Miracle-dz/UniFAR-FTUs huggingface dataset:
Displacive to Order-Disorder Crossover in the Cubic-Tetragonal Phase Transition of PbTiO3

Light scattering measurements extended down to 2 cm−1 of the laser line were performed on a single-domain PbTiO3 crystal. Spectra reveal the appearance of a central peak below the soft-phonon line when the cubic-tetragonal phase transition is approached with decreasing and increasing temperature. The relaxation process associated with this central peak presents a characteristic frequency smaller than 1 GHz and is shown to possess the main contribution to the dielectric permittivity near the transition temperature. This feature constitutes the first direct evidence of some order-disorder mechanism in the ferroelectric transition of PbTiO3 which was up to now considered as a typical example of a displacive mechanism.
Bigger uncertainties and the Big Bang

We use Bayesian hierarchical models and recent results from the theory of minimax confidence interval estimation to study the effect of prior information in a cosmological inverse problem. We consider the effect of prior information on uncertainty estimates of a linear functional of an infinite-dimensional model x, given noisy observations . The model represents the cosmic microwave background (CMB), which is the radiation left over from the Big Bang. The linear functional is related to the important cosmological question of whether the CMB temperature varies with direction in the sky; such variation is required by cosmological theories to account for the observed large-scale heterogeneity of matter and energy in the Universe. Evidence of this heterogeneity is the non-zero quadrupole term in the CMB detected by the COBE satellite in 1992. Estimation of the quadrupole is an interesting ill-posed problem that requires more information than cosmologists expected. Previously published quadrupole estimates relied on constraints such as artificially truncating the spherical harmonic expansion of the CMB fluctuations, or on modelling the effect of unestimated high-frequency terms, without accounting for model uncertainty. If these implicit constraints were relaxed, the uncertainty would be several to dozens of times larger than reported in the astrophysical literature. We study the dependence of quadrupole estimates to a series of increasingly stringent constraints. We show that no useful estimates can be obtained from COBE data without assuming a particular class of prior cosmological models. Even restricting the spectrum to lie in a two-parameter family of models commonly used in cosmology does not suffice without positing a prior probability distribution on those two parameters.
Lorentz harmonics and superfield action. D = 10, N = 1 superstring

We propose a new version of the superfield action for a closed D = 10,N = 1 superstring where the Lorentz harmonics are used as auxiliary superfields. The incorporation of Lorentz harmonics allows one to exclude the intrinsic supervielbeins from the superfield action and to consider the worldsheet geometry as induced by the superembedding. As a result, the superspace constraints of the worldsheet supergravity can be derived from the equations of motion. Moreover, it becomes evident that a so-called `Wess-Zumino part' of the superfield action is basically a Lagrangian form of the generalized action principle. We propose to use the second Noether theorem to handle the essential terms in the transformation laws of hidden gauge symmetries, which remove dynamical degrees of freedom from the Lagrange multiplier superfield.
Influence of supersonic turbulence on self-gravitating flows

Les modifications induites au niveau de l'instabilite gravitationnelle par la turbulence sont considerees. La phenomenologie de la turbulence homogene et de l'effondrement gravitationnel est examinee. Des simulations numeriques sont ensuite realisees pour les ecoulements autogravitants 2D. Les resultats renforcent l'analyse phenomenologique et montrent que dans les regimes supersoniques, la turbulence est capable d'empecher l'effondrement gravitationnel
Metalorganic vapour phase epitaxy (MOVPE) of III/V-semiconductor heterostructures using alternative precursor molecules: new developments

The standardly used source molecules in the metalorganic vapour phase epitaxy (MOVPE) of III/V-semiconductor heterostructures (trialkyl group(III)-compounds and group(V)-hydrides) have severe drawbacks. The trialkyl group(III)-compounds are pyrophoric and the group(V)-hydrides are highly toxic substances. These properties lead to problems of the MOVPE process with respect to safety concerns as well as crystal purity (incorporation of O and C especially for Al-containing epitaxial layers). In this work, we describe new developments of the interdisciplinary research for alternative precursor molecules. The principle ways for changing the molecular structure of alternative group(III)- as well as group(V)-compounds are discussed in order to overcome the above mentioned problems. Special emphasis is put on the class of the hydride group(III) amine adducts, which are in particular suitable in combination with less toxic group(V)-compounds. MOVPE growth experiments are reported for heterostructures in the GaAs/(AlGa)As material system. The applicability of the alternative precursors is established by studying the structural, electrical and optical properties of GaAs, (AlGa)As bulk layers as well as of single and multi quantum well heterostructures by high-resolution x-ray diffraction, temperature-dependent Hall as well as photoluminescence investigations.
Apparatus to measure the step and frequency responses of gas analysis instruments (respiratory gas analysis)

The authors constructed a 0.06 ml measurement chamber connected via high-speed valves (0.5 ms response time) to two 3 l reservoirs pressurized to 50 kPa with gases containing different concentrations of CO2. An electronic system opens the valves alternately depending on the polarity of a control voltage Ve. Two walls of the chamber contain narrow-band infra-red filters centred at 4.24 mu m (50% transmission points at 4.16 and 4.32 mu m) where CO2 absorption is high. A photoconductive infra-red sensor and an infra-red source are positioned on either side of the chamber. The output of the sensor is amplified by an instrumentation amplifier. Signal averaging of the sensor output in either the time or frequency domain was used to overcome the noise of the infra-red sensor. Step changes in Vc yielded exponentially changing outputs with a time constant of 1.1 ms. A quadrupole mass spectrometer's response to step changes in CO2 concentration generated in the measurement chamber fitted single exponential curves well with a maximum time constant of 37.7 ms and transport delay of 194 ms. A first-order model with delay fitted to the step response predicted the mass spectrometer frequency response well below 10 Hz but overestimated the response above 10 Hz. A third-order model with delay fitted to the frequency response predicted the step response very well. The author's results suggest that low-order models cannot predict the high-frequency performance of a mass spectrometer.
Cosmological non-linearities as an effective fluid

The universe is smooth on large scales but very inhomogeneous on small scales. Why is the spacetime on large scales modeled to a good approximation by the Friedmann equations? Are we sure that small-scale non-linearities do not induce a large backreaction? Related to this, what is the effective theory that describes the universe on large scales? In this paper we make progress in addressing these questions. We show that the effective theory for the long-wavelength universe behaves as a viscous fluid coupled to gravity: integrating out short-wavelength perturbations renormalizes the homogeneous background and introduces dissipative dynamics into the evolution of long-wavelength perturbations. The effective fluid has small perturbations and is characterized by a few parameters like an equation of state, a sound speed and a viscosity parameter. These parameters can be matched to numerical simulations or fitted from observations. We find that the backreaction of small-scale non-linearities is very small, being suppressed by the large hierarchy between the scale of non-linearities and the horizon scale. The effective pressure of the fluid is always positive and much too small to significantly affect the background evolution. Moreover, we prove that virialized scales decouple completely from the large-scale dynamics, at all orders in the post-Newtonian expansion. We propose that our effective theory be used to formulate a well-defined and controlled alternative to conventional perturbation theory, and we discuss possible observational applications. Finally, our way of reformulating results in second-order perturbation theory in terms of a long-wavelength effective fluid provides the opportunity to understand non-linear effects in a simple and physically intuitive way.
The reversible photoluminescence enhancement of a CdSe/ZnS nanocrystal thin film

We report that the storage and clearing of multi-digital data, that is, the photoluminescence (PL) intensity of CdSe/ZnS core/shell nanocrystal (NC) thin film, can be operated by a single excitation wavelength. First, a 7.4 µm-square area on the NC film was irradiated by strong light ranging in intensity from 2.64 to 1370 nW. Then, a 60 µm-square area including the pre-irradiated region was scanned with weak light (about 0.6 nW) to visualize the PL intensity difference between pre- and non-irradiated regions (I and I0, respectively). The normalized PL intensity, I/I0, increased with total pre-irradiation energy, until reaching saturation. The level of I/I0 at which the PL intensity becomes saturated reversibly increased with decreasing light intensity at pre-irradiation. The results imply that Auger ionization becomes dominant and suppresses the enhancement of the emission efficiency with higher irradiation intensities.
FIRST “Winged” and X-Shaped Radio Source Candidates

A small number of double-lobed radio galaxies (17 from our own census of the literature) show an additional pair of low surface brightness "wings," thus forming an overall X-shaped appearance. The origin of the wings in these radio sources is unclear. They may be the result of backflowing plasma from the currently active radio lobes into an asymmetric medium surrounding the active nucleus, which would make these ideal systems in which to study thermal/nonthermal plasma interactions in extragalactic radio sources. Another possibility is that the wings are the aging radio lobes left over after a (rapid) realignment of the central supermassive black hole-accretion disk system due perhaps to a merger. Generally, these models are not well tested; with the small number of known examples, previous works have focused on detailed case studies of selected sources with little attempt at a systematic study of a large sample. Using the VLA FIRST survey database, we are compiling a large sample of winged and X-shaped radio sources for such studies. As a first step toward this goal, an initial sample of 100 new candidate objects of this type are presented in this paper. The search process is described, and optical identifications from available literature data and basic radio data are presented. From the limited-resolution FIRST images (∼5″), we can already confidently classify a sufficient number of these objects as having the characteristic wing lengths of >80% of the active lobes to more than double the number of known X-shaped radio sources. We have also included as candidates radio sources with shorter wings (<80% wing-to-lobe length ratios), or simply "winged" sources, as it is probable that projection effects are important. Finally, among the candidates are four quasars (z = 0.37-0.84), and several have morphologies suggestive of Fanaroff-Riley type I (low-power) radio galaxies. While follow-up observations are necessary to confirm these identifications, this stresses the importance of source orientation and imaging limitations in finding these enigmatic objects.
Subthreshold conduction in short-channel polycrystalline-silicon thin-film transistors

A model that characterizes the subthreshold regime and the threshold voltage of a short-channel polycrystalline silicon thin-film transistor (poly-Si TFT) is developed and supported experimentally. The subthreshold variations with gate and drain voltages are reported and a stronger drain voltage dependence is observed. The subthreshold swing is calculated and its variation with channel length and doping concentration is studied. The results are compared with the available experimental data and a good match is found. The temperature dependence of subthreshold swing and drain current is also shown. The channel length dependent proposed threshold voltage shows excellent agreement with experimental data.
Optical constants of industrial liquids obtained by phase retrieval from reflectometric and surface-plasmon-resonance data

Wavelength-dependent complex refractive indices of turbid industrial liquids with very high optical densities were obtained from the reflectance. The key factor was accurate `anchor-point' detection by a surface-plasmon-resonance technique. The anchor point is needed for the phase-retrieval procedure, which is based on exploitation of the maximum-entropy method.
Search for muon signal from dark matter annihilations in the Sun with the Baksan Underground Scintillator Telescope for 24.12 years

We present a new dataset analysis of the neutrino experiment at the Baksan Underground Scintillator Telescope with muon energy threshold about 1 GeV for the longest exposure time toward the Sun. In search for a signal from self-annihilations of dark matter particles in the center of the Sun we use an updated sample of upward through-going muons for 24.12 years of live time. No observable excess has been found in measured muons relative to expected background from neutrinos of atmospheric origin. We present an improved data analysis procedure and describe it in detail. We set the 90% C.L. new upper limits on expected neutrino and muon fluxes from dark matter annihilations in the Sun, on the corresponding annihilation rates and cross sections of their elastic scattering off proton.
Modelling of sacrificial aluminium etching in complex geometries

In this paper, the modelling of sacrificial aluminium etching in complex network geometries is presented. The structures for the etching experiments are arrays of membranes for a capacitive tactile sensor for medical applications. The modelling is based on the two-dimensional diffusion equation. A one-dimensional model for correlating etch rate and diffusion coefficient in silicon dioxide etching is extended to cover two-dimensional geometries. The etch front progression can be derived from the modelled concentration of the etchant within the etch network. This allows for the extraction of numerical values of diffusion coefficients D from the data. The values of D for the three sections of the geometry in both networks studied reflect the differences in the boundary conditions of the etching process.
The susceptibility maximum of ZrZn2 at high pressure

The electronic structure of ZrZn2 is calculated by a self-consistent linear muffin-tin orbital method within the atomic sphere approximation. From fixed-spin-moment calculations the magnetic moment M is estimated as a function of magnetic field H. By fitting the calculated values of M(H) to the form H = aM + bM 3 + cM 5 + dM 7 + eM 9, the coefficients a, b, c, d, e are estimated as functions of the lattice constant. It is shown that the values of a and b are negative and positive, respectively, at the observed lattice constant at ambient pressure. With decreasing lattice constant the value of a changes its sign from negative to positive, which means that the ferromagnetic state is unstable. At a lattice constant a little smaller than the critical one, the value of b also changes its sign from positive to negative. These results, together with the other coefficients c-e, indicate a broad maximum in the temperature dependence of the susceptibility when the effect of spin fluctuations is taken into account. However, the absolute value of b is so small that the metamagnetic transition does not occur. It is shown that the anomalous temperature dependence of the susceptibility of ZrZn2 observed recently at high pressure is well described by the present calculations.
Inductive superconducting transition-edge detector for single-photon and macro-molecule detection

We present a new type of transition-edge sensor for single-photon and macro-molecule detection. In our detector the absorber element is an isolated, passive absorber of extremely low thermal mass, maintained close to, but below, its superconducting–normal transition, and strongly inductively coupled to a SQUID sensor. Incoming particles or photons are sensed in terms of a transient change in the inductive coupling, rather than a change in resistance. The detector's energy sensitivity and response time can be defined by the thermal mass of the absorber and its thermal contact with a substrate, independently of any electrical connections. We have modelled the energy sensitivity of our inductive superconducting transition-edge sensor using a sub-micron SQUID as an inductive read-out device. An ultimate energy resolution of order 10−25 J Hz−1 is theoretically estimated based on the properties of the read-out SQUID and the dimensions of the absorber. We also report our initial work on fabrication of the Nb nanoscale SQUID where we have used the same material deposited on top of the SQUID as a thin-film absorber.
Kaigorodov spaces and their Penrose limits

Kaigorodov spaces arise, after spherical compactification, as near-horizon limits of M2, M5 and D3-branes with a particular pp-wave propagating in a worldvolume direction. We show that the uncompactified near-horizon configurations K × S are solutions of D = 11 or D = 10 IIB supergravity which correspond to perturbed versions of their AdS × S analogues. We derive the Penrose–Güven limits of the Kaigorodov space and the total spaces and analyse their symmetries. An Inönü–Wigner contraction of the Lie algebra is shown to occur, although there is a symmetry enhancement. We compare the results to the maximally supersymmetric CW spaces found as limits of AdS × S spacetimes: the initial gravitational perturbation on the brane and its near-horizon geometry remains after taking non-trivial Penrose limits, but seems to decouple. One particular limit yields a time-dependent homogeneous plane-wave background whose string theory is solvable, while in the other cases we find inhomogeneous backgrounds.
The effect of virtual positronium formation on positron-atom scattering

A new method is proposed to calculate the contribution of virtual Ps formation to elastic positron-atom scattering. The calculations were performed using the many-body perturbation theory approach. It is shown that for the scattering of positrons by hydrogen and helium atoms, the virtual Ps formation contribution is about 30% and 20% of the total correlation potential, respectively. Good agreement was obtained with the results of precise variational calculations and with experimental data.
Geographical dimensions of fibers from the soleum muscle in rats exercised on treadmill: the importance of the analysis by means of digitalized images

The purpose of this paper was to assess a new methodology to analyze digitalized cross sectional images from the skeletal muscular fibers in rats submitted to physical exercise on treadmill. It was used portions of the soleum muscle of rats attained from histological cuts and tinted with hematoxylin and eosin (HE). 100 muscular fibers were assessed from each animal, and their perimeter, the area, and the maximal, medium and minimal diameters were measured by means of the segmentation process from digitalized images of the fibers’ sections using the software ImagePro Plus. The geometrical dimensions such as the area, the perimeter and the medium and minimal diameters of the cross section of muscular fibers revealed to be adequate to analyze the effect of the training in rats. The analysis revealed the existence of an interaction between the group of rats and the duration of the physical exercise. The Pearson’s correlation coefficient was higher between the medium diameter and the area of the fibers (0.97), followed by the correlation between the maximal and medium diameter with the perimeter (0.93). It can be concluded that the measurement of the grade of the hypertrophy of the muscular fibers can be performed by determining the medium diameter or the cross sectional area of the fiber, and thus constituting an adequate and effective methodology especially for muscular fibers with accentuated polymorphism.
Scheme for constructing graphs associated with stabilizer quantum codes

We propose a systematic scheme for the construction of graphs associated with binary stabilizer codes. The scheme is characterized by three main steps: first, the stabilizer code is realized as a codeword-stabilized (CWS) quantum code; second, the canonical form of the CWS code is uncovered; third, the input vertices are attached to the graphs. To check the effectiveness of the scheme, we discuss several graphical constructions of various useful stabilizer codes characterized by single and multi-qubit encoding operators. In particular, the error-correcting capabilities of such quantum codes are verified in graph-theoretic terms as originally advocated by Schlingemann and Werner. Finally, possible generalizations of our scheme for the graphical construction of both (stabilizer and nonadditive) nonbinary and continuous-variable quantum codes are briefly addressed.
Algebraic quantum hypergroups of discrete type

In this paper we will study some structures of algebraic quantum hypergroups. First, we construct more examples of algebraic quantum hypergroups of discrete type. Next, we introduce the notion of a generalized quasi-Frobenius multiplier Hopf algebra and then show that generalized quasi-Frobenius multiplier Hopf algebras are a class of algebraic quantum hypergroups of discrete type. We also give some equivalent conditions for an algebraic quantum group to be of discrete type. Finally, we study sub-algebraic quantum hypergroups of discrete type and quotients of algebraic quantum hypergroups of discrete type.
Resonance enhancement of magnetic Faraday rotation

Author(s): Figotin, Alex; Vitebskiy, Ilya | Abstract: Magnetic Faraday rotation is widely used in optics. In natural transparent materials, this effect is very weak. One way to enhance it is to incorporate the magnetic material into a periodic layered structure displaying a high-Q resonance. One problem with such magneto-optical resonators is that a significant enhancement of Faraday rotation is inevitably accompanied by strong ellipticity of the transmitted light. More importantly, along with the Faraday rotation, the resonator also enhances linear birefringence and absorption associated with the magnetic material. The latter side effect can put severe limitations on the device performance. From this perspective, we carry out a comparative analysis of optical microcavity and a slow wave resonator. We show that slow wave resonator has a fundamental advantage when it comes to Faraday rotation enhancement in lossy magnetic materials.