FE simulation of human trachea swallowing movement before and after the implantation of an endoprothesis

Background and aims

Nowadays interventions associated to the implantation of tracheal stents in patients with airway pathologies, are a very common surgery that in the post-operating period can bear many problems such as migration of the stent, development of granulation tissue at the edges of the stent with overgrowth of the tracheal lumen, or accumulation of secretions inside the prosthesis. Among the movements that trachea carries out, swallowing seems to drive harmful consequences for the tracheal tissues surrounding the prosthesis. In this work a finite element model of a human trachea has been developed and used to analyze its behavior during swallowing.

Material and methods

In the present work, a complete human trachea finite element model based on experimental study was developed. The real swallowing movement of two patients before and after the implantation of Dumon prosthesis was used to simulate and then analyze the effect that the tracheal implant has on the stress response of the trachea and on the physiological capacity to swallow.

Results

In both studied cases with an implanted Dumon prosthesis, patients showed a decrease of their ability to swallow; one lost 26.4% and the other one 18.9% of their tracheal ascending movements. Besides, the prosthesis implantation caused an increase of the stresses located in the superior contact border between the tracheal wall and the prosthesis. It could be seen that the resulting force equivalent to the elevating tracheal muscle forces for degluting, was around F = 13.5 N for the two patients both before and after the stent implantation.

Conclusion

The implantation of a Dumon prosthesis modifies the mechanical response of the trachea altering its stress distribution and its ascending movement.     

The multivalent effect in glycosidase inhibition: probing the influence of architectural parameters with cyclodextrin-based iminosugar click clusters

In contrast to most lectins, glycosidases may appear to be unpromising targets for multivalent binding because they display only a single active site. To explore the potential of multivalency on glycosidase inhibition, unprecedented cyclodextrin-based iminosugar conjugates have been designed and prepared. The synthesis was performed by way of Cu(I) -catalyzed azide-alkyne cycloaddition reaction under microwave activation between propargylated multivalent β-cyclodextrins and an azide-armed N-alkyl 1-deoxynojirimycin derivative. Evaluation with a panel of glycosidases of this new class of glycomimetic clusters revealed the strongest affinity enhancement observed to date for a multivalent glycosidase inhibitor, with binding enhancement up to four orders of magnitude over the corresponding monovalent ligand for α-mannosidase. These results demonstrate that the multivalency concept extends beyond carbohydrate-lectin recognition processes to glycomimetic-enzyme inhibition.     

An LDLT factorization based ADI algorithm for solving large-scale differential matrix equations

Large-scale differential matrix equations appear in many applications like optimal control of partial differential equations, balanced truncation model order reduction of linear time varying systems etc. Here, we will focus on matrix Riccati differential equations (RDE). Solving such matrix valued ordinary differential equations (ODE) is a highly storage and time consuming process. Therefore, it is necessary to develop efficient solution strategies minimizing both. We present an LDL^T factorization based ADI method for solving algebraic Lyapunov equations (ALE) arising in the innermost iteration during the application of Rosenbrock ODE solvers to RDEs. We show that the LDL^T-type decomposition avoids complex arithmetic, as well as cancellation effects arising from indefinite right hand sides of the ALEs appearing in the classic ZZ^T based approach. Additionally, a certain number of linear system solves can be saved within the ADI algorithm by reducing the number of column blocks in the right hand sides while the full accuracy of the standard low-rank ADI is preserved. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

CNH2 Bond Formation Mediated by Iridium Complexes

In the presence of phosphanes (PR₃), the amido‐bridged trinuclear complex [{Ir(μ‐NH₂)(tfbb)}₃] (tfbb=tetrafluorobenzobarrelene) transforms into mononuclear discrete compounds [Ir(1,2‐η²‐4‐κ‐C₁₂H₈F₄N)(PR₃)₃], which are the products of the C? N coupling between the amido moiety and a vinylic carbon of the diolefin. An alternative synthetic approach to these species involves the reaction of the 18 e^? complex [Ir(Cl)(tfbb)(PMePh₂)₂] with gaseous ammonia and additional phosphane. DFT studies show that both transformations occur through nucleophilic attack. In the first case the amido moiety attacks a diolefin coordinated to a neighboring molecule following a bimolecular mechanism induced by the highly basic NH₂ moiety; the second pathway involves a direct nucleophilic attack of ammonia to a coordinated tfbb molecule.     

A novel efficient synthetic method for 2,2′,3,3′-biphenyltetracarboxylic dianhydride

A novel approach to the synthesis of 2,2′,3,3′-biphenyltetracarboxylic dianhydride is described.The target compound was prepared by a nickel-catalyzed coupling reaction of dimethy 3-chlorophthalate(3-DMCP) for 4 h at 70-80℃,followed by subsequent hydrolysis of tetra-ester in acid solution and dehydration of tetra-acid,with overall yield of 68%.The structures of the products were characterized by IR,~1H NMR and ~(13)C NMR respectively.     

Author Index

Author Index

Author Index