Highly selective synthesis of tetra-substituted furans and cyclopropenes: copper(i)-catalyzed formal cycloadditions of internal aryl alkynes and diazoacetates

A convenient Cu(i)-catalyzed cycloaddition of electron rich internal aryl alkynes and diazoacetates was discovered for the chemoselective and regioselective synthesis of tetra-substituted furans and cyclopropenes in moderate isolated yields (18-67%), and alkyne conversion (29-73%).     

Development of sequential injection-lab-at-valve (SI-LAV) micro-extraction instrumentation for the spectrophotometric determination of an anionic surfactant.

The development of instrumentation for sequential injection analysis with a "lab-at-valve" (SIA-LAV) micro-extraction system is presented. The extractive determination of an anionic surfactant using methylene blue was selected as a model. Sample, reagents and organic solvent were sequentially aspirated into an extraction coil connected to the center of a selection valve, where extraction took place by flow reversal. The aqueous and organic phases were separated in a LAV unit attached to one port of the valve. The LAV unit situated a fiber-optic spectrophotometer to monitor the absorbance change of the extract product in the organic phase. The developed SIA-LAV system offers an alternative micro-total analysis system for automated micro-extraction.     

Dual-direction Gires-Tournois etalon based on a single complex fiber Bragg grating

We propose and demonstrate a single fiber Bragg grating-based Gires-Tournois (GT) etalon, which is realized by applying a complex apodization profile on a linearly chirped fiber Bragg grating. Such a GT etalon not only has a simplified fabrication procedure but also can operate in dual directions.     

Approaches to crystallization from ionic liquids: complex solvents-complex results, or, a strategy for controlled formation of new supramolecular architectures?

There are now more than 1200 papers a year describing research results using the 'neoteric' solvents, known as ionic liquids (ILs). If ILs are such highly studied solvents, why has there been so comparatively little research in their use in crystallization? Here we explore this question and discuss possible strategies for utilization of the mundane and the unique aspects of ILs for novel crystallization strategies including crystallization of high and low melting solids using thermal shifts; "solvothermal" techniques; slow diffusion; electrocrystallization; and use of a co-solvent. The results presented here and those appearing in the literature indicate both the complex nature of these solvents and their promise in delivering unique solvation, metal ion coordination numbers, coordination polymer motifs, and metal-anion interactions, to name but a few. These complex, but fascinating, results and the promise of much more intimate control over crystallization processes will drive a growing interest in using ILs as crystallization solvents.     

Discrete bimodal probes for thrombus imaging

Here we report a generalizable solid/solution-phase strategy for the synthesis of discrete bimodal fibrin-targeted imaging probes. A fibrin-specific peptide was conjugated with two distinct imaging reporters at the C- and N-termini. In vitro studies demonstrated retention of fibrin affinity and specificity. Imaging studies showed that these probes could detect fibrin over a wide range of probe concentrations by optical, magnetic resonance, and positron emission tomography imaging.     

Comparing the effects of reverberation and of noise on speech recognition in simulated electric-acoustic listening

Cochlear implant users report difficulty understanding speech in both noisy and reverberant environments. Electric-acoustic stimulation (EAS) is known to improve speech intelligibility in noise. However, little is known about the potential benefits of EAS in reverberation, or about how such benefits relate to those observed in noise. The present study used EAS simulations to examine these questions. Sentences were convolved with impulse responses from a model of a room whose estimated reverberation times were varied from 0 to 1 sec. These reverberated stimuli were then vocoded to simulate electric stimulation, or presented as a combination of vocoder plus low-pass filtered speech to simulate EAS. Monaural sentence recognition scores were measured in two conditions: reverberated speech and speech in a reverberated noise. The long-term spectrum and amplitude modulations of the noise were equated to the reverberant energy, allowing a comparison of the effects of the interferer (speech vs noise). Results indicate that, at least in simulation, (1) EAS provides significant benefit in reverberation; (2) the benefits of EAS in reverberation may be underestimated by those in a comparable noise; and (3) the EAS benefit in reverberation likely arises from partially preserved cues in this background accessible via the low-frequency acoustic component.