The oldest open clusters within 250 pc of the Sun, the Hyades and Praesepe, are important benchmarks for calibrating stellar properties such as rotation and magnetic activity. As they have the same age and roughly solar metallicity, these clusters serve as an ideal laboratory for testing the agreement between theoretical and empirical rotation-activity relations at ~650 Myr. The re-purposed Kepler mission, K2, has allowed me to measure rotation periods for dozens of Hyads and hundreds of Praesepe members, including the first periods measured for fully convective Hyads. These data have enabled new tests of models describing the evolution of stellar rotation; discrepancies with these models imply that we still do not fully understand how magnetic fields affect stellar spin-down. I show how we can compare the dependence of H-alpha and X-ray emission on rotation in order to test theories of magnetic field topology and stellar dynamos. These tests inform models of stellar wind-driven angular momentum loss and the age-rotation-activity relation. I also present rotation periods measured for 48 Hyads and 677 Praesepe members with K2, and discuss the impact of unresolved binaries on the study of rotational evolution.

The interstellar medium – the space between the stars in our Galaxy – is multiphase, turbulent, and magnetic. Magnetism in the interstellar medium is difficult to observe and to simulate, and the study of interstellar magnetic fields is riddled with open questions. In this Thesis we make progress in several important areas. We use analytic theory, simulations, and observations to advance our understanding of an important plasma instability, of the diffuse neutral medium, and of prospects for uncovering cosmic inflation. We take an unusual approach to the study of the magnetorotational instability, the mechanism thought to be the primary driver of turbulence and angular momentum transport in astrophysical accretion disks. We conduct a weakly nonlinear analysis of the instability in several important geometries, and derive an envelope equation that governs the evolution of the system on long length- and timescales. We show that the saturated state of the magnetorotational instability may itself be unstable on these large spatial and temporal scales, and we demonstrate that the character of these instabilities will depend on the geometry of the background magnetic field. We posit a possible new saturation mechanism for the magnetorotational instability in a local geometry, when a particular nonideal effect is considered. We derive new insights into the diffuse interstellar medium, where we present the discovery that thin, linear neutral hydrogen structures are ubiquitous in the cold neutral medium. We demonstrate that these linear features are extremely well aligned with the interstellar magnetic field, as traced by both starlight polarization and polarized dust emission. We discuss the implications of this discovery for cosmological studies. A major goal of modern cosmology is the detection of a particular signature in the polarized cosmic microwave background that would be direct evidence for inflation. This goal has thus far been thwarted by the polarized foreground emission from magnetically aligned interstellar dust grains. We demonstrate that the alignment of neutral hydrogen with the interstellar magnetic field can be used to produce higher-fidelity maps of the foreground polarization field, and we present and test a new Bayesian method for constructing improved foreground maps.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept of Physics. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / Ph.D.

Inserido no paradigma da transdisciplinaridade, o presente trabalho foi desenvolvido em etapas, com os seguintes objetivos: a) Construir um dispositivo com base de metal não magnético para ímãs permanentes, visando à geração de um Campo Magnético Estático (CME) ou de um Campo Magnético Compensado (CMC); b) Expor culturas de células mesenquimais a um CME e a um CMC, ou a nenhum campo (controle); c) Analisar a influência destes campos na viabilidade e proliferação celular e nos casos em que houve alteração em pelo menos um destes parâmetros, utilizar a análise proteômica como ferramenta para a compreensão dos mecanismos envolvidos. O dispositivo foi construído utilizando aço inoxidável, capaz de gerar dois tipos de Campos Magnéticos: Compensado (CMC) com intensidade de aproximadamente 0 mT e Estático (CME) com intensidade média de 165 mT. Estes campos foram aplicados a culturas de células mesenquimais de medula óssea de camundongos AJ (MSC/AJ), nos períodos de 0, 24, 48, 72 e 96 h (CMC) e 24 h (CME). Os efeitos sobre a proliferação e a viabilidade foram avaliados por método de contagem manual de células com marcação por azul de tripan. A análise proteômica foi realizada para os experimentos com CMC, com o objetivo de descrever as proteínas envolvidas nas alterações encontradas. A exposição ao CMC tendeu a reduzir a proliferação das células de medula óssea MSC/AJ em relação ao controle em 96 h, porém sem diferença significativa, o que poderia estar relacionado a proteínas que inibem a transcrição, como a Forkhead box protein P2 Foxp2. Este mesmo campo aumentou a viabilidade celular em relação ao baseline para todos os tempos experimentais, o que poderia estar relacionado a proteínas relacionadas à ligação ao Ca+2. Esses mecanismos, entretanto, precisam ser estudados mais profundamente para que possam ser comprovados ou não. Já a exposição ao CME levou a uma tendência à diminuição da proliferação e viabilidade celular em relação ao grupo controle, embora sem diferenças significativas, provavelmente por conta do tamanho amostral e tempo de avaliação (24 h). / Inserted in the transdisciplinarity paradigm, the present work was developed by steps with the following aims: a) To build a device of non-magnetic metal to hold permanent magnets for the generation of a Static Magnetic Field (SMF) or a Compensated Magnetic Field (CMF); b) To expose mesenchimal cells to the SMF and to CMF or to none of the fields (control); c) To analyze the influence of these fields on cell viability and cell proliferation and in the case where it occurred alteration in at least one of these parameters, to use proteomics as a tool for the comprehension of the involved mechanisms. The device was built in stainless steel, able to generate two kinds of Magnetic Fields: Compesated (CMF) with an intensity of nearly zero mT and Static (SMF) with a mean intensity of 165 mT. These fields were applied to bone marrow mesenchimal cell cultures from AJ mice (MSC/AJ), for 0, 24, 48, 72 and 96 h (CMF) and 24 h (SMF) periods. The effects on the proliferation and viability were assessed by tripan blue dying and manual counting of the cells. Proteomics was done for the experiments with CMF, aiming to describe the involved proteins on found alterations. The exposition to CMF tends to reduce the bone marrow cell proliferation of MSC/AJ in relation to control in 96 h, but with no significant difference, which may be related to proteins that inhibit the transcription, like Forkhead box protein P2 Foxp2. This very field raised the cell viability in relation to the baseline for all the experimental times that could be related to proteins connected to Ca2+ binding. However, these mechanisms need more experiments, so they can be confirmed or not. The exposition to the SMF tends to decrease both cell proliferation and viability in relation to the control group, although with no significant difference, probably because of the sample number and the exposition time (24h).

No description available.

In this thesis we study GaAs one dimensional hole systems with strong spin-orbit interaction effects. The primary focus is the Zeeman splitting of 1D subbands in the two orthogonal in-plane magnetic field directions. We study two types of 1D hole systems based on different (311)A grown heterostructures: a modulation doped GaAs/AlGaAs square quantum well and an undoped induced GaAs/AlGaAs triangular quantum well. The results from the modulation doped 1D wire show enhanced anisotropy of the effective Lande g-factor for the two in-plane field directions (parallel and perpendicular to the wire), compared to that in 2D hole systems. This enhancement is explained by the confinement induced reorientation of the total angular momentum ^ J from perpendicular to the 2D plane to in-plane and parallel to the wire. We use the intrinsic anisotropy of the in-plane g-factors to probe the 0:7 structure and the zero bias anomaly in 1D hole wires. We find that the behaviour of the 0:7 structure and the ZBA are correlated and depend strongly on the orientation of the in-plane field. This result proves the connection between the 0:7 and the ZBA and their relation to spin. We fabricate the first induced hole 1D wire with extremely stable gate characteristics and characterize this device. We also fabricate devices with two orthogonal induced hole wires on one chip, to study the interplay between the confinement, crystallographic anisotropy and spin-orbit coupling and their effect on the Zeeman splitting. We find that the ratios of the g-factors in the two orthogonal field directions for the two wires show opposite behaviour. We compare absolute values of the g-factors relative to the magnetic field direction. For B || [011] the g-factor is large for the wire along [011] and small for the wire along [233]. Whereas for B || [233], the g-factors are large irrespective of the wire direction. The former result can be explained by reorientation of ^ J along the wire, and the latter by an additional off-diagonal Zeeman term, which leads to the out-of-plane component of ^ J when B || [233], and as a result, to enhanced g-factors via increased exchange interactions.

"July 2003." / Bibliography: p. 203-211. / xxii, 211 p. : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates properties of magnetic fields in galaxy clusters via both statistical Faraday rotation measures and diffuse source polarimetry, and investigates the nature and generation mechanisms for diffuse radio emission in the ACO cluster A3667. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 2003

Based on part of a Ph.D. thesis in the Dept. of Physics, 1967. / Bibliography: p. 29.

Donald M. Dix. / "Submitted to the Department of Mechanical Engineering, M.I.T., August 25, 1961, in partial fulfillment of the requirements for the degree of Doctor of Science." "July 9, 1962." / Bibliography: p. 127-128. / Army Signal Corps Contract DA 36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000. Army Signal Corps Contract No. DA-SIG-36-039-61-G14. National Science Foundation Grant G-9330.

L.A. Harris. / "This report is identical with a doctoral thesis in the Department of Electrical Engineering, M.I.T." "August 29, 1950." / Bibliography: p. 77. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B Dept. of the Army Project No. 3-99-10-022