Narrow Results

The study of single raindrops is expected to give new and great information such as drop formation processes and pollutant scavenging mechanisms. To investigate the characteristics of individual raindrops, PIXE method was applied to elemental analysis. Size-segregated individual raindrops were collected at Kyoto University during rain event in October 2001. Detection limit of each element for polycarbonate filter used as the substrate of raindrops was calculated. The significant peaks of several elements in single raindrop corresponding to the channel number of PIXE could be resolved. Chlorine, potassium, and sulphur were found as major elements in each size raindrop. Strong raindrop size-dependence of every elemental concentration was shown. Chlorine, chromium, potassium, and calcium show the distinctively high scavenging rate at the beginning rainfall. They show 98 %, 97 %, 96 %, and 84 % scavenging rate, respectively and followed by iron and sulphur.

One-dimensional cellular automata are known to be able to present complex behaviors. In some cases, their evolution may be understood as movings, collisions, or creations of particles. In the case of the special Wolfram's rule 54, Boccara has previously pointed out basic particles. In this paper, we introduce a group which allows the formal study of interactions between these particles. Coming back to the complexity of rule 54 and using the new algebraic classification of Rapaport, we prove that rule 54 is not simple.

The unparticle field operator can be expanded in terms of creation and destruction operators corresponding to particles with a continuous mass spectrum. Hence, when the four-momentum of an unparticle is measured, then the unparticle manifests as an ordinary particle with a definite (but arbitrary) mass.

Recently data from PAMELA, ATIC, FERMI-LAT and HESS show that there are e^± excesses in the cosmic ray energy spectrum. PAMELA shown excesses only in e⁺, but not in anti-proton spectrum. ATIC, FERMI-LAT and HESS shown excesses in e⁺+e^- spectrum, but the detailed shapes are different which requires future experimental observations to pin down the correct data set. Nevertheless a lot of efforts have been made to explain the observed e^± excesses, and also why PAMELA only has excesses in e⁺ but not in anti-proton. In this brief review we discuss one of the most popular mechanisms to explain the data — the dark matter annihilation. It has long been known that about 23% of our universe is made of relic dark matter. If the relic dark matter was thermally produced, the annihilation rate is constrained resulting in the need of a large boost factor to explain the data. We will discuss in detail how a large boost factor can be obtained by the Sommerfeld and Breit–Wigner enhancement mechanisms. Some implications for particle physics model buildings will also be discussed.

About 30 years ago, I was among several students mentored by Professor Yang at Stony Brook to enter the field of particle accelerator physics. Since then, I have been fortunate to work on several major accelerator projects in USA and in China, guided and at times directly supported by Professor Yang. The field of accelerator physics is flourishing worldwide both providing indispensable tools for fundamental physics research and covering an increasingly wide spectrum of applications beneficial to our society.

In this paper, we have studied particle collision around a rotating acoustic black hole in 2 + 1 dimensions. This black hole is analog to a fluid flow in a draining bath tub with a sink. Center of mass energy for two-particle collision at the horizon of the rotating acoustic black hole is considered. There is a possibility of the two-mass collision to create infinite center of mass energy for certain fine tuning of the parameters of the theory.

This computational study focuses on the dynamics of individual ferrous particles and the flow of the incompressible Newtonian fluid under the effect of an externally applied magnetic field and pressure gradient in a two-dimensional micro channel with smooth walls. The particle dynamics is simulated as a discrete phase using MATLAB code and the fluid flow is solved as a continuous phase using Computational Fluid Dynamics Software FLUENT. Interaction between the particle and fluid phases are included as hydrodynamic forces predicated by the fluid phase simulation and updated particle locations determined by the particle phase solution under non-uniform magnetic field. Non-uniform magnetic field forces the particles to move to poles of the magnet, and results in their accumulation. This causes drastic change on the continuous phase flow and pressure distribution, which in turn influences the particle motion. Predicted dynamics of the suspended ferrous particles under magnetic field and flow of the carrier fluid with pressure gradient is in reasonably well agreement with previous work. The results show that non-uniform magnetic field generated by externally placed magnets can be used to control the locations of the particles and flow of the fluid in a micro channel.

Strontium hexaferrite is a hard magnetic material and has been extensively used as a permanent magnet. In this work a novel sol-gel auto-combustion method was used to synthesize ultra fine strontium hexaferrite. The investigations show that the model of combustion changes with the change of basic agent. The XRD results show that using ammonia or trimethylamine does not change the composition of the combustion product and it also shows that the surfactant burns completely during the combustion process. The average crystallite size of hexaferrite powders was also measured by X-ray line broadening technique employing Scherrer formula. The results show that changing the basic agent makes the particle size of the final product much smaller. Basic agent also affects the formation temperature of the single phase strontium hexaferrite.

We report studies of random sequential adsorption on the pre-patterned Bethe lattice. We consider a partially covered Bethe lattice, on which monomers and dimers deposit competitively. Analytical solutions are obtained and discussed in the context of recent efforts to use pre-patterning as a tool to improve self-assembly in micro- and nano-scale surface structure engineering.

This paper describes the influence of surface roughness of steel plate on self-assembly behavior of silica particles based on SEM observations and the wettability of the suspension. The 304 stainless steel plate having two different surface roughness and spherical silica powder were used for the investigation. The silica layer was obtained by dipping the steel plate into the suspension and drawing it under various drawing speed. As a result, silica particle layers were formed on the plate surface when the stainless steel had a rough surface. In contrast, it was difficult to obtain the silica layers for the smooth surface.

The data collected by ATIC, PPB-BETS, FERMI-LAT and HESS all indicate that there is an electron/positron excess in the cosmic ray energy spectrum above ~100 GeV, although different instrumental teams do not agree on the detailed spectral shape. PAMELA also reported clearly the excessive feature of the fraction of positron above several GeV, but with no excess in antiprotons. Here we review the observational status and theoretical models of this interesting observational feature. We pay special attention to various physical interpretations proposed in the literature, including modified supernova remnant models for the e^± background, new astrophysical sources, and new physics (the dark matter models). We suggest that although most models can make a case to interpret the data, with the current observational constraints the dark matter interpretations, especially those invoking annihilation, require much more exotic assumptions than some other astrophysical interpretations. Future observations may present some "smoking-gun" observational tests to differentiate different models and to identify the correct interpretation of the phenomenon.

This paper is devoted to the development and quantitative evaluation of the properties of the numerical algorithm of the Cartesian grid method for three-dimensional (3D) simulation of shock-wave propagation in areas of varying shape. The detailed description of the algorithm is presented. The algorithm is relatively simple to implement and does not require solving the problem of determination of the shape of the body’s boundary intersection with regular computational cell. The accuracy of the algorithm is demonstrated by comparing the simulated and experimental data in the problems of the interaction of a shock wave (SW) with a nonmoving sphere and a moving particle.

The characteristics of suspended sediment image can be reflected by the coefficients of biorthogonal wavelet transform of CDF(2,2). Based on the power distribution in different scales, an adaptive algorithm is proposed in this paper, whereby the coefficients are adjusted non-linearly. The particle information can be well retained while the useless background is removed. In this way, satisfactory binary image can be obtained for further analysis of the sediment particle.

Objectives: Magnetic drug targeting offers the latest popular alternative option to deliver magnetic drug carriers into targeting region body parts through manipulation of an external magnetic field. However, the effectiveness of using an electromagnetic field to manipulate and directing magnetic particles is yet to be established.

Methods: In this paper, a homemade cost-effective electromagnet system was built for the purpose of studying the control and directing the magnetic drug carriers. The electromagnet system was built with four electromagnetic sources and tested the capability in directing the particles’ movement in different geometry patterns. Besides that, the creation of the self-rotation of individual magnetic particle clusters was achieved by using fast switching between magnetic fields. This self-rotation allows the possibility of cell apoptosis study to carry out. The system was constructed with four electromagnets integrated with a feedback control system and built to manipulate a droplet of commercially available iron (II, III) oxide nanoparticles to steer the magnetic droplet along different arbitrary trajectories (square, circle, triangle, slanted line) in 2-dimensional.

Results: A dynamic magnetic field of 25 Hz was induced for magnetic nanoparticles rotational effect to observe the cell apoptosis. A profound outcome shows that the declining cell viability of the cell lines by 40% and the morphology of shrinking cells after the exposure of the dynamic magnetic field.

Conclusion: The outcome from the pilot study gives an idea on the laboratory setup serves as a fundamental model for studying the electromagnetic field strength in applying mechanical force to target and to rotate for apoptosis on cancer cell line study.

Physical mechanisms of laser cleaning of solid surface from soiling particles and films are discussed. Dry laser cleaning of surface from particles is considered to be a result of inertial force, appearing due to thermal expansion of absorbing particles and/or substrate (shaking-off mechanism). Steam laser cleaning is considered for the cases of absorbing particles and absorbing substrate. In the latter case, peculiarities of bubble formation in the liquid layer under the conditions of ns laser action are analyzed. Laser cleaning of surfaces from films by shaking-off and buckling mechanisms (due to thermal tension) is considered. Conditions of the action of each of them are defined. Other physical mechanisms, blasting and evaporation, are briefly discussed.

Novel processes for fabricating micro/nano sized oxide devices employing self-assembled monolayers (SAM) were developed. SAM of PTCS (phenyltrichlorosilane) was modified to have a phenyl / hydroxyl-group pattern by UV irradiation using a photomask and was used as a template to arrange inorganic fine particles. Surface modification of micro/nano sized inorganic particles and chemical reactions between those particles and SAM were studied. Two-dimensional arrangement of functional particles on a SAM in a controlled manner through the formation of strong chemical bonds, such as amide or ester bonds, can be applied to the future microelectronics and photonics.

Traveling backward in time along the timeline of the Universe, we underline what is known experimentally, how sound is our understanding at various moments of its evolution and, towards the origin, at which point hypotheses start to replace certainties.

About 30 years ago, I was among several students mentored by Professor Yang at Stony Brook to enter the field of particle accelerator physics. Since then, I have been fortunate to work on several major accelerator projects in USA and in China, guided and at times directly supported by Professor Yang. The field of accelerator physics is flourishing worldwide both providing indispensable tools for fundamental physics research and covering an increasingly wide spectrum of applications beneficial to our society.

We investigate on dynamic properties of particles in fluidized bed for separation with considering on gravity force, flotation, drag force and additional mass force for particles. The kinetic equations of particles in fluidized beds are built in detail based on the dynamic equations. It is found that the velocity of falling in fluidized bed can be described by hyperbolic tangent function and the distance of falling is described by the natural logarithm function. The results show that the particle size and the rate of density between the particle and the fluidized bed are the best of all basic factors in the course of efficiency particle separations. The theoretical study is pertinent to the application of mineral processing and efficient separations for fluidized bed.