STORRE Community: This community contains the ePrints and eTheses produced by Computing Science and Mathematics staff and students.
http://hdl.handle.net/1893/35
This community contains the ePrints and eTheses produced by Computing Science and Mathematics staff and students.Sun, 14 Apr 2024 16:52:19 GMT2024-04-14T16:52:19ZOn the non-existence of sympathetic Lie algebras with dimension less than 25
http://hdl.handle.net/1893/35815
Title: On the non-existence of sympathetic Lie algebras with dimension less than 25
Author(s): Garcia Pulido, Ana Lucia; Salgado, Gil
Abstract: In this article we investigate the question of the lowest possible dimension that a sympathetic Lie algebra g can attain, when its Levi subalgebra gL is simple. We establish the structure of the nilradical of a perfect Lie algebra g, as a gL-module, and determine the possible Lie algebra structures that one such g admits. We prove that, as a gL-module, the nilradical must decompose into at least 4 simple modules. We explicitly calculate the semisimple derivations of a perfect Lie algebra g with Levi sub-algebra gL=sl2(C) and give necessary conditions for g to be a sympathetic Lie algebra in terms of these semisimple derivations. We show that there is no sympathetic Lie algebra of dimension lower than 15, independently of the nilradicalâ€™s decomposition. If the nilradical has 4 simple modules, we show that a sympathetic Lie algebra has dimension greater or equal than 25.Fri, 08 Dec 2023 00:00:00 GMThttp://hdl.handle.net/1893/358152023-12-08T00:00:00ZModelling norovirus dynamics within oysters emphasises potential food safety issues associated with current testing & depuration protocols
http://hdl.handle.net/1893/35708
Title: Modelling norovirus dynamics within oysters emphasises potential food safety issues associated with current testing & depuration protocols
Author(s): McMenemy, Paul; Kleczkowski, Adam; Taylor, Nick G H
Abstract: Norovirus is a significant global cause of viral gastroenteritis, with raw oyster consumption often linked to such outbreaks due to their filter-feeding in harvest waters. National water quality and depuration/relaying times are often classified using Escherichia coli, a poor proxy for norovirus levels in shellfish. The current norovirus assay is limited to only the digestive tracts of oysters, meaning the total norovirus load of an oyster may differ from reported results. These limitations motivated this work, building upon previous modelling by the authors, and considers the sequestration of norovirus into observed and cryptic (unobservable) compartments within each oyster. Results show that total norovirus levels in shellfish batches exhibit distinct peaks during the early depuration stages, with each peak's magnitude dependent on the proportion of cryptic norovirus. These results are supported by depuration trial data and other studies, where viral levels often exhibit multiphase decays. This work's significant result is that any future norovirus legislation needs to consider not only the harvest site's water classification but also the total viral load present in oysters entering the market. We show that 62 h of depuration should be undertaken before any norovirus testing is conducted on oyster samples, being the time required for cryptic viral loads to have transited into the digestive tracts where they can be detected by current assay, or have exited the oyster.Fri, 01 Dec 2023 00:00:00 GMThttp://hdl.handle.net/1893/357082023-12-01T00:00:00ZModeling hippocampal theta-coupled gamma oscillations in learning and memory
http://hdl.handle.net/1893/35676
Title: Modeling hippocampal theta-coupled gamma oscillations in learning and memory
Author(s): Samba Shiva, Ashraya
Abstract: Two of the most researched domains in the hippocampus are the oscillatory activity and
encoding and retrieval of patterns in the hippocampal CA1 and CA3 regions. They are, how-
ever, not studied together; and hence, the objective of our work is to study the cross-frequency
coupling of theta-coupled gamma oscillations in CA1 and CA3 regions of the hippocampus
while encoding and retrieving information. We have studied the cross-frequency coupling
of theta-coupled gamma oscillations both individually and in our newly-proposed integrated
model of CA1-CA3 to analyze the effects of Schaffer collaterals and CA1 back-projection
cells on CA1 and CA3 regions of the hippocampus. Due to lack of literary evidence, we have
also contributed our hypotheses about the effects of CA1 back-projection cells on CA1 and
CA3 cell-types. Moreover, we have developed a deterministic rule-based cellular automata
library to study cross-frequency coupling in single-neuron level and population neuronal net-
works at the same time. The discrete model is theta-oscillations-aware and hence encoding
and retrieving of patterns takes place during the half-cycles of theta oscillations.
We have extended the septo-hippocampal population firing rate model proposed by Den-
ham and Borisyuk (2000) to study (i) the influence of inhibitory interneurons, specifically
PV-containing basket cells (BCs) and bistratified cells (BSCs) on theta and theta-coupled
gamma oscillations in both CA1 and CA3 hippocampal networks; (ii) to study Schaffer col-
laterals from CA3 to CA1 and the influence of back-projection cells in CA1 on CA3; (iii) to
analyze and compare the phases of cross-frequency coupling of theta-coupled gamma oscil-
lations among the different cell types in CA1 and CA3 regions; (iv) to study the influence of
external inputs on CA1 and CA3. In our simulations, with constant external inputs, we identify the parameter regions that
generate theta oscillations and that BCs and BSCs in CA1 are in anti-phase, as seen experi-
mentally by Klausberger et. al (2008). Slow-gamma oscillations are generated due to the ac-
tivity of BSCs and BCs in CA1 and CA3, and they are propagated from CA3 to CA1 through
the Schaffer collaterals, as seen in Klausberger et. al (2008) where BSCs were observed to
synchronize PC activity during theta-coupled gamma oscillations in CA1. In CA3, increas-
ing excitation of CA3 pyramidal cells results in theta oscillations without the slow-gamma
coupling. Increasing excitatory input to CA1 pyramidal cells results in steady state and de-
creasing the excitatory input, results in reduced oscillatory activity in both CA1 and CA3 due
to Schaffer collaterals and the feedback projections from CA1 to CA3. This demonstrates
that changes in input excitation can move the networks from oscillatory to non-oscillatory states, comparable to the differences seen in animals between exploratory and resting state.
Further, Mizuseki et. al (2009) observed experimentally that CA1, CA3 and EC are out-
of-theta-phase with each other and that the phase observed in CA1 pyramidal cells are not a
result of a simple integration of phases from CA3, EC or the medial septum. We have thus,
simulated theta-frequency sine-wave inputs from CA3 and EC of relative phases in the model
and observed the same results in our CA1 individual and CA1-CA3 integrated model.
To study encoding and retrieval of patterns in an oscillating model, we took an engineer-
ing approach by developing a discrete modeling system using cellular automata (CA) derived
from the models of Pytte et. al (1991) and Claverol et. al (2002). The aim of this model is
to (i) replicate the oscillatory and phasic results obtained using the continuous modeling ap-
proach and (ii) extend the same model to study storage and recall of patterns in CA1 taking a
theta-oscillations-aware approach.
Encoding and retrieval happen at different half-cycles of theta where information pro-
cessing takes places in the sub-cycles of the slow-gamma oscillations in each half-cycle of
theta oscillation (Cutsuridis et. al, 2010, Hasselmo et. al, 1996). A set of rules is developed
to replicate this for the CA model of CA1. The encoding and retrieval half-cycles are identi-
fied using the basket cell activity, and hence synaptic learning is enabled during the encoding
half-cycle of theta, and is disabled during the recall half-cycle of theta oscillations. This is
also a biologically realistic enhancement for studying learning and recall in theta-coupled
gamma oscillations using a discrete cellular automata approach.Sat, 30 Sep 2023 00:00:00 GMThttp://hdl.handle.net/1893/356762023-09-30T00:00:00ZDeSSR: a Decentralized, Broadcast-Based Scalable Scheduling Reservation Protocol for 6TiSCH Networks
http://hdl.handle.net/1893/35659
Title: DeSSR: a Decentralized, Broadcast-Based Scalable Scheduling Reservation Protocol for 6TiSCH Networks
Author(s): Kumar, Kaushal; Kolberg, Mario
Abstract: The emergence of IPv6 (Internet Protocol Version 6) for low-power wireless communication is considered a breakthrough allowing a densely populated multi-hop network of Internet of Things (IoT) devices to be used for data gathering over a range of 1-2 kilometer (km). However, the communication between the devices has suffered from external interferences and multi-path fading challenge. The Internet Engineering Task Force (IETF) and Institute of Electrical and Electronics Engineers (IEEE) jointly proposed The IPv6 over IEEE 802.15.4 TSCH mode (6TiSCH) to deal with existing challenges and improve network performance to meet key requirements of industrial applications. The 6Top layer integrates TSCH (Time Slotted Channel Hopping)-MAC over IEEE 802.15.4 with the rest of the IPv6 stack where the schedule allocation is performed by scheduling function (SF). However, network scalability remains an open challenge. Specifically, the 6TiSCH Working Group (WG) do not define rules towards optimal schedule allocation over Time Slotted Channel Hopping (TSCH) mode of IEEE 802.15.4. In this paper, we propose Decentralized, and Broadcast-based Scalable Scheduling Reservation Protocol for 6TiSCH Networks (DeSSR). The experimental performance analysis demonstrates strong performance under steady and bursty traffic when compared with current SFs. This makes DeSSR a strong proposal contributing towards improving scalability in large-scale 6TiSCH networks.Sun, 03 Dec 2023 00:00:00 GMThttp://hdl.handle.net/1893/356592023-12-03T00:00:00Z