359 research outputs found
Homotopy on spatial graphs and generalized Sato-Levine invariants
Edge-homotopy and vertex-homotopy are equivalence relations on spatial graphs
which are generalizations of Milnor's link-homotopy. Fleming and the author
introduced some edge (resp. vertex)-homotopy invariants of spatial graphs by
applying the Sato-Levine invariant for the constituent 2-component
algebraically split links. In this paper, we construct some new edge (resp.
vertex)-homotopy invariants of spatial graphs without any restriction of
linking numbers of the constituent 2-component links by applying the
generalized Sato-Levine invariant.Comment: 16 pages, 13 figure
Novel ordering of an S = 1/2 quasi one-dimensional Ising-like anitiferromagnet in magnetic field
High-field specific heat measurements on BaCo2V2O8, which is a good
realization of an S = 1/2 quasi one-dimensional Ising-like antifferomagnet,
have been performed in magnetic fields up to 12 T along the chain and at
temperature down to 200 mK. We have found a new magnetic ordered state in the
field-induced phase above Hc ~ 3.9 T. We suggest that a novel type of the
incommensurate order, which has no correspondence to the classical spin system,
is realized in the field-induced phase.Comment: 4pages, 4figure
Longitudinal SDW order in a quasi-1D Ising-like quantum antiferromagnet
From neutron diffraction measurements on a quasi-1D Ising-like Co
spin compound BaCoVO, we observed an appearance
of a novel type of incommensurate ordering in magnetic fields. This ordering is
essentially different from the N{\' e}el-type ordering, which is expected for
the classical system, and is caused by quantum fluctuation inherent in the
quantum spin chain. A Tomonaga-Luttinger liquid (TLL) nature characteristic of
the gapless quantum 1D system is responsible for the realization of the
incommensurate ordering.Comment: 4pages, 4figur
Development of a new, fully automated system for electron backscatter diffraction (EBSD)-based large volume three-dimensional microstructure mapping using serial sectioning by mechanical polishing, and its application to the analysis of special boundaries in 316L stainless steel
Spintronic transport and Kondo effect in quantum dots
We investigate the spin-dependent transport properties of quantum-dot based
structures where Kondo correlations dominate the electronic dynamics. The
coupling to ferromagnetic leads with parallel magnetizations is known to give
rise to nontrivial effects in the local density of states of a single quantum
dot. We show that this influence strongly depends on whether charge
fluctuations are present or absent in the dot. This result is confirmed with
numerical renormalization group calculations and perturbation theory in the
on-site interaction. In the Fermi-liquid fixed point, we determine the
correlations of the electric current at zero temperature (shot noise) and
demonstrate that the Fano factor is suppressed below the Poissonian limit for
the symmetric point of the Anderson Hamiltonian even for nonzero lead
magnetizations. We discuss possible avenues of future research in this field:
coupling to the low energy excitations of the ferromagnets (magnons), extension
to double quantum dot systems with interdot antiferromagnetic interaction and
effect of spin-polarized currents on higher symmetry Kondo states such as
SU(4).Comment: 11 pages, 5 figures. Proceedings of the 3rd Intl. Conf. on Physics
and Applications of Spin-Related Phenomena in Semiconductors, Santa Barbara,
200
Spin dependent scattering of a domain-wall of controlled size
Magnetoresistance measurements in the CPP geometry have been performed on
single electrodeposited Co nanowires exchange biased on one side by a sputtered
amorphous GdCo layer. This geometry allows the stabilization of a single domain
wall in the Co wire, the thickness of which can be controlled by an external
magnetic field. Comparing magnetization, resistivity, and magnetoresistance
studies of single Co nanowires, of GdCo layers, and of the coupled system,
gives evidence for an additional contribution to the magnetoresistance when the
domain wall is compressed by a magnetic field. This contribution is interpreted
as the spin dependent scattering within the domain wall when the wall thickness
becomes smaller than the spin diffusion length.Comment: 9 pages, 13 figure
Low tumour cell proliferation at the invasive margin is associated with a poor prognosis in Dukes' stage B colorectal cancers
The conflicting results about the prognostic impact of tumour cell proliferation in colorectal cancer might be explained by the heterogeneity observed within these tumours. We have investigated whether a systematic spatial heterogeneity exists between different compartments, and whether the presence of such a systematic heterogeneity has any impact on survival. Fifty-six Dukes' stage B colorectal cancers were carefully morphometrically quantified with respect to the immunohistochemical expression of the proliferative marker Ki-67 at both the luminal border and the invasive margin. The proliferative activity was significantly higher at the luminal border compared with the invasive margin (P < 0.001), although the two compartments were also significantly correlated with each other. Tumours with low proliferation at the invasive margin had a significantly poorer prognosis both in univariate (P = 0.014) and in multivariate survival analyses (P = 0.042). We conclude that Dukes' B colorectal cancers exhibit a systematic spatial heterogeneity with respect to proliferation, and tumours with low proliferation at the invasive margin had a poor prognosis. The present data independently confirm recent results from the authors, and provide new insights into the understanding of tumour cell proliferation in colorectal cancer. © 1999 Cancer Research Campaig
Thermodynamical limit of general gl(N) spin chains II: Excited states and energies
We consider the thermodynamical limit of a gl(N) spin chain with arbitrary
representation at each site of the chain. We consider excitations (with holes
and new strings) above the vacuum and compute their corrections in 1/L to the
densities and the energy.Comment: 29 pages misprints in the example of sect 5.1 amended and a mistake
in theorem 5.4 correcte
Mechanism of Cancer Cell Death Induced by Depletion of an Essential Replication Regulator
Background: Depletion of replication factors often causes cell death in cancer cells. Depletion of Cdc7, a kinase essential for initiation of DNA replication, induces cancer cell death regardless of its p53 status, but the precise pathways of cell death induction have not been characterized. Methodology/Principal Findings: We have used the recently-developed cell cycle indicator, Fucci, to precisely characterize the cell death process induced by Cdc7 depletion. We have also generated and utilized similar fluorescent cell cycle indicators using fusion with other cell cycle regulators to analyze modes of cell death in live cells in both p53-positive and-negative backgrounds. We show that distinct cell-cycle responses are induced in p53-positive and-negative cells by Cdc7 depletion. p53-negative cells predominantly arrest temporally in G2-phase, accumulating CyclinB1 and other mitotic regulators. Prolonged arrest at G2-phase and abrupt entry into aberrant M-phase in the presence of accumulated CyclinB1 are followed by cell death at the post-mitotic state. Abrogation of cytoplasmic CyclinB1 accumulation partially decreases cell death. The ATR-MK2 pathway is responsible for sequestration of CyclinB1 with 14-3-3s protein. In contrast, p53-positive cancer cells do not accumulate CyclinB1, but appear to die mostly through entry into aberrant S-phase after Cdc7 depletion. The combination of Cdc7 inhibition with known anti-cancer agents significantly stimulates cell death effects in cancer cells in a genotype-dependent manner, providing a strategic basis for future combination therapies
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