Small Voids Research Articles

Structure-dependent recruitment and diffusion of guest proteins in liquid droplets of FUS

Liquid droplets of a host protein, formed by liquid–liquid phase separation, recruit guest proteins and provide functional fields. Recruitment into p53 droplets is similar between disordered and folded guest proteins, whereas the diffusion of guest proteins inside droplets depends on their structural types. In this study, to elucidate how the recruitment and diffusion properties of guest proteins are affected by a host protein, we characterized the properties of guest proteins in fused in sarcoma (FUS) droplets using single-molecule fluorescence microscopy in comparison with p53 droplets. Unlike p53 droplets, disordered guest proteins were recruited into FUS droplets more efficiently than folded guest proteins, suggesting physical exclusion of the folded proteins from the small voids of the droplet. The recruitment did not appear to depend on the physical parameters (electrostatic or cation–π) of guests, implying that molecular size exclusion limits intermolecular interaction-assisted uptake. The diffusion of disordered guest proteins was comparable to that of the host FUS, whereas that of folded proteins varied widely, similar to the results for host p53. The scaling exponent of diffusion highlights the molecular sieving of large folded proteins in droplets. Finally, we proposed a molecular recruitment and diffusion model for guest proteins in FUS droplets.

Phase stability, mechanical properties, and ion irradiation effects in face-centered cubic CrFeMnNi compositionally complex solid-solution alloys at high temperatures

Two CrFeMnNi face-centered cubic complex concentrated solid-solution alloys (CSA) have been evaluated for phase stability, mechanical properties, and radiation damage effects from heavy ions. Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35 were predicted by thermodynamic calculations to phase separate and maintain a single phase at 700 °C, respectively. Aging experiments at this temperature confirmed varying degrees of precipitation of a body-centered cubic phase in both Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35. The alloys showed promising strength in tensile deformation at room temperature, with yield strengths of 155 MPa and 151 MPa for Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35, respectively. At 500 °C, the yield strength of Cr18Fe27Mn27Ni28 fell to 93 MPa, and to 100 MPa in Cr15Fe35Mn15Ni35. Unlike Cr18Fe27Mn27Ni28, Cr15Fe35Mn15Ni35 gained some ductility at 500 °C compared to room temperature. The two CSAs were irradiated to 75 dpa at 500 °C in the plateau region of the displacement curve using 3.7 MeV Ni2+ ions, alongside model alloy 709 as a reference. Irradiation results produced similar densities and sizes of dislocations loops in the two CSAs compared to the reference. However, while large voids form in the plateau region of Cr18Fe27Mn27Ni28, small voids form just beyond the displacement peak of Cr15Fe35Mn15Ni35. Atom probe tomography and energy dispersive X-ray spectroscopy-equipped scanning transmission electron microscopes were used to characterize the alloys for changes in chemical distribution.

Structural characterization and biological activities of a new polysaccharide isolated from Morchella Sextelata.

Morchella is the famous medicinal fungi in the ascomycetes. In this study, a new water-soluble polysaccharide (MSP-3-1) with an average molecular weight of 2.35 × 107 Da was extracted and purified from fruiting bodies of cultivated M. Sextelata. The structural characterization and biological activities of purified polysaccharide was further investigated. The results indicated that MSP-3-1 was mainly a α-glucan, mainly consisting of mannose (Man), glucose (Glc) and galactose (Gal) in a ratio of 5.10: 91.39: 3.51. Its surface morphology exhibited irregular lamellar structures with small voids. And the particle size analysis showed that MSP-3-1 was the homogeneous nanoparticle in water solution. Furthermore, the antioxidant activity analysis showed that MSP-3-1 possessed certain scavenging activity against hydroxyl radicals, DPPH radicals and ABTS radicals in a dose-dependent manner. Immunological tests suggested that MSP-3-1 could significantly promote the proliferation, phagocytosis and nitric oxide (NO) production of macrophage RAW264.7. Thus, our results will provide a theoretical basis for the development and utilization of Morchella Sextelata polysaccharides as an immunmodulatory component in functional foods.

High-speed penetration dynamics of polycarbonate

Ballistic impact experiments are conducted to investigate high-speed penetration of polycarbonate by steel spheres at impact velocities ranging from ∼600 to 2400 ms−1. High-speed photography is applied to capture the penetration processes, including projectile trajectories and cavity/damage evolution. Postmortem projectiles are characterized with three-dimensional laser scanning, and postmortem targets, with optical imaging and micro computed tomography. The maximum penetration depth varies nonmonotonically with impact velocity vi, and decreases with increasing vi above about 1777 ms−1. With increasing vi, the damage of polycarbonate targets increases significantly in amplitude and volume. The damage networks, consisting of cracks and voids, exhibit fractal features with similar fractal dimensions. At low vi, plate-shaped cracks are formed in the cavity, while needle-shaped cracks along with a large amount of melting-induced small voids, at high vi. Numerical simulations of impact penetration of polycarbonate reproduces well the experimental observations. Considering projectile distortion, a modified Poncelet model is derived to describe the nonmonotonic relation between the maximum penetration depth and vi.

Corrosion resistance of modified YSZ coatings subjected to CMAS attacks

ABSTRACT The deterioration of thermal barrier coatings in reaction engines due to Ca–Mg-Al–Si (CMAS) attacks has been an important issue in recent years. Al2O3–20 wt-% TiO2 (AT) powder was mechanically doped into yttria-stabilized zirconia (YSZ). The corresponding coatings were fabricated using APS to modify the CMAS corrosion resistance. The corrosion-induced microstructure evolution and the composition development in the YSZ and AT-YSZ coatings were investigated. The AT-YSZ coating contained smaller voids and fewer cracks with a much more obvious laminated structure in contrast with the YSZ coatings. After CMAS attack, the YSZ coating flaked off, while the AT-YSZ coating was strongly bonded to the substrate. Phases from tetragonal (t’-ZrO2) to monoclinic (m-ZrO2) were detected, while the MgAl2O4 spinel and gehlenite Ca2Al2Si2O8 phases were formed after the CMAS corrosion. AT20 exists independently in the AT-YSZ coating, which readily causes Al2O3 to accumulate in the CMAS and effectively arrests its infiltration.

Development of an analytical model for optimisation of the ultrasonic consolidation of composite prepreg

Mechanical properties of composite laminates are directly affected by the level of porosity of the part. Therefore, it is important to ensure that an adequate air debulking is provided during the manufacturing in order to obtain high quality products. The use of ultrasonic waves during the hand lay-up of prepreg layers can enhance this step. In a previous work we have demonstrated that this technique, named ultrasonic consolidation (UC), can lead to a large reduction in terms of manufacturing time and improvements of the Interlaminar Shear Strength (ILSS) of the final part. In this work, a model is proposed to analytically describe the influence of the ultrasonic stimulation on the air flux through the material and optimise the procedure, showing how the use of ultrasonic waves significantly increases the net air flow rate, particularly for small radius voids. The study provided some guidelines for the optimisation of the process parameters such as the frequency and location of the transducers. The efficiency of the method was experimentally validated by manufacturing several samples using UC debulking procedure with three exposition times (5-10-15 min). Microscope images showed a large decrement (up to 96%) of the voids projected area in samples section in comparison with reference. Flexural and Charpy impact properties were evaluated through mechanical tests, showing properties comparable to the reference samples, with improvements in terms of flexural modulus (up to 9%). Results from the analytical study and experimental tests indicate that the UC process is a reliable debulking procedure for the hand lay-up of prepreg that largely reduces manufacturing time and voids content, leading to improvements of the mechanical properties of the final part.

The surface mechanics of cooked rice as influenced by gastric fluids measured using a micro texture analyzer.

In this study, a micro texture analyzer (MTA) was employed to explore the texture characteristics of the surface of an individual steamed rice (SR) and fried rice (FR) grain exhibited in four simulated digestion environments in vitro. The elastic modulus, hardness and elastic index of the single cooked rice particle were measured using the MTA. The hardness of SR particles decreased by 66, 81, 89.1, and 95% after simulated digestion in distilled water, HCl, simulated gastric fluid (SGF), and simulated salivary and gastric fluid (SSF + SGF), respectively. This is in line with the most significant volume expansion and structure ruptures when digested in SSF + SGF. Similar mechanical and structural behaviors were shown for FR, but the hardness and elastic modulus decreased less than those of SR under the same digestion conditions. The different surface mechanics are consistent with the reduced expansion and more compact structure with smaller voids in FR during in vitro digestion. This could be attributed to the encapsulation by frying oil on the surface that would retard the diffusion of digestive fluids into the rice kernels. A weak negative correlation was found between the elastic modulus and the moisture content of the cooked rice. The present study has quantitatively assessed the surface mechanics of cooked rice as influenced by gastric fluids using the MTA. This is practically meaningful for gaining an in-depth understanding of the influence of textural modifications on disintegration of solid foods and release of nutrients during digestion.

Computed tomographic, ultrasonographic, MRI and radiographic findings of a venous malformation with phleboliths in the thoracic limb of a dog

AbstractAn 11‐month‐old entire male Rottweiler was referred for further investigation of raised, soft, compressible, non‐pulsatile, subcutaneous tubular structures along the right antebrachium that had been diagnosed to be a vascular malformation on histopathology of a subcutaneous biopsy. Computed tomographic (CT) with angiography did not reveal an arteriovenous malformation or fistula. Ultrasonography of the limb demonstrated a venous malformation with thrombi and phleboliths. An MRI study of the limb was consistent with a venous malformation with small rounded luminal signal voids that were confirmed to be phleboliths. Radiography at follow‐up demonstrated phleboliths. This is the first report describing the combined CT, ultrasonographic, MRI and radiographic characteristics of venous malformation with phleboliths in a limb of a dog.

Effect of Material Composition on Freeze-Thaw Resistance of Asphalt Fine Aggregate Matrix at Low-Temperatures From Mesoscopic Perspective

To explore the significant factors related to the cracking resistance at low temperatures of asphalt mixture from mesoscopic perspective, asphalt fine aggregate matrix (FAM) was selected as the researched material because of its important role in mesoscopic structure of asphalt mixture. Bending Beam Rheometer (BBR) was utilized to investigate low-temperature properties of FAM. Due to the frequent occurrence of freeze-thaw action in seasonally frozen regions, this paper introduces a freeze-thaw cycle test. The structural characteristics of internal air voids in FAM and hot-mix asphalt (HMA) were analyzed using the industrial Computerized Tomography (CT). Results indicate that frost heaving damage of FAM-2.36 is more obvious than that of FAM-1.18, and the damage level increases as the bath temperature rises. After 32 freeze-thaw cycles, FAM-1.18 exhibits the rise of creep stiffness than original beams, and the hardening degree become serious with the decease of temperature. It could be concluded that the BBR has been proved to be an effective tool in evaluating the low-temperature properties of FAM. The expanding limit of small air voids and the hardening of binder in rich asphalt FAM contribute to completely different mechanisms of freezing-thawing damage within FAM. Therefore, asphalt content, fine aggregate passing rate and air voids size could be optimized through BBR test of FAM subjected to freeze-thaw cycle.

In-situ X-ray computed tomography characterization of compaction-creep-recovery response and statistical void analysis of carbon/epoxy prepregs

Vacuum bag only (VBO) prepreg processing requires several time-consuming experimental trials in order to achieve a void volume fraction (Vv) of less than 2%. Alternatively, a limited number of in-situ X-ray computed tomography (XCT) compaction-creep experiments on prepregs under pressures that are equivalent to the VBO process can potentially reduce both time and cost whilst assisting in identifying and understanding the mechanisms associated with void formation during processing. In this study, compaction-creep tests at the first dwell temperature during the cure cycle were conducted at 0.1 MPa for different dwell periods (1, 2, and 4 h) using a specially-designed compression stage installed inside an XCT machine. Based on the thickness values measured at different stages of the test, the percentage of compaction-creep and permanent deformations were determined. Three-dimensional (3D) XCT-aided geometrical models were developed both before and after the compaction-creep tests, followed by Vv calculations at each stage. The results showed that higher levels of permanent deformation were recorded in samples tested using a dwell time of 4 h, due to a lower level of recovery compared to other dwell periods. Furthermore, the most suitable condition, in terms of the lowest Vv, was found in samples manufactured with a dwell time of 2 h, where relatively small voids, with a diameter less than 100 μm and a Vv of 0.57% were observed. These values are significantly lower than those observed in uncompressed samples which have many larger voids with a diameter greater than 200 μm and a Vv of approximately 15%.

Mechanism of void healing in cold rolled aeroengine M50 bearing steel under electroshocking treatment: A combined experimental and simulation study

M50 bearing steel, as the important material used in aeroengine bearing, exhibits low cold working capacity with high susceptibility to produce voids. This would lead to the deterioration of mechanical property, which critically limits the industrial application of cold ring rolling (CRR) in M50 bearing rings. In this work, the mechanism of void healing in cold rolled aeroengine M50 bearing steel subjected to electroshocking treatment (EST) was investigated by combining experimental and simulation studies. The experimental results obtained using the three-dimensional X-ray microscopy (3D-XRM) technique show that the porosity of the CRR samples decreases from 0.26% to 0.09% after EST. The healing effect of larger voids is not obvious, while small voids are likely to be healed under EST. The simulation results indicate that due to the inhomogeneous distribution of the physical field, the local thermal compressive stress of as high as 2565.9 MPa is generated around the ellipsoidal void and thus drives void healing process. The healing process of ellipsoidal voids under EST can be divided into elastic and plastic deformation stages considering von Mises yield criterion. In the initial stage, only a small elastic deformation of 53.53 nm occurs in the minor axis direction of the void. In the plastic deformation stage, the material flows along the normal direction of the void with a reduction in the aspect ratio, thereby compressing the void surfaces and promoting their healing. Additionally, the degree of void healing depends on the shape characteristics (curvature and aspect ratio) of the void rather than the current direction. This research elucidates a new elastoplastic mechanism of void healing under EST, which also provides a promising prospect for the application of CRR in M50 bearing steel. • In situ characterization of voids before and after EST was realized using 3D-XRM. • A new elastoplastic mechanism of void healing under EST was elucidated. • The driving force of void healing was revealed by analysing the physical field distribution. • The ellipsoidal void is healed with the reduction in the aspect ratio. • The degree of void healing depends on the shape of the void rather than the current direction.

Shear enhancement of mechanical and microstructural properties of synthetic graphite and ultra‐high molecular weight polyethylene carbon composites

AbstractUltra‐high molecular weight polyethylene (UHMWPE) has a variety of industrial and clinical applications due to its superb mechanical properties including ductility, tensile strength, and work‐to‐failure. The versatility of UHMWPE is hindered by the difficulty in processing the polymer into a well consolidated material. This study presents on the effects of shear imparted by equal channel angular pressing (ECAP) on UHMWPE composites containing Nano27 Synthetic Graphite (N27SG). Ductility and work‐to‐failure improvements up to ~60–80% are obtained in sheared N27SG‐UHMWPE composites as compared to non‐sheared N27SG‐UHMWPE controls of the same composition. Microscopy reveals increased fusion at particle boundaries and smaller voids in the sheared materials. Micro‐computed tomography results indicate different distribution of N27SG particulates in ECAP samples as compared to CM indicating enhanced grain boundary interactions. Tradeoffs are not avoided as ECAP samples were lower in conductivity as compared to compression molded (CM) billets of the same weight percent. However, ECAP samples were able to be doped with more N27SG allowing for an ~170% increase in conductivity over CM samples of the same work‐to‐failure. This work shows that ECAP is a viable processing method for obtaining stronger, more ductile conductive composite materials.

Carbon dioxide detection using polymer-coated fiber Bragg grating based on volume dilation mechanism and molecular dynamics simulation

Here, we report the polyimide-coated fiber Bragg gratings (FBGs) for CO2 detection based on the mechanism of CO2-induced volume dilation in the polyimide matrix, which resulted in a shift of the Bragg wavelength. The detection results indicate that the polyimide-coated FBGs were of good reversibility and repeatability within CO2-N2 cycles. The molecular mechanism was investigated through the analysis of radial distribution function (RDF) and free accessible volume distributions. The RDF analyses of N2, CH4 and CO2 gases reveal that CO2 has stronger intermolecular interactions with polyimide chains. In the adsorption process, the total fractional free volume inside the polyimide matrix increases as the CO2 concentration increases, simultaneously, the small voids in the polyimide matrix gradually turn into the large voids and the opposite trend is found in the desorption process. The maximum volume dilation values of two polyimide systems are 1.04% (Matrimid® 5218) and 1.13% (P84), thus the corresponding coefficients of gas-sensitive expansion are 3.47 × 10-5/vol% CO2 and 3.77 × 10-5/vol% CO2, respectively. Moreover, theoretical formulas of the relationship between the response strain of the sensor and the gas concentration were obtained, which is invaluable and generic and can be applied to detect various gases.

Multi-Dimensional Revealing the Influence Mechanism of the δ Phase on the Tensile Fracture Behavior of a Nickel-Based Superalloy on the Mesoscopic Scale.

As the key materials of aircraft engines, nickel-based superalloys have excellent comprehensive properties. Mircotensile experiments were carried out based on in situ digital image correlation (DIC) and in situ synchrotron radiation (SR) technique. The effects of the δ phase on the grain orientation, surface roughening, and strain localization were investigated. The results showed that the average kernel average misorientation (KAM) value of the fractured specimens increased significantly compared with that of the heat-treated specimens. The surface roughness decreased with an increasing volume fraction of the δ phase. The strain localization of specimens increased with the increasing ageing time. The size and volume fraction of voids gradually increased with the increase in plastic strain. Some small voids expanded into large voids with a complex morphology during micro-tensile deformation. The needle-like δ phase near the fracture broke into short rods, while the minor spherical δ phase did not break. The rod-like and needle-like δ phases provided channels for the propagation of the microcrack, and the accumulation of the microcrack eventually led to the fracture of specimens.

Giant Ln 30 -Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

Giant Ln ₃₀ -Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

Properties of spinel-type Ti-Li-M composite oxides (M = Li, Na, Cu, and Ag) predicted by density functional theory.

Spinel-type titanate is an important material already being used as a stable anode for Li-ion batteries. In addition, spinel titanate shows superconducting properties upon tuning the amount of Li+-doping; hence, research on magnetic and superconducting materials has been conducted. However, it is believed that only the tiny Li+ monocation can occupy the 8a sites due to its small voids and the charge valence with Ti cations. In recent years, new spinel-type titanium oxides have been discovered, in which 8a sites are occupied by Na+ or Ag+. Although the application of these new compounds to catalyst and electrode materials has been attempted, the effect of 8a site monocations on the physical properties of spinel-type titanium oxide is unclear. In this study, to systematise the effects of 8a-site monocations on the Ti-O framework, theoretical calculations based on density functional theory (DFT), such as GGA, GGA+U, and hybrid-DFT, were performed for the electronic structures and geometric stabilities of four spinel-titanium oxides: LTO (8a sites occupied by Li+), NTO (8a sites occupied by Na+), CTO (8a sites occupied by Cu+), and ATO (8a sites occupied by Ag+). Furthermore, to verify the effect of the partial substitution, Li+, Na+, Cu+, and Ag+ doping of LTO, NTO, CTO, and ATO was also investigated. Throughout these calculations, the performance of spinel-type titanates can be categorised by (1) the magnitude of O-displacement and (2) the orbital correlation between the Ti-O framework and the 8a site cations. By appropriately selecting cations, the spinel titanates can be applied to battery materials, catalysts, optical materials, photocatalysts, and precursors to these materials.

Effect of Pulse Frequency on Phase Composition and Properties of Amorphous Zirconium Alloy Micro-arc Oxidation Coating

The micro-arc oxidation coating was prepared on the surface of the amorphous zirconium sheet, and the influence of frequency on the micro-arc oxidation coating of the Zr-based amorphous alloy was studied. The results show that the change of the frequency of the electrical parameters of the micro-arc oxidation in the silicate micro-arc oxidation bath will promote the transformation of the t-ZrO2 phase to the m-ZrO2 phase in the coating; the frequency affects the gap, uniformity and thickness of the coating. When the frequency is 400 Hz, the coating surface has small voids and no cracks, and the thickness reaches a maximum of 15 μm. With the increase of frequency, the weight loss of the amorphous zirconium micro-arc oxidation coating first decreases and then increases. The wear resistance can be improved.

Cosmic voids in GAN-generated maps of large-scale structure

A Generative Adversarial Network (GAN) was used to investigate the statistics and properties of voids in a ΛCDM universe. The total number of voids and the distribution of void sizes is similar in both sets of images and, within the formal error bars, the mean void properties are consistent with each other. However, the generated images yield somewhat fewer small voids than do the simulated images. In addition, the generated images yield far fewer voids with central density contrast ∼−1. Because the generated images yield fewer of the emptiest voids, the distribution of the mean interior density contrast is systematically higher for the generated voids than it is for the simulated voids. The mean radial underdensity profiles of the largest voids are similar in both sets of images, but systematic differences are apparent. On small scales (r<0.5rv), the underdensity profiles of the voids in the generated images exceed those of the voids in the simulated images. On large scales (r>0.5rv), the underdensity profiles of the voids in the simulated images exceed those of the voids in the generated images. The discrepancies between the void properties in the two sets of images are attributable to the GAN struggling to capture absolute patterns in the data. In particular, the GAN produces too few pixels with density contrasts ∼−1 and too many pixels with density contrasts in the range ∼−0.88 to ∼−0.63.

Anti-fibrotic effect of tocotrienols for bladder dysfunction due to partial bladder outlet obstruction.

To investigate potential beneficial effects of tocotrienols which have been suggested to inhibit hypoxia-inducible factor (HIF) pathway, on partial bladder outlet obstruction (PBOO)-induced bladder pathology. PBOO was surgically created in juvenile male mice. Sham-operated mice were used as controls. Animals received daily oral administration of either tocotrienols (T3) or soybean oil (SBO, vehicle) from day 0 to 13 post-surgery. Bladder function was examined in vivo by void spot assay. At 2 weeks post-surgery, the bladders were subjected to physiological evaluation of detrusor contractility in vitro using bladder strips, histology by H&E staining and collagen imaging, and gene expression analyses by quantitative PCR. A significant increase in the number of small voids was observed after 1 week of PBOO compared to the control groups. At 2 weeks post-surgery, PBOO+SBO mice showed a further increase in the number of small voids, which was not observed in PBOO+T3 group. PBOO-induced decrease in detrusor contractility was similar between two treatments. PBOO induced bladder hypertrophy to the same degree in both SBO and T3 treatment groups, however, fibrosis in the bladder was significantly less prominent in the T3 group than the SBO group following PBOO (1.8- vs. 3.0-fold increase in collagen content compared to the control). Enhanced levels of HIF target genes in the bladders were observed in PBOO+SBO group, but not in PBOO+T3 group compared to the control. Oral tocotrienol treatment reduced the progression of urinary frequency and bladder fibrosis by suppressing HIF pathways triggered by PBOO.

Enhanced Reactivity of Accessible Protons in Sodalite Cages of Faujasite Zeolite

AbstractFaujasite (FAU) zeolites (with Si/Al ratio of ca. 1.7) undergo mild dealumination at moderate ion exchange conditions (0.01 to 0.6 M of NH4NO3 solutions) resulting in protons circumscribed by sodalite cages becoming accessible for reaction without conspicuous changes to bulk crystallinity. The ratio of protons in sodalite cages (HSOD) to supercages (HSUP) can be systematically manipulated from 0 to ca. 1 by adjusting ammonium concentrations used in ion exchange. The fraction of accessible protons in the sodalite cages is assessed by virtue of infrared spectra for H‐D exchange of deuterated propane based on the band area ratio of OD2620/OD2680 (ODSOD/ODSUP). Protons in sodalite cages (HSOD) show higher rate constants of propane dehydrogenation (kD) and cracking (kC) than protons in supercages (HSUP) plausibly due to confinement effects being more prominent in smaller voids. Rate constants of dehydrogenation and cracking including kD/kC ratios are also augmented as the fraction of accessible protons in the sodalite cages is enhanced. These effects of accessibility and reactivity of protons in sodalite cages hitherto inconspicuous are revealed herein via methods that systematically increase accessibility of cations located in sodalite cages.