Multi-layered Composites Using Photolithography

The mechanical properties of the parts made using solid freeform fabrication technologies are limited by their resins used. Previous research has shown that the mechanical properties of these parts can be enhanced substantially by using glass and fiber reinforcements. However, all of the published data is for single layered composites, which does not demonstrate its feasibility to manufacture multilayered real objects. In this paper experiments carried out to build multi-layered parts with glass fiber tow as reinforcement in a matrix of photopolymeric resin are described. These specimens are then tested in uniaxial tension and three point bending to determine their improvement in mechanical properties. The experimental data shows that the tensile strength and tensile modulus increased linearly with the volume fraction of the fiber in the composite, thus demonstrating that the trends observed in single layer composites can be also seen in multi-layered composites.Mechanical Engineerin

COVID-19 Pandemic Impacts on Mammalian Carnivore Activity in the Eastern United States

Lockdowns and restrictions associated with the 2020 Covid-19 pandemic altered human activity, with potential impacts on wildlife. In particular, the activity of reclusive mammalian carnivores, which often avoid humans, may have been affected with ramifications for population connectivity and viability. Here, I evaluate changes in the capture rates of humans and mammalian carnivores between 2019 and 2020 across 31 sites in the Eastern United States. Site-specific capture records were obtained from the Snapshot USA camera trapping survey. Differences in carnivore activity were modelled as a response to human activity changes and the development level of the site (urban, suburban, rural or wild) using generalized linear models. Results indicated that, when compared with 2019, there was an overall decrease in human activity at camera sites in 2020, but human activity at urban and wild sites increased slightly. The mean capture rates of all carnivores examined did not change significantly between 2019 and 2020. Capture rates of all individually examined carnivore species varied significantly among development types, with most showing the lowest activity in urban areas. Of seven species modelled individually, only fisher (Martes pennanti) activity responded positively to decreases in human activity between years. Overall, with limited exceptions, changes in human activity caused by the COVID-19 pandemic may not have impacted mammalian carnivore activity as much as expected. This lack of a relationship with human activity could imply that some reclusive carnivore species make more use of human-occupied landscapes than was previously thought, but simply go undetected

Coupled modeling for investigation of blast induced traumatic brain injury

Modeling of human body biomechanics resulting from blast exposure is very challenging because of the complex geometry and the substantially different materials involved. We have developed anatomy based high-fidelity finite element model (FEM) of the human body and finite volume model (FVM) of air around the human. The FEM model was used to accurately simulate the stress wave propagation in the human body under blast loading. The blast loading was generated by simulating C4 explosions, via a combination of 1-D and 3-D computational fluid dynamics (CFD) formulations. By employing the coupled Eulerian-Lagrangian fluid structure interaction (FSI) approach we obtained the parametric response of the human brain by the blast wave impact. We also developed the methodology to solve the strong interaction between cerebrospinal fluids (CSF) and the surrounding tissue for the closed-head impact. We presented both the arbitrary Lagrangian Eulerian (ALE) method and a new unified approach based on the material point method (MPM) to solve fluid dynamics and solid mechanics simultaneously. The accuracy and efficiency of ALE and MPM solvers for the skull-CSF-brain coupling problem was compared. The presented results suggest that the developed coupled models and techniques could be used to predict human biomechanical responses in blast events, and help design the protection against the blast induced TBI

The Limits of Lawyering: Legal Opinions in Structured Finance

Significant controversy surrounds the issuance of legal opinions in structured finance transactions, particularly where accountants separately use these opinions, beyond their traditional primary use, for determining whether to characterize the transactions as debt. Reflecting at its core the unresolved boundaries between public and private in financial transactions, this controversy raises important issues of first impression: To what extent, for example, should lawyers be able to issue legal opinions that create negative externalities? Furthermore, what should differentiate the roles of lawyers and accountants in disclosing information to investors? Resolution of these issues not only helps to demystify the mystique, and untangle the morass, of legal-opinion giving but also affects the very viability of the securitization industry, which dominates American, and increasingly global, financing

Effects of Forest Fragment Area on Interactions Between Plants and Their Natural Enemies: Consequences for Plant Diversity at Multiple Spatial Scales

Density-dependent interactions between plants and their natural enemies, including fungal pathogens and insect herbivores, help maintain plant species coexistence and diversity at local scales (α-diversity). However, turnover in plant species composition across space also contributes to biodiversity at larger spatial scales (β-diversity). Despite mounting evidence that enemies can maintain α-diversity, we know little about their contributions to β-diversity. Additionally, in the light of widespread habitat fragmentation and potentially modified insect and pathogen communities in forest fragments, the effects of fragment area on their diversity-maintaining roles are largely unknown. We carried out a field experiment to investigate how natural enemies in impact tree α and β-diversity in a fragmented rainforest landscape in the Western Ghats, India. In 21 rainforest fragments, we suppressed insects and fungi/oomycetes with pesticides, and examined changes in the diversity of tree seedlings. We found that fungicide had no effect on α-diversity, but significantly decreased β-diversity (species turnover among plots). The facilitative effects of fungi and oomycetes on β-diversity, however, weakened as fragments decreased in area, indicating that certain specialized plant-pathogen interactions may be lost when fragments become smaller. Insecticide, in contrast, increased α-diversity but tended to decrease β-diversity between distant plots. In summary, we found that interactions between plants and their natural enemies help maintain β-diversity in large forest fragments but not in small fragments. Small fragments are often viewed as future reservoirs of biodiversity in human-dominated landscapes, but our findings suggest that modified interactions with natural enemies may result in the erosion of this diversity over time

Differential growth responses in seedlings of ten species of Dipterocarpaceae to experimental shading and defoliation

The responses of plants to shade and foliar herbivory jointly affect growth rates and community assembly. We grew 600 seedlings of ten species of the economically important Dipterocarpaceae in experimental gradients of shading (0.3-47.0% of full sunlight) and defoliation (0, 25%, 50% or 75% of leaf area removed). We assessed stem diameters initially, after 2 and 4 mo, and calculated relative growth rates (RGR) with a linear model. Shading interacted with defoliation, reducing RGR by 21.6% in shaded conditions and 8.9% in well-lit conditions. We tested three hypotheses for interspecific trade-offs in growth responses to shading and defoliation. They could be positively related, because both reduce a plant's access to carbon, or inversely related because of trade-offs between herbivore resistance and tolerance. We observed, however, that species varied in their response to shading, but not defoliation, precluding an interspecific trade-off and suggesting that plants tolerate shade and herbivory with differing strategies. Shading most strongly reduced the growth of species with less-dense wood and larger seeds. The strong and variable growth responses to shade, contrasted with the weak and uniform responses to defoliation, suggest that variation in light availability more strongly affects the growth of tropical tree seedlings, and thus community assembly, than does variation in herbivor

Binding of the radioligand SIL23 to alpha-synuclein fibrils in Parkinson disease brain tissue establishes feasibility and screening approaches for developing a Parkinson disease imaging agent

Accumulation of α-synuclein (α-syn) fibrils in Lewy bodies and Lewy neurites is the pathological hallmark of Parkinson disease (PD). Ligands that bind α-syn fibrils could be utilized as imaging agents to improve the diagnosis of PD and to monitor disease progression. However, ligands for α-syn fibrils in PD brain tissue have not been previously identified and the feasibility of quantifying α-syn fibrils in brain tissue is unknown. We report the identification of the (125)I-labeled α-syn radioligand SIL23. [(125)I]SIL23 binds α-syn fibrils in postmortem brain tissue from PD patients as well as an α-syn transgenic mouse model for PD. The density of SIL23 binding sites correlates with the level of fibrillar α-syn in PD brain tissue, and [(125)I]SIL23 binding site densities in brain tissue are sufficiently high to enable in vivo imaging with high affinity ligands. These results identify a SIL23 binding site on α-syn fibrils that is a feasible target for development of an α-syn imaging agent. The affinity of SIL23 for α-syn and its selectivity for α-syn versus Aβ and tau fibrils is not optimal for imaging fibrillar α-syn in vivo, but we show that SIL23 competitive binding assays can be used to screen additional ligands for suitable affinity and selectivity, which will accelerate the development of an α-syn imaging agent for PD