High Capacity Data Rate System: Review of Visible Light Communications Technology

Wireless communications have become an integral part of global convergence as global connectedness has gradually become dependent on its efficient deployment. The need for “more-broadband” techniques in relation to the ever increasing growth rate of the data hungry society now necessitates novel techniques for the high-speed data transmission. While advancements have been made in this regard, the projection of having an eventual Internet of everything (IoE) deployment will result in an unimaginable transmission data rate requirement as huge data traffic will be conveyed per time within the communications network, which will require a capacity upgrade of the existing infrastructure. Visible light communications (VLCs), as an integral part of optical wireless communications (OWCs), have been reviewed in this article, having the capacity to extend the achievable data rate requirement of the wireless communications network. The technologies, techniques, and best practices have been presented alongside technology integration for the seamless high capacity wireless broadband deployment.     

Residence time distribution in fluidized beds: diffusion,dispersion, and adsorption

The residence time distribution (RTD) characterizes the flow patterns of tracer particles in continuous systems to identify phenomena like channelling, dispersion, dead volume, and back-mixing. Understanding the hydrodynamics in experimental reactors is imperative to derive reaction kinetics. Here, we applied the RTD methodology to examine the relationship between the physico-chemical properties of powders and gas flow patterns in an 8 mm diameter quartz micro-fluidized bed. H₂ and He tracers egressed the reactor sooner than Kr, O₂, CO, CH₄, CO₂ demonstrating that gas diffusivity is a factor to consider when choosing a tracer gas. Intraparticle porosity is a second factor that delays the RTD curve: the residence time was 7% greater for virgin vanadium pyrophosphate catalyst (VPP) with a lower particle density than an equilibrated VPP. These results suggest that RTD experiments are sensitive enough to detect phenomena like catalyst sintering and pore blocking due to coke in situ. The RTD curve of CO and CH₄ tracers with a bed of fluid catalytic cracking catalyst (FCC) had a noticeable trailing edge (tail). For the CO₂ tracer, the leading edge of the RTD curve was delayed, the peak height was 50% shorter, and the tail was extended demonstrating adsorption phenomena like a chromatographic effect. The residence time of Kr, with a similar gas diffusivity as CO₂ was also longer compared to CO or CH₄, but the tail was shorter than for CO₂, which confirms the adsorptive nature of the FCC surface with CO₂. A bolus-pulse input function detected these hydrodynamic anomalies with a greater certainty than a Heaviside-step input.     

Experimental Methods in Chemical Engineering: Particle Size Distribution by Laser Diffraction—PSD

Particle size is the top cited physical property researchers report in The Canadian Journal of Chemical Engineering and among the top properties in all science disciplines. ^[1] Techniques to measure particle size distribution (PSD) include physical operations like sieving and sedimentation, and spectroscopic techniques like laser diffraction image analysis based on optical and electron microscopy, and elecro‐zone instruments. Here we concentrate on laser diffraction analysis (LDA) and review its basic principles, operations, limitations, uncertainties, and mention how it compares to other techniques. LDA is an instantaneous, user‐friendly, convenient, and non‐destructive method to assess PSD of inorganic powders. It measures the scattering angle and intensity of light after it passes through diluted particle dispersions suspended in either a gas or liquid. The Mie theory is an exact solution to resolve the diffraction intensity of light caused by particles that applies to while the Fraunhoffer approximation applies only to particles greater than 20 m. The 95 % confidence interval of five measurements of 56 m and 0.1 m irregularly shaped polyhedrons was . Based on a bibliometric analysis of LDA of the top 10 000 cited articles in 2016 and 2017, the major research clusters are: particle measurement, powder behaviour, pharmacy, comminution, and adsorption. Future work will continue to introduce more laser sources, combine multiple technologies, implement mobile light sources (dynamic light scattering), and better define characterize irregularly shaped particles.     

VPO transient lattice oxygen contribution

n-Butane partial oxidation to maleic anhydride is practiced commercially in several reactor types with vanadium phosphorous oxide (VPO) catalyst. DuPont operated a Circulating Fluidized Bed facility in which catalyst was shuttled between a net reducing zone (a transport bed) to a net oxidizing zone (air regenerator). Several advantages have been cited for this technology but the role of oxygen is hotly debated and different models have been proposed to characterize the complicated 14e⁻ exchange. To examine the role of surface lattice oxygen, we carried out transient experiments in which catalyst was subjected to high concentrations of butane followed by an extensive re-oxidation treatment. Carbon accumulates on the surface lattice surface thereby contributing to a reduction in reaction rates and the quantity increases with the butane/oxygen ratio. This carbon reacts in the presence of molecular O₂ during the regeneration step. The surface lattice is capable of storing significant amounts of oxygen and when the catalyst is highly oxidized, both selectivity and activity are higher.     

Infection of human cells by an endogenous retrovirus of pigs

The possible use of pig organs and tissues as xenografts in humans is actively being considered in biomedical research. We therefore examined whether pig endogenous retrovirus (PERV) genomes can be infectiously transmitted to human cells in culture. Two pig kidney cell lines spontaneously produce C-type retrovirus particles. Cell-free retrovirus produced by the PK-15 kidney cell line (PERV-PK) infected pig, mink and human kidney 293 cell lines and co-cultivation of X-irradiated PK-15 cells with human cells resulted in a broader range of human cell infection, including human diploid fibroblasts and B- and T-cell lines. Kidney, heart and spleen tissue obtained from domestic pigs contained multiple copies of integrated PERV genomes and expressed viral RNA. Upon passage in human cells PERV-PK could rescue a Moloney retroviral vector and acquired resistance to lysis by human complement.