Effect of land use and survey design on trip underreporting in Montreal and Toronto’s regional surveys

This paper contributes to the literature on travel survey methods by quantifying the relationship between land use, data collection protocol and trip under-reporting in regional travel surveys. While under-reporting more broadly is a recognized problem, the significant increase in underreporting in denser, more urban-type environments identified here has never before been demonstrated or measured. Consequences of this land use-related bias for transportation planning and modelling are explored. The work is carried out by comparing the results of two very similar household travel surveys conducted in 2011 and 2013, in Toronto and Montreal respectively. Using data on over 350,000 persons, a binary logit model for discretionary trip making is estimated and the effects of land use and data collection protocol on under-reporting are isolated. This is done by controlling for mobility tool access, household type and other key determinants of travel demand. Counterintuitive effects for urban type environments found indicate the under-reporting effect is equivalent to a reduction in the pre-existing odds of reporting discretionary trip making in more urban environments of 19 to 29%. When combined with Toronto’s data collection protocol effect, the range increases to 39 to 55%. Results should be of use to transportation planning authorities wishing to make better use of the data collected in large surveys. Recognizing some of the flaws and biases in what is reported, these authorities can complement existing sources of data or modify their approaches to demandbased infrastructure provision to better account for the large number of, largely pedestrian, unreported trips

Galaxies at the extremes: Ultra-diffuse galaxies in the Virgo Cluster

We report the discovery of three large (R29 >~ 1 arcminute) extremely low surface brightness (mu_(V,0) ~ 27.0) galaxies identified using our deep, wide-field imaging of the Virgo Cluster from the Burrell Schmidt telescope. Complementary data from the Next Generation Virgo Cluster Survey do not resolve red giant branch stars in these objects down to i=24, yielding a lower distance limit of 2.5 Mpc. At the Virgo distance, these objects have half-light radii 3-10 kpc and luminosities L_V=2-9x10^7 Lsun. These galaxies are comparable in size but lower in surface brightness than the large ultradiffuse LSB galaxies recently identified in the Coma cluster, and are located well within Virgo's virial radius; two are projected directly on the cluster core. One object appears to be a nucleated LSB in the process of being tidally stripped to form a new Virgo ultracompact dwarf galaxy. The others show no sign of tidal disruption, despite the fact that such objects should be most vulnerable to tidal destruction in the cluster environment. The relative proximity of Virgo makes these objects amenable to detailed studies of their structural properties and stellar populations. They thus provide an important new window onto the connection between cluster environment and galaxy evolution at the extremes.Comment: 7 pages, 4 figures, to appear in ApJ Letters. Updated with minor revisions to match accepted versio

Galaxies at the extremes: Ultra-diffuse galaxies in the Virgo Cluster

We report the discovery of three large (R29 >~ 1 arcminute) extremely low surface brightness (mu_(V,0) ~ 27.0) galaxies identified using our deep, wide-field imaging of the Virgo Cluster from the Burrell Schmidt telescope. Complementary data from the Next Generation Virgo Cluster Survey do not resolve red giant branch stars in these objects down to i=24, yielding a lower distance limit of 2.5 Mpc. At the Virgo distance, these objects have half-light radii 3-10 kpc and luminosities L_V=2-9x10^7 Lsun. These galaxies are comparable in size but lower in surface brightness than the large ultradiffuse LSB galaxies recently identified in the Coma cluster, and are located well within Virgo's virial radius; two are projected directly on the cluster core. One object appears to be a nucleated LSB in the process of being tidally stripped to form a new Virgo ultracompact dwarf galaxy. The others show no sign of tidal disruption, despite the fact that such objects should be most vulnerable to tidal destruction in the cluster environment. The relative proximity of Virgo makes these objects amenable to detailed studies of their structural properties and stellar populations. They thus provide an important new window onto the connection between cluster environment and galaxy evolution at the extremes.Comment: 7 pages, 4 figures, to appear in ApJ Letters. Updated with minor revisions to match accepted versio

Cationic rhodium(I) and iridium(I) α-diimine complexes

AbstractCondensation of glyoxal with fluoroarylanilines [ArFNH2; ArF=4-C6H4F; 2,4-C6H3F2; 2,4,6-C6H2F3] generates new fluorine-substituted aryl α-diimines, ArFNCHCHNArF; ArF=4-C6H4F and 2,4,6-C6H2F3 have been structurally characterised. Displacement of acetonitrile from [M(COD)(MeCN)2][BF4] (M=Rh, Ir, COD=1,5-cyclooctadiene) with fluorine- and non-fluorine-substituted aryl α-diimines yields cationic rhodium(I) and iridium(I) complexes, that can be carbonylated to [M(CO)2(α-diimine)][BF4]

Medically relevant Acinetobacter species require a type II secretion system and specific membrane-associated chaperones for the export of multiple substrates and full virulence

Acinetobacter baumannii, A. nosocomialis, and A. pittii have recently emerged as opportunistic human pathogens capable of causing severe human disease; however, the molecular mechanisms employed by Acinetobacter to cause disease remain poorly understood. Many pathogenic members of the genus Acinetobacter contain genes predicted to encode proteins required for the biogenesis of a type II secretion system (T2SS), which have been shown to mediate virulence in many Gram-negative organisms. Here we demonstrate that Acinetobacter nosocomialis strain M2 produces a functional T2SS, which is required for full virulence in both the Galleria mellonella and murine pulmonary infection models. Importantly, this is the first bona fide secretion system shown to be required for virulence in Acinetobacter. Using bioinformatics, proteomics, and mutational analyses, we show that Acinetobacter employs its T2SS to export multiple substrates, including the lipases LipA and LipH as well as the protease CpaA. Furthermore, the Acinetobacter T2SS, which is found scattered amongst five distinct loci, does not contain a dedicated pseudopilin peptidase, but instead relies on the type IV prepilin peptidase, reinforcing the common ancestry of these two systems. Lastly, two of the three secreted proteins characterized in this study require specific chaperones for secretion. These chaperones contain an N-terminal transmembrane domain, are encoded adjacently to their cognate effector, and their disruption abolishes type II secretion of their cognate effector. Bioinformatic analysis identified putative chaperones located adjacent to multiple previously known type II effectors from several Gram-negative bacteria, which suggests that T2SS chaperones constitute a separate class of membrane-associated chaperones mediating type II secretion

Structural diversity in the type IV pili of multidrug-resistant Acinetobacter

Acinetobacter baumannii is a Gram-negative coccobacillus found primarily in hospital settings that has recently emerged as a source of hospital-acquired infections. A. baumannii expresses a variety of virulence factors, including type IV pili, bacterial extracellular appendages often essential for attachment to host cells. Here, we report the high resolution structures of the major pilin subunit, PilA, from three Acinetobacter strains, demonstrating thatA. baumannii subsets produce morphologically distinct type IV pilin glycoproteins. We examine the consequences of this heterogeneity for protein folding and assembly as well as host-cell adhesion by Acinetobacter. Comparisons of genomic and structural data with pilin proteins from other species of soil gammaproteobacteria suggest that these structural differences stem from evolutionary pressure that has resulted in three distinct classes of type IVa pilins, each found in multiple species