Coherently pulsed laser source

An electronically controllable apparatus is described which modulates a continuous wave laser beam so as to produce an output beam consisting of coherent pulses that are electronically controllable as to both pulse repetition rate and pulse width. The apparatus includes two acoustic devices positioned so that the laser beam passes through them in sequence, and apparatus for passing sound waves through the devices to frequency shift the laser radiation as well as to diffract it. Each acoustic device generates sound waves containing a group of frequencies which result in spaced pulses. The first acoustic device is countered by the second acoustic device to produce a collimated, coherently pulsed, laser beam

Stark cell optoacoustic detection of constituent gases in sample

An optoacoustic detector for gas analysis is implemented with Stark effect cell modulation for switching a beam in and out of coincidence with a spectral line of a constituent gas in order to eliminate the heating effect of laser energy in the cell as a source of background noise. By using a multiline laser, and linearly sweeping the DC bias voltage while exciting the cell with a multiline laser, it is possible to obtain a spectrum from which to determine the combinations of excited constituents and determine their concentrations in parts per million

The model-independence of cosmic ray source determinations

The direct inversion method of Margolis is used to explore the dependence of Z less than or equal to 28 source abundance determinations on the choice of the pathlength distribution. The source abundances do not depend strongly on the form of the truncation used, although some truncation at the lower energies (compared to a leaky box) is necessary. The decrease of mean grammage with increasing energy is required by the observations. The effects of errors and he use of other secondary to primary ratios is discussed

Correlation spectrometer having high resolution and multiplexing capability

A correlation spectrometer permanently incorporates a reference cell and an electro-optical phase modulator (EOPM) in the light path between a sample cell and a detector. The effect of the EOPM is such that its frequency modulates all of the monochromatic component of the incoherent radiation passing through it. The EOPM is adjusted so that when it is ON all of the energy in the monochromatic components is thrown into sidebands differing from the original frequencies by integral multiples of the modulation frequency with the total amount of energy absorbed from the original radiation remaining constant. When there is no coincidence between the constituents in the two cells, the detector's output is the same when the EOPM is ON and when it is OFF. However, when there is coincidence the detector's output changes when the EOPM is switched between its two states. The change in the detector's output is related to the quantity of the constituents in the sample cell

The Efficiency of Collective Bargaining in Public Schools

This paper develops a bargaining model of wage and employment determination for the public sectror. The solution to the model generates structural wage and employment equations that are estimated using data from New York State teacher-school district collective bargaining agreements. An advantage of this approach is that the major collective bargaining models (monopoly union, right to manage, efficient contracting, and inefficient contracting) are nested in the structural equations based on flexible functional forms and these models can be empirically tested as restrictions on estimated model parameters. The empirical results suggest that the allocation of resources generated by collective bargaining in New York State public schools is, by and large, not Pareto efficient. Furthermore, it is possible to estimate separate measures of union bargaining power over wages and employment. Empirically, it appears that union bargaining power over wages is around 0.53, while bargaining power over employment is around 0.71. In addition, the paper demonstrates the importance of controlling for the nature of the collective agreement when measuring the level of public services that flow to a community in the presence of a unionized public sector work force. Nous proposons un modèle de négociations collectives sur les salaires et l'emploi dans le secteur public. La solution de ce modèle implique des équations structurelles de détermination des salaires et d'emploi qui sont estimées à partir de données provenant des conventions colléctives des écoles publiques de l'état de New York. Notre approche a l'avantage d'englober tous les modèles majeurs de la littérature sur les négociations collectives (syndicat monopole, droit à gérer, négociations efficaces et négociations inefficaces) et de relier chaque modèle à une restriction d'égalité sur un ou plusieurs paramètres estimés. Nos résultats suggèrent que l'allocation des ressources spécifiée dans les conventions collectives des enseignants de l'état de New York n'est, en générale, pas efficace. De plus, notre approche nous permet d'estimer le pouvoir de négociationsur les salaires et sur l'emploi séparément. Nous trouvons un pouvoir de négociation sur les salaires de 0.53, et sur l'emploi de 0.71. Finalement, nous démontrons l'importance de contrôler le caractère endogène des salaires lors de l'analyse des flux des services publics dans un marché syndicalisé.Collective Bargaining, Efficient Contracting, Public Sector Union, Education, Négociations collectives, contrats efficaces, syndicat du secteur public, éducation

Sources of the ultraheavy cosmic rays

The suggestions that the source abundances of cosmic ray nuclei heavier then Fe differ significantly from Solar System abundances are not well supported by the data without assuming preferential acceleration. The Solar System abundances of Pb and Bi are split into r-, standard s-, and cyclic 8-process components; the apprarent deficiency of Pb seen in the HEAO-3 Heavy Nuclei Experiment data might indicate an absence of Pb from the recycling 8-process

Alfven wave scattering and the secondary to primary ratio

The cosmic ray abundances have traditionally been used to determine the elemental and isotopic nature of galactic ray sources and average measures of propagation conditions. Detailed studies of the physics of propagation are usually paired with relatively straightforward estimates of the secondary-to-primary (S/P) ratios. In the work reported here, calculations of elemental abundances are paired with a more careful treatment of the propagation process. It is shown that the physics of propagation does indeed leave specific traces of Galactic structure in cosmic ray abundances

Trace element and isotope geochemistry of Cretaceous-Tertiary boundary sediments: identification of extra-terrestrial and volcanic components

Trace element and stable isotope analyses were performed on a series of sediment samples crossing the Cretaceous-Tertiary (K-T) boundary from critical sections at Aumaya and Sopelano, Spain. The aim is to possibly distinguish extraterrestrial vs. volcanic or authigenic concentration of platinum group and other elements in K-T boundary transitional sediments. These sediments also have been shown to contain evidence for step-wise extinction of several groups of marine invertebrates, associated with negative oxygen and carbon isotope excursions occurring during the last million years of the Cretaceous. These isotope excursions have been interpreted to indicate major changes in ocean thermal regime, circulation, and ecosystems that may be related to multiple events during latest Cretaceous time. Results to date on the petrographic and geochemical analyses of the Late Cretaceous and Early Paleocene sediments indicate that diagenesis has obviously affected the trace element geochemistry and stable isotope compositions at Zumaya. Mineralogical and geochemical analysis of K-T boundary sediments at Zumaya suggest that a substantial fraction of anomalous trace elements in the boundary marl are present in specific mineral phases. Platinum and nickel grains perhaps represent the first direct evidence of siderophile-rich minerals at the boundary. The presence of spinels and Ni-rich particles as inclusions in aluminosilicate spherules from Zumaya suggests an original, non-diagenetic origin for the spherules. Similar spherules from southern Spain (Caravaca), show a strong marine authigenic overprint. This research represents a new approach in trying to directly identify the sedimentary mineral components that are responsible for the trace element concentrations associated with the K-T boundary