CFD and statistical approach to optimize the average air velocity and air volume fraction in an inert-particles spouted-bed reactor (IPSBR) system.

Inert-particles spouted bed reactor (IPSBR) is characterized by intense mixing generated by the circular motion of the inert particles. The operating parameters play an important role in the performance of the IPSBR system, and therefore, parameter optimization is critical for the design and scale-up of this gas-liquid contact system. Computational fluid dynamics (CFD) provides detailed modeling of the system hydrodynamics, enabling the determination of the operating conditions that optimize the performance of this contact system. The present work optimizes the main IPSBR operating parameters, which include a feed-gas velocity in the range 0.5-1.5 m/s, orifice diameter in the range 0.001-0.005 m, gas head in the range 0.15-0.35 m, mixing-particle diameter in the range 0.009-0.0225 m, and mixing-particle to reactor volume fraction in the range 2.0-10.0 vol % (which represents 0.01-0.1 kg of mixing particles loading). The effects of these parameters on the average air velocity and average air volume fraction in the upper, middle, and conical regions of the reactor were studied. The specific distance for each region has been measured from the orifice point to be 50 mm for the conical region, 350 mm for the middle region and 550 mm for the upper rejoin. The selected factors were optimized to obtain the minimum air velocity distribution (maximum gas residence time) and the maximum air volume fraction (maximum interfacial area concentration) because these conditions will increase the gas holdup, the gas-liquid contact area, and the mass transfer coefficient among phases. Response surface methodology (RSM) was used to determine the optimum operating conditions. The regression analysis showed an excellent fit of the experimental data to a second-order polynomial model. The interaction between the process variables was evaluated using the obtained three-dimensional surface plots. The analysis revealed that under the optimized parameters of a feed-gas velocity of 1.5 m/s, orifice diameter of 0.001 m, gas head of 0.164 m, mixing-particle diameter of 0.0225 m, and mixing-particle loading of 0.02 kg, the minimum average air velocity and highest air volume fraction were observed throughout the reactor.

Primary intracranial germinoma presenting as a central skull base lesion.

We report an unusual case of primary intracranial germinoma involving the sphenoid bone and sinus. To the best of our knowledge, paranasal sinus and bone invasion of primary intracranial germinoma has not been previously reported. Recognition of this rare form of presentation by imaging is important because early radiation and chemotherapy can result in a cure of this neoplasm.

Antifilarial IgM versus IgG antibody determination in the diagnosis of Wuchereria bancrofti infection in Egyptians.

Circulating antifilarial IgM and IgG antibodies were assessed by indirect ELISA in 184 serum specimens from 80 patients with clinically and parasitologically diagnosed filarial infections (20 with acute filariasis 40 with chronic filariasis & 20 asymptomatic microfilaraemic subjects), 64 individuals with other parasitic infections, 20 parasitologically-free subjects from filariasis endemic areas and 20 normal healthy controls. A soluble surface membrane extract from Dirofilaria immitis worms was used as the antigen. Using a single serum dilution of 1:128 and optical densities (OD) at 492 nm, the respective cut off values for IgM and IgG were found to be 0.24 and 0.22. All healthy non-endemic controls were seronegative by IgM and IgG ELISAs. The highest antifilarial IgM OD492 values were obtained in 20 patients with acute filariasis (95% sensitivity), while the highest antifilarial IgG OD492 values were observed n 40 patients with chronic filariaisis (97.5% sensitivity). Asymptomatic microfilaraemic subjects gave IgM and IgG OD492 values which were significantly lower than those of other forms of clinical disease and endemic control subjects. The antifilarial IgM and IgG respective sensitivities in asymptomatic subjects were 75% and 70%. Endemic controls had positive antifilarial IgM (65%) and IgG (75%) levels. Of 64 subjects with other parasites only one with Ancylostoma duodenale had positive IgM level (98.4% specificity); while 9 patients with nematodal infections mainly had false positive antifilarial IgG antibody levels (85.9% specificity). These results suggest that measuring circulating antifilarial IgM antibody level may have some diagnostic advantage over measuring IgG antibody level for the detection of active filarial infection and consequently better management of the disease.