Interval-Valued Rank in Finite Ordered Sets

We consider the concept of rank as a measure of the vertical levels and positions of elements of partially ordered sets (posets). We are motivated by the need for algorithmic measures on large, real-world hierarchically-structured data objects like the semantic hierarchies of ontological databases. These rarely satisfy the strong property of gradedness, which is required for traditional rank functions to exist. Representing such semantic hierarchies as finite, bounded posets, we recognize the duality of ordered structures to motivate rank functions with respect to verticality both from the bottom and from the top. Our rank functions are thus interval-valued, and always exist, even for non-graded posets, providing order homomorphisms to an interval order on the interval-valued ranks. The concept of rank width arises naturally, allowing us to identify the poset region with point-valued width as its longest graded portion (which we call the “spindle”). A standard interval rank function is naturally motivated both in terms of its extremality and on pragmatic grounds. Its properties are examined, including the relationship to traditional grading and rank functions, and methods to assess comparisons of standard interval-valued ranks.     

Light-Responsive Oligothiophenes Incorporating Photochromic Torsional Switches

We present a quaterthiophene and sexithiophene that can reversibly change their effective π-conjugation length through photoexcitation. The reported compounds make use of light-responsive molecular actuators consisting of an azobenzene attached to a bithiophene unit by both direct and linker-assisted bonding. Upon exposure to 350 nm light, the azobenzene undergoes trans-to-cis isomerization, thus mechanically inducing the oligothiophene to assume a planar conformation (extended π-conjugation). Exposure to 254 nm wavelength promotes azobenzene cis-to-trans isomerization, forcing the thiophenic backbones to twist out of planarity (confined π-conjugation). Twisted conformations are also reached by cis-to-trans thermal relaxation at a rate that increases proportionally with the conjugation length of the oligothiophene moiety. The molecular conformations of quaterthiophene and sexithiophene were characterized by using steady-state UV-vis spectroscopy, X-ray crystallography and quantum-chemical modeling. Finally, we tested the proposed light-responsive oligothiophenes in field-effect transistors to probe the photo-induced tuning of their electronic properties.     

A theoretical spectroscopy investigation of oxosumanenes

Using Density Functional Theory approaches, we investigate the structure and spectroscopic signatures of sumanene, monooxosumanene and trioxosumanene, three synthesised bowl-shaped compounds. The simulated properties include geometries, charges, polarisabilities, infrared and UV/visible spectra as well as complexation energies. Refined approaches have been considered (anharmonic frequencies, state-specific solvent model, dispersion-corrected DFT…) and a valuable agreement with experimental reference values is reached for most properties. The evolution of the electronic features of sumanene upon oxidation has been rationalised.     

Bioactive molecules in Kalanchoe pinnata leaves: extraction, purification, and identification

Kalanchoe pinnata (Lam.) Pers. (syn. Bryophyllum pinnatum; family Crassulaceae) is a popular plant used in traditional medicine in many temperate regions of the world and particularly in South America. In Guyana, the leaves are traditionally used as an anti-inflammatory and antiseptic to treat coughs, ulcers, and sores. The purpose of this study was to implement a method for targeting and identifying molecules with antimicrobial activity, which could replace chemical preservatives in cosmetic applications. The leaves were extracted by a method based on pressurized liquid extraction (PLE), using different solvents. A study of antimicrobial activity and cytotoxicity tests were performed to select the most interesting extract. To isolate one or more active molecules, the selected crude extract was fractionated by centrifugal partition chromatography (CPC) and then antimicrobial activity and cytotoxicity of each fraction were tested under the same procedure. The last step consisted of identifying the main compounds in the most active fraction by LC-MS/MS.     

Crystalline microstructure and mechanical properties of crosslinked EPDM aged under gamma irradiation

The morphology and the mechanical properties at room temperature of crosslinked EPDM irradiated or not have been studied. It has been shown that these materials are composed of two phases: semicrystalline zones with a crystallinity ratio of 20% and mainly amorphous zones. The semicrystalline zones make a continuous path through the film and therefore control the mechanical properties of the material below the melting temperature. As irradiation (in the tested range of irradiation dose) and crosslinking degree have no significant influence on the arrangement and proportion of the crystalline lamellae, all samples have nearly the same mechanical behavior at small strains. At large strains, the interactions between amorphous and crystalline parts in semicrystalline zones play the main role in the mechanical response; irradiation, by degradation of these interactions, leads to a smaller hardening phenomenon and a decrease in elongation at break. From an application point of view, in spite of the low crystallinity fraction of these materials, the presence of an important number of crystallites, as evidenced by SAXS measurements, strongly limits the consequences of irradiation on the mechanical properties. However, the mechanical reinforcement strongly depending on the presence of these crystallites, it is therefore highly sensitive to temperature: this can be an important issue for the applications of these materials since their use temperature is close to the crystallite melting temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 97–105, 2010     

Evaluation of Sample Preparation Methods for Non-Target Screening of Organic Micropollutants in Urban Waters Using High-Resolution Mass Spectrometry

Non-target screening (NTS) has gained interest in recent years for environmental monitoring purposes because it enables the analysis of a large number of pollutants without predefined lists of molecules. However, sample preparation methods are diverse, and few have been systematically compared in terms of the amount and relevance of the information obtained by subsequent NTS analysis. The goal of this work was to compare a large number of sample extraction methods for the unknown screening of urban waters. Various phases were tested for the solid-phase extraction of micropollutants from these waters. The evaluation of the different phases was assessed by statistical analysis based on the number of detected molecules, their range, and physicochemical properties (molecular weight, standard recoveries, polarity, and optical properties). Though each cartridge provided its own advantages, a multilayer cartridge combining several phases gathered more information in one single extraction by benefiting from the specificity of each one of its layers.     

Rheology and Drug Release Properties of Bioresorbable Hydrogels Prepared from Polylactide/Poly(ethylene glycol) Block Copolymers

Ring-opening polymerization of L(D)-lactide was realized in the presence of poly(ethylene glycol) (PEG), yielding PLLA/PEG and PDLA/PEG block copolymers. Bioresorbable hydrogels were prepared from aqueous solutions containing both copolymers due to interactions and stereocomplexation between PLLA and PDLA blocks. The rheological properties of the hydrogels were investigated under various conditions by changing copolymer concentration, temperature, time and frequency. The hydrogels constitute a dynamic and evolutive system because of continuous formation/destruction of crosslinks and degradation. Drug release studies were performed on hydrogel systems containing bovine serum albumin (BSA). The release profiles appear almost constant with little burst effect. The release rate depends not only on gelation conditions such as time and temperature, but also on factors such as drug load, as well as molar mass and concentration of the copolymers.     

Confocal Raman Spectroscopic Imaging for Evaluation of Distribution of Nano-Formulated Hydrophobic Active Cosmetic Ingredients in Hydrophilic Films

Film-forming systems are highly relevant to the topical administration of active ingredients (AI) to the body. Enhanced contact with the skin can increase the efficacy of delivery and penetration during prolonged exposure. However, after the evaporation of volatile solvents to form a thin film, the distribution of the ingredient should remain homogenous in order to ensure the effectiveness of the formula. This is especially critical for the use of hydrophobic molecules that have poor solubility in hydrophilic films. In order to address this concern, hydroxyphenethyl esters (PHE) of Punica granatum seed oil were prepared as a nanosuspension stabilised by poloxamers (NanoPHE). NanoPHE was then added to a formulation containing polyvinyl alcohol (PVA) as a film forming agent, Glycerol as a plasticiser and an antimicrobial agent, Sepicide^TM HB. Despite their reliability, reference methods such as high-performance liquid chromatography are increasingly challenged due to the need for consumables and solvents, which is contrary to current concerns about green industry in the cosmetics field. Moreover, such methods fail to provide spatially resolved chemical information. In order to investigate the distribution of ingredients in the dried film, Confocal Raman imaging (CRI) coupled to Non-negatively Constrained Least Squares (NCLS) analysis was used. The reconstructed heat maps from a range of films containing systematically varying PHE concentrations highlighted the changes in spectral contribution from each of the ingredients. First, using NCLS scores it was demonstrated that the distributions of PVA, Glycerol, Sepicide^TM HB and PHE were homogenous, with respective relative standard deviations (RSD) of 3.33%, 2.48%, 2.72% and 6.27%. Second, the respective relationships between ingredient concentrations in the films and their Raman responses, and the spectral abundance were established. Finally, a model for absolute quantification for PHE was be constructed using the percentage of spectral abundance. The prepared %w/w concentrations regressed against predicted %w/w concentrations, displaying high correlation (R² = 0.995), while the Root Mean Squared Error (0.0869% w/w PHE) confirmed the precision of the analysis. The mean percent relative error of 3.75% indicates the accuracy to which the concentration in dried films could be determined, further supporting the suitability of CRI for analysis of composite solid film matrix. Ultimately, it was demonstrated that nanoformulation of hydrophobic PHE provides homogenous distribution in PVA based film-forming systems independent of the concentration of NanoPHE used in the formula.     

Bulk analysis by IR laser ablation inductively coupled plasma atomic emission spectrometry

Two laser ablation systems dedicated to bulk analysis were evaluated for steel and PVC samples, using inductively coupled plasma atomic emission spectrometry detection. These systems were characterized by the use of a Nd:YAG laser operating at 1064 nm, the absence of observation device and a large laser spot size. The 1064 nm wavelength was selected to avoid the use of frequency-multiplying optics, and to be less critical to the sampling position. Calibration graphs and limits of detection are given for both types of materials. LODs were in the range 3–120 μg/g for steel, and in the range 0.07–15 μg/g for PVC. In the case of steel samples, similar calibration graph slopes were obtained between polished and unpolished samples.