712 research outputs found
Mixed-State Entanglement and Quantum Teleportation through Noisy Channels
The quantum teleportation with noisy EPR state is discussed. Using an optimal
decomposition technique, we compute the concurrence, entanglement of formation
and Groverian measure for various noisy EPR resources. It is shown analytically
that all entanglement measures reduce to zero when , where
is an average fidelity between Alice and Bob. This fact indicates
that the entanglement is a genuine physical resource for the teleportation
process. This fact gives valuable clues on the optimal decomposition for
higher-qubit mixed states. As an example, the optimal decompositions for the
three-qubit mixed states are discussed by adopting a teleportation with W-stateComment: 18 pages, 4 figure
The Spitzer c2d Survey of Nearby Dense Cores. V. Discovery of a VeLLO in the "Starless" Dense Core L328
This paper reports the discovery of a Very Low Luminosity Object (VeLLO) in
the "starless" dense core L328, using the Spitzer Space Telescope and ground
based observations from near-infrared to millimeter wavelengths. The Spitzer 8
micron image indicates that L328 consists of three subcores of which the
smallest one may harbor a source, L328-IRS while two other subcores remain
starless. L328-IRS is a Class 0 protostar according to its bolometric
temperature (44 K) and the high fraction ~72 % of its luminosity emitted at
sub-millimeter wavelengths. Its inferred "internal luminosity" (0.04 - 0.06
Lsun) using a radiative transfer model under the most plausible assumption of
its distance as 200 pc is much fainter than for a typical protostar, and even
fainter than other VeLLOs studied previously. Note, however, that its inferred
luminosity may be uncertain by a factor of 2-3 if we consider two extreme
values of the distance of L328-IRS (125 or 310 pc). Low angular resolution
observations of CO do not show any clear evidence of a molecular outflow
activity. But broad line widths toward L328, and Spitzer and near-infrared
images showing nebulosity possibly tracing an outflow cavity, strongly suggest
the existence of outflow activity. Provided that an envelope of at most ~0.1
Msunis the only mass accretion reservoir for L328-IRS, and the star formation
efficiency is close to the canonical value ~30%, L328-IRS has not yet accreted
more than 0.05 Msun. At the assumed distance of 200 pc, L328-IRS is destined to
be a brown dwarf.Comment: 29 pages, 8 figures, 1 table, to be published in Astrophysical
Journa
Amplitude Damping for single-qubit System with single-qubit mixed-state Environment
We study a generalized amplitude damping channel when environment is
initially in the single-qubit mixed state. Representing the affine
transformation of the generalized amplitude damping by a three-dimensional
volume, we plot explicitly the volume occupied by the channels simulatable by a
single-qubit mixed-state environment. As expected, this volume is embedded in
the total volume by the channels which is simulated by two-qubit enviroment.
The volume ratio is approximately 0.08 which is much smaller than 3/8, the
volume ratio for generalized depolarizing channels.Comment: 13 pages, 2 figures incluided V2: homepage address is included in
reference V3: version to appear in J. Phys. A: Mathematical and Theoretica
Polarization-selective vortex-core switching by orthogonal Gaussian-pulse currents
We experimentally demonstrate low-power-consumption vortex-core switching in
magnetic nanodisks using tailored rotating magnetic fields that are produced
with orthogonal and unipolar Gaussian-pulse currents. Optimal width of the
orthogonal pulses and their time delay are found to be determined only by the
angular eigenfrequency {\omega}_D for a given vortex-state disk of its
polarization p, such that {\sigma} = 1/{\omega}_D and {\Delta}t =
{\pi}p/2{\omega}_D, as studied from analytical and micromagnetic numerical
calculations. The estimated optimal pulse parameters are in good agreements
with the experimentally found results. This work provides a foundation for
energy-efficient information recording in vortex-core cross-point architecture.Comment: 32 pages, 10 figure
Macrocyclic colibactin induces DNA double-strand breaks via copper-mediated oxidative cleavage.
Colibactin is an assumed human gut bacterial genotoxin, whose biosynthesis is linked to the clb genomic island that has a widespread distribution in pathogenic and commensal human enterobacteria. Colibactin-producing gut microbes promote colon tumour formation and enhance the progression of colorectal cancer via cellular senescence and death induced by DNA double-strand breaks (DSBs); however, the chemical basis that contributes to the pathogenesis at the molecular level has not been fully characterized. Here, we report the discovery of colibactin-645, a macrocyclic colibactin metabolite that recapitulates the previously assumed genotoxicity and cytotoxicity. Colibactin-645 shows strong DNA DSB activity in vitro and in human cell cultures via a unique copper-mediated oxidative mechanism. We also delineate a complete biosynthetic model for colibactin-645, which highlights a unique fate of the aminomalonate-building monomer in forming the C-terminal 5-hydroxy-4-oxazolecarboxylic acid moiety through the activities of both the polyketide synthase ClbO and the amidase ClbL. This work thus provides a molecular basis for colibactin's DNA DSB activity and facilitates further mechanistic study of colibactin-related colorectal cancer incidence and prevention
Sensitivity to tumor development by TALEN-mediated Trp53 mutant genes in the susceptible FVB/N mice and the resistance C57BL/6 mice
Abstract
Background
This study was undertaken to compare the sensitivities of mice strains during tumor induction by transcription activator-like effector nucleases (TALEN)-mediated Trp53 mutant gene. Alterations of their tumorigenic phenotypes including survival rate, tumor formation and tumor spectrum, were assessed in FVB/N-Trp53em2Hwl/Korl and C57BL/6-Trp53em1Hwl/Korl knockout (KO) mice over 16weeks.
Results
Most of the physiological phenotypes factors were observed to be higher in FVB/N-Trp53em2Hwl/Korl KO mice than C57BL/6-Trp53em1Hwl/Korl KO mice, although there were significant differences in the body weight, immune organ weight, number of red blood cells, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), platelet count (PLT), total bilirubin (Bil-T) and glucose (Glu) levels in the KO mice relative to the wild type (WT) mice. Furthermore, numerous solid tumors were also observed in various regions of the surface skin of FVB/N-Trp53em2Hwl/Korl KO mice, but were not detected in C57BL/6-Trp53em1Hwl/Korl KO mice. The most frequently observed tumor in both the Trp53 KO mice was malignant lymphoma, while soft tissue teratomas and hemangiosarcomas were only detected in the FVB/N-Trp53em2Hwl/Korl KO mice.
Conclusions
Our results indicate that the spectrum and incidence of tumors induced by the TALEN-mediated Trp53 mutant gene is greater in FVB/N-Trp53em2Hwl/Korl KO mice than C57BL/6-Trp53em1Hwl/Korl KO mice over 16weeks
Anisotropic behaviors of massless Dirac fermions in graphene under periodic potential
Charge carriers of graphene show neutrino-like linear energy dispersions as
well as chiral behavior near the Dirac point. Here we report highly unusual and
unexpected behaviors of these carriers in applied external periodic potentials,
i.e., in graphene superlattices. The group velocity renormalizes highly
anisotropically even to a degree that it is not changed at all for states with
wavevector in one direction but is reduced to zero in another, implying the
possibility that one can make nanoscale electronic circuits out of graphene not
by cutting it but by drawing on it in a non-destructive way. Also, the type of
charge carrier species (e.g. electron, hole or open orbit) and their density of
states vary drastically with the Fermi energy, enabling one to tune the Fermi
surface-dominant properties significantly with gate voltage. These results
address the fundamental question of how chiral massless Dirac fermions
propagate in periodic potentials and point to a new possible path for nanoscale
electronics.Comment: 10 pages, 9 figure
Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons
Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis
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