Weak Lensing by Intergalactic Mini-Structures in Quadruple Lens Systems: Simulation and Detection

We investigate the weak lensing effects of line-of-sight structures on quadruple images in quasar-galaxy strong lens systems based on N-body and ray-tracing simulations that can resolve halos with a mass of 10^5 solar mass. The intervening halos and voids disturb the magnification ratios of lensed images as well as their relative positions due to lensing. The magnification ratios typically change by O(10%) when the shifts of relative angular positions of lensed images are constrained to <0.004 arcsec. The constrained amplitudes of projected density perturbations due to line-of-sight structures are O(10^8) solar mass per arcsec^2. These results are consistent with our new analytical estimate based on the two-point correlation of density fluctuations. The observed mid-infrared (MIR) flux ratios for 6 quasar-galaxy lens systems with quadruple images agree well with the numerically estimated values without taking into account of subhalos residing in the lensing galaxies. We find that the constrained mean amplitudes of projected density perturbations in the line-of-sight are negative, which suggests that the fluxes of lensed images are perturbed mainly by minivoids and minihalos in underdense regions. We derive a new fitting formula for estimating the probability distribution function of magnification perturbation. We also find that the mean amplitude of magnification perturbation roughly equals the standard deviation regardless of the model parameters.Comment: 22 pages, 15 figures, accepted for publication in MNRA

Convergence of atmospheric and North Atlantic CO2 trends on multidecadal timescales

The oceans&#x2019; carbon uptake substantially reduces the rate of anthropogenic carbon accumulation in the atmosphere1, and thus slows global climate change. Some diagnoses of trends in ocean carbon uptake have suggested a significant weakening in recent years2-8, while others conclude that decadal variability confounds detection of long-term trends9-11. Here, we study trends in observed surface ocean partial pressure of CO2 (pCO2) in three gyre-scale biomes of the North Atlantic, considering decadal to multidecadal timescales between 1981 and 2009. Trends on decadal timescales are of variable magnitudes and depend sensitively on the precise choice of years. As more years are considered, oceanic pCO2 trends begin to converge to the trend in atmospheric pCO2. North of 30oN, it takes 25 years for the influence of decadal-timescale climate variability to be overcome by a long-term trend that is consistent with the accumulation of anthropogenic carbon. In the permanently stratified subtropical gyre, warming has recently become a significant contributor to the observed increase in oceanic pCO2. This warming, previously attributed to both a multidecadal climate oscillation and anthropogenic climate forcing12,13, is beginning to reduce ocean carbon uptake

Constraints on long-lived electrically charged massive particles from anomalous strong lens systems

We investigate anomalous strong lens systems, particularly the effects of weak lensing by structures in the line of sight, in models with long-lived electrically charged massive particles (CHAMPs). In such models, matter density perturbations are suppressed through the acoustic damping and the flux ratio of lens systems are impacted, from which we can constrain the nature of CHAMPs. For this purpose, first we perform $N$-body simulations and develop a fitting formula to obtain non-linear matter power spectra in models where cold neutral dark matter and CHAMPs coexist in the early Universe. By using the observed anomalous quadruple lens samples, we obtained the constraints on the lifetime ($\tau_{\rm Ch}$) and the mass density fraction ($r_{\rm Ch}$) of CHAMPs. We show that, for $r_{\rm Ch}=1$, the lifetime is bounded as $\tau_{\rm Ch} < 0.96\,$yr (95% confidence level), while a longer lifetime $\tau_{\rm Ch} = 10\,$yr is allowed when $r_{\rm Ch} < 0.5$ at the 95% confidence level. Implications of our result for particle physics models are also discussed.Comment: 20 pages, 6 figure

Locally embedded presages of global network bursts

Spontaneous, synchronous bursting of neural population is a widely observed phenomenon in nervous networks, which is considered important for functions and dysfunctions of the brain. However, how the global synchrony across a large number of neurons emerges from an initially non-bursting network state is not fully understood. In this study, we develop a new state-space reconstruction method combined with high-resolution recordings of cultured neurons. This method extracts deterministic signatures of upcoming global bursts in "local" dynamics of individual neurons during non-bursting periods. We find that local information within a single-cell time series can compare with or even outperform the global mean field activity for predicting future global bursts. Moreover, the inter-cell variability in the burst predictability is found to reflect the network structure realized in the non-bursting periods. These findings demonstrate the deterministic mechanisms underlying the locally concentrated early-warnings of the global state transition in self-organized networks

Static and dynamic compression of Earth materials

The triennium, 1967–1970, has been a period of marked increase in acquisition of pressure-volume data for minerals, rocks, and compounds of geophysical interest. A wide assortment of data has been obtained by the conventional dilatometric techniques as well as by the more recently developed X-ray diffraction and shock-wave techniques. Highlights of progress during the last 3 years include hydrostatic compression measurements for Apollo 11 lunar samples [Stephens and Lilley, 1970; Schreiber et al., 1970], static compression measurements of the spinel phase of (Mg,Fe)_2SiO_4 solid solutions, which are likely constituents of the transition zone of the earth's mantle [Mao et al., 1969], and Hugoniot data for high-pressure phases of ferromagnesian silicates, which may represent the constituents of the lower mantle [McQueen et al., 1967b]

The on-farm impact of alternative grazing management options to improve sustainability in western Chinese grasslands

Chinese grasslands are suffering considerable pressures from human and livestock populations. It has been estimated that 90% of Chinese grasslands are suffering from light to heavy levels of degradation. Allied to this is the low household income of herders and farmers dependant upon livestock products for their livelihood. Although a range of reasons have been proposed for the high levels of grassland degradation, principal among these are the high stocking rates adopted by farmers. This not only results in high utilisation rates of the pasture biomass, leading to bare areas and soil erosion, but individual animal productivity rates also decline. This paper presents the results of a modelling study of a grassland system in Gansu Province and Inner Mongolia Autonomous Region in northern China. This shows that reducing stocking rates leads to not only an increase in livestock productivity, but whole-farm returns are also increased. From a sustainability perspective, the greater pasture biomass remaining on the grassland also reduces the incidence of soil erosion in the areas.sustainable grazing, bioeconomic model, China, Farm Management, Livestock Production/Industries, Resource /Energy Economics and Policy,