Reverse osmosis membrane composition, structure and performance modification by bisulphite, iron(III), bromide and chlorite exposure

Reverse osmosis (RO) membrane exposure to bisulphite, chlorite, bromide and iron(III) was assessed in terms of membrane composition, structure and performance. Membrane composition was determined by Rutherford backscattering spectrometry (RBS) and membrane performance was assessed by water and chloride permeation, using a modified version of the solution-diffusion model. Iron(III) dosage in presence of bisulphite led to an autooxidation of the latter, probably generating free radicals which damaged the membrane. It comprised a significant raise in chloride passage (chloride permeation coefficient increased 5.3–5.1 fold compared to the virgin membrane under the conditions studied) rapidly. No major differences in terms of water permeability and membrane composition were observed. Nevertheless, an increase in the size of the network pores, and a raise in the fraction of aggregate pores of the polyamide (PA) layer were identified, but no amide bond cleavage was observed. These structural changes were therefore, in accordance with the transport properties observed.Peer ReviewedPostprint (author's final draft

Composition and reversibility of fouling on low-pressure membranes in the filtration of coagulated water: insights into organic fractions behaviour

The primary problem for the application of microfiltration (MF) and ultrafiltration (UF) membrane technology is membrane fouling. Such is the case that understanding membrane fouling has become one of the major factors driving MF and UF membrane technology for- ward. Nevertheless, identifying the constituents that most contribute to membrane fouling 20 and quantifying how they are detached when backwashing (BW) and cleaning-in-place (CIP) are applied still remains a challenging task. The aim of the present study was to quan- tify membrane fouling development during filtration and membrane fouling detachment during BW and CIP in terms of membrane permeability changes and masses of inorganic and organic constituents accumulated on the membrane. The study was conducted using 25 bench-scale MF and UF modules fed with coagulated and settled water coming from a drinking water treatment plant and operated under dead-end and cross-flow operation modes. The experiments consisted inconsecutive permeation (20 min) alternated with BW with permeate water (1.0 min) (periodically chemically assisted with NaClO and NaOH) and followed by a two-stage CIP consisting first in an oxidising and basic step (NaClO and 30 NaOH) and second in an acidic step (citric acid). Feed, permeate, retentate (when present) and cleaning discharge streams were monitored for turbidity, total and dissolved organic carbon (TOC and DOC, respectively), UV 254 and inorganic ions (Al, Fe, P). DOC was frac- tionated by high-performance size exclusion chromatography to gain insight into the beha- viour of the different organic fractions. Results showed that both MF and UF membranes 35 successfully removed turbidity, Al and Fe, whereas UV 254 was moderately removed and TOC and DOC poorly removed, with removal percentages higher for UF than for MF. With regard to the organic fractions, the largest molecular weight compounds were moderately removed while the smallest organic fractions seemed to totally permeate through both membranes. The results also showed that foulants were poorly washed out from thePeer ReviewedPostprint (author's final draft

Reversibility of fouling on ultrafiltration membrane by backwashing and chemical cleaning: differences in organic fractions behaviour

Membrane fouling is an inherent phenomenon in ultrafiltration (UF) membrane processes, making it necessary to periodically perform backwashes (BW) and chemical cleanings in place (CIP) to restore the initial permeability of the membrane. The objective of this study was (1) to explore systematically the effect of distinct BW-related variables (BW transmembrane pressure, duration, frequency and composition) on the reversibility of UF membrane fouling and on the permeate quality (in terms of total organic carbon, turbidity and UV absorbance) over successive filtration/BW cycles; and (2) to identify which organic fractions were most removed by the membrane and, of these, which were most detached after BW, alkaline and oxidant CIP and acid CIP episodes. For this purpose, a bench-scale outside-in hollow fibre module operated under dead-end filtration mode at constant transmembrane pressure and treating settled water from a drinking water treatment plant was employed. Dissolved organic carbon fractionation was performed by high-performance size-exclusion chromatography. Results showed that, in general, the more intensive the BW was (in terms of high transmembrane pressure, shortened frequency and prolonged duration) the more effective it was in removing fouling from the membrane. Concerning the composition of the water used for the BW, the addition of NaClO led to maximum fouling reversibility, closely followed by the combination of NaOH+NaClO, while citric acid and NaOH contributed little compared to water alone. However, results also showed that irreversible fouling was never completely avoided whatever the BW regime applied, leading to a gradual increase in the total resistance over time. Larger differences in the behaviour of the different organic fractions were observed. UF membrane preferentially retained the heaviest fraction of biopolymers (BP), while the intermediate fraction of humic substances (HS) was removed at a lower percentage and the lighter fractions seemed to entirely pass through the UF membrane. The successive application of BW and CIPs resulted in the detachment from the membrane of a significant percentage of the retained BP, whereas only a modest percentage of the retained HS.Peer ReviewedPostprint (author's final draft

On relay user equipment activation in beyond 5G radio access networks

This paper envisages a Beyond 5G (B5G) Radio Access Network (RAN) in which the relaying capabilities offered by user equipment (UE) are used as a way to improve the coverage and robustness of the network. The paper proposes and develops the functional framework for supporting the activation of the suitable relay UEs (RUEs) in coverage constrained scenarios. It is based on characterizing each potential RUE through a utility metric that measures the coverage enhancements brought to the network when the RUE is activated. To derive this metric for all the candidate RUEs, the framework considers the use of a Network Digital Twin that allows the offline analysis of different configurations in a fast and safe way. Using the proposed framework, a RUE activation algorithm is proposed and evaluated. The obtained results reflect that significant outage probability reductions can be obtained in the scenario under different traffic distributions thanks to the activation of the RUEs with the highest utility.This paper is part of ARTIST project (ref. PID2020- 115104RB-I00) funded by MCIN/AEI/10.13039/ 501100011033. The work is also funded by the Spanish Ministry of Economic Affairs and Digital Transformation and the European Union - NextGenerationEU under project OPTIMAIX_NDT (Ref. TSI-063000-2021-35).Peer ReviewedPostprint (author's final draft

Fluid-Structure Interaction of a Reed Type Valve Subjected to Piston Displacement

In the field of reciprocating compressors, the developing of reed type valves is a challenging task. The understanding of the fluid flow behaviour through the valve reed is essential to improve the valve design. Hence, this work attempts the dynamic simulation of this fluid-structure interaction (FSI) problem, taking into account valve movement due to piston displacement. In this work attends the in-house implemented CFD&HT and moving mesh coupled code TermoFluids [1]. The CFD&HT solver consists of a three-dimensional explicit finite volume fractional-step algorithm formulated in a second-order, conservative and collocated unstructured grid arrangement. The turbulence is modelled by means of large-eddy simulation. The moving mesh technique is based on a radial basis function interpolation method, which allows the dynamic deformation of the mesh according to the displacement of the valve [2,3]. The CFD&HT and moving mesh coupling is built by the space conservation law. The newly implemented FSI global solver is based on a partitioned coupled algorithm in which the dynamic action of the valve is modelled through a specific law based on modal analysis of valve reed theory [4]. In contrast to conventional CSD solvers, this alternative performs a fast prediction of the structure displacement. As a preliminary approach, a simplified geometry of an axial hole plus a rectangular diffuser with a piston based inlet condition is considered. An immersed body procedure is used to simulate solid parts inside the domain and, particularly, to reproduce the bottom and inlet boundaries. This strategy has been enhanced with respect to previous studies [5]; thus, the flow phenomena is now better captured specially when the opening of the valve is narrow. As an addition, a parametric study will be carried out in order to analyse the influence of the valve thickness. REFERENCES [1] O. Lehmkuhl, R. Borrell, C.D. Pérez-Segarra, M. Soria, A. Oliva. TermoFluids: A new parallel unstructured CFD code for the simulation of turbulent industrial problems on low cost PC Cluster, Parallel Computational Fluid Dynamics 2007, Vol. 67, pp. 275-282, 2009. [2] O. Estruch, O. Lehmkuhl, R. Borrell, C.D. Pérez-Segarra, A. Oliva. A parallel radial basis function interpolation method for unstructured dynamics meshes, Computer and Fluids, 80:44-54, 2013. [3] O. Estruch, O. Lehmkuhl, R. Borrell, C.D. Pérez-Segarra. Large-eddy simulation of turbulent dynamics fluid-structure interaction, 7th International Synopsium on Turbulence, Heat and Mass Transfer, Palermo, 2012. [4] W. Soedel. Mechanics, simulation and design of compressor valves, gas passages and pulsation mufflers, Purdue University Short Courses, IN, USA, 1992. [5] O. Estruch, O. Lehmkuhl, J. Rigola, A. Oliva and C.D. Pérez-Segarra. Transient and dynamic numerical simulation of the fluid flow through valves based on large eddy simulation models, 8th International Conference on Compressors and their Systems, London, 2013

Self-heating in pulsed mode for signal quality improvement: application to carbon nanostructures-based sensors

Sensor signal instability and drift are still unresolved challenges in conductometric gas sensors. Here, the use of self-heating effect to operate a gas sensor in a pulsed temperature modulation mode (pulsed self-heating operation) is presented as an effective method to enhance signal stability and reduce consumption figures down to a few W. The sensor operation temperature was pulsed periodically between two levels, obtaining two different sensing states from one single device driven with self-heating, i.e. free of heater. The signal differences between both operating points correlated well with gas concentrations and displayed no drift. This methodology is exemplified with a thorough study of the response of carbon nanofibers to humidity. Specifically, after analyzing the influence of the pulse characteristics (i.e. temperature variation, pulse period and pulse duty cycle) on the sensor performance, thumb rules to select suitable pulsing conditions are provided. The methodology is successfully extended to other target gases, such as NO2 and NH3. Finally, its implementation in a real-time sensing system with low computational requirements is demonstrated and discussed in detail

Spinal anesthesia in obstetrical and gynecological operations

Universitatea de Stat de Medicină şi Farmacie „Nicolae Testemiţanu”, Catedra Anesteziologie şi Reanimatologie Nr.2Spinal anesthesia is a blockade of all types of somatic and autonomic sensitivity, including muscle relaxation and regional sympathectomy. Spinal anesthesia is widely used worldwide in clinics with obstetric-gynecological profiles

Biblioteca Virtual del Sistema Sanitari Públic de Catalunya (BVSalut)

Biblioteca virtual; Recursos d’informació; Validació d’usuarisVirtual Library; Information resources; User authentication SystemBiblioteca virtual; Recursos de información; Validación de usuariosIntroducció La Biblioteca Virtual del Sistema Sanitari Públic de Catalunya (BVSalut) s’ha creat per ser el punt d’accés als recursos i als serveis bibliogràfics digitals de suport a la presa decisions per als professionals del sector públic majoritari de salut de forma equitativa i homogènia. Material i mètode Per desenvolupar el portal BVSalut es van analitzar quins serien els serveis que s’oferirien de forma virtual i quin seria el programari necessari que facilitaria la gestió, consulta i accés al portal, als serveis i als recursos bibliogràfics de forma segura per als professionals del sector públic majoritari de salut. Es va considerar que es posarien en funcionament els serveis virtuals següents: atenció a l’usuari i referència, alertes d’informació, informació especialitzada, obtenció de documents i préstec. Pel que fa al programari, es va considerar que era necessari disposar d’un gestor de continguts, un servei d’assistència a l’usuari (help desk), un programari per a la gestió del servei d’obtenció de documents, una eina de descoberta i una llista A/Z que facilités l’accés als recursos i evités els enllaços trencats. Al mateix temps, s’havia de garantir un sistema segur de validació d’usuaris que permetés als professionals de les diferents institucions poder accedir de forma segura als recursos electrònics que es posaven a la seva disposició. Concretament, es va desenvolupar un sistema de validació Single Sing‐On (SSO), que connectat a una LDAP (Lightweight Directory Access Protocol), amb la relació dels professionals i dels recursos que tenien accés, permetia que aquests professionals poguessin entrar als recursos bibliogràfics digitals de la BVSalut de forma simple i eficaç mitjançant el servidor proxy Ezproxy. Resultats S’ha donat accés als recursos bibliogràfics subvencionats per la Biblioteca de Ciències de la Salut de Catalunya a 79 entitats. Més de 40.000 professionals ja poden accedir a aquests als recursos electrònics i s’ha iniciat la redacció d’un pla estratègic, amb la col∙laboració de les biblioteques de les institucions del sector públic majoritari de salut, que facilitarà que aquests professionals també tinguin accés a serveis de suport bibliogràfic compartits. Conclusions El portal BVSalut ha permès establir un sistema homogeni d’accés als recursos i serveis bibliogràfics digitals. Progressivament s’aniran incrementant els recursos bibliogràfics i, amb la creació de la Xarxa de Biblioteques Especialitzades en Ciències de la Salut i l’aprovació de Pla estratègic, l’oferta de serveis virtuals compartits

Спинaльная анестезия в акушерстве и гинекологии

Spinal anesthezia in obstetric and ginecological surgeryAnestezia loco-regională blochează transmiterea nervoasă a durerii în acea regiune a corpului supusă actului operator. Se realizează prin injectarea de anestezic local în proximitatea nervilor care deservesc regiunea respectivă.Спинaльная анестезия в акушерстве и гинекологи