Retention Time Of Particles Research Articles

Particle size of straw and gelation of pectin influence gastric mixing and emptying in pigs

Physicochemical properties of fibres can strongly impact gastric processes such as emptying and sieving. This study evaluated the influence of particle size of insoluble fibres, and gelation of soluble fibres when added to insoluble fibres, on gastric emptying of digesta phases from the proximal and distal stomach of pigs. Twenty-four boars (51.6 ± 4.90 kg) were assigned to one of four diets, containing either 150 g/kg coarse or finely milled wheat straw (median particle area of 5.4 vs 0.3 mm2), or 270 g/kg wheat bran without or with the addition of 100 g/kg low-methylated pectin. Tracers were used to quantify the mean retention time (MRT) of digesta liquids (Co-EDTA), fine solids (TiO2), and fibrous particles (Chromium-mordanted fibres). For all diets, digesta pH was lower in the distal stomach than in the proximal stomach (−1.1–2.1 units; P < 0.05). In the proximal stomach, particle size reduction of straw tended to decrease digesta pH (−0.8 units; P = 0.072), reduced the MRT of fine solids (−117 min; P = 0.009) and the separation between fine solids and liquids (−88 min; P = 0.030). When particle size of straw was reduced, the MRT of liquids was no longer greater in the proximal stomach compared with the distal stomach (P > 0.10), while in both regions, the MRT of fibrous particles (−213 – 238 min; P < 0.05) and the difference between fibrous particles and fine solids were reduced (−96 – 181 min; P < 0.05). Accordingly, sieving of nutrients, such as starch and non-starch polysaccharides was reduced. In the proximal stomach, the greater water holding capacity and resistance to deformation conferred by the addition of pectin decreased the MRT of fine solids (−138 min; P = 0.003), and fibrous particles (−227 min; P < 0.001), reducing the difference between fine solids and liquids (−148 min; P < 0.001), and between fibrous particles and fine solids (−89 min; P < 0.001). In the distal stomach, pectin addition reduced the MRT of fibrous particles (−203 min; P = 0.007), and the difference between fibrous particles and fine solids (−154 min; P < 0.001). Concomitantly, sieving of nutrients across stomach regions was reduced. In conclusion, particle size reduction of straw and pectin addition accelerated the emptying of fine and coarse solids, and reduced sieving of digesta phases and nutrients in the proximal and distal stomach of pigs.

Experimental study on decarburization of fine fly ash by electric separation

ABSTRACT The effect of rotary triboelectric separation parameters on decarburization of fly ash was systematically studied to prove that the technology was an effective means to purify fly ash. The results showed that obvious mismatch of carbon particles occurs when separation voltage was greater than 25 kV, while mismatch of other mineral particles was generated when separation voltage was greater than 30kV; The decarburization effect of fly ash could be significantly reduced due to the decrease of particle surface charge density when the feed frequency was greater than 20 hz. The feed was also affected by the speed and direction of the particle feed, the closer to the middle of the feed port, the higher the probability of the particle being effectively separated; when rotation speed of the friction wheel exceeded 4000 r/min, the particle mismatch in the separation chamber becomes more and more obvious. In addition, the speed of the friction wheel also affected flow field in separation chamber, which may have an adverse effect on separation effect; Co-flow velocity affected retention time of particles in the separation chamber. 6 m/s is the best co-flow velocity for fly ash decarburization. In this case, the flow field generated by the co-flow is uniform to ensure stable transport of particles.

The effect of size and density on the mean retention time of particles in reindeer (Rangifer tarandus)

Particle passage from the reticulorumen (RR) depends on particle density and size. A classic way of assessing these effects is the use of plastic markers of varying density and size that are recovered in the faeces. Here, we report results of an experiment where four fistulated reindeer (Rangifer tarandus, 96 ± 12 kg) were fed two different diets (browse, voluntary dry matter intake [DMI] 70 ± 10 g/kg0.75/d; or a pelleted diet, DMI 124 ± 52 g/kg0.75/d) and dosed via fistula with 8 different particle types combining densities of 1.03, 1.22 and 1.44 g/ml and sizes of 1, 10 and 20 mm. Generally, particles that passed the digestive tract intact (not ruminated) did so relatively early after marker dosing, and therefore had shorter mean retention times (MRT) than ruminated particles. On the higher intake, the overall mean retention time (MRT) of particles was shorter, but this was not an effect of shorter MRT for either intact or ruminated particles, but due to a higher proportion of intact particles at the higher intake. This supports the concept that ruminants do not adjust chewing behaviour depending on intake, but that a lower proportion of digesta is submitted to rumination due to pressure-driven escape from the forestomach at higher gut fills. Compared to cattle (Bos primigenius taurus), muskoxen (Ovibos moschatus) and moose (Alces alces) that had received the same markers, reindeer had a lower proportion of 1 mm particles that passed intact. Our results support the concept that the critical size threshold for particles leaving the ruminant forestomach is dependent on body size. While the results likely do not represent findings peculiar for reindeer, they indicate fundamental mechanisms operating in the forestomach of ruminants.

Motion characteristics and residence time of particles in the new cross structure under constant-pulse condition

The residence time of particles in the flow field is highly sensitive to the fluid’s flow characteristics and the particles’ motion. We proposed a dynamic entry mode with the constant-pulse (CP) condition in response to the conditions of symmetric impinging streams and asymmetric impinging streams. Single-particle motion behaviors and particle residence time in a novel cross-type structure reactor we designed were studied and discussed in this article. This was done by looking at how these variables changed depending on the impulse inlet velocity conditions, the reactor geometry, and the particle properties. The results demonstrate that when particle relaxation time is short, those particles without oscillatory motions were directly accelerated to leave the active area. When its relaxation time is reasonably set, even a single particle can hugely elevate the oscillatory motions. With the structure of the novel cross type, the particle merely exhibits three oscillatory under the condition of the symmetric pulse inlet flow and asymmetric pulse inlet flow, notwithstanding, CP contains at least three oscillatory motions. The t tot is the duration that an individual particle spends in the working region. The t tot and active area were affected by inlet velocity, parameters of particles and the shape of the reactor parameters of particles and the shape of the reactor. The t tot raised with τ* increased in a certain range. T is the inlet velocity variation period. The particle resides time at T = T b reaches a maximum in the CP. The maximum residence times T b was affected by particle relaxation time, under CP with a diameter ratio of 5 and inlet velocity difference of 0.8. The particle retention time in the novel cross-type structure reactor was heightened by 7 times. The CP and the novel cross-type structure reactor can improve the retention time of particles in the flow field.

Gastric emptying performance of stomach-partitioning gastrojejunostomy versus conventional gastrojejunostomy for treating gastric outlet obstruction: A retrospective clinical and numerical simulation study.

Purpose: This study evaluated the gastric emptying performance of stomach-partitioning gastrojejunostomy (SPGJ) versus conventional gastrojejunostomy (CGJ) for treating gastric outlet obstruction (GOO). Methods: First, 73 patients who underwent SPGJ (n = 48) or CGJ (n = 25) were involved. Surgical outcomes, postoperative recovery of gastrointestinal function, delayed gastric emptying, and nutritional status of both groups were compared. Second, a three-dimensional stomach model was constructed based on the gastric filling CT images from a GOO patient with a standard stature. The present study evaluated SPGJ numerically by comparing it with CGJ in terms of local flow parameters such as flow velocity, pressure, particle retention time, and particle retention velocity. Results: Clinical data found that SPGJ had significant advantages over CGJ in terms of time to pass gas (3 versus 4days, p < 0.001), time to oral intake (3 versus 4days, p = 0.001), postoperative hospitalization (7 versus 9days, p < 0.001), the incidence of delay gastric emptying (DGE) (2.1% versus 36%, p < 0.001), DGE grading (p < 0.001), and complications (p < 0.001) for GOO patients. Moreover, numerical simulation revealed that the SPGJ model would induce contents in stomach discharge to the anastomosis at a higher speed, and only 5% of that flowed to the pylorus. SPGJ model also had a low-pressure drop as the flow from the lower esophagus to the jejunum, reducing the resistance to food discharge. Besides, the average retention time of particles in the CGJ model is 1.5 times longer than that in the SPGJ models, and the average instantaneous velocity in CGJ and SPGJ models are 22mm/s and 29mm/s, respectively. Conclusion: Compared with CGJ, patients after SPGJ had better gastric emptying performance and better postoperative clinical efficacy. Therefore, we think that SPGJ may be a better option for treating GOO.

Is there a difference in ruminal fermentation control between cattle and sheep? A meta-analytical test of a hypothesis on differential particle and fluid retention

Ruminant species differ in digestive physiology. The species-specific ratio of mean retention time of particles and fluid (MRTparticle/MRTfluid) in the reticulorumen has been interpreted as controlling ruminal fermentation: a higher ratio indicates of a more distinct ‘washing’ of particulate digesta by liquid. This should increase the harvest of microbes from the reticulorumen, and keep the microbiome in a state of more intense growth; at the same time, this should increase the metabolic losses of faecal nitrogen of microbial origin, leading to lower values for the apparent digestibility of crude protein (aD CP). A systematic difference has been hypothesized between cattle (higher ratio) and sheep (lower ratio), with a lower MRTfluid in cattle due to a higher saliva production. Here, we test these hypotheses in a meta-analysis, using only studies that investigated cattle and sheep simultaneously. The datasets included 12 studies on MRT (of which 11 contained information on feed intake), yielding 102 (or 89) individual data; and 26 studies on protein digestibility (of which 18 contained information on intake), yielding 349 individual data. Cattle had a higher MRTparticle/MRTfluid (2.1) than sheep (1.7), mainly due to longer MRTparticle; only if body mass was included in the model, MRTfluid was significantly shorter in cattle in the larger MRT dataset (and tended to be shorter in the slightly smaller dataset). Cattle had a significantly lower aD CP than sheep, while there was no such difference in overall (dry or organic matter) digestibility. The dataset confirms a shift in fermentation strategy towards microbial production in cattle. While this has been suggested for ruminants in general, cattle appear particularly far on an evolutionary trajectory of maximizing microbial yield from the forestomach. The application of more specific digestive physiology data (like endogenous losses) gained from sheep to cattle should be done bearing these differences in mind.

Determination of running temperature in entrained flow gasifier in regard to coal ash melting thermal kinetic effects

The operating temperature of entrained flow gasifier is one of the important parameters to determine its gasification efficiency, which is empirically estimated by ash fusion temperatures (AFTs) in the industry. However, the measurements of AFTs in labs are conducted at a very low heating rate (5–10 °C/min) compared to industrial entrained flow gasifiers (several hundred °C/s). The melting behaviors of coal ash under such huge varied conditions are different due to thermo-kinetic effects. Here, the factors concerning coal ash melting thermo-kinetics including heating rate, particle size, and retention time are explored by AFTs analyzer, thermal mechanical analysis, in-situ hot stage microscope and differential scanning calorimetry. The results of the investigation demonstrated that ash particle size and retention time showed limited influence on ash fusion behavior, while the influence of heating rates can not be ignored. Furthermore, an Arrhenian-based regression model covering major thermo-kinetics was developed to quantitatively predict the running temperature. The developed model suggested using the temperature that shrinkage corresponds to 75% to extrapolate the running temperature. The model can help to determine the operating temperature of slagging gasifiers.

Simulation Experiment of Environmental Impact of Deep-Sea Mining: Response of Phytoplankton Community to Polymetallic Nodules and Sediment Enrichment in Surface Water.

In this paper, simulation experiments were conducted to study the response of phytoplankton biomass and community composition to the influence of polymetallic nodules and sediment at four stations in the western Pacific in 2021. Chlorophyll a, pico-phytoplankton cell abundance, and metal concentration were measured before and after 24 h of deck incubation. The results show that there were three different patterns of response, namely, restrained, stimulated, and unaffected patterns. The restrained pattern appeared in the filtered treatments at station Incub.01, and the stimulated pattern appeared in the unfiltered treatments at station Incub.02. The response of the phytoplankton was not detectable at stations Incub.03 and 04. Regardless, positive and negative responses were found in the dominant pico-phytoplankton group—Prochlorococcus—and with slight variation in Synechococcus. The concentration of manganese varied among the treatments compared to that of iron and other metals. The factors affecting the growth of the phytoplankton in this study were metal concentrations and turbidity. The phytoplankton biomass baseline may also have played an important role: the lower the biomass, the higher the growth rate. This study proved that deep-sea polymetallic nodule mining will have a specific impact on surface phytoplankton biomass, but turbidity and particle retention time could be important factors in mitigating the extent of the impact.

Polystyrene Microplastics Modulate the Toxicity of the Hydrophilic Insecticide Thiacloprid for Chironomid Larvae and Also Influence Their Burrowing Behavior

As there is still little knowledge of interactions between microplastics (MP) and hydrophilic compounds, we propose ways the toxicity of hydrophilic pesticides can be modulated by MP, when sorption can be excluded. Larvae of Chironomus riparius were exposed to thiacloprid (TH, 1 µg/L) and polystyrene microplastic particles (PS; &lt;50 µm; 150,000 and 1,000,000 particles/L) for 96 h, solely or in co-exposure. Burrowing behavior and mortality were observed. Larvae in treatments containing PS established themselves quicker in the sediment and kept the ability to rebury for a longer time compared to control and TH, respectively. While TH elevated the mortality, exposure to PS alone did not affect the survival of the larvae. In co-exposure of TH and PS, a concentration of 150,000 particles/L significantly reduced the toxicity of 1 µg/L TH after 96 h, an effect that was not observed at 1,000,000 particles/L. Therefore, we hypothesize that this modulation of the toxicity of TH eventually may have resulted from a combination of a ‘protective MP layer’ in the gut and a higher retention time of particles in larvae exposed to 150,000 particles/L than in those exposed to 1,000,000 particles/L due to the lower number of ingestible particles in the former.

High-Resolution Charge-Based Electrokinetic Separation of Almost Identical Microparticles

Well-established techniques, e.g., chromatography and capillary electrophoresis, are available for separating nanosized particles, such as proteins. However, similar techniques for separating micron-sized particles are still needed. Insulator-based electrokinetic (iEK) systems can achieve efficient microparticle separations by combining linear and nonlinear EK phenomena. Of particular interest are charge-based separations, which could be employed for separating similar microorganisms, such as bacterial cells of the same size, same genus, or same strain. Several groups have reported charge-based separations of microparticles where a zeta potential difference of at least 40 mV between the microparticles was required. The present work pushes the limit of the discriminatory capabilities of iEK systems by reporting the charged-based separation of two microparticles of the same size (5.1 μm), same shape, same substrate material, and with a small difference in particle zeta potentials of only 3.6 mV, which is less than 10% of the difference in previous studies. By building an accurate COMSOL Multiphysics model, which correctly accounts for dielectrophoresis and electrophoresis of the second kind, it was possible to identify the conditions to achieve this challenging separation. Furthermore, the COMSOL model allowed predicting particle retention times (tR,p) which were compared with experimental values (tR,e). The separations results had excellent reproducibility in terms of tR,e with variations of only 9% and 11% between repetitions. These findings demonstrate that, by following a robust protocol that involves modeling and experimental work, it is possible to discriminate between highly similar particles, with much smaller differences in electrical charge than previously reported.

Numerical simulation flow dynamics of an intracranial aneurysm.

Computational fluid dynamics provides a new method for the study of the blood flow characteristics of the formation and development of intracranial aneurysms. To compare blood flow characteristics between the healthy internal carotid artery and normal intracranial aneurysms. The internal carotid arteries were simulated to obtain hemodynamic parameters in one patient. The internal carotid artery associated with aneurysm presents low wall shear stress, high oscillatory shear index, and high particle retention time compared with the normal internal carotid artery. There are differences in blood flow between the normal internal carotid artery and intracranial aneurysm. The vortex of the aneurysm will produce turbulence, indicating that it is unstable, which results in the growth and rupture of the aneurysm.

Milk production, rumen function, and digestion in dairy cows fed diets differing in predominant forage and concentrate type

The objective was to determine the effect of dietary ratio of neutral detergent fibre (aNDFom) to starch within diets differing in grass to maize silage ratio on rumen function, diet digestion, serum haptoglobin, and production of lactating dairy cows. Four isonitrogenous diets were formulated with a forage to concentrate ratio of 50:50, with the forage proportion containing either a high or low ratio of grass silage to maize silage (82:18 [GS] or 18:82 [MS] on a dry matter [DM] basis, respectively) and the concentrates containing either a high (F) or low (S) aNDFom to starch ratio, giving 4 dietary ratios of aNDFom to starch. Diets were fed to 4 early lactation Holstein dairy cows in a 4 × 4 Latin square design with 28-d periods. Feed intake, eating behaviour, milk production and composition, total tract digestion, nitrogen (N) excretion, aNDFom passage rate and in-situ degradation, rumen pH, and serum haptoglobin were measured during the last week of each period. Cows fed the MS diets consumed 1.34 kg/d more DM (P = 0.047) and 2.38 kg/d more starch (P = 0.001) compared to GS diets and produced 2.46 kg/d more milk (P = 0.038). Milk fat concentration was higher (+2.88 g/kg) for cows fed GS diets compared to MS diets (P = 0.007), while cows fed S concentrates had a higher milk fat concentration (+1.8 g/kg) irrespective of forage source (P = 0.033). Digestibility of aNDFom was higher (+0.106 kg/kg) for GS diets than for MS diets (P = 0.004). Similarly, aNDFom digestibility was higher (+0.057 kg/kg) for F concentrates (P = 0.031). Rumen and total-tract particle retention times were higher (+11.9 and +9.1 h, respectively) for cows fed GS diets (P = 0.009 and P = 0.037, respectively). Milk N yield/N intake was higher for the MS diets versus GS diets (P = 0.045), due to a greater (+130 g/d) milk protein yield (P = 0.015). Cows fed the MS diets spent 187 min/d more with rumen pH below 5.8 compared to GS diets (P = 0.006). Serum haptoglobin concentration, a purported marker of gut inflammation, was 5.3 ng/ml higher for cows fed S concentrates versus F concentrates (P = 0.023). In conclusion, changes in concentrate aNDFom:starch ratio had little effect on DM intake, milk yield and composition, rumen function, and eating behaviour compared to effects of silage source (MS vs GS), where replacing a portion of diet GS with MS increased feed intake, milk yield, rumen passage rate, and N digestion, but also reduced fibre digestion and milk fat concentration. These observations suggest a greater effect of forage type on lactation performance than concentrate type per se under the conditions of the current study.

Experiment and numerical simulation investigation on wire-plate electrostatic precipitator with expanded-shrunk spoilers

In this paper, three types of wire-plate electrostatic precipitators with expanded-shrunk spoilers (ESP-ESSs) were proposed. The influences of different geometric characteristics and arrangements of the expanded-shrunk spoilers (ESSs) on the electric field intensity, airflow field, particle trajectory, and collection efficiency were investigated by experiment and numerical simulation. The ESP-ESSs was compared with ESP with parallel plates (ESP-PP). The numerical results were relatively in agreement with the experimental data. The maximum error was 6.5%. The results showed that with the increase of the ESS height, the electric field intensity increased. The ESSs could generate low-velocity vortices contributing to extend the retention time of particles, which was conducive to particle collection. In general, the collection efficiency of the ESP-ESS was superior to the ESP-PP, but there was no advantage for fine particles at high inlet gas velocity and low applied voltage.

بررسی اثر استفاده از زئولیت طبیعی کلینوپتیلولیت اصلاح شده در حذف نیترات، فسفات و شوری از زهاب کشاورزی در مدل زهکشی آزمایشگاهی

The feasibility of using zeolite clinoptilolite to filter nitrate and phosphate pollutants and salt from agricultural drainage-water was studied in the current research. Significant pollutant absorption parameters, such as adsorbent particle size, pollutant concentration, salinity, temperature, retention time, pH, and adsorbent concentration, were optimized in the batch condition. After the optimization of parameters, adsorption experiments were conducted on an experimental model, similar to subsurface drainage systems that are applied in farms. Adsorption experiments were carried out at optimized parameter levels on four models, namely a reference model (D0), a model with adsorbent around drains (D1), a model with adsorbent around plant roots (D2), and a model with adsorbent on the soil surface (D3); they were fed with untreated drainage-water from south Khuzestan farms during the fertilization season. The results were suggestive of a 63 percent Nitrate-removal efficiency, 39 percent Phosphate-removal efficiency and 79 percent salt-removal efficiency made possible by 30 g.L-1 of 1000 µm adsorbent particles, for a pH of 5, initial pollutant concentration of 80 mg.L-1 nitrate and 10 mg.L-1 phosphate, a 12 dS/m salinity, 90-minute retention time, and 50 °C ambient temperature. These parameter levels enabled nitrate, phosphate, and salt-removal efficiencies of 59.72 percent, 29.28 percent, and 77.47 percent respectively, in the model with clinoptilolite adsorbents around the drains (D1).

Microplastic evacuation in fish is particle size‐dependent

Abstract The pollution of aquatic systems with microplastics (MPs) affects marine and freshwater fish species worldwide. However, little is known about the size‐dependent retention time of these inert particles. To approach this question, the retention time of MP particles was examined in two freshwater fish species with distinct differences in gastrointestinal morphology: rainbow trout (Oncorhynchus mykiss) with a true stomach, and stomachless common carp (Cyprinus carpio). A special diet was developed that contained environmentally relevant concentrations of MPs with sizes ranging from 20 to 1,000 µm. The two species were exposed to three different concentrations and numbers of retained particle were determined up to 72 hr after administration. The results revealed significant differences in retention time between large and small MP particles in rainbow trout, in which the T50 value (time for 50% of particles to be evacuated) ranged from 12.1 hr for 42.7 µm particles to 4.0 hr for 1,086 µm particles. In contrast, the differences observed between sizes in common carp were considerably smaller, with T50 ranging from 7.3 hr for 42.7 µm particles to 4.6 hr for 1,086 µm particles. It is therefore concluded that large particles in rainbow trout must be actively transported out of the stomach, as the evacuation times are significantly shorter than those for food. Small particles, however, are passively excreted with the chyme. In common carp, the evacuation rates of all particle sizes were in the range of that for food, suggesting a passive excretion. The results are particularly relevant in the contexts of particle transfer through the food chain, the release of toxic chemicals, and the translocation into tissues and organs. For this reason, it is essential that the particle size is given more consideration in future studies of microplastics in aquatic environments.

Synthetic Microfiber and Microbead Exposure and Retention Time in Model Aquatic Species Under Different Exposure Scenarios

Synthetic microfibers have been reported in most aquatic environments and represent a large proportion of environmental microplastics. However, they remain largely under-represented in microplastic ecotoxicity studies. The present study aims to investigate particle interaction with, and retention time in, aquatic organisms comparing microfibers, and microbeads. We used brine shrimp (Artemia sp.) and fish (Gasterosteus aculeatus) as invertebrate and vertebrate models, respectively. Organisms were exposed to a mixture of microbeads (polyethylene, 27–32 μm) and microfibers (dope dyed polyester; 500 μm-long) for 2 h, at high concentrations (100,000 part./L) in order to maximize organism-particles interaction. Artemia were exposed in the presence or absence of food. Fish were exposed either via the trophic route or directly via water, and water exposures were performed either in freshwater or seawater. In the absence of food, Artemia ingested high numbers of microbeads, retained in their digestive tract for up to 96 h. Microfiber ingestion was very limited, and its egestion was fast. In the presence of food, no microfiber was ingested, microbead ingestion was limited, and egestion was fast (48 h). Limited particle ingestion was observed in fish exposed via water, and particle retention time in gut did not exceed 48 h, both for direct and trophic exposure. However, water exposures resulted in a higher number of particles present in gills, and average retention time was higher in gills, compared to gut. This suggests that gills are organs susceptible to microplastic exposure and should be taken into account in fish exposure and effect studies. Our results show that particle ingestion and retention by organisms differ between microbeads and microfibers, suggesting particle selection based on size, shape, and/or color and species-specific selective feeding. We also showed that the presence of food results in limited particle ingestion and retention in Artemia and that microbeads are more likely to be transferred to organisms from upper trophic levels than microfibers. Finally, fish exposure to particles was not significantly different between freshwater and seawater conditions.

Numerical simulation on the effects of different inlet pipe structures on the flow field and seperation performance in a hydrocyclone

Reasonable structural design for a inlet pipe is an important way of improving the hydrocyclone's separation performance. The inlet can not only guide and accelerate particles but also achieve pre-separation of particles. However, there still lacks of clear governing equation of ideal inlet pipe. In order to gain in-depth understanding of the effects of different structures of the inlet pipes on the inner flow field and separation performance of the hydrocyclone, this study employed numerical simulation to compare the performances of the inlet pipe with different structures (linear, arc-type, spiral-line inlet pipe, denoted as Type A, Type B and Type C). Moreover, a novel hydrocyclone (Type D) mainly consisted of spiral-line inlet pipe, arc-type overflow pipe and parabolic cone was developed in this study. The simulation results fit well with classical experimental data, thereby validating the accuracy of the simulation results. Based on the simulation results, using Type B and Type C inlet pipe, both pressure drop and tangential velocity increased, which facilitated the movement of coarse particles towards the wall as well as finer particles towards the center. The pressure drop and the tangential velocity were greatest in Type C but lowest in Type D. The axial velocity of the internal rotational flow in a curved inlet pipe (especially Type D) was low, which can prolong the retention time of fine particles and contribute to more thorough separation. Using Type D inlet pipe, both the short-circuit flow rate and the turbulent viscosity were effectively lowered, which reduced the occurrence probability of eddy and enhanced the smoothness of particle movement. In addition, using spiral-line inlet pipe can promote the movement of coarse particles towards the wall, which significantly enhanced the recovery rate of coarse particles. Conclusively, Type D inlet pipe exhibited the highest separation precision and the lowest cut size, accompanied with better product quality.

Accurate quantification of TiO2 nanoparticles in commercial sunscreens using standard materials and orthogonal particle sizing methods for verification

The implementation and enforcement of product labeling obligation as required, for example, by the cosmetic product regulation, needs simple and precise validated analytical methods. This also applies to the analysis of nanoparticles in products such as cosmetics. However, the provision of such methods is often hampered by inaccurate sizing due to unwanted nanoparticle changes, interference of matrix components with sizing and interactions between nanoparticles and analytical instrumentation. It is, therefore, necessary to develop appropriate sample preparation methods that preserve NP properties and reduce or remove matrix compounds that interfere with sizing. Further, accurate particle size analysis of samples containing unknown and possibly multiple nanoparticulate constituents is needed. In this study, we evaluated three sample preparation methods to identify and quantify TiO2 nanoparticles in sunscreens. Specifically, we used a combination of ultracentrifugation and hexane washing, thermal destruction of the matrix, and surfactant assisted particle extraction. The method accuracy was assessed by two internal reference samples: pristine TiO2 nanoparticles (NM104) and similar TiO2 nanoparticles dispersed in a sunscreen matrix. The PSDs were determined using an asymmetrical flow field-flow fractionation hyphenated with multi-angle light scattering and inductively coupled plasma-mass spectroscopy. Particle sizing was based on size calibration of the particle retention time in the AF4. Computation of radius of gyration from MALS data was used as an orthogonal particle sizing approach to verify ideal elution and particle size data from the AF4 calibration. Among the three tested sample preparation methods surfactant assisted particle extraction revealed TiO2 nanoparticle recoveries of above 90% and no increase in particle size due to sample preparation was observed. Finally, the sample preparation methods were applied to two commercial sunscreen samples revealing the existence of TiO2-NP < 100 nm. Conclusively, the surfactant assisted particle extraction method can provide valid data for TiO2-NPs in sunscreen and possibly for cosmetic samples of similar matrix.

Transport and fate of inhaled particles after deposition onto the airway surface liquid: A 3D numerical study

In this paper, a numerical investigation is carried out to provide insights into the fate of inhaled aerosols after their deposition on the lung lining fluid in both healthy and diseased states. Pulmonary drug delivery is a well-known non-invasive route of administration compared to intravenous delivery. Aerosol particles are formulated and used as drug carriers, which are then sent to the airways using aerosol drug delivery devices. This approach is useful for site-specific treatment of lung diseases, treatment of central nervous system (CNS) disorders and a variety of other diseases. Bioavailability of the inhaled therapeutic particles after landing on the airway lining fluid can be significantly altered by the lung muco-ciliary clearance, a process through which hairlike structures known as cilia beat in a harmonised manner and induce the mucus in the proximal direction, leading to an effective clearance of the foreign inhaled particles entrapped by this sticky layer from the airways. Here, we set up a 3D computational model of ciliary arrays interacting with periciliary liquid film (i.e. confined between the epithelium and mucus layer) and a detailed analysis is conducted to better understand the fate of drug nanoparticles that are able to penetrate the mucus. Consistent with clinical findings, we find that the actions of cilia result in a low rate of drug retention and absorption by the pulmonary tissues in healthy lungs. However, under conditions associated with abnormal ciliary beats, the retention time of particles is notably increased at the site of release. Nonetheless, the results associated with some of the ciliary impairments reveal that deposition of drug aerosols on the ciliated cells may still be a significant challenge. These findings have potentially important implications on the modification of therapeutic drug particles to achieve a higher absorption rate.

Design of a 1000 L pilot-scale airlift bioreactor for nitrification with application of a three-phase hydrodynamic mathematical model and prediction of a low liquid circulation velocity

In this study, a 1000L pilot scale internal loop airlift bioreactor was operated and compared to a mathematical model to determine the best design for optimal supply of oxygen for nitrification and sufficient air for biomass fluidization. The design model is based on parameters such as geometry, carrier density, and airflow of the 1000L pilot scale bioreactor. The model predicts a range of superficial air velocities (0.009–0.013m/s) under which the airlift bioreactor was fluidized. Three superficial air velocities (0.009m/s, 0.011m/s and 0.013m/s) were experimentally tested in the pilot plant and the obtained circulation velocities were compared with the predicted design scenarios. The predicted velocity was in agreement with the measured velocity. The aim of the mathematical model and the calculations of different geometry scenarios was to define the optimal geometry design for the physical model. The results show that the ratio of the cross-sectional area between the riser and the downcomer of 1.33 resulted in the lowest superficial liquid velocity of 0.076m/s in the riser at a relative low superficial air velocity of 0.011m/s and a carrier density of 1030kg/m3. This bioreactor design enabled longest retention time of particles in the oxygenated riser.