We present a forward-modeling simulation framework designed to model the data products from the Dark Energy Survey (DES). This forward-model process can be thought of as a transfer function-a mapping ...from cosmological/astronomical signals to the final data products used by the scientists. Using output from the cosmological simulations (the Blind Cosmology Challenge), we generate simulated images (the Ultra Fast Image Simulator) and catalogs representative of the DES data. In this work we demonstrate the framework by simulating the 244 deg super(2) coadd images and catalogs in five bands for the DES Science Verification data. The simulation output is compared with the corresponding data to show that major characteristics of the images and catalogs can be captured. We also point out several directions of future improvements. Two practical examples-star-galaxy classification and proximity effects on object detection-are then used to illustrate how one can use the simulations to address systematics issues in data analysis. With clear understanding of the simplifications in our model, we show that one can use the simulations side-by-side with data products to interpret the measurements. This forward modeling approach is generally applicable for other upcoming and future surveys. It provides a powerful tool for systematics studies that is sufficiently realistic and highly controllable.
This report describes an enzyme assay for the detection of Plasmodium falciparum. The assay is based on the observation that the lactate dehydrogenase (LDH) enzyme of P. falciparum has the ability to ...rapidly use 3-acetyl pyridine NAD (APAD) as a coenzyme in the reaction leading to the formation of pyruvate from lactate. Human red blood cell LDH carries out this reaction at a very slow rate in the presence of APAD. We measured the development of APADH and found that the formation of this product could establish the basis of an assay that detected the presence of P. falciparum from in vitro cultures at parasitemia levels of 0.02%. We also had occasion to use this assay with clinical samples. We found a correlation between levels of parasitemia and the activity of parasite LDH. Parasite LDH (pLDH) activity could be measured in blood hemolysates and in plasma and serum from patients with malaria. We used the serum assay for pLDH and followed the level of pLDH in a patient with cerebral malaria prior to antimalarial treatment and during the recovery period. From these initial studies, it is evident that the measurement of pLDH has a correlation with parasitemia and may offer a method that can be developed into a simple test for the detection of Plasmodium parasitemia.
Context. The Navarro-Frenk-White (NFW) density profile is often used to model gravitational lenses. For κs ≲ 0.1 (where κs is a parameter that defines the normalization of the NFW lens potential) – ...corresponding to galaxy and galaxy group mass scales – high numerical precision is required to accurately compute several quantities in the strong lensing regime. Aims. We obtain analytic solutions for several lensing quantities for circular NFW models and their elliptical (ENFW) and pseudo-elliptical (PNFW) extensions, on the typical scales where gravitational arcs are expected to be formed, in the κs ≲ 0.1 limit, by establishing their domain of validity. Methods. We approximate the deflection angle of the circular NFW model and derive analytic expressions for the convergence and shear for the PNFW and ENFW models. We obtain the constant distortion curves (including the tangential critical curve), which are used to define the domain of validity of the approximations, by employing a figure-of-merit to compare with the exact numerical solutions. We compute the deformation cross section as a further check of the validity of the approximations. Results. We derive analytic solutions for iso-convergence contours and constant distortion curves for the models considered here. We also obtain the deformation cross section, which is given in closed form for the circular NFW model and in terms of a one-dimensional integral for the elliptical ones. In addition, we provide a simple expression for the ellipticity of the iso-convergence contours of the pseudo-elliptical models and the connection of characteristic convergences among the PNFW and ENFW models. Conclusions. We conclude that the set of solutions derived here is generally accurate for κs ≲ 0.1. For low ellipticities, values up to κs ≃ 0.18 are allowed. On the other hand, the mapping among PNFW and the ENFW models is valid up to κs ≃ 0.4. The solutions derived in this work can be used to speed up numerical codes and ensure their accuracy in the low κs regime, including applications to arc statistics and other strong lensing observables.
The CONNIE Experiment (Coherent Neutrino Nucleus Interaction Experiment) is currently collecting reactor neutrino data to search for the undiscovered standard model process of coherent ...neutrino-nucleus scattering (CNNS). The detector is composed of a silicon target of thick, fully-depleted, low-noise CCD detectors. Results from data collected in 2015 indicate backgrounds are controlled, and allow an estimate of sensitivity to be presented for a larger scale detector. A 2016 upgrade, adding additional target mass, and reducing readout noise, has been performed, increasing the total yield of signal events by a factor of 30, and already yielding science-quality data. Low-energy nuclear calibrations have been performed, enabling calibration down to the device energy threshold. An estimate of the sensitivity expected for measuring the coherent neutrino process is presented. Future prospects with improved detector energy thresholds are estimated.
Simple models of gravitational arcs are crucial for simulating large samples of these objects with full control of the input parameters. These models also provide approximate and automated estimates ...of the shape and structure of the arcs, which are necessary for detecting and characterizing these objects on massive wide-area imaging surveys. We here present and explore the ArcEllipse, a simple prescription for creating objects with a shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a Sérsic profile for the source, recovers the total signal in real images typically within 10%−30%. The ArcEllipse+Sérsic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor that prevents ArcEllipse models from accurately describing real lensed systems.
This report compares the use of the lactate dehydrogenase (pLDH) assay with 3H-hypoxanthine incorporation and Giemsa microscopy for the evaluation of anti-malaria drug inhibition of the growth of P. ...falciparum in vitro. The inhibition profiles and IC50 determinations of the pLDH assay were directly comparable to those determined by the radioactive uptake and microscopic methods. Furthermore, the pLDH culture sensitivity assay is reproducible, easily interpreted, rapid and inexpensive to perform, suggesting field applicability.
We present the results of a search for gravitationally lensed giant arcs conducted on a sample of 825 SDSS galaxy clusters. Both a visual inspection of the images and an automated search were ...performed, and no arcs were found. This result is used to set an upper limit on the arc probability per cluster. We present selection functions for our survey, in the form of arc detection efficiency curves plotted as functions of arc parameters, for both the visual inspection and the automated search. The selection function is such that we are sensitive only to long, high surface brightness arcs with g-band surface brightness mu sub(g) less than or equal to 24.8 and length-to-width ratio l/w greater than or equal to 10. Our upper limits on the arc probability are compatible with previous arc searches. Finally, we report on a serendipitous discovery of a giant arc in the SDSS data, known inside the SDSS Collaboration as Hall's arc.
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