Asymptotic light field in the presence of a bubble-layer

We report that the submerged microbubbles are an efficient source of diffuse radiance and may contribute to a rapid transition to the diffuse asymptotic regime. In this asymptotic regime an average cosine is easily predictable and measurable.Comment: 4 pages, 3 Postscript figures, opex2.sty (enclosed), also available from the Optical Society of America htpp://epubs.osa.org/oearchive/pdf/11948.pd

Weak CSS Sources from FIRST Survey

We report early results of an observational campaign targeted on a sample of compact steep spectrum sources selected from the FIRST survey which are significantly weaker than those investigated before. The selection criteria and procedure are given in detail. We present here an assortment of MERLIN and VLBI observations and make some general comments based on the morphologies of the sources presented.Comment: A contribution to The Third Workshop on GHz-Peaked Spectrum and Compact Steep Spectrum Radio Sources, Kerastari, Greece, May 28-31, 2002. Refereed and accepted by Publications of the Astronomical Society of Australia. Final version copyedited by PASA Edito

Non-periodic long-range order for fast decaying interactions at positive temperatures

We present the first example of an exponentially decaying interaction which gives rise to non-periodic long-range order at positive temperatures.Comment: 7 pages, Late

Influence of ligand shape and steric hindrance on the composition of the nanocrystal ligand shell

Organic ligands play a key role in the synthesis of colloidal semiconductor nanocrystals or quantum dots. Generally they consist of a functional group and an aliphatic chain, with carboxylic acids, thiols and phosphonic acids as typical examples. The functional group ensures the binding to the nanocrystal surface, while the stability of the dispersion strongly depends on the interactions between the organic chains of the adjacent ligands. A number of studies already addressed the binding strength and the type of binding between the nanocrystal surface and the ligand yet none discuss the effect of the organic chain on the ligand exchange. By means of NMR spectroscopy, we examine the ligand shell composition of CdSe nanocrystals originally capped with oleic acid (OA), when exposed to a linear carboxylic acid. Regardless of chain length, we see a one-to-one exchange between the carboxylic acids. The composition of the ligand shell closely matches that of the ligand mixture in solution, indicating that the ligand shell can be seen as an ideal mixture of both ligands. As a consequence, a mixed ligand shell can easily be prepared by adding a ligand mixture with desired composition to the nanocrystal dispersion. On the other hand, when the CdSe nanocrystals are exposed to a branched carboxylic acid with two long aliphatic chains, like 2-hexyldecanoic acid, the ligand shell mainly consists of OA moieties. We interpret these results using an exchange process where the incoming ligand not only displaces oleic acid but also occupies additional space in the ligand shell to accommodate both aliphatic chains. Hence, given a one-for-one exchange reaction, steric hindrance in a fully packed ligand shell will prevent complete ligand exchange. These results can be very useful in view of producing nanocrystals with lower ligand densities by means of synthesis with these branched carboxylic acids

Forces and atomic relaxations in the pSIC approach with ultrasoft pseudopotentials

We present the scheme that allows for efficient calculations of forces in the framework of pseudopotential self-interaction corrected (pSIC) formulation of the density functional theory. The scheme works with norm conserving and also with ultrasoft pseudopotentials and has been implemented in the plane-wave basis code {\sc quantum espresso}. We have performed tests of the internal consistency of the derived expressions for forces considering ZnO and CeO$_2$ crystals. Further, we have performed calculations of equilibrium geometry for LaTiO$_3$, YTiO$_3$, and LaMnO$_3$ perovskites and also for Re and Mn pairs in silicon. Comparison with standard DFT and DFT+U approaches shows that in the cases where spurious self-interaction matters, the pSIC approach predicts different geometry, very often closer to the experimental data.Comment: 11 pages, 2 figure

Extensions of Power Transition: Applications to Political Economy

This is a paper about theory in political economy terms and political economy in theoretical terms. It unifies power transition theory and applies it to the central questions that now confront political economists. Will trade wars emerge as the security challenge declines? What are the economic effects of integration, trade and growth? How will economic patterns influence international power relationships? This paper offers a preliminary bridge whereon practitioners and theorist may meet to assess the challenges that lie at the intersection between politics and economics. The economic collapse and political dissolution of the Soviet Union left policymakers and scholars searching for new fundamentals about the nature of the international system. During the Cold War era the supreme threat to international peace and security overshadowed economic concerns. The nature of that threat was a powerful mobilizing tool for government, business, and society. The loss of the immediate security threat has forced policymakers to search for explanations which fit the new international circumstances without violating old, cherished and proven concepts. In the last 10 years the foreign policy community has gone through a difficult and wrenching exercise. The sense of uncertainty about the future of the new world stems not just from the radical changes it has undergone, but equally from the realization that the new environment requires the same level understanding of the politics of security and the politics of economics. This paper is designed to accomplish two goals. First, it offers the reader a composite picture of power transition theory, integrating the various extensions and amplifications into a coherent whole. It brings together that new research and weaves it into the rich text of the underlying theory. By providing a systematic outline of the hierarchical relationship among power and satisfaction we offers a foundation for exploring conflictual and economic interactions in world politics