Cereal Genome Evolution: Grasses, line up and form a circle

AbstractThe genomes of six major grass species can be aligned by dissecting the individual chromosomes into segments and rearranging these linkage blocks into highly similar structures

Gray Whale Calls Recorded near Barrow, Alaska, throughout the Winter of 2003–04

Since the mid-1990s, gray whales (Eschrichtius robustus) have been reported with increasing frequency near Barrow, Alaska, during summer and autumn months. In collaboration with a broad-scale oceanographic study, three autonomous acoustic recorders were moored northeast of Barrow in October 2003 to provide capability for year-round detection of calls. Two recorders were recovered in September 2004, one from the continental slope (water depth = 316 m) and one from near the base of the slope (water depth = 1258 m). The shallow instrument recorded for roughly 3 months (87 days), and the deeper instrument for roughly 7.3 months (222 days). Gray whale calls were recorded on both instruments throughout their periods of operation. The calling rate at the shallower instrument was higher than at the deeper recorder, but surprisingly, the deeper instrument detected calls throughout the 2003–04 winter, though the calling rate diminished as winter progressed. Low-frequency N1/S1 pulses, the most common of the calls produced by gray whales, were recorded from deployment through December 2003 on the shallower of the two instruments and from deployment through May 2004 on the deeper instrument. Because this is the first-ever winterlong acoustic study, we cannot be certain that gray whales have not overwintered in the Beaufort Sea in the past. However, a combination of increasing population size and habitat alteration associated with sea ice reduction and warming in the Alaskan Arctic may be responsible for the extra-seasonal gray whale occurrence near Barrow.Depuis le milieu des années 1990, des baleines grises (Eschrichtius robustus) ont été signalées de plus en plus souvent près de Barrow, en Alaska, pendant les mois d’été et d’automne. En collaboration avec une étude océanographique à grande échelle, trois enregistreurs acoustiques autonomes ont été amarrés au nord-est de Barrow en octobre 2003 afin de pouvoir détecter les cris de baleine à l’année. Deux enregistreurs ont été récupérés en septembre 2004, un de la pente continentale (à une profondeur d’eau de 316 m) et l’autre près de la base de la pente (à une profondeur de 1 258 m). L’instrument le moins profond a enregistré les sons pendant trois mois environ (87 jours), tandis que l’instrument le plus profond a enregistré les sons pendant environ 7, 3 mois (222 jours). Les cris de baleines grises ont été enregistrés au moyen des deux instruments. Le nombre de cris enregistrés à l’aide de l’instrument le moins profond était plus élevé qu’avec l’instrument le plus profond. Cependant, et fait étonnant, l’instrument le plus profond a détecté des cris pendant l’hiver 2003– 2004, bien que le nombre de cris ait diminué au fur et à mesure que l’hiver avançait. Les ondes pulsées de basse fréquence N1/S1, soit les cris les plus courants produits par les baleines grises, ont été enregistrées à partir de l’installation de l’instrument le moins profond en décembre en 2003 et de l’installation de l’instrument le plus profond jusqu’au mois de mai 2004. Puisqu’il s’agit de la première étude acoustique ayant duré pendant tout l’hiver, nous ne pouvons pas savoir avec certitude si les baleines grises n’ont pas hiverné dans la mer de Beaufort par le passé. Toutefois, l’augmentation de la population de baleines, alliée à la modification de l’habitat, à la diminution de la glace de mer et au réchauffement qui sévit dans la région arctique de l’Alaska, pourrait être responsable de la présence de baleines grises hors saison près de Barrow

Monitoring nutrient enrichment impacts in wetlands with PRS™-probes

Non-Peer Reviewe

Extended Storage for Research and Test Reactor Spent Fuel for 2006 and Beyond

This paper will examine issues associated with extended storage of a variety of spent nuclear fuels. Recent experiences at the Idaho National Engineering and Environmental Laboratory and Hanford sites will be described. Particular attention will be given to storage of damaged or degraded fuel. The first section will address a survey of corrosion experience regarding wet storage of spent nuclear fuel. The second section will examine issues associated with movement from wet to dry storage. This paper also examines technology development needs to support storage and ultimate disposition

Four-Wave mixing in degenerate Fermi gases: Beyond the undepleted pump approximation

We analyze the full nonlinear dynamics of the four-wave mixing between an incident beam of fermions and a fermionic density grating. We find that when the number of atoms in the beam is comparable to the number of atoms forming the grating, the dephasing of that grating, which normally leads to a decay of its amplitude, is suppressed. Instead, the density grating and the beam density exhibit large nonlinear coupled amplitude oscillations. In this case four-wave mixing can persist for much longer times compared to the case of negligible back-action. We also evaluate the efficiency of the four-wave mixing and show that it can be enhanced by producing an initial density grating with an amplitude that is less than the maximum value. These results indicate that efficient four-wave mixing in fermionic alkali gases should be experimentally observable.Comment: 9 pages, 8 figure

A space-based radio frequency transient event classifier

The FORTE (Fast On-Orbit Recording of Transient Events) satellite will record RF transients in space. These transients will be classified onboard the spacecraft with an Event Classifier--specialized hardware that performs signal preprocessing and neural network classification. The authors describe the Event Classifier, future directions, and implications for telecommunications satellites. Telecommunication satellites are susceptible to damage from environmental factors such as deep dielectric charging and surface discharges. The event classifier technology the authors are developing is capable of sensing the surface discharges and could be useful for mitigating their effects. In addition, the techniques they are using for processing weak signals in noisy environments are relevant to telecommunications

Magnetic monopoles from gauge theory phase transitions

Thermal fluctuations of the gauge field lead to monopole formation at the grand unified phase transition in the early Universe, even if the transition is merely a smooth crossover. The dependence of the produced monopole density on various parameters is qualitatively different from theories with global symmetries, and the monopoles have a positive correlation at short distances. The number density of monopoles may be suppressed if the grand unified symmetry is only restored for a short time by, for instance, nonthermal symmetry restoration after preheating.Comment: 5 pages, updated to match the version published in PRD (http://link.aps.org/abstract/PRD/v68/e021301) on 11 July 200

Searching for a Cosmological Preferred Axis: Union2 Data Analysis and Comparison with Other Probes

We review, compare and extend recent studies searching for evidence for a preferred cosmological axis. We start from the Union2 SnIa dataset and use the hemisphere comparison method to search for a preferred axis in the data. We find that the hemisphere of maximum accelerating expansion rate is in the direction $(l,b)=({309^\circ}^{+23^\circ}_{-3^\circ}, {18^\circ}^{+11^\circ}_{-10^\circ})$ (\omm=0.19) while the hemisphere of minimum acceleration is in the opposite direction $(l,b)=({129^\circ}^{+23^\circ}_{-3^\circ},{-18^\circ}^{+10^\circ}_{-11^\circ})$ (\omm=0.30). The level of anisotropy is described by the normalized difference of the best fit values of \omm between the two hemispheres in the context of \lcdm fits. We find a maximum anisotropy level in the Union2 data of \frac{\Delta \ommax}{\bomm}=0.43\pm 0.06. Such a level does not necessarily correspond to statistically significant anisotropy because it is reproduced by about $30$ of simulated isotropic data mimicking the best fit Union2 dataset. However, when combined with the axes directions of other cosmological observations (bulk velocity flow axis, three axes of CMB low multipole moments and quasar optical polarization alignment axis), the statistical evidence for a cosmological anisotropy increases dramatically. We estimate the probability that the above independent six axes directions would be so close in the sky to be less than $1$. Thus either the relative coincidence of these six axes is a very large statistical fluctuation or there is an underlying physical or systematic reason that leads to their correlation.Comment: 10 pages, 7 figures. Accepted in JCAP (to appear). Extended analysis with redshift tomography of SnIa, included errorbars and increased number of axes. The Mathematica 7 files with the data used for the production of the figures along with a Powerpoint file with additional figures may be downloaded from http://leandros.physics.uoi.gr/anisotrop

Theory of output coupling for trapped fermionic atoms

We develop a dynamic theory of output coupling, for fermionic atoms initially confined in a magnetic trap. We consider an exactly soluble one-dimensional model, with a spatially localized delta-type coupling between the atoms in the trap and a continuum of free-particle external modes. Two important special cases are considered for the confinement potential: the infinite box and the harmonic oscillator. We establish that in both cases a bound state of the coupled system appears for any value of the coupling constant, implying that the trap population does not vanish in the infinite-time limit. For weak coupling, the energy spectrum of the outgoing beam exhibits peaks corresponding to the initially occupied energy levels in the trap; the height of these peaks increases with the energy. As the coupling gets stronger, the energy spectrum is displaced towards dressed energies of the fermions in the trap. The corresponding dressed states result from the coupling between the unperturbed fermionic states in the trap, mediated by the coupling between these states and the continuum. In the strong-coupling limit, there is a reinforcement of the lowest-energy dressed mode, which contributes to the energy spectrum of the outgoing beam more strongly than the other modes. This effect is especially pronounced for the one-dimensional box, which indicates that the efficiency of the mode-reinforcement mechanism depends on the steepness of the confinement potential. In this case, a quasi-monochromatic anti-bunched atomic beam is obtained. Results for a bosonic sample are also shown for comparison.Comment: 16 pages, 7 figures, added discussion on time-dependent spectral distribution and corresponding figur