Isoscattering on surfaces

We construct examples of pairs of surfaces that share the same poles (with multiplicity) of the scattering operatorm, and that are particularly simple in one or more senses. In particular, we find pairs of isoscattering surfaces of small genus with a small number of ends. We also give examples of congruence surfaces which are isoscattering.     

Lateral and longitudinal coupled waveguides in semiconductor lasers

A semiconductor laser including two laterally coupled waveguides, in which one of the waveguides includes a partially reflecting surface (an internal mirror) between its facets, is analyzed. The internal mirror inserts longitudinal coupling into the system. The spectrum of the Fabry-Perot modes exhibits modulation in the gain required for lasing threshold, with a periodicity that depends on the longitudinal position of the internal mirror. The combined coupled-cavity effect may explain the observed gain spectrum in GaN lasers.     

Synchronous Chemoradiation Nanovesicles by X‐Ray Triggered Cascade of Drug Release

The approach of concurrent‐to‐synchronous chemoradiation has now been advanced by well‐designed nanovesicles that permit X‐ray irradiation‐triggered instant drug release. The nanovesicles consist of Au nanoparticles tethered with irradiation labile linoleic acid hydroperoxide (LAHP) molecules and oxidation‐responsive poly(propylene sulfide)‐poly(ethylene glycol) (PPS‐PEG) polymers, where DOX were loaded in the inner core of the vesicles (Au‐LAHP‐vDOX). Upon irradiation, the in situ formation of hydroxyl radicals from LAHP molecules triggers the internal oxidation of PPS from being hydrophobic to hydrophilic, leading to degradation of the vesicles and burst release of cargo drugs. In this manner, synchronous chemoradiation showed impressive anticancer efficacy both in vitro and in a subcutaneous mouse tumor model by one‐dose injection and one‐time irradiation.     

Sulfonium cations as versatile strongly π-acidic ligands

More than a century old, sulfonium cations are still intriguing species in the landscape of organic chemistry. On one hand they have found broad applications in organic synthesis and materials science, but on the other hand, while isoelectronic to the ubiquitous tertiary phosphine ligands, their own coordination chemistry has been neglected for the last three decades. Here we report the synthesis and full characterization of the first Rh(i) and Pt(ii) complexes of sulfonium. Moreover, for the first time, coordination of an aromatic sulfonium has been established. A thorough computational analysis of the exceptionally short S–Rh bonds obtained attests to the strongly π-accepting nature of sulfonium cations and places them among the best π-acceptor ligands available today. Our calculations also show that embedding within a pincer framework enhances their π-acidity even further. Therefore, in addition to the stability and modularity that these frameworks offer, our pincer complexes might open the way for sulfonium cations to become powerful tools in π-acid catalysis.

Back to the scene: while isolobal to the ubiquitous tertiary phosphines, sulfonium cations as ligands were neglected for decades. This work revives the coordination chemistry of these species showing their potential as ligands for π-acid catalysis.     

Phenols-useful templates for the synthesis of bi-functional orthogonally protected dendron building blocks via solid phase Mitsunobu reaction

Bi-functional dendritic building blocks for convergent dendrimer growth were successfully synthesized from phenolic templates in the solid phase via a Mitsunobu reaction. Each arm of the dendron building block carries an orthogonally protected secondary amine along the arm, and a peripheral primary amine or phenol group (building block type 1) or a tertiary amine junction with orthogonally protected peripheral primary amine or carboxyl groups (building block type 2). The synthetic routes reported in this work are general and applicable for the preparation of diverse building blocks, controlling protection, arm length, and peripheral moieties. These novel dendron units can form unusual dendritic architectures by solid-phase chemistry, which may be incorporated into specific complex structures expanding the scope of dendrimer science.     

A simple FRET-based modular design for diagnostic probes

In recent years, there has been a massive effort to develop molecular probes with optical modes of action. Probes generally produce detectable signals based on changes in fluorescence properties. Here, we demonstrate the potential of self-immolative molecular adaptors as a platform for Turn-On probes based on the FRET technique. The probe is equipped with identical fluorophore pairs or a fluorophore/quencher FRET pair and a triggering substrate. Upon reaction of the analyte of interest with the triggering substrate, the self-immolative adaptor spontaneously releases the two dye molecules to break off the FRET effect. As a result, a new measurable fluorescent signal is generated. The fluorescence obtained can be used to quantify the analyte. The modular structure of the probe design will allow the preparation of various chemical probes based on the FRET activation technique.     

MATHEMATICS TEACHERS' CHOICES OF EXAMPLES THAT POTENTIALLY SUPPORT OR IMPEDE LEARNING1

The main goal of the study reported in the paper is to highlight some features of teachers' choice of examples in the mathematics classroom, in reference to their potential contribution or impediment to student learning. Specific examples from classroom observations are presented and analyzed accordingly, pointing to the complexity of considerations required for desirable choices. The discussion addresses the potential implications of the findings to mathematics teacher education programmes.     

Enhanced Antitumor Efficacy by a Cascade of Reactive Oxygen Species Generation and Drug Release

Reactive oxygen species (ROS) can be used not only as a therapeutic agent for chemodynamic therapy (CDT), but also as a stimulus to activate release of antitumor drugs, achieving enhanced efficacy through the combination of CDT and chemotherapy. Here we report a pH/ROS dual‐responsive nanomedicine consisting of β‐lapachone (Lap), a pH‐responsive polymer, and a ROS‐responsive polyprodrug. In the intracellular acidic environment, the nanomedicine can realize pH‐triggered disassembly. The released Lap can efficiently generate hydrogen peroxide, which will be further converted into highly toxic hydroxyl radicals via the Fenton reaction. Subsequently, through ROS‐induced cleavage of thioketal linker, doxorubicin is released from the polyprodrug. In vivo results indicate that the cascade of ROS generation and antitumor‐drug release can effectively inhibit tumor growth. This design of nanomedicine with cascade reactions offers a promising strategy to enhance antitumor efficacy.     

Protonated serine octamer cluster: structure elucidation by gas-phase H/D exchange reactions

The H/D exchange kinetics of the protonated serine octamer was investigated by both flow-tube and FT-ICR experiments. The exchange was observed to be bimodal in agreement with previous observations. Quantitative analysis of the experimental results led to site-specific H/D exchange rate constants on the basis of which the structures of both ion populations were deduced. We observe the two separate conformers exchanging 33 hydrogens each-in an independent manner and at different rates. This result was achieved through a probabilistic algorithm that groups together equivalent hydrogen atoms having equal rate constants. The slower exchanging population A is assigned an all-zwitterionic structure. Its faster exchanging counterpart B is assigned an all-neutral structure. Population A was found to be more stable toward collision-induced activation than population B. All of these findings are consistent with previous experimental results, thus comprising a self-consistent picture of the protonated serine octamer and its gas-phase properties.