Modification of the conductance of single fullerene molecules by endohedral doping

We use scanning tunneling microscopy to establish controlled contacts to single molecules of endohedrally doped Ce(2)@C(80) fullerenes with C(60) as a reference. The stability of the experimental setup allows for the determination of the conductance of Ce(2)@C(80) relative to the conductance of C(60). The endohedral doping reduces the conductance of Ce(2)@C(80) by a factor of about five with respect to C(60). Ab initio calculations show that the reason for this reduced conductance is the absence of electron orbitals delocalized over the cage of Ce(2)@C(80) in the energy window of the conductance measurement. (C) 2009 American Institute of Physics. (doi:10.1063/1.3236529

Comparison between CARIBIC Aerosol Samples Analysed by Accelerator-Based Methods and Optical Particle Counter Measurements

Inter-comparison of results from two kinds of aerosol systems in the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on a Instrument Container) passenger aircraft based observatory, operating during intercontinental flights at 9–12 km altitude, is presented. Aerosol from the lowermost stratosphere (LMS), the extra-tropical upper troposphere (UT) and the tropical mid troposphere (MT) were investigated. Aerosol particle volume concentration measured with an optical particle counter (OPC) is compared with analytical results of the sum of masses of all major and several minor constituents from aerosol samples collected with an impactor. Analyses were undertaken with the following accelerator-based methods: particle-induced X-ray emission (PIXE) and particle elastic scattering analysis (PESA). Data from 48 flights during 1 year are used, leading to a total of 106 individual comparisons. The ratios of the particle volume from the OPC and the total mass from the analyses were in 84% within a relatively narrow interval. Data points outside this interval are connected with inlet-related effects in clouds, large variability in aerosol composition, particle size distribution effects and some cases of non-ideal sampling. Overall, the comparison of these two CARIBIC measurements based on vastly different methods show good agreement, implying that the chemical and size information can be combined in studies of the MT/UT/LMS aerosol

Alterações da disponibilidade de nutrientes em um Latossolo Vermelho-Amarelo degradado e outro não-degradado fertilizados com biossólido e florestados com Eucalyptus grandis.

O presente trabalho teve como objetivos avaliar os efeitos da aplicação de biossólido sobre as modificações de fertilidade do solo e o crescimento de povoamentos de Eucalyptus grandis plantados em um Latossolo Vermelho-Amarelo Distrófico não-degradado e outro degradado

Analytical solution of generalized Burton--Cabrera--Frank equations for growth and post--growth equilibration on vicinal surfaces

We investigate growth on vicinal surfaces by molecular beam epitaxy making use of a generalized Burton--Cabrera--Frank model. Our primary aim is to propose and implement a novel analytical program based on a perturbative solution of the non--linear equations describing the coupled adatom and dimer kinetics. These equations are considered as originating from a fully microscopic description that allows the step boundary conditions to be directly formulated in terms of the sticking coefficients at each step. As an example, we study the importance of diffusion barriers for adatoms hopping down descending steps (Schwoebel effect) during growth and post-growth equilibration of the surface.Comment: 16 pages, REVTeX 3.0, IC-DDV-94-00

High-field high-repetition-rate sources for the coherent THz control of matter

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasicontinuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution

Fueling the gender gap? Oil and women's labor and marriage market outcomes

This paper analyzes the effect of resource-based economic specialization on women's labor market outcomes. Using information on the location and discovery of major oil fields in the Southern United States coupled with a county-level panel derived from US Census data for 1900-1940, we specifically test the hypothesis that the presence of mineral resources can induce changes in the sectoral composition of the local economy that are detrimental to women's labor market outcomes. We find evidence that the discovery of oil at the county level may constitute a substantial male biased demand shock to local labor markets, as it is associated with a higher gender pay gap. However, we find no evidence that oil wealth lowers female labor force participation or has any impact on local marriage and fertility patterns. While our results are consistent with oil shocks limiting female labor market opportunities in some sectors (mainly manufacturing), this effect tends to be compensated by the higher availability of service sector jobs for women who are therefore not driven out of the labor market

Dynamic manipulation of mechanical resonators in the high amplitude regime through optical backaction

Cavity optomechanics enables active manipulation of mechanical resonators through backaction cooling and amplification. This ability to control mechanical motion with retarded optical forces has recently spurred a race towards realizing a mechanical resonator in its quantum ground state. Here, instead of quenching optomechanical motion, we demonstrate high amplitude operation of nanomechanical resonators by utilizing a highly efficient phonon generation process. In this regime, the nanomechanical resonators gain sufficient energy from the optical field to overcome the large energy barrier of a double well potential, leading to nanomechanical slow-down and zero frequency singularity, as predicted by early theories . Besides fundamental studies and interests in parametric amplification of small forces, optomechanical backaction is also projected to open new windows for studying discrete mechanical states, and to foster applications. Here we realize a non-volatile mechanical memory element, in which bits are written and reset via optomechanical backaction by controlling the mechanical damping across the barrier. Our study casts a new perspective on the energy dynamics in coupled mechanical resonator - cavity systems and enables novel functional devices that utilize the principles of cavity optomechanics.Comment: 22 pages, 5 figure