2,432 research outputs found
HEAO-A Observatory Description
The High Energy Astronomy Observatory Program is briefly described to introduce guest observers to the HEAO-A mission. Topics discussed include spacecraft subsystems, scientific instrumentation, and the mission operations concept. Scientific participants such as principal investigators and co-investigators are listed
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Endolithic colonization of fluid inclusion trails in mineral grains
Many scenarios for the colonization of planetary surfaces by microbial life involve endoliths. This study records microbial mass along fluid inclusion trails (healed microfractures) in quartz grains
Stress concentration investigations using NASTRAN
Parametic investigations are performed using several two dimensional finite element formulations to determine their suitability for use in predicting extremum stresses in marine propellers. Comparisons are made of two NASTRAN elements (CTRIM6 and CTRAIA2) wherein elasticity properties have been modified to yield plane strain results. The accuracy of the elements is investigated by comparing finite element stress predictions with experimentally determined stresses in two classical cases: (1) tension in a flat plate with a circular hole; and (2) a filleted flat bar subjected to in-plane bending. The CTRIA2 element is found to provide good results. The displacement field from a three dimensional finite element model of a representative marine propeller is used as the boundary condition for the two dimensional plane strain investigations of stresses in the propeller blade and fillet. Stress predictions from the three dimensional analysis are compared with those from the two dimensional models. The validity of the plane strain modifications to the NASTRAN element is checked by comparing the modified CTRIA2 element stress predictions with those of the ABAQUS plane strain element, CPE4
A new view of quiet-Sun topology from Hinode/SOT
Context.
With the recent launch of the Hinode satellite our view of the nature and evolution of quiet-Sun regions has been improved. In light of the new high resolution observations, we revisit the study of the quiet Sun's topological nature.
Aims.
Topology is a tool to explain the complexity of the magnetic field, the occurrence of reconnection processes, and the heating of the corona. This Letter aims to give new insights to these different topics.
Methods.
Using a high-resolution Hinode/SOT observation of the line-of-sight magnetic field on the photosphere, we calculate the three dimensional magnetic field in the region above assuming a potential field. From the 3D field, we determine the existence of null points in the magnetic configuration.
Results.
From this model of a continuous field, we find that the distribution of null points with height is significantly different from that reported in previous studies. In particular, the null points are mainly located above the bottom boundary layer in the photosphere (54%) and in the chromosphere (44%) with only a few null points in the corona (2%). The density of null points (expressed as the ratio of the number of null points to the number of photospheric magnetic fragments) in the solar atmosphere is estimated to be between 3% and 8% depending on the method used to identify the number of magnetic fragments in the observed photosphere.
Conclusions.
This study reveals that the heating of the corona by magnetic reconnection at coronal null points is unlikely. Our findings do not rule out the heating of the corona at other topological features. We also report the topological complexity of the chromosphere as strongly suggested by recent observations from Hinode/SOT
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Microbial preservation in sulfates in the Haughton impact structure suggests target in search for life on Mars
Microbes occur within transparent gypsum crystals in the Haughton crater. The crystals transmit light for photosynthesis, but protect from dehydration and wind. Sulfates on the Martian surface should be a priority target in the search for life
Analysing long-term interactions between demand response and different electricity markets using a stochastic market equilibrium model. ESRI WP585, February 2018
Power systems based on renewable energy sources (RES) are characterised by
increasingly distributed, volatile and uncertain supply leading to growing requirements for
flexibility. In this paper, we explore the role of demand response (DR) as a source of flexibility
that is considered to become increasingly important in future. The majority of research in this
context has focussed on the operation of power systems in energy only markets, mostly using
deterministic optimisation models. In contrast, we explore the impact of DR on generator
investments and profits from different markets, on costs for different consumers from
different markets, and on CO2 emissions under consideration of the uncertainties associated
with the RES generation. We also analyse the effect of the presence of a feed-in premium
(FIP) for RES generation on these impacts. We therefore develop a novel stochastic mixed
complementarity model in this paper that considers both operational and investment
decisions, that considers interactions between an energy market, a capacity market and a
feed-in premium and that takes into account the stochasticity of electricity generation by RES.
We use a Benders decomposition algorithm to reduce the computational expenses of the
model and apply the model to a case study based on the future Irish power system. We find
that DR particularly increases renewable generator profits. While DR may reduce consumer
costs from the energy market, these savings may be (over)compensated by increasing costs
from the capacity market and the feed-in premium. This result highlights the importance of
considering such interactions between different markets
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Hopane biomarkers traced from bedrock to recent sediments and ice at the Haughton Impact Structure, Devon Island: Implications for the search for biomarkers on Mars
Hopanoid biomarkers have been traced from bedrock to ice in the Haughton Impact Structure, suggesting that they represent a promising strategy in the search for life in ice deposits on Mars and other icy bodies
SmokeFree Sports Project Report
Children and young people are amongst the most vulnerable groups in society and are highly susceptible to smoking experimentation and addiction. In Liverpool, smoking prevalence is significantly higher than the UK average. Therefore early intervention strategies are required for smoking prevention and cessation. Research has found a negative association between smoking and physical activity. SmokeFree Sports aims to explore whether physical activity and sport can be used to promote the smoke free message to children and young people.
SmokeFree Sports is an innovative multi-dimensional campaign that incorporates social-marketing strategies alongside the provision of sports and physical activities to: a) de-normalise smoking among youth b) empower youth to stay smoke free, and c) increase awareness of the dangers of smoking using positive messaging through the medium of sport and physical activity. This project is delivered across Liverpool and aims to reduce the prevalence of smoking and prevent the uptake of smoking in children and young people.
The initiative, which is managed by Liverpool John Moores University in partnership with Liverpool PCT, employs a variety of strategies to promote and deliver the smoke free message to children and young people including a) training sports coaches and teachers to deliver the smoke free message, b) delivering SFS messages in schools and youth clubs through sport and physical activity, c) asking children to sign a pledge to be smoke free, d) support voluntary sports clubs to adopt a smoke free policy on their playing fields, e) encouraging organizations and individuals interested in health and sport to sign up to the SmokeFree Sports Charter and f) signposting children to smoking cessation services
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