Numerical investigation of high-pressure combustion in rocket engines using Flamelet/Progress-variable models

The present paper deals with the numerical study of high pressure LOx/H2 or LOx/hydrocarbon combustion for propulsion systems. The present research effort is driven by the continued interest in achieving low cost, reliable access to space and more recently, by the renewed interest in hypersonic transportation systems capable of reducing time-to-destination. Moreover, combustion at high pressure has been assumed as a key issue to achieve better propulsive performance and lower environmental impact, as long as the replacement of hydrogen with a hydrocarbon, to reduce the costs related to ground operations and increase flexibility. The current work provides a model for the numerical simulation of high- pressure turbulent combustion employing detailed chemistry description, embedded in a RANS equations solver with a Low Reynolds number k-omega turbulence model. The model used to study such a combustion phenomenon is an extension of the standard flamelet-progress-variable (FPV) turbulent combustion model combined with a Reynolds Averaged Navier-Stokes equation Solver (RANS). In the FPV model, all of the thermo-chemical quantities are evaluated by evolving the mixture fraction Z and a progress variable C. When using a turbulence model in conjunction with FPV model, a probability density function (PDF) is required to evaluate statistical averages of chemical quantities. The choice of such PDF must be a compromise between computational costs and accuracy level. State- of-the-art FPV models are built presuming the functional shape of the joint PDF of Z and C in order to evaluate Favre-averages of thermodynamic quantities. The model here proposed evaluates the most probable joint distribution of Z and C without any assumption on their behavior.Comment: presented at AIAA Scitech 201

Impacto de la convivencia escolar sobre el rendimiento académico, desde la percepción de estudiantes con desarrollo típico y necesidades educativas especiales

This descriptive correlational study aims to compare the perception about eight dimensions of school coexistence of typically developing high school students (n = 545) and students with special educational needs (n = 75) from Chile and their relationship with the general academic performance.  Based on the analysis of hierarchical and non-hierarchical clusters, multiple regression and logistic regression, it was found that students with special educational needs have a less favorable perception in almost every dimension analyzed; especially, in those aspects related to school victimization, aggression, and indiscipline. Likewise, they perceive that they have a limited peer social network, as well as limited normative adjustment and a lower perception about their own positive interpersonal skills. The multiple regression and logistic regression models allow confirming that the dimensions of school coexistence account for between 20% and 27% of the academic performance variability. The aforementioned models highlight the role and negative effect of the level of victimization perceived by students, as well as the perception about the occurrence of indiscipline situations in the classroom, and the fact of belonging to the group of students with special educational needs, and to the group of male students. The findings are analyzed and discussed in light of the implications for high social vulnerability educational contexts.This descriptive correlational study aims to compare the perception about eight dimensions of school coexistence of typically developing high school students (n = 545) and students with special educational needs (n = 75) from Chile and their relationship with the general academic performance.  Based on the analysis of hierarchical and non-hierarchical clusters, multiple regression and logistic regression, it was found that students with special educational needs have a less favorable perception in almost every dimension analyzed; especially, in those aspects related to school victimization, aggression, and indiscipline. Likewise, they perceive that they have a limited peer social network, as well as limited normative adjustment and a lower perception about their own positive interpersonal skills. The multiple regression and logistic regression models allow confirming that the dimensions of school coexistence account for between 20% and 27% of the academic performance variability. The aforementioned models highlight the role and negative effect of the level of victimization perceived by students, as well as the perception about the occurrence of indiscipline situations in the classroom, and the fact of belonging to the group of students with special educational needs, and to the group of male students. The findings are analyzed and discussed in light of the implications for high social vulnerability educational contexts.Estudio descriptivo-correlacional que busca comparar la percepción acerca de ocho dimensiones de la convivencia escolar de estudiantes chilenos de educación media con desarrollo típico (n=545) y con necesidades educativas especiales (n=75), y su relación con el rendimiento académico general. A partir de los análisis de conglomerados jerárquico y no jerárquico, regresión múltiple y regresión logística, se constata que los estudiantes con necesidades educativas especiales tienen una percepción más desfavorable en casi todas las dimensiones analizadas, especialmente en aquellos aspectos asociados a la victimización escolar y agresión e indisciplina, de igual forma, perciben tener una menor red social de iguales, menor ajuste normativo y una más baja percepción respecto de la gestión interpersonal positiva. Los modelos de regresión múltiple y regresión logística, permiten constatar que las dimensiones de la convivencia escolar explican entre el 20% y el 27% de la variabilidad del rendimiento académico. En dichos modelos destaca el papel y efecto negativo que tiene la el grado de victimización que perciben los estudiantes, como también la percepción respecto de la ocurrencia o presencia de situaciones de indisciplina al interior del aula, como también el hecho de pertenecer al grupo de estudiantes con necesidades educativas especiales, y el pertenecer al grupo de estudiantes hombres. Se analizan y discuten los hallazgos a la luz de las implicaciones para contextos educativos de alta vulnerabilidad social

Ionophore-based potentiometric PVC membrane sensors for determination of phenobarbitone in its pharmaceutical formulations

The fabrication and development of two polyvinyl chloride (PVC) membrane sensors for assaying phenobarbitone sodium are described. Sensors 1 and 2 were fabricated utilizing - or -cyclodextrin as ionophore in the presence of tridodecylmethylammonium chloride as a membrane additive, and PVC and dioctyl phthalate as plasticizer. The analytical parameters of both sensors were evaluated according to the IUPAC guidelines. The proposed sensors showed rapid, stable anionic response (–59.1 and –62.0 mV per decade) over a relatively wide phenobarbitone concentration range (5.0×10–6–1×10–2 and 8×10–6–1×10–2 mol L–1) in the pH range of 9–11. The limit of detection was 3.5×10–6 and 7.0×10–6 mol L–1 for sensors 1 and 2, respectively. The fabricated sensors showed high selectivity for phenobarbitone over the investigated foreign species. An average recovery of 2.54 µg mL–1 phenobarbitone sodium was 97.4 and 101.1 %, while the mean relative standard deviation was 3.0 and 2.1 %, for sensors 1 and 2, respectively. The results acquired for determination of phenobarbitone in its dosage forms utilizing the proposed sensors are in good agreement with those obtained by the British Pharmacopoeial method

Chicory abrogates oxidative stress, inflammation and caspase-dependent apoptosis in acute hepatic injury model induced by acetaminophen in rats

In this study the protective effect of chicory leaves hydroalcoholic extract (CIE) against acute liver injury induced by a single dose of acetaminophen (700 mg/kg, i.p.) was investigated in rats. The CIE and silymarin treatment (standard reference) were given in a dose of (100 mg/kg, p.o.) for 3 days before and at 1 and 12 h following acetaminophen administration. Treatment with CIE significantly reduced the levels of serum ALT, AST, alkaline phosphatase, bilirubin, total cholesterol, triglycerides, urea, creatinine, TNF-α and hepatic contents of malondialdehyde (MDA), nitric oxide, caspase-3 and hydroxyproline, with significant increases in serum total protein, albumin, HDL- cholesterol and hepatic activities of reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) as compared with the acetaminophen group. The histopathological alterations mediated by acetaminophen were ameliorated by CIE. It was concluded that CIE protects rat liver against acetaminophen hepatotoxicity, most probably through abrogation of oxidative stress, inflammation and caspase-3 dependent apoptosis

Serum neutrophil gelatinase-associated lipocalin as a biomarker of disease activity in pediatric lupus nephritis

Background: Neutrophil gelatinase-associated lipocalin (NGAL) is expressed in immature neutrophil precursors and in epithelial cells during both inflammation and neoplastic transformation. A recent prospective pediatric study demonstrated that concentrations of NGAL in urine and plasma represent novel, sensitive, and specific biomarkers for early identification of acute kidney injury following cardiac surgery. Objective: To assess the relationship of serum NGAL levels with disease activity in pediatric systemic lupus erythematosus (SLE) with special emphasis on lupus nephritis. Methods: The study included 30 children and adolescents with pediatric SLE with a mean age of 16.48±3.524 years. Patients were clinically and laboratory evaluated and categorized into those with nephritis and those without nephritis. Activity was assessed using SLEDAI score, NGAL levels were measured in the sera of included patients and were compared to those of 20 matched controls using ELISA. Results: Serum NGAL was significantly higher in SLE patients in comparison to the controls (z=-5.962, p < 0.001). Furthermore serum NGAL was significantly higher in SLE patients with nephritis and in those without nephritis in comparison to the controls (p < 0.001 in both). Serum NGAL was higher in SLE patients with nephritis in comparison to those without nephritis, yet the results are borderline regarding statistical significance (p=0.05). Levels of serum NGAL correlated significantly with disease activity as assessed by SLE disease activity index (SLEDAI) (r=0.485, p < 0.01). There was a significant correlation between serum NGAL and urinary protein to creatinine ratio, 24hr urinary protein and BUN of SLE patients. Conclusion: Our results suggest that serum NGAL represents a novel biomarker for disease activity in pediatric SLE patients, and a marker of severity of renal involvement.Keywords: SLE, NGAL, SLEDAI, lupus nephritisEgypt J Pediatr Allergy Immunol 2011;9(1):15-2

Computer-Based Clinical Examination (CCE) in Surgery: Would It Complement or Replace the OSCE in the Post-COVID-19 Era?

Objectives: Surgical clinical assessment of medical students is confronted by many challenges particularly the increasing numbers of students with limited resources, and pandemics. The search for new tools of assessment continues. Our objectives were: (1) To develop a computer-based clinical exam (CCE) and identify its characteristics (2) To assess its acceptability of the students. Method: The study was conducted at the Surgical Department, Alzaiem Alazhari University (AAU) between February and August, 2017. We used the modular objectoriented dynamic learning environment (MOODLE) program as a platform to upload and deliver the exam. The exam consisted of 45 questions (stations). Each consisted of a clinical scenario accompanied by a photograph (of a patient or investigation) or short video followed by multiple choice questions (MCQs). A questionnaire was designed to get the students’ feedback. We analyzed the questionnaire and scores obtained by the students and compared them to their performance in other tools of the surgical exam, using SPSS statistical program. Results: The study included 188 final year medical students. There was a highly significant correlation of the CCE scores of each student with their final result (r= 0.67), and with other tools of the surgery exam particularly the objective structured clinical examination (OSCE). Students’ acceptability was high. Conclusion: The CCE is valid and practicable. It saves time and is popular with the students and tutors. It complements the OSCE in the assessment of clinical competency and allows wide coverage of the curriculum. It is expected to gain importance and popularity in the post-COVID-19 era

Seminavis aegyptiaca sp. Nov., a new amphoroid diatom species from estuary epilithon of the river–nile damietta branch, Egypt

During a recent floristic–taxonomic study on the algal flora, including diatoms, from the estuary of the Damietta Branch of the Nile in Egypt, an interesting epilithic diatom species belonging to the genus Seminavis (Naviculaceae) was collected and investigated using both light and scanning electron microscopy. This new diatom species shares morphologically some taxonomic diagnostic features with other related taxa such as S. insignis, S. robusta, and S. ventricosa. However, it still differs by having ventral central striae that are shorter and more or less straight in the middle of the smaller frustules to be clearly radiate in the larger ones and then become geniculate and only radiate near the poles, the central raphe endings are externally more distantly spaced than in the similar species, the elongate central nodule is internally less prominent, and the areola density is much denser. Therefore, we here describe it as Seminavis aegyptiaca sp. nov. Hydrochemical analyses revealed that S. aegyptiaca commonly inhabits typical marine, with a weak tendency towards brackish water, habitats. It was found to be tolerant to meso–eutrophic, nutrient–enriched conditions, based on the data available on seasonal concentrations of N and P compounds. These findings not only contribute to the inventory of Egyptian diatoms, but also increase our understanding of the autecology and distribution of this relatively poorly–known diatom genus