753 research outputs found
Multiwavelength observations of the blazar BL Lacertae: a new fast TeV γ-ray flare
Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan (South Korea). Published in Proceeding of Science.Observations of fast TeV γ-ray flares from blazars reveal the extreme compactness of emitting regions in blazar jets. Combined with very-long-baseline radio interferometry measurements, they probe the structure and emission mechanism of the jet. We report on a fast TeV γ-ray flare from BL Lacertae observed by VERITAS, with a rise time of about 2.3 hours and a decay time of about 36 minutes. The peak flux at >200 GeV measured with the 4-minute binned light curve is (4.2±0.6)×10−6photonsm−2s−1, or ∼180% the Crab Nebula flux. Variability in GeV γ-ray, X-ray, and optical flux, as well as in optical and radio polarization was observed around the time of the TeV γ-ray flare. A possible superluminal knot was identified in the VLBA observations at 43 GHz. The flare constrains the size of the emitting region, and is consistent with several theoretical models with stationary shocks
Melting Point and Lattice Parameter Shifts in Supported Metal Nanoclusters
The dependencies of the melting point and the lattice parameter of supported
metal nanoclusters as functions of clusters height are theoretically
investigated in the framework of the uniform approach. The vacancy mechanism
describing the melting point and the lattice parameter shifts in nanoclusters
with decrease of their size is proposed. It is shown that under the high vacuum
conditions (p<10^-7 torr) the essential role in clusters melting point and
lattice parameter shifts is played by the van der Waals forces of
cluster-substrate interation. The proposed model satisfactorily accounts for
the experimental data.Comment: 6 pages, 3 figures, 1 tabl
Correlation effects during liquid infiltration into hydrophobic nanoporous mediums
Correlation effects arising during liquid infiltration into hydrophobic
porous medium are considered. On the basis of these effects a mechanism of
energy absorption at filling porous medium by nonwetting liquid is suggested.
In accordance with this mechanism, the absorption of mechanical energy is a
result expenditure of energy for the formation of menisci in the pores on the
shell of the infinite cluster and expenditure of energy for the formation of
liquid-porous medium interface in the pores belonging to the infinite cluster
of filled pores. It was found that in dependences on the porosity and,
consequently, in dependences on the number of filled pores neighbors, the
thermal effect of filling can be either positive or negative and the cycle of
infiltration-defiltration can be closed with full outflow of liquid. It can
occur under certain relation between percolation properties of porous medium
and the energy characteristics of the liquid-porous medium interface and the
liquid-gas interface. It is shown that a consecutive account of these
correlation effects and percolation properties of the pores space during
infiltration allow to describe all experimental data under discussion
Exploring the connection between parsec-scale jet activity and broadband outbursts in 3C 279
We use a combination of high-resolution very long baseline interferometry
(VLBI) radio and multi-wavelength flux density and polarization observations to
constrain the physics of the dissipation mechanism powering the broadband
flares in 3C 279 during an episode of extreme flaring activity in 2013-2014.
Six bright flares superimposed on a long-term outburst are detected at
-ray energies. Four of the flares have optical and radio counterparts.
The two modes of flaring activity (faster flares sitting on top of a long term
outburst) present at radio, optical, -ray frequencies are missing in
X-rays. X-ray counterparts are only observed for two flares. The first three
flares are accompanied by ejection of a new VLBI component (NC2) suggesting the
43 GHz VLBI core as the site of energy dissipation. Another new component, NC3,
is ejected after the last three flares, which suggests that the emission is
produced upstream from the core (closer to the black hole). The study therefore
indicates multiple sites of energy dissipation in the source. An
anti-correlation is detected between the optical percentage polarization (PP)
and optical/-ray flux variations, while the PP has a positive
correlation with optical/-rays spectral indices. Given that the mean
polarization is inversely proportional to the number of cells in the emission
region, the PP vs. optical/-ray anti-correlation could be due to more
active cells during the outburst than at other times. In addition to the
turbulent component, our analysis suggests the presence of a combined turbulent
and ordered magnetic field, with the ordered component transverse to the jet
axis.Comment: ApJ (in press), 14 pages, 19 figure
Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales
Here we report on the results of the WEBT photo-polarimetric campaign
targeting the blazar S5~0716+71, organized in March 2014 to monitor the source
simultaneously in BVRI and near IR filters. The campaign resulted in an
unprecedented dataset spanning \,h of nearly continuous, multi-band
observations, including two sets of densely sampled polarimetric data mainly in
R filter. During the campaign, the source displayed pronounced variability with
peak-to-peak variations of about and "bluer-when-brighter" spectral
evolution, consisting of a day-timescale modulation with superimposed hourlong
microflares characterized by \,mag flux changes. We performed an
in-depth search for quasi-periodicities in the source light curve; hints for
the presence of oscillations on timescales of \,h and \,h do
not represent highly significant departures from a pure red-noise power
spectrum. We observed that, at a certain configuration of the optical
polarization angle relative to the positional angle of the innermost radio jet
in the source, changes in the polarization degree led the total flux
variability by about 2\,h; meanwhile, when the relative configuration of the
polarization and jet angles altered, no such lag could be noted. The
microflaring events, when analyzed as separate pulse emission components, were
found to be characterized by a very high polarization degree () and
polarization angles which differed substantially from the polarization angle of
the underlying background component, or from the radio jet positional angle. We
discuss the results in the general context of blazar emission and energy
dissipation models.Comment: 16 pages, 17 Figures; ApJ accepte
An evaluation of seasonal variations in footwear worn by adults with inflammatory arthritis: a cross-sectional observational study using a web-based survey
Background: Foot problems are common in adults with inflammatory arthritis and therapeutic footwear can be
effective in managing arthritic foot problems. Accessing appropriate footwear has been identified as a major barrier,
resulting in poor adherence to treatment plans involving footwear. Indeed, previous New Zealand based studies
found that many people with rheumatoid arthritis and gout wore inappropriate footwear. However, these studies
were conducted in a single teaching hospital during the New Zealand summer therefore the findings may not be
representative of footwear styles worn elsewhere in New Zealand, or reflect the potential influence of seasonal
climate changes. The aim of the study was to evaluate seasonal variations in footwear habits of people with
inflammatory arthritic conditions in New Zealand.
Methods: A cross-sectional study design using a web-based survey. The survey questions were designed to elicit
demographic and clinical information, features of importance when choosing footwear and seasonal footwear
habits, including questions related to the provision of therapeutic footwear/orthoses and footwear experiences.
Results: One-hundred and ninety-seven participants responded who were predominantly women of European
descent, aged between 46–65 years old, from the North Island of New Zealand. The majority of participants
identified with having either rheumatoid arthritis (35%) and/or osteoarthritis (57%) and 68% reported established
disease (>5 years duration). 18% of participants had been issued with therapeutic footwear. Walking and athletic
shoes were the most frequently reported footwear type worn regardless of the time of year. In the summer,
42% reported wearing sandals most often. Comfort, fit and support were reported most frequently as the footwear
features of greatest importance. Many participants reported difficulties with footwear (63%), getting hot feet in the
summer (63%) and the need for a sandal which could accommodate a supportive insole (73%).
Conclusions: Athletic and walking shoes were the most popular style of footwear reported regardless of seasonal
variation. During the summer season people with inflammatory arthritis may wear sandals more frequently in
order to accommodate disease-related foot deformity. Healthcare professionals and researchers should consider
seasonal variation when recommending appropriate footwear, or conducting footwear studies in people with
inflammatory arthritis, to reduce non-adherence to prescribed footwear
The brightest gamma-ray flaring blazar in the sky: AGILE and multi-wavelength observations of 3C 454.3 during November 2010
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all
frequencies, and during the last four years it has exhibited more than one
gamma-ray flare per year, becoming the most active gamma-ray blazar in the sky.
We present for the first time the multi-wavelength AGILE, SWIFT, INTEGRAL, and
GASP-WEBT data collected in order to explain the extraordinary gamma-ray flare
of 3C 454.3 which occurred in November 2010. On 2010 November 20 (MJD 55520),
3C 454.3 reached a peak flux (E>100 MeV) of F_gamma(p) = (6.8+-1.0)E-5 ph/cm2/s
on a time scale of about 12 hours, more than a factor of 6 higher than the flux
of the brightest steady gamma-ray source, the Vela pulsar, and more than a
factor of 3 brighter than its previous super-flare on 2009 December 2-3. The
multi-wavelength data make a thorough study of the present event possible: the
comparison with the previous outbursts indicates a close similarity to the one
that occurred in 2009. By comparing the broadband emission before, during, and
after the gamma-ray flare, we find that the radio, optical and X-ray emission
varies within a factor 2-3, whereas the gamma-ray flux by a factor of 10. This
remarkable behavior is modeled by an external Compton component driven by a
substantial local enhancement of soft seed photons.Comment: Accepted for publication in ApJ Letters. 18 Pages, 4 Figures, 1 Tabl
LIMPRINT in specialist lymphedema services in United Kingdom, France, Italy and Turkey
Background: There is no standardized international model for specialist lymphoedema services, which covers the types of lymphoedema treated and the treatments provided. The aim of this study was to provide a profile of patients attending specialist lymphoedema services in different countries to explore similarities and differences.
Methods and Results: The LIMPRINT core tool was used in specialist lymphoedema services in the UK, France, Italy and Turkey. Services in Turkey saw a slightly younger age group with a higher proportion of female patients reflecting a particular focus on breast cancer-related lymphoedema. There were higher levels of obesity and restricted mobility in patients in the UK compared with other countries. Italy and France saw the highest percentage of patients with primary lymphoedema. Diabetes was a common comorbidity in the UK and Turkey. The UK saw the largest number of patients with lower limb lymphoedema.
Conclusions: The results show a wide range of complexity of patients treated in specialist lymphoedema services. Some of the differences between countries may reflect different stages in the evolution of specialist lymphoedema services, rather than a true difference in prevalence, with those with 'younger' services treating a high proportion of patients with cancer and those with more established services treating a wider range of different types of lymphoedema including more elderly people with multiple comorbidities
Alkali metal-cationized serine clusters studied by sonic spray ionization tandem mass spectrometry
Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy
During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly
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