bluuebunny/crossref_metadata_2025 huggingface dataset:
Ratchet Effect of Single Vortex Motion in Superconducting Asymmetrical Nanobridges
Authors: Kajino Kemmei , Fujita Keisuke , An Baoyu , Inoue Masumi , Fujimaki Akira
Published: May 2012

We have successfully obtained asymmetrical current–voltage (I–V) characteristics in YBa2Cu3O7-x
(YBCO) nanobridges patterned with asymmetrical geometry. These asymmetrical nanobridges (ANBs) are shown to control vortices one at a time. The critical current I
c, of 200-nm-wide and 100-nm-thick ANB changes by a maximum of 9% when a magnetic field of 2.4 mT is applied. The I
c variation ΔI
c increases monotonically with increased magnetic field from -2.2 to 2.4 mT. The asymmetrical I–V characteristics obtained in our experiment are due to the restriction of vortex motion by the asymmetrical surface barrier (the so-called vortex ratchet effect). The width and thickness dependencies of the I–V asymmetry are also studied, and indicate that the bias current and the Meissner screening current, determined by the relative width compared to the effective penetration depth of the YBCO film, dominates the I–V asymmetry characteristics.
Practical Guidance of Parameter Extraction for Device Simulation of Thin-Film Transistors
Authors: Kimura Mutsumi
Published: May 2012

We introduce practical guidelines for parameter extraction in the device simulation of thin-film transistors. First, the deep trap density is extracted by fitting the subthreshold swing, the surface-fixed charge density by the turn-on voltage, and the tail trap density by the threshold current. Next, the carrier mobility is extracted by fitting the transconductance and the cross section of the trap states by the off current. This procedure is essential because the changes in the parameters extracted later do not affect the parameters extracted formerly and we do not have to iterate the fitting, which makes the parameter extraction speedy and robust against divergence. These practical guidelines are useful for device development, characteristic prospect, and process diagnosis.
Near-Edge X-Ray Absorption Fine Structure Study of Vertically Aligned Carbon Nanotubes Grown by the Surface Decomposition of SiC
Authors: Maruyama Takahiro , Ishiguro Yuki , Nartitsuka Shigeya , Norimatsu Wataru , Kusunoki Michiko , Amemiya Kenta , Ishii Hideshi , Ohta Toshiaki
Published: May 2012

Vertically aligned carbon nanotubes (CNTs) grown by the surface decomposition of SiC were studied by angular-dependent C K-edge near-edge X-ray absorption fine structure spectroscopy (NEXAFS) with a linearly polarized X-ray beam. The NEXAFS spectra measured in total electron yield mode showed a distinct angular dependence on π* and σ* resonances and the orientation parameter was tentatively estimated to be 0.38, which is fairly larger than those reported for other vertically aligned CNTs grown by chemical vapor deposition. The high order of the vertical alignment of CNTs grown by the surface decomposition of SiC was demonstrated by NEXAFS measurements for the first time.
Theoretical Evaluation of Ballistic Electron Transport in Field-Effect Transistors with Semiconducting Graphene Channels
Authors: Tsuchiya Hideaki , Hosokawa Hiroshi , Sako Ryūtaro , Hasegawa Naomi , Ogawa Matsuto
Published: May 2012

In this paper, we present a theoretical evaluation of ballistic electron transport in field-effect transistors (FETs) with semiconducting graphehe channels; bilayer graphenes (BLGs), monolayer graphene nanoribbons (MLGNRs), and bilayer graphene nanoribbons (BLGNRs). We found that the use of BLGNRs produces little advantage in either increasing the band gap energy or improving the device performance, as compared with a pristine BLG device. We also demonstrated that BLG-based FETs exhibit quite different behavior in the drain current versus gate voltage characteristics from that of MLGNR-FETs, since a distorted dispersion relation around the conduction band minima significantly affects the drain current property.
Ultraviolet Photoresponse Properties of Single-Walled Carbon Nanotubes Decorated with Thickness-Controlled ZnO Layer by Pulsed Laser Deposition
Authors: Itabashi Kenta , Tabata Hiroshi , Wongwiriyapan Winadda , Minami Shinji , Matsushita Kazutoshi , Shimazaki Ryotaro , Ueda Tsuyoshi , Ito Tatsuya , Katayama Mitsuhiro
Published: May 2012

We fabricated single-walled carbon nanotubes (SWNTs) covered with a thickness-controlled ZnO layer (ZnO–SWNTs) by pulsed laser deposition (PLD) and investigated their UV photoresponse, induced by the photodesorption of oxygen molecules from the ZnO surface. The magnitude of the negative photocurrent and the recovery time were strongly dependent on the thickness and morphology of the ZnO layer, and were highest when the ZnO layer was 3–4 nm thick. The observed recovery curves of the negative photocurrent were fitted with double-exponential-function curves, which indicate the coexistence of two types of adsorption sites for oxygen molecules on the ZnO surface. The light intensity dependence of the negative photocurrent was also measured.
Photocatalytic Activity of WO3 Films Crystallized by Postannealing in Air
Authors: Takashima Jyunya , Oka Nobuto , Shigesato Yuzo
Published: May 2012

We devised an effective method of deposition of photocatalytic WO3 films for the decomposition of volatile organic compounds. Amorphous WO3 films were deposited on unheated fused silica glass substrates by reactive DC magnetron sputtering with a W metal target, followed by crystallization through annealing at 300–800 °C in air. Under visible light irradiation, a film annealed at 400 °C proved significantly more effective than a WO3 film crystallized during deposition on a heated (800 °C) substrate for achieving photocatalytic decomposition of CH3CHO. Even more remarkable photocatalytic results were obtained for a film that was loaded with Pt nanoparticles after postannealing.
Ge Flat Layer Growth on Heavily Phosphorus-Doped Si(001) by Sputter Epitaxy
Authors: Hanafusa Hiroaki , Hirose Nobumitsu , Kasamatsu Akifumi , Mimura Takashi , Matsui Toshiaki , Suda Yoshiyuki
Published: May 2012

We have investigated layer-by-layer Ge growth methods on phosphorus (P)-doped Si(001) with our sputter epitaxy method at a growth temperature (T
G) of 350 °C. With the sputter epitaxy method, relaxed Ge islands are formed on P-doped 3.5 Ω cm Si with Ge–Si intermixing at the Ge/Si interface; however, a partially strained flat Ge layer is grown directly on P-doped 0.015 Ω cm Si. For comparison with a gas-source molecular beam epitaxy (GS-MBE) method using GeH4, Ge islands are formed on 0.015 Ω cm Si at T
G = 350 °C. It has been suggested that the P dopants together with the sputter epitaxy method effectively suppress Ge islanding and induce Ge layer-by-layer growth.
Control of In Surface Segregation and Inter-Diffusion in GaAs on InGaP Grown by Metal–Organic Vapor Phase Epitaxy
Authors: Fukushima Yasuyuki , Nakano Takayuki , Nakano Yoshiaki , Shimogaki Yukihiro
Published: May 2012

In order to fabricate abrupt heterointerfaces of the GaAs/InGaP system by metal–organic vapor phase epitaxy (MOVPE), we studied the In atom distribution by X-ray photoelectron spectroscopy (XPS). The systematic XPS depth profile analyses revealed that the InGaP surface contains an excess amount of In atoms owing to surface segregation. The excess In atoms diffuse into the GaAs layer and cause compositional mixing at the interface of GaAs on InGaP. In order to suppress the interdiffusion and surface segregation of In atoms into GaAs on InGaP, we have developed a novel gas switching sequence for growing GaAs on InGaP. That is, after the growth of InGaP, only tertiarybutylphosphine (TBP) was introduced, and after stopping the supply of TBP, trimethylgallium (TMGa) was pre-introduced to the reactor before the growth of GaAs. Then tertiarybutylarsine (TBAs) was allowed to flow to initiate GaAs growth. This novel gas switching sequence contributed to the formation of abrupt heterointerfaces of GaAs on InGaP.
Influence of Interfacial Tantalum Oxynitride on Resistive Switching of Cu/Cu–SiO2/TaN
Authors: Jou Shyankay , Han Ming-En
Published: May 2012

We demonstrate reversible switching of the resistance of Cu/Cu–SiO2/TaN cells with and without an interfacial tantalum oxynitride (TaON) layer. The TaN, Cu–SiO2, and Cu layers were prepared by sputter deposition, and the TaON layer was produced by plasma oxidation of the TaN surface. Both cells demonstrated bipolar switching between the high resistance state (HRS) and the low resistance state (LRS). The Cu/Cu–SiO2/TaN cell had set voltages of approximately around +1.0 V, reset voltages of approximately around -0.6 V, and resistance ratios (R
HRS/R
LRS) of about 6 to 8. By inserting a thin TaON layer between the Cu–SiO2 and TaN in the cell, R
HRS/R
LRS of the Cu/Cu–SiO2/TaON/TaN cell was increased to above 400, and the set and reset voltages were decreased to about +0.3 and -0.2 V, respectively. Adding the interfacial TaON layer also improved the endurance of the cell. Furthermore, the conduction mechanisms for the Cu/Cu–SiO2/TaN cells with and without an interfacial TaON layer were discussed.
Adsorption of Pyrazine on a Si(001) Surface Partially Covered with an Indium Dimer Structure
Authors: Shimomura Masaru , Kunihara Chihiro
Published: May 2012

Pyrazine forms a molecular one-dimensional (1D) line on a bare Si(001)-2×1 surface across the Si dimer row. Indium also forms a 1D line across the Si dimer row. In this study, the adsorption of pyrazine on a Si(001)-2×1 surface on which the indium parallel dimer structure is formed was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). It was found by STM that pyrazine adsorbates were predominantly located at the lateral neighboring sites of the indium line structure during the initial stage of adsorption. This preferential adsorption of pyrazine can enhance the formation of long linear chains of pyrazine along the indium lines.
Optical and Transport Anisotropy in Poly(9,9'-dioctyl-fluorene-alt-bithiophene) Films Prepared by Floating Film Transfer Method
Authors: Dauendorffer Arnaud , Nagamatsu Shuichi , Takashima Wataru , Kaneto Keiichi
Published: May 2012

We demonstrated the fabrication of self-aligned poly(9,9'-dioctyl-fluorene-alt-bithiophene) copolymer (F8T2) thin films at ambient temperature with a new solution-process technique named floating film transfer method (FTM). Atomic force microscope topography and polarized absorption spectroscopy showed that the polymer main chains aligned perpendicularly to the film propagation direction during the fabrication process. FTM films presented absorption dichroic ratios slightly below 3. Top-contact/bottom-gate field effect transistors made with FTM films exhibited anisotropic transport properties with a hole mobility along the aligned direction of F8T2 main chains of 2.2×10-3 cm2/(V·s), which was around 2.5 times greater than that along the perpendicular direction. Dichroic and transport anisotropy ratios were further enhanced up to 7–8 by thermal annealing, although the mobility improvement remained limited due to possible trapping effect at domain boundaries.
The Diagnosis Method for High-Energy Ion Beams Using Backscattered Particles for Laser-Driven Ion Acceleration Experiments
Authors: Kanasaki Masato , Fukuda Yuji , Sakaki Hironao , Hori Toshihiko , Tampo Motonobu , Kondo Kiminori , Kurashima Satoshi , Kamiya Tomihiro , Oda Keiji , Yamauchi Tomoya
Published: May 2012

A single CR-39 detector mounted on plastic plates is irradiated with a 100 MeV He ion beam. Although the beam energy is much greater than the detection threshold limit of the CR-39 detector, a large number of etch pits having elliptical openings are observed on the rear surface. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This method allows a simple diagnosis of the ion beam profile and the presence of the high-energy component beyond the detection threshold limit of the CR-39 detector, especially in mixed-radiation fields such as laser-driven ion acceleration experiments.
Discriminated Detection of Nuclear Tracks Recorded on Multilayers of Photographic Emulsions with Different Sensitivities by Color-Development Method
Authors: Kuge Ken'ichi , Ito Ryota , Kodaira Satoshi , Yasuda Nakahiro
Published: May 2012

We have developed a new method for the detection of nuclear tracks recorded on nuclear plates composed of multiple photographic emulsion layers. Each layer of these plates contained a photographic coupler revealing a different color after color development. The developed silver grains left behind in each layer were colored with differently colored dye clouds when the bleaching process was omitted in the color-development process. The three-dimensional structure of a track was obtained from the color change of the track. The track indicated a different grain density in each layer of different sensitivity, thus expanding the dynamic range of such nuclear plates. Accurate discrimination of particles with different deposit energies by using emulsions with different properties in each layer is also expected.
Ultra-Conformal Metal Coating on High-Aspect-Ratio Three-Dimensional Structures Using Supercritical Fluid: Controlled Selectivity/Non-Selectivity
Authors: Momose Takeshi , Uejima Takeshi , Yamada Hideo , Shimogaki Yukihiro , Sugiyama Masakazu
Published: May 2012

Underlayer dependence can be controlled for supercritical fluid deposition (SCFD) of Cu. SCFD, which has a remarkable potential for ultra-conformal deposition and gap-filling, has previously required a metallic underlayer to initiate deposition. Here, this constraint has been overcome by depositing a novel catalytic layer, CuMn
x
O
y
, onto a semiconducting and insulating substrate. The stoichiometry of CuMn
x
O
y
affected both the morphology of CuMn
x
O
y
film and the catalytic effect on succeeding SCFD of Cu. By using this technique of depositing CuMn
x
O
y
as a catalytic layer, conformal SCFD of Cu was achieved on high-aspect-ratio trenches (aspect ratio 50) whose surfaces were SiO2. In conclusion, a CuMn
x
O
y
film with graded stoichiometry in the depth direction might improve the adhesion between Cu and an insulative underlayer.
Topographic Contrast in Force Modulation Atomic Force Microscopy Images
Authors: Yang Chunlai , Zheng Cheng , Chen Yuhang , Huang Wenhao
Published: May 2012

Topographic influences on force modulation microscopy (FMM) amplitude image contrasts have been investigated. Experimental results and a simple model analysis demonstrate that the amplitude has a close relevance to thex-derivative of sample topography. When the tip sample is in a single-point contact and the mechanical properties of the sample are homogeneous, the contrasts of the amplitude andx-derivative topography are almost the same. In addition, the amplitude contrast is reversed when the scan direction is opposite. When the tip sample is in a multipoint contact, the amplitude at the multipoint contact region increases markedly and the scan-direction relevant contrast reversion is still distinguishable. These results can help in the interpretation of FMM data accurately.
Magnetic Alignment of Magnetically Biaxial Diamagnetic Rods under Rotating Magnetic Fields
Authors: Tsukui Shu , Kimura Tsunehisa
Published: May 2012

The alignment behavior of magnetically biaxial diamagnetic rods under rotating magnetic fields is studied to elucidate the effects of particle shape and rotation speed on alignment manner. Three types of rod (ca.1.1 mmφ × 3 mm) are prepared: (i) rod axes parallel to χ1, (ii) parallel to χ2, and (iii) parallel to χ3, where χs are the principal axes of the diamagnetic susceptibility tensor and χ1> χ2> χ3. The motion of the rod is recorded on video and the angles required for the comparison with simulation are measured. Simulation is performed by numerically solving a torque equation including magnetic and hydrodynamic torques. The experimental results show a good agreement with simulation results. It is shown that the χ3-axis of rod sample (ii) does not align parallel to the axis of the rotating magnetic field under most experimental conditions; this is in marked contrast to the case with magnetically uniaxial particles (χ1= χ2> χ3), for which the χ3-axis aligns irrespective of particle shape and/or rotation speed. This observation is interpreted in terms of magnetic energy and orientation kinetics.
Rotation-Symmetric Multispot Focusing Phase-Shifted Grating Coupler for Integrated Semiconductor Laser
Authors: Uenishi Kengo , Uemukai Masahiro , Suhara Toshiaki
Published: May 2012

Rotation-symmetric multispot focusing grating couplers with periodic binary phase modulation are designed and fabricated. The functions of 60 and 45° rotation-symmetric multispot focusing with the same spot intensities were demonstrated.
SETI@home, BOINC, and Volunteer Distributed Computing
Authors: Korpela Eric J.
Published: May 2012

Volunteer computing, also known as public-resource computing, is a form of distributed computing that relies on members of the public donating the processing power, Internet connection, and storage capabilities of their home computers. Projects that utilize this mode of distributed computation can potentially access millions of Internet-attached central processing units (CPUs) that provide PFLOPS (thousands of trillions of floating-point operations per second) of processing power. In addition, these projects can access the talents of the volunteers themselves. Projects span a wide variety of domains including astronomy, biochemistry, climatology, physics, and mathematics. This review provides an introduction to volunteer computing and some of the difficulties involved in its implementation. I describe the dominant infrastructure for volunteer computing in some depth and provide descriptions of a small number of projects as an illustration of the variety of projects that can be undertaken.
The Role of H2O in Subduction Zone Magmatism
Authors: Grove Timothy L. , Till Christy B. , Krawczynski Michael J.
Published: May 2012

Water is a key ingredient in the generation of magmas in subduction zones. This review focuses on the role of water in the generation of magmas in the mantle wedge, the factors that allow melting to occur, and the plate tectonic variables controlling the location of arc volcanoes worldwide. Water also influences chemical differentiation that occurs when magmas cool and crystallize in Earth's continental crust. The source of H2O for arc magma generation is hydrous minerals that are carried into Earth by the subducting slab. These minerals dehydrate, releasing their bound H2O into overlying hotter, shallower mantle where melting begins and continues as buoyant hydrous magmas ascend and encounter increasingly hotter surroundings. This process is controlled by plate tectonic variables that ultimately influence the location of the active volcanic arc above subduction zones. Water also modifies the thermodynamic properties of melts, leading to the unique chemical composition of arc volcanic rocks and Earth's continental crust.
Molecular and Fossil Evidence on the Origin of Angiosperms
Authors: Doyle James A.
Published: May 2012

Molecular data on relationships within angiosperms confirm the view that their increasing morphological diversity through the Cretaceous reflected their evolutionary radiation. Despite the early appearance of aquatics and groups with simple flowers, the record is consistent with inferences from molecular trees that the first angiosperms were woody plants with pinnately veined leaves, multiparted flowers, uniovulate ascidiate carpels, and columellar monosulcate pollen. Molecular data appear to refute the hypothesis based on morphology that angiosperms and Gnetales are closest living relatives. Morphological analyses of living and fossil seed plants that assume molecular relationships identify glossopterids, Bennettitales, and Caytonia as angiosperm relatives; these results are consistent with proposed homologies between the cupule of glossopterids and Caytonia and the angiosperm bitegmic ovule. Jurassic molecular dates for the angiosperms may be reconciled with the fossil record if the first angiosperms were restricted to wet forest understory habitats and did not radiate until the Cretaceous.
Building Terrestrial Planets
Authors: Morbidelli A. , Lunine J.I. , O'Brien D.P. , Raymond S.N. , Walsh K.J.
Published: May 2012

This article reviews our current understanding of terrestrial planet formation. The focus is on computer simulations of the dynamical aspects of the accretion process. Throughout the review, we combine the results of these theoretical models with geochemical, cosmochemical, and chronological constraints to outline a comprehensive scenario of the early evolution of our solar system. Given that the giant planets formed first in the protoplanetary disk, we stress the sensitive dependence of the terrestrial planet accretion process on the orbital architecture of the giant planets and on their evolution. This suggests a great diversity among the terrestrial planet populations in extrasolar systems. Issues such as the cause for the different masses and accretion timescales between Mars and Earth and the origin of water (and other volatiles) on our planet are discussed in depth.
Reminiscences From a Career in Geomicrobiology
Authors: Ehrlich Henry L.
Published: May 2012

This is a memoir relating how the author became a geomicrobiologist and how he practiced his specialty. Born in Germany and receiving his early schooling in Berlin, he completed his secondary education, followed by college and graduate school training, after emigration to the United States in 1940. After attaining a PhD degree in 1951, he spent his entire professional career as a faculty member of the Department of Biology at Rensselaer Polytechnic Institute (RPI) in Troy, New York. He was introduced to geomicrobiology in 1959 by a question from a colleague in the Department of Geology at RPI concerning the recent discovery of acidophilic iron-oxidizing, autotrophic bacteria in acid coal mine drainage. This led him to investigate bacterial interaction with metal sulfides, Mn(II) and Mn(IV) on land and in the sea, chromate, and bauxite; to teach a course in geomicrobiology; and to write a textbook on the subject, first published in 1981.
The Future of Arctic Sea Ice
Authors: Maslowski Wieslaw , Clement Kinney Jaclyn , Higgins Matthew , Roberts Andrew
Published: May 2012

Arctic sea ice is a key indicator of the state of global climate because of both its sensitivity to warming and its role in amplifying climate change. Accelerated melting of the perennial sea ice cover has occurred since the late 1990s, which is important to the pan-Arctic region, through effects on atmospheric and oceanic circulations, the Greenland ice sheet, snow cover, permafrost, and vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation, native coastal communities, and commercial activities, as well as effects on the global surface energy and moisture budgets, atmospheric and oceanic circulations, and geosphere-biosphere feedbacks. However, a system-level understanding of critical Arctic processes and feedbacks is still lacking. To better understand the past and present states and estimate future trajectories of Arctic sea ice and climate, we argue that it is critical to advance hierarchical regional climate modeling and coordinate it with the design of an integrated Arctic observing system to constrain models.
Biomimetic Properties of Minerals and the Search for Life in the Martian Meteorite ALH84001
Authors: Martel Jan , Young David , Peng Hsin-Hsin , Wu Cheng-Yeu , Young John D.
Published: May 2012

The existence of extraterrestrial life was heralded by controversial claims made in 1996 that the Martian meteorite ALH84001 harbored relics of ancient microorganisms. We review here the accumulated evidence for and against past extraterrestrial life in this Martian meteorite. The main pro-life arguments—the presence of polycyclic aromatic hydrocarbons, magnetite crystals, carbonate globules, and structures resembling terrestrial life-forms known as nanobacteria—can be deemed ambiguous at best. Although these criteria are compatible with living processes, each one of them can be explained by nonliving chemical processes. By undergoing amorphous-to-crystalline transformations and binding to multiple substrates, including other ions and simple organic compounds, minerals—especially those containing carbonate—have been shown to display biomimetic properties, producing forms that resemble bacteria. This simple and down-to-earth explanation can account fully for the existence of mineral entities resembling putative nano- and microorganisms that have been described not only in the ALH84001 meteorite but also in the human body.
Infrasound: Connecting the Solid Earth, Oceans, and Atmosphere
Authors: Hedlin M.A.H. , Walker K. , Drob D.P. , de Groot-Hedlin C.D.
Published: May 2012

The recently reinvigorated field of infrasonics is poised to provide insight into atmospheric structure and the physics of large atmospheric phenomena, just as seismology has shed considerable light on the workings and structure of Earth's solid interior. Although a natural tool to monitor the atmosphere and shallow Earth for nuclear explosions, it is becoming increasingly apparent that infrasound also provides another means to monitor a suite of natural hazards. The frequent observation of geophysical sources—such as the unsteady sea surface, volcanoes, and earthquakes—that radiate energy both up into the atmosphere and down into the liquid or solid Earth and transmission of energy across Earth's boundaries reminds us that Earth is an interconnected system. This review details the rich history of the unheard sound in the atmosphere and the role that infrasonics plays in helping us understand the Earth system.
Climate Change Impacts on the Organic Carbon Cycle at the Land-Ocean Interface
Authors: Canuel Elizabeth A. , Cammer Sarah S. , McIntosh Hadley A. , Pondell Christina R.
Published: May 2012

Estuaries are among the most altered and vulnerable marine ecosystems. These ecosystems will likely continue to deteriorate owing to increased population growth in coastal regions, expected temperature and precipitation changes associated with climate change, and their interaction with each other, leading to serious consequences for the ecological and societal services they provide. A key function of estuaries is the transfer, transformation, and burial of carbon and other biogenic elements exchanged between the land and ocean systems. Climate change has the potential to influence the carbon cycle through anticipated changes to organic matter production in estuaries and through the alteration of carbon transformation and export processes. This review discusses the effects of climate change on processes influencing the cycling of organic carbon in estuaries, including examples from three temperate estuaries in North America. Our goal is to evaluate the impact of climate change on the connectivity of terrestrial, estuarine, and coastal ocean carbon cycles.
The Habitability of Our Earth and Other Earths: Astrophysical, Geochemical, Geophysical, and Biological Limits on Planet Habitability
Authors: Lineweaver Charles H. , Chopra Aditya
Published: May 2012

For life-forms like us, the most important feature of Earth is its habitability. Understanding habitability and using that knowledge to locate the nearest habitable planet may be crucial for our survival as a species. During the past decade, expectations that the universe could be filled with habitable planets have been bolstered by the increasingly large overlap between terrestrial environments known to harbor life and the variety of environments on newly detected rocky exoplanets. The inhabited and uninhabited regions on Earth tell us that temperature and the presence of water are the main constraints that can be used in a habitability classification scheme for rocky planets. Our compilation and review of recent exoplanet detections suggests that the fraction of stars with planets is ∼100%, and that the fraction with rocky planets may be comparably large. We review extensions to the circumstellar habitable zone (HZ), including an abiogenesis habitable zone and the galactic habitable zone.
Molecular Paleohydrology: Interpreting the Hydrogen-Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms
Authors: Sachse Dirk , Billault Isabelle , Bowen Gabriel J. , Chikaraishi Yoshito , Dawson Todd E. , Feakins Sarah J. , Freeman Katherine H. , Magill Clayton R. , McInerney Francesca A. , van der Meer Marcel T.J. , Polissar Pratigya , Robins Richard J. , Sachs Julian P. , Schmidt Hanns-Ludwig , Sessions Alex L. , White James W.C. , West Jason B. , Kahmen Ansgar
Published: May 2012

Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and terrestrial organisms can be related to the composition of their growth (i.e., environmental) water. Subsequently, compound-specific deuterium/hydrogen (D/H) ratios of sedimentary biomarkers have been increasingly used as paleohydrological proxies over a range of geological timescales. Isotopic fractionation observed between hydrogen in environmental water and hydrogen in lipids, however, is sensitive to biochemical, physiological, and environmental influences on the composition of hydrogen available for biosynthesis in cells. Here we review the factors and processes that are known to influence the hydrogen-isotopic compositions of lipids—especially n-alkanes—from photosynthesizing organisms, and we provide a framework for interpreting their D/H ratios from ancient sediments and identify future research opportunities.
Ca2+-dependent desensitization of insulin secretion by strong potassium depolarization
Authors: Willenborg M. , Belz M. , Schumacher K. , Paufler A. , Hatlapatka K. , Rustenbeck I.
Published: May 2012

Depolarization by a high K+ concentration is a widely used experimental tool to stimulate insulin secretion. The effects occurring after the initial rise in secretion were investigated here. After the initial peak a fast decline occurred, which was followed by a slowly progressive decrease in secretion when a strong K+ depolarization was used. At 40 mM KCl, but not at lower concentrations, the decrease continued when the glucose concentration was raised from 5 to 10 mM, suggesting an inhibitory effect of the K+ depolarization. When tolbutamide was added instead of the glucose concentration being raised, a complete inhibition down to prestimulatory values was observed. Equimolar reduction of the NaCl concentration to preserve isoosmolarity enabled an increase in secretion in response to glucose. Unexpectedly, the same was true when the Na+-reduced media were made hyperosmolar by choline chloride or mannitol. The insulinotropic effect of tolbutamide was not rescued by the compensatory reduction of NaCl, suggesting a requirement for activated energy metabolism. These inhibitory effects could not be explained by a lack of depolarizing strength or by a diminished free cytosolic Ca2+ concentration ([Ca2+]i). Rather, the complexation of extracellular Ca2+ concomitant with the K+ depolarization markedly diminished [Ca2+]i and attenuated the inhibitory action of 40 mM KCl. This suggests that a strong but not a moderate depolarization by K+ induces a [Ca2+]i-dependent, slowly progressive desensitization of the secretory machinery. In contrast, the decline immediately following the initial peak of secretion may result from the inactivation of voltage-dependent Ca2+ channels.
Nodal induces apoptosis through activation of the ALK7 signaling pathway in pancreatic INS-1 β-cells
Authors: Zhao Fang , Huang Fengjie , Tang Mengxiong , Li Xiaoming , Zhang Nina , Amfilochiadis Akis , Li Yiming , Hu Renming , Jin Tianru , Peng Chun , Wang Qinghua
Published: May 2012

We demonstrated previously that the activation of ALK7 (activin receptor-like kinase-7), a member of the type I receptor serine/threonine kinases of the TGF-β superfamily, resulted in increased apoptosis and reduced proliferation through suppression of Akt signaling and the activation of Smad2-dependent signaling pathway in pancreatic β-cells. Here, we show that Nodal activates ALK7 signaling and regulates β-cell apoptosis. We detected Nodal expression in the clonal β-cell lines and rodent islet β-cells. Induction of β-cell apoptosis by treatment with high glucose, palmitate, or cytokines significantly increased Nodal expression in clonal INS-1 β-cells and isolated rat islets. The stimuli induced upregulation of Nodal expression levels were associated with elevation of ALK7 protein and enhanced phosphorylated Smad3 protein. Nodal treatment or overexpression of Nodal dose- or time-dependently increased active caspase-3 levels in INS-1 cells. Nodal-induced apoptosis was associated with decreased Akt phosphorylation and reduced expression level of X-linked inhibitor of apoptosis (XIAP). Remarkably, overexpression of XIAP or constitutively active Akt, or ablation of Smad2/3 activity partially blocked Nodal-induced apoptosis. Furthermore, siRNA-mediated ALK7 knockdown significantly attenuated Nodal-induced apoptosis of INS-1 cells. We suggest that Nodal-induced apoptosis in β-cells is mediated through ALK7 signaling involving the activation of Smad2/3-caspase-3 and the suppression of Akt and XIAP pathways and that Nodal may exert its biological effects on the modulation of β-cell survival and β-cell mass in an autocrine fashion.
Evaluation of a mathematical model of diabetes progression against observations in the Diabetes Prevention Program
Authors: Hardy Thomas , Abu-Raddad Eyas , Porksen Niels , De Gaetano Andrea
Published: May 2012

The seminal publication of the Diabetes Prevention Program (DPP) results in 2002 has provided insight into the impact of major therapies on the development of diabetes over a time span of a few years. In the present work, the publicly available DPP data set is used to calibrate and evaluate a recently developed mechanistic mathematical model for the long-term development of diabetes to assess the model's ability to predict the natural history of disease progression and the effectiveness of preventive interventions. A general population is generated from which virtual subject samples corresponding to the DPP enrollment criteria are selected. The model is able to reproduce with good fidelity the observed time courses of both diabetes incidence and average glycemia, under realistic hypotheses on evolution of disease and efficacy of the studied therapies, for all treatment arms. Model-based simulations of the long-term evolution of the disease are consistent with the transient benefits observed with conventional therapies and with promising effects of radical improvement of insulin sensitivity (as by metabolic surgery) or of β-cell protection. The mechanistic diabetes progression model provides a credible tool by which long-term implications of antidiabetic interventions can be evaluated.
Regulation of glomerulotubular balance. I. Impact of dopamine on flow-dependent transport
Authors: Du Zhaopeng , Yan Qingshang , Wan Laxiang , Weinbaum Sheldon , Weinstein Alan M. , Wang Tong
Published: May 2012

In response to volume expansion, locally generated dopamine decreases proximal tubule reabsorption by reducing both Na/H-exchanger 3 (NHE3) and Na-K-ATPase activity. We have previously demonstrated that mouse proximal tubules in vitro respond to changes in luminal flow with proportional changes in Na+ and HCO3− reabsorption and have suggested that this observation underlies glomerulotubular balance. In the present work, we investigate the impact of dopamine on the sensitivity of reabsorptive fluxes to changes in luminal flow. Mouse proximal tubules were microperfused in vitro at low and high flow rates, and volume and HCO3− reabsorption (Jv and JHCO3) were measured, while Na+ and Cl− reabsorption (JNa and JCl) were estimated. Raising luminal flow increased Jv, JNa, and JHCO3 but did not change JCl. Luminal dopamine did not change Jv, JNa, and JHCO3 at low flow rates but completely abolished the increments of Na+ absorption by flow and partially inhibited the flow-stimulated HCO3− absorption. The remaining flow-stimulated HCO3− absorption was completely abolished by bafilomycin. The DA1 receptor blocker SCH23390 and the PKA inhibitor H89 blocked the effect of exogenous dopamine and produced a two to threefold increase in the sensitivity of proximal Na+ reabsorption to luminal flow rate. Under the variety of perfusion conditions, changes in cell volume were small and did not always parallel changes in Na+ transport. We conclude that 1) dopamine inhibits flow-stimulated NHE3 activity by activation of the DA1 receptor via a PKA-mediated mechanism; 2) dopamine has no effect on flow-stimulated H-ATPase activity; 3) there is no evidence of flow stimulation of Cl− reabsorption; and 4) the impact of dopamine is a coordinated modulation of both luminal and peritubular Na+ transporters.
Synthesis of Benzopyranophenazines via Isocyanide‐Based Three‐Component Reactions
Authors: Bazgir Ayoob , Astaraki Ali Mohammad
Published: May 2012

Benzo[a]pyrano[2,3‐c]phenazines were synthesized in good yields by a three‐component reaction of benzo[a]phenazin‐5‐oles, isocyanides and dialkyl acetylendicarboxylates In refluxing ethanol.
Synthesis and Characterization of Boron Trifluoride Doped High Performance Polyaniline
Authors: Basavaiah K. , Samsonu D. , Rao A. V. Prasada
Published: May 2012

We report simple synthesis of boron trifluoride (BF3) doped defect free high performance polyaniline (HPPANI) in two step method. Firstly, HPPANI was prepared via self‐stabilization dispersion polymerization method in a heterogeneous reaction medium. Second step involves doping of emeraldine base form of HPPANI with boron trifluoride under reduced vacuum. The resultants BF3 doped HPPANI have been well characterized by using UV‐Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetry. The spectroscopic data indicated that the interaction between HPPANI and BF3.Thermogravimetry studies revealed that the BF3 doping improved the thermal stability of defects free PANI.
Reduction of Carbonyl Compounds to Their Corresponding Alcohols by (Nicotine)(tetrahydroborato)zinc Complex as a New Stable and Efficient Reducing Agent
Authors: Setamdideh Davood , Rafigh Mostafa
Published: May 2012

(Nicotine)(tetrahydroborato)zinc complex, [Zn(BH4)2(nic)], as a stable yellow solid, was prepared quantitatively by complexation of an equimolar amounts of zinc tetrahydroborate and Nicotine at room temperature. This reagent can easily reduce variety of carbonyl compounds such as aldehydes, ketones, acyloins and α‐diketones to their corresponding alcohols in good to excellent yields. Reduction reactions were performed in CH3CN at room temperature.
Syntheses, Characterization, and Antimicrobial Screening of N‐(benzothiazol‐2‐yl)benzenesulphonamide and its Cu(I), Ni(II), Mn(II), Co(II), and Zn(II) Complexes
Authors: Obasi N. L. , Benedict Okoye C. O. , Ukoha P. O. , Anaga A. O.
Published: May 2012

N‐(benzothiazol‐2‐yl)benzenesulphonamide (BS2ABT) was synthesized by the condensation (by refluxing) of 2‐aminobenzothiazole and benzenesulphonylchloride in acetone at 140ºC. The resulting crude precipitates were recrystallized from dimethylformamide (DMF). Five metal complexes of copper(I), nickel(II), manganese(II), cobalt(II) and zinc(II) of the ligands were synthesized. The compounds were characterized using magnetic susceptibility measurements, UV/VIS spectrophotometry, infra red, proton and 13C nmr spectroscopies. The antimicrobial tests of the ligands and its metal complexes were carried out on both multi‐resistant bacterial strains isolated under clinical conditions and cultured species using agar‐well diffusion method. The multi‐resistant bacterial strains used were Escherichia coli, Proteus species, Pseudomonas aeroginosa and Staphylococcus aureus which were isolated from dogs. The culture species were Pseudomonas aeruginosa (ATCC 27853), Escherichia Coli (ATCC 25922) Staphylococcus aureus (ATCC 25923), and the fungi, Candida krusei (ATCC 6258) and Candida albicans (ATCC 90028). The tests were both in vitro and in vivo. Thus the Inhibition Zone Diameter (IZD), the Minimum Inhibitory Concentration (MIC), and the Lethal and Effective Concentrations (LC50 and EC50) were determined. The antimicrobial activities of the compounds were compared with those of Ciprofloxacin and trimethoprim‐sulphamethoxazole as antibacterial agents and Fluconazole as an antifungal drug. All the compounds showed varying activities against the cultured typed bacteria and fungi used. However, they were less active than the standard drugs used except Fluconazole which did not show any activity against Candida krusei (ATCC 6258) but most of the compounds synthesized were very active against it. The Lethal Concentration (LC50) ranged from 26.25±4.9‐1833.88±186.92 ppm. These are within the permissible concentrations.
A Comparative Study of the Adsorption Efficiency of the Newly Synthetic Nano Iron Oxide and Commercial Activated Charcoal Towards the Removal of the Nickel(II) Ions
Authors: Kanthimathi G. , Kotteeswaran P. , Thillai Arasu P. , Govindaraj P. , Kottaisamy M.
Published: May 2012

The synthetic nano iron oxide (SNIO) was synthesized by acid base hydrolysis and characterized by the XRD, SEM and EDAX techniques. Batch adsorption experiments were carried out to study the sorption behaviour of SNIO and commercial activated charcoal (CAC) towards Ni(II) ions as a function of initial concentration of the adsorbate, adsorbent dosage, contact time and pH. The adsorption for Ni(II) is found to be better in acidic pH for both SNIO and CAC. The equilibrium adsorption isotherm data have been tested by applying both Freundlich and Langmuir isotherm models. The Separation factor R was found to be between 0 and 1 for both the adsorbent, it clearly indicates the feasibility of adsorption.
Sensitization of Eriochromeazurol‐B in Presence of Cetyldimethylethylammonium Bromide for the Microdetermination of Some Lanthanides
Authors: Zade Anil B. , Kalbende Pawan P. , Umekar Mayuri S. , Belsare Gajanan W.
Published: May 2012

Cetyldimethylethylammonium bromide, a cationic surfactant has been used to decolorize eriochromeazurol B, an anionic triphenylmethane type of dye. Addition of specific lanthanide metal ion to this decolorized solution resulted into intense colored stable ternary complex with large bathochromic shift from 540 nm (binary complex) to 650 nm (ternary complex) with increase in absorbance values at shifted wavelength. CDMEAB thus decreases the color intensity of ECAB and increases the absorbance value of ternary complexes. This two fold advantage resulted into enhancement in molar absorptivities and sensitivities at shifted wavelength of ternary complexes with stoichiometric composition 1:(1:3)2, [Ln : (R:S)] for all lanthanides understudy namely yttrium, neodymium, europium, terbium and ytterbium. The ternary complexes at pH 6.0 exhibited absorption maxima at 650 nm with molar absorptivities 69000 L.mol-1.cm-2 for Y(III), 66000 L.mol-1.cm-2 for Nd(III), 69000 L.mol-1.cm-2 for Eu(III), 64000 L.mol-1.cm-2 for Tb(III), 70000 L.mol-1.cm-2 for Yb(III). Beer′s law were obeyed in concentration range 0.11‐0.94, 0.19‐1.53, 0.2‐1.41, 0.21‐1.69 and 0.23‐1.11 ppm for Y(III), Nd(III), Eu(III), Tb(III) and Yb(III) respectively. Conditional formation constants and various analytical parameters have been evaluated and compared the results of newly formed ternary complexes with binary complexes. Finally newly suggested modified method have been recommended for the microdetermination of lanthanides understudy.
The Influence of the Chemical Structures of Chitosan and Acid Dye on the Adsorption Process
Authors: Ben Ali Hayet , Hentati Salma Besbes , Al-Deyab Salem S. , Rzaigui Mohamed , Farouk M′henni Mohamed
Published: May 2012

The objective of this paper is the study of the influence of the chemical structures of adsorbent and adsorbate on the adsorption process. By using of crab shell chitosan (CC) and deep‐pink shrimp chitosan (CP) for removal of acid 183 and AR114 from aqueous solutions, it is shown that CP, which corresponds to the highest molecular weight, is the most efficient adsorbent material. In addition, the best extent of decolorization is obtained for AR 183 that is the smallest molecule. Langmuir model represents the best fit of the experimental data, indicating monolayer coverage of chitosan outer surface. Pseudo‐second order kinetic model describes accurately the adsorption processes, suggesting chemical rate limiting steps. The positive values of the enthalpy changes indicated endothermic attachment of dyes to the biomaterials. CP/AR183 system corresponds to the most energetically favorable phenomenon. Besides, desorption of AR from chitosan was found to be very low in acidic aqueous medium for all couples.
Influence of Air Annealing and Gamma Ray Irradiation on the Optical Properties of Cl16FePc Thin Films
Authors: Koshy Raji , Menon C. S.
Published: May 2012

Metal phthalocyanines are one of the most promising candidates to be used in the fabrication of such devices. Among various phthalocyanines, Iron Hexadecachloro Phthalocyanine (Cl16FePc) has received less attention. Basic characteristics of Cl16FePc are not reported in literature. Hexadecacholoro phthalocyanines have attracted interest as possible n‐type organic semiconductor with high electron mobility and good stability characteristics. In the present work we investigate the optical band gap of the Cl16FePc thin films from the optical absorption spectrum as a function of air annealing temperatures and their suitability for the fabrication of molecular electronic devices. Some optical properties of the samples were studied as a function of γ‐radiation doses also. Optical transition is found to be of direct type and optical band gaps are determined by analyzing the absorption spectrum. Vacuum sublimed thin films of Iron hexadecachloro phthalocyanine were prepared at room temperature onto glass substrates at a base pressure of 10-5 Torr on precleaned glass substrates using Hind Hivac 12A4 coating plant. The optical energy band gap Eg were calculated. The mechanism of optical absorption follow the rule of direct transition. In the present paper we also report refractive index, real and imaginary parts of optical dielectric constant etc. from the reflectance measurements.
Synthesis and Evaluation of Some Coumarin Containing Potential Antimicrobial Agents
Authors: Kudale Sayali D. , Deodhar Meenakshi N.
Published: May 2012

A series of the Schiff’s bases incorporating coumarin and chalcone moeities, 3‐(4‐(4‐(substituted phenyl)prop‐1‐ene‐3‐one) phenylimino) methyl)‐4‐chloro‐2h‐chromen‐2‐one 4(a‐g) were synthesized as potential antimicrobial agents. These compounds were characterized on the basis of their spectral (IR, 1H NMR) data and evaluated for antimicrobial activity in vitro against gram positive and gram negative bacteria and fungi. Compound 4b was found to be most active with an MIC of 20 µg/mL against all the tested organisms.