bluuebunny/crossref_metadata_2025 huggingface dataset:
New insights into banded tremor from the 2008–2009 Mount Etna eruption
Authors: Cannata A. , Di Grazia G. , Montalto P. , Ferrari F. , Nunnari G. , Patanè D. , Privitera E.
Published: December 2010

We investigated the banded tremor activity occurring at Mt. Etna volcano between August–October 2008 during the 2008–2009 eruption. The banded tremor occurred in episodes lasting 25–30 min with intervals in between the episodes of about 25 min. Seismic signal analyses showed that the banded tremor was characterized by spectral contents, wavefields, and source locations that differed from the “ordinary” volcanic tremor. The infrasound recordings exhibited an intermittent infrasonic tremor alternating with the banded tremor episodes. Finally, nonlinear analyses suggested that a banded tremor system can be considered chaotic, implying (1) sensitive dependence on initial conditions, suggesting not only that a banded tremor system requires particular conditions to generate but also that slight variations of these conditions are able to greatly change the features of the banded tremor or even to stop it; and (2) long‐term unpredictability, that is, the impossibility to forecast the long‐term evolution of the banded tremor. On the basis of all these results and analogies with geyser models, we suggest a model of banded tremor that invokes alternating recharge‐discharge phases. Banded tremor is due to “perturbations” in shallow aquifers, such as fluid movement and bubble growth or collapse due to hydrothermal boiling, triggered by the heat and hot fluid transfer from the underlying magma bodies. This heat‐fluid transfer also causes an increasing pressure in the aquifer, leading to fluid discharge. During this process, the seismic radiation decreases, and, if the fluid discharge is well coupled with the atmosphere, acoustic signals are generated.
Reduction of iron (III) and humic substances plays a major role in anaerobic respiration in an Arctic peat soil
Authors: Lipson David A. , Jha Mony , Raab Theodore K. , Oechel Walter C.
Published: December 2010

Arctic peat soils contain vast reserves of organic C and are largely anaerobic. However, anaerobic respiration, particularly the role of Fe(III) and humic substances as electron acceptors, is not well understood in such ecosystems. We investigated these processes in a drained thaw lake basin on the Arctic coastal plain near Barrow, Alaska. We measured concentrations of soluble Fe and other potential electron acceptors, described the microbial community, and performed experiments in the laboratory and field to measure net rates of Fe(III) reduction and the relationship of this process to C cycling. In most areas within the basin, aerobic conditions existed only in the upper few centimeters of soil, though oxygen penetrated deeper in raised areas, such as rims of ice wedge polygons. Concentrations of nitrate and sulfate in soil pore water were low or negligible. Soil pore water contained surprisingly high concentrations of Fe(II) and Fe(III), in the range of hundreds ofμM, suggesting the presence of organic chelators. The solid phase contained substantial amounts of iron minerals, with a progressively reduced oxidation state throughout the growing season. The most abundant 16S rRNA sequence in our gene survey was closely related to the Fe(III)‐reducing bacterium,Rhodoferax ferrireducens, and other sequences closely related to Fe‐transforming bacteria were found. Field and laboratory incubations with soluble Fe(III) and the quinonic compound, AQDS (a common humic analog), stimulated respiration and verified that Fe(III) reduction occurs in these soils. We conclude that reduction of Fe(III) and humic substances are major metabolic pathways in this ecosystem.
Mechanism for northward propagation of boreal summer intraseasonal oscillation: Convective momentum transport
Authors: Kang In‐Sik , Kim Daehyun , Kug Jong‐Seong
Published: December 2010

This study demonstrates that the momentum transport by cumulus convection plays a significant role in the organization and northward propagation of intraseasonal (ISO) convection anomalies over the Indian and western Pacific regions during boreal summer. A version of Seoul National University's atmosphere‐ocean coupled general circulation model simulates northward propagation when convective momentum transport (CMT) is implemented; the northward propagation disappears when CMT is disabled. An axially symmetric shallow water model with a parameterized CMT is used to understand the role of CMT in the northward propagation of ISO. The basic mechanism of northward propagation is the lower‐level convergence to the north of convection, which is induced by the secondary meridional circulation associated with large momentum mixing by convection in the region of large mean vertical shear. A large mean vertical shear exists in South Asian region during boreal summer.
Lower crustal variability and the crust/mantle transition at the Atlantis Massif oceanic core complex
Authors: Blackman Donna K. , Collins John A.
Published: December 2010

Seismic refraction data provide new constraints on the structure of the lower oceanic crust and its variability across the Atlantis Massif oceanic core complex, ∼30°N on the Mid‐Atlantic Ridge. A 40 km‐long spreading‐parallel profile constrains P‐wave velocities to depths of up to ∼7 km beneath the seafloor. Two shorter spreading‐perpendicular lines provide coverage to ∼2 km depth. The anomalous character of the massif's central dome crust is clear compared to the neighboring rift valley and similar‐age crust on the opposite ridge flank. The domal core of the massif, unroofed via detachment faulting, has velocities >7.0 km/s at depths below ∼2.5 km sub‐seafloor, increasing to 7.5–7.8 km/s over the depth range 4.8–6.8 km. Within the core complex, the Moho does not appear to be sharp as no PmP arrivals are observed. Within the axial valley, velocities do not reach mantle‐transition zone values in the uppermost 6 km. We infer that crust there is of normal thickness but that a thinner than average mafic section is present in the central massif. Near IODP Hole U1309D, located on the central dome, there is a low velocity gradient interval at 1–3 km depth with velocities of 6.6–6.8 km/s, that coincides with a 3–5 km wide region where shallower velocities are highest. Given the predominantly gabbroic section recovered from the 1.4 km deep drillhole, this seismic structure suggests that the mafic body extends a few km both laterally and vertically.
Lifting potential of solar‐heated aerosol layers
Authors: Boers R. , de Laat A. T. , Stein Zweers D. C. , Dirksen R. J.
Published: December 2010

Absorption of shortwave solar radiation can potentially heat aerosol layers and create buoyancy that can result in the ascent of the aerosol layer over several kilometres altitude within 24–48 hours. Such heating is seasonally dependent with the summer pole region producing the largest lifting in solstice because aerosol layers are exposed to sunshine for close to 24 hours a day. The smaller the Angstrøm parameter, the larger the lifting potential. An important enhancement to lifting is the diffuse illumination of the base of the aerosol layer when it is located above highly reflective cloud layers. It is estimated that aerosol layers residing in the boundary layer with optical properties typical for biomass burning aerosols can reach the extra tropical tropopause within 3–4 day entirely due to diabatic heating as a result of solar shortwave absorption and cross‐latitudinal transport. It is hypothesized that this mechanism can explain the presence and persistence of upper tropospheric/lower stratospheric aerosol layers.
Geomorphological origin of recession curves
Authors: Biswal Basudev , Marani Marco
Published: December 2010

We identify a previously undetected link between the river network morphology and key recession curves properties through a conceptual‐physical model of the drainage process of the riparian unconfined aquifer. We show that the power‐law exponent, α, of −dQ/dt vs. Q curves is related to the power‐law exponent of N(l) vs. G(l) curves (which we show to be connected to Hack's law), where l is the downstream distance from the channel heads, N(l) is the number of channel reaches exactly located at a distance l from their channel head, and G(l) is the total length of the network located at a distance greater or equal to l from channel heads. Using Digital Terrain Models and daily discharge observations from 67 US basins we find that geomorphologic α estimates match well the values obtained from recession curves analyses. Finally, we argue that the link between recession flows and network morphology points to an important role of low‐flow discharges in shaping the channel network.
Venus nightside ionospheric holes
Authors: Hoegy Walter R. , Grebowsky Joseph M.
Published: December 2010

Pioneer Venus Orbiter (PVO) measured the ionosphere and atmosphere of Venus for 13 years 10 months yielding a rich data set of archived data from a complement of instruments. One particularly striking feature seen was the occurrence of deep localized nightside ionization depletions commonly called holes. A number of theories have been put forth to explain their observed characteristics, but there is still no consensus on their source. A possibly related phenomenon in the Venus nightside ionosphere is the occurrence of “disappearing” or severely disturbed ionospheres characterized by deep, widespread plasma depletions in almost the entire nightside. This paper reexamines the holes and “disappearing ionospheres” and other characteristics of the nightside ionosphere during solar maximum using a more extensive database than earlier studies. The hole locations, occurrences, and dependencies on solar wind dynamic pressure (Psw) are analyzed, and a comparison is made with earlier studies. It is shown that there is no Psw threshold for holes to occur and at Psw values greater than ∼9 nPa, hole occurrence decreases while the occurrence of severely disturbed orbits increases, suggesting that holes may evolve into severely disturbed orbits. Other characteristics of the nightside are shown to be influenced by solar wind pressure to varying degrees; for example, the density integrated along the orbit path below the ionopause, and the median density at low altitudes exhibit strong inverse correlation with Psw, while the peak density is nearly independent of Psw.
Inductive electric fields in the inner magnetosphere during geomagnetically active periods
Authors: Ohtani S. , Korth H. , Keika K. , Zheng Y. , Brandt P. C. , Mende S. B.
Published: December 2010

The present study examines the characteristics of electric fields in the nightside inner magnetosphere during geomagnetically active periods. Electric field and magnetic field measurements made by the Cluster spacecraft on their perigee passes are used. The results are summarized as follows: (1) The duskward electric field component EY tends to be larger in the premidnight sector and off the equator, presumably corresponding to the more frequent occurrence of substorms and boundary layer crossings, respectively. (2) The occurrence distribution of EY is biased positively with an average of 0.6–0.8 mV/m, which reflects enhanced convection at active time. (3) The occurrence distribution of EY is also characterized by extending tails with a standard deviation larger than the twice the average. Although the occurrence ratio decreases sharply with increasing magnitude of EY, ∣EY∣ occasionally exceeds 5 mV/m. (4) The sign of EY is well organized by the change of magnetic field. When the local magnetic configuration becomes more dipolar, EY tends to be positive (duskward), whereas it tends to be negative (dawnward) when the configuration becomes more stretched. (5) As for strong electric fields, EY tends to be proportional to the change of the H magnetic component, and from the induction equation, the typical spatial scale of EY is estimated at 4.2 RE. Results 4 and 5 strongly suggests that those strong electric fields are inductive. However, the corresponding process/phenomenon can be different from event to event. It is also suggested that substorm(‐like) processes inside the ring current effectively intensify the ring current.
Global prediction of abyssal hill root‐mean‐square heights from small‐scale altimetric gravity variability
Authors: Goff John A.
Published: December 2010

Abyssal hills, which are pervasive landforms on the seafloor of the Earth's oceans, represent a potential tectonic record of the history of mid‐ocean ridge spreading. However, the most detailed global maps of the seafloor, derived from the satellite altimetry‐based gravity field, cannot be used to deterministically characterize such small‐scale (<10 km) morphology. Nevertheless, the small‐scale variability of the gravity field can be related to the statistical properties of abyssal hill morphology using the upward continuation formulation. In this paper, I construct a global prediction of abyssal hill root‐mean‐square (rms) heights from the small‐scale variability of the altimetric gravity field. The abyssal hill‐related component of the gravity field is derived by first masking distinct features, such as seamounts, mid‐ocean ridges, and continental margins, and then applying a newly designed adaptive directional filter algorithm to remove fracture zone/discontinuity fabric. A noise field is derived empirically by correlating the rms variability of the small‐scale gravity field to the altimetric noise field in regions of very low relief, and the noise variance is subtracted from the small‐scale gravity variance. Suites of synthetically derived, abyssal hill formed gravity fields are generated as a function of water depth, basement rms heights, and sediment thickness and used to predict abyssal hill seafloor rms heights from corrected small‐scale gravity rms height. The resulting global prediction of abyssal hill rms heights is validated qualitatively by comparing against expected variations in abyssal hill morphology and quantitatively by comparing against actual measurements of rms heights. Although there is scatter, the prediction appears unbiased.
Transport of Nordic Seas overflow water into and within the Irminger Sea: An eddy‐resolving simulation and observations
Authors: Xu X. , Schmitz W. J. , Hurlburt H. E. , Hogan P. J. , Chassignet E. P.
Published: December 2010

Results from a climatologically forced, eddy‐resolving (1/12°) Atlantic simulation using the Hybrid Coordinate Ocean Model help clarify some presently unresolved connections between volume transports of Nordic Seas overflow water at key locations in the northernmost North Atlantic Ocean. The model results demonstrate that, in addition to the known westward flow through the Charlie Gibbs Fracture Zone (CGFZ), some Iceland Scotland overflow water (ISOW) flows westward through gaps in the Reykjanes Ridge north of the CGFZ into the Irminger Sea, and some flows southward along the eastern flank of the Mid‐Atlantic Ridge into the West European Basin. These results provide insights into the well‐known inconsistency between observed westward transport of ISOW through the CGFZ (2.4 Sv) and the transports upstream at Southeast of Iceland section (3.2 Sv) and downstream in the western Irminger Sea (4.5 Sv). Although the portion of the simulated ISOW that flows through CGFZ is about 500 m deeper than observed, the model results also show two ISOW pathways of this flow into the Irminger Sea, one northward along the western flank of the Reykjanes Ridge and the other westward before turning north‐eastward on the western side of the Irminger Basin. Comparisons with the long‐term moored instrument database in the Irminger Sea show that the model‐based mean circulation is in reasonable agreement with observed volume transports of overflow water and that it gives approximately correct temperature and salinity characteristics.
Interaction between the East China Sea Kuroshio and the Ryukyu Current as revealed by the self‐organizing map
Authors: Jin Baogang , Wang Guihua , Liu Yonggang , Zhang Ren
Published: December 2010

The self‐organizing map (SOM) is used to study the linkage between the two western boundary currents, the Kuroshio Current and the Ryukyu Current, through the Kerama Gap. Four coherent ocean current patterns, extracted from a numerical model output for the Kerama Gap area, are used to describe the variability of the Kuroshio current axis and the mesoscale eddies in the Ryukyu Current system. The temporal evolution of these four patterns shows a robust cycle with an average period of 120 days. The shift of the Kuroshio current axis is found to be a dominant factor in determining the water exchange in the Kerama Gap, and the eddies associated with the Ryukyu Current are also important in affecting the strength of eddies in the Kerama Gap. The interaction between the Kuroshio Current and the Ryukyu Current through the Kerama Gap as revealed by the SOM provides new insights in understanding the water exchange between the East China Sea and the northwest Pacific.
On the usability of the ERA‐40 reanalysis in the estimation of past surface UV radiation over Europe
Authors: Kaurola J. , Lindfors A. , Lakkala K. , Hansen G. , Josefsson W. , Vuilleumier L. , Feister U. , Slaper H.
Published: December 2010

Erythemal daily UV doses have been calculated using input data from the ERA‐40 reanalysis for years 1958–2002. The quality of input parameters for UV calculations has been validated with available ground based total ozone data and estimates of Cloud Modification Factor (CMF), and the results have been compared with existing UV data. Owing to limited availability of validation data especially during 1960s and 1970s the analysis focused on sites located in central and northern Europe. The current work is the first step in deriving reliable long‐term UV time series from the ERA‐40 reanalysis. Total ozone from the ERA‐40 reanalysis is affected by significant biases, especially before satellite ozone measurements were available for assimilation. Estimations of the effect of clouds on surface UV were made using global radiation (300–3000 nm) budgets at the surface because available ERA‐40 cloud data do not allow good estimates of surface daily UV doses. There are some problems with ERA‐40 solar radiation budgets which cause systematic biases in calculated daily UV doses. Comparison of calculated daily erythemal UV doses against ground‐based UV data indicate that ERA‐40 UV doses are typically overestimated by 6–18% in central and northern Europe and underestimated by 9–17% at Davos, Switzerland. Root‐mean‐square errors of the calculated daily UV doses are usually in the range of 30–40%. Trends of UV doses were calculated for the concurrent period of the TOMS satellite UV data (1979–2002). The trends of zonally averaged ERA‐40 and TOMS UV agree well and are mostly of the same sign and magnitude.
Mixing state of aerosols and direct observation of carbonaceous and marine coatings on African dust by individual particle analysis
Authors: Deboudt Karine , Flament Pascal , Choël Marie , Gloter Alexandre , Sobanska Sophie , Colliex Christian
Published: December 2010

The mixing state of aerosols collected at M'Bour, Senegal, during the Special Observing Period conducted in January–February 2006 (SOP‐0) of the African Monsoon Multidisciplinary Analysis project (AMMA), was studied by individual particle analysis. The sampling location on the Atlantic coast is particularly adapted for studying the mixing state of tropospheric aerosols since it is (1) located on the path of Saharan dust plumes transported westward over the northern tropical Atlantic, (2) influenced by biomass burning events particularly frequent from December to March, and (3) strongly influenced by anthropogenic emissions from polluted African cities. Particle size, morphology, and chemical composition were determined for 12,672 particles using scanning electron microscopy (automated SEM‐EDX). Complementary analyses were performed using transmission electron microscopy combined with electron energy loss spectrometry (TEM‐EELS) and Raman microspectrometry. Mineral dust and carbonaceous and marine compounds were predominantly found externally mixed, i.e., not present together in the same particles. Binary internally mixed particles, i.e., dust/carbonaceous, carbonaceous/marine, and dust/marine mixtures, accounted for a significant fraction of analyzed particles (from 10.5% to 46.5%). Western Sahara was identified as the main source of mineral dust. Two major types of carbonaceous particles were identified: “tar balls” probably coming from biomass burning emissions and soot from anthropogenic emissions. Regarding binary internally mixed particles, marine and carbonaceous compounds generally formed a coating on mineral dust particles. The carbonaceous coating observed at the particle scale on African dust was evidenced by the combined use of elemental and molecular microanalysis techniques, with the identification of an amorphous rather than crystallized carbon structure.
Diurnal variations of upper tropospheric and lower stratospheric winds over Japan as revealed with middle and upper atmosphere radar (34.85°N, 136.10°E) and five reanalysis data sets
Authors: Sakazaki T. , Fujiwara M. , Hashiguchi H.
Published: December 2010

Diurnal variations in the troposphere are a source of the diurnal tides which are the prevalent dynamical phenomenon in the mesosphere and lower thermosphere. They are also discussed as contributing to the excitation of Rossby waves. Here we study diurnal variations of upper tropospheric and lower stratospheric winds (up to 22 km) over Japan from 1986 to 2008 mainly using data from the middle and upper atmosphere (MU) radar (34.85°N, 136.10°E) and JRA25/JCDAS data, as well as other four global reanalysis data sets (ERA40, ERA‐Interim, NCEP1, and NCEP2) and output data from Global Scale Wave Model (GSWM). The diurnal and semidiurnal components are extracted and analyzed. For the diurnal wind component, the MU radar data are used to validate the reanalysis data, and the reanalysis data are chosen for the analysis. The diurnal amplitude monotonically increases with height above 15–20 km. The diurnal phase shows an upward progression up to 15 to 20 km, while above 15 to 20 km, it shows a downward progression in most months. It is found that the diurnal tide, defined as the diurnal component with absolute zonal wave numbers of ≤6, is dominant in the upper troposphere (explaining 60 to 80% of the variance) and in the stratosphere (explaining 80 to 90% of the variance). It is also observed that medium‐scale waves contributed to the diurnal wind component in the upper troposphere from winter to spring (∼20% of the variance). For the semidiurnal wind component, only MU radar data are used for the analysis, which confirmed that the semidiurnal migrating tide is dominant through the troposphere and the lower stratosphere. The semidiurnal tidal amplitude shows a marked seasonal variation in the troposphere; the amplitude is largest in winter (∼0.4 m s−1) and smallest in summer (∼0.2 m s−1).
Loss of the Polycomb group gene polyhomeotic induces non‐autonomous cell overproliferation
Authors: Feng Siqian , Huang Jianhua , Wang Jian
Published: December 2010

Polycomb group (PcG) proteins are conserved epigenetic regulators that are linked to cancer in humans. However, little is known about how they control cell proliferation. Here, we report that mutant clones of the PcG gene polyhomeotic (ph) form unique single‐cell‐layer cavities that secrete three JAK/STAT pathway ligands, which in turn act redundantly to stimulate overproliferation of surrounding wild‐type cells. Notably, different ph alleles cause different phenotypes at the cellular level. Although the ph‐null allele induces non‐autonomous overgrowth, an allele encoding truncated Ph induces both autonomous and non‐autonomous overgrowth. We propose that PcG misregulation promotes tumorigenesis through several cellular mechanisms.
After the fall: The global financial crisis as a test of corporate social responsibility theories
Authors: Kemper Alison , Martin Roger L.
Published: December 2010

In this paper, we look at the development of the set of core corporate social responsibility (CSR) theories in response to Friedman's ascendancy. We assess the impact of the current economic collapse on theories built on this dialectical framework. Finally, we suggest where we might find new theoretical underpinnings for the next generation of CSR that can meet the challenges not only of the current financial crisis, but the looming ecological and geopolitical crises.
On the assumed impact of germanium doping on void formation in Czochralski-grown silicon
Authors: Vanhellemont Jan , Zhang Xinpeng , Xu Wubing , Chen Jiahe , Ma Xiangyang , Yang Deren
Published: December 2010

The assumed impact of Ge doping on void formation during Czochralski-growth of silicon single crystals, is studied using scanning infrared microscopy. It has been reported that Ge doping leads to a reduction in the flow pattern defect density and of the crystal originated particle size, both suggesting an effect of Ge on vacancy concentration and void formation during crystal growth. The present study however reveals only a marginal-if any-effect of Ge doping on grown-in single void size and density. Double and multiple void formation might however be suppressed partially by Ge doping leading to the observed decrease in flow pattern defect density. The limited effect of Ge doping on single void formation is in agreement with earlier findings that Ge atoms are only a weak trap for vacancies at higher temperatures and therefor should have a smaller impact on the vacancy thermal equilibrium concentration and on single void nucleation than, e.g., interstitial oxygen and nitrogen.
Widom line and the liquid–liquid critical point for the TIP4P/2005 water model
Authors: Abascal José L. F. , Vega Carlos
Published: December 2010

The Widom line and the liquid–liquid critical point of water in the deeply supercooled region are investigated via computer simulation of the TIP4P/2005 model. The Widom line has been calculated as the locus of compressibility maxima. It is quite close to the experimental homogeneous nucleation line and, in the region studied, it is almost parallel to the curve of temperatures of maximum density at fixed pressure. The critical temperature is determined by examining which isotherm has a region with flat slope. An interpolation in the Widom line gives the rest of the critical parameters. The computed critical parameters are \documentclass[12pt]{minimal}\begin{document}$T_c\!=\!193$\end{document}Tc=193 K, \documentclass[12pt]{minimal}\begin{document}$p_c\!=\!1350$\end{document}pc=1350 bar, and \documentclass[12pt]{minimal}\begin{document}$\rho _c\!=\!1.012$\end{document}ρc=1.012 g/cm \documentclass[12pt]{minimal}\begin{document}$^3$\end{document}3. Given the performance of the model for the anomalous properties of water and for the properties of ice phases, the calculated critical parameters are probably close to those of real water.
Cauchy problem for the Boltzmann-BGK model near a global Maxwellian
Authors: Yun Seok-Bae
Published: December 2010

In this paper, we are interested in the Cauchy problem for the Boltzmann-BGK model for a general class of collision frequencies. We prove that the Boltzmann-BGK model linearized around a global Maxwellian admits a unique global smooth solution if the initial perturbation is sufficiently small in a high order energy norm. We also establish an asymptotic decay estimate and uniform L2-stability for nonlinear perturbations.
Thermoviscoelastic finite element modeling of laser-generated ultrasound in viscoelastic plates
Authors: Sun Hong-xiang , Zhang Shu-yi
Published: December 2010

Laser-generated ultrasound in a thin composite plate with thermoviscoelastic property has been studied quantitatively. According to thermoviscoelastic theory, considering the viscoelastic and thermophysical properties of materials, a numerical model for the laser-generated Lamb waves is established in the frequency domain by using a finite element method. It is confirmed that the temperature and displacement fields calculated in the frequency domain coincide well with those obtained in the time domain. In the numerical simulations of thermoviscoelastically generated Lamb waves, the effects of viscoelastic and elastic stiffness moduli, and the thickness of the materials have been taken into account in details. The characteristics of the Lamb waves in the numerical results agree well with the features of the disperse curves. The results show that the finite element method in this paper provides a useful technique to characterize mechanical properties of composite materials.
Metallic-glass-matrix composite structures with benchmark mechanical performance
Authors: Schramm Joseph P. , Hofmann Douglas C. , Demetriou Marios D. , Johnson William L.
Published: December 2010

Metallic-glass-matrix composites demonstrating unusual combination of high strength, high toughness, and excellent processability are utilized to fabricate cellular structures of egg-box topology. Under compressive loading, the egg-box panels are capable of undergoing extensive plastic collapse at very high plateau stresses enabling absorption of large amounts of mechanical energy. In terms of specific mechanical energy absorbed, the present panels far outperform panels of similar topology made of aluminum or fiber-reinforced polymer composites, and even surpass steel structures of highly buckling-resistant topologies, thus emerging among the highest performance structures of any kind.
Strong influence of packing density in terahertz metamaterials
Authors: Singh Ranjan , Rockstuhl Carsten , Zhang Weili
Published: December 2010

We investigate the response of a terahertz metamaterial depending on the unit cell density. The fundamental inductive capacitive (LC) resonance has its highest quality (Q) factor for a critical period Pc=λ/n, with λ being the LC resonance wavelength and n being the refractive index of the substrate. This occurs due to simultaneous excitation of the lowest order lattice mode that strongly favors radiative coupling in the metamaterial plane. Increasing or decreasing the period from Pc reduces the Q factor. Our results suggest that an optimal package density exists in metamaterials to induce the strongest dispersion.
Giant exchange bias based on magnetic transition in γ-Fe2MnGa melt-spun ribbons
Authors: Tang X. D. , Wang W. H. , Zhu W. , Liu E. K. , Wu G. H. , Meng F. B. , Liu H. Y. , Luo H. Z.
Published: December 2010

Giant exchange bias with a shift up to 3.86 kOe has been observed in γ-Fe2MnGa alloy in which a ferromagnetic to antiferromagnetic transition takes place at 250 K. The transition can be suppressed to lower temperatures by higher magnetic fields at a shift rate of 10.3 K/kOe. Exchange bias and enhanced coercivity occur simultaneously, revealing an exchange coupling between the coexisting antiferromagnetic and ferromagnetic phases. Meanwhile, the internal exchange coupling inside the antiferromagnetic clusters dynamically ensures their unidirectional anisotropy during their size changing following the external magnetic field.
Evidences of oxygen-mediated resistive-switching mechanism in TiN\HfO2\Pt cells
Authors: Goux L. , Czarnecki P. , Chen Y. Y. , Pantisano L. , Wang X. P. , Degraeve R. , Govoreanu B. , Jurczak M. , Wouters D. J. , Altimime L.
Published: December 2010

In this letter, we study the influence of the Pt top-electrode thickness and of the chamber atmosphere during cell operation on the resistive switching of TiN\HfO2\Pt cells. The oxygen permeability of the Pt electrode directly in contact with the atmosphere significantly affects the resistive switching and the resistance states of the cell. The results provide strong experimental indications that the electroforming operation leads to oxygen-vacancy formation and that the subsequent reset operation relies on the available oxygen species in the filament neighborhood. Significant implications with respect to endurance and retention assessment of resistive-switching memory devices are discussed.
Effects of local structural defects on the electron transport in a carbon nanotube between Cu electrodes
Authors: Gao Feng , Qu Jianmin , Yao Matthew
Published: December 2010

Using the first-principles approach with the Landauer formalism, we studied the effects of monovacancy and Stone–Wales defects on the electrical conductance of carbon nanotube (CNT) itself and its junction with copper electrodes. We found that the Stone–Wales defect has almost negligible impact on the electrical performance of the CNT(5,5) and its junction with copper at the Fermi level, while the monovacancy can reduce the electrical conductance of the CNT(5,5) significantly and that of the Cu/CNT(5,5)/Cu junction by more than 30%.
Quantum dot-cavity strong-coupling regime measured through coherent reflection spectroscopy in a very high-Q micropillar
Authors: Loo Vivien , Lanco Loïc , Lemaître Aristide , Sagnes Isabelle , Krebs Olivier , Voisin Paul , Senellart Pascale
Published: December 2010

We report on the coherent reflection spectroscopy of a high-quality factor micropillar, in the strong-coupling regime with a single InGaAs annealed quantum dot. The absolute reflectivity measurement is used to study the characteristics of the device at low and high excitation powers. The strong coupling is obtained with a g=16 μeV coupling strength in a 7.3 μm diameter micropillar, with a cavity spectral width κ=20.5 μeV (Q=65 000). The factor of merit of the strong-coupling regime, 4g/κ=3, is the current state-of-the-art for a quantum dot-micropillar system.
Passivation effects of fluorine and hydrogen at the SiC–SiO2 interface
Authors: Liu Yingdi , Halfmoon Michael R. , Rittenhouse Christine A. , Wang Sanwu
Published: December 2010

High concentrations of defects at the SiC–SiO2 interface significantly reduce the efficiency of the SiC-based microelectronics. Investigations of the defect passivation are thus of great importance. We report first-principles density-functional-theory calculations for the effects of fluorine and hydrogen in passivating the defects at the SiC–SiO2 interface. The calculations show that the isolated point defects involving excessive carbon atoms can be passivated by atomic fluorine and hydrogen, separately or combined. The results further suggest that molecular fluorine may be more effective for the passivation of the interface defects than molecular hydrogen and hydrogen fluoride.
Increasing the coherence time of single electron spins in diamond by high temperature annealing
Authors: Naydenov Boris , Reinhard Friedemann , Lämmle Anke , Richter V. , Kalish Rafi , D’Haenens-Johansson Ulrika F. S. , Newton Mark , Jelezko Fedor , Wrachtrup Jörg
Published: December 2010

Negatively charged nitrogen-vacancy (NV−) centers in diamond produced by ion implantation often show properties different from NVs created during the crystal growth. We observe that NVs created from nitrogen ion implantation at 30–300 keV show much shorter electron spin coherence time T2 as compared to the “natural” NVs and about 20% of them show switching from NV− to NV0. We show that annealing the diamond at T=1200 °C substantially increases T2 and at the same time the fraction of NVs converting from NV− to NV0 is greatly reduced.
Is fruit anatomy involved in variation in fruit starch concentration between Actinidia deliciosa genotypes?
Authors: Nardozza Simona , Hallett Ian C. , McCartney Rosannah , Richardson Annette C. , MacRae Elspeth A. , Costa Guglielmo , Clearwater Michael J.
Published: December 2010

The role of anatomical traits in carbohydrate accumulation was investigated in fruit of Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson (kiwifruit) var. deliciosa by comparing high and low dry matter (DM) accumulating genotypes. DM was shown previously to be correlated with starch concentration in these fruit. Volume proportions of the three fruit tissues (outer pericarp, inner pericarp and central core) did not vary significantly between genotypes or contribute to variation in total fruit DM. The outer pericarp of the kiwifruit berry contains both small and large cells: the size of these cells was not correlated with final fruit size. In high DM genotypes, the relative volume of outer pericarp tissue occupied by small cells (50%) was significantly greater than that in low DM genotypes (43%). Small cells have a higher starch concentration than large cells: the larger proportion of small cells in the outer pericarp of fruit from high DM genotypes accounted for approximately +25% of the measured differences in fruit starch concentration between high and low DM genotypes. We conclude that, although anatomical traits contribute to variation in fruit starch concentration between kiwifruit genotypes, differences in starch content per small cell are important and worthy of further investigation. This is the first time anatomical investigations have been used to examine differences in fruit carbohydrate accumulation in kiwifruit.
A white mutant of Malay apple fruit (Syzygium malaccense) lacks transcript expression and activity for the last enzyme of anthocyanin synthesis, and the normal expression of a MYB transcription factor
Authors: Kotepong Panumas , Ketsa Saichol , van Doorn Wouter G.
Published: December 2010

The fruit skin of the mature Malay apple (Syzygium malaccense (L.) Merr. & L.M. Perry) is initially glossy red, then changes to purple. A mutant having mature fruits with white skin has been identified. The skin of wild-type fruit contained five glucose-based anthocyanins (cyanidin-3-O-glucoside, pelargonidin-3-O-glucoside, peonidin-3-O-glucoside, cyanidin-3,5-O-diglucoside and peonidin-3,5-O-diglucoside). Cyanidin-3-O-glucoside accounted for a large proportion of the total anthocyanin content. The accumulation cyanidin-3-O-glucoside during fruit maturation was correlated with increased activities of phenylalanine ammonia lyase (PAL) and UDPglucose : flavonoid 3-O-glucosyltransferase (UF3GlucT, F3GT). In the wild-type fruit skin, transcripts of seven genes that encode enzymes in the anthocyanin biosynthetic pathway were detected. No anthocyanins were found in the white mutant fruit skin. The skin of the white mutant fruit contained transcripts of all seven genes identified, except F3GT. It also showed no F3GT activity. The data indicate that the lack of anthocyanins in the mutant is due to lack of F3GT expression. In addition, the transcript of a MYB transcription factor, highly homologous to three Arabidopsis MYBs involved in anthocyanin synthesis, was virtually absent in the mutant but very high in the wild-type fruit. It is suggested that the lack of MYB expression is part of the cause of the lack of F3GT expression and anthocyanin synthesis during fruit maturation.
miR398 regulation in rice of the responses to abiotic and biotic stresses depends on CSD1 and CSD2 expression
Authors: Lu Yuzhu , Feng Zhen , Bian Liying , Xie Hong , Liang Jiansheng
Published: December 2010

MiR398 targets two Cu or Zn superoxide dismutases (CSD1 and CSD2) in Arabidopsis thaliana (L.) Heynh. Here we provide evidence that rice (Oryza sativa L.) miR398 mediates responses to abiotic and biotic stresses through regulating the expression of its target genes, Os-CSD1 and Os-CSD2. Rice plants were exposed to various stresses, including high Cu2+, high salinity, high light, methyl viologen, water stress, pathogens and ethylene, and the molecular response was investigated. Rice plants overexpressing Os-miR398 and the miR398-resistant form of Os-CSD2 were also exposed to these stresses. Both abiotic and biotic stresses significantly inhibited Os-miR398 expression and thus stimulated the expression of Os-CSD1 and Os-CSD2. The plant hormone ethylene produced an especially marked response. Transgenic rice lines that overexpressed Os-miR398 had a lower expression of CSD1 and -2 and were more sensitive to environmental stress. Conversely, transgenic rice lines which overexpressed the miR398-resistant form of Os-CSD2 showed more tolerance to high salinity and water stress than non-transgenic rice. We conclude that Os-miR398 regulates the responses of rice to a wide range of environmental stresses and to ethylene, and exerts its role through mediating CSDs expression and cellular ROS levels.
Consumers, crime and the downloading of music
Authors: Rutter Jason
Published: December 2010

Dr Rutter is a Marie Curie Research Fellow at the School for Mass Communication Research, Catholic University of Leuven, where his research is focused primarily on community and the piracy of digital content. He was the inaugural vice‐president of the international Digital Games Research Association (DiGRA).
INSTITUTIONALIZING THE NEW SELF
Authors: Elchardus Mark , De Keere Kobe
Published: December 2010

This paper maps the unequal development of detraditionalization in rich societies. It views detraditionalization as a shift in the mode of social control from reliance on scarcity, belief and ideology, self evident tradition and obedience, to self-control. Self-control is based upon belief in an autonomously choosing subject (individualism) and a set of institutional conditions able to guide the choices of the individuals (such as education, mass media, the world of goods, and therapy). This paper investigates the relationship between detraditionalization and the rise of such an individualist conception of the self. It shows that such a development cannot be understood in terms of individual detraditionalization, i.e., as a shift in personal attitudes, but is related to specific institutional developments, in casu the development of the psi-disciplines and the therapeutization of society. The persistent influence of Protestant tradition on the individualist conception of the self in strongly secularized societies is explained by the same institutional development.
The role of non-thermal transient plasma for enhanced flame ignition in C2H4–air
Authors: Singleton D , Pendleton S J , Gundersen M A
Published: December 2010

Transient plasma ignition, involving short ignition pulses (typically 10–50 ns), has been shown to effectively reduce ignition delays and improve engine performance for a wide range of combustion-driven engines relative to conventional spark ignition. This methodology is therefore potentially useful for many engine applications; however, at present there is limited understanding of the underlying physics. Evidence is presented here for two distinct phases of the plasma-ignition process: an initial non-equilibrium plasma phase, wherein energetic electrons transfer energy into electronically excited species that accelerate reaction rates, and a spatially distributed thermal phase, that produces exothermic fuel oxidation reactions that result in ignition. It is shown that ignition kernels are formed at the ends of the spatially separated streamer channels, at the cathode and/or anode depending on the local electric field strength, and that the temperature in the streamer channel is close to room temperature up to 100 ns after the discharge.
Preparation and optical characterization of novel Ge–Se–Sb/PVA composite films for optical limiting application
Authors: Tintu R , Nampoori V P N , Radhakrishnan P , Thomas Sheenu
Published: December 2010

We report on the nonlinear optical characterization of a new amorphous composite based on Ge28Se60Sb12/PVA. Nonlinear optical characterization of these films was studied by the Z-scan technique using an Nd : YAG laser (532 nm, 7 ns, 10 Hz).The studies show that the material is highly nonlinear. The films show reverse saturable absorption, which makes it useful for optical limiting applications.
InGaAs quantum dot molecules during selective etching using an In droplet mask
Authors: Lee Jihoon , Wang Zhiming , Hirono Yusuke , Kim Eun-Soo , Koo Sang-Mo , Dorogan Vitaliy G , Mazur Yuriy I , Song Sangmin , Park Gamyoung , Salamo Gregory J
Published: December 2010

We investigated the optical transition of InGaAs quantum dot molecules (QDMs) during selective etching of GaAs using In droplets to demonstrate low-density QDMs. During the selective etching, In droplets act as nanoscale masks and only QDMs underneath the droplets survive, by which process low-density QDMs are fabricated. The thickness of selective GaAs etching is systematically varied and a gradual red-shift is observed with the increased etching thickness. The continuing red-shift can be explained by the strain relaxation due to GaAs etching. This technique to achieve low-density QDMs by selective etching using droplets as nanoscale mask is a simple and flexible approach. This study can find applications in single QDM spectroscopy and other spectroscopic techniques.
Anomalous temperature dependence of the current in a metal-oxide-polymer resistive switching diode
Authors: Gomes Henrique L , Rocha Paulo R F , Kiazadeh Asal , De Leeuw Dago M , Meskers Stefan C J
Published: December 2010

Metal-oxide polymer diodes exhibit non-volatile resistive switching. The current–voltage characteristics have been studied as a function of temperature. The low-conductance state follows a thermally activated behaviour. The high-conductance state shows a multistep-like behaviour and below 300 K an enormous positive temperature coefficient. This anomalous behaviour contradicts the widely held view that switching is due to filaments that are formed reversibly by the diffusion of metal atoms. Instead, these findings together with small-signal impedance measurements indicate that creation and annihilation of filaments is controlled by filling of shallow traps localized in the oxide or at the oxide/polymer interface.
Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate
Authors: Naghshara H , Sobhanian S , Khorram S , Sadeghi N
Published: December 2010

In a dc-magnetron discharge with argon feed gas, densities of copper atoms in the ground state Cu(2S1/2) and metastable state Cu*(2D5/2) were measured by the resonance absorption technique, using a commercial hollow cathode lamp as light source. The operating conditions were 0.3–14 µbar argon pressure and 10–200 W magnetron discharge power. The deposition rate of copper in a substrate positioned at 18 cm from the target was also measured with a quartz microbalance. The gas temperature, in the range 300–380 K, was deduced from the emission spectral profile of N2(C 
3Πu − B 
3Πg) 0–0 band at 337 nm when trace of nitrogen was added to the argon feed gas. The isotope-shifts and hyperfine structures of electronic states of Cu have been taken into account to deduce the emission and absorption line profiles, and hence for the determination of atoms' densities from the measured absorption rates. To prevent error in the evaluation of Cu density, attributed to the line profile distortion by auto-absorption inside the lamp, the lamp current was limited to 5 mA. Density of Cu(2S1/2) atoms and deposition rate both increased with the enhanced magnetron discharge power. But at fixed power, the copper density augmented with argon pressure whereas the deposition rate followed the opposite trend. Whatever the gas pressure, the density of Cu*(2D5/2) metastable atoms remained below the detection limit of 1 × 1010 cm−3 for magnetron discharge powers below 50 W and hence increased much more rapidly than the density of Cu(2S1/2) atoms, over passing this later at some discharge power, whose value decreases with increasing argon pressure. This behaviour is believed to result from the enhancement of plasma density with increasing discharge power and argon pressure, which would increase the excitation rate of copper into metastable states. At fixed pressure, the deposition rate followed the same trend as the total density of copper atoms in the ground and metastable states. Two important conclusions of this work are (i) copper atoms sputtered from the target under ion bombardment are almost all in the ground state Cu(2S1/2) and hence in the plasma volume they can be excited into the metastable states; (ii) all atoms in the long-lived ground and metastable states contribute to the deposition of copper layer on the substrate.