638 research outputs found
The Gibbs-Thomson formula at small island sizes - corrections for high vapour densities
In this paper we report simulation studies of equilibrium features, namely
circular islands on model surfaces, using Monte-Carlo methods. In particular,
we are interested in studying the relationship between the density of vapour
around a curved island and its curvature-the Gibbs-Thomson formula. Numerical
simulations of a lattice gas model, performed for various sizes of islands,
don't fit very well to the Gibbs-Thomson formula. We show how corrections to
this form arise at high vapour densities, wherein a knowledge of the exact
equation of state (as opposed to the ideal gas approximation) is necessary to
predict this relationship. Exploiting a mapping of the lattice gas to the Ising
model one can compute the corrections to the Gibbs-Thomson formula using high
field series expansions. We also investigate finite size effects on the
stability of the islands both theoretically and through simulations. Finally
the simulations are used to study the microscopic origins of the Gibbs-Thomson
formula. A heuristic argument is suggested in which it is partially attributed
to geometric constraints on the island edge.Comment: 27 pages including 7 figures, tarred, gzipped and uuencoded. Prepared
using revtex and espf.sty. To appear in Phys. Rev.
Moons Are Planets: Scientific Usefulness Versus Cultural Teleology in the Taxonomy of Planetary Science
We argue that taxonomical concept development is vital for planetary science
as in all branches of science, but its importance has been obscured by unique
historical developments. The literature shows that the concept of planet
developed by scientists during the Copernican Revolution was theory-laden and
pragmatic for science. It included both primaries and satellites as planets due
to their common intrinsic, geological characteristics. About two centuries
later the non-scientific public had just adopted heliocentrism and was
motivated to preserve elements of geocentrism including teleology and the
assumptions of astrology. This motivated development of a folk concept of
planet that contradicted the scientific view. The folk taxonomy was based on
what an object orbits, making satellites out to be non-planets and ignoring
most asteroids. Astronomers continued to keep primaries and moons classed
together as planets and continued teaching that taxonomy until the 1920s. The
astronomical community lost interest in planets ca. 1910 to 1955 and during
that period complacently accepted the folk concept. Enough time has now elapsed
so that modern astronomers forgot this history and rewrote it to claim that the
folk taxonomy is the one that was created by the Copernican scientists.
Starting ca. 1960 when spacecraft missions were developed to send back detailed
new data, there was an explosion of publishing about planets including the
satellites, leading to revival of the Copernican planet concept. We present
evidence that taxonomical alignment with geological complexity is the most
useful scientific taxonomy for planets. It is this complexity of both primary
and secondary planets that is a key part of the chain of origins for life in
the cosmos.Comment: 68 pages, 16 figures. For supplemental data files, see
https://www.philipmetzger.com/moons_are_planets
Discovery of a Brown Dwarf Companion to Gliese 570ABC: A 2MASS T Dwarf Significantly Cooler than Gliese 229B
We report the discovery of a widely separated (258\farcs3\pm0\farcs4) T
dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was
initially identified from the Two Micron All Sky Survey (2MASS). Its
near-infrared spectrum shows the 1.6 and 2.2 \micron CH absorption bands
characteristic of T dwarfs, while its common proper motion with the Gl 570ABC
system confirms companionship. Gl 570D (M = 16.470.07) is nearly a
full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and
estimates of L = (2.80.3)x10 L_{\sun} and T = 75050
K make it significantly cooler and less luminous than any other known brown
dwarf companion. Using evolutionary models by Burrows et al. and an adopted age
of 2-10 Gyr, we derive a mass estimate of 5020 M for this object.Comment: 13 pages, 2 figures, 2 tables, accepted by ApJ
Animación sociocultural mediante el deporte en la Unidad de Salud Mental del establecimiento carcelario La Modelo de Bogotá
Servicio Social ComunitarioInvestigación realizada tuvo como objetivo la realización de una animación sociocultural en el establecimiento carcelario la Modelo ubicado en la ciudad de Bogotá- Colombia, especÃficamente en la unidad de salud mental, a través de metodologÃas participativas y alternativas de intervención como el Aprendizaje Servicio Solidario (ASS); de esta manera fue posible identificar en un primer momento algunas de las necesidades sentidas, percibidas e inferidas, tanto de la institución, como de las personas privadas de la libertad (PPL), a través del arte y el deporte. En un segundo momento se desarrolló una intervención a través de las metodologÃas ya mencionadas, utilizando el deporte como herramienta principal, buscando potencializar en los internos diferentes alternativas para la solución de problemas y la transformación de las necesidades evaluadas. En cuanto a este último objetivo de la intervención no todas las necesidades pudieron tener alguna modificación, puesto que algunas de ellas se encuentran vinculadas con lineamientos institucionales fuera del alcance de esta investigación. Para este estudio no se contó con una muestra estable, ya que para cada sesión los PPL podÃan elegir su participación de manera voluntaria y en casos particulares se evidenciaban traslados de patio o de establecimiento carcelario y, además, se presentaron situaciones de inseguridad en el patio, que no permitieron el desarrollo adecuado de las últimas sesiones de intervención.140 p.1. Marco Teórico
2. Marco Metodológico
3. Diseño Metodológico de la Intervención
4. CategorÃas de Análisis 5. Análisis de Contenido
6. Matriz Operativa del Proyecto
7. Análisis de Procesos
8. ReferenciasPregradoPsicólog
Envelope: interactive software for modeling and fitting complex isotope distributions
<p>Abstract</p> <p>Background</p> <p>An important aspect of proteomic mass spectrometry involves quantifying and interpreting the isotope distributions arising from mixtures of macromolecules with different isotope labeling patterns. These patterns can be quite complex, in particular with <it>in vivo </it>metabolic labeling experiments producing fractional atomic labeling or fractional residue labeling of peptides or other macromolecules. In general, it can be difficult to distinguish the contributions of species with different labeling patterns to an experimental spectrum and difficult to calculate a theoretical isotope distribution to fit such data. There is a need for interactive and user-friendly software that can calculate and fit the entire isotope distribution of a complex mixture while comparing these calculations with experimental data and extracting the contributions from the differently labeled species.</p> <p>Results</p> <p>Envelope has been developed to be user-friendly while still being as flexible and powerful as possible. Envelope can simultaneously calculate the isotope distributions for any number of different labeling patterns for a given peptide or oligonucleotide, while automatically summing these into a single overall isotope distribution. Envelope can handle fractional or complete atom or residue-based labeling, and the contribution from each different user-defined labeling pattern is clearly illustrated in the interactive display and is individually adjustable. At present, Envelope supports labeling with <sup>2</sup>H, <sup>13</sup>C, and <sup>15</sup>N, and supports adjustments for baseline correction, an instrument accuracy offset in the m/z domain, and peak width. Furthermore, Envelope can display experimental data superimposed on calculated isotope distributions, and calculate a least-squares goodness of fit between the two. All of this information is displayed on the screen in a single graphical user interface. Envelope supports high-quality output of experimental and calculated distributions in PNG or PDF format. Beyond simply comparing calculated distributions to experimental data, Envelope is useful for planning or designing metabolic labeling experiments, by visualizing hypothetical isotope distributions in order to evaluate the feasibility of a labeling strategy. Envelope is also useful as a teaching tool, with its real-time display capabilities providing a straightforward way to illustrate the key variable factors that contribute to an observed isotope distribution.</p> <p>Conclusion</p> <p>Envelope is a powerful tool for the interactive calculation and visualization of complex isotope distributions for comparison to experimental data. It is available under the GNU General Public License from <url>http://williamson.scripps.edu/envelope/</url>.</p
Science opportunities with solar sailing smallsats
Recently, we witnessed how the synergy of small satellite technology and
solar sailing propulsion enables new missions. Together, small satellites with
lightweight instruments and solar sails offer affordable access to deep regions
of the solar system, also making it possible to realize hard-to-reach
trajectories that are not constrained to the ecliptic plane. Combining these
two technologies can drastically reduce travel times within the solar system,
while delivering robust science. With solar sailing propulsion capable of
reaching the velocities of ~5-10 AU/yr, missions using a rideshare launch may
reach the Jovian system in two years, Saturn in three. The same technologies
could allow reaching solar polar orbits in less than two years. Fast,
cost-effective, and maneuverable sailcraft that may travel outside the ecliptic
plane open new opportunities for affordable solar system exploration, with
great promise for heliophysics, planetary science, and astrophysics. Such
missions could be modularized to reach different destinations with different
sets of instruments. Benefiting from this progress, we present the "Sundiver"
concept, offering novel possibilities for the science community. We discuss
some of the key technologies, the current design of the Sundiver sailcraft
vehicle and innovative instruments, along with unique science opportunities
that these technologies enable, especially as this exploration paradigm
evolves. We formulate policy recommendations to allow national space agencies,
industry, and other stakeholders to establish a strong scientific,
programmatic, and commercial focus, enrich and deepen the space enterprise and
broaden its advocacy base by including the Sundiver paradigm as a part of
broader space exploration efforts.Comment: 34 pages, 12 figures, 2 table
Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganismsâ€
A series of [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives have been synthesised as potential indicators of microbial nitroreductase activity. When assessed against a selection of 20 clinically important pathogenic microorganisms, microbial colonies of various colours (yellow, green, red, brown, black) were produced and attributed to nitroreductase activity. Most substrates elicited colour responses with Gram-negative microorganisms. In contrast, the growth of several species of Gram-positive microorganisms and yeasts was often inhibited by the substrates and hence coloured responses were not seen.
Graphical abstract: Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganism
Classification of Foetal Distress and Hypoxia Using Machine Learning Approaches
© 2018, Springer International Publishing AG, part of Springer Nature. Foetal distress and hypoxia (oxygen deprivation) is considered as a serious condition and one of the main factors for caesarean section in the obstetrics and Gynecology department. It is the third most common cause of death in new-born babies. Many foetuses that experienced some sort of hypoxic effects can develop series risks including damage to the cells of the central nervous system that may lead to life-long disability (cerebral palsy) or even death. Continuous labour monitoring is essential to observe the foetal well being. Foetal surveillance by monitoring the foetal heart rate with a cardiotocography is widely used. Despite the indication of normal results, these results are not reassuring, and a small proportion of these foetuses are actually hypoxic. In this paper, machine-learning algorithms are utilized to classify foetuses which are experiencing oxygen deprivation using PH value (a measure of hydrogen ion concentration of blood used to specify the acidity or alkalinity) and Base Deficit of extra cellular fluid level (a measure of the total concentration of blood buffer base that indicates the metabolic acidosis or compensated respiratory alkalosis) as indicators of respiratory and metabolic acidosis, respectively, using open source partum clinical data obtained from Physionet. Six well know machine learning classifier models are utilised in our experiments for the evaluation; each model was presented with a set of selected features derived from the clinical data. Classifier’s evaluation is performed using the receiver operating characteristic curve analysis, area under the curve plots, as well as the confusion matrix. Our simulation results indicate that machine-learning algorithms provide viable methods that could delivery improvements over conventional analysis
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