Antlia B: A faint dwarf galaxy member of the NGC 3109 association

We report the discovery of Antlia B, a faint dwarf galaxy at a projected distance of $\sim$72 kpc from NGC 3109 ($M_{V}$$\sim$$-$15 mag), the primary galaxy of the NGC 3109 dwarf association at the edge of the Local Group. The tip of the red giant branch distance to Antlia B is $D$=1.29$\pm$0.10 Mpc, which is consistent with the distance to NGC 3109. A qualitative analysis indicates the new dwarf's stellar population has both an old, metal poor red giant branch ($\gtrsim$10 Gyr, [Fe/H]$\sim$$-$2), and a younger blue population with an age of $\sim$200-400 Myr, analogous to the original Antlia dwarf, another likely satellite of NGC 3109. Antlia B has \ion{H}{1} gas at a velocity of $v_{helio,HI}$=376 km s$^{-1}$, confirming the association with NGC 3109 ($v_{helio}$=403 km s$^{-1}$). The HI gas mass (M$_{HI}$=2.8$\pm$0.2$\times$10$^{5}$ M$_{\odot}$), stellar luminosity ($M_{V}$=$-$9.7$\pm$0.6 mag) and half light radius ($r_{h}$=273$\pm$29 pc) are all consistent with the properties of dwarf irregular and dwarf spheroidal galaxies in the Local Volume, and is most similar to the Leo P dwarf galaxy. The discovery of Antlia B is the initial result from a Dark Energy Camera survey for halo substructure and faint dwarf companions to NGC 3109 with the goal of comparing observed substructure with expectations from the $\Lambda$+Cold Dark Matter model in the sub-Milky Way regime.Comment: 7 pages, 3 figures. Submitted to ApJ

A Comprehensive Archival Search for Counterparts to Ultra-Compact High Velocity Clouds: Five Local Volume Dwarf Galaxies

We report five Local Volume dwarf galaxies (two of which are presented here for the first time) uncovered during a comprehensive archival search for optical counterparts to ultra-compact high velocity clouds (UCHVCs). The UCHVC population of HI clouds are thought to be candidate gas-rich, low mass halos at the edge of the Local Group and beyond, but no comprehensive search for stellar counterparts to these systems has been presented. Careful visual inspection of all publicly available optical and ultraviolet imaging at the position of the UCHVCs revealed six blue, diffuse counterparts with a morphology consistent with a faint dwarf galaxy beyond the Local Group. Optical spectroscopy of all six candidate dwarf counterparts show that five have an H$\alpha$-derived velocity consistent with the coincident HI cloud, confirming their association, the sixth diffuse counterpart is likely a background object. The size and luminosity of the UCHVC dwarfs is consistent with other known Local Volume dwarf irregular galaxies. The gas fraction ($M_{HI}/M_{star}$) of the five dwarfs are generally consistent with that of dwarf irregular galaxies in the Local Volume, although ALFALFA-Dw1 (associated with ALFALFA UCHVC HVC274.68+74.70$-$123) has a very high $M_{HI}/M_{star}$$\sim$40. Despite the heterogenous nature of our search, we demonstrate that the current dwarf companions to UCHVCs are at the edge of detectability due to their low surface brightness, and that deeper searches are likely to find more stellar systems. If more sensitive searches do not reveal further stellar counterparts to UCHVCs, then the dearth of such systems around the Local Group may be in conflict with $\Lambda$CDM simulations.Comment: 18 pages, 4 tables, 4 figures, ApJ Accepte

Nonlinear vertical oscillations of a particle in a sheath of a rf discharge

A new simple method to measure the spatial distribution of the electric field in the plasma sheath is proposed. The method is based on the experimental investigation of vertical oscillations of a single particle in the sheath of a low-pressure radio-frequency discharge. It is shown that the oscillations become strongly nonlinear and secondary harmonics are generated as the amplitude increases. The theory of anharmonic oscillations provides a good qualitative description of the data and gives estimates for the first two anharmonic terms in an expansion of the sheath potential around the particle equilibrium.Comment: 11 pages, 4 figure

Hubble Space Telescope Imaging of Antlia B: Star Formation History and a New Tip of the Red Giant Branch Distance

A census of the satellite population around dwarf galaxy primary hosts in environments outside the Local Group is essential to understanding Λ cold dark matter galaxy formation and evolution on the smallest scales. We present deep optical Hubble Space Telescope imaging of the gas-rich, faint dwarf galaxy Antlia B (M_V = −9.4)—a likely satellite of NGC 3109 (D = 1.3 Mpc)—discovered as part of our ongoing survey of primary host galaxies similar to the Magellanic Clouds. We derive a new tip of the red giant branch distance of D = 1.35 ± 0.06 Mpc (m − M = 25.65 ± 0.10), consistent with membership in the nearby NGC 3109 dwarf association. The color–magnitude diagram (CMD) shows both a prominent old, metal-poor stellar component and confirms a small population of young, blue stars with ages ≾1 Gyr. We use the CMD fitting algorithm MATCH to derive the star formation history (SFH) and find that it is consistent with the typical dwarf irregular or transitional dwarf galaxy (dTrans) in the Local Group. Antlia B shows relatively constant stellar mass growth for the first ~10–11 Gyr and almost no growth in the last ~2–3 Gyr. Despite being gas-rich, Antlia B shows no evidence of active star formation (i.e., no Hα emission) and should therefore be classified as a dTrans dwarf. Both Antlia B and the Antlia dwarf (dTrans) are likely satellites of NGC 3109, suggesting that the cessation of ongoing star formation in these galaxies may be environmentally driven. Future work studying the gas kinematics and distribution in Antlia B will explore this scenario in greater detail. Our work highlights the fact that detailed studies of nearby dwarf galaxies in a variety of environments may continue to shed light on the processes that drive the SFH and evolution of dwarf galaxies more generally

Useful immunohistochemical indicators in canine mast cell tumours

Morphological and immunohistochemical analysis of 45 canine mast cell tumours was performed to determine whether the proteins examined are useful for a more precise description of tumour morphology and a more reliable determination of the prognosis in patients. Tissue sections were stained according to the standard haematoxylin and eosin (HE) technique and with toluidine blue to demonstrate cytoplasmic granules. Immunohistochemical studies were performed, using the cell markers CD117 (c-kit), p16 and von Willebrand factor (FVIII). In CD117 three different staining patterns were observed: (1) membranous reaction, (2) intense staining of cytoplasm, and (3) a diffuse, delicate cytoplasmic reaction. Von Willebrand antibody was evaluated on the basis of the number of blood vessels stained. p16 expression was evaluated by scoring positive nuclear reaction. Positive expression was demonstrated for all examined antigens, but their level of expression differed depending on the grades of tumour malignancy. Statistical analysis of the results documented a pronounced positive correlation between the markers studied and the grade of tumour malignancy (P < 0.001). It was shown that each of the cell markers examined represents a useful prognostic indicator for patients with mast cell tumours. The calculated correlation coefficients demonstrate a strong association between the expressions of CD117, FVIII and p16, and the histological malignancy of a tumour

Shift-Volatility Transmission in East Asian Equity Markets

This paper attempts to provide evidence of "shift-volatility" transmission in the East Asian equity markets. By shift-volatility, we mean the volatility shifts from a low level to a high level, corresponding respectively to tranquil and crisis periods. We examine the interdependence of equity volatilities between Hong-Kong, Indonesia, Japan, Malaysia, the Philippines, Singapore, Thailand and the United States. Our main issue is whether shift-volatility needs to be considered as a regional phenomenon, or from a more global perspective. We find that the timing/spans of high volatility regimes correspond adequately to years historically documented as those of crises (the Asian crisis and the years following the 2008 crisis). Moreover, we suggest different indicators that could be useful to guide the investors in their arbitrage behavior in the different regimes: the duration of each state, the sensitivity of the volatility in a market following a change in the volatility in another market. Finally, we are able to identify which market can be considered as leading markets in terms of volatility

Development of a Wild-type \u3ci\u3eEscherichia coli\u3c/i\u3e Environmental Bloom Model to Evaluate Alternatives to Formaldehyde Fumigation in Broiler Chicken Hatch Cabinets

Horizontal transmission of opportunistic Escherichia coli during hatch can have detrimental effects on early performance, particularly as pioneer colonizers. Commercially, formaldehyde is often applied in the United States to combat the bacterial bloom that occurs inside of the hatching environment. The purpose of these experiments was to develop a replicable E. coli horizontal challenge model to evaluate alternatives to formaldehyde sanitation applied to the hatching environment. In experiment 1, two trials were conducted for 2 wild-type (WT) E. coli isolates (isolate 1 [I1] or isolate 2 [I2]) to determine the appropriate in ovo challenge dose and day of embryogenesis (DOE) for challenge administration. In experiment 1 trial 1, the most appropriate inoculation dose and time point were determined to be 102 cfu/embryo on DOE 19. Experiment 1 trial 2 evaluated whether placement of seeder (direct-challenged) embryos with contact (indirect-challenged) embryos during hatch affected contact hatchability. Trial 2 showed no differences in hatchability between groups. A 7-day experiment (experiment 1 trial 2) was conducted to evaluate the effects of I1 or I2 on horizontal transmission, gram-negative bacterial (GNB) recovery from the gastrointestinal tract (GIT), and impact on BW gain (BWG). Compared with the negative control, seeder, and contact chicks challenged with I1 or I2, we observed increased (P \u3c 0.05) GNB recovered from GIT on the day of hatch. There was a marked (P \u3c 0.05) reduction in 7-day BWG between the I1 indirect-challenged group and the negative control group. To further validate the model, 2 7-day trials (experiment 2, experiment 3) were conducted to evaluate the effects of formaldehyde fumigation on coliform recovery from the hatching environment and on early performance using I1 for the challenge. Isolate 1 positive control hatchers had increased levels of circulating coliforms compared with the negative control and formaldehyde-treated hatchers, although there was no significant impact on performance induced by challenge or formaldehyde treatment in experiment 2 or experiment 3. These data provide a potential model for investigations related to horizontal transmission of WT E. coli at a low dose on DOE 19 to promote simulated commercially relevant bacterial blooms under laboratory conditions

Stellar kinematics and metallicities in the ultra-faint dwarf galaxy Reticulum II

Based on data obtained from the ESO Science Archive Facility under request number 157689

Research Note: Application of an \u3ci\u3eEscherichia coli\u3c/i\u3e Spray Challenge Model for Neonatal Broiler Chickens

Avian pathogenic Escherichia coli (E. coli) is an opportunistic pathogen often introduced to neonatal chicks during the hatching process. This commensal bacterium, particularly as a pioneer colonizer of the gastrointestinal tract, can have substantial implications in the rearing of poultry because of reduced flock performance. In order to mimic the effects of the natural bacterial bloom present during the hatch, a seeder challenge model was developed to expose neonatal chicks to virulent E. coli. On day 20 of embryogenesis, selected early hatched chicks (n = 18/hatcher) were briefly removed and sprayed challenged with saline (vehicle) or E. coli at 1 x 107 colony-forming unit (CFU)/chick (exp 1) and 2.5 x 107 CFU/chick (exp 2). These challenged chicks were returned to the hatcher to serve as seeders to transmit the pathogen to the indirect challenged or contact chicks (n = 195/hatcher). For two 7-d experiments, the efficacy of transmission was evaluated via enteric bacterial recovery, body weight gain (BWG), and mortality. For exp 1 and exp 2, significantly (P \u3c 0.0001) more gram-negative bacteria were recovered from the seeder and contact gastrointestinal samples than the negative control samples on day of hatch. In addition, there was a reduction (P \u3c 0.05) in 7-d BWG and significantly (P \u3c 0.0001) higher mortality in the contact-challenged chicks than the negative control chicks in both exp 1 and exp 2. These data suggest that this challenge model could be used to evaluate different methods of controlling the bacterial bloom that occurs in the hatching environment