Effects of California migration

California ; Emigration and immigration ; West (U.S.) ; Federal Reserve District, 12th

Housing price cycles and prepayment rates of U.S. mortgage pools.

Empirical mortgage prepayment models generally have trouble explaining differences in mortgage prepayment speeds among pools with similar interest rates on the underlying mortgages. In this paper, we model some of the sources of termination heterogeneity across mortgage pools, particularly the role of regional variations in housing prices in generating atypical prepayment speeds. Using a sample of Freddie Mac mortgage pools from 1991-1998, we find evidence that differences in house price dynamics across regions are an important source of between-pool heterogeneity. This finding is then shown to be robust to alternative ways of parameterizing pool heterogeneity in mortgage termination models.Real property ; Mortgages

Association of circulating levels of MMP-8 with mortality from respiratory disease in patients with rheumatoid arthritis.

Matrix metalloproteinases (MMPs) are implicated in the destruction of the joint and have been shown to be strongly associated with inflammation in rheumatoid arthritis (RA). Circulating MMPs have also been associated with cardiovascular disease in the general population, and are predictive of cardiovascular mortality. The purpose of the present study was to determine whether circulating levels of MMPs are predictive of mortality in RA

A Time Domain Approach to Power Integrity for Printed Circuit Boards

Power integrity is becoming increasingly relevant due to increases in device functionality and switching speeds along with reduced operating voltage. Large current spikes at the device terminals result in electromagnetic disturbances which can establish resonant patterns affecting the operation of the whole system. These effects have been examined using a finite difference time domain approach to solve Maxwell's equations for the PCB power and ground plane configuration. The simulation domain is terminated with a uniaxial perfectly matched layer to prevent unwanted reflections. This approach calculates the field values as a function of position and time and allows the evolution of the field to be visualized. The propagation of a pulse over the ground plane was observed demonstrating the establishment of a complex interference pattern between source and reflected wave fronts and then between multiply reflected wave fronts. This interference which affects the whole ground plane area could adversely affect the operation of any device on the board. These resonant waves persist for a significant time after the initial pulse. Examining the FFT of the ground plane electric field response showed numerous resonant peaks at frequencies consistent with the expected values assuming the PCB can be modelled as a resonant cavity with two electric and four magnetic field boundaries.Comment: Presented at The University of Bolton Research and Innovation Conference, Bolton, UK. 16th September, 201

Thermally activated conductance of a silicon inversion layer by electrons excited above the mobility edge

The thermally activated conductivity sigma of an n-type inversion layer on a (100) oriented silicon surface and its derivative d sigma /dT were measured in the temperature range 1.4K-4.2K. Above T approximately=2.5K both the temperature dependence of (T/ sigma ) (d sigma /dT) and the relation between this quantity and sigma cannot be reconciled with a universal pre-exponential factor, i.e. the minimum metallic conductivity, but are shown to be satisfactorily described by a prefactor which is proportional to the temperature. The experimental results presented are consistent with activation of the number of mobile electrons above a mobility edge in the lowest sub-band, and indicate a mobility which is independent of both temperature and electron density

STUDIES ON THE STRUCTURE AND FUNCTION OF THE TELEOST PSEUDOBRANCH

Four main types of pseudobranch were distinguished on the basis of their epithelial covering. The terms 'free', ‘semi-free’, 'covered' and 'buried' are used to describe these types. All pseudobranchs possess specific ‘pseudobranch type’ cells, characterised by an orderly arrangement of tubules around closely packed mitochondria. They also contain vacuoles which may play a role in osmoreception by causing changes in the size and shape of the cells. Another specialised cell type, similar to the gill 'chloride' cell was found in 'free' and 'semi-free' pseudobranchs of salt water fish. They are associated with smaller 'accessory' cells from which they are separated by 'leaky' junctions which may provide a structural basis for the proposed ion secretory nature of 'chloride type' cells. Ultrastructural changes in 'chloride type' and 'pseudobranch type' cells were noted under osmotic stress but the cells still remained distinguishable from each other, giving no reason to suggest that they were different forms of the same cell. The two other main cell types found in the pseudobranch epithelium were mucous and rodlet cells. The epithelial surface possesses numerous microridges which are thought to aid anchorage of mucous. The vascular system of the pseudobranch shows close similarities to that of the gill and contains a well developed arterio-venous pathway as well as an arterio-arterial system. Arterio-venous anastomoses were found between the efferent filament artery and the central venous sinus of the bass pseudobranch. The pseudobranch innervation is extremely complex. Morphological and denervation studies suggest an autonomic innervation and physiological evidence indicates the presence of at least two and possibly four types of receptor. The results of this study indicate that the pseudobranch has a number of inter-related functions associated with the development of specific cell types and a complex innervation linked directly or indirectly to the vascular system.THE MARINE BIOLOGICAL ASSOCIATIO

Morphological development of Aspergillus niger in submerged citric acid fermentation as a function of the spore inoculum level. Application of neural network and cluster analysis for characterization of mycelial morphology

BACKGROUND: Although the citric acid fermentation by Aspergillus niger is one of the most important industrial microbial processes and various aspects of the fermentation appear in a very large number of publications since the 1950s, the effect of the spore inoculum level on fungal morphology is a rather neglected area. The aim of the presented investigations was to quantify the effects of changing spore inoculum level on the resulting mycelial morphology and to investigate the physiology that underlines the phenomena. Batch fermentations were carried out in a stirred tank bioreactor, which were inoculated directly with spores in concentrations ranging from 10(4 )to 10(9 )spores per ml. Morphological features, evaluated by digital image analysis, were classified using an artificial neural network (ANN), which considered four main object types: globular and elongated pellets, clumps and free mycelial trees. The significance of the particular morphological features and their combination was determined by cluster analysis. RESULTS: Cell volume fraction analysis for the various inoculum levels tested revealed that by rising the spore inoculum level from 10(4 )to 10(9 )spores per ml, a clear transition from pelleted to dispersed forms occurs. Glucosamine formation and release by the mycelium appears to be related to spore inoculum level. Maximum concentrations detected in fermentations inoculated with 10(4 )and 10(5 )spores/ml, where pellets predominated. At much higher inoculum levels (10(8), 10(9 )spores/ml), lower dissolved oxygen levels during the early fermentation phase were associated with slower ammonium ions uptakes and significantly lower glucosamine concentrations while the mycelium developed in dispersed morphologies. A big increase in the main and total hyphal lengths and branching frequency was observed in mycelial trees as inoculum levels rise from 10(4 )to 10(9 )spores/ml, while in aggregated forms particle sizes and their compactness decreased. CONCLUSION: The methods used in this study, allowed for the detailed quantification of the transition between the two extreme morphological forms. The impact of spore inoculum level on the detailed characteristics of the particular morphological forms produced was high. Control of mycelial morphology is often regarded as a prerequisite to ensure increased productivities in industrial applications. The research described here demonstrates that adjusting the spore inoculum level controls effectively mycelial morphology

Premature germination of resting spores as a means of Protecting brassica crops from Plasmodiophora brassicae Wor., (clubroot)

Premature germination of resting spores as a means of protecting brassica crops from Plasmodiphora brassicae Wor., (Clubroot). Crop Protection. Clubroot disease causes substantial yield and quality losses in broadacre oil seed and intensive vegetable brassica crops worldwide. The causal microbe Plasmodiophora brassicae Wor., perennates as soil-borne dormant resting spores. Their germination is triggered by exudates from host roots. A valuable addition to sustainable integrated control strategies could be developed by identifying and synthesising the molecules responsible for stimulating resting spore germination. This paper reports experiments in which stimulatory exudates were collected from brassica roots following exposure to infective stages of P. brassicae. Analyses identified a germination signalling molecule of circa 1 kDa formed of glucose sub-units. Mass spectral analyses showed this to be a complex hexasaccharide carbohydrate with structural similarities to the components of plant cell walls. This is the first report of a host generated hexasaccharide which is capable of stimulating the germination of resting spores of P. brassicae. The implications for environmentally benign control of clubroot are discussed briefly

On the electrical and structural properties of boron delta layers in silicon

This thesis describes the first successful growth of boron δ layers using silicon MBE. SIMS has been used to demonstrate that the layer widths are ∽2nm as has been confirmed by TEM. This is probably an overestimate, an average value of (0.3+-0.5)nm being obtained from XRD, suggesting that these are the thinnest 6 layers produced to date. Hall and XRD measurements indicate that the boron dopant is fully activated up to sheet coverages of 1/2 monolayer, i. e. ∽3.5x10^14cm-2. The CV profile obtained for a B δ layer of sheet density 2.5x10^12cm-2 has FWHM ∽3nm, a result which is shown to be consisitent with δ doping in the light of recent theoretical work. Resistivity, magnetoresistance and the Hall effect have been measured at temperatures down to 0.3K using magnetic fields of up to 12T on samples of sheet density in the range 4x10^12cm-2 to 8x10^13cm-2. 2D weak localisation and associated electron-electron interaction effects have been observed in samples of sheet density above 1.8x10^13cm-2 with evidence of spin-orbit scattering. These samples are shown to undergo a "metal-insulator" transition in high magnetic fields with variable range hopping at 12T. Samples of sheet density ≤ 1x10^13cm-2, show activated transport from which it is concluded that the critical acceptor separation for the metal-insulator transition in this system is significantly less than the value found in bulk, uniformly doped, Si:B. It is suggested that this may be due to the splitting of the valence band degeneracy due to quantum confinement