Search

Some remarks are made concerning various aspects of the analysis of resonances produced in multi-particle final states resulting from high-energy collisions. The shape and position of a resonance are discussed by means of the connection between production cross-sections for stable and unstable particles, and a numerical example ofN* as seen in KN → KN* at different energies is given. The relation between the present description of the resonant effects and others (Watson’s finalstate interaction formula and the one-meson-exchange model of Chew and Low) is examined. Off-the-mass-shell corrections to the one-meson-exchange model are obtained in a relatively simple way. The bearing of the decay angular correlations on the production mechanism is explored ; co-ordinate axes appropriate for the peripheral model are specified; the equivalence of the azimuthal angular distribution and the Treiman-Yang distribution is established. Angular correlations are given for the decay of boson resonances (J=l, 2) resulting from definite spin and parity states in thet-channel. Some remarks are made about the inclusion of nonresonant contributions when there is a mixture of pseudoscalar and vector exchange.

The description of Archibaccharis prorepens by S. F. Blake (1934) was based on a single staminate specimen collected by A. F. Skutch in 1933 from the Guatemalan highlands. Apparently, Blake's decision to describe it as an Archibaccharis was primarily guided by the similarity of the habit and vegetative character of this species to Archibaccharis simplex Blake from the state of Hidalgo, Mexico. For those unfamiliar with the genus, Blake's circumscription (1924) of Archibaccharis (then Hemibaccharis) stated that it contains those herbs and shrubs with the habit of Baccharis but are polygamodioecious rather than dioecious. The major difference is subtle but constant in that the pistillate heads of Archibaccharis bear 1-15 central hermaphrodite disk flowers with apparently barren anthers and abortive achenes surrounded by fertile tubular filiform pistillate flowers. In Baccharis the pistillate heads are uniformly of tubular filiform flowers. The staminate heads of Archibaccharis are usually identical to those of Baccharis regarding general characters and floral composition, that is, the heads are uniformly of hermaphrodite disk flowers with functional anther sacs but abortive achenes. Recent investigations by the author indicate that a recircumscription of Archibaccharis is necessary. During a collecting trip by the author in early 1969 to Mexico and Guatemala, both pistillate and staminate specimens of Archibaccharis prorepens were collected at the type locality. Examinations of Archibaccharis collections from many of the major herbaria in the United States have revealed no additional specimens of the species. Thus, Jackson 1044 probably represents the first known collection of pistillate material. The characteristics of the holotype appear to perfectly match the author's collection of staminate plants. Many pistillate heads were examined, both in the field and under magnification in the laboratory. The heads did not show the central hermaphrodite disk flowers which would be required for retention of the species in the genus Archibaccharis. Also, the achenes of the pistillate flowers possessed 5-8 nerves, a characteristic of the genus Baccharis.

This note demonstrates that naive application of the usual derivative formula to estimate changes in probabilities caused by changes in independent variables in probabilistic choice models can yield nonsensical results. This can occur because the usual derivative formula does not constrain the estimated change in probability. When the probabilities are large, the usual derivative expression can lead to violations of the constraint that probabilities must sum to one. A better approach is to use the cumulative probability functions to calculate the difference in probabilities. Since this answer is based on the cumulative probability function, the answer cannot be implausibly large in absolute value. This alternative calculation eliminates the inconsistencies that are possible when the derivative expression

Over the past twelve years considerable evidence has accumulated on the extent to which intercommunity differences in property tax burdens are capitalized into property values [17; 21; 8; 7; 25]. Recently, Linneman [14] has analyzed the validity of this evidence after taking into consideration alternative models of local government finance. In the model that he believes best represents the spirit of the tax capitalization literature, local government expenditures are financed wholly by property tax receipts. He demonstrates that in this case a perfect correlation between taxes and public goods makes it econometrically impossible to estimate property value equations unless measurement errors and omitted variables are present. He therefore asserts that existing results on the tax capitalization issue are of nebulous value.

An acousto-optic isolator for a semiconductor laser diode comprises a Fabry-Perot resonator tuned to the laser optical frequency f o followed by an acousto-optic Bragg diffraction device utilizing surface acoustic waves of frequency f a launched from a transducer. Light focussed by a lens to the load has a resultant frequency f o +f a . Any light reflected from the load suffers a further change in frequency to f o +2f a in the diffraction device and hence is blocked by the resonator. Undiffracted light can be detected at a photo-detector and used in a feedback control loop to stabilize the light source to the resonator.

In recent years the impact of taxation on work hours has generated a great deal of research effort. However, the effects of taxes on other dimensions of labor supply have been largely ignored. The purpose of this paper is to investigate an important ignored issue-the effects of tax rates on the duration of job search by those who are unemployed. This issue is one which seems to us of considerable importance in resolving current debates over whether income tax changes will change unemployment. To the extent that changing tax rates affect the benefits and costs of job search such changes may affect the amount of time workers spend searching for jobs which, in turn, will affect unemployment rates. In order to estimate the effects of marginal tax rates on job search duration, we employ a maximum likelihood approach which allows us to take into account the doubly censored nature of our sample. This procedure remedies some of the econometric difficulties of earlier search duration studies. At the same time, it allows direct tests of the marginal contribution of various determinants to the length of search duration. This latter advantage is particularly important since such direct tests are not available in the currently popular re-employment hazard approach to analyzing search duration. The paper proceeds as follows. Section II provides a brief analysis of the theoretical implications of changing tax rates for job search duration. We conclude that the relationship between job search duration and income tax rates is theoretically ambiguous. The question must be addressed empirically. In section III we present our empirical methodology for addressing the question and compare it to approaches taken in prior search duration analyses. Our data and our empirical results are discussed in section IV. Section V contains our conclusions.

Mutual fund performance has long been a source of interest to financial researchers [3; 5; 6; 10; 13]. The consensus is that mutual fund managers cannot consistently outguess the market, and that information generally provided investors by mutual fund management, such as expense and turnover ratios, is not relevant to investor decision making. Nevertheless, investors continue to discriminate across alternative funds. Why? Are investors irrational, or are these studies based on a wider set of alternatives than those typically available to an individual investor operating within a specific institutional framework?