695915 research outputs found
Sort by
Secure and Efficient In-process Monitor (and Library) Protection with Intel MPK
No full textThe process reference monitor is a common technique to enforce security policies for application execution. Reference monitors can be used to enforce access control, check program integrity, detect attacks and even transform program states. Deciding where the monitor resides involves a trade-off between strong monitor isolation and low switching overheads. Running the monitor in the same address space as the protected/traced application (in-process monitors) allows for low overhead but raises isolation concerns. Thus, existing work place monitors in a separate address space, which leads to expensive monitor invocation cost. We present MonGuard, a system in which a high-performance in-process monitor is efficiently isolated from the rest of the application. To that aim, we leverage the Intel Memory Protection Key (MPK) technology to enforce execute-only memory, combined with code randomization to protect and hide the monitor. MonGuard inserts instrumentation around sensitive instructions to further prevent possible code reuse attacks. We built a prototype of MonGuard as a loader extension and implemented a multi-variant execution (MVX) monitor. The evaluation shows MonGuard enhances the monitor protection with nearly zero performance overhead
Has improved treatment contributed to the declining rate of transition to psychosis in ultra-high-risk cohorts?
No full textBackground: The factors contributing to declining psychotic disorder transition rates in ultra-high-risk populations remain unclear. We examined the contribution of longitudinal changes in standard clinical treatment (‘treatment as usual’) to this decline. Method: An audit was conducted on 105 clinical files of patients who received standard care at a specialised ultra-high-risk service. The session notes of these files were quantified, allowing examination of treatment quantity, targets, psychotherapy, and medication. Differences in these aspects across patients’ year of clinic entry were assessed. Variables with significant differences across years were examined using cox regression to assess their contribution to psychosis transition rates. Results: Findings were that, as a function of patients’ year of clinic entry, there were increases in: patients’ number of sessions, cognitive behavioural therapy (CBT), problem and solving therapy. There was a relationship between baseline year cohort and psychosis transition rate, with lower rates observed in more recent cohorts. When changes in treatment between cohorts were adjusted for, the relationship between baseline year cohort and transition rate disappeared. The relationship between baseline year and transition rate was attenuated most by increases in CBT. Conclusion: Changes in standard treatment, particularly increases in CBT, may have contributed to the decline in psychosis risk observed in recent ultra-high-risk cohorts, although these variables do not fully explain this trend. Implications for clinical practice, prediction and intervention research are discussed. Future ultra-high-risk research should investigate the impact of other treatment factors, such as therapeutic alliance. <br/
Electrical Tree Growth in Microsilica-Filled Epoxy Resin
No full textEpoxy resin is widely deployed as a high voltage electrical insulation material when compounded with inorganic fillers. However, in the laboratory, the filler prevents visual observation of the long-term degradation known as electrical treeing. To date therefore, much laboratory testing has been conducted on unrepresentative unfilled materials. Here, the impact of micro-sized fillers on the treeing phenomenon in an epoxy system has been explored. Sub-micrometre resolution 3D reconstructions of electrical trees are reported from X-ray Computed Tomography (XCT) using an advanced ‘pink beam’ synchrotron light source imaging system. The role of filler particles between 1 and 10 µm in size on tree channel propagation is reported. In highly filled materials (30% by weight) a radical change in tree growth behavior is seen, leading to bush tree rather than branch tree growth. The dielectric breakdown time at constant stress was also found to increase as the square root of the filler level. The change in geometry of tree growth may explain the extended life of filled materials in high voltage applications
Signature of Geochemistry on Density-Driven CO2 Mixing in 1 Sandstone Aquifers
No full textDensity-driven mixing resulting from CO2 injection into aquifers leads to the CO2 entrapment mechanism of solubility trapping. Crucially the coupled flow-geochemistry and effects of geochemistry on density-driven mixing process for “sandstone rocks” have not been adequately addressed. Often there are conflicting remarks in the literature as to whether geochemistry promotes or undermines dissolution-driven convection in sandstone aquifers. Against this backdrop, we simulate density driven mixing in sandstone aquifers by developing a 2D modified stream function formulation formulticomponent reactive convective-diffusive CO2 mixing. Two different cases corresponding to laboratory and field scales are studied to investigate the effect of rock-fluid interaction on density driven mixing and the role of mineralization in carbon storage over the project life time. A complex sandstone mineralogical assemblage is considered and solid-phase reactions are assumed to be kinetic to study the length- and time-scale dependency of the geochemistry effects. The study revealed nonuniform impact of rock-fluid and fluid-fluid interaction in early- and late-time stages of the process. The results show that for moderate Rayleigh (Ra) numbers, rock-fluid interactions adversely affect solubility trapping while improving the total carbon captured through mineral trapping. Simulation results in the range of 1,500 < Ra < 55,000 in the field-scale model, showed more pronounced impact of geochemistry for higher Ra numbers, as geochemistry stimulates the convective instabilities and improves the total sequestered carbon. This study gives new insights into the effect of rock-fluid interactions on density driven mixing and solubility trapping in sandstone aquifers to improve estimation of the carbon storage capacity in deep saline aquifers
Relationship of anabolic hormones with motor unit characteristics in quadriceps muscle in healthy and frail ageing men
No full textContext: Anabolic hormones are important factors in maintaining muscle mass for ageing men, but their role in overall motor unit structure and function is unclear. Objective: To determine associations of anabolic and reproductive hormone levels with motor unit characteristics in quadriceps muscle in older healthy and frail men. Design: Observational cohort study of community dwelling men. Participants: Healthy and frail men > 65 years old. Intervention: None. Outcome measure: Quantitative assessments of electromyography-derived motor unit potential size (MUP) and compound muscle action potential size (CMAP) of vastus lateralis muscle. Results: We studied 98 men (mean±SD: age 73±6 years; BMI 25.7±4.0 kg/m2; diabetes 11%) of whom 45% were prefrail and 18% frail. After adjusting for age, BMI and prevalent diabetes, higher total and free testosterone levels were significantly related to larger CMAP (total testosterone: β (95% CI): 0.3 (0.08, 0.53); free testosterone: 0.34 (0.13, 0.56)). Exploratory analysis showed the relationship between free testosterone and CMAP was stronger in frail rather than robust men. In univariate analyses, estradiol was associated with CMAP size (0.37 (0.16, 0.57)); and vitamin D was associated with MUP size (0.22 (0.01, 0.43)) but these relationships were no longer significant after adjusting for potential confounders. Conclusion: Our data highlight the associations between androgen levels and the electrophysiological characteristics of older men, particularly in the frail. Clinical trials involving administration of androgens will help to elucidate the potential benefits of intervention on neuromuscular function and/or frailty status
Imbalance Learning for Variable Star Classification
No full textThe accurate automated classification of variable stars into their respective sub-types is difficult. Machine learning based solutions often fall foul of the imbalanced learning problem, which causes poor generalisation performance in practice, especially on rare variable star sub-types. In previous work, we attempted to overcome such deficiencies via the development of a hierarchical machine learning classier. This 'algorithm-level' approach to tackling imbalance, yielded promising results on Catalina Real-Time Survey (CRTS) data, outperforming the binary and multi-class classification schemes previously applied in this area. In this work, we attempt to further improve hierarchicalclassification performance by applying 'data-level' approaches to directly augment the training data so that they better describe under-represented classes. We apply and report results for three data augmentation methods in particular: Randomly Augmented Sampled Light curves from magnitude Error (RASLE), augmenting light curves with Gaussian Process modelling (GpFit) and the Synthetic Minority Over-sampling Technique (SMOTE). When combining the 'algorithm-level' (i.e. the hierarchical scheme) together with the 'data-level' approach, we further improve variable star classification accuracy by 1-4%. We found that a higher classification rate is obtained when using GpFit in the hierarchical model. Further improvement of the metric scores requires abetter standard set of correctly identified variable stars and, perhaps enhanced features are needed
Electric Field and Thermal Analysis of 132 kV Ceramic Oil-filled Cable Sealing Ends
No full textThis paper reports on a method combining the use of finite element simulations and external measurements to provide preliminary condition diagnosis of oil-filled cable sealing ends (CSEs) without requiring downtime. Good agreement has been obtained between the predictions from the electric field and thermal simulations and the measurements on a 132 kV oil-filled CSE. The electrostatic computation combined with electric field measurements can provide information regarding the electric field distribution inside the CSE and help in identifying potential issues with the CSE design, the materials or the cable termination process. The thermal computation combined with thermal imaging can reveal potential problems, such as high resistance connection to the busbar, and provide information regarding the cooling efficiency of the liquid dielectric. The method presented can provide the starting point for prioritizing maintenance operations on CSEs
Mobility-on-demand: An empirical study of internet-based ride-hailing adoption factors, travel characteristics and mode substitution effects
No full textRide-hailing services are shaping travel behaviours and emergent urban mobility patterns. From their initial diffusion centres in North America and Europe, these on-demand mobility services are increasingly becoming available in developing countries. Yet, empirical research from these contexts on the impact of ride-hailing services is lacking. To address this gap, this paper examines the factors driving the adoption of ride-hailing and the associated travel characteristics and mode substitution effects in Ghana, Sub-Saharan Africa. Using data from a large sample survey (N = 1,188) of commuters in a multi-variable structural equation model, the paper shows that socio-demographic factors, perceived benefits and ease of use of ride-hailing, perceived safety risks and car-dependent lifestyles influence adoption and use of ride-hailing services. Similar to other contexts, individuals’ reference ride-hailing trips were mainly for ‘special occasion’ purposes (51%), but work and school travel journeys were also high (41%). Shorter travel times (≤30 minutes) and single passenger journeys within inner-suburban and outer-suburban localities typify ride-hailing trips. This contrasts with other contexts where ride-hailing is used frequently by urban dwellers and less so by those in the suburbs. Ride-hailing use replaced conventional taxis (51%), public transport (36%), private car (10%) and walking (1%), suggesting mode substitution effects for individuals’ reference trips. Further exploration of a full day’s travel mode choices also revealed that individuals use other available modes of transport in addition to ride-hailing services. However, multi-modal integration is weak, suggesting that ride-hailing tends to be used alone for full door-to-door journeys, instead of complementing other existing modes in serving first/last mile access for example. The implications of the findings for sustainable mobility are discussed
Type 2 immunity in the skin and lungs
No full textThere has been extensive progress in understanding the cellular and molecularmechanisms of inflammation and immune regulation in allergic diseases of the skin and lungs during the last few years. Asthma and atopic dermatitis are typical diseases of type 2-immune responses. IL-25, IL-33 and TSLP are essential cytokines of epithelial cell that activation by allergens, pollutants, viruses, bacteria and toxins that derive type 2 responses. Th2 cells and innate lymphoid cells produce and secrete type 2 cytokines such as interleukin (IL)-4, IL-5, IL-9 and IL-13. IL-4 and IL-13 activate B cells to class switch to IgE and also play a role in T cell and eosinophil migration to allergic inflammatory tissues. IL-13 contributes to maturation, activation, nitric oxide production and differentiation of epithelia, production of mucus as well as smooth muscle contraction and extracellular matrix generation. IL-4 and IL-13 open tight junction barrier and cause barrier leakiness in the skin and lungs. IL-5 acts on activation, recruitment and survival of eosinophils. IL-9 contributes to general allergic phenotype by enhancing all of the aspects, such as IgE and eosinophilia. Type 2 innate lymphoid cells (ILC) contribute to inflammation in atopic dermatitis and asthma by enhancing the activity of Th2 cells, eosinophils and their cytokines. Currently five biologics are licensed to suppress type 2 inflammation via IgE, IL-5 and its receptor and IL-4 receptor alpha. Some patients with severe atopic disease have little evidence of type 2 hyperactivity and do not respond to biologics which target this pathway. Studies in responder and non-responder patients demonstrate the complexity of these diseases. In addition, primary immune deficiency diseases related to T cell maturation, regulatory T cell development, T cell signaling, such as Omenn syndrome, severe combined immune deficiencies, IPEX syndrome, DOCK8, STAT3 64 and CARD11 deficiencies help in our understanding of the importance and redundancy of various type 2 immune components. The present review aims to highlight recent advances in type 2 immunity and discuss the cellular sources, targets, and roles of type 2 mechanisms in asthma and atopic dermatitis.<br/