Magnetism in AV_{3}Sb_{5} (A=Cs, Rb, and K): Origin and Consequences for the Strongly Correlated Phases.

The V-based kagome systems AV_{3}Sb_{5} (A=Cs, Rb, and K) are unique by virtue of the intricate interplay of nontrivial electronic structure, topology, and intriguing fermiology, rendering them to be a playground of many mutually dependent exotic phases like charge-order and superconductivity. Despite numerous recent studies, the interconnection of magnetism and other complex collective phenomena in these systems has yet not arrived at any conclusion. Using first-principles tools, we demonstrate that their electronic structures, complex fermiologies and phonon dispersions are strongly influenced by the interplay of dynamic electron correlations, nontrivial spin-polarization and spin-orbit coupling. An investigation of the first-principles-derived intersite magnetic exchanges with the complementary analysis of q dependence of the electronic response functions and the electron-phonon coupling indicate that the system conforms as a frustrated spin cluster, where the occurrence of the charge-order phase is intimately related to the mechanism of electron-phonon coupling, rather than the Fermi-surface nesting.

Effect of Vaccination on COVID-19 Severity and Outcome: A Comparative Study in a Tertiary Care Hospital.

INTRODUCTION: Vaccination is an important aspect of preventing/decreasing the severity of any viral disease including severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). This disease being very new in the experience of mankind has very little data on the effect of vaccination on the severity of this disease. We conducted this study with the primary objective to assess the severity and clinical outcome of COVID-19 infections among nonvaccinated and vaccinated individuals. MATERIALS AND METHODS: This was a hospital-based retrospective cohort study including all individuals developing microbiologically confirmed COVID-19 over 5 months from February to 31st July 2021. A questionnaire was used to acquire demographic details, history of vaccination with dates, severity of COVID-19 infection, comorbidities, and outcome. Patients found positive microbiologically for SARS-CoV-2 before any dose of its vaccine were considered nonvaccinated, while patients developing SARS-CoV-2 infection even after a single dose or both doses of vaccine were considered "vaccinated." The outcome and mortality among the vaccinated and nonvaccinated patients were evaluated and compared. RESULTS: The study included 2,879 patients, but complete data were obtained only from 1,500 patients. A total of 1,500 patients were analyzed, out of which 880 are male and 620 are female. The severity of the disease was categorized into mild, moderate, and severe in the age-group of <60 years and >60 years with urban (1051, 70.07%) and rural (449, 29.93%) populations. A total number of recovered patients (n = 245), died patients (n = 215) in the age-group of >60 years while the total recovered patients (n = 823) and dead patients (n = 217) in the age-group <60 years with p = 0.001. Total vaccinated patients in the age-group >60 years (n = 204) and not vaccinated (n = 256) while in the age-group of <60 years total vaccinated n = 229 and not vaccinated n = 811. The outcome of disease in the age-group of >60 years in nonvaccinated 50% recovered and 50% died during the course of illness while in the vaccinated 57.3% recoverd and 42% died p-value 0.14, while in the age-group of <60 years recovery in nonvaccinated 77.6% and death in nonvaccinated was 27.32% while in vaccinated patients 82.28% were recovered and 15% died with significant p-value 0.04. Disease outcome was not found significantly associated with a number of doses with p-values of 0.84 and 0.507 in the age-group of >60 years and <60 years, respectively. A total number of 56 patients received Covaxin and 377 patients received Covishield and disease outcome was not found significantly associated with the type of vaccine. CONCLUSION: Vaccination against COVID-19 was significantly effective in terms of hospitalization and disease severity. Vaccinated persons were less among patients with COVID-19 hospitalization and with severe disease progressing to death. These findings indicate vaccination is helpful in reducing the development of severe COVID-19 infection as compared to nonvaccinated status.

Light-responsive self-assembled microstructures of branched polyethyleneimine at low pH.

Soft materials comprising polyethyleneimine (PEI), which integrate low pH-stimulated higher-order assemblies (fibres and sheets) with light responsiveness, have been shown. Excitation wavelength light-driven interactions enable the formation of bead-necklace-type structures in fibres or volume collapse of sheets. This work can have significant implications for transfection or encapsulation through PEI-based complexes.

Strongly Correlated Excitons of Regular/Irregular Planar Quantum Dots in Magnetic Field: Size-Extensive Bi- and Triexciton (e-h-e-h and e-e-h/e-h-h) Systems by Multipole Expansion.

Excitons in parabolically confined planar quantum dots with a transverse magnetic field have been studied in various model systems. The correlations between e-h, e-e, and h-h have been incorporated in terms of exact, simply elegant, and absolutely terminating finite summed Lauricella functions which eliminate the secular divergence problem and pave way for a comprehensive understanding of certain exotic phenomena of various two-dimensional regular and irregular quantum dots. A simple yet highly accurate and exact variational wave function in terms of Whittaker-M function extensible to multiexcitonic systems has been propounded. We have also presented a formulation extending the size of the systems to triexcitonic (e-e-h/e-h-h), biexcitonic (e-h-e-h), and multiexcitonic ("N" e-h pair) planar dots by mono-, di-, quadru-, and octopole expansions. As a benchmark, we have examined the energy spectra, level-spacing statistics, heat capacities (C v at 1 K), and magnetization (T ≈ 0-1 K) of He/SiO2/BN/GaAs model systems for different lateral confinements, magnetic fields, mass ratios of e-h, and dielectric constants (ϵ).