Mixing state of individual carbonaceous particles during a severe haze episode in January 2013,Nanjing,China

Chemical composition,hourly counts,and sizes of atmospheric carbonaceous particles were measured to investigate their mixing state on clear and hazy days.623,122 carbonaceous particles with sizes0.2-2.0 μm was analyzed using a single-particle aerosol mass spectrometer from 1st to 17 th January2013.Particle types included biomass/biofuel burning particles(biomass),element carbon(EC-dominant)particles that were also mixed with biomass/biofuel burning species(EC-biomass) or secondary species(EC-secondary),organic carbon(OC),internally mixed OC and EC(OCEC),ammonium-containing(ammonium) and sodium-containing(sodium) particles.On clear days the top ranked carbonaceous particle types were biomass(48.2%),EC-biomass(15.7%),OCEC(11.1%),and sodium(9.6%),while on hazy days they were biomass(37.3%),EC-biomass(17.6%),EC-secondary(16.6%),and sodium(12.7%).The fractions of EC-secondary,ammonium(10%),and sodium particle types were elevated on hazy days.Numbers of EC-secondary particles were more than four times those on clear days(4.1%).Thus,carbonaceous particles mixed with ammonium,nitrate and sulfate during aging and transport,enhancing their light extinction effects and hygroscopic growth under high relative humidity on hazy days,further reducing visibility.Our real-time single-particle data showed that changes to mixing state had a significant impact on light extinction during haze events in Nanjing.     

Microwave-accelerated competing domino processes: a tether-controlled dual pathway into high molecular complexity

Bicyclic unsaturated diols undergo a path selective modular domino transformation upon subjection to Pb(OAc)4, the reaction being biased to the nature of the angular substituent. The magnitude of the linking chain and the nature of the angular substituent determine the reaction course. Methylene ether linkage acts as an autoremovable directing group (ring-retained domino product 5), whereas a propylene linkage switches the path toward the ring-expanded type 21 domino product. Reaction times were substantially reduced using microwave irradiation.     

Mechanism of nanocapsules formation by the emulsion-diffusion process

A detailed investigation into the mechanisms of nanocapsule formation by means of the two stages "emulsion-diffusion" process is reported. Such widely used process is still poorly understood. An emulsion of oil, polymer and ethyl acetate is fabricated as a first step; dilution with pure water allows ethyl acetate to diffuse out from the droplets, leaving a suspension of nanocapsules at the end. It has been shown that the size of nanocapsules was related to the chemical composition of the organic phase and the size of primary emulsion through a simple geometrical relationship. As a consequence, most of the properties of the nanocapsules were decided at the emulsification step. The influence of several formulation and processing parameters of the primary emulsion was studied accordingly. The thin polymer membrane of nanocapsules was observed by means of cryo-fracture electron microscopy. Finally two experiments were designed for a mechanistic investigation of the diffusion step. A step-by-step diffusion of the organic solvent takes place by successive partition equilibria of ethyl acetate between the droplets and aqueous phase. A time-resolved experiment shows the fast diffusion (less than 20 ms) related to the small droplet size of the emulsion.     

Structural evolution from the sol to the PbZrO<Subscript>3</Subscript> precursor powders prepared by an alkoxide-based sol–gel route

PbZrO₃ powders have been prepared by an alkoxide-based sol–gel route, starting from lead acetate, zirconium n-butoxide, and n-butanol as a solvent, and hydrolysed with different amounts of water in neutral and alkaline medium. The local environment of Zr and Pb atoms was pursued from the sol to the dried (150 °C) and heated (400 °C) powders, by extended x-ray absorption fine structure (EXAFS). The analysis of the sol revealed links between Pb and Zr, and even more links between Zr and Zr. The metal neighbourhoods in the dried powders are not influenced by the hydrolysis conditions. Pb-Zr correlations are gradually lost from the sol to the dried and heated powders, while the loss of Zr–Zr correlations is considerably lower.     

Enhancing <Emphasis Type="SmallCaps">l</Emphasis>-Lysine Production of Beet Molasses by Engineered <Emphasis Type="Italic">Escherichia coli</Emphasis> Using an In Situ Pretreatment Method

Reducing the viscosity of molasses environmentally and selectively removing the harmful ingredients for microbes are the keys to promoting the bioavailability of molasses. A simple and environmental in situ pretreatment method integrating surfactants and alkali was developed to reduce the viscosity of molasses prior to l-lysine production using Escherichia coli ZY0217. Adding activated carbon and modified orange peel based on the in situ pretreatment process effectively removed pigments and excessive zinc in the molasses and also significantly increased the cell growth and l-lysine yield from E. coli ZY0217. The experimental results showed that a mixture of secondary alkane sulfonate, an anionic surfactant, and HodagCB-6, a non-ionic surfactant, effectively reduced the viscosity of the molasses more so than any single surfactant. When the surfactant mixture was added at a concentration of 0.04 g/L to the molasses, the ω value was 0.4, and when ammonia was added at 0.6 %, the lowest viscosity of 705 mPa?·?s was obtained. Further, 91.5 % of the color and 86.68 % of the original levels of zinc were removed using an activated carbon and modified orange peel treatment on the molasses with the lowest viscosity, which further promoted cell growth and l-lysine production. In the fed-batch cultivation process, the l-lysine concentration achieved using a constant-speed feeding strategy was 45.89 g/L, with an l-lysine yield of 27.18 %, whereas the l-lysine yield from untreated molasses was only 10.13 %. The increase in l-lysine yield was related to the reduced viscosity and the detoxification of the molasses. Lastly, the pretreatment was found to significantly enhance the conversion of sugars in the molasses to l-lysine.     

On the model companion of partial differential fields with an automorphism

We prove that the class of partial differential fields of characteristic zero with an automorphism has a model companion. We then establish the basic model theoretic properties of this theory and prove that it satisfies the canonical base property, and consequently the Zilber dichotomy, for finite-dimensional types.     

Cross sections for low-energy electron scattering from adenine in the condensed phase

Measurements of the vibrational and electronic excitation of a sub-monolayer up to a monolayer film of adenine were performed with a high resolution electron energy-loss (HREEL) spectrometer. The integral cross sections (over the half-space angle) for excitation of the normal vibrational modes of the ground electronic state and electronically excited states are calculated from the measured reflectivity EEL spectra. Most cross sections for vibrational excitation are of the order of 10(-17) cm(2), the largest being the out-of-plane wagging of the amino-group and the six-member ring deformations. A wide resonance feature appears in the incident energy dependence of the vibrational cross sections at 3-5 eV, while a weak shoulder is present in this dependence for combined ring deformations and bending of hydrogen atoms. For the five excited electronic states, at 4.7, 5.0, 5.5, 6.1 and 6.6 eV, the cross sections are of the order of 10(-18) cm(2), except in the case of the state at the energy of 6.1 eV, for which it is two to three times higher.     

A domino-based approach toward stereodefined heavily functionalized cyclohexanes: synthesis of iridal's core structure

A stereoselective synthesis of heavily functionalized six-membered ring subunits, which possess functionality at sites appropriate for further elaboration, is described. The cyclopentanone moiety of hydrindenediol is required to achieve total facial selectivity during the pre-domino installation of the second quaternary center, while oxidative cleavage is responsible for the ring-expanding rearrangement. A microwave-assisted version of the key domino transformation and a test of concept approach toward the iridal core structure are also presented.     

Elucidation of the kijanimicin gene cluster: insights into the biosynthesis of spirotetronate antibiotics and nitrosugars

The antibiotic kijanimicin produced by the actinomycete Actinomadura kijaniata has a broad spectrum of bioactivities as well as a number of interesting biosynthetic features. To understand the molecular basis for its formation and to develop a combinatorial biosynthetic system for this class of compounds, a 107.6 kb segment of the A. kijaniata chromosome containing the kijanimicin biosynthetic locus was identified, cloned, and sequenced. The complete pathway for the formation of TDP-l-digitoxose, one of the two sugar donors used in construction of kijanimicin, was elucidated through biochemical analysis of four enzymes encoded in the gene cluster. Sequence analysis indicates that the aglycone kijanolide is formed by the combined action of a modular Type-I polyketide synthase, a conserved set of enzymes involved in formation, attachment, and intramolecular cyclization of a glycerate-derived three-carbon unit, which forms the core of the spirotetronate moiety. The genes involved in the biosynthesis of the unusual deoxysugar d-kijanose [2,3,4,6-tetradeoxy-4-(methylcarbamyl)-3-C-methyl-3-nitro-d-xylo-hexopyranose], including one encoding a flavoenzyme predicted to catalyze the formation of the nitro group, have also been identified. This work has implications for the biosynthesis of other spirotetronate antibiotics and nitrosugar-bearing natural products, as well as for future mechanistic and biosynthetic engineering efforts.