Influence of non-local damping on magnon properties of ferromagnets

We study the influence of non-local damping on magnon properties of Fe, Co, Ni and Fe$_{1-x}$Co$_{x}$ ($x=30\%,50\%$) alloys. The Gilbert damping parameter is typically considered as a local scalar both in experiment and in theoretical modelling. However, recent works have revealed that Gilbert damping is a non-local quantity that allows for energy dissipation between atomic sites. With the Gilbert damping parameters calculated from a state-of-the-art real-space electronic structure method, magnon lifetimes are evaluated from spin dynamics and linear response, where a good agreement is found between these two methods. It is found that non-local damping affects the magnon lifetimes in different ways depending on the system. Specifically, we find that in Fe, Co, and Ni the non-local damping decreases the magnon lifetimes, while in $\rm Fe_{70}Co_{30}$ and Fe$_{50}$Co$_{50}$ an opposite, non-local damping effect is observed, and our data show that it is much stronger in the former

Tunable and robust room-temperature magnon-magnon entanglement

Although challenging, realizing controllable high-temperature entanglement is of immense importance for practical applications as well as for fundamental research in quantum technologies. Here, we report the existence of entangled steady states in bipartite quantum magnonic systems at high temperatures. We consider dissipative dynamics of two magnons in a bipartite antiferromagnet or ferrimagnet subjected to a vibrational phonon mode and an external rotating magnetic field. To quantify the bipartite magnon-magnon entanglement, we use the entanglement negativity and compute its dependence on the temperature and magnetic field. We show that, for any given phonon frequency and magnon-phonon coupling rates, there are always ranges of the magnetic field amplitudes and frequencies, for which bipartite magnon-magnon entanglement persists up to and above the room temperature. The generality of the result allows for experimental observation in a variety of crystals and synthetic bipartite antiferromagnetic and ferrimagnetic materials.Comment: 6 pages, 5 figure

Metaheuristic conditional neural network for harvesting skyrmionic metastable states

We present a metaheuristic conditional neural-network-based method aimed at identifying physically interesting metastable states in a potential energy surface of high rugosity. To demonstrate how this method works, we identify and analyze spin textures with topological charge $Q$ ranging from 1 to $-13$ (where antiskyrmions have $Q<0$) in the Pd/Fe/Ir(111) system, which we model using a classical atomistic spin Hamiltonian based on parameters computed from density functional theory. To facilitate the harvest of relevant spin textures, we make use of the newly developed Segment Anything Model (SAM). Spin textures with $Q$ ranging from $-3$ to $-6$ are further analyzed using finite-temperature spin-dynamics simulations. We observe that for temperatures up to around 20\,K, lifetimes longer than 200\,ps are predicted, and that when these textures decay, new topological spin textures are formed. We also find that the relative stability of the spin textures depend linearly on the topological charge, but only when comparing the most stable antiskyrmions for each topological charge. In general, the number of holes (i.e., non-self-intersecting curves that define closed domain walls in the structure) in the spin texture is an important predictor of stability -- the more holes, the less stable is the texture. Methods for systematic identification and characterization of complex metastable skyrmionic textures -- such as the one demonstrated here -- are highly relevant for advancements in the field of topological spintronics

Birth mode is associated with earliest strain-conferred gut microbiome functions and immunostimulatory potential

The effects of caesarean section delivery on mother-to-neonate transmission of microbiota are unclear. Here the authors show that caesarean section delivery can affect the transmission of specific microbial strains and the immunomodulatory potential of the microbiota

Intestinal Epithelial Stem/Progenitor Cells Are Controlled by Mucosal Afferent Nerves

Background: The maintenance of the intestinal epithelium is of great importance for the survival of the organism. A possible nervous control of epithelial cell renewal was studied in rats and mice. Methods: Mucosal afferent nerves were stimulated by exposing the intestinal mucosa to capsaicin (1.6 mM), which stimulates intestinal external axons. Epithelial cell renewal was investigated in the jejunum by measuring intestinal thymidine kinase (TK) activity, intestinal H-3-thymidine incorporation into DNA, and the number of crypt cells labeled with BrdU. The influence of the external gut innervation was minimized by severing the periarterial nerves. Principal Findings: Luminal capsaicin increased all the studied variables, an effect nervously mediated to judge from inhibitory effects on TK activity or H-3-thymidine incorporation into DNA by exposing the mucosa to lidocaine (a local anesthetic) or by giving four different neurotransmitter receptor antagonists i.v. (muscarinic, nicotinic, neurokinin1 (NK1) or calcitonin gene related peptide (CGRP) receptors). After degeneration of the intestinal external nerves capsaicin did not increase TK activity, suggesting the involvement of an axon reflex. Intra-arterial infusion of Substance P (SP) or CGRP increased intestinal TK activity, a response abolished by muscarinic receptor blockade. Immunohistochemistry suggested presence of M3 and M5 muscarinic receptors on the intestinal stem/progenitor cells. We propose that the stem/progenitor cells are controlled by cholinergic nerves, which, in turn, are influenced by mucosal afferent neuron(s) releasing acetylcholine and/or SP and/or CGRP. In mice lacking the capsaicin receptor, thymidine incorporation into DNA and number of crypt cells labeled with BrdU was lower than in wild type animals suggesting that nerves are important also in the absence of luminal capsaicin, a conclusion also supported by the observation that atropine lowered thymidine incorporation into DNA by 60% in control rat segments. Conclusion: Enteric nerves are of importance in maintaining the intestinal epithelial barrier.Original Publication:Ove Lundgren, Mats Jodal, Madeleine Jansson, Anders T Ryberg and Lennart Svensson, Intestinal Epithelial Stem/Progenitor Cells Are Controlled by Mucosal Afferent Nerves, 2011, PLOS ONE, (6), 2, 16295.http://dx.doi.org/10.1371/journal.pone.0016295Copyright: Public Library of Science (PLoS)http://www.plos.org

Mycket läsning gör dig klok-därför läs varenda bok : Om skolan och elevers läslust

Alla elever måste läsa skönlitteratur i skolan. Ofta är det så att de själva inte får särskilt stort inflytande över den litteratur de ska läsa. Valet av litteratur står lärarna i hög utsträckning för och eleverna måste läsa böcker de inte kan relatera till från deras egen verklighet. Uppsatsen syftar till att undersöka hur elever på gymnasiets yrkesförberedande program upplever denna situation och på vilket sätt skolan påverkar deras läslust, deras inspiration att läsa skönlitteratur. Undersökningen genomförs med hjälp av lärar- och elevintervjuer samt en enkät på en gymnasieskola i en mellansvensk stad. Slutsatser som kan dras är att skolan i låg grad påverkar elevers läslust. Eleverna läser i relativt hög grad, men inte det som skolan sätter i händerna på dem. Den litteratur lärare väljer upplevs som främmande och är inget eleverna själva skulle välja. Lärarna på skolan menar i hög grad att det är andra skäl än den litteratur som de väljer, som är orsak till att elever inte känner läslust