Resilience of shallow groundwater resources and their potential for use in small-scale irrigation : a study in Ethiopia

PhD ThesisGroundwater use for small-scale irrigation in sub-Saharan Africa is low, though is expected to increase in the near future. There is currently limited understanding of shallow groundwater resources, which are most likely to be exploited by poor rural communities due to their accessibility. This PhD study aimed to determine the potential for use of shallow groundwater for small-scale irrigation and the resilience of the resources to increased abstraction, land-use change and climate variability. Research was conducted principally at a study site in northwest Ethiopia with seasonal rainfall and a predominance of rainfed agriculture. The shallow aquifer comprises a thin weathered regolith above largely impermeable basalt. Hydrochemistry analyses suggested little connection between the shallow aquifer and a deep fractured aquifer. To fill gaps in formal hydrometeorological monitoring, a community-based monitoring programme was initiated. Statistical comparisons confirmed that the datasets were of as high or higher quality as those from formal networks, remote sensing and reanalyses. A recharge assessment estimated annual recharge of 280-430 mm, confirming that a sufficient renewable shallow groundwater resource is available for small-scale irrigation. Four nested catchments were modelled using SHETRAN, a physically-based spatially-distributed modelling program. The modelling identified the foot of hillslopes and narrow valleys as showing the greatest potential for irrigated agriculture as groundwater in those locations remained available and accessible for the longest periods. Potential future scenarios were run in the SHETRAN models considering likely climate variability, land use change and increasing abstraction. Around 35% of arable land in the modelled catchments had shallow groundwater available throughout the dry season. During simulated multi-year droughts, a significant percentage of arable land still had sufficient groundwater available for irrigation of a second growing season. Conversion of pasture and scrubland to cultivated land did not have a significant impact on water resources while degradation of highlands to bareground had a positive impact. The severest impact on water resources resulted from increased coverage of Eucalyptus. Notably, simulation of increased abstraction and irrigation at smallholder levels had little impact on surface and groundwater availability. This study demonstrates the potential for greater exploitation of shallow groundwater for small-scale irrigation by rural communities and the resilience of the resource to climate variability, land use change and increasing abstraction.Newcastle University who funded this PhD through the Faculty of Science, Agriculture and Engineering (SAgE) Doctoral Training Awards (DTA) programme. I am also thankful to NERC/DfID who funded the initial AMGRAF catalyst project (grant no. NE/L002019/1) under the UPGro programme that led to the PhD. I am further grateful to Newcastle University for the award of the Harry Collinson Travel Scholarship, to the Royal Geographical Society with IBG for the Dudley Stamp Memorial Award, and to the International Association of Hydrogeologists for the John Day Bursary

Candidates for asteroid dust trails

The contribution of different sources to the circumsolar dust cloud (known as the zodiacal cloud) can be deduced from diagnostic observations. We used the Spitzer Space Telescope to observe the diffuse thermal emission of the zodiacal cloud near the ecliptic. Several structures were identified in these observations, including previously known asteroid dust bands, which are thought to have been produced by recent asteroid collisions, and cometary trails. Interestingly, two of the detected dust trails, denoted t1 and t2 here, cannot be linked to any known comet. Trails t1 and t2 represent a much larger integrated brightness than all known cometary trails combined and may therefore be major contributors to the circumsolar dust cloud. We used our Spitzer observations to determine the orbits of these trails and were able to link them to two ("orphan" or type II) trails that were discovered by the Infrared Astronomical Satellite (IRAS) in 1983. The orbits of trails t1 and t2 that we determined by combining the Spitzer and IRAS data have semimajor axes, eccentricities, and inclinations like those of the main-belt asteroids. We therefore propose that trails t1 and t2 were produced by very recent (<~100 kyr old) collisional breakups of small, <~10 km diameter main-belt asteroids

Polymeric Bladder for Storing Liquid Oxygen

A proposed system for storing oxygen in liquid form and dispensing it in gaseous form is based on (1) initial subcooling of the liquid oxygen; (2) containing the liquid oxygen in a flexible vessel; (3) applying a gas spring to the flexible vessel to keep the oxygen compressed above the saturation pressure and, thus, in the liquid state; and (4) using heat leakage into the system for vaporizing the oxygen to be dispensed. In a typical prior system based on these principles, the flexible vessel is a metal bellows housed in a rigid tank, and the gas spring consists of pressurized helium in the tank volume surrounding the bellows. Unfortunately, the welds in the bellows corrugations are subject to fatigue, and, because bellows have large ullage, a correspondingly large fraction of the oxygen content cannot be expelled. In the proposed system, the flexible vessel would be a bladder made of a liquid- crystal polymer (LCP). (LCPs are strong and compatible with liquid oxygen.) In comparison with a metal bellows, a polymeric bladder would have less ullage and would weigh less. In experiments involving fatigue cycling at liquid-nitrogen temperatures, two LCPs were found to be suitable for this application

Seizure characteristics and the use of anti-epileptic drugs in children and young people with brain tumours and epileptic seizures: analysis of regional paediatric cancer service population

PURPOSE: Epileptic seizures complicate the management of childhood brain tumours. There are no published standards for clinical practice concerning risk factors, treatment selection or strategies to withdraw treatment with antiepileptic drugs (AED). METHOD: We undertook a case note review of 120 patients with newly diagnosed brain tumours, referred to a regional paediatric cancer service. RESULTS: Data was available on 117/120 (98%) children <18 years: median age at tumour presentation was 8.1 years (IQR 25°-75°: 3.6-12.7), median follow up was 33 months (IQR 25°-75°: 24-56), and 35/117 (29%) experienced seizures. A cortical tumour location was associated with the highest risk of seizures (OR: 7.1; CI 95% 2.9-17.3). At a median follow up of 24 months (IQR25°-75°: 15-48), 22/35 (63%) with seizures, had a single seizure episode, 15/35 (43%) were seizure free (SF) on AEDs, 13/35 (37%) were SF off AEDs, and 7/35 (20%) experienced continuing epileptic seizures. Overall 34/35 (97%) were treated with AEDs after a seizure, of whom 12/35 (35%) withdrew from AED medication, and although 4/35 (12%) had seizure relapse, all were after further acute events. The median duration of AED before withdrawal was 11 months (IQR25°-75° 5-14 months), and the median follow up after withdrawal was 15 months (IQR25°-75° 5-34 months). CONCLUSIONS: Seizures affect about 1/3rd of children and young people presenting with and being treated for brain tumours particularly when the tumour is in the cerebral cortex. The low risk of recurrent seizures after AED treatment justifies consideration of early withdrawal of AED after seizure control

The quest for petascale computing

Although the challenges to achieving petascale computing within the next decade are daunting, several software and hardware technologies are emerging that could help us reach this goal. The authors review these technologies and consider new algorithms capable of exploiting a petascale computer's architecture. One petaflop per second is a rate of computation corresponding to 10[superscript 15] floating-point operations per second. To be of use in scientific computing, a computer capable of this prodigious speed needs a main memory of tens or hundreds of terabytes and enormous amounts of mass storage. Sophisticated compilers and high memory and I/O bandwidth are also essential to exploit the architecture efficiently. To mask the hardware and software complexities from the scientific end user, it would be advantageous to access and use a petascale computer through an advanced problem-solving environment. Immersive visualization environments could play an important role in analyzing and navigating the output from petascale computations. Thus, petascale computing is capable of driving the next decade of research in high-performance computing and communications and will require advances across all aspects of it

American Eel: A Symposium. Session Four

Session Four considers lessons from European eel research and conservation

American Eel: A Symposium. Session Four

Session Four considers lessons from European eel research and conservation