On the Complexity of Randomly Weighted Voronoi Diagrams

In this paper, we provide an $O(n \mathrm{polylog} n)$ bound on the expected complexity of the randomly weighted Voronoi diagram of a set of $n$ sites in the plane, where the sites can be either points, interior-disjoint convex sets, or other more general objects. Here the randomness is on the weight of the sites, not their location. This compares favorably with the worst case complexity of these diagrams, which is quadratic. As a consequence we get an alternative proof to that of Agarwal etal [AHKS13] of the near linear complexity of the union of randomly expanded disjoint segments or convex sets (with an improved bound on the latter). The technique we develop is elegant and should be applicable to other problems

Unified S-band 30-foot Antenna Side Lobe Radiation

Unified S-band thirty-foot antenna side lobe radiatio

A distinct sortase SrtB anchors and processes a streptococcal adhesin AbpA with a novel structural property.

Surface display of proteins by sortases in Gram-positive bacteria is crucial for bacterial fitness and virulence. We found a unique gene locus encoding an amylase-binding adhesin AbpA and a sortase B in oral streptococci. AbpA possesses a new distinct C-terminal cell wall sorting signal. We demonstrated that this C-terminal motif is required for anchoring AbpA to cell wall. In vitro and in vivo studies revealed that SrtB has dual functions, anchoring AbpA to the cell wall and processing AbpA into a ladder profile. Solution structure of AbpA determined by NMR reveals a novel structure comprising a small globular α/β domain and an extended coiled-coil heliacal domain. Structural and biochemical studies identified key residues that are crucial for amylase binding. Taken together, our studies document a unique sortase/adhesion substrate system in streptococci adapted to the oral environment rich in salivary amylase

TADPOL: A 1.3 mm Survey of Dust Polarization in Star-forming Cores and Regions

We present {\lambda}1.3 mm CARMA observations of dust polarization toward 30 star-forming cores and 8 star-forming regions from the TADPOL survey. We show maps of all sources, and compare the ~2.5" resolution TADPOL maps with ~20" resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpret the detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in a statistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain. We discuss three main findings: (1) A subset of the sources have consistent magnetic field (B-field) orientations between large (~20") and small (~2.5") scales. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ~1000 AU scales of protostellar envelopes. (2) Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. (3) Finally, even at ~2.5" resolution we see the so-called "polarization hole" effect, where the fractional polarization drops significantly near the total intensity peak. All data are publicly available in the electronic edition of this article.Comment: 53 pages, 37 figures -- main body (13 pp., 3 figures), source maps (32 pp., 34 figures), source descriptions (8 pp.). Accepted by the Astrophysical Journal Supplemen

Multifrequency study of the ring nebula SG13

We investigate the morphology and kinematics of the interstellar medium in the environs of the open cluster Mrk50, which includes the Wolf-Rayet star WR157 and a number of early B-type stars. The analysis was performed using radio continuum images at 408 and 1420 MHz, and HI 21cm line data taken from the Canadian Galactic Plane Survey, molecular observations of the 12CO (J=1-0) line at 115 GHz from the Five College Radio Astronomy Observatory and available mid and far IR observations obtained with the MSX and IRAS satellites, respectively. This study allowed identification of the radio continuum and molecular counterpart of the ring nebula SG13, while no neutral atomic structure was found to be associated. The nebula is also detected in images in the mid and far infrared, showing the existence of dust well mixed with the ionized gas. We estimate the main physical parameters of the material linked to the nebula. The interstellar gas distribution in the environs of Mrk50 is compatible with a stellar wind bubble created by the mass loss from WR157. The distribution of young stellar object (YSO) candidates in the region shows that stellar formation activity may be present in the molecular shell that encircles the ring nebula.Comment: Accepted for publication in MNRAS, 13 pages, 11 figure

Complex Structure in Class 0 Protostellar Envelopes III: Velocity Gradients in Non-Axisymmetric Envelopes, Infall or Rotation?

We present an interferometric kinematic study of morphologically complex protostellar envelopes based on observations of the dense gas tracers N2H+ and NH3. The strong asymmetric nature of most envelopes in our sample leads us to question the common interpretation of velocity gradients as rotation, given the possibility of projection effects in the observed velocities. Several "idealized" sources with well-ordered velocity fields and envelope structures are now analyzed in more detail. We compare the interferometric data to position-velocity diagrams of kinematic models for spherical rotating collapse and filamentary rotating collapse. For this purpose, we developed a filamentary parametrization of the rotating collapse model to explore the effects of geometric projection on the observed velocity structures. We find that most envelopes in our sample have PV structures that can be reproduced by an infalling filamentary envelope projected at different angles within the plane of the sky. The infalling filament produces velocity shifts across the envelope that can mimic rotation, especially when viewed at single-dish resolutions and the axisymmetric rotating collapse model does not uniquely describe any dataset. Furthermore, if the velocities are assumed to reflect rotation, then the inferred centrifugal radii are quite large in most cases, indicating significant fragmentation potential or more likely another component to the line-center velocity. We conclude that ordered velocity gradients cannot be interpreted as rotation alone when envelopes are non-axisymmetric and that projected infall velocities likely dominate the velocity field on scales larger than 1000 AU.Comment: 37 pages, 15 Figures, 2 Tables, Accepted to Ap

Full observation of single-atom dynamics in cavity QED

We report the use of broadband heterodyne spectroscopy to perform continuous measurement of the interaction energy between one atom and a high-finesse optical cavity, during individual transit events of $\sim 250$ $\mu$s duration. Measurements over a wide range of atom-cavity detunings reveal the transition from resonant to dispersive coupling, via the transfer of atom-induced signals from the amplitude to the phase of light transmitted through the cavity. By suppressing all sources of excess technical noise, we approach a measurement regime in which the broadband photocurrent may be interpreted as a classical record of conditional quantum evolution in the sense of recently developed quantum trajectory theories.Comment: Submitted to Applied Physics B. Uses Revtex, 13 pages with 11 EPS figure

A methodology for the efficient integration of transient constraints in the design of aircraft dynamic systems

Transient regimes experienced by dynamic systems may have severe impacts on the operation of the aircraft. They are often regulated by dynamic constraints, requiring the dynamic signals to remain within bounds whose values vary with time. The verification of these peculiar types of constraints, which generally requires high-fidelity time-domain simulation, intervenes late in the system development process, thus potentially causing costly design iterations. The research objective of this thesis is to develop a methodology that integrates the verification of dynamic constraints in the early specification of dynamic systems. In order to circumvent the inefficiencies of time-domain simulation, multivariate dynamic surrogate models of the original time-domain simulation models are generated using wavelet neural networks (or wavenets). Concurrently, an alternate approach is formulated, in which the envelope of the dynamic response, extracted via a wavelet-based multiresolution analysis scheme, is subject to transient constraints. Dynamic surrogate models using sigmoid-based neural networks are generated to emulate the transient behavior of the envelope of the time-domain response. The run-time efficiency of the resulting dynamic surrogate models enables the implementation of a data farming approach, in which the full design space is sampled through a Monte-Carlo Simulation. An interactive visualization environment, enabling what-if analyses, is developed; the user can thereby instantaneously comprehend the transient response of the system (or its envelope) and its sensitivities to design and operation variables, as well as filter the design space to have it exhibit only the design scenarios verifying the dynamic constraints. The proposed methodology, along with its foundational hypotheses, is tested on the design and optimization of a 350VDC network, where a generator and its control system are concurrently designed in order to minimize the electrical losses, while ensuring that the transient undervoltage induced by peak demands in the consumption of a motor does not violate transient power quality constraints.Ph.D.Committee Chair: Mavris, Dimitri; Committee Member: Charrier, Jean-Jacques; Committee Member: Garcia, Elena; Committee Member: Grijalva, Santiago; Committee Member: Schrage, Danie