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Search Results: 1 - 10 of 144569 matches for " Vakili F. "
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Evaluation of periodontal condition of menopause women with osteoporosis and osteopenia and comparison with control group
Khorsand A.,Paknejad M.,Vakili F.
Journal of Dental Medicine , 2006,
Abstract: Background and Aim: Several risk factors directly affect the development of periodontal diseases. Also some systemic diseases act indirectly as predisposing and aggrevating factors. Osteoporosis is one of these factors and one of its main causes is lack of physical activity in postmenopause period. The incidence of osteoporosis is increasing in our country. The goal of this study was to evaluate the periodontal condition of women with osteoporosis and osteopenia referred to bone densitometric division of Loghman hospital in 2003 and compare to control group. Materials and Methods: In this case control study based on BMD (Bone Mineral Density) measurement of back and thigh using DEXA method, 60 patients referred to bone densitometric division of Loghman hospital, were randomly selected. Cases were divided into three groups, 20 with osteoporosis, 20 with osteopenia and 20 normal cases. Periodontal indices consisting of plaque index (PI), tooth loss (TL), gingival recession (GR), probing pocket depth (PPD) and papilla bleeding index (PBI) were evaluated by clinical and radiographic examination. Data were analyzed by Kruskall Wallis and Dunn tests with p<0.05 as the limit of significance. Results: PBI, PI and TL were significantly higher in osteoporotic group than osteopenic and normal group. PPD was not different in the three groups. Due to the low prevalence of recession in our study, this parameter was not included in the statistical analysis. Conclusion: It seems that osteoporosis does not increase the incidence of periodontal diseases because it affects bone quality rather than quantity. In osteoporosis calcium deficiency and increasing age lead to decreased physical activity and ultimately affect the patient's oral hygiene performance. Thus, periodontal manifestations are presented as gingival bleeding and gingivitis.
Dark Energy From Fifth Dimensional Brans-Dicke Theory
Amir F. Bahrehbakhsh,Mehrdad Farhoudi,Hajar Vakili
Physics , 2013, DOI: 10.1142/S0218271813500703
Abstract: Following the approach of the induced-matter theory, we investigate the cosmological implications of a five-dimensional Brans-Dicke theory, and propose to explain the acceleration of the universe. After inducing in a four-dimensional hypersurface, we classify the energy-momentum tensor into two parts in a way that, one part represents all kind of the matter (the baryonic and dark) and the other one contains every extra terms emerging from the scale factor of the fifth dimension and the scalar field, which we consider as the energy-momentum tensor of dark energy. We also separate the energy-momentum conservation equation into two conservation equations, one for matter and the other for dark energy. We perform this procedure for different cases, without interacting term and with two particular (suitable) interacting terms between the two parts. By assuming the parameter of the state equation for dark energy to be constant, the equations of the model admit the power-law solutions. Though, the non-interacting case does not give any accelerated universe, but the interacting cases give both decelerated and accelerated universes. For the interacting cases, we figure out analytically the acceptable ranges of some parameters of the model, and also investigate the data analysis to test the model parameter values consistency with the observational data of the distance modulus of 580 SNe Ia compiled in Union2.1. For one of these interacting cases, the best fitted values suggest that the Brans-Dicke coupling constant ({\omega}) is -7.75, however, it also gives the state parameter of dark energy (wX) equal to -0.67. In addition, the model gives the Hubble and deceleration parameters at the present time to be H0 = 69.4 (km/s)/Mpc and q0 = -0.38 (within their confidence intervals), where the scale factor of the fifth dimension shrinks with the time.
A Control Variate Approach for Improving Efficiency of Ensemble Monte Carlo
T. Borogovac,F. J. Alexander,P. Vakili
Computer Science , 2008,
Abstract: In this paper we present a new approach to control variates for improving computational efficiency of Ensemble Monte Carlo. We present the approach using simulation of paths of a time-dependent nonlinear stochastic equation. The core idea is to extract information at one or more nominal model parameters and use this information to gain estimation efficiency at neighboring parameters. This idea is the basis of a general strategy, called DataBase Monte Carlo (DBMC), for improving efficiency of Monte Carlo. In this paper we describe how this strategy can be implemented using the variance reduction technique of Control Variates (CV). We show that, once an initial setup cost for extracting information is incurred, this approach can lead to significant gains in computational efficiency. The initial setup cost is justified in projects that require a large number of estimations or in those that are to be performed under real-time constraints.
Assessment of antibody titers and immunity to Hepatitis B in children receiving chemotherapy
Shams Shahemabadi A,Salehi F,Hashemi A,Vakili M
Iranian Journal of Pediatric Hematology Oncology , 2012,
Abstract: BackgroundThere is a decrease in vaccine-specific antibody to certain vaccine-preventable diseases inchildren after chemotherapy, but the frequency of non-immune patients is not clear. In thepresent case-control study, was taken under investigation protection level to Hepatitis B infectionin children 6 months after completing chemotherapy.Materials and MethodsIn this study 68 patients with cancer and 68 healthy children were enrolled. Patients were 1.5 -12 years old with completed standard chemotherapy at least for 6 months. All the patients andhealthy children were negative for HBsAg and HBeAg and had received Hepatitis B vaccination.IgG antibody concentrations against Hepatitis B Virus (HBV) were determined in the patientsreceiving chemotrapy and healthy subjects serum by ELISA method. IgG antibody titer > 10mIU/ml was considered as baseline protective titer for preventing HBV infection.ResultsAnti-HBs antibody titer in 19.12% of patients was less than 10 mIU/ml and 11.76% of thepatients had borderline antibody titer (10-20 mIU/ml). In healthy subjects, 2.94% and 5.88% hadantibody titer < 10 mIU/ml and 10-20 mIU/ml, respectively. According to statistical analysis,frequency of non immune subjects in children with cancer was significantly higher than those inhealthy children (P-value=0.024).ConclusionHBV vaccination post-intensive chemotherapy in the children with cancer is stronglyrecommended.
Finite Element Analysis of Thickness Effect on the Residual Stress in Butt-Welded 2.25Cr1Mo Steel Plates
F. Vakili-Tahami,A.H.D. Sorkhabi
Journal of Applied Sciences , 2009,
Abstract: In this study, a numerical method is presented to study the thickness effect on the residual stress states in butt-welds in 2.25Cr1Mo plates. Using finite element based software ANSYS, coupled thermal-mechanical three dimensional (3D) finite element models have been developed. The finite element models are employed to evaluate the transient temperature and the residual stress fields during welding. Also, in this study the variations of the physical and mechanical properties of the material with temperature have been taken into account. Results show that by increasing plate thickness, the residual stresses increase and the residual stress affected zone (distance with significant amount of residual stress) becomes larger. It has been shown that the longitudinal residual stress in weld axis, change from compressive to tensile stress by increasing plate thickness.
The Effect of Ramadan Fasting on Hemoglobin, Hematocrit and Blood Biochemical Parameters
GhR Farshidfar,H Yousfi,M Vakili,F Asadi Noughabi
Journal of Research in Health Sciences , 2011,
Abstract: Background: Physicians in Islamic countries believe that fasting in Ramadan is equal to ingestion of thirty pills regularly ingested every year for clearing the blood and fortifying the tissues. The effects of Islamic fasting on physiologic functions in normal conditions have been considered in different studies and different topics. This study was to determine the quantitative changes of hemoglobin, hematocrit and certain serum biochemical parameters during Ramadan fasting in apparently healthy Muslim college students. Methods: Sixty-two students were followed in five stages: one week before, 3rd, 15th and 28th day of Ramadan and ten days after Ramadan, by proper blood sampling in suitable time of day. Results: The findings showed a significant decrease in hemoglobin, glucose and uric acid on days 3 and 15 of Ramadan (P< 05), a significant decrease in low-density lipoprotein cholesterol and glucose on day 28 of Ramadan and a significant increase in blood urea nitrogen and high a€“density lipoprotein cholesterol on day 28 of Ramadan (P< 05) Conclusion: Changes in biochemical and hematological parameters of blood during Ramadan fasting are very important and the Islamic countries physicians should be informed about these beneficial effects of fasting. It seems that more researches are required for evaluating these effects in various physiologic and pathologic conditions and there are yet many unanswered questions in this
Stabilization of test particles in Induced Matter Kaluza-Klein theory
S. Jalalzadeh,B. Vakili,F. Ahmadi,H. R. Sepangi
Physics , 2006, DOI: 10.1088/0264-9381/23/20/021
Abstract: The stability conditions for the motion of classical test particles in an $% n $-dimensional Induced Matter Kaluza-Klein theory is studied. We show that stabilization requires a variance of the strong energy condition for the induced matter to hold and that it is related to the hierarchy problem. Stabilization of test particles in a FRW universe is also discussed.
An Efficient Routing Tree Algorithm for Combined Uplink and Downlink Subframes on Centralized Scheduling in IEEE 802.16 Based Wireless Mesh Networks  [PDF]
Ali Behfarnia, Vahid Tabataba Vakili
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2011, DOI: 10.4236/ijcns.2011.44026
Abstract: IEEE 802.16 mesh mode defines routing tree for transmitting data in centralized scheduling but it does not define any explicit proposal for combining uplink and downlink subframes. Deploying combined uplink and downlink subframes on the centralized scheduling scheme can be more flexible and utilization is improved. However, existing interferences among the transmission of neighboring nodes lead to performance reduction of the network. In this paper, an efficient routing tree algorithm is proposed with combined uplink and downlink slot allocation on the centralized scheduling scheme which can abate interferences in the network. This algorithm allows more subscriber stations to transmit concurrently and so improves spatial reuse in the network. Also, the algorithm uses multi-channel and single channel systems and considers relay model, smoothing switching frequently between transmitting and receiving in successive time slots and fairness in the network. Extensive simulation results demonstrate the effectiveness of the proposed method in terms of scheduling length, link concurrency ratio, network throughput and Channel Utilization Ratio (CUR).
Weighted Sum Rate Maximization in OFDM Based Cooperative Cognitive Radios: A Joint Optimization Approach  [PDF]
Pedram Johari, Vahid Tabataba Vakili
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2012, DOI: 10.4236/ijcns.2012.55035
Abstract: Improving utilization of the radio spectrum is the main goal of Cognitive Radio Networks (CRN). Recent studies made use of cooperative relay technology in cognitive networks, to increase transmission diversity gain. In this paper we consider an OFDM based cooperative cognitive network with a pair of Source-Destination nodes as the primary user (PU), and a pair of Source-Destination nodes—which is assisted with a relay—as the secondary (cognitive) user (SU). Both primary and secondary users share a same spectrum. In a two hop transmission, the source transmits in the first hop, and the half-duplex relay decodes the message, re-encodes and forwards it to the destination in the second hop on a different subcarrier. The cognitive network obeys an underlay paradigm where the SU is allowed to transmit simultaneously with PU, while its power is limited such that the interference caused for PU does not exceed a defined temperature. Under this constraint, a joint subcarrier pairing and power allocation is proposed for SU to maximize its weighted sum rate. The problem is transformed to a convex optimization problem and solved in the dual domain. Then an algorithm to achieve feasible solutions is used based on the optimization results. Through extensive simulations, we compare the spectrum utilization of the proposed approach with the existing ones, and show that interestingly the proposed method improves the weighted sum rate of SU.
A New Method for Sensing Cognitive Radio Network under Malicious Attacker  [PDF]
Shaahin Tabatabaee, Vahid Tabataba Vakili
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2013, DOI: 10.4236/ijcns.2013.61007
Abstract:

Cognitive radio has been designed for solving the problem of spectrum scarcity by using the spectrum of primary users who don’t use their spectrum on that time. For sensing the spectrum, collaborative spectrum sensing has been utilized because of robustness. In this paper, a new collaborative spectrum method is proposed based on Least Mean Square (LMS) algorithm. In this scheme, the weights of secondary users were updated in time and finally the sensing results were combined in the fusion center based on their trusted weights. Simulation results show that the proposed scheme can significantly reduce the effects of Spectrum Sensing Data Falsification (SSDF) attackers, when they are smart malicious, and even percentage of malicious users are more than trusted users.

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