Using Neighborhood Beyond One Hop in Disruption-Tolerant Networks

Most disruption-tolerant networking (DTN) protocols available in the literature have focused on mere contact and intercontact characteristics to make forwarding decisions. Nevertheless, there is a world behind contacts: just because one node is not in contact with some potential destination, it does not mean that this node is alone. There may be interesting end-to-end transmission opportunities through other nearby nodes. Existing protocols miss such possibilities by maintaining a simple contact-based view of the network. In this paper, we investigate how the vicinity of a node evolves through time and whether such information can be useful when routing data. We observe a clear tradeoff between routing performance and the cost for monitoring the neighborhood. Our analyses suggest that limiting a node's neighborhood view to three or four hops is more than enough to significantly improve forwarding efficiency without incurring prohibitive overhead.Comment: 5 pages, 5 figures, 1 tabl

Enhancement of moment resistance of steel beams with initial imperfections and residual stresses by using stiffeners and GFRP plates

The present study proposes three strengthening solutions for wide flange steel beams having residual stresses and initial imperfections. In Solution 1, a midspan web stiffener is applied to such beams, aiming at reducing local web buckling. In Solution 2, two GFRP plates are bonded to the beam flanges in order to reduce local flange buckling. Solution 3 is a combination of the Solutions 1 and 2. Moment resistances of the strengthening systems are numerically evaluated and compared against those of the corresponding bare beam. Key observations obtained include (i) All Solutions 1, 2 and 3 are effective in increasing the moment resistance of the beam structure, (ii) When initial imperfection and residual stresses are excluded, the failure mode of the bare beams is mostly governed by local flange buckling. The moment resistances of the steel beam in Solution 1 are approximately equal to a fully plastic section moment. Meanwhile, the moment resistances of Solutions 2 and 3 are based on GFRP rupture failure mode. The strengthening solutions by using GFRP plates are the most effective while the addition of a web stiffener only plays a minor role, (iii) When initial imperfection and residual stresses are included, the failure mode of the steel beams is governed by local web buckling. The web stiffener in Solutions 1 and 3 plays an important role to increase the beam moment resistances. And (iv) For long spans, the moment resistances of Solutions 2 and 3 are significantly higher than those of Solution 1

A NOVEL DIELECTRIC TECHNIQUE FOR MONITORING THE LYOPHILISATION OF GLOBULAR PROTEINS

Background. The moisture content of lyophilised proteins plays an important role in the stability and long-term storage of these substances. Residual moisture is mainly determined by the combination of formulation factors and the cycle-times of the various stages of lyophilisation. The final drying stage of the lyophilisation process, i.e. secondary drying, is a critical stage in determining the optimum residual moisture level. Some measurement techniques have been developed for in situ monitoring of moisture content during secondary drying. However, all these techniques involved the direct contact of a measurement probe with the freeze-dried material, which may alter the properties of the finished product. There is a challenge, therefore, to establish a non-destructive method for in situ monitoring of water content and the determination of the end point of the lyophilisation process. Aim. The framework of this study was to develop a dielectric technique that is able to monitor water content of a material inside a glass vial. The technique was based on the development of a remote-electrode system, that avoids the introduction of measurement probes into the sample. In the context of this work, a remote electrode system is defined as electrodes that are separated from the sample by a non-conductive and non-dispersive medium, i.e. the glass vial used for the freeze drying process. As an initial development, this study dealt with dielectric measurements on partially hydrated globular proteins, i.e. ovalbumin, lysozyme, and pepsin. Method. The development of the new technique is necessarily based on a detailed knowledge of the dielectric properties of water-protein interactions. The first stage of the project therefore, involved a thorough study of the low frequency dielectric properties of hydrated proteins using conventional parallel plate electrodes. The next stage involved the simulation of a simple remote electrode measurement, by placing non-conductive, non-dispersive polymer films between the sample and parallel plate electrodes. Finally, the study on dielectric measurement of hydrated proteins contained in a glass vial was undertaken with the electrodes attached to the glass vial. Other physical measurements such as FTIR, SEM, XRD, and DSC, were also employed as complementary techniques to characterise hydrated and freeze-dried protein samples. Results. The investigation of the dielectric behaviour of selected hydrated proteins showed two independent mechanisms of proton hoppings in the bulk sample, which were distinctly identified as an anomalous low frequency dispersion and a dielectric loss peak (3 dispersion). An understanding of the polarisation process underpinning the dispersion is based on the cluster model, in which the low frequency dispersion (LFD) is associated with proton hopping between clusters of water molecules (inter-cluster transport), and the 3 dispersion is associated with proton hopping between water molecules in the same cluster (intra-cluster transport). Protons were shown to be the charge carriers involved in both dispersions by investigating the dielectric behaviour of proteins hydrated with deuterated and normal water. Both the LFD and 3 dispersion moved simultaneously toward high frequency with the increase of temperature or hydration. At a certain temperature, however, both dispersions shifted back to lower frequency. This phenomena was identified as a percolation threshold. In the hydration study, the percolation threshold was recognised as critical hydration. This critical hydration was considered due to the monolayer of water molecules network covering a single macromolecule protein, therefore creating an infinite cluster, or known as percolation threshold. The critical hydration was also observed from both the calculation of fractal dimension (Df) and the activation energy (H) of the Arrhenius behaviour at below percolation threshold. For all selected proteins, it was found that below critical hydration level, the proton transport occurred along the surface of protein macromolecule (Df 1.9). With the application of the remote electrode system, it was found that the dielectric properties for the 3 dispersion was unaffected by the insertion of polyethylene films between the sample and the conventional parallel plate electrodes. The dielectric properties for the 3 dispersion was also unaffected in measurement using remote electrode system in the form of custom-made electrodes attached externally to the glass vial. Moreover, the 3 dispersion was still sensitive to the water content, irrespective of which remote electrode system was used. A reasonable correlation (R2 = 93%) was also observed between relaxation times (3) obtained using conventional parallel plate electrodes and the remote electrodes attached to glass vial. Conclusion. The study has revealed the mechanism and interaction of water-protein for hydrated globular proteins. The study has also shown that dielectric measurements using remote electrodes, attached to a glass vial, are applicable for the in situ measurement of water content in materials, for example in the determination of the end point of the lyophilisation process

Solution phase and solid state studies of lanthanoid-calixarene bottlebrush clusters

The conditions required for formation of unusual bottlebrush-shaped lanthanoid coordination clusters were investigated. The known clusters are supported by tetrazole-functionalised p-t-butylcalixarenes, and carboxylate co-ligands. It was confirmed that the lighter lanthanoids form mononuclear complexes, and heavier lanthanoids form bottlebrush clusters. Changing the carboxylate co-ligand had little impact on the complexes formed. Altering the structure of the calixarene had a significant impact. When the t-butyl group was replaced with hydrogen or allyl groups, mononuclear complexes formed

Enhancement of moment resistance of steel beams with initial imperfections and residual stresses by using stiffeners and GFRP plates

The present study proposes three strengthening solutions for wide flange steel beams having residual stresses and initial imperfections. In Solution 1, a midspan web stiffener is applied to such beams, aiming at reducing local web buckling. In Solution 2, two GFRP plates are bonded to the beam flanges in order to reduce local flange buckling. Solution 3 is a combination of the Solutions 1 and 2. Moment resistances of the strengthening systems are numerically evaluated and compared against those of the corresponding bare beam. Key observations obtained include (i) All Solutions 1, 2 and 3 are effective in increasing the moment resistance of the beam structure, (ii) When initial imperfection and residual stresses are excluded, the failure mode of the bare beams is mostly governed by local flange buckling. The moment resistances of the steel beam in Solution 1 are approximately equal to a fully plastic section moment. Meanwhile, the moment resistances of Solutions 2 and 3 are based on GFRP rupture failure mode. The strengthening solutions by using GFRP plates are the most effective while the addition of a web stiffener only plays a minor role, (iii) When initial imperfection and residual stresses are included, the failure mode of the steel beams is governed by local web buckling. The web stiffener in Solutions 1 and 3 plays an important role to increase the beam moment resistances. And (iv) For long spans, the moment resistances of Solutions 2 and 3 are significantly higher than those of Solution 1

How the Home Office does history: empire, time and the making of Britain's mass deportation regime

Since the Immigration Act of 1971, Britain’s Home Secretary has had executive administrative powers to detain and deport non-citizens from the United Kingdom. These powers are the statutory foundation of Britain’s contemporary mass deportation regime. This thesis maps the connected histories through which this regime has emerged. It examines how deportation, criminalisation, and citizenship functioned in British colonial governance, and explores how colonial forms of deportation informed Home Office policies in the long twentieth century: both before, during, and after decolonisation. The thesis argues that it is useful to understand the Home Office as 'doing history.' In other words, the Home Office can be understood as an agent that imagines and acts upon normative views as to how history should progress, how change should be managed, how events should be remembered, and how the past should be recorded and consulted. The Home Office does history in two overlapping ways. First, it entrenches the patriality clause at the heart of the 1971 Immigration Act not only in its immigration control work but also in wider approaches to managing, measuring and pacing change over time. Secondly, the Home Office does history through an expanding labyrinth of documentation regimes that embed racist burdens of proof, notions of criminality, and legal categories – forged during empire – into present-day systems of criminalisation and migration control. The thesis contextualises the administrative violence meted out by the contemporary Home Office’s so-called broken system with archival research into the making of bureaucratic power, social facts about race, and legal privilege in a range of colonial mobility regimes. Through these explorations, this thesis offers a new lens with which to view histories of deportation, foregrounding how historical narratives, archival processes and the everyday politics of time get folded into the banal routines of administrative state power

Supporting the mental health needs of young people: The spatial practices of school nurses

Purpose The purpose of this paper is to raise awareness of an understanding of how school nurses work in multiple spaces, supporting young people in relation to promoting and protecting their emotional and mental health and wellbeing. It is argued that young people’s emotional health needs are still as prevalent today as they were over 150 years ago, when Charles Dickens wrote about them in the novel Nicholas Nickleby. Design/methodology/approach Soja’s (1996) typology of spatial practice is applied to school nursing practice in an attempt to explore how different types of space influence how support is given to young people. Findings Examples are provided from previous research (Sherwin, 2016) of how Soja’s theory of Firstspace, Secondspace and Thirdspace can be identified within school nurses’ practice, thereby providing an understanding of how school nurses provide support to young people on an everyday basis. It is proposed that in an addition Fourthspace also exists and a new conceptual model of spatial practice is proposed. Originality/value School nurses have the potential to make a significant impact on preventing and protecting young people’s mental health. They provide valuable support to young people to enable them to cope with the complexities of their lives, yet relatively little is known about their everyday practice as this is an under-reported area of nursing. A new conceptual model is proposed to help provide an understanding of their practice

Identity management strategies among HIV-positive Colombian gay men in London

This study set out to explore the social-psychological aspects of living with HIV among a group of HIV-positive Colombian gay men in London, and the strategies that they deployed to manage ensuing threats to their identities. Focus group and individual interview data were collected from 14 Colombian gay men living with HIV, and were analysed using qualitative thematic analysis and identity process theory. The following themes are discussed: (1) identity struggles and conflicts in Colombia, (2), managing multiple layers of social stigma in England, and (3) changing interpersonal and intergroup dynamics, which highlight the inter-connections between sexual prejudice, sexual risk-taking and HIV stigma. Identity may be chronically threatened due to the multiple layers of stigma, which can limit the coping strategies available to individuals. Findings strongly support the need for action and programmes to highlight and tackle both racism and HIV stigma on the gay scene and to fund more specific resources for sub-communities of gay, bisexual and other men who have sex with men, which employ appropriately trained and culturally competent staff

Moment Resistances of wide flange beams with initial imperfection and residual stresses

Elastic and inelastic moment resistances of W-steel beams with considering the effects of initial imperfections and residual stresses are numerically investigated in the present study. The numerical model is implemented in ABAQUS in which residual stresses are incorporated by using initial conditions while the initial imperfection is imported through the first lateral-torsional buckling mode. By comparing the FEA moment resistances of W250x45 steel beams against those of the CSA S16 and Eurocodes 3 design standards, it is observed that (i) If the effects of initial imperfections and residual stresses are excluded, the inelastic resistances are close to a fully plasticized section moment. In contrast, if the effects are included, the inelastic resistances are significantly smaller than the fully plasticized moment. (ii) The effects of initial imperfections on the moment resistance are significant for intermediate and long spans. Although the initial imperfection taken in the present study is 4.0 mm, that is within the allowable limit specified in the design standards (i.e., not greater than L/1000), the moment resistances with the taken imperfection are considerably smaller than the design moments specified in the design standards, and (iii) When considering steel beams with the effects of initial imperfection and residual stresses, the moment resistances based on the CSA S16 and EC3-6.3.2.3 solutions are higher, while those based on EC3-6.3.2.2 solution are lower than the moment capacities of the beams with the initial imperfection. This indicates that EC3-6.3.2.2 clause is the most safety design for the moment resistances

Moment Resistances of wide flange beams with initial imperfection and residual stresses

Elastic and inelastic moment resistances of W-steel beams with considering the effects of initial imperfections and residual stresses are numerically investigated in the present study. The numerical model is implemented in ABAQUS in which residual stresses are incorporated by using initial conditions while the initial imperfection is imported through the first lateral-torsional buckling mode. By comparing the FEA moment resistances of W250x45 steel beams against those of the CSA S16 and Eurocodes 3 design standards, it is observed that (i) If the effects of initial imperfections and residual stresses are excluded, the inelastic resistances are close to a fully plasticized section moment. In contrast, if the effects are included, the inelastic resistances are significantly smaller than the fully plasticized moment. (ii) The effects of initial imperfections on the moment resistance are significant for intermediate and long spans. Although the initial imperfection taken in the present study is 4.0 mm, that is within the allowable limit specified in the design standards (i.e., not greater than L/1000), the moment resistances with the taken imperfection are considerably smaller than the design moments specified in the design standards, and (iii) When considering steel beams with the effects of initial imperfection and residual stresses, the moment resistances based on the CSA S16 and EC3-6.3.2.3 solutions are higher, while those based on EC3-6.3.2.2 solution are lower than the moment capacities of the beams with the initial imperfection. This indicates that EC3-6.3.2.2 clause is the most safety design for the moment resistances