127 research outputs found
Dynamics of a tunneling magnetic impurity: Kondo effect induced incoherence
We study how the formation of the Kondo compensation cloud influences the
dynamical properties of a magnetic impurity that tunnels between two positions
in a metal. The Kondo effect dynamically generates a strong tunneling
impurity-conduction electron coupling, changes the temperature dependence of
the tunneling rate, and may ultimately result in the destruction of the
coherent motion of the particle at zero temperature. We find an interesting
two-channel Kondo fixed point as well for a vanishing overlap between the
electronic states that screen the magnetic impurity. We propose a number of
systems where the predicted features could be observed.Comment: 4 pages, 3 figures, ReVTe
Mean-field model for magnetic orders in NpTGa5 with T=Co, Ni or Rh
Characteristics of magnetic transitions in NpTGa with T=Co, Ni, Rh are
explained in a unified way with use of a crystalline electric field (CEF) model
of localized 5 electrons. The model takes a CEF doublet and a singlet as
local states, and includes dipolar and quadrupolar intersite interactions in
the mean-field theory. Diverse ordering phenomena are derived depending on the
magnitude of interaction parameters, which qualitatively reproduce the
experimentally observed magnetic behaviors in NpTGa. The quadrupole degrees
of freedom are essential to the diverse magnetic orders. It is argued that
NpRhGa is close to a multicritical point where quadrupoles and dipoles with
different directions are competing to order.Comment: 17 pages, 10 figure
Instability of the marginal commutative model of tunneling centers interacting with metallic environment: Role of the electron-hole symmetry breaking
The role of the electron-hole symmetry breaking is investigated for a
symmetrical commutative two-level system in a metal using the multiplicative
renormalization group in a straightforward way. The role of the symmetries of
the model and the path integral technique are also discussed in detail. It is
shown that the electron-hole symmetry breaking may make the model
non-commutative and generate the assisted tunneling process which is, however,
too small itself to drive the system into the vicinity of the two-channel Kondo
fixed point. While these results are in qualitative agreement with those of
Moustakas and Fisher (Phys. Rev. B 51, 6908 (1995), ibid 53, 4300 (1996)) the
scaling equations turn out to be essentially different. We show that the main
reason for this difference is that the procedure for the elimination of the
high energy degrees of freedom used by Moustakas and Fisher leaves only the
free energy invariant, however, the couplings generated are not connected to
the dynamical properties in a straightforward way and should be interpreted
with care. These latter results might have important consequences in other
cases where the path integral technique is used to produce the scaling
equations and calculate physical quantities.Comment: latex, figures in ps file adde
Peripheral blood T-cell signatures from high-resolution immune phenotyping of γδ and αβ T-cells in younger and older subjects in the Berlin Aging Study II
Background Aging and latent infection with Cytomegalovirus (CMV) are thought
to be major factors driving the immune system towards immunosenescence,
primarily characterized by reduced amounts of naïve T-cells and increased
memory T-cells, potentially associated with higher morbidity and mortality.
The composition of both major compartments, γδ as well as αβ T-cells, is
altered by age and CMV, but detailed knowledge of changes to the γδ subset is
currently limited. Results Here, we have surveyed a population of 73 younger
(23–35 years) and 144 older (62–85 years) individuals drawn from the Berlin
Aging Study II, investigating the distribution of detailed differentiation
phenotypes of both γδ and αβ T-cells. Correlation of frequencies and absolute
counts of the identified phenotypes with age and the presence of CMV revealed
a lower abundance of Vδ2-positive and a higher amount of Vδ1-positive cells.
We found higher frequencies of late-differentiated and lower frequencies of
early-differentiated cells in the Vδ1+ and Vδ1-Vδ2-, but not in the Vδ2+
populations in elderly CMV-seropositive individuals confirming the association
of these Vδ2-negative cells with CMV-immunosurveillance. We identified the
highest Vδ1:Vδ2 ratios in the CMV-seropositive elderly. The observed increased
CD4:CD8 ratios in the elderly were significantly lower in CMV-seropositive
individuals, who also possessed a lower naïve and a larger late-differentiated
compartment of CD8+ αβ T-cells, reflecting the consensus in the literature.
Conclusions Our findings illustrate in detail the strong influence of CMV on
the abundance and differentiation pattern of γδ T-cells as well as αβ T-cells
in older and younger people. Mechanisms responsible for the phenotypic
alterations in the γδ T-cell compartment, associated both with the presence of
CMV and with age require further clarification
Childhood chronic anterior uveitis associated with vernal keratoconjunctivitis (VKC): successful treatment with topical tacrolimus. Case series
Uveitis treatment involves topical corticosteroids along with cycloplegic-mydriatics. Particularly severe cases may require systemic corticosteroids and immunosuppressive drugs. Vernal keratoconjunctivitis (VKC) treatment consists of a brief period of topical corticosteroids and/or cyclosporine. In patients refractory to traditional treatment, the use of 0.1% topical ophtalmic FK- 506 (tacrolimus) ointment has been occasionally reported
Osteoclasts Are Active in Bone Forming Metastases of Prostate Cancer Patients
BACKGROUND: Bone forming metastases are a common and disabling consequence of prostate cancer (CaP). The potential role of osteoclast activity in CaP bone metastases is not completely explained. In this study, we investigated ex vivo whether the osteolytic activity is present and how it is ruled in CaP patients with bone forming metastases. METHODOLOGY: Forty-six patients affected by newly diagnosed CaP and healthy controls were enrolled. At diagnosis, 37 patients had a primary tumour only, while 9 had primary tumour and concomitant bone forming metastases. In all patients there was no evidence of metastasis to other non-bone sites. For all patients and controls we collected blood and urinary samples. We evaluated patients' bone homeostasis; we made peripheral blood mononuclear cell (PBMC) cultures to detect in vitro osteoclastogenesis; we dosed serum expression of molecules involved in cancer induced osteoclatogenesis, such as RANKL, OPG, TNF-alpha, DKK-1 and IL-7. By Real-Time PCR, we quantified DKK-1 and IL-7 gene expression on micro-dissected tumour and healthy tissue sections. PRINCIPAL FINDINGS: CaP bone metastatic patients showed bone metabolism disruption with increased bone resorption and formation compared to non-bone metastatic patients and healthy controls. The CaP PBMC cultures showed an enhanced osteoclastogenesis in bone metastatic patients, due to an increase of RANKL/OPG ratio. We detected increased DKK-1 serum levels and tissue gene expression in patients compared to controls. IL-7 resulted high in patients' sera, but its tissue gene expression was comparable in patients and controls. CONCLUSIONS: We demonstrated ex vivo that osteoclastogenesis is an active mechanism in tumour nesting of bone forming metastatic cancer and that serum DKK-1 levels are increased in CaP patients, suggesting to deeply investigate its role as tumour marker
A Rapid Crosstalk of Human γδ T Cells and Monocytes Drives the Acute Inflammation in Bacterial Infections
Vγ9/Vδ2 T cells are a minor subset of T cells in human blood and differ from other T cells by their immediate responsiveness to microbes. We previously demonstrated that the primary target for Vγ9/Vδ2 T cells is (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), an essential metabolite produced by a large range of pathogens. Here we wished to study the consequence of this unique responsiveness in microbial infection. The majority of peripheral Vγ9/Vδ2 T cells shares migration properties with circulating monocytes, which explains the presence of these two distinct blood cell types in the inflammatory infiltrate at sites of infection and suggests that they synergize in anti-microbial immune responses. Our present findings demonstrate a rapid and HMB-PP-dependent crosstalk between Vγ9/Vδ2 T cells and autologous monocytes that results in the immediate production of inflammatory mediators including the cytokines interleukin (IL)-6, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and oncostatin M (OSM); the chemokines CCL2, CXCL8, and CXCL10; and TNF-related apoptosis-inducing ligand (TRAIL). Moreover, under these co-culture conditions monocytes differentiate within 18 hours into inflammatory dendritic cells (DCs) with antigen-presenting functions. Addition of further microbial stimuli (lipopolysaccharide, peptidoglycan) induces CCR7 and enables these inflammatory DCs to trigger the generation of CD4+ effector αβ T cells expressing IFN-γ and/or IL-17. Importantly, our in vitro model replicates the responsiveness to microbes of effluent cells from peritoneal dialysis (PD) patients and translates directly to episodes of acute PD-associated bacterial peritonitis, where Vγ9/Vδ2 T cell numbers and soluble inflammatory mediators are elevated in patients infected with HMB-PP-producing pathogens. Collectively, these findings suggest a direct link between invading pathogens, microbe-responsive γδ T cells, and monocytes in the inflammatory infiltrate, which plays a crucial role in the early response and the generation of microbe-specific immunity
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