Macrostructure Properties Research Articles

A polyolefin-based hybrid separator for durable and advanced lithium-/sodium-metal batteries

Polyolefin separators are widely used in commercial lithium metal batteries (LMBs). However, their inherent hydrophobic nature causes poor electrolyte uptake and diminished battery performance. And their low melting temperatures eventually led to inevitable dimensional shrinkage at high temperatures, raising the possibility of internal short-circuits that could lead to explosions. In this work, an advanced separator is developed to overcome safety problems and optimize overall performance. By incorporating heat-resistant boehmite (BH) and multipolar self-polymerizing dopamine (DA) into biaxially oriented poly(ethylene) (PE), which allows the separator to promote rapid electrolyte absorption, accelerate Li+/Na+ transference without sacrificing the macrostructure and physiochemical properties of the PE matrix. This hybrid separator possesses excellent thermal stability, and our tests of LMBs cells (Li || LiFePO4) using this hybrid separator demonstrated superior cycle stability compared to commercial polyolefin separators. In addition, the hybrid separator can be used in sodium-metal batteries (NMBs) as well.

SIMULACIÓN COMPUTACIONAL EN MED DEL PULIDO DE LAS NUECES DE PALMA DE TAGUA (PHYTELEPHAS AEQUATORIALIS)

For tagua, the quality of the polishing process is analyzed according to the surface finish of the material, which is obtained manually or through empirically developed machinery that does not include the study of the behavior of the material during the process, which generates an inefficient work. The objective of the work is to determine the macro structural properties of tagua nuts to simulate polishing using the discrete element method. Virtual models were developed and the corresponding physical and mechanical properties were assigned. Among the main results, a tagua nut model was achieved, with m=30.22 g and ρ=1327.3±11.23 kg/m3, friction coefficient for wood of µ_e = 0.411±0.0006 and angle of repose of β=24.644º±0.201º. These properties are the variables used as input data for the DEM model. Finally, the suitability of the Hertz-Mindlin model to simulate the process of mechanized polishing of tagua nuts is demonstrated.

Structure–property relations in graphitic pebbles for nuclear applications

This work presents an analytical approach for holistically characterizing graphitic matrix pebbles for nuclear applications whereby the macrostructure, microstructure, and thermophysical properties of pebbles are determined. A systematic sectioning method was applied to several pebbles to describe the regional properties of the samples. Intact matrix-only spheres and sections of spheres fabricated by Kairos Power were characterized via optical imaging, x-ray computed tomography, x-ray diffraction, and ellipsometry to determine 2D and 3D macrostructure and anisotropy. The thermophysical properties of these materials were determined via measurements of density, specific heat, thermal expansion, and thermal diffusivity. The results of this study indicate that the pebble fabrication methods and their resultant effect on microstructure have a nontrivial effect on thermophysical properties, confirming the importance of robust characterization of these components. A discussion of the characterization approach and its applicability to nuclear fuel development activities is also included.

Ultrasonic-assisted Pulsed TIG Welding (U-P-TIG) of Inconel 690 for Nuclear Power Plants

Inconel 690 has been extensively used in steam generator tubing materials for pressurized water reactors. In order to improve the weld quality of Inconel 690, ultrasonic-assisted pulsed tungsten inert gas (TIG) welding is studied. In this study, the macrostructure, microstructure, and mechanical properties of Inconel 690 weldments welded by TIG welding with and without ultrasonic assistance were investigated. The microstructures of the fusion zone (FZ) and heat-affected zones (HAZ) were examined by an optical microscope and the Electron Backscatter Diffraction (EBSD) technique, and weldment properties were compared through tensile and impact tests. Experimental results indicate that the base metal (BM) was composed of equiaxed crystalline austenite, and the austenite grains in the heat-affected zone were obviously grown; the fusion zone (FZ) was composed of columnar austenite. Besides, the ultrasonic assistance was effective in refining the structure and improving the strength and toughness of weld metal.

Semi-stationary shoulder bobbin-tool: A new approach in tailoring macrostructure and mechanical properties of bobbin-tool friction stir welds in magnesium alloy

Semi-stationary shoulder bobbin-tool: A new approach in tailoring macrostructure and mechanical properties of bobbin-tool friction stir welds in magnesium alloy

Grey Matter Reshaping of Language-Related Regions Depends on Tumor Lateralization.

A brain tumor in the left hemisphere can decrease language laterality as assessed through fMRI. However, it remains unclear whether or not this decreased language laterality is associated with a structural reshaping of the grey matter, particularly within the language network. Here, we examine if the disruption of the language hubs exclusively affects the macrostructural properties of the contralateral homologues or whether it affects both hemispheres. This study uses voxel-based morphometry applied to high-resolution MR T1-weighted MPRAGE images from 31 adult patients' left hemisphere, which is dominant for language. Eighteen patients had brain tumors in the left hemisphere, and thirteen had tumors in the right hemisphere. A cohort of 71 healthy individuals matched with respect to age and sex was used as a baseline. We defined 10 ROIs per hemisphere involved in language function. Two separate repeated-measure ANOVAs were conducted with the volume per region as the dependent variable. For the patients, tumor lateralization (right versus left) served as a between-subject factor. The current study demonstrated that the presence of a brain tumor generates global volumetric changes affecting the left language regions and their contralateral homologues. These changes are mediated by the lateralization of the lesion. Our findings suggest that functional mechanisms are supported by the rearrangement of the grey matter.

Correlating atomistic characteristics of zeolites to their 3D-Printed Macro structural properties for prediction of mechanical response

A wide range of mechanical properties are vital in structures, from macro (e.g., load-bearing) down to atomistic (nanomaterial) level. To design structures with the target mechanical properties, it is crucial to understand the correlation between the mechanical characteristics and structural information. To this end, we explored the similarity in the mechanical behavior between atomistic structures and actual 3D-printed zeolite structures. The zeolite structure was chosen because of its various structural parameters such as pore size, distribution, and geometry. Molecular dynamics (MD) simulations confirmed that similar behavior was observed in the mechanical responses at an atomic scale and with a 3D-printed macro-scale structure. 3D printing with ductile thermoplastic polyurethane (TPU) filaments showed a high degree of agreement with microstructure-level simulations. The mechanical response of zeolite structures is classified depending on their linearity and the characteristics with respect to the applied strain, to anticipate the potential applications of mechanical metamaterials. Further comparative analysis was conducted between the structural characteristics and mechanical properties, linking the changes in the stress to factors, such as density, porosity, angle, and bond length. This study demonstrates that metamaterial design with a mechanical response can be achieved using atomic-level structural design degrees of freedom.

Combined Effects of HA Concentration and Unit Cell Geometry on the Biomechanical Behavior of PCL/HA Scaffold for Tissue Engineering Applications Produced by LPBF.

This experimental study aims at filling the gap in the literature concerning the combined effects of hydroxyapatite (HA) concentration and elementary unit cell geometry on the biomechanical performances of additively manufactured polycaprolactone/hydroxyapatite (PCL/HA) scaffolds for tissue engineering applications. Scaffolds produced by laser powder bed fusion (LPBF) with diamond (DO) and rhombic dodecahedron (RD) elementary unit cells and HA concentrations of 5, 30 and 50 wt.% were subjected to structural, mechanical and biological characterization to investigate the biomechanical and degradative behavior from the perspective of bone tissue regeneration. Haralick's features describing surface pattern, correlation between micro- and macro-structural properties and human mesenchymal stem cell (hMSC) viability and proliferation have been considered. Experimental results showed that HA has negative influence on scaffold compaction under compression, while on the contrary it has a positive effect on hMSC adhesion. The unit cell geometry influences the mechanical response in the plastic regime and also has an effect on the cell proliferation. Finally, both HA concentration and elementary unit cell geometry affect the scaffold elastic deformation behavior as well as the amount of micro-porosity which, in turn, influences the scaffold degradation rate.

What lies beneath: White matter microstructure in pediatric myalgic encephalomyelitis/chronic fatigue syndrome using diffusion MRI.

Recent studies in adults with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) suggest that changes in brain white matter microstructural organization may correlate with core ME/CFS symptoms, and represent a potential biomarker of disease. However, this has yet to be investigated in the pediatric ME/CFS population. We examined group differences in macrostructural and microstructural white matter properties, and their relationship with clinical measures, between adolescents recently diagnosed with ME/CFS and healthy controls. Forty-eight adolescents (25 ME/CFS, 23 controls, mean age 16 years) underwent brain diffusion MRI, and a robust multi-analytic approach was used to evaluate white and gray matter volume, regional brain volume, cortical thickness, fractional anisotropy, mean/axial/radial diffusivity, neurite dispersion and density, fiber density, and fiber cross section. From a clinical perspective, adolescents with ME/CFS showed greater fatigue and pain, poorer sleep quality, and poorer performance on cognitive measures of processing speed and sustained attention compared with controls. However, no significant group differences in white matter properties were observed, with the exception of greater white matter fiber cross section of the left inferior longitudinal fasciculus in the ME/CFS group compared with controls, which did not survive correction for intracranial volume. Overall, our findings suggest that white matter abnormalities may not be predominant in pediatric ME/CFS in the early stages following diagnosis. The discrepancy between our null findings and white matter abnormalities identified in the adult ME/CFS literature could suggest that older age and/or longer illness duration influence changes in brain structure and brain-behavior relationships that are not yet established in adolescence.

Tractography passes the test: Results from the diffusion-simulated connectivity (disco) challenge

Estimating structural connectivity from diffusion-weighted magnetic resonance imaging is a challenging task, partly due to the presence of false-positive connections and the misestimation of connection weights. Building on previous efforts, the MICCAI-CDMRI Diffusion-Simulated Connectivity (DiSCo) challenge was carried out to evaluate state-of-the-art connectivity methods using novel large-scale numerical phantoms. The diffusion signal for the phantoms was obtained from Monte Carlo simulations. The results of the challenge suggest that methods selected by the 14 teams participating in the challenge can provide high correlations between estimated and ground-truth connectivity weights, in complex numerical environments. Additionally, the methods used by the participating teams were able to accurately identify the binary connectivity of the numerical dataset. However, specific false positive and false negative connections were consistently estimated across all methods. Although the challenge dataset doesn’t capture the complexity of a real brain, it provided unique data with known macrostructure and microstructure ground-truth properties to facilitate the development of connectivity estimation methods.

Microstructural evolution and strengthening mechanisms of CMT directed energy deposition-arc with interlayer ultrasonic impact treatment manufactured AZ31 magnesium alloy

The AZ31 magnesium alloy thin-wall component is fabricated by a hybrid CMT directed energy deposition-arc (DED-Arc) with interlayer ultrasonic impact treatment (UIT) process in this study. The macrostructure, microstructure, and mechanical properties of the samples before and after UIT are investigated. The results indicate that the interlayer UIT contributes to reducing the surface roughness and increasing the effective area of the deposited sample. Columnar grains are refined and transform into equiaxed grains with the introduction of interlayer UIT. Meanwhile, an interesting phenomenon was found that a large number of twins were remained in the interlayer region of UIT component while the grains occur equiaxed transformation. Furthermore, the grain orientation exhibits a random distribution under the effect of twins and recrystallization caused by UIT, reducing the anisotropy of microstructure and mechanical properties of deposited components. On the other hand, the ultimate tensile strength of the sample along horizontal and vertical directions increases by 16.82% and 14.46% respectively. The elongation, yield strength and microhardness of the deposited sample are also improved after interlayer UIT, which is mainly attributed to grain boundary strengthening and dislocation strengthening caused by grain refinement and twins. It is worth mentioning that twins play an important role in inhibiting dislocation motion and transforming the orientation of origin grains.

STUDY OF THE RHEOLOGICAL AND PHYSICOCHEMICAL PROPERTIES OF FRUCTAN FRACTIONS OF Agave tequilana cv. cenizo

The physico-mechanical properties of fructan fractions in different agave species without Tequila Denomination of Origin (DOT) need to be studied to identify and expand industrial applications. The rheological and physicochemical characterization of three fractions of Agave tequilana cv. cenizo fructans without DOT, with different degree of polymerization (DP) was carried out to propose their use as an additive in the food industry. Fractions were obtained by apparent DP enrichment (DPa) by stepwise ultradiafiltration with 10, 5 and 1 kilodalton (kDa) membranes and classified on the basis of the enriched fraction evidenced by HPLC profiling with amperometric detector. The ultradiafiltrate of the membrane with 10 kDa, called High Degree of Polymerization (HDP), showed enrichment of fructans with high DPa ≥ 30, the one with 5 kDa called Intermediate Degree of Polymerization (IDP), presents enrichment in DPa between 10 to 30, these fractions dried by spray, showed a modal particle size distribution (D [4,3] < 20 µm). In the ultradiafiltrate of the 1 kDa membrane, called Low Polymerization Grade (LDP), fructo-oligosaccharides (FOS) and fructans with maximum DPa of 15 were enriched; this sample was concentrated to 72 °Brix. The glass transition (Tg) showed a DPa-dependent increase (LDP = 152.17 °C, IDP = 216.12 °C and HDP = 227.5 °C). Viscosity was dependent on the degree of polymerization, exhibiting thermo-mechanically stable flow behavior. The reconstituted powders exhibited Newtonian and flow-stable behavior in a concentration range of 2-50 %, temperature of 5-45 °C and pH of 2-9. The macro and micro structural properties identified in the respective fractions of agave fructans, diversify possible applications with potential interest as encapsulating material, stabilizer and prebiotic sweetener, among others that agave fructans have in the food and nutraceutical industry.

The right uncinate fasciculus supports verbal short-term memory in aphasia

Verbal short-term memory (STM) deficits are associated with language processing impairments in people with aphasia. Importantly, the integrity of STM can predict word learning ability and anomia therapy gains in aphasia. While the recruitment of perilesional and contralesional homologous brain regions has been proposed as a possible mechanism for aphasia recovery, little is known about the white-matter pathways that support verbal STM in post-stroke aphasia. Here, we investigated the relationships between the language-related white matter tracts and verbal STM ability in aphasia. Nineteen participants with post-stroke chronic aphasia completed a subset of verbal STM subtests of the TALSA battery including nonword repetition (phonological STM), pointing span (lexical-semantic STM without language output) and repetition span tasks (lexical-semantic STM with language output). Using a manual deterministic tractography approach, we investigated the micro- and macrostructural properties of the structural language network. Next, we assessed the relationships between individually extracted tract values and verbal STM scores. We found significant correlations between volume measures of the right Uncinate Fasciculus and all three verbal STM scores, with the association between the right UF volume and nonword repetition being the strongest one. These findings suggest that the integrity of the right UF is associated with phonological and lexical-semantic verbal STM ability in aphasia and highlight the potential compensatory role of right-sided ventral white matter language tracts in supporting verbal STM after aphasia-inducing left hemisphere insult.

Microstructure and Mechanical Properties of Resistance Element Welded Joints for DP780 Steel and 6061 Aluminum Alloy

DP780 steels and 6061‐T6 aluminum alloys are joined using the resistance element welding (REW) process with a flat Q235 rivet. The macrostructure, microstructure, and mechanical properties of the REW joints are investigated. The nugget zone and upper‐critical heat‐affected zone (UGHAZ) microstructure exhibit lath martensite. The inter‐critical heat‐affected zone (ICHAZ) microstructure consists of ferrite and martensite. Two types of intermetallic compound (IMC) layers are formed at the steel/Al interface. A tongue‐like Fe2Al5 layer is found adjacent to the steel side, while a needle‐like Fe4Al13 layer is found adjacent to the aluminum alloy side. The welding current has a significant influence on the nugget size, peak load, and energy absorption of joints. The fracture behavior analysis of the REW joints is performed using the in situ digital image correlation (DIC) method. There are two failure modes of the REW joint under different welding currents: pull‐out failure (POF) and the base material pull‐out failure (BPF). At a welding current of 17 kA, the maximum tensile‐shear value of the REW joints is 6.27 kN with a nugget diameter of 5.37 mm. The failure mode of the REW joints is mainly BPF mode that exhibits superior lap‐shear performance.

Improve the manufacturing efficiency of steel bars by using hot-wire pulse arc additive manufacturing

With the advantages of high material utilization and freedom of structural form, wire and arc additive manufacturing (WAAM) is a feasible solution to achieve fully automated construction of buildings. However, the current manufacturing efficiency of steel bars manufacture using WAAM is not sufficient for construction industry applications. This paper uses hot-wire pulse arc additive manufacturing (HWPAAM) to improve the manufacturing efficiency of 316L stainless steel (316L SS) bars. The efficient manufacturing principle of HWPAAM 316L SS bars was analyzed in this article. The effect of different manufacturing efficiency on heat input, macrostructure, microstructure, and mechanical properties of 316L SS bars was studied. The results show that the manufacturing efficiency of the 316L SS bar manufactured by HWPAAM can reach 31 mm/min. The connection rate of hot-wire power supply can be improved to 96.7 % and the heat input of the arc can be reduced by 65 % at 31 mm/min manufacturing efficiency. With the decrease of arc heat input, the grain size decreases. The improvement of manufacturing efficiency has little effect on the macrostructure of the 316L SS bar. Under uniaxial tension, the mechanical properties of the 316L SS bar standard specimen with different manufacturing efficiencies are basically the same. By using this manufacturing process, the manufacturing efficiency of the 316L SS bar is greatly improved while the performance is not significantly reduced.

Effect of Process Parameters on Weld Quality in Vortex- Friction Stir Welding of 6061-T6 Aluminum Alloy.

Vortex- friction stir welding (VFSW) utilizes a stir bar made of an identical material to the workpiece to rub the workpiece's top surface, which avoids the keyhole defect in conventional friction stir welding. It presents great potential in the repair field of aluminum alloys. In this study, the effect of stir bar diameter, rotation speed, and welding speed on the weld formation was investigated in the VFSW of 6061-T6 aluminum alloy. The weld macrostructure, penetration, and mechanical properties were characterized. The results show that a large diameter of the stir bar can enhance the vortex material flow, increase the heat input, and eliminate the incomplete-penetration defect. The increase in rotation speed within limits can enhance the weld penetration and the mechanical properties of the weld nugget zone (WNZ). However, too high a rotation speed reduces the weld penetration and weakens the mechanical properties of the WNZ. The increase in welding speed reduces the weld penetration but enhances the mechanical properties of the heat affected zone. The incomplete-penetration defect significantly weakens the ductility of the VFSW joint. It can be eliminated by enlarging the stir bar diameter and choosing a moderate rotation speed and a lower welding speed.

Enhancing textural properties in plant-based meat alternatives: The impact of hydrocolloids and salts on soy protein-based products

Consumer studies suggest that the meat-like texture of plant-based meat alternatives is crucial for the market success of these products. Many meat analogues contain wheat gluten, because it is cost-effective and give rise to nice fibrous structures. However, individuals with celiac disease cannot consume products containing wheat gluten producing a fibrous structure. To provide meat-like textures, different hydrocolloids with appropriate salt concentrations could be used. Therefore, this study investigated the influence of different hydrocolloids, including high acyl gellan gum, low acyl gellan gum, high methoxyl pectin, low methoxyl pectin, and xanthan at 2%, as well as two types of salts (CaCl2 and NaCl) at three concentrations (0%, 0.5%, and 1%) on the macrostructure, microstructure, and mechanical properties of plant-based meat alternatives containing only soy protein isolate and without wheat gluten. The addition of hydrocolloids and salts increased the cross-link bonds and structural compactness at the microscopic level and enhanced the fibrous structure at the microscopic level at different extent. These findings provide insight into how the addition of salts and hydrocolloids can effect plant-based meat alternatives without wheat gluten, which have practical implications for the food industry and are important for their success in the market.

Investigation of abrasion resistance of geopolymer concrete cured in ambient temperature for pavement applications

The viability of eco-friendly geopolymer concrete (GPC) for engineering applications such as pavements requires investigating the abrasion resistance and understanding the improving mechanisms. The produced one-part GPC can be used in various engineering applications showing a 28-day compressive strength between 25–42 MPa and flexural strength above 4.5 MPa. GPC slabs, compared to ordinary Portland cement-based concrete (OPCC), generally experienced higher abrasion. While the abrasion of the OPCC specimen in 28 days was 2.72 mm, the GPC specimens experienced an abrasion between 3.60 and 4.11 mm. The dominance of slag and increasing water content increased the abrasion. It is concluded that the strong connection between microstructural behaviour and macrostructural properties is the key element in GPC performance. Hence, it is recommended that careful attention be paid to the refinement of the microstructure in order to find a GPC that is viable and suitable for pavement and road applications.

Postnatal maternal distress, infant subcortical brain macrostructure and emotional regulation

BackgroundMaternal distress is associated with an increased risk for adverse emotional development in infants, including difficulties with emotion regulation. Prenatal maternal distress has been associated with alterations in infant brain development. However, less is known about these associations with postnatal maternal distress, despite this being an important modifiable risk factor that can promote healthy brain development and emotional outcomes in infants. Methods & resultsInfants underwent magnetic resonance imaging (MRI) and mothers completed standardized questionnaires concerning their levels of perceived distress 2–5 months postpartum. Infant emotion regulation was assessed at 8–11 months via maternal report. When examining the associations between maternal distress and infant macrostructure, maternal anxiety was associated with infant right pallidum volumes. Increased display of negative emotions at 8–11 months of age was associated with smaller hippocampal volumes and this association was stronger in girls than boys. ConclusionFindings suggest that postnatal maternal distress may be associated with early infant brain development and emphasize the importance of maternal mental health, supporting previous work. Furthermore, macrostructural properties of infant subcortical structures may be further investigated as potential biomarkers to identify infants at risk of adverse emotional outcomes.

Analysis of slow and fast sleep spindle properties in Parkinson's disease – A comparative EEG study

Study objectivesSleep disturbances and altered sleep macrostructure are common in Parkinson's disease (PD). Few studies have addressed the changes in sleep spindle (SS) properties in this movement disorder so far. SS seem to be fundamental of both sleep architecture and memory consolidation. The aim of our comparative study was to investigate the changes of SS characteristics in PD, and reveal the relationship between SS properties and cognitive function. MethodsWe investigated 20 PD patients and 18 age-matched controls. All participants underwent a 24-hour-long polygraphic EEG recording after extensive clinical investigation. We detected slow and fast SS properties automatically using individual adjusting method (IAM). The data were statistically evaluated. ResultsWe found significantly lower fast spindle amplitude in PD comparing with controls. We did not find significant differences in SS densities, duration and oscillatory frequency between the groups. We detected significant positive correlation between fast SS amplitude and memory in PD, and between fast SS density and retrograde memory in controls. The total Addenbrooke's cognitive score correlated negatively with slow SS density and duration in controls. ConclusionsBy the time clinical diagnosis of PD is established, the pathological process is already spreading. Changes in sleep macrostructure and SS properties might become a useful biomarker of the neurodegenerative process in PD. In addition, decreased fast SS amplitude might predict further cognitive deterioration and indicate early involvement of corresponding cortical area. Our study results strengthen the importance of EEG examination in PD, and the use of IAM method in SS analysis.