Propfan Test Assessment (PTA)

The objectives of the Propfan Test Assessment (PTA) Program were to validate in flight the structural integrity of large-scale propfan blades and to measure noise characteristics of the propfan in both near and far fields. All program objectives were met or exceeded, on schedule and under budget. A Gulfstream Aerospace Corporation GII aircraft was modified to provide a testbed for the 2.74m (9 ft) diameter Hamilton Standard SR-7 propfan which was driven by a 4475 kw (600 shp) turboshaft engine mounted on the left-hand wing of the aircraft. Flight research tests were performed for 20 combinations of speed and altitude within a flight envelope that extended to Mach numbers of 0.85 and altitudes of 12,192m (40,000 ft). Propfan blade stress, near-field noise on aircraft surfaces, and cabin noise were recorded. Primary variables were propfan power and tip speed, and the nacelle tilt angle. Extensive low altitude far-field noise tests were made to measure flyover and sideline noise and the lateral attenuation of noise. In coopertion with the FAA, tests were also made of flyover noise for the aircraft at 6100m (20,000 ft) and 10,668m (35,000 ft). A final series of tests were flown to evaluate an advanced cabin wall noise treatment that was produced under a separate program by NASA-Langley Research Center

Extended Gari-Krumpelmann model fits to nucleon electromagnetic form factors

Nucleon electromagnetic form factor data (including recent data) is fitted with models that respect the confinement and asymptotic freedom properties of QCD. Gari-Krumpelmann (GK) type models, which include the major vector meson pole contributions and at high momentum transfer conform to the predictions of perturbative QCD, are combined with Hohler-Pietarinen (HP) models, which also include the width of the rho meson and the addition of higher mass vector meson exchanges, but do not evolve into the explicit form of PQCD at high momentum transfer. Different parameterizations of the GK model's hadronic form factors, the effect of including the width of the rho meson and the addition of the next (in mass) isospin 1 vector meson are considered. The quality of fit and the consistency of the parameters select three of the combined HP/GK type models. Projections are made to the higher momentum transfers which are relevant to electron-deuteron experiments. The projections vary little for the preferred models, removing much of the ambiguity in electron-nucleus scattering predictions.Comment: 18pp, 7 figures, using RevTeX with BoxedEPS macros; 1 new figure, minor textual changes; email correspondence to [email protected]

On QCD analysis of stucture function F2γF_2^{\gamma} in alternative approach

The alternative approach to QCD analysis of the photon structure function $F_2^{\gamma}$ is presented. It differs from the conventional one by the presence of the terms which in conventional approach appear in higher orders. We show that this difference concerns also the photonic parton distribution functions. In the alternative approach, the complete LO analysis of $F_2^{\gamma}$ can be performed as all required quantities are known. At the NLO, however, one of the coefficient function is so far not available and thus only the photonic parton distribution function can be computed and compared to those of standard approach. We discuss the numerical difference of these approaches at the LO and the NLO approximation and show that in case of $F_2^{\gamma}$ this difference is non-negligible and may play an important role in the analysis on photon data of the future experiments.Comment: 25 page

The frequency-dependence of drifting subpulse patterns

Drifting subpulse patterns in pulsar signals are frequently interpreted in terms of a model in which a rotating ring of sparks on the polar cap gives rise to emission from regions of the magnetsophere connected to the sparks by dipolar magnetic field lines. The spacing of drift-bands in time depends on the circulation rate of the polar cap pattern, but to first order the longitudinal phase dependence of the subpulse modulation should obey a frequency-independent relation determined by the geometrical configuration in a similar manner to the polarization position angle. We present here observations at 272-1380 MHz of PSR B0320+39 and PSR B0809+74, both of which show nearly linear drift in two longitude regions, separated by a region of reduced modulation and accompanied by a large step in the phase of the subpulse pattern. We show that the observation of Bartel et al. (1981) that the subpulse spacing for PSR B0809+74 was 1.8 times greater at 102.5 MHz than at 1720 MHz is most likely an artifact of the phase step, which is only present at high frequencies. The phase steps can be understood as a consequence of observing overlapping offset images of the polar cap spark pattern. We also detected more complicated, frequency-dependent behaviour that would require that the images do not simply differ by rotation about their centers. Detailed modelling of non-axisymmetric refraction or distorted magnetic fields is suggested as a means of pursuing an explanation for this phenomenon.Comment: 6 pages, 2 figures, accepted to A&

Effect of recent R_p and R_n measurements on extended Gari-Krumpelmann model fits to nucleon electromagnetic form factors

The Gari-Krumpelmann (GK) models of nucleon electromagnetic form factors, in which the rho, omega, and phi vector meson pole contributions evolve at high momentum transfer to conform to the predictions of perturbative QCD (pQCD), was recently extended to include the width of the rho meson by substituting the result of dispersion relations for the pole and the addition of rho' (1450) isovector vector meson pole. This extended model was shown to produce a good overall fit to all the available nucleon electromagnetic form factor (emff) data. Since then new polarization data shows that the electric to magnetic ratios R_p and R_n obtained are not consistent with the older G_{Ep} and G_{En} data in their range of momentum transfer. The model is further extended to include the omega' (1419) isoscalar vector meson pole. It is found that while this GKex cannot simultaneously fit the new R_p and the old G_{En} data, it can fit the new R_p and R_n well simultaneously. An excellent fit to all the remaining data is obtained when the inconsistent G_{Ep} and G_{En} is omitted. The model predictions are shown up to momentum transfer squared, Q^2, of 8 GeV^2/c^2.Comment: 14 pages, 8 figures, using RevTeX4; email correspondence to [email protected] ; minor typos corrected, figures added, conclusions extende

Heterologous oligonucleotide microarrays for transcriptomics in a non-model species; a proof-of-concept study of drought stress in Musa

<p>Abstract</p> <p>Background</p> <p>'Systems-wide' approaches such as microarray RNA-profiling are ideally suited to the study of the complex overlapping responses of plants to biotic and abiotic stresses. However, commercial microarrays are only available for a limited number of plant species and development costs are so substantial as to be prohibitive for most research groups. Here we evaluate the use of cross-hybridisation to Affymetrix oligonucleotide GeneChip^®microarrays to profile the response of the banana (<it>Musa </it>spp.) leaf transcriptome to drought stress using a genomic DNA (gDNA)-based probe-selection strategy to improve the efficiency of detection of differentially expressed <it>Musa </it>transcripts.</p> <p>Results</p> <p>Following cross-hybridisation of <it>Musa </it>gDNA to the Rice GeneChip^®Genome Array, ~33,700 gene-specific probe-sets had a sufficiently high degree of homology to be retained for transcriptomic analyses. In a proof-of-concept approach, pooled RNA representing a single biological replicate of control and drought stressed leaves of the <it>Musa </it>cultivar 'Cachaco' were hybridised to the Affymetrix Rice Genome Array. A total of 2,910 <it>Musa </it>gene homologues with a >2-fold difference in expression levels were subsequently identified. These drought-responsive transcripts included many functional classes associated with plant biotic and abiotic stress responses, as well as a range of regulatory genes known to be involved in coordinating abiotic stress responses. This latter group included members of the ERF, DREB, MYB, bZIP and bHLH transcription factor families. Fifty-two of these drought-sensitive <it>Musa </it>transcripts were homologous to genes underlying QTLs for drought and cold tolerance in rice, including in 2 instances QTLs associated with a single underlying gene. The list of drought-responsive transcripts also included genes identified in publicly-available comparative transcriptomics experiments.</p> <p>Conclusion</p> <p>Our results demonstrate that despite the general paucity of nucleotide sequence data in <it>Musa </it>and only distant phylogenetic relations to rice, gDNA probe-based cross-hybridisation to the Rice GeneChip^®is a highly promising strategy to study complex biological responses and illustrates the potential of such strategies for gene discovery in non-model species.</p

String Effects on Fermi--Dirac Correlation Measurements

We investigate some recent measurements of Fermi--Dirac correlations by the LEP collaborations indicating surprisingly small source radii for the production of baryons in $e^+e^-$-annihilation at the $Z^0$ peak. In the hadronization models there are besides the Fermi--Dirac correlation effect also a strong dynamical (anti-)correlation. We demonstrate that the extraction of the pure FD effect is highly dependent on a realistic Monte Carlo event generator, both for separation of those dynamical correlations which are not related to Fermi--Dirac statistics, and for corrections of the data and background subtractions. Although the model can be tuned to well reproduce single particle distributions, there are large model-uncertainties when it comes to correlations between identical baryons. We therefore, unfortunately, have to conclude that it is at present not possible to make any firm conclusion about the source radii relevant for baryon production at LEP

On the Particle Data Group evaluation of Psi' and chi_c Branching Ratios

I propose a new evaluation of $\psi'(2S)$ and $\chi_c(1P)$ branching ratios which avoids the correlations affecting the current Particle Data Group evaluation. These correlations explain the apparent technique-dependent discrepancies between the available determinations of the ${\cal B}(\chi_c(1P)\to p\bar p)$ and $\Gamma(\chi_c(1P)\to \gamma\gamma)$ under the hypotesis that the current values of the $\psi'(2S)\to\chi_c(1P)\gamma$ branching ratios are overestimated. In the process I also noticed that Particle Data Group has not restated many of the older measurements, when necessary, for the new value of ${\cal B}(J/\psi\to l^+l^-)$, which significantly affects the evaluation of some relevant $\psi'(2S)$ and $\chi_c(1P)$ exclusive branching ratios.Comment: 13 pages. Revised version. Submitted to Phys. Rev.

Pulse-to-pulse intensity modulation and drifting subpulses in recycled pulsars

We report the detection of pulse-to-pulse periodic intensity modulations, in observations of recycled pulsars. Even though the detection of individual pulses was generally not possible due to their low flux density and short duration, through the accumulation of statistics over sequences of 10^5--10^6 pulses we were able to determine the presence and properties of the pulse-to-pulse intensity variations of six pulsars. In most cases we found that the modulation included a weak, broadly quasi-periodic component. For two pulsars the sensitivity was high enough to ascertain that the modulation phase apparently varies systematically across the profile, indicating that the modulation appears as drifting subpulses. We detected brighter than average individual pulses in several pulsars, with energies up to 2--7 times higher than the mean, similar to results from normal pulsars. We were sensitive to giant pulses of a rate of occurrence equal to (and in many instances much lower than) that of PSR B1937+21 at 1400 MHz (~30 times lower than at 430 MHz), but none were detected, indicating that the phenomenon is rare in recycled pulsars.Comment: 15 pages, 17 figures, accepted to A&