Renormalized transport of inertial particles in surface flows

Surface transport of inertial particles is investigated by means of the perturbative approach, introduced by Maxey (J. Fluid Mech. 174, 441 (1987)), which is valid in the case the deflections induced on the particle trajectories by the fluid flow can be considered small. We consider a class of compressible random velocity fields, in which the effect of recirculations is modelled by an oscillatory component in the Eulerian time correlation profile. The main issue we address here is whether fluid velocity fluctuations, in particular the effect of recirculation, may produce nontrivial corrections to the streaming particle velocity. Our result is that a small (large) degree of recirculation is associated with a decrease (increase) of streaming with respect to a quiescent fluid. The presence of this effect is confirmed numerically, away from the perturbative limit. Our approach also allows us to calculate the explicit expression for the eddy diffusivity, and to compare the efficiency of diffusive and ballistic transport.Comment: 18 pages, 13 figures, submitted to JF

Astrometric Resolution of Severely Degenerate Binary Microlensing Events

We investigate whether the "close/wide" class of degeneracies in caustic-crossing binary microlensing events can be broken astrometrically. Dominik showed that these degeneracies are particularly severe because they arise from a degeneracy in the lens equation itself rather than a mere "accidental" mimicking of one light curve by another. A massive observing campaign of five microlensing collaborations was unable to break this degeneracy photometrically in the case of the binary lensing event MACHO 98-SMC-1. We show that this degeneracy indeed causes the image centroids of the wide and close solutions to follow an extremely similar pattern of motion during the time when the source is in or near the caustic. Nevertheless, the two image centroids are displaced from one another and this displacement is detectable by observing the event at late times. Photometric degeneracies therefore can be resolved astrometrically, even for these most severe cases.Comment: 11 pages, including 4 figures. Submitted to Ap

The Phoenix Deep Survey: spectroscopic catalog

The Phoenix Deep Survey is a multi-wavelength survey based on deep 1.4 GHz radio imaging, reaching well into the sub-100 microJy level. One of the aims of this survey is to characterize the sub-mJy radio population, exploring its nature and evolution. In this paper we present the catalog and results of the spectroscopic observations aimed at characterizing the optically ``bright'' (R<~ 21.5 mag) counterparts of faint radio sources. Out of 371 sources with redshift determination, 21% have absorption lines only, 11% show AGN signatures, 32% are star-forming galaxies, 34% show narrow emission lines that do not allow detailed spectral classification (due to poor signal-to-noise ratio and/or lack of diagnostic emission lines) and the remaining 2% are identified with stars. For the star-forming galaxies with a Balmer decrement measurement we find a median extinction of A(Ha)=1.9 mag, higher than that of optically selected samples. This is a result of the radio selection, which is not biased against dusty systems. Using the available spectroscopic information, we estimate the radio luminosity function of star-forming galaxies in two independent redshift bins at z~0.1 and 0.3 respectively. We find direct evidence for strong luminosity evolution of these systems consistent with L(1.4 GHz) ~ (1+z)^(2.7).Comment: 39 pages, 12 figures. References added, and minor changes to reflect published versio

The Phoenix Deep Survey: The 1.4 GHz microJansky catalogue

The initial Phoenix Deep Survey (PDS) observations with the Australia Telescope Compact Array have been supplemented by additional 1.4 GHz observations over the past few years. Here we present details of the construction of a new mosaic image covering an area of 4.56 square degrees, an investigation of the reliability of the source measurements, and the 1.4 GHz source counts for the compiled radio catalogue. The mosaic achieves a 1-sigma rms noise of 12 microJy at its most sensitive, and a homogeneous radio-selected catalogue of over 2000 sources reaching flux densities as faint as 60 microJy has been compiled. The source parameter measurements are found to be consistent with the expected uncertainties from the image noise levels and the Gaussian source fitting procedure. A radio-selected sample avoids the complications of obscuration associated with optically-selected samples, and by utilising complementary PDS observations including multicolour optical, near-infrared and spectroscopic data, this radio catalogue will be used in a detailed investigation of the evolution in star-formation spanning the redshift range 0 < z < 1. The homogeneity of the catalogue ensures a consistent picture of galaxy evolution can be developed over the full cosmologically significant redshift range of interest. The 1.4 GHz mosaic image and the source catalogue are available on the web at http://www.atnf.csiro.au/~ahopkins/phoenix/ or from the authors by request.Comment: 16 pages, 11 figures, 4 tables. Accepted for publication by A

Caustic Crossing Microlensing Event by Binary MACHOs and Time Scale Bias

Caustic crossing microlensing events provide us a unique opportunity to measure the relative proper motion of the lens to the source, and so those caused by binary MACHOs are of great importance for understanding the structure of the Galactic halo and the nature of MACHOs. The microlensing event 98-SMC-01, occurred in June 1998, is the first event for which the proper motion is ever measured through the caustic crossing, and this event may be caused by binary MACHOs as we argue in this Letter. Motivated by the possible existence of binary MACHOs, we have performed the Monte Carlo simulations of caustic crossing events by binary MACHOs and investigated the properties and detectability of the events. Our calculation shows that typical caustic crossing events have the interval between two caustic crossings ($t_{\rm cc}$) of about 5 days. We argue that with the current strategy of binary event search the proper motions of these typical events are not measurable because of the short time scale. Therefore the proper motion distribution measured from caustic crossing events suffers significantly from {`}time scale bias{'}, which is a bias toward finding long time scale events and hence slowly moving lenses. We predict there are two times more short time scale events ($t_{\rm cc}\le 10$ days) than long time scale events ($t_{\rm cc}\ge 10$ days), and propose an hourly monitoring observation instead of the nightly monitoring currently undertaken to detect caustic crossing events by binary MACHOs more efficiently.Comment: 8 pages and 3 figures, accepted for publication in ApJ Letter

Dependence of Dust Obscuration on Star Formation Rates in Galaxies

Many investigations of star formation rates (SFRs) in galaxies have explored details of dust obscuration, with a number of recent analyses suggesting that obscuration appears to increase in systems with high rates of star formation. To date these analyses have been primarily based on nearby (z < 0.03) or UV selected samples. Using 1.4 GHz imaging and optical spectroscopic data from the Phoenix Deep Survey, the SFR-dependent obscuration is explored. The use of a radio selected sample shows that previous studies exploring SFR-dependent obscurations have been biased against obscured galaxies. The observed relation between obscuration and SFR is found to be unsuitable to be used as an obscuration measure for individual galaxies. Nevertheless, it is shown to be successful as a first order correction for large samples of galaxies where no other measure of obscuration is available, out to intermediate redshifts (z ~ 0.8).Comment: 9 pages (including 5 encapsulated postscript figures), aastex, uses emulateapj5.sty. Accepted for publication in Ap

Radio observations of the CDF-South: a possible link between radio emission and star formation in X-ray selected AGN

We explore the nature of the radio emission of X-ray selected AGN by combining deep radio (1.4GHz; 60micro-Jy) and X-ray data with multiwavelength (optical, mid-infrared) observations in the Extended Chandra Deep Field South (E-CDFS). The fraction of radio detected X-ray sources increases from 9% in the E-CDFS to 14% in the central region of this field, which has deeper X-ray coverage from the 1Ms CDFS. We find evidence that the radio emission of up to 60% of the hard X-ray/radio matched AGN is likely associated with star-formation in the host galaxy. Firstly, the mid-IR (24micron) properties of these sources are consistent with the infrared/radio correlation of starbursts. Secondly, most of them are found in galaxies with blue rest-frame optical colours (U-V), suggesting a young stellar population. On the contrary, X-ray/radio matched AGN which are not detected in the mid-infrared have red U-V colours suggesting their radio emission is associated with AGN activity. We also find no evidence for a population of heavily obscured radio-selected AGN that are not detected in X-rays. Finally, we do no confirm previous claims for a correlation between radio emission and X-ray obscuration. Assuming that the radio continuum measures star-formation, this finding is against models where the dust and gas clouds associated with circumnuclear starbursts are spherically blocking our view to the central engine.Comment: Accepted by A&

Insights on treatment of a Portuguese cohort of HCV/HIV coinfected patients

Purpose of the study: This study intends to characterize a Portuguese patient population with chronic HCV and HIV coinfection, followed at our Research Unit, underline the importance of early treatment and incorporate the importance of DDA for retreatment of HCV infection. Methods: Retrospective, observational analysis of medical records of 348 HCV/HIV coinfected patients from 2001 to 2011. Demographic, epidemiological, clinical and laboratory data and virologic response were collected. Summary of results: Review of 348 HCV/HIV coinfected patients, 121 of those (34.7%) under treatment, predominantly male (77.0%) and Caucasians (94.8%) with a median age of 44 yrs old (min 25; max 77 yrs). Intravenous drug use was the main route of HCV infection, in 71.3% of patients, and 8.3% were related with MSM. Frequent morbidities were alcohol abuse (46.8%), illicit drug use (70.1%), methadone (25.6%) and mental disturbances (12.3%) of patients. Regarding HIV infection, six were HIV-2 and 342 HIV-1; 36.1% were stage A and 29.6% were stage C (CDC Atlanta), 94.8% on antiretroviral treatment and only 21.9% of them with more than 350 TCD4 cell count. Genotype 1 was the most prevalent (58.1%&#x2013;117 genotype 1a, 26 genotype 1b); 1.6% were genotype 2, 22.8% genotype 3 and 17.5% genotype 4. Previous to treatment initiation, HCV ARN was above 600.000 IU/mL in 56.9% patients. Fibrosis was evaluated by fibroelastography in 41.1% and hepatic biopsy in 26.3% of patients; in those, 44.0% had a score above F2 (METAVIR) and ALT was elevated 2 times the limit in 38.0%, with an average value of 94 UI/L. IL 28B testing was performed in only 35 patients at the time, with 45.7% CC and 17.1% CT genotype. Treatment was started in 34.8% of patients, with 1.7 treatments per individual, and regimen was based on peguilated interferon with ribavirin in 93.6% of cases (72.1% with peginterferon alfa 2a). The SVR rate was 51.2%, with 28.9% non responders, 3 relapsers and 9 treatment interruptions due to major toxicities. Conclusions: Our data presents a low HCV treatment initiation, illustrated by 65.2% patients who did not begin any treatment. The majority completed treatment and the SVR rate was similar to literature. Individualized approach is essential to determine the optimal time to initiate HCV treatment, to assess patient adherence and adverse events management, in order to optimize treatment and reserve DDA drugs to experienced patients with worse predictive factors

Rare case of bilateral anterolateral and symmetrical bowing of tibia successfully treated with a distal tibial opening wedge osteotomy

The anterolateral bowing of the tibia is closely associated with the development of its pseudarthrosis. Roughly, all deformities are unilateral so the shortening and angulation are easy to identify. We present a 6-year-old boy with an exuberant bilateral anterolateral bowing of tíbia. He has short stature, disturbed gait and callosity at the lateral border of the foot. Deformity was successfully treated by opening wedge tibia osteotomy and filled the remaining gap with structural fibular graft. It was fixed with two crossed K-wires and cast immobilization for 6 weeks. We decided to correct it before skeletal maturity due to the significant disturbance of the gait and esthetic impairment. It was obtained a satisfactory morphological and functional result with a simple and fast technique.info:eu-repo/semantics/publishedVersio