Strongly Coupled Magnon-Plasmon Polaritons in Graphene-Two-Dimensional Ferromagnet Heterostructures.

Magnons and plasmons are different collective modes, involving the spin and charge degrees of freedom, respectively. Formation of hybrid plasmon-magnon polaritons in heterostructures of plasmonic and magnetic systems faces two challenges, the small interaction of the electromagnetic field of the plasmon with the spins, and the energy mismatch, as in most systems plasmons have energies orders of magnitude larger than those of magnons. We show that graphene plasmons form polaritons with the magnons of two-dimensional ferromagnetic insulators, placed up to to half a micrometer apart, with Rabi splittings in the range of 100 GHz (dramatically larger than cavity magnonics). This is facilitated both by the small energy of graphene plasmons and the cooperative super-radiant nature of the plasmon-magnon coupling afforded by phase matching. We show that the coupling can be modulated both electrically and mechanically, and we propose a ferromagnetic resonance experiment implemented with a two-dimensional ferromagnet driven by graphene plasmons.

Excitonic instability in transition metal dichalcogenides.

When transition-metal dichalcogenide monolayers lack inversion symmetry, their low-energy single particle spectrum near some high-symmetry points can, in some cases, be described by tilted massive Dirac Hamiltonians. The so-called Janus materials fall into that category. Inversion symmetry can also be broken by the application of out-of-plane electric fields, or by the mere presence of a substrate. Here we explore the properties of excitons in TMDC monolayers lacking inversion symmetry. We find that exciton binding energies can be larger than the electronic band gap, making such materials promising candidates to host the elusive exciton insulator phase. We also investigate the excitonic contribution to their optical conductivity and discuss the associated optical selection rules.

Enhancing the hybridization of plasmons in graphene with 2D superconductor collective modes.

We explore ways in which the close proximity between graphene sheets and monolayers of 2D superconductors can lead to hybridization between their collective excitations. We consider heterostructures formed by combinations of graphene sheets and 2D superconductor monolayers. The broad range of energies in which the graphene plasmon can exist, together with its tunability, makes such heterostructures promising platforms for probing the many-body physics of superconductors. We show that the hybridization between the graphene plasmon and the Bardasis-Schrieffer mode of a 2D superconductor results in clear signatures on the near-field reflection coefficient of the heterostructure, which in principle can be observed in scanning near-field microscopy experiments.

Harnessing ultraconfined graphene plasmons to probe the electrodynamics of superconductors.

We show that the Higgs mode of a superconductor, which is usually challenging to observe by far-field optics, can be made clearly visible using near-field optics by harnessing ultraconfined graphene plasmons. As near-field sources we investigate two examples: graphene plasmons and quantum emitters. In both cases the coupling to the Higgs mode is clearly visible. In the case of the graphene plasmons, the coupling is signaled by a clear anticrossing stemming from the interaction of graphene plasmons with the Higgs mode of the superconductor. In the case of the quantum emitters, the Higgs mode is observable through the Purcell effect. When combining the superconductor, graphene, and the quantum emitters, a number of experimental knobs become available for unveiling and studying the electrodynamics of superconductors.

ß-tungsten: a promising metal for spintronics.

Ultrathin films of ß-tungsten provide very promising substrates for applications in spintronics, and the possibility of incorporating them into multilayers extends such expectations. Our calculations indicate that it is viable to deposit a single layer of Mn on two non-equivalent (0 0 1) surfaces of ß-tungsten that have easy axes along orthogonal directions [0 1 0] and [1 0 0], respectively. The ferromagnetic structure of this Mn monolayer adsorbed to either of those surfaces displays a giant in-plane magneto-crystalline anisotropy that exceeds 12 meV per Mn atom. Furthermore, when coated with additional layers of ß-tungsten the magnetization easy axis becomes perpendicular to the planes. We envisage that magnetic multilayers involving mono-crystalline thin films of ß-tungsten oriented along high-symmetry directions offer a very fruitful playground for spintronic applications.

Extracellular enzymatic profiles and taxonomic identification of endophytic fungi isolated from four plant species.

Plants of medicinal and economic importance have been studied to investigate the presence of enzyme-producing endophytic fungi. The characterization of isolates with distinct enzyme production potential may identify suitable alternatives for specialized industry. At Universidade Estadual de Maringá Laboratory of Microbial Biotechnology, approximately 500 isolates of endophytic fungi have been studied over the last decade from various host plants, including medicinally and economically important species, such as Luehea divaricata (Martius et Zuccarini), Trichilia elegans A. Juss, Sapindus saponaria L., Piper hispidum Swartz, and Saccharum spp. However, only a fraction of these endophytes have been identified and evaluated for their biotechnological application, having been initially grouped by morphological characteristics, with at least one representative of each morphogroup tested. In the current study, several fungal strains from four plants (L. divaricata, T. elegans, S. saponaria, and Saccharum spp) were identified by ribosomal DNA typing and evaluated semi-quantitatively for their enzymatic properties, including amylase, cellulase, pectinase, and protease activity. Phylogenetic analysis revealed the presence of four genera of endophytic fungi (Diaporthe, Saccharicola, Bipolaris, and Phoma) in the plants examined. According to enzymatic tests, 62% of the isolates exhibited amylase, approximately 93% cellulase, 50% pectinase, and 64% protease activity. Our results verified that the composition and abundance of endophytic fungi differed between the plants tested, and that these endophytes are a potential enzyme production resource of commercial and biotechnological value.

Molecular phylogeny and biotechnological potential of bacterial endophytes associated with Malpighia emarginata.

Acerola (Malpighia emarginata) is a shrub native to tropical and subtropical climates, which has great commercial interest due to the high vitamin C content of its fruit. However, there are no reports of the endophytic community of this plant species. The aim of this study was to verify the genetic diversity of the leaf endophytic bacterial community of two varieties (Olivier & Waldy Cati 30) of acerola, and to evaluate their biotechnological ability by assessing their in vitro control of pathogenic fungi and the enzymatic production of cellulase, xylanase, amylase, pectinase, protease, lipase, esterase, and chitinase. In total, 157 endophytic bacteria were isolated from the leaves of two varieties of the plant at 28° and 37°C. Phylogenetic analysis confirmed the molecular identification of 58 bacteria, 39.65% of which were identified at the species level. For the first time, the genus Aureimonas was highlighted as an endophytic bacterium. Furthermore, 12.82% of the isolates inhibited the growth of all phytopathogens evaluated and at least one of the above-mentioned enzymes was produced by 64.70% of the endophytes, demonstrating that M. emarginata isolates have potential use in biotechnological studies.

Investigation of mycoviruses in endophytic and phytopathogenic strains of Colletotrichum from different hosts.

Fungi belonging to the Colletotrichum genus can be categorized as endophytic or phytopathogenic. These fungi can be infected by viruses, termed mycoviruses, which are know to promote hypovirulence in infected fungi. However, there are few studies that have described mycoviral infections of endophytes. The production of secondary metabolites by endophytes with antimicrobial potential in inhibiting numerous pathogens has gained increasing attention. The aim of the current study was to investigate the presence of mycoviruses in endophytic and phytopathogenic fungi of the Colletotrichum genus, as well as to analyze the antimicrobial activity of crude extracts obtained from these samples. To detect the presence of mycoviruses in the samples, dsRNA was extracted, treated with enzymes, and analyzed following electrophoresis in agarose gel. Furthermore, isometric mycoviral particles were observed by transmission electron microscopy. Serial microdilution methodology was used to test crude extracts of Colletotrichum spp for antibacterial activity against Escherichia coli and Staphylococcus aureus, and antifungal activity against Fusarium solani. The results of the molecular and microscopic analyses indicated that a phytopathogenic strain presented infection by mycovirus. The antibacterial activity analysis revealed that the minimum inhibitory concentrations and minimum bactericidal concentrations were low for the fungal extracts of the two endophytes, indicating that these extracts were effective antibacterial agents. However, their antifungal activity against F. solani was not statistically different compared to that of the negative control.

Plasma biomarkers profile of female dogs with mammary carcinoma and its association with clinical and pathological features.

The immunological biomarkers profiles were evaluated using Luminex as putative measures to monitor canine mammary carcinomas (MCs). Forty female dogs were categorized into benign mixed tumour (MC-BMT = 28) and mammary carcinoma (MC=12). The ascendant biomarker signatures were used to compare the groups. For example, a higher frequency of MC-BMT animals producing IL-6, CXCL-8 and CXCL-10 was observed, whereas for the MC group IL-2 and CXCL-8 were detected. MC-BMT animals without metastasis had an increase in the levels of IL-2, CXCL-8, CXCL-10, IL-6, TNF-α, IL-15 and a decrease in IL-10 and CXCL-8. MC-BMT animals with metastasis showed only an increase in CXCL-10 and a decrease in IL-18. After comparing the ascendant signatures following the presence of metastasis in both groups, a higher frequency of dogs exhibiting IL-10 production was observed. Pearson correlation (P = 0.0273) and receiver operating characteristic (ROC) curve analysis revealed that this pattern was associated with worse outcome and lower survival rates in MC animals.

Magnetic response of zigzag nanoribbons under electric fields.

Spin excitations in zigzag graphene nanoribbons are studied when the system is subjected to an electric field in the transversal direction. The magnetic properties and the lifetime of the spin excitations are systematically investigated and compared using a tight-binding electron-electron model treated by a mean-field Hubbard model. The effects of electron-hole asymmetry introduced by next-nearest neighbor hopping are also investigated. We show that by increasing the electric field, the antiferromagnetic correlations between the edges of the nanoribbons are decreased due to a reduction of the magnetic moments. The results show that the spin wave lifetime may be controlled by the intensity of the transversal electric field, indicating that zigzag nanoribbons may be considered great candidates for future spintronic applications.

Graphene as a non-magnetic spin current lens.

In spintronics, the ability to transport magnetic information often depends on the existence of a spin current traveling between two different magnetic objects acting as the source and probe. A large fraction of this information never reaches the probe and is lost because the spin current tends to travel omnidirectionally. We propose that a curved boundary between a gated and a non-gated region within graphene acts as an ideal lens for spin currents despite being entirely of non-magnetic nature. We show as a proof of concept that such lenses can be utilized to redirect the spin current that travels away from a source onto a focus region where a magnetic probe is located, saving a considerable fraction of the magnetic information that would be otherwise lost.

Itinerant nature of atom-magnetization excitation by tunneling electrons.

We have performed single-atom magnetization curve (SAMC) measurements and inelastic scanning tunneling spectroscopy (ISTS) on individual Fe atoms on a Cu(111) surface. The SAMCs show a broad distribution of magnetic moments with 3.5 µB being the mean value. ISTS reveals a magnetization excitation with a lifetime of 200 fsec which decreases by a factor of 2 upon application of a magnetic field of 12 T. The experimental observations are quantitatively explained by the decay of the magnetization excitation into Stoner modes of the itinerant electron system as shown by newly developed theoretical modeling.

Dynamical magnetic excitations of nanostructures from first principles.

Within time-dependent density functional theory, combined with the Korringa-Kohn-Rostoker Green functions, we devise a real space method to investigate spin dynamics. Our scheme enables one to deduce the Coulomb potential which assures a proper Goldstone mode is present. We illustrate with application to 3d adatoms and dimers on Cu(100).

Marginal adaptation and microleakage of five root-end filling materials: an in vitro study.

AIM: Endodontic surgery consists of several procedures which involve the endodontic space or the root canal and is performed as an alternative to unsuccessful outcomes or complications following endodontic treatments. The aim of the study was to evaluate the sealing ability of five root-end filling materials. METHODS: Fifty human single rooted teeth were treated endodontically; roots were resected at 3 mm from the apex, and root end cavities were prepared with ultrasonic tips. Root ends were filled with one of the following materials: silver amalgam (control group); mineral trioxide aggregate; white Portland cement; Vitremer; and Fuji Ortho. Apical sealing was evaluated by evaluating microleakage of 50% silver nitrate solution. The apical portion of the roots was sectioned to obtain 1-mm thick transversal slices, and epoxy resin replicas of these apical slices were produced. A scanning electron microscope (SEM) was used for analyses. The Kruskal-Wallis test and a multiple comparisons test were used for statistical data analysis. RESULTS: Results showed microleakage and variable adaptation gaps on the interface between dentin and root-end filling material in all specimens. CONCLUSION: All the studied materials exhibited some degree of apical microleakage and marginal gaps. No correlation was found between data obtained from analyses of apical sealing and marginal adaptation.

Entanglement of two impurities through electron scattering.

We study how two magnetic impurities embedded in a solid can be entangled by an injected electron scattering between them and by subsequent measurement of the electron's state. We start by investigating an ideal case where only the electronic spin interacts successively through the same unitary operation with the spins of the two impurities. We find conditions for the impurity spins to be maximally entangled with a significant success probability. We then consider a more realistic description which includes both the forward and backscattering amplitudes. In this scenario, we obtain the entanglement between the impurities as a function of the interaction strength of the electron-impurity coupling. We find that our scheme allows us to entangle the impurities maximally with a significant probability.

Ground state of magnetic dimers on metal surfaces.

We present model studies of the ground state for magnetic dimers on metal surfaces. We find it can be neither ferromagnetic nor antiferromagnetic, but is often canted for nearest neighbors. Thus, the system cannot be described using bilinear exchange. We give a criterion which can be used quite generally to interrogate the local stability of ferromagnetically or antiferromagnetically aligned dimers, and which also may be used to infer the canting angle when canted states are stable.

Impurity scattering induced entanglement of ballistic electrons.

We show how entanglement between two conduction electrons is generated in the presence of a localized magnetic impurity embedded in an otherwise ballistic conductor of special geometry. This process is a generalization of beam-splitter mediated entanglement generation schemes with a localized spin placed at the site of the beam splitter. Our entangling scheme is unconditional and robust to randomness of the initial state of the impurity. The entangled state generated manifests itself in noise reduction of spin-dependent currents.