Effects of Concentration and Catalyst on the Kinetics of Biogas Production from Cattle Dung at Thermophilic Temperature

Five different reactors (Ra, Rb, Rc, Rd and Re) of equal capacity (500cm3 each) were constructed and connected to a gas-collecting device. For the investigation of the effect of concentration on biogas production (uncatalysed reaction), different concentrations of reactant (20g/250cm3, 30g/250cm3, 40g/250cm3, 50g/250cm3 and 60g/250cm3) prepared from cattle dung were respectively placed in Ra, Rb, Rc, Rd, and Re, and anaerobically fermented at thermophilic temperature (370C) for 16days. For the investigation of the combined effect of concentration and catalyst (catalysed reaction), parallel set ups were made, but in this case, 1.0g, 1.5g, 2.0g, 2.5g, and 3.0g of yeast were respectively added to the reactants (slurries) in Ra, Rb, Rc, Rd, and Re, which were also anaerobically fermented at 370C for 16days. The reactors and their contents for both the catalyzed and uncatalyzed reactions were made in triplicate and the mean (average) volume of biogas collected in each of the reactors were evaluated. The average volumes of biogas obtained were used for the kinetics studies, where the rate of biogas production, the rate constant for biogas formation from the substrate (cattle dung), the rate of catalyst substrate unstable complex formation, the fraction of total catalyst that involved in the formation of complex with substrate, the concentration of excess (free) catalyst in the slurry, the rate of substrate transformation into biogas and the saturation constant of the catalyst added to each slurry was evaluated using the appropriate equations. The research revealed that, addition of catalyst to the slurries,  enhanced biogas production; at a certain point, the volume of biogas produced, the rate of biogas formation, the rate of catalyst substrate unstable complex formation and the rate of substrate transformation into biogas were directly proportional to the concentrations of the reactants and catalyst; the rate constants for reactions (catalyzed and uncatalyzed) were inversely proportional to the concentrations of reactants and the catalyst added; the fractions of the total catalyst that involved in the formation of unstable complex  with substrate in Ra, Rb, Rc, Rd, and Re were 0.95g, 0.97g, 0.98g, 0.98g, and 0.98g, respectively; the concentrations of the excess catalyst in Ra, Rb, Rc, Rd, and (g/cm3) were 0.05, 0.53, 1.02, 1.52 and 2.02, respectively and; the saturation constants (g/g) of the catalyst added to the slurries in Ra, Rb, Rc, Rd, and Re were 0.0476, 0.0484, 0.0488, 0.0490, and 0.0492, respectively. The research also revealed that the reactions (catalyzed and uncatalyzed) carried out obeyed first order rate law equation. Key-words: Biogas; cattle dung; anaerobic fermentation; concentration; catalyst; thermophilic temperature

Comparison of ascorbic acid content of some selected fresh and dried tropical vegetables

Ascorbic acid (Vitamin C) was determined in four different tropical vegetables (Cucumber, Cabbage, Spinach and Tomatoes) sourced from Yankaba market, Kano state. Colorimetric method was used for the  determination. The ascorbic acid content in the cucumber, cabbage, spinach and tomatoes ranged from 51.67mgL-1 to 395.45mgL-1. Tomatoes were found to have the highest concentrations (395.45mgL-1) while cucumber has the lowest (181.82mgL-1 for the fresh and 60.00mgL-1 and 51.67mgL-1 respectively) for the dried vegetables. The deficiency of ascorbic acid is believed to result in scurvy, a disease characterized by spongy and sore gum, loose teeth, anaemia, swollen joint, fragile blood vessels. Frequent intake, therefore of these vegetables rich in vitamin C (especially tomatoes) will help prevent these problems in human being. This indicated that although the vegetables are rich in ascorbic acid content, their dried forms have grossly inadequate amount to ensure the provision of required dietary intake (RDI) of vitamin C for humans.Keywords: Ascorbic acid, Comparison, Vegetables, Vitamin

Effects of Treated Wood Flour on Physico-Mechanical Properties of Filled Natural Rubber

Wood flour was crushed in to particle size and given two surface treatments each with alkali and 3-chloro-2 hydroxylpropyltrimethylammoniumchloride. The raw, alkali-treated and bonding agent treated fibers were used as natural rubber composites. The samples were used to produce fiber-reinforced natural rubber composite at varying filler loadings. Properties such as tensile strength, hardness and impact resistance of the composites were investigated. The tensile strength of the composites varied such that both the alkali-treated and cationized fillers recorded higher values than the untreated fillers. The impact strength and hardness properties were also found to be better in the modified than the untreated ones. This work has shown some general improvements arising from causticization and cationization of cellulosic filler as reinforcing material for natural rubber.Keywords: Cationization, Causticization, Mechanical properties, Natural rubber, Wood flour

Anti Bacterial Activity of Ethanolic Extract of Zingiber Officinale and Pipper Nigrum against Some Clinical Isolates

Ethanolic extract of Zingiber officinale and Pipper nigrum were evaluated by testing in vitro antimicrobial activity on clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia, Escherichia coli, and proteus specie using Agar diffusion method. Proteus specie showed sensitivity to Z. officinale at disc concentration range of 50 to 800µg/ml, Staphylococcus aureus also showed sensitivity to z. officinale at concentration of 100 to 800 µg/ml and Klebsiella pneumonia showed sensitivity at disc concentration of 100 to 800 µg/ml likewise proteus specie showed sensitivity to p. nigrum at disc concentration range of 100 to 800µg/ml and staphylococcus aureus also showed sensitivity to p. nigrum at disc concentration range of 100 to 800µg/ml. However, the Ethanolic extract of z. officinale and p. nigrum showed no lethal or inhibitory effects on Pseudomonas aeruginosa and Escherichia coli at all concentration. The observed minimum inhibitory concentration (MIC) of the Ethanolic extraction for proteus species, Staphylococcus aureus and Klebsiella pneumonia were 50, 100,200µglml respectively for Z. officinale, while for P. nigrum, the minimum inhibitory concentration (MIC) were 100 and 200µg/ml for Proteus specie and staphylococcus aureus respectively. The extracts were further subjected to phytochemical tests for the presence of secondary metabolites using standard procedures. The results of phytochemical screening indicated the presence of alkaloids, Flavonoid, reducing sugar, saponins and steroids in Z. officinale, and alkaloids, Flavonoid, saponins, steroids and tannin in P. nigrum. This indicates that both Z. officinale and piper nigrum has the potential for the production of drugs against pathogenic organisms

Switching from exact scheme to nonstandard finite difference scheme for linear delay differential equation

One-dimensional models are important for developing, demonstrating and testing new methods and approaches, which can be extended to more complex systems. We design for a linear delay differential equation a reliable numerical method, which consists of two time splits as follows: (a) It is an exact scheme at the early time evolution −τ ≤ t ≤ τ, where τ is the discrete value of the delay; (b) Thereafter, it is a nonstandard finite difference (NSFD) scheme obtained by suitable discretizations at the backtrack points. It is shown theoretically and computationally that the NSFD scheme is dynamically consistent with respect to the asymptotic stability of the trivial equilibrium solution of the continuous model. Extension of the NSFD to nonlinear epidemiological models and its good performance are tested on a numerical example.Three of the authors (SMG, ASH and JM-SL) acknowledge the support of the South African DST/NRF SARChI chair in Mathematical Models and Methods in Bioengineering and Biosciences (M3B2). ASH acknowledges the support of MacArthur Foundation, Bayero University, Kano, Nigeria. ABG acknowledges, with thanks, the support, in part, of the Natural Science and Engineering Research Council (NSERC) of Canada.http://www.elsevier.com/ locate/amchb201

Transmission characteristics of MERS and SARS in the healthcare setting: a comparative study

Background: The Middle East respiratory syndrome (MERS) coronavirus has caused recurrent outbreaks in the Arabian Peninsula since 2012. Although MERS has low overall human-to-human transmission potential, there is occasional amplification in the healthcare setting, a pattern reminiscent of the dynamics of the severe acute respiratory syndrome (SARS) outbreaks in 2003. Here we provide a head-to-head comparison of exposure patterns and transmission dynamics of large hospital clusters of MERS and SARS, including the most recent South Korean outbreak of MERS in 2015. Methods: To assess the unexpected nature of the recent South Korean nosocomial outbreak of MERS and estimate the probability of future large hospital clusters, we compared exposure and transmission patterns for previously reported hospital clusters of MERS and SARS, based on individual-level data and transmission tree information. We carried out simulations of nosocomial outbreaks of MERS and SARS using branching process models rooted in transmission tree data, and inferred the probability and characteristics of large outbreaks. Results: A significant fraction of MERS cases were linked to the healthcare setting, ranging from 43.5 % for the nosocomial outbreak in Jeddah, Saudi Arabia, in 2014 to 100 % for both the outbreak in Al-Hasa, Saudi Arabia, in 2013 and the outbreak in South Korea in 2015. Both MERS and SARS nosocomial outbreaks are characterized by early nosocomial super-spreading events, with the reproduction number dropping below 1 within three to five disease generations. There was a systematic difference in the exposure patterns of MERS and SARS: a majority of MERS cases occurred among patients who sought care in the same facilities as the index case, whereas there was a greater concentration of SARS cases among healthcare workers throughout the outbreak. Exposure patterns differed slightly by disease generation, however, especially for SARS. Moreover, the distributions of secondary cases per single primary case varied highly across individual hospital outbreaks (Kruskal–Wallis test; P \u3c 0.0001), with significantly higher transmission heterogeneity in the distribution of secondary cases for MERS than SARS. Simulations indicate a 2-fold higher probability of occurrence of large outbreaks (\u3e100 cases) for SARS than MERS (2 % versus 1 %); however, owing to higher transmission heterogeneity, the largest outbreaks of MERS are characterized by sharper incidence peaks. The probability of occurrence of MERS outbreaks larger than the South Korean cluster (n = 186) is of the order of 1 %. Conclusions: Our study suggests that the South Korean outbreak followed a similar progression to previously described hospital clusters involving coronaviruses, with early super-spreading events generating a disproportionately large number of secondary infections, and the transmission potential diminishing greatly in subsequent generations. Differences in relative exposure patterns and transmission heterogeneity of MERS and SARS could point to changes in hospital practices since 2003 or differences in transmission mechanisms of these coronaviruses

Anatomy of the Epidemiological Literature on the 2003 SARS Outbreaks in Hong Kong and Toronto: A Time-Stratified Review

Weijia Xing and colleagues reviewed the published epidemiological literature on SARS and show that less than a quarter of papers were published during the epidemic itself, suggesting that the research published lagged substantially behind the need for it

A systematic review to identify areas of enhancements of pandemic simulation models for operational use at provincial and local levels

<p>Abstract</p> <p>Background</p> <p>In recent years, computer simulation models have supported development of pandemic influenza preparedness policies. However, U.S. policymakers have raised several <it>concerns </it>about the practical use of these models. In this review paper, we examine the extent to which the current literature already addresses these <it>concerns </it>and identify means of enhancing the current models for higher operational use.</p> <p>Methods</p> <p>We surveyed PubMed and other sources for published research literature on simulation models for influenza pandemic preparedness. We identified 23 models published between 1990 and 2010 that consider single-region (e.g., country, province, city) outbreaks and multi-pronged mitigation strategies. We developed a plan for examination of the literature based on the concerns raised by the policymakers.</p> <p>Results</p> <p>While examining the concerns about the adequacy and validity of data, we found that though the epidemiological data supporting the models appears to be adequate, it should be validated through as many updates as possible during an outbreak. Demographical data must improve its interfaces for access, retrieval, and translation into model parameters. Regarding the concern about credibility and validity of modeling assumptions, we found that the models often simplify reality to reduce computational burden. Such simplifications may be permissible if they do not interfere with the performance assessment of the mitigation strategies. We also agreed with the concern that social behavior is inadequately represented in pandemic influenza models. Our review showed that the models consider only a few social-behavioral aspects including contact rates, withdrawal from work or school due to symptoms appearance or to care for sick relatives, and compliance to social distancing, vaccination, and antiviral prophylaxis. The concern about the degree of accessibility of the models is palpable, since we found three models that are currently accessible by the public while other models are seeking public accessibility. Policymakers would prefer models scalable to any population size that can be downloadable and operable in personal computers. But scaling models to larger populations would often require computational needs that cannot be handled with personal computers and laptops. As a limitation, we state that some existing models could not be included in our review due to their limited available documentation discussing the choice of relevant parameter values.</p> <p>Conclusions</p> <p>To adequately address the concerns of the policymakers, we need continuing model enhancements in critical areas including: updating of epidemiological data during a pandemic, smooth handling of large demographical databases, incorporation of a broader spectrum of social-behavioral aspects, updating information for contact patterns, adaptation of recent methodologies for collecting human mobility data, and improvement of computational efficiency and accessibility.</p

Trends in parameterization, economics and host behaviour in influenza pandemic modelling: a review and reporting protocol.

BACKGROUND: The volume of influenza pandemic modelling studies has increased dramatically in the last decade. Many models incorporate now sophisticated parameterization and validation techniques, economic analyses and the behaviour of individuals. METHODS: We reviewed trends in these aspects in models for influenza pandemic preparedness that aimed to generate policy insights for epidemic management and were published from 2000 to September 2011, i.e. before and after the 2009 pandemic. RESULTS: We find that many influenza pandemics models rely on parameters from previous modelling studies, models are rarely validated using observed data and are seldom applied to low-income countries. Mechanisms for international data sharing would be necessary to facilitate a wider adoption of model validation. The variety of modelling decisions makes it difficult to compare and evaluate models systematically. CONCLUSIONS: We propose a model Characteristics, Construction, Parameterization and Validation aspects protocol (CCPV protocol) to contribute to the systematisation of the reporting of models with an emphasis on the incorporation of economic aspects and host behaviour. Model reporting, as already exists in many other fields of modelling, would increase confidence in model results, and transparency in their assessment and comparison

Influence of the topology on the dynamics of a complex network of HIV/AIDS epidemic models

In this paper, we propose an original complex network model for an epidemic problem in an heterogeneous geographical area. The complex network is constructed by coupling nonidentical instances of a HIV/AIDS epidemiological model for which a disease-free equilibrium and an endemic equilibrium can coexist. After proving the existence of a positively invariant region for the solutions of the complex network problem, we investigate the effect of the coupling on the dynamics of the network, and establish the existence of a unique disease-free equilibrium for the whole network, which is globally asymptotically stable. We prove the existence of an optimal topology that minimizes the level of infected individuals, and apply the theoretical results to the case of the Cape Verde archipelago.This research was partially supported by the Portuguese Foundation for Science and Technology (FCT) within projects UID/MAT/04106/2019 (CIDMA) and PTDC/EEI-AUT/2933/2014 (TOCCATTA), co-funded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalizac¸ao (POCI) and by national funds (FCT). Silva is also supported by national funds (OE), through FCT, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.publishe