How useful is commonality? Inventory and production decisions to maximize survival probability in start-ups

This paper deals with component commonality in start-up manufacturingfirms. We present a two-product Markov decision model that examinesthe implications of the inventory and production strategiesfor the survival probability of the firm. The advantage of usingcomponent commonality is studied for varying costs, demand correlationsand order replenishment lead times. Optimal policies are derived,and minimum stock levels for survival are obtained. Moreover,we state the conditions under which simplified production decisionscan be made. It is shown that commonality is not only usefulas a way of dealing with demand uncertainty, but that its increaseduse is preferred for strongly substitutable products, and shorterreplenishment lead times.     

Synthesis and Characterization of Silver(I) Complexes with C-Alkyl Functionalized N,N′-Diphenylamidinates: Tetrameric and Trimeric Structural Motifs

N,N–Diphenylamidines and the silver(I) complexes of their deprotonated anions have been synthesized. Previously uncharacterized tetrameric structural motifs were produced by the inclusion of alkyl substituents at the amidinate carbon. The addition of a 2-methoxy functional group to the phenyl ring resulted in a cationic silver trimer in which hydrogen bonding links silver(I)-bound water molecules to the methoxy substituents. The thermal stabilities of the tetrameric species vary with alkyl chain length. The new complexes are: tetrakis(N,N-diphenylpropamidinato) tetra silver(I), 1, tetrakis(N,N-diphenylbutamidinato) tetrasilver(I) 2, tetrakis(N,N-diphenylpentamidinato) tetra silver(I) 3, (N,N-diphenyloctamidinato)silver(I) 4, (tetrakis(N,N-di(4-n-butyl)phenylpropamidinato)tetrasilver(I), 5, bis(N,N-di(2-methoxy)phenylacetamidinato)diaquatrisilver(I) nitrate 6 and tetrakis(N,N-di(4-methoxy)phenylacetamidinato) tetrasilver(I), 7. Compounds 1, 5, 6 and 7 were structurally characterized by X-ray methods.     

Stereocontrol in organic synthesis using silicon-containing compounds. Studies directed towards the synthesis of ebelactone A

Several approaches to the synthesis of ebelactone A 2 are described, culminating in the synthesis of the benzenesulfonate of 2-epi-ebelactone A 161. All the approaches were based on three fragments A, B and C, originally defined in general terms in, but eventually used as the aldehyde 72, the allenylsilane 3 and the aldehyde 139, respectively. They were joined, first B with C, and then B+C with A. In the main routes to fragments A and C, the relative stereochemistry was controlled by highly stereoselective enolate methylations 67-->67, 68-->69, and 135-->136, in each case anti to an adjacent silyl group, and by a highly stereoselective hydroboration of an allylsilane 137-->138, also anti to the silyl group. The hydroxyl groups destined to be on C-3 and C-11 were unmasked by silyl-to-hydroxy conversions 69-->70 and 138-->139 with retention of configuration. The stereochemistry created in the coupling of fragment B to C was controlled by the stereospecifically anti S(E)2' reaction between the enantiomerically enriched allenylsilane 3 and the aldehyde 139. The double bond geometry was controlled by syn stereospecific silylcupration 148-->151, and preserved by iododesilylation 151-->152 of the vinylsilane with retention of configuration, and Nozaki-Hiyama-Kishi coupling with the aldehyde 72 gave the whole carbon skeleton 153 of ebelactone A with the correct relative configuration, all of which had been controlled by organosilicon chemistry. In the steps to remove the superfluous allylic hydroxyl, an intermediate allyllithium species 156 abstracted the proton on C-2, and its reprotonation inverted the configuration at that atom. Other routes to the fragments A and C were also explored, both successful and unsuccessful, both silicon-based and conventional, and a number of unexpected side reactions were investigated.     

Kohlen

Ohne Zusammenfassung     

Atomgewichte

Ohne Zusammenfassung     

The admissible parameter space for exponential smoothing models

We discuss the admissible parameter space for some state space models, including the models that underly exponential smoothing methods. We find that the usual parameter restrictions (requiring all smoothing parameters to lie between 0 and 1) do not always lead to stable models. We also find that all seasonal exponential smoothing methods are unstable as the underlying state space models are neither reachable nor observable. This instability does not affect the forecasts, but does corrupt the state estimates. The problem can be overcome with a simple normalizing procedure. Finally we show that the admissible parameter space of a seasonal exponential smoothing model is much larger than that for a basic structural model, leading to better forecasts from the exponential smoothing model when there is a rapidly changing seasonal pattern.     

JORS Referees 2011

Journal of the Operational Research Society -     

Die Verwendung des Cupferrons in der quantitativen Analyse

Ohne Zusammenfassung Die Zitate zu diesem Referat folgen ausnahmsweise am Schlusse des ganzen Artikels S. 66.     

Structure-activity relationship (SAR) for the prediction of gas-phase ozonolysis rate coefficients: an extension towards heteroatomic unsaturated species

Heteroatomic unsaturated volatile organic compounds (HUVOCs) are common trace components of the atmosphere, yet their diverse chemical behaviour presents difficulties for predicting their oxidation kinetics using structure-activity relationships (SARs). An existing SAR is adapted to help meet this challenge, enabling the prediction of ozonolysis rates with unprecedented accuracy. The new SAR index, x(H), correlates strongly with available literature measurements of ozonolysis rate coefficients (R(2) = 0.87), a database representing 110 species. It was found that capturing the inductive effect rather than the steric effect is of primary importance in predicting the reactivity of these species, which is to be anticipated since HUVOCs can possess a variety of functional groups with a range of electron-withdrawing and donating tendencies. New experimental measurements of ozonolysis rate coefficients were conducted for 1-penten-3-ol, 3-methyl; ethene, 1,1-dimethoxy; E-2-pentenoic acid; E-1,2-dichloroethene; Z-1,2-dichloroethene; trichloroethene; tetrachloroethene; 1-butene, 3-chloro and 2-chloropropene, and were determined to be 5.15 × 10(-18), 4.82 × 10(-16), 3.07 × 10(-18), 8.05 × 10(-20), 4.88 × 10(-21), 6.04 × 10(-22), 1.56 × 10(-24), 2.26 × 10(-18) and 1.13 × 10(-19) cm(3) molecule(-1) s(-1), respectively. The index of the inductive effect, i(H), is compared with other indices of the electron-withdrawing capacity of a substitution, notably the Taft σ* constants and the rate of reaction of a given species with the hydroxyl radical, both of which are expected to be unaffected by steric factors. i(H) correlates strongly in both cases and suggests a universal response by olefinic species towards electrophilic addition.