An intruder model for verifying termination in security protocols

We formally describe an intruder that is suitable for checking fairness properties of security protocols. The intruder is proved to be equivalent to the Dolev-Yao intruder that respects the resilient communication channels assumption, in the sense that, if a fairness property holds in one of these models, it also holds in the other

A constructive proof of the Heine-Borel covering theorem for formal reals

The continuum is here presented as a formal space by means of a finitary inductive definition. In this setting a constructive proof of the Heine-Borel covering theorem is given

Change in the behaviors and spatial use of Canada lynx (Lynx canadensis) over time at John Ball Zoo

Felines are popular attractions at zoos across the country, even more so when young animals are involved. As such caretakers strive to ensure that their animal’s needs are met, and individuals display healthy behaviors and activity levels in comparison to their wild counterparts (Mcphee & Carlstead, 2010). However, cats, being wide-ranging carnivores, are known to be prone to stereotypical behaviors which can be detrimental to an animal’s health (Clubb & Mason, 2003). At John Ball Zoo in Grand Rapids, Michigan, we observed the behaviors and spatial use of 3 Canada lynx (Lynx canadensis) during the summer of 2020; an adult male, an adult female, and the offspring of the two, a female kitten born in 2020. The adult male and adult female were also observed during the summers of 2018 and 2019. Our goal in observing the cats was to determine whether changes in the cats’ social structure and changes in their enclosure affected the overall behavior, spatial use, and activity levels of the lynx

The role of GPS2 in regulating lipid metabolism and inflammation in adipose tissue

Type 2 diabetes is an increasingly prevalent disease posing great burdens to healthcare, in which obesity and adipose tissue (AT) dysfunction are central components of disease progression. Impairment of insulin signaling and inflammation in AT can trigger insulin resistance but an improved understanding of metabolic dysfunction during disease progression is necessary to identify novel targets for therapeutics. G-protein pathway suppressor 2 (GPS2) plays an important role as a mediator of lipid metabolism and inflammatory responses, both processes regulating insulin resistance, but GPS2 exact function in AT remains unknown. These data suggest GPS2 in AT plays an important role in systemic regulation of metabolic homeostasis and dissecting GPS2 function in AT is therefore critical for understanding how metabolic and inflammatory pathways are inter-regulated during the development of insulin resistance. These studies describe the characterization of the adipocyte-specific GPS2 knockout (GPS2-AKO) mouse model. A novel layer of regulation in the insulin signaling cascade was identified, based on ubiquitin conjugating enzyme E2N (Ubc13)-mediated K63 ubiquitination of protein kinase B (AKT). GPS2 was found to be a negative regulator of this pathway through inhibition of Ubc13. Loss of GPS2 promoted AKT hyperubiquitination and activation and enhanced insulin signaling in adipocytes, a mechanism conserved in other cell types. Phenotypic characterization of GPS2-AKO mice showed they developed increased body weight and AT mass when fed chow diet. The white AT (WAT) was characterized by adipocyte hypertrophy, a result of impaired lipolysis and increased lipogenesis. Similarly, brown AT (BAT) acquired a WAT phenotype caused by increased lipid accumulation from compromised lipolysis and defective mitochondrial biogenesis. Despite significant increases in adiposity, GPS2-AKO mice had improved systemic insulin sensitivity due to enhanced insulin signaling and lipid storage capacity. Observations indicated GPS2-AKO mice on high fat diet (HFD) became excessively obese and inflamed, yet displayed reduced peripheral tissue lipid deposition and remained metabolically healthy. This work describes how GPS2 modulates systemic metabolism by regulating insulin signaling, lipid storage capacity, mitochondrial biogenesis and inflammation. Dissecting GPS2 function in AT provides insight into points of regulatory convergence among pathways connecting AT to systemic metabolic regulation, helping to uncover innovative targets for the treatment of metabolic disorders

A causal model for creating public value (in institutional voids)—the case of Lesvos

The Greek island of Lesvos is a holiday destination that became the main entry point for forced migrants to Europe during 2015 and 2016. These circumstances of disruptive societal change are used as the basis for developing a causal and dynamic model that creates public value in institutional voids. The clash between a holiday location and a humanitarian-ecological disaster and the fact that volunteers were the frontline response at the border of the EU in a politically complex situation made this, at the time, a very special case. The attention of celebrities and the media, Lesvos’ geographical proximity to Turkey, the historical conflicts between the two neighbouring countries, the lack of interaction between local people and the involvement of international NGOs spurred conflicts between various actors, causing social fragmentation on the island. The model identifies the core aspects of strengthening social capital and building trust to counter such societal fragmentation. Following Archer’s morphogenetic approach as a meta-concept, and the identification of causalities for understanding the social dynamics on Lesvos as a starting point, an extended version of Moore’s public value concept was used to build the empirical basis for the development of the model. [...] Although the paper draws on a case study that is relevant to migration studies, it is not a migration study, but rather an attempt to use and improve “social-theory reflection” by applying a systems thinking approach as we embark on addressing public value creation, social problems and social-systems transformation (in institutional voids)

The Audit Logic: Policy Compliance in Distributed Systems

We present a distributed framework where agents can share data along with usage policies. We use an expressive policy language including conditions, obligations and delegation. Our framework also supports the possibility to refine policies. Policies are not enforced a-priori. Instead policy compliance is checked using an a-posteriri auditing approach. Policy compliance is shown by a (logical) proof that the authority can systematically check for validity. Tools for automatically checking and generating proofs are also part of the framework.\u

Love it or List it: Enclosure Alterations Affect Behavior of Canada Lynx at John Ball Zoo

Environmental variables influence animal behavior, and routines of captive animals often alter when individuals are moved between zoos, their social group changed, or enclosure altered. In 2018, two Canada lynx were introduced to John Ball Zoo, then their exhibit subsequently modified in 2019. We used scan sampling with ZooMonitor to quantify behaviors and enclosure use of individuals every 30 sec in 30 minute bouts of sampling, comparing patterns in 2018 and 2019. Both cats used inconspicuous resting sites extensively, but the specific sites changed from 2018 to 2019. The male’s daily activities changed little, incorporating the same locomotion paths both years. The female was more active in 2019 than 2018, but sought resting sites above visitors both years. Overall, both cats sought sites hidden by vegetation in 2018, but adjusted to its removal in 2019

An Audit Logic for Accountability

We describe and implement a policy language. In our system, agents can distribute data along with usage policies in a decentralized architecture. Our language supports the specification of conditions and obligations, and also the possibility to refine policies. In our framework, the compliance with usage policies is not actively enforced. However, agents are accountable for their actions, and may be audited by an authority requiring justifications.Comment: To appear in Proceedings of IEEE Policy 200