Direct Investigation of Superparamagnetism in Co Nanoparticle Films

A direct probe of superparamagnetism was used to determine the complete anisotropy energy distribution of Co nanoparticle films. The films were composed of self-assembled lattices of uniform Co nanoparticles 3 nm or 5 nm in diameter, and a variable temperature scanning-SQUID microscope was used to measure temperature-induced spontaneous magnetic noise in the samples. Accurate measurements of anisotropy energy distributions of small volume samples will be critical to magnetic optimization of nanoparticle devices and media.Comment: 4 pages, 4 figures. Submitted to Physical Review Letter

The Guestworker as Metaphor: In clarification of social economic contradictions and systemic crisis.

In May 1979 the French National Assembly passed legislation giving the government sweeping powers to expel foreign workers. Yet neither the government nor the employers really want to send most of the immigrant workers home, and thereby lose them as a source of cheap labor for both public and private enterprise. It is likely that the employers hope to use the new legislation to keep foreign workers in a state of permanent insecurity, to discourage them from protesting against their low pay, poor working conditions and the racism they encounter daily. Indeed, employers would like to see foreign workers treated as a separate caL._gory of second-class citizens, without the rights of French citizens. This attempt to divide the workers is a subtle attempt to confuse French workers into believing that French society is providing charity to support foreign intruders and that this in turn is the cause of the current economic crisis. This effort contends that the plight of the guestworker can be applied toward clarifyin the political-economic and social contradictions inherent in crises of late-capitalism. 4The ratioiale for what follows lies in the argument that the problems of foreign workers in Western Europe do not remain solely relevant to or caught within a particular geographical or conceptual frame. A better understanding of the guestworker can conceivably shed light on inter-linked policies of the extant system of inequalities within which international labor migrations obtain

Airborne measurements of launch vehicle effluent: Launch of Space Shuttle (STS-1) on 12 April 1981

Launch vehicle effluent environmental impact activities from the first space shuttle (STS-1) included airborne measurements within the exhaust cloud from about 9 min after launch (T + 9) to T + 120 min. Measurements included total hydrogen chloride (gaseous plus aqueous) concentrations, particulate concentrations, temperature, and dewpoint temperature. The airborne measurements are summarized. The physical growth and behavior of exhaust clouds is presented as well as the results of laboratory analysis of elemental composition of particulate samples collected by the aircraft. Observed results from the STS-1 launch are compared with earlier Titan III results. Shuttle effluent concentrations are found to be within the range of Titan III observations

What is a robot companion - friend, assistant or butler?

The study presented in this paper explored people's perceptions and attitudes towards the idea of a future robot companion for the home. A human-centred approach was adopted using questionnaires and human-robot interaction trials to derive data from 28 adults. Results indicated that a large proportion of participants were in favour of a robot companion and saw the potential role as being an assistant, machine or servant. Few wanted a robot companion to be a friend. Household tasks were preferred to child/animal care tasks. Humanlike communication was desirable for a robot companion, whereas humanlike behaviour and appearance were less essential. Results are discussed in relation to future research directions for the development of robot companions

Normal ground state of dense relativistic matter in a magnetic field

The properties of the ground state of relativistic matter in a magnetic field are examined within the framework of a Nambu-Jona-Lasinio model. The main emphasis of this study is the normal ground state, which is realized at sufficiently high temperatures and/or sufficiently large chemical potentials. In contrast to the vacuum state, which is characterized by the magnetic catalysis of chiral symmetry breaking, the normal state is accompanied by the dynamical generation of the chiral shift parameter $\Delta$. In the chiral limit, the value of $\Delta$ determines a relative shift of the longitudinal momenta (along the direction of the magnetic field) in the dispersion relations of opposite chirality fermions. We argue that the chirality remains a good approximate quantum number even for massive fermions in the vicinity of the Fermi surface and, therefore, the chiral shift is expected to play an important role in many types of cold dense relativistic matter, relevant for applications in compact stars. The qualitative implications of the revealed structure of the normal ground state on the physics of protoneutron stars are discussed. A noticeable feature of the $\Delta$ parameter is that it is insensitive to temperature when $T \ll \mu_0$, where $\mu_0$ is the chemical potential, and {\it increases} with temperature for $T > \mu_0$. The latter implies that the chiral shift parameter is also generated in the regime relevant for heavy ion collisions.Comment: 28 pages, 6 figures; v2: title changed in journa

Cognitive consequences of clumsy automation on high workload, high consequence human performance

The growth of computational power has fueled attempts to automate more of the human role in complex problem solving domains, especially those where system faults have high consequences and where periods of high workload may saturate the performance capacity of human operators. Examples of these domains include flightdecks, space stations, air traffic control, nuclear power operation, ground satellite control rooms, and surgical operating rooms. Automation efforts may have unanticipated effects on human performance, particularly if they increase the workload at peak workload times or change the practitioners' strategies for coping with workload. Smooth and effective changes in automation requires detailed understanding of the congnitive tasks confronting the user: it has been called user centered automation. The introduction of a new computerized technology in a group of hospital operating rooms used for heart surgery was observed. The study revealed how automation, especially 'clumsy automation', effects practitioner work patterns and suggest that clumsy automation constrains users in specific and significant ways. Users tailor both the new system and their tasks in order to accommodate the needs of process and production. The study of this tailoring may prove a powerful tool for exposing previously hidden patterns of user data processing, integration, and decision making which may, in turn, be useful in the design of more effective human-machine systems

A model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory

With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behavior of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil, and aqueous solutions of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil–water interfacial tensions. The systems were characterized in detail by measuring the permeability behavior of the packed columns, the adsorption isotherms of AOT from the water to the oil–water interface and to the water–calcium carbonate interface, and oil–water–calcium carbonate contact angles. Measurements of the percent oil recovery by pumping surfactant solutions into calcium carbonate-packed columns initially filled with oil were analyzed in terms of the characterization results. We show that the measured contact angles as a function of AOT concentration are in reasonable agreement with those calculated from values of the surface energy of the calcium carbonate–air surface plus the measured adsorption isotherms. Surfactant adsorption onto the calcium carbonate–water interface causes depletion of its aqueous-phase concentration, and we derive equations which enable the concentration of nonadsorbed surfactant within the packed column to be estimated from measured parameters. The percent oil recovery as a function of the surfactant concentration is determined solely by the oil–water–calcium carbonate contact angle for nonadsorbed surfactant concentrations less than the cac. For surfactant concentrations greater than the cac, additional oil removal occurs by a combination of solubilization and emulsification plus oil mobilization due to the low oil–water interfacial tension and a pumping pressure increase