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BackgroundThe magnitude of Omicron SARS-CoV-2 variant of concern (VOC) global spread necessitates reinforcement of surveillance implementation. Conventional VOC surveillance based on genotyping of clinical samples is characterized by certain challenges related to available sequencing capacity, population sampling methodologies, and demands in terms of time, labor, and resources. Wastewater-based SARS-CoV-2 VOC surveillance constitutes a valuable supplementary practice, since it does not require extensive sampling, and provides information on the prevalence of the disease in a timely and cost-effective manner.MethodsA highly sensitive real-time RT-PCR assay was developed, for targeted Omicron VOC detection and quantification in wastewater samples. The assay exclusively amplifies sequences with the S:Δ69/70 deletion, thus its performance is not hampered by the presence of the Delta VOC. The method was incorporated in the analysis of composite daily samples taken from the main Wastewater Treatment Plant (WWTP) of Thessaloniki, Greece from 1 December 2021 to 9 January 2022.ResultsThe Omicron VOC was detected for the first time in samples from the Thessaloniki WWTP on 19 December 2021. In the following 10-day period, a rapid increase in Omicron sewage viral load was observed with an estimated early doubling time of 1.86 days. The proportion of the total SARS-CoV-2 load attributed to Omicron reached 91.09% on 7 January, revealing a fast Delta-to-Omicron VOC transition pattern. The detection of Omicron in wastewater preceded the outburst of reported (presumable) Omicron cases in the city by approximately 7 days.ConclusionsThe proposed wastewater-based surveillance approach enables rapid, real-time data acquisition on the Omicron VOC prevalence and transmission dynamics. Timely provision of these results to State authorities can readily influence the decision-making process for targeted public health interventions, including control measures, awareness, and preparedness.

Conventional SARS-CoV-2 surveillance based on genotyping of clinical samples is characterized by challenges related to the available sequencing capacity, population sampling methodologies, and is time, labor, and resource-demanding. Wastewater-based variant surveillance constitutes a valuable supplementary practice, since it does not require extensive sampling, and provides information on virus prevalence in a timely and cost-effective manner. Consequently, we developed a sensitive real-time RT-PCR-based approach that exclusively amplifies and quantifies SARS-CoV-2 genomic regions carrying the S:Δ69/70 deletion, indicative of the Omicron BA.1 variant, in wastewater. The method was incorporated in the analysis of composite daily samples taken from the main Wastewater Treatment Plant of Thessaloniki, Greece, from 1 December 2021. The applicability of the methodology is dependent on the epidemiological situation. During Omicron BA.1 global emergence, Thessaloniki was experiencing a massive epidemic wave attributed solely to the Delta variant, according to genomic surveillance data. Since Delta does not possess the S:Δ69/70, the emergence of Omicron BA.1 could be monitored via the described methodology. Omicron BA.1 was detected in sewage samples on 19 December 2021 and a rapid increase of its viral load was observed in the following 10-day period, with an estimated early doubling time of 1.86 days. The proportion of the total SARS-CoV-2 load attributed to BA.1 reached 91.09 % on 7 January, revealing a fast Delta-to-Omicron transition pattern. The detection of Omicron BA.1 subclade in wastewater preceded the outburst of reported (presumable) Omicron cases in the city by approximately 7 days. The proposed wastewater surveillance approach based on selective PCR amplification of a genomic region carrying a deletion signature enabled rapid, real-time data acquisition on Omicron BA.1 prevalence and dynamics during the slow remission of the Delta wave. Timely provision of these results to State authorities readily influences the decision-making process for targeted public health interventions, including control measures, awareness, and preparedness.

Biofilms are resilient to environmental conditions and often resistant even to strong disinfectants. It is crucial to investigate their interfacial properties, which can be effectively characterized by wetting analysis. Wetting phenomena on biofilm surfaces have been poorly investigated in literature, in particular a systematic study of wetting on real biofilm-coated substrates including the application of external body forces (forced wetting, i.e.: centrifugal and gravitational forces) is missing. The aim of this work is to study the role of nutrient and shear flow conditions on wetting properties of Pseudomonas fluorescens dehydrated biofilms, grown on glass substrates. An innovative device (Kerberos®), capable to study spreading/sliding behavior under the application of external body forces, is used here for a systematic analysis of wetting/de-wetting liquid droplets on horizontal substrates under the action of tangential forces. Results prove that, under different growth conditions, (i.e., nutrients and imposed flow), biofilms exhibit different wetting properties. At lower nutrient/shear flow conditions, biofilms show spreading/sliding behavior close to that of pure glass. At higher nutrient and shear flow conditions, droplets on biofilms show spreading followed by imbibition soon after deposition, which leads to peculiar droplet depinning during the rotation test. Wetting properties are derived as a function of the rotation speed from both top and side views videoframes though a dedicated image analysis technique. A detailed analysis of biofilm formation and morphology/topography is also provided here.

The aims of this work were to investigate the ozone mass transfer in a continuous flow pilot unit dependent on operating conditions and to study the effect of the dead-end function of hollow fiber membranes on the ozonation performance. The dead-end operation of membranes maximizes their performance, providing maximum ozone exploitation, which in turn results in considerably lower ozone gas feed demand in relation to gas flow through operation. Considering the numerous applications of ozonation in water/wastewater treatment, ensuring the significant reduction in processing cost is of high technological importance. An extensive experimental campaign was performed monitoring dissolved ozone and oxygen concentrations produced by the employment of two different membranes in a wide range of ozone gas flow rates, liquid flow velocities and water pH values. Significantly high percentages of ozone transport to the water phase were achieved (>95%) indicating that the absence of gas outflow (dead-end operation) maximizes ozone mass transfer. Dissolved ozone concentrations were proportional to the gas feed and decreased with increasing liquid flows. The impact of water pH was negligible, while the internal cross section areas of the membranes considerably affected the mass transfer coefficient and dissolution rate. The ozonation process was modeled using mass balances, mass transfer theories and ozone decomposition kinetics in order to estimate non-measurable quantities such as partial pressure in the shell and to understand the sequence of occurring phenomena.

Liquid degassing takes place in several space processes (cooling and lubrication of hardware, combustion of liquid propellants etc.) during launching and re-orbiting of rockets and workstations. The present work studies the effect of hypergravity acceleration on the two phase flow that is developed during the degassing of a liquid jet. Liquid is initially saturated with dissolved gas at 200 kPa and 400 kPa and is then injected at the bottom of a liquid column having its top open to atmospheric pressure. Due to the sudden decompression inside the column, the liquid jet becomes supersaturated with dissolved gas, thus triggering the formation of degassing bubbles within its volume. The local liquid flow pattern inside the column is tracked by recording the motion of bubbles. Experiments are conducted at 1 g, 2 g and 8 g accelerations, using the Large Diameter Centrifuge (LDC) facility of the Technology Center (ESTEC) of the European Space Agency (ESA). The liquid flow behavior registered at varying hypergavity conditions is quite interesting. For an injection pressure of 200 kPa the liquid velocity magnitude increases with acceleration level possibly because of the inertial shear force. Increasing the injection pressure to 400 kPa, not only the magnitude, but also the direction of liquid velocity varies possibly due to the larger effect of Coriolis force induced by the increased liquid velocities.

This work focuses on the investigation of the relationship between structure and oxidation behavior of particulate matter (PM) emitted from different diesel combustion systems. Commercially available graphite and carbon black materials were also studied as representing the soot with the lowest reactivity. An interpretation of the differences of soot oxidation between these materials is attempted based on the carbon morphology and microstructure; thus, various structural parameters, such as the average particle size, specific surface area, degree of nanostructural organization, average crystallite stacking height, fringe length, fringe tortuosity, and surface functional groups, have been opposed to the reactivity of the carbonaceous materials. Small structural differences were observed in between the carbonaceous samples which seem to directly affect the soot reactivity in terms of oxidation. Particulate matter composition (hydrogen-to-carbon ratio, ash content, and volatile matter) appears to have an impact on the soot reactivity.

This is an experimental study on highly subcooled flow boiling of water for assessing the effect of gravitational acceleration on flow boiling heat transfer. The experiments are conducted in a macro-channel 3 mm high, 40 mm wide and 120 mm long at water mass fluxes of 330, 630 and 830 kg/m2 s and heat fluxes in the range 200–900 kW/m2. Increased gravitational accelerations, from 1.8 to 9 times the Earth-gravity are achieved with the use of a ∼3 m radius centrifuge (Large Diameter Centrifuge, ESTEC/European Space Agency). Two distinct channel inclinations are examined; horizontal, where the gravitational acceleration is normal to the boiling surface, and vertical, where the gravitational acceleration is parallel to the boiling surface and opposite to flow direction. Experiments at hyper-gravity conditions show that for the horizontal channel inclination, flow boiling heat transfer coefficient increases, whereas for the vertical channel inclination it decreases. The observed deviations lie approximately between +15% and −40% from the Earth-g value. An interpretation of the present results is attempted based on the effect of liquid-phase natural and forced convection combined with the effect of buoyancy at vapor bubbles. The tendency of the heat transfer coefficient experimental data with respect to changes in gravitational acceleration allows the development of a gravity-modified version of the well-known two phase model of Liu-Winterton, by incorporating a linearly dependent gravity multiplier.

Wetting of dehydrated

During the COVID-19 pandemic, wastewater-based epidemiology (WBE) has been engaged to complement medical surveillance and in some cases to also act as an early diagnosis indicator of viral spreading in the community. Most efforts worldwide by the scientific community and commercial companies focus on the formulation of protocols for SARS-CoV-2 analysis in wastewater and approaches addressing the quantitative relationship between WBE and medical surveillance are lacking. In the present study, a mathematical model is developed which uses as input the number of daily positive medical tests together with the highly non-linear shedding rate curve of individuals to estimate the evolution of global virus shedding rate in wastewater along calendar days. A comprehensive parametric study by the model using as input actual medical surveillance and WBE data for the city of Thessaloniki (~700,000 inhabitants, North Greece) during the outbreak of November 2020 reveals the conditions under which WBE can be used as an early warning tool for predicting pandemic outbreaks. It is shown that early warning capacity is different along the days of an outbreak and depends strongly on the number of days apart between the day of maximum shedding rate of infected individuals in their disease cycle and the day of their medical testing. The present data indicate for Thessaloniki an average early warning capacity of around 2 days. Moreover, the data imply that there exists a proportion between unreported cases (asymptomatic persons with mild symptoms that do not seek medical advice) and reported cases. The proportion increases with the number of reported cases. The early detection capacity of WBE improves substantially in the presence of an increasing number of unreported cases. For Thessaloniki at the peak of the pandemic in mid-November 2020, the number of unreported cases reached a maximum around 4 times the number of reported cases., Graphical abstract Unlabelled Image

The COVID-19 pandemic represents an unprecedented global crisis necessitating novel approaches for, amongst others, early detection of emerging variants relating to the evolution and spread of the virus. Recently, the detection of SARS-CoV-2 RNA in wastewater has emerged as a useful tool to monitor the prevalence of the virus in the community. Here, we propose a novel methodology, called lineagespot, for the monitoring of mutations and the detection of SARS-CoV-2 lineages in wastewater samples using next-generation sequencing (NGS). Our proposed method was tested and evaluated using NGS data produced by the sequencing of 14 wastewater samples from the municipality of Thessaloniki, Greece, covering a 6-month period. The results showed the presence of SARS-CoV-2 variants in wastewater data. lineagespot was able to record the evolution and rapid domination of the Alpha variant (B.1.1.7) in the community, and allowed the correlation between the mutations evident through our approach and the mutations observed in patients from the same area and time periods. lineagespot is an open-source tool, implemented in R, and is freely available on GitHub and registered on bio.tools.

Over the last few decades, bio-based polymers have attracted considerable attention from both academic and industrial fields regarding the minimization of the environmental impact arising from the excessive use of petrochemically-based polymeric materials. In this context, poly(ethylene vanillate) (PEV), an alipharomatic polyester prepared from 4-(2-hydroxyethoxy)-3-methoxybenzoic acid, a monomer originating from lignin-derived vanillic acid, has shown promising thermal and mechanical properties. Herein, the effects of three different catalysts, namely titanium butoxide (TBT), titanium isopropoxide (TIS), and antimony trioxide (Sb2O3), on the synthesis of PEV via a two-stage melt polycondensation method are investigated. The progress of the reaction is assessed using various complementary techniques, such as intrinsic viscosity measurement (IV), end group analysis (AV), nuclear magnetic resonance spectroscopy (NMR), Fourier-transformed infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The thermal stability of the produced polyesters is studied by evolved gas analysis mass spectrometry (EGA-MS). Moreover, as the discoloration in polymers affects their applications, color measurement is performed here. Finally, theoretical kinetic studies are carried out to rationalize the experimental observations.

Facile methods for accurate fluid-mechanical characterization of haemofilters (HF) are indispensable for haemofiltration process improvements, equipment design/optimization, and reliable module specifications. Currently employed methods, implemented through specific experimental in vitro protocols, are assessed herein in detail, considering the conditions prevailing during haemofiltration. Minimum number of key parameters required to fully describe the common countercurrent flow field, in the HF active section, include membrane permeance K and friction coefficients in lumen and shell side (ff and fs ). It is shown that the countercurrent flow mode itself is incapable of yielding these parameters, based on externally measured flow rates and pressures. Similarly, the relevant ISO protocol is deficient as it can only provide rough underpredictions of permeance K. The causes of such inherent deficiencies of current standards and practices are analyzed. In contrast, a recently developed methodology, accounting for the (heretofore ignored) pressure drop in module headers and combining a mechanistic theoretical model with experimental data from 2 special haemofilter operating modes, yields an accurate determination of the key parameters (K, ff , fs ). Additionally, it permits a full description of flow field for Newtonian liquids, for both constant and axially varying viscosity in fiber-lumen due to the transmembrane flux. Development of new reliable standards is suggested, facilitated by the insights gained in this work.

Novel chitosan copolymers (CS-g-SBMA) grafted with [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) in various molar ratio 1.5:1, 5:1, 11.5:1 and 20:1, were synthesized in the present study. SBMA was selected as zwitterion molecule showing promising antibacterial properties. Grafted chitosan derivatives were fully characterized for their successful synthesis by NMR and FT-IR, for their crystallinity by XRD showing reduced crystallinity compared to CS alone. Furthermore, swelling studies were conducted with the grafted derivatives showing extensive swelling capacity (maximum degree of swelling up to 1800%) and water absorption was studied with differential scanning calorimetry and equilibrium water adsorption/desorption isotherms were analyzed. Caspofungin, a novel antifungal drug, was used to prepare a double-acting system, with both antibacterial and antifungal properties, proper for topical use. Drug loaded hydrogels were prepared with 10, 20 and 30 wt% drug content and the loaded hydrogels were fully characterized while antimicrobial studies showed enhanced properties. Caspofungin in vitro release showed an initial burst effect followed by a diffusion process while data analysis verified the initial burst release followed by a quasi Fickian diffusion-driven sustained release. Enhance antimicrobial properties was also observed in caspofungin-loaded hydrogels showing the successful fulfill of our scope; an amphiphilic system having great potential for the development of patches with inherent antimicrobial properties and prolonged antifungal properties.

Biofilm is a layer of syntrophic microorganisms stick to each other and to the surface. The importance of biofilms is enormous in various industrial applications and human everyday life. The effects of biofilm could be either positive or negative. Positive effects are encountered in industrial processes, bioremediation, and wastewater treatment. Negative effects are more common with the marine industry being one of the sectors, which confronts severe corrosion problems caused by biofouling on the surfaces of equipment and infrastructures. In space industry, microbial contamination and biofouling adversely affect both crew health and mission-related equipment, the latter including hardware, water systems, piping, and electrical tools. The capacity of biofilms to grow in space environment was confirmed already in 1991. One of the most important surface properties of biofilms is wettability, which dictates not only how a liquid spreads over the uneven external surface of biofilms but also how it penetrates into their porous and morphologically complex structure. To investigate wetting and spreading onto biofilms, model materials are often used to simulate different morphological and functional features of biofilms in a controlled way, for example, soft, deformable, soluble, structured, porous materials. Here, we review recent advances in wetting and spreading on porous and soft deformable surface together with biofilms wetting properties and its importance in space industry. We conclude with a discussion of the main directions for future research efforts regarding biofilm wetting.

The SARS-CoV-2 pandemic represents an unprecedented global crisis necessitating novel approaches for, amongst others, early detection of emerging variants relating to the evolution and spread of the virus. Recently, the detection of SARS-CoV-2 RNA in wastewater has emerged as a useful tool to monitor the prevalence of the virus in the community. Here, we propose a novel methodology, called lineagespot, for the detection of SARS-CoV-2 lineages in wastewater samples using next-generation sequencing. Our proposed method was tested and evaluated using NGS data produced by the sequencing of three wastewater samples from the municipality of Thessaloniki, Greece, covering three distinct time periods. The results showed a clear identification of trends in the presence of SARS-CoV-2 mutations in sewage data, and allowed for a robust inference between the variants evident through our approach and the variants observed in patients from the same area time periods. Lineagespot is an open-source tool, implemented in R, and is freely available on GitHub.

Detection of SARS-CoV-2 in sewage has been employed by several researchers as an alternative early warning indicator of virus spreading in communities, covering both symptomatic and asymptomatic cases. A factor that can seriously mislead the quantitative measurement of viral copies in sewage is the adsorption of virus fragments onto the highly porous solids suspended in wastewater, making them inaccessible. This depends not only on the available amount of suspended solids, but also on the amount of other dissolved chemicals which may influence the capacity of adsorption. On this account, the present work develops a mathematical framework, at various degrees of spatial complexity, of a physicochemical model that rationalizes the quantitative measurements of total virus fragments in sewage as regards the adsorption of virus onto suspended solids and the effect of dissolved chemicals on it. The city of Thessaloniki in Greece is employed as a convenient case study to determine the values of model variables. The present data indicate the ratio of the specific absorption (UV254/DOC) over the dissolved oxygen (DO) as the parameter with the highest correlation with viral copies. This implies a strong effect on viral inaccessibility in sewage caused (i) by the presence of humic-like substances and (ii) by virus decay due to oxidation and metabolic activity of bacteria. The present results suggest days where many fold corrections in the measurement of viral copies should be applied. As a result, although the detected RNA load in June 2020 is similar to that in April 2020, virus shedding in the city is about 5 times lower in June than in April, in line with the very low SARS-CoV-2 incidence and hospital admissions for COVID-19 in Thessaloniki in June., Graphical abstract Unlabelled Image, Highlights • Towards a modeling tool for reliable sewage epidemiology • Effect of sewage chemical and biological quality on quantitation of SARS-CoV-2 • Rationalization of viral copies number (VCN) by accounting adsorption on solids • VCN is affected by flow rate, suspended solids, and type/amount of organic matter • Estimated low virus shedding rate agrees with calm clinical conditions in the city

In water and wastewater, phosphate anions are considered critical contaminants because they cause algae blooms and eutrophication. The present work aims at studying the removal of phosphate anions from aqueous solutions using silica particles functionalized with polyethylenimine. The parameters affecting the adsorption process such as pH, initial concentration, adsorbent dose, and the presence of competitive anions, such as carbonate, nitrate, sulfate and chromate ions, were studied. Equilibrium studies were carried out to determine their sorption capacity and the rate of phosphate ions uptake. The adsorption isotherm data fitted well with the Langmuir and Sips model. The maximum sorption capacity was 41.1 mg/g at pH 5, which decreased slightly at pH 7. The efficiency of phosphate removal adsorption increased at lower pH values and by increasing the adsorbent dose. The maximum phosphate removal was 80% for pH 5 and decreased to 75% for pH 6, to 73% for pH 7 and to 70% for pH 8, for initial phosphate concentration at about 1 mg/L and for a dose of adsorbent 100 mg/L. The removal rate was increased with the increase of the adsorbent dose. For example, for initial phosphate concentration of 4 mg/L the removal rate increased from 40% to 80% by increasing the dose from 0.1 to 2.0 g/L at pH 7. The competitive anions adversely affected phosphate removal. Though they were also found to be removed to a certain extent. Their co-removal provided an adsorbent which might be very useful for treating waters with low-level multiple contaminant occurrence in natural or engineered aquatic systems.

In the present work, the porous metal-organic framework (MOF) Basolite&reg, F300 (Fe-BTC) was tested as a potential drug-releasing depot to enhance the solubility of the anticancer drug paclitaxel (PTX) and to prepare controlled release formulations after its encapsulation in amphiphilic methoxy poly(ethylene glycol)-poly(&epsilon, caprolactone) (mPEG-PCL) nanoparticles. Investigation revealed that drug adsorption in Fe-BTC reached approximately 40%, a relatively high level, and also led to an overall drug amorphization as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The dissolution rate of PTX-loaded MOF was substantially enhanced achieving a complete (100%) release within four days, while the neat drug only reached a 13% maximum rate (3&ndash, 4 days). This PTX-Fe-BTC nanocomposite was further encapsulated into a mPEG-PCL matrix, a typical aliphatic amphiphilic copolyester synthesized in our lab, whose biocompatibility was validated by in vitro cytotoxicity tests toward human umbilical vein endothelial cells (HUVEC). Encapsulation was performed according to the solid-in-oil-in-water emulsion/solvent evaporation technique, resulting in nanoparticles of about 143 nm, slightly larger of those prepared without the pre-adsorption of PTX on Fe-BTC (138 nm, respectively). Transmission electron microscopy (TEM) imaging revealed that spherical nanoparticles with embedded PTX-loaded Fe-BTC nanoparticles were indeed fabricated, with sizes ranging from 80 to 150 nm. Regions of the composite Fe-BTC-PTX system in the infrared (IR) spectrum are identified as signatures of the drug-MOF interaction. The dissolution profiles of all nanoparticles showed an initial burst release, attributed to the drug amount located at the nanoparticles surface or close to it, followed by a steadily and controlled release. This is corroborated by computational analysis that reveals that PTX attaches effectively to Fe-BTC building blocks, but its relatively large size limits diffusion through crystalline regions of Fe-BTC. The dissolution behaviour can be described through a bimodal diffusivity model. The nanoparticles studied could serve as potential chemotherapeutic candidates for PTX delivery.

Using moderate populations of filaments in the biomass of Membrane Bio-Reactors (MBRs) is a biological anti-fouling method which has been increasingly applied over the last few years. This study aims to quantify the effect of COD to TN ratio, Dissolved Oxygen (DO) concentration and temperature on filaments&rsquo, population and Trans-Membrane Pressure (TMP) in a pilot-scale MBR, with a view to reducing membrane fouling. The novelty of the present work concerns the development of a mathematical equation that correlates fouling rate (dTMP/dt) with the population of filamentous microorganisms, assessed by the Filament Index (FI), and with the concentration of the carbohydrate fraction of Soluble Microbial Products (SMPc). Apart from TMP and SMPc, other fouling-related biomass characteristics, such as sludge filterability and settleability, were also examined. It was shown that at high COD to TN ratio (10:1), low DO concentration in the filaments&rsquo, tank (0.5 &plusmn, 0.3 mg/L) and high temperature (24&ndash, 30 &deg, C), a moderate population of filaments is developed (FI = 1&ndash, 2), which delays the TMP rise. Under these conditions, sludge filterability and settleability were also enhanced. Finally, TMP data analysis showed that the fouling rate is affected by FI and SMPc concentration mainly in the long-term fouling stage and increases exponentially with their increase.

Biofilms prevention and removal are crucial in many industrial and medical applications. Their complex and cohesive structure provides resistance to cleaning even to strong disinfectants. A key factor for their behavior is the wetting properties of their surfaces. The main goal of this work is to study the wetting properties of biofilms produced by bacteria Pseudomonas fluorescens. Biofilms are obtained on glass coupons under well controlled flow conditions, using custom-made flow cell devices. Different nutrient concentration and shear flow conditions are investigated. Biofilm wetting properties are examined under imposed external body forces (forced wetting) through a specialized device, named Kerberos®. Kerberos® is capable of subjecting sessile droplets to varying tilting angles and centrifugal forces while monitoring the variation of the droplet shape in X, Y and Z-directions through three Wi-Fi cameras. Wetting experiments are carried out using water-based solution (dye solution) droplets on biofilm-coated glass coupons. In this work, spreading/sliding behaviour of droplets are investigated only on horizontal substrates (no tilting) under the action of centrifugal forces. Apart from wetting properties, biofilm growth kinetics and surface morphology at different nutrient and shear flow conditions are also assessed. Results show that, according to the different growth conditions, biofilms present different wetting properties. At lower nutrient concentration and shear flow conditions, spreading and sliding behaviour are similar to that observed in glass coupons in the absence of biofilm. At higher nutrient and shear flow conditions, spontaneous wicking of the biofilm occurs the moment of droplet deposition on the biofilm leading to irregular and jagged shapes of droplets, while on the contrary water droplets look like smooth spherical sections on pure glass. The spontaneous wicking affects the droplet initial shape and so the wetting behaviour during the subsequent rotation tests. In each examined condition, biofilms show hydrophilic properties.

Biofilms are bacterial communities embedded in an extracellular matrix, able to adhere to surfaces. A deeper knowledge of the biofilm as a whole will aid the development of efficient methods to control deleterious biofilms (clinical biofilms, biofouling) or to enhance beneficial ones (waste-water treatment, bio-filtration). P. fluorescens has been widely studied, this strain produces bioactive secondary metabolites, and forms biofilms[1]. Several experimental set-ups have been widely used for in vitro biofilm cultivation of P. fluorescens, even if a deep characterization among different culture conditions is still lacking in the literature. This work, based on previous studies[2], is focused on the investigation of growth conditions on biofilm structure and properties. Growth kinetics of P. fluorescens biofilms was characterized in vitro under stagnant and flow-controlled conditions, using a rotating annular bioreactor. Two different supports in borosilicate glass and polycarbonate have been used. Bacterial growth kinetics has been measured through bio-turbidity analysis and TOC/DOC quantification. Biofilm morphology has been quantified through optical microscopy and image analysis by measuring the fraction of support surface covered by biofilm. The wetting properties of the biofilm layers have been investigated by using an innovative device, named Kerberos®, able to control centrifugal and gravitational forces acting on a single droplet placed on a surface[3]. The evolution of the droplet shape and position was measured as function of the imposed stress, to quantify wetting of different biofilm coated samples, following already assessed methodologies[4]. Different chemo-physical environments, investigated by changing growth medium, physical support, and imposed flow stress, induced different growth kinetics, biofilm morphology, and wetting properties. Accurate experimental measurements allowed us to estimate in a quantitative way the influence of investigated parameters on specific morphologic measurements. [1] Brittan S. Scales and others, ‘Microbiology, Genomics, and Clinical Significance of the Pseudomonas Fluorescens Species Complex, an Unappreciated Colonizer of Humans’, Clinical Microbiology Reviews, 27.4 (2014), 927–48 . [2] Federica Recupido and others, ‘The Role of Flow in Bacterial Biofilm Morphology and Wetting Properties’, Colloids and Surfaces B: Biointerfaces, 2020 . [3] Sotiris P. Evgenidis and others, ‘Kerberos: A Three Camera Headed Centrifugal/Tilting Device for Studying Wetting/Dewetting under the Influence of Controlled Body Forces’, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017 . [4] Inmaculada Ríos-López and others, ‘Effect of Initial Droplet Shape on the Tangential Force Required for Spreading and Sliding along a Solid Surface’, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018 .

The aim of this work was to evaluate the effectiveness of neat chitosan (CS) and its derivatives with 2-acrylamido-2-methyl-1-propanesulfonic acid (A&Alpha, MPS) and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (MEDSP) as appropriate nanocarriers for the simultaneous ocular administration of dexamethasone sodium phosphate (DxP) and chloramphenicol (CHL). The derivatives CS-A&Alpha, MPS and CS-MEDSP have been synthesized by free-radical polymerization and their structure has been proved by Fourier-Transformed Infrared Spectroscopy (FT-IR) spectroscopy. Both derivatives exhibited low cytotoxicity, enhanced mucoadhesive properties and antimicrobial activity against Staphylococcus aureus (S.aureus) and Escherichia coli (E. coli). Encapsulation was performed via ionic crosslinking gelation using sodium tripolyphosphate (TPP) as the crosslinking agent. Dynamic light scattering measurements (DLS) showed that the prepared nanoparticles had bimodal distribution and sizes ranging from 50&ndash, 200 nm and 300&ndash, 800 nm. Drugs were encapsulated in their crystalline (CHL) or amorphous (DexSP) form inside nanoparticles and their release rate was dependent on the used polymer. The CHL dissolution rate was substantially enhanced compared to the neat drug and the release time was extended up to 7 days. The release rate of DexSP was much faster than that of CHL and was prolonged up to 3 days. Drug release modeling unveiled that diffusion is the main release mechanism for both drugs. Both prepared derivatives and their drug-loaded nanoparticles could be used for extended and simultaneous ocular release formulations of DexSP and CHL drugs.

This study investigates the effect of nanobubbles (NBs) on the adsorption in water. In batch adsorption experiments, as liquid medium deionized water, with or without NBs, was used in order to remove a particular heavy metal. Lead ions (Pb(II)) and low-cost activated carbon produced from pyrolysis of potato peels (ACP) were used as model pollutant and adsorbent material, respectively. The adsorption capacity of Pb(II) was found to be approximately similar either in the presence (Qmax = 171 mg/g) or absence of NBs in water (Qmax = 167 mg/g). On the contrary, the major effect of NBs was to accelerate the adsorption process by 366%. This impressively high acceleration will be the basis in future research to decrease the adsorption equilibrium time and sequentially increase the number of adsorption-desorption cycles in reuse modes. A proposed mechanism exported from the experimental results, in which NBs act as carriers (“buses”), was proposed based on the already known theory; the inherent property of NBs to accept charged particles onto their interface is considered to assist diffusion and penetration phenomena of lead ions into the activated carbon pores.

In the present study, novel block copolymers of poly(l-lactide)-block-poly(propylene adipate) (PLLA-b-PPAd) were synthesized in two ratios, 90/10 and 75/25 w/w and were further investigated as long-acting injectable (LAI) polymeric matrices in naltrexone base microparticle formulations. The synthesized polymers were characterized by 1H-NMR, 13C-NMR, FTIR, XRD, TGA and DSC. NMR and FTIR spectroscopies confirmed the successful synthesis of copolymers while DSC showed that these are block copolymers with well-defined and separated blocks. Microparticles were prepared by single emulsification method and were further characterized. Nanoparticles in the range of 0.4&ndash, 4.5 &mu, m were prepared as indicated by SEM, with copolymers giving the lowest particle size. By XRD and DSC it was found that naltrexone was present in the amorphous state in its microparticles. Dissolution study showed a drug release extending over seven days, indicating that these novel PLLA-b-PPAd copolymers could be promising matrices for naltrexone&rsquo, s LAI formulations. It was evidenced that drug release depended on the copolymer composition. Model release studies showed that drug release is controlled by diffusion.

A new technique is proposed for the assessment of aggregate morphology based on combined information of aerodynamic and mobility size distributions. Instead of formulating a complex inverse problem having aggregate morphology as unknown, the actual problem is separated to two stages. The aerodynamic distribution is determined directly by the electric low pressure impactor (ELPI) data whereas the morphology is independently assessed by matching the distribution arises from ELPI and from scanning mobility particle sizer (SMPS). The advantage of this approach is that it can estimate different fractal dimension for different aggregate size. The approach is applied to soot aggregates from three different diesel engines. In all cases, a non-monotonic behavior of fractal dimension versus aggregate size is observed. In particular, the fractal dimension initially decreases and then increases (passing through a minimum) as the mobility diameter increases.

A new software tool is developed for droplet image analysis for the study of wetting of solid substrates. The tool extracts information exclusively from images and does not require the use of any properties of the system. Moreover, its applicability covers both axisymmetric and non-axisymmetric droplets. The developed software processes independently droplet images taken from side and top perspectives. Processing of side-view images is made by polynomial fitting to the droplet shape and provides important 2D geometrical features such as contact angles, length, height, contact point coordinates and contour outline. The analysis of top-view images is achieved through active contours (snakes) and yields droplet dimensions, centroid position and contour outline. The combination of synchronized side and top images provides the reconstruction of the droplet 3D shape by means of slices of circular arc shape, which allows estimation of droplet volume and of the distribution of contact angles along its perimeter. The above is an important feature that has not been delivered by other software tools. Experimental results to support the applicability of the new tool are presented for two distinct substrates having different surface properties (glass and Teflon).

Bubbles forming due to decompression of a liquid saturated with dissolved gas at elevated pressures when it enters a low pressure liquid pool can either limit or promote the efficiency of several ground and space applications. Among the experimental parameters influencing flow decompression degassing, dissolution pressure is the most studied, yet controversial, parameter. The present work aims to shed light on how dissolution pressure of a liquid affects the final size of bubbles and the generated gas fraction by conducting gas desorption (degassing) experiments of liquid jets that decompress passing though a nozzle to a vertical column filled with the same non-degassed liquid. Bubbles size distributions at different radial positions in the column are computed analyzing high resolution digital images. A patented electrical impedance technique is employed to measure instantaneously local volumetric gas fraction. Flow dispersion in the column is studied by residence time distributions using conductivity tracers. On-line continuous dissolved oxygen measurements yield the kinetics and final extent of degassing. Experimental results are discussed to comprehend why bubbles size distributions vary with dissolution pressures and how this variation affects gas fraction in the column.

Despite the extensive study of wetting in literature, there are still many unresolved issues regarding forced wetting. One of them refers to the effect of the initial droplet shape on the force required for spreading and sliding along a solid surface; an effect that has not ever been explicitly reported. Previous experimental works, in general, assume initially axisymmetric droplet shapes. In this study, experiments are performed with an innovative device, Kerberos, capable of subjecting sessile droplets at different tilting angles to varying centrifugal forces in order to explore the spreading/sliding behavior of droplets of different volumes and different initial shapes (including non-axisymmetric). A broad validation of the technique is achieved by the repeatability and consistency of measurements. Results for initially axisymmetric and non-axisymmetric droplets concerning contact angles, droplet length, droplet shape and velocity are presented and discussed. Furthermore, detailed results for the critical tangential accelerations required for the inception of spreading and sliding are presented showing the different sensitivity of these parameters on the droplet initial shape. Experimental results are employed to test the applicability of the well-known Furmidge equation for the retention force in the case of initially non-axisymmetric droplets. On this account, the initial length of droplets is found to be a more appropriate length scale in the Furmidge equation than the initial droplet width.

This paper aims to quantify the contribution of the various factors to energy consumption in reverse osmosis (RO) desalination processes and to identify those with the greatest potential for reduction. Specific energy consumption (SEC), in kWh per m3 of permeate production, is due to the retentate osmotic pressure, the resistance to fluid permeation through the membrane, the friction losses in the retentate and permeate channels of the spiral wound membrane (SWM) modules and the non-ideal operation of high pressure pumps and energy recovery devices (ERD). Taking advantage of a recently developed SWM-module performance simulator, the aforementioned individual contributions to SEC are determined for two case studies, typical of seawater and brackish water desalination processes, for steady state operation. Detailed results are obtained with SEC itemized per SWM element in a typical 7-element pressure vessel. Comparative assessment of the results is enlightening, showing that the greatest margin for the desirable SEC reduction is related to improvements of membrane permeability and efficiency of pumps and ERD. The indirect, yet significant, effect of other key design and operating process parameters is also discussed.

Stringent regulation is endorsed to restrict global gaseous and particulate vehicle emissions by adapting advanced catalytic systems on the exhaust, incorporating costly platinum group metals (PGM) for oxidation catalysis. Porous silica and alumina particles are synthesized in the present work via a one-step aerosol spray route. The particles are doped with Pt, Ce and Na and are evaluated with respect to their pore size distribution, exhibiting surface areas between 6-269 m2/gr. The particles have been evaluated in a packed bed reactor with respect to NO oxidation in presence or absence of hydrocarbons (C2H4) in order to study the hydrocarbon inhibition effect on oxidation kinetics, showing higher conversion curves for higher surface area samples. The current work studies also the correlation between reactant accessibility to the in-pore Pt nanoparticles and catalytic activity by reaction kinetic model.

A novel device for measuring the thermal conductivity of polymeric materials (pure polymers or nanocomposites) is presented here. Its design is based on two cylindrical tanks containing cold and hot water. Each tank wets one side of a disc-shaped polymeric sample. The proper selection of construction materials (aluminum body, Teflon fittings, etc.) and geometry (shape, size, etc.) of the two tanks and of the sample (diameter, thickness) renders the accurate measurement of the low thermal conductivity of several polymeric materials possible. The disc-shaped sample is placed in-between the two cylindrical tanks of the device, filled with cold and hot water. The water temperature in the two tanks is an adjustable operational parameter of the device. Both tank temperatures are recorded and fitted by a proper mathematical model in order to estimate the thermal conductivity of the sample. Extensive experimentation shows a very small scatter of the estimated conductivity values. The device was used to measure thermal conductivity of several polymers such as silicone rubber and epoxy resin prepared with a variety of cross-linkers and cross-linker blends. Moreover, the above polymers are used as matrices for the incorporation of various (nano)additives, like mesoporous silica foams (MCF) and organoclays (I.30E), for the preparation of the relative polymer nanocomposites whose thermal conductivity is measured.

It is well documented that ionic silver prevents microbial proliferation in water systems, e.g., tanks and piping, reducing health risks and degradation of potable water quality. However, ionic silver interacts with wetted surfaces resulting in depletion of silver ions from water. This study investigates the loss of silver from water when in contact with titanium alloy Ti-6Al–4 V. Use of ionic silver in Ti-6Al–4 V water tanks is one of the options under consideration by National Aeronautics and Space Administration’s (NASA) for disinfection of potable water in future long term missions. The present tests resemble real conditions during storage in water tanks regarding the ratio of wetted surface area to liquid volume, silver ions concentration in water as well as temperature and light conditions. In all examined cases, silver ions vanish completely from the water and at the same time traces of vanadium and aluminium mitigate from the solid surface to the water. Extensive SEM and high resolution XPS analyses demonstrate that silver is present on the Ti-6Al-4 V surface in its oxidized form (Ag + and Ag +++ ). This could be explained either by the mechanism of galvanic deposition of metallic silver and its subsequent transformation to oxides or by an ion-exchange mechanism whereby silver ions are chemisorbed at negatively charged Ti-O- sites present on the surface of the Ti alloy. All present findings underline the potential risk of not achieving potable water quality standards when water is stored in Ti-6Al-4 V tanks.

An experimental investigation of subcooled flow boiling heat transfer in an orthogonal macro channel (dh = 16 mm) is undertaken. An extraordinary heat transfer performance is observed when a single copper wire mesh screen covers the heating surface of the channel. Experiments are performed with deionized water, at a mass flux range of 100–410 kg/m2s and a heat flux range of 50–850 kW/m2. A series of highly subcooled flow boiling experiments demonstrates the existence of regions of heat transfer enhancement, compared to a smooth reference surface. The addition of the mesh layer triggers a self-sustained flow instability accompanied by intense pressure oscillations which allows for remarkably thermally steady state conditions to take place. While in several heat transfer studies, the appearance of pressure oscillations has been attributed with heat transfer deterioration, in the current study we observe that a self-sustained oscillatory flow leads altogether to heat transfer enhancement, baring close resemblance to the well-known microbubble emission boiling flow phenomenology and heat transfer. Aspects of temperature, pressure and flow regimes are presented and discussed accordingly.

In this study, high surface area mesoporous silica foam with cellular pore morphology (MCF) was used for injectable delivery of paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. The aim was to enhance paliperidone solubility and simultaneously to prepare long active intractable microspheres. For this reason paliperidone was first loaded in MCF silica, and the whole system was further encapsulated into PLA and PLGA 75/25 w/w copolymer in the form of microspheres. It was found that paliperidone, after its adsorption into MCF, was transformed in its amorphous state, thus leading to enhanced in vitro dissolution profile. Furthermore, incorporation of the drug-loaded MCF to polymeric microparticles (PLA and PLGA) prolonged the release time of paliperidone from 10 to 15 days.

The use of mesenchymal stem cells (MSCs) for artificial bone graft production can meet the increasing demands of the tissue engineering market and provide off-the-shelf, safe and high quality material for grafting procedures. Herein, we present an integrated-modelling approach to describe the osteogenic differentiation of MSCs based on gene expression, cell cycle dynamics, and population balance equations.

Despite the significant effort spent over the years to study wetting and dewetting phenomena of droplets on solid substrates under applied forces, there are still many unresolved issues. To name a few, a concise theory for the two dimensional contact line is missing. Also, a controversy has recently arisen for the effect of droplet size on the tangential force required for the inception of sliding. It is clear that to resolve such issues and to better understand the underlying processes a new generation of experimental techniques and results are needed. In this spirit, a novel device, Kerberos, is proposed and constructed here. Kerberos offers two major innovative features compared to prior techniques: (a) it allows simultaneous rotation and tilting of the droplet supporting plate (these mechanisms have been employed separately in the past) and (b) three Wi-Fi cameras (viewing the droplet from X–Y–Z directions) follow the rotation/tilting motion. The above features permit on one hand the independent control of normal and tangential forces applied to the droplet and, on the other, allow real time 3D impressions of the droplet shape. Indicative results manifest the wealth of new experimental data accessible by Kerberos which were out of reach by other techniques. The theoretical background of droplet behavior in the new device is discussed, making assumptions that lead to closed form solutions. Such a model is useful for the design of experiments with the new device.

The focus of this work is on the extraction of heat transfer coefficients from experimental data during the pre-boiling regime of potato frying by employing a specially designed device. Knowledge of these coefficients is necessary for the estimation of temperature spatial profiles at the inception of frying. In this way, not only understanding but also modeling of the frying process is facilitated. Heat transfer coefficients are estimated based on a one dimensional heat conduction model through matching theoretically predicted with experimentally measured temperature evolutions at three distinct distances below, but close to, the surface of the fried item. The tests cover a variety of experimental conditions regarding the initial oil temperature, fryer geometry, frying surface orientation, type of fried item, and level of gravitational acceleration. The dependence of heat transfer coefficients on the above experimental conditions is discussed.

In this work, high surface area mesoporous silica (SBA-15) was loaded with paclitaxel (taxol, PTX) and was further entrapped into poly(lactic acid-co-glycolic acid) (PLGA) microparticles (MPs). A modified solvent evaporation-emulsion method was used in order to formulate the composite microparticles with sizes of 8-12μm. PTX loaded SBA-15 as well as the PLGA/PTX-SBA-15 composites were characterized in terms of their morphology, crystal structure and thermal properties. Drug content, loading efficiency, particle size and the in-vitro drug release kinetics of the PLGA/PTΧ-SBA-15 microspheres were also investigated. The in vitro release studies were carried out using Simulated Body Fluid (SBF) at 37°C revealing that the prepared formulations present higher dissolution rate than pure PTX and sustained pattern which is ideal for anticancer carriers. Modeling and data analysis of the in vitro drug release was also investigated. It was also shown that all microparticles have low cytotoxicity in HUVE cells. Finally, it was found that drug loaded microparticles are very effective in Human Cervical Adenocarcinoma (HeLa) cells.

Flotation is a very important separation process in the mining industry. In addition, it finds important application as a water treatment process. The better design of flotation devices and operation strategies requires development of reliable and consistent mathematical models. Flotation is much more complex than typical unit processes, involving physicochemical interactions in small size scale and hydrodynamic interactions between bubbles, particles and liquid in a variety of size scales. The only feasible integrated approach to modeling the flotation process is by incorporating multiple scales. In the heart of such an approach there is a submodel for the frequency of collisions between bubbles and particles. Literature on this subject in the absence of intense turbulence is very extensive and there are many well-accepted models. Yet, the situation is quite different for the case of turbulence being an important collision mechanism, which is exactly what happens in industrial dispersed air flotation devices. The corresponding literature models are limited and focused on different aspects of the process. The present work is a review study attempting to unify these models in a general framework. The review is not restricted to presenting existing models but all relevant physical principles and fundamental theories are examined and assessed properly. In this respect, there are two levels of classification of literature material in this work. The first is a classification as general collision models and flotation models. It is important to critically examine the general collision models of engineering and physics literature since they constitute the basis on which flotation models rely. The second classification is with respect to the level of detail and sophistication of models (from distributed multibubble/multiparticle model to lumped models based on statistical theory of turbulence). The outcome of the work comes to the conclusion that existing models focus only to specific parts of the phenomena leading to bubble-particle collisions and for this, further improvement is needed to integrate them to obtain a better and more general picture. The material and comments presented in this work are meant as a decisive milestone towards this integration procedure.

In the International Space Station (ISS), Russian and European cosmonauts drink water disinfected by dissolved silver. For this to be effective, the concentration of silver should remain above a certain threshold from the moment of its initial disposition in storage tanks on earth until its final consumption in ISS. Unfortunately, during water tanks transportation to ISS and during storage in ISS, silver concentration has been reported to decrease intensively beyond any reason. This work examines the effect of different materials used in ISS water storage and distribution systems on the reduction of silver concentration. An experimental campaign has been organized where passivated stainless steel (SS), passivated and electropolished SS and titanium alloy coupons (official ISS grades) are exposed to simulated ISS potable water at different silver concentrations, different surface to volume ratios, and at stagnant or flow conditions. The evolution of silver concentration remaining in the bulk water is recorded with respect to the exposure time. A reaction engineering model for the Ag loss to the coupons is developed. The model is fitted to the experimental data in order to derive the reaction rate expression and the corresponding parameters. For passivated SS and electropolished SS the silver deposition rate depends on the initial silver concentration in water but is rather unaffected by the progress of silver deposition on the surface. On the other hand, for Ti alloy, while silver deposition rate still depends on initial silver concentration, it decreases continuously as silver deposition on the surface advances, implying that Ti alloy surface becomes gradually saturated and so prevents further silver deposition. Such a model can be useful for material selection and design of water storage and distribution facilities for ISS.

Linear binary fragmentation of synthetic fractal-like agglomerates composed of spherical, equal-size, touching monomers is numerically investigated. Agglomerates of different morphologies are fragmented via random bond removal. The fragmentation algorithm relies on mapping each agglomerate onto an adjacency matrix. The numerically-determined fragment size distributions are U-shaped, clusters break predominantly into two largely dissimilar fragments, becoming more uniform as the fractal dimension decreases. A symmetric beta distribution reproduces the fragment distribution rather accurately. Its exponent depends on the structure (fractal dimension) and number of monomers of the initial agglomerate. A universal fragment distribution, a function only of the initial fractal dimension, is derived by requiring that it satisfy the fragmentation conversation laws and the straight-chain limit. We argue that the fragmentation rate is proportional to the initial agglomerate size., 10 pages, 9 figures, published in EPL

The formation and growth of bubbles due to decompression degassing of a liquid has been extensively studied in the past, aiming to enhance the efficiency of specific industrial applications. Even though liquid decompression degassing may interfere with the performance of space processes (such as cooling and lubrication systems, combustion and storage of liquid propellants etc.), the phenomenon has never been studied in non-terrestrial gravity conditions. The present work investigates for the first time, bubbles dynamics of a degassing liquid under various hypergravity accelerations. Degassing bubbles form due to desorption of dissolved air upon decompression of a liquid jet partially saturated with air. Accelerations up to 12 g are applied artificially by means of the Large Diameter Centrifuge facility of the European Space Agency. A patented electrical impedance spectroscopy technique provides the distribution of desorbed gas along the flow. Analysis of high resolution images indicates changes of bubbles size. Residence time distributions using conductivity tracers reveal the flow pattern in the degassing vessel. The total extent of liquid degassing is derived from dissolved oxygen measurements. Hypergravity alters the bubbles velocity and, consequently, their residence time in the liquid. Therefore, it affects the gas fraction in the degassing vessel offering unique conditions for studying the impact of acceleration on bubble dynamics. Experimental findings are useful not only for the optimization of space processes during hypergravity phases, e.g., space vehicles launch and re-orbiting, but also for the construction of controlled degassing industrial applications.