Dynamic rotor mode in antiferromagnetic nanoparticles

We present experimental, numerical, and theoretical evidence for a new mode of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering experiments on 8 nm particles of hematite display a loss of diffraction intensity with temperature, the intensity vanishing around 150 K. However, the signal from inelastic neutron scattering remains above that temperature, indicating a magnetic system in constant motion. In addition, the precession frequency of the inelastic magnetic signal shows an increase above 100 K. Numerical Langevin simulations of spin dynamics reproduce all measured neutron data and reveal that thermally activated spin canting gives rise to a new type of coherent magnetic precession mode. This "rotor" mode can be seen as a high-temperature version of superparamagnetism and is driven by exchange interactions between the two magnetic sublattices. The frequency of the rotor mode behaves in fair agreement with a simple analytical model, based on a high temperature approximation of the generally accepted Hamiltonian of the system. The extracted model parameters, as the magnetic interaction and the axial anisotropy, are in excellent agreement with results from Mossbauer spectroscopy

Extended surfaces modulate and can catalyze hydrophobic effects

Interfaces are a most common motif in complex systems. To understand how the presence of interfaces affect hydrophobic phenomena, we use molecular simulations and theory to study hydration of solutes at interfaces. The solutes range in size from sub-nanometer to a few nanometers. The interfaces are self-assembled monolayers with a range of chemistries, from hydrophilic to hydrophobic. We show that the driving force for assembly in the vicinity of a hydrophobic surface is weaker than that in bulk water, and decreases with increasing temperature, in contrast to that in the bulk. We explain these distinct features in terms of an interplay between interfacial fluctuations and excluded volume effects---the physics encoded in Lum-Chandler-Weeks theory [J. Phys. Chem. B 103, 4570--4577 (1999)]. Our results suggest a catalytic role for hydrophobic interfaces in the unfolding of proteins, for example, in the interior of chaperonins and in amyloid formation.Comment: 22 pages, 5 figure

Foliar Application of Several Nitrogen Sources as Fertilisers to Tempranillo Grapevines: Effect on Wine Volatile Composition

Foliar nitrogen applications to the vineyard make it possible to improve grape and wine phenolic and amino acid concentration. However, to our knowledge, there is little information about their impacts on the volatile composition of wine. Therefore, the aim of this work was to evaluate the effects of the application of several nitrogen sources in Tempranillo vineyards on wine volatile composition during the first season. Subsequently, two dosages of phenylalanine and urea were applied to the vineyard with the aim of evaluating their effect on wine volatile composition. The results show that the different nitrogen sources applied to the grapevines during the first season did not affect higher alcohols, fatty acids, esters and other volatile compounds in the wines. The two dosages of phenylalanine and urea applied to the vineyard during the second vintage barely affected wine volatile composition. Consequently, this study shows that foliar nitrogen treatments in vineyards did not modify the wine aromatic profile

Resighting of a Narwhal (Monodon monoceros) Instrumented with a Satellite Transmitter

On 9 August 2001, a male narwhal (Monodon monoceros) was instrumented with a satellite transmitter attached to the dorsal side of the tusk in Creswell Bay on Somerset Island in the Canadian High Arctic. The whale was identified five years later, on 22 June 2006, in a photo of a group of narwhals taken from the ice edge in Lancaster Sound. Examination of the position of the transmitter on the tusk showed that the tusk had grown approximately 17 cm in the five-year period. The transmitter was still located on the dorsal side of the tusk and this fact, together with the length of spiral grains at the position of the tag, indicates that the tusk had not turned over (rotated) in the five-year period. The whale was photographed on its spring migration back to the original summer ground where it had been tagged. This resighting confirms evidence for site fidelity of narwhals, as the individual maintained the same migratory schedule and route observed for narwhals from previous satellite tracking studies in Creswell Bay.Le 9 août 2001, un émetteur satellite a été posé sur un narval mâle (Monodon monoceros), plus précisément du côté dorsal de sa défense et ce, dans la baie Creswell, à l’île Somerset, dans l’Extrême-Arctique canadien. Cinq ans plus tard, soit le 22 juin 2006, la baleine a été aperçue dans la photo d’un groupe de narvals prise à partir de la lisière de glaces du détroit de Lancaster. L’examen de l’emplacement de l’émetteur sur la défense a permis de constater que la défense avait grandi d’environ 17 cm pendant la période de cinq ans. L’émetteur se trouvait toujours du côté dorsal de la défense et cela, allié à la longueur des fibres torses à l’emplacement de l’étiquette, indique que la défense n’avait pas subi de rotation pendant la période de cinq ans. La baleine a été photographiée pendant sa migration printanière de retour vers l’endroit où elle avait d’abord été étiquetée l’été. Ce repérage permet de confirmer les preuves relativement à la fidélité des narvals à leurs emplacements, car cette baleine avait maintenu les mêmes horaire et trajet migratoires observés chez les narvals à partir d’autres études de repérage par satellite réalisées dans la baie Creswell

Measurement of the magnetic field of small magnets with a smartphone: a very economical laboratory practice for introductory physics courses

In this work, we propose an inexpensive laboratory practice for an introductory physics course laboratory for any grade of science and engineering study. This practice was very well received by our students, where a smartphone (iOS, Android, or Windows) is used together with mini magnets (similar to those used on refrigerator doors), a 20 cm long school rule, a paper, and a free application (app) that needs to be downloaded and installed that measures magnetic fields using the smartphone's magnetic field sensor or magnetometer. The apps we have used are: Magnetometer (iOS), Magnetometer Metal Detector, and Physics Toolbox Magnetometer (Android). Nothing else is needed. Cost of this practice: free. The main purpose of the practice is that students determine the dependence of the component x of the magnetic field produced by different magnets (including ring magnets and sphere magnets). We obtained that the dependency of the magnetic field with the distance is of the form x-3, in total agreement with the theoretical analysis. The secondary objective is to apply the technique of least squares fit to obtain this exponent and the magnetic moment of the magnets, with the corresponding absolute error.AB thanks the Vicerectorship of Information Technologies of the University of Alicante (Spain) and the help of GITE-09006-UA. IE is grateful to the Ministry of Economy and Competitiveness for help provided through the project DPI2012-32994

Modeling healthcare authorization and claim submissions using the openEHR dual-model approach

<p>Abstract</p> <p>Background</p> <p>The TISS standard is a set of mandatory forms and electronic messages for healthcare authorization and claim submissions among healthcare plans and providers in Brazil. It is not based on formal models as the new generation of health informatics standards suggests. The objective of this paper is to model the TISS in terms of the openEHR archetype-based approach and integrate it into a patient-centered EHR architecture.</p> <p>Methods</p> <p>Three approaches were adopted to model TISS. In the first approach, a set of archetypes was designed using ENTRY subclasses. In the second one, a set of archetypes was designed using exclusively ADMIN_ENTRY and CLUSTERs as their root classes. In the third approach, the openEHR ADMIN_ENTRY is extended with classes designed for authorization and claim submissions, and an ISM_TRANSITION attribute is added to the COMPOSITION class. Another set of archetypes was designed based on this model. For all three approaches, templates were designed to represent the TISS forms.</p> <p>Results</p> <p>The archetypes based on the openEHR RM (Reference Model) can represent all TISS data structures. The extended model adds subclasses and an attribute to the COMPOSITION class to represent information on authorization and claim submissions. The archetypes based on all three approaches have similar structures, although rooted in different classes. The extended openEHR RM model is more semantically aligned with the concepts involved in a claim submission, but may disrupt interoperability with other systems and the current tools must be adapted to deal with it.</p> <p>Conclusions</p> <p>Modeling the TISS standard by means of the openEHR approach makes it aligned with ISO recommendations and provides a solid foundation on which the TISS can evolve. Although there are few administrative archetypes available, the openEHR RM is expressive enough to represent the TISS standard. This paper focuses on the TISS but its results may be extended to other billing processes. A complete communication architecture to simulate the exchange of TISS data between systems according to the openEHR approach still needs to be designed and implemented.</p

Fluctuations of water near extended hydrophobic and hydrophilic surfaces

We use molecular dynamics simulations of the SPC-E model of liquid water to derive probability distributions for water density fluctuations in probe volumes of different shapes and sizes, both in the bulk as well as near hydrophobic and hydrophilic surfaces. To obtain our results, we introduce a biased sampling of coarse-grained densities, which in turn biases the actual solvent density. The technique is easily combined with molecular dynamics integration algorithms. Our principal result is that the probability for density fluctuations of water near a hydrophobic surface, with or without surface-water attractions, is akin to density fluctuations at the water-vapor interface. Specifically, the probability of density depletion near the surface is significantly larger than that in bulk. In contrast, we find that the statistics of water density fluctuations near a model hydrophilic surface are similar to that in the bulk

Changes on grape volatile composition after elicitors and nitrogen compounds foliar applications to 'Garnacha', 'Tempranillo' and 'Graciano' vines

Grape volatile compounds determine the wine quality and typicity. The aim of this work was to study the effects of several foliar applications in 'Garnacha', 'Tempranillo', and 'Graciano' grapevines in order to enhance their grape volatile composition. The field trial involved the application of two nitrogen compounds, urea (Ur) and phenylalanine (Phe), and two elicitors, methyl jasmonate (MeJ) and a yeast extract (YE). The analysis of grape volatile compounds was carried out by HS-SPME-GC-MS. For 'Garnacha', most terpenes, and C13 norisoprenoids increased their grape content by applying Ur and Phe, and especially MeJ. For 'Tempranillo', treatments with Ur and MeJ improved the synthesis of most terpenoids. For 'Graciano', a trend to decrease the terpenoids content in grapes with the treatments was observed; however, Phe application increased C13 norisoprenoids content. In conclusion, foliar application of, Phe or Ur, and an elicitor, MeJ, can be a useful tool to improve grape quality