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Approximation of Wave Packets on the Real Line
No full textIn this paper we compare three different orthogonal systems in L2(R) which can be used in the construction of a spectral method for solving the semi-classically scaled time dependent Schrödinger equation on the real line, specifically, stretched Fourier functions, Hermite functions and Malmquist–Takenaka functions. All three have banded skew-Hermitian differentiation matrices, which greatly simplifies their implementation in a spectral method, while ensuring that the numerical solution is unitary – this is essential in order to respect the Born interpretation in quantum mechanics and, as a byproduct, ensures numerical stability with respect to the L2(R) norm. We derive asymptotic approximations of the coefficients for a wave packet in each of these bases, which are extremely accurate in the high frequency regime. We show that the Malmquist–Takenaka basis is superior, in a practical sense, to the more commonly used Hermite functions and stretched Fourier expansions for approximating wave packets
Measuring Risk of Re-identification in Microdata: State-of-the Art and New Directions
No full textWe review the influential research carried out by Chris Skinner in the area of statistical disclosure control, and in particular quantifying the risk of re-identification in sample microdata from a random survey drawn from a finite population. We use the sample microdata to infer population parameters when the population is unknown, and estimate the risk of re-identification based on the notion of population uniqueness using probabilistic modelling. We also introduce a new approach to measure the risk of re-identification for a subpopulation in a register that is not representative of the general population, for example a register of cancer patients. In addition, we can use the additional information from the register to measure the risk of re-identification for the sample microdata. This new approach was developed by the two authors and is published here for the first time. We demonstrate this approach in an application study based on UK census data where we can compare the estimated risk measures to the known truth. <br/
Multilevel modelling approach to analysing life course socioeconomic status and understanding missingness
No full textThis paper investigated the extent to which parental socioeconomic status was associated with life course socioeconomic status heterogeneity between adult cohort members of the 1958 National Child Development Study and how this association differed depending on methods used to address longitudinal missing data. We compared three variants of the full information maximum likelihood approach, namely available case, complete case and partially observed case and two methods designed to compensate for missing at random data, namely multilevel multiple imputation and multiple imputation chained equations. Our results highlighted the important contribution of parental socioeconomic status in explaining the divergence in achieved socioeconomic status over the adult life course, how the available case approach increasingly overestimated socioeconomic attainment as age increased and survey sample size decreased, and how the complete case approach downwardly biased the effect of parental socioeconomic status on adult socioeconomic status
IDENTIFYING VULNERABLE LINES CONSIDERING UNCERTAIN HEAT ELECTRIFICATION IN INTEGRATED GAS AND ELECTRICITY NETWORKS
No full textThe installation of heat pumps, powered from clean electricity sources, will play a key role in heat decarbonisation. However, the resulting surge in electricity demand will put the existing transmission lines under enormous strain, increasing the risk of line overloading, potential failure and even loss of load events. This paper presents a probabilistic method for assessing line overload in integrated gas and electricity networks with the consideration of heat electrification. The established model fully considers the uncertainties associated with intermittent generation and fluctuating loads. The effectiveness of the proposed method is verified via its application in an integrated 9-bus electricity and 8-node gas network. Numerical results show that the overload probability of power lines and gas pipelines increases as a result of heat electrification. The overload probability further rises when the correlations of renewable generation and loads are considered, confirming the significance of modelling correlation for an accurate estimation of power and gas flows. The overload probability of some power lines and gas pipelines soar as they become disproportionately loaded, when considering an uneven distribution of heat loads (i.e., clustering of lowcarbon technologies) in the electricity network.<br/
Prognostic and predictive factors for locoregional and systemic therapies in hepatocellular carcinoma
No full textHepatocellular carcinoma (HCC) is a growing health concern, with an estimated global incidence of over 1 million by 2025. In its intermediate and advanced stages, HCC remains a challenging condition to treat, despite a recently expanded array of systemic therapies, which continues to grow. Extensive efforts have accordingly been made to identify predictive factors to guide treatment decisions. However, currently only one predictive biomarker is in widespread clinical use, namely elevated alpha-fetoprotein for second-line systemic therapy with ramucirumab. This article reviews known prognostic and predictive biomarkers for patients with HCC who are treated with locoregional and systemic therapies, including recent controversies around the potential impact of HCC aetiology on the efficacy of systemic therapies
The effects of smoothing length on the onset of wave breaking inSmoothed Particle Hydrodynamics (SPH) simulations of highlydirectionally spread waves
No full textOcean wave breaking is a difficult-to-model oceanographic process, which has implications forextreme wave statistics, the dissipation of wave energy, and air-sea interaction. Numerical methods capable of reliably simulating real-world directionally spread breaking waves are useful for investigating the physics of wave breaking and for the design of offshore structures and floating bodies. Smoothed Particle Hydrodynamics (SPH) is capable of modelling highly steep and overturning free surfaces, which makes it a promising method for simulating breaking waves. This paper investigates the effect of smoothing length on simulated wave breaking in both following and crossing seas. To do so, we reproduce numerically the experiments of highly directionally spread breaking waves in McAllister et al. [J. Fluid Mech. vol. 860, 2019, pp. 767{786] using a range of normalised smoothing lengths: h=dp =1.4, 1.7, 2.0, 2.3, with h smoothing length and dp particle spacing. The smallest smoothing length we use appears to adversely affect the fidelity of the simulated surface elevation, so that the tallest wave crest observed in experiments is not fully reproduced (coefficient of determination r2 ≈ 0:7). For smoothing lengths h=dp = 1:7, 2:0, and 2:3, the experiments are well reproduced (r2 ≥ 0:88); in these simulations smoothing length predominantly affects the spatial extent and duration of breaking. Qualitative and quantitative comparison of our simulations show that values of h=dp in the range 1:7 - 2 best reproduce the wave breaking phenomena observed in experiments
Impact and control of fouling in radioactive environments.
No full textFouling and scaling of equipment in the nuclear industry is a significant and challenging problem that effects multiple areas across the entire nuclear fuel cycle. Consequences such as the blockage of fluid flow, accumulation of radionuclides, reduction of heat-transfer energy and enhancement of corrosion, all can have detrimental effects on safety and performance as well as incurring substantial damage and maintenance costs amounting to billions of pounds a year. This review focuses on pipelines and understanding the mechanisms of formation and radionuclide incorporation of inorganic and biological fouling, and microbially influenced corrosion (MIC) mechanisms, as well as exploring prevalent examples in the nuclear industry and parallels in the oil and gas industries. The review will also cover advancements in fouling and scale mitigation and treatment strategies, which are imperative to reduce economic loses and avoid safety hazards in nuclear as well as many other industries
Tuning porosity of coal-derived activated carbons for CO2 adsorption
No full textA simple method was developed to tune the porosity of coal-derived activated carbons (ACs), which provided a model adsorbent system to investigate the volumetric CO2 adsorption performance. Specifically, the method involved the variation of the activation temperature in a K2CO3 induced chemical activation process which could yield ACs with defined microporous (<2 nm, including ultra-microporous <1 nm) and meso-micro-porous structures. CO2 adsorption isotherms revealed that the microporous AC has the highest measured CO2 adsorption capacity (6.0 mmol·g–1 at 0 °C and 4.1 mmol·g–1 at 25 °C), whilst ultra-microporous AC with a high packing density exhibited the highest normalized capacity with respect to packing volume (1.8 mmol·cm−3 at 0 °C and 1.3 mmol·cm–3 at 25 °C), which is significant. Both experimental correlation analysis and molecular dynamics simulation demonstrated that (i) volumetric CO2 adsorption capacity is directly proportional to the ultra-micropore volume, and (ii) an increase in micropore sizes is beneficial to improve the volumetric capacity, but may lead a low CO2 adsorption density and thus low pore space utilization efficiency. The adsorption experiments on the ACs established the criterion for designing CO2 adsorbents with high volumetric adsorption capacity.Keywords coal-derived activated carbons, porosity, CO2 adsorption, molecular dynamics<br/
Ventricular arrhythmias and sudden death in non-ischemic dilated cardiomyopathy: matter of sex or scar?
No full textAimsTo evaluate the association between sex and ventricular arrhythmias (VA) or sudden death (SD) in non-ischemic dilated cardiomyopathy, including analysis of potential confounders.MethodsRetrospective cohort study of consecutive patients with DCM referred for cardiac magnetic resonance (CMR) at two tertiary hospitals. The primary combined endpoint encompassed sustained VA, appropriate ICD therapies, resuscitated cardiac arrest and SD. ResultsWe included 1165 patients with median follow-up of 36 months (interquartile range 20-58 months). The majority of patients (66%) were males. Males and females had similar LVEF but the prevalence of late gadolinium enhancement (LGE) at CMR was significantly higher among males (48% vs 30%, p<0.001). Males had higher cumulative incidence of the primary endpoint (8% vs 4%, p=0.02) and male sex was a significant predictor of the primary endpoint at univariate analysis (HR 1.93, p=0.02). However, LGE had a major confounding effect in the association between sex and the primary outcome: the HR of male sex adjusted for LGE was 1.29 (p=0.37). LGE+ females had significantly higher cumulative incidence of the primary endpoint than LGE- males (13% vs 1.8%, p<0.001).ConclusionsIn patients with DCM, the prevalence of LGE is significantly higher among males, implying a major confounding effect in the association between male sex and VA or SD. LGE+ females have significantly higher risk than LGE- males. These data do not support the inclusion of sex into risk-stratification algorithms for VA or SD in DCM.<br/
Effect of low pressure plasma surface modification on filtration performance of chitosan nanofibrous respiratory filter
No full textLow pressure drop is highly desirable for respiratory filters. Surface activation plays an important role to enhance the filtration performance of respiratory filters. In this study, a three-layer composite respiratory filter was developed using a combination of polypropylene (PP) nonwoven layers and chitosan nanofibres (CSNF) with variable coating time (h) during the electrospinning process. To study the impact of surface activation on filtration performance, the outer surface of all the samples were modified using low-pressure plasma treatment. Filtration performance testing was conducted to determine the filtration efficiency (%), pressure drop (Pa), and quality factor (Q) results, before and after the surface treatment. The maximum values of filtration efficiency and quality factor achieved were 99.99% and 0.068, respectively. The lowest value of the pressure drop was 16.12 Pa. All the low-pressure plasma-treated samples showed higher filtration efficiency and quality factor compared to untreated samples due to a more effective capturing mechanism. However, pressure drop results indicated no significant difference. Furthermore, the decay of plasma treatment impact was analysed by using drop shape analysis method to measure the water contact angle on the surface of the samples. Results showed a gradual decrease in surface modification impact and the surface of the treated samples changed from hydrophilic to hydrophobic with the passage of time.</p