bluuebunny/crossref_metadata_2025 huggingface dataset:
Early development of the veil-shaped secondary flow in horizontal buoyant jets
Authors: Deri Enrico , Monavon Arnault , Studer Etienne , Abdo Danielle , Tkatschenko Isabelle
Published: August 2011

Under specific conditions, a secondary flow can develop from a laminar horizontal buoyant jet released through a round nozzle. This secondary flow is a veil-shaped plane plume, which detaches from the main jet. The conditions for its apparition have been empirically determined and are available in the open literature. This paper aims to give theoretical basis to these conditions and to show some novel experimental observations and measurements on horizontal buoyant jets with secondary plume. One of the main results is the identification of the persistence of transversal velocity components in the release section of horizontal buoyant jets.
Room temperature and narrow intersubband electroluminescence from ZnCdSe/ZnCdMgSe quantum cascade laser structures
Authors: Yao Yu , Alfaro-Martinez Adrian , Franz Kale J. , Charles William O. , Shen Aidong , Tamargo Maria C. , Gmachl Claire F.
Published: August 2011

We report ZnCdSe/ZnCdMgSe Quantum Cascade structures with “two-phonon” and “bound-to-continuum” active region designs. The electroluminescence shows more than 3 times higher luminescence efficiency and 40% narrower linewidth (<30 meV) than previous reports. The measured turn-on voltage matches closely the calculated value, indicating the improved electron transport characteristics in these structures. A waveguide design suitable for mode confinement in this material system is also presented, which resulted in a structure with a single narrow electroluminescence peak for all temperatures from 80 to 300 K.
Correlated electron dynamics with time-dependent quantum Monte Carlo: Three-dimensional helium
Authors: Christov Ivan P.
Published: August 2011

Here the recently proposed time-dependent quantum Monte Carlo method is applied to three dimensional para- and ortho-helium atoms subjected to an external electromagnetic field with amplitude sufficient to cause significant ionization. By solving concurrently sets of up to 20 000 coupled 3D time-dependent Schrödinger equations for the guide waves and corresponding sets of first order equations of motion for the Monte Carlo walkers we obtain ground state energies in close agreement with the exact values. The combined use of spherical coordinates and B-splines along the radial coordinate proves to be especially accurate and efficient for such calculations. Our results for the dipole response and the ionization of an atom with un-correlated electrons are in good agreement with the predictions of the conventional time-dependent Hartree-Fock method while the calculations with correlated electrons show enhanced ionization that is due to the electron-electron repulsion.
High frequency capacitance-voltage technique for the extraction of interface trap density of the heterojunction capacitor: Terman’s method revised
Authors: Deen David A. , Champlain James G.
Published: August 2011

In a multi-layer heterojunction system, the interface responsible for trap charging is spatially displaced from the two-dimensional charge gas, in contrast to the typical SiO2/Si capacitor. This displacement causes the effective trap capacitance to occur in a different configuration than that of the SiO2/Si system that Terman originally considered. The adaptation of Terman’s high frequency capacitance-voltage method for interface trap density extraction is developed for the heterojunction multi-layer capacitor.
Comment on “On the role of dissipation on the Casimir-Polder potential between molecules in dielectric media” [J. Chem. Phys. 133, 164501 (2010)]
Authors: Dalvit D. A. R. , Milonni P. W.
Published: August 2011

J. J. Rodriguez and A. Salam [J. Chem. Phys. 133, 164501 (2010)]10.1063/1.3495954 find discrepancies between their calculation and a previously published one [S. Spagnolo, D. A. R. Dalvit, and P. W. Milonni, Phys. Rev. A 75, 052117 (2007)]10.1103/PhysRevA.75.052117 for the van der Waals interaction of two guest molecules in a host dielectric medium. We trace these discrepancies to what we regard as fundamental errors in the calculation by Rodriguez and Salam.
High resolution infrared spectroscopy of carbon dioxide clusters up to (CO2)13
Authors: Norooz Oliaee J. , Dehghany M. , McKellar A. R. W. , Moazzen-Ahmadi N.
Published: August 2011

Thirteen specific infrared bands in the 2350 cm−1 region are assigned to carbon dioxide clusters, (CO2)N, with N = 6, 7, 9, 10, 11, 12 and 13. The spectra are observed in direct absorption using a tuneable infrared laser to probe a pulsed supersonic jet expansion of a dilute mixture of CO2 in He carrier gas. Assignments are aided by cluster structure calculations made using two reliable CO2 intermolecular potential functions. For (CO2)6, two highly symmetric isomers are observed, one with S6 symmetry (probably the more stable form), and the other with S4 symmetry. (CO2)13 is also symmetric (S6), but the remaining clusters are asymmetric tops with no symmetry elements. The observed rotational constants tend to be slightly (≈2%) smaller than those from the predicted structures. The bands have increasing vibrational blueshifts with increasing cluster size, similar to those predicted by the resonant dipole-dipole interaction model but significantly larger in magnitude.
A scanning probe-based pick-and-place procedure for assembly of integrated quantum optical hybrid devices
Authors: Schell Andreas W. , Kewes Günter , Schröder Tim , Wolters Janik , Aichele Thomas , Benson Oliver
Published: August 2011

Integrated quantum optical hybrid devices consist of fundamental constituents such as single emitters and tailored photonic nanostructures. A reliable fabrication method requires the controlled deposition of active nanoparticles on arbitrary nanostructures with highest precision. Here, we describe an easily adaptable technique that employs picking and placing of nanoparticles with an atomic force microscope combined with a confocal setup. In this way, both the topography and the optical response can be monitored simultaneously before and after the assembly. The technique can be applied to arbitrary particles. Here, we focus on nanodiamonds containing single nitrogen vacancy centers, which are particularly interesting for quantum optical experiments on the single photon and single emitter level.
Sub-nm equivalent oxide thickness on Si-passivated GaAs capacitors with low Dit
Authors: El Kazzi M. , Czornomaz L. , Webb D. J. , Rossel C. , Caimi D. , Siegwart H. , Fompeyrine J. , Marchiori C.
Published: August 2011

A thin amorphous silicon interlayer, inserted between the III-V semiconductor and the gate dielectric is expected to prevent III-V oxidation, as required for high-mobility channel transistors. We demonstrate that the addition of a thin Al2O3 barrier layer between the a-Si and the high-k HfO2, together with optimized post-metallization annealing, is the key to reduce the a-Si consumption and to achieve a highly scaled gate stack with equivalent oxide thickness of ∼0.8 nm. The evolution of the interfaces during growth and the quality of the stack are investigated by in-situ X-ray photoelectron spectroscopy and electrical measurements on metal-oxide-semiconductors capacitors.
Electrical investigation of the interface band structure in rubrene single-crystal/nickel junction
Authors: Kitamura Yuta , Shikoh Eiji , Zulkarnaen Bisri Satria , Takenobu Taishi , Shiraishi Masashi
Published: August 2011

The electronic structure of the interface between rubrene (C42H28) single crystal and ferromagnetic Ni is studied using an electrical method from a viewpoint of spintronics applications of organic single crystals. The Schottky barrier height at the interface is estimated to be 0.56 eV, and our finding is compared with previous results in spectroscopic method. This study clarifies the importance of electrical investigations of the Schottky barriers for various ferromagnet/organic systems and suggests that functionalization and carrier doping to rubrene single crystals are potential for obtaining the thinner barriers and yielding conclusive electrical spin injection.
Photoluminescence enhancement in CdS nanoparticles by surface-plasmon resonance
Authors: Jung Dae-Ryong , Kim Jongmin , Nam Seunghoon , Nahm Changwoo , Choi Hongsik , Kim Jae Ik , Lee Junhee , Kim Chohui , Park Byungwoo
Published: August 2011

To examine the influence of metal nanoparticles on the photoluminescence of semiconductors, colloidal mixtures of CdS and Au nanoparticles were prepared with different CdS/Au fractions. Compared to the cadmium-sulfide nanocrystals (quantum efficiency ≅ 7%), the CdS/Au mixtures showed enhanced luminescence properties (quantum efficiency ≅ 14%). The existence of an optimum ratio of metal to semiconductor nanoparticles for the photoluminescence intensity indicates that interactions between the metal and semiconductor nanoparticles induced by surface-plasmon resonance occur constructively at appropriate distances.
Modulation of atomic-layer-deposited Al2O3 film passivation of silicon surface by rapid thermal processing
Authors: Lei Dong , Yu Xuegong , Song Lihui , Gu Xin , Li Genhu , Yang Deren
Published: August 2011

We have investigated the effect of a thin interfacial silicon oxide on the atomic-layer-deposited Al2O3 film passivating the silicon surface based on rapid thermal process (RTP). It is found that the effective carrier lifetime of samples strongly depends on the RTP temperature and reaches the maximum value at 550 °C. Both capacitance-voltage measurements and theoretical simulation have revealed that the RTP treatment cannot only modulate the charges in the Al2O3 film but also reduce the density of interface states responsible for the surface recombination. These results are interesting for the fabrication of high efficiency silicon solar cells in photovoltaics.
Effect of diatomic molecular properties on binary laser pulse optimizations of quantum gate operations
Authors: Zaari Ryan R. , Brown Alex
Published: August 2011

The importance of the ro-vibrational state energies on the ability to produce high fidelity binary shaped laser pulses for quantum logic gates is investigated. The single frequency 2-qubit ACNOT1 and double frequency 2-qubit NOT2 quantum gates are used as test cases to examine this behaviour. A range of diatomics is sampled. The laser pulses are optimized using a genetic algorithm for binary (two amplitude and two phase parameter) variation on a discretized frequency spectrum. The resulting trends in the fidelities were attributed to the intrinsic molecular properties and not the choice of method: a discretized frequency spectrum with genetic algorithm optimization. This is verified by using other common laser pulse optimization methods (including iterative optimal control theory), which result in the same qualitative trends in fidelity. The results differ from other studies that used vibrational state energies only. Moreover, appropriate choice of diatomic (relative ro-vibrational state arrangement) is critical for producing high fidelity optimized quantum logic gates. It is also suggested that global phase alignment imposes a significant restriction on obtaining high fidelity regions within the parameter search space. Overall, this indicates a complexity in the ability to provide appropriate binary laser pulse control of diatomics for molecular quantum computing.
An organic p-i-n homojunction as ultra violet light emitting diode and visible-blind photodiode in one
Authors: Hamwi S. , Riedl T. , Kowalsky W.
Published: August 2011

Organic p-i-n homojunctions that function both as ultra violet light emitting diode (peak wavelengths around 375 nm and 415 nm) and visible-blind photodiode are reported. They are considered as the organic counterpart to what has exclusively been known from inorganic semiconductors, as yet. The diodes are based on the ambipolar material 4,4′-Bis(carbazol-9-yl)-biphenyl (CBP) which is p- and n-type doped adjacent to the electrodes. We study the emission characteristics of the p-i-n homojunction for varied doping concentrations and subsequently focus on its characteristics as photodiode. A superlinear relation of photocurrent and incident light intensity is found and attributed to an intensity-dependent photoconductivity.
Quasi-one-dimensional miniature multiferroic magnetic field sensor with high sensitivity at zero bias field
Authors: Chen Yajie , Gillette Scott M. , Fitchorov Trifon , Jiang Liping , Hao Hongbo , Li Jiheng , Gao Xuexu , Geiler Anton , Vittoria C. , Harris V. G.
Published: August 2011

A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is presented. The magnetoelectric sensor makes use of the d31 coupling mode between a piezoelectric lead zirconate titanate tube and FeNi magnetostrictive wire. The sensors demonstrate high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency resulting in smaller, lower power consumption, and volumetric efficiency. Experiments indicate a zero bias field sensitivity of 16.5 mV/Oe at 100 Hz stemming from a magnetoelectric coefficient of 1.65 V/cm-Oe. The results are quantitatively described by a theoretical model of laminate composites.
Low interfacial trap density and sub-nm equivalent oxide thickness in In0.53Ga0.47As (001) metal-oxide-semiconductor devices using molecular beam deposited HfO2/Al2O3 as gate dielectrics
Authors: Chu L. K. , Merckling C. , Alian A. , Dekoster J. , Kwo J. , Hong M. , Caymax M. , Heyns M.
Published: August 2011

We investigated the passivation of In0.53Ga0.47As (001) surface by molecular beam epitaxy techniques. After growth of strained In0.53Ga0.47As on InP (001) substrate, HfO2/Al2O3 high-κ oxide stacks have been deposited in-situ after surface reconstruction engineering. Excellent capacitance-voltage characteristics have been demonstrated along with low gate leakage currents. The interfacial density of states (Dit) of the Al2O3/In0.53Ga0.47As interface have been revealed by conductance measurement, indicating a downward Dit profile from the energy close to the valence band (medium 1012 cm−2eV−1) towards that close to the conduction band (1011 cm−2eV−1). The low Dit’s are in good agreement with the high Fermi-level movement efficiency of greater than 80%. Moreover, excellent scalability of the HfO2 has been demonstrated as evidenced by the good dependence of capacitance oxide thickness on the HfO2 thickness (dielectric constant of HfO2 ∼20) and the remained low Dit’s due to the thin Al2O3 passivation layer. The sample with HfO2 (3.4 nm)/Al2O3 (1.2 nm) as the gate dielectrics has exhibited an equivalent oxide thickness of ∼0.93 nm.
Thermal annealing and temperature dependences of memory effect in organic memory transistor
Authors: Ren X. C. , Wang S. M. , Leung C. W. , Yan F. , Chan P. K. L.
Published: August 2011

We investigate the annealing and thermal effects of organic non-volatile memory with floating silver nanoparticles by real-time transfer curve measurements. During annealing, the memory window shows shrinkage of 23% due to structural variation of the nanoparticles. However, by increasing the device operating temperature from 20 to 90 °C after annealing, the memory window demonstrates an enlargement up to 100%. The differences in the thermal responses are explained and confirmed by the co-existence of electron and hole traps. Our findings provide a better understanding of organic memory performances under various operating temperatures and validate their applications for temperature sensing or thermal memories.
Experimental investigation of electronic states of LiCs dissociating to Li(22S) and Cs(52D) atoms
Authors: Grochola A. , Szczepkowski J. , Jastrzebski W. , Kowalczyk P.
Published: August 2011

Polarization labeling spectroscopy technique was used to measure excitation spectra of LiCs molecule in the spectral range of 16 000–18 500 cm−1. Four band systems were observed and assigned to transitions from the ground X1Σ+ state to excited states (4)Ω = 0+, (5)Ω = 0+, (5)Ω = 1, and (6)Ω = 1 (in Hund's case (c) notation proper here), the latter three states being fine structure components of the states d3Π and e3Σ+, nominally of triplet symmetry. The observed states are characterized spectroscopically and the experimental results are compared with predictions of theoretical calculations, showing accuracy of the theoretical electronic term values better than 100 cm−1 and of the ωe and Re constants within 5%.
Pulsed electric breakdown in adipose tissue
Authors: Kolb Juergen F. , Scully Noah , Paithankar Dilip
Published: August 2011

High voltage pulses of sub-microsecond duration can instigate electrical breakdown in adipose tissue, which is followed by a spark discharge. Breakdown voltages are generally lower than observed for purified lipids but higher than for air. Development of breakdown for the repetitive application of pulses resembles a gradual and stochastic process as reported for partial discharges in solid dielectrics. The inflicted tissue damage itself is confined to the gap between electrodes, providing a method to use spark discharges as a precise surgical technique.
Towards proper characterization of nonlinear metal-semiconductor contacts. Generalization of the transmission line method
Authors: Piotrzkowski R. , Litwin-Staszewska E. , Grzanka Sz.
Published: August 2011

Modern optoelectronic devices are often based on wide-bandgap semiconductors such as GaN. In such cases the current injecting contacts are usually nonlinear, especially for p-type materials. Using the standard transmission line method (TLM), which gives satisfactory results in linear cases, characterization of nonlinear contacts can lead to serious ambiguities. In this Letter, we derive exact formulas permitting to extract the current-voltage characteristics of the non-linear metal–semiconductor contact from measurements performed on standard TLM pattern, as well as to simulate behavior of such pattern for given model contact characteristic. The application of this generalized TLM method is illustrated on the example of Ni/Au contacts on p-GaN
Origin of the n-type transport behavior of azafullerene encapsulated single-walled carbon nanotubes
Authors: Thanh Cuong Nguyen , Otani Minoru , Iizumi Yoko , Okazaki Toshiya , Rotas Georgios , Tagmatarchis Nikos , Li Yongfeng , Kaneko Toshiro , Hatakeyama Rikizo , Okada Susumu
Published: August 2011

The transport properties of C59N encapsulated semiconducting single-walled carbon nanotubes (SWCNTs) (C59N-peapod) are investigated. Transport measurements of the peapods in field effect transistors (FETs) reveal that ∼14% of the C59N-peapod sample shows n-type behavior even though the electronic properties of the host SWCNTs are similar to those of C60-peapods that exhibit only p-type property. First-principles electronic-structure calculations reveal that the unique transport behavior originates from the monomer form of C59N encapsulated in SWCNTs. The singly occupied (SO) state of C59N lies in the energy gap of the SWCNT and the energy of this state increases substantially when electrons are injected. Because of this shift to higher energy, the SO state acts as a shallow donor state for the conduction band of the nanotube, which leads to n-type behavior in FET measurements.
Ion-water clusters, bulk medium effects, and ion hydration
Authors: Merchant Safir , Dixit Purushottam D. , Dean Kelsey R. , Asthagiri D.
Published: August 2011

Thermochemistry of gas-phase ion-water clusters together with estimates of the hydration free energy of the clusters and the water ligands are used to calculate the hydration free energy of the ion. Often the hydration calculations use a continuum model of the solvent. The primitive quasichemical approximation to the quasichemical theory provides a transparent framework to anchor such efforts. Here we evaluate the approximations inherent in the primitive quasichemical approach and elucidate the different roles of the bulk medium. We find that the bulk medium can stabilize configurations of the cluster that are usually not observed in the gas phase, while also simultaneously lowering the excess chemical potential of the ion. This effect is more pronounced for soft ions. Since the coordination number that minimizes the excess chemical potential of the ion is identified as the optimal or most probable coordination number, for such soft ions the optimum cluster size and the hydration thermodynamics obtained with and without account of the bulk medium on the ion-water clustering reaction can be different. The ideas presented in this work are expected to be relevant to experimental studies that translate thermochemistry of ion-water clusters to the thermodynamics of the hydrated ion and to evolving theoretical approaches that combine high-level calculations on clusters with coarse-grained models of the medium.
Density dependence of hydrogen bonding and the translational-orientational structural order in supercritical water: A molecular dynamics study
Authors: Ma Haibo , Ma Jing
Published: August 2011

Molecular dynamics simulation have been performed with a wide range of densities along a near critical isotherm of supercritical water (SCW) in order to study the density dependence of the structure order and hydrogen bonding (HB). It is revealed that the translational structure order is nearly invariant while the orientational tetrahedral structure order is very sensitive to the bulk density under supercritical conditions. Meanwhile, some energetically unfavorable intermediate water dimer structures are found to appear under supercritical conditions due to the reduced energy difference and the enhanced energy fluctuation. As a consequence, a general geometrical criterion or the inclusion of a energy-based criterion instead of currently widely adopted pure rOH-based geometric criterion is suggested to be used in the HB statistics under supercritical conditions. It is found that the average HB number per H2O molecule (nHB) reduces with the decreasing SCW bulk density although a given pair of H2O molecules are shown to have a stronger ability to form a hydrogen bond under lower SCW bulk densities. Accordingly, the orientational tetrahedral structure order q decreases with the reducing bulk density under supercritical conditions. However, when the fluid is dilute with ρ ⩽ 0.19ρc (ρc = 0.322 g/cm3), the energy fluctuation increases sharply and the short-range order is destroyed, signifying the supercritical fluid (SCF)-gas state transition. Accordingly, the orientational tetrahedral structure order q gets reversal around ρ = 0.19ρc and approaches zero under very dilute conditions. The sensitivity of the orientational order to the density implies the microscopic origin of the significant dependence of SCF’s physicochemical properties on the pressure.
Microelectromechanical resonators based on an all polymer/carbon nanotube composite structural material
Authors: Sousa P. M. , Gutiérrez M. , Mendoza E. , Llobera A. , Chu V. , Conde J. P.
Published: August 2011

Carboxylated multi-wall carbon-nanotubes (CNTs) monolayers are integrated on microfabricated all-polymer micro-electromechanical systems (pMEMS) resonator bridges on glass substrates. The structural layer of the MEMS bridges is a multilayer blended conductive polymer based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to which functionalized CNT monolayers are electrostatically attached. The resonance frequency (fres) of electrostatically actuated pMEMS bridges was measured as a function of their length (32–67 μm) for different multilayer compositions. A significant increase in fres and quality factor (Q) with the addition of CNT monolayers to the PEDOT:PSS structural material is observed, demonstrating that CNT monolayers can be used to modulate pMEMS resonator properties.
Ultra-portable explosives sensor based on a CMOS fluorescence lifetime analysis micro-system
Authors: Wang Yue , Rae Bruce R. , Henderson Robert K. , Gong Zheng , Mckendry Jonathan , Gu Erdan , Dawson Martin D. , Turnbull Graham A. , Samuel Ifor D. W.
Published: August 2011

This work explores the use of a green-light-emitting copolymer as a chemosensor to detect nitroaromatic-based explosive vapors by recording photoluminescence (PL) and time-resolved PL decay. We show successful detection of 10 ppb 1,4-dinitrobenzene (DNB) vapor. Both a conventional time-correlated single photon counting (TCSPC) device and CMOS time-resolved fluorescence lifetime micro-system are used in the DNB detection. An ultra-portable on-site explosive sensor based on the micro-system has also been demonstrated. This gives rise to the potential for real-time, reliable, inexpensive organic/inorganic hybrid explosives detection.
Melting of iron at the Earth's core conditions by molecular dynamics simulation
Authors: Wu Y. N. , Wang D. M. , Huang Y. S.
Published: August 2011

By large scale molecular dynamics simulations of solid-liquid coexistence, we have investigated the melting of iron under pressures from 0 to 364 GPa. The temperatures of liquid and solid regions, and the pressure of the system are calculated to estimate the melting point of iron. We obtain the melting temperature of iron is about 6700±200K under the inner-outer core boundary, which is in good agreement with the result of Alfè et al. By the pair analysis technique, the microstructure of liquid iron under higher pressures is obviously different from that of lower pressures and ambient condition, indicating that the pressure-induced liquid-liquid phase transition may take place in iron melts.
Steady flow of micropolar fluid in a rectangular channel under transverse magnetic field with suction
Authors: Murthy J. V. Ramana , Sai K. S. , Bahali N. K.
Published: August 2011

In this paper, the steady flow of an incompressible conducting micropolar fluid through a rectangular channel with uniform cross-section in the presence of a transverse magnetic field with suction and injection at the side walls is considered. Neglecting the induced magnetic and electric fields, velocity and micro-rotation vectors are obtained in terms of a Fourier series. The volumetric flow rate is calculated and the effect of micro-rotation parameter and geometric parameter, Hartmanns number on this are graphically shown and discussed.
Graded index and randomly oriented core-shell silicon nanowires for broadband and wide angle antireflection
Authors: Pignalosa P. , Lee H. , Qiao L. , Tseng M. , Yi Y.
Published: August 2011

Antireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm) and wide angle (from normal incidence to 60º) antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si) nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.
Job count is the leading indicator of basic research benefits
Authors: Kramer David
Published: August 2011

The paperwork accompanying ARRA-funded research grants adds costs for universities but provides more comprehensive metrics to gauge the benefits of basic research.
Old satellite dishes become new telescopes
Authors: Feder Toni
Published: August 2011

Recycling offers radio astronomers a cheap ticket to expand interferometers, train students, and boost science in developing countries.
Obama’s R&D plan seeks a renaissance in US manufacturing
Authors: Kramer David
Published: August 2011

Robotics, new materials, and improved energy efficiency are among the elements of a multiagency effort. But lawmakers bent on cutting spending will have to okay the new funding.
Particle physics, from Rutherford to the LHC
Authors: Weinberg Steven
Published: August 2011

Our understanding of fundamental particles has developed in ways that were unimaginable 100 years ago, when the atomic nucleus was first glimpsed.
Looking for mantle plumes
Authors: Humphreys Eugene , Schmandt Brandon
Published: August 2011

Seismic images of Earth’s interior offer evidence that hot columns of buoyant rock from deep in the mantle are the source of the volcanism at Yellowstone and similar hot spots. Yet mysteries remain.
Watching galaxies evolve
Authors: Conselice Christopher J.
Published: August 2011

Astronomical observations cover more than 95% of the history of galactic evolution. The considerable activity we have seen reveals the ways in which galaxies form and evolve.
The flesh and blood of embodied understanding
Authors: Forceville Charles , Jeulink Marloes
Published: August 2011

According to Conceptual Metaphor Theory (CMT), the Source-Path-Goal (SPG) schema constitutes a central concept in cognition. Apart from literally structuring “movement”, SPG also shapes our understanding of “purposive activity”, including questing and story-telling. A problem in CMT, however, is that the existence of image schemas is almost exclusively postulated on the basis of verbal expressions. To examine the claim that people recruit image schemas such as SPG to make sense of life, it is essential to examine non-verbal modalities. Animation has highly medium-specific opportunities to exploit SPG by its emphasis on “manner of movement” and “balance”. Three animation films (Father and Daughter, Quest, and O) exemplifying MOVEMENT, QUEST, and STORY are analyzed in terms of SPG to chart how they exploit this schema. We end the paper by positioning our findings with respect to recent discussions about image schemas in Hampe (2005a) and by suggesting avenues for further research.
Importance of helical pitch parameter in LHD-type heliotron reactor designs
Authors: Goto T. , Suzuki Y. , Yanagi N. , Watanabe K.Y. , Imagawa S. , Sagara A.
Published: August 2011

One of the key issues in the design of LHD-type heliotron reactors is to secure sufficient blanket spaces. In this respect, helical pitch parameter γ is quite important because it significantly affects both the coil and plasma shapes. For a quantitative understanding of the effect of helical pitch parameter on a design window, a system design code for LHD-type heliotron reactors HELIOSCOPE (HELIOtron System design COde for reactor Performance Evaluation) is developed and parametric scans are carried out with three cases of γ = 1.15, 1.20 and 1.25. It became clear that design windows of heliotron reactors depend significantly on the engineering constraints: the stored magnetic energy of the coil system, the inboard minimum blanket space and the averaged neutron wall load. In the case of a fusion power of 3 GW, γ = 1.20 is optimum for relaxing physics requirements. But γ = 1.15 is also a possible selection if a lower fusion power or a higher neutron wall load is accepted. Since design windows are quite sensitive to the engineering constraints and physics conditions, a further detailed study on design feasibility of advanced engineering components and the effect of γ on the physics conditions is expected to optimize the value of γ.
Impurity transport experiments and effects on MHD in the National Spherical Torus Experiment (NSTX)
Authors: Delgado-Aparicio L. , Stutman D. , Tritz K. , Volpe F. , Wong K.L. , Bell R. , Finkenthal M. , Fredrickson E. , Gerhardt S.P. , Kaye S. , LeBlanc B. , Menard J. , Paul S. , Roquemore L.
Published: August 2011

A first assessment of low-Z impurity transport in beam-heated NSTX H-modes has been performed using magnetic field and current scans at fixed q-profile as well as temperature scans at constant plasma density, current and toroidal field. Impurity diffusivity levels consistent with the neoclassical predictions have been found, whereas a reversal of the convective velocity at low fields indicates an anomalous effect to be at play at the gradient region. Studies on the impact of rotation in low-density H-modes have also shown that heavy and not fully stripped impurities with high Mach numbers can experience core diffusivities several times larger than that of the ‘standard’ neoclassical transport for stationary plasmas, without the need of invoking the presence of long wavelength core electrostatic turbulence. As a result of a deliberate neon impurity injection we have also observed a correlation between the strength of the emitted radiation, the earlier appearance of tearing modes activity and an enhanced plasma cooling that resulted in enlarged magnetic islands.
Design, fabrication and characterization of indefinite metamaterials of nanowires
Authors: Yao Jie , Wang Yuan , Tsai Kun-Tong , Liu Zhaowei , Yin Xiaobo , Bartal Guy , Stacy Angelica M. , Wang Yuh-Lin , Zhang Xiang
Published: August 2011

Indefinite optical properties, which are typically characterized by hyperbolic dispersion relations, have not been observed in naturally occurring materials, but can be realized through a metamaterial approach. We present here the design, fabrication and characterization of nanowire metamaterials with indefinite permittivity, in which all-angle negative refraction of light is observed. The bottom-up fabrication technique, which applies electrochemical plating of nanowires in porous alumina template, is developed and demonstrated in achieving uniform hyperbolic optical properties at a large scale. We developed techniques to improve the uniformity and to reduce the defect density in the sample. The non-magnetic design and the off-resonance operation of the nanowire metamaterials significantly reduce the energy loss of electromagnetic waves and make the broad-band negative refraction of light possible.
Predicting how populations decline to extinction
Authors: Collen Ben , McRae Louise , Deinet Stefanie , De Palma Adriana , Carranza Tharsila , Cooper Natalie , Loh Jonathan , Baillie Jonathan E. M.
Published: August 2011

Global species extinction typically represents the endpoint in a long sequence of population declines and local extinctions. In comparative studies of extinction risk of contemporary mammalian species, there appear to be some universal traits that may predispose taxa to an elevated risk of extinction. In local population-level studies, there are limited insights into the process of population decline and extinction. Moreover, there is still little appreciation of how local processes scale up to global patterns. Advancing the understanding of factors which predispose populations to rapid declines will benefit proactive conservation and may allow us to target at-risk populations as well as at-risk species. Here, we take mammalian population trend data from the largest repository of population abundance trends, and combine it with the PanTHERIA database on mammal traits to answer the question: what factors can be used to predict decline in mammalian abundance? We find in general that environmental variables are better determinants of cross-species population-level decline than intrinsic biological traits. For effective conservation, we must not only describe which species are at risk and why, but also prescribe ways to counteract this.
The influence of past and present climate on the biogeography of modern mammal diversity
Authors: Davies T. Jonathan , Buckley Lauren B. , Grenyer Richard , Gittleman John L.
Published: August 2011

Within most terrestrial groups of animals, including mammals, species richness varies along two axes of environmental variation, representing energy availability and plant productivity. This relationship has led to a search for mechanistic links between climate and diversity. Explanations have traditionally focused on single mechanisms, such as variation in environmental carrying capacity or evolutionary rates. Consensus, though, has proved difficult to achieve and there is growing appreciation that geographical patterns of species richness are a product of many interacting factors including biogeographic history and biological traits. Here, we review some current hypotheses on the causes of gradients in mammal richness and range sizes since the two quantities are intimately linked. We then present novel analyses using recent datasets to explore the structure of the environment–richness relationship for mammals. Specifically, we consider the impact of glaciation on present day mammalian diversity gradients. We conclude that not only are multiple processes important in structuring diversity gradients, but also that different processes predominate in different places.
Phylogenetic structure of mammal assemblages at large geographical scales: linking phylogenetic community ecology with macroecology
Authors: Cardillo Marcel
Published: August 2011

Phylogenetic community ecology seeks to explain the processes involved in the formation of species assemblages by analysing their phylogenetic structure, and to date has focused primarily on local-scale communities. Macroecology, on the other hand, is concerned with the structure of assemblages at large geographical scales, but has remained largely non-phylogenetic. Analysing the phylogenetic structure of large-scale assemblages provides a link between these two research programmes. In this paper, I ask whether we should expect large-scale assemblages to show significant phylogenetic structure, by outlining some of the ecological and macroevolutionary processes that may play a role in assemblage formation. As a case study, I then explore the phylogenetic structure of carnivore assemblages within the terrestrial ecoregions of Africa. Many assemblages at these scales are indeed phylogenetically non-random (either clustered or overdispersed). One interpretation of the observed patterns of phylogenetic structure is that many clades underwent rapid biome-filling radiations, followed by diversification slowdown and competitive sorting as niche space became saturated.
The historical biogeography of Mammalia
Authors: Springer Mark S. , Meredith Robert W. , Janecka Jan E. , Murphy William J.
Published: August 2011

Palaeobiogeographic reconstructions are underpinned by phylogenies, divergence times and ancestral area reconstructions, which together yield ancestral area chronograms that provide a basis for proposing and testing hypotheses of dispersal and vicariance. Methods for area coding include multi-state coding with a single character, binary coding with multiple characters and string coding. Ancestral reconstruction methods are divided into parsimony versus Bayesian/likelihood approaches. We compared nine methods for reconstructing ancestral areas for placental mammals. Ambiguous reconstructions were a problem for all methods. Important differences resulted from coding areas based on the geographical ranges of extant species versus the geographical provenance of the oldest fossil for each lineage. Africa and South America were reconstructed as the ancestral areas for Afrotheria and Xenarthra, respectively. Most methods reconstructed Eurasia as the ancestral area for Boreoeutheria, Euarchontoglires and Laurasiatheria. The coincidence of molecular dates for the separation of Afrotheria and Xenarthra at approximately 100 Ma with the plate tectonic sundering of Africa and South America hints at the importance of vicariance in the early history of Placentalia. Dispersal has also been important including the origins of Madagascar's endemic mammal fauna. Further studies will benefit from increased taxon sampling and the application of new ancestral area reconstruction methods.
Imaging Action Potentials with Calcium Indicators
Authors: Yuste Rafael , MacLean Jason , Vogelstein Joshua , Paninski Liam
Published: August 2011

INTRODUCTION

The understanding of neuronal circuits has been greatly advanced by the ability to simultaneously image action-potential generation within large populations of neurons. This protocol describes bulk loading of brain slices with acetoxymethyl (AM) ester calcium indicators to monitor action-potential activity in functional neuronal circuits. The imaging of calcium influx into neurons provides an indirect but accurate measure of action-potential generation within individual neurons. The key advantage of the technique is that it allows the researcher to densely sample the activity of a large population of neurons with single-cell resolution.
Blastomere Injection of Cleavage-Stage Zebrafish Embryos and Imaging of Labeled Cells
Authors: England Samantha J. , Adams Richard J.
Published: August 2011

INTRODUCTION

Zebrafish embryos are useful for studying morphogenesis. Their foremost advantage is their optical transparency. Because the embryos are small, they can be imaged as whole-mount preparations. Crucially, this preserves both the mechanical and the molecular integrity of the embryo. This protocol describes the preparation of live zebrafish embryos for the collection of movies using four-dimensional time-lapse confocal microscopy. Methods are presented for the labeling of cells, for the orientation and immobilization of embryos, and for establishing a robust reproducible imaging environment with which to acquire high-resolution dynamic movies of cell behaviors during morphogenesis. These methods concentrate on the visualization of notochord morphogenesis in the zebrafish embryo. However, they also apply to the analysis of many other developing tissues. Factors that can influence the success of time-lapse confocal microscopy are discussed, such as the choice of cell label, the effects of genetic manipulation, and the consequences of environmental variation during imaging—all of which may influence the rate of development.
Immunolabeling of Drosophila Embryos and Tissues
Authors: Swedlow Jason
Published: August 2011

INTRODUCTION

The fruit fly Drosophila melanogaster has long been used to study the genetic factors involved in development. The ability to localize molecules within an organism that allow genetic manipulation can be quite useful. This article provides a standard method for preparing various Drosophila tissues for analysis by immunofluorescence microscopy. Specific methods are also presented for the handling of embryos, because these are used frequently and require special consideration.
Post‐orogenic evolution of the Mesozoic Micang Shan Foreland Basin system, central China
Authors: Tian Yuntao , Kohn Barry P. , Zhu Chuanqing , Xu Ming , Hu Shengbiao , Gleadow Andrew J. W.
Published: August 2011

[Correction added after online publication 3 August 2010 ‐ ‘prelate’ has been changed to ‘pre‐late’ throughout the text]. Using apatite fission track and (U‐Th‐Sm)/He thermochronology, we report the low‐temperature thermal history of the Mesozoic Micang Shan Foreland Basin system, central China. This system, comprising the Hannan Dome hinterland, the northern Sichuan Foreland Basin and the intermediate frontal thrust belt (FB), shares a common boundary with three major tectonic terrains – Mesozoic Qinling‐Dabie Orogen, Mesozoic Sichuan Foreland Basin and Cenozoic elevated Tibetan Plateau. Results show: (1) a relatively rapid pre‐late Cretaceous cooling episode in the Hannan Dome; (2) a mid‐Cenozoic cooling phase (ca. 50°C at ca. 30 ± 5 Ma) within the northern Sichuan Basin; and (3) possible late Cenozoic cooling (ca. 25°C at ca. 16 ± 4 Ma) within the Hannan Dome‐FB, a phase which has also been reported previously from adjacent regions. The pre‐late Cretaceous cooling episode in the Hannan Dome is attributed to coeval tectonism in nearby regions. Mid‐Cenozoic cooling in the northern Sichuan Basin can possibly be attributed to either one of or a combination of shortening of the basin, onset of the Asian monsoon and drainage adjustment of the Yangtze River system, all of which are related to growth of the Tibetan Plateau. Possible late Cenozoic cooling in the hinterland and nearby regions is also probably related to the northeastward growth of the Tibetan Plateau. However, previous studies suggest a northeastward propagation for onset of cooling from the eastern Tibetan Plateau to western Qinling in response to northeastward lower crust flow from the central Tibetan Plateau. The timing of apparent late Cenozoic cooling in the Hannan Dome hinterland, at an intermediate locality, is not consistent with this trend, and supports a previous model suggesting northeastern growth of the Tibetan Plateau through reactivation of WE trending strike‐slip faults.
Seismic time‐lapse effects of solution salt mining – a feasibility study
Authors: Drijkoningen Guy , van Noort Guus , Arts Rob , Bullen Joren , Thorbecke Jan
Published: August 2011

This article addresses the question whether time‐lapse seismic reflection techniques can be used to follow and quantify the effects of solution salt mining. Specifically, the production of magnesium salts as mined in the north of the Netherlands is considered. The use of seismic time‐lapse techniques to follow such a production has not previously been investigated. For hydrocarbon production and CO2 storage, time‐lapse seismics are used to look at reservoir changes mainly caused by pressure and saturation changes in large reservoirs, while for solution mining salt is produced from caverns with a limited lateral extent, with much smaller production volumes and a fluid (brine) replacing a solid (magnesium salt).

In our approach we start from the present situation of the mine and then study three different production scenarios, representing salt production both in vertical and lateral directions of the mine. The present situation and future scenarios have been transformed into subsurface models that were input to an elastic finite‐difference scheme to create synthetic seismic data. These data have been analysed and processed up to migrated seismic images, such that time‐lapse analyses of intermediate and final results could be done.

From the analyses, it is found that both vertical and lateral production is visible well above the detection threshold in difference data, both at pre‐imaging and post‐imaging stages. In quantitative terms, an additional production of the mine of 6 m causes time‐shifts in the order of 2 ms (pre‐imaging) and 4 ms (post‐imaging) and amplitude changes of above 20% in the imaged sections. A laterally oriented production causes even larger amplitude changes at the edge of the cavern due to replacement of solid magnesium salt with brine introducing a large seismic contrast. Overall, our pre‐imaging and post‐imaging time‐lapse analysis indicates that the effects of solution salt mining can be observed and quantified on seismic data. The effects seem large enough to be observable in real seismic data containing noise.
Survival and virulence properties of multiple antibiotic‐resistant Salmonella Typhimurium under simulated gastrointestinal conditions
Authors: He Xinlong , Ahn Juhee
Published: August 2011

The transit tolerance and relative gene expression (acrA, acrB, tolC, stn, hilA and ompD) were observed in antibiotic‐sensitive Salmonella Typhimurium (ASST) and antibiotic‐resistant S. Typhimurium (ARST) exposed to simulated gastric juices (pH 2.0, pH 3.0 and pH 5.0) for 1 or 4 h, followed by small intestinal juices (0.1% and 0.5% bile salts) for 2 h. The relative expression of acrA, acrB, tolC, stn, hilA and ompD in the ARST was upregulated after exposure to simulated gastrointestinal juices. The expression of AcrAB‐TolC efflux system in ARST was highly correlated with the expression of stn and hilA encoding virulence factor and regulator. The cross‐protective effect was observed in ARST against the gastric acid and bile salts. The AcrAB‐TolC involved in enhanced survival and virulence potential, resulting in increased in pathogenicity of ARST. This study provides useful information for assessing the gastrointestinal transit tolerance and virulence potential of multiple antibiotic‐resistant pathogens.