The innermost regions of the jet in NRAO 150. Wobbling or internal rotation?

NRAO 150 is a very bright millimeter to radio quasar at redshift $z$=1.52 for which ultra-high-resolution VLBI monitoring has revealed a counter-clockwise jet-position-angle wobbling at an angular speed $\sim11^{\circ}$/yr in the innermost regions of the jet. In this paper we present new total and linearly polarized VLBA images at 43 GHz extending previous studies to cover the evolution of the jet in NRAO 150 between 2006 and early 2009. We propose a new scenario to explain the counter-clockwise rotation of the jet position angle based on a helical motion of the components in a jet viewed faced-on. This alternative scenario is compatible with the interpretation suggested in previous works once the indetermination of the absolute position of the self-calibrated VLBI images is taken into account. Fitting of the jet components motion to a simple internal rotation kinematical model shows that this scenario is a likely alternative explanation for the behavior of the innermost regions in the jet of NRAO 150.Comment: 5 pages, 4 figures, Presented in 'The Innermost Regions of Relativistic Jets and Their Magnetic Fields' conference. Granada, Spain, 201

Extended two-level quantum dissipative system from bosonization of the elliptic spin-1/2 Kondo model

We study the elliptic spin-1/2 Kondo model (spin-1/2 fermions in one dimension with fully anisotropic contact interactions with a magnetic impurity) in the light of mappings to bosonic systems using the fermion-boson correspondence and associated unitary transformations. We show that for fixed fermion number, the bosonic system describes a two-level quantum dissipative system with two noninteracting copies of infinitely-degenerate upper and lower levels. In addition to the standard tunnelling transitions, and the transitions driven by the dissipative coupling, there are also bath-mediated transitions between the upper and lower states which simultaneously effect shifts in the horizontal degeneracy label. We speculate that these systems could provide new examples of continuous time quantum random walks, which are exactly solvable.Comment: 7 pages, 1 figur

Peer Evaluation: Incentives and Co-Worker Relations

In many workplaces co-workers have the best information about each other's effort. Managers may attempt to exploit this information through peer evaluation. I study peer evaluation in a pure moral hazard model of production by two limitedly liable agents. Agents receive a signal about their colleague's effort level, and are asked to report it to the principal. The principal may give an individual bonus for the receipt of a positive evaluation by a colleague, which stimulates effort as long as signals are revealed truthfully. A cost of lying ascertains that there can be truthful revelation. I show that interpersonal relations between colleagues constrain the bonus for receiving a positive evaluation in order to keep evaluations truthful. Still, the principal will always include such a bonus in the optimal contract, and possibly complement it with a team bonus. Co-worker relations have non-monotic effects on profits in the optimal contract

Connection between type B (or C) and F factorizations and construction of algebras

In a recent paper (Del Sol Mesa A and Quesne C 2000 J. Phys. A: Math. Gen. 33 4059), we started a systematic study of the connections among different factorization types, suggested by Infeld and Hull, and of their consequences for the construction of algebras. We devised a general procedure for constructing satellite algebras for all the Hamiltonians admitting a type E factorization by using the relationship between type A and E factorizations. Here we complete our analysis by showing that for Hamiltonians admitting a type F factorization, a similar method, starting from either type B or type C ones, leads to other types of algebras. We therefore conclude that the existence of satellite algebras is a characteristic property of type E factorizable Hamiltonians. Our results are illustrated with the detailed discussion of the Coulomb problem.Comment: minor changes, 1 additional reference, final form to be published in JP

Kennisarrangementen met succes begeleiden naar innovaties

Bij systeeminnovatieve vraagstukken is kennis schaars, de toekomst onzeker en zijn de belangen van diverse partijen groot en uiteenlopend. Juist dan is de noodzaak groot dat ondernemers, kennisinstituten, overheden en maatschappelijke organisaties samen duurzame oplossingen zoeken. In kennisarrangementen worden de partijen samengebracht en begeleid. Het begeleiden vergt de nodige kennis en vaardigheid. Aan de hand van een praktijkvoorbeeld wordt duidelijk waar het allemaal om draai

Time and space-resolved spectroscopic and imaging study of a laser-produced swine muscle tissue plasma

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/We investigated the optical emission and imaging features of plasmas produced by a high-power transversely excited atmospheric CO2 laser pulses on a swine muscle tissue sample in different vacuum conditions. The analyzed plasma shows electronically excited neutral Na, K, C, Mg, H, Ca, N, and O atoms, ionized C+, C2+, C3+, Mg+, Mg2+, N+, N2+, Ca+, O+, and O2+ species and molecular band systems of CN, C2, CH, NH, OH and CaOH. Time-resolved 2D emission spectroscopy is employed to study the expanded distribution of several species ejected during ablation. The expansion of the plume front was analyzed using Shock wave and Drag models. Laser-produced plasmas (LPPs) are currently a topic of great interest in fundamental and applied areas such as fabrication of thin films by pulsed laser deposition, production of nanoparticles, spectrochemical analysis through laserinduced breakdown spectroscopy (LIBS) [1], ion source etc. Beyond traditional applications of LIBS, recent progresses lead to analysis of biological warfare agents and animal tissues. In this work, we present a spatial and temporal analysis of the LPP plume generated on a biological tissue target. Time-resolved 2D emission spectroscopy is used to study the expanded distribution of different species ejected during ablation. Fig. 1 shows a schematic overview of the temporal history of the LPP sample. The temporal shape of the CO2 laser pulse is also shown. Inset plots illustrate some spaceresolved spectral images observed at different delays for a gate width time of 100 ns. The recorded spectral intensity is indicated by a pseudo- color. By tracking the maximum brightness displacement for different plasma species gives their average expansion velocities. The expansion velocities of the ionized species towards the longitudinal direction are found to be increasing with degree of ionization. Plasma parameters such as electron density and temperature were measured from the spatial-temporal analysis of different specific species. We used the imaging data to create positiontime plots (Fig. 2) of the shockwave front at several background air pressures. The solid line represents the shockwave model fit. These images provide very useful information about the expansion and internal structure of the plasmaplume. Surface morphology of irradiated surface showed that increasing the pressure of the ambient gas, decreased the ablated mass. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Time (¿s) Plume front position, R (mm) R ¿¿(¿¿¿¿ ¿¿¿¿)¿t¿¿¿¿¿¿¿¿ 0.0 5.0x105 1.0x106 1.5x106 2.0x106 2.5x106 3.0x106 Velocity (cm/s) Fig. 2. R-t plot and velocities for the expanding plume front in vacuum (0.01 Pa). Insets show two images (0 and 4 ¿s) at 1.1 GW/cm2 incident laser power density. Acknowledgments We gratefully acknowledge the support received by the project: CTQ2013-43086. References [1] J. J. Camacho et al 2013 Spectrochimica Acta Part B 88 203. Fig. 1. Schematic overview of the temporal and spatial evolution of the LPP sample. 1 E-mail: [email protected] XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015) IOP Publishing Journal of Physics: Conference Series 635 (2015) 042005 doi:10.1088/1742-6596/635/4/042005Peer Reviewe

Particle Acceleration and Radiation associated with Magnetic Field Generation from Relativistic Collisionless Shocks

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The ``jitter'' radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.Comment: 4 pages, 1 figure, submitted to Proceedings of 2003 Gamma Ray Burst Conferenc

Particle Acceleration in Relativistic Jets due to Weibel Instability

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. While some Fermi acceleration may occur at the jet front, the majority of electron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The ``jitter'' radiation (Medvedev 2000) from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.Comment: ApJ, in press, Sept. 20, 2003 (figures with better resolution: http://gammaray.nsstc.nasa.gov/~nishikawa/apjweib.pdf