Living radical emulsion polymerization using the nanoprecipitation technique: An extension to atom transfer radical polymerization

Living radical polymerizations of styrene were performed under emulsion atom transfer radical polymerization conditions with latexes prepared by a nanoprecipitation technique recently developed for the stable free‐radical polymerization process. Latexes were prepared by the precipitation of a solution of low‐molecular‐weight polystyrene in acetone into a solution of a surfactant in water. The resulting particles were swollen with styrene and then heated. The effects of various surfactants and hydrophobic ligands, the reaction temperature, and the ligand/copper(I) bromide ratio were studied. The best results were obtained with the nonionic surfactant Brij 98 in combination with the hydrophobic ligand N,N‐bis(2‐pyridylmethyl)octadecylamine and a ligand/copper(I) bromide ratio of 1.5 at a reaction temperature of 85–90 °C. Under these conditions, latexes with good colloidal stability with average particle diameters of 200 nm were obtained. The molecular weight distributions of the polystyrenes were narrow, although the experimental molecular weights were slightly larger than the theoretical ones because not all the macroinitiator appeared to reinitiate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4027–4038, 2006     

A first regularity result for the Armstrong–Frederick cyclic hardening plasticity model with Cosserat effects

The purpose of this article is to prove the Hölder continuity up to the boundary of the displacement vector and the microrotation matrix for the quasistatic, rate-independent Armstrong–Frederick cyclic hardening plasticity model with Cosserat effects. This model is of non-monotone and non-associated type. In the case of two space dimensions we use the hole-filling technique of Widman and Morrey's Dirichlet growth theorem.     

Null-Lagrangians and the indeterminate couple stress model

The aims of this note is to present a new model based on a new representation of the curvature energy in the indeterminate couple stress model and to discuss some related choices from the literature. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of Patent Blue derivatized hydrophilic dendrons dedicated to sentinel node detection in breast cancer

In the last decade, methods for the precise localization of sentinel lymph node (SLN) have drawn tremendous attention by oncology surgeons and researchers in the field of medical diagnosis. The accurate identification and characterization of lymph nodes by imaging has important therapeutic and prognostic significance in patients with newly diagnosed cancers. The SLN is the first lymph node that receives lymphatic drainage from the site of a primary tumor. Two biocompatible dendronized phosphonates, one bearing a Patent Blue (PB VF) dye at its periphery, where synthesized. Indeed, such a blue dye is currently injected to label the lymph node system for its per-operative detection. Therefore, developing chemistry of Patent Blue VF to optimize early diagnosis is of great current interest.     

Copper-catalyzed iminoiodane-mediated aminolactonization of olefins: application to the synthesis of 5,5-disubstituted butyrolactones

A copper(I)-catalyzed reaction of a variety of 4-aryl-pent-4-enoates with nosyliminoiodane generated in situ provides the corresponding 5-aryl-5-nosylamidomethylbutyrolactones. The reaction presumably proceeds via an aziridine intermediate, which could be isolated in one case.     

Quantitative and sensitive detection of rare mutations using droplet-based microfluidics

Somatic mutations within tumoral DNA can be used as highly specific biomarkers to distinguish cancer cells from their normal counterparts. These DNA biomarkers are potentially useful for the diagnosis, prognosis, treatment and follow-up of patients. In order to have the required sensitivity and specificity to detect rare tumoral DNA in stool, blood, lymph and other patient samples, a simple, sensitive and quantitative procedure to measure the ratio of mutant to wild-type genes is required. However, techniques such as dual probe TaqMan(?) assays and pyrosequencing, while quantitative, cannot detect less than ～1% mutant genes in a background of non-mutated DNA from normal cells. Here we describe a procedure allowing the highly sensitive detection of mutated DNA in a quantitative manner within complex mixtures of DNA. The method is based on using a droplet-based microfluidic system to perform digital PCR in millions of picolitre droplets. Genomic DNA (gDNA) is compartmentalized in droplets at a concentration of less than one genome equivalent per droplet together with two TaqMan(?) probes, one specific for the mutant and the other for the wild-type DNA, which generate green and red fluorescent signals, respectively. After thermocycling, the ratio of mutant to wild-type genes is determined by counting the ratio of green to red droplets. We demonstrate the accurate and sensitive quantification of mutated KRAS oncogene in gDNA. The technique enabled the determination of mutant allelic specific imbalance (MASI) in several cancer cell-lines and the precise quantification of a mutated KRAS gene in the presence of a 200,000-fold excess of unmutated KRAS genes. The sensitivity is only limited by the number of droplets analyzed. Furthermore, by one-to-one fusion of drops containing gDNA with any one of seven different types of droplets, each containing a TaqMan(?) probe specific for a different KRAS mutation, or wild-type KRAS, and an optical code, it was possible to screen the six common mutations in KRAS codon 12 in parallel in a single experiment.     

Synthesis,Photophysical, and Two‐Photon Absorption Properties of Elongated Phosphane Oxide and Sulfide Derivatives

A series of rod‐shaped and related three‐branched push–pull derivatives containing phosphane oxide or phosphane sulfide (PO or PS)—as an electron‐withdrawing group conjugated to electron‐donating groups, such as amino or ether groups, with a conjugated rod consisting of arylene–vinylene or arylene–ethynylene building blocks—were prepared. These compounds were efficiently synthesized by a Grignard reaction followed by Sonogashira coupling. Their photophysical properties including absorption, emission, time‐resolved fluorescence, and two‐photon absorption (TPA) were investigated with special attention to structure–property relationships. These fluorophores show high fluorescence quantum yields and solvent‐dependent experiments reveal that efficient intramolecular charge transfer occurs upon excitation, thereby leading to highly polar excited states, the polarity of which can be significantly enhanced by playing on the end groups and conjugated linker. Rod‐shaped and related three‐branched systems show similar fluorescence properties in agreement with excitation localization on one of the push–pull branches. By using stronger electron donors or replacing the arylene–ethynylene linkers with an arylene–vinylene one induces significant redshifts of both the low‐energy one‐photon absorption and TPA bands. Interestingly, a major enhancement in TPA responses is observed, whereas OPA intensities are only weakly affected. Similarly, phosphane oxide derivatives show similar OPA responses than the corresponding sulfides but their TPA responses are significantly larger. Finally, the electronic coupling between dipolar branches promoted by common PO or PS acceptor moieties induces either slight enhancement of the TPA responses or broadening of the TPA band in the near infrared (NIR) region. Such behavior markedly contrasts with triphenylamine‐core‐mediated coupling, which gives evidence for the different types of interactions between branches.     

Analysis of the hollow cathode emitted electron beams in a radialmultichannel pseudospark

A radial multichannel pseudospark switch seems advantageous for switching currents exceeding 100 kA. A single common hollow cathode guarantees the same trigger conditions for all channels. The electron beams emitted out of the hollow cathode of this switch are analyzed by means of Faraday-cups by varying the circuit as well as the trigger parameters. In addition to the cup measurements, the discharge is observed using a CCD camera. It is found that each channel of the switch must receive a respective beam, before the resistance of the switch turns low, if the discharge current is to run through that channel. In addition, most of the varied parameters do not influence the electron beam