• Volume 124, Issue 5

      July 2015,   pages  909-1141

    • Geomorphological evolution of badlands based on the dynamics of palaeo-channels and their implications

      V Ranga S N Mohapatra P Pani

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      The badlands along the lower Chambal valley represent the worst case of water erosion in India. These badlands are believed to have developed due to neo-tectonic activities and, probably, strengthening of southwest monsoon in late Pleistocene–Holocene. Due to neo-tectonic activities, the Chambal River has undergone many changes before reaching to its present planform. This study reports palaeo-channels on the Chambal River’s right flank along its lower reaches. Salient features of the palaeo-channels and their relation to present spatial pattern of badlands are studied. These palaeo-channels have significantly influenced the development of badlands along the lower Chambal River and have given them distinct and conspicuous spatial patterns. In the light of the evidences, a modified schematic geomorphic evolution of badlands development is also proposed starting from a pre-incision scenario till the present day situation. A major modification in the proposed model is the multi-channel planform of the Chambal River before its incision.

    • Water use efficiency of net primary production in global terrestrial ecosystems

      Lei Xia Fei Wang Xingmin Mu Kai Jin Wenyi Sun Peng Gao Guangju Zhao

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      The carbon and water cycles of terrestrial ecosystems, which are strongly coupled via water use efficiency (WUE), are influenced by global climate change. To explore the relationship between the carbon and water cycles and predict the effect of climate change on terrestrial ecosystems, it is necessary to study the WUE in global terrestrial ecosystems. In this study, the 13-year WUE (i.e., net primary production (NPP)/evapotranspiration (ET)) of global terrestrial ecosystems was calculated based on the Moderate Resolution Imaging Spectro-radiometer (MODIS) NPP (MOD17A3) and ET (MOD16A3) products from 2000 to 2012. The results indicate that the annual average WUE decreased but not significantly, and the 13-year mean value was 868.88 mg C m−2 mm−1. The variation trend of WUE value for each pixel differed greatly across the terrestrial ecosystems. A significant variation (𝑃 < 0.05) occurred in about 18.50% of the land surface. WUE was spatially distributed from 0 to 2541 mg C m−2 mm−1, and 58.78% of the WUE values were concentrated in the interval of 600–1200 mg C m−2 mm−1. The WUE increased from north to south in Africa and Oceania and from east to west in Europe and South America. Both latitudinal and longitudinal gradients existed in Asia and North America. The following trends in the WUE of different continents and Köppen–Geiger climates were observed: Europe (1129.71 mg C m−2 mm−1) > Oceania (1084.46 mg C m−2 mm−1) > Africa (893.51 mg C m−2 mm−1) > South America (893.07 mg C m−2 mm−1) > North America (870.79 mg C m−2 mm−1) > Asia (738.98 mg C m−2 mm−1) and warm temperate climates (1094 mg C m−2 mm−1) > snowy climates (862 mg C m−2 mm−1) > arid climates (785 mg C m−2 mm−1) > equatorial climates (732 mg C m−2 mm−1) > polar climates (435 mg C m−2 mm−1). Based on the WUE value and the present or future rainfall, the maximum carbon that fixed in one region may be theoretically calculated. Also, under the background of global climatic change, WUE may be regarded as an important reference for allotting CO2 emissions offsets and carbon transactions.

    • Application of ANN and fuzzy logic algorithms for streamflow modelling of Savitri catchment

      Mahesh Kothari K D Gharde

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      The streamflow prediction is an essentially important aspect of any watershed modelling. The black box models (soft computing techniques) have proven to be an efficient alternative to physical (traditional) methods for simulating streamflow and sediment yield of the catchments. The present study focusses on development of models using ANN and fuzzy logic (FL) algorithm for predicting the streamflow for catchment of Savitri River Basin. The input vector to these models were daily rainfall, mean daily evaporation, mean daily temperature and lag streamflow used. In the present study, 20 years (1992–2011) rainfall and other hydrological data were considered, of which 13 years (1992–2004) was for training and rest 7 years (2005–2011) for validation of the models. The mode performance was evaluated by R, RMSE, EV, CE, and MAD statistical parameters. It was found that, ANN model performance improved with increasing input vectors. The results with fuzzy logic models predict the streamflow with single input as rainfall better in comparison to multiple input vectors. While comparing both ANN and FL algorithms for prediction of streamflow, ANN model performance is quite superior.

    • Water–rock interaction on the development of granite gneissic weathered profiles in Garhwal Lesser Himalaya, India

      S Vyshnavi R Islam

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      The development and sustainability of weathered profiles are very difficult in the Himalaya due to its complex lithology, tectonic history and fast erosion. Despite this, two weathered profiles namely WPa (weathered profile a) and WPb (weathered profile b) which have sustained erosion are developed on porphyry granite gneiss and granite gneissic lithology in Alaknanda valley of the Garhwal Lesser Himalaya. Systematic sampling of these two weathered profiles was done from bottom to top and they were chemically analysed to understand the elemental mobility in each profile. Major, trace and rare earth element studies show dissimilar behaviour with the advancement of weathering. In WPa profile, the CIA value of LAR (LAR) is 50 which reveals that the rock has not suffered any alteration but in WPb profile, the CIA value of LAR is 64 which indicates significant amount of chemical alteration. A–CN–K projection also exhibits similar behaviour. Further, the relative mobility of all the major and trace elements show variable elemental distribution in both the profiles. Enrichment of Mg, Fe, Ti, Al, Co, Ni, Zr, LREE and depletion of Na, K, P, Ca, Si, LILE and HFSE are observed in WPa profile; while the depletion of Na, K, Ca, P, Si, HREE and enhancement of Fe, Mn, Ti, Sc, Co, Zr, LREE are noticed in WPb profile. The rare earth elements also show a dissimilar mobilization pattern in both the profiles due to their strong dependency on lithology, and corresponding climate and tectonic interaction. Contrasting elemental mobility in both the profiles depict the major role in disparity of lithological characters and subsequent development of fractures produced by the major thrust system (Ramgarh thrust) which made an easy passage for rain water, thus causing the development of a chemically altered profile in the Lesser Himalayan region. Further, the present study infers the climate and tectonic milieu which is responsible for the development of such weathered profiles in Himalayan sector.

    • Deciphering groundwater quality for irrigation and domestic purposes – a case study in Suri I and II blocks, Birbhum District, West Bengal, India

      Shreya Das S K Nag

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      Assessment of the hydrochemical characteristics of water and aquifer hydraulic properties is important for groundwater planning and management in the study area. It is not only the basic need for human existence but also a vital input for all development activities. The present hydro-geochemical study of groundwater samples from the Suri I and II blocks of Birbhum district, West Bengal (23.76°–23.99°N; 87.42°–87.64°E) was carried out to assess their suitability for agricultural, domestic and drinking purposes. For this study, samples were collected from 26 locations during the post-monsoon and pre-monsoon sessions spanning over 2012 and 2013. Groundwater samples were analyzed for their physical and chemical properties using standard laboratory methods.

      Physical and chemical parameters of groundwater such as pH, electrical conductivity, total dissolved solids, Na, K, Ca, Mg, Fe, Cl, HCO3, SO4 and F were determined. Various water quality indices like SAR, SSP, PI, RSC, MAR and KR have been calculated for each water sample to identify the irrigational suitability standard. According to most of these parameters, the groundwater has been found to be well to moderately suitable for irrigation. In the post-monsoon session exceptionally high RSC values for around 80% samples indicate an alkaline hazard to the soil. The ion balance histogram for post-monsoon indicates undesirable ion balance values according to fresh water standards whereas in pre-monsoon, the samples show good ion balance in water. For determination of the drinking suitability standard of groundwater, three parameters have been considered – total hardness (TH), Piper’s trilinear diagram and water quality index study. Groundwater of the present study area has been found to be moderately-hard to hard during both sampling sessions and hence poses no health risk which could arise due to excess consumption of calcium or magnesium. Hydrogeochemical facies in the form of Piper’s trilinear diagram plot which helps in identification of the water ‘type’ which can render a particular taste or odour to water, indicates that groundwater in the study area is majorly of CaMgHCO3 and NaHCO3 type (fresh type) during both post-monsoon and pre-monsoon sessions barring a couple of samples which are of CaMgSO4/CaMgClSO4 type in pre-monsoon. Water quality index study reveals that close to 90% of the water samples are suitable for drinking during post-monsoon compared to pre-monsoon during which period only 60% of water samples fall under the suitable drinking water category.

      Gibbs’ diagrams, which help in identification of natural processes controlling hydrogeochemistry of groundwater indicates that for both post-monsoon and pre-monsoon sessions, the overall hydrogeochemistry of the study area is dominated by rock–water interaction processes.

    • Variability in stratification and flushing times of the Gautami–Godavari estuary, India

      B Sridevi V V S S Sarma T V R Murty Y Sadhuram N P C Reddy K Vijayakumar N S N Raju Ch Jawahar Kumar Y S N Raju R Luis M D Kumar K V S R Prasad

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      In order to examine the influence of forcing (river flow and tides) and anthropogenic activities (dredging and dam regulation) on stratification, a study was conducted over a period of 19 months (June 2008–December 2009) in the Gautami–Godavari estuary (G–GE) during spring and neap tide periods covering entire spectrum of discharge over a distance of 36 km from the mouth. The bathymetry of the estuary was recently changed due to dredging of ∼20 km of the estuary from the mouth for transportation of barges. This significantly changed the mean depth and salinity of the estuary from its earlier state. The variations in the distribution of salinity in the Godavari estuary are driven by river discharge during wet period (June–November) and tides during dry period (December–May). The weak stratification was observed during high discharge (July–August) and no discharge (January–June) periods associated with dominant fresh water and marine water respectively. The strong stratification was developed associated with decrease in discharge during moderate discharge period (October–December). Relatively stronger stratification was noticed during neap than spring tides. The 15 psu isohaline was observed to have migrated ∼2–3 km more towards upper estuary during spring than neap tide suggesting more salt enters during former than latter period. Total salt content was inversely correlated with river discharge and higher salt of about 400×106 m3 psu was observed during spring than neap tide. Flushing times varied between less than a day and more than a month during peak and no discharge periods respectively with lower times during spring than neap tide. The flushing times are controlled by river discharge during high discharge period, tides during dry period and both (river discharge and tides) under moderate discharge period. This study suggests that modification of discharge, either natural due to weak monsoon, or artificial such as dam constructions and re-routing the river flow, may have significant impact on the stratification and biogeochemistry of the Godavari estuary.

    • Influence of nutrient input on the trophic state of a tropical brackish water lagoon

      D Ganguly Sivaji Patra Pradipta R Muduli K Vishnu Vardhan Abhilash K R R S Robin B R Subramanian

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      Ecosystem level changes in water quality and biotic communities in coastal lagoons have been associated with intensification of anthropogenic pressures. In light of incipient changes in Asia’s largest brackish water lagoon (Chilika, India), an examination of different dissolved nutrients distribution and phytoplankton biomass, was conducted through seasonal water quality monitoring in the year 2011. The lagoon showed both spatial and temporal variation in nutrient concentration, mostly altered by fresh-water input, regulated the chlorophyll distribution as well. Dissolved inorganic N:P ratio in the lagoon showed nitrogen limitation in May and December, 2011. Chlorophyll in the lagoon varied between 3.38 and 17.66 mg m−3. Spatially, northern part of the lagoon showed higher values of DIN and chlorophyll during most part of the year, except in May, when highest DIN was recorded in the southern part. Statistical analysis revealed that dissolved NH$^{+}_{4}$–N and urea could combinedly explain 43% of Chlorophyll-𝑎 (Chl-𝑎) variability which was relatively higher than that explained by NO$^{-}_{3}$–N and NO$^{-}_{2}$–N (12.4%) in lagoon water. Trophic state index calculated for different sectors of the lagoon confirmed the inter-sectoral and inter-seasonal shift from mesotrophic to eutrophic conditions largely depending on nutrient rich freshwater input.

    • Provenance analysis of the Oligocene turbidites (Andaman Flysch), South Andaman Island: A geochemical approach

      P C Bandopadhyay Biswajit Ghosh

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      The Oligocene-aged sandstone-shale turbidites of the Andaman Flysch are best exposed along the east coast of the South Andaman Island. Previously undocumented sandstone-shale geochemistry, investigated here, provides important geochemical constraints on turbidite provenance. The average 70.75 wt% SiO2, 14.52 wt% Al2O3, 8.2 wt% Fe2O$^{\text{t}}_{3}$+MgO and average 0.20 Al2O3/SiO2 and 1.08 K2O/Na2O ratios in sandstones, compare with quartzwackes. The shale samples have average 59.63 wt% SiO2, 20.29 wt% Al2O3, 12.63 wt% Fe2O$^{\text{t}}_{3}$+MgO and average 2.42 K2O/Na2O and 0.34 Al2O3/SiO2 ratios. Geochemical data on CaO–Na2O–K2O diagram fall close to a granite field and on K2O/Na2O–SiO2 diagram within an active continental margin tectonic setting. The range and average values of Rb and Rb/Sr ratios are consistent with acid-intermediate igneous source rocks, while the values and ratios for Cr and Ni are with mafic rocks. Combined geochemical, petrographic and palaeocurrent data indicate a dominantly plutonic-metamorphic provenance with a lesser contribution from sedimentary and volcanic source, which is possibly the Shan–Thai continental block and volcanic arc of the north-eastern and eastern Myanmar. Chemical index of alteration (CIA) values suggests a moderate range of weathering of a moderate relief terrane under warm and humid climate.

    • No evidence for shallow shear motion on the Mat Fault, a prominent strike slip fault in the Indo-Burmese wedge

      R P Tiwari V K Gahalaut Ch U B Rao C Lalsawta B Kundu Malsawmtluanga

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      The motion between India and Sunda plates is accommodated along the Churachandpur Mao Fault (CMF) in the Indo-Burmese Wedge (IBW) and Sagaing Fault in the Myanmar region. Within the IBW, the Mat Fault is the most prominent transverse structure with prominent topographic and geomorphic expressions. We undertook Global Positioning System (GPS) measurements across this fault to investigate the current deformation across it. Modelling of these observations using locking depth of up to 4 km yields no resolvable slip (dextral slip rate as 0±5 mm/year) across the fault. Due to limited spatial extent of the GPS measurements, it is not possible to comment on the status of deeper slip, if any.

    • An application of earthquake prediction algorithm M8 in eastern Anatolia at the approach of the 2011 Van earthquake

      Masoud Mojarab Vladimir Kossobokov Hossein Memarian Mehdi Zare

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      On 23rd October 2011, an M7.3 earthquake near the Turkish city of Van, killed more than 600 people, injured over 4000, and left about 60,000 homeless. It demolished hundreds of buildings and caused great damages to thousand others in Van, Ercis, Muradiye, and Çaldıran. The earthquake’s epicenter is located about 70 km from a preceding M7.3 earthquake that occurred in November 1976 and destroyed several villages near the Turkey–Iran border and killed thousands of people. This study, by means of retrospective application of the M8 algorithm, checks to see if the 2011 Van earthquake could have been predicted. The algorithm is based on pattern recognition of Times of Increased Probability (TIP) of a target earthquake from the transient seismic sequence at lower magnitude ranges in a Circle of Investigation (CI). Specifically, we applied a modified M8 algorithm adjusted to a rather low level of earthquake detection in the region following three different approaches to determine seismic transients. In the first approach, CI centers are distributed on intersections of morphostructural lineaments recognized as prone to magnitude 7+ earthquakes. In the second approach, centers of CIs are distributed on local extremes of the seismic density distribution, and in the third approach, CI centers were distributed uniformly on the nodes of a 1°×1° grid. According to the results of the M8 algorithm application, the 2011 Van earthquake could have been predicted in any of the three approaches. We noted that it is possible to consider the intersection of TIPs instead of their union to improve the certainty of the prediction results. Our study confirms the applicability of a modified version of the M8 algorithm for predicting earthquakes at the Iranian–Turkish plateau, as well as for mitigation of damages in seismic events in which pattern recognition algorithms may play an important role.

    • Organic richness and gas generation potential of Permian Barren Measures from Raniganj field, West Bengal, India

      Annapurna Boruah S Ganapathi

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      The organic geochemistry of shales in terms of its organic richness, hydrocarbon source potential, thermal maturity, depositional environment, etc., are essential stipulations for shale gas resources assessment. In this study, a total of 32 core samples of Permian Barren Measures from four boreholes in Raniganj field of Damodar Basin were analysed to evaluate their gas generation potential using Rock–Eval pyrolysis techniques. Petrographic analysis brings out the lithofacies of Barren Measures as carbonaceous silty shale, iron rich claystone and sand-shale intercalation. The total organic content (TOC) of the shale units of Barren Measures ranges from 3.75 to 20.9 wt%, whereas hydrogen index (HI) ranges from 58.45 to 125.34 mg HC/g TOC. Present study suggests early to late maturated (0.6–1%) organic matters in Barren Measures with gas prone type III kerogen. The study analysed the effect of burial history on the preservation and maturation of organic matters. The organic richness, kerogen type, thermal maturity and petrographic properties of Barren Measures signify fair to excellent gas generation potential.

    • ArcGIS studies and field relationships of Paleoproterozoic mafic dyke swarms from the south of Devarakonda area, Eastern Dharwar Craton, southern India: Implications for their relative ages

      Amiya K Samal Rajesh K Srivastava Lokesh K Sinha

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      Google Earth Image and cross-cutting field relationships of distinct Paleoproterozoic mafic dykes from south of Devarakonda area in the Eastern Dharwar Craton has been studied to establish relative emplacement ages. The Devarakonda, covering an area of ∼700 km2, shows spectacular cross-cutting field relationships between different generations of mafic dykes, and is therefore selected for the present study. Although some recent radiometric age data are available for distinct Paleoproterozoic mafic dykes from the Eastern Dharwar Craton, there is no analogous age data available for the study area. Therefore, relative age relationships of distinct mafic dykes have been established for the study area using cross-cutting field relationships and GIS techniques, which shows slightly different picture than other parts of the Eastern Dharwar Craton. It is suggested that NE–SW trending mafic dykes are youngest in age (probably belong to ∼1.89 Ga dyke swarm), whereas NNW–SSE trending mafic dykes have oldest emplacement age. Further, the NNW–SSE mafic dykes are older to the other two identified mafic dyke swarms, i.e., WNW–ESE (∼2.18 Ga) and N–S trending (∼2.21 Ga) mafic dyke swarms, as dykes of these two swarms cross-cut a NNW–SSE dyke. It provides an evidence for existence of a new set of mafic dykes that is older to the ∼2.21 Ga and probably younger to the ∼2.37 Ga swarm. Present study also supports existence of two mafic dyke swarms having similar trend (ENE–WSW to NE–SW) but emplaced in two different ages (one is ∼2.37 Ga and other ∼1.89 Ga).

    • Attribute of trace fossils of Laisong flysch sediments, Manipur, India

      Kumar S Khaidem Hemanta S Rajkumar Ibotombi Soibam

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      The depositional basin in which the Late Eocene–Early Oligocene Laisong flysch sediments Barail Group, Manipur region (Indo-Myanmar ranges) have been deposited is generally considered to be of deep marine environment. However, field observation indicates the presence of many shallow environment signature characteristics of marginal to sublittoral marine settings, in addition to the general occurrence of deep marine turbidites. To address this aspect, ichnological analyses of the Laisong Formation has been attempted for elucidating palaeoenvironmental setting prevalent during the deposition of these sediments. Presence of 36 ichnospecies belonging to 33 ichnogenera has so far been identified. The ichnospecies may be grouped into different ichnofacies such as Skolithos–Cruziana mixed ichnofacies, Cruziana ichnofacies, Skolithos ichnofacies, Zoophycos ichnofacies, Nereites ichnofacies and Teredolites ichnofacies which decrease in abundance in this order of sequence with Skolithos–Cruziana mixed ichnofacies being the most dominant. The above-mentioned ichnofacies are found associated with sedimentary structures such as large sole marks, parallel laminations, massive and structureless beds, rip-up clasts, etc., which are characteristics of submarine fan deposits below the storm wave base and current ripples, herringbone structures, hummocky cross stratifications, pot casts, rain prints, etc., that marked shallow marginal marine setting such as tidal flats, deltas and shoreface. With such observations it is very likely that the Laisong sediments were formed in a tectonically active basin with varied bathymetric ranges indicating alternate transgressive and regressive nature.

    • Effects of geomagnetic storm on low latitude ionospheric total electron content: A case study from Indian sector

      Monti Chakraborty Sanjay Kumar Barin Kumar De Anirban Guha

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      The effect of geomagnetic storms on low latitude ionosphere has been investigated with the help of Global Positioning System Total Electron Content (GPS-TEC) data. The investigation has been done with the aid of TEC data from the Indian equatorial region, Port Blair (PBR) and equatorial ionization anomaly region, Agartala (AGR). During the geomagnetic storms on 24th April and 15th July 2012, significant enhancement up to 150% and depression up to 72% in VTEC is observed in comparison to the normal day variation. The variations in VTEC observed from equatorial to EIA latitudes during the storm period have been explained with the help of electro-dynamic effects (prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF)) as well as mechanical effects (storm-induced equatorward neutral wind effect and thermospheric composition changes). The current study points to the fact that the electro-dynamic effect of geomagnetic storms around EIA region is more effective than at the lower latitude region. Drastic difference has been observed over equatorial region (positive storm impact) and EIA region (negative storm impact) around same longitude sector, during storm period on 24th April. This drastic change as observed in GPS-TEC on 24th April has been further confirmed by using the O/N2 ratio data from GUVI (Global Ultraviolet Imager) as well as VTEC map constructed from IGS data. The results presented in the paper are important for the application of satellite-based communication and navigational system.

    • Dust storm detection using random forests and physical-based approaches over the Middle East

      Amir Hossein Souri Sanaz Vajedian

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      Dust storms are important phenomena over large regions of the arid and semi-arid areas of the Middle East. Due to the influences of dust aerosols on climate and human daily activities, dust detection plays a crucial role in environmental and climatic studies. Detection of dust storms is critical to accurately understand dust, their properties and distribution. Currently, remotely sensed data such as MODIS (Moderate Resolution Imaging Spectroradiometer) with appropriate temporal and spectral resolutions have been widely used for this purpose. This paper investigates the capability of two physical-based methods, and random forests (RF) classifier, for the first time, to detect dust storms using MODIS imagery. Since the physical-based approaches are empirical, they suffer from certain drawbacks such as high variability of thresholds depending on the underlying surface. Therefore, classification-based approaches could be deployed as an alternative. In this paper, the most relevant bands are chosen based on the physical effects of the major classes, particularly dust, cloud and snow, on both emissive infrared and reflective bands. In order to verify the capability of the methods, OMAERUV AAOD (aerosol absorption optical depth) product from OMI (Ozone Monitoring Instrument) sensor is exploited. In addition, some small regions are selected manually to be considered as ground truth for measuring the probability of false detection (POFD) and probability of missing detection (POMD). The dust class generated by RF is consistent qualitatively with the location and extent of dust observed in OMERAUV and MODIS true colour images. Quantitatively, the dust classes generated for eight dust outbreaks in the Middle East are found to be accurate from 7% and 6% of POFD and POMD respectively. Moreover, results demonstrate the sound capability of RF in classifying dust plumes over both water and land simultaneously. The performance of the physical-based approaches is found weaker than RF due to empirical thresholds that are not always true.

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