12,225 research outputs found
Vertebrate DNA in Fecal Samples from Bonobos and Gorillas: Evidence for Meat Consumption or Artefact?
Background: Deciphering the behavioral repertoire of great apes is a challenge for several reasons. First, due to their elusive behavior in dense forest environments, great ape populations are often difficult to observe. Second, members of the genus Pan are known to display a great variety in their behavioral repertoire; thus, observations from one population are not necessarily representative for other populations. For example, bonobos (Pan paniscus) are generally believed to consume almost no vertebrate prey. However, recent observations show that at least some bonobo populations may consume vertebrate prey more commonly than previously believed. We investigated the extent of their meat consumption using PCR amplification of vertebrate mitochondrial DNA (mtDNA) segments from DNA extracted from bonobo feces. As a control we also attempted PCR amplifications from gorilla feces, a species assumed to be strictly herbivorous. Principal Findings: We found evidence for consumption of a variety of mammalian species in about 16% of the samples investigated. Moreover, 40% of the positive DNA amplifications originated from arboreal monkeys. However, we also found duiker and monkey mtDNA in the gorilla feces, albeit in somewhat lower percentages. Notably, the DNA sequences isolated from the two ape species fit best to the species living in the respective regions. This result suggests that the sequences are of regional origin and do not represent laboratory contaminants. Conclusions: Our results allow at least three possible and mutually not exclusive conclusions. First, all results may represent contamination of the feces by vertebrate DNA from the local environment. Thus, studies investigating a species' diet from feces DNA may be unreliable due to the low copy number of DNA originating from diet items. Second, there is some inherent difference between the bonobo and gorilla feces, with only the later ones being contaminated. Third, similar to bonobos, for which the consumption of monkeys has only recently been documented, the gorilla population investigated (for which very little observational data are as yet available) may occasionally consume small vertebrates. Although the last explanation is speculative, it should not be discarded a-priori given that observational studies continue to unravel new behaviors in great ape species
Electron effective mass in AlGaN alloys determined by mid-infrared optical Hall effect
The effective electron mass parameter in Si-doped AlGaN is
determined to be from mid-infrared optical Hall
effect measurements. No significant anisotropy of the effective electron mass
parameter is found supporting theoretical predictions. Assuming a linear change
of the effective electron mass with the Al content in AlGaN alloys and
for GaN, an average effective electron mass of
can be extrapolated for AlN. The analysis of mid-infrared
spectroscopic ellipsometry measurements further confirms the two phonon mode
behavior of the E(TO) and one phonon mode behavior of the A(LO) phonon
mode in high-Al-content AlGaN alloys as seen in previous Raman scattering
studies
Advanced electrochemical depolarized concentrator cell development
An advanced electrochemical depolarized carbon dioxide concentrator subsystem, to collect and concentrate metabolically produced CO2 for subsequent O2 recovery in spacecraft, is discussed
Anomalous magnetoresistance peak in (110) GaAs two-dimensional holes: Evidence for Landau-level spin-index anticrossings
We measure an anomalous magnetoresistance peak within the lowest Landau level
(nu = 1) minimum of a two-dimensional hole system on (110) GaAs.
Self-consistent calculations of the valence band mixing show that the two
lowest spin-index Landau levels anticross in a perpendicular magnetic field B
consistent with where the experimental peak is measured, Bp. The temperature
dependence of the anomalous peak height is interpreted as an activated behavior
across this anticrossing gap. Calculations of the spin polarization in the
lowest Landau levels predict a rapid switch from about -3/2 to +3/2 spin at the
anticrossing. The peak position Bp is shown to be affected by the confinement
electrostatics, and the utility of a tunable anticrossing position for
spintronics applications is discussed.Comment: 4 pages, 4 figure
Aging and intermittency in a p-spin model of a glass
We numerically analyze the statistics of the heat flow between an aging
system and its thermal bath, following a method proposed and tested for a
spin-glass model in a recent Letter (P. Sibani and H.J. Jensen, Europhys.
Lett.69, 563 (2005)). The present system, which lacks quenched randomness,
consists of Ising spins located on a cubic lattice, with each plaquette
contributing to the total energy the product of the four spins located at its
corners. Similarly to our previous findings, energy leaves the system in rare
but large, so called intermittent, bursts which are embedded in reversible and
equilibrium-like fluctuations of zero average. The intermittent bursts, or
quakes, dissipate the excess energy trapped in the initial state at a rate
which falls off with the inverse of the age. This strongly heterogeneous
dynamical picture is explained using the idea that quakes are triggered by
energy fluctuations of record size, which occur independently within a number
of thermalized domains. From the temperature dependence of the width of the
reversible heat fluctuations we surmise that these domains have an exponential
density of states. Finally, we show that the heat flow consists of a
temperature independent term and a term with an Arrhenius temperature
dependence. Microscopic dynamical and structural information can thus be
extracted from numerical intermittency data. This type of analysis seems now
within the reach of time resolved micro-calorimetry techniques.Comment: 9 pages, 6 figures, europhysics letter style, to appear in Physical
Review
A compact dual atom interferometer gyroscope based on laser-cooled rubidium
We present a compact and transportable inertial sensor for precision sensing
of rotations and accelerations. The sensor consists of a dual Mach-Zehnder-type
atom interferometer operated with laser-cooled Rb. Raman processes are
employed to coherently manipulate the matter waves. We describe and
characterize the experimental apparatus. A method for passing from a compact
geometry to an extended interferometer with three independent atom-light
interaction zones is proposed and investigated. The extended geometry will
enhance the sensitivity by more than two orders of magnitude which is necessary
to achieve sensitivities better than rad/s/.Comment: 9 pages, 8 figure
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