Transverse Arrangement Research Articles

Effect of Spacing between Two Adjoining Circular Cylinders on Flow around Two-Dimensional Circular Cylinder Rows. 2nd Report, Two and Three Rows of Transverse Arrangement.

This paper describes an effect of spacing between two adjoining circular cylinders on flow around two-dimensional circular cylinder bundles. The experiment was carried out in an N. P. L. blow-down type wind-tunnel with a working section of 500 mm×500 mm×2000 mm, and under the Reynolds number 1.3×104. The surface-pressure distributions on the circular cylinder were measured and the drag coefficient was determined from these measurements. The flow-pattern around circular cylinders was observed. The power spectrum in the turbulent wake behind circular cylinders was also measured. It was found that the pressure on the rear surface of circular cylinders becomes lower and the drag coefficient increases as the spacing ratio decreases, while the step-change in the drag coefficient occurs at the spacing ratio where the flow pattern around the downstream circular cylinder changes.

Reorientation of microtubules at the outer epidermal wall of maize coleoptiles by phytochrome, blue-light photoreceptor, and auxin

The effects of red and blue light on the orientation of cortical microtubules (MTs) underneath the outer epidermal wall of maize (Zea mays L.) coleoptiles were investigated with immunofluorescent techniques. The epidermal cells of dark-grown coleoptiles demonstrated an irregular pattern of regions of parallel MTs with a random distribution of orientations. This pattern could be changed into a uniformly transverse MT alignment with respect to the long cell axis by 1 h of irradiation with red light. This response was transient as the MTs spontaneously shifted into a longitudinal orientation after 1–2 h of continued irradiation. Induction/reversion experiments with short red and far-red light pulses demonstrated the involvement of phytochrome in this response. In contrast to red light, irradiation with blue light induced a stable longitudinal MT alignment which was established within 10 min. The blue-light response could not be affected by subsequent irradiations with red or far-red light indicating the involvement of a separate blue-light photoreceptor which antagonizes the effect of phytochrome. In mixed light treatments with red and blue light, the blue-light photoreceptor always dominated over phytochrome which exhibited an apparently less stable influence on MT orientation. Long-term irradiations with red or blue light up to 6 h did not reveal any rhythmic changes of MT orientation that could be related to the rhythmicity of helicoidal cell-wall structure. Subapical segments isolated from dark-grown coleoptiles maintained a longitudinal MT arrangement even in red light indicating that the responsiveness to phytochrome was lost upon isolation. Conversely auxin induced a transverse MT arrangement in isolated segments even in blue light, indicating that the responsiveness to blue-light photoreceptor was eliminated by the hormone. These complex interactions are discussed in the context of current hypotheses on the functional significance of MT reorientations for cell development.

Microtubule arrays during mitosis in monoplastidic root tip cells ofIsoetes

Mitosis in monoplastidic root tip cells ofIsoetes was studied by fluorescence (confocal laser scanning microscopy) and transmission electron microscopy. The two major components of division polarity, spindle axis and division site, are established more or less simultaneously in preprophase. Morphogenetic plastid migration results in positioning of a daughter plastid at each pole of the future spindle. Concomitant with establishment of the spindle axis, the division site is marked by a girdling band of mirotubules (preprophase band). Endoplasmic microtubules interconnect the polar plastids and preprophase band suggesting a mechanism for communication and final alignment of spindle axis and division site. As in other monoplastidic cells, the spindle appears to emanate from the plastids. In telophase, the focus of microtubules shifts to the reforming nuclei as the phragmoplast is initiated. Microtubules which continue to emanate from plastids are incorporated into the phragmoplast as it expands beyond the interzonal region. Cortical microtubules are restored in a random fashion before assuming a transverse arrangement in interphase.

Heat transfer and interactive buoyant vortex shedding by a pair of circular cylinders in transverse arrangement

The heat transfer and fluid flow patterns in the mixed convection regimes for the double circular cylinders arranged transverse to the vertical air stream are presented. The difficulty of the non-singular grid generation for the present triply-connected region has been effectively resolved by the FEM-FDM grid blending technique which requires embedding of finite elements in the small area of major geometrical difficulty. The unsteady streamfunction values are assigned rigorously on the cylinder surfaces and on the far-field boundary. It has been found that the Karman vortex street breaks down behind the double heated cylinders in a transient manner for a certain Richardson number range due to the buoyancy effect and vortex interaction, in contrast to the sudden breakdown applicable to a single heated cylinder.

Interactive vortex shedding from a pair of circular cylinders in a transverse arrangement

AbstractInteractive vortex shedding in the multiply connected domain formed by a pair of circular cylinders is analysed by the FEM–FDM blending technique. The vorticity–streamfunction formulation is used to solve the incompressible Navier–Stokes equations at Re = 100, with the time‐dependent wall streamfunctions determined from the pressure constraint condition and the far‐field streamfunctions from the integral series formula developed earlier by the authors. The standard Galerkin finite element method is used in the relatively small FEM subdomain and the finite difference method based on the general co‐ordinate system in the rest of the flow domain. Symmetric, antisymmetric and asymmetric wake patterns are obtained confirming the earlier experimental findings. The bistable nature of the asymmetric vortex shedding as well as the intermittent drifting from one status to the other between symmetric and antisymmetric wake patterns are reported.

Organization of cortical microtubules and microfibril deposition in response to blue-light-induced apical swelling in a tip-growing Adiantum protonema cell

The arrangements of cortical microtubules (MTs) in a tip-growing protonemal cell of Adiantum capillus-veneris L. and of cellulose microfibrils (MFs) in its wall were examined during blue-light (BL)-induced apical swelling. In most protonemal cells which had been growing in the longitudinal direction under red light, apical swelling was induced within 2 h of the onset of BL irradiation, and swelling continued for at least 8 h. During the longitudinal growth under red light, the arrangement of MFs around the base of the apical hemisphere (the subapical region) was perpendicular to the cell axis, while a random arrangement of MFs was found at the very tip, and a roughly axial arrangement was observed in the cylindrical region of most cells. This orientation of MFs corresponds to that of the cortical MTs reported previously (Murata et al. 1987, Protoplasma 141, 135-138). In cells irradiated with BL, a random rather than transverse arrangement of both MTs and MFs was found in the subapical region. Time-course studies showed that this reorientation occurred within 1 h after the onset of the BL irradiation, i.e. it preceded the change in growth pattern. These results indicate that the orientation of cortical MTs and of cellulose MFs is involved in the regulation of cell diameter in a tip-growing Adiantum protonemal cell.

Cerebellar malformations in prenatally X-irradiated rats: quantitative analysis and detailed description.

Pregnant WKA/Hok rats were exposed to 100 R or 200 R X-irradiation on one of gestation days 16 through 21. Offspring were killed at 60 days of age and the cerebellum was examined. The cerebellum of animals exposed to 200 R was slightly reduced in weight but not in width. The observed reduction in the dorsoventral length of the cerebellum was more evident when the X-irradiation was early in gestation. The anteroposterior length of the hemispheres increased following exposure to X-ray on days 16 through 19, and that of the vermis and paravermis decreased following treatment on days 17 through 21. Therefore, the anterior portions of hemispheres were situated anterior to the culmen in every 200 R group. Somewhat anteroposteriorly and horizontally directed lobules, as opposed to the normal transverse arrangement, were seen in the cerebellum of rats treated on day 16 or 17. Lobule contortion and fragmentation and an increased number of sublobules were striking in cases treated later. Histologically, ectopic Purkinje cells in the granule cell layer and white matter appeared following X-irradiation on day 20 or 21, but they were not found following earlier treatment. In the cerebellum of animals exposed to 100 R the reduction in size was mild and the folial abnormalities were rare, but the number of sublobules decreased.

Stimulated fluorescence and fluorescence quenching in chlorophyll a and bacteriochlorophyll a

This communication deals with the photophysical processes that take place in chlorophyll solutions under intense nitrogen laser irradiation. The effect of the pump photon density on the fluorescence yield depends strongly on the geometry of the irradiation and the sampling set-up. If the fluorescence cell and sampling probe are placed close to the transverse arrangement used for obtaining laser output, line narrowing and gain, which are processes associated with high population inversions and stimulated fluorescence, are observed. A normal fluorescence spectrum and a decrease in fluorescence quantum yield with increasing pump power are observed in the fluorescence cells in oriented at an angle of 20–40° with respect to the transverse axis of the exciting beam. The decrease in quantum yield appears to result from absorption of the pump photons by the excited singlet of the chlorophylls, and it is suggested that an analogous mechanism may be responsible for the anomalous fluorescence quantum yield reported for in in vivo Chlorella vulgaris algae.

Argon laser with wall stabilized transverse discharge

Planar and cylindrical discharges for argon lasers are compared by plasmatheoretical calculations. The maximum laser output power available in the two arrangements is computed in dependence of various parameters neglecting saturation mechanisms. A transverse discharge arrangement confining the positive column by two parallel walls is described and experimental laser threshold values for the current and pressure are reported.

Laser–ion coaxial beams spectrometer

An apparatus has been constructed to provide laser excitation of ion beams in both coaxial and crossed configurations. The coaxial geometry provides very high sensitivity and nearly Doppler-free wavelength resolution for spectroscopic measurements, and allows the use of the Doppler shift to ’’tune’’ the wavelength. A novel transverse quadrupole electric field arrangement is used to deflect the ion beam into and out of the laser beam axis. The ion beam is highly collimated and a high-resolution 180° electrostatic analyzer is used for photofragment energy analysis. The apparatus has demonstrated a resolution of better than 10 meV for normal photofragment spectroscopy and 0.001 meV for coaxial beams photofragment spectroscopy using a single-mode laser. While providing these high resolutions the apparatus has an overall sensitivity several orders of magnitude greater than conventional ones.

Some observations on the higher temperature antiferromagnetic phase of chromium

Experiments with unpolarized neutrons on random domain single crystals are unable to distinguish between a simple spiral model and a transverse sinusoidal spin arrangement for the chromium magnetic structure above the low temperature transition. The polarization of the diffracted beams from the {100} satellite reflections of a chromium single crystal, which had been cooled through the Neel point in a strong magnetic field, have been analysed on a three-crystal polarized beam diffractometer. The observations are inconsistent with the simple spiral model and require for their interpretation a model in which each domain has orthorhombic symmetry with axes parallel to the 100 directions: in particular they are in agreement with the model in which each domain contains two sinusoidal spin arrangements with unequal populations, each oriented along a 100 direction. These inequalities, however, were far smaller (10%) than the inequalities in domain population (2:1) produced by the cooling field. The preferred spin direction within each domain is that 100 direction most nearly perpendicular to the magnetic field direction, whereas the induced domain population appears to be related only to the shape of the specimen.

Spin Arrangement of the High-Temperature Magnetic Phase in Chromium

Experiments with unpolarized neutrons on random domain single crystals are unable to distinguish between a simple spiral model and a transverse sinusoidal spin arrangement for the Cr magnetic structure above the low-temperature transition. Using a Cr single crystal which had been cooled through the Néel point in a strong magnetic field, we analysed the polarization of the diffracted beams from the {100} satellites on the three-crystal polarized beam spectrometer. The polarizations of the reflected beam in the various satellites predicted by the simple spiral model, independent of domain distribution were not observed. On the contrary our observations are consistent with each domain containing two transverse sinusoidal spin arrangements with unequal populations each oriented along a {100} direction. These inequalities, however, were far smaller (≈10%) than the inequalities in domain population (2:1) produced by the cooling field. We also observed that the preferred spin direction was that 〈100〉 direction most nearly perpendicular to the magnetic field direction, whereas the induced domain appeared to be related only to the shape of the specimen.

The fine structure of muscle in a marine turbellarian.

The fine structure of the myofibers of Notoplana acticola as studied by electron microscopy indicates that they are composed of thick myofilaments about 200 A wide with tapering ends and thin myofilaments about 50 A wide, arranged alongside each other parallel to the long axis of the cell. There is no orderly transverse arrangement of filaments; instead they appear staggered in the fiber. In cross sections 6 to 10 thin filaments form an orbit around one thick filament with possible cross-linkage between the two types of filaments.

WALL STRUCTURE AND LATERAL FORMATION IN THE ALGA BRYOPSIS

Green, Paul B. (U. Pennsylvania, Philadelphia.) Wall structure and lateral formation in the alga Bryopsis. Amer. Jour. Bot. 47(6) : 476–481. Illus. 1960.—The large multinucleate cells of Bryopsis pennata regularly produce laterals at the apical tip. Cells were freed of protoplasm and the remaining cell wall was flattened and studied in polarized light and interference microscopes. Both the cylindrical main axis and the cylindrical laterals are negatively birefringent and thus apparently have generally a transverse arrangement of microfibrils. Lateral formation is first seen in the formation of round fields of concentric microfibrils on the main axis which persist as lateral‐bases. The center of a field protrudes, making a small out‐pouching of the main axis. The thin‐walled protrusion increases first mostly in diameter and then in length to make a lateral. There is a definite correlation between wall structure (optical anisotropy) and cell shape in Bryopsis.

Structural characteristics of developing Nitella internodal cell walls.

The Nilella intermodal cell is formed by a division of the segment cell, the latter being a direct derivative of the shoot apical cell. The internodal cell is remarkable in that it elongates from an initial length of about 20 microns to a mature length of about 60 millimeters. The structures of the apical and segment cells, and the internodal cells in all stages of development were examined with the techniques of interference, polarization, and electron microscopy. The apical and segment cells were found to be isotropic. The upper part of the segment cell, destined to form a node, shows a curious pitted structure that was characteristic of certain node structures. The lower part of the segment cell, destined to become an internodal cell, shows a vague transverse arrangement of fibrils at the inner wall surface. The internodal cells, from the time they are first formed, show negative birefringence and a transverse arrangement of microfibrils at the inner wall surface. The elongation of the internodal cell is characterized by a rise, dip, and rise in both the optical thickness and retardation of the cell wall. The dip in both these variables coincides with the attainment of the maximum relative elongation rate. After the cessation of elongation, wall deposition continues, but the fibrils at .the inner surface of the wall are now seen to occur in fields of nearly parallel microfibrils. These fields, with varying fibrillar directions, may partly overlap each other or may merge with one another. Unlike the growing wall, this wall which is deposited after the end of elongation is isotropic.

The fundamental transverse arrangement of cross striae in myofibrils of striated muscle

The Anatomical RecordVolume 100, Issue 1 p. 91-100 Article The fundamental transverse arrangement of cross striae in myofibrils of striated muscle Carl Caskey Speidel, Carl Caskey Speidel School of Anatomy, Department of Medicine, University of Virginia, CharlottesvilleSearch for more papers by this author Carl Caskey Speidel, Carl Caskey Speidel School of Anatomy, Department of Medicine, University of Virginia, CharlottesvilleSearch for more papers by this author First published: January 1948 https://doi.org/10.1002/ar.1091000108Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume100, Issue1January 1948Pages 91-100 RelatedInformation

Passive Movements of Newly Formed Acrogenous Spores in Verticillium and Some Other Genera of the Hyphomycete Fungi

The development of the spores in two species of Verticillium, namely, V. Malthousei Ware and V. psalliotae Treschow, both parasitic on the cultivated mushroom Psalliota sp., was reported by Treschow1to be different. He observed the spores of V. psalliotae lying transversely across the tips of the phialides on which they were developed. He concluded from this observation that the spores, which originated as a minute globule, grew out on either side perpendicular to the long axis of the phialide. He did not observe this transverse arrangement in V. Malthousei Ware, and neither did Ware2 himself. It was, however, recorded in illustrations of this fungus by Atkins and Bulloch3. My own observations from time to time confirmed this record. More recently, I decided to compare the development of the spores in both these species under similar conditions, by continuous observation, using a moist chamber placed on slide cultures.