Search results for "optics"
showing 10 items of 10033 documents
Mapping landscape canopy nitrogen content from space using PRISMA data
2021
Abstract Satellite imaging spectroscopy for terrestrial applications is reaching maturity with recently launched and upcoming science-driven missions, e.g. PRecursore IperSpettrale della Missione Applicativa (PRISMA) and Environmental Mapping and Analysis Program (EnMAP), respectively. Moreover, the high-priority mission candidate Copernicus Hyperspectral Imaging Mission for the Environment (CHIME) is expected to globally provide routine hyperspectral observations to support new and enhanced services for, among others, sustainable agricultural and biodiversity management. Thanks to the provision of contiguous visible-to-shortwave infrared spectral data, hyperspectral missions open enhanced …
Potential of phosphonium-based ionic liquids to purify 1-propanol from water by liquid–liquid extraction at mild conditions
2022
Abstract In order to reduce the environmental of the separation of 1-propanol from water in a residual industry stream for its reuse, the capability as solvents of two different trihexyl(tetradecyl)phosphonium ionic liquids (ILs) – trihexyl(tetradecyl)phosphonium chloride ([TDTHP][Cl]) and trihexyl(tetradecyl)phosphonium bromide ([TDTHP][Br])-, was studied. The liquid–liquid equilibria data for both ternary systems, {water + 1-propanol + [TDTHP][Cl]} and {water + 1-propanol + [TDTHP][Br]} at different mild work temperatures, (283.2, 303.2 and 323.2) K, and atmospheric pressure were measured. The thermodynamic parameters for both ternary systems at different work conditions were obtained by …
Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T=25°C
2009
Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T=25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H+]-glass electrode) in NaCl, NaNO3 and mixed NaNO3+Na2SO4 ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be sim…
A fluorescence spectroscopy study of the interaction of monocationic quinine with phospholipid vesicles Effect of the ionic strength and lipid compos…
1997
Abstract The interaction of monocationic quinine with zwitterionic dimyristoyl phosphatidylcholine (DMPC) and mixed negatively-charged dimyristoylphosphatidyl glycerol (DMPG) DMPC small unilamellar vesicles in the liquid-crystalline phase was investigated by steady-state fluorescence spectroscopy at pH 7 and 37°C. The maximum fluorescence emission peak at 383 nm, upon excitation at 335 nm, shifts to lower wavelength and decreases its intensity as the ratio between the total lipid and quinine concentrations increases. This indicates that in the membrane-bound state quinine is in an environment of low polarity, more deeply buried when anionic DMPG is present in the vesicle. For monoprotonated…
Effect of the reference solution in the measurement of ion activity coefficients using cells with transference at T=298.15K
2010
Abstract This work reports individual activity coefficients of ions at T = 298.15 K in aqueous solutions obtained from voltage values of the respective half-cell ion-selective-electrode and a single-junction Ag–AgCl reference electrode, filled with different reference solutions at different concentrations. For potassium and chloride ions in KCl aqueous solutions, reference solutions of KCl, NaCl, or CsCl were used. For sodium and chloride ions in aqueous NaCl solutions, reference solutions of CsCl were used. Experimental runs were performed at molalities (1, 2, and 3) m of the reference solution. The concentration of the sample solution was increased, starting from around 1 · 10−3 m, up to …
Calculations of organic-solvent dispersions of single-wall carbon nanotubes
2005
The aqueous solubility Sw and 1-octanol–(Po), cyclohexane–(Pch), and chloroform–(Pcf) water partition coefficients are calculated. The properties of single-wall carbon nanotubes (SWNT) are related to the indices (n, m) designating the chiral vector. SWNTs are classified in zigzag (n, 0), armchair (n, n), and chiral (n, m). These properties permit classifying SWNTs according to (n, m). Correlations between (n2 + nm + m2)1/2, log Sw, log Po, log Pch, and log Pcf show that (n, m) are adequate indices. The (10,10) is the most abundant SWNT, presenting consistency between great kinetic stability, small Sw, and great {Po, Pch, Pcf}. The room temperature solubility of SWNTs is investigated in a va…
Optimization design process of a morphing winglet
2018
Aeronautic and aerospace engineering is recently moving in the direction of developing morphing wing devices, with the aim of making adaptable the aerodynamic shapes to different operational conditions. Those devices may be classified according to two different conceptual architectures: kinematic or compliant systems. Both of them embed within their body all the active components (actuators and sensors), necessary to their operations. In the first case, the geometry variation is achieved through an augmented classical mechanism, while in the second case the form modification is due to a special arrangement of the inner structure creating a distributed elastic hinges arrangement. Whatever is…
The identification of vicinally substituted cyclohexane isomers in their mixtures by 1H and 13C NMR spectroscopy.
2000
The radical addition reactions of organobromine compounds, XBr (X = CH2COOMe, PhCH2, CHBr2 and CCl3) with cyclohexene afforded mixtures of cis/trans isomer pairs of 1-X-2-Br-cyclohexanes. In addition to benzyl benzoyloxy derivatives are formed also, when benzoyl peroxide is used as an initiator. Owing to the great difficulties in separating these cis/trans isomer pairs, they are identified directly in their mixtures by NMR spectroscopy. In addition to one-dimensional (ID) 1H, proton decoupled 13C and DEPT-135, also two-dimensional (2D) 13C-13C INADEQUATE as well as 1H-13C HMQC experiments have been used in assigning the signals of each compound in their mixtures. The identification of each …
Numerical simulations demonstrate that the double tapering of the spatualae of lizards and insects maximize both detachment resistance and stability
2011
Many biological attachment devices of insects, spiders and geckos consist of arrays of hairs (setae), which are terminated by contact elements of different shapes. However, the most frequently observed shape is a thin plate-like spatula. In spite of a rather wide range of sizes, most spatulae of different animals are not uniform, but rather possess a gradient in thickness and width. Here we show that the spatulae of insects and geckos become gradually thinner and wider approaching the end. This geometrical effect is explained in the present paper, by using a numerical approach for the modelling of the van der Waals adhesion and friction between the contact elements and the substrate. The ap…
Adiabatic evolution of quantum-mechanical systems
1991
A description of the adiabatic approximation in terms of the time-evolution operator is presented. Corrections to the approximation are studied, and it is seen that these can be obtained in a simple way in the case of a rapidly oscillating Hamiltonian.