Field theoretic calculation of the surface tension for a model electrolyte system

We carry out the calculation of the surface tension for a model electrolyte to first order in a cumulant expansion about a free field theory equivalent to the Debye-H\"uckel approximation. In contrast with previous calculations, the surface tension is calculated directly without recourse to integrating thermodynamic relations. The system considered is a monovalent electrolyte with a region at the interface, of width h, from which the ionic species are excluded. In the case where the external dielectric constant epsilon_0 is smaller than the electrolyte solution's dielectric constant epsilon we show that the calculation at this order can be fully regularized. In the case where h is taken to be zero the Onsager-Samaras limiting law for the excess surface tension of dilute electrolyte solutions is recovered, with corrections coming from a non-zero value of epsilon_0/epsilon.Comment: LaTeX, 14 pages, 3 figures, 1 tabl

Correlated Anisotropies in the Cosmic Far-Infrared Background Detected by MIPS/Spitzer: Constraint on the Bias

We report the detection of correlated anisotropies in the Cosmic Far-Infrared Background at 160 microns. We measure the power spectrum in the Spitzer/SWIRE Lockman Hole field. It reveals unambiguously a strong excess above cirrus and Poisson contributions, at spatial scales between 5 and 30 arcminutes, interpreted as the signature of infrared galaxy clustering. Using our model of infrared galaxy evolution we derive a linear bias b=1.74 \pm 0.16. It is a factor 2 higher than the bias measured for the local IRAS galaxies. Our model indicates that galaxies dominating the 160 microns correlated anisotropies are at z~1. This implies that infrared galaxies at high redshifts are biased tracers of mass, unlike in the local Universe.Comment: ApJ Letters, in pres

A lensed protocluster candidate at z=7.66z=7.66 identified in JWST observations of the galaxy cluster SMACS0723-7327

According to the current paradigm of galaxy formation, the first galaxies have been likely formed within large dark matter haloes. The fragmentation of these massive haloes led to the formation of galaxy protoclusters, which are usually composed of one to a few bright objects, surrounded by numerous fainter (and less massive) galaxies. These early structures could have played a major role in reionising the neutral hydrogen within the first billion years of the Universe; especially, if their number density is significant.Taking advantage of the unprecedented sensitivity reached by the \textit{James Webb Space Telescope (JWST)}, galaxy protoclusters can now be identified and studied in increasing numbers beyond $z\geq\$6. Characterising their contribution to the UV photon budget could supply new insights into the reionisation process. We analyse the first JWST dataset behind SMACS0723-7327 to search for protoclusters at $z\geq6$, combining the available spectroscopic and photometric data. We then compare our findings with semi-analytical models and simulations. In addition to two bright galaxies ($\leq$26.5 AB in F277W), separated by $\sim$11\arcsec and spectroscopically confirmed at $z_{spec}=7.66$, we identify 6 additional galaxies with similar colors in a $\theta\sim20$\arcsec radius around these (corresponding to R$\sim60-90$ kpc in the source plane). Using several methods, we estimate the mass of the dark matter halo of this protocluster, $\sim$3.3$\times$10$^{11}$M$_{\odot}$ accounting for magnification, consistent with various predictions. The physical properties of all protocluster members are also in excellent agreement with what has been previously found at lower redshifts: star-formation main sequence and protocluster size. This detection adds to just a few protoclusters currently known in the first billion years of the universe.Comment: 7 pages, 6 Figures. Accepted for publication in A&A Lette

Comparison of absolute gain photometric calibration between Planck/HFI and Herschel/SPIRE at 545 and 857 GHz

We compare the absolute gain photometric calibration of the Planck/HFI and Herschel/SPIRE instruments on diffuse emission. The absolute calibration of HFI and SPIRE each relies on planet flux measurements and comparison with theoretical far-infrared emission models of planetary atmospheres. We measure the photometric cross calibration between the instruments at two overlapping bands, 545 GHz / 500 $\mu$m and 857 GHz / 350 $\mu$m. The SPIRE maps used have been processed in the Herschel Interactive Processing Environment (Version 12) and the HFI data are from the 2015 Public Data Release 2. For our study we used 15 large fields observed with SPIRE, which cover a total of about 120 deg^2. We have selected these fields carefully to provide high signal-to-noise ratio, avoid residual systematics in the SPIRE maps, and span a wide range of surface brightness. The HFI maps are bandpass-corrected to match the emission observed by the SPIRE bandpasses. The SPIRE maps are convolved to match the HFI beam and put on a common pixel grid. We measure the cross-calibration relative gain between the instruments using two methods in each field, pixel-to-pixel correlation and angular power spectrum measurements. The SPIRE / HFI relative gains are 1.047 ($\pm$ 0.0069) and 1.003 ($\pm$ 0.0080) at 545 and 857 GHz, respectively, indicating very good agreement between the instruments. These relative gains deviate from unity by much less than the uncertainty of the absolute extended emission calibration, which is about 6.4% and 9.5% for HFI and SPIRE, respectively, but the deviations are comparable to the values 1.4% and 5.5% for HFI and SPIRE if the uncertainty from models of the common calibrator can be discounted. Of the 5.5% uncertainty for SPIRE, 4% arises from the uncertainty of the effective beam solid angle, which impacts the adopted SPIRE point source to extended source unit conversion factor (Abridged)Comment: 13 pages, 10 figures; Incorporates revisions in response to referee comments; cross calibration factors unchange

Serodiagnosis of leishmaniasis with recombinant ORFF antigen

The serodiagnostic potential of recombinant ORFF protein (rORFF) from Leishmania infantum was assessed by ELISA. Of 49 sera from confirmed cases of visceral leishmaniasis (VL), all were seropositive using 5 ng of rORFF and serum diluted 1:20, while only 38 were positive with 500 ng of soluble antigen (SA) and 44 were positive by a direct agglutination test. There was also a positive correlation between spleen size and level of seropositivity with rORFF or SA. The reciprocal endpoint titer with rORFF was 1,280 for sera from VL patients, but < 20 with sera from malaria, filariasis, and tuberculosis patients, as well as with sera from healthy individuals from endemic and non-endemic areas. Sera from 10 confirmed cutaneous leishmaniasis cases from Turkey were negative or only weakly positive with rORFF although 9 were positive with SA. Thus, rORFF protein appears useful as a sensitive reagent for the differential diagnosis of VL caused by the Leishmania donovani complex

Spitzer 70 and 160-micron Observations of the COSMOS Field

We present Spitzer 70 and 160 micron observations of the COSMOS Spitzer survey (S-COSMOS). The data processing techniques are discussed for the publicly released products consisting of images and source catalogs. We present accurate 70 and 160 micron source counts of the COSMOS field and find reasonable agreement with measurements in other fields and with model predictions. The previously reported counts for GOODS-North and the extragalactic First Look Survey are updated with the latest calibration, and counts are measured based on the large area SWIRE survey to constrain the bright source counts. We measure an extragalactic confusion noise level of sigma_c = 9.4+/-3.3 mJy (q=5) for the MIPS 160-micron band based on the deep S-COSMOS data and report an updated confusion noise level of sigma_c = 0.35+/-0.15 mJy (q=5) for the MIPS 70-micron band.Comment: Accepted AJ, 15 Aug. 2009. Data available at http://spider.ipac.caltech.edu/staff/frayer/mycosmos/ until released by IRS

Toward a script theory of guidance in computer-supported collaborative learning

This article presents an outline of a script theory of guidance for computer-supported collaborative learning (CSCL). With its four types of components of internal and external scripts (play, scene, role, and scriptlet) and seven principles, this theory addresses the question how CSCL practices are shaped by dynamically re-configured internal collaboration scripts of the participating learners. Furthermore, it explains how internal collaboration scripts develop through participation in CSCL practices. It emphasizes the importance of active application of subject matter knowledge in CSCL practices, and it prioritizes transactive over non-transactive forms of knowledge application in order to facilitate learning. Further, the theory explains how external collaboration scripts modify CSCL practices and how they influence the development of internal collaboration scripts. The principles specify an optimal scaffolding level for external collaboration scripts and allow for the formulation of hypotheses about the fading of external collaboration scripts. Finally, the article points towards conceptual challenges and future research questions

Extremely Red Objects in The Lockman Hole

We investigate Extremely Red Objects (EROs) using near- and mid-infrared observations in five passbands (3.6 to 24 micron) obtained from the Spitzer Space Telescope, and deep ground-based R and K imaging. The great sensitivity of the IRAC camera allows us to detect 64 EROs in only 12 minutes of IRAC exposure time, by means of an R-[3.6] color cut (analogous to the traditional red R-K cut). A pure infrared K-[3.6] red cut detects a somewhat different population and may be more effective at selecting z > 1.3 EROs. We find 17% of all galaxies detected by IRAC at 3.6 or 4.5 micron to be EROs. These percentages rise to about 40% at 5.8 micron, and about 60% at 8.0 micron. We utilize the spectral bump at 1.6 micron to divide the EROs into broad redshift slices using only near-infrared colors (2.2/3.6/4.5 micron). We conclude that two-thirds of all EROs lie at redshift z > 1.3. Detections at 24 micron imply that at least 11% of 0.6 1.3 EROs are dusty star-forming galaxies.Comment: to appear in the special Spitzer issue of the ApJ