Dispersive estimates and NLS on product manifolds

We prove a general dispersive estimate for a Schroedinger type equation on a product manifold, under the assumption that the equation restricted to each factor satisfies suitable dispersive estimates. Among the applications are the two-particle Schroedinger equations on Euclidean spaces, and the nonlinear Schroedinger equation on the product of two real hyperbolic spaces

A small intruder. A Medieval marble winged lion from Ravello

An image of a 12th century marble winged lion was provocatively included among the slides accompanying a lecture by the author at a recent conference at the American Academy in Rome to illustrate Umberto Scerrato’s work on Islamic archaeology and art history in Italy. The lion, in fact, was never published by Scerrato, but it and a winged bull, both once featuring as ornaments on the “Moresque Fountain” in Ravello (originally from a medieval building most likely from Ravello itself), are the subject of this brief article. They are of undeniable Islamic taste

The iconographic transformation of the “tail of the dragon of the eclipse” into the “hunting cheetah”

Medieval Islamic iconography includes many depictions in which the tail of Sagittarius takes the form of the “dragon of the eclipse”. The current paper examines the gradual transformation of this imagery into that of a quadruped, eventually detached from the body of Sagittarius, and placed on the centaur’s back in the characteristic position of the seated “hunting cheetah”, as can also be seen in images of the chase assisted by this feline

A brief note on the Yemenite chahar taq mausoleums. The case of Baraqish

The chahartaq, a type of building frequently used as a mausoleum in Iran during the Islamic era, has an undeniable Iranian pre-Islamic origin, but its architectural form, together with its function as a mausoleum, crossed the Iranian border and was attested in Yemen too. The 17th-century chahar taq mausoleum at Baraqish seem to be a specific choice, probably of a Shi'i matrix

Enabling knowledge processes in innovative environments

The concept of organisational knowledge as a valuable strategic asset has become quite popular recently. Increased competition, globalisation and the emergence of new organisational models built on process-based organisational structures require organisations to create, capture, share and apply organisational knowledge and expertise efficiently and effectively.This thesis looks at how knowledge processes can be supported in innovative and knowledge-intensive environments. Particular emphasis is placed on the role of ICT (Information and Communication Technologies) in relation with other possible decisions stimulating knowledge processes such as organisational mechanisms and managerial systems

Magneto-Electric Effects on Sr Z-type Hexaferrite at Room Temperature

In this paper, magnetoelectric effects of Sr Z-type hexaferrite, Sr3Fe24Co2O41, at room temperature is measured. The change in remanence magnetization was measured by applying a DC voltage or electric field across a slab of hexaferrite. Changes of ~ 18% in remanence was observed in an electric field of 10,000V/cm implying a similar change in the microwave permeability at frequencies below 3GHz. Also, a change in dielectric constant at 1 GHz of ~16% in a magnetic field of only 320 Oe was measured. In these types of measurements high resistivity is critical in order to reduce current flow in the hexaferrite. The resistivity of the hexaferrite was raised to 4.28x10^8 ohm-cm by annealing under oxygen pressure. The measurements indicate that indeed electric polarization and magnetization changes were induced by the application of magnetic and electric fields, respectively. The implications for microwave applications appear to be very promising at room temperature.Comment: 8 pages, 3 figures, MMM conference and Journal of applied Physic

Converse Magnetoelectric Experiments on a Room Temperature Spirally Ordered Hexaferrite

Experiments have been performed to measure magnetoelectric properties of room temperature spirally ordered Sr3Co2Fe24O41 hexaferrite slabs. The measured properties include the magnetic permeability, the magnetization and the strain all as a function of the electric field E and the magnetic intensity H. The material hexaferrite Sr3Co2Fe24O41 exhibits broken symmetries for both time reversal and parity. The product of the two symmetries remains unbroken. This is the central feature of these magnetoelectric materials. A simple physical model is proposed to explain the magnetoelectric effect in these materials.Comment: 6 pages, 5 figure