Search results for "wave"
showing 10 items of 6009 documents
Diffusion Acceleration in Randomly Switching Sawtooth Potential
2005
We investigate an overdamped Brownian motion in symmetric sawtooth periodic potential switched by Markovian dichotomous noise between two configurations. The two configurations differ each other by a translation of half of period. The calculation of the effective diffusion coefficient is reduced to the mean first‐passage time problem, and we obtain the exact expression valid for arbitrary mean rate of switchings and arbitrary intensity of white Gaussian noise. We find the area at parameters plane where acceleration of diffusion in comparison with the free diffusion case takes place.
Extraordinary tuning of a nanocavity by a near-field probe
2011
Abstract We report here an experimental observation of an extraordinary near-field interaction between a local probe and a small-volume solid-state nanocavity. We directly compare the normally observed near-field interaction regime driven by the perturbation theory and then report the extraordinary interaction regime. Subsequently, we show that the cavity can take up to 2 min to recover from this interaction after removing the probe and that leads to an extraordinary blue-shift of the cavity resonance wavelength (∼15 nm) which depends on the probe motion above the cavity and not the position. The reasons for this effect are not fully understood yet but we try to give some explanations.
Anthracene Fluorescence Quenching by a Tetrakis (Ketocarboxamide) Cavitand
2014
Quenching of both fluorescence lifetime and fluorescence intensity of anthracene was investigated in the presence of a newly derived tetrakis (ketocarboxamide) cavitand at various concentrations. Time-correlated single photon counting method was applied for the lifetime measurements. A clear correlation between the fluorescence lifetime of anthracene as a function of cavitand concentration in dimethylformamide solution was observed. The bimolecular collisional quenching constant was derived from the decrease of lifetime. Fluorescence intensity was measured in the emission wavelength region around 400 nm as a result of excitation at 280 nm. Effective quenching was observed in the presence of…
Effects of Ultrasound-Assisted Extraction and Solvent on the Phenolic Profile, Bacterial Growth, and Anti-Inflammatory/Antioxidant Activities of Medi…
2020
© 2020 by the authors.
Phenol profiling and nutraceutical potential of Lycium spp. Leaf extracts obtained with ultrasound and microwave assisted techniques
2019
In recent years, agricultural and industrial residues have attracted a lot of interest in the recovery of phytochemicals used in the food, pharmaceutical, and cosmetic industries. In this paper, a study on the recovery of phenol compounds from Lycium spp. leaves is presented. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) have been used with alcoholic and hydroalcoholic solvents. Methanolic UAE was the most successful technique for extracting phenols from Lycium leaves, and we used on leaves from L. barbarum and L. chinense cultivated in Italy. The extracts were then characterized as regards to the antioxidant properties by in vitro assays and the phenol profil…
Valorization of Wastewater from Table Olives: NMR Identification of Antioxidant Phenolic Fraction and Microwave Single-Phase Reaction of Sugary Fract…
2021
The table olive industry is producing a huge amount of wastewater, which is a post-processing cost and an environmental concern. The present study aims to valorize this processing by-product to obtain a value-added product, thereby enhancing resource efficiency and contributing to achieving sustainable development goals (SDGs). In this sense, a chemical reaction-based platform was developed to obtain valuable components, such as levulinic acid (LA) and 5-hydromethylfurfural (HMF). The products were then analyzed using NMR identification of the antioxidant phenolic fraction and microwave single-phase reaction of the sugary fraction. According to the results, the highest concentration of phen…
Ultrasonically-Assisted and Conventional Extraction from Erodium Glaucophyllum Roots Using Ethanol:Water Mixtures: Phenolic Characterization, Antioxi…
2020
The paper presents experimental results concerning the ultrasonically-assisted extraction of bioactive compounds from Erodium glaucophyllum roots. A comparison with conventional methodology is presented, and thereby the phytochemical composition and the antioxidant and anti-inflammatory activities of extracts are evaluated. The phenolic profile of Erodium extracts was analyzed by TOF&ndash
Solvent-free microwave-assisted extraction of polyphenols from olive tree leaves: Antioxidant and antimicrobial properties
2017
International audience; Response surface methodology (RSM) and artificial neural networks (ANN) were evaluated and compared in order to decide which method was the most appropriate to predict and optimize total phenolic content (TPC) and oleuropein yields in olive tree leaf (Olea europaea) extracts, obtained after solvent-free microwave- assisted extraction (SFMAE). The SFMAE processing conditions were: microwave irradiation power 250-350 W, extraction time 2-3 min, and the amount of sample 5-10 g. Furthermore, the antioxidant and antimicrobial activities of the olive leaf extracts, obtained under optimal extraction conditions, were assessed by several in vitro assays. ANN had better predic…
Aortic stiffness in patients with early sepsis
2014
Acute and chronic systemic inflammatory conditions are associated with aortic stiffening. Carotid-femoral pulse wave velocity (PWV), a marker of aortic stiffness, increases in patients with inflammatory diseases and independently correlates to levels of C-reactive protein (CRP). The effects of massive inflammatory response in early sepsis on mechanical properties of the aorta have not been investigated. The objective of the current study was to prospectively assess aortic stiffness in patients with early severe sepsis and septic shock and relate it to inflammatory and haemodynamic variables and outcome.
A study on the essential oil Ferulago campestris. How much does exstraction method influence the oil composition?
2010
The essential oil of different parts of Ferulago campestris (Bess.) collected in Sicily has been extracted by microwave-assisted hydrodistillation (MAHD) and by classic hydrodistillation (HD). A comparative qualitative- quantitative study on the composition of the oils was carried out. A total of 100 compounds were identified in the oils obtained by MAHD, whereas 88 compounds characterized the HD oils. The most prominent components were, in all different parts of F. campestris and in both extraction methods, 2,4,5- trimethylbenzaldehyde and 2,4,6-trimethylbenzaldehyde isomers; the latter was not previously found. The attempt to evaluate where the oil components are located in all parts of t…