Average Aspect Ratio Research Articles

Modelling of functionally graded triply periodic minimal surface (FG-TPMS) plates

Functionally graded porous plates have been validated as remarkable lightweight structures with excellent mechanical characteristics and numerous applications. With inspiration from the high strength-to-volume ratio of triply periodic minimal surface (TPMS) structures, a new model of porous plates, which is called a functionally graded TPMS (FG-TPMS) plate, is investigated in this paper. Three TPMS architectures including Primitive (P), Gyroid (G), and wrapped package-graph (IWP) with different graded functions are presented. To predict the mechanical responses, a new fitting technique based on a two-phase piece-wise function is employed to evaluate the effective moduli of TPMS structures, including elastic modulus, shear modulus, and bulk modulus. In addition, this function corresponds to the cellular structure formulation in the context of relative density. The separated phases of the function are divided by the different deformation behaviours. Furthermore, another crucial mechanical property of porous structure, i.e, Poisson’s ratio, is also achieved by a similar fitting technique. To verify the mechanical characteristics of the FG-TPMS plate, the generalized displacement field is modelled by a seventh-order shear deformation theory (SeSDT). A NURBS-based isogeometric analysis (IGA) is then employed to capture the C1 continuity in approximations. Numerical examples regarding static, buckling, and free vibration analyses of FG-TPMS plates are illustrated to confirm the reliability and accuracy of the proposed approach. The influences of various porosity distributions, average relative densities, thickness-to-length ratios, aspect ratios, and boundary conditions on the plate responses are achieved. Consequently, these FG-TPMS structures can provide much higher stiffness than the same-weight isotropic plate. The greater stiffness-to-weight ratio of these porous plates compared to the full-weight isotropic ones should be considered the most remarkable feature. Thus, these complex porous structures have numerous practical applications because of these high ratios and their fabrication ability through additive manufacturing (AM) technology.

Clinical Relevance of Computationally Derived Attributes of Peritubular Capillaries from Kidney Biopsies.

The association between peritubular capillary (PTC) density and disease progression has been studied in a variety of kidney diseases using immunohistochemistry. However, other PTC attributes such as PTC shape have not been explored yet. The recent development of computer vision techniques provides the opportunity for the quantification of PTC attributes using conventional stains and whole slide images. To explore the relationship between PTC characteristics and clinical outcome, n=280 periodic acid Schiff-stained kidney biopsies (88 minimal change disease, 109 focal segmental glomerulosclerosis, 46 membranous nephropathy, and 37 IgA nephropathy) from the NEPTUNE digital pathology repository were computationally analyzed. A previously validated deep learning model was applied to segment cortical PTCs. Average PTC aspect ratio (the PTC major to minor axis ratio), size (PTC pixels per PTC segmentation), and density (PTC pixels per unit cortical area) were computed for each biopsy. Cox proportional hazards models were used to assess associations between these PTC parameters and outcome (40% eGFR decline or kidney failure). Cortical PTC characteristics, and interstitial fractional space PTC density were compared between areas of interstitial fibrosis and tubular atrophy (IFTA) and areas without IFTA. When normalized PTC aspect ratio was below 0.6, a 0.1 increase in normalized PTC aspect ratio was significantly associated with disease progression, with a hazard ratio (95% confidence interval) of 1.28 (1.04-1.59) (p=0.019), while PTC density and size were not significantly associated with outcome. Interstitial fractional space PTC density was lower in areas of IFTA compared to non-IFTA areas. Computational image analysis enables quantification of the status of the kidney microvasculature and the discovery of a previously unrecognized PTC biomarker (aspect ratio) of clinical outcome.

High-temperature vapor permeation of preferentially b-oriented zeolite MFI membranes fabricated from nanocrystal-containing nanosheets

Zeolite nanosheets can be used to effectively fabricate high-performance separation membranes; however, their direct synthesis is generally complicated, particularly when attempting to achieve an ideal two-dimensional morphology. Nanosheets for structure-type MFI were simply synthesized via the single hydrothermal treatment of nanocrystal seeds, which inevitably resulted in center thickening owing to the presence of the nanocrystal seeds and the formation of adlayers. Nevertheless, the extensive analysis of the morphology of these nanocrystal-containing nanosheets confirmed that their average thicknesses (∼13 nm) and aspect ratios (∼87) were more favorable for membrane fabrication than those of other zeolite MFI materials (e.g., plate-type MFI materials). The zeolite MFI membranes fabricated from the nanocrystal-containing nanosheets exhibited a high flux (1.2 × 10−3 mol·m−2·s−1) and separation factor (795) at high temperatures (250 °C), which were more favorable than those of zeolite MFI membranes fabricated from conventional zeolite MFI materials.

Chemical Modification of Human Decellularized Extracellular Matrix for Incorporation into Phototunable Hybrid-Hydrogel Models of Tissue Fibrosis.

Tissue fibrosis remains a serious health condition with high morbidity and mortality rates. There is a critical need to engineer model systems that better recapitulate the spatial and temporal changes in the fibrotic extracellular microenvironment and enable study of the cellular and molecular alterations that occur during pathogenesis. Here, we present a process for chemically modifying human decellularized extracellular matrix (dECM) and incorporating it into a dynamically tunable hybrid-hydrogel system containing a poly(ethylene glycol)-α methacrylate (PEGαMA) backbone. Following modification and characterization, an off-stoichiometry thiol-ene Michael addition reaction resulted in hybrid-hydrogels with mechanical properties that could be tuned to recapitulate many healthy tissue types. Next, photoinitiated, free-radical homopolymerization of excess α-methacrylates increased crosslinking density and hybrid-hydrogel elastic modulus to mimic a fibrotic microenvironment. The incorporation of dECM into the PEGαMA hydrogel decreased the elastic modulus and, relative to fully synthetic hydrogels, increased the swelling ratio, the average molecular weight between crosslinks, and the mesh size of hybrid-hydrogel networks. These changes were proportional to the amount of dECM incorporated into the network. Dynamic stiffening increased the elastic modulus and decreased the swelling ratio, average molecular weight between crosslinks, and the mesh size of hybrid-hydrogels, as expected. Stiffening also activated human fibroblasts, as measured by increases in average cellular aspect ratio (1.59 ± 0.02 to 2.98 ± 0.20) and expression of α-smooth muscle actin (αSMA). Fibroblasts expressing αSMA increased from 25.8 to 49.1% upon dynamic stiffening, demonstrating that hybrid-hydrogels containing human dECM support investigation of dynamic mechanosensing. These results improve our understanding of the biomolecular networks formed within hybrid-hydrogels: this fully human phototunable hybrid-hydrogel system will enable researchers to control and decouple the biochemical changes that occur during fibrotic pathogenesis from the resulting increases in stiffness to study the dynamic cell-matrix interactions that perpetuate fibrotic diseases.

Carbon quantum dots induced one-dimensional ordered growth of single crystal TiO2 nanowires while boosting photoelectrochemistry properties

TiO2 nanowire arrays (TNWAs) thin film of flexible substrates has great application potential in photoelectrochemical (PEC) hydrogen evolution. Moreover, the photoquantum efficiency of TNWAs can be effectively enhanced by reducing the nanoscale as much as possible or combining with other co-catalysts. This work presents a simple and effective strategy for the synthesis of ultrafine TiO2 nanowire arrays by a one-step hydrothermal method using CQDs as an inducer for single crystal growth. Meanwhile, CQDs recombine on the surface of TNWAs to form CQDs/TNWAs heterojunction during the synthesis process. The synthesized TNWAs have well ordered separability, whose average diameter is regulated at 11.21 nm with an average aspect ratio of 1097. PEC analysis showed that the performance of TNWAs was significantly improved compared with initial TiO2 with unregulated morphology. The charge separation efficiency increased by 120%, applied bias photon-to-current efficiency (ABPE) reached 0.37%(0.68 v vs RHE), and incident photon-to-current conversion efficiency (IPCE) reached 50.31% (380 nm). The influence of TiO2 nano-morphology optimization and formation of CQDs/TiO2 heterojunction on the PEC performance were discussed in detail.

Effect of Magnesium Treatment and Cooling Method on Manganese Sulfide in U75V Heavy‐Rail Steel Deoxidized by Si–Mn

The effect of magnesium (Mg) on the morphology of sulfides in silicon–manganese deoxidized low‐sulfur and low‐aluminum steels is investigated by adding different amounts of nickel–magnesium (Ni–Mg) alloy to a heavy‐rail steel U75V melt and cooling the melt from 1600 °C to room temperature under different conditions. Herein, the effects of Mg content and cooling rate on MnS inclusions are investigated. It is indicated that with an increase in the Mg content in molten steel from 0 to 64 ppm, the main composition of inclusions changes following the path of CaO–SiO2–Al2O3 → MgO–Al2O3–MnS → MgO–MnS–MgS. Mg significantly inhibits the precipitation of long‐strip MnS and can decrease the average size and aspect ratio of the inclusions. Under furnace cooling, when Mg is 41 ppm, the minimum aspect ratio of the inclusions is 1.61. The higher the cooling rate, the smaller the inclusion size; however, compared to water and furnace coolings, with cooling rates of 126.3 and 0.12 °C s−1, respectively, the inclusion aspect ratio of the air‐cooling conditions with a cooling rate of 67.7 °C s−1 is low. Finally, thermal simulations verify the effect of Mg treatment on the suppression of MnS deformation during rolling.

Leakage Flow Impact on Shrouded Stator Cavity Flow Topology and Associated High-Speed Axial Compressor Stage Performance

AbstractThis paper presents the investigation of realistic cavity leakage flow for the von Karman Institute for Fluid Dynamics H25 axial compressor stage, equipped with a shroud cavity of average Reynolds number Rer = 2.2 * 106 and average aspect ratio G = 0.06. On top of overall performance measurements, time averaged data from unprecedented experimental dataset are used to characterize the stator hub shroud cavity flow field and its interaction with the power stream. The sensitivity of the stage performance and stability as well as the cavity flow topology is evaluated against injection conditions, compressor throttling, and compressor speed. Parametric steady RANS simulations of the stage under injection are used to support the findings and state on the relevance of such approach in the preliminary design phase of axial compressor components. As an example, a stage efficiency reduction of 0.97% for a leakage fraction of 0.56% at design point is retrieved. This performance drop is attributed to the effect of cavity flow on: the blockage ratio, the boundary layer skewness, and total temperature increase at stator row inlet. It is also presented that there is a mutual interaction between the cavity geometry and the cavity flow field organization. The injection homogenizes the cavity flow field and the associated pressure gradient. The various operating conditions presented also demonstrate that the cavity flow studied is, on average (i.e., time), sensitive to changes in compressor rotation speed and changes in stage loading.

Abstract Number ‐ 59: Study on Rupture Prediction Model for Small Unruptured Cerebral Aneurysms Using Random Forest

Introduction Hemodynamic, morphological, and clinical factors have been reported to be involved in aneurysm rupture. Hemodynamic factors could be calculated by computational fluid dynamics (CFD) analysis. In addition, machine learning has been used in various medical fields in recent years, and it is expected to be applicable to the prediction of aneurysm rupture. In this study, we built a rupture prediction model for the small aneurysms (3∼10 mm) using Random Forest, which is one of the machine learning algorithms. This model included hemodynamic parameters from CFD simulations, morphological parameters of each aneurysm, and clinical information. The model was applied to the other patient dataset, and we verified the model’s prediction accuracy. Methods In this study, the ruptured case was defined as an aneurysm that ruptured during the follow‐up term. On the other hand, the unruptured case was defined as an aneurysm that remained stable during the follow‐up for more than two years (average follow‐up term is about nine years), and registered in the database of Jikei Hospital between January 1, 2003 and April 30, 2020. Only small aneurysms (3∼10 mm) were considered in the present study. Based on the criteria, we identified 507 aneurysms (ruptured: 41, unruptured: 466), in which CFD analysis has been completed. Among these aneurysms, 405 aneurysms (ruptured: 32, unruptured: 373) were used to build the rupture prediction model as Training data, and 102 aneurysms (ruptured: 9, unruptured: 93) were used to verify the prediction accuracy as Test data. We used 3‐dimensional arterial geometries that were reconstructed from computed tomography angiography images for conducting CFD simulations and morphological measurements. For the ruptured aneurysms, the image acquired before the rupture was used. We obtained 138 hemodynamic parameters, 7 morphological parameters, and 6 clinical information in each case. From the Training data, we proposed the rupture prediction model with these parameters using Random Forest. Then, we introduced the test data into the model, and its sensitivity and specificity were estimated. Results The sensitivity and specificity of this model for the Test data were 88.9% and 83.9%, respectively. In addition, aspect ratio (AR), the maximum height of the cerebral aneurysm (Hmax), and the spatially maximum values of the oscillatory shear index on the aneurysm wall (OSImax) were obtained as the top three of the important features to predict aneurysm rupture. Furthermore, the values of these parameters of ruptured aneurysms are higher than those of unruptured aneurysms. For unruptured and ruptured cases, average AR were 0.770±0.260 [‐] and 1.02±0.382 [‐], average Hmax were 3.39±1.22 [mm] and 4.96±1.96 [mm], and average OSImax were 0.399±0.105 [‐] and 0.460±0.0328 [‐], respectively. These results imply that cerebral aneurysms with high Hmax, high AR, and high OSImax are more likely to rupture. Conclusions Ruptured aneurysms tend to have high AR, high Hmax, and high OSImax. The sensitivity and specificity of our prediction model were 88.9% and 83.9%, respectively. The rupture prediction model obtained from this study may predict the aneurysm rupture in advance.

Upcycling of waste plasterboard for the synthesis of high-quality gypsum-based 3D printing powder

A large number of waste gypsum was reused of low-value or landfilled which caused serious waste of resources. In this study, a high value-added recycling scheme for waste building gypsum to synthesize a 3D printable material with high-precision was designed. The α-hemihydrate gypsum (α-HH) was synthesized from waste plasterboard by the salt solution hydrothermal method. A synergistic optimization strategy was proposed involving the effect of sodium succinate and pH on the morphology and mechanical strength of α-HH. The properties of recycled α-HH were modified to meet the requirements of 3D printing, including fluidity, setting time and green strength. When the modifier dosage is 0.05 wt% and the pH is 5, the best morphology of α-HH crystals with an average aspect ratio of 1.07 (length of 10 μm) are synthesized. The converted product has close interlocking and intergrowth after hydration, which exhibits excellent mechanical strength (25.5 MPa). The 3D printing materials prepared by the composite modification of recycled α gypsum powder has proven to achieve good printable. The print errors smaller than 4% for pore objects larger than 4.0 mm, and satisfactory results are shown in terms of the strength and resolution of printing high detail cavity structures. This work provides a high value-added upcycling scheme for waste building gypsum that has great potentiality for future industrial application.

How the existence of unstable neutral media restricts the aspect ratio of cold neutral media?

ABSTRACT The ubiquity of very thin and lengthy cold neutral medium (CNM) has been reported by multiple authors in the H i community. Yet, the reason of how the CNM can be so long and lengthy is still in debate. In this paper, we recognize a new type of instability due to the attractive nature of the pressure force in the unstable phase. We provide a new estimation of the average CNM filament aspect ratio with the consideration of force balances at the phase boundary, which is roughly 5–20 in common CNM environment. We show that most of the cold filaments are less filamentary than what usually predicted via MHD turbulence theory or inferred from observations: The average length of CNM filament is roughly 1/2 of that in isothermal MHD turbulence with similar turbulence conditions. This suggests that the ‘cold filaments’ that are identified in observations might not be in pressure equilibrium or generated via other mechanisms.

An efficient approach to extract nanocrystalline cellulose from sisal fibers: Structural, morphological, thermal and antibacterial analysis

Nanocellulose has been proposed by many researchers as a suitable bio-reinforcement material for the development of sustainable bio-nanocomposites in advanced applications due to its excellent properties. Conventional techniques for extracting nanocellulose from plant biomass are time-consuming and involve chemical wastage. This study aims to extract nanocellulose using simple processes with minimal consumption of chemicals in a minimum time. In the present work, cellulose nanocrystalline has been extracted from sisal fibers efficiently by chemical treatment assisted with steam explosion and mechanical grinding. The morphology of extracted sisal cellulose nanocrystalline (CNC-S) was analyzed by FESEM, whereas the DLS, TEM and AFM confirmed its nanosize. The average aspect ratio and zeta potential (ζ) of CNC-S were measured as 7.4 and −14.3 mV, respectively. The XRD analysis indicated that the crystallinity of the fibers considerably improved from 48.74 % for untreated fibers (UT-S) to 74.28 % for CNC-S. The chemical structure of the fibers was changed as hemicellulose and lignin were found to be eliminated after the chemical treatment which FTIR confirmed. From TGA-DTG results, it was observed that CNC-S has good thermal stability. It was also noticed that CNC-S did not show any antibacterial properties against E. coli and S. aureus due to the complete removal of lignin. This study suggests that the present extraction process can be considered as an efficient process to convert fibers into high performance nanocellulose to be used as potential reinforcing material in advanced applications.

Utilization of phosphogypsum to synthesize α-hemihydrate gypsum in H3PO4–H2O solution

Phosphogypsum (PG) is a kind of industrial solid waste with high impurity content and low utilization rate. In this study, α-hemihydrate gypsum (α-HH) was synthesized from PG in H3PO4–H2O solution (wet-process phosphoric acid solution and phosphoric acid solution) under atmospheric pressure. The crystal morphology of α-HH was controlled by adding F and Al compound regulators, and the mechanical properties of α-HH were improved. The difference of α-HH synthesized by PG with different qualities was analyzed, and the mechanism of α-HH morphology was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy-dispersive spectroscopy (EDS). Results showed that in the wet-process phosphoric acid solution, α-HH synthesized from white PG (by H3PO4–H2SO4 two-step method) had better whiteness, purity, and mechanical properties compared with that from industrial PG, and the performance indexes of the α-HH products met the requirements of α50 grade in JC/T 2038–2010 α-high-strength gypsum in China and have a good commercial application prospect. Moreover, in the phosphoric acid solution, the average diameter of the α-HH crystal increased from 8.1 µm to 54.8 µm, the average aspect (L/D) ratio decreased from 32.65 to 0.52, and the induction period and growth period of the α-HH crystal were prolonged with the increase in regulator dosage. F− and Al3+ ions were preferred to adsorb on the crystal faces. The growth of the crystal parallel to c-axis (200), (020), and (400) was inhibited, and the morphology of the α-HH crystal changed from whisker to short column. When the dosage of the regulator was 1.1 %, the 2 h bending strength of the α-HH product was 6.56 MPa, and the drying compressive strength was 52.4 MPa. This study provides a new technique and method for the synthesis of high-strength α-HH products from PG.

Effects of the Pore Morphology on Multiphase Fluid Displacement in Porous Media-A High-Resolution Modeling Investigation.

Advances in computational and image acquisition capabilities have made direct simulation of multiphase fluid flow through porous media possible. An example is application of volume of fluid modeling on images produced using the X-ray computed micro-tomography technique. Analysis of such high-resolution (both temporal and spatial) data sets provides new insights into pore-scale dynamics of previously less well-known processes. We present the outcomes of a high-resolution direct-simulation two-phase fluid displacement study performed on a series of five two-dimensional images of sandy porous media produced using erosion and dilation algorithms. This has enabled us to study the pore-scale dynamics systematically in models that are similar in connectivity but different in the morphology (pore sizes and aspect ratio). Our results show that the drainage and imbibition processes result in very distinct fluid displacement patterns in these models at the pore scale. As a result of drainage, the more open (eroded grains) models accommodate large oil clusters, while the tighter (dilated grains) models trap smaller oil clusters. The imbibition process is dominated by oil trapping in two ways: (i) bypassing larger oil clusters in the eroded models and (ii) local trapping of smaller clusters in the dilated models. This behavior is shown to arise from the relatively larger average aspect ratios of the dilated models compared to those of the eroded models. This promotes snap-off at pore throats (in competition with piston-like displacement), resulting in local trapping of the non-wetting phase. Both of these pore-scale trapping regimes seen here allow trapping of oil in as much as 50% of the pore space. Through the use of erosion and dilation operations, we show that a power-law relationship exists between the average pore size and the average grain size for these sandy media. This relationship is useful in designing engineered porous materials where pore sizes need to be estimated based on grain sizes.

Nd2O3-Ag Nanostructures for Plasmonic Biosensing, Antimicrobial, and Anticancer Applications

Green synthesis of nanomaterials with multifaceted applications in photonics as well as biomedical fields has remained a daunting challenge. Engineering multielement nanohybrid libraries with synergistic surface functionalities from dielectric and metallic nanocomponents using sustainable approaches is seldom reported. In this context, we demonstrate a 1 min, user- and eco-friendly, sunlight-based green synthesis of Nd2O3-Ag, dielectric–metal ferroplasmon nanohybrids with detailed elucidation of the mechanism. Chemical anchoring of plasmonic Ag on high refractive index (n = 1.94), rare-earth Nd2O3 nanorods (average aspect ratio: ∼3) alleviates Ohmic losses without damping the plasmon resonances. Ferroplasmon-on-a-mirror (FPoM), an analogue to conventional nanoparticle-on-a-mirror (NPoM), is presented for efficient coupling of s-polarized light on account of magnetic flux modes supported by it. Apart from realization of room temperature ferromagnetism (RTFM) for nanophotonic applications, the judicious metal–nonmetal combination displayed excellent bactericidal, fungicidal, antioxidant, and anticancer properties, establishing a convergent “one health perspective” of engineered nanohybrids. Whereas the unconventional s-polarized plasmon-coupled emission obtained is utilized for sensing of food hazard Allura Red (limit of detection, LOD: 10 aM) in the FPoM platform, the p-polarized emission is used for 4-nitrophenol sensing (LOD: 100 fM). Excellent correlation between the exceptionally high Purcell factor (of 6.5 × 105 for the composite nanohybrid Nd2O3-Ag-carbon dot-graphene oxide) from simulations and experimentally obtained plasmon-coupled >2000-fold fluorescence emission enhancements is demonstrated. The utility of the proposed sunlight-induced nanoengineering to generate a library of nanocomposites comprising dielectric, metal, and graphitic plasmons is presented. We believe that the proposed methodology to generate hybrid nanomaterials with intriguing FPoM interfaces would be utilized for transdisciplinary nanophotonics as well as biomedical sensing applications.

Passively Q-switched 3 μm erbium-doped solid state lasers using gold nanorods as broadband saturable absorber

The gold nanorods with an average aspect ratio of 30 were grown by the three-step seed-mediated wet chemistry growth method, resulting in a broadband spectral response in 3 μm region. Passive Q-switching operation of LD pumped 2.8 μm Er:YSGG and 2.9 μm Er:YAP laser was successfully realized by using the gold nanorods as saturable absorber. With regard to the Er:YSGG laser, the passively Q-switched pulses at 2796 nm with a maximum average output power of 234 mW, a minimum pulse width of 270.8 ns and a pulse repetition rate of 280.4 kHz were achieved. For the combination of Er:YAP and gold nanorods saturable absorber, a maximum average output power of 415 mW was obtained at 2919 nm. The minimum pulse width and pulse repetition rate were 313.2 ns and 196.8 kHz, respectively. The experimental results show that large-aspect-ratio gold nanorods can be used as a promising broadband saturable absorber to generate 3 μm short pulses.

Influence of swift heavy ion irradiation on bimetallic gold-silver nanoparticles in dielectric matrices and their optical properties

Nanosized gold-silver (AuAg) alloy nanoparticles (NPs) of sizes, 2 nm -25 nm embedded in fused quartz are synthesized using sequential implantation and post annealing at 900℃ for 1 h in Argon environment. The post annealed film is irradiated using swift heavy ions (SHI), 120 MeV Ag ions to investigate the effect of electronic energy deposition, (Se×ϕ), on size, shape and composition of the alloy NPs. Transmission electron microscopy (TEM) analysis of the as- implanted AuAg film reveals the formation of small sized, 1.8 nm-3.5 nm, bimetallic AuAg NPs. Rutherford backscattering spectroscopy (RBS) spectra along with its fitted graph convey the annealing induced out diffusion, mixing and formation of larger sized, 2 nm -25 nm, alloy NPs through Ostwald ripening. SHI irradiation results in deformation in shape from spherical to ellipsoidal alloy NPs with major axis align along the beam direction and the average aspect ratio is about 1.20. RBS analysis results convey the formation of Ag enriched alloy NPs after irradiation. The smaller nanoparticles are found dissolved while larger ones grow and elongate along the ion beam direction. SPR properties are modified by SHI induced processes of melting, sputtering and re-precipitation in the ion tracks.The un-irradiated film exhibits a single intense SPR peak at 536 nm, while the irradiated film gives rise two SPR peaks: Ist, a blue shifted SPR peak from 536 nm to 515 nm with significantly reduced intensity and much wider FWHM; and, IInd, a small SPR peak around 460 nm. SHI induced modifications on the NPs are understood in terms of thermal spike model. The detailed analysis shows that SHI can be used as a tool to tailor size, shape and composition of the bimetallic AuAg alloy NPs and their SPR properties.

Time-Dependent Size and Shape Evolution of Gold and Europium Nanoparticles from a Bioproducing Microorganism, a Cyanobacterium: A Digitally Supported High-Resolution Image Analysis

Herein, the particle size distributions (PSDs) and shape analysis of in vivo bioproduced particles from aqueous Au3+ and Eu3+ solutions by the cyanobacterium Anabaena sp. are examined in detail at the nanoscale. Generally, biosynthesis is affected by numerous parameters. Therefore, it is challenging to find the key set points for generating tailored nanoparticles (NPs). PSDs and shape analysis of the Au and Eu-NPs were performed with ImageJ using high-resolution transmission electron microscopy (HR-TEM) images. As the HR-TEM image analysis reflects only a fraction of the detected NPs within the cells, additional PSDs of the complete cell were performed to determine the NP count and to evaluate the different accuracies. Furthermore, local PSDs were carried out at five randomly selected locations within a single cell to identify local hotspots or agglomerations. The PSDs show that particle size depends mainly on contact time, while the particle shape is hardly affected. The particles formed are distributed quite evenly within the cells. HR-PSDs for Au-NPs show an average equivalent circular diameter (ECD) of 8.4 nm (24 h) and 7.2 nm (51 h). In contrast, Eu-NPs preferably exhibit an average ECD of 10.6 nm (10 h) and 12.3 nm (244 h). Au-NPs are classified predominantly as "very round" with an average reciprocal aspect ratio (RAR) of ~0.9 and a Feret major axis ratio (FMR) of ~1.17. Eu-NPs mainly belong to the "rounded" class with a smaller RAR of ~0.6 and a FMR of ~1.3. These results show that an increase in contact time is not accompanied by an average particle growth for Au-NPs, but by a doubling of the particle number. Anabaena sp. is capable of biosorbing and bioreducing dissolved Au3+ and Eu3+ ions from aqueous solutions, generating nano-sized Au and Eu particles, respectively. Therefore, it is a low-cost, non-toxic and effective candidate for a rapid recovery of these sought-after metals via the bioproduction of NPs with defined sizes and shapes, providing a high potential for scale-up.

Shear response evaluation of sustainable self‐compacting concrete made up of recycled steel fibers of waste tyres

AbstractUse of rapidly increasing waste tyres can fetch the demand of green construction as well as prevent priceless land from becoming land dumps. The idea of using heavy traffic vehicle end‐of‐life tyres (HTV‐ELT) steel fibers is implemented to investigate the shear crack propagation and corresponding shear strength evolution of steel fiber‐reinforced green self‐compacting concrete (SFRGSCC). Three different average aspect ratios (25,35,45) mm were employed in two dosages (0.125% and 0.25% of total volume of matrix) in this work. It was determined that with the addition of end‐of‐life tyres steel fibers the rheological properties of SFRGSCC were decreased up to some extent but lies within the limiting value of the European Federation of National Associations Representing for Concrete (EFNARC). The addition of end‐of‐life tyres steel fibers showed a positive impact on postcracking behavior in shear. Interestingly, the experimental results indicated that the addition of end‐of‐life tyres steel fibers increased the ultimate shear strength of SFRGSCC beams as well as the compressive strength and splitting tensile strength of SFRGSCC. Whereas the crack width opening was significantly decreased besides controlling the deflection.

Galvani substitution modulated self-assembly of Cu@Pt nanowires with hierarchical microstructure for highly active hydrogen evolution

Felicitously incorporating noble metals with some transition metals to fabricate composite nanoagents with diverse shape and microarchitecture is a more promising solution for obtaining highly effective and cost-cutting catalyst. Herein, we report a facile and flexible synthesizing tactics, or Galvani substitution modulated self-assembly protocol, to fabricate Cu nanowire (core)-Pt nanoparticle (shell) unique microarchitecture (Cu-NWs@Pt) with porously hiberarchy. The comprehensive characterizations reveal that as-fabricated bimetallic nanowires with average aspect ratio of ca. 80 and apparent diameter of ca 60 nm, hold the razor-thin Cu–Pt alloy sublayer in the metallic contact interface, with the prebuilt Cu nanowires cladded by orderly oriented Pt nanograins to form loose, porous and stratiform structure. The thickness and microarchitecture of the Pt shell could be duly regulated by adjusting dosage of the metal precursors and substituting time. The verified formation of electronic synergic effect in the bimetallic nanoagents avails the adsorption of H to form metal-H species, leading to enhance the catalytic activity. Their catalytic ability overall increases with rising of Pt/Cu molar ratios, of which the Cu0.6Pt0.4 even exceeds Pt-NPs, with a turnover frequency of 77.26·min−1 and apparent activation energy of 30.25 kJ·mol−1, and maintaining 89% of the incipient catalytic ability after 5 recycling runs.

A facile method to produce rodlike β‐Si3N4 seed crystallites for bimodal structure controlling

Abstractβ‐Si3N4 rodlike seed crystallites were successfully produced by single‐step heat treatment of commercial α‐Si3N4 powder at 1900°C for 20 h under an N2 gas pressure of 980 kPa. The average diameter, length, and aspect ratio of the seed crystallites were 0.73 μm, 1.37 μm, and 1.86, respectively. The α‐ ⇀ β‐Si3N4 phase transformation proceeded mainly at 1900°C, and this temperature was lower than the theoretical α‐Si3N4 dissociation temperature (1933°C) under N2 gas pressure of 980 kPa. The formation of metastable solid solution due to the dissolution of O impurity into the α‐Si3N4 crystal lattice was suggested as the driving force for the present oxide additive‐free α‐ ⇀ β‐Si3N4 phase transformation. β‐Si3N4 ceramics were fabricated by liquid phase sintering promoted by an additive system of 1 wt% MgO with 3 wt% Gd2O3. Starting α‐Si3N4 powder with 10 vol% rodlike β‐Si3N4 seed crystallites prepared in this study and an extended sintering time for up to 20 h at 1950°C resulted in the formation of bimodal microstructure composed of fine matrix grains and large elongated grains originated from the seed crystallites. The β‐Si3N4 ceramics exhibited improved fracture toughness and thermal conductivity of 5.9 ± 0.8 MPa m−1/2 and 109.3 ± 0.4 W m−1 K−1, respectively, retaining a high fracture strength of about 1 GPa.