Teacher Candidates’ Conceptual Understandings of Mathematics Concepts

As universities strive to produce the best mathematics teachers possible through both graduate and undergraduate programs, teacher educators must constantly work towards helping teacher candidates create their own conceptual understanding of mathematics. This pilot study examined the effect teaching in a constructivist manner had on teacher candidates’ conceptual understandings of the arithmetic mean and on their ability to transfer this knowledge into their instruction. Results indicated that teaching in a constructivist manner can have a positive impact on teacher candidates\u27 understanding of the arithmetic mean, but their abilities to transfer this new knowledge into their own instructional practices was inconsistent

Observation of interference between two distinct autoionizing states in dissociative photoionization of H 2

Dissociative photoionization (DPI) of randomly oriented H2 molecules has been studied using linearly polarized synchrotron radiation at selected photon energies of 31, 33, and 35 eV. Large amplitude oscillations in the photoelectron asymmetry parameter β, as a function of electron energy, have been observed. The phase of these β oscillations are in excellent agreement with the results of recent close coupling calculations [Fernández and Martín, New J. Phys. 11, 043020 (2009)]. We show that the oscillations are the signature of interferences between the 1Q1 Σu+1 and 1Q2 Πu1 doubly excited states decaying at different internuclear distances. The oscillations thus provide information about the classical paths followed by the nuclei. The presence of such oscillations is predicted to be a general phenomenon in DPIWe acknowledge NSERC, CLS, and UoW for their support. We thank Mare Nostrum BSC and CCC-UAM for allocation of computer time. Work partially supported by the MICINN Projects No. FIS2010-15127, No. ACI2008-0777, and No. CSD 2007-00010, the European MC-ITN CORINF, and the COST Action CM070

Optical photometric GTC/OSIRIS observations of the young massive association Cygnus OB2

In order to fully understand the gravitational collapse of molecular clouds, the star formation process and the evolution of circumstellar disks, these phenomena must be studied in different Galactic environments with a range of stellar contents and positions in the Galaxy. The young massive association Cygnus OB2, in the Cygnus-X region, is an unique target to study how star formation and the evolution of circumstellar disks proceed in the presence of a large number of massive stars. We present a catalog obtained with recent optical observations in r,i,z filters with OSIRIS, mounted on the $10.4\,m$ GTC telescope, which is the deepest optical catalog of Cyg OB2 to date. The catalog consist of 64157 sources down to M=0.15 solar masses at the adopted distance and age of Cyg OB2. A total of 38300 sources have good photometry in all three bands. We combined the optical catalog with existing X-ray data of this region, in order to define the cluster locus in the optical diagrams. The cluster locus in the r-i vs. i-z diagram is compatible with an extinction of the optically selected cluster members in the 2.64<AV<5.57 range. We derive an extinction map of the region, finding a median value of AV=4.33 in the center of the association, decreasing toward the north-west. In the color-magnitude diagrams, the shape of the distribution of main sequence stars is compatible with the presence of an obscuring cloud in the foreground at about 850+/-25 pc from the Sun.Comment: Accepted for publication ApJS 201

TeV gamma-rays and neutrinos from photo-disintegration of nuclei in Cygnus OB2

TeV gamma-rays may provide significant information about high energy astrophysical accelerators. Such gamma-rays can result from the photo-de-excitation of PeV nuclei after their parents have undergone photo-disintegration in an environment of ultraviolet photons. This process is proposed as a candidate explanation of the recently discovered HEGRA source at the edge of the Cygnus OB2 association. The Lyman-alpha background is provided by the rich O and B stellar environment. It is found that (1) the HEGRA flux can be obtained if there is efficient acceleration at the source of lower energy nuclei; (2) the requirement that the Lorentz-boosted ultraviolet photons can excite the Giant Dipole resonance implies a strong suppression of the gamma-ray spectrum compared to an E_\gamma^{-2} behavior at energies \alt 1 TeV (some of these energies will be probed by the upcoming GLAST mission); (3) a TeV neutrino counterpart from neutron decay following helium photo-disintegration will be observed at IceCube only if a major proportion of the kinetic energy budget of the Cygnus OB2 association is expended in accelerating nuclei.Comment: To be published in Phys. Rev.

Fifty Years of IMF Variation: The Intermediate-Mass Stars

I track the history of star count estimates of the Milky Way field star and open cluster IMFs, concentrating on the neglected mass range from 1 to 15 M${_\odot}$. The prevalent belief in a universal IMF appears to be without basis for this mass range. Two recent estimates of the field star IMF using different methods and samples give values of the average logarithmic slope $\Gamma$ between -1.7 and -2.1 in the mass range 1.1 to 4 M${_\odot}$. Two older estimates between 2 and 15 M${_\odot}$ disagree severely; the field IMF in this range is essentially unknown from star counts. Variations in $\Gamma$ among open cluster IMFs in this mass range have not decreased despite numerous detailed studies, even for studies using homogeneous data and reduction procedures and including only clusters with a significant mass range. These cluster variations \textit{might} be due to the combined effects of sampling, systematic errors, stellar evolution uncertainties, dynamical evolution, and unresolved binaries. If so, then the cluster data are consistent with a universal IMF, but are also consistent with sizeable variations. The cluster data do not allow an estimate of an average IMF or $\Gamma$ because the average depends on the choice of weighting procedure and other effects. If the spread in cluster IMFs is in excess of the effects listed above, real IMF variations must occur that do not depend much on physical conditions explored so far. The complexity of the star formation process seen in observations and simulations suggests that large realization-to-realization differences might be expected, in which case an individual cluster IMF would be in part the product of evolutionary contingency in star formation, and the function of interest is the probability distribution of IMF parameters.Comment: 18 pages, including 4 figures: invited talk presented at the conference on "IMF@50: The Stellar Initial Mass Function Fifty Years Later" held at Abbazia di Spineto, Siena, Italy, May 2004; to be published by Kluwer Academic Publishers, edited by E. Corbelli, F. Palla, and H. Zinnecke

The mediating role of shared flow and perceived emotional synchrony on compassion for others in a mindful-dancing program

While there is a growing understanding of the relationship between mindfulness and compassion, this largely relates to the form of mindfulness employed in first-generation mindfulness-based interventions such as Mindfulness-Based Stress Reduction. Consequently, there is limited knowledge of the relationship between mindfulness and compassion in respect of the type of mindfulness employed in second-generation mindfulness-based interventions (SG-MBIs), including those that employ the principle of working harmoniously as a “secular sangha.” Understanding this relationship is important because research indicates that perceived emotional synchrony (PES) and shared flow—that often arise during participation in harmonized group contemplative activities—can enhance outcomes relating to compassion, subjective well-being, and group identity fusion. This pilot study analyzed the effects of participation in a mindful-dancing SG-MBI on compassion and investigated the mediating role of shared flow and PES. A total of 130 participants were enrolled into the study that followed a quasi-experimental design with an intervention and control group. Results confirmed the salutary effect of participating in a collective mindful-dancing program, and demonstrated that shared flow and PES fully meditated the effects of collective mindfulness on the kindness and common humanity dimensions of compassion. Further research is warranted to explore whether collective mindfulness approaches, such as mindful dancing, may be a means of enhancing compassion and subjective well-being outcomes due to the mediating role of PES and shared flow.N/

Searches for the Shell Swept up by the Stellar Wind from Cyg OB2

We investigated the kinematics of ionized gas in an extended (20 degrees by 15 degrees) region containing the X-ray Superbubble in Cygnus with the aim of finding the shell swept up by a strong wind from Cyg OB2. H-alpha observations were carried out with high angular and spectral resolutions using a Fabry-Perot interferometer attached to the 125-cm telescope at the Crimean Observatory of the Sternberg Astronomical Institute. We detected high-velocity gas motions, which could result from the expansion of the hypothetical shell at a velocity of 25-50 km/s. Given the number of OB stars increased by Knoedlseder (2000) by an order of magnitude, Cyg OB2 is shown to possess a wind that is strong enough [Lw ~= (1-2)x10^39 erg/s] to produce a shell comparable in size to the X-ray Superbubble and to a giant system of optical filaments. Based on our measurements and on X-ray and infrared observations, we discuss possible observational manifestations of the shell swept up by the wind.Comment: 14 pages, Astronomy Letter

Tumour-associated carbohydrate antigens in breast cancer

Glycosylation changes that occur in cancer often lead to the expression of tumour-associated carbohydrate antigens. In breast cancer, these antigens are usually associated with a poor prognosis and a reduced overall survival. Cellular models have shown the implication of these antigens in cell adhesion, migration, proliferation and tumour growth. The present review summarizes our current knowledge of glycosylation changes (structures, biosynthesis and occurrence) in breast cancer cell lines and primary tumours, and the consequences on disease progression and aggressiveness. The therapeutic strategies attempted to target tumour-associated carbohydrate antigens in breast cancer are also discussed