Stellar clusters are born in cold and dusty molecular clouds and the youngest clusters are embedded to various degrees in a dusty dark molecular material. Such embedded clusters can be considered protocluster systems. The most deeply buried examples are so heavily obscured by dust that they are only visible at infrared wavelengths. These embedded protoclusters constitute the nearest laboratorie...

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central engine. Torus sizes of hundreds of parsecs were deduced from early theoretical modeling efforts, but high-resolution IR observations now show that the torus size is no more than a few parsecs. This conflict is resolved when the clumpy nature of the torus is taken into account. The compact torus m...

In this article, we develop a set of partial differential equations describing the flow of a dusty fluid in variable porosity media. The developed equations take into account the effect of the porous microstructure on the flowing phases. We presented and overview of the equations governing the flow of a dusty gas in various type media, including that in naturally occurring porous media. Numeric...

The ion-acoustic instability in a dusty negative ion plasma is investigated, focusing on the parameter regime in which the negative ion density is much larger than the electron density. The dynamics of the massive dust grains are neglected, but collisions of electrons and ions with dust grains in addition to other collisional processes are taken into account. The presence of a population of cha...

Submillimeter and near-infrared images of cool dusty debris disks and rings suggest the existence of unseen planets. At dusty but nonimaged stars, semimajor axes of associated planets can be estimated from the dust temperature. For some young stars these semimajor axes are greater than 100 as seen from Earth. Such stars are excellent targets for sensitive near-infrared imaging searches for warm...

Submillimeter and near-infrared images of cool dusty debris disks and rings suggest the existence of unseen planets. At dusty but non-imaged stars, semi-major axes of associated planets can be estimated from the dust temperature. For some young stars these semi-major axes are greater than an arc second as seen from Earth. Such stars are excellent targets for sensitive near-infrared imaging sear...

In this paper, we examine the combined effects of thermal radiation, buoyancy force and magnetic field on oscillatory flow of a conducting optically thin dusty fluid through a vertical channel filled with a saturated porous medium. The governing partial differential equations are obtained and solved analytically by variable separable method. Numerical results depicting the effects of various em...

We determined abundances of O, Ca, Fe, Ba and Y for a sample of dusty and dust-free A stars, taken from the list of Cheng et al. (1992). Five of the stars have an infrared-excess due to circumstellar dust. Ongoing accretion from their circumstellar surroundings might have modified the abundances in the photospheres of these stars, but our results clearly show, that there is no difference in the...

We discuss recent advances in the study of dusty, massive galaxies at z > 1 arising from the first extensive spectroscopic surveys.