Large-Area Silicon Detectors for the Advanced Composition Explorer (ACE) Solar Isotope Spectrometer (SIS)

Extensive measurements were made of the thicknesses and dead-layers of the large-area, highpurity silicon detectors used for the Solar Isotope Spectrometer (SIS), an instrument to be launched on the Advanced Composition Explorer (ACE) spacecraft. Tests using accelerated beams of heavy nuclei were also carried out to characterize the completed instrument

The ACE-CRIS Scintillating Optical Fiber Trajectory (SOFT) Detector: Calibrations at the NSCL and GSI

The Scintillating Optical Fiber Trajectory (SOFT) detector, the hodoscope for the Cosmic Ray Isotope Spectrometer (CRIS) on the NASA Advanced Composition Explorer, was calibrated using 155 MeV/n He, Li, C, N, 0, and Ar at the Michigan State University National Superconducting Cyclotron Laboratory (NSCL), and 200 - 700 MeV/n C, Si, and Fe at the GSI facility in Darrnstadt. Germany. The flight instrument consists of three hodoscope fiber planes and one trigger plane. read out by an image intensified CCD camera system and by intensified photodiodes respectively. The spatial and angular resolution of the hodoscope is described, along with the detection efficiency of both the hodoscope and trigger plane as a function of charge

Using surface integrals for checking the Archimedes' law of buoyancy

A mathematical derivation of the force exerted by an \emph{inhomogeneous} (i.e., compressible) fluid on the surface of an \emph{arbitrarily-shaped} body immersed in it is not found in literature, which may be attributed to our trust on Archimedes' law of buoyancy. However, this law, also known as Archimedes' principle (AP), does not yield the force observed when the body is in contact to the container walls, as is more evident in the case of a block immersed in a liquid and in contact to the bottom, in which a \emph{downward} force that \emph{increases with depth} is observed. In this work, by taking into account the surface integral of the pressure force exerted by a fluid over the surface of a body, the general validity of AP is checked. For a body fully surrounded by a fluid, homogeneous or not, a gradient version of the divergence theorem applies, yielding a volume integral that simplifies to an upward force which agrees to the force predicted by AP, as long as the fluid density is a \emph{continuous function of depth}. For the bottom case, this approach yields a downward force that increases with depth, which contrasts to AP but is in agreement to experiments. It also yields a formula for this force which shows that it increases with the area of contact.Comment: 15 pages, 3 figures, accepted for publication in "Eur. J. Phys." (10/20/2011

A Parasitoid Wasp Induces Overwintering Behaviour in Its Spider Host

Parasites and parasitoids control behaviors of their hosts. However, the origin of the behavior evoked by the parasitic organism has been rarely identified. It is also not known whether the manipulation is universal or host-specific. Polysphinctine wasps, koinobiont ectoparasitoids of several spider species that manipulate host web-spinning activity for their own protection during pupation, provide an ideal system to reveal the origin of the evoked behavior. Larva of Zatypota percontatoria performed species-specific manipulation of theridiid spiders, Neottiura bimaculata and Theridion varians, shortly before pupation. Parasitized N. bimaculata produced a dense web, whereas parasitized T. varians built a cupola-like structure. The larva pupated inside of either the dense web or the cupola-like structure. We discovered that unparasitized N. bimaculata produce an analogous dense web around their eggsacs and for themselves during winter, while T. varians construct an analogous ‘cupola’ only for overwintering. We induced analogous manipulation in unparasitized hosts by altering ambient conditions. We discovered that the behavior evoked by larvae in two hosts was functionally similar. The larva evoked protective behaviors that occur in unparasitized hosts only during specific life-history periods

Hyptiogastrites electrinus Cockerell, 1917, from Myanmar (Burmese) amber: Redescription and its placement within the Evanioidea (Insecta: Hymenoptera)

© The Natural History MuseumThe wasp Hyptiogastrites electrinus Cockerell, 1917, from the Lower Cretaceous (Upper Albian) Myanmar (Burmese) amber is redescribed from the well-preserved holotype and its relationship with extant Aulacidae and Gasteruptiidae (Hymenoptera: Evanioidea) evaluated. Although the wing venation is identical to the majority of extant Hyptiogastrinae (Gasteruptiidae), phylogenetic analysis places H. electrinus as sister taxon to the Aulacidae s.str., (i.e. Aulacus + Pristaulacus). Thus, Hyptiogastrinae is confirmed as having a restricted Southern Hemisphere distribution (i.e. Australasia and South America). Consistent with this result, H. electrinus is included within a slightly more broadly defined Aulacidae rather than being placed in a new monotypic family. Characters that align this species with the Aulacidae include: having small circular eyes, percurrent Y-shaped notauli, pyramidal shape of the propodeum and the presence of a groove or ovipositor guide on the hind coxae.John T. Jennings, Andrew D. Austin and Nicholas B. Steven

Observation of two new Ξb−\Xi_b^- baryon resonances

Two structures are observed close to the kinematic threshold in the $\Xi_b^0 \pi^-$ mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$ recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content $bds$ are expected in this mass region: the spin-parity $J^P = \frac{1}{2}^+$ and $J^P=\frac{3}{2}^+$ states, denoted $\Xi_b^{\prime -}$ and $\Xi_b^{*-}$. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be $m(\Xi_b^{\prime -}) - m(\Xi_b^0) - m(\pi^{-}) = 3.653 \pm 0.018 \pm 0.006$ MeV$/c^2$, $m(\Xi_b^{*-}) - m(\Xi_b^0) - m(\pi^{-}) = 23.96 \pm 0.12 \pm 0.06$ MeV$/c^2$, $\Gamma(\Xi_b^{*-}) = 1.65 \pm 0.31 \pm 0.10$ MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of $\Gamma(\Xi_b^{\prime -}) < 0.08$ MeV at 95% confidence level. Relative production rates of these states are also reported.Comment: 17 pages, 2 figure

Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)

The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08 ^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical, the second systematic and the third is associated to the ratio of fragmentation fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/- 0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table