Empty Chamber Research Articles

Model eye tool for retinal optical coherence tomography instrument calibration

Optical coherence tomography (OCT) has been extensively used as noninvasive tool for biological tissues owing to its three-dimensional imaging ability and high axial resolution. OCT quality assurance is vital in these occasions to keep the reliability and accuracy in medical diagnosis. It is necessary to develop a calibration tool for OCT product manufacture, calibration, and quality control. A practical tool is demanded in the OCT quality control and calibration of OCT. So far, there is no such a practical tool that can test all the key parameters of OCT. We design and fabricate a model eye tool, which has this function. The model eye comprises a doublet lens, a single filament, a piece of glass plate and the microsphere-embedded phantom. The doublets lens is bonded by two pieces of planoconvex lenses in the plane position. The first lens focuses parallel light onto the rear surface of the second lens. The rear surface marked with concentric circles serves as retina to measure the angular field of view (FOV). The small flat surface on the peak of the second lens is used to test signal to noise ratio (SNR). The single filament with 125[Formula: see text][Formula: see text]m diameter is used to check the co-alignment of preview and OCT scan. The empty chamber between the small plane of the second lens and the first surface of glass plate is used to measure the depth scaling of the OCT. The microspheres of 1[Formula: see text][Formula: see text]m diameter distributed uniformly in the phantom, which can test the lateral and the axial resolution of OCT equipment. Experimental results are presented to show the validity of the proposed tool. It is shown that the tool is able to be used in the calibration and quality control of retinal OCT.

Social preference in rats.

Rats were given repeated choices between social and nonsocial outcomes, and between familiar and unfamiliar social outcomes. Lever presses on either of 2 levers in the middle chamber of a 3-chamber apparatus opened a door adjacent to the lever, permitting 45-s access to social interaction with the rat in the chosen side chamber. In Experiment 1, rats preferred (a) social over nonsocial options, choosing their cagemate rat over an empty chamber, and (b) an unfamiliar over a familiar rat, choosing a non-cagemate over their cagemate. These findings were replicated in Experiment 2 with 2 different non-cagemate rats. Rats preferred both non-cagemate rats to a similar degree when pitted against their cagemate, but were indifferent when the 2 non-cagemates were pitted against each other. Similar preference for social over nonsocial and non-cagemate over cagemate was seen in Experiment 3, with new non-cagemate rats introduced after every third session. Response rates (for both cagemate and non-cagemate rats) were elevated under conditions of nonsocial (isolated) housing compared to conditions of social (paired) housing, demonstrating a social deprivation effect. Together, the experiments contribute to an experimental analysis of social preference within a social reinforcement framework, drawing on methods with proven efficacy in the analysis of reinforcement more generally.

Jet propulsion of a squid-inspired swimmer in the presence of background flow

Inspired by recent studies of a squid-like swimmer, we propose a three-dimensional jet propulsion system composed of an empty chamber enclosed within a deformable body with an opening. By prescribing the body deformation and jet velocity profile, we numerically investigate the jet flow field and propulsion performance under the influence of background flow during a single deflation procedure. Three jet velocity profiles, i.e., constant, cosine and half cosine, are considered. We find that the maximum circulation of the vortex ring is reduced at a higher background flow velocity. This is because stronger interaction between the jet flow and background flow makes it harder to feed the leading vortex ring. Regarding thrust production, our analysis based on conservation of momentum indicates that with the constant profile the peak thrust is dominated by the time derivative of the fluid momentum inside the body, while momentum flux related thrust accounts for the quasi-steady thrust. For the cosine profile, its peak is mainly sourced from momentum flux associated with the unsteady vortex ring formation. No prominent thrust peak exists with the half cosine profile whose thrust continuously increases during the jetting. For all the three jet velocity profiles, added-mass related thrust attributed to body deformation enhances the overall thrust generation non-negligibly. Under the present tethered mode, the background flow has negligible influence on the thrust attributed to momentum flux and momentum change of the fluid inside the body. However, it indeed affects the over pressure-related thrust but its effect is relatively small. The overall thrust declines due to the significantly increased drag force at large incoming flow speed despite the rise of added-mass related thrust. Unsteady thrust involving vortex ring formation becomes more important in the overall thrust generation with an increased background flow velocity, reflected by larger ratios of the unsteady impulse to jet thrust impulse.

Structure of a full-length bacterial polysaccharide co-polymerase

Lipopolysaccharides are important components of the bacterial cell envelope that among other things act as a protective barrier against the environment and toxic molecules such as antibiotics. One of the most widely disseminated pathways of polysaccharide biosynthesis is the inner membrane bound Wzy-dependent pathway. Here we present the 3.0 Å structure of the co-polymerase component of this pathway, WzzB from E. coli solved by single-particle cryo-electron microscopy. The overall architecture is octameric and resembles a box jellyfish containing a large bell-shaped periplasmic domain with the 2-helix transmembrane domain from each protomer, positioned 32 Å apart, encircling a large empty transmembrane chamber. This structure also reveals the architecture of the transmembrane domain, including the location of key residues for the Wzz-family of proteins and the Wzy-dependent pathway present in many Gram-negative bacteria, explaining several of the previous biochemical and mutational studies and lays the foundation for future investigations.

Effect of Inlays, Onlays and Endocrown Cavity Design Preparation on Fracture Resistance and Fracture Mode of Endodontically Treated Teeth: An In Vitro Study.

To evaluate the fracture resistance and failure modes of endodontically treated mandibular molars restored with different designs of inlays, onlays and endocrowns. Extracted mandibular third molars (n = 180) were used. An access cavity was prepared on the occlusal surface of each tooth and the roots were obturated with gutta percha. All specimens were randomly divided into 6 groups (n = 30/group) according to the cavity design and the restoration material used. C: control group without access cavity preparation. IE: MOD inlay preparation with EverX Posterior (GC Europe) in the pulp chamber. IG: MOD inlay preparation with G-aenial Universal Flo (GC America) in the pulp chamber. OE: onlay preparation with EverX Posterior (GC Europe) in the pulp chamber. OG: onlay preparation with G-aenial Universal Flo (GC America) in the pulp chamber. EC: endocrown with an empty pulp chamber. All restorations were fabricated with CAD/CAM system using CERASMART® (GC Dental products Europe, Belgium) CAD/CAM blocks. Specimens were thermal-cycled and were subjected to a compressive load applied at 30° angle relative to the long axis of the tooth with a universal testing machine. Results were statistically analyzed by ANOVA followed by Tukey post hoc tests. Chi-square test and Fisher Exact tests were used for the comparisons among groups. The mean fracture strength was significantly different between the groups (p < 0.001); it was significantly highest for intact teeth, followed by endocrowns (p = 0.021). The strength was significantly lower for inlays (with G-aenial Universal Flo and EverX Posterior), intermediate for onlays with EverX Posterior followed by onlays with G-aenial Universal Flo. Endocrowns exhibited higher fracture resistance than other tested composite resin groups. Endocrowns and onlays showed a more favorable failure mode than inlay restorations.

Ruger’s ‘Old Model’ Single-action Revolvers: A Cautionary Tale of Reproducing Historical Firearms in a Litigious Age

In 1953, Ruger released a single-action revolver—patterned after the original Colt Single Action Army. Whilst some changes had been made, this firearm possessed, for all intents and purposes, the handling characteristics of the original Colt design. As a result, the safety precaution was as per the original: the revolver should be loaded with five rounds, rather than six, and the hammer positioned such that it rested over an empty chamber. Despite outlining the recommended carry methods in their instruction manual, Ruger became the subject of product liability lawsuits from purchasers who incorrectly loaded and carried the firearm, resulting in negligent discharges. This article explores the history of Colt-type single-action revolvers in the post-World War II period, analyses the availability of historic mechanical safety mechanisms for double-action revolvers in the 19th and 20th centuries, and summarises the patents on single-action safeties that Ruger had received by 1973. That year, the company discontinued their initial line of Single Action Army-style revolvers—known as ‘Old Models’—for a visibly similar, but mechanically different, ‘New Model’ line of single-action revolvers featuring newly developed safety mechanisms.

Field Uniformity Assessment of a Reverberation Chamber for a Large-Scale Animal Study

An exposure system was designed and implemented for the purpose of joint large-scale animal experiments conducted in Korea and Japan using a reverberation chamber (RC) in both countries. Prior to the start of the animal experiments, the parameters S21, electric field (E-field) uniformity, and Q factor were evaluated to confirm the performance of the developed chambers. The E-field uniformity, which is the most important performance factor of an RC, was evaluated at 900 MHz on 150 measurement values taken at 150 points in a loaded chamber with 80 live rats and in an empty chamber. The conditions of the loaded chamber with the rats are almost the same as the actual experimental environment and in which the rats, watering systems, animal bedding, cages, and cage racks were included. Two mean body weights of 330 and 470 g for the 80 rats were considered. The E-field uniformity was within the mean ± 1.0 dB and mean ± 2.3 dB under the empty and the rat-loaded conditions, respectively.

Compact 2DOF liner based on a long elastic open-neck acoustic resonator for low frequency absorption

Passive acoustic liners, used in aeronautic engine nacelles to reduce radiated fan noise, have a quarter-wavelength behavior. The simplest systems are SDOF-type (single degree of freedom), consisting of a perforated sheet backed with a honeycomb, whose absorption ability is limited to frequencies near the Helmholtz frequency. Thus, to widen the absorption frequency range, manufacturers use a 2DOF (double degree of freedom) system, with an internal layer over another honeycomb (stack of two resonators). However, one constraint is the limited thickness of the overall system, which reduces the space allotted to each honeycomb. A possible approach, based on a previous concept called LEONAR (long elastic open-neck acoustic resonator), could be to link each perforated layer to hollow tubes inserted in each honeycomb layer, in order to shift resonance frequencies to lower frequencies by extending the air column lengths. The presence of an empty chamber on both sides of the internal perforated layer also allows the tube length to be increased through tubes crossing both cavities, preserving the liner thickness. The main aim of this article is to mathematically describe the principle of a 2DOF LEONAR and to show the relevance of the mathematical model through FEM simulations and experiments performed in an impedance tube. Moreover, its behavior is analyzed through a parametric study, in order to explore its potential for an aeronautic application. A remarkable feature of 2DOF LEONAR-type materials with insertion of bottom tubes in the higher cavity is the possibility of maintaining the low frequency band provided by the original LEONAR concept, while adding a second absorption peak at a higher frequency, by the second layer and the accompanying tubes. There is a fundamental difference from classical SDOF/2DOF resonators, for which the thicknesses are obviously different.

Vicarious reward unblocks associative learning about novel cues in male rats.

Many species, including rats, are sensitive to social signals and their valuation is important in social learning. Here we introduce a task that investigates if mutual reward delivery in male rats can drive associative learning. We found that when actor rats have fully learned a stimulus-self-reward association, adding a cue that predicted additional reward to a partner unblocked associative learning about this cue. By contrast, additional cues that did not predict partner reward remained blocked from acquiring positive associative value. Importantly, this social unblocking effect was still present when controlling for secondary reinforcement but absent when social information exchange was impeded, when mutual reward outcomes were disadvantageously unequal to the actor or when the added cue predicted reward delivery to an empty chamber. Taken together, these results suggest that mutual rewards can drive associative learning in rats and is dependent on vicariously experienced social and food-related cues.

Sensitivity optimisation of tuberculosis bioaerosol sampling.

Detection of Mycobacterium tuberculosis (Mtb) in patient-derived bioaerosol is a potential tool to measure source case infectiousness. However, current bioaerosol sampling approaches have reported low detection yields in sputum-positive TB cases. To increase the utility of bioaerosol sampling, we present advances in bioaerosol collection and Mtb identification that improve detection yields. A previously described Respiratory Aerosol Sampling Chamber (RASC) protocol, or "RASC-1", was modified to incorporate liquid collection of bioaerosol using a high-flow wet-walled cyclone (RASC-2). Individuals with GeneXpert-positive pulmonary TB were sampled pre-treatment over 60-minutes. Putative Mtb bacilli were detected in collected fluid by fluorescence microscopy utilising DMN-Trehalose. Exhaled air and bioaerosol volumes were estimated using continuous CO2 monitoring and airborne particle counting, respectively. Mtb capture was calculated per exhaled air volume sampled and bioaerosol volume for RASC-1 (n = 35) and for RASC-2 (n = 21). Empty chamber samples were collected between patients as controls. The optimised RASC-2 protocol sampled a median of 258.4L (IQR: 226.9-273.6) of exhaled air per patient compared with 27.5L (IQR: 23.6-30.3) for RASC-1 (p<0.0001). Bioaerosol volume collection was estimated at 2.3nL (IQR: 1.1-3.6) for RASC-2 compared with 0.08nL (IQR: 0.05-0.10) for RASC-1 (p<0.0001). The detection yield of viable Mtb improved from 43% (median 2 CFU, range: 1-14) to 95% (median 20.5 DMN-Trehalose positive bacilli, range: 2-155). These improvements represent a lowering of the limit of detection in the RASC-2 platform to 0.9 Mtb bacilli per 100L of exhaled air from 3.3 Mtb bacilli per 100L (RASC-1). This study demonstrates that technical improvements in particle collection together with sensitive detection enable rapid quantitation of viable Mtb in bioaerosols of sputum positive TB cases. Increased sampling sensitivity may allow future TB transmission studies to be extended to sputum-negative and subclinical individuals, and suggests the potential utility of bioaerosol measurement for rapid intervention in other airborne infectious diseases.

Diagnosis of Varroosis Based on Bee Brood Samples Testing with Use of Semiconductor Gas Sensors.

Varroosis is a dangerous and difficult to diagnose disease decimating bee colonies. The studies conducted sought answers on whether the electronic nose could become an effective tool for the efficient detection of this disease by examining sealed brood samples. The prototype of a multi-sensor recorder of gaseous sensor signals with a matrix of six semiconductor gas sensors TGS 823, TGS 826, TGS 832, TGS 2600, TGS 2602, and TGS 2603 from FIGARO was tested in this area. There were 42 objects belonging to 3 classes tested: 1st class—empty chamber (13 objects), 2nd class—fragments of combs containing brood sick with varroosis (19 objects), and 3rd class—fragments of combs containing healthy sealed brood (10 objects). The examination of a single object lasted 20 min, consisting of the exposure phase (10 min) and the sensor regeneration phase (10 min). The k-th nearest neighbors algorithm (kNN)—with default settings in RSES tool—was successfully used as the basic classifier. The basis of the analysis was the sensor reading value in 270 s with baseline correction. The multi-sensor MCA-8 gas sensor signal recorder has proved to be an effective tool in distinguishing between brood suffering from varroosis and healthy brood. The five-time cross-validation 2 test (5 × CV2 test) showed a global accuracy of 0.832 and a balanced accuracy of 0.834. Positive rate of the sick brood class was 0.92. In order to check the overall effectiveness of baseline correction in the examined context, we have carried out additional series of experiments—in multiple Monte Carlo Cross Validation model—using a set of classifiers with different metrics. We have tested a few variants of the kNN method, the Naïve Bayes classifier, and the weighted voting classifier. We have verified with statistical tests the thesis that the baseline correction significantly improves the level of classification. We also confirmed that it is enough to use the TGS2603 sensor in the examined context.

The Stage of the Estrus Cycle Is Critical for Interpretation of Female Mouse Social Interaction Behavior.

Female animals in biomedical research have traditionally been excluded from research studies due to the perceived added complexity caused by the estrus cycle. However, given the importance of sex differences in a variety of neurological disorders, testing female mice is critical to identifying sex-linked effects in diseases. To determine the susceptibility of simple behaviors to hormonal fluctuations in the estrus cycle, we studied the effects of sex and the estrus cycle on a variety of behavioral tasks commonly used in mouse phenotyping laboratories. Male and female C57BL/6J mice were tested in a small battery of short duration tests and, immediately on completion of each test, females were classified using cytology of vaginal lavages as sexually-receptive (proestrus and estrus) or non-receptive (NR; metestrus and diestrus). We showed that there was a significant difference in 3-chamber social interaction (SI) between female mice at different stages of their estrus cycle, with sexually-receptive mice showing no preferential interest in a novel female mouse compared with an empty chamber. NR female mice showed the same level of preference for a novel female mouse as male mice did for a novel male mouse. No differences between or within sexes were found for tests of anxiety elevated plus maze (EPM; Hole board), working memory [Novel object recognition (NOR)], and motor learning (repeated tests on rotarod). We conclude that the stage of the estrus cycle may impact SI between same-sex conspecifics, and does not impact performance in the elevated plus-maze, hole board, NOR, and rotarod.

Volatilization of ammonia from conventional sources of nitrogen and compacted urea under controlled conditions

Urea is the most used nitrogen fertilizer in tropical agriculture, but when applied to the soil surface, it can promote nitrogen (N) losses by volatilization of ammonia (NH3). The present study aimed to evaluate, under controlled laboratory conditions, the N-NH3 losses from conventional N sources and compacted urea . Fertilizers were applied on the surface of a eutrophic Red Latosol of clayey texture (Oxisol), previously moistened to 60% of its maximum water-retention capacity. Conduction of the experiment was in a completely randomized design with six replicates . The treatments were four N sources in doses equivalent to 100 kg ha-1 of N (urea, urea + N-(N-butyl) thiophosphoric triamide (NBPT), ammonium nitrate and urea compacted with additives and polymers), and the additional control groups (soil with no fertilizer and empty chamber). We evaluated the N-NH3 losses by volatilization for a period of 20 days with the aid of hermetically sealed chambers. The results demonstrated the importance of using compacted urea for reducing nitrogen losses via volatilization. These results suggest that choosing the N source can reduce its volatilization and thus improve the harnessing of N from the nitrogen fertilization, when performed with a urea basis.

Formaldehyde Vapor Characteristics in Varied Decontamination Environments

Introduction: This effort investigated formaldehyde vapor characteristics under various environmental conditions by the analyses of air samples collected over a time-course. This knowledge will help responders achieve desired formaldehyde exposure parameters for decontamination of affected spaces after a biological contamination incident. Methods: Prescribed masses of paraformaldehyde and formalin were sublimated or evaporated, respectively, to generate formaldehyde vapor. Adsorbent cartridges were used to collect air samples from the test chamber at predetermined times. A validated method was used to extract the cartridges and analyze for formaldehyde via liquid chromatography. In addition, material demand for the formaldehyde was evaluated by inclusion of arrays of Plexiglas panels in the test chamber to determine the impact of varied surface areas within the test chamber. Temperature was controlled with a circulating water bath connected to a radiator and fan inside the chamber. Relative humidity was controlled with humidity fixed-point salt solutions and water vapor generated from evaporated water. Results: Low temperature trials (approximately 10°C) resulted in decreased formaldehyde air concentrations throughout the 48-hour time-course when compared with formaldehyde concentrations in the ambient temperature trials (approximately 22°C). The addition of clear Plexiglas panels to increase the surface area of the test chamber interior resulted in appreciable decreases of formaldehyde air concentration when compared to an empty test chamber. Conclusion: This work has shown that environmental variables and surface-to-volume ratios in the decontaminated space may affect the availability of formaldehyde in the air and, therefore, may affect decontamination effectiveness.

Electroosmotically generated disinfectant from urine as a by-product of electricity in microbial fuel cell for the inactivation of pathogenic species

This work presents a small scale and low cost ceramic based microbial fuel cell, utilising human urine into electricity, while producing clean catholyte into an initially empty cathode chamber through the process of electro-osmostic drag. It is the first time that the catholyte obtained as a by-product of electricity generation from urine was transparent in colour and reached pH>13 with high ionic conductivity values. The catholyte was collected and used ex situ as a killing agent for the inactivation of a pathogenic species such as Salmonella typhimurium, using a luminometer assay. Results showed that the catholyte solutions were efficacious in the inactivation of the pathogen organism even when diluted up to 1:10, resulting in more than 5 log-fold reduction in 4 min. Long-term impact of the catholyte on the pathogen killing was evaluated by plating Salmonella typhimurium on agar plates and showed that the catholyte possesses a long-term killing efficacy and continued to inhibit pathogen growth for 10 days.

Numerical approximation of air flow, temperature distribution and thermal comfort in buildings

Thermal comfort is associated to air flow and temperature distributions in the ventilation system or air conditioning space. In this work, the principal goal is the analyzing of air flow,thermal comfort and the distribution of temperature in the chamber, using a commercial computational fluid dynamics package (ANSYS CFX 15). Calculations are performed in an empty chamber without any human or mechanical activity and the numerical results are compared and validated with measurement points. The comfort level was evaluated using the Air Diffusion PerformanceIndex, ADPI. The numerical results demonstrated that the simulations could precisely predict the temperature and air flow distribution in chamber space. Due the buoyancy effect,the air circulation and air velocity are maintained at high values and the temperature of 19 °C with velocity of 0.15 m.s − 1 gives the best EDT (Effective draft temperature) satisfy ASHRAE 55–210 criteria that V ≤ 0.35 m.s − 1 and Effective draft temperature ranges between -1.7 and 1.1.

Effects of hydrogen concentration, non-homogenous mixtures and obstacles on vented deflagrations of hydrogen-air mixtures in a 27 m3 chamber

Experimental data from vented hydrogen deflagrations with concentrations from 15% to 21% are presented. The experiments were performed in a 27 m3 cubic chamber with a vent area of either 0.78 or 1.76 m2. Uniform and stratified mixtures were used in the test matrix, and the obstacle configuration also varied to achieve different volumetric blockage ratios. The purpose of this study was to investigate the effect of hydrogen concentration, vent area, non-homogeneous mixtures and obstacles on the explosion venting for lean hydrogen-air mixtures, and to evaluate the performance of an analytical model for calculating the maximum reduced overpressure. The results show that the maximum overpressure measured inside the empty chamber increases from 3 kPa to 28.5 kPa as hydrogen concentration increases from 15.3% to 20.2%. The raised vent location may affect the pressure development during explosion venting, and a third pressure peak caused by the occurrence of the maximum flame surface area could appear in the pressure profile when a large vent is located on the upper part of the side wall. Higher volumetric blockage ratio leads to higher maximum overpressure and flame velocity, and the increment of each pressure peak with the blockage ratio is more pronounced for the back ignition. Furthermore, when comparing with the volume of unburnt gases, the obstacles have a greater effect on the flame. However, the obstructions have a limited effect on the non-homogenous hydrogen deflagration, whose combustion behaviour is governed by the maximum hydrogen concentration in the chamber. Molkov’ best-fit model over-predicts the maximum reduced overpressure measured inside the empty chamber, but the predictions are relatively acceptable for the center ignition.

Elucidating effects of component materials and flow fields on Sn–Fe hybrid flow battery performance

Component materials and flow fields are key design parameters that influence the advection-diffusion-reaction process and thereby the performance of a Sn–Fe hybrid flow battery. In this work, various electrode configurations (empty chamber and porous carbon-based electrodes), membranes (cation and anion conducting) and flow fields (serpentine and interdigitated) are systematically investigated to elucidate their effects on the unique charge/discharge behaviors of the Sn–Fe flow battery with tin metal plating/striping. It is found that the battery capacity roughly increases linearly with the porosity of the porous electrode especially at low current densities, and a highly porous electrode (graphite felt) is more desirable than an empty chamber configuration in terms of capacity and power density. In addition, as compared to cation exchange membrane (Nafion 212), the anion exchange membrane (Fumasep FAP-450) exhibits improved capacities and columbic efficiencies in sulfuric acid-based electrolytes at low current densities due to the reduction of cation crossover. Interestingly, it is showed that although a serpentine flow field and a low flow rate generally lead to poor battery performance, they tend to ameliorate the maldistribution of plated tin at the negative electrode owing to the restricted mass transfer of reactants.

An integrated and robust yolk–shell nanoreactor based on wrinkly silica microspheres loaded with Au nanoparticles and nested in a silica inverse opal

To construct secondary processes of multiscale architecturing, wrinkly silica microspheres (WSMs) are nested into the empty chamber of templated macroporous structure by using core–shell microspheres to self-assemble the colloidal crystal template and selectively removing the shells. It is a universal approach to form the binary inverse opal (IO) structures and maintain interconnected nanochannels. With gold nanoparticles loaded on the WSMs (denoted Au-WSMs@IO SiO2) in the meantime, it has been demonstrated by the reduction of 4-nitrophenol (4-NP) that the binary IO materials (Au-WSMs@IO SiO2) exhibited higher catalytic efficiency than simple nested microspheres (Au-WSMs) after recycling 15 times. Furthermore, it was nice to see it had excellent catalytic effect in the epoxidation of styrene. Owing to the outstanding catalytic activity, recyclability and mechanical stability of the binary IO materials, it will be a promising way to widely apply in heterogeneous catalysis.

Determining PM2.5 dry deposition velocity on plant leaves: An indirect experimental method

Trees and green spaces have been proved to play an important role in purifying urban atmospheric particulate matter and result to the overall improvement of air quality. However, a primary setback was the need for an accurate and easier method to measure the deposition velocity (Vd) of PM2.5 retained on plant leaves. This paper established an indirect method of measurement for determining Vd: the indirect method was derived from a closed system (smog chamber), and an exponential attenuation model was used to measure the decline in PM2.5 concentration under conditions caused by hanging leaves in the chamber, and an empty chamber without leaves, respectively. The value of Vd was thus calculated by fitting data to prevent inaccurate results caused by a single measurement error. The experimental conditions such as initial concentration, test duration, and time interval (Δt) were then determined from empirical observations. The equation showed that Vd could be determined only by measuring the attenuation rate constant, k, and the leaf area, LA. Although the particle size, tested tree species and some other experimental conditions may affect the determination results of Vd, the values of Vd tested by indirect method were still within scientifically acceptable range. Overall, along with the traditional wind tunnel method, the indirect measurement is considered as the complement for a less expensive and easier way to determine Vd, and offers a novel idea that Vd might be gained by attenuation equation, and can augment the choices for researchers to quantify the ability of retaining particles.