51,355 research outputs found

    Agenda Draft for PCAST Meeting

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    Draft agenda for meetings of the President's Council of Advisors on Science and Technology (PCAST) on April 4-5, 1991

    Spin structure and dynamics of the topological semimetal Co3Sn2-x In x S2

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    Abstract The anomalous Hall effect (AHE), typically observed in ferromagnetic (FM) metals with broken time-reversal symmetry, depends on electronic and magnetic properties. In Co3Sn2-x In x S2, a giant AHE has been attributed to Berry curvature associated with the FM Weyl semimetal phase, yet recent studies report complicated magnetism. We use neutron scattering to determine the spin dynamics and structures as a function of x and provide a microscopic understanding of the AHE and magnetism interplay. Spin gap and stiffness indicate a contribution from Weyl fermions consistent with the AHE. The magnetic structure evolves from c-axis ferromagnetism at x=0x = 0 x = 0 to a canted antiferromagnetic (AFM) structure with reduced c-axis moment and in-plane AFM order at x=0.12x = 0.12 x = 0.12 and further reduced c-axis FM moment at x=0.3x = 0.3 x = 0.3 . Since noncollinear spins can induce non-zero Berry curvature in real space acting as a fictitious magnetic field, our results revealed another AHE contribution, establishing the impact of magnetism on transport

    D. Allan Bromley Drafts for Fiscal Year 1992 Budget Memorandum

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    A set of memoranda sent for review to James W. Cicconi from D. Allan Bromley, Director of the Office of Science and Technology Policy (OSTP), intended for delivery to President Bush and Secretary of Defense Dick Cheney concerning the science and technology budget for the 1991 fiscal year. The memoranda contain edits and comments from various White House personnel, including Chief of Staff John Sununu and the staff of the Office of Management and Budget (OMB)

    FAMILY CONCERT 'Peter and the Wolf' Saturday, February 11, 2012 11:00 a.m. Stude Concert Hall

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    Presented by the Shepherd SocietyPROGRAM: Peter and the Wolf, Op. 67 / Sergei Prokofie

    Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing

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    Carbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing

    VIKTOR VALKOV Piano DOCTORAL CHAMBER RECITAL Thursday, March 8, 2012 8:00 p.m. Lillian H. Duncan Recital Hall

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    PROGRAM: Sonata for Cello and Piano in G Minor, Op. 19 / Sergei Rachmaninoff -- Piano Trio No. 2 in E Minor, Op. 92 / Camille Saint-SaensThis recital is given in partial fulfillment of the requirements for Doctor of Musical Arts degree

    BUON SAN VALENTINO! featuring voice students of Stephen King Tuesday, February 14, 2012 8:00 p.m. Lillian H. Duncan Recital Hall

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    PROGRAM: Per la gloria d'adorarvi / Giovanni Bonocini -- Sole e amore / Giacomo Puccini -- Benedetto sia'l giorno / Franz Liszt -- Visione veneziana / Renato Brogi -- Il traditor deluso / Franz Schubert -- Guarda, che bianca luna / Franz Schubert -- Me voglio fana casa / Gaetano Donizetti -- Stornello / Giuseppe Verdi -- La danza / Gioachino Rossini -- Appassionato / Ildebrando Pizzetti -- Levommi il mio pensier... / Ildebrando Pizzetti -- L'alba separa dalla luce l'ombra / Francesco Paolo Tosti -- Mi lagnero tacendo... / Gioachino Rossini -- La Bella Aurora / Nicholas Flagello -- Il bacio / Luigi Arditi -- O sole mio / Eduardo il Capu

    AARON BLAKE Tenor MASTER'S RECITAL Sunday, April 20, 2008 8:00 p.m. Lillian H. Duncan Recital Hall

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    PROGRAM: Four Arias / George Frideric Handel -- Canzonetti di camera / Vincenzo Bellini -- Vier Lieder / Richard Strauss -- Tre Sonetti di Petrarca / Franz Liszt -- Hollywood in the '30s / George and Ira GershwinThis recital is given in partial fulfillment of the requirements for the Master of Music degree

    MARTIN DIMITROV Violin MASTER'S RECITAL Monday, April 7, 2008 8:00 p.m. Lillian H. Duncan Recital Hall

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    PROGRAM: Violin Concerto No. 4 in D Major, K. 218 / Wolfgang Amadeus Mozart -- Sonate in E Minor, Op. 27 No. 4 "A Fritz Kreisler" / Eugene Ysaye -- Notturno e Tarantella, Op. 28 / Karol SzymanowskiThis recital is given in partial fulfillment of the requirements for the Master of Music degree

    Tracing oxygen cycling in the ocean by dissolved oxygen multi-isotopologues

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    Understanding the distribution and cycling of O2 is one of the core scientific questions in oceanography. The distribution of dissolved oxygen is influenced by physical, biochemical, and abiotic chemical processes. However, determining the relative importance of each mechanism in different environments remains difficult. This thesis utilizes the dissolved oxygen multiple isotopologues (16O16O, 16O17O, 16O18O, 17O18O, 18O18O), which participate biogeochemical cycling, advection, and diffusion as new direct tracers to constrain these processes. The theme of my first project is the oxygen production in the surface ocean, with a particular focus on the isotopic effects of gas exchange when the mixed layer is out of solubility equilibrium. Here we measured the kinetic and equilibrium fractionation factors for the four rare O2 isotopologues 16O17O, 16O18O, 17O18O, 18O18O relative to 16O16O in air-water gas transfer experiments. Moreover, we evaluate the possible effects of the updated fractionation factors on multiple isotopologue-based gross oxygen production (GOP) estimates and connect the observed air-water kinetic fractionation factors to dissolved-phase diffusive isotopic fractionation. Next, this thesis shifts the focus to the subsurface ocean, where uncertainties in transport flux and isotopic fractionation factors have long confounded the interpretation of the isotopic composition of dissolved oxygen. Therefore, we investigated the systematics of oxygen isotopologues in the subsurface Pacific using new data and a 2-D isotopologues-enabled isopycnal reaction-transport model. We measured multiple O2 isotopologues in the northeast Pacific, and compared them to previously published data. We find that transport and respiration rates constrained by O2 concentrations in the oligotrophic Pacific yield good measurement-model agreement across all O2 isotopologues when using a recently reported set of respiratory isotopologue fractionation factors. Estimated respiration rates range from 0.5 to 2.7 μmol/kg/yr for various isopycnal surfaces consistent with those previously inferred for the Atlantic. Lastly, this thesis attempts to address the mystery of puzzlingly low 17O/16O ratios observed for some subsurface low-oxygen samples. We resampled and remeasured the dissolved oxygen isotopologues at the San Pedro Ocean Time Series (SPOT) site, where low 17O/16O ratios were reported in previous studies. We find that this low ratio is caused by a typical analytical artifact, pressure baseline effect (PBE), which exhibits a non-linear behavior with the fraction of inert gas present in the analyte and can cause an overestimation of GOP at SPOT. A correction on these previously reported low 17O/16O ratios were applied to the GOP estimation model, in which we find that calculated GOP at SPOT can be overestimated by ~50 mmol O2/(m2d). Therefore, we underscore the necessity of a pre-purification process for insert gas removal during dissolved oxygen isotope measurements to avoid this potential PBE artifact
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