1,901 research outputs found
Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide
A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed
High-resolution antenna near-field imaging and sub-THz measurements with a small atomic vapor-cell sensing element
Atomic sensing and measurement of millimeter-wave (mmW) and THz electric
fields using quantum-optical EIT spectroscopy of Rydberg states in atomic
vapors has garnered significant interest in recent years towards the
development of atomic electric-field standards and sensor technologies. Here we
describe recent work employing small atomic vapor cell sensing elements for
near-field imaging of the radiation pattern of a K-band horn antenna at
13.49 GHz. We image fields at a spatial resolution of and measure
over a 72 to 240 V/m field range using off-resonance AC-Stark shifts of a
Rydberg resonance. The same atomic sensing element is used to measure sub-THz
electric fields at 255 GHz, an increase in mmW-frequency by more than one order
of magnitude. The sub-THz field is measured over a continuous 100 MHz
frequency band using a near-resonant mmW atomic transition
DC Electric Fields in Electrode-Free Glass Vapor Cell by Photoillumination
Rydberg-atom-enabled atomic vapor cell technologies show great potentials in
developing devices for quantum enhanced sensors. In this paper, we demonstrate
laser induced DC electric fields in an all-glass vapor cell without bulk or
thin film electrodes. The spatial field distribution is mapped by Rydberg
electromagnetically induced transparency spectroscopy. We explain the measured
with a boundary-value electrostatic model. This work may inspire new ideas for
DC electric field control in designing miniaturized atomic vapor cell devices.
Limitations and other charge effects are also discussed
Language control and parallel recovery of language in individuals with aphasia
Background: The causal basis of the different patterns of language recovery following stroke in bilingual speakers is not well understood. Our approach distinguishes the representation of language from the mechanisms involved in its control. Previous studies have suggested that difficulties in language control can explain selective aphasia in one language as well as pathological switching between languages. Here we test the hypothesis that difficulties in managing and resolving competition will also be observed in those who are equally impaired in both their languages even in the absence of pathological switching.
Aims: To examine difficulties in language control in bilingual individuals with parallel recovery in aphasia and to compare their performance on different types of conflict task.
Methods & procedures: Two right-handed, non-native English-speaking participants who showed parallel recovery of two languages after stroke and a group of non-native English-speaking, bilingual controls described a scene in English and in their first language and completed three explicit conflict tasks. Two of these were verbal conflict tasks: a lexical decision task in English, in which individuals distinguished English words from non-words, and a Stroop task, in English and in their first language. The third conflict task was a non-verbal flanker task.
Outcomes & Results: Both participants with aphasia were impaired in the picture description task in English and in their first language but showed different patterns of impairment on the conflict tasks. For the participant with left subcortical damage, conflict was abnormally high during the verbal tasks (lexical decision and Stroop) but not during the non-verbal flanker task. In contrast, for the participant with extensive left parietal damage, conflict was less abnormal during the Stroop task than the flanker or lexical decision task.
Conclusions: Our data reveal two distinct control impairments associated with parallel recovery. We stress the need to explore the precise nature of control problems and how control is implemented in order to develop fuller causal accounts of language recovery patterns in bilingual aphasia
Framework for Automatic PCB Marking Detection and Recognition for Hardware Assurance
A Bill of Materials (BoM) is a list of all components on a printed circuit
board (PCB). Since BoMs are useful for hardware assurance, automatic BoM
extraction (AutoBoM) is of great interest to the government and electronics
industry. To achieve a high-accuracy AutoBoM process, domain knowledge of PCB
text and logos must be utilized. In this study, we discuss the challenges
associated with automatic PCB marking extraction and propose 1) a plan for
collecting salient PCB marking data, and 2) a framework for incorporating this
data for automatic PCB assurance. Given the proposed dataset plan and
framework, subsequent future work, implications, and open research
possibilities are detailed.Comment: 5 pages, 3 figures, Government Microcircuit Applications & Critical
Technology Conference (GOMACTech) 202
Describing Sensory Experience: The Genre of Wine Reviews
The purpose of the article is to shed light on how experiences of sensory perceptions in the domains of VISION, SMELL, TASTE and TOUCH are recast into text and discourse in the genre of wine reviews. Because of the alleged paucity of sensory vocabularies, in particular in the olfactory domain, it is of particular interest to investigate what resources language has to offer in order to describe those experiences. We show that the main resources are, on the one hand, words evoking properties that are applicable cross-modally and properties of objects that range over more than one domain, and on the other, vivid imagery that compares the characteristics of the wine with people, building, animals and the hustle and bustle of market places and other events. The second goal is to account for the construals of the meanings of the expressions used in the recontextualization into written discourse in the light of their apparent flexibility across the descriptions of the sensory experiences. In contrast to a large body of the literature on sensory meanings in language, we argue that the descriptors of properties such as sharp, soft, lemon and cherry used to describe a wine’s qualities across the sensory domains are not polysemous synesthetic metaphors, but monosemous synesthetic metonymizations, more precisely zone activations. With regard to the imagery used, the construals represented cover both similes, metaphorizations and metonymizations proper
Arboreal ant abundance tracks primary productivity in an Amazonian whitewater river system
Little is known about consumer productivity in the tropics despite the key feedbacks that animals impose on primary productivity. In the Amazon basin, seasonally flooded and unflooded forests exist side by side, and ants (Formicidae) dominate animal biomass. Although flooding has a direct negative effect on soil-dwelling ants, it is less clear whether flooding has indirect effects on arboreal ants via associated changes in tree communities. To test whether seasonal inundation by whitewater affects arboreal ants, we investigated ant communities in adjacent flooded and unflooded forests along a major whitewater river in central-western Amazonia. Whitewater-flooded forest exhibits higher primary productivity than unflooded forest. We thus hypothesized that forest type would affect the productivity and the foraging traits of arboreal ants and that these changes would be mediated by increases in plant-derived food for ants in flooded forest. We compared ant and plant communities between flooded- and unflooded-forest transects along the Juruá River in Amazonas, Brazil. We collected, identified, and counted terrestrial and arboreal ants, and we measured ant traits with putative relationships to foraging strategy. We also identified plant stems to characterize the abundance of ant food rewards. Flooding negatively affected the diversity and abundance of terrestrial ants but did not change the diversity of arboreal ants. Arboreal ants were more abundant and exhibited higher biomass in flooded forest than in unflooded forest. Arboreal ant traits also suggested that ants may rely more heavily on plant-derived food in flooded forest than in unflooded forest. These differences were associated with a higher abundance of plant stems predicted to contain ant food rewards in flooded forest than in unflooded forest. Our results indicate that the productivity of arboreal ants is affected by that of the underlying forest. Such effects may be mediated by the predominantly herbivorous foraging strategy of canopy ants, which would link ant populations closely to primary production and stoichiometry. Given ants’ important functional roles, these differences in ant productivity between forest types may have consequences for other arthropods and feedbacks to plants throughout the Amazon basin
Development and validation of an inventory to assess conflict in sport teams: the Group Conflict Questionnaire
Convergence and divergence in the evolution of cat skulls: temporal and spatial patterns of morphological diversity
Background: Studies of biological shape evolution are greatly enhanced when framed in a phylogenetic perspective.
Inclusion of fossils amplifies the scope of macroevolutionary research, offers a deep-time perspective on tempo and mode
of radiations, and elucidates life-trait changes. We explore the evolution of skull shape in felids (cats) through morphometric
analyses of linear variables, phylogenetic comparative methods, and a new cladistic study of saber-toothed cats.
Methodology/Principal Findings: A new phylogenetic analysis supports the monophyly of saber-toothed cats
(Machairodontinae) exclusive of Felinae and some basal felids, but does not support the monophyly of various sabertoothed
tribes and genera. We quantified skull shape variation in 34 extant and 18 extinct species using size-adjusted linear
variables. These distinguish taxonomic group membership with high accuracy. Patterns of morphospace occupation are
consistent with previous analyses, for example, in showing a size gradient along the primary axis of shape variation and a
separation between large and small-medium cats. By combining the new phylogeny with a molecular tree of extant Felinae,
we built a chronophylomorphospace (a phylogeny superimposed onto a two-dimensional morphospace through time). The
evolutionary history of cats was characterized by two major episodes of morphological divergence, one marking the
separation between saber-toothed and modern cats, the other marking the split between large and small-medium cats.
Conclusions/Significance: Ancestors of large cats in the ‘Panthera’ lineage tend to occupy, at a much later stage,
morphospace regions previously occupied by saber-toothed cats. The latter radiated out into new morphospace regions
peripheral to those of extant large cats. The separation between large and small-medium cats was marked by considerable
morphologically divergent trajectories early in feline evolution. A chronophylomorphospace has wider applications in
reconstructing temporal transitions across two-dimensional trait spaces, can be used in ecophenotypical and functional
diversity studies, and may reveal novel patterns of morphospace occupation
Quantum gravity corrections to neutrino propagation
Massive spin-1/2 fields are studied in the framework of loop quantum gravity
by considering a state approximating, at a length scale much greater
than Planck length cm, a spin-1/2 field in flat
spacetime. The discrete structure of spacetime at yields corrections
to the field propagation at scale . Next, Neutrino Bursts (GeV) accompaning Gamma Ray Bursts that have travelled
cosmological distances, l.y., are considered. The dominant
correction is helicity independent and leads to a time delay w.r.t. the speed
of light, , of order s. To next order in
the correction has the form of the Gambini and Pullin effect
for photons. Its contribution to time delay is comparable to that caused by the
mass term. Finally, a dependence is
found for a two-flavour neutrino oscillation length.Comment: RevTeX, 5pp, no figures. Notation of a sum in Eq.(2) improved. Slight
modifications in redaction. Final version to appear in Phys. Rev. Let
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