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Etude de l'impact des vieillissements photochimique, thermique et climatique sur les propriétés d'aspect de polypropylènes teintés masse colorés / Study of impact of photochemical, thermal and climatic aging on appearance properties of mass-coloured polypropyleneRouillon, Camille 07 December 2015 (has links)
Sous l’impact de contraintes photochimiques, thermiques, et hydrolytiques, les polymères subissent une dégradation souvent irréversible de leurs propriétés fonctionnelles. L’étude des mécanismes à l’origine de cette dégradation est indispensable pour la compréhension des phénomènes mis en jeu à toutes les échelles et pour la prévision de la durée de vie du matériau. L’enjeu de cette thèse est de comprendre les mécanismes à l’origine de la perte des propriétés d’aspect de matériaux en polypropylène teinté dans la masse soumis à un vieillissement photochimique, en suivant une approche multi-échelles et multi-critères. La composition des matériaux a été progressivement complexifiée au cours de l’étude, afin de pouvoir comprendre l’influence de l’ajout de pigments organiques, de stabilisants, et de talc, sur les modifications d’aspect des pièces sous irradiation. Grâce aux résultats obtenus et aux valeurs-seuils alors définies pour chaque critère de dégradation identifié, un modèle analytique d’étude du vieillissement de pièces en polypropylène teinté dans la masse a pu être proposé. / Under photochemical, thermal and hydrolytic stresses, polymers undergo an often-irreversible degradation of their functional properties. The study of the mechanisms governing the degradation of the properties is important, and understanding the involved phenomena at every scale is mandatory to predict the material lifetime. This PhD thesis aims at understanding the mechanisms underlying the loss of appearance properties of mass coloured polypropylene materials, using a multi-scale and multi-criteria approach. Formulations were progressively made more complex during this study, in order to understand the influence of organic pigments, stabilizers, and talc, on the appearance changes of the material under exposure. Thanks to the obtained results and to the threshold values determined for each identified criterion during degradation monitoring, an analytical model to study mass coloured polypropylene ageing could be proposed.
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Exploring Transition Metal Oxides Towards Development of New Functional Materials : Lithium-ion Battery Cathodes, Inorganic Pigments And Frustrated Magnetic Perovskite OxidesLaha, Sourav January 2016 (has links) (PDF)
Transition metals (TMs) are ‘elements whose atoms have partially filled d-shell, or which can give rise to cations with an incomplete d-shell’. In TMs, the d-shell overlaps with next higher s-shell. Most of the TMs exhibit more than one (multiple) oxidation states. Some TMs, such as silver and gold, occur naturally in their metallic state but, most of the TM minerals are generally oxides. Most of the minerals on the planet earth are metal oxides, because of large free energies of formation for the oxides. The thermodynamic stability of the oxides is determined from the Ellingham diagram. Ellingham diagram shows the temperature dependence of the stability (free energy) for binaries such as metal oxides. Ellingham diagram also shows the ease of reducibility of metal oxides.
TM oxides of general formulas MO, M2O3, MO2, M2O5, MO3 are known to exist, many of them being the ultimate products of oxidation in air in their highest oxidation states. In addition, TM oxides also exist in lower oxidation states which are prepared under controlled conditions. The nature of bonding in these oxides varies from mainly ionic (e.g. NiO, CoO) to mainly covalent (e.g. OsO4). Simple binary oxides of the compositions, MO, generally possess the rock salt structure (e.g. NiO), while the dioxides, MO2, possess the rutile structure (e.g. TiO2); many sesquioxides, M2O3, possess the corundum structure (e.g. Cr2O3). TMs form important ternary oxides like perovskites (e.g. CaTiO3), spinels (e.g. MgFe2O4) and so on. In TM oxides, the valence (outer) d-shell could be empty, d0 (e. g. TiO2), partially filled, dn (1≤ n≤ 9) (e.g. TiO, VO, NiO etc.) or completely filled, d10 (e.g. ZnO, CdO, Cu2O etc.). The outer d electrons in TM oxides could be localized or delocalized. Localized outer d electrons give insulators/semiconductors, while delocalized/itinerant d electrons make the TM oxide ‘metallic’ (e.g. ReO3, RuO2). Partially filled dn states are normally expected to give rise to itinerant (metallic) electron behaviour. But most of TM oxides with partially filled d shell are insulators because of special electronic energy (correlation energy) involved in d electron transfer to adjacent sites. Such insulating TM oxides are known as Mott insulators (e. g. NiO, CoO etc.). Certain TM oxides are known to exhibit both localized (insulating) and itinerant (metallic) behaviour as a function of temperature or pressure. For example, VO2 shows a insulator–metal transition at ~340K. Similar transitions are also known for V2O3, metal-rich EuO and so on.
The chemical composition and bonding of TM oxides, which determine the crystal and electronic structures, give rise to functional properties. Table 1 gives representative examples. Properties like ionic conductivity and diffusion are governed by both the crystal structure and the defect structure (point defects), whereas properties such as magnetism and electron transport mainly arise from the electronic structures of the materials. Accordingly, TM oxides provide a platform for exploring functional materials properties. Among the various functional materials properties exhibited by transition metal oxides, the present thesis is devoted to investigations of lithium ion battery cathodes, inorganic pigments and magnetic perovskites.
Over the years, most of the lithium containing first row transition metal oxides of rock salt derived structure have been investigated for possible application as cathode materials in lithium ion batteries (LIBs). First major breakthrough in LIBs research was achieved by electrochemically deinserting and inserting lithium in LiCoO2. A new series of cathode materials for LIBs were prepared by incorporating excess lithium into the transition metal containing layered lithium oxides through solid solution formation between Li2MnO3–LiMO2 (M = Cr, Mn, Fe, Co, Ni), known as lithium-rich layered oxides (LLOs). LLOs exhibit improved electrochemical performance as compared to the corresponding end members and hence received significant attention as a potential next generation cathode materials for LIBs in recent times. LiCoO2 (R-3m) crystallizes in the layered α-NaFeO2 structure with the oxygens in a ccp arrangement. Li+ and Co3+ ions almost perfectly order in the octahedral sites (3a and 3b) to give alternating (111) planes of LiO6 and CoO6 octahedra.
Table 1. Materials properties exhibited by representative TM oxides.
Property Example(s)
Ferroelectricity BaTiO3, PbTiO3, Bi4Ti3O12
Nonlinear Optical Response LiNbO3
Multiferroic response BiFeO3, TbMnO3
Microwave dielectric properties Ba3ZnTa2O9
Relaxor Dielectric Properties Pb3MgNb2O9,
Colossal Magnetoresistance Tl2Mn2O7
Metallic ‘Ferroelectricity’ Cd2Re2O7
Superconductivity AOs2O6(A = K, Rb, Cs)
Redox deinsertion/insertion of LiCoO2
lithium
Photocatalysis/water splitting TiO2
Pigment Ca(1-x)LaxTaO(2-x)N1+x (yellow-red),
YIn1-xMnxO3 (blue)
Metallic Ferromagnetism CrO2
Antiferromagnetism NiO, LaFeO3
Zero thermal expansion ZrW2O8
The reversible capacity of LiCoO2 in common LIBs is relatively low at around 140 mA h g-1 (half of theoretical capacity), corresponding to:
LiCo3+O2 → Li0.5Co3+0.5Co4+0.5O2 + 0.5Li+ + 0.5e– .
Substitution of one or more transition metal ions in LiCOO2 has been explored to improve the electrochemical performance.
The structure of LLOs is described as a solid solution or nano composite of Li2MnO3 (C2/m) and LiMO2 (R-3m). The electrochemical deinsertion/insertion behaviour of LLOs is complex and also not yet understood completely.
The present thesis consists of four parts. After a brief introduction (Part 1), Part 2 is devoted to materials for Li-ion battery cathode, consisting of three Chapters 2.1, 2.2 and 2.3. In Chapter 2.1, we describe the synthesis, crystal structure, magnetic and electrochemical characterization of new LiCoO2 type rock salt oxides of formula, Li3M2RuO6 (M = Co, Ni). The M =Co oxide adopts the LiCoO2 (R-3m) structure, whereas the M = Ni oxide also adopts a similar layered structure related to Li2TiO3. Magnetic susceptibility measurements reveal that in Li3Co2RuO6, the oxidation states of transition metal ions are Co3+, Co2+ and Ru4+, whereas in Li3Ni2RuO6, the oxidation states are Ni2+ and Ru5+. Li3Co2RuO6 orders antiferromagnetically at ~10K. On the other hand, Li3Ni2RuO6 presents a ferrimagnetic behaviour with a Curie temperature of ~100K. Electrochemical Li-deinsertion/insertion studies show that high first charge capacities (between ca.160 and 180 mA h g−1) corresponding to ca.2/3 of theoretical capacity are reached albeit, in both cases, capacity retention and cyclability are not satisfactory.
Chapter 2.2 presents a study of new ruthenium containing LLOs, Li3MRuO5 (M = Co and Ni). Both the oxides crystallize in the layered LLO type LiCoO2 (α-NaFeO2) structure consisting of Li[Li0.2M0.4Ru0.4]O2 layers.
Magnetic susceptibility data suggest that the oxidation states of transition metals are Li3Co3+Ru4+O5 for the M = Co compound and Li3Ni2+Ru5+O5 for the M = Ni compound. Electrochemical investigations of lithium deintercalation–intercalation behaviour reveal that both Co and Ni phases exhibit attractive specific capacities of ca. 200 mA h g-1 at an average voltage of 4 V, that has been interpreted as due to the oxidation of Co3+ and Ru4+ in Li3CoRuO5 and Ni2+ to Ni4+ in the case of Li3NiRuO5. Thus, we find that ruthenium plays a favourable role in LLOs than in non-LLOs in stabilizing higher reversible electrochemical capacities.
In Chapter 2.3, we describe the synthesis, crystal structure and lithium deinsertion–insertion electrochemistry of two new LLOs, Li3MRuO5 (M=Mn, Fe) which are analogs of the oxides described in Chapter 2.2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m), while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R-3m) structure. Lithium electrochemistry shows typical behaviour of LLOs for both oxides, where participation of oxide ions in the electrochemical processes is observed. A long first charge process with capacities of 240 mA h g-1 (2.3 Li per f.u.) and 144 mA h g-1 (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. Further discharge–charge cycling points to partial reversibility. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn3+ and Ru4+ are partially oxidized to Mn4+ and Ru5+ in the sloping region at low voltage, while in the long plateau, O2- is also oxidized. In the Li3FeRuO5 oxide, the oxidation process appears to affect only Ru (4+ to 5+ in the sloping region) and O2- (plateau), while Fe seems to retain its 3+ state. Another characteristic feature of TMs is formation of several coloured solid materials where d–d transitions, band gap transitions and charge transfer transitions are involved in the colouration mechanism. Coloured TM oxides absorbing visible light find important applications as visible light photocatalyst (for example, yellow BiVO4 for solar water splitting and red Sr1-xNbO3 for oxidation of methylene blue) and inorganic pigments [for example, Egyptian blue (CaCuSi4O10), Malachite green (Cu2CO3(OH)2), Ochre red (Fe2O3)]. Pigments are applied as colouring materials in inks, dyes, paints, plastics, ceramic glazers, enamels and textiles. In this thesis, we have focused on the coloured TM oxides for possible application as inorganic pigments.
Generally, colours arise from electronic transitions that absorb visible light. Colours of the inorganic pigments arise mainly from electronic transitions involving TM ions in various ligand fields and charge transfer transitions governed by different selection rules. The ligand field d–d transitions are parity forbidden but are relaxed due to various reasons, such as distortion (absence of center of inversion) and vibronic coupling. The d-electrons can be excited by light absorption in the visible region of the spectrum imparting colour to the material. Charge transfer transitions in the visible region are not restricted by the parity selection rules and therefore give intense colours.
Here we have investigated the colours of manganese in unusual oxidation state (Mn5+) as well as the colours of different 3d-TM ions in distorted octahedral and trigonal prismatic sites in appropriate colourless crystalline host oxides. These results are discussed in Part 3 of the thesis.
In Chapter 3.1, we describe a blue/green inorganic material, Ba3(P1−xMnxO4)2 (I) based on tetrahedral Mn5+O4 :3d2 chromophore. The solid solutions (I) which are sky-blue and turquoise-blue for x ≤ 0•25 and dark green for x ≥ 0•50, are readily synthesized in air from commonly available starting materials, stabilizing the Mn5+O4 chromophore in an isostructural phosphate host. We suggest that the covalency/ionicity of P–O/Mn–O bonds in the solid solutions tunes the crystal field strength around Mn(V) such that a blue colour results for materials with small values of x. The material could serve as a nontoxic blue/green inorganic pigment.
In Chapter 3.2, an experimental investigation of the stabilization of the turquoise-coloured Mn5+O4 chromophore in various oxide hosts, viz., A3(VO4)2 (A = Ba, Sr, Ca), YVO4, and Ba2MO4 (M = Ti, Si), has been carried out. The results reveal that substitution of Mn5+O4 occurs in Ba3(VO4)2 forming the entire solid solution series Ba3(V1−xMnxO4)2 (0 < x ≤ 1.0), while, with the corresponding strontium derivative, only up to about 10% of Mn5+O4 substitution is possible. Ca3(VO4)2 and YVO4 do not stabilize Mn5+O4 at all. With Ba2MO4 (M = Ti, Si), we could prepare only partially substituted materials, Ba2M1−xMn5+xO4+x/2 for x up to 0.15, that are turquoise-coloured. We rationalize the results that a large stabilization of the O 2p-valence band states occurs in the presence of the electropositive barium that renders the Mn5+ oxidation state accessible in oxoanion compounds containing PO43−, VO43−, etc. By way of proof-of-concept, we synthesized new turquoise-coloured Mn5+O4 materials, Ba5(BO3)(MnO4)2Cl and Ba5(BO3)(PO4)(MnO4)Cl, based on the apatite – Ba5(PO4)3Cl – structure.
Chapter 3.3 discusses crystal structures, and optical absorption spectra/colours of 3d-transition metal substituted lyonsite type oxides, Li3Al1-xMIIIx(MoO4)3 (0< x ≤1.0) (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (0< x ≤1.0) (MII = Co, Ni, Cu). Crystal structures determined from Rietveld refinement of PXRD data reveal that in the smaller trivalent metal substituted lyonsite oxides, MIII ions occupy the octahedral (8d, 4c) sites and the lithium ions exclusively occur at the trigonal prismatic (4c) site in the orthorhombic (Pnma) structure; on the other hand, larger divalent cations (CoII/CuII) substituted derivatives show occupancy of CoII/CuII ions at both the octahedral and trigonal prismatic sites. We have investigated the colours and optical absorption spectra of Li3Al1-xMIIIx(MoO4)3 (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (MII = Co, Ni, Cu) and interpreted the results in terms of average crystal field strengths experienced by MIII/MII ions at multiple coordination geometries. We have also identified the role of metal-to-metal charge transfer (MMCT) from the partially filled transition metal 3d orbitals to the empty Mo – 4d orbitals in the resulting colours of these oxides.
B The ABO3 perovskite structure consists of a three dimensional framework of corner shared BO6 octahedra in which large A cation occupies dodecahedral site, surrounded by twelve oxide ions. The ideal cubic structure occurs when the Goldschmidt’s tolerance factor, t = (rA + rO)/{√2(rB + rO)}, adopts a value of unity and the A–O and B–O bond distances are perfectly matched. The BO6 octahedra tilt and bend the B – O – B bridges co-operatively to adjust for the non-ideal size of A cations, resulting deviation from ideal cubic structure to lower symmetries. Ordering of cations at the A and B sites of perovskite structure is an important phenomenon. Ordering of site cations in double (A2BB'O6) and multiple (A3BB'2O9) perovskites give rise to newer and interesting materials properties.
Depending upon the constituent transition metals and ordering, double perovskite oxides exhibit a variety of magnetic behaviour such as ferromagnetism, ferrimagnetism, antiferromagnetism, spin-glass magnetism and so on. We also have coupled magnetic properties such as magnetoresistance (Sr2FeMoO6), magnetodielectric (La2NiMnO6) and magnetooptic (Sr2CrWO6) behaviour. Here we have investigated new magnetically frustrated double perovskite oxides of the formula Ln3B2RuO9(B = Co, Ni and Ln = La, Nd).
The Chapter 4.1 describes Ln3B2RuO9 (B = Co, Ni and Ln = La, Nd) oxides (prepared by a solid state metathesis route) which adopt a monoclinic (P21/n) A2BB'O6 double perovskite structure, wherein the two independent octahedral 2c and 2d sites are occupied by B2+ and (B2+1/3Ru5+2/3) atoms, respectively. Temperature dependence of the molar magnetic susceptibility plots obtained under zero field cooled (ZFC) condition exhibit maxima in the temperature range 25–35K, suggesting an antiferromagnetic interaction in all these oxides. Ln3B2RuO9 oxides show spin-glass behavior and no long-range magnetic order is found down to 2 K. The results reveal the importance of competing nearest neighbour (NN), next nearest neighbor (NNN) and third nearest neighbour (third NN) interactions between the magnetic Ni2+/Co2+ and Ru5+ atoms in the partially ordered double perovskite structure that conspire to thwart the expected ferromagnetic order in these materials.
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Non-destructive assessment of leaf composition as related to growth of the grapevine (Vitis vinifera L. cv. Shiraz)Strever, Albert (Albert Erasmus) 03 1900 (has links)
Thesis (PhD(Agric))--Stellenbosch University, 2012 / ENGLISH ABSTRACT: Field spectroscopy was used to study leaf composition and selected factors (including canopy
growth manipulation and water status changes) that may impact on it in a Vitis vinifera cv. Shiraz
vineyard, showing considerable variability in vigour. Temporal and spatial variability in leaf
composition were incorporated into measurements by analysing leaves in different shoot positions
and at different developmental stages during three different growing seasons. Irrigation and
canopy manipulation treatments were also imposed in order to provide new insights into assessing
the grapevine leaf and possibly also the canopy growth and ageing dynamics as well as pigment
content, as a basis of executing a generally non-destructive measurement approach.
Despite large climatic differences between the seasons, canopy size seemed of crucial importance
in determining grapevine water relations in the grapevines from the different canopy manipulation
treatments. Drastic compensation effects in terms of secondary shoot growth also followed the
canopy reduction treatment. Despite this, canopy microclimate was apparently improved,
considering the results from light measurements as well as the ripening dynamics in the reduced
canopies. Reduced canopies also seemed to display a different canopy composition, in favour of
secondary growth. This could have impacted positively on water use efficiency as well as ripening,
due to higher photosynthetic efficiency of these leaves during the ripening stages. The reduced
canopy treatments offered the possibility of attaining technological ripeness at an earlier stage and
at comparatively lower potential alcohol levels.
This study illustrated the relevance of considering the vegetative development of the grapevine,
along with leaf ageing in the canopy, when conducting calibrated non-destructive measurements of
leaf pigments, structure and water content. The relevance of using multivariate techniques in leaf
spectroscopy was shown. This can be applied and simplified to aid in non-destructive leaf pigment,
structure and water content estimation in future studies. Even with the general variation
encountered in this vineyard, predictions of the major pigments in grapevine leaves were within
acceptable error margins. Further work is required to improve the modelling of xanthophylls, which
may require non-linear multivariate techniques.
Logistical shoot growth modelling was used in leaf age estimation and classification, which made it
possible to simplify statistical analysis of the leaf parameters mentioned. Practical application of
the modelled and predicted parameters was shown for a specific period in season two by
comparing the reaction of different treatments to developing water deficits. The results indicated
that several parameters, with special mention of the carotenoid:chlorophyll ratio and chlorophyll a:b
ratio, can be monitored on young and old leaves in the canopy in order to monitor developing water
deficit stress. The modelled parameters, however, did not seem to be sensitive enough to allow
specific prediction of predawn leaf water potential values. Specific leaf mass, equivalent water
thickness, total specific leaf mass as well as leaf chronological age were successfully predicted
from leaf spectral absorbance data, and this may be useful in future work on quantifying leaf
adaptation to the micro-environment within the canopy. / AFRIKAANSE OPSOMMING: Veldspektroskopie is gebruik om blaarsamestelling en spesifieke faktore (insluitend lowergroei
manipulasie en waterstatus veranderinge) wat ‘n impak kan hê in ‘n Vitis vinifera cv. Shiraz
wingerd, met beduidende variasie in groeikrag, te ondersoek. Ruimtelike, asook tydsgebonde,
variasie in blaarsamestelling is geïnkorporeer in die metings deur blare van verskillende
lootposisies en vir verskillende ontwikkelingstadia gedurende drie verskillende groeiseisoene te
meet. Besproeiings- en lowermanipulasie behandelings is ook uitgevoer om die dinamiek van
blaar- en lowergroei, veroudering, asook pigmentinhoud te bestudeer binne die konteks van die
uitvoering van ‘n nie-destruktiewe meetstrategie.
Ondanks groot klimaatsverskille tussen die seisoene, blyk lowergrootteverskille belangrik te wees
in die bepaling van wingerdstok-waterverhoudings in die verskillende lowermanipulasie
behandelings. Drastiese kompensasiereaksies ten opsigte van sylootgroei is waargeneem in
reaksie op die gereduseerde lowerbehandeling. Indien die resultate van ligmetings en
druifrypwording in die gereduseerde lowerbehandeling in ag geneem word, is lowermikroklimaat
egter steeds verbeter. Hierdie behandeling het oënskynlik ook veranderde lowersamestelling
gehad, tot voordeel van sylootgroei. Dit kon moontlik ‘n positiewe invloed gehad het op
waterverbruikseffektiwiteit asook druifrypwording, as gevolg van moontlike hoër fotosintetiese
effektiwiteit van die blare gedurende die rypwordingstadia. Die gereduseerde lowerbehandeling het
die moontlikheid gebied om tegnologiese rypheid by ‘n vroeër datum te bereik, met moontlike laer
alkoholvlakke in die wyn.
Hierdie studie het die belangrikheid beklemtoon om die vegetatiewe ontwikkeling van die
wingerdstok in ag te neem wanneer gekalibreerde nie-destruktiewe metings van blaarpigmente,
blaarstruktuur asook waterinhoud onderneem word. Die belang van multi-variant meettegnieke in
blaarspektroskopie is aangetoon. Dit kan verder vereenvoudig word ter ondersteuning van niedestruktiewe
meting van blaarpigment, -struktuur en -waterinhoudsbepaling in toekomstige studies.
Selfs met die variasie wat in die wingerd voorgekom het, was die voorspellings van die vlakke van
die belangrikste pigmente wat in wingerdblare aangetref word binne aanvaanbare foutgrense.
Opvolgwerk is nodig om die modellering van xanthofil te verbeter, aangesien dit moontlik nielineêre
multi-variant analise mag benodig.
Logistiese groeimodellering is gebruik om blaarouderdom te bepaal en te klassifiseer, wat dit
moontlik gemaak het om statistiese analise te vereenvoudig vir die genoemde blaarparameters.
Die praktiese toepassing van die gemodelleerde en voorspelde parameters is aangetoon vir ‘n
spesifieke gedeelte in seisoen twee, deur die reaksie van verskillende behandelings op
toenemende watertekorte te bestudeer. Resultate het aangetoon dat verskeie parameters, met
spesifieke klem op die karotenoïed:chlorofil verhouding, asook die chlorofil a:b verhouding,
gemoniteer kan word op jong en ouer blare in die lower ten einde ontwikkelende
waterstrestoestande te identifiseer. Die gemodelleerde parameters was egter klaarblyklik nie
sensitief genoeg vir akkurate voorspelling van voorsonsopkoms-waterpotensiaalvlakke nie.
Spesifieke blaarmassa, ekwivalente waterdikte, totale spesifieke blaarmassa, sowel as
blaarouderdom kon suksesvol voorspel word deur gebruik te maak van absorpsieblaarspektroskopie,
wat nuttig kan wees in toekomstige studies wat handel oor die kwantifisering
van blaaraanpassing by die mikro-omgewing binne ‘n wingerdlower.
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Skin colour, pigmentation and the perceived health of human facesStephen, Ian D. January 2009 (has links)
Many non-human animal species use colour to signal dominance, condition or reproductive status. These signals have not previously been noted in humans. This thesis investigates the effects of skin colouration and pigmentation on the apparent health of human faces. Section 2 showed that individuals with increased fruit and vegetable and carotenoid consumption have yellower skin (Study 1) due to increased carotenoid pigmentation in the skin (Study 2). In Section 3, participants enhanced the redness, yellowness and lightness of the skin portions of colour-calibrated facial photographs to optimise healthy appearance. This suggests roles for blood (red) and carotenoid/melanin (yellow) colouration in providing perceptible cues to health. The contrast between lips and facial skin colour was not found to affect the apparent health of the faces, except in the b* (yellowness) axis, where enhanced facial yellowness caused an apparent blue tint to the lips. In Section 4 participants enhanced empirically-derived oxygenated blood colour more than deoxygenated blood colour to optimise healthy appearance. In two-dimensional trials, when both blood colour axes could be manipulated simultaneously, deoxygenated blood colour was removed and replaced with oxygenated blood colour. Oxygenated blood colouration appears to drive the preference for redness in faces. In Section 5 participants increased carotenoid colour significantly more than they increased melanin colour in both single-axis and two-dimensional trials. Carotenoid colour appears to drive the preference for yellowness in faces. In a cross-cultural study (Section 6), preferences for red and yellow in faces were unaffected by face or participant ethnicity, while African participants lightened faces more than UK participants. A preference for more redness in East Asian faces was explained by this group’s lower initial redness. The thesis concludes that pigments that provide sexually-selected signals of quality in many non-human animal species – carotenoids and oxygenated blood - also provide perceptible cues to health in human faces.
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Postnatální vývoj GABAb-receptorů v přední mozkové kůře potkana / Postnatal development of GABAb-receptors in the frontal rat brain cortexKagan, Dmytro January 2015 (has links)
In this work, the detailed analysis of GABAB-R/G protein coupling in the course of pre- and postnatal development of rat brain cortex indicated the significant intrinsic efficacy of GABAB-receptors already shortly after the birth: at postnatal day 1 and 2. Subsequently, both baclofen and SKF97541-stimulated G protein activity, measured as the high-affinity [35 S]GTPγS binding, was increased. The highest level of agonist-stimulated [35 S]GTPγS binding was detected at postnatal days 14 and 15. In older rats, the efficacy, i.e. the maximum response of baclofen- and SKF97541-stimulated [35 S]GTPγS binding was continuously decreased so, that the level in adult, 90-days old rats was not different from that in newborn animals. The potency of G protein response to baclofen stimulation, characterized by EC50 values, was also high at birth but unchanged by further development. The individual variance among the agonists was observed in this respect, as the potency of SKF97541 response was decreased when compared in 2-days old and adult rats. The highest plasma membrane density of GABAB-R, determined by saturation binding assay with specific antagonist [3 H]CGP54626AA, was observed in 1-day old animals. The further development was reflected in decrease of receptor number. The adult level was ≈3- fold lower than...
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Identifikace mléčných a kolagenových pojiv používaných v barevných vrstvách uměleckých děl / Identification of milk and collagenous binders used in colour layers in art worksKofroňová, Pavla January 2012 (has links)
The task of this diploma thesis was to investigate the influence of inorganic pigments on the identification of casein oil and animal glue tempera by mass spectrometry MALDI- -TOF MS (Matrix-Assisted Laser Desorption/Ionisation - Time of Flight Mass Spectrometry). First, it was necessary to prepare a set of model colour layers containing casein and animal glue tempera together with ten inorganic pigments. Consequently, the method of peptide mass fingerprinting was used to obtain mass spectra of the samples. Finally, it was possible to compare and determine the characteristic peptide fragments for both proteinaceous binders and find pigments that most affected the identification of casein and rabbit glue temperas. The obtained values of m/z casein oil tempera and animal glue tempera were used to improve and complete reference database of protein binders that is used to identify protein binders in works of art at the Institute of Chemical Technology in Prague.
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Hybrid pigments from fibrous clays and chromophores inspired by the color of fruits, flowers and wine / Pigmentos híbridos a partir de argilas fibrosas e cromóforos inspirados nas cores de frutas, flores e vinhosSilva, Gustavo Thalmer de Medeiros 05 June 2019 (has links)
Features such as color, brightness, fluorescence and stability are extremely important in applications of pigments. Anthocyanins, the natural pigment responsible for most of the purple, blue and red colors of flowers and fruits, have great potential for practical applications as dyes or antioxidants. However, these applications are limited by their chemical reactivity, which is affected by several factors, including pH, temperature, light, and oxygen, among others. Hybrid materials inspired by the ancient Maya Blue pigment are a promising alternative to improve the properties and applicability of natural and synthetic dyes. Flavylium cations serve as models for the chemical and photochemical reactivity of anthocyanins. Likewise, pyranoflavylium cations serve as models of the fundamental chromophoric moiety of pyranoanthocyanins, molecules that can form from reactions of the grape anthocyanins in red wines during their maturation. Fibrous clays, constituents responsible by the excellent stability of Maya blue pigment, have channels that can potentially allow partial or full insertion of these dyes molecules. Therefore, in the present thesis, hybrid pigments were prepared by the adsorption of a series of synthetic flavylium cations and synthetic pyranoflavylium cations on the fibrous clays palygorskite and sepiolite and their photophysical properties and stability were evaluated. The observation of biexponential fluorescence decays is consistent with emission from dye molecules adsorbed at two distinct sites on the fibrous clays. The fluorescence properties of dye molecules can be improved, depending on the amount of dyes adsorbed on the clay, by the formation of dye/clay hybrids. The color of the adsorbed dye molecules wassomewhat more resistant to changes in external pH, photochemical stability was maintained and the thermal lability was markedly improved. Besides the development of novel hybrid flavylium cation/fibrous clay, we have achieved advances in the stabilization of these dye molecules, with regard mainly to the pH-dependent equilibrium and thermal treatment. In addition, the present work represents the first systematic study of hybrid materials prepared from pyranoflavylium cations. Therefore, the results obtained here definitively point to flavylium cations and pyranoflavylium cations as promising chromophores and fibrous clays as promising substrates for the development of novel, highly fluorescent hybrid pigments with attractive colors and marked chemical and thermal stability. / Características como cor, brilho, fluorescência e estabilidade são extremamente importantes em aplicações de pigmentos. As antocianinas, os pigmentos naturais responsáveis pela maioria das cores púrpura, azul e vermelha das flores e frutas, têm grande potencial para aplicações práticas como corantes ou antioxidantes. No entanto, estas aplicações são limitadas pela sua reatividade química, que é afetada por diversos fatores, incluindo o pH, temperatura, luz e oxigênio, entre outros. Os materiais híbridos inspirados no antigo pigmento Maya Blue são uma alternativa promissora para melhorar as propriedades e a aplicabilidade dos corantes naturais e sintéticos. Os cátions flavílios servem como modelos para a reatividade química e fotoquímica das antocianinas. Da mesma forma, os cátions piranoflavílios servem como modelos do cromóforo fundamental das piranoantocianinas, moléculas que podem se formar a partir de reações das antocianinas das uvas em vinhos tintos durante sua maturação. Argilas fibrosas, constituintes responsáveis pela excelente estabilidade do pigmento Azul Maia, possuem canais que podem potencialmente permitir a inserção parcial ou total dessas moléculas corantes. Portanto, na presente tese, pigmentos híbridos foram preparados pela adsorção de uma série de cátions flavílio e piranoflavílio sintéticos nas argilas fibrosas paligorsquita e sepiolita e suas propriedades fotofísicas e estabilidade foram avaliadas. A observação de decaimentos biexponenciais de fluorescência é condizente com a emissãode moléculas do corante adsorvidas em dois sítios distintos nas argilas fibrosas. As propriedades de fluorescência das moléculas de corante podem ser melhoradas, dependendo da quantidade de corante adsorvida na argila, aos híbridos do tipo corante/argila. A cor das moléculas de corante adsorvidas foi um pouco mais resistente a alterações no pH externo, a estabilidade fotoquímica foi mantida e a labilidade térmica foi marcadamente melhorada. Além do desenvolvimento de novos híbridos de cátions flavílios/argilas fibrosas, obtivemos avanços na estabilização dessas moléculas corantes, principalmente no que diz respeito aos equilíbrios dependentes do pH e ao tratamento térmico. Ao mesmo tempo, o presente trabalho representa o primeiro estudo sistemático de materiais híbridos preparados a partir de cátions piranoflavílios. Portanto, os resultados aqui obtidos apontam definitivamente para cátions flavílios e cátions piranoflavílios como cromóforos promissores e argilas fibrosas como substratos promissores para o desenvolvimento de novos pigmentos híbridos altamente fluorescentes com cores atrativas e estabilidade química e térmica marcante.
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[en] METROLOGICAL ASSESSMENT OF FLUORESCENCE SIGNALS OF MEASUREMENTS OF PIGMENTS IN WATER / [pt] AVALIAÇÃO METROLÓGICA DA RESPOSTA DE SINAIS DE FLUORESCÊNCIA PARA MEDIÇÕES DE PIGMENTOS EM ÁGUACARLOS EDUARDO DEODORO RODRIGUES 03 April 2008 (has links)
[pt] Objetivo. Fornecer confiabilidade às medições do LIDAR a
partir: (i) do
estabelecimento de padrões de configuração dos parâmetros
do equipamento, na
obtenção de sinais de fluorescência para medições de
pigmentos em água; (ii) da
avaliação de diferentes procedimentos para melhorar a
relação sinal-ruído,
preservando a integridade das bandas de interesse contidas
no espectro de
fluorescência; (iii) da verificação da repetitividade do
equipamento para medições de
comprimentos de onda associados aos máximos do espalhamento
Raman da água, da
banda de clorofila a, assim como, da banda de matéria
orgânica dissolvida (MOD);
(iv) e da avaliação da eficiência do processamento
desenvolvido para obtenção de
concentrações relativas da clorofila a quando comparadas
aos resultados
correlacionados à concentrações absolutas desse tipo de
pigmento. Motivação.
Contribuir para o desenvolvimento do monitoramento remoto
utilizando um sistema
LIDAR, fornecendo parâmetros que possibilitem maior
confiabilidade às informações
adquiridas pelo sistema. Contextualização. O monitoramento
ambiental é uma prática
adotada com maior freqüência por inúmeras empresas e
instituições com o objetivo
de minimizar impactos nocivos ao meio ambiente. O
monitoramento remoto é uma
ótima alternativa, pois, possibilita um levantamento prévio
de possíveis vazamentos
de diferentes tipos de poluição, sendo sensível à avaliação
de sutis alterações no
meio, possibilitando a identificação desses problemas antes
mesmo de se tornarem
aparentes. Metodologia. A prática adotada na obtenção de
êxito dos objetivos
apontados baseou-se: (i) na coleta de informação de
diferentes modelos de
monitoramento remoto, principalmente, utilizando um sistema
LIDAR; (ii) na coleta
de dados através da experimentação em laboratório e em
campo e (iii) no
desenvolvimento de processos que possibilitaram a análise
das informações contidas
nos sinais obtidos. Resultados. Na busca de um sinal-padrão
de resposta do
equipamento, o trabalho consiste em análises experimentais
e no desenvolvimento de
processos que auxiliem na análise das informações contidas
nos sinais. Dentre os
experimentos pode-se destacar duas abordagens: (i) a
primeira, no laboratório, a partir
de análise de amostras de água pura, que avalia as
flutuações do sinal de
fluorescência do espalhamento Raman da água para diferentes
parâmetros do
equipamento; (ii) e uma segunda análise, com dados in vivo,
que avalia a
concentração relativa de clorofila a para diferentes
processos a fim de obter um
processo padrão que diminui a sua incerteza na determinação
desse quantitativo.
Conclusões. O sensoriamento retomo é uma técnica útil para
a investigação
ambiental, porém, a implantação de práticas que contribuem
para o aumento da
confiabilidade dos dados fornecidos pelo sistema são
igualmente indispensáveis. / [en] Aim. Providing reliability of LIDAR readings of
fluorescence signals for
measurements of pigments in ocean water by: (i)
establishing configuration standards
for equipment parameters. (ii) assessing different
procedures to improve the signal-tonoise
relationship. (iii) preserving the integrity of the
wavelength bandwidth of the
fluorescence spectrum. (iv) verifying the repeatability of
wavelength measurements
associated with local maxima of the Raman scattering curve
of ocean water and
chlorophyll a, as well as organic materials (dissolved in
water) bandwidths. (v) and
assessing the efficiency of the methodology developed for
obtaining relative
concentrations of chlorophyll a. Motivation. Contributing
to the development of
remote monitoring when using the LIDAR technique. This
would bring about greater
reliability. Context. Over the years environmental
surveillance has been adopted by
many companies and institutions as an effective practice to
minimize harmful impacts
on the environment. The remote monitoring is unquestionably
a versatile alternative
for detecting possible leaking of noxious substances before
they become apparent.
Methodology. The procedures included: (i) collecting
information of different
physical models of remote monitoring. (ii) collecting data
from experiments carried
out in the laboratory and in situ. (iii) and developing a
procedure to analyze signal
information. Results. Two approaches were adopted when
carrying out the
experiments: (i) in the laboratory, by evaluating
fluorescence signal fluctuations of
the Raman scattering in ocean water for different equipment
parameters. (ii) and in
situ, by measuring the relative concentration of
chlorophyll a in ocean water for
different schemes in order to choose the standard one.
Conclusions. The remote
monitoring is a useful tool to carry out environmental
surveillance. But to increase
the reliability of data collected by the optical-laser
system apparatus the introduction
of metrological assessment procedures is mandatory.
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Análise de pigmentos fotossintetizantes e substâncias fenólicas em Gracilariopsis tenuifrons (C. J. Bird & E. C. Oliveira) Fredericq & Hommersand em diferentes intensidades de luz / Analysis of photosynthetic pigments and phenolic compounds in Gracilariopsis tenuifrons (C.J. Bird & E.C. Oliveira) Fredericq & Hommersand at different light intensitiesTorres, Priscila Bezerra 03 August 2012 (has links)
O estresse de luz pode afetar consideravelmente o crescimento e o desenvolvimento dos organismos fotossintetizantes. Nestas situações, é comum verificar respostas químicas que podem indicar diferentes estratégias de fotoproteção adotado pelo organismo. No presente trabalho, foram desenvolvidas metodologias de análise e extração de pigmentos fotossintetizantes e compostos fenólicos na macroalga vermelha Gracilariopsis tenuifrons com o objetivo de avaliar os efeitos do aumento intensidade de luz sobre estes compostos. Foi verificado que aumento da intensidade de luz não provocou redução na biomassa desta alga, ao contrário houve um maior incremento. Os pigmentos majoritários no extrato foram clorofila α, β-caroteno e zeaxantina. O carotenoide β-caroteno teve um comportamento correlacionado com o pigmento clorofila a, tendo as concentrações reduzidas com o aumento da intensidade de luz, sugerindo que ambos os pigmentos possuam uma mesma função na fotossíntese. Já a concentração da zeaxantina aumentou com a intensidade de luz nos dias iniciais, indicando uma função fotoproteção deste pigmento nesta alga. A capacidade redutora do extrato aumentou com a intensidade luminosa. No entanto, não foi possível afirmar se esse aumento foi realmente devido à síntese de compostos fenólicos ou a outras substâncias que desempenhem o mesmo papel. As análises em CLAE revelaram que um derivado da micosporina palitinol apresentou alta relação com o aumento da intensidade de luz, sendo essa resposta altamente correlacionada com os resultados no ensaio no Folin-Ciocalteu. Em conclusão, das substâncias analisadas neste trabalho, a zeaxantina e o derivado do palitinol foram as que apresentaram os resultados mais evidentes como antioxidantes / The high-light stress can adversely affect growth and development of photosyn-thetic organisms. In these situations, it is common to note chemical responses that may indicate different strategies of photoprotection. In this study, protocols were optimized for analysis and extraction of phenolic compounds and photosynthetic pig-ments in macrophytic red algae Gracilariopsis tenuifrons in order of evaluat-ing the effects of high-light stress on these compounds. It was found that an increase in light intensity has not caused decrease in biomass of algae; on the contrary, promotes a greater increase in biomass. Zeaxanthin, β-carotene and chlorophyll α were the major pigments present in the extract. The β-carotene and chlorophyll a were inversely dependent on the intensity of light. Both pigments were highly correlated sug-gesting the same role in photosynthesis. The concentration of the zeaxanthin was de-pendent on the intensity of light in the initial days, indicating a photoprotection function for this pigment. The reduction capacity of the extract increased with light intensity. However, it was not possible to state that this increase was actually due to the synthesis of phenolic compounds or other substances that perform the same role. The HPLC ana-lyzes revealed that a derivative of micosporina palitinol showed high correlation with the increase in light intensity. This response was highly correlated with the results for Folin-Ciocalteu assay. In conclusion, from all compounds analyzed in this work, zeax-anthin and the palitinol derivative presented clearer results as antioxidants
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Avaliação da variabilidade de biotipos de Moniliophthora perniciosa / Evaluation of Moniliophthora perniciosa biotypes variabilityGarcia, Lia Matelli 04 February 2010 (has links)
O basidiomiceto Moniliophthora perniciosa é conhecido por causar a doença vassoura-debruxa no cacau (Theobroma cacao), responsável por grandes perdas de produção nessa cultura. A população de M. perniciosa apresenta variabilidade devido à sua capacidade de colonização de outras espécies de plantas, o que permite a identificação de biótipos e conseqüente agrupamento de isolados com base no hospedeiro. A caracterização de biotipos do fungo contribui para melhor conhecimento da estrutura populacional e sua dispersão, o que é importante para utilização em programas de melhoramento. Com esse objetivo foi avaliada a variabilidade genética e fisiológica de isolados do fungo correspondentes a três biotipos considerando a análise de taxas de crescimento pelo desenvolvimento micelial em diferentes meios e ambientes de cultivo in vitro, como a incorporação de cisteína, metionina e lisina e das fontes de nitrogênio tartarato de amônio e nitrato de potássio, iluminação, suscetibilidade a fungicidas, compatibilidade somática (SCG Grupo de Compatibilidade Somática), análise de perfis protéicos por SDS-PAGE e seqüenciamento parcial do 28S rDNA. A história evolutiva do patógeno não está registrada em seqüências de genes ribossomais e proteínas totais. Além disso, crescimento e produção de pigmentos são características compartilhadas pelos biótipos, não sendo fatores primários para adaptação do patógeno, porém com provável papel na colonização do hospedeiro. / The Basidiomycete Moniliophthora perniciosa is known as the pathogen for witches\' broom disease in cocoa (Theobroma cacao), responsible for large yield losts. Population of M. perniciosa presents variability due to its ability to colonize other plant species, which allows biotype identification and strains grouping, based upon the host specie. Fungi biotype characterization contributes to the knowledge of population and its dispersion and epidemiological methods, important for breeding programs. To aim the genetic and physiological variability of three strains, characteristics as growing rates, measured by the mycelia spreading at different culture media and different culture conditions in vitro, cysteine, methionine, lysine, nitrogen sources ammonium tartrate and potassium nitrate incorporation, light, fungicide susceptibility, somatic compatibility (SCG), protein patterns by SDS-PAGE and partial sequencing of rRNA 28S region were done. The evolutional history of it is pathogen is not printed into ribosomal genes sequences and total proteins. Besides that, growing and dye production are characteristics shared by the biotypes and can not be a primary adaptation factor but it can play a role in the host colonization process.
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