bluuebunny/crossref_metadata_2025 huggingface dataset:
Continental delamination and the Colorado Plateau
Authors: Bird Peter
Published: December 2012

Continental lithosphere is in unstable mechanical equilibrium because its mantle layer is denser than the asthenosphere. If any process such as cracking, slumping, or plume erosion initially provided an elongated conduit connecting the underlying asthenosphere with the base of the continental crust, the dense lithospheric boundary layer could peel away from the crust and sink. An analytic model for sinking velocities at the critical initial time shows that instability occurs if the effective viscosities of the lower continental crust and the rising asthenosphere are no more than 1019 P. Analogies to subduction suggest that the mature instability would grow laterally at plate tectonic velocities; however, it would be almost aseismic. Loss of the cold mantle boundary layer would cause uplift, increased heat flow, reduced seismic velocities, and perhaps emplacement of basalt flows, mantle diatremes, and granodiorite sills. A one‐dimensional thermal model of the formation of a new boundary layer predicts a half life of about 3×107 years for this thermal anomaly and uplift. As an example, the geologic and geophysical data from the Colorado Plateau are shown to be consistent with the hypothesis that it was uplifted by a delamination event 30 m.y. ago and perhaps a second event about 5 m.y. ago.
Dependence of the thickness of the elastic oceanic lithosphere on age
Authors: Caldwell J. G. , Turcotte D. L.
Published: December 2012

Most bathymetric profiles of oceanic trenches show a well‐defined outer rise seaward of the trench. The widths of the observed outer rises are used with an elastic flexure model to determine the effective elastic thickness (EET) of the oceanic lithosphere as a function of the age of the lithosphere being subducted. A model for the EET is proposed in which its upper boundary is taken at a prescribed depth and its lower boundary at a prescribed temperature. It is assumed that the base temperature is the temperature at which elastic stresses are relaxed by dislocation creep on geological time scales. Using a laboratory‐derived creep law this relaxation temperature is found to be 700±100°C this result is relatively insensitive to time and stress levels. Using accepted thermal models for the oceanic lithosphere, this relaxation temperature gives values of the EET which are in good agreement with the observations.
Geodolite measurements of deformation near Hollister, California, 1971–1978
Authors: Savage J. C. , Prescott W. H. , Lisowski M. , King N.
Published: December 2012

A 24‐station trilateration network spanning the San Andreas and Calaveras faults near Hollister, California, has been surveyed each year between 1971 and 1978, inclusive. Two moderate (ML = 5) earthquakes have occurred within the network during the interval. No convincing preseismic or coseismic anomalies associated with those earthquakes have been identified. The deformation of the network can be described roughly by rigid body motion of the three blocks bounded by the two faults with accommodation occurring by right‐lateral strike slip on the San Andreas (13±2 mm/a) and Calaveras (17±2 mm/a) faults. The required slip rates are within the range of the observed fault creep on those faults. A more detailed analysis of the deformation indicates appreciable strain accumulation (0.4 μstrain/a tensor shear) within the block lying between the San Andreas and Calaveras faults. Many of the features of the observed deformation can be produced by an elementary dislocation model, indicating that most of the deformation is associated directly with slip on the major faults. The network is not extensive enough to define uniquely the relative motion across the San Andreas fault system, but the data are consistent with a value of about 38 mm/a. The rate of deformation in 1971–1978 was not uniform but rather appears to have been higher than normal in 1973–1974 and lower than normal in 1975–1976.

Supplement is available with entire article on microfiche. Order from American Geophysical Union', 2000 Florida Avenue, N.W., Washington, D.C. 20006. Document J79‐008;$01.00. Payment must accompany order.
"The Hawaii Earthquake of November 29, 1975: Low dip angle faulting due to forceful injection of magma""
Authors: Ando Masataka
Published: December 2012

The mechanism of the Hawaii earthquake of November 29, 1975 (Ms = 7.1), which took place on the south flank of Kilauea Volcano, is discussed on the basis of a comprehensive set of body wave and surface wave data, the aftershock distribution, and tsunami and crustal deformation data. The aftershock distribution defines a gently dipping plane at about 10‐km depth beneath the south flank of Kilauea. This suggests that the shallowly dipping P wave nodal plane fits the fault of the Hawaii earthquake better than the nodal plane that has a nearly vertical dip angle. The fault length is fixed well by the aftershock distribution, which is also consistent with the tsunami and crustal deformation data. The fault width which is obtained from tsunami and crustal deformation data is, however, significantly greater than that obtained from the aftershock distribution. This discrepancy implies that about half of the main shock fault plane was not associated with aftershock activity. The source parameters are strike N70°E; dip angle 20°SSE; fault length 40 km; seismic moment 1.8×1027 dyne‐cm; fault width 20–30 km; fault movement is pure normal dip slip of 3.7–5.5 m, and stress drop is 43–93 bars. Results of geodetic surveys throughout the twentieth century and a history of volcanic activity on Kilauea imply that a north‐south compression due to magma injected into rift zones may have steadily increased on the south flank of Kilauea since the 1868 earthquake, an event comparable to the 1975 shock. This compressional stress was possibly released by the 1975 Hawaii earthquake. The long‐term eruptive activity of Kilauea may be affected by large earthquakes like the 1868 and 1975 events and may also have a similar 100‐yr recurrence interval.
Two‐Ship Multichannel Seismic Experiments for deep crustal studies: Expanded spread and constant offset profiles
Authors: Stoffa Paul L. , Buhl Peter
Published: December 2012

Expanding spread profiles (ESP's) are spatially localized, wide‐angle reflection/refraction surveys using two ships, a multichannel array, and Raydist ranging. The value of the data is primarily the fidelity with which the data are recorded and the multiplicity of coverage provided by the multichannel array. We feel that the ESP technique has several distinct advantages over other methods of deep crustal studies. These are (1) very accurate range and timing information, (2) fixed and well‐known receiver separation (100 m) for accurate phase velocity determination across the array, (3) because of accurate timing and range information, traces from different shots may be used to improve velocity determination (this is limited only by the persistence of the particular arrivals), (4) true amplitude recording that allows the use of sophisticated signal processing techniques and tightly constrains models of the observed data, (5) no difficulties with receiver coupling, (6) calibration of charge size changes through overlapping receiver positions, (7) a minimum amount of explosives is required because of the redundancy provided by the multichannel receiving array, (8) minimal deployment and recovery time coupled with low equipment loss rate, (9) ‘real‐time’ data monitoring and analysis to insure the quality of the recorded data, and (10) digital recording in a readily exchangeable standard format to facilitate the use of digital computers in reducing the vast amount of data acquired. Data of this quality in range, time, and amplitude are required for any detailed inversion or modeling scheme. Dense spatial sampling is required to avoid spatial aliasing, to demonstrate phase coherence between traces, and to observe amplitude variations over short distances. Constant offset profiles (COP's) are fixed range, wide‐angle reflection/refraction surveys using two ships, a multichannel array, and Raydist ranging. Using this technique, it is possible to develop a profile of refracting type interfaces which are normally absent from the reflection record. With earlier methods, these events are recorded only as ‘spot’ measurements, and lateral variation is only coarsely determined. Since constant offset profiles are multichannel array measurements at a specific range, variations in velocity, arrival time, and signal amplitude along the profile can be accurately determined. By combining these data with near‐vertical incidence multichannel data along the same track, a detailed survey of the deep ocean crust and particularly its lateral variability is possible. This experimental technique is the only method available for a detailed continuous mapping of lateral crustal variations from nonreflecting horizones.
Acoustic anisotropy in marine sediments and sedimentary rocks
Authors: Bachman Richard T.
Published: December 2012

Marine sediments under overburden pressure commonly develop elastic anisotropy, probably of the transverse type with a single vertical axis of symmetry. Surface measurements of sound interval velocity in such materials, as by wide angle reflection profiling, provide a value between the vertical and horizontal velocities, thus introducing errors when measured velocity is used in determining section thickness. Empirical regression equations from laboratory measurements allow estimation of in situ vertical or horizontal velocity when one or the other is known in marine calcareous (Vv, km/s = 0.18 + 0.89Vh) and siltclay (Vv, km/s = 0.25 + 0.83 Vh) sediments and sedimentary rocks. These equations allow determination of the maximum error caused by anisotropy in section thickness determinations.
The Mercury soil: Presence of Fe2+
Authors: McCord Thomas B. , Clark Roger N.
Published: December 2012

The reflectance spectrum for integral Mercury is presented from 0.65 to 2.5 μm. The reflectance continues to increase from the visible spectral region into the infrared, and a weak, broad absorption band appears centered at 0.89 μm. The absorption is probably due to electronic transitions in Fe2+ ions in the soil. The band center position suggests an orthopyroxene as the major mafic mineral affecting the spectrum. The band strength and the soil albedo suggest that the amount of Fe2+ present is similar to that for lunar highland soil.
The magnetization of the Rose Hill Formation at the classical site of Graham's Fold Test
Authors: French Andrew N. , Van der Voo Rob
Published: December 2012

A reinvestigation of the middle Silurian Rose Hill Formation yields a revised pole position of 19.0°N, 129.1°E (α95= 5.8° for N = 35 samples from nine sites and three lithologies). This is based upon three separate fold tests, all of which indicate predeformational stability of the magnetization at the 99% confidence level, as well as upon normal and reversed polarity directions. Laboratory methods used to derive these results included thermal, chemical, and alternating field stepwise demagnetizations of three lithologies: gray sandstones, hematitic red sandstones, and dolomitic sandstones. Consistency among the techniques was excellent, and through vector subtraction we obtained characteristic and secondary components of magnetization. Reversed polarity directions of the hematite sandstones did not produce a positive fold test, and their resemblance to late Paleozoic directions for North America suggests that they have been remagnetized during that time. The remagnetization was probably a chemical event, since a thermal event would have also remagnetized the gray sandstones and the dolomitic sandstones. In addition to paleomagnetic experiments, rock magnetic experiments were performed to clarify the nature of the dolomites (previously called siderites). Analysis of natural and isothermal remanent magnetizations from −196°C to 680°C shows a dominance of finegrained magnetite and hematite. Thin sections show that lesser amounts of coarse‐grained magnetite and hematite are also present. Consistency between thermal, chemical, and alternating field demagnetizations indicates that both hematite and magnetite carry the characteristic direction. The mean inclination for the Rose Hill Formation, −44°, places North America in moderate southerly latitudes (about 26°) during the Middle Silurian. The declination of 330° indicates a rotation of 30° in a clockwise sense from the present‐day orientation, but it is less unambiguous than the inclination, since we cannot determine if relative rotations of blocks in this part of the Appalachians occurred, or whether the declination is truly representative of the entire North American craton. However, evidence for horizontal rotations on the scale of 1 m to 100 km is lacking, so we prefer a rotation of the entire North American craton by this amount.
Huancayo Magnetic Observatory October to December, 1934
Authors: Torreson O. W.
Published: December 2012

November 7—A mild disturbance (character 1) of short duration began with minor fluctuations of rather long period in H but was not perceptible in D or Z. Perturbations in H were rapid and comparatively large between 13h and 18h, there being five bays with from 50γ to 100γ range from crest to trough during that interval, the period of each bay (crest to crest) being about 30 minutes. Rapid, small oscillations were superposed on these bays. D and Z experienced minor perturbations during the same interval, not greatly affecting the general diurnal variation. The following day, especially during daylight‐hours (12h to 21h, G.M.T.), was somewhat disturbed also, but not unusually so, considering the character of November as a whole.2
Auroral display Forsyth, Montana
Authors: Davies F. T.
Published: December 2012

A communication received from Chester J. Nertney, Airway Observer, described an interesting auroral display occurring at Forsyth, Montana, January 28, 1936. It began at 1:50 a. m. and lasted until 5:35 a. m., 105° west meridian time. A bright glow at zenith persisted for nearly four hours, in addition to which a coronal type of display developed rapidly between 2:00 and 2:20 a. m. and faded away by 2:30 a. m. The persistence of the zenithal glow which, for part of the display was linked with a streamer running to the northwest, indicates that this part of the display was of the quiet arch‐ or band‐type.
Aurora of February 24, 1939
Authors: Cowie Alexander
Published: December 2012

During the auroral display on February 24, 1939, the ionosphere was examined at Edinburgh from 21h to 23h GMT, using a variable‐frequency transmitter operating on the Breit and Tuve pulse‐system. On this occasion no trace of echoes or other signals was evident. The examination was made using frequencies between 1.5 and 10 mc/sec. It was further noticed that the general noise‐level was abnormally high and that signals from broadcast stations (600 to 1500 kc/sec) were very erratic.
American URSI broadcasts of cosmic data, January to March, 1939, with American magnetic character‐figure CA, February to April, 1939
Authors: Johnston H. F.
Published: December 2012

The data for terrestrial magnetism, sunspots, and solar constant are the same as given in previous tables.

The first three columns of Table 1 give (1) the magnetic character according to the scale 0‐2 of the International Commission of Terrestrial Magnetism and Atmospheric Electricity, (2) the type featuring the day other than normal by the letters b, p, o, and i for days marked by day, rapid pulsations, long‐period oscillations, and iregular oscillations, respectively, and (3) the hour and minute of Greenwich mean time marking the beginning of a storm, the end of the storm being indicated in the foot‐note to the Table.
Apia Observatory January to March, 1945
Authors: Sapsford H. Bruce
Published: December 2012

(Latitude 13° 48′.4 S., longitude 171° 46′.5 or 11h 27m.1 W. of Gr.)

January 28–29—A moderate storm commenced in H at 14h 55m GMT, January 28, continuing with moderate fluctuations to a maximum at 22h 55m and a minimum at 04h 11m, January 29, and then gradually returned to normal. Only slight fluctuations were observed in D and Z. Range: H, 169 gammas.
Sitka Magnetic Observatory, January to March, 1948
Authors: Campbell Joel B.
Published: December 2012

(Latitude 57° 03′.0 N., longitude 135° 20′.1 or 9h 01m.3 W. of Gr.)
Zô‐Sè Observatory, January to March, 1948
Authors: Burgaud M.
Published: December 2012

(Latitude 31° 05′.8 N., longitude 121° 11′.2 or 8h 04m.8 E. of Gr.)
Chromatin‐dependent and ‐independent regulation of DNA replication origin activation in budding yeast
Authors: Lõoke Marko , Kristjuhan Kersti , Värv Signe , Kristjuhan Arnold
Published: December 2012

To elucidate the role of the chromatin environment in the regulation of replication origin activation, autonomously replicating sequences were inserted into identical locations in the budding yeast genome and their activation times in S phase determined. Chromatin‐dependent origins adopt to the firing time of the surrounding locus. In contrast, the origins containing two binding sites for Forkhead transcription factors are activated early in the S phase regardless of their location in the genome. Our results also show that genuinely late‐replicating parts of the genome can be converted into early‐replicating loci by insertion of a chromatin‐independent early replication origin, ARS607, whereas insertion of two Forkhead‐binding sites is not sufficient for conversion.
Substrate-diamond interface considerations for enhanced thermionic electron emission from nitrogen doped diamond films
Authors: Koeck Franz A. M. , Nemanich Robert J.
Published: December 2012

Thermionic electron emission from low work function doped diamond films can be related to materials' properties, which include donor states, surface electron affinity, and substrate-diamond interface properties. The focus of this study is on how the properties of the substrate material affect the emission. Two aspects are considered, the substrate electrical resistance and the substrate Richardson constant, and the effects of tungsten, molybdenum and rhenium substrates are explored. Low work function diamond films were deposited on the substrates, and the thermionic emission was measured to ∼530 °C and described in terms of a fit to the Richardson-Dushman formalism. The results establish that all surfaces exhibit a similar work function but the Richardson constant and maximum emission current vary considerably. The rhenium based emitter displayed a low work function of 1.34 eV, a significant Richardson constant of 53.1 A/cm2 K2, and an emission current density of ∼44 mA/cm2 at a temperature of 530 °C. The results indicated that interface carbide formation could limit the emission presumably because of increased electrical resistance. For non-carbide forming substrates, an increased substrate Richardson constant corresponded to enhanced emission from the diamond based emitter.
A three-dimensional strain model for the superconducting properties of strained International Thermonuclear Experimental Reactor Nb3Sn strands
Authors: Qiao Li , Zheng Xiaojing
Published: December 2012

The critical current density parameterization for the International Thermonuclear Experimental Reactor (ITER) Nb3Sn production accounting for the three-dimensional (3D) nature of strain is significant for the analysis of the performance of magnet systems. A simple model for the 3D strain dependence of the critical current density in ITER Nb3Sn strands is proposed in this paper. It is on the basis of the strain-induced variation in the electronic density of states at the Fermi surface. The validity of the proposed scaling law is verified by making comparisons with experimental data acquired on the bare/jacketed Nb3Sn wire. The derived 3D model in axial form is capable of adequately describing the anomalies in the strain function of the Nb3Sn wires jacketed with AISI 316 L stainless steel, which arise from a multi-dimensional strain effect, while none of the existing research models can describe such trend. The model provides a new way of identifying the scaling relation for the critical current density in Nb3Sn strands.
Two-point vorticity statistics in the inverse cascade of two-dimensional turbulence
Authors: Friedrich R. , Voßkuhle M. , Kamps O. , Wilczek M.
Published: December 2012

A statistical analysis of the two-point vorticity statistics in the inverse energy cascade of two-dimensional turbulence is presented in terms of probability density functions (PDFs). Evolution equations for the PDFs are derived in the framework of the Lundgren–Monin–Novikov hierarchy, and the unclosed terms are studied with the help of direct numerical simulations (DNS). Furthermore, the unclosed terms are evaluated in a Gaussian approximation and compared to the DNS results. It turns out that the statistical equations can be interpreted in terms of the dynamics of screened vortices. The two-point statistics is related to the dynamics of two point vortices with screened velocity field, where an effective relative motion of the two point vortices originating from the turbulent surroundings is identified to be a major characteristics of the dynamics underlying the inverse cascade.
Dielectric investigations on a bent-core liquid crystal
Authors: Marino Lucia , Ionescu Andrei Th. , Marino Salvatore , Scaramuzza Nicola
Published: December 2012

Dielectric measurements on a bent-core liquid crystal were carried out in the frequency range from 10 mHz to 100 kHz in planar aligned cells. Four relaxation ranges were detected during heating condition: two in a low frequency range of a few hertz probably due to conductivity and interface relaxation phenomena, another between 10 and 20 Hz, and another one in a range between 10 kHz and 100 kHz in smectic as in nematic and isotropic phases. The third relaxation response is no more visible during cooling conditions. Dielectric increments, distribution parameters, and relaxation frequencies have been evaluated at different temperatures by fitting data with Havriliak-Negami (H-N) relaxation function, which is an empirical modification of the Debye relaxation model. The presence of a relaxation response between 10 and 20 Hz and the relatively great values of the permittivity could suggest the presence of a ferroelectric response due to the presence of cybotactic clusters.
Negative Gaussian curvature distribution in physical and biophysical systems—Curved nanocarbons and ion-channel membrane proteins
Authors: Gupta Sanju , Saxena Avadh
Published: December 2012

Soft, polymeric and biological systems are self-assembled and hierarchical that involves a multitude of length scales, geometrical shapes and topological variation besides being elastically soft and easily deformable unlike their inorganic solid counterparts. Within the framework of topology and geometry applied to nanocarbons in our recent work [Gupta and Saxena, J. Appl. Phys. 109, 074316 (2011)], we invoke a similar approach to understanding soft/bio-macromolecular systems having structural diversity specifically within the context of minimal surfaces (i.e., mean curvature H = 0 and Gaussian curvature K < 0 everywhere). The systems of interest include non-periodic and periodic minimal surfaces such as catenoids (synthetic or natural ion-channel membrane proteins), helicoids (β-sheet proteins), and Schwarzites, respectively, which are analyzed within the framework of differential geometry to obtain the information about Gaussian curvature variation, Gaussian bending rigidity, elastic bending energy, and corresponding topological features. Specifically, we study the negative Gaussian curvature distribution providing surface structure of membrane proteins and Schwarzites and corresponding bending energy cost. We focus on ion-channel membrane proteins approximated as a symmetric catenoid, biological sheets as a helicoid and negatively curved carbons and certain mixed di- or triblock copolymers as periodic minimal surfaces, e.g., gyroids. Through these analyses, we identify the role of geometry (shape) and topology in energy storage and catalysis, nanomedicine and drug delivery applications and derive an overarching geometry/topology → property → functionality relationship paradigm.
Kinetics of hardness evolution during annealing of gamma-irradiated polycarbonate
Authors: Yeh S. H. , Chen P. Y. , Harmon Julie , Lee Sanboh
Published: December 2012

This study focuses on the evolution in microhardness values that accompany isothermal annealing in gamma-irradiated polycarbonate (PC). Hardness increases with increasing annealing time, temperature, and gamma radiation dose. A model composed of a mixture of first and zero order structure relaxation is proposed to interpret the hardness data. The rate constant data fit the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The extent of structural relaxation that controls the hardness in post-annealed PC increases with increasing annealing temperature and dose. The model demonstrates that hardness evolution in PC is an endothermic process. By contrast, when the model is applied to irradiated poly(methyl methacrylate) and hydroxyethyl methacrylate copolymer, hardness evolution is an exothermic process.
Unexpected positive role of oxygen vacancies in Na-doped ZnO
Authors: Yang X. P. , Lu J. G. , Zhang H. H. , Lu B. , Huang J. Y. , Ye C. L. , Ye Z. Z.
Published: December 2012

The interaction of Na impurities and O vacancies (VO) in ZnO was studied in theory and experiment. The VO facilitated substitutional Na (NaZn/NaZn−) acceptors with inhibiting interstitial Na (Nai/Nai+) donors, which may benefit the p-type conductivity. The formed (NaZn-VO)+/0 complexes induced the change of band structures of ZnO, with the broadening of gap energies and disappearance of the VO2+-related impurity level, which confirmed by the blue shift of the near-band-edge (NBE) UV emission and the decay of the visible emission in PL spectra. The strong and dominant NBE UV emission suggested acceptable luminescence behaviors of Na-doped ZnO.
Enhancing exchange bias and tailoring microwave properties of FeCo/MnIr multilayers by oblique deposition
Authors: Phuoc Nguyen N. , Chai Guozhi , Ong C. K.
Published: December 2012

A systematic study of the static and dynamic magnetic properties with regards to temperature for FeCo/MnIr multilayered thin films fabricated by oblique sputtering technique was carried out. Compared with the film produced by conventional non-oblique sputtering method, those films grown by oblique deposition show a significant increment of exchange bias. The magnetic anisotropy field and the ferromagnetic resonance frequency can also be enhanced and tailored by changing oblique deposition angle. In addition, thermal stability of the dynamic characteristics of the films was presented and discussed from application-oriented perspective.
Intermixing of InGaAs/GaAs quantum wells and quantum dots using sputter-deposited silicon oxynitride capping layers
Authors: McKerracher Ian , Fu Lan , Hoe Tan Hark , Jagadish Chennupati
Published: December 2012

Various approaches can be used to selectively control the amount of intermixing in III-V quantum well and quantum dot structures. Impurity-free vacancy disordering is one technique that is favored for its simplicity, however this mechanism is sensitive to many experimental parameters. In this study, a series of silicon oxynitride capping layers have been used in the intermixing of InGaAs/GaAs quantum well and quantum dot structures. These thin films were deposited by sputter deposition in order to minimize the incorporation of hydrogen, which has been reported to influence impurity-free vacancy disordering. The degree of intermixing was probed by photoluminescence spectroscopy and this is discussed with respect to the properties of the SiOxNy films. This work was also designed to monitor any additional intermixing that might be attributed to the sputtering process. In addition, the high-temperature stress is known to affect the group-III vacancy concentration, which is central to the intermixing process. This stress was directly measured and the experimental values are compared with an elastic-deformation model.
Anomalous behavior of acoustic phonon mode and central peak in Pb(Zn1/3Nb2/3)0.85Ti0.15O3 single crystal studied using Brillouin scattering
Authors: Mishra K. K. , Sivasubramanian V. , Arora A. K. , Pradhan Dillip
Published: December 2012

Brillouin spectroscopic measurements have been carried out on relaxor ferroelectric Pb(Zn1/3Nb2/3)0.85Ti0.15O3 single crystal over the temperature range 300–873 K. The frequency of longitudinal acoustic phonon (LA) begins to exhibit a strong decrease below the Burn's temperature TB followed by an increase in the line-width below the characteristic intermediate temperature T* ∼ 525 K. The line-width of the LA phonon mode exhibits a sharp Landau-Khalatnikov-like maximum at 463 K, the tetragonal-cubic phase transition temperature (Ttc). In addition, a broad central peak, found below T* exhibits critical slowing down upon approaching Ttc indicating an order-disorder nature of the phase transition. The relaxation time of polar nanoregions estimated from the broad central peak is found to be same as that obtained from LA phonon mode suggesting a strong coupling between strain and polarization fluctuations.
High energy-storage performance in Pb0.91La0.09(Ti0.65Zr0.35)O3 relaxor ferroelectric thin films
Authors: Hao Xihong , Wang Ying , Yang Jichun , An Shengli , Xu Jinbao
Published: December 2012

In this work, 1-μm-thick relaxor ferroelectric (FE) films with a typical composition of Pb0.91La0.09(Ti0.65Zr0.35)O3 (PLZT 9/65/35) were successfully deposited on platinum-buffered silicon substrates via a sol-gel technique. The microstructure, electrical properties, and energy-storage performance of the obtained thin films were investigated in detail. X-ray diffraction (XRD) analysis and field-emission scanning electron microscopy pictures indicated that the crystallized thin films showed a random orientation with uniform and dense microstructure. Electrical measurements illustrated that the relaxor FE thin films had a considerable capacitance density of 925 nF/cm2 at 1 MHz and a higher critical breakdown field of 2177 kV/cm. As a result, a large recoverable energy-storage density of 28.7 J/cm3 was obtained in the thin films at room temperature. Moreover, good charge-discharge endurance was also realized in the FE films, confirmed by the repeated polarization-electric field loops.
Classification of two-dimensional quantum systems with $\mathbb {Z}_3$Z3-graded topological symmetries
Authors: Pouladsaz D.
Published: December 2012

In this article, I have derived the general conditions on two-dimensional quantum systems possess \documentclass[12pt]{minimal}\begin{document}$\mathbb {Z}_3$\end{document}Z3-graded topological symmetries and calculated the solutions of two special cases of such systems.
Experimental and theoretical studies of the electronic transitions of BeC
Authors: Barker Beau J. , Antonov Ivan O. , Merritt Jeremy M. , Bondybey Vladimir E. , Heaven Michael C. , Dawes Richard
Published: December 2012

Electronic spectra for BeC have been recorded over the range 30 500–40 000 cm−1. Laser ablation and jet-cooling techniques were used to obtain rotationally resolved data. The vibronic structure consists of a series of bands with erratic energy spacings. Two-color photoionization threshold measurements were used to show that the majority of these features originated from the ground state zero-point level. The rotational structures were consistent with the bands of 3Π-X3Σ− transitions. Theoretical calculations indicate that the erratic vibronic structure results from strong interactions between the four lowest energy 3Π states. Adiabatic potential energy curves were obtained from dynamically weighted MRCI calculations. Diabatic potentials and coupling matrix elements were then reconstructed from these results, and used to compute the vibronic energy levels for the four interacting 3Π states. The predictions were sufficiently close to the observed structure to permit partial assignment of the spectra. Bands originating from the low-lying 15Σ− state were also identified, yielding a 5Σ− to X3Σ− energy interval of 2302 ± 80 cm−1 and molecular constants for the 15Π state. The ionization energy of BeC was found to be 70 779(40) cm−1.
A new protocol for finite-time consensus of detail-balanced multi-agent networks
Authors: Yang Shaofu , Cao Jinde , Lu Jianquan
Published: December 2012

In this paper, a finite-time consensus protocol for multi-agent networks is discussed from a new perspective. The order β of the nonlinear function in the protocol is shown to be a crucial parameter in analyzing the finite-time consensus property of multi-agent networks with a detail-balanced communication topology. When β>0, the corresponding protocol can guarantee the consensus of the multi-agent networks. In particular, if β∈(0,1), the consensus can be realized within finite time. A leader-follow model is also investigated in this paper. Finally, several concrete protocols are proposed based on our theoretical analysis, and numerical examples are given to make a comparison among different protocols from the aspect of convergence speed.
Influence of a simple magnetic bar on buoyancy-driven fingering of traveling autocatalytic reaction fronts
Authors: Mishra M. , Thess A. , De Wit A.
Published: December 2012

Magnetic fields have been shown experimentally to modify convective dynamics developing around traveling chemical fronts in presence of unfavorable density gradients. To understand the conditions in which such magnetic fields affect autocatalytic fronts, we study theoretically the influence of a simple magnetic bar on buoyancy-driven density fingering of a chemical front by numerical simulations of a reaction-diffusion-convection system. The model couples Darcy's law for the flow velocity to an evolution equation for the concentration of the autocatalytic product, which affects both the density of the solution and the magnetic force. The solutions of both products and reactants are assumed to be diamagnetic (i.e., negative magnetic susceptibility) and the magnetization is oriented perpendicularly to the plane in which the front travels. We show that, when aligned along the direction of front propagation, the magnetic force is able to suppress or enhance the convective instability depending on the value of the magnetic Rayleigh number of the problem. If the magnetic force is oriented transversely to the front propagation direction, tilted drifting convective patterns are obtained.
Capillary droplets on Leidenfrost micro-ratchets
Authors: Marín Álvaro G. , Arnaldo del Cerro Daniel , Römer Gertwillem R. B. E. , Pathiraj B. , Huis in 't Veld Albertus , Lohse Detlef
Published: December 2012

Leidenfrost ratchets are structures with the ability of transporting liquid droplets when heated over the critical Leidenfrost temperature. Once this temperature is reached, the droplet levitates over the surface and moves in the direction marked by the slope of the ratchet at terminal velocities around 10 cm/s. Here we provide new experiments with micron-sized ratchets, which have been produced with picosecond pulse laser ablation. In the following work, we use a simple method to measure the thrust driving droplets of capillary size over the micro-ratchets. The mechanism responsible for the force acting on the drop on superheated ratchets has been recently under debate. We extend the recently proposed “viscous mechanism” proposed by Dupeux et al. [Europhys. Lett. 96, 58001 (2011)10.1209/0295-5075/96/58001] to capillary droplets and find good agreement with our measurements.
Radiative lifetimes of spin forbidden a1Δ → X 3Σ− and spin allowed A3Π → X 3Σ− transitions and complete basis set extrapolated ab initio potential energy curves for the ground and excited states of CH−
Authors: Srivastava Saurabh , Sathyamurthy N.
Published: December 2012

The spin forbidden transition a1Δ → X3Σ− in CH− has been studied using the Breit-Pauli Hamiltonian for a large number of geometries. This transition acquires intensity through spin-orbit coupling with singlet and triplet Π states. The transition moment matrix including more than one singlet and triplet Π states was calculated at the multi-reference configuration interaction/aug-cc-pV6Z level of theory. The computed radiative lifetime of 5.63 s is in good agreement with the experimental (5.9 s) and other theoretical (6.14 s) results. Transition moment values of the spin allowed A3Π → X3Σ− transition have also been calculated at the same level of theory. Calculations show that the corresponding radiative lifetime is considerably low, 2.4 × 10−7 s. Complete basis set extrapolated potential energy curves for the ground state of CH and the ground state and six low lying excited states (a1Δ, b1Σ+, two 3Π, and two 1Π) of CH− are reported. These curves are then used to calculate the vibrational bound states for CH and CH−. The computed electron affinity of CH supports the electron affinity bounds reported by Okumura et al. [J. Chem. Phys. 85, 1971 (1986)10.1063/1.451140].
Evaluation of protein-protein docking model structures using all-atom molecular dynamics simulations combined with the solution theory in the energy representation
Authors: Takemura Kazuhiro , Guo Hao , Sakuraba Shun , Matubayasi Nobuyuki , Kitao Akio
Published: December 2012

We propose a method to evaluate binding free energy differences among distinct protein-protein complex model structures through all-atom molecular dynamics simulations in explicit water using the solution theory in the energy representation. Complex model structures are generated from a pair of monomeric structures using the rigid-body docking program ZDOCK. After structure refinement by side chain optimization and all-atom molecular dynamics simulations in explicit water, complex models are evaluated based on the sum of their conformational and solvation free energies, the latter calculated from the energy distribution functions obtained from relatively short molecular dynamics simulations of the complex in water and of pure water based on the solution theory in the energy representation. We examined protein-protein complex model structures of two protein-protein complex systems, bovine trypsin/CMTI-1 squash inhibitor (PDB ID: 1PPE) and RNase SA/barstar (PDB ID: 1AY7), for which both complex and monomer structures were determined experimentally. For each system, we calculated the energies for the crystal complex structure and twelve generated model structures including the model most similar to the crystal structure and very different from it. In both systems, the sum of the conformational and solvation free energies tended to be lower for the structure similar to the crystal. We concluded that our energy calculation method is useful for selecting low energy complex models similar to the crystal structure from among a set of generated models.
Domain-averaged Fermi-hole analysis for solids
Authors: Baranov Alexey I. , Ponec Robert , Kohout Miroslav
Published: December 2012

The domain-averaged Fermi hole (DAFH) orbitals provide highly visual representation of bonding in terms of orbital-like functions with attributed occupation numbers. It was successfully applied on many molecular systems including those with non-trivial bonding patterns. This article reports for the first time the extension of the DAFH analysis to the realm of extended periodic systems. Simple analytical model of DAFH orbital for single-band solids is introduced which allows to rationalize typical features that DAFH orbitals for extended systems may possess. In particular, a connection between Wannier and DAFH orbitals has been analyzed. The analysis of DAFH orbitals on the basis of DFT calculations is applied to hydrogen lattices of different dimensions as well as to the solids diamond, graphite, Na, Cu and NaCl. In case of hydrogen lattices, remarkable similarity is found between the DAFH orbitals evaluated with both the analytical approach and DFT. In case of the selected ionic and covalent solids the DAFH orbitals deliver bonding descriptions, which are compatible with classical orbital interpretation. For metals the DAFH analysis shows essential multicenter nature of bonding.
Current conduction and stability of CeO2/La2O3 stacked gate dielectric
Authors: Wong Hei , Yang B. L. , Dong Shurong , Iwai H. , Kakushima K. , Ahmet P.
Published: December 2012

The current conduction behaviors in CeO2/La2O3 stack are studied. We found that large amount of hole injection under large negative gate bias can give rise to the accumulation of neutral interstitial oxygen (OI) species which serve as acceptors and promotes the hole conduction in the La2O3 film. Whereas if the amount of hole injection is lower than that of the oxygen anions injected from the capping CeO2 layer under a sufficient large negative gate bias, the amount of OI reduces and a negative charge built-up results which further reduces the leakage current and threshold voltage of p-channel metal-oxide-semiconductor transistors.
Acoustic excitations in glassy sorbitol and their relation with the fragility and the boson peak
Authors: Ruta B. , Baldi G. , Scarponi F. , Fioretto D. , Giordano V. M. , Monaco G.
Published: December 2012

We report a detailed analysis of the dynamic structure factor of glassy sorbitol by using inelastic X-ray scattering and previously measured light scattering data [B. Ruta, G. Monaco, F. Scarponi, and D. Fioretto, Philos. Mag. 88, 3939 (2008)10.1080/14786430802317586]. The thus obtained knowledge on the density-density fluctuations at both the mesoscopic and macroscopic length scale has been used to address two debated topics concerning the vibrational properties of glasses. The relation between the acoustic modes and the universal boson peak (BP) appearing in the vibrational density of states of glasses has been investigated, also in relation with some recent theoretical models. Moreover, the connection between the elastic properties of glasses and the slowing down of the structural relaxation process in supercooled liquids has been scrutinized. For what concerns the first issue, it is here shown that the wave vector dependence of the acoustic excitations can be used, in sorbitol, to quantitatively reproduce the shape of the boson peak, supporting the relation between BP and acoustic modes. For what concerns the second issue, a proper study of elasticity over a wide spatial range is shown to be fundamental in order to investigate the relation between elastic properties and the slowing down of the dynamics in the corresponding supercooled liquid phase.
Compact high-speed reciprocating probe system for measurements in a Hall thruster discharge and plume
Authors: Dannenmayer K. , Mazouffre S.
Published: December 2012

A compact high-speed reciprocating probe system has been developed in order to perform measurements of the plasma parameters by means of electrostatic probes in the discharge and the plume of a Hall thruster. The system is based on a piezoelectric linear drive that can achieve a speed of up to 350 mm/s over a travel range of 90 mm. Due to the high velocity of the linear drive the probe can be rapidly moved in and out the measurement region in order to minimize perturbation of the thruster discharge due to sputtering of probe material. To demonstrate the impact of the new system, a heated emissive probe, installed on the high-speed translation stage, was used to measure the plasma potential and the electron temperature in the near-field plume of a low power Hall thruster.
Development of a methodology to compute solvation free energies on the basis of the theory of energy representation for solutions represented with a polarizable force field
Authors: Suzuoka Daiki , Takahashi Hideaki , Ishiyama Tatsuya , Morita Akihiro
Published: December 2012

We have developed a method of molecular simulations utilizing a polarizable force field in combination with the theory of energy representation (ER) for the purpose of establishing an efficient and accurate methodology to compute solvation free energies. The standard version of the ER method is, however, based on the assumption that the solute-solvent interaction is pairwise additive for its construction. A crucial step in the present method is to introduce an intermediate state in the solvation process to treat separately the many-body interaction associated with the polarizable model. The intermediate state is chosen so that the solute-solvent interaction can be formally written in the pairwise form, though the solvent molecules are interacting with each other with polarizable charges dependent on the solvent configuration. It is, then, possible to extract the free energy contribution δμ due to the many-body interaction between solute and solvent from the total solvation free energy Δμ. It is shown that the free energy δμ can be computed by an extension of the recent development implemented in quantum mechanical/molecular mechanical simulations. To assess the numerical robustness of the approach, we computed the solvation free energies of a water and a methanol molecule in water solvent, where two paths for the solvation processes were examined by introducing different intermediate states. The solvation free energies of a water molecule associated with the two paths were obtained as −5.3 and −5.8 kcal/mol. Those of a methanol molecule were determined as −3.5 and −3.7 kcal/mol. These results of the ER simulations were also compared with those computed by a numerically exact approach. It was demonstrated that the present approach produces the solvation free energies in comparable accuracies to simulations of thermodynamic integration (TI) method within a tenth of computational time used for the TI simulations.
Oscillations of a gas pocket on a liquid-covered solid surface
Authors: Gelderblom Hanneke , Zijlstra Aaldert G. , van Wijngaarden Leen , Prosperetti Andrea
Published: December 2012

The dynamic response of a gas bubble entrapped in a cavity on the surface of a submerged solid subject to an acoustic field is investigated in the linear approximation. We derive semi-analytical expressions for the resonance frequency, damping, and interface shape of the bubble. For the liquid phase, we consider two limit cases: potential flow and unsteady Stokes flow. The oscillation frequency and interface shape are found to depend on two dimensionless parameters: the ratio of the gas stiffness to the surface tension stiffness, and the Ohnesorge number, representing the relative importance of viscous forces. We perform a parametric study and show, among others, that an increase in the gas pressure or a decrease in the surface tension leads to an increase in the resonance frequency until an asymptotic value is reached.
Chaotic dynamics in multidimensional transition states
Authors: Allahem Ali , Bartsch Thomas
Published: December 2012

The crossing of a transition state in a multidimensional reactive system is mediated by invariant geometric objects in phase space: An invariant hyper-sphere that represents the transition state itself and invariant hyper-cylinders that channel the system towards and away from the transition state. The existence of these structures can only be guaranteed if the invariant hyper-sphere is normally hyperbolic, i.e., the dynamics within the transition state is not too strongly chaotic. We study the dynamics within the transition state for the hydrogen exchange reaction in three degrees of freedom. As the energy increases, the dynamics within the transition state becomes increasingly chaotic. We find that the transition state first looses and then, surprisingly,regains its normal hyperbolicity. The important phase space structures of transition state theory will, therefore,exist at most energies above the threshold.