Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 1 )

2019 ( 183 )

2018 ( 250 )

2017 ( 272 )

Custom range...

Search Results: 1 - 10 of 190865 matches for " Plamen G. Petrov "
All listed articles are free for downloading (OA Articles)
Page 1 /190865
Display every page Item
Compensation of eddy-current-induced magnetic field transients in a MOT
Carlos L. Garrido Alzar,Plamen G. Petrov,Daniel Oblak,Joerg H. Mueller,Eugene S. Polzik
Physics , 2007,
Abstract: The design and implementation of a current driver for the quadrupole coil of a magneto-optical trap are presented. The control and the power stages of the driver, both based on a push-pull configuration with high-speed transistors, are separated, allowing for a protection of the control electronics. Moreover, the coil current can be set by an analog voltage, a feature that makes possible both fast and adiabatic switching of the quadrupole magnetic field. In order to compensate magnetic field transients induced by eddy currents, the driver allows a quick reversal of the quadrupole coil current providing in such a way the required magnetic flux compensation. From a fit to the measured magnetic field transients, we have extracted the decay constants which confirm the efficiency of the compensation. Furthermore, we measured the influence of eddy currents on a sample of cold caesium atoms, testing at the same time the ultimate performance of the driver for our applications. The results show that the implemented electronic circuit is able to reduce substantially the transient effects with switching times of the magnetic field below 100 microseconds.
Non-destructive interferometric characterization of an optical dipole trap
Plamen G. Petrov,Daniel Oblak,Carlos L. Garrido Alzar,Niels Kjaergaard,Eugene S. Polzik
Physics , 2006, DOI: 10.1103/PhysRevA.75.033803
Abstract: A method for non-destructive characterization of a dipole trapped atomic sample is presented. It relies on a measurement of the phase-shift imposed by cold atoms on an optical pulse that propagates through a free space Mach-Zehnder interferometer. Using this technique we are able to determine, with very good accuracy, relevant trap parameters such as the atomic sample temperature, trap oscillation frequencies and loss rates. Another important feature is that our method is faster than conventional absorption or fluorescence techniques, allowing the combination of high-dynamical range measurements and a reduced number of spontaneous emission events per atom.
Quantum noise limited interferometric measurement of atomic noise: towards spin squeezing on the Cs clock transition
Daniel Oblak,Jens K. Mikkelsen,Wolfgang Tittel,Anton K. Vershovski,Jens L. Sorensen,Plamen G. Petrov,Carlos L. Garrido Alzar,Eugene S. Polzik
Physics , 2003,
Abstract: We investigate theoretically and experimentally a nondestructive interferometric measurement of the state population of an ensemble of laser cooled and trapped atoms. This study is a step towards generation of (pseudo-) spin squeezing of cold atoms targeted at the improvement of the Caesium clock performance beyond the limit set by the quantum projection noise of atoms. We calculate the phase shift and the quantum noise of a near resonant optical probe pulse propagating through a cloud of cold 133Cs atoms. We analyze the figure of merit for a quantum non-demolition (QND) measurement of the collective pseudo-spin and show that it can be expressed simply as a product of the ensemble optical density and the pulse integrated rate of the spontaneous emission caused by the off-resonant probe light. Based on this, we propose a protocol for the sequence of operations required to generate and utilize spin squeezing for the improved atomic clock performance via a QND measurement on the probe light. In the experimental part we demonstrate that the interferometric measurement of the atomic population can reach the sensitivity of the order of N_at^1/2 in a cloud of N_at cold atoms, which is an important benchmark towards the experimental realisation of the theoretically analyzed protocol.
Interaction between atoms and slow light: a waveguide-design study
Xiaorun Zang,Jianji Yang,Rémi Faggiani,Christopher Gill,Plamen G. Petrov,Jean-Paul Hugonin,Kevin Vynck,Simon Bernon,Philippe Bouyer,Vincent Boyer,Philippe Lalanne
Physics , 2015,
Abstract: The emerging field of on-chip integration of nanophotonic devices and cold atoms offers extremely-strong and pure light-matter interaction schemes, which may have profound impact on quantum information science. In this context, a long-standing obstacle is to achieve strong interaction between single atoms and single photons, while at the same time trap atoms in vacuum at large separation distances from dielectric surfaces. In this work, we study new waveguide geometries that challenge these conflicting objectives. The designed photonic crystal waveguide is expected to offer a good compromise, which additionally allows for easy manipulation of atomic clouds around the structure, while being tolerant to fabrication imperfections.
Allozyme genetic polymorphism in Bulgarian honey bee (Apis mellifera L.) populations from the south-eastern part of the Rhodopes
Journal of BioScience and Biotechnology , 2012,
Abstract: Allozyme genetic polymorphism in Bulgarian honey bee populations from four different locations in the south-eastern part of the Rhodopes Mountain was studied on six enzymic systems (MDH, ME, EST, ALP, PGM and HK) corresponding to six genetic loci. Allozyme analysis revealed that all studied loci were polymorphic in almost all investigated populations. The observed heterozygosity was found to range from 0.110 to 0.208 and Nei's genetic distance – between 0.016 and 0.061 among the studied populations. These honey bee populations were clustered in two groups in the UPGMA dendrogram. The Tihomir population was in a separate clade while other three populations (Kardzhali, Krumovgrad and Dolni Yurutci) were grouped together.
M?ssbauer, XRD, and Complex Thermal Analysis of the Hydration of Cement with Fly Ash
Vili Lilkov,Ognyan Petrov,Yana Tzvetanova,Plamen Savov,Milen Kadiyski
Journal of Spectroscopy , 2013, DOI: 10.1155/2013/231843
Abstract: Hydration of cement with and without fly ash is studied with M?ssbauer spectroscopy, XRD, and thermal analysis. Iron in cement is present as Fe3+-ions and occupies two octahedral positions, with close isomer shifts and quadrupole splittings. Iron in fly ash is present as Fe2+ and Fe3+, and the M?ssbauer spectra display three doublets—two for Fe3+ in octahedral coordination and one for Fe2+. A third doublet was registered in the hydrating plain cement pastes after the 5th day, due to Fe3+ in tetrahedral coordination in the structure of the newly formed monosulphate aluminate. In cement pastes with fly ash, the doublet of tetrahedral iron is formed earlier because the quantity of ettringite and portlandite is low and more monosulphate crystallizes. No Fe(OH)3 phase forms during hydration of C4AF. The fly ash displays pozzolanic properties, which lead to lowering of the portlandite quantity in the cement mixtures and increasing of the high temperature products. 1. Introduction Tricalcium aluminate (C3A) and tetracalcium alumoferrite (C4AF) are main clinker phases in cement. The hydration of C3A proceeds quickly, and during reaction with gypsum, ettringite is formed and at later stages, monosulphate occurs accompanied by monocarbonate and aluminates with different composition. The hydration of C4AF proceeds slower, but finally, there are formed hydrate products with composition similar to the products of the C3A hydration. In the presence of lime and gypsum, AFt phase is the main product of reaction, but the progress of hydration of C4AF is slowed down due to the formation of AFt layer at the surface of C4AF-grains. In a subsequent step, the AFt phase converts to AFm, prior to complete consumption of calcium sulphate [1]. The distinction between iron-free and iron-containing analogues is difficult to be found by use of the widely used methods for the study of cement because the structural differences between these phases are negligible [2]. M?ssbauer spectroscopy is a suitable method for the study of iron distribution in cement as well as its behaviour during the hydration process, because this approach allows to study directly the character of the bonding, the phase state, and the electronic environments of the iron ions [3, 4]. Eissa et al. [5, 6], Afifi et al. [7], and Pascual et al. [8] have proved that iron in C4AF is bivalent (Fe2+) and trivalent (Fe3+) with the latter being in tetrahedral (T) and octahedral (O) coordination. The authors have found that iron atoms are weakly bonded in strongly deformed crystal lattice, while Ekimov et al. [9] derived
Neutron star properties and the equation of state of neutron-rich matter
Plamen G. Krastev,Francesca Sammarruca
Physics , 2006, DOI: 10.1103/PhysRevC.74.025808
Abstract: We calculate total masses and radii of neutron stars (NS) for pure neutron matter and nuclear matter in beta-equilibrium. We apply a relativistic nuclear matter equation of state (EOS) derived from Dirac-Brueckner-Hartree-Fock (DBHF) calculations. We use realistic nucleon-nucleon (NN) interactions defined in the framework of the meson exchange potential models. Our results are compared with other theoretical predictions and recent observational data. Suggestions for further study are discussed.
Esthesioneuroblastoma, Thyroid Gland Carcinoma and Gastrointestinal Stromal Carcinoma  [PDF]
Plamen Nedev
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2015, DOI: 10.4236/ijohns.2015.43034
Abstract: Olfactory neuroblastoma (esthesioneuroblastoma, ЕNB) is a rare tumor arising from the olfactory neuroepithelium. We report a case of ЕNB located in inferior nasal concha, combined with thyroid gland carcinoma and gastrointestinal stromal carcinoma in a 77-year-old man. The tumor was resected endonasally. When the final diagnosis of olfactory neuroblastoma was confirmed by histopathologic examination and immunohistochemical staining, the PET/CT examination was performed. The imaging revealed a small focus of a moderately increased cancer activity in the thyroid region. A gastrointestinal stromal carcinoma was detected one year after the resection of the thyroid gland. We discuss the clinical appearance of ENB, staging systems, diagnosis and management. During the endonasal surgery, ENB was removed entirely. Seven days after operation, in order to monitor the postoperative result, PET/CT was performed and a papillary thyroid cancer was detected. One year after the thyroid surgery, gastroendoscopy showed a neoplastic formation in the stomach. In conclusion, we state that when identified as aggressive tumors such as ENB, it is necessary to provide regular examinations in order to detect distant ENB metastases or other neoplastic localisations.
Design Intranet-Systems Using UML. Pre-Stage
Mihyail G. Petrov
European Researcher , 2012,
Abstract: The article deals with the possibility and examples of UML diagrams in the predesign phase of the study.
The first fossil cyphophthalmid harvestman from Baltic amber
Dunlop, Jason A.,Mitov, Plamen G.
Arachnologische Mitteilungen , 2011, DOI: 10.5431/aramit4006
Abstract: The first fossil cyphophthalmid harvestman (Opiliones: Cyphophthalmi) from Palaeogene (Eocene) Baltic amber is described. This is only the third fossil example of this basal harvestman lineage; the others being from the probably slightly younger Bitterfeld amber and the much older, early Cretaceous, Myanmar (Burmese) amber. Although incomplete and lacking most of the appendages, the new Baltic amber fossil can be identified as a female. The somatic characters preserved, especially spiracle morphology and the coxo-genital region, allow it to be assigned with some confidence to the extant genus Siro Latreille, 1796 (Sironidae). This fossil is formally described here as Siro balticus sp. nov. It resembles modern North American Siro species more than modern European ones, and can be distinguished principally on its relatively large size and the outline form of the body.
Page 1 /190865
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.