bluuebunny/crossref_metadata_2025 huggingface dataset:
Considerations for Prenatal Counselling of Patients with Cardiac Rhabdomyomas based on their Cardiac and Neurologic Outcomes
Authors: Degueldre Sabrina C. , Chockalingam Priya , Mivelaz Yvan , Di Bernardo Stefano , Pfammatter Jean-Pierre , Barrea Catherine , Sekarski Nicole , Jeannet Pierre-Yves , Fouron Jean-Claude , Vial Yvan , Meijboom Erik J.
Published: January 2010

Cardiac rhabdomyomas are benign cardiac tumours with few cardiac complications, but with a known association to tuberous sclerosis that affects the neurologic outcome of the patients. We have analysed the long-term cardiac and neurological outcomes of patients with cardiac rhabdomyomas in order to allow comprehensive prenatal counselling, basing our findings on the records of all patients seen prenatally and postnatally with an echocardiographic diagnosis of cardiac rhabdomyoma encountered from August, 1982, to September, 2007. We analysed factors such as the number and the location of the tumours to establish their association with a diagnosis of tuberous sclerosis, predicting the cardiac and neurologic outcomes for the patients.

Cardiac complications include arrhythmias, obstruction of the ventricular outflow tracts, and secondary cardiogenic shock. Arrhythmias were encountered most often during the neonatal period, with supraventricular tachycardia being the commonest rhythm disturbance identified. No specific dimension or location of the cardiac rhabdomyomas predicted the disturbances of rhythm.

The importance of the diagnosis of tuberous sclerosis is exemplified by the neurodevelopmental complications, with four-fifths of the patients showing epilepsy, and two-thirds having delayed development. The presence of multiple cardiac tumours suggested a higher risk of being affected by tuberous sclerosis. The tumours generally regress after birth, and cardiac-related problems are rare after the perinatal period. Tuberous sclerosis and the associated neurodevelopmental complications dominate the clinical picture, and should form an important aspect of the prenatal counselling of parents.
HEYDE’S CHARACTERIZATION THEOREM FOR DISCRETE ABELIAN GROUPS
Authors: MYRONYUK MARGARYTA
Published: January 2010

Let X be a countable discrete abelian group with automorphism group Aut(X). Let ξ1 and ξ2 be independent X-valued random variables with distributions μ1 and μ2, respectively. Suppose that α1,α2,β1,β2∈Aut(X) and β1α−11±β2α−12∈Aut(X). Assuming that the conditional distribution of the linear form L2 given L1 is symmetric, where L2=β1ξ1+β2ξ2 and L1=α1ξ1+α2ξ2, we describe all possibilities for the μj. This is a group-theoretic analogue of Heyde’s characterization of Gaussian distributions on the real line.
SHARP CONSTANTS BETWEEN EQUIVALENT NORMS IN WEIGHTED LORENTZ SPACES
Authors: BARZA SORINA , SORIA JAVIER
Published: January 2010

For an increasing weight w in Bp (or equivalently in Ap), we find the best constants for the inequalities relating the standard norm in the weighted Lorentz space Λp(w) and the dual norm.
RELEVANCE LOGIC AND THE CALCULUS OF RELATIONS
Authors: MADDUX ROGER D.
Published: January 2010

Sound and complete semantics for classical propositional logic can be obtained by interpreting sentences as sets. Replacing sets with commuting dense binary relations produces an interpretation that turns out to be sound but not complete for R. Adding transitivity yields sound and complete semantics for RM, because all normal Sugihara matrices are representable as algebras of binary relations.
Can intense substorms occur under northward IMF conditions?
Authors: Lee D.‐Y. , Choi K.‐C. , Ohtani S. , Lee J. H. , Kim K. C. , Park K. S. , Kim K.‐H.
Published: January 2010

This paper reports on several substorms observed under northward interplanetary magnetic field (IMF) conditions, the intensity of which was at least as significant as that of typical substorms under moderately southward IMF conditions. Such northward IMF periods were identified during the recovery phase of three strong storms. In the case of each storm, two or more substorms occurred successively, being separated by ∼1.8–5 h, while the IMF condition continued persistently northward. The substorms are clearly evidenced by auroral and other complementary observations. For the most intense substorms, the auroral breakup occurred at the magnetic latitude of ∼58°, and for the others it was between 60° and 65°. The polar cap size prior to each onset was substantial despite the northward IMF conditions. The auroral expansion following each onset lasted from a few up to several magnetic local time hours and exhibited a clear poleward expansion feature. For most of the events studied, geosynchronous magnetic dipolarizations preceded by field stretching and/or energetic particle injections occurred. The occurrence of such (intense) substorms implies that a certain (large) amount of energy remains in the tail even under northward IMF conditions. The occurrence of two or more successive substorms further implies that even after the release of a certain amount of energy triggered by the substorm, the tail can still have a substantial amount of energy left, which can be released by a subsequent substorm(s). We conjecture that an intense substorm during a northward IMF period can be expected when such a period belongs to the recovery phase of an intense storm mainly because of large energy loading done by preceding southward IMF Bz during the storm's main (and some early recovery) phase. In addition we argue that substorm energy can also be supplied by other mechanisms of the solar wind–magnetosphere coupling under northward IMF conditions such as dayside reconnection in the presence of a substantial IMF By component.
Evidence for extended acceleration of solar flare ions from 1–8 MeV solar neutrons detected with the MESSENGER Neutron Spectrometer
Authors: Feldman William C. , Lawrence David J. , Goldsten John O. , Gold Robert E. , Baker Daniel N. , Haggerty Dennis K. , Ho George C. , Krucker Säm , Lin Robert P. , Mewaldt Richard A. , Murphy Ronald J. , Nittler Larry R. , Rhodes Edgar A. , Slavin James A. , Solomon Sean C. , Starr Richard D. , Vilas Faith , Vourlidas Angelos
Published: January 2010

Neutrons produced on the Sun during the M2 flare on 31 December 2007 were observed at 0.48 AU by the MESSENGER Neutron Spectrometer. These observations are the first detection of solar neutrons inside 1 AU. This flare contained multiple acceleration episodes as seen in type III radio bursts. After these bursts ended, both the energetic particle and neutron fluxes decayed smoothly to background with an e‐folding decay time of 2.84 h, spanning a 9 h time period. This time is considerably longer than the mean lifetime of a neutron, which indicates that either the observed neutrons were generated in the spacecraft by solar energetic particle protons, or they originated on the Sun. If most of the neutrons came from the Sun, as our simulations of neutron production on the spacecraft show, they must have been continuously produced. A likely explanation of their long duration is that energetic ions were accelerated over an extended time period onto closed magnetic arcades above the corona and then slowly pitch angle–scattered by coronal turbulence into their chromospheric loss cones. Because of their relatively low energy loss in the Neutron Spectrometer (0.5–7.5 MeV), most of these neutrons beta decay to energetic protons and electrons close to the Sun, thereby forming an extended seed population available for further acceleration by subsequent shocks driven by coronal mass ejections in interplanetary space.
High Resolution Dynamics Limb Sounder measurements of gravity wave activity in the 2006 Arctic stratosphere
Authors: Wright C. J. , Osprey S. M. , Barnett J. J. , Gray L. J. , Gille J. C.
Published: January 2010

Observations from the High Resolution Dynamics Limb Sounder (HIRDLS) instrument on NASA's Aura satellite are used to quantify gravity wave momentum fluxes in the middle atmosphere. The period around the 2006 Arctic sudden stratospheric warming (SSW) is investigated, during which a substantial elevation of the stratopause occurred. Analysis of the HIRDLS results, together with analysis of European Centre for Medium‐Range Weather Forecasting zonal winds, provide direct evidence of wind filtering of the gravity wave spectrum during this period. This confirms previous hypotheses from model studies and further contributes to our understanding of the effects of gravity wave driving on the winter polar stratopause.
Characteristics of atmospheric transport into the Antarctic troposphere
Authors: Stohl A. , Sodemann H.
Published: January 2010

We have developed a 5.5 year climatology of atmospheric transport into the Antarctic troposphere, which uses the same data set and methods as described in a recent study for the Arctic. This allows direct comparisons of transport properties for the two polar regions. The climatology is based on a simulation with the Lagrangian particle dispersion model FLEXPART, where the model atmosphere was globally filled with particles. Transport characteristics as well as emission sensitivities were derived from 6 hourly particle positions. We found that the probability for near‐surface air to originate from the stratosphere on a time scale of 10 days is an order of magnitude higher near the South Pole than near the North Pole, a result of higher topography and descent that partly compensates for the flow of air down the Antarctic Plateau with the katabatic winds. The stratospheric influence is largest in fall, which is opposite to the seasonality in the Arctic. Stratospheric influence is much smaller over the shelf ice regions and in a band around Antarctica. The average time for which air near the surface has been exposed to continuous darkness in July (continuous light in January) is longest over the Ronne Ice Shelf and Ross Ice Shelf at ∼11 days (20 days). We calculated how sensitive Antarctic air masses are to emission input up to 30 days before arriving in Antarctica if removal processes are ignored. The emission sensitivity shows strong meridional gradients and, as a result, is generally low over South America, Africa, and Australia. For a 10 day time scale, the largest emission sensitivities over these continents are 1–2 orders of magnitude smaller than over Eurasia for transport to the Arctic, showing that foreign continents have a much smaller potential to pollute the Antarctic than the Arctic troposphere. Emission sensitivities and derived black carbon (BC) source contributions over South America, Africa, and Australia are substantially (a factor 10 for Africa) larger in winter than in summer. In winter, biomass burning contributes more BC than anthropogenic sources. For typical aerosol lifetimes of 5–10 days, ship emissions south of 60°S account for half of the total BC concentrations in the lowest 1000 m of the atmosphere south of 70°S in December. The increasing number of tourists visiting Antarctica and fishing vessels operating close to Antarctica are, therefore, a matter of concern.
Striking a balance
Authors: Breithaupt Holger , Caddick Samuel , Long Sharon R.
Published: January 2010

Sharon Long, a plant scientists who advised Barack Obama during his presidential election campaign, talks about green biotechnology and the role of scientists in political decision‐making.
Charge carrier concentration and mobility in alkali silicates
Authors: Souquet Jean-Louis , Nascimento Marcio Luis Ferreira , Rodrigues Ana Candida Martins
Published: January 2010

The respective contributions of the charge carrier concentration and mobility to the ionic conductivity in glasses remain an open question. In the present work we calculate these two parameters from conductivity data as a function of temperature below and above the glass transition temperature, Tg. The basic hypothesis assumes that ionic displacement results from the migration of cationic pairs formed by a partial dissociation, which is a temperature-activated process. Below Tg their migration would follow a temperature-activated mechanism, while a free volume mechanism prevails above this temperature, leading to a deviation from the Arrhenius behavior. Expressions are formulated for the variation in ionic conductivity as a function of temperature in the supercooled and glassy states. Fitting the experimental data with the proposed expressions allows for the determination of characteristic parameters such as the charge carrier formation and migration enthalpies. Based on these values, it is then possible to calculate the charge carrier concentration and mobility in the entire temperature range. At room temperature, the mobility of effective charge carriers is estimated close to 10−4 cm2 s−1 V−1 for alkali disilicates glasses under study, while the ratio between the number of effective charge carriers and the total number of alkali cations is estimated to be from 10−8 to 10−10, comparable to the concentration of intrinsic defects in an ionic crystal or dissociated species from a weak electrolyte solution.
Optical properties of Pd thin films exposed to hydrogen studied by transmittance and reflectance spectroscopy
Authors: Avila J. I. , Matelon R. J. , Trabol R. , Favre M. , Lederman D. , Volkmann U. G. , Cabrera A. L.
Published: January 2010

The optical properties of hydrogen exposed palladium (Pd) and palladium oxide (PdO) thin films are calculated from reflectance and transmittance measurements in the visible and near infrared range (400–900nm). The time evolution of the films’ optical constants when exposed to hydrogen is shown. The real part of palladium’s refractive index increases about 5%, whereas the imaginary part decreases nearly 15% after hydrogen absorption. The Pd films’ resistance also increased upon hydrogen absorption, as expected. Pd oxide reduces to metallic palladium upon hydrogenation, showing a dramatic change in all the properties. The palladium films’ resistance initially decreases after a first exposure to 5Torr of hydrogen, and this is tentatively explained by the reaction of hydrogen with impurities trapped in the films.
Investigation of the internal electric field in cadmium zinc telluride detectors using the Pockels effect and the analysis of charge transients
Authors: Groza Michael , Krawczynski Henric , Garson Alfred , Martin Jerrad W. , Lee Kuen , Li Qiang , Beilicke Matthias , Cui Yunlong , Buliga Vladimir , Guo Mingsheng , Coca Constantine , Burger Arnold
Published: January 2010

The Pockels electro-optic effect can be used to investigate the internal electric field in cadmium zinc telluride (CZT) single crystals that are used to fabricate room temperature x and gamma radiation detectors. An agreement is found between the electric field mapping obtained from Pockels effect images and the measurements of charge transients generated by alpha particles. The Pockels effect images of a CZT detector along two mutually perpendicular directions are used to optimize the detector response in a dual anode configuration, a device in which the symmetry of the internal electric field with respect to the anode strips is of critical importance. The Pockels effect is also used to map the electric field in a CZT detector with dual anodes and an attempt is made to find a correlation with the simulated electric potential in such detectors. Finally, the stress-induced birefringence effects seen in the Pockels images are presented and discussed.
Complex impedance spectroscopy of manganese oxide thin films
Authors: Lee J. H. , Chou Hsiung , Wen G. H. , Hwang G. H.
Published: January 2010

The high-frequency properties of La0.67Ca0.33MnO3 [LCMO(113)] and La0.67Sr1.33MnO4 [LSMO(214)] thin films were investigated by complex impedance spectra (CIS) at various temperatures. The CIS were then analyzed by using an equivalent circuit model to determine the correlation of the magnetic phase transition to the dielectric and transport properties. The dielectric properties of both systems are insensitive to temperature, revealing that the dielectric behavior is independent of magnetic phase transition but strongly associated with the transport properties. The results provide insight into dielectric variation during the phase transition from a ferromagnetic metallic phase and/or an antiferromagnetic insulating phase to a paramagnetic insulating phase.
Machine vision for digital microfluidics
Authors: Shin Yong-Jun , Lee Jeong-Bong
Published: January 2010

Machine vision is widely used in an industrial environment today. It can perform various tasks, such as inspecting and controlling production processes, that may require humanlike intelligence. The importance of imaging technology for biological research or medical diagnosis is greater than ever. For example, fluorescent reporter imaging enables scientists to study the dynamics of gene networks with high spatial and temporal resolution. Such high-throughput imaging is increasingly demanding the use of machine vision for real-time analysis and control. Digital microfluidics is a relatively new technology with expectations of becoming a true lab-on-a-chip platform. Utilizing digital microfluidics, only small amounts of biological samples are required and the experimental procedures can be automatically controlled. There is a strong need for the development of a digital microfluidics system integrated with machine vision for innovative biological research today. In this paper, we show how machine vision can be applied to digital microfluidics by demonstrating two applications: machine vision-based measurement of the kinetics of biomolecular interactions and machine vision-based droplet motion control. It is expected that digital microfluidics-based machine vision system will add intelligence and automation to high-throughput biological imaging in the future.
Spin modes of triangular magnetic nanodots in the vortex, Y, and buckle states
Authors: Montoncello Federico , Nizzoli Fabrizio
Published: January 2010

We present a complete investigation on the spin normal modes of triangular nanoparticles in the vortex, Y, and buckle states. In order to get a micromagnetic representation of an equilateral triangle, we choose a base side of 360 nm and a height of 310 nm, while the thickness is 20 nm. This choice allows the vortex state as an equilibrium configuration at zero applied field. We calculate the principal modes of the three magnetic configuration through the dynamical matrix method and discuss in detail their frequencies and their profiles on the basis of the internal field behavior. We also explain the onset of the irregular nodal surfaces in the mode profiles beyond a critical node number, depending on the underlying magnetic configuration. The modes with nodal surfaces parallel to the direction of variation of the internal field are found to occur in a series with identical node number but different localization: this is related to the reduced coherent length of the modes because of the strongly varying internal field. We present also the calculated Brillouin light scattering (BLS) spectrum for each magnetic configuration, with discussion on the reasons that allow some modes to be BLS active.
Enhancement of acoustic streaming induced flow on a focused surface acoustic wave device: Implications for biosensing and microfluidics
Authors: Singh Reetu , Sankaranarayanan Subramanian K. R. S. , Bhethanabotla Venkat R.
Published: January 2010

Fluid motion induced on the surface of 100 MHz focused surface acoustic wave (F-SAW) devices with concentric interdigital transducers (IDTs) based on Y-cut Z-propagating LiNbO3 substrate was investigated using three-dimensional bidirectionally coupled finite element fluid-structure interaction models. Acoustic streaming velocity fields and induced forces for the F-SAW device are compared with those for a SAW device with uniform IDTs (conventional SAW). Both, qualitative and quantitative differences in the simulation derived functional parameters, such as device displacements amplitudes, fluid velocity, and streaming forces, are observed between the F-SAW and conventional SAW device. While the conventional SAW shows maximum fluid recirculation near input IDTs, the region of maximum recirculation is concentrated near the focal point of the F-SAW device. Our simulation results also indicate acoustic energy focusing by the F-SAW device leading to maximized device surface displacements, fluid velocity, and streaming forces near the focal point located in the center of the delay path, in contrast to the conventional SAW exhibiting maximized values of these parameters near the input IDTs. Significant enhancement in acoustic streaming is observed in the F-SAW device when compared to the conventional ones; the increase in streaming velocities was computed to be 352% and 216% for tangential velocities in propagation and transverse directions, respectively, and 353% for the normal velocity. Consequently, the induced streaming force for F-SAW is 480% larger than that for conventional SAW. In biosensing applications, this allows for the removal of smaller submicron sized particles by F-SAW which are otherwise difficult to remove using the conventional SAW. The F-SAW presents an order of magnitude reduction in the smallest removable particle size compared to the conventional device. Our results indicate that the acoustic energy focusing and streaming enhancement brought about by the F-SAW device manifests itself as enhanced biofouling removal efficiency of F-SAW throughout the device delay path compared to the conventional device, thereby providing enhanced device sensitivity, selectivity, and reusability. Furthermore, contrary to the conventional SAW in which the smallest particle is removable near the input IDTs, the F-SAW device removes the smallest particle near the device focal point. The results of this work are shown to have significant implications in typical biosensing and microfluidic applications. In a broader context, the results of the present study demonstrate a technique of enhancing streaming induced flows, which is of great importance to contemporary problems involving microfluidic and sensing applications of piezoelectric devices.
Cryogenic confocal microscopy with rotation in a magnetic field
Authors: Kehoe T. , Ediger M. , Phillips R. T. , Hopkinson M.
Published: January 2010

Two approaches to conducting magneto-optical confocal spectroscopy are described, in each of which the confocal head is rotatable with respect to the magnetic field. A coudé arrangement has been shown to give adequate performance for scanned imaging, but lower optical throughput than a system based on single-mode optical fiber transport. The design criteria for a cryogenic fiber-coupling objective are described, and the tolerances demanded in lens alignment are shown to be relatively benign, allowing manufacture without special techniques. The practical use of the rotating confocal system with commercial stick-slip positioners has been shown to be rigid enough, and asymmetric weight distribution and diamagnetic forces are small enough to permit single quantum emitters to be studied over a range of angles and field strengths.
Piezoelectric Pb(Zr0.52Ti0.48)O3 thin films on single crystal diamond: Structural, electrical, dielectric, and field-effect-transistor properties
Authors: Liao Meiyong , Gotoh Yasuhito , Tsuji Hiroshi , Nakajima Kiyomi , Imura Masataka , Koide Yasuo
Published: January 2010

The combination of piezoelectric materials and single crystal diamond offers the opportunity for the development of multifunctional micromachined devices under extreme conditions. In this work, the authors report the structural, electrical, optical, and dielectric properties of Pb(Zr0.52,Ti0.48)O3 (PZT) thin films integrated on single crystal diamond (100) substrates. The corresponding field effect transistor based on the metal-piezoelectric-insulator-semiconductor (MPIS) structure was fabricated on a homoepitaxial p-type diamond layer grown on a type-Ib diamond substrate. Different intermediate layers were deposited on single diamond substrates prior to the PZT films growth in order to achieve the best polarization properties. It was observed that the utilization of an Al2O3 buffer layer followed by a SrTiO3 seed layer favored the formation of a single perovskite PZT phase. Transmission electron diffraction patterns revealed that the PZT films included an initial layer at the SrTiO3/PZT interface followed by a well crystallized layer. The PZT film grown on SrTiO3/Al2O3/diamond exhibited much better in-plane polarization than that of the PZT film on Al2O3/diamond. The photoresponse behavior revealed that carriers trapping effect was trivial in the PZT film. The channel electrical conductivity of the MPIS field effect transistor was successfully modulated by the gate bias.
Toward quantitative deuterium analysis with laser-induced breakdown spectroscopy using atmospheric-pressure helium gas
Authors: Hedwig Rinda , Lie Zener Sukra , Kurniawan Koo Hendrik , Chumakov Alexander Nikitich , Kagawa Kiichiro , Tjia May On
Published: January 2010

An experimental study has been carried out for the development of quantitative deuterium analysis using the neodymium doped yttrium aluminum garnet laser-induced breakdown spectroscopy (LIBS) with atmospheric pressure surrounding He gas by exploring the appropriate experimental condition and special sample cleaning technique. The result demonstrates the achievement of a full resolution between the D and H emission lines from zircaloy-4 samples, which is prerequisite for the desired quantitative analysis. Further, a linear calibration line with zero intercept was obtained for the emission intensity of deuterium from a number of zircaloy samples doped with predetermined concentrations of deuterium. The result is obtained by setting a +4 mm defocusing position for the laser beam, 6 μs detection gating time, and 7 mm imaging position of the plasma for the detection, which is combined with a special procedure of repeated laser cleaning of the samples. This study has thus provided the basis for the development of practical quantitative deuterium analysis by LIBS.
Characterization of unintentional doping in nonpolar GaN
Authors: Zhu Tongtong , Johnston Carol F. , Häberlen Maik , Kappers Menno J. , Oliver Rachel A.
Published: January 2010

Unintentional doping in nonpolar a-plane (112¯0) gallium nitride (GaN) grown on r-plane (11¯02) sapphire using a three-dimensional (3D)–two-dimensional (2D) growth method has been characterized. For both 2D only and 3D–2D growth, the presence of an unintentionally doped region adjacent to the GaN/sapphire interface is observed by scanning capacitance microscopy (SCM). The average width of this unintentionally doped layer is found to increase with increasing 3D growth time. By using an intentionally doped GaN:Si staircase structure for calibration, it is shown that the unintentionally doped region has an average carrier concentration of (2.5±0.3)×1018 cm−3. SCM also reveals the presence of unintentionally doped features extending at 60° from the GaN/sapphire interface. The observation of decreasing carrier concentration with distance from the GaN/sapphire interface along these features may suggest that the unintentional doping arises from oxygen diffusion from the sapphire substrate. Low temperature cathodoluminescence spectra reveal emission peaks at 3.41 and 3.30 eV, which are believed to originate from basal plane stacking faults (BSFs) and prismatic stacking faults (PSFs), respectively. It is shown that the inclined features extending from the GaN/sapphire interface exhibit both enhanced BSF and PSF emission. We suggest that enhanced unintentional doping occurs in regions around PSFs. Where BSFs intersect this doped material their emission is also enhanced due to reduced nonradiative recombination. Transmission electron microscopy confirms the presence of PSFs extending through the film at 60° from the GaN/sapphire interface.
Flow from macroscopically long straight carbon nanopores for generation of thermoresponsive nanoparticles
Authors: Sinha-Ray S. , Yarin A. L.
Published: January 2010

Macroscopically long straight carbon nanopores produced by the nanofiber template method are used to polymerize sufficiently monodisperse thermoresponsive poly(N-isopropyl acrylamide) nanoparticles of the order of 400 nm diameter at the rate of 107 particles/s. During their formation, the nanoparticles were loaded with fluorescent dye Rhodamine 6G. The dye release kinetics from the nanoparticles was studied experimentally and theoretically under the conditions of thermal stimulation, and thermoresponsive release was demonstrated.
Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments
Authors: Shemesh Noam , Özarslan Evren , Basser Peter J. , Cohen Yoram
Published: January 2010

NMR observable nuclei undergoing restricted diffusion within confining pores are important reporters for microstructural features of porous media including, inter-alia, biological tissues, emulsions and rocks. Diffusion NMR, and especially the single-pulsed field gradient (s-PFG) methodology, is one of the most important noninvasive tools for studying such opaque samples, enabling extraction of important microstructural information from diffusion-diffraction phenomena. However, when the pores are not monodisperse and are characterized by a size distribution, the diffusion-diffraction patterns disappear from the signal decay, and the relevant microstructural information is mostly lost. A recent theoretical study predicted that the diffusion-diffraction patterns in double-PFG (d-PFG) experiments have unique characteristics, such as zero-crossings, that make them more robust with respect to size distributions. In this study, we theoretically compared the signal decay arising from diffusion in isolated cylindrical pores characterized by lognormal size distributions in both s-PFG and d-PFG methodologies using a recently presented general framework for treating diffusion in NMR experiments. We showed the gradual loss of diffusion-diffraction patterns in broadening size distributions in s-PFG and the robustness of the zero-crossings in d-PFG even for very large standard deviations of the size distribution. We then performed s-PFG and d-PFG experiments on well-controlled size distribution phantoms in which the ground-truth is well-known a priori. We showed that the microstructural information, as manifested in the diffusion-diffraction patterns, is lost in the s-PFG experiments, whereas in d-PFG experiments the zero-crossings of the signal persist from which relevant microstructural information can be extracted. This study provides a proof of concept that d-PFG may be useful in obtaining important microstructural features in samples characterized by size distributions.
Time-dependent wavepacket investigation of state-to-state reactive scattering of Cl with para-H2 including the open-shell character of the Cl atom
Authors: Sun Zhigang , Zhang Dong H. , Alexander Millard H.
Published: January 2010

We describe a time-dependent wavepacket based method for the calculation of the state-to-state cross sections for the Cl+H2 reaction including all couplings arising from the nonzero spin and electronic orbital angular momenta of the Cl atom. Reactant-product decoupling allows us to use a physically correct basis in both the reactant and the product arrangements. Our calculated results agree well with the experimental results of Yang and co-workers. We also describe a model with two coupled potential energy surfaces, which includes the spin-orbit coupling, which is responsible for the largest non-Born–Oppenheimer effects in the Cl+H2 reaction but neglects the off-diagonal electronically diabatic coupling and all Coriolis couplings due to the electronic spin and orbital angular momenta. The comparison of the results of the full six-state and two-state models with an electronically adiabatic (one-state) description reveals that the latter describes well the reaction out of the ground spin-orbit state, while the two-state model, which is computationally much faster than the full six-state model, describes well the reaction from both the ground and excited spin-orbit states.
Thickness effect on the band gap and optical properties of germanium thin films
Authors: Goh Eunice S. M. , Chen T. P. , Sun C. Q. , Liu Y. C.
Published: January 2010

The band gap and optical properties (dielectric functions and optical constants) of Ge thin films with various thicknesses below 50 nm, which were synthesized with electron beam evaporation technique, have been determined using spectroscopic ellipsometry and UV-visible spectrophotometry. The optical properties are well described with the Forouhi–Bloomer model. Both the band gap and optical properties show a strong dependence on the film thickness. For film thickness smaller than ∼10 nm, a band gap expansion is observed as compared to bulk crystalline Ge, which is attributed to the one-dimensional quantum confinement effect. However, a band gap reduction was observed for thickness larger than ∼10 nm, which is explained in terms of the amorphous effect in the Ge layers.
The smectic effect on solute order parameters rationalized by double Maier–Saupe Kobayashi–McMillan theory
Authors: Weber Adrian C. J. , Yang Xuan , Dong Ronald Y. , Burnell E. Elliott
Published: January 2010

From the dipolar couplings obtained by NMR spectroscopy we have calculated the order parameters of a wide variety of solutes in the nematic and smectic A phases of the liquid crystals 8CB and 8OCB. These measurements are then rationalized with the previously tested two Maier–Saupe Kobayashi–McMillan interaction potential from which smectic order parameters are calculated.
Sr
x
Ba
1
−
x
Nb
2
O
6
−
δ
Ferroelectric-thermoelectrics: Crystal anisotropy, conduction mechanism, and power factor
Authors: Lee Soonil , Wilke Rudeger H. T. , Trolier-McKinstry Susan , Zhang Shujun , Randall Clive A.
Published: January 2010

Nonstoichiometric tungsten bronze-structured ferroelectric SrxBa1−xNb2O6−δ (SBN) single crystals were found to be a promising n-type thermoelectric oxide. Thermopower anomalies were observed at the phase transition temperatures, depending on the degree of reduction as well as crystal anisotropy. Above 500 K, heavily reduced SBN crystals show high thermoelectric power factors (∼20 μW/cm K2 at 516 K) with both thermopower and electrical conductivity higher parallel to the c-axis. It is noted that the power factor increases with temperature due to the semiconducting behavior with high carrier concentration. The carrier transport mechanism also varies with the degree of reduction and temperature.
Solidlike coherent vibronic dynamics in a room temperature liquid: Resonant Raman and absorption spectroscopy of liquid bromine
Authors: Branigan Edward T. , van Staveren Marie N. , Apkarian V. Ara
Published: January 2010

UV-visible absorption and resonance Raman (RR) spectra of liquid bromine are presented and rigorously interpreted. The RR spectra, which show an anharmonic vibrational progression of up to 30 overtones, define the ground state potential in the range 2.05 Å<r<3.06 Å. The attractive branch of the X-state potential is softened and apparent dissociation limit of the molecule dramatically reduced by ∼30% in the liquid phase, indicating an attractive cage-molecule interaction. The excited state potentials (A′, B, and C) are extracted from the absorption spectrum. The spectrum is first inverted under assumption of the classical reflection approximation, then corrected by forward simulations through quantum time correlations. The extrapolated B and C potentials are used to simulate RR spectra. Their validity is cross-checked by the interference pattern of the polarized spectra due to two-channel RR scattering. The discrepancy between calculated and observed intensities can be entirely assigned to vibrational dephasing, which is observed to follow the exponential energy gap law—dephasing rates perfectly trace the Birge–Sponer plot of the vibrational progression—suggesting that vibrational dissipation controls the decay of coherence. Despite strong intermolecular electronic interactions and vibrational energy gaps of ∼kT, vibrational coherences are long lived: Coherence times range from ≥25 to ≥2.4 ps between v=1 and v=25. Remarkably, the RR line shapes are skewed toward the red, indicating upchirp in frequencies that develop over a period of 400 fs. Evidently, the molecular vibrations adiabatically follow the solvent cage, which is impulsively driven into expansion during the ∼20 fs evolution on the electronically excited state. Liquid bromine retains coherence in ordered sluggish local cages with quadrupolar interactions—dynamics akin to molecules isolated in structured cryogenic rare gas solids.
Surface-energy triggered phase formation and epitaxy in nanometer-thick Ni1−xPtx silicide films
Authors: Luo Jun , Qiu Zhijun , Zha Chaolin , Zhang Zhen , Wu Dongping , Lu Jun , Åkerman Johan , Östling Mikael , Hultman Lars , Zhang Shi-Li
Published: January 2010

The formation of ultrathin silicide films of Ni1−xPtx at 450–850 °C is reported. Without Pt (x=0) and for tNi<4 nm, epitaxially aligned NiSi2−y films readily grow and exhibit extraordinary morphological stability up to 800 °C. For tNi≥4 nm, polycrystalline NiSi films form and agglomerate at lower temperatures for thinner films. Without Ni (x=1) and for tPt=1–20 nm, the annealing behavior of the resulting PtSi films follows that for the NiSi films. The results for Ni1−xPtx of other compositions support the above observations. Surface energy is discussed as the cause responsible for the distinct behavior in phase formation and morphological stability.
Influence of length and measurement geometry on magnetoimpedance in La0.7Sr0.3MnO3
Authors: Rebello A. , Mahendiran R.
Published: January 2010

We show that ac magnetoresistance at room temperature in La0.7Sr0.3MnO3 is extremely high (≈−47% in μ0H=100 mT, f=3–5 MHz), and magnetic field dependence of reactance exhibits a double peak behavior. However, magnitudes of the ac magnetoresistance and magnetoreactance for a fixed length of the sample (li) decrease with decreasing separation (lv) between voltage probes unlike the dc magnetoresistance. On the contrary, change in li has a negligible influence on magnetoimpedance when lv is fixed. Our results indicate that high frequency electrical transport is sensitive to local variations in the magnetic permeability.
Sol-gel deposition and piezoelectric properties of {110}-oriented Pb(Zr0.52Ti0.48)O3 thin films
Authors: Ambika D. , Kumar Viswanathan , Imai Hideyuki , Kanno Isaku
Published: January 2010

Pb ( Zr x Ti 1 − x ) O 3 [PZT] thin films of thickness 2.0 μm were fabricated on silicon substrates (111)Pt/Ti/SiO2/Si using a sol-gel spin-coating technique. PZT films on substrates with a strontium titanate bottom layer are preferentially {110}-oriented with a columnar structure. The PZT films exhibit good dielectric properties with a dielectric permittivity, εr=1545 and dielectric loss, tan δ=0.04. Excellent piezoelectric characteristics are also exhibited by the {110}-oriented films with an average effective transverse piezocoefficient, e31∗ of −8.4 C/m2. The influence of film texture and composition on the transverse piezocoefficient have also been studied.
Density-dependent carrier dynamics in a quantum dots-in-a-well heterostructure
Authors: Prasankumar R. P. , Chow W. W. , Urayama J. , Attaluri R. S. , Shenoi R. V. , Krishna S. , Taylor A. J.
Published: January 2010

The incorporation of semiconductor quantum dots into different heterostructures for applications in nanoscale lasing and amplification has been an active area of research in recent years. Here, we use ultrafast differential transmission spectroscopy to temporally and spectrally resolve density-dependent carrier dynamics in a quantum dots-in-a-well (DWELL) heterostructure. We observe excitation-dependent shifts of the quantum dot energy levels at low densities, while at high densities we observe an anomalous induced absorption at the quantum dot excited state that is correlated with quantum well population dynamics. These studies reveal unique Coulomb interaction-induced phenomena with important implications for DWELL-based lasers and amplifiers.
Dielectric saturation of liquid propylene carbonate in electrical energy storage applications
Authors: Yang Lu , Fishbine Brian H. , Migliori Albert , Pratt Lawrence R.
Published: January 2010

Dielectric characteristics of a molecular model of liquid propylene carbonate are evaluated for utilization in molecular scale simulation of electrochemical capacitors based on nanotube forests. The linear-response dielectric constant of the bulk liquid, and its temperature dependence, is in good agreement with experiment. Dielectric saturation is studied by simulations with static uniform electric fields as large as 4 V/nm. The observed polarization is well described by the Langevin equation with the low-field/high-field crossover parameter of 0.09 V/nm. Simulation of liquid propylene carbonate confined between charged parallel graphite electrodes yields a capacitance that depends on the electric potential difference across those thin films. An effective dielectric constant inferred from the capacitance is significantly less than the uniform liquid dielectric constant, but is consistent with the nonlinear dielectric response at the strong fields applied to the electrode film. Those saturation effects reduce the weak-field capacitance.
Designing a sensitive and quantifiable nanocolloid assay with dielectrophoretic crossover frequencies
Authors: Basuray Sagnik , Chang Hsueh-Chia
Published: January 2010

Dielectrophoretic nanocolloid assay is a promising technique for sensitive molecular detection and identification, as target molecule hybridization onto the probe-functionalized nanocolloids can change their surface conductance and consequently their dielectrophoretic crossover frequencies. Thus, instead of relying on surface charge density increase after hybridization, as in many capacitive and field effect transistor impedance sensing techniques, the current assay utilizes the much larger surface conductance (and dielectrophoresis crossover frequency) changes to effect sensitive detection. Herein, we present a Poisson–Boltzmann theory for surfaces with finite-size molecular probes that include the surface probe conformation, their contribution to surface charge with a proper delineation of the slip and Stern planes. The theory shows that the most sensitive nanocolloid molecular sensor corresponds to a minimum in the dielectrophoretic crossover frequency with respect to the bulk concentration of the molecular probes (oligonucleotides in our case) during nanocolloid functionalization. This minimum yields the lowest number of functionalized probes that are also fully stretched because of surface probe-probe interaction. Our theory provides the surface-bulk oligonucleotide concentration isotherm and a folding number for the surface oligonucleotide conformation from the crossover frequency, the zeta potential, and the hydrodynamic radius data.
Theory of breakup of core fluids surrounded by a wetting annulus in sinusoidally constricted capillary channels
Authors: Beresnev Igor A. , Deng Wen
Published: January 2010

Analysis of core-annular dynamics in the presence of base flow for arbitrary fluid viscosities leads to an equation describing the temporal evolution of the fluid/fluid interface. The equation follows from the conservation of mass in the “small-slope” approximation. Its useful applications occur, for example, in chemical engineering and petroleum recovery. The nonlinear equation allows inexpensive numerical analysis. For sinusoidally constricted pores, a purely geometric criterion exists that enables or prohibits the core-fluid breakup in the necks of the constrictions. The geometrically favoring condition sets up capillary-pressure gradients that ensure a continuous outflow of the core fluid from the necks into the “crests” of the profile. Such behavior is indeed observed in the numerical solutions of the evolution equation. For relatively large slopes of the initial configuration, setting up larger pressure gradients, the interface shape remains “smooth,” the evolution times are relatively fast, and the breakup is typically achieved by the growing film-fluid collar touching the axis of the channel at a single point. No satellite droplets are produced. Decreasing the slope lengthens the evolution times, allowing the formation and growth of “wavy” disturbances on the initial interface profile, which may touch the axis of the capillary in several places forming satellite drops. Thinner initial annuli also slow down the evolution process. Instability develops for the cases of the core both more and less viscous than the film. Finally, if the geometry prohibits the snap-off altogether, the initial interface configurations decay into steady-state solutions, and no breakup takes place. The solutions of the evolution equation validate well against two computational-fluid-dynamics codes.
Enhancing erbium emission by strain engineering in GaN heteroepitaxial layers
Authors: Feng I. W. , Li J. , Sedhain A. , Lin J. Y. , Jiang H. X. , Zavada J.
Published: January 2010

Much research has been devoted to the incorporation of erbium (Er) into semiconductors aimed at achieving photonic integrated circuits with multiple functionalities. GaN appears to be an excellent host material for Er ions due to its structural and thermal stability. Er-doped GaN (GaN:Er) epilayers were grown on different templates, GaN/Al2O3, AlN/Al2O3, GaN/Si (111), and c-GaN bulk. The effects of stress on 1.54 μm emission intensity, caused by lattice mismatch between the GaN:Er epilayer and the substrate, were probed. The emission intensity at 1.54 μm increased with greater tensile stress in the c-direction of the GaN:Er epilayers. These results indicate that the characteristics of photonic devices based on GaN:Er can be optimized through strain engineering.
Nonvolatile nano-floating gate memory devices based on pentacene semiconductors and organic tunneling insulator layers
Authors: Kim Soo-Jin , Park Young-Su , Lyu Si-Hoon , Lee Jang-Sik
Published: January 2010

Controlled gold nanoparticle (AuNP)-based nonvolatile memory devices were developed based on pentacene organic transistors and polymethylmethacrylate (PMMA) insulator layers. The memory device had the following configuration: n+Si gate/SiO2 blocking oxide/polyelectrolytes/AuNP/PMMA tunneling dielectric layer/Au source-drain. According to the programming/erasing operations, the memory device showed good programmable memory characteristics with a large memory window. In addition, good reliability was confirmed by the data retention characteristics. The fabrication procedures for the charge trapping and tunneling layers were based on simple solution processes (by dipping and spin-coating) and the maximum processing temperature was <100 °C, so this method has potential applications in plastic/flexible electronics.
Extrapolated high-order propagators for path integral Monte Carlo simulations
Authors: Zillich Robert E. , Mayrhofer Johannes M. , Chin Siu A.
Published: January 2010

We present a new class of high-order imaginary time propagators for path integral Monte Carlo simulations that require no higher order derivatives of the potential nor explicit quadratures of Gaussian trajectories. Higher orders are achieved by an extrapolation of the primitive second-order propagator involving subtractions. By requiring all terms of the extrapolated propagator to have the same Gaussian trajectory, the subtraction only affects the potential part of the path integral. The resulting violation of positivity has surprisingly little effects on the accuracy of the algorithms at practical time steps. Thus in principle, arbitrarily high order algorithms can be devised for path integral Monte Carlo simulations. We verified the fourth, sixth, and eighth order convergences of these algorithms by solving for the ground state energy and pair distribution function of liquid H4e, which is representative of a dense, and strongly interacting, quantum many-body system.