Hyperbolic groups acting improperly

In this paper we study hyperbolic groups acting on CAT(0) cube complexes. The first main result (Theorem A) is a structural result about the Sageev construction, in which we relate quasi-convexity of hyperplane stabilizers with quasi-convexity of cell stabilizers. The second main result (Theorem D) generalizes both Agol's theorem on cubulated hyperbolic groups and Wise's Quasi-convex Hierarchy Theorem.Comment: 52pp. In v3, some unnecessary assumptions are dropped from some technical results, especially in Section 5 and Corollary 6.5. The main results are unchanged, but the improved technical results are expected to be useful in future work. Several other small improvements to the exposition have been mad

Precise atmospheric oxygen measurements with a paramagnetic oxygen analyzer

A methodology has been developed for making continuous, high-precision measurements of atmospheric oxygen concentrations by modifying a commercially available paramagnetic oxygen analyzer. Incorporating several design improvements, an effective precision of 0.2 ppm O-2 from repeated measurements over a 1-hour interval was achieved. This is sufficient to detect background changes in atmospheric O-2 to a level that constrains various aspects of the global carbon cycle. The analyzer was used to measure atmospheric O-2 in a semicontinuous fashion from air sampled from the end of Scripps Pier, La Jolla, California, and data from a 1-week period in August 1996 are shown. The data exhibit strongly anticorrelated changes in O-2 and CO2 caused by local or regional combustion of fossil fuels. During periods of steady background CO2 concentrations, however, we see additional variability in O-2 concentrations, clearly not due to local combustion and presumably due to oceanic sources or sinks of O-2. This variability suggests that in contrast to CO2, higher O-2 sampling rates, such as those provided by continuous measurement programs, may be necessary to define an atmospheric O-2 background and thus aid in validating and interpreting other O-2 data from flask sampling programs. Our results have also demonstrated that this paramagnetic analyzer and gas handling design is well suited for making continuous measurements of atmospheric O-2 and is suitable for placement at remote background air monitoring sites

The effect of television on the leisure time activities of sixth grade children in Medford, Massachusetts.

Thesis (Ed.M.)--Boston Universit

The vertebral endplate: its structure and function

The cause of degenerative changes to the intervertebral disc that can produce back pain are still indefinable. One newer avenue of investigation includes the analysis of vertebral endplates, which lie between vertebral bodies and their adjacent discs. This thesis investigates the structure and function of the vertebral endplate. Multiphoton microscopy was employed as the main imaging method as it has previously shown its ability to differentiate between tissue in osteochondral regions, and its ability to image label free, thick samples reduces sample processing. Animal endplate models were utilised as a healthy model, alongside degenerate human samples from surgery. This thesis aimed to investigate the structure of the vertebral endplate as well as its function. The structure of the endplate was confirmed to contain three distinct regions; the bony endplate, mineralised cartilage and non-mineralised cartilage. The thickness of the cartilage endplate was shown to be thicker in the cranial endplate (p = 0.008), and the mineralised region thicker than the non-mineralised (p = 0.005). Additionally, this study confirmed how anchorage of the intervertebral disc is achieved. Microstructurally, annular bundles penetrate through both the mineralised and non-mineralised regions of the cartilage endplate. Within these layers, the bundles sub-divide in a branched structure as an integration mechanism. Energy disperse spectroscopy showed a higher calcium to phosphate ratio in young adult ovine spines (p<0.05) compared with mature ovine spines, and age differences in the structure of the bony endplate were also noted. Additionally, Raman microscopy on bovine sections showed higher mineralisation in the endplate under the nucleus than annulus using the mineral to matrix ratio (peak ratios of 3.15 and 2.35 respectively). This work highlights the specificity of each of the tissues in the endplate, and how they change based on their location (nucleus/annulus, caudal/cranial) and with age. Degenerative human samples showed higher two photon fluorescence (TPF) signal than the bovine model, and also showed a highly aligned collagen region, parallel to the tidemark which agrees with previous literature. An important function of the endplate is its role as a nutritional pathway for the diffusion of solutes through the endplate and the convective transport of water. Vessels within the endplate were imaged using multiphoton microscopy. They were measured to be as small as 5 ¹m in diameter and within close proximity to the disc (< 70 μm), though never crossing the tide mark. Additionally, the use of a fluorescent tracer confirmed the diffusion from the disc into vessels in the endplate. Through the use of real-time imaging of a fluorescent tracer diffusing from the disc through the endplate, this study showed the tidemark as a barrier, initially holding the tracer up. The study additionally confirmed the presence of small pores in the mineralised cartilage post tidemark. Further relating to the function of the endplate, a series of compressive loading experiments were carried out in order to provide novel insight into the micromechanics of the regions of the endplate. The disc displayed the highest amount of micro-strain with measurements reaching as high as - 40 %, though initial strain appears primarily due to fibre realignment. This work highlights the importance of the cartilage components of the endplate in the micromechanics of the disc. Previously, the vertebral endplate has been underappreciated within the literature and clinical understanding of its role. This works highlights the intimacy between the intervertebral disc and vertebral endplate reinforcing the necessity for further investigation of this unique region.This PhD thesis was fully funded by Orthopaedic Research UK (ORUK, ref: 524) for the duration of three years. ORUK exist to advance understanding of orthopaedic science. They do this by funding important research, publishing that research and collaborating with multidisciplinary centres of excellence

Restoration of eucalypt grassy woodland: effects of experimental interventions on ground-layer vegetation

We report on the effects of broad-scale restoration treatments on the ground layer of eucalypt grassy woodland in south-eastern Australia. The experiment was conducted in two conservation reserves from which livestock grazing had previously been removed. Changes in biomass, species diversity, ground-cover attributes and life-form were analysed over a 4-year period in relation to the following experimental interventions: (1) reduced kangaroo density, (2) addition of coarse woody debris and (3) fire (a single burn). Reducing kangaroo density doubled total biomass in one reserve, but no effects on exotic biomass, species counts or ground cover attributes were observed. Coarse woody debris also promoted biomass, particularly exotic annual forbs, as well as plant diversity in one of the reserves. The single burn reduced biomass, but changed little else. Overall, we found the main driver of change to be the favourable growth seasons that had followed a period of drought. This resulted in biomass increasing by 67%, (mostly owing to the growth of perennial native grasses), whereas overall native species counts increased by 18%, and exotic species declined by 20% over the 4-year observation period. Strategic management of grazing pressure, use of fire where biomass has accumulated and placement of coarse woody debris in areas of persistent erosion will contribute to improvements in soil and vegetation condition, and gains in biodiversity, in the future.Funding and in-kind logistic support for this project was provided by the ACT Government as part of an Australian Research Council Linkage Grant (LP0561817; LP110100126). Drafts of the manuscript were read by Saul Cunningham and Ben Macdonald

(η5-Cyclopentadienyl)(2-naphthylethynyl)(triphenylphosphine-κP)nickel(II)

The title compound, [Ni(C₅H₅)(C₁₂H₇)(C₁₈H₁₅P)], does not contain strong hydrogen-bond donors or acceptors and the primary interactions are limited to those of the weak C-H...π(arene) type and mainly involving the arene rings