Fast determination of the tin content in cassiterite ores by photon activation method

Photon activation analysis has been success-fully applied to the fast and non-destructive analysis of tin in cassiterite ores based on the 159.7 keV gamma line of^123mSn produced in the¹²⁴Sn/γ, n/^123mSn reaction. In order to improve the accuracy of analytical results, corrections for self-absorption and pile-up effects were performed. Under typical conditions /15 μA electron beam current, 15 MeV bremsstrahlung energy, 5 min irradiation time and 10 min measurement/ the sensitivity of the analysis is 10 ppm. The proposed method can be used for routine analysis of tin in geological samples.     

On the use of a dead-time meter for pile-up corrections

Correction for pile-up losses in the amplifier is possible by the dead-time fraction indicator of the ADC in case of long-lived radionuclides. If the dead-time meter has been calibrated, an accuracy of 1.5% is feasible up to a dead-time fraction of 25%. The precision decreases from 1.5% at 10% dead-time fraction to 3% at a deadtime fraction of 30%.     

Synthesis of Jasminaldehyde by Solid-Liquid Phase Transfer Catalysis Without Solvent,Under Microwave Irradiation

α-n-amylcinnamaldehyde (jasminaldehyde) was obtained with 82 % yield by solid-liquid phase transfer catalysis without solvent within 3 days at room temperature. By use of domestic microwave irradiation, the same yield was obtained within 1 minute at a power of 600 W.     

Unexpected formation of dinaphthoaza-17-crown-5 ether containing γ-aminopiperidine subunit

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Designing liquid-crystalline dendronised hexa-adducts of [60]fullerene via click chemistry

ABSTRACT

Liquid-crystalline [60]fullerodendrimers were constructed via click chemistry based on the reaction between hexa-adducts of [60]fullerene (C₆₀) bearing 12 azide groups and alkyne-terminated cyanobiphenyl dendrons of first- and second-generation. The structure of all the new compounds was confirmed by IR, UV, ¹H and ¹³C NMR spectroscopies and mass spectrometry. The mesomorphic properties were studied by polarised optical microscopy, differential scanning calorimetry and small-angle X-ray scattering. The hexa-adduct of C₆₀ functionalised with the first-generation dendrons gave rise to the formation of a smectic A phase and a rectangular columnar phase (c2mm symmetry) while the hexa-adduct of C₆₀ decorated with the second-generation dendrons displayed only a rectangular columnar phase (c2mm symmetry). Our results show that the hexa-adduct of C₆₀ is a unique synthetic platform for the design of fullerodendrimers and dendronised materials.     

A simulation-based genetic algorithm approach for reducing emissions from import container pick-up operation at container terminal

Emissions from idle truck engines are a main source of pollution at container terminals. In this study, we focus on reducing such emission from waiting trucks as well as the related crane operations with a new truck arrival control method that gives individual truck limited time slots for entry. We develop a method to optimize the time slot assignment for individual trucks, aiming at minimizing total emissions from trucks and cranes at import yards. The method applies discrete event simulation to estimate total truck waiting times and crane moving distance, and then applies a genetic algorithm to minimize the generated emissions from these trucks and cranes. The experiment result shows that the truck arrivals should be controlled based on the stacking of import containers, and that such control is necessary for reducing truck idling emissions at a congested container terminal.     

A splitting algorithm for equilibrium problem given by the difference of two bifunctions

In this paper, we introduce a splitting algorithm for solving equilibrium problems given by the difference of two bifunctions in a real Hilbert space. Under suitable assumptions on component bifunctions, we prove strong convergence of the proposed algorithm. In contrast to most existing projection-type methods for equilibrium problems, our algorithm does not require any convexity or monotonicity conditions on the resulting bifunction. Some numerical experiments and comparisons are given to illustrate the efficiency of the proposed algorithm.     

Tuning the Product Spectrum of a Glycoside Hydrolase Enzyme by a Combination of Site-Directed Mutagenesis and Tyrosine-Specific Chemical Modification

Selective chemical modification of proteins plays a pivotal role for the rational design of enzymes with novel and specific functionalities. In this study, a strategic combination of genetic and chemical engineering paves the way for systematic construction of biocatalysts by tuning the product spectrum of a levansucrase from Bacillus megaterium (Bm-LS), which typically produces small levan-like oligosaccharides. The implementation of site-directed mutagenesis followed by a tyrosine-specific modification enabled control of the product synthesis: depending on the position, the modification provoked either enrichment of short oligosaccharides (up to 800 % in some cases) or triggered the formation of high molecular weight polymer. The chemical modification can recover polymerization ability in variants with defective oligosaccharide binding motifs. Molecular dynamic (MD) simulations provided insights into the effect of modifying non-native tyrosine residues on product specificity.