A temperature and salinity hydrographic profile climatology is assembled, evaluated for data quality, and analyzed to assess changes of the Bering and Chukchi Sea continental shelves over seasonal to ...century-long time scales. The climatology informs description of the spatial distribution and temporal evolution of water masses over the two shelves, and quantification of changes in the magnitude and throughput of heat and fresh water. For the Chukchi Shelf, linear trend analysis of the integrated shelf heat content over its 1922–2018 period of record finds a significant summer and fall warming of 1.4 °C (0.14 ± 0.07 °C decade−1); over 1990–2018 the warming rate tripled to 0.43 ± 0.35 °C decade−1. In contrast, the Bering Shelf's predominantly decadal-scale variability precludes detection of a water column warming trend over its 1966–2018 period of record, but sea surface temperature data show a significant warming of 0.22 ± 0.10 °C decade−1 over the same time frame. Heat fluxes over 1979–2018 computed by the European Centre for Medium-Range Weather Forecast (ECMWF) ERA5 reanalysis exhibit no record-length trend in the shelf-wide Bering surface heat fluxes, but the Chukchi Shelf cooling season (October–March) has a trend toward greater surface heat losses and its warming season (April–September) has a trend toward greater heat gains. The 2014–2018 half-decade exhibited unprecedented low winter and spring sea-ice cover in the Northern Bering and Chukchi seas, changes that coincided with reduced springtime surface albedo, increased spring absorption of solar radiation, and anomalously elevated water column heat content in summer and fall. Consequently, the warm ocean required additional time to cool to the freezing point in fall. Fall and winter ocean-to-atmosphere heat fluxes were anomalously large and associated with enhanced southerly winds and elevated surface air temperatures, which in turn promoted still lower sea-ice production, extent, and concentration anomalies. Likely reductions in sea-ice melt were associated with positive salinity anomalies on the Southeast Bering Shelf and along the continental slope over 2014–2018. Negative salinity anomalies during 2014–2018 on the central and northern Bering Shelf may be related to a combination of 1) long-term declines in salinity, 2) an increase of ice melt, and 3) a decline of brine production. We hypothesize that freshening on the Bering Shelf and in Bering Strait since 2000 are linked to net glacial ablation in the Gulf of Alaska watershed. We show that the heat engines of both the Bering and Chukchi shelves accelerated over 2014–2018, with increased surface heat flux exchanges and increased oceanic heat advection. During this time, the Chukchi Shelf delivered an additional 5–9 x 1019 J yr−1 (50–90 EJ yr−1) into the Arctic basin and/or sea-ice melt, relative to the climatology. A similar amount of excess heat (60 EJ yr−1) was delivered to the atmosphere, showing that the Chukchi Sea makes an out-sized contribution to Arctic amplification. A conceptual model that summarizes the controlling feedback loop for these Pacific Arctic changes relates heat content, sea ice, freshwater distributions, surface heat fluxes, and advective fluxes.
The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh ...and low‐salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.
Key Points
The Arctic Ocean Freshwater System has major intra‐Arctic and extra‐Arctic effects
The Arctic Ocean Freshwater System regulates and constrains physical and biogeochemical processes
Changes in the Arctic Ocean Freshwater System are expected in the future with substantial impacts
The loss of Arctic sea ice has emerged as a leading signal of global warming. This, together with acknowledged impacts on other components of the Earth system, has led to the term “the new Arctic.” ...Global coupled climate models predict that ice loss will continue through the twenty-first century, with implications for governance, economics, security, and global weather. A wide range in model projections reflects the complex, highly coupled interactions between the polar atmosphere, ocean, and cryosphere, including teleconnections to lower latitudes. This paper summarizes our present understanding of how heat reaches the ice base from the original sources—inflows of Atlantic and Pacific Water, river discharge, and summer sensible heat and shortwave radiative fluxes at the ocean/ice surface—and speculates on how such processes may change in the new Arctic. The complexity of the coupled Arctic system, and the logistic and technological challenges of working in the Arctic Ocean, require a coordinated interdisciplinary and international program that will not only improve understanding of this critical component of global climate but will also provide opportunities to develop human resources with the skills required to tackle related problems in complex climate systems. We propose a research strategy with components that include 1) improved mapping of the upper- and middepth Arctic Ocean, 2) enhanced quantification of important process, 3) expanded long-term monitoring at key heat-flux locations, and 4) development of numerical capabilities that focus on parameterization of heat-flux mechanisms and their interactions.
We present the results of quantum chemical calculations of the transition energies and conical intersection points for the two lowest singlet electronic states of the green fluorescent protein ...chromophore, 4′-hydroxybenzylidene-2,3-dimethylimidazolinone, in the vicinity of its cis conformation in the gas phase. Four protonation states of the chromophore, i.e., anionic, neutral, cationic, and zwitterionic, were considered. Energy differences were computed by the perturbatively corrected complete active space self-consistent field (CASSCF)-based approaches at the corresponding potential energy minima optimized by density functional theory and CASSCF (for the ground and excited states, respectively). We also report the EOM-CCSD and SOS-CIS(D) results for the excitation energies. The minimum energy S0/S1 conical intersection points were located using analytic state-specific CASSCF gradients. The results reproduce essential features of previous ab initio calculations of the anionic form of the chromophore and provide an extension for the neutral, cationic, and zwitterionic forms, which are important in the protein environment. The S1 PES of the anion is fairly flat, and the barrier separating the planar bright conformation from the dark twisted one as well as the conical intersection point with the S0 surface is very small (less than 2 kcal/mol). On the cationic surface, the barrier is considerably higher (∼13 kcal/mol). The PES of the S1 state of the zwitterionic form does not have a planar minimum in the Franck−Condon region. The S1 surface of the neutral form possesses a bright planar minimum; the energy barrier of about 9 kcal/mol separates it from the dark twisted conformation as well as from the conical intersection point leading to the cis−trans chromophore isomerization.
Corrosion resistance of concrete and reinforced concrete products is one of the main properties that affect the strength of structures built from these materials. Improving the corrosion protection ...of such products is an urgent task of modern materials science. The article is devoted to the study of the effect of a new complex additive on the physical and mechanical properties, such as water absorption and strength, of a heavy concrete mix. The object of the study was B22.5 grade concrete. The complex additive was obtained by homogenizing an aqueous emulsion of petroleum resin and C-3 superplasticizer. The water absorption and strength of the samples were determined according to State Standard 12730.3-2020 and State Standard 28570-2019, respectively. The results of the study gave evidence showing that the complex additive imparts plasticizing and water-repellent properties to a heavy concrete mix. The effect of the concentration of the complex additive on the water absorption and compressive strength was assessed, which made it possible to determine the optimal concentration range of the additive in the concrete mixture for use in the manufacture of concrete and reinforced concrete products.
The dynamic properties of enzyme-substrate complexes in the reaction of the hydrolysis of guanosine triphosphate (GTP) are compared by the native Ras enzyme and its variant
G12V
Ras with oncogenic ...point substitution using molecular dynamic methods with potentials constructed according to the theory of quantum mechanics/molecular mechanics (QM/MM). Molecular models of systems including the GTP-binding protein Ras, the GAP accelerator protein, the GTP substrate, and the catalytic water molecule are constructed based on the atomic coordinates of the complex from the database of protein structures. An analysis of the obtained distributions along molecular dynamics trajectories for the distances between the oxygen atom of the catalytic water molecule in the active center of the complex and the phosphorus atom of the γ-phosphate group of GTP showed that the G12V substitution leads to the growth of populations with large distances between the reactants, thus reducing the proportion of the fraction of reactive conformations for the hydrolysis reaction.
Gastropleural fistula is an exceptionally rare condition, the incidence of which is currently unknown (Kunieda et al. in Intern Med 51(3):331, 2012, https://doi.org/10.2169/internalmedicine.51.6823 ..., Iqbal et al. in Cureus 11(2):e4136, 2019, https://doi.org/10.7759/cureus.4136 , Kathayanatt et al. in Lung India 37(2):174-175, 2020, https://doi.org/10.4103/lungindia.lungindia_242_17 ). The etiology varies from traumatic or iatrogenic injury to perforation in a herniated stomach due to ischemia, ulceration, or malignancy.
A 27-year-old European male presented to our hospital with complaints of general weakness and shortness of breath. The patient had a single episode of hemoptysis before admission. A computed tomography scan demonstrated a left-sided pyopneumothorax, a defect in the left main bronchus, and signs of pneumonia in the lower sections of the right lung. Therefore, a rare complication of perforation of a gastric fundus ulcer with the formation of a subdiaphragmatic abscess, gastropleural fistula, gangrene of the left lung with circular necrosis of the left main bronchus and diastasis of its edges, and pleural empyema on the left is presented in this report.
Although, a radical surgery may be preferable for this suspected malignancy; it should be weighed carefully against the risk of sepsis and the morbidity associated with a prolonged procedure in a sick patient. Damage-control surgery may be a viable option for a very sick patient, with more extensive resection reserved for later, provided the risk of infection and bleeding has been mitigated.
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Development of carbon polygons for monitoring the emission and deposition of carbon compounds in terrestrial ecosystems is one of the priority tasks in the case of climate and biosphere ...conservation. Significant is the role of soils, which are not only the main source of greenhouse gas emissions into the Earth’s atmosphere but also a long-term reservoir that stores significant amounts of organic carbon in the form of soil humus. The article discusses the organization of monitoring of greenhouse gases at carbon polygons, the methods of sampling soil horizons, and methodological approaches to determine the content and stocks of organic carbon in soils. The importance of information on the qualitative and quantitative composition of soil organic matter and humic substances, which is necessary for the operation of modern simulation models and calculation of carbon units for the economic assessment of the direct and reverse carbon footprint have been revealed. Russia faces a number of challenges related to carbon offset and a low-carbon economy. The necessary volumes of monitoring data, which must be obtained at carbon polygons for the use of the ROMUL and Efimod models are considered. The necessity for an adequate spatial coverage of the territory of Russia with a network of carbon polygons is emphasized. Particular attention should be paid to the arctic territories that contain significant amounts of organic matter in permafrost and can become precursors of the formation and emission of significant amounts of carbon dioxide and methane into the atmosphere.
Nanomodified polyetherimide samples obtained by fused deposition modeling using an experimental setup for three-dimensional printing of highly heat-resistant plastics are studied. Their structure and ...thermal properties are investigated by pycnometry, scanning electron microscopy, differential scanning calorimetry, thermogravimetry, and dilatometry. It is found that the modification of polyetherimide with carbon nanofibers considerably reduces the porosity of printed samples. An analysis of cytotoxicity shows that the tested materials are bioinert.
We present a review of the main results achieved by various research groups in the studies on identifying biomarkers of lung cancer among volatile organic compounds (VOCs) in exhaled breath. Known ...methods for determining VOCs in exhaled breath, sampling and storing samples, preconcentrating VOCs, and statistical processing of the obtained data are considered; their advantages and disadvantages are discussed. A list of the main biomarkers of lung cancer is summarized. The main problems hindering the introduction of the analysis of exhaled breath into clinical practice are discussed.
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