Cyclische Diazastannylene. - XIX : Zur Reaktion eines Bis-(amino)germylens, - stannylens und -plumbylens mit Phosphortrichlorid und 2,3-Dimethyl-1,3- butadien

Das cyclische Bis(amino)germylen 1 reagiert mit PCl3 unter dreifacher Insertion in die P—Cl-Bindungen und Bildung von [Me2Si(NtBu)2Ge(Cl)]3P (4). 4 kristallisiert triklin in der Raumgruppe P1 mit den Gitterkonstanten: a = 1955,2(9), b = 1378,3(6), c = 1074,3(5) pm, alpha = 90,4(1), beta = 121,6(1), gamma = 97,9(1)° und Z = 2. Nach Röntgenstrukturanalyse besitzt 4 nahezu C3h-Symmetrie, wobei alle Germanium-, Chlor-, und Siliciumatome fast exakt in einer Ebene liegen, zu der die GeN2Si-Ringe senkrecht ausgerichtet sind. Von den schwereren Atomen stört lediglich das Phosphoratom durch eine leicht pyramidale Konfiguration (Ge—P—Ge = 115,0(2)°) die Spiegelsymmetrie. Wichtige mittlere Bindungslängen sind: Ge—P = 231,0(4), Ge—N = 182,4(7), Ge—Cl = 217,9(2) und Si—N = 173,6(7) pm. Die ungewöhnliche, nahezu trigonal planare Koordination des Phosphoratoms in 4 kann mit den besonderen sterischen Gegebenheiten erklärt werden. PCl3 oxidiert das Zinnatom im Bis(amino)stannylen 2 unter Bildung von Me2Si(NtBu)2SnCl2(5); als weiteres Produkt bildet sich ein amorpher Festkörper der analytischen Zusammensetzung (PCl)n. Im Unterschied zu 1 und 2 behält das Bleiatom bei der Umsetzung des Bis(amino)plumbylens 3 mit PCl3 seine Oxydationsstufe bei: in einer Sustitutionsreaktion entstehen Me2Si(NtBu)2PCl (6) und PbCl2. 2, 3-Dimethyl-1, 3-butadien reagiert nur mit dem Germylen 1 zu einem Cycloadditionsprodukt 7 (10%), in dem das Germaniuamtom als Spirozentrum einen SiN2Ge-Vierring mit einem GeC4-Fünfring verknüpft, und zu einem Polymer 8 (90%), dem die gleiche Bruttozusammensetzung zukommt. 2 und 3 dagegen setzen sich mit dem 1, 3-Dien nicht um

Cartel detection in procurement markets

Cartel detection is usually viewed as a key task of either competition authorities or compliance officials in firms with an elevated risk of cartelization. We argue that customers of hard core cartels can have both incentives and possibilities to detect such agreements on their own initiative through the use of market-specific data sets. We apply a unique data set of about 340,000 market transactions from 36 smaller and larger customers of German cement producers and show that a price screen would have allowed particularly larger customers to detect the upstream cement cartel before the competition authority. The results not only suggest that monitoring procurement markets through screening tools has the potential of substantial cost reductions - thereby improving the competitive position of the respective user firms - but also allow the conclusion that competition authorities should view customers of potentially cartelized industries as important allies in their endeavour to fight hard core cartels. --business economics,procurement,antitrust policy,cartels,detection,screening

Monadic second order finite satisfiability and unbounded tree-width

The finite satisfiability problem of monadic second order logic is decidable only on classes of structures of bounded tree-width by the classic result of Seese (1991). We prove the following problem is decidable: Input: (i) A monadic second order logic sentence $\alpha$, and (ii) a sentence $\beta$ in the two-variable fragment of first order logic extended with counting quantifiers. The vocabularies of $\alpha$ and $\beta$ may intersect. Output: Is there a finite structure which satisfies $\alpha\land\beta$ such that the restriction of the structure to the vocabulary of $\alpha$ has bounded tree-width? (The tree-width of the desired structure is not bounded.) As a consequence, we prove the decidability of the satisfiability problem by a finite structure of bounded tree-width of a logic extending monadic second order logic with linear cardinality constraints of the form $|X_{1}|+\cdots+|X_{r}|<|Y_{1}|+\cdots+|Y_{s}|$, where the $X_{i}$ and $Y_{j}$ are monadic second order variables. We prove the decidability of a similar extension of WS1S

The effect of broadband infrastructure on entrepreneurial activities: The case of Germany

This paper investigates whether the local infrastructure favours entrepreneurial activities. Besides the physical and knowledge infrastructure we take into account a county's broadband availability by building an index which accounts for county-related specificities. We find that broadband availability fosters entrepreneurial activities particularly in high-tech sectors for which efficient ways of knowledge transfer is crucial. --broadband provision,physical and knowledge infrastructure,local entrepreneurial activities

Assessing performance of conservation-based Best Management Practices: Coarse vs. fine-scale analysis

Background/Questions/Methods&#xd;&#xa;Animal agriculture in the Spring Creek watershed of central Pennsylvania contributes sediment to the stream and ultimately to the Chesapeake Bay. Best Management Practices (BMPs) such as stream bank buffers are intended to intercept sediment moving from heavy-use areas toward the stream. The placement of BMPs on a farm is generally based on untested assumptions about flow paths. Most often, a straight-line distance from the heavy-use area to the stream is assumed to be correct. Our objective was to compare the straight-line path to hydrologic flow paths calculated from fine-, medium- and coarse-grained Digital Elevation Models (DEMs; 1m, 10m, 30m) for 471 mapped heavy-use points within 100m of the stream. The 30m DEMs are the most widely available and require the least processing time. We anticipated that the flow path distance would be longer than the straight-line distance in all cases, that the finest resolution would lead to the most accurate measurement, but that the difference might not be great enough to justify the increased costs. Understanding the changes in path length and direction calculated using more complex methods and higher-resolution source data will enable us to make recommendations on methods to be used in developing conservation management plans.&#xd;&#xa;&#xd;&#xa;Results/Conclusions&#xd;&#xa;The medium-(10m DEM) and fine-resolution data (1m DEM) had the smallest differences between the hydrologic flow path and straight-line path: median differences in path length of 20 m for both the 1m and 10m DEMs, and 51m for the 30m DEM. Hydrologic flow paths were significantly longer than straight-line paths for all three scales; BMP placement based on straight-line distances may not be the most effective. Although the overall difference was significantly positive, calculations on the 30m DEMs sometimes produced straight-line paths that were longer than the hydrologic flow paths, apparently due to inaccuracies in the data. Where fine-scale DEMs are available, BMPs might be more effectively situated by considering the corresponding drainage pathways. The very different results produced at the three scales demonstrate that using the finest-grained elevation data may substantially improve placement of BMPs intended to mitigate for heavy animal use areas. The use of 30m DEMs for this purpose should be avoided. Fine-grained data such as 1m-resolution LiDAR-derived DEMs are available for Pennsylvania through PAMAP, and can be incorporated in the planning stages of BMP placement ultimately resulting in reducing agricultural sediment and nutrient loadings into local watersheds and the Chesapeake Bay

On the Structure and Complexity of Rational Sets of Regular Languages

In a recent thread of papers, we have introduced FQL, a precise specification language for test coverage, and developed the test case generation engine FShell for ANSI C. In essence, an FQL test specification amounts to a set of regular languages, each of which has to be matched by at least one test execution. To describe such sets of regular languages, the FQL semantics uses an automata-theoretic concept known as rational sets of regular languages (RSRLs). RSRLs are automata whose alphabet consists of regular expressions. Thus, the language accepted by the automaton is a set of regular expressions. In this paper, we study RSRLs from a theoretic point of view. More specifically, we analyze RSRL closure properties under common set theoretic operations, and the complexity of membership checking, i.e., whether a regular language is an element of a RSRL. For all questions we investigate both the general case and the case of finite sets of regular languages. Although a few properties are left as open problems, the paper provides a systematic semantic foundation for the test specification language FQL

Zur Element-Stickstoff-Doppelbindung in Kationen cyclischer Bis(amino)- phospha-, -arsa-, -stiba- und -bismutane

Bis(amino)silaphospha-, -arsa-, -stiba- und bismaetidine mit positiver Ladung und einem formal nur zweibindigen Element der 5. Hauptgruppe können aus den entsprechenden Bis(amino)elementchloriden durch Übertragung des Chloridions auf eine Lewis-Säure wie AlCl3, GaCl3 order InCl3 erhalten werden. Röntgenstrukturanalysen an den Verbindungen Me2Si(NtBu)2P+AlCl4- (2a), Me2Si(NtBu)2Sb+AlCl4- (2c) und Me2Si(NtBu)2Bi+AlCl4- (2d) zeigen, daß die Elektronenarmut am Element(V) durch zwei unterschiedliche Bindungsarten kompensiert wird: Im Falle des Phosphorderivates 2a geschieht der elektronische Ausgleich intramolekular durch die benachbarten Stickstoffatome (Mittelwert N-P+ = 163,3 pm), während in dem Antimon-(2c) und Bismut-Derivat (2d) die Chlorsubstituenten der AlCl4-Anionen intermolekular das Element(V) absättigen (Mittelwerte: ClSb = 305, ClBi = 309 pm). Die NSiN-Gruppierung, die in allen Molekülen als identischer Teil vorhanden ist, kann als Sonde für die Elektronenverteilung im Ring benutzt werden. Die Abstände und Winkel innerhalb dieser Gruppe variieren stark mit der Elektronenakzeptorfähigkeit des Elementes, an das sie gebunden ist. 2a kristallisiert orthorhombisch, Raumgruppe Pnma, Z = 8 (a = 3023,7(9), b = 1001,0(3), c = 1414,6(5) pm) und 2c und 2d sind isotyp, ebenfalls orthorhombisch, Raumgruppe Pbca mit Z = 8 (2c a = 2030,8(8), b = 1193,1(4), c = 1777,1(6) pm; 2d: a = 2025,9(8), b = 1198,0(4), c = 1761,3(6) pm)