Ichthyological Bulletin of the J.L.B. Smith Institute of Ichthyology; No. 34

The osteology and swim bladders of the perciform family Apogonidae are surveyed at the generic level based on the examination of more than 150 species. Three subfamilies are recognized—Epigoninae, Apogoninae and Pseudaminae. The genera of Epigoninae are not treated. The Cheilodipterinae and the Siphaminae are not recognized as subfamilies and the Synagropi- nae are removed from the Apogonidae to the Percichthyidae. Descriptions of 19 genera and 14 subgenera are given. Forty-three genera are placed in synonymy and three new subgenera are proposed: Pristicon, Verulux and Zapogon. Keys to the three subfamilies and to the recognized genera and subgenera in the Apogoninae and Pseudaminae are presented. Discussions of the evolution of functional bony units within the Apogonidae are linked with trends seen in the beryciform-percoid transition and continuing changes exhibited by living percoids. The evolution and relationships of the living genera in the Apogoninae and Pseudaminae are treated and their zoogeography is briefly examined.Rhodes University Libraries (Digitisation

An analysis of the relationships between subthreshold electrical properties and excitability in skeletal muscle

Skeletal muscle activation requires action potential (AP) initiation followed by its sarcolemmal propagation and tubular excitation to trigger Ca2+ release and contraction. Recent studies demonstrate that ion channels underlying the resting membrane conductance (GM) of fast-twitch mammalian muscle fibers are highly regulated during muscle activity. Thus, onset of activity reduces GM, whereas prolonged activity can markedly elevate GM. Although these observations implicate GM regulation in control of muscle excitability, classical theoretical studies in un-myelinated axons predict little influence of GM on membrane excitability. However, surface membrane morphologies differ markedly between un-myelinated axons and muscle fibers, predominantly because of the tubular (t)-system of muscle fibers. This study develops a linear circuit model of mammalian muscle fiber and uses this to assess the role of subthreshold electrical properties, including GM changes during muscle activity, for AP initiation, AP propagation, and t-system excitation. Experimental observations of frequency-dependent length constant and membrane-phase properties in fast-twitch rat fibers could only be replicated by models that included t-system luminal resistances. Having quantified these resistances, the resulting models showed enhanced conduction velocity of passive current flow also implicating elevated AP propagation velocity. Furthermore, the resistances filter passive currents such that higher frequency current components would determine sarcolemma AP conduction velocity, whereas lower frequency components excite t-system APs. Because GM modulation affects only the low-frequency membrane impedance, the GM changes in active muscle would predominantly affect neuromuscular transmission and low-frequency t-system excitation while exerting little influence on the high-frequency process of sarcolemmal AP propagation. This physiological role of GM regulation was increased by high Cl− permeability, as in muscle endplate regions, and by increased extracellular [K+], as observed in working muscle. Thus, reduced GM at the onset of exercise would enhance t-system excitation and neuromuscular transmission, whereas elevated GM after sustained activity would inhibit these processes and thereby accentuate muscle fatigue

Hunting for Hydrated Minerals on Trans-Neptunian Objects

We present new optical reflectance spectra of three potentially silicate-rich trans-Neptunian Objects (TNOs). These spectra were obtained with the aim of confirming past hints and detections of 0.7 micron absorption features associated with the presence of iron-bearing phyllosilicates. Our new spectrum of 120216 (2004 EW95) presents clearly detected absorption features that are similar in shape to hydrated mineral absorption bands present in the spectra of aqueously altered outer main belt asteroids. Four new reflectance spectra of 208996 (2003 AZ84) obtained at separate epochs all appear featureless, but vary significantly in spectral gradient (between approximately 3.5 %/0.1 micron and 8.5 %/0.1 micron) on a timescale consistent with this object's nominal rotational period. We report the first four optical reflectance spectra of 90568 (2004 GV9), finding them all to be featureless but consistent with colors previously reported for this object. We speculate that impacts are the only mechanism capable of delivering, excavating, or forming hydrated minerals at the surfaces of TNOs in detectable concentrations; as a result, any deposits of hydrated minerals on TNOs are predicted to be localized and associated with impact sites. Globally altered TNOs (as observationally suggested for 2004 EW95) plausibly formed more easily at smaller heliocentric distances (< 15 au) before being transplanted into the current trans-Neptunian population.Comment: 25 pages, 7 figures, 6 tables, accepted for publication in PSJ, v2 adjusted after proofin

Characterizing Scales of Genetic Recombination and Antibiotic Resistance in Pathogenic Bacteria Using Topological Data Analysis

Pathogenic bacteria present a large disease burden on human health. Control of these pathogens is hampered by rampant lateral gene transfer, whereby pathogenic strains may acquire genes conferring resistance to common antibiotics. Here we introduce tools from topological data analysis to characterize the frequency and scale of lateral gene transfer in bacteria, focusing on a set of pathogens of significant public health relevance. As a case study, we examine the spread of antibiotic resistance in Staphylococcus aureus. Finally, we consider the possible role of the human microbiome as a reservoir for antibiotic resistance genes.Comment: 12 pages, 6 figures. To appear in AMT 2014 Special Session on Advanced Methods of Interactive Data Mining for Personalized Medicin

174P/Echeclus and its Blue Coma Observed Post-outburst

It has been suggested that centaurs may lose their red surfaces and become bluer due to the onset of cometary activity, but the way in which cometary outbursts affect the surface composition and albedo of active centaurs is poorly understood. We obtained consistent visual-near-infrared (VNIR) reflectance spectra of the sporadically active centaur 174P/Echeclus during a period of inactivity in 2014 and six weeks after its outburst in 2016 to see if activity had observably changed the surface properties of the nucleus. We observed no change in the surface reflectance properties of Echeclus following the outburst compared to before, indicating that, in this case, any surface changes due to cometary activity were not sufficiently large to be observable from Earth. Our spectra and post-outburst imaging have revealed, however, that the remaining dust coma is not only blue compared to Echeclus, but also bluer than solar, with a spectral gradient of -7.7+/-0.6% per 0.1 micron measured through the 0.61-0.88 micron wavelength range that appears to continue up to a wavelength of around 1.3 micron before becoming neutral. We conclude that the blue visual color of the dust is likely not a scattering effect, and instead may be indicative of the dust's carbon-rich composition. Deposition of such blue, carbon-rich, comatic dust onto a red active centaur may be a mechanism by which its surface color could be neutralized.Comment: 15 pages, 4 figures, 3 tables, AJ accepted, in pres

2004 EW95: A Phyllosilicate-bearing Carbonaceous Asteroid in the Kuiper Belt

Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions amongst the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW95, exhibiting a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm which is detected at greater than 4-sigma significance. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that 2004 EW95 may share a common origin with those objects. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO.Comment: 8 pages, 3 figures, 1 table, accepted, in pres

2004 EW_(95): A Phyllosilicate-bearing Carbonaceous Asteroid in the Kuiper Belt

Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions among the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW_(95), exhibiting a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm, which is detected at greater than 4σ significance. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that 2004 EW_(95) may share a common origin with those objects. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO

Chemical Components and Effects on Soil Quality in Temperate Grazed Pasture Systems

Key points 1. Legume/grass pastures retain feedbacks on N supply that may help to reduce losses of N to the wider environment. 2. Intensive use of N fertilisers tends to increase SOM turnover and increase losses of N to the environment. 3. Increased use of fertilisers has contributed little to soil organic matter storage in grazed pastoral systems

Moral wrongs, disadvantages, and disability: a critique of critical disability studies

Critical disability studies (CDS) has emerged as an approach to the study of disability over the last decade or so and has sought to present a challenge to the predominantly materialist line found in the more conventional disability studies approaches. In much the same way that the original development of the social model resulted in a necessary correction to the overly individualized accounts of disability that prevailed in much of the interpretive accounts which then dominated medical sociology, so too has CDS challenged the materialist line of disability studies. In this paper we review the ideas behind this development and analyse and critique some of its key ideas. The paper starts with a brief overview of the main theorists and approaches contained within CDS and then moves on to normative issues; namely, to the ethical and political applicability of CDS

Impact of previous hepatitis B infection on the clinical outcomes from chronic hepatitis C? A population-level analysis

Chronic coinfection with hepatitis C virus (HCV) and hepatitis B virus (HBV) is associated with adverse liver outcomes. The clinical impact of previous HBV infection on liver disease in HCV infection is unknown. We aimed at determining any association of previous HBV infection with liver outcomes using antibodies to the hepatitis B core antigen (HBcAb) positivity as a marker of exposure. The Scottish Hepatitis C Clinical Database containing data for all patients attending HCV clinics in participating health boards was linked to the HBV diagnostic registry and mortality data from Information Services Division, Scotland. Survival analyses with competing risks were constructed for time from the first appointment to decompensated cirrhosis, hepatocellular carcinoma (HCC) and liver‐related mortality. Records of 8513 chronic HCV patients were included in the analyses (87 HBcAb positive and HBV surface antigen [HBsAg] positive, 1577 HBcAb positive and HBsAg negative, and 6849 HBcAb negative). Multivariate cause‐specific proportional hazards models showed previous HBV infection (HBcAb positive and HBsAg negative) significantly increased the risks of decompensated cirrhosis (hazard ratio [HR]: 1.29, 95% CI: 1.01‐1.65) and HCC (HR: 1.64, 95% CI: 1.09‐2.49), but not liver‐related death (HR: 1.02, 95% CI: 0.80‐1.30). This is the largest study to date showing an association between previous HBV infection and certain adverse liver outcomes in HCV infection. Our analyses add significantly to evidence which suggests that HBV infection adversely affects liver health despite apparent clearance. This has important implications for HBV vaccination policy and indications for prioritization of HCV therapy