2,562 research outputs found
Beam Dynamics Studies and Design Optimisation of New Low Energy Antiproton Facilities
Antiprotons, stored and cooled at low energies in a storage ring or at rest
in traps, are highly desirable for the investigation of a large number of basic
questions on fundamental interactions. This includes the static structure of
antiprotonic atomic systems and the time-dependent quantum dynamics of
correlated systems. The Antiproton Decelerator (AD) at CERN is currently the
worlds only low energy antiproton factory dedicated to antimatter experiments.
New antiproton facilities, such as the Extra Low ENergy Antiproton ring (ELENA)
at CERN and the Ultra-low energy Storage Ring (USR) at FLAIR, will open unique
possibilities. They will provide cooled, high quality beams of extra-low energy
antiprotons at intensities exceeding those achieved presently at the AD by
factors of ten to one hundred. These facilities, operating in the energy regime
between 100 keV down to 20 keV, face several design and beam dynamics
challenges, for example nonlinearities, space charge and scattering effects
limiting beam life time. Detailed investigations into the low energy and long
term beam dynamics have been carried out to address many of those challenges
towards the design optimisation. Results from these studies are presented in
this contribution, showing some examples for ELENA.Comment: 6 pages, 4 figures, 12th International Conference on Low Energy
Antiproton Physics, LEAP 2016. Submitted to JPS Conference Proceeding
Class A scavenger receptor 1 (MSR1) restricts hepatitis C virus replication by mediating toll-like receptor 3 recognition of viral RNAs produced in neighboring cells
Persistent infections with hepatitis C virus (HCV) may result in life-threatening liver disease, including cirrhosis and cancer, and impose an important burden on human health. Understanding how the virus is capable of achieving persistence in the majority of those infected is thus an important goal. Although HCV has evolved multiple mechanisms to disrupt and block cellular signaling pathways involved in the induction of interferon (IFN) responses, IFN-stimulated gene (ISG) expression is typically prominent in the HCV-infected liver. Here, we show that Toll-like receptor 3 (TLR3) expressed within uninfected hepatocytes is capable of sensing infection in adjacent cells, initiating a local antiviral response that partially restricts HCV replication. We demonstrate that this is dependent upon the expression of class A scavenger receptor type 1 (MSR1). MSR1 binds extracellular dsRNA, mediating its endocytosis and transport toward the endosome where it is engaged by TLR3, thereby triggering IFN responses in both infected and uninfected cells. RNAi-mediated knockdown of MSR1 expression blocks TLR3 sensing of HCV in infected hepatocyte cultures, leading to increased cellular permissiveness to virus infection. Exogenous expression of Myc-MSR1 restores TLR3 signaling in MSR1-depleted cells with subsequent induction of an antiviral state. A series of conserved basic residues within the carboxy-terminus of the collagen superfamily domain of MSR1 are required for binding and transport of dsRNA, and likely facilitate acidification-dependent release of dsRNA at the site of TLR3 expression in the endosome. Our findings reveal MSR1 to be a critical component of a TLR3-mediated pattern recognition receptor response that exerts an antiviral state in both infected and uninfected hepatocytes, thereby limiting the impact of HCV proteins that disrupt IFN signaling in infected cells and restricting the spread of HCV within the liver
Magnetic helicity transported by flux emergence and shuffling motions in Solar Active Region NOAA 10930
We present a new methodology which can determine magnetic helicity transport
by the passage of helical magnetic field lines from sub-photosphere and the
shuffling motions of foot-points of preexisting coronal field lines separately.
It is well known that only the velocity component which is perpendicular to the
magnetic field () has contribution to the helicity
accumulation. Here, we demonstrate that can be deduced
from horizontal motion and vector magnetograms, under a simple relation of
as suggested by
Dmoulin & Berger (2003). Then after dividing
into two components, as one is tangential and the other is normal to the solar
surface, we can determine both terms of helicity transport. Active region (AR)
NOAA 10930 is analyzed as an example during its solar disk center passage by
using data obtained by the Spectro-Polarimeter and the Narrowband Filter Imager
of Solar Optical Telescope on board Hinode. We find that in our calculation,
the helicity injection by flux emergence and shuffling motions have the same
sign. During the period we studied, the main contribution of helicity
accumulation comes from the flux emergence effect, while the dynamic transient
evolution comes from the shuffling motions effect. Our observational results
further indicate that for this AR, the apparent rotational motion in the
following sunspot is the real shuffling motions on solar surface
Universal measurement of quantum correlations of radiation
A measurement technique is proposed which, in principle, allows one to
observe the general space-time correlation properties of a quantized radiation
field. Our method, called balanced homodyne correlation measurement, unifies
the advantages of balanced homodyne detection with those of homodyne
correlation measurements.Comment: 4 pages, 4 figures, small misprints were corrected, accepted to Phys.
Rev. Let
Atomic entanglement near a realistic microsphere
We study a scheme for entangling two-level atoms located close to the surface
of a dielectric microsphere. The effect is based on medium-assisted spontaneous
decay, rigorously taking into account dispersive and absorptive properties of
the microsphere. We show that even in the weak-coupling regime, where the
Markov approximation applies, entanglement up to 0.35 ebits between two atoms
can be created. However, larger entanglement and violation of Bell's inequality
can only be achieved in the strong-coupling regime.Comment: 16 pages, 4 figures, Late
Quantum-state input-output relations for absorbing cavities
The quantized electromagnetic field inside and outside an absorbing high-
cavity is studied, with special emphasis on the absorption losses in the
coupling mirror and their influence on the outgoing field. Generalized operator
input-output relations are derived, which are used to calculate the Wigner
function of the outgoing field. To illustrate the theory, the preparation of
the outgoing field in a Schr\"{o}dinger cat-like state is discussed.Comment: 12 pages, 5 eps figure
Global Energetics of Thirty-Eight Large Solar Eruptive Events
We have evaluated the energetics of 38 solar eruptive events observed by a
variety of spacecraft instruments between February 2002 and December 2006, as
accurately as the observations allow. The measured energetic components
include: (1) the radiated energy in the GOES 1 - 8 A band; (2) the total energy
radiated from the soft X-ray (SXR) emitting plasma; (3) the peak energy in the
SXR-emitting plasma; (4) the bolometric radiated energy over the full duration
of the event; (5) the energy in flare-accelerated electrons above 20 keV and in
flare-accelerated ions above 1 MeV; (6) the kinetic and potential energies of
the coronal mass ejection (CME); (7) the energy in solar energetic particles
(SEPs) observed in interplanetary space; and (8) the amount of free
(nonpotential) magnetic energy estimated to be available in the pertinent
active region. Major conclusions include: (1) the energy radiated by the
SXR-emitting plasma exceeds, by about half an order of magnitude, the peak
energy content of the thermal plasma that produces this radiation; (2) the
energy content in flare-accelerated electrons and ions is sufficient to supply
the bolometric energy radiated across all wavelengths throughout the event; (3)
the energy contents of flare-accelerated electrons and ions are comparable; (4)
the energy in SEPs is typically a few percent of the CME kinetic energy
(measured in the rest frame of the solar wind); and (5) the available magnetic
energy is sufficient to power the CME, the flare-accelerated particles, and the
hot thermal plasma
Evidence of photospheric vortex flows at supergranular junctions observed by FG/SOT (Hinode)
Twisting motions of different nature are observed in several layers of the
solar atmosphere. Chromospheric sunspot whorls and rotation of sunspots or even
higher up in the lower corona sigmoids are examples of the large scale twisted
topology of many solar features. Nevertheless, their occurrence at large scale
in the quiet photosphere has not been investigated. The present study reveals
the existence of vortex flows located at the supergranular junctions of the
quiet Sun. We use a 1-hour and a 5-hour time series of the granulation in Blue
continuum and G-band images from FG/SOT to derive the photospheric flows. A
feature tracking technique called Balltracking is performed to track the
granules and reveal the underlying flow fields. In both time series we identify
long-lasting vortex flow located at supergranular junctions. The first vortex
flow lasts at least 1 hour and is ~20-arcsec-wide (~15.5 Mm). The second vortex
flow lasts more than 2 hours and is ~27-arcsec-wide (~21 Mm).Comment: 4 pages, 10 figure
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