Precipitates in two X80 pipeline steels were studied by transmission electron microscopy equipped with an energy filtering system. The steels are microalloyed with niobium and niobium–vanadium (Nb–V), respectively, and produced by continuous hot rolling. Besides the precipitates TiN and (Ti, Nb) (C, N), which were 10–100 nm in size, a large number of precipitates smaller than 10 nm distributed in the two steels have been observed. In the Nb–V microalloyed steel, only a few titanium nitrides covered by vanadium compounds on the surface have been observed. It is inferred that the vanadium exists mainly in the matrix as a solid solution element. The fact has been accepted that there was no contribution to the precipitation strengthening of the X80 steel by adding 0.04–0.06% vanadium under the present production process. By contrast, the toughness of the Nb–V steel is deteriorated. Therefore, a better toughness property of the Nb microalloyed X80 results from the optimum microalloying composition design and the suitable accelerating cooling after hot rolling.

Salt weathering is a major erosive process affecting porous materials in buildings. There have been attempts to relate erosive mass loss to physical characteristics of materials, but in the case of natural stone it is necessary to consider the effect of petrographic features that are a source of heterogeneity. In this paper, we use scanning electron microscopy before and after salt weathering tests in cubic specimens of three limestone types (two grainstones and a travertine) in an attempt to built conceptual models that relate petrographic features and salt weathering susceptibility (represented by mass loss). In the grainstones, the most relevant feature in controlling salt weathering processes is the interface between micrite aggregates and sparry cement that constitute weakness surfaces and barriers to fluid migration. Given the small size of the heterogeneities in relation to the test sample dimension and their spatial distribution, the macroscopic erosive patterns are globally homogeneously distributed, affecting edges and corners. In the travertine specimens, there are macroheterogeneities related to the presence of detritic-rich portions that cause heterogeneous erosive patterns in the specimens. Petrological modeling helps to understand results of salt weathering tests, supporting field studies for natural stone selection.

Helicobacter pylori is a Gram-negative microorganism that grows on microaerophilic conditions and has only one known natural reservoir: the gastric mucosa. The infection by H. pylori is very common worldwide and this bacterium is associated with the development of gastritis, peptic ulcer gastric cancer or gastric Mucosa Associated Lymphoid Tissue (MALT) lymphoma. Although its natural habitat is the acidic gastric mucosa, H. pylori is considered to be a neutralophile. The bacterium survives brief exposure to pHs of <4, but growth occurs only at the relatively narrow pH range of 5.5 to 8.0, with optimal growth at neutral pH. Recently we have identified a prophage sequence (prophage phiHP33) in the strain B45, isolated from a patient diagnosed with gastric MALT lymphoma. This prophage revealed to be very difficult to induce. In fact, only few phage particles were observed on electron microscopy micrographs after exposure to UV radiation.

In the present work we have compared the exposure to UV and to acidic environment in the induction of the prophage into a lytic cycle. We have tested two strains, the strain B45 carrying the prophage phiHP33 and a clinical strain 1152, isolated from a patient with peptic ulcer, that was revealed to be negative for the presence of integrase gene (a prophage gene essential for genome integration of prophage) by PCR, as negative control. Since the H. pylori reservoir is the human stomach the exposition to acid is very common, and with this experiment we intended to test if acid can trigger a phage lytic cycle.

The induction using UV radiation has been previously described. For acid induction we have used a protocol adapted from Karita and Blaser. A 48 hours culture of H. pylori was grown in Brucella broth (Oxoid) supplemented with 10% of fetal bovine serum (Gibco) and 1% of Polivitex (BioMérieaux) in microaerophilic conditions at 37ºC. The liquid culture was centrifuged and the cell pellet ressuspended in citrate-phosphate buffer pH 6 and incubated 15 minutes, centrifuged again and ressuspended in citrate-phosphate buffer pH 3 and incubated for 30 minutes. After centrifugation the supernatant was recovered and incubated for 3 hours in phage precipitant (33% polyethylene glycol [PEG], 3M NaCl). After centrifugation at 10000 rpm for 10 minutes at 4ºC the pellet was ressuspended in phage buffer. These samples were analysed by transmission electron microscopy (TEM) after negative staining with 1% aqueous uranyl acetate, using a JEOL 100SX electron microscope.

For B45 strain the induction using UV radiation (previously reported in Lehours, 2011) and acid exposure produced similar results (Figure 1 and Figure 2) showing numerous phage-like particles of about 100 nm diameter, apparently lacking a tail, after UV or acid exposition, respectively. These particles were not observed in the control strain 1152. Currently we are analysing the samples using molecular biology techniques and fixation embedding followed by ultrathin sectioning for TEM analysis, to detect the presence of phages.

These preliminary results suggest that acid also appears to induce the H. pylori prophage phiHP33. However, since the number of phage particles observed is small, we can not rule out that the observed particles were released spontaneously. The exposition to the natural acidic environment of the human stomach may induce H. pylori prophage into a lytic cycle and to the propagation of phages among different H. pylori strains colonizing the same individual. Although highly speculative, transduction may be another form of horizontal gene transfer, which has not been described for this bacterium yet.

Financial support received from the Portuguese Science and Technology foundation under the contract PTDC/EBB-EBI/119860/2010.

The main cell types of the adult bee fat body are trophocytes and oenocytes; however, in pupae of some newly emerged bees, trophocytes are modified into cells called urocytes, which possibly function as a substitute for Malpighian tubules during metamorphosis when larval tubules are not functional and/or storage of urate salts is required. This study evaluated the morphology of urocytes in the stingless bee Melipona quadrifasciata and the possibility of maintaining these cells in primary culture. The urocytes M. quadrifasciata are white spherical cells with an irregular surface as observed by stereomicroscopy. They may be found individually or in groups associated with tracheae. Urocytes have a single, small, and spherical nucleus and cytoplasm rich in neutral polysaccharides, lipid droplets, protein, and granules containing calcium and urate salts. Our findings suggest that urocytes play a role in storage of neutral polysaccharides and calcium in M. quadrifasciata pupae and that these cells can be cultured for 72 h.

Several theories have been put forward regarding the aetiology and pathogenesis of salivary calculi, although a comprehensive understanding of the nucleation and growth mechanisms involved in the formation of these structures is still lacking.

In general, sialoliths present one core partially or highly mineralized surrounded by concentric layers of organic and mineralized matter that alternate in succession following a chronologic sequence. The layers consist of fine mineralized strata intercalated with fine organic ones and threaded globular structures with variable degrees of mineralization.

The exact mechanism involved in the genesis of sialoliths remains largely unknown, theories defending an initial organic nidus or an initial precipitation of minerals, with subsequent deposition of organic and inorganic layers, can be found in the literature. Nevertheless, it remains object of discussion the etiologic factors responsible for the formation of the first nidus or the initial precipitation, since infection, inflammation of the gland, viscous nature of the mucous secretions or naturally existing sialomicroliths have all have been implicated.

Aiming at an exhaustive systematization of salivary calculi morphogenesis, their morphology has been studied by micro-computed tomography (bCT) and scanning electron microscopy (SEM). CCT studies were done on as-extracted dried samples using uCT SkyScan 1172 instrument with a 1.3 Megapixel camera, operated at the maximum available power of the source (10W). Radiographs acquisition was performed with a rotational step in the 0.70-1° range, until a maximum of 180º, with an exposure time in the 3.1-5 s range. Microscopy observations were carried out with backscattered electron (BSE) signals using a JEOL JSM 7001F operated at 15 kV, samples were previously prepared following metallographic procedures.

The submandibular and parotid calculi investigated presented similar growth patterns, which can follow either concentric (Figure 1) or perturbed-growth typologies (Figure 2), although in most situations a gradation between them has been found. Nevertheless, a single well-defined core constituted by material with low mineralization was frequently present, supporting the nucleation hypothesis of an initial organic nidus.

The combination of TCT with SEM enabled a comprehensive characterization of the sialoliths: (i) the former technique allowed for a precise localization of the core and other morphological features within the calculus volume, while (ii) investigation of details at higher resolution could be achieved with the latter method. However, due to the friable nature of the sialoliths, handling during sample preparation results often in material loss (compare (a) and (b) in both Figures).

The work was carried out with financial support of the Portuguese Foundation for Science and Technology through PTDC/SAU-ENB/111941/2009 and PEst-OE/CTM-UI0084/2011 grants.

Ultrastructural answer of bone marrow erythroid series and of red blood cells (RBCs) in Wistar rats to bee venom (BV) was analyzed by transmission and scanning electron microscopy, and corroborated with hematological data. A 5-day and a 30-day treatment with daily doses of 700 μg BV/kg and an acute-lethal treatment with a single dose of 62 mg BV/kg were performed. The 5-day treatment resulted in a reduced cellularity of the bone marrow, with necrosed proerythroblasts, polymorphous erythroblasts, and reticulocytes with cytoplasmic extensions, and a lower number of larger RBCs, with poikilocytosis (acanthocytosis) and anisocytosis, and reduced concentrations of hemoglobin. After the 30-day treatment, the bone marrow architecture was restored, but polymorphous erythroblasts and reticulocytes with thin extensions could still be observed, while the RBCs in higher number were smaller, many with abnormal shapes, especially acanthocytes. The acute treatment produced a partial depopulation of the bone marrow and ultrastructural changes of erythroblasts including abnormal mitochondrial cristae. The RBCs in lower number were bigger and crenated, with reduced concentrations of hemoglobin. Overall, BV was able to promote stress erythropoiesis in a time- and dose-related manner, mitochondrial cristae modification being a critical factor involved in the toxicity of the BV high doses.

Elucidation of protein structure using X-ray crystallography relies on the quality of the crystal. Crystals suffer from many different types of disorder, some of which occur during crystal nucleation and early crystal growth. To date, there are few studies surrounding the quality and nucleation of protein crystals partly due to difficulties surrounding viewing biological samples at high resolution. Recent research has led our current understanding of nucleation to be a two-step mechanism involving the formation of nuclei from dense liquid clusters; it is still unclear whether nuclei first start as amorphous aggregate or as crystalline lattices. Our research examines this mechanism through the use of electron microscopy. Using scanning electron microscopy imaging of the protein crystal growth process, a stacking, spiraling manner of growth is observed. The tops of the pyramid-like tetragonal protein crystal structures measure ~0.2 μm across and contain ~125,000 lysozyme units. This noncrystalline area experiences strain due to growth of the protein crystal. Our work shows that it is possible to view detailed early stage protein crystal growth using a wet scanning electron microscopy technique, thereby overcoming the problem of viewing liquids in a vacuum.

In this paper we introduce new methodology for the observation of living biological samples in an environmental scanning electron microscope (ESEM). The methodology is based on an unconventional initiation procedure for ESEM chamber pumping, free from purge–flood cycles, and on the ability to control thermodynamic processes close to the sample. The gradual and gentle change of the working environment from air to water vapor enables the study of not only living samples in dynamic in situ experiments and their manifestation of life (sample walking) but also its experimentally stimulated physiological reactions. Moreover, Monte Carlo simulations of primary electron beam energy losses in a water layer on the sample surface were studied; consequently, the influence of the water thickness on radiation, temperature, or chemical damage of the sample was considered.

The built environment is subjected to several pollutants under variable environmental conditions defined by diverse geochemical systems. These geochemical systems promote the occurrence of neoformations that can have a detrimental effect on surfaces of the building materials. Hence, the study of neoformations helps in the understanding of weathering processes that affect built structures. In the present paper we present a scanning electron microscopy study of macroscopic manifestations of neoformations detected during an extensive visual survey of several modern architectural works in urban areas of northern and central Portugal. The studies performed suggest that cementitious materials play an important role as a source of pollutants for the most common neoformations such as carbonate rich stains and coatings, as well as salt efflorescences of alkaline sulphates and carbonates. There are also indications of contributions from organic sources for alkaline nitrates and atmospheric pollution for gypsum-rich black crusts. Other less common neoformations include phosphate aggregates and silica stains that represent interesting indicators of the geochemical systems in built environments. In the case of carbonate-rich coatings, indications of recurrence related to the circulation of carbonate forming solutions relevant to the maintenance of built surfaces were detected.

Using a series of uranyl acetate stained or platinum-palladium shadowed organic samples, an empirical analytical method to extract surface information from energy-filtered transmission electron microscopy (EFTEM) images is described. The distribution of uranium or platinum-palladium atoms, which replicate the sample surface topography, have been mathematically extracted by dividing the image acquired in the valence bulk plasmon energy region (between 20 and 30 eV) by the image acquired at the carbon K ionization edge (between 284 and 300 eV). The resulting plasmon-to-carbon ratio (PCR) image may be interpreted as a precise metal replica of the sample surface. In contrast to conventional EFTEM elemental mapping, including an absolute quantification approach, this technique can be applied to 200–600 nm thick organic samples. A combination of conventional TEM and PCR imaging allows one to detect complementary transmission and topographical information with nanometer precision of the same area of carbon-based samples. The advantages and limitations of PCR imaging are highlighted.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Testate amebae are unicellular shelled protozoa commonly used as indicators in ecological and paleoecological studies. We explored the potential application of three-dimensional (3D) X-ray micro-tomography used in addition to 2D techniques (environmental scanning electron microscopy, electron probe micro-analysis, and cathodoluminescence) for detailed characterization of agglutinated shells of protozoa. We analyzed four specimens of the aquatic testate ameba Difflugia oblonga (Arcellinida), to test whether size distribution and mineral composition of shell grains diverged from sediment size distribution and mineralogical composition. From the 3D images, the geometry of the specimens (size and mass) and of the individual grains forming the specimen (grain size distribution and volume) were calculated. Based on combined chemical, mineralogical, and morphological analyses we show that D. oblonga is able to selectively pick up the small size fraction of the sediment with a preference for low-density silicates close to quartz density (~2.65). The maximum size of the grains matches the size of the pseudostome (shell aperture), suggesting the existence of a physical limit to grain size used for building the shell. This study illustrates the potential of this combined approach to characterize agglutinated shells of protozoa. This data can be useful for detailed morphological studies with applications in taxonomy and ecology.

In this study, every effort was exerted to determine and accumulate data to correlate microstructural and compositional elements in ultra-low-carbon (ULC) steels to variation of carbon content (12–44 ppm), manganese (0.18–0.36%), and sulfur (0.0066–0.001%). Quantitative analysis of the ULC steel using optical microscope, scanning electron microscope, transmission electron microscope, and three-dimensional atom probe revealed the decrease of grain size and dislocation density with the increase of carbon contents and/or increase of the final delivery temperature. For a given carbon content, the grain interior carbon concentration increases as the grain size increases.

The technological development of all kinds of lightweight transportation devices including vehicles, aircraft, ships, etc. has progressed markedly with the demand for energy saving and environmental protection. Aluminum alloy is in the spotlight as it is a suitable environmentally friendly material. However, deformation is a major problem during the welding process because aluminum alloy has a large thermal expansion coefficient. In addition, it is known that its corrosion resistance is excellent; nevertheless, in practice, considerable corrosion is generated and this is a major problem. To solve this problem, the friction stir welding (FSW) technology is applied extensively at various industrial fields as a new welding technique. This method involves a process in which materials are joined by frictional heat and physical force. Therefore, we evaluated improvements in mechanical properties and corrosion resistance through annealing heat treatment after FSW. The electrochemical experiment did not show a significant difference. However, the microstructure observation showed defectless, fine crystal particles, indicating excellent properties at 200–225°C.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

We report the development of a method to analyze receptor and β-arrestin2 mobilization between Class A and B GPCRs via time-resolved fluorescent microscopy coupled with semiautomated high-content multiparametric analysis. Using transiently expressed, tagged β2-adrenergic receptor (β2-AR) or parathyroid hormone receptor type 1 (PTH1R), we quantified trafficking of the receptors along with the mobilization and colocalization of coexpressed tagged β-arrestin2. This classification system allows for exclusion of cells with nonoptimal characteristics and calculation of multiple morphological and spatial parameters including receptor endosome formation, β-arrestin mobilization, colocalization, areas, and shape. Stimulated Class A and B receptors demonstrate dramatically different patterns with regard to β-arrestin interactions. The method provides high kinetic resolution measurement of receptor translocation, which allows for the identification of the fleeting β-arrestin interaction found with β2-AR agonist stimulation, in contrast to stronger mobilization and receptor colocalization with agonist stimulation of the PTH1R. Though especially appropriate for receptor kinetic studies, this method is generalizable to any dual fluorescence probe system in which quantification of object formation and movement is desired. These methodologies allow for quantitative, unbiased measurement of microscopy data and are further enhanced by providing real-time kinetics.

Studies on cultural metal artifacts can benefit greatly from microscopy techniques. The examination of microstructural features can provide relevant information about ancient manufacturing techniques, as well as about corrosion/degradation processes. In the present work, advantages of the use of multifocus imaging techniques in optical microscopy for the study of archaeological metals are presented. An archaeometallurgical study of a large collection of bronzes demonstrates the possibility of a microstructural study with no need for sample removal, which is a great advantage in the study of cultural objects. In addition, the study of mounted samples illustrates the advantages of the multifocus technique in the examination of particular corrosion features, with the possibility of three-dimensional reconstructions.