Modelling mechanical systems

Education should be one of the highest priorities of any country. The ability to pass on knowledge and understanding effectively is a sign of a good educational system. From an engineering perspective, better teaching tools allow for greater understanding by the students making them better engineers. Educational aids have been with us for a long time. Inventions from the abacus to the personal computer, have aided engineering students in faster understanding and application of their work. These aids are costly and sometimes become affordable only when outdated and redundant. A low-cost device that does not date would be the educationalist's ideal solution. To this end, a concept model of a conveyor sorting system was developed using Lego as the design medium. The model is a conveyor belt along which coloured blocks are sorted into bins by pneumatic cylinders. The model is controlled by a personal computer and the Lego interface box. The software is written in Visual Basic

Fundamental Bound on Epidemic Overshoot in the SIR Model

We derive an exact upper bound on the epidemic overshoot for the Kermack-McKendrick SIR model. This maximal overshoot value of 0.2984... occurs at $R_0^*$ = 2.151... Using the general analysis framework presented within, we then consider more complex SIR models, such as those that incorporate vaccination or contact heterogeneity. We analyze models that consider vaccinations and show that the presence of vaccinated individuals decreases the maximum possible overshoot. For epidemics where the contact structure is given by a network, we numerically find that increased contact heterogeneity lowers the maximal overshoot value and weakens the dependency of overshoot on transmission.Comment: 11 pages, 6 figures + 2 supplemental figure

Monitoring retinal changes with optical coherence tomography predicts neuronal loss in experimental autoimmune encephalomyelitis.

BACKGROUND:Retinal optical coherence tomography (OCT) is a clinical and research tool in multiple sclerosis, where it has shown significant retinal nerve fiber (RNFL) and ganglion cell (RGC) layer thinning, while postmortem studies have reported RGC loss. Although retinal pathology in experimental autoimmune encephalomyelitis (EAE) has been described, comparative OCT studies among EAE models are scarce. Furthermore, the best practices for the implementation of OCT in the EAE lab, especially with afoveate animals like rodents, remain undefined. We aimed to describe the dynamics of retinal injury in different mouse EAE models and outline the optimal experimental conditions, scan protocols, and analysis methods, comparing these to histology to confirm the pathological underpinnings. METHODS:Using spectral-domain OCT, we analyzed the test-retest and the inter-rater reliability of volume, peripapillary, and combined horizontal and vertical line scans. We then monitored the thickness of the retinal layers in different EAE models: in wild-type (WT) C57Bl/6J mice immunized with myelin oligodendrocyte glycoprotein peptide (MOG35-55) or with bovine myelin basic protein (MBP), in TCR2D2 mice immunized with MOG35-55, and in SJL/J mice immunized with myelin proteolipid lipoprotein (PLP139-151). Strain-matched control mice were sham-immunized. RGC density was counted on retinal flatmounts at the end of each experiment. RESULTS:Volume scans centered on the optic disc showed the best reliability. Retinal changes during EAE were localized in the inner retinal layers (IRLs, the combination of the RNFL and the ganglion cell plus the inner plexiform layers). In WT, MOG35-55 EAE, progressive thinning of IRL started rapidly after EAE onset, with 1/3 of total loss occurring during the initial 2 months. IRL thinning was associated with the degree of RGC loss and the severity of EAE. Sham-immunized SJL/J mice showed progressive IRL atrophy, which was accentuated in PLP-immunized mice. MOG35-55-immunized TCR2D2 mice showed severe EAE and retinal thinning. MBP immunization led to very mild disease without significant retinopathy. CONCLUSIONS:Retinal neuroaxonal damage develops quickly during EAE. Changes in retinal thickness mirror neuronal loss and clinical severity. Monitoring of the IRL thickness after immunization against MOG35-55 in C57Bl/6J mice seems the most convenient model to study retinal neurodegeneration in EAE

Neurological Disease Rises from Ocean to Bring Model for Human Epilepsy to Life

Domoic acid of macroalgal origin was used for traditional and medicinal purposes in Japan and largely forgotten until its rediscovery in diatoms that poisoned 107 people after consumption of contaminated mussels. The more severely poisoned victims had seizures and/or amnesia and four died; however, one survivor unexpectedly developed temporal lobe epilepsy (TLE) a year after the event. Nearly a decade later, several thousand sea lions have stranded on California beaches with neurological symptoms. Analysis of the animals stranded over an eight year period indicated five clusters of acute neurological poisoning; however, nearly a quarter have stranded individually outside these events with clinical signs of a chronic neurological syndrome similar to TLE. These poisonings are not limited to sea lions, which serve as readily observed sentinels for other marine animals that strand during domoic acid poisoning events, including several species of dolphin and whales. Acute domoic acid poisoning is five-times more prominent in adult female sea lions as a result of the proximity of their year-round breeding grounds to major domoic acid bloom events. The chronic neurological syndrome, on the other hand, is more prevalent in young animals, with many potentially poisoned in utero. The sea lion rookeries of the Channel Islands are at the crossroads of domoic acid producing harmful algal blooms and a huge industrial discharge site for dichlorodiphenyltrichloroethane (DDTs). Studies in experimental animals suggest that chronic poisoning observed in immature sea lions may result from a spatial and temporal coincidence of DDTs and domoic acid during early life stages. Emergence of an epilepsy syndrome from the ocean brings a human epilepsy model to life and provides unexpected insights into interaction with legacy contaminants and expression of disease at different life stages

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto- noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

Postnatal Proteasome Inhibition Induces Neurodegeneration and Cognitive Deficiencies in Adult Mice: A New Model of Neurodevelopment Syndrome

Defects in the ubiquitin-proteasome system have been related to aging and the development of neurodegenerative disease, although the effects of deficient proteasome activity during early postnatal development are poorly understood. Accordingly, we have assessed how proteasome dysfunction during early postnatal development, induced by administering proteasome inhibitors daily during the first 10 days of life, affects the behaviour of adult mice. We found that this regime of exposure to the proteasome inhibitors MG132 or lactacystin did not produce significant behavioural or morphological changes in the first 15 days of life. However, towards the end of the treatment with proteasome inhibitors, there was a loss of mitochondrial markers and activity, and an increase in DNA oxidation. On reaching adulthood, the memory of mice that were injected with proteasome inhibitors postnatally was impaired in hippocampal and amygdala-dependent tasks, and they suffered motor dysfunction and imbalance. These behavioural deficiencies were correlated with neuronal loss in the hippocampus, amygdala and brainstem, and with diminished adult neurogenesis. Accordingly, impairing proteasome activity at early postnatal ages appears to cause morphological and behavioural alterations in adult mice that resemble those associated with certain neurodegenerative diseases and/or syndromes of mental retardation