Spherical Volume Research Articles

Analysis of the changes in corneal optical density following small incision lenticule extraction for myopia and related influencing factors

Purpose: To examine changes in corneal optical density (COD) following small incision lenticule extraction (SMILE) for myopia and the associated factors affecting COD. Methods: One hundred and ten eyes of 110 subjects who underwent SMILE were included in this study. COD and influencing factors were evaluated before and three months after SMILE. The changes in COD were compared and analysed with those of other influencing factors. Representative positive outcomes were chosen to investigate the influence in various ways. Results: This study found significant reductions in most anterior, central, and posterior CODs following SMILE (P<0.05), but the anterior 2-6 mm COD exhibited a significant increase (P<0.001). Lenticule thickness (LT), refractive sphere, preoperative Km, and Δcorneal volume (CV) were related to some of the whole ΔCODs (P<0.05). Age, gender, intraocular pressure (IOP), refractive cylinder, corrected distance visual acuity (CDVA), preoperative central corneal thickness (CCT), and preoperative CV were not correlated with the whole ΔCODs. Further exploration revealed that an increase in LT leads to a pattern of increasing and then decreasing changes in the whole ΔCODs. Most of the ΔCODs values were significantly lower in the high central corneal stromal ablation thickness group than in the high anterior corneal stromal ablation thickness group (P<0.05). Conclusions: Changes in COD were mainly caused by LT and its associated factors. However, the relationship between LT and ΔCOD might not be linear. Deeper corneal stromal ablation may reduce the COD. Changes in COD following SMILE are a multifaceted process influenced by various circumstances.

Passive shimming of a 3T cryogen-free animal magnetic resonance imaging superconducting magnet with dense shim tray slots and small residual magnetic force.

Passive shimming is widely used in magnetic resonance imaging (MRI) systems due to its excellent efficacy and cost-effectiveness. However, conventional shim tray structures have difficulty in effectively adjusting magnetic field distributions under specific conditions. This limitation can lead to insufficient cancellation of harmonics and result in significant residual forces on the trays, impeding accurate placement of the trays. In this study, instead of using the conventional design of the shim tray slot, we propose a dedicated passive shimming tray tailored for 3T cryogen-free animal MRI superconducting magnets. Passive shimming experiments were conducted to evaluate the performance of this novel design, in which we were able to improve the peak-to-peak magnetic field homogeneity within the 180mm diameter imaging region, reducing peak-to-peak (p-p) variation from 349.35 ppm to 19.08 ppm. Furthermore, the p-p homogeneity of the magnetic field measured at the imaging area with a diameter of spherical volume (DSV) of 160mm reached 8.67 ppm. In addition, we strictly controlled the residual magnetic force of the shim tray to ensure its accurate placement. The experimental results indicate that the proposed structural optimization method and the residual magnetic force control strategy show potential in high-field MRI instruments requiring high homogeneity and handling of high residual magnetic force.

Design method of transverse gradient coils based on nonuniform rational B-spline (NURBS) curves.

To propose a hybrid transverse gradient coil design method that leverages current density-based methods and nonuniform rational B-spline (NURBS) curves to optimize the performance and manufacturability of gradient coils. Our method begins by generating an initial wire configuration using a density-based method. Then, we fit NURBS curves to the configuration, and adjust the control parameters of these curves to meet performance requirements. To ensure adequate spacing and even distribution of wires, an objective function utilizing the sigmoid function to modulate the distances between adjacent wires is constructed. Critical factors including gradient efficacy, linearity, eddy current, and torque, are incorporated as constraints. The piecewise nature of the curves provides the flexibility to independently control specific segments without impacting others. We validated our method by designing three shielded transverse gradient coils: a whole-body coil, an ultra-short whole-body coil, and an ultra-short asymmetric head coil. The primary design objectives were to improve linearity and maintain gradient efficiency. All optimized coils demonstrated significant linearity across large diameters of spherical volumes (DSVs), while gradient efficiency, eddy currents, and torque were well-balanced. The objective function effectively managed the wire concentrations required for high linearity, ensuring even wire arrangement and adequate spacing. We leveraged the flexibility of the curves to individually tailor wire paths for specific objectives, such as preventing interference between coils and passive shimming and accommodating wire connections and cooling circuits. This method provides a versatile and effective approach for designing high-performance and manufacturable gradient coils.

Study on combustion and emission characteristics of hydrogen/air mixtures in a constant volume combustion bomb

Hydrogen is an environmentally-friendly fuel with the characteristics of low carbon, high calorific value, and extensive combustible range, making it an optimal alternative fuel for internal combustion engines. In this study, an experiment using a spherical constant volume combustion bomb (CVCB) was conducted to investigate the combustion and emission characteristics of hydrogen/air mixtures. The results shows that the flame propagation velocity of hydrogen laminar flow initially increases and then decreases with the excess air coefficient (λ), reaching peak at λ = 0.6, and the flame becomes unstable on the side of lean burning (λ > 1.0). Both the NOx emissions and the average temperature in the CVCB initially rise before eventually declining with the λ, the peak values for both NOx emission and mean temperature are reached at λ = 1.0. The dilution of N2 inhibits the laminar combustion and emission of hydrogen. As the dilution rate of N2 increases, little change occurs in the Markstein length, while flame propagation velocity, NOx emission, and average temperature all decrease. An increase in initial pressure hinders the development of the initial flame, while promoting the formation of cellular structure within the flame. Consequently, unstable combustion leads to a rapid increase in flame propagation speed during later stages. The average temperature inside the CVCB and the NOx emission increase by 6.6 % and 25.9 %, respectively, with the initial pressure increasing from 0.1 MPa to 0.5 MPa. On the other hand, an increase in initial temperature can facilitate flame development and results in an increased flame propagation speed. Especially, Markstein length is less sensitive to changes in initial temperature than to changes in initial pressure. The average temperature and NOx emission present a pattern of increasing first and decreasing then with the increase in initial temperature. These results have provided empirical evidence for optimizing the combustion and emission control of hydrogen engines.

Constitutive modelling for understanding stress-stretch behaviour of Lennard-Jones non-crystalline molecular Solid

Abstract Non-crystalline molecular solid materials have many scientific and engineering applications. This study develops a constitutive equation for understanding stress-stretch behaviour of non-crystalline molecular solid using Lennard-Jones (LJ) intermolecular interaction. The strain energy derived from Lennard-Jones interactions between molecules. Based on the excluded volume (spherical volume occupied by the molecules maintaining centre to centre distance with a reference molecule) and density of the molecules, strain energy density is developed. In order to relate the molecular approach with continuum approximation, the excluded volume and density are expressed as a function of strain invariants of right Cauchy-Green deformation tensor. Finally, the constitutive equation in the form of Cauchy stress tensor is developed using the present strain energy density function. The present constitutive model is used to study finite deformations of the molecular solid like uniaxial extension. We compare our theoretical results with the experimental data of flexible polyurethane foams and obtain very good agreements. The current constitutive model can predict the deformation of micro/nano engineering system components.

A hybrid, nonlinear programming approach for optimizing passive shimming in MRI.

In magnetic resonance imaging (MRI), maintaining a highly uniform main magnetic field (B0) is essential for producing detailed images of human anatomy. Passive shimming (PS) is a technique used to enhance B0 uniformity by strategically arranging shimming iron pieces inside the magnet bore. Traditionally, PS optimization has been implemented using linear programming (LP), posing challenges in balancing field quality with the quantity of iron used for shimming. In this work, we aimed to improve the efficacy of passive shimming that has the advantages of balancing field quality, iron usage, and harmonics in an optimal manner and leads to a smoother field profile. This study introduces a hybrid algorithm that combines particle swarm optimization with sequential quadratic programming (PSO-SQP) to enhance shimming performance. Additionally, a regularization method is employed to reduce the iron pieces' weight effectively. The simulation study demonstrated that the magnetic field was improved from 462 to 3.6ppm, utilizing merely 1.2kg of iron in a 40cm diameter spherical volume (DSV) of a 7T MRI magnet. Compared to traditional optimization techniques, this method notably enhanced magnetic field uniformity by 96.7% and reduced the iron weight requirement by 81.8%. The results indicated that the proposed method is expected to be effective for passive shimming.

Monte Carlo investigation of the nucleus size effect and cell’s oxygen content on the damage efficiency of protons

Living tissues could suffer different types of DNA damage as a result of being exposed to ionizing radiations. Monte Carlo simulations of the underlying interactions have been instrumental in predicting the damage types and the processes involved. In this work, we employed Geant4-DNA and MCDS for extracting the initial DNA damage and investigating the dependence of damage efficiency on the cell’s oxygen content. The frequency-mean lineal ( y¯F ) and specific ( z¯F ) energies were derived for a spherical volume of water of various diameters between 2 and 11.1 μm. This sphere would serve as the nucleus of a cell of 100 μm diameter, engulfed by a homogeneous beam of protons. These microdosimetric quantities were calculated assuming spherical samples of 1 μm diameter in MCDS. The simulation results showed that for 230 MeV protons, an increase in the oxygen content from 0 by 10% raised the frequency of single- and double-strand breaks and lowered the base damage frequency. The resulting damage frequencies appeared to be independent of nucleus diameter. For proton energies between 2 and 230 MeV, y¯F showed no dependence on the cell diameter and an increase of the cell size resulted in a decrease in z¯F. An increase in the proton energy slowed down the decreasing rate of z¯F as a function of nucleus diameter. However, the ratio of y¯F values corresponding to two proton energies of choice showed no dependence on the nucleus size and were equal to the ratio of the corresponding z¯F values. Furthermore, the oxygen content of the cell did not affect these microdosimetric quantities. Contrary to damage frequencies, these quantities appeared to depend only on direct interactions due to deposited energies. Our calculations showed the near independence of DNA damages on the nucleus size of the human cells. The probabilities of different types of single and double-strand breaks increase with the oxygen content.

Fatigue assessment of structural components through the Effective Critical Plane factor

The integrity assessment of structural components under complex loading conditions relies on the evaluation of the fatigue damage typically arising from stress concentrations, such as geometric irregularities, notches, weld beads, grooves etc.. Various methodologies, including the Notch Stress Approach (NSA), the Theory of Critical Distances (TCD), the Strain Energy Density (SED), and the Critical Plane (CP) concept, have been pivotal in assessing fatigue strength for notched and welded components. Recent works combine some of the above mentioned methodologies, while other works propose to vary the embedded parameters accounting for the loading type or the fatigue lives, trying to improve the accuracy of the fatigue assessment process. This paper introduces a novel approach, the Effective Critical Plane (ECP), which is founded on the critical plane concept. The CP factor is, however, calculated starting from an averaged, over a small volume, stress–strain field. The size of the averaging volume is assumed to be a material parameter and is determined by a best fitting procedure over different experimental data sets. The novel approach is illustrated by means of the Fatemi-Socie and the Smith-Watson-Topper CP damage factors. Its potential application to other CP formulations is straightforward, as well. Literature experimental data for low carbon steel specimens possessing different notches and loading conditions are used to validate the method’s capability in accurately determining the fatigue life and to set the radius of the averaging volume for the given material and CP parameter. A spherical volume or circular area are used in case of fully 3D or 2D numerical models, respectively. Results are compared to those of some of already existing methods, namely SED, TCD and the Modified Wöhler Curve Method.

Generation of mouse testicular organoids with highly compartmentalized tubular lumen structure and their cryopreservation

Testicular organoids have great potential for maintaining male fertility and even restoring male infertility. However, existing studies on generating organoids with testis-specific structure and function are scarce and come with many limitations. Research on cryopreservation of testicular organoids is even more limited, and inappropriate cryopreservation methods may result in the loss of properties in resuscitated or regenerated organoids, rendering them unsuitable for clinical or research needs. In this paper, we investigated the effects of mouse age and cell number on the self-aggregation of testicular cells into spheres in low-adsorption plates. Various media compositions, culture systems, and cell numbers were used to culture cell spheres for 14 days to form testicular organoids, and the self-organization of the organoids was assessed by histological and immunofluorescence staining. We determined the appropriate cryopreservation conditions for testicular cells, cell spheres, and tissues. Subsequently, organoids derived from cryopreserved testicular tissues, testicular cells, and testicular cell spheres were compared and evaluated by histological and immunofluorescence staining. The results indicate that testicular cell spheres consisting of 30 × 104 testicular cells from 2-week-old mice were able to form organoids highly similar to the luminal structure and cell distribution of natural mouse testicular tissues. This transformation occurred over 14 days of incubation in α-MEM medium containing 10 % knockout serum replacer (KSR) using an agarose hydrogel culture system. Additionally, the Sertoli cells were tightly connected to form a blood-testis barrier. The relative rates of tubular area, germ cells, Sertoli cells, and peritubular myoid cells were 36.985 % ± 0.695, 13.347 % ± 3.102, 47.570 % ± 0.379, and 27.406 % ± 1.832, respectively. The optimal cryopreservation protocol for primary testicular cells involved slow freezing with a cryoprotectant consisting of α-MEM with 10 % dimethyl sulfoxide (DMSO). Slow freezing with cryoprotectants containing 5 % DMSO and 5 % ethylene glycol (EG) was optimal for all different volumes of testicular cell spheres. Compared to testicular organoids generated from frozen testicular tissue and cell spheres, freezing testicular cells proved most effective in maintaining organoid differentiation characteristics and cell-cell interactions. The findings of this study contribute to a “universal” testicular organoid in vitro culture protocol with promising applications for fertility preservation and restoration in prepubertal cancer patients and adult infertile patients.

Output performance of zinc tin oxide nanoparticle-based piezoelectric nanogenerators with different shapes and phases

This study reports the characteristics of a piezoelectric nanogenerator (PENG) consisting of a mixture of polydimethylsiloxane (PDMS) and zinc tin oxide (ZTO) particles (ZTO@PDMS) with different shapes and phases. The output performance of PENGs with crystalline Zinc hydroxystannate(ZHS), amorphous ZTO, and crystalline ZTO of different phases was investigated based on annealing temperature. The fabricated PENGs with amorphous ZTO (a-ZTO) cubes showed a maximum output voltage of ∼4.3V and a current of ∼470 nA with a power of 3.14 μW, which is 249 % higher than that of the crystalline ZTO (c-ZTO) cube-based one. The amorphous ZTO (a-ZTO) nanosphere showed the highest output performance. The surface area of the piezoelectric material affected the residual polarization, which led to different piezoelectric properties. Therefore, we investigated the output performance of PENGs with various shapes while maintaining the same volumes of ZTO cubes and spheres. The molar ratio of the materials was varied during synthesis, revealing that the ZTO cubes have a higher output performance. The polarization-electric loops (P-E loops) showed a high remnant polarization (Pr∼25.89μC/cm2) in ZTO@PDMS films with larger 1103 nm cubes. These values were 170.5 %, 143.7 %, and 113.2 % larger than those observed in ZTO@PDMS films with cubes of size 826 nm, 978 nm, and 1047 nm, respectively. The ZTO nanocubes have a significant advantage in the fabrication of high output performance based on PENGs.

Homogeneous B0 coil design method for open-access ultra-low field magnetic resonance imaging: A simulation study

A multimodal brain function measurement system integrating functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) is expected to be a tool that will provide new insights into neuroscience. To integrate fMRI and MEG, an ultra-low-field MRI (ULF-MRI) scanner that can generate a static magnetic field (B0) with an electromagnetic coil and turn off the B0 during MEG measurements is desirable. While electromagnetic B0 coil has the above advantages, it also has a trade-off between size and the broadness of the magnetic field homogeneity. In this study, we proposed a method for designing a B0 multi-stage circular coil arrangement that determines the number of coils required to maximize magnetic field homogeneity and minimize the total wiring length of the coils. The optimized multi-stage coil arrangement had an external shape of 600 mm in diameter and a maximum height of 600 mm, with an aperture of 600 mm in diameter and 300 mm in height. The magnetic field homogeneity was <100 ppm over a 210 mm diameter spherical volume (DSV). Compared to a previous two coil pairs arrangement with the same magnetic field homogeneity, the diameter was 1/1.9 times smaller, indicating that the newly designed B0 coil arrangement realized a smaller size and wider magnetic field homogeneity.

Active shimming for a 25 T NMR superconducting magnet by spectrum convergence method

In the design of ultrahigh field nuclear magnetic resonance (NMR) superconducting magnets, it typically requires a high homogeneous magnetic field in the diameter of spherical volume (DSV) to obtain high spectrum resolution. However, shimming technique presents challenges due to the magnet bore space limitations, as accurate measurement of magnetic field distribution is very difficult, especially for customized micro-bore magnets. In this study, we introduced an active shimming method that utilized iterative adjustment of shim coil currents to improve the magnetic field homogeneity based on the full width at half maximum (FWHM) of the spectrum. The proposed method can determine the optimal set of currents for shim coils, effectively enhancing spatial field homogeneity by converging the FWHM. Experimental validation on a 25 T NMR superconducting magnet demonstrated the efficacy of the proposed method. Specifically, the active shimming method improved the field homogeneity of a 10 mm DSV from 7.09 ppm to 2.27 ppm with only four shim coils, providing a superior magnetic field environment for solid NMR and further magnetic resonance imaging (MRI) experiment. Furthermore, the proposed method can be promoted to more customized micro-bore magnets that require high magnetic field homogeneity.

Light management by algal aggregates in living photosynthetic hydrogels

Rapid progress in algal biotechnology has triggered a growing interest in hydrogel-encapsulated microalgal cultivation, especially for the engineering of functional photosynthetic materials and biomass production. An overlooked characteristic of gel-encapsulated cultures is the emergence of cell aggregates, which are the result of the mechanical confinement of the cells. Such aggregates have a dramatic effect on the light management of gel-encapsulated photobioreactors and hence strongly affect the photosynthetic outcome. To evaluate such an effect, we experimentally studied the optical response of hydrogels containing algal aggregates and developed optical simulations to study the resultant light intensity profiles. The simulations are validated experimentally via transmittance measurements using an integrating sphere and aggregate volume analysis with confocal microscopy. Specifically, the heterogeneous distribution of cell aggregates in a hydrogel matrix can increase light penetration while alleviating photoinhibition more effectively than in a flat biofilm. Finally, we demonstrate that light harvesting efficiency can be further enhanced with the introduction of scattering particles within the hydrogel matrix, leading to a fourfold increase in biomass growth. Our study, therefore, highlights a strategy for the design of spatially efficient photosynthetic living materials that have important implications for the engineering of future algal cultivation systems.

Abstract PO2-15-10: Identifying new immune-related biomarkers in TNBC with a look at PD-L1 cell-autonomous role

Abstract Background The programmed death ligand 1 (PD-L1) has recently emerged as a target immunotherapy in Triple-negative breast cancer (TNBC). However, the tumor-intrinsic role of PD-L1 and its pathway still needs to be fully clarified. Recently, a close association between CD73, PD-L1, cancer cell steaminess and epithelial-to-mesenchymal transition phenotypes is emerging. In addition, we have previously demonstrated that miR-320a and miR-145 target PD-L1, whereas miR-30 family is known to target CD73. In this study, we aimed at investigating the role of these miRNAs as prognostic and predictive dynamic biomarkers for immunotherapy in TNBC. Additionally, we investigated whether PD-L1 exerts cellular autonomic functions in TNBC beyond its role in the immune checkpoint. Results CD73 and PD-L1 expression was assessed in a panel of breast cancer lines and the non-malignant breast cells MCF-10. We showed a significantly higher CD73 and PD-L1 expression in MDA-MB-231 (TNBC, Basal B) than in MCF-10. Conversely, in MCF-7 cells (HR +, Luminal A), CD73 and PD-L1 expression is lower than in MCF-10. Furthermore, we showed that low PDL1 expression is correlated with high levels of miR-320a and miR-145, and CD73 expression is inversely related to miR-30 expression. These putative biomarkers were also validated in two patients with different PD-L1 status. From the analysis of the data obtained by real-time qRT-PCR, we found high plasma level of CD73 and low plasma level of miR-320a, miR-145 and miR-30 in the patient with PD-L1 positive BC. On contrary, in the patient with PD-L1-negative BC, we found low plasma level of CD73 and high plasma level of miR-320a, miR-145 and miR-30. Furthermore, to explore whether PD-L1 could also have an intrinsic role in tumor development and invasiveness, we used stably MDA–MB-231 PD-L1-silenced cells. We found that cell growth, colony formation, migration rate and the ability to form spheres are consistently reduced upon shRNA-mediated PDL1 silencing. In particular, we observed a reduction in the number, diameter and volume of the 3D spheres compared to the control cells. To further demonstrate the role of PD-L1, we treated the PDL1-high expression cells MDA-MB-231, PD-L1 silenced MDA-MB-231 clones, and PD-L1 low expression cells MCF-7 with Durvalumab, an anti-PD-L1. Interestingly, we observed that in PD-L1 silenced clones and MCF-7 cells, the sphere-forming ability was increased in presence of Durvalumab treatment. On the contrary, in MDA-MB-231, Durvalumab inhibited the sphere-forming ability. Conclusion Our data confirm that PD-L1 and CD73 are targets of miR-320a/miR-145 and miR-30 respectively. These could be potential predictive dynamic biomarkers for chemotherapy, ICIs and anti-CD73 therapeutic approach. Future validations of these biomarkers in an extensive series of TNBC patients are needed to support their use in clinical practice. Here, we further characterized the cellular autonomic role of PD-L1 in breast cancer and showed a differential role of basal PD-L1 expression in PD-L1 checkpoint inhibitors treatment efficacy. This suggests a potential role in monitoring PD-L1 expression indirect biomarkers (i.e. miR-320a, miR-145 and CD73) during ICIs treatment.

Flow and clogging behavior of a mixture of particles in a silo

We investigated the clogging behavior observed during the flow of aspherical particles from a silo in the presence of spherical particles of different sizes and proportions using flow visualization experiments and discrete element method simulations. The size of the avalanche, essentially the tendency of clogging, exhibits non-monotonic dependence on the spherical particle volume fraction. For small enough content of spherical particles, the clogging tendency intensifies, whereas it reduces rapidly for high enough spherical particle fractions, with a minimum in between. The non-monotonic behavior is observed to persist over for different spherical particle sizes. The overall behavior is shown to arise due to competing effects between the localized total particle fraction influencing avalanche strength and mean size of the particles exiting the silo, influencing the probability of arch formation.

Impact of property covariance on cluster weak lensing scaling relations

ABSTRACT We present an investigation into a hitherto unexplored systematic that affects the accuracy of galaxy cluster mass estimates with weak gravitational lensing. Specifically, we study the covariance between the weak lensing signal, ΔΣ, and the ‘true’ cluster galaxy number count, Ngal, as measured within a spherical volume that is void of projection effects. By quantifying the impact of this covariance on mass calibration, this work reveals a significant source of systematic uncertainty. Using the MDPL2 simulation with galaxies traced by the SAGE semi-analytic model, we measure the intrinsic property covariance between these observables within the three-dimensional vicinity of the cluster, spanning a range of dynamical mass and redshift values relevant for optical cluster surveys. Our results reveal a negative covariance at small radial scales (R ≲ R200c) and a null covariance at large scales (R ≳ R200c) across most mass and redshift bins. We also find that this covariance results in a $2{\!-\!}3~{{\ \rm per\ cent}}$ bias in the halo mass estimates in most bins. Furthermore, by modelling Ngal and ΔΣ as multi-(log)-linear equations of secondary halo properties, we provide a quantitative explanation for the physical origin of the negative covariance at small scales. Specifically, we demonstrate that the Ngal–ΔΣ covariance can be explained by the secondary properties of haloes that probe their formation history. We attribute the difference between our results and the positive bias seen in other works with (mock)-cluster finders to projection effects. These findings highlight the importance of accounting for the covariance between observables in cluster mass estimation, which is crucial for obtaining accurate constraints on cosmological parameters.

A numerical study on homogeneity and central field with axial spacing between DP coils of HTS magnet at 65 K

A numerical study is performed with COMSOL multi-physics, to analyze the effect of axial spacing between double pancake (DP) coils on central magnetic field and field homogeneity of High temperature Superconducting (HTS) magnet. The magnet is wound in the form of DP coils having, inner winding diameter as 100 mm and is operated at 65 K. The field homogeneity is calculated over a Diameter of Spherical Volume (DSV) of 40 mm for the entire study. The analysis is carried out by considering a constant length of HTS tape of 750 m and varying the number of DP coils from 4 to 14. The number of turns in all the DP coil is equal for a given set of DP coils to maintain the length of HTS tape to be constant. The coil separation within DP coils is of constant gap from 0.5 to 2 mm, while the axial spacing between the DP coils is varied from 0 to 50 mm for all the set of DP coils. The optimum gap between DP coils was evaluated using Exhaustive search optimization techniques and decreased with the number of DP coils. The best field homogeneity of 662.5 ppm was achieved with 14 DP coils having gDP=20.3 mm and gSP=2 mm for the chosen solenoid configuration.

Когнитивни аспекти на метафорите в съвременните български политически речи

The development follows two sides of the manifestation of cognitive metaphors as a communicative mechanism in contemporary Bulgarian political discourse: the rhetorical aspects of Bulgarian political communication; the linguistic-communicative features of cognitive metaphors in political speech, through which they function as a mechanism for interaction between the parties of political discourse. An important direction in the course of the study is to clarify the mechanisms by which the interaction between the parties in communication is realized. In this regard, several specific features of the national political discourse can be identified: the authority of the speaker and his ability to control all levels in the structure of the context of the political message; the dominant role of individual discourse; aggressive linguistic presence in communication; the dominant presence of conversational speech at the expense of the official; manipulation of objectivity; low level of informative ness. The cognitive and semantic aspects of metaphors in contemporary Bulgarian political discourse impose the following differentiation of their features: specificity of archetypal metaphors - the possibility of the basic metaphor to be reproduced as a stable cognitive core in the contemporary political communicative act; specificity of variant metaphors - the cognitive projection of the archetypal metaphor and its inscription in a new metaphorical perspective (cognitive range of metaphors path and body); cognitive links between the source sphere, the conceptual sphere and the target sphere - the associative link between the target and the source is the specificity of the cognitive metaphor, and all variant projections between them make up the volume of the conceptual sphere. The summary affects the function of cognitive metaphorical models in Bulgarian political discourse.

Effect of Cu addition on the precipitation behavior of M2C carbides in maraging steel

In this study, two Ferrium S53 steels with and without 1.5% Cu were prepared. The microscopic morphology and structure of these steels during aging treatment were analyzed by transmission electron microscopy (TEM). The average equivalent spherical radius (Rv), volume fraction (ϕv), and number density (Nv) of Cu-rich precipitates and M2C carbides during aging treatment were analyzed by atom probe tomography (APT), and the spatial distribution, interfacial elemental segregation, and one-dimensional concentration profiles of the two types precipitates were also characterized. Based on the distribution of elements, 5%Cu and 9% (C + Mo) isoconcentration surfaces were selected to obtain Cu-rich precipitates and M2C carbides, respectively. The results demonstrate that the Cu-rich precipitates formed before the M2C carbides. The segregation of Cr and Mo elements at the phase interface due to the nucleation and growth of Cu-rich precipitates can promote the formation of the M2C carbides. The two types of precipitates display adjacent distribution relationship in steel. The number density of M2C carbides in steel contain 1.5%Cu can be greatly increased when the Cu-rich precipitates serving as nucleation particles. The formation of needle-like M2C carbides inhibited the coarsening of Cu-rich precipitates. More dispersive and fine M2C carbides were obtained in the steel.

Lightweight broadband electromagnetic wave absorption achieved by a like-clustered CNTs spheres modified SiC nanowires

Developing lightweight, broadband, and highly absorptive electromagnetic (EM) wave absorption materials by effectively utilizing the agglomeration effect of one-dimensional nanowires is challenging. In this work, a SiCnws/CNTs aerogel with a like-clustered CNTs sphere-modified SiCnws structure was prepared via simple freeze-drying and heat treatment techniques, where the CNTs content was controlled to adjust the quantity and volume of the CNTs spheres. This allows for effective regulation of the impedance matching characteristics and dielectric loss capability. Specifically, the SiCnws/CNTs aerogel exhibited remarkable dissipation of EM waves through the enhancement of the interface and dipole polarization, achieved by significantly increasing the presence of multiple interfaces and defects. Moreover, the aerogel structure induces conduction loss and amplifies multiple reflections and scattering, facilitating efficient dissipation of EM wave energy across multiple levels. The minimum reflection loss (RLmin) of the SiCnws/CNTs aerogel (SN-3 sample) achieves −43.4 dB at 11.2 GHz with a matching thickness of 2.6 mm. Its effective absorption bandwidth (EAB) spans from the C band to the Ku band (7.4–18 GHz) at thicknesses ranging from 2.1 to 4.4 mm. Additionally, when the matching thickness is 3.4 mm, the broadened EAB extends up to 9.8 GHz (covering the whole X and Ku bands). Furthermore, CST simulations clearly demonstrate a remarkable suppression of the incident EM wave by the samples under real-world conditions, with a substantial reduction of 42.5 dBm2 in the RCS. Considering this, SiCnws/CNTs aerogel materials pave the way for new opportunities in lightweight, broadband, and high-absorption materials.