Mineral Particles Research Articles

Res-UNet Ensemble Learning for Semantic Segmentation of Mineral Optical Microscopy Images

In geology and mineralogy, optical microscopic images have become a primary research focus for intelligent mineral recognition due to their low equipment cost, ease of use, and distinct mineral characteristics in imaging. However, due to their close reflectivity or transparency, some minerals are not easily distinguished from other minerals or background. Secondly, the number of background pixels often vastly exceeds the number of pixels for individual mineral particles, and the number of pixels of different mineral particles in the image also varies significantly. These have led to the issue of data imbalance. This imbalance results in lower recognition accuracy for categories with fewer samples. To address these issues, a flexible ensemble learning for semantic segmentation based on multiple optimized Res-UNet models is proposed, introducing dice loss and focal loss functions and incorporating a pre-positioned spatial transformer networks block. Twelve optimized Res-UNet models were used to construct multiple Res-UNet ensemble learnings using heterogeneous ensemble strategies. The results demonstrate that the system integrated with five learners using the weighted voting fusion method (RUEL-5-WV) achieved the best performance with a mean Intersection over Union (mIOU) of 91.65 across all nine categories and an IOU of 84.33 for the transparent mineral (gangue). The results indicate that this ensemble learning scheme outperforms individual optimized Res-UNet models. Compared to the classical Deeplabv3 and PSPNet, this scheme also exhibits significant advantages.

The Measurement of Metal Mineral Particle Size Under the Microscope Based on Gaussian Pyramids and Directional Maximum Intercept

With the development of mineral resources, minerals are becoming increasingly difficult to process. In order to utilize these resources more effectively, in-depth research into process mineralogy has become increasingly important in the field of mineralogy, and particle size measurement under the microscope is one of the critical aspects of process mineralogy. At present, the use of scanning electron microscopes and other equipment for measurement is very expensive, and manual measurement has problems such as poor accuracy and low efficiency. In addition, there is a lack of reference materials for the segmentation algorithm of mineral light images. This article proposes a Gaussian pyramid based on bilateral filtering combined with directional maximum intercept to measure mineral particle size under the microscope. In the experiments, different segmentation algorithms were studied, including Gaussian pyramid segmentation based on bilateral filtering, segmentation based on Fuzzy C-Means, and the rapidly developing deep learning segmentation algorithms in recent years. By comparing the segmentation effects of these three algorithms on various mineral thin-section images, the Gaussian pyramid segmentation algorithm based on bilateral filtering was selected as the optimal one. This was then combined with the directional maximum intercept method to measure the particle size of ilmenite and pyrite images. The experimental results show that the segmentation method based on the bilateral filtering Gaussian pyramid technique has higher segmentation accuracy than the other two algorithms, and can accurately measure the particle size of minerals under the microscope. Compared with manual measurement, this method can effectively and accurately measure the microscopic particle size of target minerals, greatly reducing the workload of measurement personnel and reducing the time spent on measurement.

Source variations of atmospheric particles in response to control measures in northern China during 2022 winter olympics and paralympics: Evidence from microscopic analysis.

The physicochemical properties of atmospheric particles including morphologies and composition are directly related to their sources and formation mechanisms. However, most previous studies have been limited to a few sites and small numbers of particles. In this study, we employed computer-controlled scanning electron microscopy (CCSEM) to enhance measurement efficiency and enable long-term observations across multiple sites. To investigate properties and source variations of atmospheric particles in response to control measures before, during, and after the 2022 Winter Olympic Games (WOG) and Winter Paralympic Games (WPG), ambient particles were passively collected in 15 northern Chinese cities and automatically analyzed by an advanced CCSEM (IntelliSEM EPAS). Variations in particle numbers (PN), size distribution, elemental composition, and sources were comprehensively analyzed. Over one million particles were classified into mineral, carbonaceous, fly ash, sulfur-related, metal-containing, salt, and biological particles using the user-defined classification rules. The results showed that improved air quality was witnessed during the WOG with reduced PN and anthropogenic particles, but deteriorated during the WPG due to increased coarse-mode PN, mineral, and sulfur-related particles. Beijing and Zhangjiakou exhibited lower AQI, PN, and anthropogenic particles, while non-competition cities experienced higher levels of anthropogenic and sulfur-related particles. Notably, Taiyuan and Shijiazhuang showed distinct emission reductions during the WOG, while Baoding and Tangshan demonstrated less effective control with high levels of sulfur-related and anthropogenic Fe-rich particles. This study shows the capability of CCSEM to provide microscopic evidence of particle sources and behaviors, offering valuable insights into the efficacy of control measures during major events.

Ice nucleating ability of mineral particles from subtropical South American deserts

Mineral aerosols are one of the most important ice nucleating particles (INPs) because their efficiency in nucleating ice, wide transport and largest mass contribution to particulate matter in the atmosphere. They are sourced from the arid regions of the world. In this context, this work evaluates the INP potential of fourteen topsoil samples collected from subtropical South American deserts, the major source of mineral aerosols in South America, in the immersion freezing mode. Samples were obtained from three distinct regions located in the South American Arid Diagonal and recognized as potential dust source areas: the Puna-Altiplano Plateau in the north, the central-west of Argentina, and Patagonia in the south. In general, results reveal that samples from the Puna-Altiplano and Patagonia regions, and the central-west of Argentina region exhibit the highest and lowest INP abilities, respectively. The active sites per unit surface area for a given temperature were calculated and compared with previously reported values. The results demonstrate that soil mineral particles from the region of study exhibit ice nucleating abilities comparable to the inorganic fraction of agricultural soils of central Argentina. No direct relationship was identified between INP ability and the major minerals observed in the samples. This study is the first to analyze the ice nucleation properties of soil samples collected along the South American Arid Diagonal and one of the few in South America. Since the analyzed topsoil particles were collected from potential dust source regions, this work contributes to understanding the role of aerosols in initiating atmospheric ice formation, providing valuable data for empirical parameterizations. This could contribute to the improvement in the performance of climate models, as the obtained results suggest that the underestimation of coarse and super-coarse aerosols at altitudes relevant for cloud formation may lead to underestimations in INP concentrations, particularly in regions near to the emission sources.

Physical exercise impacts bone remodeling around bio-resorbable magnesium implants

Physical exercise has been shown to induce positive reactions in bone healing but next to nothing is known about how it affects the nanostructure, in particular around implants. In this study, we established this link by using small-angle X-ray scattering tensor tomography (SASTT) to investigate nanostructural parameters in 3D such as mineral particle orientation and thickness. As a model system, rat femoral bone with a bio-resorbable implant (ultra-high purity magnesium) was used. One half of the rats underwent treadmill exercise while the other half were moving freely in a cage. At two- and six-weeks post-surgery rats were sacrificed, and samples were taken. Our results point to an earlier start and stronger remodeling when physical exercise is applied and to a stronger reorientation of the mineralized collagen fibers around the implant. This study reveals the nanostructural response of bone with bio-resorbable implants to physical exercise. Understanding this response is very important for designing post-surgery treatments. Statement of SignificancePhysical exercise is known to have beneficial effects on the human body and is often incorporated into the recovery process following orthopedic surgeries. While the response of bone to physical exercise is well-documented, the structural response of bone to early exercise after implant placement, particularly its impact on the nanostructure, has not been extensively studied. In this study, we identify the effects of physical exercise on the bone nanostructure and the remodeling process around a bioresorbable implant. These findings could help develop tailored physical exercise strategies for post-surgery recovery in patients.

Origins and Aging of Calcium-rich Mineral Particles in Asian Dust Arriving in Southwestern Japan: A Comparison of Slow- and Fast-moving Events

Origins and Aging of Calcium-rich Mineral Particles in Asian Dust Arriving in Southwestern Japan: A Comparison of Slow- and Fast-moving Events

Galvanic Interaction between Galena and Pyrite in the Presence of Sodium Lignosulfonate and Its Effects on Flotation.

In the flotation process, there is galvanic corrosion between sulfide mineral particles, which increases the difficulty of separation between minerals. Therefore, the selection of suitable reagents to weaken this corrosion is of great significance. In this article, macromolecular organic reagent sodium lignosulfonate (SLC) was used to weaken the galvanic corrosion between galena and pyrite. Meanwhile, the effect of SLC on the mineral flotation behavior was studied, and the mechanism of SLC was further studied through ion dissolution tests, contact angle tests, infrared spectrum tests, and density functional theory (DFT) calculation. The adsorption of SLC on the mineral electrode increased the charge transfer resistance on the surface of the mineral electrode and hindered the resistance transfer; therefore, it could weaken the galvanic corrosion between galena and pyrite. SLC could selectively depress pyrite at low alkalinity. CaOH+ promoted the adsorption of SLC on the pyrite surface. When the pH of the slurry was adjusted by lime, SLC was more easily adsorbed on the pyrite surface, which hindered the adsorption of the collector on the surface of pyrite.

The theoretical freezing model of sandstone considering the statistical arrangement of pore structure

It is of great significance to understand the evolution law of unfrozen water content in frozen rocks to maintain the stability of geotechnical engineering in cold regions. Due to the different particle sizes and shapes, coupled with the diversity of cements, the internal pore structures of rocks are complex and diverse. In this study, a theoretical model for freezing point of sandstone is proposed based on the characteristics of microscopic pore structures. The characteristic of freezing point is analyzed by considering the mineral particle arrangement. A statistical theoretical model of unfrozen water in sandstone is established according to the random arrangement of mineral particles. The influence of the stacking angle of mineral particles following the normal distribution on unfrozen water content is analyzed. Finally, the NMR freezing process analysis for sandstones was carried out. The results show that the statistical theoretical model of unfrozen water fits the experimental results well. The effect of the average value of stacking angle on unfrozen water content is mainly due to the change of pore size, which leads to the change of pore water content. The standard deviation of stacking angle determines the residual water content.

Comparative analysis of fretting wear behavior of steel wire subject to tensile-torsional coupling forces in typical mining environments

The complex mining environments can significantly accelerate the fretting wear among steel wires within wire rope, thereby diminishing its service life and posing severe risks to the safety of mine hoisting operations. To explore the fretting behavior of steel wires featuring complex contact structures in typical mining environments, a customized test rig was utilized to perform fretting wear experiments of steel wire under tensile-torsional coupling forces. The findings indicate that with increasing contact force, the coefficient of friction (CoF) between steel wires in different environments decreases, whereas the frictional force and wear degree increase significantly. The wear depth and wear coefficient under peak contact structure are markedly larger than those under valley contact structure. For the same contact force, the wear of steel wire without lubrication is the largest, the wear under water lubrication is the second, and the wear under grease lubrication is the least. The primary wear mechanisms of steel wire under grease lubrication are abrasive wear and fatigue wear. The presence of mineral particles in the grease can reduce the CoF, but it will exacerbate the wear and result in adhesive wear characteristics on the wear surfaces. Under no lubrication and water lubrication conditions, the wear mechanisms encompass abrasive wear, adhesive wear and fatigue wear. Furthermore, with increasing contact force, the fatigue wear of steel wire under no lubrication intensifies, while the abrasive wear characteristics become more pronounced under water lubrication.

From Green to Black Gold: Highly Microporous Carbons from Pistachio Shells by a Controlled Physical Activation Process.

Highly microporous carbons with BET surface areas of up to ca. 3300 m2 g-1 and pore volumes of up to 1.6 cm3 g-1 have been successfully synthesized from pistachio shells, a waste whose generation is growing on account of the nutritive value of pistachios and the resilience of this crop to climate change. Such a high pore development has been achieved by a simple and benign CO2 physical activation process assisted by a custom pre-treatment of the biomass. Different approaches have been explored in this work for the transformation of pistachio shells into carbon materials with diverse microstructures, mineral matter content and particle size/morphology, tuning thereby their reactivities towards CO2 and diffusion kinetics and, in this way, pore development. In particular, the most efficient route for the production of highly microporous carbons from pistachio shells involves a hydrothermal carbonization process which increases the degree of aromatization and effectively removes the mineral matter, enhancing thereby the efficiency of both carbon production and porosity generation. By increasing the activation temperature, substantial shortening of the operation time can be achieved without compromising pore development. This work provides new integral strategies towards the production of biomass-based, CO2-activated carbons with a focus on optimizing pore structure, minimizing energy consumption and maximizing product yield.

Parameters of Collision and Adhesion Process Between a Rising Bubble and Quartz in Long-Chain Amine Solution and Their Correlation with Flotation

The successful adhesion of air bubbles to mineral particles is the crucial to flotation technology. This paper systematically investigates the parameters variation in the dynamic interaction process between a rising bubble and a quartz plate in long-chain amine solutions (dodecylamine, tedecylamine, and octadecylamine). The results show that the type and concentration of long-chain amine affected the collision and adhesion process between bubbles and quartz plates remarkably. The maximum rebound distance (rebound distance after the first collision) of bubbles and the stable-state liquid film thickness gradually decreases with the increase of reagent concentration. Additionally, the collision-rebound duration and induction time shorten accordingly, the surface tension of the solution decreases, the surface hydrophobicity of quartz increases, and the deformation degree and average movement velocity of bubbles decrease. With the increase in carbon chain length, the adsorption form of the amine collector and quartz surface becomes closer to vertical, and the density of water molecules decreases. The recovery of quartz particles is highest with octadecylamine systems, corresponding well with the changing trend in steady-state liquid film thickness. This research provides an effective method for in-depth analysis of the microscopic interaction mechanism between bubbles and mineral surfaces and the prediction of flotation results.

Analyzing Morphology and Composition of Coarse Aerosol Particles in Bangkok, Thailand: Implications to Sources and Impacts of Aged Aerosols on Ecosystem Health and Climate Dynamics

During dry seasons, elevated aerosol levels across Thailand pose nationwide problems. Understanding and addressing this issue is challenging due to the dynamic nature of aerosol modification and generation during transport. This study investigates the morphology and elemental compositions of coarse aerosol particles in Bangkok, Thailand, during the dry seasons of 2020/21. Through scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDS), the study reveals a complex mixture of anthropogenic, mineral, biogenic, and marine aerosols. Anthropogenic sources, including biomass burning, vehicular emissions, and industrial activities, contribute to carbonaceous particles like soot aggregates and tar balls. Mineral dust particles, predominantly calcium-rich and aluminosilicate, originate from various sources including construction, industry, and natural processes. Aging processes alter the composition and properties of both carbonaceous and mineral particles, influencing nutrient deposition, carbon sequestration, cloud condensation nuclei formation, and light scattering. These processes have multifaceted impacts on ecosystem health and climate dynamics, highlighting the need for further research and mitigation strategies to address the environmental consequences of aged aerosol particles in urban environments like Bangkok.

Could landscape ecology principles apply at the microscale? A metabarcoding approach on Trichoptera larvae-associated microbial diversity

Landscape heterogeneity is known as a major factor of community structure and composition. Whether this effect of the landscape extends at different scales and particularly at the relevant scale for microorganisms remained to be determined. We used the cases produced by aquatic larvae of Trichoptera, which assemble organic or mineral particles, as naturally replicated experimental systems representing structured substrates to determine the effect of landscape structuration on microbial communities. A metabarcoding approach was used to characterise fungal, bacterial and diatom communities on cases produced by six Trichoptera species and related unstructured organic and mineral substrates. The structuration of the particles constituting the cases was also determined as a measure of microscale landscape. Structured substrates harboured communities of diatoms, fungi and bacteria that differed from those found on unstructured substrates. Microbial communities also differed between organic and mineral substrates. We found a higher microbial diversity on structured substrates than on unstructured substrates. The heterogeneity of the microscale landscape also affected bacterial and fungal communities within cases. These results highlight the importance of microscale landscape structuration for microbial diversity and demonstrate that approaches of landscape ecology could be downscaled to the microscale.

Search amps up for signatures of cosmic particles in ancient minerals

Advances in imaging and data handling open new possibilities.

New ichnofossil discovery in Mallorcan caves: Linking ancient and moden bat-ectoparasites coporolites.

Bat ectoparasitic ichnofossils can be useful to elucidate microbial mediation in mineralization processes of organic material, supplying valuable information on ancient parasitology and palaeoecology, among other topics. Rod-shaped features found in Cova des Pas de Vallgornera (Mallorca, Spain) are described for the first time. They are related to an ancient bat colony inhabiting the cave in the Early Pleistocene. These micro-morphologies are cylindrical in shape with sizes of a few hundred microns in length and less than one hundred microns in diameter. They are composed by a mash of microscopic calcite particles of different sizes and shapes, lying on deposits that contain phosphates and clay minerals. Some of these rod-shaped morphologies are covered in microscopic crystals, whose mineralogy is composed mainly of calcite, associated with dolomite, quartz and clays, These deposits are interpreted as fecal droplets of bat ectoparasites (probably Nycteribiidae), that infested an ancient bat colony living in the cave before the collapse blocking of its natural entrances; from 2.4 Ma to present, the cave has remained sealed, preserving these deposits as a new ichnofossil related to invertebrate's coprolites. The observation of similar micro-structures in Cova de sa Guitarreta, another Mallorcan cave nowadays used for breeding by bats, allowed to study a present-day analogue; in this case, the rod-shaped structures are composed by organic detritus with lenticular concave forms (red blood cells?) and minute mineral particles. Therefore, these cylindrical features could be envisaged as excreta from bloodsucking bat flies, being represented by present-day deposits (Cova de sa Guitarreta) as well as fossil coprolites in the case of Cova des Pas de Vallgornera.

Morphological Observation and Mineralogical Analysis of Basaltic Debris from a Chang'e 5 Drilled Sample

This paper analyzes the morphological characteristics and mineralogy of drilled basaltic clast sample CE5Z0806YJYX004, compares the variations in Chang'e-5 samples at different depths, and conducts a comparative analysis with surface-collected samples from Chang'e-5 and Apollo missions. Interestingly, Advanced electron microscopy identified bubbles and microcracks on the surface of some constituting mineral particles, and also displays crystalline particles with distinct rock textures and spherical droplets, revealing surface phenomena formed by space weathering. Based on Raman spectroscopy analysis, the main mineral phases were identified as 49.6 vol% pyroxene, 31.4 vol% plagioclase and 8.8 vol% olivine. Apatite, ilmenite and cristobalite are also found. The results indicate that the Chang’e-5 lunar soil exhibits similar mineral compositions at different depths. In short, a comparison was made between our drilling sample and the Chang'e 5 soil samples as well as samples from the Apollo mission series, demonstrating the physical similarities and some variations.

Size-based separation of fine mineral particles using inertial microfluidics: A case of jarosite and anglesite

Many metal phases in industrial hazardous waste coexist as fine mineral particles (FMPs, with particle sizes of 0.01 μm–10 μm) in a physical mixture, making conventional methods unable to achieve separation. Advanced microfluidics has demonstrated its potential in the separation of FMPs, as exemplified by jarosite and anglesite. Our study innovatively proposed an inertial microfluidic method for the separation of FMPs by force difference in curved microchannels, thus produced two distinct migration behaviors and subsequent separation. In addition, the computational fluid dynamics (CFD) simulation model was constructed to predict and analyze the migration behavior and separation trend of FMPs through flow field simulation and particle trajectory tracking. The results indicated that 2.1 μm and 3.6 μm small particles migrated to the outer outlet of the microchannel due to the dominant Dean vortex force, while 7.2 μm and 9.4 μm large particles migrated to the inner outlet relying on inertial focusing. At a flow rate of 1.2 mL/min, the separation efficiency of 3.6 μm jarosite and 9.4 μm anglesite has achieved a leap from 0 % to 60.7 %. This discovery provided feasibility and insights into the application of microfluidic technology for particle separation, and offered enormous potential for practical iron residue treatment.

Macroscopic observation of a first order one-dimensional swelling-deswelling transition in a nanolayered material

AbstractThe high purity and superior quality of the synthetic clay mineral fluorohectorite allows for studies of phenomena that are masked by imperfections and the inhomogeneous charge distribution in the case of natural clay minerals. We have exploited this opportunity offered by synthetic fluorohectorite and report here digital optical microscopy observations of salinity controlled macroscopic swelling and deswelling behavior of extra-large nanolamellar clay mineral particle accordions of various sizes. We find that clay particle accordions, immersed in a saline solution, at sufficiently high salinity, are in their crystalline swelling region, with only a few water layers hydrating the accordion interlayer nano-spaces, corresponding to an interlayer spacing of about 1.5 nm. Using a micropipette as a micro-tweezer and thereby transferring accordions carefully back and forth between high and low salinity solutions, we observe well defined macroscopic accordion transitions between the crystalline swelling regime and an osmotic swelling regime where the interlayer spacings reach tens of nanometers, calculated from accordion thicknesses measured by digital imaging. The transitions display a clear first order character as evidenced by threshold salinity levels for their abrupt onsets as well as clear hysteresis with retention of crystalline or osmotic state memory, as salinity is increased or lowered. The experimental observations are supported by a theoretical model of the accordion interlayer spacing based on a Donnan equilibrium originating from the salinity gradient between the embedding saline solution and the ionic strength in the clay interlayers in the osmotic swelling regime.

Complex assessment of ambient particulate matter in a small settlement with coal-handling port

Relevance. Russian coal exports have been steadily increasing in recent years, and Far Eastern ports, originally not adapted to dusty cargoes, have switched to coal operations. Unoptimized coal handling leads to increased content of coal-containing particles in the air and to various environmental problems. Aim. To analyze the concentration of particulate matter in the air and the chemical composition of particles on the surface of conifer needles in the Posyet settlement (Primorsky Krai, Russia), where a large coal terminal operates. Materials and methods. The chemical composition was studied on the surface of conifer needles by X-ray fluorescence and in washout of conifer needle samples using Raman spectroscopy and energy dispersive analysis. Concentrations of particles with the diameter of 2.5 and 10 μm (PM2.5 and PM10, respectively) were measured using automatic monitoring stations. Results and conclusions. Chemical composition was dominated by mineral particles (calcite, silicates, etc.). However, the presence of coal particles (up to 8.3%) and metal particles was also observed. Mean concentrations of PM2.5 and PM10 were within the Russian and international health standards, but close to their upper limits. Concentrations of both measured particle fractions were highest during the winter months (as well as in March, which is traditionally a cold month in the Far East), followed by a gradual decrease. The study obtained new data on the annual variations of concentrations of PM2.5 and PM10, as well as on the basic composition of particles from the surface of woody vegetation (needles) as an indicator of the state of air pollution in this settlement.

Tailoring anisotropic ZnO/wood-structural holocellulose hybrids for dye degradation through controlled nanoinsertion

Nanostructured inorganic/wood-structural holocellulose hybrids offer new potential applications, including mechanical energy conversion, superhydrophobic materials, gas adsorption and so on. Owing to the anisotropy of wood, controlling the morphology of mineral particles inside porous holocellulose scaffold is still far from satisfactory. In this work, a homogeneous zinc oxide (ZnO) decoration inside wood-structural holocellulose scaffold was achieved while the morphology, distribution and content of ZnO micro-nano particles were controllable through changing the conditions of hydrothermal growth. The holocellulose scaffold was prepared through delignification and periodate oxidation, which is favorable for Zn2+ capture and ZnO nuclei formation because of the surface charge increased. The controlled ZnO insertion was realized by changing metal salt concentration, temperature and hydrothermal time. The obtained multilayer ZnO could provide multiple light refractions and reflections and enhance the utilization of light. Consequently, with a minor ZnO loading (15 wt%), the ZnO/wood-structural hybrids could totally degrade methyl orange and methyl blue in 6 h. This novel and scalable synthesis method shows potential for both the design and photocatalytic activity of holocellulose hybrids.