1,307 research outputs found

    On Companion-Induced Off-Center Supernova-Like Explosions

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    We suggest that a neutron star with a strong magnetic field, spiraling into the envelope of a companion star, can generate a ``companion induced SN-like off-center explosion". The strongly magnetized neutron star ("magnetar") is born in a supernova explosion before entering into an expanding envelope of a supergiant companion. If the neutron star collapses into a black hole via the hypercritical accretion during the spiral-in phase, a rapidly rotating black hole with a strong magnetic field at the horizon results. The Blandford-Znajek power is sufficient to power a supernova-like event with the center of explosion displaced from the companion core. The companion core, after explosion, evolves into a C/O-white dwarf or a neutron star with a second explosion. The detection of highly eccentric black-hole, C/O-white dwarf binaries or the double explosion structures in the supernova remnants could be an evidence of the proposed scenario.Comment: 5 page

    Exceptional points by coupling of modes with different angular momenta in deformed microdisks: A perturbative analysis

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    Recently, it has been shown numerically and by a semiclassical approach [Phys. Rev. Lett. 120, 093902 (2018)PRLTAO0031-900710.1103/PhysRevLett.120.093902] that second-order exceptional points can appear in the spectrum of weakly deformed microdisk resonators by coupling of optical modes with different angular momentum. Here, we use a perturbation theory for weak boundary deformations to derive an effective non-Hermitian Hamiltonian from which we obtain analytical formulas to describe the formation of second-order exceptional points in such systems. The theory is extended to third-order exceptional points and confirmed by full numerical calculations. © 2018 American Physical Society.1

    Separatrix modes in weakly deformed microdisk cavities

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    Optical modes in deformed dielectric microdisk cavities often show an unexpected localization along unstable periodic ray orbits. We reveal a new mechanism for this kind of localization in weakly deformed cavities. In such systems the ray dynamics is nearly integrable and its phase space contains small island chains. When increasing the deformation the enlarging islands incorporate more and more modes. Each time a mode comes close to the border of an island chain (separatrix) the mode exhibits a strong localization near the corresponding unstable periodic orbit. Using an EBK quantization scheme taking into account the Fresnel coefficients we derive a frequency condition for the localization. Observing far field intensity patterns and tunneling distances, reveals small differences in the emission properties. © 2017 Optical Society of America.1

    Exceptional points of third-order in a layered optical microdisk cavity

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    A striking signature of the non-Hermitian physics in open systems is the existence of exceptional points (EPs) in parameter space. In contrast to a conventional degeneracy, an EP involves not only the coalescence of the eigenvalues but simultaneously that of the corresponding eigenstates as well. Here, we study EPs in optical microdisk cavities with a concentrically layered refractive index profile. For the double-layered cavity we show the existence of an EP with two coalescing modes. For a triple-layered cavity we verify and discuss the emergence of an EP involving three coalescing modes in a single microdisk cavity

    Chirality of a resonance in the absence of backscatterings

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    Chirality of a resonance localized on an islands chain is studied in a deformed Reuleaux triangular-shaped microcavity, where clockwise and counter clockwise traveling rays are classically separated. A resonance localized on a period-5 islands chain exhibits chiral emission due to the asymmetric cavity shape. Chirality is experimentally proved in a InGaAsP multiquantum-well semiconductor laser by showing that the experimental emission characteristics well coincide with the wave dynamical ones. (C) 2017 Optical Society of America1

    Functionalization of zirconia ceramic with fibronectin proteins enhanced bioactivity and osteogenic response of osteoblast-like cells

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    Introduction: To overcome the genuine bioinert properties of zirconia ceramic, functionalization of the surface with the bioactive protein fibronectin was conducted.Methods: Glow discharge plasma (GDP)-Argon was first used to clean the zirconia surface. Then allylamine was treated at three different powers of 50 W, 75 W, and 85 W and immersed into 2 different fibronectin concentrations (5 µg/ml and 10 µg/ml).Results and Discussion: After surface treatment, irregularly folded protein-like substances were attached on the fibronectin coated disks, and a granular pattern was observed for allylamine grafted samples. Infrared spectroscopy detected C-O, N-O, N-H, C-H, and O-H functional groups for fibronectin treated samples. Surface roughness rose and hydrophilicity improved after the surface modification, with MTT assay showing the highest level of cell viability for the A50F10 group. Cell differentiation markers also showed that fibronectin grafted disks with A50F10 and A85F10 were the most active, which in turn encouraged late-stage mineralization activity on 21d. Up-regulation of osteogenic related mRNA expression from 1d to 10d can be observed in RT-qPCR data for ALP, OC, DLX5, SP7, OPG and RANK biomarkers. These physical and biological properties clearly indicate that an allylamine and fibronectin composite grafted surface significantly stimulated the bioactivity of osteoblast-like cells, and can be utilized for future dental implant applications

    Unidirectional emission from a cardioid-shaped microcavity laser

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    We find unidirectional emission in a cardioid-shaped microcavity laser. When a deformation parameter is well adjusted, rays starting around a period-5 unstable periodic orbit emit unidirectionally. To confirm the emission direction, we fabricate a laser by using an InGaAsP semiconductor and investigate emission characteristics. When the laser is excited by current injection with a dc current, resonances localized on the period-5 unstable periodic orbit emit unidirectionally. © 2016 Optical Society of America.1

    High dose concentration administration of ascorbic acid inhibits tumor growth in BALB/C mice implanted with sarcoma 180 cancer cells via the restriction of angiogenesis

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    To test the carcinostatic effects of ascorbic acid, we challenged the mice of seven experimental groups with 1.7 × 10-4 mol high dose concentration ascorbic acid after intraperitoneal administrating them with sarcoma S-180 cells. The survival rate was increased by 20% in the group that received high dose concentration ascorbic acid, compared to the control. The highest survival rate was observed in the group in which 1.7 × 10-4 mol ascorbic acid had been continuously injected before and after the induction of cancer cells, rather than just after the induction of cancer cells. The expression of three angiogenesis-related genes was inhibited by 0.3 times in bFGF, 7 times in VEGF and 4 times in MMP2 of the groups with higher survival rates. Biopsy Results, gene expression studies, and wound healing analysis in vivo and in vitro suggested that the carcinostatic effect induced by high dose concentration ascorbic acid occurred through inhibition of angiogenesis

    Unidirectional emission of high-Q scarred modes in a rounded D-shape microcavity

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    We propose a deformed microcavity laser, where a high-Q mode group emits unidirectionally. The cavity comprises three circular arcs and one linear section. To minimize diffraction effects from the boundary, three circular arcs and one linear section are tangentially connected. By adjusting the sizes and the positions of the two sub-circular arcs, unidirectionality is maximized. In an experiment with an InP based InGaAsP semiconductor microcavity laser, a lasing mode group localized on a period-7 unstable periodic orbit emits unidirectionally. In our resonance calculation, a high-Q factor is confirmed. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement1

    Exponential ATP amplification through simultaneous regeneration from AMP and pyrophosphate for luminescence detection of bacteria

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    a b s t r a c t Bacteria monitoring is essential for many industrial manufacturing processes, particularly those involving in food, biopharmaceuticals, and semiconductor production. Firefly luciferase ATP luminescence assay is a rapid and simple bacteria detection method. However, the detection limit of this assay for Escherichia coli is approximately 10 4 colony-forming units (CFU), which is insufficient for many applications. This study aims to improve the assay sensitivity by simultaneous conversion of PP i and AMP, two products of the luciferase reaction, back to ATP to form two chain-reaction loops. Because each consumed ATP continuously produces two new ATP molecules, this approach can achieve exponential amplification of ATP. Two consecutive enzyme reactions were employed to regenerate AMP into ATP: adenylate kinase converting AMP into ADP using UTP as the energy source, and acetate kinase catalyzing acetyl phosphate and ADP into ATP. The PP i -recycling loop was completed using ATP sulfurylase and adenosine 5 0 phosphosulfate. The modification maintains good quantification linearity in the ATP luminescence assay and greatly increases its bacteria detection sensitivity. This improved method can detect bacteria concentrations of fewer than 10 CFU. This exponential ATP amplification assay will benefit bacteria monitoring in public health and manufacturing processes that require high-quality water. Ó 2011 Elsevier Inc. All rights reserved. Bacteria monitoring is essential for many industrial manufacturing processes, and particularly those involving food, semiconductors, and biopharmaceuticals. The presence of bacteria reduces production yield and may cause serious health problems in humans. Researchers have developed several rapid assays for detecting bacteria in water. These methods include polymerase chain reactions, fluorescence in situ hybridization [1], b-D-glucuronidase activity measurement The ATP luminescence assay is a rapid, sensitive, and easy-toperform method based on the detection of ATP, a molecule ubiquitously present in all living cells. The enzyme luciferase catalyzes the oxidation of the substrate luciferin while transforming the energy derived from ATP into light, which can be quantified by a luminometer. This assay has been widely used in bacteria monitoring for food hygiene [4] and surface cleanliness The current detection limit of the ATP luminescence method for Escherichia coli is approximately 10 4 colony-forming units (CFU) 1 [12,13], which is not sensitive enough for many industrial and medical applications. Several approaches have been adopted to improve the assay sensitivity. The first strategy involves the identification of chemical extractants that can effectively disrupt bacterial cells while not interfering with the luminescence assay. Both dimethyl sulfoxide (DMSO) 0003-2697/$ -see front matter
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