Ag-CuO/epoxy hybrid nanocomposites as anti-corrosive coating and self-cleaning on copper substrate.

This study aims to prepare Ag-CuO nanoparticles and assess their efficiency in protecting the copper substrate. The prepared Ag-CuO nanoparticle was characterized using, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope/energy-dispersive X-ray (SEM/EDX), and transmission electron microscope (TEM). The anticorrosion performance of the epoxy coatings containing various weight percentages of Ag-CuO nanoparticles was evaluated in 3.5 wt% NaCl solution using potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques. The results showed that corrosion potential shifted from - 0.211 V for uncoated copper to - 0.120 V for 5.0 wt% Ag-CuO/epoxy hybrid nanocomposite. Electrochemical measurements indicated that the coating 5.0 wt% coating exhibited excellent inhibiting properties with an efficiency of 99.9%. Wettability and mechanical properties were measured for both uncoated and coated copper substrates. The contact angle for 5.0 wt% coating is equal to 104° enhancing the hydrophobic character of the surface. The study clearly establishes that the hybrid composite has a significant potential for protecting the copper substrate.

Dose Distribution Scaling and Validation of Ultraviolet Photoreactors Using Dimensional Analysis.

Ultraviolet (UV) disinfection is commonly applied in the treatment of drinking water and wastewater. The performance of UV disinfection systems is governed by the UV dose distribution delivered to the fluid, which is an intrinsic characteristic of the reactor under a given operating condition. Current design and validation approaches are based on empirical methods that are expensive to apply and provide limited information about the UV photoreactor behavior. To address this issue, a dose distribution scaling method was developed based on dimensional analysis (i.e., application of the Buckingham-π theorem). Three dimensionless groups representing UV dose, reactor geometry, and UV absorption behavior were defined. Using these groups, the approach was applied for the analysis of 15 operating conditions, defined by process variables of volumetric flow rate, UV transmittance, and lamp power. The approach was demonstrated to allow scaling of the dose distribution with these critical, dimensionless variables and yielded close agreement between predictions of disinfection efficacy against MS2 and E. coli based on the scaling approach with conventional CFD-E' modeling results. The approach thus provides a low-cost, rapid method for predicting the performance of UV disinfection systems across a wide range of operating conditions and against essentially any microbial challenge agent.

Head and neck mycetoma: Clinical findings, investigations, and predictors for recurrence of the disease in Sudan: A retrospective study.

INTRODUCTION: Mycetoma is a unique neglected tropical disease which is found endemic in areas known as the "mycetoma belt". Head and neck mycetoma is a rarity and it has many devastating impacts on patients and communities. In this study, we assessed clinical findings, investigations, and predictors for recurrence of head and neck mycetoma in Sudan. METHODOLOGY: A retrospective study was conducted at Mycetoma Research Center in Khartoum between January 1999 and December 2020 for all patients with head and neck mycetoma. Data were analyzed using R software version 4.0.2. RESULTS: We included 107 patients with head and neck mycetoma. 65.4% were young adult males from mycetoma endemic areas in Sudan, and most of them were students (33.6%). Most of patients (64.4%) had actinomycetoma. Before presenting with head and neck mycetoma, majority (75.7%) had a long duration with mycetoma, and 30.8% had a history of trauma. The commonest invaded site was the parietal region (30.8%). The lesion started gradually in most of the patients (96.3%). 53.3% of the patients had large size lesions with no sweating, regional lymph nodes involvement, or distal vein involvement. CT scan was the most accurate diagnostic tool while 8.4% of patients were diagnosed by clinical examinations only. Laboratory investigations confirmed that 24/45 (44.4%) of actinomycetoma was caused by Streptomyces somaliensis while 13/28 (46.4%) of eumycetoma was caused by Madurella mycetomatis. All patients with recurrence of head and neck mycetoma underwent surgical excision of the lesion (n = 41/41 {100%}, p < 0.001). CONCLUSION: In head and neck mycetoma, the most common type was actinomycetes in Sudan. Majority had a long course of mycetoma and the commonest causative organism was Streptomyces somaliensis. The treatment outcome was poor and characterized by a low cure rate.

Knowledge, attitude and practices regarding COVID-19 and their associated factors in patients with type 2 diabetes attending Abdullah-Khalil diabetes center, Omdurman: A cross-sectional study.

Novel corona virus disease 2019 is the major threat for human life nowadays worldwide. This study aims to assess the knowledge, attitude and practices regarding COVID-19 among patients with type 2 diabetes attending Abdullah Khalil diabetes center (Omdurman Teaching Hospital). A facility-based observational descriptive cross-sectional study was carried out between January and February 2021, using non-probability quota sampling technique in Abdullah-Khalil diabetes center via the use of a structured close-ended interview questionnaire. It consisted of 19, 10, and 10 questions pertaining to knowledge, attitude and practices towards COVID-19 respectively. A total of 249 patients with type 2 diabetes were included. Of them, 132 (53.0%) were females and the majority (53.0%) aged between 41 and 60 years old. Concerning their education and marital status, 70 (28.1%) were primary school level and 208 (83.5%) were married. 89.6% of participants reported mass media as main source of information regarding COVID-19. Patients with type 2 diabetes attending Abdullah-Khalil diabetes center have good knowledge, positive attitude and good prevention practices towards COVID-19. Most respondents had good knowledge, positive attitude and good practices as 78.7%, 97.6%, and 69.9%, respectively. Educational level and source of information showed statistically significant association with the knowledge, attitude. However, the practice showed only statistical association with the mass media as a source of information (P = .006).

Clinical manifestations, complications, and outcomes of patients with COVID-19 in Sudan: a multicenter observational study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is a pandemic caused by a newly discovered coronavirus. Although clinical manifestations of COVID-19 are mainly pulmonary, some patients have other systemic manifestations. This study aimed to describe the clinical finding and outcomes in Sudanese patients diagnosed with COVID-19. METHODS: This retrospective observational study is based on documented files that included patients diagnosed with COVID-19 in seven selected hospitals inside Khartoum. Clinical manifestations, complications and outcomes were extracted from patients' records using an extraction form designed for this study. RESULTS: Data of 243 patients diagnosed with COVID-19 were analyzed. The mean (SD) age in years was 55.8 (18.4). Out of 116 participants, 27 of them (23.3%) had severe disease, 15 (12.9%) were critically ill. 67.5% of patients were admitted to the hospital within 7 days from onset of symptoms; most of them were admitted to the wards (n = 140,72.5%). Fever (83.2%), cough (70.7%), and shortness of breath (69.2%) were the most commonly recorded clinical manifestations. Sepsis (9.8%) and acidosis (7.8%) were the most frequently reported complications. Death was the final outcome in 21.4% (56/243). Older age and presence of diabetes were found significantly associated with in-hospital death. The laboratory results showed high CRP in 85.6% (119/139), high ferritin in 88.9% (24/27), lactate dehydrogenase had a median of 409.0 (359-760), D-dimer had a median of 3.3 (1.2-16. 6), and 53/105 (50.5%) had low albumin. CONCLUSIONS: Fever was the most mentioned sign among the participants, followed by fatigue. Cough and shortness of breath were the most commonly recorded pulmonary symptoms manifested. Our study showed multiple variables were associated with in-hospital death. The mortality rate was high among severe and critically ill patients diagnosed with COVID-19.

Robotic surgery for colorectal cancer in the Octogenarians.

BACKGROUND: We evaluated the short-term outcomes of robotic colorectal cancer surgery in octogenarian patients, focussing on postoperative morbidity and survival. METHODS: All patients ≥80 years in a prospective colorectal cancer database undergoing robotic curative colorectal cancer resection were included. Patient demographics, intraoperative findings, postoperative and oncological outcomes were recorded. Patients were further subdivided into two groups named: old (OG 80-85 years) and very old (VOG ≥ 86 years). RESULTS: Fifty-eight consecutive patients were included (median age, 83 years; male, 53.4%; median BMI, 26.5). Median total operative time was 230 min, median blood loss 20 ml, median length of stay 7 days. Major complications were seen in 12% of patients; and the 90-day mortality rate was 1.7%. Complete R0 resection achieved in 93% of cases, average lymph node harvest was 22. Overall and disease-free survival was 81% and 87.3%, respectively (median follow-up 24.5 months). We noticed a trend towards more advanced lesion staging in the VOG, but only N2 stage was significant (p = 0.03). There was a statistically significant difference in overall survival in favour of the OG (p = 0.024). CONCLUSIONS: Robotic surgery is feasible in octogenarian patients undergoing curative colorectal cancer resection and is associated with good post-operative outcomes and overall survival.

Engineering of Streptomyces lividans for heterologous expression of secondary metabolite gene clusters.

BACKGROUND: Heterologous expression of secondary metabolite gene clusters is used to achieve increased production of desired compounds, activate cryptic gene clusters, manipulate clusters from genetically unamenable strains, obtain natural products from uncultivable species, create new unnatural pathways, etc. Several Streptomyces species are genetically engineered for use as hosts for heterologous expression of gene clusters. S. lividans TK24 is one of the most studied and genetically tractable actinobacteria, which remain untapped. It was therefore important to generate S. lividans chassis strains with clean metabolic backgrounds. RESULTS: In this study, we generated a set of S. lividans chassis strains by deleting endogenous gene clusters and introducing additional φC31 attB loci for site-specific integration of foreign DNA. In addition to the simplified metabolic background, the engineered S. lividans strains had better growth characteristics than the parental strain in liquid production medium. The utility of the developed strains was validated by expressing four secondary metabolite gene clusters responsible for the production of different classes of natural products. Engineered strains were found to be superior to the parental strain in production of heterologous natural products. Furthermore, S. lividans-based strains were better producers of amino acid-based natural products than other tested common hosts. Expression of a Streptomyces albus subsp. chlorinus NRRL B-24108 genomic library in the modified S. lividans ΔYA9 and S. albus Del14 strains resulted in the production of 7 potentially new compounds, only one of which was produced in both strains. CONCLUSION: The constructed S. lividans-based strains are a great complement to the panel of heterologous hosts for actinobacterial secondary metabolite gene expression. The expansion of the number of such engineered strains will contribute to an increased success rate in isolation of new natural products originating from the expression of genomic and metagenomic libraries, thus raising the chance to obtain novel biologically active compounds.

Ray Tracing for Fluence Rate Simulations in Ultraviolet Photoreactors.

The performance of photochemical reactors is governed by the spatial distribution of radiant energy within the irradiated region of the reactor. Ray tracing has been widely used for simulation of lighting systems. The central hypothesis of this work was that ray tracing can provide accurate simulations of fluence rate fields within ultraviolet (UV) photoreactors by accounting for the physical and optical phenomena that will govern fluence rate fields in UV photoreactors. Ray tracing works by simulating the behavior of a large population of rays emanating from a radiation source to describe the spatial distribution of radiant energy (i.e., fluence rate) within a system. In this study, fluence rate calculations were performed using commercial ray tracing software for three basic UV reactors, each with a single low-pressure Hg lamp. Fluence rate calculations in the ray tracing program were based on the formal definition of fluence rate, calculated as the incident radiant power from all directions on a small spherical receptor, divided by the cross-sectional area of that sphere. The results of this study demonstrate that ray tracing can provide predictions of fluence rate in UV radiative systems that are close to experimental measurements and the predictions of other numerical methods.

Characterization of Sigma Factor Genes in Streptomyces lividans TK24 Using a Genomic Library-Based Approach for Multiple Gene Deletions.

Alternative sigma factors control numerous aspects of bacterial life, including adaptation to physiological stresses, morphological development, persistence states and virulence. This is especially true for the physiologically complex actinobacteria. Here we report the development of a robust gene deletions system for Streptomyces lividans TK24 based on a BAC library combined with the λ-Red recombination technique. The developed system was validated by systematically deleting the most highly expressed genes encoding alternative sigma factors and several other regulatory genes within the chromosome of S. lividans TK24. To demonstrate the possibility of large scale genomic manipulations, the major part of the undecylprodigiosin gene cluster was deleted as well. The resulting mutant strains were characterized in terms of morphology, growth parameters, secondary metabolites production and response to thiol-oxidation and cell-wall stresses. Deletion of SLIV_12645 gene encoding S. coelicolor SigR1 ortholog has the most prominent phenotypic effect, resulted in overproduction of actinorhodin and coelichelin P1 and increased sensitivity to diamide. The secreted proteome analysis of SLIV_12645 mutant revealed SigR1 influence on trafficking of proteins involved in cell wall biogenesis and refactoring. The reported here gene deletion system will further facilitate work on S. lividans strain improvement as a host for either secondary metabolites or protein production and will contribute to basic research in streptomycetes physiology, morphological development, secondary metabolism. On the other hand, the systematic deletion of sigma factors encoding genes demonstrates the complexity and conservation of regulatory processes conducted by sigma factors in streptomycetes.

Identification of butenolide regulatory system controlling secondary metabolism in Streptomyces albus J1074.

A large majority of genome-encrypted chemical diversity in actinobacteria remains to be discovered, which is related to the low level of secondary metabolism genes expression. Here, we report the application of a reporter-guided screening strategy to activate cryptic polycyclic tetramate macrolactam gene clusters in Streptomyces albus J1074. The analysis of the S. albus transcriptome revealed an overall low level of secondary metabolism genes transcription. Combined with transposon mutagenesis, reporter-guided screening resulted in the selection of two S. albus strains with altered secondary metabolites production. Transposon insertion in the most prominent strain, S. albus ATGSal2P2::TN14, was mapped to the XNR_3174 gene encoding an unclassified transcriptional regulator. The mutant strain was found to produce the avenolide-like compound butenolide 4. The deletion of the gene encoding a putative acyl-CoA oxidase, an orthologue of the Streptomyces avermitilis avenolide biosynthesis enzyme, in the S. albus XNR_3174 mutant caused silencing of secondary metabolism. The homologues of XNR_3174 and the butenolide biosynthesis genes were found in the genomes of multiple Streptomyces species. This result leads us to believe that the discovered regulatory elements comprise a new condition-dependent system that controls secondary metabolism in actinobacteria and can be manipulated to activate cryptic biosynthetic pathways.

Post-translational Serine/Threonine Phosphorylation and Lysine Acetylation: A Novel Regulatory Aspect of the Global Nitrogen Response Regulator GlnR in S. coelicolor M145.

Soil-dwelling Streptomyces bacteria such as S.coelicolor have to constantly adapt to the nitrogen (N) availability in their habitat. Thus, strict transcriptional and post-translational control of the N-assimilation is fundamental for survival of this species. GlnR is a global response regulator that controls transcription of the genes related to the N-assimilation in S. coelicolor and other members of the Actinomycetales. GlnR represents an atypical orphan response regulator that is not activated by the phosphorylation of the conserved aspartate residue (Asp 50). We have applied transcriptional analysis, LC-MS/MS analysis and electrophoretic mobility shift assays (EMSAs) to understand the regulation of GlnR in S. coelicolor M145. The expression of glnR and GlnR-target genes was revisited under four different N-defined conditions and a complex N-rich condition. Although, the expression of selected GlnR-target genes was strongly responsive to changing N-concentrations, the glnR expression itself was independent of the N-availability. Using LC-MS/MSanalysis we demonstrated that GlnR was post-translationally modified. The post-translational modifications of GlnR comprise phosphorylation of the serine/threonine residues and acetylation of lysine residues. In the complex N-rich medium GlnR was phosphorylated on six serine/threonine residues and acetylated on one lysine residue. Under defined N-excess conditions only two phosphorylated residues were detected whereas under defined N-limiting conditions no phosphorylation was observed. GlnR phosphorylation is thus clearly correlated with N-rich conditions. Furthermore, GlnR was acetylated on four lysine residues independently of the N-concentration in the defined media and on only one lysine residue in the complex N-rich medium. Using EMSAs we demonstrated that phosphorylation inhibited the binding of GlnR to its targets genes, whereas acetylation had little influence on the formation of GlnR-DNA complex. This study clearly demonstrated that GlnR DNA-binding affinity is modulated by post-translational modifications in response to changing N-conditions in order to elicit a proper transcriptional response to the latter.