Search results for "absorptio"
showing 10 items of 2815 documents
Low-cost set-up for Fourier-transform infrared spectroscopy in diamond anvil cell from 4000 to 400 cm−1
2011
An experimental set-up for Fourier-transform infrared (FTIR) studies at high pressure in the mid-IR region (400–4000 cm−1) is constructed using a compact TEO-400 FTIR interferometer module and an external microscopic optical bench with cassegrain focusing objectives. Cassegrain-type reflective objectives act as an excellent beam condenser that facilitates the interfacing between FTIR spectrometer and diamond anvil cell. This set-up is capable of recording transmission and reflection infrared spectra at high pressure. Preliminary results are reported both in the reflection (pressure dependence of polar phonons in CuWO4) and transmission configuration (polarized light absorption of polar phon…
"Though It Be but Little, It Is Fierce": Excited State Engineering of Conjugated Organic Materials by Fluorination.
2016
Fluorination is frequently used to significantly change the properties of conjugated organic materials due to fluorine’s exceptional properties; well-known is its impact on electronic structure, but it also impacts the geometry despite fluorine’s small size. Less known, the changes in the electronic and geometrical properties may provoke drastic changes of the excited state properties like batho- and hypsochromic shifts of absorption and emission bands (inter alia leading to excited state switching), hypo- and hyperchromic effects, spectral broadening, and changes of the nonradiative deactivation pathways. The state of the art on these issues is summarized in the current Perspective to stim…
Chemical characterization of iron in atmospheric aerosols
1992
Abstract The total Fe content, the soluble fractions of Fe(II) and Fe(III), and several species of Fe were determined in various atmospheric aerosol samples by means of atomic absorption spectrometry, ion chromatography and Mossbauer spectrometry.
An overview of the analytical methods for the determination of organic ultraviolet filters in biological fluids and tissues.
2012
Organic UV filters are chemical compounds added to cosmetic sunscreen products in order to protect users from UV solar radiation. The need of broad-spectrum protection to avoid the deleterious effects of solar radiation has triggered a trend in the cosmetic market of including these compounds not only in those exclusively designed for sun protection but also in all types of cosmetic products. Different studies have shown that organic UV filters can be absorbed through the skin after topical application, further metabolized in the body and eventually excreted or bioaccumulated. These percutaneous absorption processes may result in various adverse health effects, such as genotoxicity caused b…
Determination of Olive Oil Parameters by Near Infrared Spectrometry
2010
Publisher Summary Near infrared (NIR) covers the region between 780 and 2500 nm, and based on the absorption, transmission or reflection of the light, NIR spectroscopy provides a fast and non-destructive technique which is very useful for the simultaneous determination of several compounds in the same sample. Food NIR spectra comprise broad bands corresponding to overtones and combinations of vibrational modes involving C–H, O–H, and N–H chemical bonds, providing a great amount of information which properly treated by chemometrics is useful for classification and for the quantification of many parameters. The olive oil extraction process starts in the harvesting and transport of olive fruit…
Dyes That Bear Thiazolylazo Groups as Chromogenic Chemosensors for Metal Cations
2011
A family of dyes (L 1-L 6) that contain a thiazolylazo group as signalling subunit and several macrocyclic cavities with different ring sizes and type and number of heteroatoms as binding sites has been synthesized and characterized. Solutions of L 1-L 6 in acetonitrile show broad and structureless absorption bands in the 554-577 nm range with typicalmolar absorption coefficients that range from 20000 to 32000 M -1 cm -1. A detailed protonation study was carried out with solutions of L 1, L 2 and L 5 in acetonitrile. Addition of one equivalent of protons to L 1 and L 2 resulted in the development of a new band at 425 and 370 nm, respectively, which was ascribed to protonation in the aniline…
A Validation Methodology for a Combined Heating Cooling and Power (CHCP) Pilot Plant
2004
A great number of variables significantly influence the energetic, environmental and economic results of CHP (Combined Heating and Power) and CHCP (Combined Heating Cooling and Power) plants operation, and as a consequence their project activity is rather complex. In order to select the best layout and properly size the machines, detailed data on hourly electric, thermal, and cooling demand are necessary, so that a series of plant life cycle simulations may have to be carried out. Unfortunately, such detailed data are rarely available, because energy consumptions data for existing buildings are usually derived from aggregated monthly or bimonthly gas and electricity bills. Even more difficu…
Intestinal absorption enhancement via the paracellular route by fatty acids, chitosans and others: a target for drug delivery.
2005
Peroral delivery of hydrophilic drugs is one of the greatest challenges in biopharmaceutical research. Hydrophilic drugs usually present low bioavailability after oral administration. One of the causes of this low bioavailability is their poor intestinal permeation through the paracellular pathway. This pathway is actually restricted by the presence of tight junctions at the apical side of the enterocytes. In the last few years, great interest has been focused on the structure and cellular regulation of tight junctions, materializing in more in-depth knowledge of this intestinal barrier. Simultaneously, and on the basis of this understanding, continuous efforts are being made to develop age…
CHLOROPHYLL a AGGREGATES IN HYDROCARBON SOLUTION, A PICOSECOND SPECTROSCOPY AND MOLECULAR MODELING STUDY
1993
Chlorophyll a aggregates in 3-methylpentane solution have been studied by using picosecond absorption and fluorescence spectroscopy and molecular modeling. Chlorophyll a aggregates give rise to reversible temperature changes in the absorption and fluorescence spectra. Time-dependent anisotropies were used to estimate rotational correlation times of the aggregates. These were indicative of the sizes of the aggregates. The rotational diffusion of the monomer and the two identified aggregates was hydrodynamic over the viscosity range studied (0.29–1.8 cP). Molecular mechanics calculations were used to predict the minimum energy structures of several chlorophyll a dimers suggested earlier in th…
Iron as a source of color in river waters.
2015
Organic chromophores of total organic carbon (TOC) and those of iron (Fe) contribute to the color of water, but the relative contributions of colored organic carbon (COC%) and Fe (Fe%) are poorly known. In this study, we unraveled Fe% and COC% in 6128 unfiltered water samples collected from 94 Finnish river sites of contrasting catchment properties. According to regression analysis focusing on TOC alone, on average 84% of the mean TOC consisted of COC, while 16% was non-colored or below the color-detection limit. COC and Fe were much more important sources of color than phytoplankton (chlorophyll a as a proxy) or non-algal particles (suspended solids as a proxy). When COC and Fe were consid…