75 research outputs found

    First-order sidebands in circuit QED using qubit frequency modulation

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    Sideband transitions have been shown to generate controllable interaction between superconducting qubits and microwave resonators. Up to now, these transitions have been implemented with voltage drives on the qubit or the resonator, with the significant disadvantage that such implementations only lead to second-order sideband transitions. Here we propose an approach to achieve first-order sideband transitions by relying on controlled oscillations of the qubit frequency using a flux-bias line. Not only can first-order transitions be significantly faster, but the same technique can be employed to implement other tunable qubit-resonator and qubit-qubit interactions. We discuss in detail how such first-order sideband transitions can be used to implement a high fidelity controlled-NOT operation between two transmons coupled to the same resonator.Comment: 15 pages, 5 figure

    The morphology of polymer modified asphalt and its relationship to rheology and durability

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    Polymers are added to asphalt binders primarily to stiffen the binder at higher temperatures and thus to protect the pavement against rutting at summertime temperatures early in the pavement's life. Also, it has been noted that polymers typically increase the ductility of a binder and that some polymer-asphalt combinations are especially effective. Furthermore, it is hypothesized that enhancing a binder's ductility, and maintaining this enhancement with binder oxidative aging, contributes to enhanced binder durability in pavements. However, polymer-asphalt interactions and how they might contribute to improved binder performance is not well understood. The goal of this work was to probe the relationship of polymer morphology on asphalt binder rheology and mixture durability. Experiments were conducted on asphalt mixtures and binders, and as a function of oxidative aging. PFC mixtures, which are an open mixture designed to allow enhanced water drainage, were of specific interest. These mixtures were tested for Cantabro Loss, an indicator of a mixture's likelihood of failure by raveling. Asphalt binders were tested using dynamic shear rheometry (DSR), which provided the DSR function, (G' /η'/G'), a measure of binder stiffness that includes both the elastic modulus and the flow viscosity), ductility (used to measure the elongation a binder could withstand before failure), gel permeation chromatography (GPC), used to estimate the relative amount of polymer) and fluorescence microscopy (used to image the polymer morphology in the asphalt binder). From these data, relationships were assessed between binder morphology and binder rheology and between binder rheology and mixture durability, all as a function of binder oxidative aging. Polymer morphology related to ductility enhancement. Polymer morphology related to a change in the DSR function, relative to the amount of polymer, as measured by the polymer GPC peak height. Cantabro loss correlated to the DSR function (R2=0.963). The overall conclusion is that polymer morphology, as indicated by fluorescence microscopy, relates to both the rheological properties of the binder and the Cantabro loss of the mixture. These relationships should yield a better understanding of polymer modification, increased mixture durability (decreased raveling) and improved rheological properties (DSR function and ductility)

    The Effect of Tourniquet Use and Sterile CO2 Gas Bone Preparation on Cement Penetration in Primary Total Knee Arthroplasty

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    Introduction Tourniquetless total knee arthroplasty (TKA) is experiencing resurgence in popularity due to potential pain control benefits. Further, optimal cement technique and implant fixation remain paramount to long-term cemented TKA success, as aseptic loosening continues to be a leading cause of revision. The purpose of this study was to determine how tourniquet use and/or novel bone preparation using sterile, compressed carbon dioxide (CO2) gas affected cement penetration in TKA. Methods A retrospective review was performed on 303 consecutive primary TKAs with the same implant in three groups: (1) a tourniquet without sterile CO2 compressed gas used for bone preparation, (2) no tourniquet with CO2 gas, and (3) tourniquet use and CO2 gas bone preparation. Cement penetration was measured on radiographs by two independent, blinded raters across seven zones defined by the Knee Society Radiographic Evaluation System. Results The three groups did not differ on age, BMI, or sex (p≥0.1). Cement penetration was greater in six of seven zones with significantly greater cement penetration in three zones (Tibial AP Zone 2, Femoral Lateral Zones 3A and 3P) in groups that utilized CO2 gas bone preparation compared to the tourniquet only group (p≤0.039). Conclusion Bone prepared with CO2 gas showed significantly more cement penetration in three zones with greater cancellous bone. The results suggest use of CO2 gas bone preparation may achieve greater cement penetration than using a tourniquet with lavage only

    Kepler-445, Kepler-446 And The Occurrence Of Compact Multiples Orbiting Mid-M Dwarf Stars

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    We confirm and characterize the exoplanetary systems Kepler-445 and Kepler-446: two mid-M dwarf stars, each with multiple, small, short-period transiting planets. Kepler-445 is a metal-rich ([ Fe/H] = + 0.25 0.10) M4 dwarf with three transiting planets, and Kepler-446 is a metal-poor ([ Fe/H] = -0.30 0.10) M4 dwarf also with three transiting planets. Kepler-445c is similar toGJ 1214b: both in planetary radius and the properties of the host star. The Kepler-446 system is similar to the Kepler-42 system: both are metal-poor with large galactic space velocities and three short-period, likely rocky transiting planets that were initially assigned erroneously large planet-to-star radius ratios. We independently determined stellar parameters from spectroscopy and searched for and fitted the transit light curves for the planets, imposing a strict prior on stellar density in order to remove correlations between the fitted impact parameter and planet-to-star radius ratio for short-duration transits. Combining Kepler-445, Kepler-446, and Kepler-42, and isolating all mid-M dwarf stars observed by Kepler with the precision necessary to detect similar systems, we calculate that 21+ 7 -5 % of mid-M dwarf stars host compact multiples ( multiple planets with periods of less than 10 days) for a wide range of metallicities. We suggest that the inferred planet masses for these systems support highly efficient accretion of protoplanetary disk metals by mid-M dwarf protoplanets.NSF DGE1144152, AST-1005313NASA NAS5-26555NASA Office of Space Science NNX13AC07GAstronom

    The shadow knows: using shadows to investigate the structure of the pretransitional disk of HD 100453

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    We present GPI polarized intensity imagery of HD 100453 in Y-, J-, and K1 bands which reveals an inner gap (9189 - 18 au), an outer disk (183918-39 au) with two prominent spiral arms, and two azimuthally-localized dark features also present in SPHERE total intensity images (Wagner 2015). SED fitting further suggests the radial gap extends to 11 au. The narrow, wedge-like shape of the dark features appears similar to predictions of shadows cast by a inner disk which is misaligned with respect to the outer disk. Using the Monte Carlo radiative transfer code HOCHUNCK3D (Whitney 2013), we construct a model of the disk which allows us to determine its physical properties in more detail. From the angular separation of the features we measure the difference in inclination between the disks 45^{\circ}, and their major axes, PA = 140^{\circ} east of north for the outer disk and 100^{\circ}for the inner disk. We find an outer disk inclination of 25±1025 \pm 10^{\circ} from face-on in broad agreement with the Wagner 2015 measurement of 34^{\circ}. SPHERE data in J- and H-bands indicate a reddish disk which points to HD 100453 evolving into a young debris disk

    Computational Framework for the Identification of Bioprivileged Molecules

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    Bioprivileged molecules are biology-derived chemical intermediates that can be efficiently converted to a diversity of chemical products including both novel molecules and drop-in replacements. Bridging chemical and biological catalysis by bioprivileged molecules provides a useful and flexible new paradigm for producing biobased chemicals. However, the discovery of bioprivileged molecules has been demonstrated to require extensive experimental effort over a long period of time. In this work, we developed a computational framework for identification of all possible C6HxOy molecules (29252) that can be honed down to a manageable number of candidate bioprivileged molecules based on analysis of structural features, reactive moieties, and reactivity of species, and the evaluation of the reaction network and resulting products based on automated network generation. Required input is the structure data file (SDF) of the starting molecules and the reaction rules. On-the-fly estimation of thermodynamics by a group contribution method is introduced as a screening criterion to identify the feasibility of reactions and pathways. Generated species are dynamically linked to the PubChem database for identification of novel products and evaluation of the known products as attractive candidates. Application of the proposed computational framework in screening 29252 C6 species and identifying a list of 100 C6HxOy bioprivileged molecule candidates is presented. Each of the 100 candidate molecules falls into one of nine broad compound classes and is typically composed of carbon atoms with a different chemical environment and, as a result, distinct reactivity patterns. Sensitivity analysis of the parameters used in the filtering steps leading to the candidate molecules that were identified is discussed, and analysis of favorable structural features, reactive moieties, and functionalities of C6HxOy candidate bioprivileged molecules is performed

    Differences in the gas and dust distribution in the transitional disk of a sun-like young star, PDS 70

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    We present ALMA 0.87 mm continuum, HCO+ J=4--3 emission line, and CO J=3--2 emission line data of the disk of material around the young, Sun-like star PDS 70. These data reveal the existence of a possible two component transitional disk system with a radial dust gap of 0."2 +/- 0."05, an azimuthal gap in the HCO+ J=4--3 moment zero map, as well as two bridge-like features in the gas data. Interestingly these features in the gas disk have no analogue in the dust disk making them of particular interest. We modeled the dust disk using the Monte Carlo radiative transfer code HOCHUNK3D (Whitney et al. 2013) using a two disk components. We find that there is a radial gap that extends from 15-60 au in all grain sizes which differs from previous work

    COMPAR TIVE STUDIES IN TRACTION CONCEPTS

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    ABSTRACT The interaction between tires and soft soils is a complex process that has not yet been fully understood. Attempts to create analytical models which realistically simulate these interactions have proven to be exceedingly time consuming for each tire model and have achieved only limited success. Thus, the exploration and evaluation of traction concepts by analytical means is impractical. This paper posits that significantly more reliable, rapid, and cost effective development is achieved through the prototyping and experimental evaluation of traction concepts. Here, three traction prototypes are developed and evaluated by undergraduate teams in the course of an academic semester. These concepts explore the performance of grousers, inverted geometry (dimples), and cellular materials respectively using a wheel endurance and soft-soil traction testing system at Clemson University. Each concept is tested at different acceleration rates from 0-10km/h and at different loads while measuring the slip between the tire and soil surfaces. The results of experimental evaluation indicate that cellular materials present a unique slip profile which is superior to that of the two other purely geometric concepts studied. The worst performance was seen on the inverse geometry concept which presented a behavior of steadily increasing slip with respect to wheel velocity regardless of acceleration. Grousers also presented this behavior but only at higher accelerations. This suggests that not only that prototyping is preferable, but that traditional soft-soil traction approaches may be in error
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