Reproductive Specializations in a Viviparous African Skink: Implications for Evolution and Biological Conservation

Recent research on the African scincid lizard, Trachylepis ivensi, has significantly expanded the range of known reproductive specializations in reptiles. This species is viviparous and exhibits characteristics previously thought to be confined to therian mammals. In most viviparous squamates, females ovulate large yolk-rich eggs that provide most of the nutrients for development. Typically, their placental components (fetal membranes and uterus) are relatively unspecialized, and similar to their oviparous counterparts. In T. ivensi, females ovulate tiny eggs and provide nutrients for embryonic development almost entirely by placental means. Early in gestation, embryonic tissues invade deeply into maternal tissues and establish an intimate “endotheliochorial” relationship with the maternal blood supply by means of a yolk sac placenta. The presence of such an invasive form of implantation in a squamate reptile is unprecedented and has significant functional and evolutionary implications. Discovery of the specializations of T. ivensiillustrates why the study of a few convenient “animal models” is no substitute for broad-based studies of biological diversity as directed by phylogenetic considerations. Our study also underscores the value of museum collections to studies of biological diversity

Spectroscopic and redox properties of amine-unctionalized K_2[Os-^(II)(bpy)(CN)_4] complexes

We report the first examples of amine-functionalized K_2[Os^(II)(bpy)(CN)_4] (bpy = 2,2'-bipyridine) complexes. The tetracyanoosmate complexes were prepared by UV irradiation (λ = 254 nm) of K_4[Os^(II)(CN)_6] and primary amine-functionalized bpy ligands in acidic aqueous media. The aqueous solution pH dependences of the spectroscopic and redox properties of 4,4'- and 5,5'-substituted complexes have been investigated. The pendant amine functional groups and coordinated cyanide ligands are basic sites that can be sequentially protonated, thereby allowing systematic tuning of electrochemical and optical spectroscopic properties

Connected Network of Minima as a Model Glass: Long Time Dynamics

A simple model to investigate the long time dynamics of glass-formers is presented and applied to study a Lennard-Jones system in supercooled and glassy phases. According to our model, the point representing the system in the configurational phase space performs harmonic vibrations around (and activated jumps between) minima pertaining to a connected network. Exploiting the model, in agreement with the experimental results, we find evidence for: i) stretched relaxational dynamics; ii) a strong T-dependence of the stretching parameter; iii) breakdown of the Stokes-Einstein law.Comment: 4 pages (Latex), 4 eps figure

Potential Energy Landscape and Long Time Dynamics in a Simple Model Glass

We analyze the properties of a Lennard-Jones system at the level of the potential energy landscape. After an exhaustive investigation of the topological features of the landscape of the systems, obtained studying small size sample, we describe the dynamics of the systems in the multi-dimensional configurational space by a simple model. This consider the configurational space as a connected network of minima where the dynamics proceeds by jumps described by an appropriate master equation. Using this model we are able to reproduce the long time dynamics and the low temperature regime. We investigate both the equilibrium regime and the off-equilibrium one, finding those typical glassy behavior usually observed in the experiments such as: {\it i)} stretched exponential relaxation, {\it ii)} temperature-dependent stretching parameter, {\it iii)} breakdown of the Stokes-Einstein relation, and {\it iv)} appearance of a critical temperature below which one observes deviation from the fluctuation-dissipation relation as consequence of the lack of equilibrium in the system.Comment: 11 pages (Latex), 9 ps figure

Understanding the Use of Fauxtography on Social Media

Despite the influence that image-based communication has on online discourse, the role played by images in disinformation is still not well understood. In this paper, we present the first large-scale study of fauxtography, analyzing the use of manipulated or misleading images in news discussion on online communities. First, we develop a computational pipeline geared to detect fauxtography, and identify over 61k instances of fauxtography discussed on Twitter, 4chan, and Reddit. Then, we study how posting fauxtography affects engagement of posts on social media, finding that posts containing it receive more interactions in the form of re-shares, likes, and comments. Finally, we show that fauxtography images are often turned into memes by Web communities. Our findings show that effective mitigation against disinformation need to take images into account, and highlight a number of challenges in dealing with image-based disinformation

Gravitational wave radiometry: Mapping a stochastic gravitational wave background

The problem of the detection and mapping of a stochastic gravitational wave background (SGWB), either of cosmological or astrophysical origin, bears a strong semblance to the analysis of CMB anisotropy and polarization. The basic statistic we use is the cross-correlation between the data from a pair of detectors. In order to `point' the pair of detectors at different locations one must suitably delay the signal by the amount it takes for the gravitational waves (GW) to travel to both detectors corresponding to a source direction. Then the raw (observed) sky map of the SGWB is the signal convolved with a beam response function that varies with location in the sky. We first present a thorough analytic understanding of the structure of the beam response function using an analytic approach employing the stationary phase approximation. The true sky map is obtained by numerically deconvolving the beam function in the integral (convolution) equation. We adopt the maximum likelihood framework to estimate the true sky map that has been successfully used in the broadly similar, well-studied CMB map making problem. We numerically implement and demonstrate the method on simulated (unpolarized) SGWB for the radiometer consisting of the LIGO pair of detectors at Hanford and Livingston. We include `realistic' additive Gaussian noise in each data stream based on the LIGO-I noise power spectral density. The extension of the method to multiple baselines and polarized GWB is outlined. In the near future the network of GW detectors, including the Advanced LIGO and Virgo detectors that will be sensitive to sources within a thousand times larger spatial volume, could provide promising data sets for GW radiometry.Comment: 24 pages, 19 figures, pdflatex. Matched version published in Phys. Rev. D - minor change

A First Comparison Between LIGO and Virgo Inspiral Search Pipelines

This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.Comment: GWDAW-9 proceeding

A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data

We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.Comment: GWDAW9 proceeding