762 research outputs found
Differences in the compatibility of infection between the liver flukes Fascioloides magna and Fasciola hepatica in a Colombian population of the snail Galba sp.
Experimental infections of Galba sp. (origin, Colombia) with allopatric isolates of Fasciola hepatica from France or Fascioloides magna from the Czech Republic were carried out during five successive snail generations to determine if this lymnaeid might sustain complete larval development of either parasite. In snails exposed to F. hepatica, 7 of 400 snails harboured several rediae and only two snails contained a small number of free cercariae on day 50 post-exposure. In contrast, the intensity of F. magna infection in Galba sp. progressively increased from the F1 to F5 generations. Spontaneous cercarial shedding of F. magna occurred in 7 of 100 Galba sp. belonging to the F5 generation and the number of shed cercariae did not differ significantly from that noted in control Galba truncatula of French origin. Galba sp. from Colombia can be added to the list of potential intermediate hosts for F. magna
Susceptibility of the 2D S=1/2 Heisenberg antiferromagnet with an impurity
We use a quantum Monte Carlo method (stochastic series expansion) to study
the effects of a magnetic or nonmagnetic impurity on the magnetic
susceptibility of the two-dimensional Heisenberg antiferromagnet. At low
temperatures, we find a log-divergent contribution to the transverse
susceptibility. We also introduce an effective few-spin model that can
quantitatively capture the differences between magnetic and nonmagnetic
impurities at high and intermediate temperatures.Comment: 5 pages, 4 figures, v2: Updated data in figures, minor changes in
text, v3: Final version, cosmetic change
Free-surface grease flow on a rotating plate
Grease lubrication is traditionally used in a great variety of mechanical systems such as rolling bearings, seals, and gears where it has been shown more advantageous than oil, mainly due to its consistency allowing the grease to stay inside the system and not leak out. Knowledge of the flow dynamics of grease is important for the understanding and prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. Free-surface effects play an important role in rolling bearings and open gears as the configuration normally is filled with about 30 % grease to avoid heavy churning. In this study, an analytical model of the stationary uniform flow on a rotating disc is developed and validated with experiments. The model results in the velocity profile for the flow in the thin fully yielded viscous layer in connection to the surface as well as an expression for the plug flow region on top of the viscous layer. Furthermore, the depth-averaged velocity is derived as is the shear stress value on the plate. From the latter, follows a condition for the grease to start moving and in turn yielding an expression for the viscous layer thickness as a function of the grease yield stress value, grease density, angular velocity, and radial position. In addition, an expression of the layer thickness containing the ratio between the flow rate and the layer width which in turn can account for effects not included in the model such as wall slip and surface adhesion and thus add another degree of freedom into the model. Experiments with two different greases having NLGI grade 1 and 2, respectively, shows it is possible to obtain a good fit with the analytically obtained thickness using the rheological parameters for actual grease
Bonding mechanism in the nitrides Ti2AlN and TiN: an experimental and theoretical investigation
The electronic structure of nanolaminate Ti2AlN and TiN thin films has been
investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured
Ti L, N K, Al L1 and Al L2,3 emission spectra are compared with calculated
spectra using ab initio density-functional theory including dipole transition
matrix elements. Three different types of bond regions are identified; a
relatively weak Ti 3d - Al 3p bonding between -1 and -2 eV below the Fermi
level, and Ti 3d - N 2p and Ti 3d - N 2s bonding which are deeper in energy
observed at -4.8 eV and -15 eV below the Fermi level, respectively. A strongly
modified spectral shape of 3s states of Al L2,3 emission from Ti2AlN in
comparison to pure Al metal is found, which reflects the Ti 3d - Al 3p
hybridization observed in the Al L1 emission. The differences between the
electronic and crystal structures of Ti2AlN and TiN are discussed in relation
to the intercalated Al layers of the former compound and the change of the
materials properties in comparison to the isostructural carbides.Comment: 18 pages, 7 figures;
http://link.aps.org/doi/10.1103/PhysRevB.76.19512
Measurement with Persons: A European Network
The European âMeasuring the Impossibleâ Network MINET promotes new research activities in measurement dependent on human perception and/or interpretation. This includes the perceived attributes of products and services, such as quality or desirability, and societal parameters such as security and well-being. Work has aimed at consensus about four âgenericâ metrological issues: (1) Measurement Concepts & Terminology; (2) Measurement Techniques: (3) Measurement Uncertainty; and (4) Decision-making & Impact Assessment, and how these can be applied specificallyto the âMeasurement of Personsâ in terms of âMan as a Measurement Instrumentâ and âMeasuring Man.â Some of the main achievements of MINET include a research repository with glossary; training course; book; series of workshops;think tanks and study visits, which have brought together a unique constellation of researchers from physics, metrology,physiology, psychophysics, psychology and sociology. Metrology (quality-assured measurement) in this area is relativelyunderdeveloped, despite great potential for innovation, and extends beyond traditional physiological metrology in thatit also deals with measurement with all human senses as well as mental and behavioral processes. This is particularlyrelevant in applications where humans are an important component of critical systems, where for instance health andsafety are at stake
Plants as De-Worming Agents of Livestock in the Nordic Countries: Historical Perspective, Popular Beliefs and Prospects for the Future
Preparations derived from plants were the original therapeutic interventions used by man to control diseases (including parasites), both within humans and livestock. Development of herbal products depended upon local botanical flora with the result that different remedies tended to develop in different parts of the world. Nevertheless, in some instances, the same or related plants were used over wide geographic regions, which also was the result of communication and/or the importation of plant material of high repute. Thus, the Nordic countries have an ancient, rich and diverse history of plant derived anthelmintic medications for human and animal use. Although some of the more commonly used herbal de-wormers were derived from imported plants, or their products, many are from endemic plants or those that thrive in the Scandinavian environment. With the advent of the modern chemotherapeutic era, and the discovery, development and marketing of a seemingly unlimited variety of highly efficacious, safe synthetic chemicals with very wide spectra of activities, herbal remedies virtually disappeared from the consciousness â at least in the Western world. This attitude is now rapidly changing. There is a widespread resurgence in natural product medication, driven by major threats posed by multi-resistant pest, or disease, organisms and the diminishing public perceptions that synthetic chemicals are the panacea to health and disease control. This review attempts to provide a comprehensive account of the depth of historical Nordic information available on herbal de-wormers, with emphasis on livestock and to provide some insights on potentially rewarding areas of "re-discovery" and scientific evaluation in this field
Genetic variability in European black grouse (Tetrao tetrix)
We studied microsatellite genetic variation in 14 different geographic populations of black grouse (Tetrao tetrix) across the European range. Populations were grouped in three different fragmentation categories: isolated, contiguous and continuous, respectively. Genetic diversity, measured as observed heterozygosity (H O), expected heterozygosity (H E) and allelic richness, were lower in isolated populations as compared to the other two categories that did not differ amongst one another. These results imply that lowered genetic variability in black grouse populations is negatively affected by population isolation. Our results suggest that the connectivity of small and isolated populations in Western Europe should be improved or else these face an increased risk of extinction due to genetic and demographic stochasticity
Convolutional LSTM Networks for Subcellular Localization of Proteins
Machine learning is widely used to analyze biological sequence data.
Non-sequential models such as SVMs or feed-forward neural networks are often
used although they have no natural way of handling sequences of varying length.
Recurrent neural networks such as the long short term memory (LSTM) model on
the other hand are designed to handle sequences. In this study we demonstrate
that LSTM networks predict the subcellular location of proteins given only the
protein sequence with high accuracy (0.902) outperforming current state of the
art algorithms. We further improve the performance by introducing convolutional
filters and experiment with an attention mechanism which lets the LSTM focus on
specific parts of the protein. Lastly we introduce new visualizations of both
the convolutional filters and the attention mechanisms and show how they can be
used to extract biological relevant knowledge from the LSTM networks
Dimensionally Dependent Tensor Identities by Double Antisymmetrisation
Some years ago, Lovelock showed that a number of apparently unrelated
familiar tensor identities had a common structure, and could all be considered
consequences in n-dimensional space of a pair of fundamental identities
involving trace-free (p,p)-forms where 2p >= n$. We generalise Lovelock's
results, and by using the fact that associated with any tensor in n-dimensional
space there is associated a fundamental tensor identity obtained by
antisymmetrising over n+1 indices, we establish a very general 'master'
identity for all trace-free (k,l)-forms. We then show how various other special
identities are direct and simple consequences of this master identity; in
particular we give direct application to Maxwell, Lanczos, Ricci, Bel and
Bel-Robinson tensors, and also demonstrate how relationships between scalar
invariants of the Riemann tensor can be investigated in a systematic manner.Comment: 17 pages, 2 figure
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