1,200 research outputs found
Interacting quantum rotors in oxygen-doped germanium
We investigate the interaction effect between oxygen impurities in
crystalline germanium on the basis of a quantum rotor model. The dipolar
interaction of nearby oxygen impurities engenders non-trivial low-lying
excitations, giving rise to anomalous behaviors for oxygen-doped germanium
(Ge:O) below a few degrees Kelvin. In particular, it is theoretically predicted
that Ge:O samples with oxygen-concentration of 10cm show (i)
power-law specific heats below 0.1 K, and (ii) a peculiar hump in dielectric
susceptibilities around 1 K. We present an interpretation for the power-law
specific heats, which is based on the picture of local double-well potentials
randomly distributed in Ge:O samples.Comment: 13 pages, 11 figures; to be published in Phys. Rev.
Endomorphisms of superelliptic jacobians
Let K be a field of characteristic zero, n>4 an integer, f(x) an irreducible
polynomial over K of degree n, whose Galois group is doubly transitive simple
non-abelian group. Let p be an odd prime, Z[\zeta_p] the ring of integers in
the p-th cyclotomic field,
C_{f,p}:y^p=f(x) the corresponding superelliptic curve and J(C_{f,p}) its
jacobian. Assuming that either n=p+1 or p does not divide n(n-1), we prove that
the ring of all endomorphisms of J(C_{f,p}) coincides with Z[\zeta_p].Comment: Several typos have been correcte
Shimura varieties in the Torelli locus via Galois coverings of elliptic curves
We study Shimura subvarieties of obtained from families of
Galois coverings where is a smooth complex
projective curve of genus and . We give the complete list
of all such families that satisfy a simple sufficient condition that ensures
that the closure of the image of the family via the Torelli map yields a
Shimura subvariety of for and for all and
for and . In a previous work of the first and second author
together with A. Ghigi [FGP] similar computations were done in the case .
Here we find 6 families of Galois coverings, all with and
and we show that these are the only families with satisfying this
sufficient condition. We show that among these examples two families yield new
Shimura subvarieties of , while the other examples arise from
certain Shimura subvarieties of already obtained as families of
Galois coverings of in [FGP]. Finally we prove that if a family
satisfies this sufficient condition with , then .Comment: 18 pages, to appear in Geometriae Dedicat
Complications after surgery in patients with colorectal cancer: the evidence for nursing care
Drosophila Parkin requires PINK1 for mitochondrial translocation and ubiquitinates Mitofusin
Loss of the E3 ubiquitin ligase Parkin causes early onset Parkinson's disease, a neurodegenerative disorder of unknown etiology. Parkin has been linked to multiple cellular processes including protein degradation, mitochondrial homeostasis, and autophagy; however, its precise role in pathogenesis is unclear. Recent evidence suggests that Parkin is recruited to damaged mitochondria, possibly affecting mitochondrial fission and/or fusion, to mediate their autophagic turnover. The precise mechanism of recruitment and the ubiquitination target are unclear. Here we show in Drosophila cells that PINK1 is required to recruit Parkin to dysfunctional mitochondria and promote their degradation. Furthermore, PINK1 and Parkin mediate the ubiquitination of the profusion factor Mfn on the outer surface of mitochondria. Loss of Drosophila PINK1 or parkin causes an increase in Mfn abundance in vivo and concomitant elongation of mitochondria. These findings provide a molecular mechanism by which the PINK1/Parkin pathway affects mitochondrial fission/fusion as suggested by previous genetic interaction studies. We hypothesize that Mfn ubiquitination may provide a mechanism by which terminally damaged mitochondria are labeled and sequestered for degradation by autophagy
Spectral dependence of photoinduced spin precession in DyFeO3
Spin precession was nonthermally induced by an ultrashort laser pulse in
orthoferrite DyFeO3 with a pump-probe technique. Both circularly and linearly
polarized pulses led to spin precessions; these phenomena are interpreted as
the inverse Faraday effect and the inverse Cotton-Mouton effect, respectively.
For both cases, the same mode of spin precession was excited; the precession
frequencies and polarization were the same, but the phases of oscillations were
different. We have shown theoretically and experimentally that the analysis of
phases can distinguish between these two mechanisms. We have demonstrated
experimentally that in the visible region, the inverse Faraday effect was
dominant, whereas the inverse Cotton-Mouton effect became relatively prominent
in the near-infrared region.Comment: 27 pages, 8 figure
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