Comparison of fracture surface and plane section analysis for ceramic grain size characterisation

A method has been developed to obtain quantitative information about grain size and shape from fractured surfaces of ceramic materials. One elaborated a routine to split intergranular and transgranular grains facets of ceramic fracture surfaces by digital image processing. A commercial ceramic (ALCOA A-16, Al2O3-1.5% of CrO) was used to test the proposed method. Microstructural measurements of grain shape and size taken from fracture surfaces have been compared through descriptive statistics of distributions, with the corresponding measurements from polished and etched surfaces. The agreement between results, with the expected bias on grain size values from fractures, obtained for both types of surfaces allowed to infer that this new technique can be used to extract the relevant microstructural information from fractured surfaces, thus minimising the time consuming steps of sample preparation. (C) 2003 Elsevier Ltd. All rights reserved.

Ultramorphological characteristics of Chrysomya megacephala (Diptera, Calliphoridae) eggs and its eclosion

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CRANIOMETRIC VARIATION AND SUBSPECIFIC DIFFERENTIATION IN THRICHOMYS APEREOIDES IN NORTHEASTERN BRAZIL (RODENTIA, ECHIMYIDAE)

Thrichomys apereoides is an echimyid rodent which ranges in distribution from northeastern and central Brazil into Paraguay. Five subspecies are recognized, although each form is not well characterized and diagnosis is based primarily in pelage color variation. In this study we employed procedures from multivariate statistics to assess the systematic status of subspecies described from northeastern Brazil. The results of the craniometric analysis cannot be reconciled with the subspecies currently recognized for northeastern Brazil. Populations assigned to T. a. laurentius and T. a. inermis form a continuum of variation in cranial size, although they differ in cranial shape from a population from the locality of Bodoco in the state of Pernambuco. The implications of these findings for the systematics of T. apereoides are discussed.

Cranial differentiation and evolution in Thrichomys apereoides (Rodentia: Echimyidae)

Thrichomys apereoides is an echimyid rodent which ranges in distribution from north-eastern and central Brazil into Paraguay, and currently five subspecies are recognized. Recent morphometric analyses of population samples formally assignable to T. a. laurentius and T. a. inermis, which occur in north-eastern Brazil, have shown that a major group of populations including both subspecies differ in cranial shape from a single population allocated to T. a. laurentius. In this study we employed mathematical models of evolutionary quantitative genetics to assess the role that random drift and selection may have played in the evolution of cranial shape differences in T. apereoides. The hypothesis of evolution due to drift was rejected and the selective forces necessary to account for shape differences were estimated. Minimum selective mortalities of the order of 10(-3) per generation were sufficient to explain the observed morphologic differentiation.

Evolution of caste in neotropical swarm-founding wasps (Hymenoptera : Vespidae; Epiponini)

Reproductive castes are compared in species of swarming wasps representing all currently recognized genera of Epiponini (Polistinae). New morphometric data for nine measures of body parts and ovarian data are presented for 13 species. These are integrated with all similarly conducted available studies, giving a total of 30 species. Analysis reveals several syndromes relating reproductive and nonreproductive individuals: no meaningful distinction, physiological differences only, reproductives larger than nonreproductives with intermediate individuals present, reproductives different in shape from nonreproductives with no intermediates, and reproductives smaller in some aspects than nonreproductives. Distribution of these syndromes among species is consistent with phylogenetic relationships derived from other data. Optimizing these syndromes on the cladogram indicates that the basal condition of Epiponini is a casteless society that is not comparable to the primitively social genus Polistes where dominant queens control reproduction. Castes originate several times in Epiponini, with different results in different lineages. The best documented evolutionary sequence passes from casteless societies, to those with reproductives larger, to those with reproductives differing in shape from nonreproductives, to those with reproductives smaller in some measures. This sequence is consistent with Wheeler's theory of the origin of caste through developmental switches, and represents the most thorough test of that theory to date.

g-acceleration of gravity: its measurement from the shape of water by using a computerized rotational system

This paper proposes a different experimental setup compared with the traditional ones, in order to determine the acceleration of gravity, which is carried out by using a fluid at a constant rotation. A computerized rotational system-by using a data acquisition system with specific software, a power amplifier and a rotary motion sensor-is employed in order to evaluate the angular velocity and g. An equation to determine g is inferred from fluid mechanics. For this purpose, the fluid's parabolic shape inside a cylindrical receptacle is considered using a rotational movement.

Shading effects on community composition and food web structure of a deforested pasture stream: Evidences from a field experiment in Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic parameters of total milk yield and factors describing the shape of lactation curve in dairy buffaloes

The objective of this study was to apply factor analysis to describe lactation curves in dairy buffaloes in order to estimate the phenotypic and genetic association between common latent factors and cumulative milk yield. A total of 31 257 monthly test-day milk yield records from buffaloes belonging to herds located in the state of São Paulo were used to estimate two common latent factors, which were then analysed in a multi-trait animal model for estimating genetic parameters. Estimates of (co)variance components for the two common latent factors and cumulated 270-d milk yield were obtained by Bayesian inference using a multiple trait animal model. Contemporary group, number of milkings per day (two levels) and age of buffalo cow at calving (linear and quadratic) as covariate were included in the model as fixed effects. The additive genetic, permanent environmental and residual effects were included as random effects. The first common latent factor (F1) was associated with persistency of lactation and the second common latent factor (F2) with the level of production in early lactation. Heritability estimates for Fl and F2 were 0.12 and 0.07, respectively. Genetic correlation estimates between El and F2 with cumulative milk yield were positive and moderate (0.63 and 0.52). Multivariate statistics employing factor analysis allowed the extraction of two variables (latent factors) that described the shape of the lactation curve. It is expected that the response to selection to increase lactation persistency is higher than the response obtained from selecting animals to increase lactation peak. Selection for higher total milk yield would result in a favourable correlated response to increase the level of production in early lactation and the lactation persistency.

Extraction of Building Roof Contours From LiDAR Data Using a Markov-Random-Field-Based Approach

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Boundary identification criteria and geometry analysis of Al 7050 stretch zone from elevation profiles

This article describes the development of a method for analysis of the shape of the stretch zone surface based on parallax measurement theory and using digital image processing techniques. Accurate criteria for the definition of the boundaries of the stretch zone are established from profiles of fracture surfaces obtained from crack tip opening displacement tests on Al-7050 alloy samples. The elevation profiles behavior analysis is based on stretch zone width and height parameters. It is concluded that the geometry of the stretch zone profiles under plane strain conditions can be described by a semi-parabolic relationship. (C) Elsevier B.V., 1999. All rights reserved.

Significance of extruded nuclear chromatin (regional nuclear shape malformation) in human spermatozoa: implications for ICSI

The aim of this study was to determine the extent of DNA fragmentation and the presence of denatured single-strand or normal double-strand DNA in spermatozoa with extruded nuclear chromatin (ENC) selected by high magnification. Fresh semen samples from 55 patients were prepared by discontinuous isolate concentration gradient. Spermatozoa with normal nucleus (NN) and ENC were selected at 8400x magnification and placed on different slides. DNA fragmentation was determined by TUNEL assay. Denatured and double-stranded DNA was identified by the acridine orange fluorescence method. DNA fragmentation was not significantly different (p = 0.86) between spermatozoa with ENC (19.6%) and those with NN (20%). However, the percentage of spermatozoa with detectable denatured-stranded DNA in the ENC spermatozoon group (59.1%) was significantly higher (p < 0.0001) than in the NN group (44.9%). The high level of denatured DNA in spermatozoa with ENC suggests premature decondensation and disaggregation of sperm chromatin fibres. The results show an association between ENC and DNA damage in spermatozoa, and support the routine morphological selection and injection of motile spermatozoa at high-magnification intracytoplasmic sperm injection.

Description of a new species of Pareiorhina (Siluriformes: Neoplecostominae) from Rio Sao Francisco basin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A new species of Miogryllus Saussure, 1877 from Andean Venezuela with bizarre cephalic morphology (Orthoptera, Gryllidae, Gryllinae, Modicogryllini)

Miogryllus muranyi n. sp. is described from the Andean Acacia-Cactaceae semi-desert bush in the Chama Valley of Venezuela. The species is characterized by the unusual shape of the male head, which makes it readily distinguishable from any other congener known to date.

Comparison of the external morphology of Rhipicephalus sanguineus (Latreille, 1806) (Acari : Ixodidae) ticks from Brazil and Argentina

In the present study the external morphology of semi-engorged Rhipicephalus sanguineus females ticks from Brazil and Argentina were compared by scanning electron microscopy. Many differences were detected among the R. sanguineus collected at the two localities, such as body size, shape of the genital pore, and morphology of the sensory structures. All these characteristics are fundamental for the diagnosis of species of the genus Rhipicephalus and thus indicate the need for further comparisons and, the taxonomical revision of this species of tick in the Neotropics. (c) 2005 Elsevier B.V. All rights reserved.

Structure of chorismate synthase from Mycobacterium tuberculosis

In bacteria, fungi, plants, and apicomplexan parasites, the aromatics compounds, such as aromatics amino acids, are synthesized through seven enzymes from the shikimate pathway, which are absent in mammals. The absence of this pathway in mammals make them potential targets for development of new therapy against infectious diseases, such as tuberculosis, which is the world's second commonest cause of death from infectious disease. The last enzyme of shikimate pathway is the chorismate synthase (CS), which is responsible for conversion of the 5-enolpyruvylshikimate-3-phosphate to chorismate. Here, we report the crystallographic structure of CS from Mycobacterium tuberculosis (MtCS) at 2.65 angstrom resolution. The MtCS structure is similar to other CS structures, presenting beta-alpha-beta sandwich structural topology, in which each monomer of MtCS consists of a central helical core. The MtCS can be described as a tetramer formed by a dimer of dimers. However, analytical ultracentrifugation studies suggest the MtCS is a dimer with a more asymmetric shape than observed on the crystallographic dimer and the existence of a low equilibrium between dimer and tetramer. Our results suggest that the MtCS oligomerization is concentration dependent and some conformational changes must be involved on that event. (c) 2005 Elsevier B.V. All rights reserved.