High Particle Number Research Articles

Effects of direct hydrogen injection on particle number emissions from a lean burn gasoline engine

A new type of hardware configuration is proposed with direct hydrogen injection combined with gasoline port injection. Different fractions of hydrogen blending were tested under steady-state operating conditions. Independent parameter sweeps were conducted for excess air ratio (λ), ignition timing, and hydrogen fraction. The high laminar burning velocity of the hydrogen caused particle emissions to be insensitive to the ignition timing. With air–fuel mixing at λ = 1.1, the number of nucleation particles decreased and the number of accumulation particles increased with increasing hydrogen fraction, indicating that the temperature affected coagulation more greatly than pyrolysis. With mixing under ultra-lean conditions (λ = 1.2, 1.3, and 1.4), variation of the hydrogen fraction slightly affected the particle number, showing that the critical value for producing particles is the C/O ratio, not the whole mixture equivalence ratio. The decrease of total particle number with increasing λ indicates that this new hardware configuration can take the advantages of lean combustion and avoid the problem of high particle number which is generally associated with this kind of spark-ignition direct-injection engine.

A resampling method for parallel particle filter architectures

Particle filters are able to represent multi-modal beliefs but require a large number of particles in order to do so. The particle filter consists of three sequential steps: the sampling, the importance factor, and the resampling step. Each step processes every particle in oder to acquire the final state estimation. A high number of particles leads to a high processing time, thus reducing the particle filters usefulness for real-time embedded systems. Through parallelization, the processing time can be significantly reduced. However, the resampling step is not easily parallelizable since it requires the importance factor of each particle. In this work, a resampling scheme is proposed which uses virtual particles to solve the parallelization problem of the resampling component. Besides evaluating its performance against the multinomial resampling scheme, it is also implemented on a Xilinx Zynq-7000 FPGA.

Nanotechnology and its role in agro-ecosystem: a strategic perspective

The technology based upon the smallest possible particles is known as nanotechnology. It involves the production, manipulation and application of materials ranging in size from less than a micron to that of individual atoms. The reactivity and absorption level of nanomaterial is more than bulk material due to large surface area and high particle number per unit mass. While metal nanoparticles are being increasingly used in many sectors of the economy, there is growing interest to find out the best biological and environmentally safe methods for their production. The basic methods for nanoparticles production are chemical and physical approaches, whereas plant extract and different microorganisms have been actively pursued in recent years as an alternative method. The application of nanotechnology in agriculture system will completely revolutionize it. This technology includes different tools for disease treatment and detection and can be used as sensors, fertilizers and smart delivery system in gene transfer. The other side of this technology cannot be neglected because its application on the large scale has potential adverse effects on biological and other systems. So, the present review gives the whole idea about different approaches of nanoparticles production and its positive and negative repercussions, particularly on agricultural ecosystem. There is also a need to predict its effects on other environmental issues in near future.

A box-particle implementation of standard PHD filter for extended target tracking

This paper presents a box-particle implementation of the standard probability hypothesis density (PHD) filter for extended target tracking, called the extended target box-particle PHD (ET-Box-PHD) filter. The proposed filter can dynamically track multiple extended targets and estimate the unknown number of extended targets, in the presence of clutter measurements, false alarms and missed detections, where the extended targets are described as a Poisson model developed by Gilholm et al. To get the PHD recursion of the ET-Box-PHD filter, a suitable cell likelihood function for one given reliable partition is derived, and the main filter steps are presented along with the necessary box manipulations and approximations. The capabilities and limitations of the proposed ET-Box-PHD filter are illustrated both in linear simulation examples and in nonlinear ones. The simulation results show that the proposed ET-Box-PHD filter can effectively avoid the high number of particles and obviously reduce computational burden, compared to a particle implementation of the standard PHD filter for extended target tracking.

Climatological and radiative properties of midlatitude cirrus clouds derived by automatic evaluation of lidar measurements

Abstract. Cirrus, i.e., high, thin clouds that are fully glaciated, play an important role in the Earth's radiation budget as they interact with both long- and shortwave radiation and affect the water vapor budget of the upper troposphere and stratosphere. Here, we present a climatology of midlatitude cirrus clouds measured with the same type of ground-based lidar at three midlatitude research stations: at the Swiss high alpine Jungfraujoch station (3580 m a.s.l.), in Zürich (Switzerland, 510 m a.s.l.), and in Jülich (Germany, 100 m a.s.l.). The analysis is based on 13 000 h of measurements from 2010 to 2014. To automatically evaluate this extensive data set, we have developed the Fast LIdar Cirrus Algorithm (FLICA), which combines a pixel-based cloud-detection scheme with the classic lidar evaluation techniques. We find mean cirrus optical depths of 0.12 on Jungfraujoch and of 0.14 and 0.17 in Zürich and Jülich, respectively. Above Jungfraujoch, subvisible cirrus clouds (τ < 0.03) have been observed during 6 % of the observation time, whereas above Zürich and Jülich fewer clouds of that type were observed. Cirrus have been observed up to altitudes of 14.4 km a.s.l. above Jungfraujoch, whereas they have only been observed to about 1 km lower at the other stations. These features highlight the advantage of the high-altitude station Jungfraujoch, which is often in the free troposphere above the polluted boundary layer, thus enabling lidar measurements of thinner and higher clouds. In addition, the measurements suggest a change in cloud morphology at Jungfraujoch above ∼ 13 km, possibly because high particle number densities form in the observed cirrus clouds, when many ice crystals nucleate in the high supersaturations following rapid uplifts in lee waves above mountainous terrain. The retrieved optical properties are used as input for a radiative transfer model to estimate the net cloud radiative forcing, CRFNET, for the analyzed cirrus clouds. All cirrus detected here have a positive CRFNET. This confirms that these thin, high cirrus have a warming effect on the Earth's climate, whereas cooling clouds typically have cloud edges too low in altitude to satisfy the FLICA criterion of temperatures below −38 °C. We find CRFNET = 0.9 W m−2 for Jungfraujoch and 1.0 W m−2 (1.7 W m−2) for Zürich (Jülich). Further, we calculate that subvisible cirrus (τ < 0.03) contribute about 5 %, thin cirrus (0.03 < τ < 0.3) about 45 %, and opaque cirrus (0.3 < τ) about 50 % of the total cirrus radiative forcing.

Are viruses important in the plankton of highly turbid glacier-fed lakes?

Viruses are ubiquitous in aquatic ecosystems where they significantly contribute to microbial mortality. In glacier-fed turbid lakes, however, viruses not only encounter low host abundances, but also a high number of suspended mineral particles introduced by glacier meltwaters. We hypothesized that these particles potentially lead to unspecific adsorption and removal of free virus from the plankton, and thus significantly reduce their abundance in this type of lake. We followed the distribution of free virus-like particles (VLP) during the ice-free season across a turbidity gradient in four alpine lakes including one adjacent clear system where hydrological connectivity to the receding glacier is already lost. In the glacier-fed turbid lakes, VLP abundance increased with distance to the glacier, but the highest numbers were observed in the clear lake by the end of August, coinciding with the maximum in prokaryotic abundance. Our results suggest that viral loss by attachment to particles is less important than expected. Nevertheless, the relatively lower variability in VLP abundance and the lower virus-to-prokaryote ratio found in the turbid lakes than in the clear one point to a rather low temporal turnover and thus, to a reduced impact on microbial communities.

Assembly of citrate gold nanoparticles on hydrophilic monolayers

Self-assembled monolayers (SAMs) as model surfaces were linked onto planar gold films thorough lipoic acid or disulfide groups. The molecules used were polyethylene glycol (EG-S-S), N-[tris-(hydroxymethyl)methyl]acrylamide polymers with and without lipoic acid (Lipa-pTHMMAA and pTHMMAA) and a lipoic acid triazine derivative (Lipa-MF). All the layers, but Lipa-MF with a primary amino group were hydroxyl terminated. The layers were characterized by contact angle measurements and atomic force microscopy, AFM. Citrate stabilized nanoparticles, AuNPs in water and phosphate buffer were allowed to assemble on the layers for 10min and the binding was followed in real-time with surface plasmon resonance, SPR. The SPR resonance curves were observed to shift to higher angles and become increasingly damped, while also the peaks strongly broaden when large nanoparticles assembled on the surface. Both the angular shift and the damping of the curve was largest for nanoparticles assembling on the EG-S-S monolayer. High amounts of particles were also assembled on the pTHMMAA layer without the lipoic acid group, but the damping of the curve was considerably lower with a more even distribution of the particles. Topographical images confirmed that the highest number of particles were assembled on the polyethylene glycol monolayer. By increasing the interaction time more particles could be assembled on the surface.

Evaluating the Role of the Air-Solution Interface on the Mechanism of Subvisible Particle Formation Caused by Mechanical Agitation for an IgG1 mAb

Mechanical agitation of monoclonal antibody (mAb) solutions often leads to protein particle formation. In this study, various formulations of an immunoglobulin G (IgG) 1 mAb were subjected to different controlled interfacial stresses using a Langmuir trough, and protein particles formed at the interface and measured in bulk solution were characterized using atomic force microscopy and flow digital imaging. Results were compared to mAb solutions agitated in glass vials and unstressed controls. At lower pH, mAb solutions exhibited larger hysteresis in their surface pressure versus area isotherms and increased number of particles in bulk solution, when subjected to interfacial stresses. mAb samples subjected to 750-1000 interfacial compression-expansion cycles in 6 h contained high particle numbers in bulk solution, and displayed similar particulation trends when agitated in vials. At compression rates of 50 cycles in 6 h, however, particle levels in mAb solutions were comparable to unstressed controls, despite protein aggregates being present at the air-solution interface. These results suggest that while the air-solution interface serves as a nucleation site for initiating protein aggregation, the number of protein particles measured in bulk mAb solutions depends on the total number of compression cycles that proteins at the air-solution interface are subjected to within a fixed time.

Computational analysis of erosion in a radial inflow steam turbine

Abstract In the present work, the erosion of the blades of a radial inflow turbine due to the ingested steam flow containing solid particles was investigated in detail. The study has been conducted by designing and modeling the 3D geometry of the turbine using the CFturbo tool and by carrying out a series of CFD simulations using the software package ANSYS CFX 15.0. As compressibility effects may affect the output results, a study was conducted to ensure the validity of the incompressible flow assumption. Furthermore, the erosion simulation results indicated that there are three main surface areas where significant erosion occurs. The first and by far the most affected part of the studied radial steam turbine is the trailing edge of the stator blade, where a relatively huge number of particles with sharp angles strike the surface. This surface area is found to be affected by a concentration effect, where a high number of particles impinge on a small surface area continuously. The second but less affected part is the leading edge of the suction side of the rotor blade, where the particles strike the blade surface many times. The particles are trapped in a vortex area between the trailing edge of the stator blades and the leading edge of the rotor blades. The third surface area which is eroded significantly is the central region of the pressure side of the rotor blade. However, the blade erosion in this area is less than the other two areas. Additionally, the effects of several factors such as the rotor rotational speed, input mass flow and particle size on the erosion have been studied in detail. The relations between these factors and the erosion rate density have been determined.

The effects of vegetation barriers on near-road ultrafine particle number and carbon monoxide concentrations

Numerous studies have shown that people living in near-roadway communities (within 100m of the road) are exposed to high ultrafine particle (UFP) number concentrations, which may be associated with adverse health effects. Vegetation barriers have been shown to affect pollutant transport via particle deposition to leaves and altering the dispersion of emission plumes, which in turn would modify the exposure of near-roadway communities to traffic-related UFPs. In this study, both stationary (equipped with a Scanning Mobility Particle Sizer, SMPS) and mobile (equipped with Fast Mobility Particle Sizer, FMPS) measurements were conducted to investigate the effects of vegetation barriers on downwind UFP (particle diameters ranging from 14 to 102nm) concentrations at two sites in North Carolina, USA. One site had mainly deciduous vegetation while the other was primarily coniferous; both sites have a nearby open field without the vegetation barriers along the same stretch of limited access road, which served as a reference. During downwind conditions (traffic emissions transported towards the vegetation barrier) and when the wind speed was above or equal to 0.5m/s, field measurements indicated that vegetation barriers with full foliage reduced UFP and CO concentrations by 37.7–63.6% and 23.6–56.1%, respectively. When the test was repeated at the same sites during winter periods when deciduous foliage was reduced, the deciduous barrier during winter showed no significant change in UFP concentration before and after the barrier. Results from the stationary (using SMPS) and mobile (using FMPS) measurements for UFP total number concentrations generally agreed to within 20%.

Pathogen and Particle Associations in Wastewater: Significance and Implications for Treatment and Disinfection Processes.

Disinfection guidelines exist for pathogen inactivation in potable water and recycled water, but wastewater with high numbers of particles can be more difficult to disinfect, making compliance with the guidelines problematic. Disinfection guidelines specify that drinking water with turbidity ≥1 Nephelometric Turbidity Units (NTU) is not suitable for disinfection and therefore not fit for purpose. Treated wastewater typically has higher concentrations of particles (1–10 NTU for secondary treated effluent). Two processes widely used for disinfecting wastewater are chlorination and ultraviolet radiation. In both cases, particles in wastewater can interfere with disinfection and can significantly increase treatment costs by increasing operational expenditure (chemical demand, power consumption) or infrastructure costs by requiring additional treatment processes to achieve the required levels of pathogen inactivation. Many microorganisms (viruses, bacteria, protozoans) associate with particles, which can allow them to survive disinfection processes and cause a health hazard. Improved understanding of this association will enable development of cost-effective treatment, which will become increasingly important as indirect and direct potable reuse of wastewater becomes more widespread in both developed and developing countries. This review provides an overview of wastewater and associated treatment processes, the pathogens in wastewater, the nature of particles in wastewater and how they interact with pathogens, and how particles can impact disinfection processes.

Ambient PM2.5, Black Carbon, and Particle Size-Resolved Number Concentrations and the Ångström Exponent Value of Aerosols during the Firework Display at the Lantern Festival in Southern Taiwan

ABSTRACTThe Yanshui Beehive Firework Festival is a traditional folk activity in Southern Taiwan held during the Lantern Festival, and it is the third largest folk celebration in the world. During this festival, more than 200 firecracker towers with hundreds of thousands of firecrackers are ignited, posing a risk to public health because of an abrupt increase in particulate matter concentrations within a short period. In this study, real-time variations of PM2.5 (particles with an aerodynamic diameter less than or equal to 2.5 µm), black carbon (BC), and particle number concentrations were monitored before and during the firework display to understand the effect of the firework display on the short-term air quality. The hourly average concentrations of PM2.5, BC, total particle number, and ultrafine particle number during the firework display (episode period) were 146.9 µg m–3, 2639 ng m–3, 3.37 × 104 # cm–3, and 1.18 × 104 # cm–3, respectively. These values were 6.9, 2.3, 5.9, and 3.7 times greater than those during the same period on reference days (nonepisode period), respectively. The measured ultraviolet BC (UVBC) and BC concentrations indicated that aerosols were bound with ultraviolet-absorbing organic compounds, which were abundant, during the episode period. BC aerosols during the episode originated from vehicular traffic and firecracker burning, and the absorption Angstrom exponent value was 1.4. The particle number size distribution during the episode period showed a major accumulation mode and a minor Aitken mode of 180 and 63 nm, respectively. This particle number size distribution pattern was considerably different from that in the nonepisode period. During the episode period, particle coagulation played a crucial role in removing particles in the nucleation and Aitken modes in the ambient air at high particle number concentrations.

Development of DEM–CFD Simulation of Combustion Flow in Incinerator with the Representative Particle Model

A simulation code based on the discrete element method (DEM) and computational fluid dynamics (CFD) coupling model was developed to simulate the behavior of radioactive cesium in waste incinerators. The waste lump was represented by particles in the simulation. The energy equation for a mixed gas, diffusion equation for each gas component, as well as the energy, drying, pyrolysis, and combustion equations for each particle were solved in the simulation by adding a combustion model to the standard DEM–CFD coupling model. The particle size of the waste changed as drying, pyrolysis, and combustion progressed. At the end of the combustion process, particle waste became ash, and the number of ash particles was enormous. To avoid an excessive computational load due to the high particle number, a similar assembly model was adopted to reduce the particle number in the calculation. There was a good agreement between the simulation and experimental results for the temperature at the outlet of the furnace and the flue gas composition.

Counting-Based Particle Flux Estimation for Traffic Analysis in Live Cell Imaging

A quantitative analysis of the dynamic contents in fluorescence time-lapse microscopy is crucial to decipher the molecular mechanisms involved in cell functions. In this paper, we propose an original traffic analysis approach based on the counting of particles from frame to frame. The suggested method lies between individual object tracking and dense motion estimation (i.e., optical flow). Instead of tracking each moving particle, we estimate fluxes of particles between predefined and adjacent regions. The problem is formulated as the minimization of a global cost function and the approach allows us to process image sequences with a high number of particles and a high rate of particle appearances and disappearances. We propose to study the influence of object density, image partition scale, motion amplitude, and particle appearances/disappearances in a large variety of simulations. The potential of the method is finally demonstrated on real image sequences showing GFP-tagged Rab6 trafficking in confocal microscopy.

Characterization and micromechanical modelling of microstructural heterogeneity effects on ductile fracture of 6xxx aluminium alloys

Ductile failure of three 6xxx serie aluminium alloys has been characterized and modelled for about thirty hardening conditions each. These alloys involve relatively similar composition and volume fraction of second phase particles. The tensile mechanical properties show the expected decrease of fracture strain with increasing strength but also major differences among the different alloys with a factor ten in terms of reduction of area at fracture between best and worst case. The origin of these differences is unraveled by detailed characterization of the void nucleation, growth and coalescence process involving in situ 3D microtomography. A cellular automaton model, involving a high number of particles with distributions of position, sizes and void nucleation stress is developed to predict the fracture strain. Excellent predictions are obtained based on the same unique nucleation stress distribution versus particle size for the three alloys. The key element setting the fracture strain is the effect of particle size distribution and spatial distribution on the void nucleation and coalescence processes. The dependence of ductility on strength is properly captured as well.

Internal Combustion Engines as the Main Source of Ultrafine Particles in Residential Neighborhoods: Field Measurements in the Czech Republic

Ultrafine particles (UFP, diameter < 100 nm) exposure has already been associated with adverse effects on human health. Spatial distribution of UFP is non-uniform; they concentrate in the vicinity of the source, e.g. traffic, because of their short lifespan. This work investigates spatial distribution of UFP in three areas in the Czech Republic with different traffic load: High traffic (Prague neighborhood—Sporilov), commuter road vicinity (Libeznice), and a small city with only local traffic (Celakovice). Size-resolved measurements of particles in the 5–500 nm range were taken with a particle classifier mounted, along with batteries, GPS and other accessories, on a handcart and pushed around the areas, making one-minute or longer stops at places of interest. Concentrations along main roads were elevated in comparison with places farther from the road; this pattern was observed in all sites, while particle number distributions both close and away from main roads had similar patterns. The absence of larger particles, the relative absence of higher concentrations of particles away from the main roads, and similar number distributions suggest that high particle number concentrations cannot be readily attributed to sources other than internal combustion engines in vehicles and mobile machinery (i.e., mowers and construction machines).

Effect of the Ti, Al Contents on the Inclusion Characteristics in Steels with TiO2 and TiN Particle Additions

The effect of the Ti, Al contents on the metamorphic evolution of inclusions of Ti–Al complex oxides including TiN and MnS are investigated in common carbon steels with TiO2 and TiN particle additions. The study is carried out based on both SEM‐EDS analyses and Thermo‐Calc equilibrium calculations. Moreover, the particle size distributions are investigated by using the electrolytic extraction method. Based on the results of this study, the following is suggested: (i) the steel composition is controlled to contain small amount of the Al content (<0.005 mass%) and large amount of the Ti content (>0.035 mass%) in order to obtain a high number of fine particles containing a Ti‐rich oxide phase when adding TiO2 and TiN particles; (ii) this consideration is reasonable from the view point of the agglomeration degree of different inclusion materials, which are estimated from the attractive force (van der Waals force and liquid‐capillary force) and the contact angle.

Atmospheric extinction in solar tower plants: absorption and broadband correction for MOR measurements

Abstract. Losses of reflected Direct Normal Irradiance due to atmospheric extinction in concentrated solar tower plants can vary significantly with site and time. The losses of the direct normal irradiance between the heliostat field and receiver in a solar tower plant are mainly caused by atmospheric scattering and absorption by aerosol and water vapor concentration in the atmospheric boundary layer. Due to a high aerosol particle number, radiation losses can be significantly larger in desert environments compared to the standard atmospheric conditions which are usually considered in ray-tracing or plant optimization tools. Information about on-site atmospheric extinction is only rarely available. To measure these radiation losses, two different commercially available instruments were tested, and more than 19 months of measurements were collected and compared at the Plataforma Solar de Almería. Both instruments are primarily used to determine the meteorological optical range (MOR). The Vaisala FS11 scatterometer is based on a monochromatic near-infrared light source emission and measures the strength of scattering processes in a small air volume mainly caused by aerosol particles. The Optec LPV4 long-path visibility transmissometer determines the monochromatic attenuation between a light-emitting diode (LED) light source at 532 nm and a receiver and therefore also accounts for absorption processes. As the broadband solar attenuation is of interest for solar resource assessment for concentrated solar power (CSP), a correction procedure for these two instruments is developed and tested. This procedure includes a spectral correction of both instruments from monochromatic to broadband attenuation. That means the attenuation is corrected for the time-dependent solar spectrum which is reflected by the collector. Further, an absorption correction for the Vaisala FS11 scatterometer is implemented. To optimize the absorption and broadband correction (ABC) procedure, additional measurement input of a nearby sun photometer is used to enhance on-site atmospheric assumptions for description of the atmosphere in the algorithm. Comparing both uncorrected and spectral- and absorption-corrected extinction data from 1-year measurements at the Plataforma Solar de Almería, the mean difference between the scatterometer and the transmissometer is reduced from 4.4 to 0.57 %. Applying the ABC procedure without the usage of additional input data from a sun photometer still reduces the difference between both sensors to about 0.8 %. Applying an expert guess assuming a standard aerosol profile for continental regions instead of additional sun photometer input results in a mean difference of 0.8 %. Additionally, a simulation approach which just uses sun photometer and common meteorological data to determine the on-site atmospheric extinction at surface is presented and corrected FS11 and LPV4 measurements are validated with the simulation results. For T1 km equal to 0.9 and a 10 min time resolution, an uncertainty analysis showed that an absolute uncertainty of about 0.038 is expected for the FS11 and about 0.057 for the LPV4. Combining both uncertainties results in an overall absolute uncertainty of 0.068 which justifies quite well the mean RMSE between both corrected data sets. For yearly averages several error influences average out and absolute uncertainties of 0.020 and 0.054 can be expected for the FS11 and the LPV4, respectively. Therefore, applying this new correction method, both instruments can now be utilized to sufficiently accurately determine the solar broadband extinction in tower plants.

Evaluation of the time-resolved nanoparticle emissions and the vehicle performance characteristics for a turbocharged gasoline direct-injection vehicle with a metal-foam gasoline particulate filter

The nanoparticle emissions from gasoline direct-injection engines are of concern because of the high particle number concentrations compared with those from a gasoline port fuel injection engine. A gasoline particulate filter is a potential solution for reducing the particulate matter emissions. In this study, a 2.0 l turbocharged gasoline direct-injection vehicle with a metal-foam-type gasoline particulate filter was tested using the New European Driving Cycle and steady vehicle operating conditions. The particle number concentration, the particle-size distribution and the filtration efficiency were determined using a condensation particle counter and a fast response differential mobility spectrometer (DMS500). The particle number emissions (particle numbers per vehicle travelling distance (particles/km)) over the New European Driving Cycle were 1.95 × 1012 particles/km for a base vehicle equipped with a three-way catalytic converter and 5.68 × 1011 particles/km for the additional installation of a gasoline particulate filter on the base gasoline direct-injection vehicle. The filtration efficiency of the particle number and the particulate matter mass reached approximately 71% and 67% respectively. The nucleation-mode particles in the size range less than 23 nm for the gasoline direct-injection vehicle equipped with a three-way catalytic converter were further reduced on installation of a gasoline particulate filter at the downstream position of the three-way catalytic converter. A sharp pressure drop between the gasoline particulate filter of 21.0 mbar was obtained at a vehicle speed of 120 km/h in the New European Driving Cycle. The exhaust gas temperature before the gasoline particulate filter reached around 380–610 °C at steady vehicle speeds of 60–120 km/h. The installation of the gasoline particulate filter has the potential to satisfy the Euro 6c particle number emissions regulations for light-duty gasoline direct-injection vehicles.

Highly delayed systemic translocation of aluminum-based adjuvant in CD1 mice following intramuscular injections

Concerns regarding vaccine safety have emerged following reports of potential adverse events in both humans and animals. In the present study, alum, alum-containing vaccine and alum adjuvant tagged with fluorescent nanodiamonds were used to evaluate i) the persistence time at the injection site, ii) the translocation of alum from the injection site to lymphoid organs, and iii) the behavior of adult CD1 mice following intramuscular injection of alum (400μgAl/kg). Results showed for the first time a strikingly delayed systemic translocation of adjuvant particles. Alum-induced granuloma remained for a very long time in the injected muscle despite progressive shrinkage from day 45 to day 270. Concomitantly, a markedly delayed translocation of alum to the draining lymph nodes, major at day 270 endpoint, was observed. Translocation to the spleen was similarly delayed (highest number of particles at day 270). In contrast to C57BL/6J mice, no brain translocation of alum was observed by day 270 in CD1 mice. Consistently neither increase of Al cerebral content, nor behavioral changes were observed. On the basis of previous reports showing alum neurotoxic effects in CD1 mice, an additional experiment was done, and showed early brain translocation at day 45 of alum injected subcutaneously at 200μgAl/kg. This study confirms the striking biopersistence of alum. It points out an unexpectedly delayed diffusion of the adjuvant in lymph nodes and spleen of CD1 mice, and suggests the importance of mouse strain, route of administration, and doses, for future studies focusing on the potential toxic effects of aluminum-based adjuvants.