Modulation of Negative Work Output from a Steering Muscle of the Blowfly Calliphora Vicina

Of the 17 muscles responsible for flight control in flies, only the first basalar muscle (b1) is known to fire an action potential each and every wing beat at a precise phase of the wing-beat period. The phase of action potentials in the b1 is shifted during turns, implicating the b1 in the control of aerodynamic yaw torque. We used the work loop technique to quantify the effects of phase modulation on the mechanical output of the b1 of the blowfly Calliphora vicina. During cyclic length oscillations at 10 and 50 Hz, the magnitude of positive work output by the b1 was similar to that measured previously from other insect muscles. However, when tested at wing-beat frequency (150 Hz), the net work performed in each cycle was negative. The twitch kinetics of the b1 suggest that negative work output reflects intrinsic specializations of the b1 muscle. Our results suggest that, in addition to a possible role as a passive elastic element, the phase-sensitivity of its mechanical properties may endow the b1 with the capacity to modulate wing-beat kinematics during turning maneuvers

The Case for Omega_M = 0.33 +/- 0.035

For decades, the determination of the mean density of matter(Omega_M) has been tied to the distribution of light. This has led to a ``bias,'' perhaps as large as a factor of 2, in determining a key cosmological parameter. Recent measurements of the physical properties of clusters, cosmic microwave background (CMB) anisotropy and the power spectrum of mass inhomogeneity now allow a determination of Omega_M without ``visual bias.'' The early data lead to a consistent picture of the matter and baryon densities, with Omega_B = 0.039 +/- 0.0075 and Omega_M = 0.33 +/- 0.035.Comment: 4 ApJ LaTeX. Submitted to Astrophys J Lett. Less provocative title, same conclusion

Cosmology Solved? Quite Possibly!

The discovery of the cosmic microwave background (CMB) in 1964 by Penzias and Wilson led to the establishment of the hot big-bang cosmological model some ten years later. Discoveries made in 1998 may ultimately have as profound an effect on our understanding of the origin and evolution of the Universe. Taken at face value, they confirm the basic tenets of Inflation + Cold Dark Matter, a bold and expansive theory that addresses all the fundamental questions left unanswered by the hot big-bang model and holds that the Universe is flat, slowly moving elementary particles provide the cosmic infrastructure, and quantum fluctuations seeded all the structure seen in the Universe today. Just as it took a decade to establish the hot big-bang model after the discovery of the CMB, it will likely take another ten years to establish the latest addition to the standard cosmology and make the answer to ``Cosmology Solved?'', ``YES!'' Whether or not 1998 proves to be a cosmic milestone, the coming avalanche of high-quality cosmological data promises to make the next twenty years an extremely exciting period for cosmology.Comment: 19 pages LaTeX including 5 eps figures. Presented at Great Debate: Cosmology Solved?, October 4, 1998, Baird Auditorium, Smithsonian Natural History Museum, Washington, DC. To be published in Proc. Astron. Soc. Pacific, February 199