Evaluation of a closed-circuit television display in landing operations with a helicopter

Evaluating closed circuit television display in helicopter landing operation

Geochemical and spectral characterization of naturally altered rock surfaces

The possibility of using the visible-near infrared region for compositional analysis of remotely sensed rock surfaces is studied. This would allow mapping rock type both on the Earth's surface and on other planetary surfaces. Reflectance spectroscopy, economic geology, optical depth determination, and X-ray diffraction mineralogy are discussed

Avalanche Size Scaling in Sheared Three-Dimensional Amorphous Solid

We have studied the statistics of plastic rearrangement events in a simulated amorphous solid at T=0. Events are characterized by the energy release and the ``slip volume'', the product of plastic strain and system volume. Their distributions for a given system size $L$ appear to be exponential, but a characteristic event size cannot be inferred, because the mean values of these quantities increase as $L^{\alpha}$ with $\alpha \sim 3/2$. In contrast to results obtained in 2D models, we do not see simply connected avalanches. The exponent suggests a fractal shape of the avalanches, which is also evidenced by the mean fractal dimension and participation ratio.Comment: Accepted for publication in Physical Review Letter

Qualification tests of materials for spallation neutron sources

Several existing and planned facilities, worldwide, use protons at 650-2000 MeV to produce neutrons by spallation reactions. In the advanced spallation neutron sources, materials in the target and blanket structures will be exposed to high-energy proton fluences at 10{sup 25}-10{sup 26}/m{sup 2} per year. Information obtained in fusion reactor studies are being applied to the design of spallation neutron sources. The APT project is sponsoring a materials qualification program including irradiations in the proton beam and neutron field at the Los Alamos Spallation Radiation Damage Facility

The reconstruction of labour representation in former East Germany 1989-1992. A comparative study of two German trade unions.

This thesis examines the strategies applied by two German trade unions after the collapse of the GDR. It looks at the causes of stability and instability of corporatist systems and their institutions and how these maintain membership and organizational coherence. The study explores the reconstruction strategies of two contrasted West German trade unions seeking to maintain their organizational position and to protect the neo-corporatist industrial relations system that secures their survival. Their strategies for the organizational survival of the unions are determined partly by the neo-corporatist industrial relations structure and partly by their different organizational constraints. The first section looks at explanations of how encompassing trade unions in a neo-corporatist system maintain their membership and their organizational coherence. After delineating the various incentives which encompassing trade unions provide to their membership, the study examines the threats posed by the disintegration of the GDR to the provision of union services and thus to their ability to attract members. The effects of the collapse of the GDR could reduce their membership's willingness to define interests in collective terms (i.e. a favourable trade-off between inflation and unemployment). The study then examines the objectives for an intervention by the West German trade unions in the GDR in order to secure neo-corporatism by incorporation of the East German membership within the encompassing body of the West German unions. The second section looks at the main determinants of the reconstruction process which have been the legacy of low trust in former East German industrial relations as well as the FDGB's inadequate efforts which facilitated the intervention by the West German trade unions in the form of incorporation. The third section assesses the motives of two West German trade unions related to the reconstruction strategies of free labour representation in the GDR. Both trade unions followed the strategy of incorporating the East German workforce by narrowing the existing East-West wage gap (contractual exchange) as well as offering solidarity (diffuse exchange). In particular the motive of contractual exchange reveals the unions' desire to maintain stability within the neo-corporatist environment. As the research on corporatism rarely examines the causes of stability of corporatist systems and institutions, this thesis makes a contribution to our understanding of the strategies to maintain corporatist structures. The sudden collapse of the GDR, with its repercussions for the FRG, provides a special opportunity to analyse the strategy of corporatist institutions seeking to maintain stability

Rationale for a spallation neutron source target system test facility at the 1-MW Long-Pulse Spallation Source

The conceptual design study for a 1-MW Long-Pulse Spallation Source at the Los Alamos Neutron Science Center has shown the feasibility of including a spallation neutron test facility at a relatively low cost. This document presents a rationale for developing such a test bed. Currently, neutron scattering facilities operate at a maximum power of 0.2 MW. Proposed new designs call for power levels as high as 10 MW, and future transmutation activities may require as much as 200 MW. A test bed will allow assessment of target neutronics; thermal hydraulics; remote handling; mechanical structure; corrosion in aqueous, non-aqueous, liquid metal, and molten salt systems; thermal shock on systems and system components; and materials for target systems. Reliable data in these areas are crucial to the safe and reliable operation of new high-power facilities. These tests will provide data useful not only to spallation neutron sources proposed or under development, but also to other projects in accelerator-driven transmutation technologies such as the production of tritium

Competition between benthic cyanobacteria and diatoms as influenced by different grain sizes and temperatures

An experimental laboratory set-up was used to study the influence of different grain size compositions and temperatures on the growth of benthic cyanobacteria and diatoms, and on the competition between these 2 groups. Monospecific cultures of 3 species of cyanobacteria (Merismopedia punctata, Microcoleus chthonoplastes, Oscillatoria limosa), and of 2 species of benthic diatoms (Phaeodactylum tricornutum and Nitzschia sp.) were used. The organisms were cultured in 100 ml flasks filled with medium and 3 different kinds of sediment: (1) Sand (fine sand, 63 to 200 µm), (2) Mud-I (mixed fine sand and mud <63 µm in the ratio 80:20 wt %), (3) Mud-II (mixed fine sand and mud in the ratio 50:50 wt %). Experimental temperatures were 10, 15 and 25°C. At 10°C and 15°C, both diatom species achieved the highest biomass on the sediments of the finest grain size (50 wt % < 63 µm) while cyanobacteria achieved low biomass levels. Coarsening of sediments at the same temperature levels revealed a gradually lower biomass of the diatoms. Particularly on sand, the diatoms never reached the same concentrations of chlorophyll a as on mud. The cyanobacteria, on the other hand, had the highest biomass on sand at 15°C. In the competition experiments the benthic diatom species Nitzschia sp. dominated all types of sediments at 10°C and 15°C. The experiments at 25°C were dominated by the filamentous cyanobacterium M. chthonoplastes. This indicates the importance of abiotic conditions for the distribution and abundance of benthic phototrophic micro-organisms

Renormalization approach to many-particle systems

This paper presents a renormalization approach to many-particle systems. By starting from a bare Hamiltonian ${\cal H}= {\cal H}_0 +{\cal H}_1$ with an unperturbed part ${\cal H}_0$ and a perturbation ${\cal H}_1$,we define an effective Hamiltonian which has a band-diagonal shape with respect to the eigenbasis of ${\cal H}_0$. This means that all transition matrix elements are suppressed which have energy differences larger than a given cutoff $\lambda$ that is smaller than the cutoff $\Lambda$ of the original Hamiltonian. This property resembles a recent flow equation approach on the basis of continuous unitary transformations. For demonstration of the method we discuss an exact solvable model, as well as the Anderson-lattice model where the well-known quasiparticle behavior of heavy fermions is derived.Comment: 11 pages, final version, to be published in Phys. Rev.

Plankton ecology: The past two decades of progress

This is a selected account of recent developments in plankton ecology. The examples have been chosen for their degree of innovation during the past two decades and for their general ecological importance. They range from plankton autecology over interactions between populations to community ecology. The autecology of plankton is represented by the hydromechanics of plankton (the problem of life in a viscous environment) and by the nutritional ecology of phyto- and zooplankton. Population level studies are represented by competition, herbivory (grazing), and zooplankton responses to predation. Community ecology is represented by the debate about bottom- up vs. top-down control of community organization, by the PEG model of seasonal plankton succession, and by the recent discovery of the microbial food web