Rethinking α-RuCl3

We argue that several empirical constraints strongly restrict parameters of the effective microscopic spin model describing α-RuCl3. In particular, such constraints dictate a substantial positive off-diagonal anisotropic coupling Γ′>0, not anticipated previously. The renormalization by quantum fluctuations allows to reconcile larger values of the advocated bare parameters with their earlier assessments and provides a consistent description of the field evolution of spin excitations in the paramagnetic phase. We assert that large anisotropic terms inevitably result in strong anharmonic coupling of magnons, necessarily leading to broad features in their spectra due to decays, in accord with the observations in α-RuCl3. Using duality transformations, we explain the origin of the pseudo-Goldstone mode that is ubiquitous to the studied parameter space and is present in α-RuCl3. Our analysis offers a description of α-RuCl3 as an easy-plane ferromagnet with antiferromagnetic further-neighbor and strong off-diagonal couplings, which is in a fluctuating zigzag ground state proximate to an incommensurate phase that is continuously connected to a ferromagnetic one

Experience in the Design and Production of Recombinant Oral Vaccine «Revax VZT»

Objective of the work was the production of recombinant vaccine «RevaxVZT» in tablet dosage form against hepatitis B and pathogenic for humans orthopoxviruses for further clinical trials. Materials and methods. Recombinant strain b7.5S2-S of vaccinia virus carrying a DNA fragment of hepatitis B virus inserted into thymidinekinase gene was used as an active component of the vaccine. Microbiological, virological, physical, physical and chemical, and biotechnological methods were used for studying the quality of the drug and technological processes. Results and discussion. Results of technological control for semi-finished products and final products of the vaccine “Revax VZT” showed the possibility of using certified hardware-processing line of “TEOVac” for its manufacturing. Same technology can be potentially used with other live tableted embryo smallpox vaccines too. For the development of the vaccine “Revax VZT” with the specific activity of not less than 1.0·107 PFu/tablet, it is necessary to use a dry virus-containing material with activity not less than 2.0·108 PFU/g which is produced by freeze-drying of liquid virus-containing preparation with the activity of not less than 1.0·108 PFU/g, preferentially propagated from chorionic allantoic membranes of chicken embryos as a substrate for viral biomass accumulation

Pressure-induced amorphous-to-amorphous configuration change in Ca-Al metallic glasses

Pressure-induced amorphous-to-amorphous configuration changes in Ca-Al metallic glasses (MGs) were studied by performing in-situ room-temperature high-pressure x-ray diffraction up to about 40 GPa. Changes in compressibility at about 18 GPa, 15.5 GPa and 7.5 GPa during compression are detected in Ca80Al20, Ca72.7Al27.3, and Ca66.4Al33.6 MGs, respectively, whereas no clear change has been detected in the Ca50Al50 MG. The transfer of s electrons into d orbitals under pressure, reported for the pressure-induced phase transformations in pure polycrystalline Ca, is suggested to explain the observation of an amorphous-to-amorphous configuration change in this Ca-Al MG system. Results presented here show that the pressure induced amorphous-to-amorphous configuration is not limited to f electron-containing MGs

Enforcing higher labour standards within developing country value chains: consequences for MNEs and informal actors in a dual economy

The 2013 Rana Plaza disaster led external stakeholders to insist on higher labour standards in apparel global value chains (GVCs). Stakeholders now expect MNEs to take ‘full-chain’ responsibility. However, the increased monitoring and enforcement costs of a large network of suppliers have been non-trivial. MNEs instead implement a ‘cascading compliance’ approach, coupled with a partial re-internalization. Elevated costs are further exacerbated in developing countries where the informal and formal sector are linked, and cost competitiveness greatly depends on this duality. Monitoring actors in the informal sector is difficult, and few informal actors can achieve compliance. GVCs have therefore reduced informal sector engagement by excluding non-compliant actors and investing in greater automation. By seeking to strictly enforce compliance, MNEs are attenuating some of the positive effects of MNE investment, particularly the prospects for employment creation (especially among women), and enterprise growth in the informal sector. I discuss how these observations might inform other cross-disciplinary work in development, ethics, and sociology. Finally, I note implications for IB theory from the disparities between the ownership, control and responsibility boundaries of the firm

Damped Topological Magnons in the Kagome-Lattice Ferromagnets.

We demonstrate that interactions can substantially undermine the free-particle description of magnons in ferromagnets on geometrically frustrated lattices. The anharmonic coupling, facilitated by the Dzyaloshinskii-Moriya interaction, and a highly degenerate two-magnon continuum yield a strong, nonperturbative damping of the high-energy magnon modes. We provide a detailed account of the effect for the S=1/2 ferromagnet on the kagome lattice and propose further experiments

Field-induced dynamical properties of the XXZ model on a honeycomb lattice

We present a comprehensive 1/S study of the field-induced dynamical properties of the nearest-neighbor XXZ antiferromagnet on a honeycomb lattice using the formalism of nonlinear spin-wave theory developed for this model. The external magnetic field controls spin frustration in the system and induces noncollinearity of the spin structure, which is essential for the two-magnon decay processes. Our results include an intriguing field-evolution of the regions of the Brillouin zone wherein decays of spin excitations are prominent, a detailed classification of the decay channels involving magnons from both excitation branches, and a thorough analysis of the singularities in the magnon spectra due to coupling to the two-magnon continuum, all of which are illustrated for several field and anisotropy values. We highlight a number of features related to either the non-Bravais nature of the lattice or the existence of the Dirac-like points in the spectrum. In addition, the asymptotic behavior of the decay rates near high-symmetry points is analyzed in detail. The inelastic neutron-scattering spin-spin structure factor is obtained in the leading 1/S order and is shown to exhibit qualitatively distinct fingerprints of the decay-induced magnon dynamics such as quasiparticle peaks broadened by decays and strong spectral weight redistribution

Rethinking α-RuCl3

We argue that several empirical constraints strongly restrict parameters of the effective microscopic spin model describing α-RuCl3. In particular, such constraints dictate a substantial positive off-diagonal anisotropic coupling Γ′>0, not anticipated previously. The renormalization by quantum fluctuations allows to reconcile larger values of the advocated bare parameters with their earlier assessments and provides a consistent description of the field evolution of spin excitations in the paramagnetic phase. We assert that large anisotropic terms inevitably result in strong anharmonic coupling of magnons, necessarily leading to broad features in their spectra due to decays, in accord with the observations in α-RuCl3. Using duality transformations, we explain the origin of the pseudo-Goldstone mode that is ubiquitous to the studied parameter space and is present in α-RuCl3. Our analysis offers a description of α-RuCl3 as an easy-plane ferromagnet with antiferromagnetic further-neighbor and strong off-diagonal couplings, which is in a fluctuating zigzag ground state proximate to an incommensurate phase that is continuously connected to a ferromagnetic one

Easy-plane anisotropic-exchange magnets on a honeycomb lattice: Quantum effects and dealing with them

We provide analytical and numerical insights into the phase diagram and other properties of the extended Kitaev-Heisenberg model on the honeycomb lattice in the easy-plane limit, in which interactions are only between spin components that belong to the plane of magnetic ions. This parameter subspace allows for a much-needed systematic quantitative investigation of spin excitations in the ordered phases and of their generic features. Specifically, we demonstrate that in this limit one can consistently take into account magnon interactions in both zero-field zigzag and field-polarized phases. For the nominally polarized phase, we propose a regularization of the unphysical divergences that occur at the critical field and are plaguing the 1/S approximation in this class of models. For the explored parameter subspace, all symmetry-allowed terms of the standard parametrization of the extended Kitaev-Heisenberg model, such as K, J, and Γ, are significant, making the offered consideration relevant to a much wider parameter space. The dynamical structure factor near the paramagnetic critical point illustrates this relevance by showing features that are reminiscent of the ones observed in α-RuCl3, underscoring that they are not unique and should be common to a wide range of parameters of the model and, by extension, to other materials

Field-induced dynamical properties of the XXZ model on a honeycomb lattice

We present a comprehensive 1/S study of the field-induced dynamical properties of the nearest-neighbor XXZ antiferromagnet on a honeycomb lattice using the formalism of nonlinear spin-wave theory developed for this model. The external magnetic field controls spin frustration in the system and induces noncollinearity of the spin structure, which is essential for the two-magnon decay processes. Our results include an intriguing field-evolution of the regions of the Brillouin zone wherein decays of spin excitations are prominent, a detailed classification of the decay channels involving magnons from both excitation branches, and a thorough analysis of the singularities in the magnon spectra due to coupling to the two-magnon continuum, all of which are illustrated for several field and anisotropy values. We highlight a number of features related to either the non-Bravais nature of the lattice or the existence of the Dirac-like points in the spectrum. In addition, the asymptotic behavior of the decay rates near high-symmetry points is analyzed in detail. The inelastic neutron-scattering spin-spin structure factor is obtained in the leading 1/S order and is shown to exhibit qualitatively distinct fingerprints of the decay-induced magnon dynamics such as quasiparticle peaks broadened by decays and strong spectral weight redistribution