Response surface methodology approach to study the influence of PEG and water in cellulose acetate dialysis membranes

Flat sheet asymmetric dialysis membranes were fabricated using phase inversion method from polymer solution consisting of cellulose acetate, acetic acid, polyethylene glycol (PEG) and distilled water. The effect of acetic acid/PEG ratio and the distilled water content in the dialysis membrane were being investigated with respect to the urea clearance performance. Response surface methodology (RSM) was used to design the experiments and analysed the results obtained. The analysis revealed that the significant factor that affects the cellulose acetate dialysis membrane performance in terms of urea clearance is the ratio of acetic acid/PEG. Dialysis membrane with higher ratio of acetic acid/PEG gives higher urea clearance percentage due to the formation of finger like macrovoids. The relation between the urea clearance and the ratio of acetic acid/PEG in the given range of 4 – 14, was a quadratic model and the mathematical model suggested could adequately describe the performance indicators within the limits mentioned

PERFORMANCE ANALYSIS OF DIRECT METHANOL FUEL CELLS BY COATING DIFFERENT PROPORTIONS OF CATALYSTS ONTO FUEL CHANNELS

[[abstract]]In this study, different proportions of catalysts, including Platinum (Pt), active carbon and Selenium (Se), were coated onto anode and cathode channels composed of PDMS (polydimethylsiloxane) to promote the fuel decomposition reaction in the fuel channels and to further enhance the output of the DMFCs under various operating temperatures. The experimental results indicated that under identical operating conditions, the performances of DMFCs with catalysts coated onto their channels are always superior to that of DMFCs without an added catalyst. The results indicate that a critical catalyst loading value exists for every catalyst. When the amount of catalyst added is less than this critical value, the output of the DMFCs can be greatly enhanced by increasing the proportion of the catalyst added to the fuel channels. However, when the amount of catalyst added exceeds the critical value, efficiency enhancements are no longer apparent. Suitable coating weight percentage for every catalyst was recommended. The corresponding recommendation values for catalysts of Pt, active carbon and Se are 0.06%, 0.29% and 0.29%, respectively, under the investigated operating conditions. The maximum power density increment of 182.3% can be attained in the case with 0.29% Se catalyst loading at an operating temperature of 30 degrees C.[[notice]]補正完

FUEL CONCENTRATION AND OPERATING TEMPERATURE EFFECTS ON CRITICAL AMOUNTS OF CATALYSTS ADDED TO THE FUEL CHANNELS OF DIRECT METHANOL FUEL CELL

[[abstract]]This study modifies the geometry of fuel channel corners in order to reduce the hydroresistance of the fuel within the channels, and investigates fuel concentration and operating temperature effects on the loading weight percentages of catalysts added to the fuel channels. The intent of the study is to further improve the output efficiency of DMFCs (direct methanol fuel cells). In this study, different proportions of catalysts, including active carbon and selenium (Se), were coated onto anode and cathode channels composed of PDMS (polydimethylsiloxane) to promote a fuel decomposition reaction in the fuel channels. The output of the DMFCs was measured under different operational temperatures and different supply fuel concentrations in order to find suitable catalyst loading values under different operational conditions. The experimental results indicate that under identical operating conditions, the performances of DMFCs can be greatly boosted using rounded channel turns rather than right angle turns. Furthermore, the results indicate that critical catalyst loading values exist for each catalyst under different operating temperatures. Suitable coating weight percentages for each catalyst are recommended for different operating temperatures. It was found that under lower operating temperatures and lower fuel supply concentrations, the effect of adding catalysts to fuel channels on the performance enhancement of DMFC is more apparent than for cases with higher operating temperatures and fuel supply concentrations. We also found that the fuel concentration effect on the performance of DMFCs was not apparent for a range of fuel concentrations investigated under the same operating temperature. In other words, while the fuel cells are under operation, even the supplied fuel concentrations vary, although not beyond operational concentration limitations. The effects of concentration variations on the performance of DMFCs with catalysts added to the channels can therefore be neglected.[[notice]]補正完

Computerized inspection of real surfaces and minimization of their deviations

A method is developed for the minimization of gear tooth surface deviations between theoretical and real surfaces for the improvement of precision of surface manufacture. Coordinate measurement machinery is used to determine a grid of surface coordinates. Theoretical calculations are made for the grid points. A least-square method is used to minimize the deviations between real and theoretical surfaces by altering the manufacturing machine-tool settings. An example is given for a hypoid gear

A Case of Reactive Cervical Lymphadenopathy with Fat Necrosis Impinging on Adjacent Vascular Structures.

A tender neck mass in adults can be a diagnostic challenge due to a wide differential diagnosis, which ranges from reactive lymphadenopathy to malignancy. In this report, we describe a case of a young female with an unusually large and tender reactive lymph node with fat necrosis. The diagnostic imaging findings alone mimicked that of scrofula and malignancy, which prompted a complete workup. Additionally, the enlarged lymph node was compressing the internal jugular vein in the setting of oral contraceptive use by the patient, raising concern for Lemierre's syndrome or internal jugular vein thrombosis. This report shows how, in the appropriate clinical context, and especially with the involvement of adjacent respiratory or neurovascular structures, aggressive diagnostic testing can be indicated

Reweighting for Nonequilibrium Markov Processes Using Sequential Importance Sampling Methods

We present a generic reweighting method for nonequilibrium Markov processes. With nonequilibrium Monte Carlo simulations at a single temperature, one calculates the time evolution of physical quantities at different temperatures, which greatly saves the computational time. Using the dynamical finite-size scaling analysis for the nonequilibrium relaxation, one can study the dynamical properties of phase transitions together with the equilibrium ones. We demonstrate the procedure for the Ising model with the Metropolis algorithm, but the present formalism is general and can be applied to a variety of systems as well as with different Monte Carlo update schemes.Comment: accepted for publication in Phys. Rev. E (Rapid Communications

Myxomatous mitral valve disease in a Shih Tzu dog

An 11-year-old intact male Shih Tzu dog was referred to the University Veterinary Hospital (UVH) with history of coughing and laboured breathing. Auscultation revealed that the dog had a left systolic heart murmur grade V/VI at the base of the heart. Radiography showed findings of cardiomegaly and pulmonary oedema. Echocardiography findings revealed that dog has a myxomatous mitral valve disease. The mitral valve was severely thickened and prolapsed into the left atrium. Congestive heart failure (CHF) was treated with an angiotensin converting enzyme (ACE) inhibitor and diuretic. An anti-mucolytic agent was prescribed as a symptomatic treatment for the coughing that could be due to mild bronchitis. Dog did not response well with treatment as the frequency of cough was not reduced and the duration was longer each time. Pimobendan was then added on to the initial treatment and there was a tremendous improvement seen from the patient after that. Episodes of productive cough were noticed greatly reduced and dog was much more active at home post two weeks of ACE inhibitor, diuretic and dual-acting inodilator. We successfully maintained the dog with minimal coughing episodes. However, the prognosis is moderate to poor in this case due to possibilities of refraction towards medications

Pseudo spin-orbit coupling of Dirac particles in graphene spintronics

We study the pseudo spin-orbital (SO) effects experienced by massive Dirac particles in graphene, which can potentially be of a larger magnitude compared to the conventional Rashba SO effects experienced by particles in a 2DEG semiconductor heterostructure. In order to generate a uniform vertical pseudo SO field, we propose an artificial atomic structure, consisting of a graphene ring and a charged nanodot at the center which produces a large radial electric field. In this structure, a large pseudo SO coupling strength can be achieved by accelerating the Dirac particles around the ring, due to the small energy gap in graphene and the large radial electric field emanating from the charged nanodot. We discuss the theoretical possibility of harnessing the pseudo SO effects in mesoscopic applications, e.g. pseudo spin relaxation and switching.Comment: 12 pages, 1 figur