bluuebunny/crossref_metadata_2025 huggingface dataset:
Basis set construction for molecular electronic structure theory: Natural orbital and Gauss–Slater basis for smooth pseudopotentials
Authors: Petruzielo F. R. , Toulouse Julien , Umrigar C. J.
Published: February 2011

A simple yet general method for constructing basis sets for molecular electronic structure calculations is presented. These basis sets consist of atomic natural orbitals from a multiconfigurational self-consistent field calculation supplemented with primitive functions, chosen such that the asymptotics are appropriate for the potential of the system. Primitives are optimized for the homonuclear diatomic molecule to produce a balanced basis set. Two general features that facilitate this basis construction are demonstrated. First, weak coupling exists between the optimal exponents of primitives with different angular momenta. Second, the optimal primitive exponents for a chosen system depend weakly on the particular level of theory employed for optimization. The explicit case considered here is a basis set appropriate for the Burkatzki–Filippi–Dolg pseudopotentials. Since these pseudopotentials are finite at nuclei and have a Coulomb tail, the recently proposed Gauss–Slater functions are the appropriate primitives. Double- and triple-zeta bases are developed for elements hydrogen through argon. These new bases offer significant gains over the corresponding Burkatzki–Filippi–Dolg bases at various levels of theory. Using a Gaussian expansion of the basis functions, these bases can be employed in any electronic structure method. Quantum Monte Carlo provides an added benefit: expansions are unnecessary since the integrals are evaluated numerically.
Highly collimated electron beams from double-gate field emitter arrays with large collimation gate apertures
Authors: Helfenstein P. , Kirk E. , Jefimovs K. , Vogel T. , Escher C. , Fink H.-W. , Tsujino S.
Published: February 2011

Electron collimation in field emitter arrays with electron extraction gate and collimation gate electrodes is studied with the goal to develop a high-brightness high current cathode. Using metallic field emitter arrays prepared by the molding method, we fabricated a stacked double-gate device with the two gates differing in diameter by a process utilizing focused-ion beam milling. We measured the field-emission beam characteristics and demonstrated a reduction of the emission angle by a factor of 7.1±0.8 with minimal emission current decrease under collimating conditions, resulting in a current density increase by a factor of 13.9±1.0.
Energy transport and isochoric heating of a low-Z, reduced-mass target irradiated with a high intensity laser pulse
Authors: Nishimura H. , Mishra R. , Ohshima S. , Nakamura H. , Tanabe M. , Fujiwara T. , Yamamoto N. , Fujioka S. , Batani D. , Veltcheva M. , Desai T. , Jafer R. , Kawamura T. , Sentoku Y. , Mancini R. , Hakel P. , Koike F. , Mima K.
Published: February 2011

Heat transport in reduced-mass targets irradiated with a high intensity laser pulse was studied. Kα lines from partially ionized chlorine embedded in the middle of a triple-layered plastic target were measured to evaluate bulk electron temperature in the tracer region inside the target. Two groups of Kα lines, one from Cl+–Cl6+ (hereby called “cold Kα”), and the other from Cl9+ and Cl10+ (“shifted Kα”) are observed from different regions within the target. Two-dimensional collisional particle-in-cell simulations show two distinct heating mechanisms occurring concurrently: uniform heating by refluxing electrons and local heating by diffusive electrons in the central region. These two heating processes, which made the target temperature distribution nonuniform, are responsible for producing the two groups of Kα lines in the experiment. The blue-shift of cold Kα lines in the experiment is the signature of higher temperatures achieved by the refluxing heating in smaller-mass targets.
A model of one-dimensional current sheet with parallel currents and normal component of magnetic field
Authors: Artemyev A. V.
Published: February 2011

We develop a model of a current sheet including field-aligned currents and a finite value of the normal component of magnetic field. The model is based on the conservation of a quasiadiabatic invariant of ion motion, while for electrons a fluid approach is used. A part of the current becomes parallel to the magnetic field due to the magnetic field shear, however the perpendicular component of the current is also present. The difference in the plasma pressure between the current sheet center and its boundaries decreases is only half of the value of the model free of parallel currents. We discuss the possible application of the model developed in this paper.
Origin of ion-cyclotron turbulence in the downward Birkeland current region
Authors: Basu B. , Jasperse J. R. , Lund E. J. , Grossbard N.
Published: February 2011

Linear stability analysis of the electron velocity distributions, which are observed in the FAST satellite measurements in the downward Birkeland current region of the magnetosphere, is presented. The satellite-measured particle (electrons and protons) velocity distributions are fitted with analytic functions and the dispersion relation is derived in terms of the plasma dispersion functions associated with those distribution functions. Numerical solutions of the dispersion relation show that the bump-on-tail structure of the electron velocity distribution can excite electrostatic ion-cyclotron instabilities by the Landau resonance mechanism. Nonlinear evolution of these instabilities may explain the observed electrostatic ion-cyclotron turbulence in the Birkeland current region. Excitation of other types of instabilities by the fitted electron velocity distributions and their relevance are also discussed.
Neoclassical transport simulations for stellarators
Authors: Turkin Y. , Beidler C. D. , Maaßberg H. , Murakami S. , Tribaldos V. , Wakasa A.
Published: February 2011

The benchmarking of the thermal neoclassical transport coefficients is described using examples of the Large Helical Device (LHD) and TJ-II stellarators. The thermal coefficients are evaluated by energy convolution of the monoenergetic coefficients obtained by direct interpolation or neural network techniques from the databases precalculated by different codes. The temperature profiles are calculated by a predictive transport code from the energy balance equations with the ambipolar radial electric field estimated from a diffusion equation to guarantee a unique and smooth solution, although several solutions of the ambipolarity condition may exist when root-finding is invoked; the density profiles are fixed. The thermal transport coefficients as well as the ambipolar radial electric field are compared and very reasonable agreement is found for both configurations. Together with an additional W7-X case, these configurations represent very different degrees of neoclassical confinement at low collisionalities. The impact of the neoclassical optimization on the energy confinement time is evaluated and the confinement times for different devices predicted by transport modeling are compared with the standard scaling for stellarators. Finally, all configurations are scaled to the same volume for a direct comparison of the volume-averaged pressure and the neoclassical degree of optimization.
Magnetic collimation of fast electrons in specially engineered targets irradiated by ultraintense laser pulses
Authors: Cai Hong-bo , Zhu Shao-ping , He X. T. , Wu Si-zhong , Chen Mo , Zhou Cangtao , Yu Wei , Nagatomo Hideo
Published: February 2011

The efficient magnetic collimation of fast electron flow transporting in overdense plasmas is investigated with two-dimensional collisional particle-in-cell numerical simulations. It is found that the specially engineered targets exhibiting either high-resistivity-core-low-resistivity-cladding structure or low-density-core-high-density-cladding structure can collimate fast electrons. Two main mechanisms to generate collimating magnetic fields are found. In high-resistivity-core-low-resistivity-cladding structure targets, the magnetic field at the interfaces is generated by the gradients of the resistivity and fast electron current, while in low-density-core-high-density-cladding structure targets, the magnetic field is generated by the rapid changing of the flow velocity of the background electrons in transverse direction (perpendicular to the flow velocity) caused by the density jump. The dependences of the maximal magnetic field on the incident laser intensity and plasma density, which are studied by numerical simulations, are supported by our analytical calculations.
Development of ac corona discharge modes at atmospheric pressure
Authors: El-Koramy Reda Ahmed , Yehia Ashraf , Omer Mohamed
Published: February 2011

Corona discharges in gases exist under several distinctive forms. In this paper, a survey study has been made of ac corona discharge modes generated in some different gases fed in a wire-duct reactor with a constant rate of flowing at atmospheric pressure. The properties of different corona modes are analyzed under some condition transitions from Trichel pulses to a steady glow. In the course of the presented experimental work, numerous apparent contradictions with earlier observations necessitated further study and are given to provide more information on the physical mechanisms of the ac corona discharges. Furthermore, we have gained insight into some new technologies and applications of the environmentally friendly corona and plasma discharges.
Air-mediated self-organization of polymer semiconductors for high-performance solution-processable organic transistors
Authors: Kushida Takashi , Nagase Takashi , Naito Hiroyoshi
Published: February 2011

Air-mediated molecular ordering in the self-organized polymer semiconductor of regioregular poly(3-hexylthiophene) (P3HT) is investigated using organic field-effect transistors (OFETs) fabricated by microcontact printing using poly(dimethylsiloxane) stamps having varying surface energy. OFET measurements reveal a large difference between the P3HT thin film microstructure at the interface with air and that at the interface with the substrate and efficient charge transport through the former. These results indicate that the formation of a highly ordered microstructure at the P3HT/air interface through air-mediated self-organization is little affected by substrate-mediated molecular ordering at the other interface of the P3HT film.
Metastable properties of Cu(In1−xGax)Se2 with and without sodium
Authors: Erslev Peter T. , Shafarman William N. , Cohen J. David
Published: February 2011

We compare the electronic properties of Cu(In1−xGax)Se2 (CIGS, x=0.3) companion films with standard and nearly absent sodium levels. The films were examined over a wide range of metastable states produced by light-soaking. Admittance spectroscopy revealed that the activation energy of the dominant deep defect (hole trap) decreased monotonically from 300 to 60 meV with light-soaking time for samples with normal sodium, but remained nearly fixed (∼350 meV) for samples without sodium. Drive-level capacitance profiling indicated that the deep defect densities increased under light-soaking by roughly a factor of 20 for both samples and annealed at identical rates; however, the relative increases between the defect and hole carrier densities were dramatically different.
Slow dynamics in protein fluctuations revealed by time-structure based independent component analysis: The case of domain motions
Authors: Naritomi Yusuke , Fuchigami Sotaro
Published: February 2011

Protein dynamics on a long time scale was investigated using all-atom molecular dynamics (MD) simulation and time-structure based independent component analysis (tICA). We selected the lysine-, arginine-, ornithine-binding protein (LAO) as a target protein and focused on its domain motions in the open state. A MD simulation of the LAO in explicit water was performed for 600 ns, in which slow and large-amplitude domain motions of the LAO were observed. After extracting domain motions by rigid-body domain analysis, the tICA was applied to the obtained rigid-body trajectory, yielding slow modes of the LAO’s domain motions in order of decreasing time scale. The slowest mode detected by the tICA represented not a closure motion described by a largest-amplitude mode determined by the principal component analysis but a twist motion with a time scale of tens of nanoseconds. The slow dynamics of the LAO were well described by only the slowest mode and were characterized by transitions between two basins. The results show that tICA is promising for describing and analyzing slow dynamics of proteins.
Bias and temperature dependent charge transport in solution-processed small molecular mixed single layer organic light emitting devices
Authors: Wang Zhaokui , Lou Yanhui , Naka Shigeki , Okada Hiroyuki
Published: February 2011

The authors investigate bias and temperature dependent current density-voltage (J-V) characteristics in solution-processed small molecular mixed single layer organic light emitting devices using Au/MoO3 as hole and Al as electron injection electrode. Hole and electron injections are primarily ascribed to the Schottky thermionic emission mechanism. However, at high field of >9×105 V cm−1, hole transport is found to be bulk trapped corresponding to space charge limited current with an exponential distribution of traps. The bulk trap density, about 1018 cm−3 in mixed organic layer, is evaluated by the differential method.
Bottom-up coarse-graining of a simple graphene model: The blob picture
Authors: Kauzlarić David , Meier Julia T. , Español Pep , Succi Sauro , Greiner Andreas , Korvink Jan G.
Published: February 2011

The coarse-graining of a simple all-atom 2D microscopic model of graphene, in terms of “blobs” described by center of mass variables, is presented. The equations of motion of the coarse-grained variables take the form of dissipative particle dynamics (DPD). The coarse-grained conservative forces and the friction of the DPD model are obtained via a bottom-up procedure from molecular dynamics (MD) simulations. The separation of timescales for blobs of 24 and 96 carbon atoms is sufficiently pronounced for the Markovian assumption, inherent to the DPD model, to provide satisfactory results. In particular, the MD velocity autocorrelation function of the blobs is well reproduced by the DPD model, provided that the effect of friction and noise is taken into account. However, DPD cross-correlations between neighbor blobs show appreciable discrepancies with respect to the MD results. Possible extensions to mend these discrepancies are briefly outlined.
The enhanced binding energy for biexcitons in InAs quantum dots
Authors: Masumoto Yasuaki , Yoshida Seitaro , Ikezawa Michio , Tomimoto Shinichi , Sakuma Yoshiki
Published: February 2011

We observed that the biexciton binding energy in InAs quantum rhombic disks (QRDs) is enhanced by twice compared with that for InAs quantum dots (QDs) so far reported around 1.24 μm nearby the telecommunication wavelength. The heterodyne-detected four-wave-mixing detected the exciton-biexciton quantum beat superposed on photon echo decay, giving the biexciton binding energy of 3.4 meV to 3 monolayer (ML) InAs QRDs and 4.1 meV to 4 ML InAs QRDs, respectively. The largest biexciton binding energy of 4.1 meV in InAs QDs is ascribed to increased electron-hole overlap in confined geometry with a minimized strain distribution.
Instability and dewetting of ultrathin solid viscoelastic films on homogeneous and heterogeneous substrates
Authors: Patra Ajoy , Bandyopadhyay Dipankar , Tomar Gaurav , Sharma Ashutosh , Biswas Gautam
Published: February 2011

Instability and dewetting engendered by the van der Waals force in soft thin (<100 nm) linear viscoelastic solid (e.g., elastomeric gel) films on uniform and patterned surfaces are explored. Linear stability analysis shows that, although the elasticity of the film controls the onset of instability and the corresponding critical wavelength, the dominant length-scale remains invariant with the elastic modulus of the film. The unstable modes are found to be long-wave, for which a nonlinear long-wave analysis and simulations are performed to uncover the dynamics and morphology of dewetting. The stored elastic energy slows down the temporal growth of instability significantly. The simulations also show that a thermodynamically stable film with zero-frequency elasticity can be made unstable in the presence of physico-chemical defects on the substrate and can follow an entirely different pathway with far fewer holes as compared to the viscous films. Further, the elastic restoring force can retard the growth of a depression adjacent to the hole-rim and thus suppress the formation of satellite holes bordering the primary holes. These findings are in contrast to the dewetting of viscoelastic liquid films where nonzero frequency elasticity accelerates the film rupture and promotes the secondary instabilities. Thus, the zero-frequency elasticity can play a major role in imposing a better-defined long-range order to the dewetted structures by arresting the secondary instabilities.
The medicinal potential of Australian native plants from Toohey Forest, Australia
Authors: Kalt F. R. , Cock I. E.
Published: February 2011

Eleven methanolic extracts of ten Australian native plants from Toohey Forest, Brisbane, Australia were investigated for their potential medicinal value as antibacterial agents. All plants showed some antibacterial activity against at least one of the bacteria tested. Alcaligenes faecalis, Aeromonas hydrophilia and Bacillus cereus were the most susceptible bacteria, being inhibited by 9, 9 and 10 of the plant extracts respectively. Davallia pyxidata and Marchantia polymorpha extracts were least effective, inhibiting the growth of only 1 or 2 bacteria respectively. Acrotriche aggregata, Petalostigma pubescens, Leptospermum trinervia and Planchonella queenslandica leaf extracts were particularly effective bacterial agents being capable of inhibiting the growth of 8 (57%), 10 (71%), 9 (64%) and 9 (64%) of the bacteria tested respectively. A. aggregata, P. pubescens and L. trinervia leaf extracts displayed low toxicity in the Artemia franciscana nauplii bioassay, confirming their potential as antibacterial agents for medicinal use.
Decay form of the echo amplitude and echo phase of typical early/fast VLF event on 19.8 kHz signal
Authors: Kumar Abhikesh , Kumar Sushil
Published: February 2011

In this paper, the echo amplitude (M) and echo phase (ø) of typical early/fast events on NWC (19.8 kHz) signal received at Suva, Fiji, are modelled to determine their form of recovery (decay). We applied logarithmic and exponential fitting formulas for M and ø obtained using a simple theoretical model of VLF wave scattering from lightning-induced electron density perturbations in the lower ionosphere and found that they are highly logarithmic.
Therapeutical targeting of nucleic acid-sensing Toll-like receptors prevents experimental cerebral malaria
Authors: Franklin Bernardo S. , Ishizaka Sally T. , Lamphier Marc , Gusovsky Fabian , Hansen Hans , Rose Jeffrey , Zheng Wanjun , Ataíde Marco Antônio , de Oliveira Rosane B. , Golenbock Douglas T. , Gazzinelli Ricardo T.
Published: February 2011

Excessive release of proinflammatory cytokines by innate immune cells is an important component of the pathogenic basis of malaria. Proinflammatory cytokines are a direct output of Toll-like receptor (TLR) activation during microbial infection. Thus, interference with TLR function is likely to render a better clinical outcome by preventing their aberrant activation and the excessive release of inflammatory mediators. Herein, we describe the protective effect and mechanism of action of E6446, a synthetic antagonist of nucleic acid-sensing TLRs, on experimental cerebral malaria (ECM) induced by
Plasmodium berghei
ANKA. We show that in vitro, low doses of E6446 specifically inhibited the activation of human and mouse TLR9. Tenfold higher concentrations of this compound also inhibited the human TLR8 response to single-stranded RNA. In vivo, therapy with E6446 diminished the activation of TLR9 and prevented the exacerbated cytokine response observed during acute
Plasmodium
infection. Furthermore, severe signs of ECM, such as limb paralysis, brain vascular leak, and death, were all prevented by oral treatment with E6446. Hence, we provide evidence that supports the involvement of nucleic acid-sensing TLRs in malaria pathogenesis and that interference with the activation of these receptors is a promising strategy to prevent deleterious inflammatory responses that mediate pathogenesis and severity of malaria.
Raman study of correlation between defects and ferromagnetism in graphite
Authors: He Zhoutong , Xia Huihao , Zhou Xingtai , Yang Xinmei , Song You , Wang Tianwei
Published: February 2011

The variation of ferromagnetism induced by 12C+ ion implantation in highly oriented pyrolytic graphite was systematically studied by using Raman spectroscopy in conjunction with magnetic moment measurements and annealing treatments. It was found that the magnetization of the implanted sample was closely correlated with the density of the defects, which was characterized by the Raman spectra, produced by the implantation. It is clear that by using consecutive implantation steps at different energies to increase the vacancy defects in the implanted layer, the magnetization of the sample increases with the number of the implantation steps until the fourth step of implantation, which causes the near surface layer to be highly disordered or amorphous, weakening the magnetic coupling and thus resulting in the decrease in magnetization. The annealing treatments of the sample indicate that the ferromagnetism induced by the implantations is stable at room temperature. However, when the sample is annealed at 473 K (the Wigner energy release temperature), the density of vacancies and interstitials is abruptly decreased and the magnetism induced by the implantations is extinguished. This finding gives a clear indication of the key role of the defects produced by C+ ion implantation in graphite.
Unintentional doping of a-plane GaN by insertion of in situ SiN masks
Authors: Witte H , Wieneke M , Rohrbeck A , Guenther K-M , Dadgar A , Krost A
Published: February 2011

Undoped a-plane GaN layers grown by metal-organic vapour phase epitaxy on sapphire (1 0 − 1 2) substrates using low temperature (LT) GaN seed layers and in situ SiN masks were characterized by Hall-effect measurements, CV-characteristics and photovoltage spectroscopy. With increasing deposition time of the SiN masks the electron concentrations of the GaN layers are enhanced. The dominant activation energy between 14 and 22 meV determined by temperature-dependent Hall effect is very similar to the donor silicon on gallium site. Two other activation energies at 30 meV and between 50 and 70 meV were found corresponding well with OGa and VN defects, respectively. The depth profiles of the net donor densities show a strong increase towards the substrate/LT-GaN/high temperature(HT)-GaN interface indicating diffusion of silicon from the SiN mask towards the surface. Therefore, the Si doping is attributed to the dissolution of the SiN masks during the following HT GaN layer growth. The Si doping from the SiN masks also explains the deterioration of the band bending within the LT-GaN/HT-GaN junction found by photovoltage spectroscopy.
Modelling of dielectric barrier discharge plasma actuators with thick electrodes
Authors: Hoskinson A R , Hershkowitz N
Published: February 2011

We have developed a new two-dimensional fluid simulation to model the plasma dynamics in surface dielectric barrier discharges operating in air. Single-barrier (one electrode insulated) and double-barrier (both electrodes insulated) discharges have been observed to generate a force in the nearby air, making them potentially useful as aerodynamic actuators. Many previous simulations of such discharges have modelled the electrodes as thin strips. We instead consider plasma actuators including cylindrical electrodes of various sizes. In single-barrier actuators, the size of the exposed electrode qualitatively affects the discharge dynamics, particularly with a negative-going applied voltage. For both geometries, the simulations predict the formation of plasma structures similar to those imaged in previous experiments. Experimentally observed increases in forces for actuators with smaller high-voltage electrodes were only reproduced for the single-barrier geometry. Due to limitations of computational power, voltage rates of change for all simulations were higher than those used in experiments.
Turbulence and radiation behaviours in large-scale arc heaters
Authors: Takahashi Yusuke , Kihara Hisashi , Abe Ken-ichi
Published: February 2011

Turbulent plasma flow in large-scale arc heaters such as JAXA 750 kW and NASA 20 MW facilities was investigated and distributions of flow-field properties were successfully obtained. The turbulent flow field was described by the Navier–Stokes equations with a multitemperature model, which was tightly coupled with electric-field and radiation-field calculations. An accurate and low-cost radiation model, and a low Reynolds number two-equation turbulence model were introduced into the flow-field simulation. It was confirmed that the plasma flows in the arc-heating facilities were in a highly thermochemical nonequilibrium state in the expansion section and that the arc discharge plays a critical role in the heating section. It was quantitatively clarified that radiation and turbulence phenomena were very important in transferring heat and momentum from the high-temperature flow near the core to the cold gas region near the facility wall. To confirm the effectiveness of the present numerical model, the obtained results were compared with experimental data for the arc voltage, mass-averaged enthalpy, chamber pressure and heat efficiency. The present flow-field model was found to give good agreement for various operating conditions of the facilities.
Effects of vacuum ultraviolet photons, ion energy and substrate temperature on line width roughness and RMS surface roughness of patterned 193 nm photoresist
Authors: Titus M J , Graves D B , Yamaguchi Y , Hudson E A
Published: February 2011

We present a comparison of patterned 193 nm photoresist (PR) line width roughness (LWR) of samples processed in a well characterized argon (Ar) inductively coupled plasma (ICP) system to RMS surface roughness and bulk chemical modification of blanket 193 nm PR samples used as control samples. In the ICP system, patterned and blanket PR samples are irradiated with Ar vacuum ultraviolet photons (VUV) and Ar ions while sample temperature, photon flux, ion flux and ion energy are controlled and measured. The resulting chemical modifications to bulk 193 nm PR (blanket) and surface roughness are analysed with Fourier transform infrared spectroscopy and atomic force microscopy (AFM). LWR of patterned samples are measured with scanning electron microscopy and blanket portions of the patterned PRs are measured with AFM. We demonstrate that with no RF-bias applied to the substrate the LWR of 193 nm PR tends to smooth and correlates with the smoothing of the RMS surface roughness. However, both LWR and RMS surface roughness increases with simultaneous high-energy (⩾70 eV) ion bombardment and VUV-irradiation and is a function of exposure time. Both high- and low-frequency LWR correlate well with the RMS surface roughness of the patterned and blanket 193 nm PR samples. LWR, however, does not increase with temperatures ranging from 20 to 80 °C, in contrast to the RMS surface roughness which increases monotonically with temperature. It is unclear why LWR remains independent of temperature over this range. However, the fact that blanket roughness and LWR on patterned samples, both scale similarly with VUV fluence and ion energy suggests a similar mechanism is responsible for both types of surface morphology modifications.
Resistive switching characteristics of maghemite nanoparticle assembly
Authors: Hu Quanli , Jung Sung Mok , Lee Hyun Ho , Kim Yong-Sang , Choi Young Jin , Kang Dae-Hwan , Kim Ki-Bum , Yoon Tae-Sik
Published: February 2011

The resistive switching characteristics of the assembly of maghemite (γ-Fe2O3) nanoparticles having a diameter of ∼10 nm were investigated in the structure of Al/γ-Fe2O3 nanoparticle multilayer (∼300 nm thick)/Al-plate. The nanoparticle multilayer on Al plate was formed by repeating dip-coating processes. The multilevel (five states) resistive switching was observed with the resistance values ranging from ∼4.8 × 105 to 2.7 × 103 Ω depending on the externally applied voltage. The multilevel switching is thought to originate from the repetitive and reversible formation and rupture of multiple conducting filaments. It demonstrates the potential application of the γ-Fe2O3 nanoparticle assembly for resistive switching devices.
Dynamic actuation methods for capacitive MEMS shunt switches
Authors: Khater M E , Vummidi K , Abdel-Rahman E M , Nayfeh A H , Raman S
Published: February 2011

We develop dynamic actuation methods for capacitive MEMS shunt switches. We show that the dynamic actuation voltage is significantly less than the static actuation voltage and demonstrate 60% reduction in the actuation voltage. We also show that this reduction in the actuation voltage depends on the specific dynamic switching technique adopted. For a given operating condition, the minimum realizable switching time is that obtained using static switching. However, we developed a dynamic switching method that yields comparable switching time to that minimum. We also found that squeeze-film damping is the dominant damping mechanism for a shunt switch with a relatively slender bridge (aspect ratio of 11:1).
Time-frequency concentration of generating systems
Authors: Jaming Philippe , Powell Alexander
Published: February 2011

Uncertainty principles for generating systems

{

e
n

}

n
=
1

∞

⊂

L
2

(

R

)

\{e_n\}_{n=1}^{\infty } \subset L^2(\mathbb {R})

are proven and quantify the interplay between

ℓ
r

(

N

)

\ell ^r(\mathbb {N})

coefficient stability properties and time-frequency localization with respect to

|

t

|

p

|t|^p

power weight dispersions. As a sample result, it is proven that if the unit-norm system

{

e
n

}

n
=
1

∞

\{e_n\}_{n=1}^{\infty }

is a Schauder basis or frame for

L
2

(

R

)

L^2(\mathbb {R})

, then the two dispersion sequences

Δ
(

e
n

)

\Delta (e_n)

,

Δ
(

e
n

^

)

\Delta (\widehat {e_n})

and the one mean sequence

μ
(

e
n

)

\mu (e_n)

cannot all be bounded. On the other hand, it is constructively proven that there exists a unit-norm exact system

{

f
n

}

n
=
1

∞

\{f_n\}_{n=1}^{\infty }

in

L
2

(

R

)

L^2(\mathbb {R})

for which all four of the sequences

Δ
(

f
n

)

\Delta (f_n)

,

Δ
(

f
n

^

)

\Delta (\widehat {f_n})

,

μ
(

f
n

)

\mu (f_n)

,

μ
(

f
n

^

)

\mu (\widehat {f_n})

are bounded.
Safeguarding Children
Authors: Hempton Nicola , Williams Richard
Published: February 2011

The maltreatment of children in the UK remains an extensive problem and recent high profile cases have highlighted our responsibility to protect these children. Children will have contact with health and social professionals during their childhood and it is essential that GPs are alert to the possibility of child abuse. This article will describe important legislation to be aware of, the different types of abuse, what constitutes ‘safeguarding’, symptoms and signs to look out for in accordance with recent National Institute for Health and Clinical Excellence (NICE) guidance and what action to take if child maltreatment is suspected.
Individuality in bird migration: routes and timing
Authors: Vardanis Yannis , Klaassen Raymond H. G. , Strandberg Roine , Alerstam Thomas
Published: February 2011

The exploration of animal migration has entered a new era with individual-based tracking during multiple years. Here, we investigated repeated migratory journeys of a long-distance migrating bird, the marsh harrierCircus aeruginosus, in order to analyse the variation within and between individuals with respect to routes and timing. We found that there was a stronger individual repeatability in time than in space. Thus, the annual timing of migration varied much less between repeated journeys of the same individual than between different individuals, while there was considerable variation in the routes of the same individual on repeated journeys. The overall contrast in repeatability between time and space was unexpected and may be owing to strong endogenous control of timing, while short-term variation in environmental conditions (weather and habitat) might promote route flexibility. The individual variation in migration routes indicates that the birds navigate mainly by other means than detailed route recapitulation based on landmark recognition.
A common heritable factor influences prosocial obligations across multiple domains
Authors: Lewis Gary J. , Bates Timothy C.
Published: February 2011

Although it has been shown that prosocial behaviour is heritable, it has not yet been established whether narrower aspects of prosociality are heritable, nor whether a common mechanism influences prosociality across its multiple domains. Here, we examine civic duty, work-place commitment and concern for the welfare of others with a study of prosocial obligations in 958 adult twin-pairs. Multivariate modelling indicated the existence of genetic factors underlying general prosocial obligations in females, with familial effects (genetic and shared-environment effects were indistinguishable) influencing this general mechanism in males. At the domain-specific level, modest genetic effects were observed in females for civic and work obligations, with shared-environment effects influencing welfare obligations. In males, genetic influences were observed for welfare obligation, with unique environments affecting work and civic duty.
Bone remodelling in Neanderthal mandibles from the El Sidrón site (Asturias, Spain)
Authors: Martinez-Maza Cayetana , Rosas Antonio , García-Vargas Samuel , Estalrrich Almudena , de la Rasilla Marco
Published: February 2011

Skull morphology results from the bone remodelling mechanism that underlies the specific bone growth dynamics. Histological study of the bone surface from Neanderthal mandible specimens of El Sidrón (Spain) provides information about the distribution of the remodelling fields (bone remodelling patterns or BRP) indicative of the bone growth directions. In comparison with other primate species, BRP shows that Neanderthal mandibles from the El Sidrón (Spain) sample present a specific BRP. The interpretation of this map allows inferences concerning the growth directions that explain specific morphological traits of the Neanderthal mandible, such as its quadrangular shape and the posterior location of the mental foramen.
Ant queens adjust egg fertilization to benefit from both sexual and asexual reproduction
Authors: Aron S. , Timmermans I. , Pearcy M.
Published: February 2011

An enduring problem in evolutionary biology is the near ubiquity of sexual reproduction despite the inherent cost of transmitting only half the parent's genes to progeny. Queens of some ant species circumvent this cost by using selectively both sexual reproduction and parthenogenesis: workers arise from fertilized eggs, while new queens are produced by parthenogenesis. We show that queens of the ant
Cataglyphis cursor
maximize the transmission rate of their genes by regulating the proportion of fertilized and parthenogenetic eggs laid over time. Parthenogenetic offspring are produced in early spring, when workers raise the brood into sexuals. After the mating period, queens lay mostly fertilized eggs that will be reared as the non-reproductive caste.
Stress associated with group living in a long-lived bird
Authors: Selva Nuria , Cortés-Avizanda Ainara , Lemus Jesús A. , Blanco Guillermo , Mueller Thomas , Heinrich Bernd , Donázar José A.
Published: February 2011

Many long-lived avian species adopt life strategies that involve a gregarious way of life at juvenile and sub-adult stages and territoriality during adulthood. However, the potential associated costs of these life styles, such as stress, are poorly understood. We examined the effects of group living, sex and parasite load on the baseline concentration of faecal stress hormone (corticosterone) metabolites in a wild population of common ravens (Corvus corax). Corticosterone concentrations were significantly higher in non-breeding gregarious ravens than in territorial adults. Among territorial birds, males showed higher stress levels than their mates. Parasite burdens did not affect hormone levels. Our results suggest a key role of the social context in the stress profiles of the two population fractions, and that group living may be more energetically demanding than maintaining a territory. These findings have implications for understanding hormonal mechanisms under different life styles and may inspire further research on the link between hormone levels and selective pressures modulating gregarious and territorial strategies in long-lived birds.
Nocturnal insects use optic flow for flight control
Authors: Baird Emily , Kreiss Eva , Wcislo William , Warrant Eric , Dacke Marie
Published: February 2011

To avoid collisions when navigating through cluttered environments, flying insects must control their flight so that their sensory systems have time to detect obstacles and avoid them. To do this, day-active insects rely primarily on the pattern of apparent motion generated on the retina during flight (optic flow). However, many flying insects are active at night, when obtaining reliable visual information for flight control presents much more of a challenge. To assess whether nocturnal flying insects also rely on optic flow cues to control flight in dim light, we recorded flights of the nocturnal neotropical sweat bee,Megalopta genalis, flying along an experimental tunnel when: (i) the visual texture on each wall generated strong horizontal (front-to-back) optic flow cues, (ii) the texture on only one wall generated these cues, and (iii) horizontal optic flow cues were removed from both walls. We find thatMegaloptaincrease their groundspeed when horizontal motion cues in the tunnel are reduced (conditions (ii) and (iii)). However, differences in the amount of horizontal optic flow on each wall of the tunnel (condition (ii)) do not affect the centred position of the bee within the flight tunnel. To better understand the behavioural response ofMegalopta, we repeated the experiments on day-active bumble-bees (Bombus terrestris). Overall, our findings demonstrate that despite the limitations imposed by dim light,Megalopta—like their day-active relatives—rely heavily on vision to control flight, but that they use visual cues in a different manner from diurnal insects.
Effects of reduced dimensionality on the electronic structure and defect chemistry of semiconducting hybrid organic–inorganic PbS solids
Authors: Walsh Aron
Published: February 2011

The combination of inorganic and organic frameworks to produce crystalline hybrid semiconductors offers a pathway for obtaining novel photovoltaic and optoelectronic materials. Taking an archetypal binary semiconductor, PbS (galena), we investigate the electronic effects of the reduced dimensionality in the PbS framework on transition from bulk PbS to three-dimensional and one-dimensional hybrid inorganic–organic networks. Analysis of density functional theory calculations reveals the substantial contribution of the organic (benzenehexathiol derivates) to the band-edge states. Implications for intrinsic defect formation and potential application in solar cell devices are discussed, as well as future design pathways for engineering the electronic properties of this new class of hybrid metal–organic framework.
Effective constitutive relations for waves in composites and metamaterials
Authors: Willis J. R.
Published: February 2011

Definitions of ‘effective fields’ for a randomly inhomogeneous material are offered, which guarantee automatic satisfaction of the equations of motion. The important case of a medium with periodic microstructure is included. In this special case, the definitions are completely explicit and can be applied without reference to random media. The presentation is mostly expressed in terms of electromagnetic waves. The reasoning is applicable also to other types of waves and its realization for elastodynamics is briefly outlined towards the end. Some of the effective fields are defined directly as ensemble averages, ensuring the exact satisfaction of the equations of motion, but the effective ‘kinematic’ fields to which they are related are defined more generally, as weighted averages. The main result of this work is an explicit formula for the tensor of effective properties. The important issue of uniqueness (or not) of the effective properties is explained and resolved. Self-adjointness of the original problem is not assumed. An attractive feature of the formulation is that self-adjointness at the local level implies self-adjointness at the level of the ‘effective medium’.
Maximum-likelihood estimation of recent shared ancestry (ERSA)
Authors: Huff Chad D. , Witherspoon David J. , Simonson Tatum S. , Xing Jinchuan , Watkins W. Scott , Zhang Yuhua , Tuohy Therese M. , Neklason Deborah W. , Burt Randall W. , Guthery Stephen L. , Woodward Scott R. , Jorde Lynn B.
Published: February 2011

Accurate estimation of recent shared ancestry is important for genetics, evolution, medicine, conservation biology, and forensics. Established methods estimate kinship accurately for first-degree through third-degree relatives. We demonstrate that chromosomal segments shared by two individuals due to identity by descent (IBD) provide much additional information about shared ancestry. We developed a maximum-likelihood method for the estimation of recent shared ancestry (ERSA) from the number and lengths of IBD segments derived from high-density SNP or whole-genome sequence data. We used ERSA to estimate relationships from SNP genotypes in 169 individuals from three large, well-defined human pedigrees. ERSA is accurate to within one degree of relationship for 97% of first-degree through fifth-degree relatives and 80% of sixth-degree and seventh-degree relatives. We demonstrate that ERSA's statistical power approaches the maximum theoretical limit imposed by the fact that distant relatives frequently share no DNA through a common ancestor. ERSA greatly expands the range of relationships that can be estimated from genetic data and is implemented in a freely available software package.
ABO blood group alleles and the risk of pancreatic cancer in a Japanese population
Authors: Nakao Makoto , Matsuo Keitaro , Hosono Satoyo , Ogata Saeko , Ito Hidemi , Watanabe Miki , Mizuno Nobumasa , Iida Shinsuke , Sato Shigeki , Yatabe Yasushi , Yamao Kenji , Ueda Ryuzo , Tajima Kazuo , Tanaka Hideo
Published: February 2011

Several studies have investigated a possible association between the ABO blood group and the risk of pancreatic cancer (PC), but this association has not been fully evaluated in Asian populations. The present study aimed to assess the impact of genotype‐derived ABO blood types, particularly ABO alleles, on the risk of PC in a Japanese population. We conducted a case–control study using 185 PC and 1465 control patients who visited Aichi Cancer Center in Nagoya, Japan. Using rs8176719 as a marker for the O allele, and rs8176746 and rs8176747 for the B allele, all participants’ two ABO alleles were inferred. The impact of ABO blood type on PC risk was examined by multivariate analysis, with adjustment for potential confounders to estimate odds ratios (OR) and 95% confidence intervals (CI). An increased risk of PC was observed with the addition of any non‐O allele (trend P = 0.012). Compared with subjects with the OO genotype, those with AO and BB genotypes had significantly increased OR of 1.67 (CI, 1.08–2.57) and 3.28 (CI, 1.38–7.80), respectively. Consistent with earlier reports showing a higher risk of PC for individuals with the non‐O blood type, the previously reported protective allele (T) for rs505922 was found to be strongly correlated (r2 = 0.96) with the O allele. In conclusion, this case–control study showed a statistically significant association between ABO blood group and PC risk in a Japanese population. Further studies are necessary to define the mechanisms by which the ABO gene or closely linked genetic variants influence PC risk. (Cancer Sci 2011; 102: 1076–1080)
Monocarboxylate transporters 1 and 4 are involved in the invasion activity of human lung cancer cells
Authors: Izumi Hiroto , Takahashi Mayu , Uramoto Hidetaka , Nakayama Yoshifumi , Oyama Tsunehiro , Wang Ke‐Yong , Sasaguri Yasuyuki , Nishizawa Shigeru , Kohno Kimitoshi
Published: February 2011

Cancer cells show constitutive upregulation of glycolysis, and the concentration of lactate thus produced correlates with prognosis. Here, we examined whether lactate concentration and lactate transporter expression are related to migration and invasion activity. We found that the expression of the monocarboxylate transporters MCT1 and MCT4, but not MCT5, in human lung cancer cell lines was significantly correlated with invasiveness. To clarify the effects of MCT1 and MCT4 expression on invasion, we performed migration and invasion assays after transfection with siRNA specific for MCT1 or MCT4. Knockdown of MCT1 or MCT4 did not influence cell migration but reduced invasion; this was also observed for knockdown of the lactate transporter‐associated protein basigin. We also demonstrated that both expression and activity of MMP9 and MMP2 were not correlated with invasion activity and not regulated by MCT1, MCT4 and basigin. Furthermore, the addition of lactate did not increase migration and invasion activity, but low concentration of 4,4′‐diisothiocyanatostilbene‐2,2′‐disulphonic acid (DIDS), a general anion channel blocker, as well as other MCT inhibitors quercetin and simvastatin, inhibited cell invasion without influencing migration activity and the cellular expression of MCT1 and MCT4. This is the first report suggesting that lactate transporters are involved in human cancer cell invasiveness. As such, these proteins may be promising targets for the prevention of cancer invasion and metastasis. (Cancer Sci 2011; 102: 1007–1013)
General principles of investigating and managing drug allergy
Authors: Frew Anthony
Published: February 2011

Adverse reactions to medication are common. Some are predictable side‐effects of the drug, others involve individual sensitivity to the drug. Allergic reactions are an important subset of these, but other specific sensitivities are caused by variations in the metabolism or mode of action of the drug. Patients who have experienced adverse reactions to medication will often refer to themselves as being allergic to the drug, regardless of the actual mechanism that caused the reaction. Consequently, anyone taking a history of ‘drug allergy’ needs to keep an open mind about the mechanism that may have been involved. Fortunately, most idiosyncratic reactions are minor, but some are severe, or even life‐threatening. In most situations, there are satisfactory alternatives for the drug in question, but sometimes it is necessary to investigate and get an accurate diagnosis. The over‐riding priority is to distinguish anaphylactic, potentially life‐threatening reactions from other types of drug reaction, which are generally more protracted, less dangerous and usually managed by simple avoidance. While all doctors need to understand the underlying principles, drug challenges should only be undertaken by clinicians experienced in this area.