Abnormal CO2 and H2O Diffusion in CALF-20(Zn) Metal-Organic Framework Angstropores

Carbon mitigation is one challenging issue that the world is facing. To tackle deleterious impacts of CO2, processes emerged, including chemisorption from amine based solvents, and more recently physisorption in porous solids. While CO2 capture from amine is more mature, this process is corrosive and detrimental for environment. Physisorption in Metal-Organic Frameworks (MOFs) is currently attracting a considerable attention, however the selection of the optimum sorbent is still challenging. While CO2 adsorption by MOFs have been widely explored from a thermodynamics standpoint, dynamical aspects remain less explored. CALF-20(Zn) MOF was recently proposed as a promising alternative to the commercially used CO2 13X zeolite sorbents, however, in-depth understanding of microscopic mechanisms originating its good performance still have to be achieved. In this report, we deliver a microscopic insight of CO2 and H2O in CALF-20(Zn) by atomistic simulations. CALF-20(Zn) revealed to exhibit unconventional guest-host behaviors that give rise to abnormal thermodynamic and diffusion. The hydrophobic nature of the solid leads to a low water adsorption enthalpy at low loading followed by a gradual increase, driven by strong water hydrogen bonds, found to arrange as quasi 1D water wires in MOF porosity, recalling water behavior in carbon nanotubes and aquaporins. While no super-diffusion found, this behavior was shown to impact diffusion along with guests loading, with a minimum correlated with inflection point of adsorption isotherm corresponding to wires formation. Interestingly, diffusion of both CO2 and H2O were also found to be of the same order of magnitude with similar non-linear behaviors.Comment: 15 pages, 8 figure

Thermodynamic insight in the high-pressure behavior of UiO-66: effect of linker defects and linker expansion

In this Article, we present a molecular-level understanding of the experimentally observed loss of crystallinity in UiO-66-type metal organic frameworks, including the pristine UiO-66 to-68 as well as defect-containing UiO-66 materials, under the influence of external pressure. This goal is achieved by constructing pressure-versus-volume profiles at finite temperatures using a thermodynamic approach relying on ab initio derived force fields. On the atomic level, the phenomenon is reflected in a sudden drop in the number of symmetry operators for the crystallographic unit cell because of the disordered displacement of the organic linkers with respect to the inorganic bricks. For the defect-containing samples, a reduced mechanical stability is observed, however, critically depending on the distribution of these defects throughout the material, hence demonstrating the importance of judiciously characterizing defects in these materials

Ischemic Stroke of the Artery of Percheron with Normal Initial MRI: A Case Report

The artery of Percheron is a solitary trunk representing an uncommon anatomic variant that provides bilateral arterial supply to the paramedian thalami and the rostral midbrain. Occlusion of this artery results in bilateral thalamic and mesencephalic infarctions. The clinical diagnosis is difficult because the complex anatomy causes large clinical variability. We report a case of a comatose patient with normal early head-computed tomography and magnetic resonance imaging. A bilateral paramedian thalamic infarct due to an occlusion of the artery of Percheron was revealed two days later by a new head computed tomography. To our knowledge, this is the first report in the literature of a symptomatic patient presenting an acute Percheron stroke with normal early brain magnetic resonance imaging. Our case indicates that a normal initial magnetic resonance imaging cannot formally eliminate the diagnosis of acute stroke of the artery of Percheron. We discuss the causes of noncontributive brain magnetic resonance imaging at the onset of this acute Percheron stroke and the alternative diagnosis and therapy methods

The flexibility of modified-linker MIL-53 materials

The flexibility of eight aluminium hydroxo terephthalates [Al(OH)(BDC–X)]·n(guest) (BDC = 1,4-benzene-dicarboxylate; X = –H, –CH3, –Cl, –Br, –NH2, –NO2, –(OH)2, –CO2H) crystallising in the MIL-53-type structure was investigated upon thermal dehydration of as-made samples, superhydration and methanol adsorption/desorption using in situ powder X-ray diffraction (PXRD). Profile fitting was used to determine lattice parameters as a function of time and/or temperature to describe their structural evolution. It has thus been shown that while methanol vapour adsorption induces an opening of all the modified frameworks, except the –NH2 material, superhydration only leads to open structures for Al-MIL-53–NO2, –Br and –(OH)2. All the MIL-53 solids, except Al-MIL-53–(OH)2 are present in the open structures upon thermal dehydration. In addition to the exploration of the breathing behavior of this MIL-53 series, the issue of disorder in the distribution of the functional groups between the organic linkers was explored. As a typical illustration, density functional theory calculations were carried out on different structures of Al-MIL-53–Cl, in which the distribution of –Cl within two adjacent BDC linkers is varied. The results show that the most energetically stable configuration leads to the best agreement with the experimental PXRD pattern. This observation supports that the distribution of the selected linker substituent in the functionalised solid is governed by energetics and that there is a preference for an ordering of this arrangement

Is V̇O2peak a Valid Estimation of V̇O2max in Swimmers with Physical Impairments?

Peak and maximal oxygen uptake ([Formula: see text] and [Formula: see text], respectively) are used in assessing aerobic power. For swimmers with physical impairments, it is unclear whether the physiological variables obtained in 200-m and Nx200-m tests are similar. The objective of this study is to assess the validity of [Formula: see text] as an estimator of [Formula: see text] and complementary physiological variables, in particular, carbon dioxide production ([Formula: see text]), respiratory exchange ratio (RER), minute-ventilation ([Formula: see text] and absolute (HR) and relative (%HRmax) heart rates-which were obtained in a time trial test (200-m) and an incremental intermittent test (Nx200-m) performed by swimmers with physical impairments. Methods: Eleven well-trained swimmers with physical impairments performed 200-m all-out and Nx200-m from low to all-out (controlled by a visual pacer), both with a respiratory valve system and a portable gas analyzer. Results: A paired Student's t-test showed no statistical difference (p > .05) for all comparisons. The intraclass correlation coefficient (ICC) was 0.97 and 0.98 for [Formula: see text] in l/min and ml/kg/min, respectively; ICC = 0.75 to 0.9 for [Formula: see text] (l/min and ml/kg/min),[Formula: see text] (in l/min) and HR (beats/min); ICC = 0.5 and 0.75 for %HRmax; and ICC < 0.5 for RER. Passing-Bablok regression showed that the dispersions were acceptable, considering the proportionality, except for HR and %HRmax. Bland-Altman method showed a high level of agreement for all variables. Conclusions: The [Formula: see text] and [Formula: see text], as well as the physiological variables [Formula: see text] and HR obtained, respectively, by 200-m and Nx200-m tests in swimmers with physical impairment were not different.The study was approved by the local ethics committee (number 2.274.037) and was performed in accordance with the Declaration of Helsinki.info:eu-repo/semantics/publishedVersio

Machine Learning Potential for Modelling H2_2 Adsorption/Diffusion in MOF with Open Metal Sites

Metal-organic frameworks (MOFs) incorporating open metal sites (OMS) have been identified as promising sorbents for many societally relevant-adsorption applications including CO$_2$ capture, natural gas purification and H$_2$ storage. It is critical to derive generic interatomic potential to achieve accurate and effective evaluation of MOFs for H$_2$ adsorption. On this path, as a proof-of-concept, the Al-soc-MOF containing Al-OMS, previously envisaged as a potential candidate for H$_2$ adsorption, was selected and a machine learning potential (MLP) was derived from a dataset initially generated by ab-initio molecular dynamics (AIMD) simulations. This MLP was further implemented in MD simulations to explore the binding modes of H$_2$ as well as its temperature dependence distribution in the MOFs pores from 10K to 90K. MLP-Grand Canonical Monte Carlo (GCMC) simulations were further performed to predict the H$_2$ sorption isotherm of Al-soc-MOF at 77K that was further confirmed by gravimetric sorption measurements. As a further step, MLP-based MD simulations were conducted to anticipate the kinetics of H$_2$ in this MOF. This work delivers the first MLP able to describe accurately the interactions between the challenging H$_2$ guest molecule and MOFs containing OMS. This innovative strategy applied to one of the most complex molecules owing to its highly polarizable nature alongside its quantum-mechanical effects that are only accurately described by quantum calculations, paves the way towards a more systematic accurate and efficient in silico assessment of the MOFs containing OMS for H$_2$ adsorption and beyond to the low-pressure capture/sensing of diverse molecules.Comment: 11 pages, 4 figure

Hipertermia magnética local intracelular para terapia del cáncer

Estudio de la viabilidad del uso de ciertos tipos de nanopartículas magnéticas para producir un fenómeno de hipertermia suficientemente potente como para ser empleado en futuras aplicaciones médicas.<br /