bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of uncertainties in the geothermal heat flux distribution on the Greenland Ice Sheet: An assessment of existing heat flow models
Authors: Rogozhina I. , Hagedoorn J. M. , Martinec Z. , Fleming K. , Soucek O. , Greve R. , Thomas M.
Published: April 2012

This study analyzes the uncertainties in the models of the Greenland Ice Sheet (GIS) that arise from ill‐constrained geothermal heat flux (GHF) distribution. Within the context of dynamic GIS modeling, we consider the following questions: (i) What is the significance of the differences between the existing GHF models for the GIS modeling studies? (ii) How well does the modeled GIS controlled by the GHF models agree with the observational data? (iii) What are the relative contributions of uncertainties in GHF and climate forcing to the misfit between the observed and modeled present‐day GIS? The results of paleoclimatic simulations suggest that differences in the GHF models have a major effect on the history and resulting present‐day state of the GIS. The ice sheet model controlled by any of these GHF forcings reproduces the observed GIS state to only a limited degree and fails to reproduce either the topography or the low basal temperatures measured in southern Greenland. By contrast, the simulation controlled by a simple spatially uniform GHF forcing results in a considerably better fit with the observations, raising questions about the use of the three GHF models within the framework of GIS modeling. Sensitivity tests reveal that the misfit between the modeled and measured temperatures in central Greenland is mostly due to inaccurate GHF and Wisconsin precipitation forcings. The failure of the ice sheet model in southern Greenland, however, is mainly caused by inaccuracies in the surface temperature forcing and the generally overestimated GHF values suggested by all GHF models.
Catchment mixing processes and travel time distributions
Authors: Botter Gianluca
Published: April 2012

This work focuses on the description and the use of the probability density functions (pdfs) of travel, residence and evapotranspiration times, which are comprehensive descriptors of the fate of rainfall water particles traveling through catchments, and provide key information on hydrologic flowpaths, partitioning of precipitation, circulation and turnover of pollutants. Exploiting some analytical solutions to the transport problem derived by Botter et al. (2011), this paper analyzes the features of travel, residence and evapotranspiration time pdfs resulting from different assumptions on the mixing processes occurring during streamflow formation and plant uptake (namely, complete mixing and translatory flow). The ensuing analytical solutions are analyzed through numerical Monte Carlo simulations of a stochastic model of soil moisture and streamflow dynamics. Travel and residence time pdfs are shown to be time‐variant as they mirror the variability of the relevant hydrological fluxes. In particular, the temporal fluctuations of the mean residence time are shown to reflect rainfall dynamics, whereas the variability of the mean travel time is chiefly driven by streamflow dynamics, with lower frequency and higher amplitude fluctuations. Dry climates enhance the effect of the type of mixing on catchment transport features (e.g., mean travel times and seasonal dynamics of stream concentrations). The implications for the interpretation of tracer experiments are also discussed, showing through specific examples that models disregarding nonstationarity may significantly misestimate travel time pdfs.
Report synthesizes findings from International Polar Year
Authors: Balcerak Ernie
Published: April 2012

The International Polar Year (IPY) 2007–2008 “was an outstanding success,” according to a National Research Council (NRC) report released 3 April. The report, Lessons and Legacies of the International Polar Year 2007–2008, synthesized reports from the thousands of scientists who participated in IPY. IPY was a coordinated international field campaign of observations, research, and analysis. Scientific observing and monitoring infrastructure was expanded, and scientists from more than 60 countries in a wide range of fields, including glaciology, atmospheric science, geoscience, space science, oceanography, biology, ecology, and the social sciences, participated in IPY activities.
History of Geophysics Fellowship awarded
Authors: Lee Lauren
Published: April 2012

Inspired by an article in an issue of Eos from April 1970, Gabe Henderson discovered a legacy of correspondence from former AGU president Helmut Landsberg detailing his views in the early days of the climate science debate. Thanks to AGU donors and the creation of a new fellowship by AGU's History of Geophysics Committee, Henderson, a Ph.D. candidate at Michigan State University, is conducting research on Landsberg's papers at the University of Maryland, College Park, continuing his study of the broad history of geophysics and the link between the past and future of climate science. In April 1970, Henderson says, AGU president Helmut Landsberg called for S. Fred Singer to lead a special committee on environmental quality to evaluate the geophysical aspects of environmental problems, dispassionately (H. E. Landsberg,Eos Trans. AGU, 51, 243, doi:10.1029/EO051i004p00243). Because environmental problems were hardly given a second thought at that time, Landsberg's request could have faded from the consciousness of geoscientists and from the pages of history.
AGU selects 2012–2013 Congressional Science Fellows
Authors: Uhlenbrock Kristan
Published: April 2012

AGU has selected Erica Bickford and Kevin Reed as its 2012–2013 Congressional Science Fellows. This term will mark the 35th year that AGU has sponsored fellows to serve in Congress. Bickford and Reed will be part of a cohort comprising more than 30 fellows working on Capitol Hill in the coming year and contributing their scientific knowledge to the policy‐making process. Erica Bickford is working toward finalizing her Ph.D. in environment and resources from the University of Wisconsin this summer.
Kitanidis receives 2011 Hydrologic Sciences Award: Citation
Authors: Dagan Gedeon
Published: April 2012

Peter Kitanidis received the 2011 Hydrologic Sciences Award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. The award is for outstanding contributions to the science of hydrology.
Kitanidis receives 2011 Hydrologic Sciences Award: Response
Authors: Kitanidis Peter
Published: April 2012

Peter Kitanidis received the 2011 Hydrologic Sciences Award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. The award is for outstanding contributions to the science of hydrology.
Tracking a Jurassic reversal of the Earth's magnetic field
Authors: Schultz Colin
Published: April 2012

Roughly 180 million years ago, during the height of the Jurassic period, the Earth's magnetic field flipped, bringing the magnetic north pole once again into the Northern Hemisphere. This so‐called van Zijl reversal, named for the researcher who first described it, is the second‐oldest well‐documented geomagnetic reversal. Such perturbations of the Earth's magnetic field, which tend to take place over about 10,000 years but possibly much less, have been identified as occurring up to several billion years ago and as recently as 780,000 years ago. An open question exists about the effect of such reversals on the properties of the Earth's magnetic field, including the structure it takes, and the consequent effects on its shape, size, and strength.
Declining sea ice to lead to cloudier Arctic
Authors: Balcerak Ernie
Published: April 2012

Arctic sea ice has been declining over the past several decades as global climate has warmed. Moreover, sea ice has declined more quickly than many models predicted, indicating that climate models may not be correctly representing some processes controlling sea ice. One source of uncertainty in models is feedback from cloud cover. Sea ice can affect cloud cover, as melting sea ice and increased evaporation from the ocean surface can lead to increased cloud formation.
A general approach to spontaneous imbibition
Authors: Balcerak Ernie
Published: April 2012

Spontaneous imbibition occurs in a porous medium when, driven by capillary forces, a wetting fluid such as water displaces a nonwetting fluid like oil or air. This is a common phenomenon, relevant to many processes such as groundwater contamination, steam migration in geothermal systems, carbon dioxide sequestration, and oil recovery. Statistical physics indicates how the position of the leading edge of the water scales with time. However, although the phenomenon has been studied for more than 90 years, not even simple questions like the influence of viscosities on spontaneous imbibition were well understood.
The initial stage processes of rocket‐and‐wire triggered lightning as observed by VHF interferometry
Authors: Yoshida S. , Biagi C. J. , Rakov V. A. , Hill J. D. , Stapleton M. V. , Jordan D. M. , Uman M. A. , Morimoto T. , Ushio T. , Kawasaki Z.‐I. , Akita M.
Published: April 2012

We examine VHF interferometric images, channel‐base currents, and broadband electric field waveforms of the initial stage (IS) in two rocket‐and‐wire triggered lightning flashes. Two types of negative leaders, termed “long‐duration” and “short‐duration” leaders, were imaged by the VHF interferometers during the IS of the two flashes. There were three leaders that had relatively long durations of more than a few milliseconds. These three leaders were not accompanied by a significant change of channel‐base current during their early stages of development, indicating that they corresponded to intracloud (IC) discharges that were not connected to the grounded triggered‐lightning channel. Two of these three leaders eventually connected to the triggered‐lightning channel and initiated initial continuous current (ICC) pulses. The third long‐duration leader apparently developed from the vicinity of an isolated negative charge region toward an upper‐level positive charge region and toward a branch of the grounded channel; it served to bridge the positive charge region and the triggered‐lightning channel, resulting in the opposite polarity portion of the bipolar ICC. The short‐duration negative leaders had durations of some hundreds of microseconds. These negative leaders apparently recoiled along the conductive channels created by branches of the upward positive leader (UPL); they initiated ICC pulses when the grounded channel was sufficiently conductive. It follows that ICC pulses can be initiated either by recoil leaders or via interception of separate in‐cloud leaders by a grounded current‐carrying channel.
A comparative study of cellular uptake and cytotoxicity of multi-walled carbon nanotubes, graphene oxide, and nanodiamond
Authors: Zhang Xiaoyong , Hu Wenbing , Li Jing , Tao Lei , Wei Yen
Published: April 2012

Investigations of the interactions between carbon nanomaterials (CNMs) and living organisms and their subsequent biological responses are of fundamental significance for toxicity assessment and further biomedical applications. In this work, the cellular uptake and cytotoxicity of multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO) and nanodiamond (ND) were examined and compared. We demonstrated that all of the CNMs were readily internalized by HeLa cells through nonspecific cellular uptake. Their cell uptake ratios showed significant differences in the following order: ND > MWCNTs > GO. A series of biological assays were used to evaluate the cytotoxicity of CNMs. It was found that CNMs showed dose- and time-dependent cytotoxicity to HeLa cells. However, cytotoxicity of CNMs was not associated with their cell uptake ratios. Among them, ND exhibited the highest cell uptake ratio and the least cytotoxicity. To the best of our knowledge, this is the first study which has quantitatively determined and compared the cell uptake ratios and cytotoxicities of MWCNTs, GO and ND. And we expect that these results described here could provide useful information for the development of new strategies to design efficient drug delivery nanocarriers and therapeutic systems as well as deep insights into the mechanism of CNMs' cytotoxicity.
Induction of plasma acetylcholinesterase activity and apoptosis in mice treated with the organophosphorus toxicant, tri-o-cresyl phosphate
Authors: Jiang Wei , Duysen Ellen G. , Lockridge Oksana
Published: April 2012

Organophosphorus compounds (OP) inhibit acetylcholinesterase (AChE) activity and cause cultured cells to undergo apoptosis. Live mice treated with OP have reduced AChE activity, but after a short recovery period, their AChE activity rebounds to levels that exceed baseline by more than 2-fold. To date no information is available on whether abnormally high AChE activity is characteristic of apoptosis in animals. Our goal was to determine whether induction of AChE activity is associated with apoptosis in live mice. For this purpose we treated mice with 1500 mg kg−1tri-o-cresyl phosphate. On day one after treatment their plasma AChE activity was inhibited by 50%. On day 4, plasma AChE activity rebounded to a level 2.2-fold higher than pretreatment activity and remained elevated for about two months. On day 4, AChE activity in the lung was 1.5-fold higher than in controls. Cells in lung sections that were positive in the apoptosis TUNEL assay, stained heavily for AChE activity. In conclusion, AChE activity and apoptosis are induced in mice treated with tri-o-cresyl phosphate. Unusually high AChE activity may be a marker of exposure to apoptosis-inducing substances.
EBV up‐regulates cytochrome c through VDAC1 regulations and decreases the release of cytoplasmic Ca2+ in the NPC cell line
Authors: Feng Xuesong , Ching Chi Bun , Chen Wei Ning
Published: April 2012

EBV (Epstein—Barr virus) is considered to be a major factor that causes NPC (nasopharyngeal carcinoma), which is one of the sneakiest cancers frequently occurring in Southeast Asia and Southern China. Apoptosis and pro‐apoptotic signals have been studied for decades; however, few have extended the prevailing view of EBV to its impact on NPC in perspective of apoptosis. One of the important proteins named VDAC1 (voltage‐dependent anion protein 1) on the mitochondrial outer membrane controls the pro‐apoptotic signals in mammalian cells. The impact of EBV infection on VDAC1 and related apoptotic signals remains unclear. In order to study the VDAC1′s role in EBV‐infected NPC cells, we employ siRNA (small interfering RNA) inhibition to analyse the release of Ca2+ and Cyto c (cytochrome c) signals in the cytoplasm, as they are important pro‐apoptotic signals. The results show a decrease of Ca2+ release and up‐regulation of Cyto c with EBV infection. After siRNA transfection, the dysregulation of Cyto c is neutralized, which is evidence that the level of Cyto c release in virus‐infected NPC cells is the as same as that of non‐infected NPC cells. This result indicates that EBV infection changes the cytoplasmic level of Cyto c through regulating VDAC1. In summary, this study reports that EBV changes the release of Ca2+ and Cyto c in the cytoplasm of NPC cells, and that Cyto c changes are mediated by VDAC1 regulation.
Study of second generation, high-temperature superconducting coils: Determination of critical current
Authors: Zhang Min , Kim Jae-Ho , Pamidi Sastry , Chudy Michal , Yuan Weijia , Coombs T. A.
Published: April 2012

This paper presents the modeling of second generation (2 G) high-temperature superconducting (HTS) pancake coils using finite element method. The axial symmetric model can be used to calculate current and magnetic field distribution inside the coil. The anisotropic characteristics of 2 G tapes are included in the model by direct interpolation. The model is validated by comparing to experimental results. We use the model to study critical currents of 2 G coils and find that 100 μV/m is too high a criterion to determine long-term operating current of the coils, because the innermost turns of a coil will, due to the effect of local magnetic field, reach their critical current much earlier than outer turns. Our modeling shows that an average voltage criterion of 20 μV/m over the coil corresponds to the point at which the innermost turns’ electric field exceeds 100 μV/m. So 20 μV/m is suggested to be the critical current criterion of the HTS coil. The influence of background field on the coil critical current is also studied in the paper.
A geometrical correction for the inter- and intra-molecular basis set superposition error in Hartree-Fock and density functional theory calculations for large systems
Authors: Kruse Holger , Grimme Stefan
Published: April 2012

A semi-empirical counterpoise-type correction for basis set superposition error (BSSE) in molecular systems is presented. An atom pair-wise potential corrects for the inter- and intra-molecular BSSE in supermolecular Hartree-Fock (HF) or density functional theory (DFT) calculations. This geometrical counterpoise (gCP) denoted scheme depends only on the molecular geometry, i.e., no input from the electronic wave-function is required and hence is applicable to molecules with ten thousands of atoms. The four necessary parameters have been determined by a fit to standard Boys and Bernadi counterpoise corrections for Hobza's S66×8 set of non-covalently bound complexes (528 data points). The method's target are small basis sets (e.g., minimal, split-valence, 6-31G*), but reliable results are also obtained for larger triple-ζ sets. The intermolecular BSSE is calculated by gCP within a typical error of 10%–30% that proves sufficient in many practical applications. The approach is suggested as a quantitative correction in production work and can also be routinely applied to estimate the magnitude of the BSSE beforehand. The applicability for biomolecules as the primary target is tested for the crambin protein, where gCP removes intramolecular BSSE effectively and yields conformational energies comparable to def2-TZVP basis results. Good mutual agreement is also found with Jensen's ACP(4) scheme, estimating the intramolecular BSSE in the phenylalanine-glycine-phenylalanine tripeptide, for which also a relaxed rotational energy profile is presented. A variety of minimal and double-ζ basis sets combined with gCP and the dispersion corrections DFT-D3 and DFT-NL are successfully benchmarked on the S22 and S66 sets of non-covalent interactions. Outstanding performance with a mean absolute deviation (MAD) of 0.51 kcal/mol (0.38 kcal/mol after D3-refit) is obtained at the gCP-corrected HF-D3/(minimal basis) level for the S66 benchmark. The gCP-corrected B3LYP-D3/6-31G* model chemistry yields MAD=0.68 kcal/mol, which represents a huge improvement over plain B3LYP/6-31G* (MAD=2.3 kcal/mol). Application of gCP-corrected B97-D3 and HF-D3 on a set of large protein-ligand complexes prove the robustness of the method. Analytical gCP gradients make optimizations of large systems feasible with small basis sets, as demonstrated for the inter-ring distances of 9-helicene and most of the complexes in Hobza's S22 test set. The method is implemented in a freely available FORTRAN program obtainable from the author's website.
Adaptive Green-Kubo estimates of transport coefficients from molecular dynamics based on robust error analysis
Authors: Jones Reese E. , Mandadapu Kranthi K.
Published: April 2012

We present a rigorous Green-Kubo methodology for calculating transport coefficients based on on-the-fly estimates of: (a) statistical stationarity of the relevant process, and (b) error in the resulting coefficient. The methodology uses time samples efficiently across an ensemble of parallel replicas to yield accurate estimates, which is particularly useful for estimating the thermal conductivity of semi-conductors near their Debye temperatures where the characteristic decay times of the heat flux correlation functions are large. Employing and extending the error analysis of Zwanzig and Ailawadi [Phys. Rev. 182, 280 (1969)]10.1103/PhysRev.182.280 and Frenkel [in Proceedings of the International School of Physics “Enrico Fermi”, Course LXXV (North-Holland Publishing Company, Amsterdam, 1980)] to the integral of correlation, we are able to provide tight theoretical bounds for the error in the estimate of the transport coefficient. To demonstrate the performance of the method, four test cases of increasing computational cost and complexity are presented: the viscosity of Ar and water, and the thermal conductivity of Si and GaN. In addition to producing accurate estimates of the transport coefficients for these materials, this work demonstrates precise agreement of the computed variances in the estimates of the correlation and the transport coefficient with the extended theory based on the assumption that fluctuations follow a Gaussian process. The proposed algorithm in conjunction with the extended theory enables the calculation of transport coefficients with the Green-Kubo method accurately and efficiently.
Temperature divergence of the dynamics of a poly(vinyl acetate) glass: Dielectric vs. mechanical behaviors
Authors: Zhao Jing , McKenna Gregory B.
Published: April 2012

The dynamics of glass forming liquids as the glass transition temperature (Tg) is traversed has become of special interest because of the continuing question as to whether or not the dynamics diverge towards an ideal glass transition/Kauzmann temperature or if the apparent Vogel-Fulcher-Tammann (VFT) divergence is lost as one goes below the conventional Tg but remains in equilibrium. Here we examine the response of a poly(vinyl acetate) PVAc polymer glass-former using both dielectric and mechanical methods in the vicinity of Tg. Isothermal measurements were performed to study the aging behavior of the PVAc and to assure that the equilibrium state was achieved for temperatures as much as 16 K below the calorimetric Tg. Surprisingly, we found that the mechanical response took much longer to age into its equilibrium than did the dielectric response. Also, the temperature dependence of the time-temperature shift factors obtained from the two methods is different and the dielectric response shows a turnover to an apparent Arrhenius behavior rather than a continuation of the VFT extrapolated divergence at the lowest temperatures tested.
Nonlinear effects in transient electrothermal characterization of anatase TiO2 nanowires
Authors: Feng Xuhui , Huang Xiaopeng , Wang Xinwei
Published: April 2012

As an effective transient thermal characterization technique, the transient electrothermal (TET) technique features a capability of measuring micro/nanoscale samples of diverse electrical conducting natures. In this work, single anatase titanium dioxide (TiO2) nanowires fabricated using the electrospinning method are characterized using the TET technique. Time-dependent nonlinear effect is observed for both rise and fall stages in the voltage-time (U-t) response profile. The coated iridium film and soldered platinum pads possibly compromise the linear Ohmic effect and introduce undesired effects into the whole system. Two quantitative methods: generalized function analysis and direct capacitance derivation, are developed to suppress the nonlinear effect based on U-t profiles. Data processing is performed to determine the thermal diffusivity using global fitting under non-constant electrical heating. The effective thermal diffusivities from modified analysis processes stay in the range from 2 to 6 × 10−6 m2/s. The results from both methods agree well with each other. The general function analysis method is also applicable for samples of short time thermal transport or for an experimental instrument that has relatively long rise time.
Deoxycholate induced tetramer of αA-crystallin and sites of phosphorylation: Fluorescence correlation spectroscopy and femtosecond solvation dynamics
Authors: Chowdhury Aritra , Mojumdar Supratik Sen , Choudhury Aparajita , Banerjee Rajat , Das Kali Pada , Sasmal Dibyendu Kumar , Bhattacharyya Kankan
Published: April 2012

Structure and dynamics of acrylodan labeled αA-crystallin tetramer formed in the presence of a bile salt (sodium deoxycholate, NaDC) has been studied using fluorescence correlation spectroscopy (FCS) and femtosecond up-conversion techniques. Using FCS it is shown that, the diffusion constant (Dt) of the αA-crystallin oligomer (mass ∼800 kDa) increases from ∼35 μm2 s−1 to ∼68 μm2 s−1. This corresponds to a decrease in hydrodynamic radius (rh) from ∼6.9 nm to ∼3.3 nm. This corresponds to about 10-fold decrease in molecular mass to ∼80 kDa and suggests formation of a tetramer (since mass of αA-crystallin monomer is ∼20 kDa). The steady state emission maximum and average solvation time (〈τs〉) of acrylodan labeled at cysteine 131 position of αA-crystallin is markedly affected on addition of NaDC, while the tryptophan (trp-9) becomes more exposed. This suggests that NaDC binds near the cys-131 and makes the terminal region of αA-crystallin exposed. This may explain the enhanced auto-phosphorylation activity of αA-crystallin near the terminus of the 173 amino acid protein (e.g., at the threonine 13, serine 45, or serine 169 and 172) and suggests that phosphorylation at ser-122 (close to cys-131) is relatively less important.
Mechanism of contact resistance formation in ohmic contacts with high dislocation density
Authors: Sachenko A. V. , Belyaev A. E. , Boltovets N. S. , Konakova R. V. , Kudryk Ya. Ya. , Novitskii S. V. , Sheremet V. N. , Li J. , Vitusevich S. A.
Published: April 2012

A new mechanism of contact resistance formation in ohmic contacts with high dislocation density is proposed. Its specific feature is the appearance of a characteristic region where the contact resistance increases with temperature. According to the mechanism revealed, the current flowing through the metal shunts associated with dislocations is determined by electron diffusion. It is shown that current flows through the semiconductor near-surface regions where electrons accumulate. A feature of the mechanism is the realization of ohmic contact irrespective of the relation between the contact and bulk resistances. The theory is proved for contacts formed to III-V semiconductor materials as well as silicon-based materials. A reasonable agreement between theory and experimental results is obtained.
The electronic properties of a core/shell/well/shell spherical quantum dot with and without a hydrogenic impurity
Authors: Taş Hatice , Şahin Mehmet
Published: April 2012

In this study, we have performed a detailed investigation of the electronic properties of a core/shell/well/shell multilayered spherical quantum dot, such as energy eigenvalues, wave functions, electron probability distribution, and binding energies. The energy eigenvalues and their wave functions of the considered structure have been calculated for cases with and without an on-center impurity. For this purpose, the Schrödinger equation has been numerically solved by using the shooting method in the effective mass approximation for a finite confining potential. The electronic properties have been examined for different core radii, barrier thicknesses, and well widths in a certain potential. The results have been analyzed in detail as a function of the layer thicknesses and their physical reasons have been interpreted. It has been found that the electronic properties are strongly dependent on the layer thicknesses.
Delayed mechanical failure of the under-bump interconnects by bump shearing
Authors: Li Han , Shaw Thomas M. , Liu Xiao-Hu , Bonilla Griselda
Published: April 2012

Packaging-induced stresses can cause mechanical failures of various forms in the Cu/low-k interconnects. Here we report a time-dependent failure mode of the interconnects underneath the copper pillar bump. Delayed catastrophic fracture is observed in the interconnect dielectrics when a sustained shear load is applied on the bump using a single bump shear setup. The time to failure is found to be highly sensitive to the load level and temperature, but not to the environmental humidity. However, moisture diffusion through intentionally broken moisture seal can accelerate the failure process. Quantitative analysis suggests the delayed failure can be well captured over a wide range of testing conditions by a model based on subcritical crack growth in the interconnect dielectrics.
Low temperature anomalous field effect in SrxBa1-xNb2O6 uniaxial relaxor ferroelectric seen via acoustic emission
Authors: Dul’kin E. , Kojima S. , Roth M.
Published: April 2012

Sr0.75Ba0.25Nb2O6 [100]-oriented uniaxial tungsten bronze relaxor crystals have been studied by means of dedicated acoustic emission during their thermal cycling in 150–300 K temperature range under dc electric field (E). A 1st order transition in a modulated incommensurate tetragonal phase has been successfully detected at Tmi = 198 K on heating and Tmi = 184 K on cooling, respectively. As field E enhances, a thermal hysteresis gradually narrows and vanishes in the critical point at Eth = 0.31 kV/cm, above which a phase transition becomes to 2nd order. The Tmi(E) dependence looks as a V-shape dip, not similar that previously has been looked as a smeared minimum between both the two polar and nonpolar tetragonal phases near Tm = 220 ÷ 230 K in the same crystals (Dul’kin et al., J Appl. Phys. 110, 044106 (2011)). Due to such a V-shape dip is characteristic for Pb-based multiaxial perovskite relaxor, a rhombohedral phase is waited to be induced by a field E in the critical point temperature range. The emergence of this rhombohedral phase as a crucial evidence of an orthorhombic phase presumably existing within the modulated incommensurate tetragonal phase in tungsten bronze SrxBa1−xNb2O6 relaxor is discussed.
Resistive switching behavior in diamond-like carbon films grown by pulsed laser deposition for resistance switching random access memory application
Authors: Peng Pinggang , Xie Dan , Yang Yi , Zang Yongyuan , Gao Xili , Zhou Changjian , Feng Tingting , Tian He , Ren Tianling , Zhang Xiaozhong
Published: April 2012

In this paper, nonvolatile bipolar resistive memory effects were observed in nitrogen doped diamond-like carbon (DLC) thin films prepared by a pulsed laser deposition technique. It is observed that the fabricated Pt/Ti/DLC/Pt structure exhibits good memory performances with an ON/OFF ratio >10, data retention time >104 s, and low operation voltage (<1.5 V). The current mechanism is fitted by Ohmic and space charge limited conduction laws in low resistance state and high resistance state scenarios. The formation/rupture of metal filaments is due to the diffusion of the titanium ions.
Effect of oxygen partial pressure and Fe doping on growth and properties of metallic and insulating molybdenum oxide thin films
Authors: Tiwari Shailja , Master Ridhi , Choudhary R. J. , Phase D. M. , Ahuja B. L.
Published: April 2012

We report the effect of oxygen partial pressure (OPP) and 5% Fe doping on the structural, electrical, and magnetic properties of MoOx thin films on c-Al2O3 substrate prepared by pulsed laser deposition technique. Detailed analyses of the structural properties suggest that the grown phase of molybdenum oxides and its orientation strongly depend on the OPP as well as Fe doping. Undoped and Fe doped α-MoO3 films formed at 350 mTorr OPP value show insulating character, where as MoO2 films formed at lower OPP values reveal metallic behavior. Resistivity minima are observed in Fe doped MoO2 films, which could be due to weak localization effect or Kondo scattering of the conduction electrons from the Fe impurities. Interestingly, all the Fe doped molybdenum oxide films show magnetic hysteresis at room temperature irrespective of their insulating (MoO3 phase) or metallic (MoO2 phase) behavior.
Measurement of an inverse Compton scattering source local spectrum using k-edge filters
Authors: Golosio Bruno , Endrizzi Marco , Oliva Piernicola , Delogu Pasquale , Carpinelli Massimo , Pogorelsky Igor , Yakimenko Vitaly
Published: April 2012

X-ray sources based on the inverse Compton scattering process are attracting a growing interest among scientists, due to their extremely fast pulse, quasi-monochromatic spectrum, and relatively high intensity. The energy spectrum of the x-ray beam produced by inverse Compton scattering sources in a fixed observation direction is a quasi-monochromatic approximately Gaussian distribution. The mean value of this distribution varies with the scattering polar angle between the electron beam direction and the x-ray beam observation direction. Previous works reported experimental measurements of the mean energy as a function of the polar angle. This work introduces a method for the measurement of the whole local energy spectrum (i.e., the spectrum in a fixed observation direction) of the x-ray beam yielded by inverse Compton scattering sources, based on a k-edge filtering technique.
Complete parameterization of the dielectric function of microcrystalline silicon fabricated by plasma-enhanced chemical vapor deposition
Authors: Yuguchi Tetsuya , Kanie Yosuke , Matsuki Nobuyuki , Fujiwara Hiroyuki
Published: April 2012

The dielectric functions of microcrystalline silicon (μc-Si:H) layers deposited by plasma-enhanced chemical vapor deposition have been determined by applying real-time spectroscopic ellipsometry (SE) in an attempt to construct an optical database for μc-Si:H. The μc-Si:H dielectric functions have been parameterized completely by a dielectric function model that employs two Tauc-Lorentz peaks combined with one Harmonic oscillator peak. This parameterization scheme has been applied successfully to describe the structural variation from hydrogenated amorphous silicon (a-Si:H) to highly crystallized μc-Si:H. Moreover, to express the microstructure of μc-Si:H, the μc-Si:H structural factor κ has been defined based on the amplitude of the E2 optical transition with a critical point energy of 4.3 eV. From the value of κ, a variety of Si microstructures, including complete a-Si:H phase (κ = 0), μc-Si:H with a-Si:H-rich grain boundaries (κ ∼ 0.5), and μc-Si:H with void-rich grain boundaries (κ = 1), can be distinguished. The μc-Si:H structures estimated from the above SE analyses show excellent correlation with those deduced from the Raman spectroscopy. From the SE analysis procedure developed in this study, the layer thickness as well as the microstructure of μc-Si:H can be characterized rather easily.
Measurement of turbulent flow upstream and downstream of a circular pipe bend
Authors: Sakakibara Jun , Machida Nobuteru
Published: April 2012

We measured velocity distribution in cross sections of a fully developed turbulent pipe flow upstream and downstream of a 90° bend by synchronizing two sets of a particle image velocimetry (PIV) system. Unsteady undulation of Dean vortices formed downstream from the bend was characterized by the azimuthal position of the stagnation point found on the inner and outer sides of the bend. Linear stochastic estimation was applied to capture the upstream flow field conditioned by the azimuthal location of the stagnation point downstream from the bend. When the inner-side stagnation point stayed below (above) the symmetry plane, the conditional streamwise velocity upstream from the bend exhibited high-speed streaks extended in a quasi-streamwise direction on the outer side of the curvature above (below) the symmetry plane.
Politics is Sublime
Authors: Dikeç Mustafa
Published: April 2012

This paper examines the political aesthetic of Hannah Arendt and Jacques Rancière who in their own ways, found resources in an innovative reading of Kant's Critique of Judgment. The paper explores the Kantian legacy in the political understanding of these two thinkers. It then focuses on Rancière's notion of dissensus and argues that his politics shares the aesthetic features associated with the Kantian sublime.
Natural and human environments in areas undergoing wastewater irrigation.
Authors: Jiménez Cisneros B. E.
Published: April 2012

This paper is a review of the international literature concerning both the positive and negative effects on the environment and public health of the use of treated or non-treated wastewater for agricultural irrigation. It includes not only physical but also social and economic aspects. The extent of the use of treated and non-treated wastewater for agriculture is discussed along with its drivers. The data clearly show that non-treated wastewater is used more commonly than treated wastewater. This occurs mainly in around urban and peri-urban areas where municipal wastewater is produced that is better suited to this practice. The impacts observed on agricultural production, human health, the quality of the irrigation water, groundwater and surface water sources, food security, animal health, the local economy, reduction of poverty and food exports are presented, considering especially developing countries. These factors are further discussed to gain an understanding of how the practice, if well managed, contributes to sustainable development. Barriers to increasing the reuse of wastewater to irrigate are explained, considering the social perception in both developed and developing countries. The importance of reusing wastewater to reclaim water and nutrients are summarized. The positive and negative impacts resulting from the expected increase in the practice are discussed, together with control measures to obtain maximum benefits.
Grasshoppers in agrosystems: pest or food?
Authors: Cerritos R.
Published: April 2012

Each year, a large number of grasshopper species invade agrosystems worldwide, causing major economic losses and damages. Chemical and biological methods are used for controlling the population size of these species; however, the efficiency of these control methods is limited, as they usually lead to an increase in the size of the population, and they also cause drastic ecological damage. The ecological consequences that these control methods have on the environment are large and sometimes irreversible. An ideal alternative method for the control of these species is mechanical capture, where the removal of this biomass of insects can be used as human food, particularly because grasshoppers are edible and have a high nutritional value. This paper suggests a different strategy for the management of endemic pest species, as opposed to introduced pest species. With endemic species, it is necessary to simply reduce the population size; however, introduced species should be completely eliminated from agrosystems. This review discusses the advantages that the management strategy suggested here might have from an ecological, social and economic perspective. The central idea is to view these species as potentially sustainable resources for feeding human populations and not as pests.
A cognitive perspective on mindfulness
Authors: Holas Pawel , Jankowski Tomasz
Published: April 2012

Mindfulness, the core teaching of the Buddhist tradition, has been receiving serious attention from the West in recent decades as evidence of the efficacy of mindfulness‐based interventions for emotional distress have become available. Although traditional Buddhist texts have described the mechanisms of mindfulness and the way to cultivate it in great detail, much is still not known from the perspective of Western science. In particular, there is no general agreement on the conceptualization and operationalization of mindfulness. Several conceptual models of mindfulness (referred to as “state” or “trait”) have been put forward to elucidate different aspects of this phenomenon, but none has gained sufficient empirical validation. This article proposes a new cognitive model of mindfulness. It has been our goal to describe and interrelate a relatively comprehensive group of determinants of a state of mindfulness, the consequences of its regular practicing, the mechanisms responsible for its beneficial effects, and the feedback mechanisms operating between the various constituents of the model. Within this model, the primary emphasis has been placed on understanding the cognitive processes shaping a state of mindfulness (i.e., the links between consciousness, meta‐awareness and the unconscious), and on their determinants (i.e., the executive functions of attention and the components of working memory). A metacognitive system promoting mindfulness, as well as the general capability of the central executive system, is suggested as a factor explaining individual differences in mindfulness, whereas decentering, self‐compassion, and reduction of self‐focused attention are proposed as mechanisms mediating beneficial changes. We hope that the model presented will encourage further discussion and orient future studies in the area of mindfulness.
Unsupervised category learning with integral-dimension stimuli
Authors: Ell Shawn W. , Ashby F.Gregory , Hutchinson Steven
Published: April 2012

Despite the recent surge in research on unsupervised category learning, the majority of studies have focused on unconstrained tasks in which no instructions are provided about the underlying category structure. Relatively little research has focused on constrained tasks in which the goal is to learn predefined stimulus clusters in the absence of feedback. The few studies that have addressed this issue have focused almost exclusively on stimuli for which it is relatively easy to attend selectively to the component dimensions (i.e., separable dimensions). In the present study, we investigated the ability of participants to learn categories constructed from stimuli for which it is difficult, if not impossible, to attend selectively to the component dimensions (i.e., integral dimensions). The experiments demonstrate that individuals are capable of learning categories constructed from the integral dimensions of brightness and saturation, but this ability is generally limited to category structures requiring selective attention to brightness. As might be expected with integral dimensions, participants were often able to integrate brightness and saturation information in the absence of feedback—an ability not observed in previous studies with separable dimensions. Even so, there was a bias to weight brightness more heavily than saturation in the categorization process, suggesting a weak form of selective attention to brightness. These data present an important challenge for the development of models of unsupervised category learning.
Yoshinori Ohsumi: Autophagy from beginning to end
Authors: Sedwick Caitlin
Published: April 2012

Ohsumi's work continues to provide much of the foundation for our current understanding of autophagy.
The dynamin-like GTPase Sey1p mediates homotypic ER fusion in S. cerevisiae
Authors: Anwar Kamran , Klemm Robin W. , Condon Amanda , Severin Katharina N. , Zhang Miao , Ghirlando Rodolfo , Hu Junjie , Rapoport Tom A. , Prinz William A.
Published: April 2012

The endoplasmic reticulum (ER) forms a network of tubules and sheets that requires homotypic membrane fusion to be maintained. In metazoans, this process is mediated by dynamin-like guanosine triphosphatases (GTPases) called atlastins (ATLs), which are also required to maintain ER morphology. Previous work suggested that the dynamin-like GTPase Sey1p was needed to maintain ER morphology in Saccharomyces cerevisiae. In this paper, we demonstrate that Sey1p, like ATLs, mediates homotypic ER fusion. The absence of Sey1p resulted in the ER undergoing delayed fusion in vivo and proteoliposomes containing purified Sey1p fused in a GTP-dependent manner in vitro. Sey1p could be partially replaced by ATL1 in vivo. Like ATL1, Sey1p underwent GTP-dependent dimerization. We found that the residual ER–ER fusion that occurred in cells lacking Sey1p required the ER SNARE Ufe1p. Collectively, our results show that Sey1p and its homologues function analogously to ATLs in mediating ER fusion. They also indicate that S. cerevisiae has an alternative fusion mechanism that requires ER SNAREs.
Modeling History Dependence in Network-Behavior Coevolution
Authors: Franzese Robert J. , Hays Jude C. , Kachi Aya
Published: April 2012

Spatial interdependence—the dependence of outcomes in some units on those in others—is substantively and theoretically ubiquitous and central across the social sciences. Spatial association is also omnipresent empirically. However, spatial association may arise from three importantly distinct processes:common exposureof actors to exogenous external and internal stimuli, interdependence of outcomes/behaviors across actors (contagion), and/or the putative outcomes may affect the dimensions along which the clustering occurs (selection). Accurate inference about any of these processes generally requires an empirical strategy that addresses all three well. From a spatial-econometric perspective, this suggests spatiotemporal empirical models with exogenous covariates (common exposure) and spatial lags (contagion), with the spatial weights being endogenous (selection). From a longitudinal network-analytic perspective, the same three processes are identified as potential sources of network effects and network formation. From that perspective, actors' self-selection into networks (by, e.g., behavioralhomophily) and actors' behavior that is contagious through those network connections likewise demands theoretical and empirical models in which networks and behaviorcoevolveover time. This paper begins building such models by, on theoretical side, extending a Markov type-interaction model to allow endogenous tie-formation, and, on empirical side, merging a simplespatial-laglogit model of contagious behavior with a simplep*-logit model of network formation. One interesting consequence of network-behavior coevolution—identically, endogenous patterns of spatial interdependence—emphasized here is how it can produce history-dependent political dynamics, including equilibriumphatand path dependence (Page 2006). The paper concludes with an illustrative application to alliance formation and conflict behavior among the great powers in the first half of the twentieth century.
New Empirical Strategies for the Study of Parliamentary Government Formation
Authors: Glasgow Garrett , Golder Matt , Golder Sona N.
Published: April 2012

In recent years, a consensus has developed that the conditional logit (CL) model is the most appropriate strategy for modeling government choice. In this paper, we reconsider this approach and make three methodological contributions. First, we employ a mixed logit with random coefficients that allows us to take account of unobserved heterogeneity in the government formation process and relax the independence of irrelevant alternatives (IIA) assumption. Second, we demonstrate that the procedure used in the literature to test the IIA assumption is biased against finding IIA violations. An improved testing procedure reveals clear evidence of IIA violations, indicating that the CL model is inappropriate. Third, we move beyond simply presenting the sign and significance of model coefficients, suggesting various strategies for interpreting the substantive influence of variables in models of government choice.
Towards biodegradable wireless implants
Authors: Boutry Clémentine M. , Chandrahalim Hengky , Streit Patrick , Schinhammer Michael , Hänzi Anja C. , Hierold Christofer
Published: April 2012

A new generation of partially or even fully biodegradable implants is emerging. The idea of using temporary devices is to avoid a second surgery to remove the implant after its period of use, thereby improving considerably the patient's comfort and safety. This paper provides a state-of-the-art overview and an experimental section that describes the key technological challenges for making biodegradable devices. The general considerations for the design and synthesis of biodegradable components are illustrated with radiofrequency-driven resistor–inductor–capacitor (
RLC
) resonators made of biodegradable metals (Mg, Mg alloy, Fe, Fe alloys) and biodegradable conductive polymer composites (polycaprolactone–polypyrrole, polylactide–polypyrrole). Two concepts for partially/fully biodegradable wireless implants are discussed, the ultimate goal being to obtain a fully biodegradable sensor for
in vivo
 sensing.