Removal of 209Po from aquatic environment and its equilibrium and thermodynamic parameters.

In this study, removal of 209Po from aqueous media using a natural zeolite as an adsorbent material was investigated. The adsorption experiments were performed by batch technique. The influence of specific process parameters such as initial concentration, pH of solution, contact time and temperature was studied to predict the optimum conditions for effective removing of 210Po. Initial and equilibrium activity concentration of 209Po in solutions was counted by a ZnS(Ag) alpha scintillation counter. Adsorption yield of 209Po onto the zeolite was determined as 90 ± 2% at pH: <3 and 25 °C for 40 min of contact time. The applications of the isotherm models such as Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms were studied to evaluate adsorption characteristics of 209Po onto natural zeolite. Results indicated that the Dubinin-Radushkevich and Freundlich models gave a better fit to the experimental data than Langmuir isotherm models. The thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of adsorption process were calculated. The change in entropy (ΔSo) and enthalpy (ΔHo) were estimated to be -0.0003 J nmol-1 K-1 and 0.1008 kJ nmol-1, respectively.

Investigation of interaction behaviours of cesium and strontium ions with engineering barrier material to prevent leakage to environmental.

This study deals with performance of removal of cesium (Cs+) and strontium (Sr2+) ions from synthetic aqueous solution using amino pyridine sulfone amid resin as a barrier material for nuclear waste storage areas to reduce environmental risk. The effects of adsorbate concentration, temperature and contact time on the efficiencies of the engineering barrier material for Cs+ and Sr2+ ions were investigated and evaluated. It was found that total adsorption capacity was higher for cesium ions than strontium ions. Dubinin-Radushkevich (D-R) isotherm model was well fitted to the adsorption data for both ions. The micropore capacity of the barrier material was found as 4.20 mg for strontium ions and 5.40 mg for cesium ions. ΔH values were indicated that the interaction process is exothermic for both ions. The positive value of entropy for both ions show that randomness at the solid-solution interface increased. Pseudo-second-order model was well fitted the kinetic data.

Removal of 210Po from aqueous media and its thermodynamics and kinetics.

In this study, the composite adsorbent as granule was prepared by mixing of polyacrylonitrile (PAN) and a natural zeolite (clinoptilolite) in specific conditions. The prepared composite adsorbent was used for investigating the adsorption behaviour of 210Po. Adsorption of 210Po was studied in a column system. The effective parameters such as initial activity concentration of 210Po, pH of the aqueous solution, contact time and temperature of solution for adsorption behaviour of 210Po were studied. Adsorption yield of 210Po on composite adsorbent from aqueous solution in optimum conditions were determined as 75.00 ± 0.15%. The adsorption equilibrium data was examined using various well-known isotherm models such as Freundlich, Langmuir, Dubinin and Radushkevish and Tempkin, and it was observed that the experimental equilibrium data well fitted and found to be in good agreement with the Tempkin model. Adsorption thermodynamics and kinetics of the polonium were studied. It was found that the processes for 210Po were exothermic and spontaneous. The kinetic data conformed better to the pseudo-second order equation.

Early postoperative hemodynamic performances of stented versus stentless aortic xenografts in aortic valve replacement in elderly patients: a comparative study.

BACKGROUND AND AIM: Surgical valve replacement is the most commonly performed for aortic stenosis. Randomized trials comparing stentless to stented bioprostheses for aortic valve replacement in elderly are scarce. The aim of our study was comparing and evaluating the early hemodynamic performances of Hancock™ stented and FreeStyle™ stentless xenograft aortic valves in aortic valve replacement in elderly patients. PATIENTS AND METHODS: The study involved 40 patients (27 females and 13 males) older than 75 years old. The study was done during the postoperative period. Aortic valve replacements of stented and stentless xenografts were performed to the patients in Group I and Group II, respectively. Investigations for the echocardiographic results were completed on the postoperative 8-10th days. Parameters for the evaluation of hemodynamics were peak pressure gradient, mean pressure gradient and effective orifice area. The parameters were calculated with Doppler echocardiography by using specific formulas. RESULTS: Peak pressure gradients in patients with stented valves were significantly higher than in stentless valves [Stented valve group 32.45 ± 7.58 vs Stentless valve group 21.50 ± 4.77 mmHg] (p < 0.05). Mean pressure gradients were found to be significantly higher in stented group compared with stented group [Stented valve group 11.050 ± 3.2521 vs Stentless valve group 19.350 ± 6.6036 mmHg] (p < 0.05). The effective orifice area index of implanted valve was significantly greater in the stentless group, as well [Stentless valve group 2.5050 ± 0.6022 vs Stented valve group 1.3050 ± 0.3316 cm2] (p < 0.05). CONCLUSIONS: In early postoperative period, effective orifice areas and pressure gradients were found higher in stentless valve group.

The evaluation of microbial contamination in platelet concentrates prepared by two different methods.

The microbial contamination of platelet concentrates (PCs) prepared by two different methods both with a high risk of bacterial contamination during preparation and storage were evaluated. For apheresis platelets, the concentrates were obtained using the Haemonetics MCS 3P device. For the random method, platelets were obtained by two phase centrifugation, in the Heraeus Cryofuge 8500 I device using the Kansuk 3-way bags which permit storage for five days. 1620 plateletpheresis units prepared by apheresis, and 9838 units prepared by the random method, were included in the study. Of the 11,458 PCs studied. 32 (0.27%) were false positives and 24 (0.2%) were real positives. All of the positive results occurred in platelets prepared by the random method. C. xerosis and S. epidermidis, S. hominis, Alpha-hemolytic streptococci, all flora of the skin, were isolated in the contaminated concentrates. The risk of microbial contamination of PCs, prepared both by apheresis and from whole blood, continues at a low rate although the products were collected into specific bags following rules including appropriate disinfection of the skin, correct centrifugation collection time and optimal storage conditions including temperature and agitation. These results again emphasize the importance of: obeying phlebotomy rules and hand disinfection of the person who collects the blood as well as the need for careful skin decontamination of the donor, during donation.

An immunological approach to postpericardiotomy syndrome occurrence and its relation with autoimmunity.

OBJECTIVE: An autoimmunological approach to the pathogenesis of post-pericardiotomy syndrome. METHODS: In 100 consecutive patients, after open heart surgery, postpericardiotomy syndrome (PPS) was diagnosed in 15 patients according to clinical and laboratory criteria. These patients were prospectively followed up. Levels of serum autoantibodies against cardiac muscle antigen were studied on the 14th, 21st and 33rd day postoperatively. In order to evaluate the cardiac muscle antibody (CMA), antigenic tissue sections from primate heart tissue in solid phase with intermyofibrillar and sarcolemmal-subsarcolemmal fluorescent staining, were taken as substrate. PPS occurrence was determined according to strongly positive antibody titers on the 14th and 21st day postoperatively. RESULTS: CMA were positive in 18 patients, and 14 of them showed clinical signs of PPS. In one case PPS was apparent clinically although CMA were not detected. There was a significant difference between CMA positive and CMA negative patients on the occurrence of PPS. With the use of monoclonal antihuman IgG in the conjugate of indirect fluorescent antibody test the specificity was enhanced. Also, in our experience, the length of cardiopulmonary bypass (CPB) time was an important factor affecting the development of PPS. CONCLUSION: In this study, we found a positive correlation between the presence of CMA and PPS, which is a practical, secure and cheap criterion for the diagnosis.

Cardiac hydatid cyst in left ventricle.

Hydatid cyst of the heart is an uncommon lesion which usually develops in the left ventricle. A 34-year-old patient with hydatid cyst of the left ventricle, who was operated under cardiopulmonary bypass, is presented. Postoperative course at one year was uncomplicated.

Transaortic coronary patchplasty for isolated main left coronary ostial stenosis: a report of five cases.

The incidence of isolated ostial stenosis of the left main coronary artery varies between 0.13% and 2.7%. We performed surgical ostial angioplasty in five patients who had isolated left coronary ostial stenosis. One patient had low systemic blood pressure and, after the procedure, manifested myocardial ischaemia: conventional aortocoronary bypass was performed. The outcome of the four others was uneventful. They remained free of symptoms and resumed normal activities. Transaortic patch angioplasty might be useful operative method for the isolated coronary ostial stenosis, since it restores a more physiologic perfusion of the coronary arteries.

Use of transcutaneous electrical nerve stimulation in the control of postoperative chest pain after cardiac surgery.

The effect of continuous transcutaneous electrical nerve stimulation (TENS) on postoperative pain following median sternotomy was evaluated in 89 patients with severe chest pain who underwent cardiac surgery in a prospective, randomized, blinded trial. Pain was assessed by visual analog pain scores before and during treatment in each group. In the active TENS group, 79% of the patients were completely free of chest pain during rest at the end of 180 minutes (P less than 0.001). Among the remaining patients with TENS, 16% had slight pain not needing narcotic analgesics and 5% still had chest pain requiring narcotics. In the control group in which inactive TENS was used, the intensity of pain was reduced in 44% of the patients at the end of 90 minutes (P less than 0.001). However, this early placebo effect was noted to diminish with time and at the end of 180 minutes, 80% of the patients complained of severe chest pain and needed narcotics. These data suggest that TENS can be effective in controlling postoperative chest pain due to median sternotomy after cardiac surgery and its continuous application in the early postoperative period can reduce the need for narcotics.