Model reactions on roast aroma formation

Summary From model roastings of mixtures containing serine, threonine and sucrose about 350 volatile compounds were separated and identified by GC/MS. Among them there were more than 100 monocyclic furans, 13 furanones and 8 bicyclic furans, the mass spectra and retention indices of which are recorded. The most important mass spectrometric fragmentation pathways are described. Spectra obtained from roasting coffee under identical conditions are compared with the spectra from model roastings.

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Modell-Reaktionen zur Röstaroma-BildungII. Die massenspektrometrische Identifizierung von Furanen und Furanonen aus der Reaktion von Serin und Threonin mit Saccharose unter den Bedingungen der Kaffeeröstung

Zusammenfassung Aus Modellröstungen von Gemischen aus Serin, Threonin und Saccharose unter den Bedingungen der Kaffeeröstung wurden etwa 350 flüchtige Verbindungen mittels GC/MS getrennt und identifiziert. Unter ihnen befanden sich über 100 monocyclische Furane und 13 Furanone sowie 8 bicyclische Furane, deren Massenspektren und Retentions-indices angegeben werden. Die wichtigsten massenspektrometrischen Fragmentierungswege werden beschrieben. -Die aus einer gleich behandelten Röstung von Rohkaffee erhaltenen Spektren werden mit denen der Modellröstungen verglichen.

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Dissertation Gloria Bochmann, TU Berlin 1984     

Synthesis,Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl Ligands

The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH₂CHCHSiMe₃) ( 1 ) reacts with YCl₃ in tetrahydrofuran to give the tris-allyl complex Y(CH₂CHCHSiMe₃)₃ ( 2 ), while K(CH₂CHCHSiMe₂^tBu) ( 3 ) affords Y(CH₂CHCHSiMe₂^tBu)₃(THF)_1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(^tBu)(CH)₃SiMe₂^tBu}₂{η₂-NHC(^tBu)CH=CHCH₂SiMe₂^tBu)CH(CHCHSiMe₂^tBu)C^tBuNH}(THF)·(CH₃CH(Me)(CH₂)₂CH₃) ( 5 ), which was crystallographically characterized. The reaction of ScCl₃(THF)₃ with two equivalents of Li{1,3-C₃H₃(SiMe₃)₂} in tetrahydrofuran gives the bis-allyl complex {1,3-C₃H₃(SiMe₃)₂}₂Sc(μ-Cl)₂Li(THF)₂ ( 6 ), while the analogous reaction of K{1,3-C₃H₃(SiMe₃)₂} ( 7 ) with either LaCl₃ or YCl₃ in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C₃H₃(SiMe₃)₂}₂(THF)_x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI₂{1,3-C₃H₃(SiMe₃)₂}(THF)_1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d₆ show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene.     

FSM-based incremental conformance testing methods

The development of appropriate test cases is an important issue for conformance testing of protocol implementations and other reactive software systems. A number of methods are known for the development of a test suite based on a specification given in the form of a finite state machine. In practice, the system requirements evolve throughout the lifetime of the system and the specifications are modified incrementally. We adapt four well-known test derivation methods, namely, the HIS, W, Wp, and UIOv methods, for generating tests that would test only the modified parts of an evolving specification. Some application examples and experimental results are provided. These results show significant gains when using incremental testing in comparison with complete testing, especially when the modified part represents less than 20 percent of the whole specification.     

Environmental Control of Triplet Emission in Donor–Bridge–Acceptor Organometallics

Carbene‐metal‐amides (CMAs) are a promising family of donor–bridge–acceptor molecular charge‐transfer (CT) emitters for organic light‐emitting diodes. A universal approach is demonstrated to tune the energy of their CT emission. A blueshift of up to 210 meV is achievable in solid state via dilution in a polar host matrix. The origin of this shift has two components: constraint of thermally‐activated triplet diffusion, and electrostatic interactions between guest and polar host. This allows the emission of mid‐green CMA archetypes to be tuned to sky blue without chemical modifications. Monte‐Carlo simulations based on a Marcus‐type transfer integral successfully reproduce the concentration‐ and temperature‐dependent triplet diffusion process, revealing a substantial shift in the ensemble density of states in polar hosts. In gold‐bridged CMAs, this shift does not lead to a significant change in luminescence lifetime, thermal activation energy, reorganization energy, or intersystem crossing rate. These discoveries offer new insight into coupling between the singlet and triplet manifolds in CMA materials, revealing a dominant interaction between states of CT character. The same approach is employed using materials which have been chemically modified to alter the energy of their CT state directly, shifting the emission of sky‐blue chromophores into the practical blue range.     

Aspects of transition metal mediated polymerizations

Catalysts based on metallocene complexes of early transition metals herald a new era in Ziegler—Natta olefin polymerization. The developments are driven primarily by the flexibility and high activity of metallocene catalysts, which allow excellent control of polymer properties and have led to a remarkably wide spectrum of polymers and copolymers. In-depth mechanistic understanding is proving crucial for catalyst design and has opened up the use of metallocenes in non-Ziegler chemistry, notably as initiators for carbocations polymerizations. Recently developed late transition metal complexes have substantially added to the range of olefin (co)polymers that are now accessible, including copolymerizations with carbon monoxide and polar monomers.     

Deriving protocol specifications from service specifications written in LOTOS

Summary.  A complete communication system is broken down into a number of protocol layers each of which provides services to the layer above it and uses services provided by its underlying layer. A service specification defines a particular ordering of the operations that a given layer provides to the layer above it. The active elements in each layer are called entities and they use a protocol in order to implement their service definition. On the basis of this relation between the service and protocol concepts we have developed algorithms for deriving protocol entity specifications from a formal service specification. The derived protocol entities ensure the correct ordering of the service primitives by exchanging synchronization messages through an underlying communication medium. This paper presents an extended version of our earlier derivation algorithms. This version of the algorithm can handle all operators and unrestricted process invocation and recursion as defined by basis LOTOS. The correctness of this derivation algorithm is formally proved. Received: January 1992 / Accepted: February 1996     

A formal method for synthesizing optimized protocol converters and its application to mobile data networks

As mobile information networks are expanding rapidly, we expect to integrate voice, paging, electronic mail and other wireless information services. Interworking units that perform protocol conversion at the boundaries of different networks will play an important role. In this paper, we propose an efficient algorithm for constructing optimized protocol converters to achieve interoperability between heterogeneous data networks. This algorithm first derives constraints from two given protocols, and apply the constraints to channel specifications, thus removing message sequences that do not contribute to system progress. Then, an optimized converter is generated from a given service specification, the two protocol specifications and the modified channel specifications. A reduction relation is used to compare the service specification and the constructed internetworking system in order to deal with the problem of nondeterministic services. Compared with related works, our method has two advantages: (1) it generates an optimized converter; (2) it can be applied to the case that the service specification is nondeterministic. The application of the method to mobile networks is given by an example. This revised version was published online in June 2006 with corrections to the Cover Date.     

An approach to testing specifications

An approach to testing the consistency of specifications is explored, which is applicable to the design validation of communication protocols and other cases of step-wise refinement. In this approach, a testing module compares a trace of interactions obtained from an execution of the refined specification (e.g., the protocol specification) with the reference specification (e.g., the communication service specification). Nondeterminism in reference specifications presents certain problems. Using an extended finite state transition model for the specifications, a strategy for limiting the amount of nondeterminacy is presented. An automated method for constructing a testing module for a given reference specification is discussed. Experience with the application of this testing approach to the design of a transport protocol and a distributed mutual exclusion algorithm is described.     

Test selection based on communicating nondeterministic finite-statemachines using a generalized Wp-method

Presents a method of generating test sequences for concurrent programs and communication protocols that are modeled as communicating nondeterministic finite-state machines (CNFSMs). A conformance relation, called trace-equivalence, is defined within this model, serving as a guide to test generation. A test generation method for a single nondeterministic finite-state machine (NFSM) is developed, which is an improved and generalized version of the Wp-method that generates test sequences only for deterministic finite-state machines. It is applicable to both nondeterministic and deterministic finite-state machines. When applied to deterministic finite-state machines, it yields usually smaller test suites with full fault coverage than the existing methods that also provide full fault coverage, provided that the number of states in implementation NFSMs are bounded by a known integer. For a system of CNFSMs, the test sequences are generated in the following manner: a system of CNFSMs is first reduced into a single NFSM by reachability analysis; then the test sequences are generated from the resulting NFSM using the generalized Wp-method