A model for the distribution of aftershock waiting times

In this work the distribution of inter-occurrence times between earthquakes in aftershock sequences is analyzed and a model based on a non-homogeneous Poisson (NHP) process is proposed to quantify the observed scaling. In this model the generalized Omori's law for the decay of aftershocks is used as a time-dependent rate in the NHP process. The analytically derived distribution of inter-occurrence times is applied to several major aftershock sequences in California to confirm the validity of the proposed hypothesis.Comment: 4 pages, 3 figure

Phenological shifts of abiotic events, producers and consumers across a continent

Ongoing climate change can shift organism phenology in ways that vary depending on species, habitats and climate factors studied. To probe for large-scale patterns in associated phenological change, we use 70,709 observations from six decades of systematic monitoring across the former Union of Soviet Socialist Republics. Among 110 phenological events related to plants, birds, insects, amphibians and fungi, we find a mosaic of change, defying simple predictions of earlier springs, later autumns and stronger changes at higher latitudes and elevations. Site mean temperature emerged as a strong predictor of local phenology, but the magnitude and direction of change varied with trophic level and the relative timing of an event. Beyond temperature-associated variation, we uncover high variation among both sites and years, with some sites being characterized by disproportionately long seasons and others by short ones. Our findings emphasize concerns regarding ecosystem integrity and highlight the difficulty of predicting climate change outcomes. The authors use systematic monitoring across the former USSR to investigate phenological changes across taxa. The long-term mean temperature of a site emerged as a strong predictor of phenological change, with further imprints of trophic level, event timing, site, year and biotic interactions.Peer reviewe

Chronicles of nature calendar, a long-term and large-scale multitaxon database on phenology

We present an extensive, large-scale, long-term and multitaxon database on phenological and climatic variation, involving 506,186 observation dates acquired in 471 localities in Russian Federation, Ukraine, Uzbekistan, Belarus and Kyrgyzstan. The data cover the period 1890-2018, with 96% of the data being from 1960 onwards. The database is rich in plants, birds and climatic events, but also includes insects, amphibians, reptiles and fungi. The database includes multiple events per species, such as the onset days of leaf unfolding and leaf fall for plants, and the days for first spring and last autumn occurrences for birds. The data were acquired using standardized methods by permanent staff of national parks and nature reserves (87% of the data) and members of a phenological observation network (13% of the data). The database is valuable for exploring how species respond in their phenology to climate change. Large-scale analyses of spatial variation in phenological response can help to better predict the consequences of species and community responses to climate change.Peer reviewe

Heavy Oil Upgrading in the Presence of Water

В обзоре систематизированы результаты исследований в области облагораживания нетрадиционного (тяжелого) нефтяного сырья (ТНС) в присутствии воды в зависимости от ее фазового состояния, в температурном интервале ~150–550 ºС. В данном температурном диапазоне вода может существовать в субкритическом состоянии (Т = 100 – 374 ºС при давлении насыщенных паров воды), в форме сверхкритического флюида (Т ≥ 374 ºС, P ≥ 22,1 МПа), а также в форме перегретого водяного пара (при P < давления насыщения). Рассмотрены особенности процессов облагораживания ТНС, механизмы участия воды при взаимодействии с углеводородным сырьем и модельными соединениями, а также особенности применения катализаторов в процессеIn the review, the results of research in the field of heavy crudes upgrading in the presence of water are presented, depending on water phase states at temperatures ca. 150–550 ºС. In this temperature region, water can be in the subcritical state (compressed hot water at T = 100 – 374 ºС and saturated water vapor pressure), in the form of supercritical fluid (T ≥ 374 ºС, P ≥ 22.1 MPa) and in the form of superheated steam (at P < saturated water vapor pressure). Features of the heavy crudes upgrading including mechanisms of water involving in reactions with hydrocarbon feedstocks and model compounds as well as features of the use of catalysts are reviewe

Tetranuclear Copper(I) and Silver(I) Pyrazolate Adducts with 1,1′-Dimethyl-2,2’-bibenzimidazole: Influence of Structure on Photophysics

A reaction of a cyclic trinuclear copper(I) or silver(I) pyrazolate complex ([MPz]3, M = Cu, Ag) with 1,1′-dimethyl-2,2’-bibenzimidazole (L) leads to the formation of tetranuclear adducts decorated by one or two molecules of a diimine ligand, depending on the amount of the ligand added (0.75 or 1.5 equivalents). The coordination of two L molecules stabilizes the formation of a practically idealized tetrahedral four-metal core in the case of a copper-containing complex and a distorted tetrahedron in the case of a Ag analog. In contrast, complexes containing one molecule of diimine possess two types of metals, two- and three-coordinated, forming the significantly distorted central M4 cores. The diimine ligands are twisted in these complexes with dihedral angles of ca. 50–60°. A TD-DFT analysis demonstrated the preference of a triplet state for the twisted 1,1′-dimethyl-2,2’-bibenzimidazole and a singlet state for the planar geometry. All obtained complexes demonstrated, in a solution, the blue fluorescence of the ligand-centered (LC) nature typical for free diimine. In contrast, a temperature decrease to 77 K stabilized the structure close to that observed in the solid state and activated the triplet states, leading to green phosphorescence at ca. 500 nm. The silver-containing complex Ag4Pz4L exhibited dual emission from both the singlet and triplet states, even at room temperature

Vacuum Residue Upgrading Via Catalytic Steam Cracking in Slurry Type Reactor in Presence of Mo-based Dispersed Catalyst

Впервые проведено исследование каталитического парового крекинга гудрона в проточном реакторе типа сларри при температуре 425–450 °C и давлении 2 МПа в присутствии Мо- содержащего дисперсного катализатора. Катализатор вводили в сырье через стадию образования обратной эмульсии, которую предварительно получали из гудрона и водного раствора Мо-содержащей соли-прекурсора, с ее последующим разложением и образованием дисперсии частиц катализатора в гудроне. В случае некаталитического парового крекинга было обнаружено, что использование воды приводит к снижению коксообразования и, соответственно, увеличению выхода целевых жидких продуктов (полусинтетической нефти) с одновременным снижением содержания серы в последних по сравнению с термическим крекингом. Результаты исследования также показали, что применение Mo-содержащего дисперсного катализатора позволяет увеличить глубину взаимодействия воды и гудрона с повышением соотношения H/C и снижением содержания серы в жидких продуктах (полусинтетической нефти)The catalytic steam cracking of vacuum residue (VR) in a slurry-type reactor at a temperature of 425–450 °C and 2 MPa in the presence of a Mo-based dispersed catalyst was carried out for the first time. The catalyst was introduced into the feedstock through a reverse emulsion, which was previously prepared from VR and an aqueous solution of the Mo-based precursor salt, followed by decomposition and formation of a dispersion of catalyst particles in the VR. In the case of non-catalytic steam cracking, it was found that the use of water leads to a reduction in coke formation and, correspondingly, an increase in the yield of the target liquid products (semisynthetic oil), while reducing the sulfur content, in comparison with thermal cracking. The results of the study also showed that the use of Mo-based dispersed catalyst increases the depth of interaction between water and VR, with an increase in the H:C ratio and a reduction in sulfur content in liquid products (semisynthetic oil