The Transition between Nonorthogonal Polarization Modes in PSR B2016+28 at 1404 MHz

Polarization observations of the radio emission from PSR B2016+28 at 1404 MHz reveal properties that are consistent with two, very different, interpretations of the pulsar's viewing geometry. The pulsar's average polarization properties show a rapid change in position angle (PA) near the pulse center, suggesting that the observer's sightline nearly intersects the star's magnetic pole. But single pulse, polarization observations of the pulsar show nearly orthogonal modes of polarization following relatively flat and parallel PA trajectories across the pulse, suggesting that the sightline is far from the pole. Additionally, PA histograms reveal a "modal connecting bridge", of unknown origin, joining the modal PA trajectories over much of the pulse and following the rapid PA change shown in the average data. The nonorthogonality of polarization modes is incorporated in a statistical model of radio polarization to account for the deviations from mode orthogonality that are observed in the pulsar. The model is used to interpret the rapid PA change and modal connecting bridge as a longitudinally-resolved transition between modes of nonorthogonal polarization. Thus, the modal PA trajectories are argued to reflect the pulsar's true viewing geometry. This interpretation is consistent with the pulsar's morphological classification, preserves the Radhakrishnan & Cooke model of pulsar radio emission, and avoids the complication that the modal connecting bridge might be produced by some other emission mechanism. The statistical model's ability to simulate the rich variety of polarization properties observed in the emission lends additional support to the model's applicability and its underlying assumption that the polarization modes occur simultaneously.Comment: Accepted for publication in Ap

In situ real-time analysis of alloy film composition and segregation dynamics with parallel detection reflection electron energy loss spectroscopy

Real-time measurements of GexSi1 – x/Si(001) composition and segregation dynamics in Sn/Si(001) in molecular beam epitaxy are demonstrated using parallel detection reflection electron energy loss spectroscopy. Parallel detection enables quantitative acquisition of low-loss spectra in a time of < 500 µs and surface composition determination in GexSi1 – x/Si(001) via Ge L2,3 core loss analysis to a precision of approximately 2% in time of order 1 s. Segregation and trapping kinetics of monolayer thickness Sn films during Si epitaxy on Sn-covered Si(100) has also been studied using the Sn M4.5 core loss

Stochastic models which separate fractal dimension and Hurst effect

Fractal behavior and long-range dependence have been observed in an astonishing number of physical systems. Either phenomenon has been modeled by self-similar random functions, thereby implying a linear relationship between fractal dimension, a measure of roughness, and Hurst coefficient, a measure of long-memory dependence. This letter introduces simple stochastic models which allow for any combination of fractal dimension and Hurst exponent. We synthesize images from these models, with arbitrary fractal properties and power-law correlations, and propose a test for self-similarity.Comment: 8 pages, 2 figure

On Multifractal Structure in Non-Representational Art

Multifractal analysis techniques are applied to patterns in several abstract expressionist artworks, paintined by various artists. The analysis is carried out on two distinct types of structures: the physical patterns formed by a specific color (``blobs''), as well as patterns formed by the luminance gradient between adjacent colors (``edges''). It is found that the analysis method applied to ``blobs'' cannot distinguish between artists of the same movement, yielding a multifractal spectrum of dimensions between about 1.5-1.8. The method can distinguish between different types of images, however, as demonstrated by studying a radically different type of art. The data suggests that the ``edge'' method can distinguish between artists in the same movement, and is proposed to represent a toy model of visual discrimination. A ``fractal reconstruction'' analysis technique is also applied to the images, in order to determine whether or not a specific signature can be extracted which might serve as a type of fingerprint for the movement. However, these results are vague and no direct conclusions may be drawn.Comment: 53 pp LaTeX, 10 figures (ps/eps

Relativistic theory of tidal Love numbers

In Newtonian gravitational theory, a tidal Love number relates the mass multipole moment created by tidal forces on a spherical body to the applied tidal field. The Love number is dimensionless, and it encodes information about the body's internal structure. We present a relativistic theory of Love numbers, which applies to compact bodies with strong internal gravities; the theory extends and completes a recent work by Flanagan and Hinderer, which revealed that the tidal Love number of a neutron star can be measured by Earth-based gravitational-wave detectors. We consider a spherical body deformed by an external tidal field, and provide precise and meaningful definitions for electric-type and magnetic-type Love numbers; and these are computed for polytropic equations of state. The theory applies to black holes as well, and we find that the relativistic Love numbers of a nonrotating black hole are all zero.Comment: 25 pages, 8 figures, many tables; final version to be published in Physical Review

CD4+ T-cell responses to Epstein-Barr virus nuclear antigen EBNA1 in Chinese populations are highly focused on novel C-terminal domain-derived epitopes

Epstein-Barr virus nuclear antigen EBNA1, the one viral protein uniformly expressed in nasopharyngeal carcinoma (NPC), represents a prime target for T-cell-based immunotherapy. However, little is known about the EBNA1 epitopes, particularly CD4 epitopes, presented by HLA alleles in Chinese people, the group at highest risk for NPC. We analyzed the CD4$^+$ T-cell responses to EBNA1 in 78 healthy Chinese donors and found marked focusing on a small number of epitopes in the EBNA1 C-terminal region, including a DP5- restricted epitope that was recognized by almost half of the donors tested and elicited responses able to recognize EBNA1-expressing, DP5-positive target cells

Gravitational field and equations of motion of compact binaries to 5/2 post-Newtonian order

We derive the gravitational field and equations of motion of compact binary systems up to the 5/2 post-Newtonian approximation of general relativity (where radiation-reaction effects first appear). The approximate post-Newtonian gravitational field might be used in the problem of initial conditions for the numerical evolution of binary black-hole space-times. On the other hand we recover the Damour-Deruelle 2.5PN equations of motion of compact binary systems. Our method is based on an expression of the post-Newtonian metric valid for general (continuous) fluids. We substitute into the fluid metric the standard stress-energy tensor appropriate for a system of two point-like particles. We remove systematically the infinite self-field of each particle by means of the Hadamard partie finie regularization.Comment: 41 pages to appear in Physical Review

A rigorous formulation of the cosmological Newtonian limit without averaging

We prove the existence of a large class of one-parameter families of cosmological solutions to the Einstein-Euler equations that have a Newtonian limit. This class includes solutions that represent a finite, but otherwise arbitrary, number of compact fluid bodies. These solutions provide exact cosmological models that admit Newtonian limits but, are not, either implicitly or explicitly, averaged

On The Interaction Of D0-Brane Bound States And RR Photons

We consider the problem of the interaction between D0-brane bound state and 1-form RR photons by the world-line theory. Based on the fact that in the world-line theory the RR gauge fields depend on the matrix coordinates of D0-branes, the gauge fields also appear as matrices in the formulation. At the classical level, we derive the Lorentz-like equations of motion for D0-branes, and it is observed that the center-of-mass is colourless with respect to the SU(N) sector of the background. Using the path integral method, the perturbation theory for the interaction between the bound state and the RR background is developed. We discuss what kind of field theory may be corresponded to the amplitudes which are calculated by the perturbation expansion in world-line theory. Qualitative considerations show that the possibility of existence of a map between the world-line theory and the non-Abelian gauge theory is very considerable.Comment: LaTeX, 28 pages, 4 eps figures. v2 and v3: eqs. (3.18) and (B.2) are corrected, very small change

Gravitational-wave versus binary-pulsar tests of strong-field gravity

Binary systems comprising at least one neutron star contain strong gravitational field regions and thereby provide a testing ground for strong-field gravity. Two types of data can be used to test the law of gravity in compact binaries: binary pulsar observations, or forthcoming gravitational-wave observations of inspiralling binaries. We compare the probing power of these two types of observations within a generic two-parameter family of tensor-scalar gravitational theories. Our analysis generalizes previous work (by us) on binary-pulsar tests by using a sample of realistic equations of state for nuclear matter (instead of a polytrope), and goes beyond a previous study (by C.M. Will) of gravitational-wave tests by considering more general tensor-scalar theories than the one-parameter Jordan-Fierz-Brans-Dicke one. Finite-size effects in tensor-scalar gravity are also discussed.Comment: 23 pages, REVTeX 3.0, uses epsf.tex to include 5 postscript figures (2 paragraphs and a 5th figure added at the end of section IV + minor changes