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

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

Environmental chemical exposures and breast cancer

As a hormone-sensitive condition with no single identifiable cause, breast cancer is a major health problem. It is characterized by a wide range of contributing factors and exposures occurring in different combinations and strengths across a lifetime that may be amplified during periods of enhanced developmental susceptibility and impacted by reproductive patterns and behaviours. The vast majority of cases are oestrogen-receptor positive and occur in women with no family history of the disease suggesting that modifiable risk factors are involved. A substantial body of evidence now links oestrogen-positive breast cancer with environmental exposures. Synthetic chemicals capable of oestrogen mimicry are characteristic of industrial development and have been individually and extensively assessed as risk factors for oestrogen-sensitive cancers. Existing breast cancer risk assessment tools do not take such factors into account. In the absence of consensus on causation and in order to better understand the problem of escalating incidence globally, an expanded, integrated approach broadening the inquiry into individual susceptibility breast cancer is proposed. Applying systems thinking to existing data on oestrogen-modulating environmental exposures and other oestrogenic factors characteristic of Westernisation and their interactions in the exposure, encompassing social, behavioural, environmental, hormonal and genetic factors, can assist in understanding cancer risks and the pursuit of prevention strategies. A new conceptual framework based on a broader understanding of the “system” that underlies the development of breast cancer over a period of many years, incorporating the factors known to contribute to breast cancer risk, could provide a new platform from which government and regulators can promulgate enhanced and more effective prevention strategies

Age Estimation using Phalangeal Skeletochronology in Northern Crawfish Frogs, Lithobates areolatus circulosus (Amphibia: Anura: Ranidae), from Arkansas

As an obligate crayfish burrow dweller, crawfish frogs have historically occupied a relatively narrow ecological niche throughout their distribution in the tall grass prairies and grasslands of the central and south-central United States. In Arkansas, the Northern Crawfish Frog, Lithobates areolatus circulosus, occurs in only 19 of its 75 counties. Because of their secretive nature, late winter-early spring breeding season, and current protected status by the Arkansas Game and Fish Commission, this species remains a rarity in most museum collections in the state. Moreover, only anecdotal information exits regarding any aspect of their natural history in Arkansas. In the present study, we chose to conduct a phalangeal skeletochronological investigation using museum specimens (n = 9) deposited in the herpetological collection housed in the Arkansas Center for Biodiversity Collections located at Arkansas State University. Our results were mostly similar to the age-body length distributions from southern Illinois. Our oldest males exhibited 4 lines of arrested growth (LAGs), and this estimated age matched well with the body sizes of 4-year-old males found in Illinois. Two of our 3-year-old males had slightly larger body sizes compared to the Illinois sample. Our oldest female was 5 years old. Her body size was comparable to values found for 5-year-old females in Illinois. Also, 5 years was the maximum age recorded for this species in our study as well as for the frog in Illinois. Nine years has been reported as the maximum lifespan for this species

Resistance Stability of the Secondary Tiller of \u27Caldwell\u27 Wheat After the Primary Culm Was Infested With Virulent Hessian Fly (Diptera: Cecidomyiidae) Larvae

Secondary tiller resistance of \u27Caldwell\u27 wheat, Triticum aestivum, with the H6 gene for larval resistance to Hessian fly, Mayetiola destructor, was maintained, after the primary culm had been previously infested with virulent larvae. Earlier studies showed that a primary culm infested initially with a virulent larva allowed subsequent normally avirulent larvae to survive on that cultivar; however, in our study the resistance of secondary tillers was mainained even though the primary culm was infested earlier with virulent Hessian fly larvae. This gene stability for resistance is important for optimizing wheat yield of those cultivars that possess genes resistant to the Hessian fly that are tillering and infested with different biotypes

Toe Tip Morphology in Six Species of Salamanders, genus Ambystoma (Caudata: Ambystomatidae) from Arkansas Using Scanning Electron Microscopy

The toe tip friction surface in six species of Ambystoma (A. annulatum, A.maculatum, A.opacum, A. talpoideum, A. texanum, and A. tigrinum) from Arkansas was examined using scanning electron microscopy. We found no sexual dimorphism in cell surface ultrastructure. Variation within and between species was considerable. The most active burrower, A. tigrinum, possessed the most disorganized cell surface, whereas the least active burrowers (A.annulatum, A.maculatum, and A. opacum) had morphologically similar and relatively smooth toe tips. In A. talpoideum and A. texanum, cell surfaces exhibited microprojections. Only these two species possessed mucous pores in close proximity to the friction surface. The microstructure of cell surfaces transcended species groups in Ambystoma and would not represent a reliable taxonomic tool

Mandibular Dentition in Six Species of Salamanders, genus Plethodon (Caudata: Plethontidae), from Arkansas Using Scanning Electron Microscopy

The mandibular (dentary) dentition of six species of Plethodon (P. caddoensis, P. dorsalis, P. fourchensis, P. glutinosus, P. ouachitae, and P. serratus) from Arkansas was studied using scanning electron microscopy. In all species, the mandibular teeth were bicuspid, and each tooth possessed a prominent labial cusp and a well-developed, inward-curving lingual cusp. All species showed similar tooth crown features, except P. caddoensis which exhibited a reduced tooth height and a reduced lingual cusp (only slightly larger than the labial cusp). We compared our data with other studies on premaxillary, maxillary, and palatal teeth in Plethodon and found overall similarities in tooth types. Tooth morphology does not appear to be an effective tool for taxonomic purposes in our Plethodon species because of the range of morphological variation in tooth structure