Search results for "Frame"
showing 10 items of 1767 documents
Postsynthetic Approach for the Rational Design of Chiral Ferroelectric Metal–Organic Frameworks
2017
International audience; Ferroelectrics (FEs) are materials of paramount importance with a wide diversity of applications. Herein, we propose a postsynthetic methodology for the smart implementation of ferroelectricity in chiral metal−organic frameworks (MOFs): following a single-crystal to single-crystal cation metathesis, the Ca2+ counterions of a preformed chiral MOF of formula Ca6II{CuII24[(S,S)-hismox]12(OH2)3}·212H2O (1), where hismox is a chiral ligand derived from the natural amino acid l-histidine, are replaced by CH3NH3+. The resulting compound, (CH3NH3)12{CuII24[(S,S)-hismox]12(OH2)3}·178H2O (2), retains the polar space group of 1 and is ferroelectric below 260 K. These results op…
The dcuD (former yhcL ) gene product of Escherichia coli as a member of the DcuC family of C4-dicarboxylate carriers: lack of evident expression
1999
The dcuD gene (formerly yhcL) of Escherichia coli shows significant sequence similarity only to the dcuC gene of E. coli, which encodes a C4-dicarboxylate carrier (DcuC) that functions during anaerobic growth. Inactivation of dcuD had no effect on the growth of E. coli under a large number of conditions and led to no detectable changes in phenotype. Translational dcuD'-'lacZ gene fusions were not significantly expressed in the presence of dicarboxylates or monocarboxylates under oxic or anoxic conditions. Other potential substrates such as amino sugar derivatives, amino acids, and alpha-aspartyl dipeptides also did not lead to expression of dcuD. Changes in medium composition, pH, ionic str…
Investigation of Charge-Transfer Interactions Induced by Encapsulating Fullerene in a Mesoporous Tetrathiafulvalene-Based Metal-Organic Framework
2019
<p>The design of Metal-Organic Frameworks (MOFs) incorporating electroactive guest molecules in the pores has become a subject of great interest in order to install additional electrical functionalities within the framework while maintaining porosity. In this direction, understanding the charge-transfer (CT) process between the framework and the guest molecules is crucial towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C<sub>60</sub>) in a mesoporous tetrathiafulvalene(TTF)-based MOF. The CT process between the electron-acceptor C<sub>60 </sub>guest and the electron-donor TTF ligand is studied in detail by means…
Metal-organic frameworks-based catalysts for biomass valorization
2020
Abstract The objective of this chapter is to review the most promising metal-organic framework (MOF) catalysts in biomass valorization processes in the bulk and fine chemical industries. Either bulk metal-organic frameworks, encapsulated catalytic species in MOFs, or MOF-derived catalysts are revised in terms of activity, selectivity, and stability for biomass valorization applications. The work revised here is focused on the transformation of lignocellulose biomass through purely chemical pathways. In the first part of the chapter, the few studies of cellulose hydrolysis into monosaccharides reported are commented, since this crucial first step in the valorization of hemicellulose is expec…
Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal–Organic Framework
2013
We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal–organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: a nonporo…
Selective Gold Recovery and Catalysis in a Highly Flexible Methionine-Decorated Metal–Organic Framework
2016
A novel chiral 3D bioMOF exhibiting functional channels with thio-alkyl chains derived from the natural amino acid l-methionine (1) has been rationally prepared. The well-known strong affinity of gold for sulfur derivatives, together with the extremely high flexibility of the thioether "arms" decorating the channels, account for a selective capture of gold(III) and gold(I) salts in the presence of other metal cations typically found in electronic wastes. The X-ray single-crystal structures of the different gold adsorbates Au(III)@1 and Au(I)@1 suggest that the selective metal capture occurs in a metal ion recognition process somehow mimicking what happens in biological systems and protein r…
Bidirectional Chemo-Switching of Spin State in a Microporous Framework
2009
The ins and outs of spin: Using the microporous coordination polymer {Fe(pz)[Pt(CN)(4)]} (1, pz=pyrazine), incorporating spin-crossover subunits, two-directional magnetic chemo-switching is achieved at room temperature. In situ magnetic measurements following guest vapor injection show that most guest molecules transform 1 from the low-spin (LS) state to the high-spin (HS) state, whereas CS(2) uniquely causes the reverse HS-to-LS transition.
A methodological approach to exploring the rhythm of classroom discourse in a cumulative frame in science teaching
2014
The purpose of this study was to characterise the nature and purpose of different types of classroom discourse and to explore how the rhythm of classroom discourse provides a cumulative frame for the teaching of science. The overall data consisted of a teaching sequence of eight lessons on the moment of force as taught to physiotherapy students at a Finnish University of Applied Sciences. Our in-depth multiple timescale analysis of two episodes illustrated in this study shows examples how cumulation was instantiated by the different types of classroom discourse. The methodology and findings of this study have implications both for teacher education and further research. peerReviewed
The United Nations Framework Convention on Climate Change
2023
This document has been included as a part of the teaching materials funded by the UNESCO Chair of the University of Valencia, 2023. This paper dicusses about the United Nations Framework Convention on Climate Change
Sensory Processing Disorders in Children and Adolescents: Taking Stock of Assessment and Novel Therapeutic Tools
2022
Sensory processing disorders (SPDs) can be described as difficulty detecting, modulating, interpreting, and/or responding to sensory experiences. Because SPDs occur in many individuals with autism spectrum disorder and in other populations with neurodevelopmental disorders, it is important to distinguish between typical and atypical functioning in sensory processes and to identify early phenotypic markers for developing SPDs. This review considers different methods for diagnosing SPDs to outline a multidisciplinary approach useful for developing valid diagnostic measures. In particular, the advantages and limitations of the most commonly used tools in assessment of SPDs, such as caregiver r…