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At least 37 records · Page 2Linked to original sources
PubMed2004

One-dimensional Langevin models of fluid particle acceleration in developed turbulence.

We make a comparative analysis of some recent one-dimensional Langevin models of the acceleration of a Lagrangian fluid particle in developed turbulent flow. The class of models characterized by random intensities of noises (RIN models) provides a fit to the recent experimental data on the acceleration statistics. We review the model by Laval, Dubrulle, and Nazarenko (LDN) formulated in terms of temporal velocity derivative in the rapid distortion theory approach, and propose its extension due to the RIN framework. The fit of the contribution to fourth-order moment of the acceleration is found to be better than in the other stochastic models. We study the acceleration probability density function conditional on velocity fluctuations implied by the RIN approach to the LDN-type model. The shapes of the conditional distributions and the conditional acceleration variance have been found in a good agreement with the recent experimental data by Mordant, Crawford, and Bodenschatz [Physica D (to be published), e-print physics/0303003].

Journal Article↗
PubMed2004

Future trends in cancer therapy with particle accelerators.

Hadrontherapy is the radiotherapy technique that uses protons, neutrons or carbon ions. Protons and ions, being, heavy' charged particles, allow a more, conformal' treatment than X-rays and thus spare better the surrounding healthy tissues. By now about 35,000 patients have been treated worldwide with protons and about 1,600 with carbon ions. Since few years protontherapy of deep-seated tumours is booming with two hospital centres running in USA and three under construction. Four centres are treating patients in Japan. The list of constructions going on elsewhere is long: two in China, one in Germany, one in Korea, one in Switzerland. But the future hopes for a qualitatively different radiotherapy are centred on carbon ions: they have a larger biological effectiveness than X-rays and protons and are particularly suited to treat radio resistant tumours, as indicated by the encouraging results obtained on about 1,400 patients in HIMAC (Chiba, Japan) and on about 200 patients at GSI (Darmstadt). Two carbon centres are under construction in Europe: one (designed by GSI) in Heidelberg (Germany) and the other (designed by the TERA Foundation, in collaboration with CERN and INFN) in Pave (Italy). Other projects are moving towards the financing phase in Wiener Neustadt (Austria), Lyon (France) and Stockholm (Sweden). The five European projects are collaborating in the framework of ENLIGHT, the European Network for Light ion Therapy.

Forecasting↗
PubMed1985

[The management of particle accelerators in radiotherapy].

In this multicentric survey, the management costs and the technical problems connected with the use of electron accelerators in Radiotherapy are studied. The data were collected by a proper questionnaire and concern 11/35 accelerators in use in Italy, in public hospitals, during the period 1982-1983. The average purchase cost of an accelerator was 1113 milions lire and the amortization cost is 111 milions lire per year. The expenses for the amortization of the cost of the bunker, for ordinary and extraordinary maintenance, for the employed staff and for the electric power respectively, represent the 22%, 5%, 43% and 2% of the total management cost (395 milions lire per year). In 1983 the load per machine was 400 patients and the cost per patient was 1 milion lire. On the average, 4 years are needed from the order to the beginning of the treatments with large differences among centers. The machines average use is 7.1 hours a day and keep 2.8 technicians busy per week. The time wasted by repairs or maintenances increases (+7%) the average duration of stay in hospital of patients. An attentive evaluation of the studied parameters allows us to single out the most significant variables on which is possible to work to increase the efficiency and to reduce the management costs of an accelerator.

Cost-Benefit Analysis↗
PubMed2004

Exposure to ambient particles accelerates monocyte release from bone marrow in atherosclerotic rabbits.

Exposure to air pollution [particulate matter, particles <10 microm (PM(10))] causes a systemic inflammatory response that includes stimulation of the bone marrow (BM) and progression of atherosclerosis. Monocytes are known to play a key role in atherogenesis by migration into subendothelial lesions where they appear as foam cells. The present study was designed to quantify the BM monocyte response in Watanabe heritable hyperlipidemic (WHHL) rabbits after PM(10) exposure. WHHL rabbits were given twice weekly intrapharyngeal instillations of 5 mg of PM(10) for 4 wk to a total of 40 mg and compared with control WHHL or New Zealand White (NZW) rabbits. The thymidine analog 5'-bromo-2'-deoxyuridine was used to label dividing cells in the BM and a monoclonal antibody to identify monocytes in peripheral blood. The transit time of monocytes through the BM was faster in WHHL than in NZW rabbits (30.4 +/- 1.9 h vs. 35.2 +/- 0.9 h, WHHL vs. NZW; P < 0.05). PM(10) instillation exposure increased circulating band cell counts, caused rapid release of monocytes from the BM, and further shortened their transit time through the BM to 23.2 +/- 1.6 h (P < 0.05). The percentage of alveolar macrophages containing particles in the lung correlated with the BM transit time of monocytes (r(2) = 0.45, P <0.05). We conclude that atherosclerosis increases the release of monocytes from the BM, and PM(10) exposure accelerates this process in relation to the amount of particles phagocytosed by alveolar macrophages.

Air Pollution↗
PubMed2006

Lagrangian measurements of inertial particle accelerations in grid generated wind tunnel turbulence.

We describe Lagrangian measurements of water droplets in grid generated wind tunnel turbulence at a Taylor Reynolds number of R(lambda)=250 and an average Stokes number (St) of approximately 0.1. The inertial particles are tracked by a high speed camera moving along the side of the tunnel at the mean flow speed. The standardized acceleration probability density functions of the particles have spread exponential tails that are narrower than those of a fluid particles (St approximately 0) and there is a decrease in the acceleration variance with increasing Stokes number. A simple vortex model shows that the inertial particles selectively sample the fluid field and are less likely to experience regions of the fluid undergoing the largest accelerations. Recent direct numerical simulations compare favorably with these first measurements of Lagrangian statistics of inertial particles in highly turbulent flows.

Journal Article↗
PubMedDate not supplied

Medical use of radiation and particle accelerators.

Recently, medical use of radiation has progressed markedly with the application of newly developed techniques and modalities. And the progress of radiation diagnosis too, has felt the impact of imaging techniques since the introduction of X-ray computerized tomography (X-ray CT). In radiation therapy, efforts have been concentrated on studies to improve local control rates of radioresistant cancers and locally advanced cancers, which remained a problem even after the introduction of megavoltage radiation therapy machines. Particle radiation, characterized by an excellent dose distribution as well as the features of high LET radiation, has been introduced in to clinical research for use in radiation therapy. Other studies with particle radiation suggests that the short lived radioisotopes produced by accelerators will open up a new era for nuclear medicine. This paper looks at the present status and some of the future problems in the medical use of radiation and radioisotopes in Japan.

Computers↗
PubMed2006

Performance studies of particle acceleration for transdermal drug delivery.

We have proposed a transdermal biolistic method to accelerate a powder formulation of drugs to penetrate human skin for the treatment of a range of diseases. One of the key issues for designing and evaluating transdermal biolistic system is ensuing that the powder drugs are delivered into the skin with a controllable velocity range and spatial distribution. The aerodynamics of supersonic nozzles and performance of the delivery system were initially studied, mainly analytically and experimentally. In this paper, computational fluid dynamics is utilized to characterize two existing prototype devices, in order to further investigate the transient gas and particle dynamics in their supersonic nozzles. To validate the implemented numerical approach, calculated pressure histories, two-dimensional flow structures and particle velocity distributions are made and compared with the reported experimental measurements. The key features of gas dynamics, gas-particle interaction and performance of the prototype transdermal biolistics are discussed and interpreted.

Administration, Cutaneous↗
PubMed2006

The status and evolution of plasma Wakefield particle accelerators.

The status and evolution of the electron beam-driven Plasma Wakefield Acceleration scheme is described. In particular, the effects of the radial electric field of the wake on the drive beam such as multiple envelope oscillations, hosing instability and emission of betatron radiation are described. Using ultra-short electron bunches, high-density plasmas can be produced by field ionization by the electric field of the bunch itself. Wakes excited in such plasmas have accelerated electrons in the back of the drive beam to greater that 4 G eV in just 10 cm in experiments carried out at the Stanford Linear Accelerator Centre.

Journal Article↗