Dynamic polarization potential due to ⁶Li breakup on ¹²C

For 6Li scattering from 12C at five laboratory energies from 90 to 318 MeV, we study the dynamic polarization potential, DPP, due to the breakup of the projectile. The breakup is evaluated using standard continuum discretized coupled-channels formalism applied to a two-body cluster model of the projectile. The DPP is evaluated over a wide radial range using both direct S-matrix-to-potential inversion and trivially equivalent local potential methods which yield substantially and systematically different results. The radius at which the real DPP changes from external repulsion to interior attraction varies systematically with energy. This should be experimentally testable because, according to notch tests, this crossover radius is within a radial range to which elastic scattering should be sensitive. The imaginary DPP has an emissive (generative) region at the lower energies; this may be associated with counterintuitive properties of |SL|

Significant features of ⁸B scattering from ²⁰⁸Pb at 170.3 MeV

The scattering of proton-halo nucleus 8B from 208Pb at 170.3 MeV is shown to reveal a distinctive pattern in the change in |SL| that is induced by coupling to breakup channels. The same pattern had been found for 8B scattering from 58Ni at 30 MeV, an energy near the Coulomb barrier, and has been linked to various other respects in which scattering for this proton-halo nucleus differs from that of other light, weakly bound nuclei. The increase in |SL | forL < 80, induced by breakup coupling, is associated with a substantial repulsive region in the dynamic polarization potential as determined by exact inversion. This repulsion appears to reduce the penetration of the projectile into the absorptive region of the interaction. This accounts for the fact that the increase in the total reaction cross section, due to breakup, is much less than the breakup cross section, and is consistent with the relatively small effect of breakup on the elastic scattering angular distribution compared with the large breakup cross section

Dependence of heat transport on the strength and shear rate of prescribed circulating flows

We study numerically the dependence of heat transport on the maximum velocity and shear rate of physical circulating flows, which are prescribed to have the key characteristics of the large-scale mean flow observed in turbulent convection. When the side-boundary thermal layer is thinner than the viscous boundary layer, the Nusselt number (Nu), which measures the heat transport, scales with the normalized shear rate to an exponent 1/3. On the other hand, when the side-boundary thermal layer is thicker, the dependence of Nu on the Peclet number, which measures the maximum velocity, or the normalized shear rate when the viscous boundary layer thickness is fixed, is generally not a power law. Scaling behavior is obtained only in an asymptotic regime. The relevance of our results to the problem of heat transport in turbulent convection is also discussed.Comment: 7 pages, 7 figures, submitted to European Physical Journal

Strength and Microstructure of Geopolymer Based on Fly Ash and Metakaolin

The production of Portland cement is widely regarded as a major source of greenhouse gas emissions. This contributes to 6–7% of total CO₂ emissions, according to the International Energy Agency. As a result, several efforts have been made in recent decades to limit or eliminate the usage of Portland cement in concrete. Geopolymer has garnered a lot of attention among the numerous alternatives due to its early compressive strength, low permeability, high chemical resistance, and great fire-resistant behaviour. This study looks at the strength and microstructure of geopolymer based on fly ash and a combination of metakaolin and fly ash. Compressive strengths were measured at 7, 14, and 28 days, and microstructure was examined using SEM and XRD

Energy absorption by polymer crazing

During the past thirty years, a tremendous amount of research was done on the development of crazing in polymers. The phenomenon of crazing was recognized as an unusual deformation behavior associated with a process of molecular orientation in a solid to resist failure. The craze absorbs a fairly large amount of energy during the crazing process. When a craze does occur the surrounding bulk material is usually stretched to several hundred percent of its original dimension and creates a new phase. The total energy absorbed by a craze during the crazing process in creep was calculated analytically with the help of some experimental measurements. A comparison of the energy absorption by the new phase and that by the original bulk uncrazed medium is made

Mihai Gheorghiade, MD-Life and Concepts

How do you capture an idea, shape it, and then bring it into the world? Of his many talents, this ability was a fundamental characteristic of Mihai Gheorghiade. A quick glance through PubMed confirms his prodigious output, likely to overwhelm any novice or even expert scholar. His contribution to heart failure, especially acute heart failure (AHF), is profound, He authored several major concepts in acute heart failure, disseminated further by his students. Most concepts remained indelibly linked to his name: Digoxin trials research(1–3), AHFS (acute heart failure syndromes) definition(4), hemodynamic congestion(5), hospitalized heart failure (HHF) (6), the vulnerable phase(7,8), neutral hemodynamic agents(9), registries(10–12) and pre-trial registries(13), the “6-axis model”(14) and then the “8-axis model”(15). His work shaped the field of AHF

A comparison of high temperature fatigue crack propagation in various sub-solvus heat treated turbine disc alloys

The microstructure and fatigue performance of three sub-solvus heat treated nickel based disc superalloys for turbine disc applications are reported. The alloy variants studied are RR1000, N18 and Udimet 720 Low Interstitial (U720Li), with the latter tested both in a standard and large grain variant (LG). Their microstructures are examined in terms of grain and gamma prime size. Fatigue crack growth (FCG) rates for all materials at 650ºC show that RR1000 provides the best performance, followed by U720Li-LG, N18 and U720Li. In general, the failure modes become increasingly intergranular with increasing ?K. Some of the variations in FCG rate between the alloys are due to reduction in grain boundary oxidation processes with increased grain size, but more subtle interplays between grain boundary character, alloy composition and slip character are also importan

Effects of initial flow velocity fluctuation in event-by-event (3+1)D hydrodynamics

Hadron spectra and elliptic flow in high-energy heavy-ion collisions are studied within a (3+1)D ideal hydrodynamic model with fluctuating initial conditions given by the AMPT Monte Carlo model. Results from event-by-event simulations are compared with experimental data at both RHIC and LHC energies. Fluctuations in the initial energy density come from not only the number of coherent soft interactions of overlapping nucleons but also incoherent semi-hard parton scatterings in each binary nucleon collision. Mini-jets from semi-hard parton scatterings are assumed to be locally thermalized through a Gaussian smearing and give rise to non-vanishing initial local flow velocities. Fluctuations in the initial flow velocities lead to harder transverse momentum spectra of final hadrons due to non-vanishing initial radial flow velocities. Initial fluctuations in rapidity distributions lead to expanding hot spots in the longitudinal direction and are shown to cause a sizable reduction of final hadron elliptic flow at large transverse momenta.Comment: 17 pages in RevTex, 18 figures, final version published in PR