Constraining Dark Energy with X-ray Galaxy Clusters, Supernovae and the Cosmic Microwave Background

We present new constraints on the evolution of dark energy from an analysis of Cosmic Microwave Background, supernova and X-ray galaxy cluster data. Our analysis employs a minimum of priors and exploits the complementary nature of these data sets. We examine a series of dark energy models with up to three free parameters: the current dark energy equation of state w_0, the early time equation of state w_et and the scale factor at transition, a_t. From a combined analysis of all three data sets, assuming a constant equation of state and that the Universe is flat, we measure w_0=-1.05+0.10-0.12. Including w_et as a free parameter and allowing a_t to vary over the range 0.5<a_t<0.95 where the data sets have discriminating power, we measure w_0=-1.27+0.33-0.39 and w_et=-0.66+0.44-0.62. We find no significant evidence for evolution in the dark energy equation of state parameter with redshift. Marginal hints of evolution in the supernovae data become less significant when the cluster constraints are also included in the analysis. The complementary nature of the data sets leads to a tight constraint on the mean matter density, Omega_m and alleviates a number of other parameter degeneracies, including that between the scalar spectral index n_s, the physical baryon density Omega_bh^2 and the optical depth tau. This complementary nature also allows us to examine models in which we drop the prior on the curvature. For non-flat models with a constant equation of state, we measure w_0=-1.09+0.12-0.15 and Omega_de=0.70+-0.03. Our analysis includes spatial perturbations in the dark energy fluid, assuming a sound speed c_s^2 =1. For our most general dark energy model, not including such perturbations would lead to spurious constraints on w_et which would be tighter by approximately a factor two with the current data. (abridged)Comment: 11 pages, 13 figures, 2 tables. Accepted for publication in MNRAS. Two new figures added: Fig.9 shows the effects of including dark energy perturbations and Fig.10 compares X-ray cluster data with 2dF dat

Wind-tunnel tests of wide-chord teetering rotors with and without outboard flapping hinges

Wind tunnel tests of aeroelastically designed helicopter rotor models were conducted to obtain rotor aerodynamic performance and dynamic response data pertaining to two-bladed teetering rotors with a wider chord and lower hover tip speed than currently employed on production helicopters. The effects of a flapping hinge at 62 percent radius were also studied. Finally, the effects of changing tip mass on operating characteristics of the rotor with the outboard flapping hinge were examined. The models were tested at several shaft angles of attack for five advance ratios, 0.15, 0.25, 0.35, 0.40, and 0.45. For each combination of shaft angle and advance ratio, the rotor lift was varied over a wide range to include simulated maneuver conditions. At each test condition, rotor aerodynamic performance and dynamic response data were obtained. From these tests, it was found that wide-chord rotors may be subject to large control forces. An outboard flapping hinge may be used to reduce beamwise bending moments over a significant part of the blade radius without significantly affecting the chordwise bending moments

An improved computational procedure for determining helicopter rotor blade natural modes

An existing computer program, used for predicting the natural frequencies and mode shapes of helicopter rotor blades, was refined to improve program accuracy and versatility. The program is based on the Holzer-Myklestad approach adapted for rotating beams. Coupled vertical (out-of-plane), horizontal (in-plane), and torsional mode characteristics were determined for a variety of hub and blade configurations. The resulting program is documented by presenting the recursion equations and techniques for determining natural frequencies and mode shapes, input data requirements, and descriptions of various program outputs. The accuracy of the program is demonstrated by comparing computed results with exact solutions to classical problems and experimental data

Bronze Age tin-bronze metalwork assemblages in Kent: Composition, distribution and context

The main objectives of this thesis are to analyse and discuss Bronze Age tin-bronze assemblages in Kent, the study area, with focus on their composition, distribution and context. The purpose of this thesis is largely in response to Professor Richard Bradleys following statement; ‘All too often, studies of such deposits have been concerned with content rather than context. This is a tradition that can be traced at least as far back as the work of Sir John Evans (1881). Since so little is known about the circumstance in which this material was deposited, it is perhaps a moot point whether such chronologies can be entirely reliable, but in the present account they are followed for want of anything better.’ (Bradley, 1998, 13) The corpus of data comprises 66 assemblages identified in the subject area, given in Chapter 3 in the form of Datasheets and in the Appendices, in the form of graphs, a Compendium of Assemblages and maps. Comparisons are also made in relation to distribution alongside Bronze Age settlement, monuments and topographical data. The thesis includes Methodology for collation of the corpus of research, followed by Distribution, Analysis, Assemblages in Retrospect and Current Thinking, Discussion and a Conclusion. The Discussion focuses on context of assemblages and metalworking from the subject area and the Bronze Age in northern Europe. The Conclusion draws largely on the Analysis and data compiled from the Appendices, which have provided some fascinating and unexpected results that will hopefully provide further impetus for academic discussion and deliberation. The thesis also recommends some further areas of research that would be of great benefit, particularly in the realm of non-destructive metallurgical analysis

Classification and management of anaplastic gliomas

Purpose of review: To summarize findings, discuss problems and define new questions from the past phase III trials in anaplastic gliomas. Recent findings: The current standard of care for first-line treatment in anaplastic gliomas is radiotherapy or chemotherapy. The next steps are to define the role and optimal sequencing of combined modality treatment focusing on radiotherapy and temozolomide and to develop trials with novel targeted treatments. The feature of necrosis in oligodendroglial tumors needs to be further studied, and molecular prognosticators will take more room. These include O6-methylguanylmethyltransferase promoter methylation, isocitrate dehydrogenase mutations and epidermal growth factor receptor amplification. Further, the notion that all anaplastic oligodendroglial tumors with or without a relevant astrocytic component fall into the same prognostic category and the obvious difficulties to type and to grade anaplastic gliomas pose an enormous burden on local diagnosis. The current and upcoming trials including the European Organization for Research and Treatment of Cancer 26053/22054 trial aim at solving some of these issues with an initial central pathology review. Summary: Anaplastic gliomas are an important group of brain tumors to develop future molecularly targeted therapies and should therefore be in the main focus of academic and industrial drug development, which aims at efficacy and avoiding long-term side effects

Experimental investigation of effects of blade tip geometry on loads and performance for an articulated rotor system

Wind-tunnel tests of an aeroelastically designed helicopter rotor model were carried out to determine the effects on dynamic response and aerodynamic performance of varying the design of the outboard 8 percent of the blade lengths. Four different blade tip geometries or shapes having different amounts of planform sweep, thickness and chordwise taper, and anhedral angle were studied. Each configuration was tested at several shaft angles of attack for advance ratios of 0.20, 0.30, 0.35, and 0.40. For each combination of shaft angle and advance ratio, rotor lift was varied over a wide range to include high lift conditions

Correlating measured and predicted inplane stability characteristics for an advanced bearingless rotor

The experimental data were obtained from hover tests for a scaled model of an advanced bearingless main rotor. Both isolated rotor and ground resonance conditions were tested. Test parameters included blade built-in cone and sweep angles, rotor inplane structural damping, pitch link location and fuselage structural damping. Analytical results for the conditions tested were obtained using current Bell Helicopter analyses. In addition, variations in the analytical models were made to assess their impact on the correlation between computed and measured results. Results are presented in tabular and graphical form