scholarly journals Application of a Novel Measurement Setup for Characterization of Graphene Microelectrodes and a Comparative Study of Variables Influencing Charge Injection Limits of Implantable Microelectrodes

Sensors ◽  
2019 ◽  
Vol 19 (12) ◽  
pp. 2725 ◽  
Author(s):  
Ana Cisnal ◽  
Frank R. R. Ihmig ◽  
Juan-Carlos Fraile ◽  
Javier Pérez-Turiel ◽  
Víctor Muñoz-Martinez
Keyword(s):  
Biomedical Applications ◽  
Charge Injection ◽  
Electrochemical Characteristics ◽  
Maximum Charge ◽  
Fraunhofer Institute ◽  
Long Term Behavior ◽  
Electrochemical Evaluation

Depending on their use, electrodes must have a certain size and design so as not to compromise their electrical characteristics. It is fundamental to be aware of all dependences on external factors that vary the electrochemical characteristics of the electrodes. When using implantable electrodes, the maximum charge injection capacity (CIC) is the total amount of charge that can be injected into the tissue in a reversible way. It is fundamental to know the relations between the characteristics of the microelectrode itself and its maximum CIC in order to develop microelectrodes that will be used in biomedical applications. CIC is a very complex measure that depends on many factors: material, size (geometric and effectiveness area), and shape of the implantable microelectrode and long-term behavior, composition, and temperature of the electrolyte. In this paper, our previously proposed measurement setup and automated calculation method are used to characterize a graphene microelectrode and to measure the behavior of a set of microelectrodes that have been developed in the Fraunhofer Institute for Biomedical Engineering (IBMT) labs. We provide an electrochemical evaluation of CIC for these microelectrodes by examining the role of the following variables: pulse width of the stimulation signal, electrode geometry and size, roughness factor, solution, and long-term behavior. We hope the results presented in this paper will be useful for future studies and for the manufacture of advanced implantable microelectrodes.

scholarly journals (M,β)-Stability of Positive Linear Systems

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Octavian Pastravanu ◽  
Mihaela-Hanako Matcovschi
Keyword(s):  
Linear System ◽  
Linear Systems ◽  
Transient Behavior ◽  
Short Term ◽  
Time Dynamics ◽  
The Right ◽  
Long Term Behavior ◽  
Stability Concept

The main purpose of this work is to show that the Perron-Frobenius eigenstructure of a positive linear system is involved not only in the characterization of long-term behavior (for which well-known results are available) but also in the characterization of short-term or transient behavior. We address the analysis of the short-term behavior by the help of the “(M,β)-stability” concept introduced in literature for general classes of dynamics. Our paper exploits this concept relative to Hölder vectorp-norms,1≤p≤∞, adequately weighted by scaling operators, focusing on positive linear systems. Given an asymptotically stable positive linear system, for each1≤p≤∞, we prove the existence of a scaling operator (built from the right and left Perron-Frobenius eigenvectors, with concrete expressions depending onp) that ensures the best possible values for the parametersMandβ, corresponding to an “ideal” short-term (transient) behavior. We provide results that cover both discrete- and continuous-time dynamics. Our analysis also captures the differences between the cases where the system dynamics is defined by matrices irreducible and reducible, respectively. The theoretical developments are applied to the practical study of the short-term behavior for two positive linear systems already discussed in literature by other authors.

scholarly journals The Role of Dispersal in Interacting Patches Subject to an Allee Effect

2013 ◽  
Vol 45 (4) ◽  
pp. 1182-1197
Author(s):  
N. Lanchier
Keyword(s):  
Allee Effect ◽  
Interacting Particle Systems ◽  
Local Population ◽  
Critical Value ◽  
Initial Distribution ◽  
Interacting Particle ◽  
Strong Allee Effect ◽  
Long Term Behavior

This article is concerned with a stochastic multipatch model in which each local population is subject to a strong Allee effect. The model is obtained by using the framework of interacting particle systems to extend a stochastic two-patch model that was recently introduced by Kang and the author. The main objective is to understand the effect of the geometry of the network of interactions, which represents potential migrations between patches, on the long-term behavior of the metapopulation. In the limit as the number of patches tends to ∞, there is a critical value for the Allee threshold below which the metapopulation expands and above which the metapopulation goes extinct. Spatial simulations on large regular graphs suggest that this critical value strongly depends on the initial distribution when the degree of the network is large, whereas the critical value does not depend on the initial distribution when the degree is small. Looking at the system starting with a single occupied patch on the complete graph and on the ring, we prove analytical results that support this conjecture. From an ecological perspective, these results indicate that, upon arrival of an alien species subject to a strong Allee effect to a new area, though dispersal is necessary for its expansion, fast long-range dispersal drives the population toward extinction.

Use of Ultrasound Biomicroscopy to Predict Long-Term Outcome of Sub-Tenon Needle Revision of Failed Trabeculectomy Blebs: A Pilot Study

2011 ◽  
Vol 21 (6) ◽  
pp. 700-707 ◽  
Author(s):  
Sushmita Kaushik ◽  
Anamika Tiwari ◽  
Surinder Singh Pandav ◽  
Parul Ichhpujani ◽  
Amod Gupta
Keyword(s):  
Ultrasound Biomicroscopy ◽  
Successful Outcome ◽  
Term Outcome ◽  
Long Term Outcome ◽  
Successful Group ◽  
Aqueous Flow ◽  
Needle Revision

Purpose. To evaluate the role of ultrasound biomicroscopy (UBM) in predicting the long-term outcome of sub-Tenon needling revision of failed trabeculectomy blebs. Methods. Adult patients with a failed trabeculectomy bleb and unsatisfactory intraocular pressure (IOP) control were recruited. The aqueous flow under the partial thickness scleral flap was looked for and the blebs classified on UBM as scleral route patent (SRP) or scleral route occluded (SRO). All blebs underwent needling revision with injection of 5 mg/0.1 mL 5-fluorouracil. Survival of the revision procedure at the end of 2 years follow-up with regards to the baseline UBM characterization of the bleb was noted. Successful outcome was defined as IOP <22.0 mmHg and/or 30% reduction of baseline IOP with or without medication. Results. A total of 13 eyes had SRP and 5 eyes had SRO blebs on UBM. Only SRP blebs survived the needling procedure by the end of 2 years. Of the 13 SRP blebs, 10 blebs survived (76.9%). Needling had failed in all 5 SRO blebs. The overall success rate was 55.6 % at 2 years. There was no difference in age, IOP, and time from initial trabeculectomy between the failed and successful group. The outcome correlated significantly to the patency of the scleral route assessed by UBM (p=0.07). Conclusions. Ultrasound biomicroscopy characterization of failed blebs appears to help in predicting the outcome of needle revision. In SRO blebs, it may be better to plan a full bleb revision rather than needling alone. Ultrasound biomicroscopy may help in avoiding an unnecessary needling procedure in SRO blebs where it is likely to fail.

scholarly journals The Corinth Rift Laboratory or an in situ Investigation on Interactions between Fluids and Active Faults

2007 ◽  
Vol SpecialIssue ◽  
pp. 35-38 ◽  
Author(s):  
F. H. Cornet
Keyword(s):  
Fluid Flow ◽  
Deformation Process ◽  
Active Faults ◽  
Localization Of Deformation

Earthquakes result from the sudden acceleration of a preliminary long-term slow deformation process. The objective of the Corinth Rift Laboratory (CRL) is to investigate <i>in situ</i> this quasistatic deformation process and mechanisms leading to a sudden catastrophic acceleration. Of particular interest is the characterization of the structure of the deforming zones and of the progressive localization of deformation. Special attention is given to the role of fluids but also on the influence of faults on regional fluid flow <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.s01.20.2007" target="_blank">10.2204/iodp.sd.s01.20.2007</a>

scholarly journals Extracellular Vesicles and Exosomes: Insights From Exercise Science

2021 ◽  
Vol 11 ◽  
Author(s):  
Joshua P. Nederveen ◽  
Geoffrey Warnier ◽  
Alessia Di Carlo ◽  
Mats I. Nilsson ◽  
Mark A. Tarnopolsky
Keyword(s):  
Extracellular Vesicles ◽  
Bioactive Molecules ◽  
Blood Collection ◽  
Exercise Science ◽  
Purification And Characterization ◽  
Exercise Response ◽  
Response To Exercise

The benefits of exercise on health and longevity are well-established, and evidence suggests that these effects are partially driven by a spectrum of bioactive molecules released into circulation during exercise (e.g., exercise factors or ‘exerkines’). Recently, extracellular vesicles (EVs), including microvesicles (MVs) and exosomes or exosome-like vesicles (ELVs), were shown to be secreted concomitantly with exerkines. These EVs have therefore been proposed to act as cargo carriers or ‘mediators’ of intercellular communication. Given these findings, there has been a rapidly growing interest in the role of EVs in the multi-systemic, adaptive response to exercise. This review aims to summarize our current understanding of the effects of exercise on MVs and ELVs, examine their role in the exercise response and long-term adaptations, and highlight the main methodological hurdles related to blood collection, purification, and characterization of ELVs.

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