The early 21st century was marked by several severe winters over Central Eurasia linked to a blocking anti-cyclone centered south of the Barents Sea. Severe winters in Central Eurasia were frequent ...in the 1960s when Arctic sea ice cover was anomalously large, and rare in the 1990s featuring considerably less sea ice cover; the 1960s being characterized by a low, the 1990s by a high phase of the North Atlantic Oscillation, the major driver of surface climate variability in Central Eurasia. We performed ensemble simulations with an atmospheric general circulation model using a set of multi-year Arctic sea ice climatologies corresponding to different periods during 1966-2012. The atmospheric response to the strongly reduced sea ice cover of 2005-2012 exhibits a statistically significant anti-cyclonic surface pressure anomaly which is similar to that observed. A similar response is found when the strongly positive sea ice cover anomaly of 1966-1969 drives the model. Basically no significant atmospheric circulation response was simulated when the model was forced by the sea ice cover anomaly of 1990-1995. The results suggest that sea ice cover reduction, through a changed atmospheric circulation, considerably contributed to the recent anomalously cold winters in Central Eurasia. Further, a nonlinear atmospheric circulation response to shrinking sea ice cover is suggested that depends on the background sea ice cover.
Abstract
Precipitation extremes are widely thought to intensify with global warming due to an exponential growth following the Clausius–Clapeyron (C–C) equation which links the atmosphere water vapor ...saturation pressure with air temperature. However, a number of recent studies based on station and reanalyzes data for the contemporary period showed that scaling rates between extreme precipitation and temperature strongly depend on temperature range, moisture availability, and a region of interest. Being performed for some regions, such estimates, however, lack for Northern Eurasia, where prominent temperature changes and rapid shift from large-scale to convective precipitation are observed. Here, we examine the scaling between daily precipitation extremes and surface air temperature (SAT) over Russia for 1966–2017 using meteorological station data and for 1979–2020 using ERA5 reanalysis. The precipitation-temperature relation is examined for total precipitation and, separately, for convective and large-scale precipitation types. In winter, we reveal a general increase in extreme precipitation of all precipitation types according to the C–C relationship. For the Russian Far East region, the stratiform precipitation extremes scale with SAT following even super C–C rates, about two times as fast as C–C. However, in summer we find a peak-like structure of the precipitation-temperature scaling, especially for the convective precipitation in the southern regions. Extreme precipitation reaches their peak values at the temperature range between 15 °C and 20 °C. At higher temperatures, the negative scaling prevails. Analyzed data show a pronounced decrease in relative humidity with increasing surface temperatures beyond the 15 °C–20 °C threshold. This indicates that moisture availability is the major factor for the peak-shaped relationship between extreme precipitation and temperature revealed by our analysis.
The 1,3-dipolar cycloaddition reaction of isoquinolinium ylides to nitrostilbenes provides an approach to 1,2-diarylpyrrolo2,1-aisoquinolinium-3-carboxylates and then to a complete hexacyclic ...lamellarin core.
We studied the effect of bacterial wall peptidoglycan of 7 bacterial species on the competitive properties of human-associated microorganisms. Addition of peptidoglycan to the culture medium did not ...change the growth characteristics of the test cultures; however, an increase in the antagonism and hydrophobicity of
Bifidobacterium
sp. and
Enterococcus
sp. was observed, while the effect on enterobacteria was predominantly indifferent or inhibitory. The effect did not depend much on the source of peptidoglycan and was equally manifested on both indigenous and probiotic strains. The observed new property of peptidoglycan indicates its participation in the formation and functioning of microbiota. The obtained data on the regulation of the properties of microorganisms provide new possibilities for the correction and maintenance of host homeostasis through host-associated microbiota.
Chest MRI of patients with COVID-19 Vasilev, Yu A.; Sergunova, K.A.; Bazhin, A.V. ...
Magnetic resonance imaging,
06/2021, Letnik:
79
Journal Article
Recenzirano
Odprti dostop
During the pandemic of novel coronavirus infection (COVID-19), computed tomography (CT) showed its effectiveness in diagnosis of coronavirus infection. However, ionizing radiation during CT studies ...causes concern for patients who require dynamic observation, as well as for examination of children and young people. For this retrospective study, we included 15 suspected for COVID-19 patients who were hospitalized in April 2020, Russia. There were 4 adults with positive polymerase chain reaction (PCR) test for COVID-19. All patients underwent magnetic resonance imaging (MRI) examinations using MR-LUND PROTOCOL: Single-shot Fast Spin Echo (SSFSE), LAVA 3D and IDEAL 3D, Echo-planar imaging (EPI) diffusion-weighted imaging (DWI) and Fast Spin Echo (FSE) T2 weighted imaging (T2WI). On T2WI changes were identified in 9 (60,0%) patients, on DWI – in 5 (33,3%) patients. In 5 (33,3%) patients lesions of the parenchyma were visualized on T2WI and DWI simultaneously. At the same time, 4 (26.7%) patients had changes in lung tissue only on T2WI. (P(McNemar) = 0,125; OR = 0,00 (95%); kappa = 0,500). In those patients who had CT scan, the changes were comparable to MRI. The results showed that in case of CT is not available, it is advisable to conduct a chest MRI for patients with suspected or confirmed COVID-19. Considering that T2WI is a fluid-sensitive sequence, if imaging for the lung infiltration is required, we can recommend the abbreviated MRI protocol consisting of T2 and T1 WI. These data may be applicable for interpreting other studies, such as thoracic spine MRI, detecting signs of viral pneumonia of asymptomatic patients. MRI can detect features of viral pneumonia.
HIV infection is a major health problem in Russia. We aimed to assess HIV prevalence in different population groups and to compare the characteristics of 4th generation immunoassays from Abbott, ...Bio-Rad, Vector-Best, Diagnostic Systems, and Medical Biological Unit.
The study included 4452 individuals from the general population (GP), 391 subjects at high risk of HIV infection (HR) and 699 with potentially interfering conditions. HIV positivity was confirmed by immunoblot and by HIV RNA, seroconversion and virus diversity panels were also used. HIV avidity was employed to assess recent infections.
The prevalence in GP was 0.40%, higher in males (0.62%) and in people aged < 40 years (0.58%). Patients attending dermo-venereal centers and drug users had a high prevalence (34.1 and 58.8%). Recent infections were diagnosed in 20% of GP and in 4.2% of HR. Assay sensitivity was 100% except for one false negative (99,54%, MBU). Specificity was 99.58-99.89% overall, but as low as 93.26% on HR (Vector-Best). Small differences on early seroconversion were recorded. Only the Abbott assay detected all samples on the viral diversity panel.
HIV infection rate in the high-risk groups suggests that awareness and screening campaigns should be enhanced. Fourth generation assays are adequate but performance differences must be considered.
The ability of modern climate models to simulate ice season length in the Arctic, its recent changes and navigation season on Arctic marine routes along the Eurasian and the North American coastlines ...is evaluated using satellite ice cover observations for 1979-2007. Simulated mean sea ice season duration fits remarkably well to satellite observations and so do the simulated 20th century changes using historical forcing. This provides confidence to extend the analysis to projections for the twenty-first century. The navigation season for the Northern Sea Route (NSR) and Northwest Passage (NWP), alternative sea routes from the North Atlantic to Asia, will considerably increase during this century. The models predict prolongation of the season with a free passage from 3 to 6 months for the NSR and from 2 to 4 months for the NWP by the end of twenty-first century according to A1B scenario of the IPCC. This suggests that transit through the NSR from Western Europe to the Far East may be up to 15% more profitable in comparison to Suez Canal transit by the end of the twenty-first century.
The present study is focused on the problem of reconstruction of the magnetic configuration in the magnetic reconnection electron diffusion region (EDR). The problem is addressed in the frame of ...electron magnetohydrodynamics with kept electron inertia term. We introduce the new reconstruction model independent of divergence of the electron pressure tensor and reconnection electric field. The model is tested on the magnetotail reconnection event of July 11, 2017 observed by the Magnetospheric Multiscale (MMS) spacecraft in the course of crossing the very core part of the reconnection region, the internal EDR. This new model demonstrates considerably better accuracy of the longitudinal electron velocity reconstruction due to the lower sensitivity to the configuration deviation from the two‐dimensional time‐independent model adopted in our study. We suggest also a new technique to estimate the guide field, implementing the reconstruction of magnetic potential of the in‐plane magnetic field and relying on symmetric properties of magnetic reconnection.
Plain Language Summary
Magnetic reconnection is a fundamental plasma process responsible for the magnetic field reconfiguration and transforming magnetic energy to kinetic and thermal energy of plasma. In the Earth's magnetosphere, the magnetospheric conditions are monitored by several spacecraft missions. Among them, the NASA Magnetospheric Multiscale (MMS) mission is designed for exploring the process of reconnection. On July 11, 2017 at about 22:34 UT MMS was located in the magnetotail at a very fortunate position, intersecting the reconnection region in its very central part, the so‐called electron diffusion region (EDR).
Since MMS consists of four identical spacecraft, MMS provides an excellent tool for testing analytical models of reconnection. Taking the data of one probe as the boundary condition for the analytical model, one can compare the results of calculations with other probes data. In the present paper we suggest a new model of EDR, and compare it to the existing one using the data of 2017/07/11 event. This comparison has shown that the electron inertia term plays an important role in the EDR physics; the proper handling of this term allows considerable improvement of the EDR reconstruction accuracy.
Key Points
A model for electron diffusion region (EDR) reconstruction in electron magnetohydrodynamics (EMHD) approximation with kept electron inertia is developed
Reconstruction of the out‐of‐plane magnetic field is performed independent of the reconnection electric field and pressure anisotropy
Reconstruction is applied for self‐consistent estimate of the guide field value and local coordinate system orientation
Experiments carried out on a series of seven different polymers with molecular weights varying over a wide range have allowed us to confirm that stable jets can be obtained at concentrations much ...below the crossover point. A jet was considered as stable if its lifetime exceeds the Plateau–Rayleigh time by several orders of magnitude. The systematic study carried out for poly(ethylene oxide) solutions in a wide range of high molecular weight showed that the lowest concentration at which a stable fiber can still be formed is scaled by η−2.14±0.3 or M –1.63±0.29. However, for the domain of not so high M, the spinnability concentration corresponds to the onset of entanglements and scales as M –0.70±0.14, which is the same as the dependence of the crossover concentration on molecular weight. The difference in the scaling exponents reflects two possible regimes of stable fiber formation in fiber spinning. These exponents are close to those obtained by Palangetic et al. Polymer 2014, 55, 4920 for other polymer solutions in the electrospinning experiments. Several examples of spinnability at very low concentrations for other polymer solutions are demonstrated. A possibility of the formation of stable jets from dilute solutions is explained by an increase of the intermolecular interactions of extended macromolecular chains, resulting in the phase separation and leading to the formation of fibers created by oriented macromolecules. The theoretical considerations show that there are two sources of jet stabilization at low concentrations (high M), namely, the coil–stretch transition and demixing of the polymer solution.
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