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Attributes and frequency of forest gaps are usually described in reference to a one-dimensional gradient of light, which may relate to their disturbance dynamics. Similarly, species are customarily classified by their light response. We propose that a bi-dimensional light framework facilitates the understanding and comparison of forest systems and the understanding of plant responses to the complex light environment. This light plane is based on two spatially related components: 1) light received directly on a particular point (Focal); and 2) a statistical summary of the immediate environment representing the light conditions surrounding that point (Context). The contrast between these two values is null when Focal = Context and positive when Focal > Context or otherwise negative. Light was assessed using hemispherical photographs using a spatial arrangement of pictures spaced ~3 metres (m) in-between. Eight forest plots were surveyed, each with a central gap of different size. Sapling performance of Alnus acuminata, Cornus excelsa, Liquidambar styraciflua, Persea americana and Quercus laurina was also assessed within these plots. Measurements of stem height, basal diameter, and slenderness allometry were taken over a period of more than two years. We found in the light plane that plots were distributed in a pattern congruent with their estimated degree of disturbance (gap size), which spanned wide areas in the plane. Liquidambar styraciflua. and Quercus laurina were found to be sensitive to Focal light, irrespective of Context light. All species responded to Focal light under negative Contrast. Cornus and Persea grew taller and more slender as Focal light increased, particularly under null contrast. There is evidence suggesting that plant growth is dependent on the contrast measured. Thus, it would be relevant to devise a functional classification of tree species that considers their response to both direct light and luminosity of the immediate environment as measured by a contrast value.

The performance and construction of a microwave transmission spectrometer, which determined the microwave power as functions of temperature and applied magnetic field, was described. The spectrometer operated in the frequency range from 12.4 to 18 gHz. A solid state microwave amplifier and a calibration signal were characteristic features of the spectrometer.

Calculations of the propagation constants and transmission coefficients for a square array of cladded wires in a ferrimagnetic host are presented. The interaction between the ferrimagnet and the wire array, which destroys the negative permittivity of the wire array, can be overcome by cladding the wires with an insulating, nonmagnetic jacket.

Provides information on a study that measured the temperature dependence of electromagnetically excited sound in single crystals of iron. Methodology of the study; Results and discussion of the study; Conclusions.

Presents information on a study which measured the temperature dependence of the transmission of sound waves through polycrystalline samples of the Invar alloy Fe[sub6.3]Ni[sub3.6]Mn[sub0.4]Si[sub0.2]. Parameters involved in a transmission measurement; Operation of the data-acquisition system in two modes; Illustration of the typical transmission amplitude for an Invar sample.

Studies the effect of the entropy wave on sound and electromagnetic waves in ferromagnetic metals. Method of the study; Results and discussion; Conclusion.

Presents a study which investigated ultrasonic attenuation in nickel and iron. Cause of the ultrasonic attenuation in metals at microwave frequencies; Background on the theory of electronic attenuation of sound waves in metals; Method for generating transverse sound waves.

We present four cases of profuse gastrointestinal (GI) bleeding where the site of haemorrhage was demonstrated using multi-slice computed tomography (MSCT), with concordant findings at laparotomy and pathological examination. A review of the current literature is undertaken and the role of spiral computed tomography as a method of sourcing the bleeding point is discussed in relation to other management modalities. [ABSTRACT FROM AUTHOR]

Recent interest has been generated in composite materials for which both the dielectric constant and the magnetic permeability are negative. These composites behave as if they possess a negative index of refraction, although the broader, less specific adjective "lefthanded" has also been applied to them. Such composites possess two sets of structures which are separately responsible for the negative ∈ and µ. However, materials having a negative µ are common in the microwave frequency range and such a material can replace one set of structures in the composite. An example of a simple composite is a YIG medium (µ<0) penetrated by sets of metallic strips or wires which give rise a negative dielectric constant in the appropriate frequency range. The index of refraction of the composite can be modulated by adjusting the applied magnetic field. [ABSTRACT FROM AUTHOR]