Theoretical thermochemistry of some LiXHn and BeXHn compounds

Summary In this theoretical work, we consider the geometrical, electronic and energetic properties of some lithium and beryllium derivatives. The standard heats of formation of these compounds have been calculated at the MP4=SDTQ/6-31+G(2df, p)//MP2=FULL/6-31G(d, p) level. The values obtained at this level of the theory are also compared with the heats of formation deduced from a composite procedure in which it is assumed that some corrections can be treated separately and combined in an additive manner. We find that the values determined with the complete 6-31+G(2df, p) basis set are the more accurate.     

Über singuläre Integralgleichungen

Ohne Zusammenfassung     

Field Profile Synthesis with an Antenna Array

Two algorithms for the synthesis of a microwave beam with desired characteristics are discussed. The beam is composed by an array of either identical or non-identical antennas. In an example, the application of those algorithms for wireless power transmission is demonstrated.     

Contrast-enhanced magnetic resonance tomoangiography: A new imaging technique for studying thoracic great vessels

The authors propose a new imaging approach for studying thoracic great vessels, using high-speed MR imaging combined with intravenous rapid bolus injection of a paramagnetic contrast media. The decrease of the T₁ relaxation time of flowing blood induced by the contrast agent (Gd-DOTA) caused an increased signal intensity within the vessel lumen for a time period allowing multiplanar imaging of various vascular structures. The intraluminal signal enhancement is mainly related to the blood concentration of the contrast agent as in conventional X-ray angiography. Information on the aorta and pulmonary arteries obtained by the so-called contrast-enhanced magnetic resonance tomoangiography appears complementary to that obtained with other vascular MR imaging procedures such as cine-MRI and magnetic resonance angiography (MRA).     

Survivable networks,linear programming relaxations and the parsimonious property

We consider the survivable network design problem — the problem of designing, at minimum cost, a network with edge-connectivity requirements. As special cases, this problem encompasses the Steiner tree problem, the traveling salesman problem and thek-edge-connected network design problem. We establish a property, referred to as the parsimonious property, of the linear programming (LP) relaxation of a classical formulation for the problem. The parsimonious property has numerous consequences. For example, we derive various structural properties of these LP relaxations, we present some algorithmic improvements and we perform tight worst-case analyses of two heuristics for the survivable network design problem.The research of both authors was partially supported by the National Science Foundation under grant ECS-8717970 and the Leaders for manufacturing program at MIT.