Probing intrinsic transport properties of single metal nanowires: Direct-write contact formation using a focused ion beam

The transport characteristics of 70-nm-diameter platinum nanowires (NWs), fabricated using a pore-templated electrodeposition process and individually contacted using a focused ion beam (FIB) method, are reported. This approach yields nanowire devices with low contact resistances (similar to400 Omega) and linear current-voltage characteristics for current densities up to 65 kA/cm(2). The intrinsic nanowire resistivity (33+/-5 muOmega cm) indicates significant contributions from surface- and grain-boundary scattering mechanisms. Fits to the temperature dependence of the intrinsic NW resistance confirm that grain-boundary scattering dominates surface scattering (by more than a factor of 2) at all temperatures. Our results demonstrate that FIB presents a rapid and flexible method for the formation of low-resistance ohmic contacts to individual metal nanowires, allowing intrinsic nanowire transport properties to be probed

New Relations for Coefficients of Fractional Parentage--the Redmond Recursion Formula with Seniority

We find a relationship between coefficients of fractional parentage (cfp) obtained on the one hand from the principal parent method and on the other hand from a seniority classification. We apply this to the Redmond recursion formula which relates $n \to n+1$ cfp's to $n-1 \to n$ cfp's where the principal parent classification is used. We transform this to the seniority scheme. Our formula differs from the Redmond formula inasmuch as we have a sum over the possible seniorities for the $n \to n+1$ cfp's, whereas Redmond has only one term.Comment: RevTex4, 17 pages; added Appendix A, with proof for the new relation; corrected Eqs.(26),(38), and (39

Writing Chemistry at University

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Patient Characteristics Affect Hip Contact Forces during Gait

Objective: To examine hip contact force (HCF), calculated through multibody modelling, in a large total hip replacement (THR) cohort stratified by patient characteristics such as BMI, age and function. Design: 132 THR patients undertook one motion capture session of gait analysis at a self-selected walking speed. HCFs were then calculated using the AnyBody Modelling System. Patients were stratified into three BMI groups, five age groups, and finally three functional groups determined by their self-selected gait speed. Independent 1-dimensional linear regression analyses were performed to separately evaluate the influence of age, BMI and functionality on HCF, by means of statistical parametric mapping (SPM). Results: The mean predicted HCF were comparable to HCFs measured with an instrumented prosthesis reported in the literature. The regression analyses revealed a statistically significant positive relationship between BMI and HCF, indicating that obese patients are more likely to experience higher HCF during most of the stance phase, while a statistically significant relationship with age was found only during the late swing-phase. Patients with higher functional ability exhibited significantly increased peak contact forces, while patients with lower functional ability displayed a pathological flattening of the typical double hump force profile. Conclusions: HCFs experienced at the bearing surface are highly dependent on patient characteristics. BMI and functional ability were determined to have the biggest influence on contact force. Current preclinical testing standards do not reflect this

Hybridization and melting behavior of Peptide Nucleic Acid (PNA) oligonucleotide chimeras conjugated to gold nanoparticles

Peptide nucleic acids (PNA) and PNA-DNA chimeras carrying thiol groups were used for surface functionalization of Au nanoparticles. Conjugation of PNA to citrate-stabilized Au nanoparticles destabilized the nanoparticles causing them to precipitate. Addition of a tail of glutamic acid to the PNA prevented destabilization of the nanoparticles but resulted in loss of interaction with complementary sequences. Importantly, PNA-DNA chimeras gave stable conjugates with Au nanoparticles. The hybridization and melting properties of complexes formed from chimera-nanoparticle conjugates and oligonucleotide-nanoparticle conjugates are described for the first time. Similar to oligonucleotide- nanoparticle conjugates, conjugates with PNA-DNA chimeras gave sharper and more-defined melting profiles than those obtained with unmodified oligonucleotides. In addition, mismatch discrimination was found to be more efficient than with unmodified oligonucleotides.This work was supported by the Comission of the European Unions as part of the Information Societies Technology Programme (IST-1999-11974), by the Dirección General de Investigación Científica (BQU2003-0397 and BFU2004-02048) and The Generalitat de Catalunya (2001-SGR-0049). We thank Elisenda Ferrer for their help on the preparation of PNA-DNA chimeras.Peer reviewe

Hybridization and melting behavior of Peptide Nucleic Acid (PNA) oligonucleotide chimeras conjugated to gold nanoparticles

Peptide nucleic acids (PNA) and PNA-DNA chimeras carrying thiol groups were used for surface functionalization of Au nanoparticles. Conjugation of PNA to citrate-stabilized Au nanoparticles destabilized the nanoparticles causing them to precipitate. Addition of a tail of glutamic acid to the PNA prevented destabilization of the nanoparticles but resulted in loss of interaction with complementary sequences. Importantly, PNA-DNA chimeras gave stable conjugates with Au nanoparticles. The hybridization and melting properties of complexes formed from chimera-nanoparticle conjugates and oligonucleotide-nanoparticle conjugates are described for the first time. Similar to oligonucleotide- nanoparticle conjugates, conjugates with PNA-DNA chimeras gave sharper and more-defined melting profiles than those obtained with unmodified oligonucleotides. In addition, mismatch discrimination was found to be more efficient than with unmodified oligonucleotides.This work was supported by the Comission of the European Unions as part of the Information Societies Technology Programme (IST-1999-11974), by the Dirección General de Investigación Científica (BQU2003-0397 and BFU2004-02048) and The Generalitat de Catalunya (2001-SGR-0049). We thank Elisenda Ferrer for their help on the preparation of PNA-DNA chimeras.Peer reviewe

Writing Medicine at University

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Charge transport in a CoPt3 nanocrystal microwire

The electrical characteristics of single CoPt3 nanocrystal microwires formed by magnetic field-directed growth from colloidal solutions are presented. The wires comprise disordered assemblies of discrete nanocrystals, separated from each other by protective organic ligand shells. Electrical data indicate that the activated charge transport properties of the wires are determined by the nanocrystal charging energy, governed by the size and capacitance of the individual nanocrystals. Focused ion beam-assisted deposition of Pt metal at the wire-electrode junctions is employed to optimize the wire-electrode contacts, whilst maintaining the nanocrystal-dominated transport characteristics of these one-dimensional nanocrystal structures. (C) 2004 American Institute of Physics. (DOI:10.1063/1.1830684

Writing Education at University

Podeu consultar la versió en català i francés al recurs relacionat.User guide to written communication in academic disciplines (in this case education) for teachers and students