Decentred optical axes and aberrations along principal visual field meridians

Suggestions that peripheral imagery may affect the development of refractive error have led to interest in the variation in refraction and aberration across the visual field. It is shown that, if the optical system of the eye is rotationally symmetric about an optical axis which does not coincide with the visual axis, measurements of refraction and aberration made along the horizontal and vertical meridians of the visual field will show asymmetry about the visual axis. The departures from symmetry are modelled for second-order aberrations, refractive components and third-order coma. These theoretical results are compared with practical measurements from the literature. The experimental data support the concept that departures from symmetry about the visual axis in the measurements of crossed-cylinder astigmatism J45 and J180 are largely explicable in terms of a decentred optical axis. Measurements of the mean sphere M suggest, however, that the retinal curvature must differ in the horizontal and vertical meridians.

Flow between torsionally oscillating disks rotating about different axes at different speeds

The flow of an incompressible viscous fluid confined between two parallel infinite disks performing torsional oscillations with the same frequency, but rotating about different axes with different speeds has been studied. The solutions are presented for the symmetric and asymmetric first harmonic and steady streaming. The interesting features of the symmetric and asymmetric flow are discussed for the cases of small and large Womersley parameter at different ratios of the rotation speeds. The forces acting on one of the disks are also calculated.

A new method for generation of quasi-periodic structures withn fold axes: Application to five and seven folds

A new geometrical method for generating aperiodic lattices forn-fold non-crystallographic axes is described. The method is based on the self-similarity principle. It makes use of the principles of gnomons to divide the basic triangle of a regular polygon of 2n sides to appropriate isosceles triangles and to generate a minimum set of rhombi required to fill that polygon. The method is applicable to anyn-fold noncrystallographic axis. It is first shown how these regular polygons can be obtained and how these can be used to generate aperiodic structures. In particular, the application of this method to the cases of five-fold and seven-fold axes is discussed. The present method indicates that the recursion rule used by others earlier is a restricted one and that several aperiodic lattices with five fold symmetry could be generated. It is also shown how a limited array of approximately square cells with large dimensions could be detected in a quasi lattice and these are compared with the unit cell dimensions of MnAl6 suggested by Pauling. In addition, the recursion rule for sub-dividing the three basic rhombi of seven-fold structure was obtained and the aperiodic lattice thus generated is also shown.

The Aghadown bronze axes, Paddock Td., Co. Cork

A brief account of the two axes to be described and illustrated here was published by Power in 1926. He states that they were discovered at Aghadown near Baltimore, in a souterrain locally known as Poll-a-Talmhain

Les axes prioritaires face à l'émergence de phénomènes criminels en banlieue québécoise : l'exemple d'un quartier de laval.

Les médias renforcent l’image négative de l’émergence de zones criminelles dans certaines banlieues, mettant en avant l’impuissance des interventions policières et de la stratégie étatique. Les citoyens vivant au quotidien dans ces quartiers expriment un sentiment d’insécurité. L’impression d’un cercle vicieux entre insécurité réelle et sentiment d’insécurité persiste alors au travers de tels discours et perdure au travers des époques et des lieux, que ce soit en France, aux États-Unis ou même au Canada. Bon nombre d’études ont déjà posé la question à savoir si ces discours se fondent sur une réelle situation d’insécurité ou sur le sentiment d’insécurité des citoyens mais peu ont pris l’axe d’approfondir la réflexion et l’étude sur ces nouveaux phénomènes de désordres urbains et d’incivilités émergents dans les banlieues du Québec. Cette recherche a pour but d’approfondir cette réflexion en prenant un exemple d’un quartier de Laval au Québec. Il s’agit d’établir s’il y a réelle problématique d’incivilités et de désordres urbains ou s’il s’agit davantage d’un sentiment d’insécurité, le but étant ainsi de pouvoir établir un guide de résolutions de problèmes dans les banlieues et d’apporter une réflexion sur les interventions potentielles dans des zones sensibles. Se basant sur une méthodologique mixte, reliant une comparaison des statistiques de criminalité par quartiers à la perception d’acteurs clés de terrain de Laval, cette recherche apporte un nouveau regard sur ces résolutions de problèmes. Les résultats apportent une analyse intéressante sur cette interaction en soulignant l’importance du quartier et des caractéristiques sociodémographiques, du contrôle social informel, du tissu social mais aussi de la nécessité du cadre de l’autorité institutionnelle telle que la police, l’école ou encore le tissu associatif. Ces premiers éléments permettent d’ouvrir la discussion sur un plan partenarial d’interventions établissant une stratégie de lutte contre l’insécurité et le sentiment d’insécurité, cassant ainsi ce cercle vicieux par la mise en place d’une nouvelle gouvernance locale de sécurité et de bien-vivre ensemble.

Coriolis interactions about x-y axes in symmetric tops

Selection rules and matrix elements are derived for Coriolis interactions between vibrational levels due to rotation about (x, y) axes in symmetric top molecules. The theory is developed in detail for the case of interaction between an A1 and an E species vibrational level in a C3v molecule; perturbations to both the positions and the intensities of the rovibration transitions in the spectrum are considered. A computer program has been written which calculates exactly the perturbed spectrum of two interacting rovibration bands according to this model, the results being presented directly by a graph plotter connected to the computer. This has been used to interpret perturbations observed in two pairs of interacting fundamentals in the spectrum of CH3F (ν2 - ν5 and ν3 - ν6) and one pair in CD3Cl (ν2 - ν5). The resulting analysis of the observed spectrum leads to new values for some vibration-rotation interaction constants and also leads to a unique determination of the sign relationship between the dipole moment derivatives in each pair of interacting normal vibrations. These sign relations are summarized in Figs. 8, 12, and 15.

Metabolic disturbances in male broilers of different strains. 2. Relationship between the thyroid and somatotropic axes with growth rate and mortality

Seven male broiler strains (Arbor Acres, Avian Farms, Cobb-500, Hubbard-Peterson, ISA, Naked Neck, and Ross) were compared for their growth rate, feed efficiency, and mortality due to sudden death and ascites. In addition, weekly plasma levels of thyroid hormones [3,3′,5-triiodothyronine (T3) thyroxine (T4), T3: T4 ratio, growth hormone (GH), and insulin-like growth factor-I (IGF-I)] were determined. The highly productive, commercial strains were very similar in their endocrine profiles but differed markedly from the Naked Neck chickens. Naked Neck chickens were characterized by higher plasma T3 and lower T4 levels at similar ages as well as when compared on the same body weight basis. The present findings support the hypothesis that the slightly hypothyroid state of high productive broilers renders them more sensitive to metabolic disorders. Naked Neck chickens also had higher plasma GH levels than those of their age-matched commercial broilers. The coefficient of variation for GH was highest for Naked Neck chickens, which is indicative for an amplified GH burst amplitude. It may be stated that changes in plasma thyroid hormone concentration in indirect response to selection for low feed conversion and fast growth may be causatively linked to susceptibility for metabolic disturbances such as sudden death syndrome and ascites.