Changes In Particle Size Research Articles

Simple retrieval of the real part of the refractive index for ambient aerosols using extinction coefficient analysis via camera and volume size distribution

This study explored a novel approach for estimating the variations in the refractive index (RI) of aerosols, which is a crucial optical parameter that contains information about particle scattering and absorption. RI is often subject to constraints related to observation time, wavelength selection, and analysis methods. To overcome these limitations, we employed real-time continuous measurements using a camera and optical particle counter (OPC) equipment and applied optimization techniques based on the Mie theory to reverse-calculate changes in the refractive index. Our methodology uses a camera to measure the aerosol extinction coefficients at three different wavelengths within the RGB spectrum (597 nm, 534 nm, and 459 nm), whereas OPC observations provide information on particle size distribution (0.127–17.58 μm as radius). Because the extinction efficiency at known wavelengths varies with the refractive index according to the Mie theory, we retrieved the refractive index, which is an unknown variable, from the extinction coefficient equation. We focused on the real part of the RI because it is challenging to discern the imaginary part of the RI from the visible wavelengths. Our observations were conducted in areas near Busan Harbor and in mixed residential regions. The real part of the RI was determined to be 1.53 ± 0.12. During periods of observed dust events, the refractive index's real part was 1.62 ± 0.05, while during periods anticipated to have emissions of fine aerosols, it was 1.51 ± 0.10. The retrieved RI fell within a range similar to that in other studies, and the changes in the refractive index showed meaningful patterns when analyzed for variations in the particle size distribution and changes in the scattering coefficient. This approach has the potential to advance our understanding of aerosol optical properties and can be applied to real-time analyses with a relatively simple equipment setup, thereby opening new possibilities for its use as a critical variable in optical measurements and environmental models.

Temporal evolution of plankton and particles distribution across a mesoscale front during the spring bloom

AbstractThe effect of mesoscale features on the distribution of planktonic organisms are well documented. Yet, the interaction between these spatial features and the temporal scale, which can result in sudden increases of the planktonic biomass, is less known and not described at high resolution. A permanent mesoscale front in the Ligurian Sea (north‐western Mediterranean) was repeatedly sampled between January and June 2021 using a SeaExplorer glider equipped with an Underwater Vision Profiler 6 (UVP6), a versatile in situ imager. Both plankton and particle distributions were resolved throughout the spring bloom to assess whether the front was a location of increased zooplankton concentration and whether it constrained particle distribution. Over the 5 months, the glider performed more than 5000 dives and the UVP6 collected 1.1 million images. We focused our analysis on shallow (300 m) transects, which gave a horizontal resolution of 900 m. About 13,000 images of planktonic organisms were retained. Ordination methods applied to particles and plankton concentrations revealed strong temporal variations during the bloom, with a succession of various zooplankton communities. Changes in particle abundance and size could be explained by changes in the plankton community. The front had a strong influence on particle distribution, while the signal was not as clear for plankton, probably because of the relatively small number of imaged organisms. This work confirms the need to sample both plankton and particles at fine scale to understand their interactions, a task for which automated in situ imaging is particularly adapted.

Dry Reforming of Methane over Pyrochlore-Type La2Ce2O7-Supported Ni Catalyst: Effect of Particle Size of Support.

The properties of supports (such as oxygen vacancies, oxygen species properties, etc.) significantly impact the anti-carbon ability due to their promotional effect on the activation of CO2 in dry reforming of methane (DRM). Herein, pyrochlore-type La2Ce2O7 compounds prepared using co-precipitation (CP), glycine nitrate combustion (GNC) and sol-gel (S-G) methods, which have highly thermal stability and unique oxygen mobility, are applied as supports to prepare Ni-based catalysts for DRM. The effect of the calcining temperature (500, 600 and 700 °C) on La2Ce2O7(CP) has also been investigated. Based on multi-technique characterizations, it is found that the synthesis method and calcination temperature can influence the particle size of the La2Ce2O7 support. Changes in particle size strongly modulate the pore volume, specific surface area and numbers of surface oxygen vacancies of the La2Ce2O7 support. As a result, the distribution of supported Ni components is affected due to the different metal-support interaction, thereby altering the activity of the catalysts for cracking CH4. Moreover, the supports' abilities to adsorb and activate CO2 are also adjusted accordingly, accelerating the removal of the carbon deposited on the catalysts. Finally, La2Ce2O7(CP 600) with an appropriate particle size exhibits the best catalytic activity and stability in DRM.

Experimental Study on Tailings Deposition Distribution Pattern and Sedimentation Characteristics.

Tailings pond accidents frequently occur during an extended period, resulting in loss of life and property, wastage of resources, and environmental pollution. Relying on tailings pond engineering, this paper carried out sample particle fragmentation experiments and settling column experiments to explore the deposition distribution pattern of tailings in both horizontal and vertical directions as well as the impact of particle size distribution on the sedimentation stratification effect. The results show that the median particle size on the dry beach surface in the horizontal direction slowly decreased with the increase in the distance from the subdam. The particle size of tailings showed great fluctuations in the vertical direction, which gradually became finer with the increase in the depth overall. At the same time, saturated sedimentation experiments suggested the inconsistent variation rule with the field test, namely, coarse on the bottom and fine at the top, and the change in particle size greatly affected the tailing sedimentation stratification effect. With the increase in fine particle content in tailings, the appearance time of the water-sand interface was shortened to within 30 min, but the sedimentation and consolidation completion times were delayed to about 1400 min. The settling column results indicate that the increase in fine particle content gradually weakened the sedimentation stratification effect, and the sedimentation pattern transformed from independent sedimentation to floc-type average sedimentation, which led to the enhanced water-retaining property of the settled layer. This may lead to an increase in the saturation line and a decrease in the length of the dry beach, seriously affecting the safe operation of the tailings pond. The research results provide some theoretical guidance and basic data for analyzing the consolidation efficiency of tailings and the stability of the tailings pond.

Changes of surface properties of sucrose particles during grinding in a cocoa butter-based suspension and their influence on the macroscopic behavior of the suspension

Chocolate mass is a cocoa butter-based suspension, which mainly consists of sugar and cocoa particles dispersed in a continuous lipid phase. During chocolate manufacturing, sugar particles have to be ground to sizes below 25–30 µm. Such a fine grinding is carried out either by five roll refiners or by ball mills. Despite obtaining similar particle size distributions at the end, the grinding procedures result in different chocolate mass properties. The reasons for that are not fully understood, so far. Therefore, changes in particle sizes and surface properties of sucrose particles as well as their interactions with surrounding cocoa butter during the different grinding processes were investigated including atomic force microscopy techniques to characterize local surface states. It was found that especially the alteration of surfaces during continued grinding differed. In the case of roller grinding, surface states became more inhomogeneous and different surfaces states at microscopic level existed in parallel. More homogenous surfaces but with a higher degree of amorphous states were formed during grinding in the ball mill. Variations in macroscopic behavior of the suspension can be explained by the differences in interaction of particles with each other and with the surrounding lipid phase.

Preparation of pumpkin seed protein isolate nanoparticles by heat-assisted pH-shifting: Enhanced emulsification performance and dispersibility

A food-grade Pickering emulsifier was fabricated using heat-assisted pH-shifting (HP) method for enhancing the emulsion stability. The emulsification performance of the modified pumpkin seed protein isolate (PSPI) nanoparticles was initially tested. The results showed that the modified PSPI had substantially improved emulsifying capacity, with the internal oil phase volume fraction reaching up to 80%, and the emulsion remaining stable after centrifugation at 10,000 g for 60 min and 30 days of storage. The data from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), UV–visible, intrinsic fluorescence and fourier transform infrared spectroscopy (FTIR) indicated that the primary, secondary and tertiary structures of PSPI were disrupted, resulting in changes in interfacial tension, wettability, particle size, and dispersibility of the protein, which promoted the adsorption of modified PSPI nanoparticles to the surface of oil droplets and improved the emulsion stability. Overall, the HP modified PSPI is a promising Pickering emulsifier for various applications.

Study on Compressibility According to Mixing Ratio and Milling Time of Fe-6.5wt.%Si.

Recently, researchers have focused on improving motor performance and efficiency. To manufacture motors with performance and efficiency higher than those of motors manufactured through the additive process, compressibility verification through the parameter control of soft magnetic composites (SMCs) is essential. To this end, this study aims to select suitable powders for manufacturing high-performance, high-efficiency motors by exploring powder mixing ratios and milling times. Through physical property tests, the optimal mixing ratio is predicted using the Multi-Particle Finite Element Method (MPFEM) and powder compression molding analysis, and compressibility is predicted in view of the influence of a change in particle size as a function of the powder mixing ratio and milling time. In addition, based on the result of a comparative analysis of density through experiments and an analysis of internal defects through SEM, a 50:50 mixing ratio of hybrid atomizing and gas atomizing powders milled for 3 h provided the best compressibility. Therefore, the use of SMC cores fabricated using powder compression molding is expected to improve motor performance and efficiency.

Change in Superparamagnetic State Induced by Swift Heavy Ion Irradiation in Nano-Maghemite

The effect of swift heavy ion irradiation on sol–gel-prepared maghemite nanoparticles was studied by 57Fe transmission Mössbauer spectroscopy and X-ray diffractometry (XRD). The room temperature Mössbauer spectra of the non-irradiated nano-maghemite showed poorly resolved magnetically split, typical relaxation spectra due to the superparamagnetic state of the nanoparticles. Significant changes in the line shape, indicating changes in the superparamagnetic state, were found in the Mössbauer spectra upon irradiation by 160 MeV and 155 MeV 132Xe26+ ions with fluences of 5 × 1013 ion cm−2 and 1 × 1014 ion cm−2. XRD of the irradiated maghemite nanoparticles showed a significant broadening of the corresponding lines, indicating a decrease in the crystallite size, compared to those of the non-irradiated ones. The results are discussed in terms of the defects induced by irradiation and the corresponding changes related to the change in particle size and consequently in the superparamagnetic state caused by irradiation.

Influence of Particle Size on the Mechanical Properties of Single-Layer Particleboards

While most of the influences on the mechanical properties of particleboard appear to have been investigated, there is a lack of knowledge about the influence of particle size or particle dimensions due to the absence of a suitable particle measuring technique. The introduction of laser-based 3D scanning technology makes it possible to automatically determine the dimensions, surface area, and volume of particles. In this study, the influence of particle size on the mechanical properties of particleboards was investigated. To isolate potentially overlapping influences, single-layer particleboards with a uniform density profile were produced and analyzed. The amount of adhesive specific to the surface of the (fine) face layer particles and (coarse) core layer particles was adjusted utilizing 3D scanning of the surface areas to ensure comparability despite changes in particle size. It was found that with increasing particle size, the modulus of rupture (MOR) and modulus of elasticity (MOE) increase, while the internal bond strength (IB) decreases. It is considered whether these effects result from a particle-size-dependent orientation of the particles in the board. Furthermore, it is shown that all the aforementioned properties increase with increasing surface-specific adhesive amounts. Examples are provided to demonstrate how such fundamental relationships can be utilized to enhance the particleboard production process.

Self-Amplified pH/ROS Dual-Responsive Co-Delivery Nano-System with Chemo-Photodynamic Combination Therapy in Hepatic Carcinoma Treatment.

Chemo-photodynamic combination therapy has demonstrated significant potential in the treatment of cancer. Triptolide (TPL), a naturally derived anticancer agent, whencombined with the photosensitizer Chlorin e6 (Ce6), has shown to provide enhanced anti-tumor benefits. However, the development of stimuli-responsive nanovehicles for the co-delivery of TPL and Ce6 could further enhance the efficacy of this combination therapy. In this study, we synthesized a pH/ROS dual-responsive mPEG-TK-PBAE copolymer, which contains a pH-sensitive PBAE moiety and a ROS-sensitive thioketal (TK) linkage. Through a self-assembly process, TPL and Ce6 were successfully co-loaded into mPEG-TK-PBAE nanoparticles, hereafter referred to as TPL/Ce6 NPs. We evaluated the pH- and ROS-sensitive drug release and particle size changes. Furthermore, we investigated both the in vitro suppression of cellular proliferation and induction of apoptosis in HepG2 cells, as well as the in vivo anti-tumor efficacy of TPL/Ce6 NPs in H22 xenograft nude mice. The mPEG-TK-PBAE copolymer was synthesized through a one-pot Michael-addition reaction and successfully co-encapsulated both TPL and Ce6 by self-assembly. Upon exposure to acid pH values and high ROS levels, the payloads in TPL/Ce6 NPs were rapidly released. Notably, the abundant ROS generated by the released Ce6 under laser irradiation further accelerated the degradation of the nanosystem, thereby amplifying the tumor microenvironment-responsive drug release and enhancing anticancer efficacy. Consequently, TPL/Ce6 NPs significantly increased PDT-induced oxidative stress and augmented TPL-induced apoptosis in HepG2 cells, leading to synergistic anticancer effects in vitro. Moreover, administering TPL/Ce6 NPs (containing 0.3 mg/kg of TPL and 4 mg/kg of Ce6) seven times, accompanied by 650 nm laser irradiation, efficiently inhibited tumor growth in H22 tumor-bearing mice, while exhibiting lower systemic toxicity. Overall, we have developed a tumor microenvironment-responsive nanosystem for the co-delivery of TPL and Ce6, demonstrating amplified synergistic effects of chemo-photodynamic therapy (chemo-PDT) for hepatocellular carcinoma (HCC) treatment.

Effect of borax on the hydration and hardening of β-hemihydrate gypsum at high water–plaster ratio

The existing methods of preparing lightweight gypsum blocks are to make hollow slats or to make foamed blocks, both of which are defective and fail to meet the standards. In order to prepare lightweight gypsum blocks, this paper investigates the method of increasing the proportion of moisture to reduce the weight of gypsum blocks. To further understand the performance relation between β-hemihydrate gypsum (β-hemihydrate phosphogypsum and β-hemihydrate flue-gas desulfurization gypsum) and its products, the effect of borax on the hydration and hardening of β-hemihydrate gypsum at high water–plaster ratio was studied. The results showed that with an increase in borax dosage, the setting time of β-hemihydrate phosphogypsum (β-HPG) was evidently prolonged; the initial setting time increased from 15 to 62 min, and the final setting time increased from 22 to 93 min. The difference between the initial and final setting times also increased, and the fluidity of the gypsum slurry was improved. When the borax dosage reached 0.5%, the flexural strength of β-hemihydrate flue-gas desulfurization gypsum (β-HFGD) increased from 5.2 to 6.3 MPa and the compressive strength increased from 4.7 to 9.3 MPa after 28 d. By analyzing the changes in phase transition, hydration degree, infrared spectrum, particle size, and crystal microstructure during the hydration of β-hemihydrate gypsum, it was found that β-HPG was more sensitive to borax than β-HFGD at high water–plaster ratio and β-HFGD showed superior mechanical properties. The study findings will provide a theoretical basis for the application of β-hemihydrate gypsum products under humid conditions and expand the application range of gypsum products.

Size Effect of Yielding of Particle-Reinforced Composites

Abstract This paper illustrates how particle size affects the initial yield stress of particle-reinforced composites. A formulation in a closed form is presented to demonstrate the size effect of yielding of the composites. This paper also demonstrates that there is an upper bound and a lower bound for the size-dependent yield stress with the change of particle size. This means that decreasing particle size increases its yield stress up to an upper bound. Similarly, increasing particle size decrease its yield stress up to a lower bound. In this paper the asymptotic homogenization method is used in framework of the Cosserat elasticity. A virtual “unreinforced matrix” is introduced as a reference configuration. As a numerical example, the size effect of yielding of SiCp/Al is predicted.

Study on Wear Characteristics of a Guide Vane Centrifugal Pump Based on CFD–DEM

Guide vane submersible centrifugal pumps are a kind of submersible pump, and the fluid inside the pump is often mixed with gravel and other impurities during operation, affecting the pump’s operating efficiency and life expectancy. However, past studies on solid–liquid two-phase flow (STF) and wear characteristics in guided vane centrifugal pumps have been limited to the particle trajectory and wear region distribution. These studies have lacked research on the effect of particles on the fluid flow and the specific amount of wear on the overflow components. Additionally, most of them have used the DPM discrete-phase model, which does not consider the particle–particle and particle–wall interactions. This paper is based on the CFD–DEM method, combined with the Archard wear model. A solid–liquid two-phase flow simulation is carried out for pumps with different particle sizes and particle shapes to analyze the particle movement inside the pump, the wear distribution and average wear amount of the overflow components, and the effect of particles on the turbulent kinetic energy of the fluid. The results show that the particles mainly collide with the leading and trailing edges of the impeller blades and the leading edge of the guide vane blades and form a buildup at the trailing edge of the concave surface of the guide vane blades, resulting in the wear being mainly distributed in these regions. With an increase in particle size and a decrease in sphericity, the average wear on the overflow components increases. The change of particle size directly affects the resistance of the fluid and the structure of the flow field, which has a large impact on the fluid flow pattern and generates large turbulent kinetic energy fluctuations. The shape of the particles only changes the structure of the local flow field, which has a small impact on the fluid flow pattern.

Environmental factors influencing the soil-air partitioning of semi-volatile petroleum hydrocarbons: Laboratory measurements and optimization model

The soil-air partition coefficient (KSA) values are commonly utilized to examine the fate of organic contaminants in soils; however, their measurement has been lacking for semi-volatile petroleum hydrocarbons within soil contaminated by crude oil. This research utilized a solid-phase fugacity meter to determine the KSA values of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) under crucial environmental conditions. The results showed a notable increase in KSA values with the extent of crude oil contamination in soil. Specifically, in the 3 % crude oil treatment, the KSA values for n-alkanes and PAHs increased by 1.16 and 0.66 times, respectively, compared to the 1 % crude oil treatment. However, the KSA values decreased with changes in temperature, water content, and particle size within the specified experimental range. Among these factors, temperature played a significant role. The KSA values for n-alkanes and PAHs decreased by 0.27–0.89 and 0.61–0.83 times, respectively, with a temperature increase from 5 °C to 35 °C. Moreover, the research identified that the molecular weight of n-alkanes and PAHs contributed to variations in KSA values under identical environmental factors. With an increase in temperature from 5 °C to 35 °C, the range of n-alkanes present in the air phase expanded from C11 to C34, and PAHs showed elevated levels of acenaphthene (ACE) and benzo (b) fluoranthene (BbFA). Furthermore, heightened water content and particle size were observed to facilitate the volatilization of low molecular weight petroleum hydrocarbons. The effect of environmental variables on soil-air partitioning was evaluated using the Box-Behnken design (BBD) model, resulting in the attainment of the lowest log KSA values. These results illustrate that soil-air partitioning is a complex process influenced by various factors. In conclusion, this study improves our comprehension and predictive capabilities concerning the behavior and fate of n-alkanes and PAHs within soil-air systems.

Formulation of Microemulsion-based Gel Containing Mango Seed Kernel Extract for Application in Anti-inflammation

Published research showed that mango seeds have good anti-inflammatory and antibacterial properties. The purpose of this study is to develop a microemulsion formula containing mango seed extract for application in the treatment of inflammatory acne. Isopropyl myristate and coconut oil were selected as the fixed oil phase components. Phase diagrams for the microemulsion regions were constructed using PEG 40 hydrogenated castor oil as surfactant and PEG 400 as co-solvent. Microemulsions were prepared by titration and mixed with mango seed extract. Microemulsions and the physical and chemical stability of the microemulsion were evaluated for droplet size and PDi index using dynamic light scattering techniques. The microemulsion was gelled and evaluated for its anti-inflammatory effect by comparing it with an acne cream on the market. The selected microemulsion formula has a ratio of isopropyl myristate oil to coconut oil of 1:2, Smix/Co is PEG 40 hydrogenated castor oil to PEG 400 with a ratio of 3:1, and a high loading efficiency of 5% mango seed. The average particle size of the microemulsion reached 22.74 nm. The selected microemulsion showed good stability, with almost no change in particle size when stored at room temperature after 30 days. The microemulsion was gelled with 7% carbopol, and the permeability of polyphenols from the microemulsion gel within 6 hours was observed to be about 59.61%. The microemulsion gel inhibited the denaturation of bovine serum albumin, indicating that the microemulsion containing coconut oil and mango extract may help in treating inflammatory acne. Microemulsion gel containing mango seed kernel has been successfully studied, has anti-inflammatory activity equivalent to a modern control drug, and is promising as a natural preparation that can provide anti-inflammatory protection on acne skin. However, further clinical studies need to be conducted before use.

Formulation and validation of Candesartan cilexetil-loaded nanosuspension to enhance solubility

The following research aimed to enhance solubility by loading candesartan cilexetil into nanosuspension. Candesartan cilexetil-loaded nanosuspension was prepared with the aid of Design-Expert® software. A technique of solvent evaporation was employed to produce nanosuspensions from hydroxyl propyl methyl cellulose (HPMC E5), polyvinyl pyrrolidone (PVP K-30), and poloxamer (PXM 188). The optimised nanosuspensions’ particle size and polydispersity index (PDI) were 64.65 nm and 0.059, respectively. The entrapment efficacy (EE %) and drug loading (DL %) were 86.75 and 10.17%, respectively. The atomic force microscopy (AFM) revealed spherical and smooth nanoparticles. The Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) revealed pure, crystalline and conjugated drugs inside the nanosuspension. The release study confirmed 90% release within 10 min. No significant changes in particle sizes over three months were found, indicating stable nanoparticles. Saturated solubility of the candesartan cilexetil powder and loaded nanosuspension was 63.3 ± 6 and 344.7 ± 16 µg.ml-1, respectively, revealing more than five times increase in solubility. Candesartan cilexetil-loaded nanosuspensions were successfully prepared using different combinations of PVP K-30, HPMC E-5 and PXM 188 in various concentrations. Solubility was enhanced by loading the payload into nanosuspensions.

In vitro study of the embolic characteristics of imipenem/cilastatin particles

BackgroundImipenem/cilastatin (IPM/CS) has long been administered intravenously as a carbapenem antibiotic. However, since this agent is poorly soluble in liquid, occasional reports have described its use as a short-acting, temporary embolic agent. The purpose of this study was to elucidate the characteristics of IPM/CS particles, which are thought to have pain-relieving effects against osteoarthritis-related pain, as an embolic agent.MethodsThree aspects of IPM/CS as an embolic agent were evaluated in vitro: particle size; particle shape; and change in particle size over time. For particle size, the long diameter was measured.ResultsMean particle size (n=244) was 29.2±12.0 µm (range, 1–60 µm). Shape (n=109) was round in 18.35%, elliptical in 11.93%, and polygonal in 69.72%, showing that most particles were polygonal. In observations of changes in particle size over time (n=9), particles had decreased to 75% of their original size at 82±10.7 min, 50% at 89.3±9.14 min, 25% at 91.3±8.74 min, complete dissolved at 91.8±9.02 min. A rapid shrinkage in diameter was seen in the final period.ConclusionsIPM/CS particles are ultrafine and the majority display a polygonal shape. This substance shows ultra-short embolic activity. This study revealed the characteristics of a substance that demonstrates an embolic effect not found in existing embolic materials.

Phosphatase-degradable nanoparticles providing sustained drug release

AimThe study aimed to develop enzyme-degradable nanoparticles comprising polyphosphates and metal cations providing sustained release of the antibacterial drug ethacridine (ETH). MethodsCalcium polyphosphate (Ca-PP), zinc polyphosphate (Zn-PP) and iron polyphosphate nanoparticles (Fe-PP NPs) were prepared by co-precipitation of sodium polyphosphate with cations and ETH. Developed nanocarriers were characterized regarding particle size, PDI, zeta potential, encapsulation efficiency and drug loading. Toxicological profile of nanocarriers was assessed via hemolysis assay and cell viability on human blood erythrocytes and HEK-293 cells, respectively. The enzymatic degradation of NPs was evaluated in presence of alkaline phosphatase (ALP) monitoring the release of monophosphate, shift in zeta potential and particle size as well as drug release. The antibacterial efficacy against Escherichia coli was determined via microdilution assay. ResultsNPs were obtained in a size range between 300 – 480 nm displaying negative zeta potential values. Encapsulation efficiency was in the range of 83.73 %– 95.99 %. Hemolysis assay underlined sufficient compatibility of NPs with blood cells, whereas drug and NPs showed a concentration dependent effect on HEK-293 cells viability. Ca- and Zn-PP NPs exhibited remarkable changes in zeta potential, particle size, monophosphate and drug release upon incubation with ALP, compared to Fe-PP NPs showing only minor differences. The released ETH from Ca- and Zn-PP nanocarriers retained the antibacterial activity against E. coli, whereas no antibacterial effect was observed with Fe-PP NPs. ConclusionPolyphosphate nanoparticles cross-linked with divalent cations and ETH hold promise for sustained drug delivery triggered by ALP for parental administration.

Simulation of proppant conductivity test: effect of particle size dispersion

A conductivity test of proppant material consists in confining a sample of the granulate at high pressure and then set a flow through the pack. The proppant particle size is the main variable controlling conductivity, but also particle size dispersion is considered important. Even though several studies consider mixtures of proppants of different meshes, there are not clear evidences as to whether the changes in conductivity with respect to a monosized proppant are caused by the mix itself or by the overall change in mean particle size. Hence, we use numerical simulations to answer the question: Does particle size dispersion significantly affects the proppant conductivity if mean particle size is kept the same? We measure conductivity and permeability by simulating (via a coupled Computational Fluid Dynamics–Discrete Element Method) the flow of water through binary granular packs. We find that size dispersion does not affect conductivity (in the dispersion range explored) if the mean particle size is conserved. However, we observe that in a binary mixture the large particles are subjected to larger stresses than in a monosized system, which makes them prone to crushing.

Space weathering, grain size, and metamorphic heating effects on ordinary chondrite spectral reflectance parameters

AbstractThe exposure to irradiation from high‐energy particles alters the reflectance properties of asteroid surfaces and is referred to as space weathering. This process leads to an increase in spectral slope in visible and near‐infrared wavelengths. However, changes in the regolith particle size, which can vary dramatically among the asteroid population, are known to influence the spectral properties of meteorites and asteroids. In this context, we investigate the changes in spectral slope and absorption band depths of fresh and irradiated ordinary chondrite meteorites to quantitatively compare the effects of space weathering and grain size variations. To do so, we develop and employ the Spectral Analysis for Asteroid Reflectance Investigation routine that calculates the band parameters of reflectance spectra. We then formulate a parameter called the Space Weathering Index (SWI) that is designed to encapsulate spectral changes due to space weathering. We find that the SWI is strongly dependent on the spectral slope which complicates the interpretation of asteroid spectra in the context of grain size variations and space weathering. We also show that a second parameter, the Band Depth Index, is indicative of petrologic type. Finally, we use a linear discriminant analysis to classify asteroid reflectance spectra into H, L, LL, and unequilibrated ordinary chondrites.