The limits of ex post implementation

The sensitivity of Bayesian implementation to agents' beliefs about others suggests the use of more robust notions of implementation such as ex-post implementation, which requires that each agent' s strategy be optimal for every possible realization of the types of other agents. We show that the only deterministic social choice functions that are ex-post implementable in generic mechanism design frameworks with multi-dimensional signals, interdependent valuations and transferable utilities, are constant functions. In other words, deterministic ex-post implementation requires that the same alternative must be chosen irrespective of agents' signals. The proof shows that ex-post implementability of a non-trivial deterministic social choice function implies that certain rates of information substitution coincide for all agents. This condition amounts to a system of differential equations that are not satis�ed by generic valuation functions

Particle spectrum in modified NMSSM

The restrictions on the lightest Higgs boson mass in the minimal supersymmetric models are briefly reviewed. The particle spectrum is considered in the framework of the simplest modification of NMSSM that allows to avoid the domain wall problem and to get the self--consistent solution in the strong Yukawa coupling limit. The lightest Higgs boson mass in the investigated model can reach $125 GeV$ at values of $\tan\beta\ge 1.9$ and does not exceed $130.5\pm 3.5 GeV$.Comment: 4 pages, LaTeX2e. Talk given at the SUSY 2001 Conference in JINR, Dubna, Russi

Beef Cattle Instance Segmentation Using Fully Convolutional Neural Network

In this paper we present a novel instance segmentation algorithm that extends a fully convolutional network to learn to label objects separately without prediction of regions of interest. We trained the new algorithm on a challenging CCTV recording of beef cattle, as well as benchmark MS COCO and Pascal VOC datasets. Extensive experimentation showed that our approach outperforms the state-of-the-art solutions by up to 8% on our data

Fast ignition of inertial fusion targets by laser-driven carbon beams

Two-dimensional simulations of ion beam driven fast ignition are presented. Ignition energies of protons with Maxwellian spectrum and carbon ions with quasimonoenergetic and Maxwellian energy distributions are evaluated. The effect of the coronal plasma surrounding the compressed deuterium-tritium is studied for three different fuel density distributions. It is found that quasi- monoenergetic ions have better coupling with the compressed deuterium-tritium and substantially lower ignition energies. Comparison of quasimonoenergetic carbon ions and relativistic electrons as ignitor beams shows similar laser energy requirements, provided that a laser to quasimonoenergetic carbon ion conversion efficiency around 10% can be achieved.Comment: 8 pages, 10 figures, published in Physics of Plasma

Laser-like X-ray Sources Based on Optical Reflection from Relativistic Electron Mirror

A novel scheme is proposed to generate uniform relativistic electron layers for coherent Thomson backscattering. A few-cycle laser pulse is used to produce the electron layer from an ultra-thin solid foil. The key element of the new scheme is an additional foil that reflects the drive laser pulse, but lets the electrons pass almost unperturbed. It is shown by analytic theory and by 2D-PIC simulation that the electrons, after interacting with both drive and reflected laser pulse, form a very uniform flyer freely cruising with high relativistic gamma-factor exactly in drive laser direction (no transverse momentum). It backscatters probe light with a full Doppler shift factor of 4*gamma^2. The reflectivity and its decay due to layer expansion is discussed.Comment: 5 pages, 3 figures, submitted, invited talk on the workshop of Frontiers in Intense Laser-Matter Interaction Theory, MPQ, March 1-3, 2010

Automated quantitative analysis of single and double label autoradiographs

A method for the analysis of silver grain content in both single and double label autoradiographs is presented. The total grain area is calculated by counting the number of pixels at which the recorded light intensity in transmission dark field illumination exceeds a selected threshold. The calibration tests included autoradiographs with low (3H- thymidin) and high (3H-desoxyuridin) silver grain density. The results are proportional to the customary visual grain count. For the range of visibly countable grain densities in single labeled specimens, the correlation coefficient between the computed values and the visual grain counts is better than 0.96. In the first emulsion of the two emulsion layer autoradiographs of double labeled specimens (3H-14C- thymidin) the correlation coefficient is 0.919 and 0.906. The method provides a statistical correction for the background grains not due to the isotope. The possibility to record 14C tracks by shifting the focus through the second emulsion of the double labeled specimens is also demonstrated. The reported technique is essentially independent of size, shape and density of the grains

Radially Polarized, Half-Cycle, Attosecond Pulses from Laser Wakefields through Coherent Synchrotron Radiation

Attosecond bursts of coherent synchrotron-like radiation are found when driving ultrathin relativistic electron disks in a quasi-one-dimensional regime of wakefield acceleration, in which the laser waist is larger than the wake wavelength. The disks of overcritical density shrink radially due to the focusing wake fields, thus providing the transverse currents for the emission of an intense, radially polarized, half-cycle pulse of about 100 attoseconds in duration. The electromagnetic pulse first focuses to a peak intensity 10 times larger ($7\times10^{20}\rm W/cm^2$) than the driving pulse and then emerges as a conical beam. Saturation of the emission amplitudes is derived analytically and in agreement with particle-in-cell simulation. By making use of gas targets instead of solids to form the ultrathin disks, the new scheme allows for high repetition rate required for applications.Comment: 5 pages, 4 figure

Acceleration of ultra-thin electron layer. Analytical treatment compared with 1D-PIC simulation

In this paper, we apply an analytical model [V.V. Kulagin et al., Phys. Plasmas 14,113101 (2007)] to describe the acceleration of an ultra-thin electron layer by a schematic single-cycle laser pulse and compare with one-dimensional particle-in-cell (1D-PIC) simulations. This is in the context of creating a relativistic mirror for coherent backscattering and supplements two related papers in this EPJD volume. The model is shown to reproduce the 1D-PIC results almost quantitatively for the short time of a few laser periods sufficient for the backscattering of ultra-short probe pulses.Comment: 4 pages, 4 figures, submitted to the special issue "Fundamental Physics with Ultra-High Fields" in The European Physical Journal