Supramolecular network polymers formed from polyamidine and carboxy‐terminated telechelic poly(n‐butyl acrylate) via amidinium‐carboxylate salt bridges

We have prepared the amidinium‐carboxylate salt bridge‐based supramolecular network polymers from a carboxy‐terminated telechelic poly(n‐butyl acrylate) and a linear polyamidine having N,N′‐di‐substituted acetamidine group in the main chain. FTIR measurements indicated that the salt bridge was attributed to the three‐dimensional network formation. Virtually, no fluidity was observed for the blend containing equimolar amounts of the carboxyl group and the amidine group, which showed a high G′ value of about 1 MPa at ?5 °C. For comparison, the supramolecular network polymers crosslinked by ammonium‐carboxylate salt were prepared using a linear polyethyleneimine instead of the polyamidine. The blend with equimolar amounts of the carboxyl group and the secondary amino group showed liquid‐like fluidity with a G′ value of about 0.01 MPa at ?5 °C, which was attributed to the fact that a certain amount of the carboxyl group remained as its free form, as evidenced by FTIR analysis. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2148–2155     

Phase Separation in a Bidirectional Two-Lane Asymmetric Exclusion Process

This paper studies a bidirectional two-lane asymmetric exclusion process, in which particles move in opposite direction on the two lanes. Interaction between the two lanes is implemented as follows: particle hops with rate p when there is a particle at the same site in the other lane, otherwise it hops with rate 1. It is shown that under periodic boundary conditions, a plateau will form on the fundamental diagram if p<1. This plateau corresponds to a phase separation phenomenon. We have compared the phase separation with those reported in previous works, and it is shown that the mechanism of phase separation in our model is different from previous ones. A possible phase separation mechanism is proposed, i.e., the system always tries to maximize the probability that particles could hop with rate 1. A simple mean field approximation and a 2-cluster mean field approach have been applied to calculate the steady current. It is shown that the results of the 2-cluster mean field approach are much closer to the simulations.     

The molecular basis of myeloid malignancies

Myeloid malignancies consist of acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and myeloproliferative neoplasm (MPN). The latter two diseases have preleukemic features and frequently evolve to AML. As with solid tumors, multiple mutations are required for leukemogenesis. A decade ago, these gene alterations were subdivided into two categories: class I mutations stimulating cell growth or inhibiting apoptosis; and class II mutations that hamper differentiation of hematopoietic cells. In mouse models, class I mutations such as the Bcr-Abl fusion kinase induce MPN by themselves and some class II mutations such as Runx1 mutations induce MDS. Combinations of class I and class II mutations induce AML in a variety of mouse models. Thus, it was postulated that hematopoietic cells whose differentiation is blocked by class II mutations would autonomously proliferate with class I mutations leading to the development of leukemia. Recent progress in high-speed sequencing has enabled efficient identification of novel mutations in a variety of molecules including epigenetic factors, splicing factors, signaling molecules and proteins in the cohesin complex; most of these are not categorized as either class I or class II mutations. The functional consequences of these mutations are now being extensively investigated. In this article, we will review the molecular basis of hematological malignancies, focusing on mouse models and the interfaces between these models and clinical findings, and revisit the classical class I/II hypothesis.     

Anticipation effect in pedestrian dynamics: Modeling and experiments

In this paper, we propose the anticipation floor field (AFF) as an extension of the floor field (FF) model, which is one of the successful models in describing pedestrian dynamics. The AFF focuses on non-local interaction between pedestrians, which has not been taken into account in the FF model based on local rules. We have conducted several experiments, as well as simulations of counter flow to show the validity of our model. It is found that strength and range of anticipation significantly affect pedestrian dynamics, and there is an optimal strength of anticipation to realize the smoothest counter flow.     

Analysis of light propagation in highly scattering media by path-length-assigned Monte Carlo simulations

Numerical analysis of optical propagation in highly scattering media is investigated when light is normally incident to the surface and re-emerges backward from the same point. This situation corresponds to practical light scattering setups, such as in optical coherence tomography. The simulation uses the path-length-assigned Monte Carlo method based on an ellipsoidal algorithm. The spatial distribution of the scattered light is determined and the dependence of its width and penetration depth on the path-length is found. The backscattered light is classified into three types, in which ballistic, snake, and diffuse photons are dominant.     

Totally asymmetric simple exclusion process on a periodic lattice with Langmuir kinetics depending on the occupancy of the forward neighboring site

We generalize the totally asymmetric simple exclusion process with Langmuir kinetics on aperiodic lattice. In the extended model, the rates of attachment and detachment depend onthe occupancy of the forward neighboring site. Using a mean-field theory, we obtain theanalytical expression of the density profile in the steady state and the relaxationdynamics in our model. We verify their accuracy by comparing the results with Monte Carlosimulations.     

Synthesis of Methylene-Bridged Resorcin[4]arene Dimers

Methylene-bridged resorcin[4]arene dimers were synthesized by the Sc(OTf)₃-catalyzed hydroxymethylation of partially acetylated resorcin[4]arenes, and their preliminary complexation properties with tetraethylammonium ion were examined in CD₃OD by ¹H NMR spectroscopy. The dimers adopted a closed capsular conformation in this solvent and bound the guest molecule into their cavity.     

Facile and Versatile Synthesis of End‐Functionalized Poly(phenylacetylene)s: A Multicomponent Catalytic System for Well‐Controlled Living Polymerization of Phenylacetylenes

A rhodium‐based multicomponent catalytic system for well‐controlled living polymerization of phenylacetylenes has been developed. The catalytic system is composed of readily available and bench‐stable [Rh(nbd)Cl]₂, aryl boronic acid derivatives, diphenylacetylene, 50 % aqueous KOH, and PPh₃. This system offers a method for the facile and versatile synthesis of various end‐functionalized cis‐stereoregular poly(phenylacetylene)s because components from aryl boronic acids and diphenylacetylene were introduced to the initiating end of the polymers. The polymerization reaction shows a typical living nature with a high initiation efficiency, and the molecular weight of the resulting poly(phenylacetylene)s can be readily controlled with very narrow molecular‐weight distributions (M_w/M_n=1.02–1.09). The experimental results suggest that the present catalytic system has a higher polymerization activity than the polymerization activities of other rhodium‐based catalytic systems previously reported.     

Radical trans‐Hydroboration of Alkynes with N‐Heterocyclic Carbene Boranes

Hydroboration of internal alkynes with N‐heterocyclic carbene boranes (NHC‐boranes) occurs to provide stable NHC (E)‐alkenylboranes upon thermolysis in the presence of di‐tert‐butyl peroxide. The E isomer results from an unusual trans‐hydroboration, and the E/Z selectivity is typically high (90:10 or greater). Evidence suggests that this hydroboration occurs by a radical‐chain reaction involving addition of an NHC‐boryl radical to an alkyne to give a β‐NHC‐borylalkenyl radical. Ensuing hydrogen abstraction from the starting NHC‐borane provides the product and returns the starting NHC‐boryl radical. Experiments suggest that the observed trans‐selectivity results from kinetic control in the hydrogen‐transfer reaction.