Study of decentralised decision models in distributed environments

Many of today's complex systems require effective decision making within uncertain distributed environments. The central theme of the thesis considers the systematic analysis for the representation of decision making organisations. The basic concept of stochastic learning automata provides a framework for modelling decision making in complex systems. Models of interactive decision making are discussed, which result from interconnecting decision makers in both synchronous and sequential configurations. The concepts and viewpoints from learning theory and game theory are used to explain the behaviour of these structures. This work is then extended by presenting a quantitative framework based on Petri Net theory. This formalism provides a powerful means for capturing the information flow in the decision-making process and demonstrating the explicit interactions between decision makers. Additionally, it is also used for the description and analysis of systems that axe characterised as being concurrent, asynchronous, distributed, parallel and/ or stochastic activities. The thesis discusses the limitations of each modelling framework. The thesis proposes an extension to the existing methodologies by presenting a new class of Petri Nets. This extension has resulted in a novel structure which has the additional feature of an embedded stochastic learning automata. An application of this approach to a realistic decision problem demonstrates the impact that the use of an artificial intelligence technique embedded within Petri Nets can have on the performance of decision models

Dynamic responses of Indian Summer Monsoon variability during past warm intervals

The South Asian or Indian Summer Monsoon (ISM) is an iconic reflection of land-ocean-atmosphere inter- actions on Earth, affecting over a billion people. Future predictions of northern hemisphere monsoon rainfall are fraught with large uncertainties in the Intergovernmental Panel on Climate Change (IPCC) reports. To better understand monsoon rainfall pattern/behaviours in future, we need to investigate its response to cli- matic drivers, including past warm intervals. We present multi-proxy geochemical and vegetation records of monsoon variability from the Bay of Bengal using sediment sequences recovered during the Integrated Ocean Discovery Programme (IODP) expedition 353. We utilise these multi-proxy records to assess re- sponses of ISM dynamics to past warming by comparing Holocene and last interglacial warm intervals at sub-millennial timescale. We integrate proxies’ records and intermediate complexity climate model outputs to present evidence for heterogenous rainfall pattern across global tropical landmasses when comparing the Holocene and last interglacial warm intervals. We also find regional differences in monsoon rainfall pattern along with changing loci of the precipitation when comparing these warm intervals. Further, we will present results of seasonal rainfall variability extremes, inferred from continental and marine proxy data, covering cool and warm climate states of the late Pleistocene

Anti-plasmodial and cholinesterase inhibiting activities of some constituents of Psorospermum glaberrimum

Lenta BN, Devkota KP, Ngouela S, et al. Anti-plasmodial and cholinesterase inhibiting activities of some constituents of Psorospermum glaberrimum. Chemical & Pharmaceutical Bulletin. 2008;56(2):222-226.Glaberianthrone (1), a new bianthrone was isolated from the hexane extract of the stem bark of Psorospermum glaberrimum together with thirteen known compounds: 3-geranyloxyemodin anthrone (2), friedelan-3-one (3), 3-prenyloxyemodin anthrone (4), 3-geranyloxyemodin (5), 3-prenyloxyemodin (6), friedelan-3-ol (7), acetylvismione D (8), betulinic acid (9), 2-geranylemodin (10), bianthrone A2b (11), bianthrone 1a (12), emodin (13) and 2-prenylemodin (14). The structures of the isolated compounds were established by means of spectroscopic methods. The extracts and the isolated compounds were tested in vitro for their anti-plasmodial activity against Plasmodium falciparum (chloroquine resistant strain W2) and for their acetyl- and butyryleholinesterase inhibitory properties. The n-hexane extract showed good anti-plasmodial activity against P falciparum W2 strain, with IC50 of 0.87 mu g/ml. It also exhibited 65.5% and 98.2% of acetyl- and butyrylcholinesterase inhibition at 0.2 mg/ml, respectively. Compounds 2 and 8 showed the best potencies against P falciparum W2 strain with IC50 of 1.68 mu M and 0.12 mu M, (0.66 mu g/ml and 0.054 mu g/ml) respectively. All tested compounds showed good butyrylcholinesterase inhibition activities with compound 12 displaying the best potency (IC50 9.25 +/- 0.25 mu M). All the tested compounds showed weak inhibitory activity against acetylcholinesterase