Tissue proportions and enamel thickness distribution in the early Middle Pleistocene human deciduous molars from Tighenif, Algeria

2010 ◽  
Vol 9 (6-7) ◽  
pp. 341-348 ◽  
Author(s):  
Clément Zanolli ◽  
Priscilla Bayle ◽  
Roberto Macchiarelli
PLoS ONE ◽  
2020 ◽  
Vol 15 (6) ◽  
pp. e0233281
Author(s):  
Laura Martín-Francés ◽  
María Martinón-Torres ◽  
Marina Martínez de Pinillos ◽  
Cecilia García-Campos ◽  
Clément Zanolli ◽  
...  

2019 ◽  
Vol 91 (4) ◽  
pp. 365-384
Author(s):  
Keegan R. Selig ◽  
Sergi López-Torres ◽  
Adam Hartstone-Rose ◽  
Leanne T. Nash ◽  
Anne M. Burrows ◽  
...  

2018 ◽  
Vol 322 (3) ◽  
pp. 268-284 ◽  
Author(s):  
M.V. Golovachev ◽  
V.V. Titov

The remains of teeth of different generations and jaws of the mammoth Mammuthus intermedius from the type localities of the Khazar faunal complex Cherniy Yar / Nizhnee Zaimische (late Middle Pleistocene – early Late Pleistocene, Lower Volga Region, Astrakhan Province, Russia) are described. The specimens are stored in the collection of the Astrakhan Museum-Reserve. Teeth M3 / m3 of this elephant consist, on average, of 22–24 enamel plates, with a lamellar frequency of 7.5–7.7 per 10 cm, and an enamel thickness of 1.8–1.9 mm. This species, described from the similar age deposits of Western Europe, appeared to be widely distributed in Eurasia during the period of the Saalian and the Eemian periods. The comparative analysis showed a marked difference between the teeth of this taxon from the same of M. trogontherii from Sussenborn (Germany), Tiraspol (Transnistria) and Kagalnik sand pit (Northeast Sea of Azov Region, Russia), the M. trogontherii chosaricus holotype by lamellar frequency, the length of single plate, enamel thickness and the total number of plates. The same differences were also revealed from Late Pleistocene woolly mammoths from Taimyr and Yakutia, including the neotype of M. primigenius primigenius. The similarity of the examined teeth from the collection of the Astrakhan Museum-Reserve to the teeth of M. intermedius from Western and Eastern Europe and Western Siberia was detected. M. intermedius, probably, was the most mass species of elephants of this period and occupied steppe biotopes. Less numerous M. trogontherii chosaricus and Palaeoloxodon antiquus with which it co-existed may have been the inhabitants of more forested landscapes.


2019 ◽  
Vol 115 (9/10) ◽  
Author(s):  
Bontle Mataboge ◽  
Amélie Beaudet ◽  
Jason L. Heaton ◽  
Travis R. Pickering ◽  
Dominic Stratford

The site of the Sterkfontein Caves, South Africa, is one of the richest early hominin fossil-bearing sites in Africa. Recent excavations in the Milner Hall locality have contributed to the discovery of new hominin specimens, including StW 669, a right permanent maxillary first molar (M1). StW 669 was excavated from the T1 deposits, which consist of a mixture of sediments from Members 2 and 5 of the Sterkfontein Formation. Accordingly, the deposits have the potential to contain remains of Australopithecus, Paranthropus and Homo. In this study, we employed micro-focus X-ray tomography in order to assess dental tissue proportions, enamel thickness distribution and enamel-dentine junction morphology as approaches to investigate the taxonomy of StW 669. We compare our results to those generated on the teeth of Australopithecus africanus, Paranthropus robustus, Homo erectus, Homo antecessor, Homo neanderthalensis and Homo sapiens. Our results suggest that StW 669 shares quantitative and qualitative affinities with M1s of Homo in terms of tissue proportions (i.e. two- and three-dimensional average and relative enamel thickness of 1.2–1.3 mm and 18.4, respectively) and enamel thickness distribution (i.e. thickest enamel on the lingual aspect of the protocone). However, data on the enamel-dentine junction morphology of StW 669 are inconclusive as to the tooth’s taxonomic affinities. Pending additional morphometric analyses, our studies of inner morphology of the crown of StW 669 support its attribution to Homo.


Author(s):  
Keinosuke Kobayashi

Equidensitometry as developed by E. Lau and W. Krug has been little used in the analysis of ordinary electron photomicrographs, yet its application to the high voltage electron images proves merits of this procedure. Proper sets (families) of equidensities as shown in the next page are able to reveal the contour map of mass thickness distribution in thick noncrystalline specimens. The change in density of the electron micrograph is directly related to the mass thickness of corresponding area in the specimen, because of the linear response of photographic emulsions to electrons and the logarithmic relation between electron opacity and mass thickness of amorphous object.This linearity is verified by equidensitometry of a spherical solid object as shown in Fig. 1a. The object is a large (1 μ) homogeneous particle of polystyrene. Fig. 1b is a composite print of three equidensities of the 1st order prepared from Fig. 1a.


Author(s):  
J. V. Muruga Lal Jeyan ◽  
Akhila Rupesh ◽  
Jency Lal

The aerodynamic module combines the three-dimensional nonlinear lifting surface theory approach, which provides the effective propagated incident velocity and angle of attack at the blade section separately, and a two-dimensional panel method for steady axisymmetric and non-symmetric flow has to be involved to obtain the 3D pressure and velocity distribution on the wind mill model blade. Wind mill and turbines have become an economically competitive form of efficiency and renewable work generation. In the abroad analytical studies, the wind turbine blades to be the target of technological improvements by the use of highly possible systematic , aerodynamic and design, material analysis, fabrication and testing. Wind energy is a peculiar form of reduced form of density source of power. To make wind power feasible, it is important to optimize the efficiency of converting wind energy into productivity source. Among the different aspects involved, rotor aerodynamics is a key determinant for achieving this goal. There is a tradeoff between thin airfoil and structural efficiency. Both of which have a strong impact on the cost of work generated. Hence the design and analysis process for optimum design requires determining the load factor, pressure and velocity impact and optimum thickness distribution by finding the effect of blade shape by varying thickness on the basis of both the aerodynamic output and the structural weight.


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