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At least 739 records · Page 41

Overall assessment of alkali-silica reaction affected recycled concrete aggregate mixtures derived from construction and demolition waste

A large amount of research has been conducted on the reuse of construction and demolition waste (CDW) in concrete. Yet, CDW may display pre-existing damage which raises concerns on its use. In this work, coarse recycled concrete aggregate (RCA) is reclaimed from distinct members of an alkali-silica reaction (ASR) affected overpass. RCA mixtures incorporating 50 and 100% replacement are then manufactured and stored in conditions enabling further ASR development. Mechanical (Stiffness Damage Test- SDT) and microscopic (Damage Rating Index- DRI) analyses are conducted at a fixed “secondary” induced expansion. Results indicate that the overall damage of ASR-affected RCA mixtures is different from conventional concrete and depends upon the “past” RCA condition. Furthermore, the DRI can capture the “past” and “secondary” expansion while the SDT simply detects the “secondary” distress. Finally, an adapted DRI version is proposed to better evaluate and distinguish “past” and “secondary” damage in ASR-affected recycled concrete.

36 MATERIALS SCIENCE↗

Chemical structure and complex growth modes of magnesium silicate hydrate: Nanoparticle orientation, aggregation, and fusion

The extent of utilization of magnesium silicate hydrate (MSH) in construction is limited partly because of insufficient data ascertaining the kinetics of its precipitation. In this report MSH grown homogeneously or heterogeneously in the range of magnesium to silicon solution molar concentration ratios, [Mg]/[Si] = 0.5-1.5, and temperature = 25-80 °C was analyzed for its chemical structure and morphology. Infrared spectroscopy and geochemical modeling show that increasing the [Mg]/[Si] ratio results in less silicate polymerization in MSH. Atomic force microscopy reveals the presence of nanoparticles that aggregate and fuse to form films. Oriented attachment of nanoparticles and features indicative of enhanced crystallinity were observed at higher temperatures and longer reaction times. These data provide direct evidence for the persistence of hierarchical structures (i.e., nanoparticles forming 3D microparticles and 2D film layers) at the nanoscale to mesoscale. These findings offer insights into the precise chemical synthesis of MSH and its widespread use as a binder for construction purposes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Effects of fiber dosage, loading orientation and stress on frequency response of enhanced Carbon Nano-Fiber Aggregates

Nanomaterial additives have been broadly used in cement and concrete-based sensors to measure the stress and strain in the structure. Most of the studies focused on measuring the resistivity of sensors with Direct Current (DC) or relatively low-frequency. Here in this work, the impedance responses of enhanced Carbon Nano-Fiber Aggregates (CNFAs) at different frequencies are rigorously studied and utilized as a tool for real-time structural health monitoring (SHM). The CNFA impedance measurements at different measurement frequencies provide an extra dimension (frequency dimension) to allow the characterization of different phenomena and multimodal measurements simultaneously. First, a comprehensive physical model is established to understand the frequency responses of the CNFA impedance. Second, COMSOL Multiphysics is used to simulate the frequency responses of the CNFA impedance, which provides more insights into the electric field and current density distribution. The impedance of CNFAs decreased with the increased dosage of carbon nanofibers (CNFs). Third, experimental studies are reported in detail. The electrical impedance variation (EZV) of the CNFA in parallel orientation is 151% higher than that of perpendicular orientation at the frequency of 2612 Hz and uniaxial compression stress of 4.65 MPa. The strain-EZV curve obtained from the response spectrum is linear for frequencies ranging from 98 Hz to 463.9 kHz. The strain-EZV curve for 5625 Hz has a linear fit with the gauge factor of 147.78. At 1000 Hz, the CNFA exhibited a repeatable behavior up to 9.35 MPa and detection limit up to the stress of 18.62 MPa.

36 MATERIALS SCIENCE↗

Identifying Disadvantaged Communities in the United States: An Energy-Oriented Mapping Tool that Aggregates Environmental and Socioeconomic Burdens

This paper defines a policy-relevant nationwide composite index to identify communities disproportionately impacted by environmental, energy, and climate injustices in the United States. We review existing vulnerability indicators and indices to assess the tradeoffs of different design parameters, including variable selection, geographic unit, dimensionality reduction, weighting, and aggregation methods. From this methodological review, we create the first nationwide, census tract-level index of cumulative burden that includes energy-relevant indicators alongside climate, social, environmental, and economic indicators, and is flexible to the inclusion of additional data sources. We provide a summary of the sources of inputs used to develop a definition for "disadvantaged communities" that can be used to prioritize energy investments. We discuss use-cases for this index including the implementation of the Justice40 Initiative, which calls for 40% of certain federal clean energy benefits to flow to disadvantaged communities in the United States. We use our results to examine historic allocations of federal energy investments and show that communities that we identify as disadvantaged received about 37% fewer funds per capita than non-disadvantaged communities.

cumulative burden↗

ARCH: Large-scale knowledge graph via aggregated narrative codified health records analysis

Objective: Electronic health record (EHR) systems contain a wealth of clinical data stored as both codified data and free-text narrative notes (NLP). The complexity of EHR presents challenges in feature representation, information extraction, and uncertainty quantification. Here, to address these challenges, we proposed an efficient Aggregated naRrative Codified Health (ARCH) records analysis to generate a large-scale knowledge graph (KG) for a comprehensive set of EHR codified and narrative features. Methods: Using data from 12.5 million Veterans Affairs patients, ARCH first derives embedding vectors and generates similarities along with associated p-values to measure the strength of relatedness between clinical features with statistical certainty quantification. Next, ARCH performs a sparse embedding regression to remove indirect linkage between features to build a sparse KG. Finally, ARCH was validated on various clinical tasks, including detecting known relationships between entity pairs, predicting drug side effects, disease phenotyping, as well as sub-typing Alzheimer’s disease patients. Results: ARCH produces high-quality clinical embeddings and KG for over 60,000 codified and narrative EHR concepts. The KG and embeddings are visualized in the R-shiny powered web-API.3 ARCH achieved high accuracy in detecting EHR concept relationships, with AUCs of 0.926 (codified) and 0.861 (NLP) for similar EHR concepts, and 0.810 (codified) and 0.843 (NLP) for related pairs. It detected drug side effects with a 0.723 AUC, which improved to 0.826 after fine-tuning. Using both codified and NLP features, the detection power increased significantly. Compared to other methods, ARCH has superior accuracy and enhances weakly supervised phenotyping algorithms’ performance. Notably, it successfully categorized Alzheimer’s patients into two subgroups with varying mortality rates. Conclusion: The proposed ARCH algorithm generates large-scale high-quality semantic representations and knowledge graph for both codified and NLP EHR features, useful for a wide range of predictive modeling tasks.

Electronic health records↗

Molecular-level understanding of gibbsite particle aggregation in water

Using molecular dynamics simulations, we investigate the molecular scale origin of crystal face selectivity when one gibbsite particle attaches to another in water. A comparison of the free energy per unit surface area of particle–particle attachment indicates that particle attachment through edge surfaces, where the edge surfaces are either (1 0 0) or (1 1 0) crystal faces, is more energetically favorable compared to attachment between two basal surfaces (i.e., (0 0 1) crystal faces) or between the basal surface of one particle and the edge surface of another. This result suggests that gibbsite crystals with low basal/edge surface area ratio will preferentially attach through edge surfaces, potentially helping the crystals grow laterally. However, for larger gibbsite particles (high basal/edge surface area ratio) the total free energy, not normalized by surface area, of particle attachment through the basal surfaces is lower (more negative) than attachment through the edge surfaces, indicating that larger gibbsite particles will preferentially aggregate through basal surface attachments. The short-range electrostatic interactions including the interparticle hydrogen bonds from surface –OH groups drive particle attachment, and the dominant contribution to the free energy minimum is enthalpic rather than entropic. However, the enthalpy of basal-edge attachment is significantly offset by the entropy leading to a higher free energy (less negative) compared to that of basal-basal attachment. Study of the free energy for a few imperfect attachments of two particles indicates a higher free energy (i.e., less negative, less stable), compared to a perfect attachment

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Alkali-activated slag (AAS) and OPC-based composites containing crumb rubber aggregate: Physico-mechanical properties, durability and oxidation of rubber upon NaOH treatment

Value-added utilization of waste tires in cementitious materials has been studied for decades, whereas the synergy between rubber and alkali-activated cements deserves more investigations. To this end, we compared physico-mechanical and durability properties of alkali-activated slag (AAS) and OPC-based composites containing NaOH-pretreated/as-received crumb rubber (CR). It was found that the incorporation of CR had both positive and negative effects on specimens due to its special attributes. CR reduced electrical conductivity which was associated with the ion transport ability, since it worked as an electrical insulator and increased hydrophobicity of pore walls. The sulfate expansion decreased with CR content because the flow of sulfate ions was demobilized, and the flexibility of CR relieved the internal stress. CR also improved the freeze-thaw durability of composites if the total CR content was less than 30% in specimens. However, the low Young's modulus of CR impaired the compressive strength and failed to effectively control the total shrinkage upon drying. The composites with CR must avoid high temperature exposure which resulted in the pyrolysis of rubber. In addition, the NaOH pretreatment enhanced adhesion between CR and hydrated cement and improved overall performances of composites. The FTIR spectra confirmed the NaOH-induced accelerated oxidation of CR surface and the generation of polar functional groups including carbonyl and carboxyl groups, increasing the total surface energy of rubber. More importantly, the alkali-activation process for AAS could treat the CR aggregate in the meantime, which means the use of CR in alkali-activated cements does not require the pretreatment of CR before blending.

36 MATERIALS SCIENCE↗

Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate

Here we use a real-space formulation of orbital-free DFT to study the core energetics and core structure of an isolated screw dislocation in Aluminum. Using a direct energetics based approach, we estimate the core size of a perfect screw dislocation to be ≈ 7 |b|, which is considerably larger than previous estimates of 1–3 |b| based on displacement fields. The perfect screw upon structural relaxation dissociates into two Shockley partials with partial separation distances of 8.2 Å and 6.6 Å measured from the screw and edge component differential displacement plots, respectively. Similar to a previous electronic structure study on edge dislocation, we find that the core energy of the relaxed screw dislocation is not a constant, but strongly dependent on macroscopic deformations. Next, we use the edge and screw dislocation core energetics data with physically reasonable assumptions to develop a continuum energetics model for an aggregate of dislocations that accounts for the core energy dependence on macroscopic deformations. Further, we use this energetics model in a discrete dislocation network, and from the variations of the core energy with respect to the nodal positions of the network, we obtain the nodal core force which can directly be incorporated into discrete dislocation dynamics frameworks. We analyze and classify the nodal core force into three different contributions based on their decay behavior. Two of these contributions to the core force, both arising from the core energy dependence on macroscopic deformations, are not accounted for in currently used discrete dislocation dynamics models which assume the core energy to be a constant excepting for its dependence on the dislocation line orientation. Using case studies involving simple dislocation structures, we demonstrate that the contribution to the core force from the core energy dependence on macroscopic deformations can be significant in comparison to the elastic Peach–Koehler force even up to distances of 10–15 nm between dislocation structures. Thus, these core effects, whose origins are in the electronic structure of the dislocation core, can play an important role in influencing dislocation-dislocation interactions to much larger distances than considered heretofore.

36 MATERIALS SCIENCE↗

Aggregation and data analysis of corrosion studies in molten chloride and fluoride salts

Corrosion studies in molten fluoride and chloride salts were surveyed, and key data were aggregated into a single dataset. Studies were graphed by salt purity, temperature, sample material, container material, and experimental method (loop, capsule, crucible). To elucidate and quantify the factors that affect corrosion in molten salts, a data analysis using a newly-defined corrosion resistance score and a correlation analysis using techniques borrowed from machine learning were performed. It is shown that salt purity had the strongest correlation with corrosion rates in molten chlorides and fluorides. As a result, data analysis across varied works was inconsistent due to the lack of standardization among molten salt corrosion studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Single-crystal-like NiO colloidal nanocrystal-aggregated microspheres with mesoporous structure: Synthesis and enhanced electrochemistry, photocatalysis and water treatment properties

A new microwave-assisted hydrothermal synthetic route based on the self-assembly and subsequently controlled thermal decomposition process is proposed to fabricate nickel oxide colloidal nanocrystal aggregated microspheres (CNAMs) with mesoporous structure. XRD, EDS, SEM, TEM. FTIR, and N{sub 2} adsorption and desorption isotherm techniques are employed for morphology and structure characterizations. The as-prepared nickel oxide CNAMs, which has a high surface area (234 m{sup 2}/g) with narrow pore distribution at around 3.25 nm, are composed of numerous hexagonal mesoporous nanocrystals of approximately 50–60 nm in size, and present a single-crystal-like characteristic. The experimental results also demonstrated that the CNAMs showed outstanding performance in electrochemistry, photocatalysis and waste water treatment due to their special hierarchical and mesoporous structure, presenting the promising candidate for catalysis and catalysis support materials. - Graphical abstract: CNAMs with mesoporous structure synthesized via a simple microwave-assisted hydrothermal method was applied in electrochemistry and catalysis and exhibited enhanced performance. Display Omitted - Highlights: • CNAMs with mesoporous structure are achieved via a simple microwave-assisted hydrothermal method. • Morphology, structure and pore distribution of sample particles is specifically controlled. • The samples show enhanced properties in electrochemistry and catalysis due to hierarchical structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Grain size determination in nano-scale polycrystalline aggregates by precession illumination-hollow cone dark field imaging in the transmission electron microscope

Precession illumination hollow cone dark field (PI-HCDF) transmission electron microscopy (TEM) provides high contrast multi-beam dark field images, which are suitable for effective and robust grain size measurements in nano-scale polycrystalline aggregates. Precession illumination with slightly converged electron beam probes and precession angles up to 3 Degree-Sign has been produced using a computer-controlled system using a JEOL JEM 2000FX TEM instrument. Theoretical and practical aspects of the experimental technique are discussed using example precession illumination hollow cone diffraction patterns from single crystalline NiAl and the importance of selecting the appropriate precession angle for PI-HCDF image formation and interpretation is described. Results obtained for precession illumination are compared with those of conventional parallel beam illumination experiments. Nanocrystalline Al has been used to evaluate the influence of the precession angle on PI-HCDF image contrast with a focus on grain size analysis. PI-HCDF imaging has been applied for grain size measurements in regions of a nanocrystalline Al thin film adjacent to the edge of a pulsed laser melted and rapidly solidified region and determined the dimensions of a heat-affected zone. - Highlights: Black-Right-Pointing-Pointer New TEM method for grain size measurements combines TEM resolution with obtainability of statistically significant data sets. Black-Right-Pointing-Pointer We use precession illumination to produce time precession illumination hollow cone diffraction patterns PI-HCDP. Black-Right-Pointing-Pointer Contrast in dark field images (PI-HCDF) formed from PI-HCDP is easy to interpret as dynamical effects are reduced. Black-Right-Pointing-Pointer PI-HCDFs use several time-averaged g-rings simultaneously and contain more information than conventional DF-images. Black-Right-Pointing-Pointer Easy contrast interpretation and less dark field images required, allows fast, robust and reliable grain size determination.

36 MATERIALS SCIENCE↗

Studies on densification, mechanical, micro-structural and structure–properties relationship of magnesium aluminate spinel refractory aggregates prepared from Indian magnesite

The present work intends to study the development of magnesium aluminate spinel aggregates from Indian magnesite in a single firing stage. The raw magnesite has been evaluated in terms of chemical analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction. The experimental batch containing Indian magnesite and calcined alumina has been sintered in the temperature range of 1550 °C–1700 °C. The sintered material has been characterized in terms of physico-chemical properties like bulk density, apparent porosity, true density, relative density and thermo-mechanical/mechanical properties like hot modulus of rupture, thermal shock resistance, cold modulus of rupture and structural properties by X-ray diffraction in terms of phase identification and evaluation of crystal structure parameters of corresponding phases by Rietveld analysis. The microstructures developed at different temperatures have been analyzed by field emission scanning electron microscope study and compositional analysis of the developed phase has been carried out by energy dispersive X-ray study. - Highlights: • The studies have been done to characterize the developed magnesium aluminate spinel. • The studies reveal correlation between refractory behavior of spinel and developed microstructures. • The studies show the values of lattice parameters of developed phases.

36 MATERIALS SCIENCE↗

Template-free hydrothermal synthesis of 3D hollow aggregate spherical structure WO3 nano-plates and photocatalytic properties

Highlights: • WO{sub 3} is a promising candidate of photocatalyst. • The hollow spherical structure is synthesized by hydrothermal synthesis. • This hollow structure consists of WO{sub 3} nano-plates. • WO{sub 3} nano-plates are obtained by addition of high concentration HNO{sub 3}. • Porous WO{sub 3} structure exhibits wonderful photocatalytic activity. - Abstract: A new kind of 3D hollow aggregate spherical structure WO{sub 3} nano-plates was prepared via a simple hydrothermal synthesis without any template. In this paper, the effects of HNO{sub 3} addition on the preparation of WO{sub 3} powder were systematically investigated. With HNO{sub 3} concentration increasing, the product was converted from WO{sub 3}(H{sub 2}O){sub 0.33} to monoclinic WO{sub 3}·H{sub 2}O until the reaction to complete. Meanwhile, the morphology and size of particles changed from mocro-scale spheres to nano-plates. In the WO{sub 3}·H{sub 2}O structure, H{sub 2}O integrates the H{sub 2}O molecules via hydrogen bond, while WO{sub 3} bonds with other WO{sub 3} molecules and finally form a hollow spherical structure. During subsequent drying, WO{sub 3}·H{sub 2}O is deprived of crystal water to become monoclinic WO{sub 3}, remaining this porous spherical structure. Compared with the industry-use catalyst of Degussa P25 TiO{sub 2}, the as-prepared WO{sub 3} exhibits the wonderful photocatalytic activity due to the plate-like morphology and porous structure.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

Highlights: ► A concrete formulation was optimized using Bottom Ash and APC ash. ► 10% of APC ash achieves good compromise between economic and performance aspects. ► The crushed concrete was evaluated as secondary building granular material. ► The environmental behavior allows its use as secondary material. ► The abrasion resistance is not good enough for its use as a road sub-base material. - Abstract: The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incineration (MSWI) bottom ash (BA) and air pollution control (APC) fly ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behavior whilst maximizing the reuse of APC fly ash was considered and assessed. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC fly ash content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Platelet endothelial aggregation receptor-1 (PEAR1) is involved in C2C12 myoblast differentiation

Highlights: • PEAR1 is upregulated during murine C2C12 myoblast differentiation. • Changing PEAR1 expression alters the levels of myogenic markers. • PEAR1 is involved in muscle regeneration in vivo. • PEAR1 affects skeletal muscle cell differentiation. C2C12 murine myoblasts are a common model for studying muscle differentiation. Platelet endothelial aggregation receptor-1 (PEAR1), an epidermal growth factor repeat-containing transmembrane receptor, is known to participate in platelet contact-induced activation. In the present study, we demonstrated that PEAR1 is involved in the differentiation of C2C12 murine myoblasts. Western blotting and immunofluorescence staining were used to determine PEAR1 expression and localization during C2C12 cell differentiation. Subsequently, PEAR1 expression was activated and inhibited using clustered regularly interspaced short palindromic repeats-dCas9 technology to explore its effects on this process. PEAR1 expression was found to increase over the course of C2C12 cell differentiation. This protein was predominately localized on the membrane of these cells, where it clustered upon induction of differentiation. Expression of the myogenic markers Desmin, MYOG, and MYH2 revealed that PEAR1 positively regulated C2C12 cell differentiation. Moreover, induction of muscle injury by administration of bupivacaine to mice indicated that PEAR1 might play a role in muscle regeneration. In summary, our study confirmed the involvement of PEAR1 in C2C12 cell differentiation, contributing to our understanding of the molecular mechanisms underlying muscle development.

60 APPLIED LIFE SCIENCES↗

Polyphenols Weaken Pea Protein Gel by Formation of Large Aggregates with Diminished Noncovalent Interactions

Polyphenols are well-known native cross-linkers and gel strengthening agents for many animal proteins. However, their role in modifying plant protein gels remains unclear. In this study, multiple techniques were applied to unravel the influence of green tea polyphenols (GTP) on pea protein gels and the underlying mechanisms. We found that the elasticity and viscosity of pea protein gels decreased with increased GTP. The protein backbone became less rigid when GTP was present based on shortened T 1ρ H in relaxation solid-state NMR measurements. Electron microscopy and small-angle X-ray scattering showed that gels weakened by GTP possessed disrupted networks with the presence of large protein aggregates. Solvent extraction and molecular dynamic simulation revealed a reduction in hydrophobic interactions and hydrogen bonds among proteins in gels containing GTP. The current findings may be applicable to other plant proteins for greater control of gel structures in the presence of polyphenols, expanding their utilization in food and biomedical applications.

59 BASIC BIOLOGICAL SCIENCES↗

Highly Emissive Semi-Ladder-Type Copolymers, Aggregation State, and Solution-Processed Organic Light-Emitting Transistor

An organic light-emitting transistor (OLET) integrates the logic function of a field-effect transistor (FET) with electroluminescence of a light-emitting diode (LED) into a single device. This has the potential to play an important role in smart displays, electrically pumped organic laser, and other flexible electronic devices. For achieving high-performance solution-processed OLET, three semiladder copolymers—TPTI-CC, TPTI-C, and TPTI-F—were developed in this study. It was found that variation in the chemical structure lead to significant differences in energy level, emission color, and intermolecular aggregation. High photoluminescence quantum yields (PLQY) was obtained in these three polymers. Solution-processed trilayered OLET devices were fabricated, which exhibited strong electroluminescence, balanced charge mobility, and external quantum efficiency (EQE) of 2.8%.

36 MATERIALS SCIENCE↗

Shape Control of Colloidal Semiconductor Nanocrystals through Thermodynamically Driven Aggregative Growth

The optoelectronic properties of colloidal semiconductor nanocrystals (NCs) can be manipulated by changing their geometric shapes. The precise synthetic control over particle morphologies, however, has remained elusive. Conventional growth techniques rely on the kinetic assembly of atomic units, where supersaturation and precipitation processes can lead to a broad distribution of particle shapes. In this paper, we demonstrate that replacing atomic precursors with small-size nanocrystals as building blocks for larger colloids offers an easier, more predictive control over nanoparticle shape evolution. The reported growth strategy is illustrated via shape-selective syntheses of CdSe and CdS NC cubes, spheres, rods, as well as unprecedented “donut” and ring-like structures. Growth of desired particle morphologies was achieved by choosing an appropriate reaction solvent that minimizes the surface free energy through a unique shape formation. This so-called "aggregative growth mechanism" is explained using a thermodynamic model for interacting viscous colloids. We expect that this novel growth strategy will offer a viable platform for shape–selective synthesis of many inorganic colloids, providing pathways to optimizable optoelectronic materials.

36 MATERIALS SCIENCE↗