Application of silanes in leather tanning

Content: In order to develop a sustainable and low-cost route for tanning, the stabilization of the collagen fibers of the hides with silica compounds has been investigated for many years. In this context, silica nanoparticles have been studied for application in tanning due to their small size and ability to combine with polymeric substrates. This work investigates the potentialities and limitations of the use of alkoxysilanes in leather tanning, introducing silica nanoparticles in the hides, aim for process and product innovation in leather industry. The synthesis of silica nanoparticles was carried out by a typical sol-gel Stöber process. From the silica precursor tetraethoxysilane (TEOS), ammonium hydroxide as catalyst, ethanol and water, the formation of nanoparticles dispersion takes place. Vegetable tanning process was explored by introducing the silica nanoparticles in this stage starting from pickled cattle hide. Shrinkage temperature, tensile strength, softness and color fastness to light were evaluated in the leather samples. The results achieved show that the tanning experiment with only silica, without other tanning agent, did not reach the minimum shrinkage temperature required to be labeled as tanned leather. Conversely, in the presence of vegetable tannin, the shrinkage temperature reached 80°C. The physical-mechanical properties indicated that the enhanced on the tensile strength of vegetable leathers with nanosilica was about 50% and their softness was not affected by the introduction of silica. A lighter colored leather was generated with silica but less stable to light. The tanning chemistry involving silica nanoparticles and collagen is complex, therefore, more studies are needed to explore the influence of silanes on hide stabilization. Take-Away: The physical-mechanical properties indicated an increase on the tensile strength of vegetable leather. Silica did not affected the softness of the leather. A lighter colored leather was generated with the addition of the silica nanoparticles in vegetable tanning

NUMERICAL ANALYSIS OF A VERTICAL HELICAL EARTH-AIR HEAT EXCHANGER

The Earth-Air Heat Exchanger (EAHE) is an equipment that consists of ducts buried in the ground in which the air is forced to pass through. The heat exchange with the surrounding soil turns the air temperature in the outlet section of the EAHE milder. Due to that, the EAHE is capable of assist air conditioning systems and reduce energy consumption, by taking advantage of the temperature gradient established between the soil surface and its layers. In the current study, the operation of Vertical Helical EAHEs was numerically evaluated with different distances between helicoid curves, for the city of Viamão, located in the southern Brazil. The results stated that the Vertical Helical EAHE with dimensions between the curves equivalent to 100 and 200 mm presented the better thermal performances for cooling mode operation in the hottest seasons of the years, when compared to the Conventional Horizontal EAHE adopted as reference. Frim this comparison, the obtained average values of the Root Mean Squared Error (RMSE) were, respectively, 0.47 °C and 0.66 °C. At last, it must be highlighted a sevenfold reduction in the soil volume occupied by the installation of the Helical EAHE compared to the Conventional Horizontal EAHE

Diagnóstico nutricional de pomares de laranjeiras da fronteira oeste do Rio Grande do Sul.

A Fronteira Oeste do Rio Grande do Sul (RS) vem se destacando pela diversificação produtiva e pelo desenvolvimento do setor frutícola. A adequada nutrição dos pomares é um dos fatores essenciais para garantir o sucesso da atividade nessa nova região produtora. Devido à escassez de dados referentes à citricultura da região da Fronteira Oeste do RS, objetivou-se, neste trabalho, avaliar o estado nutricional de laranjeiras ?Lane late?, ?Navelina?, ?Salustiana?, ?Valência?, ?Valência Midknight? e ?Valência Delta Seedless? enxertadas sob Poncirus trifoliata nas condições edafoclimáticas da região. Os pomares em que se realizaram as amostragens foram constituídos por plantas adultas. Os pomares de laranjeiras da Fronteira Oeste do RS apresentam, de forma geral, deficiência foliar em N, Ca, Mn e Zn, apresentando, ainda, excesso foliar de Cu e P, indicando necessidade de adequação do manejo do solo e da adubação, visando o aumento no conteúdo de matéria-orgânica do solo, o parcelamento da adubação nitrogenada e o aprimoramento da adubação com Mn e Zn.Edição está em andamento, na modalidade de publicação contínua

Post-natal parental care in a Cretaceous diapsid from northeastern China

Post-natal parental care seems to have evolved numerous times in vertebrates. Among extant amniotes, it is present in crocodilians, birds, and mammals. However, evidence of this behavior is extremely rare in the fossil record and is only reported for two types of dinosaurs, and a varanopid ‘pelycosaur’. Here we report new evidence for post-natal parental care in Philydrosaurus, a choristodere, from the Yixian Formation of western Liaoning Province, China. We review the fossil record of reproduction in choristoderes, and this represents the oldest record of post-natal parental care in diapsids to our knowledge