Production planning with load dependent lead times: an update of research

Lead times impact the performance of the supply chain significantly. Although there is a large body of literature concerning queuing models for the analysis of the relationship between capacity utilization and lead times, and another body of work on control and order release policies that take lead times into consideration, there have been relatively few aggregate planning models that recognize the (nonlinear) relationship between the planned utilization of capacity and lead times. In this paper we provide an in-depth discussion of the state-of-the art in this area, with particular attention to those models that are appropriate at the aggregate planning level. An earlier version of this paper appeared in 4OR 3, 257–302, 2005.     

A Raman scattering study of the phase transition in the (NH4)3WO3F3 oxyfluoride

The Raman scattering spectra of polycrystalline samples of the (NH₄)₃WO₃F₃ perovskite-like oxyfluoride were measured at frequencies of 70–3600 cm^?1 in the temperature range 93–323 K, including the transition from the orientationally disordered cubic phase to the low-symmetry phase. Transitional anomalies in the spectral parameters were revealed in the frequency ranges of internal vibrations of the ammonium ions and WO₃F₃ octahedral groups. An analysis of the experimental results allowed the conclusion that the phase transition under study is associated primarily with the ordering of the octahedral groups.     

New coordination modes of iminodiacetamide type ligands in palladium(II) complexes: crystallographic and DFT studies

The reactions of N-alkyliminodiacetamide derivatives, namely N-ethyliminodiacetamide (CH₃CH₂N(CH₂CONH₂)₂; Etimda) and N-isopropyliminodiacetamide (CH₃)₂CHN(CH₂CONH₂)₂; i-Primda), with sodium tetrachloropalladate(II) in aqueous solutions were investigated. Three new palladium(II) complexes, [Pd(Etimda_?H)₂]?2H₂O (1), [Pd(i-Primda_?H)₂]?2H₂O (2) and [PdCl₂(i-Primda)] (3), were obtained and characterized by X-ray structural analysis, infrared spectroscopy and thermal analysis (TGA). The square planar coordination environments around the palladium(II) ions in complexes 1 and 2 consist of two N,N′-bidentate N-alkyliminodiacetamidato ligands, with imino N atoms in trans-position. The complex 3 also exhibits a square planar coordination environment around Pd(II), but with two chloride ions and one neutral N-isopropyliminodiacetamide ligand bound in an N,O′-bidentate coordination mode. The described coordination modes, as well as the presence of deprotonated amide groups in ligands in 1 and 2, are found for the first time in palladium(II) complexes with iminodiacetamide type ligands. The molecular geometries and infrared spectra of these three complexes were also modelled using DFT calculations, at the BP86-D3/def2-TZVPP/PCM level of theory. The RMSD values suggest a good agreement of the calculated and experimental geometries. A QTAIM analysis suggests a qualitative correlation between bond lengths and energy densities, also supported by an NBO analysis. The dimer interaction energy between complex units was estimated at about ?15 kcal/mol for all complexes.     

Enantioselective synthesis without discrete optically active additives

By an adaptation of the asymmetric autocatalysis reactions of Soai, it was found that small enantiomeric excesses may be amplified to an arbitrary extent. When this process was applied 48 times to reactions in the absence of discrete optically active additives, all ultimately afforded substantial optical activity in the product. However, observations strongly suggest that most (and likely all) of these reactions are not true examples of absolute asymmetric synthesis. Rather, the ultimate optical activity arises from optically active impurities. Trace amounts of optically active materials may dominate the outcome of reactions involving asymmetric autocatalysis, and in the presence of opposite chiral influences a single enantiomer tends to take over a reaction. The possible implications of these observations to the origin of biological homochirality are noted.     

Determination of rare-earth elements by the simultaneous gamma-neutron activation analyses using a microtron

The combination of photon and neutron activation provides an effective method of analysis of rare earths and other elements. A mixed -neutron field is obtained with electron-to-gamma /e/ and gamma-to-neutron /n/ converters combined with a lucite moderator. The samples are activated simultaneously. The sensitivities of this method have been compared with neutron activation in a graphite moderator cube using the same microtron. The advantages and shortcomings of the method are discussed.Dedicated to Prof. V.D. Nefedov on the occasion of his 70th birthday     

Einige Reaktionen der Siliciumtetrahalogenid-Pyridin-Additionsverbindungen

Zusammenfassung Siliciumtetrahalogenid-Pyridin-Addukte reagieren mit Halogenwasserstoffen schon bei Raumtemp. unter Pyridin-Übertragung (vgl. Rk. 1) und, bei positiverem Halogen am Silicium, unter gleichzeitigem Halogenaustausch (vgl. Rk. 2). Analoge Austauschreaktionen finden zwischen Siliciumhalogeniden und Pyridiniumhalogeniden statt (vgl. Rk. 3). Gemischte Silicium-halogenide ließen sich auf diesem Wege nicht darstellen; die Dismutationsneigung gemischter Siliciumhalogenide wird durch Anwesenheit von Pyridinium-Ionen offensichtlich verstärkt. Gegenüber SO₂, SO₃, NH₃ oder H₂S zeigen die Additionsverbindungen eine etwas größere Reaktionsbereitschaft als die freien Siliciumhalogenide.

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The silicontetrahalogenide-pyridine addition compounds react with hydrogen halogenides at room temperature according equation (1), in case of more positive halogen atoms on silicon with simultaneous exchange of the halogen atoms (equ. 2). Analogous exchange reactions are to be observed between silicon halogenides and pyridinium halogenides (equ. 3). It was not possible to prepare mixed silicon halogenides by this method. The addition compounds seem to react with SO₂, SO₃, NH₃ and H₂S somewhat easier than the free silicon halogenides.

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67. Mitt.:U. Wannagat, K. Hensen undF. Vielberg, Mh. Chem.99, 431, (1968).

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Zugleich 8. Mitt. über Verbindungen von Nichtmetallhalogeniden mit Pyridin und seinen Homologen; 7. Mitt. vgl.

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Mit Auszügen aus den DissertationenH. Voß, F. Vielberg undK. Hensen, Techn. Hochschule Aachen 1954 bzw. 1956 bzw. 1962, und der DiplomarbeitP. Petesch, Techn. Hochschule Aachen 1958.     

Synthesis of new 14-membered macrolide antibiotics via a novel ring contraction metathesis

[reaction: see text] A novel ring opening ring closing metathesis (ROM-RCM) was demonstrated for cyclic conjugated dienes, effecting the excision of a C(2)H(2) unit and a net ring contraction. Applying the ring contraction metathesis, new 14-membered ring macrolide antibiotics were synthesized in a single step from existing 16-membered ring macrolides. This new class of macrolide antibiotics will provide access to new therapeutics for the treatment of macrolide-resistant bacterial infections.     

Regularization of a final value problem for a nonlinear biharmonic equation

In this paper, we consider the nonlinear biharmonic equation. The problem is ill‐posed in the sense of Hadamard. To obtain a stable numerical solution, we consider a regularization method. We show rigourously, with error estimates provided, that the corresponding regularized solutions converge to the true solution strongly in uniformly with respect to the space coordinate under some a priori assumptions on the solution.