Search results for "absorption"

Determination of lead on the airborne particulates of urban Valencia city

1991

A method for the determination of lead in airborne particulates by graphite furnace atomic absorption spectrometry after extraction with HCl-HNO3 (120–150°C) is described. Particulate lead levels in the atmosphere have been measured in samples collected throughout a year, sampling has been made at eleven sites within the city of Valencia. The results obtained in this study show that annual means of lead levels are within the range of 0.526 to 7.033 μg/m3 depending upon the sampling site. Lead levels are higher in winter and autumn. Lead and nitrogen oxide levels are well correlated.

The active center of superoxide dismutase from Propionibacterium shermanii

1996

A self-consistent description of the EPR spectra and of the Mossbauer spectra of the natural superoxide dismutase from Propionibacterium shermanii with ferric iron as an active centre is presented. The spectra were measured at pH 6.5, 7.8 and 9.4. The theoretical approach is based on the use of the complete crystal field Hamiltonian for the high-spin ferric complexes with due regard for the terms of the fourth power of the electronic spin. It is shown that a SOD molecule can exist in two conformations. The low-pH conformation has predominantly trigonal symmetry, while the high-pH conformation has the symmetry close to the «extreme rhombic». This interpretation is in full agreement with EXAF…

Effect of lactoferrin addition on the dialysability of iron from infant formulas

2003

A possible enhancing effect of lactoferrin (Lf) on iron absorption by breast-fed infants has been suggested, however the available results failed to confirm this hypothesis. Nevertheless, Lf could be useful in protecting the lipid fraction of infant formulas against oxidation. Concerning the possibility of adding Lf to infant formulas with this aim, we considered it necessary to evaluate the effect of this addition on iron dialysability, which was used as a parameter indicator of bioavailability. An in vitro dialysability method was applied to three types of infant formulas, with and without Lf added, respectively. In none of the analysed formulas did the added Lf have a negative effect on …

Uranyl sorption onto birnessite: A surface complexation modeling and EXAFS study

2014

This work investigates the mechanism of the uranyl interaction with birnessite, one of the most common layer-type MnO2 mineral at the Earth's surface, by coupling macroscopic (surface complexation experiments) and microscopic (EXAFS measurements) approaches. The sorption of uranyl on synthetic hexagonal birnessite, the low-pH birnessite form, was studied under various conditions of pH (3–6), electrolyte backgrounds (0.1 M NaClO4, NaNO3 and Na2CO3), and solid/liquid ratios (from 0.27 to 4.5 g/L). Sorption isotherms exhibit a complex form indicative of at least two types of sorption sites. EXAFS data reveal the presence of two equatorial O shells at ca. 2.32 Å and 2.46 Å for all the samples, …

Phantoms Used for Mapping of Skin Chromophores by Multi-spectral Imaging

2014

Skin phantoms can be used for better understanding of diffuse reflectance imaging of skin. In this study, skin phantoms of hemoglobin, bilirubin and melanin were developed and studied for possibilities to calibrate chromophore concentration values.

A sun-induced vegetation fluorescence retrieval method from top of atmosphere radiance for the FLEX/Sentinel-3 TanDEM mission

2015

A new fluorescence retrieval method is proposed to support ESA's 8th Earth Explorer FLuorescence EXplorer/Sentinel-3 (FLEX-S3) candidate tandem mission. FLEX is the first mission specially dedicated to measure the Sun-Induced vegetation chlorophyll fluorescence (SIF) strongly related with the vegetation photosynthetic activity. Most hyperspectral fluorescence retrieval algorithms available in the literature are very sensitive to true reflectance modelization and/or they assume the atmospheric status as known. The proposed algorithm delivers the retrieval of full fluorescence spectrum at canopy level by using only Top Of Atmosphere (TOA) radiances from S3 and FLEX as input. Once the spatial …

Thioxanthone: on the shape of the first absorption band

2010

The equilibrium ground state geometry of thioxanthone (TX) has been investigated and its effect on the vertical excitation energies and photophysical behaviour has been explained. In line with this purpose, the first absorption band of TX has been simulated and analysed in detail. The calculations show that TX is planar, C(2v) symmetric in its ground state. The energy of the low-lying excited states seems to be rather insensitive along the butterfly motion coordinate. The shoulder in the first absorption band (at around 3.43 eV) is shown to be caused by vibrational progression of various in-plane modes and does not justify the hypothesis that two photophysically distinct conformers of TX ex…

Vergleichende tierexperimentelle Untersuchungen mit Kaffee und Tee

1969

14C-Coffein wurde an Ratten als Coffeinlosung bzw. als Bestandteil eines Kaffee-oder Tee-Infuses per os verabreicht. Die Resorption von Coffein erfolgte nach Verabreichung von Coffeinlosung und Kaffee-Infus verhaltnismasg schnell, nach Verabreichung von Tee-Infus dagegen mit einer gewissen Verzogerung. Die14C-Aktivitatswerte im Serum und im Rattenkorper fielen nach Erreichung ihres Maximums nach Gabe von Coffein und Kaffee sehr schnell, nach Gabe von Tee dagegen sehr langsam ab. Die14C-Ausscheidung im Harn war nach Verabreichung von Tee deutlich geringer als nach Coffein oder Kaffee.

1981

Dynamic-mechanical and dielectric measurements have been performed with some polycarbonate samples. In one set of experiments care was taken to avoid any absorption of moisture. In other sets of experiments, samples were exposed to atmospheric humidity and to boiling water. The glass transition temperature was found to be highly affected by the absorption of water and by the test conditions. Dynamisch-mechanische und dielektrische Messungen wurden an Polycarbonatproben durchgefuhrt. In einer Versuchsserie wurde die Absorption von Wasser vollstandig vermieden, in weitern Versuchen wurden die Proben der Luftfeuchte bzw. kochendem Wasser ausgesetzt. Die Glasubergangstemperatur wurde durch das …

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

2019

Two mixtures of polyaminoazides were synthesized by a nucleophilic displacement strategy providing no separation of the components. The mixtures were adequately characterized by means of combined HR-ESIMS, FTIR and NMR techniques and, despite their complexity, they were successfully used to accomplish the subsequent preparation of pH-sensitive calixarene hyper-reticulated nanosponge materials. The desired responsivity to pH variations of the nanosponges obtained was verified by means of absorption tests on a set of organic pollutant model molecules.