Rheological, electrochemical, surface, DFT and molecular dynamics simulation studies on the anticorrosive properties of new epoxy monomer compound for steel in 1 M HCl solution

A new epoxy monomer, namely, tetraglycidyl-1,2-aminobenzamide (ER), was synthesized by condensation of the amines with epichlorohydrin in a basic medium. The obtained epoxy monomer was characterized by FT-IR and ¹H NMR spectroscopy. Rheological properties of this monomer were determined using an advanced rheometer. Subsequently, the synthesized ER monomer was investigated as corrosion inhibitor for carbon steel in 1 M HCl solution. The adsorption properties of ER were analyzed by electrochemical, surface investigation and theoretical computational studies using DFT and molecular dynamics (MD). Results showed a high dependence of the viscosity of ER on temperature and concentration, and also, that ER has better inhibition performance. A good agreement between the results derived from computational (MD and DFT) and experimental methods was observed. The thermodynamic parameters, along with the kinetic parameters, showed that the adsorption of ER molecules onto carbon steel surface obeyed the Langmuir isotherm model, and the adsorption at metal–electrolyte interfaces involved both chemical and physical adsorption, but predominantly chemisorption mechanism.

A new epoxy monomer, namely, tetraglycidyl-1,2-aminobenzamide (ER), was synthesized by condensation of the amines with epichlorohydrin in a basic medium.

Adsorption and anticorrosive behavior of aromatic epoxy monomers on carbon steel corrosion in acidic solution: computational studies and sustained experimental studies

Herein, the synthesis, characterization and corrosion inhibition effectiveness of two aromatic epoxy monomers (AEMs) namely, 2-(oxiran-2-yl-methoxy)-N,N-bis(oxiran-2-yl-methyl)aniline (AEM1) and N,N-bis(oxiran-2-ylmethyl)-2-((oxiran-2-ylmethyl) thio)aniline (AEM2), in carbon steel corrosive dissolution in 1 M HCl solution is investigated using computational and experimental techniques. AEM1 and AEM2 were characterized using FT-IR, ¹H NMR and ¹³C NMR spectroscopy techniques. Electrochemical results demonstrated that AEMs act as reasonably good corrosion inhibitors for carbon steel in 1 M HCl medium and their effectiveness followed the sequence: AEM2 (95.4%) > AEM1 (94.3%). A PDP study showed that AEMs act as mixed-type inhibitors with slight anodic predominance. Adsorption of the AEMs obeyed the Langmuir isotherm model. Interactions between AEMs and the metallic surface was further studied using DFT and MD simulations that give several computational parameters such as I, A, E_HOMO, E_LUMO, ΔE, δ, χ, ρ, σ, η, ΔN and E_ads. The experimental and computational results were in good agreement and well complimented each other.

Herein, the synthesis, characterization and corrosion inhibition effectiveness of two aromatic epoxy monomers (AEMs) in carbon steel corrosive dissolution in 1 M HCl solution was investigated using computational and experimental techniques.

Dielectric and electric properties as a tool to investigate the coagulation mechanism during sludge treatment

The analysis of the complex permittivity, electrical complex modulus and the hopping conductivity have been employed in order to investigate the impacts of calcium oxide during sludge treatment in textile such as coagulation process. In this context, impedance measurement was performed on five samples, including raw sludge and four compositions containing different amounts of calcium oxide: 2%, 3%, 4% and 5% (w/w). The dielectric spectra of each composition were described by the summation of a power law and a Cole-Cole relaxation model. The relaxation time and the magnitude of the dielectric relaxation obtained from the analysis of dielectric properties showed an increase up to 3% of these parameters with the addition of calcium oxide. Above this critical value, both parameters showed a very small change, suggesting that the aggregation became more stable. In addition, the evolution of the hopping conductivity reached a minimum value at this critical amount (3%). This evolution was well described by a double power law, which allowed us to estimate the optimal amount of the calcium oxide to achieve coagulation process. The analysis of the dielectric properties was found useful in monitoring aggregation processes that occur during the coagulation mechanism in textile sludge.

Rheological and electrical properties used to investigate the coagulation process during sludge treatment

Analyses of rheological properties and electrical conductivity (σ_dc) at direct current have been employed in order to investigate the effects of calcium oxide on the coagulation process during sludge treatment in the textile industry. In this context, rheological and electrical measurements were performed on five samples - one that contained raw sludge and the other four that were prepared from the raw sludge and different amounts of calcium oxide: 2, 3, 4, 5% (w/w). Rheological behavior of these samples was analyzed using the Herschel-Bulkley modified model. The influence of calcium oxide content on the rheological parameters such as infinite viscosity, the yield stress, the consistency coefficient, and the consistency index, are presented and discussed. The impact of the calcium oxide content on pH and conductivity were also examined. Similar behaviors have been seen in the evolution of conductivity and infinite viscosity as a function of the calcium oxide content. These latter characteristics were modeled by an equation using two power laws. This equation was able to fit very well the evolution of electrical conductivity and also the viscosity versus the percentage of calcium oxide to predict the optimal amount of calcium oxide (3%) to achieve the coagulation step during sludge treatment.

[Prognostic factors in uveitis]

PURPOSE

To evaluate prognostic factors of vision loss among patients with uveitis.

MATERIAL AND METHODS

This descriptive and retrospective study included all patients diagnosed with uveitis who were seen at the teaching hospital of Rabat, Morocco, over a 5-year period. Information regarding demographic data, uveitis type, bilaterality of the disease, etiology and complications were gathered from patients' records. Statistical analysis was performed using SPSS software.

RESULTS

One hundred and thirty-nine eyes of 89 patients were included. There were 60.7 % men and 39.3 % women. The mean age (years) was 31.1±16.8. Median follow-up was 11 months. Median visual acuity (logMAR) on admission was 1.7 [0.7-2] and 1 [0.4-1.7] on the last visit (P<0.001). Fifty-nine percent of eyes had final visual acuity (VA) equal to or less than 1/10. Panuveitis (85.4 %) and posterior uveitis (72.7 %) were responsible for final VA equal to or less than 1/10 (P<0.001). Cataract, posterior synechiae, vitreous opacities, epimacular membrane (ERM) and cystoid macular edema (CME) were the most frequent complications. Using multivariate logistic regression, the prognostic factors associated with severe vision loss were the type of uveitis (posterior and panuveitis), CME, ERM, macular scarring and optic atrophy (P<0.05).

CONCLUSION

Although this study included a limited number of subjects, the results showed that final VA was equal or less than 1/10 in 59 % of eyes diagnosed with uveitis and was associated with risk factors including posterior segment involvement (panuveitis and posterior uveitis), CME and ERM.

[Prevalence of exfoliation syndrome and cardiovascular diseases in patients scheduled for cataract surgery]

PURPOSE

To study the prevalence of exfoliation syndrome (XFS) and its association with cardiovascular disease in patients scheduled for cataract surgery.

MATERIAL AND METHODS

This is a retrospective, single center, descriptive study of 260 patients admitted to a tertiary teaching hospital in Rabat, Morocco, between January 2015 and March 2016 and scheduled for cataract surgery. All patients had a preoperative cardiovascular exam, an electrocardiogram and, if needed, echocardiography. Statistical analysis was performed using SPSS software. Results with a P-value<0.05 were considered statistically significant.

RESULTS

This study included 246 patients: 146 women (59.3 %) and 100 men (40.7 %). The mean age (years) was 67.6±10.1. The percentage of XFS increased with age (P=0.02). Sixty-two percent of patients with cardiovascular disease also had exfoliation syndrome (P<0.001). Patients with XFS had hypertension in 46.5 % of cases. 14 subjects (19.7 %) had ischemic heart disease and XFS. Using multivariate logistic regression and after adjusting for age, diabetes mellitus, hypertension, ischemic heart disease and arrhythmias, smoking was the only factor associated with exfoliation syndrome (P=0.01, odds ratio=5.2, confidence interval 95 %=1.35-20.15).

CONCLUSION

Exfoliation syndrome is a common condition in the aging cataract population. Ischemic heart disease and hypertension are frequently associated with XFS. Smoking could be another factor associated with this syndrome.

[Birth-related retinal hemorrhages in the newborn: incidence and relationship with maternal, obstetric and neonatal factors. Prospective study of 2,031 cases]

PURPOSE

To assess the prevalence, morphology and distribution of retinal hemorrhages in healthy newborns and their relationship to neonatal, maternal and obstetrical factors, and to determine their natural history.

PATIENTS AND METHODS

The present study prospectively included 2,031 consecutive healthy newborns. Indirect ophthalmoscopy was performed within 24 hours after birth in all newborns. Infants with retinal hemorrhages were reexamined weekly until the hemorrhage resolved. Annual ophthalmologic follow-up was also scheduled in these children. Neonatal, maternal and obstetric parameters were analyzed in all newborns and compared between newborns with retinal hemorrhages and those without retinal hemorrhages.

RESULTS

31.8 % of newborns exhibited retinal hemorrhages. 72.6 % of hemorrhages were bilateral. They tended to be localized around the optic discs and in the posterior pole, but their distribution was variable. Retinal hemorrhages were of variable shapes. The prevalence of retinal hemorrhages was higher in newborns delivered with vacuum-assisted extraction (38 %, P<0.001), intermediate during normal vaginal delivery (32.6 %, P<0.001) and lower with cesarean section (20.8 %). Comparative analysis between elective cesarean section and emergency cesarean showed a higher incidence of retinal hemorrhages in the emergency cesarean group (P=0.006). On multivariate analysis, vacuum-assisted delivery was the only factor associated with a higher prevalence of retinal hemorrhages in newborns (P=0.045). Two thirds of hemorrhages had disappeared by one week after birth. Retinal hemorrhages had resolved in all newborns within four weeks.

CONCLUSION

Birth-related retinal hemorrhages are common (1/3 of our newborns). Vacuum-assisted delivery is the main risk factor in this study. All hemorrhages resolved by one month of age. These findings may help in differential diagnosis with shaken baby syndrome.

[Bacterial endophthalmitis: retrospective clinical and microbiological study in Rabat Specialty Hospital]

OBJECTIVES

To study and discuss the epidemiological, clinical, microbiological, and risk factors of bacterial endophthalmitis treated in the Rabat Specialty Hospital ophthalmology department.

PATIENTS AND METHODS

This is a retrospective study over a period of 10 months of patients hospitalized for suspected acute infectious endophthalmitis. An intake form was completed for each patient. Each sample underwent direct examination and culture. All patients underwent the same protocol, providing for at least one intravitreal antibiotic injection and instillation of fortified eye drops.

RESULTS

Twenty cases of endophthalmitis were recorded during the study period. Decreased visual acuity, intraocular inflammation, pain and conjunctival hyperemia were found in all patients. The median onset of symptoms was 4 days. Vitreous tap or anterior chamber paracentesis was performed in all patients. Bacteria were found in seven samples (40%). Gram positive organisms accounted for 85% of positive cultures. Amphotericin B was required in four patients, and systemic antibiotic therapy in ten patients. Corticosteroid treatment was administered secondarily in eight patients.

DISCUSSION

In this retrospective series, epidemiological, clinical and microbiological data are consistent with those already published.