Electromagnetic pulse compression and energy localization in quantum plasmas

The evolution of the intensity of a relativistic laser beam propagating through a dense quantum plasma is investigated, by considering different plasma regimes. A cold quantum fluid plasma and then a thermal quantum description(s) is (are) adopted, in comparison with the classical case of reference. Considering a Gaussian beam cross-section, we investigate both the longitudinal compression and lateral/longitudinal localization of the intensity of a finite-radius electromagnetic pulse. By employing a quantum plasma fluid model in combination with Maxwell's equations, we rely on earlier results on the quantum dielectric response, to model beam-plasma interaction. We present an extensive parametric investigation of the dependence of the longitudinal pulse compression mechanism on the electron density in cold quantum plasmas, and also study the role of the Fermi temperature in thermal quantum plasmas. Our numerical results show pulse localization through a series of successive compression cycles, as the pulse propagates through the plasma. A pulse of 100 fs propagating through cold quantum plasma is compressed to a temporal size of approximate to 1.35 attosecond and a spatial size of approximate to 1.08 10(-3) cm. Incorporating Fermi pressure via a thermal quantum plasma model is shown to enhance localization effects. A 100 fs pulse propagating through quantum plasma with a Fermi temperature of 350 K is compressed to a temporal size of approximate to 0.6 attosecond and a spatial size of approximate to 2.4 10(-3) cm. (c) 2010 Elsevier B.V. All rights reserved.

Endogenous expression and localization of myostatin and its relation to MHC distribution in C2C12 skeletal muscle cells

Myostatin is a negative regulator of skeletal muscle growth. We have previously reported that recombinant myostatin protein inhibits DNA and protein synthesis in C2C12 cells. Our objective was to assess if C2C12 cells express myostatin, determine its sub-cellular localization and the developmental stage of C2C12 cells in which myostatin mRNA and protein are expressed. To study the endogenous expression of myostatin, C2C12 myoblasts were allowed to progress to myotubes, and changes in the levels of endogenous myostatin mRNA expression were determined by RT-PCR. The myostatin protein and the two major myosin heavy chain (MHC) isoforms (MHC-I and -II) were determined by Western blot. Confirmation of the relative MHC expression patterns was obtained by a modified polyacrylamide gel electropheretic (PAGE) procedure. Imunofluorescence staining was employed to localize the site of myostatin expression and the relative distribution of the MHC isoforms. Co-expression of these proteins was studied using a dual staining approach. Expression of myostatin mRNA was found in myotubes but not in myoblasts. Myostatin protein was seen in most but not all, of the nuclei of polynucleated fibers expressing MHC-II, and myostatin was detected in the cytoplasm of myotube. The localization of myostatin protein in myotube nuclei was confirmed by Western blot of isolated nuclear and cytoplasmic fractions. Incubation of C2C12 myotubes with graded doses of dexamethasone dose-dependently increased the intensity of nuclear myostatin immunostaining and also resulted in the appearance of cytoplasmic expression. In conclusion, myostatin was expressed mostly in C2C12 myotubes nuclei expressing MHC-II. Its predominant

Morphology and localization of interstitial cells in the guinea pig bladder: structural relationships with smooth muscle and neurons.

PURPOSE: In the current study we examined the location of interstitial cell of Cajal (ICC)-like cells in the guinea pig bladder wall and studied their structural interactions with nerves and smooth muscle cells. MATERIALS AND METHODS: Whole mount samples and cryosections of bladder tissue were labeled with primary and fluorescent secondary antibodies, and imaged using confocal and multiphoton microscopy. RESULTS: Kit positive ICC-like cells were located below the urothelium, in the lamina propria region and throughout the detrusor. In the suburothelium they had a stellate morphology and appeared to network. They made connections with nerves, as shown by double labeling experiments with anti-kit and anti-protein gene product 9.5. A network of vimentin positive cells was also found, of which many but not all were kit positive. In the detrusor kit positive cells were most often seen at the edge of smooth muscle bundles. They were elongated with lateral branches, running in parallel with the bundles and closely associated with intramural nerves. Another population of kit positive cells was seen in the detrusor between muscle bundles. These cells had a more stellate-like morphology and made connections with each other. Kit positive cells were seen tracking nerve bundles and close to intramural ganglia. Vimentin positive cells were present in the detrusor, of which some were also kit positive. CONCLUSIONS: There are several populations of ICC-like cells throughout the guinea pig bladder wall. They differ in morphology and orientation but all make connections with intramural nerves and in the detrusor they are closely associated with smooth muscle cells.

On the observation of the fine structure effect in non- relativistic (e, 2e) processes

The spin asymmetry arising in an (e,2e) process using spin- polarized incoming electrons with non-relativistic energies is shown to be dominated by the fine structure effect if a suitable kinematical regime is chosen. Calculations in the distorted wave Born approximation (DWBA) for both the triple differential cross-section and the spin asymmetry are presented for the inner shell ionization of argon. This process would provide an accessible target for existing experimental set-ups.

Spin asymmetries in spatially resolved processes of ionization of heavy atoms by relativistic electrons

The triple-differential cross section for ionization of a heavy atom is shown to depend on the spin of the incident electron even if this is polarized entirely parallel or antiparallel to its direction of propagation, the atom is unpolarized, and the spins of the ejected electrons are not resolved. Quantitative predictions for the spin asymmetry are presented in a relativistic distorted-wave Born approximation. Simple physical models are introduced to understand both these results and further symmetry properties involving the reversal of a spatial momentum component also.

On the electron impact ionization of multi-charged ions: a theoretical investigation of relativistic effects

The electron impact ionization of highly charged ions is investigated. Using a relativistic distorted wave Born approximation, we explore the possible effects that should be observable in a high-energy electron impact ionization (e, 2e) coincidence experiment involving multi-charged ions. We present calculations of triple-differential cross sections. We will focus on relativistic and distortion effects and consider geometries where these may be easily observed.

Electron impact excitation of A1 XIII: A relativistic approach

Energy levels, radiative rates, collision strengths, and effective collision strengths for all transitions up to and including the n = 5 levels of AlXIII have been computed in the j j coupling scheme including relativistic effects. All partial waves with angular momentum J less than or equal to 60 have been included, and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths are tabulated at energies above thresholds in the range 170.0 less than or equal to E less than or equal to 300.0 Ryd, and results for effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are tabulated over a wide temperature range of 4.4 less than or equal to log T-e less than or equal to 6.8 K. The importance of including relativistic effects in a calculation is discussed in comparison with the earlier available non-relativistic results.

Relativistic allowed and forbidden transition probabilities for fluorine-like Fe XVIII

Energy levels and the corresponding transition probabilities for allowed and forbidden transitions among the levels of the ground configuration and first 23 excited configurations of fluorine-like Fe XVIII have been calculated using the multiconfigurational Dirac-Fock GRASP code. A total of 379 lowest bound levels of Fe XVIII is presented, and the energy levels are identified in spectroscopic notations. Transition probabilities, oscillator strengths and line strengths for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transitions among these 379 levels are also presented. The calculated energy levels and transition probabilities are compared with experimental data.

Energy dependence for pair production with electron capture in relativistic heavy-ion collisions

In 'Charge transfer from the negative-energy continuum: alternative mechanism for pair production in relativistic atomic collisions', Eichler (1995 Phys. Rev. Lett. 75 3653) proposes an alternative mechanism for capture by pair production, and from it derives an analytic expression for the total cross section with a surprisingly strong energy dependence. We show that, in fact, there is no alternative mechanism; rather the above mechanism may be more transparently viewed as an ionization-like transition in one centre with inclusion of continuum distortion by the second centre. We further show that to Centre the initial and final states on the target and projectile leads to confusion in the momentum transfer vectors, and hence, respectively that the alleged high-energy behaviour is erroneous.

Pair production and electron capture in relativistic heavy-ion collisions

Results are presented for simulations of electron-positron pair production in relativistic heavy-ion collisions leading to electron capture and positron ejection. We apply a two-center relativistic continuum distorted-wave model to represent the electron or positron dynamics during the collision process. The results are compared with experimental cross-section data for La57+ and Au79+ impact on gold, silver, and copper targets. The theory is in good agreement with experiment for La57+ impact, verifying the result that the process increases in importance with both collision energy and target atomic number, and improves upon previous simulations of this process.