Power Spectrum Constraints from Spectral Distortions in the Cosmic Microwave Background

%The content of this replacement paper is identical to the original. %We have attempted to fix the postscript so that it will print out on %a larger number of printers. Using recent experimental limits on $\mu$ distortions from COBE FIRAS, and the large lever-arm spanning the damping of sub-Jeans scale fluctuations to the scale of the COBE DMR fluctuations, we set a constraint on the slope of the primordial power spectrum $n$. It is possible to analytically calculate the contribution over the full range of scales and redshifts, correctly taking into account fluctuation growth and damping as well as thermalization processes. We find that the 95\% upper limit is weakly dependent on cosmological parameters, e.g. $n<1.54 (h=0.5)$ and $n<1.56 (h=1.0)$ for $\Omega_0=1$ with marginally weaker constraints for $\Omega_0<1$ in a flat $\Omega_0 +\Omega_\Lambda=1$ universe.Comment: 8pg, uuencoded-tarred (& hopefully more compatible!) postscript, CfPA-TH-94-1

THE CREATION AND SPREAD OF TECHNOLOGY AND TOTAL FACTOR PRODUCTIVITY IN CHINA'S AGRICULTURE

The studys overall goal is to create a framework for assessing the trends of China's national and international investment in agricultural research and to measure its impact on total factor productivity. The main methodological contribution is to provide more convincing measures of crop-specific technologies from China's national research program and of those imported from the international agricultural research system. Our results find that from 1980-95, China's total factor productivity for rice, wheat and maize grew rapidly and new technology accounts for most of the productivity growth.Productivity Analysis, Research and Development/Tech Change/Emerging Technologies,

Entangled granular media

We study the geometrically induced cohesion of ensembles of granular "u-particles" which mechanically entangle through particle interpenetration. We vary the length-to-width ratio $l/w$ of the u-particles and form them into free-standing vertical columns. In laboratory experiment we monitor the response of the columns to sinusoidal vibration (frequency $f$, peak acceleration $\Gamma$). Column collapse occurs in a characteristic time, $\tau$, which follows the relation $\tau = f^{-1} \exp(\Delta / \Gamma)$. $\Delta$ resembles an activation energy and is maximal at intermediate $l/w$. Simulation reveals that optimal strength results from competition between packing and entanglement.Comment: 4 pages, 5 figure

Still flat after all these years

The Universe could be spatially flat, positively curved or negatively curved. Each option has been popular at various times, partly affected by an understanding that models tend to evolve away from flatness. The curvature of the Universe is amenable to measurement, through tests such as the determination of the angles of sufficiently large triangles. The angle subtended by the characteristic scale on the Cosmic Microwave sky provides a direct test, which has now been realised through a combination of exquisite results from a number of CMB experiments. After a long and detailed investigation, with many false clues, it seems that the mystery of the curvature of the Universe is now solved. It's an open and shut case: the Universe is flat.Comment: 7 pages, 2 figures, submitted to the Gravity Research Foundation Essay Competition for 200

Fullerenes and proto-fullerenes in interstellar carbon dust

Laboratory spectra of hydrogenated amorphous carbon (HAC) particles prepared under a variety of conditions show spectral features at 7.05, 8.5, 17.4 and 18.9 {\mu}m (1418, 1176, 575 & 529 cm-1) that have been associated with emission from C60 molecules. These lines occur in the spectra even though C60 molecules as such are not present in our samples. It appears that these four spectral lines in HAC can instead be associated with precursor molecules or "proto-fullerenes" that subsequently react to yield C60. We develop a model tracing the evolution and de-hydrogenation of HAC dust and show that the observation of an emission feature at 16.4 {\mu}m (610 cm-1) in astronomical spectra signals the presence of the pentagonal carbon rings required for the formation of fullerenes. We suggest that the set of four IR emission lines previously identified with C60 in many objects that also show the 16.4 {\mu}m feature and other polycyclic aromatic hydrocarbon bands arise from proto-fullerenes rather than C60. Tc1 is an example of a source in which de-hydrogenation has proceeded to the point where only fullerenes are present.Comment: 17 pages, 2 figures, accepted ApJ Letter