704 research outputs found
Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
The James Webb Space Telescope will revolutionize transiting exoplanet
atmospheric science due to its capability for continuous, long-duration
observations and its larger collecting area, spectral coverage, and spectral
resolution compared to existing space-based facilities. However, it is unclear
precisely how well JWST will perform and which of its myriad instruments and
observing modes will be best suited for transiting exoplanet studies. In this
article, we describe a prefatory JWST Early Release Science (ERS) program that
focuses on testing specific observing modes to quickly give the community the
data and experience it needs to plan more efficient and successful future
transiting exoplanet characterization programs. We propose a multi-pronged
approach wherein one aspect of the program focuses on observing transits of a
single target with all of the recommended observing modes to identify and
understand potential systematics, compare transmission spectra at overlapping
and neighboring wavelength regions, confirm throughputs, and determine overall
performances. In our search for transiting exoplanets that are well suited to
achieving these goals, we identify 12 objects (dubbed "community targets") that
meet our defined criteria. Currently, the most favorable target is WASP-62b
because of its large predicted signal size, relatively bright host star, and
location in JWST's continuous viewing zone. Since most of the community targets
do not have well-characterized atmospheres, we recommend initiating preparatory
observing programs to determine the presence of obscuring clouds/hazes within
their atmospheres. Measurable spectroscopic features are needed to establish
the optimal resolution and wavelength regions for exoplanet characterization.
Other initiatives from our proposed ERS program include testing the instrument
brightness limits and performing phase-curve observations.(Abridged)Comment: This is a white paper that originated from an open discussion at the
Enabling Transiting Exoplanet Science with JWST workshop held November 16 -
18, 2015 at STScI (http://www.stsci.edu/jwst/science/exoplanets). Accepted
for publication in PAS
Construindo conhecimentos atravĂ©s do espaço sindical francĂȘs: um olhar sobre a informação e o papel do arquivo junto a uma polĂtica de memĂłria militante
Increased peptide contacts govern high affinity binding of a modified TCR whilst maintaining a native pMHC docking mode
NaturalT cell receptors (TCRs) generally bind to their cognate pMHC molecules with weak
affinity and fast kinetics, limiting their use as therapeutic agents. Using phage display, we
have engineered a high affinity version of the A6 wild-type TCR (A6wt), specific for the
human leukocyte antigen (HLA-Aïżœ0201) complexed with human T cell lymphotropic virus
type 111â19 peptide (A2-Tax). Mutations in just 4 residues in the CDR3b loop region of the
A6wt TCR were selected that improved binding to A2-Tax by nearly 1000-fold. Biophysical
measurements of this mutant TCR (A6c134) demonstrated that the enhanced binding
was derived through favorable enthalpy and a slower off-rate. The structure of the free
A6c134 TCR and the A6c134/A2-Tax complex revealed a native binding mode, similar to
the A6wt/A2-Tax complex. However, concordant with the more favorable binding enthalpy,
the A6c134TCR made increased contacts with theTax peptide compared with the A6wt/A2-
Tax complex, demonstrating a peptide-focused mechanism for the enhanced affinity that
directly involved the mutated residues in the A6c134TCR CDR3b loop.This peptide-focused
enhancedTCR binding may represent an important approach for developing antigen specific
high affinity TCR reagents for use in T cell based therapies
A chemical survey of exoplanets with ARIEL
Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planetâs birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25â7.8 ÎŒm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10â100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed â using conservative estimates of mission performance and a full model of all significant noise sources in the measurement â using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL â in line with the stated mission objectives â will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio
Search for composite and exotic fermions at LEP 2
A search for unstable heavy fermions with the DELPHI detector at LEP is
reported. Sequential and non-canonical leptons, as well as excited leptons and
quarks, are considered. The data analysed correspond to an integrated
luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV
and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172
GeV and 161 GeV. The search for pair-produced new leptons establishes 95%
confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2,
depending on the channel. The search for singly produced excited leptons and
quarks establishes upper limits on the ratio of the coupling of the excited
fermio
Sport, genetics and the `natural athlete': The resurgence of racial science
This article explores the ethical implications of recent discussions that naturalize the relationship between race, the body and sport within the frame of genetic science. Many suggestions of a racially distributed genetic basis for athletic ability and performance are strategically posited as a resounding critique of the `politically correct' meta-narratives of established sociological and anthropological forms of explanation that emphasize the social and cultural construction of race. I argue that this use of genetic science in order to describe and explain common-sense impressions of racial physiology and sporting ability is founded on erroneous premises of objectivity and disinterest, and inflates the analytical efficacy of scientific truth claims. I suggest that assertions of a value-free science of racial athletic ability reify race as inherited permanent biological characteristics that produce social hierarchies and are more characteristic of a longer history of `racial science'
Constructing Memory through Television in Argentina
La televisiĂłn representa el pasado reciente de la Argentina a travĂ©s de vĂnculos especĂficos con la memoria social: como un âemprendedor de la memoriaâ definiendo las agendas pĂșblicas, como un vehĂculo de transmisiĂłn intergeneracional sobre el pasado y como un creador de significados por medio de imĂĄgenes, sonidos y palabras, esto es, un âescenario para la memoriaâ. Un anĂĄlisis de los vĂnculos entre televisiĂłn y memorias, construido alrededor de la desapariciĂłn forzada de personas durante la dictadura militar de 1976 a 1983, revela la manera compleja en la cual los obstĂĄculos para relatar ese periodo trĂĄgico se combinan con el intento de vender un producto y entretener al espectador.Television represents Argentinaâs recent past through three specific links with social memory: as an âentrepreneur of memory,â shaping public agendas, as a vehicle of intergenerational transmission of past events, and as a creator of meaning through images, sounds, and words, a âstage for memoryâ. An analysis in terms of the links between television and the memories constructed around the forced disappearance of persons during the 1976â1983 military dictatorship reveals the complex way in which the obstacles when narrating an extreme experience are combined with the attempt to sell a product and entertain the spectator.Fil: Feld, Claudia Viviana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Centro de Investigaciones Sociales. Instituto de Desarrollo EconĂłmico y Social. Centro de Investigaciones Sociales; Argentin
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