Objectives of permanent lunar bases

Permanent manned lunar surface and orbiting base

Synthesis and reactivity of a nickel(ii) thioperoxide complex: demonstration of sulfide-mediated N2O reduction.

The thiohyponitrite ([SNNO]2-) complex, [K(18-crown-6)][L tBuNiII(κ2-SNNO)] (L tBu = {(2,6-iPr2C6H3)NC( t Bu)}2CH), extrudes N2 under mild heating to yield [K(18-crown-6)][L tBuNiII(η2-SO)] (1), along with minor products [K(18-crown-6)][L tBuNiII(η2-OSSO)] (2) and [K(18-crown-6)][L tBuNiII(η2-S2)] (3). Subsequent reaction of 1 with carbon monoxide (CO) results in the formation of [K(18-crown-6)][L tBuNiII(η2-SCO)] (4), [K(18-crown-6)][L tBuNiII(S,O:κ2-SCO2)] (5), [K(18-crown-6)][L tBuNiII(κ2-CO3)] (6), carbonyl sulfide (COS) (7), and [K(18-crown-6)][L tBuNiII(S2CO)] (8). To rationalize the formation of these products we propose that 1 first reacts with CO to form [K(18-crown-6)][L tBuNiII(S)] (I) and CO2, via O-atom abstraction. Subsequently, complex I reacts with CO or CO2 to form 4 and 5, respectively. Similarly, the formation of complex 6 and COS can be rationalized by the reaction of 1 with CO2 to form a putative Ni(ii) monothiopercarbonate, [K(18-crown-6)][L tBuNiII(κ2-SOCO2)] (11). The Ni(ii) monothiopercarbonate subsequently transfers a S-atom to CO to form COS and [K(18-crown-6)][L tBuNiII(κ2-CO3)] (6). Finally, the formation of 8 can be rationalized by the reaction of COS with I. Critically, the observation of complexes 4 and 5 in the reaction mixture reveals the stepwise conversion of [K(18-crown-6)][L tBuNiII(κ2-SNNO)] to 1 and then I, which represents the formal reduction of N2O by CO

Supercharged topping rocket propellant feed system

A rocket propellant feed system utilizing a bleed turbopump to supercharge a topping turbopump is presented. The bleed turbopump is of a low pressure type to meet the cavitation requirements imposed by the propellant storage tanks. The topping turbopump is of a high pressure type and develops 60 to 70 percent of the pressure rise in the propellant

Search for GRB afterglows in the ROSAT all-sky survey

We report on the status of our search for X-ray afterglows of gamma-ray bursts (GRBs) using the ROSAT all-sky survey data. The number of potential X-ray afterglow candidates with respect to the expected number of beamed GRBs allows to constrain the relative beaming angles of GRB emission and afterglow emission at about 1-5 hrs after the GRB.Comment: 3 pages A&A style, 1 color ps-figure; To appear in A&A Suppl. Series, Proc. of Rome 1998 GRB workshop, also available from http://www.aip.de/~jcg/publis.htm

Entanglement and its dynamics in open, dissipative systems

Quantum mechanical entanglement can exist in noisy open quantum systems at high temperature. A simple mechanism, where system particles are randomly reset to some standard initial state, can counteract the deteriorating effect of decoherence, resulting in an entangled steady state far from thermodynamical equilibrium. We present models for both gas-type systems and for strongly coupled systems. We point out in which way the entanglement resulting from such a reset mechanism is different from the entanglement that one can find in thermal states. We develop master equations to describe the system and its interaction with an environment, study toy models with two particles (qubits), where the master equation can often be solved analytically, and finally examine larger systems with possibly fluctuating particle numbers. We find that in gas-type systems, the reset mechanism can produce an entangled steady state for an arbitrary temperature of the environment, while this is not true in strongly coupled systems. But even then, the temperature range where one can find entangled steady states is typically much higher with the reset mechanism.Comment: 30 pages, 15 figure

Domain-Wall Energies and Magnetization of the Two-Dimensional Random-Bond Ising Model

We study ground-state properties of the two-dimensional random-bond Ising model with couplings having a concentration $p\in[0,1]$ of antiferromagnetic and $(1-p)$ of ferromagnetic bonds. We apply an exact matching algorithm which enables us the study of systems with linear dimension $L$ up to 700. We study the behavior of the domain-wall energies and of the magnetization. We find that the paramagnet-ferromagnet transition occurs at $p_c \sim 0.103$ compared to the concentration $p_n\sim 0.109$ at the Nishimory point, which means that the phase diagram of the model exhibits a reentrance. Furthermore, we find no indications for an (intermediate) spin-glass ordering at finite temperature.Comment: 7 pages, 12 figures, revTe

Pioneer Mars 1979 mission options

A preliminary investigation of lower cost Mars missions which perform useful exploration objectives after the Viking/75 mission was conducted. As a study guideline, it was assumed that significant cost savings would be realized by utilizing Pioneer hardware currently being developed for a pair of 1978 Venus missions. This in turn led to the additional constraint of a 1979 launch with the Atlas/Centaur launch vehicle which has been designated for the Pioneer Venus missions. Two concepts, using an orbiter bus platform, were identified which have both good science potential and mission simplicity indicative of lower cost. These are: (1) an aeronomy/geology orbiter, and (2) a remote sensing orbiter with a number of deployable surface penetrometers

Evidence for existence of many pure ground states in 3d ±J\pm J Spin Glasses

Ground states of 3d EA Ising spin glasses are calculated for sizes up to $14^3$ using a combination of genetic algorithms and cluster-exact approximation . The distribution $P(|q|)$ of overlaps is calculated. For increasing size the width of $P(|q|)$ converges to a nonzero value, indicating that many pure ground states exist for short range Ising spin glasses.Comment: 4 pages, 3 figures, 2 tables, 16 reference