bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding Sea‐Level Rise and Variability
Authors: Anderson John
Published: August 2011

The debate about climate change lingers, fueled by the complexity of weather patterns around the Earth. The oceans filter spatial and temporal changes in temperature, yielding an undisputable record of warming and expansion that manifests as accelerated sea level rise. The rate of rise in historical time is nearly 6 times the average rate for the past 4000 years. Documentation of this accelerated rise, discussion of its causes and impacts, and descriptions of the methods used to measure sea level rise are provided in this compilation of 12 papers authored by some of the leading experts in the field. The book reads more like a textbook than an edited volume, a strategy seldom achieved in edited volumes.
Research Spotlight: Did the Laki volcano eruption cause the cold winter of 1783–1784?
Authors: Tretkoff Ernie
Published: August 2011

In June 1783 the Laki volcano in Iceland began to erupt and continued erupting for months, causing a major environmental disaster. The eruption spewed out toxic sulfuric acid aerosols, which spread over northern latitudes and caused thousands of deaths. That summer, there were heat waves, widespread famines, crop failures, and livestock losses. During the following winter, temperatures in Europe were about 2°C below average for the late 1700s; the winter was also one of the most severe of the past 500 years in eastern North America. The Laki eruption has been blamed for the anomalously cold winter of 1783–1784. (Geophysical Research Letters, doi:10.1029/2011GL046696, 2011)
Research Spotlight: The 2010 Russian heat wave was largely predictable
Authors: Schultz Colin
Published: August 2011

From June to August 2010, a stable high‐pressure air mass hung in the sky over western Russia. This episode of “atmospheric blocking” drove up temperatures, causing thousands of deaths and breaking temperature records across the country. Strong heat waves like the one in Russia increase their potential to do damage the longer they persist, putting added stress on populations susceptible to dehydration, reduced air quality, and other heat‐related illnesses. Long durations of consistently high temperatures also increase the likelihood of drought‐driven crop loss and wildfires, both of which devastated the Russian countryside and economy. (Geophysical Research Letters, doi:10.1029/2010GL046557, 2011)
Research Spotlight: Deadly 2010 Russian heat wave not a consequence of climate change
Authors: Schultz Colin
Published: August 2011

Although some people may try to ascribe specific extreme weather events to climate change, global warming cannot be held responsible for recent weather events such as the 2010 Russian heat wave. Using climate simulations and a comparison against historical conditions, Dole et al. assess the influence of greenhouse gases, aerosols, anomalous sea surface temperatures, and other potential climate forcings on the likelihood and magnitude of the 2010 Russian heat wave. The authors suggest that the heat wave—which lasted from late June to mid‐August and was responsible for thousands of deaths, widespread wildfires, and devastating crop loss—fell well within the bounds of natural climate variability. The authors find that none of the tested climate factors showed appreciable ability to predict the extreme temperatures seen throughout the heat wave. Additionally, the researchers' historical analysis revealed that July temperatures, as well as the temperature variability, for the affected region of western Russia showed no significant trend over the past 130 years. They note that the top 10 hottest July days for the region were distributed randomly across the historical period, although global averages do show clustering in the past 2 decades. (Geophysical Research Letters, doi:10.1029/2010GL046582, 2011)
Perspectives on More Than 3 Decades of the Voyager Mission
Authors: Showstack Randy
Published: August 2011

Voyager 1 and Voyager 2, twin NASA probes that were launched from Cape Canaveral, Fla., in the summer of 1977 during a once‐every‐175‐year alignment of the solar system's giant outer planets, changed our understanding about those planets—Jupiter, Saturn, Uranus, and Neptune—as well as the 4 dozen moons the spacecraft have flown by and the shape of the solar system itself. Today these 722‐kilogram probes, whose instruments mostly are still operating after almost 34 years in space, are helping to rewrite the textbooks about the outer edge of our solar system as they continue to race outward from Earth. Voyager 1, currently 17.4 billion kilometers from Earth, and Voyager 2, 14.2 billion kilometers from Earth, are on their way to becoming the first human‐made objects to leave the solar system and enter interstellar space, the medium between stars. In exclusive interviews with Eos and during a 27 April news briefing at NASA headquarters in Washington, D. C., Voyager project scientist Ed Stone and several others who have worked on the project discussed mission highlights and the probes' journeys through the heliosheath. This is the final outer layer of a kind of bubble the Sun creates around itself called the heliosphere, a margin where the solar wind is slowed by the pressure of interstellar gas. All the while, the spacecraft, still responsive to ground commands, are sending back data about the solar wind, the magnetic field carried out by the wind, charged particles, and plasma waves.
Improving Hydrology in Land Ice Models
Authors: Price Stephen , Flowers Gwenn , Schoof Christian
Published: August 2011

Community Earth System Model Land Ice Working Group Meeting; Boulder, Colorado, 13 January 2011; Recent observations indicate that mass loss from glaciers and ice sheets (“land ice”) is increasing. The drivers of these changes are not well understood, and modeling the land ice response to them remains challenging. As a result, the Intergovernmental Panel on Climate Change explicitly avoided speculating on 21st‐century sea level rise from ice dynamical processes in its fourth assessment report. The mismatch between observations of land ice change and model skill at mimicking those changes is behind recent efforts to develop next‐generation land ice models. Necessary improvements to existing models include improved dynamics, coupling to climate models, and better representations of important boundary conditions and physical processes. Basal sliding, the primary control on the rate of land ice delivery to the oceans, is one such boundary condition that is largely controlled by land ice hydrology.
AGU Selects Two Congressional Science Fellows
Authors: Caves Jeremy K.
Published: August 2011

AGU will sponsor Rebecca French and Ian Lloyd as Congressional Science Fellows for the 2011–2012 term. French and Lloyd will each work for a year in the office of a senator, representative, or congressional committee, and they will join 30 other Fellows selected by other scientific societies to contribute their scientific knowledge to the policy‐making process. French and Lloyd were selected in March by a panel of AGU members who have served as past Congressional Science Fellows after a competitive review process. Their term will mark the 34th year that AGU has sponsored a Fellow and the second year that AGU has sponsored two Fellows concurrently.
Essentials of Paleomagnetism
Authors: Acton Gary
Published: August 2011

This book lives up to its title and does so in a manner that authors of modern science textbooks should seek to emulate. The book is produced as an affordable paperback and an even more affordable e‐book. It contains 16 chapters, several appendices, and more than 250 high‐quality illustrations. As a bonus, a considerable amount of related material that parallels the book is made freely available from the author's Web site (http://magician.ucsd.edu/~ltauxe), including the companion PmagPy software package, which is used throughout the book for hands‐on problem solving.
Steric sea level variations over 2004–2010 as a function of region and depth: Inference on the mass component variability in the North Atlantic Ocean
Authors: Llovel W. , Meyssignac B. , Cazenave A.
Published: August 2011

We investigate the regional‐ocean depth layer (down to 2000 m) contributions to global mean steric sea level from January 2004 to March 2010, using Argo‐based ocean temperature and salinity data from the SCRIPPS Oceanographic Institution database. We find that Indian ocean warming is almost compensated by Atlantic ocean cooling, so that the total global mean steric sea level increases only slightly over the considered period (0.35 ± 0.30 mm/yr). Salinity variations also contribute, at lower rate, to the observed steric compensation. Meanwhile, the Pacific steric sea level increases only slightly (0.35 ± 0.25 mm/yr). In the North Atlantic region, the mass component (estimated by the difference between satellite altimetry‐based minus steric sea level over the same area) is negatively correlated over 2004–2010 with the steric component. During that period, North Atlantic sea level variability seems mostly driven by the North Atlantic Oscillation (NAO). This is unlike during the previous years (1997 to 2004), a period during which we observe significant correlation between North Atlantic sea level and El Nino‐Southern Oscillation (ENSO), with positive sea level corresponding to ENSO cold phases (La Nina).
Past land use decisions have increased mitigation potential of reforestation
Authors: Pongratz J. , Reick C. H. , Raddatz T. , Caldeira K. , Claussen M.
Published: August 2011

Anthropogenic land cover change (ALCC) influences global mean temperatures via counteracting effects: CO2 emissions contribute to global warming, while biogeophysical effects, in particular the increase in surface albedo, often impose a cooling influence. Previous studies of idealized, large‐scale deforestation found that albedo cooling dominates over CO2 warming in boreal regions, indicating that boreal reforestation is not an effective mitigation tool. Here we show the importance of past land use decisions in influencing the mitigation potential of reforestation on these lands. In our simulations, CO2 warming dominates over albedo cooling because past land use decisions resulted in the use of the most productive land with larger carbon stocks and less snow than on average. As a result past land use decisions extended CO2 dominance to most agriculturally important regions in the world, suggesting that in most places reversion of past land cover change could contribute to climate change mitigation. While the relative magnitude of CO2 and albedo effects remains uncertain, the historical land use pattern is found to be biased towards stronger CO2 and weaker albedo effects as compared to idealized large‐scale deforestation.
Those Who Were Born Poor: A Qualitative Study of Philippine Poverty
Authors: Tuason Ma. Teresa G.
Published: August 2011

This qualitative study investigated the psychological experience of poverty among 2 groups of Filipinos who were interviewed about the effects of being raised poor, 12 who became rich, and 13 who remained poor. Using constructivist and critical theories as research paradigms and grounded theory as methodology, the results of the study illustrated perceived causes, coping mechanisms, and cultural factors. Surprisingly, both groups were very similar in their experiences of not having basic needs met, of negative emotions, and of generally attributing their poverty to familial circumstances. The ways of coping with poverty, such as receiving and giving assistance and imploring God for help, and the cultural features of perseverance ( pagpupunyagi) and reliance on others ( pakikipagkapwa) were similarly influential in both groups. Because the main difference between both groups is the occurrence of chance events that provided access to education and opportunities to emigrate for those who have become rich, the oppressive structures of a society that perpetuate poverty are discussed. In developing countries such as the Philippines, the psychological experience of poverty is characterized by the impossibility of upward mobility.
A Linked Data Approach to Help Identify Therapeutic Targets for Cancer
Authors: Deus Helena
Published: August 2011

Cancer is still one of the leading causes of death in the developed world. To address this problem, the US National Institutes of Health (NIH) has launched The Cancer Genome Atlas (TCGA), a large scale systematic approach to characterize tumor samples from 20 cancer types and approximately 10,000 donor patients by using multiple high-throughput approaches.Multidisciplinary projects such as TCGA and related projects across Europe aim at identifying cancer “driver” mutations to be used as therapeutic targets or diagnostic tests. Extracting and aggregating the knowledge necessary to identify such mutations remains a challenge primarily due to the need to reliably integrate the experimental datasets with heterogeneous, distributed biomedical data sources, including public databases, biomedical literature and controlled access clinical information.Linked Data is a set of best practices to integrate and link data with those characteristics. We present here a method to easily integrate and enrich high-throughput experiment results such as those generated by TCGA, with public biomedical data sources such as Diseasome, DrugBank or KEGG, available in Linked Data formats.
Investigation on the characteristics of stress-induced hump in amorphous oxide thin film transistors
Authors: Kim Jang Hyun , Kwon Dae Woong , Chang Ji Soo , Kim Sang Wan , Park Jae Chul , Kim Chang Jung , Park Byung-Gook
Published: August 2011

In this study, we investigate the instability of amorphous oxide thin film transistors using hafnium-indium-zinc oxide under simultaneous application of light and gate dc-bias. The hump characteristics are observed after negative gate bias and light stress. Based on the positive bias-induced recovery, it is proved that photo-generated holes are trapped in the gate insulator by the electrical field enhanced by the optical energy. Moreover, from simulated electric field distribution, it is clearly revealed that the hole-trapping is localized at the edge regions of the gate insulator along channel width/length directions by electric field crowding, resulting in the hump occurrence.
Evaluation of possible mechanisms behind P gettering of iron
Authors: Syre M. , Karazhanov S. , Olaisen B. R. , Holt A. , Svensson B. G.
Published: August 2011

Several possible mechanisms for phosphorus diffusion gettering (PDG) in silicon (Si) are evaluated. Float Zone (FZ) monocrystalline Si samples were intentionally contaminated with iron by ion implantation followed by a 1 h anneal at 900 °C to achieve a homogeneous iron distribution. Phosphorus gettering was then performed at different combinations of time and temperature. Depth-versus-concentration profiles of Fe, P, and O were measured by SIMS. The depth interval of Fe accumulation was found to be independent of the extension of the P profiles, unlike predictions from modeling of FexPy complex formation. The capture capability of P does not play an important role in PDG, still decreasing the P concentration below 6% in the surface source cause poor gettering efficiency. Hence accumulation of Fe close to the surface hinges on the presence of P, which is likely to be due to generation of vacancies during in-diffusion of high concentrations of P. The vacancies cause localized precipitation of oxygen in the highly P doped region. These oxygen precipitates act as gettering centers for Fe, as substantiated by a close correlation between the measured depth profiles of O and Fe after PDG. Our results suggest that interactions between oxygen, vacancies and metal impurities are the most crucial factors in PDG.
Analysis of untreated cross sections of Cu(In,Ga)Se2 thin-film solar cells with varying Ga content using Kelvin probe force microscopy
Authors: Zhang Zhenhao , Tang Xiaochen , Lemmer Uli , Witte Wolfram , Kiowski Oliver , Powalla Michael , Hölscher Hendrik
Published: August 2011

The potential distribution of the Cu(In,Ga)Se2/CdS/ZnO layer structure on untreated cross sections of Cu(In,Ga)Se2 thin-film solar cells are analyzed by Kelvin probe force microscopy under ambient conditions. The potential differences between the Cu(In,Ga)Se2 absorber and the ZnO window layer are systematically investigated, providing direct evidence for a Fermi energy shifting in Cu(In,Ga)Se2 absorbers with different Ga content.
Inertial focusing of non-spherical microparticles
Authors: Hur Soojung Claire , Choi Sung-Eun , Kwon Sunghoon , Carlo Dino Di
Published: August 2011

We have investigated the focusing and dynamics of non-spherical polymeric particles in microfluidic flows at finite Reynolds number. The rotational diameter, Dmax, of a particle, regardless of its cross-sectional shape, was found to determine the final focused position, except for the case of asymmetric disks. Additionally, elongated particles with larger Dmax exhibited longer residence times in a horizontal orientation than those with smaller Dmax. These findings inform approaches to hydrodynamically control shaped and barcoded particles for multiplexed biochemical assays.
Structural dynamics and energy flow in Rydberg-excited clusters of N,N-dimethylisopropylamine
Authors: Deb Sanghamitra , Minitti Michael P. , Weber Peter M.
Published: August 2011

In molecular beams, the tertiary amine N,N-dimethylisopropyl amine can form molecular clusters that are evident in photoelectron and mass spectra obtained upon resonant multiphoton ionization via the 3p and 3s Rydberg states. By delaying the ionization pulse from the excitation pulse we follow, in time, the ultrafast energy relaxation dynamics of the 3p to 3s internal conversion and the ensuing cluster evaporation, proton transfer, and structural dynamics. While evaporation of the cluster occurs in the 3s Rydberg state, proton transfer dominates on the ion surface. The mass-spectrum shows protonated species that arise from a proton transfer from the alpha-carbon of the neutral parent molecule to the N-atom of its ionized partner in the dimer. DFT calculations support the proton transfer mechanism between tightly bonded cluster components. The photoelectron spectrum shows broad peaks, ascribed to molecular clusters, which have an instantaneous shift of about 0.5 eV toward lower binding energies. That shift is attributed to the charge redistribution associated with the induced dipoles in surrounding cluster molecules. A time-dependent shift that decreases the Rydberg electron binding energy by a further 0.4 eV arises from the structural reorganization of the cluster solvent molecules as they react to the sudden creation of a charge.
Localized spectral asymptotics for boundary value problems and correlation effects in the free Fermi gas in general domains
Authors: Schmidt Bernd
Published: August 2011

We rigorously derive explicit formulae for the pair correlation function of the ground state of the free Fermi gas in the thermodynamic limit for general geometries of the macroscopic regions occupied by the particles and arbitrary dimension. As a consequence we also establish the asymptotic validity of the local density approximation for the corresponding exchange energy. At constant density these formulae are universal and do not depend on the geometry of the underlying macroscopic domain. In order to identify the correlation effects in the thermodynamic limit, we prove a local Weyl law for the spectral asymptotics of the Laplacian for certain quantum observables which are themselves dependent on a small parameter under very general boundary conditions.
Backbone of conductivity in two-dimensional metal-insulator composites
Authors: Reuteler Joakim , Hütter Markus , Gauckler Ludwig J.
Published: August 2011

In percolation theory, the backbone is defined by chopping off dangling ends from the percolating cluster. For structures with high degree of spatial correlation, as they are typical for porous thin films, trimming of the full structure to reveal the part determining the electrical conductivity is more subtle than the classic definition of the backbone. To expand the applicability of the concept, we present a purely geometric definition for the backbone of a two-dimensional percolating cluster. It is based on a sequence of image analysis operations defining the backbone in terms of an image filter. The change of both area fraction and effective conductivity induced by applying the backbone filter to various binary images and a two-parameter family of sets is assessed by numerical means. It is found that the backbone filter simplifies the geometry of complex microstructures significantly and at the same time preserves their electrical DC behavior. We conclude that the backbone will be useful as a first ingredient for a geometric estimator of the effective conductivity of metal-insulator composites.
Self-formation of nanocomposite Cu/Al2O3 thin films on CuAl dilute alloys by annealing in inert atmospheres
Authors: Zhu Y. F. , Liu D. , Wen Z. , Jiang Q.
Published: August 2011

Self-formation of the surface protective layer on dilute CuAl alloys by annealing in inert atmospheres is investigated with thermodynamic consideration, first principles density functional simulation, and transmission electron microscopy (TEM). The calculations predict that when Cu atoms are involved in the surface Al2O3 layer, the Cu-Al2O3 solution does not exist. Instead, a phase structure of Cu and Al2O3 should be formed. Consistent with this prediction, TEM observations showed that the surface thin film consists of the nanocomposite Cu/Al2O3 structure, in which spherical Cu nanoparticles 3–5 nm in diameter are formed and disperse in the amorphous Al2O3 matrix. The results are discussed with respect to surface segregation and the stability of Cu in Al2O3.
Exploring the tip-sample interaction regimes in the presence of hysteretic forces in the tapping mode atomic force microscopy
Authors: Korayem M. H. , Eghbal M. M. , Ebrahimi N.
Published: August 2011

In this article, the tip-sample interaction regimes in the presence of hysteretic forces are investigated using atomic force microscopy in the tapping mode. For this purpose, two samples that cause the formation of hysteretic forces, namely, silicon (stiff sample) with an adsorbed water film and polyethylene (compliant sample), are used. Also, for deriving the equation of motion of the microcantilever, the continuous beam model is used, and for determining the contact forces, depending on the sample under investigation, the Derjaguin–Muller–Toporov and Johnson–Kendall–Roberts contact mechanics models are used. The results indicate that the hysteretic interaction forces generate high-periodic and irregular responses at certain tip-sample separation distances. In fact, at these distances, a family of steady-state attractors is found that can be observed in one branch on the minimum tip-sample separation curves and in two separate branches on the average force curves. The reason for this occurrence might be the alternate formation of a liquid column between the probe tip and the sample (in the presence of ambient moisture), and for the compliant sample, the reason might be the alternate formation of an adhesion neck. In this article, the role of hysteretic forces in producing the hysteresis of the amplitude-separation curves is also explored.
Effects of postdeposition annealing ambient on hysteresis in an Al2O3/GeO2 gate-dielectric stack on Ge
Authors: Fukuda Yukio , Otani Yohei , Sato Tetsuya , Toyota Hiroshi , Ono Toshiro
Published: August 2011

We report on the effects of postdeposition annealing ambient on the hysteresis observed in the C–V measurement of Al2O3/GeO2 gate-dielectric stacks fabricated on Ge substrates. The results indicate that two types of oxide trap are responsible for the observed hysteresis: a type-I oxide trap that causes persistent C-V hysteresis and a type-II oxide trap that disappears when gate voltage is biased once in the accumulation region. We show that both types of oxide trap reside in the capacitor annealed in O2 ambient, but that only the type-II oxide trap resides in the capacitor annealed in N2 + 10% H2. Time-domain measurements of absorption current suggest that holes injected into the gate-dielectric stack induce the electronic deactivation of the type-II oxide trap.
Growth and properties of heavy fermion CeCu2Ge2 and CeFe2Ge2 thin films
Authors: Li Yize Stephanie , Zheng Mao , Mulcahy Brian , Greene Laura H. , Eckstein James N.
Published: August 2011

Epitaxial films of heavy fermion CeCu2Ge2 and CeFe2Ge2 are grown on DyScO3 and MgO substrates using molecular beam epitaxy. The growth begins via island nucleation leading to a granular morphology. The grains grow flat with c-axis orientation after nucleating, as indicated by in-situ reflection high energy electron diffraction (RHEED) and ex-situ analysis including atomic force microscopy (AFM) and x-ray diffraction (XRD). These single phase films show similar temperature dependent transport to single crystals of the materials indicating that similar collective order occurs in the films as in single crystals.
High effective terahertz radiation from semi-insulating-GaAs photoconductive antennas with ohmic contact electrodes
Authors: Shi Wei , Hou Lei , Wang Xinmei
Published: August 2011

Terahertz (THz) radiation efficiency of a photoconductive antenna with Schottky contact electrodes is low because the electrical field is limited to a narrow region close to the anode. However, the electrical field in the gap of an antenna with ohmic contact electrodes is more uniform, which contributes to improving THz generation efficiency. In this paper, the semi-insulating (SI)-GaAs antennas with ohmic contact electrodes and SI-GaAs antennas with Schottky contact electrodes were fabricated by using AuGeNi alloy electrodes and Ti/Au electrodes, respectively. The voltage-ampere characteristic and the distribution of electrical field of the two kinds of antennas were tested. At the same condition, the THz intensity from the antenna with ohmic contact electrodes was 3-8 times higher than that from the antenna with Schottky contact electrodes, and the larger gap antennas with ohmic contact electrodes have higher optical and electrical energy to THz intensity conversion efficiency.
On the existence and evolution of a spanwise vortex in laminar shallow water dipoles
Authors: Albagnac J. , Lacaze L. , Brancher P. , Eiff O.
Published: August 2011

The present work investigates the existence and evolution of a spanwise vortex at the front of shallow dipolar vortices. The vortex dipoles are experimentally generated using a double flap apparatus. Particle image velocimetry measurements are performed in a horizontal plane and in the vertical symmetry plane of the flow. The dynamics of such vortical structures is investigated through a parametric study in which both the Reynolds number Re=U0D0/ν∈[90,470] and the aspect ratio α=h/D0∈[0.075,0.7], associated with the shallowness of the flow, are varied, where U0 is the initial velocity of the vortex dipole, D0 is the initial diameter, h is the water depth, and ν is the kinematic viscosity of the fluid. The present experiments confirm the numerical results obtained in a companion paper by Duran-Matute et al. [Phys. Fluids 22, 116606 (2010)], namely that the flow remains quasi parallel with negligible vertical motions below a critical value of the parameter α2Re. By contrast, for large values of α2Re and α≲0.6, a three-dimensional regime is observed in the shape of an intense spanwise vortex generated at the front of the dipole. The present study reveals that the early-time motion and dynamics of the spanwise vortex do not scale on the unique parameter α2Re but is strongly influenced by both the aspect ratio and the Reynolds number. A mechanism for the generation of the spanwise vortex is proposed. For α≳0.6, a third regime is observed, where the spanwise vortex is replaced by a vorticity tongue.
Energy transfer between host and dopant molecules in blue organic light-emitting devices
Authors: Kim You-Hyun , Young Kim Woo , Moon C.-B.
Published: August 2011

Blue organic light-emitting devices were fabricated with an activator of 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl doped into the various host materials such as N,N′-bis-(1-naphtyl)-N,N′-diphenyl-1,1-biphenyl-4,4′-diamine; 4,4′-bis(2,2′-diphenylyinyl)-1,1′-biphenyl; 2-methyl-9,10-di(2-naphthyl) anthracene; and 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene to investigate optical properties of blue light emission in the host-dopant system. By spectroscopic analysis based on multi-peak fits to the emission spectra, we found that energy transfer between the host and dopant molecules have a strong correlation with key features; current density, luminous efficiency, and color index for the devices. Among the present dopant-host systems, the TPBi molecule was found to be the best molecule as a host material for our devices. In contrast, the DPVBi host induced a complex excimer (electromer) leading to a shoulder spectrum with a longer wavelength emission. It was found that the electromer significantly affects the optical and electrical properties of the device.
Parametric analysis with micro jitter generation for a direct current charging roller based electrophotographic device
Authors: Hoon Byeon Jeong , Kim Jang-Woo
Published: August 2011

To realize high quality electrophotography, it is important to clarify the influence of the design parameters in a charging roller (CR) system on the output image on the paper. We first analyzed the parameters related to the direct current (dc) bias CR system, and consequently confirmed micro jitter generation as a printing quality indicator for varying CR resistance and the surface roughness of the CR elastic layer. It turned out that the micro jitters were correspondingly generated for the chosen representative parameters, and therefore, the analyses can be used as a design platform to prepare an optimum dc CR system.
Satellites of Xe transitions induced by infrared active vibrational modes of CF4 and C2F6 molecules
Authors: Alekseev Vadim A. , Schwentner Nikolaus
Published: August 2011

Absorption and luminescence excitation spectra of Xe/CF4 mixtures were studied in the vacuum UV region at high resolution using tunable synchrotron radiation. Pressure-broadened resonance bands and bands associated with dipole-forbidden states of the Xe atom due to collision-induced breakdown of the optical selection rules are reported. The spectra display in addition numerous satellite bands corresponding to transitions to vibrationally excited states of a Xe-CF4 collisional complex. These satellites are located at energies of Xe atom transition increased by one quantum energy in the IR active v3 vibrational mode of CF4 (v3 = 1281 cm−1). Satellites of both resonance and dipole-forbidden transitions were observed. Satellites of low lying resonance states are spectrally broad bands closely resembling in shape their parent pressure-broadened resonance bands. In contrast, satellites of dipole-forbidden states and of high lying resonance states are spectrally narrow bands (FWHM ∼10 cm−1). The satellites of dipole-forbidden states are orders of magnitude stronger than transitions to their parent states due to collision-induced breakdown of the optical selection rules. These satellites are attributed to a coupling of dipole-forbidden and resonance states induced by the electric field of the transient CF4 (v3 = 0 ↔ v3 = 1) dipole. Similar satellites are present in spectra of Xe/C2F6 mixtures where these bands are induced by the IR active v10 mode of C2F6. Transitions to vibrationally excited states of Xe-CF4(C2F6) collision pairs were also observed in two-photon LIF spectra.
Development of high-repetition-rate laser pump/x-ray probe methodologies for synchrotron facilities
Authors: March Anne Marie , Stickrath Andrew , Doumy Gilles , Kanter Elliot P. , Krässig Bertold , Southworth Stephen H. , Attenkofer Klaus , Kurtz Charles A. , Chen Lin X. , Young Linda
Published: August 2011

We describe our implementation of a high repetition rate (54 kHz–6.5 MHz), high power (>10 W), laser system at the 7ID beamline at the Advanced Photon Source for laser pump/x-ray probe studies of optically driven molecular processes. Laser pulses at 1.06 μm wavelength and variable duration (10 or 130 ps) are synchronized to the storage ring rf signal to a precision of ∼250 fs rms. Frequency doubling and tripling of the laser radiation using nonlinear optical techniques have been applied to generate 532 and 355 nm light. We demonstrate that by combining a microfocused x-ray probe with focused optical laser radiation the requisite fluence (with <10 μJ/pulse) for efficient optical excitation can be readily achieved with a compact and commercial laser system at megahertz repetition rates. We present results showing the time-evolution of near-edge x-ray spectra of a well-studied, laser-excited metalloporphyrin, Ni(II)-tetramesitylporphyrin. The use of high repetition rate, short pulse lasers as pump sources will dramatically enhance the duty cycle and efficiency in data acquisition and hence capabilities for laser-pump/x-ray probe studies of ultrafast structural dynamics at synchrotron sources.
Combustion stabilization using serpentine plasma actuators
Authors: Wang Chin-Cheng , Roy Subrata
Published: August 2011

This letter presents a numerical model for combustion stabilization with plasma actuators. Recently, we demonstrated that serpentine actuators induce complex neighboring flow structures due to pinching and spreading effects suitable for rapid flow mixing. Here, the influence of serpentine plasma actuator is numerically investigated on inner and outer recirculation zones of a gas turbine combustor. Beyond benchmarking with reported experimental data, we show that the swirl generated by the serpentine plasma actuators creates local low velocity regions stabilizing the flame. Such simple flow-mixing device does not need any moving parts, hence may be useful in the any combustors.
Doping-enhanced hyperpolarizabilities of silicon clusters: A global ab initio and density functional theory study of Si10 (Li, Na, K)n (n = 1, 2) clusters
Authors: Karamanis Panaghiotis , Marchal Remi , Carbonniére Philippe , Pouchan Claude
Published: August 2011

A global theoretical study of the (hyper)polarizabilities of alkali doped Si10 is presented and discussed. First, a detailed picture about the low lying isomers of Si10Li, Si10Na, Si10K, Si10Li2, Si10Na2, and Si10K2 has been obtained in a global manner. Then, the microscopic first (hyper)polarizabilities of the most stable configurations have been determined by means of ab initio methods of high predictive capability such as those based on the Møller-Plesset perturbation and coupled cluster theory, paying extra attention to the (hyper)polarizabilities of the open shell mono-doped systems Si10Li, Si10Na, Si10K, and the influence of spin contamination. These results were used to assess the performance of methods of low computational cost based on density functional theory (DFT) in the reliable computation of these properties in order to proceed with an in-depth study of their evolution as a function of the alkali metal, the cluster composition, and the cluster structure. The most interesting outcomes of the performed (hyper)polarizability study indicate that while alkali doping leaves the per atom polarizability practically unaffected, influences dramatically the hyperpolarizabilities of Si10. The lowest energy structures of the mono-doped clusters are characterized by significantly enhanced hyperpolarizabilities as compared to the analogue neutral or charged bare silicon clusters Si10 and Si11, while, certain patterns governed by the type and the number of the doping agents are followed. The observed hyperpolarizability increase is found to be in close connection with specific cluster to alkali metal charge transfer excited states and to the cluster structures. Moreover, an interesting correlation between the anisotropy of the electron density, and the hyperpolarizabilities of these systems has been observed. Finally, it is important to note that the presented method assessment points out that among the various DFT functionals used in this work, (B3LYP, B3PW91, BhandHLYP, PBE0, CAM-B3LYP, LC-BLYP, LC-BPW91) only B3PW91 and PBE0 out of the seven provided a consistent quantitative performance for both polarizabilities and hyperpolarizabilities with respect to the ab initio methods utilized here. On the other hand, the long range corrected functionals LC-(U)BLYP and LC-(U)BPW91 (μ = 0.47) failed to supply quantitatively accurate hyperpolarizability results in all the studied clusters while the CAM-(U)B3LYP functional performs satisfactory only in the case of the Na and K doped systems.
Scanning tunneling spectroscopy under large current flow through the sample
Authors: Maldonado A. , Guillamón I. , Suderow H. , Vieira S.
Published: August 2011

We describe a method to make scanning tunneling microscopy/spectroscopy imaging at very low temperatures while driving a constant electric current up to some tens of mA through the sample. It gives a new local probe, which we term current driven scanning tunneling microscopy/spectroscopy . We show spectroscopic and topographic measurements under the application of a current in superconducting Al and \documentclass[12pt]{minimal}\begin{document}$\text{NbSe}_{2}$\end{document}NbSe2 at 100 mK. Perspective of applications of this local imaging method includes local vortex motion experiments, and Doppler shift local density of states studies.
Effects of the dielectric discontinuity on the counterion distribution in a colloidal suspension
Authors: dos Santos Alexandre P. , Bakhshandeh Amin , Levin Yan
Published: August 2011

We introduce a new method for simulating colloidal suspensions with spherical colloidal particles of dielectric constant different from the surrounding medium. The method uses an approximate calculation of the Green function to obtain the ion-ion interaction potential in the presence of a dielectric discontinuity at the surface of the colloidal particle. The method is very accurate and is orders of magnitude faster than the traditional approaches based on series expansions of the interaction potential.
Transition from single to multi-walled carbon nanotubes grown by inductively coupled plasma enhanced chemical vapor deposition
Authors: Bissett Mark A. , Barlow Anders J. , Shapter Joe G. , Quinton Jamie S.
Published: August 2011

In this work a simple and up-scalable technique for creating arrays of high purity carbon nanotubes via plasma enhanced chemical vapor deposition is demonstrated. Inductively coupled plasma enhanced chemical vapor deposition was used with methane and argon mixtures to grow arrays in a repeatable and controllable way. Changing the growth conditions such as temperature and growth time led to a transition between single and multi-walled carbon nanotubes and was investigated. This transition from single to multi-walled carbon nanotubes is attributed to a decrease in catalytic activity with time due to amorphous carbon deposition combined with a higher susceptibility of single-walled nanotubes to plasma etching. Patterning of these arrays was achieved by physical masking during the iron catalyst deposition process. The low growth pressure of 100 mTorr and lack of reducing gas such as ammonia or hydrogen or alumina supporting layer further show this to be a simple yet versatile procedure. These arrays were then characterized using scanning electron microscopy, Raman spectroscopy and x-ray photoelectron spectroscopy. It was also observed that at high temperature (550 °C) single-walled nanotube growth was preferential while lower temperatures (450 °C) produced mainly multi-walled arrays.
Slow dynamics of the high density Gaussian core model
Authors: Ikeda Atsushi , Miyazaki Kunimasa
Published: August 2011

We numerically study crystal nucleation and glassy slow dynamics of the one-component Gaussian core model (GCM) at high densities. The nucleation rate at a fixed supercooling is found to decrease as the density increases. At very high densities, the nucleation is not observed at all in the time window accessed by long molecular dynamics (MD) simulation. Concomitantly, the system exhibits typical slow dynamics of the supercooled fluids near the glass transition point. We compare the simulation results of the supercooled GCM with the predictions of mode-coupling theory (MCT) and find that the agreement between them is better than any other model glassformers studied numerically in the past. Furthermore, we find that a violation of the Stokes-Einstein relation is weaker and the non-Gaussian parameter is smaller than canonical glassformers. Analysis of the probability distribution of the particle displacement clearly reveals that the hopping effect is strongly suppressed in the high density GCM. We conclude from these observations that the GCM is more amenable to the mean-field picture of the glass transition than other models. This is attributed to the long-ranged nature of the interaction potential of the GCM in the high density regime. Finally, the intermediate scattering function at small wavevectors is found to decay much faster than its self part, indicating that dynamics of the large-scale density fluctuations decouples with the shorter-ranged caging motion.
Time-dependent density functional theory based Ehrenfest dynamics
Authors: Wang Fan , Yam Chi Yung , Hu LiHong , Chen GuanHua
Published: August 2011

Time-dependent density functional theory based Ehrenfest dynamics with atom-centered basis functions is developed in present work. The equation of motion for electrons is formulated in terms of first-order reduced density matrix and an additional term arises due to the time-dependence of basis functions through their dependence on nuclear coordinates. This time-dependence of basis functions together with the imaginary part of density matrix leads to an additional term for nuclear force. The effects of the two additional terms are examined by studying the dynamics of H2 and C2H4, and it is concluded that the inclusion of these two terms is essential for correct electronic and nuclear dynamics.
Power dependent oxygenation state transition of red blood cells in a single beam optical trap
Authors: Liu Rui , Zheng Lena , Matthews Dennis L. , Satake Noriko , Chan James W.
Published: August 2011

Laser tweezers Raman spectroscopy (LTRS) was used to demonstrate that a red blood cell (RBC) in a single beam optical trap transitions from an oxygenated to a partially deoxygenated state with increasing trapping power. Continuous switching between the two states is possible by repeatedly cycling between low and high trapping powers. Alterations in the hemoglobin conformation and interactions due to cell folding in the trap are proposed to be responsible for the transition. This study demonstrates that mechanically induced biochemical changes by optical forces need to be considered when applying single beam optical tweezers for cell analysis. LTRS holds promise as a functional assay to characterize normal and diseased RBCs based on their biochemical response to the forces of a single beam optical trap.
Concurrent field enhancement and high transmission of THz radiation in nanoslit arrays
Authors: Shalaby Mostafa , Merbold Hannes , Peccianti Marco , Razzari Luca , Sharma Gargi , Ozaki Tsuneyuki , Morandotti Roberto , Feurer Thomas , Weber Anja , Heyderman Laura , Patterson Bruce , Sigg Hans
Published: August 2011

We experimentally and numerically investigate the transmission of THz radiation through uniform nanoslit arrays. These structures are capable of inducing plasmon-mediated field enhancement while concurrently providing high field transmission. Combined with intense THz radiation, estimated field strengths as high as 26 MV/cm are obtained in the near-field regime which will facilitate nonlinear THz experiments.
Highest transmittance and high-mobility amorphous indium gallium zinc oxide films on flexible substrate by room-temperature deposition and post-deposition anneals
Authors: Gadre Mandar J. , Alford T. L.
Published: August 2011

Amorphous indium gallium zinc oxide (a-IGZO) thin films of the highest transmittance reported in literature were initially deposited onto flexible polymer substrates at room temperature. The films were annealed in vacuum, air, and oxygen to enhance their electrical and optical performances. Electrical and optical characterizations were done before and after anneals. A partial reversal of the degradation in electrical properties upon annealing in oxygen was achieved by subjecting the films to subsequent vacuum anneals. A model was developed based on film texture and structural defects which showed close agreement between the measured and calculated carrier mobility values at low carrier concentrations (2–6 × 1019 cm−3).
Robust bi-stable memory operation in single-layer graphene ferroelectric memory
Authors: Song Emil B. , Lian Bob , Min Kim Sung , Lee Sejoon , Chung Tien-Kan , Wang Minsheng , Zeng Caifu , Xu Guangyu , Wong Kin , Zhou Yi , Rasool Haider I. , Seo David H. , Chung Hyun-Jong , Heo Jinseong , Seo Sunae , Wang Kang L.
Published: August 2011

With the motivation of realizing an all graphene-based circuit for low power, we present a reliable nonvolatile graphene memory device, single-layer graphene (SLG) ferroelectric field-effect transistor (FFET). We demonstrate that exfoliated single-layer graphene can be optically visible on a ferroelectric lead-zirconate-titanate (PZT) substrate and observe a large memory window that is nearly equivalent to the hysteresis of the PZT at low operating voltages in a graphene FFET. In comparison to exfoliated graphene, FFETs fabricated with chemical vapor deposited (CVD) graphene exhibit enhanced stability through a bi-stable current state operation with long retention time. In addition, we suggest that the trapping/de-trapping of charge carriers in the interface states is responsible for the anti-hysteresis behavior in graphene FFET on PZT.
Influence of the Cu-Te composition and microstructure on the resistive switching of Cu-Te/Al2O3/Si cells
Authors: Goux L. , Opsomer K. , Degraeve R. , Müller R. , Detavernier C. , Wouters D. J. , Jurczak M. , Altimime L. , Kittl J. A.
Published: August 2011

In this letter, we explore the influence of the CuxTe1-x layer composition (0.2 < x < 0.8) on the resistive switching of CuxTe1−x/Al2O3/Si cells. While x > 0.7 leads to large reset power, similar to pure-Cu electrodes, x < 0.3 results in volatile forming properties. The intermediate range 0.5 < x < 0.7 shows optimum memory properties, featuring improved control of filament programming using <5 μA as well as state stability at 85 °C. The composition-dependent programming control and filament stability are closely associated with the phases in the CuxTe1−x layer and are explained as related to the chemical affinity between Cu and Te.
Vertical orientation of copper phthalocyanine in organic solar cells using a small molecular weight organic templating layer
Authors: Soo Yook Kyoung , Doo Chin Byung , Yeob Lee Jun , Lassiter Brian E. , Forrest Stephen R.
Published: August 2011

Ultrathin film material templating layers that force the morphology of subsequently grown electrically active thin films have been found to increase the performance of small molecule organic photovoltaic (OPV) cells. Here, we show that the electron-transporting material, hexaazatriphenylene-hexacarbonitrile (HAT-CN) can be used as a templating material that forces the copper phthalocyanine (CuPc) donor molecule to assume a vertical-standing morphology when deposited onto its surface on an indium tin oxide (ITO) electrode. For a device with HAT-CN as the templating buffer layer, the fill factor and short circuit current of CuPc:C60 OPVs were both significantly increased compared with cells lacking the HAT-CN template. This is explained by the reduction of the series resistance due to the improved crystallinity of CuPc grown onto the ITO surface.