Purification of tetrahydrofuran from its aqueous azeotrope by extractive distillation: Validation of model and simulation

Tetrahydrofuran (THF) purification by distillation is difficult due to the existence of its homogeneous, minimum boiling azeotrope with water. Previously conducted extractive distillation runs were used in this work to validate a rigorous model.

The validated model was then used to arrive at a feasible range of operating parameters by performing sensitivity analysis. It is shown through simulations that with the correct operating parameters, use of dimethyl sulfoxide can help obtain almost pure THF.     

Studies on detachment behavior of micron sized droplets: A comparison between pure fluid and nanofluid

Resuspension is considered as a source of indoor air pollutants. These airborne pollutants can be in the form of liquid or solid. It has been previously found that the detachment mechanism of liquid droplets is different from the solid particles on the poly(methyl methacrylate) (PMMA) surface. Liquid droplets detach by portion when they are under an increasing normal force field while droplets detach completely when under a tangential force field. In this research, droplet detachment experiments are extended to different substrate materials, which are PMMA, glass, and stainless steel by the means of centrifuge. Also, the differences in detachment between pure glycerol-water (pure fluid) and a glycerol solution with the addition of nanoparticles (nanofluid) are investigated under different substrate materials. It is found that liquid droplets, again, detach by portion under normal force for all the substrate materials. For tangential force, the droplets detach completely if the exerted force was sufficiently large and the threshold values are material dependent, which is further elaborated by retention theory. After the addition of nanoparticles, a higher removal force was required compared to the droplets of pure fluid within the same size range. Also, solid residues with a negligible amount of fluid were found on the substrate after each removal of droplets under both normal and tangential force. The involvement of nanoparticles could be the pioneer work for future studies on commonly found liquid pollutants, which are prone to be contaminated by solid particles, such as in salivary excretion.

Copyright © 2018 American Association for Aerosol Research     

Shear bond strength of PEEK and PEEK-30GF cemented to zirconia or titanium substrates

Objectives: The aim of this study was to evaluate the use of dual-cure resin cement to promote the bonding between a veneering PEEK and zirconia or titanium surfaces.

Materials and methods: The surface of titanium and sintered zirconia disks were gritblasted, ultra-sonically cleaned in distilled water, and dryed by oil-free air. Then, a adhesive system was applied on the clean and dry surfaces. Disks of PEEK or 30% glass-reinforced PEEK were cut from a rod and their surface were acid etched and therefore the PEEK roughness was analysed using a contact profilometer. A resin cement was then applied between the substrates and the veneering PEEK and light cured for 4 Shear bond strength tests were performed on PEEK-cement to zirconia or titanium interfaces. Scanning electron microscopy (SEM) analyses were performed to evaluate the samples surface, interface and failure mode.

Results: Surface treatment with acid etching decreased the average roughness of PEEK-based surfaces. oMicroscopic analyses by SEM revealed morphological aspects of a poor bonding between the resin-based cement and PEEK. Those aspects could be confirmed by the low mean values in shear bond strength. The fracture analysis showed that the main failure mode was adhesive, which explain the low values of shear bond strength.

Conclusion: PEEK is a promising material for dental applications. However, significant improvements on surface modifications and in chemical composition of the cement are still required for dental applications involving cementation of PEEK or PEEK-30GF to zirconia or titanium concerning a desirable long-term clinical performance of prosthetic structures.     

Collection of soot particles into aqueous suspension using a particle-into-liquid sampler

Steam collection devices collecting aerosol particles into liquid samples are frequently used to analyze water-soluble particulate material. The fate of water-insoluble components is often neglected. In this work, we show that fresh soot particles can be suspended into pure water using a steam collection device, the particle-into-liquid sampler (PILS, Weber et?al. 2001). The overall collection efficiency of freshly generated soot particles was found to be on the order of 20%. This shows that, depending on the analytic technique employed, the presence of insoluble, and/or hydrophobic particles in liquid samples from steam collection cannot be neglected.

Copyright © 2018 The Author(s). Published with license by Taylor & Francis Group, LLC     

Do ozone and boric acid affect microleakage in class V composite restorations?

The aim of this in vitro study was to evaluate the effects of chlorhexidine gluconate (2%), sodium hypochloride (2.5%), ozone gas, and boric acid at different concentrations (1%, 3%, 5%, and 7%) on microleakage from composite restorations.

In a total of 80 extracted human canine teeth, a class V cavity was opened on the buccal surface and the samples were separated into eight groups. In the control group, no procedure was applied for cavity disinfection, then composite restoration (Z250, 3M) was made using single-stage, self-etch adhesive (Single Bond 3M). In the other groups, seven different disinfectants were used, then the cavity was restored. The teeth were split into two in the buccolingual direction, parallel to the long axes. Stain penetration was examined under stereomicroscope and scored. Examination with SEM was made on one sample from each group, selected at random. Statistical evaluations were made using Dunnett C Post Hoc Comparison and Kruskal–Wallis H tests.

In the occlusal region evaluation, the groups with the lowest level of leakage were the 3% and 5% boric acid groups, and the highest levels of microleakage were determined in the chlorhexidine group and the 1% boric acid group. In the gingival region, the lowest level of microleakage was in the 5% boric acid group and the highest levels were determined in the 1% and 7% boric acid groups.

Boric acid disinfectants used at suitable concentrations were not seen to create a risk in respect of microleakage.     

Experimental and numerical characterization of shape memory polymer and metal laminates

The interface strength of a Shape Memory Polymer – Stainless Steel (SMP-SS) laminate system has been studied under a wide range of test conditions. The adhesive strength of the laminates has been explored using the peel test at room temperature as well as the glass transition temperature of the SMP. The analysis was also repeated at varying speeds and SMP thickness in order to quantify the effect of strain rate and adherend thickness on the bond strength of the laminate.

The experimental tests have been validated using finite element analysis of the SMP – SS laminate system. The finite element study further explores the role of polymer stresses and strains in the polymer film and adhesive layer in inducing delamination and wrinkling.

Significant decrease in strains in the adherend are observed on increasing its thickness. The adhesive strength of the laminate system is found to decrease at higher temperatures. Also the adherend is observed to wrinkle at longitudiunal strains nearing 35%.     

Numerical,wind-tunnel,and atmospheric evaluation of a turbulent ground-based inlet sampling system

The use of inlets for transferring aerosols from the environment to instrumentation can introduce uncertainty in the measurement of aerosol properties. Aerosol loss during this process is a non-negligible issue that may bias the subsequent measurements. These loss mechanisms include aspiration at the inlet head and deposition/evaporation/condensation during transport through the sampling lines. Coarse-mode aerosol is significantly impacted by the aspiration and inertial loss mechanisms within an inlet system. This work uses wind tunnel experiments to investigate aerosol losses through the Storm Peak Laboratory’s (SPL) new aerosol inlet system. The inlet is used extensively for both intensive field campaigns and long-term aerosol monitoring. The results of numerical simulations of the SPL aerosol inlet sampling efficiency are provided at several wind speeds, and experimental results demonstrate the system has a 50% cut off for the coarse-mode at an aerodynamic diameter of approximately 13?μm and wind speed of 0.5?m s^?1. This investigation will lead to improved accuracy of in situ aerosol measurements at SPL and this system can be replicated at other atmospheric stations.

Copyright © 2019 American Association for Aerosol Research     

Repeatability and intermediate precision of a mass concentration calibration system

Many aerosol instruments require calibration to make accurate measurements. A centrifugal particle mass analyzer (CPMA) and aerosol electrometer can be used to calibrate aerosol instruments that measure mass concentration. To understand the sources of uncertainty in the calibration method, two CPMA-electrometer systems were tested to measure the repeatability and intermediate precision of the system, where the repeatability is the standard deviation of several measurements using the same system over a short period of time, and the intermediate precision is the standard deviation of several measurements using different instruments with different calibrations over a long period of time. It was found that the repeatability of the CPMA and the aerosol electrometer were both 0.8%, while the intermediate precision was 1.3% and 2.2%, respectively. The intermediate precision of the aerosol electrometers determined here compares well with a broader study by national metrology institutes which determined an intermediate precision of ～1.7%. By propagation of uncertainty, it is expected that a CPMA-electrometer system would have repeatability of 1.1% and an intermediate precision of ～2.1%. This compares favorably to thermal-optical analysis methods which aim to measure black carbon mass concentrations for instrument calibration, which have a repeatability in the range of 8.5–20% and reproducibility in the range of 20–26% for elemental carbon. Thus, the CPMA-electrometer method may be a good alternative to existing instrument calibration procedures.

Copyright © 2019 American Association for Aerosol Research     

Biochemical and Computational Studies of the Interaction between a Glucosamine Derivative,NAPA, and the IKKα Kinase

The glucosamine derivative 2-(N-Acetyl)-L-phenylalanylamido-2-deoxy-β-D-glucose (NAPA), was shown to inhibit the kinase activity of IKKα, one of the two catalytic subunits of IKK complex, decreasing the inflammatory status in osteoarthritis chondrocytes. In the present work we have investigated the inhibition mechanism of IKKα by NAPA by combining computational simulations, in vitro assays and Mass Spectrometry (MS) technique. The kinase in vitro assay was conducted using a recombinant IKKα and IKKtide, a 20 amino acid peptide substrate derived from IkBα kinase protein and containing the serine residues Ser32 and Ser36. Phosphorylated peptide production was measured by Ultra Performance Liquid Chromatography coupled with Mass Spectrometry (UPLC-MS), and the atomic interaction between IKKα and NAPA has been studied by molecular docking and Molecular Dynamics (MD) approaches. Here we report that NAPA was able to inhibit the IKKα kinase activity with an IC₅₀ of 0.5 mM, to decrease the K_m value from 0.337 mM to 0.402 mM and the V_max from 0.0257 mM·min−1 to 0.0076 mM·min−1. The computational analyses indicate the region between the KD, ULD and SDD domains of IKKα as the optimal binding site explored by NAPA. Biochemical data indicate that there is a non-significant difference between K_m and K_i whereas there is a statistically significant difference between the two V_max values. This evidence, combined with computational results, consistently indicates that the inhibition is non-competitive, and that the NAPA binding site is different than that of ATP or IKKtide.     

Numerical simulation of parallel-plate particle separator for estimation of charge distribution of PM2.5

A numerical simulation of an instrument that is used to measure the charging state of PM2.5 is conducted in order to clarify its measurement uncertainty and to improve its performance. The instrument, a parallel-plate particle separator (PPPS), is designed to classify aerosol particles according to their charging states and measure their quantities. The trajectories of submicron particles in the PPPS are numerically analyzed using the Lagrangian particle tracking method, taking into account the Brownian force and the electrostatic force. First, it is confirmed that the deterioration in the classification accuracy observed in the experiment is due to Brownian diffusion. The optimal condition that improves the accuracy is investigated through a parametric study by varying the balance of flow rates at the inlets, the geometry of the inlet and exit sections, and the applied voltage. It is found that decreasing the flow rate of the central inlet for aerosol or narrowing the central inlet improves the accuracy. The dependence of the accuracy on the flow rate is found to be in accordance with the experimental results. For charged particles, an optimum voltage that maximizes the classification accuracy is found. On the basis of the simulation results, we propose a method to determine the charge distribution of aerosol from the number of particles counted at each exit of the PPPS. In the test assuming aerosol in the air, the charge distribution determined from the number count at the exits is found to perfectly agree with the charge distribution specified at the inlet.

Copyright © 2019 American Association for Aerosol Research     

Emission measurements with gravimetric impactors and electrical devices: An aerosol instrument comparison

Particulate matter in the atmosphere is known to affect Earth’s climate and to be harmful to human health. Accurately measuring particles from emission sources is important, as the results are used to inform policies and climate models. This study compares the results of two ELPI?+?devices, two PM10 cascade impactors and an eFilter, in combustion emission measurements. The comparison of the instruments in a realistic setting shows what types of challenges arise from measuring an emission aerosol with unknown particle morphologies and densities, different particle concentrations and high temperature. Our results show that the PM10 cascade impactors have very good intercorrelation when the collected mass is greater than 150?µg, but below that, the uncertainty of the results increases with decreasing mass. The raw signals of two ELPI?+?devices were nearly identical in most samples, as well as the particle number concentrations and size distributions calculated from raw signals; however, transforming the current distributions into mass distributions showed variation in the mass concentration of particles larger than 1?µm. The real-time time signal measured by eFilter was similar to the total current measured by ELPI+. The eFilter and PM10 cascade impactors showed similar particle mass concentrations, whereas ELPI?+?showed clearly higher ones in most cases. We concluded that the difference is at least partially due to volatile components being measured by ELPI+, but not by the mass collection measurements.

Copyright © 2019 American Association for Aerosol Research     

Calibration of a particle mass spectrometer using polydispersed aerosol particles

Routine calibrations of online aerosol chemical composition analyzers are important for assessing data quality during field measurements. The combination of a differential mobility analyzer (DMA) and condensation particle counter (CPC) is a reliable, conventional method for calibrations. However, some logistical issues arise, including the use of radioactive material, quality control, and deployment costs. Herein, we propose a new, simple calibration method for a particle mass spectrometer using polydispersed aerosol particles combined with an optical particle sizer. We used a laser-induced incandescence–mass spectrometric analyzer (LII-MS) to test the new method. Polydispersed aerosol particles of selected chemical compounds (ammonium sulfate and potassium nitrate) were generated by an aerosol atomizer. The LII section was used as an optical particle sizer for measuring number/volume size distributions of polydispersed aerosol particles. The calibration of the MS section was performed based on the mass concentrations of polydispersed aerosol particles estimated from the integration of the volume size distributions. The accuracy of the particle sizing for each compound is a key issue and was evaluated by measuring optical pulse height distributions for monodispersed ammonium sulfate and potassium nitrate particles as well as polystyrene latex particles. A comparison of the proposed method with the conventional DMA-CPC method and its potential uncertainties are discussed.

Copyright © 2018 American Association for Aerosol Research     

Articular cartilage: New directions and barriers of scaffolds development – review

Despite progress which has been made in recent years in the field of cell-based therapies or cell scaffolds for cartilage regeneration, a lot of work still needs to be done. Scaffolds remain a great base for tissue regeneration. However, proper implantation procedures or post-treatment still await development.

In this review we summarize paths of cartilage treatment, especially focusing on cell scaffold design and manufacture. As well as the advantages and disadvantages of available or investigated methods and materials, especially focusing on cartilage scaffold design. We show the most promising directions and barriers in the creation of healthy tissue.     

Electron tomography of soot for validation of 2D image processing and observation of new structural features

Transmission electron microscopy of soot aggregates is performed using a tilting-stage with view angles from –60 to +50 degrees. The resulting series of images was used to produce videos and solid models to aid in the visualization of the structure. The images from 31 angles for each aggregate were analyzed using various 2D image processing techniques. It was found that the measurements of primary particle size varied by less than 16% as angles changed. Projected area measurements only varied by 6% as viewing angle changed. These variations are comparable to the errors expected from the image processing. Practically, 2D images are adequate for determining primary particle size and projected area with little noise or bias introduced by random projection angles. In addition, it was found that most of the aggregates contained closed ring structures, implying that during aggregation, a small amount of rotation at contact points occurs. This structural feature is not apparent in 2D images and suggests that tomography may be useful in studying soot formation and aging processes.

Copyright © 2019 American Association for Aerosol Research     

Thermal desorption behavior of hemiacetal,acetal, ether,and ester oligomers

Thermal desorption methods are widely used in the aerosol community to obtain information on particle volatility, and are often coupled with mass spectrometry to separate chemical components prior to analysis. One of the challenges of using these methods is that it is not yet clear how different components respond to temperature, in particular whether they desorb intact or decompose by reversible or irreversible reactions prior to desorption. In this study, we analyzed the thermal desorption behavior of four major classes of oligomers: hemiacetals, acetals, ethers, and esters, which are potentially present in secondary organic aerosol (SOA) and are primarily formed through particle-phase accretion reactions. The results show that when all four of these oligomers are desorbed in our thermal desorption particle beam mass spectrometer at ～160?°C on millisecond timescales (real-time analysis) they reach the ionization region as the intact oligomer. This is also true for acetal, ether, and ester oligomers desorbed at much lower temperatures on timescales of tens of minutes, whereas hemiacetal oligomers decompose reversibly to the original alcohol and aldehyde monomers. A key factor that influences the desorption behavior of oligomers appears to be whether reversible decomposition occurs by unimolecular rearrangement or whether it involves hydrolysis, and thus requires water that may be lost from particles during heating and thus not available for reversible decomposition prior to desorption. The results should aid others in interpreting thermal desorption analyses, and in extracting information about the linkages that bind oligomers and the types of accretion reactions by which they were formed.

Copyright © 2019 American Association for Aerosol Research     

Recent Advances in Flame Retardancy of Polymeric Materials (Materials,Applications, Industry Developments,Markets)

The Fifth Annual Conference on Flame Retardancy was held May 24–26, 1994, at the Ramada Plaza Hotel, Stamford, Connecticut, USA. The conference was organized by Business Communications Company, Inc., Norwalk, Connecticut (Company President, Mr. Louis Naturman; Conference Coordinator, Mrs. Sharon D. Faust). New materials (polymers, blends, composites), their applications, industry developments, and markets were considered. Specifically, the most important topics were:

Introduction of new technological achievements and development in the field of flame retardancy (FR)

Review of the current state of science and technology in FR

Review of applications and markets for FR products

Presentation of recent developments in local and global standardization and in testing technology

Discussion of toxicity and environmental issues

Provision of a unique opportunity for newcomers to FR research technology and marketing to become acquainted with the FR field in all its aspects

Discussion of halogen-based and non-halogen-based flame retardant chemicals, syngergism, intumescence, FR mechanisms, modeling, flame parameters, inherently FR polymers, and polymer blends     

Development of balloon-borne impactor payload for profiling free tropospheric aerosol

Size-segregated aerosol vertical profiles in the troposphere are critically important for source attribution, transformation processes, atmospheric stability, and radiative forcing. For the first time, the development of a 6-stage impactor for real-time balloon-borne measurements of size-segregated (cutoff diameter [D_ae]: 0.15–5?µm) aerosol mass concentrations in the free troposphere was tested during spring 2016 over Hyderabad, India, is presented. Total aerosol mass concentrations obtained with the 6-stage impactor (M_TI) and a co-located optical particle counter (M_TOPC) measurements at the surface under ambient conditions agreed to within 15%. The effect of aerosol particle growth on the M_TI data are assessed using an urban aerosol particle model by scaling mass concentration of water-soluble (hydrophilic) aerosol particles at ambient relative humidity (RH) to that at RH = 50%. An overall uncertainty of the measurement of the M_TI was estimated to be about 19%. The altitude variation of size-segregated mass concentrations of aerosol particles along with thermodynamic variables depicted convectively well-mixed layer extending up to about 4.5?km within which aerosol particles showed two distinct layers, one at ～2?km and another at about 4.5?km. The size-resolved air samples containing aerosol particles collected using the balloon-borne 6-stage impactor will be useful for their chemical characterization and also long-range transport studies.

Copyright © 2019 American Association for Aerosol Research     

Advanced aerosol optical tweezers chamber design to facilitate phase-separation and equilibration timescale experiments on complex droplets

The phase-separation of mixed aerosol particles and the resulting morphology plays an important role in determining the interactions of liquid aerosols with their gas-phase environment. We present the application of a new aerosol optical tweezers chamber for delivering a uniformly mixed aerosol flow to the trapped droplet's position for performing experiments that determine the phase-separation and resulting properties of complex mixed droplets. This facilitates stable trapping when adding additional phases through aerosol coagulation, and reproducible measurements of the droplet's equilibration timescale. We demonstrate the trapping of pure organic carbon droplets, which allows us to study the morphology of droplets containing pure hydrocarbon phases to which a second phase is added by coagulation. A series of experiments using simple compounds are presented to establish our ability to use the cavity enhanced Raman spectra to distinguish between homogeneous single-phase, and phase-separated core–shell or partially engulfed morphologies. The core–shell morphology is distinguished by the pattern of the whispering gallery modes (WGMs) in the Raman spectra where the WGMs are influenced by refraction through both phases. A core–shell optimization algorithm was developed to provide a more accurate and detailed analysis of the WGMs than is possible using the homogeneous Mie scattering solution. The unique analytical capabilities of the aerosol optical tweezers provide a new approach for advancing our understanding of the chemical and physical evolution of complex atmospheric particulate matter, and the important environmental impacts of aerosols on atmospheric chemistry, air quality, human health, and climate change.

Copyright © 2016 American Association for Aerosol Research     

Extended log-normal method of moments for solving the population balance equation for Brownian coagulation

An extended log-normal method of moments (ELNMOM) is presented in this study for solving the population balance equation (PBE) for Brownian coagulation. The method is an extension of the log-normal method of moments (LNMOM) proposed by Lee in 1983. The ELNMOM uses the superposition of log-normal subdistributions to represent the size distribution. Unlike previous modal studies, the subdistributions are not independent modes but flexible components in this study and the closure of this method is achieved by introducing additional higher-order moment equations. Based on some simplifying assumptions, the ELNMOM is implemented with only four adjustable parameters for a preliminary exploration. The method is then validated by comparing the size distribution parameters predicted by this method with those predicted by the LNMOM and other numerical methods for Brownian coagulation in the continuum regime and the free-molecular regime. The results show that the ELNMOM more accurately predicts the total particle number concentration, the geometric standard deviation and the geometric mean particle volume than the LNMOM while not taking much more computation time.

Copyright © 2019 American Association for Aerosol Research