Increasing Surface Coverage Research Articles

Molecular Dynamics Simulations on the Adsorbed Monolayers of N-Dodecyl Betaine at the Air-Water Interface.

Betaine is a kind of zwitterionic surfactant with both positive and negative charge groups on the polar head, showing good surface activity and aggregation behaviors. The interfacial adsorption, structures and properties of n-dodecyl betaine (NDB) at different surface coverages at the air-water interface are studied through molecular dynamics (MD) simulations. Interactions between the polar heads and water molecules, the distribution of water molecules around polar heads, the tilt angle of the NDB molecule, polar head and tail chain with respect to the surface normal, the conformations and lengths of the tail chain, and the interfacial thickness of the NDB monolayer are analyzed. The change of surface coverage hardly affects the locations and spatial distributions of the water molecules around the polar heads. As more NDB molecules are adsorbed at the air-water interface, the number of hydrogen bonds between polar heads and water molecules slightly decreases, while the lifetimes of hydrogen bonds become larger. With the increase in surface coverage, less gauche defects along the alkyl chain and longer NDB chain are obtained. The thickness of the NDB monolayer also increases. At large surface coverages, tilted angles of the polar head, tail chain and whole NDB molecule show little change with the increase in surface area. Surface coverages can change the tendency of polar heads and the tail chain for the surface normal.

Study on the effect of the strengthen grinding process surface coverage on the micro-morphology, micro-hardness, roughness, and residue stress of GCr15 bearing steels

In this study, the surface integrity of GCr15 bearing steels processed by different surface coverage of the strengthen grinding process (SGP) has been theoretical and experimentally investigated. OpenCV-Python-based image processing algorithm was used to extract the evolution of the shot peening coverage. The surface morphology, roughness, equivalent plastic deformation (PEEQ), microhardness, and residual stress were analyzed. Results show that as surface coverage increase from 100 % to 400 %, the PEEQ and microhardness, and theoretical and actual residual stress, behave similarly. The highest microhardness and residual stress reach 851.3 HV and − 1182 MPa, respectively. The variation of surface roughness shows a significant difference, especially at the surface coverage of 300 %, the measured roughness is reduced by approximately 65 % compared to simulation. The possible mechanisms were further discussed. This work demonstrated that the proposed theoretical modeling method could be an efficient approach for controlling the process parameters of multiphase jet flow in practical applications.

Control of boundary slip by interfacial nanobubbles: A perspective from molecular dynamics simulations

Enhancing boundary slip using interfacial nanobubbles (INBs) has gained significant interest in nanofluidic transport. In this study, we conducted a comprehensive investigation on the influence of INBs on boundary conditions for both smooth and rough substrates using molecular dynamics simulations. We analyzed the impact of INB protrusion angle, coverage percentage, quantity, and fluidity on the slip length. Our results showed that INBs always increase the slip length on a smooth substrate, with a linear increase in slip length observed with increasing surface coverage. On a rough substrate, we found that the protrusion angle, quantity, and fluidity of INBs play a crucial role in determining the slip length. Smaller protrusion angles and fewer quantities of INBs were found to be more favorable for enhancing the slip length when the INB coverage is fixed, while the correlation between boundary slip and INB quantity depended on the wetting state of the substrate when the size of the INBs was fixed with a low protrusion angle. Additionally, we revealed that the fluidity of gas molecules inside the INBs dominated the enhancement of slip length by INBs. Overall, our findings are expected to provide valuable insight into drag reduction based on INBs.

Corrosion and Corrosion Protection of Copper Sculptures by Formation of Composite Barrier

Nitrogen dioxide, carbon dioxide and sulphur dioxide are acidic gas and they produce corrosive medium for copper sculptures. These gases absorb moisture to form nitric acid, carbonic and sulphuric acid. It forms corrosion cell on the surface of copper and accelerate corrosion reactions. The corrosion cell formation is written as: Cu|Cu2+||H+|H2 thus corrosion reactions start and copper is oxidized into Cu2+surface and it is oxidized into Cu2+ whereas H+ ion is reduced into H2 . Nitric acid environment copper exhibits galvanic, pitting, stress, crevice, blistering, embrittlement and intergranular corrosion. The corrosion reactions change physical, chemical and mechanical properties of corroded materials. Nanocoating compound tetrahydrodibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC electrospray compounds used to control the corrosion of copper in nitrogen dioxide medium. For corrosion mitigation of copper metal interface was coated with tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC. The coating compound tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone was synthesized in laboratory. Nozzle spray techniques used for nanocoating and electrospraying. The corrosion rate of copper was determined by gravimetric loss method at different temperatures, concentrations and days in nitrogen dioxide medium. Potentiostatic polarization technique used for the determination of electrode potential, corrosion current and current density. Nanocoating and electrospraying compounds formed a composite barrier on the surface of base metal by chemical bonding. The nanocoating and electrospray compounds adhered on base metal by chemisorptions to confirm by activation energy, heat of adsorption, free energy, enthalpy and entropy. The nanocoating and electrospray deposited on copper confirmed by Langmuir, Frundlich and Temkin isotherm. Copper formed a complex compound to interact with tetrahydro-dibenzo[a,d][7]annulene-5,11-disemicarbazone and SiC. Electrospraying SiC blocked porosities of nanocoating compound and checked osmosis process of nitrogen dioxide. Thenanocoating and electrospray compounds decreased corrosion rate and increased surface coverage areas and percentage coating efficiencies.

Development of computational fluid dynamics methodology for characterization of exhalation delivery system performance in a nasal airway with Draf-III surgery

Computational fluid dynamics (CFD) has been used to investigate the intranasal deposition of corticosteroid sprays. CFD Lagrangian tracking models terminate particle motion once particles come into contact with a surface (“trap” boundary condition) and disregard the liquid film buildup on the mucosal surfaces of the sinonasal cavity walls. However, the interaction between spray droplets and the mucosal surface is critical for corticosteroid delivery using the exhalation delivery system (EDS) nasal spray device. Droplets coalesce on sinonasal walls, forming a thin “wall-film” on which droplets spread along the surface, splash, and/or break into secondary particles, depending on impact energy. To advance nasal drug delivery modeling, three CFD models of fluticasone propionate deposition using the EDS device in a Draf III post-surgical geometry were developed: (1) using traditional “trap” boundary conditions; (2) using “wall-film” boundary conditions and one-way coupling; and (3) using “wall-film” boundary conditions with two-way coupling (to account for the high-mass loading in the near-nozzle spray field). Contour plots and data sets for each CFD model were qualitatively compared with physical models in the same geometry (visualized in a 3D-printed sinonasal cast). The CFD simulations showed that EDS delivers fluticasone to all sinonasal regions, including areas superiorly and posteriorly in the sinonasal cavity. In addition, deposition improved and more closely correlated with physical experiments as the CFD model complexity evolved. “Wall-film” modeling of EDS delivery demonstrated increased surface coverage compared to the “trap” model. The “wall-film/two-way coupling” model demonstrated substantially higher deposition in the remote frontal and maxillary sinuses, agreeing with physical cast experiments. In conclusion, CFD simulation of EDS delivery using the “wall-film” boundary/two-way coupling model appears to most accurately represent observations from physical model experiments in the same geometry.

Synthesis of Gemini cationic surfactants based on natural nicotinic acid and evaluation of their inhibition performance at C-steel/1 M HCl interface: Electrochemical and computational investigations

Herein, we prepare effective Gemini cationic surfactants (CSII, CSIV) and characterize them using FT-IR and 1HNMR spectroscopy. The adsorptive properties of CSII and CSIV at HCl/air and C-steel/HCl interfaces were examined with surface tension and electrochemical parameters, respectively. The critical micelle concentration (CMC) of the CSII and CSIV indicated their adsorption affinity at the HCl/air interface. Where, aliphatic chains increase surface coverage percentage and aid in surfactant adsorption. The electrochemical parameters of C-steel in 1 M HCl were studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) at different temperatures. The charge transfer resistance of the C-steel electrode was enhanced from 28.2 Ω.cm2 to 770.79 and 831.45 Ω.cm2 after adding 5 × 10−4 M of CSII and CSIV, respectively. Both CSII and CSIV act as mixed inhibitors with inhibition performance exceeding 97% due to their highly adsorption affinity. The chemical adsorption affinity of these compounds is suggested by the higher adsorption energy (∆G*ads) values (>−40 kJ mol−1) according to the Langmuir isotherm model. The theoretical calculations including DFT, and Monte Carlo simulation (MCs) provide insight into the relationship between corrosion inhibition and molecular structure, where the calculated parameters agree with the experimental results.

Computational investigation of nasal surface coverage from squeeze bottle and Neti Pot saline irrigation flow

Background and objective: Nasal saline irrigation is a common therapy for inflammatory nasal and paranasal disease or for managing post nasal and sinus surgery recovery. Two common irrigation devices include the netipot and squeeze bottles, where anecdotally, these devices alleviate congestion, facial pain, and pressure. However, a quantitative evaluation of these devices’ performance and the fluid dynamics responsible for the irrigation distribution through the nose is lacking. This study tracked the liquid surface coverage and wall shear stresses during nasal saline irrigation produced from a Neti Pot and squeeze bottle.Methods: This study used transient computational fluid dynamics (CFD) simulations to investigate the saline irrigation flow field in a subject-specific sinonasal model. The computational nasal cavity model was constructed from a high-resolution computed tomography scan (CT). The irrigation procedure applied a head position tilted at 90° forward using an 80 ml squeeze bottle and 120 ml Neti Pot.Results: The results from a single sinonasal model demonstrated that the Neti Pot irrigation was more effective in delivering saline solution to the nasal cavity on the contralateral side of irrigation due to typically larger volumes but at the expense of reduced flow and shearing rates, as the flow entered under gravitational forces. The squeeze bottle irrigation provided greater surface coverage on the side of irrigation.Conclusions: The results from the single patient model, demonstrated the Neti Pot increased surface coverage in the paranasal sinuses. Reducing the jet diameter may aid the direct targeting of a specific region at the side of irrigation by preventing the impingement of the jet to the nasal passage surface and redirection of the flow. Evaluating this performance across a wider cohort of patients can strengthen the findings.

Ascorbyl Palmitate-Vitamin C Effective Friction Modifier and Wear Inhibitor for Steel in a PAO Base Oil

Ascorbyl palmitate (AP), known as a nutrition pill, and an antioxidant agent in food, has demonstrated excellent lubricity as an additive in PAO4. Adding one wt% AP in PAO4 drastically decreases friction Coefficient (CoF) up to 66% and protects the steel surface from wear. Meanwhile, it shows a more vital friction reduction ability than conventional Mo-based additives and fatty acids, especially palmitic acid. Ascorbic acid core on AP optimises palmitic acid lubricity by forming robust chemical C-O-Fe bond on steel, increasing surface coverage rate. Masked by AP self-assembled layers, steel surfaces can also handle extreme pressure (up to 2.34 GPa) and temperature (150 °C) with unmeasurable wear. This work broadens human-friendly AP vitamin C application for industrial use and introduces a new pathway for optimizing fatty acids lubricity.

Polymer Brushes on GaAs and GaAs/AlGaAs Nanoheterostructures: A Promising Platform for Attractive Detection of Legionella pneumophila.

This work reports on the potential of polymer brushes (PBs) grown on GaAs substrates (PB-GaAs) as a promising platform for the detection of Legionella pneumophila(Lp). Three functionalization approaches of the GaAs surface were used, and their compatibility with antibodies against Lp was evaluated using Fourier transform infrared spectroscopy and fluorescence microscopy. The incorporation of PBs on GaAs has allowed a significant improvement of the antibody immobilization by increased surface coverage. Bacterial capture experiments demonstrated the promising potential for enhanced immobilization of Lp in comparison with the conventional alkanethiol self-assembled monolayer-based biosensing architectures. Consistent with an eightfold improved capture of bacteria on the surface of a PB-functionalized GaAs/AlGaAs digital photocorrosion biosensor, we report the attractive detection of Lp at 500 CFU/mL.

Wetting and Imbibition Characteristics of Pseudomonas fluorescens Biofilms Grown on Stainless Steel.

This study aims to provide insights into biofilm resistance associated with their structural properties acquired during formation and development. On this account, the wetting and imbibition behavior of dehydrated Pseudomonas fluorescens biofilms grown on stainless steel electropolished substrates is thoroughly examined at different biofilm ages. A polar liquid (water) and a non-polar liquid (diiodomethane) are employed as wetting agents in the form of sessile droplets. A mathematical model is applied to appraise the wetting and imbibition performance of biofilms incorporating the evaporation of sessile droplets. The present results show that the examined biofilms are hydrophilic. The progressive growth of biofilms leads to a gradual increase of substrate surface coverage─up to full coverage─accompanied by a gradual decrease of biofilm surface roughness. It is noteworthy that just after 24 h of biofilm growth, the surface roughness increases about 6.7 times the roughness of the clean stainless steel surface. It is further found that the imbibition of liquid in the biofilm matrix is restricted only to the biofilm region under the sessile droplet. The lack of further capillary imbibition into the biofilm structure, beyond the droplet deposition region, implies that the biofilm matrix is not in the form of an extended network of interconnected micro/nanopores. All in all, the present results indicate a resilient biofilm structure to biocide penetration despite its hydrophilic nature.

Infrared radiation transfer through semitransparent windows supporting absorbing droplets

Water droplets are commonly observed on the inner or outer surface of solar energy conversion systems due to rain or condensation. These droplets affect the systems’ efficiency and thermal load. This study experimentally and numerically investigates infrared radiation transfer through semitransparent windows covered with droplets on their front or back sides. In order to validate our previously developed numerical code and to facilitate the systematic characterization of the samples, acrylic droplets (instead of water) were deposited onto glass windows with contact angle ranging from 26 to 76° and projected surface area coverage from 0% to 60%. The measured transmittance of glass windows with slightly absorbing droplets on the front increased while the reflectance decreased with increasing contact angle and surface coverage due to antireflection effects. For slightly absorbing droplets on the back with contact angles larger than the critical angle for total internal reflection at the droplet/air interface, the transmittance decreased by up to a factor 2 with increasing contact angle and surface area coverage. In the infrared spectral range when droplets were strongly absorbing, the window transmittance decreased by up to a factor 2.5 with increasing surface coverage for droplets either on the front or back sides. Experimental measurements were in excellent agreement with numerical predictions obtained using the Monte Carlo ray-tracing method. Then, the experimentally-validated simulation tool was used to predict the solar transmittance and emittance of glass windows covered with water droplets. The solar transmittance was found to decrease significantly with water droplets on either side depending on the time of day while the emittance remained unchanged.

Control of sugarcane planting patterns on slope erosion-induced nitrogen and phosphorus loss and their export coefficients from the watershed

Globally, replanted sugarcane (Rp) on hillslopes has accelerated soil erosion and associated nutrients entering the river, causing serious water pollution. Sugarcane planting patterns (SPPs), including the area ratios of Rp and intercropping (Ic) on the hillslopes, may mitigate these negative impacts by increasing surface coverage. But the effectiveness of SPPs on these impacts has not been quantified at both hillslopes and watershed scale. We measured extreme rainfall erosion-induced nutrients losses on the upslopes with different area ratios of Rp and the deposition ratio on the downslopes with different Ic levels by using beryllium-7 (7Be) technique. We estimated the export loads and coefficients of eroding sediment nutrients from the watersheds with different spatial configuration of Rp and Ic levels by combinative use of 7Be, compound-specific stable isotope (CSSI) and watershed monitoring. Nitrogen (N) and phosphorus (P) loss increased with area ratios of Rp, ranging from 6.9 to 21.2 kg ha−1 event−1 and 2.8–9.6 kg ha−1 event−1, respectively. Delivery ratios of eroding nutrients from the upslopes decreased with intercropping levels on the downslopes, ranging between 38.0% and 49.6%. Export loads and coefficient of eroding nutrients varied with the spatial configuration of Rp ratios and Ic levels in the watershed, ranging from 0.04 kg ha−1 to 1.76 kg ha−1 and 1.09–25.15%, respectively. The magnitudes of sediment nutrient losses on the upslope were positively correlated with area ratios of Rp (P < 0.05), whereas their delivery ratios on the downslope were negatively correlated with Ic levels, although they were not statistically significant (P > 0.05). The changes in ground litter cover (Glc) caused by Rp and Ic explained the variations of 53.6–55.3% in nutrient loss rate and of 74.1–74.4% in nutrient delivery ratio. Our results suggest that regulating SPPs could effectively mitigate erosion-induced nitrogen and phosphorus loss on the slopes and their export loads from the watershed.

Bifunctional ligand-mediated amplification of polydiacetylene response to biorecognition of diethylstilbestrol for on-site smartphone detection

Polydiacetylene (PDA) is very suited for sensitively detecting large biomolecules, and its unique chromatic properties enable visual read-out. However, application to the selective detection of small molecules remains challenging. Here, bifunctional ligands are studied to amplify the color change of PDA for biorecognition of small molecules for the smartphone-based detection of diethylstilbestrol (DES). PDA is decorated with streptavidin (PDA-SA, blue), and biotin-modified DES (bio-DES) is prepared as a bifunctional ligand to couple with PDA-SA and DES antibody. Since multiple bio-DES can bind to a single SA, then multiple SAs on PDA lead to an increased surface coverage of the vesicle. In samples without DES, PDA-SA-bio-DES-DES antibody complexes will form, leading to a color transition (blue to red); this color transition is greatly amplified by antibody-induced aggregation of the complexes. When DES is present, aggregation is inhibited due to competition for the antibody and PDA-SA-bio-DES retains its blue color. A linear relationship (0.4–1250 ng mL−1) is found between the colorimetric response and the logarithmic DES concentration, with adequate selectivity, accuracy (82.24–118.64%), and precision (below 8.24%). Finally, a paper-based DES PDA biosensor is developed with visual and smartphone-based detection limits of 10 ng mL−1 and 0.85 ng mL−1 in water, respectively.

In-Line Characterization of the Temperature-Responsive Behavior of Surface-Bound Microgel Coatings by QCM-D: A Novel Strategy for Protein Repellence Evaluation.

In this work, quartz crystal microbalance with dissipation monitoring (QCM-D) was used to develop a new method to evaluate the protein repellency of microgel coatings. Compared to traditional protocols for surface analysis, QCM has the advantage of a real-time quantitative approach with high sensitivity, allowing us to describe variations of the adsorbed mass with unprecedented accuracy. To enable the detectability of the film throughout the whole operational temperature interval, a poly(N-isopropylacrylamide-co-glycidyl methacrylate) p(NIPAm-co-GMA) microgel monolayer with defined thickness and rigidity was designed. Covalent adhesion of the film to the silica surface was achieved by epoxy-thiol click chemistry and tested for repeated temperature cycles, showing substantial reproducibility. Further functionalization of microgel surfaces by grafting polyzwitterionic chains remarkably improved the protein repellence leaving the strong surface adhesion unaltered. Before and after exposure to fluorescein-tagged bovine serum albumin (FITC-BSA), the coatings showed identical responsive behavior, proving the absence of protein deposition. In nonrepellent coatings, QCM monitoring instead displayed a characteristic shift in the volume phase transition (VPT), pointing out the effect of adsorbed proteins on the swelling behavior of pNIPAm. The combination of QCM-D and UV-visible (UV-vis) was used to evaluate the effect of increasing surface coverage, enabling to distinguish between the protein deposition occurring over the coated and the uncoated portion of the sensor.

A Compact Electron Transport Layer Using a Heated Tin‐Oxide Colloidal Solution for Efficient Perovskite Solar Cells

Tin dioxide is a frequently reported electron transporting material for perovskite solar cells (PSCs) that yields high‐performance devices and can be solution processed from aqueous colloidal solutions. While being very simple to process, electron transport layers deposited in this manner often lead to nonuniform film morphology, significantly affecting the morphology of the subsequent perovskite layer, lowering the overall device performance. Herein, it is shown that heating the SnO2 colloidal solution (70 °C) results in compact SnO2 films with increased surface coverage and fewer gaps in the SnO2 film. Such films possess threefold higher lateral electrical conductivity than those obtained from room‐temperature solutions. The narrow gaps in the SnO2 film also reduce the chances of direct contact between the indium tin oxide electrode and the perovskite layer, yielding better contact with less voltage loss. The improved SnO2 surface coverage induces larger perovskite grains (≈565 nm) than those prepared from the room‐temperature solution (≈273 nm). Finally, using these compact SnO2 layers, efficient and stable PSCs that retain ≈85% of the initial power conversion efficiency of 20.67% after 100 h of maximum power point tracking are demonstrated.

Structure-property relations of β-lactoglobulin/κ-carrageenan mixtures in aqueous foam

There is a great interest in mixed protein/polysaccharide layers at air-water interfaces due to their ability to stabilize aqueous foams. Properties of β-lactoglobulin (BLG)/κ-carrageenan mixtures at different κ-carrageenan concentrations were studied using foam analysis and molecular-level characterizations at the air-water interface. Because air-water interfaces are a major element in aqueous foams, they were investigated with a combination of interface-sensitive methods such as sum-frequency generation (SFG) as well as surface tensiometry. Using SFG spectroscopy we provide new information on the changes in the interfacial charging state and composition when the BLG/κ-carrageenan mixing ratio changes. κ-carrageenan is only weakly surface active as it does not lower the surface tension to a large extend. However, BLG/κ-carrageenan mixtures showed a synergistic effect because the formation of complexes at the air-water interface and in the bulk solution can favorably influence foam stability. BLG (7.5 µM) was mixed with different κ-carrageenan concentrations from 0 to 1 mM while the bulk pH was adjusted to pH values which are below (4.5), slightly above (5.6) and well above (7.0) the isoelectric point of BLG. At pH 4.5, the positive ζ-potential of BLG was drastically reduced to negative values and large aggregates in the bulk formed that showed a reduced surface activity and caused also a reduced net charging state at the air-water interface. The interfacial and bulk properties at pH 4.5, resulted in a poor stability of foams that were likely only stabilized by the weak electrostatic disjoining forces in the foam lamella. At pH 5.6 and 7, cooperative effects of BLG and κ-carrageenan dominate and, in particular, at pH 5.6 give rise to an increase in BLG surface coverage when the κ-carrageenan concentration increases. This resulted in a substantially improved foam stability.

Assessment of Diclofenac Adsorption into Activated Sludge: Mechanism and Thermodynamic

This study aimed at understanding and characterizing the sorption process of Diclofenac (DCF) onto activated sludge under conditions similar to those of a conventional Wastewater Treatment Plant (WWTP). Two experiments were performed: kinetics test, composed of six identical pairs of control/sample with the same DCF concentration stirred under constant rotation for different intervals; and an adsorption thermodynamics test with one pair of control samples and six duplicate samples with DCF concentrations from 5 - 100 mg L-1 stirred under constant rotation for the same period. DCF concentrations in the supernatant were measured in time spectrophotometrically at 282 nm. The adsorption of diclofenac onto the activated sludge reached its equilibrium after approximately 2 hours. The results showed that the process was best described by the Freundlich and Langmuir isotherm models, which suggest that the adsorption of DCF onto the activated sludge is a non-favorable second order reaction with a monolayer coverage. The Temkin isotherm model suggests that the heat of adsorption of the DCF molecules in the layer decreases linearly as a result of the increased surface coverage and follows a chemisorption mechanism. The amount of DCF adsorbed onto the sludge particles varied between 17 and 44%, with the adsorption ratio of DCF per gram of sludge being considerably low (&lt; 1 mg per g of sludge). This might be a result of the longer hydraulic retention times (HRT) adopted, considering that DCF may be toxic to the sludge microbiota, interfering with DCF removal from the supernatant. Thus, improving diclofenac removal by aerobic WWTP might require an adjustment of HRT to enhance sorption onto the sludge and reduce its impact on bacterial community.

Spatter oxidation during laser powder bed fusion of Alloy 718: Dependence on oxygen content in the process atmosphere

In laser powder bed fusion ( L -PBF), powder degradation is mainly driven by the accumulation of highly oxidized spatter particles in the powder bed. Although the amount of spattering can be controlled by the melt pool stability, spatter formation is an unavoidable characteristic of PBF processes. Oxidized spatter risks defect formation in the printed components. However, the factors influencing the level of spatter oxidation during L -PBF processing are not yet fully understood. Herein, the residual oxygen in the process atmosphere was reduced from the traditionally applied 1000–20 ppm using an oxygen partial pressure control system to process Alloy 718 powder. Spatter particles accumulated on the gas inlet were further analyzed to reveal the effect of the oxygen content in the process atmosphere on the spatter oxidation by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Increasing the residual oxygen in the process atmosphere increased surface coverage by oxide phases rich in Al and Cr. The XPS analysis confirmed that the surface of Alloy 718 spatter particles were covered with Al- and Cr-based oxides, whose thickness increased with the oxygen content in the process atmosphere. The bulk oxygen content in the spatter powder showed the same trend with approximately thrice the oxygen content in spatters generated at 1000 ppm O 2 (608 ppm O in the sample) compared to spatters generated with oxygen at 20 ppm (206 ppm O in the sample). Thermodynamic simulations demonstrate a transition from thick Al- and Cr-based mixed corundum and spinel-type oxides to Al-based corundum oxide with decreasing oxygen partial pressure, consistent with the XPS findings. • The spatter oxidation decreased with the residual oxygen content in the L -PBF atmosphere. • Significant changes in the surface oxide chemistry of spatter particles occurred as the residual oxygen varied. • The thickness of oxide phases decreased with the residual oxygen content. • The surface oxide was significantly enriched with Al and Cr as the oxygen level in the L -PBF atmosphere increased. • Thermodynamic calculations confirm preferential Al oxidation at lower oxygen levels compared to Cr.

Use of High-Rate Ventilation Results in Enhanced Recellularization of Bioengineered Lung Scaffolds.

While transplantation is a viable treatment option for end-stage lung diseases, this option is highly constrained by the availability of organs and postoperative complications. A potential solution is the use of bioengineered lungs generated from repopulated acellular scaffolds. Effective recellularization, however, remains a challenge. In this proof-of-concept study, mice lung scaffolds were decellurized and recellurized using human bronchial epithelial cells (BEAS2B). We present a novel liquid ventilation protocol enabling control over tidal volume and high rates of ventilation. The use of a physiological tidal volume (300 μL) for mice and a higher ventilation rate (40 breaths per minute vs. 1 breath per minute) resulted in higher cell numbers and enhanced cell surface coverage in mouse lung scaffolds as determined via histological evaluation, genomic polymerase chain reaction (PCR) analysis, and immunohistochemistry. A biomimetic lung bioreactor system was designed to include the new ventilation protocol and allow for simultaneous vascular perfusion. We compared the lungs cultured in our dual system to lungs cultured with a bioreactor allowing vascular perfusion only and showed that our system significantly enhances cell numbers and surface coverage. In summary, our results demonstrate the importance of the physical environment and forces for lung recellularization. Impact statement New bioreactor systems are required to further enhance the regeneration process of bioengineered lungs. This proof-of-concept study describes a novel ventilation protocol that allows for control over ventilation parameters such as rate and tidal volume. Our data show that a higher rate of ventilation is correlated with higher cell numbers and increased surface coverage. We designed a new biomimetic bioreactor system that allows for ventilation and simultaneous perfusion. Compared to a traditional perfusion only system, recellularization was enhanced in lungs recellularized with our new biomimetic bioreactor.

Correlation between the adsorption behavior of colloidal polymer particles and the yield stress of fresh cement pastes

Correlation between adsorption behavior of colloidal polymers on cement grains and yield stress of fresh cement pastes (fcps) is studied using four polymer latexes with varied surface charge density and glass transition temperature (Tg). Adsorption isotherm of the polymers is divided into two stages: before and after adsorption plateau. Higher charge density and lower Tg are beneficial to adsorption of polymer on cement grains. Before adsorption plateau, the adsorbed polymer particles play a bridging effect among cement grains which firstly increases and then decreases with increasing surface coverage ratio. Maximum bridging effect occurs at surface coverage ratio of ca. 20%. After adsorption plateau, yield stress of the fcps is significantly lower than that of the blank fcp because the adsorbed polymer layer reduces interaction force between cement grains, by increasing the minimum distance between two cement grains and generating repulsive force due to negative charges of the polymer particles.