The potential reduction in morbidity and mortality through cancer screening cannot be realized without receipt of appropriate follow-up care for abnormalities identified via screening. In this paper, the authors critically examine the existing literature on correlates of receipt of appropriate follow-up care for screen-detected abnormalities, as well as the literature on interventions designed to increase rates of receipt of follow-up care. Lessons learned describe what is known and not known about factors that are related to or predict receipt of follow-up care. Similarly, effective interventions to increase follow-up are described and gaps identified. A conceptual model is developed that categorizes the health care system in the United States as comprising four levels: policy, practice, provider, and patient. Some patient-level factors that influence follow-up receipt are identified, but the lack of data severely limit the understanding of provider, practice, and policy-level correlates. The majority of intervention studies to increase follow-up receipt have focused on patient-level factors and have targeted follow-up of abnormal Papanicolaou smears. Insufficient information is available regarding the effectiveness of provider, practice, or policy-level interventions. Standard definitions of what constitutes appropriate follow-up are lacking, which severely limit comparability of findings across studies. The validity of various methods of obtaining outcome data has not been clearly established. More research is needed on interventions targeting provider, system, and policy-level factors, particularly interventions focusing on follow-up of colorectal and breast abnormalities. Standardization of definitions and measures is needed to facilitate comparisons across studies. Cancer 2004. Published 2004 by the American Cancer Society.
Photonic crystals (PhCs) are artificial materials with a permittivity which is a periodic function of the position, with a period comparable to the wavelength of light. The most interesting characteristic of such materials is the presence of photonic band gaps (PBGs). PhCs have very interesting properties of light confinement and localization together with the strong reduction of the device size, orders of magnitude less than the conventional photonic devices, allowing a potential very high scale of integration. These structures possess unique characteristics enabling to operate as optical waveguides, high Q resonators, selective filters, lens or superprism. The ability to mould and guide light leads naturally to novel applications in several fields.
Band gap formation in periodic structures also pertains to elastic wave propagation. Composite materials with elastic coefficients which are periodic functions of the position are named phononic crystals. They have properties similar to those of photonic crystals and corresponding applications too. By properly choosing the parameters one may obtain phononic crystals (PhnCs) with specific frequency gaps. An elastic wave, whose frequency lies within an absolute gap of a phononic crystal, will be completely reflected by it. This property allows realizing non-absorbing mirrors of elastic waves and vibration-free cavities which might be useful in high-precision mechanical systems operating in a given frequency range. Moreover, one can use elastic waves to study phenomena such as those associated with disorder, in more or less the same manner as with electromagnetic waves.
The authors present in this paper an introductory survey of the basic concepts of these new technologies with particular emphasis on their main applications, together with a description of some modelling approaches.