Utilizing Experiment and Theory to Evaluate Rhodamine B ethylenediamine as a Fluorescent Sensor for G-type Nerve Agents

Nerve gas mimic binding with Rhodamine B ethylenediamine (1) was studied in organic media. Binding of the nerve gas mimic, diethyl chlorophosphate (DCP), with the probe generated a non-fluorescent intermediate and a fluorescent product. Fluorescent and non-fluorescent products generated were identified using mass spectrometry and X-ray crystallography. Time-dependent density functional theory calculations were also used to investigate the electronic structure of the fluorescent probe in the ground and lowest lying π?→?π* singlet excited state. Though good agreement between theory and experiment can be obtained for the intense peak in the experimental spectrum using non-hybrid functionals, care must be taken when modelling these complexes due to the appearance of an n?→?π* transition that is too low in energy and appears to fall in the shoulders of the π?→?π* transitions.

     

Electron-catalyzed mutual neutralization of various anions with Ar+: evidence of a new plasma process

The mutual neutralization of anions with Ar+ has been studied by variable electron and neutral density attachment mass spectrometry. Evidence of a previously unobserved plasma loss process, electron-catalyzed mutual neutralization (ECMN), e.g., SF6-+Ar+ + e-→neutrals + e-, is reported. Results for 10 species suggest that ECMN occurs generally and significantly affects the total ion-loss rate in plasmas with electron densities exceeding 10(10) cm-3. ECMN is discussed in the context of other known three-body plasma processes, the mechanisms for which appear insufficient to explain the observed effect. A mechanism for ECMN involving an incident electron facilitating energy transfer to the internal modes of the anion is proposed.     

Sub-diffraction-limited far-field imaging in infrared

We investigated a far-field superlens operating at mid-infrared wavelength that allows resolving subwavelength features in the far-field. By utilizing evanescent enhancement provided by surface plasmon excitation of silver nanorods and Moiré effect, we numerically demonstrated that subwavelength information of an object can be converted to propagating information. This information can then be captured by conventional optical components. A simple image reconstruction algorithm can restore the subwavelength object. A sub-diffraction-limited resolution of 2.5 μm at 6-μm wavelength is demonstrated.     

Winding Clusters in Percolation on the Torus and the Möbius Strip

Using a simulation technique introduced recently, we study winding clusters in percolation on the torus and the Möbius strip for different aspect ratios. The asynchronous parallelization of the simulation makes very large system and sample sizes possible. Our high accuracy results are fully consistent with predictions from conformal field theory. The numerical results for the Möbius strip and the number distribution of winding clusters on the torus await theoretical explanation. To our knowledge, this study is the first of its kind.     

Generation of hyperentangled photon pairs

We experimentally demonstrate the first quantum system entangled in every degree of freedom (hyperentangled). Using pairs of photons produced in spontaneous parametric down-conversion, we verify entanglement by observing a Bell-type inequality violation in each degree of freedom: polarization, spatial mode, and time energy. We also produce and characterize maximally hyperentangled states and novel states simultaneously exhibiting both quantum and classical correlations. Finally, we report the tomography of a 2 x 2 x 3 x 3 system (36-dimensional Hilbert space), which we believe is the first reported photonic entangled system of this size to be so characterized.     

Improvements to air mass calculations for ground-based infrared measurements

High-resolution ground-based infrared solar spectra are routinely recorded at the Network for the Detection of Stratospheric Change (NDSC) stations. These data sets play a key role in providing a long-term record of atmospheric composition and their links to climate change. The analysis of observed infrared spectra involves comparison to a computer-modeled atmosphere where knowledge of the air mass distribution is an essential component. This note summarises improvements made to an existing and widely used computer code (FSCATM) to perform refractive ray-tracing and calculation of the air mass distribution. Changes were made towards higher vertical resolution in the troposphere and increased numerical precision. The revised FSCATM improves the analysis of infrared spectra mostly through the more accurate representation of the temperature profile. Air mass differences with respect to earlier versions are documented and are typically <0.7%, exceptions being extreme cases of inversion layers. The current version provides ray tracing and air mass calculations for any terrestrial observation site. The output files are reported in a format compatible with the SFIT and SFIT2 retrieval algorithms, which are widely used for NDSC infrared atmospheric studies. The improved computer code, documentation, reference profiles, and test cases are available electronically.     

Characteristics of vocal fold adduction related to voice onset

This study examined whether vocal fold kinematics prior to phonation differed between hard (glottal), normal, or breathy onsets in men and women. Glottal landmarks were identified and digitized from videotape recorded with a rigid laryngoscope during different voice onset types. Significant linear relationships (p 0.0055) were found among onset types on measures of (a) gesture duration when moving from 80% to 20% of maximum distance during adduction, (b) maximum velocity, (c) duration between the completion of adduction and phonation onset, and (d) ratios of maximum velocity to maximum distance between the vocal processes, an estimate of stiffness. The gesture duration was greatest for breathy onsets and least for hard onsets, while the maximum velocity, latency between adduction and phonation onset, and estimated stiffness were greatest for hard onsets and least for breathy onsets. The results suggest that one trajectory seems to be used with increases in gesture duration being accompanied by decreases in articulator stiffness when moving from hard to normal to breathy voice onset types.     

Specific and nonspecific collapse in protein folding funnels

Experiments with fast folding proteins are beginning to address the relationship between collapse and folding. We investigate how different scenarios for folding can arise depending on whether the folding and collapse transitions are concurrent or whether a nonspecific collapse precedes folding. Many earlier studies have focused on the limit in which collapse is fast compared to the folding time; in this work we focus on the opposite limit where, at the folding temperature, collapse and folding occur simultaneously. Real proteins exist in both of these limits. The folding mechanism varies substantially in these two regimes. In the regime of concurrent folding and collapse, nonspecific collapse now occurs at a temperature below the folding temperature (but slightly above the glass transition temperature).