Peculiarities in the problem of surface stability of a charged bounded helium film on a metal substrate are considered. The dependence of critical instability parameters on the in-plane film size is determined. A method is proposed for observing metastable states of a charged liquid film.
Samples from three hot springs (Alla, Seya and Garga) located in the northeastern part of Baikal rift zone (Buryat Republic, Russia) were screened for the presence of thermophilic nitrifying bacteria. Enrichment cultures were obtained solely from the Garga spring characterized by slightly alkaline water (pH 7.9) and an outlet temperature of 75 degrees C. The enrichment cultures of the ammonia- and nitrite oxidizers grew at temperature ranges of 27-55 and 40-60 degrees C, respectively. The temperature optimum was approximately 50 degrees C for both groups and thus they can be designated as moderate thermophiles. Ammonia oxidizers were identified with classical and immunological techniques. Representatives of the genus Nitrosomonas and Nitrosospira-like bacteria with characteristic vibroid morphology were detected. The latter were characterized by an enlarged periplasmic space, which has not been previously observed in ammonia oxidizers. Electron microscopy, denaturing gradient gel electrophoresis analyses and partial 16S rRNA gene sequencing provided evidence that the nitrite oxidizers were members of the genus Nitrospira.
A sequence of the real numbers $\textbf{s}=\{s_{i}\}_{i=0}^{\ell}$ is associated with the some indefinite Stieltjes moment problem and generalized Jacobi matrices. The relation between the $\alpha-$regular indefinite Stieltjes moment problem and shifted Darboux transformation of the generalized Jacobi matrix is studied. The new formulas for the Stieltjes polynomials with the shift are found and one are used to obtain the description of the solutions of the $\alpha-$regular indefinite Stieltjes moment problem.
Послідовність дійсних чисел $\textbf{s}=\{s_{i}\}_{i=0}^{\ell}$ пов'язана з деякою задачею про невизначений момент Стілтьєса та узагальненими матрицями Якобі. Досліджено зв'язок між $\alpha-$регулярною проблемою невизначеного моменту Стілтьєса та зміщеним перетворенням Дарбу узагальненої матриці Якобі. Знайдено нові формули для поліномів Стілтьєса зі зсувом та використано для отримання опису розв’язків $\alpha-$регулярної невизначеної проблеми моменту Стілтьєса.
The cohort of the ammonia-oxidizing archaea (AOA) of the phylum Thaumarchaeota is a diverse, widespread and functionally important group of microorganisms in many ecosystems. However, our understanding of their biology is still very rudimentary in part because all available genome sequences of this phylum are from members of the Nitrosopumilus cluster. Here we report on the complete genome sequence of Candidatus Nitrososphaera gargensis obtained from an enrichment culture, representing a different evolutionary lineage of AOA frequently found in high numbers in many terrestrial environments. With its 2.83 Mb the genome is much larger than that of other AOA. The presence of a high number of (active) IS elements/transposases, genomic islands, gene duplications and a complete CRISPR/Cas defence system testifies to its dynamic evolution consistent with low degree of synteny with other thaumarchaeal genomes. As expected, the repertoire of conserved enzymes proposed to be required for archaeal ammonia oxidation is encoded by N. gargensis, but it can also use urea and possibly cyanate as alternative ammonia sources. Furthermore, its carbon metabolism is more flexible at the central pyruvate switch point, encompasses the ability to take up small organic compounds and might even include an oxidative pentose phosphate pathway. Furthermore, we show that thaumarchaeota produce cofactor F420 as well as polyhydroxyalkanoates. Lateral gene transfer from bacteria and euryarchaeota has contributed to the metabolic versatility of N. gargensis. This organisms is well adapted to its niche in a heavy metal-containing thermal spring by encoding a multitude of heavy metal resistance genes, chaperones and mannosylglycerate as compatible solute and has the genetic ability to respond to environmental changes by signal transduction via a large number of two-component systems, by chemotaxis and flagella-mediated motility and possibly even by gas vacuole formation. These findings extend our understanding of thaumarchaeal evolution and physiology and offer many testable hypotheses for future experimental research on these nitrifiers.
The temperature dependence of electron mobility on the surface of liquid helium is examined. We calculate the contribution to the electron scattering rate from the surface level atoms (SLA), proposed in [A.M. Dyugaev and P.D. Grigoriev, JETP Lett. 78, 466 (2003)]. This contribution is essential at low temperatures T< 0.5 ,w hen the He vapor concentration is exponentially small. The influence of clamping field on the electron scattering rate is investigated. We also study the effect of quantum evaporation of electrons from the lowest energy subband, which leads to the increase in the electron mobility at high temperature. The results obtained explain several long-standing discrepancies between the existing theory and experiment on electron mobility on the surface of liquid helium.
An analysis of properties of a plasma with macroparticles (dust plasma) at cryogenic temperatures led us to the need to account for the effects of helium condensation on these particles. Micrometer particles in the saturated helium vapor are coated with a film of liquid helium with the thickness of about 100 Å. This limits their electronic charge, since the helium film is weakly permeable to electrons. The exceptions are clusters of Cs, Rb and K, which are not wetted by helium.
