Cone-like Structures Research Articles

On the early stagnation point during transient acoustic cavitation

We explore an acoustofluidic phenomenon, in an aqueous environment, of an emerging early stagnation point that consistently positions itself at a distance of two times the ultrasonic horn tip diameter 2D, regardless of the tip size. This was initially captured numerically in a two-dimensional domain of horn-type reactors of diameters D = 3, 6, 13, and 16 mm in a 107 × 50 mm cuvette. We deduced that the axial extension of the bubble cluster influences the rate of decay of axial flow; however, it does not affect the stagnation point. Cavitation attenuation was scrutinized by mathematically modeling the time-averaged axial flow during the cavitation transient state and solving the flow using Newman's subroutine. During fast streaming, acoustic force attenuation α decreases exponentially at a maximum rate of ≈1.70 with the doubling of Reynolds number Re. However, an inverse trend was demonstrated by the dimensionless attenuation Γ=−2αD, as it increased by a factor of ≈1.28. Similarly, Γ exponentially increased with the doubling of Re during slow streaming suggesting direct proportionality between Γ and Re. This emphasized the underlying role of the term 2D in amplifying attenuation induced by morphing structures of inertial bubble clusters. Moreover, tracking the bubble population along the horn axis revealed that mushroom-like structures formed under small horn tips have a linear bubble distribution, while cone-like structures under larger tips maintained an exponential distribution. This may suggest that a linear distribution may enhance attenuation and justify the aforementioned trends.

In situ preparation of nano cone-like structures on 3D printed titanium alloy implants via one-step femtosecond laser manufacturing for better osseointegration, anti-corrosion, and anti-fatigue

The poor surface conditions and osseointegration capacity of 3D printed Ti6Al4V implants (3DPT) significantly influence their performance as orthopedic and dental implants. In this work, we creatively introduce a one-step femtosecond laser treatment to improve the surface conditions and osteointegration. The surface characterization, mechanical properties, corrosion resistance, and biological responses were investigated. These results found that femtosecond laser eliminated defects like embedded powders and superficial cracks while forming the nano cones-like structures surface on 3DPT, leading to enhanced osseointegration, anti-corrosion, and anti-fatigue performance. Molecular dynamics simulations revealed the ablation removal mechanism and the formation of nano cone-like structures. These findings were further supported by the in vivo studies, showing that the FS-treated implants had superior bone-implant contact and osseointegration. Hence, the one-step femtosecond laser method is regarded as a promising surface modification method for improving the functional performance of Ti-based orthopedic implants.

Effect of Extended Defects on AlGaN Quantum Dots for Electron-Pumped Ultraviolet Emitters.

We study the origin of bimodal emission in AlGaN/AlN QD superlattices displaying a high internal quantum efficiency (around 50%) in the 230-300 nm spectral range. The secondary emission at longer wavelengths is linked to the presence of cone-like domains with deformed QD layers, which originate at the first AlN buffer/superlattice interface and propagate vertically. The cones originate at a 30°-faceted shallow pit in the AlN, which appears to be associated with a threading dislocation that produces strong shear strain. The cone-like structures present Ga enrichment at the boundaring facets and larger QDs within the conic domain. The bimodality of the luminescence is attributed to the differing dot size and composition within the cones and at the faceted boundaries, which is confirmed by the correlation of microscopy results and Schrödinger-Poisson calculations.

The Morphology and Ultrastructure of Dermal Telocytes Characterized by TEM and AFM.

This investigation delves into the structural foundation of human dermal telocytes (TCs) with the aim of elucidating their role in signal transmission. Dermal TCs were isolated from human foreskins via enzymatic digestion and flow cytometric sorting, and identified by immunohistochemical staining with an antibody against CD34. The ultrastructure of TCs was examined using transmission electron microscopy (TEM). The proliferation rates of sorted TCs and CD34-negative fibroblasts were compared using the MTS assay (Cell Proliferation Assay). Images of viable cultured TCs were analyzed using atomic force microscopy (AFM) under normal atmospheric pressure and temperature. Results demonstrated that dermal TCs were positive for CD34 and vimentin, predominantly distributed in the reticular dermis and subcutaneous tissue, forming interwoven networks. Each TC had a small body with a high nuclear-plasma ratio and two or three extremely long and thin telopodes (TPs), exhibiting a typical 'moniliform' appearance. Compared with CD34-negative fibroblasts, dermal TCs exhibited significantly lower proliferation rates. Cultured TCs displayed typical moniliform projections (namely, TPs) in the AFM images. The distal ends of TPs were enlarged, shaped like a broom, and extended multiple pseudopods to contact other cell bodies. Slender filamentary pseudopodia and thick, short cone-like structures were observed on the surfaces of the dilated segments and terminals of TPs. These structures are assumed to be evidence of the secretion and release of endosomes, such as exosomes, and the communication between cells. TCs form interstitial networks in the reticular dermis and subcutaneous tissue, providing a structural basis for contacts between cells and the secretion of signal-carrying substances, involving intercellular connections and communication.

Exploring the thermoelectric properties of two-dimensional organic conjugated polymers with Dirac cone-like electronic structures

2D organic conjugated polymers with Dirac cone-like structures not only exhibit unique advantages in electrical conductivity but also show excellent thermoelectric transport properties. These materials have potential application value in the field of thermoelectrics.

Decrease in phase slip rates and phase cone structures during seizure evolution and epileptogenic activities derived from microgrid ECoG data

Sudden phase changes are related to cortical phase transitions, which likely change in frequency and spatial distribution as epileptogenic activity evolves. A 100 s long section of micro-ECoG data obtained before and during a seizure was selected and analyzed. In addition, nine other short-duration epileptic events were also examined. The data was collected at 420 Hz, imported into MATLAB, downsampled to 200 Hz, and filtered in the 1–50 Hz band. The Hilbert transform was applied to compute the analytic phase, which was then unwrapped, and detrended to look for sudden phase changes. The phase slip rate (counts/s) and its acceleration (counts/s2) were computed with a stepping window of 1-s duration and with a step size of 5 ms. The analysis was performed for theta (3–7 Hz), alpha (7–12 Hz), and beta (12–30 Hz) bands. The phase slip rate on all electrodes in the theta band decreased while it increased for the alpha and beta bands during the seizure period. Similar patterns were observed for isolated epileptogenic events. Spatiotemporal contour plots of the phase slip rates were also constructed using a montage layout of 8 × 8 electrode positions. These plots exhibited dynamic and oscillatory formation of phase cone-like structures which were higher in the theta band and lower in the alpha and beta bands during the seizure period and epileptogenic events. These results indicate that the formation of phase cones might be an excellent biomarker to study the evolution of a seizure and also the cortical dynamics of isolated epileptogenic events.

In situ preparation of nano cone-like structures of rutile titanium oxides on titanium implants by one-step femtosecond laser irradiation for enhanced mechanical properties and biocompatibility

Titanium oxides (TiO2) nanostructures coating is helpful in improving the utilization of titanium in many areas due to its multifunctional properties. This study introduces a novel approach for the in-situ fabrication of nano cones-like structures of rutile titanium oxides (NCS–TiO2) on the surface of titanium utilizing femtosecond laser technology. Rutile titanium oxides were synthesized with a height of around 80 nm and a diameter of 100 nm, forming NCS that imparts higher hardness, wear resistance, and biocompatibility. Molecular dynamic simulation provides valuable insights into the three-stage formation process of NCS-TiO2. Molecular dynamic simulation revealed that the growth of rutile titanium oxides and the formation of nano cones-like structures are attributed to the interplay between femtosecond laser ablation and the accumulation of thermal energy. The proposed method offers a versatile and straightforward approach for creating functional surfaces on metal substrates, enabling broad applicability and ease of implementation, specifically in titanium and its alloys. This advancement holds great potential for expanding the scope of titanium-based materials and their applications, paving the way for improved mechanical properties and biocompatibility in diverse fields.

Conelike radiant structures

Analogues of the classical affine-projective correspondence are developed in the context of statistical manifolds compatible with a radiant vector field. These utilize a formulation of Einstein equations for special statistical structures that generalizes the usual Einstein equations for pseudo-Riemannian metrics and is of independent interest. A conelike radiant structure is a not necessarily flat affine connection equipped with a family of surfaces that behave like the intersections of the planes through the origin with a convex cone in a real vector space. A radiant structure is a torsion-free affine connection and a vector field whose covariant derivative is the identity endomorphism. A radiant structure is conelike if for every point and every two-dimensional subspace containing the radiant vector field there is a totally geodesic surface passing through the point and tangent to the subspace. Such structures exist on the total space of any principal bundle with one-dimensional fiber and on any Lie group with a quadratic structure on its Lie algebra. The affine connection of a conelike radiant structure can be normalized in a canonical way to have antisymmetric Ricci tensor. Applied to a conelike radiant structure on the total space of a principal bundle with one-dimensional fiber this yields a generalization of the classical Thomas connection of a projective structure. The compatibility of radiant and conelike structures with metrics is investigated and yields a construction of connections for which the symmetrized Ricci curvature is a constant multiple of a compatible metric that generalizes well-known constructions of Riemannian and Lorentzian Einstein–Weyl structures over Kähler–Einstein manifolds having nonzero scalar curvature. A formulation of Einstein equations for special statistical manifolds is given that generalizes the Einstein–Weyl equations and encompasses these more general examples. There are constructed left-invariant conelike radiant structures on a Lie group endowed with a left-invariant nondegenerate bilinear form, and the case of three-dimensional unimodular Lie groups is described in detail.

Three-dimensional-printed porous prosthesis for the joint-sparing reconstruction of the proximal humeral tumorous defect.

Background: Tumorous bone defect reconstructions of the proximal humerus with joint sparing is a challenge. Numerous reconstruction methods have been proposed but the proximal residual humerus is commonly sacrificed because of its extremely short length. To preserve the proximal humerus and improve clinical outcomes, we designed a three-dimensional (3D) printed uncemented prosthesis with a porous structure to treat tumorous bone defects of the proximal humerus. Methods: Our analysis included seven patients treated between March 2018 and July 2019. A 3D model was established, and related data were obtained, including the diameter of the humeral head, the resection length, and the residual length. A prosthesis was designed and fabricated based on these data. Functional and oncologic outcomes were recorded, and complications and osseointegration were evaluated. Results: The mean age of the patients was 20.3years, and the median follow-up period was 26months. The lengths of the residual proximal humerus were 17.9mm on average. All the patients had preserved humeral heads and most of the rotator cuff was intact. The average postoperative range of motion (ROM) of the affected shoulder was 83.8°; flexion was 82.5°, extension was 43.8°, and adduction was 16.3°. The average Musculoskeletal Tumor Society score (MSTS) was 94.3%. Good osseointegration was observed on the interface between the bone and prosthesis. Conclusion: A 3D printed porous prosthesis with cone-like structures successfully achieved joint-sparing reconstruction of proximal humeral tumorous defects with satisfying functional outcomes. The preservation of the rotator cuff and humeral head plays an essential role in the function of the shoulder joint.

Design and Analysis of Cone-like Structures for Broadband and Wide-Angle Antireflection Enhancement

Design and Analysis of Cone-like Structures for Broadband and Wide-Angle Antireflection Enhancement

Cone-setting in spruce is regulated by conserved elements of the age-dependent flowering pathway.

Reproductive phase change is well characterized in angiosperm model species, but less studied in gymnosperms. We utilize the early cone-setting acrocona mutant to study reproductive phase change in the conifer Picea abies (Norway spruce), a gymnosperm. The acrocona mutant frequently initiates cone-like structures, called transition shoots, in positions where wild-type P. abies always produces vegetative shoots. We collect acrocona and wild-type samples, and RNA-sequence their messenger RNA (mRNA) and microRNA (miRNA) fractions. We establish gene expression patterns and then use allele-specific transcript assembly to identify mutations in acrocona. We genotype a segregating population of inbred acrocona trees. A member of the SQUAMOSA BINDING PROTEIN-LIKE (SPL) gene family, PaSPL1, is active in reproductive meristems, whereas two putative negative regulators of PaSPL1, miRNA156 and the conifer specific miRNA529, are upregulated in vegetative and transition shoot meristems. We identify a mutation in a putative miRNA156/529 binding site of the acrocona PaSPL1 allele and show that the mutation renders the acrocona allele tolerant to these miRNAs. We show co-segregation between the early cone-setting phenotype and trees homozygous for the acrocona mutation. In conclusion, we demonstrate evolutionary conservation of the age-dependent flowering pathway and involvement of this pathway in regulating reproductive phase change in the conifer P. abies.

The effects of impurity gas seeding on the growth of fuzzy tungsten

Using the linear plasma device NAGDIS-II operating with gas mixtures of helium (He) and impurity (Ne, N 2 , Ar), fibre-form nanostructures known as “fuzz” have been grown on tungsten (W) samples. In this system, fuzzy W was grown over a range of sample temperatures and ion fluences (containing He and impurity ion mixtures), but with operator control over the impurity to helium percentage (from 5 – 10%). The ion energies were held constant at 60 eV throughout the experiments. Close inspection of the surface morphologies showed that a variation in fuzzy structure was produced on W surfaces depending on the impurity species used. Specifically, Ne impurity produced cone-like fuzz structures and Ar and N 2 caused more random tendril growth. Using a constant fluence of He and impurity ion species, the effective fuzzy layer growth rate is reduced for higher impurity atomic masses and higher concentrations. For 10 % N 2 within the He plasma, little fuzz growth was visible on the W surface. Where 7.5 – 10% of Ar was used, fuzz growth was terminated completely. From mass loss measurements the net erosion yields of W surfaces exposed to 95 % He + 5% impurity (Ne or N 2 ) discharges were measured to be lower than bulk W sputtering yields for each impurity species, decreasing sharply with increasing fuzz thickness. Under high ion fluences up to 10 27 m − 2 , steady-state thicknesses of W fuzz were attained due to the combined effect of fuzz growth and sputter erosion caused by the impurity species in the plasma. The measured steady-state thicknesses were found to be consistent with an analytical model developed for the simultaneous growth and erosion of fuzz. SEM imaging showed the presence of larger fuzzy structures, Nano-tendril bundles (NTBs), on surfaces where fuzz grew under the presence of impurity species. The formation of NTBs were characterised in terms of their surface temperature threshold ranges.

Rough-surface effect on sputtering of Cr bombarded by low-energy He plasma

• Microscopic cones grow on a Cr surface during He plasma exposure. • Angular distribution of sputtered atoms becomes more over-cosine-like (narrower). • Sputtering yield is significantly reduced. • GITR coupled with SDTrimSP simulations reproduce the experimental findings. The formation of microscopic cone-like structures on a Cr surface is observed under He plasma exposure at a low incident ion energy of ∼106 eV in the PISCES-A linear plasma device. 2D emission profiles of the Cr I line intensity, measured with a hyperspectral imaging camera, are compared with those modeled using the GITR Monte Carlo impurity transport code coupled with the SDTrimSP binary collision code. With the growth of cones, the experimental 2D emission profile becomes axially elongated and the emission intensity significantly drops, and these observations are successfully reproduced in the simulation. The simulation reveals that the deposition of sputtered Cr atoms onto the neighboring cones results in a more over-cosine-like angular distribution, i.e., a narrower distribution with more particles ejected in the surface normal direction, of sputtered Cr atoms with a significant reduction of the sputtering yield.

Diamond synthesis on Si by plasma chemical vapor deposition using microwave sheath-voltage combination plasma

Microwave sheath-voltage combination plasma (MVP) represents a new method to generate plasma and coat diamond-like carbon films onto the three-dimensional metal surfaces . The present work investigates the synthesis of diamonds using MVP deposition, focusing in particular on how pressure and bias voltage affect the diamond structure. Using MVP, silicon wafers were coated with diamond in gas mixtures of methane and hydrogen with the substrate bias ranging from 0 to −200 V and pressure ranging from 800 to 1000 Pa. Although diamond particles are created with the substrate biased between 0 and −200 V at 1% methane concentration, at −200 V the particles are affixed atop Si or SiC cones that form on the Si substrate due to plasma etching . X-ray diffraction analysis reveals that the diamond structure is created up to a bias voltage of −100 V at 3% methane concentration. Nanodiamond is produced at methane concentration of 3%. These experiments suggest that MVP, a new diamond coating method, makes depositing the diamond on 3D shape substrates possible. • Diamond coatings are deposited by microwave sheath-voltage combination plasma. • Higher substrate temperature with nonzero bias voltage than with zero bias voltage • Higher negative bias produces cone-like structures on the substrate.

Laser Activated and Electroless Metalized Polyurethane Coatings Containing Copper(II) L-Tyrosine and Glass Microspheres.

Polyurethane coatings containing copper(II) L-tyrosine and glass microspheres were laser irradiated and underwent electroless metallization. Various sizes of glass microspheres were incorporated into the polyurethane coating matrix in order to examine their effects on surface activation and electroless metallization. The surface of the coatings was activated by using ArF excimer laser emitting ultraviolet radiation (λ = 193 nm) using different number of laser pulses and their fluence. The effects of surface activation and metallization were evaluated mainly based on optical and scanning electron microcopies (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoelectron spectroscopy (XPS). It was found that the presence of glass microspheres enabled the reduction in copper complex content, intensified the ablation process (higher cone-like structures created) and resulted in higher content of copper metallic seeds. On the other hand, the glass microspheres concentration, which was higher for lower size microspheres, was advantageous for obtaining a fully metallized layer.

Experimental study of spatial frequency transition of laser induced periodic surface structures

This study shows the influence of laser fluence and pulse number on the spatial frequency distribution of laser induced periodic surface structures (LIPSS) on a stainless steel surface. Also the transition of LIPSS to larger self organized, periodic, cone-like structures has been investigated. The experiments were carried out using a Ti:Sapphire femtosecond laser system with 800 nm centre wavelength, a pulse duration of 30 fs and a repetition rate of 1 kHz. Experiments have been carried out on flat, cold-rolled stainless steel surfaces (1.4301) by variation of the laser output power and feed rate. It could be shown, that the transition of low spatial frequency LIPSS (LSFL) to high spatial frequency LIPSS (HSFL) is a continuous process, strongly depending on the laser single pulse fluence and the pulse number. At higher accumulated fluences the transition of LIPSS to larger self organized structures could be observed. As a result, hierarchical structures were created with micrometer-sized cones at the bottom and nanometer-sized LIPSS on top. By further increasing the accumulated fluence, the grooves between the micro structures are widened until the ablation threshold of the alloy is reached. These hierarchical structures could be of considerable value in improving wetting properties of technical surfaces.

Observation of single ultrashort laser pulse generated periodic surface structures on linelike defects

The formation of self-assembled laser induced periodic surface structures (LIPSSs) after ultrashort pulsed laser ablation is still a matter of controversy in the literature. There is agreement that at least two different physical driving forces lead to ripples with distinguishable spatial periodicity. High spatial frequency LIPSSs with periodicity well below the incident wavelength are discriminated from low spatial frequency LIPSSs (LSFLs) revealing longer periodic structures. In general, both types of LIPSS appear after multipulse irradiation with the linear polarization direction on all material classes from metals to dielectrics. However, single-pulse induced LSFLs at 540 ± 35 nm periodicity with subpicosecond pulse are observed at linelike surface defects, e.g., scratches and grain boundaries. Depending on the difference in orientation between the electric field vector and the scratch direction, LIPSSs evolve upon ablation with 515 nm and 1 ps pulses near the threshold. This corroborates the theory proposed by Sipe et al. [Phys. Rev. B 27, 1141–1154 (1983)], where the impinging electromagnetic wave interacts with a collectively excited surface electron wave of the respective material at a surface defect. The observations on oxygenfree pure copper, zirconia, and a stainless steel substrate are discussed. Moreover, LSFLs generated with circular polarization at defects after single pulse ablation of wide bandgap zirconia ceramic are presented. In application, this phenomena affects the attainable surface quality, where LSFLs appear at defects such as scratches, grain boundaries, and, generally, material inhomogeneity. The absorptivity and ablation characteristic change leading to an altered material-laser interaction at the surface. This could be the root cause of conelike protrusion structures observed on stainless steel.

Self-oriented growth of β-Yb2Si2O7 and X1/X2-Yb2SiO5 coatings using laser chemical vapor deposition

We demonstrated the self-oriented growth of ytterbium silicate films at high deposition rates using laser chemical vapor deposition (laser CVD). β-Yb2Si2O7, X1-Yb2SiO5, and X2-Yb2SiO5 phases preferred (001)β and (110)β, (100)X1 and (021)X2, and (221)X2 orientations, respectively. The self-oriented growth was associated with crystallographic features, namely the edge-sharing Yb–O polyhedral networks in each phase. Deposition rates of the β-Yb2Si2O7 and X1/X2-Yb2SiO5 films ranged 114–423 and 353–943 μm h−1, respectively. Post annealing implied that β-Yb2Si2O7 and X2-Yb2SiO5 were the stable phases at elevated temperatures and the obtained films maintained their cone-like and columnar structures after annealing at 1673 K in air.

Quantum caustics and the hierarchy of light cones in quenched spin chains

We show that the light cone-like structures that form in spin chains after a quench are quantum caustics. Their natural description is in terms of catastrophe theory and this implies: 1) a hierarchy of light cone structures corresponding to the different catastrophes; 2) dressing by characteristic wave functions that obey scaling laws determined by the Arnol'd and Berry indices; 3) a network of vortex-antivortex pairs in space-time inside the cone. We illustrate the theory by giving explicit calculations for the transverse field Ising model and the XY model, finding fold catastrophes dressed by Airy functions and cusp catastrophes dressed by Pearcey functions; multisite correlation functions are described by higher catastrophes such as the hyperbolic umbilic. Furthermore, we find that the vortex pairs created inside the cone are sensitive to phase transitions in these spin models with their rate of production being determined by the dynamical critical exponent. More broadly, this work illustrates how catastrophe theory can be applied to singularities in quantum fields.

Geometry of nova ejecta

AbstractWe present photo-ionization and morpho-kinematic analyses of the ejecta of novae. The sample consists of ten novae belonging to the Fe II, He/N and hybrid classes. The Fe II class of novae in the sample have bipolar cone-like structures, with or without equatorial rings with inclination angle in the range of 40°–60°. The He/N novae have bullet-nose curve along with bipolar cone-like structures and equatorial rings with an inclination angle of ~80°. The hybrid nova in the sample is a bipolar frustum of prolate spheroid along with bipolar cone-like structures and equatorial rings with an inclination angle of 63°.