A Constraint Satisfaction Problem Approach to High-Entropy Alloy Design

High-entropy alloys (HEAs) are multi-principal element alloys at near-equiatomic concentrations that can have superior properties such as high irradiation resistance, high fatigue resistance, and high temperature usage, compared to conventional alloys. Because of their properties, HEAs may find applications in industries such as nuclear, aerospace, medical, and electronic. However, the design and discovery of HEAs has been largely limited to trial and error, Edisonian, methods, and only a fraction of the possibilities have been produced. A computational alloy design methodology using the constraint satisfaction problem (CSP) approach is proposed to accelerate the design and discovery of HEAs. This approach consists of three major steps: mapping design requirements into mathematical constraints and using computational thermodynamic calculations to implement them, sampling the HEA space of composition and temperature within the constraints to search for solutions, and describing the final solution space using machine learning methods. Ultimately, the CSP approach enables the identification of potentially all regions in composition space that satisfy material design requirements. A Thermo-Calc database used to encode the thermodynamic information of all phases in a given alloy system was verified against experimental data to be implemented for phase stability calculations. With kinetic considerations, 70.8% of the 216 evaluated alloys showed good agreement between experiments and calculations using the database. This database was used to map out single-phase solid solution regions for the known CoCrFeMnNi HEA and all its subsequent near-equiatomic quaternary and ternary systems. Afterwards, regions of possible precipitation hardening potential were determined in the AlCoCrFeNi system. The results demonstrate the CSP algorithm’s capability to search HEA thermodynamic space and to accelerate HEA design and discovery

A Constraint Satisfaction Problem Approach to High-Entropy Alloy Design

High-entropy alloys (HEAs) are multi-principal element alloys at near-equiatomic concentrations that can have superior properties such as high irradiation resistance, high fatigue resistance, and high temperature usage, compared to conventional alloys. Because of their properties, HEAs may find applications in industries such as nuclear, aerospace, medical, and electronic. However, the design and discovery of HEAs has been largely limited to trial and error, Edisonian, methods, and only a fraction of the possibilities have been produced. A computational alloy design methodology using the constraint satisfaction problem (CSP) approach is proposed to accelerate the design and discovery of HEAs. This approach consists of three major steps: mapping design requirements into mathematical constraints and using computational thermodynamic calculations to implement them, sampling the HEA space of composition and temperature within the constraints to search for solutions, and describing the final solution space using machine learning methods. Ultimately, the CSP approach enables the identification of potentially all regions in composition space that satisfy material design requirements. A Thermo-Calc database used to encode the thermodynamic information of all phases in a given alloy system was verified against experimental data to be implemented for phase stability calculations. With kinetic considerations, 70.8% of the 216 evaluated alloys showed good agreement between experiments and calculations using the database. This database was used to map out single-phase solid solution regions for the known CoCrFeMnNi HEA and all its subsequent near-equiatomic quaternary and ternary systems. Afterwards, regions of possible precipitation hardening potential were determined in the AlCoCrFeNi system. The results demonstrate the CSP algorithm’s capability to search HEA thermodynamic space and to accelerate HEA design and discovery

Prescribing Antibiotics for pediatric dental patients in Jordan; knowledge and attitudes of dentists

Objective: The inappropriate use of antibiotic in treating children has been observedin the treatment of dental infections. Recent surveys reported that dentistsin several countries have modest knowledge about antibiotic prescribing. The aimof this study was to investigate the knowledge and attitude of a group of Jordaniandentists treating children towards antibiotic prescribing.Methods: A written questionnaire was distributed during a meeting of the JordanianSociety of Paediatric Dentistry. The questionnaire included questions aboutthe knowledge and attitudes of dentists toward dental antibiotic prescribing tochildren.Results: Amoxicillin was the most popular antibiotic (62.9%) to be prescribed bydentists treating children. A lesser percentage (29.7%) prescribe combination ofantibiotics, and around 37% prescribe antibiotics for duration longer than 5 days.Erythromycin was the most popular alternative to amoxicillin (77.8%) followed byclindamycin (22.2%). A number of antibiotics were prescribed for non-indicatedclinical conditions like pulpitis and gingivitis. More than 50% of the sample prescribedantibiotics for non-scientific reasons like the “need to delay treatment†and“sterilization not guaranteedâ€.Conclusion: There is a need to improve awareness of Jordanian dentists regardingantibiotic prescribing to children particularly in the aspects of type of antibiotic tobe used for patients allergic and non-allergic to penicillin, duration of prescribing,and clinical indications. Dentists also should be discouraged to prescribe antibioticsbased on non-scientific/social factors

The role of antifungal drugs in the management of denture-associated stomatitis

Background: Denture-associated stomatitis is a chronic infection of the oral cavitythat may be associated with a number of bacterial and candidal organisms aswell as some predisposing factors. Its management may prove to be difficult if thetreatment plan was not comprehensive in addressing all the factors involved in itsetiology. The aim of this review is to underline the effectiveness of antifungal drugsin the management of denture-associated stomatitis according to our personalexperience and the recently published literature.Methods: Articles were obtained from pubmed as well as by a hand search.Denture stomatitis and antifungal were used as keywords. Only articles writtenin English and which were published starting from the year 1990 were included.Conclusions: Antifungal drugs certainly have a place in the management ofdenture-associated stomatitis. However, their use should be called upon after thecontrol of factors known to cause this infection. Denture and oral hygiene, andmanagement of adverse medical conditions should be the primary goal of treatment.This should go hand in hand with the application of topical antifungal agentsparticularly those in the cream or gel form for better patients’ compliance

Tobacco Smoking, Secondhand Smoke Exposure and Cessation Perceptions by Dental Students in Al Madinah, a Conservative Saudi Society

Objective: To explore the prevalence of tobacco use and secondhand smoke (SHS) exposure in dental students and to investigate their perceptions on the role of dentists in tobacco cessation activities. Material and Methods:  A questionnaire-based study was conducted in a public university in Al Madinah, Saudi Arabia. The questionnaire investigated demographic factors, tobacco use practices, SHS exposure, and student perceptions of tobacco cessation activities. Descriptive statistics and statistical significance of differences between demographic groups were calculated. Results: A total of 228 students participated with 43.0% (n=98) males and 57.0% (n=130) females. A proportion of 30.7% (n=70) of the participants smoked tobacco, and these constituted 51 males (73%) and 19 females (27%). Only 39 students (15 females and 24 males) indicated their method of tobacco use, which was mainly cigarettes and waterpipes. One in two students was exposed to SHS. Non-smokers had better awareness of the health hazards of SHS (p<0.001), and were more likely to adopt tobacco cessation activities recommended by dentists (p<0.05). Conclusion:  A substantial proportion of dental students in a very conservative religious area smoke tobacco and are exposed to SHS. Their perceptions of the harms of SHS and attitudes on cessation need improvement. The influence of culture and religion in shaping health risk behaviors in conservative communities needs to be verified

ANALYSIS OF PHENOLIC AND FLAVONOIDS OF WILD EPHEDRA ALATA PLANT EXTRACTS BY LC/PDA AND LC/MS AND THEIR ANTIOXIDANT ACTIVITY

Background: Ephedra is among Palestinian medicinal plants that are traditionally used in folkloric medicine for treating many diseases. Ephedra is known to have antibacterial and antioxidant effects. The goal of this study is to evaluate the antioxidant activity of different extracts from the Ephedra alata plant growing wild in Palestine, and to analyze their phenolic and flavonoid constituents by HPLC/PDA and HPLC/MS. Materials and Methods: Samples of the Ephedra alata plant grown wild in Palestine were extracted with three different solvents namely, 100% water, 80% ethanol, and 100% ethanol. The extracts were analyzed for their total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (AA), as well as phenolic and flavonoids content by HPLC/PDA/MS. Results: The results revealed that the polarity of the extraction solvent affects the TPC, TFC, and AA of extracts. It was found that both TPC and AA are highest for plant extracted with 80% ethanol, followed by 100% ethanol, and finally with 100% water. TFC however was highest in the following order: 100% ethanol > 80% ethanol > water. Pearson correlation indicated that there is a significant correlation between AA and TPC, but there is no correlation between AA and TFC. Simultaneous HPLC-PDA and UHPLC-MS analysis of the ethanolic plant extracts revealed the presence of Luteolin-7-O-glucuronide flavone, Myricetin 3-rhamnoside and some other major polyphenolic compounds that share myricetin skeleton. Conclusion Ephedra alata extract is rich in potent falvonoid glycosidic compounds as revealed by their similar overlaid UV-Vis spectra and UHPLC-MS results. On the basis of these findings, it is concluded that Ephedra alata constitutes a natural source of potent antioxidants that may prevent many diseases and could be potentially used in food, cosmetics, and pharmaceutical products

Approximation of the critical buckling factor for composite panels

This article is concerned with the approximation of the critical buckling factor for thin composite plates. A new method to improve the approximation of this critical factor is applied based on its behavior with respect to lamination parameters and loading conditions. This method allows accurate approximation of the critical buckling factor for non-orthotropic laminates under complex combined loadings (including shear loading). The influence of the stacking sequence and loading conditions is extensively studied as well as properties of the critical buckling factor behavior (e.g concavity over tensor D or out-of-plane lamination parameters). Moreover, the critical buckling factor is numerically shown to be piecewise linear for orthotropic laminates under combined loading whenever shear remains low and it is also shown to be piecewise continuous in the general case. Based on the numerically observed behavior, a new scheme for the approximation is applied that separates each buckling mode and builds linear, polynomial or rational regressions for each mode. Results of this approach and applications to structural optimization are presented

Narghile (water pipe) smoking among university students in Jordan: prevalence, pattern and beliefs

<p>Abstract</p> <p>Background and objectives</p> <p>Narghile is becoming the favorite form of tobacco use by youth globally. This problem has received more attention in recent years. The aim of this study was to investigate the prevalence and pattern of narghile use among students in three public Jordanian universities; to assess their beliefs about narghile's adverse health consequences; and to evaluate their awareness of oral health and oral hygiene.</p> <p>Methods</p> <p>The study was a cross-sectional survey of university students. A self-administered, anonymous questionnaire was distributed randomly to university students in three public Jordanian universities during December, 2008. The questionnaire was designed to ask specific questions that are related to smoking in general, and to narghile smoking in specific. There were also questions about oral health awareness and oral hygiene practices.</p> <p>Results</p> <p>36.8% of the surveyed sample indicated they were smokers comprising 61.9% of the male students and 10.7% of the female students in the study sample. Cigarettes and narghile were the preferred smoking methods among male students (42%). On the other hand, female students preferred narghile only (53%). Parental smoking status but not their educational level was associated with the students smoking status. Smokers had also significantly poor dental attendance and poor oral hygiene habits.</p> <p>Conclusion</p> <p>This study confirmed the spreading narghile epidemic among young people in Jordan like the neighboring countries of the Eastern Mediterranean region. Alarming signs were the poor oral health awareness among students particularly smokers.</p