252 research outputs found
Gasification reactor engineering approach to understanding the formation of biochar properties
Operational reactor temperatures (spanning the reduction zone), pressure, and product gas composition measurements from a downdraft gasifier were compared against subsequent biochar elemental composition, surface morphology and PAH content. Pine feedstock moisture (FM), with values of 7% and 17% was the experimental variable. Moderately high steady-state temperatures were observed inside the reactor, with a ca. 50°C difference in how the gasifier operated between the two feedstock types. Both chars exhibited surface properties comparable to activated carbon, but the relatively small differences in temperature caused significant variations in biochar surface area and morphology: micropore area 584 m2.g-1 (FM7%) against 360 m2.g-1 (FM17%), and micropore volume 0.287 cm3.g-1 (FM7%) against 0.172 cm3.g-1 (FM17%). Differences in char extractable PAH content were also observed, with higher concentrations (187 μg.g-1 15 ± 18) when the gasifier was operated with FM7%, compared to 89 ± 19 μg.g-1 Σ16EPA PAH with FM17%. It is recommended that greater detail on operational conditions during biochar production should be incorporated as standard to future biochar characterisation research as a consequence of these results
Climate Change and invasibility of the Antarctic benthos
Benthic communities living in shallow-shelf habitats in Antarctica (<100-m depth) are archaic in their structure and function. Modern predators, including fast-moving, durophagous (skeleton-crushing) bony fish, sharks, and crabs, are rare or absent; slow-moving invertebrates are the top predators; and epifaunal suspension feeders dominate many soft substratum communities. Cooling temperatures beginning in the late Eocene excluded durophagous predators, ultimately resulting in the endemic living fauna and its unique food-web structure. Although the Southern Ocean is oceanographically isolated, the barriers to biological invasion are primarily physiological rather than geographic. Cold temperatures impose limits to performance that exclude modern predators. Global warming is now removing those physiological barriers, and crabs are reinvading Antarctica. As sea temperatures continue to rise, the invasion of durophagous predators will modernize the shelf benthos and erode the indigenous character of marine life in Antarctica
The stellar and sub-stellar IMF of simple and composite populations
The current knowledge on the stellar IMF is documented. It appears to become
top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr
pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing
metallicity and in increasingly massive early-type galaxies. It declines quite
steeply below about 0.07Msun with brown dwarfs (BDs) and very low mass stars
having their own IMF. The most massive star of mass mmax formed in an embedded
cluster with stellar mass Mecl correlates strongly with Mecl being a result of
gravitation-driven but resource-limited growth and fragmentation induced
starvation. There is no convincing evidence whatsoever that massive stars do
form in isolation. Various methods of discretising a stellar population are
introduced: optimal sampling leads to a mass distribution that perfectly
represents the exact form of the desired IMF and the mmax-to-Mecl relation,
while random sampling results in statistical variations of the shape of the
IMF. The observed mmax-to-Mecl correlation and the small spread of IMF
power-law indices together suggest that optimally sampling the IMF may be the
more realistic description of star formation than random sampling from a
universal IMF with a constant upper mass limit. Composite populations on galaxy
scales, which are formed from many pc scale star formation events, need to be
described by the integrated galactic IMF. This IGIMF varies systematically from
top-light to top-heavy in dependence of galaxy type and star formation rate,
with dramatic implications for theories of galaxy formation and evolution.Comment: 167 pages, 37 figures, 3 tables, published in Stellar Systems and
Galactic Structure, Vol.5, Springer. This revised version is consistent with
the published version and includes additional references and minor additions
to the text as well as a recomputed Table 1. ISBN 978-90-481-8817-
What a Plant Sounds Like: The Statistics of Vegetation Echoes as Received by Echolocating Bats
A critical step on the way to understanding a sensory system is the analysis of the input it receives. In this work we examine the statistics of natural complex echoes, focusing on vegetation echoes. Vegetation echoes constitute a major part of the sensory world of more than 800 species of echolocating bats and play an important role in several of their daily tasks. Our statistical analysis is based on a large collection of plant echoes acquired by a biomimetic sonar system. We explore the relation between the physical world (the structure of the plant) and the characteristics of its echo. Finally, we complete the story by analyzing the effect of the sensory processing of both the echolocation and the auditory systems on the echoes and interpret them in the light of information maximization. The echoes of all different plant species we examined share a surprisingly robust pattern that was also reproduced by a simple Poisson model of the spatial reflector arrangement. The fine differences observed between the echoes of different plant species can be explained by the spatial characteristics of the plants. The bat's emitted signal enhances the most informative spatial frequency range where the species-specific information is large. The auditory system filtering affects the echoes in a similar way, thus enhancing the most informative spatial frequency range even more. These findings suggest how the bat's sensory system could have evolved to deal with complex natural echoes
Fish oil administration in older adults: is there potential for adverse events? A systematic review of the literature
ackground: Omega-3 (n-3) fatty acid supplementation is becoming increasingly popular. However given its
antithrombotic properties the potential for severe adverse events (SAE) such as bleeding has safety implications,
particularly in an older adult population. A systematic review of randomized control trials (RCT) was conducted to
explore the potential for SAE and non-severe adverse events (non-SAE) associated with n-3 supplementation in
older adults.
Methods: A comprehensive search strategy using Medline and a variety of other electronic sources was conducted.
Studies investigating the oral administration of n-3 fish oil containing eicosapentaenoic acid (EPA), docosahexaenoic
acid (DHA) or both against a placebo were sourced. The primary outcome of interest included reported SAE
associated with n-3 supplementation. Chi-square analyses were conducted on the pooled aggregate of AEs.
Results: Of the 398 citations initially retrieved, a total of 10 studies involving 994 older adults aged ≥60 years were
included in the review. Daily fish oil doses ranged from 0.03 g to 1.86 g EPA and/or DHA with study durations
ranging from 6 to 52 weeks. No SAE were reported and there were no significant differences in the total AE rate
between groups (n-3 intervention group: 53/540; 9.8%; placebo group: 28/454; 6.2%; p= 0.07). Non-SAE relating to
gastrointestinal (GI) disturbances were the most commonly reported however there was no significant increase in
the proportion of GI disturbances reported in participants randomized to the n-3 intervention (n-3 intervention
group: 42/540 (7.8%); placebo group: 24/454 (5.3%); p= 0.18).
Conclusions: The potential for AEs appear mild-moderate at worst and are unlikely to be of clinical significance. The
use of n-3 fatty acids and the potential for SAE should however be further researched to investigate whether this
evidence is consistent at higher doses and in other populations. These results also highlight that well-documented data
outlining the potential for SAE following n-3 supplementation are limited nor adequately reported to draw definitive
conclusions concerning the safety associated with n-3 supplementation. A more rigorous and systematic approach for
monitoring and recording AE data in clinical settings that involve n-3 supplementation is required.The authors would like to acknowledge funding
provided for the ongoing ATLANTIC randomized controlled trial supported
by the National Health and Medical Research Council (NHMRC), Australia
Measurement of the Relative Branching Fraction of to Charged and Neutral B-Meson Pairs
We analyze 9.7 x 10^6 B\bar{B}$ pairs recorded with the CLEO detector to
determine the production ratio of charged to neutral B-meson pairs produced at
the Y(4S) resonance. We measure the rates for B^0 -> J/psi K^{(*)0} and B^+ ->
J/psi K^{(*)+} decays and use the world-average B-meson lifetime ratio to
extract the relative widths f+-/f00 = Gamma(Y(4S) -> B+B-)/Gamma(Y(4S) ->
B0\bar{B0}) = = 1.04 +/- 0.07(stat) +/- 0.04(syst). With the assumption that
f+- + f00 = 1, we obtain f00 = 0.49 +/- 0.02(stat) +/- 0.01(syst) and f+- =
0.51 +/- 0.02(stat) +/- 0.01(syst). This production ratio and its uncertainty
apply to all exclusive B-meson branching fractions measured at the Y(4S)
resonance.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Study of the Decays B0 --> D(*)+D(*)-
The decays B0 --> D*+D*-, B0 --> D*+D- and B0 --> D+D- are studied in 9.7
million Y(4S) --> BBbar decays accumulated with the CLEO detector. We determine
Br(B0 --> D*+D*-) = (9.9+4.2-3.3+-1.2)e-4 and limit Br(B0 --> D*+D-) < 6.3e-4
and Br(B0 --> D+D-) < 9.4e-4 at 90% confidence level (CL). We also perform the
first angular analysis of the B0 --> D*+D*- decay and determine that the
CP-even fraction of the final state is greater than 0.11 at 90% CL. Future
measurements of the time dependence of these decays may be useful for the
investigation of CP violation in neutral B meson decays.Comment: 21 pages, 5 figures, submitted to Phys. Rev.
A Search for
We report results of a search for in a sample of 9.7 million
charged meson decays. The search uses both and
decay modes of the , and demands exclusive reconstruction of the
companion decay to suppress background. We set an upper limit on the
branching fraction at 90%
confidence level. With slight modification to the analysis we also establish
at 90% confidence
level.Comment: 10 ages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Precise Measurement of B^{0}\to \bar{B^{0} Mixing Parameters at the S)$
We describe a measurement of B^0-B^0bar mixing parameters exploiting a method
of partial reconstruction of the decay chains B0 -> D^{*-}\pi^+ and B0 ->
D^{*-}\rho^+. Using 9.6 x 10^6 BBbar pairs collected at the Cornell Electron
Storage Ring, we find \chi_d = 0.198 +- 0.013 +- 0.014, |y_d|<0.41 at 95%
confidence level, and |Re(\epsilon_B)|<0.034 at 95% confidence level.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Measurement of B(/\c->pKpi)
The /\c->pKpi yield has been measured in a sample of two-jet continuum events
containing a both an anticharm tag (Dbar) as well as an antiproton (e+e- ->
Dbar pbar X), with the antiproton in the hemisphere opposite the Dbar. Under
the hypothesis that such selection criteria tag e+e- -> Dbar pbar (/\c) X
events, the /\c->pkpi branching fraction can be determined by measuring the
pkpi yield in the same hemisphere as the antiprotons in our Dbar pbar X sample.
Combining our results from three independent types of anticharm tags, we obtain
B(/\c->pKpi)=(5.0+/-0.5+/-1.2)
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