Dark matter voids in the SDSS galaxy survey

What do we know about voids in the dark matter distribution given the Sloan Digital Sky Survey (SDSS) and assuming the $\Lambda\mathrm{CDM}$ model? Recent application of the Bayesian inference algorithm BORG to the SDSS Data Release 7 main galaxy sample has generated detailed Eulerian and Lagrangian representations of the large-scale structure as well as the possibility to accurately quantify corresponding uncertainties. Building upon these results, we present constrained catalogs of voids in the Sloan volume, aiming at a physical representation of dark matter underdensities and at the alleviation of the problems due to sparsity and biasing on galaxy void catalogs. To do so, we generate data-constrained reconstructions of the presently observed large-scale structure using a fully non-linear gravitational model. We then find and analyze void candidates using the VIDE toolkit. Our methodology therefore predicts the properties of voids based on fusing prior information from simulations and data constraints. For usual void statistics (number function, ellipticity distribution and radial density profile), all the results obtained are in agreement with dark matter simulations. Our dark matter void candidates probe a deeper void hierarchy than voids directly based on the observed galaxies alone. The use of our catalogs therefore opens the way to high-precision void cosmology at the level of the dark matter field. We will make the void catalogs used in this work available at http://www.cosmicvoids.net.Comment: 15 pages, 6 figures, matches JCAP published version, void catalogs publicly available at http://www.cosmicvoids.ne

Tracking the formation of eumelanin from L-Dopa using coupled measurements

Melanin plays a crucial role as a pigment all through the animal kingdom. Being a macromolecule just on the divide between an ordered crystalline or a purely amorphous form melanin has proven a challenge to structure-function analysis. Melanin assembles from small molecules much like a jigsaw and much like in a jigsaw the fine detail quickly vanishes in the overall picture. With melanin being first and foremost a photo-active molecule we focus on spectral properties for the characterisation of its structure. We use absorption measurements to illustrate the complex nature of the formation process. To gain a better hold on the formation pathway we use coupled measurements of excitation and emission to identify 'areas of interest' in the excitation-emission matrix (EEM). We then probe one area for characteristic fluorescence lifetimes to track one melanin building block through the formation process. Comparison of the EEMs of L-Dopa derived melanin with natural Sepia melanin shows characteristic differences. We show how the presence of copper ions creates a melanin closer to its natural form

Mapping the formation of eumelanin using coupled measurements

Melanin plays a crucial role as a pigment all through the animal kingdom. Being a macromolecule just on the divide between an ordered crystalline or a purely amorphous form melanin has proven a challenge to structure-function analysis. Melanin assembles from small molecules much like a jigsaw and much like in a jigsaw the fine detail quickly vanishes in the overall picture. With Melanin being first and foremost a photo-active molecule we focus on spectral properties for the characterization of its structure using linked measurements of excitation and emission to identify ‘areas of interest’ in the Excitation-Emission Matrix (EEM). We then probe for characteristic fluorescence lifetimes in the identified areas to track melanin building blocks through the formation pathway

Delta breakpad : diversified binary crash reporting

This paper introduces Delta Breakpad. It extends the Breakpad crash reporting system to handle software diversity effectively and efficiently by replicating and patching the debug information of diversified software versions. Simple adaptations to existing open source compiler tools are presented that on the one hand introduce significant amounts of diversification in the code and stack layout of ARMv7 binaries to mitigate the widespread deployment of code injection and code reuse attacks, while on the other hand still supporting accurate crash reporting. An evaluation on SPEC2006 benchmarks demonstrates that the corresponding computational, storage, and communication overheads are small

Influence of ions and pH on formation of solid and liquid-like melanin

Melanin is a natural pigment with broadband absorption and effective ability to dissipate the energy absorbed. The macromolecular structure of melanin shows a delicate balance between short-range ordered and disordered structures without being a random aggregate. The presence of ions or the variation in pH or ionic strength can alter the self-assembly process which subsequently changes the structure of melanin. To understand these relationships, this study investigates the influence of ions and pH in melanin formation. The types of ions present and pH have a profound influence on the formation and structure of melanin particles, while only minor changes are observed in the absorption and excitation-emission analysis. In some conditions, the formation of discernible particles with significant refractive index contrast is avoided while retaining the spectroscopic characteristics of melanin, leading to liquid-like melanin. These findings identify potential pathways which can be used to manipulate the melanin macromolecular structure while providing the desired spectral properties to enable novel bio-engineering applications.

Revealing the photophysics of gold-nanobeacons via time-resolved fluorescence spectroscopy

We demonstrate that time-resolved fluorescence spectroscopy is a powerful tool to investigate the conformation states of hairpin DNA on the surface of gold nanoparticles (AuNPs) and energy transfer processes in Au-nanobeacons. Long-range fluorescence quenching of Cy5 by AuNPs has been found to be in good agreement with electrodynamics modelling. Moreover, time-correlated single-photon counting (TCSPC) is shown to be promising for real-time monitoring of the hybridization kinetics of Au-nanobeacons, with up to 60% increase in decay time component and 300% increase in component fluorescence fraction observed. Our results also indicate the importance of the stem and spacer designs for the performance of Au-nanobeacons