Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics

Peer reviewedPublisher PD

The Non-Relativistic Evolution of GRBs 980703 and 970508: Beaming-Independent Calorimetry

We use the Sedov-Taylor self-similar solution to model the radio emission from the gamma-ray bursts (GRBs) 980703 and 970508, when the blastwave has decelerated to non-relativistic velocities. This approach allows us to infer the energy independent of jet collimation. We find that for GRB 980703 the kinetic energy at the time of the transition to non-relativistic evolution, t_NR ~ 40 d, is E_ST ~ (1-6)e51 erg. For GRB 970508 we find E_ST ~ 3e51 erg at t_NR ~ 100 d, nearly an order of magnitude higher than the energy derived in Frail, Waxman and Kulkarni (2000). This is due primarily to revised cosmological parameters and partly to the maximum likelihood fit we use here. Taking into account radiative losses prior to t_NR, the inferred energies agree well with those derived from the early, relativistic evolution of the afterglow. Thus, the analysis presented here provides a robust, geometry-independent confirmation that the energy scale of cosmological GRBs is about 5e51 erg, and additionally shows that the central engine in these two bursts did not produce a significant amount of energy in mildly relativistic ejecta at late time. Furthermore, a comparison to the prompt energy release reveals a wide dispersion in the gamma-ray efficiency, strengthening our growing understanding that E_gamma is a not a reliable proxy for the total energy.Comment: Submitted to ApJ; 13 pages, 6 figures, 1 table; high-resolution figures can be found at: http://www.astro.caltech.edu/~ejb/NR

Limiting distributions of functionals of Markov chains

Let {Xn, n ≥ 0\s} and {Yn, n ≥ 0} be two stochastic processes such that Yn depends on Xn in a stationary manner, i.e. P(Yn ∊ A|Xn) does not depend on n. Sufficient conditions are derived for Yn to have a limiting distribution. If Xn is a Markov chain with stationary transition probabilities and Yn = f(Xn,..., Xn+k) then Yn depends on Xn is a stationary way. Two situations are considered: (i) {Xn, n ≥ 0} has a limiting distribution (ii) {Xn, n ≥ 0} does not have a limiting distribution and exits every finite set with probability 1. Several examples are considered including that of a non-homogeneous Poisson process with periodic rate function where we obtain the limiting distribution of the interevent times

Move Forward and Tell: A Progressive Generator of Video Descriptions

We present an efficient framework that can generate a coherent paragraph to describe a given video. Previous works on video captioning usually focus on video clips. They typically treat an entire video as a whole and generate the caption conditioned on a single embedding. On the contrary, we consider videos with rich temporal structures and aim to generate paragraph descriptions that can preserve the story flow while being coherent and concise. Towards this goal, we propose a new approach, which produces a descriptive paragraph by assembling temporally localized descriptions. Given a video, it selects a sequence of distinctive clips and generates sentences thereon in a coherent manner. Particularly, the selection of clips and the production of sentences are done jointly and progressively driven by a recurrent network -- what to describe next depends on what have been said before. Here, the recurrent network is learned via self-critical sequence training with both sentence-level and paragraph-level rewards. On the ActivityNet Captions dataset, our method demonstrated the capability of generating high-quality paragraph descriptions for videos. Compared to those by other methods, the descriptions produced by our method are often more relevant, more coherent, and more concise.Comment: Accepted by ECCV 201

Stability Check of Escarpment Using Finite Element Method

The valve house of the Tons Hydel Project, Madhya Pradesh, India is located just adjacent to a steep escarpment. The stability analysis of scarp near the valve house was made by the Central Water and Power Research Station, using finite element method. The problem was treated as a plain strain case. The analysis under self weight and with seepage forces indicated tensile stresses less than 4 kg/cm2 in the scarp. A proposal by the project authorities namely removing rock in the area above R.L.230 m at 74 degrees and filling lean concrete below the overhang was found to provide a stable condition. The state of stress in the scarp near the valve house was obtained under different conditions. The finite element method thus proved to be a very useful tool in analysing problem

Prevalence, Socio-cultural Restrictions and Determinants of School Absenteeism during Menstruation among Adolescent School Girls in Bangalore

Introduction: Menstrual-related problems are one of the most common problems among adolescent girls and might adversely affect their performance in academic and other activities of daily life. Aims & Objectives: 1. To determine the prevalence of school absenteeism among adolescent school girls during menstruation. 2. To assess the restrictions which are imposed on adolescent school girls during menstruation. 3. To evaluate the various factors associated with school absenteeism during menstruation. Methods: A study was conducted by carrying out a questionnaire and focus group discussion between October 2019-January 2020 in seven schools of Bangalore city after obtaining the assent and informed consent signed by their parents. Result: The mean age of the girls was 14.45 ± 1.71. The proportion of school absenteeism during menstruation was (30.25%). The majority (89.25%) of the students among the school absentees missed one day of school during menstruation. Among the school absentees, pain/discomfort was one of the main reasons for missing school, accounting for (69.42%). (46.25%) of the students were restricted from any kind of religious activities. Pain during menstruation, shame, fear of leakage, lack of toilet or water supply, lack of a place to dispose of sanitary pads and absence of a private place to manage periods were some factors that were associated with school absenteeism during menstruation. Conclusion: Considerably high school absenteeism among adolescent girls due to menstruation was noted in this study, highlighting the need for improved interventions that reach girls at a young age

Prospects for gravitational-wave observations of neutron-star tidal disruption in neutron-star/black-hole binaries

For an inspiraling neutron-star/black-hole binary (NS/BH), we estimate the gravity-wave frequency f_td at the onset of NS tidal disruption. We model the NS as a tidally distorted, homogeneous, Newtonian ellipsoid on a circular, equatorial geodesic around a Kerr BH. We find that f_td depends strongly on the NS radius R, and estimate that LIGO-II (ca. 2006-2008) might measure R to 15% precision at 140 Mpc (about 1 event/yr under current estimates). This suggests that LIGO-II might extract valuable information about the NS equation of state from tidal-disruption waves.Comment: RevTeX, 4 pages, 2 EPS figures. Revised slightly, corrected typo

Dynamic Structure Factor of Liquid and Amorphous Ge From Ab Initio Simulations

We calculate the dynamic structure factor S(k,omega) of liquid Ge (l-Ge) at temperature T = 1250 K, and of amorphous Ge (a-Ge) at T = 300 K, using ab initio molecular dynamics. The electronic energy is computed using density-functional theory, primarily in the generalized gradient approximation, together with a plane wave representation of the wave functions and ultra-soft pseudopotentials. We use a 64-atom cell with periodic boundary conditions, and calculate averages over runs of up to 16 ps. The calculated liquid S(k,omega) agrees qualitatively with that obtained by Hosokawa et al, using inelastic X-ray scattering. In a-Ge, we find that the calculated S(k,omega) is in qualitative agreement with that obtained experimentally by Maley et al. Our results suggest that the ab initio approach is sufficient to allow approximate calculations of S(k,omega) in both liquid and amorphous materials.Comment: 31 pages and 8 figures. Accepted for Phys. Rev.

The Optical Counterpart of the Isolated Neutron Star RX J1605.3+3249

We have detected the optical counterpart to the nearby isolated neutron star RX J1605.3+3249 using observations from the Space Telescope Imaging Spectrometer aboard the Hubble Space Telescope. The counterpart, with m_{50CCD}=26.84+/-0.07 mag and very blue colors, lies close to the ROSAT HRI error circle and within the Chandra error circle. The spectrum is consistent with a Rayleigh-Jeans tail whose emission is a factor of ~14 above the extrapolation of the X-ray blackbody, and the source has an unabsorbed X-ray-to-optical flux ratio of log(fX/fopt)=4.4, similar to that of other isolated neutron stars. This confirms the classification of RX J1605.3+3249 as a neutron star.Comment: 5 pages, 4 figures. Uses emulateapj5.sty, onecolfloat5.sty. Accepted by ApJL. Small changes from ver. 1 following referee's repor