Riverine biota as environmental indicators of artisanal small-scale and large-scale gold mining impacts on riverine ecosystems in Brong Ahafo Region, Ghana

A study on two adjacent small ephemeral river systems in the upper Tano River Basin in Brong Ahafo, Ghana; one impacted by ASGM and the other by a modern large gold mining (LSM), showed that impacts of mining on river sediment and water quality and quantity were reflected in the macroinvertebrate and microbial communities. This study investigated the impacts of ASGM on the ecology of the Surow River and that of a large-scale mining (LSM, the Ahafo mine) on the Subri River between February 2013 and April 2014 Macroinvertebrate communities responded to the shift in river water and sediment qualities, whilst microbial communities tended to respond to water quality only. Bioaccumulation and biomagnification of mercury were evident in fishes in the river system impacted by ASGM, although mercury was barely detected in river water and sediment. The study confirmed that impact assessment of ASGM or the modern LSM on rivers should not be limited to the physical and chemical properties of water and sediment, but also include its riverine biota

Rings and Jets around PSR J2021+3651: the `Dragonfly Nebula'

We describe recent Chandra ACIS observations of the Vela-like pulsar PSR J2021+3651 and its pulsar wind nebula (PWN). This `Dragonfly Nebula' displays an axisymmetric morphology, with bright inner jets, a double-ridged inner nebula, and a ~30" polar jet. The PWN is embedded in faint diffuse emission: a bow shock-like structure with standoff ~1' brackets the pulsar to the east and emission trails off westward for 3-4'. Thermal (kT=0.16 +/-0.02 keV) and power law emission are detected from the pulsar. The nebular X-rays show spectral steepening from Gamma=1.5 in the equatorial torus to Gamma=1.9 in the outer nebula, suggesting synchrotron burn-off. A fit to the `Dragonfly' structure suggests a large (86 +/-1 degree) inclination with a double equatorial torus. Vela is currently the only other PWN showing such double structure. The >12 kpc distance implied by the pulsar dispersion measure is not supported by the X-ray data; spectral, scale and efficiency arguments suggest a more modest 3-4 kpc.Comment: 22 pages, 5 figures, 3 tables, Accepted to Ap

Adaptive Importance Sampling for Performance Evaluation and Parameter Optimization of Communication Systems

We present new adaptive importance sampling techniques based on stochastic Newton recursions. Their applicability to the performance evaluation of communication systems is studied. Besides bit-error rate (BER) estimation, the techniques are used for system parameter optimization. Two system models that are analytically tractable are employed to demonstrate the validity of the techniques. As an application to situations that are analytically intractable and numerically intensive, the influence of crosstalk in a wavelength-division multiplexing (WDM) crossconnect is assessed. In order to consider a realistic system model, optimal setting of thresholds in the detector is carried out while estimating error rate performances. Resulting BER estimates indicate that the tolerable crosstalk levels are significantly higher than predicted in the literature. This finding has a strong impact on the design of WDM networks. Power penalties induced by the addition of channels can also be accurately predicted in short run-time

Urban sprawl and microclimate in the Ga East Municipality of Ghana

Climatic elements such as temperature and rainfall provide great and unquantifiable benefits to human health. However, rapid urban sprawl has the tendency to undermine these health consequences. The relationship between urban sprawl and microclimate in the Ga East Municipality has been assessed to present the extent of sprawl that inhibit temperature and rainfall in recent times. Methodologically, satellite imagery and meteorological data (minimum and maximum temperature and rainfall) from 1990 to 2020 were used. The results indicate that rapid urban sprawl in recent times has significantly undermined the local climate through land use and land cover changes. There was strong statistical relationships between temperature and built-up areas (p \u3c 0.05), grass/shrub cover (p \u3c 0.04) and all vegetation cover (p \u3c 0.03). There was also strong statistical relationship between rainfall and built-up areas (p \u3c 0.03), grass/shrub cover (p \u3c 0.04) and all vegetation (p \u3c 0.02). Thus, expansion in built up areas and reduced grass/shrub cover led to increases in temperature, rainfall and surface water run off while reduction in all vegetation led to increase in both temperature and rainfall. These changes in climate brought about by urban sprawl will affect crop production, increase cataclysmic floods as well as growth of some harmful insects. There is the need for the amalgamation of urban growth and climate change into spatial planning through an all-embracing approach

The contribution of seed systems to crop and tree diversity in sustainable food systems.

This chapter will review the evidence that shows that farmers’ access to seeds has an impact on the sustainability of food production and consumption. Diverse seeds are needed to support the diversification of agriculture, which in turn may contribute to more diverse diets, and to using species and varieties for the integrity of ecosystem services. In what follows, we define three functions of seed systems. We discuss the evidence that farmers’ seed access influences food production and consumption. We then discuss each of the three key functions (production and distribution, innovation, regulation) in turn and review the evidence that differences in the capacity of seed systems to perform each function make a difference to fulfilling the overall goal of seed systems, in terms of their contribution to sustainable food systems. We also describe existing work to provide data and indicators to characterize each seed system function and assess how these can be used to measure the link between agricultural biodiversity and sustainable food systems in this context

Low loss, high contrast optical waveguides based on CMOS compatible LPCVD processing

A new class of integrated optical waveguide structures is presented, based on low cost CMOS compatible LPCVD processing. This technology allows for medium and high index contrast waveguides with very low channel attenuation. The geometry is basically formed by a rectangular cross-section silicon nitride $(Si_{3}N_{4})$ filled with and encapsulated by silicon dioxide $(SiO_{2})$. The birefringence and minimal bend radius of the waveguide is completely controlled by the geometry of the waveguide layer structures. Experiments on typical geometries will be presented, showing excellent characteristics (channel attenuation ≤0.06 dB/cm, IL ≤0.6 dB, PDL ≤0.2 dB, Bg «1 x $10^{-3}$, bend radius ≤500 μm)

A low incidence of perineal hernia when using a biological mesh after extralevator abdominoperineal excision with or without pelvic exenteration or distal sacral resection in locally advanced rectal cancer patients

Background Extralevator abdominoperineal excision (ELAPE), abdominoperineal excision (APE) or pelvic exenteration (PE) with or without sacral resection (SR) for locally advanced rectal cancer leaves a significant defect in the pelvic floor. At first, this defect was closed primarily. To prevent perineal hernias, the use of a biological mesh to restore the pelvic floor has been increasing. The aim of this study, was to evaluate the outcome of the use of a biological mesh after ELAPE, APE or PE with/without SR. Methods A retrospective study was conducted on patients who had ELAPE, APE or PE with/without SR with a biological mesh (Permacol™) for pelvic reconstruction in rectal cancer in our center between January 2012 and April 2015. The endpoints were the incidence of perineal herniation and wound healing complications. Results Data of 35 consecutive patients [22 men, 13 women; mean age 62 years (range 31–77 years)] were reviewed. Median follow-up was 24 months (range 0.4–64 months). Perineal hernia was reported in 3 patients (8.6%), and was asymptomatic in 2 of them. The perineal wound healed within 3 months in 37.1% (n = 13), within 6 months in 51.4% (n = 18) and within 1 year in 62.9% (n = 22). In 17.1% (n = 6), the wound healed after 1 year. It was not possible to confirm perineal wound healing in the remaining 7 patients (20.0%) due to death or loss to follow-up. Wound dehiscence was reported in 18 patients (51.4%), 9 of whom needed vacuum-assisted closure therapy, surgical closure or a flap reconstruction. Conclusions Closure of the perineal wound after (EL)APE with a biological mesh is associated with a low incidence of perineal hernia. Wound healing complications in this high-risk group of patients are comparable to those reported in the literature