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Modeling of environmental adaptation versus pollution mitigation
No full textThe paper combines analytic and numeric tools to investigate a nonlinear optimal control problem relevant to the economics of climate change. The problem describes optimal investments into pollution mitigation and environmental adaptation at a macroeconomic level. The steady-state analysis of this problem focuses on the optimal ratio between adaptation and mitigation. In particular, we analytically prove that the long-term investments into adaptation are profitable only for economies above certain efficiency threshold. Numerical simulation is provided to estimate how the economic efficiency and capital deterioration affect the optimal policy. © EDP Sciences, 2014
Dynamics of progesterone, TNF- α, and a metabolite of pgf2 α in blood plasma of beef cows following embryo transfer
No full textLactating beef cows previously synchronized for estrus (d 0) were assigned to four treatments to assess their effectiveness in increasing blood progesterone (P4) and its effects on tumor necrosis factor-α (TNF-α) and prostaglandin F2α (PGF2α) after the transfer of embryos. At the time of transfer (d 7), cows received no treatment (control; n = 16), a controlled internal drug releasing device (CIDR; n = 16), human chorionic gonadotropin (hCG; n = 15), or gonadotropin releasing hormone (GnRH; n = 15). Blood samples were taken on d 7, 14, and 21 for analysis of P4 and tumor necrosis factor-α (TNF-α). Blood was collected (every 15 min for 2 h) in half the animals in each treatment group on d 14 and the remaining half on d 21 for analysis of prostaglandin F2α metabolite (PGFM). Retention rates were 56.2, 62.5, 46.7, and 13.3% for cows in the control, CIDR, hCG, and GnRH groups, respectively. Progesterone was greater (P ≤ 0.05) in cows receiving hCG compared to others on d 14. Progesterone in all treatment groups increased from d 7 to d 14 and declined (P ≤ 0.05) from d 14 to d 21. Contrary to pregnant cows, P4 and TNF-α declined from d 7 to d 21 in nonpregnant cows (P ≤ 0.05). Although PGFM increased by d 21, there was no difference between pregnant and nonpregnant cows
A hole in the soul of Austin: Black faculty community engagement experiences in a creative class city
No full textThis article examines how tenure and tenure-track Black faculty at a predominantly White institution (UT-Austin) make meaning of their community engagement living and working in the city of Austin, a bellwether creative class city given its demographics and history. Findings indicate that faculty experiences living in other locales greatly affected their Austin experience, and that faculty navigates a Du Boisian double-consciousness interfacing with the community as citizen-scholars. Faculty discussed the notion of welcoming and exclusionary spaces and how parental status greatly affected how they felt welcomed or excluded from opportunities to engage with the community. Participants indicated advantages of living in Austin, but also discussed dissatisfaction with a dearth of Black-centered activities. © The Journal of Negro Education, 2014
Fabrication of nanohydroxyapatite/poly(caprolactone) composite microfibers using electrospinning technique for tissue engineering applications
No full textTissue engineering fibrous scaffolds serve as three-dimensional (3D) environmental framework by mimicking the extracellular matrix (ECM) for cells to grow. Biodegradable polycaprolactone (PCL) microfibers were fabricated to mimic the ECM as a scaffold with 7.5% (w/v) and 12.5% (w/v) concentrations. Lower PCL concentration of 7.5% (w/v) resulted in microfibers with bead defects. The average diameter of fibers increased at higher voltage and the distance of tip to collector. Further investigation was performed by the incorporation of nanosized hydroxyapatite (nHA) into microfibers. The incorporation of 10% (w/w) nHA with 7.5% (w/v) PCL solution produced submicron sized beadless fibers. The microfibrous scaffolds were evaluated using various techniques. Biodegradable PCL and nHA/PCL could be promising for tissue engineering scaffold application. © 2014 Mohd Izzat Hassan et al
Bioactivity assessment of poly(ε -caprolactone)/hydroxyapatite electrospun fibers for bone tissue engineering application
No full textElectrospinning is useful for fabricating nanofibrous structure with different composition and morphologies. It offers great advantages through its geometrical structure and biomimetic property, which can provide a suitable environmental site for cell growth. The fiber diameter is entangled by the concentration of PCL with some adjustment of parameters during electrospinning process. PCL with lower concentration had bead structure while higher concentration had smooth fiber. The incorporation of nanoparticle hydroxyapatite (nHA) into poly(ε-caprolactone) fiber was studied. The fiber diameter of PCL was increased with the addition of nHA. Composition of fiber at lower concentrations of PCL and nHA into the polymer produced fiber with a homogenous distribution of nHA in PCL fiber with less agglomeration. The immersion of PCL/nHA fiber in simulated body fluid (SBF) had bone-like apatite layer on its surface while PCL showed no results. PCL/nHA showed high water uptake and had improved wettability compared to PCL alone, suggesting that PCL/nHA fibers were more hydrophilic than PCL fiber. © 2014 Mohd Izzat Hassan et al
Polycaprolactone(PCL)/gelatin(Ge)-based electrospun nanofibers for tissue engineering and drug delivery application
No full textRecent development of tissue engineering has been emphasized on tissue regeneration and repairing in order to solve the limitation of organ and tissue transplantation issues. Biomaterial scaffold, which plays an important role in this development, not only provides a promising alternative in order to improve the efficiency of cell transplantation in tissue engineering but also to deliver cells with growth factors and drugs into injured tissue to increase the survival of cell via drug delivery system. In this study, nanofibers were fabricated through blending of a synthetic polymer, polycaprolactone (PCL) and a natural polymer, Gelatin (Ge) using electrospinning technique. Processing parameters were optimized to determine the most suitable properties of PCL/Ge nanofibers. The surface morphology of PCL/Ge nanofibers were then characterized using Scanning Electron Microscopy (SEM). Six samples of nanofibers from different amount of gelatin mixed with 10% PCL (w/v) were successfully fabricated. Experimental results showed that 18kV of high voltage provided more homogenous and less beaded nanofibers. Meanwhile, the 0.8g of Ge in 10% PCL (w/v) was set as the maximum concentration while 0.2g of Ge in 10% PCL (w/v) was set as the minimum concentration to reduce the bead formation. © (2014) Trans Tech Publications, Switzerland
Synthesis of a silica-immobilized Brönsted acidic ionic liquid catalyst and hydrolysis of cellulose in water under mild conditions
No full textA silica immobilized imidazolium-type acidic ionic liquid catalyst was shown to be a better catalyst than n-propylsulfonic acid silica (PrSO 3H-SiO2) and sulfonic acid silica (SO3H- SiO2) for the hydrolysis of untreated Sigmacell Cellulose (DP ~ 450) in water. For example, new catalyst produced the highest TRS yield of 48.1% after 3 h at 190 C, whereas cellulose samples heated with PrSO 3H-SiO2 and SO3H-SiO2 catalysts produced only 19.9% and 13.2% TRS yields, respectively, under identical conditions. The new catalyst could be recycled up to four cycles with a small loss in catalytic activity. © 2014 Elsevier B.V
Rainfall-runoff modeling in a flashy tropical watershed using the distributed HL-RDHM model
No full textMany watersheds in Hawai\u27i are flash flood prone due to their small contributing areas and frequent intense rainfall. Motivated by the possibility of developing an operational flood forecasting system, this study evaluated the performance of the National Weather Service (NWS) model, the Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM) in simulating the hydrology of the flood-prone Hanalei watershed in Kaua\u27i, Hawai\u27i. This rural watershed is very wet and has strong spatial rainfall gradients. Application of HL-RDHM to Hanalei watershed required (i) modifying the Hydrologic Rainfall Analysis Project (HRAP) coordinate system; (ii) generating precipitation grids from rain gauge data, and (iii) generating parameters for Sacramento Soil Moisture Accounting Model (SAC-SMA) and routing parameter grids for the modified HRAP coordinate system. Results were obtained for several spatial resolutions. Hourly basin-average rainfall calculated from one HRAP resolution grid (4km×4km) was too low and inaccurate. More realistic rainfall and more accurate streamflow predictions were obtained with the 1/2 and 1/4 HRAP grids. For a one year period with the best precipitation data, the performance of HL-RDHM was satisfactory even without calibration for basin-averaged and distributed a priori parameter grids. Calibration and validation of HL-RDHM were conducted using four-year data set each. The model reasonably matched the observed peak discharges and time to peak during calibration and validation periods. The performance of model was assessed using the following three statistical measures: Root Mean Square Error (RMSE), Nash-Sutcliffe efficiency (NSE) and Percent bias (PBIAS). Overall, HL-RDHM\u27s performance was very good (NSE\u3e0.75, PBIAS\u3c±10) for the finer resolution grids (1/2 HRAP or 1/4 HRAP). The quality of flood forecasting capability of the model was accessed using four accuracy measures (probability of false detection, false alarm ratio, critical success index, and probability of detection) for three return periods 1.005, 1.05 and 1.25. HL-RDHM is more accurate at the lower threshold discharge (65m3s-1) than at the higher ones (140 and 248m3s-1) as indicated by lower values of probability of detection and critical success index, and a higher value of the false alarm ratio. These results suggest that HL-RDHM may be suitable for flood forecasting applications in watersheds with steep terrain and strong spatio-temporal variability of precipitation, e.g. US Pacific North-West, and tropical islands
Stochastic Modeling of a Concrete Mixture Plant with Preventive Maintenance
Get PDFIn this paper, a stochastic model for concrete mixture plant with Preventive Maintenance (PM) is analyzed in detail by using a supplementary variable technique. In a concrete mixture plant eight subsystems are arranged in a series. The system goes under PM after a maximum operation time and work as new after PM. The time to failure of each subsystem follows a negative exponential distribution while PM and repair time distributions are taken as arbitrary. A sufficient repair facility is provided to the system for conducting PM and repair of the system. Repair, maintenance and switch devices are perfect. All random variables are statistically independent. Various measures of system effectiveness such as reliability, mean time to system failure (MTSF), are derived using a supplementary variable technique. The numerical results for reliability and availability are obtained for particular values of various parameters and costs
Numerical solution for the systems of variable-coefficient coupled Burgers’ equation by two-dimensional Legendre wavelets method
Get PDFIn this paper, a numerical method for solving the systems of variable-coefficient coupled Burgers’ equation is proposed. The method is based on two-dimensional Legendre wavelets. Two-dimensional operational matrices of integration are introduced and then employed to find a solution to the systems of variable-coefficient coupled Burgers’ equation. Two examples are presented to illustrate the capability of the method. It is shown that the numerical results are in good agreement with the exact solutions for each problem