Advanced detectors and signal processing

Continued progress is reported toward development of a silicon on garnet technology which would allow fabrication of advanced detection and signal processing circuits on bubble memories. The first integrated detectors and propagation patterns have been designed and incorporated on a new mask set. In addition, annealing studies on spacer layers are performed. Based on those studies, a new double layer spacer is proposed which should reduce contamination of the silicon originating in the substrate. Finally, the magnetic sensitivity of uncontaminated detectors from the last lot of wafers is measured. The measured sensitivity is lower than anticipated but still higher than present magnetoresistive detectors

Paragonimiasis In Iowa

The presence of the lung fluke, Paragonimus kelliocotti, was first recorded in the United States in a cat in 1894. It was first recognized in domesticated animals in Iowa in a dog from Blackhawk County in 1948. Subsequently, paragonimiasis has been diagnosed in dogs from Polk and Dallas counties. An additional case was found in a dog from an unrecorded county. Also, one cat from Story County has been found to harbor P. kellicotti

Evaluation of the ALMA Prototype Antennas

The ALMA North American and European prototype antennas have been evaluated by a variety of measurement systems to quantify the major performance specifications. Nearfield holography was used to set the reflector surfaces to 17 microns RMS. Pointing and fast switching performance was determined with an optical telescope and by millimeter wavelength radiometry, yielding 2 arcsec absolute and 0.6 arcsec offset pointing accuracies. Path length stability was measured to be less than or approximately equal to 20 microns over 10 minute time periods using optical measurement devices. Dynamical performance was studied with a set of accelerometers, providing data on wind induced tracking errors and structural deformation. Considering all measurements made during this evaluation, both prototype antennas meet the major ALMA antenna performance specifications.Comment: 83 pages, 36 figures, AASTex format, to appear in PASP September 2006 issu

Interferometric Observations of Powerful CO Emission from the three Submillimeter Galaxies at z=2.30, 2.51 and 3.35

We report IRAM Plateau de Bure, millimeter interferometry of three z=~2.4 to 3.4, SCUBA deep field galaxies. Our CO line observations confirm the rest-frame UV/optical redshifts, thus more than doubling the number of confirmed, published redshifts of the faint submillimeter population and proving their high-z nature. In all three sources our measurements of the intrinsic gas and dynamical mass are large (1e10 to 1e11 Msun). In at least two cases the data show that the submillimeter sources are part of an interacting system. Together with recent information gathered in the X-ray, optical and radio bands our observations support the interpretation that the submm-population consists of gas rich (gas to dynamical mass ratio ~0.5) and massive, composite starburst/AGN systems, which are undergoing a major burst of star formation and are evolving into m*-galaxies.Comment: only minor modifications to comply with the ApJL edition rule

Effects of hydrogen on the morphology and electrical properties of GaN grown by plasma-assisted molecular-beam epitaxy

We study the effect of introducing hydrogen gas through the rf-plasma source during plasma-assisted molecular-beam epitaxy of GaN(0001). The well-known smooth-to-rough transition that occurs for this surface as a function of decreasing Ga flux in the absence of H is found to persist even with H present, although the critical Ga flux for this transition increases. Under Ga-rich conditions, the presence of hydrogen is found to induce step bunching (facetting) on the surface. Conductive atomic force microscopy reveals that leakage current through dislocation cores is significantly reduced when hydrogen is present during the growth

Millimetre-VLBI Monitoring of AGN with Sub-milliarcsecond Resolution

Global millimetre VLBI allows detailed studies of the most central jet regions of AGN with unprecedent spatial resolution of a few 100-1000 Schwartzschild radii to be made. Study of these regions will help to answer the question how the highly relativistic AGN jets are launched and collimated. Since the early 1990s, bright mm-sources have been observed with global 3 mm VLBI. Here we present new images from an ongoing systematic analysis of the available observations. In particular, we focus on the structure and structural evolution of the best observed AGN jets, taking 3C 454.3 as a characteristic example. This core-dominated and highly variable quasar shows a complex morphology with individual jet components accelerating superluminally towards the outer structure. We briefly discuss the X-ray properties of 3C 454.3 and present its radio- to X-ray large-scale brightness distribution.Comment: 4 pages, 4 figures, Proceedings of the 7th EVN Symposium held in Toledo, Spain in October 2004, needs evn2004.cl

A MEMS Phased Array Transducer for Ultrasonic Flaw Detection

Abstract Metal and have been applied for imaging [5,6] and nondestructive testing [7]. We are adapting capacitive diaphragm transducers for application to structural monitoring. In this application we intend to permanently couple the transducers to a solid structure. We propose to use a single piezoelectric transducer as a source of ultrasonic energy, while an array of capacitive transducers is to be used as the detectors. In this way we can take advantage of the high efficiency of piezoelectric emitters when coupled to solids with similar acoustic impedance. The array of MEMS detectors will be used as a phased array in order to scan for defects or cracks near the emitter

The N Enrichment and Supernova Ejection of the Runaway Microquasar LS 5039

We present an investigation of new optical and ultraviolet spectra of the mass donor star in the massive X-ray binary LS 5039. The optical band spectral line strengths indicate that the atmosphere is N-rich and C-poor, and we classify the stellar spectrum as type ON6.5 V((f)). The N-strong and C-weak pattern is also found in the stellar wind P Cygni lines of N V 1240 and C IV 1550. We suggest that the N-enrichment may result from internal mixing if the O-star was born as a rapid rotator, or the O-star may have accreted N-rich gas prior to a common-envelope interaction with the progenitor of the supernova. We re-evaluated the orbital elements to find an orbital period of P=4.4267 +/- 0.0010 d. We compared the spectral line profiles with new non-LTE, line-blanketed model spectra, from which we derive an effective temperature T_eff = 37.5 +/- 1.7 kK, gravity log g = 4.0 +/- 0.1, and projected rotational velocity V sin i = 140 +/- 8 km/s. We fit the UV, optical, and IR flux distribution using a model spectrum and extinction law with parameters E(B-V)= 1.28 +/- 0.02 and R= 3.18 +/- 0.07. We confirm the co-variability of the observed X-ray flux and stellar wind mass loss rate derived from the H-alpha profile, which supports the wind accretion scenario for the X-ray production in LS 5039. Wind accretion models indicate that the compact companion has a mass M_X/M_sun = 1.4 +/- 0.4, consistent with its identification as a neutron star. The observed eccentricity and runaway velocity of the binary can only be reconciled if the neutron star received a modest kick velocity due to a slight asymmetry in the supernova explosion (during which >5 solar masses was ejected).Comment: 38 pages, 9 figures; 2004, ApJ, 600, Jan. 10 issue, in press Discussion revised thanks to comments from P. Podsiadlowsk

Towards Quantum Repeaters with Solid-State Qubits: Spin-Photon Entanglement Generation using Self-Assembled Quantum Dots

In this chapter we review the use of spins in optically-active InAs quantum dots as the key physical building block for constructing a quantum repeater, with a particular focus on recent results demonstrating entanglement between a quantum memory (electron spin qubit) and a flying qubit (polarization- or frequency-encoded photonic qubit). This is a first step towards demonstrating entanglement between distant quantum memories (realized with quantum dots), which in turn is a milestone in the roadmap for building a functional quantum repeater. We also place this experimental work in context by providing an overview of quantum repeaters, their potential uses, and the challenges in implementing them.Comment: 51 pages. Expanded version of a chapter to appear in "Engineering the Atom-Photon Interaction" (Springer-Verlag, 2015; eds. A. Predojevic and M. W. Mitchell

Resonant capacitive MEMS acoustic emission transducers

Abstract. We describe resonant capacitive MEMS transducers developed for use as acoustic emission detectors, fabricated in the commercial three-layer polysilicon surface micromachining process (MUMPs). The 1-cm square device contains six independent transducers in the frequency range between 100 kHz and 500 kHz, and a seventh transducer at 1 MHz. Each transducer is a parallel plate capacitor with one plate free to vibrate, thereby causing a capacitance change which creates an output signal in the form of a current under DC bias voltage. With the geometric proportions we employed, each transducer responds with two distinct resonant frequencies. In our design the etch hole spacing was chosen to limit squeeze film damping and thereby produce an underdamped vibration when operated at atmospheric pressure. Characterization experiments obtained by capacitance and admittance measurements are presented, and transducer responses to physically simulated AE source are discussed. Finally, we report our use of the device to detect acoustic emissions associated with crack initiation and growth in weld metal