1,524 research outputs found
The Circumstellar Structure and Excitation Effects around the Massive Protostar Cepheus A HW 2
We report SMA 335 GHz continuum observations with angular resolution of
~0.''3, together with VLA ammonia observations with ~1'' resolution toward Cep
A HW 2. We find that the flattened disk structure of the dust emission observed
by Patel et al. is preserved at the 0.''3 scale, showing an elongated structure
of ~$0.''6 size (450 AU) peaking on HW 2. In addition, two ammonia cores are
observed, one associated with a hot-core previously reported, and an elongated
core with a double peak separated by ~1.''3 and with signs of heating at the
inner edges of the gas facing HW 2. The double-peaked ammonia structure, as
well as the double-peaked CH3CN structure reported previously (and proposed to
be two independent hot-cores), surround both the dust emission as well as the
double-peaked SO2 disk structure found by Jimenez-Serra et al. All these
results argue against the interpretation of the elongated dust-gas structure as
due to a chance-superposition of different cores; instead, they imply that it
is physically related to the central massive object within a disk-protostar-jet
system.Comment: 12 pages, 3 figures; accepted for publication in the Astrophysical
Journa
Large cities are less efficient for sustainable transport: The ABC of mobility
The distance travelled by car in a city has many negative impacts on its
population, including pollution, noise and the use of space. Yet, quantifying
the motorisation of urban mobility is a serious challenge, particularly across
cities of different regions. Here we model the number of kilometres travelled
by different modes of transport in a city by aggregating active mobility (A),
public transport (B) and cars (C), thus expressing the modal share of a city by
its ABC triplet. Data for over 800 cities across over 60 countries is used to
model kilometres travelled by car and its relationship with city size. Our
findings suggest that although public transport is more prominent in large
cities, it is insufficient to reduce the distance travelled by car users within
the city and, ultimately, their emissions. For cities outside the US, results
show that although the proportion of journeys by car decreases in larger
cities, distances become more prolonged, thus experiencing more distance
travelled by car. When a city doubles its size, it has 87\% more car journeys,
but they are 41% longer, thus experiencing 2.6 times more vehicle kilometres
travelled. Further, by matching cities of similar size inside and outside the
US, we estimate that cities in the US have 2.3 times more vehicle kilometres
travelled than cities elsewhere.Comment: 14 pages, 6 figure
Binding-incompetent adenovirus facilitates molecular conjugate-mediated gene transfer by the receptor-mediated endocytosis pathway
Molecular conjugate vectors may be constructed that accomplish high efficiency gene transfer by the receptor-mediated endocytosis pathway. In order to mediate escape from lysosomal degradation, we have incorporated adenoviruses into the functional design of the conjugate. In doing so, however, we have introduced an additional ligand, which can bind to receptors on the cell surface, undermining the potential for cell specific targeting. To overcome this, we have treated the adenovirus with a monoclonal anti-fiber antibody, which renders the virus incapable of binding to its receptor. The result is a multi-functional molecular conjugate vector, which has preserved its binding specificity while at the same time being capable of preventing lysosomal degradation of endosome-internalized conjugate-DNA complexes. This finding indicates that adenoviral binding is not a prerequisite for adenoviral-mediated endosome disruption
High-resolution study of a star-forming cluster in the Cep-A HW2 region
Due to its relatively small distance (725 pc), the Cepheus A East
star-forming region is an ideal laboratory to study massive star formation
processes. Based on its morphology, it has been suggested that the flattened
molecular gas distribution around the YSO HW2 may be a 350-AU-radius massive
protostellar disk. Goal of our work is to ascertain the nature of this
structure. We have employed the Plateau de Bure Interferometer to acquire
(sub-)arcsecond-resolution imaging of high-density and shock tracers, such as
methyl cyanide (CH3CN) and silicon monoxide (SiO), towards the HW2 position. On
the 1-arcsecond (about 725 AU) scale, the flattened distribution of molecular
gas around HW2 appears to be due to the projected superposition, on the plane
of the sky, of at least three protostellar objects, of which at least one is
powering a molecular outflow at a small angle with respect to the line of
sight. The presence of a protostellar disk around HW2 is not ruled out, but
such structure is likely to be detected on a smaller spatial scale, or using
different molecular tracers.Comment: 6 pages, 5 figures, accepted for publication in Astronomy &
Astrophysic
Political influencers. A study of Donald Trump’s personal brand on Twitter and its impact on the media and users
The personality of a political candidate, above and beyond governments and parties, is understood increasingly more as a brand image. The new political influencers are making a clean sweep of social networks and it is the media that reproduce an information model that, far from being grounded in transparency and quality, promotes a post-truth discourse, halfway between provocation and spectacle. This initial hypothesis focuses on Donald Trump’s profile, first as a presidential candidate and later on as US President. In parallel, Twitter users have swiftly succumbed to the leader’s appeal. Thus, this paper studies the impact of Trump’s tweets on the US reference press during the first 100 days of his presidency. More specifically, it analyses the correspondences between the tweets posted on his personal Twitter account (@realDonaldTrump, with more than 45 million followers) and the front page news in USA Today, The Boston Globe, The Wall Street Journal and The New York Times. Regarding public response, digital prosumer metrics (“likes,” retweets and comments) have been quantified in order to verify the degree of influence exerted by Trump on public opinion. The method employed here includes a quantitative and qualitative content analysis based on three categories: the politician’s tweets, front page news and online user metrics. The results confirm Trump’s empowerment on Twitter as both a main source of news and a political influencer as regards the media and the citizenry.La individualidad del candidato polĂtico se postula cada vez más como imagen de marca, por delante de partidos y gobiernos. Los nuevos influencers de la PolĂtica copan las redes y son los medios de comunicaciĂłn quienes reproducen un modelo informativo que, lejos de la transparencia y la calidad, promueve el discurso de la postverdad, entre la provocaciĂłn y el espectáculo. Una hipĂłtesis que se focaliza en el perfil de Donald Trump, primero como candidato a las elecciones americanas y más tarde como presidente de EUA. En paralelo, los usuarios de Twitter sucumben a la atracciĂłn del lĂder a golpe de clic. La investigaciĂłn estudia el impacto de los tuits de Trump sobre la agenda de la prensa americana de referencia durante los primeros cien dĂas de Gobierno. Se analiza la equivalencia entre los tuits emitidos desde la propia cuenta personal (@realDonaldTrump –con más de 45 millones de seguidores– y las portadas de los periĂłdicos USA Today, The Boston Globe, The Wall Street Journal y The New York Times. En orden a la respuesta ciudadana, se cuantifican las mĂ©tricas (favoritos, retuits y comentarios) de los prosumidores digitales para comprobar los niveles de influencia que ejerce Trump sobre la opiniĂłn pĂşblica. El mĂ©todo comprende un análisis de contenido de corte cuantitativo y cualitativo-discursivo mediante una categorizaciĂłn triangulada: tuits del polĂtico, portadas mediáticas y mĂ©tricas del usuario online. Los resultados confirman el empoderamiento de Trump en Twitter, como principal generador de noticias e influencer polĂtico de medios y ciudadanos
A VLA search for young protostars embedded in dense cores
Four dense cores, L1582A, L1689A, B133 and B68, classified as prestellar in
terms of the absence of detectable NIR emission, are observed at radio
wavelengths to investigate whether they nurture very young protostars. No
definite young protostars were discovered in any of the four cores observed. A
few radio sources were discovered close to the observed cores, but these are
most likely extragalactic sources or YSOs unrelated to the cores observed. In
L1582A we discovered a weak radio source near the centre of the core with radio
characteristics and offset from the peak of the submillimeter emission similar
to that of the newly discovered protostar in the core L1014, indicating a
possible protostellar nature for this source. This needs to be confirmed with
near- and/or mid-infrared observations (e.g. with Spitzer). Hence based on the
current observations we are unable to confirm unequivocally that L1582A is
starless. In L1689A a possible 4.5-sigma radio source was discovered at the
centre of the core, but needs to be confirmed with future observations. In B133
a weak radio source, possibly a protostar, was discovered at the edge of the
core on a local peak of the core submm emission, but no source was detected at
the centre of the core. Thus, B133 is probably starless, but may have a
protostar at its edge. In B68 no radio sources were discovered inside or at the
edge of the core, and thus B68 is indeed starless. Four more radio sources with
spectral indices characteristic of young protostars were discovered outside the
cores but within the extended clouds in which these cores reside. Conclusions:
We conclude that the number of cores misclassified as prestellar is probably
very small and does not significantly alter the estimated lifetime of the
prestellar phase.Comment: Accepted by A&
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