal PAs is different and the change of opening angle can be linked to the change of the arterial histological structure and mechanics.
Onset of atrial arrhythmias elicited by autonomic modulation of rabbit sinoatrial node activity: a modeling study
Authors: Muñoz Mauricio A. , Kaur Jaspreet , Vigmond Edward J.
Published: August 2011

Neuronal modulation of the sinoatrial node (SAN) plays a crucial role in the initiation and maintenance of atrial arrhythmias (AF), although the exact mechanisms remain unclear. We used a computer model of a rabbit right atrium (RA) with a heterogeneous SAN and detailed ionic current descriptions for atrial and SAN myocytes to explore reentry initiation associated with autonomic activity. Heterogeneous acetylcholine (ACh)-dependent ionic responses along with L-type Ca current ( ICa,L) upregulation were incorporated in the SAN only. During control, activation was typical with the leading pacemaker site located close to the superior vena cava or the intercaval region. With cholinergic stimulation, activation patterns frequently included caudal shifts of the leading pacemaker site and occasional double breakouts. The model became increasingly arrhythmogenic for the ACh concentration >20 nM and for large ICa,L conductance. Reentries obtained included counterclockwise rotors in the free wall, clockwise reentry circulating between the SAN and free wall, and typical flutter. The SAN was the cause of reentry with a common leading sequence of events: a bradycardic beat with shifting in the caudal direction, followed by a premature beat or unidirectional block within the SAN. Electrotonic loading, and not just overdrive pacing, squelches competing pacemaker sites in the SAN. Cholinergic stimulation concomitant with ICa,L upregulation shifts leading pacemaker site and can lead to reentry. A heterogeneous response to autonomic innervation, a large myocardial load, and an extensive SAN in the intercaval region are required for neurally induced SAN-triggered reentry.
RNA interference-mediated survivin gene knockdown induces growth arrest and reduced migration of vascular smooth muscle cells
Authors: Nabzdyk Christoph S. , Lancero Hope , Nguyen Khanh P. , Salek Sherveen , Conte Michael S.
Published: August 2011

Survivin (SVV) is a multifunctional protein that has been implicated in the development of neointimal hyperplasia. Nuclear SVV is essential for mitosis, whereas in mitochondria SVV has a cytoprotective function. Here, we investigated the effects of RNA interference (RNAi)-mediated SVV knockdown on cell cycle kinetics, apoptosis, migration, and gene expression in primary cultured vascular smooth muscle cells (VSMCs) from the human saphenous vein. Primary Human VSMCs were obtained from saphenous veins and cultured under standard conditions. SVV knockdown was achieved by either small interfering RNA or lentiviral transduction of short hairpin RNA, reducing SVV gene expression by quantitative PCR (>75%, P < 0.01) without a loss of cell viability. Subcellular fractionation revealed that RNAi treatment effectively targeted the nuclear SVV pool, whereas the larger mitochondrial pool was much less sensitive to transient knockdown. Both p53 and p27 protein levels were notably increased. SVV RNAi treatment significantly blocked VSMC proliferation in response to serum and PDGF-AB, arresting VSMC growth. Cell cycle analysis revealed an increased G2/M fraction consistent with a mitotic defect; 4′,6-diamidino-2-phenylindole staining confirmed an increased frequency of polyploid and abnormal nuclei. In a transwell assay, SVV knockdown reduced migration to PDGF-AB, and actin-phalloidin staining revealed disorganized actin filaments and polygonal cell shape. However, apoptosis (DNA content and annexin V flow cytometry) was not directly induced by SVV RNAi, and sensitivity to apoptotic agonists (e.g., staurosporine and cytokines) was unchanged. In conclusion, RNAi-mediated SVV knockdown in VSMCs leads to profound cell cycle arrest at G2/M and impaired chemotaxis without cytotoxicity. The regulation of mitosis and apoptosis in VSMC involves differentially regulated subcellular pools of SVV. Thus, treatment of VSMC with RNAi targeting SVV might limit the response to vascular injury without destabilizing the vessel wall.