Comparative study of the coprecipitation methods for the preparation of Layered Double Hydroxides

Coprecipitation is the method most frequently applied to prepare Layered Double Hydroxides (LDHs). Two variations of this method can be used, depending on the pH control conditions during the precipitation step. In one case the pH values are allowed to vary while in the other they are kept constant throughout coprecipitation. Although research groups have their preferences, no systematic comparison of the two variations of the coprecipitation method is available in the literature. On this basis, the objective of the present study was to compare the properties of LDHs prepared using the two forms of pH control in the coprecipitation method. The results showed that even though coprecipitation is easier to perform under conditions of variable pH values, materials with more interesting properties, from the point of view of technological applications, are obtained at constant pH. Higher crystallinity, smaller particle size, higher specific surface area and higher average pore diameter were found for materials obtained by coprecipitation at constant pH, when compared to the materials obtained at variable pH

Comparative Study of the Coprecipitation Methods for the Preparation of Layered Double Hydroxides

A coprecipitação é o método mais frequentemente utilizado para preparar Hidróxidos Duplos Lamelares (HDLs). Duas variações deste método podem ser utilizadas, dependendo das condições adotadas quanto ao controle de pH durante a etapa de precipitação. No primeiro caso o pH não é controlado e a síntese é conduzida em pH variável, ao passo que no segundo caso o pH é mantido constante durante a precipitação. Apesar de cada grupo de pesquisa ter suas preferências, nenhum estudo sistemático e comparativo destas duas variações do método está disponível na literatura. Desta forma, o objetivo deste estudo foi comparar as propriedades de HDLs preparados através das duas variações possíveis do método de coprecipitação. Os resultados demonstraram que, embora seja mais simples a síntese realizada sem controle de pH, materiais com propriedades mais interessantes do ponto de vista tecnológico foram obtidos pelo método que utiliza pH constante. Materiais com maior cristalinidade, partículas menores, maior área superficial e maior diâmetro médio de poros foram obtidos pelo método de coprecipitação em pH constante. Coprecipitation is the method most frequently applied to prepare Layered Double Hydroxides (LDHs). Two variations of this method can be used, depending on the pH control conditions during the precipitation step. In one case the pH values are allowed to vary while in the other they are kept constant throughout coprecipitation. Although research groups have their preferences, no systematic comparison of the two variations of the coprecipitation method is available in the literature. On this basis, the objective of the present study was to compare the properties of LDHs prepared using the two forms of pH control in the coprecipitation method. The results showed that even though coprecipitation is easier to perform under conditions of variable pH values, materials with more interesting properties, from the point of view of technological applications, are obtained at constant pH. Higher crystallinity, smaller particle size, higher specific surface area and higher average pore diameter were found for materials obtained by coprecipitation at constant pH, when compared to the materials obtained at variable pH

Comparative study of the coprecipitation methods for the preparation of Layered Double Hydroxides

Coprecipitation is the method most frequently applied to prepare Layered Double Hydroxides (LDHs). Two variations of this method can be used, depending on the pH control conditions during the precipitation step. In one case the pH values are allowed to vary while in the other they are kept constant throughout coprecipitation. Although research groups have their preferences, no systematic comparison of the two variations of the coprecipitation method is available in the literature. On this basis, the objective of the present study was to compare the properties of LDHs prepared using the two forms of pH control in the coprecipitation method. The results showed that even though coprecipitation is easier to perform under conditions of variable pH values, materials with more interesting properties, from the point of view of technological applications, are obtained at constant pH. Higher crystallinity, smaller particle size, higher specific surface area and higher average pore diameter were found for materials obtained by coprecipitation at constant pH, when compared to the materials obtained at variable pH

The cell biology of Leishmania: how to teach using animations.

Submitted by Nuzia Santos ([email protected]) on 2018-11-19T11:35:24Z No. of bitstreams: 1 The Cell Biology of Leishmania.pdf: 827064 bytes, checksum: c0a36de15baadb16d056af055b475f46 (MD5)Approved for entry into archive by Nuzia Santos ([email protected]) on 2018-11-19T11:39:57Z (GMT) No. of bitstreams: 1 The Cell Biology of Leishmania.pdf: 827064 bytes, checksum: c0a36de15baadb16d056af055b475f46 (MD5)Made available in DSpace on 2018-11-19T11:39:57Z (GMT). No. of bitstreams: 1 The Cell Biology of Leishmania.pdf: 827064 bytes, checksum: c0a36de15baadb16d056af055b475f46 (MD5) Previous issue date: 2013Universidade Federal do Rio de Janeiro. Instituto de Bioquímica Médica. Rio de Janeiro, RJ, Brasil/Fundação Cecierj. Rio de Janeiro, RJ, Brasil/Instituto Nacional de Metrologia, Qualidade e Tecnologia. Rio de Janeiro, RJ, BrasilFundação Cecierj. Rio de Janeiro, RJ, Brasil/Instituto Nacional de Metrologia, Qualidade e Tecnologia. Rio de Janeiro, RJ, Brasil/Universidade Santa Úrsula. Rio de Janeiro, RJ, BrasilInstituto Nacional de Metrologia, Qualidade e Tecnologia. Rio de Janeiro, RJ, Brasil/Universidade Federal do Rio de Janeiro. Instituto de Biofísica Carlos Chagas Filho. Rio de Janeiro, RJ, Brasil/Universidade Federal do Rio de Janeiro. Núcleo Multidisciplinar de Pesquisa. Rio de Janeiro, RJ, Brasil/Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem. Rio de Janeiro, RJ, BrasilFundação Cecierj. Rio de Janeiro, RJ, Brasil/Instituto Nacional de Metrologia, Qualidade e Tecnologia. Rio de Janeiro, RJ, BrasilFundação Oswaldo Cruz. Centro de Pesquisas René Rachou. Belo Horizonte, MG, BrasilInstituto Nacional de Metrologia, Qualidade e Tecnologia. Rio de Janeiro, RJ, Brasil,/Universidade Federal do Rio de Janeiro. Instituto de Biofísica Carlos Chagas Filho. Rio de Janeiro, RJ, Brasil/Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem. Rio de Janeiro, RJ, BrasilParasitic protozoa are important agents of human and animal diseases in Brazil and around the world. Protozoan parasites of the Leishmania genus are the causative agent of leishmaniasis, one of the most important neglected tropical diseases as designated by the World Health Organization (WHO). Leishmaniasis affects about 12 million people worldwide and can be divided into the following three main clinical manifestations: cutaneous, mucocutaneous, and visceral leishmaniasi

Schematic 3D view of the phases of interaction between the <i>Leishmania amazonensis</i> parasite and vertebrate cells (2a), and between the parasite and the sandfly (2b).

<p>(A) Attachment of a promastigote to the macrophage surface. (B) The process of internalization via phagocytosis begins with the formation of pseudopods (C), leading to the formation of the parasitophorous vacuole (PV). In the PV, the promastigote transforms into an amastigote. (D) Recruitment and fusion of host cell lysosomes with the PV takes place. (E) In the PV, amastigotes divide several times. (F–G) Intense multiplication generates several hundreds of amastigotes. (H) The host cell bursts, and the parasites reach the extracellular space. (I) Schematic view of female sandfly showing the digestive tract. (J) During a blood meal, a female sandfly ingests infected macrophages with amastigote forms present in the blood of the vertebrate host. (K) Amastigotes form “nest cells” in the abdominal midgut. (L) Amastigotes transform into procyclic promastigotes. (M) Promastigotes multiply and attach to the midgut epithelium. (N) Parasites migrate toward the anterior midgut, resume replication and start to produce promastigote secretory gel (PSG). (O) Promastigotes transform into infective metacyclic promastigotes. (P) Metacyclic promastigotes infect a new mammalian host via regurgitation during the blood meal. These images are based on micrographs obtained by scanning and transmission electron microscopy and by video microscopy.</p