Strangeness production in heavy ion collisions at SPS and RHIC within two-source statistical model

The experimental data on hadron yields and ratios in central Pb+Pb and Au+Au collisions at SPS and RHIC energies, respectively, are analysed within a two-source statistical model of an ideal hadron gas. These two sources represent the expanding system of colliding heavy ions, where the hot central fireball is embedded in a larger but cooler fireball. The volume of the central source increases with rising bombarding energy. Results of the two-source model fit to RHIC experimental data at midrapidity coincide with the results of the one-source thermal model fit, indicating the formation of an extended fireball, which is three times larger than the corresponding core at SPS.Comment: Talk at "Strange Quarks in Matter" Conference (Strangeness'2001), September 2001, Frankfurt a.M., German

Annihilation Type Radiative Decays of BB Meson in Perturbative QCD Approach

With the perturbative QCD approach based on $k_T$ factorization, we study the pure annihilation type radiative decays $B^0 \to \phi\gamma$ and $B^0\to J/\psi \gamma$. We find that the branching ratio of $B^0 \to \phi\gamma$ is $(2.7^{+0.3+1.2}_{-0.6-0.6})\times10^{-11}$, which is too small to be measured in the current $B$ factories of BaBar and Belle. The branching ratio of $B^0\to J/\psi \gamma$ is $({4.5^{+0.6+0.7}_{-0.5-0.6}})\times10^{-7}$, which is just at the corner of being observable in the $B$ factories. A larger branching ratio $BR(B_s^0 \to J/\psi \gamma) \simeq 5 \times 10^{-6}$ is also predicted. These decay modes will help us testing the standard model and searching for new physics signals.Comment: 4 pages, revtex, with 1 eps figur

Bulk Rotational Symmetry Breaking in Kondo Insulator SmB6

Kondo insulator samarium hexaboride (SmB6) has been intensely studied in recent years as a potential candidate of a strongly correlated topological insulator. One of the most exciting phenomena observed in SmB6 is the clear quantum oscillations appearing in magnetic torque at a low temperature despite the insulating behavior in resistance. These quantum oscillations show multiple frequencies and varied effective masses. The origin of quantum oscillation is, however, still under debate with evidence of both two-dimensional Fermi surfaces and three-dimensional Fermi surfaces. Here, we carry out angle-resolved torque magnetometry measurements in a magnetic field up to 45 T and a temperature range down to 40 mK. With the magnetic field rotated in the (010) plane, the quantum oscillation frequency of the strongest oscillation branch shows a four-fold rotational symmetry. However, in the angular dependence of the amplitude of the same branch, this four-fold symmetry is broken and, instead, a twofold symmetry shows up, which is consistent with the prediction of a two-dimensional Lifshitz-Kosevich model. No deviation of Lifshitz-Kosevich behavior is observed down to 40 mK. Our results suggest the existence of multiple light-mass surface states in SmB6, with their mobility significantly depending on the surface disorder level.Comment: 15 pages, 9 figure

Parallel processing architecture for computing inverse differential kinematic equations of the PUMA arm

In advanced robot control problems, on-line computation of inverse Jacobian solution is frequently required. Parallel processing architecture is an effective way to reduce computation time. A parallel processing architecture is developed for the inverse Jacobian (inverse differential kinematic equation) of the PUMA arm. The proposed pipeline/parallel algorithm can be inplemented on an IC chip using systolic linear arrays. This implementation requires 27 processing cells and 25 time units. Computation time is thus significantly reduced

Can green LED light do a magical thing to plants?

Red and blue light are the most important in driving photosynthesis to produce adequate yield. It is also believed that green light may contribute to the adaptation to growth. However, the effects of the green light which may trigger specific and necessary responses in plant growth have been underestimated in the past. In this study, lettuce (Lactuca sativa L.) was exposed to different continuous light (CL) conditions for 48 h by combination of red and blue light emitting diodes (LEDs) supplied with/without green LEDs in an environmental controlled growth chamber. Green light supplementation enhanced photosynthetic capacity by increasing net photosynthetic rate (P n), maximal photochemical efficiency (Fv/Fm), electron transport for carbon fixation (JSPII) and chlorophyll content, which led to increases of plant fresh and dry weight under CL treatment. Green light decreased malondialdehyde and H2O2 accumulation by increasing superoxide dismutase (SOD) enzyme, catalase (CAT) enzyme and ascorbate peroxidase (APX) activities after 24 h CL. Supplementary green light was also shown to lead to a significant increase in the expression of the photosynthetic genes Lhcb and psbA from 6 to 12 h and retained higher level compared with other light conditions between 12 and 24 h. The results indicate that the effects of green light on the lettuce plant growth via promoting psbA and Lhcb expression to maintain higher photosynthetic capacity and green light could alleviate the negative effects caused by CL

Continuous light-emitting Diode (LED) lighting for improving food quality

Lighting-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and positive impact compared with other artificial lighting. The combined effects of red/blue or/and green, and white LED light on plant growth and physiology, including chlorophyll fluorescence, nitrate content and phytochemical concentration before harvest, were investigated. The results showed that continuous light (CL) exposure at pre-harvest can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants, and the former is dependent on the spectral composition and continuous light duration. Lettuce plants grown under continuous combined red and blue (with or without green) LED light with a photosynthetic photon flux density (PPFD) at 200 μ mol m-2-s-1 exhibited a remarkable decrease of nitrate contents at 24 h compared to other light treatments. In addition, red and blue light (R:B=4:1) was more effective in facilitating lettuce growth than white LED light at the same PPFD. Moreover, continuous LED light for 24 h significantly enhanced the free-radical scavenging activity and increased phenolic compound concentrations. In this study, we suggest that a period of continuous LED (R/B) with green (G) light exposure is needed in order to decrease nitrate concentrations and enhance lettuce quality. 24 h appears to be the best, but this period should not exceed 48 h. It appears that continuous light could enhance the activity of nitrate reductase leading to a low level of nitrate content in the leaf. However, the reduction of nitrate is considered to be associated with the circadian clock and the light-signaling pathway as well