3,251 research outputs found
Complex organic molecules in strongly UV-irradiated gas
We investigate the presence of COMs in strongly UV-irradiated interstellar
molecular gas. We have carried out a complete millimetre line survey using the
IRAM30m telescope towards the edge of the Orion Bar photodissociation region
(PDR), close to the H2 dissociation front, a position irradiated by a very
intense far-UV (FUV) radiation field. These observations have been complemented
with 8.5 arcsec resolution maps of the H2CO 5(1,5)-4(1,4) and C18O 3-2 emission
at 0.9 mm. Despite being a harsh environment, we detect more than 250 lines
from COMs and related precursors: H2CO, CH3OH, HCO, H2CCO, CH3CHO, H2CS, HCOOH,
CH3CN, CH2NH, HNCO, H13-2CO, and HC3N (in decreasing order of abundance). For
each species, the large number of detected lines allowed us to accurately
constrain their rotational temperatures (Trot) and column densities (N). Owing
to subthermal excitation and intricate spectroscopy of some COMs (symmetric-
and asymmetric-top molecules such as CH3CN and H2CO, respectively), a correct
determination of N and Trot requires building rotational population diagrams of
their rotational ladders separately. We also provide accurate upper limit
abundances for chemically related molecules that might have been expected, but
are not conclusively detected at the edge of the PDR (HDCO, CH3O, CH3NC,
CH3CCH, CH3OCH3, HCOOCH3, CH3CH2OH, CH3CH2CN, and CH2CHCN). A non-LTE LVG
excitation analysis for molecules with known collisional rate coefficients,
suggests that some COMs arise from different PDR layers but we cannot resolve
them spatially. In particular, H2CO and CH3CN survive in the extended gas
directly exposed to the strong FUV flux (Tk = 150-250 K and Td > 60 K), whereas
CH3OH only arises from denser and cooler gas clumps in the more shielded PDR
interior (Tk = 40-50 K). We find a HCO/H2CO/CH3OH = 1/5/3 abundance ratio.
These ratios are different from those inferred in hot cores and shocks.Comment: 29 pages, 22 figures, 17 tables. Accepted for publication in A&A
(abstract abridged
Direct estimation of electron density in the Orion Bar PDR from mm-wave carbon recombination lines
A significant fraction of the molecular gas in star-forming regions is
irradiated by stellar UV photons. In these environments, the electron density
(n_e) plays a critical role in the gas dynamics, chemistry, and collisional
excitation of certain molecules. We determine n_e in the prototypical strongly
irradiated photodissociation region (PDR), the Orion Bar, from the detection of
new millimeter-wave carbon recombination lines (mmCRLs) and existing far-IR
[13CII] hyperfine line observations. We detect 12 mmCRLs (including alpha,
beta, and gamma transitions) observed with the IRAM 30m telescope, at ~25''
angular resolution, toward the H/H2 dissociation front (DF) of the Bar. We also
present a mmCRL emission cut across the PDR. These lines trace the C+/C/CO gas
transition layer. As the much lower frequency carbon radio recombination lines,
mmCRLs arise from neutral PDR gas and not from ionized gas in the adjacent HII
region. This is readily seen from their narrow line profiles (dv=2.6+/-0.4
km/s) and line peak LSR velocities (v_LSR=+10.7+/-0.2 km/s). Optically thin
[13CII] hyperfine lines and molecular lines - emitted close to the DF by trace
species such as reactive ions CO+ and HOC+ - show the same line profiles. We
use non-LTE excitation models of [13CII] and mmCRLs and derive n_e = 60-100
cm^-3 and T_e = 500-600 K toward the DF. The inferred electron densities are
high, up to an order of magnitude higher than previously thought. They provide
a lower limit to the gas thermal pressure at the PDR edge without using
molecular tracers. We obtain P_th > (2-4)x10^8 cm^-3 K assuming that the
electron abundance is equal or lower than the gas-phase elemental abundance of
carbon. Such elevated thermal pressures leave little room for magnetic pressure
support and agree with a scenario in which the PDR photoevaporates.Comment: Accepted for publication in A&A Letters (includes language editor
corrections
Editorial of Special Issue Combining Sensors and Multibody Models for Applications in Vehicles, Machines, Robots and Humans
[Abstract] The combination of physical sensors and computational models to provide additional information about system states, inputs and/or parameters, in what is known as virtual sensing, is becoming more and more popular in many sectors, such as the automotive, aeronautics, aerospatial, railway, machinery, robotics and human biomechanics sector
Exploring the Optical Resonances of Photocatalytic Bismuth Nanostructures
Symposium O—Plasmonic Nanomaterials for Energy Conversion, Boston, Massachusetts, November 29-December 4, 2015Nanostructures presenting optical resonances present a strong potential for energy applications. This potential has been first developed with noble metal nanostructures. At their plasmonic resonances, they can be used as scatterers for improved light trapping into photovoltaic photonic structures or as near-field enhancers boosting photocarrier excitation in photovoltaic media.1 Very recently, plasmoelectric potentials have been measured in resonant noble metal nanostructures, thus allowing a novel opto-electrical conversion scheme.2
Optical resonances can be excited in nanostructures beyond noble metals. Indeed, most of the metals of the periodic table can support plasmonic resonances.3 Moreover, non-Drude plasmonic-like resonances can also be achieved: for instance the so-called interband polaritonic resonances in nanostructures presenting sharp interband transitions, such as bismuth nanostructures.4,5 Based on such resonances, the potential of bismuth nanostructures for photocatalysis has been demonstrated.6,7 In the reported works, photocatalysis was achieved using bismuth nanospheres. At present, the underlying mechanism has to be discussed together with the photocatalytic potential of bismuth nanostructures in a broad range of sizes and shapes.
In this presentation, we provide a detailed description of the optical response of bismuth nanostructures as a function of their size and shape, with dimensions ranging from 50 nm to 500 nm. We demonstrate a strong dependence of the absorption, scattering and extinction cross-sections, near-field, surface charges and currents that will impact the efficiency of photocatalytic solutions based on bismuth nanostructures.
1 Polman, A. et al.; Photonic design principles for ultrahigh efficiency photovoltaics, Nature Materials 2012, 11, 174
2 Sheldon, M.T. et al.; Plasmoelectric potentials in metal nanostructures, Science 2014, 346, 828
3 Naik, G. et al.; Alternative plasmonic materials: Beyond gold and silver, Advanced Materials 2013, 25, 3264
4 Toudert, J. et al.; Exploring the optical potential of nano-bismuth: tunable surface plasmon resonances in the near ultraviolet-to-near infrared range, Journal of Physical Chemistry C 2012, 116, 20530
4 Toudert, J. et al.; Spectroscopic ellipsometry for active nano- and meta- materials, Nanotechnology Reviews 2014, 3, 223
6 Wang, Z. et al.; Investigation of the optical and photocatalytic properties of bismuth nanospheres prepared by a facile thermolysis method, Journal of Physical Chemistry C 2014, 118, 1155
7 Dong, F.; A semimetal bismuth element as a direct plasmonic photocatalyst, Chemical Communications 2014, 50, 10386Peer Reviewe
Reusable model transformation components with bentō
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-21155-8_5Building high-quality transformations that can be used in real projects is complex and time-consuming. For this reason, the ability to reuse existing transformations in different, unforeseen scenarios is very valuable. However, there is scarce tool support for this task. This paper presents bentō, a tool which supports the development and execution of reusable transformation components. In bentō, a reusable transformation is written as a regular ATL transformation, but it uses concepts as meta-models. Reuse is achieved by binding such concepts to meta-models, which induces the transformation adaptation. Moreover, composite components enable chaining transformations, and it is possible to convert an existing transformation into a reusable component. Bentō is implemented as an Eclipse plug-in, available as free software.This work was supported by the Spanish Ministry of Economy and Competitivity with project Go-Lite (TIN2011-24139), the R&D programme of the Madrid Region with project (SICOMORO S2013/ICE-3006), and the EU commission with project MONDO (FP7-ICT 2013-10, #611125)
Body Contour Surgery in Massive Weight Loss Patients
Background: Massive weight loss population presents different body deformities due to deflation and poor skin tone. Deformities in the lower trunk, upper torso, arms, and thighs are based on age, degree of skin laxity, and adipose tissue. Traditional plastic surgery techniques like abdominoplasty will not work in this kind of patients. Surgeon’s major challenge is how to restore the skin and overlaying fat in patients that do not have the same deformities. Identifying the vectors of dropping tissue will lead to classifying this kind of deformities and planning the best surgical procedure
Cytomegalovirus pneumonitis complicated by a central peribronchial pattern of organising pneumonia
We present five cases of cytomegalovirus (CMV) pneumonitis occurring in patients after recent T cell deplete allogeneic stem cell transplantation (AlloHSCT). These cases were complicated by an organising pneumonia (during the recovery period) with a predominantly central peribronchial pattern. All patients presented with evidence of active CMV pneumonitis which was treated successfully with anti-viral therapy but was followed by persistent severe dyspnoea, cough and hypoxia. High resolution computed tomography (HRCT) imaging showed widespread central peribronchial consolidation with traction bronchiectasis. There was a marked clinical and physiological improvement after treatment with systemic corticosteroids. However, in all patients the lung function remained abnormal and in some cases imaging revealed a fibrosing lung disease. These cases represent a previously undescribed central peribronchial pattern of organising pneumonia complicating CMV pneumonitis that can result in chronic lung damage
Deploying Large-Scale Datasets on-Demand in the Cloud: Treats and Tricks on Data Distribution
Public clouds have democratised the access to analytics for virtually any institution in the world. Virtual Machines (VMs) can be provisioned on demand, and be used to crunch data after uploading into the VMs. While this task is trivial for a few tens of VMs, it becomes increasingly complex and time consuming when the scale grows to hundreds or thousands of VMs crunching tens or hundreds of TB. Moreover, the elapsed time comes at a price: the cost of provisioning VMs in the cloud and keeping them waiting to load the data. In this paper we present a big data provisioning service that incorporates hierarchical and peer-to-peer data distribution techniques to speed-up data loading into the VMs used for data processing. The system dynamically mutates the sources of the data for the VMs to speed-up data loading. We tested this solution with 1000 VMs and 100 TB of data, reducing time by at least 30 % over current state of the art techniques. This dynamic topology mechanism is tightly coupled with classic declarative machine configuration techniques (the system takes a single high-level declarative configuration file and configures both software and data loading). Together, these two techniques simplify the deployment of big data in the cloud for end users who may not be experts in infrastructure management. Index Terms—Large-scale data transfer, flash crowd, big data, BitTorrent, p2p overlay, provisioning, big data distribution I
Disparidades regionales en la Unión Europea. Una aproximación a la cuantificación de la cohesión económica y social
El Tratado de la Unión Europea (UE) de 1992 y el texto de la Constitución para Europa, actualmente en proceso de aprobación por los países miembros, establecen como uno de los principales objetivos de la Unión el logro de una más alta cohesión económica y social. La cuantificación de este objetivo incluye un amplio conjunto de aspectos, aunque no están bien definidos en los distintos documentos comunitarios. El PIB por habitante se ha tomado normalmente como el indicador más útil para medir el avance hacia la reducción de las diferencias regionales y los estudios de convergencia. Ha sido, asimismo, el indicador de referencia para establecer el carácter elegible de las regiones europeas más atrasadas para recibir fondos estructurales (regiones «Objetivo 1»). Este indicador se utiliza también para valorar las mejoras comparativas de las regiones, aunque sin duda es muy simple para medir adecuadamente los avances hacia una mayor cohesión económica y social. El objetivo de este artículo es proponer una vía de aproximación más completa para medir la cohesión y estimar sus resultados, utilizando métodos multicriterio y, en particular, los del tipo Electre. A tal efecto se utiliza una amplia base de indicadores económico-sociales y el análisis se centra en la evolución de las regiones que en 1987 eran «Objetivo 1» y en aquellas con un PIB p.c. comprendido entre el 75 y el 100% de la media comunitaria. Los resultados permiten detectar importantes diferencias en las posiciones y movimientos de las regiones. Esta vía podría constituir una alternativa para definir las regiones elegibles a efectos de la Política Regional Comunitaria
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