The Potential of Natural Leaf Extracts as Green Inhibitors for Mild Steel Corrosion in Hydrochloric Acid Solutions

The inhibitive and thermodynamic behavior of Abelmoschus Esculentus and Citrus Maxima leaf extracts on the corrosion of mild steel in Hydrochloric acid solutions were investigated using potentiodynamic polarization curves measurements and electrochemical impedance spectroscopy (EIS) technique. Fourier transform infrared spectroscopy (FTIR) was done to predict some suggested chemical constituent of both leaf extracts. At any given concentration Abelmoschus Esculentus leaf extract is more efficient as a corrosion inhibitor for mild steel in 0.5 M HCl solutions than Citrus Maxima leaf extract. Potentiodynamic polarization curves indicated that both leaf extracts act as mixed type inhibitors for mild steel in 0.5 M HCl solutions. The impedance responses indicated that the corrosion process takes place under activation control. The inhibition of these plant leaf extracts depends on the physical adsorption of the chemical constituents of the extracts on mild steel surface as confirmed by Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS)

Characteristics of dental fear among Arabic-speaking children: a descriptive study

BACKGROUND: Dental fear has not only been linked to poor dental health in children but also persists across the lifespan, if unaddressed, and can continue to affect oral, systemic, and psychological health. The aim of this study was to assess the factor structure of the Arabic version of the Children’s Fear Survey Schedule-Dental Subscale (CFSS-DS), and to assess the difference in factor structure between boys and girls. METHODS: Participants were 220 consecutive paediatric dental patients 6–12 years old seeking dental care at the Faculty of Dentistry, King Abdulaziz University, Saudi Arabia. Participants completed the 15-item Arabic version of the CFSS-DS questionnaire at the end of the visit. Internal consistency was assessed using Cronbach’s alpha. Factor analysis (principal components, varimax rotation) was employed to assess the factor structure of the scale. RESULTS: The Cronbach’s alpha was 0.86. Four factors with eigenvalues above 1.00 were identified, which collectively explained 64.45% of the variance. These factors were as follows: Factor 1, ‘fear of usual dental procedures’ consisted of 8 items such as ‘drilling’ and ‘having to open the mouth’, Factor 2, ‘fear of health care personnel and injections’ consisted of three items, Factor 3, ‘fear of strangers’, consisted of 2 items. Factor 4, ‘fear of general medical aspects of treatment’, consisted of 2 items. Notably, four factors of dental fear were found in girls, while five were found in boys. CONCLUSIONS: Four factors of different strength pertaining to dental fear were identified in Arabic-speaking children, indicating a simple structure. Most items loaded high on the factor related to fear of usual dental procedures. The fear-provoking aspects of dental procedures differed in boys and girls. Use of the scale may enable dentists to determine the item/s of dental treatment that a given child finds most fear-provoking and guide the child’s behaviour accordingly. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1472-6831-14-118) contains supplementary material, which is available to authorized users

Fluorescence devices for the detection of dental caries

BACKGROUND: Caries is one of the most prevalent and preventable conditions worldwide. If identified early enough then non‐invasive techniques can be applied, and therefore this review focusses on early caries involving the enamel surface of the tooth. The cornerstone of caries detection is a visual and tactile dental examination, however alternative methods of detection are available, and these include fluorescence‐based devices. There are three categories of fluorescence‐based device each primarily defined by the different wavelengths they exploit; we have labelled these groups as red, blue, and green fluorescence. These devices could support the visual examination for the detection and diagnosis of caries at an early stage of decay. OBJECTIVES: Our primary objectives were to estimate the diagnostic test accuracy of fluorescence‐based devices for the detection and diagnosis of enamel caries in children or adults. We planned to investigate the following potential sources of heterogeneity: tooth surface (occlusal, proximal, smooth surface or adjacent to a restoration); single point measurement devices versus imaging or surface assessment devices; and the prevalence of more severe disease in each study sample, at the level of caries into dentine. SEARCH METHODS: Cochrane Oral Health's Information Specialist undertook a search of the following databases: MEDLINE Ovid (1946 to 30 May 2019); Embase Ovid (1980 to 30 May 2019); US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov, to 30 May 2019); and the World Health Organization International Clinical Trials Registry Platform (to 30 May 2019). We studied reference lists as well as published systematic review articles. SELECTION CRITERIA: We included diagnostic accuracy study designs that compared a fluorescence‐based device with a reference standard. This included prospective studies that evaluated the diagnostic accuracy of single index tests and studies that directly compared two or more index tests. Studies that explicitly recruited participants with caries into dentine or frank cavitation were excluded. DATA COLLECTION AND ANALYSIS: Two review authors extracted data independently using a piloted study data extraction form based on the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS‐2). Sensitivity and specificity with 95% confidence intervals (CIs) were reported for each study. This information has been displayed as coupled forest plots and summary receiver operating characteristic (SROC) plots, displaying the sensitivity‐specificity points for each study. We estimated diagnostic accuracy using hierarchical summary receiver operating characteristic (HSROC) methods. We reported sensitivities at fixed values of specificity (median 0.78, upper quartile 0.90). MAIN RESULTS: We included a total of 133 studies, 55 did not report data in the 2 x 2 format and could not be included in the meta‐analysis. 79 studies which provided 114 datasets and evaluated 21,283 tooth surfaces were included in the meta‐analysis. There was a high risk of bias for the participant selection domain. The index test, reference standard, and flow and timing domains all showed a high proportion of studies to be at low risk of bias. Concerns regarding the applicability of the evidence were high or unclear for all domains, the highest proportion being seen in participant selection. Selective participant recruitment, poorly defined diagnostic thresholds, and in vitro studies being non‐generalisable to the clinical scenario of a routine dental examination were the main reasons for these findings. The dominance of in vitro studies also means that the information on how the results of these devices are used to support diagnosis, as opposed to pure detection, was extremely limited. There was substantial variability in the results which could not be explained by the different devices or dentition or other sources of heterogeneity that we investigated. The diagnostic odds ratio (DOR) was 14.12 (95% CI 11.17 to 17.84). The estimated sensitivity, at a fixed median specificity of 0.78, was 0.70 (95% CI 0.64 to 0.75). In a hypothetical cohort of 1000 tooth sites or surfaces, with a prevalence of enamel caries of 57%, obtained from the included studies, the estimated sensitivity of 0.70 and specificity of 0.78 would result in 171 missed tooth sites or surfaces with enamel caries (false negatives) and 95 incorrectly classed as having early caries (false positives). We used meta‐regression to compare the accuracy of the different devices for red fluorescence (84 datasets, 14,514 tooth sites), blue fluorescence (21 datasets, 3429 tooth sites), and green fluorescence (9 datasets, 3340 tooth sites) devices. Initially, we allowed threshold, shape, and accuracy to vary according to device type by including covariates in the model. Allowing consistency of shape, removal of the covariates for accuracy had only a negligible effect (Chi(2) = 3.91, degrees of freedom (df) = 2, P = 0.14). Despite the relatively large volume of evidence we rated the certainty of the evidence as low, downgraded two levels in total, for risk of bias due to limitations in the design and conduct of the included studies, indirectness arising from the high number of in vitro studies, and inconsistency due to the substantial variability of results. AUTHORS' CONCLUSIONS: There is considerable variation in the performance of these fluorescence‐based devices that could not be explained by the different wavelengths of the devices assessed, participant, or study characteristics. Blue and green fluorescence‐based devices appeared to outperform red fluorescence‐based devices but this difference was not supported by the results of a formal statistical comparison. The evidence base was considerable, but we were only able to include 79 studies out of 133 in the meta‐analysis as estimates of sensitivity or specificity values or both could not be extracted or derived. In terms of applicability, any future studies should be carried out in a clinical setting, where difficulties of caries assessment within the oral cavity include plaque, staining, and restorations. Other considerations include the potential of fluorescence devices to be used in combination with other technologies and comparative diagnostic accuracy studies

Integration of oxazole-based fluorophores in blue organic light-emitting diodes (OLEDs)

Ce travail de thèse porte sur l'étude de l'intégration des molécules fluorescentes à base d'oxazole comme matériaux émissifs des OLEDs. Les fluorophores tels que le 2-(p-tert-butylphenyl)benzoxazole (Bzx), le 2,2'-di(p-tert-butylphenyl)-6,6'-bibenzoxazole (BBzx) et le 2-phenyl-naphth[2,3-d]oxazole (Nzx) présentent une émission duale solution-état solide (SSSE pour Solution and Solid State Emitters) dans le bleu profond/proche UV (300 nm - 450 nm). Leurs rendements quantiques de fluorescence en solution et de photoluminescence à l'état solide peuvent atteindre jusqu'à 90% et 35% respectivement. Les caractérisations opto-électriques des dispositifs OLEDs ont montré une émission efficace dans le bleu profond (420 nm - 440 nm) ; lorsque ces molécules sont intégrées comme couche émissive : soit en couche mince soit dispersées au sein de matrices organiques. Les performances les plus élevées ont été obtenues pour les diodes à hétérojonction de volume. Les molécules à base d'oxazole sous forme de couche mince présentent un comportement similaire à l'émission induite par agrégation, qui est associé à leurs structures intermoléculaires. Une dégradation des performances ainsi qu'une instabilité de la couleur d'émission ont été observées pour les OLEDs utilisant une matrice à base de carbazole. Une étude approfondie a montré que l'agrégation moléculaire induite par les excitons y joue un rôle clé dans la dégradation, par la formation d'électroplèxes et d'électromères. Des dispositifs stables, émettant à 438 nm (bleu profond), ont été réalisés en intégrant le Nzx au sein d'une matrice à base de diamine.This thesis focuses on the integration of oxazole-based fluorescent molecules as emitter into OLEDs. The fluorophores such as 2-(p-tert-butylphenyl)benzoxazole (Bzx), 2,2'-di(p-tert-butylphenyl)-6,6'-bibenzoxazole (BBzx) and 2-phenyl-naphth[2,3-d]oxazole (Nzx) exhibit dual solution and solid state emission (SSSE) in deep blue/near-UV regions (300 nm - 450 nm). Their fluorescence (in solution) and photoluminescence (in solid state) quantum efficiencies can achieve up to 90% and 35% respectively. Opto-electrical characterizations of SSSE-emitters based devices have shown an efficient deep blue emission (420 nm - 440 nm) when these molecules are integrated as neat films and dispersed within organic matrices. Higher performances were obtained for blend devices. The oxazole-based molecules as neat film exhibit a behavior similar to aggregation-induced emission, which is associated with their intermolecular structures. A degradation in performance and an instability of emission color were noted for OLED based on carbazol derivative as host material. An in-depth study highlights the key role of exciton-induced aggregation in the degradation of these OLED by electroplex and electromer formation. Stable devices, emitting at 438 nm (deep blue) have been designed from the blend of Nzx and diamine derivative

Biologische Vielfalt von auf Hexachlorocyclohexan und verwandten Verbindungen gewachsenen Biofilmgemeinschaften

γ-Hexachlorocyclohexane (γ-HCH) and 4,4`-dibromodiphenylether (BDE) are halogenated pollutants that persist in the environment for a long time. These compounds are very difficult for bacteria and fungi to degrade. However, bacteria and fungi can cooperate within a community making the degradation process easier. The purpose of this work was to determine the extent of the microbial potential for the degradation of γ-HCH and BDE in soils. This study assessed the diversity of bacteria and fungi from 12 soil samples collected around insecticide and pesticide producing factories in Egypt. From γ-HCH and BDE enrichment cultures, all samples yielded highly diverse microbes as revealed by the analyses of the16S rRNA genes for bacteria and 18S rRNA genes for fungi. Soil and sediment samples were used to inoculate γ-HCH and BDE microcrystals on a substratum (PermanoxTM) in microcosms to grow complex biofilm communities on γ-HCH and BDE. The biofilms were monitored over 42 days by community fingerprinting using single strand conformational polymorphism (SSCP) of 16S rRNA and 18S rRNA gene amplicons. All soil samples yielded biofilms on γ-HCH & BDE and SSCP analyses of the biofilms revealed rather diverse bacterial and fungal communities. The structural biofilm development was monitored by Confocal Laser Scanning Microscope (CLSM) using Bac Light Kit, for LIVE (green) / DEAD (red) bacteria and Nile Red to stain hydrophobic compounds and revealed highly diverse biofilms with a dominance of damaged cell at the end of the incubation. From the soil samples, several species were obtained and most of them could use γ-HCH and BDE as sole source of carbon in a minimal medium. While many Gram-positive bacteria were isolated this group was almost absent in the different biofilm communities. Bacteria and fungi in microbial communities play different roles and together they are able to form biofilms using γ-HCH and BDE as a carbon source acting as a functional diversity cooperation.γ-Hexachlorocyclohexan (γ-HCH) und 4,4`-Dibromdiphenylether (BDE) sind halogenierte Gefahrstoffe, welche lange in der Umwelt persistieren und für Bakterien und Pilze nur schwierig abzubauen sind. Bakterien und Pilze können jedoch in Gemeinschaften kooperieren und so den Abbauprozess erleichtern. Das Ziel dieser Arbeit war die Bestimmung des mikrobiellen Potentials in Böden für den Abbau von γ-HCH und BDE. Die Biodiversität von Bakterien und Pilzen wurde in 12 Bodenproben untersucht, welche um Insektizid- und Pestizid-produzierende Fabriken in Ägypten genommen wurden. Anreicherungskulturen auf γ-HCH und BDE ergaben bei allen Proben eine große Vielzahl unterschiedlicher Mikroorganismen, was anhand der Analysen der jeweiligen rRNA Gene gezeigt wurde. Die meisten Stämme konnten diese Substrate als einzige Kohlenstoff- und Energiequelle nutzen. Die Bodenproben wurden zudem als Inocula benutzt, um komplexe Biofilmgemeinschaften auf γ-HCH und BDE Mikrokristallen auf einem Substratum (PermanoxTM) in Mikrokosmen anzuziehen. Die Entwicklung der Biofilme wurde über 42 Tage mittels single strand conformational polymorphism (SSCP) von 16S rRNA und 18S rRNA Gen Amplicons verfolgt. Alle Bodenproben ergaben Biofilme auf γ-HCH & BDE und die SSCP Analysen der Biofilme zeigten recht diverse Bakterien- und Pilz-Gemeinschaften. Die strukturelle Entwicklung der Biofilme wurde durch konfokale Laser Raster-Mikroskopie (CLSM) verfolgt, wobei das Bac Light Kit, für lebende / tote Bakterien und Nilrot zur Färbung hydrophober Verbindungen eingesetzt wurden. Dabei zeigte sich eine große Vielfalt der Biofilme und eine Dominanz von geschädigten Zellen am Ende des Beobachtungszeitraumes. Während viele Gram-positive Bakterien isoliert wurden, fehlte diese Bakteriengruppe in den Biofilmgemeinschaften nahezu völlig. Bakterien und Pilze haben in mikrobiellen Gemeinschaften unterschiedliche Rollen, formen aber dennoch zusammen Biofilme, die zusammen diese Substrate als Kohlenstoffquelle nutzen

Estimation of Population Total using Local Polynomial Regression with Two Auxiliary Variables

In this paper, the estimation for finite population total of a study variable will be considered, and the local linear regression will be used. The study variable is available for the sample and is supplemented by two auxiliary variables, which are available for every element in the finite population. Also, the resampling methods will be combined with the local linear regression method to estimate the total. The comparisons between different methods will be performed based on the mean squared error (MSE), mean absolute error (MAE), and mean absolute percentage error (MAPE). A simulation study is carried out to assess the effects

Estimation of Population Total using Local Polynomial Regression with Two Auxiliary Variables

In this paper, the estimation for finite population total of a study variable will be considered, and the local linear regression will be used. The study variable is available for the sample and is supplemented by two auxiliary variables, which are available for every element in the finite population. Also, the resampling methods will be combined with the local linear regression method to estimate the total. The comparisons between different methods will be performed based on the mean squared error (MSE), mean absolute error (MAE), and mean absolute percentage error (MAPE). A simulation study is carried out to assess the effects

Th2 related markers in milk allergic inflammatory mice model, versus OVA

Experimental studies on allergic asthma are limited by the high cost of the administrated allergens. In this study we tested the allergic potency of low fat milk as a cheap substitute to the widely used standard allergen, ovalbumin (OVA). BALB/c female mice (4 weeks old) were sensitized intraperitoneally with low fat milk/or OVA followed by intranasal challenge with the two allergens on days 28 and 29. At day 31, serum, bronchoalveolar lavage fluid (BALF), and lungs were harvested. Mice of the low fat milk model showed infiltration of eosinophils, macrophages, lymphocytes, and neutrophils in BALF comparable to that of the OVA model. Both allergic protocols led to the production of similar numbers of Th2 cells and induced comparable expression of Th2 cytokine (IL-13) as evident by real time PCR for IL-13 and GATA3 (Th2 transcription factor) and confirmed by immunofluorescence for Th2 surface markers (T1/ST2). In addition, both mouse models had similar elevated levels of allergen specific antibody, IgG1 and IgE. Notably, HE, PAS, and LUNA stained lung sections from low fat milk treated mice had higher average pathological scores as compared to OVA treated mice. In conclusion, this study suggests that the low fat milk-induced inflammation showed hallmarks of allergic airway inflammatory model such as eosinophilic influx in BALF, increased numbers of Th2 cells, augmented expression of IL-13, elevated levels of circulatory IgG1 and IgE, signs of robust pulmonary inflammation, and most importantly it is a cheap and promising model for studying acute allergic airway inflammation and acute asthma