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El consumo de tabaco está ampliamente extendido y culturalmente aceptado en la mayoría de los países occidentales, constituyendo en la actualidad un importante problema de salud pública. Fumar cigarrillos es la principal causa de morbilidad y mortalidad prematura en los países donde su consumo esta extensamente difundido. El tabaco en la población juvenil constituye en la actualidad un importante problema de salud pública. El objetivo del estudio es conocer el consumo de tabaco de la población adolescente del barrio la Victoria de Valladolid. La metodología llevada a cabo, se trata un estudio descriptivo transversal sobre la población comprendida entre los 15 – 20 años. Se ha realizado un cuestionario de 10 preguntas, ocho de ellas relacionadas con el consumo de tabaco y dos referentes a aspectos socio-demográficos. Los resultados más significativos que se han obtenido han sido los siguientes: - La fuente principal de información del adolescente sobre este hábito son los medios de comunicación. - Las mujeres jóvenes fuman más que los hombres. - En cuanto al inicio de la adquisición de este hábito tiene una gran importancia el grupo en el que se desarrolla la persona. - Número elevado de adolescentes que asocian el tabaco con el alcohol. Como conclusión de este estudio, se deduce que la educación sanitaria y el consejo antitabaco sobre los hábitos tóxicos debemos dirigirlo cada vez a edades más tempranas, y tanto a varones como a mujeres, en un intento de promover la educación, promocionar la salud y prevenir la enfermedad.

Due to their conductive properties and optoelectronic tunability, MXenes have revolutionized the area of electrocatalysis and active materials in supercapacitors. In comparison, there are only a few reports on MXenes as thermal catalysts for general organic reactions. Herein, the unprecedented catalytic activity of Ti 3 C 2 MXene for the hydroamination of alkynes is reported, overcoming the limitations of poor activity, lack of selectivity, and stability, which are generally encountered in the solid catalysts known so far. In the case of Ti 3 C 2 , hydroamination exhibits almost complete selectivity for the anti-Markovnikov regio isomer, for both aliphatic amines and less-reactive aromatic amines. Ti 3 C 2 also efficiently catalyzes intramolecular hydroamination, leading to the formation of indol heterocycles. The catalytic hydroamination of C-C multiple bonds is a reaction with complete atom efficiency that may form C-N bonds from convenient reagents. The maximum number of hydroamination sites on the Ti 3 C 2 nanosheets is quantified by thermoprogrammed NH 3 desorption. The measured TOF values are on the order of 10 2 h -1 , with the highest TOF value being 350 h -1 for 1-hexyne hydroamination by n - butylamine. Therefore, Ti 3 C 2 is among the few heterogeneous hydroamination catalysts studied, with its activity per site being comparable to the best hydroamination catalysts reported so far. Density functional theory calculations on the models indicate the cooperation of neighboring Ti atoms in the mechanism. Considering the compositional and structural versatility of MXenes, the present findings open the door for further application of MXenes in other general organic reactions.

In this study, we present the synthesis, characterization, and structural analysis of a novel zeolite, ITQ-70, using 3D electron diffraction. This unique material was synthesized under alkaline conditions, employing tetrakis(diethylamino)phosphonium as an organic structure-directing agent, leading to the formation of a pure silica zeolite. ITQ-70 is distinguished by its extra-large pore apertures, which extend along all three axes and intersect one to the other. A notable feature of this zeolite is the presence of structurally ordered defects in very high concentrations (38 % of the silicon atoms). As a result, ITQ-70 exhibits the lowest framework density (10.0 T/1000 Å 3 ) ever reported for any zeolite except RWY (7.6 T/1000 Å 3 ), which contains sulfur instead of oxygen connecting T-atoms., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Despite extensive efforts over the past several decades, the current mechanistic understanding of zeolite crystallization is still far from satisfactory, thus precluding the synthesis of designer zeolites. Here we show that the nucleation and in situ transformation pathways during the synthesis of medium-pore zeolite TNU-9 can be altered by controlling the extent of cooperative structure direction between Na + and Cs + ions in the presence of 1,4-bis( N -methylpyrrolidinium)butane cations as an organic structure-directing agent. The intermediate phase selectivity was found to change from bikitaite to analcime to layered MCM-22 precursor when the gel Na/Cs ratio was adjusted to 7, 15, and 20, respectively. We also show that the transformation of bikitaite into TNU-9 begins at the surface of intermediate crystals, unlike that of analcime and MCM-22 precursor by a dissolution-recrystallization process. The force field simulation results suggest that the nucleation of different intermediate phases is not thermodynamically but kinetically controlled. This study provides a new basis for advancing the fundamental understanding of zeolite crystallization pathways.

Zeolites, well-known by their high selectivities in catalytic and separation processes due to their porous nature, play a crucial role in various applications. One significant long-term objective is the synthesis of enantiopure zeolites, potentially enabling enantioselective processes. Earlier attempts result in partial success, yielding some enantiomorphically enriched zeolites. In this study, we introduce a zeolite synthesis approach utilizing chiral organic structure directing agents (ch-OSDAs) derived from sugars, guiding the crystallization process toward achieving enantiomorphically pure S-STW zeolite. The purity of the zeolite is confirmed through extensive analyses of individual crystals using single-crystal X-ray diffraction, extracting Flack parameters and space groups. Theoretical and structural investigations confirm that the sugar-derived ch-OSDA perfectly fits the characteristic helicoidal channel of the zeolite structure, featuring its efficacy in achieving enantiopure zeolites., (© 2024. The Author(s).)

The quest for efficient catalysts based on abundant elements that can promote the selective CO 2 hydrogenation to green methanol still continues. Most of the reported catalysts are based on Cu/ZnO supported in inorganic oxides, with not much progress with respect to the benchmark Cu/ZnO/Al 2 O 3 catalyst. The use of carbon supports for Cu/ZnO particles is much less explored in spite of the favorable strong metal support interaction that these doped carbons can establish. This manuscript reports the preparation of a series of Cu-ZnO@(N)C samples consisting of Cu/ZnO particles embedded within a N-doped graphitic carbon with a wide range of Cu/Zn atomic ratio. The preparation procedure relies on the transformation of chitosan, a biomass waste, into N-doped graphitic carbon by pyrolysis, which establishes a strong interaction with Cu nanoparticles (NPs) formed simultaneously by Cu 2+ salt reduction during the graphitization. Zn 2+ ions are subsequently added to the Cu-graphene material by impregnation. All the Cu/ZnO@(N)C samples promote methanol formation in the CO 2 hydrogenation at temperatures from 200 to 300 °C, with the temperature increasing CO 2 conversion and decreasing methanol selectivity. The best performing Cu-ZnO@(N)C sample achieves at 300 °C a CO 2 conversion of 23% and a methanol selectivity of 21% that is among the highest reported, particularly for a carbon-based support. DFT calculations indicate the role of pyridinic N doping atoms stabilizing the Cu/ZnO NPs and supporting the formate pathway as the most likely reaction mechanism.

Ammonia selective catalytic reduction (NH 3 -SCR) over copper- and iron-exchanged zeolites is a state-of-the-art technology for removal of nitrogen oxides (NO x , NO, and NO 2 ) from exhaust emissions but suffers from poor low-temperature (i.e., 150 °C) activity. Here we show that hydrothermal aging of Fe-beta, Fe-ZSM-5, and Fe-ferrierite at 650 °C or higher leads to a remarkable increase in NO x conversion from ∼30 to ∼80% under fast NH 3 -SCR conditions at 150 °C. The practical relevance of this finding becomes more evident as an aged Fe-beta/fresh Cu-SSZ-13 composite catalyst exhibits ∼90% conversion. We propose that a neutral heteronuclear bis-μ-oxo ironaluminum dimer might be created within iron zeolites during hydrothermal aging and catalyze ammonium nitrate reduction by NO at 150 °C. Density functional theory calculations reveal that the activation free energy (125 versus 147 kJ mol -1 ) for the reaction of NO with adsorbed NO 3 - species, the rate-determining step of ammonium nitrate reduction, is considerably lower on the bis-μ-oxo ironaluminum site than on the well-known mononuclear iron-oxo cation site, thus greatly enhancing the overall SCR activity.

Photodecarboxylation of biomass-derived fatty acids to alkanes offers significant potential to obtain hydrocarbons and economic benefits due to the mild conditions and high activity. Herein, the photodecarboxylation of hexanoic acid into alkanes using TiO 2 -supported monometallic Au or Pd and bimetallic Au-Pd catalysts is reported. It was found that bimetallic Au-Pd catalysts, featuring a core-shell structure evidenced by EDX-mapping and element line profile, show better photocatalytic performance, achieving 94.7% conversion of hexanoic acid and nearly 100% selectivity to pentane under UV-vis irradiation in the absence of H 2 than the monometallic Au analogue. This remarkable enhancement in activity compared to its TiO 2 supported monometallic Au or Pd analogues can be attributed to the synergistic effect between Au and Pd within the nanostructured Au(core)-Pd(shell) alloy for achieving more efficient charge-separation efficiency upon visible light excitation. This photocatalyst exhibits a wide scope converting multiple fatty acids into hydrocarbons. Moreover, it can even photocatalyze the conversion of raw bio-oils into alkanes directly. No obvious activity loss was observed during the reusability tests, demonstrating the good stability of the present catalyst. Density functional theory (DFT) calculations indicate that oxidation of carboxylates on TiO 2 leads to alkyl radicals that become bound to metal nanoparticles. The superior catalytic performance of Au(core)-Pd(shell)/TiO 2 is derived from the weaker adsorption for H on the alloy and the lower hydrogen evolution reaction overpotential. Our research can result in an efficient bio-oil upgrading, resulting in the synthesis of biofuels from biomass under mild conditions., Competing Interests: The authors declare no competing financial interest., (© 2023 American Chemical Society.)

Many systems for controlled drug release have been developed using different types of nanoparticles modified with azobenzene moieties. In these systems, drug release is often triggered by UV irradiation (either direct or using a near-infrared photosensitizer). These drug delivery systems often face challenges to their use, such as their lack of stability in physiological environments and concerns about their toxicity and bioavailability, that have hindered their translation from pre-clinical studies to clinical trials. Here, we propose a conceptual change by shifting photoswitching activity from the vehicle (nanoparticle) to the load (drug). In this "ship in a bottle" concept, the molecule to be delivered is trapped within a porous nanoparticle and its release is accomplished through a photoisomerization process. Using molecular dynamics, we designed and synthesized a photoswitchable prodrug of the antitumor drug camptothecin that contains an azobenzene functionality, and we have prepared porous silica nanoparticles with pore diameters designed to limit its release when in the trans form. Molecular modelling was used to show that the cis isomer was smaller and better able to pass through the pores than the trans isomer, which was confirmed by stochastic optical reconstruction microscopy (STORM). Thus, prodrug-loaded nanoparticles were prepared by loading the cis prodrug and then using UV irradiation to convert cis to trans isomers, trapping them, within the pores. Release of the prodrug was then accomplished by using a different UV wavelength to convert trans isomers back to cis . In this way, prodrug encapsulation and release could be achieved "on demand" through controlled cis - trans photoisomerization, which allowed the prodrug to be delivered safely and its release to be triggered precisely at the region of interest. Finally, the intracellular release and cytotoxic activity of this novel drug delivery system has been validated in several human cell lines, confirming the ability of this system to accurately control the release of the camptothecin prodrug.

In the present study, the identification of potential α-amylase inhibitors is explored as a potential strategy for treating type-2 diabetes mellitus. A computationally driven approach using molecular docking was employed to search for new α-amylase inhibitors. The interactions of potential drugs with the enzyme's active site were investigated and compared with the contacts established by acarbose (a reference drug for α-amylase inhibition) in the crystallographic structure 1B2Y. For this active site characterization, both molecular docking and molecular dynamics simulations were performed, and the residues involved in the α-amylase-acarbose complex were considered to analyse the potential drug's interaction with the enzyme. Two potential α-amylase inhibitors (AN-153I105594 and AN-153I104845) have been selected following this computational strategy. Both compounds established a large number of interactions with key binding site α-amylase amino acids and obtained a comparable docking score concerning the reference drug (acarbose). Aiming to further analyse candidates' properties, their ADME (absorption, distribution, metabolism, excretion) parameters, druglikeness, organ toxicity, toxicological endpoints and median lethal dose (LD 50 ) were estimated. Overall estimations are promising for both candidates, and in silico toxicity predictions suggest that a low toxicity should be expected., (© 2023 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Graphene has emerged as an exciting material because of its widespread applications resulting from its unique properties. Nano-scale engineering of graphene's structure is one of the most active research areas aimed at introducing functionalities to improve the performance or endow the graphene lattice with novel properties. In this regard, conversion between the hexagon and non-hexagon rings becomes an exciting tool to tune the electronic structure of graphene due to the distinct electronic structure and functionalities induced in graphene by each type of ring. This Density Functional Theory (DFT) study is an in-depth look at the adsorption-induced conversion of pentagon-octagon-pentagon rings to hexagon rings, and systematically investigates the possibility of the conversion of pentagon-octagon-pentagon rings to pentagon-heptagon pair rings. Moreover, the bottlenecks for these atomic-level conversions in the lattice structure of graphene and the influence of heteroatom doping on the mechanisms of these transformations are established.

Photosensitized thymine<>thymine (Thy<>Thy) formation and repair can be mediated by carbazole (Cbz). The former occurs from the Cbz triplet excited state via energy transfer, while the latter takes place from the singlet excited state via electron transfer. Here, fundamental insight is provided into the role of the topology and excited state multiplicity, as factors governing the balance between both processes. This has been achieved upon designing and synthesizing different isomers of trifunctional systems containing one Cbz and two Thy units covalently linked to the rigid skeleton of the natural deoxycholic acid. The results shown here prove that the Cbz photosensitized dimerization is not counterbalanced by repair when the latter, instead of operating through-space, has to proceed through-bond.

The irradiation of ( Z )-2-phenyl-4-aryliden-5(4 H )-oxazolones 1 in deoxygenated CH 2 Cl 2 at 25 °C with blue light (465 nm) in the presence of [Ru(bpy) 3 ](BF 4 ) 2 (5% mole ratio) as a triplet photocatalyst promotes the [2+2] photocycloaddition of the C═C bonds of the 4-arylidene moiety, thus allowing the completely regio- and stereoselective formation of cyclobutane-bis(oxazolone)s 2 as single stereoisomers. Cyclobutanes 2 have been unambiguously characterized as the μ-isomers and contain two E -oxazolones coupled in an anti -head-to-head form. The use of continuous-flow techniques in microreactors allows the synthesis of cyclobutanes 2 in only 60 min, compared with the 24-48 h required in batch mode. Ring opening of the oxazolone heterocycle in 2 with a base affords the corresponding 1,2-diaminotruxinic bis-amino esters 3 , which are also obtained selectively as μ-isomers. The ruthenium complex behaves as a triplet photocatalyst, generating the reactive excited state of the oxazolone via an energy-transfer process. This reactive excited state has been characterized as a triplet diradical 3 ( E / Z )- 1* by laser flash photolysis (transient absorption spectroscopy). This technique also shows that this excited state is the same when starting from either ( Z )- or ( E )-oxazolones. Density functional theory calculations show that the first step of the [2+2] cycloaddition between 3 ( E/Z )- 1* and ( Z )- 1 is formation of the C(H)-C(H) bond and that ( Z ) to ( E ) isomerization takes place at the 1,4-diradical thus formed.

An example of zeolite selectivity (MFI → MOR) driven by synthesis aging time has been studied. Using N , N , N ', N '-tetramethyl- N , N '-dipropyl-ethylenediammonium diiodide (TMDP) as an organic structure-directing agent (OSDA), the zeolite phases obtained at 2 h (MFI 97%), 8 h (MFI 84%, MOR 16%) and 24 h (MFI 43%, MOR 57%) have been characterized by powder X-ray diffraction. The results suggest that at intermediate aging time, namely 8 h and 24 h, the dominant phase (MFI) is displaced by MOR. Different techniques (FT-IR, Raman, 13 C MAS NMR, TGA/DTG and HC microanalysis) have been employed to verify the OSDA integrity and occlusion inside the zeolite micropores as well as to quantify the water and OSDA loading. The 1 H MAS NMR of the as-made occluded zeolite was compared with the spectra of TMDP and the recovered OSDA from the sample by extraction with water. The comparison indicated that TMDP was not structurally intact, indicating the chemical transformation of TMDP to imidazolinium homologues through the Hofmann degradation process. Furthermore, careful acidic breakdown of the aluminosilicate shell, covered on the zeolite samples by hydrofluoric acid, revealed that the remaining OSDA had been partially degraded to lower molecular weight ammonium salt, confirmed by 1 H NMR and mass spectrometry measurements. A computational study was performed by using a force field based methodology, including accurate loading of water and OSDA in the zeolite (MFI and MOR) unit cells. The results show an important contribution of the presence of water. The samples with larger aging time (8 h and 24 h) incorporate less water and show partial TMDP degradation, whilst at the shortest aging time (2 h), there is a larger water content and TMDP remains intact. The larger accessible volume of MFI justifies that this is the dominant phase at short aging times (large water content) since it can accommodate a larger number of water molecules than MOR. The OSDA partial degradation also plays a role. At longer aging times the partial OSDA decomposition has been considered in the models by including TMDP + Imidaz, which is more stabilized by MOR, whilst at shorter aging times the only OSDA present, TMDP, is better stabilized by MFI.

Diffusion is generally faster at higher temperatures. Here, a counterintuitive behavior is observed in that the movement of long-chain molecules slows as the temperature increases under confinement. This report confirms that this anomalous diffusion is caused by the "thermal resistance effect," in which the diffusion resistance of linear-chain molecules is equivalent to that with branched-chain configurations at high temperature. It then restrains the molecular transportation in the nanoscale channels, as further confirmed by zero length column experiments. This work enriches our understanding of the anomalous diffusion family and provides fundamental insights into the mechanism inside confined systems., Competing Interests: The authors declare no competing interest.

In separation and catalysis applications, adsorption and diffusion are normally considered mutually exclusive. That is, rapid diffusion is generally accompanied by weak adsorption and vice versa. In this work, we analyze the anomalous loading-dependent mechanism of p -xylene diffusion in a newly developed zeolite called SCM-15. The obtained results demonstrate that the unique system of "continuum intersecting channels" (i.e., channels made of fused cavities) plays a key role in the diffusion process for the molecule-selective pathways. At low pressure, the presence of strong adsorption sites and intersections that provide space for molecule rotation facilitates the diffusion of p -xylene along the Z direction. Upon increasing the molecular uptake, the adsorbates move faster along the X direction because of the effect of continuum intersections in reducing the diffusion barriers and thus maintaining the large diffusion coefficient of the diffusing compound. This mechanism synergistically improves the diffusion in zeolites with continuum intersecting channels., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Optimising the balance between propene selectivity, propene/ethene ratio and catalytic stability and unravelling the explicit mechanism on formation of the first carbon-carbon bond are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the nature of active sites within the pores of commercial MFI-zeolites by incorporating tantalum(V) and aluminium(III) centres into the framework. The resultant TaAlS-1 zeolite exhibits simultaneously remarkable propene selectivity (51%), propene/ethene ratio (8.3) and catalytic stability (>50 h) at full methanol conversion. In situ synchrotron X-ray powder diffraction, X-ray absorption spectroscopy and inelastic neutron scattering coupled with DFT calculations reveal that the first carbon-carbon bond is formed between an activated methanol molecule and a trimethyloxonium intermediate. The unprecedented cooperativity between tantalum(V) and Brønsted acid sites creates an optimal microenvironment for efficient conversion of methanol and thus greatly promotes the application of zeolites in the sustainable manufacturing of light olefins.

Post-synthetic modification of covalent organic frameworks (COFs) is strongly demanded in order to provide additional functionalities to their structures. However, the introduction of functional groups during the synthesis of two dimensional COFs (2D COFs) is highly discouraged, as they can interfere with the π-π stacking forces, compromising framework integrity. Here, we show that direct incorporation of nucleophyllic groups (e.g., primary amines) on pore wall during the synthesis of a 2D-COF (COF-5) is possible by sequential substitution of original monomers. Subsequent bonding of the antitumor drug camptothecin results in a stable hydrophobic drug delivery system. Water adsorption isotherms modelling indicates that the insertion of CPT ligand in the framework promotes a hydrophobic effect that protects a region of COF chain from boronate ester hydrolysis and resulting degradation, which is also proven by stability testing in physiological conditions. Furthermore, this hydrophobic nature favors cell internalization kinetics by promoting interactions with the lipophilic cell membrane. To the best of our knowledge, this is the first case of a stable drug delivery system based on covalently conjugated COFs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

"Shape" was the first criterion claimed to explain the specificity between organic structure-directing agents (OSDAs) and zeolite micropores. With the advent of computational chemistry methods applied to study the effectiveness of SDA-zeolite combinations, "energy" (mainly van der Waals) became the most commonly invoked concept to explain the zeolite phase selectivity. The lower the energy, the better the SDA. In this study, we rescue the concept of shape, and we combine it with the concept of energy within the frame of a SDA screening approach to identify new SDAs for the synthesis of cage-based ITE zeolite. Once we identify an appropriate shape fingerprint, filtering through the SDA database can be done quickly and accurately. With the shape selection, an automated Monte Carlo software allows us to assess the suitability using the force-field-calculated zeo-SDA energy. The computational approach can be promptly applied to other cage-based zeolites.

The presence of organic structure directing agents (templates) in the synthesis of zeolites allows the synthesis to be directed, in many cases, toward structures in which there is a large stabilization between the template and the zeolite micropore due to dispersion interactions. Although other factors are also important (temperature, pH, Si/Al ratio, etc.), systems with strong zeolite-template interactions are good candidates for an application of new computational algorithms, for instance those based in molecular topology (MT), that can be used in combination with large databases of organic molecules. Computational design of new templates allows the synthesis of existing and new zeolites to be expanded and refined. Three zeolites with similar 3-D large pore systems, BEA, BEC, and ISV, were selected with the aim of finding new templates for their selective syntheses. Using a training set of active and inactive templates (obtained from the literature) for the synthesis of target zeolites, it was possible to select chemical descriptors related to activity, meaning a good candidate template. With a discriminant function defined upon MT, the screening through a database of organic molecules led to a small subset (preselection) of candidate templates for the synthesis of BEA, BEC, and ISV. As far as we know, this is the first time that topological/topochemical descriptors, which do not consider 3-D information on the molecules, have been used to predict the activity of zeolite structure directing agents (SDAs). Following the prediction of SDAs using MT, an automated approach of sequential template filling of micropores based on a combination of Monte Carlo and lattice energy minimization was applied for all the candidate templates in the three zeolites. Two results can be obtained from this: an evaluation of the quality of the molecular topology QSAR models leading to the preselection of templates, and a final selection of candidate templates for the selective synthesis of BEA, BEC, and ISV. Regarding the latter, a good template will be that which maximizes the zeolite-template dispersion interactions with one, and only one, of the three zeolites. The presented methodology can be used to find alternative (maybe cheaper or perhaps more selective) templates than those already known.

The methanol-to-olefins process over H-SAPO-34 is characterized by its high shape selectivity toward light olefins. The catalyst is a supramolecular system consisting of nanometer-sized inorganic cages, decorated by Brønsted acid sites, in which organic compounds, mostly methylated benzene species, are trapped. These hydrocarbon pool species are essential to catalyze the methanol conversion but may also clog the pores. As such, diffusion of ethene and propene plays an essential role in determining the ultimate product selectivity. Enhanced sampling molecular dynamics simulations based on either force fields or density functional theory are used to determine how molecular factors influence the diffusion of light olefins through the 8-ring windows of H-SAPO-34. Our simulations show that diffusion through the 8-ring in general is a hindered process, corresponding to a hopping event of the diffusing molecule between neighboring cages. The loading of different methanol, alkene, and aromatic species in the cages may substantially slow down or facilitate the diffusion process. The presence of Brønsted acid sites in the 8-ring enhances the diffusion process due to the formation of a favorable π-complex host-guest interaction. Aromatic hydrocarbon pool species severely hinder the diffusion and their spatial distribution in the zeolite crystal may have a significant effect on the product selectivity. Herein, we unveil how molecular factors influence the diffusion of light olefins in a complex environment with confined hydrocarbon pool species, high olefin loadings, and the presence of acid sites by means of enhanced molecular dynamics simulations under operating conditions.

Wastewater represents the main reusable water source after being adequately sanitized by wastewater treatment plants (WWTPs). In this sense, only bacterial quality indicators are usually checked to this end, and human pathogenic viruses usually escape from both sanitization procedures and controls, posing a health risk on the use of effluent waters. In this study, we evaluated a protocol based on aluminum adsorption-precipitation to concentrate several human enteric viruses, including norovirus genogroup I (NoV GI), NoV GII, hepatitis A virus (HAV), astrovirus (HAstV), and rotavirus (RV), with limits of detection of 4.08, 4.64, 5.46 log genomic copies (gc)/L, 3.31, and 5.41 log PCR units (PCRU)/L, respectively. Furthermore, the method was applied in two independent laboratories to monitor the presence of NoV GI, NoV GII, and HAV in effluent and influent waters collected from five WWTPs at two different sampling dates. Concomitantly, a viability PMAxx-RT-qPCR was applied to all the samples to get information on the potential infectivity of both influent and effluent waters. The ranges of the titers in influent waters for NoV GI, NoV GII, RV, and HAstV were 4.80-7.56, 5.19-7.31 log gc/L, 5.41-6.52, and 4.59-7.33 log PCRU/L, respectively. In effluent waters, the titers ranged between 4.08 and 6.27, 4.64 and 6.08 log gc/L, < 5.51, and between 3.31 and 5.58 log PCRU/L. Moreover, the viral titers detected by viability RT-qPCR showed statistical differences with RT-qPCR alone, suggesting the potential viral infectivity of the samples despite some observed reductions. The proposed method could be applied in ill-equipped laboratories, due to the lack of a requirement for a specific apparatus (i.e., ultracentrifuge).

The separation of deuterium from hydrogen still remains a challenging and industrially relevant task. Compared to traditional cryogenic methods for separation, based on different boiling points of H 2 and D 2 , the use of ultramicroporous materials offers a more efficient alternative method. Due to their rigid structures, permanently high porosity, tunable pore sizes and adjustable internal surface properties, metal-organic frameworks (MOFs), a class of porous materials built through the coordination between organic linkers and metal ions/clusters, are more suitable for this approach than zeolites or carbon-based materials. Herein, dynamic gas flow studies on H 2 /D 2 quantum sieving in MFU-4, a metal-organic framework with ultra-narrow pores of 2.5 Å, are presented. A specially designed sensor with a very fast response based on surface acoustic waves is used. On-chip measurements of diffusion rates in the temperature range 27-207 K reveal a quantum sieving effect, with D 2 diffusing faster than H 2 below 64 K and the opposite selectivity above this temperature. The experimental results obtained are confirmed by molecular dynamic simulation regarding quantum sieving of H 2 and D 2 on MOFs for which a flexible framework approach was used for the first time., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Benzophenone (BP) and drugs containing the BP chromophore, such as the non-steroidal anti-inflammatory drug ketoprofen, have been widely reported as DNA photosensitizers through triplet-triplet energy transfer (TTET). In the present work, a direct spectroscopic fingerprint for the formation of the thymine triplet ( 3 Thy*) by through-bond (TB) TTET from 3 BP* has been uncovered. This has been achieved in two new systems that have been designed and synthesized with one BP and one thymine (Thy) covalently linked to the two ends of the rigid skeleton of the natural bile acids cholic and lithocholic acid. The results shown here prove that it is possible to achieve triplet energy transfer to a Thy unit even when the photosensitizer is at a long (nonbonding) distance., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The recently presented software zeoGAsolver is discussed, which is based on genetic algorithms, with domain-dependent crossover and selection operators that maintain the size of the population in successive iterations while improving the average fitness. Using the density, cell parameters, and symmetry (or candidate symmetries) of a zeolite sample whose resolution can not be achieved by analysis of the XRD (X-ray diffraction) data, the software attempts to locate the coordinates of the T-atoms of the zeolite unit cell employing a function of 'fitness' (F), which is defined through the different contributions to the 'penalties' (P) as F = 1/(1 + P). While testing the software to find known zeolites such as LTA (zeolite A), AEI (SSZ-39), ITW (ITQ-12) and others, the algorithm has found not only most of the target zeolites but also seven new hypothetical zeolites whose feasibility is confirmed by energetic and structural criteria.

One of the main problems of gas storage in porous materials is that many molecules of interest adsorb too weakly to be retained effectively. To enhance gas storage in metal-organic frameworks (MOFs), we propose the use of kinetic trapping, i.e., a process where the guest gas is captured in the voids at loading conditions and not released immediately at normal conditions. In this approach, the diffusion-limiting pore size and the framework flexibility have to be matched to the gas, requiring flexible pore apertures to be smaller than the van der Waals diameter of the trapped guest. We selected the Metal-Organic Framework Ulm University-4 (MFU-4) with a pore aperture of 2.52 Å as a model coordination framework and used it for storage of xenon (with van der Waals diameter of 4.4 Å). Although xenon atoms are substantially larger than the MOF pore aperture, MFU-4 could be loaded with xenon by applying moderately high gas pressures. This is demonstrated to be due to the pore flexibility as confirmed by computational studies. The xenon loading could be tuned (from 0 wt % to more than 44.5 wt %) by changing the loading parameters such as pressure, temperature, and time, and the xenon atoms remained inside the pores upon exposing the material to air atmosphere at room temperature. To understand the material behavior, TGA, XRPD, and 129 Xe NMR spectroscopy and computational studies were carried out.

The development of contrast agents (CAs) for Magnetic Resonance Imaging (MRI) with T1-T2 dual-mode relaxivity requires the accurate assembly of T1 and T2 magnetic centers in a single structure. In this context, we have synthesized a novel hybrid material by monitoring the formation of Prussian Blue analogue Gd(H2O)4[Fe(CN)6] nanoparticles with tailored shape (from nanocrosses to nanorods) and size, and further protection with a thin and homogeneous silica coating through hydrolysis and polymerization of silicate at neutral pH. The resulting Gd(H2O)4[Fe(CN)6]@SiO2 magnetic nanoparticles are very stable in biological fluids. Interestingly, this combination of Gd and Fe magnetic centers closely packed in the crystalline network promotes a magnetic synergistic effect, which results in significant improvement of longitudinal relaxivity with regards to soluble Gd3+ chelates, whilst keeping the high transversal relaxivity inherent to the iron component. As a consequence, this material shows excellent activity as MRI CA, improving positive and negative contrasts in T1- and T2-weighted MR images, both in in vitro (e.g., phantom) and in vivo (e.g., Sprague-Dawley rats) models. In addition, this hybrid shows a high biosafety profile and has strong ability to incorporate organic molecules on the surface with variable functionality, displaying great potential for further clinical application.

The database of prospective zeolites () has been screened in search of feasible zeolites with the condition of having at least one strong Brønsted site. Several criteria of zeolite feasibility have been tested using energetic and structural concepts, allowing a fast elimination of unsuitable candidates. Based on improved definitions to count and enumerate rings in zeolites, Brønsted acidity has been assessed in a fast albeit inaccurate way, by calculating a structural descriptor related to ammonia desorption energy. In each zeolite, the value of this descriptor was calculated for all the possible centres where a Brønsted acid site can be located. Ranking each zeolite through the value of the strongest candidate acid site allowed obtaining a selection of potentially strong acid zeolites. With further selection criteria, a final short list of 12 structures was obtained, where accurate calculations using periodic DFT indicate that 6 of them must contain a Brønsted site of very strong acidity.

Discrimination between different gases is an essential aspect for industrial and environmental applications involving sensing and separation. Several classes of porous materials have been used in this context, including zeolites and more recently MOFs. However, to reach high selectivities for the separation of gas mixtures is a challenging task that often requires the understanding of the specific interactions established between the porous framework and the gases. Here we propose an approach to obtain an enhanced selectivity based on the use of compartmentalized coordination polymers, named CCP-1 and CCP-2 , which are crystalline materials comprising isolated discrete cavities. These compartmentalized materials are excellent candidates for the selective separation of CO 2 from methane and nitrogen. A complete understanding of the sorption process is accomplished with the use of complementary experimental techniques including X-ray diffraction, adsorption studies, inelastic- and quasi-elastic neutron scattering, magnetic measurements and molecular dynamics calculations.

Rationale: Respiratory syncytial virus (RSV) is the most frequent cause of hospitalization and an important cause of death in infants in the developing world. The relative contribution of social, biologic, and clinical risk factors to RSV mortality in low-income regions is unclear., Objectives: To determine the burden and risk factors for mortality due to RSV in a low-income population of 84,840 infants., Methods: This was a prospective, population-based, cross-sectional, multicenter study conducted between 2011 and 2013. Hospitalizations and deaths due to severe lower respiratory tract illness (LRTI) were recorded during the RSV season. All-cause hospital deaths and community deaths were monitored. Risk factors for respiratory failure (RF) and mortality due to RSV were assessed using a hierarchical, logistic regression model., Measurements and Main Results: A total of 2,588 (65.5%) infants with severe LRTI were infected with RSV. A total of 157 infants (148 postneonatal) experienced RF or died with RSV. RSV LRTI accounted for 57% fatal LRTI tested for the virus. A diagnosis of sepsis (odds ratio [OR], 17.03; 95% confidence interval [CI], 13.14-21.16 for RF) (OR, 119.39; 95% CI, 50.98-273.34 for death) and pneumothorax (OR, 17.15; 95% CI, 13.07-21.01 for RF) (OR, 65.49; 95% CI, 28.90-139.17 for death) were the main determinants of poor outcomes., Conclusions: RSV was the most frequent cause of mortality in low-income postneonatal infants. RF and death due to RSV LRTI, almost exclusively associated with prematurity and cardiopulmonary diseases in industrialized countries, primarily affect term infants in a developing world environment. Poor outcomes at hospitals are frequent and associated with the cooccurrence of bacterial sepsis and clinically significant pneumothoraxes.

Two different organic cations (structure directing agents, SDAs) have been selected because of their ability to drive the synthesis of zeolites towards the same microporous material, RUB-13 (RTH), both being organophosphorous compounds. These P containing structure directing agents are characterized by a high concentration of positive charge on the phosphorus atom. Then, in the presence of fluoride anions used in these syntheses, a strong P(+)F(-) electrostatic contribution competes with the van der Waals short range SDAzeolite interaction that drives the zeolite formation. The rotation of the methyl groups present in the SDA is expected to be nearly free if van der Waals interactions dominate, but they will be hindered if the Coulombic P(+)F(-) term forces a closer approach to the SDA towards the zeolite framework. SDAs can be designed a priori to tune which interactions dominate. The rotational mobility of the SDAs, as well as certain related bending modes, has been well tackled by inelastic neutron scattering (INS) in order to test this hypothesis. The INS results provide valuable information for the design of specific SDAs for the synthesis of zeolites.

Through-bond triplet exciplex formation in donor-acceptor systems linked through a rigid bile acid scaffold has been demonstrated on the basis of kinetic evidence upon population of the triplet acceptors (naphthalene, or biphenyl) by through-bond triplet-triplet energy transfer from benzophenone.

The influence of non-covalent σ-π orbital interactions on triplet-triplet energy transfer (TTET) through tuning of the donor excitation energy remains basically unexplored. In the present work, we have investigated intermolecular TTET using donor moieties covalently linked to a rigid cholesterol (Ch) scaffold. For this purpose, diaryl ketones of π,π* electronic configuration tethered to α- or β-Ch were prepared from tiaprofenic acid (TPA) and suprofen (SUP). The obtained systems TPA-α-Ch, TPA-β-Ch, SUP-α-Ch and SUP-β-Ch were submitted to photophysical studies (laser flash photolysis and phosphorescence), in order to delineate the influence of steric shielding and σ-π orbital interactions on the rate of TTET to a series of energy acceptors. As a matter of fact, fine tuning of the donor triplet energy significantly modifies the rate constants of TTET in the absence of diffusion control. The experimental results are rationalized by means of theoretical calculations using first principles methods based on DFT as well as molecular dynamics.

Computational screening throughout a database containing ∼138 000 metal-organic frameworks (MOFs) has been performed to select candidate structures for hydrogen storage. A total of 231 structures (of which 79 contain paddle-wheel units) have been selected that meet the gravimetric and volumetric targets at 100 atm and 77 K. Grand Canonical Monte Carlo simulations have been performed to calculate the isotherms and select structures which meet the targets at 50 atm, and also to check the adsorption in the low pressure regime (1 atm). From this a reduced set of 18 structures has been analysed in more detail, regarding not only gravimetric and volumetric uptake but also pore size distribution and pore volume. A few structures with 3% gravimetric uptake at 1 atm and 77 K perform at the best level found so far.

The metal-organic framework MFU-4 shows preferential adsorption of CO2 over N2. This cannot be explained in terms of pore size only. Computational modelling suggests that the unique structure and flexibility of its small 8Cl-cube pore shows a unique gate-diffusion behaviour with different responses to CO2 and N2.

The combination of different experimental techniques, such as solid 13 C and 1 H magic-angle spinning NMR spectroscopy, fluorescence spectroscopy and powder X-ray diffraction, together with theoretical calculations allows the determination of the unique structure directing the role of the bulky aromatic proton sponge 1,8- bis (dimethylamino)naphthalene (DMAN) towards the extra-large-pore ITQ-51 zeolite through supra-molecular assemblies of those organic molecules.