5,377 research outputs found
Theoretical insight on the LK-99 material
Two recent preprints in physics archive (arXiv) have called the attention as
they claim experimental evidence that a Cu-substituted apatite material (called
LK-99) exhibits superconductivity at room temperature and pressure. If this
proves to be true, LK-99 will be the holy grail of superconductors. In this
work, we used Density-Functional Theory calculations to elucidate some key
features of the electronic structure of LK-99. Although some aspects of our
calculations are preliminary, we found that: i) in the ground state of the
material the ferromagnetic and antiferromagnetic configurations are practically
degenerated, ii) the material is metallic, iii) the Cu atoms seem to be hosts
in the lattice with not covalent bonds to other atoms and supporting almost
flat bands around the Fermi level, and iv) the electron-phonon coupling of
these flat bands seems to be dramatically large
A developmental evaluation approach to lesson study: exploring the impact of lesson study in London schools
This article presents a methodology for the developmental evaluation of a lesson study programme in primary and secondary schools. Our approach combined the principles of (i) user-focused evaluation, in which, as evaluators, we acted as participatory members of the innovation team and sought to involve users in the design and implementation of evaluation tools, (ii) a multi-level logical model to guide data collection and impact measurement and (iii) an ‘improving rather than proving’ approach to evaluation. The evaluation tools were used on a programme to promote lesson study in London schools involving 133 teachers and 33 schools. The evaluation methodology included outcomes at school leadership, teacher and student levels. Issues of internal and external validity are discussed and strengths and weaknesses are described. Findings showed promise in the use of our scale to measure changes in teacher pedagogical outcomes and in the recording of qualitative changes to both teachers and students as a result of the lesson study cycles. Suggestions for the future use and development of this methodology are proposed, including better use of control groups and quantitative measures to record changes in learning outcomes for students. List of Abbreviations: HE: Higher Education; LS: Lesson Study; PD: Professional Developmen
Evaluación de variabilidad genética en ganado criollo colombiano mediante 12 marcadores microsatélites
El objetivo del presente trabajo fue estimar la variabilidad y las relaciones filogenéticas entre 6 razas de ganado criollo colombiano, cebú Brahman y la española Pirenaica, mediante el uso de 12 marcadores moleculares tipo microsatélite. El número promedio de alelos fue de 11.58 con los valores más altos para los marcadores HEL 13 y ETH 10. La heterocigocidad promedio de todas las razas fue de 0.7 y el coeficiente de endogamia fue de 0.097, con los valores más altos para la raza Romosinuano. Los mayores valores de diversidad se presentaron en la raza Casanareño. La distancia genética entre las razas criollas colombianas y la raza española Pirenaica fue amplia (0.7-1.7) indicando posiblemente poca intervención de esta raza en el origen de las razas criollas. En general, las mayores distancias genéticas se presentaron entre las razas de origen Bos taurus (razas criollas colombianas y Pirenaica) con respecto a la Bos índicus (Brahman).Ganado de doble propósito-Ganaderia doble proposit
Epi-and Mesopelagic Fishes, Acoustic Data, and SST Images Collected Off Lanzarote, Fuerteventura, and Gran Canaria, Canary Islands, During Cruise La Bocaina 04-97
During cruise La Bocaina 0497 a series of 14 tows with a commercial pelagic trawl at depths between 20 and 700 m and an acoustic survey with a SIMRAD EK-500 echosounder were carried out in neritic and adjacent oceanic waters off Lanzarote, Fuerteventura, and Gran Canaria, Canary islands. In addition, SST images were obtained to get some informations on the prevailing hydrological conditions in the study area.
Of the 14 trawl tows ten were successful and resulted in capture of a total of 2166 fishes belonging to 81 species, 53 genera and 28 families. Ten species proved to be new records for the area of the Canary Islands. The acoustic survey covered a total of 2404 nm2 and allowed to obtain estimates of the abundance and biomass of fishes.
Both the fishing results and the acoustic study revealed considerable spatial variability in biomass of chub mackerel, Scomber japonicus, an epipelagic species of particular fisheries interest, showing clear variations in the numerical dominance of certain age- or size classes among different collecting localities. Furthermore, some juveniles in the first year of life occurred in the oceanic epipelagic during night together with vertically migrating mesopelagic fishes. Preliminary analyses of the stomach and intestinal content suggest that these juveniles fed close to the bottom during the day before and hence may undertake diurnal horizontal migrations between the shelf and adjacent oceanic waters. It is concluded that the great spatial flexibility of this species requires further monitoring surveys at regular intervals as a basis for establishing a sustainable fisheries management.
The acoustic data together with the trawling results demonstrate the existence of a dense deep scattering layer at depths between 400 and 700 m which is composed of mesopelagic fishes and invertebrates. Clear indications of diurnal vertical migrations were found in several species with formation of a shallow scattering layer in less than 150 m depth during night. Together with typical mesopelagic species such as stomiids and myctophids also juveniles of three benthopelagic species, which typically undergo a pelagic stage during early life, were collected.
Several individuals of mesopelagic species were collected above the shelf what may reflect the ecological boundary situation at ocean rims typical for oceanic islands and seamounts. Some mesopelagic species collected in this study may be closely associated with distinct hydrological conditions such as the myctophid Ceratoscopelus maderensis which was discovered in the SE of Fuerteventura in an area of possible local upwelling. This finding points to the existence of micro-zoogeographic zones within the Canary islands which derserve further investigation using a small-scaled comparative approach
Negative Thermal Expansion Coefficient of Graphene Measured by Raman Spectroscopy
The thermal expansion coefficient (TEC) of single-layer graphene is estimated
with temperature-dependent Raman spectroscopy in the temperature range between
200 and 400 K. It is found to be strongly dependent on temperature but remains
negative in the whole temperature range, with a room temperature value of
-8.0x10^{-6} K^{-1}. The strain caused by the TEC mismatch between graphene and
the substrate plays a crucial role in determining the physical properties of
graphene, and hence its effect must be accounted for in the interpretation of
experimental data taken at cryogenic or elevated temperatures.Comment: 17 pagese, 3 figures, and supporting information (4 pages, 3
figures); Nano Letters, 201
The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA
We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3σ sensitivity before inclination correction, resolution ∼1.4 kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.Fil: Bolatto, Alberto. University of Maryland; Estados UnidosFil: Wong, Tony. University of Illinois at Urbana; Estados UnidosFil: Utomo, Dyas. University of California at Berkeley; Estados UnidosFil: Blitz, Leo. University of California at Berkeley; Estados UnidosFil: Vogel, Stuart N.. University of Maryland; Estados UnidosFil: Sánchez, Sebastián F.. Universidad Nacional Autónoma de México; MéxicoFil: Barrera-Ballesteros, Jorge. University Johns Hopkins; Estados UnidosFil: Cao, Yixian. University of Illinois; Estados UnidosFil: Colombo, Dario. Max Planck Institut Fur Radioastronomie; AlemaniaFil: Dannerbauer, Helmut. Universidad de La Laguna; EspañaFil: García-Benito, Rubén. Instituto de Astrofísica de Andalucía; EspañaFil: Herrera-Camus, Rodrigo. Max Planck Institute für Extraterrestrische Physik; AlemaniaFil: Husemann, Bernd. Max-Planck-Institut für Astronomie; AlemaniaFil: Kalinova, Veselina. Max Planck Institut für Radioastronomie; AlemaniaFil: Leroy, Adam K.. Ohio State University; Estados UnidosFil: Leung, Gigi. Max-Planck-Institut für Astronomie; AlemaniaFil: Levy, Rebecca C.. University of Maryland; Estados UnidosFil: Mast, Damian. Observatorio Astronomico de la Universidad Nacional de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Ostriker, Eve. University of Princeton; Estados UnidosFil: Rosolowsky, Erik. University of Alberta; CanadáFil: Sandstrom, Karin M.. University of California at San Diego; Estados UnidosFil: Teuben, Peter. University of Maryland; Estados UnidosFil: Van De Ven, Glenn. Max-Planck-Institut für Astronomie; AlemaniaFil: Walter, Fabian. Max-Planck-Institut für Astronomie; Alemani
Enhancement of metabolite production in high-altitude microalgal strains by optimized C/N/P ratio
This study evaluated the role of C/N/P in the increase in the synthesis of carbohydrates, proteins, and lipids in two high-mountain strains of algae (Chlorella sp. UFPS019 and Desmodesmus sp. UFPS021). Three carbon sources (sodium acetate, sodium carbonate, and sodium bicarbonate), and the sources of nitrogen (NaNO3) and phosphate (KH2PO4 and K2HPO4) were analyzed using a surface response (3 factors, 2 levels). In Chlorella sp. UFPS019, the optimal conditions to enhance the synthesis of carbohydrates were high sodium carbonate content (3.53 g/L), high KH2PO4 and K2HPO4 content (0.06 and 0.14 g/L, respectively), and medium-high NaNO3 (0.1875 g/L). In the case of lipids, a high concentration of sodium acetate (1.19 g/L) coupled with high KH2PO4 and K2HPO4 content (0.056 and 0.131 g/L, respectively) and a low concentration of NaNO3 (0.075 g/L) drastically induced the synthesis of lipids. In the case of Desmodesmus sp. UFPS021, the protein content was increased using high sodium acetate (2 g/L), high KH2PO4 and K2HPO4 content (0.056 and 0.131 g/L, respectively), and high NaNO3 concentration (0.25 g/L). These results demonstrate that the correct adjustment of the C/N/P ratio can enhance the capacity of high-mountain strains of algae to produce high concentrations of carbohydrates, proteins, and lipids
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