Fine Structure Research Articles

Fine structure of current noise spectra in nanoelectromechanical resonators

We study the frequency-dependent noise of a suspended carbon nanotube quantum dot nanoelectromechanical resonator induced by electron-vibration coupling. Using a rigorous Keldysh diagrammatic technique, we establish a formal framework connecting the vibrational properties to electrical measurements. We find that the noise power spectrum exhibits a narrow resonant peak at the frequency of the vibrational modes. However, this fine structure tends to disappear due to a coherent cancellation effect when the tunneling barriers are tuned to a symmetric point. Notably, measuring the electrical current noise spectra provides a sensitive alternative method for detecting the damping and dephasing of quantum vibrational modes.

Effect of scanning strategies on microstructure and wear behavior of Inconel 718 fabricated by selective laser melting

Abstract To study the effect of the rotating angle on microstructure and wear properties of Inconel 718 alloy manufactured by selective laser melting (SLM) technology, parts were fabricated with two different scanning strategies (67°, 90°). The results revealed that the Inconel 718 produced by SLM with a 67° rotating angle exhibits higher surface roughness and a distinct cubic texture {100} < 001 >. Additionally, rotation angle of 90° will enhance grain coarsening and weaken texture strength. The influence of rotation angles on the hardness of SLMed Inconel 718 is negligible at room temperature. The wear resistance of SLMed Inconel 718 is superior at high temperatures compared to room temperature. The wear mechanisms of SLMed Inconel 718 at room temperature and high temperature are primarily governed by abrasive wear and adhesive wear, and oxidation wear, respectively. The favorable wear properties observed at the 67° rotating angle can be attributed mainly to the fine cellular structure and the triboxide layer.

Postweld heat treatment of rotary friction welded AISI 1018 steel: microstructure, mechanical properties and corrosion resistance evaluation

The present study investigated the effect of post-heat treatment (PWHT) on the microstructure, mechanical properties and corrosion resistance of rotary friction welded AISI 1018 low-carbon steel. Metallographic analysis revealed that as-welded sample showed heterogenous microstructure consisted of fine grains of polygonal ferrite in weld zone (WZ) and coarse grains of ferrite and elongated pearlite in thermomechanical affected zone (TMAZ), while the postweld heat treated sample showed homogenous microstructure consisted of equiaxed grains ferrite and pearlite both in WZ and TMAZ. Mechanical test results showed that as-welded sample exhibited 36% tensile elongation and 82% bending elongation relative to base metal. After applying PWHT, the tensile elongation enhanced by 178% and bending elongation enhanced by 243% relative to the as-welded sample. The improved elongations after PWHT was caused by homogeneous microstructure consisted of equiaxed grains of ferrite and pearlite in weld joint. Electrochemical results revealed that the order of the corrosion rate is heat treated > base metal > as-welded in 0.5 M H2SO4 environment. The difference in corrosion behavior is primarily related to microstructure development where fine grain structure of as-welded sample with low volume fraction of pearlite showed lowest corrosion rate.

Noninvasive high-resolution deep-brain photoacoustic imaging with a negatively focused fiber-laser ultrasound transducer

Noninvasive high-resolution deep-brain imaging is essential to fundamental cognitive process study and neuroprotective drugs development. Although optical microscopes can resolve fine biological structures with good contrast without exposure to ionizing radiation or a strong magnetic field, the optical scattering limits the penetration depth and hinders its capability for deep-brain imaging. Here, in vivo high-resolution imaging of the whole mouse brain is demonstrated by using a photoacoustic computed tomography system with a negatively focused fiber-laser ultrasound transducer. By leveraging the high flexibility and low bending loss of the optical fiber, a rationally designed negatively focused fiber laser cavity exhibits a low detection limit down to 5.4 Pa and a broad view angle of ∼120 deg, enabling mouse brain imaging with a penetration larger than 7 mm and a nearly isotropic spatial resolution of ∼130 μm. In addition, the negative curvature of the fiber laser reduces the working distance, which facilitates the development of a compact and portable linear scanning imaging system. In vivo imaging of a mouse model with intracerebral hemorrhage is also showcased to demonstrate its capability for potential biomedical and clinical applications. With high spatial resolution and large tissue penetration, the system may provide a noninvasive, user-friendly, and high-performance imaging solution for biomedical research and preclinical/clinical diagnosis.

High-performance bio-based foam from agricultural waste luffa seed oil polyols

The present study aimed to develop eco-friendly polyurethane viscoelastic foam (PVF) with enhanced tear strength while preserving softness, comfort, and safety by utilizing bio-based polyols derived from luffa seed oil (LSO). Two types of bio-based polyols (PLSO-D and PLSO-M) were synthesized through the epoxidation process using diethylene glycol (DEG) and methanol (MeOH), respectively, for the production of LSO-based polyurethane viscoelastic foams (LSO-PVFs). The analyses revealed that these polyols exhibited high dispersion, appropriate hydroxyl values, and contained by-products such as oligomeric esters of fatty acids that facilitated physical and chemical crosslinking. LSO-PVFs demonstrated a uniform and fine cell structure with abundant open-cells, thick cell walls (55.5–76.6µm), and high apparent density (48.7–50.7kg/m3). Moreover, they exhibited enhanced tensile and tear strength (increasing up to 200% compared to petroleum-based PVFs), lower water absorption, excellent mildew resistance at 10% PLSO substitution. Additionally, these factors endowed LSO-PVFs with low indentation hardness and good bottom support performance, characterized by a compressive deflection coefficient of 2.30–3.54. This approach presents a sustainable alternative for foam production that offers comfort, durability while promoting the value-added utilization of agricultural waste.

Structural analysis and immunological activity of a novel low molecular weight neutral polysaccharide isolated from Hemerocallis citrina Borani.

A novel neutral water-soluble polysaccharide (HCBP1-1) was isolated and purified from Hemerocallis citrina Borani by column chromatography. The fine structure of HCBP1-1 was determined by a series of physical and chemical means. HCBP1-1 was a homogeneous low molecular weight polysaccharide of 7.25kDa. Methylation and NMR analysis revealed that HCBP1-1 consisted of α-D-Glcp-(1→, →4)-α-D-Glcp-(1→, →4)-β-D-Galp-(1→, →4,6)-α-D-Glcp-(1→, →3,4)-α-D-Glcp-(1→. In particular, the main backbone of HCBP1-1 consisted of unsubstituted (4-α-D-Glcp and 4-β-D-Galp) and monosubstituted (4,6-α-D-Glcp and 3,4-α-D-Glcp) glucose and galactose units linked by α-(1→4) and β-(1→4) glycosidic linkages. The side chain consisted of α-D-Glcp-(1→and →4)-α-D-Glcp-(1→. Furthermore, bioactivity assays show that HCBP1-1 significantly promoted the secretion of NO, TNF-α, IL-1β, and IL-6 and the expression of NF-κB p65 in RAW264.7 cells, which had good immune-enhancing activity. These results suggest that HCBP1-1 had beneficial immunomodulatory effects and could be developed into functional foods or nutraceuticals with immune-enhancing properties.

Preparation, characterization and in vitro antioxidant activities of a homogeneous polysaccharide from Prunella vulgaris.

Prunella vulgaris is a medicinal and edible homologous plant, commonly used as a folk medicine to treat diseases. The Prunella vulgaris polysaccharides (PVPs) are reported with the antioxidant activity. This work was designed to isolate, characterize, and test the antioxidant activity of purified PVPs from P. vulgaris. A new homogeneous polysaccharide (PVP-1) was prepared by the DEAE column from PVPs, and diverse chromatography/spectroscopy and chemical methods were simultaneously employed to characterize the fine structure of PVP-1. The result showed PVP-1 had a triple helix structure, and the repeating structural unit of PVP-1 was composed of →6)-β-D-Galp-(1→6)-β-D-Galp-(3,1→6)-β-D-Galp-(1→6)-β-D-Galp-(1→ as the main chain, together with →6)-β-D-Galp-(1,3→1)-α-D-Araf-(5→1)-β-D-Galp-(4→1)-α-D-Galp-(2→ and →6)-β-D-Galp-(1,3→1)-α-D-GlcAp-(4→1)-α-D-Glcp-(4→1)-α-D-Galp as the branch chains. The main monosaccharides of PVP-1 were galactose (Gal, 41.25 %), galactose-OMe (Gal-OMe, 27.73 %), arabinose (Ara, 10.63 %), mannose (Man, 9.86 %), glucose (Glc, 3.88 %), glucuronic acid (GlcA, 2.86 %), ribose (Rib, 1.79 %), and xylose (Xyl, 1.76 %). In addition, the scanning electron microscopy (SEM) displayed that the surface of PVP-1 was rough and porous. PVP-1 gave the scavenging rates of the DPPH, ABTS, and hydroxyl radical lower than vitamin C at the same concentration, with the highest scavenging rate of DPPH radical at 82.71 % ± 4.19 % (5 mg/mL).

DebSDF: Delving Into the Details and Bias of Neural Indoor Scene Reconstruction.

In recent years, the neural implicit surface has emerged as a powerful representation for multi-view surface reconstruction due to its simplicity and State-of-the-Art performance. However, reconstructing smooth and detailed surfaces in indoor scenes from multi-view images presents unique challenges. Indoor scenes typically contain large texture-less regions, making the photometric loss unreliable for optimizing the implicit surface. Previous work utilizes monocular geometry priors to improve the reconstruction in indoor scenes. However, monocular priors often contain substantial errors in thin structure regions due to domain gaps and the inherent inconsistencies when derived independently from different views. This paper presents DebSDF to address these challenges, focusing on the utilization of uncertainty in monocular priors and the bias in SDF-based volume rendering. We propose an uncertainty modeling technique that associates larger uncertainties with larger errors in the monocular priors. High-uncertainty priors are then excluded from optimization to prevent bias. This uncertainty measure also informs an importance-guided ray sampling and adaptive smoothness regularization, enhancing the learning of fine structures. We further introduce a bias-aware signed distance function to density transformation that takes into account the curvature and the angle between the view direction and the SDF normals to reconstruct fine details better. Our approach has been validated through extensive experiments on several challenging datasets, demonstrating improved qualitative and quantitative results in reconstructing thin structures in indoor scenes, thereby outperforming previous work.

Hybrid Cochlear Implant Outcomes and Improving Outcomes With Electric-Acoustic Stimulation.

Electric-acoustic stimulation (EAS) provides cochlear implant (CI) recipients with preserved low-frequency acoustic hearing in the implanted ear affording auditory cues not reliably transmitted by the CI including fundamental frequency, temporal fine structure, and interaural time differences (ITDs). A prospective US multicenter clinical trial was conducted examining the safety and effectiveness of a hybrid CI for delivering EAS. Fifty-two adults (mean age 59.9 yr) were enrolled in the study and followed up to 5 years postactivation. Testing included unaided and aided audiometric thresholds, speech perception (Consonant-Nucleus-Consonant [CNC] words in quiet and AzBio sentences +5 dB SNR), and patient-reported outcomes (Speech, Spatial, and Qualities of Hearing Scale). Functionally aidable hearing, defined as low-frequency pure-tone average (125-500 Hz) <80 dB HL, was maintained for 77% of patients through 1 year, with 66.7% maintaining through 5 years. Speech perception was significantly improved at all postoperative timepoints compared with preoperative performance with hearing aid(s), and patient-reported outcomes indicated significantly improved subjective speech understanding, spatial hearing, and sound quality. Participants with preserved acoustic hearing using EAS reported significantly higher subjective spatial hearing and sound quality than participants with electric-only hearing in the implanted ear. Patients with high-frequency hearing loss demonstrate significant long-term benefit with a hybrid CI including high rates of functional hearing preservation, significantly improved speech perception, and subjective patient-reported outcomes. EAS with binaural acoustic hearing affords benefit for subjective spatial hearing and sound quality beyond CI listening configurations using monaural acoustic hearing.

Localized Ultra‐Low Velocity Zone as a Strong Scatterer at the Core‐Mantle Boundary Beneath Central America

AbstractSmall‐scale scatterers in the lower mantle contain key information on the recycling process in the whole mantle. Resolving the fine structures of these scatterers is crucial for understanding the dynamic evolution in the deep Earth. Here, we search for scatterers in the lower mantle beneath Central America and the northwestern Pacific Ocean by events in South America and PKP recordings in Japan. In this work, we perform migration of PKP precursors on the source and receiver sides by raytracing to obtain the distribution map of scatterers, after considering 3D heterogeneous structures. Furthermore, we locate a distinct scatterer at the core‐mantle boundary (CMB) beneath Central America that generates strong PKP precursors with unique slowness and back‐azimuth by array processing, which is compatible with the migration result. Based on waveform modeling, this scatterer is essentially a localized ultra‐low velocity zone (ULVZ) with approximately P‐wave velocity reduction of 6% and a lateral extent of 3°. Heated up of the subducted lithosphere by the core or partial melting of the subducted oceanic crust are plausible sources of the localized ULVZ at the CMB we detect here in the subduction region.

JWST Observations Constrain the Time Evolution of Fine Structure Constants and Dark Energy-electromagnetic Coupling

Abstract It was hypothesized in the literature that some physical parameters may be time-evolving and the astrophysical data can serve as a probe. Recently, the James Webb Space Telescope (JWST) released its early observations. In this work, we select the JWST spectroscopic observations of the high redshift (z &gt; 7.1) galaxies with strong [O iii] (λ = 4959 Å and 5007 Å in the rest frame) emission lines to constraint the evolution of the fine structure constant (α). With the spectra from two galaxies at redshifts of 7.19 and 8.47, the deviation of α from its fiducial value is found to be as small as 0.44 − 8.3 − 1.7 + 8.4 + 1.7 × 10 − 4 and − 10.0 − 18 − 1.5 + 18 + 1.5 × 10 − 4 , respectively (the first error is statistical and the latter is systematic). The combination of our results with the previous data reveals that 1 α d α dt = 0.30 − 4.5 + 4.5 × 10 − 17 yr − 1 . Clearly, there is no evidence for a cosmic evolution of α. The prospect of further constraining the time evolution of α is also discussed. The scalar field of dark energy is hypothesized to drive the acceleration of the universe’s expansion through an interaction with the electromagnetic field. By integrating the observational data of the fine-structure constant variation, Δ α α ( z ) , we have established a stringent upper limit on the coupling strength between dark energy and electromagnetism. Our analysis yields ζ ≤ 3.92 × 10−7 at the 95% confidence level, representing the most stringent bound to date.

The role of deep layer superior colliculus neurons in prepulse inhibition and the impact of spatial separation in male rats.

Prepulse inhibition (PPI) refers to the phenomenon in which a weak sensory stimulus before a strong one significantly reduces the startle reflex caused by the strong stimulus. Perceptual spatial separation, a phenomenon where auditory cues from the prepulse and background noise are distinguished in space, has been shown to enhance PPI. This study aims to investigate the neural modulation mechanisms of PPI by the spatial separation between the prepulse stimulus and background noise, particularly in the deep superior colliculus (deepSC). The experiment used 11 anesthetized male Sprague-Dawley rats, with electrodes implanted in the left deepSC nd the right inferior colliculus (IC). The prepulse stimulus was a segment of narrowband noise, with interaural time differences adjusted so that the prepulse stimulus and background noise were perceived as either ipsilaterally leading or contralaterally leading, resulting in perceptual spatial fusion or spatial separation. The results showed that under conditions of spatial separation, the stimulus-response coherence of the envelope and fine structure components of the prepulse stimulus in the deepSC was significantly enhanced, the response of the deepSC to the stimulus was significantly reduced in the presence of the prepulse stimulus, and the envelope component of the prepulse stimulus was positively correlated with the inhibitory effect. The above results suggest that perceptual spatial dissociation can significantly enhance the expression of deepSC, particularly the precision of the envelope component, thereby significantly affecting the electrophysiological response of PPI.

Modulating the assembly of starch-lecithin inclusion complexes and its underlying mechanism for controlling starch digestibility under the dense system

Starch-lipid inclusion complexes were used to regulate starch digestibility by changing the binding affinity of digestive enzymes such as α-amylase and α-glucosidase. However, when above a critical aggregation concentration (CAC) of starch and lipid molecules, they tended to self-assemble into double helices or normal micelles respectively, rather than interacting with each other to form starch-lipid complexes. Thus, how to enhance the complexation efficiency under a dense system is the key approach for the improvement of starch bioaccessibility and nutritional function. Herein, based on the dimethyl sulfoxide (DMSO) reverse solvent method, the effect of water/DMSO ratios and starch chain structures on the interaction and assembly behaviors between starch and lecithin molecules in high concentrations were systematically investigated. The results revealed that water/DMSO in a ratio of 1.5:1 promoted the interactions between cavities of starch helices and long alkyl chains of lecithin molecules, with higher level of complexed lecithin content, relative crystallinity (RC), enthalpy (ΔH) (Tp＞100°C), ordered-aggregation structures and resistant starch (RS) content. In this kind of solvent, starch samples with higher content of amylose and longer chains (degree of polymerization (DP) of B2 chains and B3+ chains) is advantageous to the formation of VII-type inclusion starch-lecithin complexes, with a rise in RS from 14.17% to 43.64%. It provided an effective method to modulate starch digestibility under the dense system of starch and lecithin via modulating the water/DMSO ratios and starch fine structures and lay the foundation for the large-scale preparation and application of starch-lecithin complexes.

Manipulation of the Electronic Structure of Ruthenium Nanoclusters by Ni‐N4 Sites Enhances the Alkaline Hydrogen Evolution Reaction

AbstractDesigning electrocatalysts that are both highly efficient and durable is crucial for the industrial implementation of alkaline electrocatalytic hydrogen production technologies. A limitation of the current Ru‐based catalysts is that the water dissociation energy barrier tends to be too high. Here, the electronic structure of ruthenium nanoclusters (Ru NCs) is modulated by single atom Ni‐N4 sites leading to leading to lowering of the water dissociation barrier. X‐ray absorption fine structure spectrum confirms that Ru NCs are stably anchored on the carbon support through the formation of Ru‐N bonds, significantly enhancing catalytic stability. The resulting Ru/Ni‐N4C‐300 catalyst shows excellent catalytic activity toward alkaline hydrogen evolution reaction with a low overpotential of 15.0 mV at 10 mA cm−2 together with robust durability. An anion exchange membrane water electrolyzer employing Ru/Ni‐N4C‐300 can be stably operated under 500 mA cm−2 for over 1370 h, surpassing the parameters required for industrialization. Theoretical calculation indicates the single atom Ni‐N4 sites in Ru/Ni‐N4C‐300 optimize the electron distribution of Ru NCs, thereby reducing the Gibbs free energy of intermediates species in water dissociation process.

Fine Structure of the Solar Corona in High-Frequency Resolution Radio Observations

Fine Structure of the Solar Corona in High-Frequency Resolution Radio Observations

Effect of microstructure evolution on the corrosion behavior of extrusion-shearing Mg-3Zn-XCa-0.6Zr alloys

In order to promote the application of new biomedical materials Mg-Zn-Ca-Zr alloy, the Mg-3Zn-xCa-0.6Zr (x = 0.6, 1.2, 1.8 wt%) alloys were fabricated by an extrusion shearing (ES) process. The effect of secondary phase precipitation, grain size and texture on the corrosion resistance of Mg-3Zn-xCa-0.6Zr (wt%) in Hank's solution were studied using electrochemical, immersion and electron back-scattering diffraction (EBSD) tests, and the corrosion mechanism of ES alloys was discussed. With increasing the addition of Ca element, the grain size of alloys first decreased and then increased, and the constitution of second phase was transformed from MgZn and Ca2Mg6Zn3 phases to Mg2Ca and Ca2Mg6Zn3 phases, the texture changed from a bimodal texture intensity with stronger basal texture to a DRX texture intensity with a weaker texture. Mg-3Zn-0.6Ca-0.6Zr alloy showed the lowest corrosion rate of ∼0.3140 ± 0.0642 mm/y. The excellent corrosion resistance of Mg-3Zn-0.6Ca-0.6Zr alloy could be attributed to the High-potential dispersion distribution of MgZn and Ca2Mg6Zn3 phases and the strong basal texture. As well as more dense corrosion product films formed after alloying, effectively hindering local corrosion. In contrast, corrosion product films formed by the fine grain structure of Mg-3Zn-1.2Ca-0.6Zr alloy were not sufficient to resist the galvanic coupling corrosion between the Mg2Ca phase and the Ca2Mg6Zn3 phase, which caused the decreasing of its corrosion resistance.

High-resolution observational analysis of flare ribbon fine structures

High-resolution observational analysis of flare ribbon fine structures

Enhanced decoupling of conductivity relaxation from structural relaxation in non-stoichiometric protic ionic liquids involving triflic acid and 2-aminoethyl hydrogen sulfate.

The glass transition dynamics and conductivity relaxation are studied for a series of non-stoichiometric protic ionic liquids (PILs) based on 2-aminoethyl hydrogen sulfate and triflic acid with varying molar ratios (denoted as AT-55, AT-46, AT-37, AT-28, and AT-19) by broadband dielectric spectroscopy in a wide frequency (10-1-107Hz) and temperature range (173-353K). The results indicate that the addition of acid lowers the glass transition temperature, as confirmed by the activation energy fine structure analysis and a crossover in the conductivity relaxation time. Notably, samples with higher acid content deliver markedly increased conductivity. In addition, detailed analysis of the permittivity and modulus spectra reveals enhanced decoupling between the structural (α-process) and conductivity relaxation in samples with a higher acid content. Remarkably, nano-phase separation in AT-28 and AT-19 samples is observed, resulting in a second glass transition temperature indicating a more mobile phase. Based on the above-mentioned findings, we infer that increased acid content disrupts strong ionic interactions within the IL fraction, resulting in a decrease in the glass transition temperature and leading to nano-phase separation into distinct acid-rich and IL-rich phases with varying Tg values. This phase separation alters the long-range ionic pathways, shifting from being solely governed by IL cluster dynamics to a scenario where charge transport becomes largely decoupled from the dynamics of IL-rich clusters. Hence, modulating the stoichiometry of PILs appears a promising approach to enhance the conductivity together with widening the usable temperature range for applications.

A Hybrid Miniaturized Modular Probe for Minimally Invasive Neural Intervention

AbstractBrain's unique anatomical structure and physiological environment make it difficult to deliver therapeutic agents such as drug or light to a focal volume in brain for disease treatment. Physically targeting a fine structure in brain with a micro‐neural probe is an effective solution. Here, we present a hybrid miniaturized neural probe designed with micro‐fluidic channel(s) for drug delivery, micro‐electrode(s) for neural sensing and an optical fiber for optical‐related treatment. These functional components are integrated in a micro‐cannula (diameter &lt;300 µm) with modular design and fabrication properties which can be conveniently adjusted for diverse applications. In vitro and in vivo tests confirm that this probe can precisely deliver drug to a focal volume in brain bypassing the blood brain barrier, and on‐site neural sensing can be achieved with the integrated neural electrode. Leveraging near infrared light’s scattering properties in brain, we demonstrate in vivo with rat glioblastoma model that this hybrid neural probe can be a platform for photothermal treatment of brain tumor. With these merits, the hybrid miniaturized neural probe will be an effective tool with great translational potentials for minimally invasive neural intervention such as drug delivery or combination treatment of brain diseases.

Elucidation of the fine structure and anti–breast tumor activity of a glucomannan from the pseudobulbs of Pleione bulbocodioides

Pseudobulbs of Pleione bulbocodioides have been used as traditional Chinese medicine for a long time to treat cancers through decoction with water. However, as its main water-soluble ingredient, the structure of polysaccharide has not been elucidated yet. To obtain its polysaccharide with antitumor activity, a series of isolation, structural identification and antitumor evaluation experiments were performed. As a result, a newly discovered glucomannan, named PBP, was isolated and purified from the pseudobulbs of P. bulbocodioides. The molecular weight of PBP is 1.11 × 105 Da. Its monosaccharide composition comprises mannose and glucose at a molar ratio of 5:3. The fine structure of PBP was confirmed as a linear glucomannan backbone primarily comprising repeating →4)-β-d-Glc-(1 → 4)-β-d-Man-(1 → 4)-β-d-Glc-(1 → 4)-β-d-Man-(1 → 4)-β-d-Glc-(1 → 4)-β-d-Man-(1→4)-β-d-Man-(1 → 4)-β-d-Man-(1 → via a combination of analytical techniques and enzymolysis methods. PBP effectively inhibited the growth of 4T1 tumors with low toxicity in vivo. Furthermore, a noteworthy augmentation in the expression levels of CD4+ and CD8+ T cells suggested the existence of an elevated immune response. In summary, a new glucomannan with anti-breast tumor activity was obtained, which has the potential to contribute to breast cancer therapy.