We present a study of the dust-to-gas ratios in five nearby galaxies NGC 628 (M74), NGC 6503, NGC 7793, UGC 5139 (Holmberg I), and UGC 4305 (Holmberg II). Using Hubble Space Telescope broad band ...WFC3/UVIS UV and optical images from the Treasury program LEGUS (Legacy ExtraGalactic UV Survey) combined with archival HST/ACS data, we correct thousands of individual stars for extinction across these five galaxies using an isochrone-matching (reddening-free Q) method. We generate extinction maps for each galaxy from the individual stellar extinctions using both adaptive and fixed resolution techniques, and correlate these maps with neutral HI and CO gas maps from literature, including The HI Nearby Galaxy Survey (THINGS) and the HERA CO-Line Extragalactic Survey (HERACLES). We calculate dust-to-gas ratios and investigate variations in the dust-to-gas ratio with galaxy metallicity. We find a power law relationship between dust-to-gas ratio and metallicity, consistent with other studies of dust-to-gas ratio compared to metallicity. We find a change in the relation when H\(_2\) is not included. This implies that underestimation of \(N_{H_2}\) in low-metallicity dwarfs from a too-low CO-to-H\(_2\) conversion factor \(X_{CO}\) could have produced too low a slope in the derived relationship between dust-to-gas ratio and metallicity. We also compare our extinctions to those derived from fitting the spectral energy distribution (SED) using the Bayesian Extinction and Stellar Tool (BEAST) for NGC 7793 and find systematically lower extinctions from SED-fitting as compared to isochrone matching.
The American public requires that research projects use resources efficiently, that they provide answers that are beneficial, and that they are carried out ethically. Peer review of research ...protocols, results, and reports, provides one way to improve research and to reassure the public.
Massive stars play an important role in both cluster and galactic evolution and the rate at which they lose mass is a key driver of both their own evolution and their interaction with the environment ...up to and including their SNe explosions. Young massive clusters provide an ideal opportunity to study a co-eval population of massive stars. We performed 3mm continuum observations with the Atacama Large Millimetre/submillimetre Array of the Galactic cluster Westerlund 1, to study the constituent massive stars and determine mass-loss rates for the diverse post-main sequence population. We detected emission from 50 stars in Westerlund 1, comprising all 21 Wolf-Rayets within the field of view, eight cool and 21 OB super-/hypergiants. Emission nebulae were associated with a number of the cool hypergiants while, unexpectedly, a number of hot stars also appear spatially resolved. We measured the mass-loss rates for a unique population of massive post-main sequence stars at every stage of evolution, confirming a significant increase as stars transition from OB supergiant to WR states. The range of spectral types exhibited provides a critical test of radiatively driven wind theory and the reality of the bi-stability jump. The extreme mass-loss rate inferred for the interacting binary Wd1-9 in comparison to other cluster members confirmed the key role binarity plays in massive stellar evolution. The presence of compact nebulae around a number of OB and WR stars is unexpected; by analogy to the cool super-/hypergiants we attribute this to confinement and sculpting of the stellar wind via interaction with the intra-cluster medium/wind. Given the morphology of core collapse SNe depend on the nature of the pre-explosion circumstellar environment, if this hypothesis is correct then the properties of the explosion depend not just on the progenitor, but also the environment in which it is located.
The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in five bands from the near UV to ...the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near UV color-magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color-magnitude diagrams to identify stars more massive than 14 Mo, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the time scale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems.
The typical antipsychotic haloperidol is known to induce extra-pyramidal side-effects (EPS). Catalepsy in rats is generally regarded as a valid model for detecting the EPS liability of compounds in ...humans. Together with its antipsychotic and cataleptogenic actions, haloperidol causes an attenuation of instrumental responding which becomes larger in the course of a session: a within-session response decrement. The present study compared the time-course of haloperidol-induced catalepsy, measured by a bar test, to the haloperidol-induced within-session response decrements, measured by operant behaviour under a fixed ratio 10 schedule of reinforcement. Rats were trained to press a lever on a Fixed Ratio 10 schedule of food reinforcement during sessions of 15 min. When responding was stable, saline or haloperidol in 0.03 mg/kg, 0.1 mg/kg, or 0.3 mg/kg was administered intra-peritoneally either 30, 90 or 180 min prior to behavioural testing. The number of lever presses, food tray visits and latency to press the lever and to visit the food tray were analysed in five successive blocks of 3 min. Catalepsy was tested 30, 60, 90, 120, and 180 min. after injection, by placing a rat with its forepaws on a horizontal bar. The latency to remove both forepaws from the bar was scored. Within-session response decrements were present at 0.1 mg/kg and at 0.3 mg/kg, from 30 min after administration onward. At these doses, latency to press the lever was increased after 30 and 90 min, but not significantly after 180 min. Latency to visit the tray was affected only after 30 min, at 0.3 mg/kg. Haloperidol induced a dose-dependent increase in catalepsy from 60 min onwards, with maximal effect after 120 min. A dissociation between the time-course of occurrence of within-session response decrement and the cataleptogenic action of haloperidol, as well as between the latter and both latency measures, was found. Consequently, the present data suggest that within-session response decrements are not obviously caused by catalepsy-related impairments.
A series of 1,6-dihydro-5-(4H)-pyrimidinone oxime derivatives I was synthesized (Scheme 1, Tables 1 and 2) and tested for muscarinic activity (Table 3) in receptor binding assays using ...3H-oxotremorine-M (Oxo-M) and 3H-pirenzepine (Pz) as ligands. Potential muscarinic agonistic or antagonistic properties of the compounds were determined using binding studies that measured their potencies to inhibit the binding of Oxo-M and Pz. Preferential inhibition of Oxo-M binding was used as an indicator for potential muscarinic agonistic properties; this potential was confirmed in functional studies on isolated organs. The series produced a wide range of active compounds with differing degrees of selectivity in M1, M2, and M3 functional models. Several compounds that have mixed agonist/antagonist profiles were able to reduce cholinergic-related cognitive impairments in models of mnemonic function. Substitutions (I, e.g. R2 or R3 = Me) at the 1,6-dihydro-5-(4H)pyrimidine ring disrupted binding and efficacy, whereas systematic variation of the oximes substituent R1 resulted in various degrees of potency and selectivity dependent on the nature of the substitution.
Military personnel are more than twice as likely as civilians to use smokeless tobacco (ST), and recent studies indicate that military prevalence rates are rising. However, few studies have examined ...factors related to ST use in the military. The present study evaluated the characteristics of ST use in 785 active duty military personnel. The results indicated that the average age of initiation was 17.7 years, participants had used ST for 12.3 years, and they used approximately four tins or pouches of tobacco per week. Army personnel were more likely than Air Force personnel to be older, to have used ST longer, and to be heavier users. Officers had used ST longer than enlisted personnel and were more likely to have had a recent quit attempt. Enlisted personnel were more than three times as likely to report concurrent cigarette smoking. These results indicate that there are significant differences in ST use patterns in military personnel, and cessation programs should be tailored to meet these differences.
The discriminative stimulus properties of the specific type IV phosphodiesterase inhibitor, rolipram and its two Stereoisomers were assessed using standard two-lever drug discrimination procedures in ...which responding on the appropriate lever was reinforced on a FR10 schedule. In three separate drug cues based on training rats to discriminate the racemate (0.2 mg/kg, IP), the (−)-isomer (0.1 mg/kg), or the (+)-isomer (2 mg/kg) from vehicle, all forms substituted for one another, differing only in potency. In keeping with published reports, the (−)-isomer was the more potent form, the (+)-isomer being approximately 10 times less potent. Several phosphodiesterase (PDE) inhibitors were found to substitute for the racemate cue, their potencies in the behavioural measure correlating with their potency in displacing
3Hrolipram from its forebrain binding sites in vivo (
r = 0.95), suggesting that the discriminative stimulus depends on an action of the drug upon this site. Because rolipram has been reported to possess antidepressant activity, the ability of the tricyclic antidepressant imipramine to substitute for rolipram was investigated; doses of 10 and 20 mg/kg did not substitute. Amphetamine (0.156–1.25 mg/kg) also was inactive. Lisuride gave rise to drug-appropriate responding in 50% of rats only at a dose of 0.078 mg/kg, which severely disrupted responding. It is concluded that the rolipram discriminative stimulus is dependent on the selective PDE inhibititory activity of the drug and that it does not constitute a cue based on the antidepressant property of rolipram.
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