Application of enzymes in anaerobic digestion.

Owing to the very low economic value of brewer's spent grains, its utilisation for biogas production is very promising. The hydrolysis of ligno-cellulose is the rate limiting step in anaerobic digestion. Enzymatic pre-treatment promotes the hydrolysis of ligno-cellulose, breaking it down to lower molecular weight substances which are ready to be utilised by the bacteria. A cheap raw multi-enzyme produced by a solid state fermentation (SSF) process is a good substitute for expensive conventional enzyme. The SSF enzyme application to spent grain has been investigated by carrying out enzymatic solubility tests, hydrolytic experiments and two-step anaerobic fermentation of spent grain. Gas chromatograph analysis was conducted to quantify fatty acids concentrations, while CH(4), CO(2), O(2), H(2) and H(2)S were measured to determine biogas quality by means of a gas analyser. DS, oDS, pH were also measured to analyse the anaerobic digestion. The result shows that enzyme application promotes the hydrolysis of ligno-cellulose, indicated by higher enzymatic solubility and fatty acid concentration in a hydrolytic bioreactor. Moreover, biogas production is also increased. The quality of the gases produced is also enhanced. Since the anaerobic digestion can be operated in a stable performance, it can also be concluded that SSF enzyme is compatible with anaerobic digestion.     

A proof of wavelength conversion not improving the lagrangian bound of the static RWA problem

The fact that wavelength conversion hardly improves the performance of static routing and wavelength assignment (RWA) in Wavelength Division Multiplexing (WDM) networks has been observed in many previous studies. However, other than simulation results, until now there was no formal proof of such fact. In this paper, we formally prove that wavelength conversion does not improve the Lagrangian bound of the static RWA problem.     

Protocol synthesis and re-synthesis with optimal allocation of resources based on extended Petri nets

Protocol synthesis is used to derive a protocol specification, that is, the specification of a set of application components running in a distributed system of networked computers, from a specification of services (called the service specification) to be provided by the distributed application to its users. Protocol synthesis reduces design costs and errors by specifying the message exchanges between the application components, as defined by the protocol specification. In general, maintaining such a distributed application involves applying frequent minor modifications to the service specification due to changes in the user requirements. Deriving the protocol specification after each modification using the existing synthesis methods is considered expensive and time consuming. Moreover, we cannot identify what changes we should make to the protocol specification in correspondence to the changes in the service specification. In this paper, we present a new synthesis method to re-synthesize only those parts of the protocol specification that must be modified in order to satisfy the changes in the service specification. The method consists of a set of simple rules that are applied to the protocol specification written in an extended Petri net model. An application example is given along with some experimental results. Received: July 2001 / Accepted: July 2002 RID="*" ID="*" Supported by International Communications Foundation (ICF), Japan RID="**" ID="**" Supported by Communications and Information Technology Ontario (CITO) and Natural Sciences and Engineering Research Council (NSERC), Canada RID="*" ID="*" Supported by International Communications Foundation (ICF), Japan     

Influence of Heavy Atom Effect on the Photophysics of Coinage Metal Carbene-Metal-Amide Emitters

The effect of the heavy metal atom on the photophysics of carbene-metal-amide (CMA) photoemitters is explored, where the metal bridge is either Au, Ag, or Cu. Spectroscopic investigations reveal the coupling mechanism responsible for communication between the singlet and triplet manifolds. The photophysical properties do not reflect expected trends based upon the heavy atom effect, as both direct coupling between charge-transfer states and spin-vibronic coupling via a ligand-centered triplet state are present. Direct coupling is weakest for CMA(Ag), increasing the importance of the spin-vibronic pathway and rendering its properties more sensitive to inter-state energy gaps than for the Au and Cu-bridged analogues. The measured activation energy correlates with the expected exchange energy of the charge-transfer state, which is also closely related to the length of the bonds joining the carbene and amide ligands, and decreases in the order CMA(Cu) > CMA(Au) > CMA(Ag). These findings reveal that reducing interference between charge-transfer and ligand-centers excited, and minimizing exchange energy, are required for developing efficient luminescent CMA complexes.     

Automatic analysis and test case derivation for a restricted classof LOTOS expressions with data parameters

We propose an automatic analysis and test case derivation method for LOTOS expressions with data values. We introduce the class of P-LOTOS expressions where the data types are restricted to Presburger arithmetic. That is, only the integer and Boolean types are used, and the operators of the integers are restricted to addition, subtraction, and comparison. For this class, we give an algorithm for deriving a set of test cases (a test suite). The algorithm is carried out by using a decision procedure for integer linear programming problems. We also give solutions for the deadlock detection problem, the detection of nonexecutable branches, and the detection of nondeterministic behaviors. We have implemented a tool for the analysis and test selection based on our techniques. The derivation of a test suite for a simplified Session protocol is described as an example     

Deriving protocol converters for communications gateways

Gateways are introduced for interworking between several, possibly heterogeneous, distributed computer systems. A gateway has to provide for the necessary adaptation between the communication protocols used in the interconnected networks. The adaptation problem is best handled by considering the communication services of the interconnected systems. Once the problem is solved at this level, the remaining problem of conversion between the incompatible communication protocols used in the different systems can be solved automatically, as demonstrated for the case of a simple example of data transmission service from a sender to a receiver process