4,645 research outputs found
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Landscape context mediates the relationship between plant functional traits and decomposition
Aims: It has been well demonstrated that several interacting endogenous and exogenous factors influence decomposition. However, teasing apart the direct and indirect effects of these factors to predict decomposition patterns in heterogenous landscapes remains a key challenge. Methods: At 157 locations in a temperate forest, we measured decomposition of a standard substrate (filter paper) over two years, the landscape context in which decomposition took place, and the functional composition of the woody species that contributed leaf litter to the forest floor where litter bags were placed. We tested for direct and indirect effects of landscape context and direct effects of forest functional composition on decay using structural equation modelling. Results: We found that landscape context had direct effects on decay and indirect effects on decay via its influence on the functional composition of the surrounding forest. Forest functional composition also had direct effects on decay, but these effects decreased or disappeared completely over time. Moreover, community weighted mean trait values were better predictors of decay than functional dispersion of leaf traits, and leaf nitrogen content and carbon content were better predictors of decay than leaf dry matter content or leaf toughness. Conclusions: Our results highlight the importance of an integrative approach that examines the direct and indirect effects of multiple factors for understanding and predicting decomposition patterns across heterogenous landscapes
Environmental impacts of alternative cement binders.
Cement production is among the most difficult industrial activities to decarbonize. Various measures have been proposed and explored to reduce its CO2 emissions. Among these measures, the substitution of portland cement (PC) clinker with alternative materials is arguably the most effective, and consequently is an area of high research and commercial interest. However, few studies have systematically quantified environmental impacts of alternative, i.e., non-PC, clinkers. Here, we quantify and compare environmental impacts arising from the production of binders derived from several of the most commonly investigated alternative cement systems. We show that binders derived from most of these alternative cements result in lower greenhouse gas (GHG) emissions as well as other indicators of environmental impacts relative to the PC binder. The extent of these reductions varies as a function of energy requirements for production, process-related emissions from clinker formation, and raw materials demand. While utilization of alternative cements can be environmentally beneficial, similar reductions in GHG emissions can be achieved through use of partial replacement of PC with mineral admixtures. In this work, we quantitatively demonstrate the potential for alternative binders to mitigate environmental burdens and highlight the need to consider trade-offs among environmental impact categories when assessing these products
Visualization of comparative genomic analyses by BLAST score ratio
BACKGROUND: The first microbial genome sequence, Haemophilus influenzae, was published in 1995. Since then, more than 400 microbial genome sequences have been completed or commenced. This massive influx of data provides the opportunity to obtain biological insights through comparative genomics. However few tools are available for this scale of comparative analysis. RESULTS: The BLAST Score Ratio (BSR) approach, implemented in a Perl script, classifies all putative peptides within three genomes using a measure of similarity based on the ratio of BLAST scores. The output of the BSR analysis enables global visualization of the degree of proteome similarity between all three genomes. Additional output enables the genomic synteny (conserved gene order) between each genome pair to be assessed. Furthermore, we extend this synteny analysis by overlaying BSR data as a color dimension, enabling visualization of the degree of similarity of the peptides being compared. CONCLUSIONS: Combining the degree of similarity, synteny and annotation will allow rapid identification of conserved genomic regions as well as a number of common genomic rearrangements such as insertions, deletions and inversions. The script and example visualizations are available at:
Drug trafficking, use, and HIV risk: The need for comprehensive interventions
The rapid increase in communication and transportation between Africa and other continents as well as the erosion of social fabric attended by poverty, ethnic conflicts, and civil wars has led to increased trafficking and consumption of illicit drugs. Cannabis dominates illicit trade and accounts for as much as 40% of global interdiction. Due to escalating seizures in recent years, the illicit trade in heroin and cocaine has become a concern that has quickly spread from West Africa to include Eastern and Southern Africa in the past 10 years. All regions of Africa are characterized by the use of cannabis, reflecting its entrenched status all over Africa. Most alarming though is the use of heroin, which is now being injected frequently and threatens to reverse the gain made in the prevention of HIV/AIDS. The prevalence of HIV infection and other blood-bornediseases among injection drug users is five to six times that among the general population, calling for urgent intervention among this group. Programs that aim to reduce the drug trafficking in Africa and needle syringe programs as well as medication-assisted treatment (MAT) of heroin dependence while still in their infancy in Africa show promise and need tobe scaled up
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Distribution of halon-1211 in the upper troposphere and lower stratosphere and the 1994 total bromine budget
Massive Quantum Liquids from Holographic Angel's Trumpets
We explore the small-temperature regime in the deconfined phase of massive
fundamental matter at finite baryon number density coupled to the 3+1
dimensional N=4 SYM theory. In this setting, we can demonstrate a new type of
non-trivial temperature-independent scaling solutions for the probe brane
embeddings. Focusing mostly on matter supported in 2+1 dimensions, the
thermodynamics indicate that there is a quantum liquid with interesting
density-dependent low-temperature physics. We also comment about 3+1 and 1+1
dimensional systems, where we further find for example a new thermodynamic
instability.Comment: 18+1 pages, 6 figures; replaced fig. 6 and comments in sec. 5.2;
minor explanations added and typos fixed, final version published in JHEP
(modulo fig. 3); factor of \sqrt{\lambda} and corresponding comments fixe
Transport coefficients, membrane couplings and universality at extremality
We present an efficient method for computing the zero frequency limit of
transport coefficients in strongly coupled field theories described
holographically by higher derivative gravity theories. Hydrodynamic parameters
such as shear viscosity and conductivity can be obtained by computing residues
of poles of the off-shell lagrangian density. We clarify in which sense these
coefficients can be thought of as effective couplings at the horizon, and
present analytic, Wald-like formulae for the shear viscosity and conductivity
in a large class of general higher derivative lagrangians. We show how to apply
our methods to systems at zero temperature but finite chemical potential. Our
results imply that such theories satisfy universally in the
Einstein-Maxwell sector. Likewise, the zero frequency limit of the real part of
the conductivity for such systems is shown to be universally zero, and we
conjecture that higher derivative corrections in this sector do not modify this
result to all orders in perturbation theory.Comment: 29 pages, v2: Small text changes for clarity, typos correcte
Universal thermal and electrical conductivity from holography
It is known from earlier work of Iqbal, Liu (arXiv:0809.3808) that the
boundary transport coefficients such as electrical conductivity (at vanishing
chemical potential), shear viscosity etc. at low frequency and finite
temperature can be expressed in terms of geometrical quantities evaluated at
the horizon. In the case of electrical conductivity, at zero chemical potential
gauge field fluctuation and metric fluctuation decouples, resulting in a
trivial flow from horizon to boundary. In the presence of chemical potential,
the story becomes complicated due to the fact that gauge field and metric
fluctuation can no longer be decoupled. This results in a nontrivial flow from
horizon to boundary. Though horizon conductivity can be expressed in terms of
geometrical quantities evaluated at the horizon, there exist no such neat
result for electrical conductivity at the boundary. In this paper we propose an
expression for boundary conductivity expressed in terms of geometrical
quantities evaluated at the horizon and thermodynamical quantities. We also
consider the theory at finite cutoff outside the horizon (arXiv:1006.1902) and
give an expression for cutoff dependent electrical conductivity, which
interpolates smoothly between horizon conductivity and boundary conductivity .
Using the results about the electrical conductivity we gain much insight into
the universality of thermal conductivity to viscosity ratio proposed in
arXiv:0912.2719.Comment: An appendix added discussing relation between boundary conductivity
and universal conductivity of stretched horizon, version to be published in
JHE
Numerical Study of the Two Color Attoworld
We consider QCD at very low temperatures and non-zero quark chemical
potential from lattice Monte Carlo simulations of the two-color theory in a
very small spatial volume (the attoscale). In this regime the quark number
rises in discrete levels in qualitative agreement with what is found
analytically at one loop on S3xS1 with radius R_S3 << 1/{\Lambda}_QCD. The
detailed level degeneracy, however, cannot be accounted for using weak coupling
arguments. At each rise in the quark number there is a corresponding spike in
the Polyakov line, also in agreement with the perturbative results. In addition
the quark number susceptibility shows a similar behaviour to the Polyakov line
and appears to be a good indicator of a confinement-deconfinement type of
transition.Comment: 18 pages, 10 figure
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