2,277 research outputs found
A Fully Polynomial-Time Approximation Scheme for Speed Scaling with Sleep State
We study classical deadline-based preemptive scheduling of tasks in a
computing environment equipped with both dynamic speed scaling and sleep state
capabilities: Each task is specified by a release time, a deadline and a
processing volume, and has to be scheduled on a single, speed-scalable
processor that is supplied with a sleep state. In the sleep state, the
processor consumes no energy, but a constant wake-up cost is required to
transition back to the active state. In contrast to speed scaling alone, the
addition of a sleep state makes it sometimes beneficial to accelerate the
processing of tasks in order to transition the processor to the sleep state for
longer amounts of time and incur further energy savings. The goal is to output
a feasible schedule that minimizes the energy consumption. Since the
introduction of the problem by Irani et al. [16], its exact computational
complexity has been repeatedly posed as an open question (see e.g. [2,8,15]).
The currently best known upper and lower bounds are a 4/3-approximation
algorithm and NP-hardness due to [2] and [2,17], respectively. We close the
aforementioned gap between the upper and lower bound on the computational
complexity of speed scaling with sleep state by presenting a fully
polynomial-time approximation scheme for the problem. The scheme is based on a
transformation to a non-preemptive variant of the problem, and a discretization
that exploits a carefully defined lexicographical ordering among schedules
Measurement of Zγγ production in pp collisions at √s = 13 TeV with the ATLAS detector
Final states with multiple electroweak gauge bosons are important signatures for probing the non-Abelian character of the Standard Model SU(2)L x U(1)Y symmetry. The triple gauge boson production of Zγγ is measured in Run 2 of the LHC at a centre-of-mass energy of 13 TeV. The dataset contains pp collisions recorded with the ATLAS detector and corresponds to an integrated luminosity of 139 fb-1. The fully leptonic decay channel of the Z boson is analysed. Final state radiation is suppressed to obtain a pure sample of Zγγ events with prompt photons. The integrated cross section and differential cross sections of six kinematic observables are measured in a fiducial volume at particle-level, where the cross sections are corrected for detector effects. The results are compared to predictions of MC event generators at NLO QCD precision showing good agreement. The measurement with the highest sensitivity for new physics effects is used to constrain dimension-8 operators in an effective field theory approach. Existing constraints are improved by up to two orders of magnitude
Advances in the prevention, management, and treatment of community-acquired pneumonia
Despite the availability of powerful antibiotics, community-acquired pneumonia (CAP) remains one of the leading reasons for morbidity and mortality worldwide, and despite the availability of powerful antibiotics, there has been only little improvement in case fatality rates for many years. Consequently, it cannot be expected that novel antibiotics will substantially improve outcomes in CAP. Therefore, this review focuses on novel approaches that may reduce CAP-related mortality: the impact of immunomodulation by macrolides and fluoroquinolones and the prevention of CAP by pneumococcal vaccines
SARS-CoV-2 in an immunocompromised host: convalescent plasma therapy and viral evolution elucidated by whole genome sequencing
The evolution of SARS-CoV-2 within immunocompromised hosts who fail to clear the virus over many months has been proposed as a route to the development of Variants of Concern (VoCs). We present a case of an immunocompromised male patient with a prolonged SARS-CoV-2 infection. During hospitalisation, 7 weeks after first diagnosis, his condition worsened to require continuous ventilation support. Resolution of symptoms was observed after convalescent plasma therapy. Whole genome sequencing of the virus showed Pango lineage B.1.221. Between the first sample and the second from bronchoalveolar lavage fluid 7 weeks later, we identified eight mutations, including minor variants, which could be used to estimate the chronology of mutations. This suggests an elevated mutation rate, in-host accumulation of mutations and further evidence for sources of VoCs. Prolonged SARS-CoV-2 infections in immunocompromised hosts increase the likelihood of hospital stays and morbidity, and also pose an increased risk to global public health
Performance of Drift-Tube Detectors at High Counting Rates for High-Luminosity LHC Upgrades
The performance of pressurized drift-tube detectors at very high background
rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in
an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator
for applications in large-area precision muon tracking at high-luminosity
upgrades of the Large Hadron Collider (LHC). The ATLAS muon drifttube (MDT)
chambers with 30 mm tube diameter have been designed to cope with and neutron
background hit rates of up to 500 Hz/square cm. Background rates of up to 14
kHz/square cm are expected at LHC upgrades. The test results with standard MDT
readout electronics show that the reduction of the drift-tube diameter to 15
mm, while leaving the operating parameters unchanged, vastly increases the rate
capability well beyond the requirements. The development of new small-diameter
muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further
improvements of tracking efficiency and spatial resolution at high counting
rates will be achieved with upgraded readout electronics employing improved
signal shaping for high counting rates
High Rate Proton Irradiation of 15mm Muon Drifttubes
Future LHC luminosity upgrades will significantly increase the amount of
background hits from photons, neutrons and protons in the detectors of the
ATLAS muon spectrometer. At the proposed LHC peak luminosity of 5*10^34
1/cm^2s, background hit rates of more than 10 kHz/cm^2 are expected in the
innermost forward region, leading to a loss of performance of the current
tracking chambers. Based on the ATLAS Monitored Drift Tube chambers, a new high
rate capable drift tube detecor using tubes with a reduced diameter of 15mm was
developed. To test the response to highly ionizing particles, a prototype
chamber of 46 15mm drift tubes was irradiated with a 20 MeV proton beam at the
tandem accelerator at the Maier-Leibnitz Laboratory, Munich. Three tubes in a
planar layer were irradiated while all other tubes were used for reconstruction
of cosmic muon tracks through irradiated and non-irradiated parts of the
chamber. To determine the rate capability of the 15mm drift-tubes we
investigated the effect of the proton hit rate on pulse height, efficiency and
spatial resolution of the cosmic muon signals
Perspectives of Ultra Cold Atoms Trapped in Magnetic Micro Potentials
Recent work on magnetic micro traps for ultracold atoms is briefly reviewed.
The basic principles of operation are described together with the loading
methods and some of the realized trap geometries. Experiments are discussed
that study the interaction between atoms and the surface of micro traps as well
as the dynamics of ultracold gases in wave guides are discussed. The results
allow for an outlook towards future directions of research
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