Biomedical subjects

M Doula

Publications and source records attributed to M Doula.

4 recordsLinked to original sources

PubMed2002

Preparation, characterization and sorption properties for phosphates of hematite, bentonite and bentonite-hematite systems.

Hematite was prepared using Fe(NO3)3*9H2O. Bentonite was first saturated with sodium and then was transformed to the hydrogen form. The bentonite-hematite (b-h) system was prepared by the mixing of hematite and bentonite at pH 6.0, and a hematite-coated bentonite surface was created. The physical and chemical properties of the above solids were studied from the information given by X-ray, IR and NMR spectra and by measurement of specific surface and point of zero charge. The results of the above study show that the bentonite-hematite system is not a physical mixture of hematite and bentonite. Hematite moved into bentonite's interlayer space, coating these planes throughout. Consequently, Al-substitution and structural H2O/OH displacement of hematite took place. The system has a specific surface, less than bentonite and greater than hematite, while its p.z.c. is higher than bentonite and lower than hematite. Adsorption experiments of phosphates at different concentrations and pH were carried out and the constant capacitance model was used to describe phosphate adsorption by hematite, bentonite and the bentonite-hematite system. The model is characterized by a ligand exchange mechanism based on the assumption that the charge is attributed both on adsorbate and adsorbent, and is proven to successfully describe the adsorption of phosphate on these materials along with the effect of varying pH values. Ma-Za 1 and Ma-Za 2 (two computer programs) were used for this purpose. The model successfully gave a description (both quantitative and qualitative) of the adsorption of phosphate anions across the pH range (3.8-9.0). Furthermore, it can be successfully applied in systems as the bentonite-hematite system by utilizing the surface protonation-dissociation constant of hematite. The model, when applied in such systems, procreates the exact shape of the adsorption isotherms for the entire pH range of 3.8-9.0. The constant capacitance model was able to describe phosphorous adsorption on hematite and the bentonite-hematite system. The accurate fit of the model to phosphorous adsorption on hematite and the bentonite-hematite system suggests that inner sphere surface complexation is the appropriate adsorption mechanism for these materials.

Journal Article↗

PubMed2002

Copper adsorption and Si, Al, Ca, Mg, and Na release from clinoptilolite.

Copper adsorption onto clinoptilolite (natural zeolite), Al/Si dissolution, and Mg, Ca, and Na release from the substrate were the subjects of the investigation described here. Experimental variables were Cu and electrolyte concentrations and solution pH. Copper adsorption was found to increase with increased pH and with decreased electrolyte concentration. Large amounts of K were also adsorbed from electrolyte. Since solution pH was assumed as a variable, the effects of [H(+)] differentiation on Cu adsorption and on Al/Si dissolution were also examined. Al dissolution was affected mainly by electrolyte concentration, whereas Si dissolution was affected mainly by adsorbed Cu amount. It was assumed that the release of Mg, Ca, and Na occurs through ion-exchange reactions with solution K(+), because their release is affected more by electrolyte concentration than by adsorbed Cu. From the study of FTIR spectra for various samples used in the present investigation, we observed that the removal of framework Si/Al shifts the band which was attributed to O-T-O stretching vibration toward higher frequency. Significant changes were observed for the bands assigned to Si-OH-Al bridges and to monomeric and polymeric hydrogen bonds at the region between 3650 and 3200 cm(-1). It is proposed that the Cu species caused the destruction of H-bonded structures, whereas K adsorbed species were located at exchangeable sites after an ion-exchange process between K and Ca, Mg, and Na from the zeolite's surface. An expansion of the zeolite framework was detected from XRD patterns under acid conditions.

Journal Article↗

PubMedDate not supplied

European practice database: results from Greece.

The survey (EPD) took place during December 2002-January 2003 and presents renal care in Greece. A questionnaire, structured at European level and translated into Greek, was sent to all dialysis centres (114) by post. The questionnaire was returned from 74 centres (64.9%). Some important results were: low use of peritoneal dialysis (13.3%), half of PD patients over 65 years old, one ninth of patients on transplantation waiting list, isolation for HBV positive patients (less for HCV and HIV), high use of AV fistulae (71.2%), maintenance and repair of dialysis machines by company technicians, absence of renal dieticians and social workers (but availability from hospital employees) one nurse every 5.54 patients (3.72 if nurse assistants are included), disinfection between shifts carried out chemically (hot or cold) and puncturing of vascular access performed mainly by nurses and nurse assistants. Data can be used to pressurise government for more scientists in the multidisciplinary team to be hired in hospitals, develop further research topics and to develop continuous education programmes.

Age Factors↗

PubMedDate not supplied

Contribution of an effective venopuncture to recirculation.

Patency and function of permanent vascular access appears to be one of the most important elements of an adequate haemodialysis session. Since, it has been established that adequate haemodialysis is closely related to the mortality and morbidity of these patients, we all realise the importance of the strategies involved in handling the av fistula (1).

Adult↗