Evaluation of stresses developed in different bracket-cement-enamel systems using finite element analysis with in vitro bond strength tests

BACKGROUND: The purpose of this study was to determine the bond strength of different orthodontic bracket materials (ceramic, stainless steel, and titanium) as well as stresses developed in bracket-cement-enamel systems using finite element (FE) analysis. METHODS: One hundred and thirty-five extracted human caries-free upper central incisors were divided into three groups (n = 45/group) according to the type of orthodontic bracket materials (stainless steel, ceramic, and titanium). Each group was further subdivided into three subgroups (n = 15/group) according to the bond strength test loading mode (shear short side, shear long side, and tensile). After debonding, the fractured specimen was examined, and the adhesive remnant index (ARI) was determined. FE analysis models analyzed the stress distribution within the cement and enamel. Bond strengths were analyzed using ANOVA and Tukey's test, and the ARI scores were analyzed using chi-square (χ(2)) test. RESULTS: Shear loading at the short side of the bracket resulted in the highest bond strength and lowest maximum principal stress both on cement and enamel compared with the other loading modes (P < 0.05). Ceramic brackets presented with higher bond strength and lower maximum principal stress than metallic brackets (P < 0.05). There was a significant difference for ARI scores between the type of brackets (χ(2) = 64.852, P < 0.001). CONCLUSION: The findings suggest that the manner of loading orthodontic brackets and the selection of orthodontic bracket materials affect the bond strength and stresses developed both on cement and enamel

Aeroelastic stability analysis of aircraft wings with initial curvature

In this study, the aeroelastic instability of a wing with an initial out-of-plane curvature is determined. The structural dynamics of the wing is modelled by using the geometrically exact beam equations, and the aerodynamic loads are determined using an incompressible unsteady aerodynamic model. The wing is considered to have initial out-of-plane curvature, and the effect of the curvature on the flutter velocity and flutter frequency of the wing is determined. Two curved wing cases are considered here. In the first case, the length of the wing is assumed to be constant and therefore, as the wing is curved, the projected area of the wing decreases. In the second case, the wing is assumed to have a constant projected area and therefore different curvature angles result from different wing lengths. When the wing is designed to have an initial out-of-plane curvature, the wing dynamics change, and therefore the aeroelastic stability of the curved wing is also affected. It is shown that as the initial curvature of the wing increases, initially the flutter velocity decreases but then increases, and finally a sudden jump occurs in the flutter velocity due to the change of the coupled modes contributing to flutter. Moreover, the flutter frequency also first decreases as the curvature of the wing increases, and then there is a sudden jump in the frequency, and from this point again the frequency decreases. Finally, results highlighting the importance of the initial curvature and the length of the curved segment on the stability velocity and frequency of the curved wing are presented

Entropy, time irreversibility and Schroedinger equation in a primarily discrete space-time

In this paper we show that the existence of a primarily discrete space-time may be a fruitful assumption from which we may develop a new approach of statistical thermodynamics in pre-relativistic conditions. The discreetness of space-time structure is determined by a condition that mimics the Heisenberg uncertainty relations and the motion in this space-time model is chosen as simple as possible. From these two assumptions we define a path-entropy that measures the number of closed paths associated with a given energy of the system preparation. This entropy has a dynamical character and depends on the time interval on which we count the paths. We show that it exists an like-equilibrium condition for which the path-entropy corresponds exactly to the usual thermodynamic entropy and, more generally, the usual statistical thermodynamics is reobtained. This result derived without using the Gibbs ensemble method shows that the standard thermodynamics is consistent with a motion that is time-irreversible at a microscopic level. From this change of paradigm it becomes easy to derive a $H-theorem$. A comparison with the traditional Boltzmann approach is presented. We also show how our approach can be implemented in order to describe reversible processes. By considering a process defined simultaneously by initial and final conditions a well defined stochastic process is introduced and we are able to derive a Schroedinger equation, an example of time reversible equation.Comment: latex versio

Oleoquímica I: Estudios sobre la preparación y la estructura de los jabones de litio.

Lithium stéarate, palmitate, myristate, laurate, caprate and caprylate were prepared by means of fusion method. Elementary analysis and the infrared absorptions spectra of the prepared lithium soaps as well as their X-ray diffractions and the thermogravimetric analyses were carried out. The anhydrous lithium salts of fatty acids with 12 carbon atoms or less showed thermal stability up to ca. 300 ± 78 °C depending on the chain length. On other hand the salts with 14 carbon atoms or more were decomposed at 126 ± 4 °C leading to formation of lithium carbonate. The homologous lithium soaps had very similar crystal structure among them and their metal -to- oxygen bonds were similar for the acyl chains between 8 and 18 carbons. However the angle of inclination of the molecular axes to the basal plane increased with the decreasing of the number of carbon atoms of the fatty acid chain, as determined by X-ray diffraction. In addition, the ionic character of the metal -to- oxygen bond was enhanced with the decrease of the number of carbon atoms as shown by infrared spectroscopy.Se han preparado estearato, palmitato, miristato, laurato, caprato y caprilato de litio por fusión. Se ha realizado el análisis elemental, los espectros de absorción en el infrarrojo y las difracciones de rayos X de los Jabones de litio preparados, además del análisis termogravimétrico de los mismos. Las sales de litio anhidra de los ácidos con 12 átomos de carbono o menos mostraron una estabilidad térmica hasta los 300 ± 78 °C dependiendo de la longitud de la cadena. Por otro lado las sales con 14 átomos de carbono o más se descompusieron a 126 ± 4 °C formándose carbonato de litio. Los jabones homólogos de litio mostraron una estructura cristalina similar, siendo los enlaces metal-oxígeno del mismo tipo para los ácidos grasos de número de átomos de carbono entre 8 y 18. Sin embargo el ángulo de inclinación que forma la molécula con el plano basal aumentó con la disminución del número de átomos de carbono, lo que se observó por difracción de rayos X. Se comprobó por espectroscopia infrarroja la intensificación del carácter iónico del enlace metal-oxígeno al disminuir el número de átomos de carbono

Effect of case management on neonatal mortality due to sepsis and pneumonia

<p>Abstract</p> <p>Background</p> <p>Each year almost one million newborns die from infections, mostly in low-income countries. Timely case management would save many lives but the relative mortality effect of varying strategies is unknown. We have estimated the effect of providing oral, or injectable antibiotics at home or in first-level facilities, and of in-patient hospital care on neonatal mortality from pneumonia and sepsis for use in the Lives Saved Tool (LiST).</p> <p>Methods</p> <p>We conducted systematic searches of multiple databases to identify relevant studies with mortality data. Standardized abstraction tables were used and study quality assessed by adapted GRADE criteria. Meta-analyses were undertaken where appropriate. For interventions with biological plausibility but low quality evidence, a Delphi process was undertaken to estimate effectiveness.</p> <p>Results</p> <p>Searches of 2876 titles identified 7 studies. Among these, 4 evaluated oral antibiotics for neonatal pneumonia in non-randomised, concurrently controlled designs. Meta-analysis suggested reductions in all-cause neonatal mortality (RR 0.75 95% CI 0.64- 0.89; 4 studies) and neonatal pneumonia-specific mortality (RR 0.58 95% CI 0.41- 0.82; 3 studies). Two studies (1 RCT, 1 observational study), evaluated community-based neonatal care packages including injectable antibiotics and reported mortality reductions of 44% (RR= 0.56, 95% CI 0.41-0.77) and 34% (RR =0.66, 95% CI 0.47-0.93), but the interpretation of these results is complicated by co-interventions. A third, clinic-based, study reported a case-fatality ratio of 3.3% among neonates treated with injectable antibiotics as outpatients. No studies were identified evaluating injectable antibiotics alone for neonatal pneumonia. Delphi consensus (median from 20 respondents) effects on sepsis-specific mortality were 30% reduction for oral antibiotics, 65% for injectable antibiotics and 75% for injectable antibiotics on pneumonia-specific mortality. No trials were identified assessing effect of hospital management for neonatal infections and Delphi consensus suggested 80%, and 90% reductions for sepsis and pneumonia-specific mortality respectively.</p> <p>Conclusion</p> <p>Oral antibiotics administered in the community are effective for neonatal pneumonia mortality reduction based on a meta-analysis, but expert opinion suggests much higher impact from injectable antibiotics in the community or primary care level and even higher for facility-based care. Despite feasibility and low cost, these interventions are not widely available in many low income countries.</p> <p>Funding</p> <p>This work was supported by the Bill & Melinda Gates Foundation through a grant to the US Fund for UNICEF, and to Saving Newborn Lives Save the Children, through Save the Children US.</p

Efficient Multimodal Deep-Learning-Based COVID-19 Diagnostic System for Noisy and Corrupted Images

Introduction: In humanity\u27s ongoing fight against its common enemy of COVID-19, researchers have been relentless in finding efficient technologies to support mitigation, diagnosis, management, contact tracing, and ultimately vaccination. Objectives: Engineers and computer scientists have deployed the potent properties of deep learning models (DLMs) in COVID-19 detection and diagnosis. However, publicly available datasets are often adulterated during collation, transmission, or storage. Meanwhile, inadequate, and corrupted data are known to impact the learnability and efficiency of DLMs. Methods: This study focuses on enhancing previous efforts via two multimodal diagnostic systems to extract required features for COVID-19 detection using adulterated chest X-ray images. Our proposed DLM consists of a hierarchy of convolutional and pooling layers that are combined to support efficient COVID-19 detection using chest X-ray images. Additionally, a batch normalization layer is used to curtail overfitting that usually arises from the convolution and pooling (CP) layers. Results: In addition to matching the performance of standard techniques reported in the literature, our proposed diagnostic systems attain an average accuracy of 98% in the detection of normal, COVID-19, and viral pneumonia cases using corrupted and noisy images. Conclusions: Such robustness is crucial for real-world applications where data is usually unavailable, corrupted, or adulterated

Deep Learning Modalities for Biometric Alteration Detection in 5G Networks-Based Secure Smart Cities

Smart cities and their applications have become attractive research fields birthing numerous technologies. Fifth generation (5G) networks are important components of smart cities, where intelligent access control is deployed for identity authentication, online banking, and cyber security. To assure secure transactions and to protect user’s identities against cybersecurity threats, strong authentication techniques should be used. The prevalence of biometrics, such as fingerprints, in authentication and identification makes the need to safeguard them important across different areas of smart applications. Our study presents a system to detect alterations to biometric modalities to discriminate pristine, adulterated, and fake biometrics in 5G-based smart cities. Specifically, we use deep learning models based on convolutional neural networks (CNN) and a hybrid model that combines CNN with convolutional long-short term memory (ConvLSTM) to compute a three-tier probability that a biometric has been tempered. Simulation-based experiments indicate that the alteration detection accuracy matches those recorded in advanced methods with superior performance in terms of detecting central rotation alteration to fingerprints. This makes the proposed system a veritable solution for different biometric authentication applications in secure smart cities

POTENTIAL EFFECTS OF SOME NATURAL DIETARY SUPPLEMENTS ON ANTHROPOMETRIC CHARACTERISTICS AMONGST WEIGHTLIFTER ATHLETES

This work was carried out to study the effect of using some natural dietary supplements; i.e. powders of date palm pits and pollen, ginseng roots, moringa leaves and royal jelly which giving orally in capsule to improve endurance of weightlifter athletes throughout 12 weeks in camp of sport Championship Sector belongs to the Armed Forces, Ministry of Defense, Future City, Cairo, Egypt. Collecting data showed that the suggested dietary supplement capsule had the highest value of the antioxidant activity (96.3%) and significant increases in total phenolic and flavonoids content (52.42 & 63.1 mg/g, respectively). Also, the anthropometric measurements showed a significant increase in weight and height in males compared to females. likewise, waist and mid upper arm circumference had significant increases in males compared to females, Male weightlifter athletes had significant muscles mass bigger than female one, and the fat mass for male was assessed as ‘‘Fitness’’ which ranged between (14 and 17%) but the female had fat mass that assessed as ‘‘Athletes’’ which ranged between (14 and 20%). The weights lifting by male and female increased during three months, and also revealed a significant increase in the efficiency of males in lifting weights higher than in the females during the period of 12 weeks. Thus, the results indicated that by incorporating natural dietary supplement powders in suggesting capsule, it is possible to enhance the performance of weightlifter athletes