778 research outputs found
Empirical Bayes methods for the transformed Gaussian random field model with additive measurement errors
No full textIf geostatistical observations are continuous but can not be modeled by the Gaussian distribution, a more appropriate model for these data may be the transformed Gaussian model. In transformed Gaussian models it is assumed that the random field of interest is a nonlinear transformation of a Gaussian random field (GRF). For example, [9] propose the Bayesian transformed Gaussian model where they use the Box-Cox family of power transformation [3] on the observations and show that prediction for unobserved random fields can be done through posterior predictive distribution where uncertainty about the transformation parameter is taken into account. More recently, [5] consider maximum likelihood estimation of the parameters and a “plug-in” method of prediction for transformed Gaussian model with Box-Cox family of transformations. Both [9] and [5] consider spatial prediction of rainfall to illustrate their model and method of analysis. A review of the Bayesian transformed Gaussian random fields model is given in [8]. See also [6] who discusses several issues regarding the formulation and interpretation of transformed Gaussian random field models, including the approximate nature of the model for positive data based on Box-Cox family of transformations, and the interpretation of the model parameters.This is a manuscript of a chapter from Vivekananda Roy, Evangelos Evangelou, and Zhengyuan Zhu (2015), Empirical Bayes methods for Transformed Gaussian Random Fields Model with Additive Measurement Errors. In D. K. Dey, U. Singh and A. Loganathan (eds.), Current Trends in Bayesian Methodology with Applications, Chapman & Hall/CRC Press. Posted with permission.</p
Evaluating off-peak pricing strategies in public transportation with an activity-based approach
No full textEvaluating off-peak pricing strategies in public transportation using an activity-based approach
No full textPublic transportation authorities across the world are implementing various peak and off-peak pricing strategies to manage travel demand and improve the overall system performance. In this study, an activity-based demand framework is used to evaluate two off-peak pricing policies currently in use in Singapore. These policies consist of a free pre-peak travel on MRT and an off-peak discount for an integrated transit (public buses and MRT). Smart card data collected before and after the implementation of the first policy was used to calibrate the behavioral models involved, in order to properly capture travelers' preferences and choices. To evaluate both pricing strategies, a comprehensive set of key performance indicators was considered, including the changes in peak ridership, average trip fare, operator's revenue, the number of public transportation trips and mode share. The results indicate that off-peak discount pricing strategies are a viable policy option for spreading demand peaks, and that they are more effective in the afternoon peak. This study also demonstrates the capabilities and the advantages of an agent-based modeling platform SimMobility as a tool for policy analysis
Perfluorooctanesulfonate and Related Fluorochemicals in Human Blood from Several Countries
No full textPerfluorooctanesulfonyl fluoride based compounds have been used in a wide variety of consumer products, such as carpets, upholstery, and textiles. These compounds degrade to perfluorooctanesulfonate (PFOS), a persistent metabolite that accumulates in tissues of humans and wildlife. Previous studies have reported the occurrence of PFOS, perfluorohexanesulfonate (PFHxS), perfluorooctanoate (PFOA), and perfluorooctanesulfonamide (PFOSA) in human sera collected from the United States. In this study, concentrations of PFOS, PFHxS, PFOA, and PFOSA were measured in 473 human blood/serum/plasma samples collected from the United States, Colombia, Brazil, Belgium, Italy, Poland, India, Malaysia, and Korea. Among the four perfluorochemicals measured, PFOS was the predominant compound found in blood. Concentrations of PFOS were the highest in the samples collected from the United States and Poland (>30 ng/mL); moderate in Korea, Belgium, Malaysia, Brazil, Italy, and Colombia (3 to 29 ng/mL); and lowest in India (<3 ng/mL). PFOA was the next most abundant perfluorochemical in blood samples, although the frequency of occurrence of this compound was relatively low. No age- or gender-related differences in the concentrations of PFOS and PFOA were found in serum samples. The degree of association between the concentrations of four perfluorochernicals varied, depending on the origin of the samples. These results suggested the existence of sources with varying levels and compositions of perfluorochemicals, and differences in exposure patterns to these chemicals, in various countries. In addition to the four target fluorochemicals measured, qualitative analysis of selected blood samples showed the presence of other perfluorochernicals such as perfluoro-decanesulfonate (PFDS), perfluoroheptanoic acid (PFHpA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorododecanoic acid (PFDoA), and perfluoroundecanoic acid (PFUnDA) in serum samples, at concentrations approximately 5- to 10-fold lower than the concentration of PFOS. Further studies should focus on identifying sources and pathways of human exposure to perfluorochernicals
Inquiry of inclined magnetic field effects on Walter –B nanofluid flow with heat generation / absorption
No full textThe article deals with Walter-B nanoliquid flow towards a extending surface with inclined magnetic field effects. Thermal relaxation analysis is made by non fourier heat flux model. Radiation, heat generation / absorption impacts are included. The non linear Partial governing systems are rebuild into nonlinear ordinary systems with the assist of proper similarity transformations. The graphical results are portrayed for velocity, concentration and temperature profile. The physical entitles of heat and mass transfer rates are graphically reported. The comparission with previous results notified the excellent agreement.Loganathan, K.Nithyadevi, N.Boopathi, P.Mohana, K
Inhibition of EGFR-AKT axis results in the suppression of ovarian tumors in vitro and in preclinical mouse model
No full textOvarian cancer is the leading cause of cancer related deaths in women. Genetic alterations including overexpression of EGFR play a crucial role in ovarian carcinogenesis. Here we evaluated the effect of phenethyl isothiocyanate (PEITC) in ovarian tumor cells in vitro and in vivo. Oral administration of 12 μmol PEITC resulted in drastically suppressing ovarian tumor growth in a preclinical mouse model. Our in vitro studies demonstrated that PEITC suppress the growth of SKOV-3, OVCAR-3 and TOV-21G human ovarian cancer cells by inducing apoptosis in a concentration-dependent manner. Growth inhibitory effects of PEITC were mediated by inhibition of EGFR and AKT, which are known to be overexpressed in ovarian tumors. PEITC treatment caused significant down regulation of constitutive protein levels as well as phosphorylation of EGFR at Tyr1068 in various ovarian cancer cells. In addition, PEITC treatment drastically reduced the phosphorylation of AKT which is downstream to EGFR and disrupted mTOR signaling. PEITC treatment also inhibited the kinase activity of AKT as observed by the down regulation of p-GSK in OVCAR-3 and TOV-21G cells. AKT overexpression or TGF treatment blocked PEITC induced apoptosis in ovarian cancer cells. These results suggest that PEITC targets EGFR/AKT pathway in our model. In conclusion, our study suggests that PEITC could be used alone or in combination with other therapeutic agents to treat ovarian cancer. © 2012 Loganathan et al
Thermal and economic analysis of a liquid flat plate solar collector system using green carbon nanofluids / Harish Kumar Loganathan
No full textThe present investigation deals with the effects of using cost-effective, eco-friendly, non-corrosive, covalent functionalized carbon-based nanofluids to evaluate the energetic, exergetic, and economic performance of a Liquid flat-plate solar collector (LFPSC) forced circulation system. Two types of green nanostructures namely, functionalized carbon nanostructures and hybrid carbon nanostructures were synthesized using the facile, eco-friendly, free radical technique. Different natural extracts such as gallic acid, parsley leaves, hibiscus leaves, and neem leaves are utilized in the preparation of green carbon nanofluids. The green nanofluids prepared are gallic acid graphene nanoplatelets (GGNPs), parsley graphene nanoplatelets (PGNPs), parsley multi-walled carbon nanotubes (PMWCNTs), GGNPs decorated with silver nanoparticles (GGNP-Ag), PGNPs decorated with copper oxide nanoparticles (PGNP-CuO), and PMWCNTs decorated with silver nanoparticles (PMWCNTS-Ag). The functionalization and decoration of carbon structures were confirmed using characterization techniques namely FESEM, EDX, TEM, XRD, FTIR, TGA. Green carbon nanofluids with base fluid distilled water were prepared with different weight concentrations of 0.025 %,0.05 % & 0.1 %. The green nanofluids prepared showed long-term colloidal stability compared to conventional nanofluids. Thermo-physical properties investigated showed increased thermal conductivity, viscosity, and density, while a decrease in specific heat capacity. For varying concentrations, fluid flow rates of 0.8,1.2, and 1.5 L/min, heat flux intensities of 600, 800, and 1000 W/m2, and inlet temperature ranging from 303 to 323 K were considered for the conduction of experiments. Improvement in energy and exergy efficiency was achieved using green carbon nanofluids than base fluid. Thermal efficiency surges with increment in flow rate and heat flux intensities, meanwhile it decreases for increment in inlet temperature. Maximum augmentation in thermal efficiency of about 30.2 % was achieved for PMWCNT nanofluid followed by 28.4 % for PMWCNT-Ag, 24.31 % for PGNP, 24 % for GGNP, 23.56 % for PGNP-CuO, and 22.24 % for GGNP-Ag at 0.1 wt. % and 1.5 L/min, respectively than the base fluid. Analysis of exergetic performance revealed that exergy efficiency reduces with a rise in mass flow rate meanwhile enhanced with an increase in nanofluid concentration. Exergy efficiency was maximum for 0.1% PMWCNT concentration and flow rate of 0.8 L/min. The maximum increase in friction factor values is approximately 11.61 % for 0.1 % PGNP-CuO nanofluids, followed by 10.9 %, 9.2 %,8 %,7.78 %,6.97 %, respectively for 0.1 % GGNP-Ag, PMWCNT-Ag, GGNP, PGNP and PMWCNT nanofluids than distilled water. Relative pumping power slightly increases with the increment of green carbon nanofluid concentration but is quite close to that of the base fluid. Performance index greater than one is obtained with higher values achieved at an increase in the weight concentration of green nanoparticles in the aqueous medium. Economic analysis showcased a maximum reduction of 28.89 % in the size of the collector area using 0.1 % PMWCNT nanofluid instead of distilled water. The average payback period for LFPSC using green carbon nanofluids was 6.40 % lesser than that of using distilled water. The enhanced properties of green carbon nanoparticles make them a favorable candidate in enhancing the performance of different thermal systems
Temporal trends of polybrominated diphenyl ethers and hexabromocyclodecanes in marin mammals with special reference to Hong Kong, South China
No full textOwing to advances in polymer science over the past 50 years, a large number of polymers with differing properties have been developed for daily applications ranging from clothing and furniture to electronics, vehicles, and computers. However, most of these polymers are petroleum-based and hence are flammable. In order to reduce fire risks and meet fire safety regulations, certain chemicals collectively known as flame retardants are applied to combustible materials such as plastics, wood, paper, and textiles [1]. Currently, there are more than 175 compounds or groups of compounds with known flame-retarding properties, which are generally divided into four classes: inorganic, halogenated organic, nitrogen-containing, and phosphorus-containing compounds [2]. Among the halogenated flame retardants, brominated compounds comprise the largest market share because of their lower decomposition temperatures, higher performance efficiency, and low cost [2,3]. Thus, brominated flame retardants (BFRs) have been extensively used to improve the fire resistance of materials such as plastics, textiles, furnishing foam, and electronic circuit boards [4]. Based on their use in the chemical industry, BFRs can be classified as either reactive or additive. Reactive BFRs such as the tetrabromobisphenol A (TBBPA) are covalently bound to the polymer matrix. Compared to their reactive counterparts, additive BFRs are not chemically bound to the product and therefore tend to migrate out of the product much more easily and are thus more likely to be released into the environment. Examples of additive BFRs include polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), and hexabromocyclododecanes (HBCDs). Production of PBBs in the United States was phased out in the 1970s after a farm product contamination incident in Michigan [5]. In turn, production of PBDEs has increased, peaking in the mid-1990s [6]
A biochemical framework for SLC4A11, the plasma membrane protein defective in corneal dystrophies
No full textMutations in the SLC4A11 protein, reported as a sodium-coupled borate transporter of the human plasma membrane, are responsible for three corneal dystrophies (CD): congenital hereditary endothelial dystrophy type 2, Harboyan syndrome, and late-onset Fuch’s CD. To develop a rational basis to understand these diseases, whose point mutations are found throughout theSLC4A11 sequence, we analyzed the protein biochemically. Hydropathy analysis and an existing topology model for SLC4A1 (AE1), a bicarbonate transporter with the lowest evolutionary sequence divergence from SLC4A11, formed the basis to propose an SLC4A11 topology model. Immunofluorescence studies revealed the cytosolic orientation of N- and C-termini of SLC4A11.Limited trypsinolysis of SLC4A11 partially mapped the folding of the membrane and cytoplasmic domains of the protein. The binding of SLC4A11 to a stilbenedisulfonate inhibitor resin (SITS-Affi-Gel) was prevented by preincubation with H2DIDS, with a significantly higher half-maximal effective concentration than AE1. We conclude that stilbenedisulfonates interact with SLC4A11 but with a lower affinity than other SLC4 proteins. Disease-causing mutants divided into two classes on the basis of the half-maximal [H2DIDS] required for resin displacement and the fraction of protein bindingH2DIDS, likely representing mildly misfolded and grossly misfolded proteins. Disease-causing SLC4A11 mutants are retained in the endoplasmic reticulum of HEK 293 cells. This phenotype could be partially rescued in some cases by growing the cells at 30 C.Fil: Vilas, Gonzalo L.. University of Alberta; CanadáFil: Morgan, Patricio Eduardo. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares ; ArgentinaFil: Loganathan, Sampath K.. University of Alberta; CanadáFil: Quon, Anita. University of Alberta; CanadáFil: Casey, Joseph R.. University of Alberta; Canad
Quantifying the Mechanisms of Site-Specific Ion Exchange at an Inhomogeneously Charged Surface: Case of Cs+/K+ on Hydrated Muscovite Mica
No full textInternational audienceAdsorption and mobility of radioactive Cs+ isotopes in soil are among the most important factors affecting the long-term environmental footprint of nuclear accidents such as Chernobyl (1986) and Fukushima Daiichi (2011). In particular, Cs+ ions can be retained through their exchange with K+ naturally present in muscovite mica, one of the common soil mineral components. The ClayFF force field allowed us to realistically represent local inhomogeneities of the structure, composition, and charge on the muscovite (001) surface and to identify three structurally different types of adsorption sites. We performed molecular dynamics simulations of Cs+ and K+ adsorption at the hydrated muscovite surface and used quasi-one-dimensional site-specific potential of mean force calculations to quantify the energetics of ion exchange in this system for each individual site and for the entire muscovite surface on average. Irrespective of the type of adsorption site, both K+ and Cs+ cations are preferably adsorbed on the basal (001) muscovite surface at the centers of ditrigonal cavities as inner sphere surface complexes. The free energy difference between the most favorable and the least favorable surface sites for Cs+/K+ ion exchange amounts to 11.7 kJ/mol, with the most favorable sites occupying half of the surface and the least favorable type - 1/6 of the surface and the rest exhibiting an intermediate adsorption and ion exchange capacity. The simulation results are compared with available thermodynamic estimates based on recent X-ray reflectivity measurements
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