Low-background temperature sensors fabricated on parylene substrates

Temperature sensors fabricated from ultra-low radioactivity materials have been developed for low-background experiments searching for neutrinoless double-beta decay and the interactions of WIMP dark matter. The sensors consist of electrical traces photolithographically-patterned onto substrates of vapor-deposited parylene. They are demonstrated to function as expected, to do so reliably and robustly, and to be highly radio-pure. This work is a proof-of-concept study of a technology that can be applied to broad class of electronic circuits used in low-background experiments

A Semiconductor Nanowire-Based Superconducting Qubit

We introduce a hybrid qubit based on a semiconductor nanowire with an epitaxially grown superconductor layer. Josephson energy of the transmon-like device ("gatemon") is controlled by an electrostatic gate that depletes carriers in a semiconducting weak link region. Strong coupling to an on-chip microwave cavity and coherent qubit control via gate voltage pulses is demonstrated, yielding reasonably long relaxation times (0.8 {\mu}s) and dephasing times (1 {\mu}s), exceeding gate operation times by two orders of magnitude, in these first-generation devices. Because qubit control relies on voltages rather than fluxes, dissipation in resistive control lines is reduced, screening reduces crosstalk, and the absence of flux control allows operation in a magnetic field, relevant for topological quantum information

A dynamical and kinematical model of the Galactic stellar halo and possible implications for galaxy formation scenarios

We re-analyse the kinematics of the system of blue horizontal branch field (BHBF) stars in the Galactic halo (in particular the outer halo), fitting the kinematics with the model of radial and tangential velocity dispersions in the halo as a function of galactocentric distance r proposed by Sommer-Larsen, Flynn & Christensen (1994), using a much larger sample (almost 700) of BHBF stars. The basic result is that the character of the stellar halo velocity ellipsoid changes markedly from radial anisotropy at the sun to tangential anisotropy in the outer parts of the Galactic halo (r greater than approx 20 kpc). Specifically, the radial component of the stellar halo's velocity ellipsoid decreases fairly rapidly beyond the solar circle, from approx 140 +/- 10 km/s at the sun, to an asymptotic value of 89 +/- 19 km/s at large r. The rapid decrease in the radial velocity dispersion is matched by an increase in the tangential velocity dispersion, with increasing r. Our results may indicate that the Galaxy formed hierarchically (partly or fully) through merging of smaller subsystems - the 'bottom-up' galaxy formation scenario, which for quite a while has been favoured by most theorists and recently also has been given some observational credibility by HST observations of a potential group of small galaxies, at high redshift, possibly in the process of merging to a larger galaxy (Pascarelle et al 1996).Comment: Latex, 16 pages. 2 postscript figures. Submitted to the Astrophysical Journal. also available at http://astro.utu.fi/~cflynn/outerhalo.htm

Structure and Mass of a Young Globular Cluster in NGC 6946

Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have imaged a luminous young star cluster in the nearby spiral galaxy NGC 6946. The cluster has an absolute visual magnitude M(V)=-13.2, comparable to the brightest young `super-star clusters' in the Antennae merger galaxy. UBV colors indicate an age of about 15 Myr. The cluster has a compact core (core radius = 1.3 pc), surrounded by an extended envelope. We estimate that the effective radius (Reff) = 13 pc, but this number is uncertain because the outer parts of the cluster profile gradually merge with the general field. Combined with population synthesis models, the luminosity and age of the cluster imply a mass of 8.2x10^5 Msun for a Salpeter IMF extending down to 0.1 Msun, or 5.5x10^5 Msun if the IMF is log-normal below 0.4 Msun. Depending on model assumptions, the central density of the cluster is between 5300 Msun pc^-3 and 17000 Msun pc^-3, comparable to other high-density star forming regions. We also estimate a dynamical mass for the cluster, using high-dispersion spectra from the HIRES spectrograph on the Keck I telescope. The velocity dispersion is 10.0 +/- 2.7 km/s, implying a total cluster mass within 65 pc of (1.7 +/- 0.9) x 10^6 Msun. Comparing the dynamical mass with the mass estimates based on the photometry and population synthesis models, the mass-to-light ratio is at least as high as for a Salpeter IMF extending down to 0.1 Msun, although a turn-over in the IMF at 0.4 Msun is still possible within the errors. The cluster will presumably remain bound, evolving into a globular cluster-like object.Comment: 33 pages, including 10 figures and 3 tables. Accepted for publication in the Astrophysical Journa

Time lower bounds for nonadaptive turnstile streaming algorithms

We say a turnstile streaming algorithm is "non-adaptive" if, during updates, the memory cells written and read depend only on the index being updated and random coins tossed at the beginning of the stream (and not on the memory contents of the algorithm). Memory cells read during queries may be decided upon adaptively. All known turnstile streaming algorithms in the literature are non-adaptive. We prove the first non-trivial update time lower bounds for both randomized and deterministic turnstile streaming algorithms, which hold when the algorithms are non-adaptive. While there has been abundant success in proving space lower bounds, there have been no non-trivial update time lower bounds in the turnstile model. Our lower bounds hold against classically studied problems such as heavy hitters, point query, entropy estimation, and moment estimation. In some cases of deterministic algorithms, our lower bounds nearly match known upper bounds

The initial conditions of observed star clusters - I. Method description and validation

We have coupled a fast, parametrized star cluster evolution code to a Markov Chain Monte Carlo code to determine the distribution of probable initial conditions of observed star clusters, which may serve as a starting point for future $N$-body calculations. In this paper we validate our method by applying it to a set of star clusters which have been studied in detail numerically with $N$-body simulations and Monte Carlo methods: the Galactic globular clusters M4, 47 Tucanae, NGC 6397, M22, $\omega$ Centauri, Palomar 14 and Palomar 4, the Galactic open cluster M67, and the M31 globular cluster G1. For each cluster we derive a distribution of initial conditions that, after evolution up to the cluster's current age, evolves to the currently observed conditions. We find that there is a connection between the morphology of the distribution of initial conditions and the dynamical age of a cluster and that a degeneracy in the initial half-mass radius towards small radii is present for clusters which have undergone a core collapse during their evolution. We find that the results of our method are in agreement with $N$-body and Monte Carlo studies for the majority of clusters. We conclude that our method is able to find reliable posteriors for the determined initial mass and half-mass radius for observed star clusters, and thus forms an suitable starting point for modeling an observed cluster\rq{}s evolution.Comment: 39 pages, 28 figures, accepted for publication in MNRA

Hole Spin Coherence in a Ge/Si Heterostructure Nanowire

Relaxation and dephasing of hole spins are measured in a gate-defined Ge/Si nanowire double quantum dot using a fast pulsed-gate method and dispersive readout. An inhomogeneous dephasing time $T_2^* \sim 0.18~\mathrm{\mu s}$ exceeds corresponding measurements in III-V semiconductors by more than an order of magnitude, as expected for predominately nuclear-spin-free materials. Dephasing is observed to be exponential in time, indicating the presence of a broadband noise source, rather than Gaussian, previously seen in systems with nuclear-spin-dominated dephasing.Comment: 15 pages, 4 figure

Structural Parameters and Dynamical Masses for Globular Clusters in M33

Using high-dispersion spectra from the HIRES echelle spectrograph on the Keck I telescope, we measure velocity dispersions for 4 globular clusters in M33. Combining the velocity dispersions with integrated photometry and structural parameters derived from King-Michie model fits to WFPC2 images, we obtain mass-to-light ratios for the clusters. The mean value is M/LV = 1.53 +/- 0.18, very similar to the M/LV of Milky Way and M31 globular clusters. The M33 clusters also fit very well onto the fundamental plane and binding energy - luminosity relations derived for Milky Way GCs. Dynamically and structurally, the four M33 clusters studied here appear virtually identical to Milky Way and M31 GCs.Comment: 25 pages, including 7 figures and 4 tables. Accepted for AJ, Nov 200

Reconstructing hominin diets with stable isotope analysis of amino acids: new perspectives and future directions

Stable isotope analysis of teeth and bones is regularly applied by archeologists and paleoanthropologists seeking to reconstruct diets, ecologies, and environments of past hominin populations. Moving beyond the now prevalent study of stable isotope ratios from bulk materials, researchers are increasingly turning to stable isotope ratios of individual amino acids to obtain more detailed and robust insights into trophic level and resource use. In the present article, we provide a guide on how to best use amino acid stable isotope ratios to determine hominin dietary behaviors and ecologies, past and present. We highlight existing uncertainties of interpretation and the methodological developments required to ensure good practice. In doing so, we hope to make this promising approach more broadly accessible to researchers at a variety of career stages and from a variety of methodological and academic backgrounds who seek to delve into new depths in the study of dietary composition.Investigating hominin diets and environments Factors affecting isotope values - Food processing. - Digestion and metabolic processes. - Isotopic variation of dietary sources. Statistical analyses Analytical considerations Applications in archeology and paleoecology Perspectives for hominin studie