Electrical overstress and electrostatic discharge failure in silicon MOS devices

This thesis presents an experimental and theoretical investigation of electrical failure in MOS structures, with a particular emphasis on short-pulse and ESD failure. It begins with an extensive survey of MOS technology, its failure mechanisms and protection schemes. A program of experimental research on MOS breakdown is then reported, the results of which are used to develop a model of breakdown across a wide spectrum of time scales. This model, in which bulk-oxide electron trapping/emission plays a major role, prohibits the direct use of causal theory over short time-scales, invalidating earlier theories on the subject. The work is extended to ESD stress of both polarities. Negative polarity ESD breakdownis found to be primarily oxide-voltage activated, with no significant dependence on temperature of luminosity. Positive polarity breakdown depends on the rate of surface inversion, dictated by the Si avalanche threshold and/or the generation speed of light-induced carriers. An analytical model, based upon the above theory is developed to predict ESD breakdown over a wide range of conditions. The thesis ends with an experimental and theoretical investigation of the effects of ESD breakdown on device and circuit performance. Breakdown sites are modelled as resistive paths in the oxide, and their distorting effects upon transistor performance are studied. The degradation of a damaged transistor under working stress is observed, giving a deeper insight into the latent hazards of ESD damage

Relationships between the bivalve Macoma balthica and bacteria in intertidal sediments: Minas Basin, Bay of Fundy

The extensive intertidal flats of the Minas Basin, Bay of Fundy, support some of the highest population densities of Macoma balthica ever recorded. Densities of Macoma are positively correlated with density of bacteria in the sediment; correlations with tidal elevation and organic carbon content of the sediment are not significant. Macoma density appears to be related to the amount of fine material present in the sediment. Although Macoma feeds on the bacteria within the sediment, it must supplement its diet by suspension-feeding during high tide in order to acquire sufficient protein

Evidence for a charge Kondo effect in Pb(1-x)Tl(x)Te from measurements of thermoelectric power

We report measurements of the thermoelectric power (TEP) for a series of Pb(1-x)Tl(x)Te crystals with x = 0.0 to 1.3%. Although the TEP is very large for x = 0.0, using a single band analysis based on older work for dilute magnetic alloys we do find evidence for a Kondo contribution of 11 - 18 uV/K. This analysis suggests that Tk is ~ 50 - 70 K, a factor 10 higher than previously thought.Comment: 4 pages, 3 figure

An Experimental Investigation of Conformational Fluctuations in Proteins G and L

SummaryThe B1 domains of streptococcal proteins G and L are structurally similar, but they have different sequences and they fold differently. We have measured their NMR spectra at variable temperature using a range of concentrations of denaturant. Many residues have curved amide proton temperature dependence, indicating that they significantly populate alternative, locally unfolded conformations. The results, therefore, provide a view of the locations of low-lying, locally unfolded conformations. They indicate approximately 4–6 local minima for each protein, all within ca. 2.5 kcal/mol of the native state, implying a locally rough energy landscape. Comparison with folding data for these proteins shows that folding involves most molecules traversing a similar path, once a transition state containing a β hairpin has been formed, thereby defining a well-populated pathway down the folding funnel. The hairpin that directs the folding pathway differs for the two proteins and remains the most stable part of the folded protein

Diagnosis, monitoring and treatment of systemic lupus erythematosus: a systematic review of clinical practice guidelines.

Objectives: Management of SLE is complex and variability in practices exists. Guidelines have been developed to help improve the management of SLE patients but there has been no formal evaluation of these guidelines. This study aims to compare the scope, quality and consistency of clinical practice guidelines on the diagnosis, monitoring and treatment of patients with systemic lupus erythematosus (SLE). Methods: Electronic databases were searched up to April 2014. The Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument and textual synthesis was used to appraise and compare recommendations. Results: Nine clinical practice guidelines and five consensus statements were identified, which covered seven topics: diagnosis, monitoring, treatment, neuropsychiatric SLE, lupus nephritis, anti-phospholipid syndrome and other manifestations of lupus. The methodological quality of the guidelines was variable, with the overall mean AGREE II scores ranging from 31% to 75% out of a maximum 100%. Scores were consistently low for applicability, with only one guideline scoring above 50%. There was substantial variability in the treatments recommended for class II and V lupus nephritis, the recommended duration of maintenance therapy for class III/IV lupus nephritis (from 1 to 4 years), and timing of ophthalmological examination for patients on corticosteroids. Conclusion: Published guidelines on SLE cover a complex area of clinical care but the methodological quality, scope and recommendations varied substantially. Collaborative and multidisciplinary efforts to develop comprehensive, high-quality evidence-based guidelines are needed to promote best treatment and health outcomes for patients with SLE.DT is funded by a postgraduate scholarship from the Sydney Medical School, The University of Sydney

Allometric scaling of retrogressive thaw slumps

In the warming Arctic, retrogressive thaw slumping (RTS) has emerged as the primary thermokarst modifier of ice-rich permafrost slopes, raising urgency to investigate the distribution and intensification of disturbances and the cascade of effects. Tracking RTS is challenging due to the constraints of remote sensing products and a narrow understanding of complex, thaw-driven landforms; however, high-resolution elevation models provide new insights into geomorphic change. Structural traits, such as RTS depth of thaw or volume, can be obtained through allometric scaling. To address fundamental knowledge gaps related to area–volume scaling of RTS, a suitable surface interpolation technique was first needed to model pre-disturbance topography upon which volume estimates could be based. Among eight methods with 32 parameterizations, natural neighbour surface interpolation achieved the best precision in reconstructing pre-disturbed slope topography (90th percentile root mean square difference ±1.0 m). An inverse association between RTS volume and relative volumetric error was observed, with uncertainties &lt; 10 % for large slumps and &lt; 20 % for small to medium slumps. Second, a multisource slump inventory (MSI) for two study areas in the Beaufort Delta (Canada) region was developed to characterize the diverse range of disturbance morphologies and activity levels, which provided consistent characterization of thaw-slump-affected slopes between regions and through time. The MSI delineation of high-resolution hillshade digital elevation models (DEMs) for three time periods (airborne stereo-imagery, lidar, ArcticDEM) revealed temporal and spatial trends in these chronic mass-wasting features. For example, in the Tuktoyaktuk Coastlands, a +38 % increase in active RTS counts and +69 % increase in total active surface area were observed between 2004 and 2016. However, the total disturbance area of RTS-affected terrain did not change considerably (+3.5 %) because the vast majority of active thaw slumping processes occurred in association with past disturbances. Interpretation of thaw-driven change is thus dependent on how active RTS is defined to support disturbance inventories. Our results highlight that active RTS is tightly linked to past disturbances, underscoring the importance of inventorying inactive scar areas. Third, the pre-disturbance topographies, MSI digitizations, and DEMs were integrated to explore allometric scaling relationships between RTS area and eroded volume. The power-law model indicated non-linearity in the rates of RTS expansion and intensification across scales (adj-R2 of 0.85, n= 1522) but also revealed that elongated, shoreline RTS reflects outliers poorly represented by the modelling. These results indicate that variation in the allometric scaling of RTS populations is based on morphometry, terrain position, and complexity of the disturbance area, as well as the method and ontology by which slumps are inventoried. This study highlights the importance of linking field-based knowledge to feature identification and the utility of high-resolution DEMs in quantifying rates of RTS erosion beyond tracking changes in the planimetric area.</p

Patients' Attitudes and Experiences of Disease-Modifying Antirheumatic Drugs in Rheumatoid Arthritis and Spondyloarthritis: A Qualitative Synthesis

Objective.Nonadherence to disease-modifying antirheumatic drugs (DMARDS) in rheumatoid arthritis (RA) and spondy-loarthritis (SpA) results in increased disease activity and symptoms and poorer quality of life. We aimed to describepatients’ attitudes and experiences of DMARDs in RA and SpA to inform strategies to improve medication adherence.Methods.Databases (MEDLINE, Embase, PsycINFO, and CINAHL) were searched to January 2016. Thematic synthesiswas used to analyze the findings.Results.From 56 studies involving 1,383 adult patients (RA [n=1,149], SpA [n=191], not specified [n=43]), we identified 6themes (with subthemes): intensifying disease identity (severity of sudden pharmacotherapy, signifying deteriorating health,daunting lifelong therapy), distressing uncertainties and consequences (poisoning the body, doubting efficacy, conflictingand confusing advice, prognostic uncertainty with changingtreatment regimens), powerful social influences (swayed byothers’ experiences, partnering with physicians, maintaining roles, confidence in comprehensive and ongoing care, valuingpeer support), privilege and right of access to biologic agents (expensive medications must be better, right to receive a biologicagent, fearing dispossession), maintaining control (complete ownership of decision, taking extreme risks, minimizing life-style intrusion), and negotiating treatment expectations (miraculous recovery, mediocre benefit, reaching the end of the line).Conclusion.Patients perceive DMARDs as strong medications with alarming side effects that intensify their disease iden-tity. Trust and confidence in medical care, positive experiences with DMARDS among other patients, and an expectationthat medications will help maintain participation in life can motivate patients to use DMARDs. Creating a supportive envi-ronment for patients to voice their concerns may improve treatment satisfaction, adherence, and health outcomes

Phenotypic variation and fitness in a metapopulation of tubeworms (Ridgeia piscesae Jones) at hydrothermal vents

We examine the nature of variation in a hot vent tubeworm, Ridgeia piscesae, to determine how phenotypes are maintained and how reproductive potential is dictated by habitat. This foundation species at northeast Pacific hydrothermal sites occupies a wide habitat range in a highly heterogeneous environment. Where fluids supply high levels of dissolved sulphide for symbionts, the worm grows rapidly in a ‘‘short-fat’’ phenotype characterized by lush gill plumes; when plumes are healthy, sperm package capture is higher. This form can mature within months and has a high fecundity with continuous gamete output and a lifespan of about three years in unstable conditions. Other phenotypes occupy low fluid flux habitats that are more stable and individuals grow very slowly; however, they have low reproductive readiness that is hampered further by small, predator cropped branchiae, thus reducing fertilization and metabolite uptake. Although only the largest worms were measured, only 17% of low flux worms were reproductively competent compared to 91% of high flux worms. A model of reproductive readiness illustrates that tube diameter is a good predictor of reproductive output and that few low flux worms reached critical reproductive size. We postulate that most of the propagules for the vent fields originate from the larger tubeworms that live in small, unstable habitat patches. The large expanses of worms in more stable low flux habitat sustain a small, but long-term, reproductive output. Phenotypic variation is an adaptation that fosters both morphological and physiological responses to differences in chemical milieu and predator pressure. This foundation species forms a metapopulation with variable growth characteristics in a heterogeneous environment where a strategy of phenotypic variation bestows an advantage over specialization