Search Results (36)

Graphite is a critical raw material due to its pivotal role in the green transition; hence, there is a renewed interest in its exploration across Europe. The Chisone and Germanasca Valleys (Piemonte, IT) were home to significant graphite exploitation until the 20th century, owing to the widespread presence of graphite ore bodies hosted in the metasedimentary succession of the Pinerolo Unit in the Dora-Maira Massif (Western Alps). This contribution presents a renewed study on the geology, mineralogy, petrography, and geochemistry of graphite ores and their host rocks, employing OM, SEM-EDS, and BSE, μRaman, and ICP-OES/MS and INAA analyses. Mineralization occurs in two metasedimentary successions: (i) the Bourcet-type succession (meta-conglomerates and meta-sandstones intercalated with meta-siltstones/metapelites) and (ii) the Pons-type succession (meta-siltstones/metapelites intercalated with minor meta-arenites). Graphite occurs as (i) high-purity, fine-grained crystals dispersed within or concentrated in layers along the regional schistosity, or (ii) low-purity, coarse-grained crystals within shear zones. Based on crystallinity, three types of graphite were distinguished: high (Type I), intermediate (Type II), and poor (Type III) crystalline graphite, likely formed under different genetic conditions. The comparison of these findings has implications for future exploration and provides new insights into the metallogeny and geological evolution of the area. Full article

The Sredogriv greenschist facies rocks belong to the Western Balkan Zone in northwestern Bulgaria. The low-grade rocks consist of clastic-tuffaceous precursors and presumably olistostromic magmatic bodies. We present U-Pb LA-ICP-MS zircon age constraints for the Sredogriv metaconglomerate, intruding metaalbitophyre and a breccia-conglomerate of the sedimentary cover. Detrital zircons in the Sredogriv metaconglomerate yield a maximum depositional age of 523 Ma, with a prominent NeoproterozoicEarly Cambrian detrital zircon age clusters derived from igneous sources. The metaalbitophyre crystallized at 308 Ma and contains the same age clusters of inherited zircons. A 263 Ma maximum age of deposition is defined for a breccia-conglomerate of the Smolyanovtsi Formation from the sedimentary cover that recycled material from the Sredogriv metamorphics and Carboniferous–Permian magmatic rocks. The depositional setting of the Sredogriv sedimentary succession is characterized by proximity to Cadomian island arc sources and provenance from the northern periphery of Gondwana. The timing of the Variscan greenschist facies metamorphism of the Sredogriv metamorphics is bracketed between 308 Ma and the depositional age of 272 Ma of another adjacent clastic formation. These results constrain the timing of the Cadomian sedimentary history and the Variscan magmatic and tectono-metamorphic evolution in this part of the Western Balkan Zone. Full article

Dredged material is a common environmental and economic issue worldwide. Tons of highly contaminated material, derived from cleaning the bottoms of bays and harbours, are stored until depuration. These volumes occupy huge extensions and require costly treatments. The Ria of Huelva (southwest Spain) receives additionally high metal contamination inputs from the Odiel and Tinto Rivers which are strongly affected by acid mine drainage (acid lixiviates with high metal content and sulphates). These two circumstances convert the port of Huelva into an acceptor/accumulator of contamination. The current study proposes an alternative active treatment of dredged material and mining residues using ASEC (Adiabatic Sonic Evaporation and Crystallization) technology to obtain distilled water and valuable solid conglomerates. Different samples were depurated and the efficiency of the technology was tested. The results show a complete recovery of the treated volumes with high-quality water (pH~7, EC < 56 µS/cm, complete removal of dissolved elements). Also, the characterization of the dried solids enable the calculation of approximate revenues from the valorization of some potentially exploitable elements (Rio Tinto: 4 M, Tharsis: 3.7 M, dredged material: 2.5 M USD/yr). The avoidance of residue discharge plus the aggregated value would promote a circular economy in sectors such as mining and dredging activities. Full article

The spoilage of roasted coffee products is largely suppressed through industry standards regarding storage and packaging. Conversely, biological contamination can be attributed to cross-contamination. Meanwhile, the increasing trend at the upper end of the specialty coffee industry consisting of more complex (e.g., yeast inoculation and fruit infusion) and longer post-harvest processing (e.g., extended anaerobic fermentation) methods might be considered at risk for potential spoilage. Here, we report the first case of a mistakenly confused accumulation of mold mycelium on high-end roasted Coffea arabica beans (Gesha variety from Barú, Panama; natural anaerobic process and greenhouse-dried), ultimately identified through UV/Vis spectroscopy (against a caffeine solution) as a conglomerate of needle-like caffeine crystals growing over the beans’ surface. Biological spoilage was unambiguously discarded due to negligible microbial activity, as shown through colony counting and a mycotoxin analysis. Furthermore, we demonstrated that the roast degree (development time after the first crack) had a significant effect on the growth of the crystals upon storage (RT and moderate light exposure). Darker roasts (70 s after the first crack) showed a higher accumulation of caffeine crystals than lighter roasts (20 s after the first crack), most likely promoted by coffee oil secretion. However, micro-crystal growth had already been detected in lighter roasts. While uncommon in roasted beans and, so far, poorly documented, crystal formation relates to increased caffeine availability at the surface through initial seed germination. Through the migration towards the endosperm surface, the xanthophyll antibacterial function is activated. A similar confusion of spoilage can be observed in soluble coffee granules. Yet, here, crystals growth was solely related to the high caffeine concentration. In addition, apparent spoilage in soluble coffee does not have the same economic burden as in high-end roasted coffee, and it also remains unrelated to any physiological process. Full article

Many physical and chemical properties of solids, such as strength, plasticity, dispersibility, solubility and dissolution are determined by defects in the crystal structure. The aim of this work is to study in situ dynamic, dispersion, chemical, biological and surface properties of lacosamide powder after a complete cycle of mechanical loading by laser scattering, electron microscopy, FR-IR and biopharmaceutical approaches. The SLS method demonstrated the spontaneous tendency toward surface-energy reduction due to aggregation during micronisation. DLS analysis showed conformational changes of colloidal particles as supramolecular complexes depending on the loading time on the solid. SEM analysis demonstrated the conglomeration of needle-like lacosamide particles after 60 min of milling time and the transition to a glassy state with isotropy of properties by the end of the tribochemistry cycle. The following dynamic properties of lacosamide were established: elastic and plastic deformation boundaries, region of inhomogeneous deformation and fracture point. The ratio of dissolution-rate constants in water of samples before and after a full cycle of loading was 2.4. The lacosamide sample, which underwent a full cycle of mechanical loading, showed improved kinetics of API release via analysis of dissolution profiles in 0.1 M HCl medium. The observed activation-energy values of the cell-death biosensor process in aqueous solutions of the lacosamide samples before and after the complete tribochemical cycle were 207 kJmol⁻¹ and 145 kJmol⁻¹, respectively. The equilibrium time of dissolution and activation of cell-biosensor death corresponding to 20 min of mechanical loading on a solid was determined. The current study may have important practical significance for the transformation and management of the properties of drug substances in solid form and in solutions and for increasing the strength of drug matrices by pre-strain hardening via structural rearrangements during mechanical loading. Full article

Gold occurrence Maljavr is the first Archean conglomerate-hosted gold mineralization found in the Fennoscandian Shield. Gold-mineralized metasomatic rocks form a set of lenses within a 10 m thick linear zone, conformable to the bedding of host conglomerates. The lenses are up to 10 m long and up to 1 m thick and they clearly exhibit three alteration envelopes: the rock in the central part consists of garnet and quartz or garnet-only; biotite, garnet, and quartz make the intermediate biotite–garnet envelope; hornblende, hedenbergite, and quartz are the principal rock-forming minerals in the outer zone of the lenses. All metasomatic rocks contain sulfide mineralization up to 15–20 vol.% and up to 0.6 g/t Au. The main ore mineral is pyrrhotite, and the minor minerals are arsenopyrite, chalcopyrite, pentlandite, löllingite, and troilite. The age of zircon from biotite gneiss in the zone of alteration is 2664 ± 18 Ma, this is considered as the time of formation of lenses of metasomatic rocks. Biotite gneiss-conglomerate and metasomatic rocks were later intruded by tourmaline granite pegmatite 2508 ± 7 Ma. The injection of pegmatite caused re-crystallization of sulfides (mainly arsenopyrite and löllingite) and redistribution of gold. Visible gold in association with Bi minerals native bismuth, ehrigite, maldonite, bismuthinite, joseite-B, and hedleyite was found in inclusions in recrystallized arsenopyrite and löllingite. Au content in the rocks with recrystallized arsenopyrite and löllingite is >1 g/t, up to 30 g/t in hand samples. The 2508 Ma pegmatite is interpreted as synchronous with formation of gold mineralization in its present form. The linkage of gold mineralization with pegmatite and geochemical association Au-As-Se-Te-Bi in the mineralized rocks agree with characteristics of intrusion-related gold deposits worldwide. Biotite gneiss–metaconglomerate, hosting the mineralized altered rocks, was the probable primary source of arsenic and gold for mineralization. Full article

The chloro-P,N-{diphenylphosphanyl-[(5-phenyl-1,3,4-oxadiazol-2-ylamino)phenyl-me- thyl]}(p-cymene)ruthenium(II) hexafluorophosphate complex (4) was obtained in two steps from diphenylphosphanyl-[(5-phenyl-1,3,4-oxadiazol-2-ylamino)phenyl-methyl] borane (2). In the first step, the oxadiazole ring coordinated with the ruthenium atom, resulting in the formation of the dichloro-N-{diphenylphosphanyl-[(5-phenyl-1,3,4-oxadiazol-2-ylamino)phenyl-methyl]borane}(p-cymene) ruthenium(II) complex (3). During the crystallization of the P,N-chelate ruthenium complex, the formation of conglomerate crystals was revealed by X-ray structure analysis. Only two stereoisomers were obtained with (S)-Ru and (R)-C configurations in the first complex and with (R)-Ru and (S)-C configurations in the second. This deracemization during crystallization is due to the formation of a hydrogen bond between the P,N-ligand and the chlorine atom (CH•••Cl). This supramolecular interaction allows the transfer of the ligand chirality to the metal center and decrees the stereochemistry of the ruthenium atom. Full article

A lanthanide contraction(LC) of 14 lanthanides (Ln) from ₅₈Ce to ₇₁Lu consists of the interaction of Ln nucleus with 4f-electrons. Rare earth elements (REEs—R) include Sc, Y, La, and 14 Ln. They are located in 4–6th periods of the subgroup of group III. The electronic structure divides R into short (d- Sc, Y, La) and long (14 f-elements Ce-Lu) homologous series. The most important chemical consequence of LC is the creation of a new conglomerate of 16 RF₃ by mixing fluorides of d- (Y, La) and f-elements. This determines the location of YF₃ among LnF₃. The location of YF₃ depends on the structural (formula volumes—V_form) and thermochemical (temperatures and heats of phase transformations, phase diagrams) properties. The location of YF₃ between HoF₃ and ErF₃ was determined by V_form at a standard pressure (P_st) and temperature (T_st). The location of YF₃ according to heats of phase transformations ΔH_fus and ΔH_trans is in a dimorphic structural subgroup (SSGr) D (Ln = Er-Lu), but without the exact “pseudo Z_Y”. According to the temperatures of phase transformations (T_trans) in LnF₃ (Ln = Dy-Lu), YF₃ is located in the SSGr D between ErF₃ and TmF₃. The ErF₃-YF₃ and YF₃-TmF₃ phase diagrams show it to be between ErF₃ and TmF₃. The crystals of five β-LnF₃ (Ln = Ho-Lu) and β-YF₃ were obtained in identical conditions and their crystal structures were studied. V_form (at P_st and T_st) with “pseudo” atomic number Z_Y = 67.42 was calculated from the unit cell parameters, which were defined with ±5 × 10⁻⁴ Å accuracy. It determines the location of YF₃ between HoF₃ and ErF₃. Full article

(benzylthio)acetic acid (HBTA) and some aminopyrimidines, namely 2-aminopyrimidine (2-AP), 5-aminopyrimidine (5-AP), 2-amino-4,6-dimethylpyrimidine (2-A-4,6-DMP), and 2,4,6-triaminopyrimidine (2,4,6-TAP), were successfully embodied as structural units into the construction of a total of four novel supramolecular organic frameworks. The received crystalline solids were inspected by single-crystal X-ray diffraction (SC XRD) in order to obtain insight into the structural and supramolecular facets. The SOFs deriving from 2-AP, 5-AP, and 2-A-4,6-DMP crystallize in the form of co-crystals (1–3), while the one originating from 2,4,6-TAP crystallizes as a salt solvate (4). The SC XRD results indicated the different contents of structural residues present in the asymmetric units of the crystals 1–4 despite using the same molar ratio of molecular co-former components in each case. The molecular structures of co-crystals 1–3 consist of either one neutral residue of each starting component (1 and 3) or one nonionized residue of the aminopyrimidine ingredient and two neutral residues of the acidic component (2). The asymmetric unit of salt solvate 4 is composed of two ionized residues of each co-former (two 2,4,6-TAP⁺ cations and two BTA⁻ anions) and one MeOH solvent molecule. The most extensive H-bonding network is observed in the crystal structure of salt solvate 4. The relevant molecular ingredients in co-crystals 1–3 are mainly held together by the neutral O_carboxylic–H···N_pyrimidine and N_amine–H···O_carboxylic H-bonds. In the case of aggregate 4, the corresponding ionic residues are predominantly sustained by the charged-assisted N_pyrimidinium–H···O_carboxylate and N_amine–H···O_carboxylate hydrogen interactions. The MeOH solvent, incorporated into the crystal lattice of adduct 4, is also involved in H-bonding by simultaneously serving as the single donor in O_MeOH–H···S and the single acceptor in N_amine–H···O_MeOH H-bonds, which afforded the structural diversity within the 2,4,6-TAP⁺ cations and BTA⁻ anions. Other weaker sets of additional non-covalent contacts existing in the crystal structures of analyzed conglomerates are involved in the self-assembly, stabilization, and expansion of total supramolecular organic frameworks. The fact of the formation of non-covalent bonded supramolecular organic frameworks in question is also reflected in corresponding results obtained through elemental analysis (EA), Fourier transform infrared spectroscopy (FT–IR), and thermal analysis (TG/DSC). Full article

Sediments or clastic rocks can record the evolution history of basins, orogenic processes, crustal uplift and erosion, and even paleo-environments. Detrital minerals such as zircon, garnet, and apatite are useful media for studies of sedimentary sources and basin evolution. Detrital zircon has been widely taken as an indicator for provenances and tectonic evolution of geological terrenes via age distribution patterns. Apatite can remain stable during erosion and transportation and is also considered as an ideal object for source tracing. This mineral normally contains high Sr and negligible Rb. Its Sr isotopic composition can remain almost unchanged after crystallization. Unlike isotopic ages of detrital minerals, Apatite isotopic compositions have been less frequently used for tracing the provenance of sedimentary rocks in the last few decades. In the present study, we report on the Sr isotopic composition of individual apatite grains of Neogene and Jurassic conglomerates from the Hui-Cheng basin in the South Qinling orogenic belt, obtained via thermal ionization mass spectrometry. Detrital apatite grains of Jurassic rocks have narrow ranges of ⁸⁷Sr/⁸⁶Sr values from 0.7076 to 0.7100, but those of Neogene rocks gave variant ⁸⁷Sr/⁸⁶Sr values from 0.7055 to 0.7534, providing distinct evidence for complex sources of Neogene sedimentary rocks. Analytical results show that the distribution patterns of ⁸⁷Sr/⁸⁶Sr values of single-grain detrital apatite fit the distribution patterns of detrital zircon U-Pb from the isotopic ages very well. Detrital apatite Sr isotopic composition can provide essential information for tracing the origins and evolution of sedimentary sources. Full article

Inscription of embedded photoluminescent microbits inside micromechanically positioned bulk natural diamond, LiF and CaF₂ crystals was performed in sub-filamentation (geometrical focusing) regime by 525 nm 0.2 ps laser pulses focused by 0.65 NA micro-objective as a function of pulse energy, exposure and inter-layer separation. The resulting microbits were visualized by 3D-scanning confocal Raman/photoluminescence microscopy as conglomerates of photo-induced quasi-molecular color centers and tested regarding their spatial resolution and thermal stability via high-temperature annealing. Minimal lateral and longitudinal microbit separations, enabling their robust optical read-out through micromechanical positioning, were measured in the most promising crystalline material, LiF, as 1.5 and 13 microns, respectively, to be improved regarding information storage capacity by more elaborate focusing systems. These findings pave a way to novel optomechanical memory storage platforms, utilizing ultrashort-pulse laser inscription of photoluminescent microbits as carriers of archival memory. Full article

The highly metal-contaminated Odiel-Tinto River basin, located in the Iberian Pyrite Belt (IPB), has been the focus of many environmental studies as a natural lab for biodiversity and environmentally catastrophic scenarios and as a reference site for mining places with similar conditions. This study demonstrates the feasibility and effectiveness of two different technologies to recover ecosystems affected by acid mine drainage (AMD) in the area of IPB. The current study compiles results of two newest technologies for AMD remediation: passive remediation (dispersed alkaline substrate—DAS) and a new disruptive technology (Adiabatic Sonic Evaporation and Crystallization—ASE&C) that purifies the contaminated water, obtaining two by-products (high-quality water and metal conglomerates) that improve the general quality of the ecosystem including biodiversity by eliminating more than 90% of the contaminants from AMD and mining waters. The removal of contaminants, enhancement of AMD treatment efficiency, and offset operating costs were compared and analyzed for the different uses of the decontaminated effluents, including an old tailing pond failure, the Aznalcóllar mining spill. The efficiency of the removal of elements from the contaminated water is significant using both technologies, although the passive DAS does not still reach the international benchmark for some compounds (such as Fe, sulfates, and Mn); whereas ASE&C obtains distilled water fulfilling all the international benchmarks with conductivity values lower than 120 µS cm⁻¹ or metal concentrations lower than µg/L. Both technologies are eco-friendly and cost-effective as a result of the generation of valuable by-products such as fresh water and metal conglomerates as potentially commercial products while remediating aquatic ecosystems impacted by mining activities. Full article

Conglomerate formation, where enantiomers within a racemic mixture self-segregate upon crystallization, is an advantageous property for obtaining chirally pure crystals and allows large-scale chiral resolution. However, the prevalence of conglomerates is low and difficult to predict. In this report, we describe our attempts to engineer conglomerates from racemate-forming compounds by integrating them into a conglomerate-forming matrix. In this regard, we found that Ni(II) and Fe(II) form molecular alloys with Zn(II) in [M_xZn_(1−x)(bpy)₃](PF₆)₂ (where bpy = 2,2′-bipyridyl). Powder X-ray Diffraction (PXRD) and Energy-Dispersive X-ray spectroscopy (EDX) evidenced conglomerate crystallization with Ni(II) concentrations up to about 25%, while it was observed only for much lower concentrations of Fe(II). This can be attributed to the ability of [Ni(bpy)₃](PF₆)₂ to access a metastable conglomerate phase, while no such phase has been detected in [Fe(bpy)₃](PF₆)₂. Furthermore, the chiral phase appears to be favored in fast-growing precipitates, while the racemic phase is favored in slow re-crystallizations for both Ni(II) and Fe(II) molecular alloys. X-ray natural circular dichroism (XNCD) measurements on [Ni_0.13Zn_0.87(bpy)₃](PF₆)₂ demonstrate the chirality of the nickel molecules within the zinc molecular matrix. Full article

Thiazolopyrimidines are attractive to medical chemists as new antitumor agents due to their high inhibitory activity against the replication process of tumor cells and the easy modification of their structure by changing the number and nature of substituents. The presence of asymmetric C5 carbon atoms requires the development of racemic mixture separation procedures for these heterocycles. One of the most effective methods is the crystallization of a racemic compound in the form of a conglomerate. The prerequisite for such separation is the construction of chiral, supramolecular ensembles in the crystalline state. Halogen-π interactions were chosen as supramolecular synthons. In this context, ethyl 7-methyl-3-oxo-2,3-dihidro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate containing a 4-bromophenyl fragment at C5 was synthesized. The crystal structure of the resulting compound was established using SCXRD. The role of the halogen-π interaction on the formation of one-dimensional homochiral chains is revealed. Full article

A series of new 2-hydroxy-3-methoxybenzylidenethiazolo[3,2-a]pyrimidines with different aryl substituents at the 5 position are synthesized and characterized by ¹H/ ¹³C NMR and IR-spectroscopy and mass-spectrometry, as well as single crystal X-ray diffraction (SCXRD). It was demonstrated that the type of hydrogen bonding can play a key role in the chiral discrimination of these compounds in the crystalline phase. The hydrogen bond of the O–H...N type leads to 1D supramolecular heterochiral chains or conglomerate crystallization in the case of the formation of homochiral chains. The hydrogen bond of O–H...O type gave racemic dimers, which are packed into 2D supramolecular layers with a parallel or angular dimers arrangement. Halogen bonding of the N...Br or O...Br type brings a new motif into supramolecular self-assembly in the crystalline phase: the formation of 1D supramolecular homochiral chains instead 2D supramolecular layers. The study of cytotoxicity against various tumor cells in vitro was carried out. It was found that 2-hydroxy−3-methoxybenzylidenethiazolo[3,2-a]pyrimidines with 3-nitrophenyl substituent at C5 carbon atom demonstrated a high efficiency against M-HeLa (cervical adenocarcinoma) and low cytotoxicity against normal liver cells. Full article