Possible Explanation to Low CMB Quadrupole

The universe might experience many cycles with different vacua. The slow-roll inflation may be preceded by kinetic-dominated contraction occurring in "adjacent" vacua during some cycles. In this report we briefly show this phenomenon may lead to a cutoff of primordial power spectrum. Thus in some sense the CMB at large angular scale might encode the information of other vacua.Comment: 10 pages, 3 eps figures, accepted for publication in PRD, v2 revised with published versio

Brane Inflation from Rotation of D4 Brane

In this paper, a inflationary model from the rotation of D4-brane is constructed. We show that for a very wide rage of parameter, this model satisfies the observation and find that regarded as inflaton, the rotation of branes may be more nature than the distance between branes. Our model offers a new avenue for brane inflation.Comment: 6 pages, no figure

Cosmic Duality in Quintom Universe

In this paper we study the duality in two-field Quintom models of Dark Energy. We find that an expanding universe dominated by Quintom-A field is dual to a contracting universe with Quintom-B field

The Bouncing Jet: A Newtonian Liquid Rebounding off a Free Surface

We find that a liquid jet can bounce off a bath of the same liquid if the bath is moving horizontally with respect to the jet. Previous observations of jets rebounding off a bath (e.g. Kaye effect) have been reported only for non-Newtonian fluids, while we observe bouncing jets in a variety of Newtonian fluids, including mineral oil poured by hand. A thin layer of air separates the bouncing jet from the bath, and the relative motion replenishes the film of air. Jets with one or two bounces are stable for a range of viscosity, jet flow rate and velocity, and bath velocity. The bouncing phenomenon exhibits hysteresis and multiple steady states.Comment: 9 pages, 7 figures. submitted to Physical Review

Low Temperature Precursor Route for Highly Efficient Spherically Shaped LED-Phosphors M2Si5N8:Eu2+ (M = Eu, Sr, Ba)

The highly efficient nitridosilicate phosphors M2Si5N8 (M = Sr, Ba, Eu) for phosphor-converted pc-LEDs were synthesized at low temperatures using a novel precursor route involving metal amides M(NH2)2. These precursors have been synthesized by dissolution of the respective metals in supercritical ammonia at 150°C and 300 bar. The thermal behavior and decomposition process of the amides were investigated with temperature programmed powder X-ray diffractometry and thermoanalytical measurements (DTA/TG). These investigations rendered the amides as suitable intermediates for reaction with silicon diimide (Si(NH)2). Thus, the desired nitridosilicate phosphors were obtained at relatively low temperatures around 1150−1400°C which is approximately 300°C lower compared to common synthetic approaches starting from metals or oxides. The influence of the thermal treatment on the phosphor morphology has been studied extensively. The accessibility of spherical phosphor particles represents another striking feature of this route since it improves light extraction from the crystallites due to decreasing light guiding and decreasing re-absorption inside the phosphor particle. The synthesized luminescent materials M2Si5N8:Eu2+ (M = Sr, Ba) exhibit quantum efficiencies and emission band widths (FWHM 70−90 nm) comparable to standard phosphor powders. Employment of Eu(NH2)2 as dopant reagent for synthesis of Ba2Si5N8:Eu2+ proved favorable for the formation of spherical crystallites compared to doping with Eu metal, halides, or oxide

Dominance of climate warming effects on recent drying trends over wet monsoon regions

Understanding changes in background dryness over land is key information for adapting to climate change because of its critical socioeconomic consequences. However, causes of continental dryness changes remain uncertain because various climate parameters control dryness. Here, we verify dominant climate variables determining dryness trends over continental eastern Asia, which is characterized by diverse hydroclimate regimes ranging from arid to humid, by quantifying the relative effects of changes in precipitation, solar radiation, wind speed, surface air temperature, and relative humidity on trends in the aridity index based on observed data from 189 weather stations for the period of 1961–2010. Before the early 1980s (1961–1983), change in precipitation is a primary condition for determining aridity trends. In the later period (1984–2010), the dominant climate parameter for aridity trends varies according to the hydroclimate regime. Drying trends in arid regions are mostly explained by reduced precipitation. In contrast, the increase in potential evapotranspiration due to increased atmospheric water-holding capacity, a secondary impact of warming, works to increase aridity over the humid monsoon region despite an enhanced water supply and relatively less warming. Our results show significant drying effects of warming over the humid monsoon region in recent decades; this also supports the drying trends over warm and water-sufficient regions in future climate

Self calibration iso-pathlength point in cylindrical tissue geometry: Solution of steady-state photon diffusion based on the extrapolated zero-boundary

Near-infrared optical techniques permit tissue diagnosis by surface measurement. However, the geometrical shape of this interface profiles the intensity of the surface measurement, which is found to have an iso-pathlength (IPL) point allowing for absorption identification independent of tissue scattering. The IPL point was projected in Monte Carlo (MC) simulation, validated experimentally in cylindrical tissues, but remains under-appreciated through analytical approaches. In this work, we present an analytical solution of an IPL point for steady-state diffusion based on the extrapolated zero-boundary condition. The same IPL points were found when comparing this solution to 3-D MC simulations for a tissue radius range of 5-8mm.Electrical and Computer Engineerin

A Single Scalar Field Model of Dark Energy with Equation of State Crossing -1

In this paper we study the possibility of building models of dark energy with equation of state across -1 and propose explicitly a model with a single scalar field which gives rise to an equation of state larger than -1 in the past and less than -1 at the present time, consistent with the current observations.Comment: 4 pages, 1 figure, the version accepted by JCAP, presentation improved and references adde