Analytical performance of an r.f. capacitively coupled plasma for atomic emission with tip-ring electrode geometry

A low to medium power radiofrequency capacitively coupled plasma is characterized as spectral source for atomic emission. The signal to background ratio and the limits of detection were determined for 19 elements as a function of the plasma torch geometry and the observation point.     

532—Re-evaluation of Feulgen stain for image cytometry: Part II. Application to electrochemically induced chromatin reactivation

Automated cytometry has been proposed by us as an extremely sensitive probe of the electrochemical reactivation of quiescent cells, provided that quantitative and specific staining techniques are available for absorption or fluorescence measurements.A complete re-evaluation is given of cell staining by means of the Feulgen reaction for absorption image cytometry, in order to obtain quantitative specificity for DNA amount and chromatin conformation.The possibility of computing from image cytometry the number of chromatin sites accessible to intercalation of small molecules, which should be related to template activity, was previously anticipated by us on an experimental basis, and is now assessed on a theoretical basis, linking together fluorescence flow cytometry and absorption image cytometry.The Feulgen staining technique has been applied to measure the amount of DNA during reactivation of frog erythrocytes and human lymphocytes induced by exposure to electromagnetic (e.m.) fields and by chemical changes of cell environment.Static automated absorption image analysis of Feulgen stained nuclei allows us to evaluate the onset of DNA synthesis and the effectiveness of the electrochemical stimulus on chromatin conformation.     

First measurement of kaonic helium-3 X-rays

The first observation of the kaonic (3)He 3d→2p transition was made, using slow K- mesons stopped in a gaseous (3)He target. The kaonic atom X-rays were detected with large-area silicon drift detectors using the timing information of the K+K- pairs of ?-meson decays produced by the DAΦNE e+e- collider. The strong interaction shift of the kaonic (3)He 2p state was determined to be -2±2(stat)±4(syst) eV.     

Studies of the {\boldsymbol{\bar{K}}}\boldsymbol{N} interaction at DAΦNE

AMADEUS is an experiment planned to be performed at the DAΦNE e⁺e^? collider of the Frascati National Laboratories (Italy) of INFN, to investigate the antikaon-nuclei interaction at low energies. AMADEUS will perform, for the first time, full-acceptance studies of antikaon interaction in light nuclei, including a complete experimental program for the case of the kaonic nuclear clusters. The study of the absorption of antikaon by the nucleus will provide information concerning the $\bar{K}N$ interaction and the modification of the kaon mass in the nuclear medium. The experiment is being preceded by the study of the hadronic interactions of K^? in the ⁴He of the drift chamber from the KLOE experiment data.     

Quenching of the OH and nitrogen molecular emission by methane addition in an Ar capacitively coupled plasma to remove spectral interference in lead determination by atomic fluorescence spectrometry

A new method is proposed to remove the spectral interference on elements in atomic fluorescence spectrometry by quenching of the molecular emission of the OH radical (A²Σ⁺ → X²Π) and N₂ second positive system (C³Π_u → B³Σ_g) in the background spectrum of medium power Ar plasmas. The experiments were carried out in a radiofrequency capacitively coupled plasma (275 W, 27.12 MHz) by CH₄ addition. The quenching is the result of the high affinity of OH radical for a hydrogen atom from the CH₄ molecule and the collisions of the second kind between nitrogen excited molecules and CH₄, respectively. The decrease of the emission of N₂ second positive system in the presence of CH₄ is also the result of the deactivation of the metastable argon atoms that could excite the nitrogen molecules. For flow rates of 0.7 l min^− 1 Ar with addition of 7.5 ml min^− 1 CH₄, the molecular emission of OH and N₂ was completely removed from the plasma jet spectrum at viewing heights above 60 mm. The molecular emission associated to CH and CH₂ species was not observed in the emission spectrum of Ar/CH₄ plasma in the ultraviolet range. The method was experimented for the determination of Pb at 283.31 nm by atomic fluorescence spectrometry with electrodeless discharge lamp and a multichannel microspectrometer. The detection limit was 35 ng ml^− 1, 2–3 times better than in atomic emission spectrometry using the same plasma source, and similar to that in hollow cathode lamp microwave plasma torch atomic fluorescence spectrometry.     

Classical trajectory calculations with time-dependent forces in heavy-ion collisions

The applicability of a phenomenological time-dependent nucleus-nucleus potential to deep inelastic collisions is studied. We present its general shape and make a particular choice of the diabatic and adiabatic parts. From trajectory calculations we find that the angle-energy correlation is well described when a time-dependent friction force is used. We also compare our results to some TDHF calculations.     

Strouhal-Reynolds number relationship for vortex streets

A rationale for the empirically observed Strouhal-Reynolds number relation for vortex shedding in the wake of a cylinder is provided. This rationale derives from a mechanism of vortex formation observed in numerical simulations of two-dimensional vortex shedding coupled with an order of magnitude estimate of the terms in the vorticity transport equation based on this mechanism.     

PRODUCTION OF PIGMENT NANOPARTICLES USING A WET STIRRED MILL WITH POLYMERIC MEDIA

Pigment nanoparticles with a size range of 10-100 nm were produced from large agglonmerates via a stirred media mill operating in the wet-batch mode and using polymeric media,The effects of several operating variables such as the surfactant concentration,polystyrene media loading.and media size on the pigment size distribution of the product were studied.The process dynamics was also investigated.Dynamic light scattering and electron microscopy were used as the characerization techniques.The polymeric grinding media are found to be effective for the production of pigment nanoparticles.The experimental results suggest the existence of an optimum media size and surfactant concentration,A population balance model of the process reveals a transition from first-order breakage kinetice for rela-large agglomerates split in a first-order kinetics,with a delay period,for the smaller particles.The model implies that large agglomerates split in a first-order fashion whereas the breakage of individual naoparticles may depend on induced fatigue of the particles.