La pensée critique : pourquoi est-elle si difficile à enseigner

Comprend des références bibliographiques

Nucleation and growth of metals on carbon surfaces

This thesis work presents an investigation of the basic interaction between metals and the carbon surfaces HOPG and amorphous carbon. This work was motivated by the discovery of a family of metal nanowires which grow as single crystals protruding substantially perpendicular to a substrate, where the substrate is held at elevated temperature (800-1100 K). The most prolific growth is seen for Cu on amorphous carbon substrates. The fabrication and properties of these wires have been pioneered by our collaborator, Dr. Gunther Richter, at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany. They have potential uses in nanoscale mechanical/electrical devices, as chemical/optical sensors and, in the case of magnetic wires, non-rare-earth permanent magnets and high density magnetic storage media. We aim to develop an understanding of the nucleation and growth of these structures, with the ultimate goal of being able to fine-tune their growth with respect to aspect ratio, density, and orientation. HOPG provides a good starting point for our investigation of NW growth because it is a flat, homogeneous surface with a simple atomic arrangement that can be easily analyzed with STM. Determining the basic energetic parameters for the Cu/HOPG system could ultimately prove useful for modeling nanowire growth. Diffusion barrier (Ed) and critical nucleus size (i) can be extracted from systems exhibiting homogeneous nucleation based on the dependence of island density on temperature and flux, respectively. We present experiments which determine the extent to which homogeneous nucleation occurs in this system. In fact, we find that Cu island nucleation, under the conditions of our experiments, is mediated by defects that are created during the Cu deposition process itself. Since nanowire growth occurs at elevated temperature, we also explore the Cu/HOPG system at elevated temperatures (300-1300 K) and address the issues of coarsening, desorption, and possible intercalation in this system. We find that coarsening begins at temperatures of 600 K - 700 K, and desorption at 800 K - 900 K. To determine the differences or similarities between the model carbon substrate (HOPG), and the actual form used in nanowire growth (amorphous carbon), we investigate the interaction between Cu, Ag, and amorphous carbon. We explore changes in the Cu/amorphous carbon surface as a function of coverage and temperature. Ag nanowire samples are annealed to remove the Ag, and then scanned to determine the affect of nanowire growth on the underlying substrate morphology. We identify holes in the amorphous carbon which have the same number density as the metal nanostructures, and were probably caused by growth of the nanostructures. This work concludes with the growth of metal nanowires on various substrates by MBE and magnetron sputtering, including nanowires of magnetic materials Fe and Ni. Nanowire growth was done both at MPI Stuttgart and at the Ames Laboratory. Long nanowires are grouped as bundles on the surface. We interpret this to mean that growth occurs--at least in part--by incorporation of metal atoms at the base of the nanowire

Why Don’t We Have a Peace Memorial? The Vietnam War and the Distorted Memory of Dissent

First paragraph: Exactly a year before he was murdered, Martin Luther King Jr., gave one of the greatest speeches of his life, a piercing critique of the war in Vietnam. Two thousand people jammed into New York’s Riverside Church on April 4,1967, to hear King shred the historical, political, and moral claims U.S. leaders had invoked since the end of World War II to justify their counter-revolutionary foreign policy. The United States had not supported Vietnamese independence and democracy, King argued, but had repeatedly opposed it; the United States had not defended the people of South Vietnam from external Communist aggression, rather it was itself the foreign aggressor-- burning and bombing Vietnamese villages, forcing peasants off their ancestral land, and killing, by then, some one million civilians. “We are on the side of the wealthy, and the secure,” King said, “while we create a hell for the poor.”

Vietnam Rorschach

An invisible enemy strikes U.S. soldiers in a faraway land we claim to be saving; overwhelming American firepower kills thousands before many citizens realize their president used phony pretexts to justify military action; policy makers insist that while progress is steady we must be patient; anti-American guerrillas attack their own countrymen, whom they deem U.S. puppets ; only a few nations send troops to support the United States\u27 cause; talk of a quagmire fills the air

A Survey of the Literature Dealing with the Calcium-Phosphorus Metabolism of Normal Children

The purpose of this study is to collect and organize all data available to the investigator on the subject of calcium and phosphorus requirements for normal children. Since it is the business of nutrition to maintain health and prevent disorders, leaving the cure of disorders to the medical profession, this study deals with the calcium and phosphorus metabolism of normal children and avoids going into the pathological phases, taking up rickets and tetany only in so far as prevention is concerned. If this study has any value it lies in the fact that the findings of investigators seem to be scattered throughout a great many books and scientific journals, and it was thought that the collection and organization of these findings would serve as useful purpose in making this research more readily available to nutrition students. The bibliography for the study was made up from references given by such recognized authorities and sources as Sherman, McLester, Starling, Lusk, Van Slyke and Peters, Bogert, Rose, Child Development Abstracts, British Nutrition Abstracts, and Chemical Abstracts. From this bibliography were chosen those books and articles which seemed to the writer to be most promising as to reliability, amount of information, and variety of information. Part of the work has of necessity been adapted to children from experiments on adults. The importance of calcium and phosphorus in the diet of little children is emphasized by Sherman as follows: The effect of an insufficient intake of calcium is natural more serious with growing than with full grown animals. The young need more calcium because during growth and development the body in increasing not only the amount but the percentage of calcium which it contains. *** growing children whose height, weight, and appearance are normal may have a calcium-poor condition of the body*** Since this is largely a matter of the deposition of calcium phosphate in the developing bones, the phosphorus content of the body tends to remain low when the calcium is low and to rise to normal with the calcium when the calcium content of the food is increased

This is another working-class war: An Interview with Christian Appy

CHRISTIAN APPY is best known for his two books dealing with the Vietnam war, Patriots: The Vietnam War Remembered from All Sides (Penguin, 2004), and Working-Class War: American Combat Soldiers and Vietnam (University of North Carolina Press, 1993). His work on Patriots, which he calls “the most challenging and rewarding work of my life,” took him throughout Vietnam and the United States, talking to more than 350 people about their memories of that long and bitterly divisive war. The result is an oral history that stretches from the summer of 1945, when Americans first parachuted into northern Vietnam, to April 30, 1975, when the last U.S. helicopter flew off the roof of the American Embassy annex in Saigon. He spoke to the ISR’s JOE ALLEN. Joe Allen, a member of Teamsters Local 705 in Chicago, is author of a three-part ISR series on the history of the Vietnam War that can be found at www.isreview.org

Development of Oral Structure in Salmonema emphemeridarum (Nematoda: Cystidicolidae)

This paper examines the development of the oral morphology of the parasite Salmonema emphemeridarum (Nematoda: Cystidicoidae) using Scanning Electron Microscopy. Larvated eggs, taken from female worms collected from brook trout, Salvelinus fontinalis, were fed to mayflies (Ephemeroptera) where larvae developed to the third larval stage. First stage larvae possessed an oral opening, boring tooth and secretory pore. Second stage larvae possessed a circular oral opening and amphids. Third stage larvae included all the features of adult worms include pseudolabia, submediant labia, sublabia, amphids and four oral papillae. The advanced development of oral structures of third stage larvae allows the identification of larval worms to genus and in some cases species and is consistent with the precocious reproductive development of infective larvae in the Cystidicolidae