Volumetric analysis of epilepsy surgery resections using high resolution magnetic imaging: technical report

A method is described for accurately measuring the volume and site of epilepsy surgery resections utilizing magnetic resonance imaging. Accuracy has been assessed using post-mortem studies, and both the intra- and interobserver variability is consistently less than 5%. The technique has so far been applied to 25 patients following a variety of operations for medically intractable epilepsy. It provides the crucially accurate baseline required for meaningful follow-up outcome studies of epilepsy surgery. Consequently, it should allow the development of more precise prognostic indices for such operations.     

Characterization of fluoroelastomer networks. I. Infrared analysis

Fluorocarbon compounds based on vinylidene fluoride copolymers and dihydroxy nucleophiles were prepared to determine the network forming structures of the cured materials. Previous attempts to achieve this goal consisted of model compound reactions, of prevulcanization events, and of materials cured under conditions only approaching industrial vulcanization conditions. The proposed structures derived from these studies could be different from the entities that will come in contact with alternate fuels such as methanol/gasoline blends when used in automotive applications. The evolution of the solid-state chemistry during cure and the final network structure needed to be defined. Thus, infrared vibrational spectra for 25-μm thick sections from key stages of processing were recorded. These spectra established directly, for the first time, that bisphenol-AF (BPAF) serves as the crosslinker during cure. Additionally, persistent unsaturation is formed on the elastomer backbone after crosslinking. Curing for extended periods of time produces no observable effect on the network. Furthermore, postcuring reduces residual hydrofluoric acid in the compound and results in two new absorptions at 2851 and 2920 cm^?1, indicative of amorphous regions of polyvinylidene fluoride (PVF₂). Although these findings help define the final network structure, there remain uncertainties about the pathway leading to the final structure. The data serve as input to understanding the fracture behavior and long term performance of this class of materials. It also could serve as a starting point for studies dealing with the enhancement of certain fluorocarbon properties such as low temperature behavior. © 1993 John Wiley & Sons, Inc.     

Isolated triceps weakness in exercise-induced radial neuropathy

OBJECTIVE: We report a case of isolated triceps weakness resulting from radial neuropathy. PATIENT: A middle-aged healthy man, a keen athlete, developed acute weakness of the triceps brachii muscle due to radial neuropathy. No other radial nerve innervated muscles were involved. Triceps function completely recovered in six weeks clinically and electrophysiologically suggesting focal conduction block secondary to demyelination. DISCUSSION: Acute radial neuropathy after strenuous arm exercise resulting from a compression lesion with acute conduction block, has been previously described. However, all reported cases involved severe weakness of radial nerve innervated distal muscles with wrist drop, while isolated weakness of the triceps brachii muscle in radial neuropathy has never been previously described. CONCLUSIONS: We suggest that selective weakness in the triceps could be the sole manifestation of an exercise-related radial neuropathy. This particular type of radial neuropathy could be a variant of neuralgic amyotrophy.     

Permeabilities of alkyl p-aminobenzoates through living skin equivalent and cadaver skin

The in vitro permeabilities of alkyl p-aminobenzoates through living skin equivalent (LSE) and cadaver skin were compared. Methyl, ethyl, and butyl p-aminobenzoates were used as model compounds. The permeabilities of these compounds through LSE and cadaver skin from an aqueous drug suspension were determined with a flow-through diffusion cell. The permeability coefficients of these esters in LSE were an order of magnitude higher than in cadaver skin. This was primarily because of low resistances offered by the outermost layer (i.e., stratum corneum) of LSE. In the case of cadaver skin, the permeability coefficient increased as the carbon chain length increased, whereas no appreciable change in the permeability coefficients of these esters in LSE was observed. These results clearly suggest that the LSE membrane offered very little resistance as opposed to cadaver skin. Therefore, the LSE membrane may not quantitatively represent a good human skin model for evaluating skin permeation of a drug from topical or transdermal formulations.     

A matter of trust [data security]

Larger amounts of information are being exchanged by electronic means. This has many advantages, including speed and convenience, but is by no means problem free. Most forms of electronic communication (not least the Internet) are not inherently secure. Security needs vary between applications, but common requirements include ensuring the information is not changed in transit and protecting the information against unauthorised disclosure. Ensuring security for electronic information exchange is far from straightforward and there is a danger that this problem could form a significant barrier to the growth of electronic commerce. Cryptography is one method of addressing the security weaknesses, but there is a difficulty in the management of the various keys. As the demand for secure electronic communications has grown, especially in the domain of electronic commerce, new institutions, often known as trusted third parties are emerging to meet this need. Trusted third parties could become key players in ensuring the security of electronic communications. The author explains the nature of these novel organisations and discusses some of the issues associated with their development     

A system of management control information for architects

The authors, D.J. Carter, David Cheetham and John Lewis of the School of Architecture, University of Liverpool, describe a study of the information flow system from site to supervising officer on a number of case study building contracts. The study uses techniques of system analysis to determine existing methods by which architects obtain information necessary for the administration of building contracts for hospitals.     

Incidence of photosensitive epilepsy: a prospective national study

We undertook a prospective nationwide study to determine the incidence of photosensitive epilepsy (PE). Virtually all EEG departments in Great Britain (providing approximately 90% coverage of all EEGs performed on people with newly diagnosed seizures) screened cases referred to them over a 3 month period and identified all new cases of epilepsy (defined as one or more recognised seizures) whose first EEG showed a photoparoxysmal response (PPR) on intermittent photic stimulation (IPS). 191 cases were identified, 143 of whom had type 4 PPRs (generalised spike and wave on IPS) on their first EEG. The annual incidence of cases of epilepsy with type 4 PPRs on their first EEG was conservatively estimated to be 1.1 per 100,000, representing approximately 2% of all new cases of epilepsy. When restricted to the age range 7-19 years, the annual incidence rose to 5.7 per 100,000-approximately 10% of all new cases of epilepsy presenting in this age range. To ascertain if there was a significant seasonal variation in PE, 5 EEG departments (which together contributed 15% of cases in the first study period) were visited during a second 3 month study period to identify all new cases of epilepsy with type 4 PPRs on their first EEG. No significant seasonal variation in incidence between summer and winter was found.     

Quasioptical Approach for Meniscus Lens Corrected Horn: Application to Cassegrain Systems

The Beam Mode Expansion (BME) approach for corrugated conical feed horn plus meniscus lens is presented. This approach is useful for providing the radiation pattern as it propagates through an optical system. A developed theoretical model has been verified measuring near and far field of a built horn and lens. These results have been used for designing the optical system of a Cassegrain antenna at 100GHz using the fundamental Gaussian beam mode (GBM) of the new approach. Multimode analysis has been performed with the pre-designed system in order to test the fundamental GBM results.     

Quantitative brain magnetic resonance imaging in attention-deficit hyperactivity disorder

BACKGROUND: Anatomic magnetic resonance imaging (MRI) studies of attention-deficit hyperactivity disorder (ADHD) have been limited by small samples or measurement of single brain regions. Since the neuropsychological deficits in ADHD implicate a network linking basal ganglia and frontal regions, 12 subcortical and cortical regions and their symmetries were measured to determine if these structures best distinguished ADHD. METHODS: Anatomic brain MRIs for 57 boys with ADHD and 55 healthy matched controls, aged 5 to 18 years, were obtained using a 1.5-T scanner with contiguous 2-mm sections. Volumetric measures of the cerebrum, caudate nucleus, putamen, globus pallidus, amygdala, hippocampus, temporal lobe, cerebellum; a measure of prefrontal cortex; and related right-left asymmetries were examined along with midsagittal area measures of the cerebellum and corpus callosum. Interrater reliabilities were .82 or greater for all MRI measures. RESULTS: Subjects with ADHD had a 4.7% smaller total cerebral volume (P = .02). Analysis of covariance for total cerebral volume demonstrated a significant loss of normal right > left asymmetry in the caudate (P = .006), smaller right globus pallidus (P = .005), smaller right anterior frontal region (P = .02), smaller cerebellum (P = .05), and reversal of normal lateral ventricular asymmetry (P = .03) in the ADHD group. The normal age-related decrease in caudate volume was not seen, and increases in lateral ventricular volumes were significantly diminished in ADHD. CONCLUSION: This first comprehensive morphometric analysis is consistent with hypothesized dysfunction of right-sided prefrontal-striatal systems in ADHD.