Structural, Magnetic, Magnetocaloric, and Magnetostrictive Properties of Pb_1-xSr_xMnBO₄(x = 0, 0.5, and 1.0)

The solid solution Pb1-xSrxMnBO4 is reported with an orthorhombic, Pnma, structure throughout; here studies on compounds with x = 0, 0.5 and 1 are described. The structure contains chains of MnO6 octahedra that exhibit intra-chain ferromagnetic (FM) order at low temperatures. Neutron powder diffraction (NPD) reveals dominant FM order in PbMnBO4 (Tc = 30 K), whereas SrMnBO4 is primarily antiferromagnetic (AFM) with TN = 16 K; the difference is related to the link between the chains that involves the BO3 groups. PbMnBO4 has its moment along a but also has a previously unreported AFM contribution along c (magnetic space group Pnm'a'), whereas SrMnBO4 has its moment along a but also a FM canting along c (magnetic space group Pn'm'a). The end members show distinct magnetostriction at Tc/TN which correlates with the different magnetic exchange in these compounds. NPD in variable applied magnetic field shows that SrMnBO4 is converted to fully FM at 8 T. The behavior above the magnetic ordering temperature is consistent with short-range FM correlations within the chains, which is particularly apparent in PbMnBO4. The magnetocaloric effect (MCE) has been measured and compared with those previously reported for the mineral gaudefroyite. PbMnBO4 has excellent MCE behavior, especially near Tc, 30 K. The strong FM exchange within the chains and FM correlations above Tc are vital for the MC properties

Meta-model based optimization of a large diameter semi-radial conical hub engine cooling fan

Une chaine de conception numérique basée sur une méthode de sensibilité à l’ordre deux a été utilisée pour conduire une optimisation sur une turbomachine, selon un cahier des charges multi-objectifs et dans un environnement sous contraintes. Les premières étapes décrites ont démarrée à partir d’un premier dessin de roue obtenue par l’utilisation des théories classiques de dimensions et de corrélations empiriques, et ont consisté à mettre en place une chaine de simulation numérique utilisant des techniques de morphing de maillage. Ce procédé utilise la méthode des fonctions de base radiale (RBF) et permet la construction à moindre coût d’une base de données géométrique. Les variations sont issues des paramètres aérodynamiques et géométriques sélectionnés à l’issue de l’analyse de l’écoulement sur la géométrie initiale. A l’issue de ce travail, une seconde base de données aérodynamique est construite en calculant en fonction des paramètres les dérivées objectifs jusqu’à l’ordre 2, ce qui permet d’obtenir les dérivées premières, secondes et croisées. Le processus d’enchainement automatisé des simulations autorise la construction rapide de surfaces de réponse indiquant le niveau d’incertitude et la probabilité d’amélioration des objectifs en chaque point. Les bases de données sont ensuite exploitées par un optimiseur basé sur les algorithmes génétiques, et les fronts de Pareto obtenus sont analysés à l'aide d'une technique de Self Organisation Map (SOM). Cette méthode est appliquée au cas d'un ventilateur destiné au refroidissement des moteurs thermiques et pour lequel on cherche à obtenir un faible couple et un haut rendement statique. Le dessin ainsi obtenu est en rupture complète avec les concepts classique et la solution sélectionnée démontre un rendement plus élevé que pour les solutions classiques

Quantifying entropy production in active fluctuations of the hair-cell bundle from time irreversibility and uncertainty relations

We introduce lower bounds for the rate of entropy production of an active stochastic process by quantifying the irreversibility of stochastic traces obtained from mesoscopic degrees of freedom. Our measures of irreversibility reveal signatures of time's arrow and provide bounds for entropy production even in the case of active fluctuations that have no drift. We apply these irreversibility measures to experimental recordings of spontaneous hair-bundle oscillations in mechanosensory hair cells from the ear of the bullfrog. By analyzing the fluctuations of only the tip position of hair bundles, we reveal irreversibility in active oscillations and estimate an associated rate of entropy production of at least similar to 3k (B)/s, on average. Applying thermodynamic uncertainty relations, we predict that measuring both the tip position of the hair bundle and the mechano-electrical transduction current that enters the hair cell leads to tighter lower bounds for the rate of entropy production, up to similar to 10(3) k (B)/s in the oscillatory regime

Unravelling exceptional acetylene and carbon dioxide adsorption within a tetra-amide functionalized metal-organic framework

Understanding the mechanism of gas-sorbent interactions is of fundamental importance for the design of improved gas storage materials. Here we report the binding domains of carbon dioxide and acetylene in a tetra-amide functionalized metal-organic framework, MFM-188, at crystallographic resolution. Although exhibiting moderate porosity, desolvated MFM-188a exhibits exceptionally high carbon dioxide and acetylene adsorption uptakes with the latter (232 cm3 g−1 at 295 K and 1 bar) being the highest value observed for porous solids under these conditions to the best of our knowledge. Neutron diffraction and inelastic neutron scattering studies enable the direct observation of the role of amide groups in substrate binding, representing an example of probing gas-amide binding interactions by such experiments. This study reveals that the combination of polyamide groups, open metal sites, appropriate pore geometry and cooperative binding between guest molecules is responsible for the high uptakes of acetylene and carbon dioxide in MFM-188a

Exceptional capture of methane at low pressure by an iron‐based metal‐organic framework

The selective capture of methane (CH4) at low concentrations and its separation from N2 are extremely challenging owing to the weak host-guest interactions between CH4 molecules and any sorbent material. Here, we report the exceptional adsorption of CH4 at low pressure and efficient separation of CH4/N2 by MFM-300(Fe). MFM-300(Fe) shows a very high uptake for CH4 of 0.85 mmol g−1 at 1 mbar and 298 K and a record CH4/N2 selectivity of 45 for porous solids, representing a new benchmark for CH4 capture and CH4/N2 separation. The excellent separation of CH4/N2 by MFM-300(Fe) has been confirmed by dynamic breakthrough experiments. In situ neutron powder diffraction, and solid-state nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modelling, reveal a unique and strong binding of CH4 molecules involving Fe-OH···CH4 and C···phenyl ring interactions within the pores of MFM-300(Fe), thus promoting the exceptional adsorption of CH4 at low pressure

Amides do not always work: observation of guest binding in an amide-functionalised porous host

An amide-functionalised metal organic frame-work (MOF) material, MFM-136, shows a high CO2 uptake of 12.6 mmol g-1 at 20 bar and 298 K. MFM-136 is the first example of acylamide pyrimidyl isophthalate MOF without open metal sites, and thus provides a unique platform to study guest bind-ing, particularly the role of free amides. Neutron diffraction reveals that, surprisingly, there is no direct binding between the adsorbed CO2/CH4 molecules and the pendant amide group in the pore. This observation has been confirmed un-ambiguously by inelastic neutron spectroscopy. This suggests that introduction of functional groups solely may not neces-sarily induce specific guest-host binding in porous materials, but it is a combination of pore size, geometry, and functional group that leads to enhanced gas adsorption properties

Influence of IFNL3/4 polymorphisms on the incidence of cytomegalovirus infection after solid-organ transplantation

Background. Polymorphisms in the interferon-λ (IFNL) 3/4 region have been associated with reduced hepatitis C virus clearance. We explored the role of such polymorphisms on the incidence of CMV infection in solid-organ transplant (SOT) recipients. Methods. Caucasian patients participating in the Swiss Transplant Cohort Study in 2008-2011 were included. A novel functional TT/-G polymorphism (rs368234815) in the CpG region upstream of IFNL3 was investigated. Results. A total of 840 SOT recipients at risk for CMV were included, among whom 373 (44%) received antiviral prophylaxis. The 12-months cumulative incidence of CMV replication and disease were 0.44 and 0.08, respectively. Patient homozygous for the minor rs368234815 allele (-G/-G) tended to have a higher cumulative incidence of CMV replication (SHR=1.30 [95%CI 0.97-1.74], P=0.07) compared to other patients (TT/TT or TT/-G). The association was significant among patients followed by a preemptive approach (SHR=1.46 [1.01-2.12], P=0.047), especially in patients receiving an organ from a seropositive donor (D+, SHR=1.92 [95%CI 1.30-2.85], P=0.001), but not among those who received antiviral prophylaxis (SHR=1.13 [95%CI 0.70-1.83], P=0.6). These associations remained significant in multivariate competing risk regression models. Conclusions. Polymorphisms in the IFNL3/4 region influence susceptibility to CMV replication in SOT recipients, particularly in patients not receiving antiviral prophylaxi

Observation of Binding and Rotation of Methane and Hydrogen within a Functional Metal-Organic Framework

The key requirement for a portable store of natural gas is to maximize the amount of gas within the smallest possible space. The packing of methane (CH₄) in a given storage medium at the highest possible density is, therefore, a highly desirable but challenging target. We report a microporous hydroxyl-decorated material, MFM-300­(In) (MFM = Manchester Framework Material, replacing the NOTT designation), which displays a high volumetric uptake of 202 v/v at 298 K and 35 bar for CH₄ and 488 v/v at 77 K and 20 bar for H₂. Direct observation and quantification of the location, binding, and rotational modes of adsorbed CH₄ and H₂ molecules within this host have been achieved, using neutron diffraction and inelastic neutron scattering experiments, coupled with density functional theory (DFT) modeling. These complementary techniques reveal a very efficient packing of H₂ and CH₄ molecules within MFM-300­(In), reminiscent of the condensed gas in pure component crystalline solids. We also report here, for the first time, the experimental observation of a direct binding interaction between adsorbed CH₄ molecules and the hydroxyl groups within the pore of a material. This is different from the arrangement found in CH₄/water clathrates, the CH₄ store of nature