Machine Learning and the Cognitive Basis of Natural Language

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Machine Learning Theory and Practice as a Source of Insight into Universal Grammar

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The Liberian Truth and Reconciliation Commission: reconciling or re-dividing Liberia?

After 14 years of civil war and violence followed by the momentous and rather unusual elections of 2005, in which a woman defeated a footballer for the presidency, Liberia has seen over six years of state reconstruction and relative peace. Two recent announcements have, however, served as a warning to the extent of progress. The most recent is President Ellen Johnson-Sirleaf’s declaration that she will, despite previous statements to the contrary, stand for re-election in 2011 due to shortcomings in progress. The announcement preceding Johnson-Sirleaf’s was made in the form of the report of the Liberian Truth and Reconciliation Commission (TRC). It recommended that Johnson-Sirleaf, and indeed many others accused of involvement in the war, should be barred from public office for the next 30 years, and still more should stand trial on charges of war crimes. Four important questions arise. First, what was the mandate and findings of the TRC? Second, how has Liberia and the wider international community reacted to the final report? Third, has the TRC fulfilled its mandate and contributed to a process of reconciliation? Finally, and in a much broader sense, where does the TRC stand relative to the much wider liberal peace model

Biophysical and pharmacological characterisation of recombinant and native rat P2X7 receptors

P2X7 receptors exhibit a mainly non-neuronal localisation on immune and glial cells and primarily function as non-selective cation channels. After prolonged or repeated exposure to agonist, functional and cellular changes occur: the formation of a large diameter pore, cell lysis and the release of mature, biologically active interleukin-1β (IL-1β) a potent inflammatory cytokine. It is this repertoire of functions, along with its localisation that underlies the hypothesis for its involvement in pain processing. The biophysics and pharmacology of rat P2X7 receptors were investigated using stable cell lines. Increases in the current amplitude were shown to be dependent upon the agonist concentration and current deactivation was agonist application number and voltage dependent. These results increased our understanding of the receptor, but have also had implications for the design of protocols to investigate antagonist potency and efficacy. GSK31418A was identified as a potent, reversible and voltage-independent antagonist of rat and human P2X7 receptors. GSK314181A was >10000 fold selective over P2X4 receptors and >1000 fold selective over P2X2/3 receptors. GSK314181A produced a significant reversal of FCA-induced hypersensitivity when profiled in vivo, providing further validation of the role of P2X7 receptors in inflammatory pain. Although the influence of glia cells on neuronal activity in the CNS is now well documented, the role of peripheral glia, Schwann cells and satellite cells of sensory ganglia, is less well established. Non-neuronal cells in DRG cultures were shown to express P2X7 receptors by pharmacological, biophysical and immunofluorescence techniques. Native P2X7 receptors expressed on these cells were shown to have many of the properties of recombinant P2X7 receptors, in regards to the response to agonist activation and pharmacology. Finally, I have shown that Lamotrigine is an effective inhibitor of recombinant rat and human P2X7 receptors and native P2X7 receptors expressed in DRG. The potent inhibition of human P2X7 by Lamotrigine was replicated with the chemical analogue and neuroprotective agent Sipatrigine. However, little effect was recorded for a P2X7 antagonist in two models of epileptiform activity studies

Perceiving environmental structure from optical motion

Generally speaking, one of the most important sources of optical information about environmental structure is known to be the deforming optical patterns produced by the movements of the observer (pilot) or environmental objects. As an observer moves through a rigid environment, the projected optical patterns of environmental objects are systematically transformed according to their orientations and positions in 3D space relative to those of the observer. The detailed characteristics of these deforming optical patterns carry information about the 3D structure of the objects and about their locations and orientations relative to those of the observer. The specific geometrical properties of moving images that may constitute visually detected information about the shapes and locations of environmental objects is examined

Investigating steam penetration using thermometric methods in dental handpieces with narrow internal lumens during sterilizing processes with non-vacuum or vacuum processes

Background: Dental handpieces are required to be sterilized between patient use. Vacuum steam sterilization processes with fractionated pre/post-vacuum phases or unique cycles for specified medical devices, are required for hollow instruments with internal lumens to assure successful air removal. Entrapped air will compromise achievement of required sterilization conditions. Many countries and professional organisations still advocate non-vacuum sterilization processes for these devices. Aim: To investigate non-vacuum downward/gravity displacement, type-N steam sterilization of dental handpieces, using thermometric methods to measure time to achieve sterilization temperature at different handpiece locations. Methods: Measurements at different positions within air turbines were undertaken with thermocouples and dataloggers. Two examples of commonly used UK benchtop steam sterilizers were tested; a non-vacuum benchtop sterilizer (Little Sister 3, Eschmann, UK) and a vacuum benchtop sterilizer (Lisa, W&H, Austria). Each sterilizer cycle was completed with three handpieces and each cycle in triplicate. Findings: A total of 140 measurements inside dental handpiece lumens were recorded. We demonstrate that the non-vacuum process fails (time range 0-150 seconds) to reliably achieve sterilization temperatures within the time limit specified by the International standard (15 seconds equilibration time). The measurement point at the base of the handpiece failed in all test runs (n=9) to meet the standard. No failures were detected with the vacuum steam sterilization type B process with fractionated pre-vacuum and post-vacuum phases. Conclusion: Non-vacuum downward/gravity displacement, type-N steam sterilization processes are unreliable in achieving sterilization conditions inside dental handpieces and the base of the handpiece is the site most likely to fail

Failure of non-vacuum steam sterilization processes for dental handpieces

Background: Dental handpieces are used in critical and semi-critical operative interventions. Although a number of dental professional bodies recommend that dental handpieces are sterilized between patient use there is a lack of clarity and understanding of the effectiveness of different steam sterilization processes. The internal mechanisms of dental handpieces contain narrow lumens (0·8-2·3mm) which can impede the removal of air and ingress of saturated steam required to achieve sterilization conditions. Aim: To identify the extent of sterilization failure in dental handpieces using a non-vacuum process. Methods: In-vitro and in-vivo investigations were conducted on commonly used UK benchtop steam sterilizers and three different types of dental handpieces. The sterilization process was monitored inside the lumens of dental handpieces using thermometric (TM) methods (dataloggers), chemical indicators (CI) and biological indicators (BI). Findings: All three methods of assessing achievement of sterility within dental handpieces that had been exposed to non-vacuum sterilization conditions demonstrated a significant number of failures (CI=8/3,024(fails/n tests); BI=15/3,024; TM=56/56) compared to vacuum sterilization conditions (CI=2/1,944; BI=0/1,944; TM=0/36). The dental handpiece most likely to fail sterilization in the non-vacuum process was the surgical handpiece. Non-vacuum sterilizers located in general dental practice had a higher rate of sterilization failure (CI=25/1,620; BI=32/1,620; TM=56/56) with no failures in vacuum process. Conclusion: Non-vacuum downward/gravity displacement, type-N steam sterilizers are an unreliable method for sterilization of dental handpieces in general dental practice. The handpiece most likely to fail sterilization is the type most frequently used for surgical interventions

What is binocular disparity?

What are the geometric primitives of binocular disparity? The Venetian blind effect and other converging lines of evidence indicate that stereo-scopic depth perception derives from disparities of higher-order structure in images of surfaces. Image structure entails spatial variations of in-tensity, texture, and motion, jointly structured by observed surfaces. The spatial structure of bin-ocular disparity corresponds to the spatial struc-ture of surfaces. Independent spatial coordinates are not necessary for stereoscopic vision. Stere-opsis is highly sensitive to structural disparities associated with local surface shape. Disparate positions on retinal anatomy are neither neces-sary nor sufficient for stereopsis