Probing optical microfiber nonuniformities at nanoscale

We demonstrate a novel, simple, and comprehensive method for probing optical microfiber surface and bulk distortions with subnanometer accuracy. The method employs a regular optical fiber as a probe that slides along a microfiber transmitting the fundamental mode. The fraction of radiation power absorbed in the probe depends on the local distribution of the mode propagating in the microfiber. From the measured variation of the absorbed power, we determine the variation of the effective microfiber radius, which takes into account both the microfiber radius and refractive index variations. Furthermore, we verify the cylindrical symmetry of the microfiber nonuniformities by probing the microfiber from different sides. These results explain observed transmission losses in silica microfibers and open broad opportunities for microfiber investigation.     

Unusual Electro‐Optic Kerr Response in a Self‐Stabilized Amorphous Blue Phase with Nanoscale Smectic Clusters

We investigated the electro‐optic response in the “foggy” amorphous blue phase (BPIII) as well as in the isotropic phase. To the best of our knowledge, such a study has not yet been performed due to the very limited thermal range of BPIII. In this study, we used a single‐component chiral bent‐core liquid crystal with a self‐stabilized BPIII, which is stable over a wide temperature range. The results show that the response time is on the order of hundreds of microseconds in the isotropic phase and increases to 1–2 ms in the BPIII (at T_I?BP–T <1), then drastically increases up to a few tens of milliseconds upon further cooling in BPIII. Such an unusual behavior was explained on the basis of the high rotational viscosity and/or the existence of nanoscale smectic (Sm) clusters. The Kerr constant was also measured and found to be ～500 pm V^?2, which is the largest among bent‐core BP systems reported so far and comparable with that of polymer‐stabilized BPs.     

A damped hyerbolic equation with critical exponent

The aim of this paper is twofold. First, we initiate a detailed study of the so-called X^s _θ spaces attached to a partial differential operator. This include localization, duality, microlocal representation, subelliptic estimates, solvability and L^p (L^q ) estimates. Secondly, we obtain some theorems on the unique continuation of solutions to semilinear second order hyperbolic equations across strongly pseudo-convex surfaces. These results are proved using some new L^p → L^q Carleman estimates, derived using the X^s _θ spaces. Our theorems cover the subcritical case; in the critical case, the problem remains open. Similar results hold for higher order partial differential operators, provided that characteristic set satisfies a curvature conditions.     

Recording media that exhibit high dynamic range for digital holographic data storage

A general strategy for fabricating thick, optically flat photopolymer recording media with high dynamic range (M/#) that exhibit low levels of recording-induced Bragg detuning for holographic data storage is presented. In particular, media with M/# values as high as 42 in 1-mm-thick formats are obtained. We believe that these results are the first demonstration of a holographic storage medium with a dynamic range of this magnitude. In addition, we report the holographic recording and recovery of high-capacity (480-kbit) digital data pages in these media, further illustrating their data-storage capabilities.     

Interactions between cellulose nanocrystals and anionic and neutral polymers in aqueous solutions

Physical structures of aqueous cellulose nanocrystal (CNC) suspensions in anionic polyelectrolyte carboxymethyl cellulose (CMC) and non-ionic poly(ethylene oxide) (PEO) were investigated by studying their cross polarized, polarized optical microscope (POM) images and dynamic light scattering, zeta potential, ¹H spin–lattice relaxation nuclear magnetic resonance (NMR) data. The presence of anionic CMC and nonionic PEO in CNC suspensions led to two different kind of interactions. Semi-dilute CNC suspensions showed first gel-like behavior then phase separation by adding only semi-dilute un-entangled CMC polymer solutions, whereas the addition of PEO didn’t cause any significant change. POM images showed the phase transitions of CNC suspensions in the presence of CMC solutions from the isotropic state to nematic and chiral nematic phases. Dynamic light scattering, zeta potential and ¹H spin–lattice relaxation NMR data presented further arguments to explain polymer-CNC interactions in CMC and PEO solutions. ¹H NMR solvent relaxation technique determined the adsorption and depletion interactions between polymers and CNC. The minima in spin–spin specific relaxation rate constant showed the depletion of CNC nanoparticles in CMC. It is believed that the depletion flocculation was the case for the effects of CMC polymer chains in CNC suspensions. PEO was adsorbed on CNC surfaces and caused only weak depletion interactions due to the presence of soft particles.     

Identification of Phenolic Compounds by LC-MS/MS and Evaluation of Bioactive Properties of Two Edible Halophytes: Limonium effusum and L. sinuatum

This work aimed to evaluate the phenolic content and in vitro antioxidant, antimicrobial and enzyme inhibitory activities of the methanol extracts and their fractions of two edible halophytic Limonium species, L. effusum (LE) and L. sinuatum (LS). The total phenolic content resulted about two-fold higher in the ethyl acetate fraction of LE (522.82 ± 5.67 mg GAE/g extract) than in that of LS (274.87 ± 1.87 mg GAE/g extract). LC-MS/MS analysis indicated that tannic acid was the most abundant phenolic acid in both species (71,439.56 ± 3643.3 µg/g extract in LE and 105,453.5 ± 5328.1 µg/g extract in LS), whereas hyperoside was the most abundant flavonoid (14,006.90 ± 686.1 µg/g extract in LE and 1708.51 ± 83.6 µg/g extract in LS). The antioxidant capacity was evaluated by DPPH and TAC assays, and the stronger antioxidant activity in ethyl acetate fractions was highlighted. Both species were more active against Gram-positive bacteria than Gram negatives and showed considerable growth inhibitions against tested fungi. Interestingly, selective acetylcholinesterase (AChE) activity was observed with LE and LS. Particularly, the water fraction of LS strongly inhibited AChE (IC₅₀ = 0.199 ± 0.009 µg/mL). The ethyl acetate fractions of LE and LS, as well as the n-hexane fraction of LE, exhibited significant antityrosinase activity (IC₅₀ = 245.56 ± 3.6, 295.18 ± 10.57 and 148.27 ± 3.33 µg/mL, respectively). The ethyl acetate fraction and methanol extract of LS also significantly inhibited pancreatic lipase (IC₅₀ = 83.76 ± 4.19 and 162.2 ± 7.29 µg/mL, respectively). Taken together, these findings warrant further investigations to assess the potential of LE and LS as a bioactive source that can be exploited in pharmaceutical, cosmetics and food industries.