1,270 research outputs found
Study of refractive structure in the inelastic 16O+16O scattering at the incident energies of 250 to 1120 MeV
The data of inelastic 16O+16O scattering to the lowest 2+ and 3- excited
states of 16O have been measured at Elab = 250, 350, 480, 704 and 1120 MeV and
analyzed consistently in the distorted wave Born approximation (DWBA), using
the semi- microscopic optical potentials and inelastic form factors given by
the folding model, to reveal possible refractive structure of the nuclear
rainbow that was identified earlier in the elastic 16O+16O scattering channel
at the same energies. Given the known transition strengths of the 2+ and 3-
states of 16O well determined from the (e,e') data, the DWBA description of the
inelastic data over the whole angular range was possible only if the absorption
in the exit channels is significantly increased (especially, for the
16O+16O(2+) exit channel). Although the refractive pattern of the inelastic
16O+16O scattering was found to be less pronounced compared to that observed in
the elastic scattering channel, a clear remnant of the main rainbow maximum
could still be seen in the inelastic cross section at Elab = 350 - 704 MeV.Comment: 26 pages, 10 figures, Accepted for publication in Nucl. Phys.
Exposure of Vascular Smooth Muscle Cells for Analysis with the Scanning Electron Microscope
There has been interest in using the scanning electron microscope (SEM) to study the structure of tissues obscured by other cellular or non-cellular elements almost since the SEM was first used to examine biological tissues. Such interest includes the vessel wall and, in particular, the vascular smooth muscle cells. This paper presents a review of the three basic methodologies that have been employed to allow examination of the vascular smooth muscle, 1) blunt dissection, 2) digestion and 3) microdissection. Discussion of other perivascular elements was not a focus of this review. Also presented is the application of these different methodologies to different pathophysiologic conditions
Assembly of the Complex between Archaeal RNase P Proteins RPP30 and Pop5
RNase P is a highly conserved ribonucleoprotein enzyme that represents a model complex for understanding macromolecular RNA-protein interactions. Archaeal RNase P consists of one RNA and up to five proteins (Pop5, RPP30, RPP21, RPP29, and RPP38/L7Ae). Four of these proteins function in pairs (Pop5-RPP30 and RPP21–RPP29). We have used nuclear magnetic resonance (NMR) spectroscopy and isothermal titration calorimetry (ITC) to characterize the interaction between Pop5 and RPP30 from the hyperthermophilic archaeon Pyrococcus furiosus (Pfu). NMR backbone resonance assignments of free RPP30 (25 kDa) indicate that the protein is well structured in solution, with a secondary structure matching that observed in a closely related crystal structure. Chemical shift perturbations upon the addition of Pop5 (14 kDa) reveal its binding surface on RPP30. ITC experiments confirm a net 1 : 1 stoichiometry for this tight protein-protein interaction and exhibit complex isotherms, indicative of higher-order binding. Indeed, light scattering and size exclusion chromatography data reveal the complex to exist as a 78 kDa heterotetramer with two copies each of Pop5 and RPP30. These results will inform future efforts to elucidate the functional role of the Pop5-RPP30 complex in RNase P assembly and catalysis
Permeation of CO2 and N2 through glassy poly(dimethyl phenylene) oxide under steady- and presteady-state conditions
Glassy polymers are often used for gas separations because of their high selectivity. Although the dual-mode permeation model correctly fits their sorption and permeation isotherms, its physical interpretation is disputed, and it does not describe permeation far from steady state, a condition expected when separations involve intermittent renewable energy sources. To develop a more comprehensive permeation model, we combine experiment, molecular dynamics, and multiscale reaction–diffusion modeling to characterize the time-dependent permeation of N2 and CO2 through a glassy poly(dimethyl phenylene oxide) membrane, a model system. Simulations of experimental time-dependent permeation data for both gases in the presteady-state and steady-state regimes show that both single- and dual-mode reaction–diffusion models reproduce the experimental observations, and that sorbed gas concentrations lag the external pressure rise. The results point to environment-sensitive diffusion coefficients as a vital characteristic of transport in glassy polymers
Particle-unstable nuclei in the Hartree-Fock theory
Ground state energies and decay widths of particle unstable nuclei are
calculated within the Hartree-Fock approximation by performing a complex
scaling of the many-body Hamiltonian. Through this transformation, the wave
functions of the resonant states become square integrable. The method is
implemented with Skyrme effective interactions. Several Skyrme parametrizations
are tested on four unstable nuclei: 10He, 12O, 26O and 28O.Comment: 5 pages, LaTeX, submitted to Phys. Rev. Let
Targeting atypical protein kinase C iota reduces viability in glioblastoma stem-like cells via a notch signaling mechanism
In a previous study, Protein Kinase C iota (PRKCI) emerged as an important candidate gene for glioblastoma (GBM) stem-like cell (GSC) survival. Here, we show that PKCι is overexpressed and activated in patient derived GSCs compared with normal neural stem cells and normal brain lysate, and that silencing of PRKCI in GSCs causes apoptosis, along with loss of clonogenicity and reduced proliferation. Notably, PRKCI silencing reduces tumor growth in vivo in a xenograft mouse model. PKCι has been intensively studied as a therapeutic target in non-small cell lung cancer, resulting in the identification of an inhibitor, aurothiomalate (ATM), which disrupts the PKCι/ERK signaling axis. However, we show that, although sensitive to pharmacological inhibition via a pseudosubstrate peptide inhibitor, GSCs are much less sensitive to ATM, suggesting that PKCι acts along a different signaling axis in GSCs. Gene expression profiling of PRKCI-silenced GSCs revealed a novel role of the Notch signaling pathway in PKCι mediated GSC survival. A proximity ligation assay showed that Notch1 and PKCι are in close proximity in GSCs. Targeting PKCι in the context of Notch signaling could be an effective way of attacking the GSC population in GBM
Prospectus, October 14, 1981
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Real-time dynamics of the formation of hydrated electrons upon irradiation of water clusters with extreme ultraviolet light
Free electrons in a polar liquid can form a bound state via interaction with the molecular environment. This so-called hydrated electron state in water is of fundamental importance e.g.~in cellular biology or radiation chemistry. Hydrated electrons are highly reactive radicals that can either directly interact with DNA or enzymes, or form highly excited hydrogen (H∗) after being captured by protons. Here, we investigate the formation of the hydrated electron in real-time employing XUV femtosecond pulses from a free electron laser, in this way observing the initial steps of the hydration process. Using time-resolved photoelectron spectroscopy we find formation timescales in the low picosecond range and resolve the prominent dynamics of forming excited hydrogen states
Particle-gamma coincidences and coplanarity in the binary reaction
The reaction 32S (165.4 MeV) + 24Mg is studied using the binary reaction spec- trometer (BRS) coupled to the Euroball germanium array. Particle-particle-gamma and particle-gamma-gamma coincidences have been examined. The Z-identification, position and energy information for binary reaction products are shown together with the Doppler-shift corrected gamma-rays emitted from the fragments. Recent reports of evi- dence for hyper-deformation from angular correlations in similar data are also in- vestigated. Analogous out-of-plane angular correlations are observed but attributed to reactions with the target contaminants 16O and 12C
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