Small crater populations on Vesta

The NASA Dawn mission has extensively examined the surface of asteroid Vesta, the second most massive body in the main belt. The high quality of the gathered data provides us with an unique opportunity to determine the surface and internal properties of one of the most important and intriguing main belt asteroids (MBAs). In this paper, we focus on the size frequency distributions (SFDs) of sub-kilometer impact craters observed at high spatial resolution on several selected young terrains on Vesta. These small crater populations offer an excellent opportunity to determine the nature of their asteroidal precursors (namely MBAs) at sizes that are not directly observable from ground-based telescopes (i.e., below ~100 m diameter). Moreover, unlike many other MBA surfaces observed by spacecraft thus far, the young terrains examined had crater spatial densities that were far from empirical saturation. Overall, we find that the cumulative power-law index (slope) of small crater SFDs on Vesta is fairly consistent with predictions derived from current collisional and dynamical models down to a projectile size of ~10 m diameter (Bottke et al., 2005a,b). The shape of the impactor SFD for small projectile sizes does not appear to have changed over the last several billions of years, and an argument can be made that the absolute number of small MBAs has remained roughly constant (within a factor of 2) over the same time period. The apparent steady state nature of the main belt population potentially provides us with a set of intriguing constraints that can be used to glean insights into the physical evolution of individual MBAs as well as the main belt as an ensemble.Comment: Accepted by PSS, to appear on Vesta cratering special issu

Muon Spin Relaxation Studies of Superconductivity in a Crystalline Array of Weakly Coupled Metal Nanoparticles

We report Muon Spin Relaxation studies in weak transverse fields of the superconductivity in the metal cluster compound, Ga$\_{84}$[N(SiMe$\_{3}$)$\_{2}$]$\_{20}$-Li$\_{6}$Br$\_{2}$(thf)$\_{20}\cdot$2toluene. The temperature and field dependence of the muon spin relaxation rate and Knight shift clearly evidence type II bulk superconductivity below $T\_{\text{c}}\approx7.8$ K, with $B\_{\text{c1}}\approx 0.06$ T, $B\_{\text{c2}}\approx 0.26$ T, $\kappa\sim 2$ and weak flux pinning. The data are well described by the s-wave BCS model with weak electron-phonon coupling in the clean limit. A qualitative explanation for the conduction mechanism in this novel type of narrow band superconductor is presented.Comment: 4 figures, 5 page

Bedrock Denudation on Titan: Estimates of Vertical Extent and Lateral Debris Dispersion

Methane rainfall and runoff, along with aeolian activity, have dominated the sculpting of Titan s landscape. A knowledge of the vertical extent of bedrock erosion and the lateral extent of the resulting sediment is useful for several purposes [1]. For instance, what is the magnitude and expression of modification of constructional landforms (e.g., mountains)? Does highland denudation and the filling of basins with sediment cause adjustments (uplift and subsidence) in the crustal ice shell? Here we report preliminary findings of putative eroded craters and the results of landform evolution modeling (Fig. 1) that suggest that approx. 250 m of net bedrock erosion has at least locally taken place and approx.1 km of maximum local erosion

'Trust is good, control is better': the 1974 Herstatt-Bank crisis and its implications for international regulatory reform

With its international supervisory and regulatory implications, the failure of Bankhaus Herstatt is one of the landmarks of post-war financial history. This article offers the first comprehensive historical account of the Herstatt crisis, and contributes to the wider discussions on international supervisory and regulatory reform since the mid-1970s, including regulatory capture, markets' self-regulation and resolution of failed banks. In doing so, it first argues that contrary to a widely held view, the German authorities received early and repeated warnings about Herstatt's dealings but this involved only limited and ineffective regulatory/supervisory responses, then it turns to the actual collapse of the bank in June 1974, and finally explores the wider regulatory issues raised by the Herstatt case

Cone and seed insects of subalpine fir during a year of low cone production in northern Idaho

Cone and seed insects destroyed 29 percent of the seed crop of subalpine fir (<i>Abies lasiocarpa</i>) in the Freezeout Mountain area of northern Idaho in 1972 during a year of low cone production. Larvae of a coneworm, <i>Dioryctria abietivorella</i> destroyed 12 percent of the seed crop, accounting for 42 percent of the total insect damage. A newly discovered midge pest, a species of <i>Dasineura</i>, destroyed 11 percent of the seed crop, amounting to 40 percent of the total insect damage. The dipterans, <i>Hylemya abietis</i>, <i>Earoymia</i> sp., and <i>Asynapta keeni</i>, and the chalcid wasp, <i>Megastigmus lasiocarpae</i>, together destroyed 4 percent of the seed crop. Unknown causes accounted for 1.5 percent of the total seed destruction. X-ray was used to estimate seed lost to <i>M. lasiocarpae</i> and <i>Dasineura</i> sp. Regression equations are given relating cone length (mm), and the seeds on the axial surface, to total seeds. Sound and damaged seeds on the axial surface were highly correlated with the totals of sound and damaged seeds, respectively, in the cone

Epidemiologia do Boophilus microplus nas condições de cerrado.

O carrapato Boophilus microplus (Canestrini 1887), e um parasita temporário e obrigatório dos bovinos. Distribui-se geograficamente entre os paralelos 32 Norte e Sul, tendo ampla distribuição no México, América Central, América do Sul e Austrália.bitstream/item/137546/1/PESQ-EM-ANDAMENTO-23.pd

Transport properties of a superconducting single-electron transistor coupled to a nanomechanical oscillator

We investigate a superconducting single-electron transistor capacitively coupled to a nanomechanical oscillator and focus on the double Josephson quasiparticle resonance. The existence of two coherent Cooper pair tunneling events is shown to lead to pronounced backaction effects. Measuring the current and the shot noise provides a direct way of gaining information on the state of the oscillator. In addition to an analytical discussion of the linear-response regime, we discuss and compare results of higher-order approximation schemes and a fully numerical solution. We find that cooling of the mechanical resonator is possible, and that there are driven and bistable oscillator states at low couplings. Finally, we also discuss the frequency dependence of the charge noise and the current noise of the superconducting single electron transistor.Comment: 19 pages, 11 figures, published in PR

Thermal Pions at Finite Isospin Chemical Potential

The density corrections, in terms of the isospin chemical potential $\mu_I$, to the mass of the pions are studied in the framework of the SU(2) low energy effective chiral lagrangian. The pion decay constant $f_{\pi}(T, \mu_{I})$ is also analized. As a function of temperature for $\mu_I =0$, the mass remains quite stable, starting to grow for very high values of $T$, confirming previous results. However, there are interesting corrections to the mass when both effects (temperature and chemical potential) are simultaneously present. At zero temperature the $\pi ^{\pm}$ should condensate when $\mu_{I} = \mp m_{\pi}$. This is not longer valid anymore at finite $T$. The mass of the $\pi_0$ acquires also a non trivial dependence on $\mu_I$ due to the finite temperature.Comment: 13 pages, 5 figure