Analysis of membrane fouling during cross-flow microfiltration of wine

The aim of this study was to investigate the individual impact on wine molecules as tannins, pectins and mannoproteins on multichannel ceramic membrane fouling during wine cross-flow microfiltration. The characterization of fouling mechanisms involved in the previous filtrations was realized by using the classical fouling models and the analysis of the total resistance curves. It was shown that the obtained initial fluxes are dependant of the nature of the studied molecules and their concentration. According to their increasing effect on permeate flux decline, the studied wine components could be ranked as: mannoproteins < tannins < pectins. During the filtration of wine added with tannins, it was found that the filtrations were governed by the cake layer formation mechanism. The presence of pectins caused the formation of gel-type layer which is found to be compressible under high pressures. For wines added with mannoprotein filtrations, it was shown that there is a threshold concentration above which a plateau value of permeate flux is obtained. Industrial relevance: The cross-flow microfiltration applied to wine filtration has become a legitimate alternative to conventional filtration processes. However, membrane fouling which affects the operating costs and the plant maintenance, limits the widespread application of this technique. To avoid or reduce membrane fouling, it is extremely important to identify the fouling elements and the mechanisms that govern the process. A better understanding of the mechanisms whereby fouling is formed during wine microfiltration may lead to be in position to control fouling or reduce it, to improve cleaning procedures and to adapt the process to the product to be filtered. The results presented in this paper concern the investigation and the understanding of fouling mechanisms by wine colloids (tannins, pectins and mannoproteins). We found that wine colloids had a strong impact on membrane fouling. Independently of their concentrations found in wine, they can be ranked according to their increasing effect on permeate flux as: mannoproteins b tannins b pectins. Such result provides important information and a better vision on the methods which can be used to limit membrane fouling for example the use of pectinolytic enzymes before filtration in order to hydrolyze pectin chains or precipitation of unstable tannins by finning the wine with bentonite. By elucidating fouling mechanisms such as cake layer and gel type layer, we can adapt the hydrodynamic process to control membrane fouling

What can we learn (and not learn) from thought experiments in black hole thermodynamics?

Scientists investigating the thermal properties of black holes rely heavily on theoretical and non-empirical tools, such as mathematical derivations, analogue experiments and thought experiments. Although the use of mathematical derivations and analogue experiments in the context of black hole physics has recently received a great deal of attention among philosophers of science, the use of thought experiments (TEs) in that context has been almost completely neglected. In this paper, we will start filling this gap by systematically analyzing the epistemic role of the two TEs that gave birth to black hole thermodynamics, namely Wheeler’s demon and Geroch’s engine. We will argue that the two main epistemic functions of these TEs are to reveal and resolve inconsistencies, in line with El Skaf’s (Probing theoretical statements with thought experiments. Synthese 199:6119–6147, 2021) approach to TEs. We will, then, go beyond El Skaf’s approach by stressing an important difference between the strategies employed to assess the reliability of each epistemic function

Colombia y su tensa relación con la CIDH

Colombia es el segundo país de la región con más casos ante el Sistema Interamericano de Derechos Humanos, que comprende la Comisión y la Corte, sin embargo y tal vez por eso, ha sido una relación de amores y odios. Las últimas medidas cautelares de la CIDH más recordadas en el país fueron las otorgadas a las comunidades wayuú, cuyos niños mueren de hambre y sed en La Guajira y las de Gustavo Petro, exalcalde de Bogotá, cuando fue destituido por la Procuraduría. Ricardo Asturio Gil Barrera, docente de Derecho Internacional de la Universidad de Medellín, explicó que casi todos los estados esperan a que sea la CorteIDH, que es la segunda instancia del Sistema, la que dicte una sentencia definitiva, y que Colombia no es la excepción

Cross-flow microfiltration applied to oenology: A review

The cross-flow microfiltration applied to wine filtration has become a legitimate alternative to conventional filtration processes. However, membrane fouling which affects the operating costs and the plant maintenance, limits the widespread application of this technique. The aim of this review is to provide a better understanding of the development of the cross-flow microfiltration in wine industry, as well as the complexity of wine composition and its consequences on membrane fouling. This review covers also the impact of the operating conditions and the membrane characteristics on fouling mechanisms. Strategies to limit fouling as well as the latest innovations and commercial proposal are discussed in this paper

Impact of the physico-chemistry of the wine on membrane filtration performance

During the process of wine making, operation of cross-flow microfiltration allows a one-step clarification and sterilization of wine, with lower waste compared to the conventional processes of clarification and sterilization. Indeed, these processes are sources of voluminous waste (earth, Kieselguhr, additives), when discharges are becoming more and more restricted by environmental and health rules. Nevertheless, cross-flow microfiltration of wine presents a major drawback: membrane fouling causes a significant decrease in the flow rates, due to excessive retention of some wine components which could lead ultimately to the alteration of the quality of wine. The aim of this work was to study the impact of some specific wine components (phenolic compounds and yeast extract), as well as some physico-chemical parameters (pH) in regard to membrane fouling. Studies were performed using one red wine and synthetic wines, using cellulose acetate membranes (0.2 μm) operated in the dead-end mode under 2 bar pressure. The simultaneous presence of the both species of phenolic compounds (anthocyanins and tannins) in the synthetic wine was shown to be the main cause of fouling, whereas the presence of one specie leads only to standard blocking type behavior. An important decrease in the flow rates was also observed when yeast extract was added to the liquid. This yeast extract was shown to contain 300 mg/g of proteins and to be free of mannoproteins. The influence of these proteins on fouling was demonstrated while pre-treating the synthetic wine with bentonite, which was able to adsorb proteins, and in this case, no fouling was observed. It was also shown that, when decreasing the pH, the flow rate was enhanced. For all experiments, a fouling index or cake specific resistance, according to the type of fouling, was calculated in order to be used as a reference to estimate the filterability of a given wine, according to its composition in some targeted molecules. Finally, the experiments of the actual red wine exhibited complete rapid fouling of the membrane, probably due to the presence of high concentration of phenolic compounds

An algorithm proposal for a minimum cost SDR multi-standard system using graph theory

International audienceThe design of future multi-standard systems remains a challenge due to increasing flexibility requirements. Promising solutions include designing flexible radio architectures that exploit common aspects between the different set of standards cohabiting in the device. In this paper, graph theory appears and particularly the study of directed hypergraphs, which helps in the research concerning minimum cost multistandard designs. A cost function which calculates the cost of any possible option of implementation is mentioned but its derivations won't be in the scope of this paper. Our objective is to optimize this proposed cost function to its minimum possible value and thus solving the optimization problem that finds balance between flexibility and computing efficiency. For this, we propose a Minimum Cost Design (MCD) algorithm capable of selecting the option which has the minimum cost to pay and will present its complete set of instructions in this paper. This algorithm exploits various definitions and notations of directed hypergraphs

Resonance in Large Benzenoid Hydrocarbons

Pi-sextet resonance between Kekulé valence structures of benzenoid hydrocarbons are depicted by benzenoid resonance graphs. We outline the construction of the resonance graphs for families of benzenoid compounds. For the compounds considered the resonance graphs are built from fused ra-dimensional cubes. We report the leading eigenvalue of the resonance graphs (A) and two different bounds to the leading eigenvalue. Correlation between X and RE is examined

Increased 18F-FDG-PET Uptake in Granulomatosis with Polyangiitis: Case Report and Review of the Literature

We present an unusual case of granulomatosis with polyangiitis (GPA), which initially presented as a large lung mass, without renal or other systemic features. The lung mass was most concerning for malignancy, and positron emission tomography (PET) further supported this concern, with intense uptake in the mass as well as in mediastinal and hilar lymph nodes. Biopsies however were non-diagnostic, and the patient developed acute kidney injury with active urinary sediment, leading to a definitive diagnosis of GPA. With supportive care and treatment directed at GPA, she was ultimately able to discontinue hemodialysis, and the lung mass resolved. This case demonstrates that GPA can present with PET-positive lymphadenopathy which may be initially suspected to be a malignancy, especially in the absence of renal abnormalities

Live Imaging of Type I Collagen Assembly Dynamics in Osteoblasts Stably Expressing GFP and mCherry-Tagged Collagen Constructs

Type I collagen is the most abundant extracellular matrix protein in bone and other connective tissues and plays key roles in normal and pathological bone formation as well as in connective tissue disorders and fibrosis. Although much is known about the collagen biosynthetic pathway and its regulatory steps, the mechanisms by which it is assembled extracellularly are less clear. We have generated GFPtpz and mCherry-tagged collagen fusion constructs for live imaging of type I collagen assembly by replacing the α2(I)-procollagen N-terminal propeptide with GFPtpz or mCherry. These novel imaging probes were stably transfected into MLO-A5 osteoblast-like cells and fibronectin-null mouse embryonic fibroblasts (FN-null-MEFs) and used for imaging type I collagen assembly dynamics and its dependence on fibronectin. Both fusion proteins co-precipitated with α1(I)-collagen and remained intracellular without ascorbate but were assembled into α1(I) collagen-containing extracellular fibrils in the presence of ascorbate. Immunogold-EM confirmed their ultrastuctural localization in banded collagen fibrils. Live cell imaging in stably transfected MLO-A5 cells revealed the highly dynamic nature of collagen assembly and showed that during assembly the fibril networks are continually stretched and contracted due to the underlying cell motion. We also observed that cell-generated forces can physically reshape the collagen fibrils. Using co-cultures of mCherry- and GFPtpz-collagen expressing cells, we show that multiple cells contribute collagen to form collagen fiber bundles. Immuno-EM further showed that individual collagen fibrils can receive contributions of collagen from more than one cell. Live cell imaging in FN-null-MEFs expressing GFPtpz-collagen showed that collagen assembly was both dependent upon and dynamically integrated with fibronectin assembly. These GFP-collagen fusion constructs provide a powerful tool for imaging collagen in living cells and have revealed novel and fundamental insights into the dynamic mechanisms for the extracellular assembly of collagen