Rehabilitation of hearing impaired children in India – An update

The prevalence of deafness in India is fairly significant. It is the second most common cause of disability. Approximately 63 million people (6.3%) in India suffer from significant auditory loss.1 Rehabilitation of hearing impaired children in India remains a challenging task. Early detection and intervention are the mainstay of this initiative. This article does not purport to detail the clinical aspects and surgical management of hearing handicapped children.We discuss here the resources and options available in India for the education of deaf children and the role of the Government bodies in rehabilitation. Awareness abouteducation and rehabilitation of hearing handicapped is low among the general public and even among the medical fraternity.

A temporal logic for the specification and verification of real-time systems

The development of a product typically starts with the specification of the user’s requirements and ends with the design of a system to meet those requirements. Traditional approaches to the specification and analysis of a system abstracted away from any notion of time at the specification level. However, for a real-time system the specification may include timing requirements. Many specification and verification methods for real-time systems are based on the assumption that time is discrete because the verification methods using it are significantly simpler than those using continuous time. Yet real-time systems operate in ‘real’ continuous time and their requirements are often specified using a continuous time model. In this thesis we develop a temporal logic and proof methods for the specifica­tion and verification of a real-time system which can be applied irrespective of whether time is discrete, continuous or dense. The logic is based on the defini­tion of the next operator as the next time point a change in state occurs or if no state change occurs then it is the time point obtained by incrementing the current time by one. We show that this definition of the next operator leads to a logic which is expressive enough for specifying real-time systems where continuous time is required, and in which the verification and proof methods developed for discrete time can be used. To demonstrate the applicability of the logic several varied examples including communication protocols and digital circuits are specified and their real-time properties proved. A compositional proof system which supports hierarchical development of programs is also developed for a real-time extension of a CSP-like language

Correlated X-ray/UV/optical emission and short term variability in a Seyfert 1 galaxy NGC 4593

We present a detailed multi-frequency analysis of an intense monitoring programme of Seyfert 1 galaxy NGC 4593 over a duration of nearly for a month with Swift observatory. We used 185 pointings to study the variability in six ultraviolet/optical and two soft (0.3-1.5 keV) and hard X-ray (1.5-10 keV) bands. The amplitude of the observed variability is found to decrease from high energy to low energy (X-ray to optical) bands. Count-count plots of ultraviolet/optical bands with hard X-rays clearly suggest the presence of a mixture of two major components: (i) highly variable component such as hard X-ray emission and (ii) slowly varying disc-like component. The variations observed in the ultraviolet/optical emission are strongly correlated with the hard X-ray band. Cross-correlation analysis provides the lags for the longer wavelengths compared to the hard X-rays. Such lags clearly suggest that the changes in the ultraviolet/optical bands follow the variations in the hard X-ray band. This implies the observed variation in longer wavelengths is due to X-ray reprocessing. Though, the measured lag spectrum (lag vs. wavelength) is well described by {\lambda}^(4/3) as expected from the standard disc model, the observed lags are found to be longer than the predicted values from standard disc model. This implies that the actual size of the disc of NGC 4593 is larger than the estimated size of standard thin disc as reported in AGN such as NGC 5548, Fairall 9.Comment: 12 pages, 10 figures, accepted for publication in MNRAS journa