Stabilization of the compactification volume by quantum corrections.

We discuss prospects for stabilizing the volume modulus of N = 1 supersymmetric type IIB orientifold compactifications using only perturbative corrections to the Kähler potential. Concretely, we consider the known string loop corrections and tree-level alpha' corrections. They break the no-scale structure of the potential, which otherwise prohibits stabilizing the volume modulus. We argue that when combined, these corrections provide enough flexibility to stabilize the volume of the internal space without nonperturbative effects, although we are not able to present a completely explicit example within the limited set of currently available models. Furthermore, a certain amount of fine-tuning is needed to obtain a minimum at large volume.

Rational diagnosis of squamous cell carcinoma of the head and neck region: comparative evaluation of CT, MRI, and 18FDG PET.

OBJECTIVE: We sought to evaluate the efficiency of (18)FDG PET, CT, and MRI for the preoperative staging of squamous cell carcinoma (SCC) of the head and neck region. CONCLUSION: MRI is recommended as the method of choice in the preoperative evaluation of SCC of the oral cavity and the oropharynx. PET can provide relevant diagnostic information in case of equivocal findings by MRI or CT. Routine use of PET, however, does not appear to be necessary if optimized MRI is available.