3,414 research outputs found
Kepler super-flare stars: what are they?
The Kepler mission has led to the serendipitous discovery of a significant
number of `super flares' - white light flares with energies between 10^33 erg
and 10^36 erg - on solar-type stars. It has been speculated that these could be
`freak' events that might happen on the Sun, too. We have started a programme
to study the nature of the stars on which these super flares have been
observed. Here we present high-resolution spectroscopy of 11 of these stars and
discuss our results. We find that several of these stars are very young,
fast-rotating stars where high levels of stellar activity can be expected, but
for some other stars we do not find a straightforward explanation for the
occurrence of super flares.Comment: Accepted for publication in A&A, 9 pages, 4 figure
Construction and application of a questionnaire for the social scientific investigation of environmental noise effects
A social psychological questionnair has been developed to study the effects of environmental noise and was applied to 636 people living in 19 different areas of Hamburg. The theoretical foundations and the statistical means employed in its development are described. Four main reactions to noise are isolated statistically, and it is determined that these are moderated by several intervening variables, chief of which are coping capacity for noise, the perceived dangerousness of the noise souce, other daily loads and the individual's liability
Disorder induced Coulomb gaps in graphene constrictions with different aspect ratios
We present electron transport measurements on lithographically defined and
etched graphene nanoconstrictions with different aspect ratios including
different lengths (L) and widths (W). A roughly length-independent disorder
induced effective energy gap can be observed around the charge neutrality
point. This energy gap scales inversely with the width even in regimes where
the length of the constriction is smaller than its width (L<W). In very short
constrictions, we observe both resonances due to localized states or charged
islands and an elevated overall conductance level (0.1-1e2/h), which is
strongly length-dependent in the gap region. This makes very short graphene
constrictions interesting for highly transparent graphene tunneling barriers.Comment: 4 pages, 4 figure
Transport in coupled graphene-nanotube quantum devices
We report on the fabrication and characterization of all-carbon hybrid
quantum devices based on graphene and single-walled carbon nanotubes. We
discuss both, carbon nanotube quantum dot devices with graphene charge
detectors and nanotube quantum dots with graphene leads. The devices are
fabricated by chemical vapor deposition growth of carbon nanotubes and
subsequent structuring of mechanically exfoliated graphene. We study the
detection of individual charging events in the carbon nanotube quantum dot by a
nearby graphene nanoribbon and show that they lead to changes of up to 20% of
the conductance maxima in the graphene nanoribbon acting as a good performing
charge detector. Moreover, we discuss an electrically coupled graphene-nanotube
junction, which exhibits a tunneling barrier with tunneling rates in the low
GHz regime. This allows to observe Coulomb blockade on a carbon nanotube
quantum dot with graphene source and drain leads
The Chromo-Dielectric Soliton Model: Quark Self Energy and Hadron Bags
The chromo-dielectric soliton model (CDM) is Lorentz- and chirally-invariant.
It has been demonstrated to exhibit dynamical chiral symmetry breaking and
spatial confinement in the locally uniform approximation. We here study the
full nonlocal quark self energy in a color-dielectric medium modeled by a two
parameter Fermi function. Here color confinement is manifest. The self energy
thus obtained is used to calculate quark wave functions in the medium which, in
turn, are used to calculate the nucleon and pion masses in the one gluon
exchange approximation. The nucleon mass is fixed to its empirical value using
scaling arguments; the pion mass (for massless current quarks) turns out to be
small but non-zero, depending on the model parameters.Comment: 24 pages, figures available from the author
X-rays from accretion shocks in T Tauri stars: The case of BP Tau
We present an XMM-Newton observation of the classical T Tauri star BP Tau. In
the XMM-Newton RGS spectrum the O {\sc vii} triplet is clearly detected with a
very weak forbidden line indicating high plasma densities and/or a high UV flux
environment. At the same time concurrent UV data point to a small hot spot
filling factor suggesting an accretion funnel shock as the site of the X-ray
and UV emission. Together with the X-ray data on TW Hya these new observations
suggest such funnels to be a general feature in classical T Tauri stars.Comment: 4 pages, 4 figures, accepted by A&
Indoor exposure to molds and allergic sensitization.
Evidence that indoor dampness and mold growth are associated with respiratory health has been accumulating, but few studies have been able to examine health risks in relation to measured levels of indoor mold exposure. In particular, little is known about the contribution of indoor molds to the development of allergic sensitization. As a part of an ongoing study examining the effects of ambient air pollutants on respiratory health and atopic diseases in German school children, we examined the relation between viable mold levels indoors and allergic sensitization in 272 children. We examined whether allergic sensitization in children is associated with higher fungal spore count in settled house dust sampled from living room floors. Adjusting for age, sex, parental education, region of residency, and parental history of atopy, we found that mold spore counts for Cladosporium and Aspergillus were associated with an increased risk of allergic sensitization. Sensitized children exposed to high levels of mold spores (> 90th percentile) were more likely to suffer from symptoms of rhinoconjunctivitis. We conclude that elevated indoor concentrations of molds in wintertime might play a role in increasing the risk of developing atopic symptoms and allergic sensitization not only to molds but also to other common, inhaled allergens. These effects were strongest in the group of children who had lived in the same home since birth
Evaluation of a temporary vaccination recommendation in response to an outbreak of invasive meningococcal serogroup C disease in men who have sex with men in Berlin, 2013-2014
Meningococcal serogroup C (MenC) vaccination of men who have sex with men
(MSM) was temporarily recommended to control an outbreak of invasive MenC
disease among MSM in Berlin in 2012â2013. Vaccination was offered to HIV-
infected MSM free of charge; others had to request reimbursement or pay out of
pocket. We aimed to assess (i) awareness and acceptance of this recommendation
through an online survey of MSM, (ii) implementation through a survey of
primary care physicians and analysis of vaccine prescriptions, and (iii)
impact through analysis of notified cases. Among online survey respondents,
60% were aware of the recommendation. Of these, 39% had obtained vaccination
(70% of HIV-infected, 13% of HIV-negative/non-tested MSM). Awareness of
recommendation and vaccination were positively associated with HIV infection,
primary care physiciansâ awareness of respondentsâ sexual orientation, and
exposure to multiple information sources. Most (26/30) physicians informed
clients about the recommendation. Physicians considered concerns regarding
reimbursement, vaccine safety and lack of perceived disease risk as primary
barriers. After the recommendation, no further outbreak-related cases
occurred. To reach and motivate target groups, communication of a new
outbreak-related vaccination recommendation should address potential concerns
through as many information channels as possible and direct reimbursement of
costs should be enabled
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