A new selective preparation of ethyl 7-aminopteridine-6- carboxylate derivatives and related compound

A series of ethyl 7-amino-2,4-dioxopteridine-6-carboxylates 4 and ethyl 7-amino-4-oxo-2-thioxopteridine-6-carboxylates 5 , of interest biologically, has been prepared in one step from the reaction of such vicinal-diamines as 1,3-dialkyl-5,6-diaminouracils 2 or 1,3-dialkyl-5,6-diamino-2-thiouracils 3 with diethyl (E)-2,3-dicyanobutenedioate ( 1 ). Moreover, ethyl 3-amino[1,2,4]triazino[2,3-a]-1H-benzimidazole-2-carboxylate ( 11 ) was also obtained from the reaction between 1,2-diamino-1H-benzimidazole ( 10 ) and 1 . The structural studies of 4, 5 , and 11 prepared were carried out by nmr experiments in some details.     

PIV measurement of particle motion in spiral gas–solid two-phase flow

With a concise review on some basic and novel algorithms and methods for the techniques of particle-imaging velocimetry (PIV), the paper reports an application of the PIV techniques to the investigation of particle motion in a gas–solid two-phase spiral flow in a horizontal tube. Axial velocities of the transported particles are obtained. Some important features of particle motion governing high transportation efficiency of the spiral flow are revealed by investigating probability density distribution of particle locations in a pipe cross-section.     

Provenance identification of ancient pottery from Hachijojima Island,part of Izu Islands (Tokyo,Japan), using X-ray fluorescence spectrometry

A total of 47 pottery fragments were unearthed in Hachijojima Island, part of the Izu Islands (Tokyo, Japan). Among these samples, 36 found in the Kurawa site had designs resembling pottery dating back to the Jomon period (14,000–300 BC) distributed throughout Japan's main island, Honshu; five samples from the Jomon period found in the Yubama site were “undesigned”; the rest, found in the Yaene site, were undesigned Haji pottery samples dating back to the beginning of the late Kofun period (490–549 AD). X-ray fluorescence spectrometry (XRF) was used to determine the chemical composition (in terms of 10 major oxides and 12 minor elements) of the samples to identify their provenance, that is, local versus nonlocal. For this purpose, a portion of each pottery fragment was processed to obtain a glass bead specimen. The pottery samples were classified by multivariate statistical approaches, including principal component analysis and cluster analysis, on the basis of their chemical composition. Additionally, the XRF results were compared to geochemical data from Hachijojima Island using scatter diagrams. The data thus collected allowed the provenance of the pottery samples to be inferred. In particular, the 36 samples from the Kurawa site were concluded to have been brought to Hachijojima Island from Honshu in prehistoric times, whereas the other samples were concluded to have been manufactured locally.     

Entangled polymer orientation and stretch under large step shear deformations in primitive chain network simulations

Orientation and stretch of entangled polymers under large step shear deformations were investigated through primitive chain network simulations. In the simulations, entangled polymer dynamics is described by 3D motion of entanglements, 1D sliding of monomers along the chain, and creation/destruction of entanglements described by hooking/unhooking with surrounding chains at chain ends. In addition to the conventionally proposed relaxation mechanisms that are reptation, contour length fluctuations, and constraint release (both thermal and convective), the simulations also account for force balance among entanglement strands converging to an entanglement node, and nodes also fluctuate in space. Nonlinear step strain data for monodisperse polystyrene melts (Ferri and Greco, Macromolecules, 37:5931, 2006) were quantitatively reproduced by using the same two molecular-weight-independent parameters already adopted by Masubuchi et al. (J Non-Newt Fluid Mech, 149:87, 2008) to fit linear viscoelastic data of several monodisperse polystyrene melts. Analysis of the orientation tensor and of the chain stretch ratio indicates that the segment orientation and stretch realized in the simulation are quantitatively described by a simple three-chain model (Marrucci et al., Macromol Symp, 158:57, 2000a).     

A DNA-Encoded Chemical Library Based on Peptide Macrocycles

The synthesis and characterization of a novel DNA-encoded library of macrocyclic peptide derivatives are described; the macrocycles are based on three sets of proteinogenic and non-proteinogenic amino acid building blocks and featuring the use of copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction for ring closure. The library (termed YO-DEL) which contains 1 254 838 compounds, was encoded with DNA in single-stranded format and was screened against target proteins of interest using affinity capture procedures and photocrosslinking. YO-DEL selections yielded specific binders against serum albumins, carbonic anhydrases and NKp46, a marker of activated Natural Killer cells.