365 research outputs found
Apple Tree Responses to Deficit Irrigation Combined with Periodic Applications of Particle Film or Abscisic Acid
The objective of this study was to determine if the application of two antitranspirant compounds would moderate water deficit stress effects on physiological responses of “Granny Smith”, “Royal Gala” and “Golden Delicious” apple (Malus domestica Borkh.) trees on MM106 rootstock that occur during deficit irrigation. Uniform trees were grown in pots under water supply regimes of 30%, 60%, and 80% depletion of available water (DAW) before irrigation to runoff and received applications of kaolin particle film (PF) or abscisic acid (ABA) at 0, 30 and 60 days. At 120 days, genotype and deficit irrigation affected nearly all leaf traits, but antitranspirant treatment had no significant effects. As the % DAW increased, the net photosynthetic rate (Pn), transpiration rate (T), stomatal conductance, leaf water and pressure potential, variable-to-maximal chlorophyll fluorescence, leaf number, and leaf N, P and K contents were reduced. A significant genotype by deficit irrigation interaction was evident on T, water use efficiency (WUE), and leaf osmotic pressure potential. A significant deficit irrigation by antitranspirant interaction was evident on only leaf Pn, with PF and ABA reducing it at 30% DAW and only PF reducing it at 80% DAW. However, the periodic use of PF or ABA during deficit irrigation did not alleviate most physiological effects of water deficit stress due to deficit irrigation
Measurement of the Flux of Ultrahigh Energy Cosmic Rays from Monocular Observations by the High Resolution Fly's Eye Experiment
We have measured the cosmic ray spectrum above 10^17.2 eV using the two air
fluorescence detectors of the High Resolution Fly's Eye observatory operating
in monocular mode. We describe the detector, photo-tube and atmospheric
calibrations, as well as the analysis techniques for the two detectors. We fit
the spectrum to a model consisting of galactic and extra-galactic sources.Comment: 4 pages, 4 figures. Uses 10pt.rtx, amsmath.sty, aps.rtx, revsymb.sty,
revtex4.cl
On astrophysical solution to ultra high energy cosmic rays
We argue that an astrophysical solution to UHECR problem is viable. The
pectral features of extragalactic protons interacting with CMB are calculated
in model-independent way. Using the power-law generation spectrum as the only assumption, we analyze four features of the proton
spectrum: the GZK cutoff, dip, bump and the second dip. We found the dip,
induced by electron-positron production on CMB, as the most robust feature,
existing in energy range eV. Its shape is
stable relative to various phenomena included in calculations. The dip is well
confirmed by observations of AGASA, HiRes, Fly's Eye and Yakutsk detectors. The
best fit is reached at , with the allowed range 2.55 - 2.75. The
dip is used for energy calibration of the detectors. After the energy
calibration the fluxes and spectra of all three detectors agree perfectly, with
discrepancy between AGASA and HiRes at eV being not
statistically significant. The agreement of the dip with observations should be
considered as confirmation of UHE proton interaction with CMB. The dip has two
flattenings. The high energy flattening at eV
automatically explains ankle. The low-energy flattening at eV provides the transition to galactic cosmic rays. This transition is
studied quantitatively. The UHECR sources, AGN and GRBs, are studied in a
model-dependent way, and acceleration is discussed. Based on the agreement of
the dip with existing data, we make the robust prediction for the spectrum at
eV to be measured in the nearest future by
Auger detector.Comment: Revised version as published in Phys.Rev. D47 (2006) 043005 with a
small additio
An upper limit on the electron-neutrino flux from the HiRes detector
Air-fluorescence detectors such as the High Resolution Fly's Eye (HiRes)
detector are very sensitive to upward-going, Earth-skimming ultrahigh energy
electron-neutrino-induced showers. This is due to the relatively large
interaction cross sections of these high-energy neutrinos and to the
Landau-Pomeranchuk-Migdal (LPM) effect. The LPM effect causes a significant
decrease in the cross sections for bremsstrahlung and pair production, allowing
charged-current electron-neutrino-induced showers occurring deep in the Earth's
crust to be detectable as they exit the Earth into the atmosphere. A search for
upward-going neutrino-induced showers in the HiRes-II monocular dataset has
yielded a null result. From an LPM calculation of the energy spectrum of
charged particles as a function of primary energy and depth for
electron-induced showers in rock, we calculate the shape of the resulting
profile of these showers in air. We describe a full detector Monte Carlo
simulation to determine the detector response to upward-going
electron-neutrino-induced cascades and present an upper limit on the flux of
electron-neutrinos.Comment: 13 pages, 3 figures. submitted to Astrophysical Journa
Search for Point Sources of Ultra-High Energy Cosmic Rays Above 40 EeV Using a Maximum Likelihood Ratio Test
We present the results of a search for cosmic ray point sources at energies
above 40 EeV in the combined data sets recorded by the AGASA and HiRes stereo
experiments. The analysis is based on a maximum likelihood ratio test using the
probability density function for each event rather than requiring an a priori
choice of a fixed angular bin size. No statistically significant clustering of
events consistent with a point source is found.Comment: 7 pages, 7 figures. Accepted for publication in The Astrophysical
Journa
Search for Correlations between HiRes Stereo Events and Active Galactic Nuclei
We have searched for correlations between the pointing directions of
ultrahigh energy cosmic rays observed by the High Resolution Fly's Eye
experiment and Active Galactic Nuclei (AGN) visible from its northern
hemisphere location. No correlations, other than random correlations, have been
found. We report our results using search parameters prescribed by the Pierre
Auger collaboration. Using these parameters, the Auger collaboration concludes
that a positive correlation exists for sources visible to their southern
hemisphere location. We also describe results using two methods for determining
the chance probability of correlations: one in which a hypothesis is formed
from scanning one half of the data and tested on the second half, and another
which involves a scan over the entire data set. The most significant
correlation found occurred with a chance probability of 24%.Comment: 13 pages, 1 table, 5 figure
Combined Microscopy, Calorimetry and X-ray Scattering Study of Fluorinated Dimesogens
The material FDO11DFCB3 (compound 2 in this work) remains the only example of a liquid-crystalline material to exhibit a phase transition from the heliconical twist-bend phase into a lamellar smectic A mesophase, additionally this material exhibits a previously unidentified mesophase. We have prepared and characterised several homologues of this compound, with each material subjected to an in-depth analysis by optical microscopy, calorimetry and small angle X-ray scattering studies. Despite FDO11DFCB3 being similar in chemical structure to the novel materials presented herein its liquid-crystalline behaviour is rather different, indicating an unexpected sensitivity of the twist-bend phase to molecular structure
Search for Global Dipole Enhancements in the HiRes-I Monocular Data above 10^{18.5} eV
Several proposed source models for Ultra-High Energy Cosmic Rays (UHECRs)
consist of dipole distributions oriented towards major astrophysical landmarks
such as the galactic center, M87, or Centaurus A. We use a comparison between
real data and simulated data to show that the HiRes-I monocular data for
energies above 10^{18.5} eV is, in fact, consistent with an isotropic source
model. We then explore methods to quantify our sensitivity to dipole source
models oriented towards the Galactic Center, M87, and Centaurus A.Comment: 17 pages, 31 figure
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