Synthesis of a Sialic Acid Containing Complex‐Type N‐Glycan on a Solid Support

On solid ground : A new solid‐phase synthesis of N‐linked glycans featuring 1) highly stereoselective β‐mannosylation and microfluidic α‐sialylation and 2) efficient glycosylation of the N‐phenyltrifluoroacetimidate units on JandaJel resin is reported. Reagent concentration effects by a fluorous solvent are effectively applied, and the use of these methods results in the first synthesis of a sialic acid containing complex‐type N‐glycan on a solid support.

     

1:1 Adducts of 2,2′‐[isopropylidenebis(p‐phenyleneoxy)]diacetic acid with dimethylammonium and 4,4′‐bipyridine

The title compounds, dimethylammonium 2‐{4‐[1‐(4‐carboxymethoxyphenyl)‐1‐methylethyl]phenoxy}acetate, C₂H₈N⁺·C₁₉H₁₉O₆⁻, (I), and 2,2′‐[isopropylidenebis(p‐phenyleneoxy)]diacetic acid–4,4′‐bipyridine (1/1), C₁₉H₂₀O₆·C₁₀H₈N₂, (II), are 1:1 adducts of 2,2′‐[isopropylidenebis(p‐phenyleneoxy)]diacetic acid (H₂L) with dimethylammonium or 4,4′‐bipyridine. The component ions in (I) are linked by N—H...O, O—H...O and C—H...O hydrogen bonds into continuous two‐dimensional layers parallel to the (001) plane. Adjacent layers are stacked via C—H...O hydrogen bonds into a three‐dimensional network with an –ABAB– alternation of the two‐dimensional layers. In (II), two H₂L molecules, one bipy molecule and two half bipy molecules are linked by O—H...N hydrogen bonds into one‐dimensional chains and rectanglar‐shaped rings. They are assembled viaπ–π stacking interactions and C—H...O hydrogen bonds into an intriguing zero‐dimensional plus one‐dimensional poly(pseudo)rotaxane motif.     

Synthesis,Characterization and Crystal Structure of Tetraphenylphosphonium Bis(2-thioxo-1,3-dithiole-4,5-dithiolato)-Nickelate Acetone Solvate Crystal

Abstract  

A new crystal of tetraphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)-nickelate acetone solvate (BPNI) has been prepared at room temperature and characterized by elemental analysis, UV–Vis–NIR absorption spectrum and X-ray single crystal determination. The complex crystallized in monoclinic space group P2/c with unit cell dimensions a = 24.5350 (6) ?, b = 7.3097 (2) ?, c = 23.1141 (6) ?, β = 115.585 (2)°, V = 3738.89 (17) ?³, Z = 4, D _x .= 1.5081 (1) g cm⁻³. The X-ray structure determination revealed that the crystal is centro-symmetrical and there are two halves of independent cations in the molecule.     

导向相应功率定位中时延不确定项的影响

在分布式传声器网络应用中,可控波束形成器导向相应功率(SRP)声源定位算法受到导向时延不准确的影响导致定位不稳定.将导向时延不确定项引入SRP定位模型,并对引起不确定项的主要干扰因素进行了分析建模,同时提出了应对导向时延不确定项的SRP定位算法.蒙特卡罗仿真和分析表明该算法具有抑制噪声和降低定位误差的效果,实际实验数据...     

Exponential stability in mean square of impulsive stochastic difference equations with continuous time

So far there have been few results presented on the exponential stability in mean square for impulsive stochastic difference equations with continuous time. The main aim of this work is to close this gap. Unlike earlier studies, ours does not make use of general methods such as Lyapunov methods, Itô formula methods and so forth. However, we obtain the desired result by establishing a difference inequality with continuous time. Moreover, the result obtained can be applied to stochastic difference equations, without impulsive effects, with continuous time. Finally, we construct an example to illustrate the effectiveness of our result.     

Boundary Limits for Bounded Quasiregular Mappings

In this paper we establish results on the existence of nontangential limits for weighted -harmonic functions in the weighted Sobolev space , for some q>1 and w in the Muckenhoupt A _q class, where is the unit ball in . These results generalize the ones in Sect. 3 of Koskela et al., Trans. Am. Math. Soc. 348(2), 755–766, 1996, where the weight was identically equal to one. Weighted -harmonic functions are weak solutions of the partial differential equation

无记忆非拟 Newton 算法的导出和全局收敛性

In this paper, a new class of memoryless non-quasi-Newton method for solving unconstrained optimization problems is proposed, and the global convergence of this method with inexact line search is proved. Furthermore, we propose a hybrid method that mixes both the memoryless non-quasi-Newton method and the memoryless Perry-Shanno quasi-Newton method. The global convergence of this hybrid memoryless method is proved under mild assumptions. The initial results show that these new methods are efficient for the given test problems. Especially the memoryless non-quasi-Newton method requires little storage and computation, so it is able to efficiently solve large scale optimization problems.     

Facile autoreduction of iron oxide/carbon nanotube encapsulates

Facile autoreduction of iron oxide encapsulated within carbon nanotubes has been observed at a temperature 200 degrees C lower than those on the outer surface. This opens a new route to tune the state of confined nanoparticles of d-band metals by the confinement of CNTs.     

Theoretical studies on the role of pi-electron delocalization in determining the conformation of N-benzylideneaniline with three types of LMO basis sets

To understand the role of pi-electron delocalization in determining the conformation of the NBA (Ph-N==CH-Ph) molecule, the following three LMO (localized molecular orbital) basis sets are constructed: a LFMO (highly localized fragment molecular orbital), an NBO (natural bond orbital), and a special NBO (NBO-II) basis sets, and their localization degrees are evaluated with our suggesting index D(L). Afterward, the vertical resonance energy DeltaE(V) is obtained from the Morokuma's energy partition over each of three LMO basis sets. DeltaE(V) = DeltaE(H) (one electron energy) + DeltaE(two) (two electron energy), and DeltaE(two) = DeltaE(Cou) (Coulomb) + DeltaE(ex) (exchange) + DeltaE(ec) (or SigmaDeltaE(n)) (electron correction). DeltaE(H) is always stabilizing, and DeltaE(Cou) is destabilizing for all time. In the case of the LFMO basis set, DeltaE(Cou) is so great that DeltaE(two) > |DeltaE(H)|. Therefore, DeltaE(V) is always destabilizing, and is least destabilizing at about the theta = 90 degrees geometry. Of the three calculation methods such as HF, DFT, and MPn (n = 2, 3, and 4), the MPn method provides DeltaE(V) with the greatest value. In the case of the NBO basis set, on the contrary, DeltaE(V) is stabilizing due to DeltaE(Cou) being less destabilizing, and it is most stabilizing at a planar geometry. The LFMO basis set has the highest localization degree, and it is most appropriate for the energy partition. In the NBA molecule, pi-electron delocalization is destabilization, and it has a tendency to distort the NBA molecular away from its planar geometry as far as possible.     

Influence of resonance tube geometry shape on performance of thermoacoustic engine

Based on the linear thermoacoustics, a symmetrical standing-wave thermoacoustic engine is simulated with a cylindrical tube and a tapered one as the resonance tube, respectively. The experiments with both cylindrical and tapered tubes are carried out. The suppression of nonlinear effects due to tapered tube as the resonance tube is discussed. Both simulation and experimental results show that the performance of the tapered tube is better than cylindrical one as the resonance tube.