Material parameter computation for multi-layered vocal fold models

Today, the prevention and treatment of voice disorders is an ever-increasing health concern. Since many occupations rely on verbal communication, vocal health is necessary just to maintain one's livelihood. Commonly applied models to study vocal fold vibrations and air flow distributions are self sustained physical models of the larynx composed of artificial silicone vocal folds. Choosing appropriate mechanical parameters for these vocal fold models while considering simplifications due to manufacturing restrictions is difficult but crucial for achieving realistic behavior. In the present work, a combination of experimental and numerical approaches to compute material parameters for synthetic vocal fold models is presented. The material parameters are derived from deformation behaviors of excised human larynges. The resulting deformations are used as reference displacements for a tracking functional to be optimized. Material optimization was applied to three-dimensional vocal fold models based on isotropic and transverse-isotropic material laws, considering both a layered model with homogeneous material properties on each layer and an inhomogeneous model. The best results exhibited a transversal-isotropic inhomogeneous (i.e., not producible) model. For the homogeneous model (three layers), the transversal-isotropic material parameters were also computed for each layer yielding deformations similar to the measured human vocal fold deformations.     

Taming multiparticle entanglement

We present an approach to characterize genuine multiparticle entanglement by using appropriate approximations in the space of quantum states. This leads to a criterion for entanglement which can easily be calculated by using semidefinite programing and improves all existing approaches significantly. Experimentally, it can also be evaluated when only some observables are measured. Furthermore, it results in a computable entanglement monotone for genuine multiparticle entanglement. Based on this, we develop an analytical approach for the entanglement detection in cluster states, leading to an exponential improvement compared with existing schemes.     

Intramolecular Formal anti‐Carbopalladation/Heck Reaction: Facile Domino Access to Carbo‐ and Heterooligocyclic Dienes

An intramolecular domino process consisting of a formal anti‐carbopalladation followed by Heck reaction is realized. Complex oligo(hetero)cyclic scaffolds are efficiently obtained in one synthetic step from easily obtainable enyne precursors. In contrast to common syn‐carbopalladation reactions of alkyne units, the carbopalladation employed here is designed to afford an anti‐arrangement of the two new substituents across the emerging double bond. A prerequisite is that the residues next to the alkyne should lack any β‐hydrogen atoms. The method paves the way to tri‐ and tetrasubstituted double‐bond systems that have not been accessible by conventional Pd catalysis.     

Mechanistic insight into the reactivity of oxotransferases by novel asymmetric dioxomolybdenum(VI) model complexes

The asymmetric molybdenum(VI) dioxo complexes of the bis(phenolate) ligands 1,4‐bis(2‐hydroxybenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐methylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐dimethylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐flurobenzyl)‐1,4‐diazepane, and 1,4‐bis(2‐hydroxy‐4‐chlorobenzyl)‐1,4‐diazepane (H₂(L1)–H₂(L6), respectively) have been isolated and studied as functional models for molybdenum oxotransferase enzymes. These complexes have been characterized as asymmetric complexes of type [MoO₂(L)] 1–6 by using NMR spectroscopy, mass spectrometry, elemental analysis, and electrochemical methods. The molecular structures of [MoO₂(L)] 1–4 have been successfully determined by single‐crystal X‐ray diffraction analyses, which show them to exhibit a distorted octahedral coordination geometry around molybdenum(VI) in an asymmetrical cis‐β configuration. The Mo? O_oxo bond lengths differ only by ≈0.01 Å. Complexes 1 , 2 , 5 , and 6 exhibit two successive Mo^VI/Mo^V (E_1/2, ?1.141 to ?1.848 V) and Mo^V/Mo^IV (E_1/2, ?1.531 to ?2.114 V) redox processes. However, only the Mo^VI/Mo^V redox couple was observed for 3 and 4 , suggesting that the subsequent reduction of the molybdenum(V) species is difficult. Complexes 1 , 2 , 5 , and 6 elicit efficient catalytic oxygen‐atom transfer (OAT) from dimethylsulfoxide (DMSO) to PMe₃ at 65 °C at a significantly faster rate than the symmetric molybdenum(VI) complexes of the analogous linear bis(phenolate) ligands known so far to exhibit OAT reactions at a higher temperature (130 °C). However, complexes 3 and 4 fail to perform the OAT reaction from DMSO to PMe₃ at 65 °C. DFT/B3LYP calculations on the OAT mechanism reveal a strong trans effect.     

Experimental study of electrostatically stabilized colloidal particles: colloidal stability and charge reversal

We consider the interaction of colloidal spheres in the presence of mono-, di-, and trivalent ions. The colloids are stabilized by electrostatic repulsion due to surface charges. The repulsive part of the interaction potential Ψ(d) is deduced from precise measurements of the rate of slow coagulation. These "microsurface potential measurements" allow us to determine a weak repulsion in which Ψ(d) is of the order of a few k(B)T. These data are compared to ζ potential measured under similar conditions. At higher concentrations both di- and trivalent counterions accumulate at the very proximity of the particle surface leading to charge reversal. The salt concentration c(cr) at which charge reversal occurs is found to be always above the critical coagulation concentration c(ccc). The analysis of Ψ(d) and of the ζ potential demonstrates, however, that adsorption of multivalent counterions starts far below c(cr). Hence, colloid stability in the presence of di- and trivalent ions cannot be described in terms of a DLVO ansatz assuming a surface charge that is constant with regard to the ionic strength.     

Pyridazine based scorpionate ligand in a copper boratrane compound

Reaction of potassium tris(mercapto-tert-butylpyridazinyl)borate K[Tn(tBu)] with copper(II) chloride in dichloromethane at room temperature led to the diamagnetic copper boratrane compound [Cu{B(Pn(tBu))(3)}Cl] (Pn = pyridazine-3-thionyl) (1) under activation of the B-H bond and formation of a Cu-B dative bond. In contrast to this, stirring of the same ligand with copper(I) chloride in tetrahydrofuran (THF) gave the dimeric compound [Cu{Tn(tBu)}](2) (2) where one copper atom is coordinated by two sulfur atoms and one hydrogen atom of one ligand and one sulfur of the other ligand. Hereby, no activation of the B-H bond occurred but a 3-center-2-electron B-H···Cu bond is formed. The reaction of copper(II) chloride with K[Tn(tBu)] in water gave the same product 2, but a formal reduction of the metal center from Cu(II) to Cu(I) occurred. When adding tricyclohexyl phosphine to the reaction mixture of K[Tn(R)] (R = tBu, Me) and copper(I) chloride in MeOH, the distorted tetrahedral Cu complexes [Cu{Tn(R)}(PCy(3))] (R = tBu 3, Me 4) were formed. Compound 4 is exhibiting an "inverted" κ(3)-H,S,S, coordination mode. The copper boratrane 1 was further investigated by density functional theory (DFT) calculations for a better understanding of the M→B interaction involving the d(8) electron configuration of Cu.