174 research outputs found

    Environmental Noise and Nonlinear Relaxation in Biological Systems

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    We analyse the effects of environmental noise in three different biological systems: (i) mating behaviour of individuals of \emph{Nezara viridula} (L.) (Heteroptera Pentatomidae); (ii) polymer translocation in crowded solution; (iii) an ecosystem described by a Verhulst model with a multiplicative L\'{e}vy noise.Comment: 32 pages; In "Ecological Modeling" by Ed. Wen-Jun Zhang. ISBN: 978-1-61324-567-5. - Nova Science Publishers, New York, 201

    Early Observations of the Type Ia Supernova iPTF 16abc: A Case of Interaction with Nearby, Unbound Material and/or Strong Ejecta Mixing

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    Early observations of Type Ia supernovae (SNe Ia) provide a unique probe of their progenitor systems and explosion physics. Here we report the intermediate Palomar Transient Factory (iPTF) discovery of an extraordinarily young SN Ia, iPTF 16abc. By fitting a power law to our early light curve, we infer that first light for the SN, that is when the SN could have first been detected by our survey, occurred only 0.15±0.070.150.15\pm_{0.07}^{0.15} days before our first detection. In the \sim24 hr after discovery, iPTF 16abc rose by \sim2 mag, featuring a near-linear rise in flux for \gtrsim3 days. Early spectra show strong C II absorption, which disappears after \sim7 days. Unlike the extensivelyobserved SN Ia SN 2011fe, the (BV)0(B-V)_0 colors of iPTF 16abc are blue and nearly constant in the days after explosion. We show that our early observations of iPTF 16abc cannot be explained by either SN shock breakout and the associated, subsequent cooling or the SN ejecta colliding with a stellar companion. Instead, we argue that the early characteristics of iPTF 16abc, including (i) the rapid, near-linear rise, (ii) the nonevolving blue colors, and (iii) the strong C II absorption, are the result of either ejecta interaction with nearby, unbound material or vigorous mixing of radioactive 56^{56}Ni in the SN ejecta, or a combination of the two. In the next few years, dozens of very young \textit{normal} SNe Ia will be discovered, and observations similar to those presented here will constrain the white dwarf explosion mechanism.Comment: 18 pages, 12 figures, accepted by Ap

    Effects of a localized beam on the dynamics of excitable cavity solitons

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    We study the dynamical behavior of dissipative solitons in an optical cavity filled with a Kerr medium when a localized beam is applied on top of the homogeneous pumping. In particular, we report on the excitability regime that cavity solitons exhibits which is emergent property since the system is not locally excitable. The resulting scenario differs in an important way from the case of a purely homogeneous pump and now two different excitable regimes, both Class I, are shown. The whole scenario is presented and discussed, showing that it is organized by three codimension-2 points. Moreover, the localized beam can be used to control important features, such as the excitable threshold, improving the possibilities for the experimental observation of this phenomenon.Comment: 9 Pages, 12 figure

    Randomized Clinical Trial Comparing Basal Insulin Peglispro and Insulin Glargine in Patients With Type 2 Diabetes Previously Treated With Basal Insulin: IMAGINE 5

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    OBJECTIVE To evaluate the efficacy and safety of basal insulin peglispro (BIL) versus insulin glargine in patients with type 2 diabetes (hemoglobin A1c [HbA1c] ≤9% [75 mmol/mol]) treated with basal insulin alone or with three or fewer oral antihyperglycemic medications. RESEARCH DESIGN AND METHODS This 52-week, open-label, treat-to-target study randomized patients (mean HbA1c 7.42% [57.6 mmol/mol]) to BIL ( n = 307) or glargine ( n = 159). The primary end point was change from baseline HbA1c to 26 weeks (0.4% [4.4 mmol/mol] noninferiority margin). RESULTS At 26 weeks, reduction in HbA1c was superior with BIL versus glargine (−0.82% [−8.9 mmol/mol] vs. −0.29% [−3.2 mmol/mol]; least squares mean difference −0.52%, 95% CI −0.67 to −0.38 [−5.7 mmol/mol, 95% CI −7.3 to −4.2; P < 0.001); greater reduction in HbA1c with BIL was maintained at 52 weeks. More BIL patients achieved HbA1c <7% (53 mmol/mol) at weeks 26 and 52 ( P < 0.001). With BIL versus glargine, nocturnal hypoglycemia rate was 60% lower, more patients achieved HbA1c <7% (53 mmol/mol) without nocturnal hypoglycemia at 26 and 52 weeks ( P < 0.001), and total hypoglycemia rates were lower at 52 weeks ( P = 0.03). At weeks 26 and 52, glucose variability was lower ( P < 0.01), basal insulin dose was higher ( P < 0.001), and triglycerides and aminotransferases were higher with BIL versus glargine ( P < 0.05). Liver fat content (LFC), assessed in a subset of patients ( n = 162), increased from baseline with BIL versus glargine ( P < 0.001), with stable levels between 26 and 52 weeks. CONCLUSIONS BIL provided superior glycemic control versus glargine, with reduced nocturnal and total hypoglycemia, lower glucose variability, and increased triglycerides, aminotransferases, and LFC

    iPTF15dtg: a double-peaked Type Ic supernova from a massive progenitor

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    Context. Type Ic supernovae (SNe Ic) arise from the core-collapse of H- (and He-) poor stars, which could either be single Wolf-Rayet (WR) stars or lower-mass stars stripped of their envelope by a companion. Their light curves are radioactively powered and usually show a fast rise to peak (~10−15 d), without any early (in the first few days) emission bumps (with the exception of broad-lined SNe Ic) as sometimes seen for other types of stripped-envelope SNe (e.g., Type IIb SN 1993J and Type Ib SN 2008D). Aims. We have studied iPTF15dtg, a spectroscopically normal SN Ic with an early excess in the optical light curves followed by a long (~30 d) rise to the main peak. It is the first spectroscopically-normal double-peaked SN Ic to be observed. Our aim is to determine the properties of this explosion and of its progenitor star. Methods. Optical photometry and spectroscopy of iPTF15dtg was obtained with multiple telescopes. The resulting light curves and spectral sequence are analyzed and modeled with hydrodynamical and analytical models, with particular focus on the early emission. Results. iPTF15dtg is a slow rising SN Ic, similar to SN 2011bm. Hydrodynamical modeling of the bolometric properties reveals a large ejecta mass (~10 M_⊙) and strong ^(56)Ni mixing. The luminous early emission can be reproduced if we account for the presence of an extended (≳500 R_⊙), low-mass (≳0.045 M_⊙) envelope around the progenitor star. Alternative scenarios for the early peak, such as the interaction with a companion, a shock-breakout (SBO) cooling tail from the progenitor surface, or a magnetar-driven SBO are not favored. Conclusions. The large ejecta mass and the presence of H- and He-free extended material around the star suggest that the progenitor of iPTF15dtg was a massive (≳35 M_⊙) WR star that experienced strong mass loss

    Astronaut Thermal Exposure: Re-Entry After Low Earth Orbit Rescue Mission

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    The STS-125 mission, launched May 11, 2009, is the final servicing mission to the Hubble Space Telescope. The repair mission's EVA tasks are described, including: installing a new wide field camera; installing the Cosmic Origins Spectrograph; repairing the Space Telescope Imaging Spectrograph; installing a new outer blanket layer; adding a Soft Capture and Rendezvous System for eventual controlled deorbit in about 2014; replacing the 'A' side Science Instrument Command and Data Handling module; repairing the Advanced Camera for surveys; and, replacing the rate sensor unit gyroscopes, fine guidance sensors and 3 batteries. Additionally, the Shuttle crew cabin thermal environment is described. A CFD model of per person CO2 demonstrates a discrepancy between crew breathing volume and general mid-deck levels of CO2. A follow-on CFD analysis of the mid-deck temperature distribution is provided. Procedural and engineering mitigation plans are presented to counteract thermal exposure upon reentry to the Earth atmosphere. Some of the procedures include: full cold soak the night prior to deorbit; modifying deck stowage to reduce interference with air flow; and early securing of avionics post-landing to reduce cabin thermal load prior to hatch opening. Engineering mitigation activities include modifying the location of the aft starboard ICUs, eliminating the X3 stack and eliminating ICU exhaust air directed onto astronauts; improved engineering data of ICU performance; and, verifying the adequacy of mid-deck temperature control using CFD models in addition to lumped parameter models. Post-mitigation CFD models of mid-deck temperature profiles and distribution are provided

    Processing Images from the Zwicky Transient Facility

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    The Zwicky Transient Facility is a new robotic-observing program, in which a newly engineered 600-MP digital camera with a pioneeringly large field of view, 47~square degrees, will be installed into the 48-inch Samuel Oschin Telescope at the Palomar Observatory. The camera will generate 1\sim 1~petabyte of raw image data over three years of operations. In parallel related work, new hardware and software systems are being developed to process these data in real time and build a long-term archive for the processed products. The first public release of archived products is planned for early 2019, which will include processed images and astronomical-source catalogs of the northern sky in the gg and rr bands. Source catalogs based on two different methods will be generated for the archive: aperture photometry and point-spread-function fitting.Comment: 6 pages, 4 figures, submitted to RTSRE Proceedings (www.rtsre.org

    iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

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    We present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute mag M_g =- 17.2. The maximum bolometric luminosity (from optical and UV) was L_p ≃ (1.0 ± 0.15) x 10^(43) erg s^(−1), an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with L ∝ e^(-(t-t_0)/τ, where t_0 = 57631.0 (MJD) and τ ≃ 15 days. The X-ray shows a marginal detection at L_X = 2.4_(-1.1)^(1.9) x 10^(39) erg s^(−1) (Swift X-ray Telescope). No radio counterpart was detected down to 3σ, providing upper limits for monochromatic radio luminosities of vL_v < 2.3 x 10^(36) erg s^(−1) and vL_v < 1.7 x 10^(37) erg s^(−1) (Very Large Array, 6.1 and 22 GHz). The blackbody temperature, obtained from combined Swift UV and optical photometry, shows a constant value of 19,000 K. The transient spectrum at peak is characterized by broad He ii and Hα emission lines, with FWHMs of about 14,000 km s^(−1) and 10,000 km s^(−1), respectively. He i lines are also detected at λλ 5875 and 6678. The spectrum of the host is dominated by strong Balmer absorption lines, which are consistent with a post-starburst (E+A) galaxy with an age of ~650 Myr and solar metallicity. The characteristics of iPTF16fnl make it an outlier on both luminosity and decay timescales, as compared to other optically selected TDEs. The discovery of such a faint optical event suggests a higher rate of tidal disruptions, as low-luminosity events may have gone unnoticed in previous searches
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