The Arctic sedimentary basins are still poorly studied in comparison with other regions. The lack of deep wells across the eastern Russian Arctic has resulted in numerous contrasting geodynamic models for the geological evolution and age of sedimentary successions within this frontier region, where a modern mid-ocean ridge breaks through the continental crust in the Laptev Sea. The only onshore evidence of rifting processes is a number of small graben-like depressions exposed on the New Siberian Islands and along the Laptev Sea coast. We present U-Pb detrital zircon provenance and palynology study results of the Cenozoic sedimentary rocks filling graben-like depressions across western Kotel’nyi Island. Palynological data indicate that these sedimentary rocks are Early Eocene to Pleistocene in age. Based on U-Pb detrital zircon dating, Early Eocene and Late Oligocene clastic sediments were sourced from underlying deformed Palaeozoic rocks as well as by reworking of Upper Mesozoic rocks outcropping elsewhere on Kotel’nyi Island, which bear Siberian signature. Plio-Pleistocene clastic sediments were not derived from the erosion of deformed Palaeozoic rocks, suggesting the cessation of active uplift by this time and the development of a regional peneplain. Therefore, by extrapolating our onshore observations to the neighbouring offshore, we propose that graben structures imaged by seismic profiles along the eastern flank of the Laptev Rift System are likely to host Eocene and Oligocene sediments. Thus, it implies the Cenozoic extension led to formation of grabens on- and offshore in the eastern portion of Laptev Sea as early as Eocene. Further studies are necessary to evaluate the age of graben-related basins in the central and western part of the Laptev Sea.
A new shallow layer laboratory model of global atmospheric circulation is realised and studied by experiments and numerical simulations. A shallow rotating cylindrical fluid layer of 30 mm thickness and 690 mm diameter, with a localised heater at the bottom periphery and localised cooler in the central part of the upper boundary is considered. The rim heater imitates the equator heating and disc cooler – the North pole cooling. The flow transforms from the Hadley-like regime to the baroclinic wave regime through transitional states. The decrease in the thermal Rossby number for the fixed value of Taylor number results in the regularisation of the baroclinic waves. All wave regimes, even with regular wave structures, are characterised by strong non-periodic fluctuations. The observed baroclinic wave structures are a combination of temporarily evolving different baroclinic modes. The important outcome of the shallow layer model is a realisation of the Earth-like meridional three-cell structure. It is shown that the three-cell structure with analogs of polar, Ferrel and Hadley cells exist only in a limited range of parameters. A comparison of the results for the water and silicon oil demonstrated that the physical properties of the fluid can have a strong impact on the baroclinic wave structure.
We describe the calibration and imaging heuristics developed and deployed inthe ALMA interferometric data processing pipeline, as of ALMA Cycle 9. Thepipeline software framework is written in Python, with each data reductionstage layered on top of tasks and toolkit functions provided by the CommonAstronomy Software Applications package. This framework supports a variety oftasks for observatory operations, including science data quality assurance,observing mode commissioning, and user reprocessing. It supports ALMA and VLAinterferometric data along with ALMA and NRO45m single dish data, via differentstages and heuristics. In addition to producing calibration tables, calibratedmeasurement sets, and cleaned images, the pipeline creates a WebLog whichserves as the primary interface for verifying the data quality assurance by theobservatory and for examining the contents of the data by the user. Followingthe adoption of the pipeline by ALMA Operations in 2014, the heuristics havebeen refined through annual development cycles, culminating in a new pipelinerelease aligned with the start of each ALMA Cycle of observations. Initialdevelopment focused on basic calibration and flagging heuristics (Cycles 2-3),followed by imaging heuristics (Cycles 4-5), refinement of the flagging andimaging heuristics with parallel processing (Cycles 6-7), addition of themoment difference analysis to improve continuum channel identification (2020release), addition of a spectral renormalization stage (Cycle 8), andimprovement in low SNR calibration heuristics (Cycle 9). In the two most recentCycles, 97% of ALMA datasets were calibrated and imaged with the pipeline,ensuring long-term automated reproducibility. We conclude with a briefdescription of plans for future additions, including self-calibration,multi-configuration imaging, and calibration and imaging of full polarizationdata.
A new version of quantum hashing technique is developed wherein a quantumhash is constructed as a sequence of single-photon high-dimensional states(qudits). A proof-of-principle implementation of the high-dimensional quantumhashing protocol using orbital-angular momentum encoding of single photons isimplemented. It is shown that the number of qudits decreases with increase oftheir dimension for an optimal ratio between collision probability and decodingprobability of the hash. Thus, increasing dimension of information carriersmakes quantum hashing with single photons more efficient.
Thin galactic discs and nuclear stellar discs (NSDs) are fragile structuresthat can be easily disturbed by merger events. By studying the age of thestellar populations in present-day discs, we can learn about the assemblyhistory of galaxies and place constraints on their past merger events.Following on the steps of our initial work, we explore the fragility of suchdisc structures in intermediate-mass-ratio dry encounters using the previouslyconstructed $N$-body model of the Fornax galaxy NGC 1381 (FCC 170), which hostsboth a thin galactic disc and a NSD. We dismiss major and minor encounters, asthe former were previously shown to easily destroy thin-disc structures,whereas the latter take several Hubble times to complete in the specific caseof FCC 170. The kinematics and structure of the thin galactic disc aredramatically altered by the mergers, whereas the NSD shows a remarkableresilience, exhibiting only a smooth increase of its size when compared to themodel evolved in isolation. Our results suggest that thin galactic discs arebetter tracers for intermediate-mass-ratio mergers, while NSDs may be moreuseful for major encounters. Based on our simulations and previous analysis ofthe stellar populations, we concluded that FCC 170 has not experienced anyintermediate-mass-ratio dry encounters for at least $\sim$10 Gyr, as indicatedby the age of its thin-disc stellar populations.