To study the mechanism of space stem formation, the high‐speed direct imaging technique and Schlieren photography are used to simultaneously observe the space stems in a 1.35‐m air gap under the ...lightning impulse voltage. It is found that the average length and diameter of the space stem is approximately 5 and 0.5 mm, which is about 1/3 of the length and 1/10 of the diameter of the local luminous region respectively. Moreover, the space stem exhibits a non‐uniform distributed temperature with a maximum value of several hundred Kelvin for tens of microseconds. Accordingly, a possible mechanism is proposed that the space stem is formed at the primary corona streamer boundary as a result of the propagation of a secondary ionization wave from the HV electrode and survives long enough (to finish the polarization) due to the fast gas heating and production of atomic oxygen.
Plain Language Summary
It is well known that negative leaders in the air develop in a step‐wise manner, with each step originating from a space stem. However, the mechanism of space stem formation is still unknown, one of the main reasons being the lack of experimental observations. For this reason, this paper carries out laboratory research to observe the optical and thermal properties of space stems. The observations reveal that the local luminous region at the primary corona streamer boundary is not fully heated into the space stem, but only about 1/3 of its length. If based on conventional direct images, the measured length and diameter of space stems would be 2.5 and 10 times larger than the actual values, respectively. The reconstructed temperature field shows that the axial temperature and diameter of the space stem are not uniformly distributed, with higher temperatures and smaller diameters at the end away from the HV electrode. Finally, a new possible mechanism is proposed for the space stem formation, in which the secondary ionization wave from the HV electrode contributes to the initial formation of the space stem, and then the voltage changes help the space stem survive long enough to finish the polarization.
Key Points
Only a section of the local luminous region at the primary corona streamer boundary is heated to form a space stem, but not all of it
The temperature field of a space stem is reconstructed for the first time and presents a non‐uniform distribution
A secondary ionization wave may contribute to the space stem formation at the primary corona streamer burst boundary
The 2.MED1 phylogenetic branch of Yersinia pestis of the medieval biovar became widespread in the Caspian Sea region, the Caucasus, and the Northern Aral Sea region in the 20th century, causing ...outbreaks and epizootics of plague there. Some of the formed natural foci of 2.MED1 still show epizootic activity and retain their epidemic potential. In this work, we carried out a phylogenetic analysis of 46 Y. pestis strains of the medieval biovar isolated in the Caucasus, the Caspian Sea, and the Northern Aral Sea regions during epidemic outbreaks and epizootics from 1922-2014. The obtained phylogenetic data, together with epidemiological and epizootological data accumulated over a period of about a hundred years, indicate the presence of two waves of penetration of the 2.MED1 branch into the Caucasus. The first occurred, apparently, in the first half of the 20th century as a result of the penetration of 2.MED1 from the foci of the Northern and North-Western Caspian Sea. The second wave was caused by the spread of 2.MED1 from the Northern Aral to the foci of the North-Western, Northern and Eastern Caspian Sea regions at the beginning of the second half of the 20th century, followed by introduction into the Pre-Caucasus and Transcaucasia. The rapid spread of 2.MED1 could be associated with the transfer of the pathogen by land and sea transport in the process of economic activity of the population.
The INK4b-ARF-INK4a locus encodes for two cyclin-dependent kinase inhibitors, p15
INK4b
and p16
INK4a
and a regulator of the p53 pathway, ARF. In addition ANRIL, a non-coding RNA, is also transcribed ...from the locus. ARF, p15
INK4b
and p16
INK4a
are well-established tumor suppressors which function is frequently disabled in human cancers. Recent studies showed that single nucleotide polymorphisms mapping in the vicinity of ANRIL are linked to a wide spectrum of conditions, including cardiovascular disease, ischemic stroke, type 2 diabetes, frailty and Alzheimer's disease. The INK4b-ARF-INK4a locus is regulated by Polycomb repressive complexes (PRCs), and its expression can be invoked by activating signals. Other epigenetic modifiers such as the histone demethylases JMJD3 and JHDM1B, the SWI/SNF chromatin remodeling complex and DNA methyltransferases regulate the locus interplaying with PRCs. In view of the intimate involvement of the INK4b-ARF-INK4a locus on disease, to understand its regulation is the first step for manipulate it to therapeutic benefit.
The initiation of combustion of lean H2:air mixtures, ER=0.5--0.6, by nanosecond surface dielectric barrier discharge (nSDBD) was studied experimentally at high initial pressures, P=3--6 bar. The ...discharge was studied in different gas mixtures for the pressure range 1–12 bar. The ignition was initiated by two different discharge modes: streamer or filamentary nSDBD. The influence of the discharge structure and energy deposition on the ignition was demonstrated. Three regimes of multi-point ignition were observed: ignition with a few kernels, quasi-uniform ignition along the edge of the high voltage electrode and ignition along the plasma channels. The velocities of flame propagation were analyzed. The minimum ignition energy of the discharge and ignition delay time of combustion have been measured and analyzed with the help of kinetic numerical modeling.
Glacier retreat has caused the emergence of numerous moraine-dammed glacial lakes (MGL) over the last century which have become research foci in many mountain regions of the world. Outbursts of MGLs ...have caused destructive floods and debris flows, leading to numerous human casualties and significant material damage. The mountains of South-Eastern Kazakhstan have also become prone to lake outburst floods and related debris flows, specifically in the second half of the 20th century. This paper presents and reviews existing surveys and knowledge along with results of own investigations on the formation of MGLs and the characteristics of lake outburst floods and debris flows in the Kazakh part of Tien Shan. We suggest a workflow to identify the most dangerous types of lakes and provide information about their morphogenetic features and hazard criteria.
The number of MGLs increased since the 1970s with more than 160 existing in 2018. Forty were identified as being dangerous. Forty-eight lake outbursts occurred since 1950 with all the documented events happened between end of June and end of August. The most dangerous outbursts were caused by ruptures in ice-cored moraine dams. Outbursts of nine MGLs caused disastrous debris flows, with some occurring repeatedly. The number of outbursts decreased since the year 2000 compared to 1970–2000. However, due to ongoing glacier retreat new lakes are forming at higher altitudes. Their greater potential energy makes possible future outbursts more dangerous. Re-evaluation of existing methods to calculate the water volume and peak discharge based on bathymetric measurements and observed outbursts revealed that the applied equations provide suitable approximations and allow supporting mitigation and prevention measures. Finally, the presentation of implemented measures to lower the water level using siphons or artificial flow channels shows that they can reduce the lake outburst hazards. However, they are associated with risks and financial costs and it needs to be carefully considered whether protection measures of the endangered areas are more cost effective.
The main goal of the present study was to investigate the microencapsulation, in vitro release capacity and efficiency of catechin-rich
extract by Clinosorbent-5 (CLS-5) microparticles by in-depth ...detailed analyses and mathematical modelling of the encapsulation and in vitro release kinetics behaviour of the polyphenol-mineral composite system. The bioflavanol encapsulation and release efficiency on/from the mineral matrix were assessed by sorption experiments and interpretative modelling of the experimental data. The surface and spectral characteristics of the natural bioactive substance and the inorganic microcarrier were determined by Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet/Visible (UV/Vis) spectrophotometric analyses. The maximum extent of catechin microencapsulation in acidic medium was 32%. The in vitro release kinetics study in simulated enzyme-free gastric medium (pH = 1.2) approved 88% maximum release efficiency achieved after 24 h. The in vitro release profile displayed that the developed bioflavanol/clinoptilolite microcarrier system provided sustained catechin in vitro release behaviour without an initial burst effect. Thus, the results from the present study are essential for the design and development of innovative catechin-CLS-5 microcarrier systems for application in human and veterinary medicine.
A six dimensional manifold of symmetric signature (3,3) is proposed as a space structure for building combined theory of gravity and electromagnetism. Special metric tensor is proposed, yielding the ...space which combines the properties of Riemann, Weyl and Finsler spaces. Geodesic line equations are constructed where coefficients can be divided into depending on the metric tensor (relating to the gravitational interaction) and depending on the vector field (relating to the electromagnetic interaction). If there is no gravity, the geodesics turn into the equations of charge motion in the electromagnetic field. Furthermore, symmetric six-dimensional electrodynamics can be reduced to traditional four-dimensional Maxwell system, where two additional time dimensions are compactified. A purely geometrical interpretation of the concept of electromagnetic field and point electric charge is proposed.
Follicular lymphoma is an incurable malignancy, with transformation to an aggressive subtype representing a critical event during disease progression. Here we performed whole-genome or whole-exome ...sequencing on 10 follicular lymphoma-transformed follicular lymphoma pairs followed by deep sequencing of 28 genes in an extension cohort, and we report the key events and evolutionary processes governing tumor initiation and transformation. Tumor evolution occurred through either a 'rich' or 'sparse' ancestral common progenitor clone (CPC). We identified recurrent mutations in linker histone, JAK-STAT signaling, NF-κB signaling and B cell developmental genes. Longitudinal analyses identified early driver mutations in chromatin regulator genes (CREBBP, EZH2 and KMT2D (MLL2)), whereas mutations in EBF1 and regulators of NF-κB signaling (MYD88 and TNFAIP3) were gained at transformation. Collectively, this study provides new insights into the genetic basis of follicular lymphoma and the clonal dynamics of transformation and suggests that personalizing therapies to target key genetic alterations in the CPC represents an attractive therapeutic strategy.
The paper shows that it is possible to construct quantum chromodynamics as a rigorous theory on the basis of employment of hyperbolic unitary group SUh(3), which is a symmetry group for the ...three-dimensional complex space of the hyperbolic type. Such an approach allows researchers to discover a profound connection between conserved color charges of the quarks and the symmetries of the hyperbolic three-dimensional complex space. Further, it allows a correct introduction of the Hermitian operators to describe the eight gluons, which are carriers of strong interactions.
According to the whole genome SNP analysis of 38 Yersinia pestis strains isolated in the foci of the Northern Caspian and Northern Aral Sea regions in the 20th-early 21st centuries, between 1912 and ...2015, the spatial and temporal structure of the 2.MED population of a medieval biovar in this region was determined. A phylogenetic branch 2.MED4 was identified which preceded the 2.MED1 branch that diverged later. 2.MED1 strains became the etiological agent of high-mortality plague outbreaks that occurred in the Northern Caspian region at the beginning of the 20th century. Later in the 20th century, the 2.MED1 branch became widespread in the Caspian Sea region, Caucasus, and vast areas of Central Asia. Based on the data of phylogenetic analysis, as well as epidemiological and epizootiological data, we reconstructed the paths of spread of the 2.MED1 branch in the Northern Caspian Sea region and in the Northern subzone of the Central Asian deserts. It is shown, that the reason for the activation of plague foci in the Northern Caspian region in the second half of the 20th century after a long inter-epizootic period caused by cyclical climate warming was the return of 2.MED1 from the foci of the Northern Aral Sea region. This led to the formation of stable plague foci in the Northern Caspian Sea region and Pre-Caucasus, which manifested epizootic activity in the second half of the 20th and early 21st centuries.
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