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Analysis of Incomplete Longitudinal Binary Data-A Combined Markov’s Transition and Logistic Model for Non-ignorable Missingness
Get PDFThe problem of incomplete data is a common phenomenon in research that involves the longitudinal design approach. We investigate and develop a likelihood-based approach for incomplete longitudinal binary data using the disposition model when the missing value mechanism is non-ignorable. We combined Markov’s transition and a logistic regression model to build the dropout process and model the response using conditional logistic regression model. By holding the missingness parameter that is weakly identified constant, we analyzed their effects through a sensitivity analysis as the estimation of parameters in MLE for non-ignorable missing data is not generally plausible. An application of our approach to Schizophrenia clinical trial is presented
Effect of Fluid Suction on an Oscillatory MHD Channel Flow with Heat Transfer
Get PDFMagnetohydrodynamics (MHD) is generally concerned with the study of the magnetic properties (behaviour) of electrically conducting fluids (plasmas, liquid metals etc.) moving in an electromagnetic field. The importance of the concept of MHD in various fields such as astrophysics, bio-medical research, missile technology and geophysics motivates the modelling and investigation of MHD flow and transport problems. The role of fluid suction is paramount in laminar flow control and has wide applications in fields such as aeronautical engineering, automobile engineering and rocket science. This fact inspires the study of the effects of fluid suction in flow and transport models. Time dependent flows are widely encountered in engineering applications such as turbines and in physiological studies such as flow of bio-fluid (blood etc.). In the present paper, an attempt has been made to investigate analytically the problem of a time dependent channel flow with heat transfer, where the channel is bounded by two infinite parallel porous walls. The pressure gradient is assumed to be oscillatory in nature. A magnetic field of uniform strength is assumed to be applied normal to the walls. After necessary idealization of the momentum and energy equations, the governing equations of our problem are solved by adopting the regular perturbation technique. The effects of magnetic field, suction velocity, viscous dissipation, Reynolds number, Prandtl number etc. on the flow and heat transfer are studied and demonstrated graphically. It is seen that magnetic field, fluid suction, viscous dissipation, Reynolds number, Prandtl number have a significant effect on the flow and heat transfer characteristic. For instance, the imposition of the magnetic field enhances the rates of heat transfer at the walls and the fluid suction decreases the temperature and aids in laminar flow control
Acid Catalyzed Competitive Esterification and Ketalization of Levulinic Acid with 1,2 and 1,3-Diols: The Effect of Heterogeneous and Homogeneous Catalysts
No full textAbstract: Condensation reactions of levulinic acid (LA) with 1,2-ethanediol (1,2-ED), 1,2-propanediol (1,2-PD), and 1,3-propanediol (1,3-PD) were studied using Amberlyst-15 as well as p-toluenesulfonic acid catalysts in benzene under Dean–Stark conditions. In Amberlyst-15 catalyzed reactions the products are ketals and ketal-esters, whereas p-toluenesulfonic acid catalyzed reactions produce esters and ketal-esters as products. In p-toluenesulfonic acid catalyzed reactions with 1,2-ED and 1,3-PD, LA monoester product is formed as the major product after 180 min in 75 and 97 % yields respectively. Unlike the previously reported acid catalyzed ketalization of ethyl levulinate with diols, combined ketalization–esterification of LA with diols is a complex process. Graphical Abstract: [Figure not available: see fulltext.
Irrigation water requirements for seed corn and coffee under potential climate change scenarios
No full textThe impact of potential future climate change scenarios on the irrigation water requirements (IRRs) of two major agricultural crops (coffee and seed corn) in Hawai\u27i was studied using the Irrigation Management System (IManSys) model. In addition to IRRs calculations, IManSys calculates runoff, deep percolation, canopy interception, and effective rainfall based on plant growth parameters, site specific soil hydrological properties, irrigation system efficiency, and long-term daily weather data. Irrigation water requirements of two crops were simulated using historical climate data and different levels of atmospheric CO2 (330, 550, 710 and 970 ppm), temperature (+1.1 and +6.4 °C) and precipitation (±5, ±10 and ±20%) chosen based on the Intergovernmental Panel on Climate Change (IPCC) AR4 projections under reference, B1, A1B1 and A1F1 emission scenarios. IRRs decreased as CO2emission increased. The average percentage decrease in IRRs for seed corn is higher than that of coffee. However, runoff, rain canopy interception, and deep percolation below the root zone increased as precipitation increased. Canopy interception and drainage increased with increased CO2emission. Evapotranspiration responded positively to air temperature rise, and as a result, IRRs increased as well. Further studies using crop models will predict crop yield responses to these different irrigation scenarios
Applicability of screening tests for oxytetracycline in the milk of three breeds of goats
No full textAntibiotics are widely used in animal husbandry, and the presence of antibiotic residues in milk is a health hazard. The objectives of this study were to determine residual amounts of oxytetracycline in the milk of three breeds of goats using highpressure liquid chromatography (HPLC) analysis and screening tests. It was also essential to explore the safe withdrawal period of oxytetracycline in lactating goats and examine the applicability of Charm ROSA and SNAP screening tests. The qualitative results of these tests were compared with the quantitative results of the HPLC method. Fifteen milking does, five each from the Alpine, LaMancha, and Nubian breeds, were selected from the herd at Prairie View A&M University. Milk samples containing antibiotic residues were deproteinized by HCl and acetonitrile, and then oxytetracycline was extracted from the supernatant. The residues of oxytetracycline in goat\u27s milk up to 110 h after injection were qualitatively detected using the Charm ROSA test. Similarly, the SNAP test detected the antibiotic residues in milk up to 110 h after treatment. The HPLC results indicated that oxytetracycline residues in milk from Alpine goats were below the tolerance level (300 ng/ml) 82 h after drug treatment (72 h for LaManchas, 58 h for Nubians); however, the results of the screening tests would indicate longer withdrawal periods for milk from the breeds of goats studied, which would result in economic losses to goat\u27s milk producers. The results of this study also indicated that oxytetracycline was not stable in raw goat\u27s milk at refrigeration temperature or during pasteurization and that the concentrations decreased significantly. Commercial goat\u27s milk is usually exposed to several hours of refrigeration and then to pasteurization. The results of this study indicated that, if oxytetracycline was present in raw goat\u27s milk, the concentration would decrease significantly before it was marketed
Chitosan coated and non-coated composite scaffolds based on poly (Caprolactone) (PCL) and hydroxyapatite (HA)
No full textTissue engineering (TE) scaffold is an artificial structure that is implanted in our body on which tissue grows to solve the problem of a missing or damaged organ. A wide range of biomaterials can be used to produce the TE scaffolds. This study reports the comparison of chitosan coated and uncoated three-dimensional composite scaffolds composed of Hydroxyapatite (HA) and polycaprolactone (PCL)) via thermally induced phase separation (TIPS) and freeze-drying method. Three types of the scaffolds, namely, PCL and PCL/HA were coated with hydrophilic chitosan polymer. Characteristics such as wettability, morphological structure and water uptake in coated and non-coated scaffolds were studied and compared using a contact angle, a Scanning Electron Microscopy (SEM), an Energy Dispersive X-Ray (EDX). The composite scaffolds were porous and had interconnected pore structures. The ranges of pores were different from several microns to a few hundred microns. The coated layer improved the wettability of composite scaffolds. These results shows that the chitosan coated composite scaffolds were more favourable for TE application than their uncoated counterparts
Posttraumatic stress and growth in student service members and veterans: The role of personal growth initiative
No full textObjective: This study explored the extent to which personal growth initiative (PGI) may predict posttraumatic stress and growth in student service members/veterans (SSM/V). Participants: Participants were 136 SSM/V (79% men) representing multiple branches of the armed forces. Forty-four percent of participants reported having combat experience. Methods: Data collection occurred from October 2013 to February 2014. Data were collected via a Web-based survey that included demographics and measures of personal growth initiative, posttraumatic stress, posttraumatic growth, and perceived social support. Results: Results indicated that PGI is not a unique predictor of posttraumatic stress but is a unique predictor of higher levels of posttraumatic growth. PGI appears to be at least as important as perceived social support in facilitating growth in SSM/V. Conclusions: This study provides further evidence for PGI\u27s potential to facilitate growth after a traumatic event
Applicability of screening tests for oxytetracycline in the milk of three breeds of goats
No full textAntibiotics are widely used in animal husbandry, and the presence of antibiotic residues in milk is a health hazard. The objectives of this study were to determine residual amounts of oxytetracycline in the milk of three breeds of goats using highpressure liquid chromatography (HPLC) analysis and screening tests. It was also essential to explore the safe withdrawal period of oxytetracycline in lactating goats and examine the applicability of Charm ROSA and SNAP screening tests. The qualitative results of these tests were compared with the quantitative results of the HPLC method. Fifteen milking does, five each from the Alpine, LaMancha, and Nubian breeds, were selected from the herd at Prairie View A&M University. Milk samples containing antibiotic residues were deproteinized by HCl and acetonitrile, and then oxytetracycline was extracted from the supernatant. The residues of oxytetracycline in goat\u27s milk up to 110 h after injection were qualitatively detected using the Charm ROSA test. Similarly, the SNAP test detected the antibiotic residues in milk up to 110 h after treatment. The HPLC results indicated that oxytetracycline residues in milk from Alpine goats were below the tolerance level (300 ng/ml) 82 h after drug treatment (72 h for LaManchas, 58 h for Nubians); however, the results of the screening tests would indicate longer withdrawal periods for milk from the breeds of goats studied, which would result in economic losses to goat\u27s milk producers. The results of this study also indicated that oxytetracycline was not stable in raw goat\u27s milk at refrigeration temperature or during pasteurization and that the concentrations decreased significantly. Commercial goat\u27s milk is usually exposed to several hours of refrigeration and then to pasteurization. The results of this study indicated that, if oxytetracycline was present in raw goat\u27s milk, the concentration would decrease significantly before it was marketed
Extraction and characterization of triglycerides from coffeeweed and switchgrass seeds as potential feedstocks for biodiesel production
No full textBACKGROUND: Although switchgrass has been developed as a biofuel feedstock and its potential for bioethanol and bio-oil from fast pyrolysis reported in the literature, the use of the seeds of switchgrass as a source of triglycerides for biodiesel production has not been reported. Similarly, the potential for extracting triglycerides from coffeeweed (an invasive plant of no current economic value) needs to be investigated to ascertain its potential economic use for biodiesel production