76 research outputs found
Aggregation behavior and intermolecular interaction of binary surfactant mixtures based on cationic Geminis and nonionic surfactants
No full textThe Gemini surfactants of type alkylediyl-alpha-omega-bis(alkyldimethylammonium) dibromide with different alkyl groups containing m carbon atoms and an ethanediyl spacer, referred as m-2-m [C (m) H2m + 1(CH2)(2) N+(CH2)(2) N+(CH2)(2) C (m) H2m + 1, 2Br(-)] (m = 12 and 16), have been synthesized, purified, and characterized in our laboratory. The interactions between cationic Geminis and nonionic surfactants polyoxyethylene (23) lauryl ether (Brij35) and polyoxyethyleneoctyl phenyl ether (TX-100) have been studied by conductivity and steady-state fluorescence quenching techniques at a certain micellar concentration range and certain temperature. Rubingh's theory is used to evaluate the micellar interaction parameters (beta) for the mixed systems. It has been observed that mixed micelle formation in all the binary mixtures exhibited negative synergism (antagonism) or ideal behavior due to positive beta values. It was observed that contribution of conventional surfactants was always more than that of the Geminis. By using the ratio of peak intensities, micro-polarity, dielectric constant (D), and binding constant (K (sv)) of mixed systems have been found.Scientific Research Fund of Trakya University [TUBAP-2011/43]H. Akbas gratefully acknowledges the financial support of The Scientific Research Fund of Trakya University (Project No: TUBAP-2011/43)
The analogue of grad-div stabilization in DG methods for incompressible flows: Limiting behavior and extension to tensor-product meshes
No full textSchroeder, Philipp W./0000-0001-7644-4693WOS: 000442638700037grad-div stabilization is a classical remedy in conforming mixed finite element methods for incompressible flow problems, for mitigating velocity errors that are sometimes called poor mass conservation. Such errors arise due to the relaxation of the divergence constraint in classical mixed methods, and are excited whenever the spatial discretization has to deal with comparably large and complicated pressures. In this contribution, an analogue of grad-div stabilization for Discontinuous Galerkin methods is studied. Here, the key is the penalization of the jumps of the normal velocities over facets of the triangulation, which controls the measure-valued part of the distributional divergence of the discrete velocity solution. Our contribution is twofold: first, we characterize the limit for arbitrarily large penalization parameters, which shows that the stabilized nonconforming Discontinuous Galerkin methods remain robust and accurate in this limit; second, we extend these ideas to the case of non-simplicial meshes; here, broken grad-div stabilization must be used in addition to the normal velocity jump penalization, in order to get the desired pressure robustness effect. The analysis is performed for the Stokes equations, and more complex flows and Crouzeix-Raviart elements are considered in numerical examples that also show the relevance of the theory in practical settings. (C) 2018 Elsevier B.V. All rights reserved.German Academic Exchange Service (DAAD)Deutscher Akademischer Austausch Dienst (DAAD); program "Research Grants for Doctoral Candidates and Young Academics and Scientists", 2017/18 [57299291]; National Science FoundationNational Science Foundation (NSF) [DMS1522191]; U.S. ArmyUnited States Department of Defense [65294-MA]The authors would especially like to thank Christoph Lehrenfeld for several related fruitful discussions on stabilization and hybridization and the invaluable help he provided in using the finite element library NGSolve in the context of this work. Mine Akbas acknowledges support from the German Academic Exchange Service (DAAD) with the program "Research Grants for Doctoral Candidates and Young Academics and Scientists", 2017/18 (57299291). The third author was supported by National Science Foundation grant DMS1522191 and U.S. Army grant 65294-MA
Finite element-based geotechnical risk analysis for anchor-supported deep excavations
No full textEvaluation of the reliability of deep excavation support systems requires the inclusion of the soil variability in conjunction with probabilistic analysis. This is often considered a complicated process; therefore, the method is usually not followed in routine engineering practice. Recent developments in finite element modelling now enable probabilistic analyses to be performed more conveniently. As an illustrative example, the case history of a 20 m-deep excavation supported by anchored drilled shafts in the Sogutozu district of Ankara was investigated. Experimental results indicate that saturated sand-gravel bands, which are common within Ankara Clay, have the potential to cause a significant decrease in the anchor capacity. Ergo the excavation performance, including structural capacity and wall lateral displacements, was evaluated taking into regard the probabilistic nature of the effect of these bands and the variability of the soil parameters. Back-analysis was performed and compared with inclinometer readings to examine the capability of the numerical model to simulate the field behaviour. Later, additional finite element analyses were carried out through Python scripting software to investigate the reliability of the excavation. Geotechnical parameters of the Ankara Clay produced by Monte Carlo simulation method were used in these analyses. The results were evaluated within the context of recommended acceptable reliability levels. The reliability of the system was determined to be relatively low when taking into account the adverse impact of sand and gravel bands
Prognostic Factors in High Grade Osteosarcoma Patients Who Received Neoadjuvant Therapy and Subsequently Underwent Surgery: Data From the Turkish Oncology Group
No full textAkbas, Sinem/0000-0002-7197-211XBackground: Osteosarcoma is a rare but aggressive bone malignancy. Despite advances in multimodal therapy, survival remains suboptimal, highlighting the need for prognostic markers to guide treatment. Methods: This study included 162 osteosarcoma patients who received neoadjuvant chemotherapy followed by surgery between January 2009 and March 2024. Patients received either double (cisplatin + doxorubicin) or triple (MAP or PEI) chemotherapy. Survival analyses were conducted using Kaplan-Meier curves, log-rank tests, and Cox proportional hazards models. Results: The median age was 20 years (IQR: 18-29), and 53.1% were male. Patients who received triple chemotherapy regimens demonstrated significantly longer overall survival (OS) compared to those on doublet regimens. High tumor necrosis rates (>90%) and negative surgical margins were strongly associated with improved OS, while metastatic disease at diagnosis, elevated alkaline phosphatase (ALP), and male gender were linked to poorer survival. Multivariate analysis identified adjuvant therapy, age under 18, high necrosis rate, negative margins, and normal ALP as significant OS predictors. Conclusions: Triple-agent chemotherapy, necrosis rate >= 90 and negative surgical margins are strongly associated with prolonged survival in osteosarcoma. The key prognostic indicators such as ALP levels, surgical margins and age at diagnosis should guide personalized treatment strategies to improve outcomes in curable patients
Effects of Covid-19 pandemic in Turkey: Physical activity, smartphone usage, musculoskeletal system
No full textThis study aims to evaluate relationship between physical activity level, smartphone usage, back and neck health during Covid-19 pandemic. Participants between ages of 18-65 were included in study. Smartphone usage was evaluated with Smartphone Addiction Scale-Short Version, physical activity levels with short form of International Physical Activity Questionnaire. Oswestry Disability Index and Neck Bournemouth Questionnaire was used to evaluate back and neck problems. A total of 251 people (179 women, 72 men, age: 28.11±9.49 years, min-max: 18-62 years) participated in study. 134 participants (53.38%) had low physical activity levels; 35 individuals (13.94%) had sufficient physical activity levels while 82 participants (32.66%) were not physically active. A weak positive correlation was found between neck pain and total score of smartphone addiction scale, daily smartphone usage time, daily smartphone check frequency, and first check time after waking up (r=0.199, r=0.149, r=0.132, respectively). A weak negative correlation was found between neck pain and first check time after waking up (r=-0.145). As a result of study, it was observed that physical activity levels were insufficient in majority of individuals who participated in survey. The relationships we expected between physical activity level, smartphone usage characteristics, low back and neck health could not be demonstrated, only weak relationships were found between some features of smartphone use and neck health. We believe that finding solutions to increase physical activity levels of individuals during pandemic period will have both protective effects on health and will prevent problems by affecting musculoskeletal system positively. © 2021 Ondokuz Mayis Universitesi. All rights reserved.Sivas Cumhuriyet Üniversitesi, (08.07.2020, 2020-07/07
Reliability Analysis of an Anchored Contiguous Pile Wall in Ankara Clay with the Random Set Finite Element Method
No full textA deep excavation application characterized by imprecise data and lack of adequate information is used to demonstrate the efficiency, applicability, and validity of the random set theory in combination with finite element method (RS-FEM). A case history of an anchored contiguous pile wall in overconsolidated fissured Ankara Clay constructed for supporting the 15 m deep basement excavation of a nursing house in Seyranbaglari district of Ankara is considered. Existing buildings around the excavation area necessitated a careful examination of the wall deformations and the reliability of the system as a whole. However, the geotechnical parameters of the soil had to be estimated combining the results of very limited in-situ and laboratory tests with those obtained through previous experience of finite element analyses under similar conditions, i.e., expert knowledge. Plane strain finite element analyses were then performed to predict the contiguous pile retaining wall behavior. The parameters in the random set finite element model were chosen according to sensitivity analyses. Most likely bounds of the wall horizontal deformations were compared with those obtained from inclinometer readings. As suggested by previous case histories, wall deformations were observed to fall within the lower third of the range predicted by RS-FE
The Charlson Comorbidity Index: predicting readmission and severity in emergency departments
No full textIntroduction. The Charlson Comorbidity Index (CCI) is a comorbidity scale used widely throughout the world. Despite its widespread use, its relationship with patient readmission to the Emergency departments (ED) has not been evaluated previously.
Aim. To show whether there is a correlation between the CCI score and the number of repeated admissions to ED and that the CCI score can be used as a predicted factor for the serious patients.
Material and methods. This was a prospective observational cross-sectional study. Age, gender, vital signs of the patients who agreed to participate in the study was recorded. Numbers of ED readmissions of patients within six months after discharge and CCI scores have been recorded.
Results. The study was completed with 1420 patients. The admission rates of patients in the ED in the six months were significantly higher in the CCI 5+ group than in other groups (p0).
Conclusion. We believe that the CCI scoring system can be used by ED clinicians to predict the risk of readmission of patients after discharge from ED
Probabilistic Slope Stability Analyses Using Limit Equilibrium and Finite Element Methods
No full textThis paper compares the results of different probabilistic approaches and emphasizes the necessity of probabilistic analyses in slope stability studies. To do that, Limit Equilibrium Method (LEM) and Finite Element Method (FEM) are utilized and their outputs are compared in terms of probability of failure (PF), reliability index (RI), factor of safety (FS) and the failure surface. Lastly, concept of Random Finite Element Method (RFEM) is studied and effects of spatial correlation distance are investigate
Micellization and Related Behaviours of Polyoxyethylene-Type Non-ionic Surfactants on Root Elongation of Allium cepa L.
No full textInternational Conference on Global Trends in Pure and Applied Chemical Sciences (ICGTCS) -- MAR 03-04, 2012 -- Udaipur, INDIAIn this study, polyoxyethylenated fatty alcohol ether (POE) nonionic surfactants polyoxyethylene (23) lauryl ether (C12E23) (Brij 35); polyoxyethylene (10) cetyl ether (C16E10) (Brij 56); polyoxyethylene (10) stearyl ether (C18E10) (Brij 76); polyoxyethylene (10) lauryl ether (C12E10) (POE 10). A large proportion nonionic surfactants are made hydrophilic by the presence of a polyethylene glycol chain obtained by the polycondensation of ethylene oxide. They are called polyethoxylated nonionics. In this study the effects of polyoxyethylene-type nonionic surfactants on root elongation of Allium cepa L. were determined for a week under laboratory conditions in the concentration ranges of 5.00, 2.50 and 1.25 g/L (w/v) at 16 +/- 0.5 degrees C. It was determined that the stimulatory effect on root elongation becomes stronger when the number of ethylene oxide group (C2H4O) was increased in the POE surfactant. The stimulatory effect decreases in the order C18E10 > C16E10 > C12E23 > C12E10 due to the decreasing of the number hydrocarbons in the series.Asian Journal Che
Phytotoxic Effects of Non-ionic Surfactant Octylphenol Series (Triton X-100, Triton X-114, Triton X-405) on Onion
No full textInternational Conference on Global Trends in Pure and Applied Chemical Sciences (ICGTCS) -- MAR 03-04, 2012 -- Udaipur, INDIAIn this study, three widely used octylphenol series non-ionic surfactant Triton X-114, Triton X-100 and Triton X-405 were selected to I examine their phytotoxic effects. They were evaluated under laboratory conditions using onion (Allium cepa L.) as a test material. The phytotoxic effects on root were determined after 7th days. Surfactants used in study were tested at three different surfactant concentrations, 5.00, 2.50 and 1.25 g/L (w/v) concentrations. The phytotoxicity results were based on the effective concentration that reduced root growth I I by 50 % (EC50). Some differences were observed between the effects of three types of surfactants. Stimulatory effects only occurred in I Triton X-405 while inhibitory effects occured in Triton X-100 and Triton X-114 at all concentrations. It was observed that inhibitory effects increased with increasing concentrations of Triton X-114 and Triton X-100.Asian Journal Che
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