Browsing by Publisher "Maik Nauka-Interperiodica Publishing"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Voltammetric determination of timolol maleate: A β-adrenergic blocking agent
    (Maik Nauka-Interperiodica Publishing, 2001) Türkdemir M.H.; Erdögdu G.; Aydemir T.; Karagözler A.A.; Karagözler A.E.
    Timolol as a β-adrenoceptor antagonist is a potent antihypertensive and antianginal drug, which was also proved to be effective for the secondary prevention of myocardial infarction. The analysis of timolol, as with other oxprenolols, in ophthalmic solutions and biological liquids using sensitive instrumental methods has gained importance. Investigation of the electrochemical behavior of timolol maleate on a mercury drop electrode reveals the presence of a specific reduction peak of analytical significance. Analysis conditions affecting the properties of this peak were optimized by a systematic study. The limit of detection of about 2.5 ppb, obtained for the DPV technique using SMDE, is comparable with the most sensitive techniques. This method is suitable for routine analysis in that it is simpler and requires no preconcentration step for the analysis of therapeutic doses of the drug. © 2001 MAIK "Nauka/Interperiodica".
  • No Thumbnail Available
    Item
    Piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic composites
    (Maik Nauka-Interperiodica Publishing, 2016) Mamedov H.A.; Parali L.; Kurbanov M.A.; Bayramov A.A.; Tatardar F.N.; Sabikoglu I.
    In this study, piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic composites have been investigated. The results show that composites based on crystallizable polymers, such as PVDF, HDPE, and PP dispersed by semiconductors and ferropiezoelectric fillers have piezoresistive and posistor properties, respectively. At low pressure, charge carriers tunneling through the located thin polymer among filler particles into the barrier define the conductivity of the composite. When pressure value is increased from 0 to 1 MPa, the thickness of the interlayer decreases and tunnel conductivity descends exponentially depending on barrier height. The piezoresistor sensitivity of a composite based on PVDF-70 vol % + Si-30 vol % is higher than a composite based on HDPE-70 vol % + Ge-30 vol %. Furthermore, the posistor properties of polymer composites dispersed by ferropiezoceramic are determined as the maximum resistance that varies significantly with temperature. Posistor effect in composites based on polymer + ferropiezoceramic is associated with the height of the barrier layer, which changes according to properties of filler, polymer, and dielectric permittivity of two-phase composites. The highest specific resistance related to HDPE-70 vol % + BaTiO3-30 vol % composite was observed at ~403 K. © 2016, Pleiades Publishing, Ltd.