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Search Results: 1 - 10 of 480 matches for " Sepideh Razavi "
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Rotational Dynamics and Angular Locking of Nanoparticles at liquid Interfaces
Sepideh Razavi,Ilona Kretzschmar,Joel Koplik,Carlos E. Colosqui
Physics , 2013,
Abstract: Nanoparticles with different surface morphologies that straddle the interface between two immiscible liquids are studied via molecular dynamics simulations. The methodology employed allows us to compute the interfacial free energy at different angular orientations of the nanoparticle. Due to their atomistic nature, the studied nanoparticles present both microscale and macroscale geometrical features and cannot be accurately modeled as a perfectly smooth body (e.g., spheres, cylinders). Under certain physical conditions, microscale features can produce free energy barriers that are much larger than the thermal energy of the surrounding media. The presence of these energy barriers can effectively "lock" the particle at specific angular orientations with respect to the liquid-liquid interface. This work provides new insights on the rotational dynamics of Brownian particles at liquid interfaces and suggests possible strategies to exploit the effects of microscale features with given geometric characteristics.
Reaction of Rat Subcutaneous Connective Tissue to Resin Composites Polymerized with Different Light Curing Units and Different Lightening Methods
Atiyeh Feiz,Farahnaz Arbabzadeh Zavareh,Seyed Mohammad Razavi,Hamid Badrian,Sepideh Dolatyar,Mansoureh Vajihi
International Journal of Dentistry , 2012, DOI: 10.1155/2012/156352
Abstract: The aim of the study was to determine and compare the reaction of rat subcutaneous connective tissue to resin composites polymerized with different lights curing and lightening methods. In this in vivo study, 20 mature Wister Albino rats were used. The composite discs, 4?mm in diameter and 2?mm thick, were cured by QTH or LED light curing units with 4 different lightning methods (full power QTH, full power LED, pulse LED, and ramp LED). Five resin composite discs were implanted in each rat, so that 4 of 5 discs for implantation of cured composite discs differently and central one as control without implantation. After sacrificing at 7, 14, 30, and 60 days the inflammatory grade, fibrosis, and necrosis were determined. Freedman and Cochran tests were used to analyze the data using SPSS software ver. 15. The results of the study showed significant differences in inflammation grade and fibrosis among control group and 4 experimental groups at day 14 ( ). In necrosis, there was no significant difference among 4 groups in different times ( ). In conclusion, neither the type of light curing units (LED or QTH) nor the lightening methods can affect the grade of inflammatory reaction. 1. Introduction Resin composites have frequently been used as posterior restorative materials due to the demand for both aesthetic restorations and concerns over the adverse effects of mercury ingredient of amalgam. Adequate polymerization is a critical factor for increasing the physical properties and clinical performance of resin composite restorative materials. Residual uncured monomers or oligomers would cause cytotoxicity. Even in restorative materials which are fully set, substantial amounts of short-chain polymers remain unbound. Therefore there is probable elution of leachable toxic components toward the pulp. Also there is a relation between the amount of uncured reachable resin in the composite and the magnitude of the cytotoxic effect. In order to overcome the problem of inadequate polymerization, new methods, of curing, such as soft start and full power methods have been introduced [1]. Inadequate polymerization causes various problems such as inferior physical properties, solubility in the oral environment, and increased microleakage with resultant recurrent decay and pulpal irritation. The amounts of leachable residual monomers, on the other hand, could vary with the light source used for curing. Nowadays, various light curing units (LCUs) are available in dental practice, among which the halogen lamps are the most frequently used, although recently the light-emitting
Using the Discrete Dipole Approximation and Holographic Microscopy to Measure Rotational Dynamics of Non-spherical Colloidal Particles
Anna Wang,Thomas G. Dimiduk,Jerome Fung,Sepideh Razavi,Ilona Kretzschmar,Kundan Chaudhary,Vinothan N. Manoharan
Physics , 2013, DOI: 10.1016/j.jqsrt.2013.12.019
Abstract: We present a new, high-speed technique to track the three-dimensional translation and rotation of non-spherical colloidal particles. We capture digital holograms of micrometer-scale silica rods and sub-micrometer-scale Janus particles freely diffusing in water, and then fit numerical scattering models based on the discrete dipole approximation to the measured holograms. This inverse-scattering approach allows us to extract the the position and orientation of the particles as a function of time, along with static parameters including the size, shape, and refractive index. The best-fit sizes and refractive indices of both particles agree well with expected values. The technique is able to track the center of mass of the rod to a precision of 35 nm and its orientation to a precision of 1.5$^\circ$, comparable to or better than the precision of other 3D diffusion measurements on non-spherical particles. Furthermore, the measured translational and rotational diffusion coefficients for the silica rods agree with hydrodynamic predictions for a spherocylinder to within 0.3%. We also show that although the Janus particles have only weak optical asymmetry, the technique can track their 2D translation and azimuthal rotation over a depth of field of several micrometers, yielding independent measurements of the effective hydrodynamic radius that agree to within 0.2%. The internal and external consistency of these measurements validate the technique. Because the discrete dipole approximation can model scattering from arbitrarily shaped particles, our technique could be used in a range of applications, including particle tracking, microrheology, and fundamental studies of colloidal self-assembly or microbial motion.
Towards Application of Bioactive Natural Products Containing Isoprenoids for the Regulation of HMG-CoA Reductase—A Review  [PDF]
Sepideh Pakpour
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.45138
Abstract:

Recognition of the biological properties of numerous “natural products” has fueled the current focus of this field, namely, the search for new drugs, antibiotics, insecticides, and herbicides. Based on their biosynthetic origins, natural products can be divided into three major groups: the isoprenoids, alkaloids, and phenolic compounds. Isoprenoids are structurally the most diverse group of secondary natural metabolites with different roles in the growth, development, and reproduction of a diverse range of prokaryotic and eukaryotes cells. Mevalonate and 2-C-methyl-D-erythritol 4-phosphate (MEP) pathways are known to be responsible for biosynthesis of numerous isoprenoids. HMG-CoA reductase is a rate-determining enzyme in mevalonate pathway, producing intermediates such as farnesyl and geranylgeranyl pyrophosphates, which lead to by-products such as cholesterol. Earlier studies have demonstrated that the inhibition of HMG-CoA reductase is one of the most effective approaches for treating hypercholesterolemia and eventually cardiovascular disease (CVD). Statins are HMG-CoA reductase inhibitors and the most prescribed group of drugs worldwide in treating hypercholesterolemia; however the application of this group of drugs may be expensive and has side effects including rashes and gastrointestinal symptoms. For these reasons, there is an important need to examine the viability of natural products as an alternative to statin treatment. This article is a review of different aforementioned areas with a focus on isoprenoids that can be used for the regulation of HMG-CoA reductase.


A Time-Frequency Approach for Discrimination of Heart Murmurs  [PDF]
Sepideh Jabbari, Hassan Ghassemian
Journal of Signal and Information Processing (JSIP) , 2011, DOI: 10.4236/jsip.2011.23032
Abstract: In this paper, a novel framework based on a time-frequency (TF) approach is proposed for detection of murmurs from heart sound signal. First, a high-resolution TF algorithm, matching pursuit, was used to decompose each heart beat into a series of TF atoms selected from a redundant dictionary. Next, representative components of murmurs were identified by clustering the selected atoms of all the beats into a finite number of clusters. Then, Wigner-Ville distribution of the representative components was used to generate a set of 8 features which were fed to a classifier. Experiments with a dataset consisting of heart sounds from 35 normal and 35 pathological subjects showed a classification accuracy of 95.71% in distinguishing murmurs from normal heart sounds.
Botulinum toxin type-A (BoNTA) and dynamic wrist-hand orthoses versus orthoses alone for the treatment of spastic-paretic upper extremity in chronic stroke patients  [PDF]
Sepideh Pooyania, Brenda Semenko
Open Journal of Therapy and Rehabilitation (OJTR) , 2014, DOI: 10.4236/ojtr.2014.21003
Abstract: Purpose: The purpose of this study was to investigate the potential functional improvement of the spastic-paretic upper extremity of individuals with chronic hemiparesis when using a dynamic wrist-hand orthosis with and without concurrent botulinum toxin type-A (BoNTA) injections into the spastic upper extremity muscles. Methods: A three-year retrospective chart review was conducted on all stroke patients referred to out-patient occupational therapy for an upper extremity rehabilitation program, which included use of a dynamic wrist-hand orthosis (DWHO). Three charts documented concurrent treatment with a DWHO + BoNTA. Eleven charts documented DWHO use without concurrent BoNTA treatment. Pre- and post-intervention outcome measure scores were compared between the two groups. Pre- and post-interven- tion scores were also analyzed irrespective of treatment group. Results: Although improvement approached significance on three of the documented outcome measures when comparing the DWHO + BoNTA and DWHO groups, no statistically significant changes were found. A significant difference (p < 0.05) however, was found between the pre- and post-intervention scores irrespective of treatment group in 13 of 14 of the outcome measures documented. Conclusions: Further research with a larger sample size is suggested to assess the combined effect of using a dynamic wrist-hand orthosis and BoNTA injections into the spastic upper extremity muscles of individuals with chronic hemiparesis post stroke.
Electromagnetic Self-Force Mechanisms and Origin of R-1 Term  [PDF]
Saeed Fathi, Hamed Razavi
Journal of Applied Mathematics and Physics (JAMP) , 2017, DOI: 10.4236/jamp.2017.55096
Abstract: An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the whole particle, there will be a net force on the particle due to the breakdown of Newton’s third law. This symmetry breaking mechanism relies on the finite size of the particle; thus, as Feynman has stated, conceptually this mechanism doesn’t make good sense for point particles. Nonetheless, in the point particle limit, two terms survive in the self-force series: R0 and R-1 terms. The R0 term can alternatively be attributed to the well-known radiation reaction but the origin of R-1 term is not clear. In this study, we will show that this new term can be accounted for by an inductive mechanism in which the changing magnetic field induces an inductive force on the particle. Using this inductive mechanism, we derive R-1 term in an extremely easy way.
Mechanisms of cyst formation in metastatic lymph nodes of head and neck squamous cell carcinoma
Sepideh Mokhtari
Diagnostic Pathology , 2012, DOI: 10.1186/1746-1596-7-6
Abstract: The virtual slide(s) for this article can be found here:http://www.diagnosticpathology.diagnomx.eu/vs/6838476096250792 webcite.Cystic change in metastatic lymph nodes occurs in certain types of tumors and it is an unexplained, site-specific phenomenon that mostly happens in the lymph nodes of head and neck region. It is also found with decreasing frequency in the inguinal, axillary and supraclavicular regions. The reported primary tumors are most commonly squamous cell carcinoma (SCC) and thyroid papillary carcinoma. As well, cystic metastases rarely have been encountered in other tumors such as serous papillary carcinoma of the ovary or endometrium and malignant melanoma [1].In case of a cystic nodal metastasis of SCC, the primary tumor is solid [Figure 1] however metastatic lymph node presents one or multiple cystic structures [Figure 2]. In these cases, 72-90% of primary tumors, when detected, are located in Waldeyer's ring (base of the tongue, palatine tonsils, and nasopharynx) [2,3]. Larynx, hard palate, thyroid gland, salivary glands, sinuses [2,4], lung, uterine cervix [5] and esophagus [6] are the other probable sites but reported cases are rare.Although psuedocystic change is the mechanism of cyst formation in the majority of cases [7], sometimes a true cystic cavity is formed. This occurrence is not well investigated; however, some theories are introduced which form the basis of this article.Here, a thorough review on the literature is provided and the main concepts about mechanisms of cyst formation in metastatic lymph nodes of squamous cell carcinoma are summarized. There are some differences between real cysts and pseudocysts, which are presented in table 1. Primary site and metastatic lymph node are different environments and have different effects on malignant cells; these environmental conditions are also demonstrated in table 2. As well, different genetic content of primary and metastatic tumors is considered and probable associations with cyst form
Adaptation and migration of a population between patches
Sepideh Mirrahimi
Mathematics , 2012, DOI: 10.3934/dcdsb.2013.18.753
Abstract: A Hamilton-Jacobi formulation has been established previously for phenotypically structured population models where the solution concentrates as Dirac masses in the limit of small diffusion. Is it possible to extend this approach to spatial models? Are the limiting solutions still in the form of sums of Dirac masses? Does the presence of several habitats lead to polymorphic situations? We study the stationary solutions of a structured population model, while the population is structured by continuous phenotypical traits and discrete positions in space. The growth term varies from one habitable zone to another, for instance because of a change in the temperature. The individuals can migrate from one zone to another with a constant rate. The mathematical modeling of this problem, considering mutations between phenotypical traits and competitive interaction of individuals within each zone via a single resource, leads to a system of coupled parabolic integro-differential equations. We study the asymptotic behavior of the stationary solutions to this model in the limit of small mutations. The limit, which is a sum of Dirac masses, can be described with the help of an effective Hamiltonian. The presence of migration can modify the dominant traits and lead to polymorphic situations.
SEPTO-OPTICDYSPLASIA WITH AN ANTERIOR ENCEPHALOCELE AND INTACT SEPTUM PELLUCIDUM: A CASE REPORT
Z. Razavi
Iranian Journal of Child Neurology , 2008,
Abstract: ObjectiveThe diagnosis of de Morsier syndrome or septo-optic dysplasia is made on the basis of the diagnosis of optic nerve hypoplasia. Septo-optic dysplasia is defined by a variable combination of dysgenesis of midline brain structures including optic nerve hypoplasia and hypothalamic-pituitary dysfunction often associated with a wide variety of brain malformations of cortical development.The importance of direct ophthalmoscopy of optic nerve abnormalities is stressed, as well as of magnetic resonance imaging, which has become a guideline in the classification of this syndrome This article reports a 19-year-old female with bilateral optic nerve hypoplasia,anterior encephalocele and intact septum pellucidum. She was diagnosed withdiabetes insipidus, short stature and the history of seizure.
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