Dust and gas jets: Evidence for a diffuse source in Halley's coma

The distribution of dust-scattered intensity in Halley's inner coma is measured with the Vega three-channel spectrometer at three selected wavelengths: 377, 482, and 607 nm. The variation along a cometo-centric radius may be described by a p(sup -s) law where p is the distance between nucleus and optical axis and s is an exponent which is equal to 1 except in an intermediate 3000 less than p less than 7000 km region where s = 1.5. The shape of the radial distribution may be explained with a model including solar radiation pressure effect and quantum scattering efficiencies calculated from Mie theory. Monochromatic images inside an angular sector having its apex at the nucleus show evidence of two dust jets which extend to 40,000 Km. The pixel-to-pixel ratio of two images of dust intensity at 377 and 482 nm shows that the scattered intensity presents an excess of blue coloration in a zone located around the jets between 10,000 and 25,000 km. This coloration is interpreted as being due to a population of sub-micronic grains which result of the fragmentation of dust particles transported in the jets. It is suggested that the diffuse source where an additional quantity of CO was detected might be connected with the presence of a dust jet. In the present scheme, grain particles with a size of several micron or 10 micron would be transported inside a dust jet to distances of several 10,000 km where they would suffer fragmentation and produce sub-micronic particles and a release of gas which would be at the origin of the diffuse source

The Omega Counter, a Frequency Counter Based on the Linear Regression

This article introduces the {\Omega} counter, a frequency counter -- or a frequency-to-digital converter, in a different jargon -- based on the Linear Regression (LR) algorithm on time stamps. We discuss the noise of the electronics. We derive the statistical properties of the {\Omega} counter on rigorous mathematical basis, including the weighted measure and the frequency response. We describe an implementation based on a SoC, under test in our laboratory, and we compare the {\Omega} counter to the traditional {\Pi} and {\Lambda} counters. The LR exhibits optimum rejection of white phase noise, superior to that of the {\Pi} and {\Lambda} counters. White noise is the major practical problem of wideband digital electronics, both in the instrument internal circuits and in the fast processes which we may want to measure. The {\Omega} counter finds a natural application in the measurement of the Parabolic Variance, described in the companion article arXiv:1506.00687 [physics.data-an].Comment: 8 pages, 6 figure, 2 table

The Parabolic variance (PVAR), a wavelet variance based on least-square fit

This article introduces the Parabolic Variance (PVAR), a wavelet variance similar to the Allan variance, based on the Linear Regression (LR) of phase data. The companion article arXiv:1506.05009 [physics.ins-det] details the $\Omega$ frequency counter, which implements the LR estimate. The PVAR combines the advantages of AVAR and MVAR. PVAR is good for long-term analysis because the wavelet spans over $2 \tau$, the same of the AVAR wavelet; and good for short-term analysis because the response to white and flicker PM is $1/\tau^3$ and $1/\tau^2$, same as the MVAR. After setting the theoretical framework, we study the degrees of freedom and the confidence interval for the most common noise types. Then, we focus on the detection of a weak noise process at the transition - or corner - where a faster process rolls off. This new perspective raises the question of which variance detects the weak process with the shortest data record. Our simulations show that PVAR is a fortunate tradeoff. PVAR is superior to MVAR in all cases, exhibits the best ability to divide between fast noise phenomena (up to flicker FM), and is almost as good as AVAR for the detection of random walk and drift

Evolution of near UV Halley's spectrum in the inner coma

A direct way to observe the photodissociation of water vapor in a cometary coma is to detect the OH prompt emission. This emission is shifted of delta lambda = 4 nm with respect to the OH 309 nm fluorescence band. The extended data set obtained with the three-channel spectrometer on-board Vega 2 reveals at short distance of the nucleus (i.e., less than 600 km) an excess of emission on the right wing of the OH band which may be interpreted as being mainly due to prompt emission

Noise and drift analysis of non-equally spaced timing data

Generally, it is possible to obtain equally spaced timing data from oscillators. The measurement of the drifts and noises affecting oscillators is then performed by using a variance (Allan variance, modified Allan variance, or time variance) or a system of several variances (multivariance method). However, in some cases, several samples, or even several sets of samples, are missing. In the case of millisecond pulsar timing data, for instance, observations are quite irregularly spaced in time. Nevertheless, since some observations are very close together (one minute) and since the timing data sequence is very long (more than ten years), information on both short-term and long-term stability is available. Unfortunately, a direct variance analysis is not possible without interpolating missing data. Different interpolation algorithms (linear interpolation, cubic spline) are used to calculate variances in order to verify that they neither lose information nor add erroneous information. A comparison of the results of the different algorithms is given. Finally, the multivariance method was adapted to the measurement sequence of the millisecond pulsar timing data: the responses of each variance of the system are calculated for each type of noise and drift, with the same missing samples as in the pulsar timing sequence. An estimation of precision, dynamics, and separability of this method is given

Dispersion relations for the time-fractional Cattaneo-Maxwell heat equation

In this paper, after a brief review of the general theory of dispersive waves in dissipative media, we present a complete discussion of the dispersion relations for both the ordinary and the time-fractional Cattaneo-Maxwell heat equations. Consequently, we provide a complete characterization of the group and phase velocities for these two cases, together with some non-trivial remarks on the nature of wave dispersion in fractional models.Comment: 18 pages, 7 figure

PHYCOBILISOMES AND ISOLATED PHYCOBILIPROTEINS. EFFECT OF GLUTARDIALDEHYDE AND BENZOQUINONE ON FLUORESCENCE

The fluorescence of the biliproteins C-phycocyanin from Spirulina platensis, B-phycoerythrin from Porphyridium cruentum and of isolated whole P. cruentum phycobilisomes is quenched in the presence of glutardialdehyde (GA) or benzoquinone (BQ). The kinetics of fluorescence decrease thus induced is biphasic. If GA is used as a quencher, the fluorescence can be recovered at 77 K. Contrary to the GA-effect, only a minor recovery takes place with BQ at 77K, thus demonstrating a different mechanism of action of GA and BQ on biliprotein

Nonstationary heat conduction in one-dimensional models with substrate potential

The paper investigates non-stationary heat conduction in one-dimensional models with substrate potential. In order to establish universal characteristic properties of the process, we explore three different models --- Frenkel-Kontorova (FK), phi4+ ($\phi^4$+) and phi4- ($\phi^4-$). Direct numeric simulations reveal in all these models a crossover from oscillatory decay of short-wave perturbations of the temperature field to smooth diffusive decay of the long-wave perturbations. Such behavior is inconsistent with parabolic Fourier equation of the heat conduction and clearly demonstrates the necessity of hyperbolic models. The crossover wavelength decreases with increase of average temperature. The decay patterns of the temperature field almost do not depend on the amplitude of the perturbations, so the use of linear evolution equations for temperature field is justified. In all model investigated, the relaxation of thermal perturbations is exponential -- contrary to linear chain, where it follows a power law. However, the most popular lowest-order hyperbolic generalization of the Fourier law, known as Cattaneo-Vernotte (CV) or telegraph equation (TE) is not valid for description of the observed behavior of the models with on-site potential. In part of the models a characteristic relaxation times exhibit peculiar scaling with respect to the temperature perturbation wavelength. Quite surprisingly, such behavior is similar to that of well-known model with divergent heat conduction (Fermi-Pasta-Ulam chain) and rather different from the model with normal heat conduction (chain of rotators). Thus, the data on the non-stationary heat conduction in the systems with on-site potential do not fit commonly accepted concept of universality classes for heat conduction in one-dimensional models.Comment: 9 pages, 7 figures, corrected versio

Comparison of low--energy resonances in 15N(alpha,gamma)19F and 15O(alpha,gamma)19Ne and related uncertainties

A disagreement between two determinations of Gamma_alpha of the astro- physically relevant level at E_x=4.378 MeV in 19F has been stated in two recent papers by Wilmes et al. and de Oliveira et al. In this work the uncertainties of both papers are discussed in detail, and we adopt the value Gamma_alpha=(1.5^{+1.5}_{-0.8})10^-9eV for the 4.378 MeV state. In addition, the validity and the uncertainties of the usual approximations for mirror nuclei Gamma_gamma(19F) approx Gamma_gamma(19Ne), theta^2_alpha(19F) approx theta^2_alpha(19Ne) are discussed, together with the resulting uncertainties on the resonance strengths in 19Ne and on the 15O(alpha,gamma)19Ne rate.Comment: 9 pages, Latex, To appear in Phys. Rev.