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Active and relic marine methane‐seep sites are widely distributed globally and are distinguished by distinctive geology, biogeochemistry, and ecosystems. The discovery of methane‐seep sites in the Krishna‐Godavari (K‐G) basin has created exciting new opportunities for methane‐seep research in the Bay of Bengal. In this study, we document the occurrence of authigenic carbonates, including micro‐crystalline aragonite crust (arg‐crusts) admixed with chemosynthetic shells and high‐magnesium carbonate tubular structures (HMC‐tube), from the methane‐seep site SSD‐045/4 in the K‐G basin. The δ13C values of HMC‐tubes (−54.5 to −46.2‰) and arg‐crusts (−57.6 to −34.8‰) indicate biogenic methane as the likely carbon source. Enhanced porewater alkalinity driving carbonate precipitation may be attributed to microbial‐mediated SO₄2−‐AOM processes. Additionally, δ13C values (−35.2 ± 8‰) of the residual organic matter within the carbonates suggest a contribution of methanotrophic bacterial biomass. The δ18Ocarb values of HMC and aragonite indicate methane hydrate degassing and crystallization pathways, respectively. Pelloid‐filled burrows suggest the reworking of shallow HMC deposit by burrowing organisms, whereas the polyphase cementations (aragonite and HMC) within burrows indicate early and burial diagenetic pathways. The wide range in ΣLREE/ΣHREE ratios and Ceanom values in arg‐crusts reflect micro‐spatial variations in redox conditions, likely due to cementation occurring in both open and closed diagenetic systems. In contrast, more constrained Ceanom values and ΣLREE/ΣHREE ratios in HMC tubes suggest persistent sulfidic conditions. Overall, these findings provide insights into the pathways of carbonate formation at the K‐G basin methane‐seep site, highlighting the complex interplay of microbial processes, fluid dynamics, and diagenetic alterations. Plain Language Summary Methane cold‐seeps are regions on the seabed where methane (CH4) gas oozes out across the sediment‐water interface into the water column. Both active and inactive seepage sites are known across the oceans. Active methane seep sites expel significant quantities of methane into the seawater which influences the oceanic methane budget as well as the carbon cycle. In contrast, the preserved authigenic carbonate deposits and chemosynthetic fauna at the relic seep sites are archives of past seepage activities. The seep ecosystem comprises a variety of chemosynthetic and non‐chemosynthetic organisms, whereas the geological features include mounds, mud volcanoes, carbonate crusts, chimneys, etc. formed due to methane expulsion processes. Here, we investigate the origin of calcium carbonate structures formed in a cold seep region off the east coast of India. The carbonate structures include tubular‐shaped high magnesian carbonates (HMC) and crusts composed of aragonite minerals. These tubes and crusts archive biological and geological processes, including past variations in methane effusion and diffusion through the sediment. Tubular structures are formed by gas flow through the sediments as chimneys and by burrowing activities of benthic organisms. On the other hand, the aragonite crusts are formed where methane flow is high across the seabed. Key Points Relics of methanogenic high magnesian calcite tubes and aragonite crust recovered from cold seep site K‐G basin east coast of India HMC precipitation is confined to sulfidic conditions in contrast to a wider redox range for aragonite precipitation Reworking of unconsolidated HMC produced the pelloid rich tubular structures, whereas aragonite crust formed at high CH4 flow conditions

For air-breathing launch vehicle complex interactions exist between propulsion, aerodynamics and structural subsystems. The present work presents an adaptive guidance and control augmentation to the earlier work of integrated guidance and controller for the air-breathing phase, to enhance the robustness to parametric uncertainties and unmodelled dynamics. The integrated controller is a hybrid controller which blends the state feedback and classical controller philosophy to handle the coupling between longitudinal and lateral dynamics as well as translational and rotational dynamics of air-breathing vehicle. The adaptive control augmentation for hybrid controller is based on derivative-free adaptive law and stability aspects are verified analytically using Lyapunov functions, to increase the robustness to parameter perturbations. Further an adaptive predictor corrector guidance scheme based on all-coefficient adaptive control theory is also augmented to the optimal guidance law to re-target the vehicle to a sub-optimal trajectory for severe propulsion failure cases. Robustness of the augmented controller is demonstrated through Monte Carlo simulation and extreme parametric perturbation cases.

This paper presents the development of 6D trajectory, integrated guidance and control algorithm for winged cone hypersonic air-breathing vehicle. Trajectory models aerodynamics, scramjet-based propulsion, guidance and control subsystems for the ascent phase of flight regime addressing the various coupling issues between them. Reference trajectory is generated with optimal guidance law to command angle of attack, velocity and flight path angle. Integrated controller developed here considers the longitudinal, lateral states together with translational states to track angle of attack, velocity and flight path angle of the reference trajectory and to regulate side slip and roll angle. The hybrid controller consists of a decoupling controller based on a state feedback, to decouple input/output ensuring independent control of the output variables with separate command inputs. Further, a PID controller with compensator is designed to achieve the required stability margins in each channels which improves the robustness to parameter perturbations.

The control of heat conduction through the manipulation of phonons in solids is of fundamental interest and can be exploited in applications for thermoelectric conversion. In this context, the advent of novel semiconductor nanomaterials with high surface‐to‐volume ratio, e.g. nanowires, offer exciting perspectives, leading to significant leaps forwarding the efficiency of solid‐state thermoelectric converters after decades of stagnation. Beyond the high aspect ratio, the nanowire geometry offers unprecedented possibilities of materials combination and crystal phase engineering not achievable with 2D counterparts. In this work, the growth of long (up to 100 repetitions) wurtzite InAs/InP superlattice nanowires with homogeneous segment thicknesses is reported, with control down to the single digit of nanometer. By means of Raman scattering experiments, clear modifications of the phonon dispersion in superlattice nanowires are found, where both InAs‐like and InP‐like modes are present. The experimentally measured modes are well reproduced by density functional perturbation theory calculations. Remarkably, it is found that the phonon frequencies can be tuned by the superlattice periodicity, opening exciting perspectives for phonon engineering and thermoelectric applications. Phonons, i.e. the quanta of lattice vibrations, play a crucial role in the determination of many materials’ properties. The realization of materials with designed phonon dispersion has, therefore, a high impact on thermal as well as electronic and optoelectronic applications. Here, the tunability of the number and frequencies of phonon modes with a controlled growth of InAs–InP superlattice nanowires is demonstrated.

DFT quantum calculations using B3LYP level of theory have been done for Fe(CO) 5 and for the axial and equatorial isomers of [Fe(CO) 4 (SiX)] (X = O, S, Se, Te). The total energy analysis shows the equatorial isomer to be more stable than the axial isomer. The data obtained from the NPA and EDA analysis reveals the bonding nature of these complexes. The WBI analysis reveals the bond index of M-SiX bond. The HOMO-LUMO energy gap of the complexes obtained from the FMO analysis lies in the 3.75 to 5.52 eV range, which is lesser than that found in Fe(CO) 5 . NBO analysis shows that the Fe atom's bond contribution (in Fe-Si bond) is lesser than that of Si atom. It shows a similar contribution to the carbonyl (in Fe-C bond) group, but the contribution from C atom is higher when compared to that of the Si atom. Graphical abstract The molecular and electronic structural analysis is done computationally using DFT on the axial and equatorial isomers of [Fe(CO) 4 (SiX)] (where, X = O, S, Se, Te) as well as the parent complex Fe(CO) 5 . The NPA, NBO, EDA, CDA, and WBI analysis is done on the 8 different [Fe(CO) 4 (SiX)] complexes where the Si-X bond exists in the axial and equatorial position and they are subsequently reported.

After the successful operationalization of Polar Satellite Launch Vehicle and Geo Synchronous Launch Vehicle, the Indian Space Research Organisation is in the process of developing Reusable Launch Vehicle technologies to achieve low-cost access to space. Towards this programme, a winged body configuration was conceived, which can fly at subsonic, supersonic and hypersonic Mach number regime, re-enter into the earth's atmosphere and simulate the landing manoeuvre. The aerodynamic design, analysis and wind-tunnel testing, aerothermal and structural design, analysis and testing were carried out. Suitable solid motor with slow burn rate propellant was developed. Mission design, guidance and control schemes were implemented. In order to meet the above objectives, certain technologies and infrastructure were developed. The entire subsystems were integrated and a large number of flight measurements were made in the maiden successful flight of Reusable Launch Vehicle Technology Demonstrator in May 2016. The flight measurements and flight performance indicated that the design philosophy, testing schemes and approaches followed are in order, thus providing confidence to proceed to the next logical step in the development of Reusable Launch Vehicle Technologies.

Nearly twenty thousand wheat lines were phenotyped for the presence of leaf tip necrosis (LTN), a phenotypic trait linked to adult plant leaf rust resistance (APR) genes, viz. Lr34, Lr46 and Lr67 having pleiotropic association with multiple disease resistance genes. Thirty-six lines showed varied expression of LTN and moderate level of leaf rust severity at adult plant stage with slow rusting (disease progress at a retarded rate). Seedling resistance test (SRT) revealed susceptible and mixed infection types, a characteristic of adult plant resistance (APR) genes. Further molecular confirmation for the presence of these genes using available microsatellite markers revealed that of the 36 lines, five lines carried Lr46+ alone and five other lines carried Lr67+ alone. Seven lines carried the combination of Lr34+ and Lr67+ while six lines confirmed to carry the combination of Lr46+ and Lr67+. Remarkably three lines carried all the three APR genes, viz. Lr34+, Lr46+ and Lr67+. All these stocks can be a source of APR multiple disease resistance genes. Ten lines were not confirmed to carry any of the genes but still had LTN and SRT results showing an infection type typical of APR genes and these can be the source of identifying newer APR genes. The resistance based on minor APR genes when combined with a few additional minor genes in the background of high yielding cultivars is expected to have high level of race non-specific resistance and to be durable.

A multitude of inter-disciplinary technologies have been mastered indigenously for realizing a series of operational space launch vehicles. The vehicles range from relatively tiny Rohini sounding rockets to gigantic satellite launch vehicles, PSLV and GSLV. These vehicles now launch on demand, the entire IRS range of remote sensing satellites and communication satellites up to 2.5 tonnes, providing precise orbital injection. This article presents the evolution of the technologies, various major subsystems and their validation methodologies for these satellite launch vehicles of ISRO. An attempt has been made to present the conceptual foundations of the entire range of the accomplishments. The paper also includes a brief description of the facilities at the launch complex of ISRO. It delineates briefly the plans for developments in the near future in respect of reusable launch vehicles, and advanced facilities.