17,234 research outputs found
Impact of Dynamical Fermions on QCD Vacuum Structure
We examine how dynamical fermions affect both the UV and infrared structure
of the QCD vacuum. We consider large lattices from the MILC
collaboration, using a gluonic definition of the topological charge density,
founded on a new over-improved stout-link smearing algorithm. The algorithm
reproduces established results from the overlap formalism and is designed to
preserve nontrivial topological objects including instantons. At short
distances we focus on the topological charge correlator, , where
negative values at small $x$ reveal a sign-alternating layered structure to the
topological-charge density of the QCD vacuum. We find that the magnitudes of
the negative dip in the correlator and the positive
contact term are both increased with the introduction of dynamical fermion
degrees of freedom. This is in accord with expectations based on charge
renormalization and the vanishing of the topological susceptibility in the
chiral limit. At large distances we examine the extent to which instanton-like
objects are found on the lattice, and how their distributions vary between
quenched and dynamical gauge fields. We show that dynamical gauge fields
contain more instanton-like objects with an average size greater than in the
quenched vacuum. Finally, we directly visualize the topological charge density
in order to investigate the effects of dynamical sea-quark degrees of freedom
on topology.Comment: 9 pages, 8 figure
Typification and economic analysis of beef-producing farms in Spain
In spite of different economic agentsâ interests, as well as the Administrationâs effort in promoting extensive beef-producing systems over the last years, this kind of activity still hasnât reached the desirable levels, being necessary that farmers perceive an appropriate benefit which supports their activity. In this sense, this paper, using the data obtained by a statistical survey representing all the extensive beef-producing farms existing in Castile and Leon (Spain), aims to analyze the economical results of extensive beef-producing farms, previously classified in representative groups according a quantitative method. The study is a preliminary research which intends to generate additional knowledge about the role of the different variables which make part of the economic results, and takes part of a research project financed by Castile and Leon Regional Governments, Education and Culture Council, through the annual program to support research projects (Order EDU/1143/2004).Cluster Analysis, extensive beef producing systems, economic accounts, Livestock Production/Industries,
PhysBinder : improving the prediction of transcription factor binding sites by flexible inclusion of biophysical properties
The most important mechanism in the regulation of transcription is the binding of a transcription factor (TF) to a DNA sequence called the TF binding site (TFBS). Most binding sites are short and degenerate, which makes predictions based on their primary sequence alone somewhat unreliable. We present a new web tool that implements a flexible and extensible algorithm for predicting TFBS. The algorithm makes use of both direct (the sequence) and several indirect readout features of protein-DNA complexes (biophysical properties such as bendability or the solvent-excluded surface of the DNA). This algorithm significantly outperforms state-of-the-art approaches for in silico identification of TFBS. Users can submit FASTA sequences for analysis in the PhysBinder integrative algorithm and choose from >60 different TF-binding models. The results of this analysis can be used to plan and steer wet-lab experiments. The PhysBinder web tool is freely available at http://bioit.dmbr.ugent.be/physbinder/index.php
Powerful Water Masers in Active Galactic Nuclei
Luminous water maser emission in the 6_(16)-5_(23) line at 22 GHz has been
detected from two dozen galaxies. In all cases the emission is confined to the
nucleus and has been found only in AGN, in particular, in Type 2 Seyferts and
LINERs. I argue that most of the observed megamaser sources are powered by
X-ray irradiation of dense gas by the central engine. After briefly reviewing
the physics of these X-Ray Dissociation Regions, I discuss in detail the
observations of the maser disk in NGC 4258, its implications, and compare
alternative models for the maser emission. I then discuss the observations of
the other sources that have been imaged with VLBI to date, and how they do or
do not fit into the framework of a thin, rotating disk, as in NGC 4258.
Finally, I briefly discuss future prospects, especially the possibility of
detecting other water maser transitions.Comment: 45 pages, 16 figures. Refereed and greatly expanded version of my
review talk at the ASA meeting in Lorne, July 2001. To appear in Proceedings
of the Astronomical Society of Australi
Salmon smolt outmigration surveillance: a comparison of methods and a analysis of the Traffic lLght System
Masteroppgave i marin Ăžkologi - Nord universitet 202
Comparison of enzyme-linked immunosorbent assay, surface plasmon resonance and biolayer interferometry for screening of deoxynivalenol in wheat and wheat dust
A sample preparation method was developed for the screening of deoxynivalenol (DON) in wheat and wheat dust. Extraction was carried out with water and was successful due to the polar character of DON. For detection, an enzyme-linked immunosorbent assay (ELISA) was compared to the sensor-based techniques of surface plasmon resonance (SPR) and biolayer interferometry (BLI) in terms of sensitivity, affinity and matrix effect. The matrix effects from wheat and wheat dust using SPR were too high to further use this screenings method. The preferred ELISA and BLI methods were validated according to the criteria established in Commission Regulation 519/2014/EC and Commission Decision 2002/657/EC. A small survey was executed on 16 wheat lots and their corresponding dust samples using the validated ELISA method. A linear correlation (r = 0.889) was found for the DON concentration in dust versus the DON concentration in wheat (LOD wheat: 233 g/kg, LOD wheat dust: 458 g/kg)
Innovations in cryoconservation of animal genetic resources: SECTION 4 The economics of gene banking:Animal Production and Health Guideline
The livestock sector faces a range of challenges, including climate change, emerging diseases, competition for natural resources and evolving demand for animal-source foods, which is increasing globally, especially in developing countries. Genetic diversity of livestock is a key resource for allowing livestock keepers to address these challenges, but this diversity has been in a state of decline. The diminishing genetic diversity thus represents yet another obstacle for sustainable livestock production. Cryoconservation (i.e. ex situ â in vitro conservation) of genetic resources through gene banking provides one of the most powerful tools governments and other stakeholders have to manage genetic diversity in both the short and long term and thereby provide future generations with the tools to meet the challenges ahead.Gene banking genetic resources fits within the context of the Global Plan of Action forAnimal Genetic Resources, which was developed and adopted by FAO Member Nations.Specifically, Strategic Priority 9 of the Global Plan of Action is âEstablish or strengthen ex situ conservation programmesâ and Strategic Priority 11 urges countries to âDevelop approaches and technical standards for conservation. To assist countries in the implementation the Global Plan of Action, FAO worked with experts from around the world to prepare technical guidelines. In 2012 FAO published FAO Guidelines on Cryoconservation of animal genetic resources.Gene banking is a long-term effort that needs to be viewed in terms of decades rather than years, as demonstrated by similar systems for agricultural crops. The responsibility for establishing such resources lies squarely within governmentsâ roles of providing public goods and food security. Gene banking of animal genetic resources is a technology-intense undertaking and the associated technologies are in a continual state of research and development. The livestock sector also continues to evolve rapidly. Since the development and release of the previous guidelines, numerous changes have taken place. Critical among these is a greater appreciation of the opportunities for actively utilizing cryopreserved material to enhance management of in vivo populations, rather than as simply an âinsurance policyâ to protect breeds against extinction.This key development has led to further changes in gene bank management. First, interaction with users of the stored material has increased. This in turn has created a need to involve stakeholders more closely in the management of genetic collections and to better monitor and document the processes of gene banking to ensure quality management.Measures have been developed to help ensure high health and sanitary standards. New models and methods have been proposed for utilization of collections in the management of genetic diversity in vivo. Greater potential demand for stored material has also increased the need for expanded procedures and legal instruments, in some instances, to ensur
Freeze-thaw durability of recycled concrete from construction and demolition wastes
Road engineering is one of the most accepted applications for concrete including
recycled aggregates from construction and demolition wastes as a partial replacement of the natural
coarse aggregates. Amongst the durability concerns of such application, the deterioration due to
freeze-thaw cycles is one of the most important causes decreasing the life span of concrete in
countries with a continental climate. Moreover, the use of de-icing salts, which is a common
practice to prevent ice formation on roadways and walkways, increases the superficial degradation
of concrete due to frost-salt scaling. Thus, this paper aims to assess the resistance to frost salt with
de-icing salts of two recycled concrete mixtures containing a 50% replacement of the conventional
gravel by recycled aggregates both of mixed and ceramic nature, i.e. containing ceramic percentages
of 34% and 100%, in comparison to a conventional concrete made with siliceous gravel. Therefore,
the surface scaling was evaluated based on EN 1339 (2004) on 28 days cured cylinders, exposed to
7, 14, 21 and 28 freeze-thaw cycles in the presence of sodium chloride solution. Given that no airentraining
admixture was used in any of the mixtures, the scaling of both conventional and recycled
concretes exceeded the 1 kg/m2 limit established by the European standard. Nonetheless, for the
casting surface, the recycled concrete with low ceramic content exhibited a similar behaviour to the
conventional concrete, whereas the performance of the recycled concrete with high ceramic content
was better. However, as expected, trowelled surfaces showed a worse performance and both
recycled concretes had a lower freeze-thaw durability than the conventional mixture. In any case,
the results suggested that the composition of the recycled aggregates could be used as a factor to
limit the differences in performance between recycled and conventional mixtures
- âŠ