Arrangement Of Axes Research Articles

Calbindin immunoreactivity in the hippocampal formation and neocortex of schizophrenics

1. 1.The authors studied the morphology of CalbindinD28K (CaBp) immunoreactive cells and processes in the hippocampal formation and the prefrontal cortex of schizophrenics using the immunohistochemical technique of avidin-biotin-complex method (ABC method) and the results were compared with those from normal human brains. 2. 2.1n the hippocampal formation area CA2 of schizophrenics, many CaBp-immunopositive cell bodies and fibers were disordered in their arrangement compared to normal control brains. 3. 3. In the prefrontal cortex (Brodmann area 9) of schizophrenics, many immunopositive cell bodies were exhibited irregular axis arrangement and fiber disarray. 4. 4. The altered distribution pattern of CaBp-immunopositive structures in the hippocampal formation and the prefrontal cortex might indicate the existence of GABA(gamma-aminobutyric acid)ergic dysfunction in the brain of schizophrenic patients.

Investigations of Director Field Arrangement Induced in Tunable Liquid Crystalline Waveguide

Measurements of the refractive index profile have been made to provide data for obtaining local optical axis arrangement in the waveguide cross-section. Liquid crystalline planar waveguide tuned with the electric field has been. used. A new approach is proposed to accomplish refractive index profile measurements n1 a direct way. The modal line method is presented as a tool that allows one to do it and to improve the attenuated total reflection disadvantages as well. The obtained results maintain applicability of the modal line method for a direct refractive index profile measurement. To verify the method, nematic 6CHBT (4-trans-4-υ-hexyl-cyclohexyl-isothiocyanatobenzene) described earlier in the literature has been examined. A nematic mixture W602 contained 6CΗBΤ as a main component has been examined too.

Artifactual Motility of the Subcoxal Axis in a Model Insect Leg with Skew Joint Axes

Kinematic reconstructions of joint angles during walking in stick insects revealed that the subcoxal axis (SCA) was neither firm during the step (it was movable), nor was its position matched to the line between articulation condyles. It has been demonstrated on kinematic models of a leg that the application of a simplified leg model for reconstruction caused an artifactual result: apparent movement of SCA and its drift from the real firm position. Simplified models assume that the plane where leg segments lie rotates about the SCA or at least the axis of joint rotation is perpendicular to the leg segment. Real legs have joints with non-parallel or non-orthogonal axes. Models considered in this article had an oblique arrangement of joint axes. Real or artifactual motility of CAS is discussed.

Spanning minimal surfaces

Spanning minimal surfaces are 3-periodic minimal surfaces which contain straight lines, i.e. axes of 2-fold symmetry. We have used crystallographic knowledge of the space groups and of the corresponding arrangements of 2-fold axes involved for the derivation of new surfaces of this type and for their systematic description. Complete information on spanning minimal surfaces without self-intersections is given with respect to their symmetry and topology, together with some new results on spanning minimal surfaces with self-intersections along straight lines.

Multilevel master equation for bicrystal clusters

A bicrystal film is modeled as an ensemble of clusters of four particles which interact via short-range exchange coupling. Their easy axes are oriented pairwise along two randomly chosen orthogonal directions and the relaxational dynamics of the resultant clusters are described in terms of a multilevel master equation. The randomly deposited bicrystal film is compared with a randomly deposited film of uniaxial clusters. The relaxational properties of the entire array are determined by the easy axes arrangement and by the nature of coupling within the cluster. In particular, for ferromagnetic coupling the occurrence probability of fully magnetized bicrystal cluster states is high and we propose that in conjunction with the highly isotropic coercivity this property leads to a sharp transition between film regions magnetized in opposite directions.

Optical digitizing with five axes: really a must?

Many technical products can be milled with a 3-axis CNC equipment and a spherical milling tool. Optical digitizers however have problems in scanning a surface under an angle much larger than 45 °. It is therefore mandatory, especially when digitizing “naturally” looking products, to move an optical digitizer with a 5-axis manipulator into the required viewing positions. We discuss several useful arrangements of axes and digitizer probe, the production of well-ordered, complete and non-ambiguous sets of point coordinates and an intelligent, stochastic compression before exporting to CAD/CAM systems.

Analysis of the effects of manufacturing errors on the accuracy of dual-elbow and elbow manipulators

The geometry of the robotic structure directly influences the positional and orientational capabilities of a manipulator. Among the existing robot geometries, the ideal dual-elbow and elbow manipulators are the most prevalent because of their excellent posing abilities and because they provide the maximum dextrous and reachable workspaces for a given total link length. These geometries, however, are very sensitive to small manufacturing errors that distort their ideal arrangement of joint axes and impact on their accuracy. In this paper, realistic dual-elbow and elbow geometries, incorporating modeled manufacturing errors are considered and their accuracy is contrasted and compared. A set of criteria consisting of statistical measures is developed to evaluate the performance of the realistic geometries in terms of accuracy. Theoretical and experimental results demonstrate the superiority of the realistic dual-elbow geometry for the same amount of distortion and dictate its use, especially for high-precision applications.

Symmetry analysis of the 2a phase of C60.

A symmetry analysis of the 2a phase recently observed in some samples of ${\mathrm{C}}_{60}$ is presented. This phase is described by a unit cell with eight molecules in inequivalent orientations. We first show that if this structure is assumed to be exactly cubic, there are only three allowed space groups, none of which corresponds to the PA3\ifmmode\bar\else\textasciimacron\fi{} arrangement of threefold axes previously established for ${\mathrm{C}}_{60}$ by several groups. Our calculated powder diffraction spectra for these space groups are not consistent with existing experimental data. Second, if the symmetry of the PA3\ifmmode\bar\else\textasciimacron\fi{} structure is lowered by a doubling of the unit cell, we show that the resulting structure is trigonal, space group R3\ifmmode\bar\else\textasciimacron\fi{}. We calculate powder diffraction spectra for this scenario and thereby place upper limits on both the angular distortion and the trigonal lattice distortion. Third, since the microscopic origin of this distortion probably involves defects of some presently unknown type, we consider a phenomenological scenario for the origin of this trigonal distortion. Within this scenario, we study the symmetry of the interactions needed to explain this structure. We start by giving an analysis of the structural distortion within harmonic lattice dynamics. However, to obtain the correct (R3\ifmmode\bar\else\textasciimacron\fi{}) symmetry structure we were forced to study the cubic coupling between zone-corner librons and macroscopic strains. In this way we relate the development of R3\ifmmode\bar\else\textasciimacron\fi{} symmetry from the PA3\ifmmode\bar\else\textasciimacron\fi{} structure in terms of a phenomenological model of lattice dynamics. Fourth, we extend the above arguments to construct a Landau theory for the hypothesized PA3\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}R3\ifmmode\bar\else\textasciimacron\fi{} phase transition, which occurs as a function of the concentration of the presumed defects. The resulting free energy has no cubic terms (so the transition can be continuous) but has five fourth-order invariants.

Large area deposition of superconducting YBa2Cu3O x films by plasma flash evaporation

In situ superconducting YBaCuO films were prepared by RF plasma flash evaporation. By using a shifted axis arrangement between the torch and the susbtrate holder, flat temperature distribution is attained and therefore films with godd morphology and crystallinity can be obtained over the whole area of the 80 cm 2 sample holder. Also the film thickness, composition, and T c show no difference between various positions

Some magnetic properties of synthetic and natural haematite of different grain size

The behaviour of some magnetic properties of natural and synthetic haematite of different grain size is examined. The natural haematite was obtained from the hydrothermal deposit Kadaň (Czech and Slovak Federal Rep.). Six grain-size fractions ranging from 120 to 40 μm were prepared by means of sieving and two further fractions down to 5 μm by wet ultrasonic sieving. Since the behaviour of the fractions is similar, that of only four representative samples is reported. In addition, the behaviour of one submicron synthetic haematite fraction (0.5 μm) prepared by oxidation of ferrous sulphate (uniform in size and shape) was investigated. The initial remanence value ( J r) seems to increase with decreasing grain size. During alternating field (AF) demagnetization, all fractions behaved similarly, except for the submicron fraction which is considerably softer than the others. Normalized (isothermal remanent magnetization) IRM acquisition curves were similar for all fractions. Parameters of the anisotropy of magnetic susceptibility (AMS) display significant changes, mainly during IRM acquisition. During AF demagnetization, the anisotropy degree P exhibits a slight increase (some %), while the behaviour of the shape factor T is complicated. The anisotropy ellipsoid exhibits a tendency to rotate. Significant changes in the AMS parameters occur during IRM acquisition. Curves of P and T vs. IRM acquisition field, for various grain-size fractions, show no coherent pattern. For all the samples studied, the T vs. H curve exhibits a threshold value at which change in the type of arrangement of easy axis of magnetization occurs. For the IRM acquisition fields higher than some 320 kA m −1, the minimum susceptibility axis parallels the direction of the IRM acquisition field. Hysteresis curves of the fractions are similar to each other. The Preisach distribution function was determined and it indicates that the reversible part of the magnetization process plays an important role comparatively. Based on the coercivity data presented no unambiguous conclusion could be drawn from the single-domain (SD)-multidomain (MD) transition, associated with a coercivity maximum.

A Survey of One Class of 7-Jointed Serially Connected Robots: Type-Synthesis to Obtain Controllably Dexterous Workspace

A type-synthesis process, which is based on screw theory and geometry, is developed to identify certain robots, each of which can provide controllably dexterous workspace of a tool-point. The identification process is confined to only those robots which control the motion of the end-effector with seven series-connected joints, the axes for the outermost three of which are concurrent. Forty six types of robots are so identified, and, for each, the results are (i) a suitable kinematic chain for the arm and (ii) suitable angle-dimensions for the links of the arm, where the angle-choices are limited to the values 0, ± π/2, and π. A geometric description of the dominant function for control is included. The same kinematic chains are surveyed for all possible parallel and right-angle arrangements of adjacent axes in the four links of the arm. Again utilizing screw theory, 160 robots are identified which do not posses full-cycle axis-dependence among some or all of the first five axes.

Ocular Tracking of Rapidly Moving Visual Targets by Stomatopod Crustaceans

ABSTRACT Ocular tracking in two species of stomatopod crustaceans, Squilla empusa (Say) and Gonodactylus oerstedii (Hansen), was studied by presenting animals with small targets moving to their right and left. Squilla empusa showed no indication of ocular movement responses synchronized with the target’s motion, whereas Gonodactylus oerstedii often tracked the target through large angular amplitudes. The region of visual fixation in G. oerstedii is probably the ommatidial patches in line with the eyecup axis. This is suggested by the arrangement of ommatidial axes on the eye’s circumference, and by the alignment of the eyes and the rotational motions they make as they observe an approaching target. Tracking is irregular, probably because the animal pays attention to the target only intermittently. Targets are most stimulatory as they move nearly in front of an animal. Eye tracking responses become larger, more frequent and more accurate with increasingly anterior target positions. During visual tracking, the eyes perform both smooth and saccadic tracking movements. Eye movements in the size range 7·5°-15° are made to near the position of the target at movement onset, but are less accurate relative to the target’s position at the end of the movement. During visual tracking, the two eyes apparently act with complete independence. Movements of one eye are uncorrelated with movements of the other, both for extreme and central locations of the moving target. The existence of ocular independence during smooth pursuit and saccadic tracking in G. oerstedii may be possible because of the redundancy of visual fields existing in each eye, which could permit monocular measurements of distance to a viewed object. If so, each eye is capable of providing a complete description of the location of a target in space.

Ocular Tracking of Rapidly Moving Visual Targets by Stomatopod Crustaceans

1. Ocular tracking in two species of stomatopod crustaceans, Squilla empusa (Say) and Gonodactylus oerstedii (Hansen), was studied by presenting animals with small targets moving to their right and left. 2.Squilla empusa showed no indication of ocular movement responses synchronized with the target9s motion, whereas Gonodactylus oerstedii often tracked the target through large angular amplitudes. 3. The region of visual fixation in G. oerstedii is probably the ommatidial patches in line with the eyecup axis. This is suggested by the arrangement of ommatidial axes on the eye9s circumference, and by the alignment of the eyes and the rotational motions they make as they observe an approaching target. 4. Tracking is irregular, probably because the animal pays attention to the target only intermittently. Targets are most stimulatory as they move nearly in front of an animal. Eye tracking responses become larger, more frequent and more accurate with increasingly anterior target positions. 5. During visual tracking, the eyes perform both smooth and saccadic tracking movements. Eye movements in the size range 7.5°–15° are made to near the position of the target at movement onset, but are less accurate relative to the target9s position at the end of the movement. 6. During visual tracking, the two eyes apparently act with complete independence. Movements of one eye are uncorrelated with movements of the other, both for extreme and central locations of the moving target. 7. The existence of ocular independence during smooth pursuit and saccadic tracking in G. oerstedii may be possible because of the redundancy of visual fields existing in each eye, which could permit monocular measurements of distance to a viewed object. If so, each eye is capable of providing a complete description of the location of a target in space.

Acoustic levitation at high temperatures in the microgravity of space

Acoustic levitation of a small specimen is obtained in the energy well produced by a single axis arrangement consisting of a sound source and a small acoustic reflector. At high temperatures, the acoustic forces are generally insufficient to levitate a specimen except in the microgravity environment available in space. A single axis acoustic levitator (SAAL) has been built to levitate a specimen inside a high-temperature furnace where it may be heated, melted, cooled, and solidified while being positioned without physical contact. The acoustic field configuration in such a containerless processing device has been analyzed and the expected levitation or positioning forces are calculated for the specific case of the NASA-SAAL experimental hardware as flown on the Space Shuttle on the STS-61A mission. This experiment successfully levitated and processed three samples at temperatures from 600 °C to 1550 °C. Experimental data are presented and the results compared with those predicted. [Work supported by NASA.]

Room temperature EPR of Cr(CN)63-ions doped into KCl single crystals

Room temperature EPR spectra of the Cr(CN)63- ion substituting for KCl65- in single crystals of KCl show evidence for two different orthorhombic centres. The first of these shows an unexpected reduction in the number of spectral lines. This is due to the simultaneous occurrence of a crystallographic equivalence of the principal y and z axes of the spin Hamiltonian along the (110) directions, and the unusual value for the ratio E/D (where D and E represent axial and rhombic terms of the crystal field) of exactly 1/3. The second centre has E/D approximately=1/3 and a similar arrangement of magnetic axes, except that the y and z axes are at 45 degrees to (100) in the (110) planes. Models for the two centres are discussed in terms of different configurations of two charge compensating K+ vacancies.

Design of rotating aperture cones for radiographic scatter reduction.

A new multiple-scanning-slit or scanning-grid scatter-reduction geometry consisting of coaxial rotating aperture (RA) cones is described and compared with other RA assemblies such as the rotating aperture wheel (RAW) device. A unique feature of the new design is that the geometric and rotational axes of the conical RA surfaces coincide and are collinear with the x-ray focal spot. This arrangement of axes should provide the potential for greatly improved mechanical rigidity, higher rotational velocities, and the capability for static slit-pattern alignment. The common rotational axis of the cone assembly is angled obliquely to the central x-ray beam such that the intersections of the irradiated portion of the RA surfaces with the plane formed by the x-ray central beam and cone axes are straight lines parallel to the film plane. This geometry is compatible with the standard source-patient-image receptor radiographic relationship and allows for variable source-to-image-receptor distance.

Equilibrium bubble positions and effective easy axes in implanted garnet films

The disc-bubble method is used to determine bubble equilibrium positions and effective easy axes in garnets with implanted layer. The influence of tilting on the effective easy axes arrangement and charged walls subsistence is discussed. Propagation margins in four directions are measured in nontilted and tilted specimens, and the results are referred to orientation of circuits towards the effective easy axes.

The problem of thermal expansion in polyethylene spherulites

It is shown from simple considerations of the arrangement of crystal axes and from the known thermal expansion coefficients along these axes that a polyethylene spherulite would, on cooling from its crystallization temperature to room temperature, form radial voids (amounting to up to 4% of the volume) unless some reversible internal transformation prevents this. To clarify this ‘composite’ problem a co-ordinated investigation was carried out on changes in the macroscopic sample volume, in the lengths of the crystallographic axes and in the diameters of the individual spherulites with temperature. The results show that the changes in spherulite dimensions conform to those of the sample as a whole thus eliminating the necessity of void formation (which nevertheless appears to arise in thin film spherulites) leaving an inconsistency with the crystallographic data. It was noticed further that the thermally induced reversible changes in the spacing of the extinction bands did not conform to the changes in the spherulite diameter and in addition depended on the radius of the band. It is suggested that the reversible transformation needed to prevent voiding and to eliminate the above inconsistencies is also responsible for the changes in band spacing (possibly in the form of twisting and untwisting of the structure underlying the banding) and represents a novel, as yet unexplored, feature of spherulites.

The measurement of the cell cycle time in squamous epithelium using the metaphase arrest technique with vincristine.

In squamous epithelia with a single layer of germinative cells, the age distribution of cells in the cell cycle is shown to depend on the direction of the mitotic axis (i.e. a line joining the nuclei of daughter cells) relative to the plane of the basal layer. When axes are in the plane of the basal layer the age distribution is exponential; when cells divide at right angles to the plane of the basal layer, the age distribution is rectangular. When there is a ratio of vertical to horizontal axes, the age distribution is intermediate but can be calculated from knowledge of the proportion of axes in the plane of the layer. Squamous epithelia can be classified according to this arrangement of axes. When there are multiple layers of germinative cells, as in psoriasis, the age distribution is shown to be exponential to a good approximation, whatever the direction of the mitotic axes in the several layers. The importance of these observations is demonstrated by analysing metaphase arrest experiments with vincristine in the single layer of germinative cells in the mouse oesophagus, and in the several layers found in psoriatic epidermis. Choice of the wrong age distribution leads to an error of 6 h in the oesophagus and 23 h in psoriatic epidermis, when the mean cell cycle time is calculated. It is concluded that, in squamous epithelium, it is most important to know the age distribution before calculating the cell cycle time by methods involving measurement of the rate of entry of cells into mitosis or DNA synthesis.

Tectonic Regimes

AbstractThe concept of tectonic regimes is developed so as to specify the symmetry and orientation of bulk deformation for use in tectonic analysis. Four symmetry patterns combined with possible arrangements of principal axes in vertical and horizontal directions as in a compression belt give thirteen regimes which are in turn defined and tentatively related to some known tectonic structures. A theoretical orogenic sequence of regimes is developed and the paper concludes with a review of some of the difficulties.