The tiered retina of Dytiscus : a new type of compound eye

1970 ◽  
Vol 175 (1038) ◽  
pp. 83-94 ◽  
Keyword(s):  
Compound Eye ◽  
Electrical Coupling ◽  
Polarized Light ◽  
Light Sensitivity ◽  
Sectional Area ◽  
Cross Sectional ◽  
Light Passing ◽  
Small Fields ◽  
New Type ◽  
Different Levels

The retina of Dytiscus is tiered, with proximal and distal layers of receptors at different levels. Photoreceptor units of the proximal retina of the eye of Dytiscus have fields of view so wide that light entering by any facet is able to excite a receptor belonging virtually to any ommatidium in the light- or dark-adapted eye. Although the distal rhabdomeres may have small fields of view, the proximal retina is clearly not adapted for perception of form or movement. The sensitivity of proximal retinula units is compatible with the observations that light passing through many facets sums upon them and that their rhabdomeres are relatively large and jointly occupy the whole cross-sectional area of the eye. The lack of polarized light sensitivity of the proximal retinula units can be attributed to electrical coupling between cells with tubules oriented in different directions within each ommatidium.

scholarly journals MARCADORES ANATÔMICOS DO PECÍOLO E A TOLERÂNCIA À SECA DE PONTEIROS E AO DÉFICIT HÍDRICO EM EUCALIPTO

Nativa ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 591-596
Author(s):  
Samyra Alves Condé ◽  
Edgard Augusto de Toledo Picoli ◽  
Thais Roseli Corrêa ◽  
Rodrigo Dal Sasso Lourenço
Keyword(s):  
Water Stress ◽  
Vascular Tissue ◽  
Relevant Information ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Physiological Disorder ◽  
Cross Sectional ◽  
Water Nutrients ◽  
Different Levels ◽  
Selection Of

A seca de ponteiros em Eucalipto é um distúrbio fisiológico, onde o estresse hídrico vem sendo associado como um dos fatores intensificadores de sua ocorrência. A seleção precoce de genótipos de eucalipto tolerantes a essas condições, podem fornecer informações relevantes quanto a esse distúrbio. Objetivou-se avaliar possíveis marcadores anatômicos, associados a tolerância ao déficit hídrico e à seca de ponteiros. Genótipos comerciais com diferentes graus de suscetibilidade a seca de ponteiros foram submetidos a diferentes níveis de estresse hídrico em condições de casa de vegetação. A duração do experimento foi de 75 dias. Amostras de pecíolos foram coletadas e avaliadas as características das áreas anatômicas de: seção transversal, tecido vascular, xilema, floema e do córtex. Os dados foram submetidos à análise da variância (ANOVA) e para comparação de médias foi adotado o teste Tukey (p<0,05). Os resultados mostraram que há a tendência de redução de todas as variáveis avaliadas com o aumento do déficit hídrico. Entretanto, o genótipo tolerante em condições de maior restrição hídrica apresenta maior área de seção transversal e de tecidos condutores em comparação ao suscetível. A maior proporção destes tecidos sugere que o clone tolerante apresenta condição mais favorável ao transporte de água, fotoassimilados e nutrientes. Palavras-chave: melhoramento florestal; silvicultura; seleção genômica.   ANATOMICAL MARKERS OF PETIOLE AND TOLERANCE TO DIE-BACK AND WATER STRESS IN EUCALYPTUS   ABSTRACT: Die-Back in Eucalyptus is a physiological disorder where the water stress has been associated as an intensifier of this occurrence. The early selection of tolerant Eucalyptus genotypes to water stress can provide relevant information to this disorder. The research aimed to evaluate possible anatomical markers associated with tolerance to water stress and Die-Back. Commercial genotypes with different levels of susceptibility to this disorder were submitted to different levels of water stress in a greenhouse condition. The experiment lasted 75 days. Petioles samples were collected and anatomical characteristics were evaluated: cross-sectional area, area of vascular tissue, xylem area, phloem area and cortical area. The data were submitted to analysis of variance (ANOVA) and for the comparison of means was adopted Tukey test (p <0.05). The results show us that there is a tendency to reduce all variables with increasing water deficit. However, the tolerant genotype in higher water stress conditions has greater cross-sectional area and conducting tissues compared to susceptible genotype. The major proportion of these tissues suggests that the tolerant clone presents more favorable condition for transport of water, nutrients and assimilates. Keywords: forest improvement; forestry; genomic selection.

Variable Inertia Damper Using MR Fluid

2016 ◽  
Author(s):  
Taichi Matsuoka ◽  
Kazuhiko Hiramoto ◽  
Katsuaki Sunakoda ◽  
Naoto Abe
Keyword(s):  
Dynamic Property ◽  
Cross Sectional Area ◽  
Experimental Results ◽  
Moving Mass ◽  
Inertia Effect ◽  
Sectional Area ◽  
Cross Sectional ◽  
Mr Fluid ◽  
Damping Effect ◽  
New Type

Inertia damper has an inertia effect by a flywheel which is caused by a quick moving mass. In general, it is difficult to change the inertia mass physically. In order to obtain a variable inertia effect, a new type of inertia damper has a long bypass pipe is proposed in this paper. This type of damper generates a damping effect and inertia effect by the fluid. It is noted that the inertia effect is depended on a density of the fluid, cross sectional areas of cylinder and bypass pipe, and length of the bypass pipe. If the diameter of the bypass pipe can be controlled, it means that a cross sectional area of the bypass pipe can be switched by clustering particles of MR fluid under magnetization, the inertia effect might be artificially controllable. A trial damper with several electromagnets installed along the long bypass pipe is manufactured, and dynamic property is measured when MR fluid inside the bypass pipe is magnetized by the electromagnets. From experimental results, it seems to be that the inertia effect can be switched and depended on amplitude of magnetization. Finally, the calculated results are theoretically approached, and compared with the experimental results.

Preventing disproportionate displacements in an annular crossed cable-truss structure

2017 ◽  
Vol 32 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Renjie Liu ◽  
Suduo Xue ◽  
Xiongyan Li ◽  
Marijke Mollaert ◽  
Guojun Sun
Keyword(s):  
Internal Force ◽  
Cross Sectional Area ◽  
Truss Structure ◽  
Structural Members ◽  
Sectional Area ◽  
Cross Sectional ◽  
New Type ◽  
Structure Formula ◽  
The Cross ◽  
Dynamic Amplification

Disproportionate displacements in prestressed mechanisms raise concerns widely. Component rupture can result in disproportionate displacements of a major part of prestressed mechanisms. In general, increasing the cross-sectional area of structural members will be of little effect to prevent this kind of failure. A new type of prestressed mechanism named annular crossed cable-truss structure has been proposed. The new configuration shows advantages in preventing disproportionate displacements. An annular crossed cable-truss structure [Formula: see text] is analyzed to evaluate the effect of the sudden rupture of a connection through the instantaneous component removal of the elements linked to it, using ANSYS/LS-DYNA. It is illustrated by the simulations that disproportionate displacements do not occur. Increasing the cross-sectional area of structural members with an appropriate amount can be an effective way to postpone failure of the structural members in which the axial force increases due to internal force redistribution and dynamic amplification effect. Hence, it can be concluded that the annular crossed cable-truss structure has an excellent performance with respect to hazards causing individual connections to fail.

scholarly journals Tracheal Hypertrophy in Mealworms: Design and Plasticity in Oxygen Supply Systems

1989 ◽  
Vol 147 (1) ◽  
pp. 217-235 ◽  
Author(s):  
CATHERINE LOUDON
Keyword(s):  
Total Pressure ◽  
Oxygen Supply ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Tracheal System ◽  
Primary Mechanism ◽  
Ambient Oxygen ◽  
Supply Systems ◽  
Different Levels

Larval Tenebrio molitor L. (Insecta) were reared in three different levels of oxygen: 21 % (normal), 15 % and 10.5 %, all at 101.3 kPa (=1 atm) total pressure (remainder nitrogen). Some larvae were transferred from one oxygen level to another during development. The main tracheae (branching off from the spiracular tracheae) were of greater cross-sectional area in lower ambient oxygen. Compared to larvae of the same body mass reared in 21 % oxygen, larvae reared in 15 % oxygen had main tracheae 40% larger in cross-sectional area on average, and larvae in 10.5% oxygen had main tracheae 120% larger. This hypertrophy is not consistent with the widely accepted hypothesis that tracheae contribute an insignificant resistance to the net movement of oxygen in insect tracheal systems. The magnitude of the hypertrophy is consistent with predictions from Fick's law of diffusion and with the hypothesis that diffusion is the primary mechanism for oxygen movement in the larval tracheal system of holometabolous insects.

Computer Reconstruction of the Cellular Architecture of the Daphnia Magna Optic Ganglion

1975 ◽  
Vol 33 ◽  
pp. 284-285
Author(s):  
E. R. Macagno ◽  
C. Levinthal
Keyword(s):  
Daphnia Magna ◽  
Genetic Background ◽  
Compound Eye ◽  
Synaptic Connectivity ◽  
Serial Sections ◽  
Cross Sectional ◽  
Small Crustacean ◽  
Optic Ganglion ◽  
Structural Invariance ◽  
High Degree

The optic ganglion of Daphnia Magna, a small crustacean that reproduces parthenogenetically contains about three hundred neurons: 110 neurons in the Lamina or anterior region and about 190 neurons in the Medulla or posterior region. The ganglion lies in the midplane of the organism and shows a high degree of left-right symmetry in its structures. The Lamina neurons form the first projection of the visual output from 176 retinula cells in the compound eye. In order to answer questions about structural invariance under constant genetic background, we have begun to reconstruct in detail the morphology and synaptic connectivity of various neurons in this ganglion from electron micrographs of serial sections (1). The ganglion is sectioned in a dorso-ventra1 direction so as to minimize the cross-sectional area photographed in each section. This area is about 60 μm x 120 μm, and hence most of the ganglion fit in a single 70 mm micrograph at the lowest magnification (685x) available on our Zeiss EM9-S.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

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