Early Stages Of Exposure Research Articles

Experience in using low-temperature plasma after surgical treatment of breast cancer

Background.Plasma medicine is a new direction in science at the intersection of plasma physics and chemistry with biology and medicine low-temperature plasma (LTP) has a number of fundamental advantages, which include high non-specific bactericidal activity, low probability of the appearance of stable forms, the absence of ionizing radiation and highly toxic substances. In addition, LTP stimulates healing of infected wounds at the early stages of exposure, which makes LTP a promising method of treating various pathological conditions.
 Clinical case description.Low-temperature argon plasma treatment was performed for a patient with a diagnosis of: cancer of the right breast cancer T2N1M0, IIB stage. Condition after non-adjuvant PCT and radical resection of the right breast. Complication: Abscess in the area of the postoperative scar. After the 3rd treatment with plasma flow, the wound was sutured and while continuing treatment with low-temperature argon plasma, the patient began radiation therapy of the right breast and regional lymph flow zones in the mode of classical dose fractionation. During the follow-up period, the patient showed positive dynamics in the area of the postoperative scar, which did not lead to a long period of rehabilitation in the postoperative period and radiation therapy was started in a timely manner.
 Conclusion.Thus, the use of this technique in clinical practice has proven that the period of rehabilitation in the postoperative period is shortened for continuous comprehensive treatment of severe cancer patients with breast cancer.

Флуоресценция хлорофилла в оценке воздействия соединений тяжёлых металлов на водные организмы

Fluorescent methods allow to improve the bioassays because of time effectiveness. These methods give information on chlorophyll concentration and plant photosynthetic apparatus activity in a short period of time. The aim of this study was to estimate the sensitivity of aquatic organisms to heavy metals using chlorophyll fluorescent methods. The test-organisms of different taxonomic categories were used, including thermophilic strain Chlorella vulgaris Beijer, aquatic plants Elodea сanadensis Michx. and Lemna minor L., crustacean Daphnia magna Straus. Fluorimeter “Foton 10” developed in SibFU was employed to measure prompt and delayed fluorescence (PF and DF respectively). The experiments revealed that copper ions affected DF of chlorella in 30 minutes, resulting in a 50% decrease of relative indicator of DF (RIDF) in the range of concentrations 0.005-0.01 mg/l of Cu2+. Measuring the DF of duckweed was less time-consuming compared to registration the changing of morphological parameters when the plants were exposed to heavy metals. Copper, cadmium, and nickel exposures were found to decrease the RIDF of duckweed by more than 50% at the concentrations of 0.17, 0.31, and 1.89 mg/l respectively. However, zinc had no significant effect on the RIDF of Lemna minor in the range of 0.1-8 mg/l of Zn2+ within 24 h of exposure time. The analysis of fluorescent parameters of Canadian elodea showed the possibility of using the plant as a sorbent during the bioremediation of aquatic environments from heavy metals. Registration of chlorophyll fluorescence allowed revealing the toxic effects of negligible concentrations of heavy metals in experiments with the feeding rate of daphnids. The median effective concentrations (EC50) were 0.002, 0.02, 0.4, and 0.25 mg/l of Cd2+, Cu2+, Zn2+, and potassium dichromate respectively. This makes it possible to obtain information on the effects of pollution in the early stages of exposure and in a shorter time. Thus, the use of chlorophyll fluorescence in biomonitoring the state of the aquatic environment makes it possible to more quickly respond to changes in the ecological situation in water bodies.

A Study on Ecotoxicological Effects of Nano-copper Oxide Particles to Portunus trituberculatus.

As an important nano-material, nano-copper oxide particles (CuO-ENPs) harbor a vast range of characteristics, including an electronic correlation effect, thermal stability, catalytic activity, sterilization, and other properties. At present, the mechanism of ecotoxicological effects of CuO-ENPs is unclear and has been inconclusive. Therefore, we aimed to explore the ecotoxicological effects of nano-copper oxide particles (CuO-ENPs) on Portunus trituberculatus. The crabs were exposed to seawater containing different concentrations of CuO-ENPs to conduct the acute toxicity test and chronic accumulation test. Acute toxicity, metal accumulation, and SOD activity in different tissues were determined. We found that the lethal concentration of 50% 96 h LC50 of CuO-ENPs to Portunus trituberculatus belonged to low toxicity. The accumulation of CuO-ENPs in different tissues from high to low was: gill > haemolymph > muscle > hepatopancreas > heart and stomach, and decreased gradually with time after reaching the maximum. Subsequently, it was in a relatively steady state after a certain period and showed an obvious concentration effect. With the increment of exposure time and concentration of CuO-ENPs, the SOD activities in different tissues were quite different. In conclusion, the 96 h LC50 of CuOENPs to Portunus trituberculatus was 49 mg/L, and its toxicity belonged to low toxicity. With the increment of exposure time and concentration of CuO-ENPs, the SOD activities in different tissues were quite different, which were increased remarkably in gill and hepatopancreas, but were suppressed at an early stage of exposure in muscle and haemolymph.

Biochemical toxicity, lysosomal membrane stability and DNA damage induced by graphene oxide in earthworms.

With the growing production and use of carbon nanomaterials (CNMs), the risk of their releases to the environment has drawn much attention. However, their potential effect on soil invertebrates has not yet been systematically assessed. Herein, the toxic effects of graphene oxide (GO) on earthworms (Eisenia fetida) were thoroughly investigated. Exposure to different doses of GO (0, 5, 10, 20, and 30gkg-1) was conducted for 7, 14, 21, and 28 days. The results showed that enzymatic activity was stimulated at the early stages of exposure (7 days and 14 days) and inhibited after 14 days for catalase (CAT) and after 21 days for peroxidase (POD) and superoxide dismutase (SOD), especially at high GO doses. The content of MDA showed an increasing trend over the whole exposure period and was significantly elevated by GO from 21 days except at the dose of 5g kg-1on day 21. Lysosomal membrane stability and DNA damage presented dose- and time-dependent relationships. Graphene oxide remarkably decreased lysosomal membrane stability except at the dose of 5gkg-1 on day 7. The tail DNA%, tail length and olive tail moment increased with increasing GO dose throughout the exposure duration, reaching maximum values at the end of exposure (28 days). These findings suggest that GO induces oxidative stress and genotoxicity in Eisenia fetida, resulting in lipid peroxidation, decreased lysosomal membrane stability and DNA damage. Therefore, attention should be paid to the potential pollution and risk associated with graphene oxide application. The results can provide valuable information for environmental safety assessment of graphene nanomaterials in soil.

Study of early metabolic changes in experimental animals with acute toxic exposure to paracetamol and against the background of correction

Paracetamol is one of the most widely used and popular over-the-counter analgesics and antipyretic drugs in the world. The number of registered cases of paracetamol-induced liver intoxication is constantly increasing in the world every year. It seems relevant to study early metabolic disorders in the liver in acute paracetamol intoxication and assess the effectiveness of the timely use of hepatoprotective drugs. The aim of this research is to study metabolic changes in laboratory animals at the early stages of exposure to paracetamol and against the background of correction with oxymethyluracil, ademetionine and mexidol. An experimental study of metabolic changes in laboratory animals under acute exposure to toxic doses of paracetamol and against the background of correction was carried out. Biochemical parameters in the blood serum of laboratory animals were investigated. The obtained results showed that the intake of paracetamol in toxic doses was accompanied by impaired hepatic metabolism at the earliest stages of exposure. With the corrective action of the studied drugs, metabolic disturbances caused by paracetamol intoxication were restored. At the same time, OMU, as well as ademetionine and ethylmethylhydroxypyridine succinate, is able to normalize metabolic changes after the acute toxic effect of paracetamol, and has a pronounced advantage in terms of the protein-synthetic function of hepatocytes.

Understanding the Mechanisms of Early Stage Aluminum Corrosion

Aluminum alloys are widely used in many applications due to their inherent corrosion resistance, which is attributed to the formation of a protective oxide layer. However, the strength and durability of many Al-based materials is reduced in humid environments. Consequently, detailed mechanistic understanding of corrosion reactions over time is necessary to predict the cost, safety, and performance. Most of the current knowledge of atmospheric aluminum corrosion is built on response relationships upon extensive corrosion and typically involve a first-order correlation of corrosion data with environmental conditions. However, mechanistic understanding of corrosion processes is still limited, particularly at the early stages of exposure to humid environments. In addition, the effects of electrolytes such as sodium chloride present in the environment are still not fully understood. This presentation will focus on our recent efforts to reveal the mechanistic dependence of electrochemical aluminum corrosion in humid air in the presence of NaCl. The rate of corrosion is explored through complimentary experimental and theoretical analyses relating corrosion rate to electrolyte chemistry, mass uptake and corrosion products. As an experimental platform, we use quartz crystal microbalance (QCM) electrodes coated with aluminum and sodium chloride using sputtering techniques. Structure, composition, and surface morphology of the samples were characterized by grazing-incidence X-ray diffraction, FTIR spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy. The QCM provides operando data with nanogram resolution on the formation of the corrosion product layer, from which we can derive rate constants for aluminum surface reactions. We find that the reaction rate in dry air is negligible, but a dramatic acceleration is observed at 50% RH and above. In addition, this study provides additional insight into: 1) the influence of the sodium chloride film thickness on the rate and reaction products; 2) the role of surface termination and roughness on aluminum oxide/hydroxide formation; and 3) the electrochemical corrosion reaction rate acceleration as a function of temperature. Finally, based on the interplay between theory and experiment we achieved preliminary understanding of the rate-limiting steps, which we will use to develop validated computational models of early-stage (hours to several days) aluminum corrosion. Figure 1

Do the graphene nanoflakes pose a potential threat to the polychaete Hediste diversicolor?

Graphene is a promising material with a wide range of future applications that could potentially lead to its transfer from numerous water and terrestrial sources to the sea, thus fate and effects of graphene in the marine ecosystem deserve attention. Within this work, the impact of the short- and long-term exposure (36 h and 24 days) of the marine benthic polychaete Hediste diversicolor to various concentrations (36 h: 0.4, 4, 40 and 400 mg L−1; 24 days: 4 and 40 mg L−1) of the pristine graphene multilayer nanoflakes (of thickness 8–12 nm) was investigated. Experiments revealed a limited toxic effect of graphene on H. diversicolor. Although the polychaetes ingested graphene, no impact on their total energy content was found. The toxic effect expressed by significant elevation of catalase activity indicating activation of defence mechanisms was recorded but only at the early stage of exposure. Activities of other antioxidant and cellular damage biomarkers (SOD, GST, GSH, MDA, CBO) remained unaffected. Moreover, no neurotoxic effect expressed by inhibition of acetylcholinesterase (AChE) activity was observed. Substantial inter-individual variability in the activities of some biomarkers at the end of the long-term experiment was found. Polychaetes were buried deeper in the sediment with graphene than in the controls indicating an escape reaction and avoidance behaviour. The latter may lead to the transfer of graphene from the sediment surface to deeper sediment layers with unknown consequences for the benthic ecosystem.

Immunopathological mechanisms of toxic damage to the liver, thymus and spleen

Objective: to establish the features of the immune response in the early stages of diffuse toxic damage. Materials and methods. Diffuse toxic liver damage of male Wistar rats was caused by a single intraperitoneal injection of an oil solution of carbon tetrachloride (CCl4) at a dose of 50 mg/100 g. Animals were carried out from the experiment on days 3, 7 and 14. The study included hematological and histological analysis, immunohistochemical (IHC) staining of liver, thymus and spleen tissues, quantitative evaluation of CD3+, CD45RA+ (T-and B-lymphocytes), F4/80+ (macrophages), and HSP70+-cells. Results. CCl4 administration has been shown to cause structural disorders of liver, thymus, and spleen tissue. In the early stages, there is an increase in CD3+-cells in the liver and spleen, while CD45RA+-cells predominating in the thymus. On the 3rd day after CCl4 administration, the number of F4/80+-cells in the liver increases by 56.7%, in the thymus and spleen by 21% and 19.3%, respectively, there is also an increase in the number of HSP70+-cells roughly 2 times in the liver and thymus, and by 7 times in the spleen. Conclusion. Hepatotropic poison CCl4 causes damage not only the liver but the organs of immunopoesis. In the early stages of exposure to the toxicant the predominant population is T-lymphocytes (CD3+-cells) in the liver and spleen, and B – lymphocytes (CD45RA+-cells) in the thymus. In all the studied organs, the number of macrophages increases on the 3rd day of the experiment, and significantly decreases at the later term. This fact indicates that macrophages act as a target of toxic effects. The increase in the number of HSP70+-cells in the liver, thymus, and spleen in response to toxic damage is likely aimed at triggering the repair or elimination of denatured proteins that are toxic to the cell.

Potassium Deficiency Significantly Affected Plant Growth and Development as Well as microRNA-Mediated Mechanism in Wheat (Triticum aestivum L.).

It is well studied that potassium (K+) deficiency induced aberrant growth and development of plant and altered the expression of protein-coding genes. However, there are not too many systematic investigations on root development affected by K+ deficiency, and there is no report on miRNA expression during K+ deficiency in wheat. In this study, we found that K+ deficiency significantly affected wheat seedling growth and development, evidenced by reduced plant biomass and small plant size. In wheat cultivar AK-58, up-ground shoots were more sensitive to K+ deficiency than roots. K+ deficiency did not significantly affect root vitality but affected root development, including root branching, root area, and root size. K+ deficiency delayed seminal root emergence but enhanced seminal root elongation, total root length, and correspondingly total root surface area. K+ deficiency also affected root and leaf respiration at the early exposure stage, but these effects were not observed at the later stage. One potential mechanism causing K+ deficiency impacts is microRNAs (miRNAs), one important class of small regulatory RNAs. K+ deficiency induced the aberrant expression of miRNAs and their targets, which further affected plant growth, development, and response to abiotic stresses, including K+ deficiency. Thereby, this positive root adaption to K+ deficiency is likely associated with the miRNA-involved regulation of root development.

Cracking characteristics and pore development in concrete due to physical attack

This study provides a fundamental understanding on the deterioration of concrete due to physical sulfate/salt attack (PSA), including local cracking and pore structure development. The results show that sulfate salt crystals in a partially immersed concrete specimen preferred to precipitate in relatively large pores (DP-III, from 1 to 100 µm in diameter) in the concrete at the early stage of exposure. The persistent formation of small pores (DP-I and DP-II) and pore throats (PT-I and PT-II) occurred at the late stage of exposure. The gel pores, transition pores and even small capillary pores played an important role in providing space for crystal growth. The pore filling during the early stage resulted in a transient gain of specimen mass due to the capacity of pre-existing voids to accumulate the precipitated crystals (buffer effect). The later cracking degeneration induced by the pressure from the crystals was found to be limited to the subflorescence zone. This cracking degeneration was a time-dependent process that primarily developed along with relatively unsubstantial zones in the concrete, such as the interfacial transition zone (ITZ), until the extensive coalescence of these pressure-induced cracks.

Polystyrene nanoplastics cause growth inhibition, morphological damage and physiological disturbance in the marine microalga Platymonas helgolandica

Effects of nanoplastics at low level on the marine primary producer are largely unclear. To assess the potential risk of nanoplastic pollution, this study exposed marine green microalgae Platymonas helgolandica to 20, 200, and 2000 μg/L 70-nm polystyrene nanoplastics for 6 days. Nanoplastics significantly inhibited the growth of P. helgolandica during the first 4 days of exposure, and elevated heterocyst frequency was observed in 200 and 2000 μg/L exposure groups in the early exposure stage. Exposure to 200 and 2000 μg/L nanoplastics for 4 days increased the membrane permeability and mitochondrial membrane potential, and decreased light energy used in photochemical processes of microalgae. Moreover, clear morphological changes, including surface folds, fragmentation, aggregation cluster, and rupture, in the microalgae exposed to nanoplastics were observed under scanning electron microscope and transmission electron microscope. These results demonstrate that nanoplastics could reduce the microalgal vitality by the damage on cell morphology and organelle function.

Effect of microplastics and microplastic-metal combinations on growth and chlorophyll a concentration of Chlorella vulgaris

Microplastic pollution has become a global problem and it is threatening soil and water bodies around the world. In this study, i) the sole effect of 0.5 μm sized polystyrene microplastics under different concentrations (1, 5, 50, 100, and 1000 mg/L) and ii) the combined effect of the microplastic-metal combination (Cu, Zn, Mn) were investigated on the growth and chlorophyll a content of the freshwater microalgae; Chlorella vulgaris. Results showed that lower concentrations of microplastics (1, 5 mg/L) had no impact while higher concentrations (50, 100, 1000 mg/L) significantly reduced growth and chlorophyll a content of Chlorella vulgaris. Highest inhibition ratios were found between 15.71 and 28.86% on growth and 9.2–21.3% on chlorophyll a concentration for 50–1000 mg/L of microplastic. Microplastic-metal combinations showed greater inhibition on growth and chlorophyll a concentration. It has been shown that single metal-microplastic combinations reduced growth by 47.83–49.57% and chlorophyll a concentration by 44.75–50.25%. However, a much higher impact was observed for the triple metal-microplastic combination by 70.43% and 64.09% on growth and chlorophyll a content, respectively. SEM images provided insight into the probable cause of the toxic effect as the microplastic particles were adsorbed and embedded on the algal cell. Negative effects were observed generally at the early stages of exposure and weakened over time.

Accelerated Weathering and Water Absorption Behavior of Kenaf Fiber Reinforced Acrylic Based Polyester Composites

Nonwoven kenaf (KF) mat reinforced acrylic-based polyester bio-resin composites that were prepared by an impregnation process followed by compression molding. They were exposed to the durability test of accelerated weathering and water absorption. Accelerated weathering test through UV irradiation caused modification in chemical, mechanical, surface appearance and color change of the composites. Two competing reactions occurred throughout the exposure period, i.e. post crosslinking and photo-oxidation process. FTIR analysis revealed that the former occurred at the early stage of exposure while the latter towards the end of the exposure, exhibited by an accentuated increase in carbonyl and vinyl index. The post-crosslinking process contributes to the improvement in flexural properties and thermal stability of the composites, whereas the oxidation process does not. SEM observation showed that the degradation by photo-oxidation resulted in the formation of voids and blisters on composite’s sample. Water uptake of all composites was found to follow Fickian behavior. Good recoveries (exceeding 79 %) of flexural properties were obtained upon re-drying. However, a significant reduction in flexural strength and modulus was obtained in the wet state condition. SEM observation revealed that full recovery was not possible because of the impairment of the -matrix interfacial region. Relatively higher flexural properties were exhibited by alkali-treated KF composites even after the durability test due to the improved strength and –matrix adhesion following the treatment.

Effects of copper on a reconstructed freshwater rainbow trout gill epithelium: Paracellular and intracellular aspects

The barrier properties and intracellular responses of a primary cultured trout gill epithelium (containing both mitochondria-rich and pavement cells) were examined over 24 h of copper (Cu) exposure (0, 200 and 1000 μg/L) in apical fresh water. Transepithelial resistance (TER) and mRNA abundance of tight junction proteins zonula occludens-1, occludin, cingulin, claudin-8d and -28b were examined as endpoints of barrier function and the paracellular pathway. Intracellular endpoints analyzed were Cu accumulation, Na+ content, carbonic anhydrase activity and mRNA abundance of carbonic anhydrase (ca-II) and Na+/K+ ATPase (nka α1a and nka α1b isoforms). After a brief initial drop in TER in the 1000 μg Cu/L treatment, Cu at both levels increased TER over the first 6 h of exposure but there were no differences among groups from 12 h onwards. After 24 h of Cu exposure, there were no differences in mRNA abundance of any of the tight junction proteins examined. Cu accumulation occurred at 1000 μg Cu/L (5.5-fold increase), but no depletion of Na+ content. Carbonic anhydrase activity decreased significantly (by 76%), however Cu exposure did not alter the transcript abundance of ca-II, nka α1a, or nka α1b. This study provides a first report of carbonic anhydrase sensitivity to Cu exposure in a cultured model gill epithelium. We conclude that Cu impacts the permeability of this model during the early stages of exposure and that the use of carbonic anhydrase inhibition as an endpoint of metal toxicity in this model preparation may be useful for future mechanistic investigations and environmental monitoring.

Спектральные характеристики растений на ранних стадиях воздействия ионизирующих излучений

Спектральные характеристики растений на ранних стадиях воздействия ионизирующих излучений

Single and joint oxidative stress of cadmium and phenanthrene on the Bivalve Anadara subcrenata

Single and joint oxidative stress of cadmium (Cd) and phenanthrene (Phe) on Anadara subcrenata were investigated under laboratory conditions with biomarkers such as reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD) and total antioxidant capacity (TAOC). The results indicated that the ROS level in Anadara subcrenata exposed to Cd and Phe significantly (P < 0.05) increased during the early exposure stage, and the TAOC level and SOD activity were induced as the response of the antioxidant defense system, and this followed a damage, recovery or acclimation event. The MDA content was negatively correlated with SOD activity. As the time went on, the ROS level decreased gradually and was close to that in the control after 9 days; the TAOC level decreased accordingly, but the recovery rate of the SOD activity was slower than that of the TAOC level. High concentrations of Cd or Phe had a stronger oxidative stress effect on Anadara subcrenata. Phe had a stronger effect on the SOD activity of Anadara subcrenata. The joint effects of Cd and Phe on the levels of ROS and TAOC, SOD activity and MDA content in Anadara subcrenata are dependent on their concentration combination, which were called the double-dose dependent effects and time-dependent effects, respectively. The binary mixture treatments of 477.33 μg/L Cd and 48.08 μg/L Phe had the highest oxidative stress on Anadara subcrenata.

Waterborne exposure to microcystin-LR alters thyroid hormone levels, iodothyronine deiodinase activities, and gene transcriptions in juvenile zebrafish (Danio rerio).

This study investigated the effects of microcystin (MC) on the regulation of thyroid hormone (TH) metabolism in juvenile zebrafish exposed to MC-LR. The results showed that acute MC-LR exposure at concentrations ranging from 50 μg/L to 400 μg/L led to significant reductions in thyroxine (T4) and triiodothyronine (T3) levels in juvenile zebrafish. The transcription levels of genes involved in TH synthesis, such as corticotropin-releasing hormone (crh), thyroid-stimulating hormone (tsh), thyroid peroxidase (tpo) and transthyretin (ttr), were significantly decreased followed by an increase after MC-LR exposure. Transcription of the TH nuclear receptors (tr-α and tr-β) was significantly reduced during the exposure period. Moreover, the activities of iodothyronine deiodinase type Ⅰ (ID1) and iodothyronine deiodinase type Ⅱ (ID2) showed initially decreased and then increased trend, while the activity of iodothyronine deiodinase type Ⅲ (ID3) significantly decreased during MC-LR exposure. In addition, the effect of MC-LR on deiodinase activities and T4 contents were important causes of the decreased T3 at the early exposure stage. These results indicated that acute MC-LR exposure significantly interfered with the transcription of genes related to TH synthesis, transport and metabolism, and affected normal function of the thyroid which leads to decrease of T4 and T3 in juvenile zebrafish. Therefore, the thyroid function is susceptible to interference by MC-LR, and it may cause adverse effects on the growth and development of juvenile zebrafish.

Gel-Electrolyte EIS setup used for probing of IR Dried/Cured industrial coatings

Probing of IR dried/cured solvent based industrial coatings has been done by employing a two-electrode, gel-electrolyte electrochemical impedance spectroscopy setup that has enabled measurement of the coating electrical characteristics without the influence of the liquid electrolyte. In the present study, along with the coating impedance at 0.1 Hz, we suggest the use of the first derivative of the phase angle as a sensitive tool to detect the influence of the corrosion related low frequency RC circle appearance on the coating performance in the early stages of exposure. The conclusions of the EIS analysis are that the IR curing improves barrier properties of common industrial coatings and decreases the coating capacitance and dielectric constant, with respect to the laboratory ambient dried/cured referent systems. FTIR and DSC show no indications of permanent coating degradation, while the pull-off strength shows a slight, ≤ 10% decay of coating adhesion/cohesion characteristics. The water uptake calculated from the EIS data compared to the FTIR and DSC results, indicates various modes of water adsorption into the coating. It has been demonstrated that EIS may be used for obtaining quick information about the early-stage, non-visible coating degradation in the case of IR drying/curing as a time saving production process alteration that may bring significant benefit to the manufacturer of coated metallic products.

Degradation behavior and mechanism of polyurethane coating for aerospace application under atmospheric conditions in South China Sea

The polyurethane coating for aerospace application was exposed to the marine atmospheric environment for different time period, and the degradation behavior and mechanism of the coating were evaluated by morphology, appearance, chemical changes, adhesion, barrier properties and thermal stability. The results revealed that the appearance of the polyurethane coating was quickly degraded in the early exposure stage, and then changed slowly in the late exposure stage. ATR-FTIR and XPS analysis demonstrated that ultraviolet radiation was an important cause of the rupture of chemical bonds, the chain scission of the polyurethane was dominated by the C–N bond rupture. There were good corresponding relationships between the adhesion and barrier properties of the coating during the degradation process. Furthermore, the thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis showed that the marine atmospheric environment obviously reduced the thermal stability of the coating.

Influence of environment on response characteristics of a high-strength aluminum alloy

This paper presents the results of a study aimed at understanding the stress corrosion cracking behavior of aluminum (Al) alloy 2219 with specific reference to understanding the mechanisms governing initiation of cracks and their progressive growth through the alloy microstructure. The influence of stress level on the initiation of stress corrosion cracks was determined. Results of this study revealed pitting to be the main type of corrosion that occurred during the early stages of exposure of the chosen aluminum alloy to an acidic environment. After the formation and presence of a pit, the applied stress was found to induce local stress concentration, promoting the early initiation of one or more microscopic cracks, while concurrently enabling fine microscopic cracks to expand and grow through the alloy microstructure. The cracks were observed to propagate along the grain boundaries, with few of the cracks growing through the crystals. With appropriate selection of electrochemical parameters, the influence of applied stress, coupled with the use of a solid mechanics module in synergism with an electrochemical corrosion module, on the stress corrosion behavior of the chosen aluminum alloy 2219 was studied using an iterative approach, and numerical prediction of corrosion was made possible.