Low Density Research Articles

Electrocatalytic Acetylene Hydrogenation in Concentrated Seawater at Industrial Current Densities.

Electrocatalytic acetylene hydrogenation to ethylene (E-AHE) is a promising alternative for thermal-catalytic process, yet it suffers from low current densities and efficiency. Here, we achieved a 71.2% Faradaic efficiency (FE) of E-AHE at a large partial current density of 1.0 A cm-2 using concentrated seawater as an electrolyte, which can be recycled from the brine waste (0.96 M NaCl) of alkaline seawater electrolysis (ASE). Mechanistic studies unveiled that cation of concentrated seawater dynamically prompted unsaturated interfacial water dissociation to provide protons for enhanced E-AHE. As a result, compared with freshwater, a twofold increase of FE of E-AHE was achieved on concentrated seawater-based electrolysis. We also demonstrated an integrated system of ASE and E-AHE for hydrogen and ethylene production, in which the obtained brine output from ASE was directly fed into E-AHE process without any further treatment for continuously cyclic operations. This innovative system delivered outstanding FE and selectivity of ethylene surpassed 97.0% and 97.5% respectively across wide-industrial current density range (≤ 0.6 A cm-2). This work provides a significant advance of electrocatalytic ethylene production coupling with brine refining of seawater electrolysis.

Density Mediates the Predator-Induced Growth and Metamorphic Plasticity of Chinhai Spiny Newt Larvae

Predators significantly influence amphibian larval development. Predator-induced plasticity is often studied independently from conspecific density effects, but these environmental factors may interact. We conducted two-factor factorial experimental design to manipulate conspecific density and predator cues, aiming to investigate the independently or interactive impacts of these two factors on the development of Chinhai spiny newt larvae (Echinotriton chinhaiensis). Our findings reveal that both high and low conspecific densities constrain spiny newt larval growth and predators also limit growth. Interestingly, high conspecific density restricts predator-induced growth plasticity without interacting effects. Only lower density groups exhibit slower growth responses to predators. Our study investigates how density mediates predator-induced plasticity in the endangered Chinhai spiny newt larvae, providing insights into their intricate life history. These results contribute to the understanding of predator-induced plasticity in amphibians and provide insights into the adaptive strategies of endangered species like Chinhai spiny newt. Such knowledge informs the development of effective conservation strategies for their protection.

Dockless bike sharing in Singapore: perceptions of stakeholders, tensions of management, and implications for the public space

ABSTRACT Dockless bike sharing has experienced remarkable expansion, with significant impacts on public spaces and intense social debates. This paper presents a case study of Singapore to analyze perceptions of different stakeholders about dockless bike sharing within the public domain. A content analysis of 229 news articles is conducted, where the entire process and focused topics are summarized, and perceptions of four stakeholders are mapped and compared. Debates among stakeholders focused on its role in the transport system, severity and causes of indiscriminate parking, and the strictness of regulatory requirements. The core was managing its usage of public space, involving tensions between under and over management. Two dilemmas are highlighted, including oversupply against low bike density, and flexible parking against high expectations of orderliness and cleanliness. Nevertheless, it is argued that dockless bike sharing can be a catalyst for promoting cycling and reinventing public space, with advocating three interconnected opportunities.

Lipoprotein glomerulopathy with markedly increased arterial stiffness successfully treated with a combination of fenofibrate and losartan: a case report

BackgroundLipoprotein glomerulopathy (LPG) is a apolipoprotein E (ApoE)-related glomerular disease and has been associated with type III hyperlipidemia. Without appropriate treatment, chronic kidney disease (CKD) caused by LPG progresses, and approximately half of the patients develop end-stage kidney disease within 1–27 years of disease onset. However, few studies have highlighted the clinical course of cardiovascular diseases (CVDs) in patients with LPG. Herein, we report the first case of LPG in which the CVD risk was assessed using arterial stiffness.Case presentationA 32-year-old Japanese man was referred to our hospital due to persistent proteinuria. Kidney biopsy showed markedly dilated capillary lumens containing pale-stained thrombi, which stained positively with Oil Red O. Electron microscopy revealed the presence of thrombi in the capillary lumen with low electron density and vacuoles of various sizes in part of the thrombi. Toluidine blue and Sudan IV stains were used to stain the thin sections of Epon-embedded tissue samples for electron microscopy. Sudan IV-positive droplets were observed in the capillary lumens, vascular walls, and cytoplasm of tubular cells. Increased serum ApoE concentration was observed. Liquid chromatography-tandem mass spectrometry of laser-microdissected glomeruli from paraffin sections revealed an increase in ApoE. Direct deoxyribonucleic acid sequencing of ApoE revealed a heterozygous ApoE Sendai mutation (Arg145Pro). The patient was finally diagnosed with LPG with heterozygosity for ApoE-Sendai mutation (Arg145Pro). Notably, at the time of diagnosis, he had markedly increased arterial stiffness for his age. Arterial stiffness was measured using brachial-ankle pulse wave velocity (baPWV), which was equivalent to that of a 56-year-old man. After three months of treatment with fenofibrate and losartan, a significant reduction in proteinuria was achieved along with an improvement in baPWV. Furthermore, these effects were maintained despite the lack of decrease in serum ApoE levels.ConclusionHerein, we report the case of a patient with LPG with markedly increased arterial stiffness at the time of diagnosis, in whom combination therapy with fenofibrate and losartan successfully improved proteinuria and arterial stiffness. To the best of our knowledge, this is the first case report of LPG in which CVD risk was assessed using arterial stiffness.

Clinical differences between periprosthetic and native distal femur fractures: a comparative observational study

IntroductionThe incidence of periprosthetic distal femur fractures (PDFF) is increasing as the number of total knee replacements becomes more common. This study compared the demographics, fracture characteristics, treatment, and outcomes of periprosthetic versus native distal femur fractures (NDFF).Materials and methodsThis was a retrospective cohort study of patients ≥ 18 who underwent surgical fixation of NDFF or PDFF from 2012 to 2020 at a level-1 trauma center. The main variables collected included demographics, AO/OTA fracture classification, fixation construct, concomitant fractures, polytrauma rates, bone density, and reduction quality. Primary outcomes were unexpected return to the operating room (UROR), hospital length of stay, and quality of reduction. T-tests, Fisher’s exact tests, and multivariate analyses were used for statistical analysis.Results209 patients were identified, including 70 PDFF and 139 NDFF. PDFF patients were elderly females (81%) with isolated (80%) and comminuted (85%) 33 A.3 (71%) fractures. NDFF patients included 53% females, were commonly middle-aged, and displayed comminuted (92%) 33 C.2 fractures. 48% of NDFF patients had concomitant fractures. Intramedullary nailing was the primary fixation for both groups, followed by nail-plate combination (37%) for PDFF and lateral locking plates (21%) for NDFF. NDFF patients experienced significantly longer hospital stays, higher UROR rates, and worse quality of reduction (p < 0.05). PDFF patients had a significantly greater prevalence of low bone density (p < 0.05).ConclusionPDFF occur as isolated injuries with significant metaphyseal comminution in elderly females with low bone quality. NDFF commonly occurs in younger patients with less metaphyseal comminution and concomitant fractures. Intramedullary nailing was the most common treatment for both groups, although preference for nail-plate combination fixation is increasing. NDFF type 33 C fractures are at greater risk of UROR.

Molecular sibship reconstruction reveals a promiscuous mating system in brood parasitic little bronze-cuckoos (Chalcites minutillus)

Abstract In theory, emancipation from parental care is expected to favour promiscuous mating systems. However, in avian brood parasites monogamy is surprisingly widespread and it has been proposed that this may be favoured by factors such as low population density and territoriality. Correspondingly, our previous research revealed that brood parasitic Horsfield’s bronze-cuckoos (Chalcites basalis), which occur at low population densities and defend territories, are monogamous. Here, we contrast this study with the mating system of the congeneric little bronze-cuckoo (C. minutillus), an obligate brood parasite that exploits more concentrated hosts and is therefore likely to occur at higher population densities. We use single nucleotide polymorphisms to characterise the reproductive patterns of unsampled adults by inferring sibling relationships among 30 offspring. We show that 1) little bronze-cuckoos occurred at high densities, 2) polygamy was the most common mating pattern found in this study in both sexes, and 3) where multiple cuckoo eggs are laid in the same nest, they were unrelated. These results indicate that females do not defend exclusive territories and males do not defend multiple females (polygyny). Instead, little bronze-cuckoos appear to have a non-territorial, promiscuous mating system. Our results are consistent with theoretical predictions that polygamy is more likely to evolve in species that are emancipated from parental care, where there are plenty of available mates and where home ranges are not defended.

Broadband and ascendant nonlinear optical properties of the wide bandgap material GaN nanowires

Gallium nitride (GaN) nanowire, as a type of wide bandgap nanomaterial, has attracted considerable interest because of its outstanding physicochemical properties and applications in energy storage and photoelectric devices. In this study, we prepared GaN nanowires via a facile chemical vapor deposition method and investigated their nonlinear absorption responses ranging from ultraviolet to near-infrared in the z-scan technology under irradiation by picosecond laser pulses. The experiment revealed that GaN nanowires exhibit remarkable nonlinear absorption characteristics attributed to their wide bandgap and nanostructure, including saturable absorption and reverse saturable absorption. When compared to bulk GaN crystals, the nanowires provide a richer and more potent set of nonlinear optical effects. Furthermore, we conducted an analysis of the corresponding electronic transition processes associated with photon absorption. Under high peak power density laser excitation, two-photon absorption or three-photon absorption dominate, with maximum modulation depths of 73.6%, 74.9%, 63.1% and 64.3% at 266 nm, 355 nm, 532 nm, and 1064 nm, respectively, corresponding to absorption coefficients of 0.22 cm/GW, 0.28 cm/GW, 0.08 cm/GW, and 2.82 ×10−4 cm3/GW2. At lower peak energy densities, GaN nanowires demonstrate rare and excellent saturation absorption characteristics at wavelength of 355 nm due to interband transitions, while saturable absorption is also observed at 532 nm and 1064 nm due to band tail absorption. The modulation depths are 85.2%, 41.9%, and 13.7% for 355 nm, 532 nm, and 1064 nm, corresponding to saturation intensities of 3.39 GW/cm2, 5.58 GW/cm2 and 14.13 GW/cm2. This indicates that GaN nanowires can be utilized as broadband optical limiters and high-performance pulse laser modulating devices, particularly for scarce ultraviolet optical limiters, and saturable absorbers for ultraviolet and visible lasers. Furthermore, our study demonstrates the application potential of wide bandgap nanomaterials in nonlinear optical devices.

Varying primordial state fractions in exo- and endothermic SIDM simulations of Milky Way-mass haloes

Abstract Self-interacting dark matter (SIDM) is increasingly studied as a potential solution to small-scale discrepancies between simulations of cold dark matter (CDM) and observations. We examine a physically motivated two-state SIDM model with both elastic and inelastic scatterings. In particular, endothermic, exothermic, and elastic scattering have equal transfer cross sections at high relative velocities (vrel ≳ 400 km s−1). In a suite of cosmological zoom-in simulation of Milky Way-size haloes, we vary the primordial state fractions to understand the impact of inelastic dark matter self-interactions on halo structure and evolution. In particular, we test how the initial conditions impact the present-day properties of dark matter haloes. Depending on the primordial state fraction, scattering reactions will be dominated by either exothermic or endothermic effects for high and low initial excited state fractions respectively. We find that increasing the initial excited fraction reduces the mass of the main halo, as well as the number of subhaloes on all mass scales. The main haloes are cored, with lower inner densities and higher outer densities compared with CDM. Additionally, we find that the shape of the main halo becomes more spherical the higher the initial excited state fraction is. Finally, we show that the number of satellites steadily decreases with initial excited state fraction across all satellite masses.

Synergistic Improvement of Antibacterial and Osteogenic Differentiation of Thermomechanically Processed Mg-Zr-Sr-Ce Alloy: Insights into the Role of Precipitate Evolution Supported by AIMD Simulation Study.

In the present study, we have discussed the influence of forging temperature (623 K (FT623), 723 K (FT723) and 823 K (FT823)) on microstructure and texture evolution and its implication on mechanical behavior, in vitro-in vivo biocorrosion, antibacterial response, and cytocompatibility of microalloyed Mg-Zr-Sr-Ce alloy. Phase analysis, SEM, and TEM characterization confirm the presence of Mg12Ce precipitate, and its stability was further validated by performing ab initio molecular dynamic simulation study. FT723 exhibits strengthened basal texture, higher fraction of second phases, and particle-stimulated nucleation-assisted DRX grains compared to other two specimens, resulting in superior strength with comparable ductility. FT723 also exhibits superior corrosion resistance mainly due to the strengthened basal texture and lower dislocation density. All the specimens exhibit excellent antibacterial behavior with Gram-negative E. coli, Gram-positive Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. 100% reduction of bacterial growth is observed within 24 h of culture of the specimens. Cytocompatibility was determined by challenging specimen extracts with the MC3T3-E1 cell lines. FT723 specimen exhibits the highest cell proliferation and alkaline phosphatase activity (ALP) because of its superior corrosion resistance. The ability of the specimens to be used in orthopedic implant application was evaluated by in vivo study in rabbit femur. Neither tissue-related infection nor the detrimental effect surrounding the implant was confirmed from histological analysis. Significant higher bone regeneration surrounding the FT723 specimen was observed in SEM analysis and fluorochrome labeling. After 60 days, the FT723 specimen exhibits the highest bone formation, suggesting it is a suitable candidate for orthopedic implant application.

The falling of a tree in the forest is the beginning of significant changes in the soil

Abstract Aims The aim of the project was to determine the vertical variability of soil under the influence of deadwood (DWD) in a temperate forest ecosystem. Methods The laboratory analyses included soil layers of 0–5 cm, 5–10 cm, 10–20 cm and 20–40 cm, which were taken directly under the deadwood, as well as the forest litter layer and deadwood fragments. The control samples were taken 30 m away. Results The decomposition processes of deadwood are associated with a 55% increase in soil organic carbon (SOC) deposition to a depth of -40 cm and a 36% increase in total nitrogen (N) content compared to soils without deadwood. DWD significantly increases exchangeable cations, especially at a depth of -5 cm to -20 cm. Deadwood contains slightly more hydrogen (H+) and aluminum ions (Al3+) than forest litter, but soil acidification is related to pedogenic processes rather than decomposition of deadwood in hyperacid forest soils. The soil surface under deadwood with a high degree of decomposition is characterised by a lower bulk density (BD) value than the soil where only forest litter was present. Conclusions Our studies suggest that the physicochemical properties of forest soils change under the influence of deadwood such that the deeper layers beneath the logs take on propertie8s that make them similar to the shallower layers without deadwood. To summarise, leaving deadwood in the forest has a positive effect on soil fertility by enriching the soil with nutrients (Ca2+, K+, Na+, less Mg2+) and improving its physical properties.

Analysis of 3760 hematologic malignancies reveals rare transcriptomic aberrations of driver genes

BackgroundRare oncogenic driver events, particularly affecting the expression or splicing of driver genes, are suspected to substantially contribute to the large heterogeneity of hematologic malignancies. However, their identification remains challenging.MethodsTo address this issue, we generated the largest dataset to date of matched whole genome sequencing and total RNA sequencing of hematologic malignancies from 3760 patients spanning 24 disease entities. Taking advantage of our dataset size, we focused on discovering rare regulatory aberrations. Therefore, we called expression and splicing outliers using an extension of the workflow DROP (Detection of RNA Outliers Pipeline) and AbSplice, a variant effect predictor that identifies genetic variants causing aberrant splicing. We next trained a machine learning model integrating these results to prioritize new candidate disease-specific driver genes.ResultsWe found a median of seven expression outlier genes, two splicing outlier genes, and two rare splice-affecting variants per sample. Each category showed significant enrichment for already well-characterized driver genes, with odds ratios exceeding three among genes called in more than five samples. On held-out data, our integrative modeling significantly outperformed modeling based solely on genomic data and revealed promising novel candidate driver genes. Remarkably, we found a truncated form of the low density lipoprotein receptor LRP1B transcript to be aberrantly overexpressed in about half of hairy cell leukemia variant (HCL-V) samples and, to a lesser extent, in closely related B-cell neoplasms. This observation, which was confirmed in an independent cohort, suggests LRP1B as a novel marker for a HCL-V subclass and a yet unreported functional role of LRP1B within these rare entities.ConclusionsAltogether, our census of expression and splicing outliers for 24 hematologic malignancy entities and the companion computational workflow constitute unique resources to deepen our understanding of rare oncogenic events in hematologic cancers.

A warm Neptune's methane reveals core mass and vigorous atmospheric mixing.

Observations of transiting gas giant exoplanets have revealed a pervasive depletion of methane1,2,3,4, which has only recently been identified atmospherically5,6. The depletion is thought to be maintained by disequilibrium processes such as photochemistry or mixing from a hotter interior7,8,9. However, the interiors are largely unconstrained along with the vertical mixing strength and only upper limits on the CH4 depletion have been available. The warm Neptune WASP-107 b stands out among exoplanets with an unusually low density, reported low core mass10, and temperatures amenable to CH4 though previous observations have yet to find the molecule2,4. Here we present a JWST NIRSpec transmission spectrum of WASP-107 b which shows features from both SO2 and CH4 along with H2O, CO2, and CO. We detect methane with 4.2σ significance at an abundance of 1.0±0.5 ppm, which is depleted by 3 orders of magnitude relative to equilibrium expectations. Our results are highly constraining for the atmosphere and interior, which indicate the envelope has a super-solar metallicity of 43±8× solar, a hot interior with an intrinsic temperature of Tint=460±40 K, and vigorous vertical mixing which depletes CH4 with a diffusion coefficient of Kzz = 1011.6±0.1 cm2/s. Photochemistry has a negligible effect on the CH4 abundance, but is needed to account for the SO2. We infer a core mass of M⊕, which is much higher than previous upper limits10, releasing a tension with core-accretion models11.

Comparison of Current Induced Domain Wall Motion Driven by Spin Transfer Torque and by Spin Orbit Torque in Ferrimagnetic GdFeCo Wires

Current-induced domain wall motion (CIDWM) in magnetic wires can be driven by spin transfer torque (STT) originating from transferring angular momentums of spin-polarized conducting electrons to the magnetic DW and can be driven by spin orbit torque (SOT) originating from the spin Hall effect (SHE) in a heavy metal layer and Dzyaloshinsky Moriya (DMI) generated at an interface between a heavy metal layer and a magnetic layer. In this work, we carried out a comparative study of CIDWM driven by STT and by SOT in ferrimagnetic GdFeCo wires with magnetic perpendicular anisotropy based on structures of SiN (10 nm)/GdFeCo (8 nm)/SiN (10 nm) and Pt (5 nm)/GdFeCo (8 nm)/SiN (10 nm). We found that CIDWM driven by SOT exhibited a much lower critical current density (JC), and much higher DW mobility (µDW). Our work might be useful for the realization and the development of low-power and high-speed memory devices.

A pool construction using ramie fabric composite in eco-resin matrix: a cost of goods sold analysis (COGS)

One of the oldest and most traditional products made with resin and fiberglass is swimming pools; however, this product consumes large quantities of fiberglass mat and resin, both raw materials are based on non-renewable products and contribute significantly to carbon footprint and environmental damage. The increasing environmental concern has raised awareness in the industry and academia for the search of environmentally friendly materials. Natural fibers are attracting interest in engineering sectors due to specific advantages such as low density and cost, as well as renewability, biodegradability, recycling, and CO2 emission neutrality. In particular, the fiber extracted from the stem of the ramie plant is currently recognized as one of the strongest lignocellulosic fibers. In addition to natural fibers, eco-resins such as water-based acrylics have gained great attention from the industry due to their carbon footprint and environmentally friendly characteristics. The aim of this work is to calculate the cost of goods sold (COGS) for a pool constructed with composite ramie fabric in a water-based eco-resin matrix, for this purpose, a 1:30 scale prototype will be made, from which all manufacturing costs will be collected, then we will perform a mathematical extrapolation for comparison of values with products currently available in the market.

Appendicular lean mass and the risk of stroke and Alzheimer’s disease: a mendelian randomization study

BackgroundAppendicular lean mass (ALM) is a good predictive biomarker for sarcopenia. And previous studies have reported the association between ALM and stroke or Alzheimer’s disease (AD), however, the causal relationship is still unclear, The purpose of this study was to evaluate whether genetically predicted ALM is causally associated with the risk of stroke and AD by performing Mendelian randomization (MR) analyses.MethodsA two-sample MR study was designed. Genetic variants associated with the ALM were obtained from a large genome-wide association study (GWAS) and utilized as instrumental variables (IVs). Summary-level data for stroke and AD were generated from the corresponding GWASs. We used random-effect inverse-variance weighted (IVW) as the main method for estimating causal effects, complemented by several sensitivity analyses, including the weighted median, MR-Egger, and MR-pleiotropy residual sum and outlier (MR-PRESSO) methods. Multivariable analysis was further conducted to adjust for confounding factors, including body mass index (BMI), type 2 diabetes mellitus (T2DM), low density lipoprotein-C (LDL-C), and atrial fibrillation (AF).ResultsThe present MR study indicated significant inverse associations of genetically predicted ALM with any ischemic stroke ([AIS], odds ratio [OR], 0.93; 95% confidence interval [CI], 0.89–0.97; P = 0.002) and AD (OR, 090; 95% CI 0.85–0.96; P = 0.001). Regarding the subtypes of AIS, genetically predicted ALM was related to the risk of large artery stroke ([LAS], OR, 0.86; 95% CI 0.77–0.95; P = 0.005) and small vessel stroke ([SVS], OR, 0.80; 95% CI 0.73–0.89; P < 0.001). Regarding multivariable MR analysis, ALM retained the stable effect on AIS when adjusting for BMI, LDL-C, and AF, while a suggestive association was observed after adjusting for T2DM. And the estimated effect of ALM on LAS was significant after adjustment for BMI and AF, while a suggestive association was found after adjusting for T2DM and LDL-C. Besides, the estimated effects of ALM were still significant on SVS and AD after adjustment for BMI, T2DM, LDL-C, and AF.ConclusionsThe two-sample MR analysis indicated that genetically predicted ALM was negatively related to AIS and AD. And the subgroup analysis of AIS revealed a negative causal effect of genetically predicted ALM on LAS or SVS. Future studies are required to further investigate the underlying mechanisms.

Development of polyamide foam by supercritical CO2: Low density, anti-shrinkage and thermal insulation

Saving energy and reducing environmental harmful emissions have become a global concern, so the foam thermal insulation materials are of great significance for saving energy, reducing greenhouse effect and ensuring the comfort and safety requirements of buildings. Polyamide12 (PA12) has outstanding weather resistance, mechanical stability and termite resistance, which is a promising building material. Herein, we prepared a series of PA12 foams by using supercritical carbon dioxide (Sc-CO2) as foaming agent, polymethyl methacrylate (PMMA) as a blend modification material, tridehydroglycerol isocyanurate (TGIC) as chain extender improved the cells wall strength and stability. When the PA12 and PMMA blending ratio was 70:30 and TGIC content was 0.2 phr, the foam density was 0.02 g/cm3, and the thermal conductivity of the foam was as low as 0.0302 W/m·K. Moreover, the influence of viscosity gradually increased with the increase of PMMA as shown by tanδ; at the same time, as an amorphous material, PMMA enlarged the melting range of the blends and reduced the enthalpy of melting. Therefore, the introduction of PMMA increased the temperature range of the foaming window to170–190 °C. This study provided an effective method for the design of foams with low density, low shrinkage, excellent mechanical properties and high thermal insulation properties, which has broad PA12 foam application prospects in the fields of buildings, such as wall or roof insulation.

Effect of dual dispersion of carbon fiber and silica nanoparticles on recovery performance of shape memory epoxy

Abstract Shape memory polymers (SMP) are utilized in diverse fields, including deployable structures and components, owing to their advantageous properties like low density, cost-effectiveness, and ease of processing. The current study investigates the effect of dual dispersion of carbon fibers (CF) and silica nanoparticles (SN) on the recovery performance of shape memory epoxy composites. CF (0.25 wt.%) reinforced epoxy composite, SN (0.25 wt.%) reinforced epoxy composite, and dual (CF and SN 0.25 wt.% each) dispersed epoxy composite were developed using magnetic stirring and ultrasonic mixing to study the mechanical properties and shape memory behaviour. Flexural strength, tensile strength and fracture toughness of pristine epoxy was found to be 134.38 MPa, 52.15 MPa and 1.91 MPa∙m1/2, respectively. The addition of CF resulted in a flexural strength of 135.70 MPa and a tensile strength of 53.01 MPa, while the incorporation of SN led to a flexural and tensile strength of 138.40 MPa and 53.69 MPa, respectively. The fracture toughness of composites after adding CF and SN was found to be 2.22 MPa∙m1/2 and 2.39 MPa∙m1/2, respectively. With dual dispersion, the flexural strength of 139.82 MPa, tensile strength of 54.64 MPa, and fracture toughness of 2.75 MPa∙m1/2 were achieved. Dual dispersion has shown improved mechanical properties compared to single dispersion. The introduction of CF slightly decreased the shape fixity ratio (Rf) and shape recovery ratio (Rr) of the pristine epoxy from 98.67% and 96.62% to 96.67% and 95.15%, respectively. Similarly, the addition of SN further reduced these ratios to 98.00% and 91.83%, respectively. With a dual dispersion approach Rf and Rr were observed to be about 97.33% and 93.83%, respectively. The addition of fillers led to a reduction in Rf and Rr due to inhibition of polymeric chains, resulting in partial shape recovery. However, recovery time improved from 28 s to 23 s and 26 s with addition of CF and SN, respectively, in epoxy. With dual dispersion, a speedy recovery was achieved with a recovery time of 21 s. The findings of this study demonstrate the potential of dual dispersed fillers to improve the mechanical and shape memory properties of epoxy, which could find applications in the smart materials and structural engineering.

High gain NiO/ZnO heterojunction photodiodes operated in Deep-ultraviolet region

Epitaxially matched (0001) Al2O3 single substrates are utilized to design p-n heterojunctions (p-NiO/n-ZnO) as they offer low defect density for device fabrication due to small lattice mismatches. Using the radio frequency sputtering technique, the NiO/ZnO thin film-based heterojunction has been fabricated by varying the n-type film's (ZnO) thickness for ultra-violet (UV) photodiode application. It has been investigated how different ZnO film thicknesses affect junction parameters and photoresponse properties. The high photosensitivity (∼ 104), enhanced current gain (∼ 105) and fast response obtained at very low UV intensity (0.62μW/cm2) at 300 nm wavelength are attributed to the internal gain mechanism (recombination tunnelling and space-charge limited current conduction with the remarkable effect of the presence of excess free oxygen) in these devices. The prepared heterojunction photodiode with high speed and deep-UV sensitivity can be a potential solution for visible blind UV detection.

Application of laboratory micro X-ray fluorescence devices for X-ray topography

It is demonstrated that high-resolution energy-dispersive X-ray fluorescence mapping devices based on a micro-focused beam are not restricted to high-speed analyses of element distributions or to the detection of different grains, twins and subgrains in crystalline materials but can also be used for the detection of dislocations in high-quality single crystals. Si single crystals with low dislocation densities were selected as model materials to visualize the position of dislocations by the spatially resolved measurement of Bragg-peak intensity fluctuations. These originate from the most distorted planes caused by the stress fields of dislocations. The results obtained by this approach are compared with laboratory-based Lang X-ray topographs. The presented methodology yields comparable results and it is of particular interest in the field of crystal growth, where fast chemical and microstructural characterization feedback loops are indispensable for short and efficient development times. The beam divergence was reduced via an aperture management system to facilitate the visualization of dislocations for virtually as-grown, non-polished and non-planar samples with a very pronounced surface profile.

Sintering of 3D-printed aluminum specimens from the slurry-based binder jetting process

AbstractThis work investigates a novel method of producing complex-shaped aluminum parts by slurry-based binder jetting and sintering. In this process, a green body is built up by layer-wise deposition of an aqueous aluminum suspension and selective powder bonding by ink-jet printing. The powder bulk generated from the suspension shows an increased density compared to powder-based binder jetting and, thus, a high initial density for the subsequent densification step. This allows for higher final densities and reduced shrinkage. Aluminum is of special interest as it is widely available and of low density but challenging to sinter due to an oxide skin surrounding every particle. The research in this paper investigates the effects of the sintering atmosphere and sintering additives on the microstructure of powder compacts produced by slurry-based binder jetting. The incorporation of magnesium as an additive during the sintering process of aluminum has been found to substantially improve densification during sintering in an argon atmosphere.