Mixing regime simulation and cellulose particle tracing in a stacked frame photocatalytic reactor.

To sustainably meet the global energy demand, unconventional methods to produce renewable energy must emerge. Biofuels from cellulose (via fermentable sugar production) mediated via photocatalysis provides an alternative to conventional fossil fuels. In order to effectively drive photocatalytic processes an effective reactor design is required, the design of which is influenced by a number of key factors such as the catalyst to reactant ratio and residence time, catalyst illumination time, light penetration and distribution for the system, mass transfer limitations (mixing) and product recovery. In this study we use COMSOL Multiphysics® to simulate and assess one of the mentioned parameters – mixing regime of cellulose particles in a Stacked Frame Photocatalysis Reactor (SFPR). In the reactor design, we compare two mixers: a ‘plus’ shaped magnetic stirrer bar and an 8 blade Rushton impeller. The simulations reveal that the Rushton impeller offers a radial mixing pattern with a higher fluid velocity of 1.2m/s when compared to the stirrer bar that offers a fluid velocity of 0.9m/s. Cellulose particle tracing simulations confirm that the particle dispersion is superior in the case of the Rushton impeller as the vorticity generated during the mixing push the particles to the reactor's walls. Since the particles are forced towards the walls, there is a probability of more particles being illuminated than in the case of no or improper mixing

Cellulose II as bioethanol feedstock and its advantages over native cellulose.

Alternative renewable energy must emerge to sustainably meet the energy demands of the present and future. Current alternatives to fossil fuels are electricity from solar, wind and tidal energies and biofuels. Biofuels, especially bioethanol could be produced from lignocellulosic feedstock via pre-treatment and fermentation. The cellulose I content of most lignocellulosic feedstock is significant, yet its highly crystalline amphiphilic structure interlinked with the lignin network makes it difficult to process for bioethanol production. Processing lignocellulosic biomass via a range of physico-chemical, mechanical and biological pre-treatment methods have been well established, however a relatively new area on the use of cellulose II (a polymorph of native cellulose obtained via mercerisation or regeneration) for the production of bioethanol is still in its early stages. Hence, this review discusses in detail the advantages of using cellulose II over cellulose I as feedstock for bioethanol production. Furthermore, current green and sustainable methods for cellulose II production and the advantages and disadvantages of each method are discussed. In addition, examples from literature reporting higher fermentable sugar and bioethanol yields using cellulose II as feedstock are reviewed, thereby highlighting its importance in the field of bioethanol production. The conclusion from this review suggests that, in all the cases studied, fermentable sugar and/or bioethanol production was found to be higher when cellulose II was used as feedstock instead of native cellulose/lignocellulosic biomass. This higher yield could be attributed to the modified structural and lattice arrangement of cellulose II, its porous volume and degree of polymerisation

Cryptococcus neoformans ex vivo capsule size is associated with intracranial pressure and host immune response in HIV-associated cryptococcal meningitis

<p>Background. The Cryptococcus neoformans polysaccharide capsule is a well-characterised virulence factor with immunomodulatory properties. The organism and/or shed capsule is postulated to raise intracranial pressure(ICP) in cryptococcal meningitis(CM) by mechanical obstruction of cerebrospinal fluid(CSF) outflow. Little is known regarding capsule phenotype in human cryptococcosis. We investigated the relationship of ex vivo CSF capsular phenotype with ICP and CSF immune response, as well as in vitro phenotype.</p> <p>Methods. 134 HIV-infected Ugandan adults with CM had serial lumbar punctures with measurement of CSF opening pressures, quantitative cultures, ex vivo capsule size and shedding, viscosity, and CSF cytokines. 108 had complete data. Induced capsular size and shedding were measured in vitro for 48 C. neoformans isolates.</p> <p>Results. Cryptococcal strains producing larger ex vivo capsules in the baseline(pre-treatment) CSF correlated with higher ICP(P=.02), slower rate of fungal clearance(P=.02), and paucity of CSF inflammation, including decreased CSF white blood cell(WBC) count(P<.001), interleukin(IL)-4(P=.02), IL-6(P=.01), IL-7(P=.04), IL-8(P=.03), and interferon-gamma(P=.03). CSF capsule shedding did not correlate with ICP. On multivariable analysis, capsule size remained independently associated with ICP. Ex vivo capsular size and shedding did not correlate with that of the same isolates grown in vitro.</p> <P>Conclusions. Cryptococcal capsule size ex vivo is an important contributor to virulence in human cryptococcal meningitis.</P&gt

Photocatalytic conversion of cellulose into C5 oligosaccharides.

Cellulose is made up of linear polymers of glucose monomers that could be a crucial source for valuable chemicals and sustainable liquid fuels. Cellulose is however, very stable and its conversion to a useful fuel or platform chemical products remains a significant challenge (Kimura et al 2015 Sci. Rep. 5 16266; Xia et al 2016 Nat. Commun. 7 11162). Photocatalysis is a versatile technology which has demonstrated potential for solar driven processes such as water splitting or solar fuels production and has also been applied to the degradation of pollutants in air and water and for the production of useful products from biomass. Here, we focus on the products that are produced from cellulose (a glucose (C6) based polymer) photocatalysis that compliment hydrogen production. Probing the initial steps via UV-TiO2 photocatalysis, we remarkably find that an array of oligosaccharides containing only five (C5) carbon units is initially produced. As the process continues, C6 oligo oligosaccharides grow to dominate. The photocatalytic process is generally not viewed as a controllable synthetic process; however, these findings show, on the contrary that photocatalysis at semiconductor surfaces can achieve novel reaction pathways yielding new products

Solar-driven semi-conductor photocatalytic water treatment (TiO2, g-C3N4, and TiO2+g-C3N4) of cyanotoxins: proof-of-concept study with microcystin-LR.

Cyanobacteria and their toxins are a threat to drinking water safety as increasingly cyanobacterial blooms (mass occurrences) occur in lakes and reservoirs all over the world. Photocatalytic removal of cyanotoxins by solar light active catalysts is a promising way to purify water at relatively low cost compared to modifying existing infrastructure. We have established a facile and low-cost method to obtain TiO2 and g-C3N4 coated floating photocatalysts using recycled glass beads. g-C3N4 coated and TiO2+g-C3N4 co-coated beads were able to completely remove microcystin-LR in artificial fresh water under both natural and simulated solar light irradiation without agitation in less than 2 h. TiO2 coated beads achieved complete removal within 8 h of irradiation. TiO2+g-C3N4 beads were more effective than g-C3N4 beads as demonstrated by the increase reaction rate with reaction constants, 0.0485 min−1 compared to 0.0264 min−1 respectively, with TiO2 alone found to be considerably slower 0.0072 min−1. g-C3N4 based photocatalysts showed a similar degradation pathway to TiO2 based photocatalysts by attacking the C6–C7 double bond on the Adda side chain

Comparative assessment of visible light and UV active photocatalysts by hydroxyl radical quantification.

A simple method for determining hydroxyl radical yields on semiconductor photocatalysts is highly desirable, especially when comparing different photocatalyst materials. This paper reports the screening of a selection of visible light active photocatalysts such as Pt-C3N4, 5% LaCr doped SrTiO3, Sr0.95Cr0.05TiO3 and Yellow TiO2 and compares them against WO3 and ultra violet (UV) light activated TiO2 P25 (standard commercial catalysts) based on their oxidative strengths (OH radical producing capability) using a well-studied chemical probe–coumarin. 7-hydroxycoumarin, the only fluorescent hydroxylation product of this reaction can then be measured to indirectly quantify the OH radicals produced. P25 under UV light produced the highest concentration of OH radicals (16.9μM), followed by WO3 (0.56μM) and Pt-C3N4 (0.25μM). The maximum OH radical production rate for P25, WO3 and Pt-C3N4 were also determined and found to be 35.6μM/hr, 0.28μM/h and 0.88μM/h respectively. The other visible light activated photocatalysts did not produce any OH radicals primarily as a result of their electronic structure. Furthermore, it was concluded that, if any visible light absorbing photocatalysts are to be fabricated in future for the purpose of photocatalytic oxidation, their OH radical producing rates (and quantities) should be determined and compared to P25

Endocrine disruptor compounds-a cause of impaired immune tolerance driving inflammatory disorders of pregnancy?

Endocrine disrupting compounds (EDCs) are prevalent and ubiquitous in our environment and have substantial potential to compromise human and animal health. Amongst the chronic health conditions associated with EDC exposure, dysregulation of reproductive function in both females and males is prominent. Human epidemiological studies demonstrate links between EDC exposure and infertility, as well as gestational disorders including miscarriage, fetal growth restriction, preeclampsia, and preterm birth. Animal experiments show EDCs administered during gestation, or to either parent prior to conception, can interfere with gamete quality, embryo implantation, and placental and fetal development, with consequences for offspring viability and health. It has been presumed that EDCs operate principally through disrupting hormone-regulated events in reproduction and fetal development, but EDC effects on maternal immune receptivity to pregnancy are also implicated. EDCs can modulate both the innate and adaptive arms of the immune system, to alter inflammatory responses, and interfere with generation of regulatory T (Treg) cells that are critical for pregnancy tolerance. Effects of EDCs on immune cells are complex and likely exerted by both steroid hormone-dependent and hormone-independent pathways. Thus, to better understand how EDCs impact reproduction and pregnancy, it is imperative to consider how immune-mediated mechanisms are affected by EDCs. This review will describe evidence that several EDCs modify elements of the immune response relevant to pregnancy, and will discuss the potential for EDCs to disrupt immune tolerance required for robust placentation and optimal fetal development.John E. Schjenken, Ella S. Green, Tenuis S. Overduin, Chui Yan Mah, Darryl L. Russell and Sarah A. Robertso

Change in CT-measured acetabular bone density following total hip arthroplasty: a systematic review and meta-analysis

Background and purpose - Assessing peri-acetabular bone quality is valuable for optimizing the outcomes of pri- mary total hip arthroplasty (THA) as preservation of good quality bone stock likely affects implant stability. The aim of this study was to perform a meta-analysis of peri-acetabular bone mineral density (BMD) changes over time measured using quantitative computer tomography (CT) and, second, to investigate the influence of age, sex, and fixation on the change in BMD over time.Methods - A systematic search of Embase, Scopus, Web of Science, and PubMed databases identified 19 studies that measured BMD using CT following THA. The regions of interest (ROI), reporting of BMD results, and scan protocols were extracted. A meta-analysis of BMD was performed on 12 studies that reported measurements immediately postop- eratively and at follow-up.Results - The meta-analysis determined that peri- acetabular BMD around both cemented and uncemented components decreases over time. The amount of BMD loss increased relative to proximity of the acetabular component. There was a greater decrease in cortical BMD over time in females and cancellous BMD for young patients of any sex.Conclusion - Peri-acetabular BMD decreases at differ- ent rates relative to its proximity to the acetabular component. Cancellous BMD decreases more in young patients and cor- tical bone decreases more in females. Standardized reporting parameters and suggested ROI to measure peri-acetabular BMD are proposed, to enable comparison between implant and patient variables in the future.Orthopaedics, Trauma Surgery and Rehabilitatio

Networks of attribution: the cultural origins of meaning.

Despite the fact that we commonly refer to artworks as 'meaningful' things, this is not to say that meaning is a property analogous to size or shape. If meaning is not a property, then it seems reasonable to suppose that it can only be a way of using things, of treating them as if they were imbued with features that they do not actually possess. Meaning is thus an attribution in which we agree through social consensus to use objects as tokens of power, prestige, celebration, explanation, instruction and so on. I argue that such symbolic procedures originate in practices of exchange and tool-use in which the use of raw materials instantiates their identity. The purpose of this paper is to show that the ability to interpret artworks and more generally to ascribe meanings, is a highly sophisticated cultural capacity and, more specifically, a verbal skill dependent upon a network of symbolic resources and techniques that only a socially evolved linguistic culture can provide and enable

Photocatalytic removal of the cyanobacterium Microcystis aeruginosa PCC7813 and four microcystins by TiO2 coated porous glass beads with UV-LED irradiation.

Cyanobacteria and their toxic secondary metabolites are a challenge in water treatment due to increased biomass and dissolved metabolites in the raw water. Retrofitting existing water treatment infrastructure is prohibitively expensive or unfeasible, hence 'in-reservoir' treatment options are being explored. In the current study, a treatment system was able to photocatalytically inhibit the growth of Microcystis aeruginosa and remove released microcystins by photocatalysis using titanium dioxide coated, porous foamed glass beads and UV-LEDs (365 nm). A 35% reduction of M. aeruginosa PCC7813 cell density compared to control samples was achieved in seven days. As a function of cell removal, intracellular microcystins (microcystin-LR, -LY, -LW and -LF) were removed by 49% from 0.69 to 0.35 μg mL−1 in seven days. Microcystins that leaked into the surrounding water from compromised cells were completely removed by photocatalysis. The findings of the current study demonstrate the feasibility of an in-reservoir treatment unit applying low cost UV-LEDs and porous foamed beads made from recycled glass coated with titanium dioxide as a means to control cyanobacteria and their toxins before they can reach the water treatment plant