Search results for "electrodes"
showing 10 items of 231 documents
EEG and MEG primers for tracking DBS network effects
2020
Deep brain stimulation (DBS) is an effective treatment method for a range of neurological and psychiatric disorders. It involves implantation of stimulating electrodes in a precisely guided fashion into subcortical structures and, at a later stage, chronic stimulation of these structures with an implantable pulse generator. While the DBS surgery makes it possible to both record brain activity and stimulate parts of the brain that are difficult to reach with non-invasive techniques, electroencephalography (EEG) and magnetoencephalography (MEG) provide complementary information from other brain areas, which can be used to characterize brain networks targeted through DBS. This requires, howeve…
2,4,6-Triphenylpyrylium Ion Encapsulated into Zeolite Y as a Selective Electrode for the Electrochemical Determination of Dopamine in the Presence of…
2002
2,4,6-Triphenylpyrylium ion immobilized inside the supercages of zeolite Y enhances by 1-2 orders of magnitude the response of electrochemical oxidation of dopamine in neutral aqueous media accompanied by a remarkable inhibition of post-electron-transfer reactions. The negative charge of the zeolite framework in which the 2,4,6-triphenylpyrylium ion is incorporated blocks the electrochemical oxidation of the negative ascorbate ion, enabling the determination of micromolar concentrations of dopamine in the presence of a large excess (10(3)-10(4) times) of ascorbate in phosphate buffer (pH 7.4). Under optimized conditions, linear calibration plots were obtained for a differential pulse detect…
Electrochemical detection of chloride ions using Ag-based electrodes obtained from compact disc
2022
Abstract In this work electrochemical sensors fabricated from compact disc material (waste or new) are used to quantify chloride ions in different types of samples. All three electrodes, working, counter, and pseudo-reference electrodes, were fabricated from the compact disc and directly used. Different parameters were studied in order to demonstrate the possibility of using this waste material for efficient and low-cost electrochemical sensors. Chloride sensing performance was evaluated using linear scan voltammetry as the detection technique. A sensitivity of 0.174 mA mM−1 cm−2 with a limit of detection of 20 μM and excellent selectivity against many interferents was observed. Selectivity…
Determination of NH(3) in pyrolysis gases by ammonia selective electrode.
1993
The suitability of ion-selective electrode for the determination of ammonia in pyrolysis gases of fossil fuels was studied. The ammonia was absorbed into acidic solution and two kinds of determination methods were carried out. The ammonia was either measured directly from the acid solution, or ammonia was first released into the gas phase and then determined (air gap method) by the ammonia selective electrode. The electrode functioned well in both cases, but the linear calibration range was rather narrow, slightly more than one tenfold. The quantitative detection limit in the water phase was 5 × 10−6M (0.085 ppm) NH3 and in gas phase operation solutions above 5 × 10−4M (8.5 ppm) NH3 it was …
Electrochemical detection of dopamine with negligible interference from ascorbic and uric acid by means of reduced graphene oxide and metals-NPs base…
2021
Abstract Dopamine is an important neurotransmitter involved in many human biological processes as well as in different neurodegenerative diseases. Monitoring the concentration of dopamine in biological fluids, i.e., blood and urine is an effective way of accelerating the early diagnosis of these types of diseases. Electrochemical sensors are an ideal choice for real-time screening of dopamine as they can achieve fast, portable inexpensive and accurate measurements. In this work, we present electrochemical dopamine sensors based on reduced graphene oxide coupled with Au or Pt nanoparticles. Sensors were developed by co-electrodeposition onto a flexible substrate, and a systematic investigati…
Controlled transdermal iontophoresis by ion-exchange fiber
2000
The objective of this study was to assess the transdermal delivery of drugs using iontophoresis with cation- and anion-exchange fibers as controlled drug delivery vehicles. Complexation of charged model drugs with the ion-exchange fibers was studied as a method to achieve controlled transdermal drug delivery. Drug release from the cation-exchange fiber into a physiological saline was dependent on the lipophilicity of the drug. The release rates of lipophilic tacrine and propranolol were significantly slower than that of hydrophilic nadolol. Permeation of tacrine across the skin was directly related to the iontophoretic current density and drug concentration used. Anion-exchange fiber was te…
Peculiarities of Phase Formation in Mn-Based Na SuperIonic Conductor (NaSICon) Systems: The Case of Na1+2xMnxTi2–x(PO4)3 (0.0 ≤ x ≤ 1.5)
2021
This project has received funding from the European Regional Development Fund (Project no. 01.2.2-LMT-K-718-02–0005) under grant agreement with the Research Council of Lithuania (LMTLT). We thank the High Performance Computing Center “HPC Saulėtekis” at the Faculty of Physics, Vilnius University, for the use of computational resources.
Metal- and reagent-free highly selective anodic cross-coupling reaction of phenols.
2014
The direct oxidative cross-coupling of phenols is a very challenging transformation, as homo-coupling is usually strongly preferred. Electrochemical methods circumvent the use of oxidizing reagents or metal catalysts and are therefore highly attractive. Employing electrolytes with a high capacity for hydrogen bonding, such as methanol with formic acid or 1,1,1,3,3,3-hexafluoro-2-propanol, a direct electrolysis in an undivided cell provides mixed 2,2′-biphenols with high selectivity. This mild method tolerates a variety of moieties, for example, tert-butyl groups, which are not compatible with other strong electrophilic media but vital for later catalytic applications of the formed products.
Electrochemistry as an Attractive and Effective Tool for the Synthesis and Immobilization of Porphyrins on an Electrode Surface
2014
Magnesium(II) 10-phenyl-5,15-p-ditolylporphyrin is easily and cleanly transformed by electrolysis. A nitro group is first introduced at the free meso position by anodic substitution. Hydrogenation into the amine is then carried out electrocatalytically under ambient conditions with water as a hydrogen supplier. The synthesized porphyrin under the nickel(II) form can be covalently grafted onto a platinum electrode by electrochemical reduction of the diazonium cation, generated in situ by a reaction of the nickel(II) aminoporphyrin with sodium nitrite and trifluoroacetic acid. The electrosynthesized thin film gives an electrochemical response typical of a porphyrin material. Films grown under…
Intracranial measurement of current densities induced by transcranial magnetic stimulation in the human brain
2003
Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses the principle of electromagnetic induction to generate currents in the brain via pulsed magnetic fields. The magnitude of such induced currents is unknown. In this study we measured the TMS induced current densities in a patient with implanted depth electrodes for epilepsy monitoring. A maximum current density of 12 microA/cm2 was recorded at a depth of 1 cm from scalp surface with the optimum stimulation orientation used in the experiment and an intensity of 7% of the maximal stimulator output. During TMS we recorded relative current variations under different stimulating coil orientations and at different points…