Determination of the local group gravitational acceleration using all-sky red-shift surveys

A consolidation of the Local Group velocity as inferred from measurements of the Cosmic Microwave Background, and that inferred from gravitational arguments, is of major importance to modern cosmology. Agreement between the two lends strength to modern ideas of structure formation, and can in principle, be used to estimate the matter density parameter, Ωm. Measurement of the change of the Local Group velocity with respect to increasingly distant objects can also be used as a probe of the mass of nearby structures.Modern methods of velocity determination employ information about the local matter density to construct an estimate of the local gravitational field. The most effective current method of probing the local matter density is by using all-sky galaxy redshift surveys to map the 3-dimensional distribution of nearby galaxies, and then use these galaxies to infer the distribution of matter throughout the local Universe.However, any practical determination of the Local Group velocity is fraught with errors. Among these are: distortion effects on the data introduced by using an galaxy’s redshift as a measure of its distance; sampling effects caused by the approximate representation of a continuous mass distribution by a sample of discrete galaxies; intrinsic uncertainty caused by only sampling a nearby finite subset of the (effectively infinite) mass distribution; and the uncertainty in the determination of a correction for non-linear effects caused by nearby massive structures.This thesis aims to give a definitive measure of the velocity of the Local Group from gravitational arguments while attempting to minimise errors in the calculation. Iterative techniques are used to converge on a self consistent solution to the Local Group velocity and surrounding spatial galaxy distribution. To minimise intrinsic survey error, a new dataset— the Behind The Plane (B T P ) galaxy redshift survey has been completed and analysed. The BTP is the low-latitude extension to the previously completed Point Source Catalogue redshift (PSCz) survey of galaxies. Near-infrared and radio techniques were used to identify and measure optically obscured galaxies that were excluded from the PSCz, increasing the overall sky coverage from 84% to 93%. This high degree of sky coverage makes the PSCz + BTP the best available dataset for dynamical studies of the local Universe. The reduction of the gap in sky coverage significantly reduces uncertainty in dynamical predictions, especially as the missing strip behind the Milky Way is known to include the Great Attractor.The major result of this work is the possible discovery o f an unexpectedly large mass concentration beyond the Great Attractor, at an approximate distance of cz = 20,000kms-1 in the direction l = 300,b = 0. The misalignment between the inferred Local Group velocity vector and the CMB temperature dipole significantly increases, and β parameter estimates yield inconsistency with many other current and reliable estimates in the literature, if this structure is excluded. Upon the inclusion of this concentration, estimates for the Local Group velocity center upon I = 245, b = 30, and yield a value of βIRAS = 0-65 ± 0.01. Directional misalignment is consistent to within 2-σ, but is robust across significant variation in both the data and calculation method applied

Stochastic Dominance Analysis of iShares

Country indices as represented by iShares exhibit non-normal return distributions with both skewness and kurtosis. Davidson and Duclos (2000) and Memmel (2003) provide procedures for determining the statistical significance of stochastic dominance measures and the Sharpe Ratio, respectively. This study uses these refinements to compare the performance of 18 country market indices. The iShares are indistinguishable when using the Sharpe Ratio as no significant differences are found. In contrast, stochastic dominance procedures identify dominant iShares. Although the results vary over time, stochastic dominance appears to be both more robust and discriminating than the CAPM in the ranking of the iShares.Stochastic dominance; Sharpe ratio; skewness; country index funds

Divergence of opinion and risk : an empirical analysis of the Ex Ante beliefs of institutional investors

Bibliography: p. [24-25

Characterization of temperature‐dependent hemin uptake receptors HupA and HvtA in Vibrio vulnificus

The Gram‐negative pathogen Vibrio vulnificus produces several iron‐sequestration systems including a hemin uptake system in response to iron limitation as a means to acquire this essential element. Strains of this organism are capable of causing serious septicemia in humans and eels, where hemin is abundant and an advanta‐ geous source of iron. Vibrio vulnificus hemin uptake systems consist of HupA, a well studied outer membrane protein, and a recently identified HvtA protein receptor. In this study, we confirmed that the expression of the hvtA gene is iron‐regulated in a fur‐dependent manner. When analyzed for virulence in a hemin‐overloaded murine model system, the hupA gene was more important for establishing infection than the hvtA gene. Transcriptional profiling of these genes using strains of two different biotypes, biotype 1 (human pathogen) and biotype 2 (eel pathogen), showed that the expression of the two receptors was also regulated in response to temperature. The expression of hupA was highly induced in elevated temperatures in the human pathogenic strain when tested in iron‐depleted conditions. Conversely, hvtA expres‐ sion was induced significantly in the eel pathogenic strain at a lower temperature, a condition where the hupA locus was relatively repressed. Our results indicate that although both hupA and hvtA are involved for optimal hemin uptake in V. vulnificus, their expression is dually regulated by the environmental cues of iron concentration and temperature. Together, these data suggest that the virulence genes hupA and hvtA are tightly regulated and strictly induced during iron limitation combined with the physiological temperature of the host organism

Eleven Case Studies of Failures in Geotechnical Engineering, Engineering Geology, and Geophysics: How They Could Have Been Avoided

When a failure occurs, geotechnical engineers, engineering geologists, and geophysicists assign its cause to an event that immediately precedes the failure, such as an earthquake, heavy rainfall, flood, or other natural event. Assigning the failure to the immediate event is misplaced; the metastasis occurred because marginally stable conditions were allowed to exist through substandard investigations by the technical personnel, improper design, and inadequate review by the permitting agency. The fundamental cause of the failure is human error and is manifested in one or more of six categories. (1) Before the investigation, during discussions with the client. (2) During the investigation, by collecting inadequate, incomplete, or incorrect data; altering the field or test data to make them more favorable. (3) After the investigation, when the inadequate data and invalid conclusions are incorporated in the final report. (4) During the review process, when the reviewers accept the substandard report. (5) After the agency approves the substandard report. (6) After the agency grants the permit that allows construction to begin and after the work begins. Eleven case studies of failures are described including landslides, dam failures, floods, and ground subsidence. Each case study identifies (1) the immediate event, (2) the fundamental cause, (3) how the inadequacies and deficiencies in one or more of the six categories contributed to the failure, and (4) how the failure could have been prevented. Each of these failures resulted in civil or criminal court action. Depending on the facts in each case, penalties were imposed on the engineer, geologist, or geophysicist

Physics-, social-, and capability- based reasoning for robotic manipulation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 124-128).Robots that can function in human-centric domains have the potential to help humans with the chores of everyday life. Moreover, dexterous robots with the ability to reason about the maneuvers they execute for manipulation tasks can function more autonomously and intelligently. This thesis outlines the development of a reasoning architecture that uses physics-, social-, and agent capability-based knowledge to generate manipulation strategies that a dexterous robot can implement in the physical world. The reasoning system learns object affordances through a combination of observations from human interactions, explicit rules and constraints imposed on the system, and hardcoded physics-based logic. Observations from humans performing manipulation tasks are also used to develop a unique manipulation repertoire suitable for the robot. The system then uses Bayesian Networks to probabilistically determine the best manipulation strategies for the robot to execute on new objects. The robot leverages this knowledge during experimental trials where manipulation strategies suggested by the reasoning architecture are shown to perform well in new manipulation environments.by Kenton J. Williams.S.M