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Growling from the gut: co-option of the gastric mill for acoustic communication in ghost crabs.
Animal acoustic communication systems can be built upon co-opted structures that become specialized for sound production or morphological novelties. The ghost crab, Ocypode quadrata, evolved a novel stridulation apparatus on the claws that is used during agonistic interactions, but they also produce a rasping sound without their claw apparatus. We investigated the nature of these sounds and show that O. quadrata adopted a unique and redundant mode of sound production by co-opting the gastric mill (grinding teeth of the foregut). Acoustic characteristics of the sound are consistent with stridulation and are produced by both male and female crabs during aggressive interactions. Laser Doppler vibrometry localized the source of maximum vibration to the gastric region and fluoroscopy showed movement of the gastric mill that coincided with stridulation. The lateral teeth of the gastric mill possess a series of comb-like structures that rub against the median tooth to produce stridulation with dominant frequencies below 2 kHz. This previously undescribed gastric stridulation can be modulated and provide a means of assessment during aggressive interactions, similar to the use of the claw stridulation apparatus. This functional redundancy of stridulation in crabs offers unique insights into the mechanisms of evolution of acoustic communication systems
How Data Set Characteristics Influence Ocean Carbon Export Models
Ocean biological processes mediate the transport of roughly 10 petagrams of carbon from the surface to the deep ocean each year and thus play an important role in the global carbon cycle. Even so, the globally integrated rate of carbon export out of the surface ocean remains highly uncertain. Quantifying the processes underlying this biological carbon export requires a synthesis between model predictions and available observations of particulate organic carbon (POC) flux; yet the scale dissimilarities between models and observations make this synthesis difficult. Here we compare carbon export predictions from a mechanistic model with observations of POC fluxes from several data sets compiled from the literature spanning different space, time, and depth scales as well as using different observational methodologies. We optimize model parameters to provide the best match between model‐predicted and observed POC fluxes, explicitly accounting for sources of error associated with each data set. Model‐predicted globally integrated values of POC flux at the base of the euphotic layer range from 3.8 to 5.5 Pg C/year, depending on the data set used to optimize the model. Modeled carbon export pathways also vary depending on the data set used to optimize the model, as well as the satellite net primary production data product used to drive the model. These findings highlight the importance of collecting field data that average over the substantial natural temporal and spatial variability in carbon export fluxes, and advancing satellite algorithms for ocean net primary production, in order to improve predictions of biological carbon export
Spatial clustering of emergency department visits by asthmatic children in an urban area: south-western Detroit, Michigan
Objective This ecological study evaluates the correlation of asthma clusters with outdoor air pollution, race, and household income in South-western Detroit, Michigan. Design To attain this objective (1) a geographic information aystem (GIS) is utilized to evaluate the relationships between rates of emergency department (ED) admissions for asthma, race, and socio-economic status at the neighborhood block group level of analysis; (2) cluster statistical analyses are performed using Geomed software; and (3) the asthma risk from industrial air pollution was evaluated with windrose data and Screen3 air pollution model. Sample Data from five major hospitals with ED admissions of asthma patients (code 493), aged 0–15 years, are used to select a region of analysis with good geographical representation based on the catchment areas of hospitals in the study. A total of 2067 of the reported cases between 1 January 1993 and 30 June 1998, are successfully geocoded to a map, generating a no-match rate of 8.4%. Data on racial characteristics, population density, and household income levels are obtained from neighborhood block groups in the 1990 census report. Locations of major polluting industries within the study area are obtained from the Toxics Release Inventory. Results Spatial analysis identified a local asthma cluster roughly 2 km east (the predominant downwind direction) of the second and third largest air polluters (in terms of tonnage) in Wayne County. Evaluation of the industrial pollution with a focused cluster test, Screen3 air pollution model, and windrose figures, displayed weak association between ED asthma admissions and estimated levels of outdoor air pollution from these two facilities. The neighborhood block groups in the local asthma cluster are more closely correlated with high proportions of African Americans and low median household income. Implications for practice This study illustrates the strengths and weaknesses of GIS in the public health arena. It highlights the difficulty of disentangling the effects of exposure to outdoor air pollutants and socio-economic factors on ED asthmatics (reflecting asthma severity) among an urban population. This study also illustrates the need for population-based, as opposed to hospital-based, asthma data, and the need for block-groups, as opposed to zip codes, as a spatial unit of analysis in the evaluation and analysis of asthma-related risk factors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73994/1/j.1467-0658.2001.00143.x.pd
Quantized circular motion of a trapped Bose-Einstein condensate: coherent rotation and vortices
We study the creation of vortex states in a trapped Bose-Einstein condensate
by a rotating force. For a harmonic trapping potential the rotating force
induces only a circular motion of the whole condensate around the trap center
which does not depend on the interatomic interaction. For the creation of a
pure vortex state it is necessary to confine the atoms in an anharmonic
trapping potential. The efficiency of the creation can be greatly enhanced by a
sinusodial variation of the force's angular velocity. We present analytical and
numerical calculations for the case of a quartic trapping potential. The
physical mechanism behind the requirement of an anharmonic trapping potential
for the creation of pure vortex states is explained.
[Changes: new numerical and analytical results are added and the
representation is improved.]Comment: 13 Pages, 5 Figures, RevTe
Interference scheme to measure light-induced nonlinearities in Bose-Einstein condensates
Light-induced nonlinear terms in the Gross-Pitaevskii equation arise from the
stimulated coherent exchange of photons between two atoms. For atoms in an
optical dipole trap this effect depends on the spatial profile of the trapping
laser beam. Two different laser beams can induce the same trapping potential
but very different nonlinearities. We propose a scheme to measure light-induced
nonlinearities which is based on this observation.Comment: 2 figure
Relativistic and Radiative Energy Shifts for Rydberg States
We investigate relativistic and quantum electrodynamic effects for
highly-excited bound states in hydrogenlike systems (Rydberg states). In
particular, hydrogenic one-loop Bethe logarithms are calculated for all
circular states (l = n-1) in the range 20 <= n <= 60 and successfully compared
to an existing asymptotic expansion for large principal quantum number n. We
provide accurate expansions of the Bethe logarithm for large values of n, for
S, P and circular Rydberg states. These three expansions are expected to give
any Bethe logarithms for principal quantum number n > 20 to an accuracy of five
to seven decimal digits, within the specified manifolds of atomic states.
Within the numerical accuracy, the results constitute unified, general formulas
for quantum electrodynamic corrections whose validity is not restricted to a
single atomic state. The results are relevant for accurate predictions of
radiative shifts of Rydberg states and for the description of the recently
investigated laser-dressed Lamb shift, which is observable in a strong
coherent-wave light field.Comment: 8 pages; RevTeX
The Early Stages and Natural History of Antirrhea Adoptive Porphyrosticta (Watkins, 1928) in Eastern Ecuador (Lepidoptera: Nymphalidae: Morphinae)
Here we describe the immature stages and ecological associations of Antirrhea adoptiva porphyrosticta Watkins, 1928 (Lepidoptera:Nymphalidae:Morphinae). The cloud forest bamboo, Chusquea scandens Kunth (Bambusoidea: Poaceae), serves as the larval food plant for this butterfly in eastern Ecuador, the first hostplant record for Antirrhea outside the family Arecaceae. The larvae of A. adoptiva porphyrosticta are superficially similar to those of other Antirrhea species. We also provide observations on adult and larval behavior. Caterpillars of this butterfly species are parasitized by tachinid flies, as well as by Ichneumonidae and a newly described braconid wasp
Source Dimensions in Ultrarelativistic Heavy Ion Collisions
Recent experiments on pion correlations, interpreted as interferometric
measurements of the collision zone, are compared with models that distinguish a
prehadronic phase and a hadronic phase. The models include prehadronic
longitudinal expansion, conversion to hadrons in local kinetic equilibrium, and
rescattering of the produced hadrons. We find that the longitudinal and outward
radii are surprisingly sensitive to the algorithm used for two-body collisions.
The longitudinal radius measured in collisions of 200 GeV/u sulfur nuclei on a
heavy target requires the existence of a prehadronic phase which converts to
the hadronic phase at densities around 0.8-1.0 GeV/fm. The transverse radii
cannot be reproduced without introducing more complex dynamics into the
transverse expansion.Comment: RevTeX 3.0, 28 pages, 6 figures, not included, revised version, major
change is an additional discussion of the classical two-body collision
algorithm, a (compressed) postscript file of the complete paper including
figures can be obtained from Authors or via anonymous ftp at
ftp://ftp_int.phys.washington.edu/pub/herrmann/pisource.ps.
New Zealand blackcurrant extract enhances fat oxidation during prolonged cycling in endurance-trained females.
PURPOSE: New Zealand blackcurrant (NZBC) extract has previously been shown to increase fat oxidation during prolonged exercise, but this observation is limited to males. We examined whether NZBC intake also increases fat oxidation during prolonged exercise in females, and whether this was related to greater concentrations of circulating fatty acids. METHODS: In a randomised, crossover, double-blind design, 16 endurance-trained females (age: 28 ± 8 years, BMI: 21.3 ± 2.1 kg·m-2, VO2max: 43.7 ± 1.1 ml·kg-1·min-1) ingested 600 mg·day-1NZBC extract (CurraNZ™) or placebo (600 mg·day-1microcrystalline cellulose) for 7 days. On day 7, participants performed 120 min cycling at 65% VO2max, using online expired air sampling with blood samples collected at baseline and at 15 min intervals throughout exercise for analysis of glucose, NEFA and glycerol. RESULTS: NZBC extract increased mean fat oxidation by 27% during 120 min moderate-intensity cycling compared to placebo (P = 0.042), and mean carbohydrate oxidation tended to be lower (P = 0.063). Pre-exercise, plasma NEFA (P = 0.034) and glycerol (P = 0.051) concentrations were greater following NZBC intake, although there was no difference between conditions in the exercise-induced increase in plasma NEFA and glycerol concentrations (P > 0.05). Mean fat oxidation during exercise was moderately associated with pre-exercise plasma NEFA concentrations (r = 0.45, P = 0.016). CONCLUSIONS: Intake of NZBC extract for 7 days elevated resting concentrations of plasma NEFA and glycerol, indicative of higher lipolytic rates, and this may underpin the observed increase in fat oxidation during prolonged cycling in endurance-trained females
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