Quadrature frequency resolved spectroscopy of upconversion photoluminescence in GeGaS:Er<Superscript>3+</Superscript>: I. Determination of energy transfer upconversion parameter

The article presents the formulas of quadrature frequency resolved spectroscopy (QFRS) on the upconversion photoluminescence (UCPL) of rare-earth (RE) doped materials on the general M-level model. The formulas are derived in matrix-equation form with the first-order perturbation on the rate equations at the M energy-levels of RE ion. The QFRS spectra for three different UCPL processes, i.e., the excited state absorption (ESA), energy transfer upconversion (ETU) and photon avalanche (PA) via cross relaxation process (CRP) in a particular case of M?=?3 are demonstrated with the respective salient features of the excitation power dependence. We have measured the QFRS on the UCPL (⁴ S _3/2 → ⁴ I _15/2) by systematically varying Er-doping in Ge_28.1Ga_6.3S_65.6 chalcogenide glass from 0.01 to 0.5 at.% as well as 975 nm excitation power. Thereby the relaxation rates k ₁ at the intermediate level ⁴ I _11/2, k ₂ at the top level ⁴ S _3/2 and ETU parameter w are determined as a function of Er concentration. The UCPL dynamics on the basis of the formulas for the 3-level model is interpreted in terms of the determined parameters.     

A novel aggregation method for Pythagorean fuzzy multiple attribute group decision making

As an extension of fuzzy set, a Pythagorean fuzzy set has recently been developed to model imprecise and ambiguous information in practical group decision‐making problems. The aim of this paper is to introduce a novel aggregation method for the Pythagorean fuzzy set and analyze possibilities for its application in solving multiple attribute decision‐making problems. More specifically, a new Pythagorean fuzzy aggregation operator called the Pythagorean fuzzy induced ordered weighted averaging‐weighted average (PFIOWAWA) operator is developed. This operator inherits main characteristics of both ordered weighted average operator and induced ordered weighted average to aggregate the Pythagorean fuzzy information. Some of main properties and particular cases of the PFIOWAWA operator are studied. A method based on the proposed operator for multiple attribute group decision making is developed. Finally, we present a numerical example of selection of research and development projects to illustrate applicability of the new approach in a multiple attribute group decision‐making problem.     

Modified progressive random walk with chaotic PRNG

Abstract

In this paper, two modifications are proposed to the Progressive Random Walk (PRW) algorithm in order to address its potentially insufficient search space coverage. The first modification replaces the Pseudo-Random Number Generator (PRNG) with the uniform distribution by the chaotic map based PRNG for generating of the offset values and the second modification is called direction switching and is based on experiment observation. The modifications are implemented into the PRW and the resulting algorithm is called modified Progressive Random Walk. The search space coverage of the two algorithms is compared. Both algorithms are used in macro ruggedness estimation of the CEC2015 benchmark set and the results are discussed.     

The in vivo incorporation of labeled linoleic acid, α-linolenic acid and arachidonic acid into rat liver lipids

The incorporation of 1-¹⁴C-linoleic acid, 1-¹⁴C-α-linolenic acid and 1-¹⁴C-arachidonic acid into rat liver lipids was measured and the per cent distribution of radioactivity into the different lipid fractions determined. Normal rats were injected into the portal vein with the labeled solutions during a one minute period. Livers were quickly frozen, pulverized, and the lipids extracted and fractioned by thin layer chromatography. No significant differences were observed in the amounts of labeled fatty acids incorporated per gram of rat liver. While 1-¹⁴C-linoleic acid and 1-¹⁴C-α-linolenic acid were found in appreciable amounts in the 1,2 diacylglycerol fraction, about one fifth as much 1-¹⁴C-arachidonic acid was esterified in this fraction. 1-¹⁴C-arachidonic acid was the leading acid esterified in the phospholipid fractions.     

Application of diffusion dialysis in hydrometallurgical separation of nickel from spent Raney Ni catalyst

ABSTRACT

The hydrometallurgical separation of nickel from spent Raney Ni catalyst is based on the dissolution of separated nickel slurry in hot diluted sulphuric acid (H₂SO₄) with the addition of an appropriate oxidation agent. Consecutive diffusion dialysis, which was performed in a two-compartment countercurrent dialyzer with an anion-exchange membrane Neosepta-AFN at steady state, enables the removal of excess of H₂SO₄ from a solution of aluminium and nickel sulphate in H₂SO₄ and simple recycling of the isolated H₂SO₄. Next, the obtained dialysate was alkalized using excess of NaOH solution. Using this procedure, the Ni(OH)₂ contaminated with only 8.9 wt.% Al was obtained.     

Gold Nanoparticles Sliding on Recyclable Nanohoodoos—Engineered for Surface‐Enhanced Raman Spectroscopy

Robust, macroscopically uniform, and highly sensitive substrates for surface‐enhanced Raman spectroscopy (SERS) are fabricated using wafer‐scale block copolymer lithography. The substrate consists of gold nanoparticles that can slide and aggregate on dense and recyclable alumina/silicon nanohoodoos. Hot‐spot engineering is conducted to maximize the SERS performance of the substrate. The substrate demonstrates remarkably large surface‐averaged SERS enhancements, greater than 10⁷ (>10⁸ in hot spots), with unrivalled macroscopic signal uniformity as characterized by a coefficient of variation of only 6% across 4 cm. After SERS analyses, the nanohoodoos can be recycled by complete removal of gold via a one‐step, simple, and robust wet etching process without compromising performance. After eight times of recycling, the substrate still exhibits identical SERS performance in comparison to a new substrate. The macroscopic uniformity combined with recyclability at conserved high performance is expected to contribute significantly on the overall competitivity of the substrates. These findings show that the gold nanoparticles sliding on recyclable nanohoodoo substrate is a very strong candidate for obtaining cost‐effective, high‐quality, and reliable SERS spectra, facilitating a wide and simple use of SERS for both laboratorial and commercial applications.     

Integration of biofuels intermediates production and nutrients recycling in the processing of a marine algae

The cost‐effective production of liquid biofuels from microalgae is limited by several factors such as recovery of the lipid fractions as well as nutrients management. Flash hydrolysis, a rapid hydrothermal process, has been successfully applied to fractionate the microalgal biomass into solid biofuels intermediates while recovering a large amount of the nutrients in the aqueous phase (hydrolyzate) in a continuous flow reactor. The aim of the work is to enhance the quality of a high‐ash containing marine algae Nannochloropsis gaditana as biofuel feedstock while recycling nutrients directly for algae cultivation. Characterization of products demonstrated an increase in extractable lipids from 33.5 to 65.5 wt % (dry basis) while retaining the same fatty acid methyl ester profile, in addition to diminution of more than 70 wt % of ash compared to raw microalgae. Moreover, the hydrolyzate was directly used to grow a microalga of the same genus. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1494–1502, 2017     

Light and Strong SiC Networks

The directional freezing of microfiber suspensions is used to assemble highly porous (porosities ranging between 92% and 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb‐like structure and internal strut length in the order of 1–10 μm in size are aligned with an interlayer spacing ranging between 15 and 50 μm. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic microlattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large‐size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03–0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach can be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions.     

Synthesis, conformation and biological evaluation of the enantiomers of 3-fluoro-gamma-aminobutyric acid ((R)- and (S)-3F-GABA): an analogue of the neurotransmitter GABA

Gamma-aminobutyric acid or GABA (1) is one of the major inhibitory amino acid neurotransmitters of the central nervous system. This article describes the first synthesis of both the (R)- and (S)- enantiomers of 3-fluoro-GABA (2, 3F-GABA). DFT calculations were carried out in a continuum solvent model (PCM-B3LYP) to estimate the preferred conformations of 3F-GABA in aqueous solution. NMR coupling constants were calculated for each conformer and were then used to simulate the NMR spectra to evaluate the solution conformation of 3F-GABA. A preliminary evaluation of the 3F-GABA enantiomers shows that they act similarly as agonists of cloned GABA(A) receptors; however, they behave quite differently in a whole animal (Xenopus laevis tadpole model).     

Reduced-illuminance autofluorescence imaging in ABCA4-associated retinal degenerations

The health of the retinal pigment epithelium (RPE) can be estimated with autofluorescence (AF) imaging of lipofuscin, which accumulates as a byproduct of retinal exposure to light. Lipofuscin may be toxic to the RPE, and its toxicity may be enhanced by short-wavelength (SW) illumination. The high-intensity and SW excitation light used in conventional AF imaging could, at least in principle, increase the rate of lipofuscin accumulation and/or increase its toxicity. We considered two reduced-illuminance AF imaging (RAFI) methods as alternatives to conventional AF imaging. RAFI methods use either near-infrared (NIR) light or reduced-radiance SW illumination for excitation of fluorophores. We quantified the distribution of RAFI signals in relation to retinal structure and function in patients with the prototypical lipofuscin accumulation disease caused by mutations in ABCA4. There was evidence for two subclinical stages of macular ABCA4 disease involving hyperautofluorescence of both SW- and NIR-RAFI with and without associated loss of visual function. Use of RAFI methods and microperimetry in future clinical trials involving lipofuscinopathies should allow quantification of subclinical disease expression and progression without subjecting the diseased retina/RPE to undue light exposure.