New surveys of UBV photometry and absolute proper motions at intermediate latitude

A photometric and proper motion survey has been obtained in 2 directions at intermediate latitude: ($l=167.5^\circ$, $b=47.4^\circ$; $\alpha_{2000}=9^h41^m26^s$,$\delta_{2000}=+49^\circ53'27''$) and ($l=278^\circ$, $b=47^\circ$; $\alpha_{2000}=11^h42^m56^s$, $\delta_{2000}=-12^\circ31'42''$). The survey covers 7.13 and 20.84 square degrees, respectively. The limiting magnitude is about 18.5 in V for both directions. We have derived the density laws for stars (M$_{V}$ $\ge$ 3.5) as a function of distance from the galactic plane. The density laws for stars follow a sum of two exponentials with scale heights of 240 pc (thin disk) and 790 pc (thick disk), respectively. The local density of thick disk is found to be 6.1$\pm$3 % relative to the thin disk. The kinematical distribution of stars has been probed to distances up to 3.5 kpc above the galactic plane. New estimates of the parameters of velocity ellipsoid have been derived for the thick disk of the Galaxy. A comparison of our data sets with the Besan\c con model star count predictions has been performed, giving a good agreement in the magnitude range V = 13 to 18.Comment: 13 pages, 8 PS figures, To appear in A&

Adaptive homodyne phase discrimination and qubit measurement

Fast and accurate measurement is a highly desirable, if not vital, feature of quantum computing architectures. In this work we investigate the usefulness of adaptive measurements in improving the speed and accuracy of qubit measurement. We examine a particular class of quantum computing architectures, ones based on qubits coupled to well controlled harmonic oscillator modes (reminiscent of cavity-QED), where adaptive schemes for measurement are particularly appropriate. In such architectures, qubit measurement is equivalent to phase discrimination for a mode of the electromagnetic field, and we examine adaptive techniques for doing this. In the final section we present a concrete example of applying adaptive measurement to the particularly well-developed circuit-QED architecture.Comment: 9 pages, 8 figures. Published versio

Network Inference via the Time-Varying Graphical Lasso

Many important problems can be modeled as a system of interconnected entities, where each entity is recording time-dependent observations or measurements. In order to spot trends, detect anomalies, and interpret the temporal dynamics of such data, it is essential to understand the relationships between the different entities and how these relationships evolve over time. In this paper, we introduce the time-varying graphical lasso (TVGL), a method of inferring time-varying networks from raw time series data. We cast the problem in terms of estimating a sparse time-varying inverse covariance matrix, which reveals a dynamic network of interdependencies between the entities. Since dynamic network inference is a computationally expensive task, we derive a scalable message-passing algorithm based on the Alternating Direction Method of Multipliers (ADMM) to solve this problem in an efficient way. We also discuss several extensions, including a streaming algorithm to update the model and incorporate new observations in real time. Finally, we evaluate our TVGL algorithm on both real and synthetic datasets, obtaining interpretable results and outperforming state-of-the-art baselines in terms of both accuracy and scalability

A Multicolor Survey of Absolute Proper Motions : Galactic Structure and Kinematics in the Direction of Galactic Center at Intermediate Latitude

We have derived a new photographic photometry and proper motions for 20000 stars with completeness to V = 18 in the direction of galactic center at the intermediate latitude (l = 3 deg,b = 47 deg; alpha(1950)=15h 18m, delta(1950) = +02deg 16') for a 15.5 sq deg field. The combination of four glass copies of the Palomar Observatory Sky Survey (i.e. POSS 1402 E&O and POSS 1429 E&O) has been used as a first epoch for proper motion determination. The random error of the proper motions is approximately 0.''3/cen to V=17. The photometric accuracy ranges between 0.07 to 0.10 in the V, B and U bands. We stress the importance of the magnitude and color effects in astrometric surveys of field stars. Using color-magnitude diagrams of a few cluster member stars, a new distance of 6.9+-0.5 kpc is derived for M5 and 20.3+-0.8 kpc for Pal 5 globular clusters. This is in good agreement with other determinations. We have analyzed the components of U+W and V galactic space motions resulting from the accurate proper motions survey. No dependence with z distance is found in the asymmetric drift of the thick disk population. New estimates of the parameters of the velocity ellipsoid have been derived for the thin disk, thick disk and halo populations of the Galaxy.Comment: PS file, 15 pages, 13 figures (available on request), paper accepted for publication in Astron. & Astrophy

Survey for Emission-Line Galaxies: Universidad Complutense de Madrid List 3

A new low-dispersion objective-prism search for low-redshift (z<0.045) emission-line galaxies (ELG) has been carried out by the Universidad Complutense de Madrid with the Schmidt Telescope at the Calar-Alto Observatory. This is a continuation of the UCM Survey, which was performed by visual selection of candidates in photographic plates via the presence of the Halpha+[NII]6584 blend in emission. In this new list we have applied an automatic procedure, fully developed by us, for selecting and analyzing the ELG candidates on the digitized images obtained with the MAMA machine. The analyzed region of the sky covers 189 square degrees in nine fields near R.A.=14h & 17h, Dec=25 deg. The final sample contains 113 candidates. Special effort has been made to obtain a large amount of information directly from our uncalibrated plates by using several external calibrations. The parameters obtained for the ELG candidates allow for the study of the statistical properties for the sample.Comment: 13 pages, 18 PostScript figures, 6 JPEG figures, Table 2 corrected. Accepted for publication in Astrophysical Journal Supplements, also available at http://www.ucm.es/info/Astrof/opera/LIST3_ApJS99

Toeplitz Inverse Covariance-Based Clustering of Multivariate Time Series Data

Subsequence clustering of multivariate time series is a useful tool for discovering repeated patterns in temporal data. Once these patterns have been discovered, seemingly complicated datasets can be interpreted as a temporal sequence of only a small number of states, or clusters. For example, raw sensor data from a fitness-tracking application can be expressed as a timeline of a select few actions (i.e., walking, sitting, running). However, discovering these patterns is challenging because it requires simultaneous segmentation and clustering of the time series. Furthermore, interpreting the resulting clusters is difficult, especially when the data is high-dimensional. Here we propose a new method of model-based clustering, which we call Toeplitz Inverse Covariance-based Clustering (TICC). Each cluster in the TICC method is defined by a correlation network, or Markov random field (MRF), characterizing the interdependencies between different observations in a typical subsequence of that cluster. Based on this graphical representation, TICC simultaneously segments and clusters the time series data. We solve the TICC problem through alternating minimization, using a variation of the expectation maximization (EM) algorithm. We derive closed-form solutions to efficiently solve the two resulting subproblems in a scalable way, through dynamic programming and the alternating direction method of multipliers (ADMM), respectively. We validate our approach by comparing TICC to several state-of-the-art baselines in a series of synthetic experiments, and we then demonstrate on an automobile sensor dataset how TICC can be used to learn interpretable clusters in real-world scenarios.Comment: This revised version fixes two small typos in the published versio

Community empowerment - a successful model for prevention of non-communicable diseases in India - the Chennai Urban population study (CUPS - 17)

Background and objective: Randomized clinical trials have documented that lifestyle changes through physical activity can prevent diabetes. However there is no data whether such strategies are applicable at community level, that is, in a real life setting. This study demonstrates the first attempt in India, to our knowledge, of increasing physical activity through community empowerment in an attempt at primary prevention of non communicable diseases. Methods: The Chennai Urban Population Study [CUPS] was conducted in the year 1996 in two residential areas: a middle income group the Asiad colony at Tirumangalam, and a low income group at Bharathi Nagar in T. Nagar. The Asiad colony was selected for this study. Of the 524 eligible individuals available at baseline in 1998 [age ≥ 20 years], 479 individuals consented for the study (response rate:91.4%). After seven years, in 2004, the number of eligible individuals increased to 712 of whom 705 consented for the study (response rate:99%). Education regarding the benefits of physical activity was provided by mass awareness programmes like public lectures and video clippings. Both at baseline and during follow-up, details about the physical activity were collected using a validated questionnaire, which included job related and leisure time activities, and specific questions on exercise. Study individuals were then graded as having light, moderate and heavy physical activity using a scoring system. Results: In response to the awareness programmes given by our research team, the colony residents constructed a unique public park with their own funds. Though the occupation grades did not change, there was a significant change in the pattern of physical activity. At baseline, only 14.2% of the residents did some form of exercise more than three times a week, which presently increased to 58.7%[p&lt;0.001]. The number of subjects who walked more than three times a week increased from 13.8% at baseline to 52.1% during follow-up [p&lt;0.001]. Conclusion: This study is a demonstration of how community empowerment with increased physical activity could possibly lead to prevention of diabetes and other non communicable diseases at the community level. This study also highlights the importance of sharing the results of research studies with the community

Optimal estimation of one parameter quantum channels

We explore the task of optimal quantum channel identification, and in particular the estimation of a general one parameter quantum process. We derive new characterizations of optimality and apply the results to several examples including the qubit depolarizing channel and the harmonic oscillator damping channel. We also discuss the geometry of the problem and illustrate the usefulness of using entanglement in process estimation.Comment: 23 pages, 4 figures. Published versio

Dark halo baryons not in ancient halo white dwarfs

Having ruled out the possibility that stellar objects are the main contributor of the dark matter embedding galaxies, microlensing experiments cannot exclude the hypothesis that a significant fraction of the Milky Way dark halo might be made of MACHOs with masses in the range 0.5-0.8 \msun. Ancient white dwarfs are generally considered the most plausible candidates for such MACHOs. We report the results of a search for such white dwarfs in a proper motion survey covering a 0.16 sqd field at three epochs at high galactic latitude, and 0.938 sqd at two epochs at intermediate galactic latitude (VIRMOS survey), using the CFH telescope. Both surveys are complete to I = 23, with detection efficiency fading to 0 at I = 24.2. Proper motion data are suitable to separate unambiguously halo white dwarfs identified by belonging to a non rotating system. No candidates were found within the colour-magnitude-proper motion volume where such objects can be safely discriminated from any standard population as well as from possible artefacts. In the same volume, we estimate the maximum white dwarf halo fraction compatible with this observation at different significance levels if the halo is at least 14 gigayears old and under different ad hoc initial mass functions. Our data alone rules out a halo fraction greater than 14% at 95% confidence level. Combined with two previous investigations exploring comparable volumes pushes the limit below 4 % (95% confidence level) or below 1.3% (64% confidence), this implies that if baryonic dark matter is present in galaxy halos, it is not, or it is only marginally in the form of faint hydrogen white dwarfs.Comment: accepted in Astronomy and Astrophysics (19-05-2004

A constitutive law for dense granular flows

A continuum description of granular flows would be of considerable help in predicting natural geophysical hazards or in designing industrial processes. However, the constitutive equations for dry granular flows, which govern how the material moves under shear, are still a matter of debate. One difficulty is that grains can behave like a solid (in a sand pile), a liquid (when poured from a silo) or a gas (when strongly agitated). For the two extreme regimes, constitutive equations have been proposed based on kinetic theory for collisional rapid flows, and soil mechanics for slow plastic flows. However, the intermediate dense regime, where the granular material flows like a liquid, still lacks a unified view and has motivated many studies over the past decade. The main characteristics of granular liquids are: a yield criterion (a critical shear stress below which flow is not possible) and a complex dependence on shear rate when flowing. In this sense, granular matter shares similarities with classical visco-plastic fluids such as Bingham fluids. Here we propose a new constitutive relation for dense granular flows, inspired by this analogy and recent numerical and experimental work. We then test our three-dimensional (3D) model through experiments on granular flows on a pile between rough sidewalls, in which a complex 3D flow pattern develops. We show that, without any fitting parameter, the model gives quantitative predictions for the flow shape and velocity profiles. Our results support the idea that a simple visco-plastic approach can quantitatively capture granular flow properties, and could serve as a basic tool for modelling more complex flows in geophysical or industrial applications.Comment: http://www.nature.com/nature/journal/v441/n7094/abs/nature04801.htm