We propose a new theory of the topological Hall effect (THE) in systems with non-collinear magnetization textures such as magnetic skyrmions. We solve the problem of electron scattering on a magnetic ...skyrmion exactly, for an arbitrary strength of exchange interaction and the skyrmion size. We report the existence of different regimes of THE and resolve the apparent contradiction between the adiabatic Berry phase theoretical approach and the perturbation theory for THE. We traced how the topological charge Hall effect transforms into the spin Hall effect upon varying the exchange interaction strength or the skyrmion size. This transformation has a nontrivial character: it is accompanied by an oscillating behavior of both charge and spin Hall currents. This hallmark of THE allows one to identify the chirality driven contribution to Hall response in the experiments.
To feed successfully, ticks must bypass or suppress the host’s defense mechanisms, particularly the immune system. To accomplish this, ticks secrete specialized immunomodulatory proteins into their ...saliva, just like many other blood-sucking parasites. However, the strategy of ticks is rather unique compared to their counterparts. Ticks’ tendency for gene duplication has led to a diverse arsenal of dozens of closely related proteins from several classes to modulate the immune system’s response. Among these are chemokine-binding proteins, complement pathways inhibitors, ion channels modulators, and numerous poorly characterized proteins whose functions are yet to be uncovered. Studying tick immunomodulatory proteins would not only help to elucidate tick-host relationships but would also provide a rich pool of potential candidates for the development of immunomodulatory intervention drugs and potentially new vaccines. In the present review, we will attempt to summarize novel findings on the salivary immunomodulatory proteins of ticks, focusing on biomolecular targets, structure-activity relationships, and the perspective of their development into therapeutics.
The magnetic proximity effect is significant for atomically thin layers of two-dimensional materials. In this paper, we study the mechanisms of photogeneration spin-polarized carriers in graphene on ...a magnetic insulator. The magnetic proximity effect and lowered symmetry at the interface enhance the spin response of graphene in the alternating electric field of the incident light. The first leads to spin splitting of the linear spectrum of Dirac electrons. The second increases the role of the spin-orbit interaction. The main mechanisms of photogenerated spin polarization have been considered, including spin flip intersubband and interband transitions, and their contribution to the absorption coefficient of graphene.
Wetlands are the world's largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of methane emissions to environmental factors such as soil temperature and moisture has ...led to concerns about potential positive feedbacks to climate change. This risk is particularly relevant at high latitudes, which have experienced pronounced warming and where thawing permafrost could potentially liberate large amounts of labile carbon over the next 100 years. However, global models disagree as to the magnitude and spatial distribution of emissions, due to uncertainties in wetland area and emissions per unit area and a scarcity of in situ observations. Recent intensive field campaigns across the West Siberian Lowland (WSL) make this an ideal region over which to assess the performance of large-scale process-based wetland models in a high-latitude environment. Here we present the results of a follow-up to the Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP), focused on the West Siberian Lowland (WETCHIMP-WSL). We assessed 21 models and 5 inversions over this domain in terms of total CH4 emissions, simulated wetland areas, and CH4 fluxes per unit wetland area and compared these results to an intensive in situ CH4 flux data set, several wetland maps, and two satellite surface water products. We found that (a) despite the large scatter of individual estimates, 12-year mean estimates of annual total emissions over the WSL from forward models (5.34 ± 0.54 Tg CH4 yr-1), inversions (6.06 ± 1.22 Tg CH4 yr-1), and in situ observations (3.91 ± 1.29 Tg CH4 yr-1) largely agreed; (b) forward models using surface water products alone to estimate wetland areas suffered from severe biases in CH4 emissions; (c) the interannual time series of models that lacked either soil thermal physics appropriate to the high latitudes or realistic emissions from unsaturated peatlands tended to be dominated by a single environmental driver (inundation or air temperature), unlike those of inversions and more sophisticated forward models; (d) differences in biogeochemical schemes across models had relatively smaller influence over performance; and (e) multiyear or multidecade observational records are crucial for evaluating models' responses to long-term climate change.
The paper presents the results of calculations of the sampling fluctuations in Pb–LAr electromagnetic sandwich calorimeters. The GEANT4 package was used to generate showers initiated by electrons ...with energies
E
0
from 20 to 500 GeV. It is shown that the dependence of the sampling fluctuations on
E
0
and the thickness of the lead absorber
x
can be described by the formula
kx
b
/
. The exponent
b
weakly depends on the LAr gap width
d
and is close to 2/3 and
k
= 0.1985−0.0363ln
d
mm.
Intramolecular hydrogen bonds in aprotic media were studied by combined (simultaneous) NMR and UV–vis spectroscopy. The species under investigation were anionic and featured single or coupled H-bonds ...between, for example, carboxylic groups and phenolic oxygen atoms (COO···H···OC)−, among phenolic oxygen atoms (CO···H···OC)−, and hydrogen bond chains between a carboxylic group and two phenolic oxygen atoms (COO···H···(OC)···H···OC)−. The last anion may be regarded as a small molecule model for the hydrogen bond system in the active site of wild-type photoactive yellow protein (PYP) while the others mimic the corresponding H-bonds in site-selective mutants. Proton positions in isolated hydrogen bonds and hydrogen bond chains were assessed by calculations for vacuum conditions and spectroscopically for the two media, CD2Cl2 and the liquefied gas mixture CDClF2/CDF3 at low temperatures. NMR parameters allow for the estimation of time-averaged H-bond geometries, and optical spectra give additional information about geometry distributions. Comparison of the results from the various systems revealed the effects of the formation of hydrogen bond chains and changes of medium conditions on the geometry of individual H-bonds. In particular, the proton in a hydrogen bond to a carboxylic group shifts from the phenolic oxygen atom in the system COO–···H–OC to the carboxylic group in COO–H···(OC)−···H–OC as a result of hydrogen bond formation to the additional phenolic donor. Increase in medium polarity may, however, induce the conversion of a structure of a type COO–H···(OC)−···H–OC to the type COO–···H–(OC)···H–OC. Application of these results obtained from the model systems to PYP suggests that both cooperative effects within the hydrogen bond chain and a low-polarity protein environment are prerequisites for the stabilization of negative charge on the cofactor and hence for the spectral tuning of the photoreceptor.
We propose a modified extragradient method with dynamic step size adjustment to solve variational inequalities with monotone operators acting in a Hilbert space. In addition, we consider a version of ...the method that finds a solution of a variational inequality that is also a fixed point of a quasi-nonexpansive operator. We establish the weak convergence of the methods without any Lipschitzian continuity assumption on operators.
The propagation of an initially localized perturbation via an interacting many-particle Hamiltonian dynamics is investigated. We argue that the propagation of the perturbation can be captured by the ...use of a continuous-time random walk where a single particle is traveling through an active, fluctuating medium. Employing two archetype ergodic many-particle systems, namely, (i) a hard-point gas composed of two unequal masses and (ii) a Fermi-Pasta-Ulam chain, we demonstrate that the corresponding perturbation profiles coincide with the diffusion profiles of the single-particle Lévy walk approach. The parameters of the random walk can be related through elementary algebraic expressions to the physical parameters of the corresponding test many-body systems.
The topological Hall effect is used extensively to study chiral spin textures in various materials. However, the factors controlling its magnitude in technologically-relevant thin films remain ...uncertain. Using variable-temperature magnetotransport and real-space magnetic imaging in a series of Ir/Fe/Co/Pt heterostructures, here we report that the chiral spin fluctuations at the phase boundary between isolated skyrmions and a disordered skyrmion lattice result in a power-law enhancement of the topological Hall resistivity by up to three orders of magnitude. Our work reveals the dominant role of skyrmion stability and configuration in determining the magnitude of the topological Hall effect.
PDF
