Miracle-dz/UniFAR-FTUs huggingface dataset:
On the origin of cosmic rays: Some problems in high-energy astrophysics

This paper reviews the present state of the problem of the origin of cosmic rays. Primary attention is paid to galactic diffusion models with a halo, and questions of cosmic-ray chemical composition, electron component, and synchrotron galactic radioemission. The author's conclusion is that models with a large halo with a characteristic cosmic-ray age Tcr ~ 108 years are confirmed by radio data, and at least do not contradict the information on cosmic-ray chemical composition. The paper also deals with the problems of anisotropy, plasma phenomena in cosmic rays, and the prospects of gamma-ray astronomy.
Dynamics of excitonic recombination and interactions in homoepitaxial GaN

The dynamics of free and bound excitons and their interactions have been analyzed from the results of time-resolved photoluminescence (PL) in GaN layers fabricated by metalorganic chemical vapor deposition on GaN single-crystal substrates. The PL transients of an acceptor-bound exciton (A 0 X) a donor-bound exciton (D 0 X), and free excitons A and B (FX A and FX B ) at 3,467 eV, 3,472 eV, 3.478 eV, and 3,483 eV, respectively, have been measured. At low excitation density (100 W/cm 2 ), the PL decay times in GaN range from 30 ps for FX B up to 1000 ps for A 0 X. The dependence of time constants versus excitation and temperature has been analyzed. Below 50 K, the most important decay process of the FX is trapping on donors. At higher temperatures, delocalization of excitons is observed, and free-exciton emission becomes relatively strong. The delocalization of excitons influences the decay process. Consequently, decay times initially increase, then decrease with temperature. They are longest at about T = 70 K. The time constants of the FX A and D 0 X are of the order of a few hundred ps. The exciton temperature T X has been determined from the slope of the blue wing of the FX peak. Initially, the excitons are hot (due to high photon energy); then they cool due to interactions with phonons on a time scale of about 80 ps. In the same time range, a D 0 X-FX interaction leading to a broadening of the D 0 X peak is observed.
The Visual Separability of Plotting Symbols in Scatterplots

Abstract Which symbols should be used to represent different groups of data in the same scatterplot? Hypotheses are derived to predict which symbol pairs should lead to good separability, based on the contrast of the symbols' visual properties or “features. ” In two experiments, experimental scatterplots were shown to subjects on a computer screen; the dependent variable was the decision time to judge which of the two presented symbols was the more frequent one. Analyses of the within-subject effects yielded the following results: (1) Important feature contrasts are brightness, number of line endings, and curvature. (2) Symbols that differ simultaneously in two feature dimensions may be more separable than symbols that differ only in either one. (3) The contrasts between circular symbols and radial line symbols like the plus sign or the asterisk are excellent. Practical applications of these findings are discussed, as well as their contribution to the theory of visual perception.
Musical Acoustics Session 2 pMU : Musical Preference , Perception , and Processing 2 pMU 7 . Human ability of counting the number of instruments in polyphonic music

There are indications that humans are only able to correctly count up to three voices in polyphonic music pieces of homogeneous timbre, where each voice is played by the same instrument. A more general case, where voices are played by instruments of inhomogeneous timbre, has not been fully addressed so far. In order to approach this question we conducted a listening experiment with 62 participants to find out whether both scenarios instrumentation by inhomogeneous or homogeneous timbre share the same outcome. This paper describes the design of the experiment including an analysis of the results, which show that both scenarios are related. Furthermore, a detailed analysis of the error rates in correctly counting the number of instruments reveals that there are significant differences between non-musician and musician listeners, in particular regarding the upper auditory limit of the number of correctly counted instruments. Based on these results, models for the perception of instruments in auditory streams can be developed.
Probing dielectrophoretic force fields with metallic carbon nanotubes

The authors show that single-walled carbon nanotubes are effective probes for dielectrophoretic force fields by studying their deposition pattern on surfaces. Different force fields were generated by electrodes on insulating oxides, with or without conducting substrates underneath. The patterns were recorded by scanning electron microscopy and simulated by finite element calculations. The data show that a sign change of the normal component of the dielectrophoretic force close to the substrate surface can lead to a repulsion of metallic carbon nanotubes from the surface. The authors present geometrical constraints to avoid such a sign change in the dielectrophoretic force.
The Basic Reproduction Number and the Vaccination Coverage Required to Eliminate Rubella from England and Wales

Bootstrapping is used to estimate the effectiveness of different vaccination strategies for rubella in England and Wales. It is assumed that rubella infection follows the deterministic age-structured model discussed by Dietz and Schenzle (1985). The bootstrap is used to estimate percentile confidence intervals for the basic reproductive number and the minimum elimination proportions under one and two stage vaccination campaigns for rubella. The results of differing mixing assumptions and the effects of kernel smoothing are also considered. Previous estimates of the basic reproduction number and minimum elimination vaccination proportions for rubella and similar diseases are discussed and the results compared with those of the article. For homogeneous mixing only, the estimates are much lower than previous estimates. For more realistic symmetric mixing a worse ‘reasonable’ vaccination coverage estimate of around 87% of children as young as possible is needed to eliminate rubella in England and Wales.
Energy Transfer Phenomena in Liquid Helium

A spectroscopic study of the light emitted from liquid helium bombarded by alpha particles from a 50-mC /sup 210/Po source was made to investigate the temperature dependence of the emission. Observations, which support the energy transfer mechanism, are reported. The emission spectrum of liquid helium cortnining N/sub 2/ + O/sub 2/ is shown. Rough estimates of the efficiency of the scintillation process show that the light output energy is approximates 0.1% the alpha energy. (L.B.S.)
Exponential Convergence Rate Estimation for a Class of BAM Neural Networks with Time-Delays

This paper is concerned with the exponential stability analysis problem for a class of neutral bidirectional associative memory (BAM) neural networks with parameter uncertainties and mixed time-delays where the parameter uncertainties are norm-bounded and the mixed time-delays involve discrete, distributed and neutral time-delays. By utilizing free-weighting matrix method and an appropriately constructed Lyapunov-Krasovskii Functional, some nove delay-dependent and decay-rate dependent exponential stability criteria are derived in the terms of linear matrix inequalities (LMIs). Meanwhile, the maximum allowable decay rate can be estimated based on the obtained results. Two numerical examples are presented to demonstrate the effectiveness of the proposed method.
Far Field Electrocochleography. Frequency Specificity of the Response

It is commonly thought that the AP is determined by high frequency units in the most basal part of the cochlea, and that the frequency specificity of this response is rather poor. We have evaluated these relations for the 7 msec far field activity by means of masking experiments and recordings from the Vertex. Stimuli were tone bursts at 1, 2 and 4 kHz with rise-fall times from 1 to 3 msec. Peak duration 0.5 msec. Maskers were noisebands with center frequencies spaced at narrow intervals from 0.5 to 6 kHz. In all situations where the frequency for the masker and the stimulus were close to each other there were pronounced and characteristic changes in the response. The results clearly demonstrate that the 7 msec response reflects activity in the cochlea that is characteristic for each stimulus frequency. We were unable to detect any particular influence from the most basal part of the cochlea. There is thus a distinct discrepancy between the frequency selectivity for the AP and for the brainstem responses.
We Can See No Naked Supercritical Accretion Disks

The structure and emission properties of supercritical accretion disks have been well-investigated both analytically and numerically. Due to the existence of an optically thick wind, however, we cannot see the surface of the naked supercritical disks without wind, but observe the apparent photosphere formed in the wind. Using a simple wind model, we examined the observational appearance and expected spectra of the wind-disk system. We confirmed that the apparent photosphere in the wind is certainly located high above the disk surface. We also found that the comoving spectra of the apparent photosphere resembles the characteristic flat spectral energy distribution of the supercirtical disks, as long as the radiative flux is conserved in the wind, although the observed spectra remarkably depends on the velocity distribution on the apparent photosphere. We further examined the inclination angle dependence, and calculated the apparent luminosity of the wind-disk system. We found that the apparent luminosity distribution well-reproduces the observational trend of the luminosity function of the observed ultra-luminous X-ray sources.
Recombination dynamics of free and localized excitons in GaN/Ga 0.93 Al 0.07 N quantum wells

Time-resolved photoluminescence studies have been performed on GaN/Ga0.93Al0. 07N multiple quantum wells grown by molecular-beam epitaxy on a sapphire substrate. Radiative recombinations of excitons in both the wells and barriers exhibit average decay times of ∼330ps, at T=8K, with a significant spectral distribution of times. This distribution is interpreted in terms of localization of carriers by potential fluctuations due to alloy disorder and to well width and depth variations. The temperature dependence of the radiative lifetime τr of excitons in the wells is deduced from the measurement of both the photoluminescence decay time and intensity. We find that τr increases linearly with temperature dependence ∂τr/∂T=20.5±0.7psK−1, for T<60K. From this result, we deduce the radiative lifetime of free excitons in the low-temperature limit (related to the oscillator strength) to be of 2.4 ps, i.e., half one order of magnitude smaller than for GaAs/Ga-Al-As quantum wells.
Assessment of CODAR SeaSonde and WERA HF Radars in Mapping Surface Currents on the West Florida Shelf

AbstractConcurrently operated on the West Florida shelf for the purpose of observing surface currents are three long-range (4.9 MHz) Coastal Ocean Dynamics Applications Radar (CODAR) SeaSonde and two median-range (12.7 MHz) Wellen Radar (WERA) high-frequency (HF) radar systems. These HF radars overlook an array of moored acoustic Doppler current profilers (ADCPs), three of which are presently within the radar footprint. Analyzed herein are 3 months of simultaneous observations. Both the SeaSonde and WERA systems generally agree with the ADCPs to within root-mean-square differences (rmsd) for hourly radial velocity components of 5.1–9.2 and 3.8–6.5 cm s−1 for SeaSonde and WERA, respectively, and within rmsd for 36-h low-pass filtered radial velocity components of 2.8–6.0 and 2.2–4.3 cm s−1 for SeaSonde and WERA, respectively. The bearing offset and tidal and subtidal currents of total velocities are also assessed using the ADCP data. Despite differences in a variety of aspects between the direction-finding.
A multi‐time stepping integration method for the ultrasound heating problem

A two‐dimensional thermo‐acoustic problem consisting of the Pennes bioheat transfer model and a nonlinear wave equation with a temperature dependent speed of sound is considered. The large discrepancy in time scales of the wave propagation and the heat conduction processes requires a multi‐time stepping method allowing to solve both equations on different time scales. However, the standard approach considers a sequential solution process without any error control. We propose a multi‐time stepping scheme based on a fixed‐point approach resulting in a thermo‐acoustic coupling controlled by a stopping criterion. Furthermore, in most high‐intensity focused ultrasound applications the problem has to deal with absorbing boundary conditions (ABCs) in a bounded region. The use of a Lagrange multiplier based technique allows us to efficiently incorporate the second order Engquist–Majda ABC into the weak formulation of the original problem. The efficiency and robustness of the proposed multi‐time stepping method as well as improved accuracy compared to the widely used standard scheme for modeling high‐intensity focused ultrasound is demonstrated through a series of numerical examples which are typical for ultrasound heating.
A workflow for scalable benchmarking and hyperparameter tuning of transfer learning methods - Expos´e

Machine learning is increasingly important to peoples lives [1]. Especially in the field of image classification, neural networks have shown impressive results [2]. Furthermore transfer learning becomes increasingly relevant in the many field with scarce training data because of its ability to transfer information from a many sample source domain to a few sample target domain. [3]. Machine learning methods are complex and contain numerous different parameters (hyperparameters, sample sizes, validation sample sizes, .). Transfer learning multiplies the number of these parameters and further increases the complexity of machine learning [3]. The high number of configurable parameters can be overwhelming for researchers, cause mistakes in the research, and increase the time and human effort required for solving machine learning tasks. Currently, there is no standardized approach to systematically evaluate and compare transfer learning methods. In the literature, different methods tend to be evaluated on different datasets, different sample sizes, different source and target data, different underlying deep learning architectures (encoder, e.g., resnet, vgg, .), and with varying compute-budgets for hyperparameter tuning [4]. Thus, it is exceedingly difficult to meaningfully compare transfer learning methods and to make informed decisions on which method is most appropriate for a given data type and sample size. The authors of [4] created a unified re-implementation and evaluation platform for certain contrastive semi-supervised learning methods, however this platform is too specific for usage outside the intended domain.
Spectral line enhancement in laterally colliding boron-nitride plasmas

Line intensities in laterally colliding boron-nitride (BN) plasmas were compared to the line intensities in non-colliding BN plasmas. The plasmas were produced by splitting the laser beam from a ruby laser (5 J total energy, 30 ns pulse FWHM) with an optical wedge in front of the focusing lens. The stronger part of the laser beam (4 J, 2000 J/cm2 on target) was focused into the rectangular groove cut into the target surface in order to compensate for the higher expansion velocity of the hot plasma. The cold plasma was produced by the weaker part of the laser beam (1 J, 500 J/cm2 on target) that was focused onto the target surface nearby. The plasma spectra in the spectral region between 16 and 34 nm were registered with a VUV spectrograph equipped with a gateable multichannel plate (MCP) and CCD camera. Due to the low intensity of the lines, the acquired spectra are time-integrated. The spectrum of the colliding plasmas is compared to the sum of the separately produced hot and cold plasma. The nitrogen and boron lines showed different behaviours. The intensity ratio of nitrogen lines in colliding and non-colliding plasmas showed no marked change in line intensities; on the other side, the intensity of boron lines was reduced to about one-half in the colliding plasmas. The only exception was the Balmer-alpha line of B V, which showed a little enhanced intensity in the colliding plasmas. This effect is interpreted as a sign of the charge-exchange mechanism that was observed before in colliding carbon plasmas, and for which the theoretical calculations indicate a reasonably large cross-section.
Low level laser therapy reduces oxidative stress in cortical neurons in vitro

It is accepted that the mechanisms of low level laser therapy (LLLT) involves photons that are absorbed in the mitochondria of cells and lead to increase of mitochondrial metabolism resulting in more electron transport, increase of mitochondrial membrane potential, and more ATP production. Intracellular calcium changes are seen that correlate with mitochondrial stimulation. The situation with two other intermediates is more complex however: reactive oxygen species (ROS) and nitric oxide (NO). Evidence exists that low levels of ROS are produced by LLLT in normal cells that can be beneficial by (for instance) activating NF-kB. However high fluences of light can produce large amounts of ROS that can damage the cells. In oxidatively stressed cells the situation may be different. We exposed primary cultured cortical neurons to hydrogen peroxide (H2O2) or cobalt chloride (CoCl2) oxidative insults in the presence or absence of LLLT (810-nm laser at 0.3 or 3 J/cm2). Cell viability of cortical neurons was determined by lactate dehydrogenase assay. ROS in neurons was detected using an ROS probe, MitoRox with confocal microscopy. Results showed that LLLT dose-dependently reversed ROS production and protected cortical neurons against H2O2 or CoCl2 induced oxidative injury in cultured cortical neurons. Conclusion: LLLT can protect cortical neurons against oxidative stress by reversing the levels of ROS.
Hysteretic spin-wave excitation in spin-torque oscillators as a function of the in-plane field angle: A micromagnetic description

This paper describes a full micromagnetic characterization of the magnetization dynamics driven by spin-polarized current in anisotropic spin-torque oscillators (STOs). For field angles approaching the hard in-plane axis, the excited mode is uniform and a super-critical Hopf-bifurcation takes place at the critical current density JC. For field angles close to the easy axis of the free layer, the excited mode is localized (non-uniform) and a sub-critical Hopf-bifurcation occurs at JC. In this latter region, a hysteretic behaviour is, therefore, found. We demonstrate numerically that the non-linearities of the STO are strongly reduced when the oscillation frequency at the critical current is near the ferromagnetic resonance (FMR) frequency computed at zero bias current, and in particular, this condition corresponds to the field orientation at which a minimum in the FMR-frequency is achieved.
Bayesian Faces via Hierarchical Template Modeling

Abstract We consider the problem of directly extracting high-level shape information from images of scenes involving faces. The approach adopted owes much to the work of Grenander and colleagues at Brown University on pattern analysis and involves designing stochastic deformable templates for objects in the underlying image scenes. A wide range of realistic object poses can be captured by imposing a prior probability distribution over the space of allowable deformations. We show how hierarchical models can be used to organize the prior information into a coherent structure. Markov chain Monte Carlo methods are exploited to recover the deformation given observed image data.
The Asteroid Identification Problem IV: Attributions

Abstract Existing archives of asteroid observations contain many objects with very short observed arcs. In this paper we present a method that we have used with considerable success to attribute these short arc “discoveries” to other objects with better defined orbits. The method consists of a three-stage filtering process whereby several billion possible attribution/orbit pairs are systematically analyzed with more and more exact algorithms, at each stage rejecting improbable cases. The first stage compares an attributable, by definition a synthetic observation representative of all the observations over a short arc, with the predicted observation for each available orbit. The second stage compares the proposed attributable observations with predicted positions from the known orbit using conventional linear covariance techniques, considering both the position and motion on the celestial sphere. In the final filter we attempt to compute a best-fitting orbit by differential corrections using the combined dataset. With this algorithm we have found 1675 attributions in approximately one year of operations, in addition to 902 identifications found with another algorithm. We discuss the lessons learned from this one-year experiment and the possibilities of further improvement and automation of the procedure.
Hybrid fuzzy logic flight controller synthesis via pilot modeling

This paper presents an investigation of a hybrid technique developed for synthesizing fuzzy logic controllers as stability augmentation systems. The hybrid technique combines the control capabilities of fuzzy logic with the learning capabilities of genetic algorithms, to yield a fuzzy logic controller augmentation system optimized to satisfy desired handling qualities requirements. An optimal control model is used to provide the closed-loop handling qualities metrics. The optimal control model is an analytic model of the pilot which can support the computation of in-flight handling qualities metrics, such as the standard Cooper-Harper rating. A genetic algorithm is used to optimize the attributes of the fuzzy logic controller. These attributes include the parameters of the fuzzy logic controller membership functions and the rule structure. The hybrid technique was implemented and tested in an offline engineering simulation using a wide-envelope F/A-18 longitudinal model. The tests included examining the robustness of the fuzzy logic controllers, the robustness of the genetic algorithms optimization technique, and the effect of changing the number of rules used in the fuzzy logic controller. Results indicate that the approach provides a robust design technique for fuzzy logic controller stability augmentation system synthesis and also show that the synthesized fuzzy logic controllers possess good robustness qualities.
Measuring hemoglobin amount and oxygen saturation of skin with advancing age

We measured the oxygen saturation of skin at various ages using our previously proposed method that can rapidly simulate skin spectral reflectance with high accuracy. Oxygen saturation is commonly measured by a pulse oximeter to evaluate oxygen delivery for monitoring the functions of heart and lungs at a specific time. On the other hand, oxygen saturation of skin is expected to assess peripheral conditions. Our previously proposed method, the optical path-length matrix method (OPLM), is based on a Monte Carlo for multi-layered media (MCML), but can simulate skin spectral reflectance 27,000 times faster than MCML. In this study, we implemented an iterative simulation of OPLM with a nonlinear optimization technique such that this method can also be used for estimating hemoglobin concentration and oxygen saturation from the measured skin spectral reflectance. In the experiments, the skin reflectance spectra of 72 outpatients aged between 20 and 86 years were measured by a spectrophotometer. Three points were measured for each subject: the forearm, the thenar eminence, and the intermediate phalanx. The result showed that the oxygen saturation of skin remained constant at each point as the age varied.