8,663 research outputs found
Seething Horizontal Magnetic Fields in the Quiet Solar Photosphere
The photospheric magnetic field outside of active regions and the network has
a ubiquitous and dynamic line-of-sight component that strengthens from disk
center to limb as expected for a nearly horizontal orientation. This component
shows a striking time variation with an average temporal rms near the limb of
1.7 G at ~3" resolution. In our moderate resolution observations the nearly
horizontal component has a frequency variation power law exponent of -1.4 below
1.5 mHz and is spatially patchy on scales up to ~15 arcsec. The field may be a
manifestation of changing magnetic connections between eruptions and evolution
of small magnetic flux elements in response to convective motions. It shows no
detectable latitude or longitude variations.Comment: 7 pages, 6 figures, submitted to ApJ letters, quality of figures
significantly degraded here by compression requirement
Simulation System for the Wendelstein 7-X Safety Control System
The Wendelstein 7-X (W7-X) Safety Instrumented System (SIS) ensures personal
safety and investment protection. The development and implementation of the SIS
are based on the international safety standard for the process industry sector,
IEC 61511. The SIS exhibits a distributed and hierarchical organized
architecture consisting of a central Safety System (cSS) on the top and many
local Safety Systems (lSS) at the bottom. Each technical component or
diagnostic system potentially hazardous for the staff or for the device is
equipped with an lSS. The cSS is part of the central control system of W7-X.
Whereas the lSSs are responsible for the safety of each individual component,
the cSS ensures safety of the whole W7-X device. For every operation phase of
the W7-X experiment hard- and software updates for the SIS are mandatory. New
components with additional lSS functionality and additional safety signals have
to be integrated. Already established safety functions must be adapted and new
safety functions have to be integrated into the cSS. Finally, the safety
programs of the central and local safety systems have to be verified for every
development stage and validated against the safety requirement specification.
This contribution focuses on the application of a model based simulation system
for the whole SIS of W7-X. A brief introduction into the development process of
the SIS and its technical realization will be give followed by a description of
the design and implementation of the SIS simulation system using the framework
SIMIT (Siemens). Finally, first application experiences of this simulation
system for the preparation of the SIS for the upcoming operation phase OP 1.2b
of W7-X will be discussed
The Higgs Sector and CoGeNT/DAMA-Like Dark Matter in Supersymmetric Models
Recent data from CoGeNT and DAMA are roughly consistent with a very light
dark matter particle with m\sim 4-10\gev and spin-independent cross section
of order \sigma_{SI} \sim (1-3)\times 10^{-4}\pb. An important question is
whether these observations are compatible with supersymmetric models obeying
without violating existing collider constraints and
precision measurements. In this talk, I review the fact the the Minimal
Supersymmetric Model allows insufficient flexibility to achieve such
compatibility, basically because of the highly constrained nature of the MSSM
Higgs sector in relation to LEP limits on Higgs bosons. I then outline the
manner in which the more flexible Higgs sectors of the Next-to-Minimal
Supersymmetric Model and an Extended Next-to-Minimal Supersymmetric Model allow
large and at low LSP mass without violating
LEP, Tevatron, BaBar and other experimental limits. The relationship of the
required Higgs sectors to the NMSSM "ideal-Higgs" scenarios is discussed.Comment: 11 pages, 3 figures. To appear in Proceedings of PASCOS 2010. The
paper is a compilation of talks given at: PASCOS 2010, ORSAY Workshop on
"Higgs Hunting", and SLAC Workshop on "Topologies for Early LHC Searches
Update on the physics of light pseudoscalar mesons
We present an update of the MILC investigation of the properties of light
pseudoscalar mesons using three flavors of improved staggered quarks. Results
are presented for the and leptonic decay constants, the CKM matrix
element , the up, down and strange quark masses, and the coefficients
of the chiral lagrangian. We have new data for lattice spacing fm with several values of the light quark mass down to one-tenth
the strange quark mass, higher statistics for fm with the
light quark mass equal to one-tenth the strange quark mass, and initial results
for our smallest lattice spacing, fm with light quark mass
two-fifths of the strange quark mass.Comment: 7 pages, 4 figures. To be published in Proceedings of Science
(Lattice 2006) 163 (2006
Kondo effect in a one dimensional d-wave superconductor
We derive a solvable resonant-level type model, to describe an impurity spin
coupled to zero-energy bound states localized at the edge of a one dimensional
d-wave superconductor. This results in a two-channel Kondo effect with a quite
unusual low-temperature thermodynamics. For instance, the local impurity
susceptibility yields a finite maximum at zero temperature (but no
logarithmic-divergence) due to the splitting of the impurity in two Majorana
fermions. Moreover, we make comparisons with the Kondo effect occurring in a
two dimensional d-wave superconductor.Comment: 9 pages, final version; To be published in Europhysics Letter
Black Hole Lightning from the Peculiar Gamma-Ray Loud Active Galactic Nucleus IC 310
The nearby active galaxy IC 310, located in the outskirts of the Perseus
cluster of galaxies is a bright and variable multi-wavelength emitter from the
radio regime up to very high gamma-ray energies above 100 GeV. Originally, the
nucleus of IC 310 has been classified as a radio galaxy. However, studies of
the multi-wavelength emission showed several properties similarly to those
found from blazars as well as radio galaxies. In late 2012, we have organized
the first contemporaneous multi-wavelength campaign including radio, optical,
X-ray and gamma-ray instruments. During this campaign an exceptionally bright
flare of IC 310 was detected with the MAGIC telescopes in November 2012
reaching an averaged flux level in the night of up to one Crab above 1 TeV with
a hard spectrum over two decades in energy. The intra-night light curve showed
a series of strong outbursts with flux-doubling time scales as fast as a few
minutes. The fast variability constrains the size of the gamma-ray emission
regime to be smaller than 20% of the gravitational radius of its central black
hole. This challenges the shock acceleration models, commonly used to explain
gamma-ray radiation from active galaxies. Here, we will present more details on
the MAGIC data and discuss several possible alternative emission models.Comment: 8 pages, 5 figures, Proceedings of the 34th International Cosmic Ray
Conference, 30 July - 6 August, 2015, The Hague, The Netherland
Higher Structures in M-Theory
The key open problem of string theory remains its non-perturbative completion
to M-theory. A decisive hint to its inner workings comes from numerous
appearances of higher structures in the limits of M-theory that are already
understood, such as higher degree flux fields and their dualities, or the
higher algebraic structures governing closed string field theory. These are all
controlled by the higher homotopy theory of derived categories, generalised
cohomology theories, and -algebras. This is the introductory chapter
to the proceedings of the LMS/EPSRC Durham Symposium on Higher Structures in
M-Theory. We first review higher structures as well as their motivation in
string theory and beyond. Then we list the contributions in this volume,
putting them into context.Comment: 22 pages, Introductory Article to Proceedings of LMS/EPSRC Durham
Symposium Higher Structures in M-Theory, August 2018, references update
The Phase Diagram of High Temperature QCD with Three Flavors of Improved Staggered Quarks
We report on progress in our study of high temperature QCD with three flavors
of improved staggered quarks. Simulations are being carried out with three
degenerate quarks with masses less than or equal to the strange quark mass,
, and with degenerate up and down quarks with masses in the range , and the strange quark mass fixed near its physical
value. For the quark masses studied to date we find rapid crossovers, which
sharpen as the quark mass is reduced, rather than bona fide phase transitions.Comment: Lattice 2003 (Nonzero temperature and density
Insights into the particle acceleration of a peculiar gamma -ray radio galaxy IC 310
IC 310 has recently been identified as a gamma-ray emitter based on
observations at GeV energies with Fermi-LAT and at very high energies (VHE, E >
100 GeV) with the MAGIC telescopes. Despite IC 310 having been classified as a
radio galaxy with the jet observed at an angle > 10 degrees, it exhibits a
mixture of multiwavelength properties of a radio galaxy and a blazar, possibly
making it a transitional object. On the night of 12/13th of November 2012 the
MAGIC telescopes observed a series of violent outbursts from the direction of
IC 310 with flux-doubling time scales faster than 5 min and a peculiar spectrum
spreading over 2 orders of magnitude. Such fast variability constrains the size
of the emission region to be smaller than 20% of the gravitational radius of
its central black hole, challenging the shock acceleration models, commonly
used in explanation of gamma-ray radiation from active galaxies. Here we will
show that this emission can be associated with pulsar-like particle
acceleration by the electric field across a magnetospheric gap at the base of
the jet.Comment: 2014 Fermi Symposium proceedings - eConf C14102.
Headache and pregnancy. a systematic review
This systematic review summarizes the existing data on headache and pregnancy with a scope on clinical headache phenotypes, treatment of headaches in pregnancy and effects of headache medications on the child during pregnancy and breastfeeding, headache related complications, and diagnostics of headache in pregnancy. Headache during pregnancy can be both primary and secondary, and in the last case can be a symptom of a life-threatening condition. The most common secondary headaches are stroke, cerebral venous thrombosis, subarachnoid hemorrhage, pituitary tumor, choriocarcinoma, eclampsia, preeclampsia, idiopathic intracranial hypertension, and reversible cerebral vasoconstriction syndrome. Migraine is a risk factor for pregnancy complications, particularly vascular events. Data regarding other primary headache conditions are still scarce. Early diagnostics of the disease manifested by headache is important for mother and fetus life. It is especially important to identify "red flag symptoms" suggesting that headache is a symptom of a serious disease. In order to exclude a secondary headache additional studies can be necessary: electroencephalography, ultrasound of the vessels of the head and neck, brain MRI and MR angiography with contrast ophthalmoscopy and lumbar puncture. During pregnancy and breastfeeding the preferred therapeutic strategy for the treatment of primary headaches should always be a non-pharmacological one. Treatment should not be postponed as an undermanaged headache can lead to stress, sleep deprivation, depression and poor nutritional intake that in turn can have negative consequences for both mother and baby. Therefore, if non-pharmacological interventions seem inadequate, a well-considered choice should be made concerning the use of medication, taking into account all the benefits and possible risks
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