Incorporating gold into nanocrystalline silver dressings reduces grain boundary size and maintains suitable antimicrobial properties

Nanocrystalline silver dressings are widely known to be potent antimicrobial and anti‐inflammatory agents and have long been used to treat topical wounds. Gold is known to be a strong anti‐inflammatory agent and has been used in the treatment of rheumatoid arthritis for >70 years. The purpose of this work was to study the effect of incorporating gold into nanocrystalline silver dressings from antimicrobial and anti‐inflammatory perspectives. Gold and silver dressing alloys were created by direct current magnetron sputtering and compared with pure silver nanocrystalline dressings using conventional biological (log reduction and corrected zone of inhibition) and physical (X‐ray diffraction, X‐ray photoelectron spectroscopy, energy‐dispersive X‐ray spectroscopy, atomic absorption spectroscopy, atomic force microscopy and scanning electron microscopy) characterisation techniques. While the gold/silver dressings were slightly weaker antimicrobials than the pure silver nanocrystalline structures, the addition of gold to the nanostructure reduces the minimum crystallite size from 17 to 4 nm. This difference increases the number of grain boundary atoms from 12% to 40% which could augment the anti‐inflammatory properties of the dressings. The formation of gold oxide (Au₂O₃) was thought to be responsible for the observed decrease in crystallite size.     

Immersed Boundary Approach to Biofilm Spread on Surfaces

We propose a computational model to study the growth and spread of bacterial biofilms on interfaces, as well as the action of antibiotics on them. Bacterial membranes are represented by boundaries immersed in a fluid matrix and subject to interaction forces. Growth, division and death of bacterial cells follow dynamic energy budget rules, in response to variations in environmental concentrations of nutrients, toxicants and substances released by the cells. In this way, we create, destroy and enlarge boundaries, either spherical or rod-like. Appropriate forces represent details of the interaction between cells, and the interaction with the environment. We can investigate geometrical arrangements and the formation of porous structures. Numerical simulations illustrate the evolution of top views and diametral slices of small biofilm seeds, as well as the action of antibiotics. We show that cocktails of antibiotics targeting active and dormant cells can entirely eradicate a biofilm.     

A Fast Time Splitting Finite Difference Approach to Gross–Pitaevskii Equations

We propose an idea to solve the Gross–Pitaevskii equation for dark structures inside an infinite constant background density $ρ_∞$=${|ψ_∞|}^2$, without the introduction of artificial boundary conditions. We map the unbounded physical domain $\mathbb{R}^3$ into the bounded domain ${(−1,1)}^3$ and discretize the rescaled equation by equispaced 4th-order finite differences. This results in a free boundary approach, which can be solved in time by the Strang splitting method. The linear part is solved by a new, fast approximation of the action of the matrix exponential at machine precision accuracy, while the nonlinear part can be solved exactly. Numerical results confirm existing ones based on the Fourier pseudospectral method and point out some weaknesses of the latter such as the need of a quite large computational domain, and thus a consequent critical computational effort, in order to provide reliable time evolution of the vortical structures, of their reconnections, and of integral quantities like mass, energy, and momentum. The free boundary approach reproduces them correctly, also in finite subdomains, at low computational cost. We show the versatility of this method by carrying out one- and three-dimensional simulations and by using it also in the case of Bose–Einstein condensates, for which $ψ$→0 as the spatial variables tend to infinity.     

Numerical Study on Viscous Fingering Using Electric Fields in a Hele-Shaw Cell

We investigate the nonlinear dynamics of a moving interface in a Hele-Shaw cell subject to an in-plane applied electric field. We develop a spectrally accurate numerical method for solving a coupled integral equation system. Although the stiffness due to the high order spatial derivatives can be removed using a small scale decomposition technique, the long-time simulation is still expensive since the evolving velocity of the interface drops dramatically as the interface expands. We remove this physically imposed stiffness by employing a rescaling scheme, which accelerates the slow dynamics and reduces the computational cost. Our nonlinear results reveal that positive currents restrain finger ramification and promote the overall stabilization of patterns. On the other hand, negative currents make the interface more unstable and lead to the formation of thin tail structures connecting the fingers and a small inner region. When no fluid is injected, and a negative current is utilized, the interface tends to approach the origin and break up into several drops. We investigate the temporal evolution of the smallest distance between the interface and the origin and find that it obeys an algebraic law $(t_∗−t)^b,$ where $t_∗$ is the estimated pinch-off time.     

Kinetic Slip Boundary Condition for Isothermal Rarefied Gas Flows Through Static Non-Planar Geometries Based on the Regularized Lattice-Boltzmann Method

The simulation of rarefied gas flows through complex porous media is challenging due to the tortuous flow pathways inherent to such structures. The Lattice Boltzmann method (LBM) has been identified as a promising avenue to solve flows through complex geometries due to the simplicity of its scheme and its high parallel computational efficiency. It has been proposed to model the stress-strain relationship with the extended Navier-Stokes equations rather than attempting to directly solve the Boltzmann equation. However, a regularization technique is required to filter out non-resolved higher-order components with a low-order velocity scheme. Although slip boundary conditions (BCs) have been proposed for the non-regularized multiple relaxation time LBM (MRT-LBM) for planar geometries, previous slip BCs have never been verified extensively with the regularization technique. In this work, following an extensive literature review on the imposition of slip BCs for rarefied flows with the LBM, it is proven that earlier values for kinetic parameters developed to impose slip BCs are inaccurate for the regularized MRT-LBM and differ between the D2Q9 and D3Q15 schemes. The error was eliminated for planar flows and good agreement between analytical solutions for arrays of cylinders and spheres was found with a wide range of Knudsen numbers.     

A Characteristic Boundary Condition for Multispeed Lattice Boltzmann Methods

We present the development of a non-reflecting boundary condition, based on the Local One-Dimensional Inviscid (LODI) approach, for Lattice Boltzmann Models working with multi-speed stencils.We test and evaluate the LODI implementation with numerical benchmarks, showing significant accuracy gains with respect to the results produced by a simple zero-gradient condition. We also implement a simplified approach, which allows handling the unknown distribution functions spanning several layers of nodes in a unified way, still preserving a comparable level of accuracy with respect to the standard formulation.     

Accurate Boundary Conditions for Twin Boundary

In this paper, we propose accurate numerical boundary conditions for atomic simulations of twin boundary. The heterogeneity of the lattice structure induces physical reflection across the twin boundary. When numerical boundary and the twin boundary coincide, the goal is to reproduce the correct amount of physical reflection. In particular, we consider waves periodic in the direction parallel to the twin boundary and reduce the problem into a complex-valued chain motion. Using Laplace transform, we design time history kernel (THK) treatment. We further design matching boundary conditions (MBC) by reproducing physical reflection at long wave limit and a specific wave number. Reflection analysis and numerical tests demonstrate the effectiveness of the proposed THK and MBC treatments.     

A High-Accurate Fast Poisson Solver Based on Harmonic Surface Mapping Algorithm

Poisson's equations in a cuboid are frequently solved in many scientific and engineering applications such as electric structure calculations, molecular dynamics simulations and computational astrophysics. In this paper, a fast and highly accurate algorithm is presented for the solution of the Poisson's equation in a cuboidal domain with boundary conditions of mixed type. This so-called harmonic surface mapping algorithm is a meshless algorithm which can achieve a desired order of accuracy by evaluating a body convolution of the source and the free-space Green's function within a sphere containing the cuboid, and another surface integration over the spherical surface. Numerical quadratures are introduced to approximate the integrals, resulting in the solution represented by a summation of point sources in free space, which can be accelerated by means of the fast multipole algorithm. The complexity of the algorithm is linear to the number of quadrature points, and the convergence rate can be arbitrarily high even when the source term is a piecewise continuous function.     

Electrophysiologic monitoring in neurosurgery

Electrophysiologic techniques have become common in the neurosurgical operating room. This article reviews the methods used for mapping neural structures or monitoring during surgery. Mapping methods allow identification of target structures for surgery, or for identifying structures to allow avoidance or plot safe pathways to deeper structures. Monitoring methods allow for surgery on nearby structures to warn of encroachment, thereby reducing unwanted injury.     

Anatomy of the anal canal with attention to the clinical management of symptomatic hemorrhoids

Hemorrhoids are normal anatomic structures that aid in the maintenance of fecal continence. The name hemorrhoid includes structures proximal and distal to the anal canal. These structures can manifest a variety of conditions resulting in pruritus, pain, bleeding, and mucous discharge. The anatomy of the anal canal is reviewed with emphasis on structures and relationships that bear on the clinical management of symptomatic hemorrhoidal disease. A brief history of the knowledge of anal anatomy is presented. The relationship of the vascular cushions, the surrounding structures, and their innervation that allows our current management is reviewed in detail.     

Editorial Commentary: Knee Anterolateral Ligament Cadaveric,Biomechanical Analysis Should Include Tensioning of All Knee Dynamic Structures

Although most reports in the literature suggest that the knee anterolateral structures contribute to the anterolateral rotational stability of the knee, the extent of its contribution is still controversial. There are many dynamic structures that also affect the stability of the knee joint, including the iliotibial band and quadriceps muscle. Although not all of the dynamic structures surrounding the knee influence stability associated with the anterior cruciate ligament, we recommend that cadaveric, biomechanical analysis of the knee anterolateral ligament and related structures include tensioning of all knee dynamic structures to avoid potential biases.     

Lattice Boltzmann Study of Flow and Temperature Structures of Non-Isothermal Laminar Impinging Streams

Previous works on impinging streams mainly focused on the structures of flow field, but paid less attention to the structures of temperature field, which are very important in practical applications. In this paper, the influences of the Reynolds number (Re) and Prandtl number (Pr) on the structures of flow and temperature fields of non-isothermal laminar impinging streams are both studied numerically with the lattice Boltzmann method, and two cases with and without buoyancy effect are considered. Numerical results show that the structures are quite different in these cases. Moreover, in the case with buoyancy effect, some new deflection and periodic structures are found, and their independence on the outlet boundary condition is also verified. These findings may help to understand the flow and temperature structures of non-isothermal impinging streams further.     

数字化与虚拟现实技术在皮瓣移植中的应用

目的研究数字化与虚拟现实技术在股前外侧皮瓣解剖设计与可视化中的应用。方法①应用“虚拟中国人”男性3号数据集,在薄层断面图像上观察旋股外侧动脉的主要解剖结构,应用Amira 3．1 (TGS)软件对股前外侧皮瓣结构进行计算机三维重建并立体显示。②明胶一氧化铅混悬液灌注的新鲜成人下肢标本1具,行连续螺旋CT扫描,观测旋股外侧动脉分布及彼此间的吻合情况,应用Amira 3．1软件对股前外侧皮瓣结构进行计算机三维重建并立体显示。结果重建的数字化模型可准确反映股前外侧皮瓣的解剖学结构特点。结论重建的图像可以提供正常股前外侧皮瓣三维动态解剖,为临床教学术前皮瓣设计提供了直观的数字化解剖依据；同时可为下一步虚拟手术的设计奠定良好的基础。     

Mandible prognathism saved a life: a case report

An unusual case of a suicidal firearm injury is presented, in which the victim placed the gun under his chin and fired. However, none of the vital structures of the head and face were injured because the victim＇s chin was considerably anterior to other facial structures as a result of a class Ⅲ facial deformity. This resulted in thetrajectory of the bullet being anterior to vital facial structures and not causing injury to those structures.     

Exact Boundary Conditions for Periodic Waveguides Containing a Local Perturbation

We consider the solution of the Helmholtz equation −∆u(x)−n(x)²ω²u(x) = f(x), x = (x,y), in a domain Ω which is infinite in x and bounded in y. We assume that f(x) is supported in Ω⁰ := {x ∈ Ω |a⁻ < x < a⁺} and that n(x) is x-periodic in Ω\Ω⁰. We show how to obtain exact boundary conditions on the vertical segments, Γ⁻ := {x ∈ Ω |x = a⁻} and Γ⁺ := {x ∈ Ω |x = a⁺}, that will enable us to find the solution on Ω⁰ ∪Γ⁺ ∪Γ⁻. Then the solution can be extended in Ω in a straightforward manner from the values on Γ⁻ and Γ⁺. The exact boundary conditions as well as the extension operators are computed by solving local problems on a single periodicity cell.     

Ultrasound-guided epidural catheter insertion in children

Epidural catheters (EC) are often used in pediatric patients for intraoperative and postoperative pain relief. The small anatomical structures and catheter insertion under general anesthesia make it more difficult to perform EC and to prevent damage. In this study we investigated the use of ultrasound (US) in detecting neuraxial structures during insertion and placement of EC in children. ASA I-II children scheduled for elective surgery under combined general and epidural anesthesia were studied. Patients received balanced anesthesia using sevoflurane, opioids and rocuronium. Before EC insertion US examination in a lateral position was done to visualize and identify neuraxial structures. Quality of visualization and site and depth of structures were recorded. Using a sterile kit to hold the US probe in position and enable the visualization of the neuraxial structures, an epidural cannula was inserted, using the loss of resistance technique, as the EC passed under US control to the desired level. Of 25 children, 23 were evaluated. Epidural space, ligamentum flavum, and dural structures were clearly identified and the depth to skin level estimated in all patients. Loss of resistance was visualized in all patients with a lumbar epidural approach. Correlation of US measured depth and depth of loss of resistance was 0.88. In eight of 23 patients EC could be visualized during insertion and in 11 others it could be visualized with additional US planes. US is an excellent tool to identify neuraxial structures in both infants and children. The size and the incomplete ossification of the vertebra allow exact visualization and localization of the depth of the epidural space, the loss of resistance, and all relevant neuraxial structures. IMPLICATIONS: Epidural catheters in children are mostly inserted under sedation or general anesthesia. This study showed that the use of ultrasound could help visualize all relevant neuraxial structures and their site and depth from the skin.     

A Fourth-Order Kernel-Free Boundary Integral Method for Interface Problems

This paper presents a fourth-order Cartesian grid based boundary integral method (BIM) for heterogeneous interface problems in two and three dimensional space, where the problem interfaces are irregular and can be explicitly given by parametric curves or implicitly defined by level set functions. The method reformulates the governing equation with interface conditions into boundary integral equations (BIEs) and reinterprets the involved integrals as solutions to some simple interface problems in an extended regular region. Solution of the simple equivalent interface problems for integral evaluation relies on a fourth-order finite difference method with an FFT-based fast elliptic solver. The structure of the coefficient matrix is preserved even with the existence of the interface. In the whole calculation process, analytical expressions of Green’s functions are never determined, formulated or computed. This is the novelty of the proposed kernel-free boundary integral (KFBI) method. Numerical experiments in both two and three dimensions are shown to demonstrate the algorithm efficiency and solution accuracy even for problems with a large diffusion coefficient ratio.     

Rapid morphological changes in bovine brain microvascular endothelial cells on extracellular matrices.

The morphological changes in endothelial cells derived from bovine brain microvasculature, carotid artery, and aorta during growth on extracellular matrices were compared. All cells formed tubular structures on a basement membrane. Ultrastructural studies showed that the tubular structures had lumens surrounded by many endothelial cells. On type I collagen gel, brain microvascular endothelial cells still formed tubular structures, but the other two cell types formed confluent monolayers. However, when a second layer of collagen gel was laid over these cells, tubular structures developed within 2-3 days. Brain microvascular endothelial cells form tubular structures more readily than endothelial cells derived from large vessels on both basement membrane and type I collagen gel.     

Hybrid Diffuse and Sharp Interface Immersed Boundary Methods for Particulate Flows in the Presence of Complex Boundaries

A coupling framework that leverages the advantages of the diffuse and sharp interface immersed boundary (IB) methods is presented for handling the interaction among particles and particles with the static complex geometries of the environment. In the proposed coupling approach, the curvilinear IB method is employed to represent the static complex geometries, a variant of the direct forcing IB method is proposed for simulating particles, and the discrete element method is employed for particle-particle and particle-wall collisions. The proposed approach is validated using several classical benchmark problems, which include flow around a sphere, sedimentation of a sphere, collision of two sedimenting spheres, and collision between a particle and a flat wall, with the present predictions showing an overall good agreement with the results reported in the literature. The capability of the proposed framework is further demonstrated by simulating the interaction between multiple particles and a wall-mounted cylinder, and the particle-laden turbulent flow over periodic hills. The proposed method provides an efficient way to simulate particle-laden turbulent flows in environments with complex boundaries.     

Extension of the fingers. V. Anatomic approach to lesions of the extensor apparatus]

The physiopathology of the main deformities of the fingers, induced by the injury of the dorsal aponeurosis of the fingers, is caused by an imbalance of forces: proximally between extrinsic and intrinsic muscles; distally between central and collateral structures. The ulna Claw, caused by the whole paralysis of the intrinsic muscles, can be corrected by an interosseous tenodesis on the basis of the finger. The boutoniere is induced by the exaggeration of the action of the collateral structures with respect to this of the central structures. The swan neck is induced by the exaggeration of action of the central structures with respect to this of the collateral structures. The surgical treatment consist to give back those structures their normal lengthening and way, or else to create new detours or shortenings, allowing to give back the balance. So, any structures, spared by the traumatism, will not injure by the surgeon.