Phase field modeling of domain evolution in ferroelectric materials in the context of size effects

Phase field modeling provides an efficient tool for the study of domain evolution in ferroelectric materials. Such models naturally introduce an inner length scale which represents the width of the interfaces between domains (domain walls). This inner length scale is of the order of a few unit cells, i.e. about 0.8 nm–2 nm. The focus of this contribution is on size effects in a) the switching behavior of ferroelectric thin films and b) the microstructure evolution in ferroelectric nanodots. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermo-mechanical homogenisation – application to HVOF thermal-sprayed WC-Co coatings

Hard material coatings are widely employed as wear protection for highly engrossed surfaces. For example, coatings consisting of tungsten carbide (WC) and cobalt (Co) are used for sheet metal forming tools. A relatively cost-efficient coating technique is the high velocity oxygen fuel (HVOF) thermal spraying process which, as a trade-off, induces a large amount of energy into the heterogeneous coating and the substrate. Hence, this leads to a complex transient, thermomechanically coupled problem. In order to predict the residual stresses during the quenching procedure, a two scale finite element framework is established wherein the scale bridging is performed by application of two different homogenisation approaches. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase Field Approximation of Dynamic Brittle Fracture

The numerical assessment of fracture has gained importance in fields like the safety analysis of technical structures or the hydraulic fracturing process. The modelling technique discussed in this work is the phase field method which introduces an additional scalar field. The smooth phase field distinguishes broken from undamaged material and thus describes cracks in a continuum. The model consists of two coupled partial differential equations - the equation of motion including the constitutive behaviour of the material and a phase field evolution equation. The crack growth follows implicitly from the solution of this system of PDEs. The numerical solution with finite elements can be accelerated with an algorithm that performs computationally extensive tasks on a graphic processing unit (GPU). A numerical example illustrates the capability of the model to reproduce realistic features of dynamic brittle fracture. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The BOSCO solar cell – a both sides collecting and contacted structure

The BOSCO solar cell represents a bifacial structure with double‐sided collection. The structure allows the use of standard module interconnection technology and favours the use of material with low to medium diffusion length and low resistivity for maximum benefit towards other structures, such as Al‐BSF and PERC. Within this work, we present first results on different multicrystalline silicon materials yielding a monofacial efficiency of 17.4% on large‐area wafers from block‐cast mc‐Si. This value represents a gain of ～0.7%_abs compared to Al‐BSF cells processed in parallel. The applicability for bifacial operation is demonstrated by a significantly increased quantum efficiency for rear side illumination. These results make the BOSCO solar cell concept a promising candidate to further boost the output of utility‐scale PV plants even when using low‐cost wafers of low to medium diffusion length material.

     

Addition of one and two units of C2H to styrene: a theoretical study of the C10H9 and C12H9 systems and implications toward growth of polycyclic aromatic hydrocarbons at low temperatures

Various mechanisms of the formation of naphthalene and its substituted derivatives have been investigated by ab initio G3(MP2,CC)∕B3LYP∕6-311G?? calculations of potential energy surfaces for the reactions of one and two C(2)H additions to styrene combined with RRKM calculations of product branching ratios under single-collision conditions. The results show that for the C(2)H + styrene reaction, the dominant routes are H atom eliminations from the initial adducts; C(2)H addition to the vinyl side chain of styrene is predicted to produce trans or cis conformations of phenylvinylacetylene (t- and c-PVA), whereas C(2)H addition to the ortho carbon in the ring is expected to lead to the formation of o-ethynylstyrene. Although various reaction channels may lead to a second ring closure and the formation of naphthalene, they are not competitive with the direct H loss channels producing PVAs and ethynylstyrenes. However, c-PVA and o-ethynylstyrene may undergo a second addition of the ethynyl radical to ultimately produce substituted naphthalene derivatives. α- and β-additions of C(2)H to the side chain in c-PVA are calculated to form 2-ethynyl-naphthalene with branching ratios of about 30% and 96%, respectively; the major product in the case of α-addition would be cis-1-hexene-3,5-diynyl-benzene produced by an immediate H elimination from the initial adduct. C(2)H addition to the ethynyl side chain in o-ethynylstyrene is predicted to lead to the formation of 1-ethynyl-naphthalene as the dominant product. The C(2)H + styrene → t-PVA + H∕c-PVA + H∕ o-ethynylstyrene, C(2)H + c-PVA → 2-ethynyl-naphthalene + H, and C(2)H + o-ethynylstyrene → 1-ethynyl-naphthalene + H reactions are calculated to occur without a barrier and with high exothermicity, with all intermediates, transition states, and products lying significantly lower in energy than the initial reactants, and hence to be fast even at very low temperature conditions prevailing in Titan's atmosphere or in the interstellar medium. If styrene and C(2)H are available and overlap, the sequence of two C(2)H additions can result in the closure of a second aromatic ring and thus provide a viable route to the formation of 1- or 2-ethynyl-naphthalene. The analogous mechanism can be extrapolated to the low-temperature growth of polycyclic aromatic hydrocarbons (PAH) in general, as a step from a vinyl-PAH to an ethynyl-substituted PAH with an extra aromatic ring.     

Determining the DNA stability parameters for the breathing dynamics of heterogeneous DNA by stochastic optimization

We suggest that the thermodynamic stability parameters (nearest neighbor stacking and hydrogen bonding free energies) of double-stranded DNA molecules can be inferred reliably from time series of the size fluctuations (breathing) of local denaturation zones (bubbles). On the basis of the reconstructed bubble size distribution, this is achieved through stochastic optimization of the free energies in terms of simulated annealing. In particular, it is shown that even noisy time series allow the identification of the stability parameters at remarkable accuracy. This method will be useful to obtain the DNA stacking and hydrogen bonding free energies from single bubble breathing assays rather than equilibrium data.     

A New Method of Preparation of Ifosfamide and Cyclophosphamide; Synthesis of Side Products

Abstract

This study focusses on the preparation of ifosfamide (1; R¹=CH₂CH₂Cl, R²=NHCH₂CH₂Cl) and cyclophosphamide (2 R¹=H, R²=N(CH₂CH₂Cl)₂), standard drugs in tumor therapy, in order to avoid the alkylating educts like 2-chloroethylamine by introducing chlorine in the final reaction step. The reaction of the trimethylsilyl compounds (3; R¹=CH₂CH₂Cl, R²=NHCH₂CH₂0SiMe₃) and (4; R¹=H, R²=N(CH₂CH₂0SiMe₃)₂), respectively, with 2-chloro- 1,3,5-trimethyl-1,3,5-triaza-σ³λ₃-2-phosphoM-4,6-dione, followed by chlorination of the resulting product with sulphuryl chloride, furnished the cytotoxic drugs (1) and (2) [l].     

A FACILE NOVEL ACCESS TO THE ISOPHOSPHINDOLINE SYSTEM

Abstract

Synthesis of a novel isophosphindoline derivative, 1-phenyl-1,3-dihydro-2Λ⁵-benzophospholic acid (1), is described, the structure of 1 established on the basis of ¹³C, ¹H, and ³¹P NMR spectra, and the NMR and mass spectral data are discussed in detail.     

Resolving the microcosmos of complex samples: UPLC/travelling wave ion mobility separation high resolution mass spectrometry for the analysis of in vivo drug metabolism studies

In vivo drug metabolism studies with low concentrations of analytes and high matrix burden are challenging. Of special interest are ‘first-in-man’ studies in early stages of pharmaceutical development that do not use ¹⁴C labeled drug candidates. Beside conventional MS-fishing techniques which are biased towards known/expected metabolites and mass defect filtration procedures, this paper focuses on the untargeted/unbiased analysis of drug related compounds in complex matrices using two orthogonal separation techniques: UPLC and TWIMS. Standard sample material after oral administration of a drug compound to rats was investigated by UPLC/TWIMS in MS^E acquisition mode using interlaced collision energies for the parallel detection of [M+H]⁺ parent ions and fragments. Due to the fragmentation after ion mobility separation in the transfer region of the Synapt G2-triwave device, [M+H]⁺ ion species are aligned with their related fragments by virtue of possessing the same retention time and drift time profile. Four dimensional data analysis of the continuum raw data was performed by automated peak picking and alignment within the MS^E viewer software. As result, completely purified MS- and MS/MS-data of metabolites were extracted from raw mass data with high matrix burden and were used without compromise for structure elucidation. This analytical methodology is universally applicable for the unbiased/untargeted and robust analysis of any analyte of interest in complex matrices, including small molecules, peptides and proteins. The high quality data files can be used as data repositories for the purpose of retrospective analysis which is of particular interest for the long term process in drug development.     

On the Nature of Interactions between Ionic Liquids and Small Amino‐Acid‐Based Biomolecules

During the last decade, ionic liquids (ILs) have revealed promising properties and applications in many research fields, including biotechnology and biological sciences. The focus of this contribution is to give a critical review of the phenomena observed and current knowledge of the interactions occurring on a molecular basis. As opposed to the huge advances made in understanding the properties of proteins in ILs, complementary investigations dealing with interactions between ILs and peptides or oligopeptides are underrepresented and are mostly only of phenomenological nature. However, the field has received more attention in the last few years. This Review features a meta‐analysis of the available data and findings and should, therefore, provide a basis for a scientifically profound understanding of the nature and mechanisms of interactions between ILs and structured or nonstructured peptides. Fundamental aspects of the interactions between different peptides/oligopeptides and ILs are complemented by sections on the experimental (spectroscopy, structural biology) and theoretical (computational chemistry) possibilities to explain the phenomena reported so far in the literature. In effect, this should lead to the development of novel applications and support the understanding of IL–solute interactions in general.