Synthesis of Imidazole‐Based AIEgens with Wide Color Tunability and Exploration of their Biological Applications

Research on aggregation‐induced emission (AIE) has become increasingly popular recently and various AIE luminogens (AIEgens) have been developed based on tetraphenylethene, hexaphenylsilole, distyrylanthracene, tetraphenylpyrazine, etc. However, facile tuning of the AIEgen emissions in a wide range remains challenging. Herein, a novel series of AIEgens is reported, based on imidazole‐cored molecular rotors, with facile synthesis and emission colors covering the whole visible spectrum. Moreover, these imidazole derivatives exhibit biological functions unique among the AIEgens, including mitochondria‐specific imaging and antifungal activity. Benefiting from the easy preparation and the tunable emission, the imidazole derivatives are expected to not only diversify the family of AIEgens but also enrich their biological applications.     

Reconstruction from Sparsely Sampled Data by ART with Interpolated Rays

After a brief discussion of the algebraic reconstruction techniques (ART), we introduce the attenuation problem in positron emission tomography (PET). We anticipate that a generalization of ART, the so-called cyclic subgradient projection (CSP) method, may be useful for solving this problem. This, however, has not been successfully realized, due to the fact that data collected by our proposed stationary PET detector ring are too sparsely sampled. That this is, in fact, a major problem is demonstrated by showing that ordinary ART produces reconstructions with unacceptably strong artifacts even on perfect (no attenuation) data collected according to the PET geometry. We demonstrate that the source of this artifact is the sparse sampling, and we propose the use of interpolated rays to overcome the problem. This approach is successful, as is illustrated by showing reconstructions from sparsely sampled data by ART with interpolated rays.     

Photoluminescence and electroreflectance studies of modulation-doped pseudomorphic AlGaAs/InGaAs/GaAs quantum wells

In this study, we describe the correlations between the photoluminescence (PL) spectra and electrical properties of pseudomorphic modulation-doped AlGaAs/InGaAs/GaAs quantum wells (MDQWs) grown by molecular beam epitaxy. In MDQWs, the presence of a large sheet carrier density contributes significantly to the PL linewidth. At low temperatures (4.2 K), free carrier induced broadening of the PL linewidth is influenced by the material quality of the structure. At higher temperatures (77 K), differences in the material quality do not affect the linewidth significantly, and under these conditions the PL linewidth is a good measure of the sheet carrier density. The ratio of the 77 K to 4.2 K PL linewidths provides useful information about the crystalline quality of the MDQW structures as illustrated by the correlation with 77 K Hall mobility data and a simple model. We present results of Electron Beam Electroreflectance (EBER) to characterize MDQWs and undoped quantum wells in the AlGaAs/InGaAs/GaAs material system. Several transitions have been observed and fitted to excitonic Lorentzian lineshapes, providing accurate estimates of transition energy and broadening parameter at temperatures of 96 K and 300 K.     

Low‐level PGAS computing on many‐core processors with TSHMEM

Diminishing returns from increased clock frequencies and instruction‐level parallelism have forced computer architects to adopt architectures that exploit wider parallelism through multiple processor cores. While emerging many‐core architectures have progressed at a remarkable rate, concerns arise regarding the performance and productivity of numerous parallel‐programming tools for application development. Development of parallel applications on many‐core processors often requires developers to familiarize themselves with unique characteristics of a target platform while attempting to maximize performance and maintain correctness of their applications. The family of partitioned global address space (PGAS) programming models comprises the current state of the art in balancing performance and programmability. One such PGAS approach is SHMEM, a lightweight, shared‐memory programming library that has demonstrated high performance and productivity potential for parallel‐computing systems with distributed‐memory architectures. In the paper, we present research, design, and analysis of a new SHMEM infrastructure specifically crafted for low‐level PGAS on modern and emerging many‐core processors featuring dozens of cores and more. Our approach (with a new library known as TSHMEM) is investigated and evaluated atop two generations of Tilera architectures, which are among the most sophisticated and scalable many‐core processors to date, and is intended to enable similar libraries atop other architectures now emerging. In developing TSHMEM, we explore design decisions and their impact on parallel performance for the Tilera TILE‐Gx and TILEPro many‐core architectures, and then evaluate the designs and algorithms within TSHMEM through microbenchmarking and applications studies with other communication libraries. Our results with barrier primitives provided by the Tilera libraries show dissimilar performance between the TILE‐Gx and TILEPro; therefore, TSHMEM's barrier design takes an alternative approach and leverages the on‐chip mesh network to provide consistent low‐latency performance. In addition, our experiments with TSHMEM show that naive collective algorithms consistently outperformed linear distributed collective algorithms when executed in an SMP‐centric environment. In leveraging these insights for the design of TSHMEM, our approach outperforms the OpenSHMEM reference implementation, achieves similar to positive performance over OpenMP and OSHMPI atop MPICH, and supports similar libraries in delivering high‐performance parallel computing to emerging many‐core systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of Alkyl Fructosides

The anomeric alkylation of D-fructose is efficiently catalyzed by mild acid catalysts. Degradation of fructose is negligible under the conditions applied.     

The Relation between Calcium Sequestering Capacity and Oxidation Degree of Dicarboxy-Starch and Dicarboxy-Inulin

The objective of this study was to establish the relation between the calcium sequestering capacity (SC) of dicarboxy-starch and that of dicarboxy-inulin, and the oxidation degree of these products. An S-type curve is obtained when plotting the SC of oxidized starch versus the degree of oxidation. By contrast the sequestering capacity of dicarboxy-inulin increases linearly with the degree of oxidation. The difference in behaviour of these materials can be attributed to the fact that upon starch oxidation the favourable oxydiacetate structure is obtained only after substantial conversion, whereas in inulin this structure is obtained immediately and is present in each oxidized fructose unit.     

The role of prostaglandin E2 and nitric oxide in cell death in J774 murine macrophages

We investigated the role of prostaglandin E2 (PGE2) and its interactions with nitric oxide (NO) on cell death and NO-mediated cytotoxicity in the murine macrophage cell line J774. Stimulation of the J774 cells with lipopolysaccharide together with interferon-gamma resulted in a dose-dependent cytotoxicity and production of PGE2 and NO, measured as nitrite. Our results showed a linear correlation between PGE2 release and cytotoxicity. The cyclooxygenase (COX) inhibitor indomethacin completely inhibited PGE2 biosynthesis, without affecting NO production or cell death. This supports previous reports suggesting that overproduction of endogenous PGE2 is mainly the consequence of cell death and does not cause it. In contrast, the NO synthase inhibitor N(omega)-monomethyl-L-arginine (L-NMMA) gave a significant, though incomplete suppression of NO release and cell death. This points to the presence of other cytotoxic factors besides NO. To evaluate the toxic effect solely due to NO, macrophages were exposed to the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP). Incubation with SNAP also resulted in a concentration-dependent cell injury and PGE2 production. When exogenously added, PGE2 protected against SNAP-mediated cytotoxicity and simultaneously increased PGE2 release into the medium, without inducing COX-2. The cytoprotection and the stimulation of PGE2 release were both reversed by indomethacin. In conclusion, PGE2 biosynthesis may represent a mechanism by which inflammatory macrophages protect themselves against the cytotoxic effects of NO.