527 research outputs found

    Education Versus Training at the NWC

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    It has been, roughly, 89 years since Commodore Stephen B. Luce left the Atlantic Fleet off Newport, R.I., and had himself rowed over to Coasters Harbor Island, the site of the newly authorized U.S. Naval War College. There existed only one building on the island, which now stands behind the flagpole and houses the headquarters of the Naval Base Command. This modest structure was to be the site of the Navy\u27s new college for an advanced course of professional study for naval officers, -the first such institution to be established in this country.

    John Foster Dulles

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    Secretary of State John Foster Dulles was known as the notorious, fire-breathing warmonger, the self-styled brinksman ever pushing to the verge of Armageddon, the reckless brandisher of the hydrogen bomb, the truculent, intransigent, hard-line cold warrior par excellence. In reminiscing about the Geneva Summit Conference of 1955, Nikita Khrushchev referred to him as that vicious cur Dulles ... always prowling around Eisenhower, snapping at him if he got out of line. Strong indeed, but only slightly more disparaging than many epithets commonly directed at the Secretary by his own countrymen

    Comparison of the Maximum Gas Combustion Pressure of Hydrogen/Oxygen/Nitrogen-between Chemical Equilibrium Calculations and Experimental Data

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    AbstractA study was completed comparing equilibrium combustion pressures obtained using constant volume and internal energy constraints to maximum combustion pressures from an existing experimental data base for hydrogen / oxygen and nitrogen mixtures (Jo and Crowl, 2006). We found that the experimental and calculated combustion pressures were close near the stoichiometric combustion point. At other compositions, particularly near the flammable limits, the calculated equilibrium pressures were much higher. Since the maximum pressure is of interest in insuring the design of process equipment and vents, the equilibrium calculation approach can be used instead of experimental data

    Environmental Effects in Clusters: Modified Far-Infrared--Radio Relations within Virgo Cluster Galaxies

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    (abridged) We present a study on the effects of the intracluster medium (ICM) on the interstellar medium (ISM) of 10 Virgo cluster spiral galaxies using {\it Spitzer} far-infrared (FIR) and VLA radio continuum imaging. Relying on the FIR-radio correlation within normal galaxies, we use our infrared data to create model radio maps which we compare to the observed radio images. For 6 of our sample galaxies we find regions along their outer edges that are highly deficient in the radio compared with our models. We believe these observations are the signatures of ICM ram pressure. For NGC 4522 we find the radio deficit region to lie just exterior to a region of high radio polarization and flat radio spectral index, although the total 20 cm radio continuum in this region does not appear strongly enhanced. These characteristics seem consistent for other galaxies with radio polarization data in the literature. The strength of the radio deficit is inversely correlated with the time since peak pressure as inferred from stellar population studies and gas stripping simulations, suggesting the strength of the radio deficit is good indicator of the strength of the current ram pressure. We also find that galaxies having {\it local} radio {\it deficits} appear to have {\it enhanced global} radio fluxes. Our preferred physical picture is that the observed radio deficit regions arise from the ICM wind sweeping away cosmic-ray (CR) electrons and the associated magnetic field, thereby creating synchrotron tails as observed for some of our galaxies. We propose that CR particles are also re-accelerated by ICM-driven shocklets behind the observed radio deficit regions which in turn enhances the remaining radio disk brightness.Comment: 19 pages, 10 figures; Astrophysical Journa

    A Bit-String Model for Biological Aging

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    We present a simple model for biological aging. We studied it through computer simulations and we have found this model to reflect some features of real populations.Comment: LaTeX file, 4 PS figures include

    Effect of multimodal cues from a predatory fish on refuge use and foraging on an amphidromous shrimp

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    Background. Prey can alter their behavior when detecting predator cues. Little is known about which sensory channel, number of channels, or the interaction among channels that shrimp species use to evaluate the threat from predators. The amphidromous shrimp Xiphocaris elongata has an induced defense, an elongated rostrum, where predatory fishes are present. We sought to test if kairomones or visual cues when presented singly from fish either eating flakes or shrimp, had more effect on altering the temporal feeding and refuge use patterns of long-rostrum (LR) X. elongata. We were also interested in elucidating potential interactions among cues when presented simultaneously in different combinations (kairomones + visual + mechanosensory, kairomones + alarm + visual, kairomones + alarm, kairomones + visual) on the same response variables. We expected that when presented alone kairomones will significantly increase refuge use and decrease foraging, particularly late at night, in comparison to visual cues alone, and that multiple cues when presented simultaneously will further increase refuge use and decrease foraging at night. Methods. We exposed shrimp to individual or multiple cues from the predatory fish mountain mullet, Augonostomus monticola. We examined shrimp behavior with respect to refuge use and foraging activity during four time periods (after sunset, nighttime, sunrise, and sunset) in a 24-hour period. Results. Shrimp presented fish visual and chemical cues singly did not differ from one another but differed from control shrimp (no cues) with respect to refuge use or foraging. The number of shrimp using refuge in the treatment with most cues (KVM: Kairomones+ visual + mechanosensory) was higher than in all the treatments with less cues. A significant decline in foraging was observed when multiple cues were presented simultaneously. The highest number of shrimp foraged one hour after sunset and at nighttime. A significant interaction was observed between cue treatments and time periods, with shrimp in the KVM treatment foraging less and using more refuge late at night and at sunrise than shrimp in other treatments or time periods. Conclusions. The observation that fish chemical and visual cues when presented singly produced similar refuge use and foraging patterns was contrary to expectation and suggests that visual and chemical cues, when presented alone, provide redundant information to X. elongata with regards to predation threat. The significant increase in refuge use and reduction in foraging observed in the KVM treatment suggest multimodal signal enhancement in the perception of threat. This makes evolutionary sense in \u27\u27noisy\u27\u27 environments, such as streams, where detection, localization, and intention of predators is much improved when cues are received through multiple sensory channels

    Peeling back the layers: First phylogenomic insights into the Ledebouriinae (Scilloideae, Asparagaceae)

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    The Ledebouriinae (Scilloideae, Asparagaceae) are a widespread group of bulbous geophytes found predominantly throughout seasonal climates in sub-Saharan Africa, with a handful of taxa in Madagascar, the Middle East, India, and Sri Lanka. Phylogenetic relationships within the group have been historically difficult to elucidate. Here, we provide the first phylogenomic perspective into the Ledebouriinae. Using the Angiosperms353 targeted enrichment probe set, we consistently recovered four major clades (i.e., two Ledebouria clades, Drimiopsis, and Resnova). The two Ledebouria clades closely align with geography, either consisting almost entirely of sub-Saharan African taxa (Ledebouria Clade A), or East African and non-African taxa (Ledebouria Clade B). Our results suggest that the Ledebouriinae likely underwent a rapid radiation leading to rampant incomplete lineage sorting. We additionally find evidence for potential historical hybridization between Drimiopsis and a subclade within Ledebouria Clade A.Plant Biology, Ecology, and Evolutio

    Ram pressure stripping of the multiphase ISM in the Virgo cluster spiral galaxy NGC 4438

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    Ram pressure stripping of the multiphase ISM is studied in the perturbed Virgo cluster spiral galaxy NGC 4438. This galaxy underwent a tidal interaction ~100 Myr ago and is now strongly affected by ram pressure stripping. Deep VLA radio continuum observations at 6 and 20 cm are presented. We detect prominent extraplanar emission to the west of the galactic center, which extends twice as far as the other tracers of extraplanar material. The spectral index of the extraplanar emission does not steepen with increasing distance from the galaxy. This implies in situ re-acceleration of relativistic electrons. The comparison with multiwavelength observations shows that the magnetic field and the warm ionized interstellar medium traced by Halpha emission are closely linked. The kinematics of the northern extraplanar Halpha emission, which is ascribed to star formation, follow those of the extraplanar CO emission. In the western and southern extraplanar regions, the Halpha measured velocities are greater than those of the CO lines. We suggest that the ionized gas of this region is excited by ram pressure. The spatial and velocity offsets are consistent with a scenario where the diffuse ionized gas is more efficiently pushed by ram pressure stripping than the neutral gas. We suggest that the recently found radio-deficient regions compared to 24 mum emission are due to this difference in stripping efficiency.Comment: 8 pages, 6 figures, A&A, accepted for publicatio
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