The application of organic coatings is the most common and cost effective method for corrosion protection and extension of service life of many metallic structures in corrosive environments. However, ...the degradation processes rapidly develop once the disruption of the protective barrier occurs. Therefore, an active protection based on the “self-healing” of defects in coatings is necessary to attain a long-term effect.
The present paper brings a brief summary of recent works in the area of new multi-level protective systems, based on the controlled release of anticorrosion species from “smart” micro and nanocontainers incorporated into a polymer or hybrid coating matrix. Nanocontainer (or nanoreservoir) is a nanosized volume filled with an active substance confined in a porous core and/or a shell which precludes the direct contact between the active agent and the adjacent environment.
Several types of nanoreservoirs of corrosion inhibitors, nanotraps and microcapsules with water displacers have been recently developed, incorporated into coating systems and assessed in terms of active corrosion protection. A multi-level self-healing approach combining several damage prevention and restoration mechanisms within the same system, including the entrapment of corrosive ions, corrosion inhibition and water displacement from active defects, is here reviewed.
The self‐healing anticorrosion effect of layer‐by‐layer (LbL) assembled nanoreservoirs (polyelectrolyte‐coated nanoparticles) embedded in a hybrid coating deposited onto an Al alloy is investigated ...(see figure). The corrosion inhibitor, benzotriazole, is entrapped in the polyelectrolyte at the LbL assembly step; its release is initiated by local pH changes near the corrosion‐damaged zones in the alloy. The nanoreservoirs increase long‐term corrosion protection of the substrate and provide effective inhibitor storage and its prolonged release on demand.
The present work reports the synthesis of layered double hydroxides (LDHs) nanocontainers loaded with different corrosion inhibitors (vanadate, phosphate, and 2-mercaptobenzothiazolate) and the ...characterization of the resulting pigments by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The anticorrosion activity of these nanocontainers with respect to aluminum alloy AA2024 was investigated by electrochemical impedance spectroscopy (EIS). The bare metallic substrates were immersed in dispersions of nanocontainers in sodium chloride solution and tested to understand the inhibition mechanisms and efficiency. The nanocontainers were also incorporated into commercial coatings used for aeronautical applications to study the active corrosion protection properties in systems of industrial relevance. The results show that an enhancement of the active protection effect can be reached when nanocontainers loaded with different inhibitors are combined in the same protective coating system.
Investigation of the marine sponge Agelas dispar MeOH fractions using feature-based molecular networking, dereplication, and isolation led to the discovery of new bromopyrrole-derived metabolites. An ...in-house library of bromopyrrole alkaloids previously isolated from A. dispar and Dictyonella sp. was utilized, along with the investigation of an MS/MS fragmentation of these compounds. Our strategy led to the isolation and identification of the disparamides A–C (1–3), with a novel carbon skeleton. Additionally, new dispyrins B–F (4–8) and nagelamides H2 and H3 (9 and 10) and known nagelamide H (11), citrinamine B (12), ageliferin (13), bromoageliferin (14), and dibromoageliferin (15) were also isolated and identified by analysis of spectroscopic data. Analysis of MS/MS fragmentation data and molecular networking analysis indicated the presence of hymenidin (16), oroidin (17), dispacamide (18), monobromodispacamide (19), keramadine (20), longamide B (21), methyl ester of longamide B (22), hanishin (23), methyl ester of 3-debromolongamide B (24), and 3-debromohanishin (25). Antibacterial activity of ageliferin (13), bromoageliferin (14), and dibromoageliferin (15) was evaluated against susceptible and multi-drug-resistant ESKAPE pathogenic bacteria Klabsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterococcus faecalis. Dibromoageliferin (15) displayed the most potent antimicrobial activity against all tested susceptible and MDR strains. Compounds 13–15 presented no significant hemolytic activity up to 100 μM.
In the present work, for the first time Zn-Al layered double hydroxide (LDH) nanocontainers were grown in-situ on the surface and in the pores of plasma electrolytic oxidation (PEO) layer and then ...loaded with a corrosion inhibitor to provide active protection. The developed LDH-based conversion process ensures partial sealing of the pores and provides an effective corrosion inhibition on demand leading to increased fault-tolerance and self-healing properties. The structure, morphology and composition of the LDH-sealed PEO coatings on 2024 aluminum alloy were investigated using SEM, TEM/FIB, XRD and GDOES. Electrochemical impedance spectroscopy and scanning vibrating electrode techniques show a remarkable increase in the corrosion resistance and fault tolerance when PEO coating is sealed with a LDH-inhibitor treatment.
Abstract In Brazil, American visceral leishmaniasis (AVL) has become a public health concern due to its high incidence and lethality. This study aimed to analyze the clinical, epidemiological, and ...laboratory aspects of AVL in a state of Brazil. This descriptive, cross-sectional, retrospective, and quantitative study of notified cases of AVL was carried out in Alagoas between 2008 and 2017 from data obtained from DATASUS/SINAN. Sociodemographic, clinical, and laboratory variables were analyzed. A descriptive analysis was performed using absolute values and valid percentages, using tables and/or graphs. Data processing was performed using Stata 12.0®. Results with P <0.05 were considered statistically significant. During the study period, 352 cases of AVL were reported, of which 6.82% died and 38.92% had met a cure criterion. Male patients were predominant (66.76%). Of the total infected patients, 16.76% had attended only the 1st to the 4th grades, with those most affected aged 1 to 4 years (28.69%). Laboratory diagnostic criteria were most commonly used to confirm the notified cases (76.42%), whereas 51.70% and 8.52% of the cases had positive parasitological and immunofluorescence diagnoses, respectively. Finally, the study showed a higher prevalence of the disease in children, men and in rural residents. Although with low lethality, the expressive frequency of AVL in the State of Alagoas was still verified, since there was an increase in the number of cases during the years of the study.
Resumo No Brasil, a leishmaniose visceral americana (LVA) tornou-se uma preocupação de saúde pública devido à sua alta incidência e letalidade. Este estudo teve como objetivo analisar os aspectos clínicos, epidemiológicos e laboratoriais da AVL em um estado brasileiro. Este estudo descritivo, transversal, retrospectivo e quantitativo dos casos notificados de AVL foi realizado em Alagoas entre 2008 e 2017 a partir de dados obtidos do DATASUS/SINAN. Foram analisadas variáveis sociodemográficas, clínicas e laboratoriais. Foi realizada uma análise descritiva utilizando-se valores absolutos e percentuais válidos, utilizando tabelas e/ou gráficos. O processamento dos dados foi realizado por meio do Stata 12.0®. Os resultados com P<0,05 foram considerados estatisticamente significativos. Durante o período de estudo, foram notificados 352 casos de LVA, dos quais 6,82% morreram e 38,92% atenderam a um critério de cura. Os pacientes do sexo masculino foram predominantes (66,76%). Do total de pacientes infectados, 16,76% tinham sido atendidos apenas do 1º ao 4º ano, com os mais afetados entre 1 e 4 anos (28,69%). Os critérios de diagnóstico laboratorial foram mais utilizados para confirmar os casos notificados (76,42%), enquanto 51,70% e 8,52% dos casos apresentaram diagnósticos positivos parasitológicos e imunofluorescência, respectivamente. Por fim, o estudo demonstrou maior prevalência da doença em crianças, homens e nos residentes em zona rural. Embora com letalidade baixa, constatou-se ainda a expressiva frequência da LVA no Estado de Alagoas, uma vez que houve aumento do número de casos durante os anos do estudo.
Nowadays, there is a strong demand on the search of thinner, but more effective organic coatings for corrosion protection of metallic substrates, like galvanised steel, used in the automotive ...industry. In order to guarantee effective corrosion protection of these coatings, and because chromate-based pigments cannot be used, one of the most attractive strategies consists on the modification of the organic matrix with nano-additives filled with corrosion inhibitors, which can be released to the active sites. In this work, two different nano-additives are explored as potential self-healing materials for the development of active protective coatings. These additives are layered double hydroxides and cerium molybdate hollow nanospheres loaded with mercaptobenzothiazole, as a corrosion inhibitor. These additives were added to epoxy primers, individually, or combining the two nanoadditives in the same layer.
The electrochemical behaviour and the potential of self-healing ability were studied by electrochemical impedance spectroscopy, scanning vibrating electrode technique and scanning ion-selective electrode technique. The results reveal that both types of nanocontainers can provide effective corrosion inhibition on artificial induced defects, at different stages of the degradation process. Moreover, the results also show that there is a synergistic effect concerning corrosion inhibition and self-healing potential when a mixture of the two nanocontainers is used. The mechanism of self healing is presented and discussed in terms of effect of organic inhibitor and role of the nanocontainers, including effect of cerium ions released from cerium molibdate nanoparticles.
Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, ...methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a "clumped isotope" technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (<50°C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models.
Patients with ischemic heart failure (iHF) have a high risk of neurological complications such as cognitive impairment and stroke. We hypothesized that iHF patients have a higher incidence of ...impaired dynamic cerebral autoregulation (dCA). Adult patients with iHF and healthy volunteers were included. Cerebral blood flow velocity (CBFV, transcranial Doppler, middle cerebral artery), end-tidal CO
(capnography), and arterial blood pressure (Finometer) were continuously recorded supine for 5 min at rest. Autoregulation index (ARI) was estimated from the CBFV step response derived by transfer function analysis using standard template curves. Fifty-two iHF patients and 54 age-, gender-, and BP-matched healthy volunteers were studied. Echocardiogram ejection fraction was 40 (20-45) % in iHF group. iHF patients compared with control subjects had reduced end-tidal CO
(34.1 ± 3.7 vs. 38.3 ± 4.0 mmHg, P < 0.001) and lower ARI values (5.1 ± 1.6 vs. 5.9 ± 1.0, P = 0.012). ARI <4, suggestive of impaired CA, was more common in iHF patients (28.8 vs. 7.4%, P = 0.004). These results confirm that iHF patients are more likely to have impaired dCA compared with age-matched controls. The relationship between impaired dCA and neurological complications in iHF patients deserves further investigation.
para‐Quinone methides (p‐QMs) are naturally occurring molecules that have been finding increasing synthetic applications in the last few years. The presence of two electronically different exocyclic ...conjugate substituents in their structure, carbonyl and methylidene, leads to a pronounced reactivity owing to the polarization of the molecule. In this sense, those are prone to undergo the attack of nucleophiles in the terminal carbon exocyclic double bond, behaving as vinylogous electrophiles and generating 1,6‐addition products. In this context, in the last few years the development of catalytic approaches for 1,6‐nucleophilic addition reactions involving p‐QMs has attracted considerable attention. Considering the extensive applications that such molecules have found in the last decades in 1,6‐addition reactions, in this review we comprehensively discuss the historical development of this field, starting with early approaches on natural product synthesis, going through seminal non‐stereoselective processes and progressing to cutting‐edge asymmetric‐catalyzed approaches.
para‐Quinone methides (p‐QMs) are naturally occurring molecules with two electronically different exocyclic conjugate substituents in their structure, carbonyl and methylidene, which gives them a pronounced reactivity owing to the polarization of the molecule. By attack of nucleophiles in the terminal carbon exocyclic double bond, they generate 1,6‐addition products.
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