1,333 research outputs found
The CORSAGE Programme: Continuous Orbital Remote Sensing of Archipelagic Geochemical Effects
Current and pending oceanographic remote sensing technology allows the conceptualization of a programme designed to investigate ocean island interactions that could induce short-term nearshore fluxes of particulate organic carbon and biogenic calcium carbonate from pelagic island archipelagoes. These events will influence the geochemistry of adjacent waters, particularly the marine carbon system. Justification and design are provided for a study that would combine oceanographic satellite remote sensing (visible and infrared radiometry, altimetry and scatterometry) with shore-based facilities. A programme incorporating the methodology outlined here would seek to identify the mechanisms that cause such events, assess their geochemical significance, and provide both analytical and predictive capabilities for observations on greater temporal and spatial scales
Single polymer composite sheets from polypropylene nonwoven fabric and films. Influence of processing conditions on final properties
Single polypropylene (PP) composites from a film/nonwoven fabric/film was obtained by hot calendering in order to develop recyclable, flexible, and low-cost sheets. Processing temperature (Tp) influence on morphology and mechanical properties of developed single composites was analyzed. Two different values of roll temperature (140 and 150°C) were studied, keeping constant rotation speed and rolls distance. Results revealed notable differences in materials microstructure induced by a difference of only 10°C in Tp. Sheets obtained at 140°C presented a well-defined film/nonwoven fabric/film structure, meanwhile the highest Tp led to a greater melting extent of external films which penetrate into the fabric, creating a more compact structure. Moreover, results confirmed that changes in Tp can induce a differential mechanical performance showing higher strength, and ductility in sheets processed at 150°C. Homogeneous sheets with good mechanical behavior, proper nonwoven fabric/films adhesion, and uniform thickness were obtained.Fil: Vazquez, Yamila Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Castillo, Luciana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Barbosa, Silvia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentin
Kek, Cucks, and God Emperor Trump: A Measurement Study of 4chan's Politically Incorrect Forum and its Effects on the Web
The discussion-board site 4chan has been part of the Internet's dark underbelly since its inception, and recent political events have put it increasingly in the spotlight. In particular, /pol/, the “Politically Incorrect'” board, has been a central figure in the outlandish 2016 US election season, as it has often been linked to the alt-right movement and its rhetoric of hate and racism. However, 4chan remains relatively unstudied by the scientific community: little is known about its user base, the content it generates, and how it affects other parts of the Web. In this paper, we start addressing this gap by analyzing /pol/ along several axes, using a dataset of over 8M posts we collected over two and a half months. First, we perform a general characterization, showing that /pol/ users are well distributed around the world and that 4chan's unique features encourage fresh discussions. We also analyze content, finding, for instance, that YouTube links and hate speech are predominant on /pol/. Overall, our analysis not only provides the first measurement study of /pol/, but also insight into online harassment and hate speech trends in social media
Space Station Freedom data management system growth and evolution report
The Information Sciences Division at the NASA Ames Research Center has completed a 6-month study of portions of the Space Station Freedom Data Management System (DMS). This study looked at the present capabilities and future growth potential of the DMS, and the results are documented in this report. Issues have been raised that were discussed with the appropriate Johnson Space Center (JSC) management and Work Package-2 contractor organizations. Areas requiring additional study have been identified and suggestions for long-term upgrades have been proposed. This activity has allowed the Ames personnel to develop a rapport with the JSC civil service and contractor teams that does permit an independent check and balance technique for the DMS
On the possible existence of short-period g-mode instabilities powered by nuclear burning shells in post-AGB H-deficient (PG1159-type) stars
We present a pulsational stability analysis of hot post-AGB H-deficient
pre-white dwarf stars with active He-burning shells. The stellar models
employed are state-of-the-art equilibrium structures representative of PG1159
stars derived from the complete evolution of the progenitor stars. On the basis
of fully nonadiabatic pulsation computations, we confirmed theoretical evidence
for the existence of a separate PG1159 instability strip in the diagram characterized by short-period -modes excited by the
-mechanism. This instability strip partially overlaps the already
known GW Vir instability strip of intermediate/long period -modes
destabilized by the classical -mechanism acting on the partial
ionization of C and/or O in the envelope of PG1159 stars. We found that PG1159
stars characterized by thick He-rich envelopes and located inside this
overlapping region could exhibit both short and intermediate/long periods
simultaneously. we study the particular case of VV 47, a pulsating planetary
nebula nucleus that has been reported to exhibit a series of unusually short
pulsation periods. We found that the long periods exhibited by VV 47 can be
readily explained by the classical -mechanism, while the observed
short-period branch below s could correspond to modes triggered
by the He-burning shell through the -mechanism, although more
observational work is needed to confirm the reality of these short-period
modes. Were the existence of short-period -modes in this star convincingly
confirmed by future observations, VV 47 could be the first known pulsating star
in which both the -mechanism and the -mechanism of mode
driving are simultaneously operating.Comment: 9 pages, 5 figures, 2 tables. To be published in The Astrophysical
Journa
Constructive activism in the dark web: cryptomarkets and illicit drugs in the digital ‘demimonde’
This paper explores activism enacted through Silk Road, a now defunct cryptomarket where illicit drugs were sold in the dark web. Drawing on a digital ethnography of Silk Road, we develop the notion of constructive activism to extend the lexicon of concepts available to discuss forms of online activism. Monitoring of the cryptomarket took place between June 2011 and its closure in October 2013. Just before and after the closure of the marketplace we conducted anonymous online interviews with 17 people who reported buying drugs on Silk Road (1.0). These interviews were conducted synchronously and interactively through encrypted instant messaging. Participants discussed harnessing and developing the technological tools needed to access Silk Road and engage within the Silk Road community. For participants Silk Road was not just a market for trading drugs: it facilitated a shared experience of personal freedom within a libertarian philosophical framework, where open discussions about stigmatized behaviours were encouraged and supported. Tensions between public activism against drug prohibition and the need to hide one's identity as a drug user from public scrutiny were partially resolved through community actions that internalized these politics, rather than engaging in forms of online activism that are intended to have real-world political effects. Most aptly described through van de Sande's (2015) concept of prefigurative politics, they sought to transform their values into built environments that were designed to socially engineer a more permissive digital reality, which we refer to as constructive activism
VLA Observations of a New Population of Blazars
We present the first deep VLA radio images of flat-spectrum radio quasars
(FSRQ) with multiwavelength emission properties similar to those of BL Lacs
with synchrotron X-rays. Our observations of twenty-five of these sources show
that their radio morphologies are similar to those of other radio quasars.
However, their range of extended powers is more similar to that of BL Lacertae
objects (BL Lacs) and extends down to the low values typical of FR I radio
galaxies. Five out of our nine lobe-dominated sources have extended radio
powers in the range typical of both FR I and FR II radio galaxies, but their
extended radio structure is clearly FR II-like. Therefore, we have not yet
found a large population of radio quasars hosted by FR Is. Two thirds of our
sources have a core-dominated radio morpholgy and thus X-rays likely dominated
by the jet. We find that their ratios of radio core to total X-ray luminosity
are low and in the regime indicative of synchrotron X-rays. This result shows
that also blazars with strong emission lines can produce jets of high-energy
synchrotron emission and undermines at least in part the ``blazar sequence''
scenario which advocates that particle Compton cooling by an external radiation
field governs the frequency of the synchrotron emission peak.Comment: 26 pages, 33 figures. Accepted for publication in Ap
Radio Observations of the Hubble Deep Field South Region III: The 2.5, 5.2 and 8.7 GHz Catalogues and Radio Source Properties
Deep radio observations of a wide region centred on the Hubble Deep Field
South have been performed, providing one of the most sensitive set of radio
observations acquired on the Australia Telescope Compact Array to date. A
central rms of ~10 microJy is reached at four frequencies (1.4, 2.5, 5.2 and
8.7 GHz). In this paper the full source catalogues from the 2.5, 5.2 and 8.7
GHz observations are presented to complement Paper II, along with a detailed
analysis of image quality and noise. We produce a consolidated catalogue by
matching sources across all four frequencies of our survey. Radio spectral
indices are used to investigate the nature of the radio sources and identify a
number of sources with flat or inverted radio spectra, which indicates AGN
activity. We also find several other interesting sources, including a broadline
emitting radio galaxy, a giant radio galaxy and three Gigahertz Peaked Spectrum
sources.Comment: Accepted by AJ. 13 figures and 13 table
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