How a Blister Heals

We use experiments to study the dynamics of the healing of a blister, a localized bump in a thin elastic layer that is adhered to a soft substrate everywhere except at the bump. We create a blister by gently placing a glass cover slip on a PDMS substrate. The pressure jump across the elastic layer drives fluid flow through micro-channels that form at the interface between the layer and the substrate; these channels coalesce at discrete locations as the blister heals and eventually disappear at a lower critical radius. The spacing of the channel follows a simple scaling law that can be theoretically justified, and the kinetics of healing is rate limited by fluid flow, but with a non-trivial dependence on the substrate thickness that likely arises due to channelization. Our study is relevant to a variety of soft adhesion scenarios

Sierra Leone fish value chain analysis with special emphasis on Tonkolili District

The USAID-funded Sierra Leone Feed the Future (FtF) Agriculture Project implemented by WorldFish has completed its initial pilot phase (July 2015 to September 2016). During this phase, the project identified and tested interventions to develop integrated agriculture-aquaculture (IAA) farming systems and associated value chains to enhance food, nutrition and livelihood outcomes for rural households in Tonkolili District. This project emphasizes rehabilitation and improvement of fish and rice farming systems combined with nutritious vegetable crops. The assessment of existing fish and rice value chains in Sierra Leone was a key component of this initial phase to improve understanding of current farming systems and identify opportunities for interventions to increase productivity and income and improve nutrition among rural households in Tonkolili District. This report presents the key findings of the fish value chain assessment, with an emphasis on the development of the aquaculture sector and recommendations for potential value chain interventions in marine and freshwater fisheries and aquaculture sectors

A Dimensional Model of Psychopathology Among Homeless Adolescents: Suicidality, Internalizing, and Externalizing Disorders

The present study examined associations among dimensions of suicidality and psychopathology in a sample of 428 homeless adolescents (56.3% female). Confirmatory factor analysis results provided support for a three-factor model in which suicidality (measured with lifetime suicidal ideation and suicide attempts), internalizing disorders (assessed with lifetime diagnoses of major depressive episode and post-traumatic stress disorder), and externalizing disorders (indicated by lifetime diagnoses of conduct disorder, alcohol abuse, and drug abuse) were positively intercorrelated. The findings illustrate the utility of a dimensional approach that integrates suicidality and psychopathology into one model

Deduction with XOR Constraints in Security API Modelling

We introduce XOR constraints, and show how they enable a theorem prover to reason effectively about security critical subsystems which employ bitwise XOR. Our primary case study is the API of the IBM 4758 hardware security module. We also show how our technique can be applied to standard security protocols

Using Digital Traces for User Profiling: the Uncertainty of Identity Toolset

People manage a spectrum of identities in cyber domains. Profiling individuals and assigning them to distinct groups or classes have potential applications in targeted services, online fraud detection, extensive social sorting, and cyber-security. This paper presents the Uncertainty of Identity Toolset, a framework for the identification and profiling of users from their social media accounts and e-mail addresses. More specifically, in this paper we discuss the design and implementation of two tools of the framework. The Twitter Geographic Profiler tool builds a map of the ethno-cultural communities of a person's friends on Twitter social media service. The E-mail Address Profiler tool identifies the probable identities of individuals from their e-mail addresses and maps their geographical distribution across the UK. To this end, this paper presents a framework for profiling the digital traces of individuals

Discovery and Sanctions for Discovery Abuse.

Abstract Forthcoming

Discovery and Sanctions for Discovery Abuse.

Abstract Forthcoming

Relief or agricultural development? Emergency seed projects, farmer seed systems and the dissemination of modern varieties in Mali and Niger

Emergency seed projects tend to be implemented in response to natural disasters such as drought, flooding, cyclones, hurricanes, and civil conflict, particularly those involving population displacement or return. The assumption on which these projects are based presumes that farmers lose or eat their seed so that seed is no longer locally available or accessible. Recent research, however, haschallenged this assumption (Longley and Sperling 2002). Studies undertaken in southern Sudan (Jones et al. 2002), Somalia (Longley et al. 2001), southern Africa (Friis-Hansen and Rohrbach 1993), Rwanda (Sperling 1996), and Sierra Leone (Longley 1997) have shown that not all farmers lose their seed, and - even if they do - seed is often locally available through grain markets or from farmers in neighboring areas. Implicit in such findings is the need to reconsider the aims and modalities of conventional emergency seed projects. If it is assumed that farmers affected by disaster have no seed, then the aim of an emergency seed project is ostensibly to provide farmers with something to plant in the forthcoming season. However, as we shall see in section 5, there are, in practice, various other underlying objectives - often unarticulated - for which seed is given in emergencies. One of these underlying aims is the promotion of modern varieties. Some of the existing guidelines on emergency seed provisioning recommend the use of local varieties which tend to be more appropriate than modern or improved varieties (Chemonics 1996); others present a more nuanced view, advising that the choice of varieties will depend on the farming community's pre-disaster situation (ODI 1996). If the objective of an emergency seed intervention is 'to return the local farming system to a situation as close to its predisaster status as possible' (ODI 1996: 16), then modern varieties should only be given if farmers depended on modern varieties prior to the emergency. This paper challenges this position, suggesting that - in some recurrent or long-lasting crisis situations, and provided that adequate varietal trials have been undertaken - carefully chosen modern varieties may usefully increase varietal diversity. Rather than returning to the pre-disaster situation, such an approach aims to enhance the capacity of farmers' seed and agricultural systems. But an intervention that sets out to promote varietal diversity and strengthen local agricultural systems must be implemented very differently to an intervention that aims to provide emergency seed aid. As such, it might best be considered as part of a longer-term rehabilitation strategy as opposed to a short-term relief activity; in other words, seed system support rather than emergency seed provisioning1 (ODI 1996)

Coordination cages as permanently porous ionic liquids

Porous materials are widely used in industry for applications that include chemical separations and gas scrubbing. These materials are typically porous solids, although the liquid state can be easier to manipulate in industrial settings. The idea of combining the size and shape selectivity of porous domains with the fluidity of liquids is a promising one and porous liquids composed of functionalized organic cages have recently attracted attention. Here we describe an ionic-liquid, porous, tetrahedral coordination cage. Complementing the gas binding observed in other porous liquids, this material also encapsulates non-gaseous guests—shape and size selectivity was observed for a series of isomeric alcohols. Three gaseous chlorofluorocarbon guests, trichlorofluoromethane, dichlorodifluoromethane and chlorotrifluoromethane, were also shown to be taken up by the liquid coordination cage with an affinity that increased with their size. We hope that these findings will lead to the synthesis of other porous liquids whose guest-uptake properties may be tailored to fulfil specific functions

Strategic behaviours in a labour market with mobility-restricting contractual provisions: evidence from the National Hockey League

We follow workers' performance along an unbalanced panel dataset over multiple years and study how performance varies at the end of fixed-term contracts, in a labour market where some people face a mobility restricting clause (i.e., a noncompete clause). Focusing on the labour market of the National Hockey League, we analyse players' performance data and contracts with a fixed effect estimator to address empirical limitations in previous studies. We find that, on average, NHL players' performance does not vary. However, our estimations detect substantially heterogeneous behaviours, depending on tenure, perceived expected performance and mobility. Only younger players (i.e., restricted free-agents) with high expected mobility but low expected performance tend to behave strategically and perform better. Differently, older players (i.e., unrestricted free-agents) with high expected mobility tend to underperform, as the option of moving back to European tournaments is more appealing