Simple and Nearly Optimal Polynomial Root-finding by Means of Root Radii Approximation

We propose a new simple but nearly optimal algorithm for the approximation of all sufficiently well isolated complex roots and root clusters of a univariate polynomial. Quite typically the known root-finders at first compute some crude but reasonably good approximations to well-conditioned roots (that is, those isolated from the other roots) and then refine the approximations very fast, by using Boolean time which is nearly optimal, up to a polylogarithmic factor. By combining and extending some old root-finding techniques, the geometry of the complex plane, and randomized parametrization, we accelerate the initial stage of obtaining crude to all well-conditioned simple and multiple roots as well as isolated root clusters. Our algorithm performs this stage at a Boolean cost dominated by the nearly optimal cost of subsequent refinement of these approximations, which we can perform concurrently, with minimum processor communication and synchronization. Our techniques are quite simple and elementary; their power and application range may increase in their combination with the known efficient root-finding methods.Comment: 12 pages, 1 figur

Vaccination expérimentale des poulets de chair contre la maladie de Newcastle au Burkina Faso avec des grains de mil enrobés de vaccins thermotolérants LaSota/A300 et V4/276

La vaccination contre la maladie de Newcastle par la méthode de distribution des grains de mil enrobés de vaccins thermotolérants LaSota/A300 et V4/276 a été essayée à Ouagadougou, Burkina Faso, sur 298 poulets de chair d'origine européenne pourvus d'anticorps maternels. Des infections opportunistes, comme la colibacillose, ont décimé de 70 à 81 % des effectifs des trois lots vaccinés et aussi 24 % du lot témoin avant d'être éradiquées par une antibiothérapie. L'épreuve virulente avec la souche de virus Hertz 33/56, appliquée aux survivants deux mois après la vaccination, a tué 100 % des témoins, 78 % des poulets vaccinés avec le V4/276, 7 % des vaccinés avec le LaSota/A300, et n'en a tué aucun dans le groupe qui a reçu à la fois le V4/276 et le LaSota/A300 à une semaine d'intervalle. Ces deux derniers groupes possédaient aussi, avant l'épreuve, de hauts titres d'anticorps IHA. Les vaccins lyophilisés LaSota/A300 et V4/276 ont conservé de hauts titres de virus après des expositions de 8 à 34 jours à la température ambiante de la saison fraîche à Ouagadougou

Infall, the Butcher-Oemler Effect, and the Descendants of Blue Cluster Galaxies at z~0.6

Using wide-field HST/WFPC2 imaging and extensive Keck/LRIS spectroscopy, we present a detailed study of the galaxy populations in MS2053--04, a massive, X-ray luminous cluster at z=0.5866. Analysis of 149 confirmed cluster members shows that MS2053 is composed of two structures that are gravitationally bound to each other; their respective velocity dispersions are 865 km/s (113 members) and 282 km/s (36 members). MS2053's total dynamical mass is 1.2x10^15 Msun. MS2053 is a classic Butcher-Oemler cluster with a high fraction of blue members (24%) and an even higher fraction of star-forming members (44%), as determined from their [OII] emission. The number fraction of blue/star-forming galaxies is much higher in the infalling structure than in the main cluster. This result is the most direct evidence to date that the Butcher-Oemler effect is linked to galaxy infall. In terms of their colors, luminosities, estimated internal velocity dispersions, and [OII] equivalent widths, the infalling galaxies are indistinguishable from the field population. MS2053's deficit of S0 galaxies combined with its overabundance of blue spirals implies that many of these late-types will evolve into S0 members. The properties of the blue cluster members in both the main cluster and infalling structure indicate they will evolve into low mass, L<L* galaxies with extended star formation histories like that of low mass S0's in Coma. Our observations show that most of MS2053's blue cluster members, and ultimately most of its low mass S0's, originate in the field. Finally, we measure the redshift of the giant arc in MS2053 to be z=3.1462; this object is one in only a small set of known strongly lensed galaxies at z>3.Comment: Accepted by ApJ. Version with full resolution figures available at http://www.exp-astro.phys.ethz.ch/tran/outgoing/ms2053.ps.g

A Low Lyman Continuum Escape Fraction of <10%<10\% for Extreme [OIII] Emitters in an Overdensity at z∼3.5\sim3.5

Recent work has suggested extreme [OIII] emitting star-forming galaxies are important to reionization. Relatedly, [OIII]/[OII] has been put forward as an indirect estimator of the Lyman Continuum (LyC) escape fraction ($f_{esc}$) at $z\gtrsim4.5$ when the opaque IGM renders LyC photons unobservable. Using deep archival U-band (VLT/VIMOS) imaging of a recently confirmed overdensity at $z\sim3.5$ we calculate tight constraints on $f_{esc}$ for a sample (N=73) dominated by extreme [OIII] emitters. We find no Lyman Continuum signal ($f_{esc}^{rel} < 6.3^{+0.7}_{-0.7} \%$ at $1\sigma$) in a deep U-band stack of our sample (31.98 mag at 1$\sigma$). This constraint is in agreement with recent studies of star-forming galaxies spanning $z\sim1-4$ that have found very low average $f_{esc}$. Despite the galaxies in our study having an estimated average rest-frame EW([OIII]$\lambda5007$)$\sim400\AA$ and [OIII]/[OII]$\sim 4$ from composite SED-fitting, we find no LyC detection, which brings into question the potential of [OIII]/[OII] as an effective probe of the LyC--a majority of LyC emitters have [OIII]/[OII]$>3$, but we establish here that [OIII]/[OII]$>3$ does not guarantee significant LyC leakage for a population. Since even extreme star-forming galaxies are unable to produce the $f_{esc}\sim10-15\%$ required by most theoretical calculations for star-forming galaxies to drive reionization, there must either be a rapid evolution of $f_{esc}$ between $z\sim3.5$ and the Epoch of Reionization, or hitherto observationally unstudied sources (e.g. ultra-faint low-mass galaxies with $\log(M/M_\odot)\sim7-8.5$) must make an outsized contribution to reionization.Comment: 10 pages, 8 figures (key result in Figures 7, 8). Accepted for publication in MNRAS. Comments welcom

Contact force sensing in ablation of ventricular arrhythmias using a 56-hole open-irrigation catheter: a propensity-matched analysis.

PURPOSE: The effect of adding contact force (CF) sensing to 56-hole tip irrigation in ventricular arrhythmia (VA) ablation has not been previously studied. We aimed to compare outcomes with and without CF sensing in VA ablation using a 56-hole radiofrequency (RF) catheter. METHODS: A total of 164 patients who underwent first-time VA ablation using Thermocool SmartTouch Surround Flow (TC-STSF) catheter (Biosense-Webster, Diamond Bar, CA, USA) were propensity-matched in a 1:1 fashion to 164 patients who had first-time ablation using Thermocool Surround Flow (TC-SF) catheter. Patients were matched for age, gender, cardiac aetiology, ejection fraction and approach. Acute success, complications and long-term follow-up were compared. RESULTS: There was no difference between procedures utilising either TC-SF or TC-STSF in acute success (TC-SF: 134/164 (82%), TC-STSF: 141/164 (86%), p = 0.3), complications (TC-SF: 11/164 (6.7%), TC-STSF: 11/164 (6.7%), p = 1.0) or VA-free survival (TC-SF: mean arrhythmia-free survival time = 5.9 years, 95% CI = 5.4-6.4, TC-STSF: mean = 3.2 years, 95% CI = 3-3.5, log-rank p = 0.74). Fluoroscopy time was longer in normal hearts with TC-SF (19 min, IQR: 14-30) than TC-STSF (14 min, IQR: 8-25; p = 0.04). CONCLUSION: Both TC-SF and TC-STSF catheters are safe and effective in treating VAs. The use of CF sensing catheters did not improve safety or acute and long-term outcomes, but reduced fluoroscopy time in normal heart VA

Chemical pre-processing of cluster galaxies over the past 10 billion years in the IllustrisTNG simulations

We use the IllustrisTNG simulations to investigate the evolution of the mass-metallicity relation (MZR) for star-forming cluster galaxies as a function of the formation history of their cluster host. The simulations predict an enhancement in the gas-phase metallicities of star-forming cluster galaxies (10^9< M_star<10^10 M_sun) at z<1.0 in comparisons to field galaxies. This is qualitatively consistent with observations. We find that the metallicity enhancement of cluster galaxies appears prior to their infall into the central cluster potential, indicating for the first time a systematic "chemical pre-processing" signature for {\it infalling} cluster galaxies. Namely, galaxies which will fall into a cluster by z=0 show a ~0.05 dex enhancement in the MZR compared to field galaxies at z<0.5. Based on the inflow rate of gas into cluster galaxies and its metallicity, we identify that the accretion of pre-enriched gas is the key driver of the chemical evolution of such galaxies, particularly in the stellar mass range (10^9< M_star<10^10 M_sun). We see signatures of an environmental dependence of the ambient/inflowing gas metallicity which extends well outside the nominal virial radius of clusters. Our results motivate future observations looking for pre-enrichment signatures in dense environments.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter

Clay fine fissuring monitoring using miniature geo-electrical resistivity arrays

Abstract This article describes a miniaturised electrical imaging (resistivity tomography) technique to map the cracking pattern of a clay model. The clay used was taken from a scaled flood embankment built to study the fine fissuring due to desiccation and breaching process in flooding conditions. The potential of using a miniature array of electrodes to follow the evolution of the vertical cracks and number them during the drying process was explored. The imaging technique generated two-dimensional contoured plots of the resistivity distribution within the model before and at different stages of the desiccation process. The change in resistivity associated with the widening of the cracks were monitored as a function of time. Experiments were also carried out using a selected conductive gel to slow down the transport process into the cracks to improve the scanning capabilities of the equipment. The main vertical clay fissuring network was obtained after inversion of the experimental resistivity measurements and validated by direct observations

Review of patient-specific simulations of transcatheter aortic valve implantation

International audienceTranscatheter Aortic Valve Implantation (TAVI) accounts for one of the most promising new cardiovascular procedures. This minimally invasive technique is still at its early stage and is constantly developing thanks to imaging techniques, computer science, biomechanics and technologies of prosthesis and delivery tools. As a result, patient-specific simulation can find an exciting playground in TAVI. It canexpress its potential by providing the clinicians with powerful decision support, offering great assistance in their workflow. Through a review of the current scientific field, we try to identify the challenges and future evolutions of patient-specific simulation for TAVI. This review article is an attempt to summarize and coordinate data scattered across the literature about patient-specific biomechanical simulation for TAVI