The relationship between aortic valve calcification and risk of ischemic stroke

Background: Although most previous studies did not confirm the relationship between aortic valve calcification (AVC) and ischemic stroke, there are some case reports about the importance of AVC in occurrence of ischemic stroke. Objective: To investigate the relationship between aortic valve calcification and risk of ischemic stroke. Methods: This case-control study includes 600 patients (300 cases and 300 controls) admitted at Qazvin’s Bu-Ali Hospital from April 2014 to February 2015. Cases were selected from acute ischemic stroke patients admitted to the hospital Emergency Department and the control group consisted of non-stroke patients referred to cardiology clinic. Two groups were matched for sex, age and other vascular risk factors. All participants underwent transthoracic echocardiography. AVC was scored according to scaling system proposed by previous studies. Demographic, clinical and laboratory characteristics of all participants were also collected and the relationship between these parameters and echocardiographic findings were analysed using dependent t and chi-squared tests. P<0.05 was considered significant. Findings: Mean age of participants was 65.12±12.41 years (46.2% man). In 153 of stoke patients (51%), AVC was detected but only 35 participants (17.7%) of control group showed this abnormality (P<0.001). In case and control groups, aortic insufficiency was 54.3% (n=163) and 18.3% (n=55) respectively (P<0.001). Left ventricular hypertrophy was also more frequent in stroke patients (41.8% vs. 20.7%, P<0.001). Other cardiovascular risk factors were more in the patients of case group. However, the difference wasn’t statistically significant between two groups. Conclusion: According to this study, AVC and aortic insufficiency are related to ischemic stroke occurrence. More studies are needed to confirm these findings. Keywords: Ischemic Stroke, Aortic Valve Calcification, Aortic Insufficiency, Echocardiograph

Predictive modeling of material removal modes in micro ultrasonic machining

This paper presents a model to predict ductile and brittle material removal modes when a brittle material is impacted by a single sharp abrasive particle in micro ultrasonic machining process. Analyses are performed based on the basic indentation fracture theory for hard angular particles. The conditions required for occurrence of both ductile and brittle removal during the interaction between sharp particles and brittle materials in micro ultrasonic machining are discussed. Subsequently, the quantitative criteria for brittle–ductile transition in material removal are presented using the threshold kinetic energy in promoting radial and lateral cracks. Finally, the adequacy of the proposed model is verified by the experimental results from single particle impingements in micro ultrasonic machining. In the experiments, polycrystalline diamond particles ranging from 0.37 to 3 μm are used for processing of single crystalline 〈100〉 silicon and fused quartz. The ultrasonic frequency at 50 kHz is introduced at the horn tip which is set at amplitude from 0.8 to 4 μm. The constellation of the experimental results clearly showed good agreement on the basis of comparative principle for the model validation. The outcome of the present research work can be used as an important platform to build reliable models for prediction of material removal rate based on the mode by which material removal takes place in micro ultrasonic machining process. The proposed model can be employed to enhance surface quality as well as process productivity

Markov chain Monte Carlo in approximate Dirichlet and beta two-parameter process hierarchical models

We present some easy-to-construct random probability measures which approximate the Dirichlet process and an extension which we will call the beta two-parameter process. The nature of these constructions makes it simple to implement Markov chain Monte Carlo algorithms for fitting nonparametric hierarchical models. For the Dirichlet process, we consider a truncation approximation as well as a weak limit approximation based on a mixture of Dirichlet processes. The same type of truncation approximation can also be applied to the beta two-parameter process. Both methods lead to posteriors which can be fitted using Markov chain Monte Carlo algorithms that take advantage of blocked coordinate updates. These algorithms promote rapid mixing of the Markov chain and can be readily applied to normal mean mixture models and to density estimation problems. We prefer the truncation approximations, since a simple device for monitoring the adequacy of the approximation can be easily computed from the output of the Gibbs sampler. Furthermore, for the Dirichlet process, the truncation approximation offers an exponentially higher degree of accuracy over the weak limit approximation for the same computational effort. We also find that a certain beta two-parameter process may be suitable for finite mixture modelling because the distinct number of sampled values from this process tends to match closely the number of components of the underlying mixture distribution

Single abrasive particle impingements as a benchmark to determine material removal modes in micro ultrasonic machining

The modes under which the material is removed, whether it is brittle or ductile, can be controlled in micro ultrasonic machining through setting of machining conditions and process parameters at desired levels to improve the process productivity as well as surface quality. However, the micro ultrasonic machining process lacks in fundamental understanding of brittle and ductile modes of material removal which is the key to develop predictive process models. In this paper the approach of single abrasive particle impingement is presented for the first time in micro ultrasonic machining with the purpose of providing insights into material removal modes. The morphology of the craters formed by single particle impact at various vibration amplitudes and with different particle sizes is studied using confocal imaging profiler, field emission scanning electron microscopy and atomic force microscopy. The significance of this method lies in catering a benchmark for determining brittle and ductile removal conditions under various process parameters. Also, the outcome of this study can be used to validate the predictive model for brittle and ductile material removal modes, which takes into account kinetic energy of the impinging particle as well as threshold kinetic energy of the material and is crucial for estimation of material removal rate in micro ultrasonic machining

A recursive method for functionals of Poisson processes

Functionals of Poisson processes arise in many statistical problems. They appear in problems involving heavy-tailed distributions in the study of limiting processes, while in Bayesian nonparametric statistics they are used as constructive representations for nonparametric priors. We describe a simple recursive method that is useful for characterizing Poisson process functionals that requires only the use of conditional probability. Applications of this technique to convex hulls, extremes, stable measures, infinitely divisible random variables and Bayesian nonparametric priors are discussed

Design and Construction of Curcumin – Loaded Targeted Iron Oxide Nanoparticles for Cancer Treatment

BACKGROUND AND OBJECTIVE: Considering the increasing number of patients with cancer and the relative ineffectiveness of existing treatments, finding a modern technique for cancer treatment has been one of the major topics of research in recent decades. The present study aims to load curcumin anticancer drug on targeted iron oxide nanoparticles. METHODS: In this laboratory research, iron oxide nanoparticles were synthesized using polyol method. Then, they were coated with polyglycerol as a polymeric coating through ring – opening polymerization method. Folic acid (with three weight ratios of 2, 25 and 50%) was used to target the system constructed for specific penetration into the cancer cells. The experiments of loading the drug were performed with three weight ratios of 0.5, 1 and 2 µg nanoparticles on coated and targeted nanoparticles. Then, drug release rate was measured under in vitro conditions. Finally, MTT Assay was used to analyze cell toxicity of the loaded drug. FINDINGS: Results indicated successful construction of 20 nm nanoparticles. The maximum rate of drug loading into the system was about 88 and 82% for non-targeted nanoparticles and targeted nanoparticles, respectively, while increased targeting had adverse effects on drug loading. Moreover, the loaded drug had a more successful therapeutic effect compared with the free drug. CONCLUSION: Results of the study demonstrated that the constructed nanoparticles have the necessary efficiency to act as a system for transferring anticancer drug

Chiral nonet mixing in

The generalized linear sigma model for mixing among two- and four-quark components of scalar (and pseudoscalar) mesons below and above 1 GeV is applied to the $$\pi \eta$$ channel in which the isovector scalars $$a_0(980)$$ and $$a_0(1450)$$ are probed. In the leading order, the model parameters have been previously fixed by various low-energy experimental data, and then applied to $$\pi \pi$$ and $$\pi K$$ channels in which the properties of the light and broad $$\sigma$$ and $$\kappa$$ mesons are extracted in agreement with estimates reported in the literature. With the same parameters fixed in the leading order, in the present work the prediction of the model for the $$\pi \eta$$ scattering amplitude in the elastic region is given and unitarized with the K-matrix method. The poles of the unitarized scattering amplitude, which determine the mass and decay width of $$a_0(980)$$ and $$a_0(1450)$$ are computed. It is found that the model predicts an isovector scalar state below 1 GeV, with mass 984 ± 6 MeV and decay width 108 ± 30 MeV which is a clear signal for the $$a_0(980)$$. The $$a_0$$ pole extracted in this work, further supports the plausibility of the mixing patterns for scalar mesons predicted by this model according to which there is a significant underlying mixing among scalars below and above 1 GeV, with those below 1 GeV being generally of four-quark nature while those above 1 GeV being overall closer to quark–antiquark states. Predictions for various scattering lengths as well as for properties of $$a_0(1450)$$ are also presented