Search results for "Spectrophotometry"
showing 10 items of 644 documents
Color induction via non-opponent lateral interactions in the human retina
1992
Retinal connections causing colors in Benham's top (pattern induced flicker colors, PIFCs) are investigated by psychophysical experiments. PIFCs are still seen when stimuli to different cones are demodulated selectively, indicating the involvement of non-opponent channels. PIFCs also occur on retinal areas next to those affected by modulated stimuli; further, both monochromat and dark-adapted trichromats perceive PIFCs which are achromatic. These additional findings point to horizontal cells as neuronal mediators of modulated excitation leading to PIFCs. The unspecifity of the postulated connection with respect to cone types agrees with anatomic findings of Boycott, B. B., Hopkins, J. M. an…
Correlations of blood selenium with hematological parameters in West German adults.
1988
The serum selenium and the whole blood selenium of 72 healthy persons (47 women, 25 men) was determined. There exist sex specific differences of the whole blood selenium between men (98 +/- 19 micrograms Se/L) and women (89 +/- 17 micrograms Se/L). The serum selenium did not show sex specific differences, but sex specific differences are found if the total amount of extracellular selenium is calculated by correction of the serum selenium with the hematocrit. Women have more extra-cellular selenium/L whole blood (40 +/- 8 micrograms Se) than men (36 +/- 7 micrograms Se). Men have more intraerythrocyte selenium (cellular selenium = 67 +/- 14 micrograms Se) in one L whole blood than women (52 …
The arsenic content of human semen.
2009
Arsenic concentration was measured by atomic absorption spectrometer in ejaculates of 13 subfertile men, 6 control individuals and pool-ejaculate of 24 further andrological patients. While the detection limit was 1 microgram/l, arsenic concentration amounted to 2 micrograms AS/l in ejaculates. In the cellular fractions of seminal fluid, concentration of arsenic was under the detection limit. Arsenic concentration of smokers and non-smokers did not differ.
Properties of a triazolopyridine system as a molecular chemosensor for metal ions, anions, and amino acids.
2006
The characteristics as a chemosensor of the compound 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-]pyrimidine (1) have been analyzed. Interaction with Cu(2+) produces a quenching of the fluorescence, while interaction with Zn(2+) leads to a quenching of the fluorescence followed by a bathochromic shift. The crystal structure of the Zn(1)(H(2)O)(3)(ClO(4))(2) x H(2)O complex shows the coordination of Zn(2+) through the terpyridine moiety. The octahedral site is completed by three water molecules. Interactions of the Zn(2+) complex with the anions sulfate, nitrate, nitrite, and dihydrogenphosphate in ethanol produce hypsochromic shifts and restoration of the fluorescence wh…
Determination of Cd, Co, Cu, Fe, Pb, Mn, Ni and Zn in diets: Development of a method
1991
A method useful for the determination of cadmium, cobalt, copper, iron, lead, manganese, nickel and zinc in diets is described. Organic matter is destroyed applying a wet procedure, and element content is measured by flame atomic absorption spectroscopy (FAAS) in the case of copper, iron, manganese, nickel and zinc, and by graphite furnace (GF-AAS) in the case of cadmium, cobalt and lead. The matrix interference study is carried out. Values found for linearity, detection and quantitation limits as well as accuracy show that the described method is useful to determine the elements taken into account at usual levels in diets.
Preparation of 2,3-seco-5α-cholestane-2,3-diol and 4α-methyl-2,3-seco-5α-cholestane-2,3-diol and its reactions with o-nitrophenyl selenocyanate
1984
The reaction of 2,3-seco-5 alpha-cholestane-2,3-diol and 4 alpha-methyl-2,3-seco-5 alpha-cholestane-2,3-diol with o-nitrophenyl selenocyanate was studied. The diols were synthesized from cholesterol.
Synthesis, Characterization, and Cu(2+) Coordination Studies of a 3-Hydroxy-4-pyridinone Aza Scorpiand Derivative.
2016
The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by potentiometry, cyclic voltammetry, and NMR and UV-vis spectroscopy. UV-vis and NMR studies showed that phenolate group was protonated at the highest pH values [log K = 9.72(1)]. Potentiometric studies point out the formation of Cu(2+) complexes of 1:2, 2:2, 4:3, 1:1, and 2:1 Cu(2+)/L1 stoichiometries. UV-vis analysis and electrochemical studies evidence the implication of the pyridinone moieties in the metal coordination of the 1:2 Cu(2+)/L1 complexes. L1 shows …
One pot light assisted green synthesis, storage and antimicrobial activity of dextran stabilized silver nanoparticles.
2014
Background Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report green synthesis of silver nanoparticles (Ag NPs) mediated with dextran. Dextran was used as a stabilizer and capping agent to synthesize Ag NPs using silver nitrate (AgNO3) under diffused sunlight conditions. Results UV–vis spectra of as synthesized Ag nanoparticles showed characteristic surface plasmon band in the range from ~405-452 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies showed spherical Ag NPs in the size regime of ~50-70 nm. Face centered cubic lattice of Ag NPs was confirmed by powder X-ray diffraction (PXRD…
Spectroscopic and Structural Investigation of the Confinement of D and L Dimethyl Tartrate in Lecithin Reverse Micelles
2009
The confinement of D and L dimethyl tartrate in lecithin reverse micelles dispersed in cyclohexane has been investigated by FT-IR, polarimetry, electronic and vibrational circular dichroism (ECD and VCD), 1H NMR, and small-angle X-ray scattering (SAXS). Measurements have been performed at room temperature as a function of the solubilizate-to-surfactant molar ratio (R) at fixed lecithin concentration. The analysis of experimental data indicates that the dimethyl tartrate molecules are solubilized within reverse micelles in proximity to the surfactant head groups in the same way for the D and L forms. The encapsulation of dimethyl tatrate within lecithin reverse micelles involves changes in i…
Apparent content curves: new analytical applications
1993
Analytical possibilities of apparent content curves for ternary systems are studied. The mathematical method proposed is applied to UV-Vis spectrophotometric and fluorimetric techniques. Samples containing fluoresceine/eosine/acridine and methyl red/methyl orange/cresol red are resolved by fluorimetry and UV-spectroscopy, respectively. Results obtained are in agreement with the theoretical contents in both cases.