Impaired neural transduction of barosensory vessel stretch into vagal outflow is a primary determinant of reduced cardiovagal baroreflex gain with human aging. We set out to determine whether age-related reductions in this neural component of the baroreflex might be offset by enhancing the central integration/efferent responsiveness of the neural arc. Low vagotonic doses of atropine were employed to enhance central neural outflow and peripheral sinus node effects. Baroreflex gain and its neural and mechanical components were pharmacologically assessed before and after intravenous vagotonic atropine in 16 older and 14 young healthy subjects. Vagotonic atropine increased cardiovagal baroreflex gain (∼30%) and its neural component (∼20%) in older but not young individuals. Moreover, the atropine-induced increases in integrated gain and in its neural component were inversely related to baseline levels. Thus, age-related neural deficits in the baroreflex arc appear to play a determining role in reduced cardiovagal baroreflex gain with age and the compromised neural baroreflex function can be acutely improved by a single pharmacologic intervention.

For assisting the in-depth investigations of widespread electromechanical phenomena in functional materials, piezoresponse force microscopy (PFM) has gradually evolved to realize full information-flow acquisition and fit the conductive liquid working environments. Here, we designed data cube (DCUBE) based PFM to collect the electromechanical effect into a high-dimensional array of piezoresponse by adding ac bias with a wide range of frequencies to the probe. The electromechanical and mechanical spectra can be consecutively extracted at each pixel in the intermittent-contact mode. High-resolution ferroelectric domains of the poled LiNbO3 were mapped, corresponding to the ideal phase contrasts of about 180° in air, decane, and deionized water. Rich information detection and non-contact mode in DCUBE-PFM bring many merits on the electromechanical characterizations, especially for elastic-inhomogeneous surfaces and soft materials. Moreover, we systematically reveal the Debye screening effect and time-resolved field-oriented ion dynamics, which play crucial roles in the reduction of PFM spatial resolution in electrolytes. These physical discussions provide strategies to further realize high-resolution electromechanical imaging in highly conductive liquid environments.

The early-stage sintering of thin layers of micron-sized polystyrene (PS) particles, at sintering temperatures near and above the glass transition temperature Tg (~ 100°C), is studied utilizing 3D tomography, nanoindentation and confocal microscopy. Our experimental results confirm the existence of a critical particle radius (rcrit ~ 1 μm) below which surface forces need to be considered as additional driving force, on top of the usual surfacetension driven viscous flow sintering mechanism. Both sintering kinetics and mechanical properties of particles smaller than rcrit are dominated by contact deformation due to surface forces, so that sintering of larger particles is generally characterized by viscous flow. Consequently, smaller particles require shorter sintering. These experimental observations are supported by discrete particle simulations that are based on analytical models: for small particles, if only viscous sintering is considered, the model under-predicts the neck radius during early stage sintering, which confirms the need for an additional driving mechanism like elastic-plastic repulsion and surface forces that are both added to the DEM model.

Water and oil repellent coatings---so-called superamphiphobic coatings---greatly reduce the interaction between a liquid and a solid. So far, only flat or weakly curved superhydrophobic and superamphiphobic surfaces have been designed. This raises the question of whether highly curved structures or microspheres are feasible. Therefore, we coated microspheres with a superamphiphobic layer and measured the force between the spheres and a liquid. A qualitatively different dependence of the adhesion force on the applied load for superamphiphobic and smooth spheres is detected. Furthermore, we demonstrate both experimentally and theoretically that superamphiphobicity fails below a critical particle radius, depending on topological details and type of liquid. Therefore, this study sets a fundamental physical limit to the application of superamphiphobic layers for small objects with high curvature.

We report a novel and facile approach to achieve a self-cleaning, flexible, transparent, template free, cheap and non-toxic polymeric film. The superhydrophobic surface will become active only by peeling off the laminated polymer film; this kind of "instant superhydrophobic surface" can be delivered to customers as "peel and use".

Polymeric and composite microspheres can be synthesized without solvents or process liquids by using superamphiphobic surfaces. In this method, the repellency of superamphiphobic layers to monomers and polymer melts and the extremely low adhesion to particles are taken advantage of.

The DNA origami technology holds great promise for the assembly of nanoscopic technological devices and studies of biochemical reactions at the single-molecule level. For these, it is essential to establish well controlled attachment of functional materials to predefined sites on the DNA origami nanostructures for reliable measurements and versatile applications. However, the two-sided nature of the origami scaffold has shown limitations in this regard. We hypothesized that holes of the commonly used two-dimensional DNA origami designs are large enough for the passage of single-stranded (ss)-DNA. Sufficiently long ssDNA initially located on one side of the origami should thus be able to "thread" to the other side through the holes in the origami sheet. By using an origami sheet attached with patterned biotinylated ssDNA spacers and monitoring streptavidin binding with atomic force microscopic (AFM) imaging, we provide unambiguous evidence that the biotin ligands positioned on one side have indeed threaded through to the other side. Our finding reveals a previously overlooked critical design feature that should provide new interpretations to previous experiments and new opportunities for the construction of origami structures with new functional capabilities.

Our previous study has shown that the self-assembly of several neurodegenerative-disease-related peptides in ambient water nanofilm condensed on mica is very sensitive to the amount of water on the surface. In this paper, we will demonstrate our hypothesis that the introduction of ethanol into the water nanofilm alters the properties of the interfacial water, resulting in changes of the peptide nanostructures self-assembled on the substrate. The assembly behaviors of peptides under different ethanol-containing atmospheres on mica were investigated by atomic force microscopy. GAV-9a began to form bent nanofilaments under an ethanol-containing atmosphere, and the self-assembled nanofilaments became thicker when a higher ratio of ethanol to water in the vapor was used. Based on these results, we propose a possible mechanism that the peptides adopt a "tilted upright" orientation when ethanol is present in the incubation environment. The effect of the peptide's terminal groups on the self-assembled nanostructures under the ethanol-containing atmosphere was also discussed.

Many important physical, chemical, and biological processes taking place in nanoscopic confined water environments may behave very different from that in bulk. In this paper, we report an unusual nonenzymatic degradation of DNA molecules in the confined water nanofilm on mica substrate. We found that the half-time of DNA in the degradation process in the water nanofilm is about several hours under high RH at temperatures ranging from 10 to 50 °C, which is much faster than that in bulk water, ∼10(11) years at 25 °C. Careful analysis indicated that it was the formation of a water/vapor interface in the water nanofilm that played a major role in promoting DNA degradation.

Individual biomolecular binding events were recorded in situ by combining time-lapse atomic force microscopy and DNA origami. Single streptavidin molecules bound to specifically biotinyated DNA origami were simply counted as a function of time to obtain a direct measure of the binding rate.

Supramolecular structures formed by H4TPPS42- have been widely used for different applications. In this paper, the stability of H4TPPS42- nanorods on mica substrate is investigated by atom force microscopy (AFM) observation. An irreversible transformation of H4TPPS42- from nanorods (3.8 +/- 0.4 nm in height) to a lower film structure (1.9 +/- 0.4 nm in height) was found with the samples incubated at various relative humidities (RH). The transformation rate depends strongly on the RH and environment temperature.

An ambient water nanofilm condensed on a solid surface provides a good model system to study the self-assembling behaviors of peptides in a confined environment. In this paper, the self-assembly of three short amyloid-related peptides in a water nanofilm confined on a mica substrate was studied using drying microcontact printing (D-μCP) and atomic force microscopy (AFM). The three peptides, which share the same amino acid sequence but have different terminal groups, were placed on mica surfaces by D-μCP. The samples were then incubated in a chamber with a controlled temperature and relative humidity (RH) in which water nanofilms were generated on the sample surfaces. AFM images revealed that the peptides assembled into two kinds of supramolecular structures: nanofilaments and nanosheets. The peptides' terminal groups and the thickness of the water nanofilms determined the self-assembled supramolecular structures in the water nanofilm. Through AFM investigation of the formation and transformation of the peptides' supramolecular structures, we conclude that the peptides' self-assembly process was dominated by weak interactions, such as hydrophobic and electrostatic interactions and hydrogen bonding, between the peptide molecules, the mica substrate, and the water nanofilm. On the basis of these results, a model that describes the peptide arrangement in the confined water nanofilm is proposed. This study reveals the complicated interactions of the peptides at an interface, which may be a general mechanism in vivo because water confinement around biomolecules and membranes is a universal phenomenon.

Boron phosphate (BPO4) is a well known catalyst for a range of organic chemical reactions. In this paper, we report the preparations and characterizations of nano-sized BPO4 and nano-BPO4-based core-shell spheres. The samples were synthesized hydrothermally using H3BO3, H3PO4 and short chain n-alkylamines (n = 3, 4) as starting materials. The resulting products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scan electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. A possible mechanism for the formation of the materials is also discussed.

To study enzyme-DNA interactions at single molecular level, both the attachment points and the immediate surroundings of surfaces must be carefully considered such that they do not compromise the structural information and biological properties of the sample under investigation. The present work demonstrates the feasibility of enzymatic digestion of single DNA molecules attached to nanoparticle-modified surfaces. With Nanogold linking DNA to the mica surface by electrostatic interactions, advantageous conditions with fewer effects on the length and topography of DNA are obtained, and an appropriate environment for the activities of DNA is created. We demonstrate that by using Dip-Pen Nanolithography, individual DNA molecules attached to modified mica surfaces can be efficiently digested by DNase I.

Ambient water nanofilms confined on solid surfaces usually show properties not seen in bulk and play unique roles in many important processes. Here we report diffusion and self-assembly of peptides in ambient water nanofilms on mica, based on "drying microcontact printing" and ex situ atomic force microscopy imaging. We found that diffusion and self-assembly of several peptides in the water nanofilms on mica resulted in one-dimensional "epitaxial" nanofilaments. The peptide self-assembly process is sensitive to the amount of water on the surface, and different peptides with varied molecular structures show different humidity-dependent behaviors. In addition, some peptides that cannot form nanofilaments on substrates in bulk water can be successfully self-assembled into nanofilaments in the water nanofilm.

In this work, we investigate the formation of nanobubbles on a surface coated with TiO2 in an aqueous solution by in situ tapping-mode atomic force microscopy (TMAFM). The TiO2-coated surface can generate hydrogen through photocatalytic reaction in methanol/water solution when ultraviolet (UV) light (wavelength lambda < 400 nm) is illuminated on the surface. We found that nanobubbles could be produced and existed at the TiO2/water interface during the TiO2 photocatalytic process. By employing a combination of techniques, including phase imaging and contact-mode imaging, we could confirm the gas origin of such observed nanobubbles. In addition, the evolution process of nanobubbles at the TiO2/water interface has also been monitored with time of the photocatalytic reaction.

Usually, long double-stranded DNA molecules exhibit an aggregated or a random spreading behavior when deposited on a highly ordered pyrolytic graphite (HOPG) substrate. In this article, the authors report a novel phenomenon where randomly oriented DNA strands can gradually be rearranged into two-dimensional ordered nanostructures under the operation of repeatedly rotating a water droplet on the DNA sample. The process of DNA rearrangement was traced by using atomic force microscopy relocation imaging. The orientation of the ordered DNA strands shows a threefold symmetry consistent with the underlying atomic lattice of the HOPG substrate, signifying a substrate-directed ordering process. The relevant mechanism is discussed.

Controlling chemical and biochemical reactions on nanoscale at the single-molecule level is of great interest due to its possibility for exploring new phenomena and/or unraveling novel mechanisms that are inaccessible for traditional bulk systems. In this paper, we report how DNase I, a well-known and widely used nonspecific endonuclease, digested DNA at controlled sites by using an approach termed combined-dynamic dip-pen nanolithography (CDDPN). High efficient digestion has been realized even under an ambient condition on the surfaces. We attribute this phenomenon to a high effective concentration of DNase I when confined in the nanospots.

Electrogenerated microscale bubbles that are confined at the electrode surface have already been extensively studied because of their significant influence on electrochemistry. In contrast, as far as we know, whether nanoscale bubbles exist on the electrode surface has not been experimentally confirmed yet. Here, we report the observation of electrochemically controlled formation and growth of hydrogen nanobubbles on bare highly oriented pyrolytic graphite (HOPG) surface via in-situ tapping mode atomic force microscopy (TMAFM). By using TMAFM imaging, we observed that electrochemically generated hydrogen gas led to the formation of nanobubbles at the HOPG surface. We then employed a combination of techniques, including phase imaging, ex-situ degassing, and tip perturbation, to confirm the gas origin of such observed nanobubbles. We further demonstrated that the formation and growth of nanobubbles could be well controlled by tuning either the applied voltage or the reaction time. Remarkably, we could also monitor the evolution process of nanobubbles, that is, formation, growth, coalescence, as well as the eventual release of merged microbubbles from the HOPG surface.