Magnetostratigraphy of Turonian – Santonian strata on the Samara Right Bank

The paper presents the results of petro- and paleomagnetic studies of two sections of Turonian – Santonian on the Samara Right Bank – near Novodevichye, Podval’e villages and detailed geological description of the Novodevichye section. The magnetostratigraphic subdivision and detailed correlation of the sections were carried out. Unknown unconformity in the Podval’e section was recognized. Reverse polarity corresponds to a significant part of the Coniacian – Santonian deposits, the presence of which contradicts the existing ideas about the regime of the Turonian – Santonian geomagnetic field, but partly agrees with the data on deposits of the same age found in other sections in the Volga region.

SARS-CoV-2 infection and replication in human gastric organoids

COVID-19 typically manifests as a respiratory illness, but several clinical reports have described gastrointestinal symptoms. This is particularly true in children in whom gastrointestinal symptoms are frequent and viral shedding outlasts viral clearance from the respiratory system. These observations raise the question of whether the virus can replicate within the stomach. Here we generate gastric organoids from fetal, pediatric, and adult biopsies as in vitro models of SARS-CoV-2 infection. To facilitate infection, we induce reverse polarity in the gastric organoids. We find that the pediatric and late fetal gastric organoids are susceptible to infection with SARS-CoV-2, while viral replication is significantly lower in undifferentiated organoids of early fetal and adult origin. We demonstrate that adult gastric organoids are more susceptible to infection following differentiation. We perform transcriptomic analysis to reveal a moderate innate antiviral response and a lack of differentially expressed genes belonging to the interferon family. Collectively, we show that the virus can efficiently infect the gastric epithelium, suggesting that the stomach might have an active role in fecal-oral SARS-CoV-2 transmission.

Rapid eruption of the Emeishan continental flood basalts: New paleomagnetic and geochronologic constraints

The duration of the eruption of the Emeishan large igneous province is hotly debated. We conducted a magnetostratigraphic and geochronological study of the core area of the large igneous province in the Binchuan area of Yunnan Province, southwestern China, in order to constrain the duration of the eruption. The results of detailed thermal demagnetization experiments revealed two remanent magnetic components from the volcanic rocks of 11 composite sections. A low-temperature component separated below 300 °C is interpreted as a recent viscous remanence. Additionally, reliable characteristic remanent magnetizations were revealed above 400 °C, with unblocking temperatures up to 580−680 °C, which passed the fold test and record three magnetozones. Zircons from the felsic ignimbrites exposed in the final stage of the mafic volcanism are dated to 258.2 ± 0.7 Ma (n = 15; mean square of weighted deviates = 1.3) by sensitive high-resolution ion microprobe. Stratigraphic and magnetostratigraphic correlations of the Emeishan basalts in the Binchuan sections indicate that the eruption of the mafic rocks of the Emeishan large igneous province can be clearly divided into early (reverse polarity subzone), middle (normal polarity subzone), and late (reverse polarity subzone) stages, with a total duration of less than 1.7 m.y. (260.8−259.1 Ma). However, by combining this chronology with previously reported conodont biostratigraphic results from locations around the Emeishan large igneous province, and comparing the dominant normal-reverse polarity sequence in the Emeishan large igneous province with the geomagnetic polarity time scale, we obtain a much shorter duration of the main eruptive stage of <0.8 m.y. (260.4−259.6 Ma). About three quarters of the basalts of the Emeishan large igneous province record have a normal polarity and erupted within 0.4 m.y., while the other quarter, mainly distributed in the central zone, shows a reverse polarity and much shorter duration. Given the short duration of the eruption, gas volatiles would have been released into the atmosphere at high rates, which might provide a causal link between the rapid eruption and the end-Guadalupian mass extinction. Before the mantle plume eruption, localized eruptions probably occurred. After eruption of the mafic Emeishan flood basalts, an acid volcanic eruption occurred in the early Wuchiapingian, which was sporadically distributed in the Emeishan large igneous province.

Method of arc activation of the base at increasing the distance plasma spraying

Purpose. To increase the efficiency of the plasma coating by developing a method of ion-arc activation of the base using an activating electrode, which leads to an increase in the adhesion strength of the coating due to the sputtering of surface oxides of the base. Research methods. Experimental and computational, mechanical tests, optical microscopy. The development of the method of ion-arc activation of the part base with an increase in the distance of coating deposition consists in application of an activating electrode located at the surface of the base to create an additional activating arc. The influence of the activating arc on bases for creating an additional activating arc. The influence of the activating arc on the adhesion strength of the coating is determined. The estimation of the current density of the activating arc for the sputtering of surface base oxides is carried out. Results. A method of arc activation of the base surface with an increase in the coating distance is found. It is shown that application of an activating arc of reverse polarity that burns between the additional electrode and the base leads to ion bombardment of the surface by sputtering surface oxides and the creation of microcraters on the base surface. As a result, the bond strength is doubled compared to the bond strength obtained without the use of ion-arc activation of the base. The calculations of the rate of cathodic sputtering of the surface oxides of the base are carried out and the minimum activation current density of the base is determined, which leads to the complete sputtering of a layer of oxides of a given thickness. Scientific novelty. It has been determined that, despite the rapid oxidation of the base under atmospheric conditions, application of the method of ion-arc cleaning of the surface during coating leads to a significant increase in the adhesion strength of the coating to the base. Practical value. The obtained results of increasing the adhesion strength rise the efficiency, the guaranteed service life of the plasma coating on the parts of machines and mechanisms

Simultaneous Enantiomeric Separation of Carfentrazone-Ethyl Herbicide and Its Hydrolysis Metabolite Carfentrazone by Cyclodextrin Electrokinetic Chromatography. Analysis of Agrochemical Products and a Degradation Study

The different activity and toxicity that the enantiomers of agrochemicals may have requires the development of stereoselective analytical methodologies enabling the individual determination of each enantiomer. The aim of this work was to develop the first Electrokinetic Chromatography methodology enabling the simultaneous enantiomeric separation of carfentrazone-ethyl herbicide and its hydrolysis metabolite carfentrazone. The use of an anionic cyclodextrin as chiral selector (captisol at 2.5% (w/v)) in a 25 mM acetate buffer, at a temperature of 30 °C, and an applied voltage (reverse polarity) of −30 kV, allowed the simultaneous separation of the four enantiomers of the two compounds studied in 6.8 min with enantiomeric resolutions of 5.0 for carfentrazone-ethyl and 5.1 for carfentrazone. Analytical characteristics of the developed method were evaluated and found adequate to achieve the quantitation of carfentrazone-ethyl and carfentrazone. Analysis of a commercial herbicide formulation showed the potential of the method for the quality control of these agrochemical products. Degradation studies for carfentrazone-ethyl revealed that no significant degradation took place in cleaned sand samples while a significant but not stereoselective degradation took place in soils for the whole period of time considered (seven days).

Improvement of Surface Quality and Machining Depth of µ-ECDM Performances Using Mixed Electrolyte at Different Polarity

The production of miniature parts and various shape of micro-profile by electrochemical discharge micro-machining process (µ-ECDM) draw challenging attention to the researchers. Parametric influences as well as comparative analysis on machining depth (MD) and surface roughness (Ra) has been propounded using NaOH and KOH at the ratio of 1:0, 3:1, 1:1, 1:3 and 0:1 with their varying concentration(wt.%), and applied voltage (V), pulse frequency(Hz) and duty ratio (%)in straight as well as in reverse polarity using template guided stainless steel (SS) cylindrical tool with motion and spring feed mechanism for fabrication of different shapes of micro-channel like Zig-Zag, ‘Y’ shaped on glass by µ-ECDM process. Tool electrode wear rate (TEWR) has been reduced using mixed electrolyte and reversed polarity. The SEM analysis has been performed to identify the micro-crack and uncut debris into micro-channel. Machining depth has been increased up to 1850 µm with better surface quality using mixed electrolyte of NaOH:KOH::3:1 at direct polarity of 50 V and lower TEWR is found using NaOH:KOH::1:3 as electrolyte at reverse polarity.