Liquid-Liquid Extraction of Uranium(VI) from Aqueous Solution using 1-Hydroxyalkylidene-1,1-diphosphonic Acids

The extraction of uranium(VI) from aqueous solutions has been investigated using 1-hydroxyhexadecylidene-1,1-diphosphonic acid (HHDPA) and 1-hydroxydodecylidene-1, 1-diphosphonic acid (HDDPA), which were synthesized and characterized by elemental analysis and by FT-IR, ¹H NMR, ³¹P NMR spectroscopy. In this article, we propose a tentative assignment for the shifts of those two ligands and their specific complexes with uranium(VI). We carried out the extraction of uranium(VI) by HHDPA and HDDPA from [carbon tetrachloride?+?2-octanol (v/v: 90%/10%)] solutions. Various factors such as contact time, pH, organic/aqueous phase ratio, and extractant concentration were considered. The optimum conditions obtained were: contact time?=?20 min, organic/aqueous phase ratio?=?1, pH value?=?3.0, and extractant concentration?=?0.3 M. The extraction yields are more significant in the case of the HHDPA which is equipped with a hydrocarbon chain, longer than that of the HDDPA. Logarithmic plots of the uranium(VI) distribution ratio vs. pH_eq and the extractant concentration showed that the ratio of extractant to extracted uranium(VI) (ligand/metal) is 2:1. The formula of the complex of uranium(VI) with the HHDPA and the DHDPA is UO₂(H₃L)₂ (HHDPA and DHDPA are denoted as H₄L). A spectroscopic analysis showed that coordination of uranium(VI) takes place via oxygen atoms.     

A robust power control strategy to enhance LVRT capability of grid‐connected DFIG‐based wind energy systems

This paper presents a new robust and effective control strategy to mitigate symmetrical voltage dips in a grid‐connected doubly fed induction generator (DFIG) wind energy conversion system without any additional hardware in the system. The aim is to control the power transmitted to the grid so as to keep the electrical and mechanical quantities above their threshold protection values during a voltage dip transient. To achieve this, the references of the powers are readjusted to adapt the wind energy conversion system to the fault conditions. Robust control strategies, combining the merits of sliding mode theory and fuzzy logic, are then proposed in this paper. These controllers are derived from the dynamic model of the DFIG considering the variations in the stator flux generated by the voltage drop. This approach is found to yield better performance than other control design methods which assume the flux in the stator to remain constant in amplitude. This control scheme is compliant with the fault‐ride‐through grid codes which require the wind turbine generator to remain connected during voltage dips. A series of simulation scenarios are carried out on a 3‐MW wind turbine system to demonstrate the effectiveness of the proposed control schemes under voltage dips and parameter uncertainty conditions.     

Antimicrobial activity of Pistacia lentiscus and Satureja montana essential oils against Listeria monocytogenes CECT 935 using laboratory media: Efficacy and synergistic potential in minced beef

The aim of this study was to optimize the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria monocytogenes (L. monocytogenes) serovar 4b CECT 935 using laboratory media and minced beef stored at 5 ± 1 °C. Commercial EOs obtained from leave parts of Mediterranean Pistacia lentiscus (P. lentiscus) and Satureja montana (S. montana) were analyzed by gas chromatography–mass spectrometry (GC–MS). The main components of EOs obtained were β-myrcene (15.18%) and carvacrol (29.19%), respectively for P. lentiscus and S. montana. The in vitro antimicrobial activity of both EOs was evaluated against L. monocytogenes using the agar diffusion technique, the minimum inhibitory concentrations (MIC) were also determined against the same microorganism using the broth microdilution method. According to the diameters of inhibition, S. montana EO had more antibacterial effects than that from P. lentiscus. MICs showed a range of 0.03 and 0.10% (vol/vol) respectively for S. montana and P. lentiscus. S. montana and P. lentiscus EOs were added respectively in minced beef (twofold MIC values) at 0.06 and 0.20%, experimentally inoculated with L. monocytogenes at a level of 3 × 10⁵ CFU/g and stored at 5 ± 1 °C during one week. S. montana EO was the more effective (P < 0.05) against target bacteria. P. lentiscus EO also demonstrated antibacterial effect against the same bacterium. EO combinations were also investigated in minced beef and P. lentiscus combined with S. montana had synergistic effects. This work shows that the combined EOs might be more effective against L. monocytogenes when applied to minced beef at the ratio of 1/1 to 2/2 according to the MIC values. Sensory evaluation revealed that minced beef treated with EOs was acceptable by panelists at the levels used.     

A Novel Active Learning Method Using SVM for Text Classification

Support vector machines (SVMs) are a popular class of supervised learning algorithms, and are particularly applicable to large and high-dimensional classification problems. Like most machine learning methods for data classification and information retrieval, they require manually labeled data samples in the training stage. However, manual labeling is a time consuming and errorprone task. One possible solution to this issue is to exploit the large number of unlabeled samples that are easily accessible via the internet. This paper presents a novel active learning method for text categorization. The main objective of active learning is to reduce the labeling effort, without compromising the accuracy of classification, by intelligently selecting which samples should be labeled. The proposed method selects a batch of informative samples using the posterior probabilities provided by a set of multi-class SVM classifiers, and these samples are then manually labeled by an expert. Experimental results indicate that the proposed active learning method significantly reduces the labeling effort, while simultaneously enhancing the classification accuracy.     

Growth and characterization of totally relaxed InGaAs thick layers on strain-relaxed paramorphic InP substrates

In this paper, we present a technological process that can be used to prepare strain-relaxed InAsP/InGaAs bilayer membranes, 0.8% lattice mismatched to InP substrates, with diameters up to 300 μm. It is shown that high-quality thick In_0.65Ga_0.35As layers can be grown fully relaxed on these membranes, without any structural defect, as demonstrated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoluminescence (PL) characterizations. The critical thickness of InAs layers grown on InAs_0.25P_0.75 templates is enhanced from 15 ? to 60 ? when compared to InP substrates.     

Purification and characterisation of milk‐clotting and caseinolytic activities of pepsin isolated from adult sheep abomasa

Ovine pepsin was isolated and assessed for its milk‐clotting properties and caseinolytic activity in comparison with commercial chymosin. Ovine pepsin showed similar responses to variations in pH, temperature and CaCl₂ concentration of milk compared with chymosin, although its pH sensitivity was higher. SDS‐PAGE electrophoretic analysis of the casein fractions treated with ovine pepsin showed that alpha‐casein was more susceptible to proteolysis than beta‐casein, in contrast to chymosin. Curd‐firming properties of skim milk gels obtained with ovine pepsin and chymosin were evaluated by Gelograph under the same conditions. Curd produced using ovine pepsin was less firm than that made with chymosin.     

3D Printing of Small-Scale Soft Robots with Programmable Magnetization

Soft magnetic structures having a non-uniform magnetization profile can achieve multimodal locomotion that is helpful to operate in confined spaces. However, incorporating such magnetic anisotropy into their body is not straightforward. Existing methods are either limited in the anisotropic profiles they can achieve or too cumbersome and time-consuming to produce. Herein, a 3D printing method allowing to incorporate magnetic anisotropy directly into the printed soft structure is demonstrated. This offers at the same time a simple and time-efficient magnetic soft robot prototyping strategy. The proposed process involves orienting the magnetized particles in the magnetic ink used in the 3D printer by a custom electromagnetic coil system acting onto the particles while printing. The resulting structures are extensively characterized to confirm the validity of the process. The extent of orientation is determined to be between 92% and 99%. A few examples of remotely actuated small-scale soft robots that are printed through this method are also demonstrated. Just like 3D printing gives the freedom to print a large number of variations in shapes, the proposed method also gives the freedom to incorporate an extensive range of magnetic anisotropies.