37 research outputs found
COREPRO-Sim: A Tool for Modeling, Simulating and Adapting Data-driven Process Structures
Industry is increasingly demanding IT support for large engineering process structures consisting of hundreds up to thousands of synchronized processes. In technical domains, such process structures are characterized by their strong relation to the assembly of a product (e.g., a car); i.e., resulting process structures are data-driven. The strong linkage between data and processes can be utilized for automatically creating process structures as well as for (dynamically) adapting them at a high level of abstraction. This paper presents the COREPRO-Sim demonstrator which enables sophisticated support for modeling, coordinating and (dynamically) adapting data-driven process structures. COREPRO-Sim substantiates the COREPRO approach which provides a new paradigm for the integration of data and and process structures
701-704 [Rezension] Reichert, Detlef, Der Weg protestantischer Liturgik zwischen Orthodoxie und Aufklärung
Helical Jump Motions of Poly(l-Lactic Acid) Chains in the α Phase As Revealed by Solid-State NMR
The molecular dynamics of Poly(l-lactic Acid) (PLLA) chains in the α phase was investigated by Solid-State NMR spectroscopy. 13C high-resolution NMR clearly indicates that the crystalline signals split into 2, 3, and 4 signals for the CH3, CH and CO groups, respectively at 25 °C, while the amorphous signals give a broad component at the bottom of the crystalline signals. 13C NMR spectra show that the crystalline line shape changes with increasing temperatures well above the glass transition temperature (Tg) and imply the presence of the molecular dynamics in the crystalline region. Comparisons of the evolution-time dependence of CODEX data and simulation results based on reorientation of chemical shift anisotropy (CSA) indicate that the chains in the α phase perform helical jump motions in the slow dynamic range at temperatures above 115 °C. The mixing-time dependence of the CODEX data yields an activation energy of Ea of (95 ± 8) kJ/mol for the helical jump motions. Moreover, two-dimensional exchange NMR with highly resolved signals for the CO group provides cross peaks among four well resolved signals due to the helical jumps. Comparison of 2D buildup curves of the cross peaks and calculated data determines that helical jump motions prefer largely uncorrelated random back-and-forth motions between the neighboring sites, possibly enabling large-scale chain diffusion in the crystalline regions
Ion Transport Properties and Ionicity of 1,3-Dimethyl-1,2,3-Triazolium Salts with Fluorinated Anions
1,2,3-Triazolium salts are an important class of materials with a plethora of sophisticated applications. A series of three novel 1,3-dimethyl-1,2,3-triazolium salts with fluorine, containing anions of various size, is synthesized by methylation of 1,2,3-triazole. Their ion conductivity is measured by impedance spectroscopy, and the corresponding ionicities are determined by diffusion coefficients obtained from 1H and 19F pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy data, revealing that the anion strongly influences their ion conductive properties. Since the molar ion conductivities and ionicities of the 1,3-dimethyl-1,2,3-triazolium salts are enhanced in comparison to other 1,2,3-triazolium salts with longer alkyl substituents, they are promising candidates for applications as electrolytes in electrochemical devices
Bond-Shift Rearrangement in Solid Li3</sub<P7(Monoglyme)3: A 31P MAS NMR Study
The 31P MAS NMR spectrum of solid Li3P7 (monoglyme) 3 has been reinvestigated over a wide temperature range (-70 to +77°C) and under conditions of better resolution (Larmor frequency of 162 MHz and spinning rate of ˜30 kHz) than previously measured (121 MHz and 13 kHz). At low temperatures three spinning sideband (ssb) manifolds are observed: a singlet (centered at -45 ppm relative to 85% H3PO4) due to the apical atom (A) of the P7-cage trianion; a 1 : 1 : 1 triplet (at -110, -117, and -124.5 ppm) due to the negatively charged equatorial (E) atoms, and a one to two doublet (at -161 and -168.5 ppm) due to the basal (B) atoms. These results are consistent with the P7 cage having nearly, but not perfect, C3v symmetry. The compound appears to be well ordered in the solid state with very little structural dispersity. On heating, the NMR lines broaden and eventually coalesce into a single ssb manifold. This behavior is ascribed to bond-shift rearrangement similar to the Cope rearrangement in bullvalene. A MAS 2D exchange experiment and a quantitative analysis of the 1D NMR lineshapes indicate that, unlike in solution where the rearrangement involves a single bond shift at a time, in the solid the process involves a succession of two bond shifts: The first leads to an intermediate species in which the rearranged P7 cage is inverted, while in the subsequent step a second bond shift takes place that also restores the original orientation of the cage in the lattice. The overall effect of the double bond shift is equivalent to cyclic permutation of the phosphorus atoms within the five member rings of the P7-cage. The quantitative analysis of the dynamic lineshapes shows that this cyclic permutation proceeds at a different rate in one ring (kd1) than in the other two (kd2,3). The kinetic parameters for these processes are E<SMALL>α</SMALL>1=18.7 kJ/mol, E<SMALL>α</SMALL>2,3=58.0 kJ/mol, kd1 (17°C)=kd2,3 (17°C)=104 s-1. No indications for independent threefold molecular jumps of the P7 cage were found
Slow dynamics in glassy methyl α-l-rhamnopyranoside studied by 1D NMR exchange experiments
It is widely known that the ability of sugar glasses to preserve anhydrobiotic systems in nature is important but the process is not yet fully understood. Molecular motions in the glassy state are likely to be important in the process but until now have remained largely uncharacterized. Here we describe the use of 1D 13C NMR exchange experiments using CODEX (centreband only detection of exchange) methods to study the dynamics of the well characterised model glassy monosaccharide, methyl a-L-rhamnopyranoside. The glass was prepared by fast cooling of a melt inside an NMR rotor. Molecular motions in the range of seconds to milliseconds were observed in the glass, whereas identical experiments using the crystalline material displayed no observable motions in the time-scales covered by the experiment. At 13 to 14 K above Tg the nature of the motion in the glass changed probably due to the onset of larger scale reorientation. A bimodal distribution of jump angles combined with a broad distribution of correlation times was found to best represent the observed motions
Intermediate motions and dipolar couplings as studied by Lee-Goldburg cross-polarization NMR: Hartmann-Hahn matching profiles
In this article, we evaluate the use of simple Lee-Goldburg cross-polarization (LG-CP) NMR experiments for obtaining quantitative information of molecular motion in the intermediate regime. In particular, we introduce the measurement of Hartmann-Hahn matching profiles for the assessment of heteronuclear dipolar couplings as well as dynamics as a reliable and robust alternative to the more common analysis of build-up curves. We have carried out dynamic spin dynamics simulations in order to test the method's sensitivity to intermediate motion and address its limitations concerning possible experimental imperfections. We further demonstrate the successful use of simple theoretical concepts, most prominently Anderson-Weiss (AW) theory, to analyze the data. We further propose an alternative way to estimate activation energies of molecular motions, based upon the acquisition of only two LG-CP spectra per temperature at different temperatures. As experimental tests, molecular jumps in imidazole methyl sulfonate, trimethylsulfoxonium iodide, and bisphenol A polycarbonate were investigated with the new method.DFG - Deutsche Forschungsgemeinschaft[RE 1025/16](DAAD) Deutscher Akademischer Austausch Dienst, GermanyFAPESPCNPQCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES
Recoupled separated-local-field experiments and applications to study intermediate-regime molecular motions
A specific separated-local-field NMR experiment, dubbed Dipolar-Chemical-Shift Correlation (DIPSHIFT) is frequently used to study molecular motions by probing reorientations through the changes in XH dipolar coupling and T-2. In systems where the coupling is weak or the reorientation angle is small, a recoupled variant of the DIPSHIFT experiment is applied, where the effective dipolar coupling is amplified by a REDOR-like pi-pulse train. However, a previously described constant-time variant of this experiment is not sensitive to the motion-induced T-2 effect, which precludes the observation of motions over a large range of rates ranging from hundreds of Hz to around a MHz. We present a DIPSHIFT implementation which amplifies the dipolar couplings and is still sensitive to T-2 effects. Spin dynamics simulations, analytical calculations and experiments demonstrate the sensitivity of the technique to molecular motions, and suggest the best experimental conditions to avoid imperfections. Furthermore, an in-depth theoretical analysis of the interplay of REDOR-like recoupling and proton decoupling based on Average-Hamiltonian Theory was performed, which allowed explaining the origin of many artifacts found in literature data. (C) 2012 Elsevier Inc. All rights reserved.Deutsche Forschungsgemeinschaft (DFG) [FOR 1145, SA 982/6-1]Deutsche Forschungsgemeinschaft (DFG)CAPES/DAAD PROBRAL exchange projectCAPES/DAAD PROBRAL exchange project [330/09, D/08/11622, 50752585]FAPESPFAPESP [2009/18354-8, 2008/11675-0