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This study investigates the fabrication and characterization of an ultra-high temperature ceramic composite based on ZrB2-20 vol. % SiC using the spark plasma sintering method with a multi-step technique. Sintering of ZrB2 poses challenges due to its covalent nature and high sintering temperature. Adding up to 20 vol. % SiC has shown significant improvement in the sintering process and mechanical properties of the ZrB2-based composite. Therefore, the effect of adding TiC in the range of 0 to 15 vol. % on the microstructural and mechanical properties of the composite was investigated at a temperature of 1800°C and a pressure of 30 MPa. The results indicated that the sintering process and particle bonding start at a temperature of 1600°C and continue up to 1800°C, with densification being controlled by grain boundary diffusion at this temperature. Adding up to 10 vol. % TiC to the ZrB2-SiC composite and sintering at 1800°C for 5 minutes resulted in the formation of (Zr,Ti)B2 and (Ti,Zr)C solid solutions in the matrix and reactions with surface oxides of ZrB2 powder such as ZrO2 and B2O3. These changes led to a 15% increase in relative density and improvements in mechanical properties, including hardness (14%), elastic modulus (12%), fracture strength (20%), and fracture toughness (8%). However, increasing the TiC content from 10 to 15 vol. % resulted in a noticeable decline in the mechanical properties and crystallite size of the composite. [ABSTRACT FROM AUTHOR]

Multisite phosphorylation plays an important role in regulating switch-like protein activity and has been used widely in mathematical models. With the development of new experimental techniques and more molecular data, molecular phosphorylation processes emerge in many systems with increasing complexity and sizes. These developments call for simple yet valid stochastic models to describe various multisite phosphorylation processes, especially in large and complex biochemical networks. To reduce model complexity, this work aims at simplifying the multisite phosphorylation mechanism by a stochastic Hill function model. Furthermore, this work optimizes regions of parameter space to match simulation results from the stochastic Hill function with the distributive multisite phosphorylation process. While traditional parameter optimization methods have been focusing on finding the best parameter vector, in most circumstances, modelers would like to find a set of parameter vectors that generate similar system dynamics and results. This paper proposes a general α–β–γ rule to return an acceptable parameter region of the stochastic Hill function based on a quasi-Newton stochastic optimization algorithm. Different objective functions are investigated characterizing different features of the simulation-based empirical data, among which the approximate maximum log-likelihood method is recommended for general applications. Numerical results demonstrate that with an appropriate parameter vector value, the stochastic Hill function model depicts the multisite phosphorylation process well except the initial (transient) period. [ABSTRACT FROM AUTHOR]

This paper aims to develop a numerical methodology to investigate the penetration process of nanoneedles into cells and the corresponding force and indentation length. The finite element approach via the explicit dynamic method handles convergence difficulties in the nonlinear phenomenon. The cell is modeled as an isotropic elastic hemiellipsoidal shell with a thickness of 200 nm, which represents the lipid membrane and actin cortex, encapsulating cytoplasm that is regarded as an Eulerian body because of its fluid‐type behavior. Nanoneedles with diameters 400, 200, and 50 nm are considered for model development based on available experimental data. The Von Mises strain failure criterion is used for rupture detection. A parameter study using 1, 2.5, 5, 7.5, and 10 kPa shows that Young's modulus of the HeLa cell membrane is about 5 kPa. Moreover, a failure strain of 1.2 chosen among 0.2, 0.4, 0.6, 0.8, 1, and 1.2 matches best the experimental data. In addition, a diameter study shows that the relations between force‐diameter and indentation length‐diameter are linear and polynomial, respectively. Furthermore, regarding the experimental data and by using contour of minimum principal stress around needle and an analytical equation for calculation of buckling force of a woven fabric, we proposed that for a given cell, membrane structural stability—a function of the coupled effect of Young's modulus and actin meshwork size—contributes directly to needle insertion success rate for that type of cell. [ABSTRACT FROM AUTHOR]

Background and Objective: Traditional methods of medical education, despite being easy to implement, do not have long-lasting efficiency. The main aim of this study is to use the help of the learners to teach parts of the medical pharmacology course using role-playing pedagogy. This was done for the first time in Babol University of Medical Sciences with the cooperation of medical students who entered the university in 2016. Methods: Students were divided into 5 groups and a group leader was introduced for each group. Five topics were selected and corresponding scenarios were written. There were three to seven people in each group. The physician together with the hypothetical resident or student examined the patient's problems and prescribed medicine and gave them the necessary recommendations. All participants were given a pre-test and a post-test, and then the findings were statistically analyzed. Findings: 101 students (49 girls and 52 boys) with a mean age of 21.43±1.14 years participated in the study. Except for the topic of poisoning, the mean difference in pre- and post-test scores of female students was lower than that of male students. For example, this difference was observed in the topic of Parkinsonism (p<0.0001). All students involved in the performance obtained better grades in the same topics compared to other students (88.15 vs. 59.71 out of 100). 74% of female students and 79% of male students expressed satisfaction with the implementation of this method. Conclusion: According to the findings, this method has increased the motivation to learn the medical pharmacology course and stabilize the course topics. Therefore, its implementation in difficult courses with diverse and voluminous content not only helps them to learn better, but also helps them maintain their enthusiasm and increase motivation to learn more and consolidate what they have learned. [ABSTRACT FROM AUTHOR]

Orthogonal eigenstructure control is a novel control method that can be used for vibration suppression in flexible structures. The method described in this study does not need defining the desired locations of the closed-loop poles or predetermining the closed-loop eigenvectors. The method, which is applicable to linear multi-input multi-output systems, determines an output feedback control gain matrix such that some of the closed-loop eigenvectors are orthogonal to the open-loop eigenvectors. Using this, the open-loop system's eigenvectors as well as a group of orthogonal vectors are regenerated based on a matrix that spans the null space of the closed-loop eigenvectors. The gain matrix can be generated automatically; therefore, the method is neither a trial and error process nor an optimization of an index function. A finite element model of a plate is used to study the applicability of the method to systems with relatively large degrees of freedom. The example is also used to discuss the effect of operating eigenvalues on the process of orthogonal eigenstructure control. The importance of the operating eigenvalues and the criteria for selecting them for finding the closed-loop system are also investigated. It is shown that choosing the operating eigenvalues from the open-loop eigenvalues that are farthest from the origin results in convergence of the gain matrix for the admissible closed-loop systems. It is shown that the converged control gain matrix has diagonal elements that are two orders of magnitude larger than the off-diagonal elements, which implies a nearly decoupled control. [DOI: 10.1115/1.4001991] Keywords: orthogonal eigenstructure control, operating eigenvalues, eigenstructure assignment, vibration reduction, plate

Beta Thalassemia major patients receive repeated transfusions in order to compensate anemia and use desferal to remove iron overload. Comparing immunoglobulins and complement components in the serum of these patients with normal range shows a significant increase (P

For monitoring of renal transplant function, serum B2m was evaluated in 23 recipients. According to clinical diagnosis the patients were in four groups: 1) Successful renal transplant; the mean concentration of SB2m pretransplantation was 73.1±26.1 mg/L but decreased to nearly normal level (4.43±1.17 mg/L) within 24-48h and then reached to 3.1 mg/L duting 20 days after transplantation. 2) Renal dysfunction (except rejection); the maximum changes of SB2m was 1.1 mg/L/day and no significant changes of SB2m were found between this group and group 1. 3) Accelerated and acute rejection; during immunological rejection crisis, SB2m level increased and after response to antirejection therapy decreased. The daily changes of SB2m allowed to diffrentiate renal dysfunction fom rejection in 84% of cases. Moreover according to SB2m fluctuation levels, SB2m had a prognostic pattern for acute rejection due to significant differences between the level of SB2m on the day of clinical diagnosis of rejection and 4 days previously (P