Comment: Monitoring Networked Applications With Incremental Quantile Estimation

Our comments are in two parts. First, we make some observations regarding the methodology in Chambers et al. [arXiv:0708.0302]. Second, we briefly describe another interesting network monitoring problem that arises in the context of assessing quality of service, such as loss rates and delay distributions, in packet-switched networks.Comment: Published at http://dx.doi.org/10.1214/088342306000000600 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Bone marrow cells play only a very minor role in chronic liver regeneration induced by a choline-deficient, ethionine-supplemented diet

AbstractLiver progenitor (oval) cells have enormous potential in the treatment of patients with liver disease using a cell therapy approach, but their use is limited by their scarcity and the number of donor livers from which they can be derived. Bone marrow may be a suitable source. Previously the derivation of oval cells from bone marrow was examined in rodents using hepatotoxins and partial hepatectomy to create liver damage. These protocols induce oval cell proliferation; however, they do not produce the disease conditions that occur in humans. In this study we have used the choline-deficient, ethionine-supplemented (CDE) diet (which causes fatty liver) and viral hepatitis as models of chronic injury to evaluate the contribution of bone marrow cells to oval cells under conditions that closely mimic human liver disease pathophysiology. Following transplantation of lacZ-transgenic bone marrow cells into congenic mice, liver injury was induced and the movement of bone marrow cells to the liver monitored. Bone marrow-derived oval cells were observed in response to the CDE diet and viral injury but represented a minor fraction (0–1.6%) of the oval cell compartment, regardless of injury severity. In all situations only rare, individual bone marrow-derived oval cells were observed. We hypothesized that the bone marrow cells may replenish oval cells that are expended by protracted liver injury and regeneration; however, experiments involving a subsequent episode of chronic liver injury failed to induce proliferation of the bone marrow-derived oval cells that appeared as a result of the first episode. Bone marrow-derived hepatocytes were also observed in all injury models and controls at a frequency unrelated to that of oval cells. We conclude that during viral-and steatosis-induced liver disease the contribution of bone marrow cells to hepatocytes, either via oval cells or by independent mechanisms, is minimal and that the majority of oval cells responding to this injury are sourced from the liver

X-ray Signatures of an Ionized Reprocessor in the Seyfert galaxy Ton S 180

We discuss the hard X-ray properties of the Seyfert galaxy Ton S 180, based upon the analysis of ASCA data. We find the X-ray flux varied by a factor ~2 on a time scale of a few thousand seconds. The source showed significantly higher amplitude of variability in the 0.5-2 keV band than in the 2-10 keV band. The continuum is adequately parameterized as a Gamma ~ 2.5 power-law across the 0.6--10 keV band . We confirm the recent discovery of an emission line of high equivalent width, due to Fe K-shell emission from highly-ionized material. These ASCA data show the Fe line profile to be broad and asymmetric and tentatively suggest it is stronger during the X-ray flares, consistent with an origin from the inner parts of an accretion disk. The X-ray spectrum is complex below 2 keV, possibly due to emission from a blend of soft X-ray lines, which would support the existence of an ionized reprocessor, most likely due to a relatively high accretion rate in this source.Comment: 24 pages, 8 figures. LaTeX with encapsulated postscript. To appear in the Astrophysical Journa

The Melting Points of the Inert Gas Solids

The melting points of the heavy inert gases and of some other simple molecules show an excellent linear correlation with the depths of their diatomic potential wells, and the slope of the correlation line is in accord with Lindemann’s theory of melting

Mapping High-velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

We present new {\it Hubble Space Telescope} images of high-velocity H-$\alpha$ and Lyman-$\alpha$ emission in the outer debris of SN~1987A. The H-$\alpha$ images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the H$\alpha$ imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals ($-$7,500~$<$~$V_{obs}$~$<$~$-$2,800 km s$^{-1}$) and (1,000~$<$~$V_{obs}$~$<$~7,500 km s$^{-1}$), $\dot{M_{H}}$ = 1.2~$\times$~10$^{-3}$ M$_{\odot}$ yr$^{-1}$. We also present the first Lyman-$\alpha$ imaging of the whole remnant and new $Chandra$ X-ray observations. Comparing the spatial distribution of the Lyman-$\alpha$ and X-ray emission, we observe that the majority of the high-velocity Lyman-$\alpha$ emission originates interior to the equatorial ring. The observed Lyman-$\alpha$/H-$\alpha$ photon ratio, $\langle$$R(L\alpha / H\alpha)$$\rangle$ $\approx$~17, is significantly higher than the theoretically predicted ratio of $\approx$ 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-$\alpha$ emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-$\alpha$ and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-$\alpha$ production mechanism in SN 1987A at this phase in its evolution.Comment: 6 pages, 5 figures. ApJL - accepte

Hypothetico-deductive Thinking Model: Candidate Theory and Mechanism for Didactic Transposition and Teaching of the Experimental Sciences

The aim of this study was to construct and investigate the statistical and psychometric properties of the theorized model of the hypothetico-deductive thinking theory as candidate theory for didactic transposition, teaching and learning of thinking and reasoning. The survey involved 150 students of the Upper Sixth Science and Terminale D classes of both subsystems of education in Cameroon. A five point Likert scale questionnaire type was used to obtain data on students’ spontaneous views about the instructional, educational and life skills aspects of the thoracic and vertebral column of the human skeleton and their applicability to problem-solving. Data collected was used to specify a Partial Least Squares Structural Equation Model (PLS-SEM) for the theory. Its statistical and psychometric robustness was investigated using SmartPLS V.2 M3.Assessment of the measurement model revealed very significant relationships and very high cross loading regression weights between indicators and their corresponding latent constructs. Also, path model assessment revealed very strong discriminant validity, reliability and Cronbach’s alpha statistics. Association between latent constructs were also strongly significant with very adequate predictive relevance and effect sizes. However, the data showed that the model was inadequate in accounting for the variances observed in the dependent constructs judging from the very low variance explained statistic. Within limits of this study, the model furnished convincing statistic and psychometric evidence for further specifications in view of proclaiming the candidate theory as theory for didactic transposition and teaching how to think and reason

Quantum Mechanics of the Doubled Torus

We investigate the quantum mechanics of the doubled torus system, introduced by Hull [1] to describe T-folds in a more geometric way. Classically, this system consists of a world-sheet Lagrangian together with some constraints, which reduce the number of degrees of freedom to the correct physical number. We consider this system from the point of view of constrained Hamiltonian dynamics. In this case the constraints are second class, and we can quantize on the constrained surface using Dirac brackets. We perform the quantization for a simple T-fold background and compare to results for the conventional non-doubled torus system. Finally, we formulate a consistent supersymmetric version of the doubled torus system, including supersymmetric constraints.Comment: 31 pages, 1 figure; v2: references added, minor corrections to final sectio

Plasmas and Controlled Nuclear Fusion

Contains reports on five research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980

The Spectral Energy Distribution and Emission-Line properties of the NLS1 Galaxy Arakelian 564

We present the intrinsic spectral energy distribution (SED) of the NLS1 Arakelian 564, constructed with contemporaneous data obtained during a multi-wavelength, multi-satellite observing campaign in 2000 and 2001. We compare it with that of the NLS1 Ton S180 and with those obtained for BLS1s to infer how the relative accretion rates vary among the Sy1 population. Although the peak of the SED is not well constrained, most of the energy is emitted in the 10-100 eV regime, constituting roughly half of the emitted energy in the optical/X-ray ranges. This is consistent with a primary spectral component peaking in the extreme UV/soft X-ray band, and disk-corona models, hence high accretion rates. Indeed, we estimate that \dot{m}~1. We examine the emission lines in its spectrum, and we constrain the physical properties of the line-emitting gas through photoionization modeling. The line-emitting gas is characterized by log n~11 and log U~0, and is stratified around log U~0. Our estimate of the radius of the H\beta-emitting region ~10 \pm 2 lt-days is consistent with the radius-luminosity relationships found for Sy1 galaxies. We also find evidence for super-solar metallicity in this NLS1. We show that the emission lines are not good diagnostics for the underlying SEDs and that the absorption line studies offer a far more powerful tool to determine the ionizing continuum of AGNs, especially if comparing the lower- and higher-ionization lines.Comment: 15 pages, 10 figures; accepted for publication in The Astrophysical Journal, LaTeX emulateapj.st