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Search Results: 1 - 10 of 238 matches for " Poulin Shohreh "
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A survey on ectoparasite fauna of cold water fish farms in Mazandaran Province, Iran
Sara Mehdizadeh Mood,Poulin Shohreh,Javad Sahandi
Human & Veterinary Medicine , 2011,
Abstract: the important areas of this industry in Iran. The present study was carried out to survey onectoparasite fauna of cold water fish farms in Mazandaran Province (Iran) during a period of 12 months.For this aim 500 samples were obtained from 50 fish farms and after arriving to laboratory the parasiteexamination started immediately. From the total of 500 specimens, 182 fish (36.4%) were infected withectoparasites. Through the parasitic examinations five species of parasites were detected, namely:Ichthyophthirius multifillis, Trichodina sp., Chilodonella sp., Gyrodactylus sp. and Dactylogyrus sp. Theresults showed that, from total percentage (36.4%) of detection, 31.4% of detected parasites wereprotozoan (16.4% Ichthyophthirius multifillis, 14% Trichodina sp., and 1% Chilodonella sp.) and 5% weremonogenean trematodes (3% Dactylogyrus sp. and 2% Gyrodactylus sp.). The highest prevalence ofparasites in our study belonged to the Ichthyophthirius multifiliis causative agent of White Spot Disease.
Shohreh Monshizadeh
International Journal of Advances in Engineering and Technology , 2013,
Abstract: GIS substation due to its wide range of functions in power system due to its high reliability and easier maintenance are considered in the distribution network. For this Purpose in this paper the GIS 132KV substation model is studied[1]. In GIS 132KV with opening and closing the disconnect switch, the VFTO fast transient overvoltage with few nanoseconds forehead time is occurred[7]. This waves is released during the phase conductors and its caused tension in insulators and electrical equipment such as transformers. Transient electromagnetic field has been created, by these waves penetrates to environment by holes between GIS compartments and causes the effect on the electrical equipment and cables. These overvoltages have range about a few hundred MHz frequencies. In this substation the compartments transient voltage and its maximum amplitude at different points for different switching performance is calculated [2]. In this paper the simulations have been conducted with the EMTP software and simulation results are presented.
On the Evolution of Binary Neutron Stars
Shohreh Abdolrahimi
Physics , 2009,
Abstract: In this paper we investigate the evolution of binary neutron stars, namely, their magnetic field, spin, and orbital evolution. The core of a neutron star is considered to be a superfluid, superconductor type II. Flux expulsion of the magnetic field out of the core of a single neutron star has been discussed by previous authors. However, the evolution of the core magnetic field is substantially different for a binary neutron star. While for a single neutron star the fluxoids of the proton superconductor always move outward through the core, in a binary neutron star in the accretion phase fluxoids move back into the core. The subsequent increase of the core magnetic field results in the increase of the surface magnetic field. We ask weather within the framework of this model the formation of millisecond pulsars (MSPs) is possible. We show that despite the increase of the core magnetic field, MSPs are formed in this model. The evolution of the neutron star with various orbital periods, magnetic fields, spin periods, and other parameters are numerically investigated. The equation of state of the neutron star, initial orbital period of the binary, and other parameters of the binary have substantial effects on the evolution of period vs. magnetic field.
Velocity Effects on an Accelerated Unruh-DeWitt Detector
Shohreh Abdolrahimi
Physics , 2013, DOI: 10.1088/0264-9381/31/13/135009
Abstract: We analyze the response of an Unruh-DeWitt detector moving along an unbounded spatial trajectory in a two-dimensional spatial plane with constant independent magnitudes of both the four-acceleration and of a timelike proper time derivative of the four-accelration. In a Fermi-Walker frame moving with the detector, the direction of the acceleration rotates at a constant rate around a great circle. This is the motion of a charge in a uniform electric field when in the frame of the charge there is both an electric and a magnetic field. We compare the response of this detector to a detector moving with constant velocity in a thermal bath of the corresponding temperature for non-relativistic velocities, and in two regimes: ultraviolet and infrared. In infrared regime, the detector in the Minkowski space-time moving along the spatially two-dimensional trajectory should move with a higher speed to keep up with the same excitation rate of the inertial detector in a thermal bath. In ultraviolet regime, the dominant modification in the response of this detector compared to the black body spectrum of Unruh radiation is the same as the dominant modification perceived by a detector moving with constant velocity in a thermal bath.
Reporting on first sexual experience: The importance of interviewer-respondent interaction
Michelle Poulin
Demographic Research , 2010,
Abstract: Survey methodologists typically seek to improve data on sensitive topics by standardizing surveys and avoiding the use of human interviewers. This study uses data collected from 90 never-married young adults in rural Malawi to compare reports on first sexual encounters between a standard survey and an in-depth interview. A significant fraction of young women who claimed in the survey to have never been sexually active affirmed sexual experience during the in-depth interview, fielded shortly thereafter. Two elements of the in-depth interview, flexibility and reciprocal exchange, foster trust and more truthful reporting. The findings contradict the long-standing presumption that face-to-face interviews are inherently threatening when the topic is sex.
Lieb-Robinson Bound and Locality for General Markovian Quantum Dynamics
David Poulin
Physics , 2010, DOI: 10.1103/PhysRevLett.104.190401
Abstract: The Lieb-Robinson bound shows the existence of a maximum speed of signal propagation in discrete quantum mechanical systems with local interactions. This generalizes the concept of relativistic causality beyond field theory, and provides a powerful tool in theoretical condensed matter physics and quantum information science. Here, we extend the scope of this seminal result by considering general Markovian quantum evolution, where we prove that an equivalent bound holds. In addition, we use the generalized bound to demonstrate that correlations in the stationary state of a Markov process decay on a length-scale set by the Lieb-Robinson velocity and the system's relaxation time.
Macroscopic Observables
David Poulin
Physics , 2004, DOI: 10.1103/PhysRevA.71.022102
Abstract: We study macroscopic observables defined as the total value of a physical quantity over a collection of quantum systems. We show that previous results obtained for infinite ensemble of identically prepared systems lead to incorrect conclusions for finite ensembles. In particular, exact measurement of a macroscopic observable significantly disturbs the state of any finite ensemble. However, we show how this disturbance can be made arbitrarily small when the measurement are of finite accuracy. We demonstrate a tradeoff between state disturbance and measurement coarseness as a function of the size of the ensemble. Using this tradeoff, we show that the histories generated by any sequence of finite accuracy macroscopic measurements always generate a consistent family in the absence of large scale entanglement, for sufficiently large ensembles. Hence, macroscopic observables behave "classically" provided that their accuracy is coarser than the quantum correlation length-scale of the system. The role of these observable is also discussed in the context of NMR quantum information processing and bulk ensemble quantum state tomography.
Optimal and Efficient Decoding of Concatenated Quantum Block Codes
David Poulin
Physics , 2006, DOI: 10.1103/PhysRevA.74.052333
Abstract: We consider the problem of optimally decoding a quantum error correction code -- that is to find the optimal recovery procedure given the outcomes of partial "check" measurements on the system. In general, this problem is NP-hard. However, we demonstrate that for concatenated block codes, the optimal decoding can be efficiently computed using a message passing algorithm. We compare the performance of the message passing algorithm to that of the widespread blockwise hard decoding technique. Our Monte Carlo results using the 5 qubit and Steane's code on a depolarizing channel demonstrate significant advantages of the message passing algorithms in two respects. 1) Optimal decoding increases by as much as 94% the error threshold below which the error correction procedure can be used to reliably send information over a noisy channel. 2) For noise levels below these thresholds, the probability of error after optimal decoding is suppressed at a significantly higher rate, leading to a substantial reduction of the error correction overhead.
Stabilizer Formalism for Operator Quantum Error Correction
David Poulin
Physics , 2005, DOI: 10.1103/PhysRevLett.95.230504
Abstract: Operator quantum error correction is a recently developed theory that provides a generalized framework for active error correction and passive error avoiding schemes. In this paper, we describe these codes in the stabilizer formalism of standard quantum error correction theory. This is achieved by adding a "gauge" group to the standard stabilizer definition of a code that defines an equivalence class between encoded states. Gauge transformations leave the encoded information unchanged; their effect is absorbed by virtual gauge qubits that do not carry useful information. We illustrate the construction by identifying a gauge symmetry in Shor's 9-qubit code that allows us to remove 4 of its 8 stabilizer generators, leading to a simpler decoding procedure and a wider class of logical operations without affecting its essential properties. This opens the path to possible improvements of the error threshold of fault-tolerant quantum computing.
Toy Model for a Relational Formulation of Quantum Theory
David Poulin
Physics , 2005, DOI: 10.1007/s10773-006-9052-0
Abstract: In the absence of an external frame of reference physical degrees of freedom must describe relations between systems. Using a simple model, we investigate how such a relational quantum theory naturally arises by promoting reference systems to the status of dynamical entities. Our goal is to demonstrate using elementary quantum theory how any quantum mechanical experiment admits a purely relational description at a fundamental level, from which the original "non-relational" theory emerges in a semi-classical limit. According to this thesis, the non-relational theory is therefore an approximation of the fundamental relational theory. We propose four simple rules that can be used to translate an "orthodox" quantum mechanical description into a relational description, independent of an external spacial reference frame or clock. The techniques used to construct these relational theories are motivated by a Bayesian approach to quantum mechanics, and rely on the noiseless subsystem method of quantum information science used to protect quantum states against undesired noise. The relational theory naturally predicts a fundamental decoherence mechanism, so an arrow of time emerges from a time-symmetric theory. Moreover, there is no need for a "collapse of the wave packet" in our model: the probability interpretation is only applied to diagonal density operators. Finally, the physical states of the relational theory can be described in terms of "spin networks" introduced by Penrose as a combinatorial description of geometry, and widely studied in the loop formulation of quantum gravity. Thus, our simple bottom-up approach (starting from the semi-classical limit to derive the fully relational quantum theory) may offer interesting insights on the low energy limit of quantum gravity.
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