462 research outputs found
A Generalized Robust Minimization Framework for Low-Rank Matrix Recovery
This paper considers the problem of recovering low-rank matrices which are heavily corrupted by outliers or large errors. To improve the robustness of existing recovery methods, the problem is solved by formulating it as a generalized nonsmooth nonconvex minimization functional via exploiting the Schatten p-norm (0 < p ≤1) and Lq(0 < q ≤1) seminorm. Two numerical algorithms are provided based on the augmented Lagrange multiplier (ALM) and accelerated proximal gradient (APG) methods as well as efficient root-finder strategies. Experimental results demonstrate that the proposed generalized approach is more inclusive and effective compared with state-of-the-art methods, either convex or nonconvex
Polygonum cuspidatum
Anoikis has been recognized as a potential target for anticancer therapy. Polygonum cuspidatum (Huzhang) is a frequently used Chinese herb in hepatocarcinoma. In present study, we evaluated the effects of Polygonum cuspidatum extract (PCE) in hepatocarcinoma cells in suspension. The results showed that PCE inhibited the proliferation of hepatocarcinoma cells in suspension in a dose- and time-dependent manner. PCE also inhibited anchorage-independent growth of hepatocarcinoma cells in soft agar. PCE induced anoikis in human hepatocarcinoma Bel-7402 cells accompanied by caspase-3 and caspase-9 activation and poly(ADP-ribose) polymerase cleavage, which was completely abrogated by a pan caspase inhibitor, Z-VAD-FMK. In addition, PCE treatment induced intracellular reactive oxygen species (ROS) production in Bel-7402 cells. NAC, an ROS scavenger, partially attenuated PCE-induced anoikis and activation of caspase-3 and caspase-9. Furthermore, PCE inhibited expression of focal adhesion kinase (FAK) in Bel-7402 cells. Overexpression of FAK partially abrogated PCE-induced anoikis. These data suggest that PCE may inhibit suspension growth and induce caspase-mediated anoikis in hepatocarcinoma cells and may relate to ROS generation and FAK downregulation. The present study provides new insight into the application of Chinese herb for hepatocarcinoma treatment
Host Adaptation of a Bacterial Toxin from the Human Pathogen Salmonella Typhi
SummarySalmonella Typhi is an exclusive human pathogen that causes typhoid fever. Typhoid toxin is a S. Typhi virulence factor that can reproduce most of the typhoid fever symptoms in experimental animals. Toxicity depends on toxin binding to terminally sialylated glycans on surface glycoproteins. Human glycans are unusual because of the lack of CMAH, which in other mammals converts N-acetylneuraminic acid (Neu5Ac) to N-glycolylneuraminic acid (Neu5Gc). Here, we report that typhoid toxin binds to and is toxic toward cells expressing glycans terminated in Neu5Ac (expressed by humans) over glycans terminated in Neu5Gc (expressed by other mammals). Mice constitutively expressing CMAH thus displaying Neu5Gc in all tissues are resistant to typhoid toxin. The atomic structure of typhoid toxin bound to Neu5Ac reveals the structural bases for its binding specificity. These findings provide insight into the molecular bases for Salmonella Typhi’s host specificity and may help the development of therapies for typhoid fever
Storage of 1650 modes of single photons at telecom wavelength
To advance the full potential of quantum networks one should be able to
distribute quantum resources over long distances at appreciable rates. As a
consequence, all components in the networks need to have large multimode
capacity to manipulate photonic quantum states. Towards this end, a multimode
photonic quantum memory, especially one operating at telecom wavelength,
remains a key challenge. Here we demonstrate a spectro-temporally multiplexed
quantum memory at 1532 nm. Multimode quantum storage of telecom-band heralded
single photons is realized by employing the atomic frequency comb protocol in a
10-m-long cryogenically cooled erbium doped silica fibre. The multiplexing
encompasses five spectral channels - each 10 GHz wide - and in each of these up
to 330 temporal modes, resulting in the simultaneous storage of 1650 modes of
single photons. Our demonstrations open doors for high-rate quantum networks,
which are essential for future quantum internet
Characterization of loss mechanisms in a fluxonium qubit
Using a fluxonium qubit with in situ tunability of its Josephson energy, we
characterize its energy relaxation at different flux biases as well as
different Josephson energy values. The relaxation rate at qubit energy values,
ranging more than one order of magnitude around the thermal energy , can
be quantitatively explained by a combination of dielectric loss and flux
noise with a crossover point. The amplitude of the flux noise is
consistent with that extracted from the qubit dephasing measurements at the
flux sensitive points. In the dielectric loss dominant regime, the loss is
consistent with that arises from the electric dipole interaction with
two-level-system (TLS) defects. In particular, as increasing Josephson energy
thus decreasing qubit frequency at the flux insensitive spot, we find that the
qubit exhibits increasingly weaker coupling to TLS defects thus desirable for
high-fidelity quantum operations
Quantum Instruction Set Design for Performance
A quantum instruction set is where quantum hardware and software meet. We
develop new characterization and compilation techniques for non-Clifford gates
to accurately evaluate different quantum instruction set designs. We
specifically apply them to our fluxonium processor that supports mainstream
instruction by calibrating and characterizing its square root
. We measure a gate fidelity of up to with an average
of and realize Haar random two-qubit gates using
with an average fidelity of . This is an average error reduction of
for the former and a reduction for the latter compared to using
on the same processor. This shows designing the quantum
instruction set consisting of and single-qubit gates on such
platforms leads to a performance boost at almost no cost.Comment: 2 figures in main text and 21 figures in Supplementary Materials.
This manuscript subsumes version 1 with significant improvements such as
experimental demonstration and materials presentatio
Coherent phonon dynamics in spatially separated graphene mechanical resonators
Vibrational modes in mechanical resonators provide a promising candidate to
interface and manipulate classical and quantum information. The observation of
coherent dynamics between distant mechanical resonators can be a key step
towards scalable phonon-based applications. Here we report tunable coherent
phonon dynamics with an architecture comprising three graphene mechanical
resonators coupled in series, where all resonators can be manipulated by
electrical signals on control gates. We demonstrate coherent Rabi oscillations
between spatially separated resonators indirectly coupled via an intermediate
resonator serving as a phonon cavity. The Rabi frequency fits well with the
microwave burst power on the control gate. We also observe Ramsey interference,
where the oscillation frequency corresponds to the indirect coupling strength
between these resonators. Such coherent processes indicate that information
encoded in vibrational modes can be transferred and stored between spatially
separated resonators, which can open the venue of on-demand phonon-based
information processing
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