Two-Step Model of Fusion for Synthesis of Superheavy Elements

A new model is proposed for fusion mechanisms of massive nuclear systems where so-called fusion hindrance exists. The model describes two-body collision processes in an approaching phase and shape evolutions of an amalgamated system into the compound nucleus formation. It is applied to $^{48}$Ca-induced reactions and is found to reproduce the experimental fusion cross sections extremely well, without any free parameter. Combined with the statistical decay theory, residue cross sections for the superheavy elements can be readily calculated. Examples are given.Comment: 4 pages, 4 figure

Challenges associated with modeling low-oxygen waters in Chesapeake Bay: a multiple model comparison

As three-dimensional (3-D) aquatic ecosystem models are used more frequently for operational water quality forecasts and ecological management decisions, it is important to understand the relative strengths and limitations of existing 3-D models of varying spatial resolution and biogeochemical complexity. To this end, 2-year simulations of the Chesapeake Bay from eight hydrodynamic-oxygen models have been statistically compared to each other and to historical monitoring data. Results show that although models have difficulty resolving the variables typically thought to be the main drivers of dissolved oxygen variability (stratification, nutrients, and chlorophyll), all eight models have significant skill in reproducing the mean and seasonal variability of dissolved oxygen. In addition, models with constant net respiration rates independent of nutrient supply and temperature reproduced observed dissolved oxygen concentrations about as well as much more complex, nutrient-dependent biogeochemical models. This finding has significant ramifications for short-term hypoxia forecasts in the Chesapeake Bay, which may be possible with very simple oxygen parameterizations, in contrast to the more complex full biogeochemical models required for scenario-based forecasting. However, models have difficulty simulating correct density and oxygen mixed layer depths, which are important ecologically in terms of habitat compression. Observations indicate a much stronger correlation between the depths of the top of the pycnocline and oxycline than between their maximum vertical gradients, highlighting the importance of the mixing depth in defining the region of aerobic habitat in the Chesapeake Bay when low-oxygen bottom waters are present. Improvement in hypoxia simulations will thus depend more on the ability of models to reproduce the correct mean and variability of the depth of the physically driven surface mixed layer than the precise magnitude of the vertical density gradient

Dynamic Evolution Model of Isothermal Voids and Shocks

We explore self-similar hydrodynamic evolution of central voids embedded in an isothermal gas of spherical symmetry under the self-gravity. More specifically, we study voids expanding at constant radial speeds in an isothermal gas and construct all types of possible void solutions without or with shocks in surrounding envelopes. We examine properties of void boundaries and outer envelopes. Voids without shocks are all bounded by overdense shells and either inflows or outflows in the outer envelope may occur. These solutions, referred to as type $\mathcal{X}$ void solutions, are further divided into subtypes $\mathcal{X}_{\rm I}$ and $\mathcal{X}_{\rm II}$ according to their characteristic behaviours across the sonic critical line (SCL). Void solutions with shocks in envelopes are referred to as type $\mathcal{Z}$ voids and can have both dense and quasi-smooth edges. Asymptotically, outflows, breezes, inflows, accretions and static outer envelopes may all surround such type $\mathcal{Z}$ voids. Both cases of constant and varying temperatures across isothermal shock fronts are analyzed; they are referred to as types $\mathcal{Z}_{\rm I}$ and $\mathcal{Z}_{\rm II}$ void shock solutions. We apply the `phase net matching procedure' to construct various self-similar void solutions. We also present analysis on void generation mechanisms and describe several astrophysical applications. By including self-gravity, gas pressure and shocks, our isothermal self-similar void (ISSV) model is adaptable to various astrophysical systems such as planetary nebulae, hot bubbles and superbubbles in the interstellar medium as well as supernova remnants.Comment: 24 pages, 13 figuers, accepted by ApS

Pairing and Density Correlations of Stripe Electrons in a Two-Dimensional Antiferromagnet

We study a one-dimensional electron liquid embedded in a 2D antiferromagnetic insulator, and coupled to it via a weak antiferromagnetic spin exchange interaction. We argue that this model may qualitatively capture the physics of a single charge stripe in the cuprates on length- and time scales shorter than those set by its fluctuation dynamics. Using a local mean-field approach we identify the low-energy effective theory that describes the electronic spin sector of the stripe as that of a sine-Gordon model. We determine its phases via a perturbative renormalization group analysis. For realistic values of the model parameters we obtain a phase characterized by enhanced spin density and composite charge density wave correlations, coexisting with subleading triplet and composite singlet pairing correlations. This result is shown to be independent of the spatial orientation of the stripe on the square lattice. Slow transverse fluctuations of the stripes tend to suppress the density correlations, thus promoting the pairing instabilities. The largest amplitudes for the composite instabilities appear when the stripe forms an antiphase domain wall in the antiferromagnet. For twisted spin alignments the amplitudes decrease and leave room for a new type of composite pairing correlation, breaking parity but preserving time reversal symmetry.Comment: Revtex, 28 pages incl. 5 figure

Neighbouring plants modify maize root foraging for phosphorus:coupling nutrients and neighbours for improved nutrient-use efficiency

Nutrient distribution and neighbours can impact plant growth, but how neighbours shape root‐foraging strategy for nutrients is unclear. Here, we explore new patterns of plant foraging for nutrients as affected by neighbours to improve nutrient acquisition. Maize (Zea mays) was grown alone (maize), or with maize (maize/maize) or faba bean (Vicia faba) (maize/faba bean) as a neighbour on one side and with or without a phosphorus (P)‐rich zone on the other in a rhizo‐box experiment. Maize demonstrated root avoidance in maize/maize, with reduced root growth in ‘shared’ soil, and increased growth away from its neighbours. Conversely, maize proliferated roots in the proximity of neighbouring faba bean roots that had greater P availability in the rhizosphere (as a result of citrate and acid phosphatase exudation) compared with maize roots. Maize proliferated more roots, but spent less time to reach, and grow out of, the P patches away from neighbours in the maize/maize than in the maize/faba bean experiment. Maize shoot biomass and P uptake were greater in the heterogeneous P treatment with maize/faba bean than with maize/maize system. The foraging strategy of maize roots is an integrated function of heterogeneous distribution of nutrients and neighbouring plants, thus improving nutrient acquisition and maize growth. Understanding the foraging patterns is critical for optimizing nutrient management in crops

Cosmological evolution and statefinder diagnostic for new holographic dark energy model in non flat universe

In this paper, the holographic dark energy model with new infrared cut-off proposed by Granda and Oliveros has been investigated in spatially non flat universe. The dependency of the evolution of equation of state, deceleration parameter and cosmological evolution of Hubble parameter on the parameters of new HDE model are calculated. Also, the statefinder parameters $r$ and $s$ in this model are derived and the evolutionary trajectories in $s-r$ plane are plotted. We show that the evolutionary trajectories are dependent on the model parameters of new HDE model. Eventually, in the light of SNe+BAO+OHD+CMB observational data, we plot the evolutionary trajectories in $s-r$ and $q-r$ planes for best fit values of the parameters of new HDE model.Comment: 11 pages, 5 figures, Accepted by Astrophys. Space Sc

Women’s preference for laparoscopic or abdominal hysterectomy

In the present study, women’s preferences on advantages and disadvantages of laparoscopic hysterectomy (LH) and abdominal hysterectomy (AH) have been studied. Patients’ preferences were evaluated in individual, structured interviews in women scheduled for hysterectomy and questionnaires in nurses. Forty-three patients and 39 nurses were included. After general information, 84% of patients and 74% of nurses preferred LH over AH. This preference did not change after supplying more detailed information or after hysterectomy. The avoidance of complications was indicated as the most important factor in the decision. More than half of the women evaluated a difference of 1% as the maximum acceptable risk of major complications. When confronted with scenarios based on current evidence, both patients and nurses prefer LH over AH. This study supports further implementation of LH in clinical practice. The actual major complication rate in hysterectomy, however, is perceived as high

Anomalous Heat Conduction and Anomalous Diffusion in Low Dimensional Nanoscale Systems

Thermal transport is an important energy transfer process in nature. Phonon is the major energy carrier for heat in semiconductor and dielectric materials. In analogy to Ohm's law for electrical conductivity, Fourier's law is a fundamental rule of heat transfer in solids. It states that the thermal conductivity is independent of sample scale and geometry. Although Fourier's law has received great success in describing macroscopic thermal transport in the past two hundreds years, its validity in low dimensional systems is still an open question. Here we give a brief review of the recent developments in experimental, theoretical and numerical studies of heat transport in low dimensional systems, include lattice models, nanowires, nanotubes and graphenes. We will demonstrate that the phonon transports in low dimensional systems super-diffusively, which leads to a size dependent thermal conductivity. In other words, Fourier's law is breakdown in low dimensional structures