Showing papers by "Andrey Popov published in 2009"

Observation of single top-quark production

Abstract: We report observation of the electroweak production of single top quarks in pp collisions at s=1.96 TeV based on 2.3 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(pp -> tb+X,tqb+X)=3.94 +/- 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5x10(-7), corresponding to a 5.0 standard deviation significance for the observation.

Quenching of the SnSbTe cycle in the rp process

Abstract: The nuclides 104-108Sn, 106-110Sb, 108,109Te, and 111I at the expected endpoint of the astrophysical rp process have been produced in 58Ni+natNi fusion-evaporation reactions at IGISOL and their mass values were precisely measured with the JYFLTRAP Penning trap mass spectrometer. For 106Sb, 108Sb, and 110Sb these are the first direct experimental mass results obtained. The related one-proton separation energies have been derived and the value for 106Sb, Sp=424(8) keV, shows that the branching into the closed SnSbTe cycle in the astrophysical rp process is weaker than expected.

Microscopic mirrorless negative-index optical parametric oscillator

Abstract: The feasibility and extraordinary properties of mirrorless optical parametric oscillations in a microscopic strongly absorbing slab of negative-index metamaterial are shown. They stem from the backwardness of electromagnetic waves inherent with this type of metamaterial.

Resonant nonlinear optics of backward waves in negative-index metamaterials

Abstract: The extraordinary properties of resonant four-wave mixing of backward and ordinary electromagnetic waves in doped negative-index materials are investigated. The feasibility of independent engineering of the negative refractive index and the nonlinear optical response as well as quantum control of the nonlinear propagation process in such composites is shown due to the coherent energy transfer from a control field to a signal field. Laser-induced transparency, quantum switching, frequency-tunable narrow-band filtering, amplification, and realizing a miniature mirrorless optical parametric generator of the entangled backward and ordinary waves are among the possible applications of the investigated processes.

Coherent Nonlinear Optics and Quantum Control in Negative-Index Metamaterials

Abstract: The extraordinary properties of laser-induced transparency of a negative-index slab and parametric amplification for a backward-wave signal are investigated. The effects of the idler absorption and phase mismatch on the amplification of the signal are studied, and the feasibility of ensuring robust transparency for a broad range of control field intensities and slab thicknesses is shown. A particular option consisting of the independent engineering of a strong four-wave mixing response and the negative refractive index is proposed and its specific features are investigated. The feasibility of quantum control over the slab transparency in such a scheme is confirmed through numerical experiments. We thus show opportunities and conditions for the compensation of the strong absorption inherent to plasmonic negative-index metamaterials, and we further show achievable transparency through coherent energy transfer from the control optical field to the negative-index signal.

Coherent nonlinear optics and quantum control in negative-index metamaterials

Abstract: The extraordinary properties of laser-induced transparency of a negative-index slab and parametric amplification for a backward wave signal are investigated. The effects of the idler absorption and phase mismatch on the amplification of the signal are studied, and the feasibility of ensuring robust transparency for a broad range of control field intensities and slab thicknesses is shown. A particular option consisting of the independent engineering of a strong four-wave mixing response and the negative refractive index is proposed and its specific features are investigated. The feasibility of quantum control over the slab transparency in such a scheme is confirmed through numerical experiments. We thus show opportunities and conditions for the compensation of the strong absorption inherent to plasmonic negative-index metamaterials, and we further show achievable transparency through coherent energy transfer from the control optical field to the negative-index signal.

Master Robotic Net

Abstract: The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19 - 20mag. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovas (including SNIa), search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.

Transient detections and other real-time data processing from wide-field chambers MASTER-VWF

Abstract: At present time Robotic observatory making is of current importance. Having a large field of view and being able to point at anywhere, Robotic astronomical systems are indispensable when they looking for transients like grb, supernovae explosions, novae etc, as it's impossible in these cases to foresee what you should point you telescope at and when. In work are described prompt GRB observations received on wide-field chambers MASTER-VWF, and also methods of the images analysis and transients classifications applied in real-time data processing in this experiment. For 7 months of operation 6 synchronous observations of gamma-ray burst had been made by MASTER VWF in Kislovodsk and Irkutsk. In all cases a high upper limits have been received (see tabl \ref {tab_grbwf} and fig. \ref {allgrb}).

Plasmonics: nonlinear optics, negative phase and transformable transparency

Abstract: The feasibilities and specific features of coherent nonlinear-optical energy transfer from control fields to a negativephase signal are studied, and they are found to stem from the backwardness of electromagnetic waves inherent to negative-index metamaterials. Plasmonic metamaterials that possess negative group velocity for light waves promise a revolutionary breakthrough in nanophotonics. However, strong absorption inherent to such metaldielectric nanocomposites imposes severe limitations on the majority of such applications. Herein we show the feasibility and discuss different nonlinear-optical techniques of compensating such losses, producing transparency, amplification and even generation of negative-phase light waves in originally strongly absorbing microscopic samples of plasmonic metal-dielectric nanostructured composites.

Barium borate glass and transparent glass ceramics doped with Pb4Lu2YbF17

Abstract: Barium borate glasses doped with complex Pb4Lu2YbF17 fluoride have been synthesized and investigated. Heat treatment produced glass ceramics containing the crystalline BaF2:Yb3+ phase. The changes in the structural and optical properties of the glass ceramics were revealed by X-ray diffraction, Raman spectroscopy, and luminescence spectroscopy of Yb3+ ions in polycrystalline Pb4Lu2YbF17, initial glass, and glass ceramics.

Zone plates for hard X-rays fabricated with the SPCVD technology

Abstract: Fresnel X-ray zone plates, which have been extensively developed for the last 20 years, are widely used for X-ray imaging in the hard part of the X-ray spectrum. In this paper zone plates based on the SPCVD (Surface Plasma Chemical Vacuum Deposition) technology are proposed and their optical properties in the hard X-ray range 10–30 keV are discussed. It will be shown that this technology enables production of zone plates working in the 10–30 keV range based on SiO2/GeO2 multilayer structures. The first zone plate samples based on SPCVD technology have been fabricated and tested. The parameters of the zone plates are: diameter 0.1–2.5 mm, number of zones 1000–2000, focal distance 1–5 m. The X-ray zone plates suggested here, if successful, will dramatically reduce the cost of imaging experiments in the hard X-ray spectral region, while maintaining spatial resolution high enough to be useful for the X-ray microanalysis, X-ray microscopy and focusing of the X-ray radiation.

Expression of full-length human pro-urokinase in mammary glands of transgenic mice

Abstract: Human pro-urokinase expressed in the mammary glands of transgenic animals is quickly activated and converted to urokinase by proteases that are present in the milk. Thus, it is nearly impossible to isolate full-sized pro-urokinase from the milk of transgenic animals. To solve this problem, we constructed transgenic mice that express human pro-urokinase and modified ecotin, which is a potent serine protease inhibitor from E. coli, in their mammary glands. The gene encoding ecotin was modified so as to enhance its specificity for the human urokinase-type plasminogen activator. Co-expression of modified ecotin and human pro-urokinase in the mammary glands allows for purification of full-length human pro-urokinase from these transgenic mice. The results described here suggest a general way of preventing the activation of zymogens that are expressed in the mammary glands of transgenic animals by co-expression of a zymogen along with a protease inhibitor.

Controlling light with light at the nanoscale: Backward-wave optical parametric amplification and generation in negative-index metamaterials

Abstract: Negative-index (negative phase) metamaterials (NIMs) form a novel class of electromagnetic media that promises revolutionary breakthroughs in photonics [1]. A significant progress has been achieved recently in the design of bulk multilayer negative-index plasmonic structures [2–3]. The majority of NIMs realized to date consist of metal dielectric nanostructures that have highly controllable magnetic and dielectric responses. The problem, however, is that these structures have losses that are difficult to avoid, especially in the visible range of frequencies. The losses originate from a number of sources. Irrespective of their origin, losses constitute a major hurdle to the practical realization of the unique optical applications of these structures. Therefore, developing efficient loss-compensating techniques is of paramount importance. Herein, we explore the feasibility of the developing of such techniques making use the nonlinear-optical (NLO) response of the NIMs. Nonlinear optics in the NIMs remains so far a less-developed branch of optics. On a fundamental level, the NLO response of nanostructured metamaterials is not completely understood or characterized, and cannot be predicted effectively to date. Nevertheless, the fact of the local-field enhanced nonlinearities attributed to the plasmonic nanostructures is well established and some rough estimates of their magnitude can be done. The feasibility of crafting NIMs with strong NLO responses have been demonstrated in [4]. Unlike natural positive-index materials, the energy flow and the phase velocity are counter-directed in NIMs, which determines their extraordinary linear and NLO propagation properties. Counterintuitive properties of nonlinear propagation processes in NIMs, such as three-wave mixing (TWM) optical parametric amplification (OPA), second harmonic generation and changes in the optical bistability, which are in a stark contrast with their counterparts in natural materials, were shown in [5].