On some properties of the water-vapor spectrum and their relations to atmospheric radiation

In the present paper we investigate the physical consequences of the fact that the water vapor spectrum in the far infrared consists of a large number of narrow lines. It will be shown that the average width of these lines is much smaller than the intervals which could be resolved with the spectrographs used hitherto. For thick layer of vapor complete absorption is nevertheless reached in most parts of the spectrum. It can be shown that under such circumstances the total absorption is approximately proportional to the air pressure in the absorbing layers and is inversely proportional to the square root of the absolute temperature. There is an additional variation with temperature of a more complex type which cannot yet be quantitatively evaluated from the available measurements, but it is probably not very large

The Incubator Hypothesis: Evidence from Five Cities

The purpose of this paper is to review the past evidence and to offer some new data to assess whether the incubator hypothesis can be empirically supported. In particular the two general aspects of the hypothesis will be tested. First, we will examine the proposition that highly centralized locations are attracting a disproportionate number of new firms and/or the employment associated with new firms. Second, we will test the hypothesis that new firms which are formed in high density areas move outward from such sites in their early years of existence in order to expand their productive activities. We refer to these as the "simple and "dynamic" hypotheses in the rest of the paper. Our analysis is based on the experience of all manufacturers in several U.S. cities. We recognize that it is quite possible that the hypothesis could hold for certain industries even if it is unsupported for all firms together. Our intent, however, is to test the validity of the hypothesis as a general theory of intraurban location behavior. The paper consists of three sections. The first two present evidence on the "simple" and "dynamic" hypotheses. The final section summarizes our findings and offers some conclusions.