Great Structural Flexibility Research Articles

Analyzing the Impact of Wing Flexural Axis Position on the Dynamics of a Very Flexible Airplane Using Strain-based Formulation

New technologies and the needs of specific missions have allowed and stimulated the development of airplanes with great structural flexibility. In these vehicles, there is a significant coupling between aeroelastic phenomena and flight dynamics. This has been a topic of research in recent years. Different methodologies have been studied to model the complete dynamics of flexible aircraft. One of these is the NFNS_s methodology (Non linear flight dynamics, non linear structural dynamics, strain based formulation). This article presents the use of this methodology in the analysis of the aeroelastic response and flight dynamics of a transport category aircraft with high structural flexibility. The effects of the wing elastic axis and the flexural axis positions were analyzed. Trimming, calculus of eigenvalues and time-marching simulations were carried out and the results were analyzed in detail. Some results were compared with those published in the literature. Similar trends were observed. This served as a qualitative validation of the methodology used. Some limitations of the study are described. The contributions of this work lie in the use of the NFNS_s methodology to analyze the effects of the elastic and flexural axis positions. In addition, the results of time marching simulations of the airplane modeled and the analysis carried out in great detail are other important novelty.

Triggered lattice-oxygen oxidation with active-site generation and self-termination of surface reconstruction during water oxidation.

To master the activation law and mechanism of surface lattice oxygen for the oxygen evolution reaction (OER) is critical for the development of efficient water electrolysis. Herein, we propose a strategy for triggering lattice-oxygen oxidation and enabling non-concerted proton-electron transfers during OER conditions by substituting Al in La0.3Sr0.7CoO3-δ. According to our experimental data and density functional theory calculations, the substitution of Al can have a dual effect of promoting surface reconstruction into active Co oxyhydroxides and activating deprotonation on the reconstructed oxyhydroxide, inducing negatively charged oxygen as an active site. This leads to a significant improvement in the OER activity. Additionally, Al dopants facilitate the preoxidation of active cobalt metal, which introduces great structural flexibility due to elevated O 2p levels. As OER progresses, the accumulation of oxygen vacancies and lattice-oxygen oxidation on the catalyst surface leads to the termination of Al3+ leaching, thereby preventing further reconstruction. We have demonstrated a promising approach to achieving tunable electrochemical reconstruction by optimizing the electronic structure and gained a fundamental understanding of the activation mechanism of surface oxygen sites.

Chiral 1D Hybrid Metal Halides with Piezoelectric Energy Harvesting and Sensing Properties

Chiral hybrid metal halides have been widely studied in the field of photondetectors, chiral optics, and spintronics due to their great structural flexibility and suitable bandgaps. Inspired by such great progress made in the abovementioned fields, continuous efforts need to be paid to seek other interesting applications for chiral hybrid metal halides. Herein, the synthesis of a pair of one‐dimensional enantiomorphic hybrid metal halide piezoelectrics, R/SMPCdCl4(R/SMP = R/S‐2‐methylpiperazine), and their applications in piezoelectric energy harvesting and sensing are reported. Density functional theory calculations show that these chiral piezoeletrics possess low elastic properties and high piezoelectric constants (16.71, 8.39, and 7.35 pC N−1). In addition, devices made of RMPCdCl4/PDMS (PDMS = polydimethylsiloxane) composite films are fabricated for piezoelectric energy harvesting and sensing. The piezoelectric energy harvesters with optimized content of 15 wt% RMPCdCl4/PDMS show not only excellent performance with an open‐circuit voltage of 2.57 V, short‐circuit current of 0.37 μA, and power density of 0.55 μW cm−2 but also outstanding stability of more than 3500 cycles. Meanwhile, these piezoelectric energy harvesters exhibit prominent sensing properties for detecting tapping, finger bending, walking, and running. It is demonstrated that chiral hybrid metal halides hold great potential in intelligent wearable and sensing devices.

Nanostructuring of Rare-earth-based Single-Molecule Magnets as Long-range Ordered Arrays in the Framework of Organic Metal Halide Perovskites.

The nanostructuring of single-molecule magnets (SMMs) on substrates, in nanotubes and periodic frameworks is highly desired for the future magnetic recording devices. However, the ability to organize SMMs into long-range ordered arrays in these systems is still lacking. Here, we report the incorporation of magnetic (RECl2 (H2 O)6 )+ (RE=rare earths) molecular groups into the framework of an organic metal halide perovskite (OMHP)-(H2 dabco)CsCl3 . Intriguingly, we show the incorporated rare-earth groups self-organized into long-range ordered arrays that uniformly and periodically distributed in the A sites of OMHP. The ordered (RECl2 (H2 O)6 )+ groups serve as SMMs in the perovskite frameworks, exhibiting large effective magnetic moment, moderate magnetic anisotropy and two-step relaxation behavior. With the additional merit of great structural flexibility and multifunction of OMHPs, the preparation of the first SMMs@OMHP magnetic materials furthers the development of molecular spintronics.

Nanostructuring of Rare‐earth‐based Single‐Molecule Magnets as Long‐range Ordered Arrays in the Framework of Organic Metal Halide Perovskites

AbstractThe nanostructuring of single‐molecule magnets (SMMs) on substrates, in nanotubes and periodic frameworks is highly desired for the future magnetic recording devices. However, the ability to organize SMMs into long‐range ordered arrays in these systems is still lacking. Here, we report the incorporation of magnetic (RECl2(H2O)6)+ (RE=rare earths) molecular groups into the framework of an organic metal halide perovskite (OMHP)—(H2dabco)CsCl3. Intriguingly, we show the incorporated rare‐earth groups self‐organized into long‐range ordered arrays that uniformly and periodically distributed in the A sites of OMHP. The ordered (RECl2(H2O)6)+ groups serve as SMMs in the perovskite frameworks, exhibiting large effective magnetic moment, moderate magnetic anisotropy and two‐step relaxation behavior. With the additional merit of great structural flexibility and multifunction of OMHPs, the preparation of the first SMMs@OMHP magnetic materials furthers the development of molecular spintronics.

Polar Photovoltaic Effect in Chiral Alternating Cations Intercalation‐Type Perovskites Driving Self‐Powered Ultraviolet Circularly Polarized Light Detection

AbstractChiral alternating cations intercalation‐type (ACI) perovskites, which are capable of great structural flexibility and a suitable quantum well barrier thickness that facilitates better charge transport, are urgently desired for circularly polarized light (CPL) detection. However, the chiral–polar photovoltaic effect (CPPE) in chiral ACI perovskites has never been reported although CPPE will provide great opportunities for future sustainable development. Here, by transmuting the organic ligands in 2D Ruddlesden–Popper‐type (RP) perovskites, two chiral–polar photovoltaic ACI perovskites (R/S‐PPA)EAPbCl4 (1R/1S) are successfully developed, which are stabilized by the alternating ordering of the short alkyl EA (EA = ethylammonium) and chiral aromatic PPA (PPA = 1‐phenylpropylamine) cations in the interlayer space. Particularly, converting chiral RP into ACI perovskites gives rise to a remarkable CPPE and suitable quantum well barrier thickness. These features contribute to the exploration of self‐powered ultraviolet CPL detection with an asymmetry factor up to 0.4, which reaches the highest value among the reported layered chiral perovskites. This is thought to be the first realization of CPPE in ACI perovskites, which paves the way for the application of chiral perovskites for self‐powered short‐wave ultraviolet CPL detection.

Coumarins Synthesis and Transformation via C–H Bond Activation—A Review

For several decades, coumarins have attracted considerable attention due to the fact of their application in diverse fields such as medical science and biomedical research as well as several industrial branches. Recently, many compounds containing the coumarin moiety have been intensively studied, mainly due to the fact of their biological activities such as antitumor, antioxidative, anti-HIV, vasorelaxant, antimicrobial, and anticancer. They are also widely used as fluorescent dyes and probes because of their great structural flexibility and large fluorescent quantum yields. For this reason, numerous attempts have been made to develop new and more practical methods for the synthesis of these compounds. This review aims at providing a comprehensive overview of coumarin synthesis methods by direct C–H bond activation in order to demonstrate the current state-of-the-art methods as well as the current limitations.

Uranotungstite, the only natural uranyl tungstate: Crystal structure revealed from 3D electron diffraction

Abstract Uranotungstite is an uranyl-tungstate mineral that was until recently only partially characterized with a formula originally given as (Fe2+,Ba,Pb)(UO2)2(WO4)(OH)4·12H2O and an unknown crystal structure. This mineral has been reinvestigated by electron microprobe analysis coupled with three-dimensional electron diffraction. According to the electron microprobe data, the holotype material from the Menzenschwand uranium deposit (Black Forest, Germany) has the empirical formula (Ba0.35Pb0.27)Σ0.62[(U6+O2)2(W0.986+☐0.75)O4.7(OH)2.5(H2O)1.75](H2O)1.67 (average of 8 points calculated on the basis of 2U apfu; H2O content derived from the structure). According to the precession-assisted 3D ED data, holotype uranotungstite from Menzenschwand is monoclinic, P21/m, with a = 6.318(5) Å, b = 7.388(9) Å, c = 13.71(4) Å, β = 99.04(13)°, and V = 632(2) Å3 (Z = 2). The structure refinement of the 3D ED data using the dynamical approach (Robs = 0.0846 for 3287 independent observed reflections) provided a structure model composed of heteropolyhedral sheets. A β-U3O8-type sheet of idealized composition [(UO2)2W6+Fe0.253+☐0.75O4.75(OH)1.5(H2O)1.75]0.25– is composed of UO7 polyhedra linked by (W,Fe)O5 polyhedra in which the W:Fe ratio is variable as well as the bulk occupancy of this site; the W site may also host a minor proportion of Cu, Mg, or V. In uranotungstite, the interlayer spaces between adjacent U-W-O sheets host water on one side and, on the other side, a partially occupied cation site mostly occupied by Ba and, to a lesser extent, Pb, as well as a partially occupied H2O site. This work is the first structural description of a natural uranyl-tungstate mineral and confirms the great structural and chemical flexibility of β-U3O8 type of sheets.

Perspective on the pressure-driven evolution of the lattice and electronic structure in perovskite and double perovskite

Perovskite ABO3 as one of the most common structures has demonstrated great structural flexibility and electronic applications. Evolving from perovskite, the typical double perovskite A2BB′O6 has two element species (B/B′), where the ordered arrangements of BO6 and B′O6 octahedron provide much more tunability. Especially, by applying external pressure, the energetic order between different phases in perovskite and double perovskite materials can be notably modified with more fascinating physical properties. However, it is still a challenge to propose a general model to explain and predict the high-pressure structures and properties of various perovskites and double perovskites due to their flexibility and complexity. In this perspective, we will discuss pressure effects on the crystalline structure and electronic configurations in some perovskites and double perovskites. We then focus on a prediction method for the evolution of the lattice and electronic structure for such materials with pressure. Finally, we will give a perspective on current challenges and opportunities for controlling and optimizing structural and electronic states of a given material for optimized functionalities.

Iron-facilitated dynamic active-site generation on spinel CoAl2O4 with self-termination of surface reconstruction for water oxidation

The development of efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) is critical for improving the efficiency of water electrolysis. Here, we report a strategy using Fe substitution to enable the inactive spinel CoAl2O4 to become highly active and superior to the benchmark IrO2. The Fe substitution is revealed to facilitate surface reconstruction into active Co oxyhydroxides under OER conditions. It also activates deprotonation on the reconstructed oxyhydroxide to induce negatively charged oxygen as an active site, thus significantly enhancing the OER activity of CoAl2O4. Furthermore, it promotes the pre-oxidation of Co and introduces great structural flexibility due to the uplift of the oxygen 2p levels. This results in the accumulation of surface oxygen vacancies along with lattice oxygen oxidation that terminates as Al3+ leaches, preventing further reconstruction. We showcase a promising way to achieve tunable electrochemical reconstruction by optimizing the electronic structure for low-cost and robust spinel oxide OER catalysts.

Nitroalkylation of α-Synuclein by Nitro-Oleic Acid: Implications for Parkinson's Disease.

α-Synuclein (α-syn) represents the main component of the amyloid aggregates present in Parkinson's disease and other neurodegenerative disorders, collectively named synucleinopathies. Although α-syn is considered a natively unfolded protein, it shows great structural flexibility which allows the protein to adopt highly rich beta-sheet structures like protofibrils, oligomers and fibrils. In addition, this protein can adopt alpha-helix rich structures when interacts with fatty acids or acidic phospholipid vesicle membranes. When analyzing the toxicity of α-syn, protein oligomers are thought to be the main neurotoxic species by mechanisms that involve modification of intracellular calcium levels, mitochondrial and lysosomal function. Extracellular fibrillar α-syn promotes intracellular protein aggregation and shows many toxic effects as well. Nitro-fatty acids (nitroalkenes) represent novel pleiotropic anti-inflammatory signaling mediators that could interact with α-syn to exert unraveling actions. Herein, we demonstrated that nitro-oleic acid (NO2-OA) nitroalkylate α-syn, forming a covalent adduct at histidine-50. The nitroalkylated-α-syn exhibited strong affinity for phospholipid vesicles, moving the protein to the membrane compartment independent of composition of the membrane phospholipids. Moreover, NO2-OA-modified α-syn showed a reduced capacity to induce α-syn fibrillization compared to the non-nitrated oleic acid. From this data we hypothesize that nitroalkenes, in particular NO2-OA, may inhibit α-syn fibril formation exerting protective actions in Parkinson's disease.

Formation of Micron-Sized Nickel Cobalt Sulfide Solid Spheres with High Tap Density for Enhancing Pseudocapacitive Properties

The synthesis of nickel cobalt sulfide is well-established because of its good electrical conductivity and great structural flexibility with low cost. It is extremely challenging to fabricate a unique structure with high tap density to improve its volumetric energy density and practical application. Here, we report a simple one-step hydrothermal method to synthesize micron-sized Ni–Co mixed sulfide solid spheres (1–2 μm in diameter). Because of the high tap density of more than 1.0 g cm–3 and the unique structure, the Ni–Co mixed sulfides demonstrate exceptional energy-storage performance. When acting as an electrode material for supercapacitors, these Ni–Co solid spheres can deliver a specific capacitance of 1492 F g–1 at a current density of 1.0 A g–1, and a retention of 76% at 10 A g–1 after 10 000 cycles. An asymmetric supercapacitor based on these solid spheres exhibits a high energy density of 48.4 W h kg–1 at a power density of 371.2 W kg–1 with excellent long-term cycling performance (91% retentio...

Giant Bulk Photovoltaic Effect in Vinylene-Linked Hybrid Heterocyclic Polymer

The bulk photovoltaic effect refers to the generation of a steady photocurrent from a homogeneous noncentrosymmetric material. It offers an alternative to the traditional p–n junction-based photovoltaic mechanism to directly convert sunlight to electricity. In this work, we investigate the bulk photovoltaic effect in low-dimensional polar organic materials with first-principles density functional theory calculations and shift current theory. With a strategy designed to break the inversion symmetry along the polymer chain, we demonstrate that conjugated vinylene-linked hybrid heterocyclic polymers can produce a strong bulk photovoltaic response to light, outperforming benchmark inorganic materials. The high current density results from the delocalized wave functions, composed mainly of carbon p orbitals. The great structural and electronic flexibility of polymers offers a robust paradigm to enhance the shift current response through chemical and physical modifications. The development of polymer blends wit...

Performance monitoring of large-scale autonomously healed concrete beams under four-point bending through multiple non-destructive testing methods

Concrete is still the leading structural material due to its low production cost and great structural design flexibility. Although it is distinguished by such a high durability and compressive strength, it is vulnerable in a series of ambient and operational degradation factors which all too frequently result in crack formation that can adversely affect its mechanical performance. The autonomous healing system, using encapsulated polyurethane-based, expansive, healing agent embedded in concrete, is triggered by the crack formation and propagation and promises material repair and operational service life extension. As shown in our previous studies, the formed cracks on small-scale concrete beams are sealed and repaired by filling them with the healing agent. In the present study, the crack formation and propagation in autonomously healed, large-scale concrete beams are thoroughly monitored through a combination of non-destructive testing (NDT) methods. The ultrasonic pulse velocity (UPV), using embedded low-cost and aggregate-size piezoelectric transducers, the acoustic emission (AE) and the digital image correlation (DIC) are the NDT methods which are comprehensively used. The integrated ultrasonic, acoustic and optical monitoring system introduces an experimental configuration that detects and locates the four-point bending mode fracture on large-scale concrete beams, detects the healing activation process and evaluates the subsequent concrete repair.

Control geométrico del tramo atirantado del Puente de la Constitución de 1812 sobre la Bahía de Cádiz

Geometric control of bridges erected using the balanced cantilever method is always complex. In this case, this has been compounded by the great structural flexibility, weight, and dimensions of the erected segments and the cable-stayed cross-section scheme.These uncertainties, added to the process of obtaining the geometry of the tower and deck, can be fully adjusted if an exhaustive control of all bridge elements is performed throughout the entire construction sequence.The rationale was based on the detailed prior segment assembling in the dockyard, and its positioning using an angle relative to the previously erected deck, establishing some adjustments to eliminate the calculated deviations. A special procedure was established for the geometric control of the joints between different decks in order to adjust precisions to welding tolerances.

The First Residue of the PWWP Motif Modulates HATH Domain Binding, Stability, and Protein-Protein Interaction.

Hepatoma-derived growth factor (hHDGF) and HDGF-related proteins (HRPs) contain conserved N-terminal HATH domains with a characteristic structural motif, namely the PWWP motif. The HATH domain has attracted attention because of its ability to bind with heparin/heparan sulfate, DNA, and methylated histone peptide. Depending on the sequence of the PWWP motif, HRP HATHs are classified into P-type (Pro-His-Trp-Pro) and A-type (Ala-His-Trp-Pro) forms. A-type HATH is highly unstable and tends to precipitate in solution. We replaced the Pro residue in P-type HATHHDGF with Ala and evaluated the influence on structure, dynamics, and ligand binding. Nuclear magnetic resonance (NMR) hydrogen/deuterium exchange and circular dichroism (CD) measurements revealed reduced stability. Analysis of NMR backbone (15)N relaxations (R1, R2, and nuclear Overhauser effect) revealed additional backbone dynamics in the interface between the β-barrel and the C-terminal helix bundle. The β1-β2 loop, where the AHWP sequence is located, has great structural flexibility, which aids HATH-HATH interaction through the loop. A-type HATH, therefore, shows a stronger tendency to aggregate when binding with heparin and DNA oligomers. This study defines the role of the first residue of the PWWP motif in modulating HATH domain stability and oligomer formation in binding.

Au₂₄(SAdm)₁₆ nanomolecules: X-ray crystal structure, theoretical analysis, adaptability of adamantane ligands to form Au₂₃(SAdm)₁₆ and Au₂₅(SAdm)₁₆, and its relation to Au₂₅(SR)₁₈.

Here we present the crystal structure, experimental and theoretical characterization of a Au24(SAdm)16 nanomolecule. The composition was verified by X-ray crystallography and mass spectrometry, and its optical and electronic properties were investigated via experiments and first-principles calculations. Most importantly, the focus of this work is to demonstrate how the use of bulky thiolate ligands, such as adamantanethiol, versus the commonly studied phenylethanethiolate ligands leads to a great structural flexibility, where the metal core changes its shape from five-fold to crystalline-like motifs and can adapt to the formation of Au(24±1)(SAdm)16, namely, Au23(SAdm)16, Au24(SAdm)16, and Au25(SAdm)16. The basis for the construction of a thermodynamic phase diagram of Au nanomolecules in terms of ligands and solvent features is also outlined.

Transition metal complexes with thiosemicarbazide-based ligands. Part 61. Comparative analysis of structural properties of the pyridoxal thiosemicarbazone ligands. Crystal structure of PLTSC·HCl·2H2O and its complex [Fe(PLTSC)Cl2(H2O)]Cl

A novel pyridoxal thiosemicarbazone (PLTSC) compound, exhibiting ligating properties, of the formula PLTSC·HCl·2H2O (1) was synthesized and characterized by X-ray analysis. The PLTSC ligand 1 displays significantly different conformation in comparison to the five previously reported compounds of this type. The structural properties of six PLTSC ligands in different conformations were compared in order to establish the structural differences and understand the factors that facilitate particular conformations. The analysis indicated great structural flexibility of the PLTSC ligands. The PLTSC ligand 1 is essentially a planar molecule with the r.m.s deviation of all non-H atoms equal to 0.06 A. Consequently, the molecules of 1 form a layered three-dimensional structure which is stabilized by a variety of hydrogen bonds: O–H⋯O, O–H⋯N, O–H⋯Cl, O–H⋯S, N–H⋯O, N–H⋯N, N–H⋯Cl, N–H⋯S. In addition, the crystal structure of the Fe(III) complex with the ligand 1 of the formula [Fe(PLTSC)Cl2(H2O)]Cl was resolved by single-crystal X-ray analysis and structural properties of this octahedral complex were discussed and compared to those of uncoordinated PLTSC ligand.

Conformational Transitions of Heat Shock Proteins: The Case of Hsp90

The most abundant cellular protein, Hsp90, partakes in many biological pathways, not only in times of induced stress, but also under normal physiological conditions. Its role in controlling proteostasis, by assisting in protein folding and reducing aggregation, together with its direct involvement in cancer cell survival and neurological disorders, makes this protein an attractive drug target. In solution, Hsp90 is a homodimer, with each subunit composed of three dynamically independent domains, contributing to the great structural flexibility and the ability to accommodate a large number of clients. Our molecular dynamic simulations of the E. coli homologue gave us a unique insight into observing the conformational transitions at atomic resolution. We observed dramatic structural rearrangements, independent of the initial state or the presence of nucleotides. The apo state was free to shift between the compact and fully stretched states, separated by a free energy barrier that was very close to the crystal open conformation. ATP binding stabilized the extended closed state, similar to the closed crystal state of HtpG. In the ADP-bound state the dynamics was limited to local motions in the N-terminal region, although the outward twisting of middle domains indicated the transitioning into an open state. Release of the nucleotides led to the formation of a compact conformation, guided by interactions between Asp287 and Asp292 from the middle domain and Lys103 from the N-terminal domain. The electrostatic interactions between opposite subunits appear to be key in directing the conformational change and making Hsp90 amenable to evolutionary fine-tuning that may regulate the populations of different conformations between homologues.

Controlling the Molecular Assembly of Polyoxometalates from the Nano to the Micron Scale: Molecules to Materials

AbstractPolyoxometalates (POMs) represent a class of metal‐oxide units based upon oxides of Mo, W, V, and Nb. Such cluster building blocks can also be subsequently self‐organized in complex 1D, 2D, and 3D frameworks leading to functional materials with diverse properties that span size ranges from 1 to 7 nm in terms of the size of the largest molecular units/clusters. However, since the cluster building blocks have great structural flexibility, the design of architectures is non‐trivial due to the sensitive dependence on reaction parameters such as pH, cation type, temperature, templating and linking units, ionic strength, redox agents. Therefore, the ability to control the aggregation or linking of the building blocks to give pre‐defined structure‐types as well as engineering the physical properties — for example, optical, electronic, catalytic activity/reactivity — is a tremendous challenge. In this review we survey our work from the control/design point of view and show how it is becoming possible to control the assembly of POM‐based architectures. We also describe the polyoxometalate‐based molecules‐to‐material transformations that can be seen as an osmotically driven crystal morphogenesis producing tubular architectures. This can be described as a new type of emergent phenomenon.