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Noble gas and nitrogen isotopic compositions of Karimati ordinary (L5) chondrite are presented. Aliquots of the meteorite were studied in two noble gas mass spectrometers. Its cosmic ray exposure (CRE) history, trapped noble gases and nitrogen isotopic systematic are examined. The compositions of Ne and Kr in this meteorite indicate presence of mixture of solar wind and Q trapped components. In addition to the primordial components, radiogenic 129Xe (from the decay of short-lived radioactive 129I) is observed in the two aliquots (129Xe/132Xe ranges between 1.054 and 1.311). The U/Th-4He and K-40Ar ages are discordant. U/Th-4He ages are younger than the K-40Ar ages, indicating loss of helium. The trapped N component is isotopically light analogous to Q gas/solar wind. The cosmic-ray exposure ages of the two aliquots are 16.1 ± 2.7 Ma and 16.6 ± 2.0 Ma based on the cosmogenic 21Nec and 38Arc concentrations.

We have carried out detailed noble gases and nitrogen isotopic study of two eucrites Vissannapeta, Piplia Kalan and one howardite Lohawat. Neon is mainly produced by Galactic Cosmic Ray (GCR) in all the three meteorites. The estimated cosmic ray exposure ages are 23.8 ± 6.1 Ma, 28.4 ± 8.1 Ma and 46.4 ± 17.3 Ma for Piplia Kalan, Vissannapeta and Lohawat, respectively. Light nitrogen composition is present in Vissannapeta and Lohawat, while heavy nitrogen composition is observed in Piplia Kalan. The nitrogen is distinctly trapped in the eucrites. Elemental ratios of the trapped noble gases such as argon, krypton and xenon together with nitrogen composition in eucrites indicate their distinct source region in Vesta. A younger potassium-argon age for the eucrites (3.71 ± 0.42 Ga for Vissannapeta and 3.60 ± 0.15 Ga for Piplia Kalan) than the solar system formation age, indicates partial loss of the radiogenic argon during the evolutionary stages of these meteorites plausibly due to impact metamorphic events. The radiogenic ages derived from the 4He are less than 1 Ma suggesting loss of helium from the eucrites.

This is the first report of coupled noble gases (He, Ne, Ar, Kr and Xe) and nitrogen isotopic results in metal separates from the ordinary chondrites Katol (L6), Itawa Bhopji (L3-5) and Portales Valley (H6). Noble gas elemental ratios (corrected for cosmogenic) in the metal separates are mixture of several components, Q-gas, air and solar wind. The chondritic metal shows new nitrogen isotopic data, with N abundances in the range of 0.19 to 5.62 ppm and distinct isotopic signatures. Nitrogen composition observed in metal separates is inconsistent with the solar wind (SW) and Q-gas. 15N enriched nitrogen is exhibited in metal separates compared to the SW and Q-gas. In metal separates, no systematics correlation was observed between the amounts and trapped nitrogen isotopic ratios. Nitrogen isotopic ratios found in the metal separates indicate an origin from local affects that occurred on the parent body. The elemental ratios of nitrogen and noble gases in the metal separates are within the range observed in the bulk meteorites, but distinct compared to the SW and Q-gas.

The concentrations and isotopic composition of noble gases helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon(Xe) and nitrogen were measured in the Beni M'hira L6 chondrite. The cosmic ray exposure age of Beni M'hira is estimated of 15.6 ± 3.7 (Ma). The radiogenic age, of around 485 ± 64 Ma, derived from 4He, and of around 504 ± 51 Ma from 40Ar, suggests an age resetting indicating the event impact. The heavy noble gases (Ar, Kr and Xe) concentrations imply that the gas is a mixture of trapped component Q and solar wind. The measured nitrogen abundance of 0.74 ppm and the isotopic signature of δ15N = 14.6‰ are within the range of ordinary chondrites. The homogeneous chemical composition of olivine (Fa:26 ± 0.25) and low-Ca pyroxene (Fs:22.4 ± 0.29) suggest that the Beni M'hira meteorite is an equilibrated chondrite. This is further corroborated by strong chondrule-matrix textural integration (lack of chondrules, except a few relict clast). Shock metamorphism generally corresponds to S5 (>45 GPa), however, locally disequilibrium melting (shock-melt veins) suggests, that the peak shock metamorphism was at ∼75 GPa, 950 °C.

We investigated noble gas (He, Ne, Ar, Kr and Xe) and nitrogen isotopic composition in the carbonaceous chondrite Bukhara (CV3). This is the first report of N and noble gases measured in the same aliquot of bulk sample among the CV3 chondrites. Isotopic compositions of noble gases are mixtures of solar wind and Q-gases. We derive cosmic ray exposure (CRE) age of 22.6 ​± ​4.0 ​Ma from cosmogenic 21Ne and 38Ar for Bukhara. Nitrogen abundance observed in Bukhara is lowest compared with the data from CV3 chondrites. We estimate the trapped nitrogen composition of δ15N ​= ​+ 10.9 ​± ​1.6‰ for Bukhara, distinct from average (δ15N ​= ​- 16.3 ​± ​1.5‰) in the bulk CV3 chondrites. Bukhara shows signature of heavy nitrogen, which is distinct than the solar wind (SW) and Q-gas. Trapped nitrogen is mixture of the components, SW, Q and comet. It is observed that there is no correlation of nitrogen composition with N content in the CV3 chondrites.

A single piece of meteorite fell on Kamargaon village in the state of Assam in India on November 13, 2015. Based on mineralogical, chemical, and oxygen isotope data, Kamargaon is classified as an L-chondrite. Homogeneous olivine (Fa: 25 ± 0.7) and low-Ca pyroxene (Fs: 21 ± 0.4) compositions with percent mean deviation of

The Sulagiri meteorite fell in India on 12 September 2008, LL6 chondrite class is the largest among all the Indian meteorites. Isotopic compositions of noble gases (He, Ne, Ar, Kr and Xe) and nitrogen in the Sulagiri meteorite and cosmic ray exposure history are discussed. Low cosmogenic ( 22 Ne/ 21 Ne) c ratio is consistent with irradiation in a large body. Cosmogenic noble gases indicate that Sulagiri has a 4 π cosmic-ray exposure (CRE) age of 27.9 ± 3.4 Ma and is a member of the peak of CRE age distribution of LL chondrites. Radiogenic 4 He and 40 Ar concentrations in Sulagiri yields the radiogenic ages as 2.29 and 4.56 Ga, indicating the loss of He from the meteorite. Xenon and krypton are mixture of Q and spallogenic components.

Noble gases and nitrogen have been in lunar meteorite from antartcica: the polymict regolith breccias, Yamato-983885 (hereafter Y-983885). Y-983885 has highest concentration of trapped noble gases (Ar, Kr, and Xe) among all the lunar meteorites and returned lunar samples. Noble gases and nitrogen abundances measured in two samples of the lunar meteorite Y-983885. The concentration of trapped noble gases in Y-983885 (A) are, 20Ne=3.69×10−3, 36Ar=12.6×10−4, 84kr=8.57×10−7 and 132Xe=1.63×10−7 ccSTP/g. The cosmic-ray exposure ages for Y-983885 are thus calculated to be T21 (A)=1592±232 Ma and T21 (B)=574±85 Ma for 2π geometry (using production rates as per Hohenberg et al., 1978 and bulk composition ). The exposure ages of samples A and B differ, indicating that they have undergone different exposure scenarios on the lunar surface. The different irradiation ages (T21 (A)=1592±232 Ma and T21 (B)=574±85 Ma) indicates that the regolith material which constitutes the meteorite Y-983885 resided at different shielding depths on lunar surface before agglomeration into the final meteorite. Exposure ages calculated using end member compositon like norite, basalt, tractolite (1947 to 1365 and 711 to 455 for A and B respectively) indicates clearly that the two samples A and B has undergone different exposure on Moon. The 20Ne/22Ne ratio of 13.60±0.01 in temperature step 400 °C of Y-983885 (A) demonstrate a clear retention of solar wind signature in this meteorite. The presence of high contents of trapped solar wind gases indicates that Y-983885 consists of mature lunar regolith material. Variable amounts of solar gases as well as cosmogenic noble gases indicate that Y-983885 (A and B) is compacted from several fragments that were exposed at the surface and/or at various depths in the regolith, before becoming part of Y-983885.

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The 10Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre-entry radius. © The Meteoritical Society, 2017.

We present a comparative study of two offline methods, a newly developed method and an existing one, for the measurement of the stable carbon isotopic composition (δ(13)C) of dissolved inorganic carbon (DIC; δ(13)CDIC) in natural waters. The measured δ(13)CDIC values of different water samples, prepared from laboratory Na2CO3, ground and oceanic waters, and a laboratory carbonate isotope standard, are found to be accurate and reproducible to within 0.5 ‰\ (1σ). The extraction of CO2 from water samples by these methods does not require pre-treatment or sample poisoning and can be applied to a variety of natural waters to address carbon cycling in the hydrosphere. In addition, we present a simple method (based on a two-end-member mixing model) to estimate the silicate-weathering contribution to DIC in a river system by using the concentration of DIC and its δ(13)C. This approach is tested with data from the Krishna River system as a case study, thereby quantifying the contribution of silicate and carbonate weathering to DIC, particularly during peak discharge.

The Santa Lucia (2008)—one the most recent Argentine meteorite fall, fell in San Juan province, Argentina, on 23 January 2008. Several masses (total ~6 kg) were recovered. Most are totally covered by fusion crust. The exposed interior is of light-grey colour. Chemical data [olivine (Fa24.4) and low-Ca pyroxene (En77.8 Fs20.7 Wo1.6)] indicate that Santa Luica (2008) is a member of the low iron L chondrite group, corresponding to the equilibrated petrologic type 6. The meteorite name was approved by the Nomenclature Committee (NomCom) of the Meteoritical Society (Meteoritic Bulletin, no. 97). We report about the chemical composition of the major mineral phases, its bulk trace element abundance, its noble gas and nitrogen data. The cosmic ray exposure age based on cosmogenic 3He, 21Ne, and 38Ar around 20 Ma is comparable to one peak of L chondrites. The radiogenic K–Ar age of 2.96 Ga, while the young U, Th–He are of 1.2 Ga indicates that Santa Lucia (2008) lost radiogenic 4He more recently. Low cosmogenic (22Ne/21Ne)c and absence of solar wind noble gases are consistent with irradiation in a large body. Heavy noble gases (Ar/Kr/Xe) indicated trapped gases similar to ordinary chondrites. Krypton and neon indicates irradiation in large body, implying large pre-atmospheric meteoroid. Fil: Mahajan, Ramakant R.. Physical Research Laboratory; India Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentina Fil: Joron, Jean Louis. Université Paris-Saclay; Francia

A bulk sample (split from Almahata Sitta #36) and an acid resistant residue (from #44) have been analyzed for noble gases and nitrogen by step-wise combustion/pyrolysis. In the bulk sample, He and Ne are a mixture of cosmogenic and trapped components. Cosmic- ray exposure ages of 13.8 and 16.0 Ma are calculated based on 3 He, and 21 Ne, respectively. Except for a small amount of cosmogenic 3 He, He, and Ne in the acid-resistant residue are not significantly above blank level. Ar, Kr, and Xe in both the bulk and residue are dominated by a trapped component, but the elemental ratios are different. While the ratios of 36 Ar/ 132 Xe and 84 Kr/ 132 Xe are about 400 and 1, respectively, in all the combustion steps of the residue, the bulk sample has about an order of magnitude more 132 Xe in the corresponding combustion steps. It seems, an acid soluble phase is the host of this Xe-rich carrier and is different from a similar phase observed in the ureilite Allan Hills 82130. Nitrogen in the bulk sample and acid residue are 21.1 ppm (−36.8‰), and 249.5 ppm (−74.3‰), respectively. Peak release of C (monitored as CO + CO 2 ), N, Ar, Kr, and Xe occurred at the 700 ° C combustion step of the residue, confirming diamond as the principal carrier for these gases. In the residue, the isotopic ratio 38 Ar/ 36 Ar shows a monotonic increase with release temperature.

A single stone weighing about 1.6 kg fell in Kaprada village of south Gujarat, India in October, 2004. It has been studied for mineralogy, petrography, chemical and isotopic composition and cosmogenic effects. The olivine is 23.7% fayalite. The petrography, bulk chemistry and oxygen isotopic composition indicate that it belongs to L(5/6) group of chondrites. The cosmic ray exposure age of the meteorite is estimated to be 11.4 Ma based on He, Ne and Ar isotopes. A trapped nitrogen amount of 0.25 ppm with δ 15 N=4.7±0.3‰ is typical of ordinary chondrites of higher metamorphic grade. The gas retention ages, based on U/Th– 4 He and K– 40 Ar are calculated to be 2.6 and 4.1 Ga, respectively. Cosmic ray track data indicate that the pre-atmospheric radius of the meteorite was about 7 cm, and about 75% mass was ablated during its journey through the Earth's atmosphere.

We report here a chance find of a meteorite in the sand dunes of Ararki village of Hanumangarh district in the Rajasthan desert of northwest India. Chemical and petrological evidence in conjunction with isotopic composition of oxygen indicate that it is an L5 chondrite. The fayalite content of olivines is 26.3 mol%. The meteorite has some serpentinized olivines and 0.3% carbon having a terrestrial isotopic composition, indicating that it is moderately weathered. The absence of 22 Na indicate that the meteorite fell to Earth more than a decade ago. The cosmic-ray exposure age based on cosmogenic 21 Ne is 7.2 Ma. Low density of cosmic-ray heavy nuclei tracks, low 26 Al activity, the shielding parameter (( 22 Ne/ 21 Ne)C = 1.094) and absence of neutron capture effects indicate cosmic-ray shielding in a meteoroid having radius of about 16 cm, implying a meteoroid mass of about 60 kg and ablation of about 93%. The gas retention ages, based on U/Th- 4 He and K- 40 Ar are 1.1 and 0.58 Ga, respectively, suggesting a heating and degassing event late in the history of this meteorite.

Chemical and mineral analysis of the Bhawad chondrite, which fell in Rajasthan in 2002, suggest that this stone belongs to LL6 group of chondrites. Based on helium, neon, and argon isotopes, it has a cosmic ray exposure age of 16.3 Ma. The track density in the olivines shows a narrow range of 1.7-6.8 106/cm2. The 22Na/26Al ratio of 1.13 is about 25% lower than the solar cycle average value of about 1.5, but is consistent with irradiation of the meteoroid to modulated galactic cosmic ray fluxes as expected for a fall around the solar maximum. The cosmogenic records indicate a pre-atmospheric radius of about 7.5 cm. Based on U/Th-4He and K-40Ar, the gas retention ages are low (about 1.1 Ga), indicating a major thermal event or shock event that lead to the complete loss of radiogenic 4He and 40Ar and the partial loss of radiogenic 129Xe and fission Xe from 244Pu.

An extremely bright fireball was seen for over 250 km near the eastern coast of India in the evening sky on September 27, 2003. In a rare observation, the fireball was seen by two airline pilots, providing direction of the trail with reasonable accuracy, consistent with ground-based observations. A few fragments of the meteorite were subsequently recovered along the end of the trail in different parts of Kendrapara district (20°30' N; 86°26' E) of Orissa. Based on petrography and chemical composition, the meteorite is classified as H5 chondrite. The cosmogenic radionuclides 54Mn, 22Na, 60Co, and 26Al and tracks have been studied in this stony meteorite. Two of the fragments show an unusually high activity of 60Co (~160 dpm/kg) indicating a meteoroid radius of 50-150 cm. Assuming that less than 10% (by weight) of the fragments could be recovered because of difficult terrain, an atmospheric mass ablation of >95% is estimated. Based on the observations of the trail and the estimated mass ablation, orbital parameters of the meteoroid have been calculated. The aphelion is found to lie in the asteroidal belt (1.8-2.4 AU), but the inclination of the orbit is large (22°-26°) with respect to the ecliptic. Noble gases have been analysed in two samples of this meteorite. He and Ne are dominantly cosmogenic. Using production rates based on the sample depth derived from 60Co content, 21Ne-based exposure age of 4.50 ± 0.45 Ma is derived for Kendrapara. One of the samples, known to be more deeply shielded based on high 60Co activity, shows the presence of 80Kr, 82Kr, and 128Xe produced by (n, γ) reaction on 79Br, 81Br, and 127I, respectively. The (80Kr/82Kr)n ratio of 3.5 ± 0.9 is consistent with neutrons being mostly thermal. Trapped 84Kr and 132Xe are in the expected range for metamorphic grade H5.

A laser microprobe capable of analysing nitrogen and noble gases in individual grains with masses less than a milligram is described. It can be used in both continuous wave (CW) mode, useful for stepwise heating of an individual grain, as well as in pulsed mode, useful for ablating material from a small selected area of a sample, for gas extraction. We could achieve low blanks (in ccSTP units) for 4He(4.8 x 10{-12}),22Ne(1.0 x 10{-12}),36Ar(1.0 x10 -13),84Kr(2.9 x 10{-14}),132 Xe(2.6 x 10{-14}), and N (87 pg), using this system. Preliminary data for individual chondrules from the Dhajala meteorite show that noble gases and nitrogen from grains as small as 170 microgram can be analysed using the present laser microprobe setup. The amount of trapped neon in Dhajala chondrules is very small, and nitrogen in the chondrules is isotopically heavier as compared to the bulk meteorite.

A stony meteorite fell at Itawa Bhopji, Rajasthan, India on 2000 May 30. This is the fifth recorded fall in a small area of Rajasthan during the past decade. The meteorite is an ordinary chondrite with light clasts in a dark matrix, consisting of a mixture of equilibrated (mainly type 5) and unequilibrated components. Olivine is Fa24-26 and pyroxene Fs20-22 but, within the unequilibrated components, olivine (Fa5-29) and low calcium pyroxene (Fs5-37) are highly variable. Based on petrographic studies and chemical analyses, it is classified as L(3-5) regolith breccia. Studies of various cosmogenic records, including several gamma-emitting radionuclides varying in half-life from 5.6 day 52Mn to 0.73 Ma 26Al, tracks and rare gases have been carried out. The exposure age of the meteorite is estimated from cosmogenic components of rare gases to be 19.6 Ma. The track density varies by a factor of ~3 (from 4 to 12 x 10^6/cm^2) within the meteorite, indicating a preatmospheric body of ~9 cm radius (corresponding to a meteoroid mass of ~11 kg) and small ablation (1.5 to 3.6 cm). Trapped components in various rare gases are high and the solar component is present in the dark portion of the meteorite. Large excess of neutron-produced 82Kr and 128Xe in both the light and the dark lithology but very low 60Co, indicating low neutron fluxes received by the meteoroid in the interplanetary space, are clear signatures of an additional irradiation on the parent body.

The Lohawat meteorite is a texturally heterogeneous breccia having a variety of mineral and lithic fragments. Among mineral fragments, pyroxenes show a wide range of composition WOO,^^^^, 17En0,37~.78FS0, ~~~).60) whereas plagioclase is anorthitic (An0.92Abo.070ro.007). Abundant rounded "chondrule-like" objects ranging in size up to -7 mm, some with concentric layering, have been observed. Petrographic features, trace element composition and rare earth element patterns show the presence of eucritic and diogenitic components confirming that it is a typical howardite. Cosmogenic tracks, rare gases (He, Ne, and Ar) and radionuclides (22Na and 26A1) were measured. Track density in olivine and plagioclase varies between 0.7 to 6 x 106/cm2. 38Ar exposure age is estimated to be - 1 10 Ma, being the highest among howardites. The track production rates correspond to ablation of 9 to 15 cm, implying a radius for its preatmospheric size of -27 cm. 22Na /26AI = 1, as expected from the production models and solar modulation of galactic cosmic-ray fluxes before its fall, suggesting that the meteoroid did not undergo any fragmentation during the past -2 Ma in interplanetary space. The radiogenic age based on K-Ar method is 4.3 Ga while the U-Th-4He age is 3.3 Ga indicating partial loss of He.

The mineralogical and chemical characteristics of the Didwana-Rajod Meteorite are described. The mean mineral composition is found to be olivines: (Fo83.2), pyroxenes: (En83.5Wo0.7Fs15.8) and feldspar is mainly oligoclase. Oxygen isotopic analysis shows ?18O=+3.8 deg and ??17O=+2.59 deg. The nitrogen content of Didwana-Rajod is about 2 ppm with ?15N ~3.4deg. Based on microscopic, chemical, isotopic and electron probe microanalysis, the meteorite is classified as H5 chondrite. Cosmogenic tracks, radionuclides and the isotopic composition of rare gases were also measured in this meteorite. The track density in olivines varies in a narrow range with an average value of (6.5 ( 0.5) x 105/cm2 for four spot samples taken at the four corners of the stone. The cosmic ray exposure age based on neon and argon is 9.8 Ma. 22Na/26Al ~0.94 is lower than the solar-cycle average value of about 1.5 and is consistent with irradiation of the meteoroid to lower GCR fluxes as expected at the solar maximum. The track density, rare gas isotopic ratios, 60Co activity and other radionuclide data are consistent with a preatmospheric radius of about 15 cm, corresponding to a mass of about 50 kg. The cosmogenic properties are consistent with a simple exposure history in the interplanetary space.

We demonstrate the presence of solar flare as well as neutron capture effects in the isotopic composition of rare gases in the Fermo regolith breccia acquired on its parent body based on the measurements of tracks, rare gases and radionuclides. The track density along a 3.2 cm long core decreases by a factor of about 6 and by more than a factor of 13 within the meteorite, indicating small (2-9 cm) and asymmetrical ablation. Rare gases show a large trapped component; the isotopic ratios, particularly 20 Ne/ 22 Ne ≅ 11 and 20 Ne/ 36 Ar = 10 are indicative of a solar component. The galactic cosmic-ray exposure age is determined to be 8.8 Ma. Activities of a dozen radionuclides ranging in half-life from 16 day 48 V to 0.73 Ma 26 Al are consistent with their expected production rates. Track, rare gas and radionuclide data show that the meteoroid was a small body (≤ 120 kg) and had a simple, one-stage exposure history to cosmic rays in the interplanetary space. However, 82 Kr and 128 Xe show an excess due to neutron irradiation on the parent body of the meteorite. The presence of solar gases and the neutron capture effects indicate several stages of irradiation on the parent asteroid. The chemical composition of Fermo confirms that it belongs to the H group of ordinary chondrites with lithic clasts having varying compositions. δ 15 N is found to be 8.3 ± 1.2%0, close to the typical values observed in H chondrites.

Complexes of nitrocellulose (NC – low and high nitrogen content) with copper oxide (CuO) have been synthesized and studied for morphological behaviour on heating from room temperature to 500°C with the help of hot stage microscopy (HSM).

Thermal degradation of some unsaturated polyesters synthesized by ‘1-step’, ‘2-step’ and ‘3-step’ polyesterification processes and designated as NUP-I, NUP-II and NUP-III, respectively, have been studied using thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), iso-thermal TG, infrared (IR) spectroscopy and hot stage microscopy. The data from dynamic studies in static air and dynamic nitrogen suggest that the mode of degradation is different in air and nitrogen. The degradation in static air involves two stages as against single stage degradation in nitrogen. Isothermal studies in air reveal that the degradation follows a two-step first-order reaction. IR studies show that the degradation starts with the breaking of ester linkages and CO 2 is the initial gaseous product detected at 300 °C.

The thermal decomposition of nitrocellulose (NC) 12.1% N, has been studied with regard to kinetics, mechanism, morphology and the gaseous products thereof, using thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy, differential scanning calorimetry (DSC) and hot stage microscopy. The kinetics of the initial stage of thermolysis ofNC in condensed state has been investigated by isothermal high temperature infrared spectroscopy (IR). The decomposition ofNC in KBr matrix in the temperature range of 142–151°C shows rapid decrease in O−NO2 band intensity, suggesting that the decomposition of NC occurs by the rupture of O−NO2 bond. The energy of activation for this process has been determined with the help of Avrami-Erofe'ev equation (n=1) and is ≈188.35 kJ·mol−1. Further, the IR spectra of the decomposition products in the initial stage of thermal decomposition ofNC, indicates the presence of mainly NO2 gas and aldehyde.

This paper addresses the static response of geotextile-reinforced slopes resting on a firm foundation to the self-weight loading imposed in a geotechnical centrifuge at pre-failure and at failure. A series of centrifuge tests were carried out on model geotextile-reinforced sand slopes with different types of reinforcement, spacing and slope inclination. A wrap-around technique was used to represent a flexible facing. In order to initiate failure in the reinforcement layers, the ratio of the length of the reinforcement to the height of the slope was maintained as 0.85. Reinforced slope models were subjected to varied g-levels (in steps of 5g from 10g onwards) up to a maximum target g-level of 75g or to collapse, whichever occurred first. A digital image analysis technique was employed to arrive at displacement vectors of markers glued to the reinforcement layers. The displacements were used to compute and analyse the strain distribution along the reinforcement layers, and to identify the peak strain distribution pre-failure and at failure. The development of a particular type of failure mechanism was found to depend upon the tensile strength-strain characteristics of a reinforcement layer. Maximum peak strain in the reinforcement layers was observed to occur at mid-height of the slope. With an increase in slope inclination from 2V:1H to 5V:1H, the magnitude of maximum peak strain was observed to increase, and its location was observed to move downwards from mid-height of the slope. Stability analysis of the reinforced slope models was found to be in good agreement with physically observed centrifuge test results.

The petrographic and chemical characteristics of a fresh Indian meteorite fall at Sabrum are described. Its mean mineral composition is defined by olivine (Fa31.4), orthopyroxene (Fs25.1,Wo2.0), clinopyroxene (Wo45En45.6Fs9.4) and plagioclase (An10.6Ab83.6Or5.8). The meteorite shows moderate shock features, which indicate that it, belong to the S4 category. Based on mineralogical and chemical criteria the meteorite is classified as LL6 brecciated veined chondrite. Several cosmogenic radioisotopes (46Sc, 7Be, 54Mn, 22Na and 26Al), noble gas (He, Ne, Ar, Kr and Xe), nitrogen isotopes and particle tracks density have been measured. Concentrations of cosmogenic 21Ne and 38Ar indicate that its cosmic ray exposure is 24.8 Ma. Small amounts of trapped Kr and Xe, consistent with petrologic class 5/6, are present. The track density in olivines is found to be (1.3 ± 0.3 x 10^6/cm^2. Activities of most of the short lived isotopes are lower than those expected from solar cycle variation. 22Na/26Al (1.12 ± 0.02) is found to be significantly anomalous, being approximately 25% lower than expected from the climax neutron monitor data. These results indicate that the cosmic ray flux during the terminal segment of the meteoroid orbit was low. The activities of 26Al and 60Co and the track density indicate small meteoroid size with radius ~15 cm.