867 research outputs found
Riemann Surfaces of genus g with an automorphism of order p prime and p>g
The present work completes the classification of the compact Riemann surfaces
of genus g with an analytic automorphism of order p (prime number) and p > g.
More precisely, we construct a parameteriza- tion space for them, we compute
their groups of uniformization and we compute their full automorphism groups.
Also, we give affine equations for special cases and some implications on the
components of the singular locus of the moduli space of smooth curves of genus
g.Comment: 28 pages, 5 figure
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Sintering of ultrathin gold nanowires for transparent electronics
Ultrathin gold nanowires (AuNWs) with diameters below 2 nm and high aspect ratios are considered to be a promising base material for transparent electrodes. To achieve the conductivity expected for this system, oleylamine must be removed. Herein we present the first study on the conductivity, optical transmission, stability, and structure of AuNW networks before and after sintering with different techniques. Freshly prepared layers consisting of densely packed AuNW bundles were insulating and unstable, decomposing into gold spheres after a few days. Plasma treatments increased the conductivity and stability, coarsened the structure, and left the optical transmission virtually unchanged. Optimal conditions reduced sheet resistances to 50 Ω/sq
Nanofabrication and Electrochemical Characterization of Self-Assembled Monolayers Sandwiched between Metal Nanoparticles and Electrode Surfaces
Nanoscience and nanotechnology have reached the syllabi of many upper-division undergraduate and master-level courses all over the world. There is therefore a growing need for practical exercises that illustrate the fabrication, characterization, properties, and applications of nanomaterials. Here we describe an advanced-level laboratory experiment in which students had the opportunity to fabricate surfaces modified by ordered monolayers and nanostructured materials. The surface modification was quantified by means of a quartz crystal microbalance, while the electrochemical properties of the nanoarchitectures were assessed using cyclic voltammetry experiments. Electron transfer across self-assembled monolayers mediated by gold nanoparticles was presented as a topic for discussion, and consideration of potential practical applications of the observed phenomena (catalytic and electrocatalytic processes, as well as development of optical, (opto)electronic, and photovoltaic devices with enhanced properties) was proposed as a further reading exercise
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Multivalent bonds in self-assembled bundles of ultrathin gold nanowires
Ultrathin gold nanowires are unusual colloidal objects that assemble into bundles with line contacts between parallel wires. Each molecule in the contact line interacts with many ligand and solvent molecules. We used X-ray scattering and electron microscopy to study how these interactions control assembly
Bots conversacional en la información política desde la experiencia de los usuarios: Politibot
The production and distribution of news is changing. At the same time, the relationship between journalism and artificial intelligence systems is becoming stronger. Within this context, conversational bots have appeared, which are software applications that distribute personalised content (Al Johri et al., 2016) through social networks, online instant messaging apps, and mobile devices. This research presents a case study on the conversational political news bot known as Politibot, which is a pioneering, successful Spanish project that emerged during the 2016 election campaign. The study analyses users’ perceptions of the bot as a news and conversational tool based on their experience of use. An experimental methodology has been used in combination with other qualitative and quantitative research techniques (documentary analysis, direct observation, registration forms, as well as pre-test and post-test by means of questionnaires). The results show widespread acceptance in terms of reliability, comprehension, and the format regarding the information received from the bot, as well as its immediacy and customisation. However, the possibility of interacting with bots is still limited, which is also true of the case under study herein.La producción y distribución de noticias está cambiando a la vez que se hace más estrecha la relación entre periodismo y los sistemas de inteligencia artificial. En este contexto, aparecen los bots conversacionales, aplicaciones que distribuyen contenido personalizado (Al Johri et al., 2016) en las redes sociales y en las apps de mensajería instantánea vía online y a través de los dispositivos móviles. La presente investigación plantea un estudio de caso sobre el bot conversacional de información política Politibot, proyecto español pionero y de éxito surgido durante la campaña electoral de 2016. Se analiza la percepción que los usuarios tienen del bot como herramienta informativa y conversacional tras su experiencia de consumo. Se hace uso de una metodología experimental combinada con otras técnicas cualitativas y cuantitativas de investigación (análisis documental, observación directa y ficha de registro, pre-test y pos-test por medio de cuestionarios). Los resultados muestran gran aceptación en cuanto a la fiabilidad, comprensión y formato de la información recibida por el bot, así como a su inmediatez y personalización. Sin embargo, las posibilidades de interacción con bots, como el caso analizado, son aún limitadas
Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots
The temporal variation of the horizontal velocity in subsurface layers
beneath three different types of active regions is studied using the technique
of ring diagrams. In this study, we select active regions (ARs) 10923, 10930,
10935 from three consecutive Carrington rotations: AR 10930 contains a
fast-rotating sunspot in a strong emerging active region while other two have
non-rotating sunspots with emerging flux in AR 10923 and decaying flux in AR
10935. The depth range covered is from the surface to about 12 Mm. In order to
minimize the influence of systematic effects, the selection of active and quiet
regions is made so that these were observed at the same heliographic locations
on the solar disk. We find a significant variation in both components of the
horizontal velocity in active regions as compared to quiet regions. The
magnitude is higher in emerging-flux regions than in the decaying-flux region,
in agreement with earlier findings. Further, we clearly see a significant
temporal variation in depth profiles of both zonal and meridional flow
components in AR 10930, with the variation in the zonal component being more
pronounced. We also notice a significant influence of the plasma motion in
areas closest to the rotating sunspot in AR 10930 while areas surrounding the
non-rotating sunspots in all three cases are least affected by the presence of
the active region in their neighborhood.Comment: Solar Physics (in press), includes 11 figure
Relation of Diabetes to Cognitive Function in Hispanics/Latinos of Diverse Backgrounds in the United States
Objectives:To examine the association between diabetes and cognitive function within U.S. Hispanics/Latinos of Central American, Cuban, Dominican, Mexican, Puerto Rican, and South American background. Method: This cross-sectional study included 9,609 men and women (mean age = 56.5 years), who are members of the Hispanic Community Health Study/Study of Latinos. We classified participants as having diabetes, prediabetes, or normal glucose regulation. Participants underwent a neurocognitive battery consisting of tests of verbal fluency, delayed recall, and processing speed. Analyses were stratified by Hispanic/Latino subgroup. Results: From fully adjusted linear regression models, compared with having normal glucose regulation, having diabetes was associated with worse processing speed among Cubans (β = −1.99; 95% CI [confidence interval] = [−3.80, −0.19]) and Mexicans (β = −2.26; 95% CI = [−4.02, −0.51]). Compared with having normal glucose regulation, having prediabetes or diabetes was associated with worse delayed recall only among Mexicans (prediabetes: β = −0.34; 95% CI = [−0.63, −0.05] and diabetes: β = −0.41; 95% CI = [−0.79, −0.04]). No associations with verbal fluency. Discussion: The relationship between diabetes and cognitive function varied across Hispanic/Latino subgroup
Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra
With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultra-stable, double channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar atmospheric parameters (T_(eff), log g, ξ, and [Fe/H]) by means of the STEPAR code, a PYTHON implementation of the equivalent width method that employs the 2017 version of the MOOG code and a grid of MARCS model atmospheres. We compiled four Fe I and Fe II line lists suited to metal-rich dwarfs, metal-poor dwarfs, metal-rich giants, and metal-poor giants that cover the wavelength range from 5300 to 17 100 Å, thus substantially increasing the number of identified Fe I and Fe II lines up to 653 and 23, respectively, We examined the impact of the near-infrared Fe and Fen lines upon our parameter determinations after an exhaustive literature search, placing special emphasis on the 14 Gala benchmark stars contained in our sample, Even though our parameter determinations remain in good agreement with the literature values, the increase in the number of Fe l and Fe II lines when the near-infrared region is taken into account reveals a deeper T_(eff) scale that might stem from a higher sensitivity of the near-infrared lines to T_(eff)
Water waves generated by a moving bottom
Tsunamis are often generated by a moving sea bottom. This paper deals with
the case where the tsunami source is an earthquake. The linearized water-wave
equations are solved analytically for various sea bottom motions. Numerical
results based on the analytical solutions are shown for the free-surface
profiles, the horizontal and vertical velocities as well as the bottom
pressure.Comment: 41 pages, 13 figures. Accepted for publication in a book: "Tsunami
and Nonlinear Waves", Kundu, Anjan (Editor), Springer 2007, Approx. 325 p.,
170 illus., Hardcover, ISBN: 978-3-540-71255-8, available: May 200
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