Search

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.

Multiwalled carbon nanotube (CNT) arrays were grown by catalytic thermal decomposition of acetylene, over Fe-catalyst deposited on Si-wafer in the temperature range 700–750 °C. The growth parameters were optimized to obtain dense arrays of multiwalled CNTs of uniform diameter. The vertical cross-section of the grown nanotube arrays reveals a quasi-vertical alignment of the nanotubes. The effect of varying the thickness of the catalyst layer and the effect of increasing the growth duration on the morphology and distribution of the grown nanotubes were studied. A scotch-tape test to check the strength of adhesion of the grown CNTs to the Si-substrate surface reveals a strong adhesion between the grown nanotubes and the substrate surface. Transmission electron microscopy analysis of the grown CNTs shows that the grown CNTs are multiwalled nanotubes with a bamboo structure, and follow the base-growth mechanism.

Dry electrodes, which have an array of vertically aligned conducting micro-needles over a conducting substrate/base are most suitable for long-term continuous monitoring of EEG-signal, and overcomesthe disadvantages of conventional wet electrodes. A crucial design requirement for thesemicro-needlearrays, is the choice of the needle material with suitable mechanical strength to penetrate the skin without mechanical failure. This paper gives, the results of mechanical failure analysis of different needle materials that have been typically used/proposed for invasive use. A conical needle with 150μ width at the base and 10μ width at the tip, and length in the range 10μ - 200μ was taken up for calculation. The Critical load for failure, falls in the following descending order for the selected materials: viz., Carbon Nanofibre (CNF), Titanium-alloy (Ti 6-4), Single Crystal Silicon, Nickel, Tungsten, Platinum-Iridium (Pt90 percent-Ir10 percent), Stainless Steel (SS304),Poly Methyl Methacrylate (PMMA), Polyimide, Polycarbonate, Gold, Silver, Photoresist-SU8, Polyurethane and Poly DiMethylSiloxane (PDMS).Taking the most accepted value of 0.1N as the penetration force required for needle penetration into skin, it is seen that for a needle length of 100μ, the following materials, Carbon Nanofibre (CNF), Titanium-alloy (Ti 6-4), Single Crystal Silicon, Nickel, Tungsten, Platinum -Iridium (Pt90 percent-Ir10 percent) andStainless Steel (SS304), can penetrate the skin without mechanical failure.

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.

Intravenous (IV) drug administration of fluids or medication and blood drawing procedures require the medical practitioner to access the veins in patients. This procedure is of prime importance in saving an injured soldiers life on the battlefield by intravenously administering haemostatic agents to prevent blood loss due to haemorrhage. This paper presents an image acquisition system that captures images of subcutaneous veinpatterns and processes these to conclude the location for intravenous needle-insertion. The system consists of a camera, receptive to near-infrared light, which captures an image of the subcutaneous veins illuminated by a suitable source of light. The contrast-enhanced image of the veins thus obtained is processed using an algorithm to conclude an ideal site for needle-insertion. Subcutaneous vein-images were captured using a modified web-camera that works well under the illumination of near-infrared light and a DSLR (Digital Single Lens Reflex) camera with an external filter to block visible light. An algorithm was developed to extract vein-segments from these images. The system will be used for automated delivery of haemostatic agent.

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.

Carbon nanotube based electrodes can overcome the drawbacks posed by the conventional wet electrodes, used for physiological monitoring. Here, multiwalled CNT arrays were grown on highly doped n-type Si-wafers with Fe-catalyst layer, using a thermal CVD system. Acetylene was used as the carbon source gas, while Ammonia was the reducing gas and Argon was the purging inert gas, in these experiments. The thermal annealing of the catalyst layer and the carbon nanotube growth schedule, were optimized to get a dense and uniform multiwalled CNT array. SEM images reveal dense uniform growth of multiwalled carbon nanotubes over the entire catalyst deposited area. The cross-sectional images reveal a quasi-vertical alignment.

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.

Introduction of computers and image analysis systems are gaining faster momentum in order to quantitate the assessment of cells for diagnosis and prognosis, and this system aims to relieve the operator from the tedium of microscopic observation and reduce operator bias and human error. This paper discusses the design and configuration of an interactive image analysis system built in the laboratory for the purpose of cell analysis and classification. The software developed to compute various textural and morphological parameters of cells on smear are briefly described. The results of the experiments carried out to classify normal and abnormal cells on cervical smear show 94 per cent success rate.

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.

Precise measurements of 10 MHz frequency longitudinal and shear wave velocities are reported in amorphous SeGe alloys near their glass transition temperature Tg. There is a sharp decrease of the velocities near Tg, but the reduction in velocities appears smaller than expected.

The elastic constants of single crystal galena have been determined from the measured ultrasonic velocities down to liquid helium temperature. A cryostat incorporating an arrangement to inject the liquid bonding material at low temperature is described. At 5 K, the values of elastic constants are C11=14.90, C12=3.51 and C44=2.92×1010 N/m2.

Longitudinal and shear wave ultrasonic velocities are reported in Se-P glasses over the composition range 0–50 at % P. The glass transition temperaturesT g show maxima at 30 and 50 at % of P, in consonance with earlier data. The bulk modulus shows minima at these compositions, contrary to the expectation of maxima. These are discussed in relation to the formation of compounds at specific compositions and the nature of the covalent bonding in the glasses.

Electrical resistance measurements are reported for amorphous $In_{20}Te_{80}$ and $Cu_{25}Au_5Te_{70}$ alloys up to a pressure of 80 Kbar using a Bridgman anvil apparatus and a four lead arrangement to measure resistances. The amorphous samples are produced by liquisol quenching. The resistance shows time dependent changes which are analysed in detail. The contention that there is a pressure-induced transformation from the amorphous to the crystalline phase is confirmed by X-ray diffraction of samples recovered after they were pressurised to 35 Kbar in a hydrostatic environment.

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).

Precise measurements of the ultrasonic velocities and thermal expansivities of amorphous Se80Te20 and Se90Te10 alloys are reported near the glass transition. The samples are produced by liquid quenching. The longitudinal and transverse velocities are measured at 10 MHz frequency using the McSkimin pulse superposition technique. The thermal expansivities,agr, are measured using a three-terminal capacitance bridge. Theagr-values show a sharp maximum near the glass transition temperature,T g. The ultrasonic velocities also show a large temperature derivative, dV/dT nearT g. The data are discussed in terms of existing theories of the glass transition. The continuous change inagr shows that the glass transition is not a first-order transition, as suggested by some theories. The samples are found to be deformed by small loads nearT g. The ultrasonic velocities and dV/dT have contributions arising from this deformation.

Sodium nitrate is isostructural with calcite and crystallizes in the space group DQd. It is one of these substances whose physical properties have been widely investigated. However, a perusal of literature shows that the agreement between the elastic constants obtained by various investigators is not good.