353 research outputs found
Anisotropic two-orbital Hubbard model: single-site versus cluster dynamical mean-field theory
The anisotropic two-orbital Hubbard model with different bandwidths and
degrees of frustration in each orbital is investigated in the framework of both
single-site dynamical mean-field theory (DMFT) as well as its cluster extension
(DCA) for clusters up to four sites combined with a continuous-time quantum
Monte Carlo algorithm. This model shows a rich phase diagram which includes the
appearance of orbital selective phase transitions, non-Fermi liquid behavior as
well as antiferromagnetic metallic states. We discuss the advantages and
drawbacks of employing the single-site DMFT with respect to DCA and the
consequences for the physical picture obtained out of these calculations.
Finally, we argue that such a minimal model may be of relevance to understand
the nature of the antiferromagnetic metallic state in the iron-pnictide
superconductors as well as the origin of the small staggered magnetization
observed in these systems.Comment: 7 pages, 4 figures, and accepted in Annalen der Physi
Macrophage Subset Sensitivity to Endotoxin Tolerisation by Porphyromonas gingivalis
Macrophages (MĪ¦s) determine oral mucosal responses; mediating tolerance to commensal microbes and food whilst maintaining the capacity to activate immune defences to pathogens. MĪ¦ responses are determined by both differentiation and activation stimuli, giving rise to two distinct subsets; pro-inflammatory M1- and anti-inflammatory/regulatory M2- MĪ¦s. M2-like subsets predominate tolerance induction whereas M1 MĪ¦s predominate in inflammatory pathologies, mediating destructive inflammatory mechanisms, such as those in chronic P.gingivalis (PG) periodontal infection. MĪ¦ responses can be suppressed to benefit either the host or the pathogen. Chronic stimulation by bacterial pathogen associated molecular patterns (PAMPs), such as LPS, is well established to induce tolerance. The aim of this study was to investigate the susceptibility of MĪ¦ subsets to suppression by P. gingivalis. CD14hi and CD14lo M1- and M2-like MĪ¦s were generated in vitro from the THP-1 monocyte cell line by differentiation with PMA and vitamin D3, respectively. MĪ¦ subsets were pre-treated with heat-killed PG (HKPG) and PG-LPS prior to stimulation by bacterial PAMPs. Modulation of inflammation was measured by TNFĪ±, IL-1Ī², IL-6, IL-10 ELISA and NFĪŗB activation by reporter gene assay. HKPG and PG-LPS differentially suppress PAMP-induced TNFĪ±, IL-6 and IL-10 but fail to suppress IL-1Ī² expression in M1 and M2 MĪ¦s. In addition, P.gingivalis suppressed NFĪŗB activation in CD14lo and CD14hi M2 regulatory MĪ¦s and CD14lo M1 MĪ¦s whereas CD14hi M1 pro-inflammatory MĪ¦s were refractory to suppression. In conclusion, P.gingivalis selectively tolerises regulatory M2 MĪ¦s with little effect on pro-inflammatory CD14hi M1 MĪ¦s; differential suppression facilitating immunopathology at the expense of immunity
Response to comment on 'Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity'
Lambert et al. question our retrospective and holistic epidemiological assessment of the role of chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that chytridiomycosis has affected at least 501 amphibian species
On the multi-orbital band structure and itinerant magnetism of iron-based superconductors
This paper explains the multi-orbital band structures and itinerant magnetism
of the iron-pnictide and chalcogenides. We first describe the generic band
structure of an isolated FeAs layer. Use of its Abelian glide-mirror group
allows us to reduce the primitive cell to one FeAs unit. From
density-functional theory, we generate the set of eight Fe and As
localized Wannier functions for LaOFeAs and their tight-binding (TB)
Hamiltonian, . We discuss the topology of the bands, i.e. allowed and
avoided crossings, the origin of the d6 pseudogap, as well as the role of the
As orbitals and the elongation of the FeAs tetrahedron. We then
couple the layers, mainly via interlayer hopping between As orbitals,
and give the formalism for simple and body-centered tetragonal stackings. This
allows us to explain the material-specific 3D band structures. Due to the high
symmetry, several level inversions take place as functions of or
pressure, resulting in linear band dispersions (Dirac cones). The underlying
symmetry elements are, however, easily broken, so that the Dirac points are not
protected, nor pinned to the Fermi level. From the paramagnetic TB Hamiltonian,
we form the band structures for spin spirals with wavevector by coupling
and . The band structure for stripe order is studied as a
function of the exchange potential, , using Stoner theory. Gapping of
the Fermi surface (FS) for small requires matching of FS dimensions
(nesting) and -orbital characters. The origin of the propeller-shaped FS is
explained. Finally, we express the magnetic energy as the sum over
band-structure energies, which enables us to understand to what extent the
magnetic energies might be described by a Heisenberg Hamiltonian, and the
interplay between the magnetic moment and the elongation of the FeAs4
tetrahedron
Magnetism and its microscopic origin in iron-based high-temperature superconductors
High-temperature superconductivity in the iron-based materials emerges from,
or sometimes coexists with, their metallic or insulating parent compound
states. This is surprising since these undoped states display dramatically
different antiferromagnetic (AF) spin arrangements and Nel
temperatures. Although there is general consensus that magnetic interactions
are important for superconductivity, much is still unknown concerning the
microscopic origin of the magnetic states. In this review, progress in this
area is summarized, focusing on recent experimental and theoretical results and
discussing their microscopic implications. It is concluded that the parent
compounds are in a state that is more complex than implied by a simple Fermi
surface nesting scenario, and a dual description including both itinerant and
localized degrees of freedom is needed to properly describe these fascinating
materials.Comment: 14 pages, 4 figures, Review article, accepted for publication in
Nature Physic
Adult attention deficit hyperactivity disorder is associated with migraine headaches
Attention deficit hyperactivity disorder (ADHD) is now recognized as a common disorder both in child and adult psychiatry. Adult patients with a diagnosis of ADHD (nĀ =Ā 572) and community controls (nĀ =Ā 675) responded to auto-questionnaires rating past and present symptoms of ADHD, co-morbid conditions, including migraine, treatment history and work status. The prevalence of migraine was significantly higher in the patient group compared to the controls (28.3% vs. 19.2%, PĀ <Ā 0.001, ORĀ =Ā 1.67, CI 1.28ā2.17). The difference from controls was particularly marked for men (22.5% vs. 10.7%, PĀ <Ā 0.001, ORĀ =Ā 2.43, CI 1.51ā3.90) but was also significant for women (34.4% vs. 24.9%, PĀ =Ā 0.008, ORĀ =Ā 1.58, CI 1.13ā2.21). In both patients and controls, migraine was associated with symptoms of mood and anxiety disorders. These findings point to a co-morbidity of migraine with ADHD, and it is possible that these patients represent a clinical and biological subgroup of adult patients with ADHD
Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity
Anthropogenic trade and development have broken down dispersal barriers, facilitating the spread of diseases that threaten Earth's biodiversity. We present a global, quantitative assessment of the amphibian chytridiomycosis panzootic, one of the most impactful examples of disease spread, and demonstrate its role in the decline of at least 501 amphibian species over the past half-century, including 90 presumed extinctions. The effects of chytridiomycosis have been greatest in large-bodied, range-restricted anurans in wet climates in the Americas and Australia. Declines peaked in the 1980s, and only 12% of declined species show signs of recovery, whereas 39% are experiencing ongoing decline. There is risk of further chytridiomycosis outbreaks in new areas. The chytridiomycosis panzootic represents the greatest recorded loss of biodiversity attributable to a disease
Adult attention deficit hyperactivity disorder is associated with asthma
<p>Abstract</p> <p>Background</p> <p>Attention deficit hyperactivity disorder (ADHD) is increasingly recognized as a common disorder not only in children, but also in the adult population. Similarly, asthma also has a substantial prevalence among adults. Previous studies concerning a potential relationship between ADHD and asthma have not presented consistent results.</p> <p>Methods</p> <p>A cross-sectional study of 594 adult patients diagnosed with ADHD, compared with 719 persons from the general population. Information was collected between 1997 and 2005 using auto-questionnaires rating past and present symptoms of ADHD, co-morbid conditions, including asthma, and work status.</p> <p>Results</p> <p>The prevalence of asthma was significantly higher in the ADHD patient group compared to the controls, 24.4% vs. 11.3% respectively (OR = 2.54, 95% CI 1.89-3.44), and controls with asthma scored higher on ratings of both past and present symptoms of ADHD. Female ADHD patients had a significantly higher prevalence of asthma compared to male ADHD patients (30.9% vs. 18.2%, OR = 2.01, CI 1.36-2.95), but in controls a slight female preponderance was not statistically significant. In both ADHD patients and controls, having asthma was associated with an increased prevalence of symptoms of mood- and anxiety disorders.</p> <p>Conclusions</p> <p>The present findings point to a co-morbidity of ADHD and asthma, and these patients may represent a clinical and biological subgroup of adult patients with ADHD.</p
Towards the clinical implementation of pharmacogenetics in bipolar disorder.
BackgroundBipolar disorder (BD) is a psychiatric illness defined by pathological alterations between the mood states of mania and depression, causing disability, imposing healthcare costs and elevating the risk of suicide. Although effective treatments for BD exist, variability in outcomes leads to a large number of treatment failures, typically followed by a trial and error process of medication switches that can take years. Pharmacogenetic testing (PGT), by tailoring drug choice to an individual, may personalize and expedite treatment so as to identify more rapidly medications well suited to individual BD patients.DiscussionA number of associations have been made in BD between medication response phenotypes and specific genetic markers. However, to date clinical adoption of PGT has been limited, often citing questions that must be answered before it can be widely utilized. These include: What are the requirements of supporting evidence? How large is a clinically relevant effect? What degree of specificity and sensitivity are required? Does a given marker influence decision making and have clinical utility? In many cases, the answers to these questions remain unknown, and ultimately, the question of whether PGT is valid and useful must be determined empirically. Towards this aim, we have reviewed the literature and selected drug-genotype associations with the strongest evidence for utility in BD.SummaryBased upon these findings, we propose a preliminary panel for use in PGT, and a method by which the results of a PGT panel can be integrated for clinical interpretation. Finally, we argue that based on the sufficiency of accumulated evidence, PGT implementation studies are now warranted. We propose and discuss the design for a randomized clinical trial to test the use of PGT in the treatment of BD
Patterns of initiation of second generation antipsychotics for bipolar disorder: a month-by-month analysis of provider behavior
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