BALB/c小鼠的净化

应用剖腹产方法取得的BALB/c仔鼠，用SPF级KM小鼠代乳可做到净化。净化后的BALB/c小鼠，其保种群和扩大群经微生物监测均达到SPF级水平，其遗传特性未见改变。对净化后的BALB/c小鼠的1～5胎仔鼠的初生体重及离乳前的体重均属正常范围，各胎之间无明显差异。哺乳期的生长与初生体重之间无明显关系，而与母鼠的哺育能力有很大的关系。     

Aspiration Efficiency of IOM-Like Personal Aerosol Samplers from Experiments with a New Rapid Data Acquisition System

New automated instrumentation for the rapid acquisition of aerosol sampler aspiration efficiency data has been applied to an investigation of a range of personal aerosol samplers of the type developed during the 1980s at the Institute of Occupational Medicine (IOM) in Edinburgh, Scotland, U.K. The experimental research was carried out in a small wind tunnel, and the relation of the results for IOM-like samplers to full-scale life-size personal aerosol sampling scenarios—like those encountered in occupational aerosol exposure assessment—was investigated by reference to the scaling laws that have been developed based on familiar aerosol mechanics as they apply to the physics of aerosol sampling. In the small-scale experimental study, the IOM-like sampler was mounted centrally on a rectangular bluff body, simulating the wearing of the sampler on the body (e.g., as by a worker in an industrial setting). Scaling with respect to the corresponding, more-realistic full-scale system for a corresponding full-scale windspeed of 1.0 m/s was achieved by varying the inlet diameter, the windspeed and the sampling flowrate. The results for windspeeds in the scaled experiments of 1.5 m/s and lower were found to differ significantly from those for windspeeds of 2.0 m/s and higher. In particular, the measured aspiration efficiency values for the lower windspeeds were markedly higher than—and clearly not consistent with—the higher windspeed group of results. It is considered likely that such divergence may be associated with a characteristic of the small wind tunnel in which the experiments were conducted. However, the scaling laws developed were found to work well for windspeeds in the scaled experiments of 1.5 m/s and higher. The results confirm that the performance of the IOM personal inhalable aerosol sampler is in quite good general agreement with the inhalability criterion.     

Aerosol Deposition in the Vicinity of a Stagnation Point

A method is presented to compute the trajectories of aerosol particles in the vicinity of a stagnation point and thus to obtain their rates of deposition. According to this method a particle starts its motion on the initial streamline, moves from one streamline to another under the influence of inertia, and touches the collector surface while on the interceptional streamline. The method takes advantage of the fact that in stagnation flow close to the splitting streamline most of the changes take place in a small region of high streamline curvature. The method of singular perturbation analysis is applied to calculate the particle trajectory in this region. This paper considers small Stokes numbers for which the particles are shown to have a stopping distance equal to their Stokes number. The computation of the particle trajectories depends on the ratio of these stopping distances s to the radii of curvature of the fluid streamline r. For large and medium s/r ratios the trajectories exhibit boundary layer type behavior, while for small ratios no such behavior is seen. Two examples demonstrate the use of the present theory. The first is that of particle sedimentation in a fibrous filler. The second is the sedimentation of small particles in potential plane-stagnation flow. The results compare very favorably with available numerical or exact solutions.     

Aerosol Deposition in a Nasopharyngolaryngeal Replica of a 5-Year-Old Child

Particle deposition in a child's nasal cavity is much different than that in the nasal airway of an adult because of the differences in geometry and breathing patterns. However, most deposition studies have focused on adults, and only a limited number of studies have been reported in a child's nasal cavity. This study was conducted as an in vitro test and computational fluid dynamics (CFD) analysis of particle deposition in the nasal replica of a 5-year-old child; both total and regional depositions were evaluated. The geometry of the nasal replica was based on magnetic resonance images of the head of the child. The replica was made by a rapid-prototyping machine. Monodisperse oleic acid and polystyrene latex aerosols ranging in size between 1 and 20 μm were delivered into the replica at flow rates of 10 and 20 L/min. Results showed that the total deposition from the in vitro experiments and CFD predictions matched to a high degree. Good agreement was also obtained when results were compared to existing in vitro deposition data from children having comparable nasal geometries. For regional depositions, patterns between the replica and CFD data were similar in trend and magnitude for all four regions considered, although some regions deviated slightly. More tests in nasal replicas of different aged children will be carried out.

Copyright 2013 American Association for Aerosol Research     

Comparison of Voxel-Based and Mesh-Based CFD Models for Aerosol Deposition on Complex Fibrous Filters

Aerosols represent a health risk since small droplets may enter the respiratory system and cause lung cancer, allergies, or diseases like COVID-19. In this work, an Eulerian-Lagrangian computational fluid dynamics model is used based on a voxel-based (GeoDict) and a mesh-based (StarCCM+) code. For evaluating accuracy and computational time of both models, fractional filtration efficiency and pressure drop are compared to an empirical solution for a single fiber and to experimental results for a complex 3D fibrous filter material. Simulation results of both methods are in good agreement with empirical and measurement results although the complex geometry of the fibers is captured more accurately by the unstructured mesh using the same resolution. Computing times are much faster using the voxel-based code.     

Comparison and Combination of Aerosol Size Distributions Measured with a Low Pressure Impactor,Differential Mobility Particle Sizer,Electrical Aerosol Analyzer,and Aerodynamic Particle Sizer

Data from a different mobility particle sizer (DMPS) or an electrical aerosol analyzer (EAA) has been combined with data from an aerodynamic particle sizer (APS) and converted to obtain aerosol mass distribution parameters on a near real-time basis. A low pressure impactor (LPI), a direct and independent measure of this mass distribution, provided information for comparison.

The number distribution of particles within the electrical measurement range was obtained with the DMPS and EAA. Data from the APS for particles greater than that size were used to complete the number distribution. Two methods of obtaining mass distribution parameters from this number data were attempted. The first was to convert the number data, channel by channel, to mass data and then fit a log-normal function to this new mass distribution. The second method was to fit a log-normal function to the combined number distribution and then use the Hatch-Choate equations to obtain mass parameters.

Both the DMPS / APS and the EAA / APS systems were shown to successfully measure aerosol mass distribution as a function of aerodynamic diameter. Careful operation of the measurement equipment and proper data manipulation are necessary to achieve reliable results. A channel-by-channel conversion from number to mass distribution provided the best comparison to the LPI measurement. The DMPS / APS combination furnishes higher-size resolution and accuracy than the EAA / APS system. A small gap was observed in the EAA / APS combined data; however, this did not seem to adversely affect the determination of mass distribution parameters.     

Inertial Deposition of Aerosol Particles in a Periodic Row of Porous Cylinders

The aerosol flow through a periodic row of parallel porous cylinders is investigated. The air flow field outside the cylinders is described by the Navier–Stokes equations of viscous incompressible fluid. The extended Darcy–Brinkman equations are used to calculate the flow velocity inside a porous cylinder. The dependence of the efficiency of the deposition of aerosol particles by inertial impaction and interception on the Stokes number for various values of the Darcy number is studied. Comparison of the results obtained from the numerical model and an approximate analytical model is given. The combined approximate formula for the deposition efficiency of a cylindrical fiber in a parallel array proposed by Müller et al. (2014) is extended for the porous cylindrical fiber. The aerosol flow through the porous body composed by a random array of cylinders is calculated to estimate the interior deposition.

Copyright 2015 American Association for Aerosol Research     

Comparison of Particle Number Counts Measured with an Ink Jet Aerosol Generator and an Aerodynamic Particle Sizer

Aerodynamic particle sizer (APS) users typically calibrate the particle sizing capabilities, but not the counting efficiency upon which aerosol concentration results are based. Herein, comparisons were made between the counts provided by an ink jet aerosol generator (IJAG) with those measured by an APS. Near-monodisperse (geometric standard deviation of about 1.06) liquid or solid aerosols in the size range of 0.95 to 13.3 μm aerodynamic diameter (AD) generated with an IJAG were released into the inner inlet-tube of the APS in a manner that rendered APS wall and aspiration losses negligible. For most experiments, the IJAG generated 75 particles/s, which rate was maintained by the IJAG system through control of electrical pulses applied to its ink jet cartridge. For particles in the size range of 2–13.3 μm AD, the ratio of relative detection efficiency (ratio of the number of particles counted by the APS to the number reported as generated by the IJAG) was 99.3 ± 1.4%; however, for test particles between 0.95 and 2 μm AD, the relative detection efficiency was somewhat lower, but the drop off was less than about 2%. This slight drop off is likely associated with the light scattering detection approach and corresponding counting algorithm of the APS. Tests were conducted where the IJAG produced 7.0 μm AD particles at rates of 1 to 500 s^-1 and the results showed essentially a 1:1 correspondence between IJAG and APS counts. The presence of smaller-sized background particles did not affect the measured APS counts of larger-sized challenge particles.

Copyright 2014 American Association for Aerosol Research     

A DNS Study of Aerosol Deposition in a Turbulent Square Duct Flow

A particle-laden turbulent flow through a square duct was simulated using a direct numerical solution of the Navier-Stokes equations coupled with Langrangian particle tracking. Computations of particle transport were employed to elucidate the mechanisms by which particles with varying inertia deposit to the walls of a square duct. Gravity was neglected and a one-way coupling was assumed between the particles and the fluid. The computational results demonstrate that, although the aerosol penetration through a square duct is not significantly different than through a circular pipe, there exist differences in the transport and deposition mechanisms. Most notably, the off-axis secondary flows unique to the square duct preferentially deposit higher-inertia particles closer to the corners of the duct. By contrast, the same secondary flows act to suppress the deposition of lower-inertia particles to the duct corners by efficiently transporting them back towards the duct core before deposition can occur.     

Effect of Neferine on DNCB-Induced Atopic Dermatitis in HaCaT Cells and BALB/c Mice

Atopic dermatitis (AD) is a chronic and persistent inflammatory skin disease characterized by eczematous lesions and itching, and it has become a serious health problem. However, the common clinical treatments provide limited relief and are accompanied by adverse effects. Therefore, there is a need to develop novel and effective therapies to treat AD. Neferine is a small molecule compound isolated from the green embryo of the mature seeds of lotus (Nelumbo nucifera). It has a bisbenzylisoquinoline alkaloid structure. Relevant studies have shown that neferine has many pharmacological and biological activities, including anti-inflammatory, anti-thrombotic, and anti-diabetic activities. However, there are very few studies on neferine in the skin, especially the related effects on inflammatory skin diseases. In this study, we proved that it has the potential to be used in the treatment of atopic dermatitis. Through in vitro studies, we found that neferine inhibited the expression of cytokines and chemokines in TNF-α/IFN-γ-stimulated human keratinocyte (HaCaT) cells, and it reduced the phosphorylation of MAPK and the NF-κB signaling pathway. Through in vivo experiments, we used 2,4-dinitrochlorobenzene (DNCB) to induce atopic dermatitis-like skin inflammation in a mouse model. Our results show that neferine significantly decreased the skin barrier damage, scratching responses, and epidermal hyperplasia induced by DNCB. It significantly decreased transepidermal water loss (TEWL), erythema, blood flow, and ear thickness and increased surface skin hydration. Moreover, it also inhibited the expression of cytokines and the activation of signaling pathways. These results indicate that neferine has good potential as an alternative medicine for the treatment of atopic dermatitis or other skin-related inflammatory diseases.     

Seasonal Variation of Airborne Particle Deposition Efficiency in the Human Respiratory System

Particulate matter (PM) is associated with human health effects but the apparent toxicity of PM in epidemiological studies varies with season. PM toxicity may change due to seasonal shifts in composition or particle size distributions that in turn affect respiratory deposition efficiencies. In the current study, size-resolved PM composition was measured in the largest city (Fresno) in California's heavily polluted San Joaquin Valley during the summer (30 days) and winter (20 days) between 2006 and 2009 for 21 metals, organic carbon, elemental carbon, and 7 water-soluble ions. The Multiple-Path Particle Dosimetry model was applied to determine if seasonal variation in size-resolved composition influences respiratory deposition patterns. Mg, Al, S, V, Mn, Fe, Ni, Ba, SO₄ ^2-, Na⁺, and Ca²⁺ had larger total deposition efficiencies (p < 0.004) during the summer versus the winter in all three regions of the respiratory tract. This trend results from increased relative concentrations of the target analytes per μg m^?3 ambient PM_1.8 concentration and would be detected with routine PM_2.5 filter samples. V, Zn, Se, NO₃ ^-, SO₄ ^2-, and NH₄ ⁺ also experienced seasonal size distribution shifts that enhanced the specific deposition efficiency in the tracheobronchial and pulmonary regions during the summer months (p < 0.05). This enhanced deposition would not be detected by routine filter samples because all of the size distribution changes occur at particle diameters <2.5 μm. This study demonstrates that changes to the particle size distributions (<2.5 μm) can enhance respiratory deposition efficiencies for trace metals and/or water-soluble ions and this may contribute to seasonal shifts in PM toxicity.     

Efficacy Comparison of LPA2 Antagonist H2L5186303 and Agonist GRI977143 on Ovalbumin-Induced Allergic Asthma in BALB/c Mice

Lysophosphatidic acid (LPA), an intercellular lipid mediator, is increased in the bronchoalveolar fluids of patients with asthma after allergen exposure. LPA administration exaggerates allergic responses, and the type 2 LPA receptor (LPA₂) has been reported as a therapeutic target for asthma. However, results with LPA₂ agonist and antagonist along with LPA₂ gene deficient mice have been controversial and contradictory. We compared the effects of LPA₂ antagonist (H2L5186303) and agonist (GRI977143) in a single experimental protocol of ovalbumin (OVA)-induced allergic asthma by treating drugs before antigen sensitization or challenge. H2L5186303 showed strong suppressive efficacy when administered before OVA sensitization and challenge, such as suppression of airway hyper responsiveness, inflammatory cytokine levels, mucin production, and eosinophil numbers. However, GRI977143 showed significant suppression when administered before an OVA challenge. Increases in eosinophil and lymphocyte counts in the bronchoalveolar lavage fluid, Th2 cytokine levels, inflammatory scores, and mucin production were differentially ameliorated by the two drugs. The results demonstrate the multiple roles of LPA₂ in asthmatic responses. We suggest that the development of LPA₂ antagonists would achieve better therapeutic efficacy against asthma than agonists.     

Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer

The size-dependent particle transmission efficiency of the aerodynamic lens system used in the Aerodyne Aerosol Mass Spectrometer (AMS) was investigated with computational fluid dynamics (CFD) calculations and experimental measurements. The CFD calculations revealed that the entire lens system, including the aerodynamic lens itself, the critical orifice which defines the operating lens pressure, and a valve assembly, needs to be considered. Previous calculations considered only the aerodynamic lens. The calculations also investigated the effect of operating the lens system at two different sampling pressures, 7.8 × 10⁴ Pa (585 torr) and 1.0 × 10⁵ Pa (760 torr). Experimental measurements of transmission efficiency were performed with size-selected diethyl hexyl sebacate (DEHS), NH₄NO₃, and NaNO₃ particles on three different AMS instruments at two different ambient sampling pressures (7.8 × 10⁴ Pa, 585 torr and 1.0 × 10⁵ Pa, 760 torr). Comparisons of the measurements and the calculations show qualitative agreement, but there are significant deviations which are as yet unexplained. On the small size end (30 nm to 150 nm vacuum aerodynamic diameter), the measured transmission efficiency is lower than predicted. On the large size end (> 350 nm vacuum aerodynamic diameter) the measured transmission efficiency is greater than predicted at 7.8 × 10⁴ Pa (585 torr) and in good agreement with the prediction at 1.0 × 10⁵ Pa (760 torr).     

Comparison of a Quadrupole and a Time-of-Flight Aerosol Mass Spectrometer during the Feldberg Aerosol Characterization Experiment 2004

The Feldberg Aerosol Characterization Experiment (FACE-2004) took place from July 13–August 4, 2004 at the Taunus Observatory on the “Kleiner Feldberg” (825 m a.m.s.l.) in Central Germany. The experiment included (amongst others) size-resolved chemical characterization of non-refractory aerosol components. One of the experiment's objectives was to better understand and to characterize recently developed aerosol measurement instrumentation by intercomparison with other co-located instruments. One of these instruments was the Aerodyne Time-of-Flight Aerosol Mass Spectrometer (ToF-AMS).

Here we compare the datasets obtained by the ToF-AMS with those obtained by the well-characterized co-located Quadrupole Aerosol Mass Spectrometer (Q-AMS). A good agreement between the recently developed ToF-AMS with the established Q-AMS is reported here for all species measured with the two instruments for a time period where both instruments operated under well-calibrated conditions. During measurements with reduced detector gain after a pump failure changed species concentrations were measured with the ToF-AMS that did not agree with those measured with the Q-AMS. These changes were different for the individual species and could be attributed to the influence of the ion detection threshold as was shown by model calculations.

For efficient and user-friendly processing of ToF-AMS raw data a data processing software package was developed. Since this is the first time this software was used for field data, it is described in some detail here.     

Design and Performance of a New Personal Aerosol Monitor

Three particle size fractions of airborne dust are defined in Euro pean and U.S. standards for health-related dust measurements at the workplace: the respirable, the thoracic, and the inhalable fraction. We developed a novel instrument for personal, time-resolved concentration monitoring and sampling of these three fractions. The instrument combines inertial classification, filter sam pling, and photometric aerosol detection. It consists of a two-stage virtual impactor (cut-off diameters of 4 and 10 mu m), three filters, and three light scattering photometers. The virtual impactor serves as a particle size classifier and a coarse particle concentrator. This enrichment compensates for the decreasing particle mass-based photometric sensitivity with increasing particle diameter. The optical sensors are calibrated in-situ via the mass concentrations obtained gravimetrically from the filter samples. The device operates at a flow rate of 3.1 l min. There is strong agreement between the experimentally determined particle size-dependent collection efficiencies and the definition curves of the corresponding dust fractions. The size dependence of the sensitivity of the inertial concentrator and photometric detection units follow the definition curves qualitatively. Exposure data were obtained for different workplace environments characterized by temporally and spatially highly fluctuating concentrations. The field measurements have shown that the instrument is practicable under rough industrial conditions and that it enables a more comprehensive and more realistic characterization of the individ ual exposure of workers to health-endangering dusts than was previously possible.     

The Deposition of Unattached Radon Progeny in a Tracheobronchial Cast as Measured with Iodine Vapor

ABSTRACT

The deposition of the unattached radon progeny in hollow cast models of the human tracheobronchial region was studied using iodine vapor. The experiments were conducted in a replicate cast whose inner surface was coated with NaOH impregnated charcoal powder. This coating can trap iodine molecules by converting iodine into iodide and iodate, so that the iodine gas molecules behave like particles and stick to the surface upon contact. The iodine vapor is selected as a surrogate of radon progeny because the effective diffusion coefficient of iodine vapor, 0.08 cm² s^?1, is close to the diffusivities of unattached radon progeny (0.03–0.07 cm² s^?1). Deposition experiments have been conducted under constant and cyclic inspiratory flow between 5 and 30 LPM. It was found that the deposition of iodine vapor under constant flow can be described by diffusion in laminar flow. The cyclic inspiratory flow pattern does not significantly change the total deposition in the tracheobronchial cast. This observation, combined with the enhanced particle deposition due to charge (Cohen et al., 1996) suggest that particle charge plays an important role in the deposition of submicron particles in human airways.     

Deposition Uniformity and Particle Size Distribution of Ambient Aerosol Collected with a Rotating Drum Impactor

Rotating drum impactors (RDI) are cascade type impactors used for size and time resolved aerosol sampling, mostly followed by spectrometric analysis of the deposited material. They are characterized by one rectangular nozzle per stage and are equipped with an automated stepping mechanism for the impaction wheels. An existing three-stage rotating drum impactor was modified, to obtain new midpoint cutoff diameters at 2.5 μm, 1 μm, and 0.1 μm, respectively. For RDI samples collected under ambient air conditions, information on the size-segregation and the spatial uniformity of the deposited particles are key factors for a reliable spectrometric analysis of the RDI deposits. Two aerodynamic particle sizers (APS) were used for the determination of the RDI size fractionation characteristics, using polydisperse laboratory room air as quasi-stable proxy for urban ambient air. This experimental approach was suitable for the scope of this study, but was subject to numerous boundary conditions that limit a general use. Aerodynamic stage penetration midpoint diameters were estimated to be 2.4 and 1.0 μm for the first two RDI stages. Additionally, the spatial uniformity and geometrical size distribution of the deposited aerosol were investigated using micro-focus synchrotron radiation X-ray fluorescence spectrometry (micro-SR-XRF) and transmission electron microscopy (TEM), respectively. The size distribution of the particles found on the TEM samples agreed well with the results from the APS experiments. The RDI deposits showed sufficient uniformity for subsequent spectrometric analysis, but in the 2.5–10 μm size range the particle area density was very low. All of the applied methods confirmed the theoretical cutoff values of the modified RDI and showed that compared to other cascade impactors, the determined stage penetration sharpness was rather broad for the individual impactor stages.     

Aerosol Deposition Measurements as a Function of Reynolds Number for Turbulent Flow in a Ninety-Degree Pipe Bend

An experimental and numerical investigation of the effect of the Reynolds number (Re) on the deposition of aerosol particles in a 90° pipe bend for turbulent flow was performed. Deposition fraction data were measured for a range of Stokes numbers (Stk) at different flow Re (10,250, 20,500, and 30,750) higher than those of most previous studies where Re was ?10,000. The data show good agreement with previous studies for Stk > 0.4, demonstrating that increased Re does not significantly alter the trend of deposition fraction with Stokes number (Stk) in this range. However, a noticeable increase in deposition was detected for 0.1 ? Stk ? 0.4. At Stk = 0.15, an increase in Re from 10,250 to 30,750 caused a factor of 2.6 increase in deposition fraction from 0.14 to 0.36. Numerical simulations were completed, using the Reynolds Averaged Navier-Stokes (RANS) equations with the Shear Stress Transport turbulence model. Modeling with inertial impaction only (i.e., neglecting turbulent dispersion), the results accurately reproduced the general trends seen in the experimental data; however, they failed to detect the Re effect at low Stk seen experimentally. The inclusion of turbulent particle tracking in the RANS simulation via an eddy interaction model did not improve the results. However, an analytical analysis of the particle tracking equation drawing data from the numerical results, showed that the experimentally observed effect of Re at low Stk can be attributed to damped particle response to velocity fluctuations at the eddy frequency scale.     

Inspiratory Deposition Efficiency of Ultrafine Particles in a Human Airway Bifurcation Model

The inspiratory deposition efficiency of ultrafine particles in a physiologically realistic bronchial airway bifurcation model, approximating the airway generation 3-4 juncture, was computed for different particle sizes, ranging from 1 to 500 nm, under three different flow conditions, representing resting to heavy exercise breathing conditions. For the smallest particle sizes, say between 1 and 10 nm, molecular diffusion is the primary deposition mechanism, as indicated by the inverse relationship with flow rate, except for the highest flow rate where the additional effect of convective diffusion has to be considered as well. For the larger particle sizes, say above 20 nm, the independence from particle size and dependence on flow rate suggests that convective diffusion plays the major role for ultrafine particle deposition in bifurcations. A semiempirical equation for the inspiratory deposition efficiency, m (D, Q), as a function of diffusion coefficient D and flow rate Q, due to the combined effect of molecular and convective diffusion was derived by fitting the numerical data. The very existence of a mixed term demonstrates that molecular and convective diffusion are not statistically independent from each other.