Spatial Distributions of Cold and Warm Interstellar Dust in M101 Resolved with AKARI/Far-Infrared Surveyor (FIS)

The nearby face-on spiral galaxy M101 has been observed with the Far-Infrared Surveyor (FIS) onboard AKARI. The far-infrared four-band images reveal fine spatial structures of M101, which include global spiral patterns, giant HII regions embedded in outer spiral arms, and a bar-like feature crossing the center. The spectral energy distribution of the whole galaxy shows the presence of the cold dust component (18 K) in addition to the warm dust component (55 K). The distribution of the cold dust is mostly concentrated near the center, and exhibits smoothly distributed over the entire extent of the galaxy, whereas the distribution of the warm dust indicates some correlation with the spiral arms, and has spotty structures such as four distinctive bright spots in the outer disk in addition to a bar-like feature near the center tracing the CO intensity map. The star-formation activity of the giant HII regions that spatially correspond to the former bright spots is found to be significantly higher than that of the rest of the galaxy. The latter warm dust distribution implies that there are significant star-formation activities in the entire bar filled with molecular clouds. Unlike our Galaxy, M101 is a peculiar normal galaxy with extraordinary active star-forming regions.Comment: 18 pages, 9 figures, accepted for publication in PASJ AKARI special issu

Gait recognition based on shape and motion analysis of silhouette contours

This paper presents a three-phase gait recognition method that analyses the spatio-temporal shape and dynamic motion (STS-DM) characteristics of a human subject’s silhouettes to identify the subject in the presence of most of the challenging factors that affect existing gait recognition systems. In phase 1, phase-weighted magnitude spectra of the Fourier descriptor of the silhouette contours at ten phases of a gait period are used to analyse the spatio-temporal changes of the subject’s shape. A component-based Fourier descriptor based on anatomical studies of human body is used to achieve robustness against shape variations caused by all common types of small carrying conditions with folded hands, at the subject’s back and in upright position. In phase 2, a full-body shape and motion analysis is performed by fitting ellipses to contour segments of ten phases of a gait period and using a histogram matching with Bhattacharyya distance of parameters of the ellipses as dissimilarity scores. In phase 3, dynamic time warping is used to analyse the angular rotation pattern of the subject’s leading knee with a consideration of arm-swing over a gait period to achieve identification that is invariant to walking speed, limited clothing variations, hair style changes and shadows under feet. The match scores generated in the three phases are fused using weight-based score-level fusion for robust identification in the presence of missing and distorted frames, and occlusion in the scene. Experimental analyses on various publicly available data sets show that STS-DM outperforms several state-of-the-art gait recognition methods

Searches for sterile neutrinos with the IceCube detector

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320 GeV to 20 TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous nu(mu) or (nu) over bar (mu) disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3 + 1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin(2)2 theta(24) <= 0.02 at Delta m(2) similar to 0.3 eV(2) at the 90% confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99% confidence level for the global best-fit value of vertical bar U-e4 vertical bar(2)

New HST Observations of the Halo Gas of NGC 3067: Limits on the Extragalactic Ionizing Background at Low Redshift and the Lyman Continuum Escape Fraction

We present UV spectroscopy from HST/GHRS and reanalyze existing H_alpha images of the quasar/galaxy pair 3C 232/NGC 3067 and of the halo gas associated with NGC 3067. The spectra permit measurement of, or limits on, the column densities of Fe I, Fe II, Mg I, and Mg II in the absorbing cloud. Two distinct models of the extragalactic radiation field are considered: (1) the ionizing spectrum is dominated by a power-law extragalactic continuum, and (2) the power-law spectrum contains a Lyman break, implying enhanced flux longward of 912 A relative to the hydrogen-ionizing flux. The H_alpha images constrain the escape fraction of Lyman continuum photons from the galaxy to f_esc <= 0.02. With the assumption that the cloud is shielded from all galactic contributions, we can constrain the intensity and shape of the extragalactic continuum. For an AGN-dominated power-law extragalactic spectrum, we derive a limit on the extragalactic ionizing flux Phi_ion >= 2600 photons cm^-2 s^-1, or I_0 >= 10^-23 erg cm^-2 s^-1 Hz^-1 sr^-1 for an ionizing spectrum with power-law index of 1.8 and a cloud of constant density. When combined with previous upper limits from the absence of H_alpha recombination emission from intergalactic clouds, our observations require 2600 <= Phi_ion <= 10000 photons cm^-2 s^-1. We show that if galactic contributions to the incident radiation are important, it is difficult to constrain Phi_ion. These results demonstrate that galactic halo opacities and their wavelength dependence are crucial to understanding the abundance of low-ionization metals in the IGM.Comment: 25 Pages LaTex, 8 PostScript Figures, accepted for publication in AJ, Nov. 99 issu

Stochastic focusing coupled with negative feedback enables robust regulation in biochemical reaction networks

Nature presents multiple intriguing examples of processes which proceed at high precision and regularity. This remarkable stability is frequently counter to modelers' experience with the inherent stochasticity of chemical reactions in the regime of low copy numbers. Moreover, the effects of noise and nonlinearities can lead to "counter-intuitive" behavior, as demonstrated for a basic enzymatic reaction scheme that can display stochastic focusing (SF). Under the assumption of rapid signal fluctuations, SF has been shown to convert a graded response into a threshold mechanism, thus attenuating the detrimental effects of signal noise. However, when the rapid fluctuation assumption is violated, this gain in sensitivity is generally obtained at the cost of very large product variance, and this unpredictable behavior may be one possible explanation of why, more than a decade after its introduction, SF has still not been observed in real biochemical systems. In this work we explore the noise properties of a simple enzymatic reaction mechanism with a small and fluctuating number of active enzymes that behaves as a high-gain, noisy amplifier due to SF caused by slow enzyme fluctuations. We then show that the inclusion of a plausible negative feedback mechanism turns the system from a noisy signal detector to a strong homeostatic mechanism by exchanging high gain with strong attenuation in output noise and robustness to parameter variations. Moreover, we observe that the discrepancy between deterministic and stochastic descriptions of stochastically focused systems in the evolution of the means almost completely disappears, despite very low molecule counts and the additional nonlinearity due to feedback. The reaction mechanism considered here can provide a possible resolution to the apparent conflict between intrinsic noise and high precision in critical intracellular processes