Pulsed ultrasound-assisted extraction of natural antioxidants from mandarin (Citrus deliciosa Tenore) leaves: Experimental and modeling study

Pulsed ultrasound-assisted extraction (PUAE) of flavonoids and polyphenols from mandarin (Citrus deliciosa Tenore) leaves was examined. The response surface methodology (RSM) via face-centered central composite design (FCCD) was used to investigate the effects of extraction time (15–75?min), output amplitude (30–70%), and pH (4–10) to optimize the extraction process. The total phenolic material (TPM) and the total flavonoid material (TFM) and also the consumed energy of horn were measured as responses. Additionally, calorimetric calculations were done to evaluate the ultrasound energy dissipated into the solution. The calculated quadratic models were highly significant (p?R²) of 0.9722, 0.9805, and 0.9983. The results of the present study suggest that 65?min, 68.72?min, 15.00 extraction time, 61%, 59%, and 30% of ultrasound amplitude and 4, 6.7, and 4 pH of solution should be considered as optimal extraction conditions to get the optimum TPM (37.845?mg-GAE/g-DL), TFM (10.709?mg-CE/g-DL), and energy consumption (6130.275 Joule) for PUAE of mandarin leaves, respectively.     

Design of wideband microstrip power divider/combiner with input and output impedance matching for RF energy harvesting applications

Lately, it has been seen that wireless communication systems have been more developed and there has been a huge demand for multi‐spectral transactions. Using circuits for more than one function is a serious requirement in communication technology. Especially, it expected from RF output stages to show the same performance on more than one frequency. To that end, it is required to produce a solution with wideband designs. In this study, a novel power divider/combiner design with a layered conic line has been investigated for the RF energy harvesting applications. The center frequency was set at 2 GHz and concluded with three different designs. In each design, bandwidth and S parameter characteristics were compared according to the number of layers of the transmission, and it was observed that as the number of layers increases, the bandwidth also increases. According to the design result, triple layer Wilkinson power divider was selected to connect to Villard voltage doubler circuit. The Wilkinson power combiner circuit inputs were given between ?10 dBm and 5 dBm input power. As a result, when low input power was given, efficiency was observed about 70%.     

Perfluoroaryl‐Elemental Sulfur SNAr Chemistry in Covalent Triazine Frameworks with High Sulfur Contents for Lithium–Sulfur Batteries

In order to address the challenges associated with lithium–sulfur batteries with high energy densities, various approaches, including advanced designs of sulfur composites, electrolyte engineering, and functional separators, are lately introduced. However, most approaches are effective for sulfur cathodes with limited sulfur contents, i.e., <80 wt%, imposing a significant barrier in realizing high energy densities in practical cell settings. Here, elemental sulfur‐mediated synthesis of a perfluorinated covalent triazine framework (CTF) and its simultaneous chemical impregnation with elemental sulfur via S_NAr chemistry are demonstrated. S_NAr chemistry facilitates the dehalogenation and nucleophilic addition reactions of perfluoroaryl units with nucleophilic sulfur chains, achieving a high sulfur content of 86 wt% in the resulting CTF. The given sulfur‐impregnated CTF, named SF‐CTF, exhibits a specific capacity of 1138.2 mAh g^?1 at 0.05C, initial Coulombic efficiency of 93.1%, and capacity retention of 81.6% after 300 cycles, by utilizing homogeneously distributed sulfur within the micropores and nitrogen atoms of triazine units offering high binding affinity toward lithium polysulfides.     

Highly Hydrophobic ZIF‐8/Carbon Nitride Foam with Hierarchical Porosity for Oil Capture and Chemical Fixation of CO2

The introduction of hierarchical porosity into metal‐organic frameworks (MOFs) has been of considerable interest in gas separation and heterogeneous catalysis due to the efficient mass transfer kinetics through meso/macropores. Here, a facile, scalable approach is reported for the preparation of carbon nitride (CN) foams as structural templates with micrometer‐sized pores and high nitrogen content of 25.6 wt% by the fast carbonization of low‐cost melamine foam. The nitrogen functionalities of CN foam facilitate chemical anchoring and growth of ZIF‐8 (zeolitic imidazolate frameworks) crystals, which leads to the development of hierarchical porosity. The growth of ZIF‐8 crystals also renders CN foam, which is hydrophilic in nature, highly hydrophobic exhibiting 135° of water contact angle due to the enhanced surface roughness, thus creating a natural shield for the MOF crystals against water. The introduction of ZIF‐8 crystals onto the CN foam enables selective absorption of oils up to 58 wt% from water/oil mixtures and also facilitates the highly efficient conversion of CO₂ to chloropropene carbonate in a quantitative yield with excellent product selectivity. Importantly, this present approach could be extended to the vast number of MOF structures, including the ones suffering from water instability, for the preparation of highly functional materials for various applications.     

Selective adsorption of oleuropein from olive (Olea europaea) leaf extract using macroporous resin

Extraction, optimization, and adsorption of oleuropein from olive (Olea europaea) leaves were carried out, respectively. Face-centered composite design model was chosen for designing the experimental conditions for extraction of olive leaves through response surface methodology. Olive leaf extract obtained under the optimum conditions was concentrated by several macroporous resins (Amberlites XAD 2, XAD 4, XAD 7HP, and XAD 16). The crude and purified extracts were evaluated according to their total phenolic material (TPM) and oleuropein concentration. XAD 7HP showed the best performance regarding adsorption (91%) and desorption ratio (97%) for oleuropein. Pseudo-first- and second-order and Elovich kinetic models were efficient to represent the experimental data for the adsorption of TPM and oleuropein with high correlation coefficients. Equilibrium data were fitted to Langmuir and Freundlich isotherms at four different temperature values. The antioxidant capacity of the extracts was evaluated with several assays such as Cupric ion reducing antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl, and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt.     

Determination of ECoG information flow activity based on Granger causality and Hilbert transformation

Analysis of directional information flow patterns among different regions of the brain is important for investigating the relation between ECoG (electrocorticographic) and mental activity. The objective is to study and evaluate the information flow activity at different frequencies in the primary motor cortex. We employed Granger causality for capturing the future state of the propagation path and direction between recording electrode sites on the cerebral cortex. A grid covered the right motor cortex completely due to its size (approx. 8 cm × 8 cm) but grid area extends to the surrounding cortex areas. During the experiment, a subject was asked to imagine performing two activities: movement of the left small finger and/or movement of the tongue. The time series of the electrical brain activity was recorded during these trials using an 8 × 8 (0.016–300 Hz band with) ECoG platinum electrode grid, which was placed on the contralateral (right) motor cortex. For detection of information flow activity and communication frequencies among the electrodes, we have proposed a method based on following steps: (i) calculation of analytical time series such as amplitude and phase difference acquired from Hilbert transformation, (ii) selection of frequency having highest interdependence for the electrode pairs for the concerned time series over a sliding window in which we assumed time series were stationary, (iii) calculation of Granger causality values for each pair with selected frequency. The information flow (causal influence) activity and communication frequencies between the electrodes in grid were determined and shown successfully. It is supposed that information flow activity and communication frequencies between the electrodes in the grid are approximately the same for the same pattern. The successful employment of Granger causality and Hilbert transformation for the detection of the propagation path and direction of each component of ECoG among different sub-cortex areas were capable of determining the information flow (causal influence) activity and communication frequencies between the populations of neurons successfully.     

Selecting the suitable material handling equipment in the presence of vagueness

Selection of the suitable material handling equipment (MHE) is a very difficult task for the manufacturing companies because of the considerable capital investment required. There are many tangible and intangible factors for choosing the suitable MHE. Multiple criteria decision making (MCDM) has been found to be a useful approach to analyze these conflicting factors. The evaluation of MHE alternatives within the frame of various subjective criteria and the weights of the criteria are usually expressed in linguistic terms. This makes fuzzy logic a more natural approach to this kind of problems. This paper proposes a combined MCDM methodology for evaluation and selection of MHE types for a company in the steel construction industry in Istanbul, Turkey. Fuzzy analytic network process (FANP) is utilized for assigning weights of the criteria for MHE selection and fuzzy technique for order preference by similarity to ideal solution (TOPSIS) is used to determine the most proper system alternative using the criteria weights attained by FANP. The selection is based on the compatibility between MHE and production characteristics. Objective is to select the most efficient MHE considering also the cost efficiency. The study was followed by the sensitivity analyses of the results.