Free electron laser with terahertz band Bragg reflectors

Periodical Bragg structures may be considered as an effective way of controlling the electromagnetic energy fluxes and provision of spatially coherent radiation in the free electron lasers with oversized interaction space. A new scheme of terahertz band FEL with hybrid Bragg resonator is proposed consisting of advanced input Bragg mirror and traditional output Bragg mirror. An advanced Bragg mirror exploiting the coupling between the two counterpropagating modes and the quasicutoff one provides mode selection over the transverse index. The main amplification of the wave by the electron beam takes place in the regular section of the resonator. Small reflections from the output traditional Bragg mirror are sufficient for oscillator self-excitation

New Polymorph of Dehydroepiandrosterone Obtained via Cryomodification

A new anhydrous polymorph of dehydroepiandrosterone (DHEA) is detected in cryomodified powder samples and designated as form VII. The crystal structure of form VII is determined from multiphase X-ray powder diffraction (XRPD) data. Additionally, the unknown crystal structures of anhydrous form III and the new monohydrated DHEA form designated as form S5 are also determined from multiphase XRPD data. To validate the crystal structures III, VII, and S5, energy minimization with dispersion-corrected density functional theory is performed in VASP. An extended list of the DHEA forms with the known crystal structures, which now covers anhydrous forms I, II, III, VI, and VII and solvated forms S1, S2, S4 and S5, allows quantification of DHEA solid-state transformations to be carried out

Are Hamsters a Suitable Model for Evaluating the Immunogenicity of RBD-Based Anti-COVID-19 Subunit Vaccines?

Currently, SARS-CoV-2 spike receptor-binding-domain (RBD)-based vaccines are considered one of the most effective weapons against COVID-19. During the first step of assessing vaccine immunogenicity, a mouse model is often used. In this paper, we tested the use of five experimental animals (mice, hamsters, rabbits, ferrets, and chickens) for RBD immunogenicity assessments. The humoral immune response was evaluated by ELISA and virus-neutralization assays. The data obtained show hamsters to be the least suitable candidates for RBD immunogenicity testing and, hence, assessing the protective efficacy of RBD-based vaccines