Gate Voltage Controllable Non-Equilibrium and Non-Ohmic Behavior in Suspended Carbon Nanotubes

In this work, we measure the electrical conductance and temperature of individual, suspended quasi-metallic single-walled carbon nanotubes under high voltage biases using Raman spectroscopy, while varying the doping conditions with an applied gate voltage. By applying a gate voltage, the high-bias conductance can be switched dramatically between linear (Ohmic) behavior and nonlinear behavior exhibiting negative differential conductance (NDC). Phonon populations are observed to be in thermal equilibrium under Ohmic conditions but switch to nonequilibrium under NDC conditions. A typical Landauer transport model assuming zero bandgap is found to be inadequate to describe the experimental data. A more detailed model is presented, which incorporates the doping dependence in order to fit this data

Stable hydrogen and carbon isotope ratios of extractable hydrocarbons in the Murchison meteorite

A fairly fool-proof method to ensure that the compounds isolated from meteorites are truly part of the meteorites and not an artifact introduced by exposure to the terrestrial environment, storage, or handling is presented. The stable carbon and hydrogen isotope ratios in several of the chemical compounds extracted from the Murchison meteorite were measured. The results obtained by studying the amino acids in this meteorite gave very unusual hydrogen and carbon isotope ratios. The technique was extended to the different classes of hydrocarbons and the hydrocarbons were isolated using a variety of separation techniques. The results and methods used in this investigation are described in this two page paper

Antimatter, Lorentz Symmetry, and Gravity

A brief introduction to the Standard-Model Extension (SME) approach to testing CPT and Lorentz symmetry is provided. Recent proposals for tests with antimatter are summarized, including gravitational and spectroscopic tests.Comment: Presented at the 12th International Conference on Low Energy Antiproton Physics, Kanazawa Japan, March 6-11, 2016, Accepted for publication in JPS Conference Proceeding

Cover slip external cavity diode laser

The design of a 671 nm diode laser with a mode-hop-free tuning range of 40 GHz is described. This long tuning range is achieved by simultaneously ramping the external cavity length with the laser injection current. The external cavity consists of a microscope cover slip mounted on piezoelectric actuators. In such a configuration the laser output pointing remains fixed, independent of its frequency. Using a diode with an output power of 5-7 mW, the laser linewidth was found to be smaller than 30 MHz. This cover slip cavity and feedforward laser current control system is simple, economical, robust, and easy to use for spectroscopy, as we demonstrate with lithium vapor and lithium atom beam experiments.Comment: 7 pages, 6 figures, submitted to Review of Scientific Instruments 7/29/0

Observation of a baryon resonance with positive strangeness in K+ collisions with Xe nuclei

The status of our investigation of low-energy $K^+$Xe collisions in the Xenon bubble chamber DIANA is reported. In the charge-exchange reaction $K^+Xe \to K^0 p Xe'$ the spectrum of $K^0 p$ effective mass shows a resonant enhancement with $M = 1539 \pm 2$ MeV/c$^2$ and $\Gamma \le 9 MeV/c$^2$. The statistical significance of the enhancement is near$4.4\sigma$. The mass and width of the observed resonance are consistent with expectations for the lightest member of the anti-decuplet of exotic pentaquark baryons, as predicted in the framework of the chiral soliton model.Comment: 9 pages, 4 figure

Population-level variability in the social climates of four chimpanzee societies

Recent debates have questioned the extent to which culturally-transmitted norms drive behavioral variation in resource sharing across human populations. We shed new light on this discussion by examining the group-level variation in the social dynamics and resource sharing of chimpanzees, a species that is highly social and forms long-term community associations but differs from humans in the extent to which cultural norms are adopted and enforced. We rely on theory developed in primate socioecology to guide our investigation in four neighboring chimpanzee groups at a sanctuary in Zambia. We used a combination of experimental and observational approaches to assess the distribution of resource holding potential in each group. In the first assessment, we measured the proportion of the population that gathered in a resource-rich zone, in the second we assessed naturally occurring social spacing via social network analysis, and in the third we assessed the degree to which benefits were equally distributed within the group. We report significant, stable group-level variation across these multiple measures, indicating that group-level variation in resource sharing and social tolerance is not necessarily reliant upon human-like cultural norms

Further evidence for formation of a narrow baryon resonance with positive strangeness in K+ collisions with Xe nuclei

We have continued our investigation of the charge-exchange reaction K^+ Xe --> K^0 p Xe' in the bubble chamber DIANA. In agreement with our previous results based on part of the present statistics, formation of a narrow p K^0 resonance with mass of 1537+-2 MeV/c^2 is observed in the elementary transition K^+ n --> K^0 p on a neutron bound in the Xenon nucleus. Visible width of the peak is consistent with being entirely due to instrumental resolution and allows to place an upper limit on its intrinsic width: \Gamma < 9 MeV/c^2. A more precise estimate of the resonance intrinsic width, \Gamma = 0.36+-0.11 MeV/c^2, is obtained from the ratio between the numbers of resonant and non-resonant charge-exchange events. The signal is observed in a restricted interval of incident K^+ momentum, that is consistent with smearing of a narrow p K^0 resonance by Fermi motion of the target neutron. Statistical significance of the signal is some 7.3, 5.3, and 4.3 standard deviations for the estimators S/sqrt{B}, S/sqrt{S+B}, and S/sqrt{S+2B}, respectively. This observation confirms and reinforces our earlier results, and offers strong evidence for formation of a pentaquark baryon with positive strangeness in the charge-exchange reaction K^+ n --> K^0 p on a bound neutron.Comment: 13 pages, 8 figures, some chenges in text and references, more precise estimate of Theta(1540) to add, submitted to Phys.Atom.Nucl(Yad.Fiz.

Galactic Anisotropy as Signature of ``Top-Down'' Mechanisms of Ultra-High Energy Cosmic Rays

We show that ``top-down'' mechanisms of Ultra-High Energy Cosmic Rays which involve heavy relic particle-like objects predict Galactic anisotropy of highest energy cosmic rays at the level of minimum $\sim 20$. This anisotropy is large enough to be either observed or ruled out in the next generation of experiments.Comment: 8 pages, 1 figure, LaTeX. Final version appeared in Pisma Zh. Eksp. Teor. Fi

Small Scale Anisotropy Predictions for the Auger Observatory

We study the small scale anisotropy signal expected at the Pierre Auger Observatory in the next 1, 5, 10, and 15 years of operation, from sources of ultra-high energy (UHE) protons. We numerically propagate UHE protons over cosmological distances using an injection spectrum and normalization that fits current data up to \sim 10^{20}\eV. We characterize possible sources of ultra-high energy cosmic rays (UHECRs) by their mean density in the local Universe, $\bar{\rho} = 10^{-r}$ Mpc$^{-3}$, with $r$ between 3 and 6. These densities span a wide range of extragalactic sites for UHECR sources, from common to rare galaxies or even clusters of galaxies. We simulate 100 realizations for each model and calculate the two point correlation function for events with energies above 4 \times 10^{19}\eV and above 10^{20}\eV, as specialized to the case of the Auger telescope. We find that for r\ga 4, Auger should be able to detect small scale anisotropies in the near future. Distinguishing between different source densities based on cosmic ray data alone will be more challenging than detecting a departure from isotropy and is likely to require larger statistics of events. Combining the angular distribution studies with the spectral shape around the GZK feature will also help distinguish between different source scenarios.Comment: 15 pages, 6 figures, 6 tables, submitted to JCA