The effect of desiccation on the emission of volatile bromocarbons from two common temperate macroalgae

Exposure of intertidal macroalgae during low tide has been linked to the emission of a variety of atmospherically-important trace gases into the coastal atmosphere. In recent years, several studies have investigated the role of inorganic iodine and organoiodides as antioxidants and their emission during exposure to combat oxidative stress, yet the role of organic bromine species during desiccation is less well understood. In this study the emission of dibromomethane (CH2Br2) and bromoform (CHBr3) during exposure and desiccation of two common temperate macroalgae, Fucus vesiculosus and Ulva intestinalis, is reported. Determination of the impact exposure may have on algal physiological processes is difficult as intertidal species are adapted to desiccation and may undergo varying degrees of desiccation before their physiology is affected. For this reason we include comparisons between photosynthetic capacity (Fv/Fm) and halocarbon emissions during a desiccation time series. In addition, the role of rewetting with freshwater to simulate exposure to rain was also investigated. Our results show that an immediate flux of bromocarbons occurs upon exposure, followed by a decline in bromocarbon emissions. We suggest that this immediate bromocarbon pulse may be linked to volatilisation or emissions of existing bromocarbon stores from the algal surface rather than the production of bromocarbons as an antioxidant response

Analytical solution for the spread of epidemic diseases in community clustered network

We present a bond percolation model for community clustered networks with an arbitrarily specified joint degree distribution. Our model is based on the Probability Generating Function (PGF) method for multitype networks, but incorporate the free-excess degree distribution, which makes it applicable for clustered networks. In the context of contact network epidemiology, our model serves as a special case of community clustered networks which are more appropriate for modelling the disease transmission in community networks with clustering effects. Beyond the percolation threshold, we are able to obtain the probability that a randomly chosen community-$i$ node leads to the giant component. The probability refers to the probability that an individual in a community will be affected from the infective disease. Besides that, we also establish method to calculate the size of the giant component and the average small-component size (excluding the giant component). When the clustering effect is taken into account through the free-excess degree distribution, the model shows that the clustering effect will decrease the size of the giant component. In short, our model enables one to carry out numerical calculations to simulate the disease transmission in community networks with different community structure effects and clustering effects

Computation of the domain of attraction for suboptimal immunity epidemic models using the maximal Lyapunov function method

We are concerned with the estimation of the domain of attraction (DOA) for suboptimal immunity epidemic models. We establish a procedure to determine the maximal Lyapunov function in the form of rational functions. Based on the definition of DOA and the maximal Lyapunov function, a theorem and subsequently a numerical procedure are established to determine the maximal Lyapunov function and the DOA. Determination of the domain of attraction for epidemic models is very important for understanding the dynamic behaviour of the disease transmission as a function of the state of population distribution in different categories of disease states. We focus on suboptimal immunity epidemic models with saturated treatment rate and nonlinear incidence rate. Different from classical models, suboptimal immunity models are more realistic to explain the microparasite infection diseases such as Pertussis and Influenza A. We show that, for certain values of the parameter, larger k value (i.e., the model is more toward the SIR model) leads to a smaller DOA

Addressing the implementation challenge of the global biodiversity framework

A Global Biodiversity Framework (GBF) is under discussion for the period 2021–2030, which will replace the “Aichi Targets” adopted by the Convention on Biological Diversity (CBD) in 2010. Given the limited success in meeting most of the Aichi Targets, this new framework must adopt a different approach. A key challenge the GBF must address is its implementation at national scales. Four ways this implementation challenge can be addressed include:The framework must move away from numerical targets to pursue positive trends in biodiversity, through adopting a “vectors of change” approach;The framework should be structured to focus on ecosystems and processes;The framework should synergise more extensively with existing biodiversity-relevant global agreements to maximise leverage and reduce overlap of resource use;The framework must adopt a much stronger theory of change than is in the current GBF Draft, to serve as the roadmap governments can use in upscaling their implementation of biodiversity conservation, sustainable use and benefit sharing. Finally, the GBF must become a “learning framework”, committed to facilitating and enabling governments to each meet their specific biodiversity challenges, while sharing back experiences with the global community, leading ultimately to realising the 2050 CBD vision of people living in harmony with nature. © 2020, The Author(s)

Carrier de-smearing of photoluminescence images on silicon wafers using the continuity equation

Photoluminescence images of silicon wafers with non-uniform lifetime distribution are often smeared by lateral carrier diffusion. We propose a simple method to de-smear the photoluminescence images by applying the two-dimensional continuity equation. We demonstrate the method on simulated silicon wafers and measured photoluminescence-based lifetime image of multicrystalline silicon wafer. The de-smearing is very effective in recovering the actual lifetime for wafers with gradual changes in lifetime but is less effective around localised recombination centres with high contrast such as grain boundaries and dislocations. The method is sensitive to measurement noise; therefore, the implementation of suitable noise filtering is often critical.This work was supported by the Australian Research Council and the Australian Renewable Energy Agency

Evaluation of the Seca Inhibitors as Novel Anti-Microbial Agents

The misuse of conventional antibiotics and natural selection of the infectious bacterial population has produced drug resistance. Thus, novel effective antibiotic compounds that treat bacterial infections resistant to available therapies are needed. SecA is an indispensable ATPase of the protein translocation machinery present in all bacteria. SecA is responsible for the secretion of many essential proteins, some toxins and virulence factors, and is essential for bacterial survival. SecA has no counterpart in mammalian cells, thus provides an ideal target for developing antimicrobial agents. SCA-13 (HO) is a pyrimidine analog derived from virtual screening; it exerts the ability to inhibit SecA translocation ATPase activity with an IC50 of 75 µM. HO showed promising bacteriostatic activities against a vacomycin resistant strain of S. aureus Mu50 and B. anthracis Sterne. No significant difference in antimicrobial activity of HO was observed among efflux pump strains of S. aureus, suggesting that compound HO is not a substrate of NorA or MepA efflux pumps. Resistant mutants of E. coli NR698 selected from HO need to be characterized to gain a better understanding of the resistance mechanisms and subsequently will allow for the identification of the drug target

Investigation of Dislocations in GaAs Using Cathodoluminescence in the Scanning Electron Microscope

Electrically active dislocations in Si-doped {100} GaAs substrates were observed using the cathodoluminescence (CL) technique in the scanning electron microscope (SEM). CL contrast profiles were experimentally obtained from the dislocations at different beam energies. Based on the CL model for localized defects in semiconductors developed earlier by Pey, the depths of the dislocations were found by locating the beam energy at which maximum CL contrast occurred. A preferential etching technique for {100} GaAs was employed to reveal the dislocations and to measure their depths. The etched depths obtained were compared to the predicted results from the theoretical model developed. The discrepancies in the results were attributed to a Cottrell atmosphere of point defects around the dislocation core

Error Voltage Components in Quantitative Voltage Contrast Measurement Systems

This paper presents the results of computer simulation studies into the respective contributions of the potential barrier, the off-normal incidence injection of secondary electrons (SEs) into the retarding field and analyser geometry on Types I and II local field error voltages for a practical 20 mm wide planar retarding field energy analyser. Results show that the error voltage component due to the off-normal incidence injection effect of SEs into the retarding field dominates the Type I local field error. For type II LFE, the error voltage component due to analyser geometry effect is the higher contributing factor. The presence of a neighbouring electrode voltage tends to draw SEs away from the central axis of the energy analyser, thus causing the electron trajectories to be more sensitive to the influence of the analyser geometry

Cathodoluminescence Contrast of Localized Defects Part II. Defect Investigation

Cathodoluminescence contrast from defects with different geometrical and electronic properties have been studied using the numerical model developed in Part I. The contrast of a localized subsurface defect exhibits a maxima at a specific beam energy Emax which corresponds to the depth of the defect. The contrast of a dis-location which intersects the top surface perpendicularly is a decreasing function of beam energy. The differences in the image profiles of the two different kinds of defects allow the two types of imperfections to be distinguished. In addition, the resolution of a subsurface defect at beam energies lower than Emax is only a function of defect size and is insensitive to the defect strength. The defect depth, size and strength can therefore be extracted sequentially. The extension of the model to the investigation of complex or multiple defects such as dot and halo contrast is also illustrated

Cathodoluminescence Contrast of Localized Defects Part I. Numerical Model for Simulation

A three-dimensional model has been developed for cathodoluminescence contrast of localized defects in semiconductors. The numerical model incorporates electron-solid interaction effects, charge transport phenomena and optical losses. Electron-solid interaction is modelled by a Monte Carlo method. Three-dimensional continuity equation and derivative boundary conditions are discretized by a central-difference quotients scheme. Localized defects are represented by regions of enhanced non-radiative recombination. The discretized linear difference equations of the boundary value problem are solved by the successive-over-relaxation method. A method for avoiding the divergence problem during the successive-over-relaxation calculation is illustrated. The solutions of the model are compared with the analytical results of several established models