3,544 research outputs found

    A Simple Numerical Method for Pricing an American Put Option

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    We present a simple numerical method to find the optimal exercise boundary in an American put option. We formulate an intermediate function with the fixed free boundary that has Lipschitz character near optimal exercise boundary. Employing it, we can easily determine the optimal exercise boundary by solving a quadratic equation in time-recursive way. We also present several numerical results which illustrate a comparison to other methods

    A study of microbial analysis of fresh fruits and vegetables, in Sagamu markets South-West, Nigeria

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    Raw and minimally processed fruits and vegetables are essential parts of diets of people around the world. However, these food items have consistently served as vehicles for human diseases worldwide. This study was aimed at determining the microbiological quality of fresh fruits and vegetables sold at Sagamu markets, Ogun state, Nigeria. Twenty different samples of fruits and vegetables were randomly purchased from ten various vendors in Shagamu market, Ogun State, Nigeria. Aerobic plate counts, total coliform counts, yeast, mold counts and antimicrobial susceptibility study using were determined using standard microbiological methods. In Fruits, the isolation rate of Bacillus specie was predominant (44.1%), followed by Klebsiella species (44.0%) while in vegetables, the prevalent rates of 38.3% and 14.4% were respectively recorded by Staphylococcus aureus and Pseudomonas species. Malassezia species and Aspergillus species were the only fungal isolates obtained from the fruits and vegetables. Aspergillus species were predominant in vegetables, with a frequency of 13.3% while both Malassezia and Aspergillus species were observed almost at the same frequently of 24.1% and 24.4% in fruits respectively. This study showed that fruits and vegetable were contaminated with potential food borne pathogens with varying degree of antibiotic resistance thus suggesting that they could act as a vehicle for the dissemination of antibiotic resistant organisms as well as serve as a reservoir of food borne pathogens of public health significance.Keywords: Micro flora, fresh fruits and vegetables, antibiotics resistanc

    Comparative effects of washing solution and the survival of Staphylococcus aureus on tomatoes

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    Various types of fruits and vegetables are often eaten raw or consumed after minimum processing in which this has been connected to an increase in outbreaks of fresh produce associated with food borne diseases in the recent times. In order to determine the micro-flora, survival of Staphylococcus aureus on ripe and unripe tomatoes and to also asses the efficiency of some washing solutions, 100 tomatoes, both ripe and unripe were randomly bought from different selling points in Sagamu Markets, Ogun State Nigeria. Surface swabs of the tomatoes were cultured on both nutrient broth, and selenite F broth. The sample from nutrient broth was then sub cultured on Blood Agar, Mannitol Salt Agar, and MacConkey Agar, (MSA), Potato Dextrose Agar (SDA), while the one on Selenite F Broth was cultured on Salmonella Shigella Agar (SSA). Density of Staphylococcus aureus ATCC 25923 after pre-inoculation on ripe and unripe tomatoes, and after the application of washing solutions on tomatoes, was determined by surface spread count. The prevalence of any of the isolated micro-flora could not be significantly linked with either ripe or unripe tomatoes (0>0.05).Mean residual counts (log CFU/g) of bacteria was significantly higher in ripe tomatoes (3.52 ±2.40) than unripe tomatoes (2.30 ±1.96) after pre inoculation with Staphylococcus aureus (t =2.75, P< 0.05). Among the washing solution, hypochlorite was observed to be twice more efficient than hydrogen peroxide and thrice efficient than saline solution. In conclusion, Staphylococcal colonization of tomatoes skin is significantly reduced in unripe tomatoes. And also, hypochlorite solutions are better than hydrogen peroxide and saline in Staphylococcal decontamination from tomatoes.Key words: washing solution, Staphylococcus aureus, tomatoe

    Microbial biocatalytic preparation of 2-furoic acid by oxidation of 2-furfuryl alcohol and 2-furanaldehyde with Nocardia corallina

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    The preparation of 2-furoic acid via oxidation of 2-furfuryl alcohol and 2-furanaldehyde was studied by two procedures using whole cells of Nocardia corallina B-276. We describe a comparison using a batchcultivation (3-L) versus resting cells in potassium phosphate buffer (0.1 M, pH 7.0). In the 3-L bioreactor, 2-furfuryl alcohol (1.35 g/L) was biotransformed after 24 h, to the acid with 81% yield. The bioconversionof 2-furfuryl alcohol using resting cells leads to and almost quantitative yield (98%) of 2-furoic acid in 21 h. 2-furanaldehyde was also oxidized to the 2-furoic acid in 88% yield in 8 h, the ratio substrate:cellswas 1:3.5 (w/w). This method was scaled up to 9 g/L of 2-furanaldehyde

    Control of an Underactuated Double-Pendulum Overhead Crane using Improved Model Reference Command Shaping: Design, Simulation and Experiment

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    This paper presents a new control scheme based on model reference command shaping (MRCS) for an overhead crane, with double-pendulum mechanism effects. The approach has an advantage in achieving an accurate trolley positioning, with low hook and payload oscillations, under various desired trolley positions and parameter uncertainties, without the requirement for measurement or estimation of system parameters. These are challenging in practice. The previously developed MRCS algorithm is improved in order to reduce its design complexity, as well as to ensure that it can be augmented with a feedback controller so that a concurrent controller tuning can be realised. The combined MRCS and feedback controller is used to achieve both, precise trolley positioning, and low hook and payload oscillations. To evaluate the effectiveness and the robustness of the approach, simulations and experiments using a nonlinear model and a laboratory double-pendulum crane are carried out. Under various desired positions and parameter uncertainties that involve varying the cable lengths (payload hoisting) and the payload mass variations, the superiority of the proposed approach is confirmed by achieving higher hook and payload oscillation reductions when compared with a recently proposed feedback controller. In addition, the desired trolley positions are achieved with smoother responses

    Microbial status of smoked fish, scombia scombia sold in Owerri, Imo state, Nigeria

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    As one of the common sources of protein available to man, fish is highly consumed due to its lower cholesterol content and price. So it forms a rich protein source for both poor and rich. As a part of checkmating the public health risks associated with this general dependence of the population on fish, the microbiological assessment of smoked fish, Scombia, scombia sold in Owerri was embarked on with the aim of ascertaining the microbial quality, the presence and prevalence of microorganisms of public health importance. A total of one hundred and eight (108) samples were collected from the smoking Factory, Open Market and Hawkers. These were analyzed microbiologically for viable heterotrophic bacteria and fungi count on Nutrient and Potato dextrose agar respectively, using pour plate method and coliform count in MacConkey broth by multiple tube method (MPN). The mean value results from the analysis revealed high microbial contamination in all the samples. The resultant data were analyzed statistically using randomized block design of Analysis of Variance (ANOVA) at 95% level of confidence and the difference were separated using the least significance difference (LSD). The mean results of viable  heterotrophic bacteria and fungi count showed no significance difference for the collection sites; but the coliform mean results for the three sites showed marked variation at 95% level (P>0.05). Identified bacteria, include: Staphylococcus aureus, E. coli, Bacillus sp., Klebsiella sp., whereas fungi are Penicillium sp., Aspergilusl sp., Fusarium violaceum, Biospora sp., Candida sp, Botryodioplodia sp., Alternania sp. This high level of microbial contamination can be traceable to handlers, and environment to which this fish is exposed during smoking and selling exercises, and considering the danger it portends to human health, public health and  food safety authorities should intensify their monitoring efforts towards controlling such contamination.Key words: Bacteria, Yeast, Mould, Smoked fish, Contamination

    Increased Rate of Hospitalization for Diabetes and Residential Proximity of Hazardous Waste Sites

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    BACKGROUND: Epidemiologic studies suggest that there may be an association between environmental exposure to persistent organic pollutants (POPs) and diabetes. OBJECTIVE: The aim of this study was to test the hypothesis that residential proximity to POP-contaminated waste sites result in increased rates of hospitalization for diabetes. METHODS: We determined the number of hospitalized patients 25–74 years of age diagnosed with diabetes in New York State exclusive of New York City for the years 1993–2000. Descriptive statistics and negative binomial regression were used to compare diabetes hospitalization rates in individuals who resided in ZIP codes containing or abutting hazardous waste sites containing POPs (“POP” sites); ZIP codes containing hazardous waste sites but with wastes other than POPs (“other” sites); and ZIP codes without any identified hazardous waste sites (“clean” sites). RESULTS: Compared with the hospitalization rates for diabetes in clean sites, the rate ratios for diabetes discharges for people residing in POP sites and “other” sites, after adjustment for potential confounders were 1.23 [95% confidence interval (CI), 1.15–1.32] and 1.25 (95% CI, 1.16–1.34), respectively. In a subset of POP sites along the Hudson River, where there is higher income, less smoking, better diet, and more exercise, the rate ratio was 1.36 (95% CI, 1.26–1.47) compared to clean sites. CONCLUSIONS: After controlling for major confounders, we found a statistically significant increase in the rate of hospitalization for diabetes among the population residing in the ZIP codes containing toxic waste sites

    Ocean Acidification Disrupts Prey Responses to Predator Cues but Not Net Prey Shell Growth in Concholepas concholepas (loco)

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    Background Most research on Ocean Acidification (OA) has largely focused on the process of calcification and the physiological trade-offs employed by calcifying organisms to support the building of calcium carbonate structures. However, there is growing evidence that OA can also impact upon other key biological processes such as survival, growth and behaviour. On wave-swept rocky shores the ability of gastropods to self-right after dislodgement, and rapidly return to normal orientation, reduces the risk of predation. Methodology/Principal Findings The impacts of OA on this self-righting behaviour and other important parameters such as growth, survival, shell dissolution and shell deposition in Concholepas concholepas (loco) were investigated under contrasting pCO2 levels. Although no impacts of OA on either growth or net shell calcification were found, the results did show that OA can significantly affect self-righting behaviour during the early ontogeny of this species with significantly faster righting times recorded for individuals of C. concholepas reared under increased average pCO2 concentrations (± SE) (716±12 and 1036±14 ”atm CO2) compared to those reared at concentrations equivalent to those presently found in the surface ocean (388±8 ”atm CO2). When loco were also exposed to the predatory crab Acanthocyclus hassleri, righting times were again increased by exposure to elevated CO2, although self-righting times were generally twice as fast as those observed in the absence of the crab. Conclusions and Significance These results suggest that self-righting in the early ontogeny of C. concholepas will be positively affected by pCO2 levels expected by the end of the 21st century and beginning of the next one. However, as the rate of self-righting is an adaptive trait evolved to reduce lethal predatory attacks, our result also suggest that OA may disrupt prey responses to predators in nature

    New chemolysis for urological calcium phosphate calculi – a study in vitro

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    BACKGROUND: Advances in techniques have left very few indications for open surgical extraction of urinary stones currently. These advances notwithstanding, the search continues for medical approaches to urinary stone management. In this study, we perform an in vitro study analyzing the efficiency and prospect of two new complex solutions in urological calcium phosphate calculi dissolution. METHODS: Eighteen stones composed mainly of calcium phosphates were taken from patients who underwent kidney stone surgery. These stones were large enough (weight range 0.514–0.928 g) to be fragmented and matched equally into six groups. Chemolysis of phosphate stones was done with six different solvents and was repeated 3 times with 6 stones for each solution. At 24, 48 and 72 h, reduction in weight, percentage weight change, and dissolution rate; the dissolution rates at pH 5.0, 7.0 and 8.5 for each solution, using different cations (Na(+), K(+ )or Ca(2+)), according to different dilutions (1:1, 1:2, 1:3, 1:4) of S1 and S2 were simultaneously determined. RESULTS: Calcium phosphate calculi were poorly dissolved by Phys and Art, and they had a low dissolution rate in pH 8.5 EDTA. The most effective solutions were S1, S2 and R, with 72 h mean dissolution rates: 5.75 ± 0.44 mg/hr (S1), 5.2 ± 0.63 mg/hr (S2), 4.55 ± 0.46 mg/hr (R) ([Image: see text] ± s, p < 0.01 R, S1 and S2 vs Phys, Art and EDTA; p < 0.05, S1 vs R, LSD-test). The mean percentage weight loss at 72 h was: 52.1 ± 15.75 % (S1), 44.4 ± 7.37 % (S2) and 40.5 ± 3.67 % (R) ([Image: see text] ± s, p < 0.01 R, S1 and S2 vs Phys, Art and EDTA, LSD-test). Diluted twice, S1 and S2 had even better effectiveness than their initial solution. The additive of Na(+), K(+ )or Ca(2+ )greatly reduced the dissolution rates of S1, S2. CONCLUSION: Our data indicate that test solutions S1 and S2 are effective solvents in the chemolysis of calcium phosphate stones. At twice dilutions, these solutions are even more useful in the treatment of stone disease
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