Persistent organic pollutant transport and fate: Assessment by molecular tracers

Persistent organic pollutants (POPs) such as the organochlorine pesticide hexachlorocyclohexane (HCH) may undergo atmospheric transport and accumulate in regions remote from the source. It is important to develop techniques to help apportion source and identify transport or transformation processes to which HCHs and other mobile POPs may be subjected. Molecular tracers such as compound specific stable isotope and enantiomer ratios (ERs) may prove valuable in studying POP fate and transport. The objective of this study was to further develop the use of these two novel geochemical tools to evaluate the sources, transport and environmental fate of POPs, in the context of studying the fate and transport of HCH, a globally distributed POP. In the first part of my study, I evaluated the potential for using stable isotope ratios to track POP source and transport, using HCH in laboratory simulations of global distillation. I compared the relative fractionation of carbon versus deuterium isotopes during air-water gas exchange along a strong temperature gradient. The hypothesis, that perdeuterated, but not necessarily carbon-labeled compounds would show measurable and significant fractionation during air-water transfer, was validated within the confines of the experimental system. The results suggest that it may be possible to use a dual tracer approach on a larger scale, in which carbon isotopes could be used to track POP source, while fractionation of deuterium may be used to track POP transport distance. In the second part of the study, I evaluated the potential for use of ERs to evaluate HCH biodegradation. The rationale was that most enzymatic processes are stereoselective, enantiomers of pesticides may microbially degrade at significantly different rates, leading to increased environmental persistence of the non-degradable isomer. to bridge the gap between microbial and chemical information on enantioselective processes, I measured microbial activity, abundance, concentrations and enantiomer ratios of HCH in air and surface waters of the York River estuary. HCH concentrations and ERs were related with microbial activity but there were seasonal variations in enantioselectivity suggesting that seasonal as well as spatial differences in microbial communities may affect HCH ERs. The relationship between microbial parameters and enantioselective degradation appears to be complex and warrants further study before ERs can be used as effective tracers of chiral POP transport

Sparse reconstruction of ordinary differential equations with inference

Sparse regression has emerged as a popular technique for learning dynamical systems from temporal data, beginning with the SINDy (Sparse Identification of Nonlinear Dynamics) framework proposed by arXiv:1509.03580. Quantifying the uncertainty inherent in differential equations learned from data remains an open problem, thus we propose leveraging recent advances in statistical inference for sparse regression to address this issue. Focusing on systems of ordinary differential equations (ODEs), SINDy assumes that each equation is a parsimonious linear combination of a few candidate functions, such as polynomials, and uses methods such as sequentially-thresholded least squares or the Lasso to identify a small subset of these functions that govern the system's dynamics. We instead employ bias-corrected versions of the Lasso and ridge regression estimators, as well as an empirical Bayes variable selection technique known as SEMMS, to estimate each ODE as a linear combination of terms that are statistically significant. We demonstrate through simulations that this approach allows us to recover the functional terms that correctly describe the dynamics more often than existing methods that do not account for uncertainty

Finite element model to simulate impact on a soft tissue simulant

A finite element model of an impact test on a soft tissue simulant, used as part of a shoulder surrogate, was developed in Ansys© LS-DYNA®. The surrogate consisted of a metal hemicylindrical core, with a diameter of 75 mm, covered with a 15 mm thick relaxed muscle simulant. The muscle simulant consisted of a 14 mm thick layer of silicone covered with 1 mm thick chamois leather to represent skin. The material properties of the silicone were obtained via quasi-static compression testing (curve fit with hyperelastic models) and compressive stress relaxation testing (curve fit with a Prony series). Outputs of the finite element models were compared against experimental data from impact tests on the shoulder surrogate at energies of 4.9, 9.8 and 14.7 J. The accuracy of the finite element models was assessed using four parameters: peak impact force, maximum deformation, impact duration and impulse. A 5-parameter Mooney-Rivlin material model combined with a 2-term Prony series was found to be suitable for modelling the soft tissue simulant of the shoulder surrogate. This model had under 10% overall mean deviation from the experimental values for the four assessment parameters across the three impact energies. Overall, the model provided a repeatable test method that can be adapted to help predict injuries to skin tissue and the performance/efficacy of personal protective equipment

Technique of mass multiplication of Tenobracon deesae (Cam.) hymenoptera: Braconidæ for use against sugarcane and maize borers

This article does not have an abstract

Nanomedicine for glaucoma: liposomes provide sustained release of latanoprost in the eye

Purpose: To report the development and therapeutic evaluation of a liposomal nanocarrier for sustained release of latanoprost, in the rabbit eye. Methods: We fabricated latanoprost-loaded egg-phosphatidylcholine (EggPC) liposomes using the film hydration technique. The delivery vehicles were nano-sized (Z avg = 109 ± 18 nm), had a narrow poly dispersity index (PDI = 0.19 ± 0.04), and a very high loading efficiency (94% ± 5%). Based on in vitro data, we evaluated this formulation for lowering intraocular pressure (IOP) in rabbit eyes. Following a single subconjunctival injection of the latanoprost loaded formulation, the eyes were clinically monitored and the IOP recorded. Results: Latanoprost-loaded EggPC liposomes demonstrated a high drug/lipid mole ratio of 0.181, remained stable for at least 6 months on storage (4°C), and at least 1 month at 25°C. A slow and sustained release of 60% of latanoprost was achieved by 14 days in the in vitro release study. The same formulation demonstrated a greater sustained IOP lowering effect compared with daily administration of topical latanoprost beyond 90 days (4.8 ± 1.5 vs 2.5 ± 0.9 mmHg; P < 0.001). No signs of inflammation were evident in the eyes from slit-lamp examination analysis. Conclusion: The loading required for a long-term sustained delivery of latanoprost for up to 90 days in the rabbit eyes was achieved with EggPC liposomes. A single injection of latanoprost-loaded EggPC liposomes can lower the IOP for up to 90 days, with a greater IOP lowering effect than daily topical administration of latanoprost.Published versio

Sociodemographic profiles, educational attainment and physical activity associated with The Daily Mile™ registration in primary schools in England – a national cross-sectional linkage study

Objective To examine primary school and local authority characteristics associated with registration for The Daily Mile (TDM), an active mile initiative aimed at increasing physical activity in children. Design A cross-sectional linkage study using routinely collected data. Setting All state funded primary schools in England from 2012-2018(n=15,815). Results 3,502 of all 15,815(22.1%) state funded primary schools in England were registered to do TDM, ranging from 16% in the East Midlands region to 31% in Inner London. Primary schools registered for TDM had larger mean pupil numbers compared with schools that had not registered (300 vs 269 respectively). There was a higher proportion of TDM registered schools in urban areas compared with non-urban areas. There was local authority variation in the likelihood of school registration (ICC: 0.094). After adjusting for school and local authority characteristics, schools located in a major urban conurbation (OR 1.46 (95%CI:1.24-1.71) urban vs. rural) and schools with a higher proportion of disadvantaged pupils had higher odds of being registered to the TDM (OR 1.16 (95%CI:1.02-1.33)). Area based physical activity and schools’ educational attainment was not significantly associated with registration to TDM. Conclusion One in five primary schools in England has registered for The Daily Mile since 2012. TDM appears to be a wide-reaching school based physical activity intervention that is reaching more disadvantaged primary school populations in urban areas where obesity prevalence is highest. TDM registered schools include those with both high and low educational attainment and are in areas with high and low physical activit

Inverted porphyrins and expanded porphyrins: an overview

Porphyrins and metallopophyrins have attracted the attention of chemists for the past 100 years or more owing to their widespread involvement in biology. More recently, synthetic porphyrins and porphyrin-like macrocycles have attracted the attention of researchers due to their diverse applications as sensitizers for photodynamic therapy, MRI contrasting agents, and complexing agents for larger metal ions and also for their anion binding abilities. The number of π-electrons in the porphyrin ring can be increased either by increasing the numberof conjugated double bonds between the pyrrole rings or by increasing the number of heterocyclic rings. Thus, 22π sapphyrins, 26π rubyrins, 30π heptaphyrins, 34π octaphyrins and higher cyclic polypyrrole analogues containing 40π, 48π, 64π, 80π and 96π systems have recently been reported in the literature. These macrocycles show rich structural diversity where normal and different kinds of inverted structures have been identified. In this review, an attempt has been made to collect the literature of the inverted porphyrins and expanded porphyrins reported until December 2001. Since themeso aryl expanded porphyrins have tendency to form both inverted and non-inverted structures more emphasis has been given to meso aryl expanded porphyrins

Absolute light yield of the EJ-204 plastic scintillator

The absolute light yield of a scintillator, defined as the number of scintillation photons produced per unit energy deposited, is a useful quantity for scintillator development, research, and applications. Yet, literature data on the absolute light yield of organic scintillators are limited. The goal of this work is to assess the suitability of the EJ-204 plastic scintillator from Eljen Technology to serve as a reference standard for measurements of the absolute light yield of organic scintillators. Four EJ-204 samples were examined: two manufactured approximately four months prior and stored in high-purity nitrogen, and two aged approximately eleven years and stored in ambient air. The scintillator response was measured using a large-area avalanche photodiode calibrated using low energy $\gamma$-ray and X-ray sources. The product of the quantum efficiency of the photodetector and light collection efficiency of the housing was characterized using an experimentally-benchmarked optical photon simulation. The average absolute light yield of the fresh samples, 9100 $\pm$ 400 photons per MeV, is lower than the manufacturer-reported value of 10400 photons per MeV. Moreover, the aged samples demonstrated significantly lower light yields, deviating from the manufacturer specification by as much as 26\%. These results are consistent with recent work showcasing environmental aging in plastic scintillators and suggest that experimenters should use caution when deploying plastic scintillators in photon counting applications.Comment: 12 pages, 9 figure