10,601 research outputs found
Development of acoustically lined ejector technology for multitube jet noise suppressor nozzles by model and engine tests over a wide range of jet pressure ratios and temperatures
An experimental program comprising model nozzle and full-scale engine tests was undertaken to acquire parametric data for acoustically lined ejectors applied to primary jet noise suppression. Ejector lining design technology and acoustical scaling of lined ejector configurations were the major objectives. Ground static tests were run with a J-75 turbojet engine fitted with a 37-tube, area ratio 3.3 suppressor nozzle and two lengths of ejector shroud (L/D = 1 and 2). Seven ejector lining configurations were tested over the engine pressure ratio range of 1.40 to 2.40 with corresponding jet velocities between 305 and 610 M/sec. One-fourth scale model nozzles were tested over a pressure ratio range of 1.40 to 4.0 with jet total temperatures between ambient and 1088 K. Scaling of multielement nozzle ejector configurations was also studied using a single element of the nozzle array with identical ejector lengths and lining materials. Acoustic far field and near field data together with nozzle thrust performance and jet aerodynamic flow profiles are presented
Revealing natural relationships among arbuscular mycorrhizal fungi: culture line BEG47 represents Diversispora epigaea, not Glomus versiforme
Background: Understanding the mechanisms underlying biological phenomena, such as evolutionarily conservative trait inheritance, is predicated on knowledge of the natural relationships among organisms. However, despite their enormous ecological significance, many of the ubiquitous soil inhabiting and plant symbiotic arbuscular mycorrhizal fungi (AMF, phylum Glomeromycota) are incorrectly classified.
Methodology/Principal Findings:
Here, we focused on a frequently used model AMF registered as culture BEG47. This fungus is a descendent of the ex-type culture-lineage of Glomus epigaeum, which in 1983 was synonymised with Glomus versiforme. It has since then been used as ‘G. versiforme BEG47’. We show by morphological comparisons, based on type material, collected 1860–61, of G. versiforme and on type material and living ex-type cultures of G. epigaeum, that these two AMF species cannot be conspecific, and by molecular phylogenetics that BEG47 is a member of the genus Diversispora.
Conclusions: This study highlights that experimental works published during the last >25 years on an AMF named ‘G. versiforme’ or ‘BEG47’ refer to D. epigaea, a species that is actually evolutionarily separated by hundreds of millions of years from all members of the genera in the Glomerales and thus from most other commonly used AMF ‘laboratory strains’. Detailed redescriptions substantiate the renaming of G. epigaeum (BEG47) as D. epigaea, positioning it systematically in the order Diversisporales, thus enabling an evolutionary understanding of genetical, physiological, and ecological traits, relative to those of other AMF. Diversispora epigaea is widely cultured as a laboratory strain of AMF, whereas G. versiforme appears not to have been cultured nor found in the field since its original description
Asymmetric magnetic interference patterns in 0-pi Josephson junctions
We examine the magnetic interference patterns of Josephson junctions with a
region of 0- and of pi-phase shift. Such junctions have recently been realized
as c-axis YBCO-Pb junctions with a single twin boundary in YBCO. We show that
in general the junction generates self-fields which introduces an asymmetry in
the critical current under reversal of the magnetic field. Numerical
calculations of these asymmetries indicate they account well for the
unexplained features observed in single twin boundary junctions.Comment: 4 pages, 3 figure
Electronic states on a twin boundary of a d-wave superconductor
We show that an induced -wave harmonic in the superconducting gap of an
orthorhombic superconductor strongly affects the excitation
spectrum near a twinning plane. In particular, it yields bound states of zero
energy with areal density proportional to the relative weight of the -wave
component. An unusual scattering process responsible for the thermal
conductivity across the twin boundary at low temperatures is also identified.Comment: 4 pages, ReVTEX, 2 PS-figure
Deep Memory Networks for Attitude Identification
We consider the task of identifying attitudes towards a given set of entities
from text. Conventionally, this task is decomposed into two separate subtasks:
target detection that identifies whether each entity is mentioned in the text,
either explicitly or implicitly, and polarity classification that classifies
the exact sentiment towards an identified entity (the target) into positive,
negative, or neutral.
Instead, we show that attitude identification can be solved with an
end-to-end machine learning architecture, in which the two subtasks are
interleaved by a deep memory network. In this way, signals produced in target
detection provide clues for polarity classification, and reversely, the
predicted polarity provides feedback to the identification of targets.
Moreover, the treatments for the set of targets also influence each other --
the learned representations may share the same semantics for some targets but
vary for others. The proposed deep memory network, the AttNet, outperforms
methods that do not consider the interactions between the subtasks or those
among the targets, including conventional machine learning methods and the
state-of-the-art deep learning models.Comment: Accepted to WSDM'1
Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1
In this paper we discuss the radio continuum and X-ray properties of the
so-far poorly studied Galactic supernova remnant (SNR) G5.9+3.1. We present the
radio spectral energy distribution (SED) of the Galactic SNR G5.9+3.1 obtained
with the Murchison Widefield Array (MWA). Combining these new observations with
the surveys at other radio continuum frequencies, we discuss the integrated
radio continuum spectrum of this particular remnant. We have also analyzed an
archival XMM-Newton observation, which represents the first detection of X-ray
emission from this remnant. The SNR SED is very well explained by a simple
power-law relation. The synchrotron radio spectral index of G5.9+3.1, is
estimated to be 0.420.03 and the integrated flux density at 1GHz to be
around 2.7Jy. Furthermore, we propose that the identified point radio source,
located centrally inside the SNR shell, is most probably a compact remnant of
the supernova explosion. The shell-like X-ray morphology of G5.9+3.1 as
revealed by XMM-Newton broadly matches the spatial distribution of the radio
emission, where the radio-bright eastern and western rims are also readily
detected in the X-ray while the radio-weak northern and southern rims are weak
or absent in the X-ray. Extracted MOS1+MOS2+PN spectra from the whole SNR as
well as the north, east, and west rims of the SNR are fit successfully with an
optically thin thermal plasma model in collisional ionization equilibrium with
a column density N_H~0.80x cm and fitted temperatures spanning
the range kT~0.14-0.23keV for all of the regions. The derived electron number
densities n_e for the whole SNR and the rims are also roughly comparable
(ranging from ~ cm to ~ cm, where f
is the volume filling factor). We also estimate the swept-up mass of the X-ray
emitting plasma associated with G5.9+3.1 to be ~.Comment: Accepted for publication in A&
Pressure-Temperature Phase Diagram of Antiferromagnetism and Superconductivity in CeRhIn5 and CeIn3 : In-NQR Study under Pressure
We report the novel pressure() - temperature() phase diagram of
antiferromagnetism and superconductivity in CeRhIn and CeIn revealed by
the In nuclear-spin-lattice-relaxation () measurement. In the
itinerant magnet CeRhIn, we found that the N\'eel temperature is
reduced at 1.23 GPa with an emergent pseudogap behavior. In CeIn,
the localized magnetic character is robust against the application of pressure
up to 1.9 GPa, beyond which the system evolves into an itinerant
regime in which the resistive superconducting phase emerges. We discuss the
relationship between the phase diagram and the magnetic fluctuations.Comment: 4 pages, 3 figures, to be published in Phys.Rev.B. Rapid
'The Brick' is not a brick : A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.In this paper we provide a comprehensive description of the internal dynamics of G0.253+0.016 (a.k.a. 'the Brick'); one of the most massive and dense molecular clouds in the Galaxy to lack signatures of widespread star formation. As a potential host to a future generation of high-mass stars, understanding largely quiescent molecular clouds like G0.253+0.016 is of critical importance. In this paper, we reanalyse Atacama Large Millimeter Array cycle 0 HNCO data at 3 mm, using two new pieces of software which we make available to the community. First, scousepy, a Python implementation of the spectral line fitting algorithm scouse. Secondly, acorns (Agglomerative Clustering for ORganising Nested Structures), a hierarchical n-dimensional clustering algorithm designed for use with discrete spectroscopic data. Together, these tools provide an unbiased measurement of the line of sight velocity dispersion in this cloud, kms, which is somewhat larger than predicted by velocity dispersion-size relations for the Central Molecular Zone (CMZ). The dispersion of centroid velocities in the plane of the sky are comparable, yielding . This isotropy may indicate that the line-of-sight extent of the cloud is approximately equivalent to that in the plane of the sky. Combining our kinematic decomposition with radiative transfer modelling we conclude that G0.253+0.016 is not a single, coherent, and centrally-condensed molecular cloud; 'the Brick' is not a \emph{brick}. Instead, G0.253+0.016 is a dynamically complex and hierarchically-structured molecular cloud whose morphology is consistent with the influence of the orbital dynamics and shear in the CMZ.Peer reviewedFinal Accepted Versio
Josephson tunneling in high- superconductors
This article describes the Josephson tunneling from time-reversal
symmetry-breaking states and compares it with that from time-reversal invariant
states for both twinned and untwinned crystals and for both -axis and
basal-plane currents, in a model for orthorhombic YBCO. A macroscopic
invariance group describing the superconducting state of a twinned crystal is
introduced and shown to provide a useful framework for the discussion of the
results for twinned crystals. In addition, a ring geometry, which allows
-wave and -wave superconductivity in a tetragonal
superconductor to be distinguished on the basis of symmetry arguments only, is
proposed and analyzed. Finally, an appendix gives details of the experimental
Josephson tunneling evidence for a superconducting state of orthorhombic
symmetry in YBCO.Comment: Latex File, 18 pages, 6 Postscript figures, submitted to Phys. Rev.
Guidelines for the establishment of microbiological criteria for foods
O Grupo de Trabalho Ocorrência Microbiológica na Cadeia Alimentar
(GTOMCA) do Programa PortFIR considerou de grande importância o desenvolvimento
de um documento que compilasse uma seleção de legislação
e de informações relativas a Critérios Microbiológicos (CM), visando apoiar
e facilitar, aos operadores e entidades do setor alimentar, a sua aplicação
na validação do processo de produção, na segurança e/ou higiene dos géneros
alimentícios, na adesão a boas práticas de fabrico dos mesmos, e/ou,
ainda, na manutenção da sua qualidade durante o seu tempo de vida útil.
Deste modo, o GTOMCA desenvolveu o Guia para o estabelecimento de
critérios microbiológicos em géneros alimentícios, que foi publicado em
abril de 2017, contemplando a identificação, caraterísticas e propósito dos
CM, os fatores a considerar para a sua definição, nomeadamente: a categoria
do alimento, o microrganismo e/ou as suas toxinas, os metabolitos e
a virulência, os valores limite, o plano de amostragem, o tipo de utilização
e consumo assim como o método de análise laboratorial, o ponto da cadeia
alimentar onde se aplica, as medidas a tomar no caso de resultados não satisfatórios
e a necessidade de revisão e atualização dos CM.The Working Group on Microbiological Occurrence on the Food Chain
(GTOMCA) of Por tFIR Program considered unanimously, as an important
need, the existence of a document with a selection and compilation
of existing legislation and information concerning microbiological
criteria (CM) as a tool to suppor t and facilitate its application by operators
and entities in the food sector to validate the acceptability of
the production process or the food safety or hygiene, the obser vance
to good manufacturing practices or the maintenance of the food
quality during its lifetime. So, GTOMCA developed a Guide for the establishment
of microbiological criteria in foodstuf fs, which was published
in April 2017, regarding the identification, characteristics and
purpose of microbiological criteria, the factors to consider for its definition,
identification, characteristics and purpose of CM and, as impor
tant factors to consider the food categor y, the micro-organism
and its metabolites, toxins and virulence factors, the limit values, the
sampling plan, the type of food consumption as well as the analy tical
method for testing the food, the point of the food chain where it is applied,
the measures to be taken in the event of unsatisfactor y results
and the need to review and update of the CM.info:eu-repo/semantics/publishedVersio
- …