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In this investigation the influence of 24 kHz ultrasound wave upon the corrosion of carbon steel in 3N sulphuric acid at 25 degrees C in the presence of inhibitors was studied. The inhibitors were polyethylene glycols (PEG) in different molecular weights (from 400 up to 10,000 gmol(-1)). The polarization and impedance spectroscopy results show the effectiveness of polyethylene glycols on the cavitation-corrosion inhibition of carbon steel in sulphuric acid. The inhibition efficiency is increased with increasing mean molecular weight of polymer and its concentration. The weight loss method has confirmed these results. The analysis of SEM images indicates that these inhibitors prevent propagation of pits on the eroded specimen. The inhibition effect of PEGs can be attributed to cushioning effect of adsorbed polymers on cavitation phenomenon produced by bubble collapse.
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PMID:Effect of ultrasonically induced cavitation on inhibition behavior of polyethylene glycol on carbon steel corrosion. 1624 15

Paramolybdate-LDHs with MgAl or ZnAl cations within the layers have been prepared by the ion-exchange method from hydrotalcites with different interlayer anions (OH-, NO3(-), and terephthalate). The samples and the oxides obtained after their calcination were characterized by element chemical analysis, PXRD, FT-Raman spectroscopy, thermal analysis (TG/DTA), N2 adsorption at -196 degrees C, and SEM. The results show that layered solids with hydrotalcite-type structure were obtained in which the interlayer space is occupied by heptamolybdate with a small amount of MoO4(2-) units formed through hydrolysis of the polyanion; both oxomolybdenum species undergo a progressive distortion of the octahedral units from 50 degrees C but are roughly stable up to 250 degrees C as a consequence of the interaction between the polyanion and the brucite-like layers. This distortion is responsible for the observed decrease in the height of the gallery for samples heated in the temperature range, 50-250 degrees C, with respect to the original samples. Rehydration of the calcined solids allows recovering of their original structures and the initial values for the gallery heights. Calcination between 300 and 400 degrees C gives rise to a collapse of the layered structure, and amorphous phases are formed, in which molybdenum is both octahedrally and tetrahedrally coordinated. Crystalline magnesium and zinc molybdates (MgMoO4 and ZnMoO4) are formed at 450 and 600 degrees C, respectively. All solids have some microporosity, which decreases with increasing the calcination temperature.
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PMID:Structural and texture evolution with temperature of layered double hydroxides intercalated with paramolybdate anions. 1644 Nov 36

Reduced layered M(C4H4N2)V4O10 ((I, M = Co; II, M = Ni; III, M = Zn); C4H4N2 = pyrazine, pyz) hybrid solids were synthesized via hydrothermal reactions at 200-230 degrees C, and their structures determined by single-crystal X-ray diffraction (Cmcm, No. 63, Z = 4; a = 14.311(2), 14.2372(4), 14.425(1) A; b = 6.997(1), 6.9008(2), 6.9702(6) A; and c = 11.4990(8), 11.5102(3), 11.479(1) A; for I, II, and III, respectively). All three solids are isostructural and contain V4O102- layers condensed from edge- and corner-shared VO5 square pyramids. A single symmetry-unique V atom is reduced by 1/2 electron (on average) and bonds via its apical oxygen atom to interlayer Mpyz2+ chains. Magnetic susceptibility measurements show a strong temperature dependence and a Curie constant that is consistent with two randomly localized spins per V4O10(2-) formula for III. Further, the unusual discovery of a remarkably well-defined transition to a singlet ground state, as well as formation of a spin gap, is found for III at 22(1) K. The temperature-dependent electrical conductivities show apparent activation energies of 0.36 (I), 0.46 (II), and 0.59 eV (III). During heating cycles in flowing N2, the samples exhibit weight losses corresponding to the removal of predominantly pyrazine, pyrazine fragments, and CO2 via reaction of pyrazine with the vanadate layer. The complete removal of pyrazine without loss of crystallinity is found for well-ground samples of I and III. The SEM images of I and II after heating at 400-500 degrees C show relatively intact crystals, but at 600 degrees C further structural collapse results in the formation of macropores at the surfaces.
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PMID:Spin-gap formation and thermal structural studies in reduced hybrid layered vanadates. 1678 Mar 33

Bacterial biofilms, i.e. surface-associated cells covered in hydrated extracellular polymeric substances (EPS), are often studied with high-resolution electron microscopy (EM). However, conventional desiccation and high vacuum EM protocols collapse EPS matrices which, in turn, deform biofilm appearances. Alternatively, wet-mode environmental scanning electron microscopy (ESEM) is performed under a moderate vacuum and without biofilm drying. If completely untreated, however, EPS is not electron dense and thus is not resolved well in ESEM. Therefore, this study was towards adapting several conventional SEM staining protocols for improved resolution of biofilms and EPS using ESEM. Three different biofilm types were used: 1) Pseudomonas aeruginosa unsaturated biofilms cultured on membranes, 2) P. aeruginosa cultured in moist sand, and 3) mixed community biofilms cultured on substrates in an estuary. Working with the first specimen type, a staining protocol using ruthenium red, glutaraldehyde, osmium tetroxide and lysine was optimized for best topographic resolution. A quantitative image analysis tool that maps relief, newly adopted here for studying biofilms, was used to compare micrographs. When the optimized staining and ESEM protocols were applied to moist sand cultures and aquatic biofilms, the smoothening effect that bacterial biofilms have on rough sand, and the roughening that aquatic biofilms impart on initially smooth coupons, were each quantifiable. This study thus provides transferable staining and ESEM imaging protocols suitable for a wide range of biofilms, plus a novel tool for quantifying biofilm image data.
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PMID:Enhanced visualization of microbial biofilms by staining and environmental scanning electron microscopy. 1719 92

Bronchointerstitial pneumonia was diagnosed postmortem in 19 foals in a 10 year retrospective study of submissions to a diagnostic center in Ontario. Mean age at death was 2.0 +/- 0.05 (SEM) mo (range five days to four months). Fourteen of 19 were aged from 1.5 to 2.5 mo. Clinically, the disease was generally characterized by sudden onset of fever and increasingly severe dyspnea which developed into respiratory distress before death. Mean length of illness was 7.0 +/- 0.33 days (range 1-21 days). The disease appeared to affect only individual foals on 19 different farms.At postmortem, lungs were typically diffusely red, wet, firm, and failed to collapse. The major lesion recognized histologically was epithelial necrosis of alveoli and terminal bronchioles. Alveolar lumens contained large epithelioid cells, which were probably macrophages, and multinucleated syncytial cells were present in 16 of the 19 lungs. Inflammatory cells were sparse. Intraalveolar fibrin was prominent in all lungs. Bacteriological examination revealed no significant pathogen in 12 animals, but Rhodococcus equi was isolated from seven foals, associated in two animals with extensive abscesses. Viruses were not recovered from eight foals examined.On the basis of the similarity and severity of lesions, the sporadic nature of the disease, and the similar age at onset which appears to coincide with declining maternally-derived immunoglobulins, we speculate that this disease may be the result of a viral infection.
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PMID:Sporadic, severe bronchointerstitial pneumonia of foals. 1742 19

The clinician's quest for time-saving and technique-insensitive technology has led to the development of simplified self-etch adhesives that are predominantly water or solvent based. Several studies have shown that conventional air-drying procedures are incapable of eliminating all the residual water in the adhesive and that it may even cause collapse of the underlying collagen matrix. We hypothesized that heat from a light source may be effective in removing water from these adhesives. The aim of this study was, therefore, to evaluate the effectiveness of heat vs conventional air drying in eliminating water droplets from self-etch adhesive. A self-etch adhesive was applied to bur-cut dentin surfaces, which were then allotted to one of two treatment procedures for eliminating residual water from the adhesive: conventional air drying or the experimental heat application. Specimens were then prepared and analyzed using SEM. Specimens in the experimental group showed no evidence of water treeing within the adhesive layer. Thus, it was concluded that heat radiation was an effective method to remove residual water from simplified adhesives.
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PMID:Heat radiation vs air drying to remove interfacial water from self-etch adhesives. 1844 33

In order to characterize the mechanical effects of thoracic percussion per se in lung parenchyma, we analyzed respiratory impedance parameters by impulse oscillometry (12 healthy subjects) and lung mechanics by the least square method (6 healthy subjects) before (PRE-TP) and after (POS-TP) thoracic percussion, and after a deep-breath-maneuver (POS-DB). Pulmonary resistance was similar among PRE-TP, POS-TP and POS-DB while pulmonary dynamic compliance showed a significant reduction after TP (mean +/- SEM: from 0.15 +/- 0.018 L/cmH(2)O to 0.12 +/- 0.016 L/cmH(2)O; P = 0.001), returning to basal values (mean +/- SEM: 0.15 +/- 0.021; P = 0.004) after DB. Reactance parameters (AX and f (0)) evaluated by oscillometry increased significantly after TP, returning to previous values after DB. Total impedance (Z5) and respiratory system resistance at 5 Hz (R5) did not differ significantly among experimental conditions. Our data strongly suggest that thoracic percussion can promote changes in respiratory mechanics compatible with lung collapse and/or pneumoconstriction, which are, however, reversible by deep inspirations.
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PMID:Thoracic percussion yields reversible mechanical changes in healthy subjects. 1858 97

Electrophysiological recordings from hen embryo brain spheroidal reaggregates on penetrating 3D multielectrode arrays could be understood more easily if the surface structure was known in more detail. Electrophysiological activity, as grouped spikes in trains, is acquired from spheroids, indicating the inner formation a neuronal network. To this end, spheroids can be observed by environmental scanning electron microscopy. Live spheroids collapse when the supporting water is evaporated. By careful adjustment of the chamber pressure it is possible to observe fully hydrated fixed spheroids. A thin film of water tends to prevent a clear view of the surface detail. This can be evaporated to reveal the surface while taking steps to avoid both inadvertent shrinkage and rewetting. Conventional SEM shows a very different surface that is rich in protruding cell bodies and fibers. The images are compared and interpreted with some images of the surface using transmission electron microscopy.
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PMID:Optimizing environmental scanning electron microscopy of spheroidal reaggregated neuronal cultures. 1862 78

In this study, chitosan nanoparticles were prepared and incorporated in hydroxypropyl methylcellulose (HPMC) films under different conditions. Mechanical properties, water vapor and oxygen permeability, water solubility, and scanning and transmission electron microscopy (SEM and TEM) results were analyzed. Incorporation of chitosan nanoparticles in the films improved their mechanical properties significantly, while also improving film barrier properties significantly. The chitosan poly(methacrylic acid) (CS-PMAA) nanoparticles tend to occupy the empty spaces in the pores of the HPMC matrix, inducing the collapse of the pores and thereby improving film tensile and barrier properties. This study is the first to investigate the use of nanoparticles for the purpose of strengthening HPMC films.
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PMID:Properties of novel hydroxypropyl methylcellulose films containing chitosan nanoparticles. 1880 24

ABSTRACT The influence exerted by the mycoparasite Pythium oligandrum in triggering plant defense reactions was investigated using an experimental system in which tomato plants were infected with the crown and root rot pathogen Fusarium oxysporum f. sp. radicis-lycopersici. To assess the antagonistic potential of P. oligandrum against F. oxysporum f. sp. radicis-lycopersici, the interaction between the two fungi was studied by scanning and transmission electron microscopy (SEM and TEM, respectively). SEM investigations of the interaction region between the fungi demonstrated that collapse and loss of turgor of F. oxysporum f. sp. radicis-lycopersici hyphae began soon after close contact was established with P. oligandrum. Ultrastructural observations confirmed that intimate contact between hyphae of P. oligandrum and cells of the pathogen resulted in a series of disturbances, including generalized disorganization of the host cytoplasm, retraction of the plasmalemma, and, finally, complete loss of the protoplasm. Cytochemical labeling of chitin with wheat germ agglutinin (WGA)/ovomucoid-gold complex showed that, except in the area of hyphal penetration, the chitin component of the host cell walls was structurally preserved at a time when the host cytoplasm had undergone complete disorganization. Interestingly, the same antagonistic process was observed in planta. The specific labeling patterns obtained with the exoglucanase-gold and WGA-ovomucoid-gold complexes confirmed that P. oligandrum successfully penetrated invading cells of the pathogen without causing substantial cell wall alterations, shown by the intense labeling of chitin. Cytological investigations of samples from P. oligandrum-inoculated tomato roots revealed that the fungus was able to colonize root tissues without inducing extensive cell damage. However, there was a novel finding concerning the structural alteration of the invading hyphae, evidenced by the frequent occurrence of empty fungal shells in root tissues. Pythium ingress in root tissues was associated with host metabolic changes, culminating in the elaboration of structural barriers at sites of potential fungal penetration. Striking differences in the extent of F. oxysporum f. sp. radicis-lycopersici colonization were observed between P. oligandrum-inoculated and control tomato plants. In control roots, the pathogen multiplied abundantly through much of the tissues, whereas in P. oligandrum-colonized roots pathogen growth was restricted to the outermost root tissues. This restricted pattern of pathogen colonization was accompanied by deposition of newly formed barriers beyond the infection sites. These host reactions appeared to be amplified compared to those seen in nonchallenged P. oligandrum-infected plants. Most hyphae of the pathogen that penetrated the epidermis exhibited considerable changes. Wall appositions contained large amounts of callose, in addition to be infiltrated with phenolic compounds. The labeling pattern obtained with gold-complexed laccase showed that phenolics were widely distributed in Fusarium-challenged P. oligandrum-inoculated tomato roots. Such compounds accumulated in the host cell walls and intercellular spaces. The wall-bound chitin component in Fusarium hyphae colonizing P. oligandrum-inoculated roots was preserved at a time when hyphae had undergone substantial degradation. These observations provide the first convincing evidence that P. oligandrum has the potential to induce plant defense reactions in addition to acting as a mycoparasite.
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PMID:Treatment with the Mycoparasite Pythium oligandrum Triggers Induction of Defense-Related Reactions in Tomato Roots When Challenged with Fusarium oxysporum f. sp. radicis-lycopersici. 1894 62


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