Simulations of Strong Gravitational Lensing with Substructure

Galactic sized gravitational lenses are simulated by combining a cosmological N-body simulation and models for the baryonic component of the galaxy. The lens caustics, critical curves, image locations and magnification ratios are calculated by ray-shooting on an adaptive grid. When the source is near a cusp in a smooth lens' caustic the sum of the magnifications of the three closest images should be close to zero. It is found that in the observed cases this sum is generally too large to be consistent with the simulations implying that there is not enough substructure in the simulations. This suggests that other factors play an important role. These may include limited numerical resolution, lensing by structure outside the halo, selection bias and the possibility that a randomly selected galaxy halo may be more irregular, for example due to recent mergers, than the isolated halo used in this study. It is also shown that, with the level of substructure computed from the N-body simulations, the image magnifications of the Einstein cross type lenses are very weak functions of source size up to \sim 1\kpc. This is also true for the magnification ratios of widely separated images in the fold and cusp caustic lenses. This means that selected magnification ratios for different the emission regions of a lensed quasar should agree with each other, barring microlensing by stars. The source size dependence of the magnification ratio between the closest pair of images is more sensitive to substructure.Comment: 28 pages, 2 tables and 14 figures. Accepted to MNRA

A Bayesian Analogue of Gleason's Theorem

We introduce a novel notion of probability within quantum history theories and give a Gleasonesque proof for these assignments. This involves introducing a tentative novel axiom of probability. We also discuss how we are to interpret these generalised probabilities as partially ordered notions of preference and we introduce a tentative generalised notion of Shannon entropy. A Bayesian approach to probability theory is adopted throughout, thus the axioms we use will be minimal criteria of rationality rather than ad hoc mathematical axioms.Comment: 14 pages, v2: minor stylistic changes, v3: changes made in-line with to-be-published versio

Simulating multiple merger pathways to the central kinematics of early-type galaxies

Two-dimensional integral field surveys such as ATLAS^3D are producing rich observational data sets yielding insights into galaxy formation. These new kinematic observations have highlighted the need to understand the evolutionary mechanisms leading to a spectrum of fast-rotators and slow-rotators in early-type galaxies. We address the formation of slow and fast rotators through a series of controlled, comprehensive hydrodynamical simulations sampling idealized galaxy merger scenarios constructed from model spiral galaxies. Idealized and controlled simulations of this sort complement the more 'realistic' cosmological simulations by isolating and analyzing the effects of specific parameters, as we do in this paper. We recreate minor and major binary mergers, binary merger trees with multiple progenitors, and multiple sequential mergers. Within each of these categories of formation history, we correlate progenitor gas fraction, mass ratio, orbital pericenter, orbital ellipticity, and spin with remnant kinematic properties. We create kinematic profiles of these 95 simulations comparable to ATLAS^3D data. By constructing remnant profiles of the projected specific angular momentum (lambda_R = / , triaxiality, and measuring the incidences of kinematic twists and kinematically decoupled cores, we distinguish between varying formation scenarios. We find that binary mergers nearly always form fast rotators. Slow rotators can be formed from zero initial angular momentum configurations and gas-poor mergers, but are not as round as the ATLAS^3D galaxies. Remnants of binary merger trees are triaxial slow rotators. Sequential mergers form round slow rotators that most resemble the ATLAS^3D rotators.Comment: MNRAS, in press, 12 pages, 15 figure

Characterizing the early vocabulary profiles of preverbal and minimally verbal children with autism spectrum disorder

Abstract Children with autism spectrum disorder (ASD) often have significant language delays. But do they learn language differently than neurotypical toddlers? We compared the lexical skills of 64 preverbal and minimally verbal children with ASD, to 461 vocabulary-size-matched typically developing (TD) toddlers. We also examined social features of verb knowledge using a novel collection of social ratings. Children with ASD produced proportionally more verbs than TD toddlers. Children with ASD produced proportionally more action and food words, while TD toddlers produced proportionally more animal, people words, and animal sounds and sound effects. Children with ASD also produced “mommy” and “daddy” at lower rates. We discuss how these differences may reflect an association between lexical development and weaknesses in social communication. Lay abstract Although preverbal and minimally verbal (PV-MV) children with autism spectrum disorder (ASD) represent a significant portion of the ASD population, we have a limited understanding of and characterization of them. Though it is a given that their lexical profiles contain fewer words, it is important to determine whether: a) the words PV-MV children with ASD produce are similar to the first words typically developing (TD) children produce, or b) there are unique features of the limited words that PV-MV children with ASD produce. The current study compared the early word profiles of PV-MV children with ASD to vocabulary-matched TD toddlers. Children with ASD produced proportionally more verbs than TD toddlers. Also, children with ASD produced proportionally more action and food words, while TD toddlers produced proportionally more animal words, animal sounds and sound effects, and people words. Children with ASD also produced “mommy” and “daddy” at lower rates. Our findings identified several areas of overlap in early word learning; however, our findings also point to differences that may be connected to core weaknesses in social communication (i.e., people words). The findings highlight words and categories that could serve as useful targets for communication intervention with PV-MV children with ASD

A Natural Plasmid Uniquely Encodes Two Biosynthetic Pathways Creating a Potent Anti-MRSA Antibiotic

Background Understanding how complex antibiotics are synthesised by their producer bacteria is essential for creation of new families of bioactive compounds. Thiomarinols, produced by marine bacteria belonging to the genus Pseudoalteromonas, are hybrids of two independently active species: the pseudomonic acid mixture, mupirocin, which is used clinically against MRSA, and the pyrrothine core of holomycin. Methodology/Principal Findings High throughput DNA sequencing of the complete genome of the producer bacterium revealed a novel 97 kb plasmid, pTML1, consisting almost entirely of two distinct gene clusters. Targeted gene knockouts confirmed the role of these clusters in biosynthesis of the two separate components, pseudomonic acid and the pyrrothine, and identified a putative amide synthetase that joins them together. Feeding mupirocin to a mutant unable to make the endogenous pseudomonic acid created a novel hybrid with the pyrrothine via “mutasynthesis” that allows inhibition of mupirocin-resistant isoleucyl-tRNA synthetase, the mupirocin target. A mutant defective in pyrrothine biosynthesis was also able to incorporate alternative amine substrates. Conclusions/Significance Plasmid pTML1 provides a paradigm for combining independent antibiotic biosynthetic pathways or using mutasynthesis to develop a new family of hybrid derivatives that may extend the effective use of mupirocin against MRSA

Spatial and Geomorphological Analysis of Mammoth Localites in Western Oklahoma

Up until recently research on Paleoindian archaeology has focused on Clovis hunters and the demise of 35 genera of megafauna at the end of the Pleistocene. However, with increasing evidence of Pre-Clovis settlement many megafaunal sites older than Clovis are now under scrutiny. In this endeavor, geoarchaeology plays a key role, particularly with assessing the stratigraphic and geomorphological aspects of sites suspected of being Pre-Clovis. This Thesis looks at, and analyzes three mammoth sites in western Oklahoma; Helena, Grandfield, and Foss. These sites were analyzed on a geologic, geomorphologic, hydrologic, anthropologic, and soil pedogenic basis. Understanding of soils and their developmental processes can help give us a better understanding of the landscape and the environment in which they were formed. These sites were then compared to known sites Domebo, Hajny, and Burnham, all of which have had both an absolute date and an in depth soil analysis. The purpose of the comparison is to try and apply relative dating to a site when absolute dating is not obtainable, either due to funding, or technical issues that prevent obtaining a reliable date. It has been hypothesized that older mammoth finds should be found in higher terraces, while those of younger age, possibly with archaeological significance, should be found in lower terraces near flood plains. The three mammoth sites studied through this research are associated with lower terraces regardless of age. This example shows how complex the relationship is between site age and site distribution in the landscape. This research shows also how important is to evaluate soil development for estimating relative ages. This approach in turn is important for assessing late Pleistocene paleontological sites with potential association with Pre-Clovis human populations.Geograph

The flattening and the orbital structure of early-type galaxies and collisionless N-body binary disk mergers

We use oblate axisymmetric dynamical models including dark halos to determine the orbital structure of intermediate mass to massive Coma early-type galaxies. We find a large variety of orbital compositions. Averaged over all sample galaxies the unordered stellar kinetic energy in the azimuthal and the radial direction are of the same order, but they can differ by up to 40 percent in individual systems. In contrast, both for rotating and non-rotating galaxies the vertical kinetic energy is on average smaller than in the other two directions. This implies that even most of the rotating ellipticals are flattened by an anisotropy in the stellar velocity dispersions. Using three-integral axisymmetric toy models we show that flattening by stellar anisotropy maximises the entropy for a given density distribution. Collisionless disk merger remnants are radially anisotropic. The apparent lack of strong radial anisotropy in observed early-type galaxies implies that they may not have formed from mergers of disks unless the influence of dissipational processes was significant.Comment: 14 pages, 8 figures; accepted for publication in MNRA

Yield Curve Shapes and the Asymptotic Short Rate Distribution in Affine One-Factor Models

We consider a model for interest rates, where the short rate is given by a time-homogenous, one-dimensional affine process in the sense of Duffie, Filipovic and Schachermayer. We show that in such a model yield curves can only be normal, inverse or humped (i.e. endowed with a single local maximum). Each case can be characterized by simple conditions on the present short rate. We give conditions under which the short rate process will converge to a limit distribution and describe the limit distribution in terms of its cumulant generating function. We apply our results to the Vasicek model, the CIR model, a CIR model with added jumps and a model of Ornstein-Uhlenbeck type