A theoretical study of saturated sp nitrogen rings

Ab initio calculations on molecular structures composed of hexagonal rings of sp³-hybridated nitrogen atoms (the external nitrogen atoms being saturated with hydrogens) are presented. All the studied systems are local minima on the potential energy surface, and dissociate producing nitrogen dimer and ammonia in different proportions. A periodic Hartree–Fock study of the infinite layer is also presented, and it is shown that the molecular structural parameters quickly converge towards the infinite-system values. Accordingly to the computed dissociation energies, these systems have a very high energy content.     

On ring class eigenspaces of Mordell-Weil groups of elliptic curves over global function fields

If E is a non-isotrivial elliptic curve over a global function field F of odd characteristic we show that certain Mordell-Weil groups of E have 1-dimensional χ-eigenspace (with χ a complex ring class character) provided that the projection onto this eigenspace of a suitable Drinfeld-Heegner point is non-zero. This represents the analogue in the function field setting of a theorem for elliptic curves over Q due to Bertolini and Darmon, and at the same time is a generalization of the main result proved by Brown in his monograph on Heegner modules. As in the number field case, our proof employs Kolyvagin-type arguments, and the cohomological machinery is started up by the control on the Galois structure of the torsion of E provided by classical results of Igusa in positive characteristic.     

Strip-Loaded Sol-Gel Waveguides: Design and Fabrication

Sol-gel is one of the most attractive techniques for production of silica-on-silicon integrated optical devices. In fact, it combines low cost with flexibility and ease of doping; thus, nonlinear and active compounds can be effectively included in the silica matrix. Here, the feasibility of applying the sol-gel technique to the realization of an erbium-doped optical amplifier is reported on, operating in the third telecommunication window. In particular, the development of an optimum strategy for the design and fabrication of a guiding structure in the strip-loaded configuration is described. Design optimization results, as well as fabrication results and measured characteristics, are described and discussed.     

Cut problems in graphs with a budget constraint

We study budgeted variants of classical cut problems: the Multiway Cut problem, the Multicut problem, and the k-Cut problem, and provide approximation algorithms for these problems. Specifically, for the budgeted multiway cut and the k-cut problems we provide constant factor approximation algorithms. We show that the budgeted multicut problem is at least as hard to approximate as the sparsest cut problem, and we provide a bi-criteria approximation algorithm for it.     

灵活的工业以太网解决方案

本文介绍利用FPGA在一块印制板上实现多标准工业以太网功能，包括FPGA的优点以及建立通用且易于维护的解决方案的开发流程，工具和技术。     

Enantioselective reactions catalyzed by synthetic enzymes. A model for chemical evolution

Polyleucines of various lengths act as enantioselective catalysts in the aldol condensation between cyclohexanone and various aromatic aldehydes. Polyleucine and other polyamino acids behave as synthetic enzymes in the epoxidation of chalcone and other electron-deficient alkenes. Both reactions are of considerable prebiotic significance.     

Pyrene‐Excimers‐Based Antenna Systems

A series of dendrimeric compounds bearing pyrene units were synthesized to afford light‐harvesting antennae based on the formation of intramolecular excimers. The synthetic plan profited from the efficiency of the Huisgen reaction, the 1,3‐dipolar cycloaddition of azides and terminal alkynes, which allowed ready assembly of the different building blocks. The three molecular antennae obtained, of increasing generation, revealed efficient energy transfer both in solution and in the solid state.     

Optimal control of stochastic differential equations with dynamical boundary conditions

In this paper we investigate the optimal control problem for a class of stochastic Cauchy evolution problems with nonstandard boundary dynamic and control. The model is composed by an infinite dimensional dynamical system coupled with a finite dimensional dynamics, which describes the boundary conditions of the internal system. In other terms, we are concerned with nonstandard boundary conditions, as the value at the boundary is governed by a different stochastic differential equation.     

Cost allocation protocols for supply contract design in network situations

The class of Construct and Charge (CC-) rules for minimum cost spanning tree (mcst) situations is considered. CC-rules are defined starting from the notion of charge systems, which specify particular allocation protocols rooted on the Kruskal algorithm for computing an mcst. These protocols can be easily implemented in practical network situations (for instance, in supply transportation networks), are flexible to changes in the network situation and meet the requirement of continuous monitoring by the agents involved. Special charge systems, that we call conservative, lead to a subclass of CC-rules that coincides with the class of obligation rules for mcst situations. The authors thank two anonymous referees both for detailed remarks and for interesting general comments on a previous version of the paper. Stef Tijs and Rodica Branzei are indebted to Daniel Granot for useful discussions on the topics treated in this paper and his hospitality during our research visit at British Columbia University at Vancouver in July–August 2003.