Brown Glass Research Articles

Analytical and statistical study of a lake system under various processes of eutrophication

L'etude des phenomenes d'eutrophisation se heurte essentiellement a deux difficultes qui sont inherentes d'une part, a la diversite spatio-temporelle des eaux superficielles, et d'autre part, a l'action qu'exercent en retour les phenomenes d'eutrophisation sur ces eaux. - La diversite spatio-temporelle des systemes aquatiques s'accompagne d'une diversite des phenomenes d'eutrophisation qui en sont le siege et a pour consequence de rendre difficile sinon impossible l'etablissement de criteres de comparaisons entre les differents systemes aquatiques. Dans ces conditions il est peu aise de faire le choix objectif d'un etat de reference universel qui seul permettrait de determiner de maniere absolue le niveau trophique d'une eau. - La deuxieme difficulte, et sans doute la plus grande, est liee a l'action qu'exercent les phenomenes d'eutrophisation sur les variables analytiques du systeme. Cette action a pour consequence de rendre les valeurs intrinseques de ces variables impropres a l'etude de ces phenomenes et de leur evolution. Ces variables etant liees simultanement aux causes et aux consequences des diverses manifestations des phenomenes d'eutrophisation. Les 10 lacs que nous avons etudie ici, presentent l'avantage peu courant d'etre alimentes par les memes eaux traversant une zone geographique restreinte et par consequent geologique et climatique identique. Ils sont soumis a l'influence d'activites agricoles ou urbaines differentes mais bien identifiees, entrainant pour ces eaux des caracteristiques trophiques differentes. Dans un tel cas, il aurait pu sembler a priori possible d'etablir une classification des differents etats trophiques des lacs. Cependant, meme dans une situation aussi ideale, et essentiellement a cause des deux difficultes mentionnees precedemment, nous tentons de montrer ici qu'il n'en est rien. Cela amene les commentaires d'ordre general suivants: - Si pour le systeme lacustre etudie ici, probablement parmi les plus ideaux, il est difficile a partir des criteres generalement retenus dans la plupart des etudes, (nutriments azotes, phosphores , chlorophylle, oxygene dissous, etc.) d'etablir un classement trophique, il semble a fortiori peu probable que cela puisse etre realise sur des systemes moins ideaux. - La litterature actuelle fait clairement apparaitre ce probleme majeur. Cependant pour y remedier, elle propose generalement de faire le choix d'autres indicateurs physico-chimiques ou meme biologiques qui, pour les memes raisons, semblent egalement voues a l'echec. En conclusion de cette etude, nous proposons donc d'abandonner de tels indicateurs lies au milieu et de choisir de nouveaux criteres qui prendraient en compte les perturbations apportees par le phenomene aux interactions liant les variables analytiques: les differents etats trophiques d'une eau etant probablement mieux caracterises par les differents etats des relations liants les variables analytiques que par les valeurs intrinseques de ces variables.

The Limits of Windows and Herons

The Limits of Windows and Herons Ansted Moss (bio) Open bottles adorn the bar, green and brown birds that light flies through, green and brown glass meant for sacred windows. Cigar smoke makes a city of angels disappear, grayer clouds swallow clouds less gray. This atmosphere hides anything but thicker atmosphere; the best friendship to be had is with Jack Daniels and other presences from the best countries in the world in this one small place near where people first started and where killing therefore first started also. Thick diplomatic presence makes an embassy for every one here; voices twitter saying only what it won't hurt to repeat, but some of what tries to get said won't translate politely. The shine of waiter's teeth makes military medals look like coal. How can such a paradise become a place of despair? How can the bottles fly? Can Heineken mean heron? Can light that shines through the stained glass window putting patches as green as grass on bare floors where nothing grows in dirt from shoeprints be the same light that keeps freshly killed corpses warm? There is forest of corpses on the hill all around a church; the clothes of corpses are so colorful it seems a forest of cut-down Christmas trees. Every color ever wished for is there. The hotel soon has no white light; only darkness [End Page 1049] is left to do what darkness can do. Flickers, candles in the age of power; the hotel doesn't even belong to Rwanda. It is as Belgium as the popular beer. Where does hospitality end? How far can it go when it travels in bottles that don't know their limits as church windows and herons? And genies come out of bottles And nothing goes back in. The world spills. The comfort of the five star beds Five star meals, room service and five star pillows become the five star caskets of children men women As gunshots are fired, each has a certain name on it, a customized bullet as if no Tutsi mistake has been made Shattered glass forms a mosaic tribute to those whose blood crystallizes on the glass The chants of those who plan to kill become the chants of funerals Each explosive is like a personal ballad giving each person personal recognition There are only low-pitched anthems deep kettle drum rumbles like the earth itself talking: each grave that is dug opens up another mouth. Ansted Moss Ansted Moss, a fourteen-year-old high school freshman is a composer, jazz pianist, and photographer. He has performed with the Wynton Marsalis Septet. Copyright © 2005 Charles H. Rowell

EPR dosimetry using commercial glasses for high gamma doses

Commercial transparent and colored (bronze, brown, and green) glasses were studied as possible dosimeters for high gamma doses using electronic paramagnetic resonance (EPR). All EPR spectra showed the characteristic Fe 3+ signals, g = 4.27 and 2.01. The signal at g = 2.01 presented a more useable behavior for the calibration curve. All samples showed their usefulness as high dose dosimeters.

Beet necrotic yellow vein benyvirus

Beet necrotic yellow vein benyvirus

Evidence for high‐Ca boninite magmatism from Paleogene primitive low‐K tholeiite, Mukoojima, Hahajima Island group, southern Bonin (Ogasawara) forearc, Japan

Abstract High‐Ca boninitic inclusions are found in primitive low‐K tholeiite from Mukoojima (Mukoo‐Jima), an islet in the Hahajima Island group, Bonin (Ogasawara) forearc, Japan. While Chichijima Island group, 50 km north of Hahajima Island group, is well known as a type locality of boninite, there has been no report of boninitic rocks from the Hahajima Island group. The high‐Ca boninitic inclusions are aphanitic and contain olivine, Ca‐rich clinopyroxene, plagioclase, chromian spinel, opaque minerals and dark brown glass. The mode of occurrence of the inclusions and host tholeiite under the microscope indicates mingling of these two magmas, suggesting intimate association in space and time of the boninite and primitive tholeiite magmas around the Hahajima Island group in Paleogene time. Primitive compositions and slightly different Sr and Nd isotopic ratios suggest that these two magmas are derived from two distinct mantle sources. These two mantle sources were present at the same time around the Hahajima Island group, southern Bonin forearc. The source of the high‐Ca boninite was higher in water content and/or shallower in depth compared to that of the primitive tholeiite.

EPMA and µ‐SRXRF analysis and TEM‐based microstructure characterization of a set of Roman glass fragments

AbstractA set of Roman glass fragments, excavated at Bliesbruck–Reinheim (French–German border), were analysed by electron probe microanalysis (EPMA) and micro‐synchrotron radiation‐induced x‐ray fluorescence (µ‐SRXRF) in order to determine the major, minor and trace chemical composition. Based on this analysis, five classes of mono‐coloured glass could be discerned. However, one piece of this set was not mono‐coloured, but consisted of a mixture of brown and white opaque glass. This fragment was investigated using EPMA and transmission electron microscopy (TEM) in order to gain a better insight into its microstructure. Both colours proved to contain small crystalline inhomogeneities. Structural information reveals the form in which the detected elements are present and helps to explain the appearance (e.g. colour) of the material. Copyright © 2004 John Wiley & Sons, Ltd.

Studies on expansion properties in mortar containing waste glass and fibers

The utilization of waste glass in concrete can cause cracking and weakening due to expansion by alkali–silica reaction (ASR). In this study, ASR expansion and properties of strength were analyzed in terms of waste glass content, glass color (brown, green), fibers (steel fiber, polypropylene fiber) and fiber content, in anticipation of reducing ASR expansion. Results showed that green waste glass was more usable than brown because its expansion was less than that of brown glass. Using the accelerated ASTM C 1260 test of waste glass, no pessimum content was found. Furthermore, when fibers and waste glass were combined, there was an effect on the reduction of expansion and strength loss due to ASR between the alkali in the cement paste and the silica in the waste glass. In particular, adding 1.5 vol.% of steel fiber to concrete containing 20% waste glass reduced the expansion ratio by 40% and increased flexural strength by up to 110%, a vast improvement when compared with using only waste glass (80 °C H 2O curing) by itself.

Tableting and stability evaluation of enteric-coated omeprazole pellets

In this study, fluidized-bed manufactured enteric-coated omeprazole pellets were compressed into tablets. The stability of the pellets and those of compressed tablets were evaluated for remaining omeprazole and for degradation products under an accelerated stability protocol. The data were analyzed using the artificial neural network (ANN) and analysis of variance (ANOVA). It was found that enteric-coated omeprazole pellets could be compressed into quickly disintegrating tablets using microcrystalline cellulose granules as the pressure absorbing matrix. The ANN, using the multilayer perceptron model, predicted that there was a positive correlation between tablet crushing strength and microcrystalline cellulose concentration. Microcrystalline cellulose matrix showed a strong plastic deformation and all the pellets inside the tablet maintained their integrity with no significant change in their surface properties. Omeprazole degradation in acid medium was mainly dependent on microcrystalline cellulose concentration. A 90-day accelerated stability test in brown glass bottles with a desiccant showed that all prototype formulations would result in an acceptable stability profile for both remaining omeprazole, and also for the increase of impurity concentrations.

Tephrostratigraphy and tephrochronology in the Philippi peat basin, Macedonia, Northern Hellas (Greece)

Three tephra layers have been identified in the upper 15 m of a 190-m section of peat beneath the Philippi fen. They provide significant lithological and chronological markers throughout the fen and the Aegean region. The upper tephra (PhT1) consists of shards of a transparent calcalkaline felsic glass and fragments of plagioclase, augite, hypersthene, and rare hornblende, magnetite, apatite and quartz. Peat directly beneath PhT1 gave a radiocarbon approximate age of 13,000 yr. The middle tephra layer (PhT2), which resembles PhT1 in chemistry and petrography but contains more crystals and lithic fragments, rests on peat dated ca 18,000 14C yr BP. The lower tephra (PhT3) has colorless to brown glass shards with a trachytic chemistry and a mineral assemblage of sanidine, sodic plagioclase, biotite, aegirine-augite, hornblende, titanite and apatite. Bracketing radiocarbon ages imply that PhT3 accumulated about ∼30,000 14C yr BP. The likely ages of PhT1 and PhT2, together with their mineralogical and chemical characteristics, suggest that these tephras came from the volcanic field of Thera in the Hellenic arc. PhT2 particularly was derived from a major, known explosive eruption ca 18,000 yr BP, the Cape Riva eruption, correlative to the Y-2 tephra layer. Evidence for PhT3 suggests derivation from the Campanian Province of Italy, and correlation with the Campanian Ignimbrite and the Y-5 ash beneath the Mediterranean Sea.

Textural and Thermal History of Partial Melting in Tonalitic Wallrock at the Margin of a Basalt Dike, Wallowa Mountains, Oregon

Columbia River Basalt Group dikes invade biotite---hornblende tonalite to granodiorite rocks of the Wallowa Mountains. Most dikes are strongly quenched against wallrock, but rare dike segments have preserved zones of partial melt in adjacent wallrock and provide an opportunity to examine shallow crustal melting. At Maxwell Lake, the 4 m thick wallrock partial melt zone contains as much as 47 vol. % melt (glass plus quench crystals) around mineral reaction sites and along quartz--feldspar boundaries. Bulk compositional data indicate that melting took place under closed conditions (excepting volatiles). With progressive melting, hornblende, biotite, and orthoclase were consumed but plagioclase, quartz, and magnetite persisted in the restite. Clinopyroxene, orthopyroxene, plagioclase, and Fe---Ti oxides were produced during dehydration-melting reactions involving hornblende and biotite. Reacting phases became more heterogeneous with progressive melting; crystallizing phases were relatively homogeneous. Progressive melting produced an early clear glass, followed by light (high-K) and dark (high-Ca) brown glass domains overprinted by devitrification. Melts were metaluminous and granitic to granodioritic. Thermal modeling of the partial melt zone suggests that melting took place over a period of about 4 years. Thus, rare dikes with melted margins represent long-lived portions of the Columbia River Basalt dike system and may have sustained large flows.

Capitalist Abstraction and the Body Politics of Place in Toni Cade Bambara's Those Bones Are Not My Child

The autobiographical Prologue to Toni Cade Bambara's Those Bones Are Not My Child (1999) provides an intensely localized narrative cartography of a working-class, African American neighborhood in southwest Atlanta circa 1981. We witness the authorial figure “running down the streets of southwest Atlanta like a crazy woman” – running because “[a] cab can't jump the gully back of the fish joint and can't take the shortcut through the Laundromat lot.” Bambara does not detail these quotidian geographies just for the sake of it: her novel is immersed in the period (1979–81) when Atlanta's black community was both torn asunder and brought together by the disappearance and death of a number of local children. The Prologue's protagonist walks through the wooded lot because, in such secluded spaces, she might find evidence that will help to solve the Atlanta Child Murders: “You stub your toe on brown glass … you pry loose a crusty beer bottle … beneath the bottle is a rain-blurred Popsicle wrapper. Late summer, you figure, moving on.” The narrator runs frantically because she is supposed to collect her twelve-year-old child (apparently Bambara's own daughter, Karma) from school in a time and place when local youths are going missing, and being found murdered.

Stability of ranitidine in injectable solutions

Injectable solutions of ranitidine were prepared by dissolving ranitidine hydrochloride in water for injections. The following buffering system has been used: disodium phosphate (anhydrous), potassium dihydrogen phosphate, and phenol as a preservative. Inert gas (nitrogen) was used to displace oxygen from a solution and reduce the possibility of oxidative changes in the formulation. The solution was poured into 2-ml brown glass ampoules in asceptic condition. Ampoules samples have been stored at three different temperatures. They have been stored at 55 and 40 °C for 6 months, and at 25 °C for 12 months. TLC technique has been used for monitoring related substances, and HPLC technique for monitoring phenol and ranitidine content. It has been shown that only those samples that were stored at 25 °C were actually stable.

Effect of menadione (vitamin K3) addition on lipid oxidation and tocopherols content in plant oils.

The effect of added menadione (vitamin K3) on stored corn and wheat germ oil on the dissolution and dimerization of natural tocopherols and autoxidation of triacylglycerols was investigated. Samples of corn and wheat germ oils pure and with added menadione were stored at +20 degrees C in brown and transparent glass bottles. During storage their peroxide value, changes of the content of fatty acids and dissolution of tocopherols were measured. Destruction of individual tocopherols in tested oils with menadione stored in both dark and transparent glass bottles was greater than in the oil samples without menadione. However, the degradation of individual tocopherols was different in each oil. Addition of menadione to the both oils resulted in accelerated the process of autoxidation of these oils. The corn oil stored in transparent bottles was oxidized faster than the one stored in brown bottles. The pro-oxidant activity of menadione was additionally activated by light. In contrast, in the case of germ oil, the process of autoxidation was very fast regardless of sort of container. Addition of menadione to the plant oils influenced the dissolution of natural tocopherols but did not influence the dimerization of tocopherols. As from the experiment, the addition of menadione to the oils decreased their nutritive value.

Production of clenbuterol, diethylstilbestrol and trenbolone mass standards in lyophilised bovine urine

Clenbuterol (CLEN), diethylstilbestrol (DES) and trenbolone (TbOH) are xenobiotic growth promoters and have been illegally applied as repartitioning agents in meat-producing animals. In the EU, proper detection methods and control systems are established for many hormones and anabolic substances, and therefore there is a need to improve the accuracy and repeatability of quantification. In order to define a common basis for accurate measurement and quantification, standard materials were produced as lyophilised bovine urine: ‘negative’ drug free controls, and ‘positive’ standards (CLEN ∼3 μg kg −1; DES ∼2 μg kg −1, TbOH ∼3 μg kg −1). Two milligram of CLEN or DES were applied orally in milk replacer to the calves. Two gram of TbOH-acetate was given as an implant. ‘Positive’ urine was sampled frequently between 12 and 24 h after application. ‘Negative’ urine was sampled from untreated calves only fed with milk replacer. Urines were pooled separately and diluted with ‘negative’ urine to a suitable level of final concentrations. Exactly 5.0 g portions of each standard were weighed into 750 brown glass containers and lyophilised in one batch. Container filling, dry matter and residual water content were determined and optimized. A 3-year stability and homogeneity study at various storage temperatures (−20 °C, +4 °C and +20 °C and +37 °C) indicate that all standards are stable and homogeneous. Reconstituted urines were quantified via ELISA and findings after reconstitution remained constant in ‘positive’ (+) standards and ‘negative’ (−) controls: CLEN+ (2.75±0.62 μg kg −1; n=133), CLEN− (0.023 μg kg −1 equivalents; n=130), DES+ (1.75±0.52 μg kg −1; n=133), DES− (0.034 μg kg −1 equivalents; n=133), TbOH+ (2.78±0.47 μg kg −1; n=133), TbOH− (0.022 μg kg −1 equivalents; n=133). Additionally, concentrations and identities of the drugs were confirmed by two independent accredited laboratories via HPLC–ELISA, LC–MS and GC–MS.

Milburn's bump from Brown's glass ceiling

My recent visits to the Members’ Lobby have, unfortunately, not coincided with those of Alan Milburn. I have not therefore been able to see just how he conceals the bump incurred when he came full tilt into contact with the Brown glass ceiling. I hear his spin doctors have concealed it by acclaiming his three-head meeting with Tony Blair and Gordon Brown as a triumph for the ‘foundation hospitals’ favoured by Blair and Milburn.

Basalt triggering of the c. AD 1305 Kaharoa rhyolite eruption, Tarawera Volcanic Complex, New Zealand

The ∼AD 1305 Kaharoa eruption episode of Tarawera Volcanic Complex was the largest (∼4 km3 magma) eruption in New Zealand in the last 1000 years. High-silica (∼76% SiO2) rhyolite was erupted from seven vents along an 8-km linear zone to form pumiceous pyroclastic deposits and lava domes. Initial vent-clearing explosions were followed by a series of plinian pumice eruptions that spread tephra downwind, and pyroclastic density current deposits over the volcano slopes. The early pyroclastic eruptions were followed by extrusion of a dome in the summit vent and the migration of further plinian activity to adjacent vents. The episode finished with the extrusion of three summit lava domes, accompanied by block-and-ash flows. Two main types of rhyolite were erupted: (1) a low-Zr, low-Sr, high-Rb type comprising the early plinian pyroclastics and (2) a high-Zr, high-Sr, low-Rb type comprising the late eruptives including the summit domes. Basaltic material (basalt and basaltic andesite) is commonly present as free clasts within the Kaharoa pyroclastic deposits, along with rare clasts of granodiorite, diorite, gabbro and olivine clinopyroxenite. The basaltic clasts are often veneered by Kaharoa rhyolite. Basaltic material is also common as inclusions within rhyolite pumices, along with olivine and augite xenocrysts derived from the basalt. The basaltic clasts and inclusions contain complexly zoned plagioclase and corroded olivine (commonly with a reaction rim) consistent with disequilibrium caused by magma mixing. Some basaltic clasts and inclusions are hornblende-free; others contain groundmass hornblende. ‘Plumes’ of brown glass often extend from hornblende-bearing basaltic inclusions into the surrounding rhyolite. These plumes demonstrate magma mixing, as does the presence of rhyolitic glass and quartz xenocrysts in some basaltic inclusions. Most basaltic inclusions have crenulate boundaries, suggesting they were fluidal when coming into contact with the rhyolite magma. Diorite, gabbro and olivine clinopyroxenite clasts have mineralogy similar to the basalts, commonly contain patches of fine-grained basaltic material, and are considered co-magmatic with the basalts. Intrusion of basalt magma into the base of the rhyolite magma chamber appears to have occurred for some time before the Kaharoa eruptions began, allowing considerable mixing with the rhyolite magma, transfer of water to some basalt inclusions and formation of hornblende in their groundmass. Conversely, the hornblende-free basalt inclusions did not have time to react with the rhyolite magma and must have been intruded shortly before the start of the eruption. Intrusion of this hornblende-free basalt appears to have triggered the Kaharoa eruption, after the magma chamber had been primed by the earlier intrusions.

Partial melting in crustal xenoliths and anatectic migmatites: a comparison

Abstract Anatectic xenoliths from the volcanic fields of the Eifel (Germany) and the Chaine des Puys (Massif Central, France) contain a glass phase (quenched in-situ melt) along mineral grain boundaries. Microanalytical studies show that on a mm- to cm-scale melt chemistry is strongly controlled by the mineral phases involved in anatexis. Domains rich in mafic phases (biotite, orthopyroxene, spinel, garnet) contain brown glass with much higher abundances of FeO, MgO and TiO 2 than colourless glass in quartzofeldspathic layers. By contrast, K 2 O abundances are similar. Differences in melt composition in turn strongly control the crystallization of minerals from the melt as well as minor reactions between the melt and the xenolith phase assemblage. In comparison, textural features of anatectic HT-LP migmatites from SW Finland provide evidence of both prograde and retrograde reactions between minerals and melt. They reveal, that the modal and also the chemical composition of migmatites is more strongly affected by retrograde processes than in xenoliths. Hence, microanalytical and textural studies of partially melted crustal xenoliths can provide important insights in prograde processes operating in migmatitic terranes.

Dhofar 081: A new lunar highland meteorite

Abstract— The lunar meteorite Dhofar 081, found as a single fragment of 174 g in the Dhofar region of Oman, is a shocked feldspathic fragmental highland breccia dominated by anorthosite‐rich lithic and mineral clasts embedded into a fine‐grained mostly shock melted clastic matrix. Major mineral phases in the bulk rock are Ca‐rich plagioclase (An96.5–99.5), pyroxene (FS21.9–46.2Wo3.0–41.4), and olivine (Fa29.3–47.8); accessory phases include Fe‐Ni metal, ilmenite, and Ti‐Cr‐rich spinel. Dhofar 081 contains subordinate crystalline fragments of large anorthosites, intersertal impact‐melt rocks, microporphyritic impact‐melt breccias, dark fine‐grained impact‐melt breccias, large cataclastic feldspars, and irregularly shaped brown glass clasts. Mafic components are rare and no genuine regolith components were found in the sections studied. Minerals in Dhofar 081 show homogeneously distributed shock features: intergranular recrystallization, strong fracturing and mosaicism in feldspar as well as a high density of mostly irregular fractures in pyroxene and olivine. Localized impact melting caused by one or several impacts led to a strong lithification. Based on these effects an equilibration shock pressure of about 15–20 GPa is estimated for the strongest shock event in Dhofar 081. Devitrification of the “glassy” material in the rock indicates thermal annealing after shock melting suggesting that the 15–20 GPa shock event predated the ejection event. According to the concentrations of implanted solar noble gases Dhofar 081 represents a polymict clastic breccia deposit with possibly a minor regolith component. A similar noble gas record of Dhofar 081 and MacAlpine Hills 88104/05 suggests the possibility of a source crater pairing of both meteorites. As indicated by noble gas measurements pairing of Dhofar 081 with the other lunar meteorites found in Oman, Dhofar 025 and Dhofar 026, is unlikely.

Influence of added menadione (vitamin K3) on dissolution and dimerization of tocopherols and autoxidation of triacylglycerols during storage of plant oils.

The effect of added menadione (vit. K3) to stored rapeseed and soybean oil on the dissolution and dimerization of natural tocopherols and autoxidation of triacylglycerols was studied. Commercial rapeseed and soybean oils with added menadione and pure oil were stored at +20 degrees C in brown and transparent glass bottles. During storage their peroxide value, changes of the content of fatty acids and dissolution of tocopherols were measured. Destruction of individual tocopherols in tested oils with added menadione stored in both dark and transparent glass bottles were greater than in the oil samples without menadione. However, the degradation of individual tocopherols was different in each oil. Addition of menadione to the rapeseed and soybean oils resulted in the accelerated process of autoxidation of these oils. The oxidative state of the oils was lower in the oils stored in transparent bottles than in the oils stored in brown bottles. The prooxidant activity of menadione was additionally activated by light. Menadione added to the vegetable oils influenced the dissolution of natural tocopherols as well as their dimerization. It is conduced that addition of menadione to vegetable oils decreases their nutritive value.

COLOURED OPAQUE GLASS BEADS OF THE MEROVINGIANS*

Monochrome coloured opaque glass beads of the Merovingians have been examined by different analytical methods. A large number of mostly unprepared beads have been measured by X‐ray fluorescence analysis. X‐ray diffraction was used for the identification of the crystalline colouring and opacifying pigments, and electron probe micro‐analysis as well as scanning electron microscopy were applied to study the composition and the microstructure of a white, brown, green, orange and yellow glass bead. After subtracting the content of colouring oxides of the glass beads and normalizing the residual values to 100% an identical soda‐lime‐glass matrix was obtained. The origin of the colouring metal oxides is discussed.