Analysis of the breakdown of the Antarctic circumpolar vortex using TOMS ozone data

Climatological analysis of data from the Total Ozone Mapping Spectrometer (TOMS) on the Nimbus 7 satellite has shown that the annual cycles of ozone are very different in the Arctic and Antarctic. The annual cycle in the Arctic is a relatively smooth annual sine wave; but in the Antarctic the circumpolar vortex breaks down rapidly during the Southern Hemisphere spring (September through November), producing a rapid rise in total ozone and a sawtooth-shaped annual cycle. The evolution of the Antarctic total ozone field during the vortex breakdown was studied by computing areally-integrated ozone amounts from the TOMS data. This technique avoids substantial difficulties with using zonally-averaged ozone amounts to study the asymmetric breakdown phenomenon. Variability of total ozone is found to be large both within an individual year and between different years. During the last decade monthly-mean total ozone values in the Antarctic during the springtime vortex breakdown period have decreased dramatically. The ozone-area statistics indicate that the decrease has resulted in part from changes in the timing of the vortex breakdown and resultant ozone increase, which have occurred later during recent years. Analysis of the spatial scales involved in the ozone transport and mixing that occur during the vortex breakdown is now underway. Reliable calculation of diagnostic quantities like areally-integrated ozone is possible only with the high-resolution, two-dimensional, daily coverage provided by the TOMS instrument

Development of a Collaborative Design Tool for Structural Analysis in an Immersive Virtual Environment

This paper contains the results of an on-going collaborative research effort by the departments of Architecture and Computer Science of Virginia Polytechnic Institute and State University, U.S.A., to develop a computer visualization application for the structural analysis of building structures. The VIRTUAL-SAP computer program is being developed by linking PC-SAP4 (Structural Analysis Program), and virtual environment software developed using the SVE (Simple Virtual Environment) library. VIRTUAL-SAP is intended for use as a collaborative design tool to facilitate the interaction between the architect, engineer, and contractor by providing an environment that they can walk-through and observe the consequences of design alterations. Therefore, this software can be used as an interactive computer-aided analysis of building systems

Incorporating geostrophic wind information for improved space-time short-term wind speed forecasting

Accurate short-term wind speed forecasting is needed for the rapid development and efficient operation of wind energy resources. This is, however, a very challenging problem. Although on the large scale, the wind speed is related to atmospheric pressure, temperature, and other meteorological variables, no improvement in forecasting accuracy was found by incorporating air pressure and temperature directly into an advanced space-time statistical forecasting model, the trigonometric direction diurnal (TDD) model. This paper proposes to incorporate the geostrophic wind as a new predictor in the TDD model. The geostrophic wind captures the physical relationship between wind and pressure through the observed approximate balance between the pressure gradient force and the Coriolis acceleration due to the Earth's rotation. Based on our numerical experiments with data from West Texas, our new method produces more accurate forecasts than does the TDD model using air pressure and temperature for 1- to 6-hour-ahead forecasts based on three different evaluation criteria. Furthermore, forecasting errors can be further reduced by using moving average hourly wind speeds to fit the diurnal pattern. For example, our new method obtains between 13.9% and 22.4% overall mean absolute error reduction relative to persistence in 2-hour-ahead forecasts, and between 5.3% and 8.2% reduction relative to the best previous space-time methods in this setting.Comment: Published in at http://dx.doi.org/10.1214/14-AOAS756 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Lattice quark propagator with staggered quarks in Landau and Laplacian gauges

We report on the lattice quark propagator using standard and improved Staggered quark actions, with the standard, Wilson gauge action. The standard Kogut-Susskind action has errors of \oa{2} while the ``Asqtad'' action has \oa{4}, \oag{2}{2} errors. The quark propagator is interesting for studying the phenomenon of dynamical chiral symmetry breaking and as a test-bed for improvement. Gauge dependent quantities from lattice simulations may be affected by Gribov copies. We explore this by studying the quark propagator in both Landau and Laplacian gauges. Landau and Laplacian gauges are found to produce very similar results for the quark propagator.Comment: 11 pages, 15 figure

3D Computational Ghost Imaging

Computational ghost imaging retrieves the spatial information of a scene using a single pixel detector. By projecting a series of known random patterns and measuring the back reflected intensity for each one, it is possible to reconstruct a 2D image of the scene. In this work we overcome previous limitations of computational ghost imaging and capture the 3D spatial form of an object by using several single pixel detectors in different locations. From each detector we derive a 2D image of the object that appears to be illuminated from a different direction, using only a single digital projector as illumination. Comparing the shading of the images allows the surface gradient and hence the 3D form of the object to be reconstructed. We compare our result to that obtained from a stereo- photogrammetric system utilizing multiple high resolution cameras. Our low cost approach is compatible with consumer applications and can readily be extended to non-visible wavebands.Comment: 13pages, 4figure

Exactly Conservative Integrators

Traditional numerical discretizations of conservative systems generically yield an artificial secular drift of any nonlinear invariants. In this work we present an explicit nontraditional algorithm that exactly conserves these invariants. We illustrate the general method by applying it to the three-wave truncation of the Euler equations, the Lotka--Volterra predator--prey model, and the Kepler problem. This method is discussed in the context of symplectic (phase space conserving) integration methods as well as nonsymplectic conservative methods. We comment on the application of our method to general conservative systems.Comment: 30 pages, postscript (1.3MB). Submitted to SIAM J. Sci. Comput

Assessing the glycaemic and CNS response to sulphonylurea therapy in patients with KCNJ11 mutations.

ATP-dependent potassium (KATP) channels are present in the human pancreas, brain, nerve and muscle and play a crucial role in key biological pathways. In the pancreas, KATP channels regulate insulin secretion from beta cells in response to glucose. They comprise 4 Kir6.2 subunits, encoded by the KCNJ11 gene, which form the channel pore, and 4 SUR1 subunits, encoded by the ABCC8 gene, which regulate channel activity and form the binding site for sulphonylurea drugs. Mutations in KATP channel genes account for ~half of cases of neonatal diabetes, which is diabetes diagnosed in the first 6 months of life; this may be permanent (PNDM) requiring lifelong treatment, or transient (TNDM) where the diabetes remits and relapses in later childhood or adulthood. Activating mutations in the KCNJ11 gene are the commonest cause of PNDM. A genetic diagnosis is crucial for patients with these mutations because ~90% can be treated with oral sulphonylureas instead of insulin injections. Sulphonylureas can bind and close mutant KATP channels allowing endogenous insulin secretion and resulting in improved metabolic control and quality of life at least in the short-term. Severe sulphonylurea-related hypoglycaemia does not occur but mild-moderate episodes, typically related to food, have been reported by affected individuals. The long-term response to sulphonylurea therapy and the regulation of insulin secretion in response to food in people with KCNJ11 mutations remain key research questions with important clinical implications. Individuals with KCNJ11 PNDM can also have central nervous system (CNS) involvement; at its most severe this leads to Developmental delay, Epilepsy and Neonatal Diabetes (DEND) syndrome. Sulphonylurea therapy can also benefit the neurological features, which are thought to result from the action of sulphonylureas on brain KATP channels, although the response is only partial in contrast to the excellent glycaemic response. In order to provide appropriate multidisciplinary assessment and support, it is important to establish the specific neurological, psychiatric, and neuropsychological deficits that are present in children and adults with sulphonylurea-treated KCNJ11 neonatal diabetes, and their impact on affected families. The overall aim of this thesis is to assess the response to sulphonylurea therapy in patients with PNDM due to mutations in the KCNJ11 gene, by undertaking clinical studies that investigate the glycaemic response as well as the CNS features in affected individuals. In chapter 1 we assess the long-term efficacy and safety of sulphonylurea therapy in KCNJ11 PNDM, by following clinical outcomes relating to both glycaemia and neurological features over 10 years in 81 patients who transferred from insulin to sulphonylureas before December 2006. We show that sulphonylurea therapy is effective and safe long-term, with 93% of individuals remaining on sulphonylureas without adjunctive therapies at most recent follow-up with no reports of severe hypoglycaemia or severe side-effects in over 800 patient years, and normal growth and BMI in children. In addition, we show that neurological features are present in 38/81 individuals and despite initial improvement in 18 individuals on transfer to sulphonylureas, there is persistence of these features to some degree long-term. In chapter 2 we assess the physiological response to different foods in adults >18 years with sulphonylurea-treated KCNJ11 PNDM, by measuring glucose, insulin and glucagon levels after a high-protein meal and a high-carbohydrate meal in 5 affected individuals and comparing these with 5 non-diabetic controls. We show that individuals with sulphonylurea treated KCNJ11 PNDM have similar insulin levels in response to both a carbohydrate and protein meal despite having higher glucose values in response to a carbohydrate meal than to a protein meal. This contrasts with controls who have higher insulin secretion after carbohydrate than protein and therefore more tightly regulated glucose levels in response to both meals. The findings suggest that individuals with sulphonylurea-treated KCNJ11 PNDM cannot modulate insulin secretion in response to glucose, consistent with a dependence on non-KATP pathways for insulin secretion. In chapter 3 we assess the psychiatric and neuropsychological profile of children <18 years with sulphonylurea-treated KCNJ11 neonatal diabetes. In study A we use standardised questionnaires to measure psychiatric morbidity and impact in 10 children with KCNJ11 mutations and compared outcomes with school-age population norms. We show that psychiatric disorders are present in 6/10 children, mainly consisting of autism, attention deficit hyperactivity disorder (ADHD) and anxiety disorders. These disorders are related to the specific mutation (V59M or R201C), have high impact on families and frequently go unrecognised clinically. In study B we use a battery of neuropsychological tests to assess neuropsychological functioning in affected children and compare outcomes to non-diabetic sibling controls. We show that learning difficulties and specific neuropsychological impairments are frequently present even in those children with mutations not consistently associated with a severe CNS phenotype, and that such features are absent from unaffected sibling controls. In chapter 4 we investigate the neurological, neuropsychological and behavioural features in adults with KCNJ11 neonatal diabetes, by assessing 8 individuals (7 sulphonylurea-treated) with KCNJ11 mutations using standardised neuropsychological tests, questionnaires, and clinical history and examination. Outcomes are compared to 4 adults with neonatal diabetes due to mutations in the INS gene, thereby controlling for the presence of hyperglycaemia from birth. We show that adults with KCNJ11 mutations have learning difficulties, features of autism spectrum disorder (ASD), subtle motor dysfunction, moderately reduced IQ, and impaired attention, perceptual reasoning and working memory which persist despite long term sulfonylurea therapy and represent the major burden of disease once glycemia is well controlled on sulphonylureas. The severity of the CNS features varies with the specific mutation and they do not occur in individuals with neonatal diabetes due to INS mutations, suggesting they occur as a consequence of dysfunctional brain KATP channels as opposed to indirect effects of lifelong diabetes. The conclusions section summarises the data chapters and describes how the work fits together as a coherent whole, as well as identifying directions for future research specific to each of the studies undertaken. The research in this thesis offers original and novel insights into both the CNS features of KCNJ11 neonatal diabetes and the glycaemic response to sulphonylurea therapy. Patients with KCNJ11 neonatal diabetes represent a unique human experimental model for the study of KATP channel biological pathways in both the pancreas and brain. Treatment of the condition with sulphonylureas remains one of the best examples of precision medicine and illustrates the benefits of targeted treatments in monogenic disease.Diabetes UKHumane Society Internationa