Miracle-dz/UniFAR-FTUs huggingface dataset:
Internal Lifshitz tails for Schrödinger operators with random potentials

In this short note, we prove that, for periodic Schrodinger operators perturbed by an Anderson-type random potential with long-range single site potential, the density of states always show a Lifshitz tail at a band edge. Thus, we correct a mistake made in an earlier paper [F. Klopp, Duke Math. J. 98, 335–396 (1999)].
Characterization of trapped particles in rf plasmas

Charged dust particles electrostatically trapped in rf plasmas may exhibit kinetic energies greatly exceeding that of the surrounding gas. The high particle energies are a result of charged particle interactions with local potential fields perturbed by the presence of neighboring particles. Laser Doppler velocimetry is used to experimentally investigate the two-dimensional dynamics of monodisperse 10.2 μm polystyrene latex spherical particles trapped in an argon plasma. Spatially resolved particle velocities and local particle concentrations are reported for variations in rf power and pressure. The experimental results are compared with laser light scatter, often employed for studying particle dynamics. Various theories are reviewed in an attempt to interpret the experimental results.
Selective area growth of high quality InP on Si (001) substrates

In this work, we demonstrate the selective area growth of high quality InP layers in submicron trenches on exactly (001) oriented Si substrates by using a thin Ge buffer layer. Antiphase domain boundaries were avoided by annealing at the Ge surface roughening temperature to create additional atomic steps on the Ge buffer layer. The mechanism of Ge surface atomic step formation and the corresponding step density control method are illustrated. The elimination of antiphase boundaries from the optimized Ge buffer layer, together with the defect necking effect, yield defect-free top InP layers inside the trenches.
A reanalysis of substructure in clusters of galaxies and their surroundings

Subclustering in rich clusters of galaxies is studied using a variety of statistical tests which analyze information available from both the projected distribution of galaxies and their radial velocities. New techniques are presented to evaluate more uniformly the frequency with which substructure occurs. Galaxy positional data are used to construct smoothed images of clusters from which structural parameters can be extracted via the methods of surface photometry. Galaxy radial velocity data are used to develop a statistic which is sensitive to correlations between local kinematics and galaxy position that would signal the presence of substructure. Application of these techniques to about 70 clusters with good positional and/or radial velocity data shows that, while little significant substructure is found in the inner regions of most clusters, many clusters do exhibit more than one dynamical component, although it is usually in the regions surrounding clusters that the greatest degree of subclustering can be found. 58 refs.
Fault Detection Enhancement in Rolling Element Bearings Using the Minimum Entropy Deconvolution

Minimum Entropy Deconvolution (MED) has been recently introduced to the machine condition mon- itoring field to enhance fault detection in rolling element bearings and gears. MED proved to be an excellent aid to the extraction of these impulses and diagnosing their origin, i.e. the defective component of the bearing. In this paper, MED is revisited and re-introduced with further insights into its application to fault detection and diagnosis in rolling element bearings. The MED parameter selection as well as its combination with pre-whitening is discussed. Two main cases are presented to illustrate the benefits of the MED technique. The first one was taken from a fan bladed test rig. The second case was taken from a wind turbine with an inner race fault. The usage of the MED technique has shown a strong enhancement for both fault detection and diagnosis. The paper contributes to the knowledge of fault detection of rolling element bearings through providing an insight into the usage of MED in rolling element bearings diag- nostic. This provides a guide for the user to select optimum parameters for the MED filter and illustrates these on new interesting cases both from a lab environment and an actual case.
Missing North Atlantic cyclonic precipitation in ECMWF numerical weather prediction and ERA-40 data detected through the satellite climatology HOAPS II

Intense precipitation associated with wintertime North Atlantic cyclones occurs not only in connection with frontal zones but also, and often mainly, embedded in strong cold air outbreaks to the west of mature cold fronts. Coherent structures of cloud clusters organized in mesoscale postfrontal low-pressure systems are frequently found in satellite data. Such postfrontal lows (PFL) can develop into severe weather events within few hours and can even reach Europe causing intense convective rainfall and gale force winds. Despite predicting the major storm systems numerical weather prediction (NWP) additionally needs to account for PFLs due to their frequent occurrence connected with high impact weather. But while the major cyclone systems are mostly well predicted, the forecast of PFLs remains poor. Using North Atlantic weather observations from the 1997 Fronts and Atlantic Storm Track Experiment (FASTEX) along with the standard voluntary observing ship (VOS) data led to a high quality validation data set for this usually data sparse region. For individual case studies of FASTEX cyclones with mesoscale PFLs investigations were carried out using the well calibrated precipitation estimates from HOAPS (Hamburg Ocean Atmosphere Parameters and fluxes from satellite data) compared to the NWP model output of the ECMWF (European Centre for Medium-Range Weather Forecasts). Preceding studies showed that the HOAPS precipitation structure and intensities are in good agreement with the VOS observations for all observed precipitation types within the cyclones, including PFLs. To assure that the results found in the 1997 data are still valid in the more recent ECMWF model system, a PFL rainfall comparison is carried out using HOAPS and ERA-40 (ECMWF Re-Analysis) data for the winter of 2001 and 2002. The results indicate that the ECMWF model is mostly well reproducing precipitation structures and intensities associated with frontal systems as observed in the VOS and HOAPS data, whereas PFL precipitation is mostly missing. Further investigations within the regions of PFL point out that the VOS observed surface pressure is systematically lower than reproduced in the models. This leads to the conclusion that the missing PFL precipitation in ECMWF may be primarily due to the absence of the corresponding mesoscale low-pressure system.
Numerical Modeling of Hailstorms and Hailstone Growth. Part II: The Role of Low-Density Riming Growth in Hag Production

Abstract The past several years have seen a renewed interest in the importance of low-density riming growth to the development of hailstones. This paper reports on the results of a study that incorporates the physical factors controlling the density of the rime deposit in a two-dimensional, time-dependent numerical cloud model with discretized treatment of the graupel/hail size distribution. Comparisons are made between cases in which the mass-diameter relationship is fixed based on a priori assumed particle densities and cases in which the mass-diameter relationship is allowed to change in accordance with the variable particle density diagnosed from the riming density relationship and past growth history. Compared to the fixed particle density treatment common to earlier work, ice particles of lower density have enhanced surface and cross-sectional area for particles of equal mass, which in turn, increases the effective ventilation experienced by the particles and their capture volumes, thus allowing enh.
BEHAVIOR OF THERMOELASTIC THICK PLATE UNDER LATERAL LOADS

A mathematical model has been developed and solved for predicting the response of a thick thermoelastic axisymmetric solid plate subjected to sudden lateral mechanical and thermal loads. The governing equations of motion and heat conduction have been solved by using Laplace and Fourier transform methods to predict the response of the plate in the physical time domain. A modified Bessel function solution with complex argument is directly used. The model is also formulated and solved with the help of the finite element method (FEM). The results for radial and axial displacements and temperature change have been computed numerically and illustrated graphically for different theories of generalized thermoelasticity. The comparison of exact analysis with that of FEM is also discussed. Excellent agreement is found between the finite element analysis and analytical and classical solutions.
Computing Multivariate Normal Probabilities: A New Look

This article describes and compares several numerical methods for finding multivariate probabilities over a rectangle. A large computational study shows how the computation times depend on the problem dimensions, the correlation structure, the magnitude of the sought probability, and the required accuracy. No method is uniformly best for all problems and—unlike previous work—this article gives some guidelines to help establish the most promising method a priori. Numerical tests were conducted on approximately 3,000 problems generated randomly in up to 20 dimensions. Our findings indicate that direct integration methods give acceptable results for up to 12-dimensional problems, provided that the probability mass of the rectangle is not too large (less than about 0.9). For problems with small probabilities (less than 0.3) a crude Monte Carlo method gives reasonable results quickly, while bounding procedures perform best on problems with large probabilities (> 0.9). For larger problems numerical integration with quasirandom Korobov points may be considered, as may a decomposition method due to Deák. The best method found four-digit accurate probabilities for every 20-dimensional problem in less than six minutes on a 533MHz Pentium III computer.
Morphogenetic oscillations during symmetry breaking of regenerating Hydra vulgaris cells

During the process of regeneration, the fresh-water polyp Hydra vulgaris first builds a hollow sphere consisting of a cell bilayer. This cell ball undergoes subsequent shape transformations, at a later stage it creates tentacles and a foot to form an animal. We describe and analyze the transformation of the hollow sphere to the first non-spherical shape by means of contour analysis. We observe that the cell ball shows characteristic oscillations in size and shape which accompany symmetry breaking. Quantitative analysis of these oscillations provides information on the cell bilayer mechanics and hydrodynamic flows involved. In order to explain the origin of the observed oscillations, we propose three different physical scenarios of oscillation generation.
Analysis of the Pyrenees Lee Wave Event of 23 March 1982

Abstract The results of an independent analysis of mountain wave data gathered by instrumented aircraft during flights over the Pyrenees on 23 March 1982, as part of ALPEX, are presented. The prior synoptic development, cross-flow variation, vertical atmospheric structure upstream and downstream of the Pyrenees, airflow dynamics and sources of uncertainty in the observations and analyzed fields are discussed. Additionally, comparisons are made with a recently published analysis of these data by Hoinka, with differences in the calculation of the vertical flux of horizontal momentum, interpretation of the three-dimensional mesoscale thermal structure, and interpretation of the phase differences between the vertical velocity and potential temperature fields being delineated. As determined here, the northerly upper airflow over the Pyrenees had very little cross-stream variation. The data suggest that relatively weak surface flow divided and was deflected laterally around the Pyrenees. A vertically propagatin.
Small-Sample Results for the Kaplan-Meier Estimator

Abstract Whereas much is known about the asymptotic properties of the Kaplan-Meier (1958) estimator (KME) of a survival function, exact results for small samples have been difficult to obtain. In this article, we obtain an exact expression for the αth moment (α > 0) of the KME under a model of proportional hazards. This enables us, under proportional hazards, to (a) study the bias of the KME, and (b) compare the exact variance of the KME to its asymptotic variance.
Measurement of the thermal conductivity of nanofluids by the multicurrent hot-wire method

We present experimental results of the thermal conductivity of several nanofluids prepared by dispersing nanoparticles of SiO2 and CuO in water and ethylene glycol at various concentrations up to ≈5% in mass fraction. The measurements have been performed by the multicurrent hot-wire technique. Good agreement, within 2%, is found in recommended and published thermal conductivities of the pure fluids. Our experimental technique allows a very accurate determination of the enhancement in the thermal conductivity of the fluids due to the presence of dispersed nanoparticles. Measured enhancements compare well with some of the values published so far in the literature. We have compared our results with simple theoretical models that predict the thermal conductivity of solid suspensions and found that in some cases observed enhancements are several times larger than the predicted ones.
Fibrosis detection in renal artery stenosis mouse model using magnetization transfer MRI

Renal artery stenosis (RAS) promotes fibrosis by excessive and irreversible collagen deposition which may lead to end stage renal failure. Currently, invasive tissue biopsy is the main tool to assess fibrosis. Magnetization transfer imaging (MTI) is a MR-based technique that is sensitive to the interaction of macromolecules (e.g. collagen) and free water. The characteristics of these interactions are notoriously organ and tissue dependent. This study tested the hypothesis that using MTI, renal fibrosis in RAS can be detected. MTI was applied in mice (n=7) with unilateral RAS induced by partial occlusion of the renal artery. In off-resonance MTI, to achieve highest sensitivity, offset frequency, RF pulse power and bandwidth were optimized towards enhancing the contrast between the fibrotic and non-fibrotic tissue. Moreover, magnetization exchange rates (kf and kr) and the fractional size of the restricted magnetization (F), as markers of tissue molecular-morphological change, were estimated using steady-state free precession, on-resonance MTI. The optimal contrast for visual differentiation was achieved at offset frequency, RF pulse power, and effective bandwidth of 6.6kHz, 10μT, and 300Hz, respectively. On-resonance MT demonstrated significantly higher F and kf in the stenotic vs. the contra-lateral kidney. Therefore, off-resonance MT can qualitatively differentiate the fibrotic from the non-fibrotic tissue. Furthermore, kf and F may serve as biomarkers for kidney morphological changes caused by RAS.
Ohm's Law and Masking

The harmonics in the spectrum of a periodic pulse train should, according to Ohm's law, be audible separately. When trying to check this one meets two difficulties in terms of subjective spectrum analysis. First, the nth harmonic may be masked in part or completely by other harmonics. Second, even if the nth harmonic is not masked completely, one has find it among a great many others. Makins use of “Schouten's artifice” (alternatively suppressing and reintroducing the nth harmonic), these difficulties can be lessened. Once the nth harmonic is heard, one may determine its masked threshold by attenuating it. Using the method of adjustment, three experienced subjects measured the masked thresholds of the lowest 10–25 harmonics of a 50, 100, 200, and 400 Hz periodic pulse train at 30 dB SL. From these measurements masking curves are derived. The slopes of these curves show reasonable agreement with those of earlier investigations. A feature of the present method is that one need not make use of noise and stil.
A Class of Elastic‐Plastic Constitutive Laws for Brittle Rock

The inelastic behavior of fissured rock masses is due primarily to microcracking from the tips of preexisting fissures and frictional sliding on fissure surfaces. Consequently, the macroscopic inelastic response is inhibited by an increase of hydrostatic compression and exhibits volume change and strain softening. By generalizing the type of laws often used in metal plasticity, Rudnicki and Rice introduced a class of simple constitutive laws that incorporate these features and is useful for studying the inception of rupture. An important aspect of this generalization is that normality of the inelastic strain increment vector to a yield surface in stress space, as assumed in classical metal plasticity, is not appropriate. More detailed consideration of the preferential activation of sliding on differently oriented fissure surfaces during a program of loading suggests that, although this class of laws will be suitable for describing loading in which stress components increase nearly in proportion to a singl.
Abelian Subgroups of Finitely Generated Kleinian Groups are Separable

By a Kleinian group we mean a discrete subgroup of PSL(2, C). We prove that abelian subgroups of finitely generated Kleinian groups are separable. In other words, if M = H3/Γ is a hyperbolic 3‐orbifold, with Γ finitely generated, then abelian subgroups of Γ are separable in Γ. 1991 Mathematics Subject Classification 20E26, 51M10, 57M05.
Galactic pulsar population and the origin of high-energy cosmic rays

We show that assuming a simple cosmic ray (CR) acceleration scenario, where all the pulsar rotational energy is transformed into CR particles of the highest available energy at a given moment, one obtains particle fluxes of the order of the observed ones. We derive the energy spectrum of the produced particles assuming that the pulsar magnetic field decays with time. The slope of the spectrum for E > 1016 eV is determined by a power-law distribution of the pulsar initial periods and the knee in the spectrum at ~3 × 1015 eV by the decay of the pulsar magnetic fields. Moreover, the pulsar parameters at birth, fitted to describe the CR energy spectrum, reconstruct reasonably well their present equilibrium population.
Systematic study of disorder induced by neutron irradiation in MgB2 thin films

The effects of neutron irradiation on normal state and superconducting properties of epitaxial magnesium diboride thin films are studied up to fluences of 1020cm−2. All the properties of the films change systematically upon irradiation. Critical temperature is suppressed and, at the highest fluence, no superconducting transition is observed down to 1.8K. Residual resistivity progressively increases from 1to190μΩcm; c axis expands and then saturates at the highest damage level. We discuss the mechanism of damage through the comparison with other damage procedures. The normal state magnetoresistivity of selected samples measured up to high fields (28 and 45T) allows to determine unambiguously the scattering rates in each band; the crossover between the clean and dirty limit in each sample can be monitored. This set of samples, with controlled amount of disorder, is suitable to study the puzzling problem of critical field in magnesium diboride thin films. The measured critical field values are extremely high.
Dielectric Properties of Ferroelectric Lithium Tantalate Crystals Studied by Terahertz Time-Domain Spectroscopy

The terahertz (THz) dynamics of ferroelectric lithium tantalate crystals has been investigated using the latest THz time-domain spectroscopy. The intensity and phase shift of transmitted THz radiation have been accurately measured for the propagation of the THz radiation along the y-axis down to 3 cm-1 (0.1 THz). The phonon-polariton dispersion relations have been determined from the phase shift for A1(z) and E(x,y) symmetry polaritons. The dispersion relations of both symmetries show no “avoided crossing” below 60 cm-1 (1.8 THz). The complex dielectric constants εz(ω) and εx(ω) in the sub-THz to THz regions have also been determined as functions of frequency. Both the real and imaginary parts of εx(ω) are well reproduced using a single damped harmonic oscillator model. However, those of εz(ω) indicate the excess part, which may be attributed to a relaxation process related to the order-disorder nature of ferroelectricity.
Global behaviour of solutions of cyclic systems of q order 2 or 3 generalized Lyness' difference equations and of other more general equations of higher order

We study the global behaviour of the solutions of cyclic systems of q order k difference equations with q unknown sequences . If σ denotes the direct cyclic permutation , such a system is: for values of k and choices of f which correspond, first to cases of classical simple difference equations : order 2 or 3 extended Lyness' equations, order 2 generalized Lyness' type equations associated to conics, or to elliptic cubics or quartics; and then with f which becomes from other more general order k equations.
Solute alignment in liquid crystal solvents The Saupe ordering matrix for anthracene dissolved in uniaxial liquid crystals

Abstract We have described a theory for U, the potential of mean torque of rigid solutes at infinite dilution in a uniaxial liquid crystal phase; this may be used to calculate (S xx - S yy) and S zz, the principal elements of the Saupe ordering matrix. In its simplest form U(ω) contains only second-rank terms and the dependence of the biaxiality (S xx - S yy) is determined by ω, a parameter which describes the departure of the potential of mean torque from cylindrical symmetry, and is predicted to be temperature independent. If dispersion forces are responsible for the magnitude of the orientational order parameter then ω should be independent of the solvent and depend only on the anisotropy in the electric polarizability of the solute. Indeed, this independence should result for any pair potential which can be factorized into a product of solute and solvent properties. These predictions are tested here by determining values of S zz and (S xx - S yy) for anthracene-d 10 as a solute in several liquid cryst.