A simple analysis of thermodynamic properties for classical plasmas: I. theory

By eliminating the short range negative divergence of the Debye–Hückel pair distribution function, but retaining the exponential charge screening known to operate at large interparticle separation, the thermodynamic properties of one-component plasmas of point ions or charged hard spheres can be well represented even in the strong coupling regime. Predicted electrostatic free energies agree within 5% of simulation data for typical Coulomb interactions up to a factor of 10 times the average kinetic energy. Here, this idea is extended to the general case of a uniform ionic mixture, comprising an arbitrary number of components, embedded in a rigid neutralizing background. The new theory is implemented in two ways: (i) by an unambiguous iterative algorithm that requires numerical methods and breaks the symmetry of cross correlation functions; and (ii) by invoking generalized matrix inverses that maintain symmetry and yield completely analytic solutions, but which are not uniquely determined. The extreme computational simplicity of the theory is attractive when considering applications to complex inhomogeneous fluids of charged particles.

A comparison between classical techniques and eigenstructure assignment in the design of a longitudinal instrument landing system

Although modern control techniques such as eigenstructure assignment have been given extensive coverage in control literature there is a reluctance to use them in practice as they are often not believed to be as `visible' or as simple as classical methods. A simple aircraft example is used, and it is shown that eigenstructure assignment can be used easily to produce a more viable controller than with simple classical techniques.

Attic pottery in early Classical Thessaly. A case study from Achaia Phthiotis

This paper attributes a previously unnoticed Attic black-figured lekythos kept in the Archaeological Museum of Volos to the Pholos Group (ca. 470 BC) and discusses its findspot in the peripheral Thessalian district of Achaia Phthiotis. Beyond an art-historical appreciation of the hastily-drawn chariot scene on this lekythos and a discussion of stylistic parallels, which include a lekythos in Prague, it is argued that such lekythoi were socially important for their shape and small size that made them easily transportable. The assumed scarcity of Attic pottery in Thessaly can be questioned given that a considerable amount of Attic pottery from Thessalian locations is mentioned only in passing or remains unpublished in museum storage. Small late black-figured lekythoi predominate amongst Attic pottery shapes in Thessaly. The popularity of such lekythoi can become indicative of human mobility across the landscape and the consumption of imported (grave) goods by social groups other than elites.

Further evidence for variable synchrotron emission in XTE J1118+480 in outburst

We present simultaneous multicolor infrared and optical photometry of the black hole X-ray transient XTE J1118+480 during its short 2005 January outburst, supported by simultaneous X-ray observations. The variability is dominated by short timescales, ~10 s, although a weak superhump also appears to be present in the optical. The optical rapid variations, at least, are well correlated with those in X-rays. Infrared JHKs photometry, as in the previous outburst, exhibits especially large-amplitude variability. The spectral energy distribution (SED) of the variable infrared component can be fitted with a power law of slope α=-0.78+/-0.07, where F_ν~ν^α. There is no compelling evidence for evolution in the slope over five nights, during which time the source brightness decayed along almost the same track as seen in variations within the nights. We conclude that both short-term variability and longer timescale fading are dominated by a single component of constant spectral shape. We cannot fit the SED of the IR variability with a credible thermal component, either optically thick or thin. This IR SED is, however, approximately consistent with optically thin synchrotron emission from a jet. These observations therefore provide indirect evidence to support jet-dominated models for XTE J1118+480 and also provide a direct measurement of the slope of the optically thin emission, which is impossible, based on the average spectral energy distribution alone.

Infrared Observations of XTE J1118+480

Infrared observations of the outbursting black hole XTE J1118+480 (ATEL #383) were performed using SQIID on the Kitt Peak National Observatory 2.1m telescope. Observations spanning 2005 January 15.42-15.58 found it somewhat fainter than the previous outburst (IAUC # 7394 , # 7407 ), at average brightness J=12.91+/-0.03, H=12.50+/-0.03, K=11.95+/-0.03. The colors again correspond to an approximately flat spectrum in F_nu. No orbital variation is apparent, but there is substantial unresolved rapid variability with rms amplitude 22% in K (between 2s exposures). Further observations are planned nightly until Jan 21.