770 research outputs found
Ground effects on V/STOL and STOL aircraft: A survey
The flow fields encountered by jet- and fan-powered Vertical/Short Takeoff and Landing (V/STOL) aircraft operating in ground effect are reviewed and their general effects on the aerodynamic characteristics are discussed. The ground effects considered include: (1) the suckdown experienced by a single jet configuration in hover; (2) the fountain flow and additional suckdown experienced by multiple jet configurations in hover; (3) the ground vortex generated by jet and jet flap configurations in short takeoff and landing (STOL) operation and the associated aerodynamic and hot-gas-ingestion effects; and (4) the change in the downwash at the tail due to ground proximity. After over 30 years of research on V/STOL aircraft, the general flow phenomena are well-known and, in most areas, the effects of ground proximity can be established or can be determined experimentally. However, there are some anomalies in the current data base which are discussed
The new community: characteristics of migrant and non-migrant residents in the rural fringe of a metropolitan area in Ohio
Preliminary results of the Mariner IV radio occultation measurements of the upper atmosphere of Mars
Mariner IV radio occultation measurements of Mars upper atmospher
Preliminary results of the Mariner IV OCCULATION measurement of the atmosphere of Mars
Mariner IV radio occultation measurement of Mars atmospher
Recommended from our members
Pyrethroid insecticide interaction with the GABAA receptor and the peripheral-type benzodiazepine receptor of rainbow trout brain
The peripheral-type benzodiazepine receptor (PTBR) of trout brain was
pharmacologically characterized and pyrethroid interaction with this site
investigated. High-affinity binding sites for [Ā³H]PK 11195 were detected in brain
membranes of rainbow trout; these shared some of the characteristics of the
PTBR of rodent brain (i.e., high affinity for PK 11195 and an endogenous ligand
protoporphyrin IX) but were unique in the low affinity for Ro5-4864. Permethrin
displaced [Ā³H]PK 11195 binding with micromolar affinity while deltamethrin had
less than 50% efficacy at displacement. Thus the PTBR appeared not to be
relevant to pyrethroid toxicity in rainbow trout.
Pyrethroid interaction with the GABA, receptor was investigated using
[Ā³āµS]TBPS as a radioligand probe and by measurement of GABA-stimulated Ā³ā¶c1-
influx in vesicle preparations. At micromolar concentrations, deltamethrin,
cypermethrin isomers and other pyrethroids inhibited [Ā³āµS]TBPS binding by 55-
95% with limited stereoselectivity. Pyrethroids were found to effect a GABAdependent
inhibition of [Ā³āµS]TBPS binding. Ro5-4864, which showed micromolar
affinity for the trout PTBR, produced a GABA-modulated interaction with
[Ā³āµS]TBPS binding. These results delineate the reciprocal allosteric interactions
between a pyrethroid binding site, a Ro5-4864 binding site, the GABA
recognition moiety and the TBPS binding site in trout brain. However,
pyrethroids exhibited a modest affinity for this binding site on the GABAA
receptor.
Pyrethroids indirectly inhibited the GABA-dependent influx of Ā³ā¶Clā»into trout
brain synaptoneurosomes by increasing the basal uptake of chloride, thereby
compromising the ability of the vesicles to respond to applications of GABA.
This pyrethroid effect was of nanomolar potency, stereospecific, tetrodotoxinsensitive
and mimicked by veratridine. These results suggest that the primary
effect of pyrethroids in trout brain, as measured by this assay, was due to an
interaction with voltage-dependent sodium channels, increasing sodium
conductance and thereby increasing the basal uptake of Ā³ā¶Clā» through a voltagesensitive
channel.
The convulsant activity of deltamethrin was tested in rainbow trout. The
ECā
ā for convulsant severity was 32 Ī¼g /kg body weight. By comparison,
pyrethroids at these concentrations in rodents produce no overt toxicity but act
as potent proconvulsants
The Impact of Information Literacy-Related Instruction in the Science Classroom: Clickers Versus Nonclickers
The goal of information literacy instruction is to enable students to develop skills that they can use for life to facilitate their empowerment through information. Instruction librarians, particularly those teaching Millenials whose need for āhands onā instruction has been widely emphasized, are constantly searching for methodologies that will provide appropriate levels of interactive instruction. Many methods for enhancing the relevance of library instruction have been discussed in the literature. This study, designed and developed by a collaborative team of librarians and science faculty, describes the effects of providing course-integrated, interactive (with clickers) information literacy instruction to undergraduates at a small private nonprofit university in the Southeast
Application of Strength, Weakness, Opportunity and Threat (SWOT) Analysis for the Prioritization of Community Health Program Objectives
Relationship between reproductive hormones and migration distance in a polygynous songbird, the Redāwinged Blackbird (\u3ci\u3eAgelaius phoeniceus\u3c/i\u3e)
Many bird species migrate to southern overwintering locations to avoid harsh conditions at their breeding grounds, but at the cost of an energetically demanding migration that may delay their spring reproductive development. Previous work on the relationship between migration distance and reproductive readiness has primarily focused on early season baseline testosterone in both males and females. However, for females, testosterone alone may not be the appropriate measurement of reproductive development. Estradiol, a metabolite of testosterone that is essential for breeding behaviors and reproduction, should also be measured. Furthermore, baseline testosterone varies throughout the day and may change due to social interactions that occurred prior to sampling. Injection of gonadotropin-releasing hormone (GnRH) elicits an individualās maximum potential testosterone production, minimizing daily and social variation. We explored relationships between migration distance and reproductive status after arrival to the breeding ground in Red-winged Blackbirds (Agelaius phoeniceus). We predicted that individuals that travel a shorter distance will have higher levels of reproductive hormones upon arrival given they are able to invest less in migration and more in reproduction. This is important because individuals that breed earlier often have higher reproductive success. In females, we measured baseline estradiol and testosterone. In males, we assessed baseline and GnRH-induced testosterone. Hormone values were related to migration distance, estimated by stable isotope analysis of claw samples collected before breeding began in eastern North Dakota. We found that males with shorter inferred migration distances have higher baseline testosterone upon arrival. However, inferred migration distance was not correlated with GnRH-induced testosterone. Female inferred migration distance was not correlated with baseline testosterone, but it was correlated with baseline estradiol. Females with higher testosterone had lower estradiol, suggesting that testosterone in females is not a reliable indicator of estradiol levels, thus readiness to breed. Our observations suggest that baseline hormone levels were related to migration distance, but baseline testosterone alone may not provide a complete assessment of a male or femaleās preparedness to breed following spring migration
- ā¦