The Faraday effect and phase transition in the CH 3 NH 3 PbI 3 halide perovskite single crystal

The spin degree of freedom of charge carriers in halide-perovskite semiconductors can be highly useful for information photonics applications. The Faraday effect is known to be the best indicator of paramagnetism of the material and of the spin-light interaction. In this work, the Faraday effect is demonstrated, for the first time, in a hybrid organic-inorganic halide perovskite MAPbI3 (MA+=CH3NH+3). The Faraday rotation and birefringence were measured across the tetragonal-cubic phase transition at 327 K. The Faraday rotation is strongly suppressed below the phase transition temperature due to anisotropy (linear birefringence) of the tetragonal crystal phase. The situation changes drastically above the phase transition temperature, when the crystal becomes optically isotropic. The emerging Faraday rotation obeys the Curie law, demonstrating its population-related paramagnetic nature. This observation opens new prospects for application of these systems and for their investigations using methods of the polarization noise spectroscopy applicable to optically anisotropic materials.Comment: 12 pages, 5 figure

Evaluation of fetal absorbed doses from computed tomography examinations of pregnant patients: A systematic review

BACKGROUND: Currently, no systematic data are available on fetal radiation exposure as a result of radiographic studies during pregnancy. Consequently, there are no approved methods of its calculation that can be used in clinical practice. It is especially relevant for computed tomography scans as it is a widely used and highly informative method of diagnostic imaging associated with high exposure levels. AIM: to systematize currently available data on radiation dose absorbed by the fetus from computed tomography scans in pregnant women. MATERIALS AND METHODS: The search for publications in Russian and English was conducted in PubMed/Medline, Google Scholar and еLibrary. The final analysis included 12 papers including 8 studies using human body phantoms, 3 retrospective studies and one prospective clinical study. RESULTS: Abdominal and pelvic computed tomography scans as well as whole-body scans were found to be associated with the highest fetal radiation exposure. However, in none of the publications the fetal exposure limit was exceeded. CONCLUSION: Clinically indicated non-contrast-enhanced computed tomography scans in pregnant women are not likely to be associated with the fetal absorbed doses that exceed the limit of 100 mGy regardless of the scanned area. However, this limit might be exceeded in case of performing multiple studies or if multiphase abdominal or pelvic computed tomography scans, or whole-body computed tomography scans are performed in patients with multiple trauma. In these cases, a decision regarding the need for these investigations should be made by a multi-disciplinary team (including radiation safety specialists, diagnostic radiologists and clinicians) based on the results of additional risk assessment

Commercial Arctic shipping through the Northeast Passage:routes, resources, governance, technology, and infrastructure

The Russian and Norwegian Arctic are gaining notoriety as an alternative maritime route connecting the Atlantic and Pacific Oceans and as sources of natural resources. The renewed interest in the Northeast Passage or the Northern Sea Route is fueled by a recession of Arctic sea ice coupled with the discovery of new natural resources at a time when emerging and global markets are in growing demand for them. Driven by the expectation of potential future economic importance of the region, political interest and governance has been rapidly developing, mostly within the Arctic Council. However, this paper argues that optimism regarding the potential of Arctic routes as an alternative to the Suez Canal is overstated. The route involves many challenges: jurisdictional disputes create political uncertainties; shallow waters limit ship size; lack of modern deepwater ports and search and rescue (SAR) capabilities requires ships to have higher standards of autonomy and safety; harsh weather conditions and free-floating ice make navigation more difficult and schedules more variable; and more expensive ship construction and operation costs lessen the economic viability of the route. Technological advances and infrastructure investments may ameliorate navigational challenges, enabling increased shipping of natural resources from the Arctic to global markets.Albert Buixadé Farré, Scott R. Stephenson, Linling Chen, Michael Czub, Ying Dai, Denis Demchev, Yaroslav Efimov, Piotr Graczyk, Henrik Grythe, Kathrin Keil, Niku Kivekäs, Naresh Kumar, Nengye Liu, Igor Matelenok, Mari Myksvoll, Derek O'Leary, Julia Olsen, Sachin Pavithran.A.P., Edward Petersen, Andreas Raspotnik, Ivan Ryzhov, Jan Solski, Lingling Suo, Caroline Troein, Vilena Valeeva, Jaap van Rijckevorsel and Jonathan Wightin

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The International Bathymetric Chart of the Southern Ocean Version 2 (IBCSO v2)

The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation – GEBCO Seabed 2030 Project supporting the goal of mapping the world’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50°S