488 research outputs found
Muon-fluorine entangled states in molecular magnets
The information accessible from a muon-spin relaxation experiment is often
limited since we lack knowledge of the precise muon stopping site. We
demonstrate here the possibility of localizing a spin polarized muon in a known
stopping state in a molecular material containing fluorine. The muon-spin
precession that results from the entangled nature of the muon-spin and
surrounding nuclear spins is sensitive to the nature of the stopping site and
we use this property to identify three classes of site. We are also able to
describe the extent to which the muon distorts its surroundings.Comment: 4 pages, 3 figure
Knot undulator to generate linearly polarized photons with low on-axis power density
Heat load on beamline optics is a serious problem to generate pure linearly
polarized photons in the third generation synchrotron radiation facilities. For
permanent magnet undulators, this problem can be overcome by a figure-8
operating mode. But there is still no good method to tackle this problem for
electromagnetic elliptical undulators. Here, a novel operating mode is
suggested, which can generate pure linearly polarized photons with very low
on-axis heat load. Also the available minimum photon energy of linearly
polarized photons can be extended much by this method
Test for interlayer coherence in a quasi-two-dimensional superconductor
Peaks in the magnetoresistivity of the layered superconductor
-(BEDT-TTF)Cu(NCS), measured in fields T applied
within the layers, show that the Fermi surface is extended in the interlayer
direction and enable the interlayer transfer integral (
meV) to be deduced. However, the quasiparticle scattering rate is
such that , implying that
-(BEDT-TTF)Cu(NCS) meets the criterion used to identify
interlayer incoherence. The applicability of this criterion to anisotropic
materials is thus shown to be questionable.Comment: 5 pages, 4 figure
Controlling magnetic order and quantum disorder in molecule-based magnets.
We investigate the structural and magnetic properties of two molecule-based magnets synthesized from the same starting components. Their different structural motifs promote contrasting exchange pathways and consequently lead to markedly different magnetic ground states. Through examination of their structural and magnetic properties we show that [Cu(pyz)(H 2 O)(gly) 2 ](ClO 4 ) 2 may be considered a quasi-one-dimensional quantum Heisenberg antiferromagnet whereas the related compound [Cu(pyz)(gly)](ClO 4 ) , which is formed from dimers of antiferromagnetically interacting Cu 2+ spins, remains disordered down to at least 0.03 K in zero field but shows a field-temperature phase diagram reminiscent of that seen in materials showing a Bose-Einstein condensation of magnons
Gene duplication and functional divergence of the zebrafish insulin‐like growth factor 1 receptors
Insulin‐like growth factor (IGF) 1 receptor (IGF1R)‐mediated signaling plays key roles in growth, development, and physiology. Recent studies have shown that there are two distinct igf1r genes in zebrafish, termed igf1ra and igf1rb. In this study, we tested the hypothesis that zebrafish igf1ra and igf1rb resulted from a gene duplication event at the igf1r locus and that this has led to their functional divergence. The genomic structures of zebrafish igf1ra and igf1rb were determined and their loci mapped. While zebrafish igf1ra has 21 exons and is located on linkage group (LG) 18, zebrafish igf1rb has 22 exons and mapped to LG 7. There is a strong syntenic relationship between the two zebrafish genes and the human IGF1R gene. Using a MO‐based loss‐of‐function approach, we show that both Igf1ra and Igf1rb are required for zebrafish embryo viability and proper growth and development. Although Igf1ra and Igf1rb demonstrated a large degree of functional overlap with regard to cell differentiation in the developing eye, inner ear, heart, and muscle, they also exhibited functional distinction involving a greater requirement for Igf1rb in spontaneous muscle contractility. These findings suggest that the duplicated zebrafish igf1r genes play largely overlapping but not identical functional roles in early development and provide novel insight into the functional evolution of the IGF1R/insulin receptor gene family.— Schlueter, P. J., Royer, T., Mohamed, H. F., Laser, B., Chan, S. J., Steiner, D. F., Duan, C. Gene duplication and functional divergence of the zebrafish insulin‐like growth factor 1 receptors. FASEB J. 20, E462–E471 (2006)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154460/1/fsb2fj053882fje.pd
A statistical model for the intrinsically broad superconducting to normal transition in quasi-two-dimensional crystalline organic metals
Although quasi-two-dimensional organic superconductors such as
-(BEDT-TTF)Cu(NCS) seem to be very clean systems, with apparent
quasiparticle mean-free paths of several thousand \AA, the superconducting
transition is intrinsically broad (e.g K wide for K).
We propose that this is due to the extreme anisotropy of these materials, which
greatly exacerbates the statistical effects of spatial variations in the
potential experienced by the quasiparticles. Using a statistical model, we are
able to account for the experimental observations. A parameter , which
characterises the spatial potential variations, may be derived from
Shubnikov-de Haas oscillation experiments. Using this value, we are able to
predict a transition width which is in good agreement with that observed in MHz
penetration-depth measurements on the same sample.Comment: 8 pages, 2 figures, submitted to J. Phys. Condens. Matte
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