Social Media in the Sexual Lives of African American and Latino Youth: Challenges and Opportunities in the Digital Neighborhood

There has been significant interest in the role of social media in the lives of adolescents, particularly as it relates to sexual risk. Researchers have focused on understanding usage behaviors, quantifying effects of social media exposure and activity, and using social media to intervene. Much of this work has focused on college students and non-minority youth. In this paper, we examine the growing body of literature around social media use among US minority youth and its intersection with sexual risk behavior. We introduce the concept of the “digital neighborhood” and examine the intersection of social media and sexual health in two domains: 1) sexual content in social media and 2) evidence of social media effects on sexual behavior. Finally, we discuss the opportunities and challenges for researchers and practitioners engaging youth of color

Minimum Forcing Sets for Miura Folding Patterns

We introduce the study of forcing sets in mathematical origami. The origami material folds flat along straight line segments called creases, each of which is assigned a folding direction of mountain or valley. A subset $F$ of creases is forcing if the global folding mountain/valley assignment can be deduced from its restriction to $F$. In this paper we focus on one particular class of foldable patterns called Miura-ori, which divide the plane into congruent parallelograms using horizontal lines and zig-zag vertical lines. We develop efficient algorithms for constructing a minimum forcing set of a Miura-ori map, and for deciding whether a given set of creases is forcing or not. We also provide tight bounds on the size of a forcing set, establishing that the standard mountain-valley assignment for the Miura-ori is the one that requires the most creases in its forcing sets. Additionally, given a partial mountain/valley assignment to a subset of creases of a Miura-ori map, we determine whether the assignment domain can be extended to a locally flat-foldable pattern on all the creases. At the heart of our results is a novel correspondence between flat-foldable Miura-ori maps and $3$-colorings of grid graphs.Comment: 20 pages, 16 figures. To appear at the ACM/SIAM Symp. on Discrete Algorithms (SODA 2015

Effect of Equation of State and Cutoff Density in Smoothed Particle Hydrodynamics Simulations of the Moon-Forming Giant Impact

The amount of vapor in the impact-generated protolunar disk carries implications for the dynamics, devolatilization, and moderately volatile element (MVE) isotope fractionation during lunar formation. The equation of state (EoS) used in simulations of the giant impact is required to calculate the vapor mass fraction (VMF) of the modeled protolunar disk. Recently, a new version of M-ANEOS ("Stewart M-ANEOS") was released with an improved treatment of heat capacity and expanded experimental Hugoniot. Here, we compare this new M-ANEOS version with a previous version ("N-SPH M-ANEOS") and assess the resulting differences in smoothed particle hydrodynamics (SPH) simulations. We find that Stewart M-ANEOS results in cooler disks with smaller values of VMF and results in differences in disk mass that are dependent on the initial impact angle. We also assess the implications of the minimum "cutoff" density ($\rho_{c}$), similar to a maximum smoothing length, that is set as a fast-computing alternative to an iteratively calculated smoothing length. We find that the low particle resolution of the disk typically results in $>40\%$ of disk particles falling to $\rho_c$, influencing the dynamical evolution and VMF of the disk. Our results show that choice of EoS, $\rho_{c}$, and particle resolution can cause the VMF and disk mass to vary by tens of percent. Moreover, small values of $\rho_{c}$ produce disks that are prone to numerical instability and artificial shocks. We recommend that future giant impact SPH studies review smoothing methods and ensure the thermodynamic stability of the disk over simulated time.Comment: To be published in The Planetary Science Journal, 51 pages, 34 figures, 4 table

Eggshell geochemistry reveals ancestral metabolic thermal regulation in Dinosauria

Studying the origin of avian thermoregulation is complicated by a lack of reliable methods to measure body temperatures in extinct dinosaurs. Evidence from bone histology and stable isotope analysis often relies on uncertain assumptions about the relationship between growth rate and body temperature, or the isotopic composition (δ18O) of body water. By contrast, clumped isotope (Δ47) paleothermometry, which relies on the binding of 13C to 18O, provides a robust tool for determining the body temperatures of dinosaurs, but has yet to be applied across a broad phylogenetic range while accounting for the influence of paleoenvironmental conditions. Applying this method to well-preserved fossil eggshells, we find that the three major clades of dinosaurs, Ornithischia, Sauropodomorpha, and Theropoda, were characterized by warm body temperatures. Dwarf titanosaurs may have exhibited similar body temperatures to larger sauropods, although these conclusions are provisional in light of uncertainties in the taxonomic assignment of dwarf titanosaur eggshell. Regardless, our results reveal that metabolically controlled thermoregulation was the ancestral condition for Dinosauria

Eggshell geochemistry reveals ancestral metabolic thermoregulation in Dinosauria.

Studying the origin of avian thermoregulation is complicated by a lack of reliable methods for measuring body temperatures in extinct dinosaurs. Evidence from bone histology and stableisotopes often relies on uncertain assumptions about the relationship between growth rate and body temperature, or the isotopic composition (δ18O) of body water. Clumped isotope (Δ47) paleothermometry, based on binding of 13C to 18O, provides a more robust tool, but has yet to be applied across a broad phylogenetic range of dinosaurs while accounting for paleoenvironmental conditions. Applying this method to well-preserved fossil eggshells demonstrates that the three major clades of dinosaurs, Ornithischia, Sauropodomorpha, and Theropoda, were characterized by warm body temperatures. Dwarf titanosaurs may have exhibited similar body temperatures to larger sauropods, although this conclusion isprovisional, given current uncertainties in taxonomic assignment of dwarf titanosaur eggshell. Our results nevertheless reveal that metabolically controlled thermoregulation was the ancestral condition for Dinosauria

Eggshell geochemistry reveals ancestral metabolic thermoregulation in Dinosauria

Studying the origin of avian thermoregulation is complicated by a lack of reliable methods for measuring body temperatures in extinct dinosaurs. Evidence from bone histology and stableisotopes often relies on uncertain assumptions about the relationship between growth rate and body temperature, or the isotopic composition (δ18O) of body water. Clumped isotope (Δ47) paleothermometry, based on binding of 13C to 18O, provides a more robust tool, but has yet to be applied across a broad phylogenetic range of dinosaurs while accounting for paleoenvironmental conditions. Applying this method to well-preserved fossil eggshells demonstrates that the three major clades of dinosaurs, Ornithischia, Sauropodomorpha, and Theropoda, were characterized by warm body temperatures. Dwarf titanosaurs may have exhibited similar body temperatures to larger sauropods, although this conclusion isprovisional, given current uncertainties in taxonomic assignment of dwarf titanosaur eggshell. Our results nevertheless reveal that metabolically controlled thermoregulation was the ancestral condition for Dinosauria

Vaccination with live attenuated simian immunodeficiency virus for 21 days protects against superinfection

AbstractThe identification of mechanisms that prevent infection with human immunodeficiency virus (HIV) or simian immunodeficiency virus (SIV) would facilitate the development of an effective AIDS vaccine. In time-course experiments, protection against detectable superinfection with homologous wild-type SIV was achieved within 21 days of inoculation with live attenuated SIV, prior to the development of detectable anti-SIV humoral immunity. Partial protection against superinfection was achieved within 10 days of inoculation with live attenuated SIV, prior to the development of detectable anti-SIV humoral and cellular immunity. Furthermore, co-inoculation of live attenuated SIV with wild-type SIV resulted in a significant reduction in peak virus loads compared to controls that received wild-type SIV alone. These findings imply that innate immunity or non-immune mechanisms are a significant component of early protection against superinfection conferred by inoculation with live attenuated SIV

New trends in active faulting studies for seismic hazard assessment

Vulnerability to earthquakes increases steadily as urbanization and development expand in areas that are prone to the effects of significant earthquakes. As virtually all of the largest earthquakes of the past decade demonstrated, the development of large cities in high seismicity areas is often based on an insufficient knowledge or distorted perception of the local seismic hazard, a condition often worsened by the construction of seismically unsafe buildings and infrastructures