Solution of a quadratic quaternion equation with mixed coefficients

A comprehensive analysis of the morphology of the solution space for a special type of quadratic quaternion equation is presented. This equation, which arises in a surface construction problem, incorporates linear terms in a quaternion variable and its conjugate with right and left quaternion coefficients, while the quadratic term has a quaternion coefficient placed between the variable and its conjugate. It is proved that, for generic coefficients, the equation has two, one, or no solutions, but in certain special instances the solution set may comprise a circle or a 3-sphere in the quaternion space $\mathbb{H}$. The analysis yields solutions for each case, and intuitive interpretations of them in terms of the four-dimensional geometry of the quaternion space $\mathbb{H}$.Comment: 19 pages, to appear in the Journal of Symbolic Computatio

Antibiotics and drugs: residue determination

Veterinary drugs pose a real risk to human health if their residues are allowed to enter the food chain. Parent drugs and their metabolites can occur in foodstuffs individually or as multicomponent mixtures with enhanced adverse effects. In order to protect the safety of the consumers, the European Union has established lists of forbidden substances, maximum residue limits for authorized drugs, and precise criteria to perform confirmation and screening analyses and to interpret the related results. This article deals with procedures and techniques applied to monitor pharmaceutical products of major concern, discussing advancements in the past 3 years and the future trends in the food safety field. © 2016 Elsevier Ltd. All rights reserved

Chiral separation and analysis of antifungal drugs by chromatographic and electromigration techniques: Results achieved in 2010–2020

AbstractThe determination and separation of enantiomers is an interesting and important topic of research in various fields, e.g., biochemistry, food science, pharmaceutical industry, environment, etc. Although these compounds possess identical physicochemical properties, a pair of enantiomers often has different pharmacological, toxicological, and metabolic activities. For this reason, chiral discrimination by using chromatographic and electromigration techniques has become an urgent need in the pharmaceutical field. This review intends to offer the "state of the art" about the separation of chiral antifungal drugs and several related precursors by both liquid and gas chromatography, as well as electromigration methods. This overview is organized into two sections. The first one describes general considerations on chiral antifungal drugs. The second part deals with the main analytical methods for the enantiomeric discrimination of these drugs, including a brief description of chiral selectors and stationary phases. Moreover, many recent applications attesting the great interest of analytical chemists in the field of enantiomeric separation are presented

The Rare Book Collection of the Library of the Italian National Institute of Health: from the past to the present

The Library of the Istituto Superiore di Sanità (ISS), the Italian National Institute of Health, is the main library for public health and biomedical research in Italy and holds a small but valuable special collection of ancient books. Known as the Rare Book Collection, this fund consists of over 1200 scientific printed volumes published between the XVI and the XIX century. The purpose of this paper is to illustrate the challenges and the process undertaken by the Library to share and digitalize this Collection

An enantioselective high-performance liquid chromatography-mass spectrometry method to study the fate of quizalofop-P-ethyl in soil and selected agricultural products

In this study, the attention was focused on quizalofop-ethyl, a chiral herbicide whose formulation has recently been marketed as quizalofop-P-ethyl, i.e. the (+)-enantiomer exhibiting herbicidal activity. To verify the real enantiomeric purity of this product as well as to study its environmental fate, the enantioselective separation of the P- and M- enantiomers of quizalofop-ethyl was achieved on Lux Cellulose-2 column (3-chloro,4-methylphenilcarbamate cellulose) under isocratic conditions in polar organic mode. Once established that the commercial formulation contains ̃0.6% (enantiomeric fraction) of M as an impurity, an HPLC-MS/MS method was developed, validated and applied to the analysis of soil, carrots and turnips treated with the herbicide. A simple solid-liquid extraction allowed recoveries greater than 70%; limits of detections of P and M enantiomers were below 5 ng/g. The analyses of the real samples showed a modification of the enantiomeric fraction of quizalofop-M-ethyl between the commercial formulation (EFM = 0.63 & PLUSMN; 0.03%) and the analysed matrices (EFM = 7.6 & PLUSMN; 0.1% for carrots; EFM = 0% for the other matrices). This outcome highlighted the occurrence of an enantioselective biotic dissipation, responsible for a greater persistency of the distomer in carrots. On the other hand, since screening analyses revealed the occurrence of residues of the metabolite quizalofop-acid with the same EFs as the ester precursor, it was concluded that the hydrolytic conversion was an abiotic process

The rotation of white lupin (Lupinus albus L.) with metal-accumulating plant crops: A strategy to increase the benefits of soil phytoremediation

Most of the plants employed to remove metals from contaminated soils are annuals and have a seed-to- seed life cycle of a few months, usually over spring and summer. Consequently, for most of the year, fields are not actively cleaned but are completely bare and subject to erosion by water and wind. The objective of this study was to evaluate the benefits of using Lupinus albus as a winter crop in a rotation sequence with a summer crop ideally selected for phytoextraction, such as industrial hemp. Lupin plants were grown in two alkaline soil plots (heavy metal-contaminated and uncontaminated) of approximately 400 m 2 each after the cultivation and harvest of industrial hemp. A smaller-scale parallel pot experiment was also performed to better understand the lupin behavior in increasing concentrations of Cd, Cu, Ni and Zn. White lupin grew well in alkaline conditions, covering the soil during the winter season. In few months plants were approximately 40e50 cm high in both control and contaminated plots. In fields where the bioavailable fraction of metals was low (less than 12%), plants showed a high tolerance to these contaminants. However, their growth was affected in some pot treatments in which the concen- trations of assimilable Cu, Zn and Ni were higher, ranging from approximately 40e70% of the total concentrations. The lupin's ability to absorb heavy metals and translocate them to shoots was negligible with respect to the magnitude of contamination, suggesting that this plant is not suitable for extending the period of phytoextraction. However, it is entirely exploitable as green manure, avoiding the appli- cation of chemical amendments during phytoremediation. In addition, in polluted fields, white lupin cultivation increased the soil concentration of live bacteria and the bioavailable percentage of metals. On average live bacteria counts per gram of soil were 65 10 6 ± 18 10 6 and 99 10 6 ± 22*10 6 before and after cultivation, respectively. The percentages of bioavailable Cu, Pb, Ni, Zn and Cr, which were 5.7 ± 0.7, 5.3 ± 1.7, 1.2 ± 0.1, 12 ± 1.5 and 0.1 ± 0.02%, respectively, before lupin growth, increased to 9.6 ± 1.6, 7 ± 2, 2 ± 0.3, 14 ± 1.5 and 0.1 ± 0.02% after lupin harvest. On the whole, our results indicate that the winter cultivation of white lupin in sequence with a metal- accumulator summer crop can improve the recovery of soil quality during the phytoextraction period. It improves the safety of the area, limiting additional ecological and human health problems, and enhances soil health by avoiding the use of chemical amendments and by increasing the levels of viable microorganism

Room-temperature synthesis of 2D-Ti3C2Tx nano-sheets by organic base treatment

The growing demand for improved electrochemical performance in energy storage systems has stimulated research into advanced two-dimensional (2D) materials for electrodes. In this work, we obtain a layered MXene compound by exfoliating a titanium aluminum carbide precursor using tetramethylammonium hydroxide (TMAOH) ions in a full room temperature process followed by manual shaking. The hexagonal crystal structure and composition of the layered materials are characterized using different techniques. X-Ray diffraction shows the formation of 2D nano-sheets before and after the TMAOH treatment via its characteristic (002) diffraction peak, bringing to light an increase in the interlayer spacing after treatment. Scanning electron microscopy images confirm the layered morphology, whose composition is determined by energy dispersive x-ray analysis for the bulk material and by x-ray photoelectron spectroscopy for the surface of the obtained compounds. This study demonstrates a promising route to enhance delamination of this MXene 2D material in a low-cost room-temperature approach

Influence of Nanoaggregation Routes on the Structure and Thermal Behavior of Multiple-Stimuli-Responsive Micelles from Block Copolymers of Oligo(ethylene glycol) Methacrylate and the Weak Acid [2-(Hydroxyimino)aldehyde]butyl Methacrylate

In this work, we compare nanoaggregation driven by pH-induced micellization (PIM) and by the standard solvent displacement (SD) method on a series of pH-, light-, and thermosensitive amphiphilic block copolymers. Specifically, we investigate poly(HIABMA)-b-poly(OEGMA) and poly(HIABMA)-b-poly(DEGMA-r-OEGMA), where HIABMA = [(hydroxyimino)aldehyde]butyl methacrylate, OEGMA = oligo(ethylene glycol)methyl ether methacrylate, and DEGMA = di(ethylene glycol)methyl ether methacrylate. The weakly acidic HIA group (pKa ≈ 8) imparts stability to micelles at neutral pH, unlike most of the pH-responsive copolymers investigated in the literature. With SD, only some of our copolymers yield polymeric micelles (34-59 nm), and their thermoresponsivity is either poor or altogether absent. In contrast, PIM affords thermoresponsive, smaller micelles (down to 24 nm), regardless of the polymer composition. In some cases, cloud points are remarkably well defined and exhibit limited hysteresis. By combining turbidimetric, dyamic light scattering, and small-angle X-ray scattering measurements, we show that SD yields loose micelles with POEGMA segments partly involved in the formation of the hydrophobic core, whereas PIM yields more compact core-shell micelles with a well-defined PHIABMA core. We conclude that pH-based nanoaggregation provides advantages over block-selective solvation to obtain compact micelles exhibiting well-defined responses to external stimuli

The impact of televised sports on adult nonfiction sports publishing

Thyreostats can be used fraudulently to promote a rapid weight increase of breeding animals at low cost. Their severe toxicological effects impose the development of reliable analytical methods to be used in monitoring plans. This work describes an alternative approach to isolate residues of thiouracil, methyl-thiouracil, propyl-thiouracil, phenyl-thiouracil, tapazole and mercaptobenzimidazole from bovine muscle tissue. The developed procedure is based on three steps: i) matrix solid phase dispersion with C18 for the preliminary sample preparation; ii) subcritical water extraction (SWE) at 160°C and 100 bar; iii) clean-up on an Oasis HLB cartridge. The quantitative determination was performed by liquid chromatography-electrospray-tandem mass spectrometry (LC-MS/MS) in dual polarity ionization by using internal standardization. The SWE-LC-MS/MS method was validated according to the identification criteria of the Commission decision 2002/657/EC. The relative recoveries ranged from 72% to 97%; within-lab reproducibility was less than 18%. The decision limit and the detection capability of all analytes were below the recommended concentration, set at 10 µg kg−1, but the validation results demonstrated that this method could only be applied for screening of thiouracil and methyl-thiouracil. Besides the analytical advantages related to the use of water as solvent extraction, the procedure allowed significant removal of lipids, whose detrimental effects on instrumentation and MS sensitivity are well-known