Apatite Minerals Research Articles

Raman spectroscopic study and identification of multi-period osteoarthritis of canine knee joint

A home-made small-sized Raman spectrometer combined with machine learning algorithms was used to study and identify healthy and multi-period osteoarthritis (OA) canine knee joints. Nine canines were equally divided into three groups according to the post-operative (OA modeling) time of 2-month, 3-month and 7-month. Other two normal canines were used as control. It was found that the degeneration degree of cartilage was positively correlated with post-operative time by doing anatomical analysis. The mixed Raman spectra of cartilage and subchondral bone were collected and analyzed, which reveals subchondral bone demineralization and carbonate ion substituting into the apatite mineral during OA. Raman spectra combined with principal component analysis (PCA) further disclosed that collagen matrix became unordered, both content ratios of amide I/matrix and phenylalanine/matrix in OA cartilage and subchondral bone increased. Based on the PCA getting five principal components, all groups were effectively discriminated by Fisher discriminant analysis (FDA) with high accuracy of 91.07% for the validation set, as well as 95.45% for the test set. It suggests that Raman spectroscopy combined with machine learning is capable to become an effective tool to achieve in situ identification of multi-period OA with high accuracy and preclinical significance.

Enhanced photoluminescence in RE (Eu3+ , Ce3+ and Sm3+ )-activated Ca10 (PO4 )F2 phosphors by double or triple ionized mineral doping: a comparative study.

In this work, RE3+ (Eu, Ce and Sm)-activated Ca10 (PO4 )6 F2 (fluorapatite) phosphors were synthesized by doping with different apatite minerals (SO4 , VO4, WO4 ) using a solid-state diffusion method. Optical and structural characterizations were performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and photoluminescence (PL) spectroscopy. XRD characterization showed the crystalline nature of the phosphor. PL properties were investigated under ultraviolet light excitation for all three rare earths. CIE chromaticity revealed the colour emitted in the visible region. Luminescence intensity was enhanced considerably by tuning the host matrices after core-shell formation by substitution with other ions producing promising candidates for white light-emitting diode materials.

Synthesis and characterization of iron oxide-hydroxyapatite-chitosan composite coating and its biological assessment for biomedical applications

Hydroxyapatite coatings are widely employed to enhance the osseointegration ability and bioactivity of biodegradable magnesium alloys as biodegradable implants. To further enhance the efficiency of hydroxyapatite-coated magnesium alloys, iron oxide particles were used along with hydroxyapatite to produce the antimicrobial and bioactive coating via electrophoretic deposition. The coatings were integrated in a matrix of chitosan. The experiments were carried out with different iron oxide particle concentrations i.e., 1, 3 and 5 (wt. %)), respectively. The antimicrobial property was investigated in Escherichia coli and Staphylococcus aureus strains, which confirmed that the micro-organisms development was suppressed by the significant rise of iron oxide particles. Evaluation of bioactivity behavior was carried out in phosphate buffer saline for 7 days, and the composite coatings were found to enhance the apatite mineralization, as affirmed by SEM-EDX analysis. The assessment of hemocompatibility showed that the hemolysis ratio was less than 5 %, which confirms that the coatings were blood compatible in nature. The outcomes showed that hydroxyapatite-iron oxide-chitosan composite coating may be extensively utilized as an appropriate material for biomedical implant applications.

Strontium isotope analysis of apatite via SIMS

We report the development of a SIMS analytical method for in situ Sr isotope analysis of the mineral apatite at an analytical scale of 15 μm or less. Experiments were conducted on a series of reference apatites of widely differing Sr contents at three different mass resolution settings: low (3000), moderate (4200) and very high (16000), using a large-geometry CAMECA 1280 ion microprobe retrofitted with a HyperionTM oxygen plasma ion source. Peak-stripping algorithms tailored to the different mass-resolution settings were developed to correct for significant interferences on the target strontium isotope species in the mass spectra, namely Ca dimers, CaPO, Rb and SrH, and for instrumental mass fractionation. The most consistently accurate and precise 87Sr/86Sr ratios were achieved at the 3000 mass resolution setting with appropriate energy filtering and use of a cold trap. On average, corrected 87Sr/86Sr ratios by this method were elevated by ~0.8‰ above equivalent TIMS and solution ICPMS data, with consistent behaviour across the range of Sr concentrations. Individual spot precision of ± 0.001 to 0.004 (2SE) was achieved, depending on Sr content. The key advantages of SIMS analysis compared to existing LA-MC-ICP-MS methods are the high spatial resolution, low sample consumption, and the high mass resolution that allows for the elimination of problematic isobaric interferences. Our approach is particularly useful for the analysis of small or valuable targets, such as mineral inclusions or meteoric samples, and for apatite with high REE contents. However, the much larger volume of material consumed during LA-MC-ICP-MS analysis allows for substantially better precision than the SIMS method presented here. The highly variable trace element composition of natural apatites, involving both cationic and anionic substitutions, necessitates careful characterisation of prospective targets prior to any in situ analysis, in addition to matching to appropriate reference materials.

Impacts of a Nano-Laponite Ceramic on Surface Performance, Apatite Mineralization, Cell Response, and Osseointegration of a Polyimide-Based Biocomposite.

IntroductionPolyimide (PI) exhibits good biocompatibility and high mechanical strength, but biological inertness that does not stimulate bone regeneration, while laponite possesses excellent bioactivity.MethodsIn this study, to improve the bioactivity of PI, nano–laponite ceramic (LC)–PI composites (LPCs) were fabricated by melt processing as implantable materials for bone repair.ResultsThe compressive strength, hydrophilicity, and surface roughness of LPCs with 40 w% LC content (LPC40s) were higher than LPC20s, and LPC20s higher than pure PI. In addition, no apatite mineralization occurred on PI, while apatite mineralized on LPCs in simulated body fluid. Compared with LPC20, more apatite deposited on LPC40, indicating good bioactivity. Moreover, the adhesion, proliferation, and alkaline phosphatase activity of rat bone mesenchymal stem cells on LPCs significantly increased with LC content increasing in vitro. Furthermore, the evaluations of animal experiments (micro-CT, histology, and pushout load) revealed that compared with LPC20 and PI, LPC40 significantly enhanced osteogenesis and osseointegration in vivo.DiscussionIncorporation of LC into PI obviously improved not only surface physicochemical properties but also biological properties of LPCs. LPC40 with high LC content displayed good biocompatibility and bioactivity, which markedly promoted osteogenesis and osseointegration. Therefore, with its superior biocompatibility and bioactivity, LPC40 could be an alternative candidate as an implant for orthopedic applications.

High-silica rhyolites in the terminal stage of massive Cretaceous volcanism, SE China: Modified crustal sources and low-pressure magma chamber

Late Cretaceous felsic volcanism erupted as calderas in the terminal stage of the massive Cretaceous volcanism in SE China. This paper reports comprehensive geochemical and isotopic data for high-silica rhyolites from the Shiniushan and Xiaoxiong calderas in eastern Fujian–Zhejiang provinces, SE China. Zircon U-Pb dating constrains these rhyolites eruptions to 94–92 Ma and 93–89 Ma in the sites of the two calderas. All the samples possess high-silica contents with peraluminous characteristics and are enriched in light rare earth elements (LREEs), Rb, and Th-U and depleted in Ba, Nb-Ta, Sr and Eu. These samples have high whole-rock F (114–596 ppm) but low Cl (3.3–54.8 ppm) contents. Apatite minerals separated from the high-silica rhyolites are classified as fluorapatite and show F-rich (F > 3.56 wt%), Cl-poor (Cl < 0.02 wt%), low (La/Sm)N and high (Gd/Yb)N ratios, with a negative Eu anomaly. The high-silica rhyolites yield initial (87Sr/86Sr)i ratios of 0.70405 to 0.70789, negative whole-rock εNd(t) (−3.3 to −6.3), negative apatite εNd(t) (−5.2 to −6.6) and negative zircon εHf(t) values (−0.1 to −9.6). Our data suggest that their primary magma was derived from modified crustal sources that could contain a mixture of ancient and juvenile components, and it then evolved, was injected into a low-pressure magma chamber, and finally erupted with the release of volatiles at the magma chamber roof. We infer that SE China was mainly under a setting of lithospheric extension from the Early to early Late Cretaceous because of slab roll-back and steepening of the subducted Paleo-Pacific Plate.

Early Cretaceous volcanic rocks in Yunzhug area, central Tibet, China, associated with arc–continent collision in the Tibetan Plateau?

The Lhasa-Qiangtang collision prior to the Cenozoic collision of India and Asia is a key process for the early stage of tectonic history of the Tibetan Plateau; however, when and how the Lhasa-Qiangtang collision is less well known. In this paper, we present an analysis of petrological, geochemical, Sr–Nd–Hf isotopic data, and zircon LA-ICP-MS UPb data for the volcanic rocks from the Yunzhug area, northern Lhasa. Our new data reveal an important, previously unrecognized stage of tectono-magmatic event in northern Lhasa subterrane. Zircons from the andesites and rhyolites yield concordant ages of 120.24 ± 0.79 Ma (mean square of weighted deviates (MSWD) = 0.35) and 120.1 ± 1.1 Ma (MSWD = 1.18), respectively, which are younger than the age of Jurassic intra-oceanic magmatism and older than the 112–110 Ma Lhasa-Qiangtang collision. The Yunzhug volcanic rocks are composed of andesites and A-type rhyolites of high-K affinity. The andesites originated mainly from a mixed mantle source with variable degrees of contribution of continental crust, and the rhyolites were derived mainly from melting of lower continental crust. Addition of subducted flysch or oceanic sediments resulted in the high-K affinity. Fractional crystallization of plagioclase, K-feldspar, amphibole, and minor microlitic apatite and FeTi oxides minerals in the shallow level is mainly responsible for variable major and trace element contents of the andesites and rhyolites. Our results show that the early Cretaceous Yunzhug volcanic rocks can represent the early stage magmatism recording the entrance of subducted continental crust into the subduction zone, agreement with processes of arc-continent collision from intra-oceanic subduction to continental collision. The presence of oceanic sediments or monazite residual in magma source under the arc-continent zone can cause LREE enrichment to exceed the continental crust, making arc magmatic compositions close to average continental values.

Interfacial bonding between mineral platelets in bone and its effect on mechanical properties of bone

Bone is a composite material consisting principally of apatite mineral, collagen fibrils, non-collagenous proteins, and other organic species. Recent electron microscopy studies have shown that the mineral in bone occurs as stacks of thin polycrystalline sheets (“mineral lamellae,” MLs) which surround and lie between the collagen fibrils. We focus on the effect of the interface between these mineral lamellae on the mechanical properties of bone. Previous studies on bone treated with sodium hypochlorite (NaClO) to remove all organic material showed a greatly weakened mineral framework. Here, we treated femoral cortical bone with ethylenediamine (EDA), which only removes collagen, to study the effect of its removal on bone properties. We tested the degree of completion of the treatment by Raman spectroscopy and thermogravimetric analysis. When only collagen is removed, a continuous mineral structure remains and is less weakened than by NaClO treatment. Transmission electron microscopy study of finely ground particles of the EDA treated bone shows that stacks of MLs remain joined, whereas in NaClO treated bone, only isolated crystals are present. Thus, we infer that the MLs in bone are held together in stacks by an organic glue, which is destroyed by NaClO, but which survives the EDA treatment. We show that this glue may contribute to the stiffness, strength, and energy absorption of bone. Further studies are needed to discover the chemical nature of this glue. This study provides a starting point for such investigations.

EFFECTS OF NANO-HYDROXYAPATITE DENTIFRICES WITH AND WITHOUT FLUORIDE ON PRIMARY TEETH ENAMEL: A MICRO-CT AND A SEM STUDY

Objectives: The ideal remineralization system should provide sufficient ion reserves to provide mineral gain on deeper surfaces, as well as being biocompatible and easy to apply with no adverse effect. The aim of this study was to evaluate the remineralization efficiency of dentifrice form of nano-hydroxyapatite alone and its combination with fluoride on initial enamel lesions in primary teeth by micro-CT and SEM. Materials and Methods: The enamel surfaces of 30 extracted primary incisors were treated with nano-hydroxyapatite based (nHAP), nano-hydroxyapatite-fluoride-containing (nHAP+F) and fluoride-containing dentifrice (F), respectively after the pH cycle. Mineral gain and surface properties were evaluated by micro-CT and SEM.Results: nHAP group provided more mineral gain than fluoride containing paste groups but there was no statistically significant difference (p&amp;gt;0.05) according to the micro-CT evaluations.In SEM images, the micropores were completely covered with an apatite layer and mineral precipitations were observed to be wider and more pronounced in the nHAP group. Calcium fluoride crystalline structures exhibited non-homogeneous globular precipitations in the F Group.Conclusions: It was concluded that nHAP dentifrice is as effective as fluoride dentifrice on initial enamel lesions in primary teeth with less caries-resistant enamel surface and therefore it can be safely used.

Soil mineralogy and chemical properties as a basis for establishing nutrient management strategies in volcanic soils of Mount Ceremai, West Java

Soil mineralogy and its effect on chemical properties of volcanic soils located in Mount Ceremai has not been studied thoroughly. The objective of the study was to assess soil mineralogy and chemical properties of volcanic soils derived from different types and ages as an integrated strategic consideration to establish nutrient management. Field research and laboratory analysis were carried out on four soil profiles derived from different parent materials, namely young lava (KM-01), young pyroclastic fall (KM-02), old lava (KM-03), and old pyroclastic fall (KM-04). Results showed that KM-04 soil had limited nutrient reserved mineral (NRM), while KM-01, KM-02, and, unexpectedly, KM-03 soil still contained high NRM. There were no apatite and K-bearing mineral found in all soils, so regular P and K fertilization were recommended. Clay composition in the surface layer of KM-01 soil was dominated by amorphous minerals, while other soils contained amorphous mineral, gibbsite, and halloysite. Although all soils contained NRM such as labradorite, augite, and hypersthene, all soils had low exchangeable cations. P retention is a serious problem for all soils, especially KM-03 which has the highest amount of allophane. Therefore, nutrient management should be focused on accelerating NRM weathering, increasing soil CEC, and improving P fertilization efficiency.

Evolution of the Kiruna-type Gol-e-Gohar iron ore district, Sanandaj-Sirjan zone, Iran

The Gol-e-Gohar iron ore district in the Sanandaj-Sirjan zone of south-western Iran comprises six major ore bodies. The largest deposit is Gol-e-Gohar No. 3 (Gohar-Zamin) with about 643 Mt @ 53.1% Fe. The host rocks in this district are Late Neoproterozoic meta-sedimentary rocks (para-gneiss, marble), meta-basalt (ortho-amphibolite), and I-type meta-granite (ortho-gneiss). The district is characterized by potassic-sodic (albite-K-feldspar), phyllic (muscovite) and propylitic (chlorite-calcite-dolomite-magnesite with pyrite) hydrothermal alteration, and massive and brecciated Kiruna-type magnetite ± apatite mineralization. There is also boron (B) metasomatism, manifested as tourmaline blastesis. Gol-e-Gohar magnetite contains Mg, Ca and Si up to the percent range, V and Ti in the 100s ppm level, and low Cr, Co, Ni in the tens of ppm range, typical of skarn or IOCG mineralization. The oxygen isotope composition of magnetite is 4.9 ± 0.7‰ δ18O (n = 9) and the iron isotope composition is 0.49 ± 0.05‰ δ56Fe (n = 17). These data suggest that the magnetite ore formed from a magmatic-hydrothermal (high-T) fluid in equilibrium with a granitic source. The hydrothermal carbonate inclusions in late pyrite have δ11B values of 20.3 ± 2.4‰, indicating the imprint of fluids which interacted with the Early Cambrian marine country rocks of the district, such as limestone and/or evaporites. The Gol-e-Gohar iron ore district shows several similarities to the Bafq iron district, located about 400 km to the north, and seems to be a disrupted member of the Kashmar-Kerman arc.

Rare Earth Elements and Sr Isotope Ratios of Large Apatite Crystals in Ghareh Bagh Mica Mine, NW Iran: Tracing for Petrogenesis and Mineralization

The 320 Ma Ghareh Bagh mica mine is the only active mica mine in northwest Iran, and hosts Mg-bearing biotite (phlogopite) with apatite, epidote, and calcite. Chemical investigation of apatite infers the high abundances of the rare earth elements (REEs up to 5619 ppm), higher ratios of the LREE/HREE ((La/Yb)N = 28.5–36.7)) and high content of Y (236–497 ppm). REE pattern in the apatite and host A-type granite is almost the same. Ghareh Bagh apatite formed from the early magmatic-hydrothermal exsolved fluids at the high temperature from the Ghushchi alkali feldspar granite. The apatite crystals came up as suspension grains and precipitated in the brecciated zone. The early magmatic-hydrothermal fluids settle phlogopite, epidote, chlorite, K-feldspar and albite down in the brecciation zone. Due to the precipitation of these minerals, the late-stage fluids with low contents of Na+, Ca2+ and REE affected the early stage of alteration minerals. The high ratios of 87Sr/86Sr (0.70917 to 0.70950) are more consistent with crustal sources for the apatite large crystals. The same ages (320 Ma) for both brecciated mica veins and host alkali feldspar granites infer the apatite and paragenesis minerals were related to host granite A-type granite in the Ghareh Bagh area.

Globular structure of the hypermineralized tissue in human femoral neck

Bone becomes more fragile with ageing. Among many structural changes, a thin layer of highly mineralized and brittle tissue covers part of the external surface of the thin femoral neck cortex in older people and has been proposed to increase hip fragility. However, there have been very limited reports on this hypermineralized tissue in the femoral neck, especially on its ultrastructure. Such information is critical to understanding both the mineralization process and its contributions to hip fracture. Here, we use multiple advanced techniques to characterize the ultrastructure of the hypermineralized tissue in the neck across various length scales. Synchrotron radiation micro-CT found larger but less densely distributed cellular lacunae in hypermineralized tissue than in lamellar bone. When examined under FIB-SEM, the hypermineralized tissue was mainly composed of mineral globules with sizes varying from submicron to a few microns. Nano-sized channels were present within the mineral globules and oriented with the surrounding organic matrix. Transmission electron microscopy showed the apatite inside globules were poorly crystalline, while those at the boundaries between the globules had well-defined lattice structure with crystallinity similar to the apatite mineral in lamellar bone. No preferred mineral orientation was observed both inside each globule and at the boundaries. Collectively, we conclude based on these new observations that the hypermineralized tissue is non-lamellar and has less organized mineral, which may contribute to the high brittleness of the tissue.

In vitro Apatite Mineralization, Degradability, Cytocompatibility and in vivo New Bone Formation and Vascularization of Bioactive Scaffold of Polybutylene Succinate/Magnesium Phosphate/Wheat Protein Ternary Composite.

PurposeA bioactive and degradable scaffold of ternary composite with good biocompatibility and osteogenesis was developed for bone tissue repair.Materials and MethodsPolybutylene succinate (PS:50 wt%), magnesium phosphate (MP:40 wt%) and wheat protein (WP:10 wt%) composite (PMWC) scaffold was fabricated, and the biological performances of PMWC were evaluated both in vitro and vivo in this study.ResultsPMWC scaffold possessed not only interconnected macropores (400 μm to 600 μm) but also micropores (10 μm ~20 μm) on the walls of macropores. Incorporation of MP into composite improved the apatite mineralization (bioactivity) of PMWC scaffold in simulated body fluid (SBF), and addition of WP into composite further enhanced the degradability of PMWC in PBS compared with the scaffold of PS (50 wt%)/MP (50 wt%) composite (PMC) and PS alone. In addition, the PMWC scaffold containing MP and WP significantly promoted the proliferation and differentiation of mouse pre-osteoblastic cell line (MC3T3-E1) cells. Moreover, the images from synchrotron radiation microcomputed tomography (SRmCT) and histological sections of the in vivo implantation suggested that the PMWC scaffold containing MP and WP prominently improved the new bone formation and ingrowth compared with PMC and PS. Furthermore, the immunohistochemical analysis further confirmed that the PMWC scaffold obviously promoted osteogenesis and vascularization in vivo compared with PMC and PS.ConclusionThis study demonstrated that the biocompatible PMWC scaffold with improved bioactivity and degradability significantly promoted the osteogenesis and vascularization in vivo, which would have a great potential to be applied for bone tissue repair.

Rapid carbon accumulation in a peatland following Late Holocene tephra deposition, New Zealand

Contemporary measurements of carbon (C) accumulation rates in peatlands around the world often show the C sink to be stronger on average than at times in the past. Alteration of global nutrient cycles could be contributing to elevated carbon accumulation in the present day. Here we examine the effect of volcanic inputs of nutrients on peatland C accumulation in Moanatuatua Bog, New Zealand, by examining a high-resolution Late Holocene C accumulation record during which powerful volcanic eruptions occurred, depositing two visible rhyolitic tephra layers (Taupo, 232 ± 10 CE; Kaharoa, 1314 ± 12 CE). Carbon accumulation rates since c. 50 CE, well before any human presence, increased from a background rate of 23 g C m−2 yr−1 up to 110 g C m−2 yr−1 following the deposition of the Taupo Tephra, and 84 g C m−2 yr−1 following the deposition of the Kaharoa Tephra. Smaller but nevertheless marked increases in C accumulation additionally occurred in association with the deposition of three andesitic-dacitic cryptotephras (each ≤ ∼1 mm thick) of the Tufa Trig Formation between the Taupo and Kaharoa events. These five periods of elevated C uptake, especially those associated with the relatively thick Taupo and Kaharoa tephras, were accompanied by shifts in nutrient stoichiometry, indicating that there was greater availability of phosphorus (P) relative to nitrogen (N) and C during the period of high C uptake. Such P was almost certainly derived from volcanic sources, with P being present in the volcanic glass at Moanatuatua, and many of the eruptions described being associated with the local deposition of the P rich mineral apatite. We found peatland C accumulation to be tightly coupled to N and P accumulation, suggesting nutrient inputs exert a strong control on rates of peat accumulation. Nutrient stoichiometry indicated a strong ability to recover P within the ecosystem, with C:P ratios being higher than most other peatlands in the literature. We conclude that nutrient inputs, deriving from volcanic eruptions, have been very important for C accumulation rates in the past. Therefore, the elevated nutrient inputs occurring in the present day could offer a more plausible explanation, as opposed to a climatic component, for observed high contemporary C accumulation in New Zealand peatlands.

Evidence of episodically accelerated denudation on the Namche Barwa massif (Eastern Himalayan syntaxis) by megafloods

Megafloods cause widespread mobilization of sediments that have strong potential to control the geodynamic evolution of the Namche Barwa (NB) massif by changing the landscape morphology within a short time. However, the impact of catastrophic events on the denudation of the massif over the longer time scale has not been explored in detail. This contribution assesses the impact of catastrophic floods on the denudation style of the Namche Barwa (NB) massif over millennial time scales. Towards this, 21 optical ages and ∼1700 detrital thermochronometric ages of zircon and apatite minerals extracted from paleoflood sediments downstream of the massif, were integrated with decadal sediment load and aggradation data to estimate the minimum denudation rate during paleoflood events. The results indicate that the 7 ka flood eroded ∼71 m of material from the NB massif. This denudation is equivalent to the material that would be produced over ∼8000 years of erosion at a rate of ∼9 mm/a. The 3.5 ka flood eroded ∼24 m of material equaling ∼2500 years worth of erosion at a rate of ∼9 mm/a. Such relatively instantaneous denudations are three orders of magnitude higher than averaged denudation rates over million-year time scale. This study, therefore, provides the first evidence of the strong interplay of catastrophic flood events and tectonics for the rapid exhumation of the Namche Barwa massif. Megafloods from the failure of dammed lakes provide valuable information to understand the flood surge risk for human settlements in the Siang and the Assam valleys.

Beneficiation of a Low-grade Phosphate Ore Using a Reverse Flotation Technique

ABSTRACT This work aimed to upgrade a low-grade sedimentary phosphate ore through attrition scrubbing/desliming and an anionic/cationic reverse flotation technique. The mineralogical and chemical examination showed that the sample contained low-grade apatite minerals (P2O5 ~ 22.5%), and the main associated gangue minerals were gypsum and quartz. The effects of both collector and depressant dosage were investigated and optimized in each individual flotation process. The results of attrition scrubbing accompanied by desliming showed that a high content of P2O5 (27.97%) with a recovery of 72.1% was obtained in the coarse size fraction (+53 µm), and the majority of quartz and gypsum separated in the fine size fraction (−53 µm). The effect of using a new tall oil collector mixture was investigated during the anionic reverse flotation. Sodium tripolyphosphate (STPP) was used as a phosphate depressant during anionic and cationic reverse flotation. The flotation results of the deslimed sample demonstrated that cationic reverse flotation was much more desirable in terms of achieving a high grade and recovery of P2O5 compared to anionic reverse flotation. Considering the statistical design, a maximum grade of 31.23% P2O5 with a recovery of 95.22% was obtained in the non-floated fraction using 950.88 g/t of the collector (amine) and 500 g/t of the STPP.

The potential of alkaline rocks from the Fortaleza volcanic province (Brazil) as natural fertilizers

This research evaluates the potential of three alkaline rock types to be used as soil remineralizers by measuring the availability of macronutrients and micronutrients in aqueous media and soils after a three-month incubation period. The lithotypes used were (1) phonolite; (2) nepheline syenite; and (3) volcaniclastic breccia, which are from the metropolitan area of Fortaleza, capital of Ceará state, northeast Brazil. All rock types are constituted of alkali feldspar, aegirine-augite, nepheline, kaersutite with minor apatite, and opaque minerals in different proportions. These minerals carry substantial amounts of K, Ca, Mg, P, Fe, Mn, Zn, and Cu, elements that are important for plant nutrition and metabolism. The concentration of the major and trace elements in the rocks was determined to quantify the efficiency of the solubilization relative to the element's original content in the rock. The agronomic tests were conducted as a completely randomized design, which results were submitted to variance analysis. Several important elements were efficiently solubilized by the leaching experiment with citric acid diluted to 2%, indicating the potential of the studied materials to be effectively used as natural fertilizers. A typical surface soil from the region was incubated at room temperature with finely ground nepheline syenite and volcaniclastic breccia for three months. The amendment was applied at rates of 0, 2, 4, 6, 8, and 10 t ha−1 to cover situations of moderate to intensive application rates. The incubation results with the treatment using the volcaniclastic breccia indicate a high potential for soil remineralization of P, Fe, and Mn, while the nepheline syenite yields potential for P, K, Mn, Zn, and Cu. The outcomes of this research in laboratory-scale have important implications for fertilizer and soil management and should be tested in the field, including rock blending and long-term experiments to evaluate the effects of soil's improvement with time.

High‐resolution microstructural and compositional analyses of shock deformed apatite from the peak ring of the Chicxulub impact crater

AbstractThe mineral apatite, Ca5(PO4)3(F,Cl,OH), is a ubiquitous accessory mineral, with its volatile content and isotopic compositions used to interpret the evolution of H2O on planetary bodies. During hypervelocity impact, extreme pressures shock target rocks resulting in deformation of minerals; however, relatively few microstructural studies of apatite have been undertaken. Given its widespread distribution in the solar system, it is important to understand how apatite responds to progressive shock metamorphism. Here, we present detailed microstructural analyses of shock deformation in ~560 apatite grains throughout ~550 m of shocked granitoid rock from the peak ring of the Chicxulub impact structure, Mexico. A combination of high‐resolution backscattered electron (BSE) imaging, electron backscatter diffraction mapping, transmission Kikuchi diffraction mapping, and transmission electron microscopy is used to characterize deformation within apatite grains. Systematic, crystallographically controlled deformation bands are present within apatite, consistent with tilt boundaries that contain the &lt;c&gt; (axis) and result from slip in &lt;&gt; (direction) on (plane) during shock deformation. Deformation bands contain complex subgrain domains, isolated dislocations, and low‐angle boundaries of ~1° to 2°. Planar fractures within apatite form conjugate sets that are oriented within either {, {, {, or . Complementary electron microprobe analyses (EPMA) of a subset of recrystallized and partially recrystallized apatite grains show that there is an apparent change in MgO content in shock‐recrystallized apatite compositions. This study shows that the response of apatite to shock deformation can be highly variable, and that application of a combined microstructural and chemical analysis workflow can reveal complex deformation histories in apatite grains, some of which result in changes to crystal structure and composition, which are important for understanding the genesis of apatite in both terrestrial and extraterrestrial environments.

Protein nanoribbons template enamel mineralization

As the hardest tissue formed by vertebrates, enamel represents nature's engineering masterpiece with complex organizations of fibrous apatite crystals at the nanometer scale. Supramolecular assemblies of enamel matrix proteins (EMPs) play a key role as the structural scaffolds for regulating mineral morphology during enamel development. However, to achieve maximum tissue hardness, most organic content in enamel is digested and removed at the maturation stage, and thus knowledge of a structural protein template that could guide enamel mineralization is limited at this date. Herein, by examining a gene-modified mouse that lacked enzymatic degradation of EMPs, we demonstrate the presence of protein nanoribbons as the structural scaffolds in developing enamel matrix. Using in vitro mineralization assays we showed that both recombinant and enamel-tissue-based amelogenin nanoribbons are capable of guiding fibrous apatite nanocrystal formation. In accordance with our understanding of the natural process of enamel formation, templated crystal growth was achieved by interaction of amelogenin scaffolds with acidic macromolecules that facilitate the formation of an amorphous calcium phosphate precursor which gradually transforms into oriented apatite fibers along the protein nanoribbons. Furthermore, this study elucidated that matrix metalloproteinase-20 is a critical regulator of the enamel mineralization as only a recombinant analog of a MMP20-cleavage product of amelogenin was capable of guiding apatite mineralization. This study highlights that supramolecular assembly of the scaffold protein, its enzymatic processing, and its ability to interact with acidic carrier proteins are critical steps for proper enamel development.