Activity and Structure of Auditory Brain Neurons Underlying Phonotactic Behaviour in Female Crickets

A long-standing question in cricket neurobiology is what kind of neuronal mechanism the females use, to recognise the temporal pattern of the male calling song. A delay-line and coincidence detector circuit with five neurons underlying auditory pattern recognition in the bi-spotted cricket Gryllus bimaculatus was identified by Schöneich et al (2015). My results here confirmed the morphology of the five identified neurons. Moreover, the group labeling of the auditory neuropil in cricket brain shown in my thesis demonstrated that there are at least 51 neurons in the auditory neuropil. The cell bodies are grouped into six clusters with five in the hemisphere ipsilateral and one in the hemisphere contralateral to the ring structure. In the previous researches, the mechanisms underlying the temporal processing were mostly explored by testing sound patterns with varied pulse period. Recent behavioural tests were performed by systematically varying single pulse durations or inter-pulse intervals, which also led to the design of a chirp pattern with 5-20-50 ms pulses that is attractive when played forward, but non-attractive when the same pulses are played backward as a 50-20-5 ms chirp pattern. In this thesis, I used these sound paradigms to explore the mechanism underlying the processing of individual pulses and intervals by recording the identified neurons in the pattern recognition circuit in cricket brain. The recordings of the pattern recognition circuit reveal the neurophysiological response properties of the five neurons in response to these sound paradigms. The pattern recognition circuit filters the temporal patterns of the chirps progressively. The tuning of the coincidence detector (LN3) and the feature detector (LN4) to the stimuli with varied intervals matched the behavioural tuning but did not reflect the behavioural responses when the duration of pulses were varied. The results also demonstrate that the mechanisms underlying the filtering of pulses or intervals in the pattern recognition circuit may be different. The processing of a train of pulses was accumulative and the activity elicited by a sound pulse in the pattern recognition circuit influences the subsequent responses. One single long interval is sufficient for a reduced activity in LN4 compared to the normal chirp. However, when intervals were kept constant, it required at least three consecutive long pulses for LN4 to respond differently compared to the normal pulses. The attractive and non-attractive patterns elicited a very similar level of activity in the feature detector LN4 in terms of AP/chirp. Further exploration is required to clarify the possible reason for this discrepancy between the neural and behavioural activity

Efficient key management in wireless sensor network security

Wireless sensor network is a multi-hop ad hoc network formed by a large number of low-cost micro-sensor nodes which communicate through radio channels. It is widely used in many areas in modern society and attracts a lot of attention from researchers. This research is on wireless sensor network security and it focuses on key management in hierarchical wireless sensor networks. Through literature review, the drawback and weakness of existing key management schemes are analyzed from various aspects including key establishment, key distribution, key update, authentication and node operation mechanism. Assessment criteria for key management scheme are proposed under different requirements and constraints of wireless sensor networks. The security criteria cover keying model, key distribution, key update, node operation and resilience. For cluster based hierarchical wireless sensor networks, an assistant node is introduced in a cluster to deal with the situation of cluster head compromise and to keep the member nodes securely staying in the network. With introduction of assistant nodes, a complete secure efficient hierarchical key management scheme (SEHKM) for wireless sensor network is proposed. The scheme supports three types of keys and the big improvement over existing key management schemes is on group key update, which is based on pseudo-random numbers and group Diffie-Hellman. The analysis and evaluation have shown that that SEHKM offers strong security with efficient operation from energy consumption point of view

Class of Quadratic Almost Bent Functions That Is EA-Inequivalent to Permutations

The permutation relationship for the almost bent (AB) functions in the finite field is a significant issue. Li and Wang proved that a class of AB functions with algebraic degree 3 is extended affine- (EA-) inequivalent to any permutation. This study proves that another class of AB functions, which was developed in 2009, is EA-inequivalent to any permutation. This particular AB function is the first known quadratic class EA-inequivalent to permutation

Making and identifying optical superposition of very high orbital angular momenta

We report the experimental preparation of optical superpositions of high orbital angular momenta(OAM). Our method is based on the use of spatial light modulator to modify the standard Laguerre-Gaussian beams to bear excessive phase helices. We demonstrate the surprising performance of a traditional Mach-Zehnder interferometer with one inserted Dove prism to identify these superposed twisted lights, where the high OAM numbers as well as their possible superpositions can be inferred directly from the interfered bright multiring lattices. The possibility of present scheme working at photon-count level is also shown using an electron multiplier CCD camera. Our results hold promise in high-dimensional quantum information applications when high quanta are beneficial.Comment: Submitted for publication consideration (4 figures