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Passive daytime radiative cooling (PDRC) as a zero-energy cooling technology that reflects most of sunlight and emits infrared thermal radiation to outer space, has attracted much attention. However, most PDRC materials suffer dust accumulation problem during long-term use, seriously detrimental to their cooling performance. Here, we demonstrate a micro-structured polyethylene film fabricated through a scalable hot embossing lithography (named HELPE), enables good superhydrophobic property and therefore excellent self-cleaning performance as a universal protective layer for most PDRC materials. Specifically, the precisely designed three-dimensional periodic micron columns on polyethylene film allow for high water droplet contact angle of 151°, and the intrinsic molecular bindings of polyethylene endow low solar absorption (A = 3.3 %) and high mid-infrared transmission (T = 82.3 %) for negligible optical impacts on underlying PDRC materials. Taking polyvinylidene fluoride (PVDF) radiative cooler as an example, when covered with the HELPE film the net cooling performance maintains unchanged (7.5 °C in daytime and 4.5 °C in nighttime) compared to that without HELPE film. After 12 days continuous outdoor experiment, none of obvious dust accumulation can be observed on the radiative cooler covered with HELPE film. Our work offers a universal pathway for most PDRC materials toward practical applications with minimal maintenance need.

Hindered gas bubble release and limited electron conducting process represent the major bottlenecks for large scale electrochemical water splitting. Both the desorption of bubbles and continuous electron transport are achievable on the surfaces of biomimetic catalytic materials by designing multiscale structural hierarchy. Inspired by the tubular structures of the deep-sea sponges, we fabricated an exceptionally active and binder-free porous nickel tube arrays (PNTA) decorated with NiFe-Zn

Objective To study data about SARS-CoV-2 virus shedding and clarify the risk factors for prolonged virus shedding. Methods Data were retrospectively collected from adults hospitalized with laboratory-confirmed coronavirus disease-19 (COVID-19) in Wuhan Union Hospital. We compared clinical features among patients with prolonged (a positive SARS-CoV-2 RNA on day 23 after illness onset) and short virus shedding and evaluated risk factors associated with prolonged virus shedding by multivariate regression analysis. Results Among 238 patients, the median age was 55.5 years, 57.1% were female, 92.9% (221/238) were administered with arbidol, 58.4% (139/238) were given arbidol in combination with interferon. The median duration of SARS-CoV-2 virus shedding was 23 days (IQR, 17.8–30 days) with a longest one of 51 days. The patients with prolonged virus shedding had higher value of D-dimer (P=0.002), IL-6 (P8 days after symptom onset [OR: 2.447, 95% CI (1.351–4.431)], ≥3 days from onset of symptoms to first medical visitation [OR: 1.880, 95% CI (1.035–3.416)], illness onset before Jan. 31, 2020 [OR: 3.289, 95% CI (1.474–7.337)]. Arbidol in combination with interferon was also significantly associated with shorter virus shedding [OR: 0.363, 95% CI (0.191–0.690)]. Conclusion Duration of SARS-CoV-2 virus shedding was long. Early initiation of arbidol and arbidol in combination with interferon as well as consulting doctor timely after illness onset were helpful for SARS-CoV-2 clearance. Electronic Supplementary Material Supplementary material is available for this article at 10.1007/s11596-021-2434-y and is accessible for authorized users.

Several follow-up studies have found that COVID-19 (coronavirus disease 2019) patients had persistent symptoms after discharge. Gut microbiota play an important role in human health and immune responses. Therefore, this study investigated the gut microbiota of recovered COVID-19 patients and the correlations between gut microbiota and persistent symptoms after discharge. Stool samples were collected from 15 recovered healthcare workers (HCWs) with COVID-19 at three months after discharge, in addition, stool samples were collected from 14 healthy controls (HCs) to perform 16S rRNA gene sequencing between May and July 2020. Compared with HCs, recovered HCWs had reduced bacterial diversity at three months after discharge, with a significantly higher relative abundance of opportunistic pathogens, and a significantly lower relative abundance of beneficial bacteria. In addition, Escherichia unclassified was positively correlated with persistent symptoms at three months after discharge, including fatigue (r = 0.567, p = 0.028), chest tightness after activity (r = 0.687, p = 0.005), and myalgia (r = 0.523, p = 0.045). Intestinibacter bartlettii was positively correlated with anorexia (r = 0.629, p = 0.012) and fatigue (r = 0.545, p = 0.036). However, Faecalibacterium prausnitzii was negatively correlated with chest tightness after activity (r = −0.591, p = 0.02), and Intestinimonas butyriciproducens was negatively correlated with cough (r = −0.635, p = 0.011). In conclusion, the gut microbiota of recovered HCWs with COVID-19 at three months after discharge was different from that of HCs, and altered gut microbiota was correlated with persistent symptoms after discharge, highlighting that gut microbiota may play an important role in the recovery of patients with COVID-19. Electronic Supplementary Material Supplementary material is available in the online version of this article at 10.1007/s12275-021-1206-5.

Yaya Zhou,1,* Xing Shi,2,3,* Wei Fu,1,* Fei Xiang,1 Xinliang He,1 Bohan Yang,1 Xiaorong Wang,1 Wan-Li Ma1 1Department of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People’s Republic of China; 2Department of Respiratory and Critical Care Medicine, Peking University People’s Hospital, Beijing, 100044, People’s Republic of China; 3Department of Pulmonary and Critical Care Medicine, Shenzhen Institute of Respiratory Diseases, First Affiliated Hospital of Southern University of Science and Technology, Shenzhen People’s Hospital, Shenzhen, 518020, People’s Republic of China*These authors contributed equally to this workCorrespondence: Xiaorong Wang; Wan-Li MaDepartment of Respiratory and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People’s Republic of ChinaTel +86-27-85726557Fax +86-27-85726557Email rong-100@163.com; whmawl@aliyun.comBackground: Most COVID-19 patients are moderate, and fever is the most common clinical manifestation and associated with poorer prognosis. Gut microbiota may also play important roles in COVID-19 pathogenesis. However, the association between gut microbiota and fever in individuals with moderate COVID-19 remains unclear.Methods: We compared the clinical features and laboratory results of 187 moderate COVID-19 patients with fever and without fever and identified several inflammatory markers in patients with fever. Then, we performed gut metagenome-wide association study for 31 individuals to identify the microbes and their epitopes which have potential role in fever and hyperinflammation.Results: Among 187 moderate COVID-19 patients, 127 (67.9%) patients presented with fever. Lymphocytes, CD3+ T cells, CD4+ T cells and the ratio of CD4+ T cells to CD8+ T cells were significantly reduced, while AST, LDH, CRP, IL-6 and IL-10 were significantly elevated in patients with fever. Gut microbiome composition was significantly altered in patients with fever compared with those with non-fever. Opportunistic pathogens such as Enterococcus faecalis and Saccharomyces cerevisiae were enriched in patients with fever. E. faecalis was positively correlated with LDH and D-dimer and negatively correlated with CD8+T cells and IL-4, while S. cerevisiae was positively correlated with diarrhea symptom. Furthermore, several species with anti-inflammatory and protective effects, such as Bacteroides fragilis and Eubacterium ramulus, were enriched in patients with non-fever. B. fragilis was positively correlated with lymphocytes, and E. ramulus was negatively correlated with LDH, AST and IL-6. Finally, we found that several bacterial epitopes of GroEL, a homolog of human HSP60, were enriched in patients with fever and positively correlated with IL-6, IL-10, WBC, neutrophils, D-dimer, LDH, CRP, and E. faecalis.Conclusion: Gut microbiota dysbiosis correlates with abnormal immune response in moderate COVID-19 patients with fever.Keywords: moderate COVID-19, fever, shotgun metagenomic sequencing, gut microbiota, epitopes

Background: Infection is a major cause of morbidity and mortality after heart transplantation (HT). However, there have been few data on clinical manifestation, distribution, and resistance of pathogens in the infected population of heart transplant recipients. Methods: We conducted a single-center retrospective study on patients who underwent HT in Wuhan Union Hospital from August 3, 2012 to July 30, 2016. Risk factors for infections that occur within 1 year after HT were investigated by multivariable logistic regression analysis. Results: Among 299 patients, 147 patients (49.2%) confirmed infection. The most common site of infection was the respiratory system. A total of 259 pathogens were detected in 147 patients (49.2%) with infection after HT. In all, 64 multidrug-resistant (MDR) bacteria were detected in infected patients within 1 year after HT, the most common MDR bacteria were extended-spectrum β-lactamases (ESBL) Klebsiella pneumonia and methicillin-resistant Staphylococcus aureus (MRSA). In the multivariable model, diabetes (OR 3.273 [95%CI, 1.748–6.130], and p < .001) and antibiotics treatment within 1 month before transplant (OR 1.860 [95%CI, 1.093–3.166], and p = .022) were significantly associated with infections within 1 year after HT. Conclusions: This study confirmed the high rate of infections within 1 year after HT. Diabetes and antibiotics treatment within 1 month before transplant were independent risk factors for infections within 1 year after HT.

Here, a new class superhydrophobic surface based on nano-engineering was proposed and prepared to improve the durability of corrosion protect. Moreover, the durability of anticorrosion was evaluate...

A new class of robust superhydrophobic cotton fabric was prepared by chemically grafting method for removing oil from contaminated waters. Furthermore, the mechanical, chemical, and thermal durability of superhydrophobic cotton fabric was evaluated in detail. The superhydrophobic cotton fabric did not only showed excellent separation efficiency (ca.100%) and ultrafast separation rate (ca. 13,600 L/h m2) but also exhibited excellent durability. Especially, the oil/water separation rate was almost 10 times than that reported in previous works. The work provides a new method to design and large-scale prepare oil/water separation materials with high performance for industrial use.

Fe3O4@PANI@rGO/EP coating with a tunable surface roughness was prepared by a facile spraying method under the assistance of magnetic field for enhancing microwave absorption properties. The structure and microwave absorption properties of nanocomposite coating were characterized and compared as a function of magnetic field. It was found that the surface roughness of nanocomposite coating increased with increasing in magnetic field, which further improved the microwave absorption performance. Fe3O4@PANI@rGO/EP with a surface roughness of 1.93 μm showed a minimum RL value of − 28.2 dB at 10.5 GHz with a thickness of only 1.0 mm and a bandwidth of 5.5 GHz from 8.1 to 13.6 GHz (

Pleural fibrosis is defined as an excessive deposition of extracellular matrix that results in destruction of the normal pleural tissue architecture and compromised function. Tuberculous pleurisy, asbestos injury, and rheumatoid pleurisy are main causes of pleural fibrosis. Pleural mesothelial cells (PMCs) play a key role in pleural fibrosis. However, detailed mechanisms are poorly understood. Serine/arginine-rich protein SRSF6 belongs to a family of highly conserved RNA-binding splicing-factor proteins. Based on its known functions, SRSF6 should be expected to play a role in fibrotic diseases. However, the role of SRSF6 in pleural fibrosis remains unknown. In this study, SRSF6 protein was found to be increased in cells of tuberculous pleural effusions (TBPE) from patients, and decellularized TBPE, bleomycin, and TGF-β1 were confirmed to increase SRSF6 levels in PMCs. In vitro, SRSF6 mediated PMC proliferation and synthesis of the main fibrotic protein COL1A2. In vivo, SRSF6 inhibition prevented mouse experimental pleural fibrosis. Finally, activated SMAD2/3, increased SOX4, and depressed miRNA-506-3p were associated with SRSF6 upregulation in PMCs. These observations support a model in which SRSF6 induces pleural fibrosis through a cluster pathway, including SRSF6/WNT5A and SRSF6/SMAD1/5/9 signaling. In conclusion, we propose inhibition of the splicing factor SRSF6 as a strategy for treatment of pleural fibrosis.

Summary The role of corticosteroids in the treatment of Coronavirus disease 2019 (COVID-19) is controversial. In the present study, we evaluated the effects of adjuvant corticosteroids treatment on the outcome of patients with COVID-19 (n=966), using Propensity Score Matching to adjust for potential differences between the corticosteroids group (n=289) and the non-corticosteroids group (n=677). Analysis of data without adjusting differences in baseline characteristics indicated that the proportion of mechanical ventilation and the mortality was higher in the corticosteroids treatment group in total or severe/critical patients. The duration of viral shedding was longer in the non-corticosteroids treatment group in total or general/mild patients. After adjusting the difference between the corticosteroids and non-corticosteroids treatment group, the analysis revealed that the use of corticosteroids had no effect on the duration of viral shedding, in-hospital mortality or 28-day mortality. Electronic supplementary material The online version of this article (10.1007/s11596-021-2313-6) contains supplementary material, which is available to authorized users.

Background Most patients including health care workers (HCWs) survived the coronavirus disease 2019 (COVID-19), however, knowledge about the sequelae of COVID-19 after discharge remains limited. Methods A prospectively observational 3-month follow-up study evaluated symptoms, dynamic changes of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) IgG and IgM, lung function, and high resolution computed tomography (HRCT) of survivors of COVID-19 after discharge at Wuhan Union Hospital, China. Results Seventy-six survivors (55 females) with a mean age of 41.3 ± 13.8 years were enrolled, and 65 (86%) were HCWs. A total of 69 (91%) patients had returned to their original work at 3-months after discharge. Most of the survivors had symptoms including fever, sputum production, fatigue, diarrhea, dyspnea, cough, chest tightness on exertion and palpitations in the three months after discharge. The serum troponin-I levels during the acute illness showed high correlation with the symptom of fatigue after hospital discharge (r = 0.782; P = 0.008) and lymphopenia was correlated with the symptoms of chest tightness and palpitations on exertion of patients after hospital discharge (r = −0.285, P = 0.027; r = −0.363, P = 0.004, respectively). The mean values of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC, total lung capacity and diffusion capacity were all normal (> 80% predicted) and lung HRCTs returned to normal in most of the patients (82%), however, 42% of survivors had mild pulmonary function abnormalities at 3-months after discharge. SARS-CoV-2 IgG turned negative in 11% (6 of 57 patients), 8% (4 of 52 patients) and 13% (7 of 55 patients), and SARS-CoV-2 IgM turned negative in 72% (41 of 57 patients), 85% (44 of 52 patients) and 87% (48 of 55 patients) at 1-month, 2-months and 3-months after discharge, respectively. Conclusion Infection by SARS-CoV-2 caused some mild impairments of survivors within the first three months of their discharge and the duration of SARS-CoV-2 antibody was limited, which indicates the necessity of long-term follow-up of survivors of COVID-19., Graphical Abstract

In this contribution, we reported the preparation of a novel conducting polymer hydrogel (CPH) by a sol-gel method, which was subsequently employed to fabricate a flexible all-solid-state supercapacitor device. Taking advantage of the synergistic effects of the different components in the conducting polymer hydrogel and the merits of the proposed synthesis strategies, the prepared supercapacitor device with CPH as electrode exhibited high area-normalized capacitance (2.2 F cm−2), high gravimetric capacitance (1573.6 F g−1) as well as high energy density of 0.18 mWh cm−2 (or 128.7 Wh Kg−1) at 0.08 mW cm−2 (or 55.1 W kg−1). This study did not only represent a novel all-solid-state, high performance, flexible supercapacitor with potential applications in flexible energy-related devices, but also developed a new method for enhancing capacitances and mechanical stability of all-solid-state flexible supercapacitor.

ObjectivesEvaluate the risk factors of prolonged SARS-CoV-2 virus shedding and the impact of arbidol treatment on SARS-CoV-2 virus shedding.MethodsData were retrospective collected from adults hospitalized with COVID-19 in Wuhan Union Hospital. We described the clinical features and SARS-CoV-2 RNA shedding of patients with COVID-19 and evaluated factors associated with prolonged virus shedding by multivariate regression analysis.ResultsAmong 238 patients, the median age was 55.5 years, 57.1% were female, 92.9% (221/238) used arbidol, 58.4% (139/238) used arbidol combination with interferon. The median time from illness onset to start arbidol was 8 days (IQR, 5-14 days) and the median duration of SARS-CoV-2 virus shedding was 23 days (IQR, 17.8–30 days). SARS-CoV-2 RNA clearance was significantly delayed in patients who received arbidol >7 days after illness onset, compared with those in whom arbidol treatment was started≤7 days after illness onset (HR, 1.738 [95% CI, 1.339–2.257], P < .001). Multivariate regression analysis revealed that prolonged viral shedding was significantly associated with initiation arbidol more than seven days after symptom onset (OR 2.078, 95% CI [1.114-3.876], P .004), more than 7 days from onset of symptoms to first medical visitation (OR 3.321, 95% CI[1.559-7.073], P .002), illness onset before Jan.31, 2020 (OR 3.223, 95% CI[1.450-7.163], P .021). Arbidol combination with interferon was also significantly associated with shorter virus shedding (OR .402, 95% CI[.206-.787], P .008).ConclusionsEarly initiation of arbidol and arbidol combination with interferon as well as consulting doctor timely after illness onset were helpful for SARS-CoV-2 clearance.

Objectives: The role of corticosteroids in the treatment of COVID-19 is controversial. In this paper, we intend to study the application value of corticosteroid in critically ill patients with COVID-19.Methods: We collected data from 120 patients who were diagnosed with COVID-19 in the Wuhan Union Hospital. In the first part of this study, the outcome of patients given corticosteroids was compared with that of patients not given corticosteroids. The second part of the study was a matched (1:1) case–control study. After matching the baseline characteristics between the two groups, the effect of corticosteroid use on the outcome was analyzed again.Results: Analysis of data without adjusting differences in baseline characteristics indicated that the proportion of mechanical ventilation and the mortality was higher in the corticosteroid treatment group in severely ill patients. The length of hospitalization and viral shedding have no significant difference between the two groups. After adjusting the difference between the corticosteroid and non-corticosteroid treatment group, analysis revealed that the use of corticosteroids had no effect on the outcome.Conclusions: Among the critically ill patients, the use of corticosteroids has no effect on length of hospitalization, viral shedding or mortality rates.

The Fe3O4/PANI rod/rGO nanocomposites were prepared by a new synthesis process, and their microwave absorbing properties were further evaluated. Taking advantage of the synergistic effects of the different components in the nanocomposites and the merits of the proposed synthesis strategies, the Fe3O4/PANI rod/rGO nanocomposites showed excellent microwave absorption performance, especially for obtaining giant absorption bandwidth (ca. 14.6 GHz

A new class of superhydrophobic surface based on multiple hybrid coatings is proposed and prepared to improve mechanical and reproduction stability. It does not only show a large water contact angle (ca. 174.5°) but also a slight decrease (ca. 6.4%) of water contact angle after 100 mechanical abrasion cycles. Furthermore, the water contact angle changes slightly (relative standard deviation, 0.14%) for the three superhydrophobic surfaces prepared with the same procedure. The application of superhydrophobic multiple hybrid coatings in corrosion protection is further investigated by the Tafel polarization curves and electrochemical impedance spectroscopy. The superhydrophobic multiple hybrid coatings showed lower corrosion current (1.4 × 10–11 A/cm2), lower corrosion rate (ca. 1.6 × 10–7 mm/year), and larger polarization resistance (7.9 × 104 MΩ cm2) in 3.5 wt % NaCl aqueous solution compared to other superhydrophobic coatings reported in previous works. This work not only confirms the formation of robust s...

Generally, magnetostriction elastomer were based on magnetic field-induced strains of elastomer matrix, resulting from the rotation of magnetic particle in elastomer matrix. However, such magnetostriction was relatively small and large hysteresis. Here, a new class magnetic rubber foam with cellular structure was developed and synthesized by the one-step solution foam processing. The magnetic rubber foam did not only show larger magnetostriction value of ca.11.0% comparing to previous magnetostriction elastomer, but also was few remanent magnetostriction and rapid response (ca. 1.0s). Furthermore, a new mechanism of magnetostriction was proposed for explaining the high performance magnetostriction. These provide a universal route for the rational design of magnetostriction materials with high performance for various applications.

Nanoporous graphitic carbon nitride modified with N-doped graphene quantums dots (N-GQD@npg-C3N4) was prepared via a one-pot co-sintering method. The presented N-GQD@npg-C3N4 showed a high photocatalytic activity (PCA) for the degradation of organic dyes under solar radiation. This result can be ascribed to two reasons: (i) the uniform distribution of N-GQDs on the surface of npg-C3N4, which allows for an accelerated electron transfer from npg-C3N4 to N-GQD; and (ii) the unique nanoporous structure of npg-C3N4, providing a large active surface area. This work opens up a new avenue for the utilization of a robust, cost-effective and metal-free photocatalyst in practical applications, e.g. waste water treatment.

Three-dimensional graphene@Co3O4 nanowire array grown on Ni foam as a binder-free supercapacitor electrode were prepared, in which the graphene was prepared by the facile Radio frequency (RF) magnetron sputtering method. The electrochemical properties were tested by the cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectra in detail. The graphene@Co3O4 nanowire array grown on Ni foam exhibited an higher pseudocapacitive behavior comparing to pure Co3O4 nanowire array grown on Ni foam. The result was attributed to that the graphene prepared by RF magnetron sputtering method was high conductivity and high contact interaction between graphene and Co3O4 array. This work provided a novel method to synthesize 3D porous array electrode materials based on graphene for application in electrochemical energy storage.

// Yaya Zhou 1, * , Wei Sun 1, * , Ning Chen 1, * , Chen Xu 1 , Xinxin Wang 2 , Kun Dong 2 , Binxue Zhang 1 , Jian Zhang 1 , Ning Hao 1 , Aihua Sun 1 , Handong Wei 1 , Fuchu He 1, 3 and Ying Jiang 1 1 State Key Laboratory of Proteomics, National Center for Protein Sciences Beijing, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing 102206, P. R. China 2 Department of Pathology, Beijing Youan Hospital of Capital Medical University, Beijing 100069, P. R. China 3 Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, P. R. China * These authors have contributed equally to this work Correspondence to: Ying Jiang, email: jiangying304@hotmail.com Fuchu He, email: hefc@nic.bmi.ac.cn Keywords: hepatocellular carcinoma, metastasis, plasma membrane protein, NKCC1, therapeutic target Received: April 07, 2016 Accepted: July 11, 2017 Published: August 12, 2017 ABSTRACT Metastasis is the essential cause for the high mortality of hepatocellular carcinoma (HCC). In order to investigate the mechanism of metastasis, and to discover therapeutic targets for HCC, the quantitative proteomic technique was applied to characterize the plasma membrane proteins of two HCC cell lines with low (MHCC97L) or high (MHCC97H) metastatic potentials. One of the plasma membrane proteins, sodium-potassium-chloride cotransporter 1 (NKCC1), was upregulated in MHCC97H cell line. Immunohistochemistry result in HCC patients showed that NKCC1 expression was associated with poor differentiation and microvascular invasion. Knockdown of NKCC1 via RNA interference reduced HCC cell proliferation and invasion abilities in vitro and in vivo , whereas over-expression of NKCC1 significantly increased HCC cell proliferation and invasion abilities in vitro and in vivo . Additionally, blocking NKCC1 activity with bumetanide attenuated the proliferation and invasion abilities of HCC cells in vitro and limited the HCC growth in vivo . Further results suggested that NKCC1 promotes the invasion ability via MMP-2 activity, and that the WNK1/OSR1/NKCC1 signal pathway might play roles in HCC metastasis. For the first time, our study demonstrated that NKCC1 plays a role in HCC metastasis, and could be served as a potential target to inhibit HCC cell growth and metastasis.

The current reports of COVID-19 focus on the respiratory system, however, intestinal infections caused by SARS-CoV-2 are also worthy of attention. This paper reported persistence of intestinal SARS-CoV-2 infection leads to re-admission after pneumonia resolved in three cases with COVID-19.

A facile method of measuring electrical conductivity was developed to characterize the formation of rGO network in polymer matrix. The electrical conductivity, barrier and anticorrosion of PVP@rGO/epoxy nanocomposite coating were investigated as function of rGO’ loading. When the electrical conductivity sharply increased to be seven orders, it indicated the formation of rGO network in polymer matrix in the loading of 0.75wt%. Furthermore, it also confirmed that although a conducting rGO network could effectively hinder the diffusion of electrolytes, yet it also accelerated corrosion at the interface. This strategy dose not only provide a facile method to determine the formation of rGO network in polymer matrix, but also proposes a new insight about effect of rGO’ loading on anticorrosion of polymer coating.