Arthur José Vieira Porto

The Evolution of Modularity in the Mammalian Skull II: Evolutionary Consequences

Changes in patterns and magnitudes of integration may influence the ability of a species to respond to selection. Consequently, modularity has often been linked to the concept of evolvability, but their relationship has rarely been tested empirically. One possible explanation is the lack of analytical tools to compare patterns and magnitudes of integration among diverse groups that explicitly relate these aspects to the quantitative genetics framework. We apply such framework here using the multivariate response to selection equation to simulate the evolutionary behavior of several mammalian orders in terms of their flexibility, evolvability and constraints in the skull. We interpreted these simulation results in light of the integration patterns and magnitudes of the same mammalian groups, described in a companion paper. We found that larger magnitudes of integration were associated with a blur of the modules in the skull and to larger portions of the total variation explained by size variation, which in turn can exert a strong evolutionary constraint, thus decreasing the evolutionary flexibility. Conversely, lower overall magnitudes of integration were associated with distinct modules in the skull, to smaller fraction of the total variation associated with size and, consequently, to weaker constraints and more evolutionary flexibility. Flexibility and constraints are, therefore, two sides of the same coin and we found them to be quite variable among mammals. Neither the overall magnitude of morphological integration, the modularity itself, nor its consequences in terms of constraints and flexibility, were associated with absolute size of the organisms, but were strongly associated with the proportion of the total variation in skull morphology captured by size. Therefore, the history of the mammalian skull is marked by a trade-off between modularity and evolvability. Our data provide evidence that, despite the stasis in integration patterns, the plasticity in the magnitude of integration in the skull had important consequences in terms of evolutionary flexibility of the mammalian lineages.

Virtual manufacturing as a way for the factory of the future

Virtual Manufacturing represents the emerging approach the enterprises can use to improve their processes, introducing new products more quickly in the market in a cost effective way. The fundamental idea is to create an integrated and synthetic environment, composed of software tools and systems such as Virtual Reality and Simulation to support such processes. This paper presents the Virtual Manufacturing (VM) environment, highlighting the potential application areas and the resulting benefits. The role of Simulation Lab and ITIA-CNR in applying the VM is discussed, the research activities currently carried out by the institutes are presented and two significant cases developed as example of the applicability of the concept are shown.

Covariance structure in the skull of Catarrhini: a case of pattern stasis and magnitude evolution.

The study of the genetic variance/covariance matrix (G-matrix) is a recent and fruitful approach in evolutionary biology, providing a window of investigating for the evolution of complex characters. Although G-matrix studies were originally conducted for microevolutionary timescales, they could be extrapolated to macroevolution as long as the G-matrix remains relatively constant, or proportional, along the period of interest. A promising approach to investigating the constancy of G-matrices is to compare their phenotypic counterparts (P-matrices) in a large group of related species; if significant similarity is found among several taxa, it is very likely that the underlying G-matrices are also equivalent. Here we study the similarity of covariance and correlation structure in a broad sample of Old World monkeys and apes (Catarrhini). We made phylogenetically structured comparisons of correlation and covariance matrices derived from 39 skull traits, ranging from between species to the superfamily level. We also compared the overall magnitude of integration between skull traits (r2) for all Catarrhini genera. Our results show that P-matrices were not strictly constant among catarrhines, but the amount of divergence observed among taxa was generally low. There was significant and positive correlation between the amount of divergence in correlation and covariance patterns among the 30 genera and their phylogenetic distances derived from a recently proposed phylogenetic hypothesis. Our data demonstrate that the P-matrices remained relatively similar along the evolutionary history of catarrhines, and comparisons with the G-matrix available for a New World monkey genus (Saguinus) suggests that the same holds for all anthropoids. The magnitude of integration, in contrast, varied considerably among genera, indicating that evolution of the magnitude, rather than the pattern of inter-trait correlations, might have played an important role in the diversification of the catarrhine skull.

Analysis of Open CNC Architecture for Machine Tools

The evolution of digital circuit technology, leadind to higher speeds and more reliability allowed the development of machine controllers adapted to new production systems (e.g., Flexible Manufacturing Systems - FMS). Most of the controllers are developed in agreement with the CNC technology of the correspondent machine tool manufacturer. Any alterations or adaptation of their components are not easy to be implemented. The machine designers face up hardware and software restrictions such as lack of interaction among systems elements and impossibility of adding new function. This is due to hardware incompatibility and to software not allowing alterations in the source program. The introduction of open architecture philosophy propitiated the evolution of a new generation of numeric controllers. This brought the conventional CNC technology to the standard IBM - PC microcomputer. As a consequence, the characteristics of the CNC (positioning) and the microcomputer (easy of programming, system configuration, network communication etc) are combined. Some researchers have addressed a flexible structure of software and hardware allowing changes in the hardware basic configuration and all control software levels. In this work, the development of open architecture controllers in the OSACA, OMAC, HOAM-CNC and OSEC architectures is described.

SIZE VARIATION, GROWTH STRATEGIES, AND THE EVOLUTION OF MODULARITY IN THE MAMMALIAN SKULL

Allometry is a major determinant of within‐population patterns of association among traits and, therefore, a major component of morphological integration studies. Even so, the influence of size variation over evolutionary change has been largely unappreciated. Here, we explore the interplay between allometric size variation, modularity, and life‐history strategies in the skull from representatives of 35 mammalian families. We start by removing size variation from within‐species data and analyzing its influence on integration magnitudes, modularity patterns, and responses to selection. We also carry out a simulation in which we artificially alter the influence of size variation in within‐taxa matrices. Finally, we explore the relationship between size variation and different growth strategies. We demonstrate that a large portion of the evolution of modularity in the mammalian skull is associated to the evolution of growth strategies. Lineages with highly altricial neonates have adult variation patterns dominated by size variation, leading to high correlations among traits regardless of any underlying modular process and impacting directly their potential to respond to selection. Greater influence of size variation is associated to larger intermodule correlations, less individualized modules, and less flexible responses to natural selection.

Ductile and brittle modes in single-point-diamond-turning of silicon probed by Raman scattering

In recent years, considerable progress has been made on the study of the machinability of fragile materials as crystalline semiconductors because of the demand for faster fabrication processes of complex surface shapes for optoelectronic applications. The most-studied machined semiconductors are silicon and germanium [1– 3]. Some studies indicate that ductility could be related to the high-pressure metallization (brittle-to-ductile) transformation that occurs when these materials are subjected to high hydrostatic pressures [4–7]. Because of this, most of the studies reported previously are devoted mainly to microindented or microcut Si and Ge. Among the experimental techniques used to probe their effects, Raman scattering has been successfully employed, mainly to exploit the presence of residual stresses around the indentations and grooves made by indenters [8]. It is well known that, due to the machining (or to the polishing or lapping) process, semiconductor surfaces can undergo structural damage [9]. Raman scattering is a powerful characterization technique in these cases because the vibrational spectrum of the material is greatly influenced by disorder and residual strains: These lead to changes in phonon frequencies, broadening of Raman peaks and breakdown of Raman selection rules [10]. For bulk crystalline Si (c-Si), the triple degenerate optical phonons display in the first-order Raman spectrum one sharp peak at 521 cm−1. Due to the positive phonon deformation potentials of Si, compressive (tensile) strains lead to positive (or negative) frequency shifts. On the other hand, due to the loss of phonon correlation length and the consequent breakdown of the q = 0 Raman selection rules (q is the phonon wave vector), disorder effects can lead to an asymmetric broadening and shifting of Raman peaks compatible to the dispersion relation of the material [11]. In the silicon case, the frequency and asymmetry point to lower values because the dispersion relationship presents decreasing optical frequencies, increasing phonon wave vectors. At maximum disorder (amorphous material, aSi), the first-order Raman spectrum reflects the phonon density of states: It presents two broad bands centered at about 100 cm−1 (acoustic band) and 470 cm−1 (optical band) [12]. In this letter, an original (macro-) Raman investigation of single-point-diamond-turned silicon samples machined in ductile and brittle modes is presented. To probe the depth profile of disorder effects, the 457.9, 488.0 and 514.5 nm lines of an argon ion laser were used as exciting light. For these lines, the penetration depth of the light is about 140, 270 and 340 nm for c-Si, respectively. For a-Si, the optical absorption coefficient can reach one order of magnitude higher, leading to penetration depths of about tenths of nanometers, depending on the degree of amorphization [13, 14]. All measurements were performed at room temperature, with special care taken taken to avoid overheating the samples. Cutting tests were performed on Si samples on the (1 0 0) surface. The samples were single-pointdiamond-turned using a facing operation on a RankPneumo ASG 2500 diamond-turning machine. Alkalisol 900 coolant cutting fluid was continuously sprayed onto the workpiece during machining to avoid overheating the sample. A 0 (−25) degree rake angle diamond tool with nose radius R= 1.52 mm and a clearance angle of 12◦ was used in all tests. The feed rate used was 12.5 (1.25) μm rev−1 and the nominal depth of cut was 10 (1)μm. These conditions provide brittle (ductile) mode during machining, with an opaque (mirrorlike) surface. The finished surfaces were observed using scanning electron microscopy (SEM). Fig. 1 shows a

Raman characterization of structural disorder and residual strains in micromachined GaAs

Structural disorder and strain effects in ductile-regime single-point-diamond-turned gallium arsenide monocrystalline samples were probed by Raman scattering. The positive frequency shift of the longitudinal and transverse optical phonons observed in the machined samples indicate a residual compressive stress of about 1.5 GPa. This residual strain was attributed to the hysteresis of phase transformation generated by the high pressure imposed by the cutting tool tip during the machining process. The broadening of the Raman peaks indicate a high degree of structural disorder in the GaAs lattice. Moreover, the Raman spectrum of annealed samples, after machining, shows a less disordered but still misoriented matrix. In addition, it was found that crystalline arsenic formed into the surface vicinity.

Influence of the mechanical and metallurgical state of an Al-Mg alloy on the surface integrity in ultraprecision machining

This work presents the experimental results of the facing turning of an Al-Mg alloy. This aluminium alloy was mechanically and metallurgically modified, by means of cold rolling reduction and refining grain size previous to machining. The samples were cut and compared with samples in the as-received form, machined under the same cutting conditions. Surface finishing and work hardening were measured. Results show that theoretical surface roughness values are always smaller than the measured ones for all samples. Also, the surface roughness of the as-received samples is larger than that of mechanically modified samples. This difference of surface roughness was attributed to the swelling effect of the material. Microhardness values of the machined samples showed a decreasing trend with increasing loads. The surface of the cold rolled sample did not present a detectable microhardness alteration. Optical microscopy was used to observe qualitative aspects of the machined surface.

Modularity: Genes, Development, and Evolution

Modularity has emerged as a central concept for evolutionary biology, providing the field with a theory of organismal structure and variation. This theory has reframed long standing questions and serves as a unified conceptual framework for genetics, developmental biology and multivariate evolution. Research programs in systems biology and quantitative genetics are bridging the gap between these fields. While this synthesis is ongoing, some major themes have emerged and empirical evidence for modularity has become abundant. In this review, we look at modularity from an historical perspective, highlighting its meaning at different levels of biological organization and the different methods that can be used to detect it. We then explore the relationship between quantitative genetic approaches to modularity and developmental genetic studies. We conclude by investigating the dynamic relationship between modularity and the adaptive landscape and how this potentially shapes evolution and can help bridge the gap between micro- and macroevolution.

Design and development of the architecture of an agricultural mobile robot

Parameters such as tolerance, scale and agility utilized in data sampling for using in Precision Agriculture required an expressive number of researches and development of techniques and instruments for automation. It is highlighted the employment of methodologies in remote sensing used in coupled to a Geographic Information System (GIS), adapted or developed for agricultural use. Aiming this, the application of Agricultural Mobile Robots is a strong tendency, mainly in the European Union, the USA and Japan. In Brazil, researches are necessary for the development of robotics platforms, serving as a basis for semi-autonomous and autonomous navigation systems. The aim of this work is to describe the project of an experimental platform for data acquisition in field for the study of the spatial variability and development of agricultural robotics technologies to operate in agricultural environments. The proposal is based on a systematization of scientific work to choose the design parameters utilized for the construction of the model. The kinematic study of the mechanical structure was made by the virtual prototyping process, based on modeling and simulating of the tension applied in frame, using the.