Let A be a unital C -algebra with involution represented in a Hilbert space H, G the group of invertible elements of A, U the unitary group of A, G the set of invertible selfadjoint elements of A, Q = f" 2 G : " = 1g the space of re ections and P = Q \ U . For any positive a 2 G consider the a-unitary group Ua = fg 2 G : a g a = g g, i.e., the elements which are unitary with respect to the scal...

The paper addresses symmetry results for positive solutions of semilinear elliptic di erential equations on a class of non-convex symmetrical domains. An example in two dimensions is the star of David. The moving plane method just shows that solutions coincide on three alternate corners of the star. We will show that the solution is symmetric with respect to remaining re ections, that is, the s...

Many compressible ow and aeroacoustic computations rely on accurate nonre ecting or radiation boundary conditions. When the equations and boundary conditions are discretized using a nitedi erence scheme, the dispersive nature of the discretized equations can lead to spurious numerical reections not seen in the continuous boundary value problem. These re ections can lead to poor convergence to a...

The smallest spherical viruses have a diameter of at least 200 AÊ [e.g. satellite tobacco necrosis virus (Liljas et al., 1982) and satellite tobacco mosaic virus (Larson et al., 1993)]. Many spherical viruses, such as southern bean mosaic virus (Abad-Zapatero et al., 1980) or rhinoviruses (Rossmann et al., 1985), have diameters of 300 AÊ , and many other viruses have much larger diameters [e.g....

In this paper we are concerned with signal processing of acoustic signals resulting from active transmissions by high frequency sonar systems. These signals consist of structured interference related to propagation e ects in the media, re ections from targets, and measurement noise. The methods herein model these signals as replicas of the transmitted signal, scaled in amplitude and time, and d...

A new computational approach to the Takagi±Taupin equations for the analysis of X-ray optics is presented and applied to heat-loaded synchrotron monochromators. The new numerical approach is based on the assumption that the incoming wave is completely incoherent (incoherent point source). The simulation avoids any kind of simpli®cation: it takes into account the thermal deformation of the cryst...

APA is a computer program, written in C, designed to determine the three-dimensional structure of proteins using distance geometry. We present the sampling and convergence properties of APA, as tested on bovine pancreatic trypsin inhibitor (BPTI). The results con®rm the program's earlier success with poly-L-alanine, albeit with some complications. The correct overall orientation of the BPTI con...

(E;L) denotes an aÆne plane, (E;L; ) an ordered plane, and denotes the congruence relation on E E. If we assume (E;L; ) as an hyperbolic plane, there exists the corresponding theorem for hyperbolic planes (cf. [3]). For both proofs we consider rst the group of motions, in particular the line re ections. For the de nition of a motion and a line re ection we need only a congruence relation (cf. [...

The emerging function of verb in ections in German language acquisition is modeled with a connectionist network. A network that is initially presented only with a semantic representation of sentences uses the in ectional verb ending -t to mark those sentences that are low in transitivity, whereas all other verb endings occur randomly. This behavior matches an early stage in German language acqu...

A method is presented that allows the accurate measurement of the tooth pair stiVness of a pair of spur gears. The method reveals the stiVness behaviour throughout the full length of the normal path of contact and also into the extended contact region when tooth corner contact occurs. The method makes use of the properties of transmission error plots for mean and alternating components over a r...