Positron spectra from internal pair conversion observed in {238}U + {181}Ta collisions

We present new results from measurements and simulations of positron spectra, originating from 238U + 181Ta collisions at beam energies close to the Coulomb barrier. The measurements were performed using an improved experimental setup at the double-Orange spectrometer of GSI. Particular emphasis is put on the signature of positrons from Internal-Pair-Conversion (IPC) processes in the measured e+ energy spectra, following the de-excitation of electromagnetic transitions in the moving Ta-like nucleus. It is shown by Monte Carlo simulations that, for the chosen current sweeping procedure used in the present experiments, positron emission from discrete IPC transitions can lead to rather narrow line structures in the measured energy spectra. The measured positron spectra do not show evidence for line structures within the statistical accuracy achieved, although expected from the intensities of the observed $\gamma$ transitions (E$_{\gamma}~1250-1600$ keV) and theoretical conversion coefficients. This is due to the reduced detection efficiency for IPC positrons, caused by the limited spatial and momentum acceptance of the spectrometer. A comparison with previous results, in which lines have been observed, is presented and the implications are discussed.Comment: LaTeX, 20 pages including 5 EPS figures; Accepted by Eur. Phys.Jour.

Particle Ratios, Equilibration, and the QCD Phase Boundary

We discuss the status of thermal model descriptions of particle ratios in central nucleus-nucleus collisions at ultra-relativistic energy. An alternative to the ``Cleymans-Redlich'' interpretation of the freeze-out trajectory is given in terms of the total baryon density. Emphasis is placed on the relation between the chemical equilibration parameters and the QCD phase boundary. Furthermore, we trace the essential difference between thermal model analyses of data from collisions between elementary particles and from heavy ion collisions as due to a transition from local strangeness conservation to percolation of strangeness over large volumes, as occurs naturally in a deconfined medium. We also discuss predictions of the thermal model for composite particle production.Comment: Contribution to SQM2001 Conference, submitted to J. Phys.

VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars

We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey (SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.Comment: 10 pages, no figure, 3 tables, accepted for publication in PAS

Determining the optimum combination of palm kernel cake and wheat offal as maintaining ration for matured grasscutters (Thryonomus swinderianus)

Twenty (20) female grasscutters at 14 months of age were used for the study, which lasted for ten (10) weeks. The grasscutters were separated into five groups of 4 grasscutters each and fed five (5) diets, which differed in their levels of replacement of wheat offal at 0, 25, 50, 75 and 100% levels with palm kernel cake. Elephant grass and water were served ad libitum. All data were subjected to the analysis of variance. The results showed that forage intake was significantly (P<0.05) higher on the 100% (i.e. no replacement) wheat diet than on other diets. Concentrate (diet) intake and total feed intake were not significantly (P>0.05) affected by the level of replacement of wheat offal with palm kernel cake. The average daily weight gain was significantly (P<0.05) higher among grasscutters fed the 50% replacement diet than among those fed other diets. The results suggest that the synergistic effect of the biological values of wheat offal and palm kernel cake was significantly (P<0.05) higher at the 50% replacement level than at other levels

Effect of daylight hours on performance of growing grasscutters

The grasscutter (Thryonomysswinderianus) holdspromise as a source of increased protein for populations of Sub-Sahara African countries. It is inexpensive to feed and features the feed utilization characteristics of ruminants and monogastrics. It is nocturnal in its activities, especially feeding. This experimentwas carried out to determine the effect of daylight hours or photoperiod on growing grasscutters under intensive rearing conditions. The effect of daylight hours on growing grasscutters was determined using sixteen 8-months old femalegrasscutters. Thegrasscutters were separated into four groups and allotted to four  treatments of varying daylight hours. The treatments included; zero (0) hours of daylight and twenty four (24) hours (6.00 am-6.00 am) of darkness (0L:24D), six antemeridiem (am) hours (6.00 am-12.00 noon) of daylight and eighteen (18) hours (12.00 noon-6.00 am) of darkness(6L(am):18D), six post-meridiem (pm) hours (12.00 noon-6.00 pm) of daylight and eighteen (18) hours (6.00 pm-12.00 noon) of darkness (6L(pm):18D) and twelve (12) hours (6.00 am-6.00 pm) of daylight and twelve (12) hours (6.00pm- 6.00am) of darkness (12L:12D).Allgrasscutters were fedadiet containing 2200kilocalories metabolizable energy perkilogram (KcalME/kg) and crude protein (CP) level of 20%. Cassava root meal and wheat offalwere the main sources of energy, while soybean meal was the main source of protein in the diets. Elephant grass was fed as basal diet.The results showed thatforage, concentrate (diet) and total feed intake, and daily weight gain were significantly (P<0.05) higher under the 6 post-meridiem hours of daylight and 18 hours of darkness (6L(pm):18D) than under other conditions. It was, therefore, concluded that the optimum daylight conditions required for the rearing of growing grasscuttersare the six (6) hours of post-meridiem daylight, followed by eighteen (18) hours of darkness