Shock induced vaporization of anhydrite CaSO4 and calcite CaCO3

Discovery of abundant anhydrite (CaSO4) and gypsum (CaSO4.2H2O) in the otherwise carbonate sediments comprising the upper portion of the rocks contained within the Chicxulub impact crater has prompted research on the shock-induced vaporization of these minerals. We use a vaporization criterion determined by shock-induced entropy. We reanalyze the shock wave experiments of Yang [1]. He shocked 30% porous anhydrite and 46% porous calcite. Post-shock adiabatic expansion of the sample across a 5 mm-thick gap and then impact upon an aluminum witness plate backed by LiF window that is monitored with a VISAR. Reanalysis uses Herrman's P-alpha model [2] for porous materials, and a realistic interpolation gas equation-of-state for vaporization products. Derived values of the entropies for incipient and complete vaporization for anhydrite are 1.65±0.12 and 3.17±0.12 kJ(kg.K)–1, and for calcite these are 0.99±0.11 and 1.93±0.11 kJ(kg.K)–1. Corresponding pressures for incipient and complete vaporization along the Hugoniot of non-porous anhydrite are 32.5±2.5 and 122±13 GPa and for non-porous calcite are 17.8±2.9 and 54.1±5.3 GPa, respectively. These pressures are a factor of 2–3 lower than reported earlier by Yang

Shock temperatures in calcite (CaCO3): Implication for shock induced decomposition

The temperatures induced in crystalline calcite upon planar shock compression (95–160 GPa) are reported from two-stage light gas-gun experiments. The temperatures are obtained fitting 6-channel optical pyrometer radiances in the 450 to 900 nm range, to a Planck radiation law temperature varied from 3300 to 5400 K. Calculations demonstrate that the temperatures are some 400 to 1350 K lower than if either shock-induced melting and/or disproportionation of calcite behind the shock front was not occurring. Here calcite is modeled as disproportionating into a molecular liquid, or a solid CaO plus CO2 gas. For temperature calculations, specific heat at constant volume for one mole of CO2 is taken to be 6.7R as compared to 9R in the solid state; whereas calcite and CaO have their solid state values (15R and 6R). Calculations also suggest that the onset of decomposition in calcite to CaO and CO2 during loading occurs at ~75±10 GPa, along the Hugoniot whereas decomposition begins upon unloading from 18 GPa. The 18 GPa value is based on comparison of VISAR measurements of particle velocity profiles induced upon isentropic expansion with one-dimensional numerical simulation

Induction of flowering in Lemna paucicostata, a short-day plant, by chelating agents and iron

Lemna paucicostata is a short-day plant which normally flowers only in a medium supplemented with EDTA or EDDHA. On a molar basis EDDHA is more effective for induction of flowering. The chelating agent can be replaced by high concentrations of ferric citrate in the medium. Simultaneous supply of both EDDHA and a high level of ferric citrate results in flowering even under long days

Mass spectrometer calibration of Cosmic Dust Analyzer

The time of flight mass spectrometer of the Cosmic Dust Analyzer (CDA) instrument aboard the Cassini spacecraft, is expected to be placed in orbit about Saturn to sample the ring material and satellite impact ejecta. Upon impact of an incident dust particle against the target plate at velocities of 5-100 km/s, some 10–8 to 10–5 times the particle mass of positive valence, single-charged ions is induced. These are analyzed via a time-of-flight mass spectrometer. Initial experiments employing a pulsed N2 laser (>300 µJ/pulse, 4ns, 337nm) acting on a suite of samples are described. The laser beam is focussed to deliver the light pulses onto a laser power density (1011 W/cm2) to simulate the impact of particles. Laser ionization produced a charge of 4.6 pC per pulse for aluminum alloy. Estimating that each Al+1 ion require energy of 5.98 eV ionization energy/ion implies that 10–5% of the laser energy produced ions and the present system has a 5% efficiency of collecting the laser-irradiation induced ions. Employing a multi-channel plate detector in this mass spectrometer yields for Al-Mg-Cu alloy and kamacite (Fe-Ni mineral) targets well defined peaks at 24 (Mg+1), 27 (Al+1) and 64 (Cu+1), and 56 (Fe+1), 58 (Ni+1) and 60 (Ni+1) dalton, respectively

Bearing fault analysis using kurtosis and wavelet based multi-scale PCA

The vibration signal monitoring that is being generated by a rotor supported by a rolling element bearing is becoming important to define reliability of rotary machine. It is most prudent and useful method for bearing fault detection. Recently, there has been a lot of research on rolling element bearings fault. The kurtosis is most vital parameter to find inner race fault and outer race fault. It is enhanced by a proper selection of variable frame sizes and decompositions levels using wavelet based multi-scale principal component analysis (WMSPCA). It is observed that the kurtosis changes significantly as compared to the actual kurtosis of the un-decomposed faulty signals by proper selection of frame size and decompositions level

Mass spectrometer calibration of Cosmic Dust Analyzer

The time-of-flight (TOF) mass spectrometer (MS) of the Cosmic Dust Analyzer (CDA) instrument aboard the Cassini spacecraft is expected to be placed in orbit about Saturn to sample submicrometer-diameter ring particles and impact ejecta from Saturn's satellites. The CDA measures a mass spectrum of each particle that impacts the chemical analyzer sector of the instrument. Particles impact a Rh target plate at velocities of 1-100 km/s and produce some 10^(−8) to 10^(−5) times the particle mass of positive valence, single-charged ions. These are analyzed via a TOF MS. Initial tests employed a pulsed N2 laser acting on samples of kamacite, pyrrhotite, serpentine, olivine, and Murchison meteorite induced bursts of ions which were detected with a microchannel plate and a charge sensitive amplifier (CSA). Pulses from the N_2 laser (10^(11) W/cm^2) are assumed to simulate particle impact. Using aluminum alloy as a test sample, each pulse produces a charge of ∼4.6 pC (mostly Al^(+1)), whereas irradiation of a stainless steel target produces a ∼2.8 pC (Fe^(+1)) charge. Thus the present system yields ∼10^(−5)% of the laser energy in resulting ions. A CSA signal indicates that at the position of the microchannel plate, the ion detector geometry is such that some 5% of the laser-induced ions are collected in the CDA geometry. Employing a multichannel plate detector in this MS yields for Al-Mg-Cu alloy and kamacite targets well-defined peaks at 24 (Mg^(+1)), 27(Al^(+1)), and 64 (Cu^(+1)) and 56 (Fe^(+1)), 58 (Ni^(+1)), and 60 (Ni^(+1)) dalton, respectively

Utilization of chlorophyll content index (CCI) to infer yellow rust severity in wheat (Triticum aestivum L.)

Stripe rust caused by Puccinia striformis Westend. f. sp. tritici Eriks. (Pst) is a major constraint to wheat production in Northern India. In this study, 616 indigenous germplasm (IC) accessions of wheat were screened under field conditions against mixture of Pst isolates at DWR Karnal during 2012-13 crop season. Out of 616 accessions, 197 accessions were observed to be resistant (R), 115 moderately resistant (MR) to moderately susceptible (MS) and 304 as susceptible (S) against yellow rust. On the basis of days to heading, the accessions were grouped into four classes (early, medium early, medium late and late). Chlorophyll content index (CCI) recorded in flag leaf showed significant differences between resistant and susceptible lines in each classified group at 5% level of significance. The difference for CCI between resistant and moderately resistant plants was negligible, however in comparison with resistant plants, susceptible plants showed loss of 35-39% of chlorophyll. There was negative correlation (a correlation coefficient of – 0.60) between chlorophyll content and disease severity due to stripe rust in susceptible accessions

Evaluation and identification of resistance to powdery mildew in Indian wheat varieties under artificially created epiphytotic

Wheat production is globally weighed down by several biotic factors of which rusts and powdery mildew are the most important. Powdery mildew, caused by Blumeria graminis f. sp. tritici, is becoming a disease of major importance in the North Western Plains Zone and Northern Hills Zone of the country. In the present context ofclimate variability, diseases like powdery mildew can assume greater importance in wheat breeding programs. Importance of basic studies on powdery mildew is the need of hour. A set of 370 Indian bread wheat, durum, dicoccum and triticale varieties were screened using mixture of natural occurring pathotypes from four locations(viz., Karnal, Ludhiana, Dhaulakuan and Yamunanagar) under polyhouse conditions. Data were recorded on the severity of infection based on 0-9 scale. Out of 370, only 23 varieties (Amrut, DDK 1025, DWR 1006, DWR 195, GW 1139, HD 4672, HD 4530, HD 2278, HD 1981, DDK 1001, HI 8627, Jay, TL 2942, DT 46, K 8020, DDK 1029, K 9107, K 816, Lok 1, MACS 6145, DDK 1009, NP 111 and NP 200) had shown immune reaction (0) whereas 150, 83 and 114 varieties have shown resistance (1-3), moderately susceptible (4-6) and highly susceptible (>6) response respectively against powdery mildew. Data indicated that there is an urgent need to broaden the genetic base of wheat by identifying and introgressing new sources of powdery mildew resistance. With limited sources of PM resistance available, above identified genotypes can be further used and characterized for resistance breeding programs in India

Impact Sensitivity of RDX and Viton Compositions Prepared by Co-precipitation Method

Desensitisation of explosive materials using polymers is an important area in safe utilisation of explosives in various applications. The RDX/viton composition has been developed using co-precipitation method with varying content of viton, ranging from 5 to 35 wt per cent. RDX and viton were dissolved in acetone which is a common solvent for RDX and viton, and then the acetone was extracted from the solution by distillation resulting in homogeneous RDX/viton composition. Infrared spectroscopy studies indicated presence of RDX and viton in the resulting compositions. Thermogravimetric and differential thermal analysis studies made on yielded compositions confirmed that RDX is present in the composition in desired content. The shift in exotherm of RDX/viton composition as compared to RDX showed that polymer-bonded RDX compositions are more stable. The impact sensitivity studies showed that sensitivity of RDX/viton composition decreased with increasing content of viton. The similar trend was observed for friction sensitivity. The co-precipitation method has been found to be advantages to obtain homogeneous composition of RDX and viton (with viton content up to 25 wt per cent) as revealed by linear trend in sensitivity data measurements. It has been demonstrated that the sensitivity of RDX can be tailored within a wide range using viton so as to suit in desired applications.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 287-291, DOI: http://dx.doi.org/10.14429/dsj.65.864

Phenomenology of the Pokaranpne experiment

The phenomenology of the Pokaran PNE experiment (yield - 12 kiloton of TNT) conducted in a shale-sandstone rock, 107 meters underground, is described with the aid of computations using a one-dimensional spherical symmetric rock mechanics computer code developed by the authors. The calculated values of cavity radius, spall velocity and extent of rock fracturing are in good agreement with the observed values. The principal mechanism for crater formation at Pokaran was spall and the relatively smaller crater dimensions and non-venting of radioactivity gases were due to lower kinetic energy transferred to the shale-sandstone rock