C*-algebras of Hilbert module product systems

We consider a class of C*-algebras associated to one parameter continuous tensor product systems of Hilbert modules, which can be viewed as continuous counterparts of Pimsner's Toeplitz algebras. By exhibiting a homotopy of quasihomomorphisms, we prove that those algebras are $K$-contractible. One special case is closely related to the Rieffel-Wiener-Hopf extension of a crossed product by R considered by Rieffel and by Pimsner and Voiculescu, and can be used to produce a new proof of Connes' analogue of the Thom isomorphism and in particular of Bott periodicity. Another special case is closely related to Arveson's spectral C*-algebras, and is used to settle Arveson's problem of computing their K-theory, extending earlier results of Zacharias to cover the general case.Comment: 11 pages (added an example and an appendix, corrected typos and improved exposition

Alternative Certification: A Research Brief

Alternative teacher certification (ATC) encompasses a broad range of programs that prepare teachers in non-traditional, accelerated ways (Suell and Piotrowski 2007). The number of teachers prepared through alternative routes has increased considerably in the past decade. As of 2011, 16% of public school teachers nationwide had entered the profession through some kind of alternative program, and in the last five years, 40% of new hires have come through ATC programs (Feistritzer 2011). In this brief I offer a short overview of research on the outcomes of alternative certification programs compared with traditional certification, summarize findings about what makes for effective alternative certification programs, and describe ATC programs in Alaska. Generally, ATC programs are aimed at people who are interested in becoming teachers and have at least a bachelor’s degree, as well as extensive life experience. But how these programs are defined and what they include varies considerably (Humphrey and Wechsler 2007). In this brief, alternative certification is defined as a program in which teacher candidates work as the instructor of record while completing their teacher certification. These programs are considered to be both a means of alleviating teacher shortages and a way of improving the quality of the teaching workforce. In addition to shortening the preparation time and being more flexible for working participants, ATC programs also typically incorporate mentoring (Mikulecky, Shkodriani et al. 2004; Scribner and Heinen 2009). The programs range from initiatives run by school districts and state departments of education to university-operated efforts run alongside traditional teacher preparation programs (Yao and Williams 2010)

Solar wind helium enhancements following major solar flares

The observations of solar wind helium enhancements following major solar flares are reviewed, and the hypothesis that helium enhancements often mark flare piston plasma is confirmed. Helium enhancements were observed during each of the three periods (March 1966, July 1966, August/September 1966) of major solar activity that occurred from October 1965 to October 1966. No enhancements were seen during the long quiet periods that occurred that year. At 1 AU, the helium-enhanced plasma pistons had slowed so that the velocity was 80 percent of the mean transit velocity, in general agreement with theoretical models of the propagation of flare disturbances. A qualitative model, in which the piston plasma is accelerated from the flare site deep in the corona, is discussed briefly. If the model is valid in general outline, the piston plasmas provide samples of material from the lower levels of the corona