Competing charge density waves and temperature-dependent nesting in 2H-TaSe2

Multiple charge density wave (CDW) phases in 2H-TaSe2 are investigated by high-resolution synchrotron x-ray diffraction. In a narrow temperature range immediately above the commensurate CDW transition, we observe a multi-q superstructure with coexisting commensurate and incommensurate order parameters, clearly distinct from the fully incommensurate state at higher temperatures. This multi-q ordered phase, characterized by a temperature hysteresis, is found both during warming and cooling, in contrast to previous reports. In the normal state, the incommensurate superstructure reflection gives way to a broad diffuse peak that persists nearly up to room temperature. Its position provides a direct and accurate estimate of the Fermi surface nesting vector, which evolves non-monotonically and approaches the commensurate position as the temperature is increased. This behavior agrees with our recent observations of the temperature-dependent Fermi surface in the same compound [Phys. Rev. B 79, 125112 (2009)]

Fermionic Molecular Dynamics for nuclear dynamics and thermodynamics

A new Fermionic Molecular Dynamics (FMD) model based on a Skyrme functional is proposed in this paper. After introducing the basic formalism, some first applications to nuclear structure and nuclear thermodynamics are presentedComment: 5 pages, Proceedings of the French-Japanese Symposium, September 2008. To be published in Int. J. of Mod. Phys.

Effect of the Negative Ion Band on Athletic Performance

Negative Ion bands have been suggested to increase various areas of athletic performance. At this time, the authors are not aware of any studies on these bands. Purpose: To determine if a True Power Energy Band (True Power LLC, Melrose, MA) had an effect on various measures of performance. Methods: Forty-one subjects (age = 29.3±7.1 yrs, ht = 171.5±9.7 cm, wt = 85.4±23.2 kg) had their height and weight measured and were then randomized to wear the True Power band (TB) or a silver bracelet placebo band (PB) (Hobby Lobby). After 5 days, subjects were assessed on reaction time using a color response test and a response test in which the subject clicked a highlighted dot as it appeared in a 5x5 table (www.intelligencetest.com/reflex/index). The subjects then performed a standard balance test (stork test) without shoes, two flexibility tests (V-sit-and-reach & trunk rotation), and two strength tests (hand grip using a dynamometer & push-ups to exhaustion). The tests were conducted in this order with as much rest between trials as needed. One week later, this same procedure was followed but with the opposing band. Repeated measures ANOVA was used to determine if differences exist between the bands, with Alpha set at .05. Results: There were no significant differences in the tests of color (TB = 0.43±0.14, PB = 0.41±0.11 sec), dots (TB = 16.9±3.0, PB = 17.0±2.6 score), stork (TB = 4.4±3.4, PB = 4.7±4.1 sec), V-sit-and-reach (TB = 15.2±16.8, PB = 15.5±17.3 cm), trunk rotation (TB = 35.8±15.0, PB = 37.3±14.0 cm), hand grip (TB = 42.4±12.1, PB = 42.8±11.0 kg), and push-ups (TB = 23.4±10.5, PB = 25.8±11.7 total), p \u3e .05 for all tests. Conclusion: There seems to be no effect of Negative Ion bands on tests of reaction time, balance, flexibility, or muscular strength. The claims of performance in these types of bands have yet to be validated

High accuracy results for the energy levels of the molecular ions H2+, D2+ and HD+, up to J=2

We present a nonrelativistic calculation of the rotation-vibration levels of the molecular ions H2+, D2+ and HD+, relying on the diagonalization of the exact three-body Hamiltonian. The J=2 levels are obtained with a very high accuracy of 10^{-14} a.u. (for most levels) representing an improvement by five orders of magnitude over previous calculations. The accuracy is also improved for the J=1 levels of H2+ and D2+ with respect to earlier works. Moreover, we have computed the sensitivities of the energy levels with respect to the mass ratios, allowing these levels to be used for metrological purposes.Comment: 11 page

Einstein y la religión

"A pesar de sus muchas declaraciones, no sabemos del todo qué quiso significar Einstein con la palabra Dios. En su obra científica Dios fue el concepto gobernante-un concepto mal definido, porque, ¿quién puede definir a Dios?- pero un símbolo no sólo de la pasión de Einstein por lo asombroso y lo bello, sino también de aquel intuitivo sentido de comunión con el Universo, que fue el distintivo de su genio." Banesh Hoffmann, Albert Einstein.  

Scattering by a toroidal coil

In this paper we consider the Schr\"odinger operator in ${\mathbb R}^3$ with a long-range magnetic potential associated to a magnetic field supported inside a torus ${\mathbb{T}}$. Using the scheme of smooth perturbations we construct stationary modified wave operators and the corresponding scattering matrix $S(\lambda)$. We prove that the essential spectrum of $S(\lambda)$ is an interval of the unit circle depending only on the magnetic flux $\phi$ across the section of $\mathbb{T}$. Additionally we show that, in contrast to the Aharonov-Bohm potential in ${\mathbb{R}}^2$, the total scattering cross-section is always finite. We also conjecture that the case treated here is a typical example in dimension 3.Comment: LaTeX2e 17 pages, 1 figur

How envisionment of the future influences professional identity development : a longitudinal study of students’ graduate work in a social science field

This dissertation study is a longitudinal qualitative investigation of how graduate students in a social science field construct their professional identity. Among the different identities that individuals construct and have imposed upon them, their professional identity may be more distinct as compared to other identities such as gender roles, position of caretaker, and ethnicity that may develop over a longer period of time and be more diffuse. One’s professional identity is likely to become a central identity because it provides agency, power, and a socially respected position in a particular disciplinary field and in society at large. This investigation of graduate students’ disciplinary development was designed to contribute to a better understanding of the process of professional identity development. Doctoral students in a social science field were chosen as participants because they were likely to undergo intensive identity construction processes in a short time period of time. In this staggered longitudinal study, the total number of participants was 34. Participants were tracked across milestones over at least two semesters of their program. Data collection included multiple interviews, member checking, and observation of students’ activities in content classes, research meetings, social gatherings, and professional conference participation according to distinct stages that occur over time. Analyzed using grounded theory methodology, data are presented in three themes representing significant influences on professional identity development. For the first theme, graduate students’ professional identity seemed to progress through phases marked by milestones. In Theme 2, graduate students’ professional identity seemed to develop through interactions with other individuals in several learning communities. In Theme 3, graduate students seemed to forge their professional identity through their program experiences, defining their professional self as the acquisition of self-knowledge and self-regulation skills (being professional), disciplinary knowledge and skills (being a professional), and envisionment of a professional future self participating in a community of practice. Development of professional disciplinary skills including disciplinary discourse practices appeared as a core contributor for students’ professional identity development. Generalizable professional skills seemed more subtle and foundational for the other two factors (professional skills acquisition and professional affiliation). Individuals who developed both professional skills and professional affiliation seemed to have a strong professional identity. In addition, data indicated that as graduate students underwent the professional identity process, they seemed more motivated to take up their academic responsibilities and participate in their professional field. In sum, the contribution of this study is that different influences on graduate students’ professional identity development were shown, and a clearer view of the overall professional identity development process was obtained, including what factors are influencing graduate students’ professional identity development as well as their possible future self in their disciplinary community of practice.Educational Psycholog