523 research outputs found
Laboratory and greenhouse assessment of plant availability of organic N in animal manure
Laboratory data (thermal fractionation, pepsin extraction, C:No ratio) of dung and manure were mutually compared and contrasted with plant-availability of organic N (No) as found in a greenhouse experiment according to the double-pot technique. Two types of fresh cow dung (one with a relatively wide and the other with a relatively narrow C:No ratio) and four types of manure (from poultry, sheep, pigs and cow) were compared with ammonium nitrate as chemical reference fertilizer. Relative effectiveness of organic N (REo) was used as characteristic; it was calculated as the fraction of organic N that has the same availability to plants as inorganic N. REo for poultry and sheep manure could not be assessed, probably because of NH3 volatilization causing direct damage to plants and N losses. REo values decreased in the order: dung with narrow C:No > dung with wide C:No > pig manure > cow manure. Thermal fractionation did not provide a suitable index of plant-availability of organic N. Pepsin extracted organic N gave a positive, and C:No ratio a negative relationship with REo. Also between pepsin extracted organic N and C:No ratio a negative relationship was found. As C:No ratio is relatively easy to determine, it is considered the most practical laboratory index for plant availability of organic N in animal manures low in ammonia. When using the double-pot technique, application rates of manure types high in ammonia should be restricte
Aortic valve mechanics
Model and animal experiments emphasized the relevance of presence and flexibility of aortic sinuses in valve closure. In dogs the asymmetric deformation of aortic ring and the commissure displacements during the cardiac cycle were quantified. Finite element modelling made clear that the leaflet bundles are essential for a homogeneous stress distributio
Evidence for the production of copper-complexing ligands by marine phytoplankton in the subarctic northeast Pacific
The availability and toxicity of copper (Cu) to marine phytoplankton involve complexation of Cu by dissolved organic ligands of uncertain origin and structure. As part of a GEOTRACES process study we used immobilized copper(II)-ion affinity chromatography (IMAC) to isolate and obtain information about the distribution and potential sources of Cu-complexing ligands along Line P in the subarctic northeast Pacific. Filtered seawater samples were collected from up to five stations during cruises in June 2016, June 2017, August 2017, and September 2018. Copper ligand concentrations were consistently higher at coastal station P4 than at other stations, particularly in surface waters. Ligand concentrations in the upper 40 m at station P26 increased between 2016 and 2018 following the 2014–2016 warming anomaly in the northeast Pacific, whereas an increase in ligand concentration from June to August 2017 coincided with seasonal increases in dissolved organic carbon (DOC) and net community production. At all stations, the depth of highest ligand concentration and maximum chlorophyll concentration coincided. A positive linear correlation between ligand and chlorophyll concentrations suggests that marine phytoplankton are a significant source of Cu ligands along Line P. The lower than expected ligand concentrations at station P26 in June 2016 are consistent with changes in phytoplankton ecology associated with the 2014–2016 warming anomaly. Comparing results from coastal and oceanic waters with those obtained previously in the Canadian Arctic suggests that terrigenous organic matter and marine humic substances contribute to the pool of Cu ligands captured by IMAC
Patchiness and Demographic Noise in Three Ecological Examples
Understanding the causes and effects of spatial aggregation is one of the
most fundamental problems in ecology. Aggregation is an emergent phenomenon
arising from the interactions between the individuals of the population, able
to sense only -at most- local densities of their cohorts. Thus, taking into
account the individual-level interactions and fluctuations is essential to
reach a correct description of the population. Classic deterministic equations
are suitable to describe some aspects of the population, but leave out features
related to the stochasticity inherent to the discreteness of the individuals.
Stochastic equations for the population do account for these
fluctuation-generated effects by means of demographic noise terms but, owing to
their complexity, they can be difficult (or, at times, impossible) to deal
with. Even when they can be written in a simple form, they are still difficult
to numerically integrate due to the presence of the "square-root" intrinsic
noise. In this paper, we discuss a simple way to add the effect of demographic
stochasticity to three classic, deterministic ecological examples where
aggregation plays an important role. We study the resulting equations using a
recently-introduced integration scheme especially devised to integrate
numerically stochastic equations with demographic noise. Aimed at scrutinizing
the ability of these stochastic examples to show aggregation, we find that the
three systems not only show patchy configurations, but also undergo a phase
transition belonging to the directed percolation universality class.Comment: 20 pages, 5 figures. To appear in J. Stat. Phy
Non-Random mtDNA Segregation Patterns Indicate a Metastable Heteroplasmic Segregation Unit in m.3243A>G Cybrid Cells
Many pathogenic mitochondrial DNA mutations are heteroplasmic, with a mixture of mutated and wild-type mtDNA present within individual cells. The severity and extent of the clinical phenotype is largely due to the distribution of mutated molecules between cells in different tissues, but mechanisms underpinning segregation are not fully understood. To facilitate mtDNA segregation studies we developed assays that measure m.3243A>G point mutation loads directly in hundreds of individual cells to determine the mechanisms of segregation over time. In the first study of this size, we observed a number of discrete shifts in cellular heteroplasmy between periods of stable heteroplasmy. The observed patterns could not be parsimoniously explained by random mitotic drift of individual mtDNAs. Instead, a genetically metastable, heteroplasmic mtDNA segregation unit provides the likely explanation, where stable heteroplasmy is maintained through the faithful replication of segregating units with a fixed wild-type/m.3243A>G mutant ratio, and shifts occur through the temporary disruption and re-organization of the segregation units. While the nature of the physical equivalent of the segregation unit remains uncertain, the factors regulating its organization are of major importance for the pathogenesis of mtDNA diseases
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Eta-N Final State Interaction in incoherent Photoproduction of Eta-mesons from the Deuteron near Threshold
An analysis of incoherent photoproduction of mesons off the deuteron
for photon energies from threshold to 800 MeV is presented. The dominant
contribution, the N-N amplitude, is described within an isobar
model. Effects of the final state interactions in the as well as the
systems are included employing models derived within the
meson-exchange approach. It is found that their consideration is important.
Specifically, due to an interference effect the influence of the final
state interaction is enhanced in the reaction close to
threshold.Comment: 11 pages (LaTeX), 7 postscript figure
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