Theory of the time reversal cavity for electromagnetic fields

We derive a general expression of the electric dyadic Green function in a time-reversal cavity, based on vector diffraction theory in the frequency domain. Our theory gives a rigorous framework to time-reversal experiments using electromagnetic waves and suggests a methodology to design structures generating subwavelength focusing after time reversal.     

Asymmetry reversal in the reflection from a two-dimensional photonic crystal

The measured, angle-dependent, reflection spectra of a two-dimensional GaAs photonic crystal consist of an asymmetric peak on top of an oscillating background. At large angles of incidence (>70 degrees), the asymmetry of the peak is observed to flip for p-polarized light. We explain the observed spectra with a Fano model that includes loss and interference between a resonant waveguide component and direct Fresnel reflection of the layered structure. We show that the reversal of the asymmetry of the line is due to a change in sign of the direct reflection at Brewster's angle.     

Thermal diffusivity measurements in a lyotropic discotic nematic phase

The present work is focused on thermal diffusivity (D)$(D)$ measurements, via Z  -scan experiment, in a discotic nematic phase of the lyotropic mixture comprised of potassium laurate, decanol and D₂O${\text{D}}_2\text{O}$. In this experiment, the nematic sample is translated through the focal region of a focused Gaussian laser beam. The experimental data are analyzed according to the thermal lens model and the ratio between the thermal diffusivities parallel (D_∥)$(D_{\parallel })$ and perpendicular (D_⊥)$(D_{\perp })$ to the director of the nematic sample has been found to be smaller than one. The results are compared to others obtained with different liquid crystals and explained by using a simple model where this ratio is correlated to the shape anisotropy of the micelles.     

Karyotype characterization of Eurysternus caribaeus: the smallest diploid number among Scarabaeidae (Coleoptera: Scarabaeoidea)

Eurysternus caribaeus was analyzed cytologically by conventional chromosomal staining. The species presents a diploid number of 2n=8, chromosomes with two arms and an XY sex determining mechanism. This is the first karyotype described for the genus Eurysternus and the tribe Eurysternini, and is also the smallest diploid number observed in the family Scarabaeidae and superfamily Scarabaeoidea.     

Effect of mating delay on the ovary of Melipona quadrifasciata anthidioides (Hymenoptera: Apidae) queens

The effect of mating delay on the ovary structure of virgin queens of Melipona quadrifasciata anthidioides (Hymenoptera: Apidae) was investigated. Virgin queens 15, 20, 25 and 30 days old were dissected to analyze their degree of ovary degeneration. To verify whether the degeneration would cause permanent sterility, virgin queens of the same ages (15, 20, 25 and 30 days) were mated and accompanied for at least 14 days to verify whether there was physogastry and then dissected. The ovaries were analyzed by histology, histochemical tests and TUNEL to verify programmed cell death. The results showed that mating delay interrupted oogenesis preventing vitellogenesis. Mating delay results in ovary degeneration which increased with queen age. However, even when there was ovariole degeneration, 25-day-old virgin queens after mating presented normal ovariole activation.     

Pixel-by-pixel analysis of DCE MRI curve patterns and an illustration of its application to the imaging of the musculoskeletal system

Dynamic contrast enhanced (DCE) MRI is a widespread method that has found broad application in the imaging of the musculoskeletal (MSK) system. A common way of analyzing DCE MRI images is to look at the shape of the time-intensity curve (TIC) in pixels selected after drawing an ROI in a highly enhanced area. Although often applied to a number of MSK affections, shape analysis has so far not led to a unanimous correlation between these TIC patterns and pathology. We hypothesize that this might be a result of the subjective ROI approach. To overcome the shortcomings of the ROI approach (sampling error and interuser variability, among others), we created a method for a fast and simple classification of DCE MRI where time-curve enhancement shapes are classified pixel by pixel according to their shape. The result of the analysis is rendered in multislice, 2D color-coded images. With this approach, we show not only that differences on a short distance range of the TIC patterns are significant and cannot be appreciated with a conventional ROI analysis but also that the information that shape maps and conventional standard DCE MRI parameter maps convey are substantially different.     

Toward low-voltage dielectrophoresis-based microfluidic systems: A review

Dielectrophoretically driven microfluidic devices have demonstrated great applicability in biomedical engineering, diagnostic medicine, and biological research. One of the potential fields of application for this technology is in point-of-care (POC) devices, ideally allowing for portable, fully integrated, easy to use, low-cost diagnostic platforms. Two main approaches exist to induce dielectrophoresis (DEP) on suspended particles, that is, electrode-based DEP and insulator-based DEP, each featuring different advantages and disadvantages. However, a shared concern lies in the input voltage used to generate the electric field necessary for DEP to take place. Therefore, input voltage can determine portability of a microfluidic device. This review outlines the recent advances in reducing stimulation voltage requirements in DEP-driven microfluidics.     

The Impact of C2 Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine-Cored Donor–Acceptor–Donor Triads

Novel electron donor–acceptor–donor (D-A-D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7-membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C₂ insertion into well-known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine-core D-A-D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room-temperature phosphorescence and triplet–triplet annihilation. Furthermore, electrochemical analysis suggested sigma-dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results.     

Controlling the Surface Functionalization of Ultrasmall Gold Nanoparticles by Sequence-Defined Macromolecules

Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by ¹H NMR spectroscopy, ¹H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative ¹H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm² per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles.     

Methane conversion to higher value-added product and energy co-generation using anodes OF PdCu/C in a solid electrolyte reactor: alkaline fuel cell type monitored by differential mass spectroscopy

Research on Chemical Intermediates - PdxCuy/C catalysts combinations were employed to CH4 partial oxidation in mild condition using a solid electrolyte reactor—alkaline fuel cell type. The...