Change blindness and the primacy of object appearance

A large body of work suggests that the visual system is particularly sensitive to the appearance of new objects. This is based partly on evidence from visual search studies showing that onsets capture attention whereas many other types of visual event do not. Recently, however, the notion that object onset has a special status in visual attention has been challenged. For instance, an object that looms toward an observer has also been shown to capture attention. In two experiments, we investigated whether onset receives processing priority over looming. Observers performed a change detection task in which one of the display objects either loomed or receded, or a new object appeared. Results showed that looming objects were more resistant to change blindness than receding objects. Crucially, however, the appearance of a new object was less susceptible to change blindness than both looming and receding. We argue that the visual system is particularly sensitive to object onsets

A molecular switch in RCK2 triggers sodium-dependent activation of KNa.1 (KCNT1) potassium channels

The Na⁺-activated K⁺ channel KNa1.1, encoded by the KCNT1 gene, is an important regulator of neuronal excitability. How intracellular Na⁺ ions bind and increase channel activity is not well understood. Analysis of KNa1.1 channel structures indicate that there is a large twisting of the βN-αQ loop in the intracellular RCK2 domain between the inactive and Na⁺-activated conformations, with a lysine (K885, human subunit numbering) close enough to potentially form a salt bridge with an aspartate (D839) in βL in the Na⁺-activated state. Concurrently, an aspartate (D884) adjacent in the same loop adopts a position within a pocket formed by the βO strand. In carrying out mutagenesis and electrophysiology with human KNa1.1, we found alanine substitution of selected residues in these regions resulted in almost negligible currents in the presence of up to 40 mM intracellular Na⁺. The exception was D884A, which resulted in constitutively active channels in both the presence and absence of intracellular Na⁺. Further mutagenesis of this site revealed an amino acid size-dependent effect. Substitutions at this site by an amino acid smaller than aspartate (D884V) also yielded constitutively active KNa1.1, D884I had Na⁺-dependence similar to wild-type KNa1.1, whilst increasing the side chain size larger than aspartate (D884E or D884F) yielded channels that could not be activated by up to 40 mM intracellular Na⁺. We conclude that Na⁺ binding results in a conformational change that accommodates D884 in the βO pocket, which triggers further conformational changes in the RCK domains and channel activation

Spin polarization and magneto-luminescence of confined electron-hole systems

A BCS-like variational wave-function, which is exact in the infinite field limit, is used to study the interplay among Zeeman energies, lateral confinement and particle correlations induced by the Coulomb interactions in strongly pumped neutral quantum dots. Band mixing effects are partially incorporated by means of field-dependent masses and g-factors. The spin polarization and the magneto-luminescence are computed as functions of the number of electron-hole pairs present in the dot and the applied magnetic field.Comment: To appear in Phys. Rev.

Density and well width dependences of the effective mass of twodimensional holes in (100) GaAs quantum wells measured by cyclotron resonance at microwave frequencies

Cyclotron resonance at microwave frequencies is used to measure the band mass (m_b) of the two-dimensional holes (2DH's) in carbon-doped (100) GaAs/AlxGa1-xAs heterostructures. The measured m_b shows strong dependences on both the 2DH density(p) and the GaAs quantum well width (W). For a fixed W, in the density range (0.4x10^11 to 1.1x10^11 cm^-2) studied here, m_b increases with p, consistent with previous studies of the 2DHs on the (311)A surface. For a fixed p = 1.1x10^11 cm^-2, mb increases from 0.22 m_e at W = 10 nm to 0.50 m_e at W = 30 nm, and saturates around 0.51 m_e for W > 30 nm.Comment: to appear in Solid State Communication

Herschel-ATLAS/GAMA: How does the far-IR luminosity function depend on galaxy group properties?

We use the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) Phase I data to study the conditional luminosity function of far-IR (250 μm) selected galaxies in optically selected galaxy groups from the Galaxy And Mass Assembly (GAMA) spectroscopic survey, as well as environmental effects on the far-IR-to-optical colour. We applied two methods, which gave consistent results for the far-IR conditional luminosity functions. The direct matching method matches H-ATLAS sources to GAMA/SDSS (Sloan Digital Sky Survey) galaxies, then links the optical counterparts to GAMA groups. The stacking method counts the number of far-IR sources within the projected radii of GAMA groups, subtracting the local background. We investigated the dependence of the far-IR (250 μm) luminosity function on group mass in the range 1012 1012 h−1 M⊙. We also find that the far-IR-to-optical colours of H-ATLAS galaxies are independent of group mass over the range 1012 < Mh < 1014 h−1 M⊙ in the local Universe. We also compare our observational results with recent semi-analytical models, and find that none of these galaxy formation models can reproduce the conditional far-IR luminosity functions of galaxy groups

Impact of Patching and Atropine Treatment on the Child and Family in the Amblyopia Treatment Study

Objective To assess the psychosocial impact on the child and family of patching and atropine as treatments for moderate amblyopia in children younger than 7 years. Methods In a randomized, controlled clinical trial, 419 children younger than 7 years with amblyopic eye visual acuity in the range of 20/40 to 20/100 were assigned to receive treatment with either patching or atropine at 47 clinical sites. After 5 weeks of treatment, a parental quality-of-life questionnaire was completed for 364 (87%) of the 419 patients. Main Outcome Measure Overall and subscale scores on the Amblyopia Treatment Index. Results High internal validity and reliability were demonstrated for the Amblyopia Treatment Index questionnaire. The overall Amblyopia Treatment Index scores and the 3 subscale scores were consistently higher (worse) in the patching group compared with the atropine-treated group (overall mean, 2.52 vs 2.02, P<.001; adverse effects of treatment: mean, 2.35 vs 2.11, P = .002; difficulty with compliance: mean, 2.46 vs 1.99, P<.001; and social stigma: mean, 3.09 vs 1.84, P<.001, respectively). Conclusion Although the Amblyopia Treatment Index questionnaire results indicated that both atropine and patching treatments were well tolerated by the child and family, atropine received more favorable scores overall and on all 3 questionnaire subscales

Cosmic acceleration from second order gauge gravity

We construct a phenomenological theory of gravitation based on a second order gauge formulation for the Lorentz group. The model presents a long-range modification for the gravitational field leading to a cosmological model provided with an accelerated expansion at recent times. We estimate the model parameters using observational data and verify that our estimative for the age of the Universe is of the same magnitude than the one predicted by the standard model. The transition from the decelerated expansion regime to the accelerated one occurs recently (at $\sim9.3\;Gyr$).Comment: RevTex4 15 pages, 1 figure. Accepted for publication in Astrophysics & Space Scienc

The 2dF Galaxy Redshift Survey: the dependence of galaxy clustering on luminosity and spectral type

We investigate the dependence of galaxy clustering on luminosity and spectral type using the 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned using the principal-component analysis of Madgwick et al. We divide the sample into two broad spectral classes: galaxies with strong emission lines ('late types') and more quiescent galaxies ('early types'). We measure the clustering in real space, free from any distortion of the clustering pattern owing to peculiar velocities, for a series of volume-limited samples. The projected correlation functions of both spectral types are well described by a power law for transverse separations in the range 2<(σ/h-1 Mpc)<15, with a marginally steeper slope for early types than late types. Both early and late types have approximately the same dependence of clustering strength on luminosity, with the clustering amplitude increasing by a factor of 2.5 between L* and 4L*. At all luminosities, however, the correlation function amplitude for the early types is 50 per cent higher than that of the late types. These results support the view that luminosity, and not type, is the dominant factor in determining how the clustering strength of the whole galaxy population varies with luminosity

Effects of watershed land use on nitrogen concentrations and δ15 Nitrogen in groundwater

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 77 (2006): 199-215, doi:10.1007/s10533-005-1036-2.Eutrophication is a major agent of change affecting freshwater, estuarine, and marine systems. It is largely driven by transportation of nitrogen from natural and anthropogenic sources. Research is needed to quantify this nitrogen delivery and to link the delivery to specific land-derived sources. In this study we measured nitrogen concentrations and δ15N values in seepage water entering three freshwater ponds and six estuaries on Cape Cod, Massachusetts and assessed how they varied with different types of land use. Nitrate concentrations and δ15N values in groundwater reflected land use in developed and pristine watersheds. In particular, watersheds with larger populations delivered larger nitrate loads with higher δ15N values to receiving waters. The enriched δ15N values confirmed nitrogen loading model results identifying wastewater contributions from septic tanks as the major N source. Furthermore, it was apparent that N coastal sources had a relatively larger impact on the N loads and isotopic signatures than did inland N sources further upstream in the watersheds. This finding suggests that management priorities could focus on coastal sources as a first course of action. This would require management constraints on a much smaller population.This work was supported by funds from the Woods Hole Oceanographic Institution Sea Grant Program, from the Cooperative Institute for Coastal and Estuarine Environmental Technology, from Massachusetts Department of Environmental Protection to Applied Science Associates, Narragansett, RI, as well as from Palmer/McLeod and NOAA National Estuarine Research Reserve Fellowships to Kevin Kroeger. This work is the result of research sponsored by NOAA National Sea Grant College Program Office, Department of Commerce, under Grant No. NA86RG0075, Woods Hole Oceanographic Institution Sea Grant Project No. R/M-40