Optical Bonding Using Silica Nanoparticle Sol−Gel Chemistry

A simple method is described to bond optical components using silica nanoparticle sol−gel chemistry. The silica nanoparticles polymerize into highly branched networks that link the surfaces together. The nanoparticle mediated bonding has several advantages to currently used optical joining technologies. The bonding is a room-temperature process and does not require any clean room facilities. The bonded interface has a high mechanical strength and low scattering. The bonding is resistant to organic solvents on silylation with hydrophobic surface groups. This method achieves 100% successful bonding rates between soda-lime glass slides. The bond-setting time can be tailored to allow time for precision optical alignment

Ruthenium-Catalyzed Ring-Opening Addition of Anilides to 7‑Azabenzonorbornadienes: A Diastereoselective Route to Hydronaphthylamines

The ruthenium­(II)-catalyzed direct ring-opening reaction of 7-azabenzonorbornadienes with anilides via C–H activation to access hydronaphthylamines has been developed. The transformation proceeds with a high stereoselectivity to give cis-configuration products under redox-neutral conditions

Shear Thinning and Tumbling Dynamics of Single Polymers in the Flow-Gradient Plane

The conformational changes imparted on single, flexible DNA polymers by a steady, simple shear flow were directly visualized in the flow-gradient plane. Two fluorescently stained DNA double-strand sizes of 22 μm and 80 μm in contour length were employed, and Wi values of up to 584 were probed (Wi = shear rate × longest polymer relaxation time). By exploitation of the linear proportionality between polymer density and its recorded image, the accessible radius of gyration tensor elements (Gij) were measured. Of those, the ensemble-averaged 〈G22〉 and 〈G12〉 were related to the bulk shear viscosity and first normal stress coefficient, respectively, via the Giesekus stress tensor. We found their respective behaviors to follow power-law decays of Wi -0.52 and Wi -1.28 at large Wi. Polymer dynamics were also investigated. Like rigid ellipsoids of revolution, polymers displayed a constant partition between positive and negative orientations irrespective of shear rate at Wi ≫ 1. Unlike them, however, polymers preferred positive orientations, spending there ∼ 75% or their time vs 50% for rigid ellipsoids. End-over-end tumbling was observed, confirming a long-standing prediction and numerous single-chain computer simulation studies. The tumbling frequency followed Wi0.62, and an equation was derived from simple advection and diffusion arguments to reproduce these observations

Shear Thinning and Tumbling Dynamics of Single Polymers in the Flow-Gradient Plane

The conformational changes imparted on single, flexible DNA polymers by a steady, simple shear flow were directly visualized in the flow-gradient plane. Two fluorescently stained DNA double-strand sizes of 22 μm and 80 μm in contour length were employed, and Wi values of up to 584 were probed (Wi = shear rate × longest polymer relaxation time). By exploitation of the linear proportionality between polymer density and its recorded image, the accessible radius of gyration tensor elements (Gij) were measured. Of those, the ensemble-averaged 〈G22〉 and 〈G12〉 were related to the bulk shear viscosity and first normal stress coefficient, respectively, via the Giesekus stress tensor. We found their respective behaviors to follow power-law decays of Wi -0.52 and Wi -1.28 at large Wi. Polymer dynamics were also investigated. Like rigid ellipsoids of revolution, polymers displayed a constant partition between positive and negative orientations irrespective of shear rate at Wi ≫ 1. Unlike them, however, polymers preferred positive orientations, spending there ∼ 75% or their time vs 50% for rigid ellipsoids. End-over-end tumbling was observed, confirming a long-standing prediction and numerous single-chain computer simulation studies. The tumbling frequency followed Wi0.62, and an equation was derived from simple advection and diffusion arguments to reproduce these observations

Shear Thinning and Tumbling Dynamics of Single Polymers in the Flow-Gradient Plane

The conformational changes imparted on single, flexible DNA polymers by a steady, simple shear flow were directly visualized in the flow-gradient plane. Two fluorescently stained DNA double-strand sizes of 22 μm and 80 μm in contour length were employed, and Wi values of up to 584 were probed (Wi = shear rate × longest polymer relaxation time). By exploitation of the linear proportionality between polymer density and its recorded image, the accessible radius of gyration tensor elements (Gij) were measured. Of those, the ensemble-averaged 〈G22〉 and 〈G12〉 were related to the bulk shear viscosity and first normal stress coefficient, respectively, via the Giesekus stress tensor. We found their respective behaviors to follow power-law decays of Wi -0.52 and Wi -1.28 at large Wi. Polymer dynamics were also investigated. Like rigid ellipsoids of revolution, polymers displayed a constant partition between positive and negative orientations irrespective of shear rate at Wi ≫ 1. Unlike them, however, polymers preferred positive orientations, spending there ∼ 75% or their time vs 50% for rigid ellipsoids. End-over-end tumbling was observed, confirming a long-standing prediction and numerous single-chain computer simulation studies. The tumbling frequency followed Wi0.62, and an equation was derived from simple advection and diffusion arguments to reproduce these observations

Shear Thinning and Tumbling Dynamics of Single Polymers in the Flow-Gradient Plane

The conformational changes imparted on single, flexible DNA polymers by a steady, simple shear flow were directly visualized in the flow-gradient plane. Two fluorescently stained DNA double-strand sizes of 22 μm and 80 μm in contour length were employed, and Wi values of up to 584 were probed (Wi = shear rate × longest polymer relaxation time). By exploitation of the linear proportionality between polymer density and its recorded image, the accessible radius of gyration tensor elements (Gij) were measured. Of those, the ensemble-averaged 〈G22〉 and 〈G12〉 were related to the bulk shear viscosity and first normal stress coefficient, respectively, via the Giesekus stress tensor. We found their respective behaviors to follow power-law decays of Wi -0.52 and Wi -1.28 at large Wi. Polymer dynamics were also investigated. Like rigid ellipsoids of revolution, polymers displayed a constant partition between positive and negative orientations irrespective of shear rate at Wi ≫ 1. Unlike them, however, polymers preferred positive orientations, spending there ∼ 75% or their time vs 50% for rigid ellipsoids. End-over-end tumbling was observed, confirming a long-standing prediction and numerous single-chain computer simulation studies. The tumbling frequency followed Wi0.62, and an equation was derived from simple advection and diffusion arguments to reproduce these observations

Shear Thinning and Tumbling Dynamics of Single Polymers in the Flow-Gradient Plane

The conformational changes imparted on single, flexible DNA polymers by a steady, simple shear flow were directly visualized in the flow-gradient plane. Two fluorescently stained DNA double-strand sizes of 22 μm and 80 μm in contour length were employed, and Wi values of up to 584 were probed (Wi = shear rate × longest polymer relaxation time). By exploitation of the linear proportionality between polymer density and its recorded image, the accessible radius of gyration tensor elements (Gij) were measured. Of those, the ensemble-averaged 〈G22〉 and 〈G12〉 were related to the bulk shear viscosity and first normal stress coefficient, respectively, via the Giesekus stress tensor. We found their respective behaviors to follow power-law decays of Wi -0.52 and Wi -1.28 at large Wi. Polymer dynamics were also investigated. Like rigid ellipsoids of revolution, polymers displayed a constant partition between positive and negative orientations irrespective of shear rate at Wi ≫ 1. Unlike them, however, polymers preferred positive orientations, spending there ∼ 75% or their time vs 50% for rigid ellipsoids. End-over-end tumbling was observed, confirming a long-standing prediction and numerous single-chain computer simulation studies. The tumbling frequency followed Wi0.62, and an equation was derived from simple advection and diffusion arguments to reproduce these observations

Direct Measurement of Tertiary Contact Cooperativity in RNA Folding

Direct Measurement of Tertiary Contact Cooperativity in RNA Foldin

A Magneto-Optical Nanoplatform for Multimodality Imaging of Tumors in Mice

Multimodality imaging involves the use of more imaging modes to image the same living subjects and is now generally preferred in clinics for cancer imaging. Here we present multimodalityMagnetic Particle Imaging (MPI), Magnetic Resonance Imaging (MRI), Photoacoustic, Fluorescentnanoparticles (termed MMPF NPs) for imaging tumor xenografts in living mice. MMPF NPs provide long-term (more than 2 months), dynamic, and accurate quantification, in vivo, of NPs and in real time by MPI. Moreover, MMPF NPs offer ultrasensitive MPI imaging of tumors (the tumor ROI increased by 30.6 times over that of preinjection). Moreover, the nanoparticle possessed a long-term blood circulation time (half-life at 49 h) and high tumor uptake (18% ID/g). MMPF NPs have been demonstrated for imaging breast and brain tumor xenografts in both subcutaneous and orthotopic models in mice via simultaneous MPI, MRI, fluorescence, and photoacoustic imaging with excellent tumor contrast to normal tissues

A Magneto-Optical Nanoplatform for Multimodality Imaging of Tumors in Mice

Multimodality imaging involves the use of more imaging modes to image the same living subjects and is now generally preferred in clinics for cancer imaging. Here we present multimodalityMagnetic Particle Imaging (MPI), Magnetic Resonance Imaging (MRI), Photoacoustic, Fluorescentnanoparticles (termed MMPF NPs) for imaging tumor xenografts in living mice. MMPF NPs provide long-term (more than 2 months), dynamic, and accurate quantification, in vivo, of NPs and in real time by MPI. Moreover, MMPF NPs offer ultrasensitive MPI imaging of tumors (the tumor ROI increased by 30.6 times over that of preinjection). Moreover, the nanoparticle possessed a long-term blood circulation time (half-life at 49 h) and high tumor uptake (18% ID/g). MMPF NPs have been demonstrated for imaging breast and brain tumor xenografts in both subcutaneous and orthotopic models in mice via simultaneous MPI, MRI, fluorescence, and photoacoustic imaging with excellent tumor contrast to normal tissues