Urban sprawl in Kathmandu Valley of Nepal from 1964-2003: a challenge for urban policy makers and planners

This paper analyzes the conditions of the five cities—Bhaktapur, Kathmandu, Kirtipur, Lalitpur, and Madhyapur Thimi— that comprise the Kathmandu Valley conurbation and exhibit the typical characteristics of the nation’s primate city (Bhattarai, 2003). It examines the patterns and causal processes of urban sprawl for the period 1955 and 2003 by utilizing both spatial and aspatial data. It analyzes the patterns of historical aspects of the Kathmandu Valley’s settlements that acquired the characteristics of a European feudal urban agglomeration in the mid-18th century, combining political, administrative, and craft production functions (Bhattarai, 2003). Our analyses reveal that since the early 1970s, the Kathmandu Valley has become structurally differentiated into two distinct urban ‘spaces’ (KVMP, 2001). The first ‘space’ is the traditional urban core characterized by narrow alleys, cul-de-sac streets, and loops serving the densely populated area. The second ‘space’ surrounds the city core, a less populated periphery, with uneven residential densities, ranging from dense concentrations (\u3e700 people ha-1) to relatively open developments (10 person ha-1) with rural interstices

Measuring quality of life of the Central Development Region of Nepal by integration of remote sensing and census data

Our research adds to the growing number of remote sensing–based analyses that deal with land-cover dynamics, land use and cover changes in the Center Development Region (CDR) of Nepal during the last three decades. This study spatially identifies deforestation areas by using transition matrices for the periods of 1975-1990, 1990-2000 and 2000- 2005. It uses simple regression analyses for finding relationships of the above variables with deforestation

Advances in Magnetotelluric Modelling: Time-Lapse Inversion, Bayesian Inversion and Machine Learning

This thesis presents advancements to the area of magnetotelluric (MT) modelling. There are three main aims to this work. The first aim is to implement an inversion to model time-lapse MT data in a temporal dimension. The algorithm considers the entire dataset at once, with penalisations for model roughness in both the spatial and temporal dimensions. The inversion is tested on synthetic data, as well as a case-study from a coal-seam gas dewatering survey. Second is to explore the problem of nonuniqueness in MT data inversion by implementing a 1D Bayesian inversion using an efficient sampler. The implemented model includes a novel way of regularising MT inversion by allowing the strength of smoothing to vary between different models. The Bayesian inversion is tested on synthetic and case-study datasets with results matching known data. The third aim is to implement a proxy function for the 3D MT forward function based on artificial neural networks. This allows for rapid evaluation of the forward function and the use of evolutionary algorithms to invert for resistivity structures. The evolutionary search algorithm is tested on synthetic data sets and a case-study data set from the Curnamona Province, South Australia. Together, these three novel algorithms and software implementations represent a contribution to the toolkit of MT modelling.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 201

Hard X-ray footpoint sizes and positions as diagnostics of flare accelerated energetic electrons in the low solar atmosphere

The hard X-ray (HXR) emission in solar flares comes almost exclusively from a very small part of the flaring region, the footpoints of magnetic loops. Using RHESSI observations of solar flare footpoints, we determine the radial positions and sizes of footpoints as a function of energy in six near-limb events to investigate the transport of flare accelerated electrons and the properties of the chromosphere. HXR visibility forward fitting allows to find the positions/heights and the sizes of HXR footpoints along and perpendicular to the magnetic field of the flaring loop at different energies in the HXR range. We show that in half of the analyzed events, a clear trend of decreasing height of the sources with energy is found. Assuming collisional thick-target transport, HXR sources are located between 600 and 1200 km above the photosphere for photon energies between 120 and 25 keV respectively. In the other events, the position as a function of energy is constant within the uncertainties. The vertical sizes (along the path of electron propagation) range from 1.3 to 8 arcseconds which is up to a factor 4 larger than predicted by the thick-target model even in events where the positions/heights of HXR sources are consistent with the collisional thick-target model. Magnetic mirroring, collisional pitch angle scattering and X-ray albedo are discussed as potential explanations of the findings.Comment: 10 pages, 8 figures, accepted for publication in Ap

The sub-arcsecond hard X-ray structure of loop footpoints in a solar flare

The newly developed X-ray visibility forward fitting technique is applied to Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data of a limb flare to investigate the energy and height dependence on sizes, shapes, and position of hard X-ray chromospheric footpoint sources. This provides information about the electron transport and chromospheric density structure. The spatial distribution of two footpoint X-ray sources is analyzed using PIXON, Maximum Entropy Method, CLEAN and visibility forward fit algorithms at nonthermal energies from $\sim 20$ to $\sim 200$ keV. We report, for the first time, the vertical extents and widths of hard X-ray chromospheric sources measured as a function of energy for a limb event. Our observations suggest that both the vertical and horizontal sizes of footpoints are decreasing with energy. Higher energy emission originates progressively deeper in the chromosphere consistent with downward flare accelerated streaming electrons. The ellipticity of the footpoints grows with energy from $\sim 0.5$ at $\sim 20$ keV to $\sim 0.9$ at $\sim 150$ keV. The positions of X-ray emission are in agreement with an exponential density profile of scale height $\sim 150$~km. The characteristic size of the hard X-ray footpoint source along the limb is decreasing with energy suggesting a converging magnetic field in the footpoint. The vertical sizes of X-ray sources are inconsistent with simple collisional transport in a single density scale height but can be explained using a multi-threaded density structure in the chromosphere.Comment: 7 pages, 7 figures, submitted to Ap

Standardised coding of diet records: experiences from INTERMAP UK

Coding diet records is a basic element of most dietary surveys, yet it often receives little attention even though errors in coding can lead to flawed study results. In the INTERnational study of MAcro- and micronutrients and blood Pressure (INTERMAP study), efforts were made to minimise errors in coding the 18 720 diet records. Staff were centrally trained and certified before being able to process study data and ongoing quality control checks were performed. This involved the senior (site) nutritionist re-coding randomly selected diet records. To facilitate standardisation of coding in the UK, a code book was designed; it included information about coding brand items, density and portion size information, and default codes to be assigned when limited information was available for food items. It was found that trainees, despite previous experience in coding elsewhere, made coding errors that resulted in errors in estimates of daily energy and nutrient intakes. As training proceeded, the number of errors decreased. Compilation of the code book was labour-intensive, as information from food manufacturers and retailers had to be collected. Strategies are required to avoid repetition of this effort by other research groups. While the methods used in INTERMAP to reduce coding errors were time consuming, the experiences suggest that such errors are important and that they can be reduced

Top Compositeness at the Tevatron and LHC

We explore the possibility that the right-handed top quark is composite. We examine the consequences that compositeness would have on $t \bar{t}$ production at the Tevatron, and derive a weak constraint on the scale of compositeness of order a few hundred GeV from the $t \bar{t}$ inclusive cross section. More detailed studies of differential properties of $t \bar{t}$ production could potentially improve this limit. We find that a composite top can result in an enhancement of the $t \bar{t} t \bar{t}$ production rate at the LHC (of as much as $10^3$ compared to the Standatd Model four top rate). We explore observables which allow us to extract the four top rate from the backgrounds, and show that the LHC can either discover or constrain top compositeness for wide ranges of parameter space.Comment: 9 pages, 4 figure

Gridmapping the northern plains of Mars: Geomorphological, Radar and Water-Equivalent Hydrogen results from Arcadia Plantia

A project of mapping ice-related landforms was undertaken to understand the role of sub-surface ice in the northern plains. This work is the first continuous regional mapping from CTX (“ConTeXt Camera”, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centred on the 170° West line of longitude. The distribution and morphotypes of these landforms were used to understand the permafrost cryolithology. The mantled and textured signatures occur almost ubiquitously between 35° N and 78° N and have a positive spatial correlation with inferred ice stability based on thermal modelling, neutron spectroscopy and radar data. The degradational features into the LDM (Latitude Dependent Mantle) include pits, scallops and 100 m polygons and provide supporting evidence for sub-surface ice and volatile loss between 35-70° N in Arcadia with the mantle between 70-78° N appearing much more intact. Pitted terrain appears to be much more pervasive in Arcadia than in Acidalia and Utopia suggesting that the Arcadia study area had more wide-spread near-surface sub-surface ice, and thus was more susceptible to pitting, or that the ice was less well-buried by sediments. Correlations with ice stability models suggest that lack of pits north of 65-70° N could indicate a relatively young age (~1Ma), however this could also be explained through regional variations in degradation rates. The deposition of the LDM is consistent with an airfall hypothesis however there appears to be substantial evidence for fluvial processes in southern Arcadia with older, underlying processes being equally dominant with the LDM and degradation thereof in shaping the landscape