203 research outputs found
Biodiversity in drinking water distribution systems:a brief review
In drinking water distribution systems, three groups of living organisms are usually found in the biofilm and circulating water: heterotrophic bacteria, free-living protozoa, and macro-invertebrates. Indirect evidence suggests that protozoa grazing in distribution systems can partially eliminate biomass production and accidental microbiological pollution. This paper examines the biodiversit in drinking water distribution systems
Models for Photon-photon Total Cross-sections
We present here a brief overview of recent models describing the
photon-photon cross-section into hadrons. We shall show in detail results from
the eikonal minijet model, with and without soft gluon summation.Comment: 7 pages, 5 figures, laTeX, requires espcrc2.sty. To appear in the
Proceedings of Photon-99, Freiburg, 23 -27 May 99, labels in the figures
1,3,4,5 corrected, one typo in an equation correcte
Total photoproduction cross-section at very high energy
In this paper we apply to photoproduction total cross-section a model we have
proposed for purely hadronic processes and which is based on QCD mini-jets and
soft gluon re-summation. We compare the predictions of our model with the HERA
data as well as with other models. For cosmic rays, our model predicts
substantially higher cross-sections at TeV energies than models based on
factorization but lower than models based on mini-jets alone, without soft
gluons. We discuss the origin of this difference.Comment: 13 pages, 9 figures. Accepted for publication in EPJC. Changes
concern added references, clarifications of the Soft Gluon Resummation method
used in the paper, and other changes requested by the Journal referee which
do not change the results of the original versio
New physics, the cosmic ray spectrum knee, and cross section measurements
We explore the possibility that a new physics interaction can provide an
explanation for the knee just above GeV in the cosmic ray spectrum. We
model the new physics modifications to the total proton-proton cross section
with an incoherent term that allows for missing energy above the scale of new
physics. We add the constraint that the new physics must also be consistent
with published cross section measurements, using cosmic ray observations,
an order of magnitude and more above the knee. We find that the rise in cross
section required at energies above the knee is radical. The increase in cross
section suggests that it may be more appropriate to treat the scattering
process in the black disc limit at such high energies. In this case there may
be no clean separation between the standard model and new physics contributions
to the total cross section. We model the missing energy in this limit and find
a good fit to the Tibet III cosmic ray flux data. We comment on testing the new
physics proposal for the cosmic ray knee at the Large Hadron Collider.Comment: 17 pages, 4 figure
Hybrid poplar plantation establishment in Saskatchewan: first year results
Non-Peer ReviewedThe production of Short-Rotation Woody Crops (SRWC) has been growing steadily throughout
North America. In Saskatchewan, interest is focused on developing hybrid poplar (var.
‘Walker’) plantations for an expanding fibre industry, and as a means to diversify farm income
and possibly to increase sequestered carbon. Preliminary results from a small 6 year-old
plantation suggest that there is good potential for operational-scale hybrid poplar production over
a 15 to 20 year rotation period. Larger-scale field trials were established in the spring of 2002 on
two sites in the Meadow Lake region, to assess and compare select silvicultural practices that are
regarded to enhance the growth of hybrid poplars. After one growing season, both types of
rooted stock (cuttings and plugs) showed superior survivability (~92 %) compared to non-rooted
cuttings (~40 %), underscoring the reduced risk in planting rooted stock, especially during dry
years. Measurements of tree growth (tree height, stem volume, total plant biomass and root
production) all indicated a noticeable advantage of rooted versus non-rooted stock.
Observational data pointed to the necessity of thorough site preparation, adherence to proper
planting techniques, and mechanical or chemical weed control for successful plantation
establishment
Influence of shower fluctuations and primary composition on studies of the shower longitudinal development
We study the influence of shower fluctuations, and the possible presence of
different nuclear species in the primary cosmic ray spectrum, on the
experimental determination of both shower energy and the proton air inelastic
cross section from studies of the longitudinal development of atmospheric
showers in fluorescence experiments. We investigate the potential of track
length integral and shower size at maximum as estimators of shower energy. We
find that at very high energy (~10^19-10^20 eV) the error of the total energy
assignment is dominated by the dependence on the hadronic interaction model,
and is of the order of 5%. At lower energy (~10^17-10^18 eV), the uncertainty
of the energy determination due to the limited knowledge of the primary cosmic
ray composition is more important. The distribution of depth of shower maximum
is discussed as a measure of the proton-air cross section. Uncertainties in a
possible experimental measurement of this cross section introduced by intrinsic
shower fluctuations, the model of hadronic interactions, and the unknown
mixture of primary nuclei in the cosmic radiation are numerically evaluated.Comment: 12 pages, 11 figures, 4 table
Photon Total Cross-sections
We discuss present predictions for the total and
cross-sections, highlighting why predictions differ. We present results from
the Eikonal Minijet Model and improved predictions based on soft gluon
resummation.Comment: 7 pages, 10 figures, LaTeX, requires espcrc2.sty, Talk presented by
G. Pancheri at PHOTON-2003, International Meeting on Structure and
Interactions of the Photon, Frascati, Italy, April 7-11, 200
Infrared gluons, intrinsic transverse momentum and rising total cross-sections
We discuss the infrared limit for soft gluon kt-resummation and relate it to
physical observables such as the intrinsic transverse momentum and the high
energy limit of total cross-sections.Comment: 8 pages, 6 figures, Presented at Hadron Structure '09, Tatranska
Strba, September 2009, Slovacchia, to be published in the Conference
Proceeding
Hadronic Cross-sections in two photon Processes at a Future Linear Collider
In this note we address the issue of measurability of the hadronic
cross-sections at a future photon collider as well as for the two-photon
processes at a future high energy linear collider. We extend, to
higher energy, our previous estimates of the accuracy with which the \gamgam\
cross-section needs to be measured, in order to distinguish between different
theoretical models of energy dependence of the total cross-sections. We show
that the necessary precision to discriminate among these models is indeed
possible at future linear colliders in the Photon Collider option. Further we
note that even in the option a measurement of the hadron production
cross-section via \gamgam processes, with an accuracy necessary to allow
discrimination between different theoretical models, should be possible. We
also comment briefly on the implications of these predictions for hadronic
backgrounds at the future TeV energy collider CLIC.Comment: 20 pages, 5 figures, LaTeX. Added an acknowledgemen
Minijets, soft gluon resummation and photon cross-sections
We compare the high energy behaviour of hadronic photon-photon cross-sections
in different models. We find that the photon-photon cross-section appears to
rise faster than the purely hadronic ones (proton-proton and
proton-antiproton).Comment: 7 pages, 5 figures. Presented at Photon2007, Paris, July 2007.
Requires photon2007.cl
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