The Aerodynamics of Hummingbird Flight

Hummingbirds fly with their wings almost fully extended during their entire wingbeat. This pattern, associated with having proportionally short humeral bones, long distal wing elements, and assumed to be an adaptation for extended hovering flight, has lead to predictions that the aerodynamic mechanisms exploited by hummingbirds during hovering should be similar to those observed in insects. To test these predictions, we flew rufous hummingbirds (Selasphorus rufus, 3.3 g, n = 6) in a variable–speed wind tunnel (0-12 ms-1) and measured wake structure and dynamics using digital particle image velocimetry (DPIV). Unlike hovering insects, hummingbirds produced 75% of their weight support during downstroke and only 25% during upstroke, an asymmetry due to the inversion of their cambered wings during upstroke. Further, we have found no evidence of sustained, attached leading edge vorticity (LEV) during up or downstroke, as has been seen in similarly-sized insects - although a transient LEV is produced during the rapid change in angle of attack at the end of the downstroke. Finally, although an extended-wing upstroke during forward flight has long been thought to produce lift and negative thrust, we found circulation during downstroke alone to be sufficient to support body weight, and that some positive thrust was produced during upstroke, as evidenced by a vortex pair shed into the wake of all upstrokes at speeds of 4 – 12 m s-1

Paying the Price: Inequality in Education

Education has long been regarded the great equalizer of the human condition, or as Horace Mann said, the balance wheel of the social machinery. But for this to be true, we must first provide equality of educational opportunity. Why has equality of educational opportunity been such an elusive goal in this country? The answer largely comes down to the way we fund education. Heavy dependence on property taxes as a main source of revenue is inherently unfair. Wealthy suburbs have a much larger tax base from which to draw in proportion to its student population than a city occupied by thousands of poor people. Even if poor districts tax themselves at several times the rate of wealthy districts, they are still likely to end up with far less money per-pupil. State equalization efforts have proven largely ineffective in narrowing the gap. New or higher taxes as well as the redistribution of funds are politically unpalatable. As a result, policy makers are searching for different alternatives to deal with funding disparities. School choice is one such alternative. Proponents argue that the market mechanisms of choice and competition will engender school reform and improve student performance. Private school choice (also know as a voucher system) is in particular a way to extend educational opportunities to low-income families. But even if designed and implemented carefully, such a program really only has the potential of helping a small percentage of students. Where the worst funding disparities exist, choice is nothing but an empty promise. The bottom line is this: money matters. There are no quick and inexpensive solutions to the problems which exist in many of America\u27s schools. We cannot escape the fact that it\u27s going to be expensive. Conservative estimates for equalization hover around an additional $100 billion a year. What people need to understand, however, is that we either pay now or we pay more later

Letter from Emma Greenwalt

Letter concerning enrollment in courses at Utah Agricultural College

Bitcoin: The Conflicting Currency

This note will break down what bitcoins are and how the federal government is currently classifying and treating them, before moving towards analyzing how bitcoins will be classified in the future once full harmony is reached between all the branches of government

The place of the Scriptures in Augustine's conversion

Thesis (M.A.)--Boston University, 1929. This item was digitized by the Internet Archive

Role of amino acids in cell volume control in the ribbed mussel: alanine and proline metabolism

The euryhaline mollusc Modiolus demissus uses amino acids as osmotic solutes in cell volume regulation. During the initial stages of cell volume regulation, during hyperosmotic shock, isolated heart and gill tissues of M. demissus accumulate alanine, proline, (beta)-alanine and glycine. The biosynthetic pathways of alanine and proline synthesis were investigated through the use of specific metabolic inhibitors and (\u2714)C-labelled precursors, intermediates and end products;Inhibition of aminotransferase reactions during hyperosmotic shock resulted in only a small inhibition of the increase in the total intracellular free amino acid pool while inhibiting the accumulation of alanine and proline. Amino acids were identified as precursors of alanine and proline during shock. A number of (\u2714)C-labelled amino acids were converted to (\u2714)C-alanine during hyperosmotic shock and the conversion of (\u2714)C-glutamate, ornithine, arginine and proline to (\u2714)C-alanine was inhibited by aminotransferase inhibitors. Inhibition of aminotransferase reactions during hyperosmotic shock did not result in large accumulations of glutamate. Therefore, fixation of free NH(,3) by alanine dehydrogenase or glutamate dehydrogenase does not appear to be required for the synthesis of alanine during shock. (\u2714)C-alanine was synthesized from (\u2714)C-glucose and this conversion was partially inhibited by iodoacetic acid, an inhibitor of glycolysis. Alanine appears to be synthesized from both glucose and amino acid-derived tricarboxyllic acid cycle intermediates during hyperosmotic shock. The catabolism of alanine was inhibited during hyperosmotic shock. Radoactivity from (\u2714)C-alanine did not accumulate in alanopine ((alpha),(alpha)-iminodipropionic acid), proline, octopine, serine, glycine, taurine or (beta)- alanine in tissues incubated at either high or low salinity;Inhibitors of aminotransferase reactions resulted in the accumulation of ornithine in both heart and gill tissue during hyperosmotic shock. (\u2714)C-glucose and glutamate were not converted to proline, taurine or (beta)-alanine. Radioactive (\u2714)C-arginine and ornithine accumulated in proline during hyperosmotic shock. This conversion was inhibited by aminotransferase inhibitors. Therefore, the preferred route of proline biosynthesis from ornithine takes place via the transaminase route rather than the L-amino acid oxidase pathway or by synthesis from glutamate. During hyperosmotic shock, proline is synthesized primarily from arginine released from protein and/or the phosphoarginine stores and from the proline released during protein turnover. Proline appeared to be metabolized at higher rates during hyperosmotic shock