Production ofψ particles in N-N collisions and largeP T phenomenon

We calculate the yield ofψ (3105) particles in N-N collisions in a model which associates the production of heavy particles with largeP _T phenomenon. Our results show thatψ (3105) has a fairly strong coupling to other hadrons. We propose a criterion in the search for charmed particles and a parametrization for the expected yields of such particles.     

Evidence for the production of new particles in cosmic ray experiments deep underground

In the cosmic ray experiments deep underground in the Kolar Gold Mines, a special class of events has been observed, at present 6 in number, characterised by several, (in general 3), charged particles arising from a vertex, either in air or in the thin material of the detectors, with large opening angles; the vertex is at a distance of around 70–100 cms from the rock wall. The most plausible interpretation of these events is that they are due to the decay of new, massive and long-lived particles produced in neutrino collisions inside rock, or through hitherto unknown processes.     

Crucial role of the magnetic field in the evolution of life

The formation of a steady ozone layer in the earth’s atmosphere is the most significant event in the evolutionary cycle of the earth which, in turn, has been responsible for the development of life with an oxygen metabolism. In addition to protecting biological life from exposure to ultraviolet radiation the ozone layer has also been responsible for maintaining the water and oxygen balance in the atmosphere. It is argued that the magnetic field of the earth is really responsible for the formation of this steady ozone layer in the earth’s atmosphere. Because of the earth’s magnetic field and associated trapped charge particle belts and the magnetosphere, the earth’s atmosphere does not directly interact with the interplanetary space. Without such a shielding, the free oxygen atoms could have been depleted considerably causing a severe depletion in the ozone concentration to start with. The impact of charged particles from galactic and solar cosmic rays over the entire earth’s atmosphere and the consequent production of NO _x would have given rise to a major ozone sink, if earth were devoid of a magnetic field. The net result would have been the absence of a steady ozone layer and the absence of life with an oxygen metabolism, as in the case of the atmospheres of Venus and Mars, if the earth did not have a magnetic field.     

Behavior of small particles in a thermal plasma flow

In this paper computational results are presented which reveal the effects of the Knudsen number on heat transfer and drag of small particles in a flowing thermal argon plasma. The Knudsen number is restricted to moderate values so that temperature jump and velocity slip conditions may be employed, and for the governing equations the continuum approach remains valid. It is shown that the ratio of the heat fluxes with and without the Knudsen effect is almost identical to the ratio obtained by the authors for the case of pure heat conduction. This fact is very important for modeling of the behavior of particles injected into an actual plasma reactor when the Knudsen effect has to be taken into account.On leave from the Department of Engineering Mechanics, Tsinghua University, Beijing 100084, P.R.C.     

An experimental technique for characterizing dispersion in compounds of particulates in thermoplastics using small-angle light scattering

An experimental technique based on small-angle light scattering for characterizing dispersion of particles and presence of agglomerates in compounds of minerals in thermoplastics is described. The technique is critically discussed in terms of the Mie and Rayleigh-Gans theories of scattering. An experimental study of dispersion in compounds of polypropylene and polystyrene with calcium carbonate by mixing variously on two roll mills, an internal mixer, and a modular intermeshing co-rotating twin screw extruder.     

A search for heavy leptons in cosmic radiation underground

An experiment to search massive long-lived, weakly interacting particles (leptons) in cosmic radiation has been conducted at Kolar Gold Fields at a depth of 7.6 hg cm⁻² (1 hg cm⁻²=100 g cm⁻²) below surface. The apparatus was senstive to sub-relativistic (velocity<0.75 c) charged leptons of mass greater than that of a proton and life times greater than a microsecond. The method consists of selecting charged particles using a scintillator counter telescope and vetoing relativistic particles (velocity >0.75 c) by using a water Čerenkov detector. The range of the particle is observed in arrays of neon flash tubes interspersed with iron absorbers. During 3000 hours of observation 28 events were recorded satisfying the trigger and event selection criteria. Bulk of these events were interpreted as due to recoil protons (low energy) from the inelastic scattering of high energy muons in the overhead absorber. The remaining events were interpreted as either atmospheric stopping protons or stopping muons that failed to generate a Čerenkov signal. The observed events are thus consistent with the background and no heavy leptons were seen. From our observations an upper limit of 2.12×10⁻⁷ (with 90% confidence level) is set on the ratio of the flux of heavy leptons to that of all muons at this depth.     

Electron microscopy of submicron particles in natural waters — Specimen preparation by centrifugation

Particles ranging from ca. 0.1 to 1.0m in 5 ml of pond water are collected on a 10–20 nm carbon film on a gold or copper specimen grid, placed on a special holder in a 7-ml centrifuge tube, by centrifugation at 10000 r. p. m. for 18 min. The specimens thus prepared are reproducible and preserve the morphology of the particles satisfactorily. The proposed technique is more suitable than filtration, direct drying and spray drying techniques for morphological studies and elemental analysis of individual particles with scanning, transmission and analytical electron microscopes.     

PNL分子在正、负电性纳米银上的吸附取向

制备了两种不同电性的纳米银粒子的脉体,发现当邻菲罗啉分子分别吸附在这两种纳米银上时,其表面增强喇曼谱有明显的不同.在正电性纳米银上,面外弯曲模式受到增强,而在负电性纳米银上,面内伸缩模式受到增强,通过分析增强谱的差异表明,分子在这两种不同电性胶态纳米银表面上可能分别以平躺及站立方式吸附.     

Influence of particle orientation on retrieving cirrus cloud properties by use of total and polarized reflectances from satellite measurements

The influence of ice crystal orientation was investigated on retrieving cirrus optical thickness (τ) and aspect ratio of ice crystals (Q) from satellite measurements using the total and polarized reflectances at a wavelength of . We considered columnar and plate like hexagonal ice crystals whose long axes are randomly oriented in the horizontal plane (2D model) with some amplitude of oscillation expressed by a Gaussian distribution function with the standard deviation of σ.The retrieved τ and Q values significantly depend on the assumption of σ, in particular for the plate type. Furthermore, the relationship between σ and the retrieved values depends on the solar, satellite, and target geometries. In our case study, for one target area, τ value retrieved using the 2D model with σ=5° was approximately twice larger than that using the 2D model with σ=20°, while the retrieved Q value was not significantly influenced by σ. For another target area, the τ(Q) retrieved using the 2D model with σ=5° was about 1.5 (1.8) times larger than that retrieved using the 2D model with σ=20°.     

Preparation and application of a novel core–shell‐particle‐supported zirconocene catalyst

The use of functional groups bearing silica/poly(styrene‐co‐4‐vinylpyridine) core–shell particles as a support for a zirconocene catalyst in ethylene polymerization was studied. Several factors affecting the behavior of the supported catalyst and the properties of the resulting polymer, such as time, temperature, Al/N (molar ratio), and Al/Zr (molar ratio), were examined. The conditions of the supported catalyst preparation were more important than those of the ethylene polymerization. The state of the supported catalyst itself played a decisive role in both the catalytic behavior of the supported catalyst and the properties of polyethylene (PE). IR and X‐ray photoelectron spectroscopy were used to follow the formation of the supports. The formation of cationic active species is hypothesized, and the performance of the core–shell‐particle‐supported zirconocene catalyst is discussed as well. The bulk density of the PE formed was higher than that of the polymer obtained from homogeneous and polymer‐supported Cp₂ZrCl₂/methylaluminoxane catalyst systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2085–2092, 2001