Correlation of micro and nano–scale defects with WVTR for aluminium oxide barrier coatings for flexible photovoltaic modules

This paper seeks to establish a correlation between surface topographical defects and water vapour transmission rate (WVTR) measured under laboratory conditions for aluminium–oxide (Al2O3) barrier film employed in flexible photovoltaic (PV) modules. Defects in the barrier layers of PV modules causing high WVTR are not well characterised and understood. A WVTR of ~10−1 g/m2/day is sufficient for the most packaging applications, but ≤10−6 g/m2/day is required for the encapsulation of long–life flexible PV modules (Carcia et al., 2010a, 2010b). In this study, surface metrology techniques along with scanning electron microscopy (SEM) were used for a quantitative characterisation of the barrier film defects. The investigation have provided clear evidence for the correlation of surface defect density and the transmission of water vapour through the barrier coating layer. The outcomes would appear to suggest that small numbers of large defects are the dominant factor in determining WVTR for these barrier layers

Metrology of Al2O3 Barrier Film for Flexible CIGS Solar Cells

Flexible Cu (In, Ga) Se2 (CIGS) solar cells are very attractive renewable energy sources because of their high conversion efficiencies, their low cost potential and their many application possibilities. However, they are at present highly susceptible to long term environmental degradation as a result of water vapor ingress through the protective encapsulation layer to the absorber (CIGS) layer. The basic methodology to prevent the water vapor permeation is to combine an oxide layer (e.g. AlOx) coating with suitable polymer substrates. Nevertheless, micro and nano-scale defects can appear at any stage of the coating process thus affecting the module efficiency and lifespan. The main aim of this research paper is to use surface metrology techniques including: White Light Scanning Interferometry (WLSI), Atomic Force Microscopy (AFM) and Environmental Scanning Electron Microscopy (ESEM) to characterise the aluminum oxide (Al2O3) barrier film defects, which appear to be directly responsible for the water vapor permeability. This paper reports on the development of a characterisation method for defect detection based on “Wolf Pruning” method and then correlates this with measured water vapor transmission rates (WVTRs) using standard MOCON® test. The results presented in this paper provided a detailed knowledge of the nature of micro and nano-scale defects on the Al2O3 barrier films which are responsible for water vapor and oxygen ingress. This result can then be used to provide the basis for developing roll-to-roll in process metrology devices for quality control of flexible PV module manufacture

Premorbid Cognitive Deficits in Young Relatives of Schizophrenia Patients

Neurocognitive deficits in schizophrenia (SZ) are thought to be stable trait markers that predate the illness and manifest in relatives of patients. Adolescence is the age of maximum vulnerability to the onset of SZ and may be an opportune “window” to observe neurocognitive impairments close to but prior to the onset of psychosis. We reviewed the extant studies assessing neurocognitive deficits in young relatives at high risk (HR) for SZ and their relation to brain structural alterations. We also provide some additional data pertaining to the relation of these deficits to psychopathology and brain structural alterations from the Pittsburgh Risk Evaluation Program (PREP). Cognitive deficits are noted in the HR population, which are more severe in first-degree relatives compared to second-degree relatives and primarily involve psychomotor speed, memory, attention, reasoning, and social-cognition. Reduced general intelligence is also noted, although its relationship to these specific domains is underexplored. Premorbid cognitive deficits may be related to brain structural and functional abnormalities, underlining the neurobiological basis of this illness. Cognitive impairments might predict later emergence of psychopathology in at-risk subjects and may be targets of early remediation and preventive strategies. Although evidence for neurocognitive deficits in young relatives abounds, further studies on their structural underpinnings and on their candidate status as endophenotypes are needed

Biodegradation of the Alkaline Cellulose Degradation Products Generated during Radioactive Waste Disposal.

The anoxic, alkaline hydrolysis of cellulosic materials generates a range of cellulose degradation products (CDP) including α and β forms of isosaccharinic acid (ISA) and is expected to occur in radioactive waste disposal sites receiving intermediate level radioactive wastes. The generation of ISA's is of particular relevance to the disposal of these wastes since they are able to form complexes with radioelements such as Pu enhancing their migration. This study demonstrates that microbial communities present in near-surface anoxic sediments are able to degrade CDP including both forms of ISA via iron reduction, sulphate reduction and methanogenesis, without any prior exposure to these substrates. No significant difference (n = 6, p = 0.118) in α and β ISA degradation rates were seen under either iron reducing, sulphate reducing or methanogenic conditions, giving an overall mean degradation rate of 4.7×10−2 hr−1 (SE±2.9×10−3). These results suggest that a radioactive waste disposal site is likely to be colonised by organisms able to degrade CDP and associated ISA's during the construction and operational phase of the facility

Modelling water vapor permeability through atomic layer deposition coated photovoltaic barrier defects

Transparent barrier films such as Al2O3 used for prevention of oxygen and/or water vapour permeation are the subject of increasing research interest when used for the encapsulation of flexible photovoltaic modules. However, the existence of micro-scale defects in the barrier surface topography has been shown to have the potential to facilitate water vapour ingress, thereby reducing cell efficiency and causing internal electrical shorts. Previous work has shown that small defects (≤ 3 μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥ 3 μm lateral dimension) seem to be more detrimental to the barrier functionality. Experimental results based on surface topography segmentation analysis and a model presented in this paper, will be used to test the hypothesis that the major contributing defects to water vapour transmission rate are small numbers of large defects. The model highlighted in this study has the potential to be used for gaining a better understanding of photovoltaic module efficiency and performance

Using small-angle X-ray scattering to investigate the compaction behaviour of a granulated clay

The compaction behaviour of a commercial granulated clay (magnesium aluminium smectite, gMgSm) was investigated using macroscopic pressure-density measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray microtomography (XμT) and small-angle X-ray scattering (SAXS). This material was studied as a potential compaction excipient for pharmaceutical tabletting, but also as a model system demonstrating the capabilities of SAXS for investigating compaction in other situations. Bulk compaction measurements showed that the gMgSm was more difficult to compact than polymeric pharmaceutical excipients such as spheronised microcrystalline cellulose (sMCC), corresponding to harder granules. Moreover, in spite of using lubrication (magnesium stearate) on the tooling surfaces, rather high ejection forces were observed, which may cause problems during commercial tabletting, requiring further amelioration. Although the compacted gMgSm specimens were more porous, however, they still exhibited acceptable cohesive strengths, comparable to sMCC. Hence, there may be scope for using granular clay as one component of a tabletting formulation. Following principles established in previous work, SAXS revealed information concerning the intragranular structure of the gMgSm and its response to compaction. The results showed that little compression of the intragranular morphology occurred below a relative density of 0 · 6, suggesting that granule rearrangements or fragmentation were the dominant mechanisms during this stage. By contrast, granule deformation became considerably more important at higher relative density, which also coincided with a significant increase in the cohesive strength of compacted specimens. Spatially-resolved SAXS data was also used to investigate local variations in compaction behaviour within specimens of different shape. The results revealed the expected patterns of density variations within flat-faced cylindrical specimens. Significant variations in density, the magnitude of compressive strain and principal strain direction were also revealed in the vicinity of a debossed feature (a diametral notch) and within bi-convex specimens. The variations in compaction around the debossed notch, with a small region of high density below and low density along the flanks, appeared to be responsible for extensive cracking, which could also cause problems in commercial tabletting

The Bulletin, School of Nursing Alumnae Association, 1977

A Letter from the President Progress - The New Jefferson Hospital/Clinical Teaching Facility 1977 School of Nursing A Comprehensive Approach to Hand Rehabilitation Parking Garage Your Sesquicentennial Campaign Social Report Scholarship Report Sick and Welfare Committee Program Committee Resource Committee of the Board of Trustees Bulletin Administration Ways and Means Committee Report Resume of Minutes of Alumnae Association Meetings Duke University Distinguished Alumna Award to Col. Catherine T. Betz (Ret.) Patient Representatives The Joys and Sorrows of a Director of Geriatric Nursing Highlights 1976 P.N.A Convention Class News Marriages Births In Memoriam A Letter from the Former President Help Us - Help Yo

A scoping review & taxonomy of epidemiological-macroeconomic models of COVID-19.

OBJECTIVES: The COVID-19 pandemic placed significant strain on many health systems and economies. Mitigation policies decreased health impacts but had major macroeconomic impact. This paper reviews models combining epidemiological and macroeconomic projections to enable policymakers to consider both macroeconomic and health objectives. METHODS: A scoping review of epidemiological-macroeconomic models of COVID-19 was conducted, covering preprints, working papers and journal publications. We assessed model methodologies, scope, and application to empirical data. RESULTS: We found 80 papers modelling both the epidemiological and macroeconomic outcomes of COVID-19. Model scope is often limited to the impact of lockdown on health and total gross domestic product or aggregate consumption, and to high income countries. Just 14% of models assess disparities or poverty. Most models fall under four categories: compartmental-utility-maximization models, epidemiological models with stylized macroeconomic projections, epidemiological models linked to computable general equilibrium or input-output models, and epi-econ-ABMs. We propose a taxonomy comparing these approaches to guide future model development. CONCLUSIONS: The epidemiological-macroeconomic models of COVID-19 identified have varying complexity and meet different modelling needs. Priorities for future modelling include increasing developing country applications, assessing disparities and poverty, and estimating of long-run impacts. This may require better integration between epidemiologists and economists

POTs: Protective Optimization Technologies

Algorithmic fairness aims to address the economic, moral, social, and political impact that digital systems have on populations through solutions that can be applied by service providers. Fairness frameworks do so, in part, by mapping these problems to a narrow definition and assuming the service providers can be trusted to deploy countermeasures. Not surprisingly, these decisions limit fairness frameworks' ability to capture a variety of harms caused by systems. We characterize fairness limitations using concepts from requirements engineering and from social sciences. We show that the focus on algorithms' inputs and outputs misses harms that arise from systems interacting with the world; that the focus on bias and discrimination omits broader harms on populations and their environments; and that relying on service providers excludes scenarios where they are not cooperative or intentionally adversarial. We propose Protective Optimization Technologies (POTs). POTs provide means for affected parties to address the negative impacts of systems in the environment, expanding avenues for political contestation. POTs intervene from outside the system, do not require service providers to cooperate, and can serve to correct, shift, or expose harms that systems impose on populations and their environments. We illustrate the potential and limitations of POTs in two case studies: countering road congestion caused by traffic-beating applications, and recalibrating credit scoring for loan applicants.Comment: Appears in Conference on Fairness, Accountability, and Transparency (FAT* 2020). Bogdan Kulynych and Rebekah Overdorf contributed equally to this work. Version v1/v2 by Seda G\"urses, Rebekah Overdorf, and Ero Balsa was presented at HotPETS 2018 and at PiMLAI 201