Hiatal surfaces from the Miocene Globigerina Limestone Formation of Malta: Biostratigraphy, sedimentology, trace fossils and early diagenesis

The Miocene Globigerina Limestone of the Maltese islands contains widespread omission surfaces with very different characteristics and origins. The terminal Lower Globigerina Limestone hardground (TLGLHg) formed during a period of falling sea level. Coccolith assemblages suggest shallowness. Sedimentary structures and trace fossil assemblages, indicate increasing frequency of storm events and erosional episodes, towards the surface. Calcite cementation which took place around Thalassinoides burrows and formed irregular nodules was followed by dissolution of aragonite. It is suggested that lithification was linked to microbial reactions involving organic matter. In contrast two later surfaces, the terminal Middle Globigerina Limestone omissionground (TMGLOg), which marks the Lower to Middle Miocene boundary, and the Fomm-ir-Rih local hardground (FiRLHg) both contain early diagenetic dolomite. Lithification took place in two phases. The dolomite is interpreted to have formed beneath the sea floor: it was subsequently exhumed and partially corroded as the precipitation of calcitic and phosphatic cements took place around burrows open to the circulation of sea water. (C) 2008 Elsevier B.V. All rights reserved.

The timing of eukaryotic evolution: Does a relaxed molecular clock reconcile proteins and fossils?

The use of nucleotide and amino acid sequences allows improved understanding of the timing of evolutionary events of life on earth. Molecular estimates of divergence times are, however, controversial and are generally much more ancient than suggested by the fossil record. The limited number of genes and species explored and pervasive variations in evolutionary rates are the most likely sources of such discrepancies. Here we compared concatenated amino acid sequences of 129 proteins from 36 eukaryotes to determine the divergence times of several major clades, including animals, fungi, plants, and various protists. Due to significant variations in their evolutionary rates, and to handle the uncertainty of the fossil record, we used a Bayesian relaxed molecular clock simultaneously calibrated by six paleontological constraints. We show that, according to 95% credibility intervals, the eukaryotic kingdoms diversified 950-1,259 million years ago (Mya), animals diverged from choanoflagellates 761-957 Mya, and the debated age of the split between protostomes and deuterostomes occurred 642-761 Mya. The divergence times appeared to be robust with respect to prior assumptions and paleontological calibrations. Interestingly, these relaxed clock time estimates are much more recent than those obtained under the assumption of a global molecular clock, yet bilaterian diversification appears to be approximate to100 million years more ancient than the Cambrian boundary.

Predictive computed-torque control of a PUMA 560 manipulator robot

This paper describes the integration of constrained predictive control and computed-torque control, and its application on a six degree-of-freedom PUMA 560 manipulator arm. The real-time implementation was based on SIMULINK, with the predictive controller and the computed-torque control law implemented in the C programming language. The constrained predictive controller solved a quadratic programming problem at every sampling interval, which was as short as 10 ms, using a prediction horizon of 150 steps and an 18th order state space model.

Transputer control of a Puma 560 robot via the virtual bus

The robot control problem is discussed with regard to controller implementation on a multitransputer array. Some high-performance aspects required of such controllers are described, with particular reference to robot force control. The implications for the architecture required for controllers based on computed torque are discussed and an example is described. The idea of treating a transputer array as a virtual bus is put forward for the implementation of fast real-time controllers. An example is given of controlling a Puma 560 industrial robot. Some of the practical considerations for using transputers for such control are described.

The Talking Neanderthals : What do Fossils, Genetics and Archeology Say?

Did Neanderthals have language? This issue has been debated back and forth for decades, without resolution. But in recent years new evidence has become available. New fossils and archeological finds cast light on relevant Neanderthal anatomy and behavior. New DNA evidence, both fossil and modern, provides clues both to the relationship between Neanderthals and Homo sapiens, and to the genetics of language. In this paper, I review and evaluate the available evidence. My conclusion is that the preponderance of the evidence supports the presence of some form of language in Neanderthals.

A quest��o da possibilidade da liberdade na Cr��tica da Raz��o Pura : uma interpreta����o de B 560 e B 586

�� ineg��vel que as passagens B 560 e B 586 da Cr��tica da Raz��o Pura sejam paradoxais. Isso porque, embora Kant tenha afirmado haver uma possibilidade da liberdade na solu����o da terceira antinomia (B 560), de forma aparentemente contradit��ria a esse resultado, alega, numa passagem da nona se����o do segundo cap��tulo do segundo livro da dial��tica transcendental, sequer ter tido o problema de demonstrar a possibilidade daquele conceito. Esse problema, correlato �� dificuldade de compatibilizar- se aquelas passagens, �� a causa motriz do engendramento deste texto dissertativo. Logo, por meio dele, busca-se explicar por que raz��o tais passagens n��o s��o contradit��rias. N��o o s��o, porque a acep����o do termo ���possibilidade��� nelas empregadas �� amb��gua, ou seja, possui mais de um significado. Como veremos, distinguindo o significado dos conceitos de possibilidade a�� envolvidos, pode-se defender uma possibilidade l��gica da id��ia transcendental da liberdade enquanto n��meno. Mas seria tal possibilidade l��gica do conceito da liberdade transcendental um princ��pio regulativo? Que princ��pio regulativo seria ele? Ao se analisar esse segundo problema dissertativo, delimitando-se a segunda quest��o �� rela����o da possibilidade da liberdade com os princ��pios regulativos em seu uso emp��rico, conclui-se que estes conceitos t��m acep����es totalmente distintas. Isso porque, uma vez que eles possuem diferentes fun����es no itiner��rio da raz��o: enquanto um procura deixar em aberto um espa��o num��nico, o outro, abre espa��o para o regresso emp��rico das infer��ncias, a fim de que a raz��o especulativa n��o se atenha indevidamente a um incondicionado ilus��rio.

Alternative interpretations of some earliest ediacaran fossils from China

In a letter to Nature (February, 2011), Xunlai Yuan and collaborators recorded carbon compression fossils from black shales of the Lantian Formation (Ediacaran), southern Anhui Province, South China. The new fossils, described under five morphological types (Types A to E), exhibit degrees of morphological differentiation suggesting that they were multicellular eukaryotes. Some of the Lantian macrofossils were interpreted as algae, but others are of unknown affinities. For reasons noted in this discussion, Type A fossils attracted our particular attention, and we suggest an alternative interpretation of their affinities. According to our view, some of them (at least those with three faces and no globose holdfast at their base) may represent conulariid cnidarians or close medusozoan relatives. The undistorted organism probably was a three-sided cone in life. We believe that our suggested alternative interpretations of the anatomy and affinities of the fossils in question can be useful in guiding future research on the oldest currently known fossil assemblage of multicellular organisms. Copyright �� 2012.