Search results for "PIGMENT"
showing 10 items of 626 documents
Qualitative and quantitative characterization of historical pigment mixtures through non-invasive techniques
2013
Electrochemical identification of flavonoid dyes in solid work of art samples by abrasive voltammetry at paraffin-impregnated graphite electrodes.
2004
Abstract An electrochemical method for identifying flavonoid-type dyes in microsamples from works of art is reported. Square wave voltammograms of natural insoluble dyestuffs based on flavonoid structure dragoon's blood, weld, old fustic, gamboge, Brazilwood and logwood (Campeche wood) attached to paraffin-impregnated graphite electrodes in contact with 0.25 M HAc + 0.25 M NaAc aqueous buffer display characteristic peaks in the potential region between +0.85 and −0.85 V versus AgCl/Ag. Sequential experiments in contact with 0.05 M AlCl 3 and 0.05 M Na 2 MoO 4 plus HAc/NaAc and 0.05 M H 3 BO 3 + 0.10 M NaOH solutions also provide dye-characteristic signals allowing for an unambiguous identi…
Arthropod-induced neoplastic formations on trees change photosynthetic pigment levels and oxidative enzyme activities
2005
Abstract In order to test the hypothesis that arthropod-induced neoplastic formations on trees affect biochemical characteristics of both the newly formed galls and host plant tissues, biochemical characteristics with a possible adaptive role were determined in nine gall-former–host tree combinations. Photosynthetic pigments, extractable protein content, and oxidative enzyme activities were determined in gall tissues, leaf tissues of galled leaves, and leaves on ungalled tree branches. Neoplastic tissues were characterized by a low content of photosynthetic pigments, decreased chlorophyll a/b ratio, lower extractable protein content, and decreased activities of peroxidase and polyphenol oxi…
THERMOREGULATION CONSTRAINS EFFECTIVE WARNING SIGNAL EXPRESSION
2009
Evolution of conspicuous signals may be constrained if animal coloration has nonsignaling as well as signaling functions. In aposematic wood tiger moth (Parasemia plantaginis) larvae, the size of a warning signal (orange patch on black body) varies phenotypically and genetically. Although a large warning signal is favored as an antipredator defense, we hypothesized that thermoregulation may constrain the signal size in colder habitats. To test this hypothesis, we conducted a factorial rearing experiment with two selection lines for larval coloration (small and large signal) and with two temperature manipulations (high and low temperature environment). Temperature constrained the size and br…
Medication related to pigmentation of oral mucosa.
2021
The diagnosis of oral melanotic lesions is, more often than not, challenging in the clinical practice due to the fact that there are several reasons which may cause an increase in pigmentation on localized or generalized areas. Among these, medication stands out. In this work, we have carried out a review in the reference pharma database: Micromedex® followed by a review of the scientific published literature to analyse coincidences and possible discrepancies. Our findings show that there are several prescription drugs that can cause pigmented lesions in the oral mucosa. This must be known by clinicians in order to properly diagnose pigmented lesions. We have identified a set of 21 medicame…
Zilās gaismas draudu kumulatīvā analīze
2022
Maģistra darbs uzrakstīts angļu valodā uz 42 lappusēm. Tas satur 15 attēlus, 4 vienadojumi, 8 tabulas un 64 atsauces. Cilvēki katru dienu ir pakļauti zilajai gaismai. Zilā gaisma ir bīstama, ja tā pārsniedz 100 J / (cm2-sr) uz 106 ≤ t. Pirmsreceptoru makulas pigmenti, luteīns un zeaksantīns kopā ar lēcas kristālu absorbē zilo gaismu. Zilās gaismas svērtais spožums dažādos ekspozīcijas ilgumos tika modelēts ar doto datu bāzi, kas ņemta no f. fluxometrs dažādiem zilās gaismas avotiem. Rezultāti parādīja, ka gaismai, ko izstaro saules gaisma, īpaši saulainās dienās, ir visaugstākās zilās gaismas spožuma vērtības un tā tiek uzskatīta par kaitīgu, bet tomēr nepārsniedz vērtības, kas pierāda bīst…
LU FMOF optometrijas un redzes zinātnes nodaļas un Latvijas optometristu un optiķu asociācijas konferenču referātu tēzes
2020
Tēzes no LU 78.starptautiskās zinātniskās konferences Cilvēka fizioloģijas un uztveres sēdes un LU Optometrijas un redzes zinātnes nodaļas un LOOA kopīgās klīniski praktiskās konferences Rīgā, 2020.gada 14., 16. februārī
Makulas pigmenta optisko blīvumu ietekmējošie faktori skolas vecuma bērniem
2019
Bakalaura darbs ir uzrakstīts latviešu valodā uz 37 lapaspusēm un satur 14 attēlus, 6 tabulas un 71 atsauci uz literatūras avotiem. Darba mērķis bija noskaidrot makulas pigmenta optisko blīvumu skolas vecuma bērniem Mārupes pamatskolā un tā saistību ar ķermeņa masas indeksu un citiem faktoriem. Pētījumā piedalījās 253 bērni vecumā no 7 līdz 14 gadiem (vidējais vecums 9 gadi), kuriem tika noteikts makulas pigmenta optiskais blīvums ar Macular Pigment Screener iekārtu, kas balstās uz hetereohromatisko flikera fotometriju. Bakalaura darbā netika pierādīta statistiski nozīmīga saistība starp makulas pigmenta optisko blīvumu un ķermeņa masas indeksu, dzimumu un varavīksnenes krāsu.
Black Bioinks from Superstructured Carbonized Lignin Particles
2023
A renewable source of carbon black is introduced by the processing of lignin from agro-forestry residues. Lignin side streams are converted into spherical particles by direct aerosolization followed by carbonization. The obtained submicron black carbon is combined with cellulose nanofibers, which act as a binder and rheology modifier, resulting in a new type of colloidal bioink. The bioinks are tested in handwriting and direct ink writing. After consolidation, the black bioinks display total light reflectance (%R) at least three times lower than commercial black inks (reduction from 12 to 4%R). A loading of up to 20% of nanofibers positively affects the cohesion of the dried bioink (1 to 16…
Gap junctions and connexin hemichannels both contribute to the electrical properties of retinal pigment epithelium.
2022
Gap junctions are intercellular channels that permit the transfer of ions and small molecules between adjacent cells. These cellular junctions are particularly dense in the retinal pigment epithelium (RPE), and their contribution to many retinal diseases has been recognized. While gap junctions have been implicated in several aspects of RPE physiology, their role in shaping the electrical properties of these cells has not been characterized in mammals. The role of gap junctions in the electrical properties of the RPE is particularly important considering the growing appreciation of RPE as excitable cells containing various voltage-gated channels. We used a whole-cell patch clamp to measure …