Excitation Intensity Driven PL Shifts of SiGe Islands on Patterned and Planar Si(001) Substrates: Evidence for Ge-rich Dots in Islands

For randomly nucleated SiGe/Si(001) islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber. We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra. The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Electron Generation and Transport using Second Harmonic Laser Pulses for Fast Ignition Laser Fusion Energy

A team of University of Alberta researchers, in collaboration with an international team of investigators, has spearheaded an experiment to study the generation and transport of MeV electrons produced by ultra-high intensity second harmonic Nd:Glass laser pulses. Intensities of up to 5 x I O’ 9 W cm2 have been used to irradiate a variety of targets to investigate the conversion efficiency into MeV energy electrons, as well as the energy spectrum and angular divergence of such electrons. Their transport through a cone tip simulating the generation of an energetic electron beam for the fast ignition of a laser-compressed fuel core was also measured. The experiments were carried out at the Titan high intensity 1aser facility located at the Lawrence Livermore National Laboratory. The experiment is the first step towards evaluating the potential effectiveness of using prepulse-free shorter wavelength second harmonic laser pulses as ignition sources for Fast Ignition Fusion Energy

Measurement of Inclusive Monmentum Spectra and Multiplicity Distributions of Charged Particles at s∼2−5\sqrt{s}\sim 2-5 GeV

Inclusive momentum spectra and multiplicity distributions of charged particles measured with BESII detector at center of mass energies of 2.2,2.6,3.0,3.2,4.6 and 4.8 GeV are presented. Values of the second binomial moment, $R_2$, obtained from the multiplicity distributions are reported. These results are compared with both experimental data from high energy $e^+e^-$, $ep$ and $p\bar{p}$ experiments and QCD calculations.Comment: 9 pages, 7 figures, 3 tables, it will be submitted to PR

Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2

Mechanical and fresh properties of sustainable oil palm shell lightweight concrete incorporating palm oil fuel ash

Available online 23 December 2015In this investigation, agro-solid waste materials from the palm oil industry such as oil palm shell (OPS) and palm oil fuel ash (POFA) were utilized to replace conventional concrete-making materials to produce lightweight concrete. The OPS was used as replacement for conventional coarse aggregate while ground POFA was used at partial cement replacement levels of up to 25%. The inclusion of POFA up to 25% did not detrimentally affect the fresh concrete properties while the use of POFA at 10-15% replacement levels improved the compressive strength of OPS concrete (OPSC). Although there was little effect of POFA on the modulus of elasticity, increased POFA replacement levels led to reduction in both the splitting and flexural tensile strengths of OPSC. The evaluation of the cost and eco-efficiencies showed that inclusion of 10% POFA gave the most optimum performance in terms of the sustainability of the OPSC.Mohammad Momeen Ul Islam, Kim Hung Mo, U. Johnson Alengaram, Mohd Zamin Jumaa