Geometrical Component Research Articles

Single-mode-laser phase dynamics.

We study the phase dynamics of a single-mode ring laser described by the complex Maxwell-Bloch equations. We identify three reference-frame frequencies and determine the properties of the field dynamics observed in these frames. In one of these reference frames, the phase jumps are always equal to \ensuremath{\pi}, irrespective of the detuning, while in another reference frame quasiperiodic field portraits reduce to periodic field portraits. We also apply the recent theory of Ning and Haken [Phys. Rev. Lett. 68, 2109 (1992)] to prove that the laser phase can be decomposed into a geometrical component that is frame invariant and a dynamical component that is frame dependent.

Study of the resolution performance of an array of discrete detectors with independent readouts for positron emission tomography

The intrinsic resolution characteristics of an original detection system for very high resolution positron emission tomography (PET) based on arrays of small discrete crystals individually coupled to solid state photodetectors are evaluated. The results obtained demonstrate the excellent three-dimensional (3-D) resolving capability of a detection system based on the EG&G/RCA C30994 detector module. The analysis of the various components contributing to the resolution has shown that the geometry of the detector and the intercrystal scattering both contribute to limit the achievable intrinsic resolution. The geometrical component is dominant off the central region of the camera field as a result of intercrystal penetration when the array is irradiated at an angle. Intercrystal scattering must be properly rejected to achieve the intrinsic resolution determined by the detector geometry.

Some geometrical considerations on membrane insertion by exocytosis

A two-dimensional random walk model is used to describe constitutive exocytic transport. Specifically, the possibility of attaining selective vesicle insertion by purely geometrical effects is studied. The distribution of vesicle insertion on the membrane and the average time of translocation are determined as a function of Golgi apparatus size and position, cell morphology and size, walk bias due to cytoplasmic streaming or differential movement of microtubules, and steric effects caused by other organelles. The simulations suggest that significant selectivity in targeting can result from adequate Golgi positioning, in accordance with the hypothesis of Golgi reorientation by the microtubular network (Singer and Kupfer, 1986, Annu. Rev. Cell Biol. 2, 337–365). The selectivity in targeting also depends on the cellular morphology. Segregation of vesicle insertion can be obtained in the transport to the cellular front end and lateral membrane surfaces of a quadrilateral cell, thus suggesting a geometrical component in the exocytic transport in polarized cells.

Geometrical principal component analysis of planar-segments of the three-channel lissajous' trajectory of human auditory brain stem evoked potentials

Three-Channel Lissajous' Trajectories (3CLTs) of Auditory Brain Stem Evoked Potentials (ABEP) were obtained from 15 normal humans. Planar-segments of 3CLT were identified and the orientations of the first two geometrical principal components, which interact to produce the planar-segments, were calculated. Each principal component's orientation in voltage space was quantified by its coefficients (A, B and C). Intersubject variability of these orientations was comparable to the variability of plane orientations. The principal components of planar-segments can indicate the type of generator activity that is involved in the formation of planar-segments. The results of this analysis indicate that planarity of each 3CLT component is produced by the interaction of simultaneous multiple generators, or by a single synchronous generator which changes its orientation. The coefficients of these principal components may complement plane coefficients as quantitative indices of 3CLT of ABEP.

Packing and conformational contributions in binary liquid mixtures. Acoustic studies of n-hexadecane with dimethylpentanes

In order to separate internal (rotational isomeric) and external (intermolecular structural) contributions to volume effects in liquid alkane mixtures, ultrasonic attenuation and velocity measurements have been made on hexadecane and its mixtures with dimethylpentane. Within experimental error the rotational isomeric contribution is a simple sum of those of the pure components. However, the shear and volume viscosity contributions are not linearly additive, but show a negative excess quantity. This is explained on the basis of a structural equilibrium between more ordered (solid-like) and less ordered (more liquid-like) regions in the liquid mixture. The results indicate that there is a geometrical packing component in the mixture interaction parameter, χ12.

製紙用麻類の構造 ＩＩＩ こう解による非木材繊維の繊維形態およびシートの変化

Fibres of flax waste and kenaf bark were studied on their morphological changes during pulping and beating by means of scanning electron microscopy and specific surface measurement. Following results were obtained.1) Flax fibres were frozen smashed in liquid nitrogen and gently delignified with chloriteacetic acid solutions. Thus middle lamellae and the primary walls were removed and disappeared, then the secondary walls with fibrils of about 10° inclined S helics were exposed. These fibrils were split into fibril bundles of one to several μm width parallel to the fibrilar angle. Moreover, the secondary walls were delaminated easily to separate.2) Kenaf fibres, which were treated as flax fibres, exposed the secondary walls with fibrils of Z helics of about 10°. However, no fibril bundle was observed. This can be considered that a cohesion force between fibrils of kenaf fibres is stronger than that of flax fibres.3) At the same freeness level, specific surface area of handsheet from flax fibres was larger than that of kenaf. This is because flax fibre is more subjected to the external fibrillation, so fibril bundles and fibrils are easily separated from a parent fibre to form a closed sheet structure.On the other hand, kenaf fibres are least changed macroscopically during pulping and beating, so fibres are the main geometrical component of the sheet strcture.