Brain microvessel endothelial cells in tissue culture: A model for study of blood-brain barrier permeability

Endothelial cells were prepared from bovine brain microvessels and grown in tissue culture. They contained factor VIII/von Willebrand antigen, the most specific marker available for determination of the endothelial origin of cells in culture. The cultured cells formed complex tight junctions and contained few pinocytotic vessels. These properties are responsible for formation of the blood-brain barrier in vivo. When monolayers of the endothelial cells were exposed briefly to a calcium-free solution or treated with 1.6 M arabinose, distinctive morphological changes occurred in the intercellular contacts. In either case, a normal structure was reestablished following return to control medium. To assess the effect of these treatments on transcellular permeability, we measured the movement of sucrose labeled with carbon 14 across a monolayer of endothelial cells cultured on a collagen-coated nylon mesh. Removal of external calcium increased the rate of sucrose movement by 120%; the arabinose treatment increased transcellular flux by 40%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50304/1/410140403_ftp.pd

Software Assurance for Blockchain Contracts

Blockchain technology is rapidly developing and, with proper execution, is on its way to widespread adoption in many areas outside of the technology sphere. Blockchains have many use cases and one function that can be provided is the idea of “smart contracts”. Smart contracts are applications that are stored on the blockchain that allow trustless transactions between peers. There are risks involved with utilizing these contracts because they can be developed and deployed by anyone with a working knowledge of common programming languages. This leads to issues because once these contracts are pushed to the blockchain it is impossible to change them without a hard fork. This means that vulnerable smart contracts must remain on the blockchain indefinitely, where they are open to exploitation by malicious parties. One suggestion to mitigate this issue is to have a clause that invalidates old contracts if a signed update is pushed. This solution is workable, but this project’s goal is to prevent this problem entirely by developing a testing suite that will allow smart contract developers to assure that their software is as error-free as possible before deploying it to the blockchain. This paper will analyze several popular blockchain platforms that support smart contracts, common vulnerabilities in smart contracts, and the cutting edge of smart contract assurance tools. We will be aggregating and extending this data to create the proposed testing suite

Detecting Malicious Blockchain Transactions Utilizing Anomaly Detection Techniques

"One of the largest emergences in modern technologyis the use of cryptocurrencies, which are recorded transactions in a structure called Blockchain. Of these currencies, one of the largest is called Ethereum, which is a framework built to handle the use of smart contracts, or programs that are run on the Blockchain. Since this is a newer idea, there are many security flaws that come along with the adoption of it. While most of the transactions on the Blockchain can be recorded as legitimate, some are malicious, such as those in the recent DAO attack. In this paper, we want to use anomaly detection to help detect these malicious transactions. We use sites such as etherscan.io, which records all of the transactions on the Ethereum framework, to scrape the necessary data to establish a baseline of what a legitimate transaction should look like. Our goal is to conduct research to find malicious transactions and utilize clustering technology to help us detect when these malicious transactions are taking place.

Ride-Hailing for Autonomous Vehicles: Hyperledger Fabric-Based Secure and Decentralize Blockchain Platform

Ride-hailing and ride-sharing applications have recently gained popularity as a convenient alternative to traditional modes of travel. Current research into autonomous vehicles is accelerating rapidly and will soon become a critical component of a ride-hailing platforms architecture. Implementing an autonomous vehicle ride-hailing platform proves a difficult challenge due to the centralized nature of traditional ride-hailing architectures. In a traditional ride-hailing environment the drivers operate their own personal vehicles so it follows that a fleet of autonomous vehicles would be required for a centralized ride-hailing platform to succeed. Decentralization of the ride-hailing platform would remove a roadblock along the way to an autonomous vehicle ride-hailing platform by allowing owners of autonomous vehicles to add their vehicles to a community-driven fleet when not in use. Blockchain technology is an attractive choice for this decentralized architecture due to its immutability and fault tolerance. This thesis proposes a framework for developing a decentralized ride-hailing architecture that is verifiably secure. This framework is implemented on the Hyperledger Fabric blockchain platform. The evaluation of the implementation is done by applying known security models, utilizing a static analysis tool, and performing a performance analysis under heavy network load.Comment: arXiv admin note: substantial text overlap with arXiv:1910.0071

A dynamic analysis of the interplay between asynchronous and synchronous communication in online learning: the impact of motivation

With the increased affordances of synchronous communication tools, more opportunities for online learning to resemble face-to-face settings have recently become available. However, synchronous communication does not afford as much time for reflection as asynchronous communication. Therefore, a combination of synchronous and asynchronous communication in e-learning would seem desirable to optimally support learner engagement and the quality of student learning. It is still an open question though, how to best design online learning with a blend of synchronous and asynchronous communication opportunities over time. Few studies have investigated the relationship between learners' actual use of synchronous and asynchronous communication over time. Therefore, this study addressed that relationship in an online course (N = 110), taking into account student motivation, and employing a dynamic inter-temporal perspective. In line with our assumptions, we found some support for the expected association between autonomous motivation and engagement in asynchronous and synchronous communication, be it restricted primarily to the first course period. Also, positive relations between engagement in synchronous and asynchronous communication were found, with the strongest influence from using asynchronous to synchronous communication. This study adds to the knowledge base needed to develop guidelines on how synchronous communication can be combined with asynchronous learning

Leisure experiences in tourist attractions : exploring the motivations of local residents

This study was conducted to explore leisure motivations with regard to tourist attractions. A survey of a convenience sample of residents of Melbourne, Australia, was conducted. The sample was then segmented based on the likelihood of visiting a cross-section of Melbourne\u27s tourist attractions in the next 6 months. Analysis using Unger and Kernan\u27s (1983) Subjective Leisure Scale (SLS) was then undertaken to explore whether there were differences across the segments in terms of their leisure motivations. The results highlight that, within this context, intrinsic satisfaction, perceived freedom and arousal emerged as stronger underlying dimensions of motivations to visit tourist attractions, rather than mastery, spontaneity and involvement. This information provides insights for marketers of tourist attractions with regard to what residents are seeking when they visit local tourist attractions. The information can be used to develop more positive experiences at tourist attractions for this important sector of the market.<br /

A Missense Mutation in the Gene Encoding the Alpha(1) Subunit of the Inhibitory Glycine Receptor in the Spasmodic Mouse

Hereditary hyperekplexia, an autosomal dominant neurologic disorder characterized by an exaggerated startle reflex and neonatal hypertonia, can be caused by mutations in the gene encoding the alpha(1) subunit of the inhibitory glycine receptor (GLRA1). Spasmodic (spd), a recessive neurologic mouse mutant, resembles hyperekplexia phenotypically, and the two disease loci map to homologous chromosomal regions. Here we describe a Glra1 missense mutation in spd that results in reduced agonist sensitivity in glycine receptors expressed in vitro. We conclude that spd is a murine homologue of hyperekplexia and that mutations in GLRA1/Glra1 can produce syndromes with different inheritance patterns