Effects of processing on the properties and permeability of pure gases through sol-gel silica membranes

N2, O2 and CO2 pure gas permeation through sol-gel derived silica membranes were determined and the effects of processing parameters on the microstructure of the membrane was investigated. Silica sols were prepared in an alcoholic solution by hydrolysis and condensation of TEOS as a function of acid content. The thickness of the silica membranes was determined to be about 2μm and significant infiltration into the support was observed from the SEM pictures. The supported membranes were heat treated in the 50-400°C. The N2 permeabilities of silica membranes varied in the 2.2*10-10-2.7*10-8 mol/m2.s.Pa range for single layer membranes dipped for 10s. in the sol. The CO2 permeability of these membranes varied in the 1.2*10-9-6.95 *10-8 mol/m2.s.Pa range. The sols became viscous and gelled at 50°C in 16 hours. The O2 permeability increased with aging time. The optimum dipping time during processing was determined to be 10 seconds. The increase in the acid content of the sols were observed to increase permeabilities of the membranes significantly

Investigation of the permeability of pure gases in sol-gel derived Al 2O 3 membrane

Proceedings of the 8th Conference and Exhibition of the European Ceramic Society; Istanbul; Turkey; 29 June 2003 through 3 July 2003The preparation, characterization and pure gas permeation of sol-gel derived alumina membranes were investigated in this work. The effects of acid concentration/type and water content on the particle size in the sols and pore size distributions of the unsupported membrane were investigated by N 2 adsorption/desorption isotherms and Dynamic Light Scattering. Increasing the H +/Al 3+ mole ratio from 0.1 to 0.25 caused the hydrodynamic sol particle size and BJH pore size to decrease from 65 to 30 nm and 3.6 to 2.9 nm, respectively. The pore size increased from 2.8 nm to 3 nm upon increasing the calcination temperature from 500 to 600°C. Unsupported membranes were heat treated in the 200 to 1200 °C range for the characterization of the phase structure. Pinhole and crack free alumina membranes about 3 μm (2-layer) in thickness was observed from the SEM pictures with insignificant infiltration. The CO 2 permeability through the double layer γ-Al 2O 3 membrane calcined at 600 °C was 2.25*10 -7 mol/m 2.s.Pa, and had a slight pressure dependence indicating Knudsen Diffusion and Laminar Flow being the effective transport mechanisms. Upon the calcination of a similar 2-layer alumina membrane at 500°C, the CO 2 permeability decreased to 1.51 *10 -8 mol/m 2.s.Pa. without pressure dependence

MEZUNİYET ÖNCESİ KLİNİK TIP EĞİTİMİNDE TASK\' A DAYALI ÖĞRENİM VE DOKUZ EYLÜL ÜNİVERSİTESİ TIP FAKÜLTESİ ÖRNEĞİ

Bu yazıda TDO sisteminin hedefleri, gereç ve yöntemleri tanımlanmakta ve bu eğitim modelindeki eğitici ve öğrenci rolleri tartışılmaktadır

Limited Vitrectomy in Patients With Idiopathic Epiretinal Membrane

Purpose: To evaluate the safety and effectivity of limited vitrectomy in patients with epiretinal membrane. Methods: We included 58 consecutive patients who underwent epiretinal membrane surgery without performing a complete peripheral vitreous removal. The improvement in visual acuity, the incidence of retinal breaks and detachment; anatomical results and intraoperative and postoperative complications of this technique were evaluated. Results: The median visual acuity was 0.4(0.3-0.5) before the surgery, and it was 0.6 (0.3-0.8) after the surgery (p=0.016). Prophylactic laser photocoagulation was performed in 14(24,13%) patients during surgery. Retinal breaks and detachments did not occur in any of our patients. We did not observe proliferative vitreoretinopathy or surgery- related major complications in any patient. Conclusion: Limited vitrectomy without removing peripheral vitreous is safe and effective in idiopathic epiretinal membrane surgery. It reduces the risk of peripheral retinal breaks and retinal detachment

The Importance of Frozen Section-Controlled Excision in Recurrent Basal Cell Carcinoma of the Eyelids

Objectives: To show the importance of frozen section-controlled excision to avoid the re-recurrence of recurrent basal cell carcinoma (BCC) of the eyelids. Materials and Methods: Thirty-five cases who underwent eyelid tumor excision in different centers and were admitted to our clinic with recurrent eyelid tumors. Recurrent tumors were resected by excision 1-2 mm from the tumor’s visible margin and sent to pathology for frozen section examination. Eyelid reconstructions with flap and graft were performed after confirming that the surgical margins were negative. Results: Twenty-one (60%) of our patients were male and 14 (40%) were female. Median age of our group was 63.4±14.2 years. Excision and sending the excised material for frozen section control was performed once for 11 patients, 2 times for 12 patients, 3 times for 8 patients and 4 times for 4 patients to confirm that the surgical margins were clean. All pathology samples were reported as BCC. All patients had eyelid reconstruction with flap and graft. Recurrence was detected in 2 patients (5.7%) during 1 to 8 years (mean 4.3 years) of follow-up and those patients were reoperated; no recurrence was detected in the remaining 33 patients (94.3%). Conclusion: Frozen section control can provide low re-recurrence rate in patients with recurrent BCC of the eyelids