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

Optimal flip angles for in vivo liver 3D T1 mapping and B1+ mapping at 3T.

Purpose The spoiled gradient recalled echo (SPGR) sequence with variable flip angles (FAs) enables whole liver T1 mapping at high spatial resolutions but is strongly affected by B1+ inhomogeneities. The aim of this work was to study how the precision of acquired T1 maps is affected by the T1 and B1+ ranges observed in the liver at 3T, as well as how noise propagates from the acquired signals into the resulting T1 map. Theory The T1 variance was estimated through the Fisher information matrix with a total noise variance including, for the first time, the B1+ map noise as well as contributions from the SPGR noise. Methods Simulations were used to find the optimal FAs for both the B1+ mapping and T1 mapping. The simulations results were validated in 10 volunteers. Results Four optimized SPGR FAs of 2°, 2°, 15°, and 15° (TR = 4.1 ms) and B1+ map FAs of 65° and 130° achieved a T1 coefficient of variation of 6.2 ± 1.7% across 10 volunteers and validated our theoretical model. Four optimal FAs outperformed five uniformly spaced FAs, saving the patient one breath-hold. For the liver B1+ and T1 parameter space at 3T, a higher return in T1 precision was obtained by investing FAs in the SPGR acquisition rather than in the B1+ map. Conclusion A novel framework was developed and validated to calculate the SPGR T1 variance. This framework efficiently identifies optimal FA values and determines the total number of SPGR and B1+ measurements needed to achieve a desired T1 precision

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

Review of the target trial methodological approach on treatment effect estimates in kidney failure: protocol for a systematic assessment

: Background: Patients with kidney failure often lack robust evidence because they are excluded from randomized trials. Trial emulation provides an alternative approach to derive treatment effect estimates when randomized trials cannot be conducted. Critical questions about the comparative efficacy and safety of interventions in kidney failure are now being answered using this approach or parts of it. However, variations and inconsistencies in reporting cast doubt on the reliability and validity of effect estimates not derived from randomized trials. The aim of this methodological systematic review is to understand the extent to which the target study approach is used in kidney failure and the appropriateness of this approach. By identifying and evaluating studies that qualify as emulating a target trial, compared with studies that did not apply the principles. We aim to provide more specific methodological guidance to increase the clarity and reliability of reporting treatment effect estimates when running a trial in kidney failure is not feasible. Methods: This protocol is developed in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses Protocols (PRISMA-P) statement. MEDLINE, Embase, and reference lists (backwards citation chasing) will be searched up until 1st July 2023 and the search updated prior to publication to identify all studies evaluating patient outcomes in late-stage kidney disease and failure that use target trial emulation as the primary approach for analysis. Two authors (A. A., P. K.) will select articles based on title and abstract and then full text, with a third reviewer settling disagreements (J. P.). The prespecified variables will be extracted, and the risk of bias will be assessed by at least two authors (A. A., P. K., A. N.) using prespecified data forms. This will enable the determination of the robustness of the methodological quality of observational studies in using the whole or elements of the target trial approach. We will thereby assess their ability to reliably report treatment effect estimates. Discussion: We will provide specific methodological recommendations on how to design target trials and model assumptions for emulation to get reliable treatment effect estimates for therapeutic interventions in kidney failure. Methodological systematic review registration: Open Science Framework: Identifier https://doi.org/10.17605/OSF.IO/Z4Y29

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