2,509 research outputs found

    Quantum Mechanics helps in searching for a needle in a haystack

    Get PDF
    Quantum mechanics can speed up a range of search applications over unsorted data. For example imagine a phone directory containing N names arranged in completely random order. To find someone's phone number with a probability of 50%, any classical algorithm (whether deterministic or probabilistic) will need to access the database a minimum of O(N) times. Quantum mechanical systems can be in a superposition of states and simultaneously examine multiple names. By properly adjusting the phases of various operations, successful computations reinforce each other while others interfere randomly. As a result, the desired phone number can be obtained in only O(sqrt(N)) accesses to the database.Comment: Postscript, 4 pages. This is a modified version of the STOC paper (quant-ph/9605043) and is modified to make it more comprehensible to physicists. It appeared in Phys. Rev. Letters on July 14, 1997. (This paper was originally put out on quant-ph on June 13, 1997, the present version has some minor typographical changes

    Mixed Early and Late-Type Properties in the Bar of NGC 6221: Evidence for Evolution along the Hubble Sequence?

    Get PDF
    Rotation curves and velocity dispersion profiles are presented for both the stellar and gaseous components along five different position angles (P.A.=5, 50, 95, 125 and 155 degrees) of the nearby barred spiral NGC 6221. The observed kinematics extends out to about 80" from the nucleus. Narrow and broad-band imaging is also presented. The radial profiles of the fluxes ratio [NII]/Halpha reveal the presence of a ring-like structure of ionized gas, with a radius of about 9" and a deprojected circular velocity of about 280 km/s. The analysis of the dynamics of the bar indicates this ring is related to the presence of an inner Lindblad resonance (ILR) at 1.3 kpc. NGC6221 is found to exhibit intermediate properties between those of the early-type barred galaxies: the presence of a gaseous ring at an ILR, the bar edge located between the ILR's and the corotation radius beyond the steep rising portion of the rotation curve, the dust-lane pattern, and those of the late-type galaxies: an almost exponential surface brightness profile, the presence of Halpha regions along all the bar, the spiral-arm pattern. It is consistent with scenarios of bar-induced evolution from later to earlier-type galaxies.Comment: 1 File ds7406.tar.gz which contains: one latex file (ds7406.tex), and 10 encsulated postscript figures (ds7406f**.eps). To be compiled with aa-l latex2e macro style. To be published in A&A Sup. Serie

    SAGA: A project to automate the management of software production systems

    Get PDF
    The project to automate the management of software production systems is described. The SAGA system is a software environment that is designed to support most of the software development activities that occur in a software lifecycle. The system can be configured to support specific software development applications using given programming languages, tools, and methodologies. Meta-tools are provided to ease configuration. Several major components of the SAGA system are completed to prototype form. The construction methods are described

    Microstructural origin for the piezoelectricity evolution in (K0.5Na0.5)NbO3-based lead-free ceramics

    Get PDF
    Chemically modified (K0.5Na0.5)NbO3 compositions with finely tuned polymorphic phase boundaries (PPBs) have shown excellent piezoelectric properties. The evolution of the domain morphology and crystal structure under applied electric fields of a model material, 0.948(K0.5Na0.5)NbO3-0.052LiSbO3, was directly visualized using in situ transmission electron microscopy. The in situ observations correlate extremely well with measurements of the electromechanical response on bulk samples. It is found that the origin of the excellent piezoelectric performance in this lead-free composition is due to a tilted monoclinic phase that emerges from the PPB when poling fields greater than 14 kV/cm are applied. 2013 AIP Publishing LLC

    Frugivory and Seed Dispersal by Carnivorans

    Get PDF
    Seed dispersal is critical to the ecological performance of sexually reproducing plant species and the communities that they form. The Mammalian order Carnivora provide valuable and effective seed dispersal services but tend to be overlooked in much of the seed dispersal literature. Here we review the literature on the role of Carnivorans in seed dispersal, with a literature search in the Scopus reference database. Overall, we found that Carnivorans are prolific seed dispersers. Carnivorans’ diverse and plastic diets allow them to consume large volumes of over a hundred families of fruit and disperse large quantities of seeds across landscapes. Gut passage by these taxa generally has a neutral effect on seed viability. While the overall effect of Carnivorans on seed dispersal quality is complex, Carnivorans likely increase long-distance dispersal services that may aid the ability of some plant species to persist in the face of climate change

    Are We Missing an Opportunity? Prediabetes in the U.S. Military

    Get PDF
    INTRODUCTION: The prevalence of prediabetes is estimated to be one-third of Americans with approximately 80% of these individuals unaware of the diagnosis. In the active duty military population, the prevalence of prediabetes is largely unexplored. The purpose of this study was to investigate the prevalence of prediabetes in military service members by quantifying those meeting prediabetes screening criteria, those actually being screened, and those being appropriately diagnosed. MATERIALS AND METHODS: Data were analyzed from calendar years 2014 to 2018 for active duty service members 18 years of age or older. Vitals records were collected to obtain body mass index values. Composite Health Care System laboratory data were queried for hemoglobin A1c (HbA1c) results as well as fasting plasma glucose (FPG) and oral glucose tolerance test (OGTT) results. The percentage of active duty service members meeting criteria for prediabetes screening was determined by totaling members age 45 and older with members age 18- to 44-year old with a body mass index ≥25.0 kg/m2, then dividing by the total number of members for each respective military branch. The percentage of active duty service members actually screened for prediabetes was determined based on members meeting prediabetes screening criteria who in fact had FPG, OGTT, or HbA1c labs. The total number of labs meeting prediabetes criteria was determined based on those aforementioned labs with results in the prediabetes range (FPG between 100 and 125 mg/dL, OGTT between 140 and 199 mg/dL, or HbA1c range of 5.7%-6.4%). The total number of service members with appropriate prediabetes International Classification of Disease (ICD) code was determined by identifying members with ICD-9 and ICD-10 codes 790.21, 790.22, and R73.01-R73.03 in their medical record. RESULTS: From 2014 to 2018, 53.9% of 332,502, 56% of 543,081, and 47.3% of 531,313 active duty service members in the Air Force, Army and Navy, respectively, met criteria for prediabetes screening. The rates of actually screening for prediabetes were similar across the Air Force (4.8%), Army (6.7%), and Navy (5.5%). The percentage with labs meeting prediabetes criteria ranged from 17.9% to 28.4% in the Air Force, 24.2% to 30.3% in the Army, and 24.2% to 30.9% in the Navy. The rate of ICD coding for prediabetes increased from 2014 to 2018 across all branches (29.8%-65.3% for the Air Force, 24.6%-46.8% for the Army, and 40.0%-45.5% for the Navy). CONCLUSION: Screening for prediabetes in the active duty military population is grossly inadequate, and even of those screened, diagnosing those meeting prediabetes criteria is similarly inadequate. Although this scenario is not unique to the Military Health System, but reflective of a larger national problem, efforts should be made within the Military Health System to increase the screening for this common disorder. Identifying service members with prediabetes enables opportunities for targeted interventions to delay or prevent the progression to diabetes mellitus

    Perfect quantum error correction coding in 24 laser pulses

    Get PDF
    An efficient coding circuit is given for the perfect quantum error correction of a single qubit against arbitrary 1-qubit errors within a 5 qubit code. The circuit presented employs a double `classical' code, i.e., one for bit flips and one for phase shifts. An implementation of this coding circuit on an ion-trap quantum computer is described that requires 26 laser pulses. A further circuit is presented requiring only 24 laser pulses, making it an efficient protection scheme against arbitrary 1-qubit errors. In addition, the performance of two error correction schemes, one based on the quantum Zeno effect and the other using standard methods, is compared. The quantum Zeno error correction scheme is found to fail completely for a model of noise based on phase-diffusion.Comment: Replacement paper: Lost two laser pulses gained one author; added appendix with circuits easily implementable on an ion-trap compute

    When Is a Bulge Not a Bulge? Inner Disks Masquerading as Bulges in NGC 2787 and NGC 3945

    Full text link
    We present a detailed morphological, photometric, and kinematic analysis of two barred S0 galaxies with large, luminous inner disks inside their bars. We show that these structures, in addition to being geometrically disk-like, have exponential profiles (scale lengths ∼\sim 300--500 pc) distinct from the central, non-exponential bulges. We also find them to be kinematically disk-like. The inner disk in NGC 2787 has a luminosity roughly twice that of the bulge; but in NGC 3945, the inner disk is almost ten times more luminous than the bulge, which itself is extremely small (half-light radius ≈\approx 100 pc, in a galaxy with an outer ring of radius ≈\approx 14 kpc) and only ∼\sim 5% of the total luminosity -- a bulge/total ratio much more typical of an Sc galaxy. We estimate that at least 20% of (barred) S0 galaxies may have similar structures, which means that their bulge/disk ratios may be significantly overestimated. These inner disks dominate the central light of their galaxies; they are at least an order of magnitude larger than typical ``nuclear disks'' found in ellipticals and early-type spirals. Consequently, they must affect the dynamics of the bars in which they reside.Comment: LaTeX, 37 pages, 14 EPS figures. To appear in The Astrophysical Journal (November 10, 2003 issue). Version with full-resolution figures available at http://www.iac.es/galeria/erwin/research

    Spiral inflow feeding the nuclear starburst in M83, observed in H-alpha emission with the GHAFAS Fabry-Perot interferometer

    Full text link
    We present observations of the nearby barred starburst galaxy, M83 (NGC5236), with the new Fabry-Perot interferometer GHAFAS mounted on the 4.2 meter William Herschel Telescope on La Palma. The unprecedented high resolution observations, of 16 pc/FWHM, of the H-alpha-emitting gas cover the central two kpc of the galaxy. The velocity field displays the dominant disk rotation with signatures of gas inflow from kpc scales down to the nuclear regions. At the inner Inner Lindblad Resonance radius of the main bar and centerd at the dynamical center of the main galaxy disk, a nuclear 5.5(±0.9)×108M⊙5.5 (\pm 0.9) \times 10^8 M_\odot rapidly rotating disk with scale length of 60±2060 \pm 20 pc has formed. The nuclear starburst is found in the vicinity as well as inside this nuclear disk, and our observations confirm that gas spirals in from the outer parts to feed the nuclear starburst, giving rise to several star formation events at different epochs, within the central 100 pc radius of M83.Comment: Accepted for publication in ApJ Letters. High-resolution version can be found at http://www.astro.su.se/~kambiz/DOC/paper-M83.pd
    • …
    corecore