Line narrowing of AgGaSe2 optical parametric oscillator by injection seeding

Solid-state lasers are developed for atmospheric applications. Optical parametric oscillators (OPO) are being investigated as sources of tunable radiation in the 2.5-12 micron range where development of conventional lasers is subject to numerous difficulties. Parametric oscillation is a nonlinear optical technique for converting laser output to longer wavelengths. Incident photons, typically from a pulsed pump laser, are converted into two photons of longer wavelength, while satisfying energy conservation. The particular split of energy is determined by momentum conservation; the wavelength of interest is usually selected by angle orientation of the nonlinear material with respect to the direction of propagation of the pump beam. An OPO based on AgGaSe2 was considered

Flashlamp-pumped Ho:Tm:Cr:LuAG laser

A room temperature solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG host material doped with a concentration of about 0.35% Ho ions, about 5.57% Tm ions and at least about 1.01% Cr ions. A broadband energizing source such as a flashlamp is disposed transversely to the laser crystal to energize the Ho ions, Tm ions and Cr ions

Comparison of Two Methodologies for Calibrating Satellite Instruments in the Visible and Near Infrared

Traditionally, satellite instruments that measure Earth-reflected solar radiation in the visible and near infrared wavelength regions have been calibrated for radiance response in a two-step method. In the first step, the spectral response of the instrument is determined using a nearly monochromatic light source, such a lamp-illuminated monochromator. Such sources only provide a relative spectral response (RSR) for the instrument, since they do not act as calibrated sources of light nor do they typically fill the field-of-view of the instrument. In the second step, the instrument views a calibrated source of broadband light, such as lamp-illuminated integrating sphere. In the traditional method, the RSR and the sphere spectral radiance are combined and, with the instrument's response, determine the absolute spectral radiance responsivity of the instrument. More recently, an absolute calibration system using widely tunable monochromatic laser systems has been developed, Using these sources, the absolute spectral responsivity (ASR) of an instrument can be determined on a wavelength-hy-wavelength basis. From these monochromatic ASRs. the responses of the instrument bands to broadband radiance sources can be calculated directly, eliminating the need for calibrated broadband light sources such as integrating spheres. Here we describe the laser-based calibration and the traditional broad-band source-based calibration of the NPP VIIRS sensor, and compare the derived calibration coefficients for the instrument. Finally, we evaluate the impact of the new calibration approach on the on-orbit performance of the sensor

Combination of mesoscale and synoptic mechanisms for triggering an isolated thunderstorm: Observational case study of CSIP IOP 1

Copyright @ 2007 AMSAn isolated thunderstorm formed in the southern United Kingdom on 15 June 2005 and moved through the area where a large number of observational instruments were deployed as part of the Convective Storm Initiation Project. Earlier, a convergence line had formed downstream of Devon in the southwest of the United Kingdom in a southwesterly airflow, along which a series of light showers had formed. The depth of these showers was limited by a capping inversion, or lid, at around 2.5 km. The deep thunderstorm convection developed from one of these showers when the convection broke through the lid and ascended up to the next inversion, associated with a tropopause fold at around 6 km. A series of clear-air reflectivity RHIs are used to map the height of the capping inversion and its lifting resulting from the ascent along the convergence line. The origins of the lid are tracked back to some descent from the midtroposphere along dry adiabats. The strength of the lid was weaker along a northwest-to-southeast-oriented region located behind an overrunning upper cold front. The transition from shallow to deep convection occurred where this region with a weaker lid intersected the region with a raised lid, oriented southwest to northeast, downstream of Devon. A very high resolution forecast model that is being developed by the Met Office predicted the isolated thunderstorm successfully. This success depended on the accurate representation of the following two scales: the synoptic-scale and the surface-forced mesoscale convergence line. The interaction between these scales localized the convection sufficiently in space and time for the initiation and subsequent development to be highly predictable despite the relatively poor representation in the model of processes at the cloud scale.This work was funded from the Natural Environment Research Council and the Met Office National Meteorology Programme

HI Observations of Interacting Galaxy Pair NGC 4038/9

We present the results of new radio interferometer HI line observations for the merging galaxy pair NGC 4038/9 (`The Antennae'), obtained using the Australia Telescope Compact Array. The results improve substantially on those of van der Hulst (1979) and show in detail the two merging galactic disks and the two tidal tails produced by their interaction. The small edge-on spiral dwarf galaxy ESO 572-G045 is also seen near the tip of the southern tail, but distinct from it. It shows no signs of tidal interaction. The northern tidal tail of the Antennae shows no HI connection to the disks and has an extension towards the west. The southern tidal tail is continuous, with a prominent HI concentration at its tip, roughly at the location of the tidal dwarf galaxy observed optically by Mirabel, Dottori & Lutz (1992). Clear velocity structure is seen along the tidal tails and in the galactic disks. Radio continuum images at 20-cm and 13-cm are also presented, showing the disks in detail.Comment: 22 pages, 8 figures, Accepted by MNRAS (April 2001

Exploratory Steps Towards a Grammatical Manipulation Package (GRAMPA)

Very often, grammars constructed for computer languages are not in a concise form for simple parsing. For example some symbols may be unreachable or useless. If a simple precedence grammar is required, artificial symbols may have to be introduced to remove conflicts. This report describes exploratory steps taken towards the development of an Algol program to automatically manipulate grammars. Procedures are described which read and set up a grammar in a list structure form suitable for analysis and manipulation. The procedures manipulate the grammar to remove useless and unreachable symbols, and precedence conflicts, and they analyse the grammar for recursion, precedence etc.Master of Science (MS

The phylogenetics and evolution of Africa's larks (Alaudidae)

Includes bibliographical references.The larks are a group of dull coloured birds that are conservative in plumage coloration and pattern due to the requirements for camouflage in open habitats. Because many species inhabit structurally similar habitats the group is also characterised by a great deal of morphological convergence. Variation in plumage and morphology is frequently as great within species as it is between species, leading to many inconsistent and controversial taxonomic treatments and classifications at an intra- and inter-generic level, and when defining specific and sub-specific boundaries. The advent of genetic techniques and success at applying these to species complexes in southern Africa suggested that a molecular phylogeny of the family would elucidate relationships that could not be determined via traditional taxonomic practices. In this study 2009 nucleotides of two mitochondrial DNA genes, cytochrome b and 16S rRNA (Chapter 2), and 2872 nucleotides of the nuclear exon RAG-l (Chapter 3) were used to generate a robust phylogeny of the family Alaudidae. The former analysis included 55 species and the latter 25. These data were also combined to construct a combined evidence phylogeny (Chapter 7). Within the family, several genera recognised by more traditional taxonomies are polyphyletic, including Ammomanes, Eremalauda .and Certhilauda. Two other genera, Calandrella and Mirafra, are best treated as multiple genera (Chapter 2). The sampled Alaudidae can be divided into three main radiations, the ammomanid larks, mirafrid larks and alaudid larks (Chapter 3). Within the ammomanid larks, there is strong support for: (1) a southern African' radiation comprising Chersomanes, the Long-billed Lark complex (Certhilauda) and Ammomanes (Ammomanopsis) grayi ,with Alaemon allied to this radiation; and (2) a .Saharo-Sindian radiation comprising Ramphocoris c1otbey, Ammomanes cinc(urus, and A. deserti sister to the Afro-Sindian sparrowlark Eremopterix clade. The Madagascan endemic Mirafra hova was a surprise basal member of Eremopterix

A General Ecology of Bryozoans at Signy Island, Antarctica

This study set out to investigate a broad range of ecological aspects in Antarctic bryozoans, including distribution, feeding, growth and predation, and how these were influenced by environmental conditions. A number of sites, at a variety of depths, were chosen from within Borge Bay, Signy Island in the South Orkneys, using SCUBA. Some of these studies atempted to monitor populations in situ over tlie course of two years, mainly with the aid of underwater cameras. Photographic samples were taken on three vertical transects of 5.5 m rock faces and two 40 m sloping transects. The percentage cover of substratum ranged from 0-100% and the colonising communities included representitives of 10 phyla. Ice impact, depth and profile were important influences on community cover and composition. Collections of up to 200 rocks were made from each of six localities ranging from the intertidal to 42 m. Area colonised, number of colonising phyla, bryozoan species and colonies were all found to increase with substratum surface area and depth. Over 4000 competitive interactions between bryozoans were recorded, which indicated the presence of a competitive hierarchy with one ultimately dominant species. Colonisation of artificial substrata was very slow comparative to that found by similar temperate studies and suggested an essentially classical successional pattern of colonisation. Bryozoans were abundant on the externa of a variety of other macroinveitebrates, including fouling the surfaces of erect bryozoan species.Lophophore activity (feeding) occurred for most of the year in the bryozoans monitored, and environmental cues were suggested for the changes in activity of some species. Growth was generally slow but contrasted strongly in duration between the monitored species. The growth checks, formed annually by one species, showed interannual variations in growtli throughout the population. Two bryozoan species had specific nudibranch predators, though their populations seemed little influenced by predation

Voluntary Governance (VG) in the Not-for-Profit Sector: The Model for Retention and Recruitment of Boards of Directors

This research seeks to explore the current type of Voluntary Governance (VG) mechanisms used to monitor and control Not-For-Profit (NFP) entities at the Board of Directors (BOD) level. It uses case study analysis to investigate the Model rules for NFP Directors. The questions explore the Board and governance mechanisms for NFPs, particularly focusing on the value added by Voluntary Board members, to make recommendations for reporting of Voluntary Governance by NFPs. The Global Financial Crisis demonstrated the importance of Accountability, Transparency and good Corporate Governance of all types of organizations be they Not-for-Profit (NFP) or for-profit. This research demonstrates the obligations of Voluntary Directors in terms of legislation, common law duties and equitable fiduciary duties in relation to governance, social responsibility, transparency and risk management, particularly in a sector that contributes so much to the global economies in terms of employment and GDP [1], [2]

Blue Carbon on Polar and Subpolar Seabeds

When marine organisms eat and grow they capture and store carbon, termed blue carbon. Polar seas have extreme light climates and sea temperatures. Their continental shelves have amongst the most intense phytoplankton (algal) blooms. This carbon drawdown, storage and burial by biodiversity is a quantifiable ‘ecosystem service’. Most of that carbon sinks to be recycled by microbes, but some enters a wider food web of zooplankton and their predators or diverse seabed life. How much carbon becomes stored long term or buried to become genuinely sequestered varies with a wide range of factors, e.g. geography, history, substratum etc. The Arctic and Antarctic are dynamic and in a phase of rapid but contrasting, complex physical change and marine organismal carbon capture and storage is altering in response. For example, an ice shelf calving a 5000 km2 iceberg actually results in 106 tons of additional blue carbon per year. Polar blue carbon increases have resulted from new and longer climate-forced, phytoplankton blooms driven by sea ice losses and ice shelf collapses. Polar blue carbon gains with sea ice losses are probably the largest natural negative feedback against climate change. Here the current status, variability and future of polar blue carbon is considered