Observation of wave-packet propagation in the ion cyclotron range of frequencies in a tokamak plasma

Experimental observation of wave-packet propagation in the ion cyclotron range of frequencies in a tokamak plasma is reported. Studies were carried out in the Caltech Research Tokamak [Phys. Fluids 23, 614 (1980)] in a pure hydrogen plasma and in a regime where fast-wave damping was sufficiently small to permit multiple toroidal transits of the wave packet. Waves were launched by exciting a small loop antenna with a short burst of radio-frequency current and were detected with shielded magnetic probes. Probe scans revealed a large increase in wave-packet amplitude at smaller minor radii, and the packet velocity was found to be independent of radial position. Measurement of the packet transit time yielded direct information about the wave group velocity. Packet velocity was investigated as a function of the fundamental excitation frequency, plasma density, and toroidal magnetic field. Results are compared with the predictions of a cold plasma model that includes a vacuum layer at the edge

Sources, control, and effects of noise from aircraft propellers and rotors

Source noise predictions are compared with measurements for conventional low-speed propellers, for new high speed propellers (propfans), and for a helicopter. Results from a light aircraft demonstration program are described, indicating that about 5-dB reduction of flyover noise can be obtained without significant performance penalty. Sidewall design studies are described for interior noise control in light general aviation aircraft and in large transports using propfan propulsion. The weight of the added acoustic treatment is estimated and tradeoffs between weight and noise reduction are discussed. A laboratory study of passenger response to combined broadband and tonal propeller like noise is described. Subject discomfort ratings of combined tone broadband noises are compared with ratings of broadband (boundary layer) noise alone, and the relative importance of the propeller tones is examined

On the Theory of Fermionic Preheating

In inflationary cosmology, the particles constituting the Universe are created after inflation due to their interaction with moving inflaton field(s) in the process of preheating. In the fermionic sector, the leading channel is out-of equilibrium particle production in the non-perturbative regime of parametric excitation, which respects Pauli blocking but differs significantly from the perturbative expectation. We develop theory of fermionic preheating coupling to the inflaton, without and with expansion of the universe, for light and massive fermions, to calculate analytically the occupation number of created fermions, focusing on their spectra and time evolution. In the case of large resonant parameter $q$ we extend for rermions the method of successive parabolic scattering, earlier developed for bosonic preheating. In an expanding universe parametric excitation of fermions is stochastic. Created fermions very quickly, within tens of inflaton oscillations, fill up a sphere of radius $\simeq q^{1/4}$ in monetum space. We extend our formalism to the production of superheavy fermions and to `instant' fermion creation.Comment: 14 pages, latex, 12 figures, submitted for publicatio

Extracting New Physics from the CMB

We review how initial state effects generically yield an oscillatory component in the primordial power spectrum of inflationary density perturbations. These oscillatory corrections parametrize unknown new physics at a scale $M$ and are potentially observable if the ratio $H_{infl}/M$ is sufficiently large. We clarify to what extent present and future CMB data analysis can distinguish between the different proposals for initial state corrections.Comment: Invited talk by B. Greene at the XXII Texas Symposium on Relativistic Astrophysics, Stanford University, 13-17 December 2004, (TSRA04-0001), 8 pages, LaTeX, some references added, added paragraph at the end of section 2 and an extra note added after the conclusions regarding modifications to the large k power spectra deduced from galaxy survey

Point-contact spectroscopy in heavy-fermion superconductors

We develop a minimal model to calculate point-contact spectra between a metallic tip and a superconducting heavy-fermion system. We apply our tunneling model to the heavy fermion CeCoIn5, both in the normal and superconducting state. In point-contact and scanning tunneling spectroscopy many heavy-fermion materials, like CeCoIn5, exhibit an asymmetric differential conductance, dI/dV, combined with a strongly suppressed Andreev reflection signal in the superconducting state. We argue that both features may be explained in terms of a multichannel tunneling model in the presence of localized states near the interface. We find that it is not sufficient to tunnel into two itinerant bands of light and heavy electrons to explain the Fano line shape of the differential conductance. Localized states in the bulk or near the interface are an essential component for quantum interference to occur when an electron tunnels from the metallic tip of the point contact into the heavy-fermion system.Comment: 13 pages, 9 figures. Accepted for publication in Physical Review

Assessment of Connections Between Knowledge- Based Economy Characteristics and Selected Macroeconomic Categories in the European Union's Countries by Means of Panel Models

The aim of the article is to analyze the impact of knowledge-based economy variables on the selected macroeconomic categories - the share of total investments in GDP and the employment rate- in European Union's countries in the years 2000-2007, conducted with application of panel models.Celem artykułu jest analiza wpływu zmiennych opisujących gospodarkę opartą na wiedzy na podstawowe kategorie makroekonomiczne - udział całkowitych inwestycji w PKB i stopę zatrudnienia - w krajach Unii Europejskiej (z podziałem na kraje UE-15 i nowe kraje członkowskie UE) w latach 2000-2007, przeprowadzona w oparciu o modele panelowe

Clean-Up after Territorial Oil Spills in the Arctic

… The nature of a spill will depend on the local weather conditions, including the presence or absence of snow, the absorptive capacity of the ground (which is influenced by the prevailing groundwater level), and local topography. … In clean-up operations after oil spills, the first requirement is to contain the spill in as small an area as possible, and to prevent it from reaching water courses and thus contaminating their environments. Devices and techniques can then be employed to remove oil from the contaminated region and convey it to temporary storage. Thirdly, the area can be treated to remove residual oil and promote its early restoration through the use of chemical and biological techniques. … In temperate regions, terrestrial spills are most readily contained by artificial dykes or dams constructed by means of earth-moving equipment, and it is also possible to dig trenches and ditches into which oil will flow and be retained. In areas of permafrost, however, suitable damming material may not be readily available, or may be obtained only if considerable areas of permafrost are exposed - that is, at the cost of additional environmental damage. The use of heavy vehicles, even if they are available, will compact the insulating active layer of permafrost and thereby cause eventual melting of the permafrost. Containment should involve a minimum of disturbance of the area, with no removal or compaction of the active layer and exposure of permafrost. A method of containment which may be feasible is to use damming material that can be quickly transported to the site and installed without the aid of machinery. For example, corrugated metal sheeting in sections about three feet high by ten feet long (1 m x 3 m approximately), with vertical corrugations, could be driven through the active layer down to the water table or frost level or thawed clay soil, all of which provide a basement to vertical oil penetration, and retained in position by T-bar stakes driven into the ground. … The presence of permafrost ironically brings the substantial benefit of there being little of the infiltration of oil into porous soils, with subsequent ground-water contamination, which constitutes such a severe problem in temperate regions; that is, clean-up operations can be facilitated by the presence of permafrost. Another approach to containment, which was tested briefly during the summer of 1974 on wet tundra on Richards Island in the Mackenzie Delta, is to cut a trench, 30 cm wide, to permafrost level across the path of the flowing oil. The trench successfully intercepts the flow of oil, both on and below the surface, and drains it to a low-level point from where it can be pumped to storage or for disposal. … A dam or trench of the type just described, which would necessarily have to be located on the downslope side of the area of spillage, would interfere with natural drainage, and so it would be necessary to control drainage from the area while oil and water were being separated. The present authors suggest that this control could be effected by the installation of an API (American Petroleum Institute) type of oil-water separator which can be constructed easily from prefabricated metal sheeting, usually about 5 feet deep by 10 feet wide by 30 feet long (1.5 m x 3 m x 9 m approximately). … Another possibility would be the use of a compact plate-type oil-water separator. … A significant further advantage of the general technique just explained is the possibility of controlling, and even accelerating, the flow from the area of spillage. … Small-scale laboratory tests have demonstrated that significant proportions of the absorbed oil can be floated out of detritus by gravity alone and without agitation. It is likely that, due to its slow rate of evaporation, the sub-surface oil would maintain a viscosity sufficiently low for it to be floated out by water. It is generally recognized, also, that the toxic constituents of oil are the most volatile and water-soluble. Thus, it is likely that the oil would exhibit toxicity only during the first few months after spillage, and then be permanently absorbed in the vegetation and soil and become immobilized. … As a final stage of restoration of an affected area, it may prove beneficial to fertilize it and promote the growth of oil-degrading microorganisms. Since the albedo of the area will be reduced, and so there will be greater absorption of radiation and increased depth of active layer, it may be desirable to increase the albedo artificially be sprinkling the area with reflective materials. In conclusion, the present authors contend that new techniques must be developed for the clean-up of terrestrial spills in the Arctic, since methods used in temperate regions are inappropriate. &hellip