Correction to: Estimating Measurement Uncertainty on Stress-Strain Curves from SHPB

Experimental Mechanics - A correction to this paper has been published: https://doi.org/10.1007/s11340-021-00702-z     

Assessing impact force localization by using a particle swarm optimization algorithm

This paper focuses on the inverse problem regarding force localization in the case of impacts not concentrated at a point but which occur on elastic beams. Following the identification approach proposed to solve this problem and which is based on the reciprocity theorem, the impact location characteristics were determined by using particle swarm optimization algorithm. To eliminate numerical trouble due to the trivial solutions appearing in this formulation, the fitness function was customized by introducing a set of weighting coefficients. Four different formulations of the fitness function were considered and their performances with regards to the number of sensors used and their positions were analyzed. They enabled a selection of the best combination of weighting coefficients to be used in the context of an impact force localization process based on the particle swarm optimization technique. Three sensors were found to be required and comparison with a genetic algorithm has revealed the effectiveness of the proposed method in terms of accuracy and computational time.     

Estimating Measurement Uncertainty on Stress-Strain Curves from SHPB

Split Hopkinson Pressure Bar tests are commonly used to determine material stress-strain relationship at high deformation rates. Obtaining this relationship is dependant both on certain assumptions and substantial post-processing of the data recorded during the test. Measurement uncertainty rarely appears on the resulting curves. This article introduces a simple method of estimating the measurement uncertainty associated with SHPB tests.     

Palladium versus copper-catalyzed N-arylation towards an efficient access to polysubstituted dibenzophenanthrolines and carbazoles

The double amination of meta-diiodo and dibromobenzenes by anthranilic acid derivatives is described using palladium and/or copper catalysis. The resulting symmetrical and unsymmetrical phenylene diamines are key precursors to polyfunctional dibenzophenanthroline carboxaldehydes. In contrast, when ortho-dibromo benzene is used as substrate, the Pd-mediated process affords exclusively the functional carbazole.     

Correction to : Estimating Measurement Uncertainty on Stress-Strain Curves from SHPB

Experimental Mechanics - Equation (12) in the original article [1] gives the strain from the measured voltage on a full bridge configuration of the four strain gages. The full-bridge is intended to...     

Allenic Carbanions from Propargylic Acetals: Synthesis of the β-Cinnamic Ester Unit

Our previous papers in that field describe the formation of carbanions and their use in synthesis from substrates like X-C[tbnd]C-H-Z.     

Nonlinear finite element analysis of inflatable beams made from orthotropic woven fabric

This paper was devoted to the three-dimensional nonlinear finite element analysis of inflatable beams. The beams under consideration are made of modern textile materials and can be used as a load-bearing beams or arches when inflated. A 3D Timoshenko beam with a homogeneous orthotropic woven fabric (OWF) was proposed. The model took into account the geometric nonlinearities and the follower force resulting from the inflation pressure. The use was made of the usual total Lagrangian form of the virtual work principle to perform the nonlinear equilibrium equations which were discretized by the finite element method. Two kinds of solutions were then investigated: finite elements solutions for linearized problems which were obtained by the means of the linearization around the prestressed reference configuration of the nonlinear equations and nonlinear finite element solutions which were performed by the use of an optimization algorithm based on the Quasi-Newton method. As an example, the bending problem of a cantilever inflated beam under concentrated load was considered and the deflection results improve the existing theoretical models. As these beams are made from fabric, the beam models were validated through their comparison with a 3D thin-shell finite element model. The influence of the material effective properties and the inflation pressure on the beam response was also investigated through a parametric study. The finite elements solutions for linearized problems were found to be close to the theoretical results existing in the literature. On the other hand, the results for the nonlinear finite element model were shown to be close to the results for the linearized finite elements model in the case of high mechanical properties and the nonlinear finite element model was used to improve the linearized model when the mechanical properties of the fabric are low.     

Stimuli Induced Uptake of Protein-Like Peptide Brush Polymers

Recently, we presented a strategy for packaging peptides as side-chains in high-density brush polymers. For this globular protein-like polymer (PLP) formulation, therapeutic peptides were shown to resist proteolytic degradation, enter cells efficiently and maintain biological function. In this paper, we establish the role charge plays in dictating the cellular uptake of these peptide formulations, finding that peptides with a net positive charge will enter cells when polymerized, while those formed from anionic or neutral peptides remain outside of cells. Given these findings, we explored whether cellular uptake could be selectively induced by a stimulus. In our design, a cationic peptide is appended to a sequence of charge-neutralizing anionic amino acids through stimuli-responsive cleavable linkers. As a proof-of-concept study, we tested this strategy with two different classes of stimuli, exogenous UV light and an enzyme (a matrix metalloproteinase) associated with the inflammatory response. The key finding is that these materials enter cells only when acted upon by the stimulus. This approach makes it possible to achieve delivery of the polymers, therapeutic peptides or an appended cargo into cells in response to an appropriate stimulus.     

Activating peptides for cellular uptake via polymerization into high density brushes

The utility of peptide therapeutics is thwarted by an inability to enter cells, preventing access to crucial intracellular targets. Herein, we describe a simple and potentially widely applicable solution involving the polymerization of a minimally modified amino acid sequence into a high density brush polymer. Specifically, non-cell penetrating peptides can be rendered competent for cell entry by first including a single Arg or Lys in their amino acid sequence, if one is not already present, along with a norbornenyl unit. This modified monomer is then polymerized by ring opening metathesis polymerization (ROMP). To demonstrate the utility of this strategy, a known therapeutic peptide, which does not penetrate cells on its own, was polymerized. The resulting polymer proficiently entered cells while maintaining its intracellular function. We anticipate that this methodology will find broad use in medicine, increasing or enabling the in vivo efficacy of promising peptide therapeutics.     

An efficient approach to new dihydroxyquinolizidines

Using d-glyceraldehyde acetonide as a starting material, a four-step synthesis of enantiomerically pure 3,4-dihydroxyquinolizidines is described. The key steps of the synthesis consist of a Mitsunobu ring-closing reaction and the subsequent reduction of a pyridinium ring.