50 research outputs found
Optically and electrically controllable adatom spin-orbital dynamics in transition metal dichalcogenides
We analyze the interplay of spin-valley coupling, orbital physics and
magnetic anisotropy taking place at single magnetic atoms adsorbed on
semiconducting transition-metal dichalcogenides, MX (M = Mo, W; X = S, Se).
Orbital selection rules turn out to govern the kinetic exchange coupling
between the adatom and charge carriers in the MX and lead to highly
orbitally dependent spin-flip scattering rates, as we illustrate for the
example of transition metal adatoms with configuration. Our ab initio
calculations suggest that configurations are realizable by single Co, Rh,
or Ir adatoms on MoS, which additionally exhibit a sizable magnetic
anisotropy. We find that the interaction of the adatom with carriers in the
MX allows to tune its behavior from a quantum regime with full Kondo
screening to a regime of "Ising spintronics" where its spin-orbital moment acts
as classical bit, which can be erased and written electronically and optically.Comment: 6 pages, 4 figure
Bandwidth renormalization due to the intersite Coulomb interaction
The theory of correlated electrons is currently moving beyond the
paradigmatic Hubbard , towards the investigation of intersite Coulomb
interactions. Recent investigations have revealed that these interactions are
relevant for the quantitative description of realistic materials. Physically,
intersite interactions are responsible for two rather different effects:
screening and bandwidth renormalization. We use a variational principle to
disentangle the roles of these two processes and study how appropriate the
recently proposed Fock treatment of intersite interactions is in correlated
systems. The magnitude of this effect in graphene is calculated based on cRPA
values of the intersite interaction. We also observe that the most interesting
charge fluctuation phenomena actually occur at elevated temperatures,
substantially higher than studied in previous investigations.Comment: New appendix on benzen
Microfluidically supported characterization of responses of Rhodococcus erythropolis strains isolated from different soils on Cu-, Ni-, and Co-stress
We present a new methodological approach for the assessment of the susceptibility of Rhodococcus erythropolis strains from specific sampling sites in response to increasing heavy metal concentration (Cu2+, Ni2+, and Co2+) using the droplet-based microfluid technique. All isolates belong to the species R. erythropolis identified by Sanger sequencing of the 16S rRNA. The tiny step-wise variation of metal concentrations from zero to the lower mM range in 500 nL droplets not only provided accurate data for critical metal ion concentrations but also resulted in a detailed visualization of the concentration-dependent response of bacterial growth and autofluorescence activity. As a result, some of the isolates showed similar characteristics in heavy metal tolerance against Cu2+, Ni2+, and Co2+. However, significantly different heavy metal tolerances were found for other strains. Surprisingly, samples from the surface soil of ancient copper mining areas supplied mostly strains with a moderate sensitivity to Cu2+, Ni2+, and Co2+, but in contrast, a soil sample from an excavation site of a medieval city that had been covered for about eight centuries showed an extremely high tolerance against cobalt ion (up to 36 mM). The differences among the strains not only may be regarded as results of adaptation to the different environmental conditions faced by the strains in nature but also seem to be related to ancient human activities and temporal partial decoupling of soil elements from the surface. This investigation confirmed that microfluidic screening offers empirical characterization of properties from same species which has been isolated from sites known to have different human activities in the past
Single-Co Kondo effect in atomic Cu wires on Cu(111)
Linear atomic chains containing a single Kondo atom, Co, and several
nonmagnetic atoms, Cu, were assembled atom by atom on Cu(111) with the tip of a
scanning tunneling microscope. The resulting one-dimensional wires,
CuCoCu (), exhibit a rich evolution of the single-Co
Kondo effect with the variation of and , as inferred from changes in the
line shape of the Abrikosov-Suhl-Kondo resonance. The most striking result is
the quenching of the resonance in CuCoCu and CuCoCu clusters.
State-of-the-art first-principles calculations were performed to unravel
possible microscopic origins of the remarkable experimental observations.Comment: 10 pages, 9 figure
Microbial community types and signature-like soil bacterial patterns from fortified prehistoric hills of Thuringia (Germany)
16S rRNA profiling has been applied for the investigation of bacterial communities of surface soil samples from forest-
covered areas of ten prehistorical ramparts from different parts of Thuringia. Besides the majority bacterial types that are
present in all samples, there could be identified bacteria that are highly abundant in some places and absent or low abundant
in others. These differences are mainly related to the acidity of substrate and distinguish the communities of lime stone
hills from soils of sand/quartzite and basalt hills. Minority components of bacterial communities show partially large dif-
ferences that cannot be explained by the pH of the soil or incidental effects, only. They reflect certain relations between the
communities of different places and could be regarded as a kind of signature-like patterns. Such relations had also been
found in a comparison of the data from ramparts with formerly studied 16S rRNA profiling from an iron-age burial field.
The observations are supporting the idea that a part of the components of bacterial communities from soil samples reflect
their ecological history and can be understood as the “ecological memory” of a place. Probably such memory effects can
date back to prehistoric times and might assist in future interpretations of archaeological findings on the prehistoric use of
a place, on the one hand. On the other hand, the genetic profiling of soils of prehistoric places contributes to the evaluation
of anthropogenic effects on the development of local soil bacterial diversity
Coulomb Engineering of two-dimensional Mott materials
Two-dimensional materials can be strongly influenced by their surroundings. A
dielectric environment screens and reduces the Coulomb interaction between
electrons in the two-dimensional material. Since the Coulomb interaction is
responsible for the insulating state of Mott materials, dielectric screening
provides direct access to the Mottness. Our many-body calculations reveal the
spectroscopic fingerprints of Coulomb engineering. We demonstrate eV-scale
changes to the position of the Hubbard bands and show a Coulomb engineered
insulator-to-metal transition. Based on this theoretical analysis, we discuss
prerequisites for an effective experimental realization of Coulomb engineering.Comment: 5+4 page
An association study on contrasting cystic fibrosis endophenotypes recognizes KRT8 but not KRT18 as a modifier of cystic fibrosis disease severity and CFTR mediated residual chloride secretion
<p>Abstract</p> <p>Background</p> <p>F508del-CFTR, the most frequent disease-causing mutation among Caucasian cystic fibrosis (CF) patients, has been characterised as a mutant defective in protein folding, processing and trafficking. We have investigated the two neighbouring cytokeratin genes <it>KRT8 </it>and <it>KRT18 </it>in a candidate gene approach to ask whether variants in <it>KRT8 </it>and/or <it>KRT18 </it>modify the impaired ion conductance known as the CF basic defect, and whether they are associated with correct trafficking of mutant CFTR and disease severity of CF.</p> <p>Methods</p> <p>We have selected contrasting F508del-<it>CFTR </it>homozygous patient subpopulations stratified for disease severity, comparing 13 concordant mildly affected sib pairs vs. 12 concordant severely affected sib pairs, or manifestation of the CF basic defect in intestinal epithelium, comparing 22 individuals who exhibit CFTR-mediated residual chloride secretion vs. 14 individuals who do not express any chloride secretion, for an association. The <it>KRT8</it>/<it>KRT18 </it>locus was initially interrogated with one informative microsatellite marker. Subsequently, a low density SNP map with four SNPs in KRT8 and two SNPs in KRT18, each selected for high polymorphism content, was used to localize the association signal.</p> <p>Results</p> <p><it>KRT8</it>, but not <it>KRT18</it>, showed an association with CF disease severity (P<sub>best </sub>= 0.00131; P<sub>corr </sub>= 0.0185) and CFTR mediated residual chloride secretion (P<sub>best </sub>= 0.0004; P<sub>corr </sub>= 0.0069). Two major four-marker-haplotypes spanning 13 kb including the entire <it>KRT8 </it>gene accounted for 90% of chromosomes, demonstrating strong linkage disequilibrium at that locus. Absence of chloride secretion was associated with the recessive haplotype 1122 at rs1907671, rs4300473, rs2035878 and rs2035875. The contrasting haplotype 2211 was dominant for the presence of CFTR mediated residual chloride secretion. In consistency, the <it>KRT8 </it>haplotype 2211 was associated with mild CF disease while 1122 was observed as risk haplotype. Analysis of microsatellite allele distributions on the SNP background suggests that the mild <it>KRT8 </it>haplotype 2211 is phylogenetically older than its severe counterpart.</p> <p>Conclusions</p> <p>The two opposing <it>KRT8 </it>alleles which have been identified as a benign and as a risk allele in this work are likely effective in the context of epithelial cell differentiation. As the mild <it>KRT8 </it>allele is associated with CFTR mediated residual chloride secretion among F508del-<it>CFTR </it>homozygotes, the KRT8/KRT18 heterodimeric intermediary filaments of the cytoskeleton apparently are an essential component for the proper targeting of CFTR to the apical membrane in epithelial cells.</p