Spin fluctuations, magnetic long-range order and Fermi surface gapping in NaxCoO2

In this study an extended low energy phase diagram for NaxCoO2 is experimentally established with emphasis on the high x range. It is based on systematic heat capacity studies on both polycrystalline and single crystalline samples and on uSR measurements. Main features are the existence of mass enhancement, spin fluctuations without long-range order, and magnetic order with associated Fermi surface gapping. The latter is seen in the electronic density of states (DOS) and suppression of nuclear specific heat. While there is agreement between the band structure and the low energy DOS in the low x range, in the high x range (x > 0.6) the thermodynamically determined DOS is approximately three times that deduced from the angle-resolved photoemission spectroscopy (ARPES)-measured band dispersion or local-density approximation (LDA) calculations.Comment: 9 pages, 5 figure

Recent advances in understanding the roles of whole genome duplications in evolution

Ancient whole-genome duplications (WGDs)—paleopolyploidy events—are key to solving Darwin’s ‘abominable mystery’ of how flowering plants evolved and radiated into a rich variety of species. The vertebrates also emerged from their invertebrate ancestors via two WGDs, and genomes of diverse gymnosperm trees, unicellular eukaryotes, invertebrates, fishes, amphibians and even a rodent carry evidence of lineage-specific WGDs. Modern polyploidy is common in eukaryotes, and it can be induced, enabling mechanisms and short-term cost-benefit assessments of polyploidy to be studied experimentally. However, the ancient WGDs can be reconstructed only by comparative genomics: these studies are difficult because the DNA duplicates have been through tens or hundreds of millions of years of gene losses, mutations, and chromosomal rearrangements that culminate in resolution of the polyploid genomes back into diploid ones (rediploidisation). Intriguing asymmetries in patterns of post-WGD gene loss and retention between duplicated sets of chromosomes have been discovered recently, and elaborations of signal transduction systems are lasting legacies from several WGDs. The data imply that simpler signalling pathways in the pre-WGD ancestors were converted via WGDs into multi-stranded parallelised networks. Genetic and biochemical studies in plants, yeasts and vertebrates suggest a paradigm in which different combinations of sister paralogues in the post-WGD regulatory networks are co-regulated under different conditions. In principle, such networks can respond to a wide array of environmental, sensory and hormonal stimuli and integrate them to generate phenotypic variety in cell types and behaviours. Patterns are also being discerned in how the post-WGD signalling networks are reconfigured in human cancers and neurological conditions. It is fascinating to unpick how ancient genomic events impact on complexity, variety and disease in modern life

Collapse of the Magnetic Ordering and Structural Anomalies in the UxLa1-xS System: Neutron Diffraction and Specific Heat Measurements.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Collapse of the magnetic ordering and structural anomalies in the U

We report specific heat and neutron diffraction measurements of seven samples in the solid solution system UxLa1-xS. All samples have the simple fcc NaCl crystal structure. Both specific heat and neutron diffraction confirm the suggestion from the earlier magnetic measurements that the ferromagnetism disappears abruptly at xc 0.57. Near xc there is a doubling of γ the electronic contribution to the specific heat, as compared to the value of 23 mJ mol-1K-2 in pure US. Around xc the widths of the nuclear Bragg peaks show a considerable broadening, as well as anomalies in the mean lattice parameter, as compared to those expected from Vegard's law. A preliminary analysis suggests this broadening may be due to a loss of long range lattice order near xc. However, these changes are independent of temperature, so that further experiments are necessary before they can be associated with the changes in magnetic behavior at xc

CXCL4 assembles DNA into liquid crystalline complexes to amplify TLR9-mediated interferon-α production in systemic sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by fibrosis and vasculopathy. CXCL4 represents an early serum biomarker of severe SSc and likely contributes to inflammation via chemokine signaling pathways, but the exact role of CXCL4 in SSc pathogenesis is unclear. Here, we elucidate an unanticipated mechanism for CXCL4-mediated immune amplification in SSc, in which CXCL4 organizes “self” and microbial DNA into liquid crystalline immune complexes that amplify TLR9-mediated plasmacytoid dendritic cell (pDC)-hyperactivation and interferon-α production. Surprisingly, this activity does not require CXCR3, the CXCL4 receptor. Importantly, we find that CXCL4-DNA complexes are present in vivo and correlate with type I interferon (IFN-I) in SSc blood, and that CXCL4-positive skin pDCs coexpress IFN-I-related genes. Thus, we establish a direct link between CXCL4 overexpression and the IFN-I-gene signature in SSc and outline a paradigm in which chemokines can drastically modulate innate immune receptors without being direct agonists

Evolution of Magnetic Structures in NpAs-NpSe Solid Solutions.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Evolution of magnetic structures in NpAs_1-xSe_x solid solutions

We report Mössbauer spectroscopy, magnetization, and neutron-diffraction measurements on four samples (x=0.05,0.10,0.15, and 0.20) in the mixed system NpAs1−xSex. The evolution of magnetic phase diagram vs the temperature T and the Se concentration x has been determined. Up to x=0.15, three distinct phase transitions are present. The first antiferromagnetic (AF) at TN(x) is from paramagnetism to an incommensurate phase, the second, at TC(x), is to a ferromagnetic (FM) phase, the third at Tm(x) is from pure FM to a mixed phase where AF and FM ordering coexist along perpendicular directions. The temperatures of the transitions are functions of Se concentration x. The incommensurate structure is described by a longitudinal amplitude modulated sinusoidal wave with a wave vector →k in the range (000.14–0.24) that is shifted toward the center of the Brillouin zone with increasing x. A squaring up of this wave, if present, is too small to be detected. At TC(x) all Np sites become equivalent and the moment directions become ⟨111⟩. Surprisingly, at Tm(x) AF interactions again become important and cause the moments to rotate and to align along ⟨221⟩ directions. Measurements in an external magnetic field up to 4.8 T have allowed us to determine the 1→k nature of the AF component for T<Tm and to establish the moment directions. Increasing Se content reduces the incommensurate phase to a small range of T and reduces the AF interactions. At x=0.20 pure FM behavior, as shown by the magnetization measurements, is recovered. The saturated Np moments at low T decrease slightly with increasing x