Design and analysis of a novel long-distance double tendon-sheath transmission device for breast intervention robots under MRI field

Cancer represents a major threat to human health. Magnetic resonance imaging (MRI) provides superior performance to other imaging-based examination methods in the detection of tumors and offers distinct advantages in biopsy and seed implantation. However, because of the MRI environment, the material requirements for actuating devices for the medical robots used in MRI are incredibly demanding. This paper describes a novel double tendon-sheath transmission device for use in MRI applications. LeBus grooves are used in the original transmission wheels, thus enabling the system to realize long-distance and large-stroke transmission with improved accuracy. The friction model of the transmission system and the transmission characteristics model of the novel tendon-sheath structure are then established. To address the problem that tension sensors cannot be installed in large-stroke transmission systems, a three-point force measurement method is used to measure and set an appropriate preload in the novel tendon-sheath transmission system. Additionally, experiments are conducted to verify the accuracy of the theoretical model and multiple groups of tests are performed to explore the transmission characteristics. Finally, the novel tendon-sheath transmission system is compensated to improve its accuracy and the experimental results acquired after compensation show that the system satisfies the design requirements

Planimetría de alta resolución del dolmen de Menga (Antequera, Málaga) mediante escaneado láser terrestre, levantamiento 3D y fotogrametría

Dielectric metasurfaces can achieve flexible beam manipulations. Herein, we study dielectric metasurfaces with different refractive indices, periods, incident angles, and cross-sectional shapes to determine the metasurface working mechanisms. Perfect transmission mainly depends on multipolar interference that can be used to control the transmission modes through the hybrid periods, hybrid cross sections, and multilayers. Perfect reflection is strongly influenced by the period of the metasurface and occurs only when the period is shorter than incident wavelength, which can be attributed to the lattice coupling. Furthermore, lattice coupling can be classified into two types with distinct properties: vertical mode and horizontal mode coupling. The vertical mode appears when the effective wavelength matches the feature size, whereas the horizontal mode only appears when the incident wavelength is close to the period. The horizontal mode is sensitive to the incident angle. The revealed functioning mechanisms enable further practical applications of metasurfaces

Beam Manipulation Mechanisms of Dielectric Metasurfaces

Dielectric metasurfaces can achieve flexible beam manipulations. Herein, we study dielectric metasurfaces with different refractive indices, periods, incident angles, and cross-sectional shapes to determine the metasurface working mechanisms. Perfect transmission mainly depends on multipolar interference that can be used to control the transmission modes through the hybrid periods, hybrid cross sections, and multilayers. Perfect reflection is strongly influenced by the period of the metasurface and occurs only when the period is shorter than incident wavelength, which can be attributed to the lattice coupling. Furthermore, lattice coupling can be classified into two types with distinct properties: vertical mode and horizontal mode coupling. The vertical mode appears when the effective wavelength matches the feature size, whereas the horizontal mode only appears when the incident wavelength is close to the period. The horizontal mode is sensitive to the incident angle. The revealed functioning mechanisms enable further practical applications of metasurfaces

Impact of microplastics on the in situ, high-resolution of key nutrient dynamics at the soil-water interface in rice fields

Introduction: Microplastics are characterized by their small size, widespread distribution, and durability, present a significant environmental risk. Despite their omnipresence in terrestrial and aquatic systems, the potential consequences on nutrient cycling remain under-investigated. Microplastics have emerged as a focal point of current research, presenting both a challenge and a frontier in environmental science.Methods: This study explores the effects of microplastics on the high-resolution, in situ distribution and exchange dynamics of key nutrients, nitrogen (N) and phosphorus (P), at the soil-water interface in rice paddies, utilizing the Diffusive Gradients in Thin-films (DGT) technique.Results: Our results reveal distinct spatial distribution patterns for N and P across the soil-water interface. Labile phosphorus (P) concentrations were significantly higher in the soil than in the overlying water, whereas DGT-NO3− concentrations exhibited the inverse trend. Different microplastic concentrations notably impacted DGT-NO3− (P = 0.022) and DGT-NH4+ (P = 0.033), with an increase between 27.79% and 150.68%. Moreover, different particle sizes significantly influenced NH4+. Interestingly, paddy soil acted as a “source” for labile P and a “sink” for NH4+ and NO3−.Discussion: These insights provide valuable insights into the interactions between microplastics and nutrient cycles at the soil-water interface, and assess the effects on nutrient migration and transformation. The outcomes of this study will contribute to an improved understanding of the broader ecological implications of microplastic pollution in agricultural settings. It will also provide a foundation for the development of strategies to manage and mitigate the impacts of microplastic pollution in agricultural soils, particularly in rice dominated agroecosystems

Light-driven C-H bond activation mediated by 2D transition metal dichalcogenides

C-H bond activation enables the facile synthesis of new chemicals. While C-H activation in short-chain alkanes has been widely investigated, it remains largely unexplored for long-chain organic molecules. Here, we report light-driven C-H activation in complex organic materials mediated by 2D transition metal dichalcogenides (TMDCs) and the resultant solid-state synthesis of luminescent carbon dots in a spatially-resolved fashion. We unravel the efficient H adsorption and a lowered energy barrier of C-C coupling mediated by 2D TMDCs to promote C-H activation. Our results shed light on 2D materials for C-H activation in organic compounds for applications in organic chemistry, environmental remediation, and photonic materials

Discrete element simulation of particle motion in ball mills based on similarity

Discrete element (DE) simulation of a ball mill with a large number of particles is challenging when each particle is considered. Similarity principle could be adopted to reduce the number of particles in a simulation whilst still maintaining the accurate flow behaviour of particles. This paper presents a scaling relationship between particle gravitational acceleration, mill diameter and mill rotational speed. A series of scaled simulations of particle motion with different mill diameters are carried out. Consistent motion of a single particle and multiple particles in ball mills with different diameters and rotational speeds verifies the proposed relationship, which could be an effective approach to reduce the size of simulations for ball mills

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data