Soil erosion is one of the major global hazards threatening the food security of the world population.Soil erosion can be a result of both natural and anthropogenic processes.Field monitoring and models(numerical and ...Soil erosion is one of the major global hazards threatening the food security of the world population.Soil erosion can be a result of both natural and anthropogenic processes.Field monitoring and models(numerical and physical)are commonly used to quantify soil erosion.However,field methods are time-consuming and the models inherently work with a level of uncertainty.Soil erosion studies in the Himalayas have been mostly carried out using modelling but there is a lack of sufficient field data to validate the results.We quantified soil erosion in a small catchment(Pranmati)in the Himalayas using the fallout meteoric^(10)Be nuclide for the first time.Based on the^(10)Be flux delivery rates determined from global circulation models(GCM),we calculated the rates of soil erosion at discrete points in the hilltop and mid-slope regions of hillslopes.The erosion rates vary between 17 mm kyr^(-1)to 68 mm kyr^(-1).These rates were determined in pristine areas that are unaffected by anthropogenic activities,thus,indicate the background erosion rates in the region.We established empirical relationships with estimated erosion rates and topographic parameters to assess the sediment dynamics in the hillslopes.It was observed that the sediment redistribution process operates differently in the mid-slope region compared to the hilltop region,due to increasing complexity of the active processes in the mid-slope region.展开更多
The Kathalguri Pluton is a granitic pluton confined within the Palaeo-Mesoproterozoic Shillong Group of rocks in the Mikir Massif, eastern India. The pluton is vertically zoned characterized by lower medium-to coarseg...The Kathalguri Pluton is a granitic pluton confined within the Palaeo-Mesoproterozoic Shillong Group of rocks in the Mikir Massif, eastern India. The pluton is vertically zoned characterized by lower medium-to coarsegrained equigranular to porphyritic granite and upper finegrained equigranular granite. Small to large mafic magmatic enclaves(MME) are distributed within the lower granite, while homogeneous grey-coloured hybrid rocks dominate the upper granite. From field relationships, textural features, and mineral chemical analyses we infer that the Kathalguri Pluton was a vertically zoned felsic magma chamber that was intruded by mafic magma during its evolution. The lower portion of the magma chamber was occupied by crystal mush, while the upper portion was dominated by melt when mafic magma intruded it. The occurrence of upper and lower zonations was probably brought about by fractional crystallization. The presence of such zonations within the felsic reservoir caused the mafic magma to interact with the two distinct zones differently,forming MME in the lower granite and homogeneous hybrid rocks in the upper portion. The plagioclase compositions of the larger MME, smaller MME, hybrid rocks,and granitic host rocks vary between An;–An;, An;–An;, An;–An;,and An;–An;respectively. The alkali feldspar compositions of the hybrid rocks range from Or;to Or;, while that of the host granite varies from Or;to Or;. The biotite is eastonitic and siderophyllitic in composition, while the pyroxene is diopside. The apparent pressure range of biotite crystallization in the granitic rocks was calculated at 1.93 to 2.28 kbar, while the biotite crystallization temperature for the different rock types is in the range of 628 and 759 ℃. Oxygen fugacity estimates from the biotite suggest that the Kathalguri magmas crystallized at fO;conditions above the nickel-nickel oxide(NNO) buffer. Distinct disequilibrium textures indicating mixing and mingling between the mafic and felsic magmas are preserved in the smaller MME and homogeneous hybrid rocks. These textures are mainly found in plagioclase crystals, which include resorbed grains, oscillatory zoned plagioclase, boxy-cellular morphology, and overgrowth texture. Some common magma mingling and mixing textures like quartz ocelli and back-veining are also preserved in the smaller MME. An interesting feature observed in the homogeneous hybrid rocks of our study area is mantled alkali feldspar in which orthoclase is mantled by microcline. We propose that this overgrowth texture formed due to epitaxial crystallization of microcline on orthoclase owing to mixing between the felsic and mafic magmas. Such magma mixing event produces a heterogeneous system that is in an extreme state of disequilibrium and facilitates the epitaxial growth of one feldspar on another. On the other hand, the larger MME of our study domain shows limited interaction with the felsic host as indicated by the replacement of clinopyroxene crystals by amphibole and biotite.展开更多
Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing countries...Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing countries.Atmospheric radiocarbon represents an important observational constraint and utilized to trace fossil fuel derived CO_(2)(CO_(2ff))in the atmosphere.For the first time,we have presented a detailed analysis on the spatial distribution of fossil fuel derived CO_(2)(CO_(2ff))over India using radiocarbon(Δ14C)measurements during three-year period.Analysis shows that theΔ14C values are varying between 29.33‰ to-34.06‰ across India in the year 2017,where highest value belongs to a location from Gujarat while lowest value belongs to a location from Chhattisgarh.Based on the14C patterns,spatial distributions of CO_(2ff) mole fractions have been determined over India and the calculated values of CO_(2ff) mole fractions are varying between 4.85 ppm to 26.59 ppm across India.It is also noticed that the highest CO_(2ff) mole fraction is observed as 26.59 ppm from a site in Chhattisgarh.CO_(2ff) mole fraction values from four high altitude sites are found to be varied between 4.85 ppm to 14.87 ppm.Effect of sampling different crop plants from the same growing season and different crop plant organs(grains,leaves,stems)on theΔ14C and CO_(2ff) have been studied.Annual and intra seasonal variations in theΔ14C and CO_(2ff) mole fractions have also been analyzed from a rural location(Dholpur,Rajasthan).展开更多
Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydro...Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydrous uvarovite garnet having Cr_(2)O_(3) upto 19.66 wt% and CaO of 32.12–35.14 wt% in the serpentinized mantle peridotites of Naga Hills Ophiolite(NHO), India. They occur in association with low-Cr diopsides. They are enriched in LILE(Ba, Sr), LREEs, with fractionating LREE-MREE [avg.(La/Sm)_(N) = 2.16] with flat MREE/HREE patterns [avg.(Sm/Yb)_(N) = 0.95]. Raman spectra indicate the presence of hydroxyl(OH^(–)) peaks from 3500 to 3700 cm^(-1). Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low-Cr diopsides by hydrothermal slab fluids. The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low-p H solution. The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet, and their origin is attributed to the fluid-induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime.展开更多
Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap si...Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap signatures at similar temperature regimes.Electron traps are found to be within the values:0.05–1.2 eV from the conduction band edge whereas the hole traps 1.37–2.66 eV from the valence band edge on the SBDs.In the lower temperature regime,the deeper electron traps contribute to the capacitance transients with increasing r values,whereas at the higher temperatures>300 K,a slow variation of the trap levels(both electrons and holes)is observed when r is varied.These traps are found to be mainly contributed to dislocations,interfaces,and vacancies within the structure.展开更多
Variation of nonlinear optical properties with surface roughness of ZnO thin films deposited on coming glass substrates at different annealing temperature （TA） was reported. The films were characterized by X-ray dif...Variation of nonlinear optical properties with surface roughness of ZnO thin films deposited on coming glass substrates at different annealing temperature （TA） was reported. The films were characterized by X-ray diffraction （XRD）, UV-Vis-NIR transmission and single beam z-scan technique using second harmonics of Nd：YAG laser. Surface morphology of the samples was investigated by atomic force microscopy （AFM）. Surface roughness was found minimum （8.4 nm） for ZnO sample annealed at 450℃. The nonlinear optical properties （NLO） were found to be dependent on surface roughness and the highest value of third order nonlinear susceptibility （X（3）=4.3x 10-7 esu） was obtained for ZnO at TA 450℃.展开更多
The study of radiation damage of high- molecular weight substances due to MeV ion interactions is of interest for engineering and scientific applications. In the present study polystyrene (PS) was irradiated with 107A...The study of radiation damage of high- molecular weight substances due to MeV ion interactions is of interest for engineering and scientific applications. In the present study polystyrene (PS) was irradiated with 107Ag ions of three different charge states (q) 11+, 14+ and 25+ and of 130 MeV energy. The emission of hydrogen from PS was monitored as a function of the incident ion fluence. The experimental results showed that the hydrogen depletion per incident ion from PS varies as qn, where n was found to be 2.1 as compared to the value 2.7 to 3.0 reported in the literature. Radii of the nanometric damaged zones or ion tracks formed were analyzed from the slope of the hydrogen depletion versus ion fluence curves as a function of charge state of incident ion. These have values between 3.2 - 6.8 nm. These radii were found to depend upon the charge state of the incident ion and vary as qm, where m has the value 0.9.展开更多
The role of deposition rate in the structural, optical and electrical properties of SnOthin films deposited by electron beam evaporation method is investigated by varying the deposition powers viz. 50, 75, and 100 W.T...The role of deposition rate in the structural, optical and electrical properties of SnOthin films deposited by electron beam evaporation method is investigated by varying the deposition powers viz. 50, 75, and 100 W.The structural characterization of the films is done by X-ray diffraction(XRD) technique. The surface morphology of the films is studied by scanning electron microscopy(SEM). Rutherford back scattering(RBS) measurements revealed the thickness of the films ranging from 200 nm to 400 and also a change in the concentration of oxygen vacancies which is found to be the maximum in the film deposited at the lowest deposition rate. Optical absorption spectrum is recorded using the UV–V is spectroscopy and the films are found to be transparent in nature. A shift in the absorption edge is observed and is attributed to a different level of allowed energy states in conduction band minimum. The Hall effect and electrical measurements show a variation in the carrier concentrations, mobility and resistivity of the films. In order to explore a better compromise in electrical and optical properties for transparent electrode applications, skin depths calculations are also done to find the optimized values of carrier concentration and mobility.展开更多
The neutron deficient Xe nuclei with A≈120 are predicted to have strong octupole correlation at low spins.In the present study,an attempt was made to improve upon the level scheme and also to examine the signatures o...The neutron deficient Xe nuclei with A≈120 are predicted to have strong octupole correlation at low spins.In the present study,an attempt was made to improve upon the level scheme and also to examine the signatures of octupole correlation in^(118)xe via high spin γ-ray spectroscopy.High spin states in^(118)Xe have been populated via the^(93)Nb(^(28)Si,p2n)^(118)Xe fusion-evaporation reaction at a beam energy of 115 MeV provided by the 15 UD pelletron accelerator facility at IUAC,New Delhi.In the experiment,seven newγ-transitions have been found and placed appropriately in the level scheme.A theoretical study using the triaxial projected shell model(TPSM)approach suggests that the first bandcrossing is due to the alignment of two neutrons,and a parallel band tracking the yrast configuration is the γ-band built on the two-quasiparticle state.Enhanced E1 transition rates measured between opposite parity bands involving vh_(11/2)and vd_(5/2)orbitals having△j=△l=3 indicate the presence of octupole correlation in this nucleus.展开更多
基金financially supported by Council of Scientific and Industrial Research(CSIR)(grant no.09/045(1399)/2015-EMR-I)the Ministry of Earth Sciences(Mo ES),Government of India(grant no.Mo ES/P.O.(Geo)/95/2017)。
文摘Soil erosion is one of the major global hazards threatening the food security of the world population.Soil erosion can be a result of both natural and anthropogenic processes.Field monitoring and models(numerical and physical)are commonly used to quantify soil erosion.However,field methods are time-consuming and the models inherently work with a level of uncertainty.Soil erosion studies in the Himalayas have been mostly carried out using modelling but there is a lack of sufficient field data to validate the results.We quantified soil erosion in a small catchment(Pranmati)in the Himalayas using the fallout meteoric^(10)Be nuclide for the first time.Based on the^(10)Be flux delivery rates determined from global circulation models(GCM),we calculated the rates of soil erosion at discrete points in the hilltop and mid-slope regions of hillslopes.The erosion rates vary between 17 mm kyr^(-1)to 68 mm kyr^(-1).These rates were determined in pristine areas that are unaffected by anthropogenic activities,thus,indicate the background erosion rates in the region.We established empirical relationships with estimated erosion rates and topographic parameters to assess the sediment dynamics in the hillslopes.It was observed that the sediment redistribution process operates differently in the mid-slope region compared to the hilltop region,due to increasing complexity of the active processes in the mid-slope region.
基金the DST-SERB grant vide Project No.CRG/2020/002635CSIRJRF fellowship No.09/1236(0005)/2019-EMR-Ithrough DST-FIST funding (SR/FST/ ESI-152/2016)。
文摘The Kathalguri Pluton is a granitic pluton confined within the Palaeo-Mesoproterozoic Shillong Group of rocks in the Mikir Massif, eastern India. The pluton is vertically zoned characterized by lower medium-to coarsegrained equigranular to porphyritic granite and upper finegrained equigranular granite. Small to large mafic magmatic enclaves(MME) are distributed within the lower granite, while homogeneous grey-coloured hybrid rocks dominate the upper granite. From field relationships, textural features, and mineral chemical analyses we infer that the Kathalguri Pluton was a vertically zoned felsic magma chamber that was intruded by mafic magma during its evolution. The lower portion of the magma chamber was occupied by crystal mush, while the upper portion was dominated by melt when mafic magma intruded it. The occurrence of upper and lower zonations was probably brought about by fractional crystallization. The presence of such zonations within the felsic reservoir caused the mafic magma to interact with the two distinct zones differently,forming MME in the lower granite and homogeneous hybrid rocks in the upper portion. The plagioclase compositions of the larger MME, smaller MME, hybrid rocks,and granitic host rocks vary between An;–An;, An;–An;, An;–An;,and An;–An;respectively. The alkali feldspar compositions of the hybrid rocks range from Or;to Or;, while that of the host granite varies from Or;to Or;. The biotite is eastonitic and siderophyllitic in composition, while the pyroxene is diopside. The apparent pressure range of biotite crystallization in the granitic rocks was calculated at 1.93 to 2.28 kbar, while the biotite crystallization temperature for the different rock types is in the range of 628 and 759 ℃. Oxygen fugacity estimates from the biotite suggest that the Kathalguri magmas crystallized at fO;conditions above the nickel-nickel oxide(NNO) buffer. Distinct disequilibrium textures indicating mixing and mingling between the mafic and felsic magmas are preserved in the smaller MME and homogeneous hybrid rocks. These textures are mainly found in plagioclase crystals, which include resorbed grains, oscillatory zoned plagioclase, boxy-cellular morphology, and overgrowth texture. Some common magma mingling and mixing textures like quartz ocelli and back-veining are also preserved in the smaller MME. An interesting feature observed in the homogeneous hybrid rocks of our study area is mantled alkali feldspar in which orthoclase is mantled by microcline. We propose that this overgrowth texture formed due to epitaxial crystallization of microcline on orthoclase owing to mixing between the felsic and mafic magmas. Such magma mixing event produces a heterogeneous system that is in an extreme state of disequilibrium and facilitates the epitaxial growth of one feldspar on another. On the other hand, the larger MME of our study domain shows limited interaction with the felsic host as indicated by the replacement of clinopyroxene crystals by amphibole and biotite.
文摘Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing countries.Atmospheric radiocarbon represents an important observational constraint and utilized to trace fossil fuel derived CO_(2)(CO_(2ff))in the atmosphere.For the first time,we have presented a detailed analysis on the spatial distribution of fossil fuel derived CO_(2)(CO_(2ff))over India using radiocarbon(Δ14C)measurements during three-year period.Analysis shows that theΔ14C values are varying between 29.33‰ to-34.06‰ across India in the year 2017,where highest value belongs to a location from Gujarat while lowest value belongs to a location from Chhattisgarh.Based on the14C patterns,spatial distributions of CO_(2ff) mole fractions have been determined over India and the calculated values of CO_(2ff) mole fractions are varying between 4.85 ppm to 26.59 ppm across India.It is also noticed that the highest CO_(2ff) mole fraction is observed as 26.59 ppm from a site in Chhattisgarh.CO_(2ff) mole fraction values from four high altitude sites are found to be varied between 4.85 ppm to 14.87 ppm.Effect of sampling different crop plants from the same growing season and different crop plant organs(grains,leaves,stems)on theΔ14C and CO_(2ff) have been studied.Annual and intra seasonal variations in theΔ14C and CO_(2ff) mole fractions have also been analyzed from a rural location(Dholpur,Rajasthan).
基金the funding received from the Science and Engineering Research Board (SERB), Govt. of India under GAP 3291funded by Ministry of Earth Science (MoES) with project reference number Mo ES/ P.O. (Seismic) 8 (09)-Geochron/2012。
文摘Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydrous uvarovite garnet having Cr_(2)O_(3) upto 19.66 wt% and CaO of 32.12–35.14 wt% in the serpentinized mantle peridotites of Naga Hills Ophiolite(NHO), India. They occur in association with low-Cr diopsides. They are enriched in LILE(Ba, Sr), LREEs, with fractionating LREE-MREE [avg.(La/Sm)_(N) = 2.16] with flat MREE/HREE patterns [avg.(Sm/Yb)_(N) = 0.95]. Raman spectra indicate the presence of hydroxyl(OH^(–)) peaks from 3500 to 3700 cm^(-1). Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low-Cr diopsides by hydrothermal slab fluids. The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low-p H solution. The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet, and their origin is attributed to the fluid-induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime.
基金the financial support received from the Department of Science and Technology,India through DST-INSPIRE Faculty scheme(DST/INSPIRE/04/2015/001572).
文摘Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap signatures at similar temperature regimes.Electron traps are found to be within the values:0.05–1.2 eV from the conduction band edge whereas the hole traps 1.37–2.66 eV from the valence band edge on the SBDs.In the lower temperature regime,the deeper electron traps contribute to the capacitance transients with increasing r values,whereas at the higher temperatures>300 K,a slow variation of the trap levels(both electrons and holes)is observed when r is varied.These traps are found to be mainly contributed to dislocations,interfaces,and vacancies within the structure.
基金DRDO,UGC and DST for financial support under SAP and FIST program,respectively
文摘Variation of nonlinear optical properties with surface roughness of ZnO thin films deposited on coming glass substrates at different annealing temperature （TA） was reported. The films were characterized by X-ray diffraction （XRD）, UV-Vis-NIR transmission and single beam z-scan technique using second harmonics of Nd：YAG laser. Surface morphology of the samples was investigated by atomic force microscopy （AFM）. Surface roughness was found minimum （8.4 nm） for ZnO sample annealed at 450℃. The nonlinear optical properties （NLO） were found to be dependent on surface roughness and the highest value of third order nonlinear susceptibility （X（3）=4.3x 10-7 esu） was obtained for ZnO at TA 450℃.
文摘The study of radiation damage of high- molecular weight substances due to MeV ion interactions is of interest for engineering and scientific applications. In the present study polystyrene (PS) was irradiated with 107Ag ions of three different charge states (q) 11+, 14+ and 25+ and of 130 MeV energy. The emission of hydrogen from PS was monitored as a function of the incident ion fluence. The experimental results showed that the hydrogen depletion per incident ion from PS varies as qn, where n was found to be 2.1 as compared to the value 2.7 to 3.0 reported in the literature. Radii of the nanometric damaged zones or ion tracks formed were analyzed from the slope of the hydrogen depletion versus ion fluence curves as a function of charge state of incident ion. These have values between 3.2 - 6.8 nm. These radii were found to depend upon the charge state of the incident ion and vary as qm, where m has the value 0.9.
文摘The role of deposition rate in the structural, optical and electrical properties of SnOthin films deposited by electron beam evaporation method is investigated by varying the deposition powers viz. 50, 75, and 100 W.The structural characterization of the films is done by X-ray diffraction(XRD) technique. The surface morphology of the films is studied by scanning electron microscopy(SEM). Rutherford back scattering(RBS) measurements revealed the thickness of the films ranging from 200 nm to 400 and also a change in the concentration of oxygen vacancies which is found to be the maximum in the film deposited at the lowest deposition rate. Optical absorption spectrum is recorded using the UV–V is spectroscopy and the films are found to be transparent in nature. A shift in the absorption edge is observed and is attributed to a different level of allowed energy states in conduction band minimum. The Hall effect and electrical measurements show a variation in the carrier concentrations, mobility and resistivity of the films. In order to explore a better compromise in electrical and optical properties for transparent electrode applications, skin depths calculations are also done to find the optimized values of carrier concentration and mobility.
基金the contribution of the INGA collaboration,which is partially funded by the Department of Science and Technology(DST,GoIproject no.IR/S2/PF-03/2003-I)+4 种基金University Grants Commission(UGC)supported by IUAC,New Delhi(Grant No.IUAC/XIII/7/UFR-63302)financial support from the University Grants Commission(UGC),Indiathe Department of Science and Technology,Govt.of India for providing financial support under Project no.CRG/2019/004960 to carry out a part of the research workthe financial support received from SERB,INDIA under N-PDF scheme vide reference no.PDF/2022/001829
文摘The neutron deficient Xe nuclei with A≈120 are predicted to have strong octupole correlation at low spins.In the present study,an attempt was made to improve upon the level scheme and also to examine the signatures of octupole correlation in^(118)xe via high spin γ-ray spectroscopy.High spin states in^(118)Xe have been populated via the^(93)Nb(^(28)Si,p2n)^(118)Xe fusion-evaporation reaction at a beam energy of 115 MeV provided by the 15 UD pelletron accelerator facility at IUAC,New Delhi.In the experiment,seven newγ-transitions have been found and placed appropriately in the level scheme.A theoretical study using the triaxial projected shell model(TPSM)approach suggests that the first bandcrossing is due to the alignment of two neutrons,and a parallel band tracking the yrast configuration is the γ-band built on the two-quasiparticle state.Enhanced E1 transition rates measured between opposite parity bands involving vh_(11/2)and vd_(5/2)orbitals having△j=△l=3 indicate the presence of octupole correlation in this nucleus.
