Unusual Thionation via Fragmentation

Reaction of 4,4‐dichloro‐2,6‐diphenyl‐4,4‐dihydropyrane (2) with thiols in the presence of triethylamine gives interesting results. The exclusive formation of 2,6‐diphenylpyran‐4‐thione (3) in the reaction with PhSH through cleavage of C_Ar‐S bond is remarkable.     

Viscoelastic properties of sterically stabilized nonaqueous dispersions

The viscoelastic properties of a dispersion of poly(vinyl acetate) particles sterically stabilized by poly(2-ethyl hexyl methacrylate) and dispersed in Isopar G have been measured as a function of particle concentration and frequency at ambient temperature.At low particle concentrations, it was found that the loss modulus was larger than the storage modulus, while at high particle concentrations, i.e.,w>0.40, the storage modulus was found to be larger than the loss modulus. This inversion from a viscous to an elastic response as a function of particle concentration is attributable to the change in the configurational entropy of the steric barrier as a result of increasing the concentration of particles in the dispersion.     

A Concise Route to Racemic Anatoxin a from Cycloocta‐1,5‐diene

The synthesis of racemic anatoxin a ( 1a ) from cycloocta‐1,5‐diene via its 1 : 1 cycloadduct with N‐chlorosulfonyl isocyanate is described. The N‐unsubstituted β‐lactam 2b was converted to a β‐amino ester 3 which was then submitted to a Pd‐catalyzed cyclization to afford the conjugated ester 4a . The N‐tosyl derivative 4b was then elaborated into N‐tosylanatoxin a ( 1b ) via a Weinreb amide.     

Synthesis of Cryptolepine and Cryptoteckieine from a Common Intermediate

Both cryptolepine 1 and cryptotackieine 3 have been synthesized from 1,3‐bis(2‐nitrophenyl)propan‐2‐one. The approach to 1 involved reduction of the NO₂ groups, oxidative cyclization with PhI(OAc)₂, and N‐methylation, whereas 3 was obtained via bromination, Favorskii rearrangement, reduction (in situ cyclization), and N‐methylation.     

Diastereoselective amplification of an induced-fit receptor from a dynamic combinatorial library

A high-affinity, induced-fit receptor for NMe4I was discovered using dynamic combinatorial chemistry. The addition of the guest to a dynamic combinatorial library made using a racemic mixture of chiral building blocks caused the strong and highly diastereoselective amplification of the receptor at the expense of other library components. The receptor and its mode of binding were characterized by NMR, ITC, and re-equilibration experiments, from which it was deduced that the receptor probably forms a folded four-stave barrel shape on binding of the guest.     

Quantum Zeno and anti-Zeno paradoxes

Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox). We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure change of state: an anti-Zeno paradox.     

Passive micromixer for luminol-peroxide chemiluminescence detection

This paper reports a microchip with an integrated passive micromixer based on chaotic advection. The micromixer with staggered herringbone structures was used for luminol-peroxide chemiluminescence detection. The micromixer was examined to assess its suitability for chemiluminescence reaction. The relationship between the flow rate and the location of maximum chemiluminescence intensity was investigated. The light intensity was detected using an optical fiber attached along the mixing channel and a photon detector. A linear correlation between chemiluminescence intensity and the concentration of cobalt(ii) ions or hydrogen peroxide was observed. This microchip has a potential application in environmental monitoring for industries involved in heavy metals and in medical diagnostics.     

Multiresolution Network Models

Many existing statistical and machine learning tools for social network analysis focus on a single level of analysis. Methods designed for clustering optimize a global partition of the graph, whereas projection-based approaches (e.g., the latent space model in the statistics literature) represent in rich detail the roles of individuals. Many pertinent questions in sociology and economics, however, span multiple scales of analysis. Further, many questions involve comparisons across disconnected graphs that will, inevitably be of different sizes, either due to missing data or the inherent heterogeneity in real-world networks. We propose a class of network models that represent network structure on multiple scales and facilitate comparison across graphs with different numbers of individuals. These models differentially invest modeling effort within subgraphs of high density, often termed communities, while maintaining a parsimonious structure between said subgraphs. We show that our model class is projective, highlighting an ongoing discussion in the social network modeling literature on the dependence of inference paradigms on the size of the observed graph. We illustrate the utility of our method using data on household relations from Karnataka, India. Supplementary material for this article is available online.