Major Microstructural Changes Research Articles

Comparative analysis of brain age prediction using structural and diffusion MRIs in neonates

Using machine learning techniques to predict brain age from multimodal data has become a crucial biomarker for assessing brain development. Among various types of brain imaging data, structural magnetic resonance imaging (sMRI) and diffusion magnetic resonance imaging (dMRI) are the most commonly used modalities. sMRI focuses on depicting macrostructural features of the brain, while dMRI reveals the orientation of major white matter fibers and changes in tissue microstructure. However, their differential capabilities in reflecting newborn age and clinical implications have not been systematically studied. This study aims to explore the impact of sMRI and dMRI on brain age prediction. Comparing predictions based on T2-weighted(T2w) and fractional anisotropy (FA) images, we found their mean absolute errors (MAE) in predicting infant age to be similar. Exploratory analysis revealed for T2w images, areas such as the cerebral cortex and ventricles contribute most significantly to age prediction, whereas FA images highlight the cerebral cortex and regions of the main white matter tracts. Despite both modalities focusing on the cerebral cortex, they exhibit significant region-wise differences, reflecting developmental disparities in macro- and microstructural aspects of the cortex. Additionally, we examined the effects of prematurity, gender, and hemispherical asymmetry of the brain on age prediction for both modalities. Results showed significant differences (p<0.05) in age prediction biases based on FA images across gender and hemispherical asymmetry, whereas no significant differences were observed with T2w images. This study underscores the differences between T2w and FA images in predicting infant brain age, offering new perspectives for studying infant brain development and aiding more effective assessment and tracking of infant development.

Three-Dimensional Quantitative Analysis of Internal Limiting Membrane Peeling Related Structural Changes in Retinal Detachment Repair

PurposeTo assess macular microstructural changes associated with internal limiting membrane peeling (ILMP) using three-dimensional optical coherence tomography (3D-OCT) in primary macula-off rhegmatogenous retinal detachment (RRD) repairs with vitrectomy and silicone oil (SO) tamponade. DesignRetrospective, consecutive, interventional case series. MethodsSetting: Institutional practice. Patient Population: Patients who received primary RRD repair by a single experienced surgeon between January 2017 and December 2021. Main Outcome Measures: In the qualitative comparative analysis, the presence of macular changes among patients who underwent primary RRD repair with (21 eyes) or without ILMP (20 eyes) were observed. Subsequently, a detailed quantitative analysis of ILMP-related microstructural changes in 56 eyes using both 3D and 2D-OCT images were performed. ResultsIn the qualitative comparative analysis, macular microstructural changes were observed in 95% of ILMP eyes and 5% of non-ILMP eyes (p < 0.001). In the quantitative analysis, four major macular microstructural changes were detected: dimple (75%), dissociated nerve fiber layer (DONFL) (55%), ILM peeling edge thinning (IPET) (64%), and temporal macular groove (TMG) (23%). Dimples (n = 251, average 4.5 ± 5.8 per eye) could be further classified into type I (confined to the inner plexiform layer [IPL]; 73%) and type II (beyond IPL, 27%). The average depth of the deepest dimples was 58 ± 18 μm. The extent of IPET was 6.0 ± 3.7 clock hours. The average length of TMG was 1.8 ± 0.4 mm. Comparing to unoperated fellow eyes, the eyes after ILMP showed decreased inner temporal over nasal retinal thickness ratio (0.86 ± 0.07 versus 0.96 ± 0.03, p < 0.001), shorter disc-fovea distance (4.61 ± 0.32 µm versus 4.78 ± 0.37 µm, p = 0.041), and wider retinal vein trajectories (c’ = 2.48 ± 0.84 versus 3.39 ± 1.61, p = 0.002). ConclusionsMacular microstructural changes are common after ILMP in RRD repair, encompassing both focal changes (dimples, DONFL) and zonal changes (IPET, TMG). DONFL and dimples may be part of a continuum of findings stemming from the same mechanism. IPET and TMG are the results of macular tissue shift due to contracture of the optic disc and neurovascular bundle.

Application of Magnetic Flux Leakage (MFL) method to non-destructively characterize the microstructure and corrosion behaviour of API X65 grade steel

The goal of this research is to investigate the ability of the Magnetic Flux Leakage (MFL) method to characterize the microstructural features and corrosion performance of heat-treated API X65 grade steel in a non-destructive way. Various microstructures were created by austenitizing the specimens of API X65 steel at 950 °C for 45 min, followed by cooling in the furnace, air, oil, and water. SEM observations indicated that applying various heat-treating cycles led to three major microstructural changes in the ferrite phase, including volume fraction, grain size, and morphology. It was also found that an increase in cooling rate, increases the corrosion current density (icorr) obtained by the Potentiodynamic Polarization (PDP) test and decreases the charge transfer resistance (Rct) measured by Electrochemical Impedance Spectroscopy (EIS) technique. Furthermore, surface analysis of corroded samples showed that the higher ferrite (anode) to cementite (cathode) ratios in the furnace/air-cooled samples boost the corrosion performance, while uniform and localized corrosion have taken place on the oil and water quenched samples due to the higher density of dislocation and their acicular structure. Non-destructive evaluations indicated that microstructural changes as a result of various heat-treating cycles dramatically affect the magnetic permeability, which considerably influences the magnetic flux leaked from the surface and detected by the Hall effect sensor in the MFL method. Two MFL parameters, peak-to-peak amplitude, and slopes of the raw curves of the Hall sensor outputs at zero-crossing points were studied for the specimens. The results revealed good correlations between MFL parameters and values of icorr and Rct. Additionally, in this study, an “optimal range” has been proposed for the MFL outputs, which can be adjusted according to the required range of mechanical properties and corrosion behavior in the inspection process of API X65 steel specimens after heat treatment.

Novel isochoric impregnation to develop high-quality and nutritionally fortified plant materials (apples and sweet potatoes).

Isochoric impregnation was explored as a novel pressure-assisted infusion technique to fortify plant materials with bioactive compounds. Apple and potato cylinders were impregnated with a sucrose solution containing 4% ascorbic acid (AA) while freezing under isochoric conditions. Isochoric impregnation resulted in greater infusion of AA compared to infusion at atmospheric pressure, which demonstrated the feasibility of this impregnation technology. Processing temperatures (-3°C and -5°C) and processing times (1, 3, and 5h) significantly affected the AA infusion. The AA content values ranged from 446 to 516mg/100g for apples and 322 to 831mg/100g for sweet potatoes under isochoric conditions. For both plant materials, isochoric impregnation at -3°C did not cause major changes in texture and microstructure of the biological tissues. These results indicated that isochoric impregnation of solid foods could be a feasible technology for infusion of bioactive compounds without significantly altering their matrix. PRACTICAL APPLICATION: The findings of this study showed that the use of isochoric impregnation as a fortification technique is a promising way to develop fresh-like and value-added products with improved nutrition during preservation at subfreezing temperatures.

Microstructural evolution of P92 steel in IN740H/P92 dissimilar weld joints during creep deformation

In this study, we report the microstructural development of heat-affected zone in P92 heat-resistant steel during creep deformation in cross-weld specimens with dissimilar weld joints between IN740H/P92 materials. Different specimens were prepared via the interruption of creep testing at 50, 70, and 90% of the measured creep-rupture life and were carefully examined and compared. To explain the deformation behavior, finite element analysis was performed in conjunction with softening behavior measured by electron back-scattered diffraction and hardness mapping. The FGHAZ II region defined in this study could be related to the generally known inter-critical heat-affected zone, which showed major changes in microstructure during creep deformation due to the accelerated softening by dynamic recrystallization as well as to the development of a triaxial stress state. As a result, cavity formation and growth was observed only in the FGHAZ II region, which ultimately led to fracture.

Effect of micro‐structural changes on concrete properties at elevated temperature: Current knowledge and outlook

AbstractThe influence of microstructural changes on concrete properties at elevated temperatures is presented and discussed in this paper, as the exposure to elevated temperatures brings in marked changes in concrete thermal, mechanical and kinematic properties owing to the heat‐induced evolution of material's microstructure. The major microstructural changes consist in increasing pore size, occurrence of microcracking and activation of chemo‐physical processes in the hardened cement‐paste. These processes (like portlandite dissociation and crystalline change in quartzitic aggregate) occur above 400°C and are more pronounced in high‐strength than in normal‐strength concrete. Increasing pore size and microcracking, however, yield the largest contribution to concrete strength‐loss, that occurs mainly between 400 and 800°C, depending on aggregate type and initial moisture content in the mix. On the whole, calcareous (or carbonate) aggregate behaves better than siliceous aggregate face to increasing temperatures. Initial moisture content favors concrete thermal spalling, mostly between 200 and 400°C, but such a complex phenomenon is still open to investigation, as demonstrated by the various theories found in the literature, each with its chemo‐physical mechanisms and limitations. Three theories are discussed in this paper, and these theories together with other critical issues allow to focus on future work.

Juvenile Eastern Oysters More Resilient to Extreme Ocean Acidification than Their Mud Crab Predators

AbstractOcean acidification is predicted to impair marine calcifiers' abilities to produce shells and skeletons. We conducted laboratory experiments investigating the impacts of CO2‐induced ocean acidification (pCO2 = 478–519, 734–835, 8,980–9,567; Ωcalcite = 7.3–5.7, 5.6–4.3, 0.6–0.7) on calcification rates of two estuarine calcifiers involved in a classic predator‐prey model system: adult Panopeus herbstii (Atlantic mud crab) and juvenile Crassostrea virginica (eastern oyster). Both oyster and crab calcification rates significantly decreased at the highest pCO2 level. Notably, however, oysters maintained positive net calcification rates in the highest pCO2 treatment that was undersaturated with respect to calcite, while mud crabs exhibited net dissolution (i.e., net loss of shell mass) in calcite‐undersaturated conditions. Secondary electron imaging of oyster shells revealed minor microstructural alterations in the moderate‐pCO2 treatment, and major microstructural and macrostructural changes (including shell dissolution, delamination of periostracum) in the high‐pCO2 treatment. These results underscore the threat that ocean acidification poses for marine organisms that produce calcium carbonate shells, illustrate the strong biological control that some marine calcifiers exert over their shell‐building process, and shows that ocean acidification differentially impacts the crab and oyster species involved in this classical predator‐prey model system.

Investigations on the Microstructure-Property Relationship of NCM-Based Electrodes for Lithium-Ion Batteries

Abstract The microstructure of a multi-material-electrode and in particular its porosity co-determines, to a significant extent, the energy and power density of a lithium-ion cell. Moderate and high degrees of densification with several intermediate stages were applied reaching porosities of up to 18 % in order to increase the theoretical energy density of NCM-based cathodes. By applying microscopic and material analysis methods, the microstructure development during the densification could be described and a direct relationship to the electrochemical performance of the electrodes could be demonstrated. Major microstructural changes in connection with a significant drop in performance at current rates ≥ 2C arise from applying densification with porosities of &lt; 25 %. Then again, compactions of the NCM cathodes generating 20 – 22 % porosity offer the highest energy densities at moderate loads, i. e. current rates ≤ 1C.

Synergistic effect of Mg addition and hydrostatic extrusion on microstructure and texture of biodegradable low-alloyed zinc

The influence of synergic effect of different content of Mg and plastic deformation in the room temperature on microstructure and texture of low-alloyed zinc (ZnMg) was investigated in this work. Cast ZnMg alloys with three different Mg contents were hot extruded at 250 °C and subsequently subjected to hydrostatic extrusion (HE). Obtained alloys were compared to pure zinc. Detailed analysis of microstructure and local texture of ZnMg was performed on the longitudinal cross section of each sample, using scanning electron microscope equipped with electron backscatter diffraction. The macroscopic texture was investigated on the transverse cross section of each sample by means of the X-ray diffraction. Results showed that HE leads to grain refinement level unattainable with classic methods of deformation for both pure Zn and ZnMg alloys. Microstructural observation both with local and macroscopic texture analysis suggests the occurrence of dynamic recrystallization during plastic deformation. Addition of Mg caused major changes in microstructure of deformed materials and enhanced grain refinement. The bimodal structure consisted of grains elongated in the extrusion direction, as well as equiaxed ones was observed on the longitudinal cross section of ZnMg samples. Mg alloying combined with hydrostatic extrusion caused modification of the microstructure and texture in the zinc alloy samples which resulted in significant improvement of mechanical properties.

Interpreting H13 steel wear behavior for austenitizing temperature, tempering time and temperature

Hot-working die steel should possess good high temperature strength, tempering resistance, ductility and reasonable cost. Thus, H13 is widely used for forging, extrusion and die casting. Resistance to surface wear of hot working die steel plays an important role in imparting good finish to the products. The properties required of hot die steel for a given application can be obtained by controlling heat treatment parameters which produces major changes in microstructure. This paper intends to find the impact of austenitizing temperature, tempering temperature and tempering time on the wear behavior of H13 die steel. After heat treating samples at austenitizing temperature of 1020, 1040 and 1060 $$^{\circ }$$ C; tempering temperature 540, 560 and 580 $$^{\circ }$$ C; tempering time 1, 2 and 3 h, experimentation on pin-on-disc tribotester is done to measure the H13 die steel sliding wear and coefficient of friction. Using Box–Behnken design a response surface method model is developed to find the impact of above heat treatment parameters and the adequacy of model is verified through the analysis of variance (ANOVA) technique. The optimized heat treatment set predicted by desirability function approach is verified experimentally and the results are found close to the predicted results.

Highly densified NCM-cathodes for high energy Li-ion batteries: Microstructural evolution during densification and its influence on the performance of the electrodes

Abstract For positive electrodes in Lithium ion batteries LiNi1/3Co1/3Mn1/3O2 (NCM) is widely used as an active material. The performance of the electrodes in different applications is mainly influenced through the electrode manufacturing process. This work aims to contribute to a better understanding of the relation between microstructure development caused by the densification of the electrodes and its influence on electrochemical behaviour as well as ageing. Therefore, NCM-based cathodes were compacted in several interstages down to a porosity of 18%. By detailed microscopic analyses and Hg porosimetry we provide important insights concerning the electrodes microstructure, its evolution during densification and the correlation to the electrochemical performance. In doing so it will become obvious that major microstructural changes take place when electrodes are compacted to porosities below 22–25% which goes along with a significant decline of the capacity and energy density at current rates of 2C and more. However, at current rates below 1C the highest energy density is observed for cathodes with even lower porosities. Additionally, the microscopic analyses provide important information about how this problem can be tackled.

Microstructure stability of TLPS interconnects in high operating temperature applications

Abstract Interconnect materials for high operating temperature applications are becoming a limiting factor within the chain of materials. While materials such as capacitor dielectrics, semiconductor platforms (e.g. SiC), and baseplate materials (e.g. SiN composites) have paved a pathway to deploying electronics in high operating temperature applications, interconnect materials are a clearly identified weak link. As is often the case in advancements in technology, the materials technologies that were the bottlenecks to advancement give way to new solutions that create new bottlenecks in the material supply chain. Rather than a fluid march towards advancements in new frontiers in electronics, the high operating temperature sphere, like much of advanced electronic, suffers from a ‘slip-fault’ mode of development where advances occur in one segment while others lag behind creating drag on implementation. For high operating temperature applications the available interconnect solutions are becoming the jarring stop to the smooth tectonic shift. Current solutions are diverse: high-lead, gold-based, and nano-sintering and its hybrids, but none are ideal. Even disregarding he toxicity of lead and the ongoing limbo of its regulatory status, the operating temperatures of the high-lead solders are on the low end of the requirements for future harsh environment electronics applications; whereas, the gold and nano-based alternatives have significant cost barriers - either at from the constituent materials perspective or the required investment in new processes. There is also the concern about the assessment of the action of nanomaterials in the waste stream due to their fundamentally different surface reactivity in a variety of situations. Reliance on conventional, solder-type interconnection structures, regardless of composition, introduces the perennial problem of the growth of the interfacial phases due to the essentially unlimited volume of the bulk solder material. The changes in the interfacial structure with additional thermal work - as is provided by high operating temperature applications - creates an environment that is ripe for growth of a variety of failure mechanisms. These failure mechanisms are often related to the uncontrolled laminar growth of intermetallic phases at the interfaces and the mechanical characteristics of these intermetallic phases in comparison with the materials joined and the bulk constituent material of the solder. An alternative class of interconnect materials, transient liquid phase sintering (TLPS) pastes, introduce a joint microstructure that is homogeneous throughout. The interfacial metallurgical reactions with the solderable surfaces are fundamentally similar to those that occur throughout the bulk of the joint. A reactant metal is included in the composition. This reactant metal, most often copper, reacts with and converts the bulk tin in the bulk of the solder interconnect to alloy structures with melting points well above the operating temperatures currently contemplated. At the conclusion of the joining process, which is generally a near drop-in for existing solder reflow processes, there is no large source of unreacted metal (e.g. Sn) that can continue to drive major microstructural changes with the continued thermal work provided by the application environment. For this reason the joints are homogeneous and do not have the free reactants necessary to drive substantial changes in joint morphology during cycling and use conditions. In this paper, we will explore the differences between TLPS joints and solder-type joints with the anticipated thermal work that would be introduced in a high operating temperature environment.

Ex-Situ 3D Nano-Ptychography of Ni-YSZ SOFC Anode during Redox Cycling

Solid oxide cells (SOC) are used for efficient and cost-effective conversion of a wide variety of fuels (SOFC) for power generation or for energy storage via electrolysis (SOEC). However, SOC lifetime under harsh operating conditions is limited by electrode microstructure durability. In particular, the state of the art anode electrodes are composed of a porous cermet of nickel and yttria stabilized zirconia (YSZ). Electrochemical reactions occur where the ion and electron conducting phases meet the pores at the triple phase boundaries (TPB). Thus, the electrochemical activity of the electrode is strongly dependent on the density of TPBs and the quality of the connecting pathways through each phase1. Despite nickel remaining stable under reducing environments, nickel oxidation can occur in the electrode due to air leakage in the fuel system or by mechanical failure of the electrolyte. During operation, redox cycles can impact the lifetime of the electrode thus tracking their effect on the microstructure in 3D provides valuable information. 3D characterization of a Ni-YSZ electrode was first achieved in 20062 using focused ion beam scanning electron microscope (FIB-SEM) nanotomography and it has been routinely performed for the last decade followed by the development of near edge X-ray nano-tomography3 and most recently holotomography4. Near edge X-ray nano-tomography and FIB-SEM has been used to study the effects of oxidation on Ni-YSZ electrodes3 X-ray Ptychography is a scanning based technique in which a set of several local far-field scattering patterns is obtained by scanning the sample with a coherent micrometer-size X-ray beam. When used in tomography mode, ptychography provides a quantitative measurement of the local electron density of materials in 3D. Over the years, ptychography has demonstrated high sensitivity to mass density changes and the highest resolution among the X-ray imaging techniques5. As a proof of concept, we report the first results of ptycho-nanotomography applied to an “ex-situ” redox experiment performed at the cSAXS beamline at the Swiss Light Source (PSI). In the experiment the same Ni-YSZ anode microstructure is first analyzed in its pristine state, then oxidized and finally reduced again at 850°C in air and in 4%H2-96%N2 respectively. A specimen containing both Ni-YSZ electrode and YSZ electrolyte was created using a high precision mechanical polishing procedure followed by FIB ion milling. The “ex-situ” treatments were carried out in a small custom made tube furnace between each ptychography scan at the beamline. Datasets typically 20x20x12 µm in size were quantified to have a 3D spatial resolution of 55 nm using the Fourier shell correlation method5. The high mass density sensitivity of ptychography, resulted in high phase contrast between Ni, YSZ, NiO and pore, enabled us to effectively resolve all the phases present in the electrode (figure 1a,b,c). Therefore, an accurate segmentation procedure could be applied minimizing the associated geometrical errors of calculated microstructural parameters. Here we describe the major microstructural changes which can be noticed in the microstructure showing the evolution of the nickel particle size distribution, connectivity and tortuosity in this recent experiment. Moreover, the morphological changes in the YSZ phase are also discussed with emphasis on the observed micro-cracks (figure 1d) and their effect on the overall connectivity.

Evaluation of Austenite Phase in High-Carbon Steels by Ultrasonic Longitudinal Velocity

Abstract Retained austenite is a remnant product that may induce significant changes in mechanical properties of the steel. Consequently, accurate and economical measurement of retained austenite is very important. In this regard, specimens of AISI-440C and AISI-A2 steels were austenized at different temperatures ranging from 950°C to 1250°C and then air cooled. This led to major microstructural changes in these specimens. These changes were characterized by using x-ray diffraction techniques, optical and electron microscopy, Rockwell hardness testing, and ultrasonic flaw detectors. This study revealed that there is a good correlation exists between austenite phase and the longitudinal velocity. The magnitude of longitudinal velocity can be used to obtain reliable, quick, and quantitative determination of the volume percentage of the austenite phase present on production floor with relative ease, and less destructive, as compared to other methods.

Molecular mechanisms of osteoporotic hip fractures in elderly women

A common manifestation of age-related bone loss and resultant osteoporosis are fractures of the hip. Age-related osteoporosis is thought to be determined by a number of intrinsic factors including genetics, hormonal changes, changes in levels of oxidative stress, or an inflammatory status associated with the aging process. The aim of this study was to investigate gene expression and bone architecture in bone samples derived from elderly osteoporotic women with hip fractures (OP) in comparison to bone samples from age matched women with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 10 women with low-trauma hip fractures (mean age 83±6) and consecutive surgical hip replacement. Ten bone samples from patients undergoing hip replacement due to osteoarthritis (mean age 80±5) served as controls. One half of each bone sample was subjected to gene expression analysis. The second half of each bone sample was analyzed by microcomputed tomography. From each half, samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. We could show a significantly decreased expression of the osteoblast related genes RUNX2, Osterix, Sclerostin, WNT10B, and Osteocalcin, a significantly increased ratio of RANKL to Osteoprotegerin, and a significantly increased expression of the enzymes superoxide dismutase 2 (SOD2) and glutathione peroxidase GPX3, and of the inflammatory cytokine IL6 in bone samples from hip fracture patients compared to controls. Major microstructural changes in OP bone were seen in the neck and were characterized by a significant decrease of bone volume, trabecular number, and connectivity density and a significant increase of trabecular separation. In conclusion, our data give evidence for a decreased expression of osteoblast related genes and increased expression of osteoclast related genes. Furthermore, increased expression of SOD2 and GPX3 suggest increased antioxidative activity in bone samples from elderly osteoporotic women with hip fractures.

Effect of Austenizing Temperature on High-Carbon Steels and Its Characterization by Eddy Current Nondestructive Technique

The objective of this study is to investigate the effect of austenizing temperature on high-carbon steels. Two types of steels, i.e., AISI-440C and AISI-A2 were selected in this regard. Specimens of these steels were austenized from 950 to 1250°C and then air-cooled; this resulted in major microstructural changes in the specimens. These microstructural changes altered the electrical resistivity and magnetic permeability of the materials. XRD studies revealed that about 80% austenite formed when the subject steels were heat-treated to 1200°C. Eddy current technique was applied for the assessment of these microstructural changes, which influence the eddy current response in the coil. Similar hardness trend was observed for both steels. The magnitude of eddy current can be used to estimate the volume fraction of phases present in these steels. This study revealed that a good correlation existed between eddy current measurements and microstructural changes in these steels.

Effect of long time service exposure on microstructure and mechanical properties of gas turbine vanes made of IN939 alloy

In the present study, the effects of long-term service exposure have been investigated on microstructure and mechanical properties of gas turbine vanes made of IN939 superalloy. The major microstructural changes for the investigated service-exposed vanes include the formation of continuous grain boundary carbides and the transformation (degeneration) of MC carbides located at the grain boundaries. The brittle σ phase, which is predicted to be stable on the basis of thermodynamic calculations, is not observed in the microstructure of service-exposed vanes. The microstructural changes during service lead to a loss in room temperature ductility as well as in creep properties of the alloy.

Molecular evidence of osteoblast dysfunction in elderly men with osteoporotic hip fractures

Osteoporosis is extremely frequent in post-menopausal women; nevertheless, osteoporosis in men is also a severe and frequently occurring but often underestimated disease. Increasing evidence links bone loss in male idiopathic osteoporosis and age related osteoporosis to osteoblast dysfunction rather than increased osteoclast activity as seen in postmenopausal osteoporosis. The aim of this study was to investigate gene expression of osteoblast related genes and of bone architecture in bone samples derived from elderly osteoporotic men with hip fractures (OP) in comparison to bone samples from age matched men with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 12 men with low-trauma hip fractures and consecutive surgical hip replacement. Bone samples of age matched patients undergoing hip replacement due to osteoarthritis served as controls. One half of the bone samples was subjected to RNA extraction, reverse transcription, and real-time polymerase chain reactions. The second half of the bone samples was analyzed by static histomorphometry. From each half samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. OP patients displayed a significantly decreased RUNX2, Osterix and SOST expression compared to OA patients. Major microstructural changes in OP bone were seen in the subcortical region of the neck and were characterized by a significant decrease of bone volume, and a significant increase of trabecular separation. In conclusion, decreased local gene expression of RUNX2 and Osterix in men with hip fractures strongly supports the concept of osteoblast dysfunction in male osteoporosis. Major microstructural changes in the trabecular structure associated with osteoporotic hip fractures in men are localized in the subcortical region of the femoral neck.

An attempt to reproduce high burn-up structure by ion irradiation of SIMFUEL

Experiments in IC-100 and U-400 cyclotrons were conducted with SIMFUEL pellets (11.47wt.% of fission products simulators) to reproduce some aspects of the long-term irradiation conditions in epithermal reactors. Pellets were irradiated with Xe16+, Xe24+ and He+ at energies ranging from 20keV (He+) to 320keV (Xe16+) and 1–90MeV (Xe24+). Some samples were subsequently annealed to obtain larger grain sizes and to study defects recovery. The major microstructural changes consisted in grain sub-division observed on SEM and AFM images and change in composition registered by EPMA (pellets irradiated with 1–90MeV Xe24+ ions at fluence of 5×1015cm−2). Lattice distortion and increase in dislocation density is also noted according to X-ray data. At low energies and high fluences formation of bubbles (20keV He+ at 5.5×1017cm−2) was observed. Grain sub-division exhibits full coverage of the grain body and preservation of former grain boundaries. The size of sub-grains depends on local dislocation density and changes from 200nm to 400nm along the irradiated surface. Beneath it the size ranges from 150 to 600nm. Sub-grains are not observed in samples irradiated by low-energy ions even at high dislocation densities.

Microstructural evolution and mechanical properties of Ti–Zr beta titanium alloy after laser surface remelting

Abstract The effects of laser surface remelting (LSR) on the microstructural evolution and surface mechanical properties of Ti–Zr beta titanium alloy were investigated. The surfaces of the Ti–Zr alloy was re-melted using a CO2 laser. X-ray diffraction, Scanning electron microscope, Transmission electron microscope, nanoindentation, and microhardness analyses were performed to evaluate the microstructural and mechanical properties of the alloy. The results showed that the alloy microstructure in the remelting region was greatly refined and homogeneous compared with that in the base material because of the rapid remelting and resolidifying. Meanwhile, the metastable hexagonal ω phases with the size of 20–50 nm was found and uniformly distributed throughout the β matrix after LSR. Phase transformation and microstructural refinement were the major microstructural changes in the alloys after LSR. The microhardness and elastic modulus in the remelted region clearly increased by 92.9% and 21.78%, respectively, compared with those in the region without laser processing. The strengthening effect of LSR on the mechanical properties of the Ti–Zr alloy was also addressed. Our results indicated that LSR was an effective method of improving the surface mechanical properties of alloys.