Design of a scanning laser radar for spaceborne applications, phase 3

Design of scanning laser radar for spaceborne application

Construction and testing of a Scanning Laser Radar (SLR), phase 2

The scanning laser radar overall system is described. Block diagrams and photographs of the hardware are included with the system description. Detailed descriptions of all the subsystems that make up the scanning laser radar system are included. Block diagrams, photographs, and detailed optical and electronic schematics are used to help describe such subsystem hardware as the laser, beam steerer, receiver optics and detector, control and processing electronics, visual data displays, and the equipment used on the target. Tests were performed on the scanning laser radar to determine its acquisition and tracking performance and to determine its range and angle accuracies while tracking a moving target. The tests and test results are described

City regions and polycentricity: the East Midlands urban network

The aims of this paper were to clarify the meaning of the terms city region and polycentricy and to then examine evidence on urban centres in the East Midlands to see how far these terms describe the present configuration of the region

Labour problems in the sugar industry of Ile de France or Mauritius, 1790 - 1842

The island of Mauritius is situated in the south-western Indian Ocean between 19°591, 20°321 south latitude and 57°18 1 , 57° 49 1 east longitude. The nearest landmass of any considerable extent is Madagascar which Iies some 900 km due west of Mauritius; but there are a number of islands and islets in the vicinity, notably Reunion, Rodrigues and the Cargados Carajos, which together with Mauritius constitute the archipelago of the Mascarenes

Cerebral mycotic aneurysm

A case of Streptococcus viridans endocarditis with a subarachnoid haemorrhage, caused by rupture of a mycotic aneurysm of the right middle cerebral artery, is described. Treatment of the aneurysm was conservative. Postmortem findings are presented and discussed.S. Afr. Med. J., 48, 1808 (1974)

Adult nutritional osteomalacia in black patients

Three patients suffering from nutritional osteomalacia are described. Nutritional osteomalacia is rare in Southern Africa, in spite of diets with low vitamin D content, because of the high solar irradiation of the skin. All 3 patients responded biochemically and radiologically to small doses of vitamin D. In 1 patient the radiological changes of secondary hyperparathyroidism are described; this feature is uncommon in nutritional osteomalacia. The possible reasons for nutritional osteomalacia in Blacks are discussed.S. Air. Med. J., 48, 1309 (1974)

Clustering through post inhibitory rebound in synaptically coupled neurons

Post inhibitory rebound is a nonlinear phenomenon present in a variety of nerve cells. Following a period of hyper-polarization this effect allows a neuron to fire a spike or packet of spikes before returning to rest. It is an important mechanism underlying central pattern generation for heartbeat, swimming and other motor patterns in many neuronal systems. In this paper we consider how networks of neurons, which do not intrinsically oscillate, may make use of inhibitory synaptic connections to generate large scale coherent rhythms in the form of cluster states. We distinguish between two cases i) where the rebound mechanism is due to anode break excitation and ii) where rebound is due to a slow T-type calcium current. In the former case we use a geometric analysis of a McKean type model to obtain expressions for the number of clusters in terms of the speed and strength of synaptic coupling. Results are found to be in good qualitative agreement with numerical simulations of the more detailed Hodgkin-Huxley model. In the second case we consider a particular firing rate model of a neuron with a slow calcium current that admits to an exact analysis. Once again existence regions for cluster states are explicitly calculated. Both mechanisms are shown to prefer globally synchronous states for slow synapses as long as the strength of coupling is sufficiently large. With a decrease in the duration of synaptic inhibition both systems are found to break into clusters. A major difference between the two mechanisms for cluster generation is that anode break excitation can support clusters with several groups, whilst slow T-type calcium currents predominantly give rise to clusters of just two (anti-synchronous) populations

Mode Locking in a Periodically Forced Integrate-and-Fire-or-Burst Neuron Model

The minimal “integrate-and-fire-or-burst” (IFB) neuron model reproduces the salient features of experimentally observed thalamocortical relay neuron response properties, including the temporal tuning of both tonic spiking (i.e., conventional action potentials) and post-inhibitory rebound bursting mediated by the low-threshold Ca2+ current, IT. In previous work focusing on experimental and IFB model responses to sinusoidal current injection, large regions of stimulus parameter space were observed for which the response was entrained to periodic applied current, resulting in repetitive burst, tonic, or mixed (i.e., burst followed by tonic) responses. Here we present an exact analysis of such mode-locking in the integrate-and-fire-or-burst model under the influence of arbitrary periodic forcing that includes sinusoidally driven responses as one case. In this analysis, the instabilities of mode-locked states are identified as both smooth bifurcations of an associated firing time map and nonsmooth bifurcations of the underlying discontinuous flow. The explicit construction of borders in parameter space that define the instabilities of mode-locked zones is used to build up the Arnol’d tongue structure for the model. The zones for mode-locking are shown to be in excellent agreement with numerical simulations and are used to explore the observed stimulus dependence of burst versus tonic response of the IFB neuron model

Twelve tips for assessment psychometrics.

It is incumbent on medical schools to show, both to regulatory bodies and to the public at large, that their graduating students are "fit for purpose" as tomorrow's doctors. Since students graduate by virtue of passing assessments, it is vital that schools quality assure their assessment procedures, standards, and outcomes. An important part of this quality assurance process is the appropriate use of psychometric analyses. This begins with development of an empowering, evidence-based culture in which assessment validity can be demonstrated. Preparation prior to an assessment requires the establishment of appropriate rules, test blueprinting and standard setting. When an assessment has been completed, the reporting of test results should consider reliability, assessor, demographic, and long-term analyses across multiple levels, in an integrated way to ensure the information conveyed to all stakeholders is meaningful

Evaluation of peak-picking algorithms for protein mass spectrometry

Peak picking is an early key step in MS data analysis. We compare three commonly used approaches to peak picking and discuss their merits by means of statistical analysis. Methods investigated encompass signal-to-noise ratio, continuous wavelet transform, and a correlation-based approach using a Gaussian template. Functionality of the three methods is illustrated and discussed in a practical context using a mass spectral data set created with MALDI-TOF technology. Sensitivity and specificity are investigated using a manually defined reference set of peaks. As an additional criterion, the robustness of the three methods is assessed by a perturbation analysis and illustrated using ROC curves