Adjacent Parent Research Articles

Massive transformations in titanium alloys: Role of relative orientation of adjacent parent grains

Massive transformations occur in both additively and conventionally manufactured titanium (Ti) alloys. Unlike martensitic transformations, massive transformations can result in patch-like massive phases (αm) that traverse the parent prior-β grain boundaries (GBs). However, the conditions favouring the formation of these trans-GB αm-phases in Ti alloys remain largely unexplored. Through characterising the trans-GB αm-phases in α-β Ti alloys fabricated by additive and conventional processes, we find that their formation always occurs when two neighbouring prior-β grains share or nearly share a {110} pole, without exception. These trans-GB αm-phases exhibit concentrated {0001} poles while their {112¯0} poles spread widely. In addition, as metastable phases, they tend to decompose into ultrafine α-β lamellae. The role of relative orientation of adjacent parent grains in massive transformations and the implications for microstructural innovations in α-β Ti alloys are discussed.

Optimizing the Airflow Velocity Combinations Acting on Male Parent Rows for Hybrid Rice Pollination

Highlights The effect of airflow velocity on pollen distribution was investigated under a large-scale planting mode. The response surface model between pollen distribution and airflow velocity was constructed. Multi-objective optimization of airflow velocity combinations was carried out using a genetic algorithm. The optimal airflow velocity ranges of the male parents are from 22.4 to 24 m/s, 23.1 to 27 m/s, and 23.5 to 24.1 m/s. Abstract. Pollination is the key link in hybrid rice seed production. The pneumatic pollination method can significantly improve pollination efficiency under large-scale planting mode. To investigate the effect of airflow velocity on pollen distribution in hybrid rice pollination, the velocities of airflow acting on different male parent rows were taken as the experimental factors. The pollen amount in per view and the variation rate of pollen distribution in female parent rows were used as experimental indices. Field experiments were carried out using a self-made pneumatic pollination experimental platform. The results showed that when the airflow acted on the male parents in the first and second rows of the adjacent female parent, the pollen dissemination distance was short when the airflow velocity was low, and the pollen was mainly deposited in the area near the male parents. With the increase in airflow velocity, the peak pollen amount in per view in the female parent rows gradually moved away from the male parent rows. But they are all in the female parent rows of the effective area. The total amount of pollen also increased. Due to the blocking effect of the outer male parent row, the pollen dissemination was restricted when the airflow alone acted on the third male parent row. The effect of airflow velocity on pollen distribution was not obvious. The experimental results of different airflow velocities acting on the parent row alone are used as the basis. The objective functions of pollen amount, distribution variation rate, and airflow velocities of each male parent row were established by response surface methodology. The multi-objective optimization of airflow velocity combinations was carried out by a genetic algorithm. The pollen distribution under different air velocity combinations was obtained. When the optimal airflow velocity ranges of the male parents in rows 1, 2, and 3 are 22.4 to 24 m/s, 23.1 to 27 m/s, and 23.5 to 24.1 m/s, respectively, pollination is uniform and sufficient. The research results can provide a basis for the development of pneumatic pollinators and the optimization of working parameters under large-scale planting mode. Keywords: Multi-objective parameter optimization, Pneumatic pollination machinery, Response surface modeling, Rice pollination.

Effect of Zr on growth kinetics, microstructure and microtexture of Nb3Sn by bronze technique

We have experimentally studied a systematic quantitative effect of Zr on the factors influencing the critical current density of Nb3Sn, such as growth kinetics, microstructure and microtexture using a diffusion couple method. The Nb3Sn phase develops in the interdiffusion zone of the Cu(Sn)/Nb diffusion couple. For the Zr-alloyed diffusion couples, a two-phase mixture of Zr-containing Nb3Sn and sub-micron β-(Nb,Zr) solid solution second-phase develops. The growth kinetics of Zr-containing Nb3Sn is higher than the Zr-free Nb3Sn phase. Enhancement of growth kinetics is attributed to an increase in the diffusion flux of the Sn atoms along the grain boundaries of Nb3Sn owing to grain refinement. The Zr-free Nb3Sn phase has a weak crystallographic texture. On the other hand, the Zr-containing Nb3Sn phase develops not only with a strong crystallographic texture, but also has similar texture component as that of the adjacent Nb-rich parent phase.

The Effect of Mineralized Plasmatic Matrix and Chitosan on the Healing of Critical-Sized Mandibular Bone Defects in a Rabbit Model

Background: In maxillofacial surgery, critical size mandibular defects remain a challenging issue. There have been numerous attempts to improve mandibular defect healing. Recently, bone tissue engineering has provided many benefits in improving bone healing. Herein, we tried to investigate the effect of Mineralized plasmatic matrix (MPM) and Chitosan to enhance tissue healing and regeneration in mandibular bone defect. Methods: A mandibular bone defect of critical size was created in 45 New Zealand rabbits. There were three groups of rabbits: the MPM group, the Chitosan group, and the control group. Radiographical, histological, and immune histochemical evaluations were performed at 4, 8, and 12 post-operative weeks. Results: The MPM group demonstrated the highest degree of bone formation with uniform radio-opacity nearly like that of adjacent healthy parent tissue. While in the chitosan group, most of the defect area was filled with radio-opaque bone with persistent small radiolucent areas. The control group showed less bone formation than the MPM and chitosan group, with more radiolucent areas. Sections stained with (H&E) demonstrated an increase in osseous tissue formation in both the MPM and chitosan groups. Staining with Masson’s trichrome revealed an increase in fibrous connective tissue proliferation in both the MPM and chitosan groups. In both the MPM and chitosan groups, nuclear factor kappa p65 was downregulated, and matrix metalloproteinase-9 was upregulated. Conclusion: According to the current study, MPM and Chitosan may have beneficial effects on the healing of critical-sized mandibular bone defects.

Phase transformation of the Ti-5553 titanium alloy subjected to rapid heating

The α → β phase transformation upon heating in the Ti-5553 alloy with lamellar-nodular bimodal microstructure was tracked in situ with high energy X-ray diffraction. Rapid heating at 10, 50 and 100 °C s−1 from room temperature to 1050 °C was tested. Phase transformation on heating was studied by a combined analysis of the microstructural features that provides estimates of mass fractions, mean lattice parameters and full width at half maximum for the two phases. In comparison with equilibrium conditions, the experimental mass fractions reveal a shift of the transformation domain toward high temperatures when the heating rate increases. Also, the dissolution of the α phase is largely impacted by its morphology, the transformation being faster for α lamellae. The combined analysis of mean lattice parameters and full width at half maximum suggests that the α → β phase transformation on heating is diffusion controlled. The β phase therefore inherits the solute content of the adjacent parent α phase, leading to chemical heterogeneities in the β phase regardless of the heating rate.

Texture Memory in Hexagonal Metals and Its Mechanism

Texture memory is a phenomenon in which retention of initial textures occurs after a complete cycle of forward and backward transformations, and it occurs in various phase-transforming materials including cubic and hexagonal metals such as steels and Ti and Zr alloys. Texture memory is known to be caused by the phenomena called variant selection, in which some of the allowed child orientations in an orientation relationship between the parent and child phases are preferentially selected. Without such variant selection, the phase transformations would randomize preferred orientations. In this article, the methods of prediction of texture memory and mechanisms of variant selections in hexagonal metals are explored. The prediction method using harmonic expansion of orientation distribution functions with the variant selection in which the Burgers orientation relationship, {110}β//{0001}α-hex <11¯1>β//21¯1¯0α-hex, is held with two or more adjacent parent grains at the same time, called “double Burgers orientation relation (DBOR)”, is introduced. This method is shown to be a powerful tool by which to analyze texture memory and ultimately provide predictive capabilities for texture changes during phase transformations. Variation in nucleation and growth rates on special boundaries and an extensive growth of selected variants are also described. Analysis of textures of commercially pure Ti observed in situ by pulsed neutron diffraction reveals that the texture memory in CP-Ti is indeed quite well predicted by consideration of the mechanism of DBOR. The analysis also suggests that the nucleation and growth rates on the special boundary of 90° rotation about 21¯1¯0α-hex should be about three times larger than those of the other special boundaries, and the selected variants should grow extensively into not only one parent grain but also other grains in α-hex(hexagonal)→β(bcc) transformation. The model calculations of texture development during two consecutive cycles of α-hex→β→α-hex transformation in CP-Ti and Zr are also shown.

Damage behaviour in different micro-regions of P92 steel weldment under sequential low cycle fatigue and creep loading

Understanding the evolution of microstructure and micro-region properties of weldments during cyclic loading is a challenge for the reliability assessment of high-temperature components. This work is devoted to quantitatively evaluating the variation of micro-region properties and corresponding responsible microstructural features of P92 steel weldments under interrupted fatigue tests and subsequent creep fracture. To achieve this target, high-resolution characterization techniques, including electron backscatter diffraction (EBSD) and nanoindentation tester were used. The results revealed that the microstructures in the inter-critical heat affected zone (ICHAZ) and adjacent regions, fine-grained HAZ (FGHAZ) and parent metal (PM), show significant sensitivity to fatigue loading. Notably, the grain size in the ICHAZ reaches saturation after fatigue cycles of 10% fatigue lifetime, and the weld metal (WM) keeps unchanged throughout the fatigue loading. After subsequent creep fracture, only the WM presents an increasing trend in the average grain size. Nanoindentation tests uncover that the reductions of the elastic modulus and microhardness in each region also present three cyclic softening behaviour during the fatigue process due to the evolution of martensite lath structure. However, due to nucleation and growth of cavities accelerated by carbide precipitation, relatively low elastic modulus and microhardness were observed after subsequent creep loading.

Associations between haemodynamics and wall enhancement of intracranial aneurysm

Background and purposePrevious studies have reported about inflammation processes (IPs) that play important roles in aneurysm formation and rupture, which could be driven by blood flow. IPs can be identified...

Blister Aneurysm of Middle Cerebral Artery Division: Stent-Assisted Coiling Using Shelfing Technique

AbstractBlister aneurysms pose significant diagnostic and therapeutic challenge to neurointerventionists as well as neurosurgeons. Fragile nature of these aneurysms with involvement of the adjacent parent artery makes surgical options more difficult and complicated. Various endovascular treatment options such as overlapping stent, parent artery occlusion, and flow diverter placement are available in the present era. Though side wall aneurysms can be managed with flow diverter placement, bifurcation aneurysms are difficult to treat with these devices due to possibility of compromised flow in covered branch arteries. Blister aneurysms of the middle cerebral artery (MCA) are rare, and their treatment can be challenging when they are treated by endovascular methods with either overlapping stent or flow diverter placement. The authors report a case of ruptured MCA trifurcation blister aneurysm treated with shelfing technique using braided stent monotherapy along with coil embolization. The patient had good clinical outcome (modified Rankin’s scale 1 [mRS-1]) at discharge and complete aneurysm occlusion on follow-up angiogram after 6 months.

Effect of grain size on α-variant selection in a ZrTiAlV alloy

Local crystallographic orientation characteristics of grains with different sizes in a ZrTiAlV alloy after interrupted cooling from β phase region are investigated by electron backscatter diffraction (EBSD) technique. A statistical analysis of EBSD data shows that bigger parent β grains present weaker variant selection than smaller grains. The relevant influences are studied by comparing the nucleation behavior of grain boundary α (GBα) and succedent growth stage in varisized grains. In-depth analysis indicates that the deviation between pole of GBα and common pole of adjacent parent β grains is responsible for the smaller degree of variant selection inside the bigger parent β grains. The formation of more than one GBα type at the β/β grain boundary with common pole in bigger grains results in obstructing each other for these variants during the following growth stage, while only one type of GBα nucleate at the β/β grain boundary with common pole in smaller grains and it can freely grow into the interior of the grains, leading to stronger variant selection in smaller β grains.

Application of periodic density functional theory calculations for exploring copper(II) coordination effects on the mesophase behavior of p-n-alkoxybenzoic acids

Copper(II) benzoates ([Formula: see text]OBA-Cu) with various terminal alkoxy carbon numbers, [Formula: see text]–12, were prepared from [Formula: see text]-[Formula: see text]-alkoxy benzoic acids (nOBAs). Fourier transform infrared (IR) experiments suggested that dimerization through copper(II) chelating bidentate coordination created [Formula: see text]OBA-Cu with a linear rod-like structure, similar to the hydrogen-bonded structure of its parent [Formula: see text]OBA. However, the coordination structure of [Formula: see text]OBA-Cu changed during heating. Periodic density functional theory calculations provided valuable insight into the possible arrangement of the parent and copper(II)-coordinated [Formula: see text]OBAs. The formation of binuclear complexes between two adjacent [Formula: see text]OBA-Cu dimers forced [Formula: see text]OBA-Cu to arrange itself in a layer and exhibit smectic A mesophase. Accordingly, four types of IR stretching absorption of benzoyl carbonyl were observed in binuclear [Formula: see text]OBA-Cu complexes, replacing the original symmetric and asymmetric vibrations of benzoyl carboxylate in chelating bidentate coordination. The lateral association by [Formula: see text]–[Formula: see text] interactions between adjacent parent [Formula: see text]OBA dimers preferred a progressive smectic C arrangement. The origin of the odd–even effect was understood from the consideration of the molecular structure.

Assessment of endothelialization of aneurysm wall over time in a rabbit model through CD31 scoring

BackgroundIntracranial aneurysms represent a significant health concern and are poorly understood despite decades of research. Our study focused on understanding temporal patterns of endothelial cell distribution in different spatial locations...

About weldability and welding of Al alloys: case study and problem solving

Purpose: Among many disciplines within engineering, welding is probably one of the most inexact – rather more of an art than a science. As weldment is meant the complete joint comprising the weld metal, heat affected zones (HAZ) and the adjacent parent metal and should have the same properties as the parent metal. This paper aims provides a basic understanding of the metallurgical principles involved in how aluminium alloys achieve their strength and how welding can affect these properties. The most important and applied welding processes to Al alloys are here shortly introduced, as well as the preparation of parent metals prior to welding and good welding practice to avoid and/or keep under control defects and failures. Some case studies with possible failures will be introduced together with actions and suggestions to solve the observed problems. Design/methodology/approach: Two sheets of the EN AW 5454 (AlMg3Mn) alloy were weld with resistance welding process and after a mechanical processing of lamination was observed the presence of the defect. The microstructure of the defect as well as the welded part were evaluated with stereomicroscope (LEICA MS5), optical microscope (LEICA MEF4M), and with SEM analysis (LEO 1540 VP equipped with an energy dispersive X-ray spectroscope Oxford Link Pentafet). Findings: The well welded part was analysed with optical microscopy and electronic microscopy resulting with the attended mechanical properties. Micro-hardness indentations on the joint demonstrated the good mechanical properties of the joint while with the microscopic observations were identified the orientation and presence of precipitates typical of this alloy. In the defect, microscopically observations showed the presence of oxide inclusions. Research limitations/implications: There are a number of problems associated with the welding of aluminium and its alloys that make it difficult to achieve this ideal. The features and defects that may contribute to the loss of properties comprise the following: gas porosity, oxide inclusions and oxide filming, solidification (hot) cracking or hot tearing, reduced strength in the weld and HAZ, lack of fusion, reduced corrosion resistance and reduced electrical resistance. Originality/value: This case study illustrated clearly the importance of the cleaning on the surfaces to obtain a well welded joint ensuring the desired mechanical properties.

Residual Stress State of X65 Pipeline Girth Welds Before and After Local and Furnace Post Weld Heat Treatment

This research investigated the effects of global (in other words, furnace-based) and local post weld heat treatment (PWHT) on residual stress (RS) relaxation in API 5L X65 pipe girth welds. All pipe spools were fabricated using identical pipeline production procedures for manufacturing multipass narrow gap welds. Nondestructive neutron diffraction (ND) strain scanning was carried out on girth welded pipe spools and strain-free comb samples for the determination of the lattice spacing. All residual stress measurements were carried out at the KOWARI strain scanning instrument at the Australian Nuclear Science and Technology Organization (ANSTO). Residual stresses were measured on two pipe spools in as-welded condition and two pipe spools after local and furnace PWHT. Measurements were conducted through the thickness in the weld material and adjacent parent metal starting from the weld toes. Besides, three line-scans along pipe length were made 3 mm below outer surface, at pipe wall midthickness, and 3 mm above the inner surface. PWHT was carried out for stress relief; one pipe was conventionally heat treated entirely in an enclosed furnace, and the other was locally heated by a flexible ceramic heating pad. Residual stresses measured after PWHT were at exactly the same locations as those in as-welded condition. Residual stress states of the pipe spools in as-welded condition and after PWHT were compared, and the results were presented in full stress maps. Additionally, through-thickness residual stress profiles and the results of one line scan (3 mm below outer surface) were compared with the respective residual stress profiles advised in British Standard BS 7910 “Guide to methods for assessing the acceptability of flaws in metallic structures” and the UK nuclear industry's R6 procedure. The residual stress profiles in as-welded condition were similar. With the given parameters, local PWHT has effectively reduced residual stresses in the pipe spool to such a level that it prompted the thought that local PWHT can be considered a substitute for global PWHT.

Abstract 14: Size Ratio can be a Strong Predictor for Future Rupture of the Unruptured Cerebral Aneurysms

Introduction: Various factors have been nominated for the rupture of unruptured cerebral aneurysms including size, shape and specific locations of aneurysms. Size ratio, which is the quotient of maximum size of the aneurysm divided by the diameter of the adjacent parent artery, has also been nominated as a strong indicator to discriminate ruptured versus unruptured cerebral aneurysms. However, this has never been tested as a risk in the prospective cohort. In this paper, we have assimilated size ratio in cases of UCAS Japan using reported average parent arterial size and evaluated its value. Methods: We used average main intracranial artery diameter reported in anatomical studies as follows: AComA: 1.5mm, MCA: 3.9mm, ICA: 4.3mm, PComA: 1.3mm, BA: 4.1mm and VA: 3.9mm. UCAS Japan cohort, which is a Japanese prospective cohort of unruptured cerebral aneurysms in Japan, were utilized (6,312 aneurysms with 11,011 aneurysm*year follow-up). Result: Rupture risks according to this assimilated size ratio (aSR) were as follows: aSR<1.0: 0.13%/yr, aSR:1∼1.5: 0.24%/yr, aSR 1.5∼2: 1.17%/yr, aSR: 2∼3: 1.03%/yr, aSR 3-; 2.62%/yr. With multivariate logistic regression model, aSR >1.5 was significant factor along with presence of daughter sac, symptomatic presentation and age >=70. Hazard ratio for the aSR>1.5 was 6.01 and the highest among these factors. Aneurysm locations lost its significance as the influencing factor. Conclusions: While our outcome was limited because the parent artery size was not measured in individual cases, our aSR showed clear demarcation of the future rupture risk. Rather than considering specific location as the risk factor, size ratio might be more important rupture predictor in assessing natural course of unruptured cerebral aneurysms.

Relationship Between Regional Atherosclerosis and Adjacent Spinal Cord Histology

Introduction: Scant data are available regarding ischemic insult to the spinal cord and the responsible blood supply. Therefore, we aimed to investigate a correlation between atherosclerosis of adjacent vessels and spinal cord ischemia.Materials and Methods: In 20 unembalmed adult cadavers, samples of the vertebral arteries and aorta were removed and the degree of atherosclerosis with subsequent luminal occlusion was histologically analyzed. Next, adjacent segments of the spinal cord were harvested and submitted for immunohistological analysis of both neural and glial elements and blood supply.Results: We identified proximal atherosclerosis in the majority of cadavers but with varying degrees of luminal occlusion. The greatest degree of luminal occlusion was found in the descending abdominal aorta. No specimen was found to have atherosclerosis of the anterior or posterior spinal or radicular arteries. No spinal cord histology showed signs of ischemia, even in specimens with a significant large parent vessel (vertebral artery and aorta) occlusion due to atherosclerosis. Neuropathology of these adjacent cord segments revealed no signs of ischemia or demyelination.Conclusions: Spinal cord ischemia is often misdiagnosed and can cause significant neurological compromise. However, based on our study, the degree of atherosclerosis of the adjacent parent vessel supply does not appear to be a predictor of neuronal and glial tissue damage of the adjacent spinal cord.

Influence of Weld Preparation Procedure and Heat Tinting on Sulfide Stress Corrosion Cracking of Duplex Stainless Steel

Corrosion resistant alloys, such as duplex stainless steel (DSS), are increasingly the material of choice for oilfield applications as a result of the trend toward more extreme temperature, higher pressure, and elevated levels of hydrogen sulfide. However, the susceptibility of such materials to localized corrosion and sulfide stress cracking (SSC) is a major consideration, particularly in the vicinity of welds. Here we investigate the effect of surface preparation and oxygen content in the backing gas during welding on the pitting and SSC susceptibility of 22Cr DSS. Four-point bend testing of welded specimens under conditions close to the pass/fail boundary revealed a greater tendency for pitting as a function of oxygen content in the backing gas. Pitting was concentrated in the heat-tinted region, whereas cracking was mainly observed in the adjacent coarse ground parent material, with surface defects from the grinding process acting as primary crack initiation sites. The results demonstrate that control...

Characterizing patterns of endothelialization following coil embolization: a whole-mount, dual immunostaining approach

BackgroundThe extent, rate, and source of endothelialization following coil embolization of saccular aneurysms remains poorly understood. We performed a whole tissue mount, dual immunohistochemical analysis of experimental aneurysms to characterize...

Exploration of a rare population of Chinese chestnut in North America: stand dynamics, health and genetic relationships.

With the transport of plants around the globe, exotic species can readily spread disease to their native relatives; however, they can also provide genetic resistance to those relatives through hybrid breeding programmes. American chestnut (Castanea dentata) was an abundant tree species in North America until its decimation by introduced chestnut blight. To restore chestnut in North America, efforts are ongoing to test putative blight-resistant hybrids of Castanea dentata and Chinese chestnut (Castanea mollissima), but little is known about the ecology of C. mollissima. In a forest in northeastern USA in which C. mollissima has become established, we explored questions of stand dynamics, health and genetic relationships of C. mollissima offspring to an adjacent parent orchard. We found that C. mollissima was adapted and randomly distributed among native species in this relatively young forest. The genetics of the C. mollissima population compared with its parents indicated little effect of selection pressure as each of the parent trees contributed at least one offspring. The ease with which this exotic species proliferated calls to question why C. mollissima is rare elsewhere in forests of North America. It is likely that a time window of low animal predation allowed seedlings to establish, and the shallow soil at this site limited the maximum forest canopy height, permitting the characteristically short-statured C. mollissima to avoid suppression. Our results indicate that because C. mollissima exhibited pioneer species characteristics, hybrids between C. mollissima and C. dentata have the potential to be successful pioneer species of future forests in North America, and we challenge the paradigm that exotic tree species are wholly detrimental to native biodiversity. We contend that exotic tree species should be assessed not only by their level of threat to native species, but also by their potential positive impacts on ecosystems via hybrid breeding programmes.

Angle change of the parent arteries after stent-assisted coil embolization of wide-necked intracranial bifurcation aneurysms

To investigate the angle changes of the parent arteries after stent-assisted coil embolization of wide-necked intracranial bifurcation aneurysms. The adjacent parent arterial angles before and after stent-assisted coil embolization were measured in 38 patients with aneurysms of the anterior communicating artery (ACoAA) and 41 patients with bifurcation aneurysms of the middle cerebral artery (MCABA). Variables were analysed in relation to the angle changes. Vascular angles of the parent arteries significantly increased by 27.8° (±18.5°) immediately after stent-assisted coil embolization in 79 cases (p < 0.001), with 25.7° (±14.8°) in ACoAA and 29.7° (±21.4°) in MCABA, respectively. In 51 (64.6%) cases with follow-up angiography (mean interval 13.5 ± 4.1 months), vascular angles increased by 27.2° (±17.1°) immediately after treatment and further increased by 20.7° (±14.3°) at the last follow-up (all p < 0.001). More acute pre-stent angles of the parent arteries correlated with greater post-stent angle changes (p = 0.006). Younger age tended to be inversely related to post-stent angle changes (p = 0.091). Stent placement during coil embolization induced significant changes in the aneurysm-parent artery relationship. Further study is needed to elicit the association between angle change of the parent arteries and aneurysmal stability after coil embolization.