4,513 research outputs found
Serrated trailing edges for improving lift and drag characteristics of lifting surfaces
An improvement in the lift and drag characteristics of a lifting surface is achieved by attaching a serrated panel to the trailing edge of the lifting surface. The serrations may have a saw-tooth configuration, with a 60 degree included angle between adjacent serrations. The serrations may vary in shape and size over the span-wise length of the lifting surface, and may be positioned at fixed or adjustable deflections relative to the chord of the lifting surface
A nexus perspective on competing land demands: Wider lessons from a UK policy case study
As nations develop policies for low-carbon transitions, conflicts with existing policies and planning tools are leading to competing demands for land and other resources. This raises fundamental questions over how multiple demands can best be managed. Taking the UK as an empirical example, this paper critiques current policies and practices to explore the interdependencies at the water-energy-food nexus. It considers how current land uses and related policies affect the UKâs resilience to climate change, setting out an agenda for research and practice relevant to stakeholders in land-use management, policy and modelling. Despite recent progress in recognising such nexus challenges, most UK land-related policies and associated science continue to be compartmentalised by both scale and sector and seldom acknowledge nexus interconnections. On a temporal level, the absence of an over-arching strategy leaves inter-generational trade-offs poorly considered. Given the system lock-in and the lengthy policy-making process, it is essential to develop alternative ways of providing dynamic, flexible, practical and scientifically robust decision support for policy-makers. A range of ecosystem services need to be valued and integrated into a resilient land-use strategy, including the introduction of non-monetary, physical-unit constraints on the use of particular services
Many roads, one destination for T cell progenitors
The thymus manufactures new T cells throughout life but contains no self-renewing potential. Instead, replenishment depends on recruitment of bone marrowâderived progenitors that circulate in the blood. Attempts to identify thymic-homing progenitors, and to assess the degree to which they are precommitted to the T cell lineage, have led to complex and sometimes conflicting results. As described here, this probably reflects the existence of multiple distinct types of T cell lineage progenitors as well as differences in individual experimental approaches
Multiple Explanations for the Single Transit of KIC 5951458 Based on Radial Velocity Measurements Extracted with a Novel Matched-template Technique
Planetary systems that show single-transit events are a critical pathway to increasing the yield of long-period exoplanets from transit surveys. From the primary Kepler mission, KIC 5951458 b (Kepler-456b) was thought to be a single-transit giant planet with an orbital period of 1310 days. However, radial velocity (RV) observations of KIC 5951458 from the HIRES instrument on the Keck telescope suggest that the system is far more complicated. To extract precise RVs for this V â 13 star, we develop a novel matched-template technique that takes advantage of a broad library of template spectra acquired with HIRES. We validate this technique and measure its noise floor to be 4â8 m sâ»Âč (in addition to internal RV error) for most stars that would be targeted for precision RVs. For KIC 5951458, we detect a long-term RV trend that suggests the existence of a stellar companion with an orbital period greater than a few thousand days. We also detect an additional signal in the RVs that is possibly caused by a planetary or brown dwarf companion with mass in the range of 0.6â82 M_(Jup) and orbital period below a few thousand days. Curiously, from just the data on hand, it is not possible to determine which object caused the single "transit" event. We demonstrate how a modest set of RVs allows us to update the properties of this unusual system and predict the optimal timing for future observations
Multiple Explanations for the Single Transit of KIC 5951458 based on Radial Velocity Measurements Extracted with a Novel Matched-template Technique
Planetary systems that show single-transit events are a critical pathway to
increasing the yield of long-period exoplanets from transit surveys. From the
primary Kepler mission, KIC 5951458b (Kepler-456b) was thought to be a
single-transit giant planet with an orbital period of 1310 days. However,
radial velocity (RV) observations of KIC 5951458 from the HIRES instrument on
the Keck telescope suggest that the system is far more complicated. To extract
precise RVs for this star, we develop a novel matched-template
technique that takes advantage of a broad library of template spectra acquired
with HIRES. We validate this technique and measure its noise floor to be 4 - 8
m s (in addition to internal RV error) for most stars that would be
targeted for precision RVs. For KIC 5951458, we detect a long-term RV trend
that suggests the existence of a stellar companion with an orbital period
greater than a few thousand days. We also detect an additional signal in the
RVs that is possibly caused by a planetary or brown dwarf companion with mass
in the range of 0.6 - 82 and orbital period below a few thousand
days. Curiously, from just the data on hand, it is not possible to determine
which object caused the single "transit" event. We demonstrate how a modest set
of RVs allows us to update the properties of this unusual system and predict
the optimal timing for future observations.Comment: 20 pages, 14 figures, accepted for publication in the Astronomical
Journa
New Dynamical State and Habitability of the HD 45364 Planetary System
Planetary systems with multiple giant planets provide important opportunities
to study planetary formation and evolution. The HD 45364 system hosts two giant
planets that reside within the Habitable Zone (HZ) of their host star and was
the first system discovered with a 3:2 mean motion resonance (MMR). Several
competing migration theories with different predictions have previously
provided explanations regarding the observed resonance through dynamical
simulations that utilized limited data. Here, over ten years since the original
discovery, we revisit the system with a substantially increased radial velocity
(RV) sample from HARPS and HIRES that significantly extend the observational
baseline. We present the revised orbital solutions for the two planets using
both Keplerian and dynamical models. Our RV models suggest orbits that are more
circular and separated than those previously reported. As a result, predicted
strong planet-planet interactions were not detected. The system dynamics were
reanalyzed, and the planet pair was found to exhibit apsidal behavior of both
libration and circulation, indicating a quasi-resonance state rather than being
truly in MMR. The new orbital solution and dynamical state of the system
confirm migration models that predicted near circular orbits as the preferred
scenario. We also study the habitability prospects of this system and found
that an additional Earth-mass planet and exomoons in the HZ are possible. This
work showcases the importance of continued RV observation and its impact on our
knowledge of the system's dynamical history. HD 45364 continues to be an
interesting target for both planetary formation and habitability studies.Comment: 16 pages, 10 figures, accepted for publication in the Astronomical
Journa
Urban Lead in Minnesota: Soil Transect Results of Four Cities
The focus of this field study was the development of a soil collection and analysis method for the rapid assessment of urban lead (Pb) buildup in four Minnesota cities, Minneapolis, St. Paul, Duluth, and Rochester. The results show that soil Pb buildup is mainly a function of urban size, although specific geographic factors, such as a bluff that constrains city development along a narrow corridor, also play a role in Pb distribution and concentration. Maximum urban Pb concentrations were approximately 25, 70, and 100 times rural soil Pb levels, in Rochester, Duluth, and the centers of Minneapolis and St. Paul respectively. The primary source of Pb measured in this study was assumed to be Pb aerosols exhausted from the use of leaded gasoline during the past four or five decades. A portion of the total state Pb exhausts were estimated for each city from state daily vehicle mile (DVM) data. The chain of movement which exposes children to excessive Pb levels from aerosol accumulations in the soil is described along with the remedy to alleviate continued urban Pb buildup
Antiperovskite Li3OCl Superionic Conductor Films for Solid-State Li-Ion Batteries.
Antiperovskite Li3OCl superionic conductor films are prepared via pulsed laser deposition using a composite target. A significantly enhanced ionic conductivity of 2.0 Ă 10-4 S cm-1 at room temperature is achieved, and this value is more than two orders of magnitude higher than that of its bulk counterpart. The applicability of Li3OCl as a solid electrolyte for Li-ion batteries is demonstrated
What Makes Agricultural Intensification Profitable for Mozambican Smallholders? An Appraisal of the Inputs Subsector and the 1996/97 DNER/SG2000 Program
This report summarizes an appraisal of input utilization and marketing in Mozambique, focusing on the following research questions: (1) What are current smallholder yields for major commodities, and what is the potential for increasing yields through the use of improved technologies? (2) To what extent are improved technologies already being used by smallholders, and is the use of improved technologies profitable? (3) How are improved seeds, fertilizer and pesticides currently produced and distributed? and (4) What are the key constraints and opportunities for increasing the use of improved technologies by smallholders?food security, food policy, improved technologies, Farm Management, Downloads July 2008-July 2009: 9, O31,
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