Extended N=2 Superconformal Structure of Gravity and W-Gravity Coupled to Matter

We show that almost all string theories, including the bosonic string, the superstring and $W$-string theories, possess a twisted N=2 superconformal symmetry. This enables us to establish a connection between topological gravity and the field theoretical description of matter coupled to gravity. We also show how the \brs operators of the $W_n$-string can be obtained by hamiltonian reduction of $SL(n|n-1)$. The tachyonic and ground ring states of $W$-strings are described in the light of the N=2 superconformal structure, and the ground ring generators for the non-critical $W_3$-string are explicitly constructed. The relationship to $G/G$ models and quantum integrable systems is also briefly described.Comment: 48 page

Trends in Regional Inequality in China

Several recent studies have examined the tendency of regions within a nation to exhibit long-term convergence in per capita income levels. Barro and Sala-i-Martin (1991, 1992, 1995) have found a tendency towards convergence among the U.S. states, among Japanese prefectures, and among regions within Western Europe. In this paper we examine the tendency towards convergence among the provinces of China during the period 1952-1993. We find that real income convergence of provinces in China has been a relatively recent phenomenon, emerging strongly only since the reform period began in 1978. During the initial phase of central planning, 1952-1965, there is some evidence for convergence, but it is weak and sensitive to the time period being analyzed. During the cultural revolution, 1965- 1978, there is strong evidence of divergence rather than convergence. We find strong evidence for convergence during the reform period is associated with rural reforms, and is especially strong within the coastal regions where there has been liberalization of international trade and investment flows. However, since 1990 regional incomes have begun to diverge. Such a divergence is entirely explained by the variance between the coastal and interior provinces, rather than increase in variance within each other. Therefore, it seems that China is now on a dual track, with a prosperous and fast growing coastal region and a poor interior growing at a lower rate.

Flight-test of the glide-slope track and flare-control laws for an automatic landing system for a powered-lift STOL airplane

An automatic landing system was developed for the Augmentor Wing Jet STOL Research Airplane to establish the feasibility and examine the operating characteristics of a powered-lift STOL transport flying a steep, microwave landing system (MLS) glide slope to automatically land on a STOL port. The flight test results address the longitudinal aspects of automatic powered lift STOL airplane operation including glide slope tracking on the backside of the power curve, flare, and touchdown. Three different autoland control laws were evaluated to demonstrate the tradeoff between control complexity and the resulting performance. The flight test and simulation methodology used in developing conventional jet transport systems was applied to the powered-lift STOL airplane. The results obtained suggest that an automatic landing system for a powered-lift STOL airplane operating into an MLS-equipped STOL port is feasible. However, the airplane must be provided with a means of rapidly regulation lift to satisfactorily provide the glide slope tracking and control of touchdown sink rate needed for automatic landings

Imprinted Networks as Chiral Pumps

We investigate the interaction between a chirally imprinted network and a solvent of chiral molecules. We find, a liquid crystalline polymer network is preferentially swollen by one component of a racemic solvent. This ability to separate is linked to the chiral order parameter of the network, and can be reversibly controlled via temperature or a mechanical deformation. It is maximal near the point at which the network loses its imprinted structure. One possible practical application of this effect would be a mechanical device for sorting mixed chiral molecules.Comment: 4 pages, 5 figure

Radio and near-infrared observations of the steep spectrum Galactic plane radio source WKB 0314+57.8

Radio and near-infared observations towards the steep spectrum Galactic plane radio source WKB 0314+57.8 are presented, in order to clarify the nature of this source. The radio observations include archival and survey data, together with new Giant Metrewave Radio Telescope observations at 617 MHz. The near-infrared observations are in the J and K bands, from the Gemini instrument on the Shane 3-m telescope. The radio observations show that WKB 0314+57.8 is extended, with an very steep spectrum (with flux density proportional to frequency to -2.5 power between 40 MHz and 1.5 GHz). The colour--magnitude diagram constructed from near-infrared observations of the field suggests the presence of a z approx 0.08 galaxy cluster behind the Galactic plane, reddened by about 6 magnitudes of visual extinction. Although the steep spectrum source has no obvious identification, two other radio sources in the field covered by the near-infrared observations have tentative identifications with galaxies. These observations indicate that WKB 0314+57.8 is a relic source in a cluster of galaxies, not a pulsar.Comment: 6 pages, to appear in MNRAS, typos correcte

Sources of Slow Growth in African Economies

This paper offers some econometric evidence on the sources of slow growth in Sub-Saharan Africa. The evidence suggests that the continent's slow growth can be explained in an international cross-country framework, without the need to invoke a special explanation unique to Sub-Saharan Africa. We find that poor economic policies have played an especially important role in the slow growth, most importantly Africa's lack of openness to international markets. In addition, geographical factors such as lack of access to the sea and tropical climate have also contributed to Africa's slow growth