MRI appearance of disseminated osseous tuberculosis

Disseminated osseous tuberculosis is a rare disease. This is a report of two cases of disseminated osseous tuberculosis imaged with MRI at 1.5-T, CT, plain radiography and bone scintigraphy. CT and plain radiography demonstrated either highly destructive or cystic lesions with sclerotic margins. Bone scintigraphy and plain radiography were quite insensitive in detecting areas of involvement compared to MRI. On MRI the abnormal areas had short T-1 relaxation values, which is an atypical appearance for bony infections, and prolonged T-2 relaxation values. The reason for the T-1 relaxation behavior is uncertain. MRI also provided delineation of epidural extent.     

Psychophysical studies relevant to the design of a digital electrotactile speech processor

Psychophysical tests were carried out to investigate the perception of electrocutaneous stimuli delivered to the digital nerve bundles. The tests provided data for defining the operating range of a tactile aid for patients with profound-to-total hearing loss, as well as the individual differences between subjects and the information that could be transmitted. Monopolar biphasic constant current pulses with variable pulse widths were used. Threshold pulse widths varied widely between subjects and between fingers for the same subject. Thresholds were reasonably stable, but maximum comfortable levels increased with time. Perceived intensity was weakly dependent on pulse rate. Absolute identification of stimuli differing in pulse width gave information transmissions from 1.3-2.1 bits, limited by the dynamic ranges of the stimuli (3-17 dB). Stimuli from electrodes placed on either side of each finger were identified easily by all subjects. Absolute identification of stimuli differing in pulse rate gave information transmissions from 0.5-2.0 bits. Difference limens for pulse rate varied between subjects and were generally poor above 100 pps. On the basis of the results, an electrotactile speech processor is proposed, which codes the speech amplitude as pulse width, the fundamental frequency as pulse rate, and the second formant frequency as electrode position. Variable performances on tasks relying on amplitude and fundamental frequency cues are expected to arise from the intersubject differences in dynamic range and pulse rate discrimination. The psychophysical results for electrotactile stimulation are compared with previously published results for electroauditory stimulation with a multiple-channel cochlear implant.     

Heterocyclic studies—XXV: Mass spectra of some 4-trifluoromethylpteridine derivatives

Mass spectra of 4-trifluoromethylpteridine and nine of its derivatives are recorded. Electron impact induced fragmentations of 4-trifluoromethylpteridine and its 2-chloro-, 7-methyl- and 6, 7-dimethyl-derivatives resemble those of pteridine and simple methylpteridines except that loss of a trifluoromethyl radical usually intervenes at some stage. Fragmentation of 4-trifluoromethyl-pteridine derivatives with an amino, substituted-amino, alkoxy or alkylthio group in the 2-position fragment by a variety of mechanisms. Accurate mass measurements and deuterium labelling were used to help elucidate some fragmentation pathways.     

Mössbauer measurements on lattice and interstitial iron atoms in Fe1+xSb alloys

Mössbauer measurements on the Fe_1+xSb phase in seven samples of Fe : FeSb have been used to observe the independent magnetic ordering of lattice and interstitial iron atoms. An ordering temperature of (55 ± 5) K is deduced for the interstitial iron atoms. The anomalous behaviour of the lattice iron hyperfine fields at about the interstitial ordering temperature is attributed to the perturbation of the superexchange interaction between lattice atoms by the magnetic ordering of the interstitials.     

Surface aspects of the photo-degradation of bisphenol A polycarbonate,in oxygen and air as a function of relative humidity,as revealed by ESCA

The photo-degradation (λ > 290 nm) of bisphenol A polycarbonate films has been studied as a function of the partial pressure of oxygen and relative humidity at the gas/solid interface. Difference uv spectroscopy and ESCA have been employed to monitor the changes in bulk and surface chemistries, respectively. The extent of change in the bulk and the rate of oxygen uptake and nature of the oxidative functionalisation in the surface regions have been shown to be strongly dependent on the partial pressures of oxygen and water.     

Pion small-angle multiple scattering at energies spanning the (3,3) resonance

The small-angle multiple scattering of positive and negative pions has been measured for C, Al, Cu and Pb targets throughout an energy range spanning the (3, 3) resonance. The measurements were made using two-dimensional multiwire proportional counters placed in the pion beam. All previous multiple scattering data for electrons and protons as well as these new data for pions are used to recalculate the empirical terms in the Moliere theory of multiple scattering. A second-order Born approximation multiple scattering theory has been devised for spin zero particles. Modified Moliere theory gives a better fit to the experimental data than the second-order Born calculation. Because the updated Moliere theory contains much simpler equations and gives closer agreement with experiment, it is recommended in place of the more sophisticated theory for the interpretation of new experimental data.     

Plasma synthesis of polymers. A comparison of inductively coupled RF and microwave plasmas excited in the isomeric difluoroethylenes

A preliminary investigation of polymers prepared by RF and microwave glow discharge techniques is described. The polymer composition structure as revealed by ESCA is discussed and differences are shown to be subtle rather than major. Microwave prepared polymers are more sensitive to the operating conditions than the corresponding RF prepared polymers.