Search

A double-hydrophilic multiarm hyperbranched polymer with a hyperbranched poly(amidoamine) (HPAMAM) core and many poly(ethylene glycol) monomethyl ether (MPEG) arms connected by pH-sensitive acylhydrazone bonds (HPAMAM-g-MPEG) was successfully prepared. Benefiting from the cationic dendritic core and PEGylation shell, the double-hydrophilic multiarm hyperbranched polymer was used as a nanoreactor for CdS quantum dots (CdS QDs) synthesis in aqueous solution. The obtained HPAMAM-g-MPEG and CdS/HPAMAM-g-MPEG nanocomposites were carefully characterized by 1H NMR, 13C NMR, Fourier transform infrared spectroscopy (FTIR), ultraviolet−visible absorption spectroscopy (UV−vis), fluorescence spectroscopy (FL), dynamic light scattering (DLS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and electronic dispersive X-ray spectroscopy (EDS) analysis. Both 1H NMR and fluorescence spectroscopy investigations confirmed that the acylhydrazone linkage between the dendritic core and linear arms was readily broken under acidic condition (pH <5.5). When MPEG arms departed from the HPAMAM core, the fluorescence intensity of CdS/HPAMAM-g-MPEG nanocomposites greatly increased. Such pH-responsive behavior of CdS/HPAMAM-g-MPEG nanocomposites was utilized as an exploration of a novel fluorescence probe in an acidic lysosome exemplified by COS-7 cells. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are used to model the shock loading of an interface with various degrees of nanometer scale faceting between an inert binder and an energetic crystal. The facets create regions of local compression that induce exothermic reaction that leads to local hotspots and an increased shock sensitivity to detonation. Two mechanisms for compression and hotspot formation are identified that depend on the shock impedance mismatch between the binder and energetic crystal, namely shock focusing and local compression of the facets. These results provide a possible explanation for why spherical RDX crystals in cast polymer-bonded explosives appear less shock sensitive than RDX with more faceted morphologies. [ABSTRACT FROM AUTHOR]

A new strategy for the synthesis of CdS nanocrystals (NCs) within supramolecular self-assembly nanoreactors has been described. The self-assembly nanoreactors were readily constructed through the electrostatic interactions and ion pairs between palmitic acid and the terminal amine groups of hyperbranched polymer. In a chloroform/water two-phase system, aqueous Cd 2+ions were spontaneously encapsulated into the cavities of self-assembly nanoreactors in chloroform. After reaction with S 2−ions, the CdS NCs with high stability were obtained. By the addition of excess triethylamine, CdS NCs formed in the self-assembly nanoreactors were transferred from organic phase into aqueous phase. After dialysis and rotorary evaporation, aqueous CdS NCs could be redispersed into chloroform solution containing palmitic acid. [ABSTRACT FROM AUTHOR]

After the accident at the Fukushima nuclear power plant in Japan, a large amount of radioactive contaminated soil was generated, which brought great challenges for treating and disposing of the soil. The recycling of slightly polluted soil can reduce the amount of contaminated soil. This paper analyzes the main exposed scenes of 137Cs polluted soil used in the construction of highway subgrade, soil bag handling and paving. The Monte Carlo algorithm (MCNP) and RESRAD-ONSITE program are used to simulate the two scenes respectively, and the concentration of 137Cs is derived in the soil at the effective dose of 1 mSv per year. It is concluded that: the annual effective doses of porter and paver are 0.41 mSv per year and 0.23 mSv per year respectively caused by 1 Bqg-1 137Cs contaminated soil; the activity of 137Cs are 2.44 Bqg and 4.26 Bqg-1 respectively in the soil at 1 mSv per year for porter and paver; the calculated results are consistent with those reported by the Japan Atomic Research Agency. Also, they are lower than the activity concentration corresponding to the effective dose con- trol level of 1 mSv per year under low-probability events in IAEA No. RS-G-1.7 slightly. [ABSTRACT FROM AUTHOR]

Congestion is a kind of expression of instability of traffic network. Traffic signal control keeping traffic network stable can reduce the congestion of urban traffic. In order to improve the efficiency of urban traffic network, this study proposes a decentralized traffic signal control strategy based on backpressure algorithm used in Wi-Fi mesh networks for packets routing. Backpressure based traffic signal control algorithm can stabilize urban traffic network and achieve maximum throughput. Based on original backpressure algorithm, the variant parameter and penalty function are considered to balance the queue differential and capacity of downstream links in urban traffic network. For each traffic phase of intersections, phase weight is computed using queue differential and capacity of downstream links, which fixed the deficiency of infinite queue capacity in original backpressure algorithm. It is proved that the extended backpressure traffic signal control algorithm can maintain stability of urban traffic network, and also can prevent queue spillback, so as to improve performance of whole traffic network. Simulations are carried out in Vissim using Vissim COM programming interface and Visual Studio development tools. Evaluation results illuminate that it can get better performance than the backpressure algorithm just based on queue length differential in average queue length and delay of traffic network. [ABSTRACT FROM AUTHOR]

We perform oscillatory shear simulations to determine the loss modulus for three solids with identical interaction yet distinct structures: ordered, random, and glassy alloys. Random and glassy alloys show more pronounced high-frequency loss in the THz regime than the ordered alloy. Ordered and random alloys exhibit a power-law decay in damping strength as frequency decreases over nearly five decades. Glassy alloy, with a limited frequency range of power-law decay, retains significant damping at low frequencies extending down to ~ 100 MHz due to slow irreversible deformation of local clusters. [ABSTRACT FROM AUTHOR]

A response by the author of the article "Racial-Ethnic Disparities in Use of Antidepressants in Private Coverage: Implications for the Affordable Care Act," in the September 2014 issue is presented.

Hydrolysis and nitrification are the key steps of biological transformation of urea in soils, which control the loss of nitrogen (N) in terrestrial ecosystem. The inhibitory effects of plant materials on N transformation provide potential benefits for agricultural production and environmental protection. In this study, water-soluble and ethanol-soluble compounds were extracted from 24 tropical medicinal plant species in Hainan Island, southern China, with the aim of measuring their effects on urease activity (UA), nitrification potential (NP), and ammonium oxidizer number in a paddy soil, by a series of short (5 hours) and long-term (14 days) incubation experiments. Total solid yields and phenols contents of 48 medicinal plant extracts were also analyzed in this study. There were big differences in total solid yield and phenols content among the extracts of the selected tropical medicinal plant extracts. The phenols content of the plant extracts varied from 15.1 to 273.4 mg GAE/g extract (milligrams of gallic acid equivalents per gram of extract). A significant relationship between UA and NP of the soil treated with plant extracts and their phenols content was found, indicating that phenolic compounds are the major contributors to the inhibitory properties of these plants. Further studies indicated that the water extracts of Epimeredi indica aerial and Melia azedarach leaf, containing a high content of phenols, exhibited notable urease and nitrification inhibitory effects and reduced the number of soil ammonia-oxidizing bacteria, being promising sources of natural inhibitors for soil N transformation. [ABSTRACT FROM AUTHOR]

Polycrystalline copper foils are surprisingly effective in chemical vapor deposition of graphene, although only Cu(lll) facets possess the correct symmetry and low lattice mismatch. Density functional theory calculations of carbon on three copper facets show that, as the carbon cluster grows, the carbon-copper interaction weakens while the carbon-carbon interaction strengthens. At a significant distance away, and with negligible electron transfer from the substrate, large carbon clusters are blind to the atomic details of the copper substrates. [ABSTRACT FROM AUTHOR]