bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and chemical properties of the nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate under pressure
Authors: McWilliams R. Stewart , Kadry Yasmin , Mahmood Mohammad F. , Goncharov Alexander F. , Ciezak-Jenkins Jennifer
Published: August 2012

The structural and chemical properties of the bi-molecular, hydrogen-bonded, nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate C3H12N12O2 (TAG-MNT) have been investigated at room pressure and under high pressure isothermal compression using powder x-ray diffraction and Raman and infrared spectroscopy. A stiffening of the equation of state and concomitant structural relaxation between 6 and 14 GPa are found to correlate with Raman mode disappearances, frequency discontinuities, and changes in the pressure dependence of modes. These observations manifest the occurrence of a reversible martensitic structural transformation to a new crystalline phase. The onset and vanishing of Fermi resonance in the nitrimine group correlate with the stiffening of the equation of state and phase transition, suggesting a possible connection between these phenomena. Beyond 15 GPa, pressure induces irreversible chemical reactions, culminating in the formation of a polymeric phase by 60 GPa.
Ferrofluid flow in a spherical cavity under an imposed uniform rotating magnetic field: Spherical spin-up flow
Authors: Torres-Diaz I. , Rinaldi C.
Published: August 2012

An analytical solution is obtained for the ferrohydrodynamic problem of flow of a ferrofluid in a spherical cavity under the influence of a uniform rotating magnetic field produced by a fluxball winding. The ferrohydrodynamics equations are decoupled for low values of the applied magnetic field amplitude to allow analytical solution. A governing equation for the divergence of spin velocity is obtained and used to demonstrate that the divergence of the spin velocity is zero under conditions of small uniform magnetic field. The condition of zero spin viscosity results in no flow being predicted in the cavity. For the case of non-zero spin viscosity the condition of zero divergence of spin results in the inability of the ferrohydrodynamics equations to satisfy boundary conditions for both the normal and tangential components of the spin velocity at the sphere wall. Solutions are obtained for cases where boundary conditions are imposed on either the normal or tangential component of the spin velocity. In both cases, the solutions predict that the ferrofluid rotates rigid-body-like about the axis of field rotation in the core and there is a region near the outer wall where flow reduces to satisfy the no slip boundary condition on the translational velocity. However, the two solutions differ in their asymptotic behavior when the spin viscosity vanishes. It is found that when the boundary condition is applied to the tangential component of the spin velocity, the zero spin viscosity solution is recovered as η′ → 0, whereas when the boundary condition is applied to the normal component of the spin velocity the solution diverges as η′ → 0. The results indicate that studying the flow of ferrofluids in a spherical cavity could yield important tests of long-held, arguably ad hoc assumptions surrounding the governing equations and boundary conditions of ferrofluid flow.
Methane and carbon dioxide adsorption on edge-functionalized graphene: A comparative DFT study
Authors: Wood Brandon C. , Bhide Shreyas Y. , Dutta Debosruti , Kandagal Vinay S. , Pathak Amar Deep , Punnathanam Sudeep N. , Ayappa K. G. , Narasimhan Shobhana
Published: August 2012

With a view towards optimizing gas storage and separation in crystalline and disordered nanoporous carbon-based materials, we use ab initio density functional theory calculations to explore the effect of chemical functionalization on gas binding to exposed edges within model carbon nanostructures. We test the geometry, energetics, and charge distribution of in-plane and out-of-plane binding of CO2 and CH4 to model zigzag graphene nanoribbons edge-functionalized with COOH, OH, NH2, H2PO3, NO2, and CH3. Although different choices for the exchange-correlation functional lead to a spread of values for the binding energy, trends across the functional groups are largely preserved for each choice, as are the final orientations of the adsorbed gas molecules. We find binding of CO2 to exceed that of CH4 by roughly a factor of two. However, the two gases follow very similar trends with changes in the attached functional group, despite different molecular symmetries. Our results indicate that the presence of NH2, H2PO3, NO2, and COOH functional groups can significantly enhance gas binding, making the edges potentially viable binding sites in materials with high concentrations of edge carbons. To first order, in-plane binding strength correlates with the larger permanent and induced dipole moments on these groups. Implications for tailoring carbon structures for increased gas uptake and improved CO2/CH4 selectivity are discussed.
On the origin of the mobility reduction in n- and p-metal–oxide–semiconductor field effect transistors with hafnium-based/metal gate stacks
Authors: Toniutti P. , Palestri P. , Esseni D. , Driussi F. , De Michielis M. , Selmi L.
Published: August 2012

We examine the mobility reduction measured in hafnium-based dielectrics in n- and p-MOSFETs by means of extensive comparison between accurate multi-subband Monte Carlo simulations and experimental data for reasonably mature process technologies. We have considered scattering with remote (soft-optical) phonons and remote Coulomb interaction with single layers and dipole charges. A careful examination of model assumptions and limitations leads us to the conclusion that soft optical phonon scattering cannot quantitatively explain by itself the experimental mobility reduction reported by several groups for neither the electron nor the hole inversion layers. Experimental data can be reproduced only assuming consistently large concentrations of Coulomb scattering centers in the gate stack. However, the corresponding charge or dipole density would result in a large threshold voltage shift not observed in the experiments. We thus conclude that the main mechanisms responsible for the mobility reduction in MOSFETs featuring Hafnium-based high-κ dielectric have not been completely identified yet. Additional physical mechanisms that could reconcile simulations with experimental results are suggested and critically discussed.
Surface hopping dynamics using a locally diabatic formalism: Charge transfer in the ethylene dimer cation and excited state dynamics in the 2-pyridone dimer
Authors: Plasser Felix , Granucci Giovanni , Pittner Jiri , Barbatti Mario , Persico Maurizio , Lischka Hans
Published: August 2012

In this work, the advantages of a locally diabatic propagation of the electronic wave function in surface hopping dynamics proceeding on adiabatic surfaces are presented providing very stable results even in challenging cases of highly peaked nonadiabatic interactions. The method was applied to the simulation of transport phenomena in the stacked ethylene dimer radical cation and the hydrogen bonded 2-pyridone dimer. Systematic tests showed the reliability of the method, in situations where standard methods relying on an adiabatic propagation of the wave function and explicit calculation of the nonadiabatic coupling terms exhibited significant numerical instabilities. Investigations of the ethylene dimer radical cation with an intermolecular distance of 7.0 Å provided a quantitative description of diabatic charge trapping. For the 2-pyidone dimer, a complex dynamics was obtained: a very fast (<10 fs) initial S2/S1 internal conversion; subsequent excitation energy transfers with a characteristic time of 207 fs; and the occurrence of proton coupled electron transfer (PCET) in 26% of the trajectories. The computed characteristic excitation energy transfer time of 207 fs is in satisfactory agreement with the experimental value of 318 fs derived from the vibronic exciton splittings in a monodeuterated 2-pyridone dimer complex. The importance of nonadiabatic coupling for the PCET related to the electron transfer was demonstrated by the dynamics simulations.
A benchmark for non-covalent interactions in solids
Authors: Otero-de-la-Roza A. , Johnson Erin R.
Published: August 2012

A benchmark for non-covalent interactions in solids (C21) based on the experimental sublimation enthalpies and geometries of 21 molecular crystals is presented. Thermal and zero-point effects are carefully accounted for and reference lattice energies and thermal pressures are provided, which allow dispersion-corrected density functionals to be assessed in a straightforward way. Other thermal corrections to the sublimation enthalpy (the 2RT term) are reexamined. We compare the recently implemented exchange-hole dipole moment (XDM) model with other approaches in the literature to find that XDM roughly doubles the accuracy of DFT-D2 and non-local functionals in computed lattice energies (4.8 kJ/mol mean absolute error) while, at the same time, predicting cell geometries within less than 2% of the experimental result on average. The XDM model of dispersion interactions is confirmed as a very promising approach in solid-state applications.
Fast visible imaging and edge turbulence analysis in QUEST
Authors: Banerjee Santanu , Zushi H. , Nishino N. , Nagashima Y. , Hanada K. , Ishiguro M. , Ryoukai T. , Tashima S. , Inoue T. , Nakamura K. , Idei H. , Hasegawa M. , Fujisawa A. , Matsuoka K.
Published: August 2012

A fast visible imaging system is installed on the spherical tokamak QUEST to study edge turbulence. The camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1024 × 1024 at 7000 frames/s (fps) and can achieve 775 kfps at a resolution of 128 × 24. In this paper, we present the salient features of the system and its application to study edge turbulence in 8.2 GHz ECRH driven slab plasma, without plasma current. Vertical magnetic field (Bz) topology is varied with three sets of poloidal field (PF) coils and the variation in the edge turbulence is investigated as a function of the Bz strength and curvature. Fluctuation amplitude was highest for the shallow PF well. Cross-correlation coefficient shows distinct coherent mode along z direction at the steep density gradient region and it grows with the PF mirror ratio.
Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torus
Authors: Jeong-hun Yang , Chung Kyoung-Jae , An YoungHwa , Jung Bong Ki , Jo Jong Gab , Hwang Y. S.
Published: August 2012

A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device.
HELIOS: A helium line-ratio spectral-monitoring diagnostic used to generate high resolution profiles near the ion cyclotron resonant heating antenna on TEXTOR
Authors: Unterberg E. A. , Schmitz O. , Fehling D. H. , Stoschus H. , Klepper C. C. , Muñoz-Burgos J. M. , Van Wassenhove G. , Hillis D. L.
Published: August 2012

Radial profiles of electron temperature and density are measured at high spatial (∼1 mm) and temporal (⩾10 μs) resolution using a thermal supersonic helium jet. A highly accurate detection system is applied to well-developed collisional-radiative model codes to produce the profiles. Agreement between this measurement and an edge Thomson scattering measurement is found to be within the error bars (≲20%). The diagnostic is being used to give profiles near the ion cyclotron resonant heating antenna on TEXTOR to better understand RF coupling to the core.
Isospectral compression and other useful isospectral transformations of dynamical networks
Authors: Bunimovich L. A. , Webb B. Z.
Published: August 2012

It is common knowledge that a key dynamical characteristic of a network is its spectrum (the collection of all eigenvalues of the network’s weighted adjacency matrix). We demonstrated that it is possible to reduce a network, considered as a graph, to a smaller network with fewer vertices and edges while preserving the spectrum (or spectral information) of the original network [L. A. Bunimovich and B. Z. Webb, Nonlinearity 25, 211-254 (2012)]. This procedure allows for the introduction of new equivalence relations between networks, where two networks are spectrally equivalent if they can be reduced to the same network. Additionally, using this theory it is possible to establish whether a network, modeled as a dynamical system, has a globally attracting fixed point (is strongly synchronizing). In this paper, we further develop this theory of isospectral network transformations and demonstrate that our procedures are applicable to families of parameterized networks and networks of arbitrary size.
Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for spin I = 1
Authors: Nilsson Tomas , Halle Bertil
Published: August 2012

The frequency dependence of the longitudinal relaxation rate, known as the magnetic relaxation dispersion (MRD), can provide a frequency-resolved characterization of molecular motions in complex biological and colloidal systems on time scales ranging from 1 ns to 100 μs. The conformational dynamics of immobilized proteins and other biopolymers can thus be probed in vitro or in vivo by exploiting internal water molecules or labile hydrogens that exchange with a dominant bulk water pool. Numerous water 1H and 2H MRD studies of such systems have been reported, but the widely different theoretical models currently used to analyze the MRD data have resulted in divergent views of the underlying molecular motions. We have argued that the essential mechanism responsible for the main dispersion is the exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings when internal water molecules or labile hydrogens escape from orientationally confining macromolecular sites. In the EMOR model, the exchange process is thus not just a means of mixing spin populations but it is also the direct cause of spin relaxation. Although the EMOR theory has been used in several studies to analyze water 2H MRD data from immobilized biopolymers, the fully developed theory has not been described. Here, we present a comprehensive account of a generalized version of the EMOR theory for spin I = 1 nuclides like 2H. As compared to a previously described version of the EMOR theory, the present version incorporates three generalizations that are all essential in applications to experimental data: (i) a biaxial (residual) electric field gradient tensor, (ii) direct and indirect effects of internal motions, and (iii) multiple sites with different exchange rates. In addition, we describe and assess different approximations to the exact EMOR theory that are useful in various regimes. In particular, we consider the experimentally important dilute regime, for which approximate analytical results are derived. As shown by the analytical expressions, and confirmed by exact numerical calculations, the dispersion is governed by the pure nuclear quadrupole resonance frequencies in the ultraslow-motion regime, where the relaxation rate also exhibits a much stronger dependence on the electric field gradient asymmetry than in the motional-narrowing regime.
Analytic gradients for density cumulant functional theory: The DCFT-06 model
Authors: Sokolov Alexander Yu. , Wilke Jeremiah J. , Simmonett Andrew C. , Schaefer Henry F.
Published: August 2012

Density cumulant functional theory (DCFT) is one of a number of nascent electron correlation methods that are derived from reduced density matrices and cumulants thereof, instead of the wavefunction. Deriving properties from the density cumulant naturally yields methods that are size extensive and size consistent. In this work, we derive expressions for the analytic gradient, with respect to an external perturbation, for the DCFT-06 variant of density cumulant functional theory. Despite the fact that the DCFT-06 energy functional is stationary with respect to the density cumulant, the analytic gradients of the energy require the solution of perturbation-independent equations for both orbital and cumulant response. These two sets of linear response equations are coupled in nature and are solved iteratively with the solution of orbital and cumulant response equations each macroiteration, exhibiting rapid convergence. The gradients are implemented and benchmarked against coupled cluster theory with single and double excitations (CCSD) and CCSD with perturbative triple excitations [CCSD(T)], as well as accurate empirically corrected experimental data, for a test set comprising 15 small molecules. For most of the test cases, results from DCFT-06 are closer to CCSD(T) and empirical data than those from CCSD. Although the total energy and analytic gradient have the same asymptotic scaling, the present experience shows that the computational cost of the gradient is significantly lower.
Time-resolved properties of ferroelectric electron emission from [Pb(Mg1/3Nb2/3)O3]0.71[PbTiO3]0.29 single crystals
Authors: Becherer J. , Mieth O. , Eng L. M.
Published: August 2012

Ferroelectric electron emission (FEE) is an attractive and prospective application of ferroelectric thin film and bulk materials. Although extensive studies have shown that the emission is connected to a change of the ferroelectric polarization, the exact underlying emission process remained unclear to date. Here, FEE from ferroelectric relaxor [Pb(Mg1/3Nb2/3)O3]0.71[PbTiO3]0.29 (PMN-PT) single crystals was investigated by quantifying the amount of emitted electrons as a function of amplitude, pulse repetition rate, and pulse duration of the excitation voltage, hence clarifying the time-resolved emission process. It is demonstrated that FEE from PMN-PT can be described in the framework of a random field model, with the measured electron flux correlating with the amount of reversed polarization. Furthermore, our time-dependent analysis gives insight into the polarization switching and screening processes within PMN-PT. This allows us to draw general conclusions on the future applications of FEE.
Note: A method for estimating the resolution of nanopositioning systems
Authors: Fleming Andrew J.
Published: August 2012

This Note describes a new technique for estimating the resolution of nanopositioning systems. By recording the voltage applied to an actuator and performing a filtering operation, the position noise and resolution can be estimated. This technique is simple to apply in practice and does not require any additional sensors or specialized equipment.
Quantum molecular dynamics simulations for the nonmetal-metal transition in fluid nitrogen oxide
Authors: Zhang Yujuan , Wang Cong , Zheng Fawei , Zhang Ping
Published: August 2012

First-principle molecular-dynamics simulations based on density-functional theory have been used to study the thermophysical properties of fluid nitrogen oxide under extreme conditions. We have presented wide range equation of states, from which the principal Hugoniot were derived up to 200 GPa, and the results are well accordant with the experimental and theoretical data. The optical conductivity is calculated via the Kubo-Greenwood formula, from which the dc conductivity is obtained. The nonmetal-metal transition is observed at about 40 GPa, and is attributed to the dissociation of nitrogen oxide molecules. Additionally, the density of states and the distribution of the electronic charge are also investigated to study the complex behavior of fluid nitrogen oxide.
Note: A resonant fiber-optic piezoelectric scanner achieves a raster pattern by combining two distinct resonances
Authors: Li Zhi , Fu Ling
Published: August 2012

The resonant fiber-optic piezoelectric scanner (RFPS) benefits imaging systems with compactness and flexibility, but previously its scanning manner was limited to non-raster patterns that suffer various deficiencies (e.g., nonuniform in terms of spatial coverage and sampling time). Here, we propose a method for the RFPS to achieve a raster pattern by producing different order resonances in the two orthogonal directions. Resonant frequencies of the RFPS are deduced by the Euler-Bernoulli beam theory, and investigated by finite element method. We experimentally fabricated a prototype RFPS, measured its properties to investigate the feasibility for raster scanning, and finally demonstrated the imaging ability.
Adaptive feed-forward hysteresis compensation for piezoelectric actuators
Authors: Eielsen Arnfinn Aas , Gravdahl Jan Tommy , Pettersen Kristin Y.
Published: August 2012

Piezoelectric actuators are often employed for high-resolution positioning tasks. Hysteresis and creep nonlinearities inherent in such actuators deteriorate positioning accuracy. An online adaptive nonlinear hysteresis compensation scheme for the case of symmetric hysteretic responses and certain periodic reference trajectories is presented. The method has low complexity and is well suited for real-time implementation. Experimental results are presented in order to verify the method, and it is seen that the error due to hysteresis is reduced by more than 90% compared to when assuming a linear response.
Effect of hydrofluoric acid concentration on the evolution of photoluminescence characteristics in porous silicon nanowires prepared by Ag-assisted electroless etching method
Authors: Najar A. , Slimane A. B. , Hedhili M. N. , Anjum D. , Sougrat R. , Ng T. K. , Ooi B. S.
Published: August 2012

We report on the structural and optical properties of porous silicon nanowires (PSiNWs) fabricated using silver (Ag) ions assisted electroless etching method. Silicon nanocrystallites with sizes <5 nm embedded in amorphous silica have been observed from PSiNW samples etched using the optimum hydrofluoric acid (HF) concentration. The strongest photoluminescence (PL) signal has been measured from samples etched with 4.8 M of HF, beyond which a significant decreasing in PL emission intensity has been observed. A qualitative model is proposed for the formation of PSiNWs in the presence of Ag catalyst. This model affirms our observations in PL enhancement for samples etched using HF < 4.8 M and the eventual PL reduction for samples etched beyond 4.8 M of HF concentration. The enhancement in PL signals has been associated to the formation of PSiNWs and the quantum confinement effect in the Si nanocrystallites. Compared to PSiNWs without Si-Ox, the HF treated samples exhibited significant blue PL peak shift of 100 nm. This effect has been correlated to the formation of defect states in the surface oxide. PSiNWs fabricated using the electroless etching method can find useful applications in optical sensors and as anti-reflection layer in silicon-based solar cells.
Internal disruptions and sawtooth like activity in Large Helical Device
Authors: Varela J. , Garcia L. , Ohdachi S. , Watanabe K. Y. , Sanchez R.
Published: August 2012

Large Helical Device (LHD) inward-shifted configurations are unstable to resistive magnetohydrodynamic (MHD) pressure-gradient-driven modes. These modes drive sawtooth like events during LHD operation. In this work, we simulate sawtooth like activity and internal disruptions in order to improve the understanding of these relaxation events and their effect over the device efficiency to confine the plasma, with the aim to improve the LHD present and future operation scenarios minimizing or avoiding the disadvantageous MHD soft and hard limits. By solving a set of reduced non-linear resistive MHD equations, we have studied the evolution of perturbations to equilibria obtained before and after a sawtooth like event in LHD. The equilibrium β value is gradually increased during the simulation until it reaches the experimental value. Sawtooth like events and internal disruption events take place in the simulation for β0 values between 1% and 1.48%. The main driver of the sawtooth like events is the resonant and non-resonant effect of the (n = 1, m = 3) mode. The instability is stronger for resonant events, and they only appear when β0 = 1.48%. Internal disruptions are mainly driven by the (n = 1, m = 2) mode, and they extend throughout the whole plasma core. Internal disruption events do not show up when resonant sawtooth like events are triggered.
Process dependence of 1/f noise and defects in ion implanted p-type piezoresistors
Authors: Dieme Robert , Zhang Jack , Rudawski Nicholas G. , Jones Kevin , Bosman Gijs , Sheplak Mark , Nishida Toshikazu
Published: August 2012

The process dependence of 1/f noise in p-type piezoresistors was investigated in this work using both electrical and materials characterization approaches. P-type piezoresistors were fabricated with 20 keV and 40 keV boron implants with and without implant oxide and varying isochronal 900 °C inert anneals. The devices were characterized electrically using I-V, Hall Effect, and power spectral density (PSD) noise measurements. The defects were visualized using cross-section transmission electron microscopy and plane view TEM The measured 1/f noise PSDs in the p-type piezoresistors are systematically compared to the number and dimension of bulk defect densities measured with TEM after each annealing condition of the piezoresistors. The 1/f noise PSDs of the piezoresistors implanted with 20 keV boron track the TEM defect number densities while those implanted with 40 keV boron through SiO2 with inert and oxidizing anneals track the faulted loop areas.
Surface/interface effect and size/configuration dependence on the energy release in nanoporous membrane
Authors: Hu Yifeng , Li Qun , Shi Junping , Chen Yiheng
Published: August 2012

This paper deals with the surface/interface effect and the size/configuration dependence on the M-integral representing the energy release due to the self-similar expansion of multiple nanosized pores in nanoporous membrane. An explicit formulation of the M-integral is derived by considering the surface/interface effect induced from the residual surface tension and the surface Lamé constants based on the Gurtin-Murdoch surface model. It is concluded that the surface/interface effect on the energy release is primarily determined by the surface tension, whereas the surface Lamé constants yield much less influence than the surface tension. Moreover, the energy release significantly relies on the size and configuration of nanopores in nanoporous membrane, which even yields the energy absorption depending on the loading level especially when the pore size is less 20 nm. The two-state M-integral analysis is performed to clarify the mutual effects of surface/interface and size/configuration on the M-integral to explain the energy release or absorption in nanoporous membrane.
Comparing direct charge injection and Forster energy transfer into quantum dots in hybrid organic/inorganic quantum dot light emitting devices
Authors: Kumar Brijesh , Hue Ryan , Gladfelter Wayne L. , Campbell Stephen A.
Published: August 2012

Inorganic quantum dots (QDs) have excellent optoelectronic properties. But, due in part to a lack of a suitable medium for dispersion, they have not been extensively used in optoelectronic devices. With the advent of organic semiconductors, the integration of quantum dots into optoelectronic devices has become possible. Such devices are termed as hybrid organic/inorganic quantum dot light emitting devices. In hybrid organic/inorganic quantum dot light emitting devices, the mechanisms of charge and/or energy transfer into the quantum dots include Forster energy transfer and direct charge injection. Forster energy transfer involves formation of excitons on organic semiconductors, followed by an energy transfer onto the inorganic quantum dots, where the exciton recombines resulting in emission of a photon. Direct charge injection is the mechanism in which the electrons and holes are directly injected into the quantum dots and they recombine on the quantum dots to result in a photon. Which mechanism is operating in a device has been a subject of contention. In this work, by using various device configurations, we show that both these mechanisms can operate independently to maximize the quantum dot light emission in such devices.
Ab initio study of the interactions between boron and nitrogen dopants in graphene
Authors: Al-Aqtash Nabil , Al-Tarawneh Khaldoun M. , Tawalbeh Tarek , Vasiliev Igor
Published: August 2012

We present a first-principles computational study of the interactions between the boron (B) and nitrogen (N) dopant atoms in graphene. Our calculations are carried out using density functional theory combined with the generalized gradient approximation for the exchange-correlation functional. The total energies, equilibrium geometries, electronic charge distributions, and densities of states of doped graphene sheets are examined in cases of B−B, N−N, and B−N co-doped graphene. We find the B−B and N−N interactions to be repulsive and the B−N interaction to be attractive. In all cases studied, dopant-dopant interactions appear to have a relatively short range. The interaction energy between the two dopant atoms is found to be inversely proportional to the square of the separation distance. We interpret these results in terms of donor-acceptor interactions and structural relaxation. The strong bonding between the B and N atoms indicates the possibility of the formation of isolated patches of hexagonal boron nitride in B−N co-doped graphene.
Backward mode of the ion-cyclotron wave in a semi-bounded magnetized Lorentzian plasma
Authors: Ki Dae-Han , Jung Young-Dae
Published: August 2012

The backward modes of the surface ion-cyclotron wave are investigated in a semi-bounded magnetized Lorentzian plasma. The dispersion relation of the backward mode of the surface ion-cyclotron wave is obtained using the specular reflection boundary condition with the plasma dielectric function. The result shows that the nonthermal effect suppresses the wave frequency as well as the group velocity of the surface ion-cyclotron wave. It is also found that the nonthermal effect on the surface ion-cyclotron wave increases with an increase of the wave number. In addition, it is found that the propagation domain of the surface ion-cyclotron wave increases with an increase of the ratio of the electron plasma frequency to the electron gyrofrequency. It is also found that the nonthermal effect increases the propagation domain of the surface ion-cyclotron wave in a semi-bounded magnetized Lorentzian plasma.
Enhancing extreme ultraviolet photons emission in laser produced plasmas for advanced lithography
Authors: Sizyuk T. , Hassanein A.
Published: August 2012

Current challenges in the development of efficient laser produced plasma sources for the next generation extreme ultraviolet lithography (EUVL) are increasing EUV power and maximizing lifetime and therefore, reducing cost of devices. Mass-limited targets such as small tin droplets are considered among the best choices for cleaner operation of the optical system because of lower mass of atomic debris produced by the laser beam. The small diameter of droplets, however, decreases the conversion efficiency (CE) of EUV photons emission, especially in the case of CO2 laser, where laser wavelength has high reflectivity from the tin surface. We investigated ways of improving CE in mass-limited targets. We considered in our modeling various possible target phases and lasers configurations: from solid/liquid droplets subjected to laser beam energy with different intensities and laser wavelength to dual-beam lasers, i.e., a pre-pulse followed by a main pulse with adjusted delay time in between. We studied the dependence of vapor expansion rate, which can be produced as a result of droplet heating by pre-pulse laser energy, on target configuration, size, and laser beam parameters. As a consequence, we studied the influence of these conditions and parameters on the CE and debris mass accumulation. For better understanding and more accurate modeling of all physical processes occurred during various phases of laser beam/target interactions, plasma plume formation and evolution, EUV photons emission and collection, we have implemented in our heights package state-of-the art models and methods, verified, and benchmarked against laboratory experiments in our CMUXE center as well as various worldwide experimental results.
Energy enhancement of proton acceleration in combinational radiation pressure and bubble by optimizing plasma density
Authors: Bake Muhammad Ali , Shan-Zhang  , Xie Bai-Song , Hong Xue-Ren , Wang Hong-Yu
Published: August 2012

The combinational laser radiation pressure and plasma bubble fields to accelerate protons are researched through theoretical analysis and numerical simulations. The dephasing length of the accelerated protons bunch in the front of the bubble and the density gradient effect of background plasma on the accelerating phase are analyzed in detail theoretically. The radiation damping effect on the accelerated protons energy is also considered. And it is demonstrated by two-dimensional particle-in-cell simulations that the protons bunch energy can be increased by using the background plasma with negative density gradient. However, radiation damping makes the maximal energy of the accelerated protons a little reduction.
Hidden starburst galaxy pinpointed at high redshift
Authors: Smart Ashley G.
Published: August 2012

Stars may have been significantly more abundant in the infant universe than optical surveys alone suggest.
Catching a submarine volcano in the act
Authors: Wilson R. Mark
Published: August 2012

A swarm of earthquakes and a sudden rise in the sea floor herald an imminent eruption.
Scientists poke holes in carbon dioxide sequestration
Authors: Kramer David
Published: August 2012

Recent findings say earthquakes caused by CO2 injection may cause bottled-up greenhouse gas to leak.
Strange kinetics of single molecules in living cells
Authors: Barkai Eli , Garini Yuval , Metzler Ralf
Published: August 2012

The irreproducibility of time-averaged observables in living cells poses fundamental questions for statistical mechanics and reshapes our views on cell biology.
Nanotechnology in Cancer Medicine
Authors: Grossman Jennifer H. , McNeil Scott E.
Published: August 2012

Because of a previously unexploited weakness in tumor architecture, nanomaterials may offer a way to treat cancer without doing too much damage to healthy tissue. The weakness isn’t really a property of the tumors themselves but of the blood vessels that feed them.
Genetic parameter estimates for early growth traits in Naeini goat
Authors: Baneh Hasan , Najafi Mojtaba , Rahimi Ghodrat
Published: August 2012

The present study was carried out to estimate variance components for growth traits in Naeini goats. Bodyweight records were collected for two flocks under supervision of the Agriculture Organisation of the Esfahan province between 2000 and 2007. Investigated traits were birthweight (BW; n = 2483), weaning weight (WW; n = 1211) and average daily gain from birth to weaning (ADG; n = 1211). Environmental effects were investigated using fixed-effect models, while (co)variance components and genetic parameters were estimated with single- and three-trait analyses using REML methods and WOMBAT software. Six different animal models were fitted to the traits, with the best model for each trait determined by log-likelihood ratio tests (LRT). All traits were significantly influenced by herd, birth year, sex of the kid, birth type and dam age (P < 0.01). On the basis of LRT, maternal permanent environmental effects (c2) were significant for WW and ADG, while BW was affected only by direct genetic effects. Direct heritability estimates for BW, WW and ADG were 0.25 ± 0.05, 0.07 ± 0.06 and 0.21 ± 0.11, respectively. The estimate of c2 was 0.16 ± 0.06 for both WW and ADG. Estimates of genetic correlation for BW–ADG, BW–WW and ADG–WW were 0.49, 0.61 and 0.94, respectively. The estimated phenotypic correlations were positive and were between 0.03 (BW–ADG) and 0.95 (ADG–WW). These results indicate that selection can be used to improve growth traits in this goat breed.
Whole-farm systems analysis of Australian dairy farm greenhouse gas emissions
Authors: Christie K. M. , Gourley C. J. P. , Rawnsley R. P. , Eckard R. J. , Awty I. M.
Published: August 2012

The Australian dairy industry contributes ~1.6% of the nation’s greenhouse gas (GHG) emissions, emitting an estimated 9.3 million tonnes of carbon dioxide equivalents (CO2e) per annum. This study examined 41 contrasting Australian dairy farms for their GHG emissions using the Dairy Greenhouse Gas Abatement Strategies calculator, which incorporates Intergovernmental Panel on Climate Change and Australian inventory methodologies, algorithms and emission factors. Sources of GHG emissions included were pre-farm embedded emissions associated with key farm inputs (i.e. grains and concentrates, forages and fertilisers), CO2 emissions from electricity and fuel consumption, methane emissions from enteric fermentation and animal waste management, and nitrous oxide emissions from animal waste management and nitrogen fertilisers. The estimated mean (±s.d.) GHG emissions intensity was 1.04 ± 0.17 kg CO2 equivalents/kg of fat and protein-corrected milk (kg CO2e/kg FPCM). Enteric methane emissions were found to be approximately half of total farm emissions. Linear regression analysis showed that 95% of the variation in total farm GHG emissions could be explained by annual milk production. While the results of this study suggest that milk production alone could be a suitable surrogate for estimating GHG emissions for national inventory purposes, the GHG emissions intensity of milk production, on an individual farm basis, was shown to vary by over 100% (0.76–1.68 kg CO2e/kg FPCM). It is clear that using a single emissions factor, such as milk production alone, to estimate any given individual farm’s GHG emissions, has the potential to either substantially under- or overestimate individual farms’ GHG emissions.
Factor XI mutation in normally fertile and repeat breeding Holstein cows in the Middle Anatolian region of Turkey: a financial approach
Authors: Akyuz B. , Sariozkan S. , Bayram D.
Published: August 2012

The aim of this study was to compare the prevalence of factor XI deficiency (FXID) carriers and potential financial losses depending on ‘extended calving interval’ and ‘extra service’ in normally fertile and repeat breeder cows in Turkey. For this purpose, a total of 161 Holstein cows were genotyped for the FXI gene mutation originating from various herds located in the Middle Anatolian region of Turkey. In the study, animals were divided into two groups – normally fertile (n = 118) and repeat breeding (n = 43) cows. In each group, one FXID carrier animal was identified and the prevalence of the FXID carrier was found to be 0.85 and 2.33% in normally fertile and repeat breeder cows, respectively. In a financial analysis, it was determined that extended calving interval in a normally fertile cow caused $246 losses and $546 losses in a repeat breeder cow. Additionally, financial losses due to extra service per conception were calculated as $12 and $36 per cow in normally fertile and repeat breeder cows, respectively. In normally fertile and repeat breeder cows, the sum of losses due to extended calving interval and extra service was calculated as $258 (246 + 12) and $582 (546 + 36). This study found that a repeat breeder cow causes an extra $324 ($582 – $258) financial loss compared with a normally fertile cow. Consequently, unlike other genetic disorders like BLAD and DUMPS, which do not decrease the performance of carrier animals, the mutant FXI allele could lead to repeat breeder syndrome in FXID carrier cows and cause important financial losses in dairy farms.
Quantitative trait loci underlying hatching weight and growth traits in an F2 intercross between two strains of Japanese quail
Authors: Sohrabi S. S. , Esmailizadeh A. K. , Baghizadeh A. , Moradian H. , Mohammadabadi M. R. , Askari N. , Nasirifar E.
Published: August 2012

A three-generation resource population was developed using two distinct Japanese quail strains, wild and white, to map quantitative trait loci underlying hatching weight and growth traits. Eight pairs of white and wild birds were crossed reciprocally and 34 F1 birds were produced. The F1 birds were intercrossed to generate 422 F2 offspring. All of the animals from three generations (472 birds) were genotyped for eight microsatellite markers on chromosome 1. Liveweight data from hatch to 5 weeks of age were collected on the F2 birds. Quantitative trait loci (QTL) analysis was conducted applying the line-cross model and the least-squares interval mapping approach. The results indicated QTL affecting hatching weight and several growth related traits on chromosome 1. The F2 phenotypic variance explained by the detected additive QTL effects ranged from 1.0 to 3.7 for different traits. Modelling both additive and dominance QTL effects revealed additional QTL with significant dominance mode of action affecting pre-slaughter weight. However, there was no evidence for imprinting (parent-of-origin) effects. The variance due to the reciprocal cross effect ranged between 3.0 and 19.1% for weight at 1 week of age and hatching weight, respectively.
Synthesis, Characterization, and Self-Assembly of Poly(N-vinylpyrrolidone)-block-poly(vinyl acetate)
Authors: Bailly Nathalie , Pound-Lana Gwenaelle , Klumperman Bert
Published: August 2012

Poly(N-vinylpyrrolidone)-block-poly(vinyl acetate) (PVP-b-PVAc) block copolymers of varying molar mass and hydrophobic block lengths were synthesized by xanthate-mediated radical polymerization. In order to control the molar mass of the hydrophilic PVP block, a xanthate chain transfer agent, S-(2-cyano-2-propyl) O-ethyl xanthate, was used. The PVP-b-PVAc block copolymer is composed of a hydrophilic and hydrophobic segment, and has the ability to self-assemble in aqueous solution. The PVP-b-PVAc block copolymers were characterized by 1H NMR spectroscopy to confirm their self-assembly in water. The critical micelle concentration was determined by fluorescence spectroscopy. A combination of dynamic light scattering, transmission electron microscopy, and static light scattering was used to further characterize the self-assembly of the block copolymers in water.
Introducing the Azlactone Functionality into Polymers through Controlled Radical Polymerization: Strategies and Recent Developments
Authors: Ho H. T. , Levere M. E. , Fournier D. , Montembault V. , Pascual S. , Fontaine L.
Published: August 2012

Polymers containing the highly reactive azlactone group have emerged as a powerful platform useful in various application areas. This Highlight summarizes recent developments in the field of azlactone-derived polymers made in our group using controlled radical polymerizations (ATRP and RAFT) and ‘click’ chemistry methodology (thiol-Michael addition), leading to well defined reactive polymers.
Loss of deeply conserved C-class floral homeotic gene function and C- and E-class protein interaction in a double-flowered ranunculid mutant
Authors: Galimba Kelsey D. , Tolkin Theadora R. , Sullivan Alessandra M. , Melzer Rainer , Theißen Günter , Di Stilio Verónica S.
Published: August 2012

In the model plant
Arabidopsis thaliana
, a core eudicot, the floral homeotic C-class gene
AGAMOUS
(
AG
) has a dual role specifying reproductive organ identity and floral meristem determinacy. We conduct a functional analysis of the putative
AG
ortholog
ThtAG1
from the ranunculid
Thalictrum thalictroides
, a representative of the sister lineage to all other eudicots. Down-regulation of
ThtAG1
by virus-induced gene silencing resulted in homeotic conversion of stamens and carpels into sepaloid organs and loss of flower determinacy. Moreover, flowers exhibiting strong silencing of
ThtAG1
phenocopied the double-flower ornamental cultivar
T. thalictroides
‘Double White.’ Molecular analysis of ‘Double White’
ThtAG1
alleles revealed the insertion of a retrotransposon causing either nonsense-mediated decay of transcripts or alternative splicing that results in mutant proteins with K-domain deletions. Biochemical analysis demonstrated that the mutation abolishes protein–protein interactions with the putative E-class protein ThtSEP3. C- and E-class protein heterodimerization is predicted by the floral quartet model, but evidence for the functional importance of this interaction is scarce outside the core eudicots. Our findings therefore corroborate the importance and conservation of the interactions between C- and E-class proteins. This study provides a functional description of a full C-class mutant in a noncore (“basal”) eudicot, an ornamental double flower, affecting both organ identity and meristem determinacy. Using complementary forward and reverse genetic approaches, this study demonstrates deep conservation of the dual C-class gene function and of the interactions between C- and E-class proteins predicted by the floral quartet model.
The Gifts of Research – Playing with Phenomenology
Authors: Zografou Lia
Published: August 2012

In this paper I try to dispel some of the fears encountered by novice researchers embarking on qualitative research and phenomenological inquiry in particular. I outline key principles of theory and methodology and highlight the difficulties as well as the gifts afforded to a phenomenological researcher, with some emphasis on the applicability of phenomenological research to the arts therapies.
Investigation on the magnetic and electrical properties of fluorine-doped magnetites
Authors: Gao Lei , Li Ran , Chen Qianwang
Published: August 2012

A fluorine-doped magnetite was synthesized using ferroferric oxide (Fe3O4) powder and ammonium fluoride (NH4F) as starting materials by a hydrothermal method and by subsequently annealing in vacuum atmosphere at 1450 °C. The content of fluorine dopants was measured by x-ray electron spectroscopy. When an oxygen atom was replaced by a fluorine atom, it would introduce one excess electron to reduce an Fe3+ ion to an Fe2+ ion in a tetrahedral A site for charge compensation, leading to a large variation in magnetic and electrical properties. The appearance of Fe2+ ions in the tetrahedral A sites caused a decrease in the spin magnetic moment, resulting in an increase in the Landé g-factor between 110 and 200 K, and the magnetic susceptibility in the range 10–350 K. At the same time, the electrons of the Fe2+ ions in A sites may escape and turn into new carriers in the presence of an electrical bias field, resulting in a reduction in the resistance of the fluorine-doped magnetite from 30 to 292 K.
Driving frequency dependence of capacitively coupled plasmas in atmospheric argon
Authors: Atanasova M , Sobota A , Brok W , Degrez G , van der Mullen J J A M
Published: August 2012

The role of the driving field frequency f
d of a cool atmospheric plasma (CAP) is investigated for values around

using a two-dimensional fluid numerical model applied to a parallel plate configuration. It is found that keeping the voltage constant the current amplitude roughly scales with

; a tendency that can be understood using a RC circuit model of the plasma-sheath configuration. Moreover, it is seen that the electron density increases faster than the density of the excited species. This implies that plasma heating will increase relatively more than plasma reactivity so that the basic feature of the CAP, to be cool and reactive, will weaken for increasing f
d-values.