Simultaneous three-dimensional velocimetry and thermometry in gaseous flows using the stereoscopic vibrationally excited nitric oxide monitoring technique.

We present a demonstration of the simultaneous measurement of spatially resolved three-component velocity and temperature in gaseous flow fields using a variant of the vibrationally excited nitric oxide monitoring (VENOM) technique, based on planar laser induced fluorescence and molecular tagging velocimetry methods. Three-component velocity determinations were derived from two-dimensional molecular tagging velocity measurements employing sequential fluorescence image pairs obtained simultaneously by two cameras in stereoscopic configuration. Probing two different rotational states of nitric oxide (X2∏, υ''=1), produced via fluorescence and collisional quenching from initial excitation to the A Σ+2 state, for the sequential velocimetry images allows simultaneous determination of the temperature field. Experimental measurements of velocity and temperature across an oblique shock result in mean values within 21 m/s for the three components of velocity and 20 K for planar temperature when compared to oblique shock calculations.

Coherence brightened laser source for atmospheric remote sensing.

We have studied coherent emission from ambient air and demonstrated efficient generation of laser-like beams directed both forward and backward with respect to a nanosecond ultraviolet pumping laser beam. The generated optical gain is a result of two-photon photolysis of atmospheric O(2), followed by two-photon excitation of atomic oxygen. We have analyzed the temporal shapes of the emitted pulses and have observed very short duration intensity spikes as well as a large Rabi frequency that corresponds to the emitted field. Our results suggest that the emission process exhibits nonadiabatic atomic coherence, which is similar in nature to Dicke superradiance where atomic coherence is large and can be contrasted with ordinary lasing where atomic coherence is negligible. This atomic coherence in oxygen adds insight to the optical emission physics and holds promise for remote sensing techniques employing nonlinear spectroscopy.

Vibrationally excited NO tagging by NO(A²∑⁺) fluorescence and quenching for simultaneous velocimetry and thermometry in gaseous flows.

We present measurements demonstrating simultaneous determination of velocity and temperature using a variant of the Vibrationally Excited Nitric Oxide Monitoring (VENOM) technique that does not employ NO2. The variant is based on tagging by electronic excitation of NO in the A²∑(1/2)⁺ (v'=0)←X2Π1/2(v''=0) band and subsequent formation of vibrationally excited NO(X2Π) by spontaneous emission and collisional quenching. Sequential planar laser-induced fluorescence imaging of the nascent NO(X2Π, v''=1) was used to obtain spatially resolved average streamwise velocity and rotational/translational temperature. The temperature determination using this approach extends the applicability of the VENOM technique to low-density, high-speed flows, where slow thermalization of the tagged molecules represents a limiting factor.

Synthesis of fluorescent chalcones, photophysical properties, quantitative structure-activity relationship and their biological application.

The development of fluorescent pigments is an area of interest in several research fields due to their high sensitivity. In the current study-eight known and three new N,N-dimethylamino-chalcones (12a-k) were synthesized with good yields using the Claisen-Schmidt reaction. For each molecular system, the photophysical properties, including the maximum absorption wavelength (λAbsorption), molar absorption coefficient (ε), maximum excitation wavelength (λExcitation), maximum emission wavelength (λEmission), Stokes Shift (Δλ), fluorescence quantum yield (Φfl), fluorescence lifetime (τfl), radiative and non-radiative rate constants (kR and kNR, respectively) were evaluated. Variations in each of these properties were analyzed depending on the substituents present on each compound. To relate the chemical structures of the synthesized compounds to their photophysical properties, Hansch analysis (2D-QSPR) was applied. As a result of Hansch analysis, we found different photophysical properties related to molecular orbitals and the energy of their derivatives (Highest Occupied Molecular Orbital-HOMO, Lowest Unoccupied Molecular Orbital-LUMO, Difference between LUMO-HOMO-ΔLH, Chemical potential-µ, Hardness-η, Softness-S, and electrophilic global index-ω) as well as to the atomic charges on atoms C5, Cα, Cß, and CO. The application of this type of analysis has made it possible to understand and subsequently design new molecules with defined photophysical properties. Finally, the compounds were use as fluorescent pigment to get living cell imaging on breast cancer cells, obtaining the compound 12a as promissory alternative.

Simultaneous velocity and temperature measurements in gaseous flowfields using the vibrationally excited nitric oxide monitoring technique: a comprehensive study.

The performance of the vibrationally excited nitric oxide monitoring (VENOM) technique for simultaneous velocity and temperature measurements in gaseous flowfields is presented. Two different schemes were investigated, employing different methods to "write" a transient NO grid in the flow using the 355 nm photolysis of NO(2), which was subsequently probed by planar laser induced fluorescence imaging to extract velocity maps. We find that only one scheme provides full-frame temperature maps. The most accurate velocity measurement was attained by writing an NO pattern in the flow using a microlens array and then comparing the line displacement with respect to a reference image. The demonstrated uncertainty of this approach was 1.0%, corresponding to 7 m/s in a 705 m/s uniform flow. We found that the uncertainty associated with the instantaneous temperature measurements using the NO two-line thermometry technique was largely determined by the shot-to-shot power fluctuations of the probe lasers and, for the flows employed, were determined to range from 6% to 7% of the mean freestream temperature. Finally, simultaneous and local velocity/temperature measurements were performed in the wake of a cylinder in a uniform Mach 4.6 flowfield. The mean and fluctuation velocity and temperature maps were computed from 5000 single-shot measurements. The wake temperature and velocity fluctuations, with respect to the freestream values, were 15% to 30% and 5% to 20%, respectively. The spatial distributions agree with the results of computational fluid dynamics (CFD) simulations. Our results suggest that the VENOM technique holds promise for interrogating high-speed unsteady flowfields.

Resveratrol-Schiff Base Hybrid Compounds with Selective Antibacterial Activity: Synthesis, Biological Activity, and Computational Study.

Nowadays, antimicrobial resistance is a serious concern associated with the reduced efficacy of traditional antibiotics and an increased health burden worldwide. In response to this challenge, the scientific community is developing a new generation of antibacterial molecules. Contributing to this effort, and inspired by the resveratrol structure, five new resveratrol-dimers (9a−9e) and one resveratrol-monomer (10a) were synthetized using 2,5-dibromo-1,4-diaminobenzene (8) as the core compound for Schiff base bridge conformation. These compounds were evaluated in vitro against pathogenic clinical isolates of Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus sp., and Listeria monocytogenes. Antibacterial activity measurements of resveratrol-Schiff base derivatives (9a−9e) and their precursors (4−8) showed high selectivity against Listeria monocytogenes, being 2.5 and 13.7 times more potent than chloramphenicol, while resveratrol showed an EC50 > 320 µg/mL on the same model. Moreover, a prospective mechanism of action for these compounds against L. monocytogenes strains was proposed using molecular docking analysis, finding a plausible inhibition of internalin C (InlC), a surface protein relevant in bacteria−host interaction. These results would allow for the future development of new molecules for listeriosis treatment based on compound 8.

SERS study on the aggregation mechanisms resulting from the orientation of dipyridinic derivatives on gold nanoparticles.

In this work, was studied the adsorption and orientation of three dipyridinic derivatives 9,10-bis-((E)-2-(pyridin-4-yl)vinyl)anthracene (DPAC), 1,4-bis-((E)-2-(pyridin-4-yl)vinyl)naphthalene (DPNA-T) and 2,6-bis-((E)-2-(pyridin-4-yl)vinyl)naphthalene (DPNA-L) on gold nanoparticles, using Surface Enhanced Raman Scattering (SERS). Systematic modification in the shapes of the bifunctional systems (Cross-shape, T-shape and Linear-shape) shows changes significant in the preferential orientation of these analytes on the nanostructured gold surface. Additional data from UV-vis measurements and TEM images are in agreement with the Reaction Limited Colloid Aggregation (RLCA) mechanisms for DPAC and DPNA-T and Diffusion Limited Colloid Aggregation (DLCA) mechanisms for DPNA-L, showing that for the same analyte concentration, the aggregation mechanism depends on the molecular shape. These results allow us to rationalize the fundamental aspects involved in the development of devices based on plasmonic resonance with potential applications in the field of molecular electronics.

Simultaneous velocity and temperature measurements in gaseous flow fields using the VENOM technique.

We present an initial demonstration of simultaneous velocity and temperature mapping in gaseous flow fields using a new nitric oxide planar laser-induced fluorescence-based method. The vibrationally excited NO monitoring (VENOM) technique is an extension of two-component velocimetry using vibrationally excited NO generated from the photodissociation of seeded NO(2) [Appl. Opt. 48, 4414 (2009)], where the two sequential fluorescence images are obtained probing two different rotational states to provide both velocity and temperature maps. Comparisons to computational fluid dynamics simulations show that the initial VENOM measurements provide good velocity and temperature maps in the relatively high-density regions of the flow, where the rms uncertainties are approximately 5% for velocity and 9% for temperature.

Lupus relapse presented as frosted branch retinal angiitis: case report.

PURPOSE: To describe a systemic lupus erythematosus (SLE) relapse, which presented as frosted branch retinal angiitis. DESIGN: Clinical case report. METHODS: A 16-year-old female patient had an SLE relapse that appeared as frosted branch angiitis while being treated with deflazacort and azathioprine. RESULTS: Complete resolution of the vasculitis was achieved with a 3-day course of pulsed intravenous methylprednisolone and oral prednisone 3 weeks later. CONCLUSIONS: Even with proper immunosuppressive treatment, SLE can relapse. This case presented as frosted branch retinal angiitis, which is a clinical picture that is rarely described in SLE.