Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment

We study star formation histories (SFHs) of $\simeq500$ dwarf galaxies (stellar mass $M_\ast = 10^5 - 10^9\,M_\odot$) from FIRE-2 cosmological zoom-in simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies, dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated) dwarf galaxies. We reproduce observed trends wherein higher-mass dwarfs quench later (if at all), regardless of environment. We also identify differences between the environments, both in terms of "satellite vs. central" and "LG vs. individual MWvs. isolated dwarf central." Around the individual MW-mass hosts, we recover the result expected from environmental quenching: central galaxies in the "near field" have more extended SFHs than their satellite counterparts, with the former more closely resemble isolated ("true field") dwarfs (though near-field centrals are still somewhat earlier forming). However, this difference is muted in the LG-like environments, where both near-field centrals and satellites have similar SFHs, which resemble satellites of single MW-mass hosts. This distinction is strongest for $M_\ast = 10^6 - 10^7\,M_\odot$ but exists at other masses. Our results suggest that the paired halo nature of the LG may regulate star formation in dwarf galaxies even beyond the virial radii of the MW and Andromeda. Caution is needed when comparing zoom-in simulations targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.Comment: Main text: 11 pages, 8 figures; appendices: 4 pages, 4 figures. Submitted to MNRAS; comments welcom

Modeling Urban Hydrology and Green Infrastructure Using the AGWA Urban Tool and the KINEROS2 Model

Urban hydrology and green infrastructure (GI) can be modeled using the Automated Geospatial Watershed Assessment (AGWA) Urban tool and the Kinematic Runoff and Erosion (KINEROS2) model. The KINEROS2 model provides an urban modeling element with nine overland flow components that can be used to represent various land cover types commonly found in the built environment while treating runoff-runon and infiltration processes in a physically based manner. The AGWA Urban tool utilizes a Geographic Information System (GIS) framework to prepare parameters required for KINEROS2, executes the model, and imports results for visualization in the GIS. The AGWA Urban tool was validated on a residential subdivision in Arizona, USA, using 47 rainfall events (June 2005 to September 2006) to compare observed runoff volumes and peak flow rates with simulated results. Comparison of simulated and observed runoff volumes resulted in a slope of 1.00 for the regression equation with an R2 value of 0.80. Comparison of observed and simulated peak flows had a slope of 1.12 with an R2 value of 0.83. A roof runoff analysis was simulated for 787 events, from January 2006 through December 2015, to analyze the water availability from roof runoff capture. Simulation results indicated a 15% capture of the average monthly rainfall volume on the watershed. Additionally, rainwater captured from roofs has the potential to provide for up to 70% of the domestic annual per capita water use in this region. Five different scenarios (S1 - base, S2 - with retention basins, S3 - with permeable driveways, S4 - with rainwater harvesting cisterns, and S5 - all GI practices from S2, S3, and S4) were simulated over the same period to compare the effectiveness of GI implementation at the parcel level on runoff and peak flows at the watershed outlet. Simulation results indicate a higher runoff volume reduction for S2 (53.41 m3 average capacity, average 30% reduction) as compared to S3 (average 14% reduction), or S4 (3.78 m3 capacity, average 6% reduction). Analysis of peak flows reveal larger peak flow reduction for S2. S3 showed more reduction of smaller peak flows as compared to S4

A Functional Gene Array for Detection of Bacterial Virulence Elements

Emerging known and unknown pathogens create profound threats to public health. Platforms for rapid detection and characterization of microbial agents are critically needed to prevent and respond to disease outbreaks. Available detection technologies cannot provide broad functional information about known or novel organisms. As a step toward developing such a system, we have produced and tested a series of high-density functional gene arrays to detect elements of virulence and antibiotic resistance mechanisms. Our first generation array targets genes from Escherichia coli strains K12 and CFT073, Enterococcus faecalis and Staphylococcus aureus. We determined optimal probe design parameters for gene family detection and discrimination. When tested with organisms at varying phylogenetic distances from the four target strains, the array detected orthologs for the majority of targeted gene families present in bacteria belonging to the same taxonomic family. In combination with whole-genome amplification, the array detects femtogram concentrations of purified DNA, either spiked in to an aerosol sample background, or in combinations from one or more of the four target organisms. This is the first report of a high density NimbleGen microarray system targeting microbial antibiotic resistance and virulence mechanisms. By targeting virulence gene families as well as genes unique to specific biothreat agents, these arrays will provide important data about the pathogenic potential and drug resistance profiles of unknown organisms in environmental samples

Trophic consequences of non-native pumpkinseed Lepomis gibbosus for native pond fishes

Introduced non-native fishes can cause considerable adverse impacts on freshwater ecosystems. The pumpkinseed Lepomis gibbosus, a North American centrarchid, is one of the most widely distributed non-native fishes in Europe, having established self-sustaining populations in at least 28 countries, including the U.K. where it is predicted to become invasive under warmer climate conditions. To predict the consequences of increased invasiveness, a field experiment was completed over a summer period using a Control comprising of an assemblage of native fishes of known starting abundance and a Treatment using the same assemblage but with elevated L. gibbosus densities. The trophic consequences of L. gibbosus invasion were assessed with stable isotope analysis and associated metrics including the isotopic niche, measured as standard ellipse area. The isotopic niches of native gudgeon Gobio gobio and roach Rutilus rutilus overlapped substantially with that of non-native L. gibbosus, and were also substantially reduced in size compared to ponds where L. gibbosus were absent. This suggests these native fishes shifted to a more specialized diet in L. gibbosus presence. Both of these native fishes also demonstrated a concomitant and significant reduction in their trophic position in L. gibbosus presence, with a significant decrease also evident in the somatic growth rate and body condition of G. gobio. Thus, there were marked changes detected in the isotopic ecology and growth rates of the native fish in the presence of non-native L. gibbosus. The implications of these results for present and future invaded pond communities are discussed

Degradation of Host Sphingomyelin Is Essential for Leishmania Virulence

In eukaryotes, sphingolipids (SLs) are important membrane components and powerful signaling molecules. In Leishmania, the major group of SLs is inositol phosphorylceramide (IPC), which is common in yeast and Trypanosomatids but absent in mammals. In contrast, sphingomyelin is not synthesized by Leishmania but is abundant in mammals. In the promastigote stage in vitro, Leishmania use SL metabolism as a major pathway to produce ethanolamine (EtN), a metabolite essential for survival and differentiation from non-virulent procyclics to highly virulent metacyclics. To further probe SL metabolism, we identified a gene encoding a putative neutral sphingomyelinase (SMase) and/or IPC hydrolase (IPCase), designated ISCL (Inositol phosphoSphingolipid phospholipase C-Like). Despite the lack of sphingomyelin synthesis, L. major promastigotes exhibited a potent SMase activity which was abolished upon deletion of ISCL, and increased following over-expression by episomal complementation. ISCL-dependent activity with sphingomyelin was about 20 fold greater than that seen with IPC. Null mutants of ISCL (iscl−) showed modest accumulation of IPC, but grew and differentiated normally in vitro. Interestingly, iscl− mutants did not induce lesion pathology in the susceptible BALB/c mice, yet persisted indefinitely at low levels at the site of infection. Notably, the acute virulence of iscl− was completely restored by the expression of ISCL or heterologous mammalian or fungal SMases, but not by fungal proteins exhibiting only IPCase activity. Together, these findings strongly suggest that degradation of host-derived sphingomyelin plays a pivotal role in the proliferation of Leishmania in mammalian hosts and the manifestation of acute disease pathology

Trophic consequences of an invasive, small-bodied non-native fish, sunbleak Leucaspius delineatus, for native pond fishes

Assessments of the trophic consequences of invasive fishes are important for quantifying their ecological impacts on native species more generally. A small-bodied cyprinid fish native to continental Europe and introduced in the 1970s to the U.K, the sunbleak Leuciscus delineatus, has been shown previously to establish closer social associations with native species of similar size than do native species amongst themselves. To assess the potential detrimental trophic consequences of native species associations with L. delineatus, a field-based experiment was undertaken in summer 2015 in six outdoor, artificial ponds containing three native cyprinid species (rudd Scardinius erthrophthalamus, gudgeon Gobio gobio, tench Tinca tinca). Three ponds were controls (no L. delineatus) and three were treatments (L. delineatus present). The results of stable isotope analysis (SIA) of fish tissue samples provided strong evidence that the isotopic niches of both native benthic fishes were reduced in the presence of L. delineatus, although there were no significant effects on the trophic position, body size or condition of two of the three native fish species. Introduced L. delineatus maintained a core isotopic niche that was distinct from the two native benthic fishes, with no overlap detected between native and non-native fishes when including 40 % and 95% of the data. These results indicate that the response of the native fishes to the introduction of L. delineatus was niche constriction via trophic specialisation, with this response sufficient to maintain their growth rates and condition. This result is similar to studies on a range of small-bodied invasive fishes, suggesting the trophic impacts of these invaders are relatively consistent across species and systems

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article