Marked Color Change Research Articles

Color Change Evaluation of Denture Soft Lining Materials in Coffee and Tea

This study evaluated the color stability of soft denture liners after being exposed to coffee and tea solutions for different time periods. Four soft denture liners and a denture base polymer were tested. Five specimens of each material were immersed in either coffee or tea solution at 50 +/- 1 degrees C for one, three, nine, 24, 48, and 96 hours. Color measurements were made using a reflectance spectrophotometer before and after the specimens were exposed to the solutions. After 96 hours' immersion in coffee and tea solutions, coffee produced more marked color changes than did tea for all the materials tested. Surface roughness (Ra) of the materials after being cured against a stainless steel surface was also measured with a contact-type surface roughness measuring instrument. Due to the different surface structures, which thus accounted for the different Ra values, the materials behaved differently when immersed in different solutions.

Acridinium Salt Based Fluorescent and Colorimetric Chemosensor for the Detection of Cyanide in Water

A new, selective chemosensor has been developed to detect cyanide in water at micromolar concentrations. The acridinium salt used in this sensor system is prepared in a single step from an acridine orange base. Detection is based on the irreversible, 1:1 stoichiometric, nucleophilic addition of cyanide to the 9-position of the acridinium ion. This process induces a large decrease in fluorescence intensity and a marked color change. The selectivity of the system in aqueous media for CN- over other anions is remarkably high. Also, the sensitivity of both the fluorescence- and colorimetric-based assay is below the 1.9 microM suggested by the World Health Organization (WHO) as the maximum allowable cyanide concentration in drinking water. Thus, the chemodosimeter should be applicable as a practical system for the monitoring of CN- concentrations in aqueous samples. [structure: see text]

Calix[4]arene‐Based Chromogenic Chemosensor for the α‐Phenylglycine Anion: Synthesis and Chiral Recognition

AbstractCalix[4]arene‐based two‐armed chiral anion receptors 3a and 3b have been synthesized and examined for their chiral anion‐binding abilities by UV/Vis absorption and 1H NMR spectroscopy. The results of nonlinear curve fitting indicate that 3a and 3b form 1:1 stoichiometric complexes with the L‐ or D‐α‐phenylglycine anion by multiple hydrogen‐bonding interactions and exhibit good enantioselective recognition for the enantiomers of the α‐phenylglycine anions (3a: Kass(L)/Kass(D) = 4.76; 3b: Kass(D)/Kass(L) = 2.84). The marked colour changes observed for the complexation of 3a with the chiral anions and the good enantioselective recognition reveal that receptor 3a could be used as a good chiral chromogenic chemosensor for the enantiomers of the α‐phenylglycine anion. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Simple Method for Precognition of Drug Interaction between Oral Iron and Phenolic Hydroxyl Group-containing Drugs

In the present study, we devised a simple method for detecting the drug interaction between oral iron preparations and phenolic hydroxyl group-containing drugs, using the coloring reaction as indicator, due to the formation of complexes or chelates. In the method, oral iron preparations and test drugs in amounts as much as single dose for adults were added to 10 ml of purified water to make sample suspensions for testing. Thirty minutes after mixing an oral iron suspension and a test drug suspension, the change of color in the mixture was observed macroscopically and graded as 0 to 3, with a marked color change judged as grade 3 and no color change as grade 0. Screening of 14 test drugs commonly used orally was carried out. When using sodium ferrous citrate preparations as oral iron, 5 were classified as grade 3, 2 as grade 2, 4 as grade 1, and 3 as grade 0, respectively. To verify usefulness of the method, the interactions suggested by screening were pharmacokinetically assessed by measuring serum concentrations of the drug in mice. When a levodopa or droxidopa preparation, judged as grade 3 in screening, was concomitantly administered with an iron preparation, a significant reduction in bioavailability of the test drug was observed, indicating possible drug interaction between the test drug and oral iron. Combined administration of an acetaminophen preparation, judged as grade 1, and oral iron preparation showed no influence on the bioavailability of the test drug, implying no detectable interactions between them. In conclusion, the simple method devised in the present study is useful for precognition of drug interactions between oral iron preparations and phenolic hydroxyl group-containing drugs, and the drugs with a higher grade in screening may induce drug interactions with oral iron.

Staining of Intraocular Lenses with Various Dyes: A Study of Digital Image Analysis

Purpose: To evaluate the interaction of various intraocular lens (IOL) materials with commonly used dyes. Materials and Methods: One IOL of each of the five groups (polymethylmethacrylate, silicone, three-piece hydrophobic acrylic, single-piece hydrophobic acrylic and single-piece hydrophilic acrylic) was bathed in trypan blue 0.1%, fluorescein sodium 2% and indocyanine green (ICG) 0.5% for 15 min. Digital photographs of the IOLs were obtained prior to bathing and after the 15-min bath in each dye. The same IOLs were immersed in the same dye for another 15 min and digital images were reobtained to depict the 30-min dye uptake. New IOLs from the group that exhibited visible colour change after the 15-min bath were then bathed in twofold dilution and if there was still visible dye uptake, fourfold dilution was performed, repeating the 15-min bath and digital photography. The images were then processed using Adobe Photoshop 5.1 to get mean luminosity and red-green-blue values. These values were compared between the groups and the undyed control. Also, dye washout was observed in serum-containing vials. Results: None of the polymethylmethacrylate, silicone and hydrophobic acrylic IOLs were stained with the dyes used. The only IOL material that changed colour was hydrophilic acrylic and did so with all dyes. The most marked colour change was with fluorescein sodium 2%, the least was with trypan blue 0.05%. Twofold dilution of trypan blue and fourfold dilutions of fluorescein sodium and ICG still stained the hydrophilic acrylic IOL; however, fourfold dilution of trypan blue did not cause a significant colour change. Trypan blue washed out within 6 h, while the IOL stained with ICG remained stained for longer than 24 h. Comment: Hydrophilic acrylic IOLs should be used with caution together with dyes since this material demonstrates marked dye uptake and washout may also take some time.

Lipid oxidation and colour in pressure‐ and heat‐treated minced chicken thighs

AbstractLipid oxidation and colour in pressurised and heated chicken samples were evaluated. In a preliminary test, raw and overcooked (100 °C/60 min) minced chicken thighs were pressurised (500 MPa/50 °C/30 min). Samples were stored at 4 °C in contact with air. Thiobarbituric acid reactive substances (TBARS) were quantified at 1, 6 and 9 days. Pressure induced oxidation in chicken, but overcooking generated many more secondary oxidation compounds. In a second experiment, raw minced chicken thighs were pressurised (500 MPa/−10, 5, 20 and 50 °C/30 and 60 min) or cooked (90 °C/15 min). Samples were vacuum stored at 4 °C. TBARS were measured at 1 and 9 days, whereas colour parameters (L, a, b and ΔE) were determined at 1 day. No differences in TBARS values were observed between untreated and pressurised samples, whereas cooked samples presented the highest values. Pressurisation for 30 and 60 min generated similar TBARS contents. At 9 days, oxidation values did not increase. Pressurisation and cooking induced marked colour changes. Pressurised samples were lighter and less red than untreated ones. Samples pressurised at 50 °C were the palest and, together with cooked samples, presented the lowest a values. Therefore pressurised chicken thigh cannot be marketed as a fresh product but can be incorporated as an ingredient in ready‐to‐eat meals. Copyright © 2004 Society of Chemical Industry

Observations of Ice Nucleation and Propagation in Flowers of Japanese Pear (Pyrus pyrifolia Nakai) using Infrared Video Thermography

Ice formation and propagation in the flower and young fruit of Japanese pear 'Kosui' were investigated with infrared (IR) video thermography imaging system. The changes of thermal response (exotherm) in freezing events could be detected using the infrared thermography camera with exotherm rise of 2-5 °C accompanied by a marked color change in the tissues. With first bloom flowers, the temperature of peduncles decreased faster than that of the receptacle; the initial ice nucleation occurred primarily in petals, sepals and/or receptacle. Subsequently, ice was propagated along the peduncle. The temperature of receptacles was above that of peduncles during the freezing test at full bloom; the sepals and/or receptacle were initially frozen, then ice nucleation was extended to the petals along the peduncle. These results suggest that the sepals and/or receptacle where the initial nucleation occurred may be an intrinsic or extrinsic source of high ice nucleation activity in flowers of the Japanese pear 'Kosui'. In contrast with first bloom and full bloom stage, the exotherms during freezing could not be detected clearly in young fruits. However, cold injury appeared as a spotty stain on the skin of young fruits immediately upon being subjected to chilling.

PHYSICO-CHEMICAL CHANGES DURING ENZYMATIC LIQUEFACTION of MANGO PULP (cv. Keitt)

Mango pulp from Keitt variety was liquefied with 1.1 mL/kg commercial enzyme mixture preparations for 2 h at 40C. Various physico-chemical characteristics of the mango pulp at different stages of liquefaction were investigated. Apparent viscosity of pulp and serum reduced rapidly to 78% and 93% respectively, in 30 min liquefaction. No marked changes in apparent viscosity of pulp samples and percentage cell wall hydrolysis in the subsequent 60, 90 and 120 min were observed. High correlation coefficient values (R2 > 0.99) of the linear regression analysis showed the feasibility of using a power law model for fitting the shear stress-shear rate data of the pulp. the enzymetreated pulp showed 83% and 84% serum yields during 30 and 120 min reaction times respectively against 52% for fresh pulp. Slight increase in TSS (°Brix), acidity, reducing and total sugars, and slight decrease in pH was found in the pulp as well as serum fractions as the incubation continued. No marked change in color (yellowness) was observed in the enzyme-treated pulp, however, the corresponding serum showed less yellowness and color saturation indicating retention of yellow pigments in the pulp fraction. Δ-3-carene was identified as major mono terpenic compound in mango pulp comprising more than 73% of the total aroma compounds. About 9% loss in the total aroma components was observed during the liquefaction process.

Identification of Solitary and Gregarious Populations of the Desert Locust, Schistocerca gregaria, by Experimental Breeding (Caelifera: Acrididae)

Strains of Schistocerca gregaria (Forskal 1775) originating from Nigeria, Mauretania, and the Canary Islands were studied for the identification of solitary and gregarious behaviour. Under laboratory conditions, nymphs and adults were reared isolated and crowded for 4-6 generations. Various reproductive parameters were registered and compared. In gregarious strains, 4-5 generations can be bred per year under laboratory conditions. For the solitary population, only 2 generations were obtained. Differences were found also in the survival rate up to the adult stage, which was higher in gregarious than in solitary populations, independent from the consecutive generations. For isolated individuals of Nigeria, 5-6 moults were observed in both, males and females. For the offspring, the nymphal period varied between 31-42 days and the complition of 6 moults took up to 52 days. In crowded FF the pre-oviposition period was shorter than under isolated conditions, averaging between 28-32.5 days; it was much longer and more variable for the solitary than for the gregarious populations. In isolated FF of the gregarious strains the pre-oviposition period varied from 30-85 days. In gregarious strains reared crowded, means of 41 to 45 eggs/pod were deposited, while in the solitary one 52-58 eggs/pod were laid depending on the generations. In gregarious FF reared isolated, the mean number of eggs per pod varied between 44.6 and 53.5. The solitary female collected on the Canary Islands produced a mean of 75.7 eggs per pod. Under crowded and isolated conditions, the period of embryogenesis ranged between 28-34 days at 30°C, for all generations and strains. The newly hatched hoppers were dark in all populations and generations, except for some greenish individuals found in the strain from Nigeria. Reaching the 2nd instar all hoppers showed the black pattern under crowded conditions and became grey-green or light brown after isolation. During the maturation of the adults only crowd-reared males of the gregarious strains became bright yellow coloured, while crowd-grown solitary males did not drastically change their colour. In isolation, no marked colour change was observed. The results were discussed in relation to UVAROV's phase theory. Inherent solitary and gregarious populations of S gregaria do really exist in nature, besides scattered and group-building populations of the gregarious form.

Cis-andtrans-Diisothiocyanato(1,4,8,11-tetraazacyclotetradecane)chromium(III) Perchlorate

The cis isomer of the title compound, [Cr(NCS)2(C10H24N4)](ClO4), is a racemate of the Bosnich type V structure; the trans complex is a meso substance with a Bosnich type III stereochemistry. There is no appreciable change in the structures of the title compound on cooling, even though there are marked color changes. The Cr—N bond lengths are all in the range 1.983 (2)–1.998 (4) Å for the bonds to the isothiocyanate groups and in the range 2.046 (2)–2.088 (3) Å for the bonds to cyclam N atoms.

The stabilization of managese(III) by azide ions in aqueous solution

The evidences of spontaneous oxidation of Mn(II) by the dissolved oxygen in azide buffer medium, which is dependent on the N − 3 HN 3 concentration, suggested a formation of stable Mn(III) complexes due to marked colour changes. Spectrophotometric studies combined with coulometric generation of Mn(III), in presence of large excess of Mn(II), showed a maximum absorbance peak at 432 nm. The molar absorptivity increases with azide concentration (0.44–3.9 mol 1 −1) from 3100 to 6300 mol −1 1 cm −1, showing a stepwise complex formation. Potential measurements of the Mn(III) Mn(II) system in several azide aqueous buffers solutions: 1.0 × 10 −2 mol 1 −1 HN 3, (0.50–2.0 mol 1 −1) N − 3 and 5.0 × 10 −2 mol 1 −1 Mn(II) and constant ionic strength 2.0 mol 1 −1, kept with sodium perchlorate, leads to the conditional potential, E 0′ x, in several azide concentrations at 25.0 ± 0.1°C. Considering the overall formation constants of Mn(II) N − 3 , from former studies, and the potential, E 0′ s = 1.063 V versus SCE, for Mn(III) Mn(II) system in non-complexing media, it was possible to calculate the Fronaeus function, F 0( L), and the following overall formation constants: β 1 = 1.2 × 10 5 M −1, β 2 = 6.0 × 10 8 M −2, β 3 = (2.4 ± 0.7) × 10 11 M −3, β 4 = (1.5 ± 0.5) × 10 11 M −4 and β 5 = (9.6 ± 0.8) × 10 11 M −5 for the Mn(III) N − 3 complexes. These data give important support to understand the importance of Mn(II) and Mn(III) synergistic effect on the analytical method of S(IV) determination based on the Co(II) autoxidation.

Peroxide bleaches: Effect on tensile strength of composite resins

Research concerning bleaching agents on the mechanical properties of composite resin restorative materials has produced conflicting reports. Representative brands of composite resin restorative materials were studied, including microfil, hybrid, and posterior types. The bleaching agents selected were 30% hydrogen peroxide and two commercial brands of 10% carbamide peroxide. Ten specimens of each material, prepared according to American National Standards Institute/American Dental Association specification No. 27 for diametral tensile testing, were stored in bleaching agents for 1 hour and 168 hours at 37 °C. An equal number of specimens stored in deionized water with identical conditions were designated controls. Qualitative examination of bleached specimens revealed a marked change in color, especially the microfilled composite resins. There was no significant difference in tensile strength between controls and exposed samples at either time except for the diminished strength of microfilled composite resins in 30% hydrogen peroxide for one week ( p < 0.01).

Hydrothermal and supergene uranium mineralization at the Osamu Utsumi mine, Poços de Caldas, Minas Gerais, Brazil

The Osamu Utsumi uranium deposit in the Mesozoic alkaline complex of Poços de Caldas (MG, Brazil) is a product of subsequent hydrothermal and supergene processes. The lithology of the open-pit mine is composed of a sequence of volcanic and subvolcanic phonolites and nepheline syenite intrusions similar to those of the alkaline complex; volcanic breccia pipes of about 80 m in diameter also occur, characterized by UThZr-REE mineralization concentrated in the matrix. A strong hydrothermalism, related to the formation of the breccias, has resulted in the potassic alteration and pyritization of the phonolites and syenites, with a low-grade mineralization of disseminated pitch-blende. The potassic alteration has transformed all feldspars into pure potash feldspars, nepheline into illite and kaolinite, and clinopyroxenes, which are the primary REE-bearers, into mixtures of TiO 2-rich minerals, clay minerals and pyrite. The enrichment of K, S, U, Th, Pb, Rb, Ba and Mo was accompanied by a strong depletion in Ca, Na, Mg and Sr. The fluid inclusion data indicate temperatures around 250°C and a KClH 2O mixture with approximately 7 wt.% KCl for the hydrothermal fluids. For fluids in the breccia pipes that transported additional Zr, Hf, F and minor REEs, the inclusions indicate boiling and give temperatures of 210°C with 40–45 wt.% KCl for a KClNaClH 2O brine containing FeSO 4 and KF. Uraninite, pitchblende and brannerite are the main U-carriers, and monazite the major REE-bearing mineral in the high-grade mineralization of the breccias. Ultramafic dykes (dated to 76 Ma) with carbonatitic affiliation put a younger age limit to the hydrothermal event. As a result of supergene weathering below a lateritic soil cover 20 to 40 m thick and a saprolite zone 15 to 60 m thick, the pyrites in the rocks have been oxidized to varying depths of 80 to 140 m below surface, resulting in a redox front marked by a contrasting color change from oxidized (reddish-brown) to reduced (bluish-grey). In the vicinity of water-bearing fissures these redox fronts have penetrated to greater depth. Due to mobilization in the oxidized zone and precipitation immediately below the redox front, a secondary mineralization of pitchblende, partly occurring as nodules associated with secondary pyrite, has been developed. This secondary pyrite is sometimes related with CdS, and has a δS of −13% compared to δS values of −3.63 to +1.24% for hydrothermal pyrites: the low δS values of the former are attributed to bacterial action. In the immediate vicinity of the redox front, dissolution of the potash feldspar becomes apparent and the kaolinite content begins to increase. The marked color change at the redox front is caused by the presence of hydrous ferric oxides that, with time, evolve from amorphous Fe-hydroxides to goethite and hematite. On the oxidized side alunite-jarosite minerals are frequent. The porosity increases by 5 to 8% (almost doubled) at the redox front. Gibbsite is present when potash feldspar has been removed at the saprolite-laterite contact. Uranium is partly retained in the oxidized zone by adsorption onto poorly crystalline phases and due to incorporation into hydrothermal refractory minerals. Many of the REEs are associated with clay-sized phosphates (including crandallite group minerals) and seem to be hardly mobilized by the oxidizing weathering fluids. Only a slight general loss of REEs was observed between oxidized and reduced rock, with the degree of loss being greater for the light REEs. Certain indications for a fractionation of Ce and Eu from the other REEs are present.

Highly Reversible Electrochemical Insertion of Lithium, Accompanied With a Marked Color Change, Occuring in Microcrystalline Lithium Nickel Oxide Films

Thin films of lithium-nickel oxide, whose texture consists of microcrystallites with an average grain size of 50 Å, permit highly reversible electrochemical insertion of lithium ions in Li+conducting electrolytes. Therefore, the corresponding materials would be of great interest for energy storage applications. In addition, the lithium insertion/extraction reactions in the nickel-based layers are accompanied with a marked color change, making these films of interest for the development of electrochromic displays for the control of light transmission in windows (“smart windows”).

FTIR study of novel Pd 6 carbonyl clusters encaged in zeolite 5A

Infrared absorption spectra are compared with palladium carbonyl clusters encaged in zeolites Y and 5A. Marked differences are attributed, in terms of a dynamic model, to different sizes of the α-cage windows which control migration of primary clusters. Under conditions in which Pd 13(C0) x clusters prevail in zeolite Y, Pd 6(C0) x dominates the IR spectrum in 5A. Higher reduction temperatures cause formation of larger particles in zeolite Y, but in 5A the small window size prevents particle growth. Whereas doubly-bridged CO is abundant on Pd 13 carbonyls in zeolite Y, terminal and triply-bridged CO prevail in Pd 6(CO) x , as they do in Rh 6(C0) 16. Peak positions indicate different extents of electron deficiency. Marked color changes of calcined, reduced and CO-treated samples further illustrate the electronic interaction of Pd ions and clusters with the zeolite matrix.

Silver ion spray reagent for the discrimination of β- and ε-end groups in carotenoids on thin-layer chromatograms

Thin-layer chromatograms of pure carotenoids and natural carotenoid mixtures were dried and sprayed with saturated methanolic silver nitrate solution. Those carotenoids containing β-end groups showed a marked bathchromic colour change for each such end group. Thus, β-carotene, β-cryptoxanthin and zeaxanthin gave a clear red colour while α-carotene, α-cryptoxanthin and lutein gave deep organge spots after such treatment. Taraxanthin and antheraxanthin could be similarly distinguished. The method was not applicable to paper chromatography.

Dark time yellowing of white rigid vinyl outdoor weatherable compounds

AbstractWhite PVC siding which has been exposed to sunlight will after removal from the sunlight develop a darker color (yellow‐brown). The longer this sample remains unexposed to sunlight the greater the color development. Testing has indicated that one or more photochemical mechanisms are occurring during this color development. A sample which appears yellow upon arrival at the home location after outside exposure can be re‐whitened by re‐exposing the sample to sunlight. Drastic color change will occur within a short period of time, usually less than 72 hours. This sample will have attained its white color with little or no yellowing visible when an original unexposed sample is held next to it. Testing conducted at an Arizona test site has confirmed these theories. Six months and one year weathered white siding samples, when measured at the test site, both experimental and commercial, showed that when the weathered samples are removed from the test racks and tristimulus values are measured daily, marked color changes occur rapidly. This paper addresses data which indicate that color development does occur but only in the very thin surface (5 to 10 micron layer) of the weathered samples. If these samples are washed and the abrasive action is sufficient to remove the surface layer, color development will no longer occur during non‐exposure to sunlight.

The electrochromic characteristics of titanium oxide thin film electrodes

Titanium dioxide in its anatase form may react with lithium by a reversible intercalation process. This process is accompanied by a marked colour change, so that TiO 2 is of interest for the development of electrochromic displays. The electrochromic properties of thin film electrodes, obtained by a deposition on a tin oxide coated glass substrate of a TiO 2 dispersion in polyvinylalcohol, are examined in this work. The results show that the rate of the electrochromic process is controlled by the diffusion of the Li + ions throughout the TiO 2 lattice. Consequently, it is convenient to drive the electrochromic process with potentiostatic pulses and, effectively, under these conditions many cycles with initial good colour contrast and efficiencies which approach 100%, have been obtained with the TiO 2 thin film electrodes.

Vicia johannis and wild relatives of the faba bean: a taxonomic study

Preliminary taxonomic and agronomic investigation was made of close relatives of the faba bean (Vicia faba) to aid future plant breeding. Cluster analysis of 2 yr’s morphometric data showed thatV. johannis is clearly separable from other members of theV. narbonensis complex. AlsoV. faba was much more distinct from eitherV. narbonensis orV. johannis than they are from each other. Petal colours at anthesis provided a rapid method of field identification forV. faba, V. narbonensis, andV. johannis. The 2 varieties ofV. johannis can also be distinguished by their petal colours: var. procumbens shows a marked colour change at anthesis and var. johannis does not. The geographical distribution of the plant material studied suggests thatV. johannis is found in Turkey and Europe despite being omitted from the major published floras. BothV. johannis andV. narbonensis possess agronomically useful characters of importance to faba bean breeders, including increased frost tolerance and resistance to bothAphis fabae andBotrytis fabae.

Anomalous Nature of Neutral-to-Ionic Phase Transition in Tetrathiafulvalene-Chloranil

A phase transition starting at 84 K and indicated by a marked color change of the sample has been found in the organic insulator tetrathiafulvalene-chloranil. Optical, infrared, and Raman measurements indicate that this is a reversible transition from a nominally neutral (N) solid to a nominally ionic (I) salt. Surprisingly, the N-I transition is not first order, but occurs over a broad temperature region (\ensuremath{\sim}30 K), in which there is a coexistence of N and I molecules.