8,423 research outputs found
Role of the fast kinetics of pyroglutamate-modified amyloid-β oligomers in membrane binding and membrane permeability.
Membrane permeability to ions and small molecules is believed to be a critical step in the pathology of Alzheimer's disease (AD). Interactions of oligomers formed by amyloid-β (Aβ) peptides with the plasma cell membrane are believed to play a fundamental role in the processes leading to membrane permeability. Among the family of Aβs, pyroglutamate (pE)-modified Aβ peptides constitute the most abundant oligomeric species in the brains of AD patients. Although membrane permeability mechanisms have been studied for full-length Aβ1-40/42 peptides, these have not been sufficiently characterized for the more abundant AβpE3-42 fragment. Here we have compared the adsorbed and membrane-inserted oligomeric species of AβpE3-42 and Aβ1-42 peptides. We find lower concentrations and larger dimensions for both species of membrane-associated AβpE3-42 oligomers. The larger dimensions are attributed to the faster self-assembly kinetics of AβpE3-42, and the lower concentrations are attributed to weaker interactions with zwitterionic lipid headgroups. While adsorbed oligomers produced little or no significant membrane structural damage, increased membrane permeabilization to ionic species is understood in terms of enlarged membrane-inserted oligomers. Membrane-inserted AβpE3-42 oligomers were also found to modify the mechanical properties of the membrane. Taken together, our results suggest that membrane-inserted oligomers are the primary species responsible for membrane permeability
SMA and Spitzer Observations of Bok Glouble CB17: A Candidate First Hydrostatic Core?
We present high angular resolution SMA and Spitzer observations toward the
Bok globule CB17. SMA 1.3mm dust continuum images reveal within CB17 two
sources with an angular separation of about 21" (about 5250 AU at a distance of
250 pc). The northwestern continuum source, referred to as CB17 IRS, dominates
the infrared emission in the Spitzer images, drives a bipolar outflow extending
in the northwest-southeast direction, and is classified as a low luminosity
Class0/I transition object (L_bol ~ 0.5 L_sun). The southeastern continuum
source, referred to as CB17 MMS, has faint dust continuum emission in the SMA
1.3mm observations (about 6 sigma detection; ~3.8 mJy), but is not detected in
the deep Spitzer infrared images at wavelengths from 3.6 to 70 micron. Its
bolometric luminosity and temperature, estimated from its spectral energy
distribution, are less than 0.04 L_sun and 16 K, respectively. The SMA CO(2-1)
observations suggest that CB17 MMS may drive a low-velocity molecular outflow
(about 2.5 km/s), extending in the east-west direction. Comparisons with
prestellar cores and Class0 protostars suggest that CB17 MMS is more evolved
than prestellar cores but less evolved than Class0 protostars. The observed
characteristics of CB17 MMS are consistent with the theoretical predictions
from radiative/magneto hydrodynamical simulations of a first hydrostatic core,
but there is also the possibility that CB17 MMS is an extremely low luminosity
protostar deeply embedded in an edge-on circumstellar disk. Further
observations are needed to study the properties of CB17 MMS and to address more
precisely its evolutionary stage.Comment: 33 pages, 11 figures, to be published by Ap
Assessing molecular outflows and turbulence in the protostellar cluster Serpens South
Molecular outflows driven by protostellar cluster members likely impact their
surroundings and contribute to turbulence, affecting subsequent star formation.
The very young Serpens South cluster consists of a particularly high density
and fraction of protostars, yielding a relevant case study for protostellar
outflows and their impact on the cluster environment. We combined CO
observations of this region using the Combined Array for Research in
Millimeter-wave Astronomy (CARMA) and the Institut de Radioastronomie
Millim\'{e}trique (IRAM) 30 m single dish telescope. The combined map allows us
to probe CO outflows within the central, most active region at size scales of
0.01 pc to 0.8 pc. We account for effects of line opacity and excitation
temperature variations by incorporating CO and CO data for the
and transitions (using Atacama Pathfinder Experiment and
Caltech Submillimeter Observatory observations for the higher CO transitions),
and we calculate mass, momentum, and energy of the molecular outflows in this
region. The outflow mass loss rate, force, and luminosity, compared with
diagnostics of turbulence and gravity, suggest that outflows drive a sufficient
amount of energy to sustain turbulence, but not enough energy to substantially
counter the gravitational potential energy and disrupt the clump. Further, we
compare Serpens South with the slightly more evolved cluster NGC 1333, and we
propose an empirical scenario for outflow-cluster interaction at different
evolutionary stages.Comment: 26 pages, 15 figures, accepted for publication in the Astrophysical
Journa
THE STABILITY OF β-CAROTENE IN MANGO NECTAR
THE STABILITY OF β-CAROTENE IN MANGO NECTA
The UN in the lab
We consider two alternatives to inaction for governments combating terrorism, which we term Defense and Prevention. Defense consists of investing in resources that reduce the impact of an attack, and generates a negative externality to other governments, making their countries a more attractive objective for terrorists. In contrast, Prevention, which consists of investing in resources that reduce the ability of the terrorist organization to mount an attack, creates a positive externality by reducing the overall threat of terrorism for all. This interaction is captured using a simple 3×3 “Nested Prisoner’s Dilemma” game, with a single Nash equilibrium where both countries choose Defense. Due to the structure of this interaction, countries can benefit from coordination of policy choices, and international institutions (such as the UN) can be utilized to facilitate coordination by implementing agreements to share the burden of Prevention. We introduce an institution that implements a burden-sharing policy for Prevention, and investigate experimentally whether subjects coordinate on a cooperative strategy more frequently under different levels of cost sharing. In all treatments, burden sharing leaves the Prisoner’s Dilemma structure and Nash equilibrium of the game unchanged. We compare three levels of burden sharing to a baseline in a between-subjects design, and find that burden sharing generates a non-linear effect on the choice of the efficient Prevention strategy and overall performance. Only an institution supporting a high level of mandatory burden sharing generates a significant improvement in the use of the Prevention strategy
Aproximación enfermera a los cuidados no profesionales a través de las vivencias de una cuidadora
Introducción: El envejecimiento progresivo de la población española, y la creciente disminución de los recursos institucionales para el cuidado de las personas dependientes, implica que cada día sea mayor la necesidad de disponer de cuidadoras no profesionales. En la mayoría de los casos la calidad de vida de las personas dependientes depende de los cuidados no profesionales prestados por mujeres y familiares en general de la persona dependiente. Cuidados y cuidadores son a menudo invisibilizados y/o poco reconocidos desde el punto de vista social, institucional y legislativo. Es función de enfermería conocer esta problemática, identificar a las cuidadoras no profesionales y las necesidades derivadas de su rol, y dispensarles la ayuda, conocimiento y apoyo necesario para realizar esta tarea en las mejores condiciones posibles. Objetivos: Definir los conceptos relacionados con "el cuidar" dentro del sector popular de la salud para poder comprender las vivencias y la problemática de las personas que ejercen de cuidadoras dentro de este sector. Analizar e interpretar el discurso de una cuidadora informal relacionándolo con las categorías diagnósticas propuestas por la NANDA para poder descubrir los problemas relacionados con el cuidado donde sería posible la intervención enfermera al cuidador. Material y métodos: Revisión bibliográfica sistemática con inclusión de textos legislativos relevantes para este trabajo. Entrevista semiestructurada a una cuidadora no profesional. Análisis del discurso. Codificación abierta e inductiva de la información con establecimiento de dominios y categorías de análisis, tomando como modelo la “Teoría Fundamentada” de Glaser y Strauss. Resultados: dominios y categorías diagnósticas NANDA en base al discurso de una cuidadora. Conclusiones: Dada la importancia los cuidados no profesionales es fundamental que los programas de atención sanitaria de nuestra cultura y nuestra sociedad, creen las bases para garantizar el bienestar biopsicosocial de la cuidadora no profesional. Por otra parte, las cuidadoras no profesionales sufren numerosos problemas de salud en los que el profesional de enfermería puede actuar, especialmente detectando y previniendo los factores de riesgo para el cuidador
¿Qué comprensión de las conceptualizaciones del concepto de límite alcanzan los futuros profesores de matemáticas en bachillerato?
El póster contiene un resumen de una investigación de tipo experimental que se está desarrollando con 12 alumnos del máster de secundaria (4 arquitectos, 4 ingenieros y 4 matemáticos) sobre el concepto de límite. Se considera el marco teórico MKT (Ball, Thames y Phelps, 2008) relativo al conocimiento común y especializado del contenido, y las concepciones del límite intuitiva, aproximación óptima (Blázquez y Ortega, 2002) y métrica
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