Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. An all-sky survey of C(0)C(0)

We measure the smoothness of the infrared sky using the COBE DIRBE maps, and obtain interesting limits on the production of the diffuse cosmic infrared background (CIB) light by matter clustered like galaxies. The predicted fluctuations of the CIB with the DIRBE beam size of 0.7\deg\ are of the order of 10\%, and the maps are smooth at the level of $\delta\nu I_\nu \sim$ a few \nwm2sr rms from 2.2 to 100 \um. The lowest numbers are achieved at mid- to far-IR where the foreground is bright but smooth; they are $\sqrt{C(0)}$$\leq$$(1-1.5)$ \nwm2sr at $\lambda=$ 10-100 \um. If the CIB comes from clustered matter evolving according to typical scenarios, then the smoothness of the maps implies CIB levels less than $\sim (10-15)$ \nwm2sr over this wavelength range.Comment: 15 pages (LATEX) with 2 figures and 1 plate; Ap. J. Letters, in pres

Young children's referent selection is guided by novelty for both words and actions

Young children are biased to select novel, name-unknown objects as referents of novel labels (e.g., Markman, 1990) and similarly favour novel, action-unknown objects as referents of novel actions (Riggs, Mather, Hyde & Simpson, 2015). What process underlies these common behaviors? In the case of word learning, children may be driven by a novelty bias favouring novel objects as referents (Horst, Samuelson, Kucker & McMurray, 2011). Our study investigates this bias further by investigating whether novelty also affects children’s selection of novel objects when a new action is given. In a pre-exposure session, 40, three- and four-year-olds were shown eight novel objects for one minute. In subsequent referent selection trials children were shown two pre-exposed and one super-novel object and heard either a novel name or saw a novel action. The super-novel object was selected significantly more that the pre-exposed objects on both word and action trials. Our data add to the growing literature suggesting that an endogenous attentional bias to novelty plays a role in children’s referent selection and demonstrates further parallels between word and action learning

Aperiodic invariant continua for surface homeomorphisms

We prove that if a homeomorphism of a closed orientable surface S has no wandering points and leaves invariant a compact, connected set K which contains no periodic points, then either K=S and S is a torus, or $K$ is the intersection of a decreasing sequence of annuli. A version for non-orientable surfaces is given.Comment: 8 pages, to appear in Mathematische Zeitschrif

Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. I. C(0)C(0) and limits on the near-IR background

This paper is devoted to studying the CIB through its correlation properties. We studied the limits on CIB anisotropy in the near IR (1.25, 2.2, and 3.5 \um, or $J,\;K,\;L$) bands at a scale of 0.7\deg\ using the COBE\footnote{ The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) is responsible for the design, development, and operation of the {\it COBE}. Scientific guidance is provided by the {\it COBE} Science Working Group. GSFC is also responsible for the development of the analysis software and for the production of the mission data sets.} Diffuse Infrared Background Experiment (DIRBE) data. In single bands we obtain the upper limits on the zero-lag correlation signal $C(0)= \langle(\nu \delta I_\nu)^2\rangle < 3.6 \times 10^{-16},\; 5.1 \times 10^{-17},\; 5.7 \times 10^{-18}$ \w2m4sr2 for the $J,K,L$ bands respectively. The DIRBE data exhibit a clear color between the various bands with a small dispersion. On the other hand most of the CIB is expected to come from redshifted galaxies and thus should have different color properties. We use this observation to develop a `color subtraction' method of linear combinations of maps at two different bands. This method is expected to suppress the dominant fluctuations from foreground stars and nearby galaxies, while not reducing (or perhaps even amplifying) the extragalactic contribution to $C(0)$. Applying this technique gives significantly lower and more isotropic limits.Comment: 44 pages postcript; includes 5 tables, 14 figures. Astrophysical Journal, in pres

Quantitative evaluation of polymer gel dosimeters by broadband ultrasound attenuation

Ultrasound has been examined previously as an alternative readout method for irradiated polymer gel dosimeters, with authors reporting varying dose response to ultrasound transmission measurements. In this current work we extend previous work to measure the broadband ultrasound attenuation (BUA) response of irradiated PAGAT gel dosimeters, using a novel ultrasound computed tomography system