A construction of infinite sets of intertwines for pairs of matroids

An intertwine of a pair of matroids is a matroid such that it, but none of its proper minors, has minors that are isomorphic to each matroid in the pair. For pairs for which neither matroid can be obtained, up to isomorphism, from the other by taking free extensions, free coextensions, and minors, we construct a family of rank-k intertwines for each sufficiently large integer k. We also treat some properties of these intertwines.Comment: 11 page

Transversal Lattices

A flat of a matroid is cyclic if it is a union of circuits; such flats form a lattice under inclusion and, up to isomorphism, all lattices can be obtained this way. A lattice is a Tr-lattice if all matroids whose lattices of cyclic flats are isomorphic to it are transversal. We investigate some sufficient conditions for a lattice to be a Tr-lattice; a corollary is that distributive lattices of dimension at most two are Tr-lattices. We give a necessary condition: each element in a Tr-lattice has at most two covers. We also give constructions that produce new Tr-lattices from known Tr-lattices.Comment: 12 pages; 5 figure

An integrated circuit switch

Multi-chip integrated circuit switch consists of a GaAs photon-emitting diode in close proximity with S1 phototransistor. A high current gain is obtained when the transistor has a high forward common-emitter current gain

Lattice path matroids: the excluded minors

A lattice path matroid is a transversal matroid for which some collection of incomparable intervals in some linear order on the ground set is a presentation. We characterize the minor-closed class of lattice path matroids by its excluded minors.Comment: 13 pages, 2 figure

15 years of pension reform in Germany: old successes and new threats

The paper surveys the state of German pension system after a sequence of reforms aimed at achieving long-term sustainability. We argue that the latest reforms have moved pension provision in Germany in principle from a defined benefit to a defined contribution scheme, and that this move has stabilized pension finances to a large extent. We furthermore argue that the real economy consequences of global financial create threats to the core success factors of the reforms - cutting pension levels and raising mandatory pension age. Finally the paper discusses further possible reform measures, including the option to install a fourth pillar providing income in retirement through working after pension age. --Pension Financing,Financial Crisis,Fiscal Sustainability Survey,Germany

Dynamic actions on bridge slabs due to heavy vehicle impact on roadside barriers

The use of roadside safety barriers in Italy has changed in recent years: the number of installed devices has increased, and so have their stiffness and resistance. These changes were necessary because early barrier design was inadequate to contain and redirect heavy vehicles. The change in barrier design led to an increase in stiffness and resistance; consequently, the action transferred to the structure by the device increased. The need for resistance on the bridge slabs can be too high because the peculiar action of the roadside barriers was not adequately taken into account in the oldest bridge design codes. In addition, characterizing the actions transferred to the bridge slab is difficult because of the dynamic nature of vehicle impacts on roadside barriers. Given the impossibility of performing a full-scale laboratory test for every bridge deck, the use of computational mechanics applied to dynamic impact/interaction problems is one of the best ways to establish these actions in the project phase. Research was conducted into the use of a three-dimensional finite element model of the bridge slab-barrier-vehicle system to perform a numerical simulation of the impact, according to the procedure used for the roadside barrier homologation crash test, described in the European Standard EN 1317

Participation Behavior of East German Women after German Unification

The paper studies the determinants of labor force participation by East German women after unification. To isolate the role of preferences on labor force participation from individual characteristics, we develop a panel data model that simultaneously explains participation, employment, and wages. The model, estimated for East and West Germany on the basis of the German Socio-Economic Panel, indicates that distinct preferences could explain the regional difference in participation rates at unification. Afterward East German women became less willing to participate, but the negative participation trend was offset on the aggregate level by changes in characteristics and wages promoting participation.http://deepblue.lib.umich.edu/bitstream/2027.42/39862/3/wp477.pd

Photon-coupled isolation switch Quarterly report, 1 Jan. - 31 Mar. 1967

Design, development, and testing of new integrated circuit switch devic