A Shred of Credible Evidence on the Long Run Elasticity of Labor Supply

The available estimates of the wage elasticity of male labor supply in the literature have varied between -0.2 and 0.2, implying that permanent wage increases have relatively small, poorly determined effects on labor supplied. The variation in existing estimates calls for a simple, natural experiment in which men can change their hours of work, and in which wages have been exogenously and permanently changed. We introduce a panel data set of taxi drivers who choose their own hours, and who experienced two exogenous permanent fare increases instituted by the New York City Taxi and Limousine Commission. Our preferred estimate suggests that their elasticity of labor supply is about -0.2.male labor supply, effect of wage rates, long run labor supply, public policies, taxation, social safety nets, and redistribution of income, New York City Taxi and Limousine Commission

A third thing : an exploration of black hair in architectural design

“African-American architects have been unable to articulate our own truth or vision of the future except as a reflection of the very culture that marginalizes us. We are so spent by trying to get into the system that there is little time remaining to critique the historical condition that make our climb so difficult. Rather than develop a self-defined praxis of architecture that would make a real difference in the lives of our people, we mimic the values and goals that have created our oppression.” - Sharon Sutton By looking at traditions, art and architecture in the African American community, my goal is to make a case for an African American aesthetic that embraces ambiguity and empowers the community. This thesis will manifest in a public space for activism, healing and uplift. In the thesis, I look at the church as a site to question Black and White spaces. Does the church adequately accommodate this community that has been historically ignored in architectural design? I also use hair braiding as a muse for creative exploration in space making. The geographic site for the intervention is a suburban neighborhood in Deerfield Beach, Florida that is predominantly Black

The High Chromospheres of the Late A Stars

We report the detection of N V 1239 A transition region emission in HST/GHRS spectra of the A7 V stars, Alpha Aql and Alpha Cep. Our observations provide the first direct evidence of 1-3 x 10^5 K material in the atmospheres of normal A-type stars. For both stars, and for the mid-A--type star Tau3 Eri, we also report the detection of chromospheric emission in the Si III 1206 A line. At a B-V color of 0.16 and an effective temperature of 8200 K, Tau3 Eri becomes the hottest main sequence star known to have a chromosphere and thus an outer convection zone. We see no firm evidence that the Si III line surface fluxes of the A stars are any lower than those of moderately active, solar-type, G and K stars. This contrasts sharply with their coronal X-ray emission, which is >100 times weaker than that of the later-type stars. Given the strength of the N V emission observed here, it now appears unlikely that the X-ray faintness of the A stars is due to their forming very cool, <= 1 MK coronae. An alternative explanation in terms of mass loss in coronal winds remains a possibility, though we conclude from moderate resolution spectra of the Si III lines that such winds, if they exist, do not penetrate into the chromospheric Si III--forming layers of the star, since the profiles of these lines are *not* blueshifted, and may well be redshifted with respect to the star.Comment: LaTex, 12 pages, 3 Postscript figures, uses aaspp4, accepted by Ap

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Anhydrous nepheline, jadeite, and albite glasses doped with F as well as hydrous F-containing haplogranitic glasses were investigated using 19F combined rotation and multiple-pulse spectroscopy; 19F → 29Si cross-polarization/magic angle spinning (MAS); and high-power 19F decoupled 29Si, 23Na, and 27Al MAS nuclear magnetic resonance methods. Fluorine preferentially coordinates with Al to form octahedral AlF63− complexes in all glasses studied. In addition, F anions bridging two Al cations, units containing octahedral Al coordinated by both O and F, or tetrahedral Al-F complexes might be present. The presence of Si-F bonds cannot be entirely ruled out but appears unlikely on the basis of the 19F → 29Si CP/MAS spectra. There is no evidence for any significant coordination of F with alkalis in the glasses studied. 23Na spectra are identical for the samples and their F-free equivalents and the spectra do not change upon decoupling of 19F. The speciation of F in the hydrous and anhydrous glasses appears to be very similar. Over the range of F contents studied ( up to 5 wt.% ), there seems to be hardly any dependence of F speciation on the concentration of F in the samples. The spectroscopic results explain the decrease of the viscosity of silicate melts with increasing F content by removal of Al from bridging AlO4-units due to complexing with F, which causes depolymerization of the melt. The same mechanism can account for the shift of the eutectic point in the haplogranite system to more feldspar-rich compositions with increasing F content, and for the peraluminous composition of most F-rich granites. Liquid immiscibility in F-rich granitic melts might be caused by formation of (Na,K)3AlF6 units in the melt with little or no interaction with the silicate component. The presence of F in granitic melts might increase the solubility of high field strength cations by making nonbridging O atoms available which form complexes with these cations

Classical and Quantum Gravity in 1+1 Dimensions, Part III: Solutions of Arbitrary Topology

All global solutions of arbitrary topology of the most general 1+1 dimensional dilaton gravity models are obtained. We show that for a generic model there are globally smooth solutions on any non-compact 2-surface. The solution space is parametrized explicitly and the geometrical significance of continuous and discrete labels is elucidated. As a corollary we gain insight into the (in general non-trivial) topology of the reduced phase space. The classification covers basically all 2D metrics of Lorentzian signature with a (local) Killing symmetry.Comment: 39 pages, 22 figures, uses AMSTeX, extended version of former chapter 7 (Gravitational Kinks) now available as gr-qc/9707053, problem with figure 6 fixe