231 research outputs found
Meso-Scale Seabed Quantification with Geoacoustic Inversion
Abstract Knowledge of sub-seabed geoacoustic properties, for example depth dependent sound speed and porosity, is of importance for a variety of applications. Here, we present a semi-automated geoacoustic inversion method for autonomous underwater vehicle data that objectively adapts model inference to seabed structure. Through parallelized trans-dimensional Bayesian inference, we infer seabed properties along a 12 km survey track on the scale of about 10 cm and 50 m in the vertical and horizontal, respectively. The inferred seabed properties include sound speed, attenuation, density, and porosity as a function of depth from acoustic reflection coefficient data. Parameter uncertainties are quantified, and the seabed properties agree closely with core samples at two control points and the layering structure with an independent sub-bottom seismic survey. Recovering high resolution seabed properties over large areas is shown to be feasible, which could become an important tool for marine industries, navies and oceanic research organizations
Evaluation of the LEP Centre-of-Mass Energy Above the W-Pair Production Threshold
Knowledge of the centre-of-mass energy at LEP2 is of primary importance to
set the absolute energy scale for the measurement of the W-boson mass. The beam
energy above 80 GeV is derived from continuous measurements of the magnetic
bending field by 16 NMR probes situated in a number of the LEP dipoles. The
relationship between the fields measured by the probes and the beam energy is
calibrated against precise measurements of the average beam energy between 41
and 55 GeV made using the resonant depolarisation technique. The linearity of
the relationship is tested by comparing the fields measured by the probes with
the total bending field measured by a flux loop. This test results in the
largest contribution to the systematic uncertainty. Several further corrections
are applied to derive the the centre-of-mass energies at each interaction
point. In addition the centre-of-mass energy spread is evaluated. The beam
energy has been determined with a precision of 25 MeV for the data taken in
1997, corresponding to a relative precision of 2.7x10^{-4}. This is small in
comparison to the present uncertainty on the W mass measurement at LEP.
However, the ultimate statistical precision on the W mass with the full LEP2
data sample should be around 25 MeV, and a smaller uncertainty on the beam
energy is desirable. Prospects for improvements are outlined.Comment: 24 pages, 10 figures, Latex, epsfig; replaced by version accepted by
European Physical Journal
Observation of radiative spin-polarization at 60.6 GeV
Radiative spin-polarization has been used extensively at LEP to accurately measure the beam energy around the Z resonance. As the LEP physics has moved on to the W boson the calibration based on polarization must be extended towards higher beam energies. This is difficult as the depolarizing effects of spin resonances grow rapidly with beam energy. At LEP it has been possible for the first time to measure transverse beam polarization at 60.6 GeV. To allow a build-up of polarization the tunes and the energy were chosen accurately. A low phase advance optics was used and careful orbit correction was carried out using dynamic beam based alignment data. Harmonic spin matching was applied both in a deterministic and a novel semi- empirical way. (11 refs)
Excavations at Chlorakas-Palloures, New Light on Chalcolithic Cyprus
Archaeology of the Near Eas
New frontiers in belowground ecology for plant protection from root-feeding insects
Herbivorous insect pests living in the soil represent a significant challenge to food security given their persistence, the acute damage they cause to plants and the difficulties associated with managing their populations. Ecological research effort into rhizosphere interactions has increased dramatically in the last decade and we are beginning to understand, in particular, the ecology of how plants defend themselves against soil-dwelling pests. In this review, we synthesise information about four key ecological mechanisms occurring in the rhizosphere or surrounding soil that confer plant protection against root herbivores. We focus on root tolerance, root resistance via direct physical and chemical defences, particularly via acquisition of silicon-based plant defences, integration of plant mutualists (microbes and entomopathogenic nematodes, EPNs) and the influence of soil history and feedbacks. Their suitability as management tools, current limitations for their application, and the opportunities for development are evaluated. We identify opportunities for synergy between these aspects of rhizosphere ecology, such as mycorrhizal fungi negatively affecting pests at the root-interface but also increasing plant uptake of silicon, which is also known to reduce herbivory. Finally, we set out research priorities for developing potential novel management strategies
insights for ecological applications from the German Biodiversity Exploratories
Biodiversity, a multidimensional property of natural systems, is difficult to
quantify partly because of the multitude of indices proposed for this purpose.
Indices aim to describe general properties of communities that allow us to
compare different regions, taxa, and trophic levels. Therefore, they are of
fundamental importance for environmental monitoring and conservation, although
there is no consensus about which indices are more appropriate and
informative. We tested several common diversity indices in a range of simple
to complex statistical analyses in order to determine whether some were better
suited for certain analyses than others. We used data collected around the
focal plant Plantago lanceolata on 60 temperate grassland plots embedded in an
agricultural landscape to explore relationships between the common diversity
indices of species richness (S), Shannon's diversity (H'), Simpson's diversity
(D1), Simpson's dominance (D2), Simpson's evenness (E), and Berger–Parker
dominance (BP). We calculated each of these indices for herbaceous plants,
arbuscular mycorrhizal fungi, aboveground arthropods, belowground insect
larvae, and P. lanceolata molecular and chemical diversity. Including these
trait-based measures of diversity allowed us to test whether or not they
behaved similarly to the better studied species diversity. We used path
analysis to determine whether compound indices detected more relationships
between diversities of different organisms and traits than more basic indices.
In the path models, more paths were significant when using H', even though all
models except that with E were equally reliable. This demonstrates that while
common diversity indices may appear interchangeable in simple analyses, when
considering complex interactions, the choice of index can profoundly alter the
interpretation of results. Data mining in order to identify the index
producing the most significant results should be avoided, but simultaneously
considering analyses using multiple indices can provide greater insight into
the interactions in a system
Histone deacetylases as new therapy targets for platinum-resistant epithelial ovarian cancer
Introduction: In developed countries, ovarian cancer is the fourth most common cancer in women. Due to the nonspecific symptomatology associated with the disease many patients with ovarian cancer are diagnosed late, which leads to significantly poorer prognosis. Apart from surgery and radiotherapy, a substantial number of ovarian cancer patients will undergo chemotherapy and platinum based agents are the mainstream first-line therapy for this disease. Despite the initial efficacy of these therapies, many women relapse; therefore, strategies for second-line therapies are required. Regulation of DNA transcription is crucial for tumour progression, metastasis and chemoresistance which offers potential for novel drug targets. Methods: We have reviewed the existing literature on the role of histone deacetylases, nuclear enzymes regulating gene transcription. Results and conclusion: Analysis of available data suggests that a signifant proportion of drug resistance stems from abberant gene expression, therefore HDAC inhibitors are amongst the most promising therapeutic targets for cancer treatment. Together with genetic testing, they may have a potential to serve as base for patient-adapted therapies
β-Actin and γ-Actin Are Each Dispensable for Auditory Hair Cell Development But Required for Stereocilia Maintenance
Hair cell stereocilia structure depends on actin filaments composed of cytoplasmic β-actin and γ-actin isoforms. Mutations in either gene can lead to progressive hearing loss in humans. Since β-actin and γ-actin isoforms are 99% identical at the protein level, it is unclear whether each isoform has distinct cellular roles. Here, we compared the functions of β-actin and γ-actin in stereocilia formation and maintenance by generating mice conditionally knocked out for Actb or Actg1 in hair cells. We found that, although cytoplasmic actin is necessary, neither β-actin nor γ-actin is required for normal stereocilia development or auditory function in young animals. However, aging mice with β-actin– or γ-actin–deficient hair cells develop different patterns of progressive hearing loss and distinct pathogenic changes in stereocilia morphology, despite colocalization of the actin isoforms. These results demonstrate overlapping developmental roles but unique post-developmental functions for β-actin and γ-actin in maintaining hair cell stereocilia
Stochastic and epistemic uncertainty propagation in LCA
Purpose: When performing uncertainty propagation, most LCA practitioners choose to represent uncertainties by single probability distributions and to propagate them using stochastic methods. However the selection of single probability distributions appears often arbitrary when faced with scarce information or expert judgement (epistemic uncertainty). Possibility theory has been developed over the last decades to address this problem. The objective of this study is to present a methodology that combines probability and possibility theories to represent stochastic and epistemic uncertainties in a consistent manner and apply it to LCA. A case study is used to show the uncertainty propagation performed with the proposed method and compare it to propagation performed using probability and possibility theories alone. Methods: Basic knowledge on the probability theory is first recalled, followed by a detailed description of hal-00811827, version 1- 11 Apr 2013 epistemic uncertainty representation using fuzzy intervals. The propagation methods used are the Monte Carlo analysis for probability distribution and an optimisation on alpha-cuts for fuzzy intervals. The proposed method (noted IRS) generalizes the process of random sampling to probability distributions as well as fuzzy intervals, thus making the simultaneous use of both representations possible
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