Extracellular vesicles (EVs) are membrane-enclosed nanoparticles containing specific repertoires of genetic material. In mammals, EVs can mediate the horizontal transfer of various cargos and ...signaling molecules, notably miRNA and mRNA species. Whether this form of intercellular communication prevails in other metazoans remains unclear. Here, we report the first parallel comparative morphologic and transcriptomic characterization of EVs from Drosophila and human cellular models. Electronic microscopy revealed that human and Drosophila cells release similar EVs with diameters ranging from 30 to 200 nm, which contain complex populations of transcripts. RNA-seq identified abundant ribosomal RNAs, related pseudogenes and retrotransposons in human and Drosophila EVs. Vault RNAs and Y RNAs abounded in human samples, whereas small nucleolar RNAs involved in pseudouridylation were most prevalent in Drosophila EVs. Numerous mRNAs were identified, largely consisting of exonic sequences displaying full-length read coverage and enriched for translation and electronic transport chain functions. By analogy with human systems, these sizeable similarities suggest that EVs could potentially enable RNA-mediated intercellular communication in Drosophila.
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Acid catalysts including Ni, Ag and Fe-loaded zeolites of different structures were prepared either via cationic exchange or impregnation techniques from pristine H-zeolites (BEA, and MFI). Their ...catalytic activity was evaluated in the liquid-phase Friedel–Crafts acylation of anisole with propanoic acid. It turned out that, whatever the doping procedure was, the zeolite loaded with transition metals led to considerable decrease in propanoic acid conversion, regardless of the nature or the metal content. However, the extent of this detrimental effect followed the order: Ag+ > Ni2+ > Fe3+.
Pristine acidic zeolites were not only found to be the most active, but also to be the most selective toward ortho- and para-acylation products. H-ZSM-5 zeolites yielded the highest intrinsic activity, with TOF values of 0.09 h−1. The catalyst activity proved to be essentially attributed to the density and accessibility of Brønsted acid sites, playing a key role in the activation of the reactants. Brønsted sites are proposed to be the most likely catalytic species for performing this Friedel–Crafts acylation.
Des cations métalliques (Ni, Ag et Fe) ont été incorporés au sein de zéolithes BEA et ZSM-5 par des techniques d'échange cationique et d'imprégnation afin d'obtenir de nouveaux catalyseurs acides solides. Ces matériaux ont ensuite été testés dans une réaction d'acylation de Friedel–Crafts entre l'anisole et l'acide propanoïque en phase liquide. Il s'est avéré que l'ajout de métaux de transition au sein de la structure zéolithique entraîne une diminution considérable de la conversion, indépendamment de la nature ou de la quantité de métal introduite. Dans des conditions catalytiques similaires, les zéolithes parentes présentent une meilleure activité intrinsèque (TOF), en particulier H-ZSM-5, avec une production plus élevée de produits d'acylation (ortho- et para-), surpassant ainsi les performances catalytiques des zéolithes dopées par des métaux. L'accessibilité et la densité de sites acides de Brønsted se sont avérées déterminantes pour ce type de réaction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We have assembled a sample of 64 late-type spiral galaxies (T types 6.0-9.0, corresponding to Hubble types Scd-Sm) with archival Chandra data. At a signal-to-noise (S/N) threshold of 3, we find 12 ...objects with X-ray point-source detections in close proximity with the optical or near-infrared position of the nucleus (median offset delta = 16), suggestive of possible low-luminosity active galactic nuclei (AGNs). Including measurements with 3 > S/N > 1.5, our detections increase to 18. These X-ray sources range in luminosity from L X(2-10 keV) = 1037.1 to 1039.6 erg s-1. Considering possible contamination from low-mass X-ray binaries (LMXBs), we estimate that ~5 detections are possible LMXBs instead of true AGNs, based on the probability of observing an LMXB in a nuclear star cluster (NC) typically found in these late-type spiral galaxies. Given the typical ages of NCs, contamination by high-mass X-ray binaries is unlikely. This AGN fraction is higher than that observed in optical surveys, indicating that active nuclei, and hence central black holes (BHs), are more common than previously suggested. The incidence of AGN activity in such late-type spiral galaxies also suggests that nuclear massive BHs can form and grow in galaxies with little or no evidence for bulges. Follow-up multiwavelength observations will be necessary to confirm the true nature of these sources.
Propene is a key building block for the petrochemical industry whose demand is increasing strongly in recent years, even faster than that of ethene. The availability of propene is limited, and ...therefore, efforts to optimize its production are being pursued. On the occasion of the 75th anniversary of the first FCC unit, we analyze some recent advances that have been achieved in the understanding and development of zeolites aiming to increase the production of light olefins as petrochemical building blocks by means of catalytic cracking. We discuss a selected group of emerging strategies in zeolite engineering that have great prospects for research and that we consider could impact the sector in the near future. These include advances in crystal engineering and hierarchization achieved through bottom-up and top-down approaches, composite materials, tuning of the location of active sites among the different crystallographic positions available, and, importantly, how to characterize these modifications and their impact on the catalysis. Finally, we survey what advances are actually being implanted into the current industrial practice and conclude with a reflection on the future of zeolite research to satisfy light olefin demand.
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The unprecedented use of a deep eutectic solvent (DES) for the ionothermal synthesis of Ca(
ii
) based metal-organic frameworks (MOFs) has been explored. The 1 : 2 choline chloride : e-urea DES ...(e-urea = 2-imidazolidinone, ethylene urea) has been successfully employed for the preparation of Ca-MOFs with a series of dicarboxylic acid ligands. These materials have been structurally characterized by single-crystal and powder X-ray diffraction techniques as well as by thermo-gravimetric analysis and infrared, UV-visible and emission spectroscopy techniques in the crystalline state. The MOFs obtained have been found to be three-dimensional with the presence of channels occupied by coordinated e-urea solvent molecules. While the latter solvent acts as a bridging ligand in the case of terephthalate and isophthalate based MOFs, it behaves as a terminal ligand in the MOFs isolated with 2,5-dihydroxyterephthalate (dobdcH
2
2−
). With this ligand, two phases differing in the coordination mode of the dobdcH
2
2−
anion have been obtained. Interestingly, for one of them formulated as Ca(dobdcH
2
)(e-urea)
2
, the crystals rapidly lost their transparency and luster upon exposure to air. This phenomenon could be rationalized by X-ray diffraction to result from the uptake of water molecules from the ambient atmosphere leading to the replacement of one e-urea molecule by H
2
O in the Ca(
ii
) cation coordination sphere. These results demonstrate that the 1 : 2 choline chloride : e-urea DES can be considered as an effective solvent for the synthesis of water-sensitive Ca-MOFs.
The ionothermal synthesis of Ca-MOFs has been performed using the 1 : 2 choline chloride : e-urea deep eutectic solvent, allowing the preparation of water sensitive materials.
Acidic zeolites, especially faujasites, efficiently promote the intramolecular cyclization of aryl propynoates and propynethioates, which produces coumarins and thiocoumarins, usually in high yields. ...Comparison with homogeneous Lewis or BrØnsted acids and with heterogeneous related sieve materials revealed the prevalence of zeolites exhibiting large cage‐type pores (H‐USY) for such cyclizations. Various substituents proved compatible with the cyclization process, leading to a variety of substituted coumarins and thiocoumarins (20 examples, 30–99 %).
Organic synthesis: Zeolites as Nanoreactors for Green Chemistry and Fine Chemistry : New route to Coumarins and Thiocoumarins
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This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten ...articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact
We study the evolution of the incremental cost and price of efficiency for televisions in the U.S. market. We focus on televisions due to their rapid technological evolution and large number of ...annual shipments, such that costs and prices evolve on short timescales as compared to other consumer durable goods. Using the experience curve approach, we compare manufacturing costs and selling prices of two liquid crystal display (LCD) technologies. We find a mean experience rate of 27% for less efficient cold cathode fluorescent lamp LCD televisions and 14% for more efficient light emitting diode LCD televisions, using price data. This corresponds to an annual decline of approximately 17% per year in price for both television types. Our results also suggest that the incremental cost or price of efficiency, holding other major features constant, declines much more rapidly than the baseline cost or price. We find that the incremental cost or price declines at roughly 50% per year. The fitted parameters do depend on the specific technology modeled, as well as on whether cost or price data are used. Our results for LCD televisions are qualitatively similar to other display technologies, even very mature ones, suggesting that the cost and price decline extends many years after a technology is considered mature. We also analyze the selling prices of ENERGY STAR® and non-ENERGY STAR televisions, which support our main findings. These results highlight the consumer benefits of efficient display technologies, and how the dynamics of incremental costs differ from baseline costs.
•We study the evolution of the incremental cost/price of efficiency in televisions.•We use the experience curve approach.•Historical evidence suggests incremental costs/prices decline rapidly.•Incremental costs/prices decline more rapidly than average costs/prices.•Our results are qualitatively similar for several display technologies.
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This research introduces a completely new environmental benign synthesis route for obtaining two kinds of inter-mediate and high temperature CO2 sorbents, Mg-Al layered double hydroxide (LDH) and ...Li4SiO4, from vermiculite. The mineral vermiculite was leached with acid, from which the obtained SiO2 was used for the synthesis of Li4SiO4 and the leaching waste water was used for the synthesis of Mg-Al LDH. Therefore, no waste was produced during the whole process. Both Li4SiO4 and Mg-Al LDH sorbents were carefully characterized using XRD, SEM, and BET analyses. The CO2 capturing performance of these two sorbents was comprehensively evaluated. The influence of the Li/Si ratio, calcination temperature, calcination time, and sorption temperature on the CO2 sorption capacity of Li4SiO4, and the sorption temperature on the CO2 sorption capacity of LDH, were investigated. The optimal leaching acid concentration for vermiculite and the CO2 sorption/desorption cycling performance of both the Li4SiO4 and Mg-Al LDH sorbents were determined. In sum, this demonstrated a unique and environment-friendly scheme for obtaining two CO2 sorbents from cheap raw materials, and this idea is applicable to the efficient utilization of other minerals.
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