Dependence of ion charge-energy emission from Nd:YAG-laser-produced plasma on laser intensity in the 0.4 - 40 × 10 10 W/cm² range

We experimentally characterize the ionic emission, including the individual charge states Snz+ ( z = 1 , … , 8 ), from laser-produced tin plasma as a function of the intensity of the employed ns-pulsed laser. The plasma is generated in a vacuum from tin microdroplets (diameter ranging from 17 to 35 μm) using pulsed Nd:YAG laser light (laser wavelength λ = 1.064 μm) over a range of intensities (0.4- 40 × 10 10 W/cm2). We measure charge-state-resolved and integrated ion energy distributions at seven angular positions around the plasma using seven retarding field analyzers. We highlight peak features in both types of spectra and describe the dependence of their energies on laser intensity with power-law functions. The resulting power laws match those derived from plasma radiation hydrodynamics theory. The analytical scaling laws exhibit strong isotropy, while the ion energy spectra are highly anisotropic.</p

Evaluation of two repellent semiochemicals for disruption of attack by the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae)

When released from attractant-baited multiple-funnel traps, 3-methyl-2-cyclohexen-1- one (MCH) reduced catches of male and female mountain pine beetles, Dendroctonus ponderosae Hopkins, by 67.4% and 71.8%, respectively. 2-Phenyl ethanol reduced the respective catches by 96.6% and 95.1%, but only verbenone and all three compounds together reduced catches to levels no different from those in unbaited control traps. In another experiment, all three binary combinations of the above compounds, plus the ternary combination, reduced catches of both sexes by &gt;96%. In comparable tree protection experiments near Princeton BC, MCH and 2-phenyl ethanol alone and together significantly reduced the percentages of pheromone-baited lodgepole pines that were attacked by 16.0%, 33.3% and 40.0%, respectively, but verbenone alone totally protected baited trees, and many trees within 5 m of them, from attack. In identical experiments near Prince George BC, where mountain pine beetle populations were much higher, adding MCH, 2-phenyl ethanol or both together to verbenone did not cause attack to be reduced significantly beyond that achieved by verbenone alone. Our results confirm that 2-phenyl ethanol is an antiaggregation pheromone for the mountain pine beetle, and that MCH is an interspecific synomone. However, because neither was as effective as verbenone in protecting pheromone-baited trees from attack, and adding either or both to verbenone did not improve protection, neither compound warrants further consideration as a potential tool for operational disruption of attack

Lesions of the Rat Perirhinal Cortex Spare the Acquisition of a Complex Configural Visual Discrimination Yet Impair Object Recognition

Rats with perirhinal cortex lesions were sequentially trained in a rectangular water tank on a series of 3 visual discriminations, each between mirror-imaged stimuli. When these same discriminations were tested concurrently, the rats were forced to use a configural strategy to solve the problems effectively. There was no evidence that lesions of the perirhinal cortex disrupted the ability to learn the concurrent configural discrimination task, which required the rats to learn the precise combination of stimulus identity with stimulus placement (“structural” learning). The same rats with perirhinal cortex lesions were also unimpaired on a test of spatial working memory (reinforced T maze alternation), although they were markedly impaired on a new test of spontaneous object recognition. For the recognition test, rats received multiple trials within a single session in which on every trial, they were allowed to explore 2 objects, 1 familiar, the other novel. On the basis of their differential exploration times, rats with perirhinal cortex lesions showed very poor discrimination of the novel objects, thereby confirming the effectiveness of the surgery. The discovery that bilateral lesions of the perirhinal cortex can leave configural (structural) learning seemingly unaffected points to a need to refine those models of perirhinal cortex function that emphasize its role in representing conjunctions of stimulus features

Quantum interference within the complex quantum Hamilton-Jacobi formalism

Quantum interference is investigated within the complex quantum Hamilton-Jacobi formalism. As shown in a previous work [Phys. Rev. Lett. 102, 250401 (2009)], complex quantum trajectories display helical wrapping around stagnation tubes and hyperbolic deflection near vortical tubes, these structures being prominent features of quantum caves in space-time Argand plots. Here, we further analyze the divergence and vorticity of the quantum momentum function along streamlines near poles, showing the intricacy of the complex dynamics. Nevertheless, despite this behavior, we show that the appearance of the well-known interference features (on the real axis) can be easily understood in terms of the rotation of the nodal line in the complex plane. This offers a unified description of interference as well as an elegant and practical method to compute the lifetime for interference features, defined in terms of the average wrapping time, i.e., considering such features as a resonant process.Comment: revised version, 13 pages, 11 figures, 1 tabl

A Study of the Ground Level Event of April 15, 2001 with GRAND

Abstract Project GRAND, a proportional wire chamber array, is used to examine the increased counting rate of single muons during the solar Ground Level Event (GLE) of April 15, 2001. Data are presented and compared to our background rates and to that of neutron monitor stations. This GLE is seen with a statistical significance of 6.1σ

Constraints on Models for TeV Gamma Rays from Gamma-Ray Bursts

We explore several models which might be proposed to explain recent possible detections of high-energy (TeV) gamma rays in association with low-energy gamma-ray bursts (GRBs). Likely values (and/or upper limits) for the source energies in low- and high-energy gamma rays and hadrons are deduced for the burst sources associated with possible TeV gamma-ray detections by the Project GRAND array. Possible spectra for energetic gammas are deduced for three models: 1) inverse-Compton scattering of ambient photons from relativistic electrons; 2) proton-synchrotron emission; and 3) inelastic scattering of relativistic protons from ambient photons creating high-energy neutral pions, which decay into high-energy photons. These models rely on some basic assumptions about the GRB properties, e.g. that: the low- and high-energy gamma rays are produced at the same location; the time variability of the high-energy component can be estimated from the FWHM of the highest peak in the low-energy gamma ray light curve; and the variability-luminosity relation of Fenimore & Ramirez-Ruiz (2000) gives a reliable estimate of the redshifts of these bursts. We also explore the impact of each of these assumptions upon our models. We conclude that the energetic requirements are difficult to satisfy for any of these models unless, perhaps, either the photon beaming angle is much narrower for the high-energy component than for the low-energy GRB or the bursts occur at very low redshifts (z<0.01). Nevertheless, we find that the energetic requirements are most easily satisfied if TeV gamma rays are produced predominantly by inverse-Compton scattering with a magnetic field strength well below equipartition or by proton-synchrotron emission with a magnetic field strength near equipartition.Comment: 39 pages, 7 figures, accepted for publication in Astroparticle Physic

A Study of Failure Modes in the ILC Main Linac

Failures in the ILC can lead to beam loss or even damage the machine. In the paper quadrupole failures and errors in the klystron phase are being investigated and the impact on the machine protection is being considered for the main linac