Dispersive Part Research Articles

Complex extraordinary dielectric function of Mg-doped lithium niobate crystals at terahertz frequencies

We study the dispersion of the extraordinary dielectric function real and imaginary parts in the wide terahertz-frequency range of the lowest polariton branch for bulk LiNbO3 and Mg:LiNbO3 crystals. At frequencies 0.1–2.5 THz, both dispersion parts are measured by means of standard time-domain terahertz spectroscopy, and at higher frequencies up to 5.5 THz, the dielectric function real part is determined using a common scheme of spontaneous parametric down-conversion under near-forward Raman scattering by phonon polaritons. A special approach is applied for measuring of the dielectric function imaginary part at frequencies 1–3 THz, based on the analysis of visibility of three-wave second-order interference under spontaneous parametric down-conversion. The generalized approximate expressions are obtained for complex dielectric function dispersion within the lower polariton branches of LiNbO3 and Mg:LiNbO3. It is shown that the well-known decrease in terahertz-wave absorption of lithium niobate crystals under Mg-doping is caused by changes in the defect structure and reduction of coupling of the terahertz-frequency polaritons with Debye relaxational mode.

Dark matter inside early-type galaxies as function of mass and redshift

We study the behaviour of the dynamical and stellar mass inside the effective radius (re) of early-type galaxies (ETGs). We use several samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data release of the Sloan Digital Sky Survey. We consider Newtonian dynamics, different light profiles and different Initial Mass Functions (IMF) to calculate the dynamical and stellar mass. We assume that any difference between these two masses is due to dark matter and/or a non Universal IMF. The main results for galaxies in the redshift range 0.0024 < z < 0.3500 and in the dynamical mass range 9.5 < log(M) < 12.5 are: i) A significant part of the intrinsic dispersion of the distribution of dynamical vs. stellar mass is due to redshift. ii) The difference between dynamical and stellar mass increases as a function of dynamical mass and decreases as a function of redshift. iii) The difference between dynamical and stellar mass goes from approximately 0% to 70% of the dynamical mass depending on mass and redshift. iv) These differences could be due to dark matter or a non Universal IMF or a combination of both. v) The amount of dark matter inside ETGs would be equal to or less than the difference between dynamical and stellar mass depending on the impact of the IMF on the stellar mass estimation. vi) The previous results go in the same direction of some results of the Fundamental Plane (FP) found in the literature in the sense that they could be interpreted as an increase of dark matter along the FP and a dependence of the FP on redshift.

Analysis of velocity dispersion using full‐waveform multichannel sonic logging data: A case study

ABSTRACTSeismic attenuation and velocity dispersion are potentially able to reveal the rock physical properties of the subsurface. Conventionally, a frequency‐independent quality factor (Q) is measured. This Q is equivalent to the total velocity dispersion in a seismic record and is inadequate for analysing the attenuation mechanism or rock physical properties. Here a new method is proposed to extract the velocity dispersion curves so that more attributes can be obtained from full‐waveform multichannel sonic logging data, especially the critical frequency (fc) if it is within the bandwidth of the data. This method first decomposes the seismic data into a series of frequency components, computes the semblance of each frequency component for different velocity values, cross‐correlates the semblance matrices of adjacent frequency components to get the velocity gradients, and finally integrates to obtain a velocity dispersion curve. Results of this method are of satisfactory accuracy and robustness. This method is applied to the data acquired in Mallik 5L‐38 gas hydrate research well in Mackenzie Delta, Northwest Territories, Canada. The observed P‐wave velocity dispersion compares well with the geological setting. In the gas hydrate zone (about 900 m–1100 m), high concentration of gas hydrate causes very strong velocity dispersion and a distinct fc at about 15 kHz, likely due to strong scattering of centimetre‐scale inclusions of gas hydrate; concurrently, water flow in connected cracks in some ranges of this zone adds a large part of velocity dispersion and a dimmer fc at about 9.5 kHz. Immediate underneath the gas hydrate zone, abundant free water in weakly laminated sediments causes quite strong velocity dispersion and an fc at about 6.5 kHz. Velocity dispersion is mild and without an obvious fc in sediments above the gas hydrate zone.

Beringia and the global dispersal of modern humans.

Until recently, the settlement of the Americas seemed largely divorced from the out-of-Africa dispersal of anatomically modern humans, which began at least 50,000 years ago. Native Americans were thought to represent a small subset of the Eurasian population that migrated to the Western Hemisphere less than 15,000 years ago. Archeological discoveries since 2000 reveal, however, that Homo sapiens occupied the high-latitude region between Northeast Asia and northwest North America (that is, Beringia) before 30,000 years ago and the Last Glacial Maximum (LGM). The settlement of Beringia now appears to have been part of modern human dispersal in northern Eurasia. A 2007 model, the Beringian Standstill Hypothesis, which is based on analysis of mitochondrial DNA (mtDNA) in living people, derives Native Americans from a population that occupied Beringia during the LGM. The model suggests a parallel between ancestral Native Americans and modern human populations that retreated to refugia in other parts of the world during the arid LGM. It is supported by evidence of comparatively mild climates and rich biota in south-central Beringia at this time (30,000-15,000 years ago). These and other developments suggest that the settlement of the Americas may be integrated with the global dispersal of modern humans.

Surface modification of tantalum pentoxide coatings deposited by magnetron sputtering and correlation with cell adhesion and proliferation in in vitro tests

The effect was analyzed of surface treatment by argon ions on the surface properties of tantalum pentoxide coatings deposited by reactive magnetron sputtering. The structural parameters of the as-deposited coatings were investigated by means of transmission electron microscopy, atomic force microscopy and scanning electron microscopy. X-ray diffraction profiles and X-ray photoelectron spectra were also acquired. The total surface free energy (SFE), the polar, dispersion parts and fractional polarities, were estimated by the Owens-Wendt-Rabel-Kaeble method. The adhesive and proliferative potentials of bone marrow cells were evaluated for both Ta2O5 coatings and Ta2O5 coatings deposited by simultaneous bombardment by argon ions in in vitro tests.

Anisotropically Enhanced Nonlinear Optical Properties of Ensembles of Gold Nanorods Electrospun in Polymer Nanofiber Film.

Polymeric nanofibers containing gold nanorods (GNRs) are aligned in a uniform orientation through electrospinning. The dispersive and absorptive parts of the third-order optical nonlinear optical refractive index of the composite film measured by polarization dependent z-scan method are demonstrated to be anisotropically enhanced. Anisotropic optical response of the aligned GNRs and its connection with the ultrafast electron dynamics are discussed in light of the results of resonant femtosecond pump-probe experiments. The significant appearance of anisotropic nonlinear optical properties of ensembles of GNRs is attributed to the sensitive excitation of longitudinal surface plasmon resonance (LSPR) of highly aligned GNRs. For the macroscopic applications of ensembles of GNRs, such as passive mode-locking and all-optical switching, the experimental results demonstrate that the alignment of GNRs through electrospinning should be very high efficient, and economic.

Variational approach to the derivation of the Davey–Stewartson system

Whitham's averaged Lagrangian method is generalized for the three-dimensional (3D) case of the Stokes waves on the surface of an ideal fluid layer. We derive the extended Lagrangian with the explicit terms , , and which were only partially and implicitly present in the Whitham Lagrangian by the term with the nonlinear frequency, where is the complex-valued amplitude of the wave envelope. The and terms generate the additional terms with and in the dispersive part of the extended Lagrangian compared to Whitham's terms with a2 and a4, where a is the real wave amplitude. The variation of our extended Lagrangian produces the evolutional Davey–Stewartson equations for the wave envelope and velocity potential which were originally obtained by the method of multiple scales.

Eskişehir İli Balkan Muhacir Ağızları Örneğinde Geolinguistik

Language is one of the cultural factors which help individuals from various societies to learn about different life styles. Geography is a discipline which includes human and naturel environment, studies and analyses their features as part of dispersion, connection, comparison and causation principles. Geolinguistics which has not yet entered into between the traditional topics of human geography studies on social use of language and change on its dispersion including dialect and idiolect. Geolinguistics is an interdisciplinary study dealing with combination of language changes and the maps which show language regions. The term geolinguistics is relatively new in traditional studies focussing language and geo relationship. It’s not only related with maps but also culturel geography. Spatial size is just coming up on social sciences in contrast to geography. Due to recent developments in both conceptualization and theorization in social sciences, notions such as place and space has been attracting more and more interest among social scientists. Many social scientists started to use GIS on their empirical studies. This study on geolinguistic, is based on data collected between June and September 2013 from Eskisehir Linguistic Atlas Project funded by TUBITAK. In this study texts gathered from immigrant villages were analyzed based on various dialects (i.e: grammar, word, affix) and thematic maps were created by using MapInfo software.

A new comparison of marine dispersion model performances for Fukushima Dai-ichi releases in the frame of IAEA MODARIA program

A detailed intercomparison of marine dispersion models applied to the releases from Fukushima Dai-ichi nuclear power plant was carried out in the frame of MODARIA program, of the IAEA. Models were compared in such a way that the reasons of the discrepancies between them can be assessed (i.e., if they are due to the hydrodynamic part, the dispersion part, and the ultimate reasons). A sequential chain of dispersion exercises was carried out with this purpose. The overall idea is to harmonize models, making them run with the same forcing in a step-by-step procedure, in such a way that the main agent in producing discrepancy between models can be found. It was found that the main reason of discrepancies between models is due to the description of the hydrodynamics. However, once this has been suppressed, some variability between model outputs remains due to intrinsic differences between models (as numerical schemes). The numerical experiments were carried out for a perfectly conservative radionuclide and for 137Cs (including water/sediment interactions). Model outputs for this radionuclide were also compared with measurements in water and sediments.

Size Control of Monodisperse Prussian Blue Nanoparticles by Enforced-Nucleation and Additional-Growth Procedures in a Citrate Reduction System

Synthesis procedures of monodisperse Prussian blue nanoparticles have been investigated to control their size in a citric acid reduction system. Two different procedures, enforced-nucleation and additional-growth ones, are applied to decrease and to increase the particle size, respectively. In the former, small amount of ascorbic acid is added in the citric acid solution as the enforced-nucleation agent, which varies the number of nuclei and thus the particle size depending on its amount. In the latter, a part of Prussian blue dispersion preliminarily prepared is introduced into the reactant solution that provides additional reaction resources for the further growth. As a result, Prussian blue nanoparticles are prepared in the range of 20−100 nm in the mean size with narrow size distribution.

Exploration on the P(VP-co-VAc) copolymer based gel polymer electrolytes doped with quaternary ammonium iodide salt for DSSC applications: Electrochemical behaviors and photovoltaic performances

Gel polymer electrolytes (GPEs) consisting of poly(1-vinylpyrrolidone-co-vinyl acetate) P(VP-co-VAc) with the different tetrapropylammonium iodide (TPAI) salt concentration are prepared. The dielectric and electric dispersion behaviors of the GPEs are studied by dielectric relaxation spectroscopy at room temperature. The dielectric studies imply that dielectric constant (ε′) and dielectric loss (ε″) values decrease with increase in frequency at lower frequency region whereas frequency independent behavior is observed in the high frequency region. The trend of the dispersion part of the electric modulus shows a shift towards higher region of frequency indicating shorter relaxation time with an increase in TPAI concentration. The GPE samples were observed to obey Arrhenius behavior and the highest ionic conductivity obtained is 1.60×10−3Scm−1 at room temperature. The GPE samples are then fabricated into dye sensitized solar cells for photovoltaic studies. Highest efficiency of 3.07% is obtained with short circuit current density of 6.86mAcm−2, open circuit voltage of 727mV and fill factor of 62%.

Inclusion of dispersive terms in the averaged Lagrangian method: turning to the complex amplitude of envelope

Whitham’s method of averaged Lagrangian is extended to include dispersive terms on the example of Stokes waves on the surface of a layer of ideal fluid. We derive a Lagrangian with explicit \({\mathcal {A}}_ {x}\overline{\mathcal {A}}_ {x}\) and \( {\mathcal {A}}_ {x}\overline{\mathcal {A}}\) terms partially present in Whitham’s Lagrangian in implicit form in the term with nonlinear frequency, \({\mathcal {A}}\) being the complex-valued amplitude of the wave envelope. The \({\mathcal {A}}_ {x} \overline{\mathcal {A}}_ {x}\) term generates the \(a_x^2\) term in the dispersive part of the Lagrangian, in addition to Whitham’s terms with \(a^2\) and \(a^4\) (\(a\) being the real wave amplitude). The use of complex amplitude of envelope in the averaged Lagrangian allowed us to avoid the introduction of the nonlinear dispersion relation in the Whitham’s method. The variation of the generalized Lagrangian gives the correct evolution equations for the wave envelope and velocity potential.

Anomalous Phonon Dispersion of an Ultracold $$^6\mathrm{{Li}}$$ 6 Li – $$^{40}\mathrm{{K}}$$ 40 K Mixture in a Square Optical Lattice

A necessary condition for the damping of the long-wavelength excitations of the superfluid phase (referred to as superfluid phonons) due to the three-particle process is to have an anomalous phonon dispersion. The existence of anomalous phonon dispersion has been confirmed in superfluid \(^4\mathrm {He}\). There are no experimental data suggesting that this phenomenon exists in superfluid Fermi gases. To the best of our knowledge, the existence of anomalous dispersion has been theoretically predicted only in atomic spin balanced Fermi gas close to the unitarity limit. The numerical results reported here suggest that the anomalous long-wavelength dispersion can be realized in mass and spin imbalanced atomic Fermi gases away from the unitary limit. In particular, the numerical solution of the Bethe–Salpeter equation in a weak-coupling regime shows that the long-wavelength part of the collective-mode dispersion of the superfluid Fulde–Ferrell phase of a mixture of population-imbalanced Lithium-6 and Potassium-40 atoms in a square lattice at some values of polarization, interacting strength and temperature initially bends upward before bending over.

Coherent Structures in Nonlocal Dispersive Active-Dissipative Systems

We analyze coherent structures in nonlocal dispersive active-dissipative nonlinear systems, using as a prototype the Kuramoto--Sivashinsky (KS) equation with an additional nonlocal term that contains stabilizing/destabilizing and dispersive parts. As for the local generalized Kuramoto--Sivashinsky (gKS) equation (see, e.g., [T. Kawahara and S. Toh, Phys. Fluids, 31 (1988), pp. 2103--2111]), we show that sufficiently strong dispersion regularizes the chaotic dynamics of the KS equation, and the solutions evolve into arrays of interacting pulses that can form bound states. We analyze the asymptotic characteristics of such pulses and show that their tails tend to zero algebraically but not exponentially, as for the local gKS equation. Since the Shilnikov-type approach is not applicable for analyzing bound states in nonlocal equations, we develop a weak-interaction theory and show that the standard first-neighbor approximation is no longer applicable. It is then essential to take into account long-range interactions due to the algebraic decay of the tails of the pulses. In addition, we find that the number of possible bound states for fixed parameter values is always finite, and we determine when there is long-range attractive or repulsive force between the pulses. Finally, we explain the regularizing effect of dispersion by showing that, as dispersion is increased, the pulses generally undergo a transition from absolute to convective instability. We also find that for some nonlocal operators, increasing the strength of the stabilizing/destabilizing term can have a regularizing/deregularizing effect on the dynamics.

Ultrafast Dynamics of Au Nanopyramid Interfaces Prepared by Nanosphere Lithography: Effect of Substrate Chemical Composition

This work describes ultrafast spectroscopy studies of Au triangular pyramid particle arrays deposited over glass (termed Au/glass), and 190 nm indium tin oxide (ITO) film (termed Au/ITO/glass) prepared by nanosphere lithography. The linear absorption spectra of Au/glass and Au/ITO/glass exhibit surface plasmon resonances at 800 and 870 nm, respectively, in good agreement with discrete dipole approximation simulations. Ultrafast pump-probe measurements at wavelengths below resonance, at resonance, and above the surface plasmon resonance for each of these two systems are presented. The pump-probe measurements on both systems can be well fit with a model accounting for electron-electron scattering, electron-phonon coupling, and acoustic oscillations on top of cooling of the gold lattice. Numerical simulations employing a two-temperature model are consistent with the single-color pump-probe exponential decays. The wavelength-dependent pump-probe results are interpreted in terms of the complex wavelength-dependent refractive index of gold. We show that this interpretation is consistent with diffractive-optic four-wave mixing spectroscopy measurements of absorptive and dispersive parts of the third-order nonlinear polarization at 800 nm.

Fast dissolving cyclodextrin complex of piroxicam in solid dispersion Part I: Influence of β-CD and HPβ-CD on the dissolution rate of piroxicam

Sublingual drug delivery is an interesting route for drug having significant hepatic first-pass metabolism or requiring rapid pharmacological effect as for patients suffering from swallowing difficulties, nausea or vomiting. Sublingual absorption could however be limited by the kinetic of drug dissolution. This study evaluated influences of cyclodextrins (β-CD or HP-β-CD) and their different inclusion process (spray-drying or freeze-drying) on the drug dissolution kinetic of solid dispersions in poly(ethylene glycol) (PEG, Mw 6000Da) of piroxicam, used as poor hydrosoluble drug model. A secondary objective was to determine influences of drug dispersion process in PEG (evaporation or melting methods) on the drug dissolution kinetic of piroxicam. Piroxicam solid dispersions containing or not cyclodextrins were characterized by different scanning calorimetry (DSC), Thermogravometry analyser (TGA) and Fourier transform-infrared spectroscopy (FT-IR) spectroscopy. In vitro drug dissolution study of these solid dispersions was then performed. The results demonstrated the high potential and interest of solid dispersions of drug previously included in cyclodextrins for sublingual delivery of hydrophobic drugs. This study also showed the advantages of evaporation method on the melting ones during drug dispersion in PEG. Indeed, drug complexation with cyclodextrins as dispersion by melting prevented the presence in solid dispersions of drug in crystalline form which can represent up to 63%. Moreover, dispersion in PEG by evaporation method gave more porous drug delivery system than with melting methods. This allowed complete (limited at most at 80–90% with melting methods) and quick drug dissolution without rebound effect like with melting ones.

A new class of fully nonlinear and weakly dispersive Green–Naghdi models for efficient 2D simulations

We introduce a new class of two-dimensional fully nonlinear and weakly dispersive Green–Naghdi equations over varying topography. These new Green–Naghdi systems share the same order of precision as the standard one but have a mathematical structure which makes them much more suitable for the numerical resolution, in particular in the demanding case of two dimensional surfaces.For these new models, we develop a high order, well balanced, and robust numerical code relying on a hybrid finite volume and finite difference splitting approach. The hyperbolic part of the equations is handled with a high-order finite volume scheme allowing for breaking waves and dry areas. The dispersive part is treated with a finite difference approach. Higher order accuracy in space and time is achieved through WENO reconstruction methods and through an SSP-RK time stepping. Particular effort is made to ensure positivity of the water depth.Numerical validations are then performed, involving one and two dimensional cases and showing the ability of the resulting numerical model to handle waves propagation and transformation, wetting and drying; some simple treatments of wave breaking are also included. The resulting numerical code is particularly efficient from a computational point of view and very robust; it can therefore be used to handle complex two dimensional configurations.

Three-dimensional finite element method simulation study of fusion screw geometry

In this paper, a detailed three-dimensional finite element method (3D FEM) study of the mixing performance of the Fusion screw geometry by using two different rheological models is presented. Special criteria characterising the mixing performance in dependence of the barrier undercut separating the waving channels are developed. A great mixing performance is achieved when a right balance in both dispersive and distributive parts of the mixing process is found. An optimal undercut of the barrier was found to be about 2 mm. Both rheological models were successfully used to validate data of the real experiment with an error less than 15%.

AC Susceptibility of YBCO 1:2:3 Films on Silver Substrates

The YBa2Cu3Oδ lms were obtained directly on silver substrates by the sedimentation processes. The thicknesses of these lms are of the order of several tens μ. The temperature dependences of the AC susceptibility of the lms were measured and analyzed. The critical temperatures of these specimens obtained from the dispersion part of AC susceptibility vary from 89.2 K to 92.5 K. The critical currents were calculated from the absorption part of AC susceptibility using the Bean model. The temperature dependences of the critical currents were tted using the Ginzburg Landau strong coupling limit approach.

Calculation of the Kramers-Kronig transform of X-ray spectra by a piecewise Laurent polynomial method.

An algorithm is presented for the calculation of the Kramers-Kronig transform of a spectrum via a piecewise Laurent polynomial method. This algorithm is demonstrated to be highly accurate, while also being computationally efficient. The algorithm places no requirements on data point spacing and is capable of integrating across the full spectrum (i.e. from zero to infinity). Further, we present a computer application designed to aid in calculating the Kramers-Kronig transform on near-edge experimental X-ray absorption spectra (extended with atomic scattering factor data) in order to produce the dispersive part of the X-ray refractive index, including near-edge features.