Quantitative Views Research Articles

Numerical study of a Gaussian beam propagating in media with negative permittivity and permeability by using a bidirectional beam propagation method

AbstractGaussian beam propagation in structures containing meta‐materials with negative permittivity and negative permeability is numerically studied by using a bidirectional wide‐angle finite‐difference beam propagation method. Illustrative and quantitative views are given for various anomalous behaviors, such as the negative angle of refraction, beam refocusing, arbitrarily thin distributed Bragg reflector, and negative lateral shift of the reflected beam from a grounded slab, by a Gaussian beam propagating in some meta‐material structures. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 292–296, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10898

Molecular windows into the below-ground interactions of ectomycorrhizal fungi

Over the past decade the use of molecular techniques has provided new ways to study old questions about how ectomycorrhizal fungi interact with each other and their environment. In their simplest form, these methods enable researchers to identify vegetative stages of fungi that would be difficult, slow, or impossible to identify by morphological or culture-based methods. This has resulted in quantitative views of complex fungal communities, which in turn have revealed new and unexpected patterns in community structure. In addition, molecular methods have been used to identify individual genotypes of fungi. This information has provided insights into the way that particular species of ectomycorrhizal fungi spread in nature. In this article we will mention the basic techniques and briefly discuss some of the findings that have resulted. Advances in this field have recently been comprehensively reviewed for scientific audiences, and we refer readers that have a more technical interest or a need to access the current literature to these reviews (Dahlberg, 2001; Horton & Bruns, 2001).

Increasing Access to Tomographic Resources: Web-based Telemicroscopy and Database

The application of electron tomography to cell biology has led to important insights into the 3D fine structure of subcellular processes and organelles. Tomography has been particularly useful for studying relatively large, multi-component structures such as the Golgi apparatus, mitochondria and synaptic complexes. When combined with very powerful high voltage electron microscopes, tomography has also provided high resolution quantitative views of extended structures such as neuronal dendrites in very thick sections (4 μm) at electron microscopic resolution. The utility of tomography is twofold: first, it provides 3D examination of subcellular structure without the need for serial section analysis; second, because the computed slices through the tomographic volumes can be much thinner than is possible to produce by physical sectioning, it reveals structural detail in the range of 5-30 nm that tends to be obscured in conventional thin sections. Tomographic analysis has forced re-assessment of long-standing views of organelles such as mitochondria and the Golgi apparatus and as the technique advances, additional insights are likely forthcoming.Electron tomography is an expensive technique, both in terms of the instruments used and the computational resources required. The three major high voltage electron microscope resources in the United States, San Diego, Boulder and Albany, all are actively engaged in tomographic research and offer this important technology to the scientific community at large.

Measuring the impact of oral health in old age: a qualitative reaction to some quantitative views

Investigations into the oral health-related beliefs and behaviour of old people are complex and fraught with methodological difficulties. They have employed to a large extent structured interviews or questionnaires based on the Sickness Impact Profile to explain the impact of oral disorder in old age. However, despite sophisticated statistical techniques, the results have failed to explain much of the variance in the responses of the elderly subjects. This paper reviews the results of several investigations conducted in a structured and quantitative manner, and contrasts them with an alternative method of inductive investigation using a more qualitative interpretation of open-ended interviews. The alternative method of exploration with a small but intensely involved group of elderly participants revealed a view of oral health that reflects a willingness of elders to adapt constructively to changes in the mouth with advancing age. Moreover, the construction of a framework of oral health-related beliefs and behaviours that emerged from the qualitative analysis of open-ended interviews, has widened our understanding of the significance of the mouth in old age beyond the framework of biophysical, functional and disabling variables that dominated previous research on this field.

Phenomenology of life satisfaction among elderly men: Quantitative and qualitative views.

Phenomenology of life satisfaction among elderly men: Quantitative and qualitative views.