117 research outputs found
Electronic structure of AuMg and AgMg ( = Eu, Gd, Yb)
We have investigated the electronic structure of the equiatomic EuAuMg,
GdAuMg, YbAuMg and GdAgMg intermetallics using x-ray photoelectron
spectroscopy. The spectra revealed that the Yb and Eu are divalent while the Gd
is trivalent. The spectral weight in the vicinity of the Fermi level is
dominated by the mix of Mg , Au/Ag and bands, and not by the
. We also found that the Au and Ag bands are extraordinarily
narrow, as if the noble metal atoms were impurities submerged in a low density
metal host. The experimental results were compared with band structure
calculations, and we found good agreement provided that the spin-orbit
interaction in the Au an Ag bands is included and correlation effects in an
open shell are accounted for using the local density approximation +
Hubbard scheme. Nevertheless, limitations of such a mean-field scheme to
explain excitation spectra are also evident.Comment: 4 pages, 3 figures, Brief Repor
Electronic structure of SrPt_4Ge_{12}: a combined photoelectron spectroscopy and band structure study
We present a combined study of the electronic structure of the
superconducting skutterudite derivative SrPt4Ge12 by means of X-ray
photoelectron spectroscopy and full potential band structure calculations
including an analysis of the chemical bonding. We establish that the states at
the Fermi level originate predominantly from the Ge 4p electrons and that the
Pt 5d shell is effectively full. We find excellent agreement between the
measured and the calculated valence band spectra, thereby validating that band
structure calculations in combination with photoelectron spectroscopy can
provide a solid basis for the modeling of superconductivity in the compounds
MPt4Ge12 (M = Sr, Ba, La, Pr) series
Multiple spin-orbit excitons and the electronic structure of Ξ±βRuCl3
The honeycomb compound Ξ±-RuCl_{3} is widely discussed as a proximate Kitaev spin-liquid material. This scenario builds on spin-orbit entangled j =Β 1/2 moments arising for a t_{2g}^{5} electron configuration with strong spin-orbit coupling Ξ» and a large cubic crystal field. The actual low-energy electronic structure of Ξ±-RuCl_{3}, however, is still puzzling. In particular, infrared absorption features at 0.30, 0.53, and 0.75Β eV seem to be at odds with a j =Β 1/2 scenario. Also the energy of the spin-orbit exciton, the excitation from j =Β 1/2 to 3/2, and thus the value of Ξ», are controversial. Combining infrared and Raman data, we show that the infrared features can be attributed to single, double, and triple spin-orbit excitons. We find Ξ» =Β 0.16Β eV and Ξ =Β 42(4)Β meV for the observed noncubic crystal-field splitting, supporting the validity of the j = 1/2 picture for Ξ±-RuCl_{3}. The unusual strength of the double excitation is related to the underlying hopping interactions, which form the basis for dominant Kitaev exchange
Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging
Electrons in correlated insulators are prevented from conducting by Coulomb
repulsion between them. When an insulator-to-metal transition is induced in a
correlated insulator by doping or heating, the resulting conducting state can
be radically different from that characterized by free electrons in
conventional metals. We report on the electronic properties of a prototypical
correlated insulator vanadium dioxide (VO2) in which the metallic state can be
induced by increasing temperature. Scanning near-field infrared microscopy
allows us to directly image nano-scale metallic puddles that appear at the
onset of the insulator-to-metal transition. In combination with far-field
infrared spectroscopy, the data reveal the Mott transition with divergent
quasiparticle mass in the metallic puddles. The experimental approach employed
here sets the stage for investigations of charge dynamics on the nanoscale in
other inhomogeneous correlated electron systems.Comment: 22 pages (including 3 figures
Distinct Neurobehavioural Effects of Cannabidiol in Transmembrane Domain Neuregulin 1 Mutant Mice
The cannabis constituent cannabidiol (CBD) possesses anxiolytic and antipsychotic properties. We have previously shown that transmembrane domain neuregulin 1 mutant (Nrg1 TM HET) mice display altered neurobehavioural responses to the main psychoactive constituent of cannabis, Ξ9-tetrahydrocannabinol. Here we investigated whether Nrg1 TM HET mice respond differently to CBD and whether CBD reverses schizophrenia-related phenotypes expressed by these mice. Adult male Nrg1 TM HET and wild type-like littermates (WT) received vehicle or CBD (1, 50 or 100 mg/kg i.p.) for 21 days. During treatment and 48 h after withdrawal we measured behaviour, whole blood CBD concentrations and autoradiographic receptor binding. Nrg1 HET mice displayed locomotor hyperactivity, PPI deficits and reduced 5-HT2A receptor binding density in the substantia nigra, but these phenotypes were not reversed by CBD. However, long-term CBD (50 and 100 mg/kg) selectively enhanced social interaction in Nrg1 TM HET mice. Furthermore, acute CBD (100 mg/kg) selectively increased PPI in Nrg1 TM HET mice, although tolerance to this effect was manifest upon repeated CBD administration. Long-term CBD (50 mg/kg) also selectively increased GABAA receptor binding in the granular retrosplenial cortex in Nrg1 TM HET mice and reduced 5-HT2A binding in the substantia nigra in WT mice. Nrg1 appears necessary for CBD-induced anxiolysis since only WT mice developed decreased anxiety-related behaviour with repeated CBD treatment. Altered pharmacokinetics in mutant mice could not explain our findings since no genotype differences existed in CBD blood concentrations. Here we demonstrate that Nrg1 modulates acute and long-term neurobehavioural effects of CBD, which does not reverse the schizophrenia-relevant phenotypes
Cigarette smoke induces Ξ²2-integrin-dependent neutrophil migration across human endothelium
<p>Abstract</p> <p>Background</p> <p>Cigarette smoking induces peripheral inflammatory responses in all smokers and is the major risk factor for neutrophilic lung disease such as chronic obstructive pulmonary disease. The aim of this study was to investigate the effect of cigarette smoke on neutrophil migration and on Ξ²<sub>2</sub>-integrin activation and function in neutrophilic transmigration through endothelium.</p> <p>Methods and results</p> <p>Utilizing freshly isolated human PMNs, the effect of cigarette smoke on migration and Ξ²<sub>2</sub>-integrin activation and function in neutrophilic transmigration was studied. In this report, we demonstrated that cigarette smoke extract (CSE) dose dependently induced migration of neutrophils <it>in vitro</it>. Moreover, CSE promoted neutrophil adherence to fibrinogen. Using functional blocking antibodies against CD11b and CD18, it was demonstrated that Mac-1 (CD11b/CD18) is responsible for the cigarette smoke-induced firm adhesion of neutrophils to fibrinogen. Furthermore, neutrophils transmigrated through endothelium by cigarette smoke due to the activation of Ξ²<sub>2</sub>-integrins, since pre-incubation of neutrophils with functional blocking antibodies against CD11b and CD18 attenuated this transmigration.</p> <p>Conclusion</p> <p>This is the first study to describe that cigarette smoke extract induces a direct migratory effect on neutrophils and that CSE is an activator of Ξ²<sub>2</sub>-integrins on the cell surface. Blocking this activation of Ξ²<sub>2</sub>-integrins might be an important target in cigarette smoke induced neutrophilic diseases.</p
Association Between Nutritional Status and the Immune response in HIVβ+βPatients under HAART: Protocol for a Systematic Review.
Over 850 million people worldwide and 200 million adults in Sub-Saharan Africa suffer from malnutrition. Countries most affected by HIV are also stricken by elevated rates of food insecurity and malnutrition. HIV infection and insufficient nutritional intake are part of a vicious cycle that contributes to immunodeficiency and negative health outcomes. However, the effect of the overlap between HIV infection and undernutrition on the immune response following antiretroviral initiation remains unclear. A possible explanation could be the lack of consensus concerning the definition and assessment of nutritional status. Our objectives are to investigate the existence of an association between undernutrition and immune response at antiretroviral treatment initiation and the following year in low- and middle-income countries where malnutrition is most prevalent. Our systematic review will identify studies originating from low- and middle-income countries (LMICs) published from 1996 onwards, through searches in MEDLINE (PubMed interface), EMBASE (OVID interface), Cochrane Central (OVID interface) and grey literature. No language restrictions will be applied. We will seek out studies of any design investigating the association between the nutritional status (for example, undernourished versus well nourished) and the immune response, either in terms of CD4 count or immune failure, in seropositive patients initiating antiretroviral therapy or in their first year of treatment. Two reviewers will independently screen articles, extract data and assess scientific quality using standardized forms and published quality assessment tools tailored for each study design. Where feasible, pooled measures of association will be obtained through meta-analyses. Results will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement. This protocol has been registered in the PROSPERO database (registration number: CRD42014005961). Undernutrition and weight loss are prevalent amongst highly active antiretroviral therapy (HAART)-treated patients in LMICs and contribute to excess early mortality. A possible intermediate pathway could be poor immune reconstitution secondary to deficient nutritional status. In the face of limited access to second line treatments, raising HIV resistance and cut backs to HIV programs, it is crucial to identify the factors associated with suboptimal response and therapeutic failure in order to better customize the care strategies employed in LMICs
Delta-9-tetrahydrocannabinol, neural oscillations above 20 Hz and induced acute psychosis
Rationale: An acute challenge with delta-9-tetrahydrocannabinol (THC) can induce psychotic symptoms including delusions. High electroencephalography (EEG) frequencies, above 20 Hz, have previously been implicated in psychosis and schizophrenia. Objectives: The objective of this study is to determine the effect of intravenous THC compared to placebo on high-frequency EEG. Methods: A double-blind cross-over study design was used. In the resting state, the high-beta to low-gamma magnitude (21β45 Hz) was investigated (n=13 pairs+4 THC only). Also, the event-related synchronisation (ERS) of motor-associated high gamma was studied using a self-paced button press task (n=15). Results: In the resting state, there was a significant condition Γ frequency interaction (p=0.00017), consisting of a shift towards higher frequencies under THC conditions (reduced high beta [21β27 Hz] and increased low gamma [27β45 Hz]). There was also a condition Γ frequency Γ location interaction (p=0.006), such that the reduction in 21β27-Hz magnitude tended to be more prominent in anterior regions, whilst posterior areas tended to show greater 27β45-Hz increases. This effect was correlated with positive symptoms, as assessed on the Positive and Negative Syndrome Scale (PANSS) (r=0.429, p=0.042). In the motor task, there was a main effect of THC to increase 65β130-Hz ERS (p=0.035) over contra-lateral sensorimotor areas, which was driven by increased magnitude in the higher, 85β130-Hz band (p=0.02) and not the 65β85-Hz band. Conclusions: The THC-induced shift to faster gamma oscillations may represent an over-activation of the cortex, possibly related to saliency misattribution in the delusional state
Spatiotemporal segregation of human marginal zone and memory B cell populations in lymphoid tissue
Human memory and marginal zone B cells share some features including CD27 expression and somatic hypermutation, but their lineage relationship is still unclear. Here the authors use mass cytometry and sequential clustering methods to show that, despite their shared features, memory and marginal zone B cells represent distinct lineage choices
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