Technology in neurology

Promising developments in clinical neurophysiology over the last 10 years have been largely eclipsed by the dramatic evolution of magnetic resonance imaging (MRI). One exception has been encephalography (video EEG) monitoring and, of course, research in clinical neurophysiology knows no bounds. Neurosurgery has had major developments and some of these areas have involved neurophysiological co-operation such as neurophysiological sampling and stimulation in extrapyramidal movement disorders, especially Parkinson's disease. Overall, as in the rest of medical technology, digitisation and computerisation have gradually replaced all analogue systems and as the industry matured, many proprietary systems have migrated to commercial standards, particularly versions of the Windows operating systems. This development in technology has had tangible benefits in overlap with office software, ease of handling large amounts of data and increasing confidence in improved reliability and manipulation of signals. However, this technological benefit is a double-edged sword and apart from the more familiar problems common to many small computer systems, digital systems are capable of distorting or hiding signals without the unwary operator being aware of this. An example would be suspicious looking 'sharp waves' (potentially epileptogenic) on the EEG, which are the result of a noisy (bad) signal unwittingly being filtered by innocuous sounding switches ('muscle filters'). Despite the advanced technology, basic principles of a clean source of signal are still essential. Neurophysiological studies have not been exclusive to neurology and with important developments in cardiology and anaesthetics, there is greater overlap in some of the technology underlying these fields. At the same time, there has been a move to train clinical technologists who are capable of moving between even more disparate fields such as renal (dialysis) to respiratory (lung functions) to neurology. Unfortunately, the numbers of clinical technologists' posts, and hence members, have dropped significantly and such developments may be more necessary than originally planned.The training centres for clinical technology have also been drastically reduced, further hampering new recruits

Charge storage characteristics of ultra-small Pt nanoparticle embedded GaAs based non-volatile memory

Charge storage characteristics of ultra-small Pt nanoparticle embedded devices were characterized by capacitance-voltage measurements. A unique tilt target sputtering configuration was employed to produce highly homogenous nanoparticle arrays. Pt nanoparticle devices with sizes ranging from ∼0.7 to 1.34 nm and particle densities of ∼3.3–5.9 × 1012 cm−2 were embedded between atomic layer deposited and e-beam evaporated tunneling and blocking Al2O3 layers. These GaAs-based non-volatile memory devices demonstrate maximum memory windows equivalent to 6.5 V. Retention characteristics show that over 80% charged electrons were retained after 105 s, which is promising for device applications

Calculation Of Anisotropic Hyperfine Constants For Lattice Nuclei Near A Shallow Donor

A method is presented for calculating the magnetic anisotropic (dipolar) hyperfine constants for lattice nuclei near a shallow-donor impurity. The method assumes that the wave function of the donor electron can be expressed in an effective-mass form, i.e., a slowly varying envelope function times conduction-band Bloch functions. For each dipolar hyperfine constant, two separate calculations are performed. One calculation is for a local region about the lattice nucleus of interest. The greatest part of the interaction occurs in this region (about 85 ± 10%). The second calculation is for the more distant region. The dipolar constants in the distant region are calculated without considering the details of the Bloch functions and are evaluated by an integration involving only the envelope function. In the local region, the details of the Bloch functions must be considered. The Bloch functions are expressed in terms of equivalent orbitals. Symmetry arguments using the properties of these orbitals simplify the calculation. The final results show that the local contribution can be expressed as products of a few intrinsic lattice parameters, which are the dipolar matrix elements between equivalent orbitals, and a set of coefficients that is not difficult to evaluate. The resulting dipolar constants vary a great deal from one lattice site to another. Numerical results have been computed for the shallow donors - arsenic, phosphorus, and antimony - in silicon. Comparison of theoretical values with experimental values shows qualitative and semiquantitative agreement. © 1971 The American Physical Society

Neuronal Transcriptome from C9orf72 Repeat Expanded Human Tissue is Associated with Loss of C9orf72 Function

A hexanucleotide G4C2 repeat expansion in C9orf72 is the most common genetic cause of familial and sporadic cases of amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). The mutation is associated with a reduction of C9orf72 protein and accumulation of toxic RNA and dipeptide repeat aggregates. The accumulation of toxic RNA has been proposed to sequester RNA binding proteins thereby altering RNA processing, consistent with previous transcriptome studies that have shown that the C9orf72 repeat expansion is linked to abundant splicing alterations and transcriptome changes. Here, we used a subcellular fractionation method and FACS to enrich for neuronal nuclei from C9orf72 repeat expanded post-mortem human ALS/FTD brains, and to remove neuronal nuclei with TDP-43 pathology which are observed in nearly all symptomatic C9orf72 repeat expanded cases. We show that the C9orf72 expansion is associated with relatively mild gene expression changes. Dysregulated genes were enriched for vesicle transport pathways, which is consistent with the known functions of C9orf72 protein. Further analysis suggests that the C9orf72 transcriptome is not driven by toxic RNA but is rather shaped by the depletion of pathologic TDP-43 nuclei and the loss of C9orf72 expression. These findings argue against RNA binding protein sequestration in neurons as a major contributor to C9orf72 mediated toxicity

Scaling and non-Abelian signature in fractional quantum Hall quasiparticle tunneling amplitude

We study the scaling behavior in the tunneling amplitude when quasiparticles tunnel along a straight path between the two edges of a fractional quantum Hall annulus. Such scaling behavior originates from the propagation and tunneling of charged quasielectrons and quasiholes in an effective field analysis. In the limit when the annulus deforms continuously into a quasi-one-dimensional ring, we conjecture the exact functional form of the tunneling amplitude for several cases, which reproduces the numerical results in finite systems exactly. The results for Abelian quasiparticle tunneling is consistent with the scaling anaysis; this allows for the extraction of the conformal dimensions of the quasiparticles. We analyze the scaling behavior of both Abelian and non-Abelian quasiparticles in the Read-Rezayi Z_k-parafermion states. Interestingly, the non-Abelian quasiparticle tunneling amplitudes exhibit nontrivial k-dependent corrections to the scaling exponent.Comment: 16 pages, 4 figure

Camera distortion self-calibration using the plumb-line constraint and minimal Hough entropy

In this paper we present a simple and robust method for self-correction of camera distortion using single images of scenes which contain straight lines. Since the most common distortion can be modelled as radial distortion, we illustrate the method using the Harris radial distortion model, but the method is applicable to any distortion model. The method is based on transforming the edgels of the distorted image to a 1-D angular Hough space, and optimizing the distortion correction parameters which minimize the entropy of the corresponding normalized histogram. Properly corrected imagery will have fewer curved lines, and therefore less spread in Hough space. Since the method does not rely on any image structure beyond the existence of edgels sharing some common orientations and does not use edge fitting, it is applicable to a wide variety of image types. For instance, it can be applied equally well to images of texture with weak but dominant orientations, or images with strong vanishing points. Finally, the method is performed on both synthetic and real data revealing that it is particularly robust to noise.Comment: 9 pages, 5 figures Corrected errors in equation 1

Quantum Monte Carlo Calculations of Pion Scattering from Li

We show that the neutron and proton transition densities predicted by recent quantum Monte Carlo calculations for A=6,7 nuclei are consistent with pion scattering from 6Li and 7Li at energies near the Delta resonance. This has provided a microscopic understanding of the enhancement factors for quadrople excitations, which were needed to describe pion inelastic scattering within the nuclear shell model of Cohen and Kurath.Comment: 10 pages, REVTeX, 3 postscript figures; added calculation of elastic and inelastic pion scattering from 6Li at multiple energie