Mineral Crystal Size Research Articles

Valorization of acid mine drainage into potable water and valuable minerals through membrane distillation crystallization

Owing to the rise in population growth and demands for the current living standards, mineral and water resources are depleting at the alarming rate. Also, the mineral–water-energy nexus raises a concern of high-quality water and mineral production at low costs. Membrane distillation crystallization (MDC) has emerged as a promising technology capable of simultaneous water and mineral recovery from wastewater or industrially discharged brines. Herein, the MDC was evaluated for recovery of water and precious minerals from acid mine drainage discharged from the mine tailings. High quality fresh water with 99.9 % salt rejection and permeate flux of 2.32 kg·m−2·h−1 was recovered at 52 °C feed inlet temperature. Also, feed temperatures were varied to determine their impact on mineral crystal morphology, size distribution and growth rate. Predominantly recovered minerals were gypsum, manganese fluoride, potassium iron oxide, nickel oxide hydroxide, sodium sulphate and dihydrogen sulphate. Orthorhombic crystal structure of mineral salts was attained at low feed inlet temperature (34 °C). Higher feed inlet temperatures (i.e. 41° C and 52° C) promoted co-crystallization giving rise to orthorhombic polymorph structures. Narrow crystal size distribution was reported at low water recovery factor (initial growth) for all temperatures. However, the particle size distribution broadened as the recovery factor increased. The crystal sizes ranged from 3.91 ± 0.97 µm to 14.04 ± 3.31. Remarkably, crystal growth rate increased with an increase in feed inlet temperature. These findings open a research direction towards economic recovery of mineral and water to supplement the existing shortages. With a myriad of crystals obtained from the MDC process, an additional operational unit is required to selectively recover high economic minerals.

Effects of sorbitol and sucrose on soybean-urease induced calcium carbonate precipitate

This study explores the effects of two nucleating agents, sucrose and sorbitol, on soybean-urease induced calcium carbonate precipitation (SICP) at a crystal level. Comparative studies on the mineral composition, crystal size, surface morphologies and thermal stability of SICP samples with/without nucleating agent were investigated with high resolution XRD, SEM and synchronous thermal analyzer (STA), respectively. The results show the introductions of sorbitol or sucrose to SICP reduce the content of vaterite(114) from 10.07% to 1.81%–3.93%, indicating their effect on transforming vaterite into stabler calcite. Sorbitol can enlarge the crystals and improve the thermostability of SICP, indicating an improvement of the crystallinity of SICP. The sucrose-regulated SICP shows medium thermostability which is worse than SICP without the nucleating agent, indicating the addition of sucrose reduces the crystallinity of SICP. Sorbitol is an effective nucleating agent that can improve the behaviors all-around, while sucrose increases the calcite content of SICP but inhibits the crystallinity of SICP. This study reveals the regulations of SICP because of the introduction of sorbitol or sucrose, and provides guidance to the subsequent engineering application of SICP.

Induction and rescue of skeletal fragility in a high-fat diet mouse model of type 2 diabetes: An in vivo and in vitro approach.

Poor bone quality is associated with Type 2 Diabetes (T2D), with patients having a higher risk of fracture despite normal to high bone mineral density (BMD). Diabetes contributes to modifications of the mineral and organic matrix of bone. Hyperglycemia has been linked to the formation of advanced glycation end-products (AGEs) which increase the risk for skeletal fragility fractures. To this end, we investigated diabetes-induced skeletal fragility using a high-fat diet (HFD) mouse model and evaluated the efficacy of phenacyl thiazolium chloride (PTC) for in vitro removal of glycation products to rescue bone toughness. Ten-week-old C57BL/6J male mice (n=6/group) were fed a HFD or low-fat diet (LFD) for 22weeks. Mice given a HFD developed T2D and increased body mass compared to LFD-fed mice. MicroCT results showed that diabetic mice had altered microarchitecture and increased mineralization as determined by volumetric BMD and increased mineral crystal size as determined by X-ray Diffraction (XRD). Diabetic mice demonstrated loss of initiation and maximum toughness, which represent estimates of the stress intensity factor at a notch tip using yield force and ultimate force, respectively. Diabetic mice also showed higher accumulation of AGEs measured by biochemical assay (total fAGEs) and confocal Raman spectroscopy (Pentosidine (PEN), Carboxymethyl-lysine (CML)). Regression analyses confirmed the association between increased glycoxidation (CML, PEN) and loss of fracture toughness. Within the diabetic group, CML was the most significant predictor of initiation toughness while PEN predicted maximum toughness as determined by stepwise linear regression (i.e., stepAIC). Contralateral femora from HFD group were harvested and treated with PTC in vitro. PTC-treated samples showed total fAGEs decreased by 41.2%. PTC treatment partially restored bone toughness as, compared to T2D controls, maximum toughness increased by 35%. Collectively, our results demonstrate that matrix modifications in diet-induced T2D, particularly AGEs, induce bone fragility and their removal from bone matrix partially rescues T2D associated bone fragility.

Generalized Uncoupled Bone Remodeling Associated With Delayed Healing of Fatigue Fractures.

ABSTRACTFatigue fractures in bones are common injuries with load‐bearing activities, during which the remodeling aimed at removing microdamage has been suggested to play a role in increasing related fracture risk. Much attention has been given to the uncoupling between osteoclastic bone resorption and osteoblastic osteogenesis in fatigue fracture cases; however, the underlying pathophysiologic mechanisms of impaired fracture healing are yet unknown. Here we report multiple fatigue fractures in a physically active woman receiving contraceptive pills for years. Her fracture healing was remarkably slow, although she has been otherwise healthy. The patient underwent bone biopsy of the iliac crest that showed remarkable peritrabecular fibrosis with increased osteoclastic bone resorption combined with relatively low bone formation. Analysis of bone biochemical composition revealed a more complex picture: First, notable declines in bone mineral content–based parameters indicating abnormal mineralization were evident in both cancellous and cortical bone. Second, there was elevation in mineral crystal size, perfection, and collagen maturity in her bone tissues from different anatomical sites. To our knowledge, this is the first report showing generalized uncoupling in bone remodeling, increased peritrabecular fibrosis, and bone compositional changes associated with delayed healing of fatigue fractures. These results may explain delayed healing of fatigue and stress fractures. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Characterization of Bone Tissue and Bone Morphology in Taurine Transporter Knockout Mice.

Taurine, a sulfur-containing amino acid, has been shown to protect against tissue damage. It is highly accumulated in bone cells, including osteoblasts, where it enhances bone tissue formation. The quality of bone is defined by its microarchitecture, accumulated microscopic damage, collagen quality, mineral crystal size, and turnover rate. In this study, the effects of taurine depletion on bone metabolism and bone quality were investigated in taurine transporter knockout (TauT-/-) mice. The bone volume and trabecular number of 20-month-old male TauT-/- and TauT+/+ mice were measured by micro-computed tomography, and bone tissues were observed using hematoxylin and eosin and immunohistochemical staining methods. In the TauT-/- mice, the bone area of the proximal region of the femur was significantly smaller than that in the TauT+/+ mice, and the bone volume and trabecular number of the femur neck were significantly lower. Although the bone mineral densities in the mid-diaphysis and proximal regions were lower in the TauT-/- mice, the difference was significant for the proximal region only. Moreover, taurine depletion decreased the mineral density and strength parameters in the cancellous bone. The results of this study suggest that taurine plays an important role in maintaining bone quality.

LDN Protects Bone Property Deterioration at Different Hierarchical Levels in T2DM Mice Bone.

Type 2 diabetes mellitus (T2DM) commonly affects bone quality at different hierarchical levels and leads to an increase in the risk of bone fracture. Earlier, some anti-diabetic drugs showed positive effects on bone mechanical properties. Recently, we have investigated that low-dose naltrexone (LDN), a TLR4 antagonist treatment, improves glucose tolerance in high-fat diet (HFD)-induced T2DM mice and also gives protection against HFD-induced weight gain. However, effects on bone are still unknown. In this study, the effects of LDN on the bone properties at different hierarchical levels in T2DM mice bone were investigated. In order to investigate these, four different groups of bone (divided based on diet and treatment) were considered in this present study. These are (a) normal control diet treated with saline water, (b) normal control diet treated with LDN, (c) HFD treated with saline water, and (d) HFD treated with LDN. Bone properties were measured in terms of fracture toughness, nano-Young’s modulus, hardness, mineral crystal size, bone composition, and bulk mineral to matrix ratio. Results indicated that fracture toughness, nano-Young’s modulus, and hardness were decreased in T2DM bone as compared to normal bone, and interestingly, treatment with the LDN increases these material properties in T2DM mice bone. Similarly, as compared to the normal bone, decrease in the mineral crystal size and bulk mineral-to-matrix ratio was observed in the T2DM bone, whereas LDN treatment protects these alterations in the T2DM mice bone. The bone size (bone geometry) was increased in the case of HFD-induced T2DM bone; however, LDN cannot protect to increase the bone size in the T2DM mice bone. In conclusion, LDN can be used to control the T2DM-affected bone properties at different hierarchical levels.

XRD and ATR-FTIR techniques for integrity assessment of gamma radiation sterilized cortical bone pretreated by antioxidants.

Terminal sterilization of bone allograft by gamma radiation is required to reduce the risk of infection. Free radical scavengers could be utilized to minimize the deteriorating effects of gamma radiation on bone allograft mechanical properties. The objective of this research is to assess the changes in structural and chemical composition induced by hydroxytyrosol (HT) and alpha lipoic acid (ALA) free radical scavengers in gamma sterilized cortical bone. Bovine femurs specimens were soaked in different concentrations of HT and ALA for 7 and 3days respectively before irradiation with 35 KGy gamma radiation. The attenuated total reflection-Fourier transform infrared spectroscopy and the X-ray diffraction techniques were utilized to analyze the changes in chemical composition induced by irradiation in the presence of free radical scavengers. A significant increase in the proportion of amide I and amide II to phosphate was noticed in the irradiated group, while in the pretreated groups with ALA and HT this effect was minimized. In addition, gamma radiation reduced the mature to immature cross links while ALA and HT alleviated this reduction. No significant changes were noticed in the mineral crystallinity or crystal size. Bone chemical structure has been changed due to gamma irradiation and these changes are mainly relevant to amide I, amide II proportions and collagen crosslinks. The deteriorating effects of gamma sterilization dose (35kGy) on chemical structure of bone allograft can be alleviated by using (HT) and (ALA) free radical scavengers before irradiation.

Magma chamber evolution of the Ardestan pluton, Central Iran: evidence from mineral chemistry, zircon composition and crystal size distribution

AbstractThe Oligo–Miocene Ardestan quartz diorite to tonalite is part of widespread Cenozoic magmatism within the Urumieh–Dokhtar Magmatic Assemblage of Iran. The Ardestan pluton is composed mainly of varying proportions of plagioclase feldspar (normally zoned from bytownite to andesine), amphibole (magnesio-hornblende) and biotite. Biotite exhibits a range of Al values (~2–2.8 apfu) over very restricted Fe# ratios (0.42–0.56) which are characteristic of continental arc magmatic suites. High Ti2O contents of biotite (<6.1 wt.%) suggest a magmatic origin. Ti-in-biotite geothermometery gives a mean crystallisation temperature of 730 ± 56°C, slightly higher than calculated TZr.Ti°C (716 ± 50°C) and similar to the average TZr.sat°C (735 ± 26°C). These results are consistent with the low bulk-rock SiO2 contents, which provide minimum estimates of temperature and indicate zircon crystallised from a fractionated magma. Zircons from the Ardestan pluton have high (Sm/La)N (>10) ratios suggesting a magmatic origin. T–$f_{{\rm O}_{\rm 2}}$ calculations of oxygen fugacity between –13.6 to –16.9 indicate oxidising crystallisation conditions between the Ni–NiO (NNO) and Fe2O3–Fe3O4 (HM) buffers. Tight linear trends of log (XF/XOH), log (XCl/XOH) and log (XCl/XOH) vs. XMg represent a narrow range of $f_{{\rm H}_2O}$, fHF and fHCl, clearly indicating that physico-chemical conditions were essentially constant throughout the formation of magmatic biotite. The shape of crystal size distribution curves along with the medium Al and Mg contents in amphibole and biotite, respectively, are consistent with a history of magma mixing involving injections of basic magma into the evolving felsic chamber. Calculated residence time for Ardestan plagioclase crystals of ~630 years support field evidence that these plutons were emplaced at shallow depths.

Magma chamber processes and dynamics beneath northwestern Anatolia: Insights from mineral chemistry and crystal size distributions (CSDs) of the Kepsut volcanic complex (NW Turkey)

Mineral chemistry, petrography and crystal size distributions of Early Miocene mafic and intermediate lavas from the Kepsut Volcanic Complex (KVC) have been studied to decipher magma chamber processes and dynamics beneath northwestern Anatolia. KVC which is a part of the Western Anatolian Volcanic Province comprises lavas represented by various compositions ranging from basaltic andesite to rhyodacite and associated pyroclastics. Basaltic andesite and andesite lavas of the KVC, the focus of this study, present distinct petrographical features such as three plagioclase generations, patchy zoning, oscillatory reverse zoning, sieve textured crystals and clinopyroxene-mantled amphibole that are clear indicators of disequilibrium conditions in magma chamber(s). Petrography, mineral chemistry and crystal size distribution studies of andesite and basaltic andesite lavas of the KVC indicate that magma evolution occurred in four stages: (I) Near-Equilibrium Stage, (II) Mafic Input Stage, (III) Mixing/Mingling Stage and (IV) Pre-eruption Stage. Thermobarometry calculations indicate that crystallization of andesite and basaltic lavas occurred at similar pressure (mid-to-deep crustal depths, 5–7 kbar) but distinct temperature conditions (920–952 °C and 921–1069 °C, respectively) suggesting that KVC magmas evolved either in the same or different magma chambers at similar depths and experienced open-system processes. Both of these hypotheses are compatible with multistage evolution of the KVC. Combined petrography, mineral chemistry and geothermometry studies on KVC rocks indicate that mixing/mingling processes and subsequent decompression-driven crystallization were the principal mechanisms for the origin of the textural and mineralogical diversity that is characteristic of KVC lavas. Disequilibrium crystallization was probably caused by the influx of a hotter basaltic magma into crustal magma chambers during the first major period of north-south extension in western Anatolia.

Mineral chemistry and crystal size distributions of mafic dikes and sills on the eastern border of the Parnaíba Basin, NE Brazil

Crystal size distributions (CSDs) and mineral chemistry of plagioclase and clinopyroxene are used to quantify textures and estimate timescales of Mesozoic mafic sills and dikes exposed on the eastern margin of the Parnaíba Basin (NE Brazil). The diabases consist of plagioclase, clinopyroxene (augite and pigeonite) and FeTi oxides and show textures that vary from holocrystalline, to locally porphyritic, glomerophyric and hypocrystalline. Plagioclase and clinopyroxene CSDs are similar in sills and dikes, with clinopyroxene slopes systematically steeper than plagioclase slopes. Plagioclase usually records nearly log-linear negative slopes that tend to steepen approaching the wall rock contact. Plagioclase typically shows normal zoning with anorthite contents varying (An84-25) from the center to the grain margin. Calculated residence times for the log-linear segments vary from ca. one month (τ = 10−7 mm·s−1) for samples situated 20 cm from the contact to ca. four months for samples ~3 m away from the contact. Clinopyroxene consists of augite (dominant) and pigeonite and shows relatively uniform compositions. Unlike plagioclase, clinopyroxene CSDs tend to be flat or slightly positive towards the finer grains suggesting that the texture was modified during the crystallization of the residual melt. Plagioclase microlites (L < 0.5 mm), in contrast, show kinked CSDs with the steeper negative slopes including minute crystals of sanidine (orthoclase component) and alkali-sodic feldspar in addition to CaNa plagioclase. The modified textures and high nucleation density of microlites in mostly static, deep-seated magmatic reservoirs therefore resulted from chemical disequilibrium between largely solidified tholeiitic magma and late, highly fractionated alkali-rich residual melts. The estimated time for the full crystallization of the largest sills is one and one-half years.

Mineral Chemistry and Crystal Size Distributions of Mafic Dikes and Sills on the Eastern Border of the Parnaíba Basin, Ne Brazil

Mineral Chemistry and Crystal Size Distributions of Mafic Dikes and Sills on the Eastern Border of the Parnaíba Basin, Ne Brazil

Biomolecular regulation, composition and nanoarchitecture of bone mineral

Tough natural nanocomposites like bone, nacre and sea sponges contain within their hierarchy, a mineral (phosphate, silicate or carbonate) phase that interacts with an organic phase. In bone, the role of mineral ultrastructure (organization, morphology, composition) is crucial to the mechanical and biological properties of the tissue. Better understanding of mineral interaction with the organic matrix, in particular non-collagenous proteins, osteocalcin (OC) and osteopontin (OPN), can lead to better design of biomimetic materials. Using small angle x-ray scattering (SAXS) and wavelength dispersive spectroscopy (WDS) on single (OC−/− and OPN−/−) and double (OC-OPN−/−;−/−) genetic knockout mice bones, we demonstrate that both osteocalcin and osteopontin have specific roles in the biomolecular regulation of mineral in bone and together they are major determinants of the quality of bone mineral. Specifically, for the first time, we show that proteins osteocalcin and osteopontin regulate bone mineral crystal size and organization in a codependent manner, while they independently determine crystal shape. We found that OC is more dominant in the regulation of the physical properties of bone mineral, while OPN is more dominant in the regulation of the mineral composition.

Periosteum Extracellular-Matrix-Mediated Acellular Mineralization during Bone Formation.

Cell-mediated mineralization is essential for bone formation and regeneration. In this study, it is proven that extracellular matrix (ECM) of decellularized periosteum can play an initiative and independent role in bone-like apatite formation. Using decellularized periosteum scaffold, it is revealed that ECM scaffold itself can promote critical bone defect regeneration and nude mouse ectopic ossification. The natural collagen matrix of decellularized periosteum can serve as a 3D structural template for Ca-P nuclei initiation, controlling the size and orientation of bone-like mineral crystals. The naturally cross-linked and highly ordered 3D fibrillar network of decellularized periosteum not only provides a model for mimicking mineralization in vitro and in vivo to elucidate the important functions of ECM in bone formation and regeneration, but also can be a promising biomaterial for bone tissue engineering and clinical application.

Lithium saltworks of the Salar de Atacama: A model for MgSO4-free ancient potash deposits

Potash basins similar to those in the geological past no longer exist at present. There are only hypersaline lakes such as those in the Tibetan Plateau where carnallite [KCl·MgCl2·6H2O] precipitates. Given that the purpose of common saltworks is to obtain NaCl, the halitic stage is not exceeded. By contrast, saltworks extracting lithium by solar evaporation reach more advanced stages of brine evolution and saline precipitation. In the Salar de Atacama saltworks, with a relative humidity commonly below 30% (monthly average), salts precipitate following a sequence of halite [NaCl], sylvite [KCl], carnallite and bischofite [MgCl2·6H2O] and display a useful model of evolution similar to that which gave rise to MgSO4-free potash deposits in the past. Prismatic-acicular gypsum [CaSO4·2H2O], the main accessory mineral, is transformed into a less hydrated calcium sulfate, probably anhydrite [CaSO4], during carnallite precipitation. Mineral crystal size and annual sedimentary thickness of each paragenesis are compared with those in ancient potash deposits. The behavior of sylvite and carnallite as cements is observed at the onset of their precipitation in ponds where both minerals coexist with previous halite. Millimeter cyclicity due to day-night thermal variations is observed in these saltworks, whereas cm- and mm-cyclicities have been interpreted in ancient sites as annual (regular) and intra-annual (irregular), respectively. Conditions similar to those existing at the Salar de Atacama were necessary to preserve carnallite, which is commonly the most evolved mineral in the ancient deposits. The development of potash deposits in the South Pyrenean Foreland Basin and the Rhine Graben, near the Eocene-Oligocene boundary, is attributed to global aridity and cooling and to the basin restriction associated with a decrease in the ocean level caused by the spread of the Antarctic ice cap.

Protein-free formation of bone-like apatite: New insights into the key role of carbonation.

The nanometer-sized plate-like morphology of bone mineral is necessary for proper bone mechanics and physiology. However, mechanisms regulating the morphology of these mineral nanocrystals remain unclear. The dominant hypothesis attributes the size and shape regulation to organic-mineral interactions. Here, we present data supporting the hypothesis that physicochemical effects of carbonate integration within the apatite lattice control the morphology, size, and mechanics of bioapatite mineral crystals. Carbonated apatites synthesized in the absence of organic molecules presented plate-like morphologies and nanoscale crystallite dimensions. Experimentally-determined crystallite size, lattice spacing, solubility and atomic order were modified by carbonate concentration. Molecular dynamics (MD) simulations and density functional theory (DFT) calculations predicted changes in surface energy and elastic moduli with carbonate concentration. Combining these results with a scaling law predicted the experimentally observed scaling of size and energetics with carbonate concentration. The experiments and models describe a clear mechanism by which crystal dimensions are controlled by carbonate substitution. Furthermore, the results demonstrate that carbonate substitution is sufficient to drive the formation of bone-like crystallites. This new understanding points to pathways for biomimetic synthesis of novel, nanostructured biomaterials.

Role of cortical bone in hip fracture.

In this review, I consider the varied mechanisms in cortical bone that help preserve its integrity and how they deteriorate with aging. Aging affects cortical bone in two ways: extrinsically through its effects on the individual that modify its mechanical loading experience and 'milieu interieur'; and intrinsically through the prolonged cycle of remodelling and renewal extending to an estimated 20 years in the proximal femur. Healthy femoral cortex incorporates multiple mechanisms that help prevent fracture. These have been described at multiple length scales from the individual bone mineral crystal to the scale of the femur itself and appear to operate hierarchically. Each cortical bone fracture begins as a sub-microscopic crack that enlarges under mechanical load, for example, that imposed by a fall. In these conditions, a crack will enlarge explosively unless the cortical bone is intrinsically tough (the opposite of brittle). Toughness leads to microscopic crack deflection and bridging and may be increased by adequate regulation of both mineral crystal size and the heterogeneity of mineral and matrix phases. The role of osteocytes in optimising toughness is beginning to be worked out; but many osteocytes die in situ without triggering bone renewal over a 20-year cycle, with potential for increasing brittleness. Furthermore, the superolateral cortex of the proximal femur thins progressively during life, so increasing the risk of buckling during a fall. Besides preserving or increasing hip BMD, pharmaceutical treatments have class-specific effects on the toughness of cortical bone, although dietary and exercise-based interventions show early promise.

Multi-scale study of the polishing behaviour of quartz and feldspar on road surfacing aggregate

ABSTRACTIn this paper, the exact mechanisms as to how petrographic properties of aggregate influence the polishing behaviour quantitatively were identified. Since the aggregate is composed of the different rock-forming minerals, the analyses conducted in this research project focused not only on the aggregate but also on crystals/minerals. The hardest and most abundant rock-forming minerals found on earth – quartz and feldspar – were investigated with polishing tests with the Aachen Polishing Machine on granite aggregates from four sources which exhibit different mineralogical properties. Changes of the aggregate texture and minerals were studied based on texture measurements and skid resistance measurements obtained by means of the Pendulum Test and the Wehner/Schulze device. The influences of mineral composition and crystal size on the changes of the micro-texture and skid resistance of the aggregates were determined by comparing the four granites. The polishing and wearing behaviour of quartz and various feldspars (albite, microcline and plagioclase) were characterised quantitatively by means of a spectral analysis and abrasion analysis. The results show that the micro-texture of exposed minerals is greatly smoothened on wavelengths from 100 to 500 μm. Fine-grained quartz or feldspar crystals tend to be rougher than medium of large-sized crystals. Quartz exhibits more favourable properties than feldspar between 100 and 500 μm; this is especially true for fine quartz crystals. The correlation that more content of coarse-grained quartz leads to high friction value cannot be proved in this research.

On-site SEM and nanomechanical properties of human OI bone

Modulus mapping and on-site field emission-scanning electron microscopy (FE-SEM) nanoindentation are both applied for the first time on ‘undisturbed’ healthy human and osteogenesis imperfecta (OI) human cortical bones in this work. Modulus mapping reveals the elastic moduli of hydroxyapatite and collagen to be 189·9 and 2·4 GPa for the normal bone and 294·7 GPa and 2·9 GPa for the OI bone respectively. Modulus mapping also indicates a spatial variation in the elastic moduli consistent with the distribution of mineralized fibril and extrafibrillar mineral. The diameter of collagen fibers and the size of mineral crystals in OI are observed to be smaller, and the mineral crystal in OI is also observed to be less anisotropic than those from the normal bone. The median elastic moduli of the OI bone sample are greater than those of the normal bone. On-site FE-SEM nanoindentation reveals the existence of a highly mineralized inner ring with higher elastic moduli adjacent to the Haversian canal and that the elastic nanomechanical properties of interstitial lamellae are greater than those of osteonal lamellae. A periodic modulation in modulus corresponding to the width of a lamella is also observed in on-site FE-SEM nanoindentation.

Bone mineral crystal size and organization vary across mature rat bone cortex.

The macro- and micro-features of bone can be assessed by using imaging methods. However, nano- and molecular features require more detailed characterization, such as use of e.g., vibrational spectroscopy and X-ray scattering. Nano- and molecular features also affect the mechanical competence of bone tissue. The aim of the present study was to reveal the effects of mineralization and its alterations on the mineral crystal scale, by investigating the spatial variation of molecular composition and mineral crystal structure across the cross-section of femur diaphyses in young rats, and healthy and osteoporotic mature rats (N=5). Fourier transform infrared spectroscopy and scanning small- and wide-angle X-ray scattering (SAXS/WAXS) techniques with high spatial resolution were used at identical locations over the whole cross-section. This allowed quantification of point-by-point information about the spatial distribution of mineral crystal volume. All measured parameters (crystal dimensions, degree of orientation and predominant orientation) varied across the cortex. Specifically, the crystal dimensions were lower in the central cortex than in the endosteal and periosteal regions. Mineral crystal orientation followed the cortical circumference in the periosteal and endosteal regions, but was less well-oriented in the central regions. Central cortex is formed rapidly during development through endochondral ossification. Since rats possess no osteonal remodeling, this bone remains (until old age). Significant linear correlations were observed between the dimensional and organizational parameters, e.g., between crystal length and degree of orientation (R(2)=0.83, p<0.001). Application of SAXS/WAXS provides valuable information on bone nanostructure and its constituents, effects of diseases and, prospectively, mechanical competence.

Meso-mechanics simulation analysis of microwave-assisted mineral liberation

Microwave-assisted crushing and grinding can improve efficiency and reduce energy consumption. This paper takes rock grains with galena and calcite as the research object to establish a two-dimensional computational model through the finite difference software FLAC2D. It analyzes the process and law of mineral boundary failure under microwave irradiation, and assesses the effects of four factors, namely, microwave irradiation time, power density, mineral crystal size, and mineral content, on mineral boundary failure. Results indicate an optimal microwave irradiation period for the rapid failure of mineral boundary. Moreover, irradiation time and energy consumption can be reduced by increasing the microwave power density. However, irradiation time and energy consumption are basically unchanged when the microwave power density is above a certain threshold. Mineral content slightly affects the microwave irradiation time, whereas mineral crystal size significantly affects the microwave irradiation time. In addition, a larger-sized mineral crystal requires less irradiation time and energy consumption to reach the same failure rate. However, irradiation time and energy consumption slightly change when the crystal size is larger than a certain value.