288 research outputs found
The spectral problem for the dispersionless Camassa-Holm equation
We present a spectral and inverse spectral theory for the zero dispersion spectral problem associated with the Camassa-Holm equation. This is an alternative approach to that in [10] by Eckhardt and Teschl
Observation of individual molecules trapped on a nanostructured insulator
For the first time, ordered polar molecules confined in monolayer-deep
rectangular pits produced on an alkali halide surface by electron irradiation
have been resolved at room temperature by non-contact atomic force microscopy.
Molecules self-assemble in a specific fashion inside pits of width smaller than
15 nm. By contrast no ordered aggregates of molecules are observed on flat
terraces. Conclusions regarding nucleation and ordering mechanisms are drawn.
Trapping in pits as small as 2 nm opens a route to address single molecules
Recommended from our members
Single layer graphene induces load-bearing molecular layering at the hexadecane-steel interface
The influence of a single layer graphene on the interface between a polished steel surface and the model lubricant hexadecane is explored by high-resolution force microscopy. Nanometer-scale friction is reduced by a factor of three on graphene compared to the steel substrate, with an ordered layer of hexadecane adsorbed on the graphene. Graphene furthermore induces a molecular ordering in the confined lubricant with an average range of 4-5 layers and with a strongly increased load-bearing capacity compared to the lubricant on the bare steel substrate. © 2019 IOP Publishing Ltd
Distance dependence of force and dissipation in non-contact atomic force microscopy on Cu(100) and Al(111)
The dynamic characteristics of a tip oscillating in the nc-AFM mode in close
vicinity to a Cu(100)-surface are investigated by means of phase variation
experiments in the constant amplitude mode. The change of the quality factor
upon approaching the surface deduced from both frequency shift and excitation
versus phase curves yield to consistent values. The optimum phase is found to
be independent of distance. The dependence of the quality factor on distance is
related to 'true' damping, because artefacts related to phase misadjustment can
be excluded. The experimental results, as well as on-resonance measurements at
different bias voltages on an Al(111) surface, are compared to Joule
dissipation and to a model of dissipation in which long-range forces lead to
viscoelastic deformations
Revealing the Meissner Corpuscles in Human Glabrous Skin Using In Vivo Non-Invasive Imaging Techniques
The presence of mechanoreceptors in glabrous skin allows humans to discriminate textures
by touch. The amount and distribution of these receptors defines our tactile sensitivity and can
be affected by diseases such as diabetes, HIV-related pathologies, and hereditary neuropathies.
The quantification of mechanoreceptors as clinical markers by biopsy is an invasive method of
diagnosis. We report the localization and quantification of Meissner corpuscles in glabrous skin using
in vivo, non-invasive optical microscopy techniques. Our approach is supported by the discovery of
epidermal protrusions which are co-localized with Meissner corpuscles. Index fingers, small fingers,
and tenar palm regions of ten participants were imaged by optical coherence tomography (OCT) and
laser scan microscopy (LSM) to determine the thickness of the stratum corneum and epidermis and
to count the Meissner corpuscles. We discovered that regions containing Meissner corpuscles could
be easily identified by LSM with an enhanced optical reflectance above the corpuscles, caused by a
protrusion of the strongly reflecting epidermis into the stratum corneum with its weak reflectance.
We suggest that this local morphology above Meissner corpuscles has a function in tactile perception
Null sets of harmonic measure on NTA domains: Lipschitz approximation revisited
We show the David-Jerison construction of big pieces of Lipschitz graphs
inside a corkscrew domain does not require its surface measure be upper Ahlfors
regular. Thus we can study absolute continuity of harmonic measure and surface
measure on NTA domains of locally finite perimeter using Lipschitz
approximations. A partial analogue of the F. and M. Riesz Theorem for simply
connected planar domains is obtained for NTA domains in space. As a consequence
every Wolff snowflake has infinite surface measure.Comment: 22 pages, 6 figure
Human glabrous skin contains crystallized urea dendriform structures in the stratum corneum which affect the hydration levels
Glabrous skin is hair-free skin with a high density of sweat glands, which is found on
the palms, and soles of mammalians, covered with a thick stratum corneum. Dry hands
are often an occupational problem which deserves attention from dermatologists.
Urea is found in the skin as a component of the natural moisturizing factor and of
sweat. We report the discovery of dendrimer structures of crystalized urea in the stratum corneum of palmar glabrous skin using laser scanning microscopy. The chemical
and structural nature of the urea crystallites was investigated in vivo by non-invasive
techniques. The relation of crystallization to skin hydration was explored. We analysed
the index finger, small finger and tenar palmar area of 18 study participants using noninvasive optical methods, such as laser scanning microscopy, Raman microspectroscopy and two-photon tomography. Skin hydration was measured using corneometry.
Crystalline urea structures were found in the stratum corneum of about two-thirds
of the participants. Participants with a higher density of crystallized urea structures
exhibited a lower skin hydration. The chemical nature and the crystalline structure of
the urea were confirmed by Raman microspectroscopy and by second harmonic generated signals in two-photon tomography. The presence of urea dendrimer crystals in
the glabrous skin seems to reduce the water binding capacity leading to dry hands.
These findings highlight a new direction in understanding the mechanisms leading
to dry hands and open opportunities for the development of better moisturizers and
hand disinfection products and for diagnostic of dry skin
Role of friction-induced torque in stick-slip motion
We present a minimal quasistatic 1D model describing the kinematics of the
transition from static friction to stick-slip motion of a linear elastic block
on a rigid plane. We show how the kinematics of both the precursors to
frictional sliding and the periodic stick-slip motion are controlled by the
amount of friction-induced torque at the interface. Our model provides a
general framework to understand and relate a series of recent experimental
observations, in particular the nucleation location of micro-slip instabilities
and the build up of an asymmetric field of real contact area.Comment: 6 pages, 5 figure
Atomic Scale Memory at a Silicon Surface
The limits of pushing storage density to the atomic scale are explored with a
memory that stores a bit by the presence or absence of one silicon atom. These
atoms are positioned at lattice sites along self-assembled tracks with a pitch
of 5 atom rows. The writing process involves removal of Si atoms with the tip
of a scanning tunneling microscope. The memory can be reformatted by controlled
deposition of silicon. The constraints on speed and reliability are compared
with data storage in magnetic hard disks and DNA.Comment: 13 pages, 5 figures, accepted by Nanotechnolog
- …