Massive Molecular Gas as a Fuel Tank for Active Galactic Nuclei Feedback In Central Cluster Galaxies

Massive molecular gas has been discovered in giant elliptical galaxies at the centers of galaxy clusters. To reveal its role in active galactic nucleus (AGN) feedback in those galaxies, we construct a semianalytical model of gas circulation. This model especially focuses on the massive molecular gas (interstellar cold gas on a scale of ∼10 kpc) and the circumnuclear disk (≲0.5 kpc). We consider the destruction of the interstellar cold gas by star formation and the gravitational instability for the circumnuclear disk. Our model can reproduce the basic properties of the interstellar cold gas and the circumnuclear disk, such as their masses. We also find that the circumnuclear disk tends to stay at the boundary between stable and unstable states. This works as an “adjusting valve” that regulates mass accretion toward the supermassive black hole. On the other hand, the interstellar cold gas serves as a “fuel tank” in the AGN feedback. Even if the cooling of the galactic hot gas is prevented, the interstellar cold gas can sustain the AGN activity for ≳0.5 Gyr. We also confirm that the small entropy of hot gas (≲30 keV cm2) or the short cooling time (≲1 Gyr) is a critical condition for the existence of massive amounts of molecular gas in the galaxy. The dissipation time of the interstellar cold gas may be related to the critical cooling time. The galaxy behavior is described by a simple relation among the disk stability, the cloud dissipation time, and the gas cooling rate.

Correlation of radius of cathode spot of vacuum arc of metals on the size of generated droplets

The simple relation to estimate the cathode spot radius of a vacuum arc of pure metals is obtained. On its basis, is established between the cathode spot radius and the size of droplets generated by the cathode spot a correlation. This enables to find ways to reduce droplets in the plasma flow, which forms coatings by the vacuum electric arc method. The paper presents the results of experimental study of the droplet sizes depending on the vacuum arc current iд. The size and amount of the droplets on an area of 1 mm2 of the coating surface are determined using the ImageSP program. As the initial data, the microstructures of the coatings are used with an increase of: ç100, ç200, ç500, ç1000, ç1500. The droplets have been generated by a cathode spot of a vacuum arc for the alloy of the composition, at.%: 68Al–8Cr–4Nb–20Si. It is established that the number of droplets with a diameter of < 2 μm is generated most of all, and the number of droplets with a diameter > 10 μm is generated least of all. The number of generated droplets with a diameter from 2 to 10 μm slightly depends on the arc current iд. It is noted that the diameter of the alloy droplet is smaller than the diameter of the droplets generated by the cathode spot on its components due to the fact that the radius of the cathode spot on the alloy is smaller than the radius of the cathode spot on its pure components.

Radius of influence of a vortex

Using the pressure profile in and around a vortex tube a simple relation for the radius of influence of the vortex has been derived. The results have been applied to assess the region of maximum devastation in a tornado. The analysis reveals that the occurrence of 'eye wall' region in a tropical cyclone is a hydrodynamical phenomenon.

On regular and random two-dimensional packing of crosses

Packing problems, even of objects with regular geometries, are in general non-trivial. For few special shapes, the features of crystalline as well as random, irregular two-dimensional (2D) packing structures are known. The packing of 2D crosses does not yet belong to the category of solved problems. We demonstrate in experiments with crosses of different aspect ratios (arm width to length) which packing fractions are actually achieved by random packing, and we compare them to densest regular packing structures. We determine local correlations of the orientations and positions after ensembles of randomly placed crosses were compacted in the plane until they jam. Short-range orientational order is found over 2 to 3 cross lengths. Similarly, correlations in the spatial distributions of neighbors extend over 2 to 3 crosses. There is no simple relation between the geometries of the crosses and the peaks in the spatial correlation functions, but some features of the orientational correlations can be traced to typical local configurations.

Determination of the Range of Magnetic Interactions from the Relations between Magnon Eigenvalues at High-Symmetry κ Points

Magnetic exchange interactions (MEIs) define networks of coupled magnetic moments and lead to a surprisingly rich variety of their magnetic properties. Typically MEIs can be estimated by fitting experimental results. Unfortunately, how many MEIs need to be included in the fitting process for a material is unclear a priori, which limits the results obtained by these conventional methods. Based on linear spin-wave theory but without performing matrix diagonalization, we show that for a general quadratic spin Hamiltonian, there is a simple relation between the Fourier transform of MEIs and the sum of square of magnon energies (SSME). We further show that according to the real-space distance range within which MEIs are considered relevant, one can obtain the corresponding relationships between SSME in momentum space. By directly utilizing these characteristics and the experimental magnon energies at only a few high-symmetry k points in the Brillouin zone, one can obtain strong constraints about the range of exchange path beyond which MEIs can be safely neglected. Our methodology is also generally applicable for other Hamiltonian with quadratic Fermi or Boson operators.

Commercial Buildings in Town. The Influence of Discount Shops on the Trade Structure of a Small Town

Changes taking place in the spatial structure of trade in cities have been very dynamic in recent decades. The goal of the research was to determine the dynamics and direction of changes in shaping the traditional commercial structure of small towns, in the context of discount shops location. The subject matter of the research constituted more than ten towns in southern Poland. Traditional shops located there were analysed in terms of their location, the profile and length of their activity. Studies on global trade development processes are available, as well as detailed research results on individual trade assumptions. On the other hand, there is a research gap regarding studies involving the location of commercial buildings, especially in small towns. The research results are a valuable source of information for representatives of various scientific disciplines as well as city authorities. The presented research provides knowledge and constitutes the basis for further research for representatives of various research fields. The areas with the most intensive commercial activity in the last 30 years were correlated with the number of inhabitants. For a selected group of towns, their binding urban planning documentation was verified with respect to specifications facilitating or excluding the establishment of discount shops. The conclusions reached on the basis of the research do not confirm a popular view that discount shops have a negative effect on urban space. The performed analyses indicate that there is no simple relation between a discount shop location and the decreasing number of traditional shops in the investigated cities. The presented research results gain an additional advantage—they form an archive of the development of commerce structure in towns in the period starting with the fall of the centrally planned economy and finishing with the COVID–19 pandemic. The presented material forms a basis for further urban studies which will use the experience gained at this stage

PerFSeeB: Designing Long High-weight Single Spaced Seeds for Full Sensitivity Alignment with a Given Number of Mismatches

Background: Technical progress in computational hardware allows researchers to use new approaches for sequence alignment problems. A standard procedure is usually based on pre-aligning of short subsequences followed by proper comparison of neighbouring parts. For this purpose index files are created that store all subsequences (or numbers associated with them) and their positions within a reference sequence. Index files designed on subsequences of 32–64 symbols for a human reference genome can now be easily stored without any compression even on a budget computer. The main goal now is to choose a combination of symbols (a spaced seed) that will tolerate various mismatches between reference and given sequences. An ideal spaced seed should allow us to find all such positions (full sensitivity). By increasing the seed’s weight by one we usually reduce the number of candidate positions fourfold. At the same time longer seeds also reduce the number of signatures to be checked. Results: Several algorithms to assist seed generation are presented. The first one allows us to find all permitted spaced seeds iteratively. The results obtained with the algorithm show specific patterns of the seeds of the highest weight. Among the best seeds, there are periodic seeds with a simple relation between the period of a seed, its length and the length of a read. The second algorithm generates blocks for periodic seeds. A list of blocks is found for blocks of up to 50 symbols and up to 9 mismatches. The third algorithm uses those lists to find spaced seeds for reads of an arbitrary length. Conclusions: Lists of long high-weight spaced seeds are found and available in Supplementary Materials. The seeds are best in terms of weights compared to seeds from other papers and can usually be applied to shorter reads. Codes for all algorithms are available at https://github.com/vtman/PerFSeeB.

Understanding Sexual Agency. Implications for Sexual Health Programming

Debates on human agency, especially female and sexual agency, have permeated the social scientific literature and health educational practice for multiple decades now. This article provides a review of recent agency debates illustrating how criticisms of traditional conceptions of (sexual) agency have led to a notable diversification of the concept. A comprehensive, inclusive description of sexual agency is proposed, focusing on the navigation of goals and desires in the wider structural context, and acknowledging the many forms sexual agency may take. We argue there is no simple relation between sexual agency and sexual health. Next, we describe the implications of such an understanding of sexual agency for Comprehensive Sexuality Education (CSE) and for sexual health and rights (SHR) programming more generally. We put forward validation of agentic variety, gender transformative approaches, meaningful youth participation, and multicomponent strategies as essential in building young peoples’ sexual agency and their role as agents of wider societal change. We also show that these essential conditions, wherever they have been studied, are far from being realized. With this review and connected recommendations, we hope to set the stage for ongoing, well-focused research and development in the area.

An Application of the Information Entropy to Nuclei

Shannon's information entropies in position- and momentum-space and their sum $S$ are calculated for various $s$-$p$ and $s$-$d$ shell nuclei using a correlated one-body density matrix depending on the harmonic oscillator size $b_0$ and the short range correlation parameter $y$ which originates from a Jastrow correlation function. It is found that the information entropy sum for a nucleus depends only on the correlation parameter $y$ through the simple relation $S= s_{0A} + s_{1A} y^{-\lambda_{sA}}$, where $s_{0A}$, $s_{1A}$ and $\lambda_{sA}$ depend on the mass number $A$. Finally, we propose a method to determine the correlation parameter from the above property of $S$ as well as the linear dependence of $S$ on the logarithm of the number of nucleons.