Search results for "Oblate spheroid"
showing 10 items of 16 documents
Computational Fluid Dynamics Suggests Ecological Diversification among Stem-Gnathostomes.
2020
Summary The evolutionary assembly of the vertebrate bodyplan has been characterized as a long-term ecological trend toward increasingly active and predatory lifestyles, culminating in jawed vertebrates that dominate modern vertebrate biodiversity [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. This contrast is no more stark than between the earliest jawed vertebrates and their immediate relatives, the extinct jawless, dermal armor-encased osteostracans, which have conventionally been interpreted as benthic mud-grubbers with poor swimming capabilities and low maneuverability [ 9 , 10 , 11 , 12 ]. Using computational fluid dynamics, we show that osteostracan headshield morphology is compatible with a dive…
Types of Motion in the Oblate Planet Problem
1985
We consider a mass point in the gravitational field of an oblate planet and in a meridianal plane. The Hamiltonian of the problem is: $$ \frac{1}{2}\left( {p_r^2 + \frac{{p_{\theta }^2}}{{{r^2}}}} \right) - \frac{1}{r} - \frac{\varepsilon }{{{r^3}}}\left( {1 - 3{{\sin }^2}\theta } \right) $$ .
A code to evaluate prolate and oblate spheroidal harmonics
1998
Abstract We present a code to evaluate prolate ( P n m ( x ), Q n m ( x ); n ≥ m , x > 1) and oblate ( P n m ( ix ), Q n m ( ix ); n ≥ m , x > 0) spheroidal harmonics, that is, spherical harmonics ( n and m integers) for real arguments larger than one and for purely imaginary arguments. We start from the known values (in closed form) of P m m and P m +1 m and we apply the forward recurrence relation over n up to a given degree n = N Max . The Wronskian relating P 's and Q 's, together with the evaluation of the continued fraction for Q m+N staggeredMax m / Q m+N staggeredMax -1 m , allows the calculation of Q m+N staggeredMax m and Q m+N staggeredMax -1 m . Backward recurrence is then appli…
Investigation of E0 Transition in 74Kr
2000
The N = Z+2 nucleus 74Kr has been investigated by in-beam conversion electron (CE) and γ ray spectroscopy. The electric-monopole (E0) decay was examined in order to confirm the evidence for a low-lying isomeric 0+2 state and to give insight into the mixing between the predicted coexisting prolate and oblate shapes.
Potential and energy of oblate spheroidal charge distributions
1989
Abstract The Poisson equation for a large class of charge distributions contained within oblate spheroids in solved and their energies are obtained. In many cases, the potential and the energy can be found by comparison with the solutions of the Poisson equation for prolate spheroidal charge distributions obtained in preceding works. The limits of validity of this comparison procedure are established. For the simplest cases the electrostatic energy is computed and, after suitable normalization, displayed graphically.
Lifetimes of intruder states in 186Pb, 188Pb and 194Po
2008
Abstract Lifetimes of prolate intruder states in 186Pb and 188Pb and oblate intruder states in 194Po have been determined through recoil distance Doppler-shift lifetime measurements. Deformation parameters of | β 2 | = 0.29 ( 5 ) and | β 2 | = 0.17(3) have been extracted from experimental B ( E 2 ) values for the prolate and the oblate bands, respectively. The present study addresses the phenomenon of shape coexistence typical for the nuclei near Z = 82 and N = 104 , providing information on configuration mixing of intrinsic structures of the nuclei of interest. The results are compared with the available lifetime data and theoretical results for neutron-deficient Po, Pb, Hg and Pt nuclei. …
High-spin study of neutron-deficient $^{114}$Xe
2000
Abstract High-spin states have been populated in 114 54 Xe via the 58 Ni( 58 Ni, 2p) reaction at 210 MeV, using the Jurosphere γ -ray spectrometer to record γ -ray coincidences. The known level scheme has been significantly extended and includes two positive-parity and three negative-parity structures. At the highest spins, one of the negative-parity bands becomes yrast and shows the characteristics of a smoothly terminating band. Quadrupole moments for two of the bands at high spin have been estimated through a Doppler-broadened lineshape analysis; the terminating band has a reduced quadrupole moment implying that it is not far from full termination into a noncollective oblate state. Extra…
Collision orbits in the oblate planet problem
1984
Some of the properties of the oblate planet problem are derived. We use the technique of blowing up the singularity to study the collision orbits. We define some families of them in terms of their asymptotic behavior.
Transition from Prolate to Oblate to Triaxial Shapes in158Yb
1983
The decay of the entry states in ISIYb populated in the reactions of 149 MeV ,oNe with ,44Nd and lUNd has been investigated with a 4" multidetector system gated by a Ge counter. The average excitation energy, the ,.-ray spectra and the angular distribu tions as a function of multiplicity show several changes in the ,.-ray decay. These changes suggest a transition from prolate to particle aligned oblate connguration at low spin. At 1- 38-48 collective transitions with dipole and quad rupole component possibly built on high K single particle states are observed. Furthennore, above 1- 48 the dipole component disappears suggesting a further change toward more triaxial shape.
Prolate yrast cascade in183Tl
2000
The yrast sequence in ${}^{183}\mathrm{Tl}$ has been studied for the first time in recoil-mass selected \ensuremath{\gamma}-ray spectroscopic measurements. A rotational-like cascade of seven transitions is established down to the band head with probable spin and parity ${(13/2}^{+}).$ Unlike in the adjacent odd-mass Tl nuclei, prompt \ensuremath{\gamma} decay from the yrast band to a lower lying weakly deformed (oblate) structure is not observed. These features are consistent with the predicted drop of the prolate band head in ${}^{183}\mathrm{Tl}$ compared to ${}^{185}\mathrm{Tl}.$ The implications for the prolate energy minimum in odd-mass Tl nuclei at the neutron ${i}_{13/2}$ midshell $(…