The perfect paint in modern art conservation: a comparative study of 21st century vinyl emulsions

Contemporary painting places, and will continue to place, several questions about its meaning, its chemical nature, its durability and the best way to preserve it. This research aims at putting together comprehensive data on vinyl based paints, including their components, their properties, their aging behavior and their response to selected cleaning products. In this project degradation mechanisms of vinyl binders and formulations used in the 20th and 21st century were studied. Stability over time of selected vinyl polymers was assessed through natural indoor and artificially aging. The objective was to enhance knowledge and understanding of vinyl emulsion formulations and their performance over time. Overall conservation state of pictorial layers namely, adhesion, cohesion and discoloration of selected case studies from the Portuguese artist Julião Sarmento (b.1948) was correlated with the observed molecular level changes studied in laboratory experiments. Sarmento’s paintings were chosen due to conservation concerns (discoloration) on some of his works from the 90’s. Besides, research was carried out to start increasing the knowledge of what can be expected of PVAc based paints in terms of response to conservation treatments namely, surface cleaning. Artificial aging showed that the most recent formulations which are based on a poly(vinyl acetate), poly(vinyl chloride) and polyethylene terpolymer are less stable when compared to some homopolymer formulations. From the four pigments studied, titanium dioxide rutile and a carbon based black proved to be stabilizers for both types of polymer. The mixture lithopone plus calcium carbonate has showed to have a photocatalytic effect on the binders. The studied paintings showed to be in an overall good state of conservation except for the paintings created in the 90’s with white glue and a mixture of white lithoponeand calcium carbonate. Discoloration of this white paint seems to be irreversible and ongoing and is still a major concern. The disapearance of the plasticizer was the only change detected. The current works created by Sarmento are expected to be more stable as they were painted using the rutile titanium dioxide. Immersion/cleaning tests showed that vinyl based paints can be susceptible to water and organic solvents like ethanol as some evidences point to the removal/diffusion of additives from the paint. The observations made point to the need to further proceed in this research field.

Dialap – o contributo de uma fábrica de lapidação de diamantes na modernização de Lisboa

A fábrica de lapidação de diamantes, inaugurada em meados dos anos 60, constituiu um exemplo máximo da qualificação urbana e arquitectónica alcançada através de um programa industrial de ponta, respondendo excepcionalmente aos desafios colocados pelo Plano Director de 1948. A compreensão desta empresa tem de ser analisada numa estreita relação com as colónias, neste caso através das matérias-primas provenientes de Angola. Aos arquitectos coube o desígnio de projectarem um edifício que respondesse à riqueza inerente ao produto aí transformado, conciliando as linhas de produção, os paradigmas arquitectónicos defendidos pelo Movimento Moderno e a sua relação com a cidade. Com uma ambição de criarem um edifício modelar para as indústrias de lapidação de diamantes coevas existentes na Europa, os arquitectos Carlos Manuel Ramos e António Teixeira Guerra conceberam um edifício fabril que simbolizou, efectivamente, o paradigma da arquitectura industrial moderna, enquanto reflexo da evolução tecnológica associada à electricidade, devendo colocar-se a hipótese da sua classificação de âmbito nacional.

PEGylated DOTA-AHA-based Gd(III) chelates – A relaxometric study

Three PEGylated derivatives of 1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid) (DOTA-AHA) with different molecular weights were prepared and characterized. Their Gd(III) chelates were studied in aqueous solution using variable-temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17ONMR spectroscopy in view of the determination of their relaxivity and the parameters that govern it. The relaxivity varied from 5.1 to 6.5 mM-1.s-1 (37 ºC and 60 MHz) with the increasing molecular weight of the PEG chain, being slightly higher than that of the parent chelate Gd(DOTA-AHA), due to a small contribution of a slow global rotation of the complexes. A variable temperature 1H NMR study of several Ln(III) chelates of DOTA-A(PEG750)HA allowed the determination of the isomeric M/m ratio (M = square antiprismatic isomer and m = twisted square antiprismatic isomer, the latter presenting a much faster water exchange) which for the Gd(III) chelate was estimated in circa 1:0.2, very close to that of [Gd(DOTA)]-. This explains why the PEGylated Gd(III) chelate has a water rate exchange similar to that of [Gd(DOTA)]-. The predominance of the M isomer is a consequence of the bulky PEG moiety which does not favor the stabilization of the m isomer in sterically crowded systems at the substituent site, contrary to what happens with less packed asymmetrical DOTA-type chelates with substitution in one of the four acetate C(α) atoms.

Endoscopic retrograde cholangiopancreatography for suspected choledocholithiasis : from guidelines to clinical practice

Endoscopic retrograde cholangiopancreatography for suspected choledocholithiasis: From guidelines to clinical practice.

Tendências das publicações nas fases trimestral, bimestral e mensal das cinco décadas dos Arquivos Brasileiros de Cardiologia

OBJETIVO: Estudar tendências das publicações nos Arquivos Brasileiros de Cardiologia de março de 1948 a fevereiro de 1998, nas fases trimestral, bimestral e mensal de publicação. MÉTODOS: Foram sorteados aleatoriamente 25% dos fascículos de cada fase e constituída amostra de 98 fascículos: 13 (11,5%) da fase trimestral, 27 (23,5%) da fase bimestral e 58 (65%) da fase mensal. Foram estudados o tipo de texto, o número de autores, a procedência, o idioma, e as referências bibliográficas. RESULTADOS: Foram estudados 1.204 textos, 90 (7,5%) da fase trimestral, 238 (19,8%) da fase bimestral e 876 (72,8%) da fase mensal. Os textos mais freqüentes foram artigos originais (353), revisões de tema (350) e relatos de caso (205). Nas três fases de periodicidade: não houve diferença significativa das proporções de artigos originais, revisões e relatos de caso; houve maior número de autores na fase mensal; verificou-se concentração geográfica das contribuições [864 de 1204 (72%) de três Estados], diminuíram as contribuições internacionais (20,8%, 4,4% e 4,9%), houve redução de publicações em outras línguas; a média de referências internacionais superou 16,7 e de nacionais foi inferior a 4,7. CONCLUSÃO: A análise da tendência evolutiva em cinco décadas de publicação revelou hiatos que podem ser preenchidos pelos Arquivos Brasileiros de Cardiologia, para melhor acompanhar as tendências internacionais de editoração de periódicos médicos, das expectativas dos autores e dos leitores.

Notulae systematicae.

v.12-13(1945-1948)

Rhodora

v.50 (1948)

Megachilinae, bearbeitet von dr. H. Friese. Mit 132 abbildungen.

28

Manual of conchology, structural and systematic : with illustrations of the species. by George W. Tryon, Jr.

Ser.2, v.22

Archaeological explorations in Peru. by A.L. Kroeber -- ; Paul S. Martin --, editor.

v.2:no.4(1937)

Manual of conchology, structural and systematic : with illustrations of the species. by George W. Tryon, Jr.

Ser.2, v.20

Manual of conchology, structural and systematic : with illustrations of the species. by George W. Tryon, Jr.

Ser.2, v.14

Manual of conchology, structural and systematic : with illustrations of the species. by George W. Tryon, Jr.

Ser.2, v.19