José M. Sousa

Ozonation and UV254 nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater

Conventional wastewater treatment has a limited capacity to reduce antibiotic resistant bacteria and genes (ARB&ARG). Tertiary treatment processes are promising solutions, although the transitory inactivation of bacteria may select ARB&ARG. This study aimed at assessing the potential of ozonation and UV254nm radiation to inactivate cultivable fungal and bacterial populations, and the selected genes 16S rRNA (common to all bacteria), intI1 (common in Gram-negative bacteria) and the ARG vanA, blaTEM, sul1 and qnrS. The abundance of the different microbiological parameters per volume of wastewater was reduced by ∼2 log units for cultivable fungi and 16S rRNA and intI1 genes, by∼3-4 log units, for total heterotrophs, enterobacteria and enterococci, and to values close or below the limits of quantification for ARG, for both processes, after a contact time of 30min. Yet, most of the cultivable populations, the 16S rRNA and intI1 genes as well as the ARG, except qnrS after ozonation, reached pre-treatment levels after 3days storage, suggesting a transitory rather than permanent microbial inactivation. Noticeably, normalization per 16S rRNA gene evidenced an increase of the ARG and intI1 prevalence, mainly after UV254nm treatment. The results suggest that these tertiary treatments may be selecting for ARB&ARG populations.

Modeling a catalytic polymeric non-porous membrane reactor

Abstract A theoretical study on a catalytic polymeric non-porous membrane reactor is performed. The conversion enhancement over the thermodynamic equilibrium is studied when conducting an equilibrium gas-phase reaction of the type A+B⇔C+D. The model used considers perfectly mixed flow patterns and isothermal operation for the retentate and permeate. It is concluded that the conversion of a reversible reaction can be significantly enhanced when the reactants’ diffusion coefficients are lower and/or sorption coefficients are higher than the products’. This happens for Thiele modulus and contact time over certain threshold values. It was also observed that it is preferable to enhance conversion through an increase in the reactants’ sorption coefficients, since this leads to lower reactor dimensions. Since the performance of a non-porous membrane reactor depends on both the sorption and diffusion coefficients, a study of such system cannot be based exclusively on the permeabilities of the components. Favorable combinations of diffusion and sorption coefficients can provide a coupled effect over the reactor’s conversion.

Encapsulation of probiotic strains in plain or cysteine‐supplemented alginate improves viability at storage below freezing temperatures

Four probiotic bacteria (Lactobacillus paracasei L26, L. casei‐01, L. acidophilus Ki, and Bifidobacterium animalis BB‐12®) were encapsulated in plain alginate or alginate supplemented with L‐cysteine·HCl, and resulting microcapsules were stored at different temperatures, namely 21, 4, −20, or −80°C for a period of up to 6 months. The results showed that the encapsulation in calcium alginate microcapsules was only effective in promoting protection at freezing temperatures, independently of the sensitivity of the strain. Storage of calcium alginate microcapsules at −80°C indicated a protective effect upon viability of all four probiotic strains and the presence of L‐cysteine·HCl in the alginate matrix improved protection upon cell viability of B. animalis BB‐12®. An increase in storage temperature of encapsulated bacteria caused an increase in rate of loss in their viability that was strain dependent. This study suggests that microencapsulation of probiotic cells in calcium alginate can be suitable for sustaining the viability of probiotics in food products that require storage below freezing temperatures, even in the absence of cryoprotectors, contributing to an increased shelf life.

Simulation study of a dense polymeric catalytic membrane reactor with plug–flow pattern

Abstract A theoretical study on a tubular membrane reactor, assuming isothermal operation, plug–flow pattern and using a dense polymeric catalytic membrane, is performed. The reactor conversion for an A⇄B equilibrium gas-phase reaction is analyzed, considering the influence of the reactants and products diffusion and sorption coefficients, the influence of the total pressure gradient and the influence of the ratio between the membrane thickness and its internal radius as well as the influence of the feed location (tube side or shell side) and the co-current, counter-current and cross-flow operation modes. One of the most unexpected conclusion is that for a set of conditions where the co-current and counter-current flows leads to differences in the reactor performance, the co-current flow is always better than the counter-current flow, exactly the reverse of what takes place when the membrane performs only gas separation. It is also concluded that the relative permeate pressure favors or penalizes the conversion, depending on the relative permeabilities of each reaction component. It is also concluded that the best reactor’s feed location and the optimum r t / δ ratio depend on the relative sorption and diffusion coefficients of the reaction components as well as on the range of the Thiele modulus and contact time operation values.

A study on the performance of a dense polymeric catalytic membrane reactor

Abstract A theoretical study on a catalytic polymeric dense membrane reactor (CPDMR) is performed. The conversion enhancement over the thermodynamic equilibrium value is studied for an equilibrium gas-phase reaction of the type a A+ b B⇔ c C+ d D for three different conditions: Δ n >0, Δ n =0 and Δ n n =( c + d )−( a + b ). For each of these cases, it is studied the influence of the reaction product sorption and diffusion coefficients. The model used considers perfectly mixed flow patterns and isothermal operation in the retentate and permeate sides. It is concluded that the conversion of a reversible reaction can be significantly enhanced when the diffusion coefficients of the products are higher than the reactants’ and/or the sorption coefficients are lower. The extension of this enhancement depends on the reaction stoichiometry, global concentration inside the membrane, Thiele modulus and contact time values. It was also observed that it would be preferable to have a conversion enhancement based on higher product diffusion than on lower product sorption coefficients, since this leads to smaller reactor size. Since the performance of a dense membrane reactor depends on both the sorption and diffusion coefficients in a different way, a study of such a system cannot be based only on the permeabilities of the reaction components.

Tooth injury in anaesthesiology

BACKGROUND AND OBJECTIVES Dental injury is the most common complication of general anaesthesia and has significant physical, economic and forensic consequences. The aim of this study is to review on the characteristics of dental injury associated with anaesthesiology and existing methods of prevention. CONTENTS In this review, the time of anaesthesia in which the dental injury occurs, the affected teeth, the most frequent type of injury, established risk factors, prevention strategies, protection devices and medico-legal implications inherent to its occurrence are approached. CONCLUSIONS Before initiating any medical procedure that requires the use of classic laryngoscopy, a thorough and detailed pre-aesthetic evaluation of the dental status of the patient is imperative, in order to identify teeth at risk, analyze the presence of factors associated with difficult intubation and outline a prevention strategy that is tailored to the risk of dental injury of each patient.

Modeling a dense polymeric catalytic membrane reactor with plug flow pattern

Abstract A theoretical study on a tubular membrane reactor assuming isothermal operation, plug flow pattern and using a dense polymeric catalytic membrane is performed. The reactor conversion for an equilibrium gas-phase reaction generically represented by A⇄B is analyzed, considering the influence of the product’s sorption and diffusion coefficients. It is concluded that the conversion of such a reaction can be significantly improved when the overall diffusion coefficient of the reaction product is higher than the reactant’s one and/or the overall sorption coefficient is lower, and for Thiele modulus and contact time values over a threshold. Though a sorption coefficient of the reaction product lower than that of the reactant may leads to a conversion enhancement higher than that one obtained when the reaction product diffusion coefficient is higher than that of the reactant, the contact time value for the maximum conversion is much higher in the first case. In this way, a higher diffusion coefficient for the reaction product should be generally preferable, because it leads to a lower reactor size. The performance of a dense polymeric catalytic membrane reactor depends in a different way on both sorption and diffusion coefficients of reactants and products and then a study of such a system cannot be based only on their own permeabilities. Favorable combinations of diffusion and sorption coefficients can affect positively the reactor’s conversion.

Modeling catalytic membrane reactors using an adaptive wavelet-based collocation method

Abstract For certain operating conditions and reaction schemes, catalytic membrane reactors (CMRs) may present sharp concentration profiles in the membrane. Using conventional fixed grid methods for solving the model equations in such conditions may lead to inaccurate predictions of the reactor’s performance. This is demonstrated for two reaction systems: A⇌B (for which a semi-analytical solution is available) and A⇌B+3C (which describes the cyclohexane dehydrogenation). Simulation results obtained with a fixed grid method using finite differences are compared to those from an adaptive method using an algorithm based on interpolating wavelets. Showing higher accuracy and computational efficiency, the latter proved to be a useful tool in dealing with this kind of problems.

Lesão dentária na anestesiologia

BACKGROUND AND OBJECTIVES Dental injury is the most common complication of general anaesthesia and has significant physical, economic and forensic consequences. The aim of this study is to review on the characteristics of dental injury associated with anaesthesiology and existing methods of prevention. CONTENTS In this review, the time of anaesthesia in which the dental injury occurs, the affected teeth, the most frequent type of injury, established risk factors, prevention strategies, protection devices and medico-legal implications inherent to its occurrence are approached. CONCLUSIONS Before initiating any medical procedure that requires the use of classic laryngoscopy, a thorough and detailed pre-aesthetic evaluation of the dental status of the patient is imperative, in order to identify teeth at risk, analyze the presence of factors associated with difficult intubation and outline a prevention strategy that is tailored to the risk of dental injury of each patient.

Characterization of membranes for energy and environmental applications

Abstract: Industrial use of membranes for gas separation has been increasing over the past two decades. The most common gas separations are oxygen enrichment from air, carbon dioxide separation and hydrogen purification. Membranes for gas separation can have various natures, namely polymer, ceramic (e.g. zeolite), metallic, carbon or mixed matrix. For their development and application it is necessary to characterize these membranes according to their surface and inner morphologies, surface chemistry, mass transport parameters and mechanical and chemical stability. This chapter presents the most common characterization techniques of polymer, ceramic, metal and carbon membranes, with regard to morphology and mass transport parameters. It also provides some phenomenological models normally used to describe the permeating mass transport.