1,079 research outputs found
Cosmological Consequences of String Axions
Axion fluctuations generated during inflation lead to isocurvature and
non-Gaussian temperature fluctuations in the cosmic microwave background
radiation. Following a previous analysis for the model independent string axion
we consider the consequences of a measurement of these fluctuations for two
additional string axions. We do so independent of any cosmological assumptions
except for the axions being massless during inflation. The first axion has been
shown to solve the strong CP problem for most compactifications of the
heterotic string while the second axion, which does not solve the strong CP
problem, obeys a mass formula which is independent of the axion scale. We find
that if gravitational waves interpreted as arising from inflation are observed
by the PLANCK polarimetry experiment with a Hubble constant during inflation of
H_inf \apprge 10^13 GeV the existence of the first axion is ruled out and the
second axion cannot obey the scale independent mass formula. In an appendix we
quantitatively justify the often held assumption that temperature corrections
to the zero temperature QCD axion mass may be ignored for temperatures T
\apprle \Lambda_QCD.Comment: 27 pages, 4 figures; v2: References corrected; v3: Assumptions
simplified, minor corrections, conclusions unchange
Superconductor-insulator transition in granular Pb films near a superconducting ground plane
We report observations of the zero-field superconductor-insulator transition in granular quench-condensed Pb for samples within 10-15 nm of relatively thick superconducting ground planes. Resistance vs temperature measurements of sufficiently thick Pb samples exhibit broadened superconductor transitions consistent with previous results on clean dielectric substrates. The lack of any measurable influence by the superconducting planes on the Pb film resistance is discussed within the context of zero-field vortex-antivortex unbinding explanations for the transition broadening
Operational Experience with First Circulating Beam in the LHC
Following a series of injection tests, the first attempts to pass beam around both directions of the LHC were successful and led rapidly to circulating beam in the counter clockwise direction (beam 2) and many turns of beam 1. Unfortunately the beam commissioning was curtailed by the incident in sector 34. However, measurements performed during this first commissioning period showed that the magnet model of the machine had delivered optics close to nominal and also very good performance of beam instrumentation and supporting software. Details of the machine set-up and the commissioning procedures are given. The measurements performed and the key results from this period are described
The LHC Injection Tests
A series of LHC injection tests was performed in August and September 2008. The first saw beam injected into sector 23; the second into sectors 78 and 23; the third into sectors 78-67 and sectors 23-34-45. The fourth, into sectors 23-34-45, was performed the evening before the extended injection test on the 10th September which saw both beams brought around the full circumference of the LHC. The tests enabled the testing and debugging of a number of critical control and hardware systems; testing and validation of instrumentation with beam for the first time; deployment, and validation of a number of measurement procedures. Beam based measurements revealed a number of machine configuration issues that were rapidly resolved. The tests were undoubtedly an essential precursor to the successful start of LHC beam commissioning. This paper provides an outline of preparation for the tests, the machine configuration and summarizes the measurements made and individual system performance
The Metric Tide: Report of the Independent Review of the Role of Metrics in Research Assessment and Management
Anti-hLAMP2-antibodies and dual positivity for anti-GBM and MPO-ANCA in a patient with relapsing pulmonary-renal syndrome
Background Pulmonary-renal syndrome associated with anti-glomerular basement membrane (GBM) antibodies, also known as Goodpasture's syndrome, is a rare but acute and life-threatening condition. One third of patients presenting as anti-GBM antibody positive pulmonary-renal syndrome or rapidly progressive glomerulonephritis are also tested positive for anti-neutrophil cytoplasmic antibodies (ANCA). Whilst anti-GBM disease is considered a non-relapsing condition, the long-term course of double-positive patients is less predictable. Case Presentation We report a patient with such dual positivity, who presented with pulmonary hemorrhage, crescentic glomerulonephritis and membranous nephropathy. Plasmapheresis in combination with immunosuppresive therapy led to a rapid remission but the disease relapsed after two years. The serum of the patient was tested positive for antibodies to human lysosomal membrane protein 2 (hLAMP2), a novel autoantigen in patients with active small-vessel vasculitis (SVV). The anti-hLAMP2 antibody levels correlated positively with clinical disease activity in this patient. Conclusion We hypothesize that this antibody may indicate a clinical course similar to ANCA-associated vasculitis in double-positive patients. However, this needs to be confirmed on comprehensive patient cohorts
Investigations of the LHC Emittance Blow-Up During the 2012 Proton Run
About 30 % of the potential luminosity performance is lost through the different phases of the LHC cycle, mainly due to transverse emittance blow-up. Measuring the emittance growth is a difficult task with high intensity beams and changing energies. Improvements of the LHC transverse profile instrumentation helped to study various effects. A breakdown of the growth through the different phases of the LHC cycle is given as well as a comparison with the data from the LHC experiments for transverse beam size. In 2012 a number of possible sources and remedies have been studied. Among these are intra beam scattering, 50 Hz noise and the effect of the transverse damper gain. The results of the investigations are summarized in this paper. Requirements for transverse profile instrumentation for post LHC long shutdown operation to finally tackle the emittance growth are given as well
Rapid generation of endogenously driven transcriptional reporters in cells through CRISPR/Cas9
CRISPR/Cas9 technologies have been employed for genome editing to achieve gene knockouts and knock-ins in somatic cells. Similarly, certain endogenous genes have been tagged with fluorescent proteins. Often, the detection of tagged proteins requires high expression and sophisticated tools such as confocal microscopy and flow cytometry. Therefore, a simple, sensitive and robust transcriptional reporter system driven by endogenous promoter for studies into transcriptional regulation is desirable. We report a CRISPR/Cas9-based methodology for rapidly integrating a firefly luciferase gene in somatic cells under the control of endogenous promoter, using the TGFÎČ-responsive gene PAI-1. Our strategy employed a polycistronic cassette containing a non-fused GFP protein to ensure the detection of transgene delivery and rapid isolation of positive clones. We demonstrate that firefly luciferase cDNA can be efficiently delivered downstream of the promoter of the TGFÎČ-responsive gene PAI-1. Using chemical and genetic regulators of TGFÎČ signalling, we show that it mimics the transcriptional regulation of endogenous PAI-1 expression. Our unique approach has the potential to expedite studies on transcription of any gene in the context of its native chromatin landscape in somatic cells, allowing for robust high-throughput chemical and genetic screens
Measurement and application of electron stripping of ultrarelativistic
New measurements of the stripping cross-section for ultrarelativistic
hydrogen-like lead ions passing through aluminium and silicon have been
performed at the Advanced Wakefield experiment at CERN. Agreement with existing
measurements and theory has been obtained. Improvements in terms of electron
beam quality and ion beam diagnostic capability, as well as further
applications of such an electron beam, are discussed
A statistical comparison of spatio-temporal surface moisture patterns beneath a semi-natural grassland and permanent pasture:From drought to saturation
Some 60% of the agricultural land in the UK is grassland. This is mostly located in the wetter uplands of the west and north, with the majority intensively managed as permanent pasture. Despite its extent, there is a lack of knowledge regarding how agricultural practices have altered the hydrological behaviour of the underlying soils relative to the adjacent moorland covered by semiânatural grassland. Nearâsurface soil moisture content is an expression of the changes that have taken place and is critical in the generation of floodâproducing overlandâflows. This study aims to develop a pioneering pairedâplot approach, producing 1536 moisture measurements at each of the monitoring dates throughout the studied year, that were subsequently analysed by a comparison of frequency distributions, visualâcumâgeostatistical investigation of spatial patterns and mixedâeffects regression modelling. The analysis demonstrated that the practices taking place in the pasture (ploughing, reâseeding and drainage) reduced the natural diversity in moisture patterns. Compared to adjacent moorland, the topsoil dried much faster in spring with the effects requiring offset with moisture from slurry applications in summer. With the onset of autumn rains, these applications then made the topsoil wetter than the moorland, heightening the likelihood of floodâproducing overlandâflow. During the sampling within one such stormâevent, the adjacent moorland was almost as wet as the pasture with both visibly generating overlandâflow. These contrasts in soil moisture were statistically significant throughout. Further, they highlight the need to scaleâup the monitoring with numerous plotâpairs to see if the observed highly dynamic, contrasting behaviour is present at the landscapeâscale. Such research is fundamental to designing appropriate agricultural interventions to deliver sustainable sward production for livestock or methods of mitigating overlandâflow incidence that would otherwise heighten floodârisk or threaten waterâquality in rivers
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