2,735 research outputs found
Instability of reconstruction of the low CMB multipoles
We discuss the problem of the bias of the Internal Linear Combination (ILC)
CMB map and show that it is closely related to the coefficient of
cross-correlation K(l) of the true CMB and the foreground for each multipole l.
We present analysis of the cross-correlation for the WMAP ILC quadrupole and
octupole from the first (ILC(I)) and the third (ILC(III)) year data releases
and show that these correlations are about -0.52-0.6. Analysing 10^4 Monte
Carlo simulations of the random Gaussian CMB signals, we show that the
distribution function for the corresponding coefficient of the
cross-correlation has a polynomial shape P(K,l)\propto(1-K^2)^(l-1). We show
that the most probable value of the cross-correlation coefficient of the ILC
and foreground quadrupole has two extrema at K ~= +/-0.58$. Thus, the ILC(III)
quadrupole represents the most probable value of the coefficient K. We analyze
the problem of debiasing of the ILC CMB and pointed out that reconstruction of
the bias seems to be very problematic due to statistical uncertainties. In
addition, instability of the debiasing illuminates itself for the quadrupole
and octupole components through the flip-effect, when the even (l+m) modes can
be reconstructed with significant error. This error manifests itself as
opposite, in respect to the true sign of even low multipole modes, and leads to
significant changes of the coefficient of cross-correlation with the
foreground. We show that the CMB realizations, whose the sign of quadrupole
(2,0) component is negative (and the same, as for all the foregrounds), the
corresponding probability to get the positive sign after implementation of the
ILC method is about 40%.Comment: 11 pages, 5 figure
Design and Vertical Tests of SPS-series Double-Quarter Wave (DQW) Cavity Prototypes for the HL-LHC Crab Cavity System
Crab crossing is essential for high-luminosity colliders. The High Luminosity
Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1)
with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation
of deflecting RF cavities that stands out for its compactness and broad
frequency separation between fundamental and first high-order modes. The
deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity
shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may
be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6
MV. This paper describes a new, highly optimized cavity, designated DQW
SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance
requirements for beam tests at SPS and operation in LHC. Two prototypes of this
DQW SPS-series were fabricated by US industry and cold tested after following
conventional SRF surface treatment. Both units outperformed the PoP cavity,
reaching a deflecting voltage of 5.3-5.9 MV. This voltage - the highest reached
by a DQW cavity - is well beyond the nominal voltage of 3.4 MV and may even
operate at the ultimate voltage of 5.0MVwith sufficient margin. This paper
covers fabrication, surface preparation and cryogenic RF test results and
implications
FFAT motif phosphorylation controls formation and lipid transfer function of inter‐organelle contacts
Organelles are physically connected in membrane contact sites. The endoplasmic reticulum possesses three major receptors, VAP‐A, VAP‐B, and MOSPD2, which interact with proteins at the surface of other organelles to build contacts. VAP‐A, VAP‐B, and MOSPD2 contain an MSP domain, which binds a motif named FFAT (two phenylalanines in an acidic tract). In this study, we identified a non‐conventional FFAT motif where a conserved acidic residue is replaced by a serine/threonine. We show that phosphorylation of this serine/threonine is critical for non‐conventional FFAT motifs (named Phospho‐FFAT) to be recognized by the MSP domain. Moreover, structural analyses of the MSP domain alone or in complex with conventional and Phospho‐FFAT peptides revealed new mechanisms of interaction. Based on these new insights, we produced a novel prediction algorithm, which expands the repertoire of candidate proteins with a Phospho‐FFAT that are able to create membrane contact sites. Using a prototypical tethering complex made by STARD3 and VAP, we showed that phosphorylation is instrumental for the formation of ER‐endosome contacts, and their sterol transfer function. This study reveals that phosphorylation acts as a general switch for inter‐organelle contacts
General practitioners' beliefs about effectiveness and intentions to prescribe smoking cessation medications: qualitative and quantitative studies
BACKGROUND: General practitioners' (GPs) negative beliefs about nicotine dependence medications may act as barriers to prescribing them. METHODS: Study1: Twenty-five GPs from 16 practices across London were interviewed in this qualitative study. Framework analysis was used to identify key themes. Study 2: A convenience sample of 367 GPs completed an internet-based survey. Path-analysis was used to examine the relations between beliefs and intentions to prescribe smoking cessation medications. RESULTS: Study 1: Whilst nicotine replacement therapy (NRT) and bupropion were generally perceived as effective and cost-effective, the effectiveness of NRT was seen as critically dependent on behavioural support for smoking cessation. This dependence appeared to be influenced by perceptions that without support smokers would neglect psychological aspects of smoking and use NRT incorrectly. GPs perceived bupropion as dangerous and were concerned about its side-effects. Study 2: GPs' beliefs had medium (NRT, f(2 )= .23) to large (bupropion, f(2)=.45; NRT without support, f(2)=.59) effects on their intentions to prescribe medications. Beliefs about effectiveness of NRT and bupropion and the perceived danger of bupropion were the key predictors of intentions to prescribe NRT and bupropion, respectively. Beliefs about neglecting psychological aspects of smoking and incorrect use had indirect effects on intentions to prescribe NRT without support, operating via beliefs about effectiveness. CONCLUSION: GPs vary in their beliefs about the effectiveness and safety of smoking cessation medications. Their intentions to prescribe these medications vary in line with these beliefs. Interventions aimed at increasing the likelihood with which GPs prescribe these medications may be more effective if they addressed these beliefs
Influence of a magnetic field on the antiferromagnetic order in UPt_3
A neutron diffraction experiment was performed to investigate the effect of a
magnetic field on the antiferromagnetic order in the heavy fermion
superconductor UPt_3. Our results show that a field in the basal plane of up to
3.2 Tesla, higher than H_c2(0), has no effect: it can neither select a domain
nor rotate the moment. This has a direct impact on current theories for the
superconducting phase diagram based on a coupling to the magnetic order.Comment: 7 pages, RevTeX, 3 postscript figures, submitted to Phys. Rev.
Purifying Selection in Deeply Conserved Human Enhancers Is More Consistent than in Coding Sequences
(c) 2014 De Silva et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Theory of commensurable magnetic structures in holmium
The tendency for the period of the helically ordered moments in holmium to
lock into values which are commensurable with the lattice is studied
theoretically as a function of temperature and magnetic field. The
commensurable effects are derived in the mean-field approximation from
numerical calculations of the free energy of various commensurable structures,
and the results are compared with the extensive experimental evidence collected
during the last ten years on the magnetic structures in holmium. In general the
stability of the different commensurable structures is found to be in accord
with the experiments, except for the tau=5/18 structure observed a few degrees
below T_N in a b-axis field. The trigonal coupling recently detected in holmium
is found to be the interaction required to explain the increased stability of
the tau=1/5 structure around 42 K, and of the tau=1/4 structure around 96 K,
when a field is applied along the c-axis.Comment: REVTEX, 31 pages, 7 postscript figure
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