Local Structural Deformation Research Articles

Effect of yttrium-doping on the microstructures and semiconductor-metal phase transition characteristics of polycrystalline VO2 thin films

We investigate the effect of yttrium-doping on the microstructures and semiconductor-metal phase transition characteristics of polycrystalline VO2 thin films prepared by reactively co-sputtering process. XPS analyses indicate the existence of Y3+ in the Y-doped VO2 films, but Y-doping hardly influences the chemical states of V and O elements. X-ray diffraction patterns and Raman spectra reveal that both undoped and Y-doped VO2 thin films have a polycrystalline structure of monoclinic VO2. The introduction of Y greatly reduces the grain size of VO2 thin films as evidenced by scanning electron microscopy analyses. The relationship between the hysteresis width and doping level is not monotonic although the grain size is monotonically reduced with increasing the doping level. Y-doped VO2 films with optimal doping level (1.82at%) have a notably narrower hysteresis width (4.6°C) than undoped VO2 films (10.7°C). This is ascribed to increased heterogeneous nucleation centers due to Y in the VO2 lattice. With the further increase of doping level, the size effect gradually plays a prominent role in SMPT, and the hysteresis width of Y-doped VO2 films increases instead. The SMPT temperature of Y-doped VO2 films obviously decreases compared with undoped VO2 films due to reduced grain size and deformation of local structure around Y atom.

Deformation patterns in cross-sections of twisted bamboo-structured Au microwires

In order to investigate an almost pure extrinsic size effect we propose an experimental approach to investigate the deformation structure within single crystalline cross-sections of twisted bamboo-structured Au microwires. The cross-sections of individual 〈100〉 oriented grains of 25μm thick Au microwires have been characterized by Laue microdiffraction. The diffraction data were used to calculate the misorientation of each data point with respect to the neutral fiber in the center of the cross-section as well as the kernel average misorientation to map the global and local deformation structure as function of the imposed maximum plastic shear strain. The study is accompanied by crystal plasticity simulations which yield the equivalent plastic strain distributions in the cross-section of the wire. The global deformation structures are directly related to the activated slip systems, resulting from the real orientations of the investigated grains. When averaging the degree of deformation along ring segments, an almost continuous but non-linear increase of misorientation from the center toward the surface is observed, reflecting the overall strain gradient imposed by torsion. For the local deformation structure, pronounced and graded deformation traces are observed which often pass over the neutral fiber of the twisted wire and which are obviously reflecting domains of high geometrically necessary dislocations content.

Investigation of the Strong Brønsted Acidity in a Novel SAPO-type Molecular Sieve, DNL-6

By applying analysis of multiple solid-state MAS NMR spectra, the atomic coordination environment and acidity of a novel SAPO-type molecular sieve, DNL-6, are studied. 27Al MQ-MAS NMR and 31P27Al MQ-HETCOR NMR spectra reveal the existence of a SiAlSi region with Al(OSi)n (n = 14) species in the framework of DNL-6, explaining well the high concentration of single Si(OAl)4 species (3 mmol/g) accommodated in the sample. 13C MAS NMR of 2-13C-acetone adsorption indicates that there exist two kinds of strong Bronsted acid sites in DNL-6. One of them has similar strength as those in HZSM-5 and the other is even stronger, which is unusual in SAPO-type molecular sieves. Also, a discrepancy in Bronsted acid concentration between the theoretical and 1H NMR experimental results has been found, revealing the occurrence of a dehydoxylation process during the calcination. The origin of the extremely strong Bronsted acid sites in DNL-6 is investigated by density functional theory calculations, which suggest that the dehydroxylation process may lead to a local structure deformation and remarkably enhance the Bronsted acidity. More importantly, DNL-6 exhibits excellent catalytic activity in the synthesis of methylamines due to its stronger acidity.

Global hydroelastic model for springing and whipping based on a free-surface CFD code (OpenFOAM)

The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.

Spin dynamics and disorder effects in theS=12kagome Heisenberg spin-liquid phase of kapellasite

We report $^{35}\mathrm{Cl}$ NMR, ESR, $\ensuremath{\mu}\mathrm{SR}$, and specific-heat measurements on the $S=\frac{1}{2}$ frustrated kagome magnet kapellasite $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Cu}}_{3}{\text{Zn(OH)}}_{6}{\mathrm{Cl}}_{2}$, where a gapless spin-liquid phase is stabilized by a set of competing exchange interactions. Our measurements confirm the ferromagnetic character of the nearest-neighbor exchange interaction ${J}_{1}$ and give an energy scale for the competing interactions $|J|\ensuremath{\sim}10$ K. The study of the temperature-dependent ESR line shift reveals a moderate symmetric exchange anisotropy term $D$, with $|D/J|\ensuremath{\sim}3$%. These findings validate a posteriori the use of the ${J}_{1}\text{\ensuremath{-}}{J}_{2}\text{\ensuremath{-}}{J}_{d}$ Heisenberg model to describe the magnetic properties of kapellasite [Bernu et al., Phys. Rev. B 87, 155107 (2013)]. We further confirm that the main deviation from this model is the severe random depletion of the magnetic kagome lattice by 27%, due to Cu/Zn site mixing, and specifically address the effect of this disorder by $^{35}\mathrm{Cl}$ NMR, performed on an oriented polycrystalline sample. Surprisingly, while being very sensitive to local structural deformations, our NMR measurements demonstrate that the system remains homogeneous with a unique spin susceptibility at high temperature, despite a variety of magnetic environments. Unconventional spin dynamics is further revealed by NMR and $\ensuremath{\mu}\mathrm{SR}$ in the low-$T$, correlated, spin-liquid regime, where a broad distribution of spin-lattice relaxation times is observed. We ascribe this to the presence of local low-energy modes.

Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone–Ganga alluvial tract in Middle Ganga Plain, India

The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone–Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur–Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width–depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE–SW direction.

Influence of the Temperature on the Proton Transport in Poly(styrene-co-divinylbenzene) Membranes from Molecular Dynamics Simulations

The effect of the temperature on the properties of sulfonated poly(styrene-co-divinylbenzene), P(S-DVB), cation exchange membranes has been examined in the absence and presence of an external electric field of 0.7 V·nm–1. Results indicate that the temperature provokes local structural deformations around the sulfonate groups, which are manifested by the distortions at the C–S bonds (random and preferential in the absence and presence of the electric field, respectively). These distortions affect both the density and porosity of the membranes, even though the effects of the electric field decrease with increasing temperature. The electric field dominates over the thermal energy in the motion of the hydronium ions, while the external field does not affect the motion of water molecules, which follow a Brownian behavior similar to that observed for the two species in the absence of an electric field. The calculated electro-osmotic drag coefficient indicates that the hydronium flow is several times higher than the water flow in the presence of the electric field, and this effect increases the temperature. The diffusion of hydronium ions in the absence of the external field increases slowly and isotropically with the temperature, this behavior being preserved in the presence of the external electric field once the component associated with the drift velocity is discounted. Finally, the structure and dynamics of hydration shells at hydronium and sulfonate ions have been examined. Interestingly, the shells associated with two such ions as well as their response toward the temperature and electric field are significantly different, which has been attributed to the fact that sulfonate–water interactions are stronger than hydronium–water interactions.

An Approach to Structural Health Monitoring of Composite Structures Based on Embedded PZT Transducers

Abstract One approach to developing a system of continues automated monitoring of structural health is to use elastic waves excited in a given medium by a piezoelectric transducers network. Depending on their source and the geometry of the structure under consideration elastic waves can propagate over a significant distance. They are also sensitive to local structure discontinuities and deformations providing a tool for detecting local damage in large aerospace structures. This paper investigates the issue of Barely Visible Impact Damages (BVIDs) detection in composite materials. The model description and the results of impact tests verifying damage detection capabilities of the proposed signal characteristics are presented in the paper.

Damage Size Estimation of the Aircraft Structure with Use of Embedded Sensor Network Generating Elastic Waves

One of the approach to develop a system of continues, automated monitoring of the health of the structures is to use elastic waves excited in a given medium by piezoelectric transducers network. Elastic waves depending on their source and the geometry of the structure under consideration can propagate over significant distance. They are also sensitive to local structure discontinuities and deformations providing a tool to detect local damage of large aerospace structures. In the paper the issue of fatigue crack growth monitoring by means of elastic guided waves actuated by a sparse array of sensors will be presented. In particular we propose signal characteristics, robust enough to detect different kinds of damages: Barely Visible Impact Damages (BVIDs) in composite materials and fatigue cracks of metallic structures. The model description and the results of specimen tests verifying damage detection capabilities of the proposed signal characteristics are delivered in the paper. Some issues concerning the proposed damage indices and its application to damage detection and its monitoring are also discussed.

Discovery of an outcropping Mass Transport Deposit (MTD) in the Palaeogene subalpine synclines of southeastern France: Implications on flexural sub-basin deformation

We document the sedimentary facies of a large Mass Transport Deposit (MTD) within the sand-rich sediment gravity flow-dominated deposits of the Eocene–Oligocene south-western Alpine forelands (Annot Sandstone system). The MTD with an approximated volume of several hundreds of cubic kilometres fills a sub-basin located in the Mont-Tournairet confined sub-basin. Autochthonous facies are very typical sediment gravity-flow deposits (thin-bedded classical turbidites and thick-bedded hyperconcentrated to concentrated flow deposits) that stratigraphically belong to the Annot Sandstone infill. Slumps and internal metre-large fold axes of the deformed stratigraphic intervals indicate a main transport direction towards the northwest. The seafloor instability that led to the mass-flow events within the Mont-Tournairet sub-basin could have been favoured by high sedimentation rates in a small, confined and tectonically active sub-basin, possibly enhanced by local structural deformation associated with the Triassic evaporites on the eastern side of the Mont-Tournairet confined basin. The presence of the MTD suggests that a period of increased flexural subsidence rate and basin deformation occurred in this portion of the subalpine foreland basin. Therefore, the MTD forms a stratigraphic marker of a period of tectonic activity.

First-principles studies on infrared properties of semiconducting graphene monoxide

Graphene monoxide (GMO), a recently proposed 2D crystalline material in the graphene family, is attractive for next-generation nanoelectronics because of its predicted tunable band gap. As a guide to GMO experimental characterization, we calculate the vibrational properties and obtain three infrared active vibration modes (B1u, B2u, and B3u) and six Raman active modes (B1g, B2g, 2B3g, and 2Ag) for intrinsic GMO. The frequencies of the infrared active modes depend on both local structural deformations and interactions between adjacent GMO layers. These results are consistent with experimental observations and provide a means of estimating the number of layers in intrinsic GMO.

Conformation and dynamics of nucleotides in bulges and symmetric internal loops in duplex DNA studied by EPR and fluorescence spectroscopies

The dynamics and conformation of base bulges and internal loops in duplex DNA were studied using the bifunctional spectroscopic probe Ç, which becomes fluorescent (Çf) upon reduction of the nitroxide functional group, along with EPR and fluorescence spectroscopies. A one-base bulge was in a conformational equilibrium between looped-out and stacked states, the former favored at higher temperature and the latter at lower temperature. Stacking of bulge bases was favored in two- and three-base bulges, independent of temperature, resulting in DNA bending as evidenced by increased fluorescence of Çf. EPR spectra of Ç-labeled three-, four- and five-base symmetrical interior DNA bulges at 20°C showed low mobility, indicating that the spin-label was stacked within the loop. The spin-label mobility at 37°C increased as the loops became larger. A considerable variation in fluorescence between different loops was observed, as well as a temperature-dependence within constructs. Fluorescence unexpectedly increased as the size of the loop decreased at 2°C. Fluorescence of the smallest loops, where a single T·T mismatch was located between the stem region and the probe, was even larger than for the single strand, indicating a considerable local structural deformation of these loops from regular B-DNA. These results show the value of combining EPR and fluorescence spectroscopy to study non-helical regions of nucleic acids.

On the solubility of yttrium in RuO2

We have investigated the solubility of Y in rutile RuO2 using experimental and theoretical methods. Nanostructured Ru–Y–O thin films were synthesized via combinatorial reactive sputtering with an O/metal ratio of 2.6 and a Y content of 0.3 to 12.6 at. %. A solubility limit of 1.7 at. % was identified using x-ray photoelectron spectroscopy and x-ray diffraction. Based on ab initio and thermodynamic modeling, the solubility of Y can be understood. Smaller Y amounts are incorporated into the lattice, forming a metastable film, with local structural deformations due to size effects. As the Y content is increased, extensive local structural deformations are observed, but phase separation does not occur due to kinetic limitations. Nanostructured RuO2 alloyed with Y might lead to enhanced phonon scattering and quantum confinement effects, which in turn improve the thermoelectric efficiency.

Guidelines for the Design of Multiple-Use Explosion Containment Vessels Based on the Understanding of the Strain Growth Phenomenon

The strain growth phenomenon is an unsolved fundamental problem in the dynamic elastic response of containment vessels subjected to internal blast loading, which may seriously influence the design of multiple-use containment vessels. Because strain growth may cause increased local structural deformation in multiple-use containment vessels, it is important to consider this phenomenon when designing multiple-use containment vessels. In this paper, the mechanisms of strain growth, its influencing factors, and control methods are presented. Based on the understanding of the strain growth phenomenon, the guidelines and procedures for the design of multiple-use containment vessels are proposed. Employing the design guidelines, application examples are presented to demonstrate how to control strain growth in containment vessels. Because the strain growth phenomenon has not been considered in the design method or design code for multiple-use explosion containment vessels, understanding of the strain growth mechan...

Seismic Damage Detection of a Full-Scale Shaking Table Test Structure

A series of full-scale tests was conducted on the E-Defense shaking table facilities in Japan to simulate various levels of realistic seismic damage in a high-rise structural steel building. During the shaking table tests, the specimen experienced damage of the concrete slabs, beam-to-column connections, and nonstructural walls. The densely recorded test data of global and local structural deformation and the extensive acceleration records provide a unique benchmark case for evaluating the effectiveness of vibration-based damage diagnosis methods. Dynamic properties of the specimen were extracted from floor accelerations under the white noise excitations by the frequency response function curve-fitting method and autoregressive with exogenous term method. The natural frequencies of the structure decreased on average 4.1, 5.4, and 11.9% after three levels of seismic excitation, respectively, because of increasing extent of structural and nonstructural damage. The analysis of the vibration data shows that the mode shapes changed very little because the damage was distributed over the entire specimen rather than being concentrated on one floor or story for the high-rise moment frame building.

Site-Directed Spin-Labeling of Nucleic Acids by Click Chemistry: Detection of Abasic Sites in Duplex DNA by EPR Spectroscopy

This paper describes a spin label that can detect and identify local structural deformations in duplex DNA, in particular abasic sites. The spin label was incorporated into DNA by a new postsynthetic approach using click-chemistry on a solid support, which simplified both the synthesis and purification of the spin-labeled oligonucleotides. A nitroxide-functionalized azide, prepared by a short synthetic route, was reacted with an oligomer containing 5-ethynyl-2'-dU. The conjugation proceeded in quantitative yield and resulted in a fairly rigid linker between the modified nucleotide and the nitroxide spin label. The spin label was used to detect, for the first time, abasic sites in duplex DNA by X-band CW-EPR spectroscopy and give information about other structural deformations as well as local conformational changes in DNA. For example, reduced mobility of the spin label in a mismatched pair with T was consistent with the spin label displacing the T from the duplex. Addition of mercury(II) to this mispair resulted in a substantial increase in the motion of the spin label, consistent with formation of a metallopair between the T and the spin-labeled base that results in movement of the spin label out of the duplex and toward the solution. Thus, reposition of the spin label, when acting as a mercury(II)-controlled mechanical lever, can be readily detected by EPR spectroscopy. The ease of incorporation and properties of the new spin label make it attractive for EPR studies of nucleic acids and other macromolecules.

Non-invasive 3D analysis of local soil deformation under mechanical and hydraulic stresses by μCT and digital image correlation

Soil deformation is a perpetual process in the pedosphere where besides physicochemical stresses primarily alternating hydraulic and mechanical stresses continuously re-arrange the configuration of solid particles. In this study we present a local strain analysis and changes in soil structure resulting from hydraulic and mechanical stresses based on X-ray microtomography data. Digital image reconstructions were used to quantify local structural pore space characteristics and local soil deformation by 3D morphological and correlation analysis of grayscale tomograms. Swelling and shrinkage resulted in a complex heterogeneous soil structure which proofed to be very stable when mechanical loads were applied. The mechanism of soil deformation for both structure formation by internal hydraulic stresses and structure degradation by external mechanical stresses were in both cases controlled by pre-existing (micro)-structures. Especially during wetting such structures served as a nucleus for subsequent structure evolution. The results demonstrate the potential of more detailed non-invasive micromechanical analysis of soil deformation processes which could improve the conceptual understanding of the physical behavior of soil systems.

Effect of Ba incorporation on pressure-induced structural changes in the relaxor ferroelectricPbSc0.5Ta0.5O3

Pressure-induced structural changes in the canonical relaxor ${\text{Pb}}_{0.78}{\text{Ba}}_{0.22}{\text{Sc}}_{0.5}{\text{Ta}}_{0.5}{\text{O}}_{3}$ were studied with both in-house and synchrotron single-crystal x-ray diffraction as well as Raman spectroscopy at pressures up to 9.8 GPa. The results reveal that the substitution of Ba for Pb in $AB{\text{O}}_{3}$ perovskite-type structures, i.e., the substitution of a two-valent element with an isotropic electron shell for an isovalent element with a stereochemically active lone pair, leads to a ``diffuse pressure-induced phase transition,'' a structural transformation over a broad pressure range, without a well-defined critical pressure point. The smeared phase transition of the average structure results from the existence of local structural deformations in the vicinity of A-positioned Ba cations.

Contractional Structure Model of the Transition Belt between Kuche Depression and South Tianshan Uplift

The Cenozoic contractional deformation in the transitional belt between Kuche Depression and South Tianshan Uplift can be hardly deciphered by the typical “A-type” subduction model with the structural features like geological outcrop, seismic data, well-log, and CEMP (Continuous Electromagnetic Profile) data. This article advanced a “nonsubduction” contractional deformation model with “delaminate contraction and vertical stack”. The former, “delaminate contraction”, means that the basement and the cover, even multilevel cover, are of their own distinct contractional structural styles. The latter, “vertical stack”, means the strong deformation zones within various levels are stacked up vertically. No regional detachment fault developed. Detachment folds were developed in shallower cover, whereas fault system assembled with reverse fault, thrust, and inverse fault or normal fault developed in the lower cover and basement. The cover folds express structure pattern of a closed anticline combined with an opened syncline. The asymmetric anticline detached within salt rock of Eocene or coal strata of Jurassic and was cut off by a break thrust in the steep limb. A series of basement-involved thrust with high-angle dipping to South Tianshan Uplift dominate the contractional deformation in the basement. A miniscale imbricate wedge thrust system developed in the footwall of basement-involved thrust with high-angle dip and a faulted-anticline with basement-cored developed in the hang-wall. Most of the fault system in the lower level disappeared toward the salt rock of Eocene or coal strata of Jurassic. The high-angle basement-involved thrust tip in the core of detachment anticline is in the shallower level so that the salt rock of Eocene or coal strata of Jurassic might be an important transfer level. The high-angle basement-involved thrust could be an inverse fault utilizing the preexisting normal fault and leads to the local structure deformation, thus attributing to the dynamics of vertical shearing resulted from the uplift of Southern Tianshan mountains.

Ligand-induced global transitions in the catalytic domain of protein kinase A

Conformational transitions play a central role in the phosphorylation mechanisms of protein kinase. To understand the nature of these transitions, we investigated the dynamics of nucleotide binding to the catalytic domain of PKA, a prototype for the protein kinase enzyme family. The open-to-closed transition in PKA was constructed as a function of ATP association by using available X-ray data and Brownian dynamics. Analyzing the multiple kinetic trajectories at the residue level, we find that the spatial rearrangement of the residues around the nucleotide-binding pocket, along with suppressed local fluctuations, controls the compaction of the entire molecule. In addition, to accommodate the stresses induced by ATP binding at the early transition stage, partial unfoldings (cracking) and reformations of several native contacts occur at the interfaces between the secondary structure motifs enveloping the binding pocket. This suggests that the enzyme experiences local structural deformations while reaching its functional, ATP-bound state. Our dynamical view of the ligand-induced transitions in PKA suggests that the kinetic hierarchy of local and global dynamics, the variable fluctuation of residues and the necessity of partial local unfolding may be fundamental components in other large scale allosteric transitions.