485 research outputs found
A volume inequality for quantum Fisher information and the uncertainty principle
Let be complex self-adjoint matrices and let be a
density matrix. The Robertson uncertainty principle gives a bound for the quantum
generalized covariance in terms of the commutators . The right side
matrix is antisymmetric and therefore the bound is trivial (equal to zero) in
the odd case .
Let be an arbitrary normalized symmetric operator monotone function and
let be the associated quantum Fisher information. In
this paper we conjecture the inequality that gives a
non-trivial bound for any natural number using the commutators . The inequality has been proved in the cases by the joint efforts
of many authors. In this paper we prove the case N=3 for real matrices
OSETI with STACEE: A Search for Nanosecond Optical Transients from Nearby Stars
We have used the STACEE high-energy gamma-ray detector to look for fast
blue-green laser pulses from the vicinity of 187 stars. The STACEE detector
offers unprecedented light-collecting capability for the detection of
nanosecond pulses from such lasers. We estimate STACEE's sensitivity to be
approximately 10 photons per square meter at a wavelength of 420 nm. The stars
have been chosen because their characteristics are such that they may harbor
habitable planets and they are relatively close to Earth. Each star was
observed for 10 minutes and we found no evidence for laser pulses in any of the
data sets.Comment: 38 pages, 12 figures. Accepted for publication in Astrobiolog
Very high energy observations of the BL Lac objects 3C 66A and OJ 287
Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we
have observed the BL Lac objects 3C 66A and OJ 287. These are members of the
class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three
LBLs predicted by Costamante and Ghisellini to be potential sources of very
high energy (>100 GeV) gamma-ray emission. The third candidate, BL Lacertae,
has recently been detected by the MAGIC collaboration. Our observations have
not produced detections; we calculate a 99% CL upper limit of flux from 3C 66A
of 0.15 Crab flux units and from OJ 287 our limit is 0.52 Crab. These limits
assume a Crab-like energy spectrum with an effective energy threshold of 185
GeV.Comment: 24 pages, 15 figures, Accepted for publication in Astroparticle
Physic
The assessment of fetal brain growth in diabetic pregnancy using in utero magnetic resonance imaging.
AIM: To assess fetal brain growth over the third trimester in pregnant women with diabetes using in utero magnetic resonance imaging (iuMRI) to determine if greater brain growth occurs in type 1 (T1DM) when compared to gestational (GDM) diabetes mellitus. MATERIALS AND METHODS: Each consented participant was scanned at three fixed times during the third trimester using iuMRI. One hundred and fifty-seven patients were approached, 48 participants were recruited, and 36 complete data sets were analysed. Three-dimensional (3D) iuMRI volume data sets were manually segmented using software to construct models of the fetal brain from which brain volumes could be calculated. Inter-rater analysis was performed, and volume differences and growth rates were compared between T1DM and GDM. RESULTS: Recruitment proved difficult with low uptake and high attrition rates (77.1%). Inter-rater analysis revealed excellent correlation (intraclass correlation coefficient=0.93, p<0.001) and agreement with no significant difference between operators (p=0.194). There was no evidence of increased brain volume in the T1DM group. Growth rates between visit 1 and 3 for T1DM and GDM were not significantly different (p=0.095). CONCLUSION: T1DM brain volumes were not significantly larger than GDM volumes and there was no significant divergence of brain growth over the third trimester. Constructing volume models from 3D iuMRI acquisitions is a novel technique that can be used to assess fetal brain growth. No specialist software or knowledge is required. Larger studies attempting to recruit pregnant women in the later stages of pregnancy should employ multicentre recruitment to overcome recruitment difficulties and high attrition rates
Nanomolar levels of PAHs in extracts from urban air induce MAPK signaling in HepG2 cells.
Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants that
occur naturally in complex mixtures. Many of the adverse health effects of PAHs
including cancer are linked to the activation of intracellular stress response
signaling. This study has investigated intracellular MAPK signaling in response
to PAHs in extracts from urban air collected in Stockholm, Sweden and Limeira,
Brazil, in comparison to BP in HepG2 cells. Nanomolar concentrations of PAHs in
the extracts induced activation of MEK4 signaling with down-stream increased gene
expression of several important stress response mediators. Involvement of the
MEK4/JNK pathway was confirmed using siRNA and an inhibitor of JNK signaling
resulting in significantly reduced MAPK signaling transactivated by the AP-1
transcription factors ATF2 and c-Jun. ATF2 was also identified as a sensitive
stress responsive protein with activation observed at extract concentrations
equivalent to 0.1 nM BP. We show that exposure to low levels of environmental PAH
mixtures more strongly activates these signaling pathways compared to BP alone
suggesting effects due to interactions. Taken together, this is the first study
showing the involvement of MEK4/JNK/AP-1 pathway in regulating the intracellular
stress response after exposure to nanomolar levels of PAHs in environmentalFormasAccepte
Sensitivity of Salmonella YG5161 for detecting PAH-associated mutagenicity in air particulate matter.
The Salmonella/microsome assay is the most used assay for the evaluation of air
particulate matter (PM) mutagenicity and a positive correlation between strain
TA98 responses and benzo[a]pyrene (B[a]P) levels in PM has been found. However,
it seems that the major causes of PM mutagenicity in this assay are the nitro and
oxy-PAHs. Salmonella YG5161, a 30-times more responsive strain to B[a]P has been
developed. To verify if YG5161 strain was sufficiently sensitive to detect
mutagenicity associated with B[a]P mutagenicity, PM samples were collected in
Brazil and Sweden, extracted with toluene and tested in the Salmonella/microsome
microsuspension assay. PAHs and B[a]P were determined and the extracts were
tested with YG5161 and its parental strain TA1538. The extracts were also tested
with YG1041 and its parental strain TA98. For sensitivity comparisons, we tested
B[a]P and 1-nitropyrene (1-NP) using the same conditions. The minimal effective
dose of B[a]P was 155 ng/plate for TA1538 and 7 ng/plate for YG5161. Although the
maximum tested dose, 10 m(3) /plate containing 9 ng of B[a]P in the case of
Brazilian sample, was sufficient to elicit a response in YG5161, mutagenicity was
detected at a dose as low as 1 m(3) /plate (0.9 ng). This is probably caused by
nitro-compounds that have been shown to be even more potent than B[a]P for
YG5161. It seems that the mutagenicity of B[a]P present in PM is not detectable
even with the use of YG5161 unless more efficient separation to remove the
nitro-compounds from the PAH extract is performed.FormasAccepte
The Milky Way Bulge: Observed properties and a comparison to external galaxies
The Milky Way bulge offers a unique opportunity to investigate in detail the
role that different processes such as dynamical instabilities, hierarchical
merging, and dissipational collapse may have played in the history of the
Galaxy formation and evolution based on its resolved stellar population
properties. Large observation programmes and surveys of the bulge are providing
for the first time a look into the global view of the Milky Way bulge that can
be compared with the bulges of other galaxies, and be used as a template for
detailed comparison with models. The Milky Way has been shown to have a
box/peanut (B/P) bulge and recent evidence seems to suggest the presence of an
additional spheroidal component. In this review we summarise the global
chemical abundances, kinematics and structural properties that allow us to
disentangle these multiple components and provide constraints to understand
their origin. The investigation of both detailed and global properties of the
bulge now provide us with the opportunity to characterise the bulge as observed
in models, and to place the mixed component bulge scenario in the general
context of external galaxies. When writing this review, we considered the
perspectives of researchers working with the Milky Way and researchers working
with external galaxies. It is an attempt to approach both communities for a
fruitful exchange of ideas.Comment: Review article to appear in "Galactic Bulges", Editors: Laurikainen
E., Peletier R., Gadotti D., Springer Publishing. 36 pages, 10 figure
Exploring relationships between land use intensity, habitat heterogeneity and biodiversity to identify and monitor areas of High Nature Value farming
Understanding how species richness is distributed across landscapes and which variables may be used as predictors is important for spatially targeting management interventions. This study uses finely resolved data over a large geographical area to explore relationships between land-use intensity, habitat heterogeneity and species richness of multiple taxa. It aims to identify surrogate landscape metrics, valid for a range of taxa, which can be used to map and monitor High Nature Value farmland (HNV).
Results show that variation in species richness is distributed along two axes: land-use intensity and habitat heterogeneity. At low intensity land-use, species rich groups include wetland plants, plant habitat indicators, upland birds and rare invertebrates, whilst richness of other species groups (farmland birds, butterflies, bees) was associated with higher land-use intensity. Habitat heterogeneity (broadleaved woodland connectivity, hedgerows, habitat diversity) was positively related to species richness of many taxa, both generalists (plants, butterflies, bees) and specialists (rare birds, woodland birds, plants, butterflies).
The results were used to create maps of HNV farmland. The proportion of semi-natural vegetation is a useful metric for identifying HNV type 1. HNV type 2 (defined as a mosaic of low-intensity habitats and structural elements) is more difficult to predict from surrogate variables, due to complex relationships between biodiversity and habitat heterogeneity and inadequacies of current remotely sensed data.
This approach, using fine-scaled field survey data collected at regular intervals, in conjunction with remotely sensed data offers potential for extrapolating modelled results nationally, and importantly, can be used to assess change over time
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
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