Changes in the structure and geography of tourist flows during the COVID-19 pandemic

Tourism suffered more than many other sectors amid Covid-19 travel restrictions. This article looks at the impact of the pandemic on the territorial redistribution of tourist flows in the Baltic region. The study draws on regional annual and monthly data on international and domestic tourist arrivals between 2019 and 2021, available on the websites of the statistical offices of the Baltic Region countries. The regions earlier dependent on tourist arrivals from Russia experienced the largest drop in inbound tourism during the Covid-19 pandemic. Yet, domestic tourism burgeoned in most of the region’s countries. In 2021, the most dramatic increase in domestic arrivals occurred, year on year, in the border regions of Russia’s Northwest Federal District; the growth was also notable in Finland and the Baltic States. Domestic tourist flow compensated, partially or even fully, for the decrease in inbound tourist flow in most regions. The structure of inbound tourism changed markedly during the pandemic, with the share of tourists from the Baltic States growing. The strongest rise was in some regions of southern Finland and more modest in Latvia and Lithuania

Ekonomska analiza opravdanosti upotrebe sirove nafte

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Identification and tunable optical coherent control of transition-metal spins in silicon carbide

Color centers in wide-bandgap semiconductors are attractive systems for quantum technologies since they can combine long-coherent electronic spin and bright optical properties. Several suitable centers have been identified, most famously the nitrogen-vacancy defect in diamond. However, integration in communication technology is hindered by the fact that their optical transitions lie outside telecom wavelength bands. Several transition-metal impurities in silicon carbide do emit at and near telecom wavelengths, but knowledge about their spin and optical properties is incomplete. We present all-optical identification and coherent control of molybdenum-impurity spins in silicon carbide with transitions at near-infrared wavelengths. Our results identify spin $S=1/2$ for both the electronic ground and excited state, with highly anisotropic spin properties that we apply for implementing optical control of ground-state spin coherence. Our results show optical lifetimes of $\sim$60 ns and inhomogeneous spin dephasing times of $\sim$0.3 $\mu$s, establishing relevance for quantum spin-photon interfacing.Comment: Updated version with minor correction, full Supplementary Information include

Ways of Processing of Friable Scrap Waste of Alloy AD31 for Making Semi-Finished Products and Products of Various Applications

Проведена апробация в лабораторных условиях нескольких вариантов использования сыпучих стружковых отходов из сплава системы алюминий-магний-кремний для получения полуфабрикатов и изделий различного функционального назначения, минуя традиционно применяемый плавильный передел. Разработаны общая технологическая схема и ее модификации, учитывающие особенности протекания деформационных процессов и структурных изменений в зависимости от состава компактируемого материала. Выбраны значения основных параметров, характеризующих условия осуществления каждой из входящих в общую схему операций. Для каждого случая получены опытные образцы продукции, проведены механические испытания специально отобранных образцов на растяжение и сжатие, выполнены необходимые металлографические исследования, служащие в совокупности основой для дальнейшего развития каждого из рассмотренных в работе подходовLaboratory testing of using friable chip waste of alloy system aluminum-magnesium-silicon for making semi-finished products and products of various functional application without conventionally used melting processing was carried out. The general technological scheme and its adaptation for special features of the deformation processes and structural changes depending on the composition of compacted material were created. The main parameters of each operation of the general scheme were chosen. Pilot product items were made, mechanical testing of selected samples for tension and compression and metallographic research were performed, necessary for further development of each of the above approache

Observation of linear and nonlinear light localization at the edges of moiré arrays

We observe linear and nonlinear light localization at the edges and in the corners of truncated moiré arrays created by the superposition of periodic mutually twisted at Pythagorean angles square sublattices. Experimentally exciting corner linear modes in the femtosecond-laser written moiré arrays we find drastic differences in their localization properties in comparison with the bulk excitations. We also address the impact of nonlinearity on the corner and bulk modes and experimentally observe the crossover from linear quasilocalized states to the surface solitons emerging at the higher input powers. Our results constitute the first experimental demonstration of localization phenomena induced by truncation of periodic moiré structures in photonic systems.This research is funded by the research Project No. FFUU- 2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences and partially funded by the RSF Grant No. 21-12-00096. F. Y. acknowledges support from Shanghai Outstanding Academic Leaders Plan (Grant No. 20XD1402000) and the NSFC (Grant No. 91950120). S. K. I. and L. T. acknowledge support by Grants No. CEX2019-000910-S and No. PGC2018-097035-B-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER, Fundació Cellex, Fundació Mir-Puig, and Generalitat de Catalunya (CERCA).Peer ReviewedPostprint (published version

Effect of a Porous Structure of the Carbon Sorbents from Abies Wood Lignin on Sorption of the Organic Substances of Different Nature

Изучено влияние пористой структуры углеродных сорбентов, полученных щелочной термоактивацией этаноллигнина древесины пихты, на сорбцию метиленового синего и витамина В12. Показано, что их сорбционная емкость по витамину В12 зависит от содержания в них мезопор шириной 2,00 – 3,61 нм, а по метиленовому синему – от содержания микропор шириной 1,06 – 1,95 нм. Сопоставлены изотермы сорбции исследованных маркерных веществ на сорбентах с различной пористой структурой, обсуждены их отличияEffect of porous structure of carbon sorbents, obtained by alkaline thermal activation of ethanol-lignin of abies wood,on the methylene blue and the vitamin B12 sorption was studied. It was sown that their sorption capacity for vitamin B12 depends on the content of mesopores with width 2,00–3,61 nm and formethylene blue – on the content of micropores with width 1,06 – 1,95 nm. The isotherms of sorption of the studied marker substances on sorbents with different porous structure were compared and their differences were discusse

The Effect of Thermal-Alkaline Activation of Larch Bark with NaOH on the Structure and Sorption Properties of the Obtained Active Carbons

Установлено влияние способа термощелочной активации NaOH биоуглей из коры лиственницы на формирование пористой структуры активных углей. Проведено сопоставление текстурных характеристик, морфологических и сорбционных свойств активных углей, полученных путем термощелочной активации исходной и карбонизованной коры лиственницы. Показана возможность регулирования текстурных, морфологических и адсорбционных свойств активных углей путем вариации способа термохимической активации коры. Наиболее эффективное развитие пористой структуры активных углей наблюдалось при активации NaOH коры лиственницы, подвергнутой карбонизации при температурах 400 и 600 °C. Удельная поверхность этих образцов составляет 546 и 501 м2/г соответственно. Активные угли, полученные термощелочной активацией (800 °C, 10 % и 20 % NaOH) исходной коры лиственницы, имеют менее развитую удельную поверхность (260 м2/г и 380 м2/г соответственно). Предварительная карбонизация коры также способствует повышению более чем вдвое выхода активированных активных углей (61.3–83.2 мас%) по сравнению с их выходом при использовании исходной коры (29.6–32.4 мас%). Методом СЭМ установлено, что морфология активных углей из коры лиственницы зависит от способа их получения. Лучшую адсорбционную способность по отношению к бензолу (350 мг/г) демонстрирует образец активного угля, полученный щелочной активацией коры, предварительно карбонизованной при 400 °C, а по сорбции метиленового синего (94 мг/г) – образец активного угля, полученный из коры, карбонизованной при 600 °CThe influence of the method of thermal-alkaline activation of biochars from larch bark with NaOH on the formation of the porous structure of active carbons was established. A comparison was made of the textural characteristics and sorption properties of the active carbon samples obtained by thermal-alkaline activation of the original and carbonized larch bark. The possibility of regulation of the textural, morphological and sorption properties of active carbons by varying the method of thermal alkaline activation of the bark is shown. The most effective development of the porous structure of active carbons was observed after thermal-alkaline activation (800 °C, 20 % NaOH) of larch bark subjected to carbonization at temperatures 400 °C and 600 °C. The specific surface area of these samples reaches to 546 m2/g and 501 m2/g, respectively. Active carbons obtained by thermal-alkaline activation (800 °C, 10 % and 20 % NaOH) of the original bark have less developed specific surface area (260 and 380 m2/g, respectively). Pre-carbonization of the bark also helps to increase more than double the yield of active carbons (61.3–83.2 % wt.) compared their yield from non-carbonized bark (29.6–32.4 % wt.). The best adsorption capacity in relation to benzene (350 mg/g) is demonstrated by a sample of active carbon obtained by thermal-alkaline activation of bark, pre-carbonized at 400 °C, and in terms of methylene blue sorption (94 mg/g) – by a sample obtained from bark pre-carbonized at 600 °

Spin-relaxation times exceeding seconds for color centers with strong spin-orbit coupling in SiC

Spin-active color centers in solids show good performance for quantum technologies. Several transition-metal defects in SiC offer compatibility with telecom and semiconductor industries. However, whether their strong spin-orbit coupling degrades their spin lifetimes is not clear. We show that a combination of a crystal-field with axial symmetry and spin-orbit coupling leads to a suppression of spin-lattice and spin-spin interactions, resulting in remarkably slow spin relaxation. Our optical measurements on an ensemble of Mo impurities in SiC show a spin lifetime T-1 of 2.4 s at 2 K.Funding Agencies|Zernike Institute BIS program; EU H2020 project QuanTELCO [862721]; Swedish Research CouncilSwedish Research Council [VR 2016-04068, VR 2016-05362]; Knut and AliceWallenberg FoundationKnut &amp; Alice Wallenberg Foundation [KAW 2018.0071]; Carl Tryggers Stiftelse for Vetenskaplig Forskning [CTS 15:339]</p