Rounded Grains Research Articles

Aeolian Biodispersal of Terrestrial Microorganisms on Mars Through Saltation Bombardment of Spacecraft.

A major unknown in the field of planetary protection is the degree to which natural atmospheric processes remove terrestrial microorganisms from robotic and crewed spacecraft that could potentially contaminate Mars (i.e., forward contamination). We present experiments in which we measured the removal rate of Bacillus subtilis HA101 spores from aluminum surfaces under the bombardment of naturally rounded sand grains. To simulate grain impacts, we constructed a pneumatic sand-feed system and gun to accelerate grains to a desired speed, with independent control of impacting grain mass, flux, and angle. Spore counts of the resulting bombarded surfaces when using scanning electron microscopy indicate that although spores directly impacted by sand grains would likely be killed, those immediately adjacent to grain impacts might be released into the environment intact. The experiments demonstrate a linear relationship between the fractional dislodgement rate of spores and grain impact speed, which can be used to estimate input to microbial transport models (e.g., using numerical models of saltation). Even the slowest grain impacts (∼2.7 m/s) dislodged spores. Such slow events may be common and widespread on Mars, which suggests that microbial dislodgement by slow saltation near the surface is largely unavoidable.

Viability of 3D printing of andean tubers and tuberous root puree

Three-dimensional (3D) printing is revolutionizing the industry. This technology can potentially transform and improve challenges in the food industry. This study evaluated the viability of 3D printing of puree made from camote and mashua flours. Before drying and grinding, the roots were pretreated with cooking and microwaving. First, the microstructure of the flours was evaluated using A Scanning Electron Microscope (SEM). The physicochemical, rheological, and extrusion properties of the purees were assessed. Furthermore, image analysis was conducted to observe the effect of time on 3D-printed figures. Four formulations were evaluated: Camote cooked (CamC), Camote microwaved (CamM), Mashua cooked (MasC), and Mashua microwaved (MasM), all containing a percentage of whole milk. SEM results revealed that heat treatments influence grain shape in mashua, leading to round or oval grains; this behavior was not observed in camote treated by microwave. X-ray diffraction (XRD) analysis shows that microwaved camote granules retain their crystalline structure and shape. High water activity values were observed in camote samples; these results could be due to starch and sugar content. Color analysis revealed differences between samples less appreciable by the human eye in mashua. Rheological analysis indicated a solid behavior, with both G∗ and G′ values similar to or higher than G″ and significant differences among all samples. The tangent values were <1, indicating elastic properties dominated in all samples. Cooked samples showed better proportion fidelity than microwaved ones due to the retrogradation process. The study suggests camote and mashua flours pretreated by cooking present better printability than microwaving. This effect can be related to the higher starch denaturation.

Retrieval of snow and soil properties for forward radiative transfer modeling of airborne Ku-band SAR to estimate snow water equivalent: the Trail Valley Creek 2018/19 snow experiment

Abstract. Accurate snow information at high spatial and temporal resolution is needed to support climate services, water resource management, and environmental prediction services. However, snow remains the only element of the water cycle without a dedicated Earth observation mission. The snow scientific community has shown that Ku-band radar measurements provide quality snow information with its sensitivity to snow water equivalent and the wet/dry state of snow. With recent developments of tools like the snow micropenetrometer (SMP) to retrieve snow microstructure data in the field and radiative transfer models like the Snow Microwave Radiative Transfer (SMRT) model, it becomes possible to properly characterize the snow and how it translates into radar backscatter measurements. An experiment at Trail Valley Creek (TVC), Northwest Territories, Canada, was conducted during the winter of 2018/19 in order to characterize the impacts of varying snow geophysical properties on Ku-band radar backscatter at a 100 m scale. Airborne Ku-band data were acquired using the University of Massachusetts radar instrument. This study shows that it is possible to calibrate SMP data to retrieve statistical information on snow geophysical properties and properly characterize a representative snowpack at the experiment scale. The tundra snowpack measured during the campaign can be characterize by two layers corresponding to a rounded snow grain layer and a depth hoar layer. Using RADARSAT-2 and TerraSAR-X data, soil background roughness properties were retrieved (msssoil=0.010±0.002), and it was shown that a single value could be used for the entire domain. Microwave snow grain size polydispersity values of 0.74 and 1.11 for rounded and depth hoar snow grains, respectively, were retrieved. Using the geometrical optics surface backscatter model, the retrieved effective soil permittivity increased from C-band (εsoil=2.47) to X-band (εsoil=2.61) and to Ku-band (εsoil=2.77) for the TVC domain. Using the SMRT and the retrieved soil and snow parameterizations, an RMSE of 2.6 dB was obtained between the measured and simulated Ku-band backscatter values when using a global set of parameters for all measured sites. When using a distributed set of soil and snow parameters, the RMSE drops to 0.9 dB. This study thus shows that it is possible to link Ku-band radar backscatter measurements to snow conditions on the ground using a priori knowledge of the snow conditions to retrieve snow water equivalent (SWE) at the 100 m scale.

Investigation of Piezoelectric Properties in Ca-Doped PbBa(Zr,Ti)O3 (PBZT) Ceramics.

The perovskite-structured materials Pb0.75Ba0.251-xCax(Zr0.7Ti0.3)O3 for x = 1 and 2 at.% were synthesized using the conventional mixed-oxide method and carbonates. Microstructural analysis, performed using a scanning electron microscope, revealed rounded grains with relatively inhomogeneous sizes and distinct grain boundaries. X-ray diffraction confirmed that the materials exhibit a rhombohedral structure with an R3c space group at room temperature. Piezoelectric resonance measurements were conducted to determine the piezoelectric and elastic properties of the samples. The results indicated that a small amount of calcium doping significantly enhanced the piezoelectric coefficient d31. The calcium-doped ceramics exhibited higher electrical permittivity across the entire temperature range compared to the pure material, as well as a significant value of remanent polarization. These findings indicate that the performance parameters of the base material have been significantly improved, making these ceramics promising candidates for various applications.

Physicochemical and mineralogical characterization of silica sand from the Lemi region, Blue Nile Basin, central Ethiopia: Evaluating industrial applications and resource potential

Silica sand is an essential industrial mineral composed predominantly of quartz, formed through the weathering of rocks. In Ethiopia, silica deposits are geologically widespread, including the Lemi area in the Blue Nile Basin. This study investigates the physicochemical and mineralogical properties of silica sand from the Lemi region to determine its suitability for industrial applications. Samples from four villages in Lemi were collected, prepared, and analyzed using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), grain size analysis, bulk density measurement, and geochemical analysis. The results indicate that Lemi silica sand is predominantly composed of medium-sized, well-sorted, sub-rounded to rounded quartz grains with high silica purity (average SiO2 content of 96.13 %). Mineralogical analysis confirms high crystallinity and a low presence of contaminants. The grain size distribution and bulk density of Lemi silica sand meet industry standards for glass, foundry, and abrasive applications. Comparative analysis shows that Lemi silica sand has comparable or superior qualities to other Ethiopian deposits, making it a promising resource for industrial use. The study estimates a total resource of approximately 6.94 billion tons of silica sand in the Lemi area, highlighting its significant economic potential.

Appraisal of the Propping Potential of Luwa Sand in Nigeria for Hydraulic Fracturing Applications

Natural sands made of spherical and round grains are widely used as proppants during hydraulic fracturing to increase recovery rate of hydrocarbon production. Synthetic proppants with high crush strength are employed for deep reservoir fracturing; however, this type of proppants suffer the disadvantages of high density, high cost and pose environmental hazards. This research was conducted with the aim to assess sands collected from Luwa River in Toro, Bauchi state of Nigeria for possible use as natural sand proppants. An epoxy resin-coated sand was produced using a simple method to modify the sands’ properties. A series of experiments were conducted in accordance with API recommended practice to determine the propping potential of the sand and the resin coated sand. The result from sieve analysis of 20/40 mesh size of Luwa sand revealed a mean size of 625.2 microns (0.625 mm). An X-ray fluorescence (XRF) result showed the presence of aluminosilicates (Al2O3 and SiO2) composition in Luwa sands. The sands recorded a hardness of 8 on the Mohs scale. Analysis of the shape parameters for sphericity and roundness was 0.8 and 0.8 (Krumbein-Sloss) respectively; it has bulk density of 1.64 g/cm3, acid solubility of 0.7% and 4.32% for the resin-coated sand. The sand has turbidity value of 28.98 NTU, loss on ignition in the range of 1.33% to 1.64% and crush resistance varies between 2000-3000 psi for Luwa sand and 4000-5000 psi for the coated sand. A comparison of the experimental results with API standard and conventional Ottawa and Brady models showed the sand competes favourably with these standards in all parameters for consideration as a proppant except for the crush resistance where more than 10% fragments was generated at low pressure of 3000 psi. However, the sand can be applied in shallow depth reservoirs.

Appraisal of the Propping Potential of Luwa Sand in Nigeria for Hydraulic Fracturing Applications

Natural sands made of spherical and round grains are widely used as proppants during hydraulic fracturing to increase recovery rate of hydrocarbon production. Synthetic proppants with high crush strength are employed for deep reservoir fracturing; however, this type of proppants suffer the disadvantages of high density, high cost and pose environmental hazards. This research was conducted with the aim to assess sands collected from Luwa River in Toro, Bauchi state of Nigeria for possible use as natural sand proppants. An epoxy resin-coated sand was produced using a simple method to modify the sands’ properties. A series of experiments were conducted in accordance with API recommended practice to determine the propping potential of the sand and the resin coated sand. The result from sieve analysis of 20/40 mesh size of Luwa sand revealed a mean size of 625.2 microns (0.625 mm). An X-ray fluorescence (XRF) result showed the presence of aluminosilicates (Al2O3 and SiO2) composition in Luwa sands. The sands recorded a hardness of 8 on the Mohs scale. Analysis of the shape parameters for sphericity and roundness was 0.8 and 0.8 (Krumbein-Sloss) respectively; it has bulk density of 1.64 g/cm3, acid solubility of 0.7% and 4.32% for the resin-coated sand. The sand has turbidity value of 28.98 NTU, loss on ignition in the range of 1.33% to 1.64% and crush resistance varies between 2000-3000 psi for Luwa sand and 4000-5000 psi for the coated sand. A comparison of the experimental results with API standard and conventional Ottawa and Brady models showed the sand competes favourably with these standards in all parameters for consideration as a proppant except for the crush resistance where more than 10% fragments was generated at low pressure of 3000 psi. However, the sand can be applied in shallow depth reservoirs.

The Electric Conductivity of Bi7Fe3Ti3O21 Doped with Gadolinium.

Bi7-xGdxFe3Ti3O21 (x = (0, 0.2, 0.4, 0.6)) bismuth-layered perovskite structure compounds have been successfully prepared by a solid-state reaction. The results of X-ray studies indicate that a single-phase ceramic was obtained, characterized by an orthorhombic crystal structure for all compounds within the Fm2m space group. Microstructural analysis revealed that introducing gadolinium to the material altered the grain morphology, resulting in a more rounded grain shape and a somewhat disordered arrangement. Moreover, with higher gadolinium concentrations, there is a noticeable increase in the presence of the number of large plates. Impedance spectroscopy has been used to characterize the electrical properties of Bi7-xGdxFe3Ti3O21 compounds.

Microstructure and mechanical properties of a porous ceramic composite with needle‐like mullite and zirconia

AbstractPorous mullite ceramics have good properties for high‐temperature applications, but porosity gives place to ceramics with low mechanical strength, which restricts the service life in their potential applications. Therefore, performing modifications at the microscale to increase the mechanical strength has become a current challenge to expand its application fields. This work describes the properties of a porous mullite–zirconia composite produced by ceramic processing, using industrial kaolin and stabilized zirconia as raw materials. The growth of mullite needle‐like grains to reinforce the ceramic was promoted by the addition of a molybdenum oxide precursor. The effect of zirconia on the composite was analyzed through an experimental multi‐technique approach and considering a pure mullite sample, identically processed, as a reference. The novel composite has a porosity of about 50%, and presents a homogeneous microstructure, with interlocked mullite needle‐like grains and dispersed rounded zirconia grains. This morphology restricts the mullite tendency to shrink during sintering, giving the material a higher stiffness. In particular, the presence of zirconia in the composite improves both the flexural strength and the apparent Young modulus of the material (about 20% and up to 600%, respectively). These results encourage further investigations to establish this composite for different technological applications.

Relationship of evolution of slip-surface structure in Indian sandstone to changes in friction coefficient for a wide range of slip rates

Although many experimental studies have investigated the frictional properties of sandstone, few of them have considered the evolution of slip-surface structures with changes of friction coefficient over a wide range of slip rates. Here we report the results of rock-on-rock rotary shear experiments on specimens of Indian sandstone at slip rates from 2 × 10−4 to 1 m s−1. The resultant slip behaviors and microscale surface structures indicate two types of dependency on slip rate. At high slip rates (≥5 × 10−1 m s−1), the friction between the sandstone blocks fluctuated markedly and the surfaces of the blocks were intensively worn. At low slip rates (≤1 × 10−1 m s−1), the friction decreased gradually with increasing slip distance and the slip surfaces became reflective. The high slip-rate experiments produced abundant rock fragments (∼10–100 μm diameter), whereas the slip surfaces after low slip-rate experiments were highly polished fault mirrors accompanied by abundant rounded ultrafine grains (∼100 nm diameter). Such slip-rate-dependent evolution of slip-surface structures in Indian sandstone may arise from the relatively low cohesiveness of that rock. This insight may further our understanding of faulting and sliding mechanisms in sandstone near the ground surface.

Unraveling the dielectric and electrical properties of binary BaTiO3/Ba0.98Ca0.01Mg0.01Fe12O19 composites

In this study, composite materials of barium titanate (BaTiO3 or BTO) phase embedded with different contents of Ba0.96Ca0.02Mg0.02Fe12O19 (BCMFO) hexaferrite phase as (BTO)1-x/(BCMFO)x (x = 0.00, 0.02, 0.05, 0.10, and 1.00) composites were prepared. The successful formation of the desired samples was established via X-ray diffraction. Additional peaks showing a chemical reaction between the two phases as a result of the heat treatment were not found. The co-existence of the two-component phases was further confirmed via field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, wherein rounded spherical grains (with nanometric size <200 nm) correspond to the BTO phase while plates-like shaped grains with larger size (with micrometric size) correspond to the BCMFO hexaferrite phase. This study also investigates the impact of the composition ratio of BCMFO to BTO composites on electrical and dielectric properties through comprehensive parameter-based analyses using impedance spectroscopy. Parameters explored include conductivity, dielectric constant, dielectric loss, dissipation factor, and complex modulus, alongside Nyquist analysis of Cole-Cole modulus functions. The activation energies range from approximately 40 to 431 meV. The study suggests the involvement of electron-hole hopping, polaronic, and ionic mechanisms in conduction within intra-grains and grain boundaries. Results reveal strong dependencies of all dielectric parameters on both frequency and composition ratio. Nyquist plots demonstrate distinct semicircles reflecting contributions from intra-grain, grain boundary, and BCMFO components. The extent of dielectric loss is found to be influenced by factors such as porosity, density, homogeneity, and grain size, influenced by sintering and composition conditions. The presence of these semicircles in Nyquist plots indicates different relaxation phenomena associated with charge carrier mobility within the grain boundary and the grain itself. Additionally, the diameter of these semicircles correlates with the resistance values of both grain boundary and grain. These findings suggest the potential for tuning dielectric parameters by adjusting composition ratios, particularly relevant for applications in micro-device technologies such as multilayer chip capacitors and multilayer chip inductors, facing new challenges.

Low mutation rate of spontaneous mutants enables detection of causative genes by comparing whole genome sequences.

In the early 1900s, mutation breeding to select varieties with desirable traits using spontaneous mutation was actively conducted around the world, including Japan. In rice, the number of fixed mutations per generation was estimated to be 1.38-2.25. Although this low mutation rate was a major problem for breeding in those days, in the modern era with the development of next-generation sequencing (NGS) technology, it was conversely considered to be an advantage for efficient gene identification. In this paper, we proposed an in silico approach using NGS to compare the whole genome sequence of a spontaneous mutant with that of a closely related strain with a nearly identical genome, to find polymorphisms that differ between them, and to identify the causal gene by predicting the functional variation of the gene caused by the polymorphism. Using this approach, we found four causal genes for the dwarf mutation, the round shape grain mutation and the awnless mutation. Three of these genes were the same as those previously reported, but one was a novel gene involved in awn formation. The novel gene was isolated from Bozu-Aikoku, a mutant of Aikoku with the awnless trait, in which nine polymorphisms were predicted to alter gene function by their whole-genome comparison. Based on the information on gene function and tissue-specific expression patterns of these candidate genes, Os03g0115700/LOC_Os03g02460, annotated as a short-chain dehydrogenase/reductase SDR family protein, is most likely to be involved in the awnless mutation. Indeed, complementation tests by transformation showed that it is involved in awn formation. Thus, this method is an effective way to accelerate genome breeding of various crop species by enabling the identification of useful genes that can be used for crop breeding with minimal effort for NGS analysis.

Zircon U-Pb-Hf constraints on the geological evolution of the Bihar Mica Belt, Central Indian Tectonic Zone, and its link to Columbia assembly

In this study, U-Pb-Hf isotope composition and trace element chemistry of zircon from basement gneisses and quartzites of the Bihar Mica Belt (BMB), a belt of supracrustal rocks within the Central Indian Tectonic Zone, is used to constrain crustal growth and reworking. The protoliths of BMB gneisses were emplaced at 1651 ± 5 Ma. The magmas were derived from juvenile and 1747 ± 7 Ma I-type long-lived felsic precursors that survive as xenocrystic cores. Zircon grains from quartzites display two distinct morphologies. Grains with little rounding of edges have internal structures comprising 1750 ± 5 Ma inherited cores mantled by 1657 ± 4 Ma igneous zones that are identical to those from the granite gneisses. The εHf (t) and trace element composition of both the xenocrystic cores and the igneous mantles in these detrital grains are identical to those of zircon in the gneisses. They constitute molasse-like sediments derived from the nearby basement. More rounded grains furnish age clusters between 1857 and 2848 Ma, suggestive of long-distance transport and derivation from multiple sources. In-situ formed metamorphic rims around zircons in gneisses and quartzites furnish 1476–1466 Ma ages, dating the earliest metamorphic overprint. The age of sedimentation is bracketed between 1657 Ma and 1466 Ma. The 1651 ± 5 Ma gneisses and its 1747 ± 7 Ma felsic precursor were I-type, and emplaced in an arc setting. They constitute part of the expansive suite of Paleoproterozoic gneisses of the Chhota Nagpur Gneiss Complex emplaced during protracted period of arc-magmatism between 1.75 Ga and 1.65 Ga. Strongly positive εHf(t) of 2.0–2.85 Ga detrital zircons conforms to the global trend of positive εHf(t) excursions and high dT/dP gradients, and may correspond to passive margin juvenile magmatism associated with the break-up of Archean supercratons prior to Columbia assembly. The 1.86 Ga and 1.75 Ga detrital and xenocrystic zircons from the BMB have enriched εHf(t), in accordance with negative excursions seen in global zircon between 2.0 Ga and 1.70 Ga, reflecting progressive assembly of Columbia through collisional orogenesis. An excursion to strongly positive εHf(t), coinciding with low dT/dP gradients at ca. 1.65 Ga, reflects wide-spread formation of arcs linked to accretionary growth of Columbia.

RGA1 regulates grain size, rice quality and seed germination in the small and round grain mutant srg5

BackgroundGenerating elite rice varieties with high yield and superior quality is the main goal of rice breeding programs. Key agronomic traits, including grain size and seed germination characteristics, affect the final yield and quality of rice. The RGA1 gene, which encodes the α-subunit of rice G-protein, plays an important role in regulating rice architecture, seed size and abiotic stress responses. However, whether RGA1 is involved in the regulation of rice quality and seed germination traits is still unclear.ResultsIn this study, a rice mutant small and round grain 5 (srg5), was identified in an EMS-induced rice mutant library. Systematic analysis of its major agronomic traits revealed that the srg5 mutant exhibited a semi-dwarf plant height with small and round grain and reduced panicle length. Analysis of the physicochemical properties of rice showed that the difference in rice eating and cooking quality (ECQ) between the srg5 mutant and its wild-type control was small, but the appearance quality was significantly improved. Interestingly, a significant suppression of rice seed germination and shoot growth was observed in the srg5 mutant, which was mainly related to the regulation of ABA metabolism. RGA1 was identified as the candidate gene for the srg5 mutant by BSA analysis. A SNP at the splice site of the first intron disrupted the normal splicing of the RGA1 transcript precursor, resulting in a premature stop codon. Additional linkage analysis confirmed that the target gene causing the srg5 mutant phenotype was RGA1. Finally, the introduction of the RGA1 mutant allele into two indica rice varieties also resulted in small and round rice grains with less chalkiness.ConclusionsThese results indicate that RGA1 is not only involved in the control of rice architecture and grain size, but also in the regulation of rice quality and seed germination. This study sheds new light on the biological functions of RGA1, thereby providing valuable information for future systematic analysis of the G-protein pathway and its potential application in rice breeding programs.

Impact of mix proportions on particle bed 3D printed concrete properties

Additive manufacturing of concrete using particle-bed printing by selective binder activation is examined. This technique consists of spreading of a dry powder layer onto the build platform, selective liquid deposition to form a geometry on the layer, and repetition until complete. This enables the manufacturing of complex structural elements and eliminates the need of support structures during fabrication. A commercial liquid-jet 3D printer was modified and used along with a dry mixture of sand, cement, and a specially formulated aqueous solvent. The influence of the proportions of the dry powders, water/cement ratio, type and gradation of sand, type of cements, and additives on the strength and dimensional inaccuracy is examined. The results indicate that the CSA cement with round grain silica sand provides the best mechanical performance and surface quality. The use of a sand/cement ratio of 2.0, printed water/cement ratio of 0.151, and sand fineness modulus of 2.751 produced the best mechanical strength and dimensional accuracy. The results can be used to guide the design for this innovative 3D printing approach for concrete structural elements.

Pliocene to Pleistocene REE-P Metasomatism in the Subcontinental Lithosphere beneath Southeast Asia—Evidence from a Monazite- and REE-rich Apatite-bearing Peridotite Xenolith from Central Vietnam

Abstract Mantle rocks usually contain rare earth elements (REEs) in very low concentrations. Here, we document an occurrence of monazite associated with REE-rich apatites in a carbonate-bearing wehrlite xenolith from central Vietnam. The xenolith displays an equigranular matrix of rounded olivine grains while texturally primary orthopyroxene, clinopyroxene and spinel are notably absent. Scattered within the olivine matrix, two types of domains are present: domain-I contains blocky clinopyroxene grains within a matrix of quenched silicate melt and is associated with a second generation of olivine, small euhedral spinel, and rare grains of carbonates. Domain-II contains irregularly shaped patches of carbonate associated with silicate glass, secondary olivine, spinel, and clinopyroxene. Monazite and apatite occur only in domain-I: very small rounded to elongate monazite I grains are included in primary olivine, partly crosscut by fine glass veinlets, monazite II as large grains up to 300 × 200 μm in size and monazite III as small euhedral and needle-like crystals in silicate glass pools. Apatite I forms lath-shaped to rounded crystals up to 200 × 50 μm in size, whereas apatite II is present within silicate melt pools where it forms euhedral needle-like to equant grains. Monazites show compositional variation mainly with respect to ∑REE2O3 (63–69 wt %) and ThO2 (1.1–5.3 wt %) and only minor variations in P2O5 (29–32 wt %), SiO2 (&amp;lt;0.05–0.4 wt %), and CaO (0.2–0.4 wt %). Apatites are characterized by strongly variable and high REE2O3 and SiO2 contents (4–27 wt % ∑REE2O3, 0.6–6.8 wt % SiO2) as well as with significant Na2O (0.3–1.5 wt %), FeO (0.1–1.8 wt %), MgO (0.2–0.6 wt %) and SrO (0.2–0.9 wt %) contents. F and Cl contents are in the range 1.9–3.0 wt % and 0.2–0.8 wt %, respectively. The textures observed in this wehrlite xenolith are thought to be the result of an interaction of depleted (harzburgitic) mantle with cogenetic silicate and carbonatite melts formed by fractionation-driven immiscibility within a parental SiO2 undersaturated melt characterized by high P, CO2, and REE contents. The immiscibility occurred in the shallow subcontinental lithosphere at T of 700–800 °C and a depth of ~30 km and the melt–rock interaction occurred in two successive and most likely nearly simultaneous events: an initial stage of metasomatism was triggered by the P-REE-CO2-rich agent with low aH2O resulting in the co-precipitation of carbonates as patches and along micro-veins and of phosphates in a peridotitic assemblage. A second stage is characterized by pervasive infiltration of an alkali-rich basaltic melt into the carbonate + phosphate-bearing assemblage. Based on 232Th and 208Pb contents of monazite, a young age of ~2 Ma can be calculated for the timing of the monazite-forming metasomatic imprint. Based on 39Ar-40Ar extrusion ages of the xenolith-hosting alkali basalts of 2.6–5.4 Ma, this indicates that both carbonatite and basaltic melt infiltration must have occurred no more than a few hundred thousand years before extraction of the xenolith to the surface.

Variability in the Distinctive Features of Silica Sands in Central Europe

Quality quartz sand is globally utilized in construction due to its availability and economic factors, especially in the production of composite cements. Despite its positive properties, quartz sand also has several disadvantages. The dilation of quartz sand can be technologically significant for certain high-temperature applications. This dilation has a non-continuous character with sharp volume change caused by the phase transformation from β to α SiO2 at temperatures around 573 °C. The extent of dilation depends on various factors such as compaction, grain size, the quantity of sand, as well as the shape and character of the grain and chemical purity, particularly the SiO2 content. In this study, six types of quartz sand from different locations in Central Europe were examined, and the influence of chemical composition and grain shape was correlated with the final dilation of these samples. Evaluation methods included X-ray fluorescence spectroscopy (XRFS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), differential thermal analysis (DTA), and linear thermal expansion analysis. It was found that angular grains, despite their chemical purity, may exhibit minimal dilation. Conversely, the least suitable combination in terms of dilation appears to be a high SiO2 content and high roundness of grains with a smooth surface.

Structural and tunable optical properties of LiMgPO4:Tb3+ phosphor fabricated by sol–gel method

AbstractIn the study, Tb3+‐doped LiMgPO4 phosphors between .10 and 5 mol% were successfully synthesized by the sol–gel process. The crystal structure of Tb3+‐doped LiMgPO4 was identified by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS) analyses. The XRD results for LiMgPO4 ceramics doped with Tb3+ indicated a single‐phase up to 5 mol%, accompanied by lattice shrinkage. An SEM analysis of LiMgPO4 samples showed that increasing Tb3+ concentration reduced grain size but did not cause any significant change in slightly angular and round grains. The emission intensity of phosphor increased from .10 to 5 mol%, and no concentration quenching was observed. The luminescence color of LiMgPO4:Tb3+ phosphor can be tuned from blue to green through cross‐relaxation with the increase in Tb3+ concentration. The photoluminescence emissions of LiMgPO4:Tb3+ on the CIE diagram shifted from blue to green as the Tb3+ concentration increased. The color purity of the 5 mol% Tb3+‐doped phosphor showing the strongest emission was measured at 22.71%, whereas the color‐correlated temperature parameter was found to be 5573 K. The phosphors exhibited bi‐exponential decay profiles, and the observed lifetimes of 5D3 decreased with the increase of Tb3+, where the cross‐relaxation effect increased. The quantum efficiency (ɳQE) of the phosphor was determined using the cross‐relaxation process. For Tb3+ concentrations ranging from .1 to 5 mol%, the ɳQE of the 5D3 state decreased from 62.49% to 28.29%. The research may offer a new perspective and new approaches for tuning luminescence in Tb3+‐doped phosphors.

Feasibility of mechanical rice transplanting in organic Italian rice system

Abstract Rice cultivation in Italy is usually performed by direct seeding in flooded or in dry fields. Mechanical rice transplanting is a technique that can help control weeds and improve rice competition. To test the feasibility of the technique for different rice varieties in Italy, a study was conducted in the Lombardy region (northwest Italy), from 2016 to 2018. The study also evaluated the efficacy of hoeing in transplanted rice fields. The experiment consisted of two studies, a ‘field plot experiment’ (conducted from 2017 to 2018) and an ‘on-farm transplanting trial’ (conducted from 2016 to 2018). The ‘field plot experiment’ was carried out using a split plot design to determine the optimal transplanting distances within the row (12 or 17 cm) and the most suitable rice varieties for transplanting. Hoeing was performed once in 2017 and twice in 2018. Weed infestation was assessed by counting the number of weeds within a randomly placed square frame in the interrow areas, both before and after hoeing. Rice plant density, panicle density, yield, and yield components were also assessed. The ‘on-farm transplanting trial’ tested transplanting in several farms over the years. Different rice varieties were transplanted using the same machines, and hoeing was performed according to a predetermined schedule. Transplanter performance was assessed as well as rice yield data in all fields, while four fields were selected each year to assess hoeing efficacy against weeds. ANOVAs were used to test the differences in weed control and rice parameters among varieties and transplanting distances. The ‘field plot experiment’ showed that the transplanting distance did not affect weeds or rice variety. Transplanting at 12 cm within the row resulted in a higher plant density compared to 17 cm, however tillering compensated for the difference in the number of panicles. Carnaroli consistently recorded the lowest yield, less than 2 t ha−1, while Selenio, Spillo, and Laser seemed to be better suited for transplanting achieving the highest yield in 2018 (about 7 ha−1). In the ‘on-farm transplanting experiment’ hoeing was effective in controlling weeds, although the machineries used were not always able to function properly in saturated soil. Most of the transplanted field yielded approximately 3 to 5 t ha−1. Varieties with round grain exhibited the greatest yield variability among fields. The study suggests that to achieve a high yield in organic rice, the transplanting technique should be combined with an effective interrow tillage to control weeds.

Microtextures and trapped diatoms on quartz grain surfaces in the Acapulco Beach, Mexican Pacific: An insight into palaeoenvironment

In this study, we report Scanning Electron Microscopy (SEM) images of quartz grains in the Acapulco beach, Mexican Pacific. The morphology of quartz grains is angular, sub-angular, sub-rounded, rounded, and well-rounded. The variations in the morphology of quartz grains are indicating both nearby and distance sources. The rounded and well-rounded grains support for a long transport distance and a distal source. Microtextures of mechanical and chemical origins are identified in quartz grains. The mechanical features include, bulbous edges (ble), elongated depression (ed), parallel striations, crater, meandering ridges (mr), arcuate steps, conchoidal fractures (cf), v-shaped marks (v-s), and broken grain. These mechanical features indicate the combination of fluvial, aeolian, and subaqueous environments. The conchoidal fractures are characteristic of crystalline rocks. Arcuate steps and meandering ridges are indicating a high wave energy. The striations on grain surfaces are due to collision between two grains, probably during an aeolian transport. The chemical features include adhered particles (ap), solution pit (sp), silica globule, crystal overgrowth (crg), precipitation, and trapped diatoms. The solution pits and precipitation are indicating the diagenetic processes in a silica saturated coastal environment. A few grains are associated with both mechanical and chemical features, suggesting a dual environment, probably littoral and marine. Trapped diatoms identified in quartz grains are Cocconeis guttata and coccolith.