Hollow Space Research Articles

Epithelial morphogenesis, tubulogenesis and forces in organogenesis.

As multi-cellular organisms evolved from small clusters of cells to complex metazoans, biological tubes became essential for life. Tubes are typically thought of as mainly playing a role in transport, with the hollow space (lumen) acting as a conduit to distribute nutrients and waste, or for gas exchange. However, biological tubes also provide a platform for physiological, mechanical, and structural functions. Indeed, tubulogenesis is often a critical aspect of morphogenesis and organogenesis. C. elegans is made up of tubes that provide structural support and protection (the epidermis), perform the mechanical and enzymatic processes of digestion (the buccal cavity, pharynx, intestine, and rectum), transport fluids for osmoregulation (the excretory system), and execute the functions necessary for reproduction (the germline, spermatheca, uterus and vulva). Here we review our current understanding of the genetic regulation, molecular processes, and physical forces involved in tubulogenesis and morphogenesis of the epidermal, digestive and excretory systems in C. elegans.

Simulation and experimental analysis on cast metal runs behaviour rate at different gating models

Visual assessment in casting is difficult to assess due to the opacity and the high working temperature. By using the simulation tool, it can be avoided through an examination on the melt runs inside the mould cavity, pressure variation, and runs velocity in the different areas of the gating framework. Assessments are conducted for decided gating design and the sprinter aspect proportions. The MAGMASOFT, a simulation tool is preferred to study the exceptional gating proportions to achieve the velocity, force exerted at the sprinter location, and ingates. A regression version is designed to pick out the real speed and the pressure of liquid metal exists in the mould hollow space. Further, the melt velocity dissected as a detail of distance covered concerning ingate for the distinct gating propositions. A high-speed thermal camera is used to verify the actual melt motion in different gating systems and contrasted with the simulated observation.

Simulation and experimental analysis on cast metal runs behaviour rate at different gating models

Visual assessment in casting is difficult to assess due to the opacity and the high working temperature. By using the simulation tool, it can be avoided through an examination on the melt runs inside the mould cavity, pressure variation, and runs velocity in the different areas of the gating framework. Assessments are conducted for decided gating design and the sprinter aspect proportions. The MAGMASOFT, a simulation tool is preferred to study the exceptional gating proportions to achieve the velocity, force exerted at the sprinter location, and ingates. A regression version is designed to pick out the real speed and the pressure of liquid metal exists in the mould hollow space. Further, the melt velocity dissected as a detail of distance covered concerning ingate for the distinct gating propositions. A high-speed thermal camera is used to verify the actual melt motion in different gating systems and contrasted with the simulated observation.

Structural Investigations of Human A2M Identify a Hollow Native Conformation That Underlies Its Distinctive Protease-Trapping Mechanism

Human α2-macroglobulin (A2M) is the most characterized protease inhibitor in the alpha-macroglobulin (αM) superfamily, but the structure of its native conformation has not been determined. Here, we combined negative stain electron microscopy (EM), small-angle X-ray scattering (SAXS), and cross-linking–mass spectrometry (XL-MS) to investigate native A2M and its collapsed conformations that are obtained through aminolysis of its thiol ester by methylamine or cleavage of its bait region by trypsin. The combined interpretation of these data resulted in a model of the native A2M tetramer and its conformational changes. Native A2M consists of two crescent-shaped disulfide-bridged subunit dimers, which face toward each other and surround a central hollow space. In native A2M, interactions across the disulfide-bridged dimers are minimal, with a single major interface between the linker (LNK) regions of oppositely positioned subunits. Bait region cleavage induces both intrasubunit domain repositioning and an altered configuration of the disulfide-bridged dimer. These changes collapse the tetramer into a more compact conformation, which encloses an interior protease-trapping cavity. A recombinant A2M with a modified bait region was used to map the bait region’s position in native A2M by XL-MS. A second recombinant A2M introduced an intersubunit disulfide into the LNK region, demonstrating the predicted interactions between these regions in native A2M. Altogether, our native A2M model provides a structural foundation for understanding A2M’s protease-trapping mechanism, its conformation-dependent receptor interactions, and the dissociation of native A2M into dimers due to inflammatory oxidative stress.

Helix-Sense-Selective Encapsulation of Helical Poly(lactic acid)s within a Helical Cavity of Syndiotactic Poly(methyl methacrylate) with Helicity Memory.

We report a highly enantio- and helix-sense-selective encapsulation of helical poly(lactic acid)s (PLAs) through a unique "helix-in-helix" superstructure formation within the helical cavity of syndiotactic poly(methyl methacrylate) (st-PMMA) with a one-handed helicity memory, which enables the separation of the enantiomeric helices of the left (M)- and right (P)-handed-PLAs. The M- and P-helical PLAs with different molar masses and a narrow molar mass distribution were prepared by the ring-opening living polymerization of the optically pure l- and d-lactides, respectively, followed by end-capping of the terminal residues of the PLAs with a 4-halobenzoate and then a C60 unit, giving the C60-free and C60-bound M- and P-PLAs. The C60-free and C60-bound M- and P-PLAs formed crystalline inclusion complexes with achiral st-PMMA accompanied by a preferred-handed helix induction in the st-PMMA backbone, thereby producing helix-in-helix superstructures with the same-handedness to each other. The induced helical st-PMMAs were retained after replacement with the achiral C60, indicating the memory of the induced helicity of the st-PMMAs. Both the C60-free and C60-bound helical PLAs were enantio- and helix-sense selectively encapsulated into the helical hollow space of the optically active M- and P-st-PMMAs with the helicity memory prepared using chiral amines. The M- and P-PLAs are preferentially encapsulated within the M- and P-st-PMMA helical cavity with the same-handedness to each other, respectively, independent of the terminal units. The C60-bound PLAs were more efficiently and enantioselectively trapped in the st-PMMA compared to the C60-free PLAs. The enantioselectivities were highly dependent on the molar mass of the C60-bound and C60-free PLAs and significantly increased as the molar mass of the PLAs increased.

Preparation and preliminary evaluation of hepatitis B core antigen virus like nanoparticles loaded with indocyanine green.

BackgroundIn recent years, nanotechnology has attracted a plethora of attention due of its ability to effectively diagnose and treat various tumors. Virus-like particles (VLPs) have good biocompatibility, are safe and non-toxic, and have an internal hollow space, and as such they are often used as nano drug carriers. In recent years, it has become one of the hot spots in the field of biopharmaceutical engineering.MethodsIn this study, the tumor-targeting peptide RGD (Arg-Gly-Asp) was genetically inserted into the major immunodominant region (MIR) of the hepatitis B virus core protein (HBc). A series of characterization, including stability and optical properties, were evaluated. A visual diagnosis and analysis of the efficacy against tumor cells were conducted at the cell level and using a live animal model.ResultsThis study demonstrated that the recombinant HBc-based VLPs could participate in self-assembly of monodispersed nanoparticles with well-defined morphology, and the near-infrared dye indocyanine green (ICG) could be packaged into the VLPs without any chemical modification. Moreover, the HBc-based VLPs could specifically target cancer cells via the interaction with overexpressed integrin αvβ3. The treatment with ICG-loaded HBc-based VLPs showed significant inhibition of 4T1 breast cancer cell growth (84.87% tumor growth inhibition). The in vivo imaging experiments demonstrated that the ICG-loaded HBc-based VLPs generated excellent fluorescence in tumor sites in 4T1 breast cancer bearing mice. This provided crucial information on tumor mass location, boundaries, and shape. Moreover, compared to free ICG, the nanosystem showed significantly longer blood circulation time and superior accuracy in targeting the tumor.ConclusionsThe ICG-loaded HBc-based VLPs prepared in this study were of good stability and biocompatibility. It showed strong tumor targeting specificity and tumor visualization. Thus, it is expected to provide a new experimental basis and theoretical support for the integration of VLPs in the clinical diagnosis and treatment of breast cancer.

Design and Optimization of a Dextrous Robotic Finger: Incorporating a Sliding, Rotating, and Soft-Bending Mechanism While Maximizing Dexterity and Minimizing Dimensions

In this article, we introduce a new soft finger with a pneumatic-actuated movable joint that is optimized and characterized in terms of the degrees of freedom (DoF), workspace, and fingertip force. The finger consists of one soft link as the body and the bending pneumatic joint as the actuator. Due to the additional translation and rotation movement capabilities of the joint, carried out by two stepper motors, the finger can bend in any direction while having different lengths, thanks to a configurable bending point. This results in more dexterity for the finger when dealing with a target inside its 3D workspace by increasing the number of configurations it can use to reach the target and exert force. The finite element method (FEM) and the Nondominated Sorting Genetic Algorithm II (NSGA-II) algorithm are applied to optimize the joint geometry and so maximize the bending angle and minimize the joint dimensions. Furthermore, the variations of each design parameter and consequent effects on the optimization objectives are analyzed. The optimal geometrical parameters are used to fabricate a prototype with silicone rubber. Tests on the bending angle and tip force variability are conducted on the prototype to validate the numerical modeling. The experimental results show that the finger exerts force up to 650 mN with a response time of fewer than 3 s. The stiffness of the finger can be changed by applying pneumatic pressure in the hollow space inside the link. This consequently varies the amount of applied force at the tipping point of the finger up to two times.

Bio‐Inspired Conformable and Helical Soft Fabric Gripper with Variable Stiffness and Touch Sensing

AbstractThere are many instances in nature where continuum, helical manipulators are used to efficiently grasp different objects with various shapes and sizes. Inspired by nature, this paper introduces a continuum, flat, scalable, helical soft‐fabric robotic gripper that is thin and lightweight with stiffness tunability and sensory feedback. The gripper is fabricated by a facile method of simple insertion using a computerized technique from apparel engineering and controlled by a miniature hydraulic source to grasp different objects at different scales and weights. It uses a thermally activated variable stiffness structure (VSS) for high load capacity that can complete a softening‐stiffening cycle within 24 s, which is among the fastest results reported so far. In addition, a highly stretchable liquid metal‐based soft sensor with an enhanced sensing sensitivity (15 times more sensitive compared to conventional designs) is embedded into the gripper to provide real‐time touch sensing. The gripper successfully grasped various objects of different geometries and weights (up to 220 times of its mass) and retrieved them from confined hollow spaces. Its excellent performance and versatility make it an ideal candidate for various domains, including industry, exploration, rescue, and other applications in confined and hazardous environments such as gas/oil or drainage sectors.

Noble metal enhanced photocatalytic activity of heterostructured TiO2 spheres with tunable interiors and shells

Heterostructured TiO2 spheres with tunable interiors and shells were prepared by self-template technology. This structure is composed of a hollow shell and an inner core which can enhance light scattering in the hollow space and provide a large surface to generate sufficient active sites. Besides, the nanosheets grown on the shell layer not only increased their specific surface area, but also exposed more surface-active sites. The performance of photocatalysts was estimated by the RhB decolorization, and experimental results show that the photoactivity can be greatly improved by depositing noble metal nanoparticles. It improves the efficiency of charge utilization and enhances the overall catalytic performance from the three stages of charge carrier generation, separation and surface reaction. The strong metal–support interaction (SMSI) between the noble metal nanoparticles and the oxide support has been proven to inhibit the supported precious metal, one strategy for nanoparticle aggregation and growth. On the one hand, the nanoshells isolate the precious metal nanoparticles from each other, preventing the aggregation of metal nanoparticles.

Fabrication of low friction and wear carbon/epoxy nanocomposites using the confinement and self-lubricating function of carbon nanocage fillers

Epoxy resin (EP) nanocomposite materials with excellent tribological properties are highly desired for many engineering applications requiring low friction and wear. Adding carbon nanofiller is regarded as one of the most potential solutions to solve the serious dry wear problem of epoxy matrix. Herein, we report a new filler of carbon nanocages (CNC) prepared by the method of MgO templates to improve its dry friction performance through filling epoxy into the internal hollow space of CNC. Relative to neat epoxy, the friction coefficient (0.249) and wear rate (7.98 × 10−7 mm3 Nm−1) are reduced by 55.6% and 51.9% for the optimized CNC/EP nanocomposites, respectively. Even compared to typical graphene/epoxy nanocomposites, the wear rate is also reduced by up to 21.8%, as well as greatly enhancing the mechanical properties, thereby effectively protecting epoxy matrix and improving its dry friction. Such great tribological performance is attributed to unique structure of CNC, enabling the multi-functional collaboration of physical confinement, self-lubrication and wear-debris collection for CNC fillers, and making it the most potential carbon-based nanofiller for EP-based nanocomposite material system. More than that, it also provides insights for designing other advanced carbon-based nanofillers.

Structural Design and Synthesis of an SnO2 @C@Co-NC Composite as a High-Performance Anode Material for Lithium-Ion Batteries.

To overcome the drawbacks of the structural instability and poor conductivity of SnO2 -based anode materials, a hollow core-shell-structured SnO2 @C@Co-NC (NC=N-doped carbon) composite was designed and synthesized by employing the heteroatom-doping and multiconfinement strategies. This composite material showed a much-reduced resistance to charge transfer and excellent cycling performance compared to the bare SnO2 nanoparticles and SnO2 @C composites. The doped heteroatoms and heterostructure boost the charge transfer, and the porous structure shortens the Li-ion diffusion pathway. Also, the volume expansion of SnO2 NPs is accommodated by the hollow space and restricted by the multishell heteroatom-doped carbon framework. As a result, this structured anode material delivered a high initial capacity of 1559.1 mA h g-1 at 50 mA g-1 and an initial charge capacity of 627.2 mA h g-1 at 500 mA g-1 . Moreover, the discharge capacity could be maintained at 410.8 mA h g-1 after 500 cycles with an attenuation rate of only 0.069 % per cycle. This multiconfined SnO2 @C@Co-NC structure with superior energy density and durable lifespan is highly promising for the next-generation lithium-ion batteries.

Quadrilateral Spatial Diversity Circularly Polarized MIMO Cubic Implantable Antenna System for Biotelemetry

This article presents a first of its kind, coplanar waveguide (CPW)-fed 3-D multi-input-multi-output (MIMO) ground radiating cubic antenna (CA), implantable in the human upper arm for biotelemetry applications. The four antenna elements are circular in shape and loaded with a pair of slots to obtain circular polarization (CP). It excites diversified CP radiation in Industrial, Scientific, and Medical (ISM) band 2.45 and 5.8 GHz in orthogonal space to establish communication between the human body moving in random directions and base-station. The overall dimensions of the proposed antenna are 15 × 15 × 15 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Monitoring circuit PCB is placed at the top, and the bottom side of the cube and central hollow space is filled with a dry solid phantom for impedance matching. The CA is simulated in the vicinity of the canonical arm tissue model in HFSS software and examined in a realistic human model. The far-field gain is -18.5 dB with -32 dB isolation between elements. The CA is fabricated, and measurements are carried out in skin-fat-muscle phantom and minced pork. Simulated results closely match with measured results. The results show that the proposed CA is polarization and 3-D orientation insensitive and provides good MIMO properties. The low SAR value of the CA allows maximum transmit power of 5.81 mW, makes it a suitable choice to transfer high data rate (200 Mb/s) to an external antenna of diverse polarization. These features make CA an attractive solution for real-time healthcare applications.

CeVO4 yolk-shell microspheres constructed by nanosheets with enhanced lithium storage performances

In this work, the yolk–shell CeVO4 microsphere composed of nanosheets has been prepared via one-spothydrothermal method assisted with citric acid. The coexistence of microsphere, nanosheets subunits, yolk-core and the inner hollow space is helpful in solving the problem of the electrochemical agglomeration and the volume expansion/contraction, also offering easy pathways for the electrolyte to reach every available surface. Benefiting from the unique structure, the sample delivers the high discharge capacity of 661/400 mAh g−1 for the first and 450th cycle at a current density of 0.1 A g−1, respectively, with a corresponding Coulombic efficiency of 64.4/over 99.8%. The contribution from capacitive effects and diffusion-controlled Li+ were analyzed by the voltammetric sweep rate dependence. Such a rarely reported long cycle with higher capacity for CeVO4 has been achieved, which is especially desirable and regarded as a promising candidate anode material for next lithium ion batteries.

Design of a New XY Flexure Micropositioning Stage With a Large Hollow Platform

This paper presents the design of a new flexure-based xy micropositioning stage with a large hollow platform, which is suitable for practical use with a microscope. The designed mechanism has a parallel-kinematic structure and is actuated by two voice coil motors. By employing multistage compound parallelogram flexures, the stage is designed as a four-layer structure, which produces a motion output platform with a large hollow space and large range of motion. Analytical modeling was carried out for parametric design of the stage. Evaluation results show that the designed xy stage exhibits a large safety factor and high natural frequency. Moreover, the large hollow platform is well-suited for practical applications with a microscope.

Catalytic pyrolysis of poplar sawdust: Excellent hydrocarbon selectivity and activity of hollow zeolites

Hollow zeolites were investigated for catalytic fast pyrolysis (CFP) of biomass to produce hydrocarbon-rich bio-oil. A series of hollow ZSM-5 catalysts were synthesized via a dissolution-recrystallization strategy. The physicochemical properties of the catalysts were investigated by high-resolution transmission electron microscopy, N2 sorption, X-ray photoelectron spectroscopy, and ammonia temperature-programmed desorption experiments. The hollow zeolite was effective for increasing the hydrocarbon fraction in bio-oil. In particular, hollow HS-ZSM-5(50) afforded the highest hydrocarbon yield (6.8 wt%), which was ~3 times of that achieved with solid ZSM-5(50). The hollowness, acidity, and the presence of secondary wall mesopores in the hollow zeolite were found to affect bio-oil production. The hollow regions stabilized more active biomass intermediates and inhibited their repolymerization to coke, while the interior acid sites continually converted these intermediates to aromatic hydrocarbons. Secondary wall mesopores compromise the hollow space and hinder consecutive catalysis, resulting in phenols as the main product.

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

Encapsulation of metal-organic frameworks (MOFs) with a shell of mesoporous silica can boost overall performance of MOFs, offering versatility for synthetic architecture of integrated nanocatalysts with reactor-like features. Recently, Yu et al. report a green approach to make yolk-shell nanoreactors.

Self-Sacrificing Template-Derived Hollow-Structured NiCo2S4 Spheres with Highly Efficient Supercapacitance Performance

Highly efficient supercapacitance performance requires electrode materials to have large electrochemical reaction interfaces due to the surface reaction properties. In this work, a hollow-structured NiCo2S4 spinel is synthesized via an in situ preparation strategy. First, NiCo-glycolate solid spheres are obtained via a simple solvothermal method. The hollow structure is formed through a liquid sulfidation approach using NiCo-glycolate solid spheres as a self-sacrificing template, according to the Kirkendall effect. NiCo2S4 with hollow-structured spheres as supercapacitor electrodes exhibits an excellent specific capacitance of 1387.5 F·g–1 at 1 A·g–1 and a highly efficient cycling stability for over 4500 cycles. Moreover, when served as an all-solid-state asymmetric supercapacitor electrode, superior energy density (39 Wh·kg–1) is achieved at the power density of 215 W·kg–1. The superior energy storage performance is ascribed to the unique properties of the NiCo2S4 spinel, the mesoporous structure, and the large hollow space for alleviating the structure strain.

Trapped field potential of commercial Y-Ba-Cu-O bulk superconductors designed for applications

Bulk high-temperature superconductors (HTSs) that act as a trap field magnet establish a novel type of magnetic field source, which is significantly different from that of a permanent magnet or solenoid; therefore, they can be potentially used in magnetic-force-based applications. However, the primary issues related to the commercial use of the bulk HTS technology are established on the enhancement of trapped magnetic fields, as well as their reliability and reproducibility at temperatures achievable with off-the-shelf cryocoolers. This study presents experimental investigations on the strong trapped magnetic fields observed in commercial Y-Ba-Cu-O bulk HTSs produced as a double-sample stack, a cylindrical bulk, and a ring-shaped bulk. Consequently, a reliable and reproducible magnetic field of 9.5 T at 50 K was trapped in commercial Y-Ba-Cu-O assembled as a double-sample stack. In this case, shrink-fit encapsulation with either aluminum or stainless steel tube ensured equally effective reinforcement. Higher magnetization, although accompanied with partial flux jumps, yielded a trapped field of 16.85 T at 30 K, which is comparable to the reported record trapped fields. Finally, a maximum trapped field of 9.78 T - the strongest trapped field reported to date - was attained in the 6 mm hollow space of the ring-shaped bulk HTS.

Ultra-Fast Electron Microscopic Imaging of Single Molecules With a Direct Electron Detection Camera and Noise Reduction.

Time-resolved imaging of molecules and materials made of light elements is an emerging field of transmission electron microscopy (TEM), and the recent development of direct electron detection cameras, capable of taking as many as 1,600 fps, has potentially broadened the scope of the time-resolved TEM imaging in chemistry and nanotechnology. However, such a high frame rate reduces electron dose per frame, lowers the signal-to-noise ratio (SNR), and renders the molecular images practically invisible. Here, we examined image noise reduction to take the best advantage of fast cameras and concluded that the Chambolle total variation denoising algorithm is the method of choice, as illustrated for imaging of a molecule in the 1D hollow space of a carbon nanotube with ~1 ms time resolution. Through the systematic comparison of the performance of multiple denoising algorithms, we found that the Chambolle algorithm improves the SNR by more than an order of magnitude when applied to TEM images taken at a low electron dose as required for imaging at around 1,000 fps. Open-source code and a standalone application to apply Chambolle denoising to TEM images and video frames are available for download.

Iterative multi-scale approach for heat conduction with free convection problem in periodic hollow structures

This paper describes a thermal homogenization approach to the application of a multi-scale formulation for steady state heat conduction with free convection problems in a hollow structure. The presented formulation evaluates the effective macroscopic thermal properties of a hollow structure containing fluid within microstructures. This is done by scaling up and down between the microscopic and macroscopic models. The uniqueness of this approach is that it permits the solution of a heat conduction problem on a macroscopic scale, instead of solving heat conduction with free convection problem. The proposed methodology involves an iterative upscaling procedure which solves a coupled convection conduction CFD unit cell problem in each iteration. This reduces the required computational time while maintaining the required level of accuracy. Our method of multi-scale formulation has been verified using two examples of hollow structures containing air within the hollow spaces. The results are in excellent agreement with the reference solutions.