Previewing distracters reduces their effective contrast

In a visual search task, when half the distracters are presented earlier than the remainder (‘previewed’), observers find the target item more efficiently than when all the items are presented together—the preview benefit. We measured psychometric functions for contrast increments on Gabors that were presented as a valid preview for subsequent search, and when they were a non-predictive (dummy) preview. Sensitivity to contrast increments was lower (rightwards shift of the psychometric function) on valid, compared to dummy previews. This is consistent with an account of the preview benefit in terms of active inhibition, equivalent to lowering the contrast of previewed items that are being actively ignored

Induction of antibodies by Staphylococcus aureus nasal colonization in young children

AbstractIn order to develop novel antlstaphylococcal strategies, understanding the determinants of carriage and how humans respond to Staphylococcus aureus exposure is essential. Here, the primary S. aureus-specific humoral immune response and its association with nasal colonization was studied in young children. Sera from 57 colonized or non-colonized children, serially collected at birth and at 6, 14 and 24 months, were analysed for IgG, IgA and IgM binding to 19 staphylococcal proteins, using flow cytometry-based technology. The antibody responses showed extensive inter-individual variability. On average, the levels of antistaphylococcal IgA and IgM increased from birth until the age of 2 years (p <0.05), whereas the levels of IgG decreased (p <0.001). Placentally transferred maternal IgG did not protect against colonization. In colonized children, IgG and IgA levels for a number of proteins were higher than in non-colonized children. At both 14 and 24 months, the levels of IgG against chemotaxis inhibitory protein of S. aureus (at 24 months; median fluorescence intensity, 4928 vs. 24, p <0.05), extracellular fibrinogen-binding protein (987 vs. 604, p <0.05), and iron-responsive surface determinant H (62 vs. 5, p <0.05) were significantly higher in colonized children. The levels of IgA against CHIPS, IsdH and IsdA were higher (p <0.05). Therefore, CHIPS, Efb, IsdA and IsdH seem to play a role in nasal colonization of young children

Anti-staphylococcal humoral immune response in persistent nasal carriers and noncarriers of Staphylococcus aureus

BACKGROUND. Persistent carriers have a higher risk of Staphylococcus aureus infections than noncarriers but a lower risk of bacteremia-related death. Here, the role played by anti-staphylococcal antibodies was studied. METHODS. Serum samples from 15 persistent carriers and 19 noncarriers were analyzed for immunoglobulin (Ig) G, IgA, and IgM binding to 19 S. aureus antigens, by means of Luminex technology. Nasal secretions and serum samples obtained after 6 months were also analyzed. RESULTS. Median serum IgG levels were significantly higher in persistent carriers than in noncarriers for toxic shock syndrome toxin (TSST)-1 (median fluorescence intensity [MFI] value, 11,554 vs. 4291; P < .001) and staphylococcal enterotoxin (SE) A (742 vs. 218; P < .05); median IgA levels were higher for TSST-1 (P < .01), SEA, and clumping factor (Clf) A and B (P < .05). The in vitro neutralizing capacity of anti-TSST-1 antibodies was correlated with the MFI value (R(2) = 0.93) and was higher in persistent carriers (90.6% vs. 70.6%; P < .05). Antibody levels were stable over time and correlated with levels in nasal secretions (for IgG, R(2) = 0.87; for IgA, R(2) = 0.77). CONCLUSIONS. Antibodies to TSST-1 ha

Dynamics in online social networks

An increasing number of today's social interactions occurs using online social media as communication channels. Some online social networks have become extremely popular in the last decade. They differ among themselves in the character of the service they provide to online users. For instance, Facebook can be seen mainly as a platform for keeping in touch with close friends and relatives, Twitter is used to propagate and receive news, LinkedIn facilitates the maintenance of professional contacts, Flickr gathers amateurs and professionals of photography, etc. Albeit different, all these online platforms share an ingredient that pervades all their applications. There exists an underlying social network that allows their users to keep in touch with each other and helps to engage them in common activities or interactions leading to a better fulfillment of the service's purposes. This is the reason why these platforms share a good number of functionalities, e.g., personal communication channels, broadcasted status updates, easy one-step information sharing, news feeds exposing broadcasted content, etc. As a result, online social networks are an interesting field to study an online social behavior that seems to be generic among the different online services. Since at the bottom of these services lays a network of declared relations and the basic interactions in these platforms tend to be pairwise, a natural methodology for studying these systems is provided by network science. In this chapter we describe some of the results of research studies on the structure, dynamics and social activity in online social networks. We present them in the interdisciplinary context of network science, sociological studies and computer science.Comment: 17 pages, 4 figures, book chapte

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure

Toward an internally consistent astronomical distance scale

Accurate astronomical distance determination is crucial for all fields in astrophysics, from Galactic to cosmological scales. Despite, or perhaps because of, significant efforts to determine accurate distances, using a wide range of methods, tracers, and techniques, an internally consistent astronomical distance framework has not yet been established. We review current efforts to homogenize the Local Group's distance framework, with particular emphasis on the potential of RR Lyrae stars as distance indicators, and attempt to extend this in an internally consistent manner to cosmological distances. Calibration based on Type Ia supernovae and distance determinations based on gravitational lensing represent particularly promising approaches. We provide a positive outlook to improvements to the status quo expected from future surveys, missions, and facilities. Astronomical distance determination has clearly reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press (chapter 8 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV

A search for pair-production of supersymmetric particles under the assumption that R-parity is violated via a dominant LQDbar coupling has been performed using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV. The observed candidate events in the data are in agreement with the Standard Model expectation. This result is translated into lower limits on the masses of charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81 GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the 95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter