Geographic and racial variations in mortgage loan-to-value ratios

Includes bibliographical references

Three essays in regional growth, distribution, and resilience

2019 Summer.Includes bibliographical references.This work delves into two significant but less understood topics in regional labor economics. The first contribution is to growing literature examining the effects of business dynamism on regional resilience. Significant attention has, understandably, been paid to understanding why the impact of and recovery from the 2008 recession has varied across regions. Chapters 1 and 2 extend to the question of regional resilience a hypothesis that gross rates of local establishment openings, or "churn," may affect local economic performance over a business cycle. In the US, higher-churn areas are found to experience faster average employment growth over the decade spanning the recession, but with more cyclical volatility. Churn is not positively correlated with median household income growth or poverty reduction at a county level. A novel cross-country analysis reveals that in the UK, local authorities with higher churn prior to the recession did weather the financial crisis slightly better, although data limitations restrict the direct comparability between the US and UK cases. Chapter 3 turns to the growth of self-employment in the US, motivated by two observations: first, that growth in the self-employment share has been regionally heterogeneous; and second, that theory suggests workers in wage-and-salary occupations exert limited agency over their working hours. This paper investigates whether average local working hours influence subsequent changes in the county self-employment share. I find a U-shaped relationship between working hours and self-employment growth: counties with working hours furthest from the mean experienced the fastest growth in local self-employment share, adding a new wrinkle to the running debate over whether the "gig economy" is driven by opportunity or necessity

Dislocation processes accompanying the Portevin-Le Chatelier effect in Al–Mg alloys

Aluminum alloys have great potential to replace steels in automotive structures and closure applications. However, formability limitations continue to remain an obstacle in their widespread usage. Solute strengthening in AA5000 Al–Mg alloys can be exploited to increase ductility and strength simultaneously, but dynamic strain ageing and negative strain rate sensitivity in these alloys lead to Portevin-Le Chatelier (PLC) instability and cause premature failure. PLC instability is associated with the diffusion of Mg atoms to dislocations and dislocations moving away from diffusing Mg atoms, resulting in plastic strain occurring in bursts. Macroscopically, the PLC effect has been well characterized. The underlying dislocation structures and atomistic mechanisms responsible for dynamic strain ageing have not been well understood and is the subject of this study. In this investigation, AA5754 sheets have been strained in situ in the scanning electron microscope and the transmission electron microscope (TEM). Combined electron backscatter diffraction and electron dispersive X-ray spectroscopy analyses show high local Mg concentration regions to correlate well with high dislocation densities. In situ TEM straining data show that glissile dislocations contribute to both nucleation and dissolution of small Mg clusters and precipitates. Electron tomography data show the dynamic nature of the dislocation network of glissile and sessile dislocations. The implications of these observations on the mechanism governing the PLC effect in Al–Mg alloys and the current theories of dynamic strain ageing in Al–Mg alloys will be discussed

Sequential Adaptive Detection for In-Situ Transmission Electron Microscopy (TEM)

We develop new efficient online algorithms for detecting transient sparse signals in TEM video sequences, by adopting the recently developed framework for sequential detection jointly with online convex optimization [1]. We cast the problem as detecting an unknown sparse mean shift of Gaussian observations, and develop adaptive CUSUM and adaptive SSRS procedures, which are based on likelihood ratio statistics with post-change mean vector being online maximum likelihood estimators with $\ell_1$. We demonstrate the meritorious performance of our algorithms for TEM imaging using real data

Chemical and nuclear properties of Rutherfordium (Element 104)

The chemical-properties of rutherfordium (Rf) and its group 4 homologs were studied by sorption on glass support surfaces coated with cobalt(II)ferrocyanide and by solvent extraction with tributylphosphate (TBP) and triisooctylamine (TIOA). The surface studies showed that the hydrolysis trend in the group 4 elements and the pseudogroup 4 element, lb, decreases in the order Rf>Zr{approx}Hf>Th. This trend was attributed to relativistic effects which predicted that Rf would be more prone to having a coordination number of 6 than 8 in most aqueous solutions due to a destabilization of the 6d{sub 5/2} shell and a stabilization of the 7p{sub l/2} shell. This hydrolysis trend was confirmed in the TBP/HBr solvent extraction studies which showed that the extraction trend decreased in the order Zr>Hf>Rf?Ti for HBr, showing that Rf and Ti did not extract as well because they hydrolyzed more easily than Zr and Hf. The TIOA/HF solvent extraction studies showed that the extraction trend for the group 4 elements decreased in the order Ti>Zr{approx}Hf>Rf, in inverse order from the trend of ionic radii Rf>Zr{approx}Hf>Ti. An attempt was made to produce {sup 263}Rf (a) via the {sup 248}Cm({sup 22}Ne, {alpha}3n) reaction employing thenoyltrifluoroacetone (TTA) solvent extraction chemistry and (b) via the {sup 249}Bk({sup 18}O,4n) reaction employing the Automated Rapid Chemistry Apparatus (ARCA). In the TTA studies, 16 fissions were observed but were all attributed to {sup 256}Fm. No alpha events were observed in the Rf chemical fraction. A 0.2 nb upper limit production cross section for the {sup 248}Cm({sup 22}Ne, {alpha}3n){sup 263}Rf reaction was calculated assuming the 500-sec half-life reported previously by Czerwinski et al. [CZE92A]

Elastomeric actuator devices for magnetic resonance imaging

The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex