Atmospheric and soil degradation of aliphatic-aromatic polyester films

The degradation of an aliphatic-aromatic biodegradable polyester film was studied under conditions of solar exposure and soil burial in a tropical area. Film samples were evaluated for changes over 40 weeks by visual examination, scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical properties, molecular weight, gel content, and thermal properties. Photodegradation played a major role in the atmospheric degradation of the film, causing it to lose integrity and mechanical properties after week 8 due to main chain scission and crosslinking. SEM micrographs and FTIR spectra indicated that photodegradation started at the exposed side of the film and propagated through the polymer matrix after week 8. FTIR spectra also indicated that subsequent photooxidation processes took place. The reduction of molecular weight of the soil burial samples was much slower than that of the non-crosslinked portion of solar exposed film samples. The reduction of number average molecular weight of the non-crosslinked solar exposed samples followed a first order reaction, whereas the soil burial samples show a surface erosion biodegradation behavior. The relationship among total solar radiation, gel content and number average molecular weight indicated that an accumulated total solar radiation of 800 MJ/m², reached in approximately 7 weeks at the exposure site, is required for PBAT mulch film integrity loss.     

Synthesis and Study of the Photophysical Properties of a New Eu<Superscript>3+</Superscript> Complex with 3-Hydroxypicolinamide

This work reports on the synthesis and characterization of a new complex of Eu³⁺ with the 3-hydroxypicolinamide ligand (Hhpa). Here we present an approach for obtaining bis[2-carbamoyl(κO)pyridin-3-olato(κO’)] lanthanide complexes, which were characterized through elemental analysis, thermal analysis, infrared and photoluminescence spectroscopies (emission, excitation, luminescence lifetimes, quantum efficiencies, Judd-Ofelt parameters and quantum yields). Although hpa can act as a bidentate ligand in different conformations, the results attest for the occurrence of a unique coordination site of low symmetry for the Eu³⁺ ions, in which two anionic hpa ligands coordinate the cations through an O/O chelating system. The phosphorescence of the synthesized gadolinium complex provides the energy of the triplet state, which is determined to be at 20,830 cm^-1 over the ground state. This makes the Hhpa ligand very adequate for sensitizing the Eu³⁺ luminescence, which leads to a very efficient antenna effect and opens a wide range of applications for the complex in light emitting organic-inorganic devices.     

Cold nuclear matter effects on J/ψ yields as a function of rapidity and nuclear geometry in d+A collisions at sqrt[s(NN)]=200 GeV

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200 GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2相似文献   

Autoresonant excitation of antiproton plasmas

We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.     

High average power large-pitch fiber amplifier with robust single-mode operation

Ytterbium-doped large-pitch fibers with very large mode areas are investigated in a high-power fiber amplifier configuration. An average output power of 294?W is demonstrated, while maintaining robust single-mode operation with a mode field diameter of 62?μm. Compared to previous active large-mode area designs, the threshold of mode instabilities is increased by a factor of about 3.     

High-speed modal decomposition of mode instabilities in high-power fiber lasers

A high-speed mode analysis technique is required to gain fundamental understanding of mode instabilities in high-power fiber laser systems. In this work a technique, purely based on the intensity profile of the beam, is demonstrated to be ideally suited to analyze fiber laser dynamics. This technique, together with a high-speed camera, has been applied to the study of the temporal dynamics of mode instabilities at high average powers with up to 20,000 frames per second. These measurements confirm that energy transfer between the fluctuating transversal modes takes place in millisecond-time-scale.     

Psi‐series method for equality of random trees and quadratic convolution recurrences

An unusual and surprising expansion of the form as , is derived for the probability p_n that two randomly chosen binary search trees are identical (in shape, hence in labels of all corresponding nodes). A quantity arising in the analysis of phylogenetic trees is also proved to have a similar asymptotic expansion. Our method of proof is new in the literature of discrete probability and the analysis of algorithms, and it is based on the logarithmic psi‐series expansions for nonlinear differential equations. Such an approach is very general and applicable to many other problems involving nonlinear differential equations; many examples are discussed in this article and several attractive phenomena are discovered.Copyright © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 44, 67–108, 2014     

Temporal evolution of radionuclides in sludge from wastewater treatment plants

22 sludge samples were analyzed from three municipal wastewater treatment plants to assess both the occurrence and the temporal behavior of radioactivity during 8 sampling campaigns carried out over the period 2007–2009. As regards natural gamma emitters radionuclides from the natural ²³⁸U series (such as ²³⁴Th, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb) and the ²³²Th series (such as ²²⁸Ac, ²¹²Pb, ²¹²Bi and ²⁰⁸Tl) and other natural gamma emitters such as ⁷Be, ²¹⁰Pb_u or ⁴⁰K were measured. In the case of man-made radionuclides small amounts of ¹³⁷Cs were found, while significant amounts of ¹³¹I were detected in some samples. Correlations were found between radionuclides with the same origin. No seasonal variation for the ²³⁸U and ²³²Th series was found in the studied period but ⁷Be and ²¹⁰Pb_u showed seasonal variation that was explained by the monthly rainfall. The internal and external hazard indices were calculated and the results indicate that the radiological characteristics of the sludge do not present a significant radiological risk and make them suitable for future applications.     

NMR spectroscopic characterization of new 2,3‐dihydro‐1,3,4‐thiadiazole derivatives

The ¹H and ¹³C NMR resonances of twenty‐seven 2,2‐dimethyl‐5‐(2‐nitrophenyl‐5‐substituted)‐2,3‐dihydro‐1,3,4‐thiadiazoles, and twenty‐seven 3‐acyl‐5‐(2‐amino‐5‐substituted)‐2,2‐dimethyl‐2,3‐dihydro‐1,3,4‐thiadiazoles were assigned completely using the concerted application of one‐dimensional and two‐dimensional experiments (DEPT, HMQC and HMBC). NOESY experiments, X‐ray crystallography and conformational analysis confirm the preferred conformation of these compounds. Copyright © 2012 John Wiley & Sons, Ltd.