X-rays of polygons

Cutting Out Polygons with Lines and Rays

We present approximation algorithms for cutting out polygons with line cuts and ray cuts. Our results answer a number of open problems and are either the first solutions or significantly improve over previously known solutions. For the line cutting version, we prove a key property that leads to a simple, constant factor approximation algorithm. For the ray cutting version, we prove it is possib...

Subject headings: galaxies: general—galaxies: spiral—X-rays: general—X-rays: galaxies—X-rays: ISM

We present results from the analysis of deep ROSAT HRI and PSPC observations of the spiral galaxy M81. The inferred total (0.5–2 keV band) luminosity of M81 is ∼ 3×10 ergs s, excluding the contribution from identified interlopers found within the D25 ellipse. The nucleus of the galaxy alone accounts for about 65% of this luminosity. The rest is due to 26 other X-ray sources (contributing ∼ 10%)...

Diffraction of X-rays

Remembering x-rays.

On the evening of 8 November 1895, ous potential applicability to medical diWilhelm Conrad Rontgen immediately agnosis (2). recognized a remarkable new phenomOn_.zJJ~nu~ry, at his first and only enon. Fluorescent material lying on a public lecture on the discovery, Rontgen bench some distance from the cathode made an x-ray picture of the hand of Dr. ray tube with which he was experimentAlbert v...

Triboluminescence and X-Rays

Triboluminescence is shown to produce X-rays from the nanoparticles (NPs) that form as the sticky acrylic adhesive of Scotch tape is peeled from the polyethylene (PE) roll in a vacuum. Prior to peeling, atoms in the adhesive are not under electromagnetic (EM) confinement and have full thermal kT energy. But upon peeling, the atoms in NPs that form in the gap between adhesive and PE are under EM...