A green and efficient synthesis of quinoxaline derivatives catalyzed by 1-n-butyl-3-methylimmidazolium tetrafluoroborate

The room temperature ionic liquid 1-n-butyl-3-methylimmidazolium tetrafluoroborate ([bmim]BF4) was used to promote the synthesis of quinoxaline derivatives under grinding condition. The yields were ranged in 86.0-95.1%. It was shown that the proposed method is fast, efficient and environmentally benign.KEY WORDS: Ionic liquid, Quinoxaline derivatives, Synthesis Bull. Chem. Soc. Ethiop. 2011, 25(3), 455-460

Few-femtosecond Electron Beam with THz-frequency Wakefield-driven Compression

We propose and demonstrate a novel method to produce few-femtosecond electron beam with relatively low timing jitter. In this method a relativistic electron beam is compressed from about 150 fs (rms) to about 7 fs (rms, upper limit) with the wakefield at THz frequency produced by a leading drive beam in a dielectric tube. By imprinting the energy chirp in a passive way, we demonstrate through laser-driven THz streaking technique that no additional timing jitter with respect to an external laser is introduced in this bunch compression process, a prominent advantage over the conventional method using radio-frequency bunchers. We expect that this passive bunching technique may enable new opportunities in many ultrashort-beam based advanced applications such as ultrafast electron diffraction and plasma wakefield acceleration.Comment: 5 pages, 4 figure

Ethyl ent-15α-[(2-meth­oxy­benz­yloxy)meth­yl]-16-oxobeyeran-20-oate

The title compound, C31H44O5, was synthesized from isostev­iol (systematic name: ent-16-ketobeyeran-19-oic acid). In the mol­ecule, the three six-membered rings adopt chair conformations and the stereochemistry of the A/B and B/C ring junctions are trans. The five-membered ring D adopts an envelope conformation with the methyl­ene C atom as the flap

Comparison of preprocessing methods and storage times for touch DNA samples

Aim To select appropriate preprocessing methods for different substrates by comparing the effects of four different preprocessing methods on touch DNA samples and to determine the effect of various storage times on the results of touch DNA sample analysis. Method Hand touch DNA samples were used to investigate the detection and inspection results of DNA on different substrates. Four preprocessing methods, including the direct cutting method, stubbing procedure, double swab technique, and vacuum cleaner method, were used in this study. DNA was extracted from mock samples with four different preprocessing methods. The best preprocess protocol determined from the study was further used to compare performance after various storage times. DNA extracted from all samples was quantified and amplified using standard procedures. Results The amounts of DNA and the number of alleles detected on the porous substrates were greater than those on the non-porous substrates. The performances of the four preprocessing methods varied with different substrates. The direct cutting method displayed advantages for porous substrates, and the vacuum cleaner method was advantageous for non-porous substrates. No significant degradation trend was observed as the storage times increased. Conclusion Different substrates require the use of different preprocessing method in order to obtain the highest DNA amount and allele number from touch DNA samples. This study provides a theoretical basis for explorations of touch DNA samples and may be used as a reference when dealing with touch DNA samples in case work

Current reversals and metastable states in the infinite Bose-Hubbard chain with local particle loss

We present an algorithm which combines the quantum trajectory approach to open quantum systems with a density-matrix renormalization group scheme for infinite one-dimensional lattice systems. We apply this method to investigate the long-time dynamics in the Bose-Hubbard model with local particle loss starting from a Mott-insulating initial state with one boson per site. While the short-time dynamics can be described even quantitatively by an equation of motion (EOM) approach at the mean-field level, many-body interactions lead to unexpected effects at intermediate and long times: local particle currents far away from the dissipative site start to reverse direction ultimately leading to a metastable state with a total particle current pointing away from the lossy site. An alternative EOM approach based on an effective fermion model shows that the reversal of currents can be understood qualitatively by the creation of holon-doublon pairs at the edge of the region of reduced particle density. The doublons are then able to escape while the holes move towards the dissipative site, a process reminiscent---in a loose sense---of Hawking radiation