Miracle-dz/UniFAR-FTUs huggingface dataset:
Some Helical Structures Generated by Reflexions

There has recently been a revival of interest in the helical structure built up as a column of face-sharing tetrahedra, because of possible applications in structural crystallography (Nelson 1983). This structure and its analogues in spaces of different dimensions are investigated here. It is shown that the only crystallographic cases are the structures in one- and two-dimensional space. For three and higher dimensional space the structures are all non-crystallographic. For the physically important case of three dimensions, this result is implicit in an early discussion by Coxeter (1969). Results obtained here include explicit formulae for the positions of all vertices of the simplexes for dimensions n = 1-4 and a demonstration that, for arbitrary n, the ratio of the translation component of the screw to the edge of the simplex is {6/ n(n+ I)(n+ 2)}1/2
New insights into the dust properties of the Taurus molecular cloud TMC-2 and its surroundings

We present ISOPHOT observations at 120 and 200 μm of a 31 x 57 arcmin 2 region, with optical extinction Av ranging between 0.5 and 11 mag, that encloses the Taurus molecular cloud TMC-2. The far-infrared emission is separated into a warm and a cold component using the ISOPHOT data and IRAS measurements at 60 and 100 μm. This separation is based on the very different morphologies of the 60 and 200 μm emission maps. The 60 μm emission is used as a spatial template for the warm component, and the 200 μm emission [I v (200)] as a template for the cold component. The warm component presents an average colour temperature of nearly 20 K. The colour temperature map of the cold component is nearly uniform, with a mean temperature of 12.5 K. The optical depths at 200 μm of the warm and cold components (τ 200 ) were determined. The ratios I v (200)/A V and τ 200 /A V of the cold component indicate changes in the optical properties of the dust grains, which present a far-infrared emissivity that is a few times larger than that of the big grains in the diffuse interstellar medium. Comparisons of the emissions and τ 200 of the cold component with carbon monoxide measurements, which trace the molecular gas, were performed. The cold component emission, in particular at 100 μm, correlates very well with 13 CO (J = 1-0) total intensity. Very good correlations between C 18 O(J = 1-0) total intensity and especially τ 200 are found for two distinct regions, one that encloses the core TMC-2 and a northern region that also contains molecular condensations. These results confirm that τ 200 is a powerful tracer of dense cores with n(H 2 ) 10 4 cm -3 , and that the change in the properties of dust grains in the observed region takes place at densities of n(H 2 ) 10 3 cm -3 .
Pseudo-Frobenius Rings: Characterizations and Questions

Abstract Let Rbe a ring with second singular right ideal and second singular left ideal . Motivated by a result in Zhou (Zhou, Y. (2002). Rings in which certain right ideals are direct summands of annihilators. J. Australian Math. Soc. , Ser. A73:335–346 that Ris a two-sided pseudo-Frobenius ring iff Ris a two-sided Kasch ring such that both ( ) R and R ( ) are injective, we consider when a right (or two-sided) Kasch ring Rsuch that ( ) R is injective is right pseudo- Frobenius. Our study leads to a number of new characterizations of one-sided (or two-sided) pseudo-Frobenius rings. Some questions on pseudo-Frobenius rings are listed at the end of the paper.
Anisotropic Radio Scattering of NGC 6334B

The extragalactic radio source NGC 6334B is the most strongly scattered object known, with an angular size of 3'' at 20 cm wavelength. Its angular size scales as the square of the observing wavelength, and its phase structure function has a power-law dependence on projected baseline length. These properties suggest that NGC 6334B is a point source, probably a quasar, scatter broadened by an intervening region of turbulent plasma. The line of sight to the source intercepts the northern lobe of the bipolar H II region NGC 6334A, which is probably the source of the scattering. We discuss observations of NGC 6334B with the VLA at 1.4, 2, 6, 20, and 90 cm, and with the VLBA at 1.4, 3.6, and 6 cm. The VLA observations indicate that the scattering disk of NGC 6334B is anisotropic, with an axial ratio of ~1.2 at 20 and 6 cm, and ~1.5 at 2 cm. This anisotropy is probably due to the effects of a magnetic field in the scattering medium. The position angle of the scattering disk implies that the mean projected magnetic field direction is parallel to the outflow from NGC 6334A. The position angle of the scattering disk rotates slightly between 6 and 2 cm; we use this rotation to place an upper limit on the outer scale of turbulence, rout ≲ 1016 cm. We present a new algorithm to detect the presence of weak (<3 σ) fringes in interferometric data. Detections of low-level excess visibility on long VLBA baselines at 3.6 cm place an upper limit on the inner dissipative scale of turbulence rin of 1011-12 cm, while the baseline scaling of fringe visibility amplitude and the wavelength scaling of scattering-disk size place a lower limit on rin of 5 × 106 cm. Nearby high-velocity (-80 km s-1) H2O maser features show little sign of broadening, implying that they are in front of, or less than 100 pc behind, the scattering region.
INTERACTION BETWEEN $alpha$-PARTICLES.

Effective alpha - alpha potential is investigated from the standpoint of the cluster model using reliable properties of the pion-theoretical nucleon- nucleon potentials. The main features of alpha - alpha potential (outside attraction, inside repulsion, and angular momentum dependence) demanded from the analyses of low energy alpha - alpha scattering phenomena can be qualitatively reproduced. In constructing the alpha - alpha potential, the importance of the Pauli principle, which damps the relative wave function of two alpha -particles at small alpha - alpha distances, should be emphasized. Its connection with nucleon-nucleon potentials is discussed.
Effect of carbon on hydrogen behaviour in tungsten: first-principle calculations

Using the first-principle method, we investigated the effect of tungsten carbide (WC) surface layers on hydrogen retention in W. The results showed that C is not capable of capturing H atoms efficiently because of Coulomb repulsion between negatively charged C and H atoms in tungsten. Meanwhile, the repulsive force enhances the migration barrier for H to travel through WC layers. The high barrier, therefore, prevents the implanted H from escaping the W matrix. With H implanted continually, more and more H atoms are accumulated in the bulk and diffuse far from the WC layer, which contributes to blister formation in W.
A One-Dimensional Entraining/Detraining Plume Model and Its Application in Convective Parameterization

Abstract A new one-dimensional cloud model, specifically designed for application in mesoscale convective parameterization schemes (CPSs), is introduced. The model is unique in its representation of environmental entrainment and updraft detrainment rates. In particular, the two-way exchange of mass between clouds and their environment is modulated at each vertical level by a buoyancy sorting mechanism at the interface of clear and cloudy air. The new entrainment/detrainment scheme allows vertical profiles of both updraft moisture detrainment and updraft vertical mass flux to vary in a physically realistic way as a function of the cloud-scale environment. These performance characteristics allow the parameterized vertical distribution of convective heating and drying to be much more responsive to environmental conditions than is possible with a traditional one-dimensional entraining plume model. The sensitivities of the new model to variations in environmental convective available potential energy and verti.
A Raman scattering investigation of the magnetic ordering in the two-dimensional triangular lattice antiferromagnet LiCrO2

Raman scattering experiments were performed on the two-dimensional triangular lattice antiferromagnet LiCrO2 to investigate its magnetic ordering. Besides two phonon lines which are assigned to the Eg and the A1g modes of D3d point symmetry, additional lines having broader linewidth than that of the phonon lines are observed at low temperatures. Their intensity becomes weak with increasing temperature, but they are still observable above TN=62 K, a value that was determined by neutron diffraction experiments, and only become unobservable at around 150 K. The lines are found to correspond to two-magnon lines when a 120 degrees Neel structure is assumed. A possible effect of the Z2 vortex on two-magnon lines in a two-dimensional triangular lattice Heisenberg antiferromagnet is discussed.
A latent trait and a latent class model for mixed observed variables

Latent variable models are widely used in social sciences in which interest is centred on entities such as attitudes, beliefs or abilities for which there exist no direct measuring instruments. Latent modelling tries to extract these entities, here described as latent (unobserved) variables, from measurements on related manifest (observed) variables. Methodology already exists for fitting a latent variable model to manifest data that is either categorical (latent trait and latent class analysis) or continuous (factor analysis and latent profile analysis). In this paper a latent trait and a latent class model are presented for analysing the relationships among a set of mixed manifest variables using one or more latent variables. The set of manifest variables contains metric (continuous or discrete) and binary items. For the latent trait model the latent variables are assumed to follow a multivariate standard normal distribution. Our method gives maximum likelihood estimates of the model parameters and standard errors of the estimates by analysing the data as they are without using any underlying variables. The mixed latent trait and latent class models are fitted using an EM algorithm. To illustrate the use of the mixed model three data sets have been analysed. Two of the data sets contain five memory questions, the first on Thatcher's resignation and the second on the Hillsborough football disaster; these five questions were included in British Market Research Bureau International August 1993 face-to-face omnibus survey. The third data set is from the 1991 British Social Attitudes Survey; the questions which have been analysed are from the environment section.
Exploring the colours of dark light

A previously calculated universal pattern (Berry M V 2002 New J. Phys. 4 66) describes colours near an isolated phase singularity (diffraction zero), generated with white light and visible when the dark light of the singularity is scaled to isoluminance. Here the pattern is illustrated in several different situations: near the zeros of random and regular superpositions of plane waves, and near the zeros inside and outside the diffraction pattern decorating the geometrical cusp catastrophe. The universal colours emerge in miniature, close to the zeros, when an initially achromatic diffraction pattern is perturbed by switching on an asymptotic `chromaticity parameter', that can be chosen in several different ways.
An estimate for the sum of a Dirichlet series in terms of the minimum of its modulus on a vertical line segment

The behaviour of the sum of an entire Dirichlet series is analyzed in terms of the minimum of its modulus on a system of vertical line segments. Also a more general problem, connected with the Pólya conjecture is posed and solved. It concerns the minimum modulus of an entire function with Fabri gaps and its growth along curves going to infinity. Bibliography: 33 titles.
On a problem connected with quadratic regression

E(Y) = flo +/3lE(X) + . +4kE(Xk). (1.2) If k 2 and f2 t 0 (k = 1 and Ih1 + 0) then we speak of quadratic (linear) regression. If k = 0, that is if E( YjX) = E( Y) almost everywhere, then we say that Y has constant regression on X. The coefficients ,80, ,l1, . , Ak are called the regression coefficients. Let X1, X2, . , Xn be a sample of size n (independently and identically distributed random variables) from a population with distribution function F(x). We write
Development of a wearable microwave bladder monitor for the management and treatment of urinary incontinence

Urinary incontinence is defined as the inability to stop the flow of urine from the bladder. In the US alone, the annual societal cost of incontinence-related care is estimated at 12.6 billion dollars. Clinicians agree that those suffering from urinary incontinence would greatly benefit from a wearable system that could continually monitor the bladder, providing continuous feedback to the patient. While existing ultrasound-based solutions are highly accurate, they are severely limited by form-factor, battery size, cost and ease of use. In this study the authors propose an alternative bladder-state sensing system, based on Ultra Wideband (UWB) Radar. As part of an initial proof-of-concept, the authors developed one of the first dielectrically and anatomically-representative Finite Difference Time Domain models of the pelvis. These models (one male and one female) are derived from Magnetic Resonance images provided by the IT'IS Foundation. These IT'IS models provide the foundation upon which an anatomically-plausible bladder growth model was constructed. The authors employed accurate multi-pole Debye models to simulate the dielectric properties of each of the pelvic tissues. Two-dimensional Finite Difference Time Domain (FDTD) simulations were completed for a range of bladder volumes. Relevant features were extracted from the FDTD-derived signals using Principle Component Analysis (PCA) and then classified using a k-Nearest-Neighbour and Support Vector Machine algorithms (incorporating the Leave-one-out cross-validation approach). Additionally the authors investigated the effects of signal fidelity, noise and antenna movement relative to the target as potential sources of error. The results of this initial study provide strong motivation for further research into this timely application, particularly in the context of an ageing population.
Inscribing the Winch: Mechanisms by Which Students Develop Knowledge Structures for Representing the Physical World With Algebra

I propose and test an account of mechanisms by which students develop knowledge structures for modeling the physical world with algebra. The account begins to bridge the gap between current mathematics curricula, in which modeling activities play an important role, and theoretical accounts of how students learn to model, which lag behind. After describing the larger study, in which I observed 12 pairs of 8th-grade students introduce and refine algebraic representations of a physical device called a winch, I then focus on 1 pair that generated an unconventional yet sound equation. Because the prevailing genetic accounts of knowledge structures in mathematics education, cognitive science, and information-processing psychology do not explain key characteristics of the data, I begin to construct a new developmental account that does. To do so, I use forms, a class of schemata that combine patterns of algebra symbols with patterns of experience in the physical world, and 2 mechanisms, notation variation and mapping variation. I then use forms and the 2 mechanisms to analyze how the selected pair of students introduced and refined initial, faulty algebraic representations of the winch into an unconventional yet sound equation.
Towards Efficient Fully-Nonlinear Potential-Flow Solvers in Marine Hydrodynamics

Solving potential-flow problems using the Boundary Element Method (BEM) is a strong tradition in marine hydrodynamics. An early example of the application of BEM is by Bai & Yeung [1]. The bottleneck of the conventional BEM in terms of CPU time and computer memory arises as the number of unknowns increases. Wu & Eatock Taylor [2] suggested that the Finite Element Method (FEM) field solver is much faster than the BEM based on their comparisons in a wave making problem. In this paper, we aim to find a highly efficient method to solve fully-nonlinear wave-body interaction problems based on potential-flow theory. We compare the efficiency and the accuracy of five different methods for the potential flows in two dimensions (2D), two of which are BEM-based while the other three are field solvers. The comparisons indicate that it is beneficial to use either an accelerated matrix-free BEM, e.g. Fast Multipole Method accelerated BEM (FMM-BEM), or any field solvers whose resulting matrix are sparse.Another highlight of this paper is that an efficient numerical potential-flow method named the harmonic polynomial cell (HPC) method is developed. The flow in each cell is described by a set of harmonic polynomials. The presented procedure has approximately 4th order accuracy, while its resulting matrix is sparse similarly as the other field solvers, e.g. Finite Element Method (FEM), Finite Difference Method (FDM) and Finite Volume Method (FVM). The method is verified by a linear wave making problem for which the steady-state analytical solution is available, and the forced oscillation of a semi-submerged circular cylinder for which the frequency-domain added mass and damping coefficients are compared. The fully-nonlinear wave making problem and nonlinear propagating waves over a submerged bar are also studied for validation purposes. Only 2D cases are studied in this paper.Copyright © 2012 by ASME
Optical tweezers for free-solution label-free single bio-molecule studies

Nanoaperture based trapping has developed as a significant tool among the various optical tweezer systems for trapping of very small particles down to the single nanometer range. The double nanohole aperture based trap provides a method for efficient, highly-sensitive, label-free, low-cost, free-solution single molecule trapping and detection. We use the double nanohole tweezer to understand biomolecular phenomena like protein unfolding, binding, structural conformation of DNA, protein-DNA interactions, and protein small molecule interactions.
A MULTIPLE GENERALIZATION OF SLATER'S TRANSFORMATION FORMULA FOR A VERY-WELL-POISED-BALANCED 2rψ2r SERIES

The Jackson integral of type BC n is a multiple generalization of a very-well-poised-balanced 2r ψ 2r basic hypergeometric series. Based on this fact, a multiple analogue of Slater's transformation formula for the 2r ψ 2r series is presented herein. The proposed formula also provides an extension of Gustafson's multiple 6 ψ 6 summation formula of type C n .
LARGE ELASTIC COMPRESSION OF FINITE RECTANGULAR BLOCKS OF RUBBER

SUMMARY For the problem of large elastic compression of a finite rectangular rubber block which has bonded metal plates to its upper and lower surfaces, a new load-deflection relation is derived assuming an isotropic incompressible Mooney material and that the pointwise vanishing of the stress on the free faces can be replaced by the vanishing of the force resultant on these faces. The load-deflection relation so obtained is derived from a fully three-dimensional deformation which is a generalization of a plane-strain deformation given previously for infinitely long rectangular rubber pads. The 'finite' and 'infinite' load-deflection relations are compared with experimental results and with that predicted by the conventional engineering approximation deduced from the so-called 'shape-factor' method.
Flow past a sphere up to a Reynolds number of 300

The flow of an incompressible viscous fluid past a sphere is investigated numerically and experimentally over flow regimes including steady and unsteady laminar flow at Reynolds numbers of up to 300. Flow-visualization experiments are used to validate the numerical results and to provide additional insight into the behaviour of the flow. Near-wake visualizations are presented for both steady and unsteady flows. Calculations for Reynolds numbers of up to 200 show steady axisymmetric flow and compare well with previous experimental and numerical observations. For Reynolds numbers of 210 to 270, a steady non-axisymmetric regime is found, also in agreement with previous work. To advance the basic understanding of this transition, a symmetry breaking mechanism is proposed based on a detailed analysis of the calculated flow field. Unsteady flow is calculated at Reynolds numbers greater than 270. The results at a Reynolds number of 300 show a highly organized periodic flow dominated by vortex shedding. An analysis of the calculated vortical structure of the wake reveals a sequence of shed hairpin vortices in combination with a sequence of previously unidentified induced hairpin vortices. The numerical results compare favourably with experimental flow visualizations which, interestingly, fail to reveal the induced vortices. Based on the deduced symmetry-breaking mechanism, an analysis of the unsteady kinematics, and the experimental results, a mechanism driving the transition to unsteady flow is proposed.
Impedance spectroscopy and dielectric behavior in barium strontium titanate–nickel zinc ferrite composites

Polycrystalline composites of (1−x) (Ba0.7Sr0.3TiO3)–x(Ni0.5Zn0.5Fe2O4) (x = 0.00, 0.45, 1.00) were prepared by a modified wet chemical method followed by a high‐temperature sintering process. X‐ray diffraction (XRD) studies at room temperature confirmed the formation of perovskite‐spinel structure. Scanning electron micrographs suggest polycrystalline microstructure with grains of unequal size distributed throughout the samples. Dielectric studies of the composites reveal that the effect of ferrite in the composites is to shift the ferroelectric–non‐ferroelectric phase transition to the higher temperature side with a broadened Curie temperature transition. Complex impedance spectroscopy analysis indicated negative temperature coefficient of resistance behavior, identical to semiconductors. The conduction at low temperature is due to impurities, whereas at higher temperature it is due to polaron hopping.
Linear Finite Dynamical Systems

ABSTRACT A Linear Finite Dynamical System (LFDS) is a pair (E, f) where E is a finite dimensional space over a finite field k. A complete description of the dynamics of f, the behavior of f's iterates, is given, based on the natural decomposition of any linear map into a nilpotent and bijective components. The results can be used for studying the dynamics of any linear map.
The magnetic barrier at Venus

The magnetic barrier at Venus is a region within which the magnetic pressure dominates all other pressure contributions. The barrier is formed in the inner region of the dayside magnetosheath to transfer solar wind momentum flux to the ionosphere. Passes through the dayside magnetosheath and ionopause with Pioneer Venus have allowed us to probe the magnetic barrier directly. These passes have been used to construct altitude profiles of the barrier. Here we define the ionopause as the lower boundary of the barrier. The upper boundary is defined as the altitude where the magnetosheath magnetic pressure is equal to half of the upstream solar wind dynamic pressure corrected by the boundary normal angle. The magnetic barrier is strongest at the subsolar point and weakens as expected with increasing solar zenith angle. The existence of a north-south asymmetry in the barrier strength is also demonstrated. The magnetic barrier is about 200 km thick at the subsolar point and 800 km thick at the terminator, which is comparable with the so-called “mantle. ” We find that the magnetic barrier transfers most of the solar wind dynamic pressure to the ionosphere via the enhanced magnetic pressure. The convected field gasdynamic model is found to predict the correct bow shock location if the magnetic barrier is treated as the obstacle.