20,059 research outputs found
Periodic and Localized Solutions of the Long Wave-Short Wave Resonance Interaction Equation
In this paper, we investigate the (2+1) dimensional long wave-short wave
resonance interaction (LSRI) equation and show that it possess the Painlev\'e
property. We then solve the LSRI equation using Painlev\'e truncation approach
through which we are able to construct solution in terms of three arbitrary
functions. Utilizing the arbitrary functions present in the solution, we have
generated a wide class of elliptic function periodic wave solutions and
exponentially localized solutions such as dromions, multidromions, instantons,
multi-instantons and bounded solitary wave solutions.Comment: 13 pages, 6 figure
Environmental impacts of grazed pastures
Large nitrogen (N) surplus and return of excreta-N in localised patches at high N rates in intensively grazed pasture systems markedly increases the risk of N losses to waterways and the atmosphere. Here are described the main routes of N input to grazed pastures, losses via N leaching, methane (CH4) and nitrous oxide (N2O) emissions. Furthermore farm N budgets and N use efficiency in relation to management strategies that can be applied to reduce N losses are discussed. Nitrate leaching increases exponentially with increased inputs and is closely related to urine patches, which also influence the leaching of dissolved organic N. High N2O emission rates in grazed pastures are related to fertiliser-N or N in excreta combined with compaction by animal treading. Grazing may considerably reduce CH3 emissions compared to indoor housing of cows. Pastures are occasionally cultivated due to sward deterioration followed by a rapid and extended period of N mineralization, contributing to an increased potential for losses. Good management of the pasture (e.g. reduced fertiliser input and reduced length of grazing) and of the mixed crop rotation during both the grassland and the arable phase (e.g. delayed ploughing time and a catch crop strategy) can considerably reduce the negative environmental impact of grazing. It is important to consider the whole farm system when evaluating environmental impact. In particular for green house gasses since the pasture may serve as a source of N2O and indirectly of CH3, but also as a sink of CO2 influenced by management practices on the farm
The preparation, characterization, and pharmacokinetic studies of chitosan nanoparticles loaded with paclitaxel/dimethyl-β-cyclodextrin inclusion complexes.
A novel biocompatible and biodegradable drug-delivery nanoparticle (NP) has been developed to minimize the severe side effects of the poorly water-soluble anticancer drug paclitaxel (PTX) for clinical use. PTX was loaded into the hydrophobic cavity of a hydrophilic cyclodextrin derivative, heptakis (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), using an aqueous solution-stirring method followed by lyophilization. The resulting PTX/DM-β-CD inclusion complex dramatically enhanced the solubility of PTX in water and was directly incorporated into chitosan (CS) to form NPs (with a size of 323.9–407.8 nm in diameter) using an ionic gelation method. The formed NPs had a zeta potential of +15.9–23.3 mV and showed high colloidal stability. With the same weight ratio of PTX to CS of 0.7, the loading efficiency of the PTX/DM-β-CD inclusion complex-loaded CS NPs was 30.3-fold higher than that of the PTX-loaded CS NPs. Moreover, it is notable that PTX was released from the DM-β-CD/CS NPs in a sustained-release manner. The pharmacokinetic studies revealed that, compared with reference formulation (Taxol(®)), the PTX/DM-β-CD inclusion complex-loaded CS NPs exhibited a significant increase in AUC(0→24h) (the area under the plasma drug concentration–time curve over the period of 24 hours) and mean residence time by 2.7-fold and 1.4-fold, respectively. Therefore, the novel drug/DM-β-CD inclusion complex-loaded CS NPs have promising applications for the significantly improved delivery and controlled release of the poorly water-soluble drug PTX or its derivatives, thus possibly leading to enhanced therapeutic efficacy and less severe side effects
Approximate perturbed direct homotopy reduction method: infinite series reductions to two perturbed mKdV equations
An approximate perturbed direct homotopy reduction method is proposed and
applied to two perturbed modified Korteweg-de Vries (mKdV) equations with
fourth order dispersion and second order dissipation. The similarity reduction
equations are derived to arbitrary orders. The method is valid not only for
single soliton solution but also for the Painlev\'e II waves and periodic waves
expressed by Jacobi elliptic functions for both fourth order dispersion and
second order dissipation. The method is valid also for strong perturbations.Comment: 8 pages, 1 figur
New variable separation approach: application to nonlinear diffusion equations
The concept of the derivative-dependent functional separable solution, as a
generalization to the functional separable solution, is proposed. As an
application, it is used to discuss the generalized nonlinear diffusion
equations based on the generalized conditional symmetry approach. As a
consequence, a complete list of canonical forms for such equations which admit
the derivative-dependent functional separable solutions is obtained and some
exact solutions to the resulting equations are described.Comment: 19 pages, 2 fig
The COBRAS/SAMBA CMB Project
COBRAS/SAMBA is a second generation satelitte dedicated to mapping at high
resolution and sensitivity the anisotropies of the Cosmic Microwave Background
(CMB). This mission is in the assessment study phase (A) at ESA, with a
decision expected mid 1996, for a launch around 2003.Comment: PostScript, 4 pages, 4 figures in text, to appear in the Proceedings
of the 1995 Moriond Meeting on ``Clustering in the Universe'
Efficient table-top dual-wavelength beamline for ultrafast transient absorption spectroscopy in the soft X-ray region.
We present a table-top beamline providing a soft X-ray supercontinuum extending up to 370 eV from high-order harmonic generation with sub-13 fs 1300 nm driving pulses and simultaneous production of sub-5 fs pulses centered at 800 nm. Optimization of high harmonic generation in a long and dense gas medium yields a photon flux of ~ 1.4 × 106 photons/s/1% bandwidth at 300 eV. The temporal resolution of X-ray transient absorption experiments with this beamline is measured to be 11 fs for 800 nm excitation. This dual-wavelength approach, combined with high flux and high spectral and temporal resolution soft X-ray absorption spectroscopy, is a new route to the study of ultrafast electronic dynamics in carbon-containing molecules and materials at the carbon K-edge
Insights into Hydration Dynamics and Cooperative Interactions in Glycerol-Water Mixtures by Terahertz Dielectric Spectroscopy.
We report relaxation dynamics of glycerol-water mixtures as probed by megahertz-to-terahertz dielectric spectroscopy in a frequency range from 50 MHz to 0.5 THz at room temperature. The dielectric relaxation spectra reveal several polarization processes at the molecular level with different time constants and dielectric strengths, providing an understanding of the hydrogen-bonding network in glycerol-water mixtures. We have determined the structure of hydration shells around glycerol molecules and the dynamics of bound water as a function of glycerol concentration in solutions using the Debye relaxation model. The experimental results show the existence of a critical glycerol concentration of ∼7.5 mol %, which is related to the number of water molecules in the hydration layer around a glycerol molecule. At higher glycerol concentrations, water molecules dispersed in a glycerol network become abundant and eventually dominate, and four distinct relaxation processes emerge in the mixtures. The relaxation dynamics and hydration structure in glycerol-water mixtures are further probed with molecular dynamics simulations, which confirm the physical picture revealed by the dielectric spectroscopy
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