Two-dimensional computational framework of meso-scale rigid and line interface elements for masonry structures

In this paper, rigid elements along with nonlinear line interface elements are utilized to model masonry structures. The modeling approach focuses on two dimensions (2D) whereby the in-plane behavior of components is represented by rigid elements and nonlinear line interfaces instead of modeling by a traditional finite element method. In this approach, the component will be allowed to crack in predefined paths which have more likelihood for propagation. The paper discusses the model derivation and implementation. Moreover, the mesh sensitivity of this method is assessed by using different mesh sizes, and it is shown that the model captures response obtained by the experimental tests. The traditional finite element method is indeed capable of predicting the behavior of large scale masonry component, but the computational time is very high. In this study it has been shown that using rigid elements along with nonlinear line interfaces leads to a reduced number of degrees-of-freedom, which consequently reduces the computational time. The material model is implemented in a user-defined subroutine that is compiled with DIANA. The algorithms and material models are validated with well-documented experimental studies, and results clearly show the capabilities of the proposed procedures.     

Breaking anonymity of some recent lightweight RFID authentication protocols

Wireless Networks - Due to their impressive advantages, Radio Frequency IDentification (RFID) systems are ubiquitously found in various novel applications. These applications are usually in need of...     

Brain drain and brain gain in Russia: Analyzing international migration of researchers by discipline using Scopus bibliometric data 1996–2020

Scientometrics - We study international mobility in academia, with a focus on the migration of published researchers to and from Russia. Using an exhaustive set of over 2.4 million Scopus...     

In Vivo Matrigel Plug Assay as a Potent Method to Investigate Specific Individual Contribution of Angiogenesis to Blood Flow Recovery in Mice

Neovascularization restores blood flow recovery after ischemia in peripheral arterial disease. The main two components of neovascularization are angiogenesis and arteriogenesis. Both of these processes contribute to functional improvements of blood flow after occlusion. However, discriminating between the specific contribution of each process is difficult. A frequently used model for investigating neovascularization is the murine hind limb ischemia model (HLI). With this model, it is difficult to determine the role of angiogenesis, because usually the timing for the sacrifice of the mice is chosen to be optimal for the analysis of arteriogenesis. More importantly, the occurring angiogenesis in the distal calf muscles is probably affected by the proximally occurring arteriogenesis. Therefore, to understand and subsequently intervene in the process of angiogenesis, a model is needed which investigates angiogenesis without the influence of arteriogenesis. In this study we evaluated the in vivo Matrigel plug assay in genetic deficient mice to investigate angiogenesis. Mice deficient for interferon regulatory factor (IRF)3, IRF7, RadioProtective 105 (RP105), Chemokine CC receptor CCR7, and p300/CBP-associated factor (PCAF) underwent the in vivo Matrigel model. Histological analysis of the Matrigel plugs showed an increased angiogenesis in mice deficient of IRF3, IRF7, and RP105, and a decreased angiogenesis in PCAF deficient mice. Our results also suggest an involvement of CCR7 in angiogenesis. Comparing our results with results of the HLI model found in the literature suggests that the in vivo Matrigel plug assay is superior in evaluating the angiogenic response after ischemia.     

Specific targeting of folate–dendrimer MRI contrast agents to the high affinity folate receptor expressed in ovarian tumor xenografts

The need to develop target-specific MRI contrast agents to aid in disease characterization remains highly essential. In this study, we present a generation four polyamidoamine (PAMAM) folate-dendrimer that specifically targets the high affinity folate receptor (hFR) overexpressed on more than 80% of ovarian tumors. In vitro, mouse erythroleukemia cells expressing the hFR bind the radiolabeled folate-dendrimer chelate resulting in over 2700% increase in binding compared with untreated cells. The binding was inhibited by free folic acid to levels observed on folate-receptor-negative cells. In vivo, ovarian tumor xenografts resulted in a 33% contrast enhancement, following the folate-dendrimer chelate administration, that was significantly different compared with results obtained with a non-specific, extracellular fluid space agent, Gd-HP-DO3A. In addition, this contrast enhancement was absent in saline-treated animals, folate-receptor-negative tumors, and was inhibited by free folic acid. Results suggest that a macromolecular, dendrimeric MRI agent with high molecular relaxivities (1646 mM⁻¹ s⁻¹) can be used in specifically targeting the hFR on tumor cells and ovarian tumors.     

Proposed Effective Width Criteria for Composite Bridge Girders

In a composite section, in-plane shear strain in the slab (acting as a flange in the composite girder) under the applied bending causes the longitudinal displacements in the parts of the slab remote from the webs to lag behind those near the webs. This phenomenon, termed shear-lag, can result in an incorrect calculation of the displacement and extreme fiber stresses when using only the elementary theory of beam bending. The effective width concept has been introduced, widely recognized, and implemented into different codes of practice around the world as a simplified practical method for design and evaluation of structural strength and stiffness while accounting for shear-lag effects indirectly. Each code implements different ideas and approaches for specifying effective width. This paper proposes simpler and more versatile design criteria for computing the effective width (beff) in steel-concrete composite bridges. A parametric study was conducted based on finite-element analysis of bridges selected by a statistical method—namely, design of experiment concepts. Both simple-span and multiple-span continuous bridges were considered in the parametric study. The finite-element methodology was validated with companion experiments on 1/4- and 1/2-scale specimens. Effective width values at the critical sections were computed from stresses extracted from FEM models and used in developing candidate design equations. The final design criteria were selected based on assessment of impact of candidate equations. Use of full width—the most versatile, simplest, and sufficiently accurate effective width design criteria, is proposed for both positive and negative moment regions.     

Designing for chaos: applications of chaotic advection at the microscale

Chaotic advection can play an important role in efficient microfluidic mixers. We discuss a design paradigm that exploits chaotic advection and illustrate by two recent examples, namely enhancing gene expression profiling and constructing an in-line microfluidic mixing channel, how application of this paradigm has led to successful micromixers. We suggest that 'designing for chaos', that is, basing practical mixer design on chaotic advection analysis, is a promising approach to adopt in this developing field which otherwise has little to guide it and is constrained by issues of scale and manufacturability.