Chiral pyrrolidine-azole conjugates: Simple and efficient asymmetric organocatalysts for Michael addition to nitrostyrenes

Simple pyrrolidine-azole conjugates have been synthesized and found to be efficient catalysts for asymmetric Michael addition to nitrostyrenes. The identified optimal catalysts, pyrrolidine-azoles 2, 8 and 13, could catalyze the asymmetric Michael addition of a range of Michael donors and nitrostyrenes in high yields (up to 99%) and excellent stereoselectivities (up to 99:1 dr and 97% ee).     

The quest for the size of the universe in early relativistic cosmology (1917–1930)

Before the discovery of the expanding universe, one of the challenges faced in early relativistic cosmology was the determination of the finite and constant curvature radius of space-time by using astronomical observations. Great interest in this specific question was shown by de Sitter, Silberstein, and Lundmark. Their ideas and methods for measuring the cosmic curvature radius, at that time interpreted as equivalent to the size of the universe, contributed to the development of the empirical approach to relativistic cosmology. Their works are a noteworthy example of the efforts made by modern cosmologists toward the understanding of the universe as a whole, its properties, and its content.     

Identification of susceptibility genes loci associated with type 2 diabetes

In this study, we selected 10 susceptible SNPs loci to investigate their contribution to susceptibility to type 2 diabetes in Han Chinese among Hubei population. We genotyped SNPs rs5219, rs1801282, rs1470579, rs1111875, rs1081661, rs7754840, rs4506565, rs13266634, rs4402960, and rs5643981 by using the method of polymerase chain reaction-ligase detection reaction (PCR-LDR). In a case-control study, we have genotyped the 10 candidate susceptibility SNP loci, and here, we reported that the SNP rs5219 in KCNJ1...     

Synthesis and photo-responsive behaviors of hollow polyazobenzene micro-spheres

By means of distillation precipitation polymerization, the silica-hybrid particles with polyazobenzene shell (PAzo@SiO₂) micro-spheres were prepared with 6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate (Azo-M) as monomer, divinylbenzene (DVB) as cross-linker, and ~250 nm vinylated sol-gel silica particles as template. Hollow polyazobenzene microspheres were further developed after selective removal of the silica cores with HF solution. When the content of DVB related to Azo-M is 20 wt%, the acetonitrile is 200 mL, and the polymerization time is 4.5 h, the hollow PAzo microspheres with about 20 nm shell are successfully fabricated. These hollow PAzo microspheres have excellent reversible photoisomerization, and their first-order rate constant of trans-cis isomerization only decreases 11.8% compared with homopolymer of azobenzene (Homo-PAzo).     

Sequence similarity analysis of non-self CTL epitopes and mouse proteins using sequence alignment

This research analyzed amino acid sequence similarity between non-self T cell epitopes recognized by mouse antibodies and mouse proteins. Using sequence alignment,we found that only 8 of 1 108 epitopes are highly similar to mouse protein sequences. The result shows that non-self T cell epitopes are not similar or have little similarity to mouse protein sequences. Furthermore,reviewing the related literature,we also found that the eight epitopes would trigger immune responses in some particular environment,which are ignored by T cells in normal condition. The result suggests that no or low-similarity peptide vaccines can reduce the chance of collateral cross-reactions and enhance the antigen-specific immune response to vaccine.     

Photocatalytic activity of TiO<Subscript>2</Subscript> sensitized by CdS quantum dots under visible-light irradiation

In this paper, CdS quantum dots sensitized TiO2 composite powders (QD-CdS/TiO2) were synthesized by impregnating TiO2 powder into CdS sol with different concentrations. X-ray diffraction pattern (XRD) shows the crystal structures of CdS and TiO2 are cubic phase and anatase phase separately in QD- CdS/TiO2 powder samples; the crystal size of CdS in QD- CdS/TiO2 is about 3-7 nm, while TiO2 crystal size is about 20 nm. With increasing CdS content in QD-CdS/TiO2 composite, the UV-Vis absorption spectrum shifted to the longer wavelength lines, exhibiting obvious quantum size effect. The fluorescence intensity of QD-CdS/TiO2 irradiated by blue light is weaker than that of pure CdS. When the molar ratio of CdS and TiO2 is about 1∶2, the QD-CdS/TiO2 powder has the best catalytic properties under visible-light irradiation, and the degradation rate of rhodamine B (RhB) is up to 92.2% within 60 min.     

Coordinating production and recycling decisions with stochastic demand and return

In this paper, the joint production and recycling problem is investigated for a hybrid manufacturing and remanufacturing system where brand-new products are produced in the manufacturing plant and recycled products are remanufactured into as-new products in the remanufacturing facility. Both the brand-new products and remanufactured products are used to satisfy customer demands. Returns of used products that are recycled from customers are assumed to be stochastic and nonlinearly price-dependent. A mathematical model is proposed to maximize the overall profit of the system through simultaneously optimizing the production and recycling decisions, subject to two capacity constraints — the manufacturing capacity and the remanufacturing capacity. Based on Lagrangian relaxation method, subgradient algorithm and heuristic algorithm, a solution approach is developed to solve the problem. A representative example is presented to illustrate the system, and managerial analysis indicates that the uncertainties in demand and return have much influence on the production and recycling policy. In addition, twenty randomly produced examples are solved, and computational results show that the solution approach can obtain very good solutions for all examples in reasonable time.     

Hydrothermal synthesis and photoluminescence behavior of CeO<Subscript>2</Subscript> nanowires with the aid of surfactant PVP

Well-crystalline CeO₂ nanowires were prepared via a surfactant-assisted hydrothermal process. Reaction temperature and reaction time were changed for the determination of optimal synthesis parameters. The as-obtained products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The results show that single crystal CeO₂ nanowires with high yield and good uniformity can be obtained hydrothermally at 180°C for 12 h with the aid of 2.0 g surfactant (polyvinyl pyrrolidone, PVP). The role of PVP was then discussed and a possible growth mechanism was proposed. Moreover, room temperature photoluminescence (PL) spectra were obtained for these CeO₂ nanowires, which are believed to be related to the abundant defects in these nanostructures.     

Biomimetic fluorapatite films for conservation of historic calcareous stones

Fluorapatite protective films were prepared on marble substrates using a biomimetic method. By mimicking the mineralization mechanism of enamel, phosphorus and fluorine were introduced on the surface of the marble substrate. In the presence of a biological template, namely collagen, an integrated fluorapatite film was produced and the marble substrate was entirely covered. The prepared fluorapatite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. The performances of the fluorapatite films were evaluated by color changes, capillary water absorption, and acid resistance tests. The results revealed that the fluorapatite films had good compatibility with the marble substrate; the physical properties such as color and capillary water adsorption of the marble substrates were unchanged. The fluorapatite films also had good acid resistance and were stable even in heavy acid rain.     

A numerical method to simulate the coupled oscillations of flexible structures in flowing fluids

A numerical method is developed to simulate the coupled phenomena in a fluid-flexible-structure system. Specifically, a two-dimensional panel method is used to calculate the hydrodynamic forces and a modal superposition method is adopted to solve the governing equation of an Eulerian beam. The stability boundary of a single flexible beam in a uniform flow is calculated and compared with previous results to verify the validity of the code. The flow-induced flapping of a single and two flexible bodies for S=1.0, U*=7.0 are investigated. For the flow-induced vibration of a single beam, the oscillation frequency is close to the secondary natural frequency of a cantilever. For two parallel flexible beams, they oscillate in phase when the non-dimensional separating distance H<0.25. When H>0.25, the out-of-phase mode occurs with a jump in frequency. When H>1, the interaction between the two beams decouples and the frequency and forces of each beam revert to behavior associated with a single beam in the same flow. Simulations of coupled-flapping of two tandem flexible structures proved that the drag acting on the upstream body is reduced while for that downstream drag is obviously increased when the structures are closely arranged. The numerical results obtained in the present work are qualitatively consistent with early experimental results.