Dinosaur bonebed amber from an original swamp forest soil

Dinosaur bonebeds with amber content, yet scarce, offer a superior wealth and quality of data on ancient terrestrial ecosystems. However, the preserved palaeodiversity and/or taphonomic characteristics of these exceptional localities had hitherto limited their palaeobiological potential. Here, we describe the amber from the Lower Cretaceous dinosaur bonebed of Ariño (Teruel, Spain) using a multidisciplinary approach. Amber is found in both a root layer with amber strictly in situ and a litter layer mainly composed of aerial pieces unusually rich in bioinclusions, encompassing 11 insect orders, arachnids, and a few plant and vertebrate remains, including a feather. Additional palaeontological data¿charophytes, palynomorphs, ostracods¿ are provided. Ariño arguably represents the most prolific and palaeobiologically diverse locality in which fossiliferous amber and a dinosaur bonebed have been found in association, and the only one known where the vast majority of the palaeontological assemblage suffered no or low-grade pre-burial transport. This has unlocked unprecedentedly complete and reliable palaeoecological data out of two complementary windows of preservation¿the bonebed and the amber¿from the same site

Mechanisms for gas-phase molecular formation of neutral formaldehyde (H

Context. Formaldehyde is a potential biogenic precursor involved in prebiotic chemical evolution. The cold conditions of the interstellar medium (ISM) allow H2CO to be reactive, playing a significant role as a chemical intermediate in formation pathways leading to interstellar complex organic molecules. However, gas-phase molecular formation mechanisms in cold regions of the ISM are poorly understood. Aims. We computationally determine the most favored gas-phase molecular formation mechanisms at local thermodynamic equilibrium conditions that can produce the detected amounts of H2CO in diffuse molecular clouds (DMCs), in dark, cold, and dense molecular clouds (DCDMCs), and in three regions of circumstellar envelopes of low-mass protostars (CELMPs). Methods. The potential energy surfaces, thermodynamic functions, and single-point energies for transition states were calculated at the CCSD(T)-F12/cc-pVTZ-F12 and MP2/aug-cc-pVDZ levels of theory and basis sets. Molecular thermodynamics and related partition functions were obtained by applying the Maxwell-Boltzmann quantum statistics theory from energies computed at CCSD(T)-F12/cc-pVTZ-F12 with corrections for zero-point energy. A literature review on detected abundances of reactants helped us to propose the most favorable formation routes. Results. The most probable reactions that produce H2CO in cold astrophysical regions are: 1CH2 + ⋅3O2 →1H2CO + O⋅(3P) in DMCs, ⋅3CH2 + ⋅3O2 →1H2CO + ⋅O(3P) in DCDMCs, and ⋅CH3 + ⋅O(3P) →1H2CO + ⋅H in region III, ⋅CH3 +⋅O(1D) →1H2CO + ⋅H in region II, and 1CH2 + ⋅3O2 →1H2CO + ⋅O(3P) in region I belonging to CELMPs. Conclusions. Quantum chemical calculations suggest that the principal carbonaceous precursors of H2CO in cold regions for the gas-phase are CH2(a1A1), and ⋅CH2(X3B1) combined with ⋅O2(3Σg) and ⋅CH3(2A”) + ⋅O(3P) / O(1D). Reactions based on more complex reagents yield less effective thermodynamics in the gas-phase H2CO molecular formation

Gas-phase molecular formation mechanisms of cyanamide (NH

Context. Cyanamide (NH2CN) and its tautomer carbodiimide (NHCHN) are believed to have been key precursors of purines and pyrimidines during abiogenesis on primitive Earth. The detection of guanine and cytosine in meteorites and comets provides evidence of their nonterrestrial formation. Although NH2CN has been found in several molecular clouds, NHCHN has only been detected in Sgr B2(N). Their possible molecular formation mechanisms in the gas phase and therefore their respective molecular precursors remain an open subject of investigation. Aims. The main objective of this paper is to determine which reactions can produce NH2CN and HNCNH in the amounts observed under the astrophysical conditions of Sgr B2(N). The determination of their most likely precursors could serve to provide new insights into possible routes to purine and pyrimidine synthesis, and by extension to nucleosides, under the astrophysical conditions of dense molecular clouds. Methods. Initially, we proposed 120 reaction mechanisms, 60 being dedicated to NH2CN formation and the remaining 60 to HNCNH. These mechanisms were constructed using 25 chemical species that were identified in outer space. We calculated the molecular energies of reactants and products at the CCSD(T)-F12/cc-pVTZ-F12 and MP2/aug-cc-pVDZ levels of theory, and defined the values of thermodynamic functions using the Maxwell-Boltzmann statistical quantum theory. Via an extensive literature review on the abundances of reactants and products in Sgr B2(N), in addition to a detailed kinetic study for a range of 20–300 K, we identify the most likely reaction mechanisms for both cyanamides of those proposed previously and presently. Results. From the 120 analyzed reactions, only nine for NH2CN and four for HNCNH could thermodynamically account for their synthesis in Sgr B2(N). The kinetic portion of our study shows that Ra60 (CH3NH2 +·CN → NH2CN +·CH3), with a modified Arrhenius expression of ${k_{\rm{T}}} = 1.22 \times {10^{ - 9}}{\left( {{T \over {300}}} \right)^{ - 0.038}}{\exp ^ - }\left( {{{ - 147.34} \over T}} \right) \rm{cm}^3 \rm{mol}^{-1} \rm{s}^{-1}$, is the most efficient reaction at low temperatures (<60 K). Above 60 K, no reaction with known reagents in Sgr B2(N) is efficient enough. In this way, Ra37-2 (·HNCN +·NH2 → NH2CN +3NH) appears to be the most likely candidate, showing a modified Arrhenius constant of ${k_{\rm{T}}} = 2.51 \times {10^{ - 11}}{\left( {{T \over {300}}} \right)^{ - 32.18}}{\exp ^ - }\left( {{{ - 1.332} \over T}} \right) \rm{cm}^3 \rm{mol}^{-1} \rm{s}^{-1}$. In the case of carbodiimide production, Rb18 (·H2NC +·NH2 → HNCNH +·H) is the most efficient reaction, fitting a rate constant of ${k_{\rm{T}}} = 4.70 \times {10^{ - 13}}{\left( {{{300} \over T}} \right)^{ - 3.24}}{\exp ^ - }\left( {{{36.28} \over T}} \right) \rm{cm}^3 \rm{mol}^{-1} \rm{s}^{-1}$ in Sgr B2(N). Conclusions. The detected gas-phase abundances of cyanamide (NH2CN) in Sgr B2(N) can be explained as: Ra60 (·CN +·CH3NH2) from 20 to 60 K; Ra5: (·CN +·NH2) from 60 to 120 K; and Ra37-2 (·HNCN +·NH2) from 120 to 300 K. The carbodiimide (HNCNH) synthesis could proceed via Rb18 (·H2NC +·NH2). Moreover, the presence of·HNCN and·H2NC in Sgr B2(N) are predicted here, making them viable candidates for future astronomical observations. The foreseen column density for the cyanomidil radical is ~1016 cm2 s−1 at 150 K or higher, while for amino methylidine, the value is a few 1013 cm2 s−1 at 100 K

Chemobrionic Fabrication of Hierarchical Self-Assembling Nanostructures of Copper Oxide and Hydroxide

Copper oxide nanostructures have great potential use in a plethora of nanotechnology applications including nanoelectronics, photovoltaics, sensors, electrochemistry, and pharmacology. In the present work we show how hierarchically nanostructured copper oxide and hydroxide may be prepared through self-assembly from CuSO4 salt and silicate solutions using the chemobrionic growth process of a chemical garden. Procedures were explored using the cupric salt in either solid (pellet and seed growth methods) or liquid phase (fluid injection techniques). Self-assembling nanostructures were characterized by means of environmental scanning electron microscopy (ESEM) with energy-dispersive X-ray spectroscopy (EDX) analysis, micro-Raman spectroscopy and X-ray diffraction. Our results show the formation of crystalline aggregates of copper oxide and hydroxide in complex hierarchical nanostructured forms including fans, flowers, petals, skeins, lentils, and sheaves. Analytical methods corroborate that these nanostructures may be selected in shape and chemical composition with the reaction conditions.We acknowledge the Spanish MINCINN project grants FIS201677692-C2-2P and PCIN-2017-098, along with European FEDER funds and the European COST Action CA17120

Dinosaur bonebed amber from an original swamp forest soil

Dinosaur bonebeds with amber content, yet scarce, offer a superior wealth and quality of data on ancient terrestrial ecosystems. However, the preserved palaeodiversity and/or taphonomic characteristics of these exceptional localities had hitherto limited their palaeobiological potential. Here, we describe the amber from the Lower Cretaceous dinosaur bonebed of Ariño (Teruel, Spain) using a multidisciplinary approach. Amber is found in both a root layer with amber strictly in situ and a litter layer mainly composed of aerial pieces unusually rich in bioinclusions, encompassing 11 insect orders, arachnids, and a few plant and vertebrate remains, including a feather. Additional palaeontological data—charophytes, palynomorphs, ostracods— are provided. Ariño arguably represents the most prolific and palaeobiologically diverse locality in which fossiliferous amber and a dinosaur bonebed have been found in association, and the only one known where the vast majority of the palaeontological assemblage suffered no or low-grade pre-burial transport. This has unlocked unprecedentedly complete and reliable palaeoecological data out of two complementary windows of preservation—the bonebed and the amber—from the same site