Spectral solution to a problem on the axisymmetric nonlinear deformation of a cylindrical membrane shell due to pressure and edges convergence

A geometrically and physically nonlinear model of a membrane cylindrical shell, which has been built and tested, describes the behavior of a airbag made of fabric material. Based on the geometrically accurate relations of "strain-displacement", it has been shown that the equilibrium equations of the shell, written in terms of Biot stresses, together with boundary conditions acquire a natural physical meaning and are the consequences of the principle of virtual work. The physical properties of the shell were described by Fung’s hyper-elastic biological material because its behavior is similar to that of textiles. For comparison, simpler hyper-elastic non-compressible Varga and Neo-Hookean materials, the zero-, first-, and second-order materials were also considered. The shell was loaded with internal pressure and convergence of edges. The approximate solution was constructed by an spectral method; the exponential convergence and high accuracy of the equilibrium equations inherent in this method have been demonstrated. Since the error does not exceed 1 % when keeping ten terms in the approximations of displacement functions, the solution can be considered almost accurate. Similar calculations were performed using a finite element method implemented in ANSYS WB in order to verify the results. Differences in determining the displacements have been shown to not exceed 0.2 %, stresses – 4 %. The study result has established that the use of Fung, Varga, Neo-Hookean materials, as well as a zero-order material, lead to similar values of displacements and stresses, from which displacements of shells from the materials of the first and second orders significantly differ. This finding makes it possible, instead of the Fung material whose setting requires a significant amount of experimental data, to use simpler ones – a zero-order material and the Varga material

Capsid-E2 interactions rescue core assembly in viruses that cannot form cytoplasmic nucleocapsid cores

Alphavirus capsid proteins (CPs) have two domains: the N-terminal domain (NTD) that interacts with the viral RNA, and the C-terminal domain (CTD) that forms CP-CP interactions and interacts with the cytoplasmic domain of the E2 spike protein (cdE2). In this study, we examine how mutations in the CP NTD affect CP CTD interactions with cdE2. We changed the length and/or charge of the NTD of Ross River virus CP and found that changing the charge of the NTD has a greater impact on core and virion assembly than changing the length of the NTD. The NTD CP insertion mutants are unable to form cytoplasmic cores during infection but they do form cores or core-like structures in virions. Our results are consistent with cdE2 having a role in core maturation during virion assembly and rescuing core formation when cytoplasmic cores are not assembled. We go on to find that the isolated cores from some mutant virions are now assembly competent in that they can be disassembled and reassembled back into cores. These results show how the two domains of CP may have distinct yet coordinated roles. IMPORTANCE: Structural viral proteins have multiple roles during entry and assembly. The capsid protein (CP) of alphaviruses has one domain that interacts with the viral genome and another domain that interacts with the E2 spike protein. In this work we determine that the length and/or charge of the CP affects cytoplasmic core formation. However, defects in cytoplasmic core formation can be overcome by E2-CP interactions, thus assembling a core or core-like complex in the virion. In the absence of both cytoplasmic cores and CP-E2 interactions, CP is not even packaged in the released virions, but some infectious particles are still released presumably as RNA packaged in a glycoprotein containing membrane shell. This suggests that the virus has multiple mechanisms in place to ensure the viral genome is surrounded by a capsid core during its lifecycle.

MEMBRANE FINITE ELEMENT FOR MODELING HEART WALL

Modeling of heart wall deformation remains a challenge due to complex structure of tissue, which contains different group of cells and connective tissue. Muscle cells are dominant where, besides stresses coming from tissue deformation, active stresses are generated representing the load which produces heart motion and function. These cells form a helicoidal structure within so- called wall sheets and are considered as tissue fibers. Usual approach in the finite element (FE) discretization is to use 3D isoparametric elements. The dominant stresses lie in the sheet planes, while normal stresses in the wall normal directions are of the order smaller. Taking this stress state into account, we explore a possibility to model heart wall by membrane finite elements, hence considering the wall as a thick membrane (shell without bending effects). The membrane element is composite, containing layers over the thickness and variation of the direction of fibers. The formulated element is applied to a simplified left ventricle geometry to demonstrate a possibility to simulate heart mechanics by models which are much smaller and simpler for use than 3D conventional models.

On the improved interior regularity of a boundary value problem modelling the displacement of a linearly elastic elliptic membrane shell subject to an obstacle

<p style='text-indent:20px;'>In this paper we show that the solution of an obstacle problem for linearly elastic elliptic membrane shells enjoys higher differentiability properties in the interior of the domain where it is defined.</p>

Leukocyte Membrane-Coated Liquid Metal Nanoswimmers for Actively Targeted Delivery and Synergistic Chemophotothermal Therapy

We report a leukocyte membrane-coated gallium nanoswimmer (LMGNS) capable of ultrasound-propelled motion, antibiofouling, and cancer cell recognition and targeting. The LMGNS consists of a needle-shaped gallium core encapsulating an anticancer drug and a natural leukocyte membrane shell. Under the propulsion of an ultrasound field, LMGNSs could autonomously move in biological media with a speed up to 108.7 μm s−1. The velocity and motion direction of the LMGNSs can be modulated by regulating the frequency and voltage of the applied ultrasound field. Owing to the leukocyte membrane coating, LMGNSs can not only avoid biofouling during the motion in blood but also possess cancer cell recognition capability. These LMGNSs could actively seek, penetrate, and internalize into the cancer cells and achieve enhanced anticancer efficiency by combined photothermal and chemical therapy. Such biofunctionalized liquid metal nanoswimmer presents a new type of multifunctional platform for biomedical applications.