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Search Results: 1 - 10 of 324 matches for " Abolfazl Firozian "
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Comparison in Effect of Intravenous Alfentanil and Lidocaine on Airway-Circulatory Reflexes during Extubation
Mustafa Sadegi,Abolfazl Firozian,Mohammad Hossein Ghafari,Fatemeh Esfehani
International Journal of Pharmacology , 2008,
Abstract: This randomized controlled double-blind trial was designed to compare the presence of Airway-Circulatory Reflexes to tracheal extubation in groups administering IV alfentanil or lidocaine, in 150 patients undergoing cesarean surgery receiving a standardized anesthetic protocol. At the end of surgery, after return of spontaneous ventilation, patients received either alfentanil 15 μg kg-1 or lidocaine 1.5 mg kg-1. The presence of cough and it`s severity during emergence before extubation was noted. BP and HR were recorded at 2 min after end of surgery (baseline), 2 min after study drug administration and 1 min after extubation. The groups were matched according to age, baseline BP and HR. The incidence of coughing was less frequent in the alfentanil than in the lidocaine group (19% versus 75%, respectively, p<0.001). Although the severity of coughing was considerably different between two groups (lower in alfentanil g) but was not statistically different (p = 0.292). The mean BP and HR were lower in alfentanil than lidocaine group 2 min after administration and 1 min after extubation (p<0.001). The median of delay time (time between the study drug administration and extubation) was 6 min in alfentanil (Range: 4-8) and 5 min in lidocaine groups (Range: 4-8) (p<0.001). These results indicate that alfentanil decreases Airway-Circulatory Reflexes more than lidocaine during emergence from anesthesia without clinically important prolonging the time to extubation.
The Additional Effect of Magnesium Sulfate to Lidocaine in Spinal Anesthesia for Cesarean Section
M.D. Gita Shoeibi,M.D. Mustafa Sadegi,M.D. Abolfazl Firozian,M.D. Farzaneh Tabassomi
International Journal of Pharmacology , 2007,
Abstract: Different additives have been used to prolong spinal anesthesia. We designed a prospective, randomized, double-blind study to evaluate the effect of spinal anesthesia. Eighty patients scheduled for first cesarean surgery were randomly allocated into 2 groups to receive either 1.5 mL lidocaine 5% with 0.5 mL sterile water (control group, n = 40) or 1.5 mL lidocaine 5% with 0.5 mL preservative-free magnesium sulfate 10% (magnesium group, n = 40). Neither epinephrine nor opioid was added to the treatment mixture. The duration of analgesia after spinal anesthesia (the time from local anesthetic injection to the first opioid request) and the duration of analgesia after surgery (the time between termination of the procedure and the time at which the first dose opioid was requested) were compared. The durations of analgesia after spinal anesthesia was significantly longer in the magnesium (160.8±49.1) than in the control group (113.3±27.3) and the durations of analgesia after surgery was significantly longer in the magnesium (74.5±47.5) than in the control group (26.6±25.1), (p = 0.001). There was no associated increase in adverse events in the group receiving intrathecal magnesium.
A Fault-Tolerant Cooperative Spectrum Sensing Algorithm over Cognitive Radio Network Based on Wireless Sensor Network  [PDF]
Mohammad Akbari, Abolfazl Falahati
Wireless Sensor Network (WSN) , 2011, DOI: 10.4236/wsn.2011.33009
Abstract: A serious threat to cognitive radio networks that sense the spectrum in a cooperative manner is the transmission of false spectrum sensing data by malicious sensor nodes. SNR fluctuations due to wireless channel effects complicate handling such attackers even further. This enforces the system to acquire authentication. Actually, the decision maker needs to determine the reliability or trustworthiness of the shared data. In this paper, the evaluation process is considered as an estimation dilemma on a set of evidences obtained through sensor nodes that are coordinated in an underlying wireless sensor network. Then, a likelihood-based computational trust evaluation algorithm is proposed to determine the trustworthiness of each sensor node's data. The proposed procedure just uses the information which is obtained from the sensor nodes without any presumptions about node’s reliability. Numerical results confirm the effectiveness of the algorithm in eliminating malicious nodes or faulty nodes which are not necessarily conscious attackers.
Frequency Hopping Spread Spectrum Security Improvement with Encrypted Spreading Codes in a Partial Band Noise Jamming Environment  [PDF]
Amirhossein Ebrahimzadeh, Abolfazl Falahati
Journal of Information Security (JIS) , 2013, DOI: 10.4236/jis.2013.41001

Frequency Hopping Spread Spectrum (FHSS) system is often deployed to protect wireless communication from jamming or to preclude undesired reception of the signal. Such themes can only be achieved if the jammer or undesired receiver does not have the knowledge of the spreading code. For this reason, unencrypted M-sequences are a deficient choice for the spreading code when a high level of security is required. The primary objective of this paper is to analyze vulnerability of linear feedback shift register (LFSRs) codes. Then, a new method based on encryption algorithm applied over spreading codes, named hidden frequency hopping is proposed to improve the security of FHSS. The proposed encryption security algorithm is highly reliable, and can be applied to all existing data communication systems based on spread spectrum techniques. Since the multi-user detection is an inherent characteristic for FHSS, the multi-user interference must be studied carefully. Hence, a new method called optimum pair “key-input” selection is proposed which reduces interference below the desired constant threshold.

Transmission over Cognitive Radio Channel with Novel Secure LT Code  [PDF]
Elham Hosseini, Abolfazl Falahati
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53023

With the increasing of communication applications in recent years, the demand for radio spectral resources has increased significantly. Cognitive radio scenario was proposed to improve spectrum efficiency in wireless communication systems. In cognitive radio network, it is essential that control information is sent securely and reliably. Ensuring the trustworthiness of the transmitting of spectrum sensing information is important in the CR networks since spectrum sensing directly affects spectrum management and incumbent coexistence. In this paper, the first secondary link channel model is presented, then a secure LT Code is proposed to be compatible with presented channel model and acquires good QoS. As we may know, LT code overcomes packet loss when the channel of the SU is reclaimed by PU. In the new proposed combined encoding and ciphered block, a LT code matrix is used to generate a symmetric cryptographic key. Thus, less complexity observed in the processing computation. Besides, cryptographic key is not sent over the channel. As a result, an attacker has no way to eavesdrop the key unless he is prepared to consider all possible key combinations. This replaced block supplies secure controlling channel and increases spectrum efficiency too.

Developing a 3D-FEM Model for Electromagnetic Analysis of an Axial Flux Permanent Magnet Machine  [PDF]
Seyyed Mehdi Mirimani, Abolfazl Vahedi
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.24032
Abstract: Recently, many optimal designs for axial flux permanent magnet (AFPM) motors were performed based on finite- element (FE) analysis. Most of the models are based on reduction of 3D problem to 2D problem which is not accurate for design aspects. This paper describes an accurate electromagnetic analysis of a surface mounted, 28 pole AFPM with concentrated stator winding. The AFPM is modeled with three-dimensional finite-element method. This model in-cludes all geometrical and physical characteristics of the machine components. Using this accurate modeling makes it possible to obtain demanded signals for a very high precision analysis. Magnetic flux density, back-EMF, magnetic axial force and cogging torque of the motor are simulated using FLUX-3D V10.3.2. Meanwhile, the model is paramet-ric and can be used for design process and sensitivity analysis.
Radar Signal Recognition by CWD Picture Features  [PDF]
Erfan Tahbaz Tavakoli, Abolfazl Falahati
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2012, DOI: 10.4236/ijcns.2012.54031
Abstract: In this paper a system for automatic recognition of radar waveform is introduced. This technique is used in many spectrum management, surveillance, and cognitive radio and radar applications. For instance the transmitted radar signal is coded into six codes based on pulse compression waveform such as linear frequency modulation (LFM), Frank code, P1, P2, P3 and P4 codes, the latter four are poly phase codes. The classification system is based on drawing Choi Willliams Distribution (CWD) picture and extracting features from it. In this study, various new types of features are extracted from CWD picture and then a pattern recognition method is used to recognize the spectrum. In fact, signals from CWD picture are defined using biometric techniques. We also employ false reject rate (FRR) and false accept rate (FAR) which are two types of fault measurement criteria that are deploy in biometric papers. Fairly good results are obtained for recognition of Signal to Noise Ratio (-11 dB).
Employing Power Allocation to Enhance Zero Forcing Scheme Advantages over Multi-Antenna Multiple Relay Networks  [PDF]
Abolfazl Falahati, Y. Attar Izi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2012, DOI: 10.4236/ijcns.2012.511077
Abstract: A multi-antenna multiple relay (MAMR) network is considered and a variation of two-hop zero-forcing amplify-forward relaying method is proposed. Deploying ZF method together with application of diagonal power allocation matrices at the relays, it is shown that the overall MAMR network is simplified to M independent single antenna multiple relay (SAMR) networks, where M is the number of source and destination antennas. This enables to incorporate network beamforming proposed for SAMR networks. Accordingly, using the BER as the performance metric, we present simulation results to show the proposed approach outperforms the common ZF method addressed in the literature.
Investigating the Relationship between Porosity and Permeability Coefficient for Pervious Concrete Pavement by Statistical Modelling  [PDF]
Hassan Tajik Ghashghaei, Abolfazl Hassani
Materials Sciences and Applications (MSA) , 2016, DOI: 10.4236/msa.2016.72010
Abstract: A study evaluating the relationship between porosity and permeability coefficient for pervious concrete (PC) is presented. In addition, the effect of mixture design parameters particularly, water-to-cement ratio (W/C) and size of aggregate on the permeability coefficient of PC was investigated. The PC mixtures were made with 4 range of W/C and 2 range size of aggregate. PC mixes were made from each aggregate and were tested. The results showed that the W/C and aggregate size are key parameters which significantly affect the characteristic performance of PC. Permeability coefficient of coarse pervious concrete (CPC) is bigger than fine pervious concrete (FPC) and the porosity of CPC are bigger than porosity of FPC. A regression model (RM) along with analysis of variance (ANOVA) was conducted to study the significance of porosity distribution on permeability coefficient of PC. The statistical model developed in this study can facilitate prediction permeability coefficient of CPC and FPC as the sustainable pavements.
Effect of Molecular Weight and Molar Ratio of Dextran on Self-Assembly of Dextran Stearate Polymeric Micelles as Nanocarriers for Etoposide
Jaleh Varshosaz,Farshid Hassanzadeh,Hojjat Sadeghi,Farzin Firozian,Mina Mirian
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/265657
Abstract: Amphiphilic polymer surfactants are composed of hydrophilic and hydrophobic polymers and are widely used in targeted drug delivery. The purpose of this study was the evaluation of the effect of molecular weight and molar ratio of dextran on physicochemical properties of dextran stearate polymeric micelles. Dextran stearate was synthesized by acylation of dextran with stearoyl chloride. Etoposide loaded polymeric micelles were prepared by dialysis method. The resulting micelles were evaluated for particle size, zeta potential, critical micelle concentration (CMC), drug loading capacity, and release efficiency. Cytotoxicity and cellular uptake of micelles were studied in CT-26 colorectal carcinoma cell line. Molecular weight and molar ratio of dextran-stearate were impressive on zeta potential, CMC, drug loading capacity, and release efficiency. Unlike polymer molecular weight, molar ratio of stearate had a significant effect on cytotoxicity and particle size of etoposide loaded micelles. Although molecular weight of dextran had no significant effect on cytotoxicity of micelles on CT-26 cells, it had drastic attributes for stability of polymeric micelles. Consequently, both variables of molecular weight of dextran and molar ratio of stearate should be taken into account to have a stable and effective micelle of dextran-stearate. 1. Introduction Polymeric micelles are self-assembling nanocarriers which are composed of two block copolymers. There are increasing interests in their use as drug carriers due to their stability and ease of preparation. They can solubilize, stabilize, and target pharmaceutical active ingredients and diagnostic materials [1, 2]. One of the most interesting areas of application of polymeric micelles is drug delivery to cancerous tumors. Many of chemotropic agents have low solubility and stability in blood or even during their storage time before administration. Most of them have severe adverse effects because of their distribution in other compartments of body than its target organ [2, 3]. When nanoparticles are administered via intravenous route and come into the tumors, they can pass across the fenestrated wall of the tumor capillaries, while they cannot pass away in normal tissues. This phenomenon is called enhanced permeation and retention (EPR) effect which allows passive targeting of pharmaceutical active ingredients to the tumors due to pathological abnormalities in the tumor vasculature [4, 5]. Interendothelial gap defects increase vascular permeability in tumors, allowing extravasation of nanoparticles up to 400?nm [6].
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