Estrutura e composição florística de um Cerrado sensu stricto e sua importância para propostas de restauração ecológica

Bordas são áreas de transição entre dois ecossistemas e podem ter origem natural ou antrópica. A influência de borda inclui tanto os efeitos diretos, relacionados às alterações microambientais, como os efeitos indiretos que afetam as interações entre espécies. Adicionalmente, estudos sugerem que a orientação cardinal pode modificar os efeitos microambientais da borda. O objetivo deste estudo foi avaliar a influência de borda sobre os fatores microambientais, as condições edáficas locais, a densidade e a riqueza de espécies em um Cerrado sensu stricto em Itirapina, SP, Brasil. Especificamente, nós investigamos se as características microambientais (umidade relativa do ar (%), radiação fotossinteticamente ativa (PAR), temperatura e porcentagem de abertura de dossel), as condições edáficas e a composição da vegetação diferem entre parcelas (36 parcelas de 25 × 2 m distanciadas 50 m entre si) distribuídas na borda e no interior, orientadas a leste e a sul do Cerrado estudado. Todos os indivíduos lenhosos com circunferência a 30 cm da base do caule ≥ 3 cm foram amostrados e marcados. As variáveis microambientais e as amostras de solo para análises químicas e granulométricas (0-20 cm de profundidade) foram coletadas em três pontos de cada parcela. Foi registrado um total de 120 espécies distribuídas em 40 famílias. Dentre os parâmetros estruturais da vegetação, somente a densidade absoluta foi significativamente maior no interior sul do fragmento. As variáveis microambientais diferiram significativamente entre as faces leste e sul, mas não entre borda e interior. Os parâmetros microambientais e estruturais não caracterizaram uma influência da borda. Entretanto, a orientação cardinal leste e sul e fatores microambientais associados, e a presença de determinados nutrientes no solo como o Mn, influenciaram a estrutura da vegetação de Cerrado e a sua composição em espécies. Nossos resultados ressaltam a importância de considerar a orientação cardinal, além da composição de nutrientes no solo, e dos fatores microambientais, para compreender as variações da vegetação em escala local.

Influence of the tool edge geometry on specific cutting energy at high-speed cutting

This paper presents specific cutting energy measurements as a function of the cutting speed and tool cutting edge geometry. The experimental work was carried out on a vertical CNC machining center with 7,500 rpm spindle rotation and 7.5 kW power. Hardened steels ASTM H13 (50 HRC) were machined at conventional cutting speed and high-speed cutting (HSC). TiN coated carbides with seven different geometries of chip breaker were applied on dry tests. A special milling tool holder with only one cutting edge was developed and the machining forces needed to calculate the specific cutting energy were recorded using a piezoelectric 4-component dynamometer. Workpiece roughness and chip formation process were also evaluated. The results showed that the specific cutting energy decreased 15.5% when cutting speed was increased up to 700%. An increase of 1 °in tool chip breaker chamfer angle lead to a reduction in the specific cutting energy about 13.7% and 28.6% when machining at HSC and conventional cutting speed respectively. Furthermore the workpiece roughness values evaluated in all test conditions were very low, closer to those of typical grinding operations (∼0.20 μm). Probable adiabatic shear occurred on chip segmentation at HSC Copyright © 2007 by ABCM.

Influence of maxillary incisor edge asymmetries on the perception of smile esthetics among orthodontists and laypersons

Introduction: Our objective was to determine the perception of smile esthetics among orthodontists and laypeople with respect to asymmetries on the maxillary incisor edges in a frontal smile analysis. Methods: Two frontal close-up smile photos of 2 women, 1 white and 1 Afro-Brazilian, were selected for this study. Both smiles displayed healthy maxillary anterior dentitions. The images were digitally altered to create tooth wear on the maxillary left central and lateral incisors in 0.5-mm increments. The final images were randomly assembled into a photo album that was given to 120 judges, 60 orthodontists and 60 laypersons. Each rater was asked to evaluate the attractiveness of the images with visual analog scales. The data collected were statistically analyzed with 1-way analysis of variance with the Tukey post-hoc test and the unpaired Student t test. Results: The most attractive smiles in both types of smiles were those without asymmetries and the 0.5-mm wear in the lateral incisor. In general, tooth wear was considered unattractive by both groups of raters following a pattern: the more tooth wear, the more unattractive the smile; tooth wear in the central incisor was considered more unattractive than in the lateral incisor. For both group of raters, 0.5 mm of wear in the central incisor was considered unattractive, whereas the thresholds for lateral incisor discrepancies were 0.5 mm for orthodontists and 1.0 mm for laypersons. Conclusions: The result of this study corroborates the clinical assumption that symmetry between the maxillary central incisors is a paramount goal for esthetic treatments. Copyright © 2013 by the American Association of Orthodontists.

Influence of open trailing edge on laminar aerofoils at low Reynols number

This article deals with the effect of open trailing edge on the aerodynamic characteristics of laminar aerofoils at low Reynolds numbers, the attention being focussed on the influence of such a trailingedge imperfection on the aerodynamic efficiency. Wind tunnel tests have been performed at different Reynolds numbers and angles of attack, and global aerodynamic as well as pressure distributions were measured (in these tests two types of open trailing edges, either sharp or rounded were considered). From experimental results, a quantitative analysis of the influence of the trailing-edge thickness on the degradation of aerofoil aerodynamic performances has been obtained, which allows the establishment of a criterion for an acceptance limit for this kind of imperfection.

Study of the Edge and Surface Cracks Influence in the Mechanical Strength of Silicon Wafers

The objective of the present study is the estimation of the depth to which the wire sawing process causes damage to the wafer surfaces. Previous analyses were carried out by means of the four line bending test. The characteristic of this test implied that the failure could be due to surface cracks located in the central zone of the wafer or near the edges. In order to evaluate the influence of the edge or surface cracks a new study has been carried out using the ball/ring on ring test. Description and results of the tests are presented. The preliminary analysis of the failure stress using analytical methods confirms the expected results. A Finite Element model developed to get more information of the test results is also presented.

Influence of leading edge imperfections on the aerodynamic characterictics of NACA 632-215 laminar aerofoils at low Reynolds number

This article deals with the effect of leading edge imperfections on the aerodynamic characteristics of a NACA 632-215 laminar aerofoil at low Reynolds numbers. Wind tunnel tests have been performed at different Reynolds numbers and angles of attack and global aerodynamic loads were measured. To perform these tests, a NACA 632-215 aerofoil was built up in two halves (corresponding to the upper side and to the lower side), the leading edge imperfection here considered being a slight displacement of half aerofoil with respect to the other. From experimental results, a quantitative measure of the influence of the leading edge displacement on the degradation of the aerofoil aerodynamic performances has been obtained. This allows the establishment of a criterion for an acceptance limit for this kind of imperfection

Influence of the cutting edge micro-geometry of PCBN tools on the flank wear in orthogonal quenched and tempered turning M2 steel

Quenched and tempered high-speed steels obtained by powder metallurgy are commonly used in automotive components, such as valve seats of combustion engines. In order to machine these components, tools with high wear resistance and appropriate cutting edge geometry are required. This work aims to investigate the influence of the edge preparation of polycrystalline cubic boron nitride (PCBN) tools on the wear behavior in the orthogonal longitudinal turning of quenched and tempered M2 high-speed steels obtained by powder metallurgy. For this research, PCBN tools with high and low-CBN content have been used. Two different cutting edge geometries with a honed radius were tested: with a ground land (S shape) and without it (E shape). Also, the cutting speed was varied from 100 to 220 m/min. A rigid CNC lathe was used. The results showed that the high-CBN, E-shaped tool presented the longest life for a cutting speed of 100 m/min. High-CBN tools with a ground land and honed edge radius (S shaped) showed edge damage and lower values of the tool’s life. Low-CBN, S-shaped tools showed similar results, but with an inferior performance when compared with tools with high CBN content in both forms of edge preparation.

Influence of hydrocarbon contamination on clay soil microstructure

Microstructural (fabric, forces and composition) changes due to hydrocarbon contamination in a clay soil were studied using Scanning Electron Microscope (micro-fabric analysis), Atomic Force Microscope (forces measurement) and sedimentation bench test (particle size measurements). The non-polluted and polluted glacial till from north-eastern Poland (area of a fuel terminal) were used for the study. Electrostatic repelling forces for the polluted sample were much lower than for the non-polluted sample. In comparison to non-polluted sample, the polluted sample exhibited lower electric charge, attractive forces on approach and strong adhesion on retrieve. The results of the sedimentation tests indicate that clay particles form larger aggregates and settle out of the suspension rapidly in diesel oil. In non-polluted soil, the fabric is strongly aggregated – densely packed, dominate the face-to-face and edge-to-edge types of contacts, clay film tightly adheres to the surface of larger grains and interparticle pores are more common. In polluted soil, the clay matrix is less aggregated – loosely packed, dominate the edge-to-face types of contacts and inter-micro-aggregate pores are more frequent. Substantial differences were observed in the morphometric and geometrical parameters of pore space. The polluted soil micro-fabric proved to be more isotropic and less oriented than in non-polluted soil. The polluted soil, in which electrostatic forces were suppressed by hydrocarbon interaction, displays more open porosity and larger voids than non-polluted soil, which is characterized by occurrence of the strong electrostatic interaction between clay particles.

Influence of pre-exsiting surface defects on the vibrational properties of Ag nanowires

Large-scale molecular dynamics simulations are performed to characterize the effects of pre-existing surface defects on the vibrational properties of Ag nanowires. It is found that the first order natural frequency of the nanowire appears insensitive to different surface defects, indicating a defect insensitivity property of the nanowire’s Young’s modulus. In the meanwhile, an increase of the quality (Q)-factor is observed due to the presence of defects. Particular, a beat phenomenon is observed for the nanowire with the presence of a surface edge defect, which is driven by a single actuation. It is concluded that different surface defects could act as an effective mean to tune the vibrational properties of nanowires. This study sheds lights on the better understanding of nanowire’s mechanical performance when surface defects are presented, which would benefit the development of nanowire-based devices.

Molecular dynamics investigation on edge stress and shape transition in graphene nanoribbons

Graphene nanoribbon (GNR) with free edges demonstrates unique pre-existing edge energy and edge stress, leading to non-flat morphologies. Using molecular dynamics (MD) methods, we evaluated edge energies as well as edge stresses for four different edge types, including regular edges (armchair and zigzag), armchair edge terminated with hydrogen and reconstructed armchair. The results showed that compressive stress exists in the regular and hydrogen-terminated edges along the edge direction. In contrast, the reconstructed armchair edge is generally subject to tension. Furthermore, we also investigated shape transition between flat and rippled configurations of GNRs with different free edges. It was found that the pre-existing stress at free edges can greatly influence the initial energy state and the shape transition.

Edge-weighting of gene expression graphs

In recent years, considerable research efforts have been directed to micro-array technologies and their role in providing simultaneous information on expression profiles for thousands of genes. These data, when subjected to clustering and classification procedures, can assist in identifying patterns and providing insight on biological processes. To understand the properties of complex gene expression datasets, graphical representations can be used. Intuitively, the data can be represented in terms of a bipartite graph, with weighted edges corresponding to gene-sample node couples in the dataset. Biologically meaningful subgraphs can be sought, but performance can be influenced both by the search algorithm, and, by the graph-weighting scheme and both merit rigorous investigation. In this paper, we focus on edge-weighting schemes for bipartite graphical representation of gene expression. Two novel methods are presented: the first is based on empirical evidence; the second on a geometric distribution. The schemes are compared for several real datasets, assessing efficiency of performance based on four essential properties: robustness to noise and missing values, discrimination, parameter influence on scheme efficiency and reusability. Recommendations and limitations are briefly discussed. Keywords: Edge-weighting; weighted graphs; gene expression; bi-clustering