59,663 research outputs found
Flight test evaluation of drag effects on surface coatings on the NASA Boeing 737 TCV airplane
A flight test program was conducted in which the effects of various surface coatings on aerodynamic drag were investigated; results of this program are described in this report. The tests were conducted at NASA-Langley Research Center on the terminal configured vehicle (TCV) Boeing 737 research airplane. The Boeing Company, as contractor with NASA under the Energy Efficient Transport (EET) program, planned and evaluated the experiment. The NASA-TCV Program Office coordinated the experiment and performed the flight tests. The principal objective of the test was to evaluate the drag reduction potential of an elastomeric polyurethane surface coating, CAAPCO B-274, which also has been considered for application on transport airplanes to protect leading edges from erosion. The smooth surface achievable with this type of coating held some promise of reducing the skin friction drag as compared to conventional production type aircraft surfaces, which are usually anodized bare metal or coated with corrosion protective paint. Requirements for high precision measurements were the principal considerations in the experiment
Beyond naming patterns in children with WFDs: definitions for nouns and verbs
Children who experience difficulties in naming are described as having word finding difficulties (WFDs). In the present study 31 children with WFDs were identified through a wider survey of educational provision for those with language and communication difficulties. The children were included if they were between 6;4-7;10 years, had normal non-verbal intelligence, no major articulation difficulties and had WFDs as diagnosed by standard scores below 75 on Test of Word Finding Difficulties (TWF, German, 1989). Three control groups were identified who were matched on: chronological age (N = 31), naming age (N = 31) and level of receptive grammar (N = 31). Children?s accuracy of naming and latency to name were assessed for pictures of objects and actions. Children were asked to define the object and action terms at a later point. Children with WFDs were significantly less accurate in naming than their age matched peers but equivalent to that of the language matched peers. The group of children with WFDs were the slowest to accurately name all sets of items. All groups of children were less accurate in the provision of definitions for action terms than object terms. Overall the children with WFDs provided fewer accurate definitions than their chronological age matched peers. The nature of the children?s definitions indicated that they also differed from their language-matched peers. Particular difficulties were noted in the provision of semantic categorisation information. A range of standardised language assessments did not account for these difficulties. The findings are discussed in relation to the idea that WFDs are caused by impoverished semantic representations
Renewable Energy Resources Impact on Clean Electrical Power by developing the North-West England Hydro Resource Model.
This paper describes the development of a sequential decision support system to promote hydroelectric power in North-West England. The system, composed of integrated models, addresses barriers to the installation of hydroelectric power schemes. Information is linked through an economic assessment which identifies different turbine options, assesses their suitability for location and demand; and combines the different types of information in a way that supports decision making. The system is structured into five components: the hydrological resource is modelled using Low Flows 2000, the turbine options are identified from hydrological, environmental and demand requirements; and the consequences of different solutions will be fed into other components so that the environmental impacts and public acceptability can be assessed and valued. A preliminary case study is presented on an old gunpowder works to illustrate how the resource model may be employed. Historical architectural structures, power uptake and educational instruction of hydro power technology are considered
Locally normal subgroups of totally disconnected groups. Part II: Compactly generated simple groups
We use the structure lattice, introduced in Part I, to undertake a systematic
study of the class consisting of compactly generated,
topologically simple, totally disconnected locally compact groups that are
non-discrete. Given , we show that compact open subgroups of
involve finitely many isomorphism types of composition factors, and do not
have any soluble normal subgroup other than the trivial one. By results of Part
I, this implies that the centraliser lattice and local decomposition lattice of
are Boolean algebras. We show that the -action on the Stone space of
those Boolean algebras is minimal, strongly proximal, and micro-supported.
Building upon those results, we obtain partial answers to the following key
problems: Are all groups in abstractly simple? Can a group in
be amenable? Can a group in be such that the
contraction groups of all of its elements are trivial?Comment: 82 page
Limits of contraction groups and the Tits core
The Tits core G^+ of a totally disconnected locally compact group G is
defined as the abstract subgroup generated by the closures of the contraction
groups of all its elements. We show that a dense subgroup is normalised by the
Tits core if and only if it contains it. It follows that every dense subnormal
subgroup contains the Tits core. In particular, if G is topologically simple,
then the Tits core is abstractly simple, and if G^+ is non-trivial then it is
the unique minimal dense normal subgroup. The proofs are based on the fact, of
independent interest, that the map which associates to an element the closure
of its contraction group is continuous.Comment: 11 page
Clawback Provisions in Real Estate Investment Trusts
Using a sample of 195 unique real estate investment trusts (REITs), we examine factors related to the adoption of clawback provisions within managerial compensation contracts. In general, we find strong and consistent empirical evidence that clawback provision are directly related to firm size, complexity, leverage, growth options, monitoring incentives, and CEO performance incentives. We also find that clawbacks are associated with enhanced market and accounting performance, with stronger performance relations observed for adoption decisions tied directly to regulatory mandates. In sum, we conclude compensation clawback provisions represent a value-relevant, strategic governance mechanism for REITs
Locally normal subgroups of simple locally compact groups
We announce various results concerning the structure of compactly generated
simple locally compact groups. We introduce a local invariant, called the
structure lattice, which consists of commensurability classes of compact
subgroups with open normaliser, and show that its properties reflect the global
structure of the ambient group.Comment: 6 page
Estrogenic chemicals often leach from BPA-free plastic products that are replacements for BPA-containing polycarbonate products
Background: Xenobiotic chemicals with estrogenic activity (EA), such as bisphenol A (BPA), have been reported to
have potential adverse health effects in mammals, including humans, especially in fetal and infant stages. Concerns
about safety have caused many manufacturers to use alternatives to polycarbonate (PC) resins to make hard and
clear, reusable, plastic products that do not leach BPA. However, no study has focused on whether such BPA-free
PC-replacement products, chosen for their perceived higher safety, especially for babies, also release other chemicals
that have EA.
Methods: We used two, well-established, mammalian cell-based, assays (MCF-7 and BG1Luc) to assess the EA of
chemicals that leached into over 1000 saline or ethanol extracts of 50 unstressed or stressed (autoclaving,
microwaving, and UV radiation) BPA-free PC-replacement products. An EA antagonist, ICI 182,780, was used to confirm
that agonist activity in leachates was due to chemicals that activated the mammalian estrogen receptor.
Results: Many unstressed and stressed, PC-replacement-products made from acrylic, polystyrene, polyethersulfone, and
Tritan™ resins leached chemicals with EA, including products made for use by babies. Exposure to various forms of UV
radiation often increased the leaching of chemicals with EA. In contrast, some BPA-free PC-replacement products made
from glycol-modified polyethylene terephthalate or cyclic olefin polymer or co-polymer resins did not release chemicals
with detectable EA under any conditions tested.
Conclusions: This hazard assessment survey showed that many BPA-free PC- replacement products still leached
chemicals having significant levels of EA, as did BPA-containing PC counterparts they were meant to replace. That is,
BPA-free did not mean EA-free. However, this study also showed that some PC-replacement products did not leach
chemicals having significant levels of EA. That is, EA-free PC-replacement products could be made in commercial
quantities at prices that compete with PC-replacement products that were not BPA-free. Since plastic products often
have advantages (price, weight, shatter-resistance, etc.) compared to other materials such as steel or glass, it is not
necessary to forgo those advantages to avoid release into foodstuffs or the environment of chemicals having EA that
may have potential adverse effects on our health or the health of future generations.This work was supported by the following NIH/NIEHS grants: R44 ES011469,
01–03 (CZY); 1R43/44 ES014806, 01–03 (CZY); subcontract (CZY, PI) on
an NIH Grant 01–03 43/44ES018083-01 to PlastiPure (DK, SY PIs).Neuroscienc
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