Field-induced magnetic transitions in the quasi-two-dimensional heavy-fermion antiferromagnets Ce_{n}RhIn_{3n+2} (n=1 or 2)

We have measured the field-dependent heat capacity in the tetragonal antiferromagnets CeRhIn$_{5}$ and Ce$_{2}$RhIn$_{8}$, both of which have an enhanced value of the electronic specific heat coefficient $\gamma \sim 400$ mJ/mol-Ce K$^{2}$ above $T_{N}$. For $T<T_{N},$ the specific heat data at zero applied magnetic field are consistent with the existence of an anisotropic spin-density wave opening a gap in the Fermi surface for CeRhIn$_{5},$ while Ce$_{2}$RhIn$_{8}$ shows behavior consistent with a simple antiferromagnetic magnon. From these results, the magnetic structure, in a manner similar to the crystal structure, appears more two-dimensional in CeRhIn$_{5}$ than in Ce$_{2}$RhIn$_{8}$ where only about 12% of the Fermi surface remains ungapped relative to 92% for Ce$_{2}$RhIn$_{8}$. When $B||c,$ both compounds behave in a manner expected for heavy fermion systems as both $T_{N}$ and the electronic heat capacity decrease as field is applied. When the field is applied in the tetragonal basal plane ($B||a$), CeRhIn$_{5}$ and Ce$_{2}$RhIn$_{8}$ have very similar phase diagrams which contain both first- and second-order field-induced magnetic transitions .Comment: 15 pages, 4 figure

Heat capacity studies of Ce and Rh site substitution in the heavy fermion antiferromagnet CeRhIn_5;: Short-range magnetic interactions and non-Fermi-liquid behavior

In heavy fermion materials superconductivity tends to appear when long range magnetic order is suppressed by chemical doping or applying pressure. Here we report heat capacity measurements on diluted alloyes of the heavy fermion superconductor CeRhIn_5;. Heat capacity measurements have been performed on CeRh_{1-y}Ir_{y}In_5; (y <= 0.10) and Ce_{1-x}La_{x}Rh_{1-y}Ir_{y}In_5; (x <= 0.50) in applied fields up to 90 kOe to study the affect of doping and magnetic field on the magnetic ground state. The magnetic phase diagram of CeRh_{0.9}Ir_{0.1}In_5; is consistent with the magnetic structure of CeRhIn_5; being unchanged by Ir doping. Doping of Ir in small concentrations is shown to slightly increase the antiferromagnetic transition temperature T_{N} (T_{N}=3.8 K in the undoped sample). La doping which causes disorder on the Ce sublattice is shown to lower T_{N} with no long range order observed above 0.34 K for Ce_{0.50}La_{0.50}RhIn_5;. Measurements on Ce_{0.50}La_{0.50}RhIn_5; show a coexistence of short range magnetic order and non-Fermi-liquid behavior. This dual nature of the Ce 4f-electrons is very similar to the observed results on CeRhIn_5; when long range magnetic order is suppressed at high pressure.Comment: 8 pages, 9 figure

Itinerant Ferromagnetism in the Periodic Anderson Model

We introduce a novel mechanism for itinerant ferromagnetism, based on a simple two-band model. The model includes an uncorrelated and dispersive band hybridized with a second band which is narrow and correlated. The simplest Hamiltonian containing these ingredients is the Periodic Anderson Model (PAM). Using quantum Monte Carlo and analytical methods, we show that the PAM and an extension of it contain the new mechanism and exhibit a non-saturated ferromagnetic ground state in the intermediate valence regime. We propose that the mechanism, which does not assume an intra atomic Hund's coupling, is present in both the iron group and in some f electron compounds like Ce(Rh_{1-x} Ru_x)_3 B_2, La_x Ce_{1-x} Rh_3 B_2 and the uranium monochalcogenides US, USe, and UTe

Theory of the first-order isostructural valence phase transitions in mixed valence compounds YbIn_{x}Ag_{1-x}Cu_{4}

For describing the first-order isostructural valence phase transition in mixed valence compounds we develop a new approach based on the lattice Anderson model. We take into account the Coulomb interaction between localized f and conduction band electrons and two mechanisms of electron-lattice coupling. One is related to the volume dependence of the hybridization. The other is related to local deformations produced by f- shell size fluctuations accompanying valence fluctuations. The large f -state degeneracy allows us to use the 1/N expansion method. Within the model we develop a mean-field theory for the first-order valence phase transition in YbInCu_{4}. It is shown that the Coulomb interaction enhances the exchange interaction between f and conduction band electron spins and is the driving force of the phase transition. A comparison between the theoretical calculations and experimental measurements of the valence change, susceptibility, specific heat, entropy, elastic constants and volume change in YbInCu_{4} and YbAgCu_{4} are presented, and a good quantitative agreement is found. On the basis of the model we describe the evolution from the first-order valence phase transition to the continuous transition into the heavy-fermion ground state in the series of compounds YbIn_{1-x}Ag_{x}Cu_{4}. The effect of pressure on physical properties of YbInCu_{4} is studied and the H-T phase diagram is found.Comment: 17 pages RevTeX, 9 Postscript figures, to be submitted to Phys.Rev.

AMMI analysis to evaluate the adaptability and phenotypic stability of sugarcane genotypes

Sugarcane (Saccharum sp.) is one of the most important crops in Brazil. The high demand for sugarcane-derived products has stimulated the expansion of sugarcane cultivation in recent years, exploring different environments. The adaptability and the phenotypic stability of sugarcane genotypes in the Minas Gerais state, Brazil, were evaluated based on the additive main effects and multiplicative interaction (AMMI) method. We evaluated 15 genotypes (13 clones and two checks: RB867515 and RB72454) in nine environments. The average of two cuttings for the variable tons of pol per hectare (TPH) measure was used to discriminate genotypes. Besides the check RB867515 (20.44 t ha-1), the genotype RB987935 showed a high average TPH (20.71 t ha-1), general adaptability and phenotypic stability, and should be suitable for cultivation in the target region. The AMMI method allowed for easy visual identification of superior genotypes for each set of environments

The trispecific DARPin ensovibep inhibits diverse SARS-CoV-2 variants

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with potential resistance to existing drugs emphasizes the need for new therapeutic modalities with broad variant activity. Here we show that ensovibep, a trispecific DARPin (designed ankyrin repeat protein) clinical candidate, can engage the three units of the spike protein trimer of SARS-CoV-2 and inhibit ACE2 binding with high potency, as revealed by cryo-electron microscopy analysis. The cooperative binding together with the complementarity of the three DARPin modules enable ensovibep to inhibit frequent SARS-CoV-2 variants, including Omicron sublineages BA.1 and BA.2. In Roborovski dwarf hamsters infected with SARS-CoV-2, ensovibep reduced fatality similarly to a standard-of-care monoclonal antibody (mAb) cocktail. When used as a single agent in viral passaging experiments in vitro, ensovibep reduced the emergence of escape mutations in a similar fashion to the same mAb cocktail. These results support further clinical evaluation of ensovibep as a broad variant alternative to existing targeted therapies for Coronavirus Disease 2019 (COVID-19)