From X- to O-shaped spatiotemporal spectra of light filaments in water

We show that the angle-wavelength spectra of light filaments excited by ultrashort pulses experience a transition from X- to O-like structures when their carrier wavelengths are switched from normal to anomalous dispersion. Calculations confirm that the O-shaped conical emission follows the elliptic geometry of the nonlinear Schr?dinger equation with anomalous dispersion.     

Light Engineering and Silicon Diffractive Optics Assisted Nonparaxial Terahertz Imaging

The art of light engineering unveils a world of possibilities through the meticulous manipulation of photonic properties such as intensity, phase, and polarization. Precision control over these properties finds application in a variety of fields spanning communications, light–matter interactions, laser direct writing, and imaging. Terahertz (THz) range, nestled between microwaves and infrared light, stands out for its remarkable ability to propagate with minimal losses in numerous dielectric materials and compounds, making THz imaging a powerful tool for noninvasive control and inspection. In this study, a rational framework for the design and optimal assembly of nonparaxial THz imaging systems is established. The research is centered on lensless photonic systems composed solely of high-resistivity silicon-based nonparaxial elements such as the Fresnel zone plate, the Fibonacci lens, the Bessel axicon, and the Airy zone plate, all fabricated using laser ablation technology. Through a comprehensive examination through illumination engineering and scattered light collection from raster-scanned samples in a single-pixel detector scheme, the imaging systems are evaluated via diverse metrics including contrast, resolution, depth of field, and focus. These findings chart an exciting course toward the development of compact and user-friendly THz imaging systems where sensors and optical elements seamlessly integrate into a single chip.     

Layered structure of room-temperature ionic liquids in microemulsions by multinuclear NMR spectroscopic studies

Microemulsions form in mixtures of polar, nonpolar, and amphiphilic molecules. Typical microemulsions employ water as the polar phase. However, microemulsions can form with a polar phase other than water, which hold promise to diversify the range of properties, and hence utility, of microemulsions. Here microemulsions formed by using a room‐temperature ionic liquid (RTIL) as the polar phase were created and characterized by using multinuclear NMR spectroscopy. ¹H, ¹¹B, and ¹⁹F NMR spectroscopy was applied to explore differences between microemulsions formed by using 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) as the polar phase with a cationic surfactant, benzylhexadecyldimethylammonium chloride (BHDC), and a nonionic surfactant, Triton X‐100 (TX‐100). NMR spectroscopy showed distinct differences in the behavior of the RTIL as the charge of the surfactant head group varies in the different microemulsion environments. Minor changes in the chemical shifts were observed for [bmim]⁺ and [BF₄]^? in the presence of TX‐100 suggesting that the surfactant and the ionic liquid are separated in the microemulsion. The large changes in spectroscopic parameters observed are consistent with microstructure formation with layering of [bmim]⁺ and [BF₄]^? and migration of Cl^? within the BHDC microemulsions. Comparisons with NMR results for related ionic compounds in organic and aqueous environments as well as literature studies assisted the development of a simple organizational model for these microstructures.     

A preference-based multi-objective evolutionary algorithm R-NSGA-II with stochastic local search

Incorporation of a decision maker’s preferences into multi-objective evolutionary algorithms has become a relevant trend during the last decade, and several preference-based evolutionary algorithms have been proposed in the literature. Our research is focused on improvement of a well-known preference-based evolutionary algorithm R-NSGA-II by incorporating a local search strategy based on a single agent stochastic approach. The proposed memetic algorithm has been experimentally evaluated by solving a set of well-known multi-objective optimization benchmark problems. It has been experimentally shown that incorporation of the local search strategy has a positive impact to the quality of the algorithm in the sense of the precision and distribution evenness of approximation.     

Interaction of pyridine‐2,5‐dicarboxylic acid with heavy metal ions in aqueous solutions

Interactions between pyridine‐2,5‐dicarboxylic acid and Zn(II), Ni(II), Pb(II), Cd(II), and Cu(II) were characterized in aqueous solutions (20°C; I = 0.4 (KNO₃)) by means of d.c.‐polarography, spectrophotometry, and ¹H NMR spectroscopy. Polarography was used to determine the concentration of free metal ions in the presence of 10‐fold excess ligand in weakly alkaline solutions, and to determine stability constants for the Zn(II), Cd(II), and Cu(II) complexes with pyridine‐2,5‐dicarboxylic acid. ¹H NMR spectroscopy was used to further characterize complex formation. © 2005 Wiley Periodicals, Inc. 16:285–291, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20123     

Correlation of Insulin‐Enhancing Properties of Vanadium‐Dipicolinate Complexes in Model Membrane Systems: Phospholipid Langmuir Monolayers and AOT Reverse Micelles

We explore the interactions of V^III‐, V^IV‐, and V^V‐2,6‐pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood‐glucose‐lowering effects of these compounds on STZ‐induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2‐ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self‐assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V^III–phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V^IV and V^V–phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V^III‐ and V^IV‐dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V^IV complexes in reverse micelles indicate that the neutral and smaller 1:1 V^IV‐dipic complex penetrates the interface, whereas the larger 1:2 V^IV complex does not. UV/Vis spectroscopy studies of the anionic V^III‐dipic complex show only minor interactions. These results are in contrast to behavior of the V^V‐dipic complex, [VO₂(dipic)]^?, which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V^III‐, V^IV‐, and V^V‐dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds’ efficacy at lowering elevated blood glucose levels in diabetic rats.     

Pyridinyl-Carbazole Fragments Containing Host Materials for Efficient Green and Blue Phosphorescent OLEDs

Pyridinyl-carbazole fragments containing low molar mass compounds as host derivatives H1 and H2 were synthesized, investigated, and used for the preparation of electro-phosphorescent organic light-emitting devices (PhOLEDs). The materials demonstrated high stability against thermal decomposition with the decomposition temperatures of 361–386 °C and were suitable for the preparation of thin amorphous and homogeneous layers with very high values of glass transition temperatures of 127–139 °C. It was determined that triplet energy values of the derivatives are, correspondingly, 2.82 eV for the derivative H1 and 2.81 eV for the host H2. The new derivatives were tested as hosts of emitting layers in blue, as well as in green phosphorescent OLEDs. The blue device with 15 wt.% of the iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic) emitter doping ratio in host material H2 exhibited the best overall characteristics with a power efficiency of 24.9 lm/W, a current efficiency of 23.9 cd/A, and high value of 10.3% of external quantum efficiency at 100 cd/m². The most efficient green PhOLED with 10 wt% of Ir(ppy)₃ {tris(2-phenylpyridine)iridium(III)} in the H2 host showed a power efficiency of 34.1 lm/W, current efficiency of 33.9 cd/A, and a high value of 9.4% for external quantum efficiency at a high brightness of 1000 cd/m², which is required for lighting applications. These characteristics were obtained in non-optimized PhOLEDs under an ordinary laboratory atmosphere and could be improved in the optimization process. The results demonstrate that some of the new host materials are very promising components for the development of efficient phosphorescent devices.