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Extrinsic uncertainty is effective at a competitive equilibrium. This is generic if spot markets are inoperative: the only objects of exchange are assets for the contingent delivery of commodities; and the asset market is incomplete. The structure of payoffs of assets may allow for non-trivial allocations invariant with respect to the extrinsic uncertainty, and the economy with a complete asset market may well have a globally unique competitive eqUilibrium. Inoperative spot markets have a natural interpretation in economies with multiple periods; assets cannot be retraded.

In this note the decision problem of a strategic firm in a general equilibrium setting is analyzed. It is shown that under many respects the problems arising are similar to those encountered in an incomplete markets set-up, and a well known criterion used under incompleteness of markets can be applied to the imperfectly competitive framework. It is also shown under what conditions profit maximization leads to the same production decision as utility maximization.

In an incomplete asset market, firms assign values to investment plans by projecting their payoffs on the span of the payoffs of marketed assets; equivalently, firms employ the Capital Asset Pricing Model. This is a criterion that does not require firms to possess information, such as the marginal valuation of revenue across date -- events by shareholders, which is not observable; rather, it is based on information revealed by the prices and payoffs of marketed assets. Under standard assumptions, competitive equilibria exist. But, competitive equilibrium allocations need not satisfy a condition of constrained Pareto optimality that recognizes the incompleteness of the asset market; and, even in the absence of nominal assets, competitive equilibrium allocations are generically indeterminate -- they are determinate if firm consider the commodity payoffs of shares.

Figure 1: A nuclear magnetic resonance revealed a 4 × 3-cm-sized multiloculated cyst. The lesion lay anteromedially to the trapezius muscle; inferiorly, it was in contact with the distal part of the left clavicle and scalene muscles that appeared lightly medially dislocated. The left external jugular vein was placed medially to the cyst, while the left subclavian artery and vein were caudally located at a distance of 10 mm. The cyst was hyperintense on T1-weighted black-blood images not suppressed in fat suppression sequences (transversal A and frontal B view, respectively). Thus, a recurrent hydatid disease was hypothesized. No albendazole therapy was administered after the previous operation.

The behaviour of corporative firms in general equilibrium models with incomplete markets is difficult to assess, because shareholders have different evaluations of profit streams in the various states of the world. This paper examines the possibility of an approximation in which firms only look at traded assets and at their respective prices. The supply correspondence resulting from such a valuation procedure is characterized; it is also demonstrated that this is equivalent to firms using martingale pricing theory in the presence of incompleteness of markets.

It is a well known result that through national lump sum taxes and transfers everybody can gain from international trade. This is always the case when domestic lump sum tax and transfers are implemented before trade. This brief note points out that if domestic transfers are possible only after trade it may well happen that some agents' losses can no longer be compensated. This simple reasoning helps make the case for supra-national political and economical institutions.

The performance of an electromagnetic shower detector comprised only of active elements was evaluated using a tagged electron beam at various momenta from 30–100 GeV/ c . Cerenkov light from three sections of lead glass blocks provides measurements of total shower energy with a resolution of σ = (0.114±0.008) E GeV /c 2 . A plastic scintillator hodoscope situated behind the first two lead glass layers samples the transverse development of the shower, allowing position determination of the incident electron with σ = 1.4 mm resolution.

Recent attempts to operate counters for calorimetric use inside high intensity magnetic fields have resulted in interesting developments both in the construction of the counters and in the design of the vacuum photosensitive devices. In particular, a new one-stage photomultiplier has been developed. The present status of the development of gas photodiodes will finally be illustrated.

We have made a transparent electromagnetic shower absorber, sandwiching together lead glass and scintillator sheets. The energy resolution we achieve is as good as expected for a sampling calorimeter with the passive layer thickness adopted, and the signal produced is about ten times larger than the signal from the Cherenkov radiation in the lead glass. We show that this makes possible the use of vacuum photodiodes with a noise level of the order of 40 MeV, and such a counter could therefore be operated in a magnetic field. Finally, we propose and discuss possible schemes for the production of large systems, arguing that the cost per counter would be significantly lower than an equivalent lead glass counter.

The problem of handling large numbers of analog signals in fast elementary particle detectors has been approached using parallel input to an optical linear array, through a LED matrix. This method results in a much smaller cost per channel than conventional instrumentation. A prototype system is described and the results of some tests are reported. The availability of charge coupled devices (CCD) promises further interesting developments for this technique that will also be discussed.

As a part of a large experimental program aiming to produce high quality calibration data for the Forward ElectroMagnetic Calorimeter (FEMC) of the DELPHI detector at LEP, special runs were devoted to the study of the transverse profile of electromagnetic showers in lead glass. Results of this study are presented.

Ius migrandi e confini statali. Migrazioni e diritto: quali regole? Il rapporto fra Stato e straniero: la soluzione della frammentazione degli status. Gli effetti del modello stato-centrico e della frammentazione degli status. Strategie per un'effettiva tutela dei diritti nel modello stato-centrico: l'accoglienza dei non cittadini.

Atti del seminario svoltosi a Copanello (CZ) il 31 maggio-1 giugno 2002; International audience