15,240 research outputs found
System-size convergence of point defect properties: The case of the silicon vacancy
We present a comprehensive study of the vacancy in bulk silicon in all its
charge states from 2+ to 2-, using a supercell approach within plane-wave
density-functional theory, and systematically quantify the various
contributions to the well-known finite size errors associated with calculating
formation energies and stable charge state transition levels of isolated
defects with periodic boundary conditions. Furthermore, we find that transition
levels converge faster with respect to supercell size when only the Gamma-point
is sampled in the Brillouin zone, as opposed to a dense k-point sampling. This
arises from the fact that defect level at the Gamma-point quickly converges to
a fixed value which correctly describes the bonding at the defect centre. Our
calculated transition levels with 1000-atom supercells and Gamma-point only
sampling are in good agreement with available experimental results. We also
demonstrate two simple and accurate approaches for calculating the valence band
offsets that are required for computing formation energies of charged defects,
one based on a potential averaging scheme and the other using
maximally-localized Wannier functions (MLWFs). Finally, we show that MLWFs
provide a clear description of the nature of the electronic bonding at the
defect centre that verifies the canonical Watkins model.Comment: 10 pages, 6 figure
Negative effects of makeup use on perceptions of leadership ability across two ethnicities
Cosmetics alter social perceptions, and prior work suggests that cosmetic use may aid female intrasexual competition, making women appear more dominant to other women but more prestigious to other men. It is unclear whether these findings reflect general improvements in perceptions of traits related to women's dominance or if they are specific to mating contexts only. Here, across two ethnicities, we examined effects of cosmetics used for a social night out on perceptions of women's leadership ability, a trait that denotes competence/high status outside of mating contexts. Participants of African and Caucasian ethnicity judged faces for leadership ability where half of the trials differed in ethnicity (own- vs. other-ethnicity face pairs) and the subtlety of the color manipulation (50% vs. 100%). Regardless of the participant's sex or ethnicity, makeup used for a social night out had a negative effect on perceptions of women's leadership ability. Our findings suggest that, in prior work, women are afforded traits related to dominance, as makeup enhances perceptions of traits that are important for successful female mating competition but not other components of social dominance such as leadership
The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries Does the observational evidence support their existence?
Context. Period variations have been detected in a number of eclipsing close
compact binary subdwarf B stars (sdBs) and these have often been interpreted as
caused by circumbinary massive planets or brown dwarfs. Various evolutionary
scenarios have been proposed for these stars, but a definite mechanism remains
to be established. Equally puzzling is the formation of these putative
circumbinary objects which must have formed either from the remaining post
common envelope circumbinary disk or survived its evolution. Aims. In this
paper we review the eclipse time variations (ETVs) exhibited by seven such
systems and explore if there is conclusive evidence that the ETVs observed over
the last two decades can reliably predict the presence of circumbinary bodies.
Methods. We report 246 new observations of the seven sdB systems made between
2013 September and 2017 July using a worldwide network of telescopes. We
combined our new data with previously published measurements to analyse the
ETVs of these systems. Results. Our data shows that period variations cannot be
modelled simply on the basis of circumbinary objects. This implies that more
complex processes may be taking place in these systems. From eclipse time
variations, it has historically been suggested that five of the seven binary
systems reported herein had circumbinary objects. Based on our recent
observations and analysis only three systems remain serious contenders. We find
agreement with other observers that at least a decade of observations is
required to establish reliable ephemeris. With longer observational baselines
it is quite conceivable that the data will support the circumbinary object
hypothesis of these binary systems. Also we generally agree with other
observers that larger values of (O-C) residuals are found with secondary
companions of spectral type M5/6 or earlier as a result of an Applegate type
mechanismComment: 15 pages, 13 figures, 4 tables. 3 tables archived on CD
Study of guidance techniques for aerial application of agricultural compounds
Candidate systems were identified for evaluation of suitability in meeting specified accuracy requirements for a swath guidance system in an agriculture aircraft. Further examination reduced the list of potential candidates to a single category, i.e., transponder type systems, for detailed evaluation. Within this category three systems were found which met the basic accuracy requirements of the work statement. The Flying Flagman, the Electronic Flagging and the Raydist Director System. In addition to evaluating the systems against the specified requirements, each system was compared with the other two systems on a relative basis. The conclusions supported by the analyses show the Flying Flagman system to be the most suitable system currently available to meet the requirements
Automated Retrieval of Non-Engineering Domain Solutions to Engineering Problems
Organised by: Cranfield UniversityBiological inspiration for engineering design has occurred through a variety of techniques such as creation
and use of databases, keyword searches of biological information in natural-language format, prior
knowledge of biology, and chance observations of nature. This research focuses on utilizing the reconciled
Functional Basis function and flow terms to identify suitable biological inspiration for function based design.
The organized search provides two levels of results: (1) associated with verb function only and (2) narrowed
results associated with verb-noun (function-flow). A set of heuristics has been complied to promote efficient
searching using this technique. An example for creating smart flooring is also presented and discussed.Mori Seiki – The Machine Tool Compan
Exploration Medical System Demonstration
BACKGROUND: Exploration class missions will present significant new challenges and hazards to the health of the astronauts. Regardless of the intended destination, beyond low Earth orbit a greater degree of crew autonomy will be required to diagnose medical conditions, develop treatment plans, and implement procedures due to limited communications with ground-based personnel. SCOPE: The Exploration Medical System Demonstration (EMSD) project will act as a test bed on the International Space Station (ISS) to demonstrate to crew and ground personnel that an end-to-end medical system can assist clinician and non-clinician crew members in optimizing medical care delivery and data management during an exploration mission. Challenges facing exploration mission medical care include limited resources, inability to evacuate to Earth during many mission phases, and potential rendering of medical care by non-clinicians. This system demonstrates the integration of medical devices and informatics tools for managing evidence and decision making and can be designed to assist crewmembers in nominal, non-emergent situations and in emergent situations when they may be suffering from performance decrements due to environmental, physiological or other factors. PROJECT OBJECTIVES: The objectives of the EMSD project are to: a. Reduce or eliminate the time required of an on-orbit crew and ground personnel to access, transfer, and manipulate medical data. b. Demonstrate that the on-orbit crew has the ability to access medical data/information via an intuitive and crew-friendly solution to aid in the treatment of a medical condition. c. Develop a common data management framework that can be ubiquitously used to automate repetitive data collection, management, and communications tasks for all activities pertaining to crew health and life sciences. d. Ensure crew access to medical data during periods of restricted ground communication. e. Develop a common data management framework that allows for scalability, extensibility, and interoperability of data sources and data users. f. Lower total cost of ownership for development and sustainment of peripheral hardware and software that use EMSD for data management. g. Provide a better standard of healthcare for crew members through reductions in the time required by crew and ground personnel to provide medical treatment and the number of crew errors experienced during treatment
Controlling Artificial Viscosity in SPH simulations of accretion disks
We test the operation of two methods for selective application of Artificial
Viscosity (AV) in SPH simulations of Keplerian Accretion Disks, using a ring
spreading test to quantify effective viscosity, and a correlation coefficient
technique to measure the formation of unwanted prograde alignments of
particles. Neither the Balsara Switch nor Time Dependent Viscosity work
effectively, as they leave AV active in areas of smooth shearing flow, and do
not eliminate the accumulation of alignments of particles in the prograde
direction. The effect of both switches is periodic, the periodicity dependent
on radius and unaffected by the density of particles. We demonstrate that a
very simple algorithm activates AV only when truly convergent flow is detected
and reduces the unwanted formation of prograde alignments. The new switch works
by testing whether all the neighbours of a particle are in Keplerian orbit
around the same point, rather than calculating the divergence of the velocity
field, which is very strongly affected by Poisson noise in the positions of the
SPH particles.Comment: 8 pages, 5 figure
New Host and Geographic Distribution Records for the Fish Leech Myzobdella reducta (Meyer, 1940) (Hirudinida: Piscicolidae)
The role of ECL2 in CGRP receptor activation: a combined modelling and experimental approach
The calcitonin gene-related peptide (CGRP) receptor is a complex of a calcitonin receptor-like receptor (CLR), which is a family B G-protein-coupled receptor (GPCR) and receptor activity modifying protein 1. The role of the second extracellular loop (ECL2) of CLR in binding CGRP and coupling to Gs was investigated using a combination of mutagenesis and modelling. An alanine scan of residues 271–294 of CLR showed that the ability of CGRP to produce cAMP was impaired by point mutations at 13 residues; most of these also impaired the response to adrenomedullin (AM). These data were used to select probable ECL2-modelled conformations that are involved in agonist binding, allowing the identification of the likely contacts between the peptide and receptor. The implications of the most likely structures for receptor activation are discussed.</jats:p
Warming trends in summer heatwaves
The frequency and severity of heatwaves is expected to increase as the global climate warms. We apply crossing theory for the first time to determine heatwave properties solely from the distribution of daily observations without time‐correlation information. We use Central England Temperature timeseries to quantify how the simple increased occurrence of higher temperatures makes heatwaves (consecutive summer days with temperatures exceeding a threshold) more frequent and intense. We find an overall 2‐3‐fold increase in heatwave activity since the late 1800's. Week‐long heatwaves that on average return every 5 years were typically below ∼28°C and now typically exceed it. Our analysis takes as inputs average user‐specific heatwave properties. Its output pinpoints the range of temperatures for which changes in the distribution must be well‐resolved statistically in order to track how these heatwave properties are changing. This provides a quantitative benchmark for models used for the attribution of heatwaves
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