551 research outputs found
History of the Study of Theology
Traces the study of theology from its beginning until the beginning of the 20th centur
History of the Study of Theology
Traces the study of theology from its beginning until the beginning of the 20th centur
Separation of river networkâscale nitrogen removal among the main channel and two transient storage compartments
Transient storage (TS) zones are important areas of dissolved inorganic nitrogen (DIN) processing in rivers. We assessed sensitivities regarding the relative impact that the main channel (MC), surface TS (STS), and hyporheic TS (HTS) have on network denitrification using a model applied to the Ipswich River in Massachusetts, United States. STS and HTS connectivity and size were parameterized using the results of in situ solute tracer studies in firstâ through fifthâorder reaches. DIN removal was simulated in all compartments for every river grid cell using reactivity derived from Lotic Intersite Nitrogen Experiment (LINX2) studies, hydraulic characteristics, and simulated discharge. Model results suggest that although MCâtoâSTS connectivity is greater than MCâtoâHTS connectivity at the reach scale, at basin scales, there is a high probability of water entering the HTS at some point along its flow path through the river network. Assuming our best empirical estimates of hydraulic parameters and reactivity, the MC, HTS, and STS removed approximately 38%, 21%, and 14% of total DIN inputs during a typical base flow period, respectively. There is considerable uncertainty in many of the parameters, particularly the estimates of reaction rates in the different compartments. Using sensitivity analyses, we found that the size of TS is more important for DIN removal processes than its connectivity with the MC when reactivity is low to moderate, whereas TS connectivity is more important when reaction rates are rapid. Our work suggests a network perspective is needed to understand how connectivity, residence times, and reactivity interact to influence DIN processing in hierarchical river systems
The Angular Power Spectrum of BATSE 3B Gamma-Ray Bursts
We compute the angular power spectrum C(sub l) from the BATSE 3B catalog of 1122 gamma-ray bursts and find no evidence for clustering on any scale. These constraints bridge the entire range from small scales (which probe source clustering and burst repetition) to the largest scales (which constrain possible anisotropics from the Galactic halo or from nearby cosmological large-scale structures). We develop an analysis technique that takes the angular position errors into account. For specific clustering or repetition models, strong upper limits can be obtained down to scales l approx. equal to 30, corresponding to a couple of degrees on the sky. The minimum-variance burst weighting that we employ is visualized graphically as an all-sky map in which each burst is smeared out by an amount corresponding to its position uncertainty. We also present separate bandpass-filtered sky maps for the quadrupole term and for the multipole ranges l = 3-10 and l = 11-30, so that the fluctuations on different angular scales can be inspected separately for visual features such as localized 'hot spots' or structures aligned with the Galactic plane. These filtered maps reveal no apparent deviations from isotropy
The Angular Power Spectrum of BATSE 3B Gamma-Ray Bursts
We compute the angular power spectrum C1 from the BATSE 3B catalog of 1122 gamma-ray burts and find no evidence of clustering on any scale. These constraints bridge the entire range from samall scales (which probe source clustering and burst repetition) to the largest scales (which constrain possible anisotropies from the Galactic hal or from nearby cosmological large-scale structures). We develop an analysis tecnique that takes the angular position errors into account. For specific clustering or repetition models, strong upper limits can be obtained down to scales l ~ 30, corresponding to abou couple of degrees on the sky. The minimum-variance burst weighting that we employ to visulaized graphically as an all-sky map in which each burts is smeared out by an amount correponding to its position uncertainity. We also present separate bandpas-filtered sky maps for the quadrupole term and for the multipole ranges l = 3-10 and l - 11-30, so that the fluctuations on different angular scales can be inspected separately for visual features such as localized hot spots or structures aligned wit the Galactic plane. These filtered maps reveal no apparent deviations from isotropy
Average Emissivity Curve of BATSE Gamma-Ray Bursts with Different Intensities
Six intensity groups with ~150 BATSE gamma-ray bursts each are compared using
average emissivity curves. Time-stretch factors for each of the dimmer groups
are estimated with respect to the brightest group, which serves as the
reference, taking into account the systematics of counts-produced noise effects
and choice statistics. A stretching/intensity anti-correlation is found with
good statistical significance during the average back slopes of bursts. A
stretch factor ~2 is found between the 150 dimmest bursts, with peak flux
4.1 ph
cm^{-2} s^{-1}. On the other hand, while a trend of increasing stretching
factor may exist for rise fronts for burst with decreasing peak flux from >4.1
ph cm^{-2} s^{-1} down to 0.7 ph cm^{-2} s^{-1}, the magnitude of the
stretching factor is less than ~ 1.4 and is therefore inconsistent with
stretching factor of back slope.Comment: 21 pages, 3 figures. Accepted to Ap
Do Gamma-Ray Burst Sources Repeat?
The demonstration of repeated gamma-ray bursts from an individual source
would severely constrain burst source models. Recent reports (Quashnock and
Lamb 1993; Wang and Lingenfelter 1993) of evidence for repetition in the first
BATSE burst catalog have generated renewed interest in this issue. Here, we
analyze the angular distribution of 585 bursts of the second BATSE catalog
(Meegan et al. 1994). We search for evidence of burst recurrence using the
nearest and farthest neighbor statistic and the two-point angular correlation
function. We find the data to be consistent with the hypothesis that burst
sources do not repeat; however, a repeater fraction of up to about 20% of the
observed bursts cannot be excluded.Comment: ApJ Letters, in press, 13 pages, including three embedded figures.
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