1,779 research outputs found
Effects of incubation time and filtration method on Kd of indigenous selenium and iodine in temperate soils
In this study, the effects of incubation time and the method of soil solution extraction and filtration on the empirical distribution coefficient (Kd) obtained by de-sorbing indigenous selenium (Se) and iodine (I) from arable and woodland soils under temperate conditions were investigated.
Incubation time had a significant soil- and element- dependent effect on the Kd values, which tended to decrease with the incubation time. Generally, a four-week period was sufficient for the desorption Kd value to stabilise. Concurrent solubilisation of soil organic matter (OM) and release of organically-bound Se and I was probably responsible for the observed decrease in Kd with time. This contrasts with the conventional view of OM as a sink for Se and I in soils. Selenium and I Kd values were not significantly affected by the method of soil solution extraction and filtration.
The results suggest that incubation time is a key criterion when selecting Se and I Kd values from the literature for risk assessments. Values derived from desorption of indigenous soil Se and I might be most appropriate for long-term assessments since they reflect the quasi-equilibrium state of their partitioning in soils
GPCR-OKB: the G protein coupled receptor oligomer knowledge base
Rapid expansion of available data about G Protein Coupled Receptor (GPCR) dimers/oligomers over the past few years requires an effective system to organize this information electronically. Based on an ontology derived from a community dialog involving colleagues using experimental and computational methodologies, we developed the GPCR-Oligomerization Knowledge Base (GPCR-OKB). GPCR-OKB is a system that supports browsing and searching for GPCR oligomer data. Such data were manually derived from the literature. While focused on GPCR oligomers, GPCR-OKB is seamlessly connected to GPCRDB, facilitating the correlation of information about GPCR protomers and oligomers
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The influence of clouds on radical concentrations: Observations and modelling studies of HOx during the Hill Cap Cloud Thuringia (HCCT) campaign in 2010
The potential for chemistry occurring in cloud droplets to impact atmospheric composition has been known for some time. However, the lack of direct observations and uncertainty in the magnitude of these reactions led to this area being overlooked in most chemistry transport models. Here we present observations from Mt SchmĂĽcke, Germany, of the HO2 radical made alongside a suite of cloud measurements. HO2 concentrations were depleted in-cloud by up to 90% with the rate of heterogeneous loss of HO2 to clouds necessary to bring model and measurements into agreement, demonstrating a dependence on droplet surface area and pH. This provides the first observationally derived assessment for the uptake coefficient of HO2 to cloud droplets and was found to be in good agreement with theoretically derived parameterisations. Global model simulations, including this cloud uptake, showed impacts on the oxidising capacity of the troposphere that depended critically on whether the HO2 uptake leads to production of H2O2 or H2O
N=31, D=11
We show that eleven-dimensional supergravity backgrounds with thirty one
supersymmetries, N=31, admit an additional Killing spinor and so they are
locally isometric to maximally supersymmetric ones. This rules out the
existence of simply connected eleven-dimensional supergravity preons. We also
show that N=15 solutions of type I supergravities are locally isometric to
Minkowski spacetime.Comment: 17 page
Toeplitz operators on symplectic manifolds
We study the Berezin-Toeplitz quantization on symplectic manifolds making use
of the full off-diagonal asymptotic expansion of the Bergman kernel. We give
also a characterization of Toeplitz operators in terms of their asymptotic
expansion. The semi-classical limit properties of the Berezin-Toeplitz
quantization for non-compact manifolds and orbifolds are also established.Comment: 40 page
On the Testing of Seismicity Models
Recently a likelihood-based methodology has been developed by the
Collaboratory for the Study of Earthquake Predictability (CSEP) with a view to
testing and ranking seismicity models. We analyze this approach from the
standpoint of possible applications to hazard analysis. We arrive at the
conclusion that model testing can be made more efficient by focusing on some
integral characteristics of the seismicity distribution. This is achieved
either in the likelihood framework but with economical and physically
reasonable coarsening of the phase space or by choosing a suitable measure of
closeness between empirical and model seismicity rate in this space.Comment: To appear at Acta Geophysic
Linewidth of single photon transitions in Mn-acetate
We use time-domain terahertz spectroscopy to measure the position and
linewidth of single photon transitions in Mn-acetate. This linewidth is
compared to the linewidth measured in tunneling experiments. We conclude that
local magnetic fields (due to dipole or hyperfine interactions) cannot be
responsible for the observed linewidth, and suggest that the linewidth is due
to variations in the anisotropy constants for different clusters. We also
calculate a lower limit on the dipole field distribution that would be expected
due to random orientations of clusters and find that collective effects must
narrow this distribution in tunneling measurements.Comment: 5 pages, accepted to Physical Review
Daily Parent-Adolescent Digital Exchanges
The present study tracked adolescents via mobile phones to describe how parents and their adolescent children are using digital technologies in daily life (i.e. facilitating warmth and behavioral control), and whether these uses are associated with the quality of offline parent-adolescent interactions and with adolescents’ mental health. A sample of young adolescents (N = 388; mean age 13.37) completed a 14-day ecological momentary assessment in 2016- 2017, reporting on their daily digital contact and offline interactions with their parents and their mental health. Adolescents reported using texting and calling to communicate somewhat infrequently with their parents (i.e., on 29% of days), but days with more digital contacts (for both warmth and behavioral control) were also more likely to be characterized by more positive offline interactions with parents. Furthermore, adolescents struggling with mental health symptoms across the study period reported using texts/calls more frequently to seek out parent support, and parents were more likely to do text/call “check ins” on young people who were experiencing more behavioral problems. Results highlight the potential for digital communication devices to be used as tools in fostering parent-adolescent connection, support provision, and behavioral control in the digital era
Migration transforms the conditions for the achievement of the Sustainable Development Goals
This is the final version. Available on open access from Elsevier via the DOI in this recordEconomic and Social Research Council (ESRC
The holonomy of the supercovariant connection and Killing spinors
We show that the holonomy of the supercovariant connection for M-theory
backgrounds with Killing spinors reduces to a subgroup of SL(32-N,\bR)\st
(\oplus^N \bR^{32-N}). We use this to give the necessary and sufficient
conditions for a background to admit Killing spinors. We show that there is
no topological obstruction for the existence of up to 22 Killing spinors in
eleven-dimensional spacetime. We investigate the symmetry superalgebras of
supersymmetric backgrounds and find that their structure constants are
determined by an antisymmetric matrix. The Lie subalgebra of bosonic generators
is related to a real form of a symplectic group. We show that there is a
one-one correspondence between certain bases of the Cartan subalgebra of
sl(32, \bR) and supersymmetric planar probe M-brane configurations. A
supersymmetric probe configuration can involve up to 31 linearly independent
planar branes and preserves one supersymmetry. The space of supersymmetric
planar probe M-brane configurations is preserved by an SO(32,\bR) subgroup of
SL(32, \bR).Comment: 27 pages, a key reference was added. v3: minor change
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