On the Low and High Frequency Correlation in Quasi-Periodic Oscillations Among White Dwarfs, Neutron Star and Black Hole Binaries

We interpret the correlation over five orders of magnitude between high frequency and low frequency in a quasi-periodic oscillations (QPO) found by Psaltis, Belloni & van der Klis (1999) for black hole (BH), neutron star (NS) systems and then extended by Mauche (2002) to white dwarf (WD) binaries. We argue that the observed correlation is a natural consequence of the Keplerian disk flow adjustment to the innermost sub-Keplerian boundary conditions near the central object. In the framework of the transition layer model the high frequency is related to the Keplerian frequency at the outer (adjustment) radius and the low frequency is related to the magnetoacoustic oscillation (MA) frequency. Using a relation between the MA frequency the magnetic and gas pressure and the density and the hydrostatic equilibrium condition in the disk we infer a linear correlation the Keplerian frequency and the MA frequency. We estimate the magnetic field strength near the TL outer radius for BHs NSs and WDs. The fact that the observed high-low frequency correlation over five orders of magnitude is valid for BHs, NSs, and down to WDs strongly rules out relativistic models for QPO phenomena. We come to the conclusion that the QPOs observations indicate the adjustment of the geometrically thin disk to sub-Keplerian motion near the central object. This effect is a common feature for a wide class of systems, starting from white dwarf binaries up to black hole binaries.Comment: 8 pages, 1 figure, accepted for publication in the ApJ. Letters 2002 August

Unlocking the Secrets of Ancient Writing. The Parallel Lives of Michael Ventris and Linda Schele and the Decipherment of Mycenaean and Mayan Writing

Catalogue of an exhibition conducted in conjunction with the Eleventh International Mycenological Colloquium held at the University of Texas at Austin in 2000. This program features brief histories of the CIPEM Mycenological conferences and PASP, followed by comparative retrospectives on both Michael Ventris, who deciphered Linear B, and Linda Schele, who performed a similar feat for Mayan glyphs.Classic

Beam energy measurement at linear colliders using spin precession

Linear collider designs foresee some bends of about 5-10 mrad. The spin precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it changes proportional to the energy. Measurement of the spin direction using Compton scattering of laser light on electrons before and after the bend allows determining the beam energy with an accuracy about of 10^{-5}. In this paper the principle of the method, the procedure of the measurement and possible errors are discussed. Some remarks about importance of plasma focusing effects in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept 2-6, 200

The 1982 NASA/ASEE Summer Faculty Fellowship Program

A NASA/ASEE Summer Faculty Fellowship Research Program was conducted to further the professional knowledge of qualified engineering and science faculty members, to stimulate an exchange of ideas between participants and NASA, to enrich and refresh the research and teaching activities of participants' institutions, and to contribute to the research objectives of the NASA Centers

Research reports: The 1980 NASA/ASEE Summer Faculty Fellowship Program

The Summer Faculty Fellowship Research Program objectives are: to further the professional knowledge of qualified engineering and science faculty members; to stimulate an exchange of ideas between participants and NASA; to enrich and refresh the research and teaching activities of participants and institutions; and to contribute to the research objectives at the NASA centers. The Faculty Fellows engaged in research projects commensurate with their interests and background and worked in collaboration with a NASA/MSFC colleague

Mesenchymal Stem Cell Spheroids Retain Osteogenic Phenotype Through α2β1 Signaling.

Unlabelled: The induction of mesenchymal stem cells (MSCs) toward the osteoblastic lineage using osteogenic supplements prior to implantation is one approach under examination to enhance their bone-forming potential. MSCs rapidly lose their induced phenotype upon removal of the soluble stimuli; however, their bone-forming potential can be sustained when provided with continued instruction via extracellular matrix (ECM) cues. In comparison with dissociated cells, MSC spheroids exhibit improved survival and secretion of trophic factors while maintaining their osteogenic potential. We hypothesized that entrapment of MSC spheroids formed from osteogenically induced cells would exhibit better preservation of their bone-forming potential than would dissociated cells from monolayer culture. Spheroids exhibited comparable osteogenic potential and increased proangiogenic potential with or without osteogenic preconditioning versus monolayer-cultured MSCs. Spheroids were then entrapped in collagen hydrogels, and the osteogenic stimulus was removed. In comparison with entrapped dissociated MSCs, spheroids exhibited significantly increased markers of osteogenic differentiation. The capacity of MSC spheroids to retain their osteogenic phenotype upon withdrawal of inductive cues was mediated by α2β1 integrin binding to cell-secreted ECM. These results demonstrate the capacity of spheroidal culture to sustain the mineral-producing phenotype of MSCs, thus enhancing their contribution toward bone formation and repair.SignificanceDespite the promise of mesenchymal stem cells (MSCs) for cell-based therapies for tissue repair and regeneration, there is little evidence that transplanted MSCs directly contribute to new bone formation, suggesting that induced cells rapidly lose their osteogenic phenotype or undergo apoptosis. In comparison with dissociated cells, MSC spheroids exhibit increased trophic factor secretion and improved cell survival. The loss of phenotype represents a significant clinical challenge for cell therapies, yet there is no evidence for whether MSC spheroids retain their osteogenic phenotype upon entrapment in a clinically relevant biomaterial. These findings demonstrate that MSC spheroids retain their osteogenic phenotype better than do dissociated MSCs, and this is due to integrin engagement with the cell-secreted extracellular matrix. These data provide evidence for a novel approach for potentiating the use of MSCs in bone repair

The 1981 NASA/ASEE Summer Faculty Fellowship Program: Research reports

Research reports related to spacecraft industry technological advances, requirements, and applications were considered. Some of the topic areas addressed were: (1) Fabrication, evaluation, and use of high performance composites and ceramics, (2) antenna designs, (3) electronics and microcomputer applications and mathematical modeling and programming techniques, (4) design, fabrication, and failure detection methods for structural materials, components, and total systems, and (5) chemical studies of bindary organic mixtures and polymer synthesis. Space environment parameters were also discussed

Directional Distributions in Tracking of Space Debris

Directional distributions play an important role in describing uncertainty in spherical coordinates. A review is given of some standard distributions on the sphere which arise as special cases of the Fisher-Bingham distribution. A new distribution, called the “extreme FB5” istribution, is introduced to describe semi-concentrated behavior on the sphere, that is, patterns of data that are unimodal and concentrated near a great circle. This behavior is particularly relevant to tracking problems. Properties of the new distribution are discussed and methods are given for simulation and estimation. Two simple error propagation illustrations are given to demonstrate the usefulness of the new model

Application of the Group Conference Method of Teaching to Beginning Classes in Plant Pathology

The teacher\u27s ability to stimulate and to work with each student largely determines the value derived from a course by the student. The contact of teacher with the individual student is more difficult to effect in large classes (50 students or more) than in small classes. In the large classes a restraint and formality may prevail that are lacking in groups of 20 students or fewer