Evaluation of solar cell welds by scanning acoustic microscopy

Scanning laser acoustic microscopy was used to nondestructively evaluate solar cell interconnect bonds made by resistance welding. Both copper-silver and silver-silver welds were analyzed. The bonds were produced either by a conventional parallel-gap welding technique using rectangular electrodes or new annular gap design with a circular electrode cross section. With the scanning laser acoustic microscope, it was possible to produce a real time television image which reveales the weld configuration as it relates to electrode geometry. The effect of electrode misalinement with the surface of the cell was also determined. A preliminary metallographic analysis was performed on selected welds to establish the relationship between actual size and shape of the weld area and the information available from acoustic micrographs

Monitoring crack extension in fracture toughness tests by ultrasonics

An ultrasonic method was used to observe the onset of crack extension and to monitor continued crack growth in fracture toughness specimens during three point bend tests. A 20 MHz transducer was used with commercially available equipment to detect average crack extension less than 0.09 mm. The material tested was a 300-grade maraging steel in the annealed condition. A crack extension resistance curve was developed to demonstrate the usefulness of the ultrasonic method for minimizing the number of tests required to generate such curves

Functional screening in Drosophila reveals the conserved role of REEP1 in promoting stress resistance and preventing the formation of Tau aggregates

Pathological modifications in the microtubule-associated protein Tau is a common characteristic observed in different neurological diseases, suggesting that analogous metabolic pathways might be similarly affected during neurodegeneration. To identify these molecules and mechanisms, we utilized Drosophila models of human Tau-mediated neurodegeneration to perform an RNA interference functional screening against genes considered to be implicated in the pathogenesis of different neurodegenerative disorders. We found that the downregulation of the Drosophila REEP1 homolog protein enhanced Tau toxicity with increased formation of insoluble aggregates. On the contrary, the overexpression of either the Drosophila or the human REEP1 protein was able to revert these phenotypes and promote neuronal resistance to ER stress. These studies identify a new function for the REEP1 protein in vivo and a novel cellular mechanism to prevent Tau toxicity

Evaluation of electrode shape and nondestructive evaluation method for welded solar cell interconnects

Resistance welds of solar cell interconnect tabs were evaluated. Both copper-silver and silver-silver welds were made with various heat inputs and weld durations. Parallel gap and annular gap weld electrode designs were used. The welds were analyzed by light microscope, electron microprobe and scanning laser acoustic microscope. These analyses showed the size and shape of the weld, the relationship between the acoustic micrographs, the visible electrode footprint, and the effect of electrode misalignment. The effect of weld heat input on weld microstructure was also shown

Multi-Agent Learning for Security and Sustainability

This thesis studies the application of multi-agent learning in complex domains where safety and sustainability are crucial. We target some of the main obstacles in the deployment of multi-agent learning techniques in such domains. These obstacles consist of modelling complex environments with multi-agent interaction, designing robust learning processes and modelling adversarial agents. The main goal of using modern multi-agent learning methods is to improve the effectiveness of behaviour in such domains, and hence increase sustainability and security. This thesis investigates three complex real-world domains: space debris removal, critical domains with risky states and spatial security domains such as illegal rhino poaching. We first tackle the challenge of modelling a complex multi-agent environment. The focus is on the space debris removal problem, which poses a major threat to the sustainability of earth orbit. We develop a high-fidelity space debris simulator that allows us to simulate the future evolution of the space debris environment. Using the data from the simulator we propose a surrogate model, which enables fast evaluation of different strategies chosen by the space actors. We then analyse the dynamics of strategic decision making among multiple space actors, comparing different models of agent interaction: static vs. dynamic and centralised vs. decentralised. The outcome of our work can help future decision makers to design debris removal strategies, and consequently mitigate the threat of space debris. Next, we study how we can design a robust learning process in critical domains with risky states, where destabilisation of local components can lead to severe impact on the whole network. We propose a novel robust operator κ which can be combined with reinforcement learning methods, leading to learning safe policies, mitigating the threat of external attack, or failure in the system. Finally, we investigate the challenge of learning an effective behaviour while facing adversarial attackers in spatial security domains such as illegal rhino poaching. We assume that such attackers can be occasionally observed. Our approach consists of combining Bayesian inference with temporal difference learning, in order to build a model of the attacker behaviour. Our method can effectively use the partial observability of the attacker’s location and approximate the performance of a full observability case. This thesis therefore presents novel methods and tackles several important obstacles in deploying multi-agent learning algorithms in the real-world, which further narrows the reality gap between theoretical models and real-world applications

Sonoelastography of the Common Flexor Tendon of the Elbow with Histologic Agreement: A Cadaveric Study.

Purpose To determine the correlation of the results of conventional B-mode ultrasonography (US) and compression sonoelastography with histologic results in common flexor tendons of the elbow in human cadavers. Materials and Methods Twenty-five common flexor tendons were evaluated in 16 fresh, unembalmed cadavers of 11 women with a median age of 85 years (range, 71-101 years) and five men with a median age of 78 years (range, 70-88 years). Informed consent was provided according to the last will of the donors. B-mode US results were classified as grade 1, normal tendon with homogeneous fibrillar pattern; grade 2, tendon thickening or hypoechoic areas and/or calcifications in less than 30% of the tendon; or grade 3, hypoechoic areas and/or calcifications greater than 30% of the tendon. Sonoelastographic results were grade 1, blue (hardest) to green (hard); grade 2, yellow (soft); and grade 3, red (softest). The intraclass correlation coefficient was calculated to determine agreement with histologic findings for each B-mode US, sonoelastographic, and combined B-mode US and sonoelastographic examination. Histologic results were grade 1, normal, with parallel fibrillar pattern; grade 2, mild tendinopathy, with cellular infiltration, angiogenesis, or fatty vacuoles; or grade 3, severe tendinopathy, with loss of parallel collagen structure and necrosis. Results Histologic alterations were detected in 44% (11 of 25) of biopsy specimens. Intraclass correlation with histologic results was 0.57 for B-mode US, 0.68 for sonoelastography, and 0.84 for the combination of the two approaches. Conclusion The addition of sonoelastography to B-mode US provided statistically significant improvement in correlation with histologic results compared with the use of B-mode US alone (P \u3c .02). (©) RSNA, 2016 Online supplemental material is available for this article

Aggregate formation prevents dTDP-43 neurotoxicity in the Drosophila melanogaster eye

TDP-43 inclusions are an important histopathological feature in various neurodegenerative disorders, including Amyotrophic Lateral Sclerosis and Fronto-Temporal Lobar Degeneration. However, the relation of these inclusions with the pathogenesis of the disease is still unclear. In fact, the inclusions could be toxic themselves, induce loss of function by sequestering TDP-43 or a combination of both. Previously, we have developed a cellular model of aggregation using the TDP-43 Q/N rich amino acid sequence 331-369 repeated 12 times (12xQ/N) and have shown that these cellular inclusions are capable of sequestering the endogenous TDP-43 both in non-neuronal and neuronal cells. We have tested this model in vivo in the Drosophila melanogaster eye. The eye structure develops normally in the absence of dTDP-43, a fact previously seen in knock out fly strains. We show here that expression of EGFP 12xQ/N does not alter the structure of the eye. In contrast, TBPH overexpression is neurotoxic and causes necrosis and loss of function of the eye. More important, the neurotoxicity of TBPH can be abolished by its incorporation to the insoluble aggregates induced by EGFP 12xQ/N. This data indicates that aggregation is not toxic per se and instead has a protective role, modulating the functional TBPH available in the tissue. This is an important indication for the possible pathological mechanism in action on ALS patients. © 2014