A neurocomputational model of learning to select actions

We present an extension of a schema-based architecture for action selection, where competition between schemas is resolved using a variation of a neuroanatomically detailed model of the basal ganglia. The extended model implements distinct learning mechanisms for cortical schemas and for units within the basal ganglia. We demonstrate the functionality of the proposed mechanisms by applying the model to two classic neuropsychological tasks, the Wisconsin Card Sorting Task (WCST) and the Probabilistic Reversal Learning Task (PRLT). We discuss how the model captures existing behavioural data in neurologically healthy subjects and PD patients and how to overcome its shortcomings

A signal amplification assay for HSV type 1 viral DNA detection using nanoparticles and direct acoustic profiling

Background: Nucleic acid based recognition of viral sequences can be used together with label-free biosensors to provide rapid, accurate confirmation of viral infection. To enhance detection sensitivity, gold nanoparticles can be employed with mass-sensitive acoustic biosensors (such as a quartz crystal microbalance) by either hybridising nanoparticle-oligonucleotide conjugates to complimentary surface-immobilised ssDNA probes on the sensor, or by using biotin-tagged target oligonucleotides bound to avidin-modified nanoparticles on the sensor. We have evaluated and refined these signal amplification assays for the detection from specific DNA sequences of Herpes Simplex Virus (HSV) type 1 and defined detection limits with a 16.5 MHz fundamental frequency thickness shear mode acoustic biosensor.Results: In the study the performance of semi-homogeneous and homogeneous assay formats (suited to rapid, single step tests) were evaluated utilising different diameter gold nanoparticles at varying DNA concentrations. Mathematical models were built to understand the effects of mass transport in the flow cell, the binding kinetics of targets to nanoparticles in solution, the packing geometries of targets on the nanoparticle, the packing of nanoparticles on the sensor surface and the effect of surface shear stiffness on the response of the acoustic sensor. This lead to the selection of optimised 15 nm nanoparticles that could be used with a 6 minute total assay time to achieve a limit of detection sensitivity of 5.2 × 10M. Larger diameter nanoparticles gave poorer limits of detection than smaller particles. The limit of detection was three orders of magnitude lower than that observed using a hybridisation assay without nanoparticle signal amplification.Conclusions: An analytical model was developed to determine optimal nanoparticle diameter, concentration and probe density, which allowed efficient and rapid optimisation of assay parameters. Numerical analysis and subsequent associated experimental data suggests that the response of the mass sensitive biosensor system used in conjunction with captured particles was affected by i) the coupled mass of the particle, ii) the proximal contact area between the particle and the sensor surface and iii) the available capture area on the particle and binding dynamics to this capture area. The latter two effects had more impact on the detection limit of the system than any potential enhancement due to added mass from a larger nanoparticle

Charge-ice dynamics in the negative thermal expansion material Cd(CN)2_2

We use variable-temperature (150--300\,K) single-crystal X-ray diffraction to re-examine the interplay between structure and dynamics in the ambient phase of the isotropic negative thermal expansion (NTE) material Cd(CN)$_2$. We find strong experimental evidence for the existence of low-energy vibrational modes that involve off-centering of Cd$^{2+}$ ions. These modes have the effect of increasing network packing density---suggesting a mechanism for NTE that is different to the generally-accepted picture of correlated Cd(C/N)$_4$ rotation modes. Strong local correlations in the displacement directions of neighbouring cadmium centres are evident in the existence of highly-structured diffuse scattering in the experimental X-ray diffraction patterns. Monte Carlo simulations suggest these patterns might be interpreted in terms of a basic set of `ice-rules' that establish a mapping between the dynamics of Cd(CN)$_2$ and proton ordering in cubic ice VII.Comment: 5 pages, 5 figures, submitted to PR

A Desktop Universe for the Introductory Astronomy Laboratory

What is a well-intentioned astronomy instructor to do? There is no argument that experience with the real world is desirable in any astronomy course, especially the introductory classes that fulfill the science distribution requirements at many colleges and universities. Though it is a simple matter to take students out of doors, show them the motions of the Sun, Moon, and stars, and have them squint for a few seconds at Saturn\u27s rings through a telescope, these activities represent only a small portion of the subject matter of modern astronomy. It is simply not possible, given the constraints of time, weather, and equipment at most schools, to have students determine the photometric distance of a star cluster, measure the dispersion distance of a pulsar, or confirm Hubble\u27s redshift-distance relation for themselves. [excerpt

Lessons from the TAPS study - Message handling and appointment systems

The Threats to Australian Patient Safety (TAPS) Study collected 648 anonymous reports about threats to patient safety from a representative random sample of Australian general practitioners. These contained any events the GPs felt should not have happened, and would not want to happen again, regardless of who was at fault or the outcome of the event. This series of articles presents clinical lessons resulting from the TAPS study.2 page(s

The Chico Mendes Extractive Reserve: trajectories of agro-extractive development in Amazonia

The Chico Mendes Extractive Reserve (CMER) located in Acre, Brazil in the southwest Amazon is a powerful symbol of the rubber tapper social movement. Created in 1990, the Reserve is named after rubber tapper and union leader Francisco “Chico” Mendes, who was assassinated by ranchers in 1988. The concept of the extractive reserve, a type of sustainable-use protected area, was conceived by rubber tappers to secure land rights and to protect the forests from which they derived their livelihoods. Thirty years since its creation, non-timber forest product (NTFP) extraction maintains a critical role in CMER resident livelihoods, but it is now one of multiple and dynamic trajectories of income generating activities in the CMER. The state government has promoted sustainable development policies aimed at productive and multiple use of forests, including community-based timber management (CBTM). Concomitantly, the scale and scope of small-scale cattle ranching reflecting a growing “cowboy culture” pervasive in Eastern Acre is growing. These forces have brought sociocultural changes to the reserve as CMER residents engage these intertwined trajectories to improve their livelihoods. This article explores the trajectories of multiple development strategies in the CMER. We do this by revisiting and expanding on the principal themes of research of the co-authors – NTFP extraction, cattle ranching, and CBTM.  Increasingly diverse CMER households demand multiple pathways to improve livelihoods, and these trajectories have created new economic opportunities for reserve residents. Although the NTFP sector has experienced some success in market development and valued-added initiatives, investments have not produced a sustainable and diversified extractive sector. Cattle ranching and CBTM have provided economic benefits to reserve residents’ livelihoods, but they have also created internal tensions across the social movement and governments agencies. A strategic vision is required that brings diverse government, non-government and reserve residents together and articulates how these dynamic, linked, and sometimes conflicting trajectories can synergize within a balanced, diversified livelihood framework to ensure long-term sustainability of the CMER

Challenges and pitfalls of antipsychotic prescribing in people with learning disability

No abstract available