Some “laws” of gastropod shell form

Paleobiology ◽  
1977 ◽  
Vol 3 (2) ◽  
pp. 196-206 ◽  
Author(s):  
Robert M. Linsley
Keyword(s):  
Center Of Mass ◽  
Mantle Cavity ◽  
Center Of Gravity ◽  
The Body ◽  
Water Current ◽  
Gastropod Shell ◽  
Shell Form ◽  
Body Whorl ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

Five generalizations derived from the shell form of prosobranch gastropods are developed. (1) A univalve of more than one volution whose aperture lies in a plane that passes through the axis of coiling does not live with the aperture parallel to the substrate. (2) A univalve of more than one volution whose aperture lies in a plane that is tangential to the body whorl does live with the plane of the aperture parallel to the substrate. (3) Gastropods with tangential apertures, when extended, support the shell so that the center of mass of the shell and its contents is over the midline of the cephalopedal mass; this balancing of the shell may be accomplished either by regulatory detorsion, by inclination or by a combination thereof, to keep the center of gravity of the shell as low as possible. (4) Angulations or re-entrants in the gastropod aperture are usually indicative of inhalent or exhalent areas; inhalent areas are directed as far anteriorly as possible. (5) Gastropods having elongated apertures possess only a single gill and develop a water current through the mantle cavity from anterior to posterior along the long axis of the aperture; this axis is subparallel to the anterior-posterior axis of the foot.These generalizations are then used as the basis for some deductive interpretations of behavioral modes of Paleozoic Gastropoda.

Ultrabithorax is a regulator of beta 3 tubulin expression in the Drosophila visceral mesoderm

Development ◽  
1992 ◽  
Vol 116 (3) ◽  
pp. 543-554 ◽  
Author(s):  
U. Hinz ◽  
A. Wolk ◽  
R. Renkawitz-Pohl
Keyword(s):  
Developmental Stages ◽  
Regulatory Elements ◽  
The Body ◽  
Homeotic Genes ◽  
Tubulin Gene ◽  
Enhancer Element ◽  
Visceral Mesoderm ◽  
Early Action ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

beta 3 tubulin expression accompanies the specification and differentiation of the Drosophila mesoderm. The genetic programs involved in these processes are largely unknown. Our previous studies on the regulation of the beta 3 tubulin gene have shown that upstream sequences guide the expression in the somatic musculature, while regulatory elements in the first intron are necessary for expression in the visceral musculature. To further analyse this mode of regulation, which reflects an early embryonic specification program, we undertook a more detailed analysis of the regulatory capabilities of the intron. The results reveal not only a certain degree of redundancy in the cis-acting elements, which act at different developmental stages in the same mesodermal derivatives, but they also demonstrate in the visceral mesoderm, which forms a continuous epithelium along the body axis of the embryo, an early action of regulators guiding gene expression along the anterior-posterior axis of the embryo: an enhancer element in the intron leads to expression in a subdomain restricted along the anterior-posterior axis. This pattern is altered in mutants in the homeotic gene Ultrabithorax (Ubx), whereas ectopic Ubx expression leads to activity of the enhancer in the entire visceral mesoderm. So this element is likely to be a target of homeotic genes, which would define the beta 3 tubulin gene as a realisator gene under the control of selector genes.

scholarly journals System of differential equations of aircraft spatial motion dynamics with arbitrary tensor of inertia and center of gravity position

2021 ◽  
Vol 20 (2) ◽  
pp. 7-18
Author(s):  
D. V. Vereshchikov
Keyword(s):  
Differential Equations ◽  
Center Of Mass ◽  
Center Of Gravity ◽  
The Body ◽  
Spatial Motion ◽  
System Of Differential Equations ◽  
Aircraft Flight ◽  
Analytic Expressions ◽  
Tensor Of Inertia ◽  
Arbitrary Tensor

Derivation of analytic expressions making up the basis of a mathematical model of aircraft flight dynamics for the differential equations describing the change in the rate of roll, yaw and pitch, as well as flight velocity components in projections on the body-fixed coordinate axes is presented. The origin of the coordinate system does not in general coincide with the center of mass of the plane, and the axes are not the same as its main central axes of inertia. The differential equations for angular and linear velocities are reduced to the form convenient for the use of numerical methods and computer systems and make it possible to get consistent results of simulating the dynamics of aircraft spatial motion with an arbitrary tensor of inertia and center of gravity position.

The Role of Ankle Plantarflexors in Maintaining Dynamic Balance During Human Walking

2012 ◽  
Author(s):  
Richard R. Neptune ◽  
Craig P. McGowan ◽  
Allison L. Hall
Keyword(s):  
Angular Momentum ◽  
Dynamic Balance ◽  
Center Of Mass ◽  
The Body ◽  
Whole Body ◽  
Human Walking ◽  
Ground Reaction Forces ◽  
Reaction Forces ◽  
Anterior Posterior

The regulation of whole-body angular momentum is essential for maintaining dynamic balance during human walking and appears to be tightly controlled during normal and pathological movement (e.g., [1, 2]). The primary mechanism to regulate angular momentum is muscle force generation, which accelerates the body segments and generates ground reaction forces that alter angular momentum about the body’s center-of-mass to restore and maintain dynamic balance. Previous modeling studies have shown the ankle plantarflexors are important contributors to the anterior/posterior, vertical and medial/lateral ground reaction forces during human walking [3, 4], and therefore appear critical to regulating angular momentum and maintaining dynamic balance during walking.

On the motion of bodies based on changes in the kinetic moment

2019 ◽  
Vol 20 (4) ◽  
pp. 267-275
Author(s):  
Yury N. Razoumny ◽  
Sergei A. Kupreev
Keyword(s):  
Center Of Mass ◽  
Stellar Dynamics ◽  
Elementary Particles ◽  
The Body ◽  
Accelerated Motion ◽  
Indirect Confirmation ◽  
Physical Principles ◽  
Two Bodies ◽  
Central Gravitational Field ◽  
Kinetic Moment

The controlled motion of a body in a central gravitational field without mass flow is considered. The possibility of moving the body in the radial direction from the center of attraction due to changes in the kinetic moment relative to the center of mass of the body is shown. A scheme for moving the body using a system of flywheels located in the same plane in near-circular orbits with different heights is proposed. The use of the spin of elementary particles is considered as flywheels. It is proved that using the spin of elementary particles with a Compton wavelength exceeding the distance to the attracting center is energetically more profitable than using the momentum of these particles to move the body. The calculation of motion using hypothetical particles (gravitons) is presented. A hypothesis has been put forward about the radiation of bodies during accelerated motion, which finds indirect confirmation in stellar dynamics and in an experiment with the fall of two bodies in a vacuum. The results can be used in experiments to search for elementary particles with low energy, explain cosmic phenomena and to develop transport objects on new physical principles.

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