In 1985 a powerful and practical public-key scheme was produced by ElGamal; his work was applied using large prime integers. El-Kassar et al. and El-Kassar and Haraty modified the ElGamal public-key encryption scheme from the domain of natural integers, Z, to two principal ideal domains, namely the domain of Gaussian integers, Z[ i ], and the domain of the rings of polynomials over finite field...

Thanks to INTEGRAL’s long exposures of the Galactic Plane, the two brightest Soft Gamma-Ray Repeaters, SGR 1806-20 and SGR 1900+14, have been monitored and studied in detail for the first time at hard-X/softgamma rays. SGR 1806-20, lying close to the Galactic Centre, and being very active in the past two years, has provided a wealth of new INTEGRAL results, which we will summarise here: more th...

The recent discoveries of giant planets around nearby stars has galvanized the planetary science community, astronomers, and the public at large. Since direct detection is now feasible, and is suggested by the recent acquisition of Gl229 B, it is crucial for the future of extrasolar planet searches that the fluxes, evolution, and physical structure of objects from Saturn's mass to 15 Juipter ma...

Using a new technique we have determined a value for the constant of proportionality between submillimetre (submm) emission and dust mass, the dust mass absorption coefficient (κd) at 850μm. Our method has an advantage over previous methods in that we avoid assumptions about the properties of dust in the interstellar medium. Our only assumption is that the fraction of metals incorporated in the...

We present a discovery of a giant stellar halo in NGC 6822, a dwarf irregular galaxy in the Local Group. This halo is mostly made of old red giants, showing striking features: 1) it is several times larger than the main body of the galaxy seen in the optical images, and 2) it is elongated in the direction almost perpendicular to the HI disk of NGC 6822. The structure of this stellar halo looks ...

An expression for the radiation force from a cw-laser on a fluidfluid interface is derived that is able to model the giant deformations observed in modern experiments when the fluid system is close to the critical point implying that the surface tension is very small. The core of our argument is that the system is modelled as a step-index optical fiber. Then, observing that the dominant HE11 mo...

Acanthamoeba is a free-living amoeba causing a potentially blinding infection of the cornea. Contact lens wearers are most at risk and account for some 95% of cases. Hydrogen peroxide is used for contact lens disinfection due to its broad antimicrobial activity. Lenses must be neutralized before use to avoid pronounced stinging and possible corneal damage. Neutralization is achieved by adding a...

In this chapter, we will first address general issues of the art and craft of modeling contents, concepts, methodology. Then, we will focus on modeling in contact mechanics, which will give the opportunity to discuss these issues in connection with non-smooth problems. It will be shown that the non-smooth character of the contact laws raises difficulties and specificities at every step of the m...

Two approaches are commonly used for handling frictional contact within the framework of the Discrete Element Method (DEM). One relies on the Complementarity Method (CM) to enforce a non-penetration condition and the Coulomb dry-friction model at the interface between two bodies in mutual contact. The second approach, called the Penalty Method (PM), invokes an elasticity argument to produce a f...

The paper analyzes a continuous and discrete version of the Neumann-Neumann domain decomposition algorithm for two-body contact problems with Tresca friction. Each iterative step consists of a linear elasticity problem for one body with displacements prescribed on a contact part of the boundary and a contact problem with Tresca friction for the second body. To ensure continuity of contact stres...