bluuebunny/crossref_metadata_2025 huggingface dataset:
Paleoreconstruction of cool season precipitation and warm season streamflow in the Pacific Northwest with applications to climate change assessments
Authors: Lutz Eric R. , Hamlet Alan F. , Littell Jeremy S.
Published: December 2011

Long‐term streamflow reconstructions help characterize climate variability and extreme climatic events, such as droughts, which play a crucial role in water resource planning. Dendrohydrological reconstructions generally build on indirect associations between streamflow and radial tree growth, both of which depend on cool season precipitation in the Pacific Northwest. We develop a new approach that integrates a tree ring reconstruction of cool season precipitation with historical meteorological data and a physically based hydrologic model to reconstruct warm season streamflow and streamflow uncertainty. The Upper Yakima Basin in Washington state is used as a test case. We applied objective screening, principal components analysis, and multiple linear regression to reconstruct 366 years of basin‐average cool season precipitation. The reconstruction was integrated with five temporally and spatially distributed cool season precipitation patterns spanning the historical range of natural variability. These distributed meteorological reconstructions were used as inputs to the Variable Infiltration Capacity (VIC) hydrologic model over the Yakima basin to produce an ensemble of warm season streamflows for each reconstructed year. The resultant streamflow reconstruction retains dendroclimatic information and quantifies the inherent uncertainty in warm season streamflow associated with historical meteorology. Finally, the meteorological reconstructions were systematically perturbed and used to drive the VIC to examine the potential impacts of climate change on warm season streamflow over the 366‐year record. Despite projected wetter conditions in the future, less precipitation is stored as snowpack (due to warmer winter temperatures) and consequently warm season streamflow will be systematically reduced. The combination of long records of variability and systematic changes related to climate change provides useful information about the combined effects of natural variability and projected systematic changes in climate to support 21st‐century water planning.
Modeling the impacts of future climate change on water resources for the Gállego river basin (Spain)
Authors: Majone B. , Bovolo C. I. , Bellin A. , Blenkinsop S. , Fowler H. J.
Published: December 2011

Global changes in climate may have large impacts on regional water resources and the frequency of drought or flood events. Changes in precipitation or temperature may also severely modify the available water resources for users in several sectors. Here, we examine climate change scenarios for the Gállego river (a tributary of the larger Ebro river in Spain) in the context of quantitative water resources management for the basin. Projected changes to precipitation and temperature are derived from an ensemble of 6 Regional Climate Models (RCMs) run for the period 2071–2100 under the SRES A2 emissions scenario and are subsequently bias corrected before input into a hydrological model. The use of RCM ensembles is important for the incorporation of uncertainties derived from different model structures, parameterizations and boundary conditions into the hydrological modeling process and subsequent climate change impact assessment. All 6 RCMs project decreases in annual precipitation with some RCMs projecting a slight increase between December and February. Additionally, all models project a >3°C increase in annual mean temperature over the basin, with some models projecting a 9°C temperature increase during summer months. Hydrological simulations using the GEOTRANSF model, with the climate change scenarios as input, show that projected water availability for the Gállego is lower for the 2071–2100 period than for 1961–1990, with an increasing number of dry years. During the water‐storage period (October to March), medium to low flows are reduced, while during the irrigation period (April to September), streamflow is reduced across the entire range of flows. The projected changes vary across the basin and are also not uniform throughout the year. Stronger drying occurs during the summer with potentially important implications for water resource management across many sectors including agriculture, with a reduction in the amount of water available for irrigation and hydropower generation, due to projected seasonal reductions in reservoir levels.
Epidermal growth factor induces tumour marker AKR1B10 expression through activator protein-1 signalling in hepatocellular carcinoma cells
Authors: Liu Ziwen , Yan Ruilan , Al-Salman Ahmed , Shen Yi , Bu Yiwen , Ma Jun , Luo Di-Xian , Huang Chenfei , Jiang Yuyang , Wilber Andrew , Mo Yin-Yuan , Huang Mei Chris , Zhao Yupei , Cao Deliang
Published: December 2011

AKR1B10 (aldo-keto reductase 1B10) is overexpressed in liver and lung cancer, and plays a critical role in tumour development and progression through promoting lipogenesis and eliminating cytotoxic carbonyls. AKR1B10 is a secretory protein and potential tumour marker; however, little is known about the regulatory mechanism of AKR1B10 expression. The present study showed that AKR1B10 is induced by mitogen EGF (epidermal growth factor) and insulin through the AP-1 (activator protein-1) signalling pathway. In human HCC (hepatocellular carcinoma) cells (HepG2 and Hep3B), EGF (50 ng/ml) and insulin (10 nM) stimulated endogenous AKR1B10 expression and promoter activity. In the AKR1B10 promoter, a putative AP-1 element was found at bp −222 to −212. Deletion or mutation of this AP-1 element abrogated the basal promoter activity and response to EGF and AP-1 proteins. This AP-1 element bound to nuclear proteins extracted from HepG2 cells, and this binding was stimulated by EGF and insulin in a dose-dependent manner. Chromatin immunoprecipitation showed that the AP-1 proteins c-Fos and c-Jun were the predominant factors bound to the AP-1 consensus sequence, followed by JunD and then JunB. The same order was followed in the stimulation of endogenous AKR1B10 expression by AP-1 proteins. Furthermore, c-Fos shRNA (short hairpin RNA) and AP-1 inhibitors/antagonists (U0126 and Tanshinone IIA) inhibited endogenous AKR1B10 expression and promoter activity in HepG2 cells cultured in vitro or inoculated subcutaneously in nude mice. U0126 also inhibited AKR1B10 expression induced by EGF. Taken together, these results suggest that AKR1B10 is up-regulated by EGF and insulin through AP-1 mitogenic signalling and may be implicated in hepatocarcinogenesis.
Cosmic rays—astronomy with energetic particles
Authors: Meyer Peter , Ramaty Reuven , Webber William R.
Published: December 2011

Since the discovery of the cosmic radiation the question of the origin of these high-energy particles has been an astrophysical problem of foremost importance. Rapid progress toward an understanding of this problem has been made in the past ten to twenty years as experimental techniques became available that permitted a study of the cosmic radiation either near the outer fringes of the atmosphere, with high-altitude balloons, or in space, totally uninhibited by the Earth's atmosphere. The picture that has unfolded displays an enormous variety. All nuclei in the periodic table of the elements, as well as electrons and positrons, are present in the stream of cosmic-ray particles; their energies span the range from at least 106 eV to 1020 eV.
Modeling the switching kinetics in ferroelectrics
Authors: Kliem Herbert , Kuehn Markus
Published: December 2011

The switching process in ferroelectrics with a maximum in time for the switching current as observed by Merz [Phys. Rev. 95, 690 (1954)] is simulated. To this end, the Weiss molecular mean-field model is combined with the fluctuation of dipoles in double-well potentials. A first-order rate equation for the polarization with time-dependent coefficients results. This equation is solved for the time-dependent switching process, as well as for the static polarization hysteresis loop.
Multistage Zeeman deceleration of metastable neon
Authors: Wiederkehr Alex W. , Motsch Michael , Hogan Stephen D. , Andrist Markus , Schmutz Hansjürg , Lambillotte Bruno , Agner Josef A. , Merkt Frédéric
Published: December 2011

A supersonic beam of metastable neon atoms has been decelerated by exploiting the interaction between the magnetic moment of the atoms and time-dependent inhomogeneous magnetic fields in a multistage Zeeman decelerator. Using 91 deceleration solenoids, the atoms were decelerated from an initial velocity of \documentclass[12pt]{minimal}\begin{document}$\mathrm{580\;\mathrm{m}\mathrm{/}\mathrm{s}}$\end{document}580m/s to final velocities as low as \documentclass[12pt]{minimal}\begin{document}$\mathrm{105\;\mathrm{m}\mathrm{/}\mathrm{s}}$\end{document}105m/s, corresponding to a removal of more than 95% of their initial kinetic energy. The phase-space distribution of the cold, decelerated atoms was characterized by time-of-flight and imaging measurements, from which a temperature of \documentclass[12pt]{minimal}\begin{document}$\mathrm{10\;\mathrm{m}\mathrm{K}}$\end{document}10mK was obtained in the moving frame of the decelerated sample. In combination with particle-trajectory simulations, these measurements allowed the phase-space acceptance of the decelerator to be quantified. The degree of isotope separation that can be achieved by multistage Zeeman deceleration was also studied by performing experiments with pulse sequences generated for 20Ne and 22Ne.
Unification of three multiphonon trap-assisted tunneling mechanisms
Authors: Zhang Manhong , Huo Zongliang , Yu Zhaoan , Liu Jing , Liu Ming
Published: December 2011

There are three basic multiphonon trap-assisted tunneling (TAT) mechanisms in the gate leakage current of a metal-oxide-semiconductor (MOS) structure: the short-ranged trap potential, nonadiabatic interaction and electric field induced trap-band transitions. In this paper, a comparison of these three mechanisms is made for the first time in a single (Schenk’s model) MOS structure. A properly box-normalized electron wave function in the SiO2 conduction band in an electric field is used to calculate the field ionization rate of a deep neutral trap. It is found that capture and emission rates of a deep neutral trap are almost the same in the short-ranged trap potential and nonadiabatic interaction induced TAT processes, so the two mechanisms give a similar contribution to the total TAT current. The calculated TAT current and the average relaxation energy (∼1.5 eV) due to these two mechanisms are in good agreement with the experimental results. In contrast, capture and emission rates in Schenk’s model are several orders smaller. The TAT current induced by this mechanism is also much smaller and can be ignored.
Scaling of maximum probability density functions of velocity and temperature increments in turbulent systems
Authors: Huang Y. X. , Schmitt F. G. , Zhou Q. , Qiu X. , Shang X. D. , Lu Z. M. , Liu Y. L.
Published: December 2011

In this paper, we introduce a new way to estimate the scaling parameter of a self-similar process by considering the maximum probability density function (pdf) of its increments. We prove this for H-self-similar processes in general and experimentally investigate it for turbulent velocity and temperature increments. We consider turbulent velocity database from an experimental homogeneous and nearly isotropic turbulent channel flow, and temperature data set obtained near the sidewall of a Rayleigh-Bénard convection cell, where the turbulent flow is driven by buoyancy. For the former database, it is found that the maximum value of increment pdf pmax(τ) is in a good agreement with lognormal distribution. We also obtain a scaling exponent α≃0.37, which is consistent with the scaling exponent for the first-order structure function reported in other studies. For the latter one, we obtain a scaling exponent αθ≃0.33. This index value is consistent with the Kolmogorov-Obukhov-Corrsin scaling for passive scalar turbulence but different from the scaling exponent of the first-order structure function that is found to be ζθ(1)≃0.19, which is in favor of Bolgiano-Obukhov scaling. A possible explanation for these results is also given.
Absorption enhancement analysis of crystalline Si thin film solar cells based on broadband antireflection nanocone grating
Authors: Zhang R. Y. , Shao B. , Dong J. R. , Zhang J. C. , Yang H.
Published: December 2011

1 μm thick Si solar cells based on nanocone grating (NCG) with height of 100-800 nm and period of 100, 500, and 800 nm are numerically investigated through reflectivities, absorption enhancement factors, absorption spectra, optical generation rates, ultimate efficiencies, and diffraction angles. Compared with the planar Si solar cell, absorption enhancement are observed in any solar cells with NCG surface. Their absorption enhancement mechanism varies with the incident wavelength range. When incident wavelength λ < 500 nm, antireflection of their front surface dominates the absorption enhancement behavior due to their stronger absorption coefficients. When 600 nm > λ > 500 nm, even though the absorption enhancement is still dominated by antireflection of the front surface, cavity-resonance effect and guided-mode excitation induced by high order diffraction start to make contribution. When λ > 600 nm, the contribution of guided-mode excitation induced by lower-order diffraction becomes larger and larger once the diffraction angle is larger than its critical angle. For the structure with P = 100 nm, high-order diffraction cut-off at the longer wavelength range is the main reason of its lower absorption enhancement and ultimate conversion efficiency. For P = 800 nm, the lower absorption enhancement and ultimate efficiency is also observed due to the high reflection loss and mode leakage induced by 1st order diffraction where its diffraction angle is lower than its critical angle. Higher absorption and ultimate conversion efficiencies are achieved in P = 500 nm due to the good balance between antireflection performance and guide-mode excitation induced by the high order diffraction is achieved. Moreover, such absorption enhancement is closely related with its height of NCG gratings. Reflection loss reduction, the interaction volume reduction between the incident light and Si material, and higher photon density in NCG structure coexists with H increasing, which results in absorption enhancement in P = 500 nm and P = 800 nm, but absorption reduction in P = 100 nm where high order diffraction cut-off. Based on these analysis, we do believe that high absorption and ultimate conversion efficiency should be achieved in NCG-based solar cells where both the lower reflection in short wavelength domain and guide-mode excitation induced by 1st and 2nd diffraction in longer wavelength domain can be achieved. According to this rule, the optimized structure is NCG with P = 559 nm and H = 500 nm, by which, the highest optical generation rate of 536.57 × 104 W/cm3 and ultimate efficiency of 28.132% are achieved. Such analysis should benefit the design of the thin film solar cells with nano-structured diffraction gratings.
Forward and backward cavity pressure acceleration of macroparticles
Authors: Borodziuk S. , Chodukowski T. , Kalinowska Z. , Kasperczuk A. , Pisarczyk T. , Ullschmied J. , Krousky E. , Pfeifer M. , Rohlena K. , Skala J. , Pisarczyk P.
Published: December 2011

In this paper we present our new results obtained during the experiment performed on Prague Asterix Laser System. We used cavity pressure acceleration method [Borodziuk et al., Appl. Phys. Lett. 95, 231501 (2009)] to obtain superfast macroparticles. Two different ways of macroparticle acceleration were investigated: “forward” and “backward” acceleration. The best results for the velocity (obtained for 20 μm polystyrene foil) approach 1.0 × 108 cm/s. Also, the hydrodynamic efficiency of the energy transfer to the accelerated macroparticle is much higher compared to conventional ablative experiments. Additionally, application of the “covered channel” targets gives an evident increase of density of accelerated plasma outbursting from the channel, which is a key problem from the point of view of possible applications in impact fast ignition area.
Turbulence modification and heat transfer enhancement by inertial particles in turbulent channel flow
Authors: Kuerten J. G. M. , van der Geld C. W. M. , Geurts B. J.
Published: December 2011

We present results of direct numerical simulation of turbulence modification and heat transfer in turbulent particle-laden channel flow and show an enhancement of the heat transfer and a small increase in the friction velocity when heavy inertial particles with high specific heat capacity are added to the flow. The simulations employ a coupled Eulerian-Lagrangian computational model in which the momentum and energy transfer between the discrete particles and the continuous fluid phase are fully taken into account. The effect of turbophoresis, resulting in an increased particle concentration near a solid wall due to the inhomogeneity of the wall-normal velocity fluctuations, is shown to be responsible for an increase in heat transfer. As a result of turbophoresis, the effective macroscopic transport properties in the region near the walls differ from those in the bulk of the flow. To support the turbophoresis interpretation of the enhanced heat transfer, results of simulations employing no particle-fluid coupling and simulations with two-way coupling at considerably lower specific heat, or considerably lower particle concentration are also included. The combination of these simulations allows distinguishing contributions to the Nusselt number due to mean flow, turbulent fluctuations and explicit particle effects. We observe an increase in Nusselt number by more than a factor of two for heavy inertial particles, which is the net result of a decrease in heat transfer by turbulent velocity fluctuations and a much larger increase in heat transfer stemming from the mean temperature difference between the fluid and the particles close to the walls.
Studies on the structure, stability, and spectral signatures of hydride ion-water clusters
Authors: Prakash M. , Gopalsamy K. , Subramanian V.
Published: December 2011

The gas-phase structure, stability, spectra, and electron density topography of H−Wn clusters (where n = 1−8) have been calculated using coupled-cluster CCSD(T) and Møller-Plesset second-order perturbation (MP2) theory combined with complete basis set (CBS) approaches. The performance of various density functional theory (DFT) based methods such as B3LYP, M05-2X, M06, M06-L, and M06-2X using 6-311++G(d,p), and aug-cc-pVXZ (aVXZ, where X = D, T, and Q) basis sets has also been assessed by considering values calculated using CCSD(T)/CBS limit as reference. The performance of the functionals has been ranked based on the mean signed/unsigned error. The comparison of geometrical parameters elicits that the geometrical parameters predicted by B3LYP/aVTZ method are in good agreement with those values obtained at MP2/aVTZ level of theory. Results show that M05-2X functional outperform other functionals in predicting the energetics when compared to CCSD(T)/CBS value. On the other hand, values predicted by M06-2X, and M06 methods, are closer to those values obtained from MP2/CBS approach. It is evident from the calculations that H−Wn (where n = 5–8) clusters adopt several interesting structural motifs such as pyramidal, prism, book, Clessidra, cubic, cage, and bag. The important role played by ion-water (O–H⋅⋅⋅H−) and water-water (O–H⋅⋅⋅O) interactions in determining the stability of the clusters has also been observed. Analysis of the results indicates that the most stable cluster is made up of minimum number of O–H⋅⋅⋅H− interaction in conjugation with the maximum number of O–H⋅⋅⋅O interactions. The Bader theory of atoms in molecules (AIM) and natural bond orbital (NBO) analyses has also been carried out to characterize the nature of interactions between hydride ion and water molecules. It can be observed from the vibrational spectra of H−Wn clusters, the stretching frequencies involving ion-water interaction always exhibit larger redshift and intensities than that of water-water (inter solvent) interactions.
Coarse-graining entropy, forces, and structures
Authors: Rudzinski Joseph F. , Noid W. G.
Published: December 2011

Coarse-grained (CG) models enable highly efficient simulations of complex processes that cannot be effectively studied with more detailed models. CG models are often parameterized using either force- or structure-motivated approaches. The present work investigates parallels between these seemingly divergent approaches by examining the relative entropy and multiscale coarse-graining (MS-CG) methods. We demonstrate that both approaches can be expressed in terms of an information function that discriminates between the ensembles generated by atomistic and CG models. While it is well known that the relative entropy approach minimizes the average of this information function, the present work demonstrates that the MS-CG method minimizes the average of its gradient squared. We generalize previous results by establishing conditions for the uniqueness of structure-based potentials and identify similarities with corresponding conditions for the uniqueness of MS-CG potentials. We analyze the mapping entropy and extend the MS-CG and generalized-Yvon-Born-Green formalisms for more complex potentials. Finally, we present numerical calculations that highlight similarities and differences between structure- and force-based approaches. We demonstrate that both methods obtain identical results, not only for a complete basis set, but also for an incomplete harmonic basis set in Cartesian coordinates. However, the two methods differ when the incomplete basis set includes higher order polynomials of Cartesian coordinates or is expressed as functions of curvilinear coordinates.
Efficient and accurate local single reference correlation methods for high-spin open-shell molecules using pair natural orbitals
Authors: Hansen Andreas , Liakos Dimitrios G. , Neese Frank
Published: December 2011

A production level implementation of the high-spin open-shell (spin unrestricted) single reference coupled pair, quadratic configuration interaction and coupled cluster methods with up to doubly excited determinants in the framework of the local pair natural orbital (LPNO) concept is reported. This work is an extension of the closed-shell LPNO methods developed earlier [F. Neese, F. Wennmohs, and A. Hansen, J. Chem. Phys. 130, 114108 (2009)10.1063/1.3086717; F. Neese, A. Hansen, and D. G. Liakos, J. Chem. Phys. 131, 064103 (2009)10.1063/1.3173827]. The internal space is spanned by localized orbitals, while the external space for each electron pair is represented by a truncated PNO expansion. The laborious integral transformation associated with the large number of PNOs becomes feasible through the extensive use of density fitting (resolution of the identity (RI)) techniques. Technical complications arising for the open-shell case and the use of quasi-restricted orbitals for the construction of the reference determinant are discussed in detail. As in the closed-shell case, only three cutoff parameters control the average number of PNOs per electron pair, the size of the significant pair list, and the number of contributing auxiliary basis functions per PNO. The chosen threshold default values ensure robustness and the results of the parent canonical methods are reproduced to high accuracy. Comprehensive numerical tests on absolute and relative energies as well as timings consistently show that the outstanding performance of the LPNO methods carries over to the open-shell case with minor modifications. Finally, hyperfine couplings calculated with the variational LPNO-CEPA/1 method, for which a well-defined expectation value type density exists, indicate the great potential of the LPNO approach for the efficient calculation of molecular properties.
Confirmed assignments of isomeric dimethylbenzyl radicals generated by corona discharge
Authors: Wook Yoon Young , Kuk Lee Sang
Published: December 2011

The controversial vibronic assignments of isomeric dimethylbenzyl radicals were clearly resolved by using different precursors. By employing corresponding dimethylbenzyl chlorides as precursors, we identified the origins of the vibronic bands of the dimethylbenzyl radicals generated by corona discharge of 1,2,4-trimethylbenzene. From the analysis of the spectra observed from the dimethylbenzyl chlorides in a corona excited supersonic expansion, we revised previous assignments of the 3,4-, 2,4-, and 2,5-dimethylbenzyl radicals. Spectroscopic data of electronic transition and vibrational mode frequencies in the ground electronic state of each isomer were accurately determined by comparing them with those obtained by an ab initio calculation and with the known vibrational data of 1,2,4-trimethylbenzene.
Influence of quantum effects on the physisorption of molecular hydrogen in model carbon foams
Authors: Martínez-Mesa A. , Yurchenko S. N. , Patchkovskii S. , Heine T. , Seifert G.
Published: December 2011

The physisorption of molecular hydrogen in model carbon foams has been investigated from \documentclass[12pt]{minimal}\begin{document}$50\text{ K}$\end{document}50K to room temperature. The study is carried out within the framework of the density functional theory for quantum liquids at finite temperatures. Calculations are performed in the grand canonical ensemble, i.e., the adsorbed fluid is assumed to be in equilibrium with an external gas of hydrogen molecules with concentrations ranging from \documentclass[12pt]{minimal}\begin{document}$8 \times 10^{-4}\; \text{kg}\, \text{m}^{-3}$\end{document}8×10−4kgm−3 to \documentclass[12pt]{minimal}\begin{document}$n=71\; \text{kg\,} \text{\emph {\emph {m}}}^{-3}$\end{document}n=71kgm−3. It is shown that, while strong zero-point energy effects are present even at room temperature, the adsorption isotherms exhibit only a weak dependence on the explicit incorporation of the bosonic exchange symmetry of hydrogen molecules. The increase of the average particle density prevents the deviations from the Maxwell-Boltzmann statistics to become noticeable if the system is cooled down. The volumetric storage capacity of these materials at low temperatures is about one half of the U. S. Department of Energy goal, while the gravimetric capacity is still far from the standards required by mobile applications. The relation between the microscopic structure of the hydrogen fluid and the calculated adsorption properties is also addressed.
A coarse-grained model for polyethylene glycol polymer
Authors: Wang Qifei , Keffer David J. , Nicholson Donald M.
Published: December 2011

A coarse-grained (CG) model of polyethylene glycol (PEG) was developed and implemented in CG molecular dynamics (MD) simulations of PEG chains with degree of polymerization (DP) 20 and 40. In the model, two repeat units of PEG are grouped as one CG bead. Atomistic MD simulation of PEG chains with DP = 20 was first conducted to obtain the bonded structural probability distribution functions (PDFs) and nonbonded pair correlation function (PCF) of the CG beads. The bonded CG potentials are obtained by simple inversion of the corresponding PDFs. The CG nonbonded potential is parameterized to the PCF using both an inversion procedure based on the Ornstein-Zernike equation with the Percus-Yevick approximation (OZPY−1) and a combination of OZPY−1 with the iterative Boltzmann inversion (IBI) method (OZPY−1+IBI). As a simple one step method, the OZPY−1 method possesses an advantage in computational efficiency. Using the potential from OZPY−1 as an initial guess, the IBI method shows fast convergence. The coarse-grained molecular dynamics (CGMD) simulations of PEG chains with DP = 20 using potentials from both methods satisfactorily reproduce the structural properties from atomistic MD simulation of the same systems. The OZPY−1+IBI method yields better agreement than the OZPY−1 method alone. The new CG model and CG potentials from OZPY−1+IBI method was further tested through CGMD simulation of PEG with DP = 40 system. No significant changes are observed in the comparison of PCFs from CGMD simulations of PEG with DP = 20 and 40 systems indicating that the potential is independent of chain length.
The electronic spectrum of SiH4: Jahn-Teller Rydberg series
Authors: Velasco A. M. , Lavín C. , Sánchez de Merás A. M. J. , Sánchez Marín J.
Published: December 2011

The aim of the present theoretical work is to provide data necessary for a better understanding of the electronic spectrum of the silane molecule, which is affected by the Jahn-Teller effect. By selecting an adequate distorted C2v geometry of SiH4, the three lower Koopmans ionization potentials are evaluated with the equation of motion coupled cluster of singles and doubles method. Vertical excitation energies for the different Rydberg series converging to the three Jahn-Teller components are inferred from ab initio coupled cluster linear response calculations. Absorption oscillator strengths for dipole-allowed electronic transitions are also determined with the molecular-adapted quantum defect orbital methodology. Predictions of new spectroscopic data on SiH4 are reported.
$\hbox{SF-[2]}_{\text{R12}}$
SF-[2]
R12
: A spin-adapted explicitly correlated method applicable to arbitrary electronic states
Authors: Kong Liguo , Valeev Edward F.
Published: December 2011

The $[2]_{\text{R12}}$[2]R12 method [M. Torheyden and E. F. Valeev, J. Chem. Phys. 131, 171103 (2009)10.1063/1.3254836] is an explicitly correlated perturbative correction that can greatly reduce the basis set error of an arbitrary electronic structure method for which the two-electron density matrix is available. Here we present a spin-adapted variant (denoted as $\hbox{SF-[2]}_{\text{R12}}$SF-[2]R12) that is formulated completely in terms of spin-free quantities. A spin-free cumulant decomposition and multi-reference generalized Brillouin condition are used to avoid three-particle reduced density matrix completely. The computational complexity of $\hbox{SF-[2]}_{\text{R12}}$SF-[2]R12 is proportional to the sixth power of the system size and is comparable to the cost of the single-reference MP2-R12 method. The $\hbox{SF-[2]}_{\text{R12}}$SF-[2]R12 method is shown to decrease greatly the basis set error of multi-configurational wave functions.
About the internal pressure in cavities derived from implantation-induced blistering in semi-conductors
Authors: Parry G. , Coupeau C. , Dion E. , David M.-L. , Colin J. , Grilhé J.
Published: December 2011

Silicon and germanium wafers were implanted with hydrogen at high fluence and then submitted to thermal treatment at low temperature. By means of atomic force microscopy observations and finite elements simulations, the internal pressure under the resulting blisters appearing onto the surface has been determined. It is found that the internal pressure could be strongly overestimated from calculation if the internal compressive stresses in the implanted layers are neglected and/or incorrect boundary conditions are used.
Area dependent deep depletion behavior in the capacitance-voltage characteristics of metal-oxide-semiconductor structures with ultra-thin oxides
Authors: Chen Kuan-Ming , Hwu Jenn-Gwo
Published: December 2011

The deep depletion behaviors in the C-V curves of metal-oxide-semiconductor (MOS) structure with various gate areas are studied. A model with three regions of depletion-inversion, edge deep depletion, and bulk deep depletion was proposed. The larger gate area shows a larger effective uniform area ratio Keff than the smaller one. The effective non-uniform edge width Xeff was extracted according to the data of two various gate areas. The extracted Xeff’s at large bias for three areas are used to simulate the experimental data further, and the results are satisfactory for devices with three gate areas in bulk deep depletion region.
Increased grain boundary critical current density Jcgb by Pr-doping in pulsed laser–deposited Y1−xPrxBCO thin films
Authors: Irjala M. , Huhtinen H. , Awana V. P. S. , Falter M. , Paturi P.
Published: December 2011

A comparative study has been performed on Pr-doped Y1-xPrxBCO (x=0-0.20) thin films deposited by pulsed laser deposition on MgO and buffered NiW substrates to study the effect of Pr-doping on the grain boundary critical current density (Jcgb). Our earlier work on bulk materials and SrTiO3 substrates indicated that, whereas Pr increases Jc in bulk samples, it does not increase Jc in film samples without grain boundaries. In this work, we present increased Jc in low concentrations of Pr3+-doping (x< 0.04) at temperatures above 60 K in film samples on MgO substrates and at all temperatures and fields in film samples on buffered NiW substrates. Results indicate that Pr segregates into grain boundary regions, improving the local hole concentration and carrier density, hence, increasing Jcgb.
Size effects on the fatigue behavior of bulk metallic glasses
Authors: Wang G. Y. , Liaw P. K. , Yokoyama Y. , Inoue A.
Published: December 2011

Size effects on bending fatigue characteristics are investigated on Zr-based bulk-metallic glasses (BMGs). The fatigue lifetimes and endurance limits of the large-size samples are greater than those of the small-size samples. The results suggest that although a BMG exhibits good ductility due to the formation of multiple shear bands when its size decreases, the fatigue resistance of BMGs might degrade when the specimen size becomes smaller. The current study finds that small-size BMG samples under bending fatigue could fail in the flexural or fracture mode.
An acoustic bending waveguide designed by graded sonic crystals
Authors: Wu Liang-Yu , Chen Lien-Wen
Published: December 2011

The acoustic bending waveguide can be designed by engineering the index distribution in a bending structure. We employ a two-dimensional graded sonic crystal (GSC) to realize a graded index medium. The refractive indices of a graded index medium can be discretized and the discrete refractive indices are approximated by using GSCs. The effective refractive indices of the sonic crystals are obtained by using the plane wave expansion method. Simulations and transmission spectra of the bending waveguides with the continuous index variation and the GSC approximation are calculated by using the finite-element-method. The results show that the acoustic bending waveguide based on the GSC can be achieved in the low frequency limit and its operating frequency is broadband.
Heavy atom nitroxyl radicals. VI. The electronic spectrum of jet-cooled H2PO, the prototypical phosphoryl free radical
Authors: Gharaibeh Mohammed A. , Clouthier Dennis J. , Tarroni Riccardo
Published: December 2011

The previously unknown electronic spectrum of the H2PO free radical has been identified in the 407–337 nm region using a combination of laser-induced fluorescence and single vibronic level emission spectroscopy. High level ab initio predictions of the properties of the ground and first two excited doublet states were used to identify the spectral region in which to search for the electronic transition and were used to aid in the analysis of the data. The band system is assigned as the ${\rm \tilde B}$B̃2A′−${\rm \tilde X}^{2}$X̃2A′ electronic transition which involves promotion of an electron from the π to the π* molecular orbital. The excited state r0 molecular structure was determined by rotational analysis of high resolution LIF spectra to be r(PO) = 1.6710(2) Å, r(PH) = 1.4280(6) Å, θ(HPO) = 105.68(7)°, θ(HPH) = 93.3(2)°, and the out-of-plane angle = 66.8(2)°. The structural changes on electronic excitation, which include substantial increases in the PO bond length and out-of-plane angle, are as expected based on molecular orbital theory and our previous studies of the isoelectronic H2AsO, Cl2PS, and F2PS free radicals.
Ionodeterioration of the silicon nanocrystal photoluminescence
Authors: Demarche J. , Barba D. , Ross G. G. , Terwagne G.
Published: December 2011

The photoluminescence (PL) of Si nanocrystals (Si-nc) embedded in fused silica has been investigated under simultaneous excitations by laser and low energy proton beam. Ionodegradation of the sample, characterized by a rapid decrease and a spectral blueshift of the PL emission has been observed. These effects are associated with the creation of non-radiative centers in the Si-nc. Micro-Raman spectroscopy analysis shows that the proton beam has not changed the average size of Si-nc, but has disturbed a fraction of Si-Si bonds inside the Si-nc, which is consistent with both simulations and direct measurements. A post-annealing performed at 400 °C for 1 h can restore the structural properties of the Si-nc, but only a part of their nominal PL emission intensity is recovered. Characterization of the damage induced by low energy proton irradiation reported in this paper makes the use of light ion beams relevant for the experimental investigation of nanostructured systems, such as ionoluminescence measurements.
Influence of temperature on dynamics of birefringence switching in photochromic nematic phase
Authors: Mysliwiec Jaroslaw , Czajkowski Maciej , Bartkiewicz Stanislaw , Zygadlo Krystian , Galewski Zbigniew , Sahraoui Bouchta
Published: December 2011

We present results of dynamic and fast switching of birefringence in a photochromic liquid-crystalline system as a function of the sample temperature. The system consists of photochromic molecules of 4-heptyl-4′-methoxyazobenzene showing a liquid-crystalline nematic state close to room temperature. An experiment of dynamic birefringence switching was done in optical Kerr-effect set-up, where for the sample excitation, a picosecond-pulsed laser was used. Measurements were done for different temperatures of the sample in the liquid-crystalline nematic phase. We have proposed a mathematical model of dynamic, fast, and fully reversible birefringence changes. Theoretical estimations and experimental results have shown very good agreement.
Thermal conductance modulator based on folded graphene nanoribbons
Authors: Ouyang Tao , Chen Yuanping , Xie Yuee , Stocks G. M. , Zhong Jianxin
Published: December 2011

Based on folded graphene nanoribbons, we report a thermal conductance modulator which performs analogous operations as the rheostat in electronic circuits. This fundamental device can controllably and reversibly modulate the thermal conductance by varying the geometric structures and its tuning range can be up to 40% of the conductance of unfolded nanoribbons (∼1 nm wide and 7–15 nm long). Under this modulation, the conductance shows a linearly dependence on the folded angle, while undergoes a transition with the variation of the inter-layer distance. This primary thermal device may have great potential applications for phononic circuits and nanoscale thermal management.
Raman spectrometry study of phase stability and phonon anharmonicity of Al3BC3 at elevated temperatures and high pressures
Authors: Xiang Huimin , Li Fangzhi , Li Jingjing , Wang Jiemin , Wang Xiaohui , Wang Jingyang , Zhou Yanchun
Published: December 2011

In situ Raman spectra of Al3BC3 have been measured at elevated temperatures of up to 1000 °C and high pressures of up to 32 GPa. It is shown that there are no abnormal phonon shifts when the measurement conditions were up to 1000 °C or up to 27 GPa, which indicates a good structural stability of Al3BC3 at high temperatures and pressures. The Raman active phonon modes were assigned comprehensively to the corresponding vibration modes by first-principles calculations. Interestingly, an abnormal softening of the E1g(559 cm–1) and E2g(578 cm–1) phonon modes were observed when the pressure was higher than 27 GPa. Correlating the results with previous theoretical predictions of polymorphism in Al3BC3, the mode softening at higher pressures might originate from the structural transformation (from hexagonal to tetragonal symmetry) involving changes of Al and C coordination numbers. In addition, the phonon anharmonicity has been investigated by studying the temperature and pressure dependence of the Raman peak shifts and broadenings. Finally, the present work has highlighted that in situ Raman spectrometry study is a sensitive method for investigating the structural stability and phonon anharmonicity of complex ceramics.
Study on electrodynamic sensor of multi-modality system for multiphase flow measurement
Authors: Deng Xiang , Chen Dixiang , Yang Wuqiang
Published: December 2011

Accurate measurement of multiphase flows, including gas/solids, gas/liquid, and liquid/liquid flows, is still challenging. In principle, electrical capacitance tomography (ECT) can be used to measure the concentration of solids in a gas/solids flow and the liquid (e.g., oil) fraction in a gas/liquid flow, if the liquid is non-conductive. Electrical resistance tomography (ERT) can be used to measure a gas/liquid flow, if the liquid is conductive. It has been attempted to use a dual-modality ECT/ERT system to measure both the concentration profile and the velocity profile by pixel-based cross correlation. However, this approach is not realistic because of the dynamic characteristics and the complexity of multiphase flows and the difficulties in determining the velocities by cross correlation. In this paper, the issues with dual modality ECT/ERT and the difficulties with pixel-based cross correlation will be discussed. A new adaptive multi-modality (ECT, ERT and electro-dynamic) sensor, which can be used to measure a gas/solids or gas/liquid flow, will be described. Especially, some details of the electrodynamic sensor of multi-modality system such as sensing electrodes optimum design, electrostatic charge amplifier, and signal processing will be discussed. Initial experimental results will be given.
Simple alignment technique for polarisation maintaining fibres
Authors: Arora P. , Agarwal A. , Gupta A. Sen
Published: December 2011

We describe a simple technique for rapid alignment of input state of polarisation with respect to the preferred axis of polarisation maintaining fibres. In this technique a combination of a half-wave and a quarter-wave plate is used to turn the polarisation of incoming beam and to compensate for stress-induced perturbation of polarisation states in a laid-out fibre, respectively. The angular alignment technique is tested with temperature excursion on the fibre. The technique is easy to implement, affordable, and gives quick and accurate alignment.
Influences of electric field on living cells in a charged water-in-oil droplet under electrophoretic actuation
Authors: Im Do Jin , Noh Jihoon , Yi Nam Woo , Park Jaesung , Kang In Seok
Published: December 2011

We experimentally investigate the effects of high electric field on living cells inside a charged droplet under electrophoretic actuation. When an aqueous droplet suspended in a dielectric liquid contacts with electrified electrode, the droplet acquires charge. This charged droplet undergoes electrophoretic motion under strong electric field (1–3 kV/cm), which can be used as a droplet manipulation method in biomicrofluidic applications. However, because strong electric field and use of dielectric oil can be a harmful environment for living cells, the biological feasibilities have been tested. Trypan blue test and cell growth test have been performed to check the viability and proliferation of cells in a droplet under various electric field strengths and actuation times. We have not observed any noticeable influence of electric field and silicone oil on the viability and proliferation of cells, which indicates that electrophoresis could be safely used as a manipulation method for a droplet containing living biological system.
Droop improvement in blue InGaN/GaN multiple quantum well light-emitting diodes with indium graded last barrier
Authors: Sheng Xia Chang , Simon Li Z. M. , Lu Wei , Hua Zhang Zhi , Sheng Yang , Wen Cheng Li
Published: December 2011

Blue InGaN/GaN multiple quantum well light-emitting diodes with the conventional and graded last barriers (GLB) are numerically investigated. When the last GaN barrier is replaced by a linearly graded InxGa1 − xN barrier with increasing indium composition in the growth direction, the forward voltage is reduced from 3.60 V to 3.25 V, and the efficiency droop is improved from 36% to 13%. Simulation results indicate that these improvements can be attributed to the formation of a deep potential well in the GLB which enhances the electron confinement and improves the hole injection efficiency.
Enhanced refrigerant capacity and magnetic entropy flattening using a two-amorphous FeZrB(Cu) composite
Authors: Álvarez Pablo , Sánchez Llamazares José L. , Gorria Pedro , Blanco Jesús A.
Published: December 2011

The temperature dependence of the isothermal magnetic entropy change, ΔSM, and the magnetic field dependence of the refrigerant capacity, RC, have been investigated in a composite system xA + (1 − x)B, based on Fe87Zr6B6Cu1 (A) and Fe90Zr8B2 (B) amorphous ribbons. Under a magnetic field change of 2 T, the maximum improvement of the full-width at half maximum of ΔSM(T) curve (47% and 29%) and the RC (18% and 23%), in comparison with those of the individual alloys (A and B), is observed for x ≈ 0.5. Moreover, a flattening over 80 K in the ΔSM(T) curve around room temperature range is observed, which is a key feature for an Ericsson magnetic refrigeration cycle.
Mechanically tunable microlasers based on highly viscous chiral liquid crystals
Authors: Shibaev Petr V. , Crooker Benjamin , Manevich Michael , Hanelt Eckhard
Published: December 2011

Chiral composition is designed for highly viscous lasing microemitters. The composition forms cholesteric liquid crystal and after doping with pyrromethene 597 was used as an active lasing media in stretchable aluminized silicone cavities. Optical pumping of the system led to lasing at the wavelengths defined by a degree of cavity deformation. Lasing thresholds were lower in aluminized cavity than in transparent cavity. A simple model allowing to predict the shift of lasing wavelength as a function of deformation is developed.
Edge surface modes in magnetically biased chemically doped graphene strips
Authors: Sounas Dimitrios L. , Caloz Christophe
Published: December 2011

The characteristics of surface modes along magnetically biased chemically doped graphene strips at terahertz frequencies are investigated. Both edge and bulk modes exist, with power densities concentrated near the edges and in the middle of the strip, respectively. It is shown that placing a perfect electric conductor plate near one of the strip edges shorts the modes propagating along this edge. This results in strong non-reciprocity, which may be used for the realization of non-reciprocal phase shifters.
Note: Phase-locked loop with a voltage controlled oscillator based on a liquid crystal cell as variable capacitance
Authors: Marcos Carlos , Sánchez-Pena José M. , Torres Juan C. , Pérez Isabel , Urruchi Virginia
Published: December 2011

A phase-locked loop is demonstrated using a twisted-nematic liquid crystal cell as a capacitance that can be varied as a function of applied voltage. The system is formed by a phase detector, a low-pass filter, as well as a voltage controlled oscillator including such variable capacitance. A theoretical study is proposed and experimentally validated. Capture and locked ranges of hundreds of kHz have been obtained for the configuration used in this circuit. An application as frequency demodulator using a practical implementation of this circuit has been demonstrated.