Commercial Aerosol Research Articles

Inhalable Mucociliary-On-Chip System Revealing Pulmonary Clearance Dynamics in Nanodrug Delivery.

The development of a inhaled nanodrug delivery assessment platform is crucial for advancing treatments for chronic lung diseases. Traditional in vitro models and commercial aerosol systems fail to accurately simulate the complex human respiratory patterns and mucosal barriers. To address this, we have developed the breathing mucociliary-on-a-chip (BMC) platform, which replicates mucociliary clearance and respiratory dynamics in vitro. This platform allows for precise analysis of drug deposition and penetration, providing critical insights into how liposomes and other nanocarriers interact with lung tissues under various airflow conditions. Our results reveal that liposomes penetrate deeper into the cellular layer under high shear stress, with both static and dynamic airflows distinctly affecting their drug release rates. The BMC platform integrates dynamic inhalation systems with mucociliary clearance functionality, enabling a comprehensive evaluation of drug delivery efficacy. This approach highlights the importance of airflow dynamics in optimizing inhalable nanodrug delivery systems, improving nanocarrier design, and tailoring drug dosages and release strategies. The BMC platform represents a significant advancement in the field of inhaled nanodrug delivery, offering a more accurate and reliable method for assessing the performance of therapies. By providing a detailed understanding of drug interactions with lung tissues, this platform supports the development of personalized inhaled therapies and offers promising strategies for treating pulmonary diseases and advancing nanodrug development.

Amazon tropical fishes of commercial interest show human-cell contamination but no SARS-CoV-2 in a real-life scenario.

Amazonas was one of the most impacted Brazilian states by the COVID-19 pandemic. Mortality rates were high, and the health systems collapsed. It is important to identify possible intermediate reservoirs to avoid animal-to-human contamination. Several tropical fish are of commercial interest and are sold in large open-air markets in the region, representing a large economic and dietary importance. This study aimed to verify if fish species of commercial importance, aerosols, and fish wastewater in local open-air markets, at a major capital city in the western Brazilian Amazon, are contaminated by SARS-CoV-2. 488 fish, 50 aerosol, and 45 wastewater samples were analyzed for the presence of SARS-CoV-2. The samples were subjected to extraction using the BIOGENE Viral DNA/RNA Extraction kit, and the molecular diagnosis was tested for SARS-CoV-2 using the Bio-Manguinhos SARS-CoV-2 (EDx) Molecular Kit. It was not possible to detect the virus (Ct≤40, for Gene E) in these samples, however, in 181 samples of fish it was possible to detect the human RP gene (Ct≤35, for the RP Gene), indicating human contact. There was a high number of COVID-19 diagnoses in all city districts in which the samples were collected, showing that SARS-CoV-2 was circulating. This study indicates that fish of local commercial importance do not carry SARS-CoV-2 viral particles, despite circulation of SARS-CoV-2, and are not an important source of animal-to-human contamination. Despite these results, the human RP gene was found detectable in fish, air, and fish wastewater, showing that such places may carry human pathogens.

Determining the ultraviolet radiation dose experienced by aerosols using ultraviolet-sensitive dyes

Abstract. ​​​​​​​The application of ultraviolet (UV)-light-based air disinfection methods holds promise but also presents several challenges. Among these, the quantitative determination of the required UV radiation dose for aerosols is particularly significant. This study explores the possibility of determining the UV dose experienced by aerosols without the use of virus-containing aerosols, circumventing associated laboratory safety issues. To achieve this, we developed a model system comprised of UV-sensitive dyes dissolved in di-ethyl-hexyl-sebacate (DEHS), which facilitates the generation of non-evaporating and UV-degradable aerosols. For the selection of UV-sensitive dyes, 20 dyes were tested, and 2 of them were selected as being the most suitable, according to several selection criteria. Dye-laden aerosol droplets were generated using a commercial aerosol generator and subsequently exposed to UV-C radiation in a laboratory-built UV irradiation chamber. We designed a low-pressure impactor to collect the aerosols pre- and post-UV exposure. Dye degradation, as a result of UV light exposure, was then analyzed by assessing the concentration changes in the collected dye solutions using a UV-visible spectrophotometer. Our findings revealed that a UV dose of 245 mW s cm−2 resulted in a 10 % degradation, while a lower dose of 21.6 mW s cm−2 produced a 5 % degradation. In conclusion, our study demonstrates the feasibility of using aerosol droplets containing UV-sensitive dyes to determine the UV radiation dose experienced by an aerosol.

Riboflavin based setup as an alternative method for a preliminary screening of face mask filtration efficiency

Face masks are essential in reducing the transmission of respiratory infections and bacterial filtration efficiency, a key parameter of mask performances, requires the use of Staphylococcus aureus and specialised staff. This study aims to develop a novel method for a preliminary screening of masks or materials filtration efficiency by a green, easy and rapid setup based on the use of a riboflavin solution, a safe autofluorescent biomolecule. The proposed setup is composed of a commercial aerosol generator commonly used for aerosol therapy, custom 3D printed aerosol chamber and sample holder, a filter for downstream riboflavin detection and a vacuum pump. The filtration efficiency of four different masks was assessed using the riboflavin-based setup and the bacterial filtration efficiency (BFE). The averaged filtration efficiency values, measured with both methods, were similar but were higher for the riboflavin-based setup (about 2% for all tested samples) than bacterial filtration efficiency. Considering the good correlation, the riboflavin-based setup can be considered validated as an alternative method to bacterial filtration efficiency for masks and related materials fabrics filtration efficiency screening but This study aims to develop a novel method for a preliminary screening of masks or materials filtration efficiency by a green, easy and rapid setup based on the use of a riboflavin solution, a safe autofluorescent biomolecule, but not to replace regulation approaches. The proposed setup can be easily implemented at low price, is more rapid and eco-friendly and can be performed in chemical-physical laboratories without the needing of biosafety laboratory and specialised operators.

Gum Arabic-stabilized upconverting nanoparticles for printing applications

Gum Arabic-stabilized upconverting nanoparticles for printing applications

3D computational fluid and particle dynamics simulations: metrics of aerosol capture by impaction filters * *Contribution of NIST; not subject to U.S. copyright. Certain commercial equipment, instruments, software, or materials are identified in this paper in order to specify the experimental procedure and virtual experimentation adequately. Such identification is not intended to imply recommendation or endorsement by NIST, nor is

Human studies provide valuable information on components or analytes recovered from exhaled breath, but there are limitations due to inter-individual and intra-individual variation. Future development and implementation of breath tests based on aerosol analysis require a clear understanding of how human factors interact with device geometry to influence particle transport and deposition. The computational fluid and particle dynamics (CFPD) algorithm combines (i) the Eulerian approach to fluid dynamics and (ii) the Lagrangian approach to single particle transport and deposition to predict how particles are carried in fluids and deposited on surfaces. In this work, we developed a 3D multiscale CFPD model to provide insight into human factors that could be important to control or measure during sampling. We designed the model to characterize the local transport, spatial distribution, and deposition of polydisperse particles in a single impaction filter of a commercial aerosol collection device. We highlight the use of decoupling numerical strategies to simultaneously quantify the influence of filter geometry, fluid flowrate, and particle size. Our numerical models showed the remarkable effect of flowrate on aerosol dynamics. Specifically, aerosol mass deposition, spatial distribution, and deposition mechanisms inside the filter. This work as well as future studies on the effect of filter geometry and human factors on aerosol collection will guide the development, standardization, and validation of breath sampling protocols for current and emerging breath tests for forensic and clinical applications.

Under High Radon Environment α Energy Spectrum Analysis

Energy spectrum processing technology is one of the key technologies to realize the rapid monitoring of artificial radioactive aerosol. At present, most commercial aerosol continuous monitoring equipment are suitable for the measurement of artificial radioactive aerosol under natural radon background. The energy spectrum processor technology used is also aimed at the situation of low radon background, which is not suitable for the measurement of artificial radioactive aerosol in high radon environment. In this paper, the combination of energy spectrum fitting (fitting method) and variable tailing proportional coefficient method (ratio deduction method) is used, and the program written on MATLAB platform is used to analyze α by deducting radon daughters in the energy spectrum, the energy spectrum measurement in high radon environment can be realized. By analyzing the energy spectrum of mixed samples of U and Ra with different concentrations and comparing with the measurement results after cooling, it shows good consistency, which verifies the feasibility of understanding the spectrum method and provides a reference for the energy spectrum analysis in high radon environment α Energy spectrum analysis provides an important technical means.

Evaluation of commercial aerosol insecticides for control of Aedes aegypti susceptible or resistant to pyrethroids

Objective. To evaluate indoor use of commercial aerosols for dengue vector mosquito control, and estimate the number of treatable houses per can. Materials and methods. Four aerosol products containing combinations of pyrethroids (two containing propoxur and one containing synergists too), were evaluated with mosquitoes in a room of a Tapachulastyle house. Eight cages containing 20 insecticide susceptible or resistant females were hung from tripods, another set was placed in sheltered areas of the room. From the entrance of the room, one of 4-9 concentrations was sprayed for each aerosol, leaving the mosquitoes for 30 min after sprayed. Mortality was recorded after 24 h and lethal concentrations were calculated. Results. Aerosol A had the highest LC50, with 0.308 g for mosquitoes hanging from tripods and 0.453 g for sheltered mosquitoes; followed by aerosols C, D and B, with statistical differences between types of exposure. Conclusions. Aerosols B-D could spray 20-25 3-room houses (56 m3-room), killing all resistant mosquitoes. Aerosols may become a good tool for indoor mosquito control, if the optimal concentration and correct spray method are used.

Evaluation of a commercial aerosol lidar scanner for industrial pollution monitoring

In recent years, light detection and ranging (LiDAR) technology has gained popularity in various applications, including remote sensing of Particulate Matter (PM) absolute concentrations. Raymetrics PMeye is a unique platform consisting of a state-of-the-art scanning lidar, innovative algorithms and auxiliary sensors, used for large areas PM concentrations monitoring. Using a novel inversion scheme for transforming raw signals to aerosol concentrations, PMeye is one of its kind for aerosol monitor in urban or/and industrial areas. Measurements performed at a steel factory in Latin America, a highly variable area in terms of emission sources, support the effectiveness of the overall system. Measurements evaluation against a light scattering in situ PM counter, placed at major emission sources on various ranges and directions from the lidar, present high correlation and very low mean relative differences.

Biocompatibility evaluation of encapsulated silver-based printed circuits for in-vitro long-term sensing devices

Metal-based inks, such as silver nanoparticle (AgNPs) dispersions, are standard solutions in printed electronics (PE) due to their high bulk conductivity, stability, and commercial availability. Conductive functional printed patterns have been exploited for several applications, such as (wearable) sensors, antennas, transistors, batteries. Recently, PE has also been widely investigated for biomedical and bioelectronic interfaces. In this case, the choice of biocompatible materials is crucial to ensure biological activities of the seeded cells. For instance, the release of Ag + ions in the medium culture in in-vitro cultures, is known to induce cytotoxicity, in a dose-, size-, and time-dependent way, causing oxidative stress and eventually cellular death. Hence, an encapsulation step of the printed pattern is usually performed to reduce such risk, by inducing however additional limitations and complications on the design and production. This work investigates the biocompatibility of a commercial Aerosol Jet® Printed (AJ®P) AgNPs-based ink (Ø avg,particle size = 35 nm, Ag content ~50 wt%) use to print conductive circuits for in-vitro bioelectrical sensing. Particularly, the ink was AJ® printed on the top of stereolithography (SLA) samples coated with Parylene-C, and further encapsulated with polydimethylsiloxane (PDMS). Cell viability assays were evaluated using both in adhesion and suspension cell type, such fibroblasts and B-Lymphoblastoid cell line respectively, at different time points from 7 days till 21 days to verify cellular activity and proliferation for long term usage. This work provides new insights concerning the use of encapsulated conductive AgNPs-based circuits for in-vitro long-term sensing devices.

Characterizing the Chemical Landscape in Commercial E-Cigarette Liquids and Aerosols by Liquid Chromatography-High-Resolution Mass Spectrometry.

The surge in electronic cigarette (e-cig) use in recent years has raised questions on chemical exposures that may result from vaping. Previous studies have focused on measuring known toxicants, particularly those present in traditional cigarettes, while fewer have investigated unknown compounds and transformation products formed during the vaping process in these diverse and constantly evolving products. The primary aim of this work was to apply liquid chromatography-high-resolution mass spectrometry (LC-HRMS) and chemical fingerprinting techniques for the characterization of e-liquids and aerosols from a selection of popular e-cig products. We conducted nontarget and quantitative analyses of tobacco-flavored e-liquids and aerosols generated using four popular e-cig products: one disposable, two pod, and one tank/mod. Aerosols were collected using a condensation device and analyzed in solution alongside e-liquids by LC-HRMS. The number of compounds detected increased from e-liquids to aerosols in three of four commercial products, as did the proportion of condensed-hydrocarbon-like compounds, associated with combustion. Kendrick mass defect analysis suggested that some of the additional compounds detected in aerosols belonged to homologous series resulting from decomposition of high-molecular-weight compounds during vaping. Lipids in inhalable aerosols have been associated with severe respiratory effects, and lipid-like compounds were observed in aerosols as well as e-liquids analyzed. Six potentially hazardous additives and contaminants, including the industrial chemical tributylphosphine oxide and the stimulant caffeine, were identified and quantified in the e-cig liquids and aerosols analyzed. The obtained findings demonstrate the potential of nontarget LC-HRMS to identify previously unknown compounds and compound classes in e-cig liquids and aerosols, which is critical for the assessment of chemical exposures resulting from vaping.

Efficacy of five commercial household insecticide aerosol sprays against pyrethroid resistant Aedes aegypti and Culex quinquefasciatus mosquitoes in Thailand

Commercial insecticide aerosol sprays are widely used in households for controlling Aedes aegypti and Culex quinquefasciatus, the primary vectors of dengue virus and filarial worm, respectively. In Thailand, however, both mosquitoes are resistant to pyrethroids conferred by knockdown resistance (kdr) mutations, V1016G and F1534C in Ae. aegypti and L1014F in Cx. quinquefasciatus. This study evaluated the efficacy of five sprays (coded as AS1-AS5) with different formulations of pyrethroids against wild mosquitoes by using a cage bioassay in a furnished bedroom of a house. Five cages containing wild mosquitoes and five cages containing a pyrethroid susceptible strain of Ae. aegypti (25 females each), as a bio-indicator, were allocated in the room and spraying was operated for 15s. Survivors and dead mosquitoes were genotyped individually for the kdr mutations using allele-specific PCR methods. Both mosquito species showed a high resistance to permethrin and deltamethrin with 12.5-58.0% mortality rates. For controlling Ae. aegypti, the spray AS4 showed the highest efficacy (mortality rates 76.0-100.0%, mean 95.2%), followed by AS2 (73.0-100.0%, mean 93.8%). For controlling Cx. quinquefasciatus, the best result was obtained from AS4 (66.0-98.0% mortality, mean 89.8%), followed by AS2 (73.0-97.0%, mean 84.5%). The sprays (AS4 and AS2) containing both type I and type II pyrethroids were more effective than those containing only type I pyrethroids or pyrethrum with the synergist piperonyl butoxide. The mutant G1016 and F1014 allele frequencies were significantly higher in the survivor groups than the dead groups of Ae. aegypti and Cx. quinquefasciatus, respectively, (P<0.05). The efficacy of the sprays varied depending on the mosquito species, formulations, nozzles and locations of caged mosquitoes. The V1016G and L1014F mutations are associated with the reduced efficacy of sprays used in households for controlling resistant Ae. aegypti and Cx. quinquefasciatus mosquitoes, respectively.

A PM2.5 Sensor Module Based on a TPoS MEMS Oscillator and an Aerosol Impactor

In this work, a real-time PM2.5 sensor module with high mass resolution and wide detection range is successfully demonstrated while the module consists of a two-stage aerosol impactor, a Thin-film Piezoelectric-on-Silicon (TPoS) MEMS oscillator, and a micro-pump. The aerosol impactor's collection efficiency of 51% for $2.54~\mu \text{m}$ and 50% for $1.03~\mu \text{m}$ is verified for stage 1 and stage 2, respectively. A length-extensional mode TPoS MEMS resonator is implemented, featuring a resonant frequency of 4.05 MHz and a quality factor (${Q}$ ) of 438 in air. To achieve a portable sensor module, a board-level sustaining circuit, which includes a transimpedance amplifier (TIA), a phase shifter, a band-pass filter, and a buffer circuit are integrated to fulfill the condition of Barkhausen criteria for oscillation. Phase noise of -111.92 dBc/Hz at 1 kHz offset was recorded under ambient pressure and room temperature for a carrier frequency of 4.05 MHz. The mass resolution for the PM2.5 sensor implemented in this work is 0.71 pg. Finally, an incense was used to produce the liquid type particles continuously for the aerosol measurement. The coefficient of determination (${R} ^{2}$ ) of 0.81 between the frequency slope of the proposed sensor and the aerosol concentration of the commercial optical aerosol sensor within a range of $10~\mu $ g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> to $1000~\mu $ g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . This work successfully integrated MEMS, circuit, and air flow technologies to realize a complete mass sensing module, and has the potential to be implemented in the particulate matter concentration monitoring applications of air.

Superhydrophobic Water-Solid Contact Triboelectric Generator by Simple Spray-On Fabrication Method.

Energy harvesting is a method of converting energy from ambient environment into useful electrical energy. Due to the increasing number of sensors and personal electronics, energy harvesting technologies from various sources are gaining attention. Among energy-harvesting technologies, triboelectric nanogenerator (TENG) was introduced as a device that can effectively generate electricity from mechanical motions by contact-electrification. Particularly, liquid-solid contact TENGs, which use the liquid itself as a triboelectric material, can overcome the inevitable friction wear between two solid materials. Using a commercial aerosol hydrophobic spray, liquid-solid contact TENGs, with a superhydrophobic surface (contact angle over 160°) can be easily fabricated with only a few coating processes. To optimize the fabrication process, the open-circuit voltage of sprayed superhydrophobic surfaces was measured depending on the number of coating processes. To demonstrate the simple fabrication and applicability of this technique on random 3D surfaces, a liquid-solid contact TENG was fabricated on the brim of a cap (its complicated surface structure is due to the knitted strings). This simple sprayed-on superhydrophobic surface can be a possible solution for liquid-solid contact TENGs to be mass produced and commercialized in the future.

An innovative and sustainable approach to spray paint graffiti removal from Istrian stone through the silica sol-gel chemistry: A preliminary assessment

Abstract A sustainable methodology to synthesise and screen libraries of new low-environmental impact products, suitable for removing graffiti and murals from historic building, masonries and stone artworks has been developed. This approach provided a novel series of two-component systems by combining silica sol-gel chemistry and dimethyl carbonate. The solid matrixes were hybrid silica gels, which were synthesised in basic conditions by using ethylene and propylene glycols as organic co-solvents. Dimethyl carbonate (DMC) was the green organic solvent to load into the gel. The efficiency of three new systems in adsorbing/trapping commercial red aerosol spray paint was investigated through an ad hoc test tube extraction evaluation and on mock stained samples of Istrian stones. Data provided by NMR spectroscopy and FT-IR spectroscopy led to the identification of a promising cleaning agent, paving the way to its full characterisation and features improvement.

Design and Evaluation of an Aerosol Electrometer with Low Noise and a Wide Dynamic Range.

A low-noise aerosol electrometer with a wide dynamic range has been designed for measuring the total net charge on high concentration aerosol particles within the range of −500 pA to +500 pA. The performance of the aerosol electrometer was evaluated by a series of experiments to determine linearity, sensitivity and noise. The relative errors were controlled within 5.0%, 1.0% and 0.3% at the range of −40 pA to +40 pA, ±40 pA to ±100 pA, and ±100 pA to ±500 pA respectively. The stability of the designed aerosol electrometer was found to be highly sensitive to temperature variations, but under temperature control, the root mean square noise and the peak-to-peak noise were 1.040 fA and 5.2 fA respectively, which are very close to the calculated theoretical limit of the current noise. The excellent correlation and the advantage of a wide dynamic range have been demonstrated by comparing with the designed aerosol electrometer to a commercial aerosol electrometer. A 99.7% (R2) statistical correlation was obtained; meanwhile, the designed aerosol electrometer operated well even when an overrange phenomenon appeared in the commercial aerosol electrometer.

Evaluation of the New Capture Vaporizer for Aerosol Mass Spectrometers (AMS): Elemental Composition and Source Apportionment of Organic Aerosols (OA)

To reduce the quantification uncertainty of commercial aerosol mass spectrometers (AMS) and aerosol chemical speciation monitors (ACSM), a new capture vaporizer (CV) was recently built to replace the standard vaporizer (SV). A collection efficiency (CE) ∼ 1 in the CV AMS/ACSM has been demonstrated for ambient aerosols, but the CV also leads to increased thermal decomposition of the analytes because of longer residence time and vaporizer surface contact. This study reports on the performance of the CV for analyzing organic aerosol (OA) elemental composition and source apportionment, using both HR-ToF-AMS and ACSM for the first time. The methodology for obtaining elemental ratios from AMS spectra is updated to account for differences in OA fragmentation between the CV and SV. An artifact CO+ signal is observed for some chemically reduced laboratory compounds. If that signal is included in elemental analysis, the O:C is substantial overestimated, while accurate results are observed if the anomalous CO+ is ig...

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OBJECTIVES/SPECIFIC AIMS: This study investigates the process configuration parameters involved in targeted drug delivery to the avian respiratory system. Previously, direct intratracheal aerosol delivery in an avian model using a commercial atomizer was found to result in delivery of a high portion of the total dose into one lung lobe. We hypothesize that controlling process configuration will decrease the asymmetric distribution. METHODS/STUDY POPULATION: A 3D printed model of an avian trachea and mainstream bronchi was constructed to create a representative model for direct instillation of aerosols. Construction of the model respiratory tract included the trachea and the first mainstream bronchi bifurcation to measure left/right (L/R) distribution of aerosol delivered. Both liquid aerosol delivery (LAD) using a commercial atomizer and dry aerosol delivery (DAD) using a custom-built dry powder insufflator device were tested. Two experimental variables were controlled: (1) retraction distance from the carina and (2) centering of device shaft in the lumen of the trachea. Measurement of device efficiency (dose delivered to the 3D model at as fraction of total dose), aerosol delivery efficiency (dose captured at L/R bifurcations as a fraction of total dose), and aerosol lateralization (L/R) was conducted. RESULTS/ANTICIPATED RESULTS: The aerosol delivery efficiency for both LAD and DAD devices [73.9% (95% CI: 68.2–79.2) and 73.4% (95% CI: 55.5–91.3), respectively] did not have an appreciable difference. However, the LAD device had a higher efficiency as compared with the DAD device. The L/R distribution for the DAD device was found to be highly dependent on both retraction distance and shaft centering. Appreciable improvement in the L/R distribution was seen using the DAD device by increasing the retraction distance distal to the carina. DISCUSSION/SIGNIFICANCE OF IMPACT: The use of targeted drug delivery to treat pulmonary pathogens requires a careful design, manufacture, and therapeutic positioning of devices. In particular, clinically relevant animal models and treatment regimes requires a sound understanding of the physical processes controlling aerosol distribution in the respiratory system. By using a simulated respiratory model, many of the physical parameters of drug delivery can be tested before using a live animal model. This is especially important from an animal welfare perspective as well as an animal subject availability aspect.

Knock down efficacy of commercially available insecticides against Anopheles gambiae

Abstract: Knockdown efficacy of commercial aerosol insecticides against laboratory reared Anopheles gambiae Kisumu strain mosquitoes and suppression of indoor resting density of An. gambiae complex mosquitoes in the field were investigated in the study. Laboratory reared 2-5 days old female An. gambiae mosquitoes were released into Peet-Grady chambers, sprayed with 0.3±0.1g of insecticides. Knock down rates were observed for one hour and mortality rates after 24hrs of spraying. Field efficacy studies were carried out by spraying houses with near uniform indoor resting densities of An. gambiae complex mosquitoes with aerosol insecticides and mosquitoes collected. Morphological and molecular characterization of mosquitoes was done. Probit analysis on knock down rates was carried out. Mortality rates and Mean indoor resting densities were compared using ANOVA in SPSS version 16. The KT50 and KT95 of Kenyan Baygon® and Kenyan raid® differed significantly with the other insecticides. Nigerian Baygon® achieved the lowest mortality rate of 87% and differed significantly (P0.05). Collected An. gambiae complex mosquitoes corresponded to An. arabiensis. The low knock down values by Kenyan Baygon®, Kenyan raid® and the low mortality rate by Nigerian Baygon® can be attributed to reduced efficacy rather than development of resistance. Whether the low deterrence of Anopheles gambiae complex mosquitoes into houses is due to development of pyrethroid insecticide resistance can be authenticated in another study. Key Words: Anopheles gambiae, Knock down time, Mortality rate, Indoor resting density.

A scattering methodology for droplet sizing of e-cigarette aerosols

Context: Knowledge of the droplet size distribution of inhalable aerosols is important to predict aerosol deposition yield at various respiratory tract locations in human. Optical methodologies are usually preferred over the multi-stage cascade impactor for high-throughput measurements of aerosol particle/droplet size distributions.Objective: Evaluate the Laser Aerosol Spectrometer technology based on Polystyrene Sphere Latex (PSL) calibration curve applied for the experimental determination of droplet size distributions in the diameter range typical of commercial e-cigarette aerosols (147–1361 nm).Materials and methods: This calibration procedure was tested for a TSI Laser Aerosol Spectrometer (LAS) operating at a wavelength of 633 nm and assessed against model di-ethyl-hexyl-sebacat (DEHS) droplets and e-cigarette aerosols. The PSL size response was measured, and intra- and between-day standard deviations calculated.Results: DEHS droplet sizes were underestimated by 15–20% by the LAS when the PSL calibration curve was used; however, the intra- and between-day relative standard deviations were < 3%. This bias is attributed to the fact that the index of refraction of PSL calibrated particles is different in comparison to test aerosols. This 15–20% does not include the droplet evaporation component, which may reduce droplet size prior a measurement is performed. Aerosol concentration was measured accurately with a maximum uncertainty of 20%. Count median diameters and mass median aerodynamic diameters of selected e-cigarette aerosols ranged from 130–191 nm to 225–293 nm, respectively, similar to published values.Discussion and conclusion: The LAS instrument can be used to measure e-cigarette aerosol droplet size distributions with a bias underestimating the expected value by 15–20% when using a precise PSL calibration curve. Controlled variability of DEHS size measurements can be achieved with the LAS system; however, this method can only be applied to test aerosols having a refractive index close to that of PSL particles used for calibration.