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Tunable Diode Laser Absorption Spectroscopy (TDLAS) based gas sensing technology, has widespread applications, ranging from use in biomedical industry to aerospace applications. An experimental set-up was established to measure concentration of oxygen gas in the range 0–100% using TDLAS technique. The oxygen absorption at 760.241 nm was scanned with a tunable DFB laser, and wavelength modulation spectroscopy was used to obtain the harmonics (1f, 2f, 3f & 4f) of the oxygen absorption signal. The modulation parameters such as the modulation voltage, modulation frequency, reference phase, time constant of lock in amplifier, the tuning voltage, and the tuning frequency were optimized to obtain the harmonics of high amplitude and narrow half width. Keeping the experimental parameters constant, the oxygen concentration measurements were obtained by the following three methodologies, viz, (i) using only the 2nd harmonic, (ii) using the 2nd and 4th harmonics and, (iii) using the 1st and 2nd harmonics. The results of these measurements were compared and the merits and drawbacks of these methods are discussed.

Submarine Escape Set (SES) is used by submariners to escape from a sunken submarine. This set caters for breathing needs of the submariner under water, until he reaches the surface. Evaluation of such life-saving equipment is of paramount importance. This paper describes the submarine escape set and various constructional features and schedules of operation of test facilities designed indegenously and which can evaluate the SES. The test facility is divided into two parts: the reducer test facility, and the breathing bag test facility. The equipment has been rigorously tested and accepted by Indian Navy. Two such test facilities have been developed, one of which is installed at INS Satavahana, Visakhapatnam, and are working satisfactorily.

Introduction of computers and image analysis systems to quantify the assessment of living cells for prognosis and diagnosis is gaining momentum. It also aims at relieving the operator from the tedium of microscopic observation and reducing operator bias and human error. This paper discusses the design and configuration of an interactive image analysis system built indigenounsly for cell analysis and classification. It also discusses the progress made in the diagnosis of cervical cancer and in the prognosis of breast cancer using computerised interactive morphometry

Oxygen Concentration Monitoring is an important requirement in fighter aircrafts. This paper reports the results of performance evaluation of an indigenous Zirconia Oxygen Sensor, which meets the requirements of a fighter aircraft environment. The Oxygen Sensor uses a solid state electrolyte, Zirconia stabilized with 8mol% Yttria, in the form of a Nernst Cell, which when heated above 600°C, develops an emf proportional to the ratio of partial pressures of Oxygen across its two electrodes. The reference gas used is air (21% O 2 ). The sensor performs satisfactorily in a wide range of environments faced in the fighter aircraft, such as altitudes upto 50K feet, the extreme temperatures of −40C to 65C, arrestor-hook shock, etc. These results are presented here.

The value of nuclear parameters were determined using interactive computer image analysis system on 100 preoperative FNAC smears of breast lesion were radical mastectomy was performed subsequently. Twenty cases of benign lesion were taken as control. The lymph node status was correlated with the nuclear and nucleolar variables. It is found that few nuclear parameters have good discriminatory power. Computerised interactive morphometry proved to be far superior to eye-piece measurements with respect to accuracy, reproducibility and time taken for parameter estimation which leads to the determination of better prognostic indicator.

The bioelectrical potentials generated within the human body are the result of electrochemical activity in the excitable cells of the nervous, muscular or glandular tissues. The ionic potentials are measured using biopotential electrodes which convert ionic potentials to electronic potentials. The commonly monitored biopotential signals are Electrocardiogram (ECG), Electroencephalogram (EEG) and Electromyogram (EMG). The electrodes used to monitor biopotential signals are Ag-AgCl and gold, which require skin preparation by means of scrubbing to remove the dead cells and application of electrolytic gel to reduce the skin contact resistance. The gels used in biopotential recordings dry out when used for longer durations and add noise to the signals and also prolonged use of gels cause irritations and rashes to skin. Also noises such as motion artifact and baseline wander are added to the biopotential signals as the electrode floats over the electrolytic gel during monitoring. To overcome these drawbacks, dry electrodes are used, where the electrodes are held against the skin surface to establish contact with the skin without the need for electrolytic fluids or gels. The major drawback associated with the dry electrodes is the high skin-electrode impedance in the low frequency range between 0.1-120 Hz, which makes it difficult to acquire clean and noise free biopotential signals. The paper presents the design and development of biopotential data acquisition and processing system to acquire biopotential signals from dry electrodes. The electrode-skin-electrode- impedance (ESEI) measurements was carried out for the dry electrodes by impedance spectroscopy. The biopotential signals are processed using an instrumentation amplifier with high CMRR and high input impedance achieved by boot strapping the input terminals. The signals are band limited by means of a second order Butterworth band pass filters to eliminate noise. The processed biopotential signals are digitized and transmitted wirelessly to a remote monitoring station.

The temperature dependence of the longitudinal and shear ultrasound wave velocities in (As2S3)1-x(PbS)x glasses has been determined from 77 to 300K using a pulse echo interferometer. Elastic constants of the prepared glasses at room temperature have been computed from the experimental data. Both longitudinal and shear ultrasound wave velocities in these glasses show a linear temperature dependence with a negative temperature coefficient.

The six independent elastic constants of sodium nitrate are determined using 10 MHz ultrasonic pulse echo superposition technique over the temperature interval 77 to 300 K. The values obtained at 300 K are C11 = 5.71, C12 = 2.16, C33 = 3.3, C13 = 1.66, C44 = 1.24, C14 = 0.82, and at 77 K C11 = 6.63, C12 = 2.07, C33 = 3.99, C13 = 1.67, C44 = 1.69, C14 = 1.16 all expressed in units of 1011 dyn/cm2. Die sechs unabhangigen elastischen Konstanten von Natriumnitrat werden bestimmt, indem im Temperaturbereich 77 bis 300 K die Echouberlagerungsmethode von 10 MHz Ultraschallimpulsen benutzt wird. Die bei 300 K erhaltenen Werte sind C11 = 5,71; C12 = 2,16; C33 = 3,3; C13 = 1,66; C44 = 1,24; C14 = 0,82 und bei 77 K C11 = 6,63; C12 = 2,07; C33 = 3,99; C13 = 1,67; C44 = 1,69; C14 = 1,16 (alle in Einheiten von 1011 dyn/cm2).