Spin currents and ferromagnetic resonance in magnetic thin films

2017 Summer.Includes bibliographical references.Spin currents represent a new and exciting phenomenon. There is both a wealth of new physics to be discovered and understood, and many appealing devices which may result from this area of research. To fully realize the potential of this discipline it is necessary to develop new methods for realizing spin currents and explore new materials which may be suitable for spin current applications. Spin currents are an inherently dynamic phenomenon involving the transfer of angular momentum within and between different thin films. In order to understand and optimize such devices the dynamics of magnetization must be determined. This dissertation reports on novel approaches for spin current generation utilizing the magnetic insulators yttrium iron garnet (YIG) and M-type barium hexagonal ferrite (BaM). First, the light-induced spin Seebeck effect is reported for the first time in YIG. Additionally, the first measurement of the spin Seebeck effect without an external magnetic field is demonstrated. To accomplish this the self-biased BaM thin films are utilized. Second, a new method for the generation of spin currents is presented: the photo-spin-voltaic effect. In this new phenomenon, a spin current may be generated by photons in a non-magnetic metal that is in close proximity to a magnetic insulator. On exposure to light, there occurs a light induced, spin-dependent excitation of electrons in a few platinum layers near the metal/magnetic insulator interface. This excitation gives rise to a pure spin current which flows in the metal. This new effect is explored in detail and extensive measurements are carried out to confirm the photonic origin of the photo-spin-voltaic effect and exclude competing effects. In addition to the spin current measurements, magnetization dynamics were probed in thin films using ferromagnetic resonance (FMR). In order to determine the optimal material configuration for magnetic recording write heads, FMR measurements were used to perform damping studies on a set of FeCo samples with different numbers of lamination layers. The use of lamination layers has the potential to tune the damping in such films, while leaving the other magnetic properties unchanged. Finally, the sensitivity of the vector network analyzer FMR technique was improved. The use of field modulation and lock-in detection, along with the background subtraction of a Mach-Zehnder microwave interferometer working as a notch filter, is able to increase the sensitivity and lower the background noise of this measurement technique. This improved system opens the possibility of probing previously difficult samples with extremely low signals

On the Links between Microwave and Solar Wavelength Interactions with Snow-Covered First-Year Sea Ice

Electromagnetic (EM) energy at solar and microwavelengths will interact with a snow-covered sea ice volume as a function of its geophysical properties. The seasonal metamorphosis of the snow cover modulates the relative distribution of the three main interaction mechanisms of EM energy: reflection, transmission, and absorption. We use a combination of modeling and observational data to illustrate how the total relative scattering cross section (Sigma 0) at microwavelengths can be used to estimate the surface climatological shortwave albedo and the transmitted Photosynthetically Active Radiation (PAR) for a snow-covered, first-year sea ice volume typical of the Canadian Arctic. Modeling results indicate that both 5.3 and 9.25 GHz frequencies, at HH polarization and incidence angles of 20 degrees, 30 degrees, and 40 degrees can be used to estimate the daily averaged integrated climatological albedo (Alpha). The models at 5.3 GHz, HH polarization, at 20 degree, 30 degree, and 40 degree incidence angles were equally precise in predications of Alpha. The models at 9.25 GHz were slightly less precise, particularly at the 40 degree incidence angle. The reduction in precision at the 40 degree incidence angle was attributed to the increased sensitivity at both 5.3 and 9.25 GHz to the snow surface scattering term (Sigma 0 ss) used in computation of the total relative scattering cross section (Sigma 0). Prediction of subsnow PAR was also possible using the same combination of microwave sensor variables utilized in prediction of Alpha, but because subice algal communities have evolved to be low light sensitive, the majority of the growth cycle occurs prior to significant changes in Sigma 0. A method of remote estimation of snow thickness is required to be scientifically useful. Observational data from the European ERS-1 SAR were used to confirm the appropriateness of the modeled relationships between Sigma 0, Alpha, and PAR. Over a time series spanning all conditions used in the modeled relationships, the same general patterns were observed between Sigma, Alpha, and PAR.Key words: microwave scattering models, snow, sea ice, climatological shortwave radiation, photosynthetically active radiation, microwave remote sensingL'énergie électromagnétique à des ondes ultra-courtes et solaires va interagir avec un volume de glace de mer couverte de neige, en fonction de ses propriétés géophysiques. La métamorphose saisonnière du couvert nival module la distribution relative des trois grands mécanismes d'interaction de l'énergie électromagnétique: réflexion, transmission et absorption. On utilise une combinaison de résultats de modélisation et de données d'observation pour illustrer la façon dont la coupe transversale totale de diffusion relative (sigma-zero) à des longueurs d'onde ultra-courtes peut être utilisée pour estimer l'albédo climatologique en ondes courtes de la surface et le rayonnement photosynthétiquement utilisable (RPU) pour un volume de glace de mer nouvelle couverte de neige, typique de l'Arctique canadien. Les résultats de modélisation indiquent qu'on peut utiliser les deux fréquences de 5,3 et 9,25 GHz, ayant une polarisation HH et des angles d'incidence de 20, 30 et 40° pour estimer la moyenne quotidienne de l'albédo climatologique intégré (alpha). Les modèles à 5,3 GHz, ayant une polarisation HH et des angles d'incidence de 20, 30 et 40° prédisaient alpha avec le même degré de précision. Les modèles à 9,25 GHz étaient légèrement moins précis, surtout en ce qui concerne l'angle d'incidence de 40°. La réduction de précision à l'angle d'incidence de 40° était attribuée à une augmentation de sensibilité, aux deux fréquences de 5,3 et 9,25 GHz, au terme de diffusion de la surface nivale (sigma-zero-ss) utilisé dans le calcul de la coupe transversale totale de diffusion relative (sigma-zero). Pour prédire le RPU sous la couche nivale, on a également pu utiliser la même combinaison de variables de capteurs d'ondes ultra-courtes que celle utilisée pour prédire alpha. Mais parce que les communautés d'algues vivant sous la glace ont développé un niveau de photosensibilité élevé, la plupart du cycle de croissance se produit avant que des changements importants n'aient lieu dans sigma-zero. Il faut développer une méthode d'estimation de l'épaisseur nivale par la télédétection pour que cette méthode soit utilisable du point de vue scientifique. On a utilisé des données d'observation prises au RALS dans le cadre du ERS-1 européen pour confirmer la pertinence des rapports de modélisation entre sigma-zero, alpha et le RPU. Dans une série chronologique couvrant toutes les conditions utilisées dans les rapports de modélisation, on a observé les mêmes grandes tendances entre sigma-zero, alpha et le RPU.Mots clés: modèles de diffusion d’hyperfréquences, neige, glace de mer, rayonnement climatologique de courtes longueurs d’onde, rayonnement photosynthétiquement utilisable, télédétection des ondes ultra-courte

Seismotectonics of the San Andreas Fault System Between Point Arena and Cape Mendocino in Northern California\u27 Implications for the Development and Evolution of a Young Transform

The northernmost and relatively youthful segment of the San Andreas fault system is situated within a 100+ km wide zone of northwest trending strike-slip faults that includes, from west to east, the San Andreas, Maacama, and Bartlett Springs faults. Although the San Andreas fault is the principal strike-slip fault in this system, it has been virtually aseismic since the 1906 earthquake. Moderate levels of seismicity locate to the east along the Maacama fault and, to a lesser extent, the Bartlett Springs fault at focal depths typical of other strike-slip faults within the San Andreas fault system in central California. North of the San Andreas fault system, within the Cape Mendocino area, earthquakes occur at depths of up to 40 km and primarily reflect internal deformation of the subducting Garda slab, and slip along the Mendocino Fracture Zone. Seismicity along the Maacama and Bartlett Springs faults is dominated by right-lateral to oblique-reverse slip along fault planes that dip 50 °-75 ° to the northeast. The northern extent of seismicity along these faults terminates near the surface projection of the southern edge of the Garda slab. The onset of seismicity along these faults may be related to the abrupt change in the elastic thickness of the North American plate as it enters the asthenaspheric window. The Maacama and Bartlett Springs faults are strike-parallel with active reverse faults within the forearc region of the Cascadia subductian zone. This preexisting structural fabric of northwest trending reverse faults in the forearc area appears to have strongly influenced the initial slip and complexity of these faults. Continuation of the moderately dipping Maacama fault to the southeast along the steeply dipping Healdsburg and Rodgers Creek fault zones and the near-vertical Hayward and Calaveras fault zones in the San Francisco Bay area suggests that these faults evolve toward a more vertical dip to minimize the shear stresses that tend to resist plate motion

The SIMMS Program: A Study of Change and Variability within the Marine Cryosphere

This paper describes the scientific context of an experimental program for an eight year study of change and variability within the marine cryosphere in the Canadian Arctic and summarizes the field program since its inception in 1990. The focus is on understanding the process linkages between the atmosphere, cryosphere and ocean at the sea ice interface and in establishing a method by which these processes can be modeled numerically. Remote sensing plays a significant role as a major source of temporally and spatially consistent data in this relatively inaccessible region. In this program, we combine in situ measurement of geophysical characteristics of the sea ice interface, electromagnetic radiation interactions with the interface, and numerical modeling of marine cryosphere processes operating across this interface. Our primary objective is to observe and simulate the mechanisms that may contribute to change and variability. We conclude by proposing a conceptual spatial signature of an icescape as the basis for integration of these processes and illustrate how remote sensing data can be used to identify these functional signatures.Key words: Canadian Arctic, marine cryosphere, remote sensing, atmosphere-cryosphere interactions, snow and sea iceCet article décrit le contexte scientifique d'un programme expérimental consistant en une étude portant sur une période de huit ans des changements et de la variabilité au sein de la cryosphère marine dans l'Arctique canadien, et il résume le programme de terrain depuis sa création en 1990. On se concentre sur la compréhension des liens entre les processus à l'oeuvre, à l'interface de la glace de mer, qui impliquent l'atmosphère, la cryosphère et l'océan, ainsi que sur l'élaboration d'une méthode permettant de faire une modélisation numérique de ces processus. La télédétection joue un rôle important comme source principale de données cohérentes sur les plans temporel et spatial provenant de cette région relativement inaccessible. Dans ce programme on combine les mesures in situ des caractéristiques géophysiques de l'interface de la glace de mer, les interactions du rayonnement électromagnétique avec l'interface et la modélisation numérique des processus de la cryosphère agissant à cette interface. Notre objectif premier est d'observer et de simuler les mécanismes qui peuvent contribuer au changement et à la variabilité. On conclut en proposant sur le plan conceptuel une signature spatiale d'un panorama glaciaire comme base d'intégration de ces processus, et on illustre la façon dont les données obtenues par la télédétection peuvent servir à identifier ces signatures fonctionnelles.Mots clés: Arctique canadien, cryosphère marine, télédétection, interactions atmosphère-cryosphère, neige et glace de me

Breast Cancer in the Personal Genomics Era

Breast cancer is a heterogeneous disease with a complex etiology that develops from different cellular lineages, progresses along multiple molecular pathways, and demonstrates wide variability in response to treatment. The “standard of care” approach to breast cancer treatment in which all patients receive similar interventions is rapidly being replaced by personalized medicine, based on molecular characteristics of individual patients. Both inherited and somatic genomic variation is providing useful information for customizing treatment regimens for breast cancer to maximize efficacy and minimize adverse side effects. In this article, we review (1) hereditary breast cancer and current use of inherited susceptibility genes in patient management; (2) the potential of newly-identified breast cancer-susceptibility variants for improving risk assessment; (3) advantages and disadvantages of direct-to-consumer testing; (4) molecular characterization of sporadic breast cancer through immunohistochemistry and gene expression profiling and opportunities for personalized prognostics; and (5) pharmacogenomic influences on the effectiveness of current breast cancer treatments. Molecular genomics has the potential to revolutionize clinical practice and improve the lives of women with breast cancer

The Effect of Porosity Density and Configuration in Composite Materials on the Ultrasonic Waveform

Current practice is to accept or reject composite parts based upon ultrasonic C-scan results. Normally, this is based only on ultrasonic attenuation data. However, attenuation data alone does not account for variations in porosity distribution or type, and ignores the fact that other variables can influence attenuation besides porosity. This work was directed at determining additional parameters which can be used to define the defect structure in a composite

Functional liver-image guided hepatic therapy (FLIGHT): A technique to maximize hepatic functional reserve

Introduction: Radiation planning approaches for liver radiation often do not consider the regional variation that can exist in liver function. This study dosimetrically compares functional liver image-guided hepatic therapy (FLIGHT) to standard stereotactic body radiation therapy (SBRT) plans. In the FLIGHT plans, functional data from hepatobiliary iminodiacetic acid (HIDA) single photon emission computed tomography (SPECT) scans serve as a road map to guide beam arrangement. While meeting the same target volume coverage, plans are optimized to reduce dose to high-functioning liver. Materials and Methods: The study included 10 patients with hepatocellular carcinoma (HCC) with baseline HIDA SPECT imaging. Standard SBRT plans which did not systematically incorporate these scans had previously been completed on all 10 plans. Retrospectively, FLIGHT plans were created based on the use of contours of relative liver function from the HIDA SPECT as avoidance structures. Resulting dose to each relative functional liver structure was examined and compared qualitatively and using Wilcoxin rank-sum tests. Target coverage, doses to organs at risk (OARs), conformity index (CI), and gradient index (GI) were also evaluated. Results: While maintaining the same target coverage, FLIGHT plans reduced the mean dose to the high functioning liver by a median of 3.0 Gy (range 0.7 to 4.6 Gy), which represented a 31.4% mean reduction compared to standard planning. FLIGHT plans reduced the volume of high functioning liver receiving 15 Gy by a mean of 59.3 cc (range 7 to 170 cc), for a mean reduction of 41.9%. The mean dose to areas of liver function defined by 25% to 100% and 50% to 100% maximum was reduced with FLIGHT from 10.5 Gy to 8.5 Gy and from 10.5 Gy to 7.5 Gy, respectively ( p < 0.005 for both comparisons). The FLIGHT plans’ mean CI and GI did not differ significantly from the standard plans’ ( p = 0.721 and 0.169, respectively). Conclusion: FLIGHT SBRT allows for field design and plan optimization individualized to a patient's baseline regional liver function to maximize hepatic functional reserve. This personalized approach is achieved without compromising target coverage or OAR sparing

Pulmonary Mucormycosis in Chronic Lymphocytic Leukemia and Neutropenia.

Pulmonary mucormycosis is a rare life-threatening fungal infection associated with high mortality. We present the case of a 61-year-old man with history of chronic lymphocytic leukemia who presented with fever and cough, eventually diagnosed with pulmonary mucormycosis after right lung video-assisted thoracoscopic surgery. The patient was successfully treated with amphotericin B and right lung pneumonectomy; however, he later died from left lung pneumonia

Thesis Statement

The work which I am presenting for my Masters Thesis represents a culmination of ideas which I feel are integral to an understanding of my art as a whole. Although I began the period of my masters study working in a direction of minimal concerns, I have moved toward more complex presentations of my work in order to satisfy my artistic needs. I use cast flexible resin because it allows me to demonstrate these theories and needs in a highly dynamic and comprehensive fashion. The major concern of my work deals with the usage of line. In the beginning, I dealt primarily with woven lines and patterns, as one might experience in a piece of cloth viewed under a microscope. Color, transparency, the multiplication of form, and the subtlety of three-dimensionality developed into primary ideas for my artistic expression. &nbsp;</p

Plant species richness, elevated CO 2 , and atmospheric nitrogen deposition alter soil microbial community composition and function

We determined soil microbial community composition and function in a field experiment in which plant communities of increasing species richness were exposed to factorial elevated CO 2 and nitrogen (N) deposition treatments. Because elevated CO 2 and N deposition increased plant productivity to a greater extent in more diverse plant assemblages, it is plausible that heterotrophic microbial communities would experience greater substrate availability, potentially increasing microbial activity, and accelerating soil carbon (C) and N cycling. We, therefore, hypothesized that the response of microbial communities to elevated CO 2 and N deposition is contingent on the species richness of plant communities. Microbial community composition was determined by phospholipid fatty acid analysis, and function was measured using the activity of key extracellular enzymes involved in litter decomposition. Higher plant species richness, as a main effect, fostered greater microbial biomass, cellulolytic and chitinolytic capacity, as well as the abundance of saprophytic and arbuscular mycorrhizal (AM) fungi. Moreover, the effect of plant species richness on microbial communities was significantly modified by elevated CO 2 and N deposition. For instance, microbial biomass and fungal abundance increased with greater species richness, but only under combinations of elevated CO 2 and ambient N, or ambient CO 2 and N deposition. Cellobiohydrolase activity increased with higher plant species richness, and this trend was amplified by elevated CO 2 . In most cases, the effect of plant species richness remained significant even after accounting for the influence of plant biomass. Taken together, our results demonstrate that plant species richness can directly regulate microbial activity and community composition, and that plant species richness is a significant determinant of microbial response to elevated CO 2 and N deposition. The strong positive effect of plant species richness on cellulolytic capacity and microbial biomass indicate that the rates of soil C cycling may decline with decreasing plant species richness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72693/1/j.1365-2486.2007.01313.x.pd