ALMA Thermal Observations of Europa

We present four daytime thermal images of Europa taken with the Atacama Large Millimeter Array. Together, these images comprise the first spatially resolved thermal dataset with complete coverage of Europa's surface. The resulting brightness temperatures correspond to a frequency of 233 GHz (1.3 mm) and a typical linear resolution of roughly 200 km. At this resolution, the images capture spatially localized thermal variations on the scale of geologic and compositional units. We use a global thermal model of Europa to simulate the ALMA observations in order to investigate the thermal structure visible in the data. Comparisons between the data and model images suggest that the large-scale daytime thermal structure on Europa largely results from bolometric albedo variations across the surface. Using bolometric albedos extrapolated from Voyager measurements, a homogenous model reproduces these patterns well, but localized discrepancies exist. These discrepancies can be largely explained by spatial inhomogeneity of the surface thermal properties. Thus, we use the four ALMA images to create maps of the surface thermal inertia and emissivity at our ALMA wavelength. From these maps, we identify a region of either particularly high thermal inertia or low emissivity near 90 degrees West and 23 degrees North, which appears anomalously cold in two of our images.Comment: 9 pages, 3 figures, accepted for publication in the Astronomical Journa

Synthesis of α-hydroxy-β,β-difluoro-γ-ketoesters via [3,3]sigmatropic rearrangements

Readily available γ,γ-difluorinated allylic alcohols obtained from trifluoroethanol were esterified efficiently. Exposure to strong base (LDA) afforded the ester enolates, in which chelation both controlled configuration and stabilised against fragmentation, which were trapped as their silyl ketene acetals. Rearrangement occurred to afford base-sensitive acid products. Esterification under mild conditions afforded the purifiable methyl esters in which the masked ketone had been released. Educts with either a benzyloxy or an allyloxy group at the α-position could be deprotected releasing the alcohols

The many assembly histories of massive void galaxies as revealed by integral field spectroscopy

We present the first detailed integral field spectroscopy study of nine central void galaxies with M*>10¹⁰Mʘ using the Wide Field Spectrograph to determine how a range of assembly histories manifest themselves in the current day Universe.While the majority of these galaxies are evolving secularly, we find a range of morphologies, merger histories and stellar population distributions, though similarly low Hα-derived star formation rates (10¹⁰Mʘ have similarly low star formation rates

Tidal interactions at the edge of the Local Group: New evidence for tidal features in the Antlia Dwarf Galaxy

Using deep B band imaging down to mu_{B} = 26 mag arcsec^{-2}, we present evidence for tidal tails in the Antlia Dwarf galaxy, one of the most distant members of the Local Group. This elongation is in the direction of Antlia's nearest neighbor, the Magellanic-type NGC 3109. The tail is offset by less than 10 degrees from a vector linking the centers of the two galaxies, indicative of interactions between the pair. Combined with the warped disc previously identified in NGC 3109, Antlia and NGC 3109 must be at a small separation for tidal features to be present in Antlia. We calculate that Antlia cannot be completely disrupted by NGC 3109 in a single interaction unless its orbit pericenter is less than 6 kpc, however multiple interactions could significantly alter its morphology. Therefore despite being located right at the edge of the Local Group, environmental effects are playing an important role in Antlia's evolution.Comment: 8 pages, 4 figures, accepted for publication in ApJ

Nonlinear Optical Corneal Crosslinking, Mechanical Stiffening, and Corneal Flattening Using Amplified Femtosecond Pulses.

Purpose:We have shown that nonlinear optical corneal crosslinking (NLO CXL) and stiffening can be achieved in ex vivo rabbit corneas using an 80-MHz, 760-nm femtosecond (FS) laser, however the required power was beyond the American National Standard Institute limit. The purpose of this study was to test the efficacy of amplified FS pulses to perform CXL to reduce power by increasing pulse energy. Methods:A variable numerical aperture laser scanning delivery system was coupled to a 1030-nm laser with a noncollinear optical parametric amplifier to generate 760 nm, 50 to 150 kHz amplified FS pulses with 79.5-μm axial and 2.9-μm lateral two-photon focal volume. Ex vivo rabbit corneas received NLO CXL, and effectiveness was assessed by measuring collagen autofluorescence (CAF) and mechanical stiffening. NLO CXL was also performed in 14 live rabbits, and changes in corneal topography were measured using an Orbscan. Results:Amplified pulses (0.3 μJ) generated significant CAF that increased logarithmically with decreasing scan speed; achieving equivalent CAF to UVA CXL at 15.5 mm/s. Indentation testing detected a 62% increase in stiffness compared to control, and corneal topography measurements revealed a significant decrease of 1.0 ± 0.8 diopter by 1 month (P < 0.05). Conclusions:These results show that NLO CXL using amplified pulses can produce corneal collagen CXL comparable to UVA CXL. Translational Relevance:NLO CXL using amplified pulses can produce corneal CXL comparable to UVA CXL, suggesting a potential clinical application in which NLO CXL can be used to perform personalized crosslinking for treatment of refractive errors and keratoconus

Estimating the rate of intersubtype recombination in early HIV-1 group M strains

West Central Africa has been implicated as the epicenter of the HIV-1 epidemic, and almost all group M subtypes can be found there. Previous analysis of early HIV-1 group M sequences from Kinshasa in the Democratic Republic of Congo, formerly Zaire, revealed that isolates from a number of individuals fall in different positions in phylogenetic trees constructed from sequences from opposite ends of the genome as a result of recombination between viruses of different subtypes. Here, we use discrete ancestral trait mapping to develop a procedure for quantifying HIV-1 group M intersubtype recombination across phylogenies, using individuals' gag (p17) and env (gp41) subtypes. The method was applied to previously described HIV-1 group M sequences from samples obtained in Kinshasa early in the global radiation of HIV. Nine different p17 and gp41 intersubtype recombinant combinations were present in the data set. The mean number of excess ancestral subtype transitions (NEST) required to map individuals' p17 subtypes onto the gp14 phylogeny samples, compared to the number required to map them onto the p17 phylogenies, and vice versa, indicated that excess subtype transitions occurred at a rate of approximately 7 × 10(−3) to 8 × 10(−3) per lineage per year as a result of intersubtype recombination. Our results imply that intersubtype recombination may have occurred in approximately 20% of lineages evolving over a period of 30 years and confirm intersubtype recombination as a substantial force in generating HIV-1 group M diversity

Highly polymorphic microsatellites in the North American snakeweed grasshopper, Hesperotettix viridis

Microsatellite markers are preferred for fine-scale population genetic studies requiring high resolution. The grasshopper Hesperotettix viridis (Thomas) is an oligophagous species that feeds on composites and often exhibits locally restricted diets. Divergence in host plant use in some localities is seen where co-occurring subpopulations select alternate plant species, as expected with the evolution of host shifts and associated lineage divergence. To characterize the host-associated divergence patterns among populations of H. viridis, we developed markers from two microsatellite-enriched genomic libraries. Here we report the characterization and optimization of seven polymorphic di- and tri-nucleotide microsatellite loci for this species. One hundred and six individuals from 5 populations were tested for polymorphism. The number of alleles varied from 4 to 38 in all the populations. Ho ranged from 0.339 to 0.790. Homozygote excess was observed across loci, perhaps due to inbreeding. This is the first report of microsatellite markers for the subfamily Melanoplinae

Transmission dynamics of Avian Influenza A virus

Influenza A virus (AIV) has an extremely high rate of mutation. Frequent exchanges of gene segments between different AIV (reassortment) have been responsible for major pandemics in recent human history. The presence of a wild bird reservoir maintains the threat of incursion of AIV into domestic birds, humans and other animals. In this thesis, I addressed unanswered questions of how diverse AIV subtypes (classified according to antigenicity of the two surface proteins, haemagglutinin and neuraminidase) evolve and interact among different bird populations in different parts of the world, using Bayesian phylogenetic methods with large datasets of full genome sequences. Firstly, I explored the reassortment patterns of AIV internal segments among different subtypes by quantifying evolutionary parameters including reassortment rate, evolutionary rate and selective constraint in time-resolved Bayesian tree phylogenies. A major conclusion was that reassortment rate is negatively associated with selective constraint and that infection of wild rather than domestic birds was associated with a higher reassortment rate. Secondly, I described the spatial transmission pattern of AIV in China. Clustering of related viruses in particular geographic areas and economic zones was identified from the viral phylogeographic diffusion networks. The results indicated that Central China and the Pearl River Delta are two main sources of viral out flow; while the East Coast, especially the Yangtze River delta, is the major recipient area. Simultaneously, by applying a general linear model, the predictors that have the strongest impact on viral spatial diffusion were identified, including economic (agricultural) activity, climate, and ecology. Thirdly, I determined the genetic and phylogeographic origin of a recent H7N3 highly pathogenic avian influenza outbreak in Mexico. Location, subtype, avian host species and pathogenicity were modelled as discrete traits and jointly analysed using all eight viral gene segments. The results indicated that the outbreak AIV is a novel reassortant carried by wild waterfowl from different migration flyways in North America during the time period studied. Importantly, I concluded that Mexico, and Central America in general, might be a potential hotspot for AIV reassortment events, a possibility which to date has not attracted widespread attention. Overall, the work carried out in this thesis described the evolutionary dynamics of AIV from which important conclusions regarding its epidemiological impact in both Eurasia and North America can be drawn

Longitudinal association of physical activity during pregnancy with maternal and infant outcomes: Findings from the Australian longitudinal study of women’s health

Background: Physical activity has known benefits during pregnancy; however, the optimum volume of physical activity through the different stages of pregnancy is not well known. Objectives: The aims of this study were to investigate the associations of physical activity volume in pregnant women in each trimester of pregnancy with maternal and infant outcomes. Design: The study involved 1657 pregnant women from the Australian Longitudinal Study on Women’s Health, who completed surveys from 2006 to 2012 (aged 28–39 years). Methods: Women reported being in either the first, second or third trimester of pregnancy. Women were grouped into four groups according to their self-reported physical activity during pregnancy: (1) Nil (0–<33.3 MET.min/week), (2) Low (33.3–<500 MET.min/week), (3) Moderate (500–<1000 MET.min/week) and (4) High (⩾1000 MET.min/week). Women who reported their physical activity during pregnancy completed a survey within three years after the birth, relating to outcomes associated with pregnancy and childbirth (gestational diabetes, hypertension, and antenatal depression and anxiety) and infant outcomes (birthweight and prematurity). Results: There was no association of physical activity in any trimester with infant birthweight, prematurity, gestational diabetes, hypertension or antenatal depression. Antenatal anxiety was less prevalent in women who reported low (1.7%) or moderate (1.1%) physical activity than in those who reported no activity (4.7%; p = 0.01). Conclusion: Different amounts of physical activity during pregnancy were not associated with the measured adverse health outcomes. However, low and moderate amounts of physical activity were associated with reduced incidence of antenatal anxiety