Mercury Cadmium Telluride Photoconductive Long Wave Infrared Linear Array Detectors

Mercury cadmium telluride (Hg1-x, CdxTe) (MCT) photoconductive long wave infrared linear arrays are still in demand due to several advantages. The linear array technology is well established, easier, economical and is quite relevant to thermal imaging even today. The scan thermal imaging systems based on this technology offer wider field of view coverage and capacity for higher resolution in the scan direction relative to staring systems that use expensive and yet to mature focal plane array detector technology. A critical review on photoconductive n-Hg1-x CdxTe linear array detector technology for the long wave infrared range has been presented. The emphasis lies on detector design and processing technology. The critical issues of diffusion and drift effects, Hi-Lo and heterostructure blocking contacts, surface passivation, and other related aspects have been considered from the detector design angle. The device processing technology aspects are of vital importanc

Analysis of Crosstalk in HgCdTe based Vertical Photoconductive LWIR Detector Arrays

HgCdTe is a well known material for Infrared detection applications because of its special properties like high absorption coefficient, adjustable bandgap and moderate dielectric constant etc. Vertical PC detectors of HgCdTe are very easy to fabricate as compared to the other detectors with the desired uniformity and therefore, these detectors may be proved better choice if the cost and the yield are considered. The proposed vertical PC detector design improves the fill factor of the detector array and allows the access of individual elements without the need of integrated circuit for their readout. The structure virtually does not have any optical crosstalk due to diffusion current, but suffers from the electrical crosstalk because of the networking of its element. This paper presents an analysis of the crosstalk for the focal plane array (FPA) of vertical PC detectors. We demonstrate that the networking reduces the detectivity by a factor strongly dependent on the number of rows and columns in the FPA

Original Article

Abstract Objectives: To observe if there is any connectivity between oxidative stress and cardiovascular diseases (CVDs). Materials and methods: Patients suffering from different cardiovascular diseases (hypertension, ischemic heart disease, rheumatic heart disease) attending Manipal Teaching Hospital, Pokhara and strictly matched controls were selected for this study. Oxidative stress (OS) was measured by plasma thiobarbituric acid reacting substances (TBARS) where as antioxidant status was measured by estimating vitamin E, vitamin C and total antioxidant activity (TAA) in plasma. Results: The mean level of TBARS, TAA, vitamin C and E were 2.20+0.43 nmol/ml, 547+98 µmol/l, 0.88+0.15 mg/dl and 0.75+0.20 mg/dl respectively in patients. The respective values in controls were 1.86+0.43 nmol/ml, 859+139 µmol/l, 0.94+0.15 mg/dl and 1.10+0.30 mg/dl. Although the OS seems to be raised in patients, is practically insufficient to oxidize biomolecules and induce CVDs. Despite vitamin C and E levels being well within normal limits, the TAA was significantly and considerably lower in patients. This is a highly interesting observation suggesting that dietary antioxidants other than these vitamins were preferentially consumed to control OS because procedure for TAA used in this study practically measures only total dietary antioxidants. Conclusion: OS does not appear to be an etiological factor for the cardiovascular diseases; rather slightly raised OS in patients seems to be a consequence. Further the raised OS was not due to lower nutrient antioxidant (vit. C and vit. E) in the local population studied herein

Observations of trace gases and aerosols over the Indian Ocean during the monsoon transition period

Characteristics of trace gases (O3, CO, CO2, CH4 and N2O) and aerosols (particle size of 2.5 micron) were studied over the Arabian Sea, equatorial Indian Ocean and southwest part of the Bay of Bengal during the monsoon transition period (October-November, 2004). Flow of pollutants is expected from south and southeast Asia during the monsoonal transition period due to the patterns of wind flow which are different from the monsoon period. This is the first detailed report on aerosols and trace gases during the sampled period as the earlier Bay of Bengal Experiment (BOBMEX), Arabian Sea Monsoon Experiment (ARMEX) and Indian Ocean Experiments (INDOEX) were during monsoon seasons. The significant observations during the transition period include: (i) low ozone concentration of the order of 5 ppbv around the equator, (ii) high concentrations of CO2, CH4 and N2O and (iii) variations in PM2.5 of 5-20μg/m3

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Estimation of Electron Heating Rates in the Topside Ionosphere during Medium Solar Activity

269-271Considering the heat balance in the topside ionosphere, the heat input rates Q6 for electron gas are calculated from the election heat loss rates using electron density, electron temperature and ion composition measurements at different altitudes obtained by incoherent back-scatter radar during medium solar activity conditions. The relative importance of various collisional and conduction heat loss terms are examined in detail. The values of Q6 estimated in this manner vary from 1·5 x 104 eV cm-2 sec-1 at 300 km to 1·5 x 102 eV cm-3 sec-1 at 600 km

Solar Activity Variation of Electron & Ion Temperatures in Equatorial Topside Ionosphere

273-277The daytime electron and ion temperature (Te and Ti) profiles in the topside ionosphere in the equatorial region are theoretically investigated for low and medium solar activity conditions. The available ion composition data from incoherent back-scatter radar and satellite in situ measurements are used in studying the thermal structure. The local and non-local electron heating rates due to photoelectrons are evaluated for these solar activity conditions. The results show that the plasma temperature at 400 km as well as at 1000 km increases from low to medium solar activity conditions, while it decreases at 700 km, The altitudinal extent of isothermal region around 500 km increases with increasing solar activity and the temperature gradient above the isothermal region is lower for medium solar activity as compared to low solar activity. The calculated temperature profiles are in fair agreement with the direct measurements of Te and Ti taken at Jicamarca for similar conditions

Thermal Structure of the Equatorial Topside Ionosphere

151-153The thermal structure of the equatorial topside ionosphere is theoretically investigated to explain the experimentally observed features, viz. (i) isothermal region in the 400-500 km range, (ii) close coupling of electron and ion temperatures, and (iii) lower temperatures compared to mid-latitudes. The main reasons for these features seem to be the larger electron densities in the 400-500 km range and the absence of protonospheric heat flux flowing into the topside ionosphere. The theoretical profiles, calculated on the above basis, are found to be in good agreement with the experimentally observed profiles in the 400-1000 km region

Photoelectron Escape Fluxes over the Equatorial & Midlatitude Regions

198-201Satellite measurements of photoelectron escape flux around noontime made by Explorer-31 in 600-800 km altitude range are reported for the equatorial and midlatitude regions. The pitch angle distributions and the spectral distributions are derived from the data. The analyzed data Show that the flux for equatorial region is lower by a factor 2 to 3 in comparison to that of mindlatitude region. Theoretical calculations of the escape flux are also made and compared with the observed escape fluxes, which are about 3 x 106 el cm-3 sec eV-1 for 10 eV electrons in the equatorial region