Simulation of epiretinal prostheses - evaluation of geometrical factors affecting stimulation thresholds.

Background: An accurate understanding of the electrical interaction between retinal prostheses and retinal tissue is important to design effective devices. Previous studies have used modelling approaches to simulate electric fields generated by epiretinal prostheses in saline and to simulate retinal ganglion cell (RGC) activation using passive or/and active biophysical models of the retina. These models have limited scope for studying an implanted human retinal prosthesis as they often do not account for real geometry and composition of the prosthesis-retina interface.

Total synthesis of (±)-cylindricine C.

A concise synthesis of (±)-cylindricine C and its C(13)-epimer is described. Starting from 1-octyne, cylindricine C and 13-epi-cylindricine C were prepared in 11% and 15% yields, respectively. The synthesis involves the preparation of the central tricyclic moiety via a radical α-iodoketone carboazidation/bis-reductive amination sequence.

A radical procedure for the anti-Markovnikov hydroazidation of alkenes.

A one-pot procedure for the efficient hydroazidation of alkenes involving hydroboration with catecholborane followed by reaction with benzenesulfonyl azide in the presence of a radical initiator is described. The regioselectivity is controlled by the hydroboration step and corresponds in most cases to an anti-Markovnikov regioselectivity. This procedure is applicable to a wide range of alkenes and gives excellent results with 1,2-disubstituted and trisubstituted alkenes.

A novel approach to dielectrophoresis using carbon electrodes.

Carbon-electrode dielectrophoresis (carbon-DEP) is demonstrated here as an alternative to more traditional DEP techniques. Carbon-DEP combines advantages of metal-electrode and insulator-based DEP by using low-cost fabrication techniques and low voltages for particle manipulation. The use of 3-D electrodes is proved to yield significant advantages over the use of traditional planar electrodes.

Real-time functional magnetic imaging-brain-computer interface and virtual reality promising tools for the treatment of pedophilia.

This chapter proposes a prospective view on using a real-time functional magnetic imaging (rt-fMRI) brain-computer interface (BCI) application as a new treatment for pedophilia. Neurofeedback mediated by interactive virtual stimuli is presented as the key process in this new BCI application. Results on the diagnostic discriminant power of virtual characters depicting sexual stimuli relevant to pedophilia are given.

Diastereoselective radical mediated alkylation of a chiral glycolic acid derivative.

Radical alkylation of 2-(tert-butyl)-2-methyldioxolan-4-one, a chiral equivalent of glycolic acid, occurs with good to high diastereoselectivity that compares favorably with the corresponding enolate alkylation. The importance of the position of the transition state position, early or late, is highlighted.

Distinguishing drug-induced minor morphological changes from major cellular damage via label-free impedimetric toxicity screening.

We present a novel perfusion-based microfluidic platform for label-free drug toxicity screening which can single out non-lethal morphological changes from cellular death using electrical impedance spectroscopy. Minor cellular changes such as cell-cell contacts and major cell injury were identified via impedance phase angle analysis and follow-up of impedance magnitude at different frequencies. Having exposed HepG2/C3A cells to acetaminophen (AP), we showed that continuous drug perfusion caused a time and concentration-dependent impedance decrease.

Development of a microfluidics biosensor for agarose-bead immobilized Escherichia coli bioreporter cells for arsenite detection in aqueous samples.

Contamination with arsenic is a recurring problem in both industrialized and developing countries. Drinking water supplies for large populations can have concentrations much higher than the permissible levels (for most European countries and the United States, 10 μg As per L; elsewhere, 50 μg As per L). Arsenic analysis requires high-end instruments, which are largely unavailable in developing countries.

Improving benthic monitoring by combining trawl and grab surveys.

Environmental monitoring is performed on seafloor communities since these organisms are relatively stationary and integrate the environmental conditions over many years. Standard practices involve sampling by grab. Epifaunal taxa, often missed by grab sampling, are likely to have different ecological functions.

Design considerations for a novel MRI compatible manipulator for prostate cryoablation.

Purpose: Prostate carcinoma is a commonly diagnosed cancer in men. Nonsurgical treatment of early stage prostate cancer is an important alternative. The use of MRI for tumor cryoablation is of particular interest: it offers lower morbidity compared with other localized techniques.

Tracking and synchronization of the yeast cell cycle using dielectrophoretic opacity.

Cell cycle synchronization is an important tool for the study of the cell division stages and signalling. It provides homogeneous cell cultures that are of importance to develop and improve processes such as protein synthesis and drug screening. The main approach today is the use of metabolic agents that block the cell cycle at a particular phase and accumulate cells at this phase, disturbing the cell physiology.

Co-pathological connected primary neurons in a microfluidic device for Alzheimer studies.

This communication presents a novel experimental model for Alzheimer studies, where connected primary neurons were set into subtend, co-pathological states. Cortical neurons were cultured in two separated cell compartments in a microfluidic device. A neurite network was generated in a main channel through the neurite outgrowth from both cell compartments.

Simulations to study spatial extent of stimulation and effect of electrode-tissue gap in subretinal implants.

We present a finite element based simulation and analysis method to describe the spatial extent of stimulation and the effects of electrode-tissue interactions in subretinal prostheses. In particular, we estimate the threshold stimulation current needed to depolarise and evoke action potentials in the ganglion cells to be stimulated at a particular distance from the electrode. This is achieved through the application of a threshold electric field to a spherical neuronal soma model of a retinal ganglion cell under consideration.

Link between alginate reaction front propagation and general reaction diffusion theory.

We provide a common theoretical framework reuniting specific models for the Ca(2+)-alginate system and general reaction diffusion theory along with experimental validation on a microfluidic chip. As a starting point, we use a set of nonlinear, partial differential equations that are traditionally solved numerically: the Mikkelsen-Elgsaeter model. Applying the traveling-wave hypothesis as a major simplification, we obtain an analytical solution.

Radical chain reduction of alkylboron compounds with catechols.

The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes.

Concise synthesis of pyrrolidine and indolizidine alkaloids by a highly convergent three-component reaction.

The synthesis of pyrrolidine and indolizidine derivatives through radical carboazidation of alkenes with α-iodoketones, followed by reductive amination, is described. When properly substituted, further lactamization afforded pyrrolizidinones in good yield. This carboazidation/reductive amination sequence was efficiently applied to the total synthesis of three different simple alkaloids, including (±)-monomorine I.

Micropatterning neural cell cultures in 3D with a multi-layered scaffold.

Cortical neurons, in their native state, are organized in six different cell layers; and the thickness of the cell layer ranges from 0.12 mm to 0.4 mm.

Efficient carboazidation of alkenes using a radical desulfonylative azide transfer process.

The radical-mediated carboazidation of terminal alkenes using electrophilic alkanesulfonyl azides is reported. A single reagent delivers the necessary electrophilic alkyl radical as well as the azido group, and good yields are obtained by using a moderate excess of the carboazidating reagent (1.5-2 equiv).

Sexual affordances, perceptual-motor invariance extraction and intentional nonlinear dynamics: sexually deviant and non-deviant patterns in male subjects.

Sexual arousal and gaze behavior dynamics are used to characterize deviant sexual interests in male subjects. Pedophile patients and non-deviant subjects are immersed with virtual characters depicting relevant sexual features. Gaze behavior dynamics as indexed from correlation dimensions (D2) appears to be fractal in nature and significantly different from colored noise (surrogate data tests and recurrence plot analyses were performed).

Fluidic microstructuring of alginate hydrogels for the single cell niche.

Controlling alginate gel formation by diffusion of Ca(2+) ions through a filter barrier, a layer-by-layer deposition technique with resolution on the size scale of a single cell is presented. It offers the possibility of exposing cells under biocompatible conditions to microheterogeneous three-dimensional environments, mimicking the layered structure of extracellular matrix in tissues.

A miniaturized continuous dielectrophoretic cell sorter and its applications.

There is great interest in highly sensitive separation methods capable of quickly isolating a particular cell type within a single manipulation step prior to their analysis. We present a cell sorting device based on the opposition of dielectrophoretic forces that discriminates between cell types according to their dielectric properties, such as the membrane permittivity and the cytoplasm conductivity. The forces are generated by an array of electrodes located in both sidewalls of a main flow channel.

A unified approach to dielectric single cell analysis: impedance and dielectrophoretic force spectroscopy.

In this review we present a unified approach for single cell dielectric spectroscopy. Impedance spectroscopy and dielectrophoretic cell sorting, current microtechnologies applied in electrical analysis of single cells are discussed based on their closely related physical principles. In addition, examples of microfluidic devices will be presented: a microfabricated flow cytometer for single cell discrimination based on impedance analysis and a miniaturized continuous dielectrophoretic cell sorter, both using the concept of liquid electrodes.

Synthesis of unusual oxime ethers by reaction of tetranitromethane with B-alkylcatecholboranes.

The reaction of tetranitromethane with B-alkylcatecholboranes leads to the formation of unusual dinitrooxime ethers. A tentative mechanism is provided, which suggests the involvement of extremely fast addition of alkyl radicals to tetranitromethane. The substitution of one of the nitro groups in the oxime ethers by nucleophiles (such as secondary amines, halogens and styrene) and by radicals generated from B-alkylcatecholboranes is reported.