Combat helmets provide protection against ballistic threats and blunt impact forces, and wearing them has greatly reduced head injuries and saved lives of many soldiers. With the new challenges from ...improvised explosive devices and urban combat operations in modern asymmetric military conflicts, future combat helmets are required to be highly protective, lightweight, comfortable to wear, and compatible with communication and other systems. The aim of this paper is to provide a comprehensive review of existing combat helmets based on aramid and UHMWPE fibers by addressing the critical issues including materials, ballistic impact mechanisms, design, manufacturing, performance, and head injury protection. Various ballistic fabrics and composites used for combat helmets are discussed. The ballistic impact mechanisms and mechanical responses of helmet composites are examined in view of experimental methods, analytical models, and numerical simulations. The strategies for helmet designs, including head coverage and curvature of helmet shell, manufacturing processes, and liner foam pads, are outlined. The performance of combat helmets as evaluated by ballistic testing and finite element simulations is summarized. Finally, the ballistic and blast impact induced head injuries are elaborated, and the possibility of behind armor blunt trauma predicted by available injury criteria is discussed. The state-of-the-art knowledge of combat helmets reviewed in this paper provides the foundation for the development of next-generation combat helmets, which are expected to protect against ballistic, blunt, and blast impacts to minimize traumatic brain injuries, while enabling wearing comfort and effective communications.
The study of topology in elastic media has been primarily focused on achieving non-trivial topological states in discrete elastic lattices through active or chiral microscopic interactions. ...Realization of such topological states in continuous elastic media remains largely unexplored. In this study, a new continuum theory of micropolar gyroelasticity is developed and applied to attain non-trivial topological boundary states in elastic continua. According to the new theory, an elastic continuum is composed of elastically interacting micro-volume elements that can translate and rotate and are connected at their mass centers to gyroscopes, which contribute to the linear and orbital angular momenta but not to the spin angular momentum of the continuum. By applying this micropolar gyroelasticity theory to elastic media with both periodic and finite domains, the emergence of topological boundary states in 2D micropolar gyroelastic continua is demonstrated. Through using the Floquet–Bloch method for periodic domains, the bulk-boundary correspondence is analytically established, and the emergence of non-trivial topological bulk states characterized by Mexican-hat band structures is observed. In addition, by employing an asymptotic analytical model based on the extended Bloch theorem and performing numerical analyses of micropolar gyroelastic continua with finite domains of different geometries, it is shown that the non-trivial Mexican-hat band structure is associated with and provides protection for topological boundary states confined at the boundaries. Finally, the application of the newly developed micropolar gyroelasticity theory to Zinc-blende structured materials (including ZnTe, GaP, InP and ZnS) reveals that the emergence of the topological boundary states in an elastic continuum is not triggered solely by the gyroscopic effect but also depends on the material properties of the micropolar continuum. This study provides new insights into extending notions and methods of topology to analyze elastic continua, paving the way for the practical implementation of topological mechanical systems in various engineering applications.
•A new theory of micropolar gyroelasticity is developed to attain non-trivial topological boundary states in continua.•The emergence of topological boundary states in 2D continua is shown for elastic media with periodic and finite domains.•The bulk-boundary correspondence is established, and the emergence of non-trivial topological bulk states is observed.•The non-trivial Mexican-hat band structure provides protection for topological boundary states confined at the boundaries.•The emergence of the topological boundary states depends on both the gyroscopic effect and properties of the continuum.
Posterior capsule opacification (PCO) is the most common complication after cataract surgery. So far, the only method for PCO treatment is the precisely focused laser surgery. However, it causes ...severe complications such as physical damages and neuron impairments. Here, a nanostructured photothermal ring integrated intraocular lens (Nano‐IOLs) is reported, in which the rim of commercially available IOLs (C‐IOLs) is decorated with silica coated Au nanorods (Au@SiO2), for high‐efficient prevention of PCO after cataract surgery. The Nano‐IOLs is capable of eliminating the residual lens epithelial cells (LECs) around Nano‐IOLs under mild laser treatment and block the formation of disordered LECs fibrosis, which eventually leads to the loss of vision. The Nano‐IOLs shows good biocompatibility as well as extraordinary region‐confined photothermal effect. In vivo studies reveal that PCO occurrence in rabbit models is about 30%–40% by using Nano‐IOLs, which is significantly lower than the control group that treated with C‐IOLs (100% PCO occurrence) 30 d postsurgery. To the best of our knowledge, it is the first example to integrate nanotechnology with intraocular implants aiming to clinically relevant PCO. Our findings indicate that spatial controllability of photothermal effect from nanomaterials may provide a unique way to intervene the PCO‐induced loss of vision.
An intraocular lens with a Au@SiO2 nanorod‐modified rim (Nano‐IOLs) is reported. Compared to the commercially available IOLs, these Nano‐IOLs retain the intrinsic biocompatibility and optical properties and meanwhile exhibit extraordinary region‐confined photothermal effect. In vitro and rabbit experimental results confirm that the Nano‐IOLs can effectively kill LECs near to the rim and effectively prevent the occurrence of posterior capsule opacification.
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The treatment of wastewater not only helps to alleviate the scarcity of water and environmental challenges but also generates a by-product called Municipal Sewage Sludge (MSS). The ...MSS is a high moisture precipitant with plentiful organic and inorganic components. However, some pollutants in MSS components and its high-water content complicate its valorization, and thus, special attention is required for its valorization. Hydrothermal treatments (HTs) can be applied to feedstocks with high moisture content without pre-drying. These processes are gaining more attention to processing MSS into fuels and value-added materials. This work systematically reviews the findings recently emerged from HTs of MSS. The related chemical reactions and the effect of reaction parameters are highlighted based on most recent works. The problems addressed and those not yet addressed are also discussed. Some suggestions are made for the plausible applications of end products with the aim to optimize the whole process. Finally, insight is given into the future of MSS HTs and the concerns that might be the focus of substantial studies.
Electronic skin (e‐skin) capable of acquiring environmental and physiological information has attracted interest for healthcare, robotics, and human–machine interaction. However, traditional 2D ...e‐skin only allows for in‐plane force sensing, which limits access to comprehensive stimulus feedback due to the lack of out‐of‐plane signal detection caused by its 3D structure. Here, a dimension‐switchable bioinspired receptor is reported to achieve multimodal perception by exploiting film kirigami. It offers the detection of in‐plane (pressure and bending) and out‐of‐plane (force and airflow) signals by dynamically inducing the opening and reclosing of sensing unit. The receptor's hygroscopic and thermoelectric properties enable the sensing of humidity and temperature. Meanwhile, the thermoelectric receptor can differentiate mechanical stimuli from temperature by the voltage. The development enables a wide range of sensory capabilities of traditional e‐skin and expands the applications in real life.
A flexible multimodal receptor can achieve a reversible transformation from 2D to 3D structure by bending or stretching the sensor, drawing inspiration from the morphological switch observed in the hummingbird feathers. Interestingly, a single‐unit receptor is capable of sensing multiple stimuli, including in‐plane deformation (pressure and bending), out‐of‐plane deformation (force and airflow), temperature, and humidity.
Tumor metastasis is one of the big challenges in cancer treatment and is often associated with high patient mortality. Until now, there is an agreement that tumor invasion and metastasis are related ...to degradation of extracellular matrix (ECM) by enzymes. Inspired by the formation of natural ECM and the in situ self-assembly strategy developed in our group, herein, we in situ constructed an artificial extracellular matrix (AECM) based on transformable Laminin (LN)-mimic peptide 1 (BP-KLVFFK-GGDGR-YIGSR) for inhibition of tumor invasion and metastasis. The peptide 1 was composed of three modules including (i) the hydrophobic bis-pyrene (BP) unit for forming and tracing nanoparticles; (ii) the KLVFF peptide motif that was inclined to form and stabilize fibrous structures through intermolecular hydrogen bonds; and (iii) the Y-type RGD-YIGSR motif, derived from LN conserved sequence, served as ligands to bind cancer cell surfaces. The peptide 1 formed nanoparticles (1-NPs) by the rapid precipitation method, owing to strong hydrophobic interactions of BP. Upon intravenous injection, 1-NPs effectively accumulated in the tumor site due to the enhanced permeability and retention (EPR) effect and/or targeting capability of RGD-YIGSR. The accumulated 1-NPs simultaneously transformed into nanofibers (1-NFs) around the solid tumor and further entwined to form AECM upon binding to receptors on the tumor cell surfaces. The AECM stably existed in the primary tumor site over 72 h, which consequently resulted in efficiently inhibiting the lung metastasis in breast and melanoma tumor models. The inhibition rates in two tumor models were 82.3% and 50.0%, respectively. This in vivo self-assembly strategy could be widely utilized to design effective drug-free biomaterials for inhibiting the tumor invasion and metastasis.
A new microstructure-dependent non-classical model for Kirchhoff plates is developed by using a reformulated strain gradient elasticity theory that incorporates both the strain gradient and couple ...stress effects. The equation of motion and the boundary conditions are simultaneously obtained through a variational formulation based on Hamilton's principle. The new plate model contains one material constant to account for the strain gradient effect and one material length scale parameter to capture the couple stress effect. The newly developed non-classical plate model includes the plate model incorporating the couple stress effect alone and the plate model based on the classical elasticity as two special cases. To illustrate the new model, the buckling, static bending and free vibration problems of a simply supported rectangular plate are analytically solved by directly applying the general formulas derived. The numerical results reveal that the presence of the strain gradient and couple stress effects leads to reduced plate deflections, enlarged critical buckling loads and increased natural frequencies. These microstructure effects are significant when the plate is very thin, but they are diminishing as the plate thickness increases. These predicted trends of the size effects at the micron scale agree with those observed experimentally.
A new non-classical model for spatial rods incorporating surface energy effects is developed using a surface elasticity theory. A variational formulation based on the principle of minimum total ...potential energy is employed, which leads to the simultaneous determination of the equilibrium equations and complete boundary conditions. The newly developed spatial rod model contains three surface elasticity constants to account for surface energy effects. The new model recovers the classical elasticity-based Kirchhoff rod model as a special case when the surface energy effects are not considered. To illustrate the new spatial rod model, two sample problems are analytically solved by directly applying the general formulas derived. The first one is the buckling of an elastic rod of circular cross-section with fixed-pinned supports, and the other is the equilibrium analysis of a helical rod deformed from a straight rod. An analytical formula is derived for the critical buckling load required to perturb the axially compressed straight rod, and two closed-form expressions are obtained for the force and couple needed in deforming the helical rod. These formulas reduce to those based on classical elasticity when the surface energy effects are suppressed. For the buckling problem, it is found that the critical buckling load predicted by the current new model is always higher than that given by the classical elasticity-based model, and the difference between the two sets of predicted values is significantly large when the radius of the rod is sufficiently small but diminishes as the rod radius increases. For the helical rod problem, the numerical results reveal that the force and couple predicted by the current model are, respectively, significantly larger and smaller than those predicted by the classical model when the rod radius is very small, but the difference is diminishing with the increase of the rod radius.
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•HBF of the soybean straw biocrude was effectively hydrotreated in an HDS mixture.•H2 and Pt, particular the HDS played a critical role during the hydrotreatment process.•The S was ...the easiest heteroatom to be removed, followed by N and O.•98.6% S, 96.2% N, and 87.1% O were removed from the initial feedstock.•The resulting product oil had better properties than the 0# diesel.
In this study, a high-boiling point fraction (HBF, 141-220 °C) from vacuum distillation of a biocrude produced from hydrothermal liquefaction of soybean straw was hydrotreated in a hydrogen donor solvent (HDS) mixture consisting of tetralin and decalin at a mass ratio of 1:1. Effects of temperature (300–450 °C), time (1–6 h), H2 pressure (0.01–10 MPa), and Pt/C loading (0–40 wt%) on the products distribution and properties of the treated oil were examined. Increasing the temperature, time, and catalyst loading or decreasing the H2 pressure would reduce the treated oil yield and increase the gas and solid product yields. The presence of HDS mixture played a critical role in favoring the production of treated oil, reducing the formation of gas and solid products, and the removal of N, O, and S from the HBF. Under optimal reaction conditions, 96.3% of N, 87.1% of O, and 98.5% of S were removed from the initial feedstock. The treated oil mainly consisted of saturated hydrocarbon(∼40%, C8-C20) and aromatics(∼41%, naphthalene and benzene derivatives), which was had a comparable cetane number and better combustion characteristics relative to the market 0# diesel.
Abstract
Epstein-Barr virus (EBV) is a γ-herpesvirus associated with the occurrence of several human malignancies. BBRF2 and BSRF1 are two EBV tegument proteins that have been suggested to form a ...hetero-complex and mediate viral envelopment, but the molecular basis of their interaction and the functional mechanism of this complex remains unknown. Here, we present crystal structures of BBRF2 alone and in complex with BSRF1. BBRF2 has a compact globular architecture featuring a central β-sheet that is surrounded by 10 helices, it represents a novel fold distinct from other known protein structures. The central portion of BSRF1 folds into two tightly associated antiparallel α-helices, forming a composite four-helix bundle with two α-helices from BBRF2 via a massive hydrophobic network. In vitro, a BSRF1-derived peptide binds to BBRF2 and reduces the number of viral genome copies in EBV-positive cells. Exogenous BBRF2 and BSRF1 co-localize at the Golgi apparatus. Furthermore, BBRF2 binds capsid and capsid-associated proteins, whereas BSRF1 associates with glycoproteins. These findings indicate that the BBRF2-BSRF1 complex tethers EBV nucleocapsids to the glycoprotein-enriched Golgi membrane, facilitating secondary envelopment.
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