1,453 research outputs found
On the formation of low-mass black holes in massive binary stars
Recently (Brown \& Bethe 1994) it was suggested that most stars with main
sequence mass in the range of about explode, returning
matter to the Galaxy, and then go into low-mass () black
holes. Even more massive main-sequence stars would, presumably, chiefly g o
into high-mass () black holes. The Brown-Bethe estimates
gave approximately low-mass black holes in the Galaxy. A
pressing question, which we attempt to answer here, is why, with the possible
exception of the compact objects in SN1987A and 4U\,1700--37, none of these
have been seen.
We address this question in three parts. Firstly, black holes are generally
``seen'' only in binaries, by the accretion of matter from a companion star.
High mass black holes are capable of accreting more matter than low-mass black
holes, so there is a selection effect favoring them. This, in itself, would not
be sufficient to show why low-mass black holes have not been seen, since
neutron stars (of nearly the same mass) are seen in abundance.
Secondly, and this is our main point, the primary star in a binary ---the
first star to evolve--- loses its hydrogen envelope by transfer of matter to
the secondary and loss into space, and the resulting ``naked'' helium star
evolves differently than a helium core, which is at least initially covered by
the hydrogen envelope in a massive main-sequence star. We show that primary
stars in binaries can end up as neutron stars even if their initial mass
substantially exceeds the mass limit for neutron star formation from single
stars (). An example is 4U\,1223--62, in which we suggest
that the initial primary mass exceeded , yet X-ray pulsationsComment: uuencoded compressed postscript. The preprint is also available at
http://www.ast.cam.ac.uk/preprint/PrePrint.htm
The annual heat balance of the surface 100 meters of the northwest Gulf of Alaska shelf
Thesis (M.S.) University of Alaska Fairbanks, 1980Oceanographic and meteorologic data collected from 1970 to 1978 on the northern Gulf of Alaska shelf are used to compute monthly heat budgets within the surface 100 m for a composite year. During months of net heat gain, radiation is the primary source. Latent and sensible heat transfer dominate during months of net heat loss. Persistent downwelling is the second most important route for heat loss. During winter, alongshore advection is the principal contributor of heat to this region. Cross-shelf advection and diffusion of heat are of minor importance throughout the year and generally counter each other. The prevalence of onshore Ekman transport explains the cross-shelf variation in the annual amplitude of heat content and the differential propagation rates of surface temperature anomalies to greater depths. No significant linear relationships were determined between anomalies of surface heat transfer and sea surface temperature. Several hypotheses are presented to explain this result
Improving Readiness for Nursing Practice via Simulation in Workplace Violence Mitigation
Workplace Violence (WPV), a significant problem in health care in the United States and worldwide, causes emotional and physical harm to nurses, negatively affects quality care delivery, and contributes to burn out, job dissatisfaction, and attrition. Clinical simulation was used to educate registered nursing students about WPV and train them in mitigation techniques in an effort to improve their awareness and readiness for professional nursing practice. Data from 37 students in their final semester of nursing school were collected anonymously prior to and after reviewing online materials about WPV and attending a 3-hour simulation experience in which two scenarios were presented. Measures of student learnersâ perceptions of knowledge, skills, ability, confidence, and preparedness to manage aggressive or violent patient behaviors pre- and post-simulation showed statistically significant improvement in all five categories
Murders, Memories, and Uncle Al\u27s War: Reflections on the Killing of Prisoners of War in World War II
In 2003, I was invited to give a talk at the St. Louis Soldiersâ Memorial Museum. The topic was war crimes, international law, and war crimes trials. It was conceived with the events of 9/11/2001 fresh in mind, but was focused on those subjects within the context of World War II, my area of expertise. Forgotten in the intervening 20 years, I rediscovered it recently while organizing my papers in preparation for donating them to the Southern Illinois University, Edwardsville archives. Itâs a simple story that blends some of my own childhood memories of World War II with bits of my much later research on battlefield criminality and its legal ramifications. Itâs a mercifully brief piece that I thought might be of interest to a broader audience than that which originally heard it. If Iâm wrong, you wonât have wasted much time in reading it.
As something created as an oral presentation, it lacks footnotes, but I refer readers who desire more information to my book, Americans, Germans, and War Crimes Justice. Law, Memory, and âThe Good War.
Michael C. Astour: A Biographical Essay
Michael Astour\u27s scholarly productivity was prodigious and was recognized and respected by the international community of historians of the ancient Near East. His accomplishments would have been impressive in anyone, but were especially so given the tumultuous and tragic events of his personal life, which were part and parcel of the tragic and tumultuous century in which he lived. The Festschrift that grew out of a celebratory conference in his honor begins with a paraphrase of an ancient Sumerian proverb: âA scribe who does not know Sumerian, what kind of a scribe is he?â It reads, âScholars of Mediterranean, Biblical and Near Eastern Studies who do not know the work of Michael Astour, what kind of scholars are they?â[1] Obviously, thatâs a rhetorical and somewhat hyperbolic question, and I lack the knowledge to pass judgment with any confidence on his work. Ignorance is easily impressed. Nevertheless, the story of Michael Astourâs life deserves to be told, if only by someone who is definitely not a scholar of the ancient Near East, but who knew him as a colleague. Many of his friends and colleagues urged him over the years to write a memoir, something he adamantly refused to do. This may have been due in part to the pain that such an effort would have caused him, although he argued that others had told similar stories better than he could. But, finally, he may have regarded such an undertaking simply as an unwelcome distraction from the scholarship that he loved and that he pursued almost to his dying day.[2]
This essay is based largely on Astourâs voluminous correspondence spanning a half- century. He meticulously saved letters he received, as well as copies of those he sent. His papers fill dozens of boxes in SIUEâs archives. Many of his letters are multi-paged and are uniformly thoughtful and frequently witty. They stand in stark contrast to the brief and often superficial electronic communications that pass for inter-personal correspondence today which is, in most cases and, perhaps appropriately, transitory. They exemplify a category of historical source material that, sadly, is no longer being generated.
[1] Gordon Young, Mark Chavalas, Richard Averbeck, eds., Crossing Boundaries and Linking Horizons: Studies in Honor of Michael C. Astour on His 80th Birthday [Bethesda, MD., 1997], xi.
[2] Astour to Chavalas, March 2, 1992, Box 25
Strange Alliance: An American, a Nazi, and the Battle of the Bulge
One of the stranger episodes in the history of World War II occurred over a period of 90 hours in the Belgian village of La Gleize in December 1944. During the bloody Battle of the Bulge, Hal McCown, a major in the U.S. 30th Infantry Division, was captured by troops of the Nazi Waffen SS and taken to La Gleize, where ObersturmbannfĂŒhrer (Lieutenant Colonel) Joachim Peiper had established his headquarters. Peiper commanded a battlegroup whose orders were to capture crossings over the Meuse river, thus opening the way to Antwerp, the primary German objective. It was also the battlegroup responsible for the murder of American POWs near the town of MalmĂ©dy. Over those 90 hours, McCown and Peiper forged an improbable relationship of mutual admiration and trust that is unique and which this essay analyzes and places in broad historical context
A Nazi War Criminal Reflects On The War In Russia
The name Joachim (or âJochenâ) Peiper is instantly recognizable to any American with a passing knowledge of World War II. He was the commander of the Waffen-SS battlegroup held responsible for the âMalmĂ©dy massacreâ of American prisoners of war during Hitlerâs Ardennes offensive. At the time of his 1946 trial by a U.S. Army court, he was called âthe most hated man in the United States.â Given the crimes of which he was accused â the slaughter of hundreds of POWs and Belgian civilians âthis is easy to understand. Less so is the attention that this man- a relatively minor figure in the host of World War II villains-has attracted over the three-quarters of a century since its end. Peiperâs life and career have been the subjects of multiple biographies, some superficial, others the product of prodigious research, and have inspired a stage play by a Pulitzer Prize-winning playwright. This is due in part to the notoriety engendered by the much publicized MalmĂ©dy massacre, the worst atrocity committed by Nazi Germany against U.S. forces, and the war crimes trial that followed, the most controversial of the many trials conducted by the United States. But it is also the outgrowth of Peiperâs personality, one that some people who came in contact with him including, ironically, Americans, found appealing. He was intelligent and well-read, good-looking (a dead-ringer for the actor Ray Milland, one person who met him thought), and fluent in English, a vital advantage in his interactions with largely monolingual Americans. His mysterious death in a remote French village early on the morning of Bastille Day, 1976, has served to further stimulate public interest in Peiper
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