Some effects of hippocampal lesions on the behaviour of pigeons

The behavioural effects of hippocampal lesions in birds have not previously been investigated, although there is now considerable evidence, which is reviewed here, of structural and histochemical similarities between the avian and the mammalian hippocampus. Therefore, a series of experiments were carried out to study the effects of hippocampal lesions in pigeons, and it was found that they performed more efficiently on both the acquisition and reversal of a 70:30 colour probability discrimination, confirming a prediction derived from the cognitive mapping theory of hippocampal function (O'Keefe and Nadel, 1978). Hippocampal pigeons were also impaired on the serial reversal of a spatial discrimination and on a DRL 10 schedule of reinforcement, but not on the acquisition or the reversal of a simultaneous visual form discrimination, a delayed spatial alternation task, or a delayed colour alternation task. Furthermore, they did not show increased resistance to extinction, except following DRL 10 training, or increased response perseveration in reversal. These effects show many similarities to those that have been found to occur in hippocampal mammals in comparable tasks, and it is proposed, therefore, that the results of the experiments reported in this thesis provide good evidence that the avian hippocampus and the mammalian hippocampus are behaviourally homologous. These results extend the findings by others of structural similarities between the hippocampus in birds and mammals and therefore lend considerable support to the proposal that they are homologous structures. Moreover, in common with much of the mammalian hippocampal data, the present results do not support the response-inhibition, response-shift, or selective attention theories of hippocampal function, but it is argued that they support instead the hypothesis that the hippocampus is involved in the processing of spatial information, and that they are consistent with the cognitive mapping model of the hippocampus proposed by O'Keefe and Nadel (1978)

Professional Reading: Can America Win the Next War?

Believing that conflict characterizes human affairs and that the Soviet leadership considers conflict inevitable and is preparing for it, Drew Middleton, long a military correspondent for The New York Times, suggests that sooner or later the United States may be at war again

The statistics of particle velocities in dense granular flows

We present measurements of the particle velocity distribution in the flow of granular material through vertical channels. Our study is confined to dense, slow flows where the material shears like a fluid only in thin layers adjacent to the walls, while a large core moves without continuous deformation, like a solid. We find the velocity distribution to be non-Gaussian, anisotropic, and to follow a power law at large velocities. Remarkably, the distribution is identical in the fluid-like and solid-like regions. The velocity variance is maximum at the core, defying predictions of hydrodynamic theories. We show evidence of spatially correlated motion, and propose a mechanism for the generation of fluctuational motion in the absence of shear.Comment: Submitted to Phys. Rev. Let

Instability-induced ordering, universal unfolding and the role of gravity in granular Couette flow

Linear stability theory and bifurcation analysis are used to investigate the role of gravity in shear-band formation in granular Couette flow, considering a kinetic-theory rheological model. We show that the only possible state, at low shear rates, corresponds to a 'plug' near the bottom wall, in which the particles are densely packed and the shear rate is close to zero, and a uniformly sheared dilute region above it. The origin of such plugged states is shown to be tied to the spontaneous symmetry-breaking instabilities of the gravity-free uniform shear flow, leading to the formation of ordered bands of alternating dilute and dense regions in the transverse direction, via an infinite hierarchy of pitchfork bifurcations. Gravity plays the role of an 'imperfection', thus destroying the 'perfect' bifurcation structure of uniform shear. The present bifurcation problem admits universal unfolding of pitchfork bifurcations which subsequently leads to the formation of a sequence of a countably infinite number of 'isolas', with the solution structures being a modulated version of their gravity-free counterpart. While the solution with a plug near the bottom wall looks remarkably similar to the shear-banding phenomenon in dense slow granular Couette flows, a 'floating' plug near the top wall is also a solution of these equations at high shear rates. A two-dimensional linear stability analysis suggests that these floating plugged states are unstable to long-wave travelling disturbances.The unique solution having a bottom plug can also be unstable to long waves, but remains stable at sufficiently low shear rates. The implications and realizability of the present results are discussed in the light of shear-cell experiments under 'microgravity' conditions

The patient safety practices of emergency medical teams in disaster zones: a systematic analysis

Introduction: Disaster zone medical relief has been criticised for poor quality care, lack of standardisation and accountability. Traditional patient safety practices of Emergency Medical Teams (EMT) in disaster zones were not well understood. Improving the quality of healthcare in disaster zones has gained importance within global health policy. Ascertaining patient safety practices of EMTs in disaster zones may identify areas of practice that can be improved. Methods: A systematic search of OvidSP, Embase and Medline databases, key journals of interest, key grey-literature texts, the databases of the World Health Organisation (WHO), Médecins Sans Frontieres (MSF) and the International Committee of the Red Cross (ICRC), and Google Scholar were performed. Descriptive studies, case reports, case series, prospective trials and opinion pieces were included with no limitation on date or language of publication. Results: There were 9,685 records, evenly distributed between the peer-reviewed and grey literature. Of these, 30 studies and 9 grey literature texts met the inclusion criteria and underwent qualitative synthesis. From these articles, 302 patient safety statements were extracted. Thematic analysis categorised these statements into 84 themes (total frequency 632). The most frequent themes were limb injury (9%), medical records (5.4%), surgery decision making (4.6%), medicines safety (4.4%) and protocol (4.4%) Conclusion: Patient safety practices of EMTs in disaster zones are weighted towards acute clinical care, particularly surgery. The management of Non-Communicable Disease (NCD) is underrepresented. There is widespread recognition of the need to improve medical record keeping. High-quality data and institutional level patient safety practices are lacking. There is no consensus on disaster zone specific performance indicators. These deficiencies represent opportunities to improve patient safety in disaster zones

How Important Are Those Fracture Zones? Scale Dependent Characteristics Revealed Through Field Studies and an Integrated Hydrological Model of a Mountain Headwater Catchment

Modeling groundwater flow in bedrock can be particularly challenging due to heterogeneities associated with fracture zones. However, fracture zones can be difficult to map, particularly in forested areas where tree cover obscures land surface features. This study presents the evidence of fracture zones in a small, snowmelt-dominated mountain headwater catchment and explores the significance of these fracture zones on groundwater flow in the catchment. A newly acquired bare earth image acquired using LiDAR identifies a previously undetected linear erosion zone that passes near a deep bedrock well at low elevation in the catchment. Borehole geophysical logs indicate more intense fracturing in this well compared to two wells at higher elevation. The well also exhibited a linear flow response during a pumping test, which is interpreted to reflect the influence of a nearby vertical fracture zone. The major ion chemistry and stable isotope composition reveal a slightly different chemical composition and a more depleted isotopic signature for this well compared to other groundwaters and surface waters sampled throughout the catchment. With this evidence of fracturing at the well scale, an integrated land surface – subsurface hydrologic model is used to explore four different model structures at the catchment scale. The model is refined in steps, beginning with a single homogeneous bedrock layer, and progressively adding 1) a network of large-scale fracture zones within the bedrock, 2) a weathered bedrock zone, and 3) an updated LiDAR-derived digital elevation model, to gain insight into how increasing subsurface geological complexity and land surface topography influence model fit to observed data and the various water balance components. Ultimately, all of the models are considered plausible, with similar overall fit to observed data (snow, streamflow, pressure heads in piezometers, and groundwater levels) and water balance results. However, the models with fracture zones and a weathered zone had better fits for the low elevation well. These models contributed slightly more baseflow (~14% of streamflow) compared to models without a weathered zone (~1%). Thus, in the watershed scale model, including a weathered bedrock zone appears to more strongly influence the hydrology than only including fracture zones

Variational approximation for mixtures of linear mixed models

Mixtures of linear mixed models (MLMMs) are useful for clustering grouped data and can be estimated by likelihood maximization through the EM algorithm. The conventional approach to determining a suitable number of components is to compare different mixture models using penalized log-likelihood criteria such as BIC.We propose fitting MLMMs with variational methods which can perform parameter estimation and model selection simultaneously. A variational approximation is described where the variational lower bound and parameter updates are in closed form, allowing fast evaluation. A new variational greedy algorithm is developed for model selection and learning of the mixture components. This approach allows an automatic initialization of the algorithm and returns a plausible number of mixture components automatically. In cases of weak identifiability of certain model parameters, we use hierarchical centering to reparametrize the model and show empirically that there is a gain in efficiency by variational algorithms similar to that in MCMC algorithms. Related to this, we prove that the approximate rate of convergence of variational algorithms by Gaussian approximation is equal to that of the corresponding Gibbs sampler which suggests that reparametrizations can lead to improved convergence in variational algorithms as well.Comment: 36 pages, 5 figures, 2 tables, submitted to JCG