Large Foam Research Articles

Integration of surface swab with optical microscopy for detection and quantification of bacterial cells from stainless-steel surfaces.

Swab sampling is a common method for recovering microbes on various environmental surfaces. Its successful application for a specific target depends on the proper swab method and the following detection assay. Herein, we evaluated critical factors influencing surface swab sampling, aiming to achieve the optimal detection and quantification performance of optical detection for bacterial cells on stainless-steel surfaces. Our results showed the recovery rate of Salmonella enterica (SE1045) cells from the 10×10cm2 stainless-steel surface reached up to 92.71±2.19% when using ammonia bicarbonate-moistened polyurethane foam swabs for gentle collection, followed by ultrasound-assisted release in NH4HCO3 solution. Among the six different foam swabs, the Puritan™ Sterile Large Foam Swab contributed the lowest background noise and highest recovery efficiency when integrated with the optical detection assay. Notably, our method exhibited a strong linear relationship (r2=0.9983) between the detected cell numbers and the theoretical number of SE1045 cells seeded on surfaces in the range of 104-107 Colony Forming Units (CFU), with a limit of detection of 7.2×104 CFU 100cm-2. This integration was completed within 2 h, exhibiting the applicable potential in various settings.

Coating powder beds with liquids and foams based on viscous formulations using a twin screw mixer: A continuous process study

Coating with viscous formulations has been essential in numerous industries as it can be a means for providing functionalization, additional properties, as well as other benefits. However, there have been scarce studies that have investigated and proposed methodologies in literature. Continuous coating of powders with viscous liquids poses as a promising technology, which has been mentioned in some studies, but has not yet been thoroughly investigated. This paper employs the use of image processing and analysis, in combination with statistical analysis of particles to evaluate the effectiveness of foams and liquids as a means of coating powder beds. Two different sizes of twin screw mixers that are working in continuous operation are employed, and a new continuous foaming device is fabricated and used for the experiments of coating. The effect of materials and process parameters (as for example rotational speed, and flowrate) on the quality of coating are investigated. Image analysis is used to assess the coating quality. The results clearly showcase the potential of using twin screw mixers for coating purposes and not only for mixing. The hypothesis that using large bubble foams to improve the coating of viscous liquids on particles is proven correct, as they provide higher quality coatings compared to their equivalent liquids, when used in the twin screw mixer. Surprisingly, using a larger scale twin screw mixer, does not show a substantial effect on the mixing, regarding quality, however there is still a requirement for mix optimization for achieving scale-up of this process. These results provide a new pathway for coating powders with viscous formulations in industrial applications, requiring less energy and effort in this process, and can pave the way towards introducing more sustainable industrial methodologies for coating.

Adult niemann-pick disease: A case report

Adult niemann-pick disease: A case report

Highly sensitive analysis of trace germanium derived from the efficient electrosynthesis and spectral introduction of GeH4 on foam electrode

BackgroundThe electrochemical hydride generation technology, which uses electrolysis instead of chemical reagents to generate reducing species to achieve gaseous transformation and sample introduction of the tested elements, has received widespread attention in the field of atomic spectroscopy due to its simple, economical, and green characteristics. However, limited by the effective area of the electrode, the introduction efficiency and spectral signal of most elements (e.g., germanium) in practical applications are lower than traditional chemical hydride generation. ResultsIn this paper, an efficient electrochemical hydride generation (EHG) method based on metal foam electrode for μg L−1 level germanium was constructed. Systematic electrochemical and spectral tests showed that the low charge transfer resistance and the high electrochemical activity of nickel-based foam electrodes jointly promoted the efficient electroreduction of Ge(IV). Besides, the porous network structure of the metal foam material improves the contact probability of reactants while reducing the gas-evolution effect caused by bubble accumulation. Interestingly, adequate reaction sites are crucial for the conversion of germanium, but large foam electrodes are not always compatible with analytical performance. After coupling atomic fluorescence spectroscopy, this new electrolysis method has been proven to be suitable for efficient conversion and quantitative detection of Ge over a wide concentration range (5–150 μg L−1). SignificanceOur proposal to improve the electrosynthesis efficiency of germanane (GeH4) by using metal foam electrode is extremely effective for the detection of trace or ultra-trace germanium. The exploration of electrode material, structure, and especially effective area will also provide ideas for the establishment of highly sensitive analysis methods in the future.

Foam Systems for Enhancing Heavy Oil Recovery by Double Improving Mobility Ratio

The recovery of heavy oil is challenging due to its high viscosity. Especially in water flooding, the high viscosity of heavy oil induces a high water/oil mobility ratio, resulting in frequent channeling and fingering. In the present work, the viscosity reduction in heavy oil caused by foaming agents is studied. Among the studied foam systems, the KX-048 foaming agent had the best oil viscosity reduction performance. It also shows excellent foaming performance, including large foam volume, long foam half-life, and high foam comprehensive index. With the reduction in oil viscosity, the KX-048 foaming agent decreases the foam/oil mobility to 0.28, which is beneficial for controlling gas channeling and fingering in foam flooding. Moreover, Foam flooding experiments in heterogeneous sand-pack models indicate that KX-048 has excellent efficiency in improving oil recovery, especially in the low-permeable tube. The chosen KX-048 foaming agent could provide a promising pathway for improving heavy oil recovery.

Molecular design of multiple ligand metal–organic framework (ML-MOF) collectors for efficient flotation separation of minerals

Metal–organic framework (MOF) collectors formed by the coordination of lead ions and benzohydroxamic acid (Pb–BHA) are favorably selective for the flotation separation of calcium-containing minerals. However, the large dosage requirement and foam instability have hindered the industrial applications of MOF collectors. To enhance the collecting ability and hydrophobicity of the Pb–BHA structure, this paper introduces new ligands to form multiple ligand–MOF (ML–MOF) collectors. Through a molecular-design approach, the study analyzes the crystal and electronic structures of the target and gangue minerals, calculates the quantum chemical properties of the organic ligands, constructs the ML–MOF collectors, and determines the interaction strengths between the ML–MOF collectors and mineral surfaces to predict the flotation performances. Finally, the flotation performance of the newly developed collector is confirmed through a series of micro-flotation tests. Among the ML–MOF collectors constructed with four candidate ligands—octylhydroxamic acid (OHA), sodium dodecyl sulfate (SDS), oleic acid, and styrene phosphonic acid—Pb–BHA–SDS and Pb–BHA–OHA excellently and selectively absorbed scheelite, wolframite, and cassiterite in flotation. In addition, they form stable froths and can be applied at low dosage. The correctness of the design results was quantified in terms of their collecting-ability index and selectivity index obtained in a flotation test. The proposed design methodology realizes ML–MOF collectors for the flotation separation of complex multi-mineral systems.

Foaming Behavior of Microsized Aluminum Foam Using Hot Rolling Precursor

Aluminum foam that is lightweight with high specific strength, high energy absorption and other characteristics can be used in aerospace, transportation, machinery manufacturing and other fields. The PCM method is usually used to prepare closed-cell aluminum foams. The microsized aluminum foams made by this process can solve the non-uniform pore structures caused by liquid drainage during the foaming process of large aluminum foams. The surface morphology and internal pore structure of microsized aluminum foams are affected by the quality of the precursor used for foaming. In this paper, foamable precursors were obtained via either hot rolling or hot extrusion and subsequently foamed. By analyzing the micromorphology and foaming process of the precursor, the influence of the technological method on the macroscopic pore structure of the final aluminum foam was studied. The results show that the aluminum powder particles in the precursor prepared with the hot rolling method had metallurgical bonding, and the outer surface was dense, with almost no porosity and holes in the interior. The microsized aluminum foam obtained after foaming was smooth in appearance, and the internal pore structure was round and uniform. The reason is that during the foaming process of microsize aluminum foam, the foaming agent was evenly distributed in the precursor of the hot rolling process because of its compact structure. During the foaming process, the decomposed gas of the foaming agent will not escape, and the evenly distributed foaming agent tends to nucleate in situ. In the process of rapid foaming, the pressure in the bubble is enough to resist the liquid drainage phenomenon caused by gravity, and the growth direction of the gas core is isotropic, which promotes the foam structure to be more rounded and uniform.

Numerical Study of the Effects of Surface Tension and Initial Volume Fraction on Gas-Liquid-Foam Three-Phase Flow Separation Process

Since it is low in cost and low in toxicity and has good biodegradability, gas-liquid-foam three-phase flow has been widely used in industrial fire protection. Due to the different characteristics of gas, liquid, and foam, liquid precipitation is liable to occur under static conditions, resulting in unstable performance of the mixture. To improve fire extinguishing efficiency, it is of great significance to study the separation process of gas-liquid-foam. In the present study, the effects of the surface tension (range from 0.04 to 0.07) and initial liquid volume fraction (range from 0.2 to 0.5) on the gas-liquid-foam separation process are investigated with the numerical tool Fluent. The liquid volume fraction is mainly influenced by two inverse effects: (a) the transformation of liquid into foam, and (b) the liquid drainage and bursting of foam. In the separation process, the volume fraction of small foam decreases monotonically while the volume fraction of medium and large foam increases slightly. Since the volume fraction of small foam is much greater than medium and large foam and its bursting process is dominant, the liquid volume fraction presents a monotonic increasing trend. The volume of the separated liquid increases almost linearly with time at various surface tensions and initial volume fractions, and the increase rate is about 0.004. In the range of the surface tension examined, the separation process is insensitive to the surface tension, resulting in almost the same drainage time. On the other hand, the separation process depends on the initial liquid volume fraction non-monotonically; namely, when the initial volume fraction is small, with the increase of the initial volume fraction, the liquid is more easily separated from the mixture, and when the initial volume fraction is over a critical value (about 0.4), the separation process is decelerated.

Experimental measurements of thermal–hydraulic performance of aluminum-foam water-to-air heat exchangers for a HVAC application

In this paper, thermal and hydraulic performance of in-house made prototypes of water-to-air heat exchangers are experimentally investigated and compared to those of a compact heat exchanger, used in a commercial fan-coil. The prototypes are built replacing the fins with aluminum foam surfaces characterized by a large porosity, higher than 96%. In order to evaluate the performance of the foam-based heat exchangers in a real-scale application, the geometry of the prototypes was based on that of the reference model and, moreover, experimental tests were performed placing the heat exchangers within the commercial cabinet, under the same fan power. Different bonding techniques were also tested to couple metal foams to copper tubes. Results show that similar hydraulic performance can be obtained with the foam-based heat exchangers, if compared to the commercial device. However, the large foam porosity accounts for a lower value of the surface-to-volume ratio of the aluminum foam media, thus yielding a strong penalty, up to 60%, of the heat transfer rate with respect to that of the conventional finned surface. Moreover, experimental results highlight how the bonding technique and the foam packaging have a strong influence on the contact thermal resistance and, consequently, on the overall heat transfer coefficient. Epoxy bonding allows to increase the thermal performance of the heat exchanger, if compared to press fitting, between 15% and 110%. In conclusion, results presented in this paper suggest that metal foams can be considered as a potential alternative to fins in water-to-air heat exchangers only if the foam-tube bonding is obtained by welding or brazing.

Experimental investigations of a novel pressure microfoam preparation device for dust removal

Abstract Compared with large size foam, pressure microfoam has the characteristics of a good pipeline transportation stability, good jet orientation, strong impact force, and strong ability to capture fine dust, which is more suitable for dust removal. The traditional foam preparation device has the disadvantages of high-pressure loss, poor foaming effect, and foam uniformity. To overcome the above shortcomings, the annular air supply vertical foam preparation device was proposed in the article. The foaming cylinder of the device adopts a vertical design to avoid the influence of uneven distribution of foam caused by gravity; the spiral nozzle is used to evenly spray the foaming liquid on the foaming mesh to increase the contact area between foam and airflow. The stainless steel wire mesh and cotton wire mesh are adopted to improve the reliability and durability of concave foaming mesh. The performance of the new device was obtained by the self-built experimental system. Finally, the field test shows that the conditions of the heading face could fully meet the requirements of the device for pressure water and compressed air, and the produced pressure microfoam can effectively control dust.

Structured large-pore foams improve thermal performance of LiMIT-style liquid lithium PFC

As magnetically confined fusion devices improve, the conditions at the walls become increasingly intense. Plasma facing components (PFCs) must withstand these extreme heat and particle loads without damage or degradation. Liquid lithium PFCs are known to be quite resilient, and the presence of lithium also serves to improve plasma properties. The liquid metal infused trench (LiMIT) concept is an open surface liquid lithium PFC design that has been tested extensively at the University of Illinois and in fusion devices around the world. LiMIT utilizes thermoelectric magnetohydrodynamics (TEMHD) to passively drive liquid lithium flow. This work demonstrates an extension of the LiMIT trench geometry to three dimensions. Additively manufactured large pore metallic foams maintain TEMHD drive while drastically improving heat flux handling and resistance to lithium dryout, a phenomenon where locally high TEMHD forces depresses the lithium level and exposes underlying solid structure. COMSOL multiphysics modeling of the system yields insight into the forces at play in dryout development, and shows the 3D structures can eliminate dryout. Low heat proof-of-concept experimental testing of the system matches computational results, and high heat flux electron beam tests more than double the proven operational range of a LiMIT-style PFC, to 6.8 MW m−2, with no indications of dryout or impending damage.

Foaming of Binary Mixtures: Link with the Nonlinear Behavior of Surface Tension in Asymmetric Mixtures.

The lifetimes of single bubbles or foams that are formed in mixtures of liquids can be several orders of magnitude larger than the ones formed in pure liquids. We recently demonstrated that this enhanced stability results from differences between bulk and interfacial concentrations in the mixture, which induce a thickness dependence of the surface tension in liquid films, and thus a stabilizing Marangoni effect. Concentration differences may be associated with nonlinear variations of surface tension with composition and we further investigate their link with foamability of binary mixtures. We show that, for asymmetric binary mixtures, that is, made of molecules of very different sizes, strong nonlinearities in surface tension can be measured, that are associated with large foam lifetimes. When the molecules that occupy the largest surface areas have the smallest surface tension, the surface tension of the mixture varies sublinearly with composition, reflecting an enrichment in this species at the interface with air, as classically reported in the literature. In contrast, when they exhibit the largest surface tension, superlinear variations of surface tension are observed, despite a similar enrichment. We discuss these variations in light of a simple thermodynamic model for ideal mixtures and we demonstrate why foam stability is enhanced for both sublinear and superlinear surface tension variations, thus, shedding new light on foamability without added surfactants.

The microplastic pollution in beaches that served as historical nesting grounds for green turtles on Hainan Island, China

This study evaluated microplastic pollution in beaches that have served as historical nesting grounds for green turtles in Hainan Island, China and explored the sources of microplastic pollutants to conduct habitat restoration for sea turtles. The average abundance of the microplastics in the beach surface sediments was 2567.38 ± 2937.37 pieces·m−2 or 641.85 ± 734.34 thousand pieces·m−3, foam and plastic block were the main microplastics identified. Microplastic size was predominantly within the 0.05–1 mm category (small microplastic particles), and most microplastic particles were white. Polystyrene and polyethylene were the dominant plastic compositions. The type and compositions of microplastics indicate that most microplastics in this study were broken from large plastic blocks and foam. To reduce the threat of microplastic pollution to marine life, including sea turtles, we suggested removing plastic litter, especially small plastic on beaches, and replacing and recovering the foam used in aquaculture before it ages and fragments.

The Symmpact: A Direct-Impact Hopkinson Bar Setup Suitable for Investigating Dynamic Equilibrium in Low-Impedance Materials

BackgroundMeasuring the dynamic behavior of low-impedance materials such as foams is challenging. Their low acoustic impedance means that sensitive force measurement is required. The porous structure of foams also gives rise to dynamic compaction waves, which can result in unusual behavior, in particular if the foam material is so thick, that dynamic force equilibrium is not reached.ObjectiveThis work investigates comparatively large polyurethane foam specimens with densities in the range of 80 – 240 kg/m3 to deliberately achieve a state away from force equilibrium during high-rate compaction. The aim is to understand how an increase in strain rate leads to a reduction in strength for such materials.MethodsA specialized direct-impact Hopkinson bar is employed. It uses polycarbonate bars to achieve the required long pulse duration of 2.6 ms to compress the large specimens into the densification regime. In contrast to existing setups, both striker and output bar are instrumented with strain gauges to monitor force equilibrium. The absence of an input bar allows monitoring force equilibrium more accurately. Special attention is paid to the calibration of strain gauges, taking non-linear effects, wave dispersion and attenuation into account. Digital Image Correlation is employed to analyze elastic and plastic compaction waves by means of Lagrange diagrams.ResultsDepending on density, the specimens show saturation of dynamic strength increase at high rates of strain approx 500 /s, or even negative strain rate sensitivity in case of the lowest density. The occurrence of apparent negative strain rate sensitivity is accompanied by a localized structural collapse front, moving at a low velocity of approx 10 m/s through the material. This apparent strain rate sensitivity is a structural effect which is related to the thickness of the specimen.ConclusionsThe primary aim of material characterization using Hopkinson bars is to achieve a state of force equilibrium. For this reason, very thin specimens are usually employed. However, data gathered in this way is not representative for thick foam layers. Here, an increase of strain rate can lead to a decrease of strength if homogeneous deformation is replaced by a dynamic compaction wave. This behavior can occur at strain rates encountered under conditions such as automotive crash.

Nanoarchitectonics of highly sensitive and with large working range 3D piezoresistive microporous foam based on carbon nanotubes and elastomer

HypothesisNanocarbon/polymeric 3D porous composites have been widely developed as piezoresistive sensors due to their improved performances. Functionalized nanocarbon is usually used to allow its adsorption on the surface of porous polymeric material. However, both the functionalization and the surface localized distribution of the nanomaterial can limit the nanocarbon effect on conductivity and mechanical stability of the material thus affecting piezoresistive performances. ExperimentsA novel nanoarchitectonics strategy to prepare an elastomeric/carbon nanotubes (CNTs) 3D porous piezoresistive nanocomposite is developed. The fabrication route does not require complex apparatus and CNTs chemical functionalization. Moreover, foams of any shape and dimensions can be produced with neither complex machinery and procedures nor wastes production. FindingsThe obtained material is characterized by the presence of well dispersed pristine CNTs on both surface and bulk of the polymeric matrix. The foam exhibited improved piezoresistive properties with excellent compressive stress (>150 kPa), sensitivity at low displacement (29 kPa−1) and limit of detection for both pressure (2 Pa) and extension (130 nm). These excellent features could allow the use of the as prepared nanocomposite in different applications ranging from wearable devices to robotic or infrastructure monitoring with outstanding flexibility.

Enhanced forensic DNA recovery with appropriate swabs and optimized swabbing technique

Efficient sampling with swabs is crucial for optimal forensic DNA analysis. The DNA recovery is determined by the skill of the practitioner and the compatibility between the applied swab and the surface. Here we investigate the impact of swabbing technique and swab type on the DNA yield. Thirteen different swabs from four categories (cotton, flocked nylon, small foam and large foam) provided equal DNA yields for smooth/non-absorbing surfaces. Large foam swabs gave higher DNA recovery for an absorbing wood surface. Factorial design of experiments and ANOVA was applied to study swabbing techniques for cotton swabs. Two key factors for efficient sampling were found to be 1) holding the swab with an approximate 60° angle against the surface and 2) to rotate the swab during sampling. For absorbing wood, it was beneficial to wet the swab heavily. The results of the factorial experiments were used to develop swabbing protocols for different surfaces. When ten experienced practitioners sampled according to these protocols, the DNA yield was increased for ridged plastic (around 1.25 times more DNA) and absorbing wood (2.2–6.2 times more DNA). For window glass, representing a smooth/non-absorbing surface, sampling according to the protocol gave DNA yields equivalent to applying individual sampling techniques. The protocol lowered person-to-person variation for ridged plastic. In conclusion, we have developed instructive protocols for cotton swab sampling on three types of surfaces: smooth/non-absorbing, ridged/non-absorbing and smooth/absorbing. We believe that such swabbing protocols will streamline and simplify the training of new practitioners and improve sampling efficiency for invisible DNA residues in casework.

Lightweight concrete based on crushed foam glass aggregate

Increased requirements for energy saving in the operation of buildings and structures, as well as the need to adjust the raw material base, presupposes the development and improvement of lightweight concrete technologies, including the use of effective lightweight aggregates, which include granulated foam glass. The goal of the study was to develop a method for selecting the composition of lightweight concrete with foam glass gravel as a large aggregate and foam glass powder as a fine aggregate. To achieve this goal, an experiment was carried out to optimize the composition of lightweight concrete and determine the optimal proportions of the used fractions of foam glass gravel. The raw mix for producing lightweight concrete included the following components: Portland cement, foam glass gravel (mixture of fractions), glass powder (crushed foam glass gravel of 0.315 mm in size), soda glass, super plasticizing admixture, air-entraining agent and water. As a result of the implementation of the experiment and the use of the apparatus for mathematical planning, processing and optimization of the data obtained, the optimal costs of main components were established, as well as the proportions of the content of coarse aggregate fractions.

A Novel Approach to Negative Pressure Wound Therapy: Use of High Suction Capillary Device to Improve Wound Healing.

Negative Pressure Wound Therapy (NPWT) is a procedure used for nonhealing wounds. In NPWT, a special sealed dressing of large cell foam (>400 µm) or gauze is connected to a pump. Most commonly, negative pressures between -10 and -125 millimeters of mercury (mm Hg) are used. The mechanism of healing is unknown but maybe attributable to removal of the exudate and bacteria, and the stimulation of tissue repair through microdeformation. Reticulated foams with micron-size open cells, Capillary Suction Devices (CSD; 100 to 5 µm) exert capillary suction between 10 and 70 mm of Hg with a multilayered foam dressing. Yorkshire pigs received 5 surgical excision wounds, 3 cm2, on each side of the back. The wounds were covered with a NPWT dressing (110 mm Hg negative pressure by a pump), CSD with capillary suctions of 30 mm Hg (CSD-30) and 70 mm Hg (CSD-70), and a conventional gauze dressing. The wounds were measured on day 2, and then every 4-5 days thereafter; the total fluid collected by the various dressing over time. By post-wound day 20, the wounds treated with CSD-70 and NPWT were 100% closed while the wounds treated with CSD-30 and gauze were 65% and 45%, respectively. This indicated comparable wound closure efficacies for CSD-70 and NPWT. The average total fluid uptake measured in grams dry weight were similar for CSD-70 and NPWT, 36 and 38 g, respectively, while the values were 24 g for CSD-30 and 12 g for gauze. However, the maximum fluid uptake observed at day 2 indicated that CSD-70 and CSD 30, 24 and 14 g, respectively, were superior to NPWT and gauze 12 and 7 g, respectively. This data indicate comparable wound closure efficacies for CSD-70 and NPWT. It is felt that CSD is an effective, safe, and lower cost alternative to vacuum-assisted NPWT.

Processing and characterization of Al-Si alloy/SiC foam interpenetrating phase composite

Interpenetrating phase composites (IPCs) are a class of composites consisting of two or more topologically co-continuous phases and have three-dimensionally percolating interconnected structure. The co-continuous and interconnected architecture of the IPCs can provide superior properties compared to the conventional particulate reinforced composites at room and elevated temperatures. IPCs having metal/ceramic phases are finding applications in various fields like (thermal management materials, aerospace, automobile industries, light-weight armor materials, etc.). In the present work, Al-Si alloy/SiC foam IPC was fabricated by infiltrating the alloy melt into SiC foam via the squeeze-casting process. Open porous SiC foams, fabricated via the replication method, and having two different pore sizes (10 and 20 PPI) were used for IPC fabrication. The SiC foams had both macropores between the SiC foam struts and micropores within the strut walls. Results show that the Brinell hardness of the composite fabricated using a small pore size (20 PPI) SiC foam is higher than the composite fabricated with a large pore size SiC foam (10 PPI). Thorough structural characterization via scanning electron microscope and localized study of hardness distribution in different regions of the composite using nanoindentation were carried out.

Synthesis of Carbon Foam Using Xanthan-Gum Additive and Characterization for its Heat Absorbing and Retarding Properties

In this work a facile synthesis method is adopted to demonstrate the large mesoporous carbon foam. The green foam was made from fine flour, yeast and xanthan gum were used as a base, leaving agent and binding agent respectively. After the blowing process the foam is placed in a tube furnace for pyrolysis. Finally, the foam heat absorption properties as well as heat retarding properties were established in contrast to traditional aluminum-based heat sink as well as K23 (aluminosilicate refractory) brick.