5,963 research outputs found
The evolution of resistance through costly acquired immunity
We examine the evolutionary dynamics of resistance to parasites through acquired immunity. Resistance can be achieved through the innate mechanisms of avoidance of infection and reduced pathogenicity once infected, through recovery from infection and through remaining immune to infection: acquired immunity. We assume that each of these mechanisms is costly to the host and find that the evolutionary dynamics of innate immunity in hosts that also have acquired immunity are quantitatively the same as in hosts that possess only innate immunity. However, compared with resistance through avoidance or recovery, there is less likely to be polymorphism in the length of acquired immunity within populations. Long-lived organisms that can recover at intermediate rates faced with fast-transmitting pathogens that cause intermediate pathogenicity (mortality of infected individuals) are most likely to evolve long-lived acquired immunity. Our work emphasizes that because whether or not acquired immunity is beneficial depends on the characteristics of the disease, organisms may be selected to only develop acquired immunity to some of the diseases that they encounter
Disempowerment and resistance in the print industry? Reactions to surveillance-capable technology
This article offers a critique of recent characterisations of the effects of electronic technologies in the workplace. It presents detailed case study evidence that calls into question a number of common theoretical assumptions about the character of surveillance at work and the responses of employees to it
Providential Tides: the Double Low Water of Narragansett Bay
We investigate a mechanism for producing double-lows and double-highs in the semi-diurnal tide by selective amplification of higher harmonics in a resonant gulf. A double low water is observed at Providence, RI, near the head of Narragansett Bay on days when there is a flattening of the low water tidal curve at Newport, at the mouth of the bay. The flattening is caused by an unusually large quarter-diurnal component to the tide at Newport. The quarter diurnal component has the right phase (a maximum close to the time of the minimum in the semi-diurnal tide) to produce a prolonged flattening of the tidal curve around low water. The natural period of Narragansett Bay (for quarter-wavelength resonance) is close to 4 h and the quarter diurnal tide is amplified, relative to the semi-diurnal tide, within the bay. The selective amplification of the higher harmonic further prolongs the flattening effect at Providence and, occasionally, is sufficient to create a double low water at the head of the bay from quarter and semi-diurnal tides alone. More often, though, a sixth-diurnal harmonic produced within the bay, added to the flattened low water at Providence, creates the double low water. This mechanism of selective amplification of tidal harmonics could be relevant to double tides elsewhere
Characterizing upward lightning with and without a terrestrial gamma-ray flash
We compare two observations of gamma-rays before, during, and after lightning
flashes initiated by upward leaders from a tower during low-altitude winter
thunderstorms on the western coast of Honshu, Japan. While the two leaders
appear similar, one produced a terrestrial gamma-ray flash (TGF) so bright that
it paralyzed the gamma-ray detectors while it was occurring, and could be
observed only via the weaker flux of neutrons created in its wake, while the
other produced no detectable TGF gamma-rays at all. The ratio between the
indirectly derived gamma-ray fluence for the TGF and the 95% confidence
gamma-ray upper limit for the gamma-ray quiet flash is a factor of
. With the only two observations of this type providing such
dramatically different results -- a TGF probably as bright as those seen from
space and a powerful upper limit -- we recognize that weak, sub-luminous TGFs
in this situation are probably not common, and we quantify this conclusion.
While the gamma-ray quiet flash appeared to have a faster leader and more
powerful initial continuous current pulse than the flash that produced a TGF,
the TGF-producing flash occurred during a weak gamma-ray "glow", while the
gamma-ray quiet flash did not, implying a higher electric field aloft when the
TGF was produced. We suggest that the field in the high-field region approached
by a leader may be more important for whether a TGF is produced than the
characteristics of the leader itself.Comment: 21 pages, 6 figures, accepted for publication by the Journal of
Geophysical Research - Atmosphere
Single color and single flavor color superconductivity
We survey the non-locked color-flavor-spin channels for quark-quark (color superconducting) condensates in QCD, using an NJL model. We also study isotropic quark-antiquark (mesonic) condensates. We make mean-field estimates of the strength and sign of the self-interaction of each condensate, using four-fermion interaction vertices based on known QCD interactions. For the attractive quark pairing channels, we solve the mean-field gap equations to obtain the size of the gap as a function of quark density. We also calculate the dispersion relations for the quasiquarks, in order to see how fully gapped the spectrum of fermionic excitations will be. We use our results to specify the likely pairing patterns in neutral quark matter, and comment on possible phenomenological consequences
Tidal amplification of seabed light
Because solar irradiance decreases approximately exponentially with depth in the sea, the increase in irradiance at the seabed from mid to low tide is greater than the decrease from mid to high tide. Summed over a day, this can lead to a net amplification of seabed irradiance in tidal waters compared to nontidal waters with the same mean depth and transparency. In this paper, this effect is quantified by numerical and analytical integration of the Lambert-Beer equation to derive the ratio of daily total seabed irradiance with and without a tide. Greatest amplification occurs in turbid water with large tidal range and low tide occurring at noon. The theoretical prediction is tested against observations of seabed irradiance in the coastal waters of North Wales where tidal amplification of seabed light by up to a factor of 7 is both observed and predicted. Increasing the strength of tidal currents tends to increase the turbidity of the water and hence reduce the light reaching the seabed, but this effect is made less by increasing tidal amplification, especially when low water is in the middle of the day. The ecological implications of tidal amplification are discussed. The productivity of benthic algae will be greater than that predicted by simple models which calculate seabed irradiance using the mean depth of water alone. Benthic algae are also able to live at greater depths in tidal waters than in nontidal waters with the same transparency
1 May 1913 property agreement
Agreement between G. M. D. Bowers, W. W. Colson, and B. R. Colson to hold Dixieland Park land for Theophilus Brown Larimore. The one-page typewritten document is dated 1 May 1913
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