Correlation of Impedance and Effective Electrode Area of Iridium Oxide Neural Electrodes

Iridium oxide is routinely used for bionic applications owing to its high charge injection capacity. The electrode impedance at 1 kHz is typically reported to predict neural recording performance. In this article, the impedance of activated iridium oxide films (AIROFs) has been examined. The impedance of unactivated iridium electrodes was half that of platinum electrodes of similar geometry, indicating some iridium oxide was present on the electrode surface. A two time constant equivalent circuit was used to model the impedance of activated iridium. The impedance at low and intermediate frequencies decreased with increasing number of activation pulses and total activation charge. The impedance at 12 Hz correlated with the steady-state diffusion electroactive area. The impedance at 12 Hz also correlated with the charge density of the electrode. The high charge density and low impedance of AIROFs may provide improved neural stimulation and recording properties compared with typically used platinum electrodes

Predicting neural recording performance of implantable electrodes

Recordings of neural activity can be used to aid communication, control prosthetic devices or alleviatedisease symptoms. Chronic recordings require a high signal-to-noise ratio that is stable for years. Currentcortical devices generally fail within months to years after implantation. Development of novel devices toincrease lifetime requires valid testing protocols and a knowledge of the critical parameters controllingelectrophysiological performance. Here we present electrochemical and electrophysiological protocolsfor assessing implantable electrodes. Biological noise from neural recording has significant impact on signal-to-noise ratio. A recently developed surgical approach was utilised to reduce biological noise. This allowed correlation of electrochemical and electrophysiological behaviour. The impedance versus frequency of modified electrodes was non-linear. It was found that impedance at low frequencies was astronger predictor of electrophysiological performance than the typically reported impedance at 1 kHz.Low frequency impedance is a function of electrode area, and a strong correlation of electrode area with electrophysiological response was also seen. Use of these standardised testing protocols will allow future devices to be compared before transfer to preclinical and clinical trials

The Release of Tissue Factor Pathway Inhibitor and Platelet Factor 4 After Heparin Injection in Patients with Thrombocytosis.

Platelet factor 4 (PF4) and tissue factor pathway inhibitor (TFPI) are two proteins with high affinity for heparin. They are each stored in platelets, as well as on endothelial cell surfaces, from where both are displaced or released following an injection of heparin with a rapid and marked increase in serum levels. Prior work has demonstrated that the platelet count is one of the factors affecting the levels of heparin-releasable PF4. We therefore characterized the response to a dose of intravenous heparin previously demonstrated to completely displace PF4 from the non-platelet pool in subjects with normal or increased platelet counts. Seventeen patients with essential thrombocytosis (ET), 10 patients with polycythemia vera and high platelet counts (PV-H), 7 patients with polycythemia vera and normal platelet counts (PV-N) and 10 controls received an initial bolus of 40 I.U./kg of unfractionated heparin, followed 2 hours later by a 2nd bolus of a fixed dose of 1000 I.U. TFPI activity did not show any variation among the different groups, either before (TFPI) or after (HR-TFPI) the first bolus of heparin: ET, TFPI 92.6 ± 21.5%, HR-TFPI 298.3 ± 165.8; PV-H, TFPI 91.5 ± 32.0, HR-TFPI 210 ± 1.0; PV-N, TFPI 69.4 ± 24.0, HR-TFPI 203.0 ± 79.0; C, TFPI 109.5 ± 33.5, HR-TFPI 234.0 ± 60.4. TFPI activity returned to basal values prior to the 2nd injection of heparin, which again elicited a rise in TFPI, albeit smaller due to the lower level of heparin injected. In contrast to the lack of any difference between groups with respect to TFPI, the level of heparin-releasable PF4 (HR-PF4) was significantly higher in ET and PV-H patients compared to PV-N patients or controls. However when normalized for platelet count, both PV-H and PV-N had HR-PF4 levels after the 1st heparin injection that were significantly higher than observed in ET patients (PV-H 1.163 + 0.108, PV-N 1.411 + 0.019, ET 0.737 + 0.086 ng/10/3 platelets) supporting an increased platelet activation in PV. Thus, although platelets contain approximately 5-10% of the total amount of TFPI in plasma, they do not affect the major intravascular pool of TFPI mobilizable by heparin. However, since the concentration at the site of vessel wall injury is enhanced several-fold, TFPI could play a role in competing with PF4 to limit thrombus formation in patients with high platelet count

The 2016–2017 earthquake sequence in Central Italy: macroseismic survey and damage scenario through the EMS-98 intensity assessment

In this paper we describe the macroseismic effects produced by the long and destructive seismic sequence that hit Central Italy from 24 August 2016 to January 2017. Starting from the procedure adopted in the complex field survey, we discuss the characteristics of the building stock and its classification in terms of EMS-98 as well as the issues associated with the intensity assessment due to the evolution of damage caused by multiple shocks. As a result, macroseismic intensity for about 300 localities has been determined; however, most of the intensities assessed for the earthquakes following the first strong shock on 24 August 2016, represent the cumulative effect of damage during the sequence. The earthquake parameters computed from the macroseismic datasets are compared with the instrumental determinations in order to highlight critical issues related to the assessment of macroseismic parameters of strong earthquakes during a seismic sequence. The results also provide indications on how location and magnitude computation can be strongly biased when dealing with historical seismic sequences.Presidenza del Consiglio dei Ministri - Dipartimento della Protezione Civile (DPC)Published2407–24314T. Sismicità dell'Italia1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami2SR TERREMOTI - Gestione delle emergenze sismiche e da maremoto5SR TERREMOTI - Convenzioni derivanti dall'Accordo Quadro decennale INGV-DPCJCR Journa

Association of kidney disease measures with risk of renal function worsening in patients with type 1 diabetes

Background: Albuminuria has been classically considered a marker of kidney damage progression in diabetic patients and it is routinely assessed to monitor kidney function. However, the role of a mild GFR reduction on the development of stage 653 CKD has been less explored in type 1 diabetes mellitus (T1DM) patients. Aim of the present study was to evaluate the prognostic role of kidney disease measures, namely albuminuria and reduced GFR, on the development of stage 653 CKD in a large cohort of patients affected by T1DM. Methods: A total of 4284 patients affected by T1DM followed-up at 76 diabetes centers participating to the Italian Association of Clinical Diabetologists (Associazione Medici Diabetologi, AMD) initiative constitutes the study population. Urinary albumin excretion (ACR) and estimated GFR (eGFR) were retrieved and analyzed. The incidence of stage 653 CKD (eGFR < 60 mL/min/1.73 m2) or eGFR reduction > 30% from baseline was evaluated. Results: The mean estimated GFR was 98 \ub1 17 mL/min/1.73m2 and the proportion of patients with albuminuria was 15.3% (n = 654) at baseline. About 8% (n = 337) of patients developed one of the two renal endpoints during the 4-year follow-up period. Age, albuminuria (micro or macro) and baseline eGFR < 90 ml/min/m2 were independent risk factors for stage 653 CKD and renal function worsening. When compared to patients with eGFR > 90 ml/min/1.73m2 and normoalbuminuria, those with albuminuria at baseline had a 1.69 greater risk of reaching stage 3 CKD, while patients with mild eGFR reduction (i.e. eGFR between 90 and 60 mL/min/1.73 m2) show a 3.81 greater risk that rose to 8.24 for those patients with albuminuria and mild eGFR reduction at baseline. Conclusions: Albuminuria and eGFR reduction represent independent risk factors for incident stage 653 CKD in T1DM patients. The simultaneous occurrence of reduced eGFR and albuminuria have a synergistic effect on renal function worsening

Effective area and charge density of chondroitin sulphate doped PEDOT modified electrodes

Neural electrodes have been coated with electrodeposited poly-3,4-ethylenedioxythiophene doped with chondroitin sulphate. Optical and electrochemical methods were used to determine the effective electrode area, charge injection capacity and charge density of the modified electrodes. Deposition times of 15 to 60 s slightly increased the geometric and steady state diffusion electroactive areas while the linear diffusion electroactive area grew significantly, indicating an increase in electrode roughness. The effective electrode area and charge injection capacity were significantly smaller than PEDOT doped with previously tested dopants. In contrast to other dopant ions, the charge density determined from the geometric and steady state diffusion electroactive areas was nearly constant with increased deposition time while the linear diffusion charge density decreased

The effect of pulsatile intracochlear electrical stimulation on intracellularly recorded cochlear nucleus neurons

This is a publisher’s version of a paper from XVI World Congress of Otohinolaryngology Head and Neck Surgery 1997, published by Monduzzi Editore. This version is reproduced with the permission of the publisher.The anterior division of the ventral cochlear nucleus (AVCN) is the first relay station of the auditory pathway. We examined responses of neurons in the A VCN to intracochlear electrical stimulation using in vivo intracellular recordings. Twin pulse stimulation results indicated that these neurones evoke action potentials which are able to follow pulsatile stimulation at high rates. This ability to respond to each pulse along the stimulus train diminished when stimulus duration was increased to 50 ms. At rates 400 Hz and below in all neurones tested a deterministic response was seen to this longer duration pulsatile stimulation. With increasing rate of stimulation the response become more stochastic with apparent loss of encoding ability. These results have in1pIications in the clinical application of cochlear implants operating at high stimulus rates.2-7 Marc

Intracellular responses of the rat anteroventral cochlear nucleus to intracochlear electrical stimulation

Publisher’s permission requested and denied.Unavailable due to copyright

Temporal coding for sound and tempor-spatial patterns of electrical stimulation [Abstract]

The anterior division of the ventral cochlear nucleus (AVCN) is the first relay station of the auditory pathway. It receives auditory information via the auditory nerves emanating from the cochlea. Electrical stimulation via current cochlear implants [ ] does not lead to responses at the cochlear nucleus that exactly match tho elicited by comparable auditory stimulation. Complex temporal patterns of electrical stimulation may provide a better simulation of the acoustic input.2-7 Marc