Miracle-dz/UniFAR-FTUs huggingface dataset:
The Effect of Gradient and Curvature Drift on Cosmic-Ray Forbush Decreases

When Forbush decreases are analyzed separately in the periods 1959-1969 and 1971-1980, it is found that during the former period there typically is a slower reset than in the latter. This is in agreement with what one would expect from drift motions of charged particles in the interplanetary magnetic field during these two periods. The effect is quite small, however, and it is barely statistically significant. Therefore, beyond establishing its existence, further detailed conclusions cannot be drawn. 16 references
Inhibition of star formation in barred spiral galaxies

The lack of star formation associated with the straight dust lanes within the bar of barred spiral galaxies suggests that star formation is strongly inhibited there. I have shown that the inhibition may be an effect of the high velocities, relative to the gas in the dust lanes, of the dense clouds whose orbits intersect the dust lanes. These clouds, which presumably undergo gravitational collapse upon entering the dust lanes of normal spiral galaxies, are the precursors of star formation. In barred galaxies, the clouds in the bar enter the dust lanes at a velocity an order of magnitude higher than those in normal spirals. The high velocity can cause a quick compression of the clouds followed by a rapid expansion which disperses the majority of the cloud. In the outer parts of the barred spiral galaxy, and at the very center, the cloud velocities are lower, and star formation is not inhibited. This creates the typical appearance of a barred spiral galaxy, with star formation at the ends of the bar, and in the center, but not along the predominant straight dust lanes which lie along the bar. I have tested the effectiveness of this technique by calculating themore » orbits of the dense, prestellar clouds in the expected gravitational field of NGC 5383. A cloud is presumed to be destroyed if its velocity relative to the intercloud gas exceeds an arbitrary minimum velocity and is presumed to collapse into stars if the intercloud density around it is enhanced by an arbitrary minimum amount. « less
Intense laser ionization of transiently aligned CO

We have measured the ionization rate for CO molecules exposed to intense 30 fsec 780 nm laser pulses as a function of the angle between the molecular and laser polarization axes. Nonionizing, 70 fsec laser pulses are used to coherently prepare the molecules, preferentially aligning them for the strong-field ionization experiments. We find a 2:1 ionization-rate ratio for molecules aligned parallel or perpendicular to the ionizing field.
Discussion of ‘Parametric versus nonparametrics: two alternative methodologies’

In his article, Lehmann deftly summarises the key issues which arise when choosing between a parametric test or a nonparametric test. Although the context is the two-sample shift model, the salient points apply more generally. This article serves as a valuable reminder that simple rank tests are robust and fairly efficient. In situations where no uniformly most wonderful procedure exists, the case for the Wilcoxon test is strong, and is done in such a pedagogically clear manner that the article can serve as a basis for lecture in many of our classes. In my discussion below, I will focus on three issues. First, I consider the comparison of the Wilcoxon test to the t-test in the infinite variance case. Next, I will discuss the behaviour of the classical t-statistic t and the Wilcoxon statistic W when G is not necessarily a shift of F . Finally, I will touch upon the comparison in the context of multiple testing.
Evidence of multipolar excitations in surface enhanced Raman scattering

Visible and near-infrared extinction spectra of regular arrays of gold nanorods display several bands depending on polarization of the electromagnetic incident field. When setting the incident field perpendicular to the nanorod axis (transverse polarization), a single band is observed, which is assigned to a dipolar plasmon mode. The several bands obtained under an incident polarization along the nanorod axis (longitudinal polarization) are attributed to multipolar plasmon resonances. Raman scattering experiments carried out under transverse and longitudinal laser excitations on methylene blue adsorbed on these arrays show that multipolar plasmon resonances can give rise to strongly enhanced spectra with an amplification per molecule similar to that obtained for dipolar plasmon excitation.
Effects of a Problem-based Structure of Physics Contents on Conceptual Learning and the Ability to Solve Problems

A model of teaching/learning is proposed based on a ‘problem-based structure’ of the contents of the course, in combination with a training in paper and pencil problem solving that emphasizes discussion and quantitative analysis, rather than formulae plug-in. The aim is to reverse the high failure and attrition rate among engineering undergraduates taking physics. A number of tests and questionnaires were administered to a group of students following a traditional lecture-based instruction, as well as to another group that was following an instruction scheme based on the proposed approach and the teaching materials developed ad hoc. The results show that students following the new method can develop scientific reasoning habits in problem-solving skills, and show gains in conceptual learning, attitudes and interests, and that the effects of this approach on learning are noticeable several months after the course is over.
On the measure of totally real algebraic integers

For totally real algebraic integers x of degree D(x), we examine the stucture of the set of values M(x)1D(x). where M(x) is the measure of x. We find a small limit point λ of this set, and show that the set is everywhere dense in (λ x).
Density-functional theory calculations of bare and passivated triangular-shaped ZnO nanowires

The authors employ density functional theory within the generalized-gradient approximation to investigate infinitely long [0001] ZnO nanowires. The authors report on atomic relaxations, formation energies, and electronic structure of bare and hydrogen passivated ZnO wires with triangular cross sections. The authors find that surface reconstruction plays an important role in stabilizing the nanowires. The authors have shown that the band gap can be tuned by changing the wire diameter and by passivating with hydrogen. While bare and completely passivated wires are semiconducting, wires with intermediate hydrogen passivation exhibit metallic behavior.
A New Correlation for Pressure Drop in Arrays of Rectangular Blocks in Air-Cooled Electronic Units

An experimental work is carried out to investigate the pressure drop and to visualize the flow field in the entrance region of an array of rectangular modules attached to the lower wall of a duct. The modules are positioned in an in-line arrangement to simulate the geometry often encountered in the cooling passages of electronic units. The investigation is performed in both laminar and turbulent regions with Reynolds number ranging from 400 to 15,000. The geometric parameters range from H/L = 0.125 to 1.5 and S/L = 0.125 to 0.5, while the value of B/L is fixed to 0.5. The flow visualization revealed a highly separated region on the first module of the array. The pressure drops are correlated for the range of Re, H/L, and S/L employed in this work
Lyapunov exponents with multiplicity 1 for deterministic products of matrices

We exhibit an explicit criterion for the simplicity of the Lyapunov spectrum of linear cocycles, either locally constant or dominated, over hyperbolic (Axiom A) transformations. This criterion is expressed by a geometric condition on the cocycle's behaviour over periodic points and associated homoclinic orbits. It allows us to prove that for an open dense subset of dominated linear cocycles over a hyperbolic transformation and for any invariant probability with continuous local product structure (including all equilibrium states of Hölder continuous potentials), all Oseledets subspaces are one-dimensional. Moreover, the complement of this subset has infinite codimension and, thus, is avoided by any generic family of cocycles described by finitely many parameters. This improves previous results of Bonatti, Gomez–Mont and Viana where it was shown that some Lyapunov exponent is non-zero, in a similar setting and also for an open dense subset.
Evolution of the Solar Nebula. VI. Mixing and Transport of Isotopic Heterogeneity

Meteoritical studies have shown that the solar nebula was basically well mixed, as shown by the homogeneity of many isotopes of refractory elements. However, isotopic anomalies in certain elements, such as the short-lived isotope 26Al, imply the presence of either spatial or temporal heterogeneity. Spatial heterogeneity could result from the injection of short-lived isotopes into the solar nebula following their production in a supernova or from spraying these isotopes across the nebula's surface following their production by solar flares and transport outward by an X-wind. If the nebula was thoroughly mixed soon after the introduction of spatially heterogeneous 26Al, producing a homogeneous spatial distribution of 26Al, then the measured abundances of 26Al would provide a chronometer for early solar system processes. For these reasons and others it is important to understand the efficiency of mixing and transport processes in the solar nebula. Here we study mixing and transport in fully three-dimensional models of gravitationally unstable disks that are likely to occur during the phase when planetesimal growth is beginning. The three-dimensional models show that isotopes that are sprayed onto an annular region of the surface of a disk around 9 AU remain remarkably concentrated after ~103 yr, in spite of mixing by convection, which transports material between the surface and midplane on timescales of ~30 yr, and radially inward and outward as well. Mixing caused by a generic turbulent viscosity dominates only when α ≥ 0.01, implying that the effective α of the convective motions and gravitational torques is α ~ 10-3. The three-dimensional models show that spatial heterogeneity can persist in a disk evolving by gravitational torques for significant periods, even in the most dynamically active region. This period, ~103 yr, is similar to the timescale for presolar dust grains to coagulate while settling to the midplane and growing to centimeter size. If such solids can be preserved and incorporated into chondrites, then it is conceivable that some observed isotopic anomalies could have been derived from a spatially heterogeneous nebula.
Cirrus Cloud Simulation Using Explicit Microphysics and Radiation. Part II: Microphysics, Vapor and Ice Mass Budgets, and Optical and Radiative Properties

Abstract The 2D/3D cloud model complex with explicit microphysics and radiation described in Part I is used to simulate the development of a midlatitude cirrus cloud, including interaction with radiation. To account for the effects of the interaction of various scales of motion on cloud development, a synoptic-scale vertical velocity field is superimposed on the mesoscale velocity field generated by the model, mimicking the effects of an upper-level shortwave trough. The main results under the conditions simulated here are the following. Cirrus cloud growth is much slower than assumed previously, because the process of vapor deposition to ice crystals is far from instantaneous: the crystal phase relaxation time (i.e., the characteristic time of vapor absorption by crystals) takes 0.5–2.0 h. Even after 1 h of cloud development, supersaturation with respect to ice can remain 5%–10%, while the condensed ice is only 40%–60% of the amount that would be realized assuming that all excess vapor is transformed int.
Magnetic field variations in the Jovian magnetotail induced by solar wind dynamic pressure enhancements

[1] In order to understand the response of the Jovian magnetosphere to solar wind dynamic pressure enhancements, we investigate magnetic field variations observed by the Galileo spacecraft. The lack of solar wind monitoring just upstream of the Jovian magnetosphere is overcome by simulating a one-dimensional magnetohydrodynamic (MHD) propagation of the solar wind from the Earth. We identify the events with an increase of the solar wind dynamic pressure >0.25 nPa at the Jovian orbit. Characteristic magnetic field variations are found in the Jovian magnetosphere for all of the nine events. The rectangular waveform due to the Jovian rotation disappears for eight of the nine events. Magnetic field disturbances in the frequency range from 0.3 to 10 mHz are enhanced simultaneously. The maximum amplitude of the disturbances is in proportional to the maximum amplitude of the solar wind dynamic pressure. We suggest that the current sheet is greatly deformed and reconnection bursts are induced under the compressed magnetosphere.
A proof of Whitman’s representation theorem for finite lattices

The theorem to be proved states that every finite lattice is isomorphic to a sublattice of the lattice 8 (S) of all equivalence relations on a countable set S. Our proof combines concreteness with freedom from long routine computations. Earlier proofs appear in [1 ] and [2 ]. Let L be a finite lattice. Without loss of generality assume that the elements of L are subsets of {1, **, m}, that the unit and zero of L are {1, , m} and 4 respectively, and that the meet operation of L is set intersection. Write V for the join in L, U for set union. If r = (a1, , am) CNm define (r)z=aI (1= 1, , i); if r, sENm and cx-L define r =,s , (r) = (s)1 for all lIea; finally let y (r, s) be the greatest y L such that r_s if there is a greatest such y, y(r, s) undefined otherwise. It is sufficient to find a set SCNm such that the equivalence relations-form a sublattice of 8(S) dually isomorplhic to L, which will certainly be the case if: I. For each a, fC-L with aofl there are r, sCS such that r=,s but r # as. II. -y(r, s) is defined for all r, sEES. III. For each r, sES and a,fC.L such that r-afnos, there are u, v, w E S such that r-=-_ v-=w _= ,S. Now it is easy to construct a finite SoCNm satisfying I and II. Suppose SnCNm is finite and satisfies I and II. If Sn also satisfies III let S+,=S,. If not let r, sES, and a, f3CL be the least (in some previously fixed well-ordering of type X of Nm X Nm XL XL) counterexample to III. Define w C Nm by (w)j = (s) I if I E f, b5 if I ([-f where bCN is distinct from all (q)z with qESn. Then for all qESn, ,y(q, w) =flnQy(q, s). Thus S ' =Sn U{w} still satisfies I and II. Now define u, vENm by Received by the editors December 12, 1969. AMS Subject Classifications. Primary 0630.
Magnetic Free Energies of Breakout Coronal Mass Ejections

A critical issue in understanding and eventually predicting coronal mass ejections (CMEs) is determining the magnetic free energy that can drive the explosive eruption. We present calculations of this free energy for the breakout CME model, which postulates that the preeruption magnetic topology is a multipolar field with a null point in the corona. Using analytical and numerical methods, we determine the free energies for two broad families of photospheric flux distributions, parameterized by the radius of the coronal null and the degree to which flux is concentrated near the poles and equator. The available CME energy attains a broad maximum for distributions whose potential null resides between about 1.25 and 1.75 solar radii, and falls off toward zero as the null approaches the surface or moves out to infinity. These results may explain the wide range of energies observed for CMEs and their associated flares. We find that concentrating the surface flux to narrower latitude bands near the poles and equator, on the other hand, has little effect on the available energy. Our mathematical approach currently is restricted to spherically axisymmetric systems. Its generalization to fully three-dimensional fields might provide the foundation of a first-principles forecasting technique for solar eruptions.
Evaluation of WRF Model Simulations of Tornadic and Nontornadic Outbreaks Occurring in the Spring and Fall

Recent studies, investigating the ability to use the Weather Research and Forecasting (WRF) model to distinguish tornado outbreaks from primarily nontornadic outbreaks when initialized with synoptic-scale data, have suggested that accurate discrimination of outbreak type is possible up to three days in advance of the outbreaks. However, these studies have focused on the most meteorologically significant events without regard to the season in which the outbreaks occurred. Because tornado outbreaks usually occur during the spring and fall seasons, whereas the primarily nontornadic outbreaks develop predominantly during the summer, the results of these studies may have been influenced by climatological conditions (e.g., reduced shear, in the mean, in the summer months), in addition to synoptic-scale processes. This study focuses on the impacts of choosing outbreaks of severe weather during the same time of year. Specifically, primarily nontornadic outbreaks that occurred during the summer have been replaced with outbreaks that do not occur in the summer. Subjective and objective analyses of the outbreak simulations indicate that the WRF’s capability of distinguishing outbreak type correctly is reduced when the seasonal constraints are included. However, accuracy scores exceeding 0.7 and skill scores exceeding 0.5 using 1-day simulation fields of individual meteorological parameters, show that precursor synoptic-scale processes play an important role in the occurrence or absence of tornadoes in severe weather outbreaks. Low-level stormrelative helicity parameters and synoptic parameters, such as geopotential heights and mean sea level pressure, appear to be most helpful in distinguishing outbreak type, whereas thermodynamic instability parameters are noticeably both less accurate and less skillful.
On the global existence and small dispersion limit for a class of complex Ginzburg–Landau equations

In this paper we consider a class of complex Ginzburg–Landau equations. We obtain sufficient conditions for the existence and uniqueness of global solutions for the initial‐value problem in d‐dimensional torus 𝕋d, and that solutions are initially approximated by solutions of the corresponding small dispersion limit equation for a period of time that goes to infinity as dispersive coefficient goes to zero. Copyright © 2008 John Wiley & Sons, Ltd.
Algebraically Stable and Implementable Runge-Kutta Methods of High Order

There are three interesting properties of methods for (stiff) ordinary differential equations: order, stability and efficiency of implementation. This paper constructs Runge–Kutta methods of orders 5 and 6 which possess these properties to a high extent. We further classify all algebraically stable methods of an arbitrary order and give various relationships between contractivity and order of implicit methods.
Steady-state and transient electron transport within bulk wurtzite indium nitride: An updated semiclassical three-valley Monte Carlo simulation analysis

Recent experimentation, performed on bulk wurtzite InN, suggests that the energy gap, the effective mass of the electrons in the lowest-energy valley, and the nonparabolicity coefficient of the lowest-energy valley are not as originally believed for this material. Using a semiclassical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk wurtzite InN using a revised set of material parameters, this revised set of parameters taking into account this recently observed phenomenology. We find that the peak electron drift velocity is considerably greater than that found previously. The impact that this revised set of parameters has upon the transient electron transport is also found to be significant.
Improved quantitative description of Auger recombination in crystalline silicon

An accurate quantitative description of the Auger recombination rate in silicon as a function of the dopant density and the carrier injection level is important to understand the physics of this fundamental mechanism and to predict the physical limits to the performance of silicon based devices. Technological progress has permitted a near suppression of competing recombination mechanisms, both in the bulk of the silicon crystal and at the surfaces. This, coupled with advanced characterization techniques, has led to an improved determination of the Auger recombination rate, which is lower than previously thought. In this contribution we present a systematic study of the injection-dependent carrier recombination for a broad range of dopant concentrations of high-purity n-type and p-type silicon wafers passivated with state-of-the-art dielectric layers of aluminum oxide or silicon nitride. Based on these measurements, we develop a general parametrization for intrinsic recombination in crystalline silicon at 300 K consistent with the theory of Coulomb-enhanced Auger and radiative recombination. Based on this improved description we are able to analyze physical aspects of the Auger recombination mechanism such as the Coulomb enhancement.
Hadron-induced reactions: From basic research to new technological applications

We focus on nucleon- and pion-induced reactions on light elements, over the energy range from MeVs to GeVs. We discuss their significance in several important technological applications: 1) single event upsets (SEUs) in microelectronic systems, and 2) particle-beam radiology. We describe the work of nuclear modeling at IBM (NUSPA model) which is applied to simulations of cosmic-ray-induced SEUs at the device and circuit levels. We discuss some current modeling issues. The modeling of recoil spectra of 80 MeV proton on Si is stringently tested by a recent experiment at the National Superconducting Cyclotron Laboratory of Michigan State University, using reverse kinematics. We also report new simulation results of thick targets irradiated by high-energy protons (50–250 MeV). They show significant secondary radiation due to nuclear fragments, a basic problem, which up till now, has not been systematically tackled. We discuss the implications of these results on future SEU studies and radiation-related problems.
Atomic Data for Resonance Absorption Lines. III. Wavelengths Longward of the Lyman Limit for the Elements Hydrogen to Gallium

This compilation revises the 1991 listing of atomic data for the lighter elements from hydrogen to gallium. The tabulation emphasizes resonance lines, i.e., lines whose lower level is the ground state, or an excited fine-structure state of the ground term, and is restricted to wavelengths longward of the H I Lyman limit at 911.753 Å. All but the very weakest known and predicted electric-dipole transitions are included, but no forbidden lines. This paper has attempted to review all data published by the end of 2002. The tables contain the best data available to the author on ionization potentials, level designations, vacuum and air wavelengths, lower and upper energy levels, statistical weights, transition probabilities, natural damping constants (reciprocal lifetimes), oscillator strengths, and the often used combinations of log gf and log λf. All ion stages with relevant classified lines are included. Individual components resulting from isotope shift and hyperfine structure are listed explicitly for certain species. The accompanying text provides references, explanations for the critical selection of data, and notes indicating where new measurements or calculations are needed. This compilation should be particularly useful in the analysis of interstellar and quasar absorption lines and other astrophysical sites where the density of particles and radiation is low enough to excite only the lowest atomic levels. The data also are relevant to the study of stellar atmospheres, and gaseous nebulae. An Appendix summarizes new data relevant to the similar compilation in Paper II for the elements germanium to uranium.