Development and assessment of methods for detecting dementia using the human electroencephalogram

This paper makes an outline case for the need for a low-cost, easy to administer method for detecting dementia within the growing at risk population. It proposes two methods for electroencephalogram (EEG) analysis for detecting dementia that could fulfil such a need. The paper describes a fractal dimension-based method for analyzing the EEG waveforms of subjects with dementia and reports on an assessment which demonstrates that an appropriate fractal dimension measure could achieve 67% sensitivity to probable Alzheimer's disease (as suggested by clinical psychometric testing and EEG findings) with a specificity of 99.9%. An alternative method based on the probability density function of the zero-crossing intervals is shown to achieve 78% sensitivity to probable Alzheimer's disease and an estimated sensitivity to probable Vascular (or mixed) dementia of 35% (as suggested by clinical psychometric testing and EEG findings) with a specificity of 99.9%. This compares well with other studies, reported by the American Academy of Neurology, which typically provide a sensitivity of 81% and specificity of 70%. The EEG recordings used to assess these methods included artefacts and had no a priori selection of elements "suitable for analysis." This approach gives a good prediction of the usefulness of the methods, as they would be used in practice. A total of 39 patients (30 probable Alzheimer's Disease, six Vascular Dementia and three mixed dementia) and 42 healthy volunteers were involved in the study. However, although results from the preliminary evaluation of the methods are promising, there is a need for a more extensive study to validate the methods using EEGs from a larger and more varied patient cohorts with neuroimaging results, to exclude other causes and cognitive scores to correlate results with severity of cognitive status.     

Morphologic and functional changes in the unilateral 6-hydroxydopamine lesion rat model for Parkinson’s disease discerned with μSPECT and quantitative MRI

Object

In the present study, we aimed to evaluate the impact of neurodegeneration of the nigrostriatal tract in a rodent model of Parkinson’s disease on the different MR contrasts (T₂, T₁, CBF and CBV) measured in the striatum.

Material and methods

Animals were injected with 6-hydroxydopamine (6OHDA) in the substantia nigra resulting in massive loss of nigrostriatal neurons and hence dopamine depletion in the ipsilateral striatum. Using 7T MRI imaging, we have quantified T₂, T₁, CBF and CBV in the striata of 6OHDA and control rats. To validate the lesion size, behavioral testing, dopamine transporter μSPECT and tyrosine hydroxylase staining were performed.

Results

No significant differences were demonstrated in the absolute MRI values between 6OHDA animals and controls; however, 6OHDA animals showed significant striatal asymmetry for all MRI parameters in contrast to controls.

Conclusions

These PD-related asymmetry ratios might be the result of counteracting changes in both intact and affected striatum and allowed us to diagnose PD lesions. As lateralization is known to occur also in PD patients and might be expected in transgenic PD models as well, we propose that MR-derived asymmetry ratios in the striatum might be a useful tool for in vivo phenotyping of animal models of PD.     

A proposed confinement modulated gap nanowire transistor based on a metal (tin)

Energy bandgaps are observed to increase with decreasing diameter due to quantum confinement in quasi-one-dimensional semiconductor nanostructures or nanowires. A similar effect is observed in semimetal nanowires for sufficiently small wire diameters: A bandgap is induced, and the semimetal nanowire becomes a semiconductor. We demonstrate that on the length scale on which the semimetal-semiconductor transition occurs, this enables the use of bandgap engineering to form a field-effect transistor near atomic dimensions and eliminates the need for doping in the transistor's source, channel, or drain. By removing the requirement to supply free carriers by introducing dopant impurities, quantum confinement allows for a materials engineering to overcome the primary obstacle to fabricating sub-5 nm transistors, enabling aggressive scaling to near atomic limits.     

A new F(ast)-CMS NEGF algorithm for efficient 3D simulations of switching characteristics enhancement in constricted tunnel barrier silicon nanowire MuGFETs

In this paper, we present 3D quantum simulations based on Non-Equilibrium Green’s Function (NEGF) formalism using the Comsol Multiphysics^? software and on the implementation of a new Fast Coupled Mode-Space (FCMS) approach. The FCMS algorithm allows one to simulate transport in nanostructures presenting discontinuities, as the normal Coupled Mode-Space (CMS) algorithm does, but with the speed of a Fast Uncoupled-Mode Space (FUMS) algorithm (a faster algorithm that cannot handle discontinuities). We then use this new algorithm to explore the effect of local constrictions on the performance of nanowire MultiGate Field-Effect Transistors (MuGFETs). We show that cross-section variations in a nanowire result in the formation of energy barriers that can be used to improve the on/off current ratio and switching characteristics of transistors: (1) A small constriction resulting in a barrier of the order of a 0.1 eV can be used as an effective means to improve the subthreshold slope and minimize the on/off current ratio degradation resulting from SD tunneling in ultra scaled transistor, and (2) We also report a new variable barrier transistor (VBT) device concept that is able to achieve sub-kT/q subthreshold slope without using impact ionization or band-to-band tunneling. Intra-band tunneling through constriction barriers is used instead. The device is, therefore, fully symmetrical and can operate at very low supply voltages. A subthreshold slope as low as 56.5 mV/decade is reported at T=300 K. The VBT reported here breaks the 60 mV/dec barrier over more than five decades of subthreshold current, which is the widest current range reported so far.     

Influence of sampler configuration on the uptake kinetics of a passive air sampler

Passive air samplers (PAS) are simple and cost-effective tools to monitor semivolatile organic compounds in air. Chemical uptake occurs by molecular diffusion from ambient air to a passive sampling medium (PSM). Previous calibration studies indicate that even for the same type of PAS, passive air sampling rates (R, m(3)(air)/d) can be highly variable due to the influence of a number of factors. Earlier studies mainly focused on factors (e.g., wind speed and temperature) influencing R via the kinetic resistance posed by the air boundary layer surrounding the PSM because that layer was deemed to be the main factor determining the uptake kinetics. Whereas recent calibration studies suggest that the PAS configuration can influence R, so far few studies have specifically focused on this factor. In this study, with the objective to understand the effect of PAS configurations on R, we applied a gravimetrical approach to study the kinetics of water vapor uptake from indoor air by silica gel placed inside cylindrical PAS of various configurations. We also conducted an indoor calibration for polychlorinated biphenyls on the same type of PAS using XAD-resin as the PSM. R was found to be proportional to the interfacial transfer area of the PSM but not the amount of the PSM because chemicals mainly accumulated in the outer layer of the PSM during the deployment time of the PAS. The sampler housing and the PSM can introduce kinetic resistance to chemical uptake as indicated by changes in R caused by positioning the PSM at different distances from the opening of the sampler housing and by using PSM of different diameters. Information gained from this study is useful for optimizing the PAS design with the objective to reduce the material and shipping costs without sacrificing sampling efficiency.     

A Sensitive Analytical Method for Quantifying Petromyzonol Sulfate in Water as a Potential Tool for Population Monitoring of the Southern Pouched Lamprey, Geotria Australis, in New Zealand Streams

The migratory southern pouched lamprey, Geotria australis, is a culturally important fish native to New Zealand. Anecdotal evidence suggests that populations of G. australis have declined from historic levels, and presently, this species is rare in many New Zealand rivers and streams. Migratory sea lamprey (Petromyzon marinus) use a pheromone mixture to locate suitable spawning sites. This mixture is comprised of three steroids: petromyzonol sulfate (PS), petromyzonamine disulfate (PADS), and petromyzosterol disulfate (PSDS). We examined the migratory pheromone mixture released by G. australis ammocetes and found that they excrete predominantly PS. PADS has been detected on some occasions in low concentrations, and PSDS either is not released, or is released in extremely low concentrations. By using a recently developed sensitive mass spectrometry method, we compared passive sampling techniques against more traditional active water sampling as methods for estimating lamprey populations in local streams. Passive sampling provided quantitative data for PS from all sites surveyed, with uptake rates of 0.3 to 45.7 pg/day observed. Conversely, active sampling returned only one positive result out of 19 samples, and with a method detection limit of 2.5 × 10^-14 M, this suggests that concentrations of PS in these streams are either extremely low or variable. The combination of passive sampling and triple quadrupole mass spectrometry is a promising tool for monitoring of G. australis in New Zealand streams.     

Challenges and opportunities for next-generation intracortically based neural prostheses

Neural prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding computer cursors, prosthetic arms, and other assistive devices. Intracortical electrode arrays measure action potentials and local field potentials from individual neurons, or small populations of neurons, in the motor cortices and can provide considerable information for controlling prostheses. Despite several compelling proof-of-concept laboratory animal experiments and an initial human clinical trial, at least three key challenges remain which, if left unaddressed, may hamper the translation of these systems into widespread clinical use. We review these challenges: achieving able-bodied levels of performance across tasks and across environments, achieving robustness across multiple decades, and restoring able-bodied quality proprioception and somatosensation. We also describe some emerging opportunities for meeting these challenges. If these challenges can be largely or fully met, intracortically based neural prostheses may achieve true clinical viability and help increasing numbers of disabled patients.