Rare Earth Doped Optical Fibre From Oxide Nanoparticles

Rare earth (RE) doped optical fibres were fabricated by using RE oxides coated silica nanoparticles. The fibre properties are comparable to those prepared by conventional techniques. The process offers better control over RE incorporation and homogeneity in the preform.     

Holographic entropy packing inside a black hole

If general relativity is spontaneously induced, the black hole limit is governed by a phase transition which occurs precisely at the would-have-been horizon. The exterior Schwarzschild solution then connects with a novel core of vanishing spatial volume. The Kruskal structure, admitting the exact Hawking imaginary time periodicity, is recovered, with the conic defect defused at the origin, rather than at the horizon. The entropy stored inside any interior sphere is universal, equal to a quarter of its surface area, thus locally saturating the 't Hooft-Susskind holographic bound. The associated Komar mass and material energy functions are nonsingular.     

Preparation of enzyme nanoparticles and studying the catalytic activity of the immobilized nanoparticles on polyethylene films

Using high-intensity ultrasound, in situ generated α-amylase nanoparticles (NPs) were immobilized on polyethylene (PE) films. The α-amylase NP-coated PE films have been characterized by E-SEM, FTIR, DLS, XPS and RBS. The PE was reacted with HNO₃ and NPs of the α-amylase were also deposited on the activated PE. The PE impregnated with α-amylase (4 μg per 1 mg PE) was used for hydrolyzing soluble potato starch to maltose. The immobilization improved the catalytic activity of α-amylase at all the reaction conditions studied. The kinetic parameters, K_m (5 and 4 g L^?1 for the regular and activated PE, respectively) and V_max (5 × 10^?7 mol ml^?1 min^?1, almost the same numbers were obtained for the regular and activated PEs) for the immobilized amylase were found to slightly favor the respective values obtained for the free enzyme (K_m = 6.6 g L^?1, V_max = 3.7 × 10^?7 mol ml^?1 min^?1). The enzyme remained bound to PE even after soaking the PE in a starch solution for 72 h and was still found to be weakly active.     

More on sonolytic and sonocatalytic decomposition of Diclofenac using zero-valent iron

The study is an extension of our previous work on sonolytic and sonocatalytic decomposition of Diclofenac-Na (DCF) to depict and highlight further operation parameters of significance, and to assess the effect of a novel home-made catalyst made of magnetic nanoparticles of zero-valent iron (ZVI). It was found that high-frequency was more effective than power ultrasound (20 kHz), and the efficiency was a maximum at 861 kHz, acetate-buffered pH 3.0 and air bubbling provided that samples were prepared from a pre-heated stock solution to enhance solubility of the compound. As such, 40-min sonication rendered nearly complete transformation of DCF to intermediate products that were more biodegradable than itself, but with little mineralization of organic carbon. Catalytic sono-treatment showed that the effect of the catalyst was largest in a non-buffered acidic solution and the rate of DCF elimination increased with increasing concentrations of solids up to a “critical” mass, above which it declined via the coalescence of particles and bubbles. Sonocatalysis using the “effective” solid mass also enhanced the overall degradation or mineralization of the compound as portrayed by the accumulation of chloride and nitrate ions in solution after prolonged contact. The production of excess H₂O₂ during catalysis with ZVI was attributed to the presence of additional and major routes of OH and/or H₂O₂ formation (other than water pyrolysis). The initial rate of DCF degradation in the presence of nanoparticles was found highly sensitive to the mass of solids in solution, declining sharply as the mass exceeded a “critical” effective level. A catalyst efficacy factor was defined as a function of the initial mass ratio of Fe⁰ to DCF and found to be one order of magnitude larger than that obtained by using commercial microparticles with a threefold larger Fe content. The result signifies that the role of aqueous Advanced Fenton reactions (Fe⁰/H₂O₂) was less significant in the presence of nanoparticles relative to that of heterogeneous reactions with reactive Fe and oxygen species on the massive surface areas with enriched reaction/adsorption and nucleation sites.     

Electron Spin Resonance Imaging Probes and a Sample Holder for Thin and Long One-Dimensional Samples

Most electron spin resonance (ESR) experiments involve the use of samples that can be easily placed in millimeter-size tubes and measured efficiently in conventional resonators. However, in some cases, the samples must remain intact, due to which conventional commercial resonators may not be suitable to measure them. Here, we describe a set of three resonators, which can be combined and incorporated as part of a 1-D continuous wave ESR imaging probe to measure and image very thin (~50–500 μm) and very long (~10–30 mm) objects. The dielectric resonators we employ make it possible to greatly enhance spin sensitivity per unit of length––compared to the use of a rectangular ESR cavity, at ~9.3 GHz. In addition, a special sample holder was developed to facilitate the handling and measurement of such thin and long delicate objects, which in our case are the Arabidopsis roots. A detailed design of the resonators, imaging probe, and the sample holder is provided, along with experimental results for the resonator properties, its spin sensitivity, and imaging capability.     

Sonochemical deposition of magnetite on silver nanocrystals

Sonochemical irradiation of iron (II) acetate aqueous solution in presence of silver nanopowder resulted in deposition of magnetite nanoparticles on silver nanocrystals, and imparted them with magnetic properties. The Ag-Fe(3)O(4) nanocomposite is well attracted to a permanent magnet, and demonstrates superparamagnetic behavior typical of nanomaterials in a magnetic field. The characterization of the product by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR TEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS) reveal the presence of two phases of the silver and the magnetite, but no chemical interaction between them has been found. The strong anchoring of magnetite to the nanosilver surface was explained as a result of local melting of silver when the magnetite nucleus is thrown at the silver surface by high speed sonochemical microjets.     

Loading magnetic nanoparticles into sperm cells does not affect their functionality

The spontaneous loading of magnetite nanoparticles into sperm cell was carried out by mixing an aqueous colloidal solution of Fe3O4-PVA with sperm cells (10(8) cells/ml) for 2 h at 37 degrees C suspended in glucose-free modified Tyrode solution. The penetration of the magnetite nanoparticles into the sperm cells was monitored by conventional analytical chemistry. We have demonstrated that the motility and the ability to undergo the acrosome reaction (i.e., the ability to fertilize the egg) were not affected by the presence of the magnetite nanoparticles.     

Electroholographic tunable volume grating in the g44 configuration

The g(44) grating is an electroholographic transmission grating in which the applied field is perpendicular to both the grating vector and the wave vector of the incident beam. It is argued that in this configuration the incident beam traverses through a periodically rotating index ellipsoid. It is shown that in the g(44) configuration the Bragg condition is fulfilled for a specific value of the applied field and for a diffracting beam polarization that is perpendicular to that of the incident beam. Consequently, the g(44) grating can be used as an electrically controlled filter. Tunability of 7 nm is demonstrated in a 2mm thick grating.     

The CoMirror algorithm for solving nonsmooth constrained convex problems

We introduce a first-order Mirror-Descent (MD) type algorithm for solving nondifferentiable convex problems having a combination of simple constraint set X (ball, simplex, etc.) and an additional functional constraint. The method is tuned to exploit the structure of X by employing an appropriate non-Euclidean distance-like function. Convergence results and efficiency estimates are derived. The performance of the algorithm is demonstrated by solving certain image deblurring problems.     

Coating zinc oxide submicron crystals on poly(methyl methacrylate) chips and spheres via ultrasound irradiation

Ultrasound irradiation is used for anchoring zinc oxide submicron crystals with a main diameter and length of 280 nm and 470 nm, respectively, onto the surface of poly(methyl methacrylate) PMMA chips (2 mm diameter), and zinc oxide crystals with a mean diameter and length of 150 nm and 230 nm, respectively, onto the surface of the PMMA spheres (1–10 μm). The zinc oxide crystals were obtained by sonochemical irradiation of a mixture containing the PMMA, zinc (II) acetate dihydrate, ethanol, water, and 24 wt.% aqueous ammonia for 2 h, yielding a PMMA–zinc oxide composite. By controlling the atmosphere and reaction conditions, we could achieve well-adhered zinc oxide crystals on the surface of poly(methyl methacrylate). The resulting zinc oxide–PMMA composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDX), high-resolution scanning electron microscopy (HRSEM), and photoluminescence (PL) spectroscopy. The zinc oxide-deposited PMMA chips (loaded with 0.03–1.0 wt.% ZnO) were successfully homogenized in melt by extrusion and then injection molded into small, disc-shaped samples. These samples were analyzed with respect to their directional spectral optical properties in UV, Vis and IR spectroscopy.