Efficient multiple time scale molecular dynamics: using colored noise thermostats to stabilize resonances

Multiple time scale molecular dynamics enhances computational efficiency by updating slow motions less frequently than fast motions. However, in practice the largest outer time step possible is limited not by the physical forces but by resonances between the fast and slow modes. In this paper we show that this problem can be alleviated by using a simple colored noise thermostatting scheme which selectively targets the high frequency modes in the system. For two sample problems, flexible water and solvated alanine dipeptide, we demonstrate that this allows the use of large outer time steps while still obtaining accurate sampling and minimizing the perturbation of the dynamics. Furthermore, this approach is shown to be comparable to constraining fast motions, thus providing an alternative to molecular dynamics with constraints.Comment: accepted for publication by the Journal of Chemical Physic

Late Light Curves of Normal Type Ia Supernovae

We present late-epoch optical photometry (BVRI) of seven normal/super-luminous Type Ia supernovae: SN 2000E, SN 2000ce, SN 2000cx, SN 2001C, SN 2001V, SN 2001bg, SN 2001dp. The photometry of these objects was obtained using a template subtraction method to eliminate galaxy light contamination during aperture photometry. We show the optical light curves of these supernovae out to epochs of up to ~640 days after the explosion of the supernova. We show a linear decline in these data during the epoch of 200-500 days after explosion with the decline rate in the B,V,& R bands equal to about 1.4 mag/100 days, but the decline rate of the I-band is much shallower at 0.94 mag/100 days.Comment: 33 pages, 11 figures, Accepted for publication in The Astronomical Journa

Experimental determination of the 6s^2 ^1S_0 -> 5d6s ^3 D_1 magnetic-dipole transition amplitude in atomic ytterbium

We report on a measurement of the highly forbidden 6s^2 ^1S_0 \to 5d6s ^3 D_1 magnetic-dipole transition in atomic ytterbium using the Stark-interference technique. This amplitude is important in interpreting a future parity nonconservation experiment that exploits the same transition. We find $| | ~ = ~ 1.33(6)_{Stat}(20)_{\beta} \times 10^{-4} \mu_0$, where the larger uncertainty comes from the previously measured vector transition polarizability $\beta$. The $M1$ amplitude is small and should not limit the precision of the parity nonconservation experiment.Comment: 4 pages, 5 figures Paper resubmitted with minor corrections and additions based on comments from referee

Non-rigidity of spherical inversive distance circle packings

We give a counterexample of Bowers-Stephenson's conjecture in the spherical case: spherical inversive distance circle packings are not determined by their inversive distances.Comment: 6 pages, one pictur

Micro-resonator soliton generated directly with a diode laser

An external-cavity diode laser is reported with ultralow noise, high power coupled to a fiber, and fast tunability. These characteristics enable the generation of an optical frequency comb in a silica micro-resonator with a single-soliton state. Neither an optical modulator nor an amplifier was used in the experiment. This demonstration greatly simplifies the soliton generation setup and represents a significant step forward to a fully integrated soliton comb system.Comment: 7 pages, 5 figure

Near Infrared Spectra of Type Ia Supernovae

We report near infrared (NIR) spectroscopic observations of twelve ``Branch-normal'' Type Ia supernovae (SNe Ia) which cover the wavelength region from 0.8-2.5 microns. Our sample more than doubles the number of SNe Ia with published NIR spectra within three weeks of maximum light. The epochs of observation range from thirteen days before maximum light to eighteen days after maximum light. A detailed model for a Type Ia supernovae is used to identify spectral features. The Doppler shifts of lines are measured to obtain the velocity and, thus, the radial distribution of elements. The NIR is an extremely useful tool to probe the chemical structure in the layers of SNe Ia ejecta. This wavelength region is optimal for examining certain products of the SNe Ia explosion that may be blended or obscured in other spectral regions. We identify spectral features from MgII, CaII, SiII, FeII, CoII, NiII and possibly MnII. We find no indications for hydrogen, helium or carbon in the spectra. The spectral features reveal important clues about the physical characteristics of SNe Ia. We use the features to derive upper limits for the amount of unburned matter, to identify the transition regions from explosive carbon to oxygen burning and from partial to complete silicon burning, and to estimate the level of mixing during and after the explosion.Comment: 44 pages, 7 figures, 3 tables, accepted by Ap

A Mi\u27kmaq First Nation cosmology: investigating the practice of contemporary Aboriginal Traditional Medicine in dialogue with counselling – toward an Indigenous therapeutics

This paper explores from a Mi’kmaq and Aboriginal standpoint foundational knowledge in Indigenous therapeutics. Based on an eco-social-psycho-spiritual way of working, the article proposes Indigenous cultural models that open a window to a rich cultural repository of meanings associated with Indigenous cosmology, ontology and epistemology. The three layers of meaning, theory and practice within the symbolic ‘Medicine Lodge’ or ‘Place of The Dreaming’ give rise to ways of working that are deeply integrative and wholistic. These forms of Indigenous theory and practice have much to offer the counselling and complimentary health professions