Science: Theses and Dissertations
http://hdl.handle.net/10092/841
2017-01-14T09:39:50ZEnduring cognitive, emotional and neurogenic alterations induced by alcohol and methamphetamine exposure in adolescent rats.
http://hdl.handle.net/10092/13059
Enduring cognitive, emotional and neurogenic alterations induced by alcohol and methamphetamine exposure in adolescent rats.
Loxton, David A.
A high proportion of young methamphetamine (MA) users simultaneously consume alcohol. However, the potential neurological and behavioural alterations induced by such a drug combination have not been systematically examined. Here, we studied in adolescent rats the long-term effects of alcohol, MA, and an alcohol-MA combination on anxiety-like behaviour, memory, and neurogenesis in the adult hippocampus. Rats received saline (control), ethanol (ETOH, 1.5 g/kg), MA (MA, 2 mg/kg), or ethanol and MA combined (ETHOH-MA, 1.5 g/kg ethanol plus 2 mg/kg MA) via oral gavage, once daily for 5 consecutive days. Open field (OF), elevated plus maze (EPM) and radial arm maze (RAM) tests were conducted following a 15-day withdrawal period. The results showed alterations in exploratory behaviour in the OF in the MA and ETOH-MA groups, and anxiety-like effects in the EPM in all three drug treatment groups. Further, all three drug groups exhibited reference memory deficits in the RAM, but only the combination treatment group displayed alterations in working memory performance. Neurogenesis was assessed by measuring the number of doublecortin(DCX)-void gaps, the length of such gaps and the pattern of arborisation of DCX+ neurons in the dentate gyrus (DG). Both MA and ETOH-MA treatments increased the length of DCX-void gaps in the DG but only ETOH-MA treatment increased the number of such gaps. An increased occurrence and length of the DCX-void gaps correlated with decreased exploratory activity in the OF, and impaired working memory in the RAM was associated with an augmented number of gaps. These findings suggest that persistent behavioural deficits are linked to the alterations in adult hippocampal neurogenesis produced by alcohol and MA exposure, and highlight the potential mental health risks associated with the simultaneous use of both substances.
2016-01-01T00:00:00ZGroundwater contamination in the Heathcote/Woolston area, Christchurch, New Zealand.
http://hdl.handle.net/10092/13050
Groundwater contamination in the Heathcote/Woolston area, Christchurch, New Zealand.
Hertel, Ingrid
Christchurch City (population 360,000) depends entirely on an underlying stratified,
leaky, confined, artesian aquifer system to provide untreated water for its residents
-----and-industries~.------------------------------
Concerns have been raised by the Canterbury Regional Council about brackish water
entering the aquifer system in a localised area in the south-eastern part of the City
(Woolston/Heathcote). Due to the coastal, urban, and geological, setting of the area
several possible groundwater contaminant sources exist and needed to be investigated.
These include: seawater, urban wastes, thermal groundwater, and connate seawater.
A potentiometric survey carried out in the area, combined with water quality
sampling, hydrogeological information from previous studies, and previously
obtained water quality data, provided the basis for a conceptual model of groundwater
contamination. Downward leakage of estuarine water through the confining layer
appears to be the dominant contaminant source.
In the past, the potential risk of seawater intrusion has been regarded as low for the
Christchurch artesian aquifer system. The freshwater/seawater interface was
considered to be located 40km offshore where the uppermost confined aquifer
intersects with the sea at its submarine outcrop. To enhance the understanding of
freshwater and saltwater flow dynamics of the aquifer system, a steady-state crosssectional
finite-difference model along the coast of Christchurch has been constructed
and calibrated. The modelling indicated that the location of the freshwater/seawater
interface is dominated by leakage from the sea through the confining layer and not, as
presumed before, by lateral inflow of seawater through the offshore outcrop.
Consequently the interface location is to be expected much closer to the shoreline at
approximately 3km offshore.
Groundwater contamination in a localised area in Christchurch has demonstrated that
the uppermost confining layer does not act as an effective barrier towards seawater
intrusion where the hydraulic gradient between the sea and the aquifer is directed
downward.
A groundwater level and quality monitoring network, and a groundwater model
specific to the study area, have been constructed to facilitate the future management
of the resource. Immediate pumping restrictions are needed on 3 major abstraction
wells to increase potentiometric heads that currently sit below sea level. An upward
hydraulic gradient between the uppermost aquifer, the estuary, and the confining
layer, is essential to protect the aquifer from ongoing downward leakage of saline
contaminant sources. Ongoing monitoring of water levels and groundwater quality is
recommended. This data will allow more refined modelling of management
scenarios.
1998-01-01T00:00:00ZRing laser dynamics.
http://hdl.handle.net/10092/13048
Ring laser dynamics.
King, Benjamin Thomas
The departure of the behaviour of large ring laser gyros from the ideal
is examined. A detailed description of the experimental operation of
large ring lasers is provided along with several new innovations in
equipment layout, data collection and especially in data reduction.
The limits on gyro performance due to noise are investigated. A review
of literature regarding the fundamental limit placed on gyro resolution
is provided. This limit is due to spontaneous emission in the
gain medium of the laser and it is demonstrated that our ring lasers
approach this quantum limit. Two entirely independent methods for
evaluating the quantum noise induced linewidth are demonstrated to
agree well. One of the methods, which uses a second order autoregressive
model, is able to make accurate linewidth estimates in sub-second
gate times.
A complex model is proposed which accounts for specific observed
light scattering phenomena within a ring laser. This model is compared
with dual beam data taken from C-I and is able to describe
frequency shifts and waveform distortion accurately. The model also
performs favourably when describing locking profiles for low rotation
rates and externally induced perimeter modulation. When locked to
an external signal the ring laser is found to be an extremely sensitive
low frequency vibration detector.
The commissioning of a very large (14 m perimeter) prototype ring
laser gyro, GO, is described along with a comparison with the smaller
( 4 m perimeter) gyros C-I and C-II. This prototype has proven to be
an invaluable testing ground for designs and techniques to be used on
a proposed high precision 16 m perimeter gyro named the Grossring
(G).
1999-01-01T00:00:00ZImproved shortest path algorithms for nearly acyclic graphs.
http://hdl.handle.net/10092/13045
Improved shortest path algorithms for nearly acyclic graphs.
Saunders, Shane
Dijkstra's algorithm solves the single-source shortest path problem on any directed
graph in O(m+nlogn) worst-case time when a Fibonacci heap is used
as the frontier set data structure. Here n is the number of vertices and m is the
number of edges in the graph. If the graph is nearly acyclic, then other algorithms
can achieve a time complexity lower than that of Dijkstra's algorithm.
Abuaiadh and Kingston gave a single source shortest path algorithm for nearly
acyclic graphs with O(m + nlogt) worst-case time complexity, where the new
parameter t is the number of delete-min operations performed in priority queue
manipulation. For nearly acyclic graphs, the value of t is expected to be small,
allowing the algorithm to outperform Dijkstra's algorithm. Takaoka, using a
different definition for acyclicity, gave an algorithm with 0 ( m + n log k) worstcase
time complexity. In this algorithm, the new parameter k is the maximum
cardinality of the strongly connected components in the graph.
This thesis presents several new shortest path algorithms that define trigger
vertices, from which efficient computation of shortest paths through underlying
acyclic structures in the graph is possible. Various definitions for
trigger vertices are considered. One definition decomposes a graph into a
unique set of acyclic structures, where each single trigger vertex dominates
a single corresponding acyclic structure. This acyclic decomposition can be
computed in O(m) time, thus allowing the single source problem to be solved
in 0 ( m + r log r) worst-case time, where r is the resulting number of trigger
vertices in the graph. For nearly acyclic graphs, the value of r is small and
single-source can be solved in close to O(m) worst-case time. It is possible to
define both monodirectional and bidirectional variants of this acyclic decomposition.
This thesis also presents decompositions in which multiple trigger
vertices dominate a single acyclic structure. The trigger vertices of such decompositions
constitute feedback vertex sets. If trigger vertices are defined as
a set of precomputed feedback vertices, then the all-pairs shortest path problem
can be solved in O(mn + nr2 ) worst-case time. This allows all-pairs to
be solved in O(mn) worst-case time when a feedback vertex set smaller than
the square root of the number of edges is known. For suitable graph types,
these new algorithms offer an improvement on the time complexity of previous
algorithms.
2004-01-01T00:00:00Z