820 research outputs found
Mesoscopic transport beyond linear response
We present an approach to steady-state mesoscopic transport based on the
maximum entropy principle formulation of nonequilibrium statistical mechanics.
Our approach is not limited to the linear response regime. We show that this
approach yields the quantization observed in the integer quantum Hall effect at
large currents, which until now has been unexplained. We also predict new
behaviors of non-local resistances at large currents in the presence of dirty
contacts.Comment: 14 pages plus one figure (with an insert) (post-script codes
appended), RevTeX 3.0, UCF-CM-93-004 (Revised
Magnetic resonance in the antiferromagnetic and normal state of NH_3K_3C_60
We report on the magnetic resonance of NH_3K_3C_60 powders in the frequency
range of 9 to 225 GHz. The observation of an antiferromagnetic resonance below
the phase transition at 40 K is evidence for an antiferromagnetically ordered
ground state. In the normal state, above 40 K, the temperature dependence of
the spin-susceptibilty measured by ESR agrees with previous static measurements
and is too weak to be explained by interacting localized spins in an insulator.
The magnetic resonance line width has an unusual magnetic-field dependence
which is large and temperature independent in the magnetically ordered state
and decreases rapidly above the transition. These observations agree with the
suggestion that NH_3K_3C_60 is a metal in the normal state and undergoes a
Mott-Hubbard metal to insulator transition at 40 K.Comment: 4 pages, 5 figures. Submitted to Phys. Rev.
Novel mechanism of photoinduced reversible phase transitions in molecule-based magnets
A novel microscopic mechanism of bi-directional structural changes is
proposed for the photo-induced magnetic phase transition in Co-Fe Prussian blue
analogues on the basis of ab initio quantum chemical cluster calculations. It
is shown that the local potential energies of various spin states of Co are
sensitive to the number of nearest neighbor Fe vacancies. As a result, the
forward and backward structural changes are most readily initiated by
excitation of different local regions by different photons. This mechanism
suggests an effective strategy to realize photoinduced reversible phase
transitions in a general system consisting of two local components.Comment: 4 pages, LaTex, 3 figures, to appear in Phys. Rev. Let
Ferromagnetism and giant magnetoresistance in the rare earth fullerides Eu6-xSrxC60
We have studied crystal structure, magnetism and electric transport
properties of a europium fulleride Eu6C60 and its Sr-substituted compounds,
Eu6-xSrxC60. They have a bcc structure, which is an isostructure of other M6C60
(M represents an alkali atom or an alkaline earth atom). Magnetic measurements
revealed that magnetic moment is ascribed to the divalent europium atom with S
= 7/2 spin, and a ferromagnetic transition was observed at TC = 10 - 14 K. In
Eu6C60, we also confirm the ferromagnetic transition by heat capacity
measurement. The striking feature in Eu6-xSrxC60} is very large negative
magnetoresistance at low temperature; the resistivity ratio \rho(H = 9
T)/\rho(H = 0 T) reaches almost 10^{-3} at 1 K in Eu6C60. Such large
magnetoresistance is the manifestation of a strong pi-f interaction between
conduction carriers on C60 and 4f electrons of Eu.Comment: 5 pages, 4 figure
Optical Identification of the ASCA Large Sky Survey
We present results of optical identification of the X-ray sources detected in
the ASCA Large Sky Survey. Optical spectroscopic observations were done for 34
X-ray sources which were detected with the SIS in the 2-7 keV band above 3.5
sigma. The sources are identified with 30 AGNs, 2 clusters of galaxies, and 1
galactic star. Only 1 source is still unidentified. The flux limit of the
sample corresponds to 1 x 10^{-13} erg s^{-1} cm^{-2} in the 2-10 keV band.
Based on the sample, the paper discusses optical and X-ray spectral
properties of the AGNs, contribution of the sources to the Cosmic X-ray
Background, and redshift and luminosity distributions of the AGNs. An
interesting result is that the redshift distribution of the AGNs suggests a
deficiency of high-redshift (0.5 10^{44}
erg s^{-1}) absorbed narrow-line AGNs (so called type 2 QSOs).Comment: Accepted for publication in ApJ. 57 pages with 13 figures, 9 JPG
plates, 5 additional PS tables. Original EPS plates (gzipped format
~1Mbyte/plate) and TeX tables are available from
ftp://ftp.kusastro.kyoto-u.ac.jp/pub/akiyama/0001289
Impact of functional studies on exome sequence variant interpretation in early-onset cardiac conduction system diseases
Aims
The genetic cause of cardiac conduction system disease (CCSD) has not been fully elucidated. Whole-exome sequencing (WES) can detect various genetic variants; however, the identification of pathogenic variants remains a challenge. We aimed to identify pathogenic or likely pathogenic variants in CCSD patients by using WES and 2015 American College of Medical Genetics and Genomics (ACMG) standards and guidelines as well as evaluating the usefulness of functional studies for determining them.
Methods and Results
We performed WES of 23 probands diagnosed with early-onset (<65 years) CCSD and analyzed 117 genes linked to arrhythmogenic diseases or cardiomyopathies. We focused on rare variants (minor allele frequency < 0.1%) that were absent from population databases. Five probands had protein truncating variants in EMD and LMNA which were classified as “pathogenic” by 2015 ACMG standards and guidelines. To evaluate the functional changes brought about by these variants, we generated a knock-out zebrafish with CRISPR-mediated insertions or deletions of the EMD or LMNA homologs in zebrafish. The mean heart rate and conduction velocities in the CRISPR/Cas9-injected embryos and F2 generation embryos with homozygous deletions were significantly decreased. Twenty-one variants of uncertain significance were identified in 11 probands. Cellular electrophysiological study and in vivo zebrafish cardiac assay showed that 2 variants in KCNH2 and SCN5A, 4 variants in SCN10A, and 1 variant in MYH6 damaged each gene, which resulted in the change of the clinical significance of them from “Uncertain significance” to “Likely pathogenic” in 6 probands.
Conclusions
Of 23 CCSD probands, we successfully identified pathogenic or likely pathogenic variants in 11 probands (48%). Functional analyses of a cellular electrophysiological study and in vivo zebrafish cardiac assay might be useful for determining the pathogenicity of rare variants in patients with CCSD. SCN10A may be one of the major genes responsible for CCSD.
Translational Perspective
Whole-exome sequencing (WES) may be helpful in determining the causes of cardiac conduction system disease (CCSD), however, the identification of pathogenic variants remains a challenge. We performed WES of 23 probands diagnosed with early-onset CCSD, and identified 12 pathogenic or likely pathogenic variants in 11 of these probands (48%) according to the 2015 ACMG standards and guidelines. In this context, functional analyses of a cellular electrophysiological study and in vivo zebrafish cardiac assay might be useful for determining the pathogenicity of rare variants, and SCN10A may be one of the major development factors in CCSD
STM observation of electronic wave interference effect in finite-sized graphite with dislocation-network structures
Superperiodic patterns near a step edge were observed by STM on
several-layer-thick graphite sheets on a highly oriented pyrolitic graphite
substrate, where a dislocation network is generated at the interface between
the graphite overlayer and the substrate. Triangular- and rhombic-shaped
periodic patterns whose periodicities are around 100 nm were observed on the
upper terrace near the step edge. In contrast, only outlines of the patterns
similar to those on the upper terrace were observed on the lower terrace. On
the upper terrace, their geometrical patterns gradually disappeared and became
similar to those on the lower terrace without any changes of their periodicity
in increasing a bias voltage. By assuming a periodic scattering potential at
the interface due to dislocations, the varying corrugation amplitudes of the
patterns can be understood as changes in LDOS as a result of the beat of
perturbed and unperturbed waves, i.e. the interference in an overlayer. The
observed changes in the image depending on an overlayer height and a bias
voltage can be explained by the electronic wave interference in the ultra-thin
overlayer distorted under the influence of dislocation-network structures.Comment: 8 pages; 6 figures; Paper which a part of cond-mat/0311068 is
disscussed in detai
Effects of tool coating and tool wear on the surface quality and flexural strength of slotted CFRP
Machining of carbon fibre reinforced polymer (CFRP) is abrasive and causes significant tool wear. The effect of tool wear on static flexural strength is investigated, using edge trimming with uncoated carbide and chemical vapour deposition (CVD) diamond coated burr style tools. Edge rounding (ER) criteria along with flank wear are used to observe tool degradation with ER shown to preferentially wear allowing the tool to become cyclically sharper and duller, corresponding to fluctuating dynamometer readings, a novelty for CFRP machining. Areal surface metrics degraded for an uncoated tool due to changes in cutting mechanism, whilst for up to 16.2 m of linear traverse, the coated tool showed limited changes. Tool wear, caused by edge trimming 7.2 m of CFRP, using an uncoated carbide tool, provided a flexural strength reduction of up to 10.5 %, directly linking tool wear to reduced mechanical strength
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