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Search Results: 1 - 10 of 23810 matches for " Paul Sereno "
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Corrigenda: Sereno PC (2012) Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs. ZooKeys 226: 1–225
Paul Sereno
ZooKeys , 2012, DOI: 10.3897/zookeys.227.4091
Abstract:
Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs
Paul Sereno
ZooKeys , 2012, DOI: 10.3897/zookeys.226.2840
Abstract: Heterodontosaurids comprise an important early radiation of small-bodied herbivores that persisted for approximately 100 My from Late Triassic to Early Cretaceous time. Review of available fossils unequivocally establishes Echinodon as a very small-bodied, late-surviving northern heterodontosaurid similar to the other northern genera Fruitadens and Tianyulong. Tianyulong from northern China has unusual skeletal proportions, including a relatively large skull, short forelimb, and long manual digit II. The southern African heterodontosaurid genus Lycorhinus is established as valid, and a new taxon from the same formation is named Pegomastax africanus gen. n., sp. n. Tooth replacement and tooth-to-tooth wear is more common than previously thought among heterodontosaurids, and in Heterodontosaurus the angle of tooth-to-tooth shear is shown to increase markedly during maturation. Long-axis rotation of the lower jaw during occlusion is identified here as the most likely functional mechanism underlying marked tooth wear in mature specimens of Heterodontosaurus. Extensive tooth wear and other evidence suggests that all heterodontosaurids were predominantly or exclusively herbivores. Basal genera such as Echinodon, Fruitadens and Tianyulong with primitive, subtriangular crowns currently are known only from northern landmasses. All other genera except the enigmatic Pisanosaurus have deeper crown proportions and currently are known only from southern landmasses.
Corrigenda: Sereno PC, Larsson HCE (2009) Cretaceous Crocodyliforms from the Sahara. ZooKeys 28: 1–143.
Paul Sereno,Hans Larsson
ZooKeys , 2009, DOI: 10.3897/zookeys.29.368
Abstract:
Cretaceous Crocodyliforms from the Sahara
Paul Sereno,Hans Larsson
ZooKeys , 2009, DOI: 10.3897/zookeys.28.325
Abstract: Diverse crocodyliforms have been discovered in recent years in Cretaceous rocks on southern landmasses formerly composing Gondwana. We report here on six species from the Sahara with an array of trophic adaptations that significantly deepen our current understanding of African crocodyliform diversity during the Cretaceous period. We describe two of these species (Anatosuchus minor, Araripesuchus wegeneri) from nearly complete skulls and partial articulated skeletons from the Lower Cretaceous Elrhaz Formation (Aptian-Albian) of Niger. The remaining four species (Araripesuchus rattoides sp. n., Kaprosuchus saharicus gen. n. sp. n., Laganosuchus thaumastos gen. n. sp. n., Laganosuchus maghrebensis gen. n. sp. n.) come from contemporaneous Upper Cretaceous formations (Cenomanian) in Niger and Morocco.
Inverse Kinematics
Joel Sereno
Undergraduate Journal of Mathematical Modeling : One + Two , 2010, DOI: 10.5038/2326-3652.3.1.18
Abstract: Inverse kinematics is the process of converting a Cartesian point in space into a set of joint angles to more efficiently move the end effector of a robot to a desired orientation. This project investigates the inverse kinematics of a robotic hand with fingers under various scenarios. Assuming the parameters of a provided robot, a general equation for the end effector point was calculated and used to plot the region of space that it can reach. Further, the benefits obtained from the addition of a prismatic joint versus an extra variable angle joint were considered. The results confirmed that having more movable parts, such as prismatic points and changing angles, increases the effective reach of a robotic hand.
Bertilla e Berta: il ruolo di Santa Giulia di Brescia e di San Sisto di Piacenza nel regno di Berengario I Bertilla and Berta: the role of St. Giulia of Brescia and St. Sisto of Piacenza in the reign of Berengar I
Cristina Sereno
Reti Medievali Rivista , 2012, DOI: 10.6092/1593-2214/367
Abstract: Di nessuna delle due mogli di Berengario I – Bertilla, la prima, un’aristocratica di origine supponide e Anna, la seconda, una principessa bizantina – si sono conservate le carte dei dotari. Di entrambe, inoltre, nessuna carta ricorda attività economiche o patrimoniali. Nel contesto familiare di Berengario I emerge però una delle due figlie, Berta, che fu badessa del monastero di San Salvatore di Brescia e poi anche, per nomina paterna, del monastero di San Sisto di Piacenza, fondato pochi decenni prima da Angelberga. Entrambi i monasteri avevano raccolto nei loro patrimoni larghe quote del fisco regio, spesso in prima istanza transitati nei dotari delle regine: le curtes e i monasteri dipendenti erano sparsi in tutta la parte settentrionale della penisola e, in taluni casi, oltrepassavano la linea degli Appennini. Berta appare così assumere presso la corte di Berengario una funzione di grande rilievo nella gestione e nella salvaguardia dei patrimoni di tali monasteri. Of none of the two wives of Berengar I - Bertilla, the first, an aristocratic woman from the Supponids and Anna, the second, a Byzantine princess - have been preserved dower charters; moreover no charter reminds businesses or assets. In the family context of Berengar I emerges, however, one of his two daughters, Berta, who was abbess of the monastery of St. Salvatore in Brescia and later, by his father's appointment, of the monastery of St. Sisto in Piacenza, founded a few decades earlier by Angelberga. Both monasteries were collected in their assets large shares of royal treasury, often in the first instance passed through in doweries of the queens: the curtes and the dependent monasteries were spread across the northern part of the peninsula and, in some cases, they passed the line of the Apennines. It looks like as at the court of Berengar Berta assumes a role of great importance in the management and safeguarding of the assets of these monasteries.
Site of the Institut für Frühmittelalterforschung of Münster University Sito dell’Institut für Frühmittelalterforschung dell’Università di Münster
Cristina Sereno
Reti Medievali Rivista , 2007, DOI: 10.6092/1593-2214/139
Abstract: Review of the Site of the Institut für Frühmittelalterforschung of Münster University Recensione del sito dell’Institut für Frühmittelalterforschung dell’Università di Münster
On aberration in gravitational lensing
M. Sereno
Physics , 2008, DOI: 10.1103/PhysRevD.78.083003
Abstract: It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light-rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild spacetime of the lens, and, then, light-ray detection in the moving observer's frame. Due to the transverse motion images are displaced and distorted in the observer's celestial sphere, whereas the radial velocity along the line of sight causes an effective re-scaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still point-like. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor (1+z_d) with respect to the static case, z_d being the relativistic Doppler shift of the deflector. From the observational point of view, the orbital motion of the Earth can cause potentially observable corrections of the order of the microarcsec in lensing towards the super-massive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of cluster of galaxies bring about a typical flexion in images of background galaxies in the weak lensing regime but future measurements seem to be too much challenging.
On the influence of the cosmological constant on gravitational lensing in small systems
M. Sereno
Physics , 2007, DOI: 10.1103/PhysRevD.77.043004
Abstract: The cosmological constant Lambda affects gravitational lensing phenomena. The contribution of Lambda to the observable angular positions of multiple images and to their amplification and time delay is here computed through a study in the weak deflection limit of the equations of motion in the Schwarzschild-de Sitter metric. Due to Lambda the unresolved images are slightly demagnified, the radius of the Einstein ring decreases and the time delay increases. The effect is however negligible for near lenses. In the case of null cosmological constant, we provide some updated results on lensing by a Schwarzschild black hole.
The role of Lambda in the cosmological lens equation
M. Sereno
Physics , 2008, DOI: 10.1103/PhysRevLett.102.021301
Abstract: The cosmological constant Lambda affects cosmological gravitational lensing. Effects due to Lambda can be studied in the framework of the Schwarzschild-de Sitter spacetime. Two novel contributions, which can not be accounted for by a proper use of angular diameter distances, are derived. First, a term 2m b Lambda/3 has to be added to the bending angle, where "m" is the lens mass and "b" the impact parameter. Second, Lambda brings about a difference in the redshifts of multiple images. Both effects are quite small for real astrophysical systems (contribution to the bending < 0.1 microarcsec and difference in redshift < 10^{-7}).
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