Shearing Box Simulations of the MRI in a Collisionless Plasma

We describe local shearing box simulations of turbulence driven by the magnetorotational instability (MRI) in a collisionless plasma. Collisionless effects may be important in radiatively inefficient accretion flows, such as near the black hole in the Galactic Center. The MHD version of ZEUS is modified to evolve an anisotropic pressure tensor. A fluid closure approximation is used to calculate heat conduction along magnetic field lines. The anisotropic pressure tensor provides a qualitatively new mechanism for transporting angular momentum in accretion flows (in addition to the Maxwell and Reynolds stresses). We estimate limits on the pressure anisotropy due to pitch angle scattering by kinetic instabilities. Such instabilities provide an effective ``collision'' rate in a collisionless plasma and lead to more MHD-like dynamics. We find that the MRI leads to efficient growth of the magnetic field in a collisionless plasma, with saturation amplitudes comparable to those in MHD. In the saturated state, the anisotropic stress is comparable to the Maxwell stress, implying that the rate of angular momentum transport may be moderately enhanced in a collisionless plasma.Comment: 20 pages, 9 figures, submitted to Ap

Large magnetocrystalline anisotropy in tetragonally distorted Heuslers: a systematic study

With a view to the design of hard magnets without rare earths we explore the possibility of large magnetocrystalline anisotropy energies in Heusler compounds that are unstable with respect to a tetragonal distortion. We consider the Heusler compounds Fe$_2$YZ with Y = (Ni, Co, Pt), and Co$_2$YZ with Y = (Ni, Fe, Pt) where, in both cases, Z = (Al, Ga, Ge, In, Sn). We find that for the Co$_2$NiZ, Co$_2$PtZ, and Fe$_2$PtZ families the cubic phase is always, at $T=0$, unstable with respect to a tetragonal distortion, while, in contrast, for the Fe$_2$NiZ and Fe$_2$CoZ families this is the case for only 2 compounds -- Fe$_2$CoGe and Fe$_2$CoSn. For all compounds in which a tetragonal distortion occurs we calculate the MAE finding remarkably large values for the Pt containing Heuslers, but also large values for a number of the other compounds (e.g. Co$_2$NiGa has an MAE of -2.11~MJ/m$^3$). The tendency to a tetragonal distortion we find to be strongly correlated with a high density of states at the Fermi level in the cubic phase. As a corollary to this fact we observe that upon doping compounds for which the cubic structure is stable such that the Fermi level enters a region of high DOS, a tetragonal distortion is induced and a correspondingly large value of the MAE is then observed.Comment: 8 pages, 5 figure

Phase Transitions in Adsorbates: Part III - Vapour Pressure Studies on Formic Acid, tert-Butyl Alcohol & Cyclohexane Adsorbed on Charcoal

649-65

Phase Transitions in Adsorbates: Part IV - Behaviour of Acetic Acid Dioxane & p-Xylene Adsorbed on Silica Gel

276-27

Industrial Revolution and Smart Farming: A Critical Analysis of Research Components in Industry 4.0

Purpose of the Research: The domains of Industry 4.0 and Smart Farming encompass the application of digitization, automation, and data-driven decision-making principles to revolutionize conventional sectors. The intersection of these two fields has numerous opportunities for industry, society, science, technology, and research. Relatively, this intersection is new, and still, many grey areas need to be identified. This research is a step toward identifying research areas and current trends. Methodology Followed: The present study examines prevailing research patterns and prospective research prospects within Industry 4.0 and Smart Farming. This is accomplished by utilizing the Latent Dirichlet Allocation (LDA) methodology applied to the data procured from the Scopus database. Results Obtained: By examining the available literature extensively, the researchers have successfully discovered and developed three separate research questions. The questions mentioned above were afterward examined with great attention to detail after using Latent Dirichlet Allocation (LDA) on the dataset. The paper highlights a notable finding on the lack of existing scholarly research in the examined combined field. The existing database consists of a restricted collection of 51 scholarly papers. Nevertheless, the forthcoming terrain harbors immense possibilities for exploration and offers a plethora of prospects for additional investigation and cerebral evaluation. The originality of the research: Based on a thorough examination of existing literature, it has been established that there is a lack of research specifically focusing on the convergence of Industry 4.0 and Smart Farming. However, notable progress has been achieved in the field of seclusion. To date, the provided dataset has not been subjected to analysis using the Latent Dirichlet Allocation (LDA) technique by any researcher. Practical Implications: This study examines the Industrial Revolution's and Smart Farming's practical effects, focusing on Industry 4.0 research. The proposed method could help agricultural practitioners implement Industry 4.0 technology. It could additionally counsel technology developers on innovation and ease technology transfer. Research on regulatory frameworks, incentive programs, and resource conservation may help policymakers and government agencies

Confinement and Viscoelastic effects on Chain Closure Dynamics

Chemical reactions inside cells are typically subject to the effects both of the cell's confining surfaces and of the viscoelastic behavior of its contents. In this paper, we show how the outcome of one particular reaction of relevance to cellular biochemistry - the diffusion-limited cyclization of long chain polymers - is influenced by such confinement and crowding effects. More specifically, starting from the Rouse model of polymer dynamics, and invoking the Wilemski-Fixman approximation, we determine the scaling relationship between the mean closure time t_{c} of a flexible chain (no excluded volume or hydrodynamic interactions) and the length N of its contour under the following separate conditions: (a) confinement of the chain to a sphere of radius D, and (b) modulation of its dynamics by colored Gaussian noise. Among other results, we find that in case (a) when D is much smaller than the size of the chain, t_{c}\simND^{2}, and that in case (b), t_{c}\simN^{2/(2-2H)}, H being a number between 1/2 and 1 that characterizes the decay of the noise correlations. H is not known \`a priori, but values of about 0.7 have been used in the successful characterization of protein conformational dynamics. At this value of H (selected for purposes of illustration), t_{c}\simN^3.4, the high scaling exponent reflecting the slow relaxation of the chain in a viscoelastic medium

Identification of a novel N-acetylmuramic acid (MurNAc) transporter in Tannerella forsythia.

Tannerella forsythia is a Gram-negative periodontal pathogen lacking the ability to undergo de novo synthesis of amino sugars N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) that form the disaccharide-repeating unit of the peptidoglycan backbone. T. forsythia relies on the uptake of these sugars from the environment, which is so far unexplored. Here, we identified a novel transporter system of T. forsythia involved in the uptake of MurNAc across the inner membrane and characterized a homolog of the Escherichia. coli MurQ etherase involved in the conversion of MurNAc-6P to GlcNAc-6P. The genes encoding these components were identified on a three gene cluster spanning Tanf_08375 to Tanf_08385 located downstream from a putative peptidoglycan recycling locus. We show that the three genes, Tanf_08375, Tanf_08380, and Tanf_08385, encoding a MurNAc transporter, a putative sugar kinase, and a MurQ etherase, respectively, are transcriptionally linked. Complementation of the Tanf_08375 and Tanf_08380 genes together in trans, but not individually rescued the inability of an E. coli mutant deficient in the PTS (phosphotransferase system)-dependent MurNAc transporter MurP as well as that of a double mutant deficient in MurP and components of the PTS system to grow on MurNAc. In addition, complementation with this two-gene construct in E. coli caused depletion of MurNAc in the medium, further confirming this observation. Our results show that the products of Tanf_08375 and Tanf_08380 constitute a novel non-PTS MurNAc transporter system that seems to be widespread among bacteria of the Bacteroidetes phylum. To the best of our knowledge, this is the first identification of a PTS-independent MurNAc transporter in bacteria. IMPORTANCE: In this study we report the identification of a novel transporter for peptidoglycan amino-sugar N-acetylmuramic acid (MurNAc) in the periodontal pathogen T. forsythia It has been known since the late 1980s that T. forsythia is a MurNAc auxotroph relying on environmental sources for this essential sugar. Most sugar transporters, and the MurNAc transporter MurP in particular require a PTS phosho-relay to drive the uptake and concurrent phosphorylation of the sugar through the inner membrane in Gram-negative bacteria. Our study uncovered a novel type of PTS-independent MurNAc transporter, and although so far unique to T. forsythia, may be present in a range of bacteria both of the oral cavity and gut especially of the phylum Bacteroidetes