Frequency and time profiles of metric wave isolated Type I solar noise storm bursts at high spectral and temporal resolution

Type I noise storms constitute a sizeable faction of the active-Sun radio emission component. Observations of isolated instances of such bursts, in the swept-frequency-mode at metric wavelengths, have remained sparse, with several unfilled regions in the frequency coverage. Dynamic spectra of the burst radiation, in the 30 - 130 MHz band, obtained from the recently commissioned digital High Resolution Spectrograph (HRS) at the Gauribidanur Radio Observatory, on account of the superior frequency and time resolution, have unravelled in explicit detail the temporal and spectral profiles of isolated bursts. Apart from presenting details on their fundamental emission features, the time and frequency profile symmetry, with reference to custom-specific Gaussian distributions, has been chosen as the nodal criterion to statistically explain the state of the source regions in the vicinity of magnetic reconnections, the latent excitation agent that contributes to plasma wave energetics, and the quenching phenomenon that causes damping of the burst emission.Comment: 9 pages 7 black and white / grey-scale figures (inclusive of 3 composite). MNRAS - accepte

Cosmology and large-scale structure from quasar redshift surveys

Our aim in this thesis is to use the clustering of QSOs to investigate large- scale structure and cosmology. We are particularly concerned with estimating the cosmological parameters which govern the evolution of structure in the Universe. We first investigate how QSOs trace the distribution of 'normal' galaxies by measuring the correlation between a sample of ~ 150 QSOs and faint, b(_j) 1500 QSOs including the LBQS and Durham/AAT QSO surveys. This data set has a clustering amplitude Ɛ(10 h(^-1) Mpc) = 0.83 ± 0.29 for Ωₒ = 1 at z = 1.27. On ~ 100 – 1000 h(^-1) Mpc scales the limit on detected signals in Ɛ is ±0.025. A model of clustering evolution which includes the effect of bias was used to compare QSO clustering to the clustering of low redshift galaxies and Seyfert galaxies. If Seyferts and QSOs are similarly clustered, then the data prefer a low Ωₒ or high bias for QSOs and galaxies. In contrast, comparisons to the CMB measurements of COBE assuming a CDM-type power spectrum suggest low bias. This might be taken as evidence for low do, but the data is still consistent with Ωₒ = 1 and b(_gp) ~ b(gp) ~ 2..We consider the possibility that nearby galaxy clusters can gravitationally lense background QSOs. We apply the lensing hypothesis to the result of Boyle et al., (1988) and find that cluster masses required are too large. A small dust component could retrieve the lensing model and allow more reasonable mass estimates for clusters from this method. The requirement for a new, deep, wide-field, QSO survey is clear. We discuss the construction of the candidate catalogue for the 2dF QSO Redshift Survey, which will contain ~ 25000 QSOs. We calibrate the photographic plates used for the candidate catalogue and assess the sources of errors and incompleteness. From preliminary spectroscopic observations we conclude that the completeness of the 2dF catalogue is ~ 71.1 ± 7.1%, compared with an estimated completeness of ~ 80%. We propose to substantially increase the catalogue completeness (to ~ 90%), by the introduction of UKST r plates into our candidate catalogue

AOIPS water resources data management system

A geocoded data management system applicable for hydrological applications was designed to demonstrate the utility of the Atmospheric and Oceanographic Information Processing System (AOIPS) for hydrological applications. Within that context, the geocoded hydrology data management system was designed to take advantage of the interactive capability of the AOIPS hardware. Portions of the Water Resource Data Management System which best demonstrate the interactive nature of the hydrology data management system were implemented on the AOIPS. A hydrological case study was prepared using all data supplied for the Bear River watershed located in northwest Utah, southeast Idaho, and western Wyoming

Whole-genome sequencing of Aspergillus tubingensis G131 and overview of its secondary metabolism potential

Background : Black Aspergilli represent one of the most important fungal resources of primary and secondary metabolites for biotechnological industry. Having several black Aspergilli sequenced genomes should allow targeting the production of certain metabolites with bioactive properties. In this study, we report the draft genome of a black Aspergilli, A. tubingensis G131, isolated from a French Mediterranean vineyard. This 35 Mb genome includes 10,994 predicted genes. A genomic-based discovery identifies 80 secondary metabolites biosynthetic gene clusters. Genomic sequences of these clusters were blasted on 3 chosen black Aspergilli genomes: A. tubingensis CBS 134.48, A. niger CBS 513.88 and A. kawachii IFO 4308. This comparison highlights different levels of clusters conservation between the four strains. It also allows identifying seven unique clusters in A. tubingensis G131. Moreover, the putative secondary metabolites clusters for asperazine and naphtho-gamma-pyrones production were proposed based on this genomic analysis. Key biosynthetic genes required for the production of 2 mycotoxins, ochratoxin A and fumonisin, are absent from this draft genome. Even if intergenic sequences of these mycotoxins biosynthetic pathways are present, this could not lead to the production of those mycotoxins by A. tubingensis G131

Developement of simulation tools for the analysis of variability in advanced semiconductor electron devices

The progressive down-scaling has been the driving force behind the integrated circuit (IC) industry for several decades, continuously delivering higher component densities and greater chip functionality, while reducing the cost per function from one CMOS technology generation to the next. Moore’s law boosts IC industry profits by constantly releasing high-quality and inexpensive electronic applications into the market using new technologies. From the 1 m gate lengths of the eighties to the 35 nm gate lengths of contemporary 22 nm technology, the industry successfully achieved its scaling goals, not only miniaturizing devices but also improving device performance

Electronic Properties of Next-Generation Semiconductors

The need for efficient, cheap, and durable semiconductors for photovoltaic and optoelectronic applications has spurred a number of dramatic recent developments in semiconductor quantum physics. Aided by advanced synthetic and characterization techniques, the development of high-quality, nano-structured, tunable materials has resulted in the observation of many novel phenomena. The goal of this thesis is to develop and apply methods in theoretical condensed matter science to the study of these promising materials. In Chapter 1 I explore methylammonium lead iodide (MAPbI3), a paradigmatic hybrid organic-inorganic perovskite system. To explain charge carrier dynamics in this material, I develop a microscopic tight-binding model. The average band structure is calculated and the magnitude of the temperature-dependent band gap opening and Urbach energy is quantified. The charge carrier mobility is calculated within a linear response formalism and its temperature dependence is characterized. Overall, the fully ab initio model is found to explain several non-trivial experimental phenomena while making minimal assumptions concerning the nature of the electron-phonon coupling and the character of the nuclear motion in these materials. In Chapters 2 and 3, I turn to the subject of atomically-thin transition metal dichalcogenides. I improve upon past variational calculations of exciton and trion binding energies in these materials by applying diffusion Monte Carlo to exactly calculate exciton, trion, and biexciton binding energies within an effective few-body Hamiltonian. Carriers are assumed to experience two-body interactions of the Keldysh type that have been parameterized previously from electronic structure calculations. The structures of the exact ground state wavefunctions are calculated and compared to those of the previous variational trial wavefunctions. Next, I calculate the doping dependence of the rate of exciton and trion elastic scattering with free electrons within first-order time-dependent perturbation theory. The calculation provides the first theoretical estimate of the intrinsic trion linewidth in these materials. Finally, in Chapter 4, I study variants of the GW approximation to the one-particle Green's function for calculating correlation energies and spectral weights for the three-dimensional homogeneous electron gas. By relating the cumulant generating function to the improper GW self-energy, I develop a new cumulant-based GW approximation. The approach is compared to existing methods first via solution of a simple linearly-coupled electron phonon model and later through application to the electron gas problem

Computation methods for the eigenvalue analysis of large structures by component synthesis

Imperial Users onl

Digital computer processing of LANDSAT data for North Alabama

Computer processing procedures and programs applied to Multispectral Scanner data from LANDSAT are described. The output product produced is a level 1 land use map in conformance with a Universal Transverse Mercator projection. The region studied was a five-county area in north Alabama