135 research outputs found

    A Turnover in the Galaxy Main Sequence of Star Formation at M1010MM_{*} \sim 10^{10} M_{\odot} for Redshifts z<1.3z < 1.3

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    The relationship between galaxy star formation rates (SFR) and stellar masses (MM_\ast) is re-examined using a mass-selected sample of \sim62,000 star-forming galaxies at z1.3z \le 1.3 in the COSMOS 2-deg2^2 field. Using new far-infrared photometry from HerschelHerschel-PACS and SPIRE and SpitzerSpitzer-MIPS 24 μ\mum, along with derived infrared luminosities from the NRK method based on galaxies' locations in the restframe color-color diagram (NUVr)(NUV - r) vs. (rK)(r - K), we are able to more accurately determine total SFRs for our complete sample. At all redshifts, the relationship between median SFRSFR and MM_\ast follows a power-law at low stellar masses, and flattens to nearly constant SFR at high stellar masses. We describe a new parameterization that provides the best fit to the main sequence and characterizes the low mass power-law slope, turnover mass, and overall scaling. The turnover in the main sequence occurs at a characteristic mass of about M01010MM_{0} \sim 10^{10} M_{\odot} at all redshifts. The low mass power-law slope ranges from 0.9-1.3 and the overall scaling rises in SFR as a function of (1+z)4.12±0.10(1+z)^{4.12 \pm 0.10}. A broken power-law fit below and above the turnover mass gives relationships of SFRM0.88±0.06SFR \propto M_{*}^{0.88 \pm 0.06} below the turnover mass and SFRM0.27±0.04SFR \propto M_{*}^{0.27 \pm 0.04} above the turnover mass. Galaxies more massive than M1010 MM_\ast \gtrsim 10^{10}\ M_{\rm \odot} have on average, a much lower specific star formation rate (sSFR) than would be expected by simply extrapolating the traditional linear fit to the main sequence found for less massive galaxies.Comment: 16 pages, 7 figures. Accepted for publication in Ap

    Ultra-broadband Light Absorption by a Sawtooth Anisotropic Metamaterial Slab

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    We present an ultra broadband thin-film infrared absorber made of saw-toothed anisotropic metamaterial. Absorbtivity of higher than 95% at normal incidence is supported in a wide range of frequencies, where the full absorption width at half maximum is about 86%. Such property is retained well at a very wide range of incident angles too. Light of shorter wavelengths are harvested at upper parts of the sawteeth of smaller widths, while light of longer wavelengths are trapped at lower parts of larger tooth widths. This phenomenon is explained by the slowlight modes in anisotropic metamaterial waveguide. Our study can be applied in the field of designing photovoltaic devices and thermal emitters.Comment: 12 pages, 4 picture

    Improved differential evolution based on mutation strategies

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    Abstract: Differential Evolution (DE) has been regarded as one of the excellent optimization algorithm in the science, computing and engineering field since its introduction by Storm and Price in 1995. Robustness, simplicity and easiness to implement are the key factors for DE’s success in optimization of engineering problems. However, DE experiences convergence and stagnation problems. This paper focuses on DE convergence speed improvement based on introduction of newly developed mutation schemes strategies with reference to DE/rand/1 on ac-count and tuning of control parameters. Simulations are conducted using bench-mark functions such as Rastrigin, Ackley and Sphere, Griewank and Schwefel function. The results are tabled in order to compare the improved DE with the traditional DE

    A hyperchaotic system without equilibrium

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    Abstract: This article introduces a new chaotic system of 4-D autonomous ordinary differential equations, which has no equilibrium. This system shows a hyper-chaotic attractor. There is no sink in this system as there is no equilibrium. The proposed system is investigated through numerical simulations and analyses including time phase portraits, Lyapunov exponents, and Poincaré maps. There is little difference between this chaotic system and other chaotic systems with one or several equilibria shown by phase portraits, Lyapunov exponents and time series methods, but the Poincaré maps show this system is a chaotic system with more complicated dynamics. Moreover, the circuit realization is also presented

    Self-Assembled Polymeric Micellar Nanoparticles as Nanocarriers for Poorly Soluble Anticancer Drug Ethaselen

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    A series of monomethoxy poly(ethylene glycol)-poly(lactide) (mPEG-PLA) diblock copolymers were synthesized, and mPEG-PLA micelle was fabricated and used as a nanocarrier for solubilization and delivery of a promising anticancer drug ethaselen. Ethaselen was efficiently encapsulated into the micelles by the dialysis method, and the solubility of ethaselen in water was remarkably increased up to 82 μg/mL before freeze-drying. The mean diameter of ethaselen-loaded micelles ranged from 51 to 98 nm with a narrow size distribution and depended on the length of PLA block. In vitro hemolysis study indicated that mPEG-PLA copolymers and ethaselen-loaded polymeric micelles had no hemolytic effect on the erythrocyte. The enhanced antitumor efficacy and reduced toxic effect of ethaselen-loaded polymeric micelle when compared with ethaselen-HP-β-CD inclusion were observed at the same dose in H22human liver cancer cell bearing mouse models. These suggested that mPEG-PLA polymeric micelle nanoparticles had great potential as nanocarriers for effective solubilization of poorly soluble ethaselen and further reducing side effects and toxicities of the drug

    Preparation and Evaluation of Poly(Ethylene Glycol)–Poly(Lactide) Micelles as Nanocarriers for Oral Delivery of Cyclosporine A

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    A series of monomethoxy poly(ethylene glycol)–poly(lactide) (mPEG–PLA) diblock copolymers were designed according to polymer–drug compatibility and synthesized, and mPEG–PLA micelle was fabricated and used as a nanocarrier for solubilization and oral delivery of Cyclosporine A (CyA). CyA was efficiently encapsulated into the micelles with nanoscaled diameter ranged from 60 to 96 nm with a narrow size distribution. The favorable stabilities of CyA-loaded polymeric micelles were observed in simulated gastric and intestinal fluids. The in vitro drug release investigation demonstrated that drug release was retarded by polymeric micelles. The enhanced intestinal absorption of CyA-loaded polymeric micelles, which was comparable to the commercial formulation of CyA (Sandimmun Neoral®), was found. These suggested that polymeric micelles might be an effective nanocarrier for solubilization of poorly soluble CyA and further improving oral absorption of the drug
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