Twin Relationship Research Articles

Identification of a coherent twin relationship from high-resolution reciprocal-space maps.

Twinning is a common crystallographic phenomenon which is related to the formation and coexistence of several orientation variants of the same crystal structure. It may occur during symmetry-lowering phase transitions or during the crystal growth itself. Once formed, twin domains play an important role in defining physical properties: for example, they underpin the giant piezoelectric effect in ferroelectrics, superelasticity in ferroelastics and the shape-memory effect in martensitic alloys. Regrettably, there is still a lack of experimental methods for the characterization of twin domain patterns. Here, a theoretical framework and algorithm are presented for the recognition of ferroelastic domains, as well as the identification of the coherent twin relationship using high-resolution reciprocal-space mapping of X-ray diffraction intensity around split Bragg peaks. Specifically, the geometrical theory of twinned ferroelastic crystals [Fousek & Janovec (1969). J. Appl. Phys. 40, 135-142] is adapted for the analysis of the X-ray diffraction patterns. The necessary equations are derived and an algorithm is outlined for the calculation of the separation between the Bragg peaks, diffracted from possible coherent twin domains, connected to one another via a mismatch-free interface. It is demonstrated that such separation is always perpendicular to the planar interface between mechanically matched domains. For illustration purposes, the analysis is presented of the separation between the peaks diffracted from tetragonal and rhombohedral domains in the high-resolution reciprocal-space maps of BaTiO3 and PbZr1-xTixO3 crystals. The demonstrated method can be used to analyse the response of multi-domain patterns to external perturbations such as electric field, change of temperature or pressure.

Adolescent attachment to parents and peers in singletons and twins born with assisted and natural conception.

STUDY QUESTIONDoes adolescent attachment to parents and peers differ between singletons and twins born with ART or natural conception (NC)?SUMMARY ANSWERAdolescent attachment anxiety with the father was higher among NC singletons than among ART and NC twins, whereas attachment avoidance with the father was higher in ART singletons than in NC singletons and NC twins. No differences were found in attachment to the mother, best friend or romantic partner.WHAT IS KNOWN ALREADYMost studies have not found differences between ART and NC singletons in parent–adolescent relationships, but twin relationships may be more at risk. No previous study has examined all four groups in the same study, or specifically looked at attachment relationships.STUDY DESIGN, SIZE, DURATIONThis was an 18-year, prospective and controlled longitudinal study with families of 496 ART singletons, 101 ART twin pairs, 476 NC singletons and 22 NC twin pairs. Families were recruited during the second trimester of pregnancy; the ART group was recruited from five infertility clinics in Finland and the control group was recruited from a hospital outpatient clinic during a routine visit.PARTICIPANTS/MATERIALS, SETTING, METHODSMothers and fathers gave background information for this study during pregnancy, and during the child’s first year and early school age (7–8 years). For the ART group, infertility characteristics and prenatal medical information was also obtained from the patient registry of the infertility clinics. Children (originally 50% girls) filled in electronic questionnaires related to their attachment to mother, father, best friend and romantic partner (Experiences in Close Relationships—Relationship Structures) at 17–19 years of age.MAIN RESULTS AND THE ROLE OF CHANCEAdolescent attachment anxiety to father was higher in NC singletons than in ART twins, P = 0.004 and marginally higher than in NC twins, P = 0.06. Adolescent attachment avoidance to father was higher in ART singletons than in NC singletons, P = 0.006 and marginally higher than in NC twins, P = 0.055.LIMITATIONS, REASONS FOR CAUTIONThe sample size was small especially in the NC twin group and there was drop-out over the 18-year time period, especially among boys and families with lower parental education level. The study only included native Finnish-speaking families. The results could differ in a more diverse population. ART singletons were younger and had fewer siblings than ART twins and NC children, and ART and NC twins had more newborn health risks than ART and NC singletons.WIDER IMPLICATIONS OF THE FINDINGSThe study adds to a growing body of evidence that neither ART treatments nor being a twin places mother–child relationships or peer relationships at long-term risk. However, in our study, which was the first to examine both ART and twinhood simultaneously, we found that there may be more problems in father–adolescent relationships, but only in ART singletons and only related to attachment avoidance. Our findings suggest that men, as well as women, should receive enough support in pre- and peri-natal health care during and after infertility treatments.STUDY FUNDING/COMPETING INTEREST(S)This study was funded by Academy of Finland (grant number 2501308988), the Juho Vainio Foundation and the Finnish Cultural Foundation. The authors report no conflict of interest.TRIAL REGISTRATION NUMBERN/A.

Environmental Justice in Nigeria: Spotlight on Activism of Nongovernmental Organisations over Petroleum Development in the Oil-Rich Delta Region

Environmental justice (EJ) is a progressively advancing subject, social movement and practice, which requires fair treatment and meaningful involvement of all humans, regardless of sex, age, class, income, race, colour or nationality, in the development, management, implementation and enforcement of plans, policies, laws and regulatory practices, towards the protection and management of the environment in the course of socio-economic development programmes, including projects. It also requires equitable and thus indiscriminate exposure of all to environmental good and harm. It is an advancing social movement that advocates a healthy and eco-balanced environment, towards human wellbeing, sustainable communities and all-embracing sustainable development (SD) in the overall interest of society within our Planet (Mother Earth). EJ may thus be discussed within the rubrics of the twin relationship of the environment to development, in the ongoing effort of the UN to achieve SD around the world. Hence, this socio-legal study examines efforts of EJ Nongovernmental Organisations in the oil-rich ethnic minority Niger Delta region, towards greater wellbeing of the environment, humans and society at large in the region and beyond. The study makes a case for application of international benchmarked norms, guidelines, standards and practices on EJ beyond advanced countries, particularly to underprivileged areas of the developing world, such as the marginalized and neglected oil-rich ethnic minority communities of the Niger Delta region and other such deprived resource-rich areas of other developing countries.

KINSHIP AND POWER RELATIONSHIPS IN COON’S FLESH OF THE WILD OX AND THE RIFFIAN

This study explores two novels titled Flesh of the Wild Ox (1932) and The Riffian (1933) written by Carleton S. Coon about the Moroccan Rif. These roughly unexplored novels are by an ethnographer and derive from an ethnography titled Tribes of the Rif (1931). Indeed, they “boast” themes usually seen as ethnographic in nature: kinship, marriage, polygyny, honour and shame, magic, subsistence pattern and inter-tribal warfare. This study is set within the convergence of literature and ethnography, striving to foreground the ethnographicity within the novels. It brings kinship into focus, notably investigating how kinship works in relation to power. It distinguishes twin kin power relationships: intra-kin and inter-kin. Intra-kin power relationships are domestic, involving individuals of a single kin group while inter-kin power relationships are transdomestic, involving individuals of different descent groups or the groups themselves. In both relationships, kinship operates inclusively as the Riffian characters strive to expand the number of individuals and groupings who, in Schweitzer’s words, can be “made into relatives” (210). The Riffians use inclusive strategies, including polygyny, exogamy and shame compulsion, so they can extend kin ties to non-kin. Those kinship strategies validate the the elasticity of kin boundaries among the Riffians. 
 
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Elementary Composite Binary and Grain Alignment Locked in Dust Growth

Abstract Planets are known to grow out of a star-encircling disk of the gas and dust inherited from an interstellar cloud; their formation is thought to begin with coagulation of submicron dust grains into aggregates, the first foundational stage of planet formation. However, with nanoscale and submicron solids unobservable directly in the interstellar medium (ISM) and protoplanetary disks, how dust grains grow is unclear, as are the morphology and structure of interstellar grains and the whereabouts and form of “missing iron.” Here we show an elementary composite binary in 3D sub-10 nm detail—and the alignments of its two subunits and nanoinclusions and a population of elongated composite grains locked in a primitive cosmic dust particle—noninvasively uncovered with phase-contrast X-ray nanotomography. The binary comprises a pair of oblate, quasi-spheroidal grains whose alignment and shape meet the astrophysical constraints on polarizing interstellar grains. Each member of the pair contains a high-density core of octahedral nanocrystals whose twin relationship is consistent with the magnetite’s diagnostic property at low temperatures, with a mantle exhibiting nanoscale heterogeneities, rounded edges, and pitted surfaces. This elongated binary evidently formed from an axially aligned collision of the two similar composite grains whose core–mantle structure and density gradients are consistent with interstellar processes and astronomical evidence for differential depletion. Our findings suggest that the ISM is threaded with dust grains containing preferentially oriented iron-rich magnetic nanocrystals that hold answers to astronomical problems from dust evolution, grain alignment, and the structure of magnetic fields to planetesimal growth.

Dating martian mafic crust; microstructurally constrained baddeleyite geochronology of enriched shergottites Northwest Africa (NWA) 7257, NWA 8679 and Zagami

Baddeleyite (monoclinic; m-ZrO2) is a widespread accessory phase within shergottites. However, the effects of shock loading on baddeleyite U-Pb isotopic systematics, and therefore its reliability as a geochronometer within highly shocked lithologies, are less well constrained. To investigate the effects of shock metamorphism on baddeleyite U-Pb chronology, we have conducted high-resolution microstructural analysis and in-situ U-Pb isotopic measurements for baddeleyite within enriched basaltic shergottites Northwest Africa (NWA) 7257, NWA 8679 and Zagami. Electron backscatter diffraction (EBSD) analyses of baddeleyite reveal significant microstructural heterogeneity within individual thin sections, recording widespread partial to complete reversion from high-pressure (≥3.3 GPa) orthorhombic zirconia polymorphs. We define a continuum of baddeleyite microstructures into four groupings on the basis of microstructural characteristics, including rare grains that retain magmatic twin relationships. Uncorrected U-Pb isotopic measurements form Tera-Wasserburg discordia, yielding new 238U-206Pb discordia ages of 195 ± 15 Ma (n = 17) for NWA 7257 and 220 ± 23 Ma (n = 10) for NWA 8679. Critically, there is no resolvable link between baddeleyite microstructure and U-Pb isotope systematics, indicating negligible open-system behaviour of U-Pb during zirconia phase transformations. Instead, we confirm that high post-shock temperatures exert the greatest control on Pb mobility within shocked baddeleyite; in the absence of high post-shock temperatures, baddeleyite yield robust U-Pb isotope systematics and date the age of magmatic crystallization. Low bulk post-shock temperatures recorded within Zagami (≤220 °C), and suggested within NWA 7257 and NWA 8679 by baddeleyite microstructure and other petrological constraints, confirm that the previously derived baddeleyite age of Zagami records magmatic crystallization, and provide greater age diversity to 225 Ma to 160 Ma enriched shergottites. While our data yield no resolvable link between microstructure and U-Pb isotopic composition, we strongly recommend that microstructural analyses should represent an essential step of baddeleyite U-Pb chronology within planetary (e.g., martian, lunar, asteroidal) and shocked terrestrial samples, allowing full contextualisation prior to destructive isotopic techniques. Microstructurally constrained in-situ U-Pb analyses of baddeleyite thus define new opportunities for the absolute chronology of martian meteorites and, more broadly, shocked planetary materials.

Structural characterization and nanoscale strain field analysis of α/β interface layer of a near α titanium alloy

Abstract In this article, the structural and nanoscale strain field of the α/β phase interface layer in Ti80 alloy were studied by using high-resolution transmission electron microscopy (HRTEM) and geometric phase analysis (GPA). The α/β interface layer was observed in forged and different annealed Ti80 alloys, which is mainly composed of lamellar face-centered cubic (FCC) phase region and α′ + β region. The FCC phases between α and β phases show a twin relationship, and the twinning plane is ( 1 1 ¯ 1 ) (1\bar{1}1) . The orientation relationship of the β phase, the α phase, and the FCC phase is (110)β//(0001)α// ( 1 1 ¯ 1 ) (1\bar{1}1) FCC and [ 1 ¯ 11 \bar{1}11 ]β//[ 2 1 ¯ 1 ¯ 0 2\bar{1}\bar{1}0 ]α//[011]FCC. The nanoscale strain field of FCC + α and β + α′ regions was analyzed by using the GPA technology. The FCC + α region shows more significant strain gradient than the α′ + β region, and ε FCC > ε α, ε α′ > ε β. The influence of element addition on the formation mechanism of the FCC phase was discussed. The addition of Zr promotes the formation of the FCC phase by inducing lattice distortion and reducing the stacking fault energy of the α phase. In addition, the Al element forms an obvious concentration gradient around the interface layer during the cooling process of the alloy, which provides a driving force for the formation of the FCC phase.

Influence of High-pressure Quenching on the Microstructure, Martensite Transformation, and Mechanical Properties of 0.2 Mass% C Steel

Low-carbon steel (0.2 mass%) samples were austenitized and quenched at a cooling rate of 10°C/s under GPa level high pressure. The morphology, lattice constant, and order degree of C atom distribution of high-pressure quenching martensite were characterised and analyzed by TEM, EBSD, XRD, and Mössbauer. Besides, the transformation characteristics and strengthening mechanisms were discussed. The results show that the microstructure of 0.2 mass% C steel is fine hierarchical lath martensite with almost no residual austenite, and its laths mostly follow {112} <111> twin relationship, indicating the self-accommodation effect among martensite variants. Compared to atmospheric pressure, the order degree of carbon atom distribution increases in high-pressure quenched martensite, meanwhile the tetragonality (c/a) of martensite lattice increases from 1.009 at atmospheric pressure to 1.012 at 4 GPa. The significant promotion of hardness in 0.2 mass% C steel subjected to high-pressure treatment can be ascribed to a large number of dislocations in the structure, grain refinement strengthening caused by twin boundary, and solution strengthening caused by large distortion due to the increase of the order degree for C atom distribution and the decrease of lattice constant. These findings provide new insights into the carbon steel martensite transformation mechanism, and a new martensite transformation technique can be developed.

The Schumpeterian creative response: export and innovation: evidence for OECD countries 1995–2015

The Schumpeterian creative response provides an effective framework to understand the determinants of the twin and self-supporting loop relationship between export and innovation in the global economy. Exports spur the creative response and innovation efforts which lead to the introduction and adoption of technological innovations that increase labor productivity and, in turn, exports. There is significant and robust empirical evidence for eight manufacturing industries in 13 OECD countries during the period 1995–2015 confirming the central role of the creative response in the Schumpeterian loop between innovation and export.

AN APPEARANCE OF A SEASONABLE SILVER LINING WITHIN THE DUO INTERSPECIES RELATIONSHIPS: A RELATIVE REVIEW

This paper rests on how the two bestseller horror novels chosen to compare actually connect to each other. It reviews twin interspecies relationships. The first one is a young adult debut novel The Silver Kiss (2009) by English born American author Annette Curtis Klause. It was published in 1990 and republished in 2009 with two additional short stories, “The Summer of Love” and “The Christmas Cat.” Michigan Library Association picked it as the ‘Best Book of the Year Honor Book‘ in 1990. School Library Journal too gave it place among the Best Books in the same year and American Library Association, in 1991, considered it among the Best Books for Young Adults. The other is also a debut work Let the Right One In (original Swedish: Lat denratteKomma in), also known as Let Me In (2004). It is a vampire fiction novel written by Swedish writer John Ajvide Lindqvist and translated by Ebba Segerberg into English (2008).The subject of both the works taken into consideration here is loss, relationships and vampires. ‘Species’ means type or class of individuals sharing common characteristics, whereas inter-species means taking place between species. The Silver Kiss unfolds the tale of the teenager heroine Zoe’s life, taking into account her mother’s battle with cancer and death. She is very courageous, but all alone. She is in need of someone who can hold her in sleepless nights. Late one night, she takes a walk around the garden where she meets the dashing and silver haired Simon. He realizes the agony of desolation and death and Zoe’s pensive contemplation of her sinking mother. Both of them become reconciled to emotional loss via their budding inter-relation and are strongly concerned for each other. Let the Right One In revolves around the affinity betwixt Oskar Eriksson, who is twelve years of age and an age-old vampire in the figure of Eli who also happens to be a child. Oskar is all the time teased in school by a bunch of bullies, who take pleasure in inflicting severe pain and shame upon him. With Eli’s support, he is able to retaliate against his cuss harassers. A distinctive impression of vampirism has been created by both Klause and Lindqvist together. Connectively, the inferno strikes one with all the returning warmth. Details of the figures’ everyday lives have been shared with the readers appealingly. Initially, the whole lot of selves give the impression of being unattached, after all they come to be interrelated before long. By-and-large, the novels under discussion in this place are manifold and come up with the matters in question for the reviewers to ponder over.&#x0D; &#x0D; &lt;p&gt; &lt;/p&gt;&lt;p&gt;&lt;strong&gt; Article visualizations:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;img src="/-counters-/edu_01/0771/a.php" alt="Hit counter" /&gt;&lt;/p&gt;

A tale of the new and the old: renovation of Yong\u2019an Warehouse at Yangpu waterfront, Shanghai

The urban riverside space of Shanghai is transforming. How to renovate industrial heritage buildings to renew their vitality while retaining their historical memories and integrate them into the contemporary cityscape and today’s urban lifestyle is a common challenge encountered by contemporary architects. This article takes the renovation of Yong’an Warehouse as an example to showcase a typical heritage conservation project’s design process. The architects took different approaches to accommodate the different statuses of the twin buildings of the Yong’an Warehouse, seeking to create a symbiotic twin relationship between the past and the present. This project adopted a conservation and utilisation approach that involves multilateral participation, emphasising value-oriented mythology, and providing an alternative thread for the renovation of historical architecture.

“Side by side”: Development of twin relationship dimensions from early to middle childhood and the role of zygosity and parenting

Twin relationships have a significant effect on the twins’ life and their families. In the first comprehensive study of this topic, our purpose was to examine the developmental courses of four dyadic dimensions of twins’ relationships: closeness, dependence, conflict and rivalry, and the impact of zygosity and parenting on their relationships. Parents reported on their twins’ relationships ( N = 1547 mothers and 536 fathers with data from at least one of four measurement points from 3 to 8–9 years of age). The sample included 322 monozygotic twin dyads (sharing virtually 100% of their genes), and 1194 dizygotic twin dyads (sharing 50% of their genetic variance, on average). Our findings indicated that closeness and dependence decreased while rivalry increased through childhood. Dependence and rivalry also presented quadratic change. The twins’ conflict increased only for dizygotic twins. As expected, we found that the twins’ closeness and dependence were highly associated, as did the associations between conflict and rivalry. The mostly nonsignificant associations of closeness with conflict and rivalry reinforced the notion that they are not bi-polar opposites. However, dependence was positively related to the twins’ conflict and rivalry. A zygosity effect was also evident as monozygotic twins had higher levels of closeness and dependence than dizygotic twins through childhood, but there was no significant difference in the levels of their conflict and rivalry. In congruence with family system theories, parental positivity predicted the twins’ closeness and dependence, and parental negativity predicted the twins’ dependence, conflict and rivalry. The results were discussed in light of an evolutionary perspective and the twins’ developmental challenges through childhood.

Diffusion properties of the fornix assessed by deterministic tractography shows age, sex, volume, cognitive, hemispheric, and twin relationships in young adults from the Human Connectome Project.

The fornix is the primary efferent pathway of the hippocampus and plays a central role in memory circuitry. Diffusion tensor imaging has shown changes in the fornix with typical development and aging. Here, the fornix was investigated in 903 healthy young adult participants aged 22-36years old from the high-spatial resolution 1.25mm isotropic Human Connectome Project (HCP) diffusion dataset. Manual deterministic tractography was used to assess relationships between fornix diffusion parameters and age, sex, laterality, hippocampus volume, memory scores, and genetic effects in a subgroup of mono- and dizygotic twins. Fornix diffusion metrics were weakly correlated with age over the given age span. While significant hemispheric and sex differences were observed (greater fractional anisotropy (FA) and volume in the right hemisphere; greater FA and volume in females), there was great overlap between the groups. Hippocampus volume measurements showed greater volume in the right hemisphere, were found to be larger in males, and were weakly correlated with fornix FA and volume. Interestingly, all fornix diffusion measurements correlated strongly with fornix volume, suggesting the presence of partial volume effects despite the high-spatial resolution of the data. Both fornix diffusion parameters and hippocampal volumes were able to explain some variance (0.6-5.5%) in the memory tests evaluated. The fornix diffusion parameters were influenced by both genetic and shared environmental factors, displaying greater variability in dizygotic than in monozygotic twins. These findings provide a comprehensive depiction of the fornix in healthy, young individuals, upon which future typical development/aging and pathological studies could anchor.

An examination of microstructural evolution in a Pb–Sn eutectic alloy processed by high-pressure torsion and subsequent self-annealing

Abstract The Pb–Sn alloy has a wide use in the electronic, energy storage and nuclear industries and a fine-grained Pb–Sn alloy may open up new possibilities for applications in these industries. In order to understand the behavior of grain refinement, a Pb-62% Sn eutectic alloy was processed by high-pressure torsion (HPT), stored at room temperature (RT) and then the microstructures of the alloy after HPT were repeatedly investigated during the course of self-annealing using electron backscatter diffraction, scanning electron microscopy and transmission electron microscopy. It is demonstrated that there is a large fraction of twin boundaries with a twin relationship of 62.8° in the microstructure of the initial as-cast condition. Due to the presence of the high imposed pressure, the mobility of Ʃ21 boundaries at 71° is greatly favoured during processing by HPT. After the high pressure is removed, the mobility of dislocation-twin boundaries near 62.8° is then favoured. Processing by HPT significantly increases the solubility of Sn in the Pb phase. The supersaturated state of Sn in Pb is not stable during self-annealing at RT and instead a decomposition of Sn from the Pb-rich phase is observed after storage for 16 days. The main mechanism for this decomposition is lattice diffusion.

An automated procedure built on MTEX for reconstructing deformation twin hierarchies from electron backscattered diffraction datasets of heavily twinned microstructures

This paper presents a set of algorithms built on the MTEX and MATLAB graph toolboxes for automatic reconstruction of deformation twin hierarchies from Electron Backscatter Diffraction (EBSD) datasets with a focus on developing methods for heavily twinned microstructures (twin fractions >0.5). The algorithms address key issues arising at large strains, mainly: missing twin relationships, grouping of heavily deformed grain fragments into families of similar orientation originating from a single initial grain, identification of parent fragments for large twin volume fractions, and classification of families having twin relationships with multiple families. To facilitate the development of these algorithms, large-grained ultra-high purity α-Ti deformed in compression along two directions is investigated. Graphs are utilized to handle non-local geometric merging and to represent relationships throughout the reconstruction process. When determining if a grain fragment is from the undeformed microstructure, the combined metrics of the fragment's orientation volume fraction in the initial texture and the directed graph centrality measure of out-closeness (the number of nodes reached in a graph from a given node) are essential. To address automation in reconstructing the sequence of twinning and relating fragments originating from a single grain in the initial microstructure, the twin family tree is formulated as a minimum spanning tree emanating from the initial grain family. A scheme constructing the distances associated with twin relationship comprising the spanning tree is developed, and a novel quasi-directional Prim spanning tree algorithm is used to determine the twin family tree. The procedure is demonstrated to significantly improve the level of automation in reconstructing twin hierarchies in heavily twinned microstructure compared to other methodologies in literature. The procedure can readily be applied to analyses of twinning in metals, as well as provide an approach for routinely extracting twin statistics at larger deformation levels than previously possible. Significantly, the procedure is demonstrated to be capable of identifying third generation twinning in α-Ti microstructures.

Orientation patterns of aragonitic crossed-lamellar, fibrous prismatic and myostracal microstructures of modern Glycymeris shells

The shells of the bivalves Glycymeris glycymeris and Glycymeris nummaria are widely used for environmental studies. They consist of aragonite and comprise four different microstructures and textures from outer to inner shell surfaces: crossed-lamellar, myostracal, complex crossed-lamellar and fibrous prismatic. We characterize with SEM, EBSD, laser-confocal microscopy and AFM imaging mineral unit size, morphology and orientation of crystallites in the different microstructural arrangements and at the transition from one microstructure to the other. We also characterize the microstructure and texture of adductor and pedal retractor myostraca and address structural characteristics at the transition from crossed-lamellar to myostracal assemblies. We find that the crossed-lamellar layer has a three-dimensional crystallographic orientational order. Each set of first-order lamellae consists of twinned aragonite; the two sets of first-order lamellae are misoriented to each other by about 30 to 40° while retaining an approximately parallel a-axis; they do not show any particular twin relationship. Myostracal aragonite grows homoepitactically onto the crossed-lamellar aragonite, but is clearly a separate microstructure, with its own crystallite size and morphology. Within adductor and pedal myostraca, prisms increase in size towards inner surfaces. In contrast to the other shell layers, the myostraca form through competitive growth. The complex crossed-lamellar aragonite initially inherits the three-dimensional texture of the crossed-lamellar microstructure, but with growth develops an axial texture, which is transmitted to the underlying fibrous prismatic microstructure. With this work we provide a modern, unaltered, reference for fossil Glycymeris shells to be used for detection of diagenetic overprint in fossil Glycymeris analogs.

Geometry and energy barrier of martensite in the initial stage martensitic transformation in B19’ TiNi shape memory alloy

This study addresses the selectivity of self-accommodation microstructures in the initial stage of martensitic transformation in B19’ TiNi. It is known that specific habit plane variant (HPV) pairs, including {111¯}mtype I twin planes that are called initial stage microstructure (ISM) in this study, are preferentially formed in the initial stage of martensitic transformations. To elucidate on the selectivity of the ISM, the energy barrier at the formation of the twin plane, which is the candidate for the starting point of HPV pair formation, and the geometry of the HPV pair are theoretically analyzed in this paper. Using geometrical non-linear theory analysis, the compatible twin plane which has exact twin orientation relationship can be formed in the specific five groups of HPV pair. Using ab-initio simulations and Eshelby theory analysis results, {111¯}mtype I twin is determined to have a relatively small energy barrier among the twins in TiNi. Therefore, this paper shows that the HPV pair having a twin plane with a small energy barrier of formation and a structure that can effectively reduce the elastic strain is preferentially formed as the ISM.

In-situ observation of nucleation, growth and interaction of deformation-induced [formula omitted] martensite in metastable Ti–10V–2Fe–3Al

Microstructure evolution, dominated by the formation of deformation-induced α″ martensite during the 3-point bending of a metastable β Ti–10V–2Fe–3Al alloy containing 5% α, was observed in-situ using forward-scatter electron imaging and electron backscattering diffraction. α″ plates nucleated heterogeneously from {580}α″ habit planes at α-β interfaces and triggered the nucleation of additional α″ plates at the advancing interface during growth and upon impingement with high-angle boundaries. Further thickening of the impinged α″ plates led to a build-up of strain energy which induced 13031‾0α'' twinning within obstacle-forming α″ plates. Until now, this twinning system was observed in Nb and Ta alloyed Ti shape memory alloys only. This in-situ study is also the first to document the activation of 13031‾0α'' twinning by α″ impingement in a metastable β matrix. The first forming variants were {011}α″ compound twin-related variant pairs, each forming from up to two individual habit planes. These variant pairs were consistently predicted by determining the grain-average stress with finite element analysis and computing the available work from the transformation strain of the α″ variants. At higher indenter loads, grains that were unfavourably oriented to martensite formation accommodated the local stress by forming aggregates of different α″ variants, obeying either {111}α″ type I or 211α'' type II twin relationships. Scanning transmission electron microscopy revealed α″ substructures comprising columnar domains oriented perpendicular to the habit plane along with the absence of lattice invariant deformation. The growth of α″ plates involved ledge formation at α″-β interfaces.

Triplet grain growth in a-texture polycrystalline ZnO thin films

A growth of grain triplets is identified in vapor deposited, a-texture polycrystalline zinc oxide thin films, using a combination of transmission electron microscopy-based automated crystal orientation mapping and high-resolution imaging. Each triplet consists of three wurtzite phase grains, coordinated to near tetrahedral relative growth angles by the close-packed planes of a few nanometer diameter core of metastable zinc blende phase ZnO located at their triple junction. The triplets are aligned such that two of the grains have their fast growing [21¯1¯0] axes (near-) parallel to the substrate normal, and so coarsen under the principle of competitive grain growth. In contrast, growth of the third grain with a (101¯3) texture is impeded, such that it forms a small wedge between the ends of its two larger neighbors. Remarkably, all three boundaries between the grains adhere to a [21¯1¯0]/(011¯3) coherent twin orientation relationship, which corresponds to a grain geometry that is incommensurate with a perfect crystallographic nature. This coherency is primarily achieved via the small grain having an orientation that rotates internally by 10±2° across its volume, when going between the two interfaces formed with the neighboring large grains. The energy associated with this structural distortion is compensated by the formation of the coherent twin boundaries, such that the triplets are a stable or semi-stable growth form that are abundant in the film. The small (101¯3) texture grains may renucleate persistently, taking either of two possible orientations from the underlying tetrahedral coordination. By developing a phenomenological model for the triplet geometry and form, we associate these two orientations to small hexagonal caps and angled wedges seen in the surface morphology of the film. These findings potentially carry relevance for a wide range of vapor deposited compact films and free-standing nanostructures of wurtzite phase octet binary semiconductor compounds. We therefore believe that these insights can stimulate new research, for instance to obtain a more fundamental understanding of the growth mechanisms at the atomistic level.

Structural origin of reversible martensitic transformation and reversible twinning in NiTi shape memory alloy

Much progress has been made over the past few decades in resolving the mechanism for the transformation from ordered body-centered-cubic (B2) austenite to monoclinic martensite (B19′) in NiTi shape memory alloy, as well as the twinning mechanisms in martensite. However, so far no lattice correspondence analyses on the atomic scale have been conducted, as a result, these mechanisms have not been completely understood in terms of the pathways for reversible phase transition and reversible twinning in martensite. In this work, atomistic simulations were performed to investigate how B2 austenite transforms to B19′ martensite and how twins are formed during phase transformation. In particular, lattice correspondence in the structural evolutions was carefully analyzed to reveal the martensitic transformation mechanism and twinning mechanism with much better clarity. The simulation results show that, when martensite grains were nucleated in austenite, they already formed a twin relationship as a natural result of the crystal structure. Thus, self-accommodation is achieved naturally. Coalescence occurred subsequently and some martensite grains grew at the expense of their neighbors, indicating that the interfaces are elastically mobile and their migration is reversible. Eventually twinned martensite variants were created. It is shown that, in the B2 → B19′ transformation, the B19′ monoclinic structure can be treated as a distorted hexagonal close-packed (HCP) structure. With this treatment, it is demonstrated that the martensitic transformation is essentially similar to BCC ↔ HCP transformation which only involves atomic shuffles and is reversible, and twinning in martensite is essentially similar to {101¯2} twinning in HCP metals which only involves atomic shuffles and is reversible as well. Another significant discovery is that the B19′ martensite exhibits a very special dual-lattice structure: the relatively weak Ti-Ti bonding of the monoclinic unit cell permits easy reorientation of lattice units. As a result, two differently oriented lattice units co-exist in the same martensite grain which loses long range periodicity, providing an extra degree of freedom for accommodating external and internal strains. These results explain well why B19′ martensite is extremely adaptive to straining and why deformation is reversible.