PubMed Health⌕ Search

Biomedical subjects

B Lowkis

Publications and source records attributed to B Lowkis.

14 recordsLinked to original sources
PubMed1998

An assessment of athrombogenic properties of electret polyethylene film.

This paper shows the results of an investigation into the effect of an electric charge on blood platelet adhesion. All of the experiments were made on a polyethylene film. The electrets were formed using the electron beam method. The assessment of the electret effect on blood platelet adhesion was performed microscopically. It was found out that an electric charge plays a major role in the process of adhesion of blood morphological elements.

Biocompatible Materials↗
PubMed1997

An investigation into vascular prosthesis modified with an electron beam.

The present paper shows the results of an investigation into the effect of implanted electric charge on blood platelet adhesion to woven surfaces of "Dallon" polyester vascular prosthesis. The electrets were formed using the electron beam method. The assessment of the electret effect on blood platelet adhesion was performed on the basis of microscopic studies. It was shown that an implanted negative electric charge remarkably suppresses thrombocyte adhesion to the prosthesis surface. The electret effect was found to play a significant role in the process of preparing nonthrombogenic surfaces.

Biocompatible Materials↗
PubMed1995

Does the liquid method of electret forming influence the adhesion of blood platelets?

This work presents the results of the effect of the electric charge on the adhesion of blood platelets. All experiments were carried out on polyethylene foil. The liquid method was used to form electrets. The evaluation of the electret effect influence on the adhesion of blood platelets was made on the basis of the observation of the electret surface after the contact with fresh citrate human blood group O Rh+ in an electron scanning microscope. Experimental results confirmed the essential influence of the electric charge on the process of adhesion of blood platelets. It was noticed that the preliminary aging of electrets decreases the density of the surface charge and improves the athrombogenic characteristics of polyethylene foil.

Biocompatible Materials↗
PubMed1993

Effect of electric charge on the adhesion of human blood platelets.

The paper presents the results of research into the effect of the size and depth of the implanted electric charge on the adhesion of human blood platelets. The experiments were carried out on polyethylene terephthalate PET foil of 36 microns thickness. The electret formation process was carried out in an electron-beam device. The electrization conditions were such that electrets with the excess electric charge accumulated at various depths were obtained. The selection of conditions was verified by investigating the space charge distribution with the use of the virtual electrode method. The microscopic observation of non-electrified foils and electrets as well as the quantitative examination of the adhesion of human blood platelets has explicitly confirmed the positive influence of the electret effect on the thrombogenesis of PET foil. This made it possible to define the optimum electrization conditions. The research has additionally indicated that the relationship between the amount of adherent blood platelets and the size of the electric charge is not a simple relation of the kind: the larger negative charge, the more thrombogenic material. The decisive and positive effect of the space charge has been confirmed by analysing the effectiveness of the surface and space charge.

Biocompatible Materials↗
PubMed1993

Effect of the electret-blood contact time on the adhesion of human blood platelets.

The paper presents the results of research into the time characteristics of adhesion of platelets to the electret surface made from polyethylene terephthalate PET foil of 36 microns thickness. The electrets were formed by using the electron beam method. The method based on the electrostatic induction phenomenon was utilized to measure the electric charge surface density. Evaluation of the time characteristics of the adhesion of blood platelets was performed on the basis of microscopic examination and with the use of the chamber method for determining the number of blood platelets in the phase microscopy. The results obtained have confirmed the influence of the electret effect on PET foil thrombogenesis. The number of spacious aggregates found on the surfaces being analysed did not undergo any changes despite the extension of the electret--blood contact time. The stationary course of the adhesion process as well as the unappreciable amount of blood platelets on the surface have proved that the negative electric charge makes it possible to obtain thrombogenic materials.

Biocompatible Materials↗
PubMed1990

In vitro testing method of polymers candidate destined for contact with blood.

Research aiming at obtaining athromobogenic biomaterials destined for contact with blood have been the subject of interdisciplinary studies carried out since 1980. When testing candidate materials, it is advisable that preliminary classification as well as elimination of materials not conforming to the requirements of athromobogenesis should be performed. Practicable laboratory methods were selected facilitating in vitro evaluation of materials of modified surface and conforming to the definite requirements. The testing of candidate materials of athromobogenic properties comprises basic research methods enabling instantaneous classification. The applied experimental model comprises the following: scanning electron microscopy (SEM), thromboelastography (TEG), formula: [see text] examining clotting systems by determining calcium, cephalincalcium times as well as the amount of blood platelets, biochemical examination. Application of the above-mentioned methods enables objective preliminary evaluation of candidate materials that may be applied in obtaining implantation products and medical appliances for the contact with blood.

Blood↗
PubMed1983

[Effect of an electric charge on athrombogenic properties of polyvinyl chloride foil].

The authors present the results of investigation of fresh, human citrate blood after and before the contact with monoelectret of polyvinyl chloride (PVC). The investigations concerned the influence of electric charge of the results of thromboelastographic test and the outcome of microscopic examination. It was proved that blood after the contact with monoelectret contrary to the blood after the contact with sample lacking electret effect, had markedly prolonged thromboelastographic coagulation time and time of clot formation to standard elasticity.

Blood Coagulation↗
PubMed1983

[Liquid method of electret formation].

The work presents the results of investigations of electrets formed according to the liquid method. This method utilizes transmission of electric charge from conductive liquid to dielectric surface. Electrets were made of poliester foil "Hostaphan". Various liquids such as acetone, ethanol, Ringer solution and distilled water were used for charging. It was established that surface densities of electret charge formed by Ringer solution and acetone are about from 15 to 20 nC/cm2, whereas those formed by ethanol and distilled water from 5 to 10 nC/cm2. These electrets are characterized by big stability of charge and their survival time is about 100 years. Deelectrization of electrets in liquids that were formerly used for formation was also performed. It appeared that the survival time of the samples after deelectrization was several times longer than the survival time of electrets. The longest survival time have samples formed by ethanol and deelectrized by Ringer solution (about 10(9) years).

Acetone↗
PubMed1980

[Methods of measurement of electrostatic properties of polymer foils].

Two methods of electrization of polymer foils are presented: the corona method and the thermoelectric method. The techniques of measurement of the following properties of electrets are reviewed: the average surface charge density, the charge distribution along the sample diameter, the charge decay half-time and the surface charge as well as the excess charge with temperature rising linearly in time. These techniques set a development of the electrostatic induction and of the thermostimulated depolarisation (TSD) methods.

Chemistry Techniques, Analytical↗
PubMed1980

[Effect of biological fluids on the electrostatic properties of polyester foil electrets].

Thermoelectrets of "Hostaphan" polyester foil in two biological liquids, plasma and Ringer liquid, were investigated. Electrostatic parameters of the specimen immersed in the liquids at 37 degrees C as a function of the immersing time were studied. The following parameters were measured: the surface charge density, the excess charge, the polarization and the surface charge distribution along the specimen diameter before and after the immersing in the liquids. From the thermostimulated depolarization studies it appeared that, due to the immersing in the liquids, the charge is removed from the specimen surface, but stays in the bulk.

Chemistry Techniques, Analytical↗
PubMed1978

[Physical and biological examinations of polyester electret foil. Preliminary report].

The results of tissue reaction to polyester thermoelectret foil samples are evaluated. The electrostatic measurement of the foils was performed before implantation. The experimental animals were divided into four groups depending on the surface charge density of the foils. The autopsy of the animals was performed three days after the operation. The tissues of close contact to the foil were examined under the microscope and the electrostatic measurement of the foils.

Animals↗