Miracle-dz/UniFAR-FTUs huggingface dataset:
Indium-surfactant-assisted growth of high-mobility AlN/GaN multilayer structures by metalorganic chemical vapor deposition

AlN/GaN single and multilayer structures with various AlN and GaN layer thicknesses were grown by metalorganic chemical vapor deposition. Step flow growth of AlN was achieved using trimethylindium as a surfactant. Defect formation in the AlN layer could be largely prevented for AlN layers thinner than 2.9 nm. In the multiquantum-well samples, which consisted of five (AlN/GaN) periods, a two-dimensional electron gas (2DEG) was formed at the interface between the GaN base layer and the first AlN barrier layer. When the thickness of the AlN barrier layer in the multiquantum well was increased from 0.9 to 2.6 nm at a constant GaN well thickness of 5 nm, the sheet carrier density of the 2 DEG increased from 5×1012 to 2.1×1013 cm−2 and the electron mobility measured at 77 K decreased from 11780 to 3140 cm2/V s. The effect of the GaN well thickness was also investigated.
On the relation between photospheric magnetic field and chromospheric emission in the quiet Sun

Abstract In this contribution we present an observational study of the interaction of the photosphere with different chromospheric layers. We study the correlations between emissions at varying temperature from the temperature minimum region (UV continuum at 1600 Å from TRACE) through the low chromosphere (CaII K-line from BBSO) to the middle chromosphere (continuum at 3.5 mm from BIMA) and photospheric magnetic field from MDI/SOHO. For the first time millimeter observational data are included in such analysis. We report a high degree of correlation between considered emissions formed at different heights in the chromosphere. A power law is found to be a good representation for the relationship between photospheric magnetic field and chromospheric emissions at all considered wavelengths. Our analysis shows that the dependence of chromospheric intensities on magnetic field is different for the network and internetwork regions. In the network a power law provides the best fit with the exponent being close to 0.5–0.6, while almost no dependence of chromospheric intensity on magnetic flux is found for the cell interiors. The obtained results support the idea of different heating mechanisms acting in the network (magnetic) and cell interiors (acoustic).
The electron distribution in silicon - I. Experiment

We have completed absolute measurements of the X-ray structure factors of silicon by the Pendellösung method using the techniques developed by Hart & Milne (1969). The 111, 220, 311, 400, 331, 422, 333, 511, 440, 444, 642, 660, 555, 844 and 880 reflexions were all measured in the symmetric Laue case with both MoKα1, and AgKα1 radiations and at 92.2 and 293.2 K. The internal consistency of the results indicates that probable errors of order 0.1% are realistic.
A hydrogen-deficient flow in the centre of the planetary nebula A58

Images and high-resolution spectra of the hydrogen-deficient knot at the centre of the old planetary nebula A58 are presented. The spectra confirm that this region contains essentially no hydrogen, as previously suspected. Emission lines from the knot are broad (FWHM ∼ 180 and 270 km/s for [N II] and [O III] lines respectively) and are blueshifted by ∼ 100 km/s relative to the systemic velocity
Heavy-hole and light-hole quantum beats in the polarization state of coherent emission from quantum wells

Dual-channel spectral interferometry is used to measure the vectorial dynamics of the the four-wave-mixing signal from a GaAs-AlGaAs multiple quantum well when both heavy-and light-hole excitons are excited. The ellipticity, the orientation, and the sense of rotation of the polarization ellipse associated with this emission are observed to oscillate dramatically at the heavy-hole-light-hole quantum beat frequency. The qualitative nature of the beating can be described by a simple model based on the density matrix equations for two independent three-level systems without the inclusion of many body effects; however, these beats are superposed on a polarization that is dominated by many-body effects.
A Periodicity Threshold Theorem for Some Nonlinear Integral Equations

We consider a parametrized family of nonlinear integral equations $F_\tau (x) = x$ which arise in the theory of epidemics. We study the equations by means of bifurcation theory and establish a best possible value $\tau _0 $ (a “periodicity threshold”) such that for $\tau > \tau _0 $ the equation has positive, periodic solutions. The value of $\tau _0 $ is determined by the spectral radius $r(L_\tau )$ of $L_\tau $, where $L_\tau $ is an associated family of linear operators, so we also study properties of the map $\tau \to r(L_\tau )$.
Supersonic domain wall in magnetic microwires

Received 21 June 2007; revised manuscript received 30 July 2007; published 22 October 2007Here, we present experimental evidence for the very fast domain wall in microwires that can reach wall-motion velocity approaching 18.5 km/s, which is much higher than the sound velocity in the magnetic wires.We show that the domain wall speed can be adjusted by counterbalancing between the longitudinal magneticanisotropy leading to small damping and the strong transversal anisotropy.DOI: 10.1103/PhysRevB.76. 132406 PACS number s : 75.60. Ej, 75.60. Jk
C iv absorption-line variability in X-ray-bright broad absorption-line quasi-stellar objects

We report the kinematic shift and strength variability of the C IV broad absorption-line (BAL) trough in two high-ionization X-ray-bright quasi-stellar objects (QSOs): SDSS J085551 + 375752 (at z em ∼ 1.936) and SDSS J091127 + 055054 (at z em ∼ 2.793). Both these QSOs have shown a combination of proﬁle shifts and the appearance and disappearance of absorption components belonging to a single BAL trough. The observed average kinematic shift of the whole BAL proﬁle resulted in an average deceleration of ∼− 0.7 ± 0.1, − 2.0 ± 0.1 cm s − 2 over rest-frame time-spans of 3.11 and 2.34 yr for SDSS J085551 + 375752 and SDSS J091127 + 055054, respectively. To our knowledge, these are the largest kinematic shifts known, exceeding by factors of about 2.8 and 7.8 the highest deceleration reported in the literature; this makes both objects potential candidates to investigate outﬂows using mul-tiwavelength monitoring of their line and continuum variability. We explore various possible mechanisms to understand the observed proﬁle variations. Outﬂow models involving many small self-shielded clouds, probably moving in a curved path, provide the simplest explanation for the C IV BAL strength and velocity variations, along with the X-ray-bright nature of these sources.
Electric Conduction in Phosphorus Doped Silicon at Low Temperatures

The impurity conduction in phosphorus doped n -type silicon has been investigated at temperatures between 1.1°K and 300°K. The samples ranged in concentration of excess donors from 1.2. 10 18 to 2.5. 10 20 cm -3 . A metallic type impurity conduction and a negative magnetoresistance are observed in samples containing higher than 4.10 18 cm -3 excess donors. An intermediate type impurity conduction is observed in samples containing from 1.7. 10 18 to 4.10 18 cm -3 excess donors. In metallic samples with donor concentration higher than 6.10 18 cm -3 , the resistivity increases monotonically with temperature T up to the Fermi degeneracy temperature T D of respective samples according to a simple formula, ρ( T )=ρ(4.2^°K)[1+ A ( T / T D ) B ], where A and B are constants.
A high-resolution H I survey of the Rosette Nebula

As part of the Boston University-Arecibo Galactic H I Survey, we analyzed the gross physical properties of the atomic gas associated with the Rosette Molecular Complex (RMC) which was derived from a new, high-resolution 21 cm survey. At the distance of the RMC, the 4' angular resolution of the survey corresponds to a linear size of 2 pc. The H I maps presented here cover an area of 110×60 pc. If the 21 cm emission is optically thin, then the survey mapped and H I mass of 1.5±0.1×10 5 M ○. The optical nebula is surrounded by three dense H I regions, which roughly trace out the boundary of an H I shell
Analytical derivation of the stationarity and the ergodicity of a field scattered by a slightly rough random surface

In the framework of the small perturbation method, we present a new theoretical derivation of the statistical and spatial properties of a field scattered by a one-dimensional slightly rough random surface. The work concerns the intermediate field zone where the scattered field is reduced to the contribution of the progressive plane waves. The surface is assumed to be stationary, ergodic and Gaussian. First, from a statistical point of view, we demonstrate that under oblique incidence the scattered field is not stationary while it is strictly stationary under normal incidence. For an infinite surface, the scattered field modulus obeys to Hoyt law and the phase is not uniform. Second, from a spatial point of view, for a given altitude and under all incidences, we show that the scattered field is ergodic. Under oblique incidence, the phase is spatially uniform and the modulus is given by a Rayleigh law. Under normal incidence, the phase is not uniform and the modulus is given by a Hoyt law. Third, from a practical point of view, we show that the field measured by a directional antenna is ergodic and stationary if the angular transfer function of the antenna does not contain the specular direction.
Spectroastrometry: a new approach to astronomy on small spatial scales

The technique of spectroastrometry (measuring the wavelength dependence of the position of an object) provides a means of studying the spatial structure of astronomical sources on scales much smaller than the seeing disk size or the diffraction limit. Despite successful demonstrations in the past, the method does not seem to be widely known. This paper describes techniques used at the Anglo-Australian Telescope to obtain such observations with standard instrumentation, and presents some examples of astronomical results on sources including binary stars and active galactic nuclei. The potential for combining spectroastrometry with interferometry to observe structure on microarcsecond scales is described.
Logistic regression in meta-analysis using aggregate data

We derived two methods to estimate the logistic regression coefficients in a meta-analysis when only the 'aggregate' data (mean values) from each study are available. The estimators we proposed are the discriminant function estimator and the reverse Taylor series approximation. These two methods of estimation gave similar estimators using an example of individual data. However, when aggregate data were used, the discriminant function estimators were quite different from the other two estimators. A simulation study was then performed to evaluate the performance of these two estimators as well as the estimator obtained from the model that simply uses the aggregate data in a logistic regression model. The simulation study showed that all three estimators are biased. The bias increases as the variance of the covariate increases. The distribution type of the covariates also affects the bias. In general, the estimator from the logistic regression using the aggregate data has less bias and better coverage probabilities than the other two estimators. We concluded that analysts should be cautious in using aggregate data to estimate the parameters of the logistic regression model for the underlying individual data.
The theory of difference analogues of special functions of hypergeometric type

CONTENTS Introduction ? 1. Preliminary information ? 2. Construction of particular solutions for a difference equation of hypergeometric type on non-uniform lattices ? 3. Some properties of difference functions of hypergeometric type ? 4. Classical orthogonal polynomials of a discrete variable on non-uniform lattices ? 5. Functions of a discrete variable of the second kind ? 6. Some solutions of a difference equation of hypergeometric type on non-uniform lattices Conclusion Appendix. A transformation of the original equation References
Non-invasive measurement of arterial longitudinal movement

In arterial vessel wall characterisation the longitudinal movements of vessels have gained little or no attention. It has been presumed that the arterial vessels move very little in the longitudinal direction. With modern high resolution ultrasound it can, however, be seen that arterial vessels move not only in the circumferential, but also in longitudinal direction. This paper describes a non-invasive, ultrasound based method which estimates the longitudinal and the circumferential movement, respectively. The method is demonstrated in a limited in vivo study of the common carotid artery. Results show that, apart from the well known circumferential movement, there is a distinct longitudinal movement.
High Angular Resolution Observations of Late-Type Stars

This paper presents speckle observations of Mira (o Cet) and late-type stars with the PISCO speckle camera of Pic du Midi during the period 1995-1998. A survey for binarity among a sample of late-type stars was performed, which led to seven positive detections out of 36 objects. Photometric and color variations of the companion of Mira were searched for, but no significant brightness variations could be found over a timescale of ∼5-10 minutes. The position and photometry measurements, the restored images with high angular resolution of the binary system Mira A-B (ADS 1778) are in full agreement with Hubble Space Telescope data obtained at the same epoch. A new orbit has been derived for Mira A-B.
On Robust Trend Function Hypothesis Testing

In this paper we build upon the robust procedures proposed in Vogelsang (1998) for testing hypotheses concerning the deterministic trend function of a univariate time series. Vogelsang proposes statistics formed from taking the product of a (normalised) Wald statistic for the trend function hypothesis under test with a specific function of a separate variable addition Wald statistic. The function of the second statistic is explicitly chosen such that the resultant product statistic has pivotal limiting null distributions, coincident at a chosen level, under I(0) or I(1) errors. The variable addition statistic in question has also been suggested as a unit root statistic, and we propose corresponding tests based on other well-known unit root statistics. We find that, in the case of the linear trend model, a test formed using the familiar augmented Dickey-Fuller [ADF] statistic provides a useful complement to Vogelsang's original tests, demonstrating generally superior power when the errors display strong serial correlation with this pattern tending to reverse as the degree of serial correlation in the errors lessens. Importantly for practical considerations, the ADF-based tests also display significantly less finite sample over-size in the presence of weakly dependent errors than the original tests.
The influence of magnetospheric refraction on the apparent spatial structure of a pulsar emission region

The refraction of ordinary superluminous waves in a pulsar plasma is considered. The effect is found essentially to inﬂuence the apparent spatial structure of a pulsar emission region. This is of particular importance for the interpretation of the observations of pulsar interstellar scintillations, which provide an opportunity of resolving the magnetospheres of nearby pulsars. When calculated with account for magnetospheric refraction, the dependence of transverse ray separation on pulse longitude appears to be similar to that inferred by means of interstellar interferometry. It is shown that the differences in the character of the dependences observed at various frequencies may be attributed to the frequency-dependent efﬁciency of refraction. Taking into account magnetospheric refraction makes it necessary to reconsider the estimate of the emission altitude derived from the apparent size of the emission region. The renewed estimate appears to be almost an order of magnitude less, so that it is consistent with the emission altitudes obtained by other methods.
Existence of solutions to a phase transition model with microscopic movements

We prove the existence of weak solutions for a 3D phase change model introduced by Michel Frémond in (Non‐smooth Thermomechanics. Springer: Berlin, 2002) showing, via a priori estimates, the weak sequential stability property in the sense already used by the first author in (Comput. Math. Appl. 2007; 53:461–490). The result follows by passing to the limit in an approximate problem obtained adding a superlinear part (in terms of the gradient of the temperature) in the heat flux law. We first prove well posedness for this last problem and then—using proper a priori estimates—we pass to the limit showing that the total energy is conserved during the evolution process and proving the non‐negativity of the entropy production rate in a suitable sense. Finally, these weak solutions turn out to be the classical solution to the original Frémond's model provided all quantities in question are smooth enough. Copyright © 2008 John Wiley & Sons, Ltd.
The squint Moon and the witch ball

A witch ball is a reflecting sphere of glass. Looking into the disk that it subtends, the whole sky can be seen at one glance. This feature can be exploited to see and photograph the squint Moon illusion, in which the direction normal to the illuminated face of the Moon—its ‘attitude vector’—does not appear to point towards the Sun. The images of the Sun and Moon in the disk, the geodesic connecting them, the Moon’s attitude, and the squint angle (distinct from the tilt), can be calculated and simulated, for all celestial configurations and viewing inclinations. The Moon direction antipodal to the Sun, corresponding to full Moon, is a singularity of the attitude vector field, with index +1. The main features of the witch ball images also occur in other ways of imaging the squint Moon.
Sensitivity of the Water‐Immersed Ear to High‐ and Low‐Level Tones

Two experiments are reported regarding man's sensitivity to waterborne sound. The first study investigated the threshold sensitivity to tones of 250, 500, 1000, 1500, 2000, 3000, 4000, and 6000 cps and the attenuation due to the diver's hood. The second experiment obtained data on the “tolerance” to a high‐intensity tone of 1500 cps.The sound‐pressure level needed to reach threshold in water is about 40–70 db higher than the MAP threshold in air. The greatest loss in sensitivity occurs in the regions of greatest air sensitivity. The diver's hood was found to provide about 20 db or more of attenuation of underwater sound at frequencies above 1000 cps.The “tolerance” limits for hoodless divers is approximately 174 db re 0.0002 dyne/cm2. When wearing the hood divers were able to tolerate at least 180 db, the system's maximum output. Above 165 db all divers reported some distortion of the visual field.
Improved asymptotic expansion for the error function with imaginary argument

1. F. B. HILDEBRAND, Introduction to Numerical Analysis, McGraw-Hill Book Co., New York, 1956, p. 261-269. 2. F. B. HILDEBRAND, op. cit., p. 287-288. 3. A. S. HOUSEHOLDER, Principles of Numerical Analysis, McGraw-Hill Book Co., New York, 1953, p. 221. 4. R. W. HAMMING, Numerical Methods for Scientists and Engineers, McGraw-Hill Book Co., New York, 1962, p. 242. 5. NBS APPLIED MATHEMATICS SERIES, No. 9, Tables of Chebyshev Polynomials Sn(a) and C,(a), U. S. Govt. Printing Office, Washington, D. C. , 1952; Introduction.
Étude mathématique de modèles quantiques et classiques pour les matériaux aléatoires à l'échelle atomique

Les contributions de cette these portent sur deux sujets.La premiere partie est dediee a l'etude de modeles de champ moyen pour la structure electronique de materiaux avec des defauts.Dans le chapitre~ref{chap:ergodic_crystals}, nous introduisons et etudions le modele de Hartree-Fock reduit (rHF) pour des cristaux desordonnes. Nous prouvons l'existence d'un etat fondamental et etablissons, pour les interactions de Yukawa (a courte portee), certaines proprietes de cet etat. Dans le chapitre~ref{chap:defauts_etendus}, nous considerons des materiaux avec des defauts etendus. Dans le cas des interactions de Yukawa, nous prouvons l'existence d'un etat fondamental, solution de l'equation auto-coherente. Nous etudions egalement le cas de cristaux avec une faible concentration de defauts aleatoires. Dans le chapitre~ref{chap:numerical_simuation}, nous presentons des resultats de simulations numeriques de systemes aleatoires en dimension un.Dans la deuxieme partie, nous etudions des modeles Monte-Carlo cinetique multi-echelles en temps. Nous prouvons, pour les trois modeles presentes au chapitre~ref{chap:kMC}, que les variables lentes convergent, dans la limite de la grande separation des echelles de temps, vers une dynamique effective. Nos resultats sont illustres par des simulations numeriques.
Effective electrical properties of heterogeneous earth models

An attempt is made to examine critically the basic formulations of current flow in heterogeneous media such as brine- saturated rocks with the grains having a regular form. The pore space dependence on the conductivity and permittivity is given special attention. The extension of the small volume loading mixture formulas to large volume loading is carried through explicitly, following the procedure of Bruggeman, Hanai, Cohen, Sen, and others. We indicate that the particle shape plays a major role.
An Algorithm for a Letter-Based Representation of All-Pairwise Comparisons

All-pairwise comparisons among a set of t treatments or groups are one of the most frequent tasks in applied statistics. Users of statistical software are accustomed to the familiar lines display, in which treatments that do not differ significantly, are connected by a common line or letter. Availability of the lines display is restricted mainly to the balanced analysis of variance setup. This limited availability is at stark variance with the diversity of statistical methods and models, which call for multiple comparisons. This article describes a general method for graphically representing any set of t(t−1)/2 all-pairwise significance statements (p values) for t treatments by a familiar letter display, which is applicable regardless of the underlying data structure or the statistical method used for comparisons. The method reproduces the familiar lines display in case of the balanced analysis of variance. Its broad applicability is demonstrated using data from an international multienvironment wheat yield trial and from a fish catching survey.
Mixing in turbulent axially symmetric free jets

An analysis to solve mixing problems involving momentum, energy, and mass transfer in turbulent axially symmetric compressible flow is presented. The method is based on the linearization of the conservation equations in the plane of the von Mises variables while retaining the essential nonlinear nature of the equations in the physical plane. The application of this method to a laminar flow problem has been shown to be in good agreement with a numerical solution of the boundary-layer equations obtained by Pai. The extension of the method to turbulent flow requires an expression for the eddy viscosity. A possible modification of Prandtl's formulation, suggested by Ferri, is investigated. When this expression for eddy viscosity is introduced, the application of the present method to compressible turbulent flow yields analytical results that are in good agreement with available experimental data.