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An electrical-equivalent circuit model of the cerebrovascular system is proposed, components of which directly relate to cerebrospinal fluid (CSF) compartment compliance and the determination of intracranial pressure (ICP). The model is based on three premises: 1) Under normal, physiologic conditions, the conversion of pulsatile arterial to nonpulsatile venous flow occurs primarily as a result of arterial compliance. Nonpulsatile venous flow is advantageous because less energy is required to maintain constant flow through the venous system, which comprises 75-80% of total blood volume. 2) Dynamic CSF movement across the foramen magnum is the primary facilitator by which intracranial arterial expansion occurs. Interference of the displacement of CSF during systole results in pulsatile venous flow and increased venous flow impedance. 3) Tissue hydrostatic pressure (here defined as ICP) is a dependent variable which is a function of capillary hydrostatic pressure and the osmotic/oncotic pressure gradient created by the blood-brain-barrier (BBB). An interference of transcranial CSF movement results in a decrease in cerebral blood flow (CBF) due to inertial effects impeding pulsatile venous flow. Feedback regulation in response to this decreased CBF leads to arteriolar vasodilatation (decreased resistance), thereby lowering the pressure difference between internal carotid and capillary pressures. Assuming no changes in the BBB potential, ICP increases linearly as capillary pressure increases.

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A variable-duration notched-noise experiment was conducted in a noise context. Broadband noise preceded and followed a tone and notched noise of similar duration. Thresholds were measured at four durations (10, 30, 100, and 300 ms), two center frequencies (0.6, 2.0 kHz), and five relative notch widths (0.0, 0.1, 0.2, 0.4, 0.8). At 0.6 kHz, 10-ms thresholds decrease 6 dB across notch widths, while 300-ms thresholds decrease over 35 dB. These trends are similar but less pronounced at 2 kHz. In a second experiment, the short-duration notched noise was replaced with a flat noise which provided an equivalent amount of simultaneous masking and thresholds dropped by as much as 20 dB. A simple combination of simultaneous and nonsimultaneous masking is unable to predict these results. Instead, it appears that the elevated thresholds at short durations are dependent on the spectral shape of the simultaneous masker.

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A model for predicting the masked thresholds of the voiceless plosive bursts /k,t,p/ in background noise is proposed. Because plosive bursts are brief, are generated by a noise source, and have different spectral characteristics, the modeling approach accounts for duration, center frequency, and signal bandwidth. Noise-in-noise masking experiments are conducted using a broadband masker and bandpass noise signals of varying bandwidth (100-5483 Hz), duration (10-300 ms), and center frequency (0.4-4 kHz). Data from these experiments are used to parametrize an auditory filter model in which the effective bandwidth and the signal-to-noise ratio at threshold for each filter are duration dependent. The duration-dependent filter model is then used to predict the thresholds of synthetic and naturally spoken plosive bursts in background noise. Finally, results from pilot notched-noise experiments are presented which support duration-dependent frequency selectivity.

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Magnetic resonance images of the vocal tract during the sustained phonation of /l/ (both dark and light allophones) by four native American English talkers are employed for measuring lengths, area functions, and cavity volumes and for the analysis of 3-D vocal tract and tongue shapes. Electropalatography contact profiles are used for studying inter- and intra-talker variabilities and as a source of converging evidence for the magnetic resonance imaging study. The general 3-D tongue body shapes for both allophones of /l/ are characterized by a linguo-alveolar contact together with inward lateral compression and convex cross sections of the posterior tongue body region. The lateral compression along the midsagittal plane enables the creation of flow channels along the sides of the tongue. The bilateral flow channels exhibit somewhat different areas, a characteristic which is talker-dependent. Dark /l/s show smaller pharyngeal areas than the light varieties due to tongue-root retraction and/or posterior tongue body raising. The acoustic implications of the observed geometries are discussed.

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Acoustic waveforms of the strident fricatives /s/, /z/, /integral of/, and /3/ spoken by two native American English speakers are analyzed using modern chaotic analysis techniques. Fricative data are extracted from both intervocalic and sustained utterances. For comparison, acoustic waveforms of the vowels /a/, /i/, and /u/ are also analyzed. For 44% of the unvoiced fricative tokens in VCV contexts and 59% of the sustained voiced fricatives, indications of low-dimensional dynamics could be found with the given limitations of stationarity. The low-dimensional chaotic behavior is exhibited by a correlation dimension (D2) ranging between 3 and 7.2, and by positive maximum Lyapunov exponents (LEs). For the remaining fricatives, results suggest that the dimensional complexity therein is greater than the maximum D2 value that could be reliably estimated from the available data (about 7.8 for the intervocalic cases and 9 for the sustained cases). Intervocalic voiced fricatives are excluded from the analysis due to stationarity requirements. Analysis of vowels, on the other hand, indicates nonchaotic behavior demonstrated by folded limit cycles and nonpositive maximum LEs; this is consistent with results of previous studies. Findings are interpreted in terms of posited articulatory and aerodynamic parameters of turbulence in the production of fricative consonants.

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Rapid socioeconomic development, urbanization and improved survival have given rise to a progressive increase in the occurrence of noncommunicable diseases in the Eastern Mediterranean Region. Cardiovascular diseases have emerged as a leading cause of morbidity and mortality in many countries. The prevalence of hypertension is already high in many countries of the Region and the number of hypertensives is likely to increase further in the coming years. Although the influence of geographical, ethnic and socioeconomic factors has not been studied adequately, it seems that the epidemiological and clinical patterns of hypertension do not differ markedly from those in developed countries. The growing impact of cardiovascular disease is already understood in most countries. The human and economic costs are enormous, there is a growing demand for medical services, and the need to take action is increasingly acknowledged. Most countries have either initiated or indicated the need to establish programmes in collaboration with WHO on the prevention and control of cardiovascular disease during 1992 and 1993. In view of the scarcity of precise epidemiological information, data collection and the assessment of risk factors for coronary heart disease are expected to form the basis of preliminary activities.

PIP: The author examines morbidity and mortality associated with cardiovascular diseases in the eastern Mediterranean region, with a focus on coronary heart disease, hypertension, and rheumatic heart disease. (SUMMARY IN FRE)

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The government of Democratic Yemen started an essential drugs programme in 1984. Every month quantities of 30 drugs are delivered in prepacked kits to health units and standard treatment schedules have been agreed. The quantities of each drug were estimated by applying the standard treatment schedules to the typical morbidity patterns seen at these facilities. Most health workers attended a training course on the correct use of the standard treatment schedules. Hospital and health centres have been included in the programme to a more limited extent. In March 1988 an evaluation of the programme was carried out. Comparisons were made between random samples of health units included in the programme and those where it had not yet been implemented. The adequacy of knowledge necessary for reasonable use of drugs was assessed by interviewing health workers. Actual drug prescription was studied by means of quantitative indicators. A more qualitative insight was obtained by reviewing drug prescriptions for four tracer diseases at a sample of health centre and hospital out-patient departments. Health workers at units included in the programme had significantly (P less than 0.05) higher levels of rational drug knowledge and 'better' actual drug prescription in terms of proportions of patients receiving injections (25% vs 58%), antibiotics (45% vs 67%) and the average number of drugs per patient (1.5 vs 2.4)--all P less than 0.001. Many patients treated at health centres and hospitals were receiving irrational drug treatment for the tracer conditions. It is suggested that the methods used in this evaluation to measure rational drug prescription could be appropriate in the assessment of other essential drugs programmes.

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The prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency was estimated in 318 diabetic patients using Beulter's fluorescent Spot test. A significantly (p less than 0.001) higher prevalence of G6PD deficiency was detected among diabetic patients (19.6%) as compared to controls (10.4%). The distribution of G6PD deficiency varied with age, sex, and duration of diabetes. Among diabetic men, the prevalence of deficiency was significantly higher than controls in both age groups; 40 years and below, and 41 years and above (p less than 0.005 and p less than 0.02, respectively). Among diabetic women, the significantly higher prevalence of deficiency was observed only in the young age group (p less than 0.005), whereas the difference among the older age group was not significant (p greater than 0.1). A significant increase in the prevalence of deficiency with increase in duration of diabetes was detected among men (p less than 0.05), but not in women. The results of the study suggest a positive association between G6PD deficiency and diabetes mellitus.

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Whereas normal liver and spleen scintiphotos with 99mTc- tin colloid are characterized by homogenous distribution of radiocolloid in the liver and slight uptake of radiotracer over the spleen in the anterior view, this report demonstrates that there is high radiotracer uptake in the spleen and slight uptake in the posterior view in a case of situs inversus.

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