Clearing Contamination in Large Networks

In this work, we study the problem of clearing contamination spreading through a large network where we model the problem as a graph searching game. The problem can be summarized as constructing a search strategy that will leave the graph clear of any contamination at the end of the searching process in as few steps as possible. We show that this problem is NP-hard even on directed acyclic graphs and provide an efficient approximation algorithm. We experimentally observe the performance of our approximation algorithm in relation to the lower bound on several large online networks including Slashdot, Epinions and Twitter. The experiments reveal that in most cases our algorithm performs near optimally

A Review of Ten Years Assistance to the Mine Action Programme in Mozambique

Mine action has played a role in Mozambique\u27s achievements over the past decade by opening infrastructure networks, reducing the toll of casualties from landmines and unexploded ordnance (UXO), assisting landline survivors, and clearing hazards that posed a danger to lives and a constraint on development for many communities. As is true for most activities in Mozambique, observers with the benefit of hindsight can point to many ways in which mine action organisations and the programme overall could have done better. But in broad terms, the outcomes are positive. Casualties are down dramatically, and travel in the country is basically unimpeded by explosive contamination. Large areas that were suspected of contamination have been released for safe use by civilians through survey and clearance. The wellbeing of people in hundreds of communities has been enhanced - in many cases, dramatically so - by mine action. In addition, Mozambique has played an active and high profile within the Ottawa process, and has met its international treaty obligations to date

Voxel-wise comparisons of cellular microstructure and diffusion-MRI in mouse hippocampus using 3D Bridging of Optically-clear histology with Neuroimaging Data (3D-BOND)

A key challenge in medical imaging is determining a precise correspondence between image properties and tissue microstructure. This comparison is hindered by disparate scales and resolutions between medical imaging and histology. We present a new technique, 3D Bridging of Optically-clear histology with Neuroimaging Data (3D-BOND), for registering medical images with 3D histology to overcome these limitations. Ex vivo 120 × 120 × 200 μm resolution diffusion-MRI (dMRI) data was acquired at 7 T from adult C57Bl/6 mouse hippocampus. Tissue was then optically cleared using CLARITY and stained with cellular markers and confocal microscopy used to produce high-resolution images of the 3D-tissue microstructure. For each sample, a dense array of hippocampal landmarks was used to drive registration between upsampled dMRI data and the corresponding confocal images. The cell population in each MRI voxel was determined within hippocampal subregions and compared to MRI-derived metrics. 3D-BOND provided robust voxel-wise, cellular correlates of dMRI data. CA1 pyramidal and dentate gyrus granular layers had significantly different mean diffusivity (p > 0.001), which was related to microstructural features. Overall, mean and radial diffusivity correlated with cell and axon density and fractional anisotropy with astrocyte density, while apparent fibre density correlated negatively with axon density. Astrocytes, axons and blood vessels correlated to tensor orientation

Monitoring of Single-Cell Responses in the Optic Tectum of Adult Zebrafish with Dextran-Coupled Calcium Dyes Delivered via Local Electroporation

Kassing V, Engelmann J, Kurtz R. Monitoring of Single-Cell Responses in the Optic Tectum of Adult Zebrafish with Dextran-Coupled Calcium Dyes Delivered via Local Electroporation. PLoS ONE. 2013;8(5): e62846.The zebrafish (Danio rerio) has become one of the major animal models for in vivo examination of sensory and neuronal computation. Similar to Xenopus tadpoles neural activity in the optic tectum, the major region controlling visually guided behavior, can be examined in zebrafish larvae by optical imaging. Prerequisites of these approaches are usually the transparency of larvae up to a certain age and the use of two-photon microscopy. This principle of fluorescence excitation was necessary to suppress crosstalk between signals from individual neurons, which is a critical issue when using membrane-permeant dyes. This makes the equipment to study neuronal processing costly and limits the approach to the study of larvae. Thus there is lack of knowledge about the properties of neurons in the optic tectum of adult animals. We established a procedure to circumvent these problems, enabling in vivo calcium imaging in the optic tectum of adult zebrafish. Following local application of dextran-coupled dyes single-neuron activity of adult zebrafish can be monitored with conventional widefield microscopy, because dye labeling remains restricted to tens of neurons or less. Among the neurons characterized with our technique we found neurons that were selective for a certain pattern orientation as well as neurons that responded in a direction-selective way to visual motion. These findings are consistent with previous studies and indicate that the functional integrity of neuronal circuits in the optic tectum of adult zebrafish is preserved with our staining technique. Overall, our protocol for in vivo calcium imaging provides a useful approach to monitor visual responses of individual neurons in the optic tectum of adult zebrafish even when only widefield microscopy is available. This approach will help to obtain valuable insight into the principles of visual computation in adult vertebrates and thus complement previous work on developing visual circuits

Socio-economic impact of GMOs on African consumers

The debate surrounding genetically modified organisms (GMOs) remains an important one for consumers and consumer organisations the world over, and is characterized by strong views for, and against the technology. The debate is of particular interest to Africa, where the countries are yet to embrace the new technology and where food security challenges tend to amplify the dilemma faced by decision-makers. Consumers, represented through the work of consumer organizations, are a very active and vocal constituency in this debate, as it unfolds in Africa.The objective of this paper is to inform the reader on how the consumer movement has contributed to the GMO debate in Africa in the past few years and to highlight the potential socio-economic impacts on African consumers. Firstly, the paper summarises the consumer movement and its work with the Joint Advocacy Project on GMOs; and secondly looks at the potential social, ethical and cultural impacts. Economic and environmental impacts are also discussed. The Socio-Economic Impact Assessment tool is highlighted as one of several tools to guide bio-safety decision-making policy. A few recommendations and policy implications are given at the end of the paper

THE ECOLOGICAL IMPACT OF TRANSPORTATION INFRASTRUCTURE

Abstract There is a long-standing debate over whether new roads unavoidably lead to environmental damage, especially forest loss, but causal identification has been elusive. Using multiple causal identification strategies, we study the construction of new rural roads to over 100,000 villages and the upgrading of 10,000 kilometers of national highways in India. The new rural roads had precisely zero effect on local deforestation. In contrast, the highway upgrades caused substantial forest loss, which appears to be driven by increased timber demand along the transportation corridors. In terms of forests, last mile connectivity had a negligible environmental cost, while expansion of major corridors had important environmental impacts