Many Body Problems with "Spin"-Related Contact Interactions

We study quantum mechanical systems with "spin"-related contact interactions in one dimension. The boundary conditions describing the contact interactions are dependent on the spin states of the particles. In particular we investigate the integrability of $N$-body systems with $\delta$-interactions and point spin couplings. Bethe ansatz solutions, bound states and scattering matrices are explicitly given. The cases of generalized separated boundary condition and some Hamiltonian operators corresponding to special spin related boundary conditions are also discussed.Comment: 13 pages, Late

Magneto-structural coupling and harmonic lattice dynamics in CaFe2_2As2_2 probed by M\"ossbauer spectroscopy

In this paper we present detailed M\"ossbauer spectroscopy study of structural and magnetic properties of the undoped parent compound CaFe$_2$As$_2$ single crystal. By fitting the temperature dependence of the hyperfine magnetic field we show that the magneto-structural phase transition is clearly first-order in nature and we also deduced the compressibility of our sample to be $1.67\times10^{-2}\,GPa^{-1}$. Within the Landau's theory of phase transition, we further argue that the observed phase transition may stem from the strong magneto-structural coupling effect. Temperature dependence of the Lamb-M\"ossbauer factor show that the paramagnetic phase and the antiferromagnetic phase exhibit similar lattice dynamics in high frequency modes with very close Debye temperatures, $\Theta_D \sim$270\,K.Comment: 6 pages,5 figures Accepted by J. Phys.: Condens. Matte

On the dynamics of transfer-ionization in fast ion-atomic collisions

We consider trasfer-ionization in collisions of fast (3.6 -- 11 MeV/u) protons, alpha-particles and lithium nuclei with helium atoms. There are just a few basic mechanisms contributing to this process which can be grouped into correlated ones, which crucially depend on the electron-electron interaction, and uncorrelated, which do not need this interaction to proceed. We show that by exploring momentum spectra of the emitted electrons the correlated and uncorrelated mechanisms can be cleary separated from each other. This exploration also enables one to get insight into subtle details of the dynamics of transfer-ionization.Comment: 12 pages. 7 figure

The Effect of COVID-19 On Antibiotic Resistance

Over three years have passed since the beginning of the COVID-19 pandemic. During these times we have experienced significant changes in all areas of our life. In healthcare, more attention was focused on COVID-19 than other concerns. An unexpected consequence of the pandemic was a silent progression of an increased spread of multi-resistant pathogens. While antibiotic use during the pandemic varied across healthcare settings, antibiotics were prescribed for COVID-19 patients, even though antibiotics are known not to be effective against viruses.1 In dentistry, antibiotics were prescribed to prevent potential dental infections, since many dental offices were not open. Antimicrobial resistance was one of our greatest public health concerns prior to the COVID-19 pandemic, and it remains so

Evolutionary biology: a basic science for psychiatry?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65529/1/j.1600-0447.1992.tb03234.x.pd

Electronic Structure, Magnetism and Superconductivity of Layered Iron Compounds

The layered iron superconductors are discussed using electronic structure calculations. The four families of compounds discovered so far, including Fe(Se,Te) have closely related electronic structures. The Fermi surface consists of disconnected hole and electron cylinders and additional hole sections that depend on the specific material. This places the materials in proximity to itinerant magnetism, both due to the high density of states and due to nesting. Comparison of density functional results and experiment provides strong evidence for itinerant spin fluctuations, which are discussed in relation to superconductivity. It is proposed that the intermediate phase between the structural transition and the SDW transition in the oxy-pnictides is a nematic phase.Comment: Proceedings ISS200

New Fe-based superconductors: properties relevant for applications

Less than two years after the discovery of high temperature superconductivity in oxypnictide LaFeAs(O,F) several families of superconductors based on Fe layers (1111, 122, 11, 111) are available. They share several characteristics with cuprate superconductors that compromise easy applications, such as the layered structure, the small coherence length, and unconventional pairing, On the other hand the Fe-based superconductors have metallic parent compounds, and their electronic anisotropy is generally smaller and does not strongly depend on the level of doping, the supposed order parameter symmetry is s wave, thus in principle not so detrimental to current transmission across grain boundaries. From the application point of view, the main efforts are still devoted to investigate the superconducting properties, to distinguish intrinsic from extrinsic behaviours and to compare the different families in order to identify which one is the fittest for the quest for better and more practical superconductors. The 1111 family shows the highest Tc, huge but also the most anisotropic upper critical field and in-field, fan-shaped resistive transitions reminiscent of those of cuprates, while the 122 family is much less anisotropic with sharper resistive transitions as in low temperature superconductors, but with about half the Tc of the 1111 compounds. An overview of the main superconducting properties relevant to applications will be presented. Upper critical field, electronic anisotropy parameter, intragranular and intergranular critical current density will be discussed and compared, where possible, across the Fe-based superconductor families