Distal Urogenital Anatomy of Male Southern Coal Skinks, Plestiodon anthracinus pluvialis (Reptilia: Scincidae)

I investigated the morphology and histology of the distal urogenital anatomy of male southern coal skinks (Plestiodon anthracinus pluvialis) from reproductively active individuals collected in Arkansas in order to provide comparative information with recent studies on squamate urogenital anatomy. Specifically, I focused on the basic anatomy and positioning of posterior ducts in this skink, which included portions of the ductus deferens, the ampulla ductus deferentis, the sexual segment of the kidney, the ureter and collecting ducts, as well as aspects of the urodaeal chamber and urogenital papillae. I found a much reduced ampulla ductus deferentis comprising only 0.7 mm in length in the caudal region of the ductus deferens. The sexual segment of the kidney was well developed, being located in collecting ducts of the kidney proper, in walls of collecting ducts leading away from the kidney as well as within anterior portions of the ureter. The anterior dorsal recess of the urodaeum possessed epithelial crypts within a highly folded epithelium. Finally, a ductal triad (ductus deferens, ureter, and a single collecting duct) terminates at each orifice of the paired urogenital papillae. The distal urogenital anatomy of this scincid lizard revealed anatomical features similar to other species within the genus Plestiodon

The Laser Interferometer Gravitational Wave Observatory (LIGO) project

The LIGO (Laser Interferometer Gravitational-Wave Observatory) project is designed to open a new field of science by detecting and studying the gravitational waves from astrophysical sources, including neutron stars, black holes, and possibly, supernovae and the big bang. LIGO will consist of two scientific facilities, each incorporating an L-shaped vacuum system with 4-kilometers arms to house sensitive interferometers. A detector system consists of three interferometers, two at one site and one at the other. Each interferometer measures the motion of a set of test masses which are suspended from seismically isolated supports and free to move in response to gravitational waves. Correlations among the three interferometers will be used to eliminate local noise. LIGO is designed to support a sequence of detector systems of increasing sensitivity over the next twenty years or longer. In its initial configuration, it will have just one detector system. However, its design permits expansion to support three simultaneous detector systems. The project received funding in 1992 to begin design and construction. Sites for the two facilities (Hanford, Washington and Livingston, Louisiana) have been selected. Under the present schedule, the facilities will be completed by 1997 and initial observations will begin in 1998. Ultimately, the LIGO will be operated in coordination with interferometers in Europe and elsewhere, to form a worldwide gravitational wave observatory network

Ground-based gravitational-wave detection: now and future

In the past three years, the first generation of large gravitational-wave interferometers has begun operation near their design sensitivities, taking up the mantle from the bar detectors that pioneered the search for the first direct detection of gravitational waves. Even as the current ground-based interferometers were reaching their design sensitivities, plans were being laid for the future. Advances in technology and lessons learned from the first generation devices have pointed the way to an order of magnitude improvement in sensitivity, as well as expanded frequency ranges and the capability to tailor the sensitivity band to address particular astrophysical sources. Advanced cryogenic acoustic detectors, the successors to the current bar detectors, are being researched and may play a role in the future, particularly at the higher frequencies. One of the most important trends is the growing international cooperation aimed at building a truly global network. In this paper, I survey the state of the various detectors as of mid-2007, and outline the prospects for the future

Using causal models to distinguish between neurogenesis-dependent and -independent effects on behaviour

There has been a substantial amount of research on the relationship between hippocampal neurogenesis and behaviour over the past fifteen years, but the causal role that new neurons have on cognitive and affective behavioural tasks is still far from clear. This is partly due to the difficulty of manipulating levels of neurogenesis without inducing off-target effects, which might also influence behaviour. In addition, the analytical methods typically used do not directly test whether neurogenesis mediates the effect of an intervention on behaviour. Previous studies may have incorrectly attributed changes in behavioural performance to neurogenesis because the role of known (or unknown) neurogenesis-independent mechanisms were not formally taken into consideration during the analysis. Causal models can tease apart complex causal relationships and were used to demonstrate that the effect of exercise on pattern separation is via neurogenesis-independent mechanisms. Many studies in the neurogenesis literature would benefit from the use of statistical methods that can separate neurogenesis-dependent from neurogenesis-independent effects on behaviour

Hyla versicolor-chrysoscelis Species Complex of Gray Treefrogs in Arkansas: Histological and Ultrastructural evidence

We investigated the Hyla versicolor-chrysoscelis species complex (tetraploid and diploid species, respectively) of cryptic gray treefrogs from Arkansas using light and scanning electron microscopy. From previous studies of this treefrog complex in other states, H. versicolor has been shown to exhibit larger nuclear diameters and larger toe pad epithelial cells than H. chrysoscelis. Based upon average nuclear diameters of eyelid epithelial cells, we found two or possibly three groups of frogs. The presumed H. versicolor exhibited greatly enlarged toe pad epithelial cells using scanning electron microscopy and were found in four counties, three of which are in the Ozark Mountains. Hyla chrysoscelis occurs throughout the stat

Improving basic and translational science by accounting for litter-to-litter variation in animal models

Background: Animals from the same litter are often more alike compared with animals from different litters. This litter-to-litter variation, or "litter effects", can influence the results in addition to the experimental factors of interest. Furthermore, an experimental treatment can be applied to whole litters rather than to individual offspring. For example, in the valproic acid (VPA) model of autism, VPA is administered to pregnant females thereby inducing the disease phenotype in the offspring. With this type of experiment the sample size is the number of litters and not the total number of offspring. If such experiments are not appropriately designed and analysed, the results can be severely biased as well as extremely underpowered. Results: A review of the VPA literature showed that only 9% (3/34) of studies correctly determined that the experimental unit (n) was the litter and therefore made valid statistical inferences. In addition, litter effects accounted for up to 61% (p <0.001) of the variation in behavioural outcomes, which was larger than the treatment effects. In addition, few studies reported using randomisation (12%) or blinding (18%), and none indicated that a sample size calculation or power analysis had been conducted. Conclusions: Litter effects are common, large, and ignoring them can make replication of findings difficult and can contribute to the low rate of translating preclinical in vivo studies into successful therapies. Only a minority of studies reported using rigorous experimental methods, which is consistent with much of the preclinical in vivo literature.Comment: http://www.biomedcentral.com/1471-2202/14/37/abstrac

Updown categories: Generating functions and universal covers

A poset can be regarded as a category in which there is at most one morphism between objects, and such that at most one of Hom(c,c') and Hom(c',c) is nonempty for distinct objects c,c'. If we keep in place the latter axiom but allow for more than one morphism between objects, we have a sort of generalized poset in which there are multiplicities attached to covering relations, and possibly nontrivial automorphism groups. We call such a category an "updown category". In this paper we give a precise definition of such categories and develop a theory for them. We also give a detailed account of ten examples, including updown categories of integer partitions, integer compositions, planar rooted trees, and rooted trees.Comment: arXiv admin note: substantial text overlap with arXiv:math/040245