Variation of the area-to-mass ratio of high area-to-mass ratio space debris objects

An unexpected space debris population with the unique property of a very high area-to-mass ratio (HAMR) was detected in 2004 by Schildknecht and colleagues. Ever since, attempts have been made to investigate the dynamical properties of these objects further. Their orbits are heavily perturbed by the effect of direct radiation pressure, and unknown attitude motion complicates orbit prediction. The area-to-mass ratio of the objects seems to be unstable over time. Only sparse optical data are available for these objects in drift orbits. This paper makes use of optical observations of five HAMR objects, observed over several years, and investigates the variation of their area-to-mass ratio and orbital parameters. A normalized orbit determination setup is established and validated with two low- and two high-area-to-mass-ratio-objects, to ensure that comparable orbits over longer time spans are determined even with sparse optical dat

Variation of Area-to-Mass-Ratio of HAMR Space Debris Objects

An unexpected space debris population has been detected in 2004 Schildknecht et al. (2003, 2004) with the unique properties of a very high area-to-mass ratio (HAMR) Schildknecht et al. (2005a). Ever since it has been tried to investigate the dynamical properties of those objects further. The orbits of those objects are heavily perturbed by the effect of direct radiation pressure. Unknown attitude motion complicates orbit prediction. The area-to-mass ratio of the objects seems to be not stable over time. Only sparse optical data is available for those objects in drift orbits. The current work uses optical observations of five HAMR objects, observed over several years and investigates the variation of their area-to-mass ratio and orbital parameters. A normalized orbit determination setup has been established and validated with two low and two of the high ratio objects, to ensure, that comparable orbits over longer time spans are determined even with sparse optical data.Comment: 10 pages, accepted Monthly Notices of Royal Astronomical Society, MN-11-1785-MJ.R1, The definitive version is available at www.blackwell-synergy.co

Diffractive production and the total cross section in deep inelastic scattering

We explore the consequences for diffractive production, gamma* p --> X p, in deep inelastic scattering at low values of x\sim Q^2/W^2 <<1 that follow from our recent representation of the total photoabsorption cross section, sigma_{gamma* p}, in the generalized vector dominance/ color dipole picture(GVD/CDP) that is based on the generic structure of the two-gluon-exchange from QCD. Sum rules are derived that relate the transverse and the longitudinal (virtual) photoabsorption cross section to diffractive forward production of q q-bar states that carry photon quantum numbers ("elastic diffraction"). Agreement with experiment in the W^2 and Q^2 dependence is found for M_X^2/Q^2<<1, where M_X is the mass of the produced system X. An additional component ("inelastic diffraction"), not actively contributing to the forward Compton amplitude, is needed for diffractive production at high values of M_X. Our previous theoretical representation of the total photoabsorption cross section sigma_{gamma* p}=sigma_{gamma* p}(eta), in terms of the scaling variable eta=(Q^2+m_0^2)/Lambda^2(W^2) is extended to include the entire kinematic domain, x==0, where scaling in eta holds experimentally.Comment: 19 pages with 4 figures,(eps and ps files), Late

Deep inelastic scattering and "elastic" diffraction

We examine the total cross section of virtual photons on protons, $\sigma_{\gamma^* p}(W^2,Q^2)$, at low $x \cong Q^2/W^2 \ll 1$ and its connection with ``elastic'' diffractive production $\gamma^*_{T,L}p \to X^{J=1}_{T,L} p$ in the two-gluon exchange dynamics for the virtual forward Compton scattering amplitude. Solely based on the generic structure of two-gluon exchange, we establish that the cross section is described by the (imaginary part of the) amplitude for forward scattering of $q \bar q$ vector states, $(q \bar q)^{J=1}_{T,L} p \to (q \bar q)^ {J=1}_{T,L} p$. The generalized vector dominance/color dipole picture (GVD/CDP) is accordingly established to only rest on the two-gluon-exchange generic structure. This is explicitly seen by the sum rules that allow one to directly relate the total cross section to the cross section for elastic diffractive forward production, $\gamma^*_{T,L} p\to (q \bar q)^{J=1}_{T,L} p$, of vector states.Comment: 24 pages, latex file with three eps figures. BI-TP 2002/2

Multipole analysis of spin observables in vector meson photoproduction

A multipole analysis of vector meson photoproduction is formulated as a generalization of the pseudoscalar meson case. Expansion of spin observables in the multipole basis and behavior of these observables near threshold and resonances are examined.Comment: 15 pages, latex, 2 figure

Refinement of IntelliCage protocols for complex cognitive tasks through replacement of drinking restrictions by incentive-disincentive paradigms

The IntelliCage allows automated testing of cognitive abilities of mice in a social home cage environment without handling by human experimenters. Restricted water access in combination with protocols in which only correct responses give access to water is a reliable learning motivator for hippocampus-dependent tasks assessing spatial memory and executive function. However, water restriction may negatively impact on animal welfare, especially in poor learners. To better comply with the 3R principles, we previously tested protocols in which water was freely available but additional access to sweetened water could be obtained by learning a task rule. While this purely appetitive motivation worked for simple tasks, too many mice lost interest in the sweet reward during more difficult hippocampus-dependent tasks. In the present study, we tested a battery of increasingly difficult spatial tasks in which water was still available without learning the task rule, but rendered less attractive either by adding bitter tasting quinine or by increasing the amount of work to obtain it. As in previous protocols, learning of the task rule provided access to water sweetened with saccharin. The two approaches of dual motivation were tested in two cohorts of female C57BL/6 N mice. Compared to purely appetitive motivation, both novel protocols strongly improved task engagement and increased task performance. Importantly, neither of the added disincentives had an adverse impact on liquid consumption, health status or body weight of the animals. Our results show that it is possible to refine test protocols in the IntelliCage so that they challenge cognitive functions without restricting access to water

On the Energy Dependence of the Dipole-Proton Cross Section in Deep Inelastic Scattering

We study the dipole picture of high-energy virtual-photon-proton scattering. It is shown that different choices for the energy variable in the dipole cross section used in the literature are not related to each other by simple arguments equating the typical dipole size and the inverse photon virtuality, contrary to what is often stated. We argue that the good quality of fits to structure functions that use Bjorken-x as the energy variable - which is strictly speaking not justified in the dipole picture - can instead be understood as a consequence of the sign of scaling violations that occur for increasing Q^2 at fixed small x. We show that the dipole formula for massless quarks has the structure of a convolution. From this we obtain derivative relations between the structure function F_2 at large and small Q^2 and the dipole-proton cross section at small and large dipole size r, respectively.Comment: 27 page

Evidence for As lattice location and Ge bound exciton luminescence in ZnO implanted with 73As and 73Ge

The results of photoluminescence (PL) measurements performed on high quality single crystal ZnO implanted with radioactive 73Ga and 73As, both of which decay to stable 73Ge, are presented. Identical effects are observed in the two cases, with a sharp line at 3.3225(5) eV found to grow in intensity in accordance with the growth rate of the Ge daughter atom populations. On the strength of the well-established result that Ga occupies Zn sites, we conclude from the identical outcomes for 73Ga and 73As implantations that implanted As also preferentially occupies Zn sites. This result supports the findings of others that As preferentially occupies the Zn rather than the O site in ZnO. The thermal quenching energy of the 3.3225(5) eV line is found to be only 2.9(1) meV in contrast to its large spectral shift of 53.4(1) meV with respect to the lowest energy free exciton. The PL is attributed to exciton recombination at neutral Ge double donors on Zn sites involving transitions that leave the donor in an excited state

Production of Three Vector Bosons in e+e- Annihilation as a Test of W+-, Z, gamma Self-Interactions

We study the vector-boson production processes e+e- --> WWZ and e+e- -->WWgamma which are directly affected by the trilinear and quadrilinear self couplings of the W, Z and gamma. Our analysis is based upon a single-parameter effective-Lagrangian model for these self interactions which contains the standard model as a special case. Consequences for the phenomenology at an e+e- collider of 500 GeV (NLC) are discussed, and fits of the free parameter around its standard model value are carried out.Comment: BI-TP 92/30, July 1992 (Enlarged Version October 1992) One section added to the old version. Figures (unchanged) no more included but available by reques

Elastic electron deuteron scattering with consistent meson exchange and relativistic contributions of leading order

The influence of relativistic contributions to elastic electron deuteron scattering is studied systematically at low and intermediate momentum transfers ($Q^2\leq 30$ fm$^{-2}$). In a $(p/M)$-expansion, all leading order relativistic $\pi$-exchange contributions consistent with the Bonn OBEPQ models are included. In addition, static heavy meson exchange currents including boost terms and lowest order $\rho\pi\gamma$-currents are considered. Sizeable effects from the various relativistic two-body contributions, mainly from $\pi$-exchange, have been found in form factors, structure functions and the tensor polarization $T_{20}$. Furthermore, static properties, viz. magnetic dipole and charge quadrupole moments and the mean square charge radius are evaluated.Comment: 15 pages Latex including 5 figures, final version accepted for publication in Phys.Rev.C Details of changes: (i) The notation of the curves in Figs. 1 and 2 have been clarified with respect to left and right panels. (ii) In Figs. 3 and 4 an experimental point for T_20 has been added and a corresponding reference [48] (iii) At the end of the text we have added a paragraph concerning the quality of the Bonn OBEPQ potential