Synthesis of 6-amino-1,2,3-triazolo[4,5-c] pyridin-4(5H)one (8-aza-3-deazaguanine) and 6-amino-1-(β-D-ribofuranosyl)-1,2,3-triazolo[4,5-c] pyridin-4(5H)one (8-Aza-3-deazaguanosine) via novel ring closure procedures

The total synthesis of 6-amino-1,2,3-triazolo[4,5-c]pyridin-4(5H)one (8-aza-3-deazaguanine, 3 ) and 6-amino-1-(β-D-ribofuranosyl)-1,2,3-triazolo[4,5-c]pyridin-4(5H)one (8-aza-3-deazaguano-sine, 22 ) has been described for the first time by a novel base-catalyzed ring closure of 4(5)-cyanomethyl-1,2,3-triazole-5(4)carboxamide (14) and methyl 5-cyanomethyl-1-(2,3,5-tri-O-ben-zoyl-β-D-ribofuranosyl)-1,2,3-triazole-4-carboxylate (17) , respectively. Under the catalysis of DBU, 2,4-dinitrophenylhydrazone of dimethyl 1,3-acetonedicarboxylate (7) was converted to methyl 5-methoxycarbonylmethyl-1-(2,4-dinitroanilino)-1,2,3-triazole-4-carboxylate (12) via dimethyl 2-diazo-3-iminoglutarate (8) . Catalytic reduction of 12 gave methyl 4(5)methoxycar-bonylmethyl-1,2,3-triazole-5(4)carboxylate (11) from which methyl 4(5)carbamoylmethyl-1,2,3-triazole-5(4)carboxylate (10) was obtained by ammonolysis. Dehydration of 10 provided methyl 4(5)cyanomethyl-1,2,3-triazole-5(4)carboxylate (13) which on amination gave 14 . The 1,2,3-triazole nucleosides 17, 18 and 19 were obtained from the stannic chloride-catalyzed condensation of the trimethylsilyl 13 and a fully acylated β-D-ribofuranose. The yield and ratio of the ribofuranosyl derivatives of 13 markedly depends on the ratio of stannic chloride used. The structures of the nucleosides 22 and 23 were established by a combination of NOE, ¹H-nmr and ¹³C-nmr spectroscopy.     

Instructions to authors

In a cylindrical-beam plasma system with ω_pe < ω_ce, large-amplitude (W/nT ～ 1) bursts of spatially localized (length ～λ/2) electron plasma waves are observed to be correlated with accelerated background electrons and an increase in the luminosity of the plasma.     

Flow-induced noise of a wall-mounted finite airfoil at low-to-moderate Reynolds number

This paper presents an experimental investigation of the flow-induced noise created by a wall-mounted finite airfoil at low-to-moderate Reynolds number and zero angle of attack. Far-field noise measurements have been taken at a single observer location and with two perpendicular microphone arrays in an anechoic wind tunnel at Reynolds numbers of _Rec=9.2×10⁴–1.6×10⁵${\mathit{Re}}_c=9.2\times {10}^4–1.6\times {10}^5$, based on chord, and for a variety of airfoil aspect ratios (length to chord ratio of L/C=0.2–2$L/C=0.2–2$, corresponding to length to thickness ratio of L/T=1.7–16.7$L/T=1.7–16.7$). Additionally, surface oil-film visualisation images and unsteady velocity measurements taken in the near trailing edge wake are related to far-field noise measurements to determine the flow mechanisms responsible for noise generation. The results show that the wall-mounted finite airfoil radiates noise similar to a two-dimensional airfoil when L/T>8.3$L/T>8.3$. Despite the incoming boundary layer height at the junction being 1.30≤δ/T≤1.46$1.30\le \delta /T\le 1.46$, junction and tip flow suppresses tonal noise production for airfoil?s up to L/T=8.3$L/T=8.3$ at _Rec=9.2×10⁴–1.2×10⁵${\mathit{Re}}_c=9.2\times {10}^4–1.2\times {10}^5$. Trailing edge noise is found to be the dominant airfoil noise generation mechanism at frequencies above 1 kHz with the position of the noise source along the trailing edge determined by the proportion of the airfoil span influenced by flow at the airfoil–wall junction.     

大豆中Glycinol的分离与鉴定

 Glycinol是大豆中主要的植物抗毒素和植物雌激素glyceollins的直接前体,是研究大豆中异戊烯转移酶必需的重要底物。该研究以新鲜大豆为原料，采用硝酸银诱导大豆子叶使glycinol 在其中累积,再用甲醇提取，经制备高效液相色谱分离获得单一成分;经液相色谱/四极杆-飞行时间串联质谱及紫外光谱鉴定,并与标准品对照,确定所获得的单一成分为glycinol。采用该分离方法可从390 g鲜重的大豆中分离得到100 mg高纯度的glycinol。该研究提供了一种分离纯化和较大量制备glycinol 的方法。     

Modeling and simulation of magnetically confined low-pressureplasmas in two dimensions

A hybrid electron fluid-particle ion model of a cylindrical axisymmetric discharge with conducting walls and a uniform axial magnetic field has been developed. The chamber is 30 cm in length and 15 cm in diameter. Power is deposited into electrons with a uniform axial profile and two model radial profiles: uniform power per electron (flat), and power per electron varying as the square of a J₀ Bessel function (peaked). The major results of the study are that it is possible to treat two-dimensional systems with very small Debye-length-to-system-chamber-length scale ratios, and that the radial power deposition profile appears to have a marked effect on the nature of the plasma profiles, including the ion flux profiles