Corneal biomechanical properties distribution in myopic population

AIM: To evaluate distribution of corneal biomechanical measurements in normal myopia and myopic-astigmatism population.<p>METHODS:One hundred and eighty eyes with myopia and myopic-astigmatism candidated for laser refractive surgery were included in this study. Complete examination of anterior and posterior segments, manifest refraction spherical equivalent(MRSE), Orbscan and Zywave were performed preoperatively. Ocular response analyzer(ORA)was used to measure corneal hysteresis(CH), corneal resistance factor(CRF), Goldmann-correlated intraocular pressure(IOPg)and corneal compensated IOP(IOPcc). Distribution of all corneal biomechanical properties and correlation between these parameters and MRSE, age and sex were determined. Statistical analysis was performed using SPSS 17 software and a <i>P</i>-Value less than 0.05 was considered significant. <p>RESULTS: Mean age was 28.20±6.78 years. Mean MRSE was -4.21±1.19D. Mean CH, CRF, IOPg and IOPcc was 10.00±1.28mmHg, 10.17±1.45mmHg, 15.71±2.67mmHg and 16.68±2.41mmHg respectively. 28.4% of all myopic population had CH about 10mmHg, and 71% had CH, 9mmHg up to 11mmHg. CRF in 25.9% of myopic population was 10mmHg, and in 48.7% was 9mmHg up to 11mmHg. There was very poor positive correlation between MRSE& CH(Rs=0.001, <i>P</i>=0.71)and MRSE& CRF(Rs=0.01, <i>P</i>=0.18).<p>CONCLUSION: Our study demonstrated the distribution of corneal biomechanical properties(CH, CRF, IOPg, IOPcc)in normal myopia and myopic-astigmatism population in Iran, and confirmed that, there was no statistically significant correlation between CH, CRF and MRSE, age and sex but there was significant correlation between IOPg, IOPcc and formerly mentioned parameters

A theory of flow network typings and its optimization problems

Many large-scale and safety critical systems can be modeled as flow networks. Traditional approaches for the analysis of flow networks are whole-system approaches in that they require prior knowledge of the entire network before an analysis is undertaken, which can quickly become intractable as the size of network increases. In this thesis we study an alternative approach to the analysis of flow networks, which is modular, incremental and order-oblivious. The formal mechanism for realizing this compositional approach is an appropriately defined theory of network typings. Typings are formalized differently depending on how networks are specified and which of their properties is being verified. We illustrate this approach by considering a particular family of flow networks, called additive flow networks. In additive flow networks, every edge is assigned a constant gain/loss factor which is activated provided a non-zero amount of flow enters that edge. We show that the analysis of additive flow networks, more specifically the max-flow problem, is NP-hard, even when the underlying graph is planar. The theory of network typings gives rise to different forms of graph decomposition problems. We focus on one problem, which we call the graph reassembling problem. Given an abstraction of a flow network as a graph G = (V,E), one possible definition of this problem is specified in two steps: (1) We cut every edge of G into two halves to obtain a collection of |V| one-vertex components, and (2) we splice the two halves of all the edges, one edge at a time, in some order that minimizes the complexity of constructing a typing for G, starting from the typings of its one-vertex components. One optimization is minimizing “maximum” edge-boundary degree of components encountered during the reassembling of G (denoted as α measure). Another is to minimize the “sum” of all edge-boundary degrees encountered during this process (denoted by β measure). Finally, we study different variations of graph reassembling (with respect to minimizing α or β) and their relation with problems such as Linear Arrangement, Routing Tree Embedding, and Tree Layout

Stress, Strain, or Energy: Which One Is the Superior Parameter to Estimate Fatigue Life of Notched Components? An Answer by a Novel Machine Learning-Based Framework

This paper introduces a simple framework for accurately predicting the fatigue lifetime of notched components by employing various machine learning algorithms applied to a wide range of materials, loading conditions, notch geometries, and fatigue lives. Traditional approaches for this task have relied on empirical relationships involving one of the mechanical properties, such as stress, strain, or energy. This study goes further by exploring which mechanical property serves as a better measure. The key idea of the framework is to use the gradient of the mechanical properties (stress, strain, and energy) to distinguish between different notch geometries. To demonstrate the accuracy and broad applicability of the framework, it is initially validated using isotropic materials, subsequently applied to samples produced through additive manufacturing techniques, and ultimately tested on carbon fiber laminated composites. The research demonstrates that the gradient of all three measures can be effectively employed to estimate fatigue lifetime, with stress-based predictions exhibiting the highest accuracy. Among the machine learning algorithms investigated, Gradient Boosting and Random Forest yield the most successful results. A noteworthy finding is the significant improvement in prediction accuracy achieved by incorporating new data generated based on the Basquin equation

Optimized PID Controller with Bacterial Foraging Algorithm

Fish robot precision depends on a variety of factors including the precision of motion sensors, mobility of links, elasticity of fish robot actuators system, and the precision of controllers. Among these factors, precision and efficiency of controllers play a key role in fish robot precision.  In the present paper, a robot fish has been designed with dynamics and swimming mechanism of a real fish. According to equations of motion, this fish robot is designed with 3 hinged links. Subsequently, its control system was defined based on the same equations. In this paper, an approach is suggested to control fish robot trajectory using optimized PID controller through Bacterial Foraging algorithm, so as to adjust the gains. Then, this controller is compared to the powerful Fuzzy controller and optimized PID controller through PSO algorithm when applying step and sine inputs. The research findings revealed that optimized PID controller through Bacterial Foraging Algorithm had better performance than other approaches in terms of decreasing of the settling time, reduction of the maximum overshoot and desired steady state error in response to step input. Efficiency of the suggested method has been analyzed by MATLAB software

Corneal collagen cross-linking effects on pseudophakic bullous keratopathy

AIM: To evaluate the efficacy of riboflavin administration and ultraviolet A(UVA)cross-linking on advanced symptomatic bullous keratopathy. <p>METHODS: Fifteen patients with symptomatic pseudophakic bullous keratopathy(PBK)were included. Slit-lamp examination, visual acuity, foreign body sensation(FBS)questionnaire, corneal clarity grading, ocular pain intensity scale and corneal thickness measures with Pentacam and ultrasound pachymetry(UP), were performed before corneal cross-linking and 1 and 6mo thereafter. After using sodium chloride solution, for one week, the central 8mm(diameter)of the corneal epithelium was removed, and cross-linking, with riboflavin instillation every 3min for 30min, and UVA irradiation for 30min was performed. <p>RESULTS: Five males and 10 females with mean age of 66±13y were included. Mean follow up time was 6.2mo. Corneal transparency in all eyes was statistically significantly better 1 month after treatment than preoperatively(<i>P</i><0.05). At 6mo, however, corneal transparency was better in 8 eyes, the same in 5 eyes, and worse in 2 eyes compared with preoperative levels(<i>P</i>= 0.218). Foreign body sensation subsided in 70% of patients. The average CCT decreased within 1mo after the procedure(<i>P</i><0.05). At 6mo, all but 3 eyes had progressive swelling, and the CCT increased; however, the CCT was still statistically significantly thinner than preoperatively(<i>P</i>=0.006). The improvement in mean CDVA from preoperatively to 1mo postoperatively was statistically significant(<i>P</i>=0.010). At 6mo, no significant differences were observed(<i>P</i>=0.130). The pain scores at 1mo were statistically significantly better than preoperatively(<i>P</i>=0.007). At 6mo, however the mean pain score was higher than at 1mo and not statistically significantly different from the preoperative score(<i>P</i>=0.070). <p>CONCLUSION: Corneal CXL significantly improved corneal transparency, corneal thickness, and ocular pain 1 month postoperatively. However, it did not seem to have a long-lasting effect in decreasing pain and maintaining corneal transparency in patients with PBK. This procedure extends the time interval for corneal transplantation and increases visualization at DSAEK procedure

Improving the CFD modelling of cross-ventilation in highly-packed urban areas

Computational Fluid Dynamics (CFD) simulations are widely used in many wind-related urban morphology studies in urban areas, including cross-ventilation. The accuracy of the CFD models, however, is still a challenging issue for accurate prediction of the complex flow behavior around and inside the buildings. The RANS models, although broadly preferred, provide poor results in predicting the cross-ventilation in street canyons.Thus, this study aims to understand and quantify limitations of the steady RANS models for cross-ventilation applications in highly-packed urban areas. To this end, a series of experimentally validated CFD simulations were conducted for a group of buildings, which were arranged in regular and staggered orders with different urban area densities. The improvement possibility of the RANS model accuracy was investigated using a parametric sensitivity study over the closure coefficients, and consequently a series of new closure coefficients were found for urban area densities between 0.25 and 0.4. Furthermore, as an interesting finding of this study, CFD results for urban area densities above 0.4 showed a high discrepancy compared to the expected measurement ranges for surface wind pressure; this implies that the CFD modelling of higher density urban areas should be treated with more caution and thus further studies are required to develop a guideline for such applications

The outcomes of behavioral abnormalities of human resources of the Ministry of Health and Medical Education

Background: The last criterion for behavioral abnormality occurs outside social and cultural norms. The present study aimed to design a model of behavioral abnormalities of human resources of the Ministry of Health and Medical Education. Methods: The outcomes were identified through library studies, and the fuzzy Delphi technique was used with the opinion of experts until we reached a theoretical consensus. First, 13 factors were confirmed using the opinion of 50 experts. Then, a questionnaire was designed based on the results of the first stage of the study, and the experts were asked to specify the importance of each identified stage using verbal variables. Then, the verbal variables were converted into fuzzy triangular numbers, and the triangular fuzzy mean was de-fuzzified using the Minkowski formula by Excel and SPSS-21 software. Results: The members of the expert group reached a consensus on all components (dissatisfaction, drug abuse, alcohol consumption, reduction of motivation, moral corruption, malice and revenge, suicide, absenteeism, early and excessive leaves, theft and destruction of property, procrastination, arguments and physical violence, sexual harassment, violation of laws and character assassination and humiliation of colleagues). The de-fuzzified mean difference of experts' opinions in the two stages was less than 0.1, indicating the intensity of experts' agreement with each of the components of the conceptual model of the study. Conclusion: Behavioral abnormality is one of the problems of today's organizations, and the development of behavioral models in organizations is one way to guide employees' behavior and prevent the occurrence of abnormal behaviors

Assessment of Health Literacy and Self-care Behaviors among Patients Discharged from COVID-19 Wards

Introduction: The rapid outbreak of the new COVID-19 virus has become an international health challenge. Confronting the prevalence of this pathogenic virus requires, in the first step, health literacy and self-care on people’s part. Materials and Methods: This descriptive cross-sectional study was carried out over three months. A total of 67 patients discharged from a COVID-19 ward were selected randomly. Data were collected using a validated researcher-made questionnaire on health literacy and self-care. The data were then analyzed using SPSS software version 16. Results: Sixty-seven patients (mean age: 45.32 ± 9.39; age range: 29 - 87) were assessed. The majority were male (64.2%), married (79.1%), illiterate (44.8%), and homemaker or unemployed (37.3%). The overall mean score of health literacy and self-care was moderate. The results of the Pearson correlation test showed a significantly positive association between overall health literacy and its components as well as the total self-care and its components among the patients studied (p &lt;.001). Conclusion: Since self-care increases with health literacy among COVID-19 patients, it demands educational interventions in this area to improve health literacy