Anti‐Stokes Raman spectroscopy as a method to identify the metallic and semiconducting configurations of double‐walled carbon nanotubes

Although Raman spectra reveal, as a signature of double‐walled carbon nanotubes (DWCNTs), two radial breathing mode (RBM) lines associated with the inner and outer tubes, the specification of their nature as metallic or semiconducting remains a topic for debate. Investigating the spectral range of the RBM lines, we present a new procedure of the indexing of the semiconducting or metallic nature of the inner and outer shell that forms the DWCNT. The procedure exploits the difference between the intensities of recorded anti‐Stokes Raman spectrum and the anti‐Stokes spectrum calculated by applying the Boltzmann formulae to the recorded Stokes spectrum. The results indicate that the two spectra do not coincide with what should happen in a normal Raman process, namely, that there are RBM lines of the same intensity in both spectra, as well as RBM lines of higher intensity that are observed in the calculated spectrum. This discrepancy results from the surface‐enhanced Raman scattering mechanism that operates differently on metallic or semiconducting nanotubes. In this context, the analysis of the RBM spectrum can reveal pairs of lines associated with the inner/outer shell structure of DWCNT, and when the intensities between the recorded and calculated spectra coincide, the nanotube is metallic; otherwise, the nanotube is semiconducting. Copyright © 2014 John Wiley & Sons, Ltd.     

Securing a Supramolecular Architecture by Tying a Stopper Knot

We report on a rotaxane‐like architecture secured by the in situ tying of an overhand knot in the tris(2,6‐pyridyldicarboxamide) region of the axle through complexation with a lanthanide ion (Lu³⁺). The increase in steric bulk caused by the knotting locks a crown ether onto the thread. Removal of the lutetium ion unties the knot, and when the axle binding site for the ring is deactivated, the macrocycle spontaneously dethreads. When the binding interaction is switched on again, the crown ether rethreads over the 10 nm length of the untangled strand. The overhand knot can be retied, relocking the threaded structure, by once again adding lutetium ions.     

Characterization of two electrode systems for corona-charging of non-woven filter media

The aim of this paper is to provide a better understanding of the corona-charging process of non-woven electret filters for automotive and medical applications. The experiments were performed on polypropylene samples: 500-μm-thick non-woven fabrics (fiber diameter: 24 μm), laid on a grounded plate electrode and subjected to positive or negative corona generated either by a dual wire–cylinder electrode or by a triode-type electrode set. The paper reports the results of current–voltage characteristics measurements, as well as the repartition of the current density at the surface of the grounded electrode.     

Discrete element modeling of triboelectric charging of insulating materials in vibrated granular beds

The triboelectric charging of granular insulating materials is very difficult to predict because of the complex physical mechanism involved in this process. The aim of this paper is to describe in detail the implementation of a numerical model of the tribocharging process taking place in vertically-vibrated beds of granular plastics. The charge exchanged in granule-to-granule and granule-to-wall collisions is computed by taking into account some electrical properties of the respective materials, their area of contact and the effect of the electric field generated by a system of high-voltage electrodes and by the charges of the granules themselves. The electrical model is coupled with the Discrete Element Method (DEM) which undertakes the whole granular dynamics and allows to compute accurately the contact surface of two colliding particles which is involved in the triboelectric charging model.Beside the numerical simulations an experiment has been conducted with mixtures of mm-size polyamide and polycarbonate granules in a laboratory vibrated bed to validate the model. The numerical results have been found to be in good agreement with the experimental ones.     

Tannins analysis from different medicinal plants extracts using MALDI-TOF and MEKC

The matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF) and micellar electrokinetic chromatography (MEKC) methods were used to identify and quantify five tannins, (+)-catechin, (?)-epigallocatechin, (?)-epigallocatechin gallate, (?)-epicatechin gallate and (?)-epicatechin, from aqueous, ethanolic and acetonic extracts of Calendula officinalis, Hy-pericum, perforatum, Galium verum and Origanum vulgare. The MALDI-TOF technique was used for screening tannins monomers and oligomers in plant extracts. The sandwich method and matrix 2,5-dihydroxybenzoic acid with a concentration of 10 mg mL^?1 in acetonitrile/ultrapure water/trifluoroacetic acid (20: 80: 0.1, vol.) were used. The electrophoretic method developed for the separation and quantification of 5 catechins in 15 min exhibited good efficiency and precision, low limits of detection (0.0032–0.0153 μ.g mL-¹) and quantification (0.0096–0.0466 μ.g mL^?1). The correlation coefficients (R²) exceeded 0.9986 and the recovery values ranged between 94.25 % and 102.50 %. The present work provides new information on some of the less studied compounds present in plants frequently used in traditional medicine.     

Neuroprotective and Antioxidant Enhancing Properties of Selective Equisetum Extracts

The sterile stems belonging to the Equisetum species are often used in traditional medicine of various nations, including Romanians. They are highly efficient in treating urinary tract infections, cardiovascular diseases, respiratory tract infections, and medical skin conditions due to their content of polyphenolic derivatives that have been isolated. In this regard, this study aimed to provide the chemical composition of the extracts obtained from the Equisetum species (E. pratense, E. sylvaticum, E. telmateia) and to investigate the biological action in vitro and in vivo. For the chemical characterization of the analyzed Equisetum species extracts, studies were performed by using ultra-high-performance liquid chromatography (UHPLC-DAD). In vitro evaluation of the antioxidant activity of the plant extracts obtained from these species of Equisetum genus was determined. The neuroprotective activity of these three ethanolic extracts from the Equisetum species using zebrafish tests was determined in vivo. All obtained results were statistically significant. The results indicate that E. sylvaticum extract has a significant antioxidant activity; whereas, E. pratense extract had anxiolytic and antidepressant effects significantly higher than the other two extracts used. All these determinations indicate promising results for the antioxidant in vitro tests and neuroprotective activity of in vivo tests, particularly mediated by their active principles.     

Multifractality through Non-Markovian Stochastic Processes in the Scale Relativity Theory. Acute Arterial Occlusions as Scale Transitions

By assimilating biological systems, both structural and functional, into multifractal objects, their behavior can be described in the framework of the scale relativity theory, in any of its forms (standard form in Nottale’s sense and/or the form of the multifractal theory of motion). By operating in the context of the multifractal theory of motion, based on multifractalization through non-Markovian stochastic processes, the main results of Nottale’s theory can be generalized (specific momentum conservation laws, both at differentiable and non-differentiable resolution scales, specific momentum conservation law associated with the differentiable–non-differentiable scale transition, etc.). In such a context, all results are explicated through analyzing biological processes, such as acute arterial occlusions as scale transitions. Thus, we show through a biophysical multifractal model that the blocking of the lumen of a healthy artery can happen as a result of the “stopping effect” associated with the differentiable-non-differentiable scale transition. We consider that blood entities move on continuous but non-differentiable (multifractal) curves. We determine the biophysical parameters that characterize the blood flow as a Bingham-type rheological fluid through a normal arterial structure assimilated with a horizontal “pipe” with circular symmetry. Our model has been validated based on experimental clinical data.     

Rapid,non-destructive determination of butter adulteration by means of photopyroelectric (PPE) calorimetry

The study focuses on the application of the photopyroelectric (PPE) technique combined with gas chromatography to detect adulteration of cow milk-obtained butter. The thermal diffusivity and effusivity have been directly measured using back and front PPE detection, respectively, and the results have been correlated with the composition of adulterated butter samples. The back detection configuration has been used in the case of butter adulterated with palm oil, and a possible correlation of the thermal diffusivity with total amount of monounsaturated fatty acids composition has been proposed. For butter adulterated with soy milk, we used the front PPE configuration in order to measure the samples’ thermal effusivity. A strong dependence of the value of thermal effusivity as a function of soy milk content was found.